Métodos por imagem da aterosclerose em estudos de progressão/regressão: marcador substituto ou janela direta para o processo patológico da aterosclerose?

A DAC continua sendo uma das principais causas globais de morbimortalidade. Programas amplos de desenvolvimento de drogas para novas estratégias de tratamento medicamentoso freqüentemente utilizam estudos com desfechos de mortalidade/morbidade tradicionais e outros com desfechos substitutos. Essa abordagem paralela permite uma avaliação da eficácia vários anos antes dos dados de estudos com desfechos clínicos estarem disponíveis. Vários marcadores imagenológicos de aterosclerose foram introduzidos nessas estratégias de desenvolvimento de drogas, incluindo angiografia, ultrassonografia de carótida, USIV, RM e TC. Esta revisão discutirá a situação atual dos métodos por imagem da aterosclerose como um desfecho em estudos de progressão/regressão, com ênfase em dados baseados em evidências. Além de uma discussão sobre os resultados das modalidades de métodos por imagem individuais, serão apresentados os dados que têm surgido comparando as diferentes modalidades e abordagens.

Revisão sistemática e meta-análise de estudos de diagnóstico e prognóstico: um tutorial

As revisões sistemáticas com meta-análise de estudos de exames diagnósticos ou de fatores prognósticos são ferramentas de pesquisa ainda em fase de desenvolvimento. O objetivo do presente texto é descrever a metodologia de revisão sistemática e de meta-análise deste tipo de estudos, passo a passo. Foi feita a revisão da literatura sobre o tema, compilando as recomendações e organizando o texto em: a) Introdução, b) Setalhamento dos oito passos a serem seguidos, c) Forma de publicação da revisão sistemática com meta-análise e d) Conclusão. Foram descritos os métodos de revisão sistemática de forma detalhada, com análise crítica dos métodos de compilação estatística dos resultados, com ênfase na utilização da curva Summary Receiver Operator Characteristic. Forneceu-se referência para os detalhes de cada técnica estatística utilizada na meta-análise. Concluímos que as revisões sistemáticas com meta-análise de exames diagnósticos ou de fatores prognósticos são valiosas na compilação de dados de vários estudos sobre o mesmo tema, reduzindo vieses e aumentando o poder estatístico da pesquisa primária.

Realce tardio e perfusão miocárdica em cardiomiopatia hipertrófica (comparação entre grupos)

FUNDAMENTO: A ressonância magnética é um método eficaz para estudo da cardiomiopatia hipertrófica. OBJETIVO: Avaliar, pela ressonância magnética, os parâmetros de função sistólica, perfusão e viabilidade miocárdica em pacientes portadores de cardiomiopatia hipertrófica, comparando os grupos com e sem obstrução na via de saída do ventrículo esquerdo. MÉTODO: Vinte e um pacientes com diagnóstico de cardiomiopatia hipertrófica realizaram estudos de função, viabilidade e perfusão miocárdica nas fases de estresse e de repouso pela ressonância magnética. RESULTADOS: Os segmentos ventriculares mais comprometidos pela hipertrofia foram os da região septal. O grupo obstrutivo apresentou distribuição segmentar de espessura miocárdica semelhante ao não-obstrutivo, porém com maiores médias que o primeiro grupo. A média da fração de ejeção dos pacientes do grupo obstrutivo foi maior que o grupo não-obstrutivo, enquanto as médias dos volumes sistólico e diastólico finais foram menores no grupo obstrutivo. Houve correlação positiva entre a espessura segmentar do ventrículo e a massa segmentar do realce tardio. A indução de estresse determinou aumento do número de segmentos com alteração de perfusão e essa alteração foi mais evidente no grupo obstrutivo. CONCLUSÃO: Os segmentos ventriculares com maior espessura são os septais. As regiões hipertróficas estão associadas à maior extensão de realce tardio. Houve correlação positiva entre as áreas de hipertrofia ventricular e perfusão miocárdica alterada, e esses achados foram mais evidentes no grupo obstrutivo.

Preditores de viabilidade em pacientes com resposta negativa à ecocardiografia de estresse com dobutamina de baixa dose

FUNDAMENTO: A ecocardiografia de estresse com dobutamina de baixa dose é um teste específico para predizer disfunção de contratilidade reversível, mas mesmo assim, sua sensibilidade é menor do que ideal. OBJETIVO: Avaliar os preditores de recuperação miocárdica contrátil após a revascularização, em pacientes sem viabilidade na ecocardiografia de estresse com dobutamina de baixa dose. MÉTODOS: Trinta pacientes consecutivos foram selecionados consecutivamente, que apresentavam estenose coronária/oclusão significantes, tratáveis através de revascularização, anormalidade de motilidade de parede regional na distribuição da artéria afetada e ausência de viabilidade na ecocardiografia de estresse com dobutamina de baixa dose. Os pacientes foram submetidos a estudo de imagem com 99mTc-sestamibi em repouso e então submetidos à revascularização coronária bem sucedida. A ecocardiografia de seguimento foi realizada três meses depois. Os pacientes foram classificados em 2 grupos: grupo 1: com evidência de recuperação miocárdica contrátil após a revascularização na ecocardiografia de seguimento e grupo 2: sem evidência de recuperação miocárdica. Os dois grupos foram comparados em relação aos dados clínicos, ecocardiográficos e cintilográficos. RESULTADOS: A média da idade era 52,3 ± 5,9 anos e 97% eram do sexo masculino. A porcentagem de captação total de 99mTc-sestamibi foi significantemente mais alta no grupo 1 quando comparado ao grupo 2 (p < 0,01) e foi o preditor independente mais forte de recuperação miocárdica contrátil no seguimento de 3 meses na análise de regressão multivariada. A curva ROC (Receiver Operating Characteristic) mostrou que um valor de corte da porcentagem de captação total do 99mTc-sestamibi uptake de 72%, foi o melhor preditor da recuperação miocárdica contrátil, com uma sensibilidade de 100% e especificidade de 95.7%. CONCLUSÃO: Em pacientes sem evidência de viabilidade na ecocardiografia de estresse com dobutamina de baixa dose, a porcentagem de captação total do 99mTc-sestamibi prediz, de forma independente, a recuperação miocárdica contrátil após a revascularização coronária.

Precisão do aparelho Omron HEM-705 CP na medida de pressão arterial em grandes estudos epidemiológicos

FUNDAMENTO: A medida precisa da pressão arterial (PA) é de grande importância na pesquisa da hipertensão. No contexto de estudos clínicos e epidemiológicos, dispositivos oscilométricos frequentemente oferecem importantes vantagens para superar algumas das limitações do método auscultatório. Embora sua acurácia tenha sido avaliada em estudos múltiplos no ambiente clínico, há pouca evidência de seu desempenho em grandes estudos epidemiológicos. OBJETIVO: Avaliamos a precisão do Omron HEM-705-CP, um dispositivo automático para medida de PA, quando comparado com o método padrão auscultatório com esfigmomanômetro de mercúrio em um grande estudo de coorte. MÉTODOS: Três medidas auscultatórias foram obtidas, seguidas por duas mensurações com o dispositivo Omron em 1.084 indivíduos. O viés foi estimado como a média de duas medidas pelo dispositivo Omron menos a média das duas últimas medidas auscultatórias, com seus correspondentes limites de concordância (LC) de 95%. RESULTADOS: O dispositivo Omron superestimou a pressão arterial sistólica (PAS) por 1,8 mmHg (LC:-10,1, 13,7) e subestimou a pressão arterial diastólica (PAD) por 1,6 mmHg (LC:-12,3, 9,2). O viés foi significantemente maior em homens. O viés na PAS aumentou com a idade e diminuiu com o nível da PA, enquanto o viés na PAD diminuiu com a idade e aumentou com o nível da PA. A sensibilidade e a especificidade do dispositivo Omron para detectar hipertensão foram 88,2% e 98,6%, respectivamente. O uso das medidas do dispositivo Omron resultou em viés mínimo na estimativa dos efeitos de vários fatores. CONCLUSÃO: Nossos resultados demonstraram que o dispositivo Omron HEM-705-CP pode ser utilizado para medir a PA em grandes estudos epidemiológicos sem comprometer a validade do estudo ou sua precisão.

Angioplastia coronariana versus cirurgia de revascularização: revisão de estudos randomizados

Realizamos uma revisão com agregação de resultados dos ensaios randomizados que compararam intervenção coronariana percutânea (ICP) com cirurgia de revascularização miocárdica (CRM). Os 25 ensaios selecionados envolveram 12.305 pacientes dos quais 11.103 pertenciam a estudos em multiarteriais e 1.212 pertenciam a estudos em lesão única de descendente anterior (DA). Nos estudos em multiarteriais a ICP mostrou uma tendência a menor mortalidade precoce (1,2% versus 2%) e menor incidência de acidente vascular cerebral (AVC): 0,7% versus 1,65%. Não houve diferença na mortalidade intermediária (3,8% versus 3,8%). Houve tendência à superioridade da CRM na mortalidade tardia (10,5% versus 9,6%). A diferença deveu-se exclusivamente aos estudos da era balão, tendendo a inverter-se na era stent (9,6% versus 9,9%). Nos estudos de lesão única de DA não houve diferença significativa em nenhum desfecho. A agregação de resultados de nove estudos que avaliaram a mortalidade tardia em diabéticos mostrou diferença favorável à cirurgia (21,3% versus 15,9%). Dois estudos que avaliaram lesão de tronco não mostraram diferença significativa na mortalidade em um ano (3,9% versus 4,7%). A incidência de nova revascularização foi consistentemente maior na ICP, apesar de progressiva melhora dos resultados na era stent.

Estudos cardiopulmonares recentes

Entre 2009 e 2010, a Clinics publicou um número relativamente grande de estudos originais, que tratam do sistema cardiovascular e pulmonar. Vinte desses estudos têm atraído um número significativo de citações dentro deste intervalo de tempo relativamente curto. Esta revisão aborda esses aspectos de pesquisas recentes com interesse direto para os cardiologistas. Os artigos foram agrupados em três categorias: Cardiologia, Pneumologia e Assuntos Multidisciplinares.

Treinamento muscular inspiratório em pacientes com insuficiência cardíaca: metanálise de estudos randomizados

Pacientes com Insuficiência Cardíaca Crônica (ICC) podem ter menor força e resistência muscular inspiratória, o que pode contribuir para a intolerância ao exercício. O Treinamento Muscular Inspiratório (TMI) tem demonstrado efeitos benéficos nesses pacientes. Dessa forma, o objetivo desse estudo foi revisar sistematicamente os efeitos do TMI comparado a grupo controle (TMI placebo ou outra intervenção) em pacientes com ICC. A busca incluiu as bases MEDLINE, PEDro e Cochrane CENTRAL, além de referências de estudos publicados, de 1960 a 2011. Ensaios randomizados comparando TMI e grupo controle no tratamento de pacientes com ICC foram incluídos. O GRADE foi utilizado para determinar a qualidade da evidência para cada desfecho. Dos 119 artigos identificados, sete estudos foram incluídos. O TMI aumentou a distância percorrida no teste de caminhada de 6 minutos [69 m (IC95%: 7,21 a 130,79)] (evidência muito baixa) e a pressão inspiratória máxima [23,36 cmH20 (IC95%: 11,71 a 35,02)] comparado aos grupos controles (evidência baixa). Entretanto, o TMI promoveu uma melhora significativa no consumo máximo de oxigênio somente nos estudos que realizaram TMI por 12 semanas, comparado a nenhuma carga inspiratória em pacientes com fraqueza muscular inspiratória [3,02 ml/kg/min-1 (IC95%: 0,43 a 5,61)]. Assim, concluiu-se que o TMI melhora capacidade funcional e força muscular inspiratória, merecendo consideração como uma intervenção adicional em pacientes com ICC. Entretanto, estudos maiores e com maior qualidade são necessários para esclarecer o potencial benefício do TMI nessa população.

Pressão arterial e discriminação interpessoal: revisão sistemática de estudos epidemiológicos

A relação entre pressão arterial e discriminação tem sido investigada recentemente, havendo intensos debates na literatura sobre o tema. Este trabalho objetivou atualizar as revisões de literatura sobre discriminação e pressão arterial ou hipertensão. Foi conduzida pesquisa no PubMed, entre janeiro/2000 e dezembro/2010, incluindo estudos epidemiológicos, que avaliaram a discriminação interpessoal e sua relação com pressão arterial/hipertensão. Os 22 estudos identificados originaram-se dos Estados Unidos; 96% deles empregaram o delineamento transversal, com amostras de conveniência e compostas, em 59% dos casos, exclusivamente por negros. Os instrumentos mais utilizados para aferir discriminação foram Everyday Discrimination Scale e Perceived Racism Scale, enfatizando a discriminação étnico-racial, ocorrida ao longo da vida ou cotidianamente. Nos 22 estudos avaliados, a relação entre discriminação e os desfechos foi analisada 50 vezes. Em 20 (40%) resultados, não foi encontrada qualquer associação e, em apenas 15 (30%), observaram-se associações positivas globais, sendo 67% destas estatisticamente significativas. Foram também observadas oito associações inversas, sugerindo que maior exposição à discriminação estaria associada com menor pressão arterial/hipertensão. Os estudos não permitiram apoiar consistentemente a hipótese de que a discriminação está associada à maior pressão arterial. Isto pode ser atribuído, em parte, às limitações dos estudos, relacionadas à mensuração da discriminação e de eventos que podem modificar sua associação com os desfechos. Para consolidar a discriminação como um fator de risco epidemiológico, é necessário utilizar estratégias metodológicas mais rigorosas e revisar os marcos teóricos que propõem relações de causa e efeito entre discriminação e pressão arterial.

Estudos experimentais sôbre a origem do milho

1) It may seem rather strange that, in spite of the efforts of a considerable number of scientists, the problem of the origin of indian corn or maize still has remained an open question. There are no fossil remains or archaeological relics except those which are quite identical with types still existing. (Fig. 1). The main difficulty in finding the wild ancestor- which may still exist - results from the fact that it has been somewhat difficult to decide what it should be like and also where to look for it. 2) There is no need to discuss the literature since an excellent review has recently been published by MANGELSDORF and REEVES (1939). It may be sufficient to state that there are basically two hypotheses, that of ST. HILAIRE (1829) who considered Brazilian pod corn as the nearest relative of wild corn still existing, and that of ASCHERSON (1875) who considered Euchlaena from Central America as the wild ancestor of corn. Later hypotheses represent or variants of these two hypotheses or of other concepts, howewer generally with neither disproving their predecessors nor showing why the new hypotheses were better than the older ones. Since nearly all possible combinations of ideas have thus been put forward, it har- dly seems possible to find something theoretically new, while it is essential first to produce new facts. 3) The studies about the origin of maize received a new impulse from MANGELSDORF and REEVES'S experimental work on both Zea-Tripsacum and Zea-Euchlaena hybrids. Independently I started experiments in 1937 with the hope that new results might be obtained when using South American material. Having lost priority in some respects I decided to withold publication untill now, when I can put forward more concise ideas about the origin of maize, based on a new experimental reconstruction of the "wild type". 4) The two main aspects of MANGELSDORF and REEVES hypothesis are discussed. We agree with the authors that ST. HILAIRE's theory is probably correct in so far as the tunicata gene is a wild type relic gene, but cannot accept the reconstruction of wild corn as a homozygous pod corn with a hermaphroditic tassel. As shown experimentally (Fig. 2-3) these tassels have their central spike transformed into a terminal, many rowed ear with a flexible rachis, while possessing at the same time the lateral ear. Thus no explanation is given of the origin of the corn ear, which is the main feature of cultivated corn (BRIEGER, 1943). The second part of the hypothesis referring to the origin of Euchlaena from corn, inverting thus ASCHERSON's theory, cannot be accepted for several reasons, stated in some detail. The data at hand justify only the conclusion that both genera, Euchlaena and Zea, are related, and there is as little proof for considering the former as ancestor of the latter as there is for the new inverse theory. 5) The analysis of indigenous corn, which will be published in detail by BRIEGER and CUTLER, showed several very primitive characters, but no type was found which was in all characters sufficiently primitive. A genetical analysis of Paulista Pod Corn showed that it contains the same gene as other tunicates, in the IV chromosome, the segregation being complicated by a new gametophyte factor Ga3. The full results of this analysis shall be published elsewhere. (BRIEGER). Selection experiments with Paulista Pod Corn showed that no approximation to a wild ancestor may be obtained when limiting the studies to pure corn. Thus it seemed necessary to substitute "domesticated" by "wild type" modifiers, and the only means for achieving this substitution are hybridizations with Euchlaena. These hybrids have now been analysed init fourth generation, including backcrosses, and, again, the full data will be published elsewhere, by BRIEGER and ADDISON. In one present publication three forms obtained will be described only, which represent an approximation to wild type corn. 6) Before entering howewer into detail, some arguments against ST. HILAIRE's theory must be mentioned. The premendelian argument, referring to the instability of this character, is explained by the fact that all fertile pod corn plants are heterozygous for the dominant Tu factor. But the sterility of the homozygous TuTu, which phenotypically cannot be identified, is still unexplained. The most important argument against the acceptance of the Tunicata faetor as wild type relic gene was removed recently by CUTLER (not yet published) who showed that this type has been preserved for centuries by the Bolivian indians as a mystical "medicine". 7) The main botanical requirements for transforming the corn ear into a wild type structure are stated, and alternative solutions given. One series of these characters are found in Tripsacum and Euchlaena : 2 rows on opposite sides of the rachis, protection of the grains by scales, fragility of the rachis. There remains the other alternative : 4 rows, possibly forming double rows of female and male spikelets, protection of kernels by their glumes, separation of grains at their base from the cob which is thin and flexible. 8) Three successive stages in the reconstruction of wild corn, obtained experimentally, are discussed and illustrated, all characterized by the presence of the Tu gene. a) The structure of the Fl hybrids has already been described in 1943. The main features of the Tunicata hybrids (Fig. -8), when compared with non-tunicate hybrids (Fig. 5-6), consist in the absence of scaly protections, the fragility of the rachis and finally the differentiation of the double rows into one male and one female spikelet. As has been pointed out, these characters represent new phenotypic effects of the tunicate factor which do not appear in the presence of pure maize modifiers. b) The next step was observed among the first backcross to teosinte (Fig. 9). As shown in the photography, Fig. 9D, the features are essencially those of the Fl plants, except that the rachis is more teosinte like, with longer internodes, irregular four-row-arrangement and a complete fragility on the nodes. c) In the next generation a completely new type appeared (Fig. 10) which resembles neither corn nor teosinte, mainly in consequence of one character: the rachis is thin and flexible and not fragile, while the grains have an abscission layer at the base, The medium sized, pointed, brownish and hard granis are protected by their well developed corneous glumes. This last form may not yet be the nearest approach to a wild grass, and I shall try in further experiments to introduce other changes such as an increase of fertile flowers per spikelet, the reduction of difference between terminal and lateral inflorescences, etc.. But the nature of the atavistic reversion is alveadwy such that it alters considerably our expectation when looking for a still existing wild ancestor of corn. 9) The next step in our deductions must now consist in an reversion of our question. We must now explain how we may obtain domesticated corn, starting from a hypothetical wild plant, similar to type c. Of the several changes which must have been necessary to attract the attention of the Indians, the following two seem to me the most important: the disappearance of all abscission layers and the reduction of the glumes. This may have been brought about by an accumulation of mutations. But it seems much more probable to assume that some crossing with a tripsacoid grass or even with Tripsacum australe may have been responsible. In such a cross, the two types of abscission layer would be counterbalanced as shown by the Flhybrids of corn, Tripsacum and Euchlaena. Furthermore in later generations a.tu-allele of Tripsacum may become homozygous and substitute the wild tunicate factor of corn. The hypothesis of a hybrid origin of cultivated corn is not completely new, but has been discussed already by HARSHBERGER and COLLINS. Our hypothesis differs from that of MANGELSDORF and REEVES who assume that crosses with Tripsacum are responsible only for some features of Central and North American corn. 10) The following arguments give indirects evidence in support of our hypothesis: a) Several characters have been observed in indigenous corn from the central region of South America, which may be interpreted as "tripsacoid". b) Equally "zeoid" characters seem to be present in Tripsacum australe of central South-America. c) A system of unbalanced factors, combined by the in-tergeneric cross, may be responsible for the sterility of the wild type tunicata factor when homozygous, a result of the action of modifiers, brought in from Tripsacum together with the tuallele. d) The hybrid theory may explain satisfactorily the presence of so many lethals and semilethals, responsible for the phenomenon of inbreeding in cultivated corn. It must be emphasized that corn does not possess any efficient mechanism to prevent crossing and which could explain the accumulation of these mutants during the evolutionary process. Teosinte which'has about the same mechanism of sexual reproduction has not accumulated such genes, nor self-sterile plants in spite of their pronounced preference for crossing. 11) The second most important step in domestication must have consisted in transforming a four rowed ear into an ear with many rows. The fusion theory, recently revived byLANGHAM is rejected. What happened evidently, just as in succulent pXants (Cactus) or in cones os Gymnosperms, is that there has been a change in phyllotaxy and a symmetry of longitudinal rows superimposed on the original spiral arrangement. 12) The geographical distribution of indigenous corn in South America has been discussed. So far, we may distinguish three zones. The most primitive corn appears in the central lowlands of what I call the Central Triangle of South America: east of the Andies, south of the Amazone-Basin, Northwest of a line formed by the rivers São Prancisco-Paraná and including the Paraguay-Basin. The uniformity of the types found in this extremely large zone is astonishing (BRIEGER and CUTLER). To the west, there is the well known Andian region, characterized by a large number of extremely diverse types from small pop corn to large Cuszco, from soft starch to modified sweet corn, from large cylindrical ears to small round ears, etc.. The third region extends along the atlantic coast in the east, from the Caribean Sea to the Argentine, and is characterized by Cateto, an orange hard flint corn. The Andean types must have been obtained very early, and undoubtedly are the result of the intense Inca agriculture. The Cateto type may be obtained easily by crosses, for instance, of "São Paulo Pointed Pop" to some orange soft corn of the central region. The relation of these three South American zones to Central and North America are not discussed, and it seems essential first to study the intermediate region of Ecuador, Colombia and Venezuela. The geograprical distribution of chromosome knobs is rapidly discussed; but it seems that no conclusions can be drawn before a large number of Tripsacum species has been analysed.

Estudos citológicos em Hemíoteros da família Coreidae

A more or less detailed study of the spermatogenesis in six species of Hemiptera belonging to the Coreid Family is made in the present paper. The species studied and their respective chromosome numbers were: 1) Diactor bilineatus (Fabr.) : spermatogonia with 20 + X, primary spermatocytes with 10 + X, X dividing equationaliv in the first division and passing undivided to one pole in the second. 2) Lcptoglossus gonagra (Fabr.) : spermatogonia with 20 + X, primary spermatocytes with 10 + X, X dividing equationally in the first division and passing undivided to one pole in the second. 3) Phthia picta (Drury) : spermatogonia with 20 + X, primary spermatocytes with 10 + X, X dividing equationally in the first division and passing undivided to one pole in the second. 4) Anisocelis foliacea Fabr. : spermatogonia with 26 + X fthe highest mumber hitherto known in the Family), primary .spermatocytes with 13 + X, X dividing equationally in the first division an passing undivided to one pole in the second. 5) Pachylis pharaonis (Herbtst) : spermatogonia with 16 + X, primary spermatocytes with 8 + X. Behaviour of the heteroehromosome not referred. 6) Pachylis laticornis (Fabr.) : spermatogonia with 14 + X, primary spermatocytes with 7 + X, X passing undivided to one pole in the first division and therefore secondary spermatocytes with 7 + X and 7 chromosomes. General results and conclusions a) Pairing modus of the chromosomes (Telosynapsis or Farasynapsis ?) - In several species of the Coreld bugs the history of the chromosomes from the diffuse stage till diakinesis cannot be follewed in detail due specially to the fact that lhe bivalents, as soon as they begin to be individually distinct they appear as irregular and extremely lax chromatic areas, which through an obscure process give rise to the diakinesis and then to the metaphase chomosomes. Fortunately I was able to analyse the genesis of the cross-shaped chromosomes, becoming thus convinced that even in the less favorable cases like that of Phthia, in which the crosses develop from four small condensation areas of the diffuse chromosomes, nothing in the process permit to interpret the final results as being due to a previous telosynaptic pairing. In the case of long bivalents formed by two parallel strands intimately united at both endsegments and more or less widely open in the middle (Leptoglossus, Pachylis), I could see that the lateral arms of the crosses originate from condensation centers created by a torsion or bending in the unpaired parts of the chromosomes In the relatively short bivalents the lateral branches of the cross are formed in the middle but in the long ones, whose median opening is sometimes considerable, two asymetrical branches or even two independent crosses may develop in the same pair. These observations put away the idea of an end-to-end pairing of the chromosomes, since if it had occured the lateral arms of the crosses would always be symetrical and median and never more than two. The direct observation of a side- toside pairing of the chromosomal threads at synizesis, is in foil agreement with the complete lack of evidence in favour of telosynapsis. b) Anaphasic bridges and interzonal connections - The chromosomes as they separate from each other in anaphase they remain connected by means of two lateral strands corresponding to the unpaired segmenas observed in the bivalents at the stages preceding metaphase. In the early anaphase the chromosomes again reproduce the form they had in late diafcinesis. The connecting threads which may be thick and intensely coloured are generally curved and sometimes unequal in lenght, one being much longer than the other and forming a loop outwardly. This fact points to a continuous flow of chromosomal substance independently from both chromosomes of the pair rather than to a mechanical stretching of a sticky substance. At the end of anaphase almost all the material which formed the bridges is reduced to two small cones from whose vertices a very fine and pale fibril takes its origin. The interzonal fibres, therefore, may be considered as the remnant of the anaphasic bridges. Abnormal behaviour of the anaphase chromosomes showed to be useful in aiding the interpretation of normal aspects. It has been suggested by Schrader (1944) "that the interzonal is nothing more than a sticky coating of the chromosome which is stretched like mucilage between the daughter chromosomes as they move further and further apart". The paired chromosomes being enclosed in a commom sheath, as they separate they give origin to a tube which becomes more and more stretched. Later the walls of the tube collapse forming in this manner an interzonal element. My observations, however, do not confirm Schrader's tubular theory of interzonal connections. In the aspects seen at anaphase of the primary spermatocytes and described in this paper as chromosomal bridges nothing suggests a tubular structure. There is no doubt that the chromosomes are here connected by two independent strands in the first division of the spermatocytes and by a single one in the second. The manner in which the chromosomes separate supports the idea of transverse divion, leaving little place for another interpretation. c) Ptafanoeomc and chromatoid bodies - The colourabtlity of the plasmosome in Diactor and Anisocelis showed to be highly variable. In the latter species, one may find in the same cyst nuclei provided with two intensely coloured bodies, the larger of which being the plasmosome, sided by those in which only the heterochromosome took the colour. In the former one the plasmosome strongly coloured seen in the primary metaphase may easily be taken for a supernumerary chromosome. At anaphase this body stays motionless in the equator of the cell while the chromosomes are moving toward the poles. There, when intensely coloured ,it may be confused with the heterochromosome of the secondary spermatocytes, which frequently occupies identical position in the corresponding phase, thus causing missinterpretation. In its place the plasmosome may divide into two equal parts or pass undivided to one cell in whose cytoplasm it breaks down giving rise to a few corpuscles of unequal sizes. In Pachylis pharaonis, as soon as the nuclear membrane breate down, the plasmosome migrates to a place in the periphery of the cell (primary spermatocyte), forming there a large chromatoid body. This body is never found in the cytoplasm prior to the dissolution of the nuclear membrane. It is certain that chromatoid bodies of different origin do exist. Here, however, we are dealing, undoubtedly, with true plasmosomes. d) Movement of the heterochromosome - The heterochromosome in the metaphase of the secondary spermatocytes may occupy the most different places. At the time the autosomes prient themselves in the equatorial plane it may be found some distance apart in this plane or in any other plane and even in the subpolar and polar regions. It remains in its place during anaphase. Therefore, it may appear at the same level with the components of one of the anaphase plates (synchronism), between both plates (succession) or between one plate and tbe pole (precession), what depends upon the moment the cell was fixed. This does not mean that the heterochromosome sometimes moves as quickly as the autosomes, sometimes more rapidly and sometimes less. It implies, on the contrary, that, being anywhere in the cell, the heterochromosome m he attained and passed by the autosomes. In spite of being almost motionless the heterochromosome finishes by being enclosed in one of the resulting nuclei. Consequently, it does move rapidly toward the group formed by the autosomes a little before anaphase is ended. This may be understood assuming that the heterochromosome, which do not divide, having almost inactive kinetochore cannot orient itself, giving from wherever it stays, only a weak response to the polar influences. When in the equator it probably do not perform any movement in virtue of receiving equal solicitation from both poles. When in any other plane, despite the greater influence of the nearer pole, the influence of the opposite pole would permit only so a slow movement that the autosomes would soon reach it and then leave it behind. It is only when the cell begins to divide that the heterochromosome, passing to one of the daughter cells scapes the influence of the other and thence goes quickly to join the autosomes, being enclosed with them in the nucleus formed there. The exceptions observed by BORING (1907) together with ; the facts described here must represent the normal behavior of the heterocromosome of the Hemiptera, the greater frequency of succession being the consequence of the more frequent localization of the heterochromosome in the equatorial plane or in its near and of the anaphase rapidity. Due to its position in metaphase the heterochromosome in early anaphase may be found in precession. In late anaphase, oh the contrary ,it appears almost always in succession. This is attributed to the fact of the heterochromosome being ordinairily localized outside the spindle area it leaves the way free to the anaphasic plate moving toward the pole. Moreover, the heterochromosome being a round element approximately of the size of the autosomes, which are equally round or a little longer in the direction of the movement, it can be passed by the autosomes even when it stands in the area of the spindle, specially if it is not too far from the equatorial plane. e) The kinetochore - This question has been fully discussed in another paper (PIZA 1943a). The facts treated here point to the conclusion that the chromosomes of the Coreidae, like those of Tityus bahiensis, are provided with a kinetochore at each end, as was already admitted by the present writer with regard to the heterochromosome of Protenor. Indeed, taking ipr granted the facts presented in this paper, other cannot be the interpretation. However, the reasons by which the chromosomes of the species studied here do not orient themselves at metaphase of the first division in the same way as the heterochromosome of Protenor, that is, with the major axis parallelly to the equatorial plane, are claiming for explanation. But, admiting that the proximity of the kinetochores at the ends of chromosomes which do not separate until the second division making them respond to the poles as if they were a single kinetochore ,the explanation follows. (See PIZA 1943a). The median opening of the diplonemas when they are going to the diffuse stage as well as the reappearance of the bivalents always united at the end-segments and open in the middle is in full agreement with the existence of two terminal kinetochores. The same can be said with regard to the bivalents which join their extremities to form a ring.

Estudos genéticos sôbre o milho tunicata

The study of pod corn seems still of much importance from different points of view. The phylogenetical importance of the tunicate factor as a wild type relic gene has been recently discussed in much detail by MANGELSDORF and REEVES (1939), and by BRIEGER (1943, 1944a e b). Selection experiments have shown that the pleiotropic effect of the Tu factor can be modified very extensively (BRIEGER 1944a) and some of the forms thus obtained permitt comparison of male and female inflorescences in corn and related grasses. A detailed discussion of the botanical aspect shall be given shortly. The genetic apect, finally, is the subject of the present publication. Pod corn has been obtained twice: São Paulo Pod Corn and Bolivia Pod Corn. The former came from one half ear left in our laboratory by a student and belongs to the type of corn cultivated in the State of São Paulo, while the other belongs to the Andean group, and has been received both through Dr. CARDENAS, President of the University at Cochabamba, Bolivia, and through Dr. H. C. CUTLER, Harvard University, who collected material in the Andes. The results of the studies may be summarized as follows: 1) In both cases, pod corn is characterized by the presence of a dominant Tu factor, localized in the fourth chromosome and linked with sul. The crossover value differs somewhat from the mean value of 29% given by EMERSON, BEADLE and FRAZER (1935) and was 25% in 1217 plants for São Paulo Pod Corn and 36,5% in 345 plants for Bolivia Pod Corn. However not much importance should be attributed to the quantitative differences. 2) Segregation was completely normal in Bolivia Pod Corn while São Paulo Pod Corn proved to be heterozygous for a new com uma eliminação forte, funcionam apenas 8% em vez de 50%. Existem cerca de 30% de "jcrossing-over entre o gen doce (Su/su) e o fator gametofítico; è cerca de 5% entre o gen Tu e o fator gametofítico. A ordem dos gens no cromosômio IV é: Ga4 - Tu - Sul. 3) Using BRIEGER'S formulas (1930, 1937a, 1937b) the following determinations were made. a) the elimination of ga4 pollen tubes may be strong or weak. In the former case only about 8% and in the latter 37% of ga4 pollen tubes function, instead of the 50% expected in normal heterozygotes. b) There is about 30,4% crossing-over between sul and ga4 and 5,3% between Tu and ga3, the order of the factors beeing Su 1 - Tu - Ga4. 4) The new gametophyte factor differs from the two others factors in the same chromosome, causing competition between pollen tubes. The factor Gal, ocupies another locus, considerably to the left of Sul (EMERSON, BEADLE AND FRAZSER, 1935). The gen spl ocupies another locus and causes a difference of the size of the pollen grains, besides an elimination of pollen tubes, while no such differences were observed in the case of the new factor Ga4. 5) It may be mentioned, without entering into a detailed discussion, that it seems remarquable that three of the few gametophyte factors, so far studied in detail are localized in chromosome four. Actuality there are a few more known (BRIEGER, TIDBURY AND TSENG 1938), but only one other has been localized so far, Ga2, in chromosome five between btl and prl. (BRIEGER, 1935). 6) The fourth chromosome of corn seems to contain other pecularities still. MANGELSDORF AND REEVES (1939) concluded that it carries two translocations from Tripsacum chromosomes, and BRIEGER (1944b) suggested that the tu allel may have been introduced from a tripsacoid ancestor in substitution of the wild type gene Tu at the beginning of domestication. Serious disturbances in the segregation of fourth chromosome factors have been observed (BRIEGER, unpublished) in the hybrids of Brazilian corn and Mexican teosinte, caused by gametophytic and possibly zygotic elimination. Future studies must show wether there is any relation between the frequency of factors, causing gametophyte elimination and the presence of regions of chromosomes, tranfered either from Tripsacum or a related species, by translocation or crossing-over.

Estudos sobre o gênero Melipona

1° - Cita-sé a evolução das abelhas segundo MICÍÍENÉR" (1944). 2.° - A evolução dos Melíponíneos é estudada sob o ponto de vista da sua biologia, estabelecendo-se o tipo do meliponíneo primitivo. 3.° - São feitas considerações sobre a distribuição geográfica dos meliponíneos, entrando-se em detalhes sobre os seus fosseis, sobre a influência dos deslocamentos geológicos do cenozoico sobre sua distribuição, com particular referência ao seu estabelecimento na América do Sul. Considera-se também o e$eito das glaciações e a descontinuidade por ela provocada na distribuição dos meliponíneos. 4.° - São feitas hipóteses sobre a época em que se formaram as Meliponas, sobre o processo de determinação das castas e sua influência na evolução das mesmas. O tipo M. marginata é considerado o mais primitivo dos existentes atualmente. É dada uma hipótese, baseada na biologia e genética das Meliponas, para explicar sua evolução a partir de uma Trígona primitiva. 5.° - Sugere-se que a M. fascisrfta (excluidas a M. punc-ticollis e M. concinnula, que necessitam de estudos) seja do tipo da Meliponatrifatorial primitiva, tomando-se por base a sua proximidade a M. marginata, sua distribuição e sua variação. 6.° - Sugere-se como centro de origem das Meliponas a Bacia Amazônica, por ser esse lugar a zona onde há maior variação e por ser o centro geográfico da área habitada pelas Meliponas.

Estudos sôbre a coloração da gema de ôvo de galinhas - IV. Efeito da raça e da quantidade de milho amarelo na ração

This paper deals with experiments on the yolk color of chicken eggs. The results obtained can be summarized as follows: a) no differences were observed when different breeds (S. C. W. Leghorn and Rhode Island Red) were fed whith the same ration: yellow corn grains or green feed. b) 30% of yellow corn grain (orange or yellow) in the ration are sufficient to give satisfactory color to the yolk eggs.