Effect of mouse antisera targeting the Phlebotomus papatasi midgut chitinase PpChit1 on sandfly physiology and fitness

In sandflies, the absence of the peritrophic matrix (PM) affects the rate of blood digestion. Also, the kinetics of PM secretion varies according to species. We previously characterised PpChit1, a midgut-specific chitinase secreted in Phlebotomus papatasi (PPIS) that is involved in the maturation of the PM and showed that antibodies against PpChit1 reduce the chitinolytic activity in the midgut of several sandfly species. Here, sandflies were fed on red blood cells reconstituted with naïve or anti-PpChit1 sera and assessed for fitness parameters that included blood digestion, oviposition onset, number of eggs laid, egg bouts, average number of eggs per bout and survival. In PPIS, anti-PpChit1 led to a one-day delay in the onset of egg laying, with flies surviving three days longer compared to the control group. Anti-PpChit1 also had a negative effect on overall ability of flies to lay eggs, as several gravid females from all three species were unable to lay any eggs despite having lived longer than control flies. Whereas the longer survival might be associated with improved haeme scavenging ability by the PM, the inability of females to lay eggs is possibly linked to changes in PM permeability affecting nutrient absorption.

Abdominal tuberculosis: a radiological review with emphasis on computed tomography and magnetic resonance imaging findings

AbstractTuberculosis is a disease whose incidence has increased principally as a consequence of HIV infection and use of immunosuppressive drugs. The abdomen is the most common site of extrapulmonary tuberculosis. It may be confused with several different conditions such as inflammatory bowel disease, cancer and other infectious diseases. Delay in the diagnosis may result in significantly increased morbidity, and therefore an early recognition of the condition is essential for proper treatment. In the present essay, cases with confirmed diagnosis of abdominal tuberculosis were assessed by means of computed tomography and magnetic resonance imaging, demonstrating the involvement of different organs and systems, and presentations which frequently lead radiologists to a diagnostic dilemma. A brief literature review was focused on imaging findings and their respective prevalence.

Guava fruit loss caused by rust

The aim of this paper was to estimate the loss caused by rust (Puccinia psidii) to 'Paluma' guava production in orchards located in Rio de Janeiro State. The disease intensity on the reproductive organs of plants was observed during two chemical control experiments carried out in 2003 and 2004. The loss was estimated based on simple linear regression and the production reduction (fruit number and weight ha-1) on the incidence of diseased buds and fruits. In the first experiment, no relationship was established between incidence of diseased buds and loss since there was a delay in spraying and the incidence of buds showing rust was high (mean of 47%) at the beginning of flowering. In the second experiment (2003-2004), spraying occurred at the beginning of the epidemics and there was a linear relationship between incidence of diseased buds and loss, justifying fungicide intervention at this stage. For the fruiting stage, a significant relationship was found between incidence of diseased fruits and loss in both experiments. In the absence of chemical control, rust reduced fruit production by around 90%.

WATER USE EFFICIENCY, GROWTH AND YIELD OF WHEAT CULTIVATED UNDER COMPETITION WITH Setaria

ABSTRACT Understanding the critical period of weed competition is indispensable in the development of an effective weed management program in field crops. Current experiment was planned to evaluate the critical growth period ofSetaria and level of yield losses associated with delay in weeding in rain-fed drip irrigated wheat production system of Saudi Arabia. Field experiment was conducted to evaluate the effect of weeding interval (07-21, 14-28, 21-35, 28-42 and 35-49 days after sowing) and drought stress (75% and 50% of field capacity) on Setaria growth, wheat yield and water use efficiency. Season long weedy check and wellwatered (100% FC) plots were also maintained for comparison. Weeding interval and drought stress significantly (p ≤ 0.05) affected the growth and yield of Setaria and wheat. Drought stress from 75% to 50% FC resulted in reductions of 29-40% in Setaria height, 14-27% in Setaria density and 11-26% in Setaria dry biomass. All weeding intervals except 35-49 DAS significantly suppressedSetaria growth as compared with control. Delay in weeding increased weed-crop competition interval and reduced wheat yield and yield contributors. Therefore, the lowest yield of 1836 kg ha-1 was attained for weeding interval of 35-49 DAS at 50% FC. Water use efficiency and harvest index increased with decreasing FC levels but reduced with delay in weeding. Correlation analysis predicted negative association ofSetariadensity with wheat yield and yield contributors and the highest negative association was for harvest index (-0.913) and water use efficiency (-0.614). Early management of Setaria is imperative for successful wheat production otherwise yield losses are beyond economical limits.

Population ecology of Paepalanthus polyanthus (Bong.) Kunth: demography and life history of a sand dune monocarpic plant

Aspects of population dynamics and life history of Paepalanthus polyanthus (Bong.) Kunth, a sand dune monocarpic plant, were evaluated. A five year study was carried out on three permanent plots (5 m x 5 m) in a sand dune slack at Joaquina beach, Santa Catarina State, Brazil. From December 1986 to June 1989, the population decreased due to the death of the post reproductive plants and a low emergence of seedlings. In June 1989, a great recruitment occurred, but no plants survived. The population re-established itself by 1990-1991. The emergence and high survival of seedlings depended on periods of high pluviosity. Nevertheless, the summer flooding and episodes of drought represented key factors in mortality. The birth and mortality rates varied among the areas. It is suggested that these differences are related with depth of the ground water and with vegetation cover at each site. Paepalanthus polyanthus can reproduce in the second year of life, but few plants do this. The chances of survival and reproduction increase with the size of the basal leaf rosette. Although the production of seeds increases with size, the risk of unexpected flooding, for instance, suggest that a great delay in reproduction might not be the most favorable strategy.

Food intake and weight of lactating rats maintained on different protein-calorie diets, and pup growth

Studies on rats maintained on low-protein-calorie diets during the lactation period show that food intake decreases. This process results in weight loss and a delay in litter development. The purpose of the present study was to determine the alterations in food intake, maternal weight and litter growth during lactation when dams were exposed to diets with different levels of protein and carbohydrate. Female Wistar rats receiving one of 4 different diets, A (N = 14), B (N = 14), C (N = 9) and D (N = 9), were used. Diet A contained 16% protein and 66% carbohydrate; diet B, 6% protein and 77% carbohydrate; diet C, 6% protein and 66% carbohydrate; diet D, 16% protein and 56% carbohydrate. Thus, C and D diets were hypocaloric, while A and B were isocaloric. The intake of a low-protein diet in groups B and C affected the weight of dams and litters during the last two weeks of lactation, while the low-calorie diets limited the growth of D litters at 21 days compared with A litters, but had no effect on the weight of D dams. Group B showed an increase in intake during the first five days of lactation, resulting in a behavioral calorie compensation due to the increase in carbohydrate content, but the intake decreased during the last part of lactation. Food intake regulation predominantly involves the recruitment of a variety of peripheral satiety systems that attempt to decrease the central feeding command system.

One hundred million years of interhemispheric communication: the history of the corpus callosum

Analysis of regional corpus callosum fiber composition reveals that callosal regions connecting primary and secondary sensory areas tend to have higher proportions of coarse-diameter, highly myelinated fibers than callosal regions connecting so-called higher-order areas. This suggests that in primary/secondary sensory areas there are strong timing constraints for interhemispheric communication, which may be related to the process of midline fusion of the two sensory hemifields across the hemispheres. We postulate that the evolutionary origin of the corpus callosum in placental mammals is related to the mechanism of midline fusion in the sensory cortices, which only in mammals receive a topographically organized representation of the sensory surfaces. The early corpus callosum may have also served as a substrate for growth of fibers connecting higher-order areas, which possibly participated in the propagation of neuronal ensembles of synchronized activity between the hemispheres. However, as brains became much larger, the increasingly longer interhemispheric distance may have worked as a constraint for efficient callosal transmission. Callosal fiber composition tends to be quite uniform across species with different brain sizes, suggesting that the delay in callosal transmission is longer in bigger brains. There is only a small subset of large-diameter callosal fibers whose size increases with increasing interhemispheric distance. These limitations in interhemispheric connectivity may have favored the development of brain lateralization in some species like humans. "...if the currently received statements are correct, the appearance of the corpus callosum in the placental mammals is the greatest and most sudden modification exhibited by the brain in the whole series of vertebrated animals..." T.H. Huxley (1).

Rescuing axons from degeneration does not affect retinal ganglion cell death

After a traumatic injury to the central nervous system, the distal stumps of axons undergo Wallerian degeneration (WD), an event that comprises cytoskeleton and myelin breakdown, astrocytic gliosis, and overexpression of proteins that inhibit axonal regrowth. By contrast, injured neuronal cell bodies show features characteristic of attempts to initiate the regenerative process of elongating their axons. The main molecular event that leads to WD is an increase in the intracellular calcium concentration, which activates calpains, calcium-dependent proteases that degrade cytoskeleton proteins. The aim of our study was to investigate whether preventing axonal degeneration would impact the survival of retinal ganglion cells (RGCs) after crushing the optic nerve. We observed that male Wistar rats (weighing 200-400 g; n=18) treated with an exogenous calpain inhibitor (20 mM) administered via direct application of the inhibitor embedded within the copolymer resin Evlax immediately following optic nerve crush showed a delay in the onset of WD. This delayed onset was characterized by a decrease in the number of degenerated fibers (P<0.05) and an increase in the number of preserved fibers (P<0.05) 4 days after injury. Additionally, most preserved fibers showed a normal G-ratio. These results indicated that calpain inhibition prevented the degeneration of optic nerve fibers, rescuing axons from the process of axonal degeneration. However, analysis of retinal ganglion cell survival demonstrated no difference between the calpain inhibitor- and vehicle-treated groups, suggesting that although the calpain inhibitor prevented axonal degeneration, it had no effect on RGC survival after optic nerve damage.

Dissecando o GEN

In thee present paper the classical concept of the corpuscular gene is dissected out in order to show the inconsistency of some genetical and cytological explanations based on it. The author begins by asking how do the genes perform their specific functions. Genetists say that colour in plants is sometimes due to the presence in the cytoplam of epidermal cells of an organic complex belonging to the anthocyanins and that this complex is produced by genes. The author then asks how can a gene produce an anthocyanin ? In accordance to Haldane's view the first product of a gene may be a free copy of the gene itself which is abandoned to the nucleus and then to the cytoplasm where it enters into reaction with other gene products. If, thus, the different substances which react in the cell for preparing the characters of the organism are copies of the genes then the chromosome must be very extravagant a thing : chain of the most diverse and heterogeneous substances (the genes) like agglutinins, precipitins, antibodies, hormones, erzyms, coenzyms, proteins, hydrocarbons, acids, bases, salts, water soluble and insoluble substances ! It would be very extrange that so a lot of chemical genes should not react with each other. remaining on the contrary, indefinitely the same in spite of the possibility of approaching and touching due to the stato of extreme distension of the chromosomes mouving within the fluid medium of the resting nucleus. If a given medium becomes acid in virtue of the presence of a free copy of an acid gene, then gene and character must be essentially the same thing and the difference between genotype and phenotype disappears, epigenesis gives up its place to preformation, and genetics goes back to its most remote beginnings. The author discusses the complete lack of arguments in support of the view that genes are corpuscular entities. To show the emharracing situation of the genetist who defends the idea of corpuscular genes, Dobzhansky's (1944) assertions that "Discrete entities like genes may be integrated into systems, the chromosomes, functioning as such. The existence of organs and tissues does not preclude their cellular organization" are discussed. In the opinion of the present writer, affirmations as such abrogate one of the most important characteristics of the genes, that is, their functional independence. Indeed, if the genes are independent, each one being capable of passing through mutational alterations or separating from its neighbours without changing them as Dobzhansky says, then the chromosome, genetically speaking, does not constitute a system. If on the other hand, theh chromosome be really a system it will suffer, as such, the influence of the alteration or suppression of the elements integrating it, and in this case the genes cannot be independent. We have therefore to decide : either the chromosome is. a system and th genes are not independent, or the genes are independent and the chromosome is not a syntem. What cannot surely exist is a system (the chromosome) formed by independent organs (the genes), as Dobzhansky admits. The parallel made by Dobzhansky between chromosomes and tissues seems to the author to be inadequate because we cannot compare heterogeneous things like a chromosome considered as a system made up by different organs (the genes), with a tissue formed, as we know, by the same organs (the cells) represented many times. The writer considers the chromosome as a true system and therefore gives no credit to the genes as independent elements. Genetists explain position effects in the following way : The products elaborated by the genes react with each other or with substances previously formed in the cell by the action of other gene products. Supposing that of two neighbouring genes A and B, the former reacts with a certain substance of the cellular medium (X) giving a product C which will suffer the action, of the latter (B). it follows that if the gene changes its position to a place far apart from A, the product it elaborates will spend more time for entering into contact with the substance C resulting from the action of A upon X, whose concentration is greater in the proximities of A. In this condition another gene produtc may anticipate the product of B in reacting with C, the normal course of reactions being altered from this time up. Let we see how many incongruencies and contradictions exist in such an explanation. Firstly, it has been established by genetists that the reaction due.to gene activities are specific and develop in a definite order, so that, each reaction prepares the medium for the following. Therefore, if the medium C resulting from the action of A upon x is the specific medium for the activity of B, it follows that no other gene, in consequence of its specificity, can work in this medium. It is only after the interference of B, changing the medium, that a new gene may enter into action. Since the genotype has not been modified by the change of the place of the gene, it is evident that the unique result we have to attend is a little delay without seious consequence in the beginning of the reaction of the product of B With its specific substratum C. This delay would be largely compensated by a greater amount of the substance C which the product of B should found already prepared. Moreover, the explanation did not take into account the fact that the genes work in the resting nucleus and that in this stage the chromosomes, very long and thin, form a network plunged into the nuclear sap. in which they are surely not still, changing from cell to cell and In the same cell from time to time, the distance separating any two genes of the same chromosome or of different ones. The idea that the genes may react directly with each other and not by means of their products, would lead to the concept of Goidschmidt and Piza, in accordance to which the chromosomes function as wholes. Really, if a gene B, accustomed to work between A and C (as for instance in the chromosome ABCDEF), passes to function differently only because an inversion has transferred it to the neighbourhood of F (as in AEDOBF), the gene F must equally be changed since we cannot almH that, of two reacting genes, only one is modified The genes E and A will be altered in the same way due to the change of place-of the former. Assuming that any modification in a gene causes a compensatory modification in its neighbour in order to re-establich the equilibrium of the reactions, we conclude that all the genes are modified in consequence of an inversion. The same would happen by mutations. The transformation of B into B' would changeA and C into A' and C respectively. The latter, reacting withD would transform it into D' and soon the whole chromosome would be modified. A localized change would therefore transform a primitive whole T into a new one T', as Piza pretends. The attraction point-to-point by the chromosomes is denied by the nresent writer. Arguments and facts favouring the view that chromosomes attract one another as wholes are presented. A fact which in the opinion of the author compromises sereously the idea of specific attraction gene-to-gene is found inthe behavior of the mutated gene. As we know, in homozygosis, the spme gene is represented twice in corresponding loci of the chromosomes. A mutation in one of them, sometimes so strong that it is capable of changing one sex into the opposite one or even killing the individual, has, notwithstading that, no effect on the previously existing mutual attraction of the corresponding loci. It seems reasonable to conclude that, if the genes A and A attract one another specifically, the attraction will disappear in consequence of the mutation. But, as in heterozygosis the genes continue to attract in the same way as before, it follows that the attraction is not specific and therefore does not be a gene attribute. Since homologous genes attract one another whatever their constitution, how do we understand the lack cf attraction between non homologous genes or between the genes of the same chromosome ? Cnromosome pairing is considered as being submitted to the same principles which govern gametes copulation or conjugation of Ciliata. Modern researches on the mating types of Ciliata offer a solid ground for such an intepretation. Chromosomes conjugate like Ciliata of the same variety, but of different mating types. In a cell there are n different sorts of chromosomes comparable to the varieties of Ciliata of the same species which do not mate. Of each sort there are in the cell only two chromosomes belonging to different mating types (homologous chromosomes). The chromosomes which will conjugate (belonging to the same "variety" but to different "mating types") produce a gamone-like substance that promotes their union, being without action upon the other chromosomes. In this simple way a single substance brings forth the same result that in the case of point-to-point attraction would be reached through the cooperation of as many different substances as the genes present in the chromosome. The chromosomes like the Ciliata, divide many times before they conjugate. (Gonial chromosomes) Like the Ciliata, when they reach maturity, they copulate. (Cyte chromosomes). Again, like the Ciliata which aggregate into clumps before mating, the chrorrasrmes join together in one side of the nucleus before pairing. (.Synizesis). Like the Ciliata which come out from the clumps paired two by two, the chromosomes leave the synizesis knot also in pairs. (Pachytene) The chromosomes, like the Ciliata, begin pairing at any part of their body. After some time the latter adjust their mouths, the former their kinetochores. During conjugation the Ciliata as well as the chromosomes exchange parts. Finally, the ones as the others separate to initiate a new cycle of divisions. It seems to the author that the analogies are to many to be overlooked. When two chemical compounds react with one another, both are transformed and new products appear at the and of the reaction. In the reaction in which the protoplasm takes place, a sharp difference is to be noted. The protoplasm, contrarily to what happens with the chemical substances, does not enter directly into reaction, but by means of products of its physiological activities. More than that while the compounds with Wich it reacts are changed, it preserves indefinitely its constitution. Here is one of the most important differences in the behavior of living and lifeless matter. Genes, accordingly, do not alter their constitution when they enter into reaction. Genetists contradict themselves when they affirm, on the one hand, that genes are entities which maintain indefinitely their chemical composition, and on the other hand, that mutation is a change in the chemica composition of the genes. They are thus conferring to the genes properties of the living and the lifeless substances. The protoplasm, as we know, without changing its composition, can synthesize different kinds of compounds as enzyms, hormones, and the like. A mutation, in the opinion of the writer would then be a new property acquired by the protoplasm without altering its chemical composition. With regard to the activities of the enzyms In the cells, the author writes : Due to the specificity of the enzyms we have that what determines the order in which they will enter into play is the chemical composition of the substances appearing in the protoplasm. Suppose that a nucleoproteln comes in relation to a protoplasm in which the following enzyms are present: a protease which breaks the nucleoproteln into protein and nucleic acid; a polynucleotidase which fragments the nucleic acid into nucleotids; a nucleotidase which decomposes the nucleotids into nucleoids and phosphoric acid; and, finally, a nucleosidase which attacs the nucleosids with production of sugar and purin or pyramidin bases. Now, it is evident that none of the enzyms which act on the nucleic acid and its products can enter into activity before the decomposition of the nucleoproteln by the protease present in the medium takes place. Leikewise, the nucleosidase cannot works without the nucleotidase previously decomposing the nucleotids, neither the latter can act before the entering into activity of the polynucleotidase for liberating the nucleotids. The number of enzyms which may work at a time depends upon the substances present m the protoplasm. The start and the end of enzym activities, the direction of the reactions toward the decomposition or the synthesis of chemical compounds, the duration of the reactions, all are in the dependence respectively o fthe nature of the substances, of the end products being left in, or retired from the medium, and of the amount of material present. The velocity of the reaction is conditioned by different factors as temperature, pH of the medium, and others. Genetists fall again into contradiction when they say that genes act like enzyms, controlling the reactions in the cells. They do not remember that to cintroll a reaction means to mark its beginning, to determine its direction, to regulate its velocity, and to stop it Enzyms, as we have seen, enjoy none of these properties improperly attributed to them. If, therefore, genes work like enzyms, they do not controll reactions, being, on the contrary, controlled by substances and conditions present in the protoplasm. A gene, like en enzym, cannot go into play, in the absence of the substance to which it is specific. Tne genes are considered as having two roles in the organism one preparing the characters attributed to them and other, preparing the medium for the activities of other genes. At the first glance it seems that only the former is specific. But, if we consider that each gene acts only when the appropriated medium is prepared for it, it follows that the medium is as specific to the gene as the gene to the medium. The author concludes from the analysis of the manner in which genes perform their function, that all the genes work at the same time anywhere in the organism, and that every character results from the activities of all the genes. A gene does therefore not await for a given medium because it is always in the appropriated medium. If the substratum in which it opperates changes, its activity changes correspondingly. Genes are permanently at work. It is true that they attend for an adequate medium to develop a certain actvity. But this does not mean that it is resting while the required cellular environment is being prepared. It never rests. While attending for certain conditions, it opperates in the previous enes It passes from medium to medium, from activity to activity, without stopping anywhere. Genetists are acquainted with situations in which the attended results do not appear. To solve these situations they use to make appeal to the interference of other genes (modifiers, suppressors, activators, intensifiers, dilutors, a. s. o.), nothing else doing in this manner than displacing the problem. To make genetcal systems function genetists confer to their hypothetical entities truly miraculous faculties. To affirm as they do w'th so great a simplicity, that a gene produces an anthocyanin, an enzym, a hormone, or the like, is attribute to the gene activities that onlv very complex structures like cells or glands would be capable of producing Genetists try to avoid this difficulty advancing that the gene works in collaboration with all the other genes as well as with the cytoplasm. Of course, such an affirmation merely means that what works at each time is not the gene, but the whole cell. Consequently, if it is the whole cell which is at work in every situation, it follows that the complete set of genes are permanently in activity, their activity changing in accordance with the part of the organism in which they are working. Transplantation experiments carried out between creeper and normal fowl embryos are discussed in order to show that there is ro local gene action, at least in some cases in which genetists use to recognize such an action. The author thinks that the pleiotropism concept should be applied only to the effects and not to the causes. A pleiotropic gene would be one that in a single actuation upon a more primitive structure were capable of producing by means of secondary influences a multiple effect This definition, however, does not preclude localized gene action, only displacing it. But, if genetics goes back to the egg and puts in it the starting point for all events which in course of development finish by producing the visible characters of the organism, this will signify a great progress. From the analysis of the results of the study of the phenocopies the author concludes that agents other than genes being also capaole of determining the same characters as the genes, these entities lose much of their credit as the unique makers of the organism. Insisting about some points already discussed, the author lays once more stress upon the manner in which the genes exercise their activities, emphasizing that the complete set of genes works jointly in collaboration with the other elements of the cell, and that this work changes with development in the different parts of the organism. To defend this point of view the author starts fron the premiss that a nerve cell is different from a muscle cell. Taking this for granted the author continues saying that those cells have been differentiated as systems, that is all their parts have been changed during development. The nucleus of the nerve cell is therefore different from the nucleus of the muscle cell not only in shape, but also in function. Though fundamentally formed by th same parts, these cells differ integrally from one another by the specialization. Without losing anyone of its essenial properties the protoplasm differentiates itself into distinct kinds of cells, as the living beings differentiate into species. The modified cells within the organism are comparable to the modified organisms within the species. A nervo and a muscle cell of the same organism are therefore like two species originated from a common ancestor : integrally distinct. Like the cytoplasm, the nucleus of a nerve cell differs from the one of a muscle cell in all pecularities and accordingly, nerve cell chromosomes are different from muscle cell chromosomes. We cannot understand differentiation of a part only of a cell. The differentiation must be of the whole cell as a system. When a cell in the course of development becomes a nerve cell or a muscle cell , it undoubtedly acquires nerve cell or muscle cell cytoplasm and nucleus respectively. It is not admissible that the cytoplasm has been changed r.lone, the nucleus remaining the same in both kinds of cells. It is therefore legitimate to conclude that nerve ceil ha.s nerve cell chromosomes and muscle cell, muscle cell chromosomes. Consequently, the genes, representing as they do, specific functions of the chromossomes, are different in different sorts of cells. After having discussed the development of the Amphibian egg on the light of modern researches, the author says : We have seen till now that the development of the egg is almost finished and the larva about to become a free-swimming tadepole and, notwithstanding this, the genes have not yet entered with their specific work. If the haed and tail position is determined without the concourse of the genes; if dorso-ventrality and bilaterality of the embryo are not due to specific gene actions; if the unequal division of the blastula cells, the different speed with which the cells multiply in each hemisphere, and the differential repartition of the substances present in the cytoplasm, all this do not depend on genes; if gastrulation, neurulation. division of the embryo body into morphogenetic fields, definitive determination of primordia, and histological differentiation of the organism go on without the specific cooperation of the genes, it is the case of asking to what then the genes serve ? Based on the mechanism of plant galls formation by gall insects and on the manner in which organizers and their products exercise their activities in the developing organism, the author interprets gene action in the following way : The genes alter structures which have been formed without their specific intervention. Working in one substratum whose existence does not depend o nthem, the genes would be capable of modelling in it the particularities which make it characteristic for a given individual. Thus, the tegument of an animal, as a fundamental structure of the organism, is not due to gene action, but the presence or absence of hair, scales, tubercles, spines, the colour or any other particularities of the skin, may be decided by the genes. The organizer decides whether a primordium will be eye or gill. The details of these organs, however, are left to the genetic potentiality of the tissue which received the induction. For instance, Urodele mouth organizer induces Anura presumptive epidermis to develop into mouth. But, this mouth will be farhioned in the Anura manner. Finalizing the author presents his own concept of the genes. The genes are not independent material particles charged with specific activities, but specific functions of the whole chromosome. To say that a given chromosome has n genes means that this chromonome, in different circumstances, may exercise n distinct activities. Thus, under the influence of a leg evocator the chromosome, as whole, develops its "leg" activity, while wbitm the field of influence of an eye evocator it will develop its "eye" activity. Translocations, deficiencies and inversions will transform more or less deeply a whole into another one, This new whole may continue to produce the same activities it had formerly in addition to those wich may have been induced by the grafted fragment, may lose some functions or acquire entirely new properties, that is, properties that none of them had previously The theoretical possibility of the chromosomes acquiring new genetical properties in consequence of an exchange of parts postulated by the present writer has been experimentally confirmed by Dobzhansky, who verified that, when any two Drosophila pseudoobscura II - chromosomes exchange parts, the chossover chromosomes show new "synthetic" genetical effects.

Risk factors for excess weight loss and hypernatremia in exclusively breast-fed infants

Data were prospectively obtained from exclusively breast-fed healthy term neonates at birth and from healthy mothers with no obstetric complication to determine risk factors for excess weight loss and hypernatremia in exclusively breast-fed infants. Thirty-four neonates with a weight loss > or = 10% were diagnosed between April 2001 and January 2005. Six of 18 infants who were eligible for the study had hypernatremia. Breast conditions associated with breast-feeding difficulties (P < 0.05), primiparity (P < 0.005), less than four stools (P < 0.001), pink diaper (P < 0.001), delay at initiation of first breast giving (P < 0.01), birth by cesarean section (P < 0.05), extra heater usage (P < 0.005), extra heater usage among mothers who had appropriate conditions associated with breast-feeding (P < 0.001), mean weight loss in neonates with pink diaper (P < 0.05), mean uric acid concentration in neonates with pink diaper (P < 0.0001), fever in hypernatremic neonates (P < 0.02), and the correlation of weight loss with both serum sodium and uric acid concentrations (P < 0.02) were determined. Excessive weight loss occurs in exclusively breast-fed infants and can be complicated by hypernatremia and other morbidities. Prompt initiation of breast-feeding after delivery and prompt intervention if problems occur with breast-feeding, in particular poor breast attachment, breast engorgement, delayed breast milk "coming in", and nipple problems will help promote successful breast-feeding. Careful follow-up of breast-feeding dyads after discharge from hospital, especially regarding infant weight, is important to help detect inadequate breast-feeding. Environmental factors such as heaters may exacerbate infant dehydration.