Effectiveness of estradiol valerate on sex reversion in Astyanax altiparanae (Characiformes, Characidae)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Morphometric changes associated with sex and development in the Malpighian tubules of Aedes aegypti

The Malpighian tubules of Aedes aegypti showed significant differences in their diameters between male and female larvae, male and female pupae, male larvae and male adults and male pupae and male adults. in every case, female values were greater than in males. Measurements of mean nuclear areas of the principal and stellate cells from Malpighian tubules, taken in males and females during development, showed that this parameter in both types of cell was significantly greater in females than in male larvae, pupae and adult stages. In males, significant differences between developmental stages were observed only in comparison with the nuclear area of larvae and adults in the principal cells, but in females, every comparison between stages showed significant differences except between pupae and adults in stellate cells. The frequency distribution of nuclear area values, in development, for male stellate and principal cells, were mostly concentrated in the first seven classes among the 30 classes considered in every stage, while for females, the frequency dropped drastically in the same classes from larvae to pupae and adults, moving to classes of higher values. Considering the importance of Malpighian tubules in insect physiology, the meaning of the differences detected are discussed on the basis of different metabolic levels, between sexes and developmental stages.

Ploidy, sex and crossing over in an evolutionary aging model

Nowadays, many forms of reproduction coexist in nature: Asexual, Sexual, apomictic and meiotic parthenogenesis, hermaphroditism and parasex. The mechanisms of their evolution and what made them successful reproductive alternatives are very challenging and debated questions. Here, using a simple evolutionary aging model, we give I possible scenario. By studying the performance of Populations where individuals may have diverse characteristics-different ploidies, sex with or without crossing over, as well as the absence of sex-we find all evolution sequence that may explain why there are actually two major or leading groups: Sexual and asexual. We also investigate the dependence of these characteristics on different conditions of fertility and deleterious mutations. Finally, if the primeval organisms oil Earth were, in fact, asexual individuals we conjecture that the sexual form of reproduction could have more easily been set and found its niche during a period of low-intensity mutations. (c) 2005 Elsevier B.V. All rights reserved.

Karyotype description and evidence of multiple sex chromosome system X1X1X2X2/X1X2Y in Potamotrygon aff. motoro and P. falkneri (Chondrichthyes: Potamotrygonidae) in the upper Paraná River basin, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Sex Determination and Female Reproductive Development in the GenuSchistosoma: A Review

Os parasitas do gênero Schistosoma situam-se entre os primeiros metazoários que desenvolveram sexos separados, determinado cromossomicamente no ovo fertilizado. Apesar da ocorrência de cromossomos sexuais específicos, as fêmeas de Schistosoma não atingem a maturidade somática e sexual sem a presença dos machos. Na verdade, um dos aspectos mais controversos e, ao mesmo tempo, mais fascinantes, envolvendo o desenvolvimento sexual das fêmeas está em se desvendar a natureza do estímulo que controla e mantém tal processo. Muito embora a natureza do estímulo (físico ou químico) seja motivo de controvérsia, concordam os mais diferentes autores que o acasalamento é um requisito indispensável para que ocorra a maturação e migração das fêmeas para o sítio definitivo de permanência no sistema vascular do hospedeiro vertebrado. Admite-se, ainda, que o estímulo não é espécie-específico e, em alguns casos, nem mesmo gênero-específico. Não obstante a existência de um número considerável de artigos dedicados ao tema, não há um consenso sobre o processo (ou processos) que controla(m) o encontro de machos e fêmeas no sistema circulatório do hospedeiro vertebrado, bem como está por ser determinada a natureza do estímulo, oriundo dos machos, que controla e mantém o desenvolvimento somático e sexual das fêmeas. Ao longo dos anos os machos de Schistosoma têm sido considerados, por vezes pejorativamente, os irmãos, os músculos ou o fígado das fêmeas. em síntese, resta saber se a natureza do estímulo responsável pelo desenvolvimento das fêmas envolve a transferência de hormônios, nutrientes, a mera estimulação tátil ou a combinação de dois ou mais desses fatores

Description of a ZZ/ZW sex chromosome system in Thoracocharax cf. stellatus (Teleostei, Characiformes, Gasteropelecidae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Evidence of an XX/XY sex chromosome system in the fish Dormitator maculatus (Teleostei, Eleotrididae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

SEX-RELATED DIFFERENCES IN THE ANALGESIC RESPONSE TO THE RAT TAIL IMMERSION TEST

The analgesic response was evaluated by the tail immersion test in adult male (N = 30), female (N = 21) and androgenized female Wistar rats (N = 15). The reaction time for tail withdrawal from the hot water bath was faster for male than for female rats (3.48 +/- 0.12 vs 6.46 +/- 0.42 s). The reaction time of androgenized female rats was similar to that of male rats (3.08 +/- 0.16 s). Blockade of opiate receptors with naloxone (2 mg/kg, ip) decreased the sensitivity to the noxious stimuli in males (4.08 +/- 0.10 s) and in androgenized females (3.69 +/- 0.19 s) but increased it in female rats (5.01 +/- 0.41 s). These data show sex-related differences in the analgesic response evaluated by the tail immersion test and indicate that administration of androgens to newborn female rats affects their pain sensitivity.

CHROMOSOME-STUDIES IN HYPOPTOPOMATINAE (PISCES, SILURIFORMES, LORICARIIDAE) .2. ZZ ZW SEX-CHROMOSOME SYSTEM, B-CHROMOSOMES, AND CONSTITUTIVE HETEROCHROMATIN DIFFERENTIATION IN MICROLEPIDOGASTER-LEUCOFRENATUS

Cytogenetic analysis of two local populations of microlepidogaster leucofrenatus showed a basic diploid chromosome number (2N) of 54 in both populations. Some fishes were found to have a 2N = 55 or 56 chromosomes due to the presence of one or two large heterochromatic B chromosomes. Specimens of M. leucofrenatus from the Poco Grande stream had 24 metacentrics, 24 submetacentrics, four subtelocentrics, and one submetacentric homomorphic pair in males and one submetacentric/subtelocentric heteromorphic pair in females, whereas individuals of this species from the Marumbi River had 22 metacentrics, 24 submetacentrics, four subtelocentrics, two acrocentrics, and one submetacentric/subtelocentric heteromorphic pair in females. The occurrence of the heteromorphic pair in the females was due to the presence of an extra C-banded segment on the W chromosome. Ag-NORs in both populations were located interstitially on the short arm of the largest metacentric pair. The Poco Grande population had less constitutive heterochromatin than did the Marumbi River population. The speciation process in this fish species is discussed on the basis of heterochromatin distribution.

SEX-CHROMOSOME POLYMORPHISM AND HETEROGAMETIC MALES REVEALED BY 2 CLONED DNA PROBES IN THE ZW ZZ FISH LEPORINUS-ELONGATUS

In order to study the divergence of teleost sex chromosomes, subtractive cloning was carried out between genomic DNA of males and females of the rainbow trout (XX/XY) and of Leporinus elongatus (ZW/ZZ). Inserts cloned in a plasmid vector were individually tested on Southern blots of DNA of males and females for sex specificity. No sex-specific insert was obtained from trout, but two out of ten inserts cloned from L. elongatus showed sex-specific patterns in this species: one corresponds to a sequence present on both Z and W chromosomes, while the other is W specific. Sequences of these two inserts show neither clear homology with other known sequences, nor an open reading frame. They cross-hybridize with the genomic DNA of Leporinus friderici, but without sex-specific patterns. Twenty-four L. elongatus adults were sexed by gonadal observation, chromosomed examination and Southern hybridization with one or the other insert. Ten males and 11 females had chromosomes and hybridization patterns typical of their sex. One ZW female was recognized as a male with the W-specific probe. This was also the case for two unusual ZW males, one having a male hybridization pattern with the other probe. These three atypical individuals may result from single genetic exchanges between four regions of the Z and the W, giving rise to three atypical W chromosomes. Finding males with such atypical heterochromosomes in a female heterogametic species may indicate that a gradual transition occurs between the heterogametic systems.

SEX DETERMINATION IN BEES .30. EFFECTS OF JUVENILE-HORMONE ON THE DEVELOPMENT OF TERGAL GLANDS IN MELIPONA

Worker larvae of Melipona rufiventris, M. quadrifasciata and M. compressipes were treated topically with juvenile hormone (JH) during the cocoon-spinning phase. Examination of the tergites of the queens obtained following JH application showed induced differentiation into adults with full female (queen) traits. Melipona workers had tergal glands only in tergite II, whereas natural and JH-induced queens had tergal glands in tergite II plus additional glands in at least one other of tergites Ill to VII.

Dose- and sex-related carcinogenesis by N-bis(2-hydroxypropyl)nitrosamine in Wistar rats

An initiation-promotion medium-term bioassay for detection of chemical carcinogens, developed in the male F344 rat, uses 0.1% N-bis(2-hydroxypropyl)nitrosamine (DHPN) among five genotoxic chemicals for the initiation of carcinogenesis in multiple organs. To establish this bioassay in the Wistar strain, the effects of two dose levels of DHPN were evaluated on the main DHPN rat target organs: lung, thyroid gland, kidneys and liver. Four groups of male and female animals were studied: Control--untreated group; Multi-organ initiated group (also referred to as DMBDD, based on the initials of the five initiators)-treated sequentially with N-diethylnitrosamine (DEN, i.p.), N-methyl-N-nitrosourea (MNU, i.p.), N-butyl-N-(4-hydroxy butyl)nitrosamine (BBN, drinking water), N, N'-dimethylhydrazine (DMH, s.c.) and DHPN (drinking water) for 4 weeks; a third group treated with 0.1% DHPN in drinking water for 2 weeks and the last group treated with 0.2% DHPN in drinking water for 4 weeks. The animals were sacrificed after 30 weeks. DHPN at 0.2% induced preneoplasia in the liver and kidneys of rats of both sexes, the number and area of the putative preneoplastic liver glutathione S-transferase-positive hepatocyte foci being significantly increased in these animals. It also induced benign and malignant tumors in female and in male rats. However, there was no relationship between the increased incidence of preneoplastic lesions and tumor development in the 0.2% DHPN-exposed groups of both sexes. DHPN at 0.1% induced only a few preneoplastic lesions in the liver and kidney and no tumors in both male and female rats. A clear dose and sex-related carcinogenic activity of DHPN was registered, although Wistar rats of both sexes showed a relative resistance to the carcinogenic activity of this compound.

2 PERMANENT LINEAR-CHAINS OF SEX-CHROMOSOMES IN NEOTERMES-FULVESCENS AND KARYOTYPES OF 2 OTHER NEOTROPICAL KALOTERMITIDAE SPECIES (INSECTA, ISOPTERA)

Meiosis and (or) mitosis of males and females of Cryptotermes brevis, Eucryptotermes wheeleri, and Neotermes fulvescens, all of them from the neotropical region, were analyzed. Cryptotermes brevis showed a similar karyotype to that obtained by other authors for specimens of the neartic and Australian regions (2n = 36 for females and 2n = 37 for males, with XX and XYY sex mechanisms, respectively). Eucryptotermes wheeleri, the only species that has been described in this genus, showed the lowest number of chromosomes reported for Isoptera (2n = 22) until now. The male meiosis of this species presents a linear chain of six sex chromosomes, three of them being X and three of them Y chromosomes. Neotermes fulvescens showed a diploid number of 40 for males and 42 for females and, in the first male meiosis, two linear chains of chromosomes, both related to sex. One of the chains, named A, presented nine chromosomes and the other, named B, seven chromosomes. Hypotheses to explain these mechanisms are formulated in this paper and putative ancestral relationships with other species of Kalotermitidae are presented.

SYNAPTONEMAL COMPLEX-ANALYSIS OF THE SEX BIVALENT IN GOATS

Synaptonemal complex (SC) analysis of XY pairing in the goat (Capra hircus; 2n = 60) was investigated by electron microscopy for the first time in this species. Synapsis of the X and Y chromosomes begins during the mid-late zygotene stage as the autosomes complete their pairing. Only a small portion of the total length of the Y is paired with the X chromosome at this time. By the early pachytene, almost 90% of the Y is paired with the X. All the observed stages of the sex bivalent pairing showed the structural difference between the differential and pairing regions. In the pairing region, a synaptonemal complex is formed, while in the differential region the chromosome axes remain free.