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PubMed2002

Strong inbreeding depression in a Daphnia metapopulation.

The deleterious effects of inbreeding have long been known, and inbreeding can increase the risk of extinction for local populations in metapopulations. However, other consequences of inbreeding in metapopulations are still not well understood. Here we show the presence of strong inbreeding depression in a rockpool metapopulation of the planktonic freshwater crustacean Daphnia magna, which reproduces by cyclical parthenogenesis. We conducted three experiments in real and artificial rockpools to quantify components of inbreeding depression in the presence and the absence of competition between clonal lines of selfed and outcrossed genotypes. In replicated asexual populations, we recorded strong selection against clones produced by selfing in competition with clones produced by outcrossing. In contrast, inbreeding depression was much weaker in single-clone populations, that is, in the absence of competition between inbred and outbred clones. The finding of a competitive advantage of the outbred genotypes in this metapopulation suggests that if rockpool populations are inbred, hybrid offspring resulting from crosses between immigrants and local genotypes might have a strong selective advantage. This would increase the effective gene flow in the metapopulation. However, the finding of low inbreeding depression in the monoclonal populations suggests that inbred and outbred genotypes might have about equal chances of establishing new populations.

Animals↗

PubMed2002

Preparation of Meloidogyne javanica near-isogenic lines virulent and avirulent against the tomato resistance gene Mi and preliminary analyses of the genetic variation between the two lines.

Meloidogyne javanica, reproducing by mitotic parthenogenesis, is an economically important pathogen of a wide range of crops. A pair of near-isogenic lines virulent and avirulent toward the tomato resistance gene Mi were prepared for M. javanica by continuously selecting an avirulent population on the resistant tomato cultivar Momotaro over 19 generations. Random amplified polymorphic DNA (RAPD) analysis with 102 primers revealed that RAPD patterns were highly conserved between the virulent and avirulent lines, confirming that the two lines were genomically very similar. Nevertheless, with one of the primers a distinct polymorphic fragment, specific for the avirulent lines, was amplified. Southern hybridization results indicated that the polymorphic fragment and its homologs were deleted from the genome of the virulent line during the process of virulence acquisition. Sequence analysis and homology searches of public data bases, however, revealed no published sequences significantly similar to the sequence of the fragment, precluding a prediction of the potential function of the sequence. The successful preparation of the near-isogenic Mi-virulent and avirulent lines laid a firm foundation for the further identification and isolation of virulence-related genes in M. javanica.

Animals↗

PubMed1992

Cytogenetic analysis of oocytes and embryos.

Abnormal embryo development represents the major cause of implantation failures and accounts for the low rate of human infertility in vivo or in vitro. Chromosome abnormalities are widely involved in this process. Indeed, 28.4% of oocytes carry a chromosome aberration, i.e. 25.6% aneuploidy and 2.8% structural anomalies. Fertilisation abnormalities (possibly increased by in vitro procedures) were recorded: 7 to 28% of oocytes from fertilisation failure showed a sperm premature chromosome condensation probably resulting from ooplasmic immaturity. Moreover, 1.6% and 3.8% of inseminated oocytes had either a single or 3 pronuclei demonstrating parthenogenesis or triploidy, respectively. In vitro developmental capacities of embryos depends on the degree of ploidy. Parthenogenetic embryos display a fairly normal development until implantation. Triploid zygotes show an original way of division: half of them divide first into 3 cells and then into 6 cells (via a tripolar spindle) whereas diploid zygotes divide into 2 and then 4 cells. As a consequence of either meiotic or mitotic non disjunctions or fertilisation anomalies, 25 to 71% preimplantation embryos carry a chromosome disorder. As an outgrowth of in vitro fertilisation and embryo transfer, detection of genetic and metabolic defects prior to implantation might be possible in the future. So far, 6 girls have been born in couples at risk of transmitting X-linked disease. This technic will increase the efficiency of IVF and avoid the trauma of repeated abortions.

Animals↗

PubMedDate not supplied

[Orthonectida's life cycle].

Analysis of original and literary data permits to conclude that the life cycle in Orthonectida may be characterized as a monohost--monoxenous one, including regular interchange of three generations: asexual and parthenogenetic ones, which are represented by parasitic plasmodiums, and sexual generation, represented by free living and non-feeding males and females or, rarely, hermaphrodites. The sexual individuals are bilaterial, while the parasitic ones are anaxonic. The life cycle of Orthonectida includes the agamic reproduction, apomictic parthenogenesis and sexual reproduction regularly following one another. The life cycle of Orthonectida can be considered as a combination of metagenesis and heterogony. So far, such combination has not been described in any group of metazoan parasites.

Animals↗

PubMed2004

Experimental hybridisation between X0 and XY chromosome races in the grasshopper Podisma sapporensis Shir. (Orthoptera, Acrididae). I. Cytological analysis of embryos and F1 hybrids.

The results of experimental hybridisation between some chromosome subraces belonging to the X0 and XY chromosome races of the brachypterous grasshopper P. sapporensis are presented. Pre-zygotic reproductive isolation mechanisms in experimental pairs were not confirmed. In crossings of XY-standard x X0-standard and XY-standard x X0-Naganuma chromosome subraces, a zygotic barrier has been found. All embryos of XY-standard x X0-standard crosses and the vast majority of embryos of XY-standard x X0-Naganuma crosses were obtained from female diploid or haploid/diploid cells as a result of parthenogenesis. In very rare cases, when the zygotic barriers had been surmounted, normal embryo heterozygotes and a F1 hybrid generation were obtained in XY-standard x X0-Naganuma crosses. On the contrary, crosses between the XY-Tanno and X0-standard subraces gave viable offspring in spite of many chromosome differences such as a X-A translocation and fixed pericentric inversions in four pairs of autosomes. The results obtained do not support the hypothesis that chromosomal differences play a key role in restricting gene flow between X0 and XY races of P. sapporensis. The presence of crossing barriers explains the phenomena of the purity of the X0 and XY chromosomes races.

Animals↗

PubMed2005

Hybridization of Schistosoma mansoni and Schistosoma japonicum in mice.

Crossing experiments in mice with two human species of Schistosoma japonicum (Taiwan strain) and Schistosoma mansoni (Puerto Rican strain) were performed. The hybrid miracidia from the cross between female S. japonicum and male S. mansoni infected both Biophalaria glabrata and Oncomalania h. chiui. However, those from the reciprocal crossing could infect only B. glabrata. B. glabrata infected with hybrid miracidia of female S. mansoni x male S. japonicum survived up to 30 days while those infected with miracidia of S. mansoni remained alive for more than 100 days after the first shedding of cercariae. Relatively few hybrid eggs reached maturity either in tissues or in the feces of infected mice. A low percentage of F1 eggs hatched and the infectivity of F1 miracida was also low. Morphology and behavior of hybrid eggs, miracidia, cercariae, and adults were similar to the maternal species. The daily egg production of the hybrid worm pair was less than that of the normal one. The observations in the present study may be attributed to the maternal effects. However, the phenomenon of parthenogenesis in schistosomes cannot be confirmed.

Animals↗

PubMedDate not supplied

[Ecological approach to the problem of monophyly of Neodermata (Platyhelminthes)].

The ecological scenario of the evolution of main branches of Neodermata is described. The first neodermateans (= promonogeneans) were parasites of the gill lamellae of Paleozoic jawless vertebrates, which were microphagous suspension-feeding animals. The main apomorphic characters of the primary neodermateans are neodermis, cercomer (posterior hooked attachment organ) and swimming infective larva. All subsequent evolution of Neodermata was related with their acquisition new niches in hosts, which were intensively diverging in that time adapting to new food types and conquering new ecological niches. The acquisition of new microhabitats was accompanied by the development of morphological diversity in Neodermata especially in a structure of attachment and genital organs. Trematoda, Cestoda and Polyopisthocotylea comprise specialized evolutionary lineages and Monopisthocotylea is a basal taxon. Polyopisthocotylea is specialized to the blood feeding on fish gills. The common ancestors of the Trematoda and Cestoda inhabited walls of gills and pharyngeal cavities, from where they penetrated the digestive tract. The aspidogastridean multiloculate hold fast appears to be a highly specialized attachment organ of the monogenean ancestor, which inhabited muscular pharyngeal walls of Paleozoic vertebrates. The loss of cercomer hooks probably took place when mollusk-hosts have been involved in the aspidogastridean life cycle. The extinction of many chondrichthiean groups and progress of small plankton fishes (Teleostei) has led to the appearance Digenea. New vertebrate hosts needed a new infestation type and the cercaria appeared. Parthenogenesis has been developed in stages living in mollusks to counterbalance the loss of individuals at two transmission stages in the digenean cycle; this was resulted in a strong specificity to mollusk-host. Evolutionary tendencies of Trematoda and Cestoda show noticeable similarities.

Animals↗

PubMed2005

[Features of crossability, haploidy and polyembryony in hybrid combinations between common barley Hordeum vulgare L. (2n = 14) and wheat-rye substitution lines Triticum aestivum L., cultivar Saratovskaya 29/Secale cereale L., cultivar Onokhoiskaya].

The role of individual chromosomes of rye in the manifestation of crossability and seedling development in hybrid combinations between common barley Hordeum vulgare L., cultivar Nepolegayushchii (2n = 14) and five wheat-rye substitution lines Triticum aestivum L., cultivar Saratovskaya 29/Secale cereale L., cultivar Onokhoiskaya (2n = 40 wheat + 2 rye chromosomes). Crossability, which was measured by two parameters--frequency of set grains and frequency of grains with embryos--was shown to be significantly affected by each of the five rye chromosomes examined: 1R, 2R, 3R, 5R, and 6R; the development of barley haploids was affected by rye chromosomes 1 R, 3R, and 5R. We were the first to demonstrate that polyembryony could be induced by mutual effects of barley cytoplasm and rye chromosome 1R. Possible mechanisms controlling the development of haploids and twins in hybrid combinations H. vulgare x T. aestivum/S. cereale are discussed. The conclusion is drawn that hybrid combinations between common barley and wheat-rye substitution lines can serve as new models for studying incompatibility mechanisms in distant crosses and genetic control of parthenogenesis.

Chimera↗

PubMedDate not supplied

[Sexual reproduction of insects is regulated by cytoplasmic bacteria].

The effects have been considered that the intracellular symbiotic alpha-proteobacteria Wolbachia pipientis induces in its hosts, such as insects and other arthropods: cytoplasmic incompatibility upon mating, feminization, parthenogenesis, and androcide. Specific features of the bacterium genome and possible mechanisms of its action on hosts are discussed.

Animals↗

PubMed2006

Rare sexual reproduction events in the clonal reproduction system of introduced populations of the little fire ant.

A unique reproductive system has previously been described in Wasmannia auropunctata, a widespread invasive ant species, where males are produced clonally, female queens are parthenogens, and female workers are produced sexually. However, these findings were mostly based on samples originating from only a limited part of the native range of the species in South America. We used microsatellite markers to uncover the reproductive modes displayed by a large number of nests collected in various invasive W. auropunctata populations introduced 40 years ago into New Caledonia, where the species now forms a single 450-km-long supercolony. Although the main reproduction system in New Caledonia remained clonality for both male and female reproductives, we found evidence of rare sexual reproduction events that led to the production of both new queen and male clonal lineages. All clonal lineages observed in New Caledonia potentially derived from sexual reproduction, recombination, and mutation events from a single female and a single male genotype. Hence, the male and female gene pools are not strictly separated in New Caledonia and the two sexes do not follow independent evolutionary trajectories. Our results also suggest genetic determination for both parthenogenesis and caste. We discuss the evolutionary implications of the emergence of sex in the clonal reproduction system of introduced populations of W. auropunctata.

Animals↗

PubMed1990

[Evaluation of tumor marker in ovarian dermoid cyst].

Since ovarian dermoid cyst originates in parthenogenesis of the oocyte, it contains various kinds of tissues. Therefore, some tumor markers are expected to be positive. Clinical features of 174 pathologically confirmed dermoid cysts between Jan., 1985 and Aug., 1989 were reviewed, especially concerning tumor markers. The age of the patients was 11 years to 71 years (Mean 35.0 +/- 0.9 years). The weight of the dermoid cyst was 5g to 2.540g (mean 225.9 +/- 26.3g), while most of them were below 200g. The site of the tumors was similar on both the right and left. CA19-9 showed the highest positive rate of 45.5% (40/80). CA125 was second 12.7% (16/126) in markers with more than 20 examined cases, while the rate for AFP, Ferritin, CEA, LDH and TPA was 2.7% (3/110), 2.6% (1/38), 1.6% (2/128), 0.6% (1/161), 0% (0/24), respectively. SCC, IAP and beta 2-MG were examined in less than 20 cases and the positive rate was 18.8% (3/16), 9.1% (1/11) and 8.3% (1/12), respectively. There was no significant relationship between tumor weight and the CA19-9 concentration. In some cases, the serum CA19-9 concentration was followed up after the operation. The half life of CA19-9 was clinically estimated at 4.9 +/- 1.1 days.

Adolescent↗

PubMed1989

[Sterility: the demand for in vitro fertilization].

We carried out several non-directed preservations (greater than 3) with 110 patients who were asking for in vitro fertilisation. As a result we have tried to point out the problems that have been found in these patients and to assess the specific characteristics that accompany the technique of IVF. In this way we allude to: the specific problems of IVF patients, the sexuality of the couple, the difference between the different techniques for assisted reproduction, the role for the technique of IVF. It seems that: There is no specific psycho-pathological feature of IVF in patients. On the other hand, IVF patients frequently show infantile conflicts that have not been resolved on the psychological level (the problems tend to be more pre-oedipal than oedipal). In vitro fertilisation confirms the original existing fantasies (the fantasy of parthenogenesis, of maternal virginity and of absence of parental coitus). The medicalization of IVF puts pressure on the patient of having to be available at a certain time and it causes an intrusion into the female body and into the couple's sexuality, and this carries with it an iatrogenic risk. It seems to us that particularly in IVF treatments the psyche of the couple has to be taken into consideration. We report our experience on sterile couples treated with in vitro fertilisation. We have researched to see if there was a specific psychic make-up in patients who ask for IVF and whether there is a specific relationship in the couple. We have tried to follow closely some patients who ask for IVF throughout the whole long treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1988

[Failure of embryonic development].

Abnormal embryo development represents the major cause of implantation failures and accounts for the low rate of human fertility in vivo or in vitro. Chromosome abnormalities are widely involved in this process as 26% of oocytes, 8% of fertilizing spermatozoa and 29% of preimplantation embryos carry a chromosome aberration induced by meiotic (aneuploidy) or mitotic (mosaic) non disjunctions. Fertilization anomalies (possibly increased by in vitro procedures) were recorded: 1.6% of embryos resulted from parthenogenesis and 6.4% were polyploid (mainly polyspermic). A morphological, histological and ultrastructural study of embryos recovered after in vivo or in vitro fertilization showed some anomalies: multinucleated blastomeres, cytoplasmic fragments in the perivitelline space, vacuoles, associated or not with developmental impairement. Finally, a few embryos appeared to be free of abnormalities. The analysis of in vitro developmental capacities of normal or abnormal embryos showed great differences: parthenones exceptionally reached the blastocyst stage and therefore probably did not implant. The diploid embryos used in this study were (for ethical reasons) more or less fragmented and gave evidence of low developmental capacities, limited to the 3rd cleavage. Triploid embryos were able to further develop as some of them reached the early blastocyst stage; they represented the major cause of chromosomal 1st trimester abortions. It is interesting to note that 47% of tripronucleated ova divided directly into 3 and 6 cells (probably via a tripolar spindle) instead of 2 and 4 cells as classically described. Finally, tetraploid embryos expressed a precocious lethality as none developed beyond the 3rd cleavage. To conclude, many embryos carry genetic and/or cytological abnormalities which may be enhanced by superovulation treatments. The selection proceeds through all pre- and postimplantation steps, and as a matter of fact nor more than 0.6% newborns are abnormal.

Chromosome Aberrations↗

PubMed1985

Familial occurrence of mature ovarian teratomas.

It has been suggested that genetic predisposing factors play a role in the development of ovarian teratomas. Familial occurrence of these tumors would support this view. Reported herein are identical twins, both of whom had a right ovarian mature teratoma. In both cases the presenting symptoms were acute torsion. The diagnosis was confirmed at laparotomy and subsequent histopathologic examination. The origin of ovarian teratomas seems to be linked to the process of parthenogenesis. This process probably involves a germ cell after its first meiotic division.

Adult↗

PubMed1983

[Pierre Masson. A precursor and re-discoverer (1880-1959)].

Pierre Masson, born in Dijon in November 1880, intended to be a clinician doctor. After being seriously troubled with bad health and following the advice of his master Eugène Bataillon, a researcher who found out the parthenogenesis of batrachian ova, he turned towards a scientific carrier as a biologist. Appointed Chairman in Strasbourg where he held the chair of pathology as early as the first world war, he left France in 1927 to assume the same functions in Montreal. There, he died in May 1959, after creating one of the most brilliant schools of pathology of the XXth century. Most of Pierre Masson's works are precursory as regards the scientific conceptions of his period. He gave them two predominant orientations: on the one hand, works of pure technical histology, resulting in original processes of fixation, coloration and argentation which are still used today; on the other hand, numerous works of oncologic pathology, which allowed him to individualize new tumors, such as the "spermatocytoma" or the "glomus tumor". An observed endowed with a vast culture in biology, Pierre Masson considers the pathologic fact as a real "natural experience" which reveals unsuspected properties of the tissues or allows to discover normal structures which could not be found out easily without it. In this regard he gave pathology a renewed vitality.

France↗

PubMed1984

Pure yolk sac carcinoma of the mouse uterus: report of 8 cases.

This report covered the pathologic features, behavior, metastases, and results of transplantation of pure yolk sac carcinomas that were primary in the uterine horn of 8 mice; 6 mice were strain C3H and 2 were strain HR, and they varied from 10 to 23 months of age. Three of the mice had never been treated. Of the 5 that had, the treatment was different for each mouse. Therefore, treatment could not be correlated with tumor development. At least 5 mice were nulliparous; in fact they had never been mated, so in these some mechanism involving parthenogenesis must have been operative to account for the tumor. The tumors were identified as being primary in the uterus and occupied and distended the cavity of one uterine horn where they were polypoid or plaquelike. The neoplastic yolk cells replaced the endometrial stroma forming a support for the original endometrial glands. In time the tumor cells destroyed many of the endometrial glands. That the glands present in the primary uterine horn tumors were the original glands of the endometrium and not neoplastic glands was attested by their absence from the secondary neoplastic deposits in 4 mice in which the tumor had spread to areas outside the cavity of the uterus and from the neoplastic tissue of the tumor transplants in the recipient mice.

Aging↗

PubMed1984

[Important roles of oocytes, follicles and corpora lutea in ovarian teratocarcino-genesis in mice].

In strains LT/Sv and LTXBJ mice, susceptible to spontaneous ovarian teratocarcinogenesis, ovarian teratomas are derived from parthenogenetically activated ovarian eggs. The follicles containing the parthenotes are the abnormal ones in which granulosa cells show histochemically high activity of beta-glucuronidase (beta-G). To investigate whether ovarian teratocarcinogenesis depends on the genetic nature of eggs themselves or the microenvironment in the abnormal follicles, we used chimeras derived from aggregates of eight-cell embryos of strains LTXBJ or (LTxLTXBJ) F1 and of normal nonsusceptible strain C3H/HeJ which shows low activity of beta-G genetically. The original strain of teratomas and follicles in chimeras were histochemically determined by activity of beta-G as a marker. The results showed that both teratomas and the follicles containing parthenotes originate from the susceptible strains. Then, we examined for presence of activated oocytes, teratomas and corpora lutea in LT ovaries untreated or treated with PMSG-HCG implantation. These results showed that parthenogenetic blastocysts closely adhere to the follicle tissue as if a kind of and develop to post implantation stages in the ovaries in which corpora lutea were formed near the parthenotes. In conclusion, it was suggested that ovarian parthenogenesis in mice occurs most frequently when eggs with genetically susceptible nature, were exposed to the microenvironment produced by the abnormal follicles, and these parthenotes adhere to the ovarian tissues and differentiate three germ layers by some roles of corpora lutea and undergo teratocarcinogenesis.

Animals↗

PubMed1994

Chromosome complement, gametogenesis, and development of Strongyloides stercoralis.

Gametogenesis and development were studied in free-living adults of the human parasitic nematode Strongyloides stercoralis. The diploid chromosome number is 6 in germ-line tissue of females and in embryos that will develop into parasitic females. Reproduction appears to be by meiotic parthenogenesis and pseudogamy, as in other species in the genus. Fecundity may be limited by the short lifespan of males. Newly hatched larvae contain about 500 cells, whereas adult females have about 840 somatic cells and a variable number of germ-line cells. The apical vegetative zones of both ovary and testis are occupied by cells with large amounts of DNA in their nuclei.

Anaphase↗