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A review of experimental studies of nuclear transplantation in mammals. The possibility of parthenogenesis in mammals is discussed on the basis of the results reviewed. Discrepancies in the data obtained by different authors are also discussed.
The efficiency of 7% ethanol and cycloheximide (CH) as activators of parthenogenesis was compared on the in vitro matured oocytes of the CBA/C57BL (F1) mice. CH is a more potent activator but the oocytes are activated by ethanol more synchronously. The oocytes matured in the F12, F10 and RPMI 1640 media were activated by ethanol reliably better than those matured in the Minimum Essential Medium Eagle or in the M3 medium. Addition of five amino acids (arginine, alanine, serine, aspartic and glutamic acids), only ornithine or arginine, as well as prolongation of oocyte cultivation in M3 from 19.5 to 26.5 h reliably increased the percentage of activated oocytes.
The percentage of laying females and laying time, are compared between mature females (diapause break by chilling) and diapause strain females (diapause not broken by chilling) reared with mature male or diapause male or without male. For the same physiological state of the females (mature or diapause) there is no difference in the percentage of females laying, when they are reared with mature male or with diapause one or none; but the laying time is shortest with mature male, longer with male in diapause, even longer without male. Parthenogenetic egg-pods can be obtain. Rearing with mature males does not break the reproductive diapause of females. In parthenogenetic egg-pods the number of eggs is short for low diapause females; greater for mature ones and greatest for females with strong diapause broken by a corpus allatum implant of mature female of Locusta migratoria. Corpus allatum of the low diapause strain of females of Tetrix undulata have less activity than that of mature females. Few parthenogenetic eggs develop, even less hatch. In Tetrix undulata parthenogenesis is accidental.
Opposition to abortion is based in part on the assumption that personhood is achieved at or shortly after fertilization of the egg. This interpretation of personhood arises from a contemporary application of the ancient doctrine of preformationism, a doctrine which holds that there is a preformed individual, in an ontological sense, within the developing entity. The assumption that the fertilized egg is unique in its capacity to develop into a human being is at least in part responsible for the opinions of those opposed to abortion. Yet, the uniqueness of the zygote in its capacity to develop into an adult organism is qualified by the discovery that development may be possible in a number of other ways. Consideration of the phenomena of cloning, parthenogenesis and chimerism can relieve moral ambiguity about abortion and may reduce opposition to that practice.
The mite Haemogamasus ambulans is characterized by a mixed type of feeding such as haematophagy, zoophagy and schizophagy with a prevalence of haematophagy. Maximum fecundity of females took place when they were kept on complex diet (blood and living objects). When fed only with blood mites exhibited pronounced cannibalism that resulted in the reduction of their progeny. In addition to gamogenesis parthenogenesis was noted.
In vitro maturation (IVM) and fertilization are potentially useful for propagating threatened or endangered species. The domestic cat is currently used in this field as an experimental model for studies aimed at non-domestic Felidae. At present optimal conditions for obtaining IVM of cat oocytes have not yet been completely defined. The aim of this study was to evaluate two parameters derived from the procedures that currently ensure high maturation rates in domestic ruminants: (1) the suitability of a complex medium (M-199) for IVM of cat oocytes; (2) the effect of different concentrations of fetal calf serum in the culture medium with or without the addition of gonadotrophins. The maturation rate at two different intervals from the onset of culture (24 and 48 h) was also evaluated. The use of M-199 allowed resumption of meiosis in 4.3-18.7% of cat oocytes, according to the supplements and culture periods used. No significant differences were recorded among the treatment groups (P > 0.05). Meiosis was completed in 90.9% of cases within 24 h with no significant differences between the three treatment groups (P > 0.05). A 3.2% rate of parthenogenesis was observed at the end of the maturation period with no significant differences between the culture systems (P > 0.05). However, the percentage cleavage of oocytes was much higher (29%) when correlated with the percentage that had matured. In this case significant differences among treatments were also observed (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
Due to some suggestion [8] the parthenogenesis in vertebrates is the result of interspecies hybridization, and some species seem to be the main candidates participating in this process. DNA parts, which may be revealed using polymerase chain reaction in AP-RAPD modification, were compared in parthenogenetic lizards forms and in supposed parental species for them. As it was shown by other authors and confirmed by us, arbitrary primed randomly amplified DNA products are species specific and may be used as a molecular taxonomic criterion. It was shown that each parthenogenetic species studied has the patterns containing only the bands of one or another supposed parents and no more. This is in favour of the hypothesis mentioned above. Investigation of 103 10-nucleotide primers in PCR was done.
Parthenogenetic mammalian embryos show reduced placental development and do not develop beyond the 25-somite stage. But non-parthenogenetic embryos in culture, without a functional placenta, can develop to 40 somites or more. We have therefore examined the possibility that parthenogenetic embryos might also show prolonged development in culture. After parthenogenetic activation and diploidization, 23% of CBA and 56-58% of hybrid (CBAxC57BL/6) F1 mouse eggs developed in culture to blastocysts. When transferred to pseudopregnant recipients: 60% of the CBA blastocysts implanted and 26% of these developed to somite stage embryos; 71-72% of the hybrid blastocysts implanted and 11-17% of these developed to somite stage embryos. Improved development of postimplantation embryos explanted into culture at about the 15-20 somite stage was obtained by opening the visceral yolk sac (without exteriorizing the embryo). All the normal (non-parthenogenetic) embryos cultured in this way developed to more than 35 somites and many reached 45-55 somites. Under the same conditions, 11/17 diploid parthenogenetic CBA embryos developed in culture to more than 35 somites and 5 of these reached 45 somites; and 9/28 diploid parthenogenetic (CBAxC57BL/6) F1 embryos developed to 35 somites or more and 5 of these reached 45 somites. The size and protein content of the parthenogenetic embryos after culture was less than that of the normal embryos of equivalent stages. These results raise new possibilities for the analysis of parthenogenesis and genomic imprinting, including studies of the effects of adding to the culture medium specific growth factors and demethylating agents.
The LT/Sv mouse strain is characterized by its abnormally high incidence of spontaneous ovarian teratomas. These tumors have been shown to originate from parthenogenetic oocytes, which are spontaneously induced to divide. Both spontaneous parthenogenesis and ovarian teratomas are extremely rare for other mouse strains, including C57BL/6J. To identify the genes responsible for this unique phenotype of female LT/Sv mice, we performed linkage analysis of female (C57BL/6J x LT/Sv)F2 mice. A locus on chromosome 6 designated Ots1 (ovarian teratoma susceptibility) was identified as the single major locus that increases the frequency of teratomas in a semidominant manner.
In zebrafish it is possible to create viable diploid fish whose genomic DNA is derived only from the female parent (parthenogenesis) or, as was more recently shown, only from the male (androgenesis). Androgenesis requires holding zebrafish eggs in an inactivated state in vitro for an hour or more. Previously this was achieved by placing the zebrafish eggs in ovary fluid obtained from rainbow trout (Onchorhynchus mykiss) or coho salmon (Onchorhynchus kisutch). Here we report that adding bovine serum albumin (BSA) to Hank's buffered saline prevents zebrafish egg activation in vitro. Of the zebrafish eggs placed in Hank's saline plus 0.5% BSA, 85% +/- 8.7% were fertilizable after incubation for one hour at room temperature (23 degrees C). Longer incubations are possible but with lower efficiency of fertilization. This technique not only could facilitate androgenesis, but also might be useful when making transgenics by microinjection, when performing antibody or RNA injections before fertilization, or for studying the mechanisms of egg activation in zebrafish.
BACKGROUND: Mature ovarian cystic teratomas, which are commonly observed benign ovarian tumors, consist of ectodermal, mesodermal, and endodermal components that are generally disorganized. In this report, we document a case in which the solid portion of an ovarian teratoma demonstrated considerable differentiation, forming a doll-like structure. CASE: A 25-year-old virginal Japanese woman underwent surgery for an ovarian tumor that was diagnosed as a mature teratoma. A solid mass within the tumor was found to have a head, trunk, and extremities. Consequently, this mass was diagnosed as a mature fetiform teratoma (homunculus). Brain, eye, spinal nerve, ear, teeth, thyroid gland, bone, bone marrow, gut, trachea, blood vessels, and phallic cavernous tissue were confirmed microscopically. Distinctive features were the clear anterior-posterior, ventral-dorsal, and left-right axes, with a spatially well-organized arrangement of the organs. An eye was located on the front of the head, a spinal nerve lay dorsal to the spinal bones, the thyroid gland was anterior to the trachea, and the gut was deep inside the trunk. CONCLUSIONS: These findings indicate that the information necessary for organization of the body plan may be conserved and transmitted, even with parthenogenesis. Mature cystic teratomas of the ovary are mostly benign and do not always attract detailed attention. However, precise analyses of such tumors may significantly enhance our understanding of both parthenogenetic and normal human development.
Research using human embryos and embryonic stem cells is viewed as important for various reasons. Apart from questions concerning legal regulations, numerous ethical objections are raised pertaining to the use of surplus embryos from reproductive medicine as well as the creation of embryos and stem cells through cloning. In the hopes of avoiding ethical problems, alternatives have been proposed including the extraction of egg cells from "dead" embryos derived from in vitro fertilization procedures, the extraction of pluripotent stem cells from blastocysts, technologies such as "altered nuclear transfer" (ANT) and "oocyte-assisted reprogramming" (ANT-OAR) as well as parthenogenesis. Initial ethical assessments show that certain questions pertaining to such strategies have remained unanswered. Furthermore, with the help of new or more differentiated biotechnological procedures, it is possible to create chimeras and hybrids in which human and non-human cells are combined. Human-animal chimeras, in which gametes or embryonic tissue have been mixed with embryonic or adult stem cells, demonstrate a different "quality" and "degree of penetration" from those produced in previous experiments. Not only does this have consequences regarding questions of patentability, this situation also raises fundamental questions concerning the human being's self image, the concept of person, identity and species and the moral rights and duties that are connected with such concepts. There is a need for legal regulation, on the national as well as the international level.
Fertilization abnormalities are commonly encountered following in vitro fertilization. The widespread introduction of assisted fertilization methods has rapidly led to a changes in both the incidence and types of these aberrations. Such abnormalities can be identified by careful morphological evaluation at the early zygote stage, of pronuclei as well as of polar body formation, and may be confirmed by cytogenetic assessment. The recognition and understanding of fertilization abnormalities have led to the development of novel techniques aimed at preventing them, as well as recent bold attempts at correction. Removal of one pronucleus may allow some triploid embryos to revert to a normal diploid stage. These new developments should provide insight into the understanding of parthenogenesis, androgenesis, and gynogenesis in the human. Microsc. Res. Tech. 61:358-361, 2003.
Daphnids (Daphnia magna) utilize cyclic parthenogenesis as a reproductive strategy. During periods of abundant resources, these organisms reproduce asexually. In response to environmental cues that signal the onset of environmental adversity, daphnids produce males and reproduce sexually. The environmental cues that stimulate the sexual reproductive phase are well known; however, the endocrine signals that transduce these environmental cues remain unknown. The present study was undertaken to test the hypothesis that the crustacean juvenoid hormone, methyl farnesoate, is a male sex determinant in this species. Continuous exposure to aqueous concentrations of methyl farnesoate greater than approximately 30 nM stimulated a concentration-dependent production of male-containing broods of organisms. Short-term exposures to methyl farnesoate during periods of egg and embryo maturation revealed that male sex determination occurred during a specific 12-hour period of ovarian egg development. Exposure of eggs to 400 nM methyl farnesoate during this sensitive developmental period resulted in the production of all-male broods of offspring, while exposure to concentrations as low as 52 nM produced mixed broods of males and females. This active concentration range of methyl farnesoate is consistent with levels measured in the hemolymph of some decapod crustaceans. These results demonstrate that methyl farnesoate is capable of programming daphnid embryos to develop into males and is likely the endocrine factor responsible for initiating the sexual reproductive phase in these organisms.
The objectives of the present study were: 1) to develop a simple and more efficient technique for sperm microinjection than is currently available, using the rabbit as a model, and 2) to evaluate the development of rabbit oocytes fertilized by single or multiple sperm microinjection. Hyperosmotic sucrose in phosphate-buffered saline (SPBS) was employed to dehydrate oocytes to increase the perivitelline space for sperm microinjection and prevent possible injury to the vitellus. In the first experiment, 58% (n = 29) oocytes treated with 0.5 M SPBS developed to morulae following multiple sperm microinjection compared, respectively, to 47% (n = 34) and 60% (n = 15) for control IVF with or without sucrose exposure (P greater than 0.05). Blastocyst development from microinjected oocytes, however, was much lower (P less than 0.05) than that of controls (14% vs. 42% and 40%, respectively). Sham operation by puncturing the zona pellucida of the sucrose-treated oocytes with the microinjection pipette did not increase parthenogenesis (P greater than 0.05). In Experiment 2 a smaller-size injection pipette and shorter sucrose exposure time after sperm microinjection resulted in 41% (n = 42) of the oocytes developing into blastocysts for the microinjection group, whereas only 21% (n = 24) developed to blastocysts in the control IVF group (P less than 0.05). When relatively older oocytes (17 hr post ovulation injection) were used to test if microinjection could reduce the time to fertilization and cleavage (Expt. 3), an average of 27% (n = 63) blastocysts resulted from microinjection vs. 0% (n = 28) for the control IVF group.
Cross-fertilization between sea urchin eggs (Strongylocentrotus nudus) and starfish sperm (Asterina pectinifera) was induced by treatment with polyethylene glycol (PEG). Without treatment with PEG, the denuded egg surface (jelly coat- and vitelline coat-free) engulfed the head of acrosome-reacted sperm; however, sperm penetration did not occur [Kyozuka and Osanai, 1988]. When these eggs were exposed briefly to PEG (molecular weight 3,000) in seawater, the sperm entered the egg by membrane fusion. Cortical granules were discharged, and embryogenesis began following sperm penetration. PEG did not induce parthenogenesis in Strongylocentrotus eggs. Egg activation is thus closely linked with gamete membrane fusion.
Advances in understanding insecticide resistance in the peach-potato aphid, Myzus persicae (Sulzer), at the genotypic, biochemical and molecular levels have led to rapid and precise methods for the detection of several resistance mechanisms (elevated carboxylesterase, modified acetylcholinesterase or MACE, and knockdown resistance or kdr) in individual insects, and for monitoring their frequencies over space and time. This paper summarises the results of two long-term surveys of resistance dynamics in M persicae in England, based on samples collected directly from field and glasshouse crops or from four 12.2-m suction traps. The study showed marked fluctuations in resistance frequencies that probably reflect the counteracting forces of selection imposed by insecticides for aphids possessing more copies of esterase resistance genes, and selection against these forms when insecticide use is relaxed. There is growing evidence that several different resistance mechanisms in M persicae have associated fitness costs. In the case of esterase and MACE, these costs are apparently strong enough to effect a decline in resistance frequency over winter, and a more prolonged decline over successive cropping seasons when aphid numbers are insufficient to trigger intensive chemical applications. Changes in the overall frequency of resistance genotypes may also be influenced by the predominance of year-round parthenogenesis in M persicae in the UK, leading to non-random associations between mechanisms and selection operating on clonal lineages rather than individual genotypes.
The marsupials represent a separate evolutionary lineage from eutherians from which they diverged over 100 million years ago. In order to explore the origin and mode of centrosome inheritance amongst this group of mammals, this study investigates the microtubule organization during fertilization, parthenogenesis, and polyspermy in the didelphid, Monodelphis domestica. Microtubules and DNA were visualized in maturing ovarian oocytes, parthenogenetically activated oocytes, monospermic and polyspermic zygotes, and early embryos. Ovarian oocytes had a central region of yolky cytoplasm that, after fertilization, became polarized; much of the yolk was then extruded into the perivitelline space as an enucleated cytoplasmic mass. Immunofluorescence microscopy, using a monoclonal antibody to beta-tubulin, demonstrated microtubules in the meiotic spindle in unfertilized oocytes, but cytasters were not detected. After fertilization, a cluster of microtubules forming into a sperm aster was evident around the male pronucleus. The sperm aster remained largely restricted to the nonyolky region of the egg cytoplasm, resulting in a cytoplasmic heterogeneity between a microtubule-rich region and one in which microtubules were largely absent. Once the two pronuclei came close together, abundant microtubules were found surrounding both pronuclei. In the early embryo, microtubules were found in the outer cortical region of the blastomeres and, in addition, there was an extensive and elaborate network of microtubules throughout the yolk mass. Disruption of the meiotic spindle microtubules with nocodazole or cold treatment did not result in chromosome dispersion in the cortex and recovery from drug or cold depolymerization demonstrated that microtubules might not be as dynamic as those in eutherian mammals. Taxol stabilization resulted in an increase in cortical microtubules. In this marsupial species, therefore, the centrosome appears to be of paternal origin, and the radiating microtubules that form may well be involved both in bringing the pronuclei together and in the cytoplasmic polarization that results in extrusion of the yolk mass.