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PubMed1978

The evolution of sexual reproduction as a repair mechanism. Part I. A model for self-repair and its biological implications.

The theory is presented that the sexual process is a repair mechanism which maintains redundancy within the sub-structure of hierarchical, self-reproducing organisms. In order to keep the problems within mathematically tractable limits (see Part II), a simple model is introduced: a wheel with 6 spokes, 3 of them vital and 3 redundant, symbolizes the individual (cell or organism). Random accidents destroy spokes; the wheels replicate at regular cycles and engage periodically in pairing and repair phases during which missing spokes are copy-reproduced along the intact spokes of the partner wheel. The hierarchical structure of such a system is analysed and an 'autonomous unit' is defined: this is the unit of minimal hierarchical complexity which is capable of perpetuating autonomously all higher and all lower levels of the hierarchy; this is the central unit of selection. Four basic, physical parameters are isolated which determine the essential features of any eucaryotic life cycle: 1. The number of levels of the hierarchy (unicellular, multicellular, colonial, etc.); 2. the relation between the phases of replication (asexual generations) and repair (sexual generations); 3. the duration of potential repair (haplo-diplo-phase); 4. the position of the sexual partners within the hierarchy (selfing, monecy, dioecy, reproductive individuals within colonies, etc.). The evaluation of fitness components is considered in relation to trends of reproductive patterns in evolution.

Animals↗
PubMed2002

Heterosis and recombination effects on pig reproductive traits.

The objective was to estimate breed, heterosis, and recombination effects on pig reproductive traits in two different four-breed composite populations. Breeds included Yorkshire, Landrace, Large White, and Chester White in Exp. 1 and Duroc, Hampshire, Pietrain, and Spot in Exp. 2. Data were recorded on purebred pigs, two-breed cross pigs, and pigs from generations F1 through F6, where F1 pigs were the first generation of a four-breed cross. Litter traits were considered a trait of the gilt. There were 868 first parity litters in Exp. 1 and 865 in Exp. 2. Direct heterosis significantly increased sow weight at 110 d of gestation and litter weight at 14 and 28 d (weaning) in both experiments. Direct heterosis significantly increased number of nipples, weight at puberty, lactation weight loss, litter size, and litter birth weight in Exp. 2. Gestation length in Exp. 1 and age at puberty in Exp. 1 and Exp. 2 were significantly decreased by direct heterosis. Maternal heterosis significantly increased age at puberty in Exp. 2 and decreased sow weight at 110 d of gestation in Exp. 1. Recombination significantly increased sow weight at 110 d of gestation and tended to increase total number born and litter birth weight in Exp. 1. Recombination significantly decreased age at puberty in Exp. 2. Litter heterosis significantly increased number of pigs at 14 and 28 d; litter weights at birth, 14, and 28 d; and tended to increase lactation weight loss in Exp. 1. Litter heterosis decreased litter size in Exp. 2. Maternal heterosis and recombination effects had a sampling correlation of -0.97 in Exp. 1 and -0.91 in Exp. 2 for number of fully formed pigs. Therefore, maternal heterosis and recombination effects were summed, and their net effect was tested. This net effect tended to increase number of nipples, lactation weight loss, and litter birth weight and significantly increased number of fully formed pigs in Exp. 1. Direct, maternal, and litter heterosis and recombination effects significantly influenced reproductive traits.

Animals↗
PubMed2004

The nature of genetic variation in sex and reproduction-related genes among sibling species of the Drosophila melanogaster complex.

Much is known about the biology of Drosophila melanogaster. As a model organism, a comprehensive understanding of its development, physiology and reproduction has been acquired. As a result, a broad variety of transferable genetic tools and information has allowed sibling species of the D. melanogaster complex to emerge as an important speciation model system. By comparing D. melanogaster with its close relative, Drosophila simulans, as well as its other sibling species, we are beginning to understand the nature of genetic changes during the early stages of speciation. In general, we find that genes and traits involved in sex and reproduction are more variable. A large assortment of genes and traits that are involved in various aspects of mating and fertility reveal diagnostic differences between these sibling species. Sex and reproduction-related (SRR) genes are, on average, more diverged than genes with no apparent reproductive function. Furthermore, SRR genes appear more permissive at opting in novel function. These results follow a general trend observed in other taxa and demonstrate the preferential involvement of SRR genes in reproductive isolation and species formation.

Animals↗
PubMedDate not supplied

The development of male reproductive organ abnormalities after neonatal exposure to tamoxifen is genetically determined.

Responses of the male reproductive organs to neonatal exposures of tamoxifen (Tx) were examined in seven different strains of mice (A/J, AKR/J, BALB/cAnN, C3H/HeJ, C57BL/6J, DBA/ 2J, and FVB/N). Male mice were given daily subcutaneous injections of 2 microg Tx from postnatal day 1 to 5, and the testes, epididymides, ductus deferens, and seminal vesicles were examined at 3 months of age. At necropsy, the testes and seminal vesicles of Tx-treated groups were significantly smaller in size than those of the control groups in all strains. Histologically, the testes of AKR/J, BALB/cAnN, and FVB/N mice showed no abnormality after neonatal treatment with Tx. In contrast, the testes of A/J, C3H/HeJ, C57BL/6J, and DBA/ 2J mice were often necrotic and highly disorganized, with severe inflammation. In the connective tissue surrounding these testes, relatively large arteries were involved in the inflammation, and the vascular lumen was occluded by the thickened tunica interna, suggesting that these testicular changes were due to infarction. Similarly, the epididymides and ductus deferens of Tx-treated A/J, C3H/HeJ, C57BL/6J, DBA/2J, and FVB/N mice showed chronic pyogranulomatous inflammation. The epithelium of the seminal vesicles of Tx-treated A/J, C3H/HeJ, C57BU6J, DBA/2J, and FVB/N mice also exhibited moderate hyperplasia, with squamous metaplasia. These results indicate that neonatal exposure to Tx causes various abnormalities of the male reproductive organs in postpubertal mice, depending on the strains, and suggest that a genetic component plays a major role in determining the phenotypic variation observed.

Abnormalities, Drug-Induced↗
PubMed1986

Heritabilities and genetic correlations of growth and reproductive measurements in Hereford bulls.

Weight, hip height, heart girth, pelvic height, pelvic width and scrotal circumference were measured at 403 and 490 d on 427 Hereford bulls. The bulls were members of a random-selection herd so estimates of genetic parameters should have a minimum of bias due to selection. Heritabilities and genetic correlations were estimated by normal paternal half-sib (PHS) correlation procedures. In addition, 256 son-sire pairs (RSS) were used to estimate heritabilities and genetic correlations by regression and covariance methods. The PHS method produced heritability estimates in the range of .41 to .58 for all measures at both ages, with the exceptions of hip height at 403 d (.24) and pelvic height at 490 d (.23). The estimates derived in the RSS method ranged from .10 to .60. The RSS relationship would contain a portion of any maternal X direct covariance effects. A difference in heritability estimated by the two methods could be a reflection of this covariance. Genetic correlations tended to be larger than phenotypic and, in several cases, were negative. The difference in the correlation between two measurements taken at 403 d vs the same correlation estimated at 490 d was not readily explainable but may be evidence for differences in maturation rates or maternal effects. Scrotal circumference had a positive genetic correlation with weight and heart girth and near 0 or negative genetic correlations with pelvic measures. Hip height had positive genetic correlations with weight and heart girth at 403 and 490 d and with pelvic measurements at 403 d, but the correlations were not as large at 490 d.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

Reproductive soundness of captive southern and northern white rhinoceroses (Ceratotherium simum simum, C.s. cottoni): evaluation of male genital tract morphology and semen quality before and after cryopreservation.

White rhinoceroses suffer from a low rate of reproduction in captivity. This study examines the role of male reproductive function as a contributing factor. We used ultrasonography to image accessory sex glands, testis and epididymis. Electroejaculation provided 36 ejaculates from 21 rhinoceroses. Based on the percentage of progressively motile spermatozoa, semen was categorized in three groups, high (I: >75%), intermediate (II: 50-70%) or low (III: <50%) quality. Only 52% of the males showed high semen quality. Ejaculates in the high motility category also had the highest proportion of morphologically intact spermatozoa. Both semen parameters, sperm motility and morphology, were found to positively correlate with size of the accessory sex glands. The semen category was associated with group size suggesting that the social status influenced functional reproductive parameters. Change of territorial status (n = 1) improved semen quality. Testicular fibrosis was characterized as a sign of reproductive ageing in all males older than 15 years of age (n = 13); although, this ageing process did not notably affect semen parameters. Furthermore, for the benefit of assisted-reproduction and genetic banking programs protocols for the storage of cooled semen and the cryopreservation of spermatozoa were designed using different cryodiluents. This report provides basic data for the evaluation of reproductive components and of breeding management in male rhinoceros. Our results indicate that low rate of reproduction in captivity can be attributed to reduced male reproductive fitness. Changes in management of white rhinoceroses may positively affect male reproductive function.

Animals↗
PubMed1987

Genetic markers for assessment of retinoblastoma predisposition.

Here we provide a conceptual framework for the application of current approaches in the analysis of retinoblastoma to the clinical setting. The aim of genetic medicine is to minimize the burden of inherited disease through appropriate diagnosis and management of patients and to maximize information, so that families can make reasonable decisions about reproduction. Recent genetic, cytogenetic and molecular genetic approaches have improved our understanding of the biological events leading to the occurrence of retinoblastoma and, in addition, have provided tools for the enhanced assessment of risk for some individuals. The knowledge, however, is incomplete and the tools imperfect, as indicated by our continued provision of risk probabilities that are neither one nor zero. We therefore hope to emphasize both the scope and the limitations of these techniques so that their application can be effectively considered.

Child↗
PubMed2006

Genetic diversity and mating system of the threatened plant Kirengeshoma palmata (Saxifragaceae) in Korea.

The endangered herb Kirengeshoma palmata, from eastern Asia, has had its population severely reduced in number through habitat loss and fragmentation. All of the individuals within five subgroups at Mt. Baek-un-san, in the southern part of Korea, were genetically surveyed by allozyme analysis. Genetic diversity levels within subgroups were relatively high, and a consistently high outcrossing rate as well as a negligible biparental mating rate were confirmed by this study. Several groups of visibly connected ramets were observed in a clustered distribution which suggested cloning. Absence of mating partner rather than pollinators decreased seed production in small mating groups. The present genetic structure of the five subgroups was probably the result of local extinction of intervening populations. Because K. palmata may be a self-incompatible species, populations with few genets face lowered seed set due to mate scarcity. Thus, this type of population may be at an increased risk of extinction as a result of inbreeding depression, loss of genetic variability, and reduced sexual reproduction. The small, genetically depauperate subgroups may need an input of seeds or plants from other populations in China or Japan in order to regenerate, but the possibility of outcrossing depression leads us to recommend outbreeding among the local subgroups of Mt. Baek-un-san to restore genetic variability.

Flowers↗
PubMed2000

Molecular and morphologic approaches to discrimination of variability patterns in chub mackerel, Scomber japonicus.

The systematic status and the evolutionary biology of chub mackerel (Scomber japonicus) in the South West Atlantic Ocean is confusing with an unknown degree of genetic differentiation and reproductive isolation between units. Simultaneous genetic and morphologic analyses were made on 227 fish collected from two areas of the South West Atlantic Ocean and one from the Mediterranean Sea. The genetic analysis was based on 36 protein-coding loci, 16 of which were variable. The morphologic analyses include six morphometric length measurements and a meristic character. Correspondence between genetic and morphologic variability patterns indicates isolated Mediterranean and Southwest Atlantic subgroups of S. japonicus and, less clearly, possible additional divergence in two regional stocks within the latter group. The most conservative approach to management is to manage the stocks independently of one another.

Journal Article↗
PubMed2006

What choices should we be able to make about designer babies? A Citizens' Jury of young people in South Wales.

BACKGROUND: Young people will increasingly have the option of using new technologies for reproductive decision making but their voices are rarely heard in debates about acceptable public policy in this area. Capturing the views of young people about potentially esoteric topics, such as genetics, is difficult and methodologically challenging. DESIGN: A Citizens' Jury is a deliberative process that presents a question to a group of ordinary people, allows them to examine evidence given by expert witnesses and personal testimonies and arrive at a verdict. This Citizens' Jury explored designer babies in relation to inherited conditions, saviour siblings and sex selection with young people. PARTICIPANTS: Fourteen young people aged 16-19 in Wales. RESULTS: Acceptance of designer baby technology was purpose-specific; it was perceived by participants to be acceptable for preventing inherited conditions and to create a child to save a sibling, but was not recommended for sex selection. Jurors stated that permission should not depend on parents' age, although some measure of suitability should be assessed. Preventing potential parents from going abroad was considered impractical. These young people felt the Human Fertilisation and Embryology Authority should have members under 20 and that the term 'designer baby' was not useful. CONCLUSIONS: Perspectives on the acceptability of this technology were nuanced, and based on implicit value judgements about the extent of individual benefit derived. Young people have valuable and interesting contributions to make to the debate about genetics and reproductive decision making and a variety of innovative methods must be used to secure their involvement in decision-making processes.

Adolescent↗
PubMed1997

A rapid stain-clearing method for video based cytological analysis of cotton megagametophytes.

Optical "clearing" is a cost saving method for preparing large numbers of whole, dissected or thickly sectioned cytological specimens such as plant ovules and ovaries. Minimal labor is required and specimens retain three-dimensional integrity. Previous development of high contrast stain-clearing methods using hemalum to impart contrast has facilitated analysis and photography under bright field illumination for small ovules. The deep stain intensity of hemalum, however, often precludes adequate light transmission and contrast within internal focal planes, limiting the applicability of hemalum-based stain-clearing to small specimens. Having encountered this problem for nucelli of cotton (Gossypium barbadense L.), which are roughly 300 microns thick at fertilization, we have developed a modified stain-clearing system. The two key features of these new methods are the use of azure, C, which allows the intensity of staining to be readily regulated, and contrast manipulation via video signal and image processing. Intensity of azure C stain was readily controlled by modifying the staining and/or dehydration media to produce relatively low contrast specimens. Analysis was facilitated by indirect viewing on a video monitor using adjustments of sensitivity, exposure, and contrast of the charge-coupled device (CCD) camera. Digital processing provided further enhancement. Acceptable images were obtained from virtually all specimens. These methods, which combine low contrast (high transmittance) specimens with high contrast imaging, should facilitate data acquisition on reproduction, thus the developmental and genetic characterization of reproductive mutants. Other applications, e.g., in pathology and embryology, are readily envisioned.

Coloring Agents↗
PubMed2005

Ethical guidelines in genetics and genomics. An Islamic perspective.

We are at a time of unprecedented increase in knowledge of rapidly changing technology. Such biotechnology especially when it involves human subjects raises complex ethical, legal, social and religious issues. A World Health Organization expert consultation concluded that "genetics advances will only be acceptable if their application is carried out ethically, with due regard to autonomy, justice, education and the beliefs and resources of each nation and community." Public health authorities are increasingly concerned by the high rate of births with genetic disorders especially in developing countries where Muslims are a majority. Therefore, it is imperative to scrutinize the available methods of prevention and management of genetic disorders. A minimum level of cultural awareness is a necessary prerequisite for the delivery of care that is culturally sensitive, especially in Islamic countries. Islam presents a complete moral, ethical, and medical framework, it is a religion which encompasses the secular with the spiritual, the mundane with the celestial and hence forms the basis of the ethical, moral and even juridical attitudes and laws towards any problem or situation. Islamic teachings carry a great deal of instructions for health promotion and disease prevention including hereditary and genetic disorders, therefore, we will discuss how these teachings play an important role in the diagnostic, management and preventive measures including: genomic research; population genetic screening pre-marital screening, pre-implantation genetic diagnosis; assisted reproduction technology; stem cell therapy; genetic counseling and others.

Female↗
PubMed2001

Identification of genetically diverse sequences (ORF 5) of porcine reproductive and respiratory syndrome virus in a swine herd.

The ability of genetically diverse strains of porcine reproductive and respiratory syndrome virus (PRRSV) to coexist in a 1750-sow farm was assessed through the case study describing a chronically infected farm, and also by an animal experiment involving the use of swine bioassay. The case study employed a program of monitoring sera from suckling, nursery, and finishing pigs for the presence of PRRSV by polymerase chain reaction (PCR) and virus isolation (VI). The swine bioassay tested homogenates, consisting of lymphoid and pulmonary tissues, collected from 60 breeding animals from the same farm. The open reading frame (ORF) 5 portion of selected positive PRRSV detected from sera or tissues were nucleic acid sequenced and their phylogenies compared. The results indicated the presence of 3 genetically diverse groups, designated PRRSV-A, -B, and -C. Sequence heterology ranged from 5.8 to 11% between groups. Sequence homology ranged from 98.7 to 99.8% within groups. Swine bioassay verified the presence of PRRSV-A in 1 of 60 animals, and no evidence of strains B or C were detected. This paper indicates that based on the evaluation of ORF 5, genetically diverse strains of PRRSV appear to coexist, although the frequency and significance of this observation is not understood.

Amino Acid Sequence↗
PubMed2004

[Importance of genetic testing in couples with reproductive disorders].

OBJECTIVE: To determine the prevalence of chromosomal aberrations in infertile couples undergoing in vitro fertilization (IVF). DESIGN: Cytogenetic analysis of peripheral blood lymphocytes in the group of patients undergoing IVF. Detection of chromosomal aberrations in the fetuses after IVF. SETTING: Department of Medical Genetics and Fetal Medicine, Medical Faculty, Palacký University and the University Hospital, Olomouc. METHODS: Cultivation of peripheral blood lymphocytes or fibroblasts of amniotic fluid. Using fluorescent in situ hybridization in cases of mosaicism. RESULTS: Out of 638 patients undergoing treatment for male or female infertility, 595 had normal karyotype and 43 (6.8%) had abnormal karyotype. There were detected 9 (1.4%) cases of balanced chromosomal rearrangements, 2 (0.31%) cases of deletion of Y chromosome, 2 (0.31%) cases of inversion, 2 (0.31%) cases of marker chromosome, 5 (0.78%) cases of gonosomal aneuploidy (47,XXY) and 23 (3.65%) cases of gonosomal mosaicism--out of the 22 (3.5%) cases of low-level mosaicism. In the small group of pregnant patients after IVF investigated for the risk of genetic disorders included in our study (n = 60) the frequency of chromosomal abnormalities was 9 (15%). CONCLUSIONS: Our data show that a high number of infertile couples is affected by chromosomal aberrations which occur more frequently in females than in males. It is caused by high frequency of low-level gonosomal mosaicism in the group of infertile women. Chromosomal analyses are highly recommended before each IVF procedure.

Chromosome Aberrations↗
PubMed2003

Sex slows down the accumulation of deleterious mutations in the homothallic fungus Aspergillus nidulans.

Coexistence of sexual and asexual reproduction within the same individual is an intriguing problem, especially when it concerns homothallic haplonts, like the fungus Aspergillus nidulans. In this fungus asexual and sexual offspring have largely identical genotypes. This genetic model organism is an ideal tool to measure possible fitness effects of sex (compared to asex) resulting from causes other than recombination. In this article we show that slightly deleterious mutations accumulate at a lower rate in the sexual pathway than in the asexual pathway. This secondary sex advantage may contribute to the persistence of sexual spores in this fungus. We propose that this advantage results from intra-organismal selection of the fittest gametes or zygotes, which is more stringent in the costly sexual pathway.

Aspergillus nidulans↗
PubMed2003

The role of preimplantation genetic diagnosis in women of advanced reproductive age.

PURPOSE OF REVIEW: More than half of in-vitro fertilization patients are of advanced reproductive age and at risk for producing offspring with age-related aneuploidies, which contribute significantly to spontaneous abortions and implantation failure. RECENT FINDINGS: Fluorescent in-situ hybridization analysis of thousands of oocytes and preimplantation embryos obtained from these patients revealed an aneuploidy rate of over 50%, suggesting practical relevance of preimplantation genetic diagnosis for aneuploidy to women of advanced reproductive age. The overall preimplantation genetic diagnosis experience for age-related aneuploidies comprising more than 3000 clinical cycles indicates the positive impact of preselection and transfer of aneuploidy-free embryos on implantation and pregnancy rates and outcome of pregnancies in women of advanced reproductive age. SUMMARY: These patients will need to be informed about preimplantation genetic diagnosis availability, in order use this option to improve their relatively poor chances of becoming pregnant, especially with the current tendency of limiting the number of transferred embryos to avoid complications due to multiple pregnancies. This may contribute significantly to improving standards of assisted reproduction technology, substituting the current practice of selection of embryos for transfer using morphological parameters with the preselection of aneuploidy-free embryos with a higher potential to result in pregnancy.

Adult↗
PubMed2005

New insights into the genetic diversity of European porcine reproductive and respiratory syndrome virus (PRRSV).

The complete ORF5 sequences of 66 porcine reproductive and respiratory syndrome (PRRS) field virus strains (1991-2001) and three European modified live vaccine strains were determined, as well as ORFs 6 and 7 of 19 selected strains. The variability of the deduced ORF5 amino acid sequences was analysed using statistical process control (SPC), allowing for the objective assessment of variable and conserved regions. Four variable and four conserved regions as well as five hypervariable amino acid positions were defined. The effects of genetic variability on possible structural and functional properties were discussed with emphasis on immunogenic features. Phylogenetic analysis and pairwise comparison of the nucleotide sequences revealed that the genetic distances between the strains has greatly increased over time. The data do not support an evolutionary influence of the geographical location or the time of sample collection, nor of PRRSV vaccination on strain development. In contrast to other authors who tended to concentrate on the samples from either a common geographic origin or a short sampling period, we could not confirm geographically separate PRRSV clusters nor did we find evidence of positive selective pressure as measured by the ratio of synonymous to non-synonymous substitutions in ORF5, 6 or 7. Immunological implications and vaccination strategies are discussed.

Amino Acid Sequence↗