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PubMed2003

The cryopreservation of ovarian tissue: uses and indications in veterinary medicine.

Animal experiments have shown that cryopreservation of the ovarian cortex, containing primordial follicles, could be used to preserve gametes thereby restoring fertility in humans and animals. During the last 100 years, many hundreds of species have been lost, and a third of the breeding animals are threatened with extinction. To preserve genetic diversity, notably for the conservation of endangered species, it is essential to conserve female and male gametes. Today, biotechnologies such as artificial insemination and embryo transfer are used in breeding programs and are well developed. However, even using these advanced techniques, there are problems due to the limited number of individuals used as the source of gametes, so that the risk of inbreeding is high, even in large populations. To preserve genetic diversity, it is necessary to create gene banks of male and female gametes and embryos, using a very large number of individual donors. Cryopreservation of ovarian tissue could present a means for enlarging the gene pool. Cryopreserved ovarian tissue could be used in auto- or xenografts, or for in vitro maturation (IVM) of primordial follicles. In this review, we describe the processes for cryopreservation of ovarian tissue and the various possibilities for using it.

Animals↗
PubMedDate not supplied

Genes as gerontological variables: genetically heterogeneous stocks and complex systems.

In gerontological research utilizing animal models, a major general strategy has been the use of uniform genotypes of inbred strains or their F1 hybrids. These animal models provide standard reference groups that are of major importance in establishing a reliable data base on aging phenomena. There are limitations to their usage, however, particularly in respect to descriptions or evaluations of variances or of covariance relationships. For these purposes, genetically heterogeneous stocks have the advantage that phenotypic variance (and covariance) has a genetic as well as an environmental component. The advantages of genetic heterogeneity are best realized when the stock has been systematically derived (usually by intercrossing of inbred strains) and maintained by a mating scheme of sufficient size to minimize inbreeding. Genetically heterogeneous stocks are of particularly high potential value in the study of complex systems. Some examples of their use in a gerontological context are provided.

Aging↗
PubMed2002

On the occurrence of Leydig cell tumors in the F344 rat.

Dunning began inbreeding, what is now the Fischer F344 rat, in 1931. Because of her publications showing a low incidence of spontaneous tumors to 35 months of age, we selected the F344 rat for most of the studies in the National Cancer Institute (NCI) Bioassay Program, beginning in 1964. We were surprised by the finding that untreated male F344 rats displayed a high incidence of Leydig cell tumors of the testes beginning at about 17 months of age. The key difference between the results of Dunning and the NCI Bioassay Program was that her animals were retired breeders, whereas the NCI studies utilized virgin rats. The question of breeding was, therefore, examined as a possible protective factor. Groups of male F344 CDF/Crl rats were kept as virgin animals, or permitted access to bilaterally tube ligated female F344/Crl rats that were replaced twice over a 52-week period. At that time, all males from both groups were housed three per cage to 85 weeks when they were killed in a CO(2) atmosphere and necropsied. Sections were prepared from the fixed tissues, stained and studied by histopathology. The results were evaluated by appropriate statistical methods. Virgin and sexually active F344 rats displayed monolateral or bilateral Leydig cell tumors. There was no statistical difference between the two groups. Despite the early difference between breeding and virgin F344 rats, a control experiment failed to disclose an effect of sexual activity on the occurrence of Leydig cell cancers. This disease displays some difference in incidence in various parts of the world, with the higher socioeconomic groups having a greater incidence. Etiological factors on the occurrence of this disease in animals and in humans remain to be discovered.

Animals↗
PubMed2000

Genetically caused retarded growth in animals.

Growth process of animals is regulated by a multitude of physiological pathways among which components of the somatotropic axis play a key role. A number of severe, simply inherited growth disturbances have been identified in humans, laboratory and farm animals. These disorders are controlled by defective alleles at major loci referring to hormones or hormone receptors, e.g. growth hormone receptor for the recessive sex-linked dwarfism (dw) in chickens and the recessive autosomal Laron-type dwarfism in man, and growth hormone releasing hormone receptor for the recessive "little" mutation (lit) in mice. Apart from these particular cases, growth rate is a quantitative polygenic trait which has a moderate heritability (close to 0.30) and is influenced by prenatal and postnatal maternal effects. Increase in the average coefficient of inbreeding in a population is also known to result in lower growth rate. Divergent selection experiments have shown that upward or downward selection on growth is effective, sometimes with asymmetrical responses, but patterns of changes in underlying physiological traits appear to differ among experiments.

Alleles↗
PubMed2003

Cholesterol and copper in the liver of rabbit inbred strains with differences in dietary cholesterol response.

In order to investigate whether cholesterol intake influences the hepatic copper content of rabbits, we compared the hepatic copper content of two rabbit inbred strains after feeding the animals a control or a cholesterol-rich diet. One strain was not reactive to dietary cholesterol (IIIVO/JU), whereas the other strain was reactive to dietary cholesterol (AX/JU). The coefficient of inbreeding (F) >0.95 for both strains. Dietary cholesterol-reactive rabbits when compared with their non-reactive counterparts had a higher hepatic copper content. The consumption of a hypercholesterolemic diet decreased liver copper concentration (expressed in micro g/g dry weight) in both strains of rabbits, which was (in part) due to dietary-induced hepatomegaly. A decrease in the absolute hepatic copper content was found only in the dietary cholesterol-reactive inbred strain. It is discussed that differences in glucocorticoid levels may be responsible for the strain difference in liver copper content. The cholesterol effect on the hepatic copper content in the reactive strain might be caused by an increased bilirubin secretion.

Animals↗
PubMed2001

Breeding systems and genome evolution.

The profound effects of inbreeding and other non-recombining breeding systems on genetic variability and molecular evolution are now beginning to be understood. Theoretical models predict how such populations are expected to differ from outcrossed populations, and DNA sequence data are being collected and used to test the predictions.

Animals↗
PubMed2001

Evolution of gametocyte sex ratios in malaria and related apicomplexan (protozoan) parasites.

'Survival of the fittest' is usually interpreted to mean that natural selection favours genes that maximize their transmission to the next generation. Here, we discuss recent applications of this principle to the study of gametocyte sex ratios in malaria and other apicomplexan parasites. Sex ratios matter because they are an important determinant of fitness and transmission success -- and hence of disease epidemiology and evolution. Moreover, inbreeding rates can be estimated from gametocyte sex ratios. The sex ratio is also an excellent model trait for testing the validity of important components of what is being marketed as 'Darwinian medicine'.

Adaptation, Physiological↗
PubMed1995

Response to selection from new mutation and effective size of partially inbred populations. II. Experiments with Drosophila melanogaster.

Divergent artificial selection for abdominal bristle number in Drosophila melanogaster has been carried out starting from a genetically homogeneous base population. Lines with two different systems of mating, random (P lines) or between full sibs whenever possible (about 50%), random otherwise (I lines) were compared. Responses after 40 generations of selection were mostly due to one or two mutations of large effect (0.2 to 2 phenotypic standard deviations) per line. Ten mutations affecting the selected trait were individually studied (five lethal and five non-lethal, these being predominantly additive). These mutations satisfactorily explain the response attained, although some minor mutations may also be involved. No evidence of epistasis for bristle number was found. The average final divergence was 57% larger in the P lines, but it was mostly due to lethals or highly deleterious mutations. Thus, after relaxation of selection, the ranking reversed and the mean divergence became significantly larger in the I lines (14%). Analysis of inbreeding showed that the very small amount of variation created by spontaneous mutations (a heritability for the selected trait of about 3%) was responsible for a reduction in the effective size of about 50% in the I lines (relative to the case with random selection), but only about 10% in the P lines. Mutational heritabilities estimated from the response to selection (0.05-0.18%) were within the range usually found for this trait in previous experiments. REML estimates account for correlations between relatives, and were much larger in those lines where the response was due to lethal mutations, as these do not contribute to response after reaching maximum frequency.

Animals↗
PubMed2001

Biodemographic study of a central Apennine area (Italy) in the 19th and 20th centuries: marriage seasonality and reproductive isolation.

This study investigates seasonality of marriages and reproductive isolation in six long-isolated communities in the central Apennines (Italy). It had two objectives: (1) the identification of an Apennine biodemographic model in comparison with mountain communities of other regions, and with non-Apennine communities in Abruzzo, and (2) to identify the possible effects of the drainage of Lake Fucino (1854-1876) on that area. Marriages in this region show two very stable seasonal patterns: one is typical of sedentary rural societies, with summer migrations and marriages preferentially celebrated in the winter, and the other has marriages that are strongly concentrated in the summer months, i.e. between 75% and 93.5% of marriages were celebrated between June and October in these communities in the 1800s. These were traditionally pastoral communities with winter transhumance of the flocks and their shepherds towards the lowlands of southern Italy. In both groups, restrictions imposed by the Catholic Church do not seem to have affected the timing of marriages. Indeed, economic factors related to work activities seem to have had more influence. Concerning reproductive isolation, the results show high rates of endogamy: between 85% and 98% in both the 19th and 20th centuries. Rates of consanguineous marriages were between 5% and 20%, and those of isonymous marriages rarely exceeded 9%. The coefficient of inbreeding a shows that there was a delayed, limited period of increased consanguinity in the few decades around the turn of the century. This is different from the national situation, and thus could be a consequence of the Lake Fucino drainage.

Altitude↗
PubMed1975

On some theoretical studies on gene differentiation in natural populations.

Different mathematical approaches to study the extent of genetic variation of natural populations are reviewed. The modern understanding of the gene structure permits new interpretations of existing concepts like fixation or inbreeding. A more recent measure of genic divergence, which at molecular level is designed to measure net codon differences is also seen to be related with gene diversity in a substructed population. It is argued that such variations are produced and preserved possibly by simultaneous action of migration, mutation, selection, and random genetic drift. At the present moment it is very difficult to isolate out the effect of each factor because of varying degrees of variation at the different gene sites and between different sets of populations.

Biological Evolution↗
PubMed2001

Selective recovery of founder genetic diversity in aquacultural broodstocks and captive, endangered fish populations.

Hatchery broodstocks used for genetic conservation or aquaculture may represent their ancestral gene pools rather poorly. This is especially likely when the fish that found a broodstock are close relatives of each other. We re-analysed microsatellite data from a breeding experiment on red sea bream to demonstrate how lost genetic variation might be recovered when gene frequencies have been distorted by consanguineous founders in a hatchery. A minimal-kinship criterion based on a relatedness estimator was used to select subsets of breeders which represented the maximum number of founder lineages (i.e., carried the fewest identical copies of ancestral genes). UPGMA clustering of Nei's genetic distances grouped these selected subsets with the parental gene pool, rather than with the entire, highly 'drifted' offspring generation. The selected subsets also captured much of the expected heterozygosity and allelic diversity of the parental gene pool. Independent pedigree data on the same fish showed that the selected subsets had more contributing parents and more founder equivalents than random subsets of the same size. The estimated mean coancestry was lower in the selected subsets, meaning that inbreeding in subsequent generations would be lower if they were used as breeders. The procedure appears suitable for reducing the genetic distortion due to consanguineous and over-represented founders of a hatchery gene pool.

Alleles↗
PubMed1999

Rehousing periadolescent male guinea pigs (Cavia porcellus) apart from their mothers for 24 hours increases maternally directed sexual behavior and plasma testosterone.

Periadolescent male guinea pigs (Cavia porcellus) housed continuously with their mother displayed little or no sexual behavior when they were tested with her in a novel environment. However, if males were rehoused without their mother for 24 hr before testing, they frequently directed courtship and sexual behavior toward her. This effect occurred whether the mother was isolated or not during the rehousing period. In addition, rehousing without the mother produced a significant rise in the plasma testosterone levels of the males. It appears that continuous housing with the mother inhibits sexual and courtship behavior directed toward her, as well as gonadal activity, in periadolescent male guinea pigs. These effects may serve to prevent inbreeding.

Animals↗
PubMed1981

Effects of domestication on production and perception of mallard maternal alarm calls: developmental lag in behavioral arousal.

The process of domestication involves intense inbreeding. Field and laboratory studies were conducted to assess the effects of such intense genetic selection on the production and perception of the maternal alarm calls of domestic (Peking) and wild mallard ducks (Anas platyrhynchos). With respect to production, the calls of wild and domestic ducks were comparable in four acoustic features and differed only slightly on two features. With respect to perception, the calls of wild and domestic hens were equally effective in promoting behavioral inhibition in wild and domestic ducklings. Although these data revealed little or no effect of domestication on the structure and function of the maternal alarm call, an unexpected effect was found regarding the domestic ducklings' behavior. Specifically, Pekings showed a greater level of behavioral inhibition than did mallards at 24 hr of age. Further experiments indicated that the differential level of inhibition in the wild and domestic birds reflects a developmental lag in arousal consequent to domestication: 72-hr-old Peking ducklings are behaviorally more aroused than 24-hr-old Peking ducklings and are similar to 24-hr-old mallard ducklings in that respect. This appears to be the first demonstration of behavioral heterochrony, which is believed to be an important mechanism of behavioral evolution.

Animals↗
PubMed1982

Altered salivary amylase gene in the mouse strain BXD-16.

An electrophoretic salivary amylase variant in the recombinant inbred mouse strain BXD-16 segregated in crosses as an allele at the salivary amylase locus. No other strain was found with the same combination of electrophoretic types of salivary and pancreatic amylase, and no sign of contamination by foreign genes from other strains was found. The variant therefore seems to have arisen during the inbreeding of the strain by a genetic alteration in the amylase complex. Purified variant amylase had a lower heat stability and an altered net charge of one or more CNBr fragments, but had the same size distribution of peptides from restricted proteolysis and CNBr cleavage as salivary amylase from the progenitor strains. Radioactive pulse labelling of the variant amylase showed that its relative rate of synthesis was the same as that in the progenitor strains. The variant is therefore, most likely, the result of a missense mutation that has altered the structure of all the salivary amylase produced in the strain. This indicates that only a single structural gene for the enzyme is expressed in the strain BXD-16.

Amylases↗
PubMed1988

Breeding structure of a colonising species: Aedes albopictus (Skuse) in the United States.

Allelic and genotypic frequencies were monitored at seven enzymatic loci in newly established Aedes albopictus (Skuse) populations in the United States. Populations were sampled within the cities of New Orleans, Louisiana, Houston, Texas, three counties surrounding Houston, Memphis, Tennessee, Jacksonville, Florida, and Evansville and Indianapolis, Indiana. Unique alleles and relatively high levels of heterozygosity were detected in New Orleans, Houston, surrounding counties and Indianapolis suggesting relatively large and independent introductions in these cities. No unique alleles and low heterozygosities were detected in Memphis, Evansville and Jacksonville suggesting that a population bottleneck may have accompanied the founding of these populations. The bottleneck may have resulted from a small number of founding individuals or may have been generated through repeated control efforts. Genetic distance estimates indicated that Houston, New Orleans and Indianapolis were genetically similar. Evansville and Memphis were also found to be similar. Significant differentiation of allele frequencies existed among and within cities. Variance in allele frequencies among all samples was partitioned into the variance among cities and among locations within cities. Most of the variance was attributable to local differentiation. The most parsimonious explanation of this result is that much genetic drift accompanied the establishment of local populations in cities and that there has been little subsequent gene flow. Analysis of genotypic frequencies detected a slight but consistent excess of homozygotes suggesting inbreeding.

Aedes↗
PubMed2006

Compartmentalization of S-RNase and HT-B degradation in self-incompatible Nicotiana.

Pollen-pistil interactions are crucial for controlling plant mating. For example, S-RNase-based self-incompatibility prevents inbreeding in diverse angiosperm species. S-RNases are thought to function as specific cytotoxins that inhibit pollen that has an S-haplotype that matches one of those in the pistil. Thus, pollen and pistil factors interact to prevent mating between closely related individuals. Other pistil factors, such as HT-B, 4936-factor and the 120 kDa glycoprotein, are also required for pollen rejection but do not contribute to S-haplotype-specificity per se. Here we show that S-RNase is taken up and sorted to a vacuolar compartment in the pollen tubes. Antibodies to the 120 kDa glycoprotein label the compartment membrane. When the pistil does not express HT-B or 4936-factor, S-RNase remains sequestered, unable to cause rejection. Similarly, in wild-type pistils, compatible pollen tubes degrade HT-B and sequester S-RNase. We suggest that S-RNase trafficking and the stability of HT-B are central to S-specific pollen rejection.

Antibodies↗
PubMed2006

Self-incompatibility in Papaver targets soluble inorganic pyrophosphatases in pollen.

In higher plants, sexual reproduction involves interactions between pollen and pistil. A key mechanism to prevent inbreeding is self-incompatibility through rejection of incompatible ('self') pollen. In Papaver rhoeas, S proteins encoded by the stigma interact with incompatible pollen, triggering a Ca2+-dependent signalling network resulting in pollen tube inhibition and programmed cell death. The cytosolic phosphoprotein p26.1, which has been identified in incompatible pollen, shows rapid, self-incompatibility-induced Ca2+-dependent hyperphosphorylation in vivo. Here we show that p26.1 comprises two proteins, Pr-p26.1a and Pr-p26.1b, which are soluble inorganic pyrophosphatases (sPPases). These proteins have classic Mg2+-dependent sPPase activity, which is inhibited by Ca2+, and unexpectedly can be phosphorylated in vitro. We show that phosphorylation inhibits sPPase activity, establishing a previously unknown mechanism for regulating eukaryotic sPPases. Reduced sPPase activity is predicted to result in the inhibition of many biosynthetic pathways, suggesting that there may be additional mechanisms of self-incompatibility-mediated pollen tube inhibition. We provide evidence that sPPases are required for growth and that self-incompatibility results in an increase in inorganic pyrophosphate, implying a functional role for Pr-p26.1.

Inbreeding↗
PubMed2002

Genome-wide deleterious mutation favors dispersal and species integrity.

Here I develop the idea that ubiquitous harmful genome-wide mutation with local differentiation favors dispersal, even though migration reduces average fitness. Historical contingency of the mutational process means that demes (sub-populations) differentiate from one another. Deleterious or lethal partially recessive mutations carried by migrants then do not encounter similar mutations in the recipient deme. Migrant offspring have higher fitness than offspring of residents, because migrant offspring are heterozygous rather than homozygous for harmful mutations. The advantage is inversely related to local inbreeding depression. Genome-wide deleterious mutation favors the evolution of dispersal, which in turn enhances the genetic integrity of the species.

Animals↗