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PubMed1996

[Comparative analysis of morphologic traits in Mediterranean and Chinese chicken breeds. The problem of the origin of the domestic chicken].

The degree of similarity between chicken breeds of Mediterranean and Chinese origin, on one hand, and red jungle fowl (Gallus gallus), on the other, was determined with respect to 35 discrete morphological traits. The results confirm the similarity between Mediterranean breeds and the wild form of Gallus gallus, noticed by many authors, and demonstrate the considerable typological diversity of Chinese chicken breeds. As certain ancient Chinese breeds clustered with Mediterranean breeds and wild fowl, the conclusion was drawn concerning the existence in ancient times of a chicken originating in Asia but resembling the Mediterranean type. This fact and several archeological findings provide evidence that the archetypal domestic chicken was of the light egg type. Centers of the origin and formation of domestic chicken types proved to coincide with certain centers of the origin of cultivated plant varieties discovered by N.I. Vavilov.

Animals↗
PubMed1997

Influences of breed, sex, and susceptibility to malignant hyperthermia on lipid composition of skeletal muscle and adipose tissue in swine.

OBJECTIVE: To determine influences of breed, sex, and susceptibility to malignant hyperthermia on composition of skeletal muscle and adipose tissue in swine. ANIMALS: 35 male and female swine of German Landrace and Pietrain breeds and of 2 genotypes, normal (MHN) and susceptible to malignant hyperthermia (MHS). PROCEDURE: Pigs were fed a standard diet ad libitum. After attaining body weight of approximately 100 kg, pigs were slaughtered and skeletal (longissimus thoracis and supraspinatus) muscle and adipose tissue (3 sites) specimens were removed. For each specimen, lipids were extracted by chloroform/methanol and fatty acid (FA) pattern, and cholesterol concentration was determined by gas chromatography. RESULTS: The overall lipid contents differed significantly between breeds and genotypes; the MHS Pietrain pigs had the lowest lipid quantities. The relative amounts of saturated FA in all tissues were highest in Landrace pigs (P < 0.05), whereas the relative contents of monoenic FA were lower. In addition, for both breeds, the MHN pigs had significantly higher saturated and lower polyunsaturated FA values in all tissues, compared with MHS pigs. More specifically, MHS females of both breeds had the highest relative amounts of polyunsaturated FA. In general, relative cholesterol contents were found to vary little between identified groups. CONCLUSIONS: These data may indicate that, not only does mutation of the calcium release channel of the sarcoplasmatic reticulum, which occurs in MHS swine, influence secondary changes in lipid composition, but so do hormone concentrations and other genotypic factors. Observed differences in lipid content and FA composition could consequently influence specific membrane properties, such as fluidity and cell signaling.

Adipose Tissue↗
PubMed1999

Multigeneration reproductive toxicity assessment of 60-Hz magnetic fields using a continuous breeding protocol in rats.

Male and female reproductive functions have been proposed as possibly sensitive targets for the biological effects of 60-Hz (power frequency) magnetic fields (MF). However, experimental data relevant to this hypothesized association are very limited. In the present study, the "reproductive assessment by continuous breeding" design was used to identify possible effects of MF exposure on reproductive performance, fetal development, and early postnatal growth in rats. Groups of age-matched Sprague-Dawley rats (40 breeding pairs/group) were exposed continuously (18.5 hr per day) to linearly polarized, transient-free 60-Hz MF at field strengths of 0 Gauss (G; sham control), 0.02 G, 2.0 G, or 10.0 G. An additional group of 40 breeding pairs received intermittent (1 hr on/1 hr off) exposure to 10.0 G fields. F0 breeding pairs were exposed to MF or sham fields for 1 week prior to mating, during a 14-week period of cohabitation, and during a 3-week holding period after cohabitation. The duration of the cohabitation period was selected to be sufficient for the delivery of five litters in the sham control group. Pups from the final F1 litter from each breeding pair were exposed to MF or sham fields until sexual maturity, were cohabitated in MF or sham fields for 7 days with nonsiblings from the same exposure group, and were held in the MF or sham fields for 22 days to permit delivery of F2 pups for evaluation. No evidence of exposure-related toxicity was identified in any rat in the F0, F1, or F2 generations. Fetal viability and body weights in all litters of groups exposed to MF were comparable to those of sham controls. No significant differences between sham controls and MF-exposed groups were seen in any measure of reproductive performance (litters/breeding pair, percent fertile pairs, latency to parturition, litter size, or sex ratio) in either the F0 or F1 generation. Exposure of Sprague-Dawley rats to 60-Hz MF strengths of up to 10.0 G either during their peak reproductive period (F0) or during gestation and throughout their life span (F1) has no biologically significant effects on reproductive performance. These results do not support the hypothesis that exposure to pure, linearly polarized 60-Hz MF is a significant reproductive or developmental toxicant.

Animals↗
PubMed2002

Morphological and hormonal parameters in two species of macaques: impact of seasonal breeding.

To compare physiological and developmental differences between two cogeneric species that differ by seasonal vs. aseasonal breeding, values for morphological measurements, testicular volume, serum testosterone, estradiol, and dehydroepiandrosterone-sulfate levels were obtained from 53 rhesus during the early breeding season, as well as 41 pig-tailed macaque males maintained at the Tulane Primate Center. The two species exhibited similar body size, testosterone, and estradiol levels, but differed substantially in testicular volume (3.00 +/- 1.7 vs. 1.72 +/- 1.3 cc), abdominal skinfold measures (15.7 +/- 9.2 vs. 9.0 +/- 7.7 mm), and DHEA-S levels (18.0 +/- 11.7 vs. 7.6 +/- 5.4 microg/dl). Significant interaction effects for species by age group were found for weight, tricep circumference, length, and estradiol level. In addition, length was more closely related to testicular volume among rhesus compared to pig-tailed macaques, suggesting different developmental patterns between the species. Predictors of hormonal levels differed between the two species. In the rhesus, estradiol levels were related to testicular volume and testosterone levels while there were no anthropometric predictors of testosterone or DHEA-S. For the pig-tailed macaques, testicular volume was related to tricep circumference, testosterone to triceps skinfold and testicular volume, and estradiol to weight. It is argued that rhesus have larger testes for body size and more abdominal fat deposits during the early breeding season relative to pig-tailed macaques reflecting the increased demands of sperm competition in a seasonally breeding species. Hormonal differences associated with the difference in breeding system appear to be primarily related to adrenal rather than testicular activity.

Adjuvants, Immunologic↗
PubMed2000

Territorial intrusions and copulation patterns in red kites, Milvus milvus, in relation to breeding density.

Two main paternity assurance strategies are generally found in birds: mate guarding and frequent copulations. The latter is expected particularly in species such as raptors that cannot guard their mates efficiently because of ecological constraints, such as frequent courtship feeding. I investigated the prelaying behaviour of red kites, in which the males courtship feed. I compared pair behaviour in situations of varying breeding density and simulated male territorial intrusions by presenting decoys. Males' certainty of paternity was likely to decrease with increasing breeding density, because of the proximity of other males and more frequent male territorial intrusions during the presumed fertile period. The percentage of time spent by males within their breeding territory during the prelaying period was positively related to the number of close breeding neighbours, suggesting territory surveillance and mate guarding. The kites copulated frequently and over a long period. Copulation frequency prior to and during laying increased with breeding density, and in isolated pairs in response to simulated male territorial intrusions. The results support the idea of paternity assurance through frequent copulations during the presumed fertile period of the female, and suggest that early copulation activity is related to functions other than fertilization, such as pair bonding or mate assessment. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1996

Changes in bioactive prolactin-like activity in plasma and its relationship to incubation behavior in breeding ring doves.

Previous radioimmunoassay (RIA) data indicate that plasma prolactin (PRL) is elevated during the late incubation and the early posthatching periods of the ring dove breeding cycle. Although these changes are temporally associated with changes in PRL-dependent crop sac growth, the precise relationship between immunoreactive and bioactive PRL has not been directly examined. To investigate this question and to further explore the relationship between sitting behavior and PRL secretion, we used rat Nb2 lymphoma cell proliferation to estimate the concentration of bioactive PRL-like activity (PLA) in the plasma of breeding ring doves. Serial dilutions of dove pituitary homogenate and dove plasma stimulated mitogenic responses that were parallel to those observed with purified ovine PRL. Changes in plasma PLA during the breeding cycle closely resembled changes in PRL that have been previously reported by RIA, although the relative changes in PLA were more pronounced. In both sexes, PLA remained at basal levels prior to egg laying and during early incubation (Day 4-5) but then abruptly increased to reach peak values near the time of hatching (Day 14-15). Activity remained high for 3-4 days after hatching, declined gradually thereafter, and returned to baseline values by Posthatching Days 14-17. Plasma PLA levels of birds sampled at the end of incubation were correlated with those of their breeding partners. In the majority of pairs, females had higher PLA levels than their mates at this stage even though no significant overall sex differences in PLA levels were observed. Plasma PLA declined precipitously in birds that were nest deprived on the last day of the incubation period. Nevertheless, plasma PLA levels of normally breeding birds at the end of incubation were not correlated with the average time spent in the nest during the incubation period. However, day-to-day variability in time spent in the nest correlated negatively with plasma PLA in incubating males, and females exhibited a similar trend that approached significance. These data suggest (1) that published RIA estimates of PRL are reasonably accurate reflections of changes in bioactive PLA in dove plasma and (2) that while sitting duration itself is not strongly related to plasma PLA, large day-to-day fluctuations in nest occupation time are associated with reduced PLA levels in incubating doves.

Animals↗
PubMed2000

Year-class differences in the reproductive system, plasma prolactin and corticosterone concentrations, and onset of prebasic molt in male dark-eyed juncos (Junco hyemalis) during the breeding period.

Year-class differences in reproductive function were investigated in a free-living population of adult male Dark-eyed Juncos, Junco hyemalis, breeding in interior Alaska. Second-year males (SY, entering their first breeding season) were compared with after-second-year males (ASY, entering at least their second breeding season). We measured body mass, size of the cloacal protuberance (CP), testis mass, onset of prebasic molt, and concentrations of plasma luteinizing hormone (LH), testosterone (T), corticosterone (CORT), and prolactin (PRL) throughout the reproductive season (April to mid-July). There were no differences in SY and ASY body weights but SY males had smaller CPs and testis masses than ASY males during gonadal recrudescence and at the end of the breeding season. Plasma LH was elevated from April until mid-June and then decreased in the same way in both year classes. In contrast, plasma T was high from April until mid-May and was lower in SY than in ASY juncos shortly after they arrived on their breeding grounds at the end of April, but not at other times. In July, SY males started to molt earlier, suggesting that they became photorefractory earlier than ASY males. Plasma PRL increased progressively in both year classes between April and early June and decreased in early July. At this time, plasma PRL decreased earlier in SY than in ASY males. Plasma CORT changed seasonally, but did not differ between SY and ASY juncos. Thus, year-class differences in CP sizes and testis mass apparently did not result from SY males secreting less LH or more PRL or CORT than ASY males. It is suggested that differences in reproductive condition in SY and ASY juncos are mediated by interactions with conspecific birds and do not result from an intrinsic effect of age.

Animals↗
PubMed1995

Behavioral and hormonal changes in female naked mole-rats (Heterocephalus glaber) following removal of the breeding female from a colony.

Colonies of naked mole-rats (Heterocephalus glaber) contain a single dominant, breeding female, or "queen", which suppresses reproduction in subordinate females. In this study, the queen and breeding male were removed from a colony at Brookfield Zoo. We examined behavioral and endocrine changes in the remaining colony females. Behavioral observations were conducted weekly and urine samples were collected beginning 3 months prior to the planned removal of animals. Prior to the removal, only the queen displayed the high frequencies of aggressive shoving typical of breeding females. In the first 2 months following removal of the queen, three non-breeding females markedly increased their frequencies of shoving. Urinary progesterone showed that one of three females had probably ovulated both before and after queen removal. Histological examination following fatal agonistic interactions confirmed ovulatory function in two of these three females. Similar behavioral and endocrinological results were obtained for three more females, following the combat deaths of the first three females. These findings suggest that ovarian activation facilitates intrasexual aggression in female naked mole-rats and might contribute to attainment of breeding status.

Aggression↗
PubMed1999

The roles of stimuli from young, previous breeding experience, and prolactin in regulating parental behavior in ring doves (Streptopelia risoria).

In addition to stimulating crop "milk" formation in ring doves, prolactin (PRL) may promote the parental regurgitation behavior that transfers this "milk" to the young at the time of hatching. Although earlier studies suggest that previous breeding experience is an important modulator of PRL-induced parental regurgitation behavior in ring doves, the ways in which experience, hormones, and stimuli from young interact to promote parental behavior have not been well characterized in this species. In the first study, untreated, nonbreeding female doves with and without previous breeding experience were given 10 daily parental behavior tests (2 h/day) with a hungry 5- to 10-day-old foster squab. Experienced females exhibited a higher incidence of regurgitation behavior, defensive behavior, and crouching or sitting in the nest than did inexperienced females. In a second study, nonbreeding females were given 10 daily tests for parental behavior while they received sc injections of ovine PRL or vehicle. Prolactin reduced squab-directed aggression and increased the incidence of regurgitation feeding behavior of foster squabs in both experienced and inexperienced females. However, the average number of regurgitation feeding acts displayed by those PRL-treated females that showed the behavior was over eight times higher in experienced females than in inexperienced females. Previous experience also enhanced the stimulatory effects of PRL on defensive behavior and crouching or sitting in the nest. The parental behavior exhibited by nonbreeding, PRL-treated experienced females was qualitatively and quantitatively similar to that observed in normally breeding females during a single test with their own hungry 5- to 10-day-old squabs. These findings indicate that PRL and previous breeding experience both enhance the parental responsiveness of nonbreeding female doves and that under optimal hormonal, experiential, and squab exposure conditions, nonbreeding doves exhibit levels of parental activity that rival those of normally breeding parents.

Animals↗
PubMed2001

Patterns of testosterone and prolactin concentrations and reproductive behavior of helpers and breeders in the cooperatively breeding red-cockaded woodpecker (Picoides borealis).

We examined the proximate causes of delayed breeding and alloparental behavior in the cooperatively breeding red-cockaded woodpecker by measuring plasma concentrations of testosterone (T) and prolactin (PRL) in female breeders, male breeders, and male helpers during different stages of the reproductive cycle. Male breeders and helpers have low T during the prebreeding period, highest T during copulation, and low concentrations of T during the egg-laying/incubation and nestling provisioning stages. Helpers appear physiologically capable of reproducing; their T concentrations equal that of male breeders. Helpers unrelated to the breeding female have higher T than helpers sharing a territory with their mother. Sexual inactivity by male helpers might be explained by behavioral suppression resulting from interactions of male helpers with the breeding pair that somehow differ in accordance with the helper's relatedness to the breeding female (e.g., female breeders are generally unreceptive to courtship from male helpers and least receptive to related helpers). Female breeder, male breeder, and male helper PRL levels did not differ and increased from the prebreeding stage through the copulation and egg-laying/incubation stages. During the nestling provisioning stage, male breeder and helper PRL declined, while female PRL continued to increase. Based on these results, we conclude that the physiological bases of alloparental behavior have not diverged from those that mediate parental behavior in this species.

Animals↗
PubMed1994

Rare alleles, MHC and captive breeding.

In recent years, more detailed genetic information has become available for individuals of endangered species in captive breeding programs. There have been suggestions that this information be used to identify rare alleles, particularly those at the MHC, that can be subsequently selected for captive breeding programs. First, we summarize the current information on the MHC relevant to conservation genetics, so that such a possible breeding program is seen in a proper perspective. For example, very few specific alleles at the MHC have been identified as selectively advantageous, even though there has been substantial effort to find such alleles in humans and a few other organisms. Further, many of the balancing selection models suggested for MHC variation are based on heterozygotes in general having a higher fitness than homozygotes and not on specific selectively advantageous alleles. Because there is no detailed data on MHC variability in captive populations, we used transferrin data in Przewalski's horses to evaluate a breeding program to select for rare alleles. In this species, one individual, 1060, has been identified to have the transferrin allele J. We determine the effect on founder contribution of multiply mating 1060 to increase the number of copies of this allele. Since there were 485 individuals in the population at this time, this extra mating had little detrimental effect on the distribution of founder contributions and the number of founder equivalents. We then selected 65, an ancestor of 1060, which had a high likelihood of being the individual that passed on the J allele in the lineage of 1060. We examined the effect of increasing the number of copies of alleles of 65 at a time when the population had only 22 other individuals. In this case, even though the founder contributions were changed more, there was also little effect on the founder contributions and the number of founder equivalents. Overall, it appears that selection that results in a limited change in the number of copies of rare alleles may not always have an overall detrimental effect. However, because other pedigrees may have very different properties, it is essential to perform a detailed pedigree analysis of any such selective breeding program to determine its effect before such a selection program is implemented.

Alleles↗
PubMed2004

Metabolic control analysis as a mechanism that conserves genetic variance during advanced cycle breeding.

The recycling of elite inbreds (i.e., advanced cycle breeding) has led to significant genetic gains but also to a narrow gene pool in plant breeding programs. Sustained yield improvements in many crops have suggested that genetic variance is not depleted at a rate predicted by an additive genetic model. Unlike the additive model in classical quantitative genetic theory, metabolic control analysis relates the variation in a biochemical process with the genetic variation in a quantitative trait. Our objective was to determine whether metabolic control analysis is a mechanism that slows the decrease in genetic variance during advanced cycle breeding. Three cycles of advanced cycle breeding were simulated with 10, 50, or 100 quantitative trait loci (QTL) controlling a trait. In metabolic control analysis, these QTL coded for enzymes involved in a linear metabolic pathway that converted a substrate into a product. In the absence of selection, both the additive model and the metabolic control analysis model led to about a 50% reduction in genetic variance from cycle to cycle. With selection, the additive model led to a 50-58% reduction in genetic variance, but the metabolic control analysis model generally led to only a 12-54% reduction. We suggest selection in a metabolic control analysis model as a mechanism that slows the decrease in genetic variance during advanced cycle breeding. This conservation of genetic variance would allow breeders to achieve genetic gains for a longer period than expected under the additive model.

Conserved Sequence↗
PubMed2003

The effects of anti-androgenic and estrogenic disrupting contaminants on breeding gland (nuptial pad) morphology, plasma testosterone levels, and plasma vitellogenin levels in male Xenopus laevis (African clawed frog).

Nuptial pads are areas, digits, and forearm characterized by epidermal keratin hooks and dermal breeding glands opening on the epidermis surface in male frogs. The presence of the epidermal hooks and secretory activity of the breeding glands are androgen-dependent and considered functioning during mating. Chemical pollutants released into the aquatic environment by humans are suspected of disrupting the normal hormonal pathways and functioning. Among the best known of these endocrine-disrupting contaminants (EDCs) are compounds that mimic the steroid 17beta-estradiol. However, recently specific anti-androgenic activity by certain EDCs, including DDE and several fungicides, have been shown in mammalian studies. The African clawed frog, Xenopus laevis, has been proposed as an ideal species to be used as a model system for screening of endocrine disruptors. In this study we employed a newly developed ELISA for the measurement of plasma vitellogenin (VTG), normally produced in the liver of females under the influence of estrogens but also in males when exposed to exogenous estrogens. Furthermore, we investigated the potential of breeding (nuptial) gland activity to be employed as a biomarker system for screening for anti-androgenic activity by certain EDCs. Our results indicate that the pharmaceutic anti-androgen flutamide did significantly (p < 0.05) effect the androgen-dependent breeding (nuptial) glands and plasma testosterone concentrations in male X. laevis. Our results further confirm that the dicarboximide fungicide vinclozolin mimics the anti-androgenic action of flutamide. Vinclozolin, however, did not significantly effect the plasma testosterone concentration. Results also confirm the ability of 17beta-estradiol to stimulate production and release of VTG in the liver of male X. laevis, although we could not confirm the in vivo induction of VTG by estrogenic mimics octylphenol and nonylphenol. Although more dose-response research is needed, this preliminary study confirms the potential of VTG production and breeding gland activity as biomarkers to screen chemicals and environmental samples for estrogenic and anti-androgenic activity using X. laevis males.

Androgen Antagonists↗
PubMed2003

Tests of candidate genes in breed cross populations for QTL mapping in livestock.

In recent years, several F(2) crosses between outbred lines of livestock have been developed to identify quantitative trait loci (QTL). These populations are valuable for further genetic analysis, including positional candidate gene loci (CGL). Analysis of CGL in F(2) populations is, however, hindered by extensive between-breed linkage disequilibrium (LD). The objectives here were to develop and evaluate three tests for CGL in simulated F(2) breed-cross populations. 1) A standard association test, based on the fixed effect of CGL genotype. This test was significant for CGL at considerable distances from the QTL. 2) A marker-assisted association test, based on a test at the CGL of the fixed effect of CGL genotype in a breed-cross QTL interval mapping model. This removed the impact of between-breed LD, but was not powerful in detecting CGL closely linked to the QTL, unless the CGL was the QTL. 3) An F-drop test, comparing F ratios for a QTL at the CGL with and without the CGL included as fixed effect. It had low power to distinguish close from distant CGL. Power to distinguish two CGL within 10 cM from the QTL was limited and little improved by including QTL effects associated with markers to remove between-breed LD, although the power was greater when one of the CGL was the causative mutation. Therefore, while we conclude that candidate gene tests in QTL mapping populations must be interpreted with caution, we now have a clearer picture of the value of candidate gene tests in these populations.

Animals↗
PubMed2003

Breeding suppression in free-ranging grey-sided voles under the influence of predator odour.

The breeding suppression hypothesis predicts that females of certain small mammal species will reduce reproduction as a response to the odour of a specialised mammalian predator. This was tested in a field experiment with grey-sided voles (Clethrionomys rufocanus) during three summer seasons (1997-1999) in the subalpine tundra of northern Norway, which is a natural habitat of this species. In a first phase free-ranging voles in six unfenced 1-ha plots were monitored by live-trapping from June to August each year. In a second phase from August to September, three of the plots were sprayed with weasel (Mustela nivalis) odour to simulate increased apparent predation risk, while the remaining three plots served as untreated controls. On all plots voles were individually marked with ear tattoos and were regularly live-trapped during the whole breeding season to follow their performance. On the treatment plots the recruitment rate of juveniles did not increase in late summer as it did on the control plots. The proportion of reproductively non-active adult females was significantly higher on the treatment plots for both old and young females. Our results thus verify the breeding suppression hypothesis for the first time under natural conditions. However, the response in overwintered females is in conflict with the original hypothesis because the assumed fitness benefits from breeding delayed until the next season are inaccessible to them. As an alternative explanation we propose a short-term response of reduced activity and interrupted breeding until the predator has exploited and left the feeding patch. Such a "duck and cover" strategy would increase the fitness of females of all age classes when prey habitats are patchy.

Adaptation, Physiological↗
PubMed2005

Warmer springs advance the breeding phenology of golden plovers Pluvialis apricaria and their prey (Tipulidae).

Most studies of climate-driven changes in avian breeding phenology have focused on temperate passerines, yet the consequences of such environmental change may be more deleterious for other avian taxa, such as arctic and sub-arctic waders (Charadrii). We therefore examine large-scale climatic correlates of the breeding phenology of one such species (golden plover Pluvialis apricaria), and the timing of emergence of their adult tipulid prey, to assess the potential for climate change to disrupt breeding performance. Golden plover first-laying dates were negatively correlated with both March and April temperature, the mean laying date of first clutches was additionally negatively correlated with March rainfall. The timing of final laying dates were negatively correlated with April temperature only. The timing of tipulid emergence was negatively correlated with May temperature. In combination with historical climatic data, these models suggest a 9-day advancement of golden plover first-laying dates occurred during the 1990s, although this remains within the range of natural variation for the twentieth century. The magnitudes of predicted changes in mean and final laying dates, and the timing of tipulid emergence, were smaller. Climate predictions for 2070-2099 suggest potential advances in first-laying dates by 25 days, whilst the timings of mean and final laying dates are predicted to change by 18 days and 13 days, and tipulid emergence by 12 days. Given the importance of adult tipulids to young golden plover chicks, these changes may result in a mismatch between the timing of first-laying dates and tipulid emergence, so reducing the success of early breeding attempts. Modelling suggests that these changes could reduce breeding success in a South Pennines population by about 11%.

Animals↗
PubMed2006

Prion protein gene (PRNP) polymorphisms in Xinjiang local sheep breeds in China.

Amino acid polymorphisms of the prion protein (PrP) gene (PRNP), particularly those occurring at codons 136, 154, and 171 have a significant influence on scrapie pathogenesis in many sheep breeds. We isolated blood samples from 222 sheep representing the eight main local sheep breeds in the Xinjiang Autonomous Region, the territory with the most abundant local sheep breeds in China, to identify the PRNP polymorphisms and to determine whether these breeds were at risk for developing scrapie. A new PRNP polymorphism encoding either glycine (G) or arginine (R) at codon 85 as well as eight previously reported polymorphisms at codons 101, 112, 127, 141, 146, 154, 171, and 189 in other sheep breeds were detected. Interestingly, the alanine (A)/V polymorphism at codon 136 was not observed in this study, all sheep being homozygous for A at this position. While the previously identified polymorphism of argine (R) or histidine (H) at codon 154 was detected, the H polymorphism was rare (2.25%). Four polymorphisms at codon 171 encoding glutamine (Q), R, H, or lysine (K) were detected. The predominant ARQ allele occurred at a high frequency of 77.48%, suggesting an increased risk of scrapie in Xinjiang Autonomous Region.

Alleles↗
PubMed1990

Changes in plasma levels of gonadotropins and sex steroids in the toad, Bufo japonicus, in association with behavior during the breeding season.

Plasma levels of gonadotropins and sex steroids in Bufo japonicus were surveyed at different behavioral stages during the breeding period in March. All hormone levels were lower in torpid toads, which were found underground 1 week before the start of the breeding migration, than in active toads in the breeding season, although the levels were higher than those in the other months. LH and FSH levels in toads migrating toward a breeding pond were still low or only slightly elevated. Gonadotropin levels increased markedly when toads arrived at the pond and were highest for individuals actually in the pond. These LH and FSH surges occurred in both sexes, although peak levels were higher in females. Gonadotropin levels decreased in individuals of both sexes when they left the pond after breeding ("landed" individuals). LH and FSH levels in solitary males were significantly lower than those in amplexing males. In females, there was no significant difference in the level of any hormone between amplexing and solitary individuals. Circulating testosterone increased to the highest level in migrating males; this elevated level was maintained after arrival in the pond. DHT in males showed a pattern similar to that of testosterone. Both androgens decreased to the lowest level in landed males. In females, estradiol was dominant during migration, while progesterone became dominant shortly after arriving near or in the pond. This progesterone surge coincided with the LH surge. Androgen may stimulate amplexus behavior in male toads, and then amplexus seems to induce the LH surge that is necessary for spermiation. In females, however, amplexus seems to have no direct correlation with the gonadotropin surge, and the LH surge may induce the progesterone surge which causes ovulation.

Animals↗