Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Reproductive Isolation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed1986

Males, parthenogenesis, and the maintenance of anisogamous sex.

The problem of the maintenance of anisogamous sex is addressed by considering the effect of fertilization on the fitness of parthenogenetic females when such fertilization yields inviable triploid progeny. We consider four types of parthenogenesis: (i) apomixis, (ii) homogametic amphimixis, (iii) heterogametic amphimixis, and (iv) homogametic automixis. Homozygous sexual populations are genetically stable if males or selection eliminate the excess females produced by heterozygous parthenogenetic genotypes. Homozygous parthenogenetic populations are stable if the parthenogenetic output of homozygotes exceeds that of heterozygotes. In turn, sex can only invade heterozygous parthenogenetic populations when sexual output of parthenogens is larger than their parthenogenetic output. The existence of interior stable equilibria generally requires the instability of at least one boundary and some degree of heterosis. In a two-locus model, we study the evolution of mechanisms protecting either sex or parthenogenesis in reproductively polymorphic populations. We find that males do not respond to the presence of parthenogenesis in such a way as to eliminate it, but parthenogenesis is subject to selective pressures increasing reproductive isolation, and thus the success of parthenogenesis. The results suggest that reproductively polymorphic populations are ephemeral.

Animals↗
PubMed1987

[The role of the cholinergic system in the regulation of blood flow through the reproductive organs of swine during the estrous cycle].

The flow in uterine artery (ua) and ovarian artery (oa) of isolated reproductive organs of sows (100-130 kg/head) perfounded with animal own blood and Krebs-Henseleit fluid at the constant pressure of 100 mm Hg was measured. Together with measuring the flow, the tension of the smooth muscle of organ was controlled. Applying acetylocholine (ACh), atropine (A), hexamethonium (H) and phentolamine (F) the analysis of the functions of muscarine (M) and nicotine (N) receptors of the cholinergic system in regulation of blood flow through the reproductive organs during the oestrous cycle was carried out. It was found that application of 0.3 microgram ACh into ua, and 0.5 microgram ACh into oa causes slight increase in the blood flow. Application of ACh in doses of 1 microgram into these vessels causes decrease of the flow and increase in tension and motorics of the organ. A eliminates the influence of ACh upon the tension and motorics of the studied organ and potencializes the decreasing influence of ACh applied in the dose of 1 microgram upon the blood flow. A decreases the flow limiting action of 1 microgram ACh upon the flow, and also eliminates the effect of decrease of flow caused by application of 1 microgram ACh after A. H potencializes the influence of small doses of ACh increasing the flow in ua and oa, but does not influence the flow limiting and tension increasing action of 1 microgram dose of ACh. Both A and H in doses applied cause increase in blood flow in the vessel areas under study. The results of the research indicate that changes in the blood flow through the areas under investigation induced by application of ACh are the resultant of three factors. 1. The vasodilatative effect resulting from the stimulation of the receptor M. 2. Stimulation of the cholinergic receptor N and connected with it freeing catecholamines responsible for the tension of vessels and contraction of smooth muscles of the organ. 3. Pressing influence upon the vessels of contracting smooth muscles connected with stimulation of M and N receptors. The sensitivity of vessels in the oa area to M-cholinergic stimulation is lower than that in the ua artery and it is higher in the luteal phase than in pre- and post-ovulation phases in both vessel areas. The magnitude of nicotine reaction of endogenous catecholamines freeing does not undergo significant changes during the oestrous cycle.

Animals↗
PubMed1991

Nucleotide sequence analysis of Adh genes estimates the time of geographic isolation of the Bogota population of Drosophila pseudoobscura.

The population of Drosophila pseudoobscura at Bogota, Columbia, is geographically and partially reproductively isolated from populations in the main body of the species in North America. The degree of genetic differentiation and time of divergence between populations at Bogota and Apple Hill, CA, were estimated by comparison of 3388 nucleotides in the alcohol dehydrogenase region (Adh and Adh-Dup genes) of 18 strains. Of the 146 polymorphic nucleotide sites detected, 68 and 31 were unique to the Apple Hill and Bogota samples, respectively, and 53 were shared. On the basis of an observed net divergence per nucleotide site of 0.264% between the two samples, the Bogota and North American populations were estimated to have been separated for at least 155,000 years. This divergence time suggests that D. pseudoobscura extended its range from North America to South America in a period of Pleistocene glaciation, when habitat suitable for the species presumably existed in lowland Central America.

Alcohol Dehydrogenase↗
PubMed1992

A dual level model for speciation by multiple pericentric inversions.

A considerable body of evidence suggests that the deleterious meiotic effects of pericentric inversions in F1 hybrids can be overcome by changes in chiasma location and various means of non-homologous pairing. Such overriding mechanisms may render pericentric inversions benign and increase the likelihood of their fixation in population isolates. It has been argued that overriding mechanisms of this type negate the involvement of pericentric inversions as reproductive isolating mechanisms in speciation. It is suggested, however, that the involvement of pericentric inversions in speciation should be considered on two levels. First, that by reducing meiotic effects in F1 hybrids, overriding mechanisms facilitate the fixation of pericentric inversions. Secondly, when contact hybridization occurs between the chromosomally derived and parental populations second-level effects may be encountered. That is, the recombinational effects of pericentric inversion differences on coadapted gene complexes (sensu Brncic, 1954, Shaw & Coates, 1983) enforce profound inviability barriers in F2 and backcross matings. In this way, multiple pericentric inversions may act as significant post-mating isolating mechanisms, whereas individual inversions with less significant second-level effects may not.

Animals↗
PubMed1988

[Analysis of the effects of oxytocin, vasopressin, angiotensin, serotonin and histamine on the blood flow in the reproductive organs of swine the during estrous cycle].

We have measured the magnitude of flow in the uterine artery (ua) and in ovarian artery (oa) in the isolated reproductive organs of pig (100-130 kg/per head) perfused with their own blood or Krebs-Henseleit's solution. The pressure was kept on the constant level 100 mm Hg. Were administered intraarterially Oxytocin (O), vasopressin (W), histamine (H), serotonin (5-HT) and hypertensin (A). Their possible influence on the processes of regulation of blood flow in the porcine reproductive organs during oestrus cycle was analysed. It was stated that O produced a decrease of blood flow (bf) in the periovulatory period (1-2 and 16-18 day of cycle). On the other hand doses many times bigger did not cause significant changes in ua in the luteal phase and in oa in all phases of the cycle. Action of O is connected with its pressing action on the uterine vessels, contracted by the smooth muscular coat of this organ. Limiting bf action of W and A is mainly connected with their direct vasoconstructive effect. Our results indicated that in physiological conditions during oestrous cycle O, W and A did not evoke significant changes in the regulation of blood flow in the porcine reproductive organs. High sensitivity of the investigated vessels on 5-HT in the luteal phase and lower sensitivity in the periovulatory phase could indicate serotonin's influence on the regulating changes of blood flow during oestrous cycle. Vessels of both investigated areas were very sensitive to H. Especially high sensitivity of oa vessels on H is correlated with an increase of sensitivity of the vessels on 5-HT and catecholamines in the luteal phase. It seem that H has significant importance as a factor antagonising influence of 5-HT and catecholamines in the luteal phase of cycle in the pig. Sensitivity of oa vessels on the investigated drugs was lower in all phases of the cycle studied than sensitivity of ua vessels, the only exception was when H was used. We observed similar reaction on used drugs, both in experiments with perfusion with the blood and with the Krebs-Henseleit's solution. It may suggest that vessels reaction depends upon the functional state of the organ and it is not directly connected with the hormones present in the blood.

Angiotensin II↗
PubMed1985

Symmetrical and asymmetrical sexual isolation among laboratory strains of Drosophila ananassae.

Male-choice experiments using five isofemale lines of Drosophila ananassae originating from different localities were performed to study sexual isolation within the species. In most of the crosses homogamic matings outnumber heterogamic ones, and deviation from randomness is statistically significant in 11 of 20 crosses. This provides evidence for positive assortative mating within D. ananassae. Isolation indices range from -0.057 to 0.555. Eleven positive isolation indices are significantly greater than zero. Both types of sexual isolation, symmetrical and asymmetrical, have been observed among different strains. Thus the present results clearly indicate that the laboratory strains of D. ananassae have developed behavioural reproductive isolation as a result of genetic divergence.

Animals↗
PubMed1991

Identification of a serum protein polymorphism via two-dimensional electrophoresis. Family and population studies in two genetically isolated groups: North American Hutterites and Australian aborigines.

We report the identification and initial family and population studies of a previously undescribed serum protein polymorphism with two allelic forms. It was discovered in Hutterites, a reproductively isolated religious sect, and is also present in Australian aborigines and a sample of Chicago residents. A two-allele model is consistent with the segregation pattern observed in five kindreds within our initial study group. This polymorphism, provisionally designated SPPM-158, appears as a horizontal (charge-based) doublet in silver-stained ISO-DALT high-resolution two-dimensional electrophoresis gels. It is a low-concentration polypeptide (approximately 1 mg/dL) that has an apparent MWSDS of 43.6 kD and an isoelectric point of approximately 5.5. We infer that it circulates as a multimer or in a high-molecular-weight (greater than 200 kD) complex with other proteins because it is not observed in normal body fluids derived from physiologically ultrafiltered plasma such as amniotic fluid, urine, or cerebrospinal fluid; however, it is present in urine of patients with glomerular proteinuria. The high heterozygosity rates imply utility of this new serum protein marker for both forensic and population studies.

Australia↗
PubMed1986

Inverted Y chromosome polymorphism in the Gujerati Muslim Indian population of South Africa.

An inverted Y chromosome has been found at a very high frequency in a Muslim Indian community living in the Johannesburg-Witwatersrand area of the Transvaal Province of South Africa: 8 of 141 (5.7%) retrospectively identified Indian males had an inv(Y)(p11.2q11.23) and all were of the Muslim faith. The inversion was found in 22 of 72 (30.5%) prospectively studied normal Muslim Indian males. All the carriers of the inversion were Gujarati-speakers whose families migrated to the Transvaal from the Gujerat Province of India during the first half of this century. The origins of the ancestors of the individuals with inv(Y) were traced to a small village, Kholvad, near the city of Surat, and some neighbouring villages. The polymorphic frequency of the inv(Y) has probably been produced through random genetic drift in a reproductively isolated community, maintained by strict endogamous marriage customs based on religious and linguistic affiliations. There was no indication that the inverted Y was associated with any reproductive disadvantages.

Black People↗
PubMed1977

The Cajuns of Southern Alabama: morphology and serology.

A survey was conducted of 324 members of the Cajun isolate of Southern Alabama. Tradition and appearance suggest that this population of about 3,000 are not entirely White, Black, or Indian but constitute a triracial community somewhat reproductively isolated and inbred. The earliest American settlement in the area, along the banks of the Mobile and Tombigbee Rivers, lay between Spaniards to the South and Indian tribes on the other sides: Creek, Choctaw, and Cherokee. Physical measurements are reported for 71 adults, plus color of skin, eyes, and hair. X-rays were taken of wrist and ankle bones of some 253 children. Red blood samples were typed on adults and children, and haptoglobin, Gm, and Gc types were determined from serum. History and physical examinations were also made. Physical measurements and observations suggest predominantly White ancestry, and D2 analysis confirms this, with least similarity to Indians. Analysis of serological traits implies almost 70% White, almost 30% Black, and very little Indians genes. Few defects of clear genetic etiology were discovered. Growth patterns judged from X-rays appeared normal. All genetic loci testable were in Hardy-Weinberg equilibrium except Gc. While history and some common surnames suggest endogamy in the past, the medical and serological findings, plus some additional surnames, indicate that the isolate has already been largely diluted or dissolved.

Adolescent↗
PubMed1989

Purification and properties of cyclic-3',5'-GMP-dependent protein kinase from the nematode Ascaris suum.

A cyclic-3',5'-GMP-dependent protein kinase was purified 7400-fold from the reproductive tract of female ascarids to a specific activity of 718 nmol min-1 mg-1 (histone as substrate). The yield of the preparation was 25%. The enzyme protein obtained was homogeneous as judged by isoelectrofocusing and polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The native enzyme behaved as a dimer of two 82-kDa subunits in gel permeation chromatography on Superose 12. The protein kinase was inactive in the absence of cyclic purine nucleotides. Half-maximum velocity was obtained in the presence of 18 nM cGMP, whereas 400-fold higher concentrations of cAMP were required for the same activity. The enzyme underwent autophosphorylation in first-order kinetics (rate constant 0.054 min-1), leading to maximum incorporation of 0.96 phosphate per subunit. The autophosphorylation led to a 4-fold increase in Vmax, while the Km remained almost unchanged. In an extract from the reproductive tract, cGMP-stimulated phosphorylation was primarily observed in five proteins (molecular masses of 66, 60, 43, 30, and 25 kDa). These proteins also incorporated phosphate when isolated reproductive tracts were incubated in the presence of [32P]phosphate. The phosphate content in cellular proteins was enhanced when the incubation was performed in the presence of 10(-4) M of either octyl-cAMP or octyl-cGMP. In addition to the proteins mentioned above, however, six more electrophoretic bands containing radioactive phosphate were identified after in situ labeling of reproductive tracts with radioactive phosphate.

Animals↗
PubMedDate not supplied

[A perfusion device for the survival of isolated organs of the reproductive system].

A perfusion device for life supporting in isolated reproductive organs is described. With the device, the following functions are possible: gas exchange in recirculating blood flow, perfusate replacement in the course of perfusion, blood flow generation in a circular circuit with simultaneous provision of hemodynamic parameters closely approximating native ones.

Animals↗
PubMed1993

Differentiation of U.S. and European isolates of porcine reproductive and respiratory syndrome virus by monoclonal antibodies.

Monoclonal antibodies (MAbs) to two U.S. isolates of porcine reproductive and respiratory syndrome (PRRS) virus were prepared. Two MAbs specifically recognized a conserved epitope on the putative 15-kDa nucleocapsid protein of U.S. and European isolates of PRRS virus. Four other MAbs recognized epitopes on the 15-kDa protein of U.S. but not European isolates of PRRS virus. Collectively, this indicates that PRRS viruses contain both conserved and divergent epitopes on the 15-kDa viral protein.

Animals↗
PubMed1981

Patterns of mortality in the the Old Order Amish. I. Background and major causes of death.

The major causes of death were studied in the Old Order Amish people in three settlements in Indiana, Ohio and Pennsylvania to determine if lifestyle and genetic isolation altered their mortality risk compared to neighboring non-Amish. The Amish are a conservative religious group who live in farm settlements, use horses for work and travel, exercise vigorously, and avoid cigarettes and alcohol. They are reproductively isolated and highly inbred. Death certificates and Amish censuses were used to determine mortality risks, which were summarized using age-adjusted mortality ratio (MRs). Amish mortality patterns were not systematically higher or lower than those of the non-Amish, but differed by age, sex, and cause. Amish males had slightly higher all-cause MRs as children and significantly lower MRs over the age of 40, due primarily to lower rates of cancer (MR = 0.44, age 40-69), and cardiovascular diseases (MR = 0.65, age 40-69). Amish females MRs for all causes of death were lower from age 10-39, not different from 40-69, and higher over age 69. MRs were not significantly different for all cancer sites combined in Amish women and they had higher cardiovascular mortality ratio aged 70 and over (MR =1.34). Other major causes of death were also examined. Because the Amish and other farming groups have similar mortality patterns, it is suggested that lifestyle may be the primary determinant of the overall mortality patterns in the Amish.

Adolescent↗
PubMedDate not supplied

Counter current transfer and back transport of 3H-PGF2 alpha in the cow's broad ligament vasculature ipsilateral and contralateral to the corpus luteum.

Eight cows of similar age (5-7 years) were chosen for the experiment. Isolated reproductive tract was supplied with autologous oxygenated and heated (40 degrees C) blood through the uterine artery and ovarian artery. 3H-PGF2 alpha in total dose of 2 MBq (10(7) cpm) was injected into each of the uterine lumen of isolated organ. Blood samples were collected at 5 min intervals during 120 min of experiment using cannulae inserted into the branches of uterine arteries about 1 cm below the horns and from ovarian arteries inserted 0.5 cm below the ovaries. The concentration of 3H-PGF2 alpha found in blood plasma taken from uterine artery or from ovarian artery on the side with active corpus luteum (CL) was significantly lower (p less than 0.001) compare with contralateral side to active CL. Radioactive PGF2 alpha found in branches of uterine arteries on both ipsilateral and contralateral side to CL was significantly higher (p less than 0.001) compare to ovarian artery of the same side. It is concluded that absorption of 3H-PGF2 alpha from uterine lumen into venous blood as well as its counter current transfer in area of broad ligament vasculature were reduced on the side of uterine horn with active CL probably as an effect of estrogen:progesterone ratio on vascular constriction in area of uterine vasculature.

Adnexa Uteri↗
PubMed1995

Wolbachia and cytoplasmic incompatibility in mycophagous Drosophila and their relatives.

Bacterial symbionts belonging to the genus Wolbachia are associated with postzygotic reproductive incompatibility in a number of insect species. Using polymerase chain reaction (PCR) amplification of bacterial gene sequences, strains from 10 species belonging to the closely related quinaria, testacea and tripunctata groups of Drosophila were screened for the presence of Wolbachia in their reproductive tissues. Those screened included the mycophagous species D. falleni, D. recens, D. phalerata, D. testacea, D. neotestacea, D. orientacea, D. putrida and D. tripunctata, and the nonmycophagous species D. palustris and D. quinaria. Two species, D. recens and D. orientacea, were found to be infected with Wolbachia. Subsequent tests of four additional strains of D. recens found all to be infected with the bacteria. It was established that these bacteria cause partial cytoplasmic incompatibility in D. recens by antibiotic curing followed by crosses between cured and uncured strains. Curing was confirmed by a PCR assay. Although most species of insects shown to be infected with Wolbachia are cosmopolitan and/or have undergone recent range expansion in association with human activity, D. recens and D. orientacea are endemic species with specialized ecological habits. Preliminary molecular phylogenetic analysis indicates that, among the species we examined, D. quinaria is most closely related to D. recens. To determine whether the bacteria are involved in reproductive isolation between these two species, reciprocal crosses were carried out between D. quinaria and both infected and uninfected (cured) strains of D. recens. Although these species did mate with each other, all interspecific crosses failed to yield hybrid progeny, indicating that the bacteria are not responsible for reproductive incompatibility between these species.

Animals↗
PubMed1986

The heterochromatin of grasshoppers from the Caledia captiva species complex. I. Sequence evolution and conservation in a highly repeated DNA family.

The restriction enzyme TaqI digests 0.2% of the genomic DNA from the grasshopper Caledia captiva to a family of sequences 168 bp in length (length of consensus sequence). The sequence variation of this "Taq family" of repeat units was examined among four races from C. captiva to assay the pattern of evolution within this highly repeated DNA. The Taq-family repeats are located in C-banded heterochromatin on at least one member of each homologous pair of chromosomes; the locations range from centromeric to telomeric. Thirty-nine cloned repeats isolated from two population 1A individuals along with 11 clones from seven populations taken from three of the races demonstrated sequence variation at 72 positions. Pairwise comparisons of the cloned repeats, both within an individual and between different races, indicate that levels of intraspecific divergence, as measured by reproductive incompatibility, do not correlate with sequence divergence among the 168-bp repeats. A number of subsequences within the repeat remain unchanged among all 50 clones; the longest of these is 18 bp. That the same 18-bp subsequence is present in all clones examined is a finding that departs significantly (P less than 0.01) from what would be expected to occur at random. Two other cloned repeats, from a reproductively isolated race of C. captiva, have sequences that show 56% identity with this 18-bp conserved region. An analysis showed that the frequency of occurrence of an RsaI recognition site within the 168-bp repeat in the entire Taq family agreed with that found in the cloned sequences. These data, along with a partial sequence for the entire Taq family obtained by sequencing uncloned repeats, suggest that the consensus sequence from the cloned copies is representative of this highly repeated family and is not a biased sample resulting from the cloning procedure. The 18-bp conserved sequence is part of a 42-bp sequence that possesses dyad symmetry typical of protein-binding sites. We speculate that this may be significant in the evolution of the Taq family of sequences.

Animals↗
PubMed1976

Olfactory discrimination as an isolating mechanism in speciating mole rats.

Olfactory discrimination was tested in two chromosome forms of the speciating fossorial rodent, Spalax ehrenbergi, in Israel. Females of the chromosome forms 2n = 52 and 2n = 58 were tested for male odour discrimination, the source of odour being either case litter or urine. Estrous females of both forms preferred homochromosomal odurs, whereas diestrous females showed no discrimination. These results suggest that olfactory discrimination may serve as a reproductive isolating mechanism in the speciation of mole rats.

Animals↗
PubMed1995

Sexual isolation in Drosophila melanogaster: a possible case of incipient speciation.

It is generally believed that Drosophila melanogaster has no closely related species with which it can produce the viable and fertile hybrids that are essential for the genetic analysis of speciation. Following the recent report of molecular differentiation between a Zimbabwe, Africa, population and two United States populations, we provide evidence that strong sexual isolation exists between the D. melanogaster population in Zimbabwe and populations of other continents. In the presence of males of their own kind, females from most isofemale lines of Zimbabwe would not mate with males from elsewhere; the reciprocal mating is also significantly reduced, but to a lesser degree. The genes for sexual behaviors are apparently polymorphic in Zimbabwe and postmating reproductive isolation between this and other populations has not yet evolved. Whole chromosome substitutions indicate significant genetic contributions to male mating success by both major autosomes, whereas the X chromosome effect is too weak to measure. In addition, the relative mating success between hybrid and pure line males supports the interpretation of strong female choice. These observations suggest that we are seeing the early stages of speciation in this group and that it is driven by sexual selection. The genetic and molecular tractability of D. melanogaster offers great promise for the detailed analysis of this apparent case of incipient speciation.

Animals↗