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S J O'Brien

Publications and source records attributed to S J O'Brien.

At least 343 records · Page 19Linked to original sources
PubMed1983

Unique seminal quality in the South African cheetah and a comparative evaluation in the domestic cat.

Analysis of 40 semen samples collected by electroejaculation from 18 cheetahs revealed no major differences in seminal traits among Transvaal, South West (Namibia) or hybrid (Transvaal X South West) males. However, mean spermatozoal concentration (14.5 X 10(6) spermatozoa/ml of ejaculate) and percent motility (54.0%) were less in cheetahs than in domestic cats (147.0 X 10(6) spermatozoa/ml of ejaculate, 77.0% motility) subjected to the same electroejaculation regimen. On the average, cheetah ejaculates contained 71.0% morphologically abnormal spermatozoa compared to 29.1% aberrant spermatozoal forms in the domestic cat. These results indicate that seminal characteristics in the cheetah are markedly inferior compared to the domestic cat, particularly with respect to the incidence of pleiomorphic spermatozoa. Because a recent parallel study demonstrates that the cheetah lacks genetic variation, it appears likely that spermatozoal abnormalities are a genetic consequence of genomic homozygosity characteristic of this endangered species.

Acinonyx↗
PubMed1983

Murine retroviral restriction genes Fv-4 and Akvr-1 are alleles of a single locus.

The two murine retroviral restriction genes, Fv-4 and Akvr-1, are very similar in their effects, distributions, ranges of action, and phenotypes. Akvr-1 has been shown to segregate independently in backcrosses with a variety of retroviral restriction loci, including Fv-1, Fv-2, Ril-1, and Ril-2. An allelism test cross of FRG (Fv-4R) X LCRR (Akvr-1R) hybrids mated to AKR mice failed to produce any viremic offspring. These results suggested that Akvr-1R and Fv-4R are alleles of a single locus, Fv-4, on mouse chromosome 12.

Alleles↗
PubMed1982

Genetic mapping in mammals: chromosome map of domestic cat.

A genetic map of 31 biochemical loci located on 17 feline syntenic (linkage) groups has been derived by somatic cell genetic analysis of cat-rodent hybrids. Most of these syntenic groups have been assigned to one of the 19 feline chromosomes. Comparative linkage analysis of the feline biochemical loci and homologous human loci revealed considerable conservation of linkage associations between the primates and the Felidae (order Carnivora). Many of these same linkage groups have not been conserved in the murine genome. The genetic and evolutionary implications of comparative mapping analysis among mammalian species are discussed.

Animals↗
PubMed1982

Evidence for the horizontal acquisition of murine AKR virogenes by recent horizontal infection of the germ line.

Several recent reports (8, 10, 11, 13) have established the biological and molecular genetic similarity between the endogenous AKV virus of strain AKR, and an N-ecotropic endogenous virus found in the genome of feral Japanese mice, Mus musculus molossinus. The similarities are so striking as to suggest a common origin of these viruses, which are present in some, but not all, inbred mouse strains. The virogenes of AKR mice may have been acquired by either: (a) common descent of AKR (and other AKV(+) strains) from a common ancestor of AKR and molossinus animals, or (b) horizontal germ line infection of the AKR strains by molossinus virus at 1;he strain's inception followed by fixation through inbreeding. The sexual descent model carries with it a prediction of relative consanguinity of the AKR strain and molossinus, whereas the horizontal infection model does not. We have examined the polymorphic allozyme (allelic isozyme) genotype of 51 nonvirus-related loci in 17 strains of mice including AKR, C58, BALB/c, Swiss, and molossinus. By comparing the composite allozyme genotype of different inbred and outbred mouse strains, the "genetic distance" statistic was derived. Genetic distance measures the degree of allelic substitution between populations and increases proportionately with the amount of time the populations have been reproductively isolated. The genetic distance computed between molossinus and AKR is large, nearly 5-10 times the distance between known related populations and strains (e.g., C57L vs. C57BL/6). Molossinus had a similarly large distance from AKV negative strains (Swiss, C57L) as it did from AKV- positive strains. Cellular DNA sequences that flank the integrated AKV provirus were analyzed by restriction enzyme digestion of liver DNA from molossinus, AKR, and additional inbred strains that express ecotropic murine leukemia virus. The integration flanks of three AKR provirus sequences, Akv-1, Akv-2, and a third uncharacterized sequence, were not evident in molossinus cell DNA, which contained at least six different proviral integration fragments. These data effectively exclude the interpretation of consanguinity of AKR and molossinus and support the notion of acquisition of the endogenous virus in AKR by horizontal infection of the molossinus virus.

AKR murine leukemia virus↗
PubMed1982

Conserved regions of homologous G-banded chromosomes between orders in mammalian evolution: carnivores and primates.

The recent derivation of a biochemical map of 33 loci of the domestic cat (Felis catus) revealed a striking conservation of chromosomal linkage associations between the cat and humans. A comparison of homologous (by linkage criteria) chromosomes by using conventionally extended and high-resolution G-banding of human and feline chromosomes is presented. Four criteria for establishing probable cytogenetic homologies of chromosomal regions were invoked: (i) map placement of homologous genes to the same chromosomes; (ii) cytological correlation of G-banding pattern; (iii) placement of homologous genes, by regional gene mapping, in the region of cytological homology; and (iv) a requirement that the putative region of homology be ancestral and evolutionarily conserved within their respective orders. Five subchromosomal regions (homologous to human chromosome 1p, 2p, 2q, 12, and X) were found to be conserved and homologous by all the stated criteria. The conserved regions constitute nearly 20% by length of the human chromosomal genome. The implications of conservation of chromosome homologies between mammalian orders whose last common ancestor became extinct more than 60 million years ago is discussed.

Animals↗
PubMed1981

Contamination of Hodgkin's disease cell cultures.

Several laboratories have recently reported the establishment and characterization of long-term cell lines thought to be related to the neoplastic cell of Hodgkin's disease. Here, Harris et al. discuss evidence that some of these lines are, in fact, not related to Hodgkin's disease but are non-human contaminants.

Animals↗
PubMed1981

Analysis of multiple isoenzyme expression among twenty-two species of Mycoplasma and Acholeplasma.

Crude extracts of triple-cloned, purified cultures of 22 species of Mycoplasma and Acholeplasma were examined for expression of 21 isozyme systems routinely used to type mammalian cells. Nine previously described enzymes (purine nucleoside phosphorylase, adenylate kinase, dipeptidase, esterase, glyceraldehyde-3-phosphate dehydrogenase, glucose phosphate isomerase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and superoxide dismutase) and three enzymes not previously reported in mycoplasma (triose phosphate isomerase, inorganic pyrophosphatase, and acid phosphatase) were detected in some or all of the species examined. These findings provide new information on the enzymatic expressions of these organisms. Three of the isozyme systems (superoxide dismutase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase) were present in Acholeplasma species but not in any Mycoplasma species. The characteristic pattern of electrophoretic mobility of the 12 isozyme systems also provides a useful biochemical property for identification, characterization, and classification of these mycoplasmas. Mycoplasma isozyme expression for seven of the enzymes were readily detected in various infected-cell culture lines by using either cell extracts or concentrated cell culture fluids. Mycoplasma-specific enzymes found in infected-cell extracts had the same electrophoretic mobility patterns as enzymes obtained from broth-grown mycoplasmas of the same species. Expression of homologous mammalian enzymes was not detectably altered by infection with mycoplasmas.

Acholeplasma↗
PubMed1980

Correlative genetic variation in natural populations of cats, mice and men.

The study of the extent and basis of gene-enzyme variation has long been a principal concern of population genetics. Numerous surveys have indicated considerable amounts of genetic variation detectable in natural populations, with few exceptions. The variances of average heterozygosities (H) between species and among populations within species are large, prompting Lewontin to emphasize the importance of large gene sample sizes and Selander to encourage analysis of variation of homologous gene-enzyme systems when making species comparisons. We present here a comparative genetic analysis of electrophoretic variation at 57 homologous biochemical loci of cats, mice and men. The distribution of polymorphism among the sampled loci in the three species was nonrandom. A large group of sampled loci (60%) were monomorphic in all three species, whereas a second group (30%) of the loci were polymorphic in two or more species. This conservation of the tolerance of genetic polymorphism is apparently more a characteristic of a particular locus than of the vertebrate species or of the genome. The current hypotheses for classifying polymorphic and monomorphic loci in terms of physiological and physical enzyme characteristics have been re-examined.

Animals↗
PubMed1980

Genetic variance of laboratory outbred Swiss mice.

The extent of allelic variation has been estimated at 46 structural gene loci within three major colonies of Swiss mice and between inbred derivative strains. The colonies have retained nearly the same amount and type of variation found in natural murine or human populations despite laboratory propagation for more than 50 years (175 generations). The population genetic structures of the Swiss mouse colonies were comparable to an island population in which random fixation, and not inbreeding or population bottlenecks, is apparently responsible for slight losses in genetic variance.

Alleles↗
PubMed1980

Genetic diversity in leukemia-prone feral house mice infected with murine leukemia virus.

The Lake Casitas (LC) mouse population located in south western Ventura county in California is unusual insofar as 85% of these mice are persistently viremic with congenitally transmitted murine leukemia virus (MuLV). The virus has been identified as the etiological agent responsible for lymphoma and neuromotor paralysis in large numbers of the mice. The majority of other wild mouse populations are generally free of infectious MuLV despite the presence of endogenous cellular DNA sequences homologous to infectious virus isolated from wild mice. Electrophoretic variation in 46 gene-enzyme systems was surveyed using mice from Lake Casitas and from a virus-negative population located in Bouquet Canyon (BC) approximately 40 miles from Lake Casitas. The LC and BC populations are genetically very similar to each other and to feral mouse populations previously studied in California and Europe. In the LC population 24% of the loci are polymorphic compared to 17% in the BC population. The average heterozygosities for the LC and Bc populations are 0.094 and 0.073, respectively. The large amount of genic variation in LC fails to support the concept of the derivation of the colony from a small number of founders. Tests for linkage disequilibrium and/or selective association of viremia and polymorphism at 15 loci located on nine mouse chromosomes did not reveal any nonrandom assortments. The viremic LC population, then, appears indistinguishable within the limits of experimental resolution from the virus-negative BC population in its population genetic structure.

Animal Population Groups↗
PubMed1980

A molecular approach to the identification and individualization of human and animal cells in culture: isozyme and allozyme genetic signatures.

The electrophoretic resolution of a group of genetically monomorphic gene-enzyme systems that are developmentally and biologically ubiquitous has been used to provide a species-specific and type-specific biochemical characterization of various cultured cells. The relative mobilities of gene-enzyme systems representing nine distinct gene products from cell cultures of 25 species from Drosophila to man are presented. These isoenzymes effectively discriminate interspecies cell-to-cell contamination and almost invariably serve to identify the contaminating species. The resolution of eight polymorphic gene-enzyme systems in human cell cultures provides a virtually unique allozyme genetic signature as a monitor of intraspecies cellular contamination. The genetic signatures of 47 commonly used human cells are presented. Included in the test were seven putative HeLa (human cervical carcinoma) contaminants each of which expressed a signature identical with that of HeLa. The probability that an unrelated human cell line will have a signature identical to a typed cell is computed for each line from the genotypic frequencies at each locus in a population of cultured human cells. The gene frequencies of this cell population are comparable to the same frequencies in natural human populations. The most common human signature has a frequency (and therefore a probability) of 0.02. The majority of the 17,010 possible signatures are far less probable. A calculation of the theoretical incidence of chance matching of signatures within test groups of two or more individuals is presented. The probability of a chance match between any two randomly selected individuals is 0.004 and among five randomly selected individuals is 0.034. The allozyme genetic signature represents a definitive monitor of cell identity and is presented as a standard of cell and tissue identification for a variety of biological studies.

Animals↗
PubMed1980

Akvr-1, a dominant murine leukemia virus restriction gene, is polymorphic in leukemia-prone wild mice.

We describe a restriction gene (Akvr-1, for AKR virus restriction) that is polymorphic for two alleles, Akvr-1R (restrictive) and Akvr-1r (susceptible), in a feral population of mice (Mus) musculus domesticus) at a squab farm near Lake Casitas (LC) in southern California. Akvr-1k is a dominant allele that exhibits 100% penetrance in prevention of viremia of AKR endogenous retrovirus and of virus-mediated lymphoma in LC (Akvr-1RR) X AKR F1 hybrids. The restriction phenotype segregates as a single Mendelian locus in backcrosses to AKR mice. Akvr-1R likewise is effective in restriction of NB-tropic Moloney murine leukemia virus-induced viremia and NB-tropic Friend virus-induced splenomegaly but fails to restrict expression or pathogenesis of LC-derived amphotropic retrovirus. Pleiotropic restriction of AKR, Friend, and Moloney ecotropic viruses, but not of amphotropic virus, suggests that the viral targets of Akvr-1 in the three ecotropic viruses are similar to each other and distinct from the target in the LC-amphotropic virus. The relationship of Akvr-1 to previously reported murine restriction loci Fv-1, Fv-2, and Fv-4 is discussed.

AKR murine leukemia virus↗
PubMed1980

Characteristics of HeLa strains: permanent vs. variable features.

Characteristic rearranged human chromosome markers have been observed in a variety of HeLa cell sublines and in five suspected HeLa contaminant lines originally thought to be derived from differentiated tissues of different individual patients. The allozyme genetic signatures, representing the composite enzyme phenotype at eight polymorphic loci, of each of the studied contaminant lines were identical to each other and to those of HeLa cells. The probability that each of these lines would have an identical genetic signature (since the frequency of the HeLa genotype is 0.0017) is 4.2 X 10(-15). Differences between cell lines, however, could be detected by isoelectric focussing of the isoenzymes for glucose-6-phosphate dehydrogenase. The cell lines, including CLL 74, the older Chang liver line, failed to express five liver-specific proteins. One protein was detected in a new liver cell culture. Variations in cytogenetic, biochemical, and differentiated functions during continuous cell culture are discussed.

Cell Differentiation↗