Biomedical subjects

S J O'Brien

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

At least 217 records · Page 12Linked to original sources

PubMed1991

Mammalian genome mapping: lessons and prospects.

The recent emphasis on human genome mapping has stimulated the development of gene maps in close to thirty mammalian species. Animal gene maps provide an invaluable resource for genetic analysis and manipulation of phenotypic characters, as well as a retrospective glimpse at the patterns and processes of genome evolution. An empirical strategy for developing new gene maps in mammals by emphasizing two important classes of index or anchor marker loci is presented.

Animals↗

PubMed1991

Unfit survivors: exercise as a resource for aging women.

Some researchers have suggested that about 50% of aging decline is preventable through improved life-style habits such as participation in regular exercise, yet exercise as a resource for healthier survival is being ignored by many aging women. Though recent research findings highlight regular physical activity as a potent factor in combatting hypokinesis (the disease of inactivity), numerous real and perceived barriers to exercise stand between the older woman and her ability to achieve a better quality of life. Among strategies that have been developed to overcome these barriers are social empowerment initiatives that may encourage women to combat disability by engaging in regular exercise.

Aged↗

PubMed1991

Molecular distance and divergence time in carnivores and primates.

Numerous studies have used indices of genetic distance between species to reconstruct evolutionary relationships and to estimate divergence time. However, the empirical relationship between molecular-based indices of genetic divergence and divergence time based on the fossil record is poorly known. To date, the results of empirical studies conflict and are difficult to compare because they differ widely in their choice of taxa, genetic techniques, or methods for calibrating rates of molecular evolution. We use a single methodology to analyze the relationship of molecular distance and divergence time in 86 taxa (72 carnivores and 14 primates). These taxa have divergence times of 0.01-55 Myr and provide a graded series of phylogenetic divergences such that the shape of the curve relating genetic distance and divergence time is often well defined. The techniques used to obtain genetic distance estimates include one- and two-dimensional protein electrophoresis, DNA hybridization, and microcomplement fixation. Our results suggest that estimates of molecular distance and divergence time are highly correlated. However, rates of molecular evolution are not constant; rather, in general they decline with increasing divergence time in a linear fashion. The rate of decline may differ according to technique and taxa. Moreover, in some cases the variability in evolutionary rates changes with increasing divergence time such that the accuracy of nodes in a phylogenetic tree varies predictably with time.

Animals↗

PubMed1991

Rescue and maturation in vitro of follicular oocytes collected from nondomestic felid species.

The potential for rescuing immature oocytes from the ovaries of females of rare felid species which die or undergo medical ovariohysterectomy was evaluated. Ovaries were recovered from 13 species representing 35 individuals in good-to-poor health. Although the majority of females were 10 yr of age or older and in fair-to-poor health, a total of 846 oocytes were recovered of which 608 (71.9%) were classified as fair-to-excellent quality. One hundred of these oocytes were used for initial maturation classification and as parthogenetic controls. Overall, of the 508 fair-to-excellent quality oocytes placed in culture, 164 (32.3%) matured to metaphase II in vitro. For species in which 3 or more individuals yielded oocytes, mean oocyte maturation rates were as follows: 36.2%, tiger; 27.9% leopard; and 8.3%, cheetah. In vitro insemination of oocytes resulted in fertilization (2 polar bodies, 2 pronuclei, or cleavage) rates of 9.1% to 28.6% (leopard) using homologous fresh spermatozoa and 4.0% (lion) to 40.0% (puma) using homologous frozen-thawed spermatozoa. Inseminations using heterologous (domestic cat) spermatozoa also resulted in fertilized oocytes in the tiger, leopard, snow leopard, puma, serval, and Geoffroy's cat (range in fertilization rate, 5.0% for leopard to 46.2% for puma). Cleaved embryos resulted from the insemination of leopard oocytes with homologous sperm (n = 1 embryo) and puma oocytes with domestic cat sperm (n = 3 embryos). These results demonstrate that immature ovarian oocytes from rare felid species can be stimulated to mature in vitro despite an excision-to-culture interval as long as 36 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Developmental changes in pituitary-gonadal function in free-ranging lions (Panthera leo leo) of the Serengeti Plains and Ngorongoro Crater.

Pituitary-gonadal function was examined in male lions free-ranging in the Serengeti Plains or geographically isolated in the Ngorongoro Crater of Tanzania. Lions were classified by age as adult (6.1-9.8 years), young adult (3.3-4.5 years) or prepubertal (1.4-1.6 years, Serengeti Plains only). Each animal was anaesthetized and then bled at 5-min intervals for 100 min before and 140 min after i.v. administration of saline or GnRH (1 micrograms/kg body weight). Basal serum LH and FSH concentrations were similar (P greater than 0.05) among age classes and between locations. In Serengeti Plains lions, net LH peak concentrations after GnRH were approximately 35% greater (P less than 0.05) in prepubertal than in either adult or young adult animals. GnRH-stimulated LH release was similar (P greater than 0.05) between adult and young adult lions, and these responses were similar (P greater than 0.05) to those measured in Ngorongoro Crater lions. Basal and GnRH-stimulated testosterone secretion was higher (P less than 0.05) in adult than in young adult lions and lowest (P less than 0.05) in prepubertal lions. Age-class differences in testosterone production were related directly to the concentrations of LH receptors in the testis (P less than 0.05). Basal and GnRH-stimulated testosterone secretion and gonadotrophin receptor concentrations within age classes were similar (P greater than 0.05) between lions of the Serengeti Plains and Ngorongoro Crater. Lower motility and higher percentages of structurally abnormal spermatozoa were observed in electroejaculates of young adult compared to adult Serengeti Plains males (P less than 0.05) and were associated with decreased steroidogenic activity. In contrast, there were no age-related differences in ejaculate characteristics of Ngorongoro Crater lions. Seminal quality in the Crater population was poor in adult and young adult animals and was unrelated to alterations in pituitary or testicular function. In summary, only seminal quality in adult male lions was affected by location, whereas age significantly affected both basal and GnRH-stimulated testosterone secretion and seminal quality (Serengeti Plains only) in sexually mature males. The striking seminal/endocrine differences among pride (breeding) males of different ages raises questions about the impact of age on individual reproductive performance in this species.

Aging↗

PubMed1991

Semen characteristics in free-living koalas (Phascolarctos cinereus).

Spermic electroejaculates (range in motile sperm/ejaculate, 0.50-122.9 x 10(6); mean +/- s.e.m., 38.6 +/- 4.9) were recovered from 47 of 48 adult koalas captured from 3 wild populations in Australia. Semen was characterized by (i) a high density of globular bodies, which prevented the estimation of sperm motility without dilution; (ii) a brownish colour; and (iii) an acidic pH. Spermatozoa were categorized on the basis of 10 head forms, most cells being a curved or hooked shape. The koala populations differed in sperm concentration and motility ratings, but not in testes size, testosterone production or proportions of spermatozoa with various head shapes. These data confirm that free-living koalas normally produce spermatozoa with a high incidence of structural heterogeneity almost solely confined to the head region; and demonstrate the utility and safety of conventional gamete and endocrine studies, approaches which will be useful for determining the impact of genetic isolation and venereal disease on species fertility.

Animals↗

PubMed1991

Influence of temperature and gas atmosphere on in-vitro fertilization and embryo development in domestic cats.

The influence of culture temperature and gas atmosphere on in-vitro fertilization and embryo development was examined in the domestic cat. In Exp. 1, eggs were fertilized and cultured in 5% CO2 in air at 37, 38 or 39 degrees C. Experiment 2 evaluated the effects of 5% CO2 in air; 5% CO2, 5% O2 and 90% N2; and 10% CO2 in air. Fertilization (cleavage) and development to the morula/blastocyst stage were not influenced (P greater than 0.05) by variations in temperature and gas composition. Despite changing these culture conditions, egg cleavage averaged approximately 75% and greater than 80% of the 2-cell embryos proceeded to morulae in vitro. However, the partial in-vitro morula-to-blastocyst developmental block normally observed in this species was not removed.

Animals↗

PubMed1991

No time to look back: approaching the finish line of life's course.

Gerontologists have labelled individuals who do not follow the normal aging pattern of reduced physical activity and declining health as "successfully aging" adults. Competitive and sport-involved elder persons represent a kind of elderly elite who may exhibit special psychological characteristics that help to explain their active approach to late life. As part of a larger study on the physical fitness and body composition of participants at seniors' games, a qualitative exploration of personal life philosophy was undertaken in order to initiate understanding about the cognitive make-up of competitive older men and women. Content analysis of open-ended survey questions about life in review and future goals permitted insight into life orientation differences between men and women. The responses provided evidence that sport and physical recreation may be an important type of coping strategy for some elderly adults who find life meaning and a sense of achievement in challenging themselves physically. Beyond a general optimism in life orientation, uncertainties about the nature of the future left many with a sense of urgency combined with specific short-term goal setting.

Adaptation, Psychological↗

PubMed1991

Genetic mapping of the beta 1 GABA receptor gene to human chromosome 4, using a tetranucleotide repeat polymorphism.

As more coding loci for functional human genes are described, there is a growing need to identify DNA polymorphisms in specific genes. By examining DNA sequences within the introns of the beta 1 subunit of the gamma-aminobutyric acid receptor gene, GABARB1, we found a tetranucleotide repeat sequence (GATA). Amplification of this region by using PCR revealed seven alleles and a high degree of polymorphism (PIC = .75) in human populations. DNAs from the CEPH families were typed for the GABARB1 intron polymorphism and were analyzed with respect to 20 linked markers on chromosome 4. The results permit placement of GABARB1 on the linkage map of chromosome 4, between D4S104 and ALB. These results affirm that sequence analysis of noncoding segments included within or adjacent to functional genes has value as a strategy to detect highly informative polymorphisms.

Alleles↗

PubMed1991

Detecting high-resolution polymorphisms in human coding loci by combining PCR and single-strand conformation polymorphism (SSCP) analysis.

A strategy is described that allows the development of polymorphic genetic markers to be characterized in individual genes. Segments of the 3' untranslated regions are amplified, and polymorphisms are detected by digestion with frequently cutting enzymes and with the detection of single-stranded conformation polymorphisms. This allows these genes, or DNA segments, to be placed on the linkage maps of human chromosomes. Polymorphisms in two genes have been identified using this approach. A HaeIII polymorphism was detected in the KIT proto-oncogene, physically assigned to chromosome 4q11-12. This polymorphism is linked to other chromosome 4p markers and is in linkage disequilibrium with a HindIII polymorphism previously described at this locus. We have also identified in the insulin-like growth factor1 receptor gene (IGF1R) a 2-bp deletion that is present at a frequency of .25 in the Caucasian population. Pedigree analysis with this insertion/deletion polymorphism placed the IGF1R gene at the end of the current linkage map of chromosome 15q, consistent with the physical assignment of 15q2526. Thus, polymorphisms in specific genes can be used to related the physical, genetic, and comparative maps of mammalian genomes and to simplify the testing of candidate genes for human diseases.

DNA, Single-Stranded↗

PubMed1991

Reconstruction of the chronically insufficient anterior cruciate ligament with the central third of the patellar ligament.

The results of reconstruction of the anterior cruciate ligament with the central third of the patellar ligament as a free, autogenous, non-vascularized graft were retrospectively reviewed at our institution. Eighty reconstructions in seventy-nine patients were evaluated after a minimum of two years. In forty-eight (60 per cent) of the knees, the reconstruction was augmented with an extra-articular lateral sling of iliotibial band. The patients were evaluated with a physical examination, a KT-1000 arthrometer, radiographs, a subjective questionnaire, and a revision of the scale of The Hospital for Special Surgery for rating ligaments. Postoperatively, seventy-six (95 per cent) of the eighty knees no longer gave way, and the pivot-shift test was negative in sixty-seven (84 per cent) of the knees. The average score on the ligament-rating scale was 93 points. All of the patients who had clinical instability at the time of the most recent follow-up had associated ligamentous instability that had not been appreciated or addressed at the time of reconstruction. Arthrometric evaluation revealed that the laxity differed by three millimeters or less from that of the untreated knee in sixty (76 per cent) of the treated knees. In the patient who had bilateral reconstruction, the laxity was the same in both knees. Seventeen patients, who had more than three millimeters of translation, also had additional related ligamentous instability, most commonly posterolateral instability and insufficiency of the medial collateral ligament. We think that major associated ligamentous instability predisposes the reconstruction to failure and should be corrected in conjunction with the reconstruction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1990

Sequence and chromosomal location of the I-309 gene. Relationship to genes encoding a family of inflammatory cytokines.

We previously reported the isolation and characterization of a cDNA clone, I-309, that encodes a small secreted protein produced by activated human T lymphocytes. This protein is structurally related to a large number of recently identified proteins that are secreted upon cellular activation. In this report we describe the isolation and characterization of the gene encoding I-309. The genomic organization is essentially identical to that found in the genes encoding the structurally similar proteins TCA-3, hJE/MCP-1, and mJE, strengthening the hypothesis that these genes are evolutionarily related. The region of the I-309 gene 5' of the mRNA cap site exhibits extensive nucleotide sequence homology with the same region of the murine gene TCA-3, providing additional evidence that I-309 and TCA-3 are likely to be homologs. Finally, panels of rodent-human somatic cell hybrids were used to map the I-309 gene to human chromosome 17. In conjunction with recent mapping data from other laboratories, this result suggests the presence of a cluster of related genes on this chromosome.

Amino Acid Sequence↗

PubMed1990

DNA recombination and natural selection pressure sustain genetic sequence diversity of the feline MHC class I genes.

Sequence comparisons of seven distinct MHC class I cDNA clones revealed that feline class I molecules have a remarkable similarity to human HLA genes in their organization of functional domains as well as in the nonrandom partitioning of genetic variability according to the functional constraints ascribed to different regions of the MHC molecule. The distribution of the pattern of sequence polymorphism in the cat as compared with genetic diversity of human and mouse class I genes provides evidence for four coordinate factors that contribute to the origin and sustenance of abundant allele diversity that characterizes the MHC in the species. These include: (a) a gradual accumulation of spontaneous mutational substitution over evolutionary time; (b) selection against mutational divergence in regions of the class I molecule involved in T cell receptor interaction and also in certain regions that interact with common features of antigens; (c) positive selection pressure in favor of persistence of polymorphism and heterozygosity at 57 nucleotide residues that comprise the antigen recognition site; and (d) periodic intragenic (interallelic) and intergenic recombination within the class I genes. We describe a highly conserved 23-bp nucleotide sequence within the coding region of the first alpha-helix that separates two relatively polymorphic segments located in the alpha 1 domain that may act as a template or "hot spot" for homologous recombination between class I alleles.

Amino Acid Sequence↗

PubMed1990

Genetic fingerprinting reflects population differentiation in the California Channel Island fox.

Restriction fragment profiles generated by hybridization of hypervariable minisatellite DNA probes have been used for paternity analysis but not for comparisons at the level of populations, because the profiles are thought to evolve too rapidly to be informative over large time intervals. But in small isolated populations, the fixation of restriction-fragment polymorphisms can outpace the generation of fragment-length variability through recombination. Here we report on an analysis of DNA fingerprints of the California Channel Island fox (Urocyon littoralis). These foxes comprise an island dwarf species found only on six of the Channel Islands off the coast of southern California. Variability of restriction-fragment profiles within fox populations, as indicated by the average percentage difference (APD), varied widely among the islands, from 0.0% (no variation) to 25.3%. The APDs between populations were considerably greater (43.8% to 84.4%). In addition, foxes on each island can be distinguished by the presence of diagnostic restriction fragments. Maximum parsimony and phenetic trees relating foxes from different islands are consistent with the archaeozoological and geological record. Therefore, in small populations of genetically isolated mammals, differences among hypervariable restriction-fragment profiles can be used to estimate relative genetic variability and to reconstruct the evolutionary relationships of natural populations.

Animals↗

PubMed1990

Influence of seasonal migration on geographic distribution of mitochondrial DNA haplotypes in humpback whales.

Humpback whales (Megaptera novaeangliae) migrate nearly 10,000 km each year between summer feeding grounds in temperate or near-polar waters and winter breeding grounds in shallow tropical waters. Observations of marked individuals suggest that major oceanic populations of humpback whales are divided into a number of distinct seasonal subpopulations which are not separated by obvious geographic barriers. To test whether these observed patterns of distribution and migration are reflected in the genetic structure of populations, we looked for variation in the mitochondrial DNA of 84 individual humpback whales on different feeding and wintering grounds of the North Pacific and western North Atlantic oceans. On the basis of restriction-fragment analysis, we now report a marked segregation of mitochondrial DNA haplotypes among subpopulations as well as between the two oceans. We interpret this segregation to be the consequence of maternally directed fidelity to migratory destinations.

Animals↗

PubMed1990

Monocyte-derived neutrophil chemotactic factor (MDNCF/IL-8) resides in a gene cluster along with several other members of the platelet factor 4 gene superfamily.

Monocyte-derived neutrophil chemotactic factor (MDNCF/IL-8, suggested gene symbol IL8) is a cytokine that chemoattracts and activates neutrophils. Using a panel of human-rodent cell hybrids that preferentially segregate human chromosomes and in situ hybridization, the MDNCF/IL-8 gene was placed on the human gene map at position 4q12-q21. This is the same location where at least three other members (platelet factor 4, melanoma growth stimulatory activity, and interferon-gamma induced factor) of the platelet factor 4 gene super-family reside. In addition, a restriction fragment length polymorphism was identified using MDNCF as a probe in screening genomic DNA digested with HindIII from unrelated individuals.

Chemotactic Factors↗

PubMed1990

Chromosomal localization of the genes encoding two forms of the G protein beta polypeptide, beta 1 and beta 3, in man.

The signal-transducing G proteins are heterotrimers composed of three subunits, alpha, beta, and gamma. Multiple distinctive forms of the alpha, beta, and gamma subunits, each encoded by a distinct gene, have been described. To investigate further the structural diversity of the beta subunits, we recently cloned and characterized a novel cDNA encoding a third form of the G protein beta subunit, which we have termed beta 3. The protein corresponding to beta 3 has not yet been identified. The three forms of the beta subunit show 81-90% amino acid sequence identity. Previous studies had localized the human genes for the beta 1 and beta 2 subunits to chromosomes 1 and 7, respectively. The present studies were designed to determine whether the gene encoding beta 3 is linked to either the beta 1 or the beta 2 gene. Genomic DNA was isolated from a panel of rodent-human hybrid cell lines and analyzed by hybridization to cDNAs for beta 1 and beta 3. Discordancy analysis allowed assignment of the beta 3 gene to chromosome 12 and confirmed the previous assignment of the beta 1 gene to chromosome 1. These results were confirmed and extended by using in situ chromosome hybridization, which permitted the regional localization of the beta 1 gene to 1pter----p31.2 and the beta 3 gene to 12pter----p12.3. Digestion of human genomic DNA with 10 restriction enzymes failed to disclose a restriction fragment length polymorphism for the beta 3 gene. These data indicate that there is considerable diversity in the genomic organization of the beta subunit family.

Animals↗

PubMed1990

DNA variation of the mammalian major histocompatibility complex reflects genomic diversity and population history.

The major histocompatibility complex (MHC) is a multigene complex of tightly linked homologous genes that encode cell surface antigens that play a key role in immune regulation and response to foreign antigens. In most species, MHC gene products display extreme antigenic polymorphism, and their variability has been interpreted to reflect an adaptive strategy for accommodating rapidly evolving infectious agents that periodically afflict natural populations. Determination of the extent of MHC variation has been limited to populations in which skin grafting is feasible or for which serological reagents have been developed. We present here a quantitative analysis of restriction fragment length polymorphism of MHC class I genes in several mammalian species (cats, rodents, humans) known to have very different levels of genetic diversity based on functional MHC assays and on allozyme surveys. When homologous class I probes were employed, a notable concordance was observed between the extent of MHC restriction fragment variation and functional MHC variation detected by skin grafts or genome-wide diversity estimated by allozyme screens. These results confirm the genetically depauperate character of the African cheetah, Acinonyx jubatus, and the Asiatic lion, Panthera leo persica; further, they support the use of class I MHC molecular reagents in estimating the extent and character of genetic diversity in natural populations.

Animals↗