Search PubMed⌕ Search

Biomedical subjects

S J O'Brien

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

At least 235 records · Page 13Linked to original sources
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↗
PubMed1990

Large sequence divergence among mitochondrial DNA genotypes within populations of eastern African black-backed jackals.

In discussions about the relative rate of molecular evolution, intraspecific variability in rate is rarely considered. An underlying assumption is that intraspecific sequence differences are small, and thus variations in rate would be difficult to detect or would not affect comparisons among distantly related taxa. However, several studies on mammalian mitochondrial DNA (mtDNA) have revealed considerable intraspecific sequence divergence. In this report, we test for differences in the rate of intraspecific evolution by comparing mtDNA sequences, as inferred from restriction site polymorphisms and direct sequencing, between mtDNA genotypes of the eastern African black-backed jackal, Canis mesomelas elongae, and those of two other sympatric jackal species. Our results are unusual for several reasons. First, mtDNA sequence divergence within several contiguous black-backed jackal populations is large (8.0%). Previous intraspecific studies of terrestrial mammals have generally found values of less than 5% within a single population, with larger divergence values most often occurring among mtDNA genotypes from geographically distant or isolated localities. Second, only 4 mtDNA genotypes were present in our sample of 64 jackals. The large sequence divergence observed among these mtDNA genotypes suggests there should be many more genotypes of intermediate sequence divergence if they had evolved in sympatry. Finally, estimates of the rate of mtDNA sequence evolution differ by approximately 2- to 4-fold among black-backed jackal mtDNA genotypes, thus indicating a substantial heterogeneity in the rate of sequence evolution. The results are difficult to reconcile with ideas of a constant molecular clock based on random fixation of selectively neutral or nearly neutral mtDNA sequence mutations.

Africa, Eastern↗
PubMed1990

Dissociative anaesthesia in free-ranging male koalas and selected marsupials in captivity.

Forty seven free-ranging, adult, male koalas were captured and administered an intramuscular injection of the dissociative anaesthetic, Telazol (tiletamine HCl plus zolazepam HCl), at dose rates of 5.0 to 7.7 mg/kg body weight. Anaesthesia induction was rapid and smooth and resulted in a surgical plane of anaesthesia lasting 30 to 45 min. There was no depression of heart rate or respiration. Mild salivation occurred in most animals, but was not a problem because the swallowing reflex was retained. There was no mortality or morbidity and the anaesthesia level was sufficient to allow electroejaculation and multiple blood sampling with no apparent animal discomfort. For 10 of 19 males in which anaesthesia was required for a 90 min protocol, a supplementary Telazol injection (average, 2.5 mg/kg) was necessary. All koalas recovered completely within 3 to 4 h of the initial injection. The results suggest that the optimal Telazol dosage for the adult male koala is 7.0 mg/kg body weight. The retrospective analysis of 259 anaesthesia records involving 14 species indicated that Telazol was equally effective and safe in other captive marsupials.

Anesthesia↗
PubMed1990

An oncogenic chromosome 8-9 gene fusion isolated following transfection of human ovarian carcinoma cell line DNA.

Transfection of NIH3T3 cells with genomic DNA from the human ovarian adenocarcinoma tumor cell line OVCAR-3 identified ovc, a rearranged human DNA sequence which was generated during transfection and which induced both morphological transformation and tumorigenesis. A human alu repeat positive 10.5 kb EcoRI fragment present in all transformants was cloned, and two alu-free fragments of 1.8 kb and 2.2 kb were subcloned. The cloned 10.5 kb fragment is not biologically active in DNA transfection assays. Probe from the 2.2 kb fragment hybridizes to poly A + RNA from the transformants and several human tumor cell lines, including OVCAR-3. The 2.2 kb fragment maps to a site on human chromosome 9 (9p24) not known to contain oncogenic sequences, and identifies a two allele polymorphic restriction site. The 1.8 kb fragment maps to human chromosome 8. The ovc transforming sequences fail to hybridize to probes to any of 14 known oncogenes, indicating that they may represent a previously unknown human transforming gene.

Blotting, Northern↗
PubMed1990

Application of DNA fingerprints for cell-line individualization.

DNA fingerprints of 46 human cell lines were derived using minisatellite probes for hypervariable genetic loci. The incidence of 121 HaeIII DNA fragments among 33 cell lines derived from unrelated individuals was used to estimate allelic and genotypic frequencies for each fragment and for composite individual DNA fingerprints. We present a quantitative estimate of the extent of genetic difference between individuals, an estimate based on the percentage of restriction fragments at which they differ. The average percent difference (APD) among pairwise combinations from the population of 33 unrelated cell lines was 76.9%, compared with the APD in band sharing among cell lines derived from the same individual (less than or equal to 1.2%). Included in this survey were nine additional cell lines previously implicated as HeLa cell derivatives, and these lines were clearly confirmed as such by DNA fingerprints (APD less than or equal to 0.6%). On the basis of fragment frequencies in the tested cell line population, a simple genetic model was developed to estimate the frequencies of each DNA fingerprint in the population. The median incidence was 2.9 X 10(-17), and the range was 2.4 X 10(-21) to 6.6 X 10(-15). This value approximates the probability that a second cell line selected at random from unrelated individuals will match a given DNA fingerprint. Related calculations address the chance that any two DNA fingerprints would be identical among a large group of cell lines. This estimate is still very slight; for example, the chance of two or more common DNA fingerprints among 1 million distinct individuals is less than .001. The procedure provides a straightforward, easily interpreted, and statistically robust method for identification and individualization of human cells.

Alleles↗
PubMed1990

The contact neodymium-yttrium aluminum garnet laser. A new approach to arthroscopic laser surgery.

Arthroscopic treatment of meniscal lesions has been modified as technological advances have occurred. However, alternatives to conventional arthroscopic cutting tools, including electrocautery and CO2 lasers, have thus far met with limited success. The recent development of a sapphire tip has enabled the use of the neodymium-yttrium aluminum garnet (Nd-YAG) laser in a contact mode in a saline medium. This study compares the biology of the Nd-YAG laser to that of electrocautery and scalpel techniques with respect to its effects on articular cartilage and the meniscus. The contact Nd-YAG laser has advantages over both scalpel and electrocautery with regard to its effects on articular cartilage. It also has significant biologic advantages over electrocautery for meniscal lesions. Although in its infancy in the clinical setting, the contact Nd-YAG laser represents the possible beginning of a new era for application of laser energy in arthroscopy.

Aluminum↗
PubMed1990

Chromosome assignment by polymerase chain reaction techniques: assignment of the oncogene FGF-5 to human chromosome 4.

We describe a new chromosomal assignment method based on the polymerase chain reaction mediated amplification of target sequences in DNAs from somatic cell hybrids. The new method is faster, much more sensitive and less labor intensive than the standard method of chromosome assignment by Southern hybridization analysis of somatic cell hybrid DNAs. The feasibility of the new approach was demonstrated by verifying the assignment of the previously mapped acidic fibroblast growth factor gene to human chromosome 5. The method was employed to assign the related oncogene, FGF-5, to human chromosome 4.

Animals↗
PubMed1989

Cloning and comparative mapping of a human class III (chi) alcohol dehydrogenase cDNA.

A cDNA encoding human class III (chi ADH5) alcohol dehydrogenase was isolated, sequenced and used to comparatively map this unusual ADH. In their coding sequences, the three major ADH classes were approximately equisimilar, class II and III ADHs sharing the highest sequence identity (67%). A class III-like ADH was mapped to mouse chromosome 3, site of the ADH gene complex, and synteny of ADH5 with four other ADH loci on human chromosome 4 was confirmed. The nearly full-length 1613 nucleotide cDNA contained 433 nucleotides of 3' nontranslated sequence and two possible initiation sites for translation. A protein of 374 amino acid residues could be synthesized using the potential initiation codon at nucleotide 59. However, use of the likely initiation codon at nucleotide 5 would produce a protein of 392 residues with 19 additional N-terminal residues as compared to the known protein sequence. The derived protein sequence also differs at residue 166, where Tyr is found. This difference, due to a single base substitution, could result from cloning artifact, polymorphism, or two expressed class III ADH genes.

Alcohol Oxidoreductases↗
PubMed1989

Chromosomal localization of nucleic acid-binding proteins by affinity mapping: assignment of the IRE-binding protein gene to human chromosome 9.

Three human mRNAs are regulated post-transcriptionally by iron via iron-responsive elements (IREs) contained in each mRNA. A cytoplasmic protein (IRE-BP) binds to these cis-acting elements and mediates the translational regulation of ferritin H- and L-chain mRNA and the iron-dependent stability of transferrin receptor (TfR) mRNA. We have taken advantage of the different mobilities of the human and rodent IRE/IRE-BP complexes on non-denaturing polyacrylamide gels to determine the chromosomal localization of the gene encoding the IRE-BP. Utilizing a panel of 34 different human/rodent hybrid cell lines we have assigned the IRE-BP gene to human chromosome 9. This new technique based on nucleic acid/protein interaction may allow determination of the chromosomal localization of other RNA- or DNA-binding proteins.

Animals↗
PubMed1989

Characterization of MHC cDNA clones in the domestic cat. Diversity and evolution of class I genes.

The abundant functional polymorphism and evolutionary divergence of mammalian MHC class I genes has been affirmed recently by sequence analysis of more than 40 mouse H-2 and human HLA transcripts. In a comparative approach to the evolution of the MHC, we isolated eight molecular clones of feline MHC (termed FLA for feline leukocyte antigen) class I genes from a cDNA library of a cat T cell lymphoma line. DNA sequence analysis of eight clones revealed that they all fell into one of two internally identical allelic groups which differed by 9% of their nucleotide sequences. The occurrence of only two allelic cDNA clones is consistent with the expression of a single heterozygous functional class I gene in the studied cell line despite the occurrence of more than 20 class I copies estimated to be present in the cat genome. Comparison of the FLA class I coding sequence with other class I genes from other species revealed that the domestic cat genes display 81 to 82% sequence identity with human, and 73 to 79% sequence identity with mouse class I genes. Feline and human class I genes have similar sequences and protein structures, with three (alpha) extracellular domains, one transmembrane domain, and one cytoplasmic domain. Variable codons detected in FLA class I alleles were, in most cases, in positions which were also variable in humans and mice, whereas invariant positions with defined functional constraints were generally conserved and invariant between the three species as well. Southern analysis of DNA from diverse species of Felidae revealed a similar numerosity and restriction pattern indicating conservation of the organization of class I genes during the Felidae radiation.

Alleles↗
PubMed1989

Feline lymphomas: immunological and cytochemical characterization.

The immunological and cytochemical phenotypes of five primary feline lymphomas and six feline lymphoma lines are reported. Thymic lymphomas induced by the Rickard strain of FeLV (FeLV-R) are of prothymocyte or (immature) cortical thymocyte origin, as these express terminal deoxynucleotidyl transferase, the guinea pig erythrocyte rosette receptor, Ia antigens, partial cortisone sensitivity, and nonspecific esterase. Lymphomas associated with other strains of FeLV form rosettes with guinea pig erythrocytes, frequently have Ia antigens and cytoplasmic nonspecific esterase, and probably originate from helper T-cells, monocyte/macrophages, or null cells. These data belie previous conclusions that FeLV leukemogenesis is restricted to mature T-cells; rather, the considerable heterogeneity in the surface and cytochemical phenotype of feline lymphomas probably reflects transformation of multipotent lymphoid or monocytoid precursors in the bone marrow by FeLV.

Animals↗
PubMed1989

In vitro maturation and fertilization of domestic cat follicular oocytes.

The time course and conditions necessary for oocyte maturation and subsequent fertilization in vitro were studied in the domestic cat. Darkly pigmented oocytes surrounded by cumulus cells and a tight corona radiata were collected from ovaries removed at ovariohysterectomy. After culture in Eagle's minimum essential medium, oocytes were evaluated for nuclear maturation by analyzing chromosomal spreads. Oocytes achieved metaphase II after intervals of 40-48 hr of in vitro incubation. The incidence of maturation was enhanced (P less than 0.05) when oocytes were recovered from inactive (54%) or follicular (56%) stage donors compared to those recovered from luteal phase (29%) or pregnant (35%) cats. The proportion of oocytes successfully maturing in vitro in medium containing no hormone supplementation (37%) was less (P less than 0.01) than counterparts cultured in follicle-stimulating hormone (FSH) only (48%) or FSH and luteinizing hormone (LH) (54%). The efficiency of maturation was not influenced (P greater than 0.05) by either maintenance/transport temperature (4 degrees C vs. 22 degrees C) or delaying recovery of oocytes from antral follicles (2-8 hr vs. 24-32 hr). Approximately 36% of the in vitro matured oocytes cocultured with spermatozoa demonstrated evidence of fertilization; however, there appeared to be a critical development period for maximizing the incidence of fertilization. These results demonstrate that domestic cat antral oocytes are capable of maturing in vitro, and maturation is influenced by the reproductive status of the donor and the presence of gonadotropins in the culture medium. These oocytes are capable of forming embryos and developing to at least the 16-cell stage in vitro.

Animals↗
PubMed1989

Comparative features of a coronavirus isolated from a cheetah with feline infectious peritonitis.

A coronavirus which was isolated from a cheetah (Acinonyx jubatus) that succumbed to feline infectious peritonitis was characterized in vitro. The virus was determined to be highly cell-associated with Crandell feline kidney (CrFK) cells and was routinely maintained as a persistent infection (CrFK 83-4497). The cheetah coronavirus was compared with other members of the feline coronavirus group including the feline enteric coronavirus (FECV) 79-1683 and the feline infectious peritonitis viruses (FIPV), 79-1146, and UCD-1. The cheetah coronavirus was demonstrated to have a restricted host-cell range with limited cytopathic effect. Indirect immunofluorescence with antisera to FIPV UCD-1 revealed the concentration of viral antigens in the perinuclear region of cells infected with the cheetah coronavirus. Ultrastructural studies of the cheetah coronavirus indicated a limited number of immature viral particles within cytoplasmic vesicles and at the cell surface. This was in contrast to electron microscopy results of FECV 79-1683 and FIPV 79-1146, which had numerous mature virus particles within the cytoplasmic vesicles, as well as at the cell surface. The cheetah coronavirus was tentatively placed in the feline coronavirus family based upon its antigenic reactivity by immunofluorescence; however, the possibility that it represents a unique coronavirus of cheetahs should not be dismissed without further analyses at the host and genomic levels.

Acinonyx↗
PubMed1989

The use of the contact Nd:YAG laser in arthroscopic surgery: effects on articular cartilage and meniscal tissue.

The contact Nd:YAG laser's small size, tip variety, fiberoptic application, and suitability for use in a saline medium make it a particularly appealing tool for use in arthroscopic procedures. This study was performed to investigate the laser's effects on articular cartilage and meniscal tissue with respect to depth of damage (canine cadaver model) and healing response (rabbit model). Depth of damage in the canine cadaver model was greater in meniscal tissue than in articular cartilage at each wattage level. In the presence of a saline bath, depth damage in both tissues was diminished. Scalpel articular cartilage lesions showed no response over time. Electrocautery lesions uniformly showed significant wide margins of hyaline cartilage necrosis which increased over time. Laser articular cartilage lesions showed vigorous healing responses characterized by fibrocartilage healing by 6 weeks. Scalpel meniscectomies showed characteristic fibrocartilagenous remodeling by 6 weeks, while electrocautery meniscectomies showed wide margins of necrosis with no specimen showing remodeling capability. Laser meniscectomies showed an intermediate response with a small number of menisci remodeling in a normal fashion. This article represents the first comprehensive look at the effects of the Nd:YAG laser on articular cartilage and meniscal tissue in terms of depth of damage and healing response over time, and indicates this laser's biological advantage over scalpel and electrocautery in arthroscopic procedures.

Animals↗