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S J O'Brien

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

At least 379 records · Page 21Linked to original sources
PubMed1973

Segmental aneuploidy as a probe for structural genes in Drosophila: mitochondrial membrane enzymes.

A method for detecting possible structural genes in D. melanogaster based on gene dosage dependency is presented. By making thirty crosses between Y-autosome translocations, and an attached-4 cross, it is possible to produce large duplications (approximately 150 salivary gland chromosome bands in length) for every autosomal region with the exception of 83DE. The usefulness of the technique was demonstrated by dosage dependency of three known gene-enzyme systems: alpha-glycerophosphate dehydrogenase-1, alcohol dehydrogenase and malate dehydrogenase. A screen for genes affecting two enzymes localized on the inner membrane of the mitochondrion, alpha-glycerophosphate oxidase (alphaGPO) and succinic dehydrogenase (SHD), produced a dosage-sensitive region in each case. Region 50C-52E affected alphaGPO activity and region 28D-29F affected SDH activity. The latter region apparently includes the malic dehydrogenase-1 gene. The methodology and limitations of the technique are discussed.

Alcohol Oxidoreductases↗
PubMed1972

The -glycerophosphate in Drosophila melanogaster. II. Genetic aspects.

Seven alleles of the alpha-Glycerophosphate dehydrogenase-1 (alphaGpdh-1) locus of Drosophila melanogaster have been described. These include two naturally occurring electrophoretic variants, one EMS-induced electrophoretic variant, and four EMS-induced "null" or "zero" mutants. With the electrophoretic variants, the locus was mapped to II-20.5 +/- 2.5. A complementation matrix was prepared utilizing the null mutants. Three of the four mutants and a deletion of the locus (Grell 1967) exhibit dosage dependency. The dosage independent mutant exhibits complementation with two of the other null alleles. Flies genetically deficient in alpha-glycerophosphate dehydrogenase are fertile, but their relative viability is severely diminished. Such flies also lose the ability to sustain flight, an observation consistent with the enzyme's function in energy production. The levels of mitochondrial alpha-glycerophosphate oxidase, measured in flies genetically deficient in the cytoplasmic enzyme, were normal.

Alleles↗
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Cytogenetic methodologies for gene mapping and comparative analyses in mammalian cell culture systems.

Presented here are the detailed methods employed in our laboratory for gene mapping and cytogenetic analyses in human beings, in the domestic cat, and in other mammalian species. Induced in the procedures are: 1) establishment of primary fibroblast and lymphoid cell cultures; 2) heterologous cell fusion for production of rapidly proliferating cell hybrids; 3) cellular transformation of primary fibroblasts using an oncogenic retrovirus; 4) cell synchronization for high-resolution banding of promethaphase chromosomes; 5) chromosome-banding procedures, including G-banding, alkaline G-11, and Q-banding; and 6) in situ hybridization of radiolabeled molecular clones to metaphase chromosomes for regional gene localization.

Animals↗
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Anterior cruciate ligament injury and patella dislocation: a report of nine cases.

Nine patients had combined anterior cruciate ligament (ACL) disruption and patella dislocation and underwent surgical reconstruction of one or both of these injuries. Six patients had both the ACL reconstructed and the patella realigned, and three had only the ACL reconstructed. Associated injuries were present in eight cases; these included meniscal tears in eight patients and medial collateral ligament injuries in two of these same patients. At final follow-up, at an average 19.7 months, examination revealed an average grade 1A Lachman and no pivot on all patients who underwent ACL reconstruction. No patients had hypermobile patellae or apprehension. One patient had a 4 degrees loss of extension and none had a loss of flexion. Two patients had continued anterior knee pain at final follow-up; one of these patients was the same person who had a loss of extension. None had recurrent instability of the ACL and none had recurrent instability of the patella.

Adolescent↗
PubMedDate not supplied

Acute elbow injuries in the National Football League.

We performed a retrospective review to evaluate acute medial collateral ligament injuries of the elbow in professional football players from 1991 to 1996 (5 seasons). There were 5 acute medial collateral ligament injuries in 4 players (1 player with bilateral involvement). All injuries occurred with the hand planted on the playing surface while a valgus or hyperextension force was applied to the elbow. There were 2 centers, both involved with long-snapping situations, 1 running back, and 1 quarterback. All elbows had valgus instability on physical examination. Despite this instability, all players were able to function without operative reconstruction of the medial collateral ligament. No evidence of valgus instability was seen at the time of follow-up (average, 3.4 years). Next, we reviewed all acute elbow injuries in the National Football League from the same 5-season period. Ninety-one acute elbow injuries were reviewed. Overall, there were 70 (76.9%) elbow sprains, 16 (17.6%) dislocation/subluxation patterns, 4 (4.4%) fractures, and 1 (1.1%) miscellaneous injury. Review of the acute elbow sprains revealed 39 (55.7%) hyperextension injuries, 14 (20%) medial collateral ligament injuries, 2 (2.9%) lateral collateral ligament sprains, and 15 (21.4%) nonspecific sprains. The epidemiology of the 14 medial collateral ligament injuries was studied in more detail. The 2 most common mechanisms of injury were blocking at the line of scrimmage (50%) and the application of a valgus force with the hand planted on the playing surface (29%). There were 8 linemen, 4 receivers, 1 running back, and 1 quarterback. All injuries were managed with nonoperative treatment. The average time lost was 0.64 games (range, 0 to 4). We report 19 acute medial collateral ligament injuries of the elbow in elite football players, 2 of whom are considered overhead throwing athletes, who were able to function at a competitive level without surgical repair or reconstruction, in contrast to baseball players, in whom the mechanics and demands may differ.

Adult↗
PubMedDate not supplied

Capsular restraints to anterior-posterior motion of the abducted shoulder: a biomechanical study.

Twenty-three fresh-frozen cadaver shoulders free of degenerative arthritis or rotator cuff disease were tested biomechanically to quantitate the contribution of specific capsular structures to restricting anterior-posterior translation of the abducted shoulder. With the glenohumeral joint in 90 degrees of abduction on a servohydraulic control testing system, translation was measured in 30 degrees of forward flexion (with regard to the coronal plane of the scapula), 0 degree, and 30 degrees of extension while a 25 N anterior-posterior load was applied. Measurements were taken both in the intact (vented) shoulder and after selective cutting of different capsuloligamentous structures was performed. In the intact shoulder the largest anterior-posterior translation occurred in 0 degree of horizontal flexion and extension with regard to the scapular plane, with equal amounts of anterior and posterior translation noted. The primary anterior-posterior stabilizer of the abducted shoulder is the inferior glenohumeral ligament complex. The anterior band is the primary stabilizer in 30 degrees of horizontal extension and at 0 degree (neutral). The posterior band is the primary stabilizer in 30 degrees of horizontal flexion. This study quantifies for the first time the normal amount of anterior-posterior translation in the intact cadaveric shoulder model. In addition, it demonstrates the relative role of the anterior and posterior band of the inferior glenohumeral ligament complex in stabilizing the glenohumeral joint at 90 degrees of abduction, where most clinical instability of the shoulder occurs.

Adult↗
PubMedDate not supplied

Role of the long head of the biceps brachii in glenohumeral stability: a biomechanical study in cadavera.

Ten cadaveric shoulders were tested to evaluate the effect of simulated contraction of the long head of the biceps brachii on glenohumeral translation. The shoulders were mounted on a special apparatus attached to a servo-controlled hydraulic testing device. Sequential 50 N anterior, posterior, superior, and inferior forces and a 22 N joint compressive load were applied to the shoulders. An air cylinder applied a constant force to the tendon of the long head of the biceps brachii. The shoulders were tested in seven positions of glenohumeral elevation and rotation. Application of a force to the long head of the biceps brachii resulted in statistically significant decreases in humeral head translation. The influence of the long head of the biceps was more pronounced at middle and lower elevation angles. When the shoulder was placed in 45 degrees of elevation and neutral rotation, application of a 55 N force to the biceps tendon reduced anterior translation by 10.4 mm (p = 0.001), inferior translation by 5.3 mm (p = 0.01), and superior translation by 1.2 mm (p = 0.004).

Analysis of Variance↗
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Thermal modification of collagen.

Shoulder capsular shrinkage has recently been proposed as a therapeutic modality in a select group of patients with instability. Basic science research studying the mechanism of collagen shrinkage and the effect of shrinkage on the tissue's mechanical properties is essential to define the ideal process by which to achieve optimal tissue shrinkage. Tissue shrinkage is a function of both time and temperature. This relationship was studied, and a model was derived to describe the relationship mathematically. Tissue shrinkage rate was extremely sensitive to temperature changes. The purpose of this study, was to shrink collagenous tissue thermally and then to measure the mechanical property changes as a function of tissue shrinkage. Uniaxial tensile testing of normal and heat-shrunken bovine tendon was carried out, and a model was developed to express the relationship between shrinkage and mechanical properties. We found that the mechanical properties decreased with increasing shrinkage, and that the maximal allowable shrinkage before significant material property changes occurred was between 15% to 20%. Ultrastructural analysis with transmission electron microscopy showed denaturation of the collagen fibrillar structure and provided direct support for the observed material changes.

Animals↗
PubMedDate not supplied

Mapping of an endogenous retroviral sequence to human chromosome 18.

The application of recombinant DNA technologies has allowed the detection of at least three families of moderately repetitive DNA segments in the human genome that are homologous to retroviruses previously isolated from mice and primates. One of these DNA segments has been shown by nucleotide sequence comparisons to be distantly related to both Moloney murine leukaemia virus (MoMuLV) and the endogenous baboon retrovirus and to have the sequence organization characteristic of an integrated retrovirus. Isolation of the homologous locus from chimpanzee DNA indicated that the integration event preceded the evolutionary divergence of chimpanzees and man. Here we have used a panel of rodent x human somatic cell hybrids to assign the chromosomal localization of this segment, called ERV1 (endogenous retrovirus-1), to human chromosome 18 (HSA 18).

Chromosome Mapping↗
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Isolation of HTLV-transformed B-lymphocyte clone from a patient with HTLV-associated adult T-cell leukaemia.

The human T-cell leukaemia/lymphoma virus (HTLV) is an exogenous retrovirus which has been associated with adult T-cell leukaemia/lymphoma (ATL). This malignancy of T lymphocytes is endemic to southern Japan, the West Indies, and to a lesser extent, the Middle East, Central Africa and the southeastern United States. ATL cells from patients of diverse geographical origins have been found to be infected with HTLV-1 (ref.6). HTLV is normally tropic for mature T lymphocytes, especially those expressing the helper-inducer surface antigen phenotype (OKT4 or Leu-3-positive), and the neoplastic T cells infected with HTLV generally express receptors for T-cell growth factor (detected by reactivity with anti-Tac antibody). However, we report here the isolation of a HTLV-infected B-lymphocyte clone from the peripheral blood of a patient with ATL. This clone is cytogenetically normal and is not infected with Epstein-Barr virus (EBV). Co-culture of cells from this clone with cord blood lymphocytes resulted in transmission of HTLV and the immortalization of either T or B lymphocytes. These results suggest that HTLV may be associated with a broader range of host cells than previously recognized.

Antigens, Surface↗
PubMedDate not supplied

A molecular solution to the riddle of the giant panda's phylogeny.

Although it is generally agreed that the giant panda (Ailuropoda melanoleuca) is a member of the order Carnivora, there has long been disagreement over whether it should be classified with bears, raccoons or as a single member of its own family. Four independent molecular and genetic measures lead to a consensus phylogeny for the giant and lesser pandas. The lesser panda diverged from New World procyonids at approximately the same time as their departure from ursids, while ancestors of the giant panda split from the ursid lineage much later, just before the radiation which led to modern bears. The giant panda's divergence was accompanied by a chromosomal reorganization which can be partially reconstructed from the ursid karyotype, but not from that of procyonids or the lesser panda. The apparently dramatic, but actually limited, distinctions between the giant panda and the bears in chromosomal and anatomical morphology provide a graphic mammalian example of the discordance of molecular and morphological (and chromosomal) evolutionary change.

Animals↗
PubMedDate not supplied

Tracking the evolution of the elusive Andean mountain cat (Oreailurus jacobita) from mitochondrial DNA.

Rarely observed in the wild, the existence of the Andean mountain cat (Oreailurus jacobita) has been established based on only 3 skulls and 14 museum skins. The Andean mountain cat's evolutionary relationship to other felids based on morphological characters is largely contradictory, with evidence aligning it with South American small spotted cats (ocelot lineage) or alternatively with pantherine lineage felids. Here we describe the phylogenetic distinctiveness and placement of the Andean mountain cat using DNA extracted from pieces of nine independent pelt specimens, including one confiscated from a trapper in 1995. A phylogenetic analysis of DNA sequences from three rapidly evolving mitochondrial genes (16S rRNA, NADH-5, and ATP-8) indicate that the Andean mountain cat is a distinct species belonging to the ocelot lineage. Our findings suggest that the Andean mountain cat diverged from a common ancestor with the ocelot (Leopardus paradalis) and margay (L. wiedii) and exhibits moderate levels of genetic variation.

Animals↗
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Development of comparative anchor tagged sequences (CATS) for canine genome mapping.

The development of a useful genetic map of the domestic dog would benefit by the inclusion of type I markers; coding genes that can connect the canine map to the homologous gene maps of other mammalian species. A group of 280 comparative anchor tagged sequences (CATS), and universal mammalian sequence tagged sites (UM-STS), were optimized for canine assessment. One hundred and five were screened for genetic polymorphism among nine canine breeds and three wild species of Canis in an attempt to promote gene mapping of comparative type I markers. Three categories of variation--size, restriction fragment length polymorphism (RFLP), and single-strand conformation polymorphism (SSCP)--were assessed. The data showed that 50% of the type I markers discriminate between species and 40% showed genetic variation among dog breeds. Although polymorphism incidence between nominated breeds for gene mapping is more limited than found for established reference pedigrees in other species, the concept and application of these CATS and UM-STS markers is useful in capturing the comparative information required for the full application and efficacy of the dog gene map.

Animals↗
PubMedDate not supplied

A human genome map of comparative anchor tagged sequences.

Effective comparative mapping inference utilizing developing gene maps of animal species requires the inclusion of anchored reference loci that are homologous to genes mapped in the more "gene-dense" mouse and human maps. Nominated anchor loci, termed comparative anchor tagged sequences (CATS), have been ordered in the mouse linkage map, but due to the dearth of common polymorphisms among human coding genes have not been well represented in human linkage maps. We present here an ordered framework map of 314 comparative anchor markers in humans based on mapping analysis in the Genebridge 4 panel of radiation hybrid cell lines, plus empirically optimized CATS PCR primers which detect these markers. The ordering of these homologous gene markers in human and mouse maps provides a framework for comparative gene mapping of representative mammalian species.

Animals↗
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Genomic ancestry of the American puma (Puma concolor).

Puma concolor, a large American cat species, occupies the most extensive range of any New World terrestrial mammal, spanning 110 degrees of latitude from the Canadian Yukon to the Straits of Magellan. Until the recent Holocene, pumas coexisted with a diverse array of carnivores including the American lion (Panthera atrox), the North American cheetah (Miracynonyx trumani), and the saber toothed tiger (Smilodon fatalis). Genomic DNA specimens from 315 pumas of specified geographic origin (261 contemporary and 54 museum specimens) were collected for molecular genetic and phylogenetic analyses of three mitochondrial gene sequences (16S rRNA, ATPase-8, and NADH-5) plus composite microsatellite genotypes (10 feline loci). Six phylogeographic groupings or subspecies were resolved, and the entire North American population (186 individuals from 15 previously named subspecies) was genetically homogeneous in overall variation relative to central and South American populations. The marked uniformity of mtDNA and a reduction in microsatellite allele size expansion indicates that North American pumas derive from a recent (late Pleistocene circa 10,000 years ago) replacement and recolonization by a small number of founders who themselves originated from a centrum of puma genetic diversity in eastern South America 200,000-300,000 years ago. The recolonization of North American pumas was coincident with a massive late Pleistocene extinction event that eliminated 80% of large vertebrates in North America and may have extirpated pumas from that continent as well.

Americas↗
PubMedDate not supplied

Molecular dating and biogeography of the early placental mammal radiation.

The timing and phylogenetic hierarchy of early placental mammal divergences was determined based on combined DNA sequence analysis of 18 gene segments (9779 bp) from 64 species. Using rooted and unrooted phylogenies derived from distinct theoretical approaches, strong support for the divergence of four principal clades of eutherian mammals was achieved. Minimum divergence dates of the earliest nodes in the placental mammal phylogeny were estimated with a quartet-based maximum-likelihood method that accommodates rate variation among lineages using conservative fossil calibrations from nine different nodes in the eutherian tree. These minimum estimates resolve the earliest placental mammal divergence nodes at periods between 64 and 104 million years ago, in essentially every case predating the Cretaceous-Tertiary (K-T) boundary. The pattern and timing of these divergences allow a geographic interpretation of the primary branching events in eutherian history, likely originating in the southern supercontinent Gondwanaland coincident with its breakup into Africa and South America 95-105 million years ago. We propose an integrated genomic, paleontological, and biogeographic hypothesis to account for these earliest splits on the placental mammal family tree and address current discrepancies between fossil and molecular evidence.

Animals↗