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Biomedical subjects

S J Clark

Publications and source records attributed to S J Clark.

At least 145 records · Page 8Linked to original sources
PubMed1987

Similarities in sequences and cellular expression between rat CD2 and CD4 antigens.

The MRC OX-34 antigen of rat T lymphocytes was purified and peptide sequences were obtained. Oligonucleotide probes were synthesized and cDNA clones coding for the antigen were isolated and sequenced to yield a predicted protein sequence for the molecule that fitted the peptide data. Comparison of this sequence with that for human CD2 determined by Sewell et al. showed that OX-34 is rat CD2. The primary structure of the molecule was notable for a moderately large cytoplasmic domain of unusual sequence and also for its highly significant relationship to CD4 antigen in the membrane proximal extracellular region and the transmembrane sequence. A relationship to the Ig superfamily can be argued for the two extra cellular domains of CD2, even though neither fits the standard pattern for Ig-related domains. Within the T lymphocyte lineage, rat CD2 seemed to be present on all stages with the exception of approximately 50% of the thymic CD4-,CD8- cells. In addition, the antigen was prominent on most macrophages in the spleen but not found on peritoneal or liver macrophages. CD4 antigen is also expressed on T lymphocytes and macrophages, and thus CD2 and CD4 appear similar in their cellular expression as well as structural characteristics.

Amino Acid Sequence↗
PubMed1987

Seasonal distribution of live births in a rural community in the southern United States.

"Births in Greene County, Alabama for the years 1980-1984 were examined and an overall seasonal trend was found with a peak from August through November. This trend was found to be most pronounced among women greater than 24 years old, and among multiparous women, and to be negatively correlated with seasonal variations in temperature and daylight. The phenomenon is likely multifactorial in origin, with sociocultural factors playing a considerable role. The influence of increasing maternal age and parity in the expression of the seasonal trend may be a function of age-related changes in families, with nuclear families acting as the most powerful potentiators of seasonality."

Age Factors↗
PubMed1987

Peptide and nucleotide sequences of rat CD4 (W3/25) antigen: evidence for derivation from a structure with four immunoglobulin-related domains.

The rat W3/25 antigen was the first marker antigen of helper T lymphocytes to be identified. Subsequently, the human OKT4 antigen (now called CD4) was described, and cell distribution and functional data suggested that W3/25 and OKT4 antigens were homologous. This is now confirmed by the matching of peptide sequences from W3/25 antigen with sequence predicted from rat cDNA clones detected by cross-hybridization with a cDNA probe for human CD4. Analysis of the two sequences suggests an evolutionary origin from a structure with four immunoglobulin-related domains, although only domain 1 at the NH2 terminus meets the standard criteria for an immunoglobulin-related sequence. CD4 domains 2 and 4 contain disulfide bonds but seem like truncated immunoglobulin domains, whereas domain 3 may have a pattern of beta-strands like an immunoglobulin variable domain, but without the disulfide bond.

Amino Acid Sequence↗
PubMed1986

ESS equations sometimes do not specify an ESS.

The equations used to find an evolutionarily stable strategy in the basic game theory model (Maynard Smith, 1974, 1982; Maynard Smith & Price, 1973), and in sexual conflict models (Maynard Smith, 1977; Parker, 1979) do not, in fact, specify an ESS when the expected number of contests entered is not the same for each strategy. This means that the conclusions of many game theory models may be incorrect. This is particularly likely to be true when the mean durations of contests for different strategies are not the same, or when the probability that an individual enters a contest is not the same for all strategies. New ESS equations are developed which incorporate the expected number of contests entered.

Animals↗
PubMed1986

Class 4 choledochal cyst.

We have described a class 4 choledochal cyst in a 24-year-old black woman treated with choledochocystoduodenostomy.

Adult↗
PubMed1985

Opiate-induced inhibition of the visceral distension reflex by peripheral and central mechanisms.

Distension of the proximal ileum by elevation of the intraluminal pressure, caused a transient, reflex fall in blood pressure of urethane-anaesthetised rats. The threshold intraluminal pressure required to evoke a reflex response was increased by codeine, but not by the quaternary opiate agonist N-methylmorphine. The magnitude of the reflex hypotension was decreased by codeine, morphine and N-methylmorphine. The quaternary opiate antagonist N-methylnalorphine reduced the effects of N-methylmorphine, but not those of codeine or morphine. Codeine-induced inhibition of reflex depressor responses was reduced by pretreatment with naloxone. Bilateral vagotomy caused a significant decrease in effects of codeine on the threshold, but not the magnitude, of reflex depressor responses. Furthermore N-methylnalorphine antagonised both codeine- and morphine-induced inhibition of depressor responses following transsection of the vagus nerves. Effects of opiates on the threshold for the reflex appear to be centrally mediated and to require an intact vagal innervation. The magnitude of depressor responses is largely independent of vagal innervation and may be influenced by opiates acting via peripheral mechanisms.

Anesthesia↗
PubMed1985

An evaluation of the Sequoia-Turner Cell Dyn 900.

A formal evaluation of the Sequoia-Turner Cell Dyn 900, a compact eight-parameter semi-automated blood cell counter, was carried out in a small paediatric haematology laboratory. The instrument's precision, linearity and carry-over were adequate. Comparison with a Coulter ZF6 system plus visual platelet count showed good agreement, and results in the UK National External Quality Assessment Scheme also compared well with 'all methods' values. Throughput was assessed at 54 eight-parameter counts per hour. The machine proved to be reasonably economical, highly reliable and easy to operate. It was popular with staff and can be recommended, particularly for the smaller laboratory.

Autoanalysis↗
PubMed1984

Hormone ontogeny in the ovine fetus. XVII. Demonstration of pulsatile luteinizing hormone secretion by the fetal pituitary gland.

To determine whether pulsatile gonadotropin secretion occurs in the fetus, plasma immunoreactive ovine LH (oLH) concentrations were determined by homologous RIA in serial samples obtained in 51 chronically catheterized fetuses between 79 and 140 days gestation. Pulsatile secretion of LH was detected in 39 fetuses, with a peak amplitude ranging from 1.2-11.5 ng/ml (mean +/- SD, 4.5 +/- 2.3 ng/ml). The mean plasma oLH concentration between pulses was 0.4 +/- 0.23 ng/ml. The mean amplitudes of the LH pulses were similar in the age range studied, and a sex difference was not detected. The estimated interpulse interval (determined by dividing the total number of hours during which blood samples were obtained by the number of pulses demonstrated) was 2.4 h between 91 and 110 days gestation. The pattern of plasma oFSH concentration was examined in 20 fetuses between 98 and 123 days gestation. Six fetuses with gestational ages between 106 and 115 days had FSH pulses that were equal or more than 2 times the sensitivity of the RIA. This study demonstrates a pulsatile mode of LH secretion by the ovine fetal pituitary as early as 81 days gestation and provides indirect evidence for pulsatile LRF secretion by the fetal hypothalamus and an operative LRF pulse generator by midgestation, the earliest stage in gestation studied.

Animals↗
PubMed1983

The release of Met-enkephalin from the guinea-pig ileum at rest and during peristaltic activity.

Segments of guinea-pig ileum maintained at an intraluminal pressure of 0cm H2O released methionine-enkephalin-like material (ME) into the bathing fluid. Elevation of intraluminal pressure to 5 cm H2O induced peristalsis and reduced ME release both in the absence and presence of naloxone (0.27 microM). Following prolonged distension, tissues developed intermittent peristaltic activity. ME release during intermittency was consistently and significantly (p less than 0.05) greater than that observed from tissues exhibiting continuous peristalsis. These results suggest that ME release is associated with nonpropulsive activity in the guinea-pig ileum.

Animals↗
PubMed1983

The influences of sample distribution and age on reference intervals for adult males.

This investigation was designed to improve reference information and to evaluate the influences of sample distribution and age on the derived reference intervals. Specimens from 127 men were collected after a 12- to 14-hour fast and analyzed by 60 different laboratory procedures. Differences in the reference intervals derived, using three separate statistical methods, appeared to be unimportant clinically, but the percentile method was preferred because it required no assumptions concerning the frequency distribution. Relationships between age and analyte concentrations were examined by linear regression analysis, and the analytes were placed in one of three groups, according to the significance of this relationship: greatest significance (P less than or equal to 0.01), 18 analytes; intermediate significance (0.01 less than or equal to P less than or equal to 0.05), 12 analytes; and least significance (P greater than 0.05), 30 analytes. The age-related changes for each analyte were evaluated according to analytic variation, population dispersion, and clinical relevance. Age-dependent reference intervals for adult males are recommended for albumin, cholesterol, phosphorus, and sedimentation rate.

Adult↗
PubMed1982

Cefoperazone: regression analysis, disk content, and disk susceptibility testing considerations.

Cefoperazone agar dilution minimal inhibitory concentration (MIC) susceptibility results were compared with zones of inhibition produced by disk diffusion susceptibility testing. Disks containing 30, 50, 75, and 100 micrograms of cefoperazone were tested for purposes of regression line comparisons and error rate-bounded analysis. Results suggest that if the MIC equivalent of susceptibility is 32 micrograms/ml, either a 50-micrograms disk with zone sizes of susceptibility (S) greater than or equal to 15 mm and resistance (R) less than or equal to 12 mm or a 75-micrograms disk with zone sizes of S greater than or equal to 17 mm and R less than or equal to 14 mm may be appropriate. If the MIC equivalent of susceptibility is 64 micrograms/ml, this would dictate use of a 75-micrograms disk with zone sizes of S greater than or equal to 17 mm and R less than or equal to 12 mm. Disks containing either less than or equal to 30 or greater than or equal to 100 micrograms of cefoperazone did not adequately discriminate among susceptible and resistant bacterial strains at either the 32- or 64-micrograms/ml MIC equivalent.

Anti-Bacterial Agents↗
PubMed1981

Isolation of a clone containing human histone genes.

A recombinant clone containing human histone genes has been isolated. The clone, lambda HH-01, was selected from a genomal library using chicken histone cDNA and a cloned fragment containing chicken histone genes as probes. Sub-clones from lambda HH-01 have been mapped and coding regions located with cDNA. The human H3 gene has been identified by DNA sequence analysis.

Amino Acid Sequence↗
PubMed1981

Peristalsis abolishes the release of methionine-enkephalin from guinea-pig ileum in vitro.

The release of methionine-enkephalin from superfused guinea-pig ileum has been demonstrated. Methionine-enkephalin, as measured by radioimmunoassay, was shown to be released from tissues maintained at an intraluminal pressure of O cm water (resting conditions). Increased intraluminal pressure (5 cm water) induced peristalsis and abolished the release of methionine-enkephalin. These results provide further evidence that endogenous opioids may be involved in the modulation of contractile activity in the guinea-pig ileum.

Animals↗
PubMed1978

Comparison of micro-ID, API 20E, and conventional media systems in identification of Enterobacteriaceae.

The Micro-ID, a new identification kit for Enterobacteriaceae, consists of 15 biochemical tests, with substrates and reagents impregnated in filter paper disks. A 0.2-ml amount of an organism suspension equal to a 0.5 McFarland standard is pipetted into each of the compartments. After 4 h of incubation and addition of potassium-hydroxide (KOH) to the Voges-Proskauer test, the color reactions are read according to the recommendations of the manufacturer. A five-digit octal code number is derived from each set of reactions from which an identification is derived by using a code book. In a single-blind, comparative study of the Micro-ID system with the API 20E system (Analytab Products Inc.) and conventional biochemical tube media, we found that the Micro-ID and the API 20E systems gave a 90% identification correlation when each was compared with the conventional tube media. A comparison of all three systems gave an 82% overall identification correlation. When the common tests of Micro-ID and API 20E were compared with conventional tube media, we found that the tests in the Micro-ID performed as well as or better than those of the API 20E. Certain groups of organisms, i.e., Citrobacter, Enterobacter, Proteus, Salmonella, and Serratia genera, were found to give low correlation on certain common tests. When using primary isolation MacConkey plates from the clinical laboratory, only 74% of the plates with Enterobacteriaceae had sufficient numbers of colonies of each enteric organism to produce the 0.5 McFarland inoculum density required. Problems concerning the misidentification of some organisms are discussed.

Bacteriological Techniques↗
PubMed1977

Skin surface lipids of the dog.

The skin surface lipid of the dog has been reported to contain a high proportion of diol diesters having a lower mobility on thin layer chromatography than diesters from other species in spite of containing similar fatty acid and diol components. In the present study, dog skin surface lipid was separated by preparative thin layer chromatography into sterol esters (42%), wax diesters (32%), free sterols (9%), polar lipids (7%), and unidentified components (10%). The diesters contained 1,2-diols, each estrified with one long chain fatty acid and one isovaleric acid moiety. The diols were principally branched chain C21 and C22 compounds while the long chain fatty acids esterified with them were mainly C20 and C21 branched compounds. The fatty acids from the sterol esters were mostly saturated, branched chain C19 TO C23, together with 7% of straight chain monoenoic acids, principally C21 and C22. There were only trace amounts of free sterols other than cholesterol, while the esterified sterols contained 96% cholesterol and 4% lathosterol.

Animals↗