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Biomedical subjects

M S Johnson

Publications and source records attributed to M S Johnson.

At least 199 records · Page 11Linked to original sources
PubMed1992

Injuries in the Alaskan Arctic.

In recent years, the State of Alaska has developed a Trauma Registry data collection system on injuries which result in hospitalization or death. All 25 acute care hospitals in Alaska have agreed to participate in this Trauma Registry. Data are presented from this registry on injuries which occurred between March 1988 and December 31, 1990 in the North Slope Borough, the Northwest Arctic Borough, and the Norton Sound Region. Causes of death and serious injury are presented and comparisons made among regions and between Natives (primarily Inupiat Eskimos) and non-Natives. Use of firearms accounted for the majority of fatalities (32%), while falls were the most reported injury (19%). Trauma Registry Data can be used to target high risk groups and activities for the development and evaluation of prevention programs. This database also is used for quality assurance reviews of patient care and outcomes.

Alaska↗
PubMed1992

Juvenile hypertrophy presenting as a discrete breast mass.

Juvenile hypertrophy of the breast usually presents as diffuse enlargement of the breasts in young women. The authors describe a patient in whom hypertrophy presented as a discrete mass, which was both visible in mammograms and palpable.

Adult↗
PubMed1991

Inhibition of depolarisation-induced calcium influx into GH3 cells by arachidonic acid: the involvement of protein kinase C.

The influx of 45Ca2+ induced in GH3 cells by exposure to 60 mM K+ medium was inhibited by arachidonic acid (AA) in a concentration-dependent manner. This action of AA was not prevented by inhibitors of its metabolism but was reversed by the inhibitors of protein kinase C (PKC), H7 and staurosporine but not their less active congeners HA 1004 and K252a, respectively. Presumed down-regulation of PKC by pretreatment with phorbol 12,13-dibutyrate (PDBu) also greatly diminished the effect of AA. Experiments to assess effects of AA on 45Ca2+ efflux and on cytosolic Ca2+ concentrations indicated that an additional PKC-independent action of AA involving the release of intracellularly stored calcium was present. Both direct activation of certain PKC isoform(s) by AA and the synergistic influence on PKC activity by its concomitant raising of intracellular Ca2+ concentrations, may be physiologically important in the regulation of depolarisation-induced Ca2+ entry.

Animals↗
PubMed1991

Behavior and toxicity of antimony in the short-tailed field vole (Microtus agrestis).

Laboratory experiments were undertaken to study uptake and retention of antimony and to investigate whether the elevated organ antimony concentrations found previously in a population of Microtus agrestis at a contaminated site could cause harmful effects. Antimony trioxide in the diet produced elevated organ concentrations, but even in a 60-day experiment no harmful effects were evident. An equilibrium between uptake and excretion of antimony seemed to be rapidly established and progressive increases in organ concentrations did not occur. When dietary intake was terminated antimony was rapidly cleared. Comparison of findings from the laboratory and field suggested that inhalation was an additional route of intake in the field. It seems that present levels of antimony are unlikely to cause toxic effects in the wild population.

Animals↗
PubMed1991

Mercury in the stomach contents of dab (Limanda limanda) from the North East Irish Sea and Mersey Estuary.

A study of mercury concentrations in the stomach contents of fish from the north-east Irish Sea and Mersey Estuary has been shown to provide a means for surveillance of geographical and time-based changes in environmental exposure of fish biota to mercury in marine and estuarine ecosystems. This paper describes data for the flatfish dab (Limanda limanda), caught during the period 1986-1988. The low degree of variability in the data enables confirmation of clear trends in mercury concentration in stomach contents over time. As the inputs of mercury to the sewage sludge dumping ground in Liverpool Bay have decreased, there has been a corresponding decrease in mercury in fish food items. The mean mercury value in stomach contents around the dump site has declined to 100 microg kg(-1) (wet weight) which now predominates over the whole of Liverpool Bay. In 1986, mercury concentrations in stomach contents of fish ranged to over 750 microg kg(-1) although the majority of values were below 200 microg kg(-1). Most of the sites within the Mersey Estuary produced mean concentrations which were similar to those in the open sea, except for Garston which is the site closest to an inland, and principal alternative, source of mercury.

Journal Article↗
PubMed1991

Kinetic evidence for two components in the priming effect of LH-releasing hormone in the rat.

The priming effect of LHRH on LH release from prooestrous rat hemipituitary glands in vitro was analysed by kinetic approaches. Concentration-response curves for LHRH-, K(+)- and ionomycin-induced LH release were constructed for initial exposure to the secretagogues and after 'priming' with a low dose of LHRH (100 pg/ml). These data were analysed by a non-linear curve-fitting programme to reveal the potency and maxima of the responses before and after priming. The parameters obtained from the curves fitted to the LHRH concentration-response curves showed that two changes had occurred as a result of priming. There was an increase in the maximum amount of hormone released and also a relatively greater ability for low concentrations of LHRH to cause release (increased potency). The data for K+ and ionomycin revealed only one change as a result of priming, an increase in the maximum amount of hormone available for release. The data indicate that LHRH, after self-priming, releases more hormone by at least two routes, one represented by a general increase in stimulus-secretion coupling (which is available to K+ and ionomycin), the other a specific up-regulation of signal transduction by the LHRH receptor-effector system.

Animals↗
PubMed1990

Tertiary structural constraints on protein evolutionary diversity: templates, key residues and structure prediction.

The pattern of residue substitution in divergently evolving families of globular proteins is highly variable. At each position in a fold there are constraints on the identities of amino acids from both the three-dimensional structure and the function of the protein. To characterize and quantify the structural constraints, we have made a comparative analysis of families of homologous globular proteins. Residues are classified according to amino acid type, secondary structure, accessibility of the sidechain, and existence of hydrogen bonds from sidechain to other sidechains or peptide carbonyl or amide functions. There are distinct patterns of substitution especially where residues are both solvent inaccessible and hydrogen bonded through their sidechains. The patterns of residue substitution can be used to construct templates or to identify 'key' residues if one or more structures are known. Conversely, analysis of conversation and substitution across a large family of aligned sequences in terms of substitution profiles can allow prediction of tertiary environment or indicate a functional role. Similar analyses can be used to test the validity of putative structures if several homologous sequences are available.

Amino Acid Sequence↗
PubMed1990

Retrovirus phylogeny and evolution.

The elucidation of complete genomic sequences from a wide variety of retroviruses and retrotransposons has allowed the construction of sequence-based phylogenies that reveal their evolutionary history. True retroviruses, whether exogenous or endogenous, tend to cluster into four major groups. Not only is there no distinction between exogenous and endogenous viruses, but their evolutionary limb lengths on the phylogenetic trees are comparable. This can be taken as evidence favoring a dynamic equilibrium balancing a constant invasion of germlines by infectious retroviruses on the one hand, with subsequent escape of endogenous viruses to alternative hosts on the other. Retroviruses share a common ancestry with a wide variety of retrotransposons and other reverse transcriptase-bearing entities. One of these retrotransposon groups, the Gypsy group, resembles the Moloney mouse group of retroviruses much more closely than it does other retroviruses. The simplest explanation is that the evolutionary rate of the retrotransposon is much slower than the retrovirus rate and that among the retroviruses the Moloney mouse group has been evolving more slowly than the other three groups, leaving the two short-limbed taxa more similar. The alternative explanation that these two groups actually shared a common ancestor more recently than has either with the other retrovirus groups is not supported by residue-by-residue character assessment.

Animals↗
PubMed1990

Molecular anatomy: phyletic relationships derived from three-dimensional structures of proteins.

A distance measure that reflects the dissimilarity among structures has been developed on the basis of the three-dimensional structures of similar proteins, this being totally independent of sequence in the sense that only the relative spatial positions of mainchain alpha-carbon atoms need be known. This procedure leads to phyletic relationships that are in general correlated with the sequence phylogenies based on residue type. Such relationships among known protein three-dimensional structures are also a useful aid to their classification and selection in knowledge-based modeling using homologous structures. We have applied this approach to six homologous sets of proteins: immunoglobulin fragments, globins, cytochromes c, serine proteinases, eye-lens gamma crystallins, and dinucleotide-binding domains.

Amino Acid Sequence↗
PubMed1990

Distribution of antimony in contaminated grassland: 1--Vegetation and soils.

Antimony concentrations in surface soils were found to decrease with increasing distance from an antimony smelter. This pattern was also found in moss bags exposed in the same area. At three sites close to the smelter, antimony concentrations in soil and vegetation were much higher than at a rural control site and published background levels. Maximum soil and plant concentrations on a dry weight basis of 1489 mg kg(-1) and 336 mg kg(-1), respectively, were found, compared to background levels of <1 mg kg(-1). Field exposure of grass in pots of uncontaminated soil and a laboratory experiment using soils from near the smelter suggested that the antimony in vegetation was largely due to continued aerial deposition and not to uptake from soil.

Journal Article↗
PubMed1990

Distribution of antimony in contaminated grassland: 2--Small mammals and invertebrates.

Concentrations of antimony in invertebrates and small mammals from grasslands in the vicinity of an antimony smelter were significantly elevated compared to a control site. Higher concentrations of antimony were recorded in liver, lung and kidney tissue of herbivorous and insectivorous mammals from the contaminated sites. However, there is little evidence of bioaccumulation of antimony in food chains represented by the soil-vegetation-invertebrate-insectivore pathway of the grasslands, and little indication of significant accumulation by herbivorous mammals despite marked contamination of their diet.

Journal Article↗