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Biomedical subjects

K Erwin

Publications and source records attributed to K Erwin.

7 recordsLinked to original sources
PubMed2000

Comparison of sensitivity of sodium currents to tetrodotoxin in equine muscle specimens with that in murine and human muscle specimens.

OBJECTIVE: To determine sensitivity of equine skeletal muscle to tetrodotoxin and compare that with sensitivity of murine and human skeletal muscles. SAMPLE POPULATION: Semimembranosus, vastus lateralis, triceps brachii, and masseter muscle specimens from 22 euthanatized horses, vastus lateralis muscle biopsy specimens from 25 clinically normal humans, and diaphragmatic muscle specimens from 6 mice. PROCEDURE: Electrically elicited twitch responses were measured in muscle specimens incubated in medium alone and with tetrodotoxin (100 nM, 400 nM, 1.6 microM for equine specimens and 100 nM, 200 nM, 400 nM, 800 nM, 1.6 microM for murine and human specimens). Percentages of tetrodotoxin-sensitive and -resistant sodium channels were determined and compared among muscles and species. RESULTS: 2 sodium channels with different sensitivities to tetrodotoxin were identified in equine muscle. One was blocked with 100 nM tetrodotoxin and the other was unaffected by tetrodotoxin at concentrations up to 1.6 microM. The only difference detected among the 4 equine muscles was that masseter muscle specimens had a higher percentage of tetrodotoxin-sensitive channels than triceps brachii muscle specimens. Tetrodotoxin-resistant sodium channels constituted 31 to 66% of the equine muscle twitch response, which was greater than that determined for normal human and murine muscle (< 5%). CONCLUSION AND CLINICAL RELEVANCE: Equine skeletal muscle contains a high percentage of tetrodotoxin-resistant sodium channels. The 4 equine muscles evaluated were more similar to each other than to murine and human muscles. Shifts in expression of sodium channel subtypes may play a role in the manifestation of certain myopathies.

Animals↗
PubMed1993

Phenytoin increases specific triacylglycerol fatty esters in skeletal muscle from horses with hyperkalemic periodic paralysis.

Previous studies have demonstrated that phenytoin decreases the levels of triacylglycerols in several tissues other than skeletal muscle. Since phenytoin is clinically effective in several skeletal muscle disorders, triacylglycerol metabolism in skeletal muscle from four normal Quarter horses and four Quarter horses with hyperkalemic periodic paralysis was examined. The horses with hyperkalemic periodic paralysis had low levels of 18:3 in the phospholipids, low levels of 16:0, 16:1 and 18:3 in the free fatty acids and low levels of 20:4 in triacylglycerols. Triacylglycerol levels were increased in skeletal muscle from seven (three controls, four hyperkalemic periodic paralysis) of the eight horses on treatment with oral phenytoin for one week. Instead of an increase in all fatty ester types only 16:0, 16:1, 18:1 and 18:2 were significantly increased. Total lipid phosphorus and the distribution of phospholipid fatty esters and free fatty acids were not significantly altered by phenytoin treatment in most cases. An alteration in triacylglycerol metabolism by phenytoin was also observed in primary cultures of normal equine skeletal muscle radiolabeled with 18:1, but not in those radiolabeled with 18:2. These findings suggest that phenytoin does not just increase the levels of triacylglycerol in skeletal muscle, but alters the utilization and incorporation of fatty esters. These findings suggest a potential involvement of triacylglycerol metabolism in the clinical efficacy of phenytoin in hyperkalemic periodic paralysis.

Animals↗
PubMed1993

Interpreting the evidence: competing paradigms and the emergence of lesbian and gay suicide as a "social fact".

Almost two decades after the American Psychiatric Association acknowledged that homosexuality should no longer be considered a pathological condition, studies continue to show significantly higher rates of suicide, depression, substance abuse, and other indicators of psychological distress among lesbians and gay men than among heterosexuals in the United States. If homosexuality is not, in fact, pathological, then what accounts for such self-destructive behavior? This article examines contending causal theories of homosexual suicide and psychological distress ranging from religious and medical-psychiatric theories that problematize individual behavior to societal explanations that locate the cause in social intolerance and internalized oppression. Illuminating the origins of myths that persist today, it demonstrates how historical, social, and political forces have been instrumental in shaping the scientific and medical response to gay and lesbian psychological distress. Emphasis is on the need to question the "objective validity" of scientific theories in order to develop more effective responses to gay and lesbian mental health problems. Finally, this article considers alternative views of sexuality that are emerging from such sources as feminists and gay Native Americans, and proposes new directions for mental health research that encompass issues of diversity within the gay and lesbian population.

Female↗
PubMed1992

Managing conflict.

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Conflict, Psychological↗
PubMed1990

Fatty acids modulate calcium-induced calcium release from skeletal muscle heavy sarcoplasmic reticulum fractions: implications for malignant hyperthermia.

Based on studies in swine, the malignant hyperthermia syndrome has been postulated to result from an enhanced sensitivity (low threshold) of the Ca2(+)-induced Ca2(+)-release process. However, fatty acid production is elevated in homogenates of skeletal muscle from pigs and humans susceptible to malignant hyperthermia. In the present study, we demonstrate that the threshold of Ca2(+)-induced Ca2+ release is normal in susceptible humans and in susceptible swine depleted of triglycerides. Exogenously added unsaturated fatty acids decreased the threshold of Ca2(+)-induced Ca2+ release to a much greater extent in porcine and equine muscle than in human muscle. When triglyceride and free fatty acid values were reduced to about 40 and 60%, respectively, of control values, malignant hyperthermia-susceptible swine did not exhibit muscle rigidity when challenged in vivo with halothane and succinylcholine and the threshold of the Ca2(+)-induced Ca2(+)-release process in heavy sarcoplasmic reticulum fractions was normal. Despite the reduced triglyceride and fatty acid levels, these swine had a positive in vitro contracture test for malignant hyperthermia. A low Ca2(+)-induced Ca2(+)-release threshold is not essential for malignant hyperthermia susceptibility, but appears to be the result of excessive free fatty acids produced during organelle isolation.

Animals↗
PubMed1990

Fatty acid uptake and catecholamine-stimulated phospholipid metabolism in immortalized airway epithelial cells established from primary cultures.

The incorporation of [14C]oleic and [14C]linoleic acid into phospholipids and neutral lipids was compared in two recently immortalized airway epithelial cell lines. In addition, the effects of adrenergic stimulation on phospholipid turnover was examined. Both cell lines readily incorporated the fatty acids into all phospholipid and neutral lipid fractions. Isoproterenol (1 microM) induced Ca2+ transients in both cell lines, indicating a functional beta-adrenergic response. Epinephrine (10 microM; 15 min) stimulation of cells prelabeled with [14C]linoleic acid increased the percentage of label in phosphatidylcholine in one cell line. Lipid metabolism can now be extensively studied in human airway epithelia.

Calcium↗