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Biomedical subjects

J Mitchell

Publications and source records attributed to J Mitchell.

At least 325 records · Page 18Linked to original sources
PubMed1985

Interaction of calcitonin and calcitonin gene-related peptide at receptor sites in target tissues.

Discrete receptor sites for calcitonin (CT) and calcitonin gene-related peptide (CGRP) were found in the nervous system and in peripheral tissues. Each peptide was capable of cross-reacting with the specific receptor of the other. In contrast to CT receptors, CGRP receptors were not linked to adenylate cyclase. However, CGRP could stimulate adenylate cyclase in CT target tissues apparently by interacting with CT receptors. The relative abilities of CGRP and mammalian CT to inhibit CT binding suggest that CGRP could serve as an endogenous ligand for CT receptors in the central nervous system.

Adenylyl Cyclases↗
PubMed1985

Economic impact of an epizootic of bovine vesicular stomatitis in California.

A recent outbreak of vesicular stomatitis in California's San Joaquin Valley caused economic loss at 2 dairies of $225,000 during a 2-month period. These losses amounted to $202/cow for dairy 1 and $97/cow for dairy 2. The most notable economic losses were associated with high cull rates. The rapid spread of the disease (attack rates were 72% in 66 days for dairy 1 and 38% in 41 days for dairy 2) suggests that high-density herds particularly may be vulnerable to the disease. Factors that may have accounted for this rapid spread included common water troughs, open corrals, and inability of the dairy operator to isolate cows due to lack of space.

Animals↗
PubMed1985

Axonal regeneration through a peripheral nerve implanted into a brain cavity.

A cavity was prepared in the rat parietal cortex by suction, filled with gel foam and left for 3 weeks during which time it became highly vascularised. Into this 3-week-old capillary bed a 5 mm length of autologous common peroneal nerve was implanted. Animals were killed at various time intervals up to 7 months after implantation of the nerve segment. The ultrastructural features of the vascular bed before and after implantation of the nerve segment were compared. In the absence of a peripheral nerve implant no axons were found within the cavity. However, at 5 weeks after implantation numerous axon-like profiles and capillaries containing fenestrations were observed within the implant. Eight weeks after implantation of the peripheral nerve both myelinated and non-myelinated axons were observed within the implant and in the surrounding capillary bed. No obvious increase in the number of axons was observed with increasing time periods. To investigate the origin of the axons within the vascular bed and/or implant the fluorochrome true blue was injected into the cavity 7 months after implantation of the nerve. Three days later selected areas of the brain, the trigeminal, superior cervical and otic ganglia were examined for retrogradely labelled fluorescent cells. Labelled cells were found adjacent to the cavity and in the ipsilateral trigeminal and superior cervical ganglia. The significance of these results in relation to the enhancement of axonal regeneration from the damaged central nervous system (CNS) is discussed.

Animals↗
PubMed1985

The variation of OER with dose rate.

The oxygen enhancement ratio (OER) has been measured as a function of dose rate from 276 Gy/hr to 0.89 Gy/hr for V-79 cells irradiated at 23 degrees C or 37 degrees C. As dose rate is decreased, the OER initially increases, from a value of 3.0, to a maximum value of 3.7 to 4.0, at a dose rate between 20 and 60 Gy/hr. The OER subsequently decreases with further dose rate reduction to a minimum value of 2.4 at the lowest dose rate. Similar experiments conducted with cells in nutrient deprived conditions exhibited a monotonic decrease in OER from 3.0 to 1.7 with dose rate reduction. These experimental findings can be understood in terms of the sublethal damage repair capability of cells under different pO2 and nutrient conditions.

Animals↗
PubMed1985

A longitudinal study of possible allergy to enzyme detergents.

One hundred and thirty-six subjects with asthma and/or hay fever were surveyed for possible sensitization to the Bacillus licheniformis protease present in the commercial antigenically identical enzymes (Alcalase and Maxatase) used in household detergents. Prick-test reactions reported as minimally positive were given by one subject to both commercial enzyme preparations at the same standard non-irritating concentrations and by four others to one but not the other antigenically identical enzyme. Two of the five, and an additional seven, gave weak prick tests to the purified enzyme (Koch-Light Protease) at test protein concentrations 100 times stronger and to which non-specific irritation occurs. The findings are strongly against interpretation of these reactions as positive and were on no occasion comparable with those in sensitive workers. The skin-test reactions are attributable to non-specific effects. Neither enzyme-specific RAST IgE tests nor clinical histories suggested clinical sensitivity. Enzyme-specific RAST IgE for eighty-eight subjects over a period of 5 years showed no correlation with exposure. None had developed specific IgE levels like those of sensitized workers, and their RAST levels did not differ significantly from cord blood, unexposed subjects and prick-test-negative workers. The eight with the largest increase in specific IgE were prick-test-negative and their clinical reactions to enzyme detergents were comparable to those of non-enzyme detergents. There is no evidence from this study that exposure to modern, non-dusty household enzyme-containing detergents is likely to lead to clinical sensitization.

Adult↗
PubMed1985

Evaluation of a modified enzyme immunoassay for Neisseria gonorrhoeae in high- and low-risk females.

A recently modified commercial enzyme immunoassay (Gonozyme; Abbott Laboratories, North Chicago, IL) for Neisseria gonorrhoeae antigens was compared with bacteriological culture for diagnostic sensitivity, specificity, and predictive value. A total of 480 specimens were tested by both methods; 355 from females attending a sexually transmitted disease clinic ("high-risk") and 125 from female Family Planning clients ("low-risk"). Sensitivity and specificity of enzyme immunoassay for sexually transmitted disease clinic specimens were 79.7 and 97.9%, respectively (55 positive, 280 negative, 6 false positive, 14 false negative). In the low-risk population, sensitivity and specificity were 100 and 97.5%, respectively (3 positive, 119 negative, 3 false positive, 0 false negative). Despite modification, sensitivity of the method remains low for our sexually transmitted disease clinic population, but the test may have applicability for preliminary screening in low-prevalence settings.

Antigens, Bacterial↗
PubMed1985

Comparison of renal and osseous binding of parathyroid hormone and hormonal fragments.

We compared receptor binding and adenylate cyclase stimulation of intact bovine parathyroid hormone (bPTH)-(1-84) and the synthetic amino-terminal fragments, bPTH-(1-34) and rat PTH (rPTH)-(1-34). Radioligands for binding studies were prepared by the lactoperoxidase technique and purified by high-pressure liquid chromatography. In both canine renal membranes and cloned rat osteosarcoma cells the amino-terminal fragments bound to a single order of sites; the affinity of rPTH-(1-34) exceeded that of bPTH-(1-34), correlating with its higher potency in stimulating adenylate cyclase. In studies with oxidized bPTH-(1--84), the middle and carboxyl regions of intact PTH were found to bind to both tissues but with higher affinity to osteosarcoma cells than to renal membranes. Our results demonstrate that rPTH-(1--34) is the most favorable probe of amino-terminal PTH binding and the most potent of the PTH peptides in stimulating renal and osseous adenylate cyclase. The results also show that midregion and carboxyl determinants within intact PTH contribute to hormone binding, which does not correlate with adenylate cyclase activation and appears more significant for skeletal than for renal binding.

Adenylyl Cyclases↗
PubMed1985

Examination of circulating parathyroid hormone in pseudohypoparathyroidism.

We examined characteristics of circulating PTH in three patients with pseudohypoparathyroidism type I. All patients were normocalcemic while receiving vitamin D therapy at the time of study. In all three, immunoreactive PTH levels were elevated, whereas bioactive levels were low or low normal. Analysis of plasma immunoreactivity by high performance liquid chromatography revealed a relative increase in hydrophobic moieties compared to patterns in patients with other hyperparathyroid states. Plasma or serum from these patients inhibited the stimulatory action of exogenous bovine PTH in an in vitro renal cytochemical bioassay and an in vitro renal adenylate cyclase assay. Such inhibition persisted after partial reduction, in one patient, of circulating immunoreactive PTH levels by an acute calcium challenge. Patient plasma did not bind bioactive 125I-labeled PTH in vitro. The results demonstrate abnormal persistence of elevated immunoreactive PTH levels in normocalcemic patients with pseudohypoparathyroidism, indicate that this circulating hormone may be altered, and suggest that a defect in PTH release and/or metabolism may accompany the other biochemical abnormalities known to occur in this disorder.

Adenylyl Cyclases↗
PubMed1985

Effect of dietary alpha- and gamma-linolenic acid on tissue fatty acids in guinea pigs.

Guinea pigs were fed regular chow diets supplemented with 5% (by weight) safflower oil, evening primrose oil, or linseed oil for 6 weeks. The unsaturated fatty acid content of these oils was 78.9% of 18:2n6, 74.1% of 18:2n6, and 9.2% of 18:3n6, or 21.5% of 18:2n6 and 46.9% of 18:3n3, respectively. In comparison with 18:2n6, dietary supplementation with 18:3n6 significantly increased the tissue levels of 18:3n6 and 20:3n6, whereas dietary 18:3n3 significantly elevated the levels of 18:3n3 in plasma and liver lipids. Dietary 18:3n3 also significantly increased 22:5n3 and 22:6n3 in total phospholipids. The tissue levels of 20:4n6, on the other hand, were not affected by either treatment. These data suggest that both delta 6- and delta 5 desaturation of n-6 fatty acids in guinea pigs are low, and that the metabolism of n-3 and n-6 fatty acids may be regulated by two different enzyme systems.

Animals↗
PubMed1985

Composition of glycosaminoglycans from aortas from deoxycorticosterone-induced hypertensive pigs.

Hypertension was induced in young male pigs by subcutaneous implantation of deoxycorticosterone acetate in a Silastic rubber carrier. Hemodynamic variables were periodically monitored. Six to eight weeks after implantation, the animals were necropsied and aortas were dissected. Glycosaminoglycans (GAG) were isolated from aortas from hypertensive pigs and from normotensive controls. Individual glycosaminoglycans in mixtures were fractionated and quantitated by chromatography on Dowex 1 Cl- column. No differences were noted in total glycosaminoglycan concentration between hypertensive and control animal aortas; the differences in individual GAG in aorta media-adventitia between the groups were not statistically significant. The relative proportions of heparan sulfate and dermatan sulfate in aorta intima were significantly greater (p less than 0.05) in hypertensive aortas than in normotensive intima. These two glycosaminoglycans increased in hypertensive animals at the expense of chondroitin 4-sulfate and hyaluronic acid. There was no difference in chondroitin 6-sulfate between the groups. A possible explanation of changes of glycosaminoglycans in hypertension because of altered lysosomal activity is suggested.

Animals↗