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Biomedical subjects

R W Nelson

Publications and source records attributed to R W Nelson.

At least 127 records · Page 7Linked to original sources
PubMed1985

Effect of o,p'DDD therapy on endogenous ACTH concentrations in dogs with hypophysis-dependent hyperadrenocorticism.

The effect of o,p'DDD therapy on the endogenous plasma ACTH concentration was evaluated in 15 dogs with hypophysis-dependent hyperadrenocorticism. Adequate control of hyperadrenocorticism with o,p'DDD was based on the reduction of water consumption to within the normal range, disappearance of clinical signs of lethargy, weakness, alopecia, thin skin, or pendulous abdomen, and an increase in blood cortisol below the normal range after exogenous ACTH administration. Endogenous ACTH concentrations were determined for each dog after the disease was controlled and while they were given o,p'DDD on a maintenance schedule. Endogenous ACTH concentrations increased in 14 of 15 dogs after o,p'DDD therapy, indicating a lack of suppressive effects of o,p'DDD on hypophysis ACTH secreting cells.

Adrenal Cortex Function Tests↗
PubMed1985

Thyrotropin-releasing hormone stimulation testing in healthy dogs.

Serum triiodothyronine (T3) and thyroxine (T4) concentrations were determined after IV administration of 200 micrograms of thyrotropin-releasing hormone (TRH) to 10 healthy euthyroid dogs. Significant (P less than 0.05) changes were not found in the T3 concentration throughout an 8-hour sampling interval. All dogs had a significant increase (P less than 0.05) in the T4 concentration at 4, 5, 6, 7, and 8 hours after TRH administration. The largest increase in the serum T4 concentration occurred 4 hours after TRH injection. From 4 to 8 hours after TRH administration, the mean increase above basal T4 concentrations was 13.9 +/- 5.4 ng/ml.

Animals↗
PubMed1984

Oligomeric regulation of the later reaction steps of the sarcoplasmic reticulum calcium ATPase.

The phosphorylated intermediate of the sarcoplasmic reticulum Ca2+ ATPase (EP) was formed from [gamma-32P] ATP, and its decomposition was monitored by chasing with either ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) or an excess amount of [gamma-31P]ATP. Chasing in the initial phase of E32P formation leads to monophasic and rapid decomposition, whereas chasing after the maximal level of E32P has been reached leads to biphasic decomposition. If a portion of EPtotal is formed from [gamma-31P]ATP (E31P) and the rest from [gamma-32P]ATP (E32P), decomposition of the later portion (E32P) is roughly monophasic and the rate of decomposition is about the same as that of the slow phase of the biphasic decomposition. Initiation of the EP reaction by concurrent addition of [gamma-32P]ATP and EGTA, conditions that permit the selective monitoring of the EP reaction via one of the subunits of the putative dimer (Ikemoto, N., Garcia, A. M., Kurobe, Y., and Scott, T. L. (1981) J. Biol. Chem. 256, 8593-8601) leads to monophasic decomposition at a rate comparable with the fast phase of biphasic decomposition. The kinetics of biphasic EP decomposition is reversibly affected by the nonionic detergent ethylene glycol monoether and the cleavable cross-linker dithiobissuccinimidyl propionate, both of which presumably affect subunit-subunit interactions. The results suggest that the biphasic EP decomposition is due to sequential liberation of Pi from different subunits (EI and EII) forming an oligomer as shown in the following model.

Animals↗
PubMed1984

Lymphocytic-plasmacytic colitis in the cat.

Lymphocytic-plasmacytic colitis was diagnosed in 6 cats. Owners sought veterinary care because of semiformed -to-liquid feces, tenesmus , fresh blood and/or mucus in the feces, or increased frequency of defecation in their cats. Lymphocytic, plasmacytic infiltration in the colonic lamina propria was found on colon biopsies. Clinical signs resolved in all 6 cats after dietary management, utilizing lamb and rice, horsemeat , or a feline prescription diet. Clinical improvement also occurred in 1 cat following sulfasalazine therapy.

Animals↗
PubMed1983

Reversible control of oligomeric interaction of the sarcoplasmic reticulum calcium ATPase with the use of a cleavable cross-linking agent.

Reversible cross-linking with a cleavable homobifunctional reagent, dithiobissuccinimidyl propionate, of the Ca2+ ATPase polypeptides of fragmented sarcoplasmic reticulum produces oligomers in the range of 2 to 4 X 100,000 Da (cf. Louis, C. F., and Holroyd, J. A., (1979) Biochim. Biophys. Acta 535, 222-232). The presence of millimolar ATP during the dithiobissuccinimidyl propionate reaction protects the enzyme from inactivation without affecting cross-linking. In the presence of both ATP (e.g. 1 mM) and Ca2+ (e.g. 0.21 mM), there is no inhibition of phosphoenzyme (EP) formation and presteady state Ca2+ translocation, whereas Ca2+-induced conformational changes of the enzyme, and EP decomposition are inhibited. Cleavage of the S-S bond of the cross-links reverses the inhibition of conformational changes but has little effect on the inhibited EP decomposition. This indicates that the inhibition of conformational changes is due to cross-linking, while that of EP decomposition is due to the chemical modification as such. If [Ca2+] is low during the dithiobissuccinimidyl propionate reaction (e.g. pCa 7.6), the Ca2+-induced conformational changes of the enzyme, EP formation, presteady state Ca2+ translocation, and EP decomposition are inhibited, even in the presence of ATP. Cleavage of the cross-links reverses the inhibition of conformational changes and EP formation, but again has little effect on EP decomposition. Thus, the primary effect of cross-linking at high and low [Ca2+] is the inhibition of the Ca2+-induced conformational change, suggesting that extensive interaction of subunits is involved in this reaction step. The fact that EP formation and presteady state Ca2+ translocation are inhibited by cross-linking carried out at low but not at high [Ca2+] suggests that cross-linking takes place at different regions of the enzyme molecule at different [Ca2+].

Animals↗
PubMed1982

Treatment of canine pyometra and endometritis with prostaglandin F2 alpha.

Seventeen bitches with pyometra or postpartum endometritis were treated with prostaglandin F2 alpha. Response to the treatment included cessation of uterine discharge, decrease in uterine diameter, reduction in plasma progesterone concentration, and return of a normal leukogram. Treatment of 14 bitches was successful, and 13 of these bitches subsequently experienced estrus. Of those 13 bitches, 11 were bred and 9 became pregnant. In 2 bitches, pyometra developed again, within 6 weeks of the following estrus, illustrating that bitches so affected are susceptible to recurrence of the disease. Of 4 bitches with closed cervix, one failed to respond to treatment, and two bitches with closed cervix required ovariohysterectomy shortly after instituting treatment.

Animals↗
PubMed1982

Insulin-induced hyperglycemia in diabetic dogs.

Insulin-induced hyperglycemia was diagnosed in 8 dogs with diabetes mellitus. Owners sought veterinary care because of polydipsia, polyuria, polyphagia, persistent morning glycosuria, or seizures in their dogs. These abnormalities had persisted despite increasing the dosage of insulin. Insulin-induced posthypoglycemic hyperglycemia was diagnosed by determining blood glucose concentrations every 2 hours during a 24-hour period, beginning at 8 A.M. Wide fluctuations in the blood glucose concentration were reduced by decreasing the daily insulin dose. The signs observed by the owners disappeared after the insulin dose was reduced.

Animals↗