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Biomedical subjects

S Cleveland

Publications and source records attributed to S Cleveland.

36 records · Page 2Linked to original sources
PubMed1986

Monozygotic triplets with Crohn's disease of the colon.

Female monozygotic triplets all developed Crohn's disease within a period of 11 mo. The monozygosity was demonstrated by analysis of 24 genetic markers of different chromosomal localization. Crohn's disease was diagnosed using clinical, radiologic, and endoscopic findings. Histologic evaluation of bowel tissue was consistent with Crohn's disease. All 3 patients had colon involvement; the terminal ileum appeared normal. The patient in whom Crohn's disease was first diagnosed had the severest course. Our observations support the role of a genetic influence in the manifestation of Crohn's disease. Nevertheless, environmental factors or microorganisms, or both, have to be taken into account, perhaps as factors promoting the outbreak of Crohn's disease.

Adult↗
PubMed1984

Chronic inflammatory polyneuropathy. Reduction of nerve conduction velocities in monkeys by systemic passive transfer of immunoglobulin G.

In chronic (relapsing) inflammatory polyneuropathy (CRIP), successful treatment with plasma exchange has led to the concept of pathogenic humoral factors. In 6 patients with CRIP, 5 of whom improved after plasma exchange, the potential pathogenic role of circulating immunoglobulin (Ig) fractions was tested by applying the systemic passive transfer model to marmoset monkeys. After continuous treatment with intramuscular injections for 2-8 weeks, monkeys injected with the crude immunoglobulin fractions or with purified IgG from 5 of the 6 patients showed a significant and partially reversible reduction of the motor nerve conduction velocity (mean 34%, P less than 0.001) when compared with pre-treatment values. In control animals the reduction was 4%. Morphological examination revealed only minor ultrastructural changes of the myelin sheath. Immunocytochemistry revealed that human IgG was able to cross the blood-nerve barrier. It is concluded that the circulating IgG-fraction of patients with CRIP contains a factor that may contribute to the disordered nerve function after crossing the blood-nerve barrier. It may be the removal of this particular factor which is responsible for the rapid recovery of nerve conduction in patients after plasma exchange.

Animals↗
PubMed1982

Dynamic properties of Renshaw cells: equivalence of responses to step changes in recruitment and discharge frequency of motor axons.

In decerebrate cats, the dynamic responses of Renshaw cells to step changes in input were determined separately both for changes in the number of alpha-axons excited and for changes in the frequency at which they were stimulated. Together, these two input variables to the Renshaw cells describe the level of activity in the motor output from the spinal cord. In either case, the dynamic responses of the interneurons depend only on their static activity before and after an input step occurs, but are otherwise indistinguishable. This favors the interpretation that the two input variables are equivalent under dynamic conditions, i.e., Renshaw cells respond to total motor output.

Animals↗
PubMed1981

Static input-output relations in the spinal recurrent inhibitory pathway.

The static discharge rate of Renshaw cells (studied in deafferented, intercollicularly decerebrate cats) has a nonlinear dependence on the frequency of trains of stimulus impulses to alpha-motor axons in the ventral root. This dependence is well described by a rectangular hyperbola that approaches saturation with increasing stimulus frequency. The tendency to saturate is independent of the number of motor axons exciting a Renshaw cell. On average, the stimulus frequency at which the discharge rate reaches half its saturation value lies between 10 and 15 Hz. The effect of Renshaw cell activity -- measured as the antidromic inhibition of individual alpha-motoneurons -- reflects the forms of the static frequency characteristics. An electric circuit analog of the Renshaw cell membrane is presented which serves to explain the qualitative features of the static input-output relations; the nonlinearity is the result of synapses with linear properties acting together at the cell membrane.

Animals↗
PubMed1978

Lactoperoxidase-catalyzed oxidation of [4-14C]estradiol.

The conversion of [4-14C]estradiol to water-soluble products by lactoperoxidase (EC 1.11.1.7) in the presence of added or generated H2O2 was studied using albumin or tyrosine as acceptor. The enzyme was able to catalyze the oxidation and binding of estradiol to albumin even in the absence of 2,4-dichlorophenol at very low concentrations of hydrogen peroxide. Other systems in which H2O2 was replaced by oxygen and Mn2+, light-sensitized riboflavin or glutathione was also shown to be active in the conversion of estradiol to water-soluble products and the effect of inhibitors on these reactions was investigated. Possible mechanisms for the peroxidase-catalyzed formation of these estradio metabolites are discussed.

Carbon Radioisotopes↗
PubMed1976

Effect of oxotremorine on the response of antidromically activated Renshaw cells in decerebrate cats.

In intercollicular decerebrate cats, some of which were made spinal in addition, the effect of oxotremorine (intravenous injection, 10-30 mug/kg) was tested on antidromically activated Renshaw cells. Methylatropine premedication prevented the otherwise often fatal drop in blood pressure; ipsilateral dorsal roots L6-S1 and contralateral hindlimb nerves were cut to exclude segmental receptor interference. During supramaximal stimulation of ventral root L7 or the gastrocnemius nerves, an increase of activity ranging from 10-110% was observed. The drug occasionally evoked spontaneous discharges in Renshaw cells, or enhanced activity already present. Alpha motoneuron activity decreased in most cases. The interaction of oxotremorine with atropine and eserine was also investigated on Renshaw cells. Our results suggest that one of the effects of oxotremorine may be a disbalance between motor output and recurrent inhibition.

Animals↗
PubMed1975

Metabolism of (4-14C)estradiol by 7,12-dimethylbenz(a) anthracene-induced mammary tumor peroxidase.

The peroxidase and estradiol-metabolizing activities of mammary tumors induced by 7,12-dimethylbenz(a)anthracene were determined in fresh and stored tissue. In both cases, a wide variation in peroxidase activity was observed in 47 different tumors tested. The properties of the enzyme found in the tumors were similar to those of lactoperoxidase. It is suggested that the amount of peroxidase present might reflect the ability of tumor cells to differentiate in response to hormonal stimulation and be indicative of the degree of tumor progression.

9,10-Dimethyl-1,2-benzanthracene↗