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Biomedical subjects

R G Cheron

Publications and source records attributed to R G Cheron.

7 recordsLinked to original sources
PubMed1986

The effects of thyroid hormones on the formation of stress ulcers in the rat.

The Low T3 Sick Syndrome is a syndrome of low triiodothyronine (T3), low to normal thyroxine (T4), and a nonelevated thyrotropin despite the low T3 levels. This syndrome is frequently encountered in critically ill patients. These same patients are also at higher risk to develop acute stress ulcerations. The objective of this study was to access the effects of low circulating thyroid hormone levels on the development of stress ulcers in the rat. Rats having had previous surgical thyroidectomies were subjected to individual restraint stress; these animals had a significantly increased incidence of stress ulcers when compared to euthyroid stressed controls (1.6 +/- 0.4 ulcers vs 0.5 +/- 0.2 ulcers per animal, P less than 0.05). Surgically thyroidectomized (hypothyroid) animals who were given T3 replacement and then stressed, had ulcer rates similar to normal stressed controls (0.5 +/- 0.2 ulcers per animal). We conclude that low circulating thyroid hormones have an ulcerogenic effect, and that replacement of T3 in rats with surgical hypothyroidism reverses this effect.

Animals↗
PubMed1985

Long-term efficacy of deferoxamine iron chelation therapy in adults with acquired transfusional iron overload.

Transfusional iron overload in adult patients with acquired anemias may result in widespread organ dysfunction. Long-term deferoxamine mesylate therapy was administered by continuous subcutaneous infusion to six such patients, who have been followed up for up to 66 months of therapy while continuing to be transfusion-dependent. During deferoxamine therapy, liver density by computed tomographic scan decreased in four of five patients, liver iron content decreased in two of three patients, and liver function normalized in two patients. Plasma cortisol response to insulin-induced hypoglycemia improved in three of five patients receiving therapy. Pituitary growth hormone reserve normalized in two patients and remained normal in the other three tested. One patient, treated concurrently with ascorbic acid, died suddenly. The other five patients have had no cardiac deterioration by noninvasive testing. We conclude that long-term deferoxamine iron chelation therapy is effective not only in retarding but, in some cases, even reversing organ damage caused by transfusional iron overload.

Adult↗
PubMed1981

Clinical consequences of acquired transfusional iron overload in adults.

We assessed the clinical sequelae of transfusional iron overload in 15 nonthalassemic adults (40 to 71 years of age) with anemias requiring transfusions. Iron loading had been present for less than four years in 14 patients. The number of units of blood transfused ranged from 60 to 210 (mean, 120). Liver-biopsy specimens in 10 patients contained seven to 26 times the normal amount of iron and typically showed focal portal fibrosis. Left ventricular cardiac function was impaired in only the most heavily transfused patients or in those with coexisting coronary-artery disease, All patients had glucose intolerance associated with significantly reduced insulin output, compared with controls (P < 0.01). Pituitary reserve of ACTH was limited in 10 of 12 patients, and that of gonadotropin in five of 13. We conclude that widespread subclinical organ dysfunction can result from transfusional iron overload developing in adulthood. The pattern of organ involvement resembles that encountered in idiopathic hemochromatosis.

Adult↗
PubMed1979

Physiological and pharmacological influences on thyroxine to 3,5,3'-triiodothyronine conversion and nuclear 3,5,3'-triiodothyronine binding in rat anterior pituitary.

Our recent in vivo studies have suggested that intrapituitary l-thyroxine (T(4)) to 3,5,3'-triiodo-l-thyronine (T(3)) conversion with subsequent nuclear binding of T(3) is an important pathway by which circulating T(4) can inhibit thyrotropin release. The present studies were performed to evaluate various physiological and pharmacological influences on these two processes in rat anterior pituitary tissue. Intact pituitary fragments were incubated in buffer-1% bovine serum albumin containing 0.14 ng/ml [(131)I]T(3) and 3.8 ng/ml [(125)I]T(4). Nuclei were isolated after 3 h of incubation and the bound iodothyronines identified by paper chromatography. There was 0.3-1% [(125)I]T(3) contaminating the medium [(125)I]T(4), and this did not change during incubation. Nuclear [(125)I]T(4) was not decreased by 650-fold excesses of medium T(3) or T(4), suggesting that it was nonspecifically bound. The ratio of nuclear to medium [(131)I]- and [(125)I]T(3) were expressed as nuclear counts per minute per milligram wet weight of tissue:counts per minute per microliter medium. Intrapituitary T(4) to T(3) conversion was evidenced by the fact that the nuclear:medium (N:M) ratio for [(131)I]T(3) was 0.45+/-0.21, whereas that for [(125)I]T(3) was 2.23+/-1.28 (mean+/-SD, n = 51). A ratio (R), the N:M [(125)I]T(3) divided by the N:M [(131)I]T(3), was used as an index of intrapituitary T(4) to T(3) conversion. Increasing medium T(3) concentrations up to 50 ng/ml caused a progressive decrease in the N:M ratio for both T(3) isotopes, but no change in the value for R, indicating that both competed for the same limited-capacity nuclear receptors. Increasing concentrations of medium T(4) caused no change in the N:M [(131)I]T(3) but did cause a significant decrease in R in three of four experiments. These results suggest saturation of T(4)-5'-monodeiodination occurred at lower T(4) concentrations than saturation of nuclear T(3) binding sites. In hypothyroid rats, the N:M ratios for both [(131)I]T(3) and [(125)I]T(3) were increased (P < 0.005), but R was three-fold higher than in controls (P < 0.005). Animals given 10 mug T(4)/100 g body wt per d for 5 d had significantly decreased N:M ratios for both [(131)I]T(3) and [(125)I]T(3), as well as a decreased value for R. In fasted rats, neither N:M ratio was depressed, although hepatic T(4) to T(3) conversion in the same animals was 50% of control (P < 0.005). Iopanoic acid (13 muM), but not 6-n-propylthiouracil (29 muM), decreased the N:M [(125)I]T(3) with a significant decrease in the value for R (P < 0.025 or less). Neither sodium iodide (6 muM) nor thyrotropin-releasing hormone (7-700 nM) affected the T(3) N:M ratios. These results indicate that intrapituitary T(4) to T(3) conversion is stimulated in hypothyroidism and depressed in T(4)-treated animals, whereas opposite changes occur in hepatic T(4)-5'-monodeiodination. Unlike liver, anterior pituitary T(4)-5'-monodeiodination is not affected by fasting or incubation with 6-n-propyl-2-thiouracil, but T(4) to T(3) conversion is inhibited in both by iopanoic acid. These results indicate that there are important differences between anterior pituitary and other tissues in the regulation of T(4)-5'-monodeiodination.

Animals↗
PubMedDate not supplied

Anaphylaxis and immunologic insulin resistance in a diabetic woman with ketoacidosis.

A diabetic woman presented with diabetic ketoacidosis after demonstrating immediate-type hypersensitivity to heterologous insulin. She had had interrupted insulin therapy in the past. Insulin requirements during the course of treatment for the acidosis suggested marked resistance, with 50,000 U of insulin needed in the first 36 h. Anaphylaxis requiring intubation and emergency treatment developed after intravenous purified pork insulin was administered. Elevated titers of insulin-specific IgG (441.6 U/L serum) demonstrated immunologic insulin resistance. Positive intradermal skin tests for beef and pork insulins and detection of insulin-specific IgE by RAST assay revealed concurrent immediate-type allergy. A review of the literature revealed the unique occurrence in this patient of simultaneous ketoacidosis, insulin allergy, anaphylaxis, and immunologic resistance. Interrupted insulin therapy in susceptible individuals remains a potential danger, even with the availability of purified insulin preparations.

Anaphylaxis↗