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Biomedical subjects

E A Ryan

Publications and source records attributed to E A Ryan.

At least 73 records · Page 4Linked to original sources
PubMed1990

Diet fat composition alters membrane phospholipid composition, insulin binding, and glucose metabolism in adipocytes from control and diabetic animals.

The present study was designed to determine if diet fat-induced alteration in the fatty acid composition of the adipocyte plasma membrane alters insulin binding and the insulin responsiveness of glucose metabolism in control and diabetic states. Normal (control) and diabetic (streptozotocin-induced) rats were fed high fat semipurified diets providing a high or low polyunsaturated to saturated fatty acid (P/S) ratio. Feeding a high P/S diet increased the polyunsaturated fatty acid content of major membrane phospholipids of the adipocyte plasma membrane from both normal and diabetic animals. The diabetic state was associated with an elevated content of linoleic acid and a reduced level of arachidonic acid consistent with reduced delta 6-desaturation. Feeding the high P/S diet to diabetic animals increased membrane linoleic acid content and prevented the decrease observed in the arachidonic acid of membrane phospholipids. The high P/S diet was associated with increased insulin binding in nondiabetic animals but did not change the amount of insulin bound by cells from diabetic animals. Significantly (p less than 0.05) increased rates of insulin-stimulated glucose transport and lipogenesis (glucose incorporation into lipids) were observed in control animals fed the high as compared to the low P/S diet. The rates of insulin-stimulated glucose transport, oxidation, and lipogenesis were lower (p less than 0.05) for cells from diabetic as compared to control animals. However, feeding a high P/S diet significantly improved rates for all three of these functions (p less than 0.05). It is concluded that diet-induced alterations in membrane composition may provide a mechanism for improving the cellular response to insulin in cells from diabetic animals.

Adipose Tissue↗
PubMed1990

Measurement of kynurenic acid in mammalian brain extracts and cerebrospinal fluid by high-performance liquid chromatography with fluorometric and coulometric electrode array detection.

Kynurenic acid is a broad-spectrum excitatory amino acid (EAA) receptor antagonist which is present in the mammalian central nervous system. We describe a method for the measurement of kynurenic acid using isocratic reverse-phase high-performance liquid chromatography (HPLC) with fluorometric detection enhanced by Zn2+ as a postcolumn reagent. The method requires no prior sample preparation procedures other than extraction with 0.1 M HClO4. The reliability of the primary fluorometric method was verified by comparing measurements of tissue concentrations of kynurenic acid in human cerebral cortex and putamen using three different methods of separation with fluorometric detection, as well as four methods utilizing HPLC with coulometric electrode array system (CEAS) detection. All seven methods produced comparable results. The concentration of kynurenic acid in human cerebral cortex was 2.07 +/- 0.61 pmol/mg protein, and in human putamen, 3.38 +/- 0.81 pmol/mg protein. Kynurenic acid was also found to be present in human cerebrospinal fluid (CSF) at a concentration of 5.09 +/- 1.04 nM. The regional distribution of kynurenic acid in the rat brain was examined. Kynurenic acid concentrations were highest in brainstem (149.6 fmol/mg protein) and olfactory bulb (103.9 fmol/mg protein) and lowest in thalamus (26.0 fmol/mg protein). There were no significant postmortem changes in kynurenic acid concentrations in cerebral cortex, hippocampus, and striatum at intervals ranging from 0 to 24 h. Perfusion of the cerebral vasculature with normal saline prior to sacrifice did not significantly alter kynurenic acid content in rat hippocampus, cerebral cortex, or striatum. The analytical methods described are the most sensitive (10-30 fmol injection-1) and specific (utilizing both excitation and emissions properties and electrochemical reaction potentials, respectively) methods for determining kynurenic acid in brain tissue extracts and CSF. These methods should prove useful in examining whether kynurenic acid modulates EAA-mediated neurotransmission under physiologic conditions, as well as in determining the role of kynurenic acid in excitotoxic neuronal death.

Animals↗
PubMed1988

Dietary fat and the diabetic state alter insulin binding and the fatty acyl composition of the adipocyte plasma membrane.

Control and diabetic rats were fed on semi-purified high-fat diets providing a polyunsaturated/saturated fatty acid ratio (P/S) of 1.0 or 0.25, to examine the effect of diet on the fatty acid composition of major phospholipids of the adipocyte plasma membrane. Feeding the high-P/S diet (P/S = 1.0) compared with the low-P/S diet (P/S = 0.25) increased the content of polyunsaturated fatty acids in membrane phospholipids in both control and diabetic animals. The diabetic state decreased the content of polyunsaturated fatty acids, particularly arachidonic acid, in adipocyte membrane phospholipids. The decrease in arachidonic acid in membrane phospholipids of diabetic animals tended to be normalized to within the control values when high-P/S diets were given. For control animals, altered plasma-membrane composition was associated with change in insulin binding, suggesting that change in plasma-membrane composition may have physiological consequences for insulin-stimulated functions in the adipocyte.

Adipose Tissue↗
PubMed1988

Lack of metabolic effects of a triphasic formulation containing norethindrone in normal women studied prospectively.

The glucose and insulin responses to oral glucose tolerance tests and lipid values in normal women taking a triphasic pill containing norethindrone (Ortho 7/7/7) were performed. After three months, no significant changes in these metabolic indices were found. These results confirm and expand the knowledge regarding the metabolic safety of norethindrone-containing triphasic formulations.

Adult↗
PubMed1988

Primary hypothyroidism presenting as growth delay and pituitary enlargement.

We report the case of a young boy being considered for pituitary surgery because of pituitary enlargement found during assessment of growth delay. There was no goitre but he was hypothyroid clinically and biochemically. The finding of an elevated TSH suggested primary thyroid disease with thyrotroph hyperplasia. Treatment with L-thyroxine resulted in prompt resolution of his pituitary enlargement and improvement in his visual fields.

Child↗
PubMed1988

Role of gestational hormones in the induction of insulin resistance.

Pregnancy is associated with insulin resistance. We studied insulin binding and postbinding function in isolated adipocytes from pregnant and nonpregnant rats. We also used a primary culture system for female virgin rat adipocytes to assess the effects of gestational hormones in vitro on insulin binding and postbinding function. Insulin binding to adipocytes was normal during pregnancy, but [14C]3-O-methylglucose transport was reduced. When hCG or estradiol was added to the culture medium, no change in maximum [14C]3-O-methylglucose transport was found; however, maximum insulin binding was increased with estradiol. Progesterone and cortisol both decreased maximum insulin binding and [14C]3-O-methylglucose transport. PRL and placental lactogen decreased maximum [14C]3-O-methylglucose transport, but did not change insulin binding. When these hormones were added concurrently no change in insulin binding was found, but maximum [14C]3-O-methylglucose transport was reduced. We conclude that the insulin resistance of pregnancy is associated with a postbinding defect in insulin action. Estradiol increased insulin receptor binding, but during pregnancy this effect may be offset by the reduction in insulin binding induced by progesterone and cortisol. The postbinding defect in insulin action during pregnancy is probably related to increasing amounts of progesterone, cortisol, PRL, and placental lactogen.

3-O-Methylglucose↗
PubMed1988

Insulin action is altered in hyperthyroidism.

We have assessed insulin action in five hyperthyroid patients, pre- and post-radioactive iodine therapy using oral glucose tolerance tests, monocyte insulin binding and dose response curves generated with the euglycemic clamp technique. All patients had become euthyroid after radioactive iodine therapy with a decline in the plasma free T4 index level from 278 +/- 43 to 105 +/- 9. Fasting glucose was modestly, but significantly elevated in the thyrotoxic patients compared to when they were rendered euthyroid (p less than 0.05). Oral glucose tolerance tests showed no difference in either glucose or insulin values after the glucose load. Insulin receptor binding and affinity were similar regardless of their thyroid status. Hepatic glucose production in the basal state was elevated in the thyrotoxic patients, 61 +/- 5 mg/M2/min vs 49 +/- 3 mg/M2/min (p less than 0.05). At the lowest level of insulin infusion no difference in glucose disposal was found. At maximum insulin concentrations the glucose disposal rate was enhanced in the thyrotoxic patients, 686 +/- 19 vs 567 +/- 26 mg/M2/min (p less than 0.01). These results indicate that higher fasting glucose levels may result from increased hepatic glucose production in thyrotoxicosis, but as indicated by the oral glucose tolerance tests, this defect in insulin action is usually of minor significance. However, insulin responsiveness measured at pharmacological insulin levels is augmented in thyrotoxicosis.

Adult↗
PubMed1987

Insulin action does not change during the menstrual cycle in normal women.

Normal women have alterations in carbohydrate metabolism during pregnancy and when taking oral contraceptives, and clinical observations suggest that diabetic women need more insulin during menstruation. We, therefore, studied insulin action in normal women during the menstrual cycle in the follicular, luteal, and menstrual phases. Glucose tolerance was similar at all three times. Specific insulin receptor binding to monocytes did not change during the menstrual cycle. Euglycemic insulin clamp studies at four different insulin infusion rates (15, 40, 120, and 240 mU/M2 X min) showed no differences in insulin sensitivity or responsiveness throughout the menstrual cycle, and hepatic glucose output did not change. These studies suggest that if insulin action is impaired during menstruation in diabetic women it is because of factors that are not detected in normal women.

Adult↗
PubMed1985

A case report of primary adenocarcinoma of the fallopian tube.

The apparently smallest primary adenocarcinoma (2.3 mm in diameter) of the fallopian tube ever described was diagnosed by repeated blind sectioning of the surgical specimen after the preoperative finding of an abnormal cervical Papanicolaou smear and the subsequent finding of abnormal cells in fluid obtained by laparoscopic peritoneal lavage, although a survey of the patient for a primary cancer was negative.

Adenocarcinoma↗
PubMed1985

Sleep-inducing N-alkyl-5-[m-(trifluoromethyl)phenyl]-5-hydroxy-2-pyrrolidinones and N-alkyl-3-(trifluoromethyl)cinnamamides.

A series of N-alkyl-3-[m-(trifluoromethyl)phenyl]-5-hydroxy-2-pyrrolidinones and N-alkyl-3-(trifluoromethyl)-cinnamamides were prepared and screened in a series of tests designed to detect potential sleep inducers. The more active members of the series were evaluated for their ability to induce sleep in Cebus monkeys. The most active compound, N-methyl-5-[m-(trifluoromethyl)phenyl]-5-hydroxy-2-pyrrolidinone, was equal to methaqualone.

Animals↗
PubMed1985

Insulin action during pregnancy. Studies with the euglycemic clamp technique.

To assess the mechanisms responsible for the insulin resistance associated with both normal human pregnancy and gestational-onset diabetes, we have measured exogenous glucose disposal using sequential insulin infusions with the euglycemic glucose clamp technique and erythrocyte insulin binding. Three groups of women were studied: nonpregnant women with normal glucose tolerance (N = 7, mean age 32.9 +/- 2.1 yr), pregnant women with normal glucose tolerance (N = 5, mean age 24.8 +/- 3.5 yr), and pregnant women with gestational-onset diabetes (N = 5, mean age 34.6 +/- 2.6 yr). Despite normal plasma glucose levels obtained during a 100-g oral glucose tolerance test, plasma insulin levels were significantly elevated in the pregnant women compared with the nonpregnant control subjects, suggesting a state of insulin resistance. Insulin binding to erythrocytes was similar in all three groups (maximum specific binding being 5.0 +/- 0.6%, 5.5 +/- 1.1%, and 6.0 +/- 0.7% in nonpregnant, nondiabetic pregnant, and gestational-onset diabetic women, respectively). In vivo peripheral insulin action was measured using the euglycemic glucose clamp technique during an insulin infusion of 40 mU/m2 X min, with blood glucose clamped at a concentration of 75 mg/dl using a variable glucose infusion. Glucose infusion rates were 213 +/- 11 mg/m2 X min, 143 +/- 23 mg/m2 X min, and 57 +/- 18 mg/m2 X min in nonpregnant, nondiabetic pregnant, and gestational-onset diabetic women, respectively. This demonstrates that pregnant subjects display a state of insulin resistance, and that this appears to be more marked in gestational-onset diabetic subjects. To further define the possible mechanism of insulin resistance during pregnancy, the insulin infusion rate was increased to 240 mU/m2 X min and further euglycemic clamp measurements performed. Glucose infusion rates were 372 +/- 11 mg/m2 X min, 270 +/- 31 mg/m2 X min, and 157 +/- 26 mg/m2 X min, in nonpregnant, nondiabetic pregnant, and gestational-onset diabetic women, respectively. This demonstrates a shift to the right of the dose-response curve of insulin action and suggests that the insulin resistance of pregnancy may include a decrease in presumed "maximum" insulin responsivity. In four subjects, studies were repeated in the postpartum period, and these demonstrated that the insulin resistance of pregnancy is ameliorated shortly after delivery. These studies suggest that the insulin resistance of pregnancy results from a target cell defect in insulin action beyond the initial step of insulin binding to cellular receptors, a postreceptor (or postbinding) defect in insulin action.

Adult↗
PubMed1984

Oncogenous osteomalacia. Review of the world literature of 42 cases and report of two new cases.

The clinical and biochemical data in 42 reported cases of oncogenous osteomalacia are reviewed, and data in two previously unreported cases are recorded. It is likely that the syndrome is more common than suggested by the paucity of reports and may account for a substantial fraction of nonfamilial, adult-onset "idiopathic" osteomalacia. Tumors associated with the syndrome are characteristically benign, of mesenchymal origin, highly vascular, and composed principally of giant and spindle cells. Complete excision of tumors results in cure of the osteomalacia in the majority of patients. The syndrome presumably represents an instance of humor-induced phosphaturia but supporting experimental data are scanty. Plasma levels of 1,25-dihydroxycholecalciferol are uniformly low, and treatment with this metabolite is generally very effective; however, abnormal vitamin D metabolism cannot by itself account for the syndrome.

Adolescent↗
PubMed1982

Glycemic control in insulin-dependent diabetes mellitus. Comparison of outpatient intensified conventional therapy with continuous subcutaneous insulin infusion.

We compared glycemic control achieved on an outpatient basic with three insulin regimens in 10 patients with insulin-dependent diabetes mellitus. The regimens studied included: (1) intensified conventional therapy with twice-daily regular and lente insulin; (2) intensified conventional therapy with long-acting ultralente insulin plus multiple preprandial injections of regular insulin; (3) continuous subcutaneous insulin infusion. Each treatment period was two months long. At the beginning of the study and the close of each study period, patients were hospitalized for a 48-hour evaluation of glycemic control. Each new insulin regimen was begun after discharge, with the dosage adjusted using preplanned algorithms, patient self-monitoring of blood glucose and defined blood glucose targets. Glycemic control markedly improved on all three treatment regimens, to a comparable degree, as assessed by mean plasma glucose level, mean amplitude of glycemic excursions, M value (an index of glycemic lability), urinary glucose excretion and glycosylated hemoglobin level.

Adolescent↗
PubMed1982

Nanophthalmos with uveal effusion: clinical and embryologic considerations.

Three brothers were found to have nanophthalmos as evidenced by marked hyperopia, decreased global axial length, and shallow anterior chambers. The thickness of the lens, measured with A-scan ultrasound biometry in two cases, was much greater than normal. Choroidal thickening with shallow retinal detachments without breaks was found in those patients. Fluorescein angioscopy demonstrated leaks beneath the serous retinal detachments in one. The spontaneous presence of choroidal effusions and retinal detachments in nanophthalmic patients has been reported only rarely. The present findings emphasize that careful examination of the posterior segment should be done prior to anterior segment surgery in these patients to alert the surgeon to the possibility of serious intra- and post-operative choroidal effusions and retinal detachments. An attempt is made to explain some of the clinical findings in nanophthalmos by extrapolating from results obtained on experimental animals. It is postulated that the increased lens size in nanophthalmos may be due to the abnormal accumulation of a factor influencing lens fiber differentiation. The overall small size of the eye may be the result of the formation of a smaller than usual optic vesicle anlage.

Aged↗