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Biomedical subjects

J R Turtle

Publications and source records attributed to J R Turtle.

At least 73 records · Page 4Linked to original sources
PubMed1986

Dissociation of insulin binding from insulin stimulation of 2-deoxyglucose transport by ruthenium red.

Ruthenium red increased specific insulin binding to isolated adipocytes 5.4 fold and 2.6 fold over binding determined in the absence and presence of Ca2+ and Mg2+. The increase in insulin binding was not accompanied by an increase in insulin sensitivity. The lack of effect of ruthenium red on insulin action argued strongly against an increase in intracellular Ca2+ as a potential messenger/transducer of insulin action and suggested that the enhancing effect of Ca2+ on insulin action was a result of increased receptor affinity.

Adipose Tissue↗
PubMed1986

The activity of the pyruvate dehydrogenase complex in heart muscle in the previously obese mouse model.

Obese gold thioglucose injected mice were reduced to lean control weight by food restriction. When pair fed with lean controls these animals then gained weight (were metabolically more efficient). Serum glucose was also elevated in this group (14.5 +/- 0.4 (14) vs 12.1 +/- 0.3 mmol/L, p less than 0.001). If previously obese animals were weight maintained with lean controls (by mild food restriction), serum glucose remained at control levels. The activity of the pyruvate dehydrogenase complex in heart muscle was decreased in both obese and pair fed previously obese, whilst it was similar to that of lean controls in the weight maintained previously obese and in obese mice actually dieted. In all obese and previously obese animals serum insulin was elevated. In hearts from control animals subjected to mild food restriction the pyruvate dehydrogenase complex was activated (11.53 +/- 1.80 (5) vs 3.34 +/- 0.62 (9) U/g dry weight), despite a reduced serum insulin level (42 +/- 2 vs 74 +/- 10 microU/ml, p less than 0.01). These diverse changes in the proportion of the pyruvate dehydrogenase complex in the active form and insulin levels argue for a persistent alteration in the sensitivity of the pyruvate dehydrogenase complex to insulin in obesity, as well as indicating that glucose metabolism in obese animals is altered by both body weight and diet amount.

Animals↗
PubMed1986

Bioactive luteinizing hormone in plasma of uraemic men and men with primary testicular damage.

Elevation of immunoreactive LH and reduced testosterone production are consistent features of Leydig cell dysfunction in uraemic hypogonadism. To investigate further Leydig cell regulation in uraemia, we measured plasma bioactive LH (B-LH) and immunoreactive LH (I-LH), as well as FSH, testosterone, creatinine, urea and albumin in seven uraemic men before and after haemodialysis and compared them to levels both in eugonadal controls (n = 10) and in men with primary testicular damage (n = 10). Plasma B-LH was increased in uraemic men compared with both nonuraemic control groups. Plasma I-LH and FSH were increased and testosterone decreased in uraemic men compared to eugonadal controls. In comparison with nonuraemic men with primary testicular damage, plasma I-LH levels were similar but FSH and testosterone lower in uraemic men. As a consequence, the ratio of B-LH to I-LH (LH:B/I ratio) was decreased in men with primary testicular damage but normal in uraemic men. A single session of haemodialysis decreased creatinine (50.5%) and urea (58.5%) and increased B-LH (47.7%), I-LH (32.9%), FSH (24.4%), testosterone (15.8%) and albumin (17.8%) levels, but the LH:B/I ratio was unchanged. Increases in gonadotrophin levels were greater than could be accounted for by haemoconcentration suggesting that dialysis may also ameliorate uraemic suppression of the hypothalamus and pituitary. Ultrafiltrates of human uraemic plasma (mol wt less than 25 000) had no inhibitory effect on in-vitro steroidogenesis by isolated rat Leydig cells making circulating uraemic 'middle-molecule'-type toxins unlikely to be involved in causing lowered testosterone levels in uraemic men.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Long-term survival of human fetal pancreatic tissue transplanted into an insulin-dependent diabetic patient.

The explants of two human fetal pancreases of 15 weeks gestational age were cultured for 6-7 days before being implanted in a 29-year-old insulin-dependent diabetic woman who had received a renal graft two months previously. One pancreas was placed in the flexor muscles of the forearm whilst the other was implanted in an omental pouch. To reduce the chances of rejection the tissue was cultured in vitro, the donor of the tissue placed in the forearm was DR antigen matched with the recipient and the patient remained on cyclosporin and prednisone therapy. At 3 months a mass developed in the forearm muscle at the site of transplantation, and continued to grow. Biopsy at 13 months showed a small area of original pancreas surrounded by a large collection of mature lymphocytes and fibrous tissue. A and D cells could be seen around pancreatic ducts but B cells and acinar tissue were absent. At no stage during follow-up was plasma C-peptide detected in the recipient.

Administration, Oral↗
PubMed1986

The prevention and reversibility of tissue non-enzymatic glycosylation in diabetes.

The time course of non-enzymatic glycosylation (NEG) of liver, kidney, tail collagen, and haemoglobin was studied in diabetic rats. Increased NEG of liver, kidney, and collagen was detectable within 4 weeks of diabetes. The abnormal NEG of liver, kidney, and haemoglobin present after 4 weeks of untreated diabetes could be normalized by 4-8 weeks of intensive insulin therapy given by continuous subcutaneous infusion. However, the same treatment was ineffective in reversing the abnormal NEG and thermal stability of tail collagen. The differences in the development and reversibility of these tissue changes may be due to different tissue turnover rates. Insulin therapy, given from the onset of diabetes, was effective in preventing the development of collagen abnormalities. This suggests that early and vigorous treatment of diabetes is necessary to prevent collagen changes which are potentially irreversible.

Animals↗
PubMed1986

Abnormalities of granulation tissue and collagen formation in experimental diabetes, uraemia and malnutrition.

The formation of granulation tissue and collagen was studied in rats made diabetic with streptozotocin. Granulation tissue was harvested from the inside of steelmesh cylinders implanted in the back of diabetic and control animals. Four weeks after implantation there was a reduction in the quantity of granulation tissue and its collagen content in diabetic animals compared to controls. Rats with renal failure or malnutrition but no diabetes also formed less granulation tissue but in these animals the content of collagen in the granulation tissue was normal. These results suggest that the decrease of collagen, but not granulation tissue, in diabetes is a relatively specific phenomenon which was not due to the toxic effects of streptozotocin as the changes were prevented by insulin treatment. The hydroxyproline/proline ratio of diabetic collagen was found to be normal, excluding defective hydroxylation of proline as an important factor in the reduction of collagen in diabetes. Treatment with an aldose reductase inhibitor did not prevent the abnormalities of granulation tissue and collagen in diabetes, making it unlikely that increased activity of this enzyme played an important pathogenetic role. The observed reduction of granulation tissue mass and collagen content in diabetes may be important factors in the impairment of wound healing in diabetes.

Aldehyde Reductase↗
PubMed1986

Gestational diabetes--infant malformations and subsequent maternal glucose tolerance.

The frequency of abnormal glucose tolerance in the first 12 months after gestational diabetes was found to be 33.3%, which is much higher than previously accepted. Women with gestational diabetes (Group 1 = 54 requiring insulin, Group 2 = 32 treated with diet alone) attending a metropolitan teaching hospital over a 3 1/2 year period were followed-up after delivery to determine their subsequent glucose tolerance. Of 86 seen 3 months after delivery, 2 had developed insulin-dependent diabetes mellitus (IDDM) and 2 noninsulin dependent diabetes mellitus (NIDDM), diagnosed by glucose tolerance testing. Another 38 returned for follow-up glucose tolerance testing at 12 months; of these 3 had impaired glucose tolerance (IGT), 7 had NIDDM, and one who had had NIDDM at 3 months now showed IGT after 9 months dietary treatment. Thus, 12 months after delivery, the cumulative prevalence of abnormal glucose tolerance was 14/42 (33.3%), 10 of the 42 being frankly diabetic (26%). Of the remaining 44 patients, 21 have not yet reached 12 months or were pregnant again, and 23 did not attend for glucose tolerance testing. Although the trend was for gestational diabetes mellitus (GDM) to recur earlier and more severely in subsequent pregnancies, in 3 instances the diabetes did not recur. Major congenital malformations occurred in 4 of the 86 babies (4.7%); minor malformations were found in a further 13 (15%) with no difference in frequency between Group 1 and Group 2.

Adult↗
PubMed1986

Growth and hormonal content of human fetal pancreas passaged in athymic mice.

While the usefulness of the human fetal pancreas transplanted into diabetic humans has yet to be realized, its transplantation into nude mice has revealed some of its potential. In this animal the organ grows in size, during which time differentiation of its endocrine component and maturation of the insulinogenic response to glucose occurs. The results reported in this article expand these results by providing data on the weight and both the insulin and glucagon content of these passaged organs. Human fetal pancreata of gestational age 14-19 wk were implanted subcutaneously (s.c.) in nude mice and maintained in vivo for 5-54 wk (absolute age 19-68 wk). The implants were then removed and their insulin and glucagon content determined. Both the weight of these implants and their insulin content were positively correlated with the absolute age of the tissue (weight: r = 0.61, P less than 0.001; insulin content: r = 0.62, P = 0.0003). The glucagon content bore no relationship to the age. The maximum level of insulin extracted from 30 passaged human fetal pancreata was 0.8 U, a level far below the daily insulin requirements in adult humans. It is suggested that an explanation for this is the site of transplantation used. To compare the s.c. site with the renal subcapsular space, the explants of four fetal pancreata were evenly divided between these two sites. After 11-13 wk, the implants were removed. Those beneath the renal capsule were larger and contained a greater amount of insulin and glucagon than those transplanted s.c.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Maturation of the response of human fetal pancreatic explants to glucose.

The release of insulin from the human pancreas in response to glucose is known to be either poor or absent in the fetus, whereas in the infant and adult, the response is much greater. The maturation of this response was examined systematically in this study using pancreases that were initially obtained at 14-20 weeks gestation and maintained either in culture alone or by passaging them in diabetic nude mice. Stimulation with glucose was carried out in vitro using tissue of ages ranging from 14 to 58 weeks. A response to glucose was initially seen at 25 weeks and this dramatically increased in the fetal tissue that had reached an age of 55 weeks or more. One of the nude mice used for passage developed normoglycaemia and when the pancreatic implant of age 52 weeks was removed, diabetes recurred. Our findings support the idea of the use of human fetal pancreatic tissue in the treatment of diabetes mellitus.

Age Factors↗
PubMed1985

A high prevalence of obesity in a diabetic population: results of a survey of food patterns in 252 patients in a 2 year period.

Dietary patterns were reviewed and correlated with the patients' clinical details in 252 patients seen at the initial visit to a diabetic clinic of a major metropolitan teaching hospital. Except in the subgroup of male patients with insulin-dependent diabetes, there was an extremely high prevalence of obesity, especially in females (70% greater 120% of standard weight; 28% greater than 150%). Traditional 'low-carbohydrate' diets were commonly found irrespective of ethnic origin, particularly in those individuals who had received previous dietary education. This study highlights the urgent need for public health education programmes in order to try to prevent the development of obesity since therapy remains unsatisfactory once it is established.

Adolescent↗
PubMed1985

Testicular function in experimental uremia.

A model for the study of testicular function in experimental uremia induced by subtotal nephrectomy in mature male rats is described. Glomerular filtration rate was reduced by 87%, resulting in stable uremia for up to 13 weeks with characteristic biochemical changes and reduction in weight of testes, prostate, seminal vesicles, and epididymis but not of heart, liver, spleen, or epididymal fat-pads in comparison with pair-fed and sham-operated, ad libitum-fed littermate controls. Basal serum LH, FSH, and testosterone were reduced and PRL levels increased in chronic uremic rats compared with pair-fed and sham-operated controls. Intratesticular and peripheral venous testosterone levels were reduced by 73-85%, whereas spermatic vein testosterone levels were reduced by 47% suggesting a reduction in blood flow to the uremic rat testis. Sensitivity of uremic Leydig cells to human CG stimulation was normal to increased both in vivo and in vitro without changes in LH receptor affinity or numbers. Fertility was markedly impaired in uremic rats but was restored to normal by either human CG or testosterone treatment. Spermatogenesis was minimally depressed after up to 3 months of uremia. These studies suggest that this experimental paradigm is a suitable model for studying the pathogenesis of early changes in uremic hypogonadism. The predominant early changes of uremic hypogonadism are due to central defects in regulation of pituitary LH secretion with consequent testicular and peripheral hypoandrogenism but initial preservation of spermatogenesis.

Animals↗
PubMed1985

Hypothalamic-pituitary function in experimental uremic hypogonadism.

In companion studies we have shown that chronic uremic male rats are infertile and hypoandrogenic and have lowered basal LH levels. Fertility was restored by either human CG (hCG) or testosterone treatment. Testicular steroidogenic responses to hCG in vivo and in vitro were normal or excessive, indicating that hypothalamic-pituitary dysfunction was the predominant early lesion in uremic hypogonadism. Further studies were undertaken to characterize the nature of the central defects in regulation of pituitary LH secretion. Uremic rats have reduced MCRs for rat LH (rLH) (61%), rat FSH (rFSH) (47%), and LHRH (41%). Pituitary gonadotropin and hypothalamic LHRH content were unchanged in uremic rats. Pituitary rLH and rFSH responses to LHRH stimulation in vivo and in vitro were quantitatively normal or excessive, with delayed peaks suggesting that uremic pituitary gonadotrope secretion is deficient due to lack of appropriate hypothalamic LHRH drive rather than intrinsic pituitary defects. Despite reduced pituitary gonadotropin secretion in intact uremic rats, castration induced paradoxical excessive increases in pituitary LHRH binding, serum rLH, and rFSH beyond those of nonuremic controls. Paradoxical postcastration hyperresponses of serum rLH and rFSH were not due to circulating immunoreactive fragments of gonadotropins or undernutrition. Dysfunction of the uremic hypothalamus was further characterized in vivo by lack of rLH responsiveness to naloxone and hypersensitivity to negative testicular feedback in castrate-steroid-replaced and intact rats. These data demonstrate that uremic hypogonadism is principally due to aberrant hypothalamic regulation of pituitary LH secretion resembling those of the immature rat or seasonally regressed animal. This recrudescence of the inactive regulatory state in a disease model suggests that common mechanisms are operative in orderly gonadal withdrawal under hostile or inappropriate environments and may underly the reversibility of human uremic hypogonadism with successful renal transplantation.

Animals↗