Search PubMed⌕ Search

Biomedical subjects

D W Gray

Publications and source records attributed to D W Gray.

At least 127 records · Page 7Linked to original sources
PubMed1986

Successful autotransplantation of isolated islets of Langerhans in the cynomolgus monkey.

A recently described method for isolation of islets of Langerhans from the human pancreas has been adapted to the cynomolgus monkey pancreas. The mean yield of islets obtained from 13 monkey pancreata was 1319 islets per gram of pancreatic tissue (range 533-1800) and the usual purity of the preparation varied from 5 to 15 per cent islet tissue. Twelve cynomolgus monkeys underwent total pancreatectomy, preparation of islets from the excised pancreas and autotransplantation to either the spleen or the liver. Three animals received no transplant and became immediately diabetic, surviving 4-8 days. Four animals became normoglycaemic after intrasplenic islet transplantation, and survived 6 weeks, at which time splenectomy was performed with immediate onset of diabetes. Splenic vein insulin sampling confirmed the spleen as the source of insulin, and histological examination showed implanted islet tissue in all cases. Five animals became normoglycaemic after intrahepatic islet implantation. Three animals subsequently became diabetic at 4 and 5 months and two animals still have functioning grafts, the longest function being 9 months. These results suggest that in the cynomolgus monkey sufficient islets can be extracted from a single donor pancreas to reverse diabetes.

Animals↗
PubMed1986

The use of spleen transplantation and cyclosporine treatment to induce unresponsiveness to pancreatic islet transplantation in rats.

One way of achieving permanent survival of allografted islets in the rat has been to first transplant a kidney of the same strain as the islets and induce acceptance of the kidney using cyclosporin A treatment. Rats bearing long-surviving renal allografts will then accept islets of the same strain without further immunosuppression. Such an approach may be effective for combined renal and islet grafting, but transplantation of the kidney as well as islets may not always be desirable, and the question arises as to whether another organ could be used to achieve the same effect. Auxiliary spleen transplants were performed from LEW to DA rats, followed by cyclosporine 10 mg/kg for 14 days. Twelve rats with long-surviving grafts were then made diabetic with streptozotocin and given LEW islets placed under the kidney capsule, 6 rats being given a further course of cyclosporine 10 mg/kg for 7 days after islet transplantation. Rats that did not reject their islets then underwent removal of the spleen transplant, and if this did not result in rejection islet function was proven by removal of the kidney bearing the islets. The results show that spleen allograft rejection can be prevented by cyclosporine treatment and that 50% of animals with long-surviving spleen allografts will accept subsequent islet allografts from rats of the same donor strain. The acceptance of islet allografts can be increased to 100% by a further short course of cyclosporine treatment. It is concluded that spleen allografts can be used to produce unresponsiveness to islets in rats.

Animals↗
PubMed1986

The effect of hyperglycemia on isolated rodent islets transplanted to the kidney capsule site.

The effect of hyperglycemia on transplanted rat pancreatic islets was studied using a new technique for transplanting a defined number of islets in a blood clot. Normal or streptozotocin-diabetic DA rats were given 400 DA islets under the left kidney capsule (a number shown to be insufficient to reverse diabetes). After 2 weeks the diabetic rats were given a further 1000 islets under the right kidney capsule to reverse diabetes. Kidneys from both groups were examined at 2 weeks after the initial islet implant and at 3 months for both gross and histological appearance and for insulin content. After 2 weeks left kidneys from nondiabetic rats showed abundant islet tissue, with an insulin content of 116 (+/- 14 SEM) milliunits, compared to 1 +/- 0.5 milliunits in the right kidney. Kidneys from diabetic rats showed no islets recognizable grossly. Histological examination showed vacuolated tissue scarcely recognizable as islet tissue, and the insulin content of the left kidney was reduced to 18 +/- 5 milliunits. However, 3 months after reversal of diabetes by transplantation of 1000 islets to the right kidney, histologically "normal" islet tissue was again visible on the left kidney, and the insulin content was 160 +/- 36 milliunits. Islets left in normal animals for 3 months contained 195 +/- 50 milliunits. These experiments show that islets implanted beneath the kidney capsule in diabetic rats are not destroyed by two weeks hyperglycemia. This suggests that protection of islets after implantation by insulin treatment is unnecessary, even in the presence of a persistently raised blood sugar.

Animals↗
PubMed1985

Properties of isolated human islets of Langerhans: insulin secretion, glucose oxidation and protein phosphorylation.

In the present study, human islets were isolated by collagenase digestion from the pancreases of three kidney donors. Maintainance of the islets in tissue culture enabled insulin release, glucose oxidation and Ca2+ -calmodulin-dependent protein phosphorylation to be determined using the same islets. Increasing glucose over a range 0-20 mmol/l resulted in a sigmoidal stimulation of insulin release (28.8 +/- 5.2 to 118.4 +/- 25.8 microU . islet-1 . h-1, n = 10; threshold less than 4 mmol/l). There was a marked correlation between the insulin secretory response of the islets to glucose and their rate of glucose oxidation (5.9 +/- 0.3 at glucose 2 mmol/l up to 25.8 +/- 1.8 pmol . islet-1 . h-1 at 20 mmol/l, r = 0.98). N-acetylglucosamine (20 mmol/l) failed to elicit a secretory response from the islets. Stimulation of insulin secretion by glucose was dependent upon the presence of extracellular Ca2+. Extracts of the islets contained a Ca2+ -calmodulin-dependent protein kinase which phosphorylated a 48-kdalton endogenous polypeptide. Myosin light-chain kinase activity was demonstrated in the presence of exogenous myosin light chains. This report demonstrates for the first time the sigmoidal nature of glucose-stimulated insulin release from isolated human islets, and its correlation with enhanced glucose oxidation. Furthermore, this is the first report of the presence of Ca2+ -dependent protein kinases in human islets.

Adult↗
PubMed1984

Isolated pancreatic islet allografts in rats rendered immunologically unresponsive to renal allografts. The effect of the site of transplantation.

Long-surviving Lewis (RT-1(1)) renal allografts (LS-LEW) were induced in 20 DA (RT-1a) rats by 14-day treatment with cyclosporine . All were made diabetic 100 days after transplantation using streptozotocin; 7 LS-LEW were untreated and all remained diabetic; 5 LS-LEW were given Lewis islets beneath the kidney capsule without further immunosuppression. Prolonged graft survival (greater than 100 days) was seen in 4 rats. Lewis islets were given into the portal vein in 5 LS-LEW. Prolonged graft survival was seen in 4 rats. Third-party BN islets were given beneath the kidney capsule in 3 LS-LEW; these islets were rejected in less than 9 days. In contrast Lewis islets transplanted into untreated diabetic DA rats beneath the renal capsule or into the portal vein survived for a mean of 8.3 days and 4 days, respectively. In a separate experiment long-surviving Lewis renal allografts were induced in 7 PVG rats (LS-PVG) by cyclosporine treatment. These animals were made diabetic 100 days after transplantation and then were given Lewis islets under the renal capsule of the transplant kidney. Prolonged islet graft survival was seen in 6 rats, and 5 diabetic PVG rats given Lewis islets beneath the renal capsule rejected the islets within 8 days. Thus, once a recipient rat has accepted a renal allograft under the influence of cyclosporine treatment, it will accept permanently an islet allograft of the same strain as the kidney. This effect applies to both strain combinations tested, is not influenced by the site of islet implantation, and is specific for islets of the same strain as the renal allograft.

Animals↗
PubMed1984

A method for isolation of islets of Langerhans from the human pancreas.

A method has been developed for the isolation of islets of Langerhans from the human pancreas. The average number of islets isolated was 1011 islets per gram of pancreas (SD 475, range 752-2111), and the purity of the preparation as defined by histologic examination and specific staining for insulin varied from 10% to 40%. Islet structure was well preserved and the islets were shown to be viable by supravital staining, demonstration of insulin response to glucose, and by transplantation of isolated islets beneath the renal capsule of nude mice. The essential features of this technique for isolation of human islets include injection of a high concentration of collagenase (6 mg/ml) into the pancreatic duct under pressure, followed by a short incubation (23 min) at 39 degrees C. The gland is then dispersed by a process of teasing and shaking, and the islets are separated by a two-stage process of filtration on a nylon mesh to remove the larger islets and centrifugation on a preformed Ficoll density gradient to separate the small islets.

Animals↗
PubMed1984

The results of Ramstedt's operation: room for complacency?

The results of 101 pyloromyotomies performed from 1972 to 1980 have been analysed; 34 operations were performed using local anaesthesia and 67 using general anaesthesia. The use of local anaesthesia was not associated with any advantage related to postoperative or other complications. A high postoperative complication rate of 20% was found (excluding postoperative vomiting), and there were 2 deaths; 11 patients suffered wound infection, with Staphylococcus aureus isolated from 5 of these wounds. The use of prophylactic antibiotics active against Staphylococcus aureus is suggested.

Adolescent↗
PubMed1983

The use of the dye neutral red as a specific, non-toxic, intra-vital stain of islets of Langerhans.

The development of improved methods of islet isolation from the pancreas is hampered by difficulty in identification of islets. A method described by Bensley in 1911 uses neutral red to stain the islets selectively. In the present study the method has been simplified and selective staining of islets in the rat, dog and pig demonstrated by use of light and electron microscopy. Staining of islets with neutral red does not appear to affect their viability as judged by insulin secretion and transplantation in rats.

Animals↗
PubMed1983

The role of prophylactic antibiotics in appendectomy using delayed primary closure.

A prospective randomized trial of prophylactic antibiotics in 202 patients undergoing appendectomy is reported upon. The antibiotics used were metronidazole and cephradine. Half of the patients received antibiotics preoperatively. The other half received antibiotics at operation only upon finding perforation, gangrene or pus formation. All wounds were treated by delayed primary closure. No instance of wound infection, defined as abscess formation or cellulitis, occurred in either group. Antibiotics given prophylactically in every instance appear to have no advantage in preventing wound infection when delayed primary closure is used.

Adolescent↗
PubMed1982

Regulation of phenylalanine hydroxylase activity by phenylalanine in vivo, in vitro, and in perfused rat liver.

We show that phenylalanine is able to control the extent of activation and, as a result, the catalytic activity of rat liver phenylalanine hydroxylase in vivo, in perfused liver, and in vitro. Both phosphorylated and unphosphorylated enzyme activities are controlled by phenylalanine activation and, overall, this mechanism appears to be a major means of regulating the enzyme's activity in rat liver. At normal phenylalanine levels in vivo, phenylalanine hydroxylase is at most 1-4% activated, and phosphorylated enzyme (glucagon-induced) appears at most 5-7% activated under similar conditions. In both cases, a phenylalanine load increased the percentage of activated enzyme found in vivo to about 40% of maximal. In perfused rat livers, a plasma phenylalanine concentration of only 4 times normal induced a 4-fold increase in the amount of activated enzyme present and a corresponding functional increase in the rate of phenylalanine hydroxylation by the tissue. Under the latter conditions, more than 25% of the amino acid could be hydroxylated in a single pass through the organ. Purified phosphorylated phenylalanine hydroxylase must be activated to be catalytically active. The activation with phenylalanine, at equilibrium, is a cooperative process, and the phosphorylated enzyme is activated more rapidly at pH 6.8 and 8.0 and at lower phenylalanine concentration than the unphosphorylated species. Overall, phosphorylation appears to allow phenylalanine hydroxylase to be more easily activated at relatively low phenylalanine concentrations.

Animals↗
PubMed1982

The surface structure of the epithelium of the hamster cheek pouch.

Cheek pouches were removed from 9 BIO 87.20 adult-male hamsters, pinned out on cork sheets and fixed, then divided into segments and processed. Mallory stain showed complete orthokeratinization of the pouch epithelium with regular keratohyaline granules. With scanning electron microscopy, the morphology of the walls was similar, with ridged areas alternating with flatter areas. In all areas, blunt projections and larger dome-shaped elevations were found. The superficial surfaces of all stratum corneum cells were covered by an interconnecting network of ridges surrounding depressions; their deep surfaces were covered by a complementary array of protuberances separated by narrow grooves. On superficial surfaces in some areas, cell boundaries consisted of double ridges separated by a gap; cell imprints were delineated by single ridges or depressions and involved several cells, suggesting that the cells in these areas were not stacked in vertical columns. Elsewhere, the linear ridges were paralleled by depressions, suggesting that the cells were stacked in columns. The morphology of cell boundaries and imprints on the undersurface of the desquamating squames were complementary to those of the opposing surface. Transmission electron microscopy supported the findings. Although most of the cells of the stratum corneum were electron dense and contained only tonofilaments and interfilamentous material, less electron-dense cells which contained only tonofilaments and small keratohyaline granules were occasionally found.

Animals↗