Polybrominated diphenyl ethers (PBDEs), used as flame retardants, have been detected in the environment and in mammalian tissues and fluids. Evidence indicates that PBDE mixtures induce CYPs through aryl hydrocarbon receptor (AhR)-dependent and -independent pathways. The present work has investigated the effects of individual components of a commercial PBDE mixture (DE71) on expression of CYP1A1, a biomarker for activation of the AhR (dioxin-like), and CYP2B and CYP3A, biomarkers for activation of the constitutive androstane and pregnanexreceptors (CAR and PXR), respectively, in the rat. Male F344 rats were dosed orally on three consecutive days with either DE71, PBDE components, 2,2',4,4'-tetraBDE (BDE47), 2,2',4,4',5-pentaBDE (BDE99), 2,2',4,4',5,5'-hexaBDE (BDE153), representative polybrominated dibenzofurans (PBDFs) present in DE71, or reference PCBs. Differential expression of target genes was determined in liver 24 h after the last dose. Quantitative PCR analysis indicated up-regulation of CYP1A1 by DE71; however, the response was weak compared to that for dioxin-like PCB126. Individual PBDE components of DE71 up-regulated CYP1A1 only at the highest administered dose (100 micromol/kg/day). Representative PBDFs efficiently up-regulated CYP1A1; therefore, they, along with other PBDFs and polybrominated dibenzodioxins detected in DE71 and individual PBDE components, may be responsible for most, if not all, dioxin-like properties previously observed for PBDEs. Conversely, PBDEs appear capable of up-regulating CYP2B and CYP3A in rats at doses similar to that for non-dioxin-like PCB153. These results indicate that in vivo PBDE-mediated toxicity would be better categorized by AhR-independent mechanisms, rather than the well-characterized AhR-dependent mechanism associated with exposure to dioxin-like chemicals.

SummaryType 1 diabetes (T1D) is caused by the selective destruction of the insulinproducing b cells of the pancreas by an autoimmune response. Due to ethical and practical difficulties, the features of the destructive process are known from a small number of observations, and transcriptomic data are remarkably missing. Here we report whole genome transcript analysis validated by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and correlated with immunohistological observations for four T1D pancreases (collected 5 days, 9 months, 8 and 10 years after diagnosis) and for purified islets from two of them. Collectively, the expression profile of immune response and inflammatory genes confirmed the current views on the immunopathogenesis of diabetes and showed similarities with other autoimmune diseases; for example, an interferon signature was detected. The data also supported the concept that the autoimmune process is maintained and balanced partially by regeneration and regulatory pathway activation, e.g. nonclassical class I human leucocyte antigen and leucocyte immunoglobulin-like receptor, subfamily B1 (LILRB1). Changes in gene expression in islets were confined mainly to endocrine and neural genes, some of which are T1D autoantigens. By contrast, these islets showed only a few overexpressed immune system genes, among which bioinformatic analysis pointed to chemokine (C-C motif) receptor 5 (CCR5) and chemokine (CXC motif) receptor 4) (CXCR4) chemokine pathway activation. Remarkably, the expression of genes of innate immunity, complement, chemokines, immunoglobulin and regeneration genes was maintained or even increased in the long-standing cases. Transcriptomic data favour the view that T1D is caused by a chronic inflammatory process with a strong participation of innate immunity that progresses in spite of the regulatory and regenerative mechanisms.

The encapsulation of islets of Langerhans in alginate-poly-l-lysine has been proposed as a method for the immunoprotection of transplanted islets. Although several capsule compositions have been reported, there has been no published study concerning the effect of capsule composition on the severity of the foreign body reaction. Empty capsules were prepared from high mannuronic acid alginate and were coated with: (1) poly-l-lysine alone, (2) poly-l-lysine plus high guluronic acid alginate, or (3) poly-l-lysine plus high mannuronic acid alginate. The capsules were placed in the renal subcapsular space or the peritoneal cavity, and retrieved after three weeks of histological examination. The recipients were WAG/01a, nude (athymic), diabetic BB, and non-diabetes prone BB rats. The severity of reaction to the capsules was determined by measuring the thickness of the pericapsular cell infiltrate or by a scoring system. The severity of the reaction to the capsules was strain-dependent in both the renal and peritoneal sites, with the BB and nude rats displaying the most severe responses. The degree of response was not affected by capsule composition in the renal subcapsular space, but in the peritoneum, the high mannuronic acid alginate capsules provoked the weakest response, and this type of capsule will be used for future transplantation work. The infiltrating cells were characterised by immunohistochemistry and electron microscopy and found to be mostly fibroblasts and macrophages.

Mastoparan, a tetradecapeptide component of wasp venom, activates heterotrimeric G-proteins and stimulates exocytosis in several cell types, including the pancreatic beta-cell. In this study, its effects on insulin secretion were assessed in both rat and human pancreatic islets, along with the ability of glucose and alpha-ketoisocaproate (alpha-KIC) to augment mastoparan-stimulated release. In Ca2+-free Krebs-Ringer bicarbonate buffer containing 2.8 mmol/l glucose, 20 micromol/l mastoparan stimulated insulin secretion 12- and 14-fold in rat and human islets, respectively. The inactive analog mastoparan-17 had no effect on release. Under the same Ca2+-free conditions, 11.1 mmol/l glucose had no effect on insulin release alone, but augmented mastoparan-stimulated release by 74% in both rat and human islets. Stimulation of release by mastoparan and augmentation of release by glucose were unaffected by treatment with pertussis toxin. The effect of cellular GTP depletion on the mastoparan stimulation of release and augmentation by alpha-KIC was studied by culturing rat islets in the presence of 25 microg/ml mycophenolic acid for 20 h. In the control islets, alpha-KIC augmented mastoparan-stimulated insulin release by 80%. In the GTP-depleted rat islets, mastoparan-stimulated insulin release was not changed, while the augmentation by alpha-KIC was eliminated. Mannoheptulose completely blocked the augmentation by glucose. In conclusion, mastoparan stimulates insulin release by activation of a signal transduction pathway that can be augmented by nutrients such as glucose and alpha-KIC. Nutrient augmentation of this pathway is heavily dependent on GTP.

The original report on the microencapsulation of islets of Langerhans used sodium alginate and poly-L-lysine (PLL) to form the capsules. Although several alternative materials have subsequently been used with vary-mg degrees of success, it is those studies using islets encapsulated in alginate-PLL-alginate which are reviewed in detail in this article. Since the first report of islet microencapsulation, many studies have demonstrated excellent in vitro viability of encapsulated islets. However, transplantation experiments into chemically induced diabetic recipients have yielded varied results, with some studies showing good long-term graft function whilst in others grafts failed due to pericapsular fibrosis. The use of naturally occurring animal models of type 1 (insulin-dependent) diabetes has demonstrated a decline in graft function, suggesting that this presents a more complex problem to be solved than that in chemically induced diabetic recipients. Fibrosis of capsules has been the major problem causing graft failure, and this has been demonstrated to be more severe in spontaneously diabetic models. However, recent advances in alginate purification and attempts to reduce the size of the encapsulated islets are major steps towards encapsulated islet transplants becoming a viable proposition for the treatment of type 1 diabetic patients.

There are many factors which can explain the failure of achieving insulin-independence after islet allotransplantation. These include the use of diabetogenic immunosuppressive agents to abrogate both islet allo-immunity and auto-immunity, the critical islet mass to achieve insulin-independence and the detrimental effects of transplanting islets in an ectopic site. However recent evidence most notably from the Edmonton group demonstrates that islet allotransplantation still has great potential to become an established treatment option for diabetic patients.

Summary Fatty acids were determined in erythrocytes in 49 patients with colorectal cancer and compared with age and sex-matched controls. Marginally increased levels of stearic acid (P=0.057) and oleic acid (P=0.064) and decreased arachidonic acid (P=0.043) occurred in cancer patients. There was no difference in the stearic to oleic acid ratio between the two groups. Dietary intake, assessed by dietary recall and adipose tissue analysis was also not different. In control subjects the polyunsaturated:saturated (P:S) fatty acid ratio correlated betwen diet and adipose tissue (P<0.001) but not erythrocytes; there was a three way correlation between dietary, erythrocyte and adipose linoleic acid (P<0.01, at least). In contrast cancer patients showed different correlations; in particular dietary and erythrocyte P:S fatty acid ratios correlated (P<0.01).These findings may indicate disturbed fat metabolism in cancer patients. The erythrocyte stearic to oleic acid ratio is of no diagnostic value.Recently much interest has been aroused by reports of abnormalities of fatty acids in erythrocytes obtained from patients with a variety of solid tumours arising from the gastrointestinal tract (Wood et al., 1985;Habib et al., 1987). In particular, a reduced ratio of stearic acid (18:0) to oleic acid (18:1, n-9) has been found (Wood et al., 1985). This has been attributed to a circulating desaturation factor of cell membrane fatty acids in cancer patients (Habib et al., 1987). A close correlation has been reported between this ratio and the Dukes' stage of colonic cancers (Habib et al., 1986) and curative resection results in the fatty acid ratio returning to normal (Wood et al., 1985). However, others have raised objections about the matching of the patients with control subjects (Metcalfe et al., 1985).The present study was therefore undertaken to assess the erythrocyte fatty acid profile in a relatively homogeneous group of patients with cancer (colon and rectum) using closely matched controls. The possible influence of dietary fat on the red cell fatty acid profile was also assessed by determining intake using seven-day dietary recall and measuring the fatty acid composition of adipose tisue. Patients and methodsForty-nine patients with colorectal cancer were studied, of whom 42 were admitted for elective surgery. None of these patients had sutained any weight loss. Eleven had Dukes' A, 20 had Dukes' B and 11 had Dukes' C adenocarcinomas. The other seven patients had clinically recurrent colorectal cancer following previous resection, although only four had sustained a > 10% weight loss. The mean age was 69.0 years (range 49-92 years) of whom 30 were men and 19 were women. Patients presenting as emergencies with obstruction, perforation and bleeding requiring blood transfusion were deliberately excluded.The control population consisted of an equal number of patients admitted for elective surgery for benign diseases (e.g., varicose veins or abdominal wall herniae) at the same time as those with cancer and were matched for age...

The effects of the mixed alpha/beta-agonist adrenaline on insulin secretion from isolated human islets of Langerhans were studied. In static incubation experiments, adrenaline (0.1 nmol/l to 10 mumol/l) caused a concentration-dependent inhibition of glucose-induced insulin secretion from isolated human islets. However, perifusion experiments revealed that the time-course of the secretory changes induced by adrenaline was complex. When employed at a high concentration (1 mumol/l), adrenaline caused a sustained inhibition of glucose-induced insulin secretion, which could be relieved by the addition of the alpha 2-antagonist yohimbine (10 mumol/l). By contrast, infusion of adrenaline at a lower concentration (10 nmol/l), produced a large initial potentiation of glucose-induced insulin secretion. This response was, however, short-lived and followed by sustained inhibition of secretion, which could be relieved by yohimbine (10 mumol/l). The initial stimulation of insulin secretion provoked by 10 nmol adrenaline/l was abolished when islets were incubated in the presence of the beta-antagonist, propranolol (1 mumol/l), consistent with activation of beta-adrenoceptors. In support of this, treatment of human islets with the selective beta 2-agonist clenbuterol, was also associated with marked stimulation of insulin secretion. By contrast, each of two selective beta 3-agonists tested failed to alter insulin secretion from human islets. The results indicate that human pancreatic B-cells are equipped with both alpha 2- and beta 2-adrenoceptors which can affect insulin secretion. Adrenaline interacts with both of these but the alpha 2-response is predominant and can overcome the tendency of beta 2-adrenoceptors to potentiate insulin release.