Proefschrift (Med.) Maastricht. / Lijst van werken van R. T. Evenwel: p. 149-151. Lit. opg. Met samenv. i.h. Nederlands.

Proefschrift Universiteit Maastricht. / Met bibliogr., lit. opg. - Met samenvatting in het Nederlands.

Th.--Sci. pharm.--Paris 5, 1981. N°: 57.

Th. 3e cycle--Pharm.--Paris 5, 1981. N°: 21.

Th. 3e cycle--Pharm., physiol--Paris 5, 1982. N°: 36.

Th. 3e cycle--Pharmacodyn.--Paris 5, 1980. N°: 11.

No description available.

No description available.

In order to develop a radioimmunoassay for rat C-peptide, rat insulinoma, which contains large quantities of insulin and was expected also to contain large quantities of C-peptide, was chosen as a starting material. However, the tissue was found not to contain extractable C-peptide. Instead, a novel peptide (rat insulinoma peptide, RIP) was isolated. Rat insulinoma peptide (RIP) which appears to be either a fragment of, or an altered rat C-peptide was isolated and purified by dialysis. The purity of this peptide was investigated using polyacrylamide gel electrophoresis with sodium dodecyl sulphate, isoelectric focussing, and high performance liquid chromatography. RIP may contain two peptides similar to each other but differing in their isoelectric points. The molecular weight of RIP was found to be 1,982 daltons by fast atom bombardment mass spectrometry giving a chain length of approximately 22 amino acid residues. From information obtained using radioimmunoaasay employing antiserum R901, RIP appears to share a common C-terminus with rat C-peptide. A radioimmunoassay for RIP was developed using the purified RIP as immunogen and for standards and tracers. An indirect enzyme linked immunosorbent assay (ELISA) for rat insulinoma peptide was developed using purified RIP for immunogen and semi-purified RIP as a standard. Rat C-peptide I and II were successfully synthesised using the technique of solid phase peptide synthesis. The crude synthetic peptides were purified by dialysis, and their purity was assessed by high performance liquid chromatography. The molecular weight of these synthetic peptides was determined by fast atom bombardment mass spectrometry to be 3,183 daltons. These two synthetic peptides can be detected by rat C-peptide I radioimmunoassay employing antiserum R901. A radioimmunoassay for rat C-peptide I was developed using synthetic rat C-peptide I for immunogen, standard and tracer. The rat C-peptide I and II antisera were shown to produce positive staining of the islets of Langerhans of normal rat pancreas.

The effects of di-2 ethylhexyl phthalate (DEHP) over periods of 3 days to 9 months were examined in both male and female rats using biochemical, histological and ultrastructural techniques. Responses occurred in a characteristic order. Initial effects included : changes in the. distribution of lipid in the liver, proliferation of hepatic peroxisomes and induction of laurate hydroxylases. More slowly developing changes were (1) hypertrophy of the hepatocytes, (2) centrilobular loss of glycogen and (3) a fall in glucose-6-phosphatase activity. After 9 months of treatment, accumulation of lipid-loaded lysosomes were observed. All these changes were observed in rats treated with 1000 or 200 mg/kg/day of DEHP, but rats treated with 50 mg/kg/day of DEHP did not show the later changes. In addition to these sustained alterations, two transient changes were observed. Male rats, treated with 1000 mg/kg/day of DEHP showed changes in the biliary system as shown by electron microscopy, by examination of bile flow, bile enzymes and proteins. Furthermore, a burst of mitosis occurred immediately after commencement of treatment of DEHP, the magnitude and time of which was dose-dependent. Changes in female rats were qualitatively similar, but quantitatively smaller, than in male rats. Mature male rats treated for 3 or 13 days with either DEHP or the hypolipidaemic drugs fenofibrate or clofibrate, showed similar changes to young rats with the exception of the mitotic burst which did not occur in these animals. The initial short term effects of DEHP and the straight chain analogues, di-n-octyl phthalate (DN0P) and di-n- hexyl phthalate (DNHP) in vivo and their respective esters, MEHP and MNHP, were reproduced in cultured hepatocytes. There was induction of peroxisomal enzymes in response to treatment with DEHP or MEHP but little or no induction after treatment with DNOP, MNOP or MNHP. Accumulation of lipid was seen after 24 hours of treatment With MEHP, MNOP and MNHP. However, the mitotic burst was not reproduced in cultured hepatocytes treated with MEHP, neither was there a fall in glucose-6-phosphatase activity. There was no increase in H[2]O[2] production either in vitro in cultured hepatocytes treated with MEHP, or in vivo as measured by catalase compound I in perfused liver from rats treated with DEHP in the diet. There was no evidence for mutagenic activity of DEHP or MEHP in the Ames Test. Treatment of isolated hepatocytes with MEHP, straight chain phthalate esters or clofibrate, resulted in early marked pertubations in lipid metabolism, namely, an increase in production of neutral fats and generally in fatty acid oxidation. This may explain the increased storage of lipid, in the liver. There was a marked difference in response between hepatocytes isolated from fed and fasted rats, the latter being more sensitive to all compounds. Indeed with fed rats there was, in some cases, a slight decrease in fatty acid oxidation. The effects on lipid metabolism were observed at concentrations which produced peroxisome proliferation in cultured cells.