Activation of phosphoprotein phosphatases by growth hormone sequences with insulin-like activity

The N-terminal part sequences of pituitary growth hormone, N-acetyl-hGH 7–13 and hGH 6–13, promoted conversion of glycogen synthase b to glycogen synthase a in skeletal muscle and adipose tissue when injected intravenously. The peptides also caused conversion of phosphorylase a to phosphorylase b in liver and adipose tissue, but not in muscle, where the peptides antagonised activation of phosphorylase. Synthase phosphatase activity in muscle and phosphorylase phosphatase activity in liver increased after injection of peptide, with time courses of change similar to those seen for muscle synthase and liver phosphorylase activities. Injection of peptide also decreased both the cyclic AMP dependent and independent synthase kinase activities in muscle. These results show that the insulin-like activities of these peptides on glycogen synthase and phosphorylase involve both increases in protein phosphatase activities and inhibition of protein kinase activities. These results are discussed in relation to the insulin-like activities of growth hormone.     

The methyltrienolone binding protein of JEG-3 cells and human placenta is localized within the nucleus and is tightly associated with chromatin.

Human placenta contains the methyltrienolone binding protein (MTBP), an androgen binding protein which is distinct from the androgen receptor. This study demonstrates that the human choriocarcinoma cell line (JEG-3) also contains the MTBP and that in both human placenta and JEG-3 cells the MTBP is located exclusively in the nucleus and in particular is associated with DNase 1 resistant chromatin.     

Diabetes mellitus in Mohawks of Kahnawake,PQ: a clinical and epidemiologic description.

The authors report the rates of obesity, hypertension, hypercholesterolemia, smoking, and macrovascular and microvascular complications among Mohawks of Kahnawake, PQ, who have non-insulin-dependent diabetes mellitus. The data were derived from a study comparing rates of macrovascular and microvascular complications among the diabetic subjects and a nondiabetic group matched for age and sex. The data for both groups were collected by means of chart review, interview and body measurement. There were no important differences between the male and female diabetic subjects. Both sexes had high levels of obesity, hypertension, hypercholesterolemia and diabetic complications. A total of 86% of the diabetic subjects were obese; the rate was also very high (74%) among the nondiabetic subjects. The mean age at onset of diabetes, 59 years, was 10 years higher than that observed in Oneida Iroquois of Ontario. The rates of macrovascular disease among the diabetic subjects were higher than those found among Cree/Ojibwa in Ontario and Manitoba. Our findings add to the knowledge of non-insulin-dependent diabetes in North American Indians in Canada and show that there are differences between our Mohawk subjects and diabetic people of other native communities.     

Characterisation and covalent labeling of the human placental methyltrienolone binding protein

Human placental cytosol contains an androgen binding protein which binds the synthetic androgen methyltrienolone (R 1881) with high affinity (Kd 8.7 nM) and with an average binding capacity of 518 fmol/mg cytosol protein. This study provides further evidence that this protein is distinguishable from classical androgen receptors on the basis of steroid specificity and sulphydryl group sensitivity. Covalent labeling studies have shown this protein, which we have called "the methyltrienolone binding protein", to have a mol. wt of 67,000 daltons.     

Extraction and genetic control of two new water-soluble proteins of mature barley seed

This paper describes the genetic control of two new water-soluble proteins in barley. Water-soluble proteins (WSPs) of mature barley seed form part of the albumin/globulin class of seed proteins. They can be extracted from hand-milled grain with water, though some WSPs are more efficiently extracted with a solution of 10 mM dithiothreitol. Polymorphisms for WSPs were detected in isoelectric focusing gels incorporating various ampholine combinations. Two new controlling genes (Wsp4 andWsp5) have been identified and located using wheat/barley chromosome addition lines and barley doubled haploids.Wsp4 is located on chromosome 2 (2H), andWsp5 was found to be tightly linked toWsp2 on the long arm of chromosome 7 (5HL). Segregation of a sixth gene (Wsp6) is also described, but this has not been mapped. The results are discussed with respect to other previously mappedWsp loci.This work was funed by the Scottish Office of Agriculture and Fisheries Department and the Agricultural and Food Research Council.     

Development of molecular agents for IGF receptor targeting.

The type 1 insulin-like growth factor receptor (IGF1R) is a promising anticancer treatment target, being frequently overexpressed by tumours, and mediating proliferation, motility and apoptosis protection. Design of specific kinase inhibitors is problematic because of homology between the IGF1R and insulin receptor. This obstacle can be circumvented using sequence-specific molecular agents including antisense, triplex and ribozymes. Recent studies indicate that profound sequence-specific IGF1R gene silencing can be induced by small interfering RNAs that mediate RNA interference in mammalian cells. IGF1R downregulation blocks tumour growth and metastasis, and enhances sensitivity to cytotoxic drugs and irradiation. In murine melanoma cells, radiosensitisation is associated with impaired activation of Atm, which is required for initiation of cell cycle checkpoints and DNA repair pathways after double-strand DNA breaks. Furthermore, tumour cells killed in vivo following IGF1R downregulation can provoke an immune response, protecting against tumour rechallenge. After years of studying the role of the IGF system in tumour biology, novel agents for IGF1R targeting will soon be available for clinical testing. This review summarises the development of molecular agents, and considers factors that will influence clinical activity, including the requirement of established tumours for IGF signalling, and the efficacy and toxicity of IGF1R inhibitors.     

Microsomal and cytosolic cytochrome P450 mediated benzo(a)pyrene hydroxylation in Pleurotus pulmonarius

Summary Microsomal and soluble fractions of Pleurotus pulmonarius exhibited a reduced carbon monoxide difference spectrum with P450 maxima at 448nm and 450–452nm respectively. Substrate induced Type I spectra were observed on addition of benzo(a)pyrene to both fractions. Benzo(a)pyrene hydroxylation was measured using the aryl hydrocarbon hydroxylase assay and was observed to be P450 dependent as indicated by carbon monoxide inhibition together with the substrate binding characteristics. The activity of the fractions were observed to give K_m of 200mM and 660mM and V_max of 1.25 nmol/min/nmol P450 and 0.57 nmol/min/nmol P450 for the microsomal and cytosolic fractions respectively.     

Characteristics of triplex-directed photoadduct formation by psoralen-linked oligodeoxynucleotides.

A triplex-forming oligopyrimidine has been attached at its 5'-end to a photoreactive psoralen derivative and used to target a sequence which forms part of the coding region of the human aromatase gene. The 20 base pair sequence is not a perfect triplex target since it contains three pyrimidine interruptions within the purine-rich strand. Despite this, we have detected triplex-directed photoadduct formation at pH 7.0 between the psoralen-linked oligonucleotide and a 30mer duplex representing the aromatase target. Photoadduct formation was found to be sensitive to pH, temperature, cation concentration and the base composition of the third strand. By varying the base sequence of the target duplex around the psoralen intercalation site, we have characterised the site and mode of psoralen intercalation. The attached psoralen has been found to intercalate at the triplex-duplex junction with a strong preference for one orientation. We have shown that the psoralen will bind at the junction even when there is a preferred TpA step at an adjacent site. We have also compared the binding affinity and photoreactivity of oligodeoxyribonucleotides linked to two different psoralen derivatives and found differences in the rate of crosslinking and the extent of crosslink formation. Finally, we have examined oligodeoxyribonucleotides which are attached to psoralen by polymethylene linkers of different lengths.