Protein kinase C increases the activity of the polyoma virus middle T antigen-associated phosphatidylinositol kinase

Exposure of polyoma virus-transformed fibroblasts to the protein kinase C-stimulating phorbol ester 12-O-tetradecanoyl phorbol-13-acetate (TPA) is known to increase the transforming potential of the virus's middle T antigen. Here it is shown that this TPA treatment also stimulates an 85 kDa phosphatidylinositol kinase associated with the middle T antigen. Since activation of this kinase is known to be necessary, although not by itself sufficient for the transformation of cells by polyoma virus, bursts of protein kinase C activity, triggered by TPA or various cellular receptors, might enhance the oncogenicity of polyoma virus by stimulating this middle T antigen-associated phosphatidylinositol kinase.     

Polyomavirus transforms rat F111 and mouse NIH 3T3 cells by different mechanisms.

Polyomavirus middle tumor antigen (mT) was expressed in a line of mouse NIH 3T3 cells under control of the dexamethasone-regulatable mouse mammary tumor virus promotor. Contrary to rat F111 cells which were rendered anchorage independent by mT expression alone (L. Raptis, H. Lamfrom, and T.L. Benjamin, Mol. Cell. Biol. 5:2476-2487, 1985), mT-producing NIH 3T3 cells were unable to grow in agar even after full mT induction. The mT:pp60c-src-associated phosphatidylinositol kinase was activated in these cells to a degree similar to that in fully transformed cells expressing the small and large T antigens, in addition to mT. We therefore propose that the stimulation of this phosphatidylinositol kinase, although apparently necessary, is not sufficient for transformation of NIH 3T3 cells by polyomavirus.     

Extended somatostatin treatment of a patient with bleeding ulcer.

The results of a 67 hour cyclic somatostatin continuous infusion in a patient with a bleeding ulcer are reported. The subject was a 65 year old male with very heavy gastrointestinal bleeding on the 9th postoperative day following a high BI-resection. Endoscopy revealed the bleeding to be caused by two residual ulcers in the area of the anastomosis. Somatostatin treatment led to an immediate cessation of the bleeding after 1 hour. Gastric secretion as well as gastrin, insulin and growth hormone levels were significantly inhibited by somatostatin. Endoscopy at the end of the treatment period showed two ulcers in the process of healing. The raised blood glucose levels caused by somatostatin were easily controlled with max. 14 IU cristalline insulin daily. Except for dryness in the mouth, no adverse side effects were apparent. There was no evidence from laboratory investigations of hemostatic defects or bleeding tendency in the patient.     

Body composition determinants of metabolic phenotypes of obesity in nonobese and obese postmenopausal women

Objective : Although obesity is typically associated with increased cardiovascular risk, a subset of obese individuals display a normal metabolic profile (“metabolically healthy obese,” MHO) and conversely, a subset of nonobese subjects present with obesity‐associated cardiometabolic abnormalities (“metabolically obese nonobese,” MONO). The aim of this cross‐sectional study was to identify the most important body composition determinants of metabolic phenotypes of obesity in nonobese and obese healthy postmenopausal women. Design and Methods : We studied a total of 150 postmenopausal women (age 54 ± 7 years, mean ± 1 SD). Based on a cardiometabolic risk score, nonobese (body mass index [BMI] ≤ 27) and obese women (BMI > 27) were classified into “metabolically healthy” and “unhealthy” phenotypes. Total and regional body composition was assessed with dual‐energy X‐ray absorptiometry (DXA). Results : In both obese and nonobese groups, the “unhealthy” phenotypes were characterized by frequent bodyweight fluctuations, higher biochemical markers of insulin resistance, hepatic steatosis and inflammation, and higher anthropometric and DXA‐derived indices of central adiposity, compared with “healthy” phenotypes. Indices of total adiposity, peripheral fat distribution and lean body mass were not significantly different between “healthy” and “unhealthy” phenotypes. Despite having increased fat mass, MHO women exhibited comparable cardiometabolic parameters with healthy nonobese, and better glucose and lipid levels than MONO. Two DXA‐derived indices, trunk‐to‐legs and abdominal‐to‐gluteofemoral fat ratio were the major independent determinants of the “unhealthy” phenotypes in our cohort. Conclusions : The “metabolically obese phenotype” is associated with bodyweight variability, multiple cardiometabolic abnormalities and an excess of central relative to peripheral fat in postmenopausal women. DXA‐derived centrality ratios can discriminate effectively between metabolic subtypes of obesity in menopause.     

Gap junctional intercellular communication in cells isolated from urethane-induced tumors in A/J mice

Studies using normal or neoplastically transformed established mouse lung epithelial cell lines revealed a reduction in gap junctional, intercellular communication (GJIC) with transformation. To determine the stage in tumor development at which GJIC is interrupted, we used the well-established model of lung tumors induced in strain A/J mice by urethane. In this system, tumor development follows a well-characterized pattern; hyperplasias, adenomas, and carcinomas are manifested at approximately 8, 16, and 40 weeks after urethane treatment, respectively. GJIC levels were examined using a novel technique where cells are grown on a glass slide, half of which is coated with electrically conductive, optically transparent, indium-tin oxide. An electric pulse that opens transient pores on the plasma membrane is applied in the presence of the fluorescent dye, Lucifer yellow, causing dye penetration into cells growing on the conductive part of the slide. Migration of the dye through gap junctions to nonelectroporated cells growing on the nonconductive area is then microscopically observed under fluorescence illumination. Unexpectedly, primary cells cultured from urethane-induced tumors, even late stage carcinomas, possessed extensive GJIC immediately upon isolation. Upon passage for several months however, these cells lost GJIC. These results suggest that the molecular changes that lead to the formation of the tumor in vivo are not sufficient to interrupt gap junctions. Propagation of tumor cells in culture induces additional alterations that can lead to gap junction closure.     

The influence of glucan polymer structure and solution conformation on binding to (1-->3)-beta-D-glucan receptors in a human monocyte-like cell line

Glucans are (1-3)-beta-D-linked polymers of glucose that are produced as fungal cell wall constituents and are also released into the extracellular milieu. Glucans modulate immune function via macrophage participation. The first step in macrophage activation by (1-3)-beta-D-glucans is thought to be the binding of the polymer to specific macrophage receptors. We examined the binding/uptake of a variety of water soluble (1-3)-beta-D-glucans and control polymers with different physicochemical properties to investigate the relationship between polymer structure and receptor binding in the CR3- human promonocytic cell line, U937. We observed that the U937 receptors were specific for (1-->3)-beta-D-glucan binding, since mannan, dextran, or barley glucan did not bind. Scleroglucan exhibited the highest binding affinity with an IC(50)of 23 nM, three orders of magnitude greater than the other (1-->3)-beta-D-glucan polymers examined. The rank order competitive binding affinities for the glucan polymers were scleroglucan>schizophyllan > laminarin > glucan phosphate > glucan sulfate. Scleroglucan also exhibited a triple helical solution structure (nu = 1.82, beta = 0.8). There were two different binding/uptake sites on U937 cells. Glucan phosphate and schizophyllan interacted nonselectively with the two sites. Scleroglucan and glucan sulfate interacted preferentially with one site, while laminarin interacted preferentially with the other site. These data indicate that U937 cells have at least two non-CR3 receptor(s) which specifically interact with (1-->3)-beta-D-glucans and that the triple helical solution conformation, molecular weight and charge of the glucan polymer may be important determinants in receptor ligand interaction.     

Visfatin, TNF-alpha and IL-6 mRNA expression is increased in mononuclear cells from type 2 diabetic women.

Visfatin, is a new adipokine, highly expressed in the visceral fat of both mice and humans. To examine whether visfatin is expressed in human peripheral monocyte-enriched mononuclear cells and whether its expression is altered in type 2 diabetes (DM2), we compared 24 DM2 women [17 overweight (BMI >25) and 7 lean (BMI<25)] to 26 healthy women (14 overweight and 12 lean), all premenopausal. Relative visfatin mRNA levels were significantly higher (approximately 3-fold) in DM2 compared to healthy control women (p<0.02), independently of the presence of overweight/obesity. Mononuclear TNF-alpha and IL-6 mRNA expression was also elevated in DM2 compared to control women (p=0.001 and p=0.004, respectively), an increase observed in both lean and overweight DM2 women. By contrast, circulating visfatin, TNF-alpha, and IL-6 levels showed no difference between DM2 and control women, while adiponectin plasma levels were significantly decreased in the DM2 women (p<0.001). Circulating visfatin and TNF-alpha levels did not differ either between the lean and the overweight subgroups of DM2 and control women, while IL-6 plasma levels were significantly higher in both overweight subgroups compared to their lean counterparts. In conclusion, visfatin, TNF-alpha, and IL-6 mRNA expressions are increased in peripheral mononuclear-monocytic cells from women with type 2 diabetes, independent of their BMI, which may enhance the effects of their adipose-derived levels and may contribute to the increased insulin resistance and atherogenic risk of these patients.