To examine the transforming potential of the × gene product of hepatitis B virus (HBV), the X‐gene‐containing region (referred to as the HBx region) was introduced into mouse NIH3T3 cells. Each transformed cell line expressed X‐coding mRNA at a different level. A positive correlation was found between the level of X‐coding mRNA and the saturation density of the cells. The HBx‐transformed cell lines exhibited × protein production and tumor formation in nude mice. The function of HBV in oncogenesis may involve the continuous expression of the X‐gene‐coded product in the HBV DNA‐integrated cells.

ABSTRACT. To examine the influence of insulin on megakaryocytopoiesis, we tested its effect on murine bone marrow cultures in a liquid culture system. In the presence of pokeweed mitogen-stimulated spleen cell conditioned medium in culture, insulin markedly enhanced megakaryocyte colony formation and increased the number and size of free megakaryocytes seen after 7 days. Many of the cells in cultures with insulin, however, were classified as immature, since they had a basophillic cytoplasm, a low cytoplasmic/nuclear ratio and low acetylcholinesterase activity. It is suggested that insulin potentiates murine marrow megakaryocytopoiesis in vitro, but that this is not accompanied by differentiation of the cells from the immature to mature state.

We have purified alpha2-glycoprotein (alpha2-GP), an insulin antagonist from human plasma which is induced by growth hormone (GH), and shown that pure alpha2-GP is a potent antagonist of severe insulin-induced hypoglycemia, producing acute hyperglycemia in intact rats and ketonuria in diabetic rats. The N-terminal amino acid sequence of alpha2-GP and the reactivity of alpha2-GP with an antitransferrin monoclonal antibody show that alpha2-GP is identical to human serum transferrin. Furthermore, pure human serum transferrin and non-glycosylated recombinant human transferrin reproduce the insulin antagonist effects of alpha2-GP in rats, whereas ovotransferrin shows no such effect. The neutralization of the insulin antagonism of human serum transferrin by an anti-transferrin monoclonal antibody shows that transferrin has a new function as a potent insulin antagonist. This novel role for human serum transferrin in the regulation of glucose metabolism provides a reasonable mechanism for the diabetogenic effect of GH, and has important implications for the etiology and progression of diabetes.

Rats with chemical diabetes were submitted to repeated restraint in order to investigate the diabetogenic potentiality of stress. Material and MethodUnfasted, adult Sprague-Dawley rats of about 150 g initial b.w. were employed. Blood and urine glucose determinations were performed by the glucose oxidase strip method (Vargas, Bronfman and Kawada 1974). Basal glycemia for normal rats was 92 + 0.6 mg% (M + SEM of 104 determinations). The samples were taken immediately before stress (time 0), every 60 min along 240 minutes. Restraint stress was provoked by immobilization of the rats on the operating table by moans of rubber bands tied to their extremities, procedure that permits escape movements.Two series of rats, 67 with 80% pancreatectomy and 14 with 90 % pancreatectomy (80%-P~ and 90%-P~), were submitted to repeated restraint stress. The stress began 7 days and 3 months after pancreatectomy, respectively. The 80% pancreatectomy was performed following the procedure reported by Bates and Garrison (1967).A third series of 20 intact male and 25 intact female rats was used as control. Another series consisting of 5 controls and 5 80 %-P~rats was studied at mid-day by the Oral Glucose Test (200 mg/100 g, 40% glucose solution).The post-stress glycemia-glycosuria response was classified as: a) hyperglycemic response when glycemia was between 150 and 179 mg%, without glycosuria; b) diabetic response when glycemia rose over 180 mg% accompanied by glycosuria, and came back to normal values within 4 hours; c) transient diabetes when the diabetic response lasted 8 hours or more, but returned to normal levels, and d) permanent diabetes when the diabetic response was irreversible.