Prevention of T cell anergy by signaling through the gamma c chain of the IL-2 receptor

When stimulated through their antigen receptor without requisite costimulation, T cells enter a state of antigen-specific unresponsiveness termed anergy. In this study, signaling through the common gamma chain of the interleukin-2 (IL-2), IL-4, and IL-7 receptors in the presence of antigen was found to be sufficient to prevent the induction of anergy. After culture with IL-2, IL-4, or IL-7, Jak3 kinase was tyrosine-phosphorylated, which correlated with the prevention of anergy. Therefore, a signal through the common gamma chain may regulate the decision of T cells to either clonally expand or enter a state of anergy.     

Cytotoxicity of bile in human Hep G2 cells and in primary cultures of rat hepatocytes

There has been increasing interest in the development of a hepatocyte bioreactor for the treatment of acute hepatic failure; however, little is known about the effect of hepatocyte byproducts on the viability of the cells in the bioreactor environment. We investigated the effects of increasing concentrations of bile on the growth and viability of the human hepatoma cell line Hep G2 and on the cytochrome P-450 content and dependent mixed function oxidase (MFO) activities, reduced glutathione (GSH) content, and glutathione S-transferase (GST) activity of primary cultures of rat hepatocytes. Our purpose was to determine whether or not it would be necessary to pretreat the plasma from patients with acute liver failure to remove elevated bile concentrations which might be toxic to the hepatocytes in an artificial liver device. Bile was found to inhibit Hep G2 cell growth at concentrations as low as 0.1% and to decrease viability at concentrations above 0.5%. The cytochrome P-450 and GSH contents and the activities of the MFO system and of GST were decreased in the primary cultures of hepatocytes following 24 h treatment with concentrations of bile at and above 0.5%. The MFO activities associated with different cytochrome P-450 isoenzymes decreased to different extents in the presence of bile with the O-dealkylation of pentoxyresorufin being more labile than that of ethoxyresorufin. Our data indicate that elevated bile concentrations are cytotoxic to liver cells, and it may be necessary to pretreat patient plasma to decrease its bile content to protect the cells during the clinical operation of a hepatocyte bioreactor device.     

Fentanyl and its analogs desensitize the cloned mu opioid receptor

Fentanyl, and its structural analogs lofentanil and sufentanil, are potent analgesics used clinically in the management of pain. However, the high analgesic potency of these compounds is limited by the development of tolerance after chronic use. To investigate whether their tolerance development may be related to mu receptor desensitization, the cloned mouse mu receptor as well as mutant forms of the receptor were stably expressed in HEK 293 cells and tested for their response to continuous opioid treatment. Fentanyl and its analogs potently bound to the mu receptor and effectively inhibited cAMP accumulation. Three-hour pretreatment of mu receptors with fentanyl and its analogs desensitized the mu receptor by uncoupling it from adenylyl cyclase. The fentanyl analogs caused a slight internalization of the mu receptor as accessed by antibody binding to the epitope-tagged mu receptor. Truncation of the mu receptor by removal of its carboxyl terminus at Glu341 did not affect the ability of the fentanyl analogs to bind to and activate the mu receptor nor did it prevent the fentanyl analogs from desensitizing the receptor. In a previous study we showed that morphine did not desensitize the cloned mu receptor even though it is a potent and effective agonist at the mu receptor. Mutagenesis studies revealed that morphine interacts differently with the mu receptor to activate it than do the fentanyl analogs which may explain its lack of desensitization of the mu receptor. These results indicate that desensitization of the mu receptor may be a molecular basis for the development of tolerance to fentanyl and its analogs.     

Escherichia coli O157:H7 requires intimin for enteropathogenicity in calves

Enterohemorrhagic Escherichia coli (EHEC) strains require intimin to induce attaching and effacing (A/E) lesions in newborn piglets. Infection of newborn calves with intimin-positive or intimin-negative EHEC O157:H7 demonstrated that intimin is needed for colonization, A/E lesions, and disease in cattle. These results suggest that experiments to determine if intimin-based vaccines reduce O157:H7 levels in cattle are warranted.     

Isolation of canine prolactin by polyacrylamide gel electrophoresis

The electrophoretic mobility of prolactin obtained from canine pituitary extract was studied with the aid of polyacrylamide disc electrophoresis. Using a preparative gel electrophoretic system the immunoreactive material was purified on a quantitative scale which was then used to develop a homologous radioimmunoassay for canine prolactin. The radioimmunoassay system was able to detect prolactin in the plasma of dogs after the administration of agents which would be expected to affect prolactin secretion.     

Pancytopenia and aplastic anemia: a retrospective study

During January 1971--June 1975 we examined 195 patients with pancytopenia. The cause was bone marrow failure in 67.7% of cases (classic aplastic anaemia in 11.3%) hypersplenism in 7.7%, massive blood transfusions in 1.5%, severe infections in 9.7% (Gram-negative in 3%), and various other conditions in 7.8%. Records were insufficient for diagnosis in 5.6% of cases. Analysis of the 22 patients with aplastic anaemia showed no apparent aetiology in 16 (72.7%), previous phenylbutazone ingestion in 2, and Fanconi-type anaemia in 4 of 7 children. One-year survival was 73.7%, 2-year survival 71.4%, 3-year survival 63.6% and 4-year survival 57.1%. Marrow-investigation of the 21 available samples showed that 6 were acellular, 11 hypocellular and 4 normocellular. All patients received at least temporary therapy with anabolic steroids but its effectivity could not be satisfactorily assessed. Five patients died within 7 months and 5 patients went into remission, needing no further therapy. The initial haematological features of the 5 patients who died were not significantly different from those of the rest of the patients.