Effect of α-difluoromethylornithine on polyamine and DNA synthesis in regenerating rat liver: Reversal of inhibition of DNA synthesis by putrescine

The possibility that α-difluoromethylornithine, a specific, irreversible inhibitor of ornithine decarboxylase could be used to prevent the rise in hepatic putrescine and spermidine content following partial hepatectomy was tested. Administration of α-difluoromethylornithine at a dose of 400 mg/kg every 4 h reduced hepatic putrescine to <2 nmol/g, but had only a small effect on the rise in spermidine seen at 28 h after partial hepatectomy. Such treatment also reduced the rise in DNA synthesis produced by partial hepatectomy by up to 70%. The inhibitory effect towards DNA synthesis could be reversed by administration of putrescine which increased the hepatic putrescine content to about 30–40% of that in the regenerating control livers. These results suggest that accumulation of putrescine rather than spermidine is needed for DNA synthesis after partial hepatectomy. They also suggest that part, but not all of the rise in putrescine normally seen in the liver after partial hepatectomy is needed for the enhanced DNA synthesis associated with liver regeneration. Experiments with lower doses of α-difluoromethylornithine showed that a substantial part of the rise in hepatic ornithine decarboxylase activity could be abolished without affecting either the rise in spermidine content or the increase in DNA synthesis after partial hepatectomy.     

Aspirin inhibits arachidonic acid metabolism via lipoxygenase and cyclo-oxygenase in hamster isolated lungs

The effect of aspirin on the fate of exogenous arachidonic acid (AA) was investigated in isolated perfused lungs of female hamsters. During pulmonary infusion of aspirin (10 μM, 100 μM or 1 mM) 45 nmol of ¹⁴C-AA was infused in two minutes into the pulmonary circulation. The nonrecirculating perfusion effluent was collected for 6 minutes after the beginning of the AA infusion. Arachidonate infusion increased the perfusion pressure. This pressor response was completely abolished by 1 mM aspirin. When aspirin was infused into the pulmonary circulation, the amount of radioactivity was increased in the perfused lungs and decreased dose dependently in the nonrecirculating perfusion effluent. The amount of unmetabolized free arachidonate was not changed significantly by aspirin in the perfused lungs or in the perfusion effluent. In the effluent the amounts of all arachidonate metabolites, which were extracted with ethyl acetate first at pH 7.4 and then at pH 3.5 and analysed by thin layer chromatography, were decreased quite similarly by aspirin. The formation of arachidonate metabolites was completely inhibited by 1 mM aspirin. In the perfused lung tissue the amount of ¹⁴C-AA was increased by aspirin in phospholipids and neutral lipids. The present study indicates that the metabolism of arachidonic acid is inhibited by aspirin in hamster lungs not only via cyclo-oxygenase but also via other lipoxygenases.     

Subcellular Location and Neuronal Release of Diazepam Binding Inhibitor

Diazepam binding inhibitor (DBI), a peptide located in CNS neurons, blocks the binding of benzodiazepines and beta-carbolines to the allosteric modulatory sites of gamma-aminobutyric acid (GABAA) receptors. Subcellular fractionation studies of rat brain indicate that DBI is compartmentalized. DBI-like immunoreactivity is highly enriched in synaptosomes obtained by differential centrifugation in isotonic sucrose followed by a Percoll gradient. In synaptosomal lysate, DBI-like immunoreactivity is primarily associated with synaptic vesicles partially purified by differential centrifugation and continuous sucrose gradient. Depolarization induced by high K+ levels (50 mM) or veratridine (50 microM) released DBI stored in neurons of superfused slices of hypothalamus, hippocampus, striatum, and cerebral cortex. The high K+ level-induced release is Ca2+ dependent, and the release induced by veratridine is blocked by 1.7 microM tetrodotoxin. Depolarization released GABA and Met5-enkephalin-Arg6-Phe7 together with DBI. DBI is also released by veratridine depolarization, in a tetrodotoxin-sensitive fashion, from primary cultures of cerebral cortical neurons, but not from cortical astrocytes. Depolarization fails to release DBI from slices of liver and other peripheral organs. These data support the view that DBI may be released as a putative neuromodulatory substance from rat brain neurons.     

A p50 surface antigen restricted to human urinary bladder carcinomas and B lymphocytes

Summary We have previously described the derivation of a monoclonal antibody, S2C6, to a novel 50 Kdalton antigen associated with human urinary bladder carcinoma. No reactions were obtained with carcinomas of unrelated origin or with normal urothelial cells. However, the antibody also reacted with a similar antigen on some cell lines of B lymphocyte origin. Using large panels of target cells we have now shown that this reactivity was entirely restricted to cells of the B lineage within the haematopoietic system. As opposed to its apparent restriction to malignant cells of the urothelium, the S2C6 antigen was expressed by normal B lymphocytes as well as by many malignant B cells (chronic lymphocytic leukaemia, hairy cell leukaemia and immunocytoma). Pre-B cells derived from acute lymphocytic leukaemia and plasma cells from multiple myeloma lacked the antigen. Expression was significantly enhanced on cultured B cells from Burkitt lymphomas and on Epstein-Barr virus-transformed lymphoblastoid cell lines including those of the pre-B phenotype derived from fetal bone marrow. As judged from the molecular size and the distribution pattern displayed by the S2C6 antigen it appears to be distinct from other B cell antigens previously described. A possible relation of the S2C6 antigen to a receptor for B cell growth factors is discussed.     

Heterogeneity of intercellular adhesion in rat liver cells in culture

The intercellular homotypic adhesive properties of 14 clones derived from a nontumorigenic rat liver epithelial cell line (LEC), derived from neonatal Fischer rats, were examined and compared to those of the hepatoma H4-II-E cell line. Each clone was assayed also for the degree of chromosomal aneuploidy and the ability to grow in soft agar. Over 100-fold differences in adhesive properties were observed among the clones, but no correlation was observed between the degree of aneuploidy in the clones and intercellular adhesive properties. The parent LEC cell line and the clones derived from it were unable to grow in soft agar. The H4-II-E cells showed negligible capacity to reaggregate after dissociation into single cells and these cells readily formed colonies in soft agar. Many of the LEC clones were similar to the H4-II-E cells in their adhesive properties, which suggests that reduced cell-to-cell adhesiveness per se is not a necessary prerequisite of epithelial cells to be able to grow independent of anchorage. Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) of concanavalin A (Con A)-binding glycoproteins in the "most adhesive" clone 67 and the "least adhesive" clone 201 showed markedly elevated amounts of acidic 105 and 67-kDa glycoproteins in clone 67. Proteins with similar migration patterns in 2D-PAGE have previously been reported to participate in specific homotypic intercellular adhesion of liver cells. The Con A-binding glycoprotein pattern in H4-II-E cells was markedly different from that of LEC cells with a set of six proteins missing and nine proteins appearing new in the H4-II-E cells. It is suggested that, in addition to identifying known epithelial cell polypeptides, systematic screening of cell surface-associated glycoproteins in normal and transformed epithelial cells in vitro and in vivo may lead to identification of novel polypeptides intimately associated with the transformed phenotype.     

Pancreatic Duct Obstruction in the Pig: Light Microscopy of Chronic Pancreatitis

Morphological changes of pancreatic tissue in young pigs caused by surgical ligation of the main pancreatic duct are described. Nineteen animals from 6 to 7 weeks in age were operated on and necropsied 3 or 6 to 8 weeks later. Twelve pigs developed a pronounced chronic pancreatitis with complete exocrine insufficiency. Of the 7 animals failing to develop ectasia of pancreatic ducts, 2 died due to surgical complications. In addition, 3 pigs were sham-operated and served as controls. In macroscopical studies it was observed that in the pronounced pancreatitis cases the ligated duct was greatly dilated by a clear watery fluid. Only remnants of pale and firm grandular tissues were seen around the ectatic ducts. Microscopically, typical changes of chronic pancreatitis were noted. Complete disappearance of acini was followed by ductular cell proliferations. Glandular tissues were divided into lobuli by fibrotic tissues and fat cells. The wall of the main pancreatic duct was greatly thickened and fibrotic, presenting intensely proliferating ductular cells and round cell infiltrates. Furthermore, enlarged endocrine islets surrounded by connective tissue fibres were seen.     

Determination of inorganic phosphate. A method for the determination of phosphatase activities by a continuous flow system

A sensitive and accurate method for the determination of inorganic phosphate is described. The method enables the estimation of 10 nanomoles of inorganic phosphate with a coefficient of variation of 3.6% for ten replicates. The method is suitable for the estimation of the activities of thiamine triphosphatase, adenosine triphosphatase, and alkaline and acid phosphatase by a continuous flow system.