Elevation of brain prostaglandin E2 levels in rodents by delta 1-tetrahydrocannabinol.

An isotopic dilution procedure using specific prostaglandin E2 (PGE2) brain receptors was utilized to determine the changes in brain PGE2 levels subsequent to drug exposure. Delta-1-tetrahydrocannabinol (delta 1-THC) stimulated PGE2 synthesis resulting in increased brain concentrations when compared with vehicle treated rats and mice. Indomethacin markedly inhibited the delta 1-THC elevated rise in PGE2 levels presumably by inhibition of prostaglandin synthetase. The delta 1-THC-induced increase in PGE2 brain levels was also suppressed by i.v. administered rabbit PGE2-antiserum. This suggests that one of the sites of delta 1-THC action is extracerebral and from here a portion of the released prostaglandins are transported to the brain. These results add further support to previous data that delta 1-THC given orally results in an increase in brain PGE2 levels.     

A population balance model of enzymatic lysis of microbial cells

A model is proposed for enzymatic lysis of microbial cells based on number balances over the distribution of cell-wall mass in a population of cells. Analytical solutions to the population balance equations were obtained by the method of characteristics for simple reaction kinetics. The model has been used to analyze the following cases of lysis in a nonhomogeneous cell population: wall hydrolysis with cell rupture and product release, the effect of a distribution of lysis rates, and lysis of two-layer cell walls. Rate expressions for the reactions of lysis can be derived from bulk-phase experiments; the distributions of cell size and product content can be measured independently by flow cytometric techniques. The population model also provides an explanation for the initial lag seen in lysis kinetics for virtually any initial distribution. The model demonstrates patterns of lysis and product recovery for heterogeneous populations of cells and also applies to the more general problem of soluble-enzyme reactions with heterogeneous solid substrates.     

Evidence for the presence of a phosphatidylinositol anchor on the lipoarabinomannan and lipomannan of Mycobacterium tuberculosis

The recent availability (Hunter, S.W., Gaylord, H., and Brennan, P.J. (1986) J. Biol. Chem. 261, 12345-12351) of the well known arabinomannan of Mycobacterium leprae and Mycobacterium tuberculosis as the pure native lipoarabinomannan has resulted in its implication in key aspects of the immunopathogenesis of leprosy and tuberculosis. We had indicated that the lipid moiety of lipoarabinomannan is probably based on a diacylglycerol unit in that glycerol and the two fatty acids, hexadecanoate and 10-methyloctadecanoate, were identified. In addition, lipoarabinomannan was also shown to contain myo-inositol 1-phosphate. Evidence is now presented, based on selective radiolabeling and analysis of various cleavage fragments, that the inositol phosphate exists as both an alkalilable phosphodiester and as part of a phosphatidylinositol "membrane anchor." The mannan of M. tuberculosis was also isolated as the native lipomannan. It also apparently contains a phosphatidylinositol unit but is devoid of the alkali-labile inositol phosphate residues. These lipopolysaccharides are apparently multiglycosylated versions of the well known myocobacterial mannosyl phosphatidylinositols and are prokaryotic versions of the growing list of phosphatidylinositol-anchored macromolecules. Immunogold labeling demonstrates that lipoarabinomannan is a true antigenic capsular or extracellular product of M. tuberculosis. The presence of a phosphatidylinositol residue on lipoarabinomannan may explain its interaction with macrophage membranes and role in mycobacterial pathogenesis.     

The status of cacao (Theobroma cacao,sterculiaceae) in the western hemisphere

There are, at the present time, effectively no long-range, ongoing programs in any tropical country of the western hemisphere dedicated to the improvement of cacao (Theobroma cacao, Sterculiaceae). While some effort is currently made to obtain new acquisitions of cacao cultivars exhibiting desirable characteristics and to maintain genepools of these trees, there are few data from field trials to prove and substantiate these qualities. In addition, there is a growing concern regarding the disparities between predicted yields of cacao trees through the use of “hybrid” seed and from actual production under field conditions. This has stimulated an awareness of the current inadequate understanding of the genetics of cacao and the lack of comprehension as to which cultivars, under distinct ecological conditions, are precocious, resistant to disease, or heavy bearing, or indeed demonstrate those traits vital to the success of farming programs adapted to today’s market conditions. This paper examines the events that have led to the current status of selection, development, and breeding of cacao. Alternative approaches are suggested.     

Two structurally and functionally different forms of the transforming protein of PRC II avian sarcoma virus.

The primary translation product of the PRC II avian sarcoma virus genome is a protein of 105,000 daltons (P105), and we have previously shown that approximately 50% of the P105 molecules are converted to molecules of 110,000 daltons (P110) by posttranslational modification. Fractionation of PRC II-infected cells showed that P105 was contained primarily in a nonionic detergent-soluble compartment, whereas P110 partitioned almost exclusively with a nonionic detergent-insoluble or crude cytoskeletal fraction. The tyrosine-specific protein kinase activity previously observed in immunoprecipitates which presumably contained both P110 and P105 was found predominantly in the P110-containing immunoprecipitates made from the cytoskeletal fraction and was essentially absent from the P105-containing immunoprecipitates prepared from the soluble fraction. Individual analysis of 32P-labeled P110 and P105 prepared by this fractionation technique revealed that P110 contained more phosphotyrosine per mole of protein than did P105. Examination of the tryptic peptide maps of 32P-labeled P110 and P105 suggested that the additional phosphotyrosine in P110 resulted from phosphorylation at discrete sites within the protein. From these experiments, we conclude that PRC II-infected cells contain two discrete forms, P105 and P110, of the transforming protein and that each of these proteins exhibits distinct structural and functional characteristics.     

Expression of the PRC II avian sarcoma virus genome.

We found that the genomic RNA of the replication-defective avian sarcoma virus PRC II was 4.0 kilobases long. A Northern blot analysis of the viral RNAs present in PRC II-transformed cells showed that the PRC II genome was expressed as a single 4.0 kilobase mRNA species. In vitro translation of polyadenylic acid-containing 70S virion RNA yielded two highly related proteins of 110,000 and 105,000 daltons (P110 and P105), which were synthesized from messenger activity that sedimented as expected for the 4.0 kilobase PRC II genome (at 25 to 27S). P110 and P105 were identified as in vitro translation products of the PRC II genome by immunoprecipitation and tryptic peptide mapping and were the only PRC II-specific polypeptides detected by in vitro synthesis. In addition, we found that immune complexes prepared from PRC II 70S virion RNA in vitro translation products contained a tyrosine-specific protein kinase activity. A comparison of the in vitro- and in vivo-synthesized proteins revealed that PRC II-transformed cells also contained 110,000- and 105,000-dalton proteins, which were indistinguishable from in vitro-synthesized P110 and P105 by electrophoretic mobility and tryptic peptide analysis. Both P110 and P105 were present in producer cells and in seven individual nonproducer clones. A pulse-chase analysis showed that P105 was the primary translation product of the PRC II genome and that P110 was derived from P105 by post-translational modification. Under conditions of long-term labeling with [35S]methionine, P110 and P105 were present in a molar ratio of approximately 1:1. These results indicated that the transformation-specific product of the PRC II genome, previously referred to as a single component (P105), actually consists of two polypeptides related by post-translational modification.     

Analysis in vivo of translational mutants of the rIIB cistron of bacteriophage T4

We have mapped the mutants isolated by Nelson et al. (1981) that reduce the amount of rIIB protein synthesized during bacteriophage T4 infection of Escherichia coli B and characterized their rIIB expression in vivo. These mutants fall into four distinct groups in terms of mapping and phenotype. We have located the probable site of each mutation on the DNA sequence. We have also analyzed a number of other mutations near the initiating AUG of rIIB with respect to their rIIB expression. In some of these mutants, ribosomal recognition of the wild-type initiating AUG is precluded and so initiation occurs at a different AUG, which, in some instances, we have identified.     

Epidermal growth factor induces rapid tyrosine phosphorylation of proteins in A431 human tumor cells

Addition of EGF to A431 cells at physiological concentrations causes a rapid three- to four-fold increase in the abundance of phosphotyrosine in cellular protein. The increase is essentially complete within 1 min and is maintained for several hours. No change in phosphotyrosine levels is found with fibroblast growth factor or insulin. Two phosphoproteins (molecular weights of 39 and 81 kd) containing phosphotyrosine appear de novo upon administration of EGF to A431 cells. The EGF receptor itself is a phosphoprotein containing phosphotyrosine as well as phosphoserine and phosphothreonine. Changes in the phosphorylation pattern of the EGF receptor are seen upon treatment of A431 cells with EGF. Increased phosphorylation of tyrosine is the most rapid response of cells to EGF known, and may play an important role in the biological effects of EGF.     

Self-monitoring of blood glucose in diabetic pregnancy.

Admission to hospital is usually recommended to achieve the best possible diabetic control during pregnancy. We have used blood glucose monitoring at home to find out if patients can achieve equally good control outside hospital. Twenty-five consecutive diabetic patients were studied, of whom 20 had taken insulin before pregnancy. Six of their 14 previous pregnancies had ended in perinatal death. The 25 women performed 4247 blood glucose measurements during their pregnancies. Overall the mean blood glucose concentration was 7.1 mmol/l (128 mg/100 ml); before meals the mean was 6.5 mmol/l (117 mg/100 ml). Mean concentrations were lower in the third trimester, but at no stage was control in hospital significantly better than at home. The mean hospital stay before delivery was 22 days, and all patients had live babies. Monitoring blood glucose concentrations at home produces greater understanding and motivation among patients, improves control early in pregnancy, and shortens time spent in hospital.     

In vitro polyoma DNA synthesis: requirement for cytoplasmic factors.

Purified nuclei from polyoma-infected mouse (3T3) cells were found to be greatly reduced in their ability to synthesize viral DNA in vitro when compared with a crude system consisting of an unfractionated hypotonic lysate of the infected cells. The synthetic capacity of the nuclei could be fully reconstituted when a high-speed cytoplasmic supernatant was added back to them. Cytosols from uninfected mouse, monkey, and hamster cells were equally as effective in stimulating purified nuclei as that of virus-infected mouse cells. Optimal complementation required high concentrations of the cytosol, and most of the complementing activity was destroyed by heating to 60 C. Dialysis had no effect on the activity. Analysis of the viral DNA synthesized in purified nuclei showed an accumulation of Okazaki-type short DNA chains, which could be chased into viral progeny DNA strands if cytosol was added back to the nuclei. Kinetic analysis of the pulse-labeling pattern of viral replicative DNA showed a strong dependence of the extension of viral progeny strands and of the processing of Okazaki-type fragments on the amount of cytosol present during the reaction. It is suggested that the cytoplasmic DNA polymerase might be one of the active components in the cytosol, but most likely not the only one.