Activation of striatal tyrosine hydroxylase by in vivo electrical stimulation: Comparison with cyclic AMP-mediated activation

These studies were carried out to characterize the activation of rat striatal tyroxine hydroxylase produced by depolarization of the medial forebrain bundle and to evaluate the possible role of cyclic AMP as a mediator of this activation. The enzymatic properties of tyrosine hydroxylase following in vivo depolarization were compared to those produced by treatment of striatal synaptosomes with dibutyryl cyclic AMP (dbcAMP). Similar effects were observed with regard to enzyme distribution, altered sensitivity to dopamine-induced inhibition, and activity as a function of tyrosine concentration. However, differences between the two treatments were also apparent. First, treatment with dbcAMP shifted the pH optimum from 6.2 to 7.0. In contrast, electrical stimulation decreased the rate of decline in activity as the pH was increased above the optimum, but did not shift the pH optimum. Second, plots of tyrosine hydroxylase activity versus cofactor concentration revealed two enzyme forms for both control and electrically stimulated preparations. However, dbcAMP treatment converted the enzyme to a single high affinity form. These results can be explained by one of the following: (1) cyclic AMP is the sole mediator of enzyme activation, but does not produce a maximally activated enzyme following in vivo depolarization (2) cyclic AMP is only one of several mediators involved or (3) cyclic AMP is not involved in depolarization-induced activation, with activation occurring via the mediation of other intracellular messengers, such as calcium.     

An improved assay for bacterial methane mono-oxygenase: some properties of the enzyme from Methylomonas methanica.

Extracts of Methylomonas methanica catalyse the O2-and NAD(P)H-dependent disappearance of bromomethane. The activity is unstable at 2 degrees C but is stable at --70 degrees C for several weeks. Bromomethane mono-oxygenase is particulate and is inhibited by metal-binding reagents, by compounds SKF 525A and Lilly 53325, by some metal ions and by acetylene. Evidence is presented that indicates that bromomethane mono-oxygenase is the enzyme responsible for methane oxidation in vivo.     

Fate of mRNA of L-Cells Infected with Mengovirus

Mengovirus infection of L-cells results in an inhibition of host protein synthesis which is detectable in vivo by a decreased rate of incorporation of radioactive amino acids into acid-insoluble material and by a concomitant reduction in polysome content. The inhibition of host protein synthesis occurs early in the infection cycle, at a time when there is little synthesis of viral proteins. In this paper the stability of polyadenylic acid [poly(A)]-containing mRNA of uninfected L-cells and cells infected with mengovirus is compared. Our results suggest that there is no increase in the rate of degradation of cellular mRNA upon virus infection. The continued integrity of host mRNA throughout infection was verified by acrylamide gel electrophoresis.     

Cell kill and tumor control after heat treatment with and without vascular occlusion in RIF-1 tumors

RIF-1 tumors (100-300 mg) were exposed in vivo to heat treatment (41-48 degrees C) for 30 min and then assayed for either cell survival or tumor control. The tumors were heated either with normal perfusion or with temporary vascular occlusion (clamped for 30 min prior to and during the 30-min treatment). The physical technique of water bath heating ensured temperature uniformity in both the perfused and vascularly occluded tumors. Survival curves for tumor cells heated under both conditions had a shoulder and exponential regions. While the T0's were not statistically different in the two cases, cells from the tumors whose blood flow had been occluded showed an enhanced sensitivity to heat as evidenced by a reduction of the shoulder by 2.5 degrees C. A similar increase in sensitivity was measured with the tumor cure assay with the TCT50 decreasing from 47 degrees C for unclamped tumors to 45 degrees C for clamped tumors. The two assays are therefore in excellent agreement in assessing the effectiveness of heat treatment and the influence of vascular occlusion on the heat sensitivity of this tumor. Since the clonogenic assay was performed immediately after treatment, this agreement between assays indicates that direct cell kill by heat is the major factor in determining cure in this tumor.     

Phosphorylation of tyrosine-416 is not required for the transforming properties and kinase activity of pp60v-src

A mutant in src, the oncogene of Rous sarcoma virus, has been constructed in which the major phosphorylated tyrosine (Tyr-416, located in the carboxy-terminal half of the protein) has been replaced by phenylalanine. Mouse cells transformed with this mutant src form foci and grow in soft agar, indicative of a transformed state. Also, the mutant protein retains the wild-type ability to phosphorylate proteins on tyrosine. Partial proteolysis revealed that the carboxy-terminal half of the mutant protein was still phosphorylated, although apparently to a lesser extent. Analysis indicated that this residual phosphorylation was on tyrosine. We conclude that the major tyrosine phosphorylation in pp60v-src is not required for two of the protein's notable properties--protein kinase activity and transformation of cultured cells.     

An analogue study of the initial carryover effects of meditation,hypnosis, and relaxation Using naive college students

An analogue study involving two experiments was conducted to test the initial carryover effects of hypnosis, meditation, and relaxation upon self-reports of awareness. In the first experiment, concentrative meditators reported fewer nonsensorial events than controls. In the second experiment, concentrative meditators again reported fewer nonsensorial events, but covariate analysis and pretest/posttest comparisons revealed that it was the controls who had changed, increasing their nonsensorial reports. In addition, the relaxation group increased its reports of somatic awareness. Results were discussed in terms of the effects of performance demands and the possibility that meditation and hypnosis might be able to disinhibit awareness processes otherwise inhibited by normal daily routines.This article represents in part findings from a masters thesis completed at Appalachian State University, Donald L. Clark, Ph.D., Director, and a doctoral dissertation completed at The University of North Carolina at Chapel Hill, David P. Rogers, Ph.D., and George S. Welsh, Ph.D., Co-Directors. The research was supported in part by a Grant-in-Aid of Research from Sigma Xi, the Scientific Research Society, with additional monies from the Smith Fund for graduate research at the University of North Carolina. Thanks go to Michelle Batchelder, Elizabeth Barbee, Lisa Barboun, Susan Durham, Lee Earl, Elizabeth Evans, Pam Gilmore, Sally Hall, Willian Hatch, Anne Mahaffie, Sally Parker, Lee Pusser, Susan Roach, Jennifer Rosenbaum, Skip Salguerro, Jeannette Smith, Michael Smith, Sylvia Sutton, and Lourdes Vinuales for their help in conducting the second experiment, with special thanks also to Susan Woodard (Experiment 1) and Alisa Huffman and Melanie Thackston (Experiment 2) for their help in coding the data. Helpful comments were made by Arthur N. Wiens, Ruth G. Matarazzo, Mary Lawrence Cawthon, W. Grant Dahlstrom, and Aija Ozolins on earlier drafts of this article.     

Relationship between mitochondrial lipid peroxidation and alpha-tocopherol levels in the guinea-pig adrenal cortex

Lipid peroxidation in mitochondria from the functionally distinct inner (zona reticularis) and outer (zona fasciculata + zona glomerulosa) zones of the guinea-pig adrenal cortex was investigated. Ferrous ion (Fe2+)-induced lipid peroxidation was far greater in inner than outer zone mitochondria. Ascorbic acid similarly initiated lipid peroxidation to a greater extent in inner zone mitochondrial preparations. Differences in the unsaturated fatty acid content of inner and outer zone mitochondria could not account for the regional differences in lipid peroxidation. Total fatty acid concentrations were greater in the outer than in the inner zone, and the relative amounts of each fatty acid were similar in the two zones. However, mitochondrial concentrations of alpha-tocopherol, an antioxidant known to inhibit lipid peroxidation, were approx. 5-times greater in the outer than inner zone. The results demonstrate that there are regional differences in mitochondrial lipid peroxidation in the adrenal cortex which may be attributable to differences in alpha-tocopherol content. Thus, alpha-tocopherol may serve to protect outer zone mitochondrial enzymes from the consequences of lipid peroxidation and thereby contribute to some of the functional differences between the zones of the adrenal cortex.     

Genetic Diversity of Bangladeshi Jackfruit (Artocarpus heterophyllus) over Time and Across Seedling Sources

Economic Botany - Crop genetic diversity is important, but may be lost due to intentional or non-intentional selection processes. Jackfruit (Artocarpus heterophyllus) is the national fruit of...