Chemical carcinogenesis by the two-stage protocol in the skin ofMastomys natalensis (Muridae) using topical initiation with 7,12-dimethylbenz(a)anthracene and topical promotion with 12-0-tetradecanoylphorbol-13-acetate

Virchows Archiv B Cell Pathology - The long-term (34 weeks) topical administration of 7,12-dimethylbenz(a)anthracene (DMBA) to the skin of male and femaleMastomys induced a broad spectrum of benign...     

Proteolytic modification of mouse liver catalase

When catalase was immunoprecipitated from different subfractions of mouse liver homogenates, the enzyme which was obtained from extracts of the large granular fraction exhibited a lower molecular weight than that from either the cytosol or purified peroxisomal fractions, as judged by sodium dodecyl sulphate polyacrylamide gel electrophoresis. This modification of the enzyme could be prevented by the addition of proteolytic inhibitors to extraction buffers; and consequently, unmodified catalase was able to be purified in the presence of 5 mM iodoacetamide. Electrophoretic comparison of the catalases against standards of known molecular sizes indicated that the unmodified enzyme had a subunit mass approximately 2,000 daltons larger than the modified enzyme. The significance of these proteolytic modifications has been discussed in relation to the involvements of catalase and peroxisome turnover.     

A polymorphic variant of human erythrocyte carbonic anhydrase I with a widespread distribution in Australian aborigines,CAIAustralia-9 (8 Asp → Gly): Purification,properties, amino acid substitution,and possible physiological significance of the variant enzyme

Carbonic anhydrase I (EC 4.2.1.1) purified from the pooled packed red blood cells of 100 individuals typed as heterozygous for the common Australian Aboriginal carbonic anhydrase I variant CAI Australia-9 had a slightly higher specific CO2 hydratase or esterase (toward p-nitrophenyl acetate) activity than the normal component and a higher Km and Vmax using the esterase substrate. The variant enzyme was slightly more resistant to heat inactivation. The extent of inhibition of both enzymes by the specific inhibitor acetazolamide was identical, as was their immunological behavior and the lability of the active-site zinc ion. The variant enzyme was more resistant to chloride inhibition. The physiological importance of this observation is discussed in the context of a proposed adaptive advantage of the variant gene in the arid western and central regions of Australia. The amino acid substitution in the Aboriginal variant of a glycine for an aspartic acid residue has been located at residue 8 from the N terminus (i.e., 8 Asp leads to Gly), by proteolytic and partial acid hydrolyses. The possible effects of this substitution on the structure and function of the molecule are discussed.     

Human T cell responses to gp63, a surface antigen of Leishmania

gp63, an abundant and conserved leishmania cell surface protein, has been implicated in the ability of these parasitic protozoa to infect macrophages in vitro and has shown potential as a protective immunogen in mice. However, little is known regarding human immune responses to this glycoprotein Ag. In this study, human T lymphocyte responses to Leishmania amazonensis native gp63 and to recombinant gp63 (rgp63) produced in Escherichia coli were evaluated in individuals with active or cured cutaneous, mucosal or visceral leishmaniasis. Both native and rgp63 elicited strong proliferative responses in all patients tested. In addition, IFN-gamma was produced in response to stimulation with both forms of the protein. T cell lines generated from PBMC by stimulation with native or rgp63 were phenotypically similar, and proliferated and produced IFN-gamma in response to stimulation with both forms of the molecule. These results suggest that gp63 is a strong T cell immunogen and that the recombinant and native forms can elicit the same type of T cell response from infected patients. In order to compare the immunogenic properties of these two forms of gp63, PBMC from naive (uninfected) donors were sensitized in vitro with native or rgp63. T cell lines generated against rgp63 proliferated in response to rgp63, but failed to proliferate in response to native gp63 or to promastigote lysate. Thus, rgp63 was effective in eliciting T cell responses from patients with active or cured leishmania infection, but did not effectively induce T cell responses under the conditions used.     

Phylogenetic relationships within the class Oligohymenophorea,phylum Cilophora,inferred from the complete small subunit rRNA gene sequences ofColpidium campylum,Glaucoma chattoni,andOpisthonecta henneguyi

Summary Phylogenetic relationships within the class Oligohymenophorea, phylum Ciliophora, were investigated by determining the complete small subunit rRNA (SSrRNA) gene sequences for the hymenostomesColpidium campylum, Glaucoma chattoni, and the peritrichOpisthonecta henneguyi. The affiliations of the oligohymenophoreans were assessed using both distance matrix (DM) and maximum parsimony (MP) analyses. Variations do exist in the phylogenies created by the two methods. However, the basic tree topologies are consistent. In both the DM and MP analyses the hymenostomes (C. campylum, G. chattoni, and the tetrahymenas) all form a very tight group associated with the peritrichO. henneguyi. TheTetrahymena lineage was monophyletic whereasColpidium andGlaucoma were more closely related to each other than either was to the tetrahymenas. The monophyly of the genusTetrahymena in the present analysis supports the phylogenies determined from morphological data and molecular sequence data from the histone H3II/H4II region of the genome. The perplexing and controversial phylogenetic position of the peritrichs is once again depicted in the present analysis. The distinctiveness of the peritrichOpisthonecta from both hymenostome and nassophorean ciliates based on evolutionary distances suggests that the elevation of the peritrichs to a higher taxonomic rank should be reconsidered.     

Identification of pristanoyl-CoA oxidase as a distinct, clofibrate non-inducible enzyme in rat liver peroxisomes.

In this paper we describe the identification of pristanoyl-CoA oxidase activity in rat liver peroxisomes. This activity was not stimulated by clofibrate feeding. Furthermore, the activity was found in multiple tissues. These results show that pristanoyl-CoA oxidase is different from any of the known oxidases which include a clofibrate-inducible acyl-CoA oxidase and the recently identified cholestanoyl-CoA oxidase. Gelfiltration and chromatofocusing experiments provide conclusive evidence that we are dealing with a novel acyl-CoA oxidase with a unique function in peroxisomal beta-oxidation.     

Interleukin-6 is used as a growth factor by virulent Mycobacterium avium: presence of specific receptors.

In this paper, we examined the contribution of the lymphokine interleukin-6 (IL-6) to the growth of four virulent strains of Mycobacterium avium and the nature of the binding moieties on the mycobacteria. First, we showed that human or mouse recombinant interleukin-6 are potent growth factors for four strains of virulent M. avium. This was shown to occur in tissue culture medium, which does not support maximal growth of M. avium. Bioactive IL-6 was required, inasmuch as heat-activating IL-6 or adding an antibody against IL-6 blocked this growth-enhancing ability. The rapid uptake of IL-6 by M. avium was indicated by the fact that the incubation of IL-6 with the four M. avium strains led to a rapid removal of the bioactivity from the culture medium and a rapid removal of radiolabeled IL-6. Scatchard analysis of receptor interaction showed that the M. avium strains had a single receptor species with a Kd of 50 nM and the number of receptor sites was approximately 15,000 bacterium. Blocking experiments showed that the binding of radiolabeled IL-6 was fully displaceable with cold IL-6, but not with other lymphokines. These data suggest that IL-6 may play an important role in the pathogenesis of M. avium infections, notably by promoting growth of M. avium, and that some virulent M. avium strains bind IL-6 in a specific manner.     

Sulfite inhibition of photochemical activity of intact pea leaves

Sulfite treatment of pea leaf disks in light caused a significant decrease in the relative quantum yield of photosynthetic oxygen evolution and energy storage (ES) as measured by photoacoustic (PA) spectroscopy. The inhibition was concentration dependent and was less in darkness than in light, indicating light-dependent inhibitory site(s) on the photosynthetic electron transport chain. Further, in darksulfite-treated leaves, the energy storage was more affected than the relative quantum yield of oxygen evolution, suggesting that photophosphorylation and/or cyclic electron transport around PS I are sites of sulfite action in darkness. The R_fd values, the ratio of fluorescence decrease (fd) to the steady-state fluorescence (fs), decreased significantly in leaves treated with sulfite in light but were not affected in dark-treated ones, confirming the photoacoustic observations. Similarly, the ratio of variable fluorescence (F_v) to maximum fluorescence (F_m), a measure of PS II photochemical efficiency, was affected by sulfite treatment in light and not changed by treatment in darkness. An attempt was made to explain the mechanism of sulfite action on photosynthetic electron transport in light and in darkness.Abbreviations A_PT amplitude of photothermal signal - A_ox amplitude of oxygen signal - ES energy storage - fd fluorescence decrease - fs steady-state fluorescence - F_m maximum fluorescence - F_v variable fluorescence - PA photoacoustic(s)