Lobomicosis

The ninth Colombian case of Lobomycosis is presented, along with a review of the Colombian literature. The clinical, histopathological, and mycological aspects are summarized emphasizing the peculiar birefringent appearance of Lobomyces when examined under polarized light.     

Effects of mutation on the downfield proton nuclear magnetic resonance spectrum of the 5S RNA of Escherichia coli

The imino proton spectra of several mutants of the 5S RNA of Escherichia coli are compared with that of the wild type. Three of the variants discussed are point mutations, and the fourth is a deletion mutant lacking bases 11-69 of the parent sequence, all obtained by site-directed mutagenesis techniques. The spectroscopic effects of mutation are limited in all cases, and the differences between normal and mutant spectra can be used to make or confirm the assignments of resonances. Several new assignments in the 5S spectrum are reported. Spectroscopic differences due to sequence differences permit the products of single genes within the 5S gene family to be distinguished and their fates followed by NMR.     

Subcellular localization of tissue polypeptide antigen and cytokeratins in epithelial cells (salivary ad mammary glands). Combined use of the cryoultramicrotomy and the protein A-gold technique

Epithelial cells from various sites and at various stages of differentiation reveal distinct cytokeratin polypeptide patterns. WE have localized these heterogeneous elements at the subcellular level in human salivary glands and in a solid tumor of the breast using a monoclonal and a polyclonal antibody against cytokeratin, and an antibody against tissue polypeptide antigen (TPA) which seems to be related to some cytokeratins. Labeling by the cytokeratin antibodies was more intense in squamous and duct cells than in acinar cells. The TPA:B1 antibody reacted predominantly with duct cells and to a lesser extent with acinar and squamous cells. A precise evaluation of the labeling pattern and a well-preserved cell structure appeared to be important factors in obtaining more detailed information about intermediate filament proteins. The cryoultramicrotomy and the protein A-gold technique are suitable for these studies.     

A comparative study of the characteristics of eIF-2 and eIF-2-ancillary factor activities from yeast Saccharomyces cerevisiae and rabbit reticulocytes

The characteristics of yeast eukaryotic initiation factor 2 (eIF-2) and Co-eIF-2A have been studied and compared with those of the corresponding factors from rabbit reticulocytes. 1) Unlike eIF-2r, purified eIF-2y did not contain bound GDP. 2) Purified eIF-2y preparation contained GTPase activity and dephosphorylated GTP to GDP. 3) An anti-eIF-2r preparation which predominantly precipitated the gamma-subunit (Mr 54,000) of eIF-2r also precipitated the larger subunit (Mr 54,000) of eIF-2y. 4) Unlike eIF-2r, ternary complex formation by eIF-2y was not inhibited by Mg2+. 5) Both Co-eIF-2A20y and Co-eIF-2r significantly enhanced Met-tRNAf binding to eIF-2y and, again, Mg2+ did not have any effect on this stimulated Met-tRNAf binding to eIF-2y. 6) Both Co-eIF-2A20y and Co-eIF-2r were similarly effective in stimulating Met-tRNAf binding to eIF-2r in the absence of Mg2+. However, in the presence of Mg2+, Co-eIF-2A20y was significantly less effective than Co-eIF-2r as Co-eIF-2A20y did not promote displacement of GDP from eIF-2r X GDP. 7) eIF-2y bound [3H]GDP and this binding was significantly enhanced in the presence of Mg2+. Also, [3H]GDP in the preformed eIF-2y X [3H]GDP complex was rapidly exchanged with exogenously added unlabeled GDP in the presence of Mg2+. Co-eIF-2A20y had no effect on GDP binding to eIF-2y nor on GDP exchange reactions. 8) Reticulocyte heme-regulated protein synthesis inhibitor, which phosphorylated almost completely (in excess of 80%) the alpha-subunit (Mr 38,000) of eIF-2r, also phosphorylated similarly the smaller subunit (Mr 36,000) of eIF-2y. However, such phosphorylation had no significant effect on ternary complex formation, GDP binding, and GDP exchange reactions.     

Effects of preparation and fixation on three quantitative fluorescent cytochemical procedures

A series of experiments was undertaken in which cells dissociated from the abdominal lymph nodes of mice were lightly centrifuged into slides and fixed either wet or after drying in 70% ethanol, 1% glutaraldehyde, 1% formaldehyde, or neutral formalin. Three fluorescent cytochemical methods were evaluated: staining of DNA with mithramycin; fluorochroming of basic groups of proteins with brilliant sulfaflavine (BSF); and staining of sulfhydryl and disulfide groups with N-(7-dimethylamino-4-methylcoumarinyl)maleimide (DACM). In the case of mithramycin, the best results were obtained after fixation in 70% ethanol without drying. Staining of dried preparations fixed in 1% glutaraldehyde also yielded reasonably consistent results, although the fluorescence was lower, and the variability higher, than in the group fixed without drying in 70% ethanol. The use of fixatives containing formaldehyde resulted in fluorescence values of only about one-third those of the other two groups, and the variability of the data was higher. In material stained with BSF, satisfactory results were obtained in preparations fixed without drying in neutral formalin containing mersalyl acid. Other fixatives could be used, but the resulting coefficients of variation were higher than those of formalin-fixed material. Sulfhydryl to disulfide ratios approaching those expected from biochemical evidence were obtained in DACM-stained material only after fixation without drying in neutral formalin containing mersalyl acid. Inverted sulfhydryl-disulfide ratios were observed in material fixed without drying in 70% ethanol; and in dried material fixed in 1% formaldehyde, neutral formalin, or 1% glutaraldehyde.     

Recombinant plasmid conferring proline overproduction and osmotic tolerance

A recombinant plasmid carrying the proBA (pro-74) mutant allele which governs osmotic tolerance and proline overproduction was constructed by using the broad-host-range plasmid vector pQSR49. The physiological, biochemical, and genetic properties of strains carrying the pQSR49 derivatives pMJ101 and pMJ1, mutant and wild type, respectively, were investigated. pMJ101 conferred enhanced osmotolerance compared with strains carrying the wild type, pMJ1. These results are in contrast to those obtained previously with strains carrying recombinant plasmids based on pBR322 that failed to confer the osmotic tolerance phenotype. gamma-Glutamyl kinase (first step in proline biosynthesis) from strains carrying pMJ101 was 200-fold less sensitive to feedback inhibition than was the wild-type enzyme. As expected, the intracellular proline levels of strains carrying pMJ101 were more than an order of magnitude higher than those of the wild type. An analysis of copy number revealed that the pQSR49 constructs were present in the cell at a level six- to eightfold lower than those of the pBR322 recombinants, which may account for the difference in phenotype. We found that the genetic stability of the pQSR49 derivative in a variety of gram-negative bacteria was dependent on the insert orientation and the presence of foreign DNA on the plasmid. These factors may be significant in future studies aimed at expanding the osmotolerance phenotype to a broad range of gram-negative bacteria.     

Evolution of a multigene family of chorion proteins in silkmoths.

The evolution of the A family of chorion genes was examined by comparing new protein and DNA sequences from the silkmoths Antheraea pernyi and Bombyx mori with previously known sequences from Antheraea polyphemus. The comparisons indicated that the A family and its major subfamilies are ancient and revealed how parts of the genes corresponding to distinct regions of the protein structure have evolved, both by base substitutions and by segmental reduplications and deletions.