Entamoeba histolytica: collagenolytic activity and virulence

Several axenic strains of pathogenic and nonpathogenic Entamoeba histolytica were tested for their capacity to digest native radioactive type I collagen gels and to produce liver abscesses when injected into the liver of newborn hamsters. The results demonstrate that the pathogenic strains of amebas (HM1:IMSS, HM3:IMSS, HM38:IMSS and HK9) have a collagenolytic activity that closely correlates with their in vivo capacity to produce liver lesions. The nonpathogenic isolate (Laredo) did not show collagenolytic activity and failed to produce lesions in the liver of newborn hamsters. The results also demonstrate that type I collagen obtained from rodents and cats is degraded less by amebic collagenase than is bovine collagen, which is similar to human collagen. These findings suggest that species susceptibility to invasive infection may depend, among other factors, on the characteristics of the extracellular components of host tissues.     

Studies on the sugar chains of interferon-gamma from human peripheral-blood lymphocytes

Sugar chains of interferon-gamma (IFN-gamma) from human peripheral-blood lymphocytes (PBL) were liberated by hydrazinolysis. After N-acetylation, the reducing end residues of the sugar chains were tagged with 2-aminopyridine and the pyridylamino (PA-) derivatives were purified by gel filtration and reversed-phase HPLC. Five major PA-sugar chains were obtained. The structure of each PA-sugar chain was estimated by comparing its elution times on anion exchange, reversed-phase, and size-fractionation HPLC with those of PA-sugar chains of IFN-gamma from the human myelomonocyte cell line HBL-38 (Yamamoto, S. et al. (1989) J. Biochem. 105, 547-555) as standards, and also by comparison of their elution times after partial desialylation. The results showed that IFN-gamma (PBL) contained mono- and disialo-biantennary structures with 0 or 1 mol of fucose residue, as found for IFN-gamma (HBL-38), but the N-acetylneuraminyl alpha 2-6 linkage was dominant in IFN-gamma (PBL), unlike IFN-gamma (HBL-38), which contains both N-acetylneuraminyl alpha 2-3 and alpha 2-6 linkages.     

Allosteric regulation of NAD(NADP)-dependent glyceraldehyde-3-phosphate dehydrogenase from Chlorella by α-amino acids,dithiothreitol and ATP

α-Amino acids (glycine, serine, histidine, aspartic acid and cysteine) and dithiothreitol (DTT) have been shown to activate both activities of the NAD(NADP)-dependent glyceraldehyde-3-phosphate dehydrogenase from Chlorella. The activation is allosteric and reaches 200–700%. The Hill coefficient values are close to 2 with all activators. ATP activates NADP-dependent but inhibits NAD-dependent activity, n_app and K values being the same for both enzyme activities. In this case positive cooperativity is also observed (n_app = 2.2). The present findings reveal the possible regulation of GAPD function in Chlorella with each of the coenzymes.     

Additional genes essential for replication of the mini-F plasmid from origin I

Summary We isolated a series of Tn5-insertional mutants from the mini-F plasmid, which has a deletion in the origin II region and replicates exclusively from origin I, and found that the mutants that had Tn5 in either the F4 or the F5 gene were defective in their replication. It is concluded that, in addition to the F3 gene on which we have reported previously, both the F4 and the F5 genes are essential for the replication from origin I.     

Light and electron microscopic observations on the normal structure of the vomeronasal organ of garter snakes

The vomeronasal epithelium of adult garter snakes (Thamnophis sirtalis and T. radix) was studied by light and electron microscopy. The sensory epithelium is extraordinarily thick, consisting of a supporting cell layer, a bipolar cell layer, and an undifferentiated cell layer. The supporting cell layer is situated along the luminal surface and includes supporting cells and the peripheral processes (dendrites) of bipolar neurons. The luminal surfaces of both supporting cells and bipolar neurons are covered with microvilli. Specializations of membrane junctions are always observed between adjacent cells in the subluminal region. Below the supporting cell layer, the epithelium is characterized by a columnar organization. Each column contains a population of bipolar neurons and undifferentiated cells. These cells are isolated from the underlying vascular and pigmented connective tissue by the presence of a thin sheath of satellite cells and a basal lamina. Heterogeneity of cell morphology occurs within each cell column. Generative and undifferentiated cells occupy the basal regions and mature neurons occupy the apical regions. Transitional changes in cell morphology occur within the depth of each cell column. These observations suggest that the vomeronasal cell column is the structural unit of the organ and may represent the dynamic unit for cell replacement as well. A sequential process of cell proliferation, neuronal differentiation, and maturation appears to occur in the epithelium despite the adult state of the animal.