Evaluation of selected features of Staphylococcus cohnii enabling colonization of humans

Based on iron utilization, sensitivity to skin fatty acids, lipolytic and proteolytic activity the potential abilities ofStaphylococcus cohnii strains to colonize humans were evaluated. The investigation included 60 strains that belong to both subspecies,viz. S. cohnii ssp.cohnii andS. cohnii ssp.urealyticus. Strains were isolated from different sources of theIntensive Care Unit and from non-hospital environment. Most of the strains were multiple antibiotic-resistant. Strains of both subspecies revealed a relatively low iron requirement. These strains were capable of utilizing iron bound in oxo acids and from host iron-binding proteins.S. cohnii ssp.urealyticus were more effective in iron uptake thanS. cohnii ssp.cohnii. All investigated strains revealed sensitivity to skin fatty acids, butS. cohnii ssp.urealyticus strains were more resistant. Special features of strains of this subspecies promote colonization of humans.     

Differential binding of lectins IL-2 and CSL to candida albicans and cancer cells

The demonstration that interleukin 2 (IL-2) is a lectin specific for oligomannosides allows to understand a new function for this cytokine: as a bifunctional molecule when bound to its receptor ss, IL-2 associates the latter which the CD3/TCR complex, interacting with oligosaccharides of CD3 through its carbohydrate-recognition domain (Zanetta et al. , 1996, Biochem. J., 318, 49-53). This induces the tyrosine phosphorylation of the IL-2R beta by ++p56(lck) , the first step of the IL-2-dependent signaling. Since this specific association is disrupted in vitro by oligomannosides with five and six mannose residues, we made the hypothesis that pathogenic cells or microorganisms could bind IL-2, consequently disturbing the IL-2- dependent response. This study shows that the pathogenic yeast Candida albicans (in contrast with nonpathogenic yeasts) binds high amounts of IL-2 as did cancer cells. In contrast with cancer cells, yeasts do not bind the Man6GlcNAc2-specific lectin CSL, an endogenous "amplifier of activation signals" (Zanetta et al. , 1995, Biochem. J., 311, 629-636).      

Effect of insulin on ultrastructure and glycogenesis in primary cultures of adult rat hepatocytes

Insulin in the presence of high concentrations of glucose has a beneficial trophic effect on the development of primary cultures of hepatocytes. Compared to the situation observed in hormone-free control cultures, the flattening of the reaggregated hepatocytes is enhanced, and the reconstituted cell trabeculae are enlarged and tend to form a confluent monolayer after 3 days; the survival time is prolonged from 3 to 5 or 6 days. Ultrastructural modifications are also initiated by insulin; numerous glycogen particles appear after 24 h, in between the cisternae of the proliferated smooth endoplasmic reticulum. After 48 h, large amounts of glycogen are stored, and numerous polysomes are present. A small number of cells showed an increased synthesis of lipid droplets in the lumen of the smooth endoplasmic reticulum and form liposomes at the same time. After 72 h, cytolysomes filled with glycogen develop, simulating glycogenosis type II. Simultaneously, microtubules and microfilaments, closely related to numerous polysomes, appear in cytoplasmic extensions constituting undulating membranes. The biochemical data demonstrate that, in the absence of insulin, a high concentration of glucose stimulates glycogenesis and hinders glycogenolysis. This effect of glucose on polysaccharide synthesis is progressively lost. The addition of insulin to the culture induces after 48 and 72 h, a three- to fivefold increase of the glucose incorporation into glycogen, as compared to the controls. The presence of insulin is required to maintain the hepatocyte's capacity to store glycogen. Glycogen synthetase is converted into its active form under the influence of glucose. Insulin increases the rate of activation.     

Estimation of heterozygosity for single-probe multilocus DNA fingerprints

In spite of the increasing application of DNA fingerprinting to natural populations and to the genetic identification of humans, explicit methods for estimation of basic population genetic parameters from DNA fingerprinting data have not been developed. Contributing to this omission is the inability to determine, for multilocus fingerprinting probes, relatively important genetic information, such as the number of loci, the number of alleles, and the distribution of these alleles into specific loci. One of the most useful genetic parameters that could be derived from such data would be the average heterozygosity, which has traditionally been employed to measure the level of genetic variation within populations and to compare genetic variation among different loci. We derive here explicit formulas for both the estimation of average heterozygosity at multiple hypervariable loci and a maximum value for this estimate. These estimates are based upon the DNA restriction-pattern matrices that are typical for fingerprinting studies of humans and natural populations. For several empirical data sets from our laboratory, estimates of average and maximal heterozygosity are shown to be relatively close to each other. Furthermore, variances of these statistics based on simulation studies are relatively small. These observations, as well as consideration of the effect of missing alleles and alternate numbers of loci, suggest that the average heterozygosity can be accurately estimated using phenotypic DNA fingerprint patterns, because this parameter is relatively insensitive to the lack of certain genetic information.      

The metabolic heterogeneity of pathogenic and nonpathogenic coagulase negative staphylococci

The coagulase negative staphylococci are a metabolically heterogenous group of strains. The investigated pathogenic and nonpathogenic strains differed markedly in respiration activity and character of endogenous metabolism.     

Mast cells in the mouse mammary gland--correlation with the development of lactiferous structures

Specimens of mouse mammary glands obtained from animals being in different phases of reproductive cycle were collected. After staining MCN, the total mast cell area (TMC), mean mast cell area (MMC), and lactiferous structure density index (LDI) were examined in sections, using a computer image analysis system. Statistically significant (P < 0.05) results were: 1. An increase in MCN observed in Group I (4-5 and 9-10 days of pregnancy), a decrease in MCN observed in Group II (2nd and 10th day of lactation); 2. Changes of TMC fully corresponding to changes of MCN; 3. Increase in MMC observed in Group I at mid (days 9-10) and at the end (days 18-19) of pregnancy, decrease in MMC observed in Group IIB (10th day of lactation); 4. LDI (%) higher at the end of pregnancy (Group IC) and during lactation (groups IIA, IIB), compared with control (23.5 +/- 4.12, 37.6 +/- 3.24, 71.0 +/- 4.33 vs. 3.8 +/- 0.39). The observed changes in the number and size of MC strictly correspond to physiological phenomena leading to alternation of the mouse mammary gland functional status by development/involution of the lactiferous structures.