Stabilities of leucine zipper dimers estimated by an empirical free energy method.

The leucine zipper motif is a characteristic amino acid sequence found in dimeric DNA-binding proteins. Computer-generated models for leucine zippers were constructed as alpha-helical coiled dimers with leucine repeated every seventh residue. An empirical Gibbs free energy, delta G, function which incorporates hydrophobic force, electrostatic interactions, and conformational entropy loss as the major intermolecular interactions was used to estimate the delta G of dimer formation in fos, jun, and GCN4 zipper sequences. The calculations showed that complexes known to form stable homo- or heterodimers have favorable (negative) delta G, while other less stable complexes have unfavorable (positive) delta G. Leucines in position d of the coiled coil contribute large hydrophobic stabilization energies while residues in the a position contribute less to dimer stability. Hydrophobic contributions show little sequence specificity, however, and do not contribute significantly to homo/heterodimer preference. Charged residues in the e and g positions, on the other hand, determine homo/heterodimer specificity. In GCN4 homodimers, residues GLU el, Glu b2, Lys g2, and Lys e4 greatly contribute to dimer stability. The preferential stability of fos-jun heterodimer over the jun-jun and fos-fos homodimers is primarily due to the side chains Asp b1, Glu g1, Asp b2, Glu e2, Glu g2, Glu g3, and Lys a5 of the fos helix, and Arg c1, Lys g1, Lys b2, Lys e2, Arg e4, and Glu g4 of the jun helix.     

Purification and properties of D-mannitol-1-phosphate dehydrogenase and D-glucitol-6-phosphate dehydrogenase from Escherichia coli.

D-Mannitol-1-phosphate dehydrogenase (EC 1.1.1.17) and D-glucitol-6-phosphate dehydrogenase (EC 1.1.1.140) were purified to apparent homogeneity in good yields from Escherichia coli. The amino acid compositions, N-terminal amino acid sequences, sensitivities to chemical reagents, and catalytic properties of the two enzymes were determined. Both enzymes showed absolute specificities for their substrates. The subunit molecular weights of mannitol-1-phosphate and glucitol-6-phosphate dehydrogenases were 40,000 and 26,000, respectively; the apparent molecular weights of the native proteins, determined by gel filtration, were 40,000 and 117,000, respectively. It is therefore concluded that whereas mannitol-1-phosphate dehydrogenase is a monomer, glucitol-6-phosphate dehydrogenase is probably a tetramer. These two proteins differed in several fundamental respects.     

Intraepidermal nerves in human digital skin

Summary Intraepidermal nerve fibers of human glabrous digital skin were investigated using a new silver impregnation method. Nerves were observed to enter the epidermis without regional preference, and to extend into the stratum granulosum. They are non-varicose (smooth) or varicose and range from less than 0.2 m to approximately 2 m in diameter, with varicosities up to 3 m in diameter. Some axons branch profusely within the epithelium, giving off fine branches of differing diameters, while others appear to remain unbranched. At least some intraepidermal axons are fine branches of larger axons taking a horizontal course below the epithelial layer. Others are, at least topically, closely associated with Meissner's corpuscles. At 57 nerves per mm² surface area, the density of intraepidermal nerves found in this investigation is much greater than that reported in recent publications, and agrees closely with values given in several older studies.Dedicated to Prof. Dr. A. Hopf on the occasion of his 65th birthday     

Sequence analysis of the URA1 gene encoding orotidine-5'-monophosphate decarboxylase of Schizophyllum commune

The URA1 gene (encoding orotidine-5'-monophosphate decarboxylase) of the basidiomycete fungus Schizophyllum commune was mapped to a 1.4-kb BglI-BamHI fragment of two independent phage lambda clones previously isolated from a Schizophyllum genomic library. The fragment was identified by its ability to complement Schizophyllum ura1 mutants via transformation. The complete nucleotide sequence of the fragment containing the URA1 gene was determined. Sequence analysis revealed that the coding region of the URA1 gene encompasses a polypeptide of 279 amino acids (aa) interrupted by two small introns. The deduced aa sequence corresponds to 30.3 kDa and is substantially similar to the sequences of analogous polypeptides from other organisms. No canonical 5'-TATA sequence nor 3'-AATAAA polyadenylation signal are evident in the flanking regions of the URA1 gene.     

Testicular toxicity of cyanobacterial biomass in Japanese quails

Previous studies demonstrated the toxic effects of cyanobacteria in Japanese quails (Coturnix coturnix japonica) in various experimental set-ups including acute, sub-chronic and reproduction toxicity, co-exposures with toxic metals and the Newcastle vaccination. This study aimed to assess the testicular toxicity of a complex cyanobacterial biomass administered to Japanese quails in the feed for eight weeks (daily dose of 61.62 μg microcystins pro toto including 26.54 μg MC-RR, 7.62 μg MC-YR and 27.39 μg MC-LR). There was no mortality in the controls or the biomass-exposed birds. However, males exposed to cyanobacteria in the feed showed moderate to marked atrophy of the seminiferous tubular epithelium with only sparse numbers of the developmental stages of spermatozoa and Sertoli cells. Biomass-exposed birds had elevated catalase activities but decreased glutathione peroxidase activities and surprisingly lower levels of lipid peroxides in the testes. The other biochemical parameters studied (i.e., glutathione level and glutathione reductase, glutathione-S-transferase and superoxide dismutase activities) showed no differences. The cell defensive system protecting testicular tissue from the damage associated with toxic effects of the complex cyanobacterial biomass seemed to be insufficient and partly depleted after the chronic exposure of male birds to this biomass.     

Rate of growth in length of Bangladeshi infants as a function of attained length.

We examine variation in the rate of growth in length of breast-feeding infants from rural Bangladesh. These data were collected between November 1985 and February 1986 from two rural sites. Eighty-eight infants, ranging from birth to 4 months of age at the start of the study and their mothers were measured monthly for 4 months. Length increased linearly with age over this 4-month period (infants' average bias-adjusted R2 = 0.90). The relationship between infant rate of growth in length and attained length was analyzed by two different methods: Oldham's (1962) method of regressing rate of growth on mean length and Blomqvist's (1977) method of regressing rate of growth on estimated initial length. The methods gave similar results. The rate of growth was negatively associated with mean infant length over the 4-month period (p less than 0.001); that is, shorter infants grew at a faster rate than longer infants. For every centimeter shorter the infant was, the rate of growth was 0.1 cm/mo faster on average; the effect was greater among males than among females. The average rate of growth was greater for males than for females and greater in financially solvent households and varied by site. Infant growth rate was slower among older infants than among younger infants, as expected. However, after adjusting for mean infant length, age was no longer significantly associated with infant growth rate, although mean infant length remained highly significant. Forty-one percent of the variation in infant rate of growth in length was explained by mean infant length, sex, sex by length interaction, household financial solvency, and site.     

Comparison of human axillary odour profiles obtained by gas chromatography/mass spectrometry and skin microbial profiles obtained by denaturing gradient gel electrophoresis using multivariate pattern recognition

Several studies have shown that microbial action is responsible for many compounds responsible for human odour. In this paper, we compare the pattern of microbial profiles and that of chemical profiles of human axillary odour by using multivariate pattern matching techniques. Approximately 200 subjects from Carinthia, Austria, participated in the study. The microbial profiles were represented by denaturing gradient gel electrophoresis (DGGE) analysis and the axillary odour profiles were determined in the sweat samples collected by a stir-bar sampling device and analysed by gas chromatography/mass spectrometry (GC/MS). Both qualitative and quantitative distance metrics were used to construct dissimilarity matrices between samples which were then used to represent the patterns of these two types of profiles. The distance matrices were then compared by using the Mantel test and the Procrustean test. The results show that on the overall dataset there is no strong correlation between microbial and chemical profiles. When the data are split into family groups, correlations vary according to family with a range of estimated p values from 0.00 to 0.90 that the null hypothesis (no correlation) holds. When 32 subjects who followed four basic rules of behaviour were selected, the estimated p-values are 0.00 using qualitative and <0.01 using quantitative distance metrics, suggesting excellent evidence that there is a connection between the microbial and chemical signature.     

Common molecular pathways involved in human CD133+/CD34+ progenitor cell expansion and cancer

Background  

Uncovering the molecular mechanism underlying expansion of hematopoietic stem and progenitor cells is critical to extend current therapeutic applications and to understand how its deregulation relates to leukemia. The characterization of genes commonly relevant to stem/progenitor cell expansion and tumor development should facilitate the identification of novel therapeutic targets in cancer.