Vanadate-stimulated oxidation of NAD(P)H

Vanadate stimulates the oxidation of NAD(P)H by biological membranes because such membranes contain NAD(P)H oxidases which are capable of reducing dioxygen to O₂⁻ and because vanadate catalyzes the oxidation of NAD(P)H by O₂⁻, by a free radical chain mechanism. Dihydropyridines, such as reduced nicotinamide mononucleotide (NMNH), which are not substrates for membrane-associated NAD(P)H oxidases, are not oxidized by membranes plus vanadate unless NAD(P)H is present to serve as a source of O₂⁻. When [NMNH] greatly exceeds [NAD(P)H], in such reaction mixtures, one can observe the oxidation of many molecules of NMNH per NAD(P)H consumed. This reflects the chain length of the free radical chain mechanism. We have discussed the mechanism and significance of this process and have tried to clarify the pertinent but confusing literature.     

Behavioral adaptations for raiding in the slave-making ant,Polyergus breviceps

We studied recruitment behavior of the slavemaking ant Polyergus breviceps,which typically raids colonies of Formica gnava.The first test series demonstrated the importance of social context, by showing that recruitment was high during raiding, but virtually absent during preraid circling and during the return trip after a slave raid. The second test series showed that Formicapupae (alone or together with adults) must be present for workers of Polyegrusto recruit nestmates. The third test series demonstrated that panic alarm by raided Formicais caused by a pheromone, and we suggest that adults of Formicamay be the source of this secretion. Finally, the fourth test series showed that formic acid is lethal to adults of Formicabut has almost no adverse effect on Polyergus.This relative immunity by Polyergusmay enable them to remain organized while entering nests of Formicaduring slave raids.     

Extensive changes in cytokeratin expression patterns in pathologically affected human gingiva

The stratified squamous epithelium of the oral gingiva and the hard palate is characterized by a tissue architecture and a cytoskeletal composition similar to, although not identical with, that of the epidermis and fundamentally different from that of the adjacent non-masticatory oral mucosa. Using immunocytochemistry with antibodies specific for individual cytokeratins, in situ hybridization and Northern blots of RNA with riboprobes specific for individual cytokeratin mRNAs, and gel electrophoresis of cytoskeletal proteins of microdissected biopsy tissue samples, we show changes in the pattern of expression of cytokeratins and their corresponding mRNAs in pathologically altered oral gingiva. Besides a frequently, although not consistently, observed increase in the number of cells producing cytokeratins 4 and 13 (which are normally found as abundant components in the sulcular epithelium and the alveolar mucosa but not in the oral gingiva) and a reduction in the number of cells producing cytokeratins 1, 10 and 11, the most extensive change was noted for cytokeratin 19, a frequent cytokeratin in diverse one-layered and complex epithelia. While in normal oral gingiva cytokeratin 19 is restricted to certain, sparsely scattered cells of --or near--the basal cell layer, probably neuroendocrine (Merkel) cells, in altered tissue of inflamed samples it can appear in larger regions of the basal cell layer(s) and, in apparently more advanced stages, also in a variable number of suprabasal cells. Specifically, our in situ hybridization experiments show that this altered suprabasal cytokeratin 19 expression is more extended at the mRNA than at the protein level, indicating that cytokeratin 19 mRNA synthesis may be a relatively early event during the alteration. These changes in cytokeratin expression under an external pathological influence are discussed in relation to other factors known to contribute to the expression of certain cytokeratins and with respect to changes occurring during dysplasia and malignant transformation of oral epithelia.     

Dual Effects of K+ Depoiarisation on Inositol Polyphosphate Production in Rat Cerebral Cortex

Depolarisation of [3H]inositol-prelabelled slices of rat cerebral cortex with elevated extracellular K+ induced a rapid and marked increase in inositol polyphosphate accumulation. Addition of the muscarinic antagonist atropine (10 microM) markedly inhibited the K+-induced accumulation of inositol tetrakisphosphate (InsP4), with only a slight reduction in stimulated inositol bis- and trisphosphate levels. Inhibitory effects on InsP4 were noted at the earliest time period measured (30 s) and suggested the involvement of released endogenous acetylcholine in part of the response. The atropine-insensitive component of depolarisation did not appear to be secondary to release of noradrenaline, histamine, or 5-hydroxytryptamine, because addition of prazosin, mepyramine, or ketanserin was without effect on the K+ response. Furthermore, secretion of a neuropeptide that could stimulate phosphoinositide hydrolysis was unlikely, because the peptidase inhibitor bacitracin was also without effect. The results suggest that endogenous acetylcholine can stimulate phosphoinositide metabolism by interacting with muscarinic receptors and that this is particularly evident on InsP4 accumulation. Atropine-insensitive responses may be secondary to Ca2+ entry via voltage-sensitive channels.     

Conversion of fat into yeast biomass in protein-containing waste-water

Summary Candida tropicalis S001 was grown on the lipid fraction of a protein-containing waste-water in order to (i) remove fat from the water, and (ii) produre yeast biomass for feed. The yeast cells were separated from the waste-water by sedimentation. Defatted waste-water was used for methane production and gave a yield of a 0.3 m³ methane/kg reduced chemical oxygen demand. The maximum specific growth rate (µ_max) of C. tropicalis growing on waste-water fat at pH 4.0 was 0.35 h^–1; the fat content was decreased from 8 g/l to about 0.1 g/l within 24 h. In continous culture a corresponding reduction was maintained at dilution rates up to 0.36 h^–1. The effect on growth of pH, temperature and CO₂ concentration was studied with triolein as the major carbon source. The µ_max was nearly constant (0.16 h^–1) in the pH and temperature range of 3.2–4.0 and 30°–38° C, respectively; 10% CO₂ was optimal for growth. Growth on triolein resulted in a biomass yield of 0.70 g dry weight/g fat. Offprint requests to: S. Rydin     

Interaction of nuclear factors with upstream sequences of a lipid body membrane protein gene from carrot.

To study the regulation of gene expression during embryo development, we isolated a gene, DC 59, expressed in embryos but not in mature carrot plants. Sequence and S1 analysis showed that the gene was composed of one exon encoding a polypeptide of 19 kilodaltons and was highly homologous to the lipid body membrane protein gene L3 from maize. The plant hormone abscisic acid regulated the accumulation of DC 59 mRNA. To understand the mechanism of embryo-specific and hormonal regulation of DC 59, 5' DNA fragments were incubated with nuclear proteins. Two adjacent regions (from -706 to -235) interacted with nuclear extracts from embryos, resulting in the formation of four complexes (C1, C2, C3, and C4). Factors involved in the formation of the C3 and C4 complexes could be competed with sequences upstream of DC 8, a gene that is coordinately expressed with DC 59 during embryo development. DNase I footprinting analysis revealed that nuclear extracts from embryos bound to four AT-rich sequences, and the protected motifs within fragment V were located in the highly homologous upstream regions of DC 59 and DC 8 genes.     

Formalin fixation strongly influences biomechanical properties of the spine

As fresh human cadaveric spine specimens for in vitro testing are hard to obtain and carry a potential risk of infection, the possibility of using embalmed spine specimens has been considered. The cross-linking effect of formalin fixation, however, raises uncertainties regarding the biomechanical likeness of preserved specimens. They have been reported to be stiffer, but no quantitative data exist.

The purpose of this study was to determine the biomechanical differences between fresh and formalin-fixed spine specimens, using L1–2 motion segments from six 16-week-old calf spines. The range of motion and neutral zone were determined in flexion-/extension, left/right axial rotation, and right/left lateral bending.

The range of motion decreased in the formalin fixed specimens by as much as 80%, and the neutral zone by as much as 96%. The results of this study therefore imply that, for biomechanical testing, formalin-fixed specimens are not representative of the in vivo conditions.     

Evolution of structure and substrate specificity ind-alanine:d-Alanine ligases and related enzymes

Thed-alanine:d-alanine-ligase-related enzymes can have three preferential substrate specificities. Usually, these enzymes synthesized-alanyl-d-alanine. In vancomycin-resistant Gram-positive bacteria, structurally related enzymes synthesized-alanyl-d-lactate or Dalanyl-d-serine. The sequence of internal fragments of eight structurald-alanine:d-alanine ligase genes from enterococci has been determined. Alignment of the deduced amino acid sequences with those of other related enzymes from Gram-negative and Gram-positive bacteria revealed the presence of four distinct sequence patterns in the putative substrate-binding sites, each correlating with specificity to a particular substrate (d-alanine:d-lactate ligases exhibited two patterns). Phylogenetic analysis showed different clusters. The enterococcal subtree was largely superimposable on that derived from 16S rRNA sequences. In lactic acid bacteria, structural divergence due to differences in substrate specificity was observed. Glycopeptide resistance proteins VanA and VanB, the VanC-type ligases, and Dd1A and DdlB from enteric bacteria andHaemophilus influenzae constituted separate clusters. Correspondence to: P. Courvalin