Biosynthesis and preparation of fiveAlternaria metabolites

Metabolites ofAlternaria alternata were produced on rice as a solid substrate, chosen out of 6 substrates as the most useful. Optimal methods of extraction, purification, and separation of 5 metabolites were elaborated, using liquid — liquid partition, column chromatography, and preparative TLC. Alternariol, alternariol methyl ether, and copper salt of tenuazonic acid were obtained as crystals, altertoxin and altenuene as a film.     

The effect of fish predation on Cyclops life cycle

Two populations of Cyclops abyssorum tatricus studied in neighbouring alpine lakes in Tatra Mountains (southern Poland) differed in their life cycles. In the lake with planktivorous fishes, Cyclops was typically monocyclic, with highly synchronized reproduction during two winter months, while in the fishless lake its reproduction was asynchronous and continued for six months. Direct and indirect effects of fish predation on Cyclops life cycles are discussed.     

gltBDF operon of Escherichia coli.

A 2.0-kilobase DNA fragment carrying antibiotic resistance markers was inserted into the gltB gene of Escherichia coli previously cloned in a multicopy plasmid. Replacement of the chromosomal gltB+ gene by the gltB225::omega mutation led to cells unable to synthesize glutamate synthase, utilize growth rate-limiting nitrogen sources, or derepress their glutamine synthetase. The existence of a gltBDF operon encoding the large (gltB) and small (gltD) subunits of glutamate synthase and a regulatory peptide (gltF) at 69 min of the E. coli linkage map was deduced from complementation analysis. A plasmid carrying the entire gltB+D+F+ operon complemented cells for all three of the mutant phenotypes associated with the polar gltB225::omega mutation in the chromosome. By contrast, plasmids carrying gltB+ only complemented cells for glutamate synthase activity. A major tricistronic mRNA molecule was detected from Northern (RNA blot) DNA-RNA hybridization experiments with DNA probes containing single genes of the operon. A 30,200-dalton polypeptide was identified as the gltF product, the lack of which was responsible for the inability of cells to use nitrogen-limiting sources associated with gltB225::omega.     

Phospholipid species containing long and very long polyenoic fatty acids remain with rhodopsin after hexane extraction of photoreceptor membranes

About one-fourth the phosphatidylcholines (PCs) from bovine disk photoreceptor membranes contain very long chain (24-36 carbons) polyunsaturated (4, 5, and 6 double bonds) fatty acids of the n-3 and n-6 series (VLCPUFA). Such fatty acids, exclusively occurring in dipolyunsaturated species, are esterified to the sn-1 position of their glycerol backbone, docosahexaenoate being the major fatty acid at sn-2. Chromatographically, such PCs display a weakly polar character relative to other species, ascribable to their exceedingly large number of carbons. After hexane extraction of lyophilized disks, PC is the major component of the fraction of lipids that remains associated with rhodopsin, followed by phosphatidylserine, while a large proportion of the phosphatidylethanolamine is removed. The fatty acid composition of the hexane-removable and protein-bound lipid fractions markedly differs, the latter being enriched in lipid species containing long-chain and very long chain polyenes. This is observed for all lipid classes except free fatty acids. VLCPUFA-containing PCs are the most highly concentrated species in the rhodopsin-associated lipid fraction. The very long chain polyenes these PCs have at sn-1 may account for their resistance to being separated from the protein. It is hypothesized that their unusually long polyenoic fatty acids could be well suited to partially surround alpha-helical segments of rhodopsin.     

Sulfated glycosaminoglycans synthesized by human smooth muscle cells isolated from different organs

The sulfated glycosaminoglycans synthesized by human smooth muscle cells isolated from different organs were identified on the basis of electrophoretic mobility, enzymatic degradation with specific mucopolysaccharidases and by the type of degradation products formed. The results obtained indicated that chondroitin sulfate and heparan sulfate were the main glycosaminoglycans found, that most of the labeled glycosaminoglycans were found in the pericellular pool, and that no marked differences were observed in the sulfated glycosaminoglycan composition of the smooth muscle cells obtained from different organs. 'Liver connective tissue cells', isolated from pathological livers (which had been shown to possess biochemical and physiological features typical of smooth muscle cells) showed a pattern of glycosaminoglycan synthesis similar to that of the smooth muscle cells.     

Long-term hyperalgesia in rats induced by neonatal administration of vasopressin antiserum

Vasopressin antiserum was given to two day old rats and the nociceptive thresholds were evaluated three months later. The rats were hypersensitive to pain when electrical current, but not heat, was used as the noxious stimulus. These animals were also insensitive to cold-water swim, a non-opioid form of stress analgesia. The vasopressin content in the pituitary or in the hypothalamus was not however modified by the neonatal treatment. The present results suggest a physiological role for vasopressin in non-opioid pain inhibitory systems.     

Molecular cloning and characterization of the trpC gene from Penicillium chrysogenum

Summary We cloned the Penicillium chrysogenum trpC gene from a genomic library by complementation of an Escherichia coli trpC mutant lacking phosphoribosylanthranilate isomerase activity. The gene ecodes a 2.7 kb poly(A)⁺ RNA. We localized the gene by sequence analysis in a 2.9 kb DNA insert found in the smallest plasmid selected from the library. Sequence data strongly suggest that the organization of the gene is similar to that described in other Ascomycetes. We found that a DNA fragment which codes only for the carboxy-terminal protion of the polypeptide is sufficient for complementation of the E. coli trpC9830 mutation.     

Isolation of cDNA clones and complete amino acid sequence of human erythrocyte glycophorin C

Two cDNA clones for glycophorin C, a transmembrane glycoprotein of the human erythrocyte which carries the blood group Gerbich antigens, have been isolated from a human reticulocyte cDNA library. The clones were identified with a mixture of 32 oligonucleotide probes (14-mer) which have been synthetized according to the amino acid sequence Asp-Pro-Gly-Met-Ala present in the N-terminal tryptic peptide of the molecule. The primary structure of glycophorin C deduced from the nucleotide sequence of the 460 base-pair insert of the pGCW5 clone indicates that the complete protein is a single polypeptide chain of 128 amino acids clearly organized in three distinct domains. The N-terminal part (residues 1-57, approximately) which is N- and O-glycosylated is connected to a hydrophilic C-terminal domain (residues 82-128, approximately) containing 4 tyrosine residues by a hydrophobic stretch of nonpolar amino acids (residues 58-81, approximately) probably interacting with the membrane lipids and permitting the whole molecule to span the lipid bilayer. Northern blot analysis using a 265-base-pair restriction fragment obtained by DdeI digestion of the inserted DNA shows that the glycophorin C mRNA from human erythroblasts is approximately 1.4 kilobases long and is present in the human fetal liver and the human K562 and HEL cell lines which exhibit erythroid features. The glycophorin C mRNA, however, is absent from adult liver and lymphocytes, indicating that this protein represents a new erythrocyte-specific probe which might be useful to study erythroid differentiation.     

Differential regulation of the brain and gut immunoreactive dynorphin by the serotonin system

Administration of drugs such as fenfluramine, 20-40 mg/kg, and m-chlorophenylpiperazine (m-CPP), 2.5-5 mg/kg, which release serotonin or activate postsynaptic serotonin receptors, respectively, induced a dramatic decrease in the duodenal content of immunoreactive dynorphin (ir-DYN). The effect was antagonized by cyproheptadine, 1 mg/kg. Similarly, acute administration of the specific serotonin reuptake blockers fluvoxamine, 15 mg/kg, or femoxetine, 10 mg/kg, and 5-hydroxytryptophan (5-HTP), 40-160 mg/kg, evoked a marked decrease in the duodenal content of ir-DYN. A combined administration of fluvoxamine or femoxetine and 5-HTP failed to potentiate the effect of individual treatment. Only a higher dose of fenfluramine, 40 mg/kg, increased the ir-DYN content in the hypothalamus. These results suggest that the brain and gut ir-DYN is independently regulated by the serotonin system and that a serotonin mechanism might stimulate release of the gut dynorphin content.