Some aspects of the regulation of pyruvate kinase levels in Neurospora crassa

Pyruvate kinase levels were monitored in Neurospora crassa mycelium (grown on different carbon sources for varying time intervals) by immunoprecipitation using polyclonal antibodies raised against a purified enzyme preparation. Pyruvate kinase specific mRNA was demonstrated by hybridization of Northern and dot blots of total RNA with a N. crassa pyruvate kinase gene fragment. Two pyruvate kinase specific mRNA species were detected in mycelia of all ages examined. An age-dependent and carbon source dependent variation in the pyruvate kinase protein and mRNA levels was encountered: both registered an increase for up to about 20 h and a subsequent decline; growth on acetate and sucrose resulted in significantly higher yields of both, relative to that on medium containing ethanol and alanine. Stress caused by heat shock depressed the pyruvate kinase mRNA levels.     

Cholesterol binding reserve of hyperlipemic rat serum lipoproteins in chronic ethanol administration

Chronic administration of ethanol in rats caused the reduction of serum cholesterol binding reserve. The very low density and high density lipoproteins, main serum cholesterol binding reserves, were slightly increased with corresponding increases in their lipid and protein components during initial stage of alcohol consumption. However, these capacities get deminished during reversal of hyperlipemia induced by prolonged action of ethanol. This situation may be an early indicator for the initiation of hepatic damage and a variety of secondary effects of ethanol.     

Effects of lanthanum in cellular systems

Lanthanum belongs to the group of elements known as “lanthanons,” which also includes cerium, europium, promethium, and thulium. It is the most electropositive element of the rare earth group, is uniformly trivalent, and is similar in its chemical properties to the alkaline earth elements. The effects of this element and its compounds on cellular systems are of considerable interest because of their increasing use in industry and as a substitute or antagonist for calcium in a variety of cellular reactions. Lanthanum is also being employed extensively in studying anatomical barriers, membrane structure, and subcellular transport systems, particularly the calcium pathway.     

Immobilization of Saccharomyces uvarum cells in porous beads of polyacrylamide gel for ethanolic fermentation

Summary A procedure which does not involve the use of an immiscible organic solvent phase is described for the entrapment of yeast cells in porous beads of polyacrylamide gel. The cells are rapidly dispersed at 4° C in an aqueous solution containing sodium alginate and acrylamide-N,Nmethylene-bis-acrylamide monomer, and the suspension is immediately dropped into a solution of calcium formate to give calcium alginate coated beads. Polyacrylamide gel forms within the bead. The calcium alginate is subsequently leached out of the composite bead with either sodium citrate or potassium phosphate buffer solution. Cells of Saccharomyces uvarum ATCC 26 602 entrapped in such polyacrylamide beads ferment cane molasses in batch mode at higher specific ethanol productivity than a free cell suspension. Their volumetric productivity in continuous fermentation is higher than that of Ca²⁺-alginate immobilized cells.NCL Communication No. 4383     

Chromosomal aberrations induced by cobaltous chloride in mice in vivo

The effects of cobaltous chloride in inducing chromosomal aberrations were observed on laboratory bred mice in vivo after single oral administration of different fractions (1/10, 1/20, 1/40) of the lethal toxic dose of the salt. Bone marrow cells were flushed out and processed for chromosome studies following colchicine, hypotonic, giemsa, air drying procedure. The parameters screened were chromosomal aberrations, with and without gaps and break per cell. Slides were screened after the expiry of 6, 12, 18, and 24 h. Statistical analysis indicated the clastogenic effects of the salt. The degree of chromosome damage was directly related to the concentration, and also to the period after administration. The different stages of the cell cycle were affected.     

Extracellular localization of cyclic GMP in the house cricket male accessory reproductive gland and its fate in mating

The male accessory reproductive gland (ARG) of the house cricket, Acheta domesticus (L.), contains an exceedingly high concentration of cyclic GMP, about 1,000 pmol/mg protein. Immunofluorescent localization and radioimmunoassay measurements show that cyclic GMP is concentrated in a small number of tubules. It accumulates in the tubule lumina where it is protected from degradation by phosphodiesterases. Cyclic GMP is secreted by the ARG and is incorporated into spermatophores. Over 80% of spermatophore cyclic GMP is found in the handle-capillary tube, a thin conduit through which sperm pass during transfer to the female. The concentration of cyclic GMP in the insemination fluid is about 20 microM but does not appear to be specifically associated with the sperm. Cyclic GMP enters the female spermatheca during insemination but disappears rapidly. Physiological effects of cyclic GMP on sperm were not observed nor was an effect of cyclic GMP observed on egg laying by mated females. Cyclic AMP was localized on sperm flagella in the spermatophore and in the spermatheca. These studies indicate that cyclic nucleotides have important roles in insect reproduction and that the house cricket is a good model for elucidating these functions.     

Endogenous phosphorylation of retinal photoreceptor outer segment proteins by calcium phospholipid-dependent protein kinase

A calcium phospholipid-dependent protein kinase (C-kinase) activity was detected in the soluble fraction of rod outer segments (ROS) of the bovine retina. The enzyme required calcium, phosphatidylserine (PS) and diacylglycerol for maximal activity. In the presence of calcium and PS, C-kinase endogenously phosphorylated proteins with molecular weights of 95,000, 91,000, 31,000, 21,000, 19,000, 18,000, 16,000, 14,000 and 11,000. Addition of diolein in the reaction mixture further enhanced the endogenous phosphorylation of these proteins. Retinal was found to inhibit the phosphorylation of endogenous proteins by C-kinase in a concentration dependent manner. Half-maximal inhibition of enzyme activity was obtained at a retinal concentration of about 12μM. These results suggest that calcium, phospholipids and the C-kinase enzyme may play an important role in the functional regulation of rod photoreceptors and, with retinal, perhaps in the visual process as well.     

Physical properties of chondroitin sulphate/dermatan sulphate proteoglycans from bovine aorta.

Bovine aortic chondroitin sulphate/dermatan sulphate proteoglycans (PG-25, PG-35 and PG-50) were differentially precipitated with ethanol and analysed by a variety of chemical and physical techniques. The glycosaminoglycan chains of PG-25 and PG-35 contained a mixture of glucuronic acid and iduronic acid, whereas the uronic acid component of PG-50 was primarily glucuronic acid. In addition, various amounts of oligosaccharides containing small amounts of mannose, a galactose/hexosamine ratio of 1:1 and an absence of uronic acid were covalently linked to the core protein of all proteoglycans. The weight-average Mr (Mw) values of the proteoglycans determined by light-scattering in 4 M-guanidinium chloride were 1.3 X 10(6) (PG-25), 0.30 X 10(6) (PG-35) and 0.88 X 10(6) (PG-50). The s0 values of the proteoglycans were distributed between 7 and 8 S, and the reduced viscosities, eta sp./c, of all proteoglycans were dependent on the shear rate and polymer concentration. Electron microscopy of spread molecules revealed that PG-25 contained small structural units that appeared to self-associate into large aggregates, whereas PG-35 and PG-50 appeared mainly as monomers consisting of a core with various numbers of side projections. Hyaluronic acid-proteoglycan complexes occurred only with a small proportion of the molecules present in PG-35, and their formation could be inhibited by oligosaccharides. These results suggest the presence in the aorta of subspecies of chondroitin sulphate and dermatan sulphate proteoglycans, which show large variations in their physicochemical and inter- and intra-molecular association properties.