HYLAS: program for generating H curves (abstract three-dimensional representations of long DNA sequences)

The computer program HYLAS generates from a standard DNA lettersequence a three-dimensional space curve (H curve) which embodiesthe entire information content of the original nucleotide sequence.The program can display H curves either as two-dimensional (frontand side view) projections or as stereo-pair images. The curvescan be marked at specific nucleotide locations, annotated, rotatedfor observation from any viewing angle, and manipulated forconvenient side-by-side comparisons. Unlike the cumbersome lettersequences, H curves can be drastically condensed in size withoutlosing their ability to reflect the global nucleotide-distributionpattern of the entire DNA sequence. Often, biologically importantloci can be visually identified on the H curves. HYLAS is writtenin FORTRAN with separate mainframe (IBM- VM/CMS) and microcomputer(MS-DOS) versions. It uses the Tektronix-TCS library of graphicsubroutines. Received on October 24, 1988; accepted on July 15, 1989     

A computer algorithm to determine the recognition site of restriction enzymes

A new algorithm is proposed to determine the type-II restrictionendonucleases' recognition site knowing the digested DNA sequenceand fragment lengths in an actual case. The algorithm is implementedfor the Commodore 64 microcomputer. Received on January 6, 1987; accepted on June 19, 1987     

The in vitro cellular immune response to quartz

It is known that macrophages release into medium in vitro biologically active substances which modulate immune response. In recent years, increase attention has been directed towards the role of prostaglandin in macrophage function. Guinea pig splenic lymphocytes and peritoneal macrophage cultures were incubated with quartz (DQ12), Corundum and aspirin as prostaglandin inhibitor. Lymphocyte proliferation measured by 3H-thymidine incorporation, and lymphokine release by Bendixen-Soborg capillary test (MIF) were applied. EA rosetting and phagocytosis were determined for macrophage function assessment. Quartz suppressed the immune response evidenced by reduced 3H-thymidine incorporation and decreased lymphokine production. Aspirin (as a specific prostaglandin synthesis inhibitor) restored the affected by quartz immunological parameters. This observation gives support to the hypothesis that the immunological response to quartz involves macrophage prostaglandin release, presumably as a first step of lipid peroxidation.     

The effect of oxidants on biomembranes and cellular metabolism

During the reductive process in the tissues, the aerobes generate a number of oxidants. Unless these oxidants are reduced, oxidative damage and cell death would occur. Oxidation of plasma membrane lipids leads to autocatalytic chain reactions which eventually alter the permeability of the cell. The role of oxidative damage in the pathophysiology of diabetic complications and ischemic reperfusion injury of myocardium, especially the changes in the channel activity which may lead to arrhythmia have been studied. Hyperglycemia activates aldose reductase which could efficiently reduce glucose to sorbitol in the presence of NADPH. Since NADPH is also aldose required by glutathione reductase for reducing oxidants, its diversion would lead to membrane lipid oxidation and permeability changes which are probably responsible for diabetic complications such as cataractogenesis, retinopathy, neuropathy etc. Antioxidants such as butylated hydroxy toluene (BHT) and also reductase inhibitors prevent or delay some of these complications. By using patch-clamp technique in isolated frog myocytes, we have shown that hydroxy radicals generated by ferrous sulfate and ascorbate as well as lipid peroxides such as t-butyl hydroperoxide facilitate the entry of Na⁺ by oxidizing Na⁺-channels. Increased intracellular Na⁺ leads to an increase in Na⁺/Ca²⁺ exchange. The increased Na⁺ concentration by itself may produce electrical disturbance which would result in arrhythmia. Increased Ca²⁺ may affect proteases and may help in the conversion of xanthine dehydrogenase to xanthine oxidase, consequently increased production of super oxide radicals. Increased membrane lipid peroxidation and other oxygen free-radical associated membrane damage in myocytes has been demonstrated.     

Kinetic Modulation by GABAergic Agents of High- and Low-Affinity Binding of [3H]Methyl β-Carboline-3-Carboxylate

The kinetics of dissociation of [3H]methyl beta-carboline-3-carboxylate (beta-CCM) binding was studied in a synaptosomal membrane preparation of rat cerebral cortex. Dissociation was biphasic: a faster phase (10-30% contribution) was followed by a slower phase. Picrotoxin pretreatment at 22 degrees C enhanced the equilibrium binding of [3H]beta-CCM. The half-life of the slower phase of beta-CCM dissociation (t1/2II) was increased by 60 muM picrotoxin from 1.7 min to 3.3 min. The dissociation of [3H]beta-CCM was identical when initiated by an excess of either diazepam or beta-CCM. Quasi-equilibrium Scatchard analysis of [3H]beta-CCM binding was performed by a kinetic separation of the rapid and slow phases of dissociation. The slow and rapid phases represented beta-CCM binding sites of high and low affinity, respectively. The dissociation of [3H]beta-CCM (control t1/2II = 2.0 min) was decelerated by the gamma-aminobutyric acid (GABA) antagonist 3-alpha-hydroxy-16-imino-5 beta-17-aza-androstan-11-one (R 5135) (t1/2II = 2.5 min) and accelerated by GABA (t1/2II = 1.6 min). GABA inhibited both high- and low-affinity beta-CCM bindings.     

Effects of drought on host and endophyte development in mycorrhizal soybeans in relation to water use and phosphate uptake

Bethlenfalvay, G. J., Brown, M. S., Ames, R. N. and Thomas, R. S. 1988. Effects of drought on host and endophyte development in mycorrhizal soybeans in relation to water use and phosphate uptake. - Physiol. Plant. 72: 565–571.
Soybean [ Glycine max (L.) Merr.] plants were grown in pot cultures and inoculated with the vesicular-arbuscular mycorrhizal (VAM) fungus Glomus mosseae (Nicol. & Gerd.) Gerd. and Trappe or provided with P fertilizer (non-VAM plants). After an initial growth period (21 days), plants were exposed to cycles of severe, moderate or no drought stress over a subsequent 28-day period by rewatering at soil water potentials of -1.0, -0.3 or -0.05 MPa. Dry weights of VAM plants were greater at severe stress and smaller at no stress than those of non-VAM plants. Phosphorus fertilization was applied to produce VAM and non-VAM plants of the same size at moderate stress. Root and leaf P concentrations were higher in non-VAM plants at all stress levels. All plants were stressed to permanent wilting prior to harvest. VAM plants had lower soil moisture content at harvest than non-VAM plants. Colonization of roots by G. mosseae did not vary with stress, but the biomass and length of the extraradical mycelium was greater in severely stressed than in non-stressed plants. Growth enhancement of VAM plants relative to P-fertilized non-VAM plants under severe stress was attributed to increased uptake of water as well as to more efficient P uptake. The ability of VAM plants to deplete soil water to a greater extent than non-VAM plants suggests lower permanent wilting potentials for the former.     

Nutrient transfer between the root zones of soybean and maize plants connected by a common mycorrhizal mycelium

The objective of the study was to determine whether nutrient fluxes mediated by hyphae of vesicular-arbuscular mycorrhizal (VAM) fungi between the root zones of grass and legume plants differ with the legume's mode of N nutrition. The plants, nodulating or nonnodulating isolines of soybean [ Glycine max (L.) Merr.], were grown in association with a dwarf maize ( Zea mays L.) cultivar in containers which interposed a 6-cm-wide root-free soil bridge between legume and grass container compartments. The bridge was delimited by screens (44 μm) which permitted the passage of hyphae, but not of roots and minimized non VAM interactions between the plants. All plants were colonized by the VAM fungus Glomus mosseae (Nicol. & Gerd.) Gerd. and Trappe. The effects of N input to N-sufficient soybean plants through N₂-fixation or N-fertilization on associated maize-plant growth and nutrition were compared to those of an N-deficient (nonnodulating, unfertilized) soybean control. Maize, when associated with the N-fertilized soybean, increased 19% in biomass, 67% in N content and 77% in leaf N concentration relative to the maize plants of the N-deficient association. When maize was grown with nodulated soybean, maize N content increased by 22%, biomass did not change, but P content declined by 16%. Spore production by the VAM fungus was greatest in the soils of both plants of the N-fertilized treatment. The patterns of N and P distribution, as well as those of the other essential elements, indicated that association with the N-fertilized soybean plants was more advantageous to maize than was association with the N₂-fixing ones.     

Effects of selective cholecystokinin antagonists L364,718 and L365,260 on food intake in rats

The selective type A and B cholecystokinin (CCK) receptor antagonists L364,718 and L365,260 were used to identify the receptor subtype that mediates the satiety effect of endogenous CCK. Male rats (n = 12–13/group), fed ground rat chow ad lib, received L364,718 (0, 1, 10, 100, or 1000 μg/kg IP) or L365,260 (0, 0.1, 1, 10, 100, 1000, or 10,000 μg/kg IP) 2 h after lights off, and food intake was measured 1.5, 3.5, and 5.5 h later. L364,718 significantly stimulated 1.5-h food intake by more than 40% at 10 μg/kg and higher doses; cumulative intake at 3.5 and 5.5 h remained elevated by about 20% at 1000 and 100 μg/kg of L364,718, respectively. In contrast, L365,260 had no significant stimulatory effect on feeding at any dose. The potency of L365,260 for antagonizing gastrin-stimulated gastric acid secretion was examined in unanesthetized rats. Male rats (n = 14), prepared with gastric and jugular vein cannulas, received doubling doses of gastrin (G-17I) (0.16–5 nmol/kg/h IV), each dose for 30 min, and gastric juice was collected for each 30-min period. G-17I stimulated gastric acid output dose dependently; the minimal effective dose was 0.16 nmol/kg/h, while maximal output (5-fold above basal) occurred at 5 nmol/kg/h. L365,260 (0, 1, 10, 100, 1000, or 10,000 μg/kg IV), administered 30 min before continuous infusion of G-17I (1.25 or 5 nmol/kg/h), significantly inhibited acid output only at 10,000 μg/kg; cumulative 60-min output was decreased by 60%. These results suggest that CCK acts at CCK-A receptors to produce satiety during the dark period in ad lib-feeding rats.