Differing Neurochemical and Morphological Sequelae of Global Ischemia: Comparison of Single- and Multiple-Insult Paradigms

The purpose of this investigation was to investigate pathomechanisms responsible for the deleterious effects of repeated episodes of brief forebrain ischemia. Halothane-anesthetized male Wistar rats were subjected to either (a) a single 15-min period or (b) three 5-min periods (separated by 1 h) of global forebrain ischemia by bilateral carotid artery occlusions plus hypotension (50 mm Hg), followed by various periods of recirculation. Brain temperature was normothermic throughout. In one series of rats, extracellular levels of glutamate, glycine, and gamma-aminobutyric acid (GABA) were measured in the dorsolateral striatum (n = 6-8 per group) and lateral thalamus (n = 4-6 per group) by microdialysis and HPLC before and during ischemia and during 3-5 h of recirculation. In a parallel series of rats (n = 6 per group), ischemic cell change was quantified at 2 (dark neurons), 24, or 72 h following either single or multiple ischemic insults. A single 15-min ischemic period led to massive glutamate release (13-fold increase; p = 0.001), which returned to normal by 20-30 min of recirculation and remained normal thereafter. By contrast, in rats with three 5-min periods of ischemia, the glutamate level rise with each repeated insult (four- to 4.5-fold; p < or = 0.02) was smaller than that observed during the single 15-min insult, but a late sustained rise (five- to six-fold; p < 0.05) occurred at 2-3 h of recirculation. Brief ischemia-induced elevations of glycine and GABA levels were detected in both the single- and multiple-insult groups, with normalization during recirculation. In contrast, the excitotoxic index, a composite measure of neurotransmitter release ([glutamate] x [glycine]/[GABA]), differed markedly following single versus multiple insults (p = 0.002 by repeated-measures analysis of variance) and increased by seven- to 12-fold (p < 0.05) at 1-3 h following the third insult. The total amount of glutamate released was 3.3-fold higher in the multiple-insult than in the single-insult group (p < 0.02). At 2 h of recirculation, histopathological analysis of dorsolateral striatum showed a significantly greater frequency of dark neurons in the multiple- than in the single-insult group (p < 0.05 by analysis of variance). In the thalamus, a higher frequency of ischemic neurons was seen in the multiple-than in the single-insult group at all intervals studied. Thus, in rats with multiple ischemic insults, accelerated ischemic damage was found in the striatum, and severe ischemic injury was documented in the thalamus.(ABSTRACT TRUNCATED AT 400 WORDS)     

Chemotaxis and nod Gene Activity of Bradyrhizobium japonicum in Response to Hydroxycinnamic Acids and Isoflavonoids

For Bradyrhizobium japonicum, the chemotactic and the nod gene-inducing effects of hydroxycinnamic acids and two of their derivatives were compared with those of isoflavonoids. Only the hydroxycinnamic acids were strong chemoattractants, while the other substances tested were chemotactically inactive. Besides the known nod gene induction by isoflavonoids, a weak nod gene induction by coniferyl alcohol, chlorogenic acid, and ferulic acid was found.     

Ultrastructural evidence for a triple structure of the lateral element of the synaptonemal complex.

This study describes composition and localization of several substructures of the synaptonemal complex (SC) using different techniques. The techniques which were used were surface spreading, critical point drying of isolated SCs, and sectioning of Lowicryl embedded testis material. The lateral elements (LEs) of the SC appear to be composed of three lateral substructures: two morphologically identical major strands and a third strand which is considerably thinner. The thinner strand is localized on the inner side of the two major strands of the lateral element. In late pachytene/early diplotene stages when the SC starts to disintegrate more than three strands can be observed in the LEs. A model is presented and the function of the different substructures is speculated upon.     

Purification and substrate specificity of heparitinase I and heparitinase II from Flavobacterium heparinum. Analyses of the heparin and heparan sulfate degradation products by 13C NMR spectroscopy

The purification of two heparitinases and a heparinase, in high yields from Flavobacterium heparinum was achieved by a combination of molecular sieving and cation-exchange chromatography. Heparinase acts upon N-sulfated glucosaminido-L-iduronic acid linkages of heparin. Substitution of N-sulfate by N-acetyl groups renders the heparin molecule resistant to degradation by the enzyme. Heparitinase I acts on N-acetylated or N-sulfated glucosaminido-glucuronic acid linkages of the heparan sulfate. Sulfate groups at the 6-position of the glucosamine moiety of the heparan sulfate chains seem to be impeditive for heparitinase I action. Heparitinase II acts upon heparan sulfate producing disulfated, N-sulfated and N-acetylated-6-sulfated disaccharides, and small amounts of N-acetylated disaccharide. These and other results suggest that heparitinase II acts preferentially upon N,6-sulfated glucosaminido-glucuronic acid linkages. The total degradation of heparan sulfate is only achieved by the combined action of both heparitinases. The 13C NMR spectra of the disaccharides formed from heparan sulfate and a heparin oligosaccharide formed by the action of the heparitinases are in accordance to the proposed mode of action of the enzymes. Comparative studies of the enzymes with the commercially available heparinase and heparitinase are described.     

Enhancement of specific nitrogenase activity inAzospirillum brasilense andKlebsiella pneumoniae,inhibition inRhizobium japonicum under air by phenol

Specific nitrogenase activity inAzospirillum brasilense ATCC 29145 in surface cultures under air is enhanced from about 50 nmol C₂H₄·mg protein^-1·h^-1 to 400 nmol C₂H₄ by the addition of 1 mM phenol. 0.5 and 2 mM phenol added increase the rate 5-fold and 4-fold. This enhancement effect is observed only between 2 and 3 days after inoculation, with only a small reduction of the growth of the cells by the phenol added. In surface cultures under 1% O₂, nitrogenase activity is slightly reduced by the addition of 1–0.01 mM phenol. Utilization of succinate is enhanced during the period of maximum enhancement of nitrogenase activity by 60% by addition of 1 mM phenol. The cells did not produce¹⁴CO₂ from [U-¹⁴C] phenol, neither in surface cultures nor in liquid cultures and less than 0.1% of the phenol was incorporated into the cells. A smaller but significant enhancement of nitrogenase activity by about 100% in surface cultures under air was found withKlebsiella pneumoniae K 11 after addition of 1 mM phenol. However, inRhizobium japonicum 61-A-101 all phenol concentrations above 0.01 mM reduced nitrogenase activity. With 1 mM phenol added activity was reduced to less than 10% with no effect on the growth in the same cultivation system. With thisRhizobium japonicum strain significant quantities of phenol (25 mol in 24 h by 2·10¹² cells) were metabolized to¹⁴CO₂, with phenol as sole carbon source. WithAzospirillum brasilense in liquid culture under 1% and 2% O₂ in the gas phase, no enhancement of nitrogenase activity by phenol was noticed.     

Primary structure of the southern bean mosaic virus coat protein: First results

Studies on the southern bean mosaic virus coat protein have established the molecular weight of this protein, its amino acid composition, the nature of its C-terminal amino acid, and the blockage of the N-terminal residue by an acetyl group. After hydrolysis of the protein by trypsin, the hydrolysate was fractionated by ion-exchange chromatography. Among the purified tryptic peptides were isolated the N- and the C-terminal peptides where sequences were determined, principally by mass spectrometry.     

Effect of human leukocyte interferon on human lymphocytes in vitro: cytogenetic studies

Mitogen-stimulated lymphocytes from 8 healthy donors were exposed to interferon, and cytogenetic studies were preformed. The response of lymphocytes to the mitogens phytohemagglutinin (PHA), concanavalin A (con A) and pokeweed mitogen (PWM) was inhibited by interferon, whereas an increased number of structural chromosomal aberrations was not detected. Further investigations of the cytogenetic effects of interferon are needed.     

Limnology and performance of waste treatment lagoons

By arranging sewage ponds in series, some feedback relationships within the food web are disconnected, but stability may increase. This particularly applies to a persistent clearwater-state in the last cell caused by mass growths of Daphnia or other zooplankton in the absence of fish. Microbial pollution in this case is reduced to a level which may permit nearly unrestricted irrigation. The oxygen balance of lagoons is, apart from the diurnal cycle, subject to substantial temporal variations. This also applies to continuous-flow laboratory models with a constant (BOD-load, temperature) or a constant-cycle (light) chemical and physical environment. An example is given illustrating a high adjustment stability of a lagoon in consequence of a catastrophic perturbation.The strong tendency of lagoons towards an oligomictic behaviour is promoted by thermal stratification and by a vertical gradient in the metabolic activity (oxidation/reduction potential). The hydrodynamic conditions oscillate between plug flow in periods of convective overturn and short-circuiting if thermal stratification has developed. Nevertheless, the average performance (BOD removal) for a particular season could be calculated with a reasonable accuracy. As a basis for this calculation, nomographs were developed from which the rate coefficient K₁ of BOD removal for a given combination of residence time and BOD load can be read.     

Chinning by maleTupaia belangeri: The effects of scent marks of conspecifics and of other species

Journal of Comparative Physiology A -