Mitochondrial DNA as a genetic marker for brown trout, Salmo trutta L., populations

Mitochondrial DNA was examined in natural and hatchery-reared stocks of brown trout, using different methods of restriction analysis. The methods included the development of a brown trout mt DNA hybridization probe through cloning part of the brown trout mitochondrial genome. In addition, fragments were analysed by ethidium bromide staining and end-labelling. The relative merits of each of these methods in assessing levels of genetic relatedness between the natural and hatchery-reared brown trout stocks were evaluated. In addition, the study revealed a diagnostic mtDNA restriction pattern which could be used as a genetic marker for the discrimination of these two groups of brown trout.     

Life cycle assessment standards

The newly emerging LCA standards provide an opportunity to review and improve upon the current LCA methodology. As more industrial practitioners enter the arena, the opportunity arises to not only demand environmental improvement from industrial service and product providers but also to fill LCA data gaps. A framework is suggested for improvement in the current LCA framework that focuses on the business relationships of the industrial practitioner. The framework seeks to promote environmental improvement from industrial sectors through the identification of state-of-the-art technologies used throughout a life cycle. Basing LCAs on the best performers in an industry will create a market for a high level of environmental performance, disperse the responsibility of inventory data gathering, and improve upon the advancements already anticipated through the widespread application of LCA.     

Self-Incorporation of coenzymes by ribozymes

RNA molecules that are assembled from the four standard nucleotides contain a limited number of chemical functional groups, a characteristic that is generally thought to restrict the potential for catalysis by ribozymes. Although polypeptides carry a wider range of functional groups, many contemporary protein-based enzymes employ coenzymes to augment their capabilities. The coenzymes possess additional chemical moieties that can participate directly in catalysis and thereby enhance catalytic function. In this work, we demonstrate a mechanism by which ribozymes can supplement their limited repertoire of functional groups through RNA-catalyzed incorporation of various coenzymes and coenzyme analogues. The group I ribozyme of Tetrahymena thermophila normally mediates a phosphoester transfer reaction that results in the covalent attachment of guanosine to the ribozyme. Here, a shortened version of the ribozyme is shown to catalyze the self-incorporation of coenzymes and coenzyme analogues, such as NAD⁺ and dephosphorylated CoA-SH. Similar ribozyme activities may have played an important role in the RNA world, when RNA enzymes are thought to have maintained a complex metabolism in the absence of proteins and would have benefited from the inclusion of additional functional groups.Correspondence to: G.F. Joyce     

Is hyperglycaemia an independent predictor of poor outcome after acute stroke? Results of a long-term follow up study.

OBJECTIVE: To determine whether raised plasma glucose concentration independently influences outcome after acute stroke or is a stress response reflecting increased stroke severity. DESIGN: Long-term follow up study of patients admitted to an acute stroke unit. SETTING: Western Infirmary, Glasgow. SUBJECTS: 811 patients with acute stroke confirmed by computed tomography. Analysis was restricted to the 750 non-diabetic patients. MAIN OUTCOME MEASURES: Survival time and placement three months after stroke. RESULTS: 645 patients (86%) had ischaemic stroke and 105 patients (14%) haemorrhagic stroke. Cox''s proportional hazards modelling with stratification according to Oxfordshire Community Stroke Project categories identified increased age (relative hazard 1.36 per decade; 95% confidence interval 1.21 to 1.53), haemorrhagic stroke (relative hazard 1.67; 1.22 to 2.28), time to resolution of symptoms > 72 hours (relative hazard 2.15; 1.15 to 4.05), and hyperglycaemia (relative hazard 1.87; 1.43 to 2.45) as predictors of mortality. The effect of glucose concentration on survival was greatest in the first month. CONCLUSIONS: Plasma glucose concentration above 8 mmol/l after acute stroke predicts a poor prognosis after correcting for age, stroke severity, and stroke subtype. Raised plasma glucose concentration is therefore unlikely to be solely a stress response and should arguably be treated actively. A randomised trial is warranted.     

Parturition and alate morph determination in the aphid Megoura viciae

In reproducing apterae of Megoura viciae, parturition is often completely arrested during periods of isolation from the host plant. In contrast, surgical removal of the rostrum (including the stylets), amputation of the extremities of the legs, or decapitation, all stimulate parturition away from the plant. These operations also induce alata-producing aphids to revert immediately to the production of apterae, but have no detectable effect on aptera-producers. Carbon dioxide or ether anaesthesia and nitrogen narcosis have a similar action on this maternally controlled response. Although the rostrum and tibio-tarsus bear sensilla whose removal might well be involved in inducing parturition, the influence on morph change is probably indirect and is to a great extent associated with the delay in the resumption of parturition. The effect can be reproduced by isolating individual aphids away from the food plant. The morph change cannot, however, be attributed to starvation since it also occurs when the genital pore of an actively feeding aphid is temporarily occluded. The change in physiology appears to be associated with the retention of embryos at a time when there is no sensory input from crowding.

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Résumé Chez les Megoura viciae aptères, la parturition est souvent complètement arrêtée pendant les périodes de séparation de la plante hôte. Par opposition, l'amputation chirurgicale du rostre (y compris les stylets), de l'extrémité des pattes (tarse et une partie du tibia), ou la décapitation, stimulent toutes la parturition en l'absence de la plante. Les pucerons induits à produire des ailés (élevage antérieur en groupe) retournent, après ces opérations, immédiatement vers la production d'aptères. Le dioxyde de carbone ou l'anesthésie à l'éther et la narcose à l'azote ont une action semblable sur ce déterminisme maternel. Bien que l'élimination des sensilla portées par le rostre et par l'ensemble tarse-tibia puisse être déterminante dans l'induction de la parturition, l'action sur le changement de type semble être principalement associée au retard consécutif dans la reprise de la parturition. Les anesthésiants qui, eux aussi, retardent l'apparition ou la reprise de la parturition, ont probablement une action indirecte du même type.Les pucerons groupés, isolés de la plante hôte pendant plus de 24 h, ont aussi tendance à retourner immédiatement à la production d'aptères. Ce changement de type ne peut, cependant, être attribué au jeûne puisqu'il se produit aussi quand, chez un puceron s'alimentant activement, le pore génital est momentanément bouché. Le changement physiologique semble être associé à la rétention des embryons à un moment où il n'y a pas l'influence sensorielle du groupement.Aucun de ces traitements, à l'exception du groupement, n'induit des pucerons antérieurement isolés à devenir des producteurs d'ailés.

     

THE DISTRIBUTION OF GLYCINE, GABA, GLUTAMATE AND ASPARTATE IN RABBIT SPINAL CORD, CEREBELLUM AND HIPPOCAMPUS

The distribution of glycine, GABA, glutamate and aspartate was measured among about 60 subdivisions of rabbit spinal cord, and among the discrete layers of cerebellum, hippocampus and area dentata. A more detailed mapping for GABA was made within the tip of the dorsal horn of the spinal cord. Spinal ventral horn and dorsal root ganglion cell bodies were analyzed for the amino acids and for total lipid. The distribution of lipid and lipid-free dry weight per unit volume was also determined in spinal cord. Calculated on the basis of tissue water, glycine in the cord is highest in lateral and ventral white matter immediately adjacent to the ventral grey. The distribution of GABA is almost the inverse of that of glycine with highest level in the tip of dorsal horn. It is most highly concentrated in the central 75% of Rexed layers III and IV. Aspartate in the tip of ventral horn is 4-fold higher than in the tip of the dorsal horn and 3 times the average concentration in brain. Glutamate was much more evenly distributed and is relatively low in concentration with slightly higher levels in dorsal than in ventral grey matter. Large cell bodies in both ventral horn and dorsal root ganglion contained high levels of glycine. As reported by others, GABA was found to be high in cerebellar grey layers, area dentata, and regio inferior of hippocampus. Glycine was moderately high in cerebellar layers but moderate to low in hippocampus and area dentata.     

Proline excretion in Escherichia coli: A comparison of an argD + strain and a proline-excreting argD − derivative

In an attempt to deduce the physiological basis of proline excretion in argD ^– strains of Escherichia coli K12, several properties of an argD ⁺ (nonexcreting) and an argD ^– (excreting) derivative were compared. No difference was found in the transport or in the utilization of either proline or its immediate precursor, ¹-pyrroline-5-carboxylate (PCA). Furthermore, no differences were found in the physical or kinetic properties of partially purified preparations of the enzyme mediating the final step in proline biosynthesis, PCA reductase. The specific activity of PCA reductase was, however, consistently higher in crude extracts prepared from the argD ^– mutant.This work was supported by grants from the National Institutes of Allergy and Infectious Diseases (Public Health Service No. AI-10862) and The University of Connecticut Research Foundation (to C. M. B.). J. J. R. was supported by an NDEA Predoctoral Fellowship.     

Plasma free and sulfate conjugated catecholamine levels during acute physiological stimulation in man

The responses of plasma free and sulfate-conjugated catecholamines to acute physiological stimulation was examined in normal male subjects. Catecholamines were measured with a sensitive radioenzymatic assay incorporating simultaneous hydrolysis of sulfate conjugates and O-methylation of free norepinephrine and epinephrine. Following 20 minutes recumbency after venepuncture 30 +/- 3% of norepinephrine and 16 +/- 5% of epinephrine was in thr free form. Free catecholamines generally increased during standing, cold immersion and isometric handgrip, but sulfates did not change. Bicycle ergometry markedly increased free catecholamines which rapidly returned to basal levels at the end of exercise. In contrast, sulfated norepinephrine decreased substantially with exercise in all subjects but returned to basal levels 3 minutes after stopping exercise. Epinephrine sulfate varied considerably between subjects but showed a similar, although smaller, fall with exercise. Thus, during physiological stimulation, which caused increases in free norepinephrine and epinephrine levels in plasma, the only consistent change in sulfated catecholamines was a marked fall in norepinephrine sulfate after bicycle exercise. This may indicate saturation of sulfotransferase activity, substrate inhibition or impaired tissue conjugation.