Comparative radiosensitivity in the class insecta.

A “radiosensitivity index” (LT₅₀/mean longevity) was correlated with the mean longevity and dry weight of 37 insect species (both sexes of 12 species) representing eight orders. Curvilinear regression analysis relating radiosensitivity to mean longevity and mean dry weight indicated that 46·3% of the observed variation could be attributed to longevity and 32·6% to the dry weight of the species. In general, large long-lived adults were more radiosensitive than small short-lived adults. Correlation of the phylogeny of insect orders and order groupings with the radio-sensitivity index was found to be poor. However, when the index was related to longevity, there was a tendency for species comprising the major orders investigated to occur in groups along the predicted curve.     

Seed esterases,leucine aminopeptidases and catalases of species of the genus Gossypium

Summary Polyacrylamide and starch gel electrophoresis were used to analyze the isozyme makeup of three enzyme systems (esterases, leucine aminopeptidases and catalases) from the dormant seeds of twenty-nine species within the genus Gossypium.Isozyme variation was observed for all three enzymes between the species of the different genome groups. The within species polymorphism noted for the esterases was not observed for the leucine aminopeptidase and catalase patterns. In general, only minor qualitative banding pattern differences distinguished the A and B genome species, whereas, band variations were greatest between the more distantly related species in the C, D and E genomes. Gossypium longicalyx (F genome) showed an overall banding pattern unique to itself. The species of the genomes (C, D, E and F) removed from the postulated area of genetic origin (Southern Africa) also exhibited greater isozyme variability than that of the wild species of the A and B genomes, both located in Southern Africa.Synthetic mixtures of seed extracts from parent species of recently formed synthetic allopolyploids produced additive isozyme patterns for esterase, leucine aminopeptidase and catalase that were closely comparable to the zymograms produced by their hybrids. In contrast all three enzyme systems showed significant qualitative isozyme variations between the three natural allotetraploids, G. tomentosum, G. barbadense and G. hirsutum when compared to the zymograms of the synthetic mixtures of their alleged parental forms.This paper is part of a dissertation by the first author for the degree of Doctor of Philosophy in Genetics. Journal paper 1763 of the Arizona Agricultural Experiment Station.National Research Council Postdoctoral Research Associate.     

The effect of the presence of integral membrane protein (human band 3) on the membrane lytic properties of melittin in reconstituted systems

Abstract Reconstitution of the anion exchange protein from human erythrocytes (band 3) into phospholipid vesicles was shown to have a protective effect on melittin lysis of the vesicles when compared to pure lipid vesicles. Low salt buffer was found to cause an inhibition of lysis in both proteoliposomes and pure lipid vesicles compared to salt buffer. High phosphate concentration did not seem to cause inhibition of lysis in the reconstituted system. However, an inhibition is observed in pure lipid vesicle control, which is contradictory to previous reports.     

Molluscan cellulolytic activity responses to zinc exposure in laboratory and field stream comparisons

Changes in cellulolytic activity of Asiatic clams (Corbicula fluminea) and snails (Mudalia dilatata) were monitored throughout 30-d exposures to constant additions (0.0, 0.025, 0.05, 0.50, and 1.0 mg l⁻¹) of zinc (Zn). All exposures of 0.05 mg Zn 1⁻¹ or greater significantly reduced enzyme activity (exo- and endocellulase) in both molluscs as early as 10 d following exposures in outdoor laboratory streams incorporating New River water as diluent. More sterile laboratory stream exposures were less consistent in yielding quantifiable differences that could be attributed to metal induced stress apart from effects of nutritional stress. Tests conducted under natural field conditions during all seasons did not differ significantly with respect to changes in annual energetics of either clams or snails. However, evidence of differing uptake routes, with respect to two ecologically and physiologically distinct molluscs, was apparent in bioaccumulation, growth, and enzyme activity throughout exposure and following 60-d recovery.     

Pyruvate stabilizes electrocardiographic and hemodynamic function in pigs recovering from cardiac arrest

Cardiac electromechanical dysfunction may compromise recovery of patients who are initially resuscitated from cardiac arrest, and effective treatments remain elusive. Pyruvate, a natural intermediary metabolite, energy substrate, and antioxidant, has been found to protect the heart from ischemia-reperfusion injury. This study tested the hypothesis that pyruvate-enriched resuscitation restores hemodynamic, metabolic, and electrolyte homeostasis following cardiac arrest. Forty-two Yorkshire swine underwent pacing-induced ventricular fibrillation and, after 6 min pre-intervention arrest, 4 min precordial compressions followed by transthoracic countershocks. After defibrillation and recovery of spontaneous circulation, the pigs were monitored for another 4 h. Sodium pyruvate or NaCl were infused i.v. (0.1 mmol·kg⁻¹·min⁻¹) throughout precordial compressions and the first 60 min recovery. In 8 of the 24 NaCl-infused swine, the first countershock converted ventricular fibrillation to pulseless electrical activity unresponsive to subsequent countershocks, but only 1 of 18 pyruvate-treated swine developed pulseless electrical activity (relative risk 0.17; 95% confidence interval 0.13–0.22). Pyruvate treatment also lowered the dosage of vasoconstrictor phenylephrine required to maintain systemic arterial pressure at 15–60 min recovery, hastened clearance of excess glucose, elevated arterial bicarbonate, and raised arterial pH; these statistically significant effects persisted up to 3 h after sodium pyruvate infusion, while infusion-induced hypernatremia subsided. These results demonstrate that pyruvate-enriched resuscitation achieves electrocardiographic and hemodynamic stability in swine during the initial recovery from cardiac arrest. Such metabolically based treatment may offer an effective strategy to support cardiac electromechanical recovery immediately after cardiac arrest.     

Purification and characterization of two tyrosyl-tRNA synthetase activities from soybean cotyledons

The tyrosyl-tRNA synthetases located in cytoplasm and chloroplasts of soybean cotyledons were purified to near homogeneity by ammonium sulfate precipitation, DEAE-cellulose chromatography, hydroxylapatite chromatography, and DEAE-Sephadex A-25 chromatography. Purified cytoplasmic tyrosyl-tRNA synthetase shows only a single band in acrylamide gel electrophoresis which corresponds to a MW of 126000. In SDS-acrylamide gel electrophoresis the enzyme again shows only a single band which corresponds to a MW of 61 000. Chloroplast tyrosyl-tRNA synthetase shows only one band in both acrylamide and SDS-acrylamide gel electrophoresis with MWs being 98 000 and 43 000, respectively. For cytoplasmic tyrosyl-tRNA synthetase the apparent K_ms determined are 6.8 μM L-tyrosine, 49 μM ATP, and 8.9 × 10^?8 M tRNA (as total tRNA). Apparent K_ms for chloroplast tyrosyl-tRNA synthetase are 4.9 μM L-tyrosine, 214 μM ATP and 2.2 × 10^?8 M tRNA (as BDC-ethanol fraction tRNA). Fractionation of soybean cotyledon-tRNA on RPC-5 columns gives 4 tyrosyl-tRNA species, the first two species (tRNA_{1 and 2}^Tyr) are acylated only by cytoplasmic tyrosyl-tRNA synthetase while the last two species (tRNA_{3 and 4}^Tyr) are acylated only by chloroplast tyrosyl-tRNA synthetase.