Heparin Prophylaxis against Fatal Postoperative Pulmonary Embolism

Low-dose heparin prophylaxis against fatal pulmonary embolism has been studied in a random and prospective trial in 300 patients over the age of 50 who underwent major surgery. A dose of 5,000 IU mucous heparin sodium given two hours preoperatively and for five days post operatively prevented fatal pulmonary embolism in all 156 patients so treated, whereas out of 144 patients in the unheparinized group 6 (4·2%) died of pulmonary embolism. This difference is statistically significant. There was no increase in operative or post-operative bleeding or in the formation of wound haematomas in the heparinized group.     

Helix–coil stability constants for amino acids in nonaqueous solvents. Studies of random poly(γ-benzyl-L-glutamate-co-L-alanine) and poly(γ-benzyl-L-glutamate-co-L-leucine) in a mixed solvent

The host–guest technique has been applied to the determination of the helix–coil stability constants of two naturally occurring amino acids, L -alanine and L -leucine, in a nonaqueous solvent system. Random copolymers containing L -alanine and L -leucine, respectively, as guest residues and γ-benzyl-L -glutamate as the host residue were synthesized. The polymers were fractionated and characterized for their amino acid content, molecular weight, and helix–coil transition behavior in a dichloroacetic acid (DCA)–1,2-dichloroethane (DCE) mixture. Two types of helix–coil transitions were carried out on the copolymers: solvent-induced transitions in DCA–DCE mixtures at 25°C and thermally induced transitions in a 82:18 (wt %) DCA–DCE mixture. The thermally induced transitions were analyzed by statistical mechanical methods to determine the Zimm-Bragg parameters, σ and s, of the guest residues. The experimental data indicate that, in the nonaqueous solvent, the L -alanine residue stabilizes the α-helical conformation more than the L -leucine residue does. This is in contrast to their behavior in aqueous solution, where the reverse is true. The implications of this finding for the analysis of helical structures in globular proteins are discussed.     

Conductance studies on the interaction of lactose with alkali-metal halides in water and in formamide

The interaction of lactose with alkali-metal halides in solution in water and in formamide has been studied by employing conductance measurements. Conductance data of sodium and potassium halides in water and in formamide saturated with lactose at 50.0 ±0.05° are reported at several temperatures within a range of 25 to 70°. Plots of —log- K against 1/T showed a break at the saturation temperature, where two straight lines intersect one another. Divergence of the pairs of straight lines in these ternary, homogeneous systems has been found to be highly influenced by the structural properties of the solutes. The transitional behavior in the conductance values is explained for the system in terms of solute-solvent interactions involved in the electrolyte-solvent-nonelectrolyte systems.     

Metabolism of saturated 1-14C-labelled fatty acids in the silkworm Bombyx mori L

1. Only a small percentage of 1-(14)C-labelled saturated fatty acids injected in the silkworm is respired as carbon dioxide. 2. The rate of utilization of fatty acids is low both at the larval and pupal stages. 3. The insect has the ability to elongate C(12) and C(16) saturated fatty acids and to desaturate C(18) saturated fatty acids. 4. Much of the administered radioactivity is found in the triglyceride fraction, followed by the phospholipid and diglyceride fractions. 5. Diglycerides seem to be the transport form of fatty acids. 6. The insect seems to metabolize both natural and unnatural fatty acids in the same manner.     

Involvement of Calcium and Calmodulin in Membrane Deterioration during Senescence of Pea Foliage

The prospect that Ca(2+) promotes senescence by activating calmodulin has been examined using cut pea (Pisum sativum co Alaska) foliage as a model system. Senescence was induced by severing 17-day-old plants from their roots and maintaining them in aqueous test solutions in the dark for an additional 4 days. Treatment of the foliage with the Ca(2+) ionophore (A23187) during the senescence-induction period promoted a lateral phase separation of the bulk lipids in microsomal membranes indicating that internalization of Ca(2+) facilitates membrane deterioration. In addition, microsomal membranes from ionophore-treated tissue displayed an increased capacity to convert 1-aminocyclopropane-1-carboxylic acid to ethylene and an increased propensity to produce the superoxide anion (O(2) (tau)). Treatment of the tissue with fluphenazine during the senescence-induction period, which prevents binding of the Ca:Calmodulin complex to enzymes, delayed membrane deterioration as measured by these criteria. It also proved possible to simulate these in situ effects of the Ca(2+) ionophore on ethylene production and O(2) (tau) formation by treating microsomal membranes isolated from young tissue with phospholipase A(2) in the presence of Ca(2+) and calmodulin, and these effects of phospholipase A(2) and Ca:calmodulin were inhibited by calmodulin antagonists. The observations collectively suggest that internalized Ca(2+) promotes senescence by activating calmodulin, which in turn mediates the action of phospholipase A(2) on membranes.     

Interaction for food and space between populations of Galaxias vulgaris Stokell and juvenile Salmo trutta L. in a New Zealand stream

The trophic and spatial interrelationships between a native ( Galaxias vulguris Stokell, Galaxiidae) and an exotic ( Salmo trutta L., Salmonidae) fish species were investigated over a 24-h period in a New Zealand stream. Interspecific overlap in feeding was greatest at dusk and dawn, as G. vulgaris fed primarily from dusk to post-dawn and S. trutta fed primarily from pre-dawn to post-dusk. Both species fed mainly on benthic and drifting aquatic invertebrates, with larval Deleatidium (Ephemeroptera). Hydora (Coleoptera) and Chironomidae (Diptera) being their preferred prey, although Trichoptera imagos were also preferred by S. trutta . Both species were found primarily in runs and riffles with G. vulgaris occupying slightly shallower (≤0.3 m) and faster (0.3–0.7 m s¹) waters than did S. trutta (≤0.5 m deep and 0.2–0.4 m s⁻¹ water velocity). We suggest that these rather subtle interspecifc differences in die1 feeding periodicities, diets and microdistributions play a part in lessening the interaction between co-occurring populations of G. wlguris and S. trutta .     

Relationship Between Conformation and Antiviral Activity-III. 3′-Azidothymidine (AZT) and 3′-Azido-2′, 3′-dideoxy-5-hydroxymethyluridine

Abstract

3′-Azido-2′,3′-dideoxy-5-hydroxymethyluridine (AZHMddUrd) was synthesized to improve the potency of 5-hydroxymethyl-2′-deoxyuridine (HMdUrd) against human immunodeficiency virus (HIV). AZHMddUrd was a very poor inhibitor of HIV replication (ED₅₀ >200 μM) and was also nontoxic up to 400 μM (highest concentration tested) to HT4-6C (HeLa CD₄) cells. AZT was phosphorylated by human cellular thymidine kinase. In contrast, AZHMddUrd and HMdUrd were poor substrates for the kinase. The relationship between molecular conformation and antiretroviral activity for 3′-azidothymidine (AZT), HMdUrd and AZHMddUrd is discussed.