Toxicity of enzymically-oxidized low-density lipoprotein

Intravenous injection of cholesterol oxidase into hyperlipidemic rabbits in which aortic atheromatous lesions have been induced by dietary means is lethal within hours, whereas injection of the same enzyme into normal rabbits has no visible adverse effect. The lethal effect of the enzyme is explicable by the finding that injection of cholesterol-oxidase treated low-density lipoprotein kills normal rabbits, in contrast to untreated low-density lipoprotein which does not. Enzymically oxidized low-density lipoprotein was also found to be cytotoxic for two human cell lines and for cultured bovine aortic endothelial cells. We suggest that in vivo enzymic conversion of low-density lipoprotein cholesterol to low-density lipoprotein cholestenone may possibly play a role in the initiation of atheromatous lesions in humans.     

Characterization of cuticle-degrading proteases produced by the entomopathogen Metarhizium anisopliae

Two chymoelastases and three trypsinlike proteases were separated from culture filtrates of the entomopathogen Metarhizium anisopliae. A chymoelastase (Pr1) (pI 10.3 Mr 25,000) and trypsin (Pr2) (pI 4.42, Mr 28,500) were purified to homogeneity by ammonium sulphate precipitation, isoelectric focusing, and affinity chromatography. Inhibition studies showed that both enzymes possessed essential serine and histidine residues in the active site. Pr1 shows greater activity than Pr2 or mammalian enzymes against locust cuticle and also possesses activity vs elastin. Pr1 shows a broad primary specificity toward amino acids with hydrophobic side groups in synthetic ester and amide substrates. The kinetic properties of Pr1 demonstrate a preference for extended peptide chains with the active site recognising at least five substrate residues. The S5 and S4 subsites show a preference for negatively charged succinyl and hydrophobic acetyl groups, respectively. The S3 and S2 subsites both discriminated in favor of alanine and against proline. Pr2 rapidly hydrolyzed casein and synthetic substrates containing arginine or lysine. It possessed little or no activity vs cuticle, elastin, or synthetic substrates for chymotrypsin and elastase. Specific active site inhibitors confirmed the similarities between Pr2 and trypsin.     

Purification and characterization of Rhodobacter sphaeroides acyl carrier protein

Acyl carrier protein (ACP) has been purified from the facultative phototrophic bacterium Rhodobacter sphaeroides. The ACP preparation was greater than 95% homogeneous as determined by native and disodium dodecyl sulfate (Na2DodSO4)-polyacrylamide gel electrophoreses and N-terminal amino acid analysis. Amino acid compositional analysis revealed that the protein contains approximately 75 amino acids, has a calculated minimum molecular weight of 8700, and lacks the amino acids tyrosine and tryptophan. The presence of the characteristic 4'-phosphopantetheine prosthetic group was indicated by the occurrence of equimolar quantities of beta-alanine and taurine in amino acid hydrolysates and was confirmed by independent chemical analysis. The protein displayed a pI of 3.8 and had a calculated partial specific volume of 0.732 mL/g. The primary structure of the protein has been determined for the first 46 amino acid residues from the N terminus of the molecule, and the region of the molecule encompassing the amino acids from residues 31 to 44 was found to have 100% homology with the identical residues in Escherichia coli ACP. In contrast to E. coli ACP, R. sphaeroides ACP migrated according to its molecular weight during Na2DodSO4 gel electrophoresis, was resistant to pH-induced denaturation, and comigrated with the cis-vaccenoyl-ACP derivative during native gel electrophoresis. It is proposed that the basis for these properties is the enhanced hydrophobic character of the protein.     

Monotonic Change of the Mean Phenotype in Two-Locus Models

It is shown that the mean phenotype monotonically approaches the optimum in a class of symmetric, two-locus, two-allele models with stabilizing selection. In this model, mean fitness does not change monotonically. Thus, Fisher's fundamental theorem does not hold, even though another quantity of evolutionary interest, the mean phenotype, can be shown to change monotonically. Using this quantity, it is proven that global stability results for this model.     

Cycles in cannibalistic egg-larval interactions

A model of a cannibalistic larval-egg interaction such as occurs in Tribolium is developed which leads to a system of nonlinear Volterra integral equations. I determine the local stability properties of the unique equilibrium point of the model. A Hopf bifurcation analysis shows that the model always undergoes a subcritical bifurcation when stability is lost. Numerical solutions confirm the presence of multiple attractors over a range of parameter values. The form of the cycles observed in the numerical solutions is analogous to that observed in laboratory populations of Tribolium.     

Mutants of polyomavirus middle-T antigen

Polyomavirus middle-T antigen induces the transformation of established cell lines in culture and is known to interact with and/or modulate the activity of several enzymes (pp60^c.src, protein kinase C and phosphatidylinositol kinase) in vitro. This review is a compilation of the reported mutants of middle-T antigen and their biochemical and biological properties as they relate to the transformation event. The mutants of polyomavirus middle-T antigen have been previously classified phenotypically. Given the now large number of mutants, the classification presented here is based upon the position within the molecule. A model of middle-T is presented in which the protein is considered as consisting of three domains: a hydrophobic domain (the putative membrane-binding domain), the amino-terminal half of the molecule (the putative pp60^c.src-binding domain) and the intervening amino acids (the putative modulatory domain). A current model for the induction of transformation by polyomavirus middle-T is presented.     

Diagnosis of genetic disease using recombinant DNA. Supplement

Summary Recombinant DNA methodology has greatly increased our knowledge of the molecular pathology of the human genome at the same time as providing the means to diagnose inherited disease as the DNA level. We present here a list of recent reports of both direct and indirect analysis of human inherited disease which is intended to serve as a guide to current molecular genetic approaches to diagnostic medicine.     

Population biology of two land snails (Mesomphix spp.): variation among six southern appalachian sites with differing disturbance histories

Summary Ecological and genetic properties of two North American terrestrial gastropods (Mesomphix spp.) were characterized in paired control and previously logged watersheds in two North Carolina forests (Coweeta and the Great Smoky Mountains National Park) of the Southern Appalachian Biosphere Reserve Cluster. Shell growth was greater in the control sites, but density and mortality were largely independent of prior logging history and forest reserve. Based on starch gel electrophoresis data, both species showed their highest levels of genetic diversity in the Coweeta forest, the component of the reserve cluster which had the most extensive and variable history of logging disturbance. M. subplanus also exhibited higher levels of heterozygosity in logged than in control watersheds, and M. andrewsae showed over twice as many rare alleles in disturbed sites as in control sites. F-statistic analysis depicted both excess levels of homozygosity and moderate genetic differentiation among the populations, reflecting the effects of small population size and perhaps drift and inbreeding. Estimated gene flow was relatively low. These results correspond to the recent finding by Bryant et al. (1987) and others on the effects of bottlenecks, and to the contrasting history of habitat instability of the two major study forests.     

The effects of ultraviolet-B radiation on loblolly pine. I. Growth, photosynthesis and pigment production in greenhouse-grown seedlings

One-year old loblolly pine ( Pinus taeda L.) seedlings were grown in an unshaded greenhouse for 7 months under 4 levels of ultraviolet-B (UV-B) radiation simulating stratospheric ozone reductions of 16, 25 and 40% and included a control with no UV-B radiation. Periodic measurements were made of growth and gas exchange characteristics and needle chlorophyll and UV-B-absorbing-compound concentrations. The effectiveness of UV-B radiation on seedling growth and physiology varied with the UV-B irradiance level. Seedlings receiving the lowest supplemental UV-B irradiance showed reductions in growth and photosynthetic capacity after only 1 month of irradiation. These reductions persisted and resulted in lower biomass production, while no increases in UV-B-absorbing compounds in needles were observed. Seedlings receiving UV-B radiation which simulated a 25% stratospheric ozone reduction showed an increase in UV-B-absorbing-compound concentrations after 6 months, which paralleled a recovery in photosynthesis and growth after an initial decrease in these characteristics. The seedlings grown at the highest UV-B irradiance (40% stratospheric ozone reduction) showed a more rapid increase in the concentration of UV-B-absorbing compounds and no effects of UV-B radiation on growth or photosynthetic capacity until after 4 months at this irradiance. Changes in photosynthetic capacity were probably the result of direct effects on light-dependent processes, since no effects were observed on either needle chlorophyll concentrations or stomatal conductance. Further studies are necessary to determine whether these responses persist and accumulate over subsequent years.