The interaction of apolipoproteins with lecithin:cholesterol acyltransferase

The rate of lecithin:cholesterole acyltransferase reaction was measured in a cholesterol-containing single bilayer lecithin vesicle system. ApolipoproteinA-I (apoA-I) activated the enzyme by itself; the other components of apolipoproteins of high density lipoproteins (HDL) (rho = 1.08--1.2 g/cm3), or rabbit serum gamma globulin inhibited the reaction. The reaction which was activated by pure apoA-I was strongly inhibited by anti-apoA-I antibody. Quantitative analysis of the results showed that the lecithin:cholesterol acyltransferase reaction was activated by the binding of apoA-I to the surface of lipid substrates. The rate of the lecithin:cholesterol acyltransferase-catalyzed reaction was strictly proportional to the surface density of apoA-I. The inhibition was due to the decrease of the amount of apoA-I on the lipid surface, either through competitive exclusion by apoA-II or by other proteins, or through specific extraction with antibody. The presence of components of apoHDL, other than apoA-I, prevented the inhibitory action of anti-apoA-I antibody.     

Preparation and chemical properties of the outer membrane of a moderately halophilic gram-negative bacterium.

Outer membranes, almost free from peptidoglycan components, were prepared from a moderately halophilic gram-negative bacterium grown in a medium containing 2 M NaCl. The outer membrane was easily released, leaving mureinoplasts, by mild desalting in a 20% sucrose solution containing 50 mM tris(hydroxymethyl)aminomethane-HCl buffer, pH 7.8. The membrane was recovered by treatment with DNase I and CsCl buoyant density centrifugation. Chemical analyses revealed that the outer membrane was mainly composed of 31% protein, about 20% extractable lipids (mainly phospholipids), and lipopolysaccharides. The proteins had about 18 mol % excess of acidic over basic amino acids. The phospholipids comprised phosphatidyl ethanolamine, phosphatidyl glycerol, cardiolipin, and an unidentified phospholipid containing glucose, which seemed mainly associated with the outer membrane. The content of lipopolysaccharides in the outer membrane was calculated arbitrarily as 30% from the heptose content. A unique feature of these lipopolysaccharides seemed to be higher lipid content than found in lipopolysaccharides of other gram-negative bacteria. The major fatty acids of bound lipids of the outer membrane resembled those of the lipopolysaccharides obtained from cell envelope preparation and contained high concentrations of 3-hydroxy lauric acid.     

Hypothalamic and hormonal control of the photoperiodically induced vernal functions in the White-crowned Sparrow,Zonotrichia leucophrys gambelii

To assess the role of the hypothalamo-hypophysial complex in the control of photoperiodically induced vernal premigratory responses in the White-crowned Sparrow, the effects of hypothalamic lesions and systemic administration of several hormones on these responses were investigated. Lesions that destroyed the posterior median eminence (PME) or the entire median eminence (ME) inhibited photoperiodically induced testicular growth, premigratory fattening and Zugunruhe. Lesions in the basal infundibular nucleus (IN) that resulted in complete inhibition of testicular growth abolished Zugunruhe, but allowed varying degrees of fattening. The systemic administration of prolactin, testosterone propionate (TP) or the combination thereof in the PME-lesioned birds induced fattening similar to that observed in photostimulated controls but did not induce Zugunruhe. It is concluded that testosterone and prolactin are the most important hormones involved in the control of vernal premigratory fattening. The role of these hormones in the induction of vernal Zugunruhe is not positively proven.     

The Evolutionary Advantage of Recombination. II. Individual Selection for Recombination

Based on the Fisher-Muller theory of the evolution of recombination, an argument can be constructed predicting that a recessive allele favoring recombination will be favored, if there are either favorable or deleterious mutants occurring at other loci. In this case there is no clear distinction between individual and group selection. Computer simulation of populations segregating for recessive or dominant recombination alleles showed selection favoring recombination, except in the case of a dominant recombination allele with deleterious background mutants. The relationship of this work to parallel investigations by Williams and by Strobeck, Maynard Smith, and Charlesworth is explored. All seem to rely on the same phenomenon. There seems no reason to assume that the evolution of recombination must have occurred by group selection.     

Effects of 4-[beta-(diethylamino)-ethoxy]-benzophenone upon carotenogenesis in Rhodospirillum rubrum.

Carotenoid production was determined in illuminated anaerobically maintained cultures of Rhodospirillum rubrum in media with and without 4-[beta-(diethylamino)-ethoxy]-benzophenone. In treated cultures, lycopene--which normally is not produced by R. rubrum--accumulated as the predominant pigment, and total carotenoids increased five- to sixfold.     

Structure--activity relationships of chemical inducers of carotenoid biosynthesis

Fifteen amines having a profound effect on carotenogenesis in Marsh seedless grapefruit are reported. The compounds fall into three series: Et₂N(CH₂)_nMe (n = 4–8), Et₂N(CH₂)_nPh (n = 1–5), and Et₂NCH₂CH₂OC₆H₄R (R=H, p-Me, p-Et, p-iso-Pr, p-tert-Bu), There was up to an 11-fold increase in the total carotene content. Lycopene, not normally accumulated, became a major pigment. The inducing ability of the amines on carotenoid biosynthesis is correlated with the octanol-water partition coefficient. The mode of action appears to be similar to that of 2-(4-chlorophenylthio)triethylamine hydrochloride.     

Transmission of Thelohanellus hovorkai Achmerov, 1960 (Myxosporea: Myxozoa) to common carp Cyprinus carpio through the alternate oligochaete host

Thelohanellus hovorkai (Myxosporea: Myxozoa) was transmitted to common carp Cyprinus carpio by exposing fish to Aurantiactinomyxon spores collected from the oligochaete Branchiura sowerbyi. The morphological characteristics of the actinosporean stage are described in detail. B. sowerbyi were exposed to T. hovorkai spores isolated from the experimentally infected carp, and after 3 and 4 months the worms exhibited prevalences of the actinosporean stage at 19.47% (7/36) and 14.6% (6/41), respectively. Control, unexposed worms were negative for the actinosporean infection. This is the first report of an Aurantiactinomyxon transforming into a myxosporean belonging to the suborder Platysporina.     

Properties of common wheat ferredoxin, and a comparison with ferredoxins from related species of triticum and aegilops.

Wheat ferredoxin was purified from the leaves of common wheat (Triticum aestivum). The absorption spectrum showed maxima at 465, 425, 332, and 278 nm. The absorbance ratio, A425 nm/A278 nm was 0.49, and the millimolar extinction coefficient at 425 nm was 10.8 mM-1. cm-1. The amino acid composition was determined to be Lys5, His2, Arg1, Asp11, Thr5, Ser7, Glu18, Pro5, Gly6, Ala7, Cys5, Val7, Met1, Ile4, Leu7, Tyr4, Phe1, and Trp1. The total number of amino acid residues was 97. The molecular weight was calculated from the amino acid composition to be 10,829, including iron and sulfur atoms. This value was confirmed by other methods, which were based on the contents of non-heme iron and of terminal amino acid. The N-terminal amino acid was alanine, and the C-terminal amino acid sequence was -Glu-Leu-Thr-AlaCOOH. Comparative studies were performed between T. aestivum ferredoxin and ferredoxins isolated from closely related species; these were T. aegilopoides, T. durum, Ae. squarrosa, and Ae. ovata. No significant differences in the properties of these ferredoxins were detected. It was also shown that these ferredoxins are immunologically homologous. It is, therefore, likely that one molecular species of ferredoxin is distributed through two genera of Triticum and Aegilops.     

Effect of reproductive compensation and the desire to have male offspring on the incidence of a sex-linked lethal disease.

The effects of reproductive compensation on an X-linked recessive lethal are examined. Complete compensation without regard to the sex of the offspring increases the incidence of female carriers by a factor of 1.5, and of affected males by 1.33. However, if families reproduce until they have a healthy male offspring, the incidence of the X-linked lethal can be increased two or three orders of magnitude. Even only 1% of the population reproducing until a male is born can inflate the incidence of the disease by an order of magnitude, provided this pattern of family planning is culturally inherited. Similarly, reproducing until there is at least one child of each sex increases the incidence of an X-linked lethal. The impact of these types of sex-biased family planning on the fraction of new mutants among affect males is discussed.