Pathophysiologic changes in obesity.

Obesity is the common expression of several diverse interacting genetic, familial and environmental factors. In addition to having hypertrophic fat cells because of inordinate triglyceride accumulation, many patients with childhood-onset obesity and those who are massively obese regardless of age at onset have an excessive number of adipocytes. Several endocrinologic and metabolic abnormalities are associated with obesity. Triglyceride formation in and lipid mobilization from hypertrophic adipocytes are exaggerated. The increased availability of free fatty acids to the liver contributes to the excessive synthesis of triglycerides and very-low-density lipoproteins; thus, hypertriglyceridemia is frequently associated with obesity. Hepatic synthesis and biliary excretion of cholesterol are also increased. Most of the excess cholesterol is stored in fat cells. The plasma concentrations of high-density lipoproteins are decreased. Hyperinsulinemia, which is characteristically found in the obese, leads to a decreased number of insulin receptors in target cells. The relative insulin insensitivity of the obese frequently results in glucose intolerance. The endocrinologic and metabolic abnormalities are correctable by an appropriate program of meal planning and physical activity.     

Ferralterin: An iron-sulfur protein functional in enzyme regulation in photosynthesis

The chloroplast new protein factor that was recently shown to link light to the activation of fructose 1,6-bisphosphatase was identified as a previously unrecognized iron-sulfur protein. This protein, given the name “ferralterin,” was purified to homogeneity from spinach leaves and from the blue-green alga (cyanobacterium) Nostoc muscorum. Ferralterin from both sources showed a visible absorption peak at 410nm, a molecular weight of about 30,000 and (provisionally) 4 g-atoms per mole each of nonheme iron and acid labile sulfide. The homogeneous ferralterin preparations catalyzed a light-dependent activation of chloroplast fructose 1,6-bisphosphatase that was dependent only on chlorophyll-containing membranes.     

Leaf analysis as a diagnosis of nutritional deficiency or excess in the soilless culture of lettuce

Summary The results are given of experiments to test wether leaf analyses can be used for diagnostic determinations of deficiency and excess in mineral nutrition of lettuce in soilless culture. re]19760127     

Isolation and properties of crystalline ferredoxin from lactuca sativa

Lettuce ferredoxin has been purified to homogeneity, with a yield of 18 mg/kg of denerved leaves. It crystallizes in magnificent needles, often clustered in broom-like sheaves. The absorption spectrum showed maxima at 460, 422, 330 and 274 nm,with a ratio A₄₂₂/A₂₇₄, of 0.46. The mM absorption coefficient was 9.74 at 422 nm, and 21.62 at 274 nm. This ferredoxin showed a pI = 4.7 and an E′₀ = ?425 mV (at pH = 7.7). MWs of 12 400, 11480 and 13000 were obtained by sucrose gradient centrifugation, and on the basis of the amino acid composition and the iron content, respectively, with an average of 12 300. The amino acid analysis showed the existence of one methionine residue per mole, with 105 amino acid residues. There are two iron atoms and two labile sulfide groups per mole; 4 half-cystine residues were found by performic acid oxidation, and 5 cysteine groups when determined by titration with pHMB. The native protein is not fixed on thiol-Sepharose 4B, but it is quantitatively retained after incubation with 8 M urea. Lettuce ferredoxin showed a 62, 58 and 78% effectiveness with the spinach ferredoxin-NADP reductase, nitrite reductase and fructose-1,6-diphosphatase (FDPase), respectively, when compared with the spinach ferredoxin. This different behaviour of both ferredoxins is joined to genetic-structural relationships, and suggests that the role of ferredoxin in FDPase activation is more sophisticated than that of a mere nonspecific reductant.     

Effect of papulacandin B on β-glucan synthesis in Schizosaccharomyces pombe

Abstract The antifungal antibiotic papulacandin β inhibited B(1,3)glucan-synthase activity, in vitro, from Schizosaccharomyces pombe . Levels of β(1,3)glucan-synthase from antibiotic-treated cultures were lower than the control cultures whereas mannan-synthase and β(1,3)glucanase activities were almost unaffected. The presence of an osmotic stabilizer reduced the inhibition of growth caused by the antibiotic. Addition of papulacandin β to a culture of S. pombe specifically inhibited incorporation of glucose into the β-glucan cell wall fraction. The fatty acids as well as the hydroxyl groups on the phenol residue of the papulacandin β molecule were essential for the inhibitory activity.     

Evolution of the nucleotide sequence of influenza virus RNA segment 7 during drift of the H3N2 subtype

The complete genetic information contained in the influenza virus RNA segment 7 of the A/Bangkok/ $\text{1}\text{79}$ (H3N2) strain has been cloned by in vitro synthesis of the complementary dsDNA and its insertion into plasmid pBR322. The nucleotide sequence of the viral RNA segment has been determined from the cDNA insert. It is 1027 nucleotides long, and contains two open reading frames, as shown for other influenza virus strains. When compared with the previously published sequence for the A/Udorn/72 (H3N2) strain, 15 nucleotide exchanges are observed, most of them silent mutations, and only two causing amino acid changes in each of the M1 and M2 protein sequences.     

Dipole moments of random coil polypeptides

The Rotational Isomeric States model is applied to calculate dipole moments of polypeptides of the twenty natural α-amino acids in the random coil state. Dipole moments of each repeat unit (μ_i), are evaluated using a quantum mechanics procedure. Dipole moment ratios ($\text{D}{}_{\mathrm{x}}\text{=}\text{〈μ}{}^2\text{〉}\text{x}\text{μ}{}_{\mathrm{i}}{}^2\text{,}\text{x = number of repeat units}$) of homopolypeptides are calculated and extrapolated to x →?. With a few exceptions, D_? = 0.36 ± 0.1. Ten actual proteins and three enzymes are also studied; their dipole ratios (D_x′ =〈μ〉/x) range from 7.34 to 10.57 in 10^?59 C² m² (6.6–9.5 D²). Diffferences in the values of D_x′ are due mainly to the different contributions, μ_i, of the amino acid residues contained in each polymer, whereas the sequence of amino acids has a very minor effect.     

ADH and phylogenetic relationships ofDrosophila lebanonensis (Scaptodrosophila)

Summary Increasing data onDrosophila alcohol dehydrogenase (ADH) sequences have made it possible to calculate the rate of amino acid replacement per year, which is 1.7×10^–9. This value makes this protein suitable for reconstructing phylogenetic relationships within the genus for those species for which no molecular data are available such asScaptodrosophila. The amino acid sequence ofDrosophila lebanonensis is compared to all of the already knownDrosophila ADHs, stressing the unique characteristic features of this protein such as the conservation of an initiating methionine at the N-terminus, the unique replacement of a glycine by an alanine at a very conserved position in the NAD domain of all dehydrogenases, the lack of a slowmigrating peptide, and the total conservation of the maximally hydrophilic peptide. The functional significance of these features is discussed.Although the percent amino acid identity of the ADH molecule inDrosophila decreases as the number of sequences compared increases, the conservation of residue type in terms of size and hydrophobocity for the ADH molecule is shown to be very high throughout the genusDrosophila. The distance matrix and parsimony methods used to establish the phylogenetic relationships ofD. lebanonensis show that the three subgenera,Scaptodrosophila, Drosophila, andSophophora separated at approximately the same time.     

Peptide Subunits of γ-Aminobutyric AcidA/Benzodiazepine Receptors from Bovine Cerebral Cortex

The gamma-aminobutyric acidA/benzodiazepine receptor complexes from bovine cerebral cortex were purified by immunoaffinity chromatography, and the main component peptide subunits were characterized. The peptide band originally thought to be a single beta subunit [57,000 Mr band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)] is composed of at least four different peptides of 54,000-57,000 Mr. Two peptides of 55,000 and 57,000 Mr were recognized by the beta subunit-specific monoclonal antibody 62-3G1. Peptides in the range of 54,000-57,000 Mr were photoaffinity-labeled with [3H]muscimol. A different 57,000 Mr peptide was photoaffinity-labeled by [3H]flunitrazepam, but neither was recognized by the monoclonal antibody 62-3G1 nor photoaffinity-labeled with [3H]muscimol. Some peptides could be identified by their differential mobility shift in SDS-PAGE after treatment with endoglycosidase H. Two additional subunit peptides of 51,000 and 53,000 Mr were also photoaffinity-labeled by [3H]flunitrazepam and reacted with antiserum A. However, the 57,000 Mr peptide that also was photoaffinity-labeled by [3H]flunitrazepam did not react with antiserum A.     

Modulation of Quinolinic and Kynurenic Acid Content in the Rat Brain: Effects of Endotoxins and Nicotinylalanine

Quinolinic acid, an endogenous excitotoxin, and kynurenic acid, an antagonist of excitatory amino acid receptors, are believed to be synthesized from tryptophan after the opening of the indole ring. They were measured in the rat brain and other organs using gas chromatography-mass spectrometry or HPLC. The enzyme indoleamine 2,3-dioxygenase, capable of cleaving the indole ring of tryptophan, was induced by administering bacterial endotoxins to rats, which significantly increased the brain content of both quinolinic and kynurenic acids. Nicotinylalanine, an analogue of kynurenine, inhibited this endotoxin-induced accumulation of quinolinic acid while potentiating the accumulation of kynurenic acid. The possibility of significantly increasing brain concentrations of kynurenic acid without a concomitant increase in quinolinic acid may provide a useful approach for studying the role of these electrophysiologically active tryptophan metabolites in brain function and preventing the possible toxic actions of abnormal synthesis of quinolinic acid.