Alpha-hydroxylation of lignoceroyl-CoA by a cyanide-sensitive oxygenase in rat brain microsomes

The enzymatic mechanism of alpha-hydroxylation of lignoceroyl-CoA, an intermediate in the synthesis of hydroxyceramide, was studied. In the presence of NADPH, sphingosine and microsomes from 20-day-old rat brain, 14C from [1-14C]lignoceroyl-CoA was incorporated into hydroxyceramide. Activity was linear with time (up to 40 min) and with protein (up to 0.8 mg). The apparent Km for lignoceroyl-CoA was about 10 microM. NADPH was a more efficient electron donor than NADH. Oxygen was required for activity, which increased linearly up to 20% O2. In 5 and 10% oxygen, the reaction was inhibited by 0.1 mM cyanide and by electron transfer chain inhibitors, cytochrome c, ferricyanide, menadione, and p-chloromercuriphenyl sulphonate; CO and SKF-525A had no effect. Moreover none of the inhibitors affected the formation of hydroxyceramide. Lignoceroyl-CoA alpha-hydroxylase appears to be an oxygenase requiring NADPH and oxygen, which involves cyanide-sensitive enzyme.     

Selection of an atrazine-resistant tobacco cell line having a mutant psbA gene

Summary A mutant cell line that shows high resistance to the photosynthesis-inhibiting herbicide atrazine was selected from cultured photomixotrophic Nicotiana tabacum cv. Samsun NN cells by repeated exposure to toxic levels of the herbicide. This resistance was confirmed by measurements of Hill reaction activity in isolated thylakoid membranes. Nucleotide sequencing revealed that the resistant cell line had a point mutation in its chloroplast psbA gene. The 264th codon, AGT (serine) was changed to ACT (threonine) in this mutant. This new type of mutation also conferred moderate cross-resistance to diuron and subsequently was stable in the absence of continued selection pressure.     

Application of fast atom bombardment mass spectrometry to chlorogenic acids

The technique of positive- and negative-ion fast atom bombardment mass spectrometry has been shown to be capable of producing molecular mass and useful fragmentation information for the structural elucidation of chlorogenic acids. The mass spectra of chlorogenic acid and the related compounds 3′-O-methylchlorogenic acid, neochlorogenic acid, 4,5-dicaffeoyl quinic acid and 1,5-dicaffeoyl quinic acid are compared with those obtained by electron impact mass spectrometry.     

Reverse effect of gram-positive bacteria vs. gram-negative bacteria on adjuvant-induced arthritis in germfree rats

Germfree (GF) F344 rats developed severe adjuvant-induced arthritis with a 100% incidence after a single intradermal injection of heat-killed Mycobacterium bovis (BCG). Specific pathogene-free (SPF) rats developed less severe arthritis with a lower incidence. The rats colonized with Escherichia coli or Bacteroides developed mild disease comparable to that in SPF rats. The rats colonized with Bifidobacterium, Propionibacterium acnes, Lactobacillus casei, L. fermentum, L. murini, and L. acidophilus developed more severe disease than that in GF rats. Furthermore, the rats colonized with a mixture of E. coli and the above lactobacilli developed very mild disease similar to that in SPF rats. These results suggest that gram-negative bacteria, such as E. coli and Bacteroides, may suppress the disease, possibly through their lipopolysaccharides, and may be responsible for the lower susceptibility of SPF rats; gram-positive bacteria, such as Bifidobacterium, P. acnes, and lactobacilli, may enhance the disease, possibly through their peptidoglycans; and E. coli may play a dominant role in modulating the development of adjuvant-induced arthritis.     

Localization of atrial natriuretic peptide, ANP-(99-126) binding sites in the rat thymus and spleen with quantitative autoradiography

Binding sites for atrial natriuretic peptide, ANP-(99-126) were studied in lymphoid organs of the rat with quantitative autoradiography. Tissue sections were incubated in the presence of 0.13 nM 125I-ANP-(99-126) followed by autoradiography using [3H]-Ultrofilm, and the results were analyzed by computerized densitometry and comparison to 125I-standards. Specific ANP binding sites were localized in the medulla and the cortex of the rat thymus and in the white pulp of the rat spleen, with apparent binding sites concentrations of 93, 65, and 126 fmol/mg protein, respectively. The presence of ANP binding sites in areas related to the maturation and function of lymphocytes, and to the production of thymic hormones, suggests the possibility of a role of circulating ANP in the modulation of the immune response.     

Molecular and enzymatic properties of 1,2-α-d-mannosidase fromAspergillus saitoi

The molecular properties, such as molecular weight, N-and C-terminal amino acids, amino acid composition, and circular dichroism, of 1,2--mannosidase isolated from the culture filtrate ofAspergillus saitoi were determined.The enzyme had aK _m of 0.67 mM andk _cat of 1.27/s with mannobiose at pH 50.0 and 30°C. The anomeric configuration of the reaction products of the enzyme was examined by studying the -anomer. A single Manl2Man linkage in intact Taka-amylase A fromAspergillus oryzae was hydrolyzed, producing free mannose.     

Flavonoids from Rhamnus pallasii

A new dihydroflavonol, pallasiin, together with kaempferol, quercetin, isorhamnetin, mearnsetin, aromadendrin, eriodictyol and taxifolin, has been isolated from the bark of Rhamnus pallasii and its structure elucidated as 2,3-dihydromyricetin 4′-O-methyl ether.     

Early Gravi-Electrical Responses in Bean Epicotyls

The relationship between gravitropism and surface electrical potentials was studied using etiolated epicotyls of adzuki bean (Phaseolus angularis). Early downward curvature (or transient positive gravitropic response) was observed about 1 min after gravistimulation. The downward curvature was closely related to the speed of the subsequent upward curvature. Surface electrical potentials decreased cooperatively in a limited region on the upper side within only 0.5 to 2 min. This is the earliest event found so far to follow gravistimulation of intact epicotyls. The rapid change in the potential had a high correlation with the early downward curvature and also the subsequent negative gravitropism. It is suggested that the rapid potential change plays an important role in gravity perception.     

Detection of the changes in protein distribution of rat plasma induced by carbon tetrachloride administration by means of two-dimensional electrophoresis

The changes in rat plasma protein distribution after carbon tetrachloride administration were examined using two-dimensional electrophoresis, utilizing isoelectric focusing in polyacrylamide gel in the first dimension and pore gradient polyacrylamide gel electrophoresis in the second dimension. Drastic changes in amount of protein were observed at more than 20 spot positions including those of transferrin, Gc-globulin and low-density lipoprotein. The time course of the changes was examined, and the most drastic changes were observed at 2 days after carbon tetrachloride administration.     

Differential effects of body weight, hyperinsulinemia and oral glucose load on serum C-peptide/insulin molar ratio.

Serum C-peptide immunoreactivity (CPR)/immunoreactive insulin (IRI) molar ratio was determined in 136 subjects without renal, hepatic and thyroid disorders, at fasting, and during the initial period of 75 g-oral glucose tolerance test. The subjects were divided into 4 groups based on their body weight and age; Group A, young (< 55 years) and normal body weight (body mass index [BMI, kg/m2] < or = 25) subjects; Group B, young and overweight (BMI > 25) subjects; Group C, aged (> or = 55 years) and normal body weight (BMI < or = 25) subjects; Group D, aged and overweight subjects. Fasting CPR/IRI ratio and absolute CPR level negatively correlated in Groups B and D but not in A and C. After oral glucose load with elevation of insulin, CPR/IRI ratio invariably declined in all groups and significant negative correlation between CPR/IRI and CPR was found in Groups A, B and D but not in C. Slope of the regression lines obtained for correlation between CPR/IRI ratio and CPR were significantly steeper at fasting compared to the post-stimulation phase. CPR/IRI ratio is affected by hyperinsulinemia and oral glucose load but not by obesity alone. Assuming that CPR/IRI ratio reflects hepatic extraction of insulin, the insulin clearance at fasting is progressively reduced with increasing insulin secretion in overweight subjects: failure to detect such phenomenon in normal body weight subjects may be due to a narrower CPR range in this population. Insulin metabolism at fasting and during glucose stimulation is likely to be regulated by distinct factors.