Modulation of A and B cell functions by tolbutamide and arginine in the pancreas of thiamine-deficient rats

The effects of administration of glucose orally and tolbutamide or arginine intravenously on insulin and glucagon secretion and blood glucose level were studied in normal and thiamine-deficient rats. In thiamine deficiency, insulin secretion and glucose tolerance were impaired during glucose ingestion. Tolbutamide decreased the blood glucose level in both control and thiamine-deficient rats but its stimulatory effect on insulin secretion was minimal in thiamine-deficient rats unlike the control animals. Arginine did not alter substantially the blood glucose or insulin in thiamine-deficient rats, whereas it increased the insulin level in control rats. The fasting plasma glucagon level was high in thiamine deficiency. Tolbutamide increased the plasma glucagon in control rats, but did so only marginally in thiamine-deficient rats. Arginine also increased the glucagon secretion throughout the period of study in control rats. In thiamine-deficient rats the glucagon secretion was pronounced only after 20 min of arginine administration. These results suggest that an unimpaired glucose metabolism is a prerequisite to induce proper insulin secretion. Only proper insulin secretion can check the glucagon secretion rather than the increased glucose level. Hypoglycemia can induce glucagon secretion independent of the insulin level.     

Resistogram typing as an epidemiological tool for Escherichia coli isolates of poultry origin

A rapid method for the detection of corynetoxins, tunicamycin-like antibiotics, is described. Test samples were applied to or grown on an agar medium and overlain with Clavibacter tritici which is highly sensitive to the toxins. The method could detect 50 ng of tunicamycin. Corynetoxins in a range of field and laboratory samples were readily detected.     

Somatic excision of the Mu1 transposable element of maize.

The Mu transposons of the Robertsons's Mutator transposable element system in maize are unusual in many respects, when compared to the other known plant transposon systems. The excision of these elements occurs late in somatic tissues and very rarely in the germ line. Unlike the other plant transposons, there is no experimental evidence directly linking Mu element excision and integration. We have analyzed the excision products generated by a Mu1 transposon inserted into the bronze 1 locus of maize. We find that the excision products or 'footprints' left by the Mu1 element resemble those of the other plant transposable elements, rather than those of the animal transposable element systems. We also find some novel types of footprints resembling recombinational events. We suggest that the Mu1 element can promote intrachromosomal crossovers and conversions near its site of insertion, and that this may be another mechanism by which transposons can accelerate the evolution of genomes.     

Human parainfluenza type 3 virus hemagglutinin-neuraminidase glycoprotein: nucleotide sequence of mRNA and limited amino acid sequence of the purified protein.

The nucleotide sequence of mRNA for the hemagglutinin-neuraminidase (HN) protein of human parainfluenza type 3 virus obtained from the corresponding cDNA clone had a single long open reading frame encoding a putative protein of 64,254 daltons consisting of 572 amino acids. The deduced protein sequence was confirmed by limited N-terminal amino acid microsequencing of CNBr cleavage fragments of native HN that was purified by immunoprecipitation. The HN protein is moderately hydrophobic and has four potential sites (Asn-X-Ser/Thr) of N-glycosylation in the C-terminal half of the molecule. It is devoid of both the N-terminal signal sequence and the C-terminal membrane anchorage domain characteristic of the hemagglutinin of influenza virus and the fusion (F0) protein of the paramyxoviruses. Instead, it has a single prominent hydrophobic region capable of membrane insertion beginning at 32 residues from the N terminus. This N-terminal membrane insertion is similar to that of influenza virus neuraminidase and the recently reported structures of HN proteins of Sendai virus and simian virus 5.     

Proteins associated with human parainfluenza virus type 3.

The polypeptides associated with human parainfluenza virus type 3 were identified. Five proteins were present in detergent- and salt-resistant viral cores. Of these, three proteins designated NP0, NP1, and NP2 of 68,000, 58,000, and 52,000 daltons, respectively, were stably associated with 50S RNA in CsCl gradient-purified nucleocapsids. The amounts of NP1 and NP2 were variable, and these proteins were shown to be structurally related to the major nucleocapsid protein (NP0) by partial Staphylococcus aureus V8 protease mapping. The other core proteins included a 240K protein designated L (candidate for the viral polymerase) and an 84K protein designated as the phosphoprotein (P) on the basis of a predominant incorporation of Pi. The viral envelope had four prominent proteins (72, 53, 40, and 12K) under reducing conditions of electrophoresis. The 72 and 53K proteins were specifically labeled with [3H]glucosamine and [3H]mannose. When sulfhydryl reagents were removed, a new 62K protein was visualized in place of the 72, 53, and 12K proteins. The 53 and 12K proteins were interpreted to be the two subunits (F1 and F2) of the fusion protein, and the 72K protein was designated as the HN (hemagglutinin-neuraminidase) glycoprotein. The unglycosylated 40K protein represented the viral matrix protein (M). Immunoprecipitation of infected cell lysates with rabbit hyperimmune antiserum against purified virus confirmed the viral origin of these polypeptides.     

The nonenzymic hydrolysis of Δ-thiazoline-2-carboxylate: The product of the suspected physiological reaction catalyzed by -amino acid oxidase

Δ²-Thiazoline-2-carboxylate, the product of the suspected physiological reaction catalyzed by -amino acid oxidase, is stable to hydrolysis at 37°C and pH 7 or above, but it hydrolyzes readily at pH 5 or below to give a mixture of N- and S-oxalylcysteamines; the N-oxalyl derivative predominates at pH's above 1 while the S-oxyalyl compound is the major product at high acidities. The pH-rate profile looks like the superposition of two bell-shaped curves. The initial increase in the rate as the pH is lowered is controlled by a pK_a of 3.95 and from pH 1 to 3 the rate is relatively constant (k = 6.7 × 10⁻⁴s⁻¹ at 37°C and ionic strength 0.5 ). Below pH 1 the rate increases again to a maximum in 1 HCl and then decreases in more highly acidic solutions. The rate of conversion of S-oxalylcysteamine to N-oxalylcysteamine is inversely proportional to the hydrogen ion concentration from pH 3 to 5 but becomes largely independent of pH from pH 1 to 2. In the pH-independent region the rate is comparable with that observed by others for S-acetylcysteamine but in the pH-dependent region the rate is 20 to 25 times faster for the oxalyl derivative than for the acetyl compound. At pH 1, N-oxalylcysteamine is partially converted to the S-oxalyl derivative but the rate of hydrolysis (k = 1.0 × 10⁻⁵s⁻¹ at 37°C) to cysteamine and oxalate of this partially equilibrated system occurs at a comparable rate. The results of this investigation are rationalized in terms of what is known about other thiazoline hydrolyses and intramolecular S to N acyl migrations. The main differences in the present case are presumably due to the fact that thiazoline-2-carboxylate can undergo hydrolysis by two reaction manifolds, one with the carboxyl unprotonated and the other with it protonated. The relevance of these results to possible reactions of thiazoline-2-carboxylate in vivo is briefly considered.     

Modulation of the activity of 5'-nucleotidase by the transfer of non-esterified cholesterol to rat-liver microsomal fraction and evidence for regulation of the concentration of non-esterified cholesterol in plasma membranes in vivo

The effect of the plasticizer di(2-ethylhexyl)phthalate on the intracellular membranes of hepatocytes was investigated. Supplementation of the diet with 2% plasticizer resulted in the appearance of a large number of peroxisomes, and the number of mitochondria was also greatly increased. No significant change in the amount or appearance of the endoplasmic reticulum was detected. The oxidation of palmitoyl-CoA in peroxisomes and the activities of carnitine-acyltransferases are increased to a great extent in both mitochondria and peroxisomes. Intact respiratory control and oxidative phosphorylation indicated that mitochondrial integrity was maintained during the induction. In microsomes, cytochrome P-450 and NADPH-cytochrome c reductase are elevated. The increased incorporation of glycerol into phospholipids indicated an increased rate of synthesis. The induction of peroxisomal and mitochondrial membranes and enzymes, but not of the membranes of the endoplasmic reticulum, by phthalate esters is an unusual and valuable induction pattern not seen with other inducers.     

Metabolic studies on retinoic acid in the rat

The nature of metabolites in the urine arising from differentially labelled retinoic acid was investigated after injection of physiological doses into retinol-deficient rats. Distribution of radioactivity after partition of urine into ether-soluble, acidic and water-soluble fractions revealed that there were at least six metabolites in urine. Of these, the major metabolite(s) was one lacking both C-14 and C-15 of retinoic acid. Enzymic or alkaline hydrolysis of acidic and water-soluble fractions did not release any retinoic acid, thus indicating that retinoyl beta-glucuronide was not present in urine in significant amounts.