2-Mercaptoethylamine, a competitive inhibitor of spermidine synthase in mammalian cells

Spermidine synthase from rat ventral prostate was inhibited by 2-mercaptoethylamine (MEA). Inhibition of spermidine synthase by MEA was competitive with respect to one of the substrates putrescine, but not competitive with respect to the other substrate decarboxylated S-adenosylmethionine. MEA markedly depressed spermidine and spermine contents in human erythroid leukemia K562 cells, suggesting that these changes resulted from the inhibitory effect of MEA on spermidine synthase in situ.     

Superoxide production from nonenzymatically glycated protein

Nonenzymatically glycated human serum albumin and glycated poly-lysine(Lys) in vitro brought about the reduction of nitroblue tetrazolium and ferricytochrome c at pH 9.06 and pH 7.8, respectively. This reduction was inhibited partially by superoxide dismutase (SOD). Glycated poly-Lys caused the oxidation of NADH in the presence of LDH at pH 7.0 which was completely inhibited by SOD. Glycated material was found to function both as a reductant and an oxidant. The reactivity of glycated material is discussed and a possible mechanism by which superoxide is produced is proposed. Results may give a clue to diabetic complications.     

Non-enzymatic glycation of antithrombin III in vitro

Non-enzymatic glycation of antithrombin III (AT-III) has been proposed as a significant contributor to the increased incidence of thrombo-occlusive events in diabetics. AT-III, isolated from normal human plasma by means of heparin affinity and ion-exchange chromatography, was incubated with 0-0.5 M glucose in neutral phosphate buffer at 37 degrees C. The extent of non-enzymatic glycation could be monitored by uptake of radioactivity as well as by binding to a phenylboronate affinity resin, which effectively retards AT-III containing ketoamine-linked glucose. Non-enzymatically glycated AT-III (approx. 1 mol glucose/mol protein) bound heparin nearly as efficiently as non-glycated AT-III. The two AT-III preparations were equally active in inhibiting thrombin cleavage of chromogenic substrate. Following incubation with [14C]glucose, structural analyses of cyanogen-bromide-cleaved peptides of enzymatically glycated AT-III showed that the [14C]glucose adducts were distributed over many sites on the molecule. This lack of specificity contrasts with the restricted sites of modification on hemoglobin, albumin and ribonuclease A, and explains why non-enzymatic glycation of AT-III has little if any effect on its function.     

Cloning of mRNA sequence coding for sex-specific storage protein of Bombyx mori

A major plasma protein, referred to as SP 1, exhibits sex- and stage-specific expression during the larval development of the silkworm, Bombyx mori. We have isolated a plasmid clone bearing a part of mRNA sequence coding for SP 1 and quantitated the amount of SP 1 mRNA by means of RNA blot hybridization using the cDNA probe. The developmental change in the amount of SP 1 mRNA in the fat body closely reflected that of the hemolymph concentration of SP 1, indicating that the biosynthesis of SP 1 is regulated in a sex- and developmental stage-specific fashion at the level of mRNA.     

Alpha 1 type IV collagen gene evolved differently from fibrillar collagen genes

Type IV collagen is a major structural component in basement membranes. It is considerably different from the fibrillar collagens, types I-III. For example, unlike fibrillar collagens, the triple helical domain of type IV collagen is frequently interrupted by nonhelical regions. In this report, we demonstrate several overlapping genomic clones which cover most of the mouse alpha 1(IV) chain. Electron microscopic analysis of R-loops revealed that there were at least 28 exons within 35 kilobases of the gene segment. The sizes of six exons were determined by DNA sequence analysis to be 81, 178, 134, 73, 129, and 213 base pairs. These sizes do not appear to be related to the 54-base pair coding unit which is characteristic of fibrillar collagen exons, suggesting that the alpha 1 type IV collagen gene evolved differently from the fibrillar collagen genes.     

delta 9-Tetrahydrocannabinol elicited ipsilateral circling behavior in rats with unilateral nigral lesion

The present study was designed to examine the influence of delta 9-tetrahydrocannabinol (THC) on the central dopaminergic system using circling behavior. THC 5 mg/kg i.p. produced ipsilateral circling in rats with unilateral nigral lesion by 6-hydroxy-dopamine. THC-induced ipsilateral circling was completely antagonized by 0.2 mg/kg of haloperidol. These findings suggest that THC may cause a presynaptic stimulation of nigrostriatal dopaminergic neurons.     

Effect of Methanol on the Nucleotide Binding to High-Affinity Sites on Chloroplast Coupling Factor 1

The effects of methanol on the nucleotide binding to isolatedchloroplast coupling factor 1 (CF₁) were investigated. IsolatedCF₁ has four kinds of nucleotide binding sites; a barely dissociableADP-binding site (site A), two slowly exchangeable high-affinitysites with different affinities for ADP (sites B and C) whichare not catalytic sites, and several low-affinity sites (Hisaboriand Sakurai 1984). Methanol at 20% (v/v) slightly acceleratedthe binding of ADP to CF₁ but did not influence the number ofbinding sites. Methanol at 10–24% (v/v) affected neitherthe total amounts of bound adenine nucleotides (2.5 mol/molCF₁) nor the incorporation of labeled ADP from the medium (1.5mol/mol CF₁ into the slowly exchangeable sites (sites A, B,C). These results indicate that no appreciable exchange of ADPoccurred at site A at 10–24% (v/v) methanol and excludethe possibility of direct participation of nucleotide bindingat this site in the regulation of ATPase. In 32% methanol, theamount of the labeled ADP bound increased, suggesting some exchangeat site A. Methanol at 20% (v/v) greatly increased the affinitiesof sites B and C for ADP, CDP, GDP, UDP and PP_i. Conformational change of CF₁ induced by the binding of nucleotidesto site(s) B (and C) increased the resistance of CF₁ to inactivationby methanol at high concentrations or by cold treatment. (Received August 16, 1984; Accepted January 23, 1985)     

Congenital absence of flexor pollicis longus without hypoplasia of thenar muscles

A 7-year-old girl who was unable to flex her left thumb at the interphalangeal joint proved to have an extremely hypoplastic flexor pollicis longus with normal thenar muscles, which is very rare. The flexor digitorum superficialis of the ring finger was transferred to the inserting portion of the flexor pollicis longus tendon with good results. The patient's cooperation seems to be a factor determining the prognosis.     

Graphics of RNA secondary structure; towards an object-oriented algorithm

We present a new algorithm for the display of RNA secondarystructure. The principle of the algorithm is entirely differentfrom those currently in use in that our algorithm is ‘objectoriented’ while currrent algorithms are ‘procedural’.The circular RNA molecule of chrysanthemum stunt viroid wasused as input data for demonstrating the operation of the program.The major interest of this method will be found in its potentialuse in simulation graphics of RNA folding processes. Received on October 9, 1986; accepted on February 17, 1987