NADH: Nitrate reductase activity restoration by rhodanese

The NADH: nitrate reductase from durum wheat leaves was inactivated by cyanide and its activity restored by thiosulphate and beef kidney rhodanese. Rhodanese and thiosulphate, added to NADH-nitrate reductase before cyanide treatment protected NADH-nitrate reductase activity. No oxidizing agent was required for the protection or restoration of cyanide treated NADH-nitrate reductase.     

Thiol groups of chicken liver LDH (author's transl)]

Crystallized chicken liver H4 lactatedehydrogenase with PCBM and DTNB, proved to have sic thiol groups per enzyme molecule. Sulphydryl groups seemed necessary for activity since the enzyme became inactive when the groups were blocked by PCMB, DTNB or by Zn (II), Cu (II) or Hg (II). LDH inhibited by Hg (II) recovered its activity after treatment with beta-mercaptoentanol. LDH reversible inactivation, caused by PCMB, was partially impeded by NAD, NADH hand L-lactate but inactivation caused by DTNB was impeded in any way by coenzymes or substrates. PCMB is a competitive inhibitor with the coenzymes but is non-competitive with the substrates whereas DTNB is a competitive inhibitor with NADH or L-lactate. Kinetic studies of the DTNB inactivation suggest the possible formation of a DTNB-LDH-NADH complex. The formation of LDH-NADH and LDH-NAD pyruvate inactive complexes have been detected by U.V. absorbancy measurements. Such inactive complexes have equally been observed experimenting with the PCMB of Hg (II) previously treated enzyme. The results showed that these essential sulphydryl groups are not involved in th attaching of coenzymes or substrates to the chicken liver LDH molecule, but they seem to suggest the participation of --SH groups during the reversible hydrogen transfer between NADH and pyruvate.     

The structure of two alanine containing ferrichromes: Sequence determination by proton magnetic resonance

Summary Metal coordination confers an extraordinary structural stability to the ferrichromes which, independent of their variable amino acid composition, results in a basically unperturbed conformation for all the homologous peptides in the series. The proton magnetic resonance (pmr) characteristics for Al³⁺ analogues (alumichromes) reflect this conformational isomorphism in usual solvents so that single site substitutions are clearly recognized in the pmr spectra. Thus, the substitution of glycine byl-alanine orl-serine introduce new resonances characteristic of the sidechains and alter the pattern of the amide NH pmr region in that doublets substitute for glycyl triplets at the same site. Since for glycine- andl-serine-containing alumichromes the resonances have already been identified, it is possible to unequivocally establish the primary structure of the twol-alanyl homologues ferrichrome C ( ) and sake colorant A ( ) on the basis of the comparative pmr spectra of their Al³⁺ analogues, namely, alumichrome C and alumisake. The resonance assignment, and hence the site occupancy, is substantiated by the temperature coefficients of the NH chemical shifts, rates of¹H-²H exchange and homonuclear proton spin decoupling experiments centered on the NH spectral region. Occupancy of site 1 by a glycine residue is observed for all known ferrichromes, which serves to conserve a hairpin turn. This method of obtaining sequence information should prove of general use for other systems of homologous polypeptides, provided their conformations are not affected by the residue substitutions.     

Partial trisomy 21 (21q21 - 21q22.2)]

An abnormal chromosome 21 is reported in a child with a phenotype strongly reminiscent of trisomy 21 syndrome. It is shown to result from duplication of the segment 21q21 leads to 21q22.2. Comparison of the phenotype with that of other partial and total trisomics shows that the characteristic features of the trisomy 21 syndrome (mongolism), the mental retardation in particular - is due to trisomy 21q22.2 and perhaps 21q22.2.     

Decrease in maximum consumption of oxygen after blockage of beta-andrenergic receptors]

VO2 max, maximum oxygen uptake, has been measured in 4 normal young men, before and after beta-adrenergic blockade (0.5 to 5 mg Pindolol by mouth). Pindolol induces bradycardia and reduces VO2 max. A statistically significant positive correlation appears between posology of Pindolol and bradycardia, this posology and reduction of VO2 max, and finally between bradycardia and reduction of VO2 max. These correlations indicate that the reduction of VO2 max is best explained by a circulatory limitation of oxygen supply to active muscles.     

Electrophoretic demonstration and initial characterization of human red cell NAD(P)+ase

A method for electrophoretic detection of NAD(P)+ase solubilized from red cell membranes is described. The method reveals both NAD+ase and NADP+ase and can be applied to a screening procedure for the detection of electrophoretic variants. The initial chracterization of the solubilized enzyme is also described.     

Nature of progesterone action on amino acid uptake by isolated full-grown oocyte of Xenopus laevis

l-leucine uptake into full-grown oocytes of Xenopus laevis is a saturable process which is Na⁺ dependent and presumably coupled to Na⁺ gradient. Our results indicate that progesterone (10^?6 M) blocks abruptly, around the germinal vesicle breakdown, the saturable transport of l-leucine. $\text{p-}\text{Chloromercuribenzoate}$ (10^?4 M) induces maturation and after a short lag of time strongly inhibits l-leucine uptake. Cycloheximide prevents progesterone-induced maturation and permeability changes.