Esterase and malate dehydrogenase isozyme polymorphisms in 15 Artemia populations.

1. Starch gel electrophoresis of adult brine shrimps from 15 populations revealed little intrapopulation polymorphism in NAD-dependent malate dehydrogenase (MDH) isozymes or in the two fastest esterases (demonstrated with alpha-naphthyl propionate as substrate). 2. Interpopulation differences could be summarized as three different electrophoresis band patterns for the five- to seven-banded MDH isozymes and another three patterns for the two fastest esterases. 3. These differences in electrophoresis patterns divide the 15 Artemia populations into four categories (each containing one to seven populations) which may be distinguished by isozyme content and which are congruent with categories established by the criterion of reproductive isolation in an earlier study.     

Metabolism of [14C]diethylstilboestrol epoxide by rat liver in vitro.

1. The trans-epoxide of diethylstilboestrol and its pinacolone were synthesized chemically and the pinacolone shown to be formed from the epoxide by a non-enzymic process. 2. [14C]Diethylstiboestrol epoxide was converted by rat liver microsomal fraction into 4'-hydroxypropiophenone by a new type of cleavage reaction involving mono-oxygenase. Conditions for the formation of this metabolite and also water-soluble products were investigated together with the effect of inhibitors. A sex-difference in the conversion of diethylstilboestrol epoxide into 4'-hydroxypropiophenone and to polar and water-soluble products was observed. 3. Diethylstilboestrol epoxide was found to be a relatively stable compound that did not form a glutathione conjugate readily without further microsomal activation. A purified preparation of epoxide hydratase did not enhance its rate of conversion into the pinacolone. 4. Diethylstilboestrol epoxide was found to have about one-tenth the oestrogenic activity of diethylstilboestrol as measured by the increase in uterine weight or the induction of peroxidase in immature rat uteri. It was inactive as a mutagen when tested for its ability to inhibit bacteriophage phi X174 DNA viral replication. 5. The possible role of diethylstilboestrol epoxide as an intermediate in the metabolism of diethylstilboestrol and in mediating the harmful effects of this synthetic estrogen is discussed.     

DNA fragments associated with chromosome scaffolds

Following extensive digestion of HeLa metaphase chromosomes with either Hae III endonuclease or micrococcal nuclease, nonhistone protein scaffolds may be isolated. Scaffolds isolated after Hae III digestion have about 1.5% of the chromosomal DNA attached to them. This DNA is heterogeneous in size, ranging from about 0.2 to 20 kbp. It can be cleaved with either Eco RI or Hae III - Eco RI, producing a series of repeated fragments, of which the most abundant is 1.7 kbp in length. The 1.7-kdp fragment is tandemly repeated and is enriched (about 50-fold) in the scaffold-associated DNA. It is located primarily on human chromosome 1 and is probably a component of human satellites II and III. Scaffolds isolated after micrococcal nuclease digestion have about 0.1% of chromosomal DNA attached. This DNA is present in two size classes - fragments larger than 10 kbp and fragments approximately 0.2 kbp long. Restriction enzyme digestion of this DNA gives no prominent repeated fragments. Its reassociation kinetics are similar to those of total DNA, indicating that it is not enriched in either highly repetitive or middle repetitive sequences.     

Baseline and sodium arsenite-induced sister chromatid exchanges in cultured lymphocytes from patients with Blackfoot disease and healthy persons

Summary A significantly higher frequency of baseline sister chromatid exchange (SCE) was found in the cultured lymphocytes of 13 Blackfoot disease patients (BFP) in comparison with that of healthy persons (HP). Twelve of these BFP consumed well water containing a high concentration of arsenic for 15 years or longer and had switched to drinking tap water 12 years before the time of this study. Sodium arsenite was found to be effective in increasing the SCE frequency and delaying the cell growth of the lymphocytes from both BFP and HP. However, the SCE increment induced by sodium arsenite as well as the progression of the cell divisions in the cultured lymphocytes showed no significant difference between BFP and HP.     

A comparison of viable counts and adenine nucleotide analysis to determine the effect of antimicrobial agents on dental plaque

The effects of three antimicrobial agents on smooth surface dental plaque in monkeys were assessed using a plaque index, bacterial viable count, and adenine nucleotide analysis. The effects of the agents were revealed equally well when, viability was assayed by extractable adenosine triphosphate (ATP) or conventional viable cell counts. A persistent effect of one of the agents was revealed by both viable count and extractable ATP. These interpretations were supported by calculations of adenylate energy charge from the adenine nucleotide content of the smooth surface dental plaque samples.     

固定化葡萄糖异构酶最适pH值的调节

用多孔强碱性三乙醇胺基聚苯乙烯树脂作为载体,用CNBr与载体上多羟基作用共价偶联葡萄糖异构酶(GI)。最适偶联条件表明:CNBr量增多,蛋白载量增加,但比活下降。固定化葡萄糖异构酶(IGI)最适反应温度比天然酶提高15℃。并系统地研究了影响IGI活力-pH的曲线的各种因素:用具有不同平均孔径的载体(R=137A,185A,230A,365A)固定化GI,在低离子强度条件下(0.0064mol/L),测定其最适pH值分别7.76,7.56,7.50,8.20。选择平均孔径为230A且具有不同数量三乙醇胺基的载体(0.94,1.05,1.13,1.37mmol/g干胶)分别固定化GI,其最适pH值分别为7.70,7.50,7.46,7.36。     

Characterisation of the Glycine Modulatory Site of the N-Methyl-d-Aspartate Receptor-Ionophore Complex in Human Brain

[3H]Glycine binding and glycine modulation of [3H]MK-801 binding have been used to study the glycine allosteric site associated with the N-methyl-D-aspartate receptor complex in postmortem human brain. The effect of glycine on [3H]MK-801 binding appeared sensitive to duration of terminal coma, and possibly postmortem delay. Thirty percent of the binding occurred in a subfraction of brain tissue and did not show enhancement by glycine and glutamic acid. [3H]Glycine binding to a subfraction free from this component was studied and showed high specific binding. KD and Bmax values showed considerable intersubject variability which did not appear to be due to demographic features or to tissue content of amino acids with an affinity for this site. The pharmacological characteristics of binding in this subfraction and a correlation between Bmax values and the maximal enhancement of [3H]MK-801 binding by glycine are consistent with [3H]glycine binding occurring to an N-methyl-D-aspartate receptor complex associated site. Further support for this is provided by a significantly lower Bmax value for [3H]glycine binding in subjects with Alzheimer's disease and reduced glycine enhancement of [3H]MK-801 binding. However, the effect of perimortem factors makes it difficult to confidently attribute this solely to a disease-related change in the receptor. The possible role of the glycine allosteric site in the treatment of neuropsychiatric disorders is discussed.     

Isolation, expression, and mutation of a rabbit skeletal muscle cDNA clone for troponin I. The role of the NH2 terminus of fast skeletal muscle troponin I in its biological activity.

A cDNA for rabbit fast skeletal muscle troponin I (TnI) was isolated and sequenced. The clone contains a coding sequence predicting a 182-amino-acid protein with a molecular mass of 21,162 daltons. The translated sequence is different from that reported by Wilkinson and Grand (Wilkinson, J. M., and Grand, R. J. A. (1978) Nature 271, 31-35) in that Arg-153, Asp-154, and Leu-155 must be inserted into their original sequence. Amino acid sequencing of adult rabbit TnI confirmed this result. In order to investigate the role of the NH2 terminus of TnI in its biological activity, we have expressed a recombinant deletion mutant (TnId57), which lacks residues 1-57, in a bacterial expression system. Both wild type TnI (WTnI) and TnId57 inhibited acto-S1-ATPase activity and this inhibition could be fully reversed by troponin C (TnC) in the presence of Ca2+. Additionally both WTnI and TnId57 bound to an actin affinity column. Thus, both inhibitory actin binding and Ca(2+)-dependent neutralization by TnC were retained in TnId57. TnC affinity chromatography was used to compare the binding of TnI and TnId57 to TnC. Using this method, two types of interaction between TnC and TnI were observed: 1) one which is metal independent (or structural) and 2) one dependent on Ca2+ or Mg2+ binding to the Ca(2+)-Mg2+ sites of TnC. The same experiments with TnId57 demonstrated that the type 1 interaction was weakened, and type 2 binding was lost. This method also revealed an interaction between TnC and TnI which is dependent upon Ca2+ binding to the Ca(2+)-specific sites of TnC and which is retained in TnId57. Taken together, these results suggest that the NH2 terminus of TnI may constitute a Ca(2+)-Mg(2+)-dependent interaction site between TnC and TnI and play, in part, a structural role in maintaining the stability of the troponin complex while the COOH terminus of TnI contains a Ca(2+)-specific site-dependent interaction site for TnC as well as the previously demonstrated Ca(2+)-sensitive inhibitory and actin binding activities.     

Inhibition of phosphoinositide turnover by praziquantel in Schistosoma mansoni.

The effect of praziquantel on phosphoinositide turnover was examined in Schistosoma mansoni to determine if this anthelminthic modulates signal transduction pathways in parasites. Adult worms were radiolabeled with [3H]myoinositol for 24 hr and total inositol phosphate levels determined in the presence of praziquantel. Praziquantel inhibited inositol phosphate turnover when activated with NaF plus AlCl3 or with the nonhydrolyzable guanine nucleotide-binding protein analogue GTP gamma S. Furthermore, praziquantel decreased basal turnover of inositol phosphates. Inhibition was seen in both male and female worms as well as in schistosomula. These data indicate that inhibition of phosphoinositide turnover may contribute to the effect of praziquantel on parasite survival within the definitive host.     

Molecular cloning and mapping of phenol degradation genes from Bacillus stearothermophilus FDTP-3 and their expression in Escherichia coli.

Two genes of the meta pathway of phenol degradation were cloned from a phenol-utilizing strain of Bacillus stearothermophilus and were mapped by subcloning and by use of a Tn5 insertion mutation. They code for phenol hydroxylase and catechol 2,3-dioxygenase, respectively. The gene encoding catechol 2,3-dioxygenase, which is more thermostable than catechol 2,3-dioxygenase encoded by the other gene, shares rather limited homology with that from Pseudomonas putida.