Insulin-induced expression of human heat-shock protein gene hsp70

In human hepatoma cell line Hep3B/T2, the human heat-shock-inducible gene hsp70 could be induced by insulin. The dose-dependent insulin effect correlates very well with the dissociation constant of the insulin receptor, indicating that the insulin effect is mediated by the insulin receptor. The expression of hsp70 gene was neither significantly induced by growth factors of epidermal and platelet-derived growth factors, nor by tumor promoter, calcium ionophore, cAMP, and glucocorticoids. These results indicate that the induction of expression of hsp70 gene by insulin is very specific and not cell cycle-related. Furthermore, the insulin-induced expression of hsp70 gene is transient, occurring specifically from 4 to 8 h after insulin addition.     

Evaluation of the quality of bedside monitoring of the blood glucose level in a teaching hospital.

We evaluated the precision and accuracy of monitoring of the blood glucose level in the laboratory and at the bedside with one of four glucose meters by an experienced operator and by 39 nurses in a teaching hospital. For precision studies aqueous quality control materials were used. A total of 85 blood samples were tested. The precision of the glucose meters (expressed as the coefficient of variation [CV]) in the hands of the experienced operator ranged from 6.7% to 11.1%. The correlation between the values obtained by the experienced operator and the reference values obtained in the laboratory was high (0.95 to 0.98). The precision of the values obtained by the nurses using the meters ranged from 13.7% on medical wards to 45.7% in the intensive care unit (ICU). The correlation between these values and those obtained in the central laboratory ranged from 0.72 to 0.82. Twenty-four percent of the glucose values determined on medical wards and 62% of those determined in the ICU deviated from the reference value by at least 20%. Of the 85 patients 12 (14%) would have received different insulin dosages had the reference value been available at the same time as the glucose meter reading: in 3 of the patients the discrepancy was 6 units of insulin or greater. Continuous quality control of bedside monitoring of the blood glucose level is needed. In addition, personnel who use glucose meters should receive adequate training.     

Effects of Various Levels of CO(2) on the Induction of Crassulacean Acid Metabolism in Portulacaria afra (L.) Jacq

In response to water stress, Portulacaria afra (L.) Jacq. (Portulacaceae) shifts its photosynthetic carbon metabolism from the Calvin-Benson cycle for CO₂ fixation (C₃) photosynthesis or Crassulacean acid metabolism (CAM)-cycling, during which organic acids fluctuate with a C₃-type of gas exchange, to CAM. During the CAM induction, various attributes of CAM appear, such as stomatal closure during the day, increase in diurnal fluctuation of organic acids, and an increase in phosphoenolpyruvate carboxylase activity. It was hypothesized that stomatal closure due to water stress may induce changes in internal CO₂ concentration and that these changes in CO₂ could be a factor in CAM induction. Experiments were conducted to test this hypothesis. Well-watered plants and plants from which water was withheld starting at the beginning of the experiment were subjected to low (40 ppm), normal (ca. 330 ppm), and high (950 ppm) CO₂ during the day with normal concentrations of CO₂ during the night for 16 days. In water-stressed and in well-watered plants, CAM induction as ascertained by fluctuation of total titratable acidity, fluctuation of malic acid, stomatal conductance, CO₂ uptake, and phosphoenolpyruvate carboxylase activity, remained unaffected by low, normal, or high CO₂ treatments. In well-watered plants, however, both low and high ambient concentrations of CO₂ tended to reduce organic acid concentrations, low concentrations of CO₂ reducing the organic acids more than high CO₂. It was concluded that exposing the plants to the CO₂ concentrations mentioned had no effect on inducing or reducing the induction of CAM and that the effect of water stress on CAM induction is probably mediated by its effects on biochemical components of leaf metabolism.     

Confidence Intervals on Ratios of Variance Components for the Unbalanced Two Factor Nested Model

The model considered in this article is the two-factor nested unbalanced variance component model: for p = 1, 2, …, P; q = 1, 2, …, Q_p; and r = 1, 2, …, R_pq. The random variables Y_pqr are observable. The constant μ is an unknown parameter, and A_p, B_pq and C_pqr are (unobservable) normal and independently distributed random variables with zero means and finite variances σ²_A, σ²_B, and σ²_C, respectively. Approximate confidence intervals on ?_A and ?_B using unweighted means are derived, where The performance of these approximate confidence intervals are evaluated using computer simulation. The simulated results indicate that these proposed confidence intervals perform satisfactorily and can be used in applied problems.     

Age, gender and circadian or circasemidian blood pressure and heart rate variation of children.

Systolic (S) and diastolic (D) blood pressure (BP) and heart rate (HR) of clinically healthy children (24 boys and 15 girls) 3 to 7 years of age were measured with a standard mercury sphygmomanometer at 3-hour intervals for 24 hours in April 1991. The children slept and/or rested from 2100 to 0700 and napped from 1230 to 1530; they had meals at 0730, 1200 and 1800. A statistically significant circadian and about 12-hour (circasemidian) component of variation is documented for SBP and DBP of boys and girls and for HR of boys. No gender difference was found for the circadian and circasemidian components. A positive correlation with age is found for the MESOR and circadian amplitude of SBP and DBP (p < 0.05); a negative correlation with age is found for the MESOR of HR (p < 0.001).     

Amino acid substitution analysis of E. coli thymidylate synthase: The study of a highly conserved region at the N-terminus

Amino acid substitution analysis within a highly conserved region of Escherichia coli thymidylate synthase (TS), using suppression of amber mutations by tRNA suppressors, has yielded a bank of 124 new mutationally altered TS proteins. These mutant proteins have been used to study the structure-function relationship of the Escherichia coli TS protein at the N-terminus corresponding to residues 20 through 35. This region contains a block of amino acids whose sequence has been well conserved among other known TS proteins from various organisms. Positions 20 through 25 contain a surface loop structure and positions 26 through 35 encompass a β-strand. We find that residues surrounding a β-bulge structure within the β-strand are particularly sensitive to amino acid substitution, suggesting that this structure is maintained by a highly ordered packing arrangement. Three residues in the surface loop that are present at the base of the substrate binding pocket are also sensitive to amino acid substitution. The remainder of the conserved sites, including those at the dimer interface, are tolerant to most, if not all, of the substitutions tested. © 1992 Wiley-Liss, Inc.     

Production of hepatitis delta virus and suppression of helper hepatitis B virus in a human hepatoma cell line.

The hepatitis delta virus (HDV) is a defective virus with a coat composing of the surface antigen of its helper virus, hepatitis B virus (HBV). Replication of HDV in the absence of HBV has been shown in cell cultures by transient transfection of the HDV plasmid. However, the formation and release of HDV virions have not been observed. In this report, a human hepatoma cell line HuH-7 was transiently cotransfected with HDV and HBV plasmids. The production of monomeric and multimeric antigenomic RNAs of HDV in the transfected cells indicated replication of the HDV genome. The major 3.5- and 2.1-kb RNAs of HBV were also expressed. Virions of both HDV and HBV were released from the cotransfected cells, as shown by the detection of monomeric genomic HDV RNA and partially double-stranded HBV DNA in the culture medium. Thus, this is the first report that describes the assembly and the release of HDV viral particles in an in vitro cell culture. The HDV virions released possessed physicochemical properties identical to those of the HDV virions found in infected human serum. Furthermore, expression of both the 3.5- and 2.1-kb RNAs of HBV was shown to be dramatically decreased by the presence of HDV, indicating suppression of the expression of HBV genes by HDV. The amount of HBV virions released was similarly suppressed by HDV. Cotransfection of HBV with an expression plasmid of the HDV delta antigen remarkably reduced the levels of the 3.5- and 2.1-kb HBV RNAs, indicating that suppression of the expression of HBV RNAs by HDV occurs via the action of the delta antigen. This HBV- and HDV-cotransfected human hepatoma cell line should provide an excellent system for the study of the function of the delta antigen and the interaction between HDV and its helper, HBV.     

Identification and characterization of an {alpha}-mannosidase from Trypanosoma cruzi

In this report we describe the first purification and characterizationof the acid -mannosidase from the human parasite Trypanosomacruzi. The purified enzyme exhibited a native mol. wt of 240000 Da and is apparently composed of four identical subunitsof mol. wt 58 000 Da. Each of the four subunits contains oneN-linked high-mannose-type oligosaccharide. The -mannosidaseexhibited a pH optimum of 3.5 and a pI of 5.9. This low pH optimumand the ability of swainsonine to inhibit its activity suggestthat the -mannosidase is a lysosomal enzyme. Antibodies againstthe T.cruzi enzyme did not react with mammalian lysosomal -mannosidaseand, conversely, antibody against a rat lysosomal -mannosidasedid not react with the T.cruzi enzyme. Thus, the T.cruzi enzymeappears to be distinct from its mammalian counterpart. -mannosidase lysosomal enzyme Trypanosoma cruzi