Relation between the radioprotective effect of helium-neon laser radiation on bacterial cells and the time period between 2 types of irradiation

The effect of helium-neon laser radiation (lambda = 633 nm) given to E. coli K-12 cells of various genotypes 4 h following X- or alpha-irradiation was shown to increase the number of viable cells. The irreversible ingradient of a radiation injury to cells remained invariable during the first 60 min after irradiation its values being minimal.     

The effect of egg incubation temperature on the activity of cytochrome oxidase and anionic ATPase in chicken ontogenesis

The short-term cooling of hen eggs under incubation was studied for its effect on the dynamics of the activity of cytochrome oxidase (CO) and anion ATPase in the brain and liver of 15- and 20-day hen embryos and 5-day chickens. The temperature fall in the embryonal period was established to stimulate the activity of bicarbonate-dependent ATPase in the brain and to suppress it in the liver tissue. The CO activity was also subjected to similar alterations.     

Thermoregulatory uncoupling of oxidation and phosphorylation in the chick brain in embryogenesis]

The cooling of hen incubated eggs to 28 degrees C brings to disconnection of oxidative phosphorylation in brain on the 12th day of development. The addition of DNP (5 x 10(-5) M) takes off the cooling effect.     

Analysis of insulin-specific T cell clones. I. Strategy for production of clonotypic antibody

A novel strategy for production of T cell clone-specific antiserum is described. Clones that are both antigen-specific and alloreactive can be injected in small numbers i.v. into a strain which expresses the appropriate alloantigens, inducing consistently high-titered antisera containing antibodies to the unique T cell receptor molecules on these cells. The antisera characterized in this report block activation of these cells by either antigen plus autologous class II products or alloantigen. Furthermore, in the absence of antigen, the antiserum strongly stimulates the specific clones to divide, and to synthesize and secrete various proteins. Consistent with the findings of other investigators, the antiserum immunoprecipitates a disulfide-linked dimer of 90,000 m.w. from the surfaces of cells with the appropriate specificity.     

Some properties of human and bovine brain cathepsin B

Cathespin B has been purified 750-fold to apparent homogeneity from human and bovine brain cortex using ammonium sulfate fractionation (30–70%), chromatography on Sephadex G-100, CM-Sephadex C-50, and concanavalin A-Sepharose. Enzyme was assayed fluorometrically at pH 4.0 with pyridoxyl-hemoglobin in the presence of 1 mM DTT and 1 mM EDTA. Properties of the enzyme from the two sources proved to be similar. On disc PAGE the purified preparation produced two bands associated with proteinase activity that are due to existence of two multiple forms of brain cathepsin B with pI 6.1 and 6.8. The enzyme is completely inactivated by thiol-blocking reagents, leupeptin, E-64, and demands thiol compounds for its ultimate activity. Z-Phe-Ala-CHN₂ is a potent inhibitor of the enzyme (K _2nd=1280 M⁻¹s⁻¹) in contrast to Z-Phe-Phe-CHN₂ (K _2nd=264 M⁻¹s⁻¹). pH optimum in the reaction of hydrolysis of Pxy-Hb is 4.0–6.0,K _M(app.) =10⁻⁵ M. Cathepsin B splits azocasein: pH optimum 5.0–6.0,K _M(app.)=2.2·10⁻⁵ M, but inclusion of urea in the incubation medium depresses the azocaseinolytic activity of the enzyme 1.5-fold. It does not split Lys-NNap, Arg-NMec and is not inhibited by bestatin. The specific activity of brain cathepsin B with Z-Arg-Arg-NNapOMe at pH 6.0 is 10-fold higher than with Bz-Arg-NNap, Z-Gly-Gly-Arg-NNap is a poor substrate. With Z-Arg-Arg-NMec and Bz-Phe-Val-Arg-NMec the specific acitivity is 80 and 35%, respectively of that with Z-Phe-Arg-NMec. Special Issue dedicated to Dr. Eugene Kreps.     

Osmosensitivity of the 2H+−K+-exchange and the H+-ATPase complex F0F1 in anaerobically grownEscherichia coli

Escherichia coli grown anaerobically for osmotic studies upon increased osmolarity in alkaline medium carried out H⁺–K⁺-exchange in two steps, the first of which was DCCD¹ sensitive and osmo-dependent and had the 2H⁺/K⁺ stoichiometry. H⁺-efflux in the presence of protonophore (CCCP) upon increase of osmolarity was shown to be high and inhibited by DCCD, whereas H⁺-efflux induced by a decrease of osmolarity was small and not inhibited by DCCD. The 2H⁺/K⁺-exchange was absent intrkA anduncA mutants. InuncB mutant 2H⁺/K⁺-exchange was not DCCD-and osmosensitive. Competition between DCCD and osmoshock on inhibition of 2H⁺/K⁺-exchange was found. Osmosensitivity of this exchange disappeared in spheroplasts. Osmosensitivity of both 2H⁺/K⁺-exchange and the F₀F₁ and osmoregulation of the F₀F₁ via F₀ and a periplasmic space are postulated.Abbreviations F₀F₁ H⁺-ATPase complex - F₀ H⁺-channel, proteolipid - F₁ H⁺-ATPase - Trk constitutive system for K⁺ uptake - PV periplasmic protein valve - DCCD N,N-dicyclohexylcarbodiimide - CCCP carbonylcyanide-m-chlorophenylhydrazone - _H or _K transmembrane electrochemical gradient for H⁺ or K⁺ respectively - membrane potential - upshock or downshock increase or decrease of medium osmolarity, respectively - CGSC E. coli Genetic Stock Center, Yale University, USA     

Effects of hydrocortisone on the hypercalcemia and plasma levels of 13,14-dihydro-15-keto-prostaglandin E2 in mice bearing the HSDM1 fibrosarcoma

In mice bearing the prostaglandin-producing HSDM₁ fibrosarcoma, the plasma concentration of 13,14-dihydro-15-keto-PGE₂ was elevated before the development of hypercalcemia, and the magnitude of the rise was greater than that of PGE₂. When hydrocortisone, which inhibits synthesis of PGE₂ by HSDM₁ cells in culture, was administered to tumor-bearing mice, the steroid hormone prevented the rises in plasma PGE₂ metabolite and calcium concentrations. At the dose levels used, hydrocortisone did not inhibit the calcium-mobilizing action of parathyroid hormone $\text{in vivo}$ or the bone resorption-stimulating activity of $\text{PGE}{}_2\text{in vitro}$. These findings are consistent with our hypothesis that the hypercalcemic syndrome in HSDM₁ tumor-bearing mice is due to the secretion of PGE₂ by the tumor.     

Proteins synthesized by inducer T cells: evidence for a mitogenic peptide shared by inducer molecules that stimulate different cell types

Inducer T lymphocytes synthesize and secrete peptides that stimulate growth and differentiation of many cell types, including lymphocytes and monocytes that kill foreign organisms, B lymphocytes, mast cells and hematopoietic precursor cells. To define these inducer molecules more precisely, we have generated clones of these T cells as a source of homogeneous material for biochemical analysis. These clones synthesize peptides that stimulate T and B cells to divide and that also induce the latter cells to secrete immunoglobulin. Inducer cells synthesize a 14 kilodalton growth polypeptide that stimulates T and B lymphocytes, as well as other cell types, to divide. This 14 kilodalton peptide is normally associated with different, larger peptides that appear to focus its mitogenic activity to one or another target cell.     

Genetic and Segregation Analysis of Escherichia coli Strains Containing a Tandem Duplication of the trpD-purB Region of the Chromosome

Genetic and segregation analysis of Escherichia coli strains containing a partial duplication of the trp operon reveal that the 2.5-min-long region trpD-purB is duplicated in tandem in the chromosome. The adjacent loci cysB and fabD are not duplicated. Although one copy of the duplicated region is longer than the maximum size of bacteriophage P1kc transducing fragments, the frequency at which the duplicated segment trpDCBA is transferred by transduction to tonB-trp deletion strains is equal to that observed for transfer of the normal trp operon. This suggests that three-point recombination events believed to account for transduction of long duplications occur as frequently as two-point recombination events believed to account for normal transduction. Cotransduction frequencies of trpDCBA with the duplicated loci tonB, galU, tyrT, and hemA are very similar to those for the trp operon with the same loci. This indicates that normal genetic linkage is maintained during the three-point recombination event. However, purB, which is normally unlinked to trp by transduction, is closely linked to trpDCBA and thus must be near the repeat point of the duplication. Transduction tests with point mutations in the trp operon indicated that the repeat point occurs near the normal boundary between trpE and trpD. Segregation analysis of heterogenotes constructed from tonB-trp deletion strains shows that the frequency at which a marker is lost is approximately proportional to its distance from the repeat point. This finding is consistent with a random, singlesite crossover event during segregation. Several observations indicate that non-reciprocal genetic exchange also occurs between copies of the duplication. Analysis of heterogenotes containing dadR1 and dadR(+) demonstrate that the mutant allele is transdominant.