The pre-Columbian dog from Arica,Chile

Burials and mummies of dogs from the Arica, Chile, area are described. It is concluded that these dogs were brought to this area 2500 years ago by shepherds from the highlands and are still present, relatively unchanged.     

Effect of nickel on oxygen free radical metabolism

The effect of nickel on superoxide dismutase activity (SOD), as well as on rate of hydroxydopamine oxidation, was studied in vitro since lipid peroxidation has been implicated in cell damage by nickel, whose toxicity and carcinogenicity are well established. Nickel strongly inhibits SOD activity. The degree of inhibition is directly proportion to the nickel concentration (tested range 0.066 to 0.33 microgram/mL in the reaction mixture); to the substrate concentration (tested range 0.4 x 10 4M to 1.1 x 10 4M 6-hydroxydopamine); and to reaction mixture. Autoxidation of 6-hydroxydopamine was increased by nickel concentrations higher than 15 micrograms/mL. The combination of excessive oxygen free radical production and inhibition of their elimination by inhibition of SOD activity may contribute to the nickel toxicity that has been reported in industrial accidents, as well as to the high incidence of cancer occurring in nickel workers. It may also contribute to many complications in uremic patients, in whom increased serum nickel levels were reported to be in a similar range to those inhibiting SOD.     

Natural antibodies to interferon-gamma

Natural antibodies to interferon (IFN)-γ were detected in the serum of virus-infected patients and also, at a low titre, in the serum of healthy subjects. The increased titre of antibodies to IFN-γ in the sera of virus-infected patients, and its decrease with clinical resolution, indicate that these antibodies are related to viral infection and probably reflect IFN-γ production as a result of antigenic stimulationin vivo. Natural antibodies to IFN-γ were affinity purified and studied for their capability to interferein vitro with the multiple activities of the lymphokine. Data obtained show that these human anti-IFN-γ antibodies have no inhibitory effect on the antiviral and antiproliferative activity of IFN-γ and do not interfere with the binding of the lymphokine to its specific cell receptor. Instead, they can inhibit the expression of HLA-DR antigens induced by IFN-γ on U937 cells and interfere, in mixed lymphocyte culture, with the proliferation of lymphocytes and the generation of cytotoxic lymphocytes. Experiments in animal models suggest that natural antibodies to IFN-γ may have a role in the immunoregulatory process limiting the intensity and/or duration of immune response. As they can interfere only with the immunomodulating activities of IFN-γ, these antibodies might open up new therapeutic approaches to diseases with evidence of activated cell-mediated immunity.     

Organization and nucleotide sequence of the genes for ribosomal protein S2 and elongation factor Ts in Spirulina Platensis

A 6.5 kb region from the genome of the cyanobacterium Spirulina platensis was cloned using as a probe the Escherichia coli gene for ribosomal protein S2. Sequence analysis revealed, in this region, the presence of the gene for ribosomal protein S2 and part of the gene for the elongation factor Ts (EF-Ts). The arrangement rpsB-spacer-tsf resembles that reported for E. coli. The deduced amino acid sequences of the platensis S2 and EF-Ts show significant homology with the E. coli counterparts.     

Structure and function of hemoglobin in antarctic fishes and evolutionary implications

Summary The hematological features of cold-adapted, red-blooded Antarctic teleosts has prompted this study on the relationship between hemoglobin molecular structure and oxygen-binding properties. The hemolysates from 21 species of 5 families contained one component (Hb 1), often accompanied by an additional, minor one (Hb 2, 5%–10% of total). On the other hand, 3 species of Zoarcidae, a non-endemic family, had 4–5 components. All purified hemoglobins from the former group, but only 1–2 of the 4–5 hemoglobins of Zoarcidae, showed a strong Root effect (pH regulation of oxygen binding). Globins from each hemoglobin have been purified and characterised with respect to molecular structure in several species. The similarity between the complete amino acid sequence of one -chain and those of non-Antarctic -chains is lower than that among the latter sequences, suggesting independent pathways of evolution.Presented at the 5th SCAR Symposium on Antarctic Biology, Hobart, Australia (August 29th-September 3rd, 1988)     

Identification, cloning, nucleotide sequence and chromosomal map location of hns, the structural gene for Escherichia coli DNA-binding protein H-NS

Summary Beginning with a synthetic oligonucleotide probe derived from its amino acid sequence, we have identified, cloned and sequenced the hns gene encoding H-NS, an abundant Escherichia coli 15 kDa DNA-binding protein with a possible histone-like function. The amino acid sequence of the protein deduced from the nucleotide sequence is in full agreement with that determined for H-NS. By comparison of the restriction map of the cloned gene and of its neighboring regions with the physical map of E. coli K12 as well as by hybridization of the hns gene with restriction fragments derived from the total chromosome, we have located the hns gene oriented counterclockwise at 6.1 min on the E. coli chromosome, just before an IS30 insertion element.     

Human erythrocyte glucose-6-phosphate dehydrogenase. Identification of a reactive lysyl residue labelled with pyridoxal 5'-phosphate

Human erythrocyte glucose-6-phosphate dehydrogenase contains a reactive lysyl residue, which can be labelled with pyridoxal 5'-phosphate. The binding of one mole of pyridoxal 5'-phosphate per mole of enzyme subunit produces substantial inactivation. The substrate glucose-6-phosphate prevents the loss of activity, suggesting that the reaction site is close to the substrate-binding site. A tryptic peptide containing the pyridoxal-5'-phosphate-binding lysyl residue has been isolated and characterised. The reactive lysyl residue has been identified in the glucose-6-phosphate dehydrogenase amino acid sequence. Comparison with glucose-6-phosphate dehydrogenase from other sources shows a high homology with a peptide containing a reactive lysyl residue, isolated from the enzyme from Saccharomyces cerevisiae; glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides also contains a region highly homologous with the sequence around the reactive lysyl residue in the human enzyme. The results of this communication provide the first direct evidence for the association of an essential catalytic function with a specific region of the molecule of human erythrocyte glucose-6-phosphate dehydrogenase.     

Cyclic AMP activation of a triglyceride lipase in broken cell preparations of rat heart

The effect of CAM [cyclic AMP, Mg-ATP, and 3-isobutyl, 1-methylxanthine (MIX)] on triacylglycerol (TG) lipase activity in extracts from heparin-perfused rat heart was determined. TG lipase activity in homogenate, 10,000g supernatant, 105,000g supernatant, ammonium sulfate supernatant, and the eluate from heparin-Sepharose was increased between 62 and 151% when incubated with a combination of 0.3 mM cyclic AMP, 5 mM MgCl2, and 2 mM ATP. The addition of Mg-ATP + cyclic AMP caused a greater activation of TG lipase in the various fractions than did Mg-ATP + MIX or cyclic AMP + MIX. These results suggest that activation may be mediated by the classical cyclic AMP-protein kinase cascade. Control and CAM-stimulated activities were increased by heparin and inhibited by NaCl and protamine sulfate. In the absence of serum in the assay, the CAM system caused a relatively greater stimulation of lipolytic activity in each fraction compared to when serum was present in the assay. However, the absolute values were 6.1 to 16.3-fold greater with serum in the assay than without serum. In a similar manner, TG lipase activity was stimulated by CAM between 1.75 and 4.26-fold at pH 7.4, and only between 1.62 and 2.51-fold at pH 8.1. However, the absolute values at pH 8.1 were 6.77 to 31.83-fold greater than those seen at pH 7.4. These data demonstrate, for the first time, the cyclic AMP activation of a TG lipase above basal levels in cell-free fractions of rat heart. It is intriguing to speculate that the intracellular fraction of lipoprotein lipase may play a role in the hormonal regulation of cardiac TG lipolysis.