An experimental analysis of cache recovery in Clark's nutcracker

Five hypotheses of cache recovery behaviour in Clark's nutcracker (Nucifraga columbiana) were examined experimentally. Most caches were made in soil within 5 cm of conspicuous large objects. Both seed-caching and non-seed-caching nutcrackers were able to locate caches. Seed-caching nutcrackers relocated caches using large objects as remembered visual cues. Soil microtopography and small (<2 cm diameter) objects may be used as cues to facilitate cache recovery but are not essential. Non-seed-caching nutcrackers located caches by using soil disturbances at cache sites as visual cues and by searching preferentially near objects where caches were concentrated. Success rates of seed-caching nutcrackers ranged from 52 to 78% and those of non-seed-caching nutcrackers ranged from 8 to 12%. Nutcrackers do not use random search or olfactory cues to locate caches.     

Analogs of oxytocin containing a modified peptide bond

Analogs of deamino-oxytocin and deamino-oxypressin containing a CH2-NH group instead of an amide bond between positions 8 and 9 were synthesized. All tested compounds exhibit significantly lowered biological activities.     

Increased demand for NAD+ relative to ATP drives aerobic glycolysis

1. Download : Download high-res image (172KB)
2. Download : Download full-size image

     

Insulin-mediated modifications of myocardial lipoprotein lipase and lipoprotein metabolism

Recirculating organ perfusion in vitro was conducted with hearts from control rats, animals given a single dose of streptozotocin (65 mg/kg) 48 h earlier, and streptozotocin-treated rats administered insulin (5 units), 2 h prior to organ perfusion. During 45-min perfusions, the lipolysis of very low density lipoprotein (VLDL) triglyceride was significantly less in hearts from diabetics than in controls (41.9 +/- 7.3% of control). This was associated with significant reductions in heparin-releasable (functional) lipoprotein lipase and tissue lipoprotein lipase of perfused hearts. The decreases in VLDL triglyceride metabolism and the levels of myocardial lipoprotein lipase were completely reversed by treatment of diabetic rats with insulin 2 h prior to study. Similar improvement of VLDL triglyceride metabolism and increases in myocardial lipoprotein lipase activity were observed in hearts from diabetic rats by direct addition of 100 milliunits/ml of insulin to the recirculating perfusion media. Under these conditions, the increase in both fractions of lipoprotein lipase in response to insulin was completely inhibited, and utilization of VLDL triglyceride was partially inhibited by pre-perfusion with cycloheximide for 10 min. The data derived from either VLDL triglyceride lipolysis in organ perfusion or direct measurement of myocardial lipoprotein lipase demonstrate a direct effect of insulin on myocardial lipoprotein lipase activity, and suggest that the response to insulin may be due in part to effects on protein synthesis.     

Characterization of adenine phosphoribosyltransferase from the human malaria parasite, Plasmodium falciparum

Because of their inability to synthesize purines de novo, malaria parasites rely on purine phosphoribosyltransferases (PRTases) to convert purine bases salvaged from the host cell (the erythrocyte) into the corresponding purine nucleoside monophosphates. Our studies with late trophozoites of the human malaria parasite, Plasmodium falciparum, showed that virtually all of the purine PRTase activity is accounted for by two distinct enzymes. One enzyme utilizes hypoxanthine, guanine and xanthine (Queen, S.A., Vander Jagt, D. and Reyes, P. (1988) Mol. Biochem. Parasitol. 30, 123-134). The second enzyme utilizes only adenine and is the subject of this paper. This latter enzyme exhibits a biphasic pH-activity profile and is moderately to weakly inhibited by several divalent metal ions. Several of the properties of the P. falciparum enzyme were found to differ significantly from those of human erythrocyte adenine PRTase. (1) The molecular weight (18,000) of the parasite enzyme is smaller than that of the host cell enzyme. (2) The parasite enzyme, unlike the erythrocyte enzyme, is not significantly inhibited by sulfhydryl reagents. (3) 6-Mercaptopurine and 2,6-diaminopurine proved to be competitive inhibitors of the parasite enzyme (Ki 0.70 and 1.0 mM, respectively); on the other hand, the human enzyme is not inhibited by these agents. (4) The Km for adenine (0.80 microM) and 5-phosphoribosyl-1-pyrophosphate (0.70 microM) displayed by the parasite enzyme are significantly smaller than the corresponding Km values shown by the erythrocyte enzyme. These distinctions between the parasite and host enzymes point to the possibility that adenine PRTase of P. falciparum may represent a potential target for chemotherapeutic attack.     

N2-Succinylornithine in ornithine catabolism of Pseudomonas aeruginosa

Most Pseudomonas aeruginosa PAO mutants which were unable to utilize l-arginine as the sole carbon and nitrogen source (aru mutants) under aerobic conditions were also affected in l-ornithine utilization. These aru mutants were impaired in one or several enzymes involved in the conversion of N²-succinylornithine to glutamate and succinate, indicating that the latter steps of the arginine succinyltransferase pathway can be used for ornithine catabolism. Addition of aminooxyacetate, an inhibitor of the N²-succinylornithine 5-aminotransferase, to resting cells of P. aeruginosa in ornithine medium led to the accumulation of N²-succinylornithine. In crude extracts of P. aeruginosa an ornithine succinyltransferase (l-ornithine:succinyl-CoA N²-succinyltransferase) activity could be detected. An aru mutant having reduced arginine succinyltransferase activity also had correspondingly low levels of ornithine succinyltransferase. Thus, in P. aeruginosa, these two activities might be due to the same enzyme, which initiates aerobic arginine and ornithine catabolism.Abbreviations OAT ornithine 5-aminotransferase - SOAT N²-succinylornithine 5-aminotransferase - Oru ornithine utilization - Aru arginine utilization     

Inhibition of human immunodeficiency virus type 1 multiplication by antisense and sense RNA expression.

Human immunodeficiency virus type 1 (HIV-1) primarily infects CD4+ lymphocytes and macrophages and causes AIDS in humans. Retroviral vectors allowing neomycin phosphotransferase (npt) gene expression were engineered to express 5' sequences of HIV-1 RNA in the antisense or sense orientation and used to transform the human CD4+ lymphocyte-derived MT4 cell line. Cells expressing antisense or sense RNA to the HIV-1 tat mRNA leader sequence, as part of the 3' untranslated region of the npt mRNA, remained sensitive to HIV-1 infection. In contrast, resistance to HIV-1 infection was observed in cells expressing antisense RNA to the HIV-1 primer-binding site or to the region 5' to the primer-binding site as part of the 3' region of the npt mRNA. Cells expressing the tat mRNA leader sequence in the sense orientation as a precise replacement of the 5' untranslated region of npt mRNA were also resistant to HIV-1. These results indicate that sense and antisense approaches can be used to interfere with HIV-1 multiplication.     

Wound closure of the myelomeningocoele defect

Our experience with 74 neonates with myelomeningocoele is reported. Management in the first phase of the study period consisted of primary closure in 37 patients by wide undermining and skin advancement, marked by a high wound-complication rate. Latissimus dorsi muscle closure, either "reverse" or advanced, was performed in a transitional phase in 5 patients, characterized by increased operative time and blood loss. In the last portion of the study period, 32 patients were managed by immediate dural closure and skin grafts either simultaneously or on a delayed basis at 48 to 72 hours with a low incidence of graft loss, CSF leak, or sepsis. Back ulceration and follow-up in either the primary closure or the skin-grafted group has been infrequent.     

Fly pupae as attractant carriers for toxic baits for red imported fire ants (Hymenoptera: Formicidae)

Eight laboratory-reared ant species were fed baits of house fly, Musca domestica L., pupae treated with hydramethylnon. Two fire ant species, Solenopsis invicta Buren and Solenopsis geminata (F.), and Pheidole morrissi (Forel) were killed; average percentage of mortality of the five other species was less than 20%. In contrast, all species that were fed the commercial fire ant bait containing hydramethylnon (Amdro) died or were adversely affected. In the field, applications of house fly pupae and eye gnat, Hippelates pusio Loew, pupae dipped in acetone solutions of fenoxycarb significantly reduced population indices of the red imported fire ant, S. invicta, compared with commercial formulations of fenoxycarb (Logic) and hydramethylnon (Amdro). Field observations showed that the pupae of either species can be carried or moved by one or two worker ants. The smooth, hard cuticle of the pupae make them easy to handle and apply with application equipment. The current cost of house fly pupae is considerably more than the cost of a granular carrier, pregel defatted corn grits. However, if mass-production methods reduce this price differential, fly pupae could become an effective and more species-specific fire ant bait carrier.