Does conditioned taste aversion learning in the pond snail Lymnaea stagnalis produce conditioned fear?

In conditioned taste aversion (CTA) training performed on the pond snail Lymnaea stagnalis, a stimulus (the conditional stimulus, CS; e.g., sucrose) that elicits a feeding response is paired with an aversive stimulus (the unconditional stimulus, US) that elicits the whole-body withdrawal response and inhibits feeding. After CTA training and memory formation, the CS no longer elicits feeding. We hypothesize that one reason for this result is that after CTA training the CS now elicits a fear response. Consistent with this hypothesis, we predict the CS will cause (1) the heart to skip a beat and (2) a significant change in the heart rate. Such changes are seen in mammalian preparations exposed to fearful stimuli. We found that in snails exhibiting long-term memory for one-trial CTA (i.e., good learners) the CS significantly increased the probability of a skipped heartbeat, but did not significantly change the heart rate. The probability of a skipped heartbeat was unaltered in control snails given backward conditioning (US followed by CS) or in snails that did not acquire associative learning (i.e., poor learners) after the one-trial CTA training. These results suggest that as a consequence of acquiring CTA, the CS evokes conditioned fear in the conditioned snails, as evidenced by a change in the nervous system control of cardiac activity.     

Unraveling the plant diversity of the Amazonian canga through DNA barcoding

The canga of the Serra dos Carajás, in Eastern Amazon, is home to a unique open plant community, harboring several endemic and rare species. Although a complete flora survey has been recently published, scarce to no genetic information is available for most plant species of the ironstone outcrops of the Serra dos Carajás. In this scenario, DNA barcoding appears as a fast and effective approach to assess the genetic diversity of the Serra dos Carajás flora, considering the growing need for robust biodiversity conservation planning in such an area with industrial mining activities. Thus, after testing eight different DNA barcode markers (matK, rbcL, rpoB, rpoC1, atpF‐atpH, psbK‐psbI, trnH‐psbA, and ITS2), we chose rbcL and ITS2 as the most suitable markers for a broad application in the regional flora. Here we describe DNA barcodes for 1,130 specimens of 538 species, 323 genera, and 115 families of vascular plants from a highly diverse flora in the Amazon basin, with a total of 344 species being barcoded for the first time. In addition, we assessed the potential of using DNA metabarcoding of bulk samples for surveying plant diversity in the canga. Upon achieving the first comprehensive DNA barcoding effort directed to a complete flora in the Brazilian Amazon, we discuss the relevance of our results to guide future conservation measures in the Serra dos Carajás.     

Studies on DNA markers (D4S10 and D4S43/S127) genetically linked to Huntington's disease in Japanese families

Summary This is the first full report on the genetic linkage between Japanese Huntington's disease and the DNA markers D4S10 and D4S43/S127. With use of the HindIII, BglI, and EcoRI polymorphisms detected at D4S10, and the combination of all these polymorphisms to give composite haplotypes, nine Japanese Huntington's disease families were found to be informative. Three recombinants for D4S10 were detected in these families, giving a maximum lod score of 1.662 at a of 0.10. Similarly, when we used the MspI and PvuII polymorphisms detected by D4S43/S127, five families gave informative results. No recombinant was detected in these families, giving a maximum lod score of 3.348 at a of 0.00. These results clearly support the view that the Japanese Huntington's disease gene may be identical with the Western gene, in spite of the lower prevalence rate in Japan.     

Antibody-mediated in vitro neutralization of human immunodeficiency virus type 1 abolishes infectivity for chimpanzees.

This study was undertaken to establish whether antibody directed against the human immunodeficiency virus type 1 (HIV-1) principal gp120 type-specific neutralization determinant can abolish the infectivity of HIV-1 in chimpanzees. Challenge inocula of the IIIb virus isolate were mixed in vitro with either immunoglobulin G (IgG) from an uninfected chimpanzee, nonneutralizing IgG from an HIV-seropositive human, a virus-neutralizing murine monoclonal antibody directed against the HIV-1 IIIb isolate, or virus-neutralizing IgG from a chimpanzee infected with the IIIb isolate. Both neutralizing antibodies were directed against the principal neutralization determinant of the challenge isolate. Establishment of infection following inoculation of each virus-antibody mixture into chimpanzees was assessed by virus-specific antibody development and by virus isolation. No protective effect was noted either with the control IgG or with the nonneutralizing anti-HIV IgG. By contrast, the polyclonal chimpanzee virus-neutralizing IgG prevented HIV-1 in vivo infection, while the neutralizing monoclonal antibody notably decreased the infectivity of the challenge virus. Hence, antibody to the gp120 principal neutralization determinant is able both to prevent HIV-1 infection in vitro and to inhibit infection in vivo.     

Production of Nucleic Acid-Related Substances by Fermentative Processes

An adenine-requiring mutant (KY7208) of Brevibacterium ammoniagenes ATTC 6872 was found to accumulate an appreciable quantity of IMP and hypoxanthine in the culture liquid.

Crystalline IMP was isolated from culture broth of KY7208 by the use of ion-exchange columns. The preparation obtained was definitely identified as 5′-IMP, based on the results on paperchromatography, UV and IR absorption spectra, and analyses of its hydrolysates.

Growth responses of this mutant were demonstrated to adenine and adenosine, but not to 5′-AMP, 3′-AMP and 5′-AMP.

Over 5 mg of IMP per ml of broth were produced by the organism in natural medium consisting of glucose, yeast extract, urea, high concentrations of phosphate and magnesim salts, and others. The chemical changes showed that hypoxanthine first accumulated in the earlier stage of fermentation, and IMP synthesis then took place with the disappearance of hypoxanthine in the later stage of fermentation.     

Production of Nucleic Acid Related Substances by Fermentative Processes

It was found that a guanine and adenine-requiring mutant of Micrococcus glutamicus accumulated the ultraviolet-absorbing substance in the culture fluid. A KY9978 strain, which accumulated the largest amount of the substance, we selected from the guanine auxotrophs derived from the guanineadenine doubleless mutant. The substance was isolated in a crystalline form from the culture fluid by the use of ion exchange resins, Diaion SA 21A and SK No. 1, and identified chemically and enzymatically as 5′-xanthylic acid, an intermediate from 5′-inosinic acid to 5′-guanylic acid on the purine nucleotide biosynthesis.     

Liver mevalonate 5-pyrophosphate decarboxylase is responsible for reduced serum cholesterol in stroke-prone spontaneously hypertensive rat.

Spontaneously hypertensive rat (stroke-prone) (SHRSP) has an interestingly low serum cholesterol level due to a reduced biosynthesis of cholesterol in the liver (Iritani, N., Fukuda, E., Nara, Y., and Yamori, Y. (1977) Atherosclerosis 28, 217-222). In this study, we examined the mechanism underlying the reduction of hepatic cholesterol biosynthesis in the rat. Our initial findings in SHRSP, as compared with normotensive Wistar Kyoto rat (WKY), showed that 1) the incorporation of [14C]acetate into cholesterol in the liver slices was markedly less, 2) 3-hydroxyl-3-methylglutaryl (HMG) CoA reductase activity was not reduced, and 3) the incorporation of [3H]mevalonic acid into both cholesterol and squalene was significantly less. The above initial findings suggested that the reduction in the hepatic cholesterol biosynthesis took place in one or more enzymatic processes starting with mevalonic acid and continuing to squalene. When the incorporation of [3H]mevalonic acid into phosphomevalonate derivatives was studied using an ion exchange column, only the radioactivity incorporated into isopentenyl-pyrophosphate (isopentenyl-PP) was less in SHRSP. Furthermore, the specific activity of diphosphomevalonate (mevalonate-PP) decarboxylase in the liver-soluble fractions was reduced 50% in SHRSP as compared with WKY. Kinetic studies using liver crude extracts indicated a lower Vmax value in SHRSP (SHRSP, 0.47; WKY, 2.05 nmol/min/mg), and an unchanged Km value (SHRSP, 18.2; WKY, 19.6 microM). The activity of mevalonate-PP decarboxylase was also found to be reduced in other tissues, including the brain, testis, small intestine, and cultured vascular smooth muscle cells. From the above observations, we concluded that the lower activity of mevalonate-PP decarboxylase was responsible for the reduced cholesterol biosynthesis in the liver of SHRSP.     

Preferential recognition of zwitterionic dipeptides as transportable substrates by the high-affinity peptide transporter PEPT2.

We investigated the interaction of rat PEPT2, a high-affinity peptide transporter, with neutral, anionic, and cationic dipeptides using electrophysiological approaches as well as tracer uptake methods. D-Phe-L-Gln (neutral), D-Phe-L-Glu (anionic), and D-Phe-L-Lys (cationic) were used as representative, non-hydrolyzable, dipeptides. All three dipeptides induced H+-dependent inward currents in Xenopus laevis oocytes heterologously expressing rat PEPT2. The H+:peptide stoichiometry was 1:1 in each case. A simultaneous measurement of radiolabeled dipeptide influx and charge transfer in the same oocyte indicated a transfer of one net positive charge into the oocyte per transfer of one peptide molecule irrespective of the charged nature of the peptide. We conclude that the zwitterionic peptides are preferentially recognized by PEPT2 as transportable substrates and that the proton/peptide stoichiometry is 1 for the transport process.