Olfactory responses of aquatic and terrestrial tiger salamanders to airborne and waterborne stimuli

Summary Electro-olfactograms (EOGs) were used to assess olfactory responding by aquatic larval and terrestrial adult tiger salamanders (Ambystoma tigrinum) to airborne volatile compounds, and volatile and non-volatile compounds in aqueous solution. Both forms of salamander showed saturation effects to presentations of airborne stimuli (Fig. 2). Saturation was not observed, however, to stimulus presentations in aqueous solution (Figs. 2, 3). When threshold values and concentration-response curve parameters were compared, non-volatile amino acids in solution were more potent stimuli for larvae while airborne volatiles were more potent stimuli for adults (Tables 1, 2). We infer that metamorphosis in the tiger salamander is accompanied by changes in olfactory response characteristics, due possibly to changes in receptor population, changes in perireceptor properties (e.g. mucus) or to changes in stimulus access.Abbreviations EOG electro-olfactogram - PPM (ppm) parts per million     

Isolation and Characterization of a Virus Inhibitor from Spinach (Spinacia oleracea L.)

A virus inhibiting protein (VI) was isolated from spinach (Spinacia oleracea L.). The VI inhibited infections of test plants with plus- and minus-strand RNA viruses. Inoculation of both local lesion and systemic hosts with TMV in the presence of varying amounts of the VI resulted in typical dose response curves for the number of local lesions or the amount of virus respectively. The lowest concentration of VI leading to a significant reduction in the number of local lesions was 0.06 μg/ml. The VI was found to inhibit local lesion formation only when applied within 2–3 h p.i. but still reduced the number of local lesions when applied up to 9 h prior to virus inoculation. The antiviral activity could be attributed to a protein of molecular weight 29,000 dalton with an isoelectric point of 10.3. Its activity was destroyed by heating for 30 min to 70°C. These characteristics resemble those of other virus inhibiting proteins described for members of the order Caryophyllales such as the Phytolacca inhibitor against which a serological relationship was obtained.     

Inhibition of exogenous NADH oxidation in plant mitochondria by chlorotetracycline in the presence of calcium ions

Chlorotetracycline inhibits the uncoupled oxidation of exogenous NADH by Jerusalem artichoke (Helianthus tuberosus L.) mitochondria extensively (over 80%) and rapidly (inhibition complete in 10 s) in the presence of added Ca²⁺. Half-maximal inhibition is observed at 15 μM chlorotetracycline in the presence of 2 mM Ca²⁺. The oxidation of succinate is only affected marginally by chlorotetracycline plus Ca²⁺. The inhibition of NADH oxidation and the fluorescence of CTC are well correlated. Mn²⁺ is the only other cation which shows an (increased) inhibition in the presence of chlorotetracycline. The inhibition by Ca²⁺ and chlorotetracycline disappears at acid pH, and the pH optimum in their presence is 6.4. The inhibition caused by other lipid-soluble Ca²⁺-chelators is not reversible or is enhanced by the addition of excess Ca²⁺. In contrast, inhibition caused by relatively water-soluble chelators is completely reversed by added Ca²⁺. It is suggested that a neutral 1:2 complex is formed between Ca²⁺ and chlorotetracycline which can substitute for Ca²⁺ bound at sites in the lipophilic phase of the inner mitochondrial membrane, which are essential for the activity of the external NADH dehydrogenase.     

Incidence of antibiotic-resistant Escherichia coli in milk produced in the west of Scotland

Antibiotic-resistant Esch. coli were found in 10.6% of milk samples collected from 998 farms in the west of Scotland. The incidence of both Esch. coli and antibiotic-resistant Esch. coli in milk was higher when the cattle were housed day and night than when they were outdoors. Of the 1125 Esch. coli isolates tested 22.2% were antibiotic resistant and of these 42.4% were resistant to more than one antibiotic. Escherichia coli carrying up to six resistance determinants were isolated. The possible implications to animal and human health are discussed.     

Metabolism of arachidonic acid and prostanoids in human endometrial stromal cells in monolayer culture

In the present investigation, we compared the metabolism of arachidonic acid in human endometrial stromal cells maintained in monolayer culture with that in human decidual tissues. By gas-chromatographic analysis, the distribution of arachidonic acid in glycerophospholipids and in the neutral lipids of decidual tissues and stromal cells in culture was similar. After the addition of [14C]arachidonic acid to the culture medium, steady-state conditions with respect to radioactive labeling of the lipids of the cells were attained after 24 h, except for phosphatidylethanolamine and neutral lipids. The percentage distribution of [14C]arachidonic acid in the lipids of the cells in culture was as follows: phosphatidylcholine, 41%; phosphatidylserine, 5%; phosphatidylinositol, 19%; phosphatidylethanolamine, 22%; neutral lipids, 11%. This distribution of arachidonic acid among the lipids is similar to that in decidual tissue, except for that in phosphatidylethanolamine. The amount of radioactivity in phosphatidylethanolamine continued to increase up to 72 h whereas that in neutral lipids declined after a maximum amount was present at 4 h. In the cells in monolayer culture, [14C]prostaglandin E2 and [14C]prostaglandin F2 alpha were produced from [14C]arachidonic acid, as is true in superfused decidual tissue. The similarities in arachidonic acid metabolism in these cells to that in decidual tissue are supportive of the proposition that endometrial stromal cells in monolayer culture are an appropriate model for the study of the regulation of arachidonic acid release and prostaglandin formation by endometrium and decidua vera.     

Nutrient control of brain neurotransmitter synthesis and function

Dietary fluctuations in nutrient availability are factors in the regulation of brain function. Until recently the prevailing view was that brain biochemistry and function were influenced by diet only when biochemical and clinical evidence of nutrient deficiency was present. It is now clear, however, that the brain is sensitive and responsive to diet composition. Preliminary data show that variation in vitamin and mineral nutrient intakes over ranges that are considered to maintain normal nutritional status may impact on brain biochemistry, owing to their many coenzyme roles. Furthermore, the synthesis of at least five brain neurotransmitters, namely serotonin, the catecholamines, acetylcholine, histamine, and glycine responds to dietary fluctuations in availability of their nutrient precursors, tryptophan, tyrosine, choline, histidine, and threonine, respectively. Not only are these biochemical events altered by normal variations in diet composition, but considerable evidence now exists to show that the brain uses this information to regulate many functions. Future studies can be expected to continue to elucidate the links between diet, brain neurotransmission, and brain function, and to exploit the application of these links in understanding the function of the brain under normal and disease conditions.     

Identification of phospholipid platelet-activating factor (1-0-alkyl-2-acetyl-sn-glycero-3-phosphocholine) in human amniotic fluid and urine

Human amniotic fluid and fetal urine were examined for the presence of phospholipid platelet-activating factor (PAF). PAF was detected in lipid extracts of some samples of amniotic fluid obtained from women in labor but it was undetectable in samples of amniotic fluid obtained before the onset of labor. PAF was identified by chromatographic mobility, platelet aggregation and chemical modifications. LysoPAF was also present in amniotic fluid at higher concentrations than those of PAF. Both PAF and lysoPAF were identified also in newborn and adult urine.     

Cloned nodulation genes of Rhizobium leguminosarum determine host-range specificity

Summary Three nodulation-deficient (nod) mutants of Rhizobium leguminosarum were isolated following insertion of the transposon Tn5 into pRL1JI, the R. leguminosarum plasmid known to carry the nodulation genes. DNA adjacent to the nod: Tn5 alleles was subcloned and used to probe a cosmid clone bank containing DNA from a Rhizobium strain carrying pRL1JI. Two cosmid clones which showed homology with the probe contained about 10 kb of DNA in common. The R. leguminosarum host-range determinants were found to be present within this 10 kb common region since either of the cosmid clones could enable a cured R. phaseoli strain to nodulate peas instead of Phaseolus beans, its normal host. Electron microscopy of nodules induced by Rhizobium strains cured of their normal symbiotic plasmid but containing either of the two cosmid clones showed bacteroid-forms surrounded by a peri-bacteroid membrane, indicating that normal infection had occurred. Thus it is clear that this 10 kb region of nodDNA carries the genes that determine host range and that relatively few bacterial genes may be involved in nodule and bacteroid development.     

Correlative changes in sucrose uptake, ATPase activity and membrane fluidity in carnation petals during senescence

Apparent sucrose uptake. ATPase activity and membrane fluidity changes were studied during the development and senescence of carnation flowers ( Dianthus caryophyllus L., cv. Cerise Royallette). Typical changes associated with senescence of a cut flower, such as respiration, ethylene production and fresh weight, were measured. Concomitant with a rise in respiration and ethylene production and a decline in fresh weight, a sharp decrease in apparent sucrose uptake was observed. Sucrose uptake was pH dependent (pH optimum, 5.5) and influenced by membrane integrity. Apparently, the activity of ATPase is related to sucrose uptake, because similar changes occurred during flower development. In addition, the activity of ATPase was well correlated with membrane fluidity.
It is suggested that sucrose uptake is controlled by ATPase activity, which in turn is modulated by membrane lipid fluidity. The decline in membrane fluidity associated with senescence leads to a corresponding reduction in ATPase activity and sucrose uptake. Further evidence supporting this view comes from experiments in which senescence was enhanced by 1-aminocyclopropane-l-carboxylic acid. It shortened the time to decline in fresh weight, rise in respiration and ethylene production. In parallel, reduction in membrane fluidity, ATPase activity and sucrose uptake were observed.