Preparation of scirpentriol and triacetoxyscirpenol in good yield from cultures of Fusarium sambucinum NRRL 13495

Crude extracts of filtrates of cultures of Fusarium sambucinum NRRL 13495 were acetylated or hydrolyzed. After chromatography on cartridge columns of silica gel and recrystallization three times from mixtures of ethyl acetate and hexane, 3,4,15-triacetoxyscirpenol (435 +/- 10 mg/liter of filtrate; mean +/- standard error [n = 3]) and the parent alcohol scirpentriol were isolated (261 +/- 29 mg/liter of filtrate; mean +/- standard error [n = 3]) in 68 and 53% yield for a 130- and 14-fold improvement, respectively, over prior reports.     

Species-specific algal responses to zooplankton: experimental and field observations in three nutrient-limited lakes

A series of 4-day manipulations of zooplankton biomass and nutrientavailability was performed in enclosures in three lakes to determinespecies-specific algal responses to herbivory and nutrient enrichment.Algal performance in enclosures was compared to the relationshipsbetween weekly algal growth rates and the zooplankton in situ.When in situ growth rates were significant functions of zooplanktonbiomass, the responses were generally consistent with responsesin the enclosure experiments. The importance of both nutrientsand zooplankton in mediating algal growth was demonstrated bynumerous observations: strong algal community response to enrichment,unimodal or positive responses of certain algal taxa to zooplanktonbiomass, differences in degree of nutrient limitation amongthe algal response types, lack of nutrient limitation of non-grazedalgal taxa and a preponderance of taxa with no net responseto increasing zooplankton biomass. Variation in the zooplanktoncommunity may be the largest source of variability in nutrientsupply rate during summer in stratified lakes, and causes substationalvariability in the algae. Algae responded more strongly to changesin zooplankton composition than to changes in zooplankton biomass.We conclude that, due to the close coupling of phytoplanktonand zooplankton communities in these nutrient-limited lakes,major compositional changes in the zooplankton have greatereffects on the algae than do changes in biomass of grazers alreadypresent. ¹Present address: Division of Environmental Studies, Universityof California, Davis, CA 95616, USA ²Present address: Division of Biological Sciences, Universityof California, Davis, CA 95616, USA     

Genetic association between nest building and brown adipose tissue thermogenesis in female house mice

Summary Mice selectively bred for either high or low levels of thermoregulatory nest building were cold-acclimated (5°C) for 3 weeks without nesting material; then body weight and food intake were measured. The mice selected for low nest building (Lows) of both sexes showed lower feed efficiencies than the high nest-building mice (Highs), although their body weights were not significantly different (Table 1). This adds to a large body of evidence which suggests that nest building and feed efficiency were influenced by a common mechanism (Lacy et al. 1978; Sulzbach and Lynch 1984; Lunch et al. 1981; Lynch and Roberts 1984).Brown adipose tissue mitochondrial GDP binding and cytochrome c oxidase activity were measured in the above mice. In females, the Lows had 100% higher levels of total GDP binding than the Highs, while no difference between the lines was seen in males (Fig. 2). Thus in the High females, lower energy expenditure through brown fat thermogenesis may account for their greater feed efficiency. In males, the genetic differences in feed efficiency must be due to differences in either thermogenesis in tissues other than brown fat, or mechanisms which reduce heat loss.Abbreviations Highs Mice from lines selectively bred for high levels of nest-building;Lows mice from the low nest-building selected lines     

Altered Mitochondrial Respiration in Selectively Vulnerable Brain Subregions Following Transient Forebrain Ischemia in the Rat

Mitochondrial respiratory function, assessed from the rate of oxygen uptake by homogenates of rat brain subregions, was examined after 30 min of forebrain ischemia and at recirculation periods of up to 48 h. Ischemia-sensitive regions which develop extensive neuronal loss during the recirculation period (dorsal-lateral striatum, CA1 hippocampus) were compared with ischemia-resistant areas (paramedian neocortex, CA3 plus CA4 hippocampus). All areas showed reductions (to 53-69% of control) during ischemia for oxygen uptake rates determined in the presence of ADP or an uncoupling agent, which then recovered within 1 h of cerebral recirculation. In the ischemia-resistant regions, oxygen uptake rates remained similar to control values for at least 48 h of recirculation. After 3 h of recirculation, a significant decrease in respiratory activity (measured in the presence of ADP or uncoupling agent) was observed in the dorsal-lateral striatum which progressed to reductions of greater than 65% of the initial activity by 24 h. In the CA1 hippocampus, oxygen uptake rates were unchanged for 24 h, but were significantly reduced (by 30% in the presence of uncoupling agent) at 48 h. These alterations parallel the development of histological evidence of ischemic cell change determined previously and apparently precede the appearance of differential changes between sensitive and resistant regions in the content of high-energy phosphate compounds. These results suggest that alterations of mitochondrial activity are a relatively early change in the development of ischemic cell death and provide a sensitive biochemical marker for this process.     

Correlation of adenosine receptor affinities and cardiovascular activity

Binding affinities of 28 adenosine analogs at A1 adenosine receptors (rat whole brain membranes, [3H]N6-cyclohexyladenosine, CHA), and at A2 adenosine receptors (rat striatal membranes, [3H]NECA) were compared to their EC25 values for decreasing heart rate and increasing coronary flow in the isolated rat heart. Heart rate (an A1 response) correlated with A1 binding affinity (r2 = 0.71, p less than 0.0001) but not with A2 binding affinity (r2 = 0.007, n.s.); conversely, coronary flow (an A2 response) correlated with A2 binding affinity (r2 = 0.83, p less than 0.0001) but not with A1 binding affinity (r2 = 0.05, n.s.). These results confirm that the brain A1 and A2 receptors, studied by binding methods, bear close similarities to their respective counterparts in the heart, studied by means of functional responses.     

Variations in Membrane Sensitivity of Brain Region Synaptosomes to the Effects of Ethanol In Vitro and Chronic In Vivo Treatment

The effects of chronic ethanol treatment on the membrane order of synaptosomes from the cerebral cortex, striatum, cerebellum, brainstem, and hippocampus of rats were determined by measuring the fluorescence polarization of diphenylhexatriene (DPH) that had been incorporated into the synaptosomal membranes. Fischer-344 rats either were fed a nutritionally complete ethanol-containing liquid diet for 5 months or pair-fed with a diet that contained sucrose substituted isocalorically for ethanol. Polarization values for synaptosomes from all the brain regions studied were similar except for those from cerebral cortical synaptosomal membranes, which were significantly less ordered. Ethanol in vitro (30-500 mM) decreased the polarization values in synaptosomes from sucrose-control rats for all brain regions, although the sensitivity of cerebellar synaptosomes to the membrane disordering effects of ethanol in vitro was significantly greater that of synaptosomes from other brain regions. Chronic ethanol treatment did not alter baseline polarization for any brain region. Cerebellar and brainstem synaptosomes from the ethanol-fed rats were significantly less susceptible to the membrane disordering effects of ethanol in vitro compared to their sucrose controls, suggesting that chronic ethanol administration results in tolerance to ethanol's membrane effects. Striatal synaptosomes exhibited intermediate tolerance, whereas the sensitivities of cortical and hippocampal synaptosomes to membrane disordering by ethanol in vitro were not significantly affected by the chronic ethanol treatment. These results suggest that synaptosomal membranes have different membrane order requirements depending on the brain region from which they are prepared. Variations in brain regional neuronal membrane sensitivity to ethanol and differential tolerance development may contribute to some of the acute and chronic behavioral effects of ethanol.     

Clostridium acetobutylicum Mutants That Produce Butyraldehyde and Altered Quantities of Solvents

Spontaneous mutants of Clostridium acetobutylicum NRRL B643 that were resistant to allyl alcohol (AA) were selected and characterized. These mutants contained 10- to 100-fold reduced activities of butanol and ethanol alcohol dehydrogenase. The AA mutants formed two groups and produced no ethanol. Type 1 AA mutants produced significant amounts of a new solvent, butyraldehyde, and contained normal levels of the coenzyme A-dependent butyraldehyde dehydrogenase (BAD). Type 2 AA mutants produced no significant butyraldehyde and lower levels of all solvents, and they contained 45- to 100-fold lower activity levels of BAD. Following ethyl methanesulfonate mutagenesis, low-acid-producing (Acid⁻) mutants were selected and characterized as superinduced solvent producers, yielding more than 99% of theoretical glucose carbon as solvents and only small amounts of acetate and butyrate. Following ethyl methanesulfonate mutagenesis, 13 sporulation-negative (Spo⁻) mutants were characterized; and 3 were found to produce only butyrate and acetate, a minor amount of acetone, and no alcohols. These Spo⁻ mutants contained reduced butanol dehydrogenase activity and no BAD enzyme activity. The data support the view that the type 2 AA, the Acid⁻, and the Spo⁻ mutants somehow alter normal regulated expression of the solvent pathway in C. acetobutylicum.     

Transbilayer movement of bile acids in model membranes

The ability of bile acids to traverse membranes has important implications for their reabsorption from the gut, recirculation to and uptake into the liver, and resecretion into bile. The rate constant for transbilayer movement, or "flip-flop", of three common, unconjugated bile acids was determined by 13C nuclear magnetic resonance spectroscopy. At high pH, the sodium salts of the bile acids did not appreciably traverse the bilayer; however, upon protonation a rapid equilibration between the inner and outer monolayers occurred. The rate of flip-flop of each bile acid at 37 degrees C was found to be dependent on both number and location of hydroxyl groups but not on concentration in the bilayer over the range studied (2-4 wt%) nor on the presence of a different bile acid in the same bilayer.     

Gene recombination in X-ray-sensitive hamster cells.

Recombination was measured in Chinese hamster ovary (CHO-K1) cells and in the X-ray-sensitive mutants xrs1 and xrs7, which show a defect in DNA double-strand break repair. To assay recombination, pairs of derivatives of the plasmid pSV2gpt were constructed with nonoverlapping deletions in the gpt gene region and cotransferred into the different cell types. Recombination efficiencies, measured as the transformation frequency with a pair of deletion plasmids relative to that with the complete pSV2gpt plasmid, were about 6% in both CHO-K1 and the xrs mutants for plasmids linearized at a site outside the gpt gene. However, these efficiencies were substantially enhanced by the introduction of a double-strand break into the homologous region of the gpt gene in one of a pair of deletion plasmids before cotransfer. This enhancement was apparently only about half as great for the xrs cells as for CHO-K1, but variation in the data was considerable. A much larger difference between CHO-K1 and the xrs mutants was found when the DNA concentration dependence of transformation was explored. While the transformation frequency of CHO-K1 increased linearly with DNA concentration, no such increase occurred with the xrs mutants irrespective of whether complete plasmids or pairs of deletion plasmids were transferred. The fraction of cells taking up DNA, assayed autoradiographically, was similar in all cell types. Therefore we suggest that while homologous recombination of plasmid molecules may not be substantially reduced in the xrs mutants,processes involved in the stable integration of plasmid DNA into genomic DNA are significantly impaired.