Hydrocarbon production in Anacystis montana and Botryococcus braunii

The production of labelled aliphatic hydrocarbons in Anacystis montana and Botryococcus braunii has been studied using Na₂CO₃ [¹⁴C] as a carbon source. The major hydrocarbon produced by A. montana is pentadecane (ca 93%) accompanied by a pentadecene (ca 4%) and other hydrocarbons in the range C₁₃-C₁₇. Long chain (C₂₁-C ₃₃) hydrocarbons could not be detected in this organism. The variety of unsaturated hydrocarbons (C₂₅-C₃₁) previously reported in Botryococcus braunii is confirmed and contrasts with the synthesis of unsaturated C₁₇ hydrocarbons only, in axenic cultures prepared from single cell isolates of this colonial alga.     

Survival of toxigenic Pasteurella multocida in aerosols and aqueous liquids.

The survival of toxigenic Pasteurella multocida in air and liquids was studied to identify possible risk factors in the etiology of atrophic rhinitis. In aerosols, at low relative humidity (28%), the viability of toxigenic P. multocida 5 min after aerosolization was at least 22% of its initial value. Viability at low relative humidity declined to 8% after 45 min. Viability at high relative humidity (79%) was 69% after 5 min and declined to 2% after 45 min. Survival of toxigenic P. multocida in liquids depended on storage and constituents in the liquid. Toxigenic P. multocida became nonculturable 1 to 14 days after inoculation in water and artificial seawater, depending on the storage temperature. Toxigenic P. multocida stored at 37 degrees C could be detected for up to 6 days in pig slurry and more than 36 days in Bacto Tryptose broth and nasal lavages. However, in Bacto Tryptose broth and nasal lavages stored at 4 degrees C, P. multocida was detected for up to 14 days whereas at 15 and 37 degrees C it was detected for more than 49 days. These results suggest that aerosols and fomites can play a role in the transmission of atrophic rhinitis.     

Examination of phenylalanine microenvironments in proteins by second-derivative absorption spectroscopy

We have employed near ultraviolet derivative absorption spectroscopy to study the microenvironments of phenylalanine residues in proteins. The use of second-derivative uv spectra in the 250- to 270-nm range effectively suppresses spectral contributions from tryptophan and tyrosine residues. Fitting a polynomial to the numerically calculated second-derivative spectrum allows precise determination of the position of the negative derivative peak near 258 nm. This position is shown to be correlated with the polarity of the microenvironments of phenylalanine residues. This approach allows monitoring of changes in the state of phenylalanine side chains during folding/unfolding of the proteins. In addition, this method permits perturbation of protein samples with ethylene glycol to be used to establish the relative degree of solvent exposure of protein phenylalanine.     

Feeding rats a diet enriched with saturated fatty acids prevents the inhibitory effects of acute and chronic ethanol exposure on the in vitro uptake of hexoses and lipids

Chow-fed rats were given 15% ethanol in their drinking water for 4 weeks, and then for the next 2 weeks of ethanol exposure they were fed isocaloric semisynthetic diets enriched in either saturated (S) or polyunsaturated (P, linoleic acid) fats. Food intake was lower in ethanol-fed (ETH) than in control (C) rats, but the average body weight gain was similar in ETH and C fed S or P. Intestinal dry weight and the percentage of the intestinal wall comprised of mucosa were more than 2-fold higher in ETH than C fed P, whereas these values were 50% lower in ETH than C fed S. The in vitro jejunal uptake of glucose and galactose was higher in ETH than C fed S, whereas the converse was true when feeding P. These effects were due to differences in the values of the maximal transport rate (Vmax), the Michaelis constant (Km), and the contribution of passive permeation. The relative permeability of the intestine to lipids was unchanged by giving ethanol or by feeding S or P, but the individual rates of uptake of most medium- and long-chain fatty acids and cholesterol were lower in ETH fed P as compared with S. In a second series of studies the acute effect of ethanol exposure was examined: animals were fed S or P for 2 weeks and the intestine was then removed: when 5% ethanol was added directly to the test solutions, there was lower in vitro jejunal and ileal uptake of glucose and higher jejunal uptake of 18:2 when rats were previously fed P, but not in those fed S. In summary; (1) feeding an isocaloric polyunsaturated fatty acid diet has a trophic effect on the intestinal mucosa of animals chronically drinking ethanol; and (2) feeding rats a diet enriched with saturated fatty acids prevents the inhibitory effects of acute and chronic ethanol exposure on the in vitro jejunal uptake of glucose, galactose and lipids observed in animals fed a polyunsaturated diet. Thus, the effect of chronic consumption of ethanol on the active and passive jejunal uptake of nutrients is influenced by the type of lipids in the animal's diet.     

Immunomodulation: suppression, enhancement and autoimmunity.

Recent reports highlight new approaches to immunointervention (suppression or enhancement) based on the known roles of lymphocyte populations, cytokines and their receptors, and adhesion molecules in immune responses. Considerable interest over the past year has focused on immunophilins (cyclophilin and the FK506-binding protein) which appear to play key roles in signal transduction within activated T cells and provide a molecular basis for new advances in immunosuppressive drug therapy.     

Salmonella serotype typhimurium phage typing. A critical evaluation

Of 12,930 Salmonella serotype typhimurium strains, phage typed during 1985-1988, 45.68% were "nontypable" by Anderson's set; the percent of typable strains decreased from 54.17 in 1986 to 30.54 in 1988. Of 90 phage patterns of sensitivity, 22 were currently encountered. Phage types 1, 18 and 104 were most frequent to strain of both human and non-human origin. In food generating S. typhimurium outbreaks, phage types 1 and 36 were prevalent. Except lysotypes 198 and 95, isolated from "single cases" in man only, all other phage types were common in man and animals, too. Introducing other typing methods to serotype typhimurium "nontypable" strains (by Anderson's set) was considered necessary for epidemiological purposes.     

pH dependence of the urea and guanidine hydrochloride denaturation of ribonuclease A and ribonuclease T1

To investigate the pH dependence of the conformational stability of ribonucleases A and T1, urea and guanidine hydrochloride denaturation curves have been determined over the pH range 2-10. The maximum conformational stability of both proteins is about 9 kcal/mol and occurs near pH 4.5 for ribonuclease T1 and between pH 7 and 9 for ribonuclease A. The pH dependence suggests that electrostatic interactions among the charged groups make a relatively small contribution to the conformational stability of these proteins. The dependence of delta G on urea concentration increases from about 1200 cal mol-1 M-1 at high pH to about 2400 cal mol-1 M-1 at low pH for ribonuclease A. This suggests that the unfolded conformations of RNase A become more accessible to urea as the net charge on the molecule increases. For RNase T1, the dependence of delta G on urea concentration is minimal near pH 6 and increases at both higher and lower pH. An analysis of information of this type for several proteins in terms of a model developed by Tanford [Tanford, C. (1964) J. Am. Chem. Soc. 86, 2050-2059] suggests that the unfolded states of proteins in urea and GdnHCl solutions may differ significantly in the extent of their interaction with denaturants. Thus, the conformations assumed by unfolded proteins may depend to at least some extent on the amino acid sequence of the protein.