Polymorphisms of DQ β genes in HLA-DR4 haplotypes from healthy and diabetic individuals

The restriction fragment length polymorphism (RFLP) of DQ was assessed in a panel of control and insulin-dependent diabetes (IDD) patients who were serologically typed as HLA-DR4 homozygotes or HLA-DR3, DR4 heterozygotes. Digestions of genomic DNA with Barn HI, Bg1 II, Pst I, Xba I, and Hind III revealed a total of 15 RFLPs in the panel of 71 HLA-DR4 chromosomes. These RFLPs were organized into six allelic groups on the basis of segregation analysis in families. Complete RFLP haplotypes for the 5 restriction enzymes could be constructed for 42 of the HLA-DR4 chromosomes. This analysis revealed 18 RFLP haplotypes of DQ associated with the DR4 chromosomes tested. Two of these haplotypes, designated DQ3.DR4.a and DQ3.DR4.b, accounted for over 50 % of the DR4 chromosomes analyzed. These two haplotypes were antithetical for the RFLPs detected by all five enzymes, indicating that they represent very distinct forms of DQ . The remaining 16 haplotypes were infrequent or unique and were closely related to either a DQ3.DR4.a or DQ3.DR4.b. Two of the RFLPs detected, a 5.8 kb Bg1 II fragment and a 10.5 kb Barn HI fragment, had increased frequencies in disease-associated chromosomes. However, none of the RFLPs we detected exhibited a statistically significant increase in IDD or control populations. In contrast, the DQ3.DR4.b DQ haplotype was significantly decreased in IDD-associated DR4 chromosomes. (P=0.04). These results suggest that the DQ3.DR4.b DQ allele may be protective for the development of IDD.     

Characterization of phycoerythrin-containing Synechococcus spp. populations by immunofluorescence

Using an immunofluorescence assay developed to identify serogroups(i.e. clusters of strains labelled by one antiserum), the compositionof natural populations of phycoerythrin-containing Synechococcusspp. was examined. The 7803 (open ocean clone)-serogroup wasfound in most oceanic regions, but was most prevalent (up to85%) in tropical and subtropical waters during spring and summer.At coastal Long Island stations it was most abundant (up to65%) when water temperatures were >22°C. The seasonaland geographic distribution of the 7803-serogroup appeared tobe limited by water temperature. No consistent pattern was observedin the per cent composition with depth in the Sargasso Sea orat coastal to offshore stations in the North-west Atlantic Oceanor eastern tropical North Pacific Ocean. The 8016 (coastal clone)-serogroupwas abundant at coastal and estuarine stations off Long Island(up to 95 %) and its appearance was also correlated with warmwater temperature (> 15°C). However, this serogroup remaineda constant proportion of the population at the Long Island Soundstation during early winter months (through January) when abundanceof the 7803-serogroup was negligible. Owing to limited data,the oceanic distribution of the 8016-serogroup is not yet discernible.Lastly, antisera to the phycocyanin-dominant Synechococcus spp.clones failed to label any cells in samples collected from severaloceanic stations. Thus, these strains appear to be limited tocoastal and estuarine regions, which is consistent with predictionsfrom experiments comparing the photosynthetic performance ofthe phycoerythrin-dominant and phycocyanin-dominant clones. ¹Present address: Department of Oceanography, University ofHawaii, Honolulu, HI 96822, USA     

Biochemical Characterization of Molybdenum-Cofactor in a Cyanobacterium, Nostoc muscorum

Cell-free extracts of nitrate-grown Nostoc muscorum containnitrate reductase and molybdenum-cofactor activities. Whilenitrate reductase activity is associated with the paniculatefraction, cofactor activity is found predominantly in the solublefraction. This activity was distributed between two pools. Inone pool, the molybdenumcofactor is associated with a carrier(protein) of approximately 30,000 Da with an S_{20, w} between2.3 and 2.5. The carrier-bound cofactor is non-dialyzable andis found along with the major proteins during filtration inSephadex G-25 and G-100. The second pool contains free or unboundcofactor. It is separated from soluble proteins by dialysiswith a membrane with a pore-size of 10 to 15 kDa. However, itis retained with a membrane with a pore size of 1 kDa. It isin the included volume during chromatography through SephadexG-25. Its molecular mass is estimated to be between 1,000 and5,000 Da. The molybdenum content was proportional to cofactoractivity in both pools. Reducing agents increased cofactor activity.However, activity in both pools was sensitive to heat, acid,and oxidative treatments. The carrier protein appears to givesome protection. ¹Fulbright Scholar from Department of Biological Sciences, R.D. University, Jabalpur-482001, India. To whom reprint requestsshould be addressed. (Received June 22, 1987; Accepted August 21, 1987)     

Calcium Dependence of Vasoactive Intestinal Peptide-Stimulated Cyclic AMP Accumulation in Rat Hippocampal Slices

Previous work has shown that incubation of hippocampal slices in medium without added calcium markedly attenuates the capacity of vasoactive intestinal peptide (VIP) to elevate cyclic AMP levels. The present studies examined the mechanism that confers calcium dependence on VIP stimulation of cyclic AMP accumulation in hippocampal slices. Calcium dependence was apparent immediately on slice preparation and was reversible only if calcium ions were added back very early during slice incubation (within 5 min). The cyclic AMP response to VIP was not abolished by preincubating slices in 100 microM adenosine, suggesting that calcium-dependent, VIP-induced release of adenosine does not mediate VIP elevation of cyclic AMP. VIP-stimulated cyclic AMP accumulation was not decreased by agents that block calcium influx (verapamil, nifedipine, magnesium ions), or by calmodulin antagonists (trifluoperazine, calmidozolium). In fact both verapamil (100 microM) and magnesium (14 mM) augmented VIP stimulation of cyclic AMP generation. Incubation of slices with the phosphodiesterase inhibitor 1-methyl-3-isobutylxanthine (MIX) did not affect VIP activation of cyclic AMP accumulation if slices were incubated without added calcium, but MIX did enhance VIP elevation of cyclic AMP content in slices incubated with calcium. Thus calcium dependence of the cyclic AMP response to VIP in hippocampal slices is unlikely to result from VIP-dependent calcium influx, from interactions with calmodulin, or from calcium-inhibited phosphodiesterase(s).(ABSTRACT TRUNCATED AT 250 WORDS)     

Detection of phospholipid peroxides in biological samples

Peroxidation of membrane lipids has been hypothesized to play a key role in various types of tissue degeneration and pathology. Lipid peroxides are formed when oxygen reacts with an unsaturated fatty acid chain. Virtually all of the unsaturated fatty acids in biological systems are bound by ester linkages in phospholipids or triglycerides. Phospholipid and triglyceride peroxides are primary products of lipid peroxidation and have rarely been measured. Most of the commonly used methods for detection of lipid peroxidation are based on detection of malondialdehyde or other chemical species that are derived from oxidized fatty acids. This review presents an overview of recently developed methods aimed at identifying and measuring oxidized phospholipids and triglycerides which are direct evidence of the occurrence of lipid peroxidation in vivo.     

Ecology of heath communities dominated by Cassiope tetragona at Alexandra Fiord, Ellesmere Island, Canada

At a high arctic lowland on Ellesmere Island, heath communities dominated by Cassiope tetragona were widespread, and occurred in a variety of habitats that differred in time of snowmelt, relative site moisture, soil thaw depth, and air and soil temperature. Cover, standing crop, and production were dominated by woody plants, notably Cassiope tetragona and Dryas integrifolia . The Cassiope -dominated heaths were similar in composition to those at other Canadian high arctic localities, but were less similar to localities in Greenland and Spitzbergen. Compositional relationships among Cassiope -dominated heaths in different habitats at the study site may be largely determined by two interrelated environmental factors, time of snowmelt and site moisture.
Aboveground vascular plant biomass was concentrated near the ground surface, resulting in simple vertical structure that takes advantage of relatively warm soil and air temperatures in summer, and a protective snow cover in winter. Aboveground vascular plant standing crop was largely comprised of attached dead tissue, and there were equal proportions of above- and belowground biomass. Low community production was due to dominance by long-lived, slow-growing species, and to short growing seasons and cold temperatures. Overall character of Cassiope -dominated heaths reflects the conservative, stress tolerant growth strategy of the dominant species, Cassiope tetragona .     

Distinct phases of the fluorescence response of the lipophilic probe N-phenyl-1-naphthylamine in intact cells and membrane vesicles of Escherichia coli

The fluorescence of the lipophilic prbe N-phenyl-1-naphthylamine (NPN) bound to intact cells of Escherichia coli is quenched by the addition of glucose, succinate, -lactate, pyruvate, formate and glycerol. Partial recovery of fluorescence occurs on anaerobiosis. Use of mutants with defects in the ATP synthase or the respiratory chain show that quenching of fluorescence may be energized either by ATP hydrolysis or by substrate oxidation through the respiratory chain. Permeabilization of the outer membrane by treatment of intact cells with EDTA, or use of a mutant with an outer membrane permeable to lipophilic substances, results in a more rapid binding of NPN and in a decrease in quenching observed on substrate addition. NPN binds rapidly to everted membrane vesicles, but does not respond to membrane energization. It is proposed that inner membrane energization in intact cells alters the binding or environment of NPN in the outer membrane. The fluorescence recovery which occurs on anaerobiosis has two components. One component represents a reversal of the changes which occur on membrane energization. The other component of the fluorescence change is insensitive to the uncoupler CCCP and resembles the behaviour of NPN with everted membrane vesicles. It is suggested that a portion of the fluorescence events seen with NPN involves a response of the probe to changes in the inner membrane.     

Aging alterations in the modulation of central dopaminergic cilioinhibition by etorphine in the marine mussel,Mytilus edulis: Decrease in the inhibition of presynaptic dopamine release

1. This report further demonstrates that etorphine influences presynaptic dopamine release, which in turn centrally modulates peripheral cilioinhibition. 2. In older animals cilioinhibition has become enhanced due to a lack of responsiveness to endogenous opioids which results in greater dopamine release, causing a higher level of cilioinhibition as demonstrated by challenging the visceral ganglia with etorphine or destroying the dopaminergic component with 6-hydroxydopamine. 3. Only the central cilioinhibitory, not the peripheral inhibitory response, mechanism appears to be altered in older animals. Thus, the alteration appears in the central integrative mechanisms involved with regulating ciliary activity. 4. The KCl-stimulated release of dopamine is unaltered in both young and old organisms, whereas the opiate inhibition of the KCl-stimulated release of dopamine is reduced in older organisms. Thus, the aging-associated alteration is associated with a specific process. 5. The reduction of opioid influence and the resulting enhanced cilioinhibitory activity may make the organisms more susceptible to environmental stress.     

Biological reductive dechlorination of tetrachloroethylene and trichloroethylene to ethylene under methanogenic conditions

A biological process for remediation of groundwater contaminated with tetrachloroethylene (PCE) and trichloroethylene (TCE) can only be applied if the transformation products are environmentally acceptable. Studies with enrichment cultures of PCE- and TCE-degrading microorganisms provide evidence that, under methanogenic conditions, mixed cultures are able to completely dechlorinate PCE and TCE to ethylene, a product which is environmentally acceptable. Radiotracer studies with [14C]PCE indicated that [14C]ethylene was the terminal product; significant conversion to 14CO2 or 14CH4 was not observed. The rate-limiting step in the pathway appeared to be conversion of vinyl chloride to ethylene. To sustain reductive dechlorination of PCE and TCE, it was necessary to supply an electron donor; methanol was the most effective, although hydrogen, formate, acetate, and glucose also served. Studies with the inhibitor 2-bromoethanesulfonate suggested that methanogens played a key role in the observed biotransformations of PCE and TCE.     

Conformational differences between two wheat (Triticum aestivum) ''high-molecular-weight'' glutenin subunits are due to a short region containing six amino acid differences.

'High-molecular-weight' (HMW, high-Mr) glutenin subunits are protein constituents of wheat (Triticum aestivum) seeds and are responsible in part for the viscoelasticity of the dough used to make bread. Two subunits, numbered 10 and 12, are the products of allelic genes. Their amino acid sequences have been derived from the nucleic acid sequences of the respective genes. Subunit 10 has fewer amino acids than subunit 12, but migrates more slowly on SDS/PAGE (polyacrylamide-gel electrophoresis). This anomaly is due to between one and six of the amino acid differences between the subunits, localized towards the C-terminal end of the proteins. This has been established by making chimaeric genes between the genes for subunits 10 and 12, transcribing and translating them in vitro and analysing the products by SDS/PAGE. The postulated conformational differences between subunits 10 and 12 are discussed in relation to current hypotheses for the structure of HMW glutenin subunits.