Conformation of NAD+ bound to allosteric L-lactate dehydrogenase activated by chemical modification

On modification of arginine residues with 2,3-butanedione, the Thermus caldophilus L-lactate dehydrogenase is converted to an activated form that is independent of an allosteric effector, fructose 1,6-bisphosphate (Fru-1,6-P2). The conformation of NAD+ bound to the modified enzyme in the absence of Fru-1,6-P2 was investigated by means of proton NMR, analyzing the time dependence of the transferred nuclear Overhauser effect (TRNOE) and TRNOE action spectra. The inter-proton distances determined on TRNOE analysis indicated that both the nicotinamide riboside moiety and the adenosine moiety of NAD+ were in the anti conformation, the ribose rings being in the C3'-endo form. This conformation was almost the same as that of NAD+ bound to the native enzyme-Fru-1,6-P2 complex, rather than that of NAD+ bound to the free native enzyme. These results suggest that the C3'-endo-anti form of the enzyme-bound NAD+ is essential for the activation of the T. caldophilus L-lactate dehydrogenase.     

Chain conformation of copoly(γ-methyl D,L-glutamate)

Copolymers of γ-methyl D - and L -glutamates with various D /L ratios were prepared. Infrared absorption spectra of solid films were measured and sums of right- and left-handed helix contents were determined from intensities of amide V bands. Farultraviolet absorption spectra and optical rotatory dispersion of these copolymers in solutions are used to ascertain their helical character. Chain conformations of DL -copolypeptides are discussed.     

Particle size of airborne mouse crude and defined allergens

Laboratory animal allergy is a serious occupational diseases of many workers and scientists engaged in animal experimentation. Control measures depend upon characterization of allergens including airborne particles. This study measured the particle size of crude mouse urine and pelt aeroallergens generated in mouse housing rooms and compared them with mouse serum albumin, a defined major allergen. Allergens were detected by specific immunological methods. Most crude and defined allergens (74.5-86.4%) concentrated on a filter with a retention size greater than 7 microns. In distrubed air, allergen concentration increased 1.4 (albumin) to 5 (crude) fold and the proportion of small particles increased from 1.4% in calm air to 4.5% in distrubed air. This information on the generation and size distribution of aeroallergens will be important in the development of effective counter measures.     

Differential Cellular Enrichment of Gangliosides in the Mouse Cerebellum: Analysis Using Neurological Mutants

Abstract: The cellular distribution of gangliosides in the cerebellum was studied in a series of adult mouse mutants that lose specific populations of neurons. The weaver ( wv ) mutation destroys the vast majority of granule cells, whereas the Purkinje cell degeneration mutation ( pcd ) destroys the vast majority of Purkinje cells. The staggerer ( sg ) and lurcher ( Lc ) mutations, on the other hand, destroy the vast majority of both granule and Purkinje cells. A proliferation of reactive glial cells, which occurs as a consequence of neuronal loss, has been reported in the sg/sg and pcd/pcd mutants, but not in the wv/wv mutant. Compared with the normal (+/+) mice, the concentration (μg/100 mg dry weight) of G_D1a was significantly reduced in those mutants that lost granule cells, but was not reduced in the pcd/pcd mutant. The concentration of G_TIa, on the other hand, was significantly reduced in those mutants that lost Purkinje cells, but was not reduced in the wv/wv mutant. A significant elevation in the concentration of G_D3, which may be related to the proliferation of reactive glial cells, was observed in the pcd/pcd, sglsg , and Lc /+ mutants, but was not observed in the wv/wv mutant. Because these ganglioside abnormalities were confined to the cerebellum, they cannot result from genetic defects in ganglioside metabolism. Instead, these abnormalities result from a differential enrichment of gangliosides in neural membranes. Our findings suggest that G_DT1a is more heavily concentrated in granule cells than Purkinje cells, whereas the opposite appears true for G_Tla. It also appears that GD3 is enriched in reactive glial cells and may play an important role during the morphological transformation of neural membranes.     

The promoter of rbcS in a C3 plant (rice) directs organ-specific,light-dependent expression in a C4 plant (maize), but does not confer bundle sheath cell-specific expression

The small subunit of ribulose-bisphosphate carboxylase (Rubisco), encoded by rbcS, is essential for photosynthesis in both C3 and C4 plants, even though the cell specificity of rbcS expression is different between C3 and C4 plants. The C3 rbcS is specifically expressed in mesophyll cells, while the C4 rbcS is expressed in bundle sheath cells, and not mesophyll cells. Two chimeric genes were constructed consisting of the structural gene encoding -glucuronidase (GUS) controlled by the two promoters from maize (C4) and rice (C3) rbcS genes. These constructs were introduced into a C4 plant, maize. Both chimeric genes were specifically expressed in photosynthetic organs, such as leaf blade, but not in non-photosynthetic organs. The expressions of the genes were also regulated by light. However, the rice promoter drove the GUS activity mainly in mesophyll cells and relatively low in bundle sheath cells, while the maize rbcS promoter induced the activity specifically in bundle sheath cells. These results suggest that the rice promoter contains some cis-acting elements responding in an organ-pecific and light-inducible regulation manner in maize but does not contain element(s) for bundle sheath cell-specific expression, while the maize promoter does contain such element(s). Based on this result, we discuss the similarities and differences between the rice (C3) and maize (C4) rbcS promoter in terms of the evolution of the C4 photosynthetic gene.     

Dietary supplementation with docosahexaenoic acid,but not with eicosapentaenoic acid,reduces host resistance to fungal infection in mice

The effect of dietary docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on host resistance to Paracoccidioides brasiliensis infection was investigated. Mice fed palm oil supplemented with DHA showed reduced antifungal activity in the spleen and liver, as compared with mice fed palm oil or soybean oil without supplementation with DHA. Mice fed DHA-supplemented soybean oil also showed reduced antifungal activity in the liver, but the extent of reduction was less profound. This reduction in antifungal activity was not observed with EPA-supplemented palm or EPA-supplemented soybean oil. These results suggest that two factors, DHA and palm oil in combination, are involved in reducing the host resistance. DHA-enriched palm oil was also responsible for an increase in DHA concentration and a marked decrease in arachidonic acid content in the spleen and liver. However, this group did not show elevated spleen and liver phospholipid hydroperoxide levels compared with the other groups, excluding the possibility that the reduction in antifungal activity observed with DHA-enriched palm oil is due to acceleration of in vivo lipid peroxidation. Greater infection-induced increases in spleen and serum interferon-gamma concentrations were observed in mice fed DHA-enriched palm oil compared with the other groups.     

Retinal Gangliosides in RCS Mutant Rats

Abstract: The distribution of retinal gangliosides was studied in normal and mutant rats with retinal dystrophy at 30 and 180 days of age. The loss of photoreceptor cells in the retinal dystrophic RCS rats was not associated with a significant reduction in the relative distribution of any of the major retinal gangliosides. The loss of photoreceptors, however, caused a marked increase in total retinal ganglioside concentration. These findings suggest that photoreceptor cells contain a low concentration of gangliosides and that no major retinal ganglioside is localized or concentrated in these cells. The cellular localization and function of the most abundant retinal ganglioside, G_D3, is discussed.     

Advantages of a mechanistic codon substitution model for evolutionary analysis of protein-coding sequences

BACKGROUND: A mechanistic codon substitution model, in which each codon substitution rate is proportional to the product of a codon mutation rate and the average fixation probability depending on the type of amino acid replacement, has advantages over nucleotide, amino acid, and empirical codon substitution models in evolutionary analysis of protein-coding sequences. It can approximate a wide range of codon substitution processes. If no selection pressure on amino acids is taken into account, it will become equivalent to a nucleotide substitution model. If mutation rates are assumed not to depend on the codon type, then it will become essentially equivalent to an amino acid substitution model. Mutation at the nucleotide level and selection at the amino acid level can be separately evaluated. RESULTS: The present scheme for single nucleotide mutations is equivalent to the general time-reversible model, but multiple nucleotide changes in infinitesimal time are allowed. Selective constraints on the respective types of amino acid replacements are tailored to each gene in a linear function of a given estimate of selective constraints. Their good estimates are those calculated by maximizing the respective likelihoods of empirical amino acid or codon substitution frequency matrices. Akaike and Bayesian information criteria indicate that the present model performs far better than the other substitution models for all five phylogenetic trees of highly-divergent to highly-homologous sequences of chloroplast, mitochondrial, and nuclear genes. It is also shown that multiple nucleotide changes in infinitesimal time are significant in long branches, although they may be caused by compensatory substitutions or other mechanisms. The variation of selective constraint over sites fits the datasets significantly better than variable mutation rates, except for 10 slow-evolving nuclear genes of 10 mammals. An critical finding for phylogenetic analysis is that assuming variable mutation rates over sites lead to the overestimation of branch lengths.     

Tori lines mitigate seabird bycatch in a pelagic longline fishery

Reviews in Fish Biology and Fisheries - Albatross bycatch has been increasing over the past decade in the US tuna longline fishery of the central North Pacific. A controlled field...     

Some common properties of lectins from marine algae

Twelve kinds of lectins isolated from four species of marine algae, Boodlea coacta (Chlorophyta) and Hypnea japonica, Carpopeltis flabellata and Solieria robusta (Rhodophyta), were compared for their chemical and biological properties. These lectins were proteins or glycoproteins, similar to terrestrial plant lectins. However, unlike most terrestrial plant lectins, they had a small molecular size (4,200 to 25,000 daltons), were mostly monomeric, and had no affinity for monosaccharides. They strongly agglutinated trypsin-treated rabbit erythrocytes, and their activities commonly were inhibited by glycoproteins bearing N-glycans. From hemagglutination-inhibition tests with various glycoproteins and related compounds, it was found that B. coacta lectins recognize high-mannose N-glycans; H. japonica lectins complex N-glycans, and C. flabellata and S. robusta lectins recognize both types of N-glycans.