Comparative analyses of human immunodeficiency virus type 1 (HIV-1) and HIV-2 Vif mutants.

Virion infectivity factor (vif), a gene found in all lentiviruses, plays an essential role in virus replication in certain target cells. We examined the replication competence of the human immunodeficiency virus type 2 (HIV-2) vif mutant in different T-cell lines and primary cells in comparison with that of the HIV-1 vif mutant. Both mutant viruses were unable to replicate in peripheral blood-derived mononuclear cells but replicated with wild-type efficiency in certain T-cell lines, such as SupT1 and MOLT-4/8. These results confirm the importance of vif in the infection of relevant target cells and imply that some cellular factor(s) could compensate for vif function. However, HIV-1 and HIV-2 vif mutant viruses also show differential replications in other cell lines, suggesting either different threshold requirements for the same cellular factor(s) or the involvement of different factors to compensate for vif-1 and vif-2 functions. By cross complementation experiments, we showed that vif-1 and vif-2 have similar functions. Our studies further indicate the existence of two kinds of nonpermissive cells: H9 is unable to complement HIV-1 delta vif but is susceptible to a one-round infection with HIV-1 delta vif produced from permissive cells. In contrast, U937 is nonpermissive for HIV-2 delta vif produced from permissive cells but, once infected, is able to complement the delta vif function. In both types of nonpermissive cells, a step prior to proviral DNA synthesis is affected.     

Chemistry in environmentally benign media Part 1. Synthesis and characterization of 1,2-bis[bis(hydroxymethyl)phosphino]ethane (‘HMPE’). X-ray structure of [Pt{(HOH2C)2PCH2CH2P(CH2OH)2}2](Cl)2

The water-soluble bisphosphine, 1,2-bis(bis(hydroxymethyl)phosphino)ethane (1), was synthesized in near quantitative yield by the reaction of bisphosphine, H₂PCH₂CH₂PH₂, with an aqueous formaldehyde in the presence of K₂PtCl₄. The reaction of this water-soluble bisphosphine 1 with cis-Pt(COD)Cl₂ affords the mononuclear bischelate complex, [Pt{(HOH₂C)₂PCH₂CH₂P(CH₂OH)₂}₂](Cl)₂ (2), in near quantitative yield. The new ligand and complex have been characterized spectroscopically and the structure of the metal complex, 2, was determined by X-ray crystallography. The Pt(II) complex 2 crystallizes in the orthorhombic space group Pbca(a=14.623(1), B=16.216(2), C=9.319(4) Å) with Z=4. The final R value is 0.024.     

Forms and distribution of inorganic phosphorus in sediments of two shallow eutrophic lakes in Florida

Physicochemical attributes were measured and aquatic macroinvertebrates were collected from six wetlands near Perth, Western Australia at three weekly intervals over a 13 month period from August 1988 to September 1989. The six wetlands encompassed a range of depths, pH, concuctivities, nutrient concentrations and colours. Temporal changes in the macroinvertebrate communities appeared to be related to seasonal changes in the physical and chemical characteristics of the wetlands. Community composition differed more between the less enriched wetlands then the higly enriched wetlands where communities were generally similar. High species richness was associated with seasonal drying. High macro invertebrate abundance appeared to be associated with the presence of either green algal or cyanobacterial blooms in the enriched wetlands. The highest macroinvertebrate biomass was recorded in wetlands with both cyanobacterial blooms and abundant macrophytes present.     

Crystal structure of the hydroxylase component of methane monooxygenase from Methylosinus trichosporium OB3b.

Methane monooxygenase (MMO), found in aerobic methanotrophic bacteria, catalyzes the O2-dependent conversion of methane to methanol. The soluble form of the enzyme (sMMO) consists of three components: a reductase, a regulatory "B" component (MMOB), and a hydroxylase component (MMOH), which contains a hydroxo-bridged dinuclear iron cluster. Two genera of methanotrophs, termed Type X and Type II, which differ markedly in cellular and metabolic characteristics, are known to produce the sMMO. The structure of MMOH from the Type X methanotroph Methylococcus capsulatus Bath (MMO Bath) has been reported recently. Two different structures were found for the essential diiron cluster, depending upon the temperature at which the diffraction data were collected. In order to extend the structural studies to the Type II methanotrophs and to determine whether one of the two known MMOH structures is generally applicable to the MMOH family, we have determined the crystal structure of the MMOH from Type II Methylosinus trichosporium OB3b (MMO OB3b) in two crystal forms to 2.0 A resolution, respectively, both determined at 18 degrees C. The crystal forms differ in that MMOB was present during crystallization of the second form. Both crystal forms, however, yielded very similar results for the structure of the MMOH. Most of the major structural features of the MMOH Bath were also maintained with high fidelity. The two irons of the active site cluster of MMOH OB3b are bridged by two OH (or one OH and one H2O), as well as both carboxylate oxygens of Glu alpha 144. This bis-mu-hydroxo-bridged "diamond core" structure, with a short Fe-Fe distance of 2.99 A, is unique for the resting state of proteins containing analogous diiron clusters, and is very similar to the structure reported for the cluster from flash frozen (-160 degrees C) crystals of MMOH Bath, suggesting a common active site structure for the soluble MMOHs. The high-resolution structure of MMOH OB3b indicates 26 consecutive amino acid sequence differences in the beta chain when compared to the previously reported sequence inferred from the cloned gene. Fifteen additional sequence differences distributed randomly over the three chains were also observed, including D alpha 209E, a ligand of one of the irons.     

The prevalence of Fasciola hepatica in its snail intermediate host determined by DNA probe assay

Accurate snail intermediate host infection prevalence data have the potential to be extremely useful in determining seasonal transmission dynamics of Fasciola hepatica. Because the microscopic techniques currently used lack the sensitivity and specificity necessary to obtain meaningful infection prevalence data, we developed a highly accurate and efficient DNA probe assay. The assay has a sensitivity of 100%, a specificity of >99%, easily detects a single miracidia and does not cross-hybridize with DNA of Fascioloides magna, Paramphistomum liorchis or Heterobilharzia americana, trematodes that share the same intermediate host and enzootic range as Fasciola hepatica. Using this assay, we determined the prevalence of F. hepatica in its snail intermediate host, Fossaria cubensis, during the second year of a 2-year study on the epizootiology of Fasciola hepatica in Florida. The overall infection prevalence of snails assayed in this study (n = 5246) was 1.5% and ranged from 0.1% to 3.1% for individual cattle ranches. Additionally, infection prevalence differed significantly for successive size groupings of snails, varying from 0% for 1-mm snails to 18.5% for 9- and 10-mm snails. The accuracy and efficiency of the DNA probe assay reported here for determining snail infection prevalence offers an inexpensive alternative to tracer animal studies for determining the epizootiology of F. hepatica.     

Interaction of Fusarium oxysporum f. sp. ciceri and Meloidogyne javanica on Cicer arietinum

Interaction of Meloidogyne javanica and Fusarium oxysporum f. sp. ciceri was studied on Fusarium wilt-susceptible (JG 62 and K 850) and resistant (JG 74 and Avrodhi) chickpea cultivars. In greenhouse experiments, inoculation of M. javanica juveniles prior to F. oxysporum f. sp. ciceri caused greater wilt incidence in susceptible cultivars and induced vascular discoloration in roots of resistant cultivars. Nematode reproduction was greatest (P = 0.05) at 25 °C. Number of galls and percentage of root area galled increased when the temperature was increased from 15 °C to 25 °C. Wilt incidence was greater at 20 °C than at 25 °C. Chlorosis of leaves and vascular discoloration of plants did not occur at 15 °C. The nematode enhanced the wilt incidence in wilt-susceptible cultivars only at 25 °C. Interaction between the two pathogens on shoot and root weights was significant only at 20 °C, and F. o. ciceri suppressed the nematode density at this temperature. Wilt incidence was greater in clayey (48% clay) than in loamy sand (85% sand) soils. The nematode caused greater plant damage on loamy sand than on clayey soil. Fusarium wilt resistance in Avrodhi and JG 74 was stable in the presence of M. javanica across temperatures and soil types.     

Lectin recognition of host-like saccharide motifs in streptococcal cell wall polysaccharides

Viridans streptococci that participate in the microbial colonizationof teeth have cell wall polysaccharides composed of linear phosphodiester-linkedhexa- or heptasaccharide repeating units, each containing ahost-like disaccharide motif, either Galß1     

Purification of rabbit liver phosphofructokinase and its properties under simulatingin vivo conditions

Phosphofructokinase (EC 2.7.1.11) from rabbit liver was purified to homogeneity. Preincubation of enzyme results in nonlinearity of enzyme activity with enzyme concentration. Therefore K_0.5 of enzyme for fructose 6 phosphate in the absence or presence of fructose 2,6 bisphosphate or polyethylene glycol or in the presence of both was determined at physiological concentrations of its various effectors by taking the initial rate obtained by adding the enzyme last. They decrease the K_0.5 value from 4.1 mM to about 0.2mM. The K_0.5 of enzyme for fructose 2,6 bisphosphate was also determined under the above conditions. It is about 4.3ΜM. Transient kinetics of phosphofructokinase at varying concentrations of enzyme in the presence of fructose 2,6 bisphosphate or polyethylene glycol or in the presence of both were studied. It was found that although they decrease t_1/2 i.e. the time to reach half the maximal steady rate by about 5–8 fold, it was about constant at varying concentrations of the enzyme. These results indicate that fructose 2,6 bisphosphate and polyethylene glycol decrease K_0.5 of the enzyme for fructose 6 phosphate not by associating the enzyme to higher aggregates, but by a different mechanism.     

Intracellular glycosidases of human colon Bacteroides ovatus B4-11.

Activity of various glycosidases in the intracellular enzyme fraction of Bacteroides ovatus B4-11 was investigated. During 120 h of incubation at 37 degrees C, ca. 30% of the crude hemicellulose was hydrolyzed by an intracellular enzyme fraction of strain B4-11. Xylose was the major sugar released from crude hemicellulose. Glycosidases (alpha-1,6-glucosidase, alpha-1,4-glucosidase, beta-1,4-glucosidase, and beta-1,4-xylosidase) were induced in B. ovatus B4-11 by crude hemicellulose and heteroxylan. When B. ovatus B4-11 was grown on either crude hemicellulose or heteroxylan, the predominant enzyme in the intracellular enzyme fraction was beta-1,4-xylosidase.