An X-ray-crystallographic study of beta-lactamase II from Bacillus cereus at 0.35 nm resolution.

Crystals of beta-lactamase II (EC 3.5.2.6., 'penicillinase') from Bacillus cereus were grown with Cd(II) in place of the natural Zn(II) cofactor and stabilized by cross-linking with glutaraldehyde. Their space group is C2, the cell dimensions are a = 5.44 nm, b = 6.38 nm, c = 7.09 nm and beta = 93.6 degrees, and there is one molecule in the asymmetric unit. Diffraction data were collected from cross-linked crystals of the Cd(II)-enzyme, the apoenzyme and six heavy-atom derivatives. The electron-density map calculated at 0.35 nm resolution reveals the essential Cd(II) ion surrounded by three histidine residues and one cysteine residue. The position of a glutamic acid residue, modification of which destroys activity [Little, Emanuel, Gagnon & Waley (1986) Biochem. J. 233, 465-469], suggests the probable location of the active site of the enzyme. Two minor Cd(II) sites not essential for activity were also located. The structure of the apoenzyme at this resolution appears to differ from that of the Cd(II)-enzyme only in the orientation of two of the histidine residues and the cysteine residue that surround the metal ion.     

Plasmid profiles and antibiotic susceptibility of Haemophilus pleuropneumoniae serotypes 1, 3, 5, and 7

Abstract This paper describes the plasmid profiles obtained for 73 of 96 field isolates of Haemophilus pleuropneumoniae serotypes 1, 3, 5, and 7. We also characterized the antibiotic susceptibilities of these 96 isolates. Because of the high proportion of isolates resistant to some of the antibiotics, no conclusions can be drawn as to the role of plasmids in antibiotic resistance.     

Canine lymphoma-associated antigens defined by murine monoclonal antibodies

Summary Lymphoma in dogs resembles human non-Hodgkin's lymphoma in pathological presentation, immunophenotype, and response to therapy, thus representing a good model for comparative studies with human disease. Monoclonal antibodies (MAbs) were derived from mice immunized with a dog lymphoma cell line. Three MAbs were selected for further application in immunophenotyping and immunotherapy. The binding specificities, antigen characterization, and isotypes for these MAbs are described.Supported by NCI grant CA-10815     

Consequences of terbium (111) binding on the conformation and enzymatic activity of Guinea pig liver transglutaminase

Calcium ions are crucial for expression of transglutaminase activity. Although lanthanides have been reported to substitute for calcium in a variety of protein functions, they did not replace the calcium requirement during transglutaminase activity measurements. Furthermore, lanthanides strongly inhibited purified liver transglutaminase activity using either casein or fibrinogen as substrates. Terbium (III) inhibition of transglutaminase-catalyzed putrescine incorporation into casein was not reversed by the presence of 10–200 fold molar excess of calcium ions (Ki for Tb(III)=60 µM). Conformational changes in purified liver transglutaminase upon Tb(III) binding were evident from a biphasic effect of Tb(III) on transglutaminase binding to fibrin. Low concentrations of Tb(III) (1 µM to 10 µM inhibited the binding of transglutaminase to fibrin, whereas higher concentrations (20 µM to 100 µM promoted binding. Conformational changes in purified liver transglutaminase consequent to Tb(III) binding were also demonstrated by fluorescence spectroscopy due to Forster energy transfer. Fluorescence emission was stable to the presence of 200 mM NaCl and 100 mM CaCl₂ only partially quenched emission. Purified liver transglutaminase strongly bound to Tb(III)-Chelating Sepharose beads and binding could not be disrupted by 100 mM CaCl₂ solution. Our data suggest that Tb(III)-induced conformational changes in transglutaminase are responsible for the observed effects on enzyme structure and function. The potential applications of Tb(III)-transglutaminase interactions in elucidating the structure-function relationships of liver transglutaminase are discussed.     

Growth dynamics of a ctenophore (Mnemiopsis) in relation to variable food supply. I. Carbon biomass, feeding, egg production, growth and assimilation efficiency

This paper contains new experimental data on the growth dynamicsof a lobate coastal ctenophore, Mnenmiopsis mccradyi, whichadd significantly to our understanding of the nutritional ecologyof ctenophores and their role as opportunistic predators. Theseexperimental observations were necessary to refine the dynamiccarbon budget presented as a simulation model in another report.The ratio of carbon biomass to dry weight may vary several-folddepending on the nutritional state and size from >12% inwell-fed larvae to <1% in starved adults. Feeding effort(clearance rate) is higher for previously starved animals, fallingsharply within a few hours after re-exposure to food. Directvisual observations of feeding activity of animals confirmedthis. Assimilation efficiency can be high (72%) in these animalsbut if they continue to feed at high food concentrations, incomingfood displaces material which is only partially digested andassimilation efficiency decreases substantially. Except at verylow food concentrations, growth efficiency ranges between 20and 45%. Mnemiopsis, begins to produce eggs at a size much lessthan its maximum. Egg production is very sensitive to food supply,and somatic growth is favored over egg production at low fooddensities. Even though several thousand eggs may be producedover a few days, they represent <2% day^–1 of the carbonbiomass of the ctenophore and several-fold less than respiratorycarbon.     

Contribution à la connaissance de la faune parasitaire d' Argentine,XV. Etude morphologique de Heteroxynema (Cavioxyura) viscaciae n. sp. (Nematoda,Heteroxynematidae) parasite de Lagidium viscacia boxi (Mammalia,Rodentia)

Résumé Heteroxynema (Cavioxyura) viscaciae n. sp., parasite du caecum et du gros intestin d'un rongeur caviomorphe d' Argentine, Lagidium viscacia boxi Thomas, est décrit. Cette nouvelle espèce est très proche de Heteroxynema (Cavioxyura) chiliensis Quentin, 1975, parasite d' Octodon degus (Molina) au Chili, dont elle se distingue essentiellement par ses mensurations et par la disposition de certaines papilles génitales des mâles. L'étude de cette nouvelle espèce montre l'existence: (i) au niveau des structures buccales d'un dimorphisme sexuel d'un type peu fréquent chez les Oxyuroidea; (ii) de quatre paires seulement de papilles génitales mâles voisinant avec des reliefs cuticulaires qui, dans d'autres espèces, ont peut-être été confondus avec des terminaisons nerveuses supplémentaires; (iii) d'un gubernaculum et d'un spicule, organes rarement observés chez les Heteroxynematidae, mais dont la présence dans d'autres espèces du groupe pourrait avoir été ignorée; (iv) au niveau de l'ovéjecteur, d'un sphincter particulièrement différencié et développé.

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Heteroxynema (Cavioxyura) viscaciae n. sp., parasitic in the caecum and large intestine of Lagidium viscacia boxi Thomas, is described. The most closely related species is Heteroxynema (Cavioxyura) chiliensis Quentin, 1975, a parasite of Octodon degus (Molina) from Chile, from which the new species differs by its measurements and disposition of the male's genital papillae. Study of this new species shows the existence of: (i) a type of sexual dimorphism infrequent in the Oxyuroidea, at the level of the buccal structures; (ii) only four pairs of male genital papillae adjoining cuticular protuberances which in other species may have been confused with supplementary nerve endings; (iii) a gubernaculum and a spicule, structures infrequently observed in the Heteroxynematidae, and possibly overlooked or ignored in other species; (iv) a sphincter which is strongly differentiated and developed.

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Resumen Se describe a Heteroxynema (Cavioxyura) viscaciae n. sp. paràsito del ciego intestino grueso del rodeor Lagidium viscacia boxi Thomas. Esta nueva especie se asemeja a Heteroxynema (Cavioxyura) chiliensis Quentin, 1975, paràsito de Octodon degus (Molina) de Chile de la cual se diferencie esencialmente por sus medidas y por la disposicion de las papilas genitales del macho. El estudio de esta nueva especie muestra la existencia de: (i) un tipo poco frecuente en los Oxyuroidea de dimorfismo sexual a nivel de las estructuras bucales; (ii) cuatro pares de papilas genitales en el macho ubicadas proximas a relieves cuticulares que en otras especies pueden haber sido confundidos con terminaciones nerviosas suplementarias; (iii) de un gubernàculo y una espicula, organos raramente observables en los Heteroxynematidae, pero cuya presencia en otras especies del grupo pudo haber sido ignorada; (iv) de un sphincter particularmente diferenciado y desarollado.

     

The haplotype distribution of the ΔF508 mutation in cystic fibrosis families in Scotland

Summary The gene defective in cystic fibrosis (CF) has recently been isolated and the major mutation identified. The haplotype distribution of this mutation (ΔF508) has been determined for 215 CF chromosomes in the Scottish population. ΔF508 represents 73% of all CF mutations in this group. There remains considerable linkage disequilibrium between XV2c and KM19 and other mutations in the CF gene.     

The effect of salinity on the composition of fatty acid double-bond isomers andsn-1/sn-2 positional distribution in membrane phospholipids of a moderately halophilic eubacterium

We report the first study of the effect of NaCl on the double-bond isomeric composition of fatty acids and theirsn-1/sn-2 positional distribution in the membrane phospholipids of a moderately halophilic eubacterium. The major phospholipids, phosphatidylethanolamine and phosphatidylglycerol, ofVibrio costicola grown in 1M or 3M NaCl both have ansn-1 saturated,sn-2 unsaturated distribution of fatty acids. There is a greater effect of salinity on the fatty acid composition of phosphatidylglycerol compared with phosphatidylethanolamine. The fatty acids in phosphatidylethanolamine of cultures grown in 1M compared with 3M NaCl have the same unsaturation index and average chain length, but different double-bond isomeric compositions. In comparison, the fatty acid composition of phosphatidylglycerol is more unsaturated, with a different double-bond isomeric distribution, and has a shorter average chain length in cultures grown in 3M compared with 1M NaCl. The pattern of fatty acid isomers of 16:1 and 18:1 shows thatV. costicola uses the anaerobic pathway of fatty acid biosynthesis. The presence of the isomers 16:1c11 and 18:1c13 in the phospholipids of cultures grown in 3M but not in 1M NaCl indicates that external salinity affects the specificity of fatty acid synthetase in this moderately halophilic bacterium.     

Suppression of protein kinase C and the stimulation of glucocorticoid receptor synthesis by dexamethasone in human fibroblasts derived from tumor tissue

Exposure of fibroblasts derived from keloid tissues, desmoid and dermal tissue from individuals with Gardner's syndrome (GS) to dexamethasone resulted in the suppression of protein kinase C (PKC) activity and [3H]thymidine incorporation into DNA, and a 20-fold induction of glutamine synthetase activity. Treatment of GS and keloid fibroblasts with 0.1 microM dexamethasone for 36 h increased glucocorticoid receptor (GR) synthesis, as determined by [35S]methionine labeling and immunoprecipitation with a monoclonal antibody to the human GR. The suppression of PKC activity by dexamethasone was shown to result from a loss of protein mass as determined by immunoblotting using an antibody to PKC type III. In contrast to these results, exposure of fibroblasts isolated from normal tissues to dexamethasone did not result in the suppression PKC and [3H]thymidine incorporation, there was only a sixfold induction of glutamine synthetase, and a decrease of GR synthesis. As no primary receptor binding defect could be detected, the altered response of tumor cells to steroid-occupied receptor indicates a partial post-receptor binding defect in GS and keloid cells.