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Biomedical subjects

A Linden

Publications and source records attributed to A Linden.

At least 19 recordsLinked to original sources
PubMed2002

A role for the Clostridium perfringens beta2 toxin in bovine enterotoxaemia?

Non-enterotoxigenic type A Clostridium perfringens are associated with bovine enterotoxaemia, but the alpha toxin is not regarded as responsible for the production of typical lesions of necrotic and haemorrhagic enteritis. The purpose of this study was to investigate the putative role of the more recently described beta2 toxin. Seven hundred and fourteen non-enterotoxigenic type A C. perfringens isolated from 133 calves with lesions of enterotoxaemia and high clostridial cell counts (study population) and 386 isolated from a control population of 87 calves were tested by a colony hybridisation assay for the beta2 toxin. Two hundred and eighteen (31%) C. perfringens isolated from 83 calves (62%) of the study population and 113 (29%) C. perfringens isolated from 51 calves (59%) of the control population tested positive with the beta2 probe. Pure and mixed cultures of four C. perfringens (one alpha+beta2+, one alpha+enterotoxin+ and two alpha+) were tested in the ligated loop assay in one calf. Macroscopic haemorrhages of the intestinal wall, necrosis and haemorrhages of the intestinal content, and microscopic lesions of necrosis and polymorphonuclear and mononuclear cell infiltration of the intestinal villi were more pronounced in loops inoculated with the alpha and beta2-toxigenic C. perfringens isolate. These results suggest in vivo synergistic role of the alpha and beta2 toxins in the production of necrotic and haemorrhagic lesions of the small intestine in cases of bovine enterotoxaemia. However, isolation of beta2-toxigenic C. perfringens does not confirm the clinical diagnosis of bovine enterotoxaemia and a clostridial cell counts must still be performed.

Animals↗
PubMed2002

Comparison of sampling procedures for isolating pulmonary mycoplasmas in cattle.

Three sampling procedures were compared to determine the optimal technique for isolating mycoplasmas in cattle with respiratory diseases. The prevalence of mycoplasmas isolated from these animals is also reported. In the first group, bronchoalveolar lavage (BAL) and nasal swab cultures were compared with the corresponding lung cultures from cattle necropsied for fatal respiratory diseases (n = 20). In a second group, nasal swabs were compared with corresponding BAL cultures in living animals with recurrent respiratory pathologies (n = 49). There was complete agreement between the paired BAL and lung cultures. In contrast, nasal cultures were not representative of the mycoplasmas present in the lower respiratory airways. The relative sensitivity and specificity of the nasal swab technique compared to BAL in living animals confirmed that the nasal swab cultures were not predictive of lower respiratory airway pathogens, such as Mycoplasma bovis. BAL is considered to be the best method for isolating M. bovis in cattle with respiratory diseases as it combines reliability and feasibility under field sampling conditions. In the present study, Mycoplasma dispar (43%) and M. bovis (29%) were mainly isolated in mixed infections. This confirms the need to search for mycoplasmas in routine examinations and to take them into account in therapeutic strategies for respiratory diseases in cattle.

Animals↗
PubMed2001

Two ethyl 2-deoxy-alpha-D-hexo-3,7-pyranoso-3-octulosonate derivatives.

In each of the two pyranoid sugars, ethyl 2-deoxy-4,5,6,8-tetra-O-acetyl-alpha-D-gluco-3,7-pyranoso-3-octulosonate, C18H26O12, and ethyl 2-deoxy-4,5,6,8-tetra-O-benzyl-alpha-D-galacto-3,7-pyranoso-3-octulosonate, C38H42O8, the anomeric configuration is alpha. The acetoxymethyl substituent on the hexopyranose ring of the former compound and the ethoxycarbonylmethyl substituents in both sugars all have the gauche-trans conformation, while the benzyloxymethyl substituent of the galactopyranose sugar has the trans-gauche conformation. In each structure, the anomeric hydroxy group forms an intramolecular hydrogen bond with the carbonyl O atom of the ethoxycarbonylmethyl substituent.

Journal Article↗
PubMed2001

Two halodeoxy sucrose analogues.

At 160 K, the structure of 4-bromo-4-deoxysucrose, C(12)H(21)BrO(10), is very similar to that of sucrose, particularly with respect to the conformation of the glycosidic linkage. As in sucrose, an intramolecular hydrogen bond exists between the glucopyranosyl and the fructofuranosyl rings. Conversely, the structure of 1',6'-dibromo-4-fluoro-4,1',6'-trideoxysucrose monohydrate, C(12)H(19)Br(2)FO(8) x H(2)O, shows large conformational differences when compared with the structures of both sucrose and sucralose. This compound does not exhibit any intramolecular hydrogen bonds. In each compound, a complex series of intermolecular hydrogen bonds link the molecules into an infinite three-dimensional framework. The absolute configuration of each molecule has been determined.

Crystallography, X-Ray↗
PubMed2001

3-O-acetyl-4-deoxy-4-iodo-beta-D-fructofuranosyl 2,3,6-tri-o-acetyl-4-chloro-4-deoxy-alpha-D-glucopyranoside.

At 160 K, the glucopyranosyl ring of the title compound, C(20)H(28)ClIO(13), has a near-ideal (4)C(1) conformation and the fructofuranosyl ring has a twist (4)T(3) conformation. The two hydroxy groups are involved in intra- and intermolecular hydrogen bonds, with the latter interactions linking the molecules into infinite one-dimensional chains. The absolute configuration of the molecule has been determined.

Carbohydrate Conformation↗
PubMed2001

A beta-lactam-based stereoselective access to beta,gamma-dihydroxy alpha-amino acid-derived peptides with either alpha,beta-like or unlike configurations.

A concise access to alpha,beta-dihydroxy alpha-amino acid-derived N-carboxy anhydrides (NCAs) with either like or unlike relative configuration is described. The key steps of the synthetic route are the preparation of the nonracemic 4-alkenyl beta-lactams, through either Horner-type olefination of a common 4-formyl beta-lactam or the Corey-Winter alkene synthesis applied to 4-dihydroxyalkyl beta-lactams, followed by the Sharpless AD reaction, and a subsequent ring expansion of the corresponding 4-substituted 3-hydroxy beta-lactams promoted by TEMPO. The opening of thus-prepared NCAs upon treatment with different O- and N-nucleophiles, including alpha-amino esters which lead to peptides, has also been studied under various reaction conditions.

Amino Acids↗
PubMed2001

Dispiro[fluorene-9,5'-[1,2,3,4]tetrathiane-6',9"-fluorene.

The tetrathiane ring of the title compound, C26H16S4, has a chair conformation and the molecule has approximate C2 symmetry. Each of the two fluorene ring systems is virtually planar, with the ring planes intersecting at an angle of 67.58 (5) degrees. This novel compound has been formed as a side product from the treatment of 9H-fluorene-9-thione with methyl N-[(benzylidene)phenyl]glycinate in the presence of LiBr and 1,6-diazabicyclo[5.4.0]undecane.

Journal Article↗
PubMed2001

(+/-)-6-Benzyl-3,3-dimethylmorpholine-2,5-dione and its 5-monothio and 2,5-dithio derivatives.

The morpholine ring of the title dione, C(13)H(15)NO(3), shows a boat conformation that is distorted towards a twist-boat, with the boat ends being the two Csp(3) atoms of the ring. The benzyl substituent is in the favoured 'exo' position. In the monothione derivative, (+/-)-6-benzyl-3,3-dimethyl-5-thioxomorpholin-2-one, C(13)H(15)NO(2)S, this ring has a much flatter conformation that is midway between a boat and an envelope, with the dimethyl end being almost planar. The orientation of the benzyl group is 'endo'. The dithione derivative, (+/-)-6-benzyl-3,3-dimethylmorpholine-2,5-dithione, C(13)H(15)NOS(2), has two symmetry-independent molecules, which show different puckering of the morpholine ring. One molecule has a flattened envelope conformation distorted towards a screw-boat, while the conformation in the other molecule is similar to that in the monothione derivative. Intermolecular hydrogen bonds link the molecules in the three compounds, respectively, into centrosymmetric dimers, infinite chains, and dimers made up of one of each of the symmetry-independent molecules.

Journal Article↗
PubMed2001

Flavonoid, iridoid, and lignan glycosides from Putoria calabrica.

From the aerial parts of Putoria calabrica, two new flavonol triglycosides were isolated and their structures were elucidated as quercetin-3-O-[alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranoside]-7-O-beta-D-glucopyranoside (1, calabricoside A) and quercetin-3-O-[4' "-O-caffeoyl-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranoside]-7-O-beta-D-glucopyranoside (2, calabricoside B). Additionally, seven iridoid and three lignan glycosides were isolated and characterized. Radical scavenging activities of all compounds were determined by quantifying their effects on luminol-enhanced chemiluminescence in formyl-methionyl-leucyl-phenylalanine (FMLP) stimulated human polymorphonuclear neutrophils (PMNs). Calabricoside A and B showed strong radical scavenging activity with IC(50) values of 0.25 and 0.3 microM, respectively.

Chromatography↗
PubMed2000

Camphor-based alpha-bromo ketones for the asymmetric darzens reaction

(1R)-2-endo-Bromoacetyl-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ol (endo-2-bromoacetylisoborneol) 4 and its trimethylsilyl ether 3 are presented as efficient reagents for the asymmetric Darzens reaction. From the alpha,beta-epoxy ketone adducts the chiral inductor camphor is removed, by treatment with ceric(IV) ammonium nitrate, to yield the corresponding epoxy acids which are isolated as their dicyclohexylammonium salts.

Journal Article↗
PubMed2000

Single-step purification of a recombinant thermostable alpha-amylase after solubilization of the enzyme from insoluble aggregates.

The expression of the gene encoding a thermostable alpha-amylase (EC 3.2.1.1) (optimal activity at 100 degrees C) from the hyperthermophilic archaeon Pyrococcus woesei in the mesophilic hosts Escherichia coli and Halomonas elongata resulted in the formation of insoluble aggregates. More than 85% of the recombinant enzyme was present within the cells as insoluble but catalytically active aggregates. The recombinant alpha-amylase was purified to homogeneity in a single step by hydrophobic interaction chromatography on a phenyl superose column after solubilization of the enzyme under nondenaturing conditions. The enzyme was purified 258-fold with a final yield of 54%.

Chromatography, Liquid↗
PubMed2000

alpha-Oxymethyl Ketone Enolates for the Asymmetric Mannich Reaction. From Acetylene and N-Alkoxycarbonylimines to beta-Amino Acids This work was supported by the University of the Basque Country, the Basque Government (Projects UPV 170.215-G47/98, EX-1998-124) and in part by M. E. C. (Project PB 98-0549). Grants to A.S. and M.C.G. from the Basque Government, and to C.L. from the Government of Navarra and M.E.C. are acknowledged.

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Journal Article↗
PubMed2000

Increased elastase and myeloperoxidase activity associated with neutrophil recruitment by IL-17 in airways in vivo.

BACKGROUND: A recent study demonstrated that intratracheal administration of the T-lymphocyte cytokine IL-17 recruits neutrophils into airways in vivo by C-X-C chemokine release. It is not known whether IL-17 may also activate airway neutrophils. OBJECTIVE: Our purpose was to evaluate whether IL-17 activates neutrophils in airways in vivo and, if so, whether the proinflammatory cytokine IL-1beta modulates this action of IL-17. METHODS: Intratracheal administration of human (h) IL-17 or rat (r) IL-1beta or hIL-17 plus rIL-1beta in anesthetized, spontaneously breathing rats was followed by bronchoalveolar lavage (BAL) 6 hours later. The BAL fluid was characterized in terms of neutrophil count, of the activity for myeloperoxidase (MPO), and in some cases of the activity for elastase (ELA). Isolated rat neutrophils were stimulated with hIL-17 in vitro, followed by characterization of MPO activity in the cell medium. RESULTS: hIL-17 (1 microg) increased the ELA and the MPO activity, as well as the neutrophil count in BAL fluid, whereas the proinflammatory cytokine rIL-1beta (2.5 ng) did not. Pretreatment with rIL-1beta enhanced IL-17induced ELA and MPO activity, without increasing the neutrophil count. The BAL ELA activity was inhibited by a specific inhibitor of neutrophil serine proteases. Stimulation with hIL-17 in vitro did not increase MPO activity in isolated neutrophils. CONCLUSION: IL-17 can activate neutrophils in association with their recruitment into the airways in vivo and this effect is probably achieved through induced release of mediators from other airway cells.

Animals↗
PubMed2000

Novel extracellular diterpenoids with biological activity from the cyanobacterium Nostoc commune.

Five novel extracellular metabolites with an unprecedented diterpenoid skeleton, 5-[(5-carboxy-2-hydroxy)benzyl]-11-hydroxymethyl-2,5,6,8a, 11-pentamethyldodecahydrocyclopenta naphthalene (1), 5-[(5-carboxy-2-hydroxy)benzyl]-11-formyl-2,5,6,8a, 11-pentamethyl-dodecahydrocyclopenta naphthalene (2), 5-[(5-carboxy-2-hydroxy)benzyl]-11-carboxy-2,5,6,8a, 11-pentamethyl-dodecahydrocyclopenta naphthalene (3), 5-[(5-carboxy-2-hydroxy)benzyl]-11-dihydroxymethyl-2,5,6,8a, 11-pentamethyldodecahydrocyclopenta naphthalene (4), and 5-[(5-carboxy-2-hydroxy)benzyl]-11-acetyl-2,5,6, 8a-tetramethyldodecahydrocyclopenta naphthalene (5), have been isolated from the culture medium of the terrestrial cyanobacterium Nostoc commune by means of bioguided isolation. The molecules were designated as comnostins A-E. The structures were determined by spectroscopic methods, mainly NMR and mass spectrometry. The relative stereochemistry of comnostin A was confirmed by single-crystal X-ray structure analysis. All comnostins showed antibacterial activities. Additionally, cytotoxic and molluscicidal activities were found for comnostin B.

Cyanobacteria↗