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Biomedical subjects

M L Huber

Publications and source records attributed to M L Huber.

12 recordsLinked to original sources
PubMed1997

Assessment of current techniques for determining tracheal luminal stenosis in dogs.

OBJECTIVE: To assess the accuracy of current antemortem and postmortem techniques for determining tracheal luminal stenosis. ANIMALS: 15 dogs. PROCEDURE: Percentage of tracheal luminal stenosis (PTLS) was determined by 6 methods, using measurements obtained by radiography, tracheoscopy, and necropsy after selected tracheostomy techniques were performed. To calculate PTLS, dorsoventral tracheal diameter was measured from preoperative and postoperative lateral cervical radiographic views. Preoperative or normal tracheal segments adjacent to the stenotic area were used to obtain normal tracheal diameter measurements. Planimetrically determined cross-sectional area (CSA), obtained from pre- and postoperative tracheoscopic photographs, was used to calculate PTLS. The CSA of tracheal specimens obtained at necropsy was determined, using the formula for an ellipse. Percentage of luminal stenosis was calculated, using CSA of the stenotic site and of segments craniad and caudad to the site obtained at necropsy or at surgery. All methods were compared with the control method of planimetrically determined CSA of sections obtained at necropsy of the tracheostomy and segments craniad and caudad to the site. RESULTS: Correlation was poor for radiographic and tracheoscopic techniques (r = 0.146 to 0.458, P > 0.05) The formula for an ellipse accurately predicted PTLS when measurements obtained at surgery (r = 0.516, P = 0.049) or segments craniad and caudad (r = 0.853, P < 0.001) to the site were used. CONCLUSION: Antemortem methods of assessing PTLS did not correlate with control planimetric methods. Methods using CSA determined by tracheal diameter were weakly correlated to control planimetric techniques. CLINICAL RELEVANCE: Accurate measurement of the degree of tracheal stenosis cannot be made in clinical patients using current techniques.

Animals↗
PubMed1990

Branched-chain fatty acids produced by mutants of Streptomyces fradiae, putative precursors of the lactone ring of tylosin.

Three branched-chain fatty acids (7-hydroxy-4,6-dimethylnona-2,4-dienoic acid [compound 1], its 7-epimer [compound 2], and 7-keto-4,6-dimethylnona-2,4-dienoic acid [compound 3]) and a ketone (9-hydroxy-6,8-dimethylundeca-4,6-dien-3-one [compound 4]) were isolated from the culture broth of mutants of Streptomyces fradiae which were blocked in the biosynthesis of the macrolide antibiotic tylosin. Two phenotypic classes of mutants of this organism which were blocked in the addition of mycaminose to tylactone (compound 6) accumulated these compounds. These compounds were not produced by mutants which were blocked in lactone synthesis, in steps beyond mycaminose addition, or by the wild-type strain. Synthesis of these compounds, like synthesis of tylosin, was inhibited by the addition of cerulenin. Compounds 1, 2, and 3 were partially interconvertible by these mutants; but they were not produced from the degradation of tylactone and they were not directly incorporated into tylosin by intact cells. The structures of compounds 1 and 2 were equivalent to that of a predicted intermediate (S. Yue, J. S. Duncan, Y. Yamamoto, and C. R. Hutchinson, J. Am. Chem. Soc. 109:1253-1255, 1987) in the biosynthesis of tylactone. The ketone (compound 4) reported previously (N. D. Jones, M. O. Chaney, H. A. Kirst, G. M. Wild, R. H. Baltz, R. L. Hamill, and J. W. Paschal, J. Antibiot. 35:420-425, 1982) appears to be the decarboxylation product of the intermediate following that represented by compound 1. This represents the first report of the isolation of putative precursors of tylactone from tylosin-producing organisms.

Alcohols↗
PubMed1990

Cloning of spiramycin biosynthetic genes and their use in constructing Streptomyces ambofaciens mutants defective in spiramycin biosynthesis.

Several cosmid clones from Streptomyces ambofaciens containing the spiramycin resistance gene srmB were introduced into S. fradiae PM73, a mutant defective in tylosin synthesis, resulting in tylosin synthesis. The DNA responsible for this complementation was localized to a 10.5-kilobase EcoRI fragment. A 32-kilobase DNA segment which included the srmB spiramycin resistance gene and DNA which complemented the defect in strain PM73 were mutagenized in vivo with Tn10 carrying the gene for Nmr (which is expressed in Streptomyces spp.) or in vitro by insertional mutagenesis with a drug resistance gene (Nmr) cassette. When these mutagenized DNA segments were crossed into the S. ambofaciens chromosome, three mutant classes blocked in spiramycin synthesis were obtained. One mutant accumulated two precursors of spiramycin, platenolide I and platenolide II. Two mutants, when cofermented with the platenolide-accumulating mutant, produced spiramycin. Tylactone supplementation of these two mutants resulted in the synthesis of a group of compounds exhibiting antibiotic activity. Two other mutants failed to coferment with any of the other mutants or to respond to tylactone supplementation.

Chromosomes, Bacterial↗
PubMed1989

Production of a hybrid macrolide antibiotic in Streptomyces ambofaciens and Streptomyces lividans by introduction of a cloned carbomycin biosynthetic gene from Streptomyces thermotolerans.

The structurally related macrolide antibiotics carbomycin (Cb) and spiramycin (Sp) are produced by Streptomyces thermotolerans and Streptomyces ambofaciens, respectively. Both antibiotics contain 16-membered lactone rings to which deoxysugars are attached. There are three sugars in Sp (forosamine, mycaminose and mycarose) and two sugars in Cb (mycaminose and a derivative of mycarose containing an isovaleryl group at position 4). We have identified the gene from S. thermotolerans (designated carE), which appears to encode an enzyme that acylates this mycarose sugar, and have shown that recombinant strains containing carE can use Sp as a substrate and convert it to the hybrid antibiotic, isovaleryl Sp (ivSp). Expression of carE was demonstrated in two heterologous hosts: in S. ambofaciens, where endogenously synthesized Sp was converted to ivSp, and in Streptomyces lividans where exogenously added Sp was converted to ivSp. The carE gene was isolated on a cosmid that also encodes genes required for Cb-lactone formation. These genes reside on a DNA segment of about 70 kb and are part of a Cb biosynthetic gene cluster that is flanked by two Cb-resistance genes, carA and carB. Mapping studies and nucleotide sequence analysis revealed that carE is located at one end of this gene cluster, immediately adjacent to the carB gene. Genes carB and carE are transcribed convergently and may share a common transcriptional terminator sequence.

Acyltransferases↗
PubMed1978

A general method for the lysis of Streptomyces species.

A procedure for the gentle lysis of Streptomyces is described. Complete lysis is obtained and covalently closed circular (CCC) DNA remains intact. This procedure was successfully used to lyse 14 different species of Streptomyces.

Bacteriological Techniques↗
PubMedDate not supplied

Interlocking box jejunostomy: a new technique for enteral feeding.

A new jejunostomy tube placement technique is described and compared to traditional methods. The interlocking box technique was compared to a simple purse-string with jejunopexy and an inverting serosal tunnel (Witzel technique) with jejunopexy. Procedures performed in fresh canine cadavers were fluid pressure tested following tube removal. Mean+/-standard deviation (SD) intraluminal pressure necessary to induce leakage at the jejunopexy site of the interlocking box group (87.63+/-40.56 cm H2O) was significantly greater (p less than 0.001) than the simple purse-string (43.17+/-31.69 cm H2O) and serosal tunnel (46.33+/-23.60 cm H2O) groups. Significant differences were not identified between the latter groups. The interlocking box technique resisted leakage following acute removal better than conventional techniques and should be tested clinically.

Analysis of Variance↗