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Biomedical subjects

J Duncan

Publications and source records attributed to J Duncan.

171 records · Page 10Linked to original sources
PubMedDate not supplied

Biosynthesis of the ansamycin antibiotic ansatrienin (mycotrienin) by Streptomyces collinus.

The biosynthesis of ansatrienin (mycotrienin) has been studied in radioactive and stable isotope feeding experiments with Streptomyces collinus Tü 1892. The m-C7N unit of the ansa ring is efficiently and specifically derived from 3-amino-5-hydroxybenzoic acid; shikimic acid is not incorporated into this part of the molecule but does label the cyclohexanecarboyxlic acid moiety, providing all seven of its carbon atoms. Incorporation of methionine confirms origin of the methoxy group by transmethylation. The D-alanine moiety is derived directly from D-alanine rather than L-alanine. The terminal steps in the conversion of shikimic acid into cyclohexanecarboyxlic acid seem to be sequential reduction of 2,5-dihydrobenzoic acid and cyclohexene-1-carboxylic acid as evidenced by feeding experiments and the detection of a new ansatrienin containing a 1-cyclohexene instead of the cyclohexane moiety.

Chemical Phenomena↗
PubMedDate not supplied

Production of 'hybrid' antibiotics by genetic engineering.

The recent development of molecular cloning systems in Streptomyces has made possible the isolation of biosynthetic genes for some of the many antibiotics produced by members of this important genus of bacteria. Such clones can now be used to test the idea that novel antibiotics could arise through the transfer of biosynthetic genes between streptomycetes producing different antibiotics. The likelihood of a 'hybrid' compound being produced must depend on the substrate specificities of the biosynthetic enzymes, about which little is known. In attempts to demonstrate hybrid antibiotic production, we therefore began with strains producing different members of the same chemical class of compounds in order to maximize the chance of success. Here we report the production of novel compounds by gene transfer between strains producing the isochromanequinone antibiotics actinorhodin, granaticin and medermycin. These experiments were made possible by the recent cloning of the whole set of genes for the biosynthetic pathway of actinorhodin from Streptomyces coelicolor A3(2) (ref. 8). We believe that this represents the first report of the production of hybrid antibiotics by genetic engineering.

Anthraquinones↗
PubMedDate not supplied

Medical image databases: a content-based retrieval approach.

Information contained in medical images differs considerably from that residing in alphanumeric format. The difference can be attributed to four characteristics: (1) the semantics of medical knowledge extractable from images is imprecise; (2) image information contains form and spatial data, which are not expressible in conventional language; (3) a large part of image information is geometric; (4) diagnostic inferences derived from images rest on an incomplete, continuously evolving model of normality. This paper explores the differentiating characteristics of text versus images and their impact on design of a medical image database intended to allow content-based indexing and retrieval. One strategy for implementing medical image databases is presented, which employs object-oriented iconic queries, semantics by association with prototypes, and a generic schema.

Abstracting and Indexing↗
PubMedDate not supplied

PathMaster: content-based cell image retrieval using automated feature extraction.

OBJECTIVE: Currently, when cytopathology images are archived, they are typically stored with a limited text-based description of their content. Such a description inherently fails to quantify the properties of an image and refers to an extremely small fraction of its information content. This paper describes a method for automatically indexing images of individual cells and their associated diagnoses by computationally derived cell descriptors. This methodology may serve to better index data contained in digital image databases, thereby enabling cytologists and pathologists to cross-reference cells of unknown etiology or nature. DESIGN: The indexing method, implemented in a program called PathMaster, uses a series of computer-based feature extraction routines. Descriptors of individual cell characteristics generated by these routines are employed as indexes of cell morphology, texture, color, and spatial orientation. MEASUREMENTS: The indexing fidelity of the program was tested after populating its database with images of 152 lymphocytes/lymphoma cells captured from lymph node touch preparations stained with hematoxylin and eosin. Images of "unknown" lymphoid cells, previously unprocessed, were then submitted for feature extraction and diagnostic cross-referencing analysis. RESULTS: PathMaster listed the correct diagnosis as its first differential in 94 percent of recognition trials. In the remaining 6 percent of trials, PathMaster listed the correct diagnosis within the first three "differentials." CONCLUSION: PathMaster is a pilot cell image indexing program/search engine that creates an indexed reference of images. Use of such a reference may provide assistance in the diagnostic/prognostic process by furnishing a prioritized list of possible identifications for a cell of uncertain etiology.

Abstracting and Indexing↗
PubMedDate not supplied

Effects of Theraband and lightweight dumbbell training on shoulder rotation torque and serve performance in college tennis players.

The purpose of this study was to determine whether a 4-week isotonic resistance training program using Theraband elastic tubing and lightweight dumbbells would significantly increase concentric shoulder rotator strength or velocity of serve or both in a group of elite-level tennis players. Twenty-two male and female varsity college tennis players were randomly assigned to control or 4-week training groups. Subjects were pre- and posttested in concentric internal and external rotation torque using an isokinetic dynamometer. Functional performance was assessed before and after training by recording the peak and average velocities of eight maximal serves. The experimental group exhibited significant gains in internal rotation torque at both slow (120 deg/sec) and fast speeds (300 deg/sec) for total work and in peak torque to body weight ratio and torque acceleration energy at the fast speed. This group also exhibited significant gains in external rotation torque for the same parameters at fast speed. Regarding speed to serve, the experimental group exhibited significantly greater increase in peak speed (+6.0% compared with -1.8%) and average speed (+7.9% compared with -2.3%) compared with the control group. Men exhibited greater internal and external rotation torque on all parameters and in peak and mean speed of serve on both evaluations. Men also exhibited greater imbalance in external to internal rotation torque ratios. In conclusion, resistance training using Theraband tubing and lightweight dumbbells may have beneficial effects on strength and functional performance in college-level tennis players.

Acceleration↗
PubMedDate not supplied

Supported employment: a three-way partnership.

This article outlines changes over the years in patients' vocational and industrial training at Whitby Psychiatric Hospital in Greater Metropolitan Toronto. The transition from traditional workshops to an integrated community-based vocational training program--supported employment--is discussed, as is the importance of partnership among the hospital, the client, and the employer for success in such a program.

Commerce↗