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Biomedical subjects

J S Huntley

Publications and source records attributed to J S Huntley.

12 recordsLinked to original sources
PubMed1996

Nature of the cation leak induced in erythrocyte membranes by Kanagawa haemolysin of Vibrio parahaemolyticus.

Vibrio parahaemolyticus is an important enteric pathogen that produces an exotoxin prepared as Kanagawa haemolysin (KH). Isotope flux techniques were used to analyse toxin action on the basal permeability of human erythrocytes. KH induced a cation leak that was (i) rapid in onset (lag phase < 1 min), (ii) 'pore-like' in terms of kinetic characteristics, and (iii) of high magnitude initially (first 10 min) and then subsequently lower (but still raised with reference to control cells). The susceptibilities of the induced flux pathway to washout in initial and later periods suggested a protracted binding time course for toxin action. Neuraminidase treatment of erythrocytes enhanced both haemolysis and flux induced by KH, suggesting that the affinity of the toxin for the membrane had increased, possibly as a result of additional toxin receptors being unmasked by this enzyme. These results show that KH elevates the basal permeability of human erythrocytes in a complex manner, a process that probably underlies the deleterious effects of this toxin on cellular function.

Bacterial Toxins↗
PubMed1996

Changes to erythrocyte membrane cation permeability induced by a bacterial toxin.

Vibrio parahaemolyticus secretes an exotoxin prepared as Kanagawa haemolysin (KH) which causes marked alterations to the function of epithelial, cardiac and other cell types, but whose cellular mode of action is poorly understood. Using human red cells as a model system with radiotracer flux techniques, we have shown that KH (1) markedly elevated the basal leak to K+, (2) raised Ca2+ influx, and as a consequence of this, (3) stimulated the Ca2+-activated K+ channel. These results suggest that an important deleterious effect of this toxin is to elevate cation permeability, which will have both direct and indirect actions on the behaviour of a variety of cell types in vivo.

Adult↗
PubMed1994

The multimedia textbook. A revolutionary tool for pediatric education.

Textbooks are now available via computers. These new electronic or multimedia textbooks appears similar to conventional books but differ in function. In addition to text and images, they contain video and audio clips and allow readers to interact with the content. Multimedia textbooks contain digital media, can be quickly and inexpensively updated and repurposed for lectures and handouts, and are available on-line via computer networks for distance learning. We present the concept of computer-generated multimedia text-books; describe their creation by an easy-to-use, sophisticated authoring system; and describe the underlying instructional design approach to guide future authors of multimedia textbooks.

Computer-Assisted Instruction↗
PubMed1994

Aspects of the haemolytic reaction induced by Kanagawa haemolysin of Vibrio parahaemolyticus.

Vibrio parahaemolyticus, an important enteric pathogen, produces toxin (Kanagawa haemolysin, KH), the presence of which correlates well with pathogenicity. KH induced lysis of human red blood cells (HRBC); the kinetics were strongly dependent on KH concentration (0-1 HU/ml) and rather independent of target cell concentration [0.5 < or = haematocrit (%) < or = 6] and the ratio KH:HRBC. The suggestion that KH-induced haemolysis is due to colloid osmosis is supported by results indicating: (1) osmotic protection (by suspension in iso-osmotic choline chloride, D-sorbitol or L-valine, or MOPS-buffered saline with added sucrose), (2) a cell volume increase prior to lysis, and (3) an increase in HRBC cation (86Rb+) influx after KH addition, indicating raised passive cation permeation. The effect of temperature on KH-induced haemolysis indicates the importance of processes other than the action of a simple water-filled pore, because of the high activation energy [53.30 +/- 2.79 kJ (mol.)-1] involved. Although haemolytic rate was attenuated by washout after 5 min KH exposure, the KH-induced lesion itself was not susceptible to washout by either extracellular volume expansion (at constant osmolarity) or centrifugation/resuspension. This suggests that HRBC binding of KH from aqueous solution still continues after 5 min exposure at 37 degrees C. Pre-vortexing KH with dibutyl phthalate (DBP) dramatically reduced the haemolytic activity of the aqueous toxin preparation, suggesting a protein-lipid interaction, which may support the contention that KH can move from a hydrophilic to a hydrophobic environment. Two features were identified that are characteristic of highly purified TDH preparations: (1) thermostability of haemolysin, and (2) monovalent cation selectivity series of lesion: Cs+ > Li+ > K+ > Rb+ > Na+, confirming that TDH is the important leak-inducing agent of KH.

Adult↗
PubMed1993

Interactive videodisc and compact disc-interactive for ophthalmic basic science and continuing medical education.

BACKGROUND: The authors designed and implemented a complete curriculum in ophthalmic pathology using IBM- and Macintosh-based interactive videodisc (IVD) technology. They also redesigned a portion of this curriculum for a new television-based platform, compact disc-interactive (CD-I). METHODS: The following issues were addressed: curriculum design, instructional design, the assembly of illustrations and the ownership of such materials, the generation of computer-based medical art and animation, and programming. The issue of academic credit for faculty participating in this effort also was considered. RESULTS: The computer-based IVD program provides the following features: (1) rapid access to thousands of high-quality illustrations with the option of superimposing graphic labels and text directly over pictures; (2) the ability to view enlargements of photographs; (3) an online glossary to view definition of terms coupled with high-quality photographs; and (4) a dynamic introduction to pathophysiology using interactive animation sequences. The authors were able to incorporate the same interactive features into the CD-I version. High-quality medical illustrations can be used effectively on the CD-I platform. CONCLUSIONS: Computer-based multimedia workstations are relatively expensive for personal use but may be useful if the equipment can be shared in a learning center or library. Compared with interactive computer-based solutions, consumer-oriented television-based technology such as CD-I is a relatively inexpensive vehicle for providing continuing medical education programs intended for use in the individual practitioner's office or home.

Compact Disks↗
PubMed1993

The instructional effectiveness of a radiology multimedia textbook (HyperLung) versus a standard lecture.

RATIONALE AND OBJECTIVES: Information overload is a significant problem for the modern radiologist. This prospective study compares the instructional effectiveness of a multimedia textbook (HyperLung) with a lecture. HyperLung is a radiologic multimedia textbook about imaging diffuse lung disease created using a multimedia authoring tool, the Annotator (the University of Iowa Second Look Computing, Iowa City, IA), on the Apple Macintosh computer (Apple Computer, Cupertino, CA). METHODS: Forty-nine staff physicians and residents in the Department of Radiology were randomized to receive instruction either by HyperLung or by a lecture. The instructional content was the same in both groups, and both groups were tested before and after instruction. The actual time spent in each instructional situation was recorded. RESULTS: The instructional effectiveness of the multimedia textbook and lecture was equal. The instructional efficiency of HyperLung was only 60% of the lecture. Users of the multimedia textbook found it enjoyable and straightforward to use. CONCLUSIONS: Multimedia textbooks have a promising future in radiology education.

Education, Medical, Continuing↗
PubMed1993

Cation flux studies of the lesion induced in human erythrocyte membranes by the thermostable direct hemolysin of Vibrio parahaemolyticus.

Vibrio parahaemolyticus, an important agent of seafood-borne gastroenteritis, expresses several putative virulence factors that could account for the disease symptoms of infected humans, namely, diarrhea, nausea, and abdominal cramps. The pathogenicity of V. parahaemolyticus correlates well with the Kanagawa phenomenon (the hemolytic ability of strains grown on Wagatsuma blood agar), implicating the thermostable direct hemolysin (TDH) as the predominant toxin responsible for pathogenicity. TDH-induced hemolysis could be inhibited by the addition of the osmolyte sorbitol to the extracellular solution, supporting the hypothesis that hemolysis occurs through colloid osmosis secondary to an increase in the cation permeability of the membrane. The effect of TDH on cation permeability was investigated by measuring K+ (congener, 86Rb+) influx into human erythrocytes in which the endogenous cation transporters had been blocked (by use of ouabain, bumetanide, and nitrendipine). TDH increased K+ influx into these cells; this increase was rapid in onset and constant in magnitude, suggesting a direct action by TDH on the membrane. The kinetics of leak generation were examined; the relationship between counts accumulated and hematocrit indicated that the TDH-induced lesion is multihit in nature. TDH-induced K+ influx was sensitive to Zn2+. Time courses of hemolysis in isosmotic solutions of monovalent cation chlorides were used to obtain the selectivity series for the TDH-induced leak: Cs+ > Li+ > K+ > Rb+ > Na+. Both the Zn2+ sensitivity and this selectivity series were obtained for crude culture supernatants, suggesting that TDH is the predominant leak-inducing agent. Thus, we have identified several features of the TDH-induced leak likely to be important in the diarrhetic action of V. parahaemolyticus in the human intestine.

Adult↗
PubMed1993

An approach to the creation of multimedia textbooks for radiology instruction.

We developed a standardized approach for creating computerized multimedia textbooks based on four principles: (1) multimedia textbooks should resemble printed books, (2) the creation of multimedia textbooks should be relatively inexpensive, (3) multimedia textbooks should be completely digital, and (4) the construction of multimedia textbooks should be simple. To facilitate this approach, an inexpensive, user-friendly multimedia authoring tool called The Annotator was used. The Annotator, a Hypercard-based program that runs on any Macintosh computer, helps authors rapidly create sophisticated radiologic multimedia textbooks. This program provides a textbooklike shell that can be filled with digitized media (video clips, audio clips, images, and text). This approach, which is applicable to any multimedia hardware platform, allows the authorship of multimedia textbooks that can be easily transported to any future multimedia platform.

Computer Graphics↗
PubMed1984

The pediatrician's guide to computer videodiscs.

Computer-videodisc technology is currently redefining the uses and possibilities of media-assisted education. A specific videodisc program developed for use in pediatric education is described; the present state of videodisc technology is explained; possible future medical applications of this technology are suggested.

Academic Medical Centers↗
PubMed1984

Development of an interactive computer-videodisc program in pediatrics.

There is growing interest in the use of videodisc technology in health sciences education. This article describes the process of developing an interactive computer-videodisc program to teach health care professionals in training. It deals with techniques for examining infants with neuromotor problems. The program was developed at the University of Iowa and is the first of its kind to be used in pediatrics.

Computers↗