Search PubMed⌕ Search

Biomedical subjects

A W Hahn

Publications and source records attributed to A W Hahn.

At least 37 records · Page 2Linked to original sources
PubMed1997

Data model development as a prelude to implementing a hospital information system.

We developed a data model for use in a veterinary teaching hospital using modern object oriented database diagramming. Since we deal with more than one species and often with herds or flocks, the problem became even more complex than the situation in human medicine. We chose to follow, insofar as possible, standards set forth by the HL7 consortium and the American Society for Testing and Materials (ASTM), two organizations deeply involved in setting standards for the health care record. Some modifications became necessary in order to fit the veterinary medical record to these standards but these were straightforward and did not disrupt the overall model. As a first step in constructing a hospital information system we have developed, and present herein, a data model which adequately addresses our needs in both the clinical and financial arenas and which conforms to appropriate standards as completely as possible.

Animals↗
PubMed1997

Heart rate variability in the horse by ambulatory monitoring.

Using a microprocessor controlled Ambulatory Monitoring System (AMS) developed by one of us (LvD), we have been studying the changes in and control of heart rate in the resting horse. The system provides us with InterBeat Intervals (IBI in milliseconds), motion sensing, and a time domain measure (mean successive differences: MSD) of heart rate variability for periods up to 72 hours. Thoracic impedance is also available but parameters for the equine chest are not currently available. The system is completely noninvasive, small, and carried on a surcingle worn by the subject. The equine subject is confined to a stall in our teaching hospital but not otherwise restrained. Recording is virtually unobtrusive. Ten horses (judged to be clinically normal) were used in this preliminary study. After collection, the data were "offloaded" to a laptop computer for additional analysis. The electrocardiogram could be recorded on each of the ten animals. Complete data, suitable for spectral analysis, were obtained from four of the animals. Spectral estimates were calculated on periods of varying lengths (3-5 minutes) with more stable spectral estimates associated with longer recording periods. Results indicated the preponderance of parasympathetic control in equid heart rate. These results provide support for the utility of this method for the study of heart rate variability in the freely behaving horse.

Animals↗
PubMed1996

Studies on the influence of insulin on cyclic adenosine monophosphate in human vascular smooth muscle cells: dependence on cyclic guanosine monophosphate and modulation of catecholamine effects.

Insulin increases both cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP) in human vascular smooth muscle cells (hVSMC) and attenuates noradrenaline-induced vasoconstriction. In the present study, we aimed at investigation in hVSMC: 1) the interrelationships between insulin-induced increases of cGMP and cAMP; 2) the insulin effect on the catecholamine modulation of cAMP. Catecholamines cause both vasoconstriction and vasodilation. Vasoconstriction is attributable to the reduced synthesis of cAMP in hVSMC through alpha 2-adrenoceptors and to direct effects on calcium fluxes through alpha 1-adrenoceptors; vasodilation is attributable to the increased synthesis of cAMP through beta-adrenoceptors. In the present study, we determined the influence of insulin on cAMP in hVSMC incubated with or without: a) the inhibitor of guanylate cyclase methylene blue or the inhibitor of nitric oxide synthase NG-monomethyl-L-arginine (L-NMMA); b) the beta-adrenergic agonists isoproterenol and salbutamol; c) the physiological catecholamines noradrenaline and adrenaline; d) noradrenaline+the beta-adrenergic antagonist propranolol or the alpha 2-adrenergic antagonist yohimbine; e) noradrenaline+methylene blue of L-NMMA. We demonstrated that: 1) the inhibition of the insulin-induced cGMP synthesis blunts the insulin-induced increase of cAMP; 2) insulin induces a significant increase of cAMP also in the presence of isoproterenol, salbutamol, noradrenaline and adrenaline: the combined effects of insulin and catecholamines were additive in some, but not in all the experiments; 3) insulin enhances the cAMP concentrations induced by noradrenaline also in the presence of alpha 2- or beta-adrenergic antagonists; 4) in the presence of methylene blue or L-NMMA insulin does not modify the noradrenaline effects on cAMP.

Adrenergic alpha-Antagonists↗
PubMed1996

Nonenzymatic glycation of fibronectin impairs adhesive and proliferative properties of human vascular smooth muscle cells.

Nonenzymatic glycation of proteins is involved in the pathogenesis of diabetes vascular complications. Extracellular matrix proteins are a prominent target for nonenzymatic glycation because of their slow turnover rates. The aim of this study was to investigate the influence of human fibronectin (F) nonenzymatic glycation on adhesion and proliferation of cultured human vascular smooth muscle cells (hVSMC). Incubation of human F with 500 mmol/L D-glucose at 37 degrees C induced a time-dependent increase in fluorescence detectable at 440 nm after excitation at 363 nm. Nonenzymatic glycation did not affect binding of F itself to the plates. Adhesion of hVSMC to F increased with the increase of incubation time of the cells on the protein from 30 minutes up to 120 minutes and remained stable thereafter. Adhesion to glycated fibronectin (GF) was reduced in comparison to control F at all the different adhesion times. Adhesion of hVSMC to GF was reduced when F was exposed to glucose for 4, 9, or 28 days (P=.0417 to .0025), but not when F was exposed for 1 day. Adhesion of hVSMC to GF was reduced compared with adhesion to nonglycated F at all coating concentrations from 0.2 to 10 micrograms/mL (P=.05 to .014). Thus, nonenzymatic glycation of F impairs adhesion of hVSMC in vitro. Proliferation of hVSMC on F increased with increasing concentrations of the protein as coating agent (ANOVA:P<.0001 for both nonglycated F and GF). Proliferation with F glycated for 4, 9, and 28 days was reduced at concentrations of 1, 3, and 10 micrograms/mL as compared with proliferation with nonglycated F (P=.0253 to .0001). Proliferation on F glycated for only 1 day was not significantly reduced. When the number of hVSMC plated on control F was reduced by 25% to take into account the reduced adhesion, the number of cells that proliferated on F was still reduced. In conclusion, nonenzymatic glycation of F impairs adhesive and proliferative properties of hVSMC.

Cell Adhesion↗
PubMed1996

Effective written communication in biomedical sciences.

The written word is the biomedical scientist's most important and most enduring communication tool. Nevertheless, the development of writing skills receives little attention in most scientific disciplines and the ability to conduct research is often viewed as more important than the ability to communicate the results of that research. Consequently, many scientists lack the writing skills necessary to effectively convey essential aspects of their research. In this paper, we will discuss the importance of good writing skills, give examples of common mistakes that are made in biomedical science writing and offer suggestions on how to improve written communication.

Writing↗
PubMed1995

Stretch affects phenotype and proliferation of vascular smooth muscle cells.

The exertion of periodic dynamic strain on the arterial wall is hypothesized to be relevant to smooth muscle cell morphology and function. This study has investigated the effect of cyclic mechanical stretching on rabbit aortic smooth muscle cell proliferation and expression of contractile phenotype protein markers. Cells were cultured on flexible-bottomed dishes and cyclic stretch was applied (frequency 30 cycles/min, 15% elongation) using a Flexercell Strain unit. Cyclic stretch potentiated smooth muscle cell proliferation in serum-activated cultures but not in cultures maintained in 0.5% fetal calf serum. Stretching induced a serum-independent increase of h-caldesmon expression and this effect was reversible following termination of mechanical stimulation. Strain was without effect on smooth muscle myosin or calponin expression. In cells grown on laminin stretch-induced h-caldesmon expression was more prominent than in cells cultured on collagen types I and IV, poly-L-lysine and gelatin. These data suggest that cyclic mechanical stimulation possesses dual effect on vascular smooth muscle cell phenotype characteristics since it: 1) potentiates proliferation, an attribute of a dedifferentiated phenotype; and 2) increases expression of h-caldesmon considered a marker of a differentiated smooth muscle cell state.

Animals↗
PubMed1995

Endothelium-modulated proliferation of medial smooth muscle cells: influence of angiotensin II and converting enzyme inhibition.

This study investigated the role of the endothelium and angiotensin II (Ang II) in regulating medial smooth muscle cell (SMC) proliferation. [3H]-thymidine incorporation into medial SMC of rat arteries was examined in vivo, using ballooned rat carotid arteries, as well as in vitro, using cultures of aortic tissue rings (organoids). In vivo, maximal medial [3H]-thymidine incorporation occurred within 3 days post-ballooning. In endothelium-denuded organoids, maximum medial DNA synthesis was achieved after 7 days of culture. [3H]-thymidine-labelling of SMC in intact organoids (with endothelium) increased minimally during culture, indicating that the endothelium provided protection with respect to medial proliferation under basal conditions (culture in the presence of 1% plasma-derived serum). Inclusion of 10(-7) M Ang II significantly elevated medial [3H]-thymidine incorporation above that in control cultures. The stimulatory effect of Ang II was much more pronounced in intact organoids that in endothelium-denuded organoids, indicating synergistic growth regulation by Ang II and endothelium-derived factors. When organoids were cultured in the combined presence of Ang II and the ACE inhibitor cilazaprilat, labelling indices of intact organoids were also significantly increased above control, but to a lower level than those obtained in the presence of Ang II alone. However, for endothelium-denuded organoids, medial [3H]-thymidine incorporation in the combined presence of Ang II and cilazaprilat was not significantly different from that in untreated controls. Thus, cilazaprilat exerts both endothelium-dependent and endothelium-independent negative regulatory effects on medial SMC proliferation.

Angiotensin II↗
PubMed1995

Escherichia coli O157:H7 restriction pattern recognition by artificial neural network.

An artificial neural network model for the recognition of Escherichia coli O157:H7 restriction patterns was designed. In the training phase, images of two classes of E. coli isolates (O157:H7 and non-O157:H7) were digitized and transmitted to the neural network. The system was then tested for recognition of images not included in the training set. Promising results were achieved with the designed network configuration, providing a basis for further study. This application of a new generation of computation technology serves as an example of its usefulness in microbiology.

Animals↗
PubMed1995

Collecting, storing and transmitting heart sounds.

We have developed a system whereby heart sounds and accompanying electrocardiogram may be recorded in digital format, stored as files and transmitted as any other digital file. The present system is implemented on a Macintosh System 7.1 platform, but will run under System 7.0 to System 7.5. The code is written in object oriented C++. The data are presently taken using a standard heart sound microphone and ECG amplifier. The data collection program stores the sampled channels as 16 bit words. Each channel is sampled at 2 kb/s for periods of time ranging from 10 to 30 seconds. Our program then reads the file, displays it under a viewer and allows for high fidelity reproduction of the sounds.

Computers↗
PubMed1995

Representation of clinical problem assessment phrases in U.S. family practice using Read version 3.1 terms: a preliminary study.

The Read Codes from the United Kingdom are a comprehensive clinical vocabulary, and one of the most likely candidates for adoption as a standard for use in Computer-Based Patient Record (CPR) systems. The new version 3.1 codes represent a major enhancement to the content and structure of the coding system, including incorporation of a new hierarchy and an explicit model for the use of qualifier terms. This is a preliminary study investigating the suitability of these codes for representing clinical problem assessment phrases in U.S. family practice. Problem assessment phrases from outpatient progress notes were encoded into the equivalent Read terms. The problem assessment phrases were evaluated for complexity and clarity. The coded representations of the phrases were evaluated for clinical acceptability. A list of coding difficulties was compiled. The most common difficulties were (1) qualifier terms present but not allowable for that Read concept (24%), and (2) qualifier terms not present (20%). British spelling and abbreviation variants were noted, but were relatively insignificant. The Read codes appear to be suitable for use in U.S. primary care practice with fairly minor modifications, but further development is required to expand the content and structure of the model for qualifier terms.

Family Practice↗
PubMed1995

Comparing clinical vocabularies using coding system fidelity.

Much effort has been directed toward the development of an ideal multipurpose controlled medical vocabulary for use in human and veterinary medicine. SNOMED International is one effort that has resulted in a larger and more complex nomenclature system. Although it was able to code more concepts, SNOMED International failed to statistically improve vocabulary fidelity when compared with the 30+ year old SNVDO vocabulary. We found that SNOMED has a lower intercoder consistency than SNVDO and that a greater number of codes were necessary to represent an individual concept. Our study shows a significant Coder-Vocabulary interaction which suggests that more emphasis should be placed on coding guidelines and coder training. Clinician data entry and coding may be necessary for maximum vocabulary fidelity.

Abstracting and Indexing↗
PubMed1995

Effects of electrocardiograph frequency filters on P-QRS-T amplitudes of the feline electrocardiogram.

OBJECTIVE--To determine whether standard manual frequency filters in the ON and OFF settings affected P-QRS-T voltages, discover whether recorded P-QRS-T voltages vary between commercial electrocardiographs, assess effects of frequency filters on base-line artifact, and evaluate ECG frequency content by high-fidelity recordings subjected to digital filters with variable frequencies. DESIGN--Sequential 10-lead ECG were recorded in 30 cats, using 3 commercial electrocardiographs to assess effects of manual frequency filters on the P-QRS-T wave forms. Three clinically normal cats were evaluated for ECG frequency content. ANIMALS--Thirty cats (13 with hypertrophic cardiomyopathy; 4 with restrictive cardiomyopathy; 3 hyperthyroid; 1 with ventricular septal defect; 1 with aortic stenosis; and 8 with no detectable cardiovascular disease). Three additional clinically normal cats were studied for effects of frequency filters on the ECG frequency content. PROCEDURES--Ten-lead ECG were recorded on each cat by use of 3 commercial electrocardiographs sequentially. For each machine, a recording was made with manual filters ON, immediately followed by a recording with manual filters OFF. High-fidelity lead-II ECG recordings were made with filters set with their rolloff frequency at 0.1 Hz and 3.0 kHz; output voltage (0.2 mV/V) was fed to an analog-to-digital converter, then to attendant software, which sampled the signal at 6 kHz with a 12-bit sampler, and were digitally filtered at various corner frequencies. RESULTS--Voltages recorded by all 3 electrocardiographs were greatest when filters were OFF (most prominent on R- and S-wave voltages). In all recorded leads, R-wave voltage was significantly greater when filters were OFF than ON. Comparison of voltages indicated significant (P < 0.05) differences between R-wave voltages recorded in all leads with manual filters ON, but not with filters OFF. With filters ON, each electrocardiograph produced a smaller percentage of recordings with moderate to severe baseline artifact than with filters OFF. R-Wave amplitudes of high-fidelity lead-II ECG were significantly decreased with digital filters set at corner frequencies < 150 Hz. CONCLUSIONS--Significant (P < 0.05) voltage attenuation was recorded by each of the 3 commercial electrocardiographs when frequency filters were ON, compared with OFF. Comparison of waveform voltages among electrocardiographs with filters ON indicated significant variation in R-wave amplitudes in all leads. With manual filters ON, each electrocardiograph recorded a smaller percentage of recordings with baseline artifact than with filters OFF. Substantial frequency components > or = 150 Hz are present in the feline ECG waveform. Thus, filters with frequencies < 150 Hz markedly attenuate the feline R wave. CLINICAL RELEVANCE--Attenuation of feline ECG signals occurs with use of commercial electrocardiographs and varies greatly between manufacturers. This is attributable largely to internal manual frequency filters. These consequences may be important when applying standard feline reference values or when equivocal voltage measurements are recorded.

Animals↗
PubMed1994

Activation of human peripheral monocytes by angiotensin II.

This study has investigated the ability of the vasoconstrictor peptide angiotensin II to activate human peripheral blood monocytes. Activation was monitored by measuring both the release of tumor necrosis factor alpha from monocytes and their adhesion to monolayers of human endothelial cells. Angiotensin II-elicited activation of monocytes was dose-dependent (half-maximally effective concentration approximately 0.2 nM), saturable (maximally effective concentration approximately 5 nM), and sensitive to inhibition by the angiotensin type 1 receptor antagonist ZD 7155. Such direct actions imply that angiotensin II is an important candidate stimulus for the subendothelial infiltration of monocytes observed in atherogenesis and hypertension.

Angiotensin II↗
PubMed1994

Characterization of angiotensin II receptors in cultured adult rat cardiac fibroblasts. Coupling to signaling systems and gene expression.

Cardiac hypertrophy is largely due to cardiac fibroblast growth and increased synthesis of extracellular matrix. This study has investigated the contribution of the vasoactive hormone, angiotensin II, toward this hypertrophic process. We have demonstrated that cultures of adult rat cardiac fibroblasts express AT1 but not AT2 receptors for angiotensin II. The ability of angiotensin II to stimulate phosphoinositide catabolism and to elevate intracellular calcium concentrations in these cells was blocked by losartan, a specific AT1 receptor antagonist, but not by the AT2 receptor antagonist CGP 42112. Exposure of adult cardiac fibroblasts to angiotensin II resulted in the induction of several growth-related metabolic events including c-fos protooncogene expression and increased synthesis of DNA, RNA, and protein. Angiotensin II was also found to induce collagen type I, alpha 1 chain transcript expression in cardiac fibroblasts as well as the synthesis and secretion of collagen by these cells. The data demonstrate that angiotensin II, via AT1 receptors, can stimulate cardiac fibroblast growth and increase collagen synthesis in cardiac tissue. Thus, angiotensin II may contribute toward the development of cardiac hypertrophy in conditions of hypertension that are associated with elevated concentrations of angiotensin II.

Animals↗
PubMed1994

A system for browsing the SNOMED International vocabulary.

We have developed a means for "browsing" an extremely large vocabulary of over 130,000 medical terms (SNOMED International, 3rd ed.). This vocabulary someday hopes to become a standard vocabulary and coding scheme for patient medical records. After obtaining the vocabulary in machine readable form (ASCII in standard data format--SDF) we wrote a meta program in Turbo Pascal which parsed and embedded control codes into an input file for importing the data into an "infobase" known as FolioVIEWS. Using this infobase, it became possible to rapidly and reliably navigate around the SNOMED vocabulary in a manner impossible with printed material. The FolioVIEWS search engine is robust and rapid and allows for easy access to the terms. The utility of the infobase in evaluating the SNOMED vocabulary has been quite good. The actual utility of SNOMED as a standard vocabulary remains to be evaluated.

Information Storage and Retrieval↗
PubMed1994

A force plate and display system for studying ground reaction forces in dogs.

We have developed and implemented a low cost system for measuring ground reaction forces in dogs with normal and abnormal ambulation as they walk or trot over a floor mounted plate that measures vertical and horizontal forces. Orthogonally mounted strain gages measure the forces imposed. A bridge amplifier conditions the signals which are sampled and converted to digital form for display on an operator initiated graphical user interface (GUI) which displays the forces as a function of time on the screen of a Macintosh computer. The system also allows the input of timing of the velocity of approach to the plate and the foot strike can be monitored (via tap reply) on the computer screen to verify the fidelity of the foot strike on the active surface of the plate. The data gathered on a particular strike is stored as a "raw" signal, analyzed and recorded in a spread sheet text format for later analysis.

Analog-Digital Conversion↗