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J D Myers

Publications and source records attributed to J D Myers.

At least 19 recordsLinked to original sources
PubMed1997

The role of the plant properties in point-to-point arm movements: a robustness study.

In recent papers we demonstrated by means of a modeling study that the smoothness of hand paths and the bell-shaped character of hand velocity profiles which have been experimentally observed in point-to-point arm movements can be largely attributed to the biomechanical properties of the arm rather than to specific planning by the central nervous system. In this paper we present a study of the robustness of our earlier results comprising two goals: (i) the determination of the range of model parameters for which such observations remain valid, (ii) the identification of possible relationships between model parameters and kinematic variables. The results of this study imply three conclusions: (i) the valid range of the tested model parameters (namely the main muscle parameters) is large, (ii) the modeled phenomena are well behaved in that parametric changes do not give rise to bifurcations or other behavioral discontinuities in the analyzed ranges, (iii) there exist precise relationships between certain muscle parameters and the time course of the hand velocity. These results point out that the phenomena observed in our previous work are indeed robust and can lead to useful insights into the mechanisms comprising the regulatory action of the central nervous system as well as into the design principles for biologically inspired artificial arms.

Arm↗
PubMed1997

Attenuation of propranolol-induced bronchoconstriction by frusemide.

BACKGROUND: Inhaled propranolol causes bronchoconstriction in asthmatic subjects by an indirect mechanism which remains unclear. Inhaled frusemide has been shown to attenuate a number of indirectly acting bronchoconstrictor challenges. The aim of this study was to investigate whether frusemide could protect against propranolol-induced bronchoconstriction in patients with stable mild asthma. METHODS: Twelve asthmatic subjects were studied on three separate days. At the first visit subjects inhaled increasing doubling concentrations of propranolol (0.25-32 mg/ml), breathing tidally from a jet nebuliser. The provocative concentration of propranolol causing a 20% reduction in FEV1 (PC20FEV1 propranolol) was determined from the log concentration-response curve for each subject. At the following visits nebulised frusemide (4 ml x 10 mg/ml) or placebo (isotonic saline) was administered in a randomised, double blind, crossover fashion. FEV1 was measured immediately before and five minutes after drug administration. Individual PC20FEV1 propranolol was then administered and FEV1 was recorded at five minute intervals for 15 minutes. Residual bronchoconstriction was reversed with nebulised salbutamol. RESULTS: Frusemide had no acute bronchodilator effect but significantly reduced the maximum fall in FEV1 due to propranolol: mean fall 18.2% after placebo and 11.8% after frusemide. The median difference in maximum % fall in FEV1 within individuals between study days was 3.6% (95% CI 1.2 to 11.7). CONCLUSIONS: Frusemide attenuates propranolol-induced bronchoconstriction, a property shared with sodium cromoglycate. Both drugs block other indirect challenges and the present study lends further support to the suggestion that frusemide and cromoglycate share a similar mechanism of action in the airways.

Adrenergic beta-Antagonists↗
PubMed1990

Pathogenesis of caprine arthritis encephalitis virus. Cellular localization of viral transcripts in tissues of infected goats.

Pathologic specimens of 18 goats with classical lesions of caprine arthritis-encephalitis (CAE) virus infection were examined morphologically and by in situ hybridization using molecularly cloned CAEV deoxyribonucleic acid (DNA) to determine which tissues and cells of naturally infected goats supported virus replication. Large numbers of cells with viral transcripts were detected in inflamed brain, spinal cord, lung, joints, and mammary gland. These cells were morphologically compatible with macrophages. Fewer cells with viral transcripts were seen in noninflamed tissues. Viral RNA was identified in macrophagelike cells in lung, liver, spleen, and lymph nodes, in cells lining the vessels of brain and synovium, and in epithelial cells of intestinal crypts, renal tubules, and thyroid follicles. These data suggest that the cell tropism of lentiviruses may extend beyond the narrow boundaries of lymphocytes and macrophages.

Age Factors↗
PubMed1989

Development and application of immunocytochemical staining techniques: a review.

Since the field of immunocytochemistry was pioneered almost half a century ago, over 30 different immunostaining methods have been developed. Most laboratory investigators, however, are aware of only a few of the more popular techniques. This article, therefore, reviews and places in historical perspective many of the less common methodologies. A discussion of the progression of immunostaining methodology from purely immunologic techniques (employing only antigens, antibodies, and free enzymatic preparations) to procedures that use non-immunologic substances (such as avidin, biotin, and protein A) is presented. Basic principles of immunostaining, including specimen preparation, fixation, control procedures, interpretation, and problems unique to cytopathology, are also discussed. Schematic diagrams that illustrate the nature and arrangement of the immunochemical reagents employed in most of these techniques are provided in order to demonstrate how various materials can be combined to create a desired staining effect.

Antibodies↗
PubMed1989

Applications of combination wavelength (1060-nm and 530-nm) and pulsed Nd:YAG laser for contact laser surgery.

Two pulsed neodimium yittrium aluminum garnet (Nd:YAG) laser systems were evaluated for contact surgery through a fiberoptic system with a sapphire tip. Pulsed Nd:YAG laser at 1060 nm was as effective as continuous-wave Nd:YAG laser in producing tissue incisions. A combination of 1060-nm and 530-nm wavelengths achieved smooth cutting at lower energy levels. Corneal endothelial cell damage occurred at the high power level (7 watts) required for smooth underwater incisions with both continuous wave and pulsed lasers.

Animals↗
PubMed1988

Sensitive and specific monoclonal antibody recognition of human lung cancer antigen on preserved sputum cells: a new approach to early lung cancer detection.

Murine monoclonal antibodies (Mabs) to a glycolipid antigen of small-cell (SCC) and a protein antigen of non-small-cell lung cancer (NSCC) were applied to preserved sputum specimens from individuals who participated in The Johns Hopkins Lung Project (JHLP). In that study, undertaken in 1973 to evaluate the efficacy of sputum cytology screening, half of the high-risk participants (5,226 men, greater than or equal to 45 years of age, currently smoking greater than or equal to 1 pack of cigarettes per day) were randomly assigned to produce specimens for cytopathological analysis. During regular screenings over the next 5 to 8 years, 626 (12%) showed moderate (or greater) atypia. Sixty-nine of these (26 who progressed to cancer, 43 who did not) were randomly selected for a blinded improved Mab immunostaining protocol in the present study. Satisfactory specimens with morphologic atypia immunostained positively in 14 of the 22 patients who eventually progressed to cancer (sensitivity 64%), and were nonreactive in 35 of the 40 patients who did not progress to lung cancer (specificity 88%). Review of the true positive specimens (14/22 atypias) showed that they were collected 24 months in advance of diagnosis. In contrast, the 8/22 false negative atypias (failure to stain) showed that they were collected for an average of 57 months preceding the diagnosis of cancer. Subsequent specimens (average, 26 months before cancer) from participants who were originally considered "false negative" did stain positively improving sensitivity to 91% among specimens collected for an average of 2 years in advance of the clinical appearance of lung cancer. Specificity remained at 88%. Recognition of neoplastic antigen expression 2 years in advance of clinical cancer may be a valuable intermediate end point in studies of lung cancer prevention, detection, and therapy.

Aged↗
PubMed1986

The computer as a diagnostic consultant, with emphasis on use of laboratory data.

In this preliminary study concerning the applicability of expert computer systems, such as INTERNIST-I, to providing advice to clinical pathologists regarding patients' diagnoses and the pertinence of performing further laboratory tests, 32 complex cases, drawn from Case Records of the Massachusetts General Hospital, were analyzed diagnostically by computer, on the basis of clinical laboratory data only. Half (16 cases) were diagnosed correctly, but in 15 of the rest no diagnostic conclusion could be reached. However, no diagnostic errors were made. The study provides preliminary evidence that expert computer systems can be useful to clinical pathologists and clinical internists in guiding the laboratory workup of patients toward correct diagnosis.

Artificial Intelligence↗
PubMed1986

The INTERNIST-1/QUICK MEDICAL REFERENCE project--status report.

INTERNIST-1 and its successor, QUICK MEDICAL REFERENCE (QMR), are computer programs designed to provide health care professionals with diagnostic assistance in general internal medicine. Both programs rely on the INTERNIST-1 computerized knowledge base, which comprehensively describes 570 diseases in internal medicine. The philosophies behind the development of each program differ. Whereas INTERNIST-1 functions solely as a high-powered diagnostic consultant program, the QMR program acts more as an information tool, providing users with multiple ways of reviewing and manipulating the diagnostic information in the program's knowledge base. At the lowest level, the program can be viewed as an electronic textbook of medicine. In addition, the QMR program has the ability to assist users with generating hypotheses in complex patient cases. The QMR program has not been evaluated formally as an information tool for practicing physicians. A preliminary study indicates that QMR's case-analysis capabilities are of potential benefit in most patients in internal medicine admitted for diagnostic evaluation.

Diagnosis, Computer-Assisted↗
PubMed1985

INTERNIST-I properties: representing common sense and good medical practice in a computerized medical knowledge base.

INTERNIST-I is an experimental diagnostic consultant program for use on clinically challenging cases in internal medicine. Properties are a part of the INTERNIST-I knowledge representation scheme which embody essential information about the medical facts contained in the knowledge base. Properties provide the INTERNIST-I program with a measure of common sense and encourage the program to follow good medical practice. Properties substantially influence the behavior of the INTERNIST-I diagnostic program during case analyses. This paper reviews the implementation and significance of properties.

Artificial Intelligence↗
PubMed1982

Internist-1, an experimental computer-based diagnostic consultant for general internal medicine.

Internist-I is an experimental computer program capable of making multiple and complete diagnoses in internal medicine. It differs from most other programs for computer-assisted diagnosis in the generality of its approach and the size and diversity of its knowledge base. To document the strengths and weaknesses of the program we performed a systematic evaluation of the capabilities of INTERNIST-I. Its performance on a series of 19 clinicopathological exercises (Case Records of the Massachusetts General Hospital) published in the Journal appeared qualitatively similar to that of the hospital clinicians but inferior to that of the case discussants. The evaluation demonstrated that the present form of the program is not sufficiently reliable for clinical applications. Specific deficiencies that must be overcome include the program's inability to reason anatomically or temporally, its inability to construct differential diagnoses spanning multiple areas, its occasional attribution of findings to improper causes, and its inability to explain its "thinking".

Diagnosis, Computer-Assisted↗
PubMed1977

Urea transport in the dogfish kidney.

There is increasing evidence that urea movement across many epithelia involves more than passive diffusion. Of particular interest is the observation that urea transport across the erythrocyte membrane and across the vasopressin-stimulated urinary bladder of the toad occurs by facilitated diffusion, and can be selectively inhibited by phloretin and chromate. These inhibitory agents have been employed in studies of renal urea reabsorption by the spiny dogfish Squalus acanthias. Both agents inhibit urea reabsorption; the effect of chromate is of particular interest, since it blocks urea reabsorption to a proportionately greater extent than sodium reabsorption, and does so irreversibly.

Animals↗
PubMed1977

The effects of failure and depression on subsequent aggression.

Two experiments assessed the effects of repeated failure on subsequent aggressive responses to increasing attack. In the first experiment, male subjects who had been assigned randomly to a treatment involving failure at a task evidence smaller increments in aggressive responses to attack than did those who succeeded at the initial task. In the second experiment, prior failure inhibited the aggressive increments to escalating attack on the part of depressed male subjects but faciliated the aggressive increments of nondepressed male subjects. The results are discussed in terms of learned helplessness theory and a belief in the ability to control the consequences one's behavior.

Achievement↗
PubMed1977

Recertification.

Explore the source record for details and available documents.

Certification↗