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Biomedical subjects

M Hubbard

Publications and source records attributed to M Hubbard.

At least 37 records · Page 2Linked to original sources
PubMed1993

Computer simulation in sport and industry.

The last several decades have brought decreases in the specific cost of computer memory and increases in processor throughput. As a result simulation has become correspondingly more important as a component of industrial design and as a method for the study of general biomechanics and sports techniques. This paper illustrates, by way of examples, several of the more important aspects of the application of computer simulation to dynamic problems. Topics include (1) the ideas of suitable model complexity and its tradeoff with interpretability; (2) the sequential and iterative nature of model building and the importance of experimental data in the modelling and validation process; (3) the essential role of user-friendly software and graphical interfaces in the interchange of information between simulation programs and the users; and 4) the role of computer simulation in learning feedback loops, both in the field and in the computer laboratory. Most industrial use of simulation is in the design process. A similar approach is equally valid in biomechanics and sport applications through the incorporation of design variables, which may be easily changed in the model experiment.

Biomechanical Phenomena↗
PubMed1991

Axial forces and normal distributed loads in twining stems of morning glory.

In analysing the mechanics of twining, we hypothesize that contact forces are important in maintaining the twining habit of viny stems. This hypothesis is formalized with a description of the force balance in the natural coordinate system associated with the Frenet vectors attached to the 'generative helix' of the vine. The force balance indicates that, if shear forces are neglected, an axial force within the stem is balanced by a normal load distributed along the line of contact between the supporting pole and the stem. Two kinds of empirical studies were conducted to verify the importance of the putative normal load. Firstly, vine geometry was measured on and off the supporting pole. When removed from the pole, the helical stem forms a coil of smaller radius, smaller wavelength and larger torsion. Next, forces were estimated from observations of the pressure exerted by a stem twining around a water-filled balloon. Twining around a dowel 0.95 cm in diameter, a typical stem of morning glory (Pharbitis nil) sustains a tension of 100 g balanced by a normal distributed load of -30 g cm-1. Thus the twining stem puts itself into tension and uses a helical geometry to generate contact forces which are large relative to the stem weight of 40 mg cm-1.

Elasticity↗
PubMed1990

The incidence of human immunodeficiency virus (HIV) in fetal cord samples utilized as serum supplements for in vitro fertilization.

Prior to initiating routine fetal cord serum (FCS) supplementation in our in vitro laboratory, the incidence of HIV in 306 random fetal cord samples obtained at the Labor and Delivery Unit of the Johns Hopkins Hospital from July 1985 to January 1988 was determined from a cross-sectional patient sample. Of 306 samples, 3 (0.98%) were positive for HIV, and confirmed by Western blot analysis, enzyme immunoassay (ELISA), a prevalence significantly higher than a national sample (0.012%). The use of FCS in this setting was determined to be an unacceptable risk to patients undergoing in vitro fertilization. The 90-day quarantine period for verification of HIV seronegativity applied to semen donors may not be applicable to FCS sampling. Patient risk may also increase with pooling of FCS samples prior to HIV testing.

Blotting, Western↗
PubMed1990

Effect of serum from patients with minimal to mild endometriosis on mouse embryo development in vitro.

Two-cell mouse embryos were cultured at 37 degrees C in 5% CO2, 95% air with a 7.5% serum supplement from patients with minimal to mild endometriosis, (group I, n = 31), tubal factor (group II, n = 33), male factor (group III, n = 17), fetal cord samples (group IV, n = 37), and Ham's F-10 medium (Gibco, Grand Island, NY) without a serum supplement (group V, n = 30). The progression to blastocyst stage (mean percent +/- SE) at 96 hours in groups I, II, III, IV, and V was 29.9% +/- 3.7%, 60.6% +/- 4.9%, 56.2% +/- 5.2%, 61.7% +/- 5.8%, and 63.2% +/- 6.9%, respectively. Serum factors appear to be associated with an inhibition of early embryogenesis, which may explain the decreased fertility rates observed in patients with minimal to mild endometriosis.

Animals↗
PubMed1990

Fall-off in reporting life events: effects of life change, desirability, and anticipation.

The influence of event characteristics on recall was examined by directly comparing fall-off in reporting life events as a function of life change, desirability, and anticipation. We collected information from a sample of 1,669 blue-collar workers on stressful life events that occurred in a 1-year interval before the questionnaire was administered. The results indicated no fall-off in reporting events associated with marked life changes (ie, salient events). In contrast, significant fall-off was observed for events characterized by varying degrees of desirability and anticipation. Although ratings of desirability and saliency were not independent, saliency of life events emerged as the dimension most closely associated with accuracy of event reporting. Research on the reliability of measures of life events and the association between event characteristics and illness should consider the kinds of systematic reporting differences observed here.

Aged↗
PubMed1989

Comparison of monocyte separation methods using flow cytometric analysis.

We isolated normal, nonactivated human monocytes from peripheral blood by four different methods: (1) rosetting with sheep erythrocytes pretreated with 2-aminoethylisothiouronium bromide hydrobromide (AET) followed by monoclonal antibody (OKT3 (CD3), B1 (CD19), Leu7, Leu11 (CD16] and complement treatment; (2) adherence to gelatin/plasma-coated flasks; (3) adherence to plastic dishes; and (4) separation by the Sepracell technique. We monitored these monocyte separations by determining cell recoveries, OKT4A+ lymphocyte contamination, monocyte binding to human immunodeficiency virus (HIV), number of non-specific esterase-positive cells, and proportion of mononuclear cells reactive with a battery of monoclonal antibodies specific for monocytes. Our results indicate that of the four methods compared, adherence to gelatin/plasma-coated flasks produced the highest purity, recovery, and satisfactory binding to HIV with the fewest contaminating CD4+ T cells.

Antibodies, Monoclonal↗
PubMed1989

Controlled study of haloperidol, pimozide and placebo for the treatment of Gilles de la Tourette's syndrome.

The results of this controlled study of the treatment of 57 patients with Gilles de la Tourette's syndrome suggested that both haloperidol and pimozide were more effective than placebo, but that haloperidol was slightly more effective than pimozide. Adverse effects occurred more frequently with haloperidol vs placebo than with pimozide vs placebo, but the frequency was not significantly different for haloperidol compared with pimozide. Clinically significant cardiac effects did not occur at a maximum dosage of 0.3 mg/kg or 20 mg/d for pimozide and 10 mg/d for haloperidol. However, the QTc interval was prolonged during pimozide treatment compared with that during haloperidol treatment, although the values for both medications were not in an abnormal range.

Adolescent↗
PubMed1989

Bloodstream infections in the elderly.

PURPOSE: Bacteremia in the elderly is associated with a different clinical course and a higher mortality rate when compared with that in younger age groups. In order to examine these issues in the aged, we reviewed the clinical course and factors involved in the outcome of 100 episodes of bloodstream infections in patients over 65 years of age. PATIENTS AND METHODS: The hospital records of all patients over 65 years of age at The Mount Sinai Hospital with a positive blood culture result during the period October 1984 to October 1986 were reviewed. Place of residence before hospital admission, site of acquisition of infection, source of bloodstream infection, and microorganism were analyzed. Antimicrobial therapy was defined as appropriate if initial therapy included one agent to which the isolate was sensitive, or inappropriate if the isolate was resistant. The following factors affecting survival were analyzed: age, sex, underlying diseases, clinical parameters on admission, white blood cell count, mental status, source of infection, microorganism isolated, antibiotic toxicity, and appropriate versus inappropriate antibiotic therapy. RESULTS: Most patients were female (63 percent), were febrile (90 percent), had an altered mental status (52 percent), and had a neutrophilic response (61 percent). Eighty-three percent of patients were admitted from the community (home), 14 percent were from long-term-care facilities, and 3 percent were transferred from other hospitals. Fifty percent of infections were nosocomial, and 44 percent were community (home and nursing home)-acquired. Gram-negative organisms accounted for 60 percent of isolates, with Escherichia coli (22 percent) and Klebsiella species (11 percent) predominating; 30 percent were gram-positive organisms, with Staphylococcus aureus (13 percent) and Streptococcus faecalis (10 percent) the most common. The overall survival was 60 percent; the survival rate was 65.8 percent for community-acquired (home) bacteremia, 75 percent for nursing home-acquired bacteremia, and 52.8 percent for hospital-acquired bacteremia. Survival for gram-negative isolates was 65 percent, versus 51.7 percent for gram-positive isolates. Survival was greatest in patients whose source of bacteremia was either the genitourinary tract (70 percent) or an intravascular device (78 percent) and poorest in patients with lower respiratory tract source (42 percent); all three patients with endocarditis died. Increased survival was observed in patients treated with appropriate antimicrobial agents regardless of age, source of infection, or bloodstream isolates.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗
PubMed1989

Rapid and accurate estimation of release conditions in the javelin throw.

We have developed a system to measure initial conditions in the javelin throw rapidly enough to be used by the thrower for feedback in performance improvement. The system consists of three subsystems whose main tasks are: (A) acquisition of automatically digitized high speed (200 Hz) video x, y position data for the first 0.1-0.2 s of the javelin flight after release (B) estimation of five javelin release conditions from the x, y position data and (C) graphical presentation to the thrower of these release conditions and a simulation of the subsequent flight together with optimal conditions and flight for the sam release velocity. The estimation scheme relies on a simulation model and is at least an order of magnitude more accurate than previously reported measurements of javelin release conditions. The system provides, for the first time ever in any throwing event, the ability to critique nearly instantly in a precise, quantitative manner the crucial factors in the throw which determine the range. This should be expected to much greater control and consistency of throwing variables by athletes who use system and could even lead to an evolution of new throwing techniques.

Algorithms↗
PubMed1989

Trendelenburg position and passive leg raising do not significantly improve cardiopulmonary performance in the anesthetized patient with coronary artery disease.

The effects of the Trendelenburg (TREND) position and passive straight leg raising (PLR) on cardiopulmonary performance in 18 anesthetized patients undergoing myocardial revascularization were studied with a two-dimensional transesophageal echocardiography probe and a thermodilution right ventricular ejection fraction (RVEF) pulmonary artery catheter. The TREND position (at 20 degrees) and PLR (at 60 degrees) were studied in relation to the level-supine position in random order. At 3 min, the TREND caused significant (p less than .05) decreases in heart rate (62 +/- 9 to 58 +/- 10 [SD] beat/min) and RVEF (0.48 +/- 0.11 to 0.44 +/- 0.10), and significant increases in mean arterial pressure (77 +/- 11 to 82 +/- 11 mm Hg), mean pulmonary artery pressure (16 +/- 4.3 to 19 +/- 5.5 mm Hg), wedge pressure (11 +/- 4 to 13 +/- 4 mm Hg), cardiac index (CI) (2.36 +/- 0.79 to 2.52 +/- 0.93 L/min.m2), right ventricular end-systolic volume index (44 +/- 21 to 58 +/- 21 ml/m2), right ventricular end-diastolic volume index (83 +/- 24 to 102 +/- 22 ml/m2), and shunt fraction (0.16 +/- 0.06 to 0.19 +/- 0.06). CVP and left ventricular areas did not change significantly. PLR had similar effects as the TREND position, except CI did not change significantly. Thus, the TREND and PLR resulted in minor hemodynamic improvement with right ventricular dilation, decreased RVEF, and impaired oxygenation in the anesthetized cardiac surgical patient.

Anesthesia, General↗
PubMed1987

The normal pericardium does not affect left ventricular function.

Whether the normal pericardium exerts a constraining effect on left ventricular (LV) diastolic compliance and/or systolic function is controversial. Left ventricular filling and performance were studied in 15 patients by two-dimensional transesophageal echocardiography (2D-TEE) measuring end-diastolic area (EDa), end-systolic area (ESa), ejection fraction area (EFa), and hemodynamics immediately pre- and post-pericardiotomy. To diminish the influences of other variables such as surgical stimulation, chest wall constraint, and autoregulation, measurements were performed in deeply anesthetized patients with the chest fully opened immediately before and after pericardiotomy (PC). No significant echocardiographic or hemodynamic changes were observed after PC. Although alterations in compliance cannot be excluded, no significant changes in LV diastolic filling (EDa, pulmonary capillary wedge pressure [PCWP]) or systolic performance (EFa, cardiac output [CO]) were found. Therefore, it is concluded that the normal pericardium does not exert a measurable constraining effect on LV performance.

Coronary Artery Bypass↗
PubMed1986

Antigen detection in immune complexes by a modified staphylococci binding assay and Western blot analysis.

The combination of a modified Staphylococci binding assay for immune complexes and Western blot analysis is described for the isolation and detection of antigen in immune complexes from human sera. The strategy of the procedure is to preclear immune complexes from other serum components by sequential polyethylene glycol precipitation and incubation with insoluble protein A under conditions in which immune complexes are preferentially bound. Immune complexes are eluted from protein A in sodium dodecyl sulfate buffer and dissociated by acrylamide electrophoresis. Resolved proteins are then transblotted to nitrocellulose, and antigen is detected with specific antibody. Immune complexes were prepared in vitro with an antigen (keyhole limpet hemocyanin) that focuses well on electrophoresis and for which a potent immunologic probe (antibody) was available. In this system, antigen could be detected when immune complexes were present in sera in concentrations as low as 20 micrograms aggregated-IgG eq/ml, regardless of antigen-antibody ratio. We demonstrate the detection of horse globulin in immune complexes from a patient with acute serum sickness and hepatitis B virus antigen in complexes from a patient with vasculitis.

Adult↗
PubMed1985

Immune complexes in the acquired immunodeficiency syndrome (AIDS): relationship to disease manifestation, risk group, and immunologic defect.

Immune complex assays (and other immunologic tests) were performed on sera from 162 patients with the acquired immunodeficiency syndrome (AIDS) and 275 AIDS-related subjects. Immune complexes were detected in 89% of AIDS patients and 93% of homosexual men with lymphadenopathy. Immune complex levels in AIDS patients were not associated with a particular risk group or with types of opportunistic infection or malignancy; however, they correlated with other laboratory features of the immune defect (depression in T helper cells and T helper/suppressor-cell ratio, and IgG levels). Immune complexes were also detected in a lesser proportion of risk-group controls (homosexual men, hemophiliacs, Haitians). In risk-group controls, immune complex levels were associated with certain features reflecting sexual practice, blood product exposure, or infection, but these features did not account for the higher levels found in AIDS patients. In appropriate situations, immune complex assays may be of value as screening tests or, possibly, as prognostic indicators for AIDS or AIDS-related syndromes.

Acquired Immunodeficiency Syndrome↗
PubMed1985

Exposure to human T-lymphotropic virus type III/lymphadenopathy-associated virus and immunologic abnormalities in asymptomatic homosexual men.

Immunologic and serologic studies were done in 120 homosexual men who reportedly had no symptoms related to the acquired immunodeficiency syndrome. Forty-nine men (41%) had antibody to the retrovirus human T-lymphotropic virus type III/lymphadenopathy-associated virus (HTLV-III/LAV), and 37 (31%) had an abnormal T-cell subset ratio and other immunologic abnormalities. These abnormalities were almost exclusively confined to men seropositive for the retrovirus. Multivariate statistical analysis showed that exposure to HTLV-III/LAV was the single best predictor of T-cell (and other) immunologic abnormalities. Sexual practice, particularly receptive anal intercourse, predicted exposure to HTLV-III/LAV but was not independently related to T-cell abnormalities. The association of other microbial serologic findings with HTLV-III/LAV seropositivity or T-cell changes was a coincidental function of sexual activity. Immunologic abnormalities in asymptomatic homosexual men are mostly related to exposure to HTLV-III/LAV.

Antibodies, Viral↗
PubMed1985

Immunoassay for IgG rheumatoid factor with a murine monoclonal anti-Fd antibody.

Conventional radioimmunoassays for IgG rheumatoid factors (RF) detect the binding of IgG RF (or their F(ab')2 fragments) to solid-phase human IgG Fc fragments or rabbit IgG. Binding is detected with a radiolabeled antibody that is IgG-specific but is nonreactive with human Fc (i.e., an alpha-Fd reagent) or with rabbit IgG. Anti-Fd reagents are quite laborious to produce. We developed a murine monoclonal alpha-Fd antibody, confirmed its specificity, and compared it with conventional rabbit alpha-Fd in the IgG RF radioimmunoassay. We also adapted the assay to an enzyme-linked assay with both human Fc and rabbit IgG as antigen. We compared the four assay methods with each other and examined their relationship to certain clinical and laboratory features of rheumatoid arthritis.

Animals↗
PubMed1984

Simulation of javelin flight using experimental aerodynamic data.

This paper discusses computer simulation of the differential equations which describe javelin dynamics in flight. It is shown that the use of experimental aerodynamic forces and moments in the equations is preferable to theoretical approximations for these forces and moments which have been used in previous studies. An example which is characteristic of a good throw is presented and analyzed and many interesting features of the trajectory are pointed out.

Computers↗