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Biomedical subjects

M Hubbard

Publications and source records attributed to M Hubbard.

At least 19 recordsLinked to original sources
PubMed2006

Dynamics of the basketball shot with application to the free throw.

A completely general three-dimensional dynamic model is presented for the motion of basketball shots that may contact the rim, the backboard, the bridge between the rim and board, and possibly the board and the bridge simultaneously. Non-linear ordinary differential equations with six degrees of freedom describe the ball angular velocity and ball centre position. The model includes radial ball compliance and damping and contains five sub-models: purely gravitational flight, and ball-rim, ball-bridge, ball-board, and ball-bridge-board contact. Each contact sub-model has both slipping and non-slipping motions. Switching between the sub-models depends on the reaction force at, and velocity of, the contact point. Although the model can be used to study shots from any point on the court, we here use it to study the sets of free throw release angle, velocity, angular velocity, and lateral deviation angle that result in success (capture), as well as underhand free throws and those using an under-inflated ball. Free throw shots with larger backspin, lower inflation pressures, and underhand release conditions are shown to result in larger capture percentages.

Basketball↗
PubMed2006

Menopausal symptoms in a hospital-based sample of women in southern Thailand.

OBJECTIVE: To evaluate menopausal symptoms and quality of life in middle-aged women. STUDY DESIGN: Hospital-based, cross-sectional study. METHODS: A survey was conducted among 270 women aged 45-65 years who attended the gynecological and menopause clinic, Songklanagarind Hospital. We used the MENQOL questionnaire as the instrument. RESULTS: The average age at menopause of the postmenopausal women was 48.7 years (range 40-57 years). The prevalences of the classical menopausal symptoms--hot flushes, night sweats, and vaginal dryness--in the women aged 45-65 years were 36.8%, 20.8 and 55.3%, respectively. The three most prevalent symptoms in perimenopause were aching in muscles and joints, experiencing poor memory, and change in sexual desire. Within the four domains (vasomotor, psychological, physical, and sexual symptoms), more suffering was reported in the perimenopausal and postmenopausal subjects than in the premenopausal subjects (p < 0.001). CONCLUSIONS: Peri- and postmenopausal women had a significant decrease in quality of life compared to premenopausal women.

Adult↗
PubMed2003

Altered arousal response in infants exposed to cigarette smoke.

AIMS: A failure of the arousal mechanism is a key feature in the apnoea theory for sudden infant death syndrome (SIDS). In infants studied at an age when the incidence of SIDS is highest, we evaluated whether in utero smoke exposed infants have altered arousal response to standardised auditory stimuli, and/or sleep pattern, as recorded on overnight complex sleep polysomnography. METHODS: A standardised sequence of audiology stimuli was applied binaurally to 20 in utero smoke and non-smoke exposed infants aged 8-12 weeks during a rapid eye movement (REM) and NREM epoch, in a controlled (temperature, position, pacifier use, noise) sleep environment. Infants were monitored for 10-12 hours using complex sleep polysomnography. RESULTS: Five infants exposed to in utero tobacco smoke did not have behavioural arousal response, whereas all non-smoke exposed infants aroused during NREM (p = 0.016). There was, however, no difference in REM sleep, and the groups did not differ in routine overnight complex sleep polysomnography parameters. CONCLUSION: At the age when the incidence of SIDS is at its peak, infants of smoking mothers are less rousable than those of non-smoking mothers in NREM sleep; this may partly explain why such infants are more at risk of SIDS.

Adult↗
PubMed2001

Intracellular cytokines in the acute response to highly active antiretroviral therapy.

OBJECTIVES: Successful highly active antiretroviral therapy (HAART) is usually associated with a rapid decline in HIV plasma RNA levels and a gradual increase in CD4 T cells. We examined whether changes in cytokine production and profile precede other immunological changes and whether these might occur in temporal association with plasma HIV RNA changes. DESIGN AND METHODS: Eleven HIV-1-infected patients were enrolled into a prospective cohort study; eight patients were naive to antiretroviral therapy. Blood samples were collected pre-therapy (week 0) and at 1, 2, and 3 weeks post-initiation of therapy. RESULTS: All 11 patients enrolled remained on triple HAART for 1 week, eight for 2 weeks, and six for > or = 3 weeks. When compared to week 0, these patients had a > or = 2-log10 decline in HIV plasma RNA levels and/or a decline to < or = 400 copies/ml by week 3 of therapy (p = 0.004). The numbers and percentages of CD4 and CD8 T cells, and the percentage of naive, memory, and activated T cells did not change significantly between weeks 0 and 1 or 0 and 3. Of all the immune parameters examined only: the percentage of CD4 T cells spontaneously producing tumor necrosis factor (TNF)-alpha (median, 2.4 versus 0.5% P = 0.025); the percentage of CD8 T cells spontaneously producing TNF-alpha (median, 0.6 versus 0.2% P = 0.037); and the percentage of CD3 T cells spontaneously producing interleukin-4 (median, 1.8 versus 0.8% P = 0.004) changed significantly between weeks 0 and 3. CONCLUSIONS: In these patients, decreases in the percentage of T cells spontaneously producing TNF-alpha or interleukin-4 preceded changes in CD4 T cells. If confirmed by others, these observations may be useful as early predictors of response to and early failure of HAART.

Adult↗
PubMed2001

Correcting out-of-plane errors in two-dimensional imaging using nonimage-related information.

Two-dimensional imaging with a single camera assumes that the motion occurs in a calibrated plane perpendicular to the camera axis. It is well known that kinematic errors result if the object fails to remain in this plane and that if both the distance to the calibration plane from the camera and the distance out-of-plane are known, an analytical correction for the out-of-plane error can be made. Less well appreciated is that out-of-plane distance can frequently be acquired from other, nonimage-related information. In the two examples given, the mediolateral center of pressure coordinate of the foot measured from a force plate and the measured landing point of a shot put throw were used. In both cases, the resulting out-of-plane correction improved the accuracy of the 2-D kinematic data dramatically. These examples also demonstrate that the use of nonimage-related data can increase the accuracy of kinematic data without an increase in the complexity of the experiment.

Diagnostic Errors↗
PubMed2001

Dependence of release variables in the shot put.

When the shot is released above a horizontal plane, range from this point depends on release height, speed and angle. Measured distance is the sum of this range and horizontal distance of the release point from the throwing circle edge. Optimal release conditions can be calculated only if the dependence of release velocity on other variables, due to thrower limitations, is known. Experiments on two shot-putters investigated the hypothesis that there are constraint relationships among these four release parameters. A variable scaling scheme, using measurement of impact point and the known magnitude of g, corrected 2D data from one camera for out-of-plane motion and yielded accurate estimates of release parameters. Multivariate regression analyses determined approximate constraint surfaces limiting performance. Achievable release speed decreases with increasing release angle at about 1.7(m/s)/rad and decreases with increasing release height at about 0.8(m/s)/m, with only small differences in sensitivities between the throwers. Horizontal release distance also decreases with increasing release angle at about 1.7m/rad and increases with increasing release height at about 1.3m/m, again with only small differences between the two throwers. Optimal release conditions producing maximum range for a particular athlete can be determined using similar constraints for that athlete.

Humans↗
PubMed2001

Experimental determination of baseball spin and lift.

The aim of this study was to develop a new method for the determination of lift on spinning baseballs. Inertial trajectories of (a) ball surface markers during the first metre of flight and (b) the centre of mass trajectory near home-plate were measured in a pitch using high-speed video. A theoretical model was developed, incorporating aerodynamic Magnus-Robins lift, drag and cross forces, which predicts the centre of mass and marker trajectories. Parameters including initial conditions and aerodynamic coefficients were estimated iteratively by minimizing the error between predicted and measured trajectories. We compare the resulting lift coefficients and spin parameter values with those of previous studies. Lift on four-seam pitches can be as much as three times that of two-seam pitches, although this disparity is reduced for spin parameters greater than 0.4.

Baseball↗
PubMed2000

Severe obstructive sleep apnoea secondary to pressure garments used in the treatment of hypertrophic burn scars.

Obstructive sleep apnoea (OSA) secondary to pressure garments used to treat hypertrophic scarring of burns has never been reported. The present study describes two children who presented with OSA following introduction of such garments for management of hypertrophic scars following severe facial and upper body burns. Complex sleep polysomnography confirmed severe OSA with desaturations sufficient to result in physiological dysfunction that significantly improved on removal of the garments. As there is little evidence to suggest that the use of such garments alters the end result, the potentially serious side effect of obstructive sleep apnoea should be considered before their use is advised.

Adolescent↗
PubMed1999

Evaluation of stabilized whole blood control materials for lymphocyte immunophenotyping.

We evaluated stabilized whole blood control materials for their performance as a routine control material for immunophenotyping using flow cytometry. These materials serve as the method control, controlling for both the binding of monoclonal antibodies to the cells and the efficiency of the red-blood-cell lysing reagent. Three products (FluoroTrol, StatusFlow, and CD-Chex): were tested. The controls performed very well in evaluating both CD4 and CD8 percentages and absolute cell counts using flow cytometry. Light scattering patterns and fluorescence intensity of antibody binding were slightly different from those of normal whole blood. These products are not appropriate for quantitative fluorescence standards. Cytometry (Comm. Clin. Cytometry) 38:268-273, 1999. Published 1999 Wiley-Liss, Inc.

Blood Chemical Analysis↗
PubMed1998

Prescribing for persistent cough in children.

To identify the medications general practitioners consider for the treatment of persistent isolated cough, we undertook a postal questionnaire survey of a sample of general practitioners in east London. Fewer than 10% indicated that they never prescribed for such cough. About 70% sometimes considered antibiotics and/or bronchodilators in all age groups. Inhaled steroids and cromoglycate were considered by about 30% of prescribers for infants compared with over 60% for older age groups. As yet there is no evidence that medication is beneficial for persistent isolated cough. The role of asthma drugs for children with this symptom needs to be evaluated so that we can better identify those who are likely to benefit.

Age Factors↗
PubMed1998

Metabolic status of children with growth hormone insensitivity syndrome and responses to treatment with IGF-I.

Studies to date on the treatment with insulin-like growth factor I (IGF-I) of children with growth hormone (GH) insensitivity syndrome (GHIS) have concentrated principally on the effects of IGF-I therapy on the GH-IGF-I axis and on growth velocity. Little is known, however, about the metabolic status of children with GHIS and the consequences of IGF-I treatment on circulating intermediary metabolites involved in glucose homeostasis. We have studied 5 children with GHIS, aged 4.5-9 years, 3 male and 2 female, before and after 3 months of treatment with recombinant IGF-I, 80 microg/kg s.c. twice a day. The children were short (height SDS -3.8 to -7.3) and growing slowly (height velocity 1.8-3.4 cm/year). All were neurodevelopmentally normal at the time of the study with no history of severe symptomatic hypoglycaemia, in particular during the neonatal period. Before treatment, 4 of the 5 children demonstrated spontaneous hypoglycaemia (blood glucose <2.6 mmol/l), particularly at night, accompanied by substantial hyperketonaemia (range 1.43-4. 63 mmol/l) and hyperfattyacidaemia (range 1.11-3.08 mmol/l). After 3 months of IGF-I treatment, the blood glucose concentrations in the diurnal profile were increased, with improvement in spontaneous hypoglycaemia and with increased fasting tolerance. The postprandial insulin-to-glucose ratio was reduced. GHIS is thus associated with asymptomatic nocturnal hypoglycaemia without apparent neurological deficit. Despite functional GH deficiency, brisk counter-regulation to hypoglycaemia occurred as evidenced by hyperfattyacidaemia and hyperketonaemia. Treatment with IGF-I twice a day improved fasting glucose tolerance, diurnal blood glucose concentrations, and postprandial insulin-to-glucose ratios. There was no exacerbation of hypoglycaemia on treatment. We suggest that in severe GH resistance, a protective mechanism exists for the brain from the effects of hypoglycaemia, at least partially mediated by excessive production of counter-regulatory metabolic fuels.

Blood Glucose↗
PubMed1997

Surface remodeling of trabecular bone using a tissue level model.

We propose a two-dimensional mathematical model of trabecular bone remodeling that simulates the surface-based addition and removal of material in the actual physiological process. The model is based on a finite element representation of individual trabecular struts in which the material properties of the subtrabecular elements are constant. The remodeling stimulus is strain energy density, sensed and communicated through the osteocytic network as proposed by Mullender et al. We propose a modified osteocyte communication scheme that incorporates bone-lining cells and examines the implications of set point locations in one or the other of these two cell types. This model produces trabecular struts that align with its general loading direction. Placing the set point in the bone-lining cells rather than in the osteocytes makes the model more sensitive to changes in the other biological parameters. Introduction of a dead zone causes the model to reach a less oscillatory equilibrium in fewer iterations and produces better in-filling of trabecular strut intersections. The model gravitates to equilibrium states in which the average strain energy density is inversely proportional to the bone volume fraction to the 3.2 power.

Bone Remodeling↗
PubMed1997

Evaluation of a method for counting absolute numbers of cells with a flow cytometer.

We evaluated a method for performing absolute cell counts of lymphocyte populations with a flow cytometer. In this method, TruCount, test tubes that contain a known number of brightly fluorescent polystyrene beads are provided by the manufacturer. Whole anticoagulated blood is accurately pipetted into the tubes and mixed with fluorochrome-labeled monoclonal antibodies, the erythrocytes are lysed, and this mixture is analyzed on the flow cytometer. Absolute counts of lymphocyte subsets are calculated by determining the ratio of beads to the cell population of interest and then multiplying this ratio by the number of beads in the tube. We found this method to be reproducible. The values we obtained by the TruCount method were 5 to 10% higher than those obtained by conventional methods (flow cytometry and automated hematology) used to determine absolute numbers of cells. We believe that these differences are due to the methods of determining absolute cell counts and not to faulty identification of lymphocyte subsets.

Adolescent↗
PubMed1996

Use of CD45 fluorescence and side-scatter characteristics for gating lymphocytes when using the whole blood lysis procedure and flow cytometry.

The light-scatter characteristics of lymphocytes are commonly used to gate lymphocytes for further analysis in a lysed whole-blood assay. Because lymphocytes can be identified by antigens that they possess, a light-scatter gate can be validated by measuring parameters other than light scatter. When a specimen possesses poor light scatter (usually from contaminating nonlymphocytes within the light-scatter gate for lymphocytes), the quality of the gate and, thus, the analyses of lymphocyte subsets can be compromised. We present data to demonstrate the use of CD45 fluorescence combined with side scatter (SSC) for analyzing lysed whole-blood specimens. When we compared CD45/SSC to light scatter (forward and side scatter) for validating a lymphocyte gate, both methods performed similarly in recovering as many lymphocytes as possible in the gate (lymphocyte recovery); however, the CD45/SSC gate had fewer contaminants within the gate (lymphocyte purity). Replicate CD3 values from the CD45/SSC gate were less variable than those from the light-scatter gate, confirming that most of the variability in a light-scatter gate is due to nonlymphocyte contaminants in the gate. We propose that lymphocytes be gated using CD45 fluorescence as well as side-scattering properties and that CD3 also be included in each data analysis tube for quality control.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Use of specific immunoradiometric assay to determine preterm neonatal insulin-glucose relations.

Highly specific immunoradiometric assays were used to measure plasma concentrations of insulin, proinsulin, and 32-33 split proinsulin in neonates (n = 16). Neonatal plasma insulin concentrations were high relative to blood glucose concentrations and compared with adult insulin-glucose relations. Concentrations of proinsulin and 32-33 split proinsulin together accounted for 34-70% of the total concentration of insulin and pro-peptides. This study confirms the need to use a specific assay and neonatal reference data in the diagnosis of neonatal hyperinsulinism, and shows that neonatal pancreatic beta cell function may differ from that of older subjects.

Blood Glucose↗
PubMed1993

CD4 T-lymphocyte determinations on whole blood specimens using a single-tube three-color assay.

We evaluated a flow cytometric method for determining the proportion of CD4-positive T lymphocytes in whole blood using a single three-color tube containing fluorochrome-labeled CD45, CD3, and CD4. Various ways of gating this sample were evaluated and results were compared with data obtained in our standard six-tube, two-color assay gated on light scatter parameters. Excellent correlation was found between the three-color analysis using a CD45/side scatter gate and the standard two-color analysis with a light scatter gate. This single-tube three-color test is a promising assay for monitoring CD4+ T-lymphocytes.

Adult↗