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Biomedical subjects

D Hawkins

Publications and source records attributed to D Hawkins.

At least 73 records · Page 4Linked to original sources
PubMed1995

Neurophysiological evaluation of zidovudine in asymptomatic HIV-1 infection: a longitudinal placebo-controlled study.

The effect of early antiretroviral medication with zidovudine on neurophysiological functions was evaluated in subjects with asymptomatic HIV-1 infection. Patients were recruited participants of a larger double-blind randomised placebo-controlled treatment trial with zidovudine (Concorde). The main outcome measures included: quantitative electroencephalography (QEEG), auditory event-related potentials (AEP) and pattern-reversal visual evoked potentials (PRVEP), as well as standard clinical, virological and immunological markers. No significant impairment and no difference between treatment groups was found in visual P100 latency and auditory long-latency P3 responses which is in agreement with the absence of neurological and neuropsychological impairment over the study period. Significant treatment effects were revealed by quantitative electroencephalography (QEEG). While the placebo group showed a significant increase in delta and theta slow frequency QEEG activity over the study period, slow wave amplitude remained unchanged in the zidovudine group after a mean follow-up period of 28 months. In summary, the data provide evidence for a low level neuropathological process in asymptomatic HIV-1 infection which can be effectively suppressed by antiretroviral medication.

Adult↗
PubMed1995

Long-term zidovudine reduces neurocognitive deficits in HIV-1 infection.

OBJECTIVE: To determine the efficacy of zidovudine (ZDV) in preventing decline of neurocognitive functions in HIV-1 infection. DESIGN: Retrospective evaluation of subjects enrolled in a natural history study. Two analyses were made to evaluate the effect of (1) current ZDV, irrespective of length of treatment and (2) long-term ZDV treatment for at least 1 year. SETTING: Subjects were recruited from HIV out-patient clinics. PATIENTS: HIV-1-seropositive subjects were assigned to one of three groups according to the Centers for Disease Control and Prevention classification: asymptomatic infection (n = 60), symptomatic infection but without AIDS (n = 51), and AIDS (n = 32). MAIN OUTCOME MEASURES: Standardized neuropsychological and neurophysiological measures [electroencephalogram (EEG) and long-latency evoked potentials]. RESULTS: Long-term ZDV use was associated with improved cognitive performance in subjects with early symptomatic HIV-1 infection and AIDS, compared to subjects in the same clinical stage but without previous ZDV treatment. This was corroborated by neurophysiological evidence of reduced slow-wave EEG amplitude in the ZDV-treated subjects. The advantage of ZDV treatment was evident despite lower immune status in most treated subjects. CONCLUSIONS: The findings in this natural history study indicate that long-term ZDV treatment may be an effective prophylactic to reduce neurocognitive deficits in symptomatic HIV-1 infection, thereby lowering the risk for developing HIV-1-associated dementia.

Acquired Immunodeficiency Syndrome↗
PubMed1994

20 hot job tracks.

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Data Collection↗
PubMed1994

A modeling and computer simulation approach to determine optimal lower extremity joint angular velocities based on a criterion to maximize individual muscle power.

A computer program was developed in conjunction with a musculoskeletal modeling scheme to determine lower extremity joint angular velocity profiles which allow specific muscles, if activated tetanically, to generate their greatest power. As input the program requires subject anthropometric and joint configuration data. Muscle-tendon (MT) attachment location data and a straight line MT model are used to calculate MT lengths for each joint configuration. The shortening velocity which allows an active muscle to generate its greatest power is calculated based on muscle architecture and a relationship between power and shortening velocity. A finite difference technique is used to calculate the time between sequential joint configurations which will produce the optimal muscle shortening velocity. This time is then used to calculate optimal joint angular velocities for each muscle and and for each joint configuration. The utility of this program is demonstrated by calculating optimal joint angular velocities for fifteen muscles and comparing calculated knee extension velocities with experimental results cited in the literature.

Anthropometry↗
PubMed1994

A comprehensive approach for studying muscle-tendon mechanics.

A comprehensive approach for studying the mechanics of partially intact muscle-tendon (MT) complexes was developed. This approach utilizes a work station which integrates state-of-the-art equipment and software. The hardware includes a nerve stimulator, ergometer, high speed video camera and recorder, computer, and temperature regulated chamber. When used in conjunction with a small animal muscle model, the work station provides accurate control of muscle stimulation, MT length, and MT shortening or stretching velocity. Simultaneously, muscle force and both muscle and tendon kinematics can be recorded. This approach is unique in that it allows simultaneous testing of both muscle and tendon under physiological conditions. Additionally, both gross and local deformations of the muscle and tendon can be determined. Sample results from a study of a rat tibialis anterior muscle illustrate the utility of this approach.

Animals↗
PubMed1994

[Triplet and quadruplet pregnancy: management and perinatal outcome].

The frequency of multiple pregnancies with more than two fetuses has increased considerably since the introduction of methods of ovulation induction, in vitro fertilization, and embryo transfer. We have analyzed the evolution, complications, delivery and perinatal outcome of 23 triplet and 3 quadruplet pregnancies occurred during a four-year period in one medical center. The most frequent complication was preterm labor (62%). The mean gestational age at delivery was 32.5 weeks for the quadruplets and 31.5 weeks for the triplets and the mean birth weight was 1461 and 1526 for quadruplets and triplets, respectively. Perinatal mortality for the whole group was 148/1000.

Embryo Transfer↗
PubMed1993

Detection of subclinical motor dysfunctions in early symptomatic HIV infection with topographical EEG.

Motor dysfunctions are amongst the earliest and most common signs of brain impairment caused by human immunodeficiency virus (HIV) infection. Topographical EEG was recorded in patients both with asymptomatic and early symptomatic infection (without acquired immunodeficiency syndrome (AIDS) defining illness), as well as in seronegative controls under resting and motor activation conditions. While patients' motor performance did not differ from control values, the EEG showed a consistent increase in rhythmic activity in Theta, Alpha and Beta frequency bands in Symptomatics. This amplitude increase was evident in different topographical regions during resting states as compared with motor activation, findings which suggest concurrent involvement of several motor areas possibly due to a functional impairment in subcortical integratory mechanisms. Comparing motor task and baseline both patient groups showed less consistent patterns of task-related EEG amplitude reduction than found in the control group. Here topographical EEG in connection with motor activation procedures was found to be more sensitive than behavioral measures of motor performance and offers a technique to assess treatment effects before the development of motor abnormalities in patients with HIV infection.

Adult↗
PubMed1993

Muscle force as affected by fatigue: mathematical model and experimental verification.

The effects of muscle fatigue have been included in a comprehensive muscle model derivation. The fiber-based muscle model calculates muscle force as the sum of individual fiber forces, determined based on fiber kinematics and activation information. Three fiber types are considered in the model derivation. Fiber force is modified using indices of fatigue which were derived based on the data from experimental work conducted by others. In this paper, derivations of the indices for each of the fiber types are presented. An elbow extension study was performed to validate the modeled fatigue relationship for maximal effort activities. Triceps brachii forces generated during both isometric and dynamic fatigue tests were determined using both the muscle model and a direct approach based on rigid-body dynamics. The forces obtained from the two approaches were not significantly different for times either less than 50 s for the isometric tests, or greater than 40 s for the dynamic tests. Results from the statistical comparison indicate the utility of the modeling approach presented.

Adult↗
PubMed1993

The reliability and validity of two HIV-specific health-related Quality-of-Life measures: a preliminary analysis.

OBJECTIVE: To evaluate the reliability and validity of two HIV-specific Quality-of-Life (QoL) questionnaires in a UK sample. METHOD: Subjects were 99 HIV-seropositive gay men (23 were asymptomatic, 41 were asymptomatic, 35 had AIDS). QoL was measured using two HIV-specific QoL questionnaires. MEASURES: An adaptation of the Medical Outcomes Study questionnaire and a self-completion version of the Health-Related Quality-of-Life Questions. Affect was measured using the Hospital Anxiety and Depression (HAD) Scale. Disease measures included Centers for Disease Control and Prevention (CDC) stage, and CD4 and CD8 cell count. RESULTS: Both QoL instruments showed good internal reliability on all scales used. Many of the scales, particularly those related to physical health and functional performance, showed significant correlations with CD4 cell count and other measures of disease progression. Measures of physical health showed a deterioration in QoL as disease progressed from asymptomatic disease to AIDS. In contrast, most subscales purporting to measure psychological aspects of QoL did not correlate significantly with measures of disease progression, nor was there any difference between CDC stages. Subjects' global ratings of QoL were most strongly correlated with the HAD depression scale, although there were also significant correlations with most other QoL scales. CONCLUSION: This study provides further evidence for the reliability and validity of two HIV-specific QoL questionnaires in a wider range of disease stages than hitherto reported and raises issues relevant to the practical use of QoL scales in HIV disease.

CD4 Antigens↗
PubMed1993

The use and toxicity of didanosine (ddI) in HIV antibody-positive individuals intolerant to zidovudine (AZT)

One hundred and fifty-one patients intolerant to zidovudine (AZT) received didanosine (ddI) to a maximum dose of 12.5 mg/kg/day. Patient response was assessed using changes in CD4+ lymphocyte subset count, HIV p24 antigen, weight, and quality of life. Seventy patients developed major opportunistic infections whilst on therapy; this was the first AIDS diagnosis in 17. Only minor changes in CD4+ lymphocyte subset count were observed in AIDS patients, although a more significant rise occurred in those with earlier stages of disease. Of those positive for p24 antigen at the commencement of the study 67% showed a positive response, and this was most likely in those with CD4+ lymphocyte subset counts above 100 mm3. A positive weight response was seen in 16% of patients. Most patients showed improvement in individual parameters and global score of quality of life. Adverse reactions possibly attributable to didanosine were common. The most common side-effect was diarrhoea, which resulted in cessation of therapy in 19 individuals. Peripheral neuropathy occurred in 12 patients and pancreatitis in six. Thirteen patients developed a raised serum amylase without abdominal pain. Seven patients developed glucose tolerance curves characteristic of diabetes but these were mild, did not require treatment and returned to normal on ceasing didanosine.

AIDS-Related Complex↗
PubMed1992

Three-dimensional knee joint loading during seated cycling.

The hypothesis which motivated the work reported in this article was that neglecting pure moments developed between the foot and pedal during cycling leads to a substantial error in computing axial and varus/valgus moments at the knee. To test this hypothesis, a mathematical procedure was developed for computing the three-dimensional knee loads using three-dimensional pedal forces and moments. In addition to data from a six-load-component pedal dynamometer, the model used pedal position and orientation and knee position in the frontal plane to determine the knee joint loads. Experimental data were collected from the right leg of 11 male subjects during steady-state cycling at 90 rpm and 225 W. The mean peak varus knee moment calculated was 15.3 N m and the mean peak valgus knee moment was 11.2 N m. Neglecting the pedal moment about the anterior/posterior axis resulted in an average absolute error of 2.6 N m and a maximum absolute error of 4.0 N m in the varus/valgus knee moment. The mean peak internal and external axial knee moments were 2.8 N m and 2.3 N m, respectively. The average and maximum absolute errors in the axial knee moment for not including the moment about an axis normal to the pedal were found to be 2.6 N m and 5.0 N m, respectively. The results strongly support the use of three-dimensional pedal loads in the computation of knee joint moments out of the sagittal plane.

Acceleration↗
PubMed1992

Psychosocial concomitants of children's feeding disorders.

Compared behavior problems, child developmental skills, home environment, and parent emotional distress for 50 families of children aged 11-70 months with differing etiologies of feeding disorders (FD). Results showed that psychosocial functioning differed across FD classifications. Children with nonorganic characteristics to FD had more behavior problems compared to those with only organic FD. Children with primarily or only organic FD displayed lower developmental skills and their parents had higher emotional distress than children with primarily nonorganic FD. High parent distress was associated with older children who had poor feeding skills, less positive disciplinary practices, and higher social status. The findings imply that clinical services to families often are warranted and that service needs vary depending on the nature of FD. Mixed organic and nonorganic FD occurred in the majority of children, which supports the need for more detailed classification than an organic-nonorganic dichotomy used in prior research.

Child Behavior Disorders↗
PubMed1991

Model of care for the hospital treatment of individuals with HIV infection.

This study was undertaken and completed in 1988, in an attempt to determine the reasons for admission to hospital, and the optimum care required for patients with Human Immunodeficiency Virus related illnesses. Approximately half of the total medical admissions stayed for less than a week, and patients admitted for terminal care and social care occupied a relatively small proportion of the beds. The single largest group of admissions were those for inpatient management of AIDS-related pneumonias. The results of this study provide a greater understanding of the resources currently required for such care, and suggest initiatives for meeting future needs.

Bed Occupancy↗