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Biomedical subjects

D Hawkins

Publications and source records attributed to D Hawkins.

142 records · Page 8Linked to original sources
PubMedDate not supplied

Modeling energy expenditure associated with isometric, concentric, and eccentric muscle action at the knee.

This study was designed to derive and test a model of energy expenditure (dE/dt) during different modes of human muscle action in vivo. dE/dt for the quadriceps muscle was expressed as: dEquad/dt = Kl(omega) + K2(Tiso) + dW/dt. where K1 and K2 are constants, (omega) is joint angular velocity (degree/sec), (Tiso) represents the knee extension torque that could be developed by the active muscle if the muscle action were isometric (N-m), and (dW/dt) is the rate of work performed (W). Volunteers performed a series of repetitive 2- to 4-min knee extension exercises, while varying either the knee extension torque or velocity. The average joint torque, angular velocity, rate of work performed, and net energy expenditure (E) above resting and dE/dt were determined for each muscle action. The best fit values for K1 and K2 for concentric, eccentric, and isometric muscle actions were 0.044, -0.55, and 0 W/degree/sec, and 4.14, 5.28, and 2.17 W/N-m, respectively. The coefficients of determination (r2) for the model predictions of dEquad/dt for the three modes of muscle action were 0.78, 0.71, and 0.71, respectively. The correlation coefficient between predicted and experimental dE/dt for all modes of muscle action combined was 0.93. These findings indicate the model provides a useful tool for predicting the rate of energy expenditure associated with cyclic knee extension efforts.

Adult↗
PubMedDate not supplied

Software for determining lower extremity muscle-tendon kinematics and moment arm lengths during flexion/extension movements.

A computer program was developed to calculate lower extremity muscle-tendon (MT) kinematics and flexion/extension moment arm (MA) lengths for any subject performing movements constrained to occur in the sagittal plane. The program requires as input subject anthropometric and time series ankle, knee, and hip angle data. Using these data a lower extremity link-segment model is constructed for each time element. Muscle-tendon attachment data and a straight line muscle model are used to calculate MT and flexion/extension moment arm lengths. A finite difference technique is used to determine MT shortening velocity. The utility of this program is demonstrated by calculating MT kinematics and MA lengths for six muscles of a single subject both as a function of joint angles and during gait.

Adult↗
PubMedDate not supplied

Auditory and visual event-related potentials in a controlled investigation of HIV infection.

Auditory and visual event-related brain potentials (ERPs) were used to complement neuropsychological and medical assessment in neurologically healthy subjects with asymptomatic and symptomatic human immunodeficiency virus type 1 (HIV-1) infection. Auditory and visual ERPs, recorded using standard oddball paradigms, disclosed delays in late waves (N2 and P3) in symptomatic subjects (CDC stage IV) when compared with matched controls. Abnormally delayed P3 waves in at least one modality were recorded in 41% of symptomatics and this was associated with deficits in neuropsychological performance, particularly psychomotor slowing. However, no differences in late wave latencies between asymptomatic and control subjects were found, though asymptomatics showed delays in auditory N1 and P2 latencies. The number of morphological abnormalities, such as indiscernible late waves as well as topographical variability of the P3 wave, was increased in both HIV seropositive groups and possibly indicates a distinct mechanism of impairment, different from latency delay. Whilst P3 delay in symptomatics was not associated with changes in immune function (T4 cells) there was, however, a link with anaemia and subclinical hepatic dysfunction.

Adult↗
PubMedDate not supplied

Diabetes insipidus as a presenting symptom of acute myelogenous leukemia.

This report describes a case of diabetes insipidus associated with acute myelogenous leukemia. An 11-year-old boy presented with fatigue, polydipsia and polyuria. His evaluation revealed a diagnosis of acute myelogenous leukemia FAB-M2, and a water deprivation test confirmed the diagnosis of central diabetes insipidus. His brain magnetic resonance imaging (MRI) showed a thickened, enhancing pituitary stalk with absence of the normal hyperintense signal in the posterior pituitary. He was treated with systemic chemotherapy, intensive intrathecal therapy, and 1,000 cGy to the pituitary. The patient achieved a remission but continued to need desmopressin therapy to control his diabetes insipidus. Diabetes insipidus is a rare complication of acute myelogenous leukemia that can be caused by leukemic infiltration of the pituitary. The diabetes insipidus is irreversible despite intensive systemic and central nervous system chemotherapy and radiation.

Child↗
PubMedDate not supplied

Role of high-dose chemotherapy with hematopoietic stem cell rescue in the treatment of metastatic or recurrent rhabdomyosarcoma.

PURPOSE: This review summarizes the published data on the use of high-dose chemotherapy and hematopoietic stem cell rescue (HSCR) in the treatment of recurrent or metastatic rhabdomyosarcoma (RMS). PATIENTS AND METHODS: Three hundred eighty-nine patients were identified from 22 articles selected by computer generated searching of MEDLINE (1979-present). One hundred seventy-seven patients had stage 4 disease and were treated during first complete remission (CRI). The remaining patients were treated during CR1/first partial remission (PR1) (110 patients), CR2/PR2 (53 patients), CR2 (12 patients), CR3 (1 patient), or treated with disease (36 patients). RESULTS: Patients treated during CR1 or CR1/PR1 had event-free survival (EFS) rates ranging from 24% to 29% at 3 to 6 years from diagnosis and overall survival (OS) rates ranging from 20% to 40% at 2 to 6 years after diagnosis according to data provided as Kaplan-Meier estimates. Studies without Kaplan-Meier estimates (n = 32) indicate that 12 patients (38%) with stage IV RMS treated during CR1 or CR1/PR1 were surviving 7 to 60 months from diagnosis, similar to patients with stage IV RMS treated on Intergroup Rhabdomyosarcoma Studies II or III. Patients treated during CR2, CR3, or with evidence of disease had a worse outcome with an estimated 3 years OS of 12% (n = 51). Studies without Kaplan-Meier estimates (n = 27) indicate that four patients (15%) treated during CR2, CR3, or with disease were surviving 17 to 33 months after transplant. CONCLUSIONS: Based on these data, there does not appear to be a significant advantage to undergoing high-dose chemotherapy with HSCR for patients with relapsed or refractory high-risk RMS. Clearly, there is a need for incorporating new treatment strategies for patients with high-risk RMS.

Antineoplastic Combined Chemotherapy Protocols↗
PubMedDate not supplied

The link between Down's syndrome and Alzheimer's disease: 1.

This article, the first of two parts, considers the link between Down's syndrome and Alzheimer's disease and how this link has been a significant factor with regards to research into the aetiology of Alzheimer's disease. It describes some of the suggested causes of Alzheimer's disease in people with Down's syndrome. The diagnosis, signs and symptoms of Alzheimer's disease are briefly discussed. The second article concludes with the implications of Alzheimer's disease in people with Down's syndrome for family careers, services and nurses.

Alzheimer Disease↗
PubMedDate not supplied

The link between Down's syndrome and Alzheimer's disease: 2.

In this article, the second of two parts, the needs of family and professional carers of people with Down's syndrome and Alzheimer's disease are examined. Substantial numbers of people with Down's syndrome survive to the age of 50 and beyond and so work still needs to be done on finding solutions to the problems faced by this client group and its carers. As well as the difficulties faced by any family carer of a person with dementia, those caring for someone with Down's syndrome and Alzheimer's disease may also have to deal with additional worries and problems. Consideration is given to service provision and the implications for nursing. A case study will illustrate some of the points made.

Alzheimer Disease↗
PubMedDate not supplied

Individual assessment of antihypertensive response by self-starting cumulative sums.

A self-interpreted control chart, on an individualized basis, assesses the effect of a switch from beta-blockers to an angiotensin-converting enzyme (ACE)-inhibitor in a patient with occasional blood pressure (BP) excess. In dense and long data series, the BP and heart rate (HR) of this patient respond to the change in treatment by the test criterion of a self-starting Cumulative Sum (cusum), which reaches values outside a decision interval with a lowering of BP and an increase in HR and vice versa, at least for BP, after treatment cessation. Thereafter, minimal sampling requirements are sought in the same data by applying the same control chart approach to decimated data. Skeleton sampling schemes in a system of chronobiologic self-analysis and interpretation of manually recorded data obtained at strategically placed times (established on the basis of data decimations) could complement control charts that are used on a home computer or preferably would be built into the output of ambulatory monitors used at the outset as a minimum and routinely as an optimum.

Adrenergic beta-Antagonists↗
PubMedDate not supplied

Hepatic abnormalities in adult onset Still's disease.

Five patients with adult onset Still's disease are reported. Three had abnormal liver function tests (LFT) prior to receiving salicylates. Liver biopsy in 1 of these 3 and in another with normal LFT was abnormal. The elevated LFT returned to normal with high dose salicylate therapy coincident with remission of disease activity. It is proposed that hepatic abnormalities in Still's disease frequently reflect the underlying disease and not salicylate hepatotoxicity (SH).

Adolescent↗