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Biomedical subjects

W M Roberts

Publications and source records attributed to W M Roberts.

68 records · Page 4Linked to original sources
PubMed1984

Voltage clamp of rat and human skeletal muscle: measurements with an improved loose-patch technique.

Intact fibres of human intercostal and rat omohyoid muscles were studied at 23 degree C with a loose-patch voltage-clamp technique that employed two concentric micropipettes to electrically isolate small-diameter (10-15 microns) patches of sarcolemma. This method allows investigation of membrane excitability under highly physiological conditions. Step depolarizations to 0 mV elicited sodium inward currents that reached peak values of up to 20 mA/cm2 within 250 microseconds, and then declined. In human muscle, the reversal potential (ENa) was approximately 40 mV, and maximal conductances (GNa) ranged from 44 to 360 mS/cm2. In rat muscle, ENa was 42 mV and GNa ranged from 100 to 250 mS/cm2. Sodium channels in rat and human muscle were indistinguishable in most aspects of their kinetic behaviour and voltage dependence. Outward potassium currents were small by comparison (usually less than 2 mA/cm2) and saturated at positive potentials. The maximum potassium conductance (GK) ranged from 0 to 19 mS/cm2 (human) and from 4 to 12 mS/cm2 (rat muscle).

Action Potentials↗
PubMed1979

Optimal recognition of neuronal waveforms.

Statistically optimal methods for identifying single unit activity in multiple unit recordings are discussed. These methods take into account both the nerve impulse waveforms and the firing patterns of the units. A generalized least-squares fit procedure is shown to be the optimal recognition scheme under some reasonable statistical assumptions, but the amount of computation becomes prohibitively large when the method is applied to the problem of sorting superimposed waveforms. A linear filter technique which relies on simultaneous recording from several electrodes is shown to give good separation of superimposed waveforms. An iterative recognition procedure can be applied to improve the results and reduce the number of recording electrodes required.

Animals↗
PubMed1976

Some clinical problems in patients undergoing thrombolytic therapy.

A total of 25 patients (7 with arterial occlusion and 18 with venous thrombosis) were treated with streptokinase for 72 hours, followed by heparin for 24 hours. The clinical problems, complications and results obtained are discussed. Within the limits imposed by the study, it is concluded that streptokinase offers safe and effective therapy for early iliofemoral venous thrombosis.

Adult↗
PubMed1975

Separation of multi-unit nerve impulse trains by a multi-channel linear filter algorithm.

We have applied a technique involving multi-channel linear filtering to the problem of sorting and identifying singly unit neuronal activity in records containing several simultaneously active units. The technique is effective even when the waveforms of two or more nerve impulses are superimposed. We have applied it successfully to data involving up to 6 units, and in theory it is applicable to substantially more. Current limitations are that the waveform of the impulse from each unit must first be determined by identifying and averaging several isolated examples, and that the number of recording electrodes must approximate the number of units present.

Animals↗
PubMedDate not supplied

Economic and resource utilization analysis of outpatient management of fever and neutropenia in low-risk pediatric patients with cancer.

PURPOSE: To measure resource allocation in outpatient management of fever and neutropenia in low-risk pediatric patients with cancer and its impact on their families. PATIENTS AND METHODS: A prospective clinical trial was conducted. Eligible patients received a single dose of intravenous (IV) antibiotics and were observed for several hours in clinic. Patients were randomly assigned to continue either IV or oral antibiotics and were seen daily as outpatients. Charges were calculated based on the number of resources used and Medicare/Medicaid reimbursement schedules. A questionnaire was used to measure the impact of outpatient treatment on the family. RESULTS: Seventy-three episodes of fever and neutropenia were studied. The median duration of treatment was 4 days. Eighty-six percent of the episodes were managed without hospitalization. The median calculated charge was $1840. The median calculated charge for patients receiving oral antibiotics was $1544 and was significantly less than the $2039 median charge for outpatients treated with IV antibiotics. The estimated charge for comparable inpatient treatment was $4503. Nearly all families preferred outpatient care, and few reported a loss of work hours or increased child care expenses. CONCLUSIONS: Outpatient treatment of low-risk episodes of fever and neutropenia is substantially less costly than inpatient care and is preferred by most families.

Administration, Oral↗