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Biomedical subjects

D F Young

Publications and source records attributed to D F Young.

At least 55 records · Page 3Linked to original sources
PubMed1983

Diffuse bone marrow metastasis by glioblastoma: premortem diagnosis by peroxidase-antiperoxidase staining for glial fibrillary acidic protein.

Extraneural metastases from malignant glioma and glioblastoma are believed to be rare. The most common sites of metastases are lung, lymph nodes, bone, and liver. We recently encountered two patients with glioblastoma multiforme who presented with pain and thrombocytopenia caused by diffuse metastasis to bone marrow. A premortem diagnosis was established in the first patient with the aid of peroxidase-antiperoxidase staining of the bone marrow biopsy specimen for glial fibrillary acidic protein, a glial-specific marker. In the second patient glial fibrillary acidic protein staining confirmed the glial nature of the primary brain tumor as well as the metastatic tumor in bone marrow. The first patient also had metastatic nodules on the pleural surface and on the fifth rib. All three metastatic foci had similar cellular morphology, suggesting selection of a population of tumor cells with extraneural metastatic potential.

Adult↗
PubMed1982

A finite-element simulation of pulsatile flow in flexible obstructed tubes.

A finite-element model for pulsatile flow in a straight flexible partially obstructed tube is developed. In the unobstructed sections of the tube the model considers the continuity equation, the one-dimensional momentum equation, and an equation of state relating tube cross-sectional area to pressure. For the obstructed region, a nonlinear relationship between the flow and the pressure drop across the stenosis is considered. The applicability of a model is checked by comparing predicted flow and pressure waveforms with corresponding in-vitro experimental measurements obtained on a mechanical system. These comparisons indicated that the model satisfactorily predicts pressures and flows under variety of frequencies of oscillation and stenosis severities.

Arterial Occlusive Diseases↗
PubMed1977

Hemodynamics of arterial stenoses at elevated flow rates.

This study is concerned with the pressure drop that develops across an arterial stenosis, with particular emphasis on the effect of the stenosis at high blood flow rates induced by a locally administered vasodilator drug. Stenoses, ranging in severity from 55.7% to 91.0% reduction in lumen area were artificially induced in the femoral and carotid arteries of large mongrel dogs. Instantaneous flow rates and pressure drops were measured over a wide range of flow conditions. Mean velocities varied from 3.9 to 88.8 cm/sec. Experimental data support the applicability of a relatively simple equation for predicting the pressure drop over this wide range of velocities and stenosis geometries. Results show that blood flow through a particular artery can increase by a large factor, in the range of 4-5, under conditions of vasodilation with a corresponding large decrease in pressure distal to the stenosis. The pressure drop increases in a nonlinear manner with velocity and thereby accentuates the importance of the stenosis at elevated flow rates. We suggest that a critical stenosis be defined in terms of its effect on maximal flow rather than resting flow.

Acetylcholine↗
PubMed1976

Treatment of malignant glioma. A controlled study of chemotherapy and irradiation.

Thirty-three patients with malignant glioma were randomly divided into two groups after extensive tumor resection. Those in group A received, every five to eight weeks, a course of chemotherapy consisting of intravenously administered carmustine, 80 mg/sq m/day for three days, and vincristine sulfate, 1.4mg/sq m on days 1 and 8. Patients in group B were treated identically and received radiation therapy (RT) as well, 4,500 rads whole brain plus 1,500 rads to the side of the tumor. The median survival time of group A was 30 weeks, while that of group B was 44.5 weeks, but the overall survival curves were not significantly different. The median survival times exceeded the 17 weeks reported elsewhere in comparable patients not receiving postoperative therapy. Estimates of the quality of survival suggested (1) the two groups were not comparable following randomization, possibly influencing the results; and (2) postoperative radiation and chemotherapy do not increase morbidity and offer a longer period than other treatments during which patients' conditions remain stable or improve.

Brain Neoplasms↗
PubMed1975

Methotrexate: distribution in cerebrospinal fluid after intravenous, ventricular and lumbar injections.

The kinetics and distribution of methotrexate in intraventricular and intrathecal cerebrospinal-fluid spaces were studied in patients with meningeal leukemia and meningeal carcinomatosis after drug administration by intravenous infusion, indwelling intraventricular subcutaneous reservoir (Ommaya), or standard lumbar puncture. Negligible ventricular concentrations followed a single intravenous dose. During an intravenous infusion (500 mg per square meter for 24 hours) the ventricular cerebrospinal-fluid concentration rose to 6 times 10-minus 7 M. Methotrexate administered by Ommaya reservoir, at a dose of 6.25 mg per square meter, rapidly distributed in the subarachnoid space; the peak ventricular concentration of 2 times 10-minus 4 M declined exponentially over 48 hours. Lumbar cerebrospinal-fluid concentration reached a maximum of 5 times 10-minus 5 M four hours after injection and then fell exponentially. Administration by lumbar puncture occasionally produced epidural and subdural leakage; even with successful lumbar puncture, ventricular methotrexate concentration varied considerably from patient to patient despite similar doses. Administration by Ommaya reservoir more reliably produced adequate cerebrospinal fluid distribution than administration by lumbar puncture.

Adolescent↗
PubMed1975

Pressure drop across artificially induced stenoses in the femoral arteries of dogs.

Stenoses were artificially induced in 13 large mongrel dogs by implanting small hollow cylindrical plugs in their femoral arteries. The instantaneous pressure drop across the stenosis and the flow rate were measured for a series of stenoses varying in severity from 52.3 to 92.2%. Mean pressure drops ranged from approximately 2 to 30 mm Hg with peak pressure drops ranging from 9 to 53 mm Hg. The pressure drop could be estimated from a relatively simple equation that was originally developed for flow through model stenoses. With this equation, the effects of several factors that contribute to the pressure drop, including stenosis size and shape, artery lumen diameter, blood density, blood viscosity, and velocity and acceleration of flow, could be clearly delineated. For severe stenoses, unsteady flow effects were small and flow could be treated as quasi-steady. Calculations based on data obtained from the dog experiments revealed that the mean pressure drop across a stenosis increased nonlinearly with percent stenosis and showed quantitatively that the value of critical stenosis decreased with increasing demand for blood flow.

Animals↗