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Biomedical subjects

J Foster

Publications and source records attributed to J Foster.

At least 145 records · Page 8Linked to original sources
PubMed1983

Control of muscle contractile force through indirect high-frequency stimulation.

With a view to possible application in an orthotic device, study was made of the attenuation of background, indirectly induced muscle tetanus produced by superimposing high-frequency electrical stimulation of the muscle nerve. The effects of varying duration, current and frequency of pulses of the stimulus were outlined, and it was concluded that optimal application might be obtained using a stimulus frequency of 500 Hz, a pulse duration of 50 musec, and varying the frequency to gradate the effect.

Acoustics↗
PubMed1983

Fatigue considerations of muscle contractile force during high-frequency stimulation.

In a model for control of muscle force, wherein an induced background tetanus is attenuated by concurrent indirect stimulation at frequencies in the 0.6- to 10-kHz range, evaluation was made for effects on muscle fatigue of differing rates of the tetanic and high-frequency stimuli. Relatively little fatigue, and yet nearly the complete range of attenuation, were favored by lower frequencies of both these stimuli, e.g., tetanic stimulation at 50 Hz and a blocking frequency of 600 Hz.

Animals↗
PubMed1982

Cerebral monoamines and lidocaine toxicity in rats.

The effect of alterations in whole brain monoamine content on the plasma lidocaine concentration resulting in seizures was studied in rats. Reductions in brain monoamine content were produced by treatment with one of the following drugs: reserpine, parachlorophenylalanine (PCPA), or alpha methyl paratyrosine (AMPT). Reserpine depleted norepinephrine (NE), and dopamine (DA) by 75 per cent and serotonin (5HT) by 54 per cent; PCPA reduced brain 5HT 56 per cent without changing NE and DA; AMPT reduced brain NE and DA by 54 and 60 per cent, respectively, without altering 5HT content. Treatment with 5-hydroxytryptophan, a serotonin precursor combined with the peripheral decarboxylase inhibitor RO4-4602 increased brain 5HT content by 400 per cent without changes in DA and NE. Whole brain NE concentrations were assayed fluorometrically, DA brain concentrations were assayed by HPLC, and lidocaine concentrations in plasma were determined by gas chromatography. Plasma lidocaine concentrations at the onset of convulsions were found to be elevated significantly only by drugs causing serotonin depletion; increasing to 128 per cent of control with reserpine treatment and 139 per cent of control with PCPA treatment. Depletion of NE and DA had no effect on the lidocaine seizure threshold. Increases in brain 5HT caused a small but not statistically significant decrease to 94 per cent of control in the mean plasma lidocaine concentration at seizure onset.

Animals↗
PubMed1982

Nucleoside salvage pathway for NAD biosynthesis in Salmonella typhimurium.

A previously undescribed nucleoside salvage pathway for NAD biosynthesis is defined in Salmonella typhimurium. Since neither nicotinamide nor nicotinic acid is an intermediate in this pathway, this second pyridine nucleotide salvage pathway is distinct from the classical Preiss-Handler pathway. The evidence indicates that the pathway is from nicotinamide ribonucleoside to nicotinamide mononucleotide (NMN) and then to nicotinic acid mononucleotide, followed by nicotinic acid adenine dinucleotide and NAD. The utilization of exogenous NMN for NAD biosynthesis has been reexamined, and in vivo evidence is provided that the intact NMN molecule traverses the membrane.

NAD↗
PubMed1981

Problems in retrospectively evaluating a large-scale health intervention program.

Some of the major problems encountered in retrospectively evaluating the effectiveness of ongoing community intervention programs, and some approaches to their solution, are illustrated through a detailed description of the methods employed to assess the performance of the Newark Childhood Lead Screening and Control Program between 1970 and 1976. A process analysis, along with a limited product analysis, provided some basis for judging the effectiveness of the intervention program, despite the absence of an a priori research design, the changing characteristics of the population screened, and the limitations to the measurements used to assess the impact of the program. Even through rigorous scientific control is often unattainable when evaluating community programs, some level of critical assessment of programs is needed to determine whether or not they merit continuing public support.

Child↗
PubMed1980

Lidocaine as an analgesic for experimental pain.

The purpose of this study was to evaluate the analgesic contribution of intravenously administered lidocaine and to correlate it with blood levels of the drug. In a double-blind manner, 14 healthy male volunteers received saline solution or lidocaine, 0.2 per cent, at three increasingly greater rates of infusion on two separate days. Experimental pain was produced by means of the submaximal tourniquet-induced ischemia test of Beecher and Smith. The times to the onset of ischemic (threshold) and unbearable (tolerance) pain were recorded for three control trials to two tests for the same end points during each infusion rate. Between the two ischemic trials, while the test solution continued to be infused, venous blood samples were drawn and analyzed for lidocaine by gas chromatography. No statistically significant difference in analgesia between the control and lidocaine values for threshold or tolerance was observed at blood levels from 1 to 3 micrograms/ml. The data suggest that lidocaine at these blood levels produces sedation but not analgesia.

Analgesics↗
PubMed1978

Ultrastructure of malignant paraganglioma of organ of Zuckerkandl.

Electron microscopic study of a malignant paraganglioma of the organ of Zuckerkandl revealed similarities between the tumor and the normal paraganglia. The well-differentiated portion of the tumor recapitulated the structure of the basic functional units of the paraganglion. In addition there signs of anaplasia both at the histologic and ultrastructural level. Large neurosecretory granules were noted in some of the tumor cells, but most of the cells were agranular. Crystaloids resembling those seen in alveolar soft part sarcoma were also noted. The study supports the theory on the common origin and histogenesis of paragangliomas and alveolar soft part sarcomas.

Chromaffin System↗
PubMed1978

Angiographic findings following surgical treatment for renovascular hypertension.

The authors present the postoperative angiographic appearance of the revascularized renal artery in 128 patients. The angiographic findings in four types of surgical procedures (saphenous bypass graft, dacron graft, endarterectomy, and reimplantation of the renal artery) are discussed. Postoperative angiography accurately demonstrates graft patency or occlusion.

Adolescent↗