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Biomedical subjects

M S Young

Publications and source records attributed to M S Young.

At least 19 recordsLinked to original sources
PubMed1999

Transcranial magnetic stimulation identifies upper motor neuron involvement in motor neuron disease.

OBJECTIVE: To evaluate the sensitivity of transcranial magnetic stimulation (TMS) to identify upper motor neuron involvement in patients with motor neuron disease. BACKGROUND: Diagnosis of ALS depends on upper and lower motor neuron involvement. Lower motor neuron involvement may be documented with electromyography, whereas definite evidence of upper motor neuron involvement may be elusive. A sensitive, noninvasive test of upper motor neuron function would be useful. METHODS: TMS and clinical assessment in 121 patients with motor neuron disease. RESULTS: TMS revealed evidence of upper motor neuron dysfunction in 84 of 121 (69%) patients, including 30 of 40 (75%) patients with only probable upper motor neuron signs and unsuspected upper motor neuron involvement in 6 of 22 (27%) patients who had purely lower motor neuron syndromes clinically. In selected cases, upper motor neuron involvement identified with TMS was verified in postmortem examination. Increased motor evoked potential threshold was the abnormality observed most frequently and was only weakly related to peripheral compound muscle action potential amplitude. In a subset of 12 patients reexamined after 11+/-6 months, TMS showed progression of abnormalities, including progressive inexcitability of central motor pathways and loss of the normal inhibitory cortical stimulation silent period. CONCLUSIONS: TMS provides a sensitive means for the assessment and monitoring of excitatory and inhibitory upper motor neuron function in motor neuron disease.

Adult↗
PubMed1998

Effect of stimulator orientation on F-wave persistence.

Most electrodiagnosis texts advocate cathode distal stimulation (CDS) for nerve conduction, but suggest cathode proximal stimulation (CPS) for F waves, because of anodal block. We postulated that CDS and CPS elicit F waves of similar persistence. We studied 657 (207 median, 204 ulnar, 136 tibial, and 110 peroneal) nerves in 225 consecutive subjects. In the median nerve, CDS elicited F waves of slightly greater persistence than CPS. Stimulator orientation did not affect F-wave persistence in the remaining nerves.

Electric Stimulation↗
PubMed1998

Angiotensinogen gene polymorphism is associated with insulin resistance in nondiabetic men with or without coronary heart disease.

BACKGROUND: Variants of the angiotensinogen gene may increase the risk of having arterial hypertension and coronary heart disease (CHD), but their effect on insulin resistance remains unknown. METHODS: We determined M235 and T174 allele status and fasting plasma glucose, insulin, and lipids values in nondiabetic men with CHD documented on angiography (n = 102) and in a control group (n = 145). Plasma glucose and insulin responses to 75 gm oral glucose tolerant test and insulin resistance as measured by an insulin suppression test were also carried out in 46 (45%) patients with CHD and in 73 (50%) members of a control group. RESULTS: We found no association between M235T status and blood pressure, fasting plasma glucose, insulin, most of the lipids values, and insulin resistance in patients with CHD and normal subjects. Nevertheless, compared with individuals with homozygotes T174, subjects with heterozygotes T174M were associated with greater glucose and insulin response to the oral glucose tolerance test and insulin resistance indicated by higher steady state plasma glucose concentrations in patients with CHD (14.7+/-0.9 vs 11.3+/-0.7 mmol/L, p < 0.04). Similar findings were found in the control group, with higher steady-state plasma glucose values in individuals with heterozygotes T174M than in those with homozygotes T174 (10.1+/-1.4 vs 7.7+/-0.4 mmol/L, p < 0.05). CONCLUSION: We suggest that the angiotensinogen T174M allele might be associated with insulin resistance in nondiabetic men with and without CHD.

Alleles↗
PubMed1997

Ultrasonic analysis of tremorine and cold tremor activity in unanesthetized rats.

In order to quantify the tremorine and cold tremor activity in unanesthetized rats, a new ultrasonic motion transducer method was used. Both kinds of activity are reported as vibratory body motion that occurred between 18-32 Hz as determined by spectral analysis. The recorded signal was analyzed and its power spectrum was obtained through a fast Fourier transform operation. It was found that a negative linear relation occurs between shiver amplitude and ambient temperature (r = 0.999). A negative linear relation also occurs between metabolic rate and ambient temperature (r = 0.997). In addition, a positive linear relation between metabolic rate and cold shiver exists (r = 0.999). Both tremorine (30 mg/kg, i.p.) and cold tremor (Ta = 2-22 degrees C) activity monitored by the ultrasonic method were completely abolished by premedication with 1 mg/kg atropine. Thus, it appears that the advantages of this tremor detection method are that is non-invasive and non-contact. Therefore, the ultrasonic method provides a good choice for quantifying tremorine and cold tremor activity in unanesthetized animals during studies of thermoregulatory physiology or motor disorders.

Animals↗
PubMed1997

Effectiveness of an organized follow-up system for elder patients released from the emergency department.

OBJECTIVES: To determine whether an effective telephone callback system can be successfully implemented in a busy ED and to quantify the benefits that can be obtained related to the follow-up care of elder patients. METHODS: This was a prospective, cohort study conducted at a community teaching hospital during a 6-month period. Consecutive patients > or = 60 years old and released from the ED were selected for telephone follow-up. Calls were made by a research nurse within 72 hours after the patient's ED visit. Follow-up information included current medical status, problems encountered during the ED visit, compliance, and impact of the illness on self-care capabilities. RESULTS: Seventy-nine percent (831/1,048) of the patients selected for telephone follow-up were successfully contacted. The calls lasted an average of 4 +/- 2.5 minutes. Although 94% (778/831) of these patients had a regular physician, 14% failed to make their recommended follow-up arrangements. Compliance was significantly improved when a follow-up physician was contacted during the patient's ED visit. Approximately 96% of the patients were either satisfied or very satisfied with their ED care. However, 13% (109/831) had moderate deterioration in their ability to care for themselves. Of the patients contacted, 333 (40%) required further clarification of their home care instructions, 31 were advised to return to the ED for reevaluation, and 26 were referred to a medical social worker for psychosocial concerns. CONCLUSION: A telephone callback system is a feasible and effective method to improve follow-up care of elder patients released from the ED.

Activities of Daily Living↗
PubMed1997

Stereotactic pallidotomy lengthens the transcranial magnetic cortical stimulation silent period in Parkinson's disease.

We compared the duration of the EMG cortical stimulation silent period (CSSP) elicited in abductor pollicis brevis using transcranial magnetic stimulation (TMS) before and after stereotactic unilateral globus pallidus internus pallidotomy (PAL) in 12 patients with Parkinson's disease. We used TMS stimulus intensities of 200, 150, 120, and 100% of motor evoked potential (MEP) threshold before and after (86 +/- 25 days) PAL. PAL increased CSSP duration at stimulus intensities of 200% of MEP threshold in the hand contralateral to the stereotactic lesion. In a subset of five patients able to remain at rest during pre-PAL testing sessions, PAL decreased the resting MEP/M-wave area ratio in the hand contralateral to the lesion at a stimulus intensity of 120% of MEP threshold. PAL did not significantly modify the effects of TMS in the hand ipsilateral to the globus pallidus lesion. The results suggest that PAL improves the function of cortical motor inhibitory circuits in Parkinson's disease.

Aged↗
PubMed1996

A new ultrasonic method for measuring minute motion activities of rats.

A new ultrasonic method is presented for measuring the minute motion activities of rats. A pair of low-cost 40 kHz ultrasonic transducers are used to transmit ultrasound toward a rat and receive the ultrasound reflected from the rat. The relative motion of the rat modulates the phase difference between the transmitted and received ultrasound signals. An 8-bit digital phase meter was designed to record the phase difference signal which was used to reconstruct the relative motion waveform of the rat in an 8751 single-chip microcomputer. The reconstructed data are then sent to a PC-AT microcomputer for further processing. This method employs a spectrum analysis for the reconstructed data and can measure three minute motion activities including locomotor activity (LMA), tremor and myoclonia. Finally, the method has been tested with real animal experiments. The main advantages of this new method are that it is non-invasive, non-contact, low cost and high precision. This new method could also be profitably employed for other behavioral studies and offer potential for research in basic medicine.

Animals↗
PubMed1995

Facilitation of magnetic motor evoked potentials during the mixed nerve silent period.

We studied motor neuron excitability during the mixed nerve silent period (MNSP) in a hand muscle using magnetic motor evoked potentials (MEPs) and F-waves. MEPs elicited between the V1 and V2 potentials of the MNSP were much larger than control MEPs elicited at rest, and were even comparable in size to control MEPs elicited during voluntary contraction. This facilitation of MEPs occurred without shortening of MEP latency, suggesting a supraspinal mechanism. MEPs were facilitated during the MNSP when elicited with a figure-8-shaped coil in a posterior-anterior orientation, but not when MEPs of the same size were elicited with the coil held in a lateral-medial orientation. F-waves elicited during the MNSP were variable between subjects, and not consistently different from control F-waves elicited at rest. Our findings may reflect increased cortical motor excitability during the MNSP, possibly related to activation of muscle afferents by mixed nerve stimulation.

Adult↗
PubMed1995

A new automated method for detection and recording of animal moving path.

A new electronic system has been developed to trace the location and movement of small animals in an open-field environment. The system, incorporated with a conventional touch panel position sensor (TPPS) and an IBM AT compatible computer, automtically digitizes and records the moving path of the animal. The detection principle of the TPPS is based on the pressure effect. Whenever an animal is put on the TPPS, the location of the animal can be detected. The personal computer system is in corporate to record the locomotion data of the animal. The system described here is shown to be a reliable and accurate tool to record the moving path of an animal. This measurement did not require extra light or other stimuli, and the apparatus is low priced, and simple to build up and user friendly.

Animals↗
PubMed1994

A high-precision ultrasonic system for vertical movement counts in rats.

A microcomputer-aided ultrasonic system was used to measure vertical displacement of rats in response to drug injection. The system utilizes an inexpensive PC/AT microcomputer for data collection and can distinguish between number of vertical movements of small (i.e., greater than 5 mm, but less than 15 mm), and large (i.e., greater than 15 mm) displacements. In addition, rest time denotes the time elapsed for the vertical motion of less than 5-mm displacements. As little as 0.32 mg/kg of d-amphetamine increased the average amount of both small and large activity (i.e., number of movements), but decreased the average amount of rest time in rats. On the contrary, as little as 2.5 mg/kg of chlorpromazine decreased the average amount of both small and large activity, but increased the rest time in rats. When the animal activity was measured with an infrared light system, the activity responses to drugs were not detectable. Thus, it appears that the ultrasonic method provides a high-precision system for measuring animal behaviors.

Animals↗
PubMed1994

Heart failure due to chronic experimental aortic regurgitation.

Previously reported experimental models of aortic regurgitation generally have manifested normal systolic performance and have not developed heart failure [Magid et al. Am. J. Physiol. 263 (Heart Circ. Physiol. 32): H226-H233, 1992]. To determine whether more severe chronic experimental aortic regurgitation would generate systolic malperformance, heart failure, and emulate the human disease process, 11 New Zealand White rabbits underwent surgical induction of aortic regurgitation and 5 control animals underwent sham operation. Doppler echocardiography was performed serially for up to 3 yr, and pathological studies were performed at necropsy. Left ventricular internal dimension at end diastole increased 80% (P < 0.00002) and left ventricular weight increased 250% (P < 0.0002) in aortic regurgitant rabbits (regurgitant fraction 52 +/- 13%) compared with baseline values. Six of 11 aortic regurgitant animals died with pathological evidence of congestive heart failure at 1.5 +/- 0.8 yr postoperatively; 2 of these developed severe systolic malperformance, manifest as fractional shortenings of 15 and 19% at 1.6 and 1.7 yr, respectively. Five of 11 aortic regurgitant animals survived until killed at 2.9 +/- 0.1 yr. Thus moderate-to-severe chronic aortic regurgitation in rabbits frequently results in heart failure and systolic dysfunction and may usefully model chronic aortic regurgitation and heart failure in humans.

Animals↗
PubMed1994

Electromyographic biofeedback use in the treatment of voluntary posterior dislocation of the shoulder: a case study.

Voluntary posterior dislocation of the shoulder has been difficult to treat successfully. Electromyographic biofeedback is a nonoperative treatment measure that has been successfully used for this condition in three previously reported cases. The purpose of this article is to present a case history in which electromyographic biofeedback was used successfully as part of a nonoperative treatment program for voluntary posterior dislocation of the shoulder.

Adolescent↗
PubMed1994

Primary malignant cardiac tumor: an analysis of seven cases.

BACKGROUND: Primary malignant cardiac tumor is a rare disorder which has a myriad of clinical manifestations. It dominates about one-fourth of all cardiac tumors, exhibiting typically malignant histological characteristics and invasive behavior. METHODS: Seven cases of primary malignant cardiac tumor were collected over eight years (1985-1993) in this hospital. Each case had different manifestations. All cases were diagnosed by physical examination, echocardiogram and were subsequently proved by tissue pathology. RESULTS: The majority of these seven cases of primary malignant cardiac tumor had clinical symptoms of chest distress, shortness of breath and paroxysmal nocturnal dyspnea. The relatively young ages of the patients ranged from 11 to 62 years. One case of angiosarcoma, one case of fibrosarcoma, one case of leiomyosarcoma and three cases of lymphoma had the characteristics of cardiac hemodynamic obstruction which was induced by location and size of the tumors in the heart. Five cases of those primary malignant cardiac tumor were mortal; the average life span was nine months following surgical resection and chemotherapy. CONCLUSIONS: From a clinical viewpoint, primary malignant cardiac tumor characteristically displays a rapid downhill course. Death most often occurs from a few weeks to two years after the onset of symptoms. Because these tumors are rare and have a poor clinical outcome, early diagnosis and treatment are vital.

Adult↗
PubMed1993

Antagonistic effects of stimulation of the paramedian reticular nucleus in the rat medulla oblongata and of amphetamine on locomotor activity and striatal release of dopamine-like material.

The effects of stimulation of the paramedian reticular nucleus (PRN) in the rat medulla oblongata on both amphetamine-induced locomotor activity and striatal release of dopamine-like material were assessed. PRN stimulation (by intra-PRN injection of the excitatory amino acid, kainic acid) decreased vertical motion and total distance travelled, and increased postural freezing, in freely moving rats. On the other hand, a small dose (e.g. 1.25 mg/kg, i.p.) of amphetamine increased locomotor activity (including horizontal motion, vertical motion, total distance travelled and lines crossed counts), increased the number of turnings (both clockwise and anti-clockwise), induced locomotor stereotypy (including both gamma value and number of trip types), and inhibited postural freezing. The changes in activity induced by amphetamine administration were suppressed following PRN stimulation. In vivo voltammetric data revealed that electrical stimulation of the PRN decreased the release of dopamine-like material in the corpus striatum. This effect could be mimicked by intra-PRN injection of kainic acid in anesthetized rats. In contrast, i.p. administration of amphetamine increased the release of dopamine-like material in the corpus striatum. Furthermore, the enhanced release of dopamine-like material induced by amphetamine was attenuated by simultaneous stimulation of the PRN. The results reported here indicate that PRN stimulation decreases the striatal dopamine release and results in attenuation of the amphetamine-induced locomotor activity responses in rats.

Amphetamine↗
PubMed1993

A modularized infrared light matrix system with high resolution for measuring animal behaviors.

The current study provides a new modularized infrared light matrix system (about $200 cost) which is designed to measure the horizontal gross or fine movements, vertical motion, clockwise or anticlockwise turnings, freezing time, and total distance traveled in rats. The system records the sequences of animal's activity in a computer-aided system with a resolution of 0.2 s in time or 1.6 cm in space, and permanently stores all the resulting data in file. The behavioral apparatus was tested for its sensitivity and usability by amphetamine-injected rats. It was found that intraperitoneal administration of amphetamine (1.25-2.50 mg/kg), but not normal saline, produced a dose-related increase in either the horizontal gross or fine movements, vertical motion, clockwise or anticlockwise turnings, or total distance traveled. However, amphetamine injections produced a dose-related decrease in freezing time. Apparently, most of the amphetamine-induced responses obtained by other detecting apparatus can be reproduced easily by the present apparatus. The current detection system possesses the following advantages: a) high resolution, b) high expansion potential, and c) precise and simplified algorithms for behavioral parameter analysis.

Algorithms↗
PubMed1993

A simplified method for selecting a carbon-fiber electrode in pulse voltammetry.

A method for selecting a usable carbon-fiber electrode using the equivalent resistance and capacitance is presented. This method uses an instrument with a PC-based look-up table for measuring the electrical characteristics of a carbon-fiber electrode in pulse voltammetry. Using this instrument, the equivalent resistance and capacitance of the carbon-fiber electrode in saturated sodium chloride solution can be obtained. This instrument includes a decade resistance box, a peak current detection and hold circuit, a half peak comparator and a decay duration counter. A look-up table is established by using RC circuits to emulate the electrochemical reaction of the carbon-fiber electrode in pulse voltammetry. The equivalent resistance is obtained from the decade resistance box according to Kirchhoff's law. Then the equivalent capacitance is determined from the decay duration counter reading and equivalent resistance with the look-up table via a PC interpolation program. After obtaining the equivalent resistance and capacitance of an electrode, the values are compared with the usable thresholds. This method provides an effective quality evaluation index of carbon-fiber electrode for the user in order to reduce electrode-induced experimental failure. The method is also available for other kinds of carbon-fiber electrodes as long as their look-up table and desired thresholds are established.

Electric Conductivity↗
PubMed1993

Suppression of protein degradation in progressive cardiac hypertrophy of chronic aortic regurgitation.

BACKGROUND: The heart adapts to the volume overload of aortic regurgitation with dilation and hypertrophy. The development of left ventricular hypertrophy at the protein level is a dynamic process resulting from an imbalance between cardiac protein synthesis and degradation. The objective of the present study was to determine in vivo the relative contributions of cardiac protein synthesis and degradation to the progressive hypertrophy that occurs in response to chronic aortic regurgitation and to compare these with responses earlier in the course of this stress. METHODS AND RESULTS: Continuous intravenous infusions of [3H]-leucine were administered 3 days and 1 month after surgical induction of aortic regurgitation and sham operation in rabbits. Total cardiac protein and myosin heavy chain fractional synthesis rates were obtained by analysis of plasma and protein hydrolysate data using [14C]-dansyl chloride assays. Left ventricular growth rates were determined from serial echocardiographic and postmortem left ventricular weight and protein concentration measurements; protein degradation rates were determined by subtraction of growth rates from synthesis rates. CONCLUSIONS: In comparison with sham-operated control rabbits, protein fractional synthesis rates were increased at 3 days but not at 1 month after induction of aortic regurgitation Progressive cardiac hypertrophy occurring at 1 month was caused by a decrease in protein fractional degradation rates. An increase in protein synthesis contributes only to the early phase of hypertrophy caused by acute aortic regurgitation, whereas progressive eccentric hypertrophy in chronic volume overload is due to suppression of protein degradation.

Animals↗