Biomedical subjects

A K Ho

Publications and source records attributed to A K Ho.

166 records · Page 10Linked to original sources

PubMedDate not supplied

Interactions between methaqualone and ethanol in rats and mice during acute and chronic states.

1. The effects of acute and chronic treatment of methaqualone on ethanol preference, the rate of disappearance of ethanol and on toxicity were studied in mice and rats. 2. Acute treatment with methaqualone showed a dose-dependent suppression in the voluntary intake of ethanol in C57Bl/6J mice in rats. No significant change in ethanol intake was observed during chronic methaqualone treatment and withdrawal. 3. Methaqualone pretreatment significantly (P less than 0.005) delayed the disappearance of ethanol in the blood and brain over a period of 50 and 200 min after a loading dose of 2.0 g/kg, i.p., of ethanol. 4. Methaqualone pretreatment at doses of 140 and 200 mg/kg significantly increased ethanol toxicity by 11% and 28%, respectively. Co-administration of ethanol using 6.0, 7.0 and 8.0 g/kg also reduced the LD50 of methaqualone by 19%, 24% and 40%, respectively. 5. Chronic administration with ethanol decreased the toxicity due to methaqualone. Potentiation of ethanol toxicity by methaqualone may be of clinical importance in view of the narrow range of safety margin of ethanol.

Alcohol Drinking↗

PubMedDate not supplied

Stopping-power and mass energy-absorption coefficient ratios for Solid Water.

The AAPM Task Group 21 protocol provides tables of ratios of average restricted stopping powers and ratios of mean energy-absorption coefficients for different materials. These values were based on the work of Cunningham and Schulz. We have calculated these quantities for Solid Water (manufactured by RMI), using the same x-ray spectra and method as that used by Cunningham and Schulz. These values should be useful to people who are using Solid Water for high-energy photon calibration.

Absorption↗

PubMedDate not supplied

Charge storage in electron-irradiated phantom materials.

A recent article by Galbraith et al. [Med. Phys. 11, 197 (1984)] revealed the existence of dose errors due to charge storage in electron-irradiated plastic phantoms. We have subsequently studied the same effect using similar materials, plus some others including "solid water," which is an epoxy-based phantom material manufactured by Radiation Measurement, Inc. Our work shows that there is minimal charge storage in solid water, as compared to polymethylmethacrylate (PMMA) and polystyrene. Since existing dosimetry protocols allow PMMA and polystyrene to be used for calibration phantoms, users should beware of the possible dosimetry errors resulting from charge storage in those plastics, and consider choosing other water-substitute media, such as solid water, that do not display this effect.

Electrons↗

PubMedDate not supplied

Motor instability in parkinsonian speech intensity.

OBJECTIVE: This study examined progressive speech intensity decay using two speech tasks: sustained vowel phonation (Experiment 1) and sentence reading (Experiment 2). BACKGROUND: Parkinsonian speech intensity has often been clinically observed to fade out or trail off. This gradual diminution of intensity is not unlike the well-documented progressive reduction of force underlying (upper limb) micrographic parkinsonian handwriting and (lower limb) marche à petit pas. Motor instability in speech intensity has yet to be investigated in a controlled experimental setting, however. METHOD: Thirteen Parkinson disease (PD) patients and their matched controls participated in Experiment 1: data from 6 PD patients and controls who naturally (i.e., without prior instruction) read the target sentence within a breath span were included in the analysis for Experiment 2. Participants were instructed to inhale maximally before vocalizing, and the extent of intensity declination over the breath span was measured. RESULTS: Parkinson disease patients demonstrated a consistently greater level of progressive intensity decay compared with matched controls for both speech tasks. This successful documentation and analysis of fading speech was interpreted as evidence for motor instability within the speech motor system in PD. CONCLUSIONS: It was concluded that the control of force in complex motor sequences involving speech and limb movement is affected by a common deficit in the frontostriatal circuit.

Aged↗