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Biomedical subjects

G K York

Publications and source records attributed to G K York.

16 recordsLinked to original sources
PubMed1995

Hughlings Jackson's theory of recovery.

John Hughlings Jackson proposed a mechanism of neurologic compensation based on his theory of cerebral localization. According to Hughlings Jackson, there are three levels of evolution of the nervous system. Each element of each level contains a complete representation of the next lower level. Each element of the middle and highest levels contain a representation of the entire body, weighted for a particular part of the body. If the nervous system is damaged so that an area heavily weighted for a particular part of the body is destroyed, less heavily weighted areas are immediately activated according to their weighting. This activation partially compensates for the function of the destroyed tissue. As time passes, the weighting of representation in the unaffected areas changes, amplifying the degree of recovery. Recent clinical studies and PET cerebral blood flow studies show that various ipsilateral and contralateral areas are activated in recovery. The activated areas reside in what Hughlings Jackson would call the middle and highest evolutionary levels. Modern clinical and neurophysiologic observations are therefore consistent with Hughlings Jackson's theory of compensation.

Brain Diseases↗
PubMed1979

Paroxysmal genital pain: an unusual manifestation of epilepsy.

A male patient who is now 15 years old has experienced a seizure disorder since age 9 years. The seizures were expressed as episodes of excruciating pain localized to the genital region. Appropriate anticonvulsant medication has controlled both pain and seizures.

Cerebral Cortex↗
PubMed1971

Quick counting method for estimating the number of viable microbes on food and food processing equipment.

A rapid method for estimating the extent of microbial contamination on food and on food processing equipment is described. Microbial cells are rinsed from food or swab samples with sterile diluent and concentrated on the surface of membrane filters. The filters are incubated on a suitable bacteriological medium for 4 hr at 30 C, heated at 105 C for 5 min, and stained. The membranes are then dried at 60 C for 15 min, rendered transparent with immersion oil, and examined microscopically. Data obtained by the rapid method were compared with counts of the same samples determined by the standard plate count method. Over 60 comparisons resulted in a correlation coefficient of 0.906. Because the rapid technique can provide reliable microbiological count information in extremely short times, it can be a most useful tool in the routine evaluation of microbial contamination of food processing facilities and for some foods.

Bacteria↗
PubMed1966

Effect of pimaricin on the resistance of Saccharomyces cerevisiae to heat, freezing, and ultraviolet irradiation.

Exposure of washed cells of Saccharomyces cerevisiae C-299 to inhibitory concentrations of pimaricin decreased resistance to lethal temperatures and to freezing and thawing. Varying the pH of the recovery medium had little effect on the decrease in heat resistance, but addition of peptone or yeast extract resulted in a partial recovery of apparent heat resistance. Addition of peptone or calcium ion to the heating menstruum did not affect the reduction in resistance caused by pimaricin. Varying the composition of the recovery medium similarly affected the resistance to freezing the thawing of pimaricin-exposed and unexposed cells. Sensitivity to ultraviolet light was apparently not affected by pimaricin either by preliminary exposure or when irradiated in the presence of pimaricin. It is suggested that pimaricin lowers the heat resistance of S. cerevisiae by depleting essential nutrients of the cells through a disruption of permeability, and that heat-damaged cells cannot resynthesize these nutrients. It is also suggested that spoilage of acid foods by S. cerevisiae may be retarded by a combination of mild heat treatment and the addition of pimaricin.

Antifungal Agents↗
PubMed1965

Effect of several environmental conditions on the "thermal death rate" of endospores of aerobic, thermophilic bacteria.

The composition of the recovery medium affected the apparent heat resistance of Bacillus stearothermophilus when the pH of the medium was 7.0 but not when the pH was 6.5. The rate of thermal death at 110 C was exponential. Deviations from exponential rates of thermal death during the initial phases of heating at 96 C were observed with endospores of B. coagulans under different conditions of sporulation. Additionally, the apparent heat resistance was influenced by the composition of the media used for sporulation and recovery and by the composition of the suspending menstruum. The presence of 0.001 m sorbic acid in the suspending menstruum at pH 7.0 and the temperature of incubation of the cultures after heating did not affect the apparent heat resistance of B. coagulans. Several explanations are discussed for the observed deviations from exponential thermal death rates and the effect of the environment on the apparent heat resistance of B. coagulans.

Bacillus↗
PubMedDate not supplied

Stimulation by cigarette smoke of glutathione peroxidase system enzyme activities in rat lung.

This study was undertaken to evaluate the effect of in vivo cigarette smoke exposure on glutathione peroxidase--related enzyme systems of the rat lung. These enzymes, acting in concert, are thought to be responsible for disposing of toxic lipid peroxides in pulmonary tissue. Thirty-day-old rats were exposed to thirteen cigarettes per day for 21 days with a Walton reverse-smoking exposure apparatus. After 21 days of smoke exposure, the activities of glutathione peroxidase, glutathione reductase, and glucose-6-phosphate dehydrogenase were increased 34%, 24%, and 38%, respectively, over control values. This level of cigarette smoke exposure did not cause detectable histological lesions. We present the hypothesis that short-term, low-level cigarette smoke exposure is capable of initiating metabolic alterations in lung cells at exposures at which histological changes are not detectable by light microscopy.

Animals↗
PubMedDate not supplied

Biochemical effect of ozone exposure in rats exposed to cigarette smoke.

Rats were exposed to three cigarettes per day for 35 days, under realistic conditions. Pulmonary glucose-6-phosphate dehydrogenase (G-6-PD) activity in the exposed animals increased 27% over control values (P less than .05). Subsequent exposure to acute, high-dose ozone (3 ppm for 4 hr) decreased the augmented G-6-PD activities to near normal levels, whereas ozone exposures in animals not exposed to cigarette smoke caused mild decreases in pulmonary G-6-PD activities. The importance of these findings with respect to the susceptibility of the smoker to oxidant exposures is unknown.

Animals↗