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Biomedical subjects

J H Ryu

Publications and source records attributed to J H Ryu.

136 records · Page 8Linked to original sources
PubMedDate not supplied

Second-order vestibular adaptation and cupular dynamics.

The magnitude of initial response and slope of continued response of 45 neurons in the vestibular nuclei of cats to constant and interrupted accelerations were investigated. Eighty-eight percent exhibited adaptation, the magnitude of which was proportional to the stimulus. Comparison of slope and intercept of the response to continuous acceleration before and after a superimposed inhibitory velocity change suggests that the adaptation phenomenon is unrelated to cupular position.

Acceleration↗
PubMedDate not supplied

The effect of blood pressure on compression-induced facial nerve neuropraxia in the cat.

The facial nerves of 21 adult anesthetized cats were exposed from the parotid gland to the orbicularis oculi muscle. The summated action potential (SAP) of the orbicularis oculi muscle was recorded. A calibrated pressure block was applied to the intact facial nerve between the stimulating electrode and the muscle. Pressures of between 150 and 200 mm Hg caused a rapid stable neuropraxia. In ten animals the blood pressure was elevated by a constant levarterenol infusion. In 11 animals the blood pressure was elevated by coarcting the abdominal aorta and volume overloading the rostral vascular system. In both groups, in all animals, when the systolic blood pressure exceeded the pressure applied to the nerve, a substantial increase in SAP amplitude was noted. If the systolic pressure was allowed to fall below the pressure on the nerve, the neuropraxia rapidly returned. This data suggest that within a physiologic pressure range of 150 to 200 mm Hg there is a reversible ischemic phase of compression neuropraxia and it is in complete accord with the earlier work of Devriese.

Animals↗
PubMedDate not supplied

Cis-diamminedichloroplatinum (II) ototoxicity in the guinea pig.

Cochleas from 12 guinea pigs were evaluated using light, scanning, and transmission electron microscopy after systemic administration of cis-diamminedichloroplatinum (cis-DDP). Administration of cis-DDP resulted in loss of the Preyer reflex and degeneration of outer hair cells (OHC) with increased dose. The OHC degeneration was most pronounced in the basal turns of the cochlea with greatest severity in the inner row. Ultrastructural evidence of OHC degeneration included dilatation of the parietal membranes, softening of the cuticular plate, increased vacuolization and increased numbers of lysosome-like bodies in the apical portion of the cell. Supporting cells appeared more sensitive than OHC. Alteration of supporting cell ultrastructure preceded detectable change in OHC. Injury to the supporting cells was noted with intracellular vesiculation and increased autophagocytosis.

Animals↗
PubMedDate not supplied

Survival of implanted irradiated cartilage.

As a result of our study the following conclusions may be drawn: 1. Irradiated homograft costal cartilage appears to survive as a nonviable implant in part replaced by host tissue in the cat. 2. Such replacement may be minimized by leaving as much perichondrium intact as is feasible. 3. Boiling or freezing fresh autogenous cartilage in an attempt to alter its warping characteristics is asking for increased resorption.

Animals↗
PubMedDate not supplied

Neuronal habituation in the vestibular nuclei of the cat.

This is a study of the effects of repeated angular acceleration on the activity of vestibular nuclei units in anesthetized and in conscious cats. The experimental animals were subjected to trains of repeated and consecutive constant acceleration-deceleration ramps (4-8 degrees/sec2). In a few cases nystagmus was recorded along with extracellular unit activity. The effect of stimulus repetition on vestibular neuronal activity consisted of one of the following: 1. No change in response. 2. Progressive response decline. 3. An initial maintenance of a constant response level throughout the first part of the stimulus paradigm, followed by a progressive decline. 4. An initial gradual enhancement of response followed by a progressive decline. This classification is based on results of polynomial and non-linear broken-line regression analyses. Categories 3 and 4 were found predominantly in units recorded from conscious cats. The majority of neurons recorded from anesthetized cats that exhibited response changes upon stimulus repetition manifested a progressive response decline. The response decline in anesthetized cat units was usually on a faster time scale than in conscious cats. Correlations between unit response modification patterns and simultaneously recorded nystagmus were mostly of a moderate degree.

Acceleration↗
PubMedDate not supplied

Produce handling and processing practices.

In the past decade, outbreaks of human illness associated with the consumption of raw vegetables and fruits (or unpasteurized products produced from them) have increased in the United States. Changes in agronomic, harvesting, distribution, processing, and consumption patterns and practices have undoubtedly contributed to this increase. Pathogens such as Listeria monocytogenes, Clostridium botulinum, and Bacillus cereus are naturally present in some soil, and their presence on fresh produce is not rare. Salmonella, Escherichia coli O157:H7, Campylobacter jejuni, Vibrio cholerae, parasites, and viruses are more likely to contaminate fresh produce through vehicles such as raw or improperly composted manure, irrigation water containing untreated sewage, or contaminated wash water. Contact with mammals, reptiles, fowl, insects, and unpasteurized products of animal origin offers another avenue through which pathogens can access produce. Surfaces, including human hands, which come in contact with whole or cut produce represent potential points of contamination throughout the total system of growing, harvesting, packing, processing, shipping, and preparing produce for consumption. Treatment of produce with chlorinated water reduces populations of pathogenic and other microorganisms on fresh produce but cannot eliminate them. Reduction of risk for human illness associated with raw produce can be better achieved through controlling points of potential contamination in the field; during harvesting; during processing or distribution; or in retail markets, food-service facilities, or the home.

Chlorine↗