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Biomedical subjects

R W Young

Publications and source records attributed to R W Young.

At least 55 records · Page 3Linked to original sources
PubMed1981

Comparison of accelerod and rotarod sensitivity in detecting ethanol- and acrylamide-induced performance decrement in rats: review of experimental considerations of rotating rod systems.

The relative sensitivity of two rotating rod techniques in detecting performance decrement in rats was assessed after treatment with either ethanol or acrylamide. Performance on the rod during acceleration at approximately 1 rpm/sec (accelerod) was compared to that obtained on the same rod operated at a constant speed of 20 rpm (rotarod). Rats trained to either task received a single oral dose of ethanol (0.5, 1.0, 1.5, or 2.0 g/kg) or a series of ip doses of acrylamide (25 or 50 mg/kg/day) before testing. Accelerod performance was significantly more disrupted at lower doses and for longer periods of time after ethanol ingestion than was rotarod performance. Likewise, task disruption resulted from repeated injections of acrylamide also appeared at lower cumulative doses using the accelerod. A higher proportion of the native subjects were successfully trained and the mean time for training to minimum performance standards was significantly less using the accelerod. The greater sensitivity of the accelerod technique in detecting neurotoxic effects is attributed primarily to the fact that this test provides a continuous measure of the upper limit of performance rather than the quantal or arbitrarily truncated measure that one usually obtains from the rotarod. In light of these findings, a review is presented of the primary experimental variables that affect the reliability of data obtained in neurotoxic evaluations using the accelerod and rotarod procedures.

Acrylamides↗
PubMed1981

Acute and chronic propylene glycol dinitrate exposure in the monkey.

Rhesus monkeys (Macaca mulatta) were exposed to propylene glycol 1,2-dinitrate (PGDN) vapors on either an acute (4-h) or chronic (125-d) schedule. During acute exposures, PGDN concentrations ranged from a low of 2 ppm (parts per million) to a high of 33 ppm. Free operant avoidance behavior and visual evoked responses were monitored and free operant avoidance was not affected at any dose level. The late positive (100-150 ms) wave of the visual evoked response increased 20% at 2 ppm and decreased 25% at concentrations up to 33 ppm. Although these changes were statistically different from control values, they were within the limits caused by distracting events (+/-40%), and might possibly have been caused by the irritating or distracting properties of the vapor. Other monkeys were exposed to successively increasing concentrations of PGDN vapors at 0.3-4.2 ppm. 23 h/d, for 125 d. Daily performance testing included alternating sessions of discrete-trial cued avoidance and free operant avoidance. Non of the PGDN concentrations had a discernible effect on either type of avoidance performance.

Animals↗
PubMed1980

Use of chlorophyllin in the care of geriatric patients.

In a test group of 62 geriatric nursing home patients, the administration of chlorophyllin tablets was found to be helpful in controlling body and fecal odors. It aided also in easing chronic constipation, served at times as a useful and morale-building placebo, and assisted in abating excessive flatus. No toxic or other ill effects were observed. Bacteriologic studies failed to confirm reports in the literature of antibacterial properties for chlorophyllin. Further investigation of this possibility is recommended.

Aged↗
PubMed1978

Rhythmic daily shedding of outer-segment membranes by visual cells in the goldfish.

Goldfish were placed on a daily light cycle of 12 h light and 12 h darkness for 18 days or longer. The visual cells and pigment epithelium of the retina were then examined by microscopy at many intervals throughout the cycle. Goldfish rods and cones follow a rhythmic pattern in eliminating packets of photosensitive membranes from their outer segments. Rods shed membranes early in the light period. The detached membranes are ingested by pigment epithelial cells or by ameboid phagocytes, which degrade them during the remainder of the light period. Cones discard membranes from the ends of their outer segments early in the dark period. During the next several hours, this debris is digested by the pigment epithelium or by ameboid phagocytes. Thus, the disposal phase of the outer-segment renewal process is similar in rods and cones, but is displaced in time by about 12 h. There is evidence that this daily rhythm of membrane disposal in rods and cones is a general property of vertebrate visual cells.

Animals↗
PubMed1978

The daily rhythm of shedding and degradation of rod and cone outer segment membranes in the chick retina.

Newly hatched chickens were maintained on a daily light cycle of 12 hr of light and 12 hr of darkness for 12 days. The pigment epithelium was then examined by electron microscopy at different times of day. Shortly after the beginning of the light period, the rods discarded groups of outer segment membranes. During the remainder of the light period, the membranes were degraded by the pigment epithelium. Early in the dark period, the cones shed membranes, which were digested by the pigment epithelial cells during the subsequent hours of darkness. Available evidence suggests that at least some of the chemical activities of the visual cells and pigment epithelium oscillate with a daily rhythm, which is synchronized with the daily fluctuation of light in the environment.

Animals↗
PubMed1978

Lead and other elements in tissues of guinea pigs fed crown vetch grown adjacent to a highway.

Forty-four elements were determined in crown vetch sampled along a heavily travelled highway in Virginia. Twenty-four elements including Ba, Br, Cr, Pb, Sn, and Sr were higher in this vegetation than in control vetch. When the highway-grown vetch was fed as 45% (dry weight) of the diet to guinea pigs for 100 days, Ba, Br, Cr, Pb, Sn and Sr were found at higher concentrations in the various animal tissues than in those of guinea pigs similarly fed the control crown vetch.

Animal Feed↗
PubMed1977

The effects of hibernation on cone visual cells in the ground squirrel.

The cone visual cells of active, hibernating, and aroused 13-line ground squirrels have been studied by microscopy and autoradiography. Major changes occur throughout the cells during hibernation. The outer segments are shortened, and the diameters of the membranous discs may be reduced. Mitochondria are diminished in size and number, ribosomes are depleted, and the Golgi complex is fragmented into vesicles. Calycal processes are thickened, and synaptic ribbons become aggregated ectopically within the synaptic body. When hibernation is terminated, the cells recover rapidly. First, the basic synthetic machinery (mitochondria, ribosomes, Golgi complex) is regenerated,, and then the outer segments are repaired. This process is completed within 1 week. Many of the structural changes observed during hibernation are interpreted as effects of a temporary metabolic imbalance in which degradative mechanisms, including autophagy, are emphasized. In contrast, recovery is achieved by a comparable imbalance in which there is a transient accentuation of formative mechanisms. The recovered cells thereafter maintain a steady state of continuous self-renewal, in which formation and degradation are in balance.

Animals↗
PubMed1975

Emesis in monkeys following exposure to ionizing radiation.

There were 129 male rhesus monkeys (Macaca mulatta) exposed to prompt radiations (neutron/gamma = 0.4 and pulse width = 50 ms) ranging from 700 to 5600 rad (midhead dose). The animals were fasted 18 h preexposure and observed for incidence of vomiting for 2 h postexposure. For doses less than 1000 rads the number of animals that vomited increased directly with dose. Above 1000 rads, the number of animals that vomited decreased with increasing dose. The total number of vomits per dose group followed a nearly identical pattern to the incidence of emesis. In all dose groups, most of the emetic episodes occurred between 20 and 50 min postirradiation.

Animals↗
PubMed1974

Renewal of fatty acids in the membranes of visual cell outer segments.

The renewal of fatty acids in the visual cells and pigment epithelium of the frog retina was studied by autoradiographic analysis of animals injected with tritiated palmitic, stearic, or arachidonic acids. Most of the radioactive material could be extracted from the retina with chloroform-methanol, indicating that the fatty acids had been esterified in lipids. Analysis of the extracts, after injection of [(3)H]palmitic acid, revealed that the radioactivity was predominantly in phospholipid. Palmitic acid was initially concentrated in the pigment epithelium, particularly in oil droplets which are storage sites for vitamin A esterified with fatty acid. The cytoplasm, but not the nucleus of these cells, was also heavily labeled. Radioactive fatty acid was bound immediately to the visual cell outer segment membranes, including detached rod membranes which had been phagocytized by the pigment epithelium. This is believed to be due to fatty acid exchange in phospholipid molecules already situated in the membranes. Gradually, the concentration of radioactive material in the visual cell outer segment membranes increased, apparently as a result of the addition of new phospholipid molecules, possibly augmented by the transfer from the pigment epithelium of esterified vitamin A. Injected fatty acid became particularly concentrated in new membranes which are continually assembled at the base of rod outer segments. This localized concentration was short-lived, apparently due to the rapid renewal of fatty acid. The results support the conclusion that rods renew the lipids of their outer segments by membrane replacement, whereas both rods and cones renew the membrane lipids by molecular replacement, including fatty acid exchange and replacement of phospholipid molecules in existing membranes.

Animals↗
PubMed1974

Renewal of glycerol in the visual cells and pigment epithelium of the frog retina.

The renewal of glycerol in the visual cells and pigment epithelium of the frog retina was studied by autoradiographic analysis of animals injected with [2-(3)H]glycerol. Assay of chloroform:methanol extracts showed that the labeled precursor was used mainly in lipid synthesis, although there was also some utilization in the formation of protein. Radioactive glycerol was initially concentrated in the myoid portion of rods and cones, indicating that this is the site of phospholipid synthesis in visual cells. The glycogen bodies (paraboloids) of accessory cones were also heavily labeled, suggesting the diversion of some glycerol into glycogenic pathways. In the pigment epithelium, only the oil droplets became significantly radioactive. The outer plexiform layer (which contains the visual cell synaptic bodies) and the cone oil droplets gradually accumulated considerable amounts of labeled material. Within 1-4 h, labeled molecules began to appear in the visual cell outer segments, evidently having been transported there from the myoid portion of the inner segment. Most of these were phospholipid molecules which became distributed throughout the outer segments, presumably replacing comparable constituents in existing membranes. In rods only, there was also an aggregation of labeled material at the base of the outer segment due to membrane biogenesis. These highly radioactive membranes, containing labeled molecules of lipid and protein, were subsequently displaced along the rod outer segments due to repeated membrane assembly at the base. The distribution of radioactivity supported the conclusion that membrane renewal by molecular replacement is more rapid for lipid than it is for protein.

Animals↗