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Biomedical subjects

T K Akers

Publications and source records attributed to T K Akers.

At least 19 recordsLinked to original sources
PubMed1991

The physiology teacher, a facilitator of learning at all levels.

Academic physiologists in universities have three jobs: teaching, research, and service. They also operate at many levels of education: undergraduate, graduate, and medical. Each level carries special problems and special rewards. It is argued in this paper that teachers should be facilitators in learning no matter what level or what aspect of the job. If physiologists behave as facilitators of learning at all levels, then they will be able to help undergraduates by the most appropriate choice of textbooks and handbooks; to develop case histories, scenarios, and summaries; and to show students how physiology got to where it is, developing in the students a healthy concept of skepticism. This can be expanded when the students are graduate students and the teacher acts as an advisor and is still facilitating the students' learning.

Education, Graduate↗
PubMed1991

Commonalities between gas anesthetics (nitrous oxide, nitrogen and/or argon) and ethanol intoxication in hot and cold selection line mice.

Argon, nitrogen, nitrous oxide were administered hyperbarically in doses (atmosphere) that caused loss of righting reflex (LORR). Nitrous oxide requires pressure somewhat less than two atmospheres, eighteen atmospheres were required for argon and thirty-six atmospheres roughly for nitrogen all in 0.5 atmospheres oxygen. Loss of righting reflex was assessed by using a rolling cage method of Wilson and Miller. Since nitrogen is the least liposoluble and nitrous oxide the most liposoluble of these three gases, greater pressures were needed for nitrogen to attain sufficient concentration in the membrane for anesthesia. Due to the low lipid solubility (1.4), nitrous oxide was administered hyperbarically at a compression rate of less than 0.5 atm/min at chamber temperature of 86 degrees plus or minus 2 degrees. Body temperatures were measured by minimitter transmitters. Two types of transmitters: an AM frequency and an FM frequency were used; a comparison of the two systems were made. The ED50 (atmospheres) required to produce a given score on the LORR were determined for each strain or line of mice. This ED50 value was determined for the Hot and Cold selection lines which have been specifically bred to differ as much as possible in a hypothermic response to acute doses of ethanol. These experiments demonstrate quite clearly a degree of commonality exists among CNS depressants with regard to anesthesia, loss of righting reflex and hypothermia.

Anesthetics↗
PubMed1991

Low magnetic field effects on embryonic bone growth.

Pulsed electromagnetic fields [EMF] and electric fields have been demonstrated to promote osteogenesis and wound healing. Pulsed EMF's have been approved since 1979 by the FDA, and are highly effective in the treatment of non-union fractures. Increased linear growth, cellular proliferation, cAMP and uptake of tritiated thymidine have been documented on short term exposure. Yet the mechanisms and the changes that occur have been difficult to quantify. Fluorescence, light, and electron microscopy were utilized in this study to assess any histological changes in bone. During incubation chick embryos were exposed to magnets oriented in various positions. Controls were oriented similarly using galvanized steel plugs. Field density in the center of the field was measure by a gaussmeter with a transverse probe. Each chick embryo in its magnetic field was isolated from the magnetic fields of others by being encased in a steel box. Intramembranous [calvaria] and endochondral [tibia] ossification were studied. Fluorescent dyes were micropipetted intravascularly at various stages of chick development. The tissues were fixed in methacrylate and stained for histomorphological study.

Animals↗
PubMed1989

Muscle afferents and the neural dynamics of limb position and velocity sensations.

Today muscle spindles are thought to be the primary receptor responsible for limb position and velocity. A mathematical model describing the muscle spindle's complex dynamical behavior was developed recently by Hasan. Other researchers have observed neuronal firing in the cortex of primates when muscles surrounding a joint have been passively stretched by joint movement. The purpose of this paper is to apply the muscle spindle model to a "two-muscle joint" and quantitate the resultant firing rates for various joint positions and velocities. With this information insights into the required neuronal dynamics for extracting position and velocity information from muscle spindles can be gained.

Afferent Pathways↗
PubMed1987

Effect of high voltage stimulation on edema reduction in the rat hind limb.

The purpose of this study was to test the effect of high voltage stimulation (HVS) on edema reduction in the rat hindpaw. The animals were divided into a control group (n = 20) and a treated group (n = 20). The right hindpaw volume was measured, and then the animal's paw was traumatized. The animals in the treated group were treated with HVS at 24, 48, and 72 hours posttrauma. Paw volume measurements were made on all animals at 0, 24, 48, 72, and 96 hours posttrauma. In addition, the paw volume was measured in the treated group both before and after HVS. The results showed that animals in both groups had a significant decrease in paw volume over the experimental period, but no significant difference was found between the two groups in the amount of edema reduction. The HVS treatment did not produce a significant change in paw volume immediately after treatment.

Animals↗
PubMed1987

Effect of high voltage stimulation on blood flow in the rat hind limb.

The purpose of this study was to test the effect of high voltage stimulation (HVS) on blood flow velocity (BFV) in the rat hind limb. A 20-MHz pulsed Doppler device was used to measure BFV changes in the femoral artery of 20 anesthetized rats after electrical stimulation. The animals were stimulated under the following conditions: four different pulse rates, changes in stimulus voltage, and changes in polarity. Blood flow velocity also was measured in the unstimulated hind limb. Although each of the four pulse rates caused significant increases in BFV, the 20-pulse-per-second rate produced BFV increases significantly greater than the other three pulse rates. The BFV changes, on the average, occurred less than 1 minute from the onset of stimulation and lasted up to 14 minutes after the cessation of the stimulation. The BFV increased with increases in voltage intensity. Both the positive and negative poles elicited significant increases in BFV, but the negative pole produced the greatest increases. Blood flow in the unstimulated hind limb was unchanged after stimulation. This study indicates that HVS of muscle does cause significant increases in blood flow to the stimulated rat hind limb.

Animals↗
PubMed1978

Analysis of frog neuromuscular function at hyperbaric pressures.

Nerve and muscle compound action potentials were measured in the frog sciatic nerve-gastrocnemius muscle preparation in a hyperbaric helium-air environment. Helium pressure to 69 ATA induced a reversible depression in muscle compound action potential amplitude without significantly affecting other parameters. Blockade other parameters. Blockade induced by tetraethylammonium while at pressure could be partially reversed by decompression. A desensitization-type of neuromuscular block produced at pressure after neostigmine infusion could also be partially reversed by decompression. These results suggest a possible involvement of the acetylcholine receptor complex in pressure-induced depression of synaptic transmission.

Acetylcholine↗
PubMed1978

Vitamins limiting for growth of subjects fed a normal diet under hyperbaric He-O2 conditions.

A growth study was conducted of rats continuously exposed for 4 weeks to ambient air, 1 ATA He-O2, or 11 ATA He-O2 conditions and fed one of 16 diets. The diets were the standard diet alone (adequate according to National Research Council standards); the standard diet with additional casein (50%), fat (25%), and all vitamins (25%); or the standard diet with all vitamins (25%), or all vitamins increased (25%) except one, which was supplied at the standard level. The standard diet was inadequate to support a normal rate of growth when fed under 11 ATA He-O2 conditions. Supplemental casein, fat, and vitamins or all vitamins alone adequately provided nutrients necessary for a normal rate of growth by hyperbaric exposed rats. The standard levels of thiamine, pantothenic acid, biotin, and vitamin K were inadequate and the standard levels of niacin, and vitamins A, D, and E were marginal in supporting growth when fed under hyperbaric conditions.

Animals↗
PubMed1978

Testicular growth and functional capability after 4-24 weeks of continuous exposure to 11 ATA He-O2.

A study of testicular developmental and functional capabilities was made of rats continuously exposed for 4, 8, 12, 16, 20, or 24 weeks to 1 ATA He-O2, 11 ATA He-O2, or ambient pressure air environmental conditions. Other groups of rats were exposed for 24 sequential weeks to the same three sets of environmental conditions with brief interruptions for decompression and recompression at the end of each 4 weeks. The rats were comfortably housed and adequately fed in accord with earlier investigations. Visual observations of the testes at the time of slaughter, dry matter content of the testes, and histological examinations--all revealed normal growth and active spermatid formation from healthy germinal epithelia in all semeniferous tubules. The stress of hyperbaria or of helium to 11 ATA did not inhibit or destroy male germinal epithelial functional capabilities.

Animals↗
PubMed1976

Scanning electron microscopy of normoxic and hyperoxic hyperbaric exposed lungs.

Lungs from adult guinea pigs exposed to 1 ATA He-O2 with 200 mm Hg PO2 and 20 ATA He-O2 with 200, 400, and 600 mm Hg PO2 were studied with scanning electron microscopy. The appearance of normal alveoli is described. Even before pulmonary O2 toxicity became symptomatic, subtle changes occurred in the alveoli, such as an increase in macrophages and a marked increase in length of alveolar type-II cell microvilli. These changes occurred in animals exposed to 400 mm Hg PO2, heretofore considered below toxic levels. With increased toxic involvement, the number of alveolar type-II cells increased. A thick layer of material appeared in some of the alveoli, obscuring the Kohns pores and type-I and -II cell surfaces. The alveolar-capillary network with underlying erythrocytes was no longer observable. Lungs with the greatest toxic involvement possessed large numbers of macrophages encompassed by a fibrin-like matrix. The alveolar walls were broken down in many instances, and the alveoli were no longer discrete units but took on the appearance of an amorphous mass of lung tissue.

Animals↗