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Biomedical subjects

R I Gamow

Publications and source records attributed to R I Gamow.

15 recordsLinked to original sources
PubMed1990

A human breathing simulator designed to test the life support system of a hyperbaric tent.

A self contained life support system which can maintain a breathable atmosphere for up to eight hours was recently developed for use with a portable hyperbaric tent. To facilitate further life support system studies, the practicality of a human breathing simulator (HBS), which would remove oxygen and release carbon dioxide at the same rate as a human, was tested. The HBS consists of a cylinder of carbon dioxide bled into the chamber via a flow regulator and a Vanadous bubbler to chemically remove oxygen from the chamber. First experiments show that the HBS works, but that a larger chemical system is needed to remove oxygen at the desired rate. Scale up calculations have been completed.

Ecological Systems, Closed↗
PubMed1989

A self-contained life support system designed for use with a portable hyperbaric chamber.

Recently, the Gamow Bag, a portable hyperbaric chamber, has been demonstrated to relieve the symptoms of acute mountain sickness (AMS). The patient is completely enclosed in the bag which is inflated and pressurized to simulate descent in altitude. CO2 produced by the patient is vented from the airtight bag by means of a pressure relief valve, while fresh air is brought in from the outside via a high volume foot pump. In order to eliminate the vigorous pumping that is necessary to maintain a suitable atmosphere in the bag, we have designed a completely portable, self-contained life support system that supplies oxygen as it is consumed and removes the waste CO2 as it is produced. The entire rebreathing unit, which maintains a homeostatic atmosphere in the chamber for six to eight hours weighs less than six pounds. The chamber with the self-contained life support system weights less than 18 pounds. It would find its greatest use in medical mountain clinics, isolated ski areas and should become standard equipment for mountain search and rescue units.

Altitude Sickness↗
PubMed1984

Phycomyces: detailed analysis of the anemogeotropic response.

Stage IVb sporangiophores of Phycomyces grow into the wind--the anemotropic response--and away from gravity--the geotropic response. A procedure has been designed to measure the equilibrium bend angle that results when the two stimuli are given simultaneously over a long period of time. This angle will be referred to as the anemogeotropic equilibrium angle. This measurement of a sensory response is analogous to the photogeotropic equilibrium angle in which the variable stimulus is light instead of wind. We have found that the anemogeotropic angle, measured relative to the vertical, increases with both increasing wind speed and increasing relative humidity of the wind stimulus. This finding is new and argues against a major prediction of the mass transfer model that anemogeotropism and relative humidity are inversely related. Data from these anemogeotropic experiments further suggest that the self-emitted gas responsible for both the anemotropic response and the avoidance response is water.

Air Movements↗
PubMed1982

Avoidance and rheotropic responses in phycomyces. Evidence for an 'avoidance gas" mechanism.

If a mature sporangiophore is placed next to a barrier that is moving in a clockwise direction, it grows both away from the barrier and into the wind; the wind is generated by the moving barrier itself. When the barrier is moving in a counterclockwise direction, the sporangiophore grows towards both the barrier and the wind. The net direction of growth appears to be the vector sum of the rheotropic response and the avoidance aiming error and does not involve the classic stationary-barrier avoidance response. Our experiments all support the suggestion that the avoidance response, the rheotropic response and the variety of reported wind responses can be explained by the presence of a self-emitted, growth-simulating avoidance gas. We present data that suggest that it is the direction of the net flux (mass transfer) of this gas that determines both the direction and the magnitude of the sporangiophore growth. We further suggest that the region of the cell wall showing maximum mass transfer will show a minimum growth rate, i.e., the direction of growth will always be in the direction of maximum transfer. If water is the avoidance gas, then it would follow that the total hydration of the cell wall in an aqueous salt solution should result in cell wall softening; cell wall softening has been correlated directly to cell wall growth. Using the Instron technique, we now show that submerging the entire sporangiophore in an aqueous salt solution for 4 min causes an increase in cell wall extensibility.

Air Movements↗
PubMed1981

Phycomyces: irregular growth patterns in stage IVb sporangiophores.

Net rotation and net elongation of a stage IVb Phycomyces growing zone were simultaneously measured minute by minute with a photographic apparatus coupled with a rotating stage. A direct correlation between a growth response and a twist response after either a light stimulus or a house stimulus was found. There were significant irregularities in growth rate in both the elongation and rotation that were not a result of measurement error; these irregularities were poorly, if at all, correlated. We believe that these fluctuations reflect the underlying molecular mechanism of cell wall synthesis.

Fungi↗
PubMed1971

Snake infrared receptors: thermal or photochemical mechanism?

It appears that the two most sensitive infrared receptors known in the biological world are found in two widely different families of snakes, the pit vipers and the boas. After an infrared stimulus from a carbon dioxide laser, which has a monochromatic output at 10.6 micrometers, we find evoked potentials in boas with chronically implanted electrodes. Our data suggest that the receptors operate on a thermal principle.

Animals↗
PubMed1971

Analysis of chemotaxis in white blood cells.

We wish to report the development of an assay system for the study of white blood cells in vitro. With this system we have demonstrated that a yet unidentified substance found in red blood cell membranes and cyclic adenosine monophosphate (cAMP) cause the chemotactic response in white blood cells. We have not yet determined whether the substance released from the membrane is cAMP.

Animals↗
PubMed1971

The avoidance response in Phycomyces.

Phycomyces sporangiophores grow away from stationary objects, a phenomenon known as the avoidance response. Evidence is presented suggesting that a growth-stimulating gas is emitted from the sporangiophore and is then swept to the leeward side by air currents resulting in higher gas concentration on that side. The presence of a stationary barrier decreases the passive movement of the gas away from the leeward side. It is proposed that an increase of this gas on one side causes that side to grow faster. Indirect evidence suggests that the gas is water vapor.

Dark Adaptation↗
PubMed1970

Phycomyces: habituation of the light growth response.

Phycomyces sporangiophores respond to four distinct physical stimuli: gravity, light, stretch, and an avoidance stimulus. Saturating the organism with a light stimulus so that it does not respond to any additional light program does not decrease its ability to respond to an avoidance stimulus. This demonstrates that the organism has the potential to respond after a saturating light stimulus and that the an avoidance stimulus acts at some point past or parellel or parellel to the light-receiving mechanism.

Fungi↗
PubMed1968

Chemically induced cofactor requirement for bacteriopage T4D.

The treatment of bacteriophage T4D with 2-hydroxy-5-nitrobenzyl bromide, a specific reagent for alkylating the indole ring of tryptophan residues, converts these particles from a cofactor-independent form to a cofactor-sensitive form. These treated T4D particles phenotypically resemble T4B particles in certain respects. Their ability to form plaques on minimal medium plates is increased by the addition of l-tryptophan and is inhibited by the addition of indole. In liquid medium, their rate of adsorption is dependent on the presence of the cofactor l-tryptophan. l-Tryptophan-requiring phage have been produced by in vitro assembly of treated tail-fiberless particles of a T4D amber mutant plus untreated tail fiber preparation. When treated tail fibers were used with untreated tail-fiberless particles, the newly assembled particles did not require cofactor. A model of the tail structure of all the T-even bacteriophages is presented which postulates that the active configuration of the tail fibers requires that there be either (i) an endogenous tryptophan residue of the phage particle itself or (ii) an exogenously added l-tryptophan molecule complexed with a specific tryptophan receptor site, most likely on the phage base plate.

Adsorption↗