The influence of high hydrostatic pressure on cocaine and veratrine action in a vertebrate nerve

The application of high hydrostatic pressure to toad sciatic nerve causes a gain in sodium and a loss of potassium which are not affected by cocaine. However, cocaine action is enhanced by high pressure when counteracting veratrine depolarization and when blocking the action potential. Various effects of elevated pressure on the after-potentials are presented and the role of ions in these processes is discussed.

Growth, reproduction, and death rates of Escherichia coli at increased hydrostatic pressures

ZoBell, Claude E. (University of California, La Jolla) and Andre B. Cobet. Growth, reproduction, and death rates of Escherichia coli at increased hydrostatic pressures. J. Bacteriol. 84:1228-1236. 1962.-Pressures ranging from 100 to 500 atm were found to retard the growth and reproduction of Escherichia coli in nutrient medium. Reproduction (as manifested by cell division or an increase in the number of viable cells) was retarded more than was growth (as manifested by increase in cell size or the formation of biomass). When incubated near the threshold of pressure tolerance (about 475 atm at 30 C), some cells of E. coli grew into long slender filaments showing little evidence of fission or cell division. Compression prolonged the lag phase of E. coli in nutrient medium, particularly at pressures higher than 400 atm. The inhibiting effects of pressure on reproduction and growth were found to be less at 30 than at 20 or 40 C. Pressures of 400 to 1,000 atm accelerated the death rate of E. coli cultures in nutrient medium. The lethal effects of pressure were greater at 40 than at 30 C and greater at 30 than at 20 C.

Comparison of oxygen tensions in normal tissues and Yoshida sarcoma of the rat breathing air or oxygen at 4 atmospheres

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OXYGEN INHIBITION OF GROWTH OF MYCOBACTERIUM TUBERCULOSIS

Gottlieb, S. F. (Linde Division, Union Carbide Corporation, Tonawanda, N.Y.), Noel R. Rose, Jerome Maurizi, and Edward H. Lanphier. Oxygen inhibition of growth of Mycobacterium tuberculosis. J. Bacteriol. 87:838-843. 1964.-Continuous or intermittent exposure to 3 atm of oxygen in the presence or absence of 40 mm of Hg CO(2) resulted in marked delay or inhibition of growth of Mycobacterium tuberculosis. This inhibition was more pronounced with newly inoculated cultures, as compared to young, actively growing cultures. Oxygen inhibition of growth was observed on both Lowenstein-Jensen and blood agar media. Bacteriostatic effects of oxygen are a direct function of exposure time. A more marked effect of oxygen was observed in the presence of isoniazid, streptomycin, or p-aminosalicyclic acid.

IN VIVO BLOOD VISCOSITY AND HINDRANCE

This paper presents an in vivo method for measuring peripheral resistance and differentiating between the role of blood viscosity and hindrance. A vascular bed was connected to a pressure generator and recording system. At rest the vascular bed was perfused by the animal, but during the short duration of an experimental run the perfusing pressure was supplied solely by the pressure generator. The apparatus was constructed so that the flow rate was proportional to the rate of change of pressure. The shape of a portion of the curve of pressure versus time is determined solely by total resistance in the vascular bed. Total resistance is a function of hindrance and blood viscosity, and therefore a change in either of these produces a change in the shape of the pressure versus time curves. Since the change in shape produced by a change in viscosity differs from that produced by a change in hindrance, it is possible to differentiate between these two factors.

AN ISOTHERMAL SYSTEM FOR MANOMETRIC MEASUREMENT OF CHANGES OF VOLUME

The volume of gas to be measured is displaced into a reservoir which is so constructed that its contents undergo nearly perfect isothermal compression, raising the pressure by up to 1 mm Hg relative to the pressure in an identical compensating reservoir. The conditions of compression ensure a stable calibration over a wide range of rates of gas displacement, and the use of a compensating reservoir makes the system quite independent of fluctuations in barometric pressure, and largely independent of fluctuations in ambient temperature.

volume recorder; air displacement recorder; barometric measurement of volume

Submitted on December 9, 1963

MECHANISM OF DECREASE IN CARDIAC OUTPUT CAUSED BY OPENING THE CHEST

The cardiac output in ten dogs fell an average of 18.8% (±1.1 sem) when the chest was opened. Opening the chest, which increased the extracardiac pressure, shifted the cardiopulmonary-function curve (relating right atrial pressure to cardiac output) toward higher atrial pressure levels. This caused the cardiopulmonary curve to equate with the animal's systemic-function curve at a lower cardiac output; the greater the extracardiac pressure the lower the output. Thus, changes in extracardiac pressure can alter cardiac output even though the pumping ability of the heart is not altered.

HYPERBARIC EXPOSURE OF MICE TO PRESSURES OF 60 TO 90 ATMOSPHERES

Albino mice breathing helium-oxygen mixtures remained in good condition for periods of 1 to 13 hours at pressure-equivalent depths of 396 to 914 meters of sea water. They were successfully decompressed to normal atmospheric pressure in less than 5 hours. There were no immediate or delayed adverse effects that could be attributed to the hyperbaric helium-oxygen environment. An occasional death was attributable to hypoxia or the decompression procedure.