[Complete dentures. Theoretic principles for "functional vacuum" system].

The hydrolytic activity of lambda exonuclease, a highly processive enzyme, is inhibited by high pressure. When assayed at 67 MPa, the activity is 87% of the atmospheric rate; increasing the pressure to 336 MPa causes a greater than 99% inhibition of the enzyme activity. Decreasing the pressure from 336 MPa to 67 MPa at 20 degrees C reverses the inhibition. The use of hydrostatic pressure to control the activity of lambda exonuclease has potential practical application in DNA sample preparation, analysis, and sequencing.

Atmospheric Pressure↗

PubMed1997

Insensitivity of VO2max to hemoglobin-P50 as sea level and altitude.

O2 uptake in the lungs, and therefore arterial oxygenation, is favored by a low Hb-P50 but this inhibits tissue O2 extraction, raising the question of optimal P50 during maximal exercise when VO2 is limited by O2 supply. Using a model of the lungs and muscles connected by the circulation so that O2 transport is simultaneously considered in both sites, sensitivity of VO2max to P50 was determined at three altitudes: PB = 760, 464 and 253 Torr, encompassing sea level and Mt. Everest. At Pb = 760 Torr, VO2max peaked at P50 = 30 Torr, was 99.4% (of that at 30) at normal P50 (26.8) and exceeded 95% (of that at P50 = 30) over the P50 range from 24 to 43 Torr. Optimal P50 at PB = 464 Torr was 25 Torr, VO2max at P50 = 26.8 was reduced only 0.1% and exceeded 95% over the P50 range from 19 to 41 Torr. At Pb = 253, optimal P50 was 20 Torr, VO2max at P50 = 26.8 was reduced only 0.4% and exceeded 95% over the wide P50 range from 15 to 47 Torr. While this analysis shows that technically, optimal P50 falls with altitude, VO2max is insensitive to P50 over a range that widens with altitude, so that P50 changes over a realistic interval would not measurably affect VO2max.

Atmospheric Pressure↗

PubMed1997

Vacuum-assisted closure: a new method for wound control and treatment: clinical experience.

Despite numerous advances, chronic and other difficult-to-manage wounds continue to be a treatment challenge. Presented is a new subatmospheric pressure technique: vacuum-assisted closure (The V.A.C.). The V.A.C. technique entails placing an open-cell foam dressing into the wound cavity and applying a controlled subatmospheric pressure (125 mmHg below ambient pressure). Three hundred wounds were treated: 175 chronic wounds, 94 subacute wounds, and 31 acute wounds. Two hundred ninety-six wounds responded favorably to subatmospheric pressure treatment, with an increased rate of granulation tissue formation. Wounds were treated until completely closed, were covered with a split-thickness skin graft, or a flap was rotated into the health, granulating would bed. The technique removes chronic edema, leading to increased localized blood flow, and the applied forces result in the enhanced formation of granulation tissue. Vacuum-assisted closure is an extremely efficacious modality for treating chronic and difficult wounds.

Atmospheric Pressure↗