Protein purification with vapor-phase carbon dioxide.

Gaseous CO2 was used as an antisolvent to induce the fractional precipitation of alkaline phosphatase, insulin, lysozyme, ribonuclease, trypsin, and their mixtures from dimethylsulfoxide (DMSO). Compressed CO2 was added continuously and isothermally to stationary DMSO solutions (gaseous antisolvent, GAS). Dissolution of CO2 was accompanied by a pronounced, pressure-dependent volumetric expansion of DMSO and a consequent reduction in solvent strength of DMSO towards dissolved proteins. View cell experiments were conducted to determine the pressures at which various proteins precipitate from DMSO. The solubility of each protein in CO2-expanded DMSO was different, illustrating the potential to separate and purify proteins using gaseous antisolvents. Polyacrylamide gel electrophoresis in sodium dodecyl sulfate (SDS-PAGE) was used to quantify the separation of lysozyme from ribonuclease, alkaline phosphatase from insulin, and trypsin from catalase. Lysozyme biological activity assays were also performed to determine the composition of precipitates from DMSO initially containing lysozyme and ribonuclease. SDS-PAGE characterizations suggest that the composition and purity of solid-phase precipitated from a solution containing multiple proteins may be accurately controlled through the antisolvent's pressure. Insulin, lysozyme, ribonuclease, and trypsin precipitates recovered substantial amounts of biological activity upon redissolution in aqueous media. Alkaline phosphatase, however, was irreversibly denaturated. Vapor-phase antisolvents, which are easily separated and recovered from proteins and liquid solvents upon depressurization, appear to be a reliable and effective means of selectively precipitating proteins.

Intra-anesthetic awareness.

Awareness during anesthesia is as old as anesthesia itself. Using muscle relaxing drugs, operations can be done on a relaxed but fully aware patient. The problem of intra-anesthetic awareness still exists despite the advances in anesthetic drugs and monitoring. This article reviews the subject from some aspects including its causes, signs, tests and medico-legal points. Awareness during anesthesia can be looked at as 'the invisible scars of surgery.'

Use of low-dose neostigmine intravenously in the treatment of supraventricular tachycardia: an immediate bradycardic effect.

Neostigmine was first used 50 years ago to treat sinus tachycardia and paroxysmal auricular tachycardia. Then there were reports of successful treatment by neostigmine of other forms of supraventricular tachycardias. However, reports of sudden death using neostigmine for reversal of neuromuscular blockade at the end of an operation, which were not properly treated with atropine abandoned the use of neostigmine as an antiarrhythmic drug. Low-dose neostigmine intravenously was used in the treatment of supraventricular tachycardia in three patients described herein. It gave an immediate bradycardic effect in all three patients. The use of a low-dose neostigmine intravenously for an immediate treatment of supraventricular tachycardia is a novel suggestion. It has to be further evaluated and compared to the conventional drugs used like digoxin, verapamil, propranolol or esmolol.

Open chest cardiac massage: a review.

Open-chest cardiopulmonary resuscitation (CPR) is physiologically superior to all external CPR methods studied thus far (P. Safer, Ann. Emerg. Med., 13 (1984) 856). Open-chest CPR should again be taught to physicians, and used more often after prolonged cardiac arrest. An extensive review on open cardiac massage is presented herein.

Neostigmine reversal of D-tubocurarine and pancuronium bromide combinations in man.

This study measured the neostigmine reversal of a non-depolarizing block in 17 patients, each given d-tubocurarine and pancuronium bromide in an alternating sequence. Reversal times were similar to those previously reported for pancuronium bromide alone. It is concluded that the anaesthetist may alternate between d-tubocurarine and pancuronium bromide without fear of difficulty with neostigmine reversal.

A new method for measuring PCO2 during anaesthesia.

We have evaluated a new method for measuring the oxygenated mixed venous PCO2 (PVCO2) in patients undergoing general anaesthesia. The lungs were inflated with a gas mixture containing 0% carbon dioxide and then 12% carbon dioxide and the expired gas was analysed both before and after a brief period of breath-holding. PVCO2 was estimated from the differences in carbon dioxide concentration before and after the apnoeic period. Simultaneous measurments of PaCO2 were made in blood obtained from radial artery puncture. The range of PaCO2 studied was 3.2--6.13 kPa. The relationship between mixed venous and arterial PCO2 was found to be PaCO2 = 0.87 PVCO2--0.44 (r = 0.91). We conclude that this method for measuring PVCO2 can be used during anaesthesia allowing PaCO2 to be estimated with considerable accuracy.

The linear relation of cerebral blood flow to arterial oxygen saturation in hypoxic hypoxia induced with nitrous oxide or nitrogen.

This study has demonstrated a linear relationship between cerebral blood flow and arterial oxygen saturation (Sao2) in the cerebral blood flow response in the hypoxic range of Pao2 values, which we believe is documented for the first time. The cerebral blood flow increased 1.02 per cent for each percentage decrease in Sao2 in hypoxia induced with nitrogen. Hypoxia induced with nitrous oxide increased cerebral blood flow at the rate of 2.09 per cent for each one per cent decrease in Sao2 which was dramatically more than the increase associated with hypoxia induced with nitrogen. Increased survival rates at lower Sao2 levels suggested that nitrous oxide also exerts a protective effect on dog myocardium. The mechanism by which hypoxia increases cerebral blood flow is unclear but the prevalent theory is one of neurogenic control which causes cerebral blood flow to increase as the intracellular hydrogen ion ([H+]I) increases in the progressive lactacidosis of hypoxia. The demonstration of a linear relationship between cerebral blood flow and Sao2 will provide the statistician, the researcher and the clinician with a useful tool for the neurophysiological assessment of cerebral blood flow.

A noninvasive method for measuring the PCO2 of mixed venous blood.

A breath-holding method for measuring the PCO2 of mixed venous blood has been developed. Two gas mixtures, 100 per cent O2 and 12 per cent CO2 in O2, were inspired, and the expired gas was analyzed after 5 and 15 sec of breathholding. The oxygenated mixed venous PCO2 was calculated using an exponential equation. The method was applied in healthy subjects, patients with lung disease, and unconscious mechanically ventilated patients. The mixed venous PCO2 correlated well with arterial PCO2 (r = 0.96), the PCO2 obtained by rebreathing (r = 0.97), and the PCO2 in blood drawn from the pulmonary artery (r = 0.97). The method is noninvasive, has a low coefficient of variance, and allows arterial PCO2 to be estimated by multiplying the breath-holding mixed venous PCO2 by 0.8.