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Biomedical subjects

W S Liu

Publications and source records attributed to W S Liu.

At least 55 records · Page 3Linked to original sources
PubMed1982

Epinephrine-induced arrhythmias during halothane anesthesia with the addition of nitrous oxide, nitrogen, or helium in dogs.

The arrhythmogenicity of epinephrine was examined in 34 male mongrel dogs awake and during 1.1 MAC steady state halothane-O2 anesthesia with the addition of 50% N2O, nitrogen, or helium. All anesthetized dogs required more epinephrine than did awake dogs to produce ventricular extrasystoles. Dogs given halothane-N2O were more sensitive to the epinephrine infusion than those given halothane-nitrogen or halothane-helium. The dogs given halothane-N2O also showed a small, but statistically significant difference from dogs given halothane-O2. These results suggest that the addition of N2O to halothane increases the cardiac arrhythmic potential of epinephrine in the dog.

Animals↗
PubMed1981

Biological activity of aspartic proteinase inhibitors related to pepstatin.

We have synthesized eight tripeptide analogs of pepstatin in which both the side-chain and stereochemistry of the novel amino acid statine have been altered. They have been compared to pepstatin for inhibition of pepsin and cathepsin D activity, inhibition of autolysis at pH 4, and inhibition of protein degradation in cultured cells. Effective inhibition of aspartic proteinase activity appears to require the novel amino acid to have a bulky hydrophobic side-chain and the S-configuration at both chiral centers. However, the Cbz-Val-Val-(3S4S)-statine peptide was more effective than pepstatin in cultured cells, and inhibition was also achieved, and in some cases enhanced relative to pepstatin, by its stereoisomers and by tripeptides containing valyl and alanyl analogs of statine.

Amino Acids↗
PubMed1981

Hemodynamic effects of butorphanol-oxygen anesthesia in dogs.

The cardiovascular effects of two intravenous rates of butorphanol infusion (0.1 and 0.2 mg/kg/min) were measured in 32 dogs breathing oxygen and nitrous oxide in oxygen. Sixteen dogs were premedicated with atropine and the other 16 were unpremedicated. Of the dogs receiving the higher dose infusion rate, 25% moved with a tail-clamp stimulus whereas 75% moved with the lower doses. Butorphanol produced significant but similar cardiovascular depression with the two rates of infusion irrespective of the presence or absence of atropine medication. Addition of nitrous oxide resulted in further cardiac depression in all groups studied. The data suggest that butorphanol is not an attractive alternative to morphine or fentanyl as a narcotic anesthetic.

Animals↗
PubMed1980

Comparison of haemodynamic effects of anaesthetic doses of alphaprodine and sulfentanil in the dog.

The haemodynamic effects of equi-anaesthetic doses of alphaprodine and sulfentanil were evaluated in mongrel dogs ventilated mechanically. The effects of the addition of atropine were assessed for each drug, as were the effects of breathing nitrous oxide 60 per cent with oxygen and nitrogen 60 per cent with oxygen and the administration of naloxone. The results of this study demonstrate that anaesthetic doses of sulfentanil produce little change in cardiovascular dynamics in atropinized dogs and only small changes in dogs without atropine premedication, irrespective of the infusion rate. In contrast alphaprodine causes a significant cardiovascular depression irrespective of the presence or absence of atropine premedication. Naloxone reversed the anaesthetic effects in all dogs anaesthetized with alphaprodine but did not reverse the anaesthetic state in any dog given sulfentanil. Our data suggest that sulfentanil deserves evaluation as a narcotic anaesthetic in man.

Alphaprodine↗
PubMed1980

Cardiovascular responses to nitrous oxide exposure for two hours in man.

Cardiovascular responses to increasing (20, 40, and 60%) concentrations of nitrous oxide or nitrogen in oxygen for 15 minutes as well as responses to 2 hours of exposure to 60% nitrous oxide or nitrogen in oxygen were determined and compared in 30 healthy, supine, untrained volunteers who received no other drugs or medications. No concentration of nitrogen produced a significant change in any cardiovascular variable measured, nor did 20 and 40% N2O. Sixty percent nitrous oxide for 15 minutes significantly increased PaCO2, heart rate, stroke volume, cardiac output, mean arterial blood pressure, and central venous pressure. Inhalation of 60% nitrogen also produced no significant change in any cardiovascular variable. In contrast, inhalation of nitrous oxide for 2 hours transiently increased arterial blood pressure (at 15 minutes), heart rate (at 15 and 30 minutes), stroke volume (at 15, 30, and 45 minutes) and decreased systemic vascular resistance (at 15 minutes). Cardiac output significantly increased for the 1st hour of exposure to 60% nitrous oxide but returned to values similar to control (room air) during the 2nd hour. Prolonged inhalation of nitrous oxide resulted in a constant increase in PaCO2 and progressive but mild decreases in arterial pH and calculated base deficit but no change in dead space/tidal volume ratios. These findings demonstrate that nitrous oxide stimulates the cardiovascular system in supine, healthy, untrained volunteers but that the stimulation is transient. The data suggest that early stimulation of the cardiovascular system during nitrous oxide breathing may be related to central nervous system excitation secondary to incomplete anesthesia and/or an increase in PaCO2.

Adult↗
PubMed1979

Synthesis of all the stereoisomers of statine (4-amino-3-hydroxy-6-methylheptanoic acid). Inhibition of pepsin activity by N-carbobenzoxy-L-valyl-L-valyl-statine derived from the four stereoisomers.

Synthesis of all four stereoisomers of the novel amino acid statine, 4-amino-3-hydroxy-6-methylheptanoic acid, found in pepstatin, a potent acid protease inhibitor, has been accomplished. Carbobenzoxy-L-valyl-L-valyl-statine tripeptides derived from all four stereoisomers have been prepared and their effect on pepsin activity is compared to that of pepstatin.

Amino Acids↗