Biomedical subjects
Publications and source records attributed to A Bali.
Replacement of the C-2 ester group in phosphatidylcholine by the carbamyloxy function rendered its liposomes completely stable and longer living in the circulation of rats.
The effect of premedication with an oral antacid (magnesium trisilicate), oral cimetidine or a combination of both was studied in 80 patients undergoing elective Caesarean section. Twenty patients served as untreated controls. Seventy per cent of the patients were in the high risk range for acid aspiration pneumonitis (pH less than 2.5 plus gastric content volume greater than 25 ml). Antacid therapy was effective in raising pH but the gastric volume remained high in 50 per cent of the patients. Cimetidine was effective in decreasing gastric volume and raising pH but the pH was still less than 2.5 in two patients. None of the patients given the cimetidine-antacid combination were in the high risk range for acid aspiration pneumonitis. The combination of an oral dose of cimetidine 400 mg, three to four hours before the operation followed by 20 ml of magnesium trisilicate one hour preoperatively proved to be the most efficacious regimen for prophylaxsis against Mendelson's syndrome in elective Caesarean section. Recent reports have suggested that non-particulate antacids (e.g., sodium citrate) may be preferable to particulate antacids such as magnesium trisilicate.
The effects of continuous lumbar epidural analgesia for normal labour were studied in 28 women with pre-eclampsia and in 15 normal women who served as control. Maternal hemodynamics, acid-base and blood gas findings were examined. Newborn infants were assessed by Apgar Scores together with umbilical vein and artery blood gas and acid-base values. Mild significant reduction in maternal mean arterial blood pressure occurred in the pre-eclamptic patients which was corrected easily by intravenous crystalloid infusion. Maternal and newborn acid-base and blood gas findings showed no significant changes between the pre-eclamptic and control groups. Apgar Scores in both groups were good. The study indicates that continuous epidural analgesia is a useful form of therapy in the management of normal labour in women with pre-eclampsia.
The phase behavior of the sphingolipid analogue 1-palmitoyl-2-tridecanylcarbamyloxy-sn-glycero-3-phosphocholine (CM-PC) has been studied by differential scanning calorimetry. When CM-PC is cooled at rates greater than 5 K/min, subsequent heating runs exhibit metastable behavior: a low enthalpy exotherm is observed at about 9 degrees C (delta H = -(1-2)kcal/mol), followed by a high enthalpy endotherm at 38 degrees C (delta H = 13 kcal/mol). Systematic variation of cooling/heating protocols indicates that CM-PC exhibits two low temperature states, one metastable and the other stable. Cooling from the liquid crystalline state results in formation of the metastable low-temperature polymorph I, which must transform into the stable low-temperature polymorph II before the liquid crystalline state can be reached again. This metastable thermal behavior is virtually identical to that recently reported for synthetic palmitoyl cerebroside (Ruocco, M.J., Atkinson, D., Small, D.M., Skarjune, R.P., Oldfield, E. and Shipley, G.G. (1981) Biochemistry 20, 5957-5966) and for bovine brain n-acylcerebrosides (Curatolo, W. (1982) Biochemistry, 21, 1761-1764). The observation of the metastable phase behavior of CM-PC indicates that the sphingosine backbone is not a prerequisite for such metastable behavior. Furthermore, the carbamyl group in CM-PC is reversed in orientation compared with the amide of sphingolipids (-NH-CO- vs. -CO-NH-), suggesting that the intermolecular hydrogen bonding potential, rather than some highly specific steric or conformational constraint, is responsible for the observed metastability of sphingolipids.
Previous studies have revealed that the replacement of the C-2 ester group in phosphatidylcholine by the carbamyloxy function renders the resulting lipids, without affecting the properties of the liposomes, resistant to hydrolysis by phospholipase A2 (Gupta, C.M. Bali, A. (1981) Biochim. Biophys, Acta 663, 506-515). As an extension of this work, the effect of serum on the stability of liposomes, prepared from 1-palmitoyl-2-heptadec-10-cis-enylcarbamyloxyphosphatidylcholine (carbamylphosphatidylcholine), has been examined. The stability has been measured in terms of (a) bilayer permeability to solutes, and (b) the lipid transfer to serum proteins. Replacement of egg phosphatidylcholine in liposomes by the carbamyl analog prevented serum-induced leakage of the entrapped solutes and also inhibited the lipid (phospholipid and cholesterol) transfer. Manipulation of the cholesterol content of the liposomes had no effect on the stability. These observations indicate that the interaction of serum proteins with liposomes probably involves a highly specific binding of the proteins to the liposome surface.
A novel class of phospholipase-resisting phosphatidylcholine analogs, in which the C-2 ester group or both C-1 and C-2 ester groups have been replaced by carbomyloxy functions (Formula--see text), have been synthesized. These lipids were not degraded by phospholipase A2, while complete hydrolysis occurred with phospholipase C. Ultrasonic irradiation of the aqueous dispersions of the phospholipids in the presence as well as in the absence of cholesterol resulted in the formation of closed bilayer structures as evidenced by negative staining electron microscopy and also by their ability to entrap [14C]glucose. The leakage rates of glucose at 37 degrees C from liposomes of these compounds have also been measured. Liposomes consisting of 1,2-dipentadecanylcarbamyloxy-sn-glycero-3-phosphorylcholine were found to be more leaky (2.1%/h) as compared to the liposomes of 1-palmitoyl-2-pentadecanylcarbamyloxy-sn-glycero-3-phosphorylcholine (0.5%/h). Moreover, inclusion of cholesterol (33 mol%) into the bilayers of the former phospholipid had no effect on the leakage rate (2.4%/h) while it effectively reduced permeability of the latter (0.22%/h). These phosphatidylcholines are useful for studying the possible role of phospholipases in the capture and lysis of liposomes in vivo.
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Systemic absorption of irrigating fluid during TUR prostatectomy under spinal anaesthesia was measured in 40 patients and correlations made under clinical, hemodynamic and laboratory observations. Results showed that the CVP monitoring is a helpful parameter in early detection of the hypervolemic hyponatremic syndrome. Serial determination of serum sodium level is important in detecting hyponatremia. Out of the 40 patients, one patient developed acute hypervolemic hyponatremic syndrome. The syndrome was detected early by the significant rise in CVP and the drop in serum sodium level and P.C.V. Intravenous infusion of 250 ml hypertonic saline slowly was followed by marked diuresis and uneventful recovery.