Pietro Palatini

A Comparison Between Different Methods for the Determination of Reduced and Oxidized Glutathione in Mammalian Tissues

In this study, three rapid assay techniques for the determination of glutathione, one enzymatic, one fluorometric and one newly patented colorimetric method, were compared by measuring reduced (GSH) and oxidized (GSSG) glutathione in guinea-pig heart and liver. The HPLC technique was used as a standard, since it is considered the most reliable assay method. In heart, all methods measured the same levels of GSH (about 1 mumole/g wet tissue), whereas in liver the fluorometric assay gave GSH levels about half as high as those measured by the other methods (about 3 vs. 7 mumoles/g wet tissue). Conversely, the fluorometric assay grossly overestimated GSSG concentration (by 5 to 8 times) in both heart and liver. These results confirm previous doubts about the use of the fluorometric technique for GSSG determination in mammalian tissues and also raise some questions about its use for the measurement of GSH in liver. In this tissue, the GSH concentration determined by the fluorometric method was shown to be inversely correlated with the size of the sample, suggesting the presence of some quenching material.

Cytochrome P450 1A2 is a major determinant of lidocaine metabolism in vivo: Effects of liver function

This study was designed (1) to evaluate the effect of a cytochrome P450 (CYP) 1A2 inhibitor, fluvoxamine, on the pharmacokinetics of intravenous lidocaine and its 2 pharmacologically active metabolites, monoethylglycinexylidide (MEGX) and glycinexylidide (GX), to confirm recent in vitro results indicating that CYP1A2 is the main isoform responsible for lidocaine biotransformation and (2) to assess whether liver function has any influence on the fluvoxamine‐lidocaine interaction.

Hyperthermic intraoperative intraperitoneal chemotherapy with cisplatin and doxorubicin in patients who undergo cytoreductive surgery for peritoneal carcinomatosis and sarcomatosis - Phase I study

Hyperthermic intraperitoneal intraoperative chemotherapy (HIIC) combined with cytoreductive surgery (CS) has been proposed as a new multimodal treatment mainly for carcinomatosis of gastrointestinal origin. To evaluate whether this regimen could be used for other tumor types, the authors conducted a Phase I study on HIIC with doxorubicin and cisplatin in patients with peritoneal carcinomatosis or sarcomatosis.

Activation of (Na+ + K+)-dependent ATPase by lipid vesicles of negative phospholipids.

1. Kidney (Na+ + K+)-stimulated ATPase was depleted of phospholipids by extraction with lubrol and inserted in lipid structures of known composition. Both ouabain-sensitive ATPase and phosphatase reactions could be partially restored by lipid replacement. 2. Lipid vesicles of natural and synthetic negative phospholipids proved to be effective. The low activity of uncharged liposomes was increased when negative charges were included into the bilayer structure. 3. Reactivation by negative phospholipids was accompanied by spontaneous re-assembly of a stable lipid-protein complex. By contrast, the interaction of lipid deficient ATPase complex with uncharged lamellae was possible only after sonication of lipid-protein suspension. Reactivation did not ensue. 4. The ouabain-sensitive ATPase reactivated by synthetic dioleoylphosphatidylglycerol yielded curvilinear Arrhenius plots. The same pattern was seen with the original undepleted microsomal preparation. A discontinuity close to the temperature of fluid-order transition was found with dimyristoyl phosphatidylglycerol. 5. It is concluded that reassembly of lipid-deficient (Na+ + K+)-stimulated ATPase requires the addition of diacylphospholipids with fluid acyl-chains and negatively charged polar heads able to assemble in an expanded lamellar configuration.

Needle and Trocar Injuries in Diagnostic Laparoscopy under Local Anesthesia: What Is the True Incidence of These Complications?

Laparoscopy is a relatively safe invasive procedure, but complications can occur, mainly related to Veress needle and trocar insertion. The rate of these complications is generally reported to be low, but the true incidence may be higher because of underreporting. We retrospectively studied the records of 2650 consecutive diagnostic laparoscopies performed by the same operator with the aim of assessing the true incidence and nature of these complications. Major complications occurred in 0.41% of cases and included bladder injury, bowel perforation, hemoperitoneum, and abdominal wall hematoma. Minor complications, including omental and subcutaneous emphysema, occurred in 1.58% of cases. Some of these resolved spontaneously, whereas others required surgical or medical treatment. We believe that all laparoscopic complications should be reported to a registry so that their potential risk can be quantified. Simply reporting complications as major or minor on the basis of the follow-up does not allow laparoscopists to understand their true incidence completely.

Differential effect of chronic renal failure on the pharmacokinetics of lidocaine in patients receiving and not receiving hemodialysis

The effect of chronic renal failure (CRF) on the pharmacokinetics of lidocaine, a drug cleared almost exclusively by hepatic metabolism, has thus far only been evaluated in patients undergoing regular hemodialysis. This study had 2 objectives: (1) to investigate the effect of CRF on the pharmacokinetics of lidocaine in both patients undergoing hemodialysis and patients not undergoing hemodialysis and (2) to test the effects of plasma from the patients examined and of lidocaine metabolites possibly accumulated in vivo on lidocaine biotransformation in vitro.

Pharmacokinetics of intraperitoneal cisplatin and doxorubicin

Intraperitoneal chemotherapy, mainly when performed during HIIC after cytoreductive surgery, is considered potentially curative for the treatment of solid tumors with spread to the peritoneal surface. When selecting antiblastic agents to be administered intraperitoneally, it is important to bear in mind that a low lipophility and a high molecular weight are the ideal drug characteristics. Drugs with these features allow a favorable ratio to be achieved between peritoneal and plasma concentrations, due to the reduced tendency to diffuse through the plasma-peritoneal barrier, even after extensive removal of the peritoneum. Moreover, a low rate of diffusion through the tumor capillaries implies a low rate of drug clearance, with a higher intratumoral drug accumulation. Among the drugs used so far for intraperitoneal chemotherapy, the combination of CDDP and DXR appears to be one of the most effective available regimens with acceptable local-regional toxicity. CDDP has also been extensively employed as a single agent for ovarian and gastrointestinal cancers, under both normal and hyperthermic conditions, while intraperitoneally administered DXR appears to be of greater potential efficacy when associated with CDDP and hyperthermia (41.5 degrees C) following cytoreductive surgery. In our clinical experience with this drug combination, DXR showed a much more advantageous plasma/peritoneal AUC ratio than CDDP (162 +/- 113 and 20 +/- 6, respectively). On the other hand, it has been demonstrated that very high intraperitoneal concentrations of CDDP can be achieved without incurring significant systemic toxicity by using intravenous injection of sodium thiosulphate during HIIC. Penetration of the tumor mass by CDDP is greater than DXR. This phenomenon is enhanced by hyperthermia and by hypotonic solutions of sodium chloride used as the perfusate. Following experimental and clinical results of TNF alpha-based isolated limb perfusion for locally advanced soft tissue sarcoma or melanoma, greater efforts are being made to exploit the potential effect of this cytokine used in association with hyperthermia and other drugs (i.e., CDDP and DXR) suitable for intraperitoneal infusion/perfusion. However, it is not yet clear whether the observed effect of TNF alpha on the peritoneal-plasma barrier, which seems to favor the passage of both drugs into the systemic circulation, is overcome by the positive effect of this agent on drug penetration into tumor. Further pharmacologic studies should be undertaken to clarify whether or not these interactions will be of benefit to the patient. Likewise, liposomes, which in animal models seem to favor tumor uptake of encapsulated DXR, should now be tested in the clinical setting.

Reversal by phospholipids of the oligomycin induced inhibition of membrane associated adenosintriphosphatases

Abstract The inhibitory effect of oligomycin on sodium, potassium-stimulated ATPase and on mitochondrial ATPase was removed by the addition of purified phospholipids to the incubation medium. Ouabain effect was not modified. Phospholipids with isoelectric ionic portion (particularly lecithins) were found more active than phosphatidylethanolamines and bovine brain phosphatidylserine. Differences in the activity of lecithins from various sources were also seen. This indicates that the composition of hydrophobic fatty acid chains influences the reversal of oligomycin effect. The antagonism by the external added phospholipids may reflect the affinity of oligomycin with the phospholipids of the enzyme preparation.

Reactivation of a phospholipid-depleted sodium, potassium-stimulated ATPase

Abstract 1. 1. The effect of phospholipids on (Na + -K + )-ATPase was studied in a particulate preparation from bovine heart. 2. 2. After treatment with ultrasonic oscillations the complex became partially soluble in a solution of nonionic detergent lubrol. Fractionation of “solubilized” ATPase with (NH 4 ) 2 SO 4 , followed by washing in NaCl solutions, resulted in a preparation depleted of phospholipids as well as cholesterol and largely devoid of ATPase activity. 3. 3. Total phospholipids from various sources as well as individual purified phospholipids restored the ATPase activity which was 90% inhibited by ouabain. Reconstruction was accompanied by reuptake of lost phospholipids. Differences among phospholipids were recorded: phosphatidylserine and disphosphatidylglycerol were the most effective but active preparations were also obtained with phosphatidylcholine and phosphatidylethanolamine. Cholesterol added as aqueous emulsion was ineffective. 4. 4. It is concluded that activation of (Na + -K + )-ATPase by phospholipids is a rather aspecific process. Although phosphatidylserine shows remarkable affinity for the enzyme complex and presumably plays an important role in maintaining the activity of the ATPase, it can not be considered as a specific activator. In agreement with recent observations on particulate mitochondrial ATPase from rat liver, acidic phospholipids showed greater effectiveness in the reactivation of transport ATPase and could be bound better.

Irreversible CYP3A inhibition accompanied by plasma protein-binding displacement: a comparative analysis in subjects with normal and impaired liver function.

In this study, quinine was used as a probe substrate and erythromycin as a prototypical irreversible inhibitor of CYP3A to ascertain whether, like reversible CYP inhibition, the magnitude of irreversible inhibition is also strictly dependent on the status of liver function. The effect of erythromycin on oral quinine disposition was studied in 10 healthy subjects and in 20 patients with cirrhosis of the liver who had varying degrees of liver dysfunction. This effect was shown to be the result of two types of interaction: (i) irreversible inhibition of CYP3A‐mediated quinine metabolism, the extent of which proved to be independent of liver function, and (ii) displacement of quinine from plasma protein–binding sites, the magnitude of the displacement increasing dramatically as liver function worsened. Such an interaction causes limited increases in the total concentration of the displaced drug but disproportionate increases in its free concentration; the latter increases are magnified by liver dysfunction, thereby requiring that the monitoring of free drug concentrations be made mandatory.