Effect of the antiarrhythmic drug procainamide on the toxicity and antitumor activity of cis-diamminedichloroplatinum(II)

The class I antiarrhythmic drug procainamide (Pd) was tested on BDF1 mice for its chemoprotective activity against cis-diamminedichloroplatinum(II) (DDP) toxicity. Pd at the dose of 50 mg/kg protected mice against otherwise lethal doses of DDP (survivors at Day 14 after 25 mg/kg DDP or 25 mg/kg DDP-Pd treatment: 0% vs 100%) and greatly reduced the weight loss induced by DDP. Moreover, the increased plasma urea nitrogen levels caused by a single ip administration of DDP in water (8 or 16 mg/kg) as well as the tubular degenerative changes detected by light microscopy were prevented by Pd. Pd had no effect on the sensitivity of P388 leukemic cells to DDP in vitro, but the administration of DDP (16 mg/kg) and Pd (50 mg/kg) to BDF1 mice bearing P388 leukemic cells produced a significant increase in survivals compared to mice receiving ip DDP alone diluted in 0.9% NaCl solution. The increased efficacy of this combination therapy in P388 leukemic mice compared to a single DDP treatment at the same dose was observed both when the drugs were administered ip simultaneously (p = 0.042) and when DDP and Pd were given ip and iv, respectively (p = 0.018). Since procaine, which differs from Pd merely in the replacement of the amide by the ester linkage, has also been reported to significantly enhance DDP efficacy (M. Esposito et al., 1990, J. Natl. Cancer Inst. 82, 677-684.), a comparison of their effects in tumored mice exposed to DDP has been made. Although both drug combinations were superior to that of DDP alone, in terms of both survival time and numbers of cures, Pd treatment seems to offer better protection against DDP-induced lethality than did procaine.

Patterns in ionizable side chain interactions in protein structures

In a selected set of 44 high-resolution, non-homologous protein structures, the intramolecular hydrogen bonds or salt bridges formed by ionizable amino acid side chains were identified and analyzed. The analysis was based on the investigation of several properties of the involved residues such as their solvent exposure, their belonging to a certain secondary structural element, and their position relative to the N- and C-termini of their respective structural element. It was observed that two-thirds of the interactions made by basic or acidic side chains are hydrogen bonds to polar uncharged groups. In particular, the majority (78%) of the hydrogen bonds between ionizable side chains and main chain polar groups (sch:mch bonds) involved at least one buried atom, and in 42% of the cases both interacting atoms were buried. In alpha-helices, the sch:mch bonds observed in the proximity of the C- and N-termini show a clear preference for acidic and basic side chains, respectively. This appears to be due to the partial charges of peptide group atoms at the termini of alpha-helices, which establish energetically favorable electrostatic interactions with side chain carrying opposite charge, at distances even greater than 4.5 angstrom. The sch:mch interactions involving ionizable side chains that belong either to beta-strands or to the central part of alpha-helices are based almost exclusively on basic residues. This results from the presence of main chain carbonyl oxygen atoms in the protein core which have unsatisfied hydrogen bonding capabilities.

Effect of para-aminobenzoic acid on the pharmacokinetics and urinary excretion of cis-diamminedichloroplatinum(II) in rats

Para-aminobenzoic acid (PABA) has been previously reported as being an inhibitor of DDP toxicity, and its use did not result in any observable loss in antitumor activity of DDP. The following studies investigated the effect of PABA on the pharmacokinetics and urinary excretion of cis-diamminedichloroplatinum(II) (DDP) in male Sprague-Dawley rats. DDP was injected i.p. at the dose of 7.5 mg/kg in normal saline alone and with a concurrent i.p. injection of PABA (100 mg/kg). The combined treatment with PABA produced a significant increase in the plasma concentrations of total platinum, without affecting the levels of platinum species in the plasma ultrafiltrate. Similar results were also obtained in additional studies in rats receiving the same dose of DDP plus PABA through different routes of administration (i.e. DDP i.v. and PABA i.p.). Both the area under the total platinum plasma concentration-time curve (AUC) up to 60 min and AUC0-120 min were increased by PABA by an average of 113% and 66% respectively. The administration of PABA in rats was followed by a substantial reduction in total urinary excretion of platinum (P < 0.05) and by a significant (P < 0.01) lower concentration of DDP derived platinum in the urine collected during the first 4 h after treatment. The renal clearance of filterable platinum was reduced by PABA by an average of 67.5% from 1.11 to 0.36 ml/min/100 g body wt. Total 24-h urinary excretion of platinum was also decreased, although not significantly, by PABA. Urine volumes from rats treated with DDP+PABA were similar to those from animals receiving DDP alone. HPLC studies indicate that PABA reacts readily with the species generated from DDP in vitro, while the agent is essentially unreactive toward the parent DDP and does not influence its decomposition rate. The overall data of this study suggest that the protective effect exerted by PABA on DDP toxicity may be at least partially due to its ability to interact with aquated DDP as well as to alter the renal excretion of platinum.

Structural domains and conformational changes in nuclear chromatin: a quantitative thermodynamic approach by differential scanning calorimetry

A good deal of information on the thermodynamic properties of chromatin was derived in the last few years from optical melting experiments. The structural domains of the polynucleosomal chain, the linker, and the core particle denature as independent units. The differential scanning calorimetry profile of isolated chromatin is made up of three endotherms, at approximately 74, 90, and 107 degrees C, having an almost Gaussian shape. Previous work on this matter, however, was mainly concerned with the dependence of the transition enthalpy on external parameters, such as the ionic strength, or with the melting of nuclei from different sources. In this paper we report the structural assignment of the transitions of rat liver nuclei, observed at 58, 66, 75, 92, and 107 degrees C. They are representative of the quiescent state of the cell. The strategy adopted in this work builds on the method developed for the investigation of complex biological macromolecules. The heat absorption profile of the nucleus was related to the denaturation of isolated nuclear components; electron microscopy and electrophoretic techniques were used for their morphological and molecular characterization. The digestion of chromatin by endogenous nuclease mimics perfectly the decondensation of the higher order structure and represented the source of several misinterpretations. This point was carefully examined in order to define unambiguously the thermal profile of native nuclei. The low-temperature transitions, centered around 58 and 66 degrees C, arise from the melting of scaffolding structures and of the proteins associated with heterogeneous nuclear RNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Regional pharmacokinetic selectivity of intraperitoneal cisplatin in ovarian cancer

Five patients with intraabdominal ovarian cancer, 4 of whom with concomitant ascites, refractory to cisplatin-containing combination chemotherapy were treated with intraperitoneal cisplatin. Cisplatin, 90 mg/m2, was administered intraperitoneally in 2 liters of warm 0.9% NaCl with a 4-hour dwelling time on day 1 q 21 days. Platinum concentrations in plasma, ascites, ultrafiltrates of plasma and ascites, and urine were assayed by flameless atomic absorption spectrophotometry and determinations were verified by neutron activation analysis. Peak total and ultrafiltrable plasma platinum levels were 1.63 +/- 0.6 and 0.76 +/- 0.3 microgram/ml, respectively. Peritoneal clearance of total platinum (PA) was 21 ml/min whereas body clearance of total platinum was on the average 13.8 times PA, varying from 171 to 429 ml/min; the mean AUC (peritoneum) to AUC (plasma) ratio was 11 +/- 3. In 2 patients control of ascites was obtained, in 1 of these patients prior positive cytology became negative after her first intraperitoneal course. No nephrotoxicity was observed and gastrointestinal toxicity was mild. No catheter-related infections were observed. Intraperitoneal cisplatin therapy is well tolerated, pharmacokinetically rational and may be useful in managing ovarian cancer patients with malignant ascites or minimal residual disease at second-look laparotomy.

Models of fibronectin

The radius of gyration of human plasma fibronectin was determined by light scattering both under conditions in which the molecule is in an extended conformation (ionic strength 1.01 M, pH 8) and close to its native, more compact conformation (ionic strength 0.16 M, pH 8). These values were found to be 17.5 +/- 0.8 nm and 10.7 +/- 0.9 nm respectively, for a constant mol. wt of 533,000 +/- 8000, in excellent agreement with the value of 520,000 deduced from its known composition. A set of models, each made of two identical, end-to-end joined chains of 28 beads, was then constructed, and their calculated physico-chemical parameters were compared with those available for the whole fibronectin molecule and for some of its proteolytic fragments in both conformations. Two possible models for the circulating form are presented here: in both, the fibronectin molecule is in a compact, tangled conformation, with the amino-terminal end of one chain folded over to the carboxy end of itself or of the other chain either in a hairpin or in a circular fashion. With the exception of the carboxy-terminal fibrin(ogen)-binding domains, all the domains appear to be well exposed to the solvent, and thus free to interact with potential ligands.

Serum, urine and peritoneal fluid levels of 5-FU following intraperitoneal administration

Seven patients with advanced colon cancer, refractory to conventional chemotherapy, and malignant disease confined to the intra-abdominal space received a total of 24 consecutive courses of ip 5-Fluorouracil (5-FU). 5-FU 1000 mg was administered in 2 L of warm (37 degrees C) dialysate daily for five consecutive days every 28 days. 5-FU concentrations in serum, peritoneal fluid and urine were measured by high pressure liquid chromatography (HPLC). The mean disappearance half-life of 5-FU from the peritoneal fluid was 1.6 hours with a mean permeability area product (PA) of 22.4 ml/min. The mean peritoneal AUC was 450 +/- 165 times greater than the mean serum AUC. Ip 5-FU treatment is well tolerated, can be safely administered on an outpatient basis and produces a significant pharmacological advantage over conventional routes of administration.

Dyspepsia among young conscripts: correlations with psychoemotional state and eating habits

The prevalence of dyspepsia was evaluated in 83 young conscripted soldiers: 38 of them were normally resident in the town where the barracks was sited (Genoa) while 45 came from different districts. Dyspepsia was observed in 49.4% of total cases, and there were significant differences in the incidence between the two groups. In 40 out of 41 cases, dyspepsia was of the functional type. Psychoneurotic reactions were found in 69.8% of total cases and these reactions were closely correlated with the occurrence of dyspepsia both in soldiers who were local residents and those who were not. Dyspepsia could not however be correlated with eating habits, or with the consumption of alcohol, coffee or tobacco.

Cyclosporin A serum and blood levels in marrow graft recipients: correlation with administered dose, serum creatinine and graft-versus-host disease

23 patients undergoing marrow transplantation for leukemia or aplastic anemia were given cyclosporin A (CyA) for graft-versus-host disease (GvHD) prophylaxis. A radioimmunoassay was used to monitor CyA serum levels in 13 patients and whole blood levels in 10. Serum creatinine levels were recorded daily until day 30 and then weekly. The severity of acute GvHD was recorded daily for a total of 1,738 patient days. CyA dose was then correlated with CyA serum or blood levels, serum creatinine levels and severity of acute GvHD. The daily dose of administered CyA correlated with serum CyA levels (p = 0.001) but not with whole-blood CyA levels. The cumulative CyA dose correlated with serum creatinine. There was an inverse correlation between the daily CyA dose and the severity of acute GvHD (p = 0.05). On the other hand the total amount of CyA given within 10 days after bone marrow transplantation had no influence on the severity of acute GvHD developing after day 10. Serum and whole-blood levels did not correlate with severity of GvHD nor with creatinine levels. The results of this study point out the nephrotoxicity of CyA, and a low GvHD score with high doses of administered CyA, at least on a daily basis. Serum but not blood levels reflect the dose of CyA given, but are not correlated with nephrotoxicity or GvHD.