Solid-phase precipitation and extraction, a new separation process applied to the isolation of synthetic peptides.

A new method for separation and purification is described. The process, referred to as solid-phase precipitation and extraction (SPPE), was developed and applied to postcleavage isolation of synthetic peptides. The technique uses normal approaches of chromatography and solid-phase extraction sorbents with a precipitation or drying procedure so that the sorbent becomes a support matrix for thin-film deposition of the compounds of interest. This procedure causes precipitated compounds of interest to be trapped on the large surface area or in the pores of the matrix so that by-products and impurities can be removed by strong wash solvents. In application to solid-phase peptide synthesis chemistry, by-products from the cleavage and deprotection are selectively extracted from the crude sample mixture under mild conditions. In comparison to the ether precipitation method used in peptide chemistry, the SPPE process provides isolated products that are 14-17% (w/w) higher purity.

A review of cancer induction by extremely low frequency electromagnetic fields. Is there a plausible mechanism?

A body of epidemiological evidence suggests an association between residential or occupational exposure to extremely low frequency (ELF) electromagnetic fields (EMF) and an increased incidence of cancer in children and adults. Experimental studies at the whole-animal and cellular level are ambiguous; bioeffects suggestive of a carcinogenic effect have been reported, but a similar volume of negative reports can also be assembled. This literature is critically reviewed based on the hypothesis that the epidemiological results are correct, and asking what plausible mechanism could explain a small increase in the incidence of a range of tumors with a non-specific increased exposure to ELF EMF? We focus on four likely mechanisms: 1) disruption of cell communication, 2) modulation of cell growth via changes in calcium ion flux, 3) activation of specific oncogenic gene sequences, and 4) action as a stress factor operating through disruption of hormonal and immune system tumor control mechanisms. We discuss the implications of epidemiologic and experimental results in the context of hypothetical mechanisms of cancer induction, and suggest experiments likely to help define putative EMF hazards.

Dose proportionality of nadolol pharmacokinetics after intravenous administration to healthy subjects.

To support the increasing use of intravenous beta-blockers during cardiovascular emergency and surgery, dose proportionality of pharmacokinetics of nadolol was evaluated after intravenous administration of 14C-nadolol at doses of 1, 2 and 4 mg to nine healthy volunteers. There were no observed differences in the excretion or the pharmacokinetics of nadolol with respect to the dose administered. Over a 72-h period after drug administration, an average of about 60% of the dose was excreted in the urine and about 15% was excreted in the feces. The range of values for total body clearance (219 to 250 ml.min-1), renal clearance (131 to 150 ml.min-1), mean residence time (10.5 to 11.3 h), half-life (8.8 to 9.4 h), and steady-state volume of distribution (Vss) (147 to 157 l) indicated that nadolol was extensively distributed and slowly cleared from the body. There was a linear correlation (r2 = 0.97) between the area under the plasma concentration of nadolol versus time curve (AUC) and the dose. All pharmacokinetics parameters, except Vss, were slightly, but significantly, different at the 4 mg dose. Superposition of the dose-normalized average concentrations indicated that despite these minor differences in parameters, the pharmacokinetic behavior of nadolol was linear with respect to dose. Urinary excretion of nadolol was dose independent.

Pharmacokinetics of intravenous captopril in healthy men.

The pharmacokinetic characteristics of intravenously-administered captopril were investigated in 7 healthy men 20 to 33 years old. Capropril, labeled with 14C, was given by injection over a 1 min period at mean doses of 2.78 mg (13.8 microCi), 5.67 mg (28.2 microCi) and 11.4 mg (56.8 microCi). Concentrations of unchanged captopril, captopril disulfide, and other metabolites (collectively) were determined in body fluids. Pharmacokinetic parameters were calculated for unchanged captopril, and it was shown that the disposition of intravenously-administered drug was linear with respect to dose over the dosage range studied.

Pharmacokinetics of captopril in elderly healthy male volunteers.

The pharmacokinetics of captopril were studied in 12 healthy male volunteers aged 65 to 76 years, who each received a single 100-mg oral dose. Blood and urine samples were collected over a 24-hour period, and assayed for unchanged captopril (CAP), S-methylcaptopril (Me-CAP, plasma concentrations from 2 subjects only), and total captopril levels (TOT, a mixture of CAP and its dimer and mixed disulfides with endogenous thiol-containing compounds such as glutathione and cysteine). Mean values for the maximum concentration (Cmax) were 803 and 66.3 ng/mL for CAP and Me-CAP, respectively. Mean time to maximum concentration (tmax) was determined as 1.0, 1.4, and 1.0 for CAP, TOT, and Me-CAP, respectively. Mean areas under the plasma concentration-time curve (AUC) were 1,394 hr-ng/mL (CAP, 0-8 hr) and 17,316 hr-ng/mL (TOT, 0-24 hr). The mean estimated half-life (t 1/2) for CAP was 1.4 hr, and its renal clearance was 187 mL/hr/kg. Mean urinary excretion over 24 hr was 20.8 and 53.1 for CAP and TOT, respectively. Cmax, and AUC for CAP were 9% less and 13% greater, respectively, than in a historical control group of 18-35-year-old men, treated in the same clinic, by the same personnel, using the same analytic procedures, whereas the 24-hour urinary excretion was 25% lower and eight-hour renal clearance 36% lower in the older population. Since the values for Cmax, AUC, and t 1/2 were similar in the two populations, it does not appear that the pharmacokinetics of CAP are altered markedly with age alone.

Pharmacokinetics of aztreonam in elderly male volunteers.

The pharmacokinetics of aztreonam were studied in 12 healthy male volunteers aged 65 to 75 years who received 1 g of the antibiotic intravenously. Data were fitted to a two-compartment open model to yield the following parameters: t 1/2, lambda 1, 0.15 h; t 1/2,z, 2.06 h; area under the 24-h serum concentration-time curve, 231.8 micrograms ml-1 h; Cmax, 120.1 micrograms/ml; V1 area, 0.16 l/kg; and serum clearance, 0.94 ml min-1 kg. Twenty-four hour urinary elimination reached 63.1% of dose as aztreonam and 3.1% as the open ring metabolite SQ 26,992. These data were similar to those obtained for healthy males aged 18 to 35 years. Thus, age per se is not a major therapeutic consideration in treating elderly patients, and other factors, primarily the parameters of renal function, should serve as the basis for any dose reduction.

Pharmacokinetic interaction of aztreonam with other antibiotics.

The pharmacokinetic interaction of the monobactam antibiotic aztreonam with cephradine, clindamycin, gentamicin, metronidazole, and nafcillin was investigated in five separate studies in 48 healthy male volunteers. All drugs were administered by 30-minute intravenous infusions in single-dose, three-way balanced cross-over studies. Drug levels were measured in serum, protein-free filtrate of serum, and urine. Small changes of no clinical significance were seen when aztreonam was given simultaneously with another antibiotic as compared with each drug alone. Maximum serum concentrations of aztreonam were reduced by 12.6 and 9.8 per cent when it was given with gentamicin and metronidazole, respectively. The percentage of serum aztreonam bound to protein fell by a maximum of 5.0 per cent when the monobactam was given in conjunction with nafcillin and rose by 5.1 per cent when accompanied by cephradine. Twenty-four-hour cumulative urinary excretion of aztreonam and clindamycin rose by 5.2 and 10.9 per cent, respectively, when they were administered simultaneously.

Action of (S)-10-hydroxycamptothecin on P388 leukemia and distribution of the drug in mice.

As an inhibitor of the growth of P388 leukemia in mice, (S)-10-hydroxycamptothecin (OPT) was as potent as the parent compound camptothecin (CPT). Incorporation of thymidine into DNA was the parameter most sensitive to OPT in vitro (ED50 approximately 4 micrograms/ml), but incorporation of cytidine into RNA and of acetate into lipids was also reduced significantly in the presence of the drug. The cytofluorometric profile suggested suppression of the S and G2/M phases. The distribution of OPT in mice at 2 and 24 hours after ip injection (10 mg/kg) was essentially similar to that of CPT, with the exception of a somewhat greater concentration of CPT in the liver. In their pharmacology, OPT and CPT appear to be very similar, despite reports that the hydroxy derivative is less toxic.

Genetic and physical studies of restriction-deficient mutants of the Inc FIV plasmids R124 and R124/3.

R124 and R124/3 are R plasmids that carry the genes for two different restriction and modification systems. The phenotype of strains carrying either of these plasmids along with the F'lac+ plasmid, is restriction-deficient (Res-). The Res- phenotype is not due to selection of pre-existing mutants but rather to a complex mutational event caused by the F plasmid. Restriction-deficient mutants carry extensive deletions and other DNA rearrangements. Tn7 insertion is used to locate the restriction gene. Many of the Res- mutants are genetically unstable and revert at exceptionally high frequencies. Reversion is accompanied by DNA rearrangements which result in a net gain of 9 kb of DNA. F derivates of F+ which do not cause restriction-deficiency but do cause deletion were used to distinguish between the DNA rearrangements associated with restriction-deficiency and those associated with deletion. From Res+ revertants of strains carrying F'lac+ and R124 or R124/3 we have isolated F plasmids that now carry the genes for the R124 or R124/3 restriction and modification systems. It is suggested that interaction between part of the F plasmid and that segment of the R plasmid which controls the switch in Res-Mod specificity which has been observed (Glover et al. 1983) is responsible for the production of restriction-deficiency.

Pharmacokinetic and anti-tumor studies with the radiosensitizer misonidazole in dogs with spontaneous fibrosarcomas.

Nine dogs with spontaneous oral fibrosarcomas were given the radiosensitizer misonidazole (Ro-07-0582) In combination with orthovoltage radiotherapy. Although there appeared to be a trend toward greater disease-free survival of these animals as compared with a group of 13 dogs with similar tumors treated by orthovoltage x-rays alone, on analysis there was no significant difference. The plasma half-life and the volume of distribution of misonidazole were determined as 4.95 hours and 15.1 L/m2, respectively. In 3 dogs with evidence of misonidazole toxicosis, plasma concentrations at 4 hours after the dose exceeded 85 microgram/ml, and the areas under the concentration vs time curve for this first 10 hours were greater than 850 microgram.hr/ml.

Clinical effects and pharmacokinetics of different dosage schedules of adriamycin.

Adriamycin was administered to 60 adults and 21 children by 3 different dosage schedules: 22.5 mg/sq m (0.6 mg/kg) daily for 4 days, 15 mg/sq m (0.4 mg/kg) every 8 hr for a total of 6 doses, and 50 to 120 mg/sq m as a single dose every 3 to 4 weeks. Objective responses lasting more than 1 month occurred in 5 subjects with acute leukemias or lymphoma, 3 with transitional cell carcinomas, 2 with sarcomas, 2 with Ewing's sarcoma and 1 each with bronchogenic carcinoma, orchidoblastoma, and thymoma. Toxic reactions included nausea, vomiting, stomatitis, alopecia, and hematopoietic depression, but significant cardiac toxicity occurred in only 1 patient. Pharmacokinetic data, collected in 25 patients by fluorometric and chromatographic assay, suggested a biphasic plasma clearance of drug with initial and secondary half-lives of about 1.5 and 14 to 21 hr, respectively. When drug was given every 8 hr there was evidence of loss of an initial very rapid phase of distribution of adriamycin and its metabolites. Urinary excretion accounted for 3.4 to 38.1% of administered fluorescence over a 72-hr period; in the first 24 hr, between 48.2 and 100% of this urinary material was in the form of adriamycin; leter, this fraction declined. No adriamycin or its fluorescent metabolites could be extracted from the stools.

Pharmacological studies with vinblastine in the dog.

Tritiated vinblastine was prepared by catalytic exchange and its metabolism was studied in dogs. Plasma levels of drug fell in biphasic mode with initial and secondary phase half-lives of 17 to 38 min and 3 to 5 hr, respectively. Between 28.6 and 79.1% of plasma tritium was precipitable with cold trichloroacetic acid and thus was presumably protein bound. Blood leukocytes had levels of intracellular tritium between 2.4 and 11.8 times those of the coincident plasma samples. Over a 9-day period, urinary excretion accounted for 12.1 to 16.8% and fecal excretion accounted for 30.1 to 36.1% of the administered radioactivity. Ratios of biliary to plasma radioactivity varied between 7.3 and 56.9, with unchanged vinblastine being the mamor component (46.8 to 80.7%) in the bile.