Prospective evaluation of eligibility for thrombolytic therapy in acute myocardial infarction

OBJECTIVES

To determine the proportion of patients presenting with acute myocardial infarction who are eligible for thrombolytic therapy.

DESIGN

Cohort follow up study.

SETTING

The four coronary care units in Auckland, New Zealand.

SUBJECTS

All 3014 patients presenting to the units with suspected myocardial infarction in 1993.

MAIN OUTCOME MEASURES

Eligibility for reperfusion with thrombolytic therapy (presentation within 12 hours of the onset of ischaemic chest pain with ST elevation > or = 2 mm in leads V1-V3, ST elevation > or = 1 mm in any other two contiguous leads, or new left bundle branch block); proportions of (a) patients eligible for reperfusion and (b) patients with contraindications to thrombolysis; death (including causes); definite myocardial infarction.

RESULTS

948 patients had definite myocardial infarction, 124 probable myocardial infarction, and nine ST elevation but no infarction; 1274 patients had unstable angina and 659 chest pain of other causes. Of patients with definite or probable myocardial infarction, 576 (53.3%) were eligible for reperfusion, 39 had definite contraindications to thrombolysis (risk of bleeding). Hence 49.7% of patients (537/1081) were eligible for thrombolysis and 43.5% (470) received this treatment. Hospital mortality among patients eligible for reperfusion was 11.7% (55/470 cases) among those who received thrombolysis and 17.0% (18/106) among those who did not.

CONCLUSIONS

On current criteria about half of patients admitted to coronary care units with definite or probable myocardial infarction are eligible for thrombolytic therapy. Few eligible patients have definite contraindications to thrombolytic therapy. Mortality for all community admissions for myocardial infarction remains high.

Simultaneous quantitation of pioglitazone and its metabolites in human serum by liquid chromatography and solid phase extraction

A high-performance liquid chromatographic (HPLC) method for the simultaneous determination of pioglitazone (U-72107) and its potential metabolites (M-1 to M-6) in human serum was developed. The method involved a solid phase extraction (SPE) of pioglitazone, its metabolites, and the internal standard (U-92573) from serum using C18 SPE columns with an elution solvent of 0.5 ml of acetonitrile-water (35:65, v/v). Separation of the eight analytes was achieved within 20 min using a reversed-phase Zorbax RX-C8 analytical column (250 mm x 4.6 mm i.d., 5 microns particle size) with a mobile phase of acetonitrile-water (40:60, v/v) containing 3 ml acetic acid per liter mobile phase (apparent pH 5.5). An ultraviolet detector operated at 269 nm was used with a linear response observed from 0.02 to 2 micrograms ml-1 for these analytes except for M-4 which was best fitted with a polynomial regression. Limit of quantitation was found to be 0.02 microgram ml-1 for pioglitazone, M-3, M-5, and M-6; 0.04 microgram ml-1 for M-2 and M-4; and 0.5 microgram ml-1 for M-1 when using a 0.5 ml serum sample for extraction. Obtained from the method validation, intra- and inter-assay precision was < or = 9% and accuracy ranged from -8.2 to 13.4% for all analytes. The applicability of this method has been demonstrated by successfully analyzing clinical serum samples. The strategies in the HPLC characterization and in the SPE procedure development for this method are discussed as well.

Kaolinosis in a cotton mill worker

A 62-year-old white male employed for 43 years in the polishing room of a cotton textile mill was admitted to a tertiary care center with progressive dyspnea and productive cough that had not responded to therapy for tuberculosis. In spite of aggressive antibiotic therapy and respiratory support, the patient died as a consequence of respiratory failure. Small rounded and irregular opacities had been noted on the chest radiograph. Review of job-site spirometry demonstrated a worsening restrictive pattern over a 4-year period prior to his death. Additional occupational history revealed long-term exposure to kaolin in the polishing room, and pathologic examination of lung tissue confirmed extensive fibrosis and substantial quantities of kaolin. Kaolinosis is a disease typically found among individuals involved in mining or processing this material rather than in user industries. This case illustrates the importance of obtaining a complete occupational history in reaching a diagnosis. The clinicopathologic aspects of kaolinosis are also reviewed.

Trends in pediatric cardiac pacing

OBJECTIVE

To review retrospectively a 31-year experience with pediatric cardiac pacing at the University of Toronto, with an emphasis on the changing trends in pacemaker implantation in infants and children.

DATA SOURCE

Data were obtained from the pediatric pacemaker follow-up clinic at The Hospital for Sick Children, Toronto, Ontario or from the referring pediatric centre. Follow-up was normally continued until the death of the child or referral to an adult hospital at age 18 years.

PATIENT SELECTION

The study comprised 397 children (under 18 years of age) who underwent initial pacemaker implantation at The Hospital for Sick Children between January 1962 and December 31, 1992. Follow-up was 99% complete (five children lost) and ranged from one month to 32 years (mean 6.5 years).

DATA SYNTHESIS

The use of endocardial versus epicardial leads increased significantly over time (P < 0.001). In addition, significantly more children receiving pacemakers had sick sinus syndrome (P < 0.001). No difference in survival was found between children paced by endocardial versus epicardial leads or between children paced for sick sinus syndrome versus atrioventricular block. The frequency of exit block, by lifetable analysis, did not differ between children who received epicardial versus endocardial leads.

CONCLUSIONS

Guidelines for permanent pacemaker implantation in children continue to evolve as developments in lead technology alter trends in pediatric cardiac pacing.

The umpA gene of Escherichia coli encodes phosphatidylglycerol:prolipoprotein diacylglyceryl transferase (lgt) and regulates thymidylate synthase levels through translational coupling

Using a combination of biochemical, physical, and genetic techniques, we have shown that the umpA gene of Escherichia coli is allelic with the lgt (phosphatidylglycerol:prolipoprotein diacylglyceryl transferase) of Salmonella typhimurium. These genes are essential for the viability of the respective organism and exhibit 92.8% sequence identity at the amino acid level. In E. coli, lgt and thyA (thymidylate synthase) form an operon. Thymidylate synthase levels are regulated by transcription from the lgt promoter and by translational coupling.

First-pass effect of cis-3,4-dichloro-N-methyl-N-(2-(1-pyrrolidinyl)- cyclohexyl)-benzamide (U-54494) in rats--a model with multiple cannulas for investigation of gastrointestinal and hepatic metabolism

A multiple cannulated rat model was utilized to investigate the relative contribution of the gut and liver as sites of first-pass metabolism of orally administered U-54494A, an anticonvulsant drug candidate. Each rat received a dose of U-54494A by oral, intraportal, and intravenous routes on three separate occasions. Intraportal and intravenous doses were administered through chronic cannulas surgically implanted in the portal vein and superior vena cava, respectively. Blood samples were collected over a 6-hr period from the superior vena cava cannula. The mean (n = 3) bioavailability of orally dosed U-54494A was 4.5 +/- 1.1%, while that dosed intraportally was 19.1 +/- 3.0%. The relative contribution of the gut and liver as sites of first-pass extraction and/or metabolism of orally administered drug was 69.9 +/- 14.0% and 24.5 +/- 12.2%, respectively. Approximately 35 to 40% of the total plasma clearance was attributeds to the liver. The plasma concentrations of the four known metabolites of U-54494A were apparently higher for the oral and intraportal routes compared to that after intravenous administration. This investigation confirms that the low oral bioavailability of U-54494A in the rat can be primarily attributed to both extensive intestinal and hepatic first-pass metabolism.

Iron associated with asbestos bodies is responsible for the formation of single strand breaks in phi X174 RFI DNA

The ability of amosite cored asbestos bodies isolated from human lungs to catalyse damage to phi X174 RFI DNA in vitro was measured and compared with that of uncoated amosite fibres with a similar distribution of length. Asbestos bodies (5000 bodies) suspended for 30 minutes in 50 mM NaCl containing 0.5 micrograms phi X174 RFI DNA, pH 7.5, did not catalyse detectable amounts of DNA single strand breaks. Addition of the reducing agent ascorbate (1 mM), however, resulted in single strand breaks in 10% of the DNA. Asbestos bodies in the presence of a low molecular weight chelator (1 mM) and ascorbate catalysed the formation of single strand breaks in 21% of the DNA with citrate or 77% with ethylenediamine tetra-acetic acid (EDTA), suggesting that mobilisation of iron may increase damage to DNA. Preincubation for 24 hours with desferrioxamine B, which binds iron (Fe (III)) and renders it redox inactive, completely inhibited the reactivity of asbestos bodies with DNA, strongly suggesting that iron was responsible. Amosite fibres (5000 fibres/reaction), with a similar length distribution to that of the asbestos bodies, did not catalyse detectable amounts of single strand breaks in DNA under identical reaction conditions. The results of the present study strongly suggest that iron deposits on the amosite core asbestos bodies were responsible for the formation of DNA single strand breaks in vitro. Mobilisation of iron by chelators seemed to enhance the reactivity of asbestos bodies with DNA. It has been postulated that the in vivo deposition of the coat material on to fibres may be an attempt by the lung defenses to isolate the fibre from the lung surface and thus offer a protective mechanism from physical irritation. These results suggest, however, that the iron that is deposited on asbestos fibres in vivo may be reactive, potentially increasing the damage to biomolecules, such as DNA, above that of the uncoated fibres.

Quantitative determination of cis-3,4-dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzamide and three of its metabolites in plasma by high-performance liquid chromatography

A sensitive HPLC method was developed for simultaneous quantitation of cis-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]-benzamide and three of its metabolites in dog plasma. The method involved selective solid-phase extraction of the compounds of interest from dog plasma and HPLC separation of the analytes on a cyano column. Absorbance of the column effluent was monitored at 230 nm by a UV detector. The analytical procedure has a linear range of 10 ng/mL to 20 micrograms/mL, with a low limit of quantitation of 10 ng/mL for each analyte. The accuracy and intra- and interassay precision for each compound were < or = 11% in the concentration range evaluated. Applicability of this method to the quantitation of 1 and its metabolites was assessed in a preclinical pharmacokinetic study.

Percutaneous transluminal coronary angioplasty in chronic coronary artery occlusion

OBJECTIVES

This study was conducted to determine the procedural success rate, complication rate and long-term outcome of percutaneous transluminal coronary angioplasty in chronically occluded coronary arteries.

BACKGROUND

Coronary angioplasty of chronically occluded vessels has a lower success rate than has angioplasty of nonoccluded vessels, but it is frequently considered safe because the target vessel is already occluded. The purpose of this study was to determine the reliability of these assumptions at our institution, with the objectives stated above.

METHODS

We identified from the angioplasty data base at our institution 100 consecutive coronary angioplasty procedures performed between 1987 and 1991 for chronic total occlusion, defined as complete occlusion (Thrombolysis in Myocardial Infarction [TIMI] grades 0 and 1 flow) for > or = 3 months. The records of the 95 patients who underwent these procedures were reviewed to determine procedural outcome and medium-term results.

RESULTS

Procedural success was obtained in 47 occluded vessels (47%). Significantly fewer successes were obtained in the right coronary artery (26.8%) than in either the left anterior descending (57.1%) or the left circumflex (45%) coronary artery (p < 0.05). A procedural failure without serious adverse consequences occurred in 45 procedures (45%), but in eight patients (right coronary artery in five, left anterior descending artery in three) attempted recanalization was complicated by extensive coronary dissection with acute myocardial ischemia, and one of these patients died. There were no emergency operations, but elective coronary artery bypass surgery was undertaken in 26 patients (in 3 after extensive dissection, in 7 after an apparently good result and in 16 in whom the procedure failed). At 12 months after the procedure, 64.1% of those with a procedural success were event free compared with 32.6% of those whose procedure was both unsuccessful and uncomplicated (p < 0.025) and 25% of those in whom it was unsuccessful and complicated by coronary dissection (p < 0.025).

CONCLUSIONS

In this series of recanalization of chronically occluded coronary arteries, there was a low procedural success rate, particularly for the right coronary artery. However, when procedural success was obtained, the long-term outlook was good. The overall risk of coronary dissection was comparable to the risk in nonoccluded vessels but was particularly high in the right coronary artery (13%).

Effect of glucose deprivation of GLUT 1 expression in 3T3-L1 adipocytes

Elevated glucose transport rates during glucose deprivation are phenomena that have been observed in several different types of cells in culture. We show here that glucose transport rates in 3T3-L1 adipocytes increased by 10-fold within 18 h in response to glucose deprivation, confirming earlier work by Van Putten and Krans (Van Putten, J. P. M., and Krans, H. M. J. (1985) J. Biol. Chem. 260, 7996-8001). Mannose and 3-O-methylglucose (a nonmetabolizable glucose analog), but not fructose or galactose, blocked the increase in transport activity. Although the increase in transport was dependent on new protein synthesis, only a small and transient increase in GLUT 1 mRNA (less than 2-fold) was observed. In addition, the level of the normal isoform of GLUT 1 (46 kDa) did not increase. A lower molecular mass isoform (37 kDa) was observed but not until 15 h after glucose removal, the appearance of which was clearly not correlated with the increase in activity. Further, the extracellular glucose concentration required to elicit accumulation of this form (p37) was 2 orders of magnitude less than that required for transport stimulation (5 microM versus 500 microM glucose; p37 accumulation and transport activation, respectively). Interestingly, p37 was seen in the presence of galactose, but not fructose, despite elevated transport activity with either sugar. The p37 isoform was slightly larger than N-glycosidase F-treated GLUT 1 (36 kDa), implying that this form is still glycosylated, albeit incompletely. It is not known if p37 is functional, but the time- and sugar-dependent appearance of the lower isoform suggests that p37 is not responsible for starvation-induced transport but potentially represents an underglycosylated precursor of the normal, 46-kDa isoform of GLUT 1.

Cloning of a lactate dehydrogenase gene from Clostridium acetobutylicum B643 and expression in Escherichia coli

A lactate dehydrogenase (LDH) gene of Clostridium acetobutylicum B643 was cloned on two recombinant plasmids, pPC37 and pPC58, that were selected by complementation of Escherichia coli PRC436 (acd), a fermentation-defective mutant that does not grow anaerobically on glucose. E. coli PRC436(pPC37) and PRC436(pPC58) grew anaerobically and fermented glucose to mostly lactate. When pPC37 and pPC58 were transformed into E. coli FMJ39 (ldh pfl), an LDH-deficient strain, the resulting strains grew anaerobically on glucose and produced lactate. Crude extracts of E. coli FMJ39(pPC37) and FMJ39(pP58) contained high LDH activity only when assayed for pyruvate reduction to lactate, and the LDH activity was activated 15- to 30-fold by the addition of fructose 1,6-diphosphate (FDP). E. coli FMJ39 had no detectable LDH activity, and E. coli LDH from a wild-type strain was not activated by FDP. Maxicell analysis showed that both plasmids pPC37 and pPC58 expressed a protein with an apparent Mr of 38,000 in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Restriction endonuclease mapping of pPC37 and pPC58 and DNA hybridization studies indicated that a 2.1-kb region of these two clones of C. acetobutylicum DNA encodes the FDP-activated LDH.

Asbestos content of lung tissue, lymph nodes, and pleural plaques from former shipyard workers

Autopsy samples from eight former shipyard workers were collected from lung parenchyma, tracheal lymph nodes, and pleural plaques. The tissue from each respective area was prepared by a modified bleach digestion technique, and the residue was collected on a 0.2-micron pore polycarbonate or 0.22-micron mixed cellulose ester filter. Quantitation of ferruginous bodies and uncoated fibers was done by light and transmission electron microscopy, respectively. Differences in the asbestos burden were noted for each site. Ferruginous bodies were observed in both parenchyma and nodes but not in plaques. Three subjects were found to have more ferruginous bodies per gram dry weight in their lymph nodes than in their lung parenchyma. Likewise, all subjects were found to have more uncoated fibers per gram in the nodes than in the parenchyma. Amphibole and chrysotile fibers were noted in the lung and extrapulmonary sites, with chrysotile being the predominant asbestiform in plaques. The majority of the uncoated fibers in both the nodes and the plaques were less than or equal to 5 microns in length. However, some fibers with dimensions conforming to the "Stanton hypothesis" reached both areas. These residual patterns most likely reflect the impact of clearance on lung burden as opposed to the eventual accumulation and stasis in the extrapulmonary areas.

Clinical outcome following coronary balloon angioplasty in 100 consecutive patients with multivessel coronary artery disease

Prompted by current uncertainties regarding the precise role of percutaneous transluminal coronary balloon angioplasty (PTCA) in patients with multivessel disease, we reviewed the records of 100 such patients undergoing their first PTCA at our centre between 1 March 1987 and 23 March 1989. Thirty had three-vessel coronary disease (stenoses greater than or equal to 70% in all three major coronary artery territories), 51 had a previous myocardial infarction and 25 had undergone previous coronary bypass surgery. The mean number of lesions of greater than or equal to 70% per patient was 2.7 (0.8) [mean (SD)]. Successful angioplasty was achieved in 88 of these 100 patients. One year following successful angioplasty, the overall event-free rate [freedom from death, myocardial infarction, need for further revascularisation by either aortocoronary bypass graft surgery or repeat angioplasty, and recurrence of severe (class III/IV) angina] was 73%. These data suggest that, in patients with multivessel disease, angioplasty may be an effective technique for short-term symptomatic management. Definitive guidelines regarding the role of PTCA in such patients must await the results of ongoing large-scale clinical trials.

Prevention of central nervous system toxicity of the antitumor antibiotic acivicin by concomitant infusion of an amino acid mixture

Acivicin is an investigational amino acid antitumor antibiotic currently being evaluated in Phase II clinical trials. In humans acivicin causes reversible, dose-limiting central nervous system (CNS) effects including somnolence, ataxia, personality changes, and hallucinations. We have observed and reported previously that acivicin-treated cats exhibit symptoms (ataxia, sedation, somnolence) resembling CNS toxicity reported in humans. We hypothesized that if acivicin uptake into brain were mediated by a saturable transport system common to endogenous amino acids, drug uptake and CNS toxicity might be blocked by elevation of normal amino acid concentrations in circulating plasma. To test this hypothesis, cats received constant-rate i.v. infusions of either saline or Aminosyn, 10% (a commercially available mixture of 16 amino acids not containing glutamine, glutamate, aspartate, or cysteine) for 4 h prior to and 18 h subsequent to administration of acivicin at a dose producing marked behavioral changes in control cats. Presence or absence of ataxia and sedation were noted at intervals after acivicin treatment. Results showed that Aminosyn infusion prevented CNS symptoms in six of eight cats. Subsequent experiments showed that acivicin levels in brain tissue of Aminosyn-treated cats were 13% of the drug levels in saline-infused cats. Acivicin levels in most peripheral tissues were also decreased significantly by Aminosyn infusion but not to the extent observed in brain. Decreased brain uptake was shown to be due to a combination of amino acid blockade of drug transport into that organ and of increased total body clearance of drug. Concomitant Aminosyn treatment did not alter the efficacy of acivicin in mice bearing L1210 leukemia or MX-1 human mammary carcinoma. Further studies demonstrated that a solution containing only four large neutral amino acids (leucine, isoleucine, phenylalanine, and valine) could also protect cats from acivicin-induced CNS toxicity, apparently without increasing acivicin total body clearance. However, a mixture of several other amino acids contained in Aminosyn (alanine, arginine, tyrosine, histidine, proline, serine, and glycine) failed to prevent CNS toxicity. We conclude that cotreatment with Aminosyn or a mixture of large neutral amino acids could protect cancer patients from acivicin-induced CNS toxicity without ablating antitumor efficacy.

Usefulness of combined light and electron microscopy: evaluation of sputum samples for asbestos to determine past occupational exposure

Ferruginous bodies (FB) in sputa are recognized as an indicator of past exposure to asbestos. However, a great variability exists in FB production, even in individuals with a history of occupational exposure. A further complication in interpreting the presence of FBs in sputa is that all individuals in modern society are exposed to asbestos and, in lung tissue studies, have been shown to harbor appreciable numbers of asbestos fibers. Thus, some of these individuals should occasionally produce FBs in their sputa. The present study was undertaken to determine if uncoated asbestos fiber content could be used to better discriminate occupationally exposed individuals from the general population. Randomly selected sputum samples from 12 former workers in an amosite asbestos plant and 12 controls were studied. The samples were prepared for the study by digesting the sputa in sodium hypochlorite. The digests were filtered through 0.2-microns polycarbonate filters for collection of particulates. The filters were screened for FBs by light microscopy at 200 X, and the presence or absence of uncoated asbestos fibers was determined at 5000 X in an AMRAY 1000A scanning electron microscope. The use of electron microscopy revealed the presence of commercial amphiboles in the sputa of the occupationally exposed individuals and enabled a differentiation of these samples from those of the general population.

Animal behavioral and neurochemical effects of the CNS toxic amino acid antitumor agent, acivicin

The investigational amino acid antitumor agent, acivicin, has been reported to cause dose-related and reversible CNS toxicity in humans characterized by sedation, ataxia, hallucinations, personality changes, and other symptoms. In a series of studies aimed at characterizing this toxicity, we investigated several species as potential animal models, determined the effects of acivicin on neuronal action potentials, and measured drug effects on the brain content of several putative amino acid neurotransmitters. In mice, we were unable to demonstrate any effects of acivicin in a battery of tests used in identifying and classifying CNS-active agents of potential therapeutic utility. In rats, unlike phencyclidine and certain other psychotomimetic drugs, acivicin produced no impairment of shock avoidance or brightness discrimination in animals trained on an automated Y-maze. In contrast to the rodent species, acivicin effects were perceived as resembling those of cyclazocine by rhesus monkeys trained to discriminate between psychoactive drugs and saline by food reinforcement. Cats treated with acivicin exhibited dose-related symptoms of sedation, somnolence, and ataxia. Iontophoretically applied acivicin was shown to have no effect on the spontaneous firing rate of dorsal horn interneurones in spinal cats. At the time of peak CNS symptoms in cats treated with 100 mg/kg acivicin, content of gamma-aminobutyric acid (GABA; nmoles/mg protein) was elevated from 57-140% in cerebellum, diencephalon, midbrain, and corpus callosum compared to control animals. Brain contents of glutamate, glutamine, and aspartate were not altered in cats experiencing neurotoxicity. These studies have shown that some symptoms of acivicin CNS toxicity are shared by humans and higher non-human species such as the cat and the monkey but not by rodents. Acivicin itself is apparently not a CNS excitant or depressant, but metabolites of the drug could be. Acivicin may also cause increases in the GABA content of localized regions of brain.

Identification and genetic mapping of the structural gene for an essential Escherichia coli membrane protein

Attempts to isolate conditionally lethal recB and recC mutations of Escherichia coli K-12 by P1 localized mutagenesis led to the identification of the structural gene for an essential membrane protein. Located on a 1.5-kilobase-pair DNA fragment which physically mapped immediately 5' to the thyA gene, the product of the umpA (unidentified membrane protein) gene is a 25,000 Mr membrane-associated polypeptide. These results provide an explanation for why several research groups have been unable to obtain chromosomal deletions of the entire thyA gene. A possible interaction between the umpA and thyA genes is also discussed.

Comparison of light and electron microscopy for defining occupational asbestos exposure in transbronchial lung biopsies

Since asbestos burden in the lung can very among areas, the usefulness of small tissue samples for identifying past occupational exposure is examined. Simulated transbronchial biopsy samples and open lung biopsy samples were collected from autopsy material from 12 former amosite asbestos workers and ten persons from the general population. Tissue evaluation included (1) paraffin embedment and light microscopy screening for fibrosis and ferruginous bodies, and (2) tissue digestion, which was analyzed by the combination of (A) light microscopy screening for ferruginous bodies and (B) electron microscopy (EM) screening for uncoated fibers. Using standard pathology techniques to classify the small samples was generally unsuccessful, the samples being too small or their size compounding other random sampling problems. The most reliable method of establishing which transbronchial biopsy tissue samples were from the occupationally exposed group occurred when light and EM analyses were used to evaluate digested tissue. The combined data from the EM analysis of two samples per subject indicated controls had two or fewer observed asbestos fibers, while the amosite asbestos workers had six or more fibers. This distinction was valid even in those who, 21 years before sampling, had worked for only a few weeks in the asbestos plant.

Evaluation of DNA binding characteristics of some CC-1065 analogs

The factors influencing the binding of CC-1065 to DNA were examined using racemic analogs with varying chain lengths. The ability of these agents to bind DNA appeared to be related to cytotoxic potency, however this did not appear to be a direct quantitative correlation. Two enantiomers of a bis-indole analog of CC-1065 were studied for DNA binding and cytotoxic activity. The agent with the same stereochemical configuration as CC-1065 was a potent cytotoxin, but its enantiomer was essentially inactive. Both enantiomers showed significant binding to DNA, but the biologically less active isomer showed less overall binding. In all cases, the agents preferred AT-rich DNA, and all bound to similar regions in DNA as evidenced by positions of drug-initiated thermal breaks in single end-labelled fragments of phi X 174RF DNA. The overall similarity in site specificity for binding of the structurally diverse agents suggests that much of the specificity observed in binding of the agent to DNA lies in the DNA itself. Thus, it may be difficult to change minor groove specificity for agents of this type simply by designing structures that can encompass guanine or cytosine residues. Other modifications, such as changing the specificity of the alkylating moiety, may be required to achieve this goal.

Interspecies comparison of acivicin pharmacokinetics

Pharmacokinetic studies with the amino acid antineoplastic agent, acivicin, were carried out in the Sprague-Dawley rat, cynomolgus monkey, and beagle dog. Data were analyzed together with previously published studies in the mouse and rhesus monkey. Log-log plots of body weight (B, kg) versus total body clearance (ClB, ml/min), elimination half-life (t1/2, hr), and volume of distribution (V, ml) in the five species were linear with high correlation coefficients (r greater than or equal to 0.98) despite large differences in the extent of nonrenal clearance in the various species (ranging from approximately 30% of the dose in the mouse to 90% in the dog). Linear regression on the plots yielded allometric expressions (ClB = 4.0 x B0.62; t1/2 = 1.8 x B0.31; V = 620 x B0.95) which were extrapolated mathematically to predict acivicin pharmacokinetic parameters in humans prior to the first clinical trials. Predicted versus measured (mean +/- SD, N = 21 patients) pharmacokinetic values in humans were: ClB (ml/min), 50 vs. 49 +/- 13; t1/2 (hr), 6.4 vs. 9.5 +/- 3.5; VB (ml/kg), 500 vs. 580 +/- 110. Thus, the animal data were successfully extrapolated to yield reasonable predictions of human pharmacokinetic parameters, despite varying extents of renal and nonrenal clearance in the species examined. With one exception, plasma concentration-time data in six species spanning a 3000-fold body weight range and a 120-fold dose range were plotted on a single curve after plasma concentrations were normalized for the dose administered and chronological times were adjusted for body weight to yield "physiological times."(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of arg genes of Escherichia coli during arginine limitation dependent upon stringent control of translation

The transcription and translation of operons for arginine biosynthetic enzymes after arginine removal (arginine down shift) were studied in relA and relA+ strains of Escherichia coli. After arginine down shift, derepression of synthesis of the arginine biosynthetic enzymes ornithine carbamoyltransferase (argF) and argininosuccinate lyase (argH) began at about 15 min in relA+ cells but was delayed in relA cells for more than 2 h. However, both relA+ and relA cells accumulated high levels of argCBH mRNA, as shown by dot blot hybridization, after arginine down shift. After 15 min of arginine limitation, the proportion of ribosome-bound argCBH mRNA was equivalent in both relA+ and relA cells. During the 15 min after the arginine down shift, relA+ cells produced a significant burst of argF and argH enzyme synthesis when arginine was added back to the culture, whereas relA cells did not produce this burst of enzyme synthesis. The relA cells regained the ability to produce a burst of argF and argH enzyme synthesis when alpha-methylglucose-induced glucose starvation was combined with arginine limitation. Significant guanosine 5'-diphosphate 3'-diphosphate accumulated in relA cells under this condition. Our results support the view that during periods of severe amino acid limitation guanosine 5'-diphosphate 3'-diphosphate acts in some way to ensure the translation of argCBH mRNA.

Umbilical versus peripheral tobramycin administration

This study evaluated the disposition of tobramycin (T) after umbilical artery catheter (UAC), intravenous (i.v.), and intramuscular administration to a group of 12 premature neonates. Patients varied in gestational age (31-42 weeks) and weight (1.76-3.98 kg). Each neonate received a 2 mg/kg dose of T at 12-h intervals for 2-15 days. Multiple blood samples after the first and last doses of T, as well as daily measurements, were made during the course of therapy. Analysis of drug concentration data revealed a biphasic distribution of T, which required a two-compartment model for description. Mean values for the alpha and beta elimination phases, t1/2 beta, Vc, and Vdss after the first dose of T were 7.604 h-1, 0.087 h-1, 11.18 h, 0.214 L/kg, and 0.645 L/kg, respectively. Average drug clearance (ClT) increased during therapy from 71 to 103 ml/min, associated with an increase in the renal function of patients. Serum concentrations of T were out of the therapeutic range in 50% of study patients. The variability of drug clearance in the neonate requires the measurement of T concentration in order to ensure safe and effective therapy.