GC-MS identification of sympathomimetic amine drugs in urine: rapid methodology applicable for emergency clinical toxicology

A method was developed that permitted rapid identification in urine of the following sympathomimetic amines: amphetamine, benzphetamine, cathinone, desmethylsegiline, diethylpropion, ephedrine, fenfluramine, mazindol, methylenedioxyamphetamine, methylenedioxyethylamphetamine, methylenedioxymethamphetamine, mescaline, methamphetamine, methcathinone, methylaminorex, methylphenidate, pemoline, phendimetrazine, phenylepherine, phentermine, phenylpropanolamine, pseudoephedrine, and selegiline. In addition, two alpha-phenylethylamine-like monoamine oxidase inhibitors, phenelizine and tranylcypromine, were studied. Those sympathomimetic amines containing a primary or secondary amine, a hydrazine, and/or hydroxyl (except mazindol) functional groups were derivatized effectively using an on-column derivatization technique that used a reagent consisting of 10% fluoroanhydride in hexane, whereas the other sympathomimetic amines, including mazindol, were analyzed underivatized. Three different fluoroanhydrides, trifluoroacetic (TFAA), pentafluoropropionic (PFPA), and heptafluorobutyric (HFBA), and three different injection-port temperatures (160, 200, and 260 degrees C) were investigated. Both TFAA and PFPA gave sympathomimetic amine derivatives with essentially identical retention times, whereas HFBA gave longer retention times and better separation of individual compounds. The base fragmentation ion was noted to increase 50 amu (CF2) for each derivatized sympathomimetic amine as the length of the carbon-fluorine chain increased. Fragmentation ion abundance was maximized at an injection-port temperature of 260 degrees C, and this enhanced sensitivity coupled with the better chromatographic resolution of the individual sympathomimetic amines prompted the selection of HFBA as the derivatizing agent of choice. Assignments were made for the fragmentation ions produced by each derivatized drug. The developed method was adapted to analyze urine specimens that might be encountered in emergency toxicology testing. For identification of sympathomimetic amines requiring derivatization, 0.1 mL of the patient specimen had amphetamine-d5 and methamphetamine-d5 added as internal standard followed by adjustment of pH to 9.3 with borate buffer, extraction with 9:1 chloroform/isopropanol, centrifugation and separation of the organic phase, addition of 10% methanolic HCI and evaporation under nitrogen, reconstitution with HFBA reagent, and on-column derivatization during gas chromatographic-mass spectrometric (GC-MS) analysis. For those sympathomimetic amines not requiring derivatization, 1.0 mL of urine specimen had diazepam-d5 added as internal standard followed by the same extraction procedure and reconstitution accomplished with ethyl acetate. Because precolumn derivatization was eliminated and only 8 min was required for GC-MS analysis, complete analysis time was approximately 30 min, making the method suitable for clinical emergency toxicology purposes.

The use of nuclear magnetic resonance spectroscopy in the detection of drug intoxication

The use of nuclear magnetic resonance (NMR) spectroscopy as a method for drug analysis has the advantages of reduced pre-analytical preparation time and the potential to detect and quantitate drug conjugates and metabolites simultaneously. NMR was investigated as a method to screen for organic substances (and metabolites) in 25 patients who presented to the Emergency Department with clinical indications of a drug overdose. Urine specimens were examined by 1H NMR spectroscopy at 300 MHz and the results compared with gas chromatography-mass spectrometry (GC-MS) results. There was a 56% concordance (14 of 25 samples) between NMR and GC-MS. NMR identified acetaminophen, ibuprofen, aspirin, valproate, carbamazepine, and pseudoephedrine as parent compounds or metabolites. For a patient for whom GC-MS results were negative, NMR strongly suggested the presence of erythromycin. NMR was most successful in identifying analgesics and antiepileptic drugs (sensitivity 83-100%). In 10 patients, signals from 1,2-propanediol, a common vehicle for some pediatric medications, were observed by NMR spectroscopy. NMR had 0% sensitivity in identifying tricyclic antidepressants and antipsychotic drugs. In these samples, GC-MS detected a variety of compounds, including tricyclic antidepressants and their metabolites and chlorpromazine. In addition, other substances that had not been disclosed as having been ingested, such as caffeine, diphenhydramine, and nicotine, were detected by GC-MS. NMR spectroscopy represents an emerging supplementary analytical technique that is applicable to a wide range of possible intoxicants and to the evaluation of the intoxicated patient, particularly when larger amounts of the intoxicant (> 200 mg) are ingested.

Ionized magnesium concentrations in critically ill children

OBJECTIVE

To test the hypothesis that many critically ill children exhibit ionized hypomagnesemia despite having normal total magnesium (TMg) concentrations.

DESIGN

A prospective, observational study with convenience sampling.

SETTING

Pediatric and cardiovascular intensive care units of a large children's hospital.

PATIENTS

Patients aged 1 day to 21 yrs admitted from January 1 to October 31, 1996. Patients with chronic renal failure or weight <3 kg were excluded. A group of healthy children involved in a school-based nutritional assessment study were also studied.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Sixty-seven patients (5.4+/-5.7 [SD] yrs) and 24 healthy children (10.84+/-0.93 yrs, p< .001) were studied. Plasma was assayed for ionized magnesium (IMg) using a blood analyzer. Forty (59%)/67 critically ill subjects had IMg concentrations <0.40 mmol/L, the lowest published normal value and the lowest value observed in our group of healthy children. Of these, 24 (60%)/40 had normal TMg concentrations. IMg was significantly (p=.00) lower in critically ill subjects than in the group of healthy children (0.37+/-0.10 mmol/L vs. 0.46+/-0.03 mmol/L). IMg did not correlate strongly with ionized calcium (r2=0.49), albumin (r2=0.09), or pH (r2=0.18).

CONCLUSION

Many critically ill children exhibit ionized hypomagnesemia with normal TMg concentrations. These children would not be recognized as magnesium-deficient based on routine TMg testing. Critically ill children exhibited significantly lower concentrations of IMg than a group of healthy children.

Phenotypic and genotypic characterization of clinical strains of CDC group IVc-2

CDC group IVc-2 is a gram-negative, oxidase-positive, nonfermentative bacillus that has been implicated in human infections, including septicemia and peritonitis. Biochemically it most closely resembles Bordetella bronchiseptica and Alcaligenes sp. Results of cellular fatty acid (CFA) and 16S rRNA gene analysis were combined with biochemical data to assist in identification and classification. The predominant CFAs were hexadecanoic acid (16:0), cis-9-hexadecanoic acid (16:1omega7c), cis-11-octadecanoic acid (18:1omega7c), and Delta-cis-9,10-methylenehexadecanoic acid (17:0cyc). Small amounts (2 to 5%) of 3-hydroxytetradecanoic acid (3-OH-14:0), tetradecanoic acid (14:0), 2-hydroxyhexadecanoic acid (2-OH-16:0), and Delta-cis-11,12-methyleneoctadecanoic acid (19:0cyc) were also consistently present. The highest 16S rRNA gene similarity was with Ralstonia eutropha and Ralstonia solanacearum. The CFA and 16S rRNA gene sequence data support the inclusion of CDC group IVc-2 in the recently created genus Ralstonia, which includes R. eutropha, R. pickettii, and R. solanacearum.

Sympathomimetic drug use in adolescents presenting to a pediatric emergency department with chest pain

BACKGROUND

Drug use has been associated with chest pain in adults presenting for emergency care. The association of drug use and chest pain in adolescents presenting to a pediatric emergency department has not been evaluated.

METHODS

Urine drug testing was conducted in a convenience sample of healthy adolescents with chest pain (cases) and compared to a control group of adolescents presenting with other complaints to a pediatric emergency department. Exclusion criteria were known diagnoses associated with chest pain (e.g., cardiac disease, sickle cell disease) and major trauma (due to its association with drug use). Urine drug testing consisted of 2 screening tests and gas chromatography-mass spectrometry confirmation of all positive or indeterminate results. All patients completed a questionnaire regarding recently prescribed, over-the-counter, and illicit drug use.

RESULTS

Twenty-eight cases and 26 controls completed the study over an 11-month study period. No cases or controls were positive for cocaine whereas marijuana was detected in 7 (25.0%) cases and in 7 (26.7%) controls. Five (17.8%) of the cases but none of the controls were positive for ephedrine (p = 0.05).

CONCLUSIONS

Ephedrine exposure appeared to be associated with chest pain in adolescents presenting for emergency care and marijuana was the most common drug of abuse, regardless of presenting complaint.

Clinical and toxicological findings in two young siblings and autopsy findings in one sibling with multiple hospital admissions resulting in death. Evidence suggesting Munchausen syndrome by proxy

A 15-month-old girl underwent several emergency department (ED) visits and two admissions for parent-reported histories of ingestions, apnea, and seizures. She was initially admitted following reports of several unusual episodes of syncope accompanied by convulsive movements and was discharged on mephobarbital with a diagnosis of atypical seizure disorder. The day after discharge, she was brought to the ED in cardiopulmonary arrest and was resuscitated after a prolonged period. She was declared brain dead 2 days later. Ante- and postmortem toxicology produced several inconclusive findings, none of which explained death. Autopsy findings, including neuropathology, failed to demonstrate any significant disease processes. Approximately 3 months later, a 4-month-old female sibling was brought to the ED with a parent-reported history of apnea and seizures similar to the deceased child. A stool specimen obtained 2 days after admission contained numerous tiny seeds, which were found by gas chromatography-mass spectrometry analysis to contain lorazepam and temazepam. The role of these benzodiazepines in the apnea episodes in this infant was unknown, but the presence of the seeds in such a young infant coupled with the parent's aberrant behavior, led to the tentative diagnosis of Munchausen syndrome by proxy. This diagnosis was strengthened when results from these studies persuaded legal authorities to remove the surviving sibling from the parents, resulting in an asymptomatic recovery.

Environmental occurrence of selenium in waters and related health significance

Appreciable amounts of selenium in spring and well waters can be found due to geological occurrence. Concentrations of as much as 400-9000 micrograms/l have been reported in U.S. waters. These levels are 8 to 180 times the current EPA drinking water standard and approximate dietary exposures of 4900 micrograms in selenosis regions of China. Reviews of health significance of the elevated drinking water exposures to U.S. populations revealed elevated concentrations of selenium in urine and blood. A decrease in glutathione peroxidase activity in such instances was noted. However noticeable symptoms and signs seem absent in studies reviewed. A comparison of intake levels (diet or drinking water) to urinary excretion for residents of China and the U.S. produced a correlation coefficient, r = 0.82 (P < 0.01) for the three research studies available.

Pharmacokinetics of tertiary butyl alcohol in male and female Fischer 344 rats

Tertiary butyl alcohol (TBA) is a small aliphatic alcohol with multiple industrial and scientific uses. A comprehensive pharmacokinetic profile for TBA has not been determined in rats. The purpose of this study was to fully characterize the pharmacokinetics of TBA in male and female F-344 rats following intravenous administration of 37.5, 75, 150 and 300 mg/kg TBA. TBA was observed to undergo a rapid distribution phase followed by a slower elimination phase. The steady-state volume of distribution for TBA was roughly 4.5 times greater than total body water, and the clearance was lower than the estimated glomerular filtration rate. The elimination of TBA appears to saturate at higher doses, as evidenced by a disproportional increase in area under the concentration-time curve and decreased rate of clearance.

Disposition of butadiene epoxides in Sprague-Dawley rats

1,2-Epoxybutene (BMO) and diepoxybutane (BDE) are metabolic products of 1,3-butadiene in rodents. Both BMO and BDE are suspect in the development of tumors in rats and mice. To understand the distribution and elimination of these compounds in the absence of the rate-limiting production from butadiene, the pharmacokinetics of BMO and BDE in blood were determined in adult male Sprague-Dawley rats following intravenous administration. All animals were dually cannulated in these studies. For the BMO studies, rats were dosed with 71, 143, or 286 mumol/kg BMO (n = 3 for each dose group). For the BDE studies, rats were dosed with 523 mumol/kg BDE (n = 3). All animals tolerated the BMO and BDE doses without grossly observable adverse effects. Blood was drawn at predetermined time points and extracted in methylene chloride. BDE and BMO concentrations were quantitated by gas chromatography or gas chromatography/mass spectrometry. The BMO distribution half-lives were short and ranged from 1.4 min at the lowest dose to 1.8 min at the highest dose. Volume of distribution at steady state ranged from 0.53 +/- 0.17 to 0.59 +/- 0.31 l/kg. Systemic clearances ranged from 67 +/- 17 to 114 +/- 20 ml/min per kg. The terminal elimination half-lives were also short and ranged from 5.7 to 8.5 min among the doses. The pharmacokinetic parameters after an i.v. dose of 523 mumol/kg BDE were a distribution half-life of 2.7 min, terminal elimination T1/2 of 14 min, volume of distribution at steady state of 0.73 +/- 0.06 l/kg, and systemic clearance of 76 +/- 8 ml/min per kg. These pharmacokinetic parameters demonstrate the similarity between disposition of the two epoxides in rats, that include a rapid distribution after i.v. administration into a small extravascular body compartment as well as a rapid elimination from blood. These pharmacokinetic data provide useful blood clearance information for assessing the critical physiological and biochemical determinants underlying the disposition of butadiene epoxides.

Dextromethorphan in nonketotic hyperglycinaemia: metabolic variation confounds the dose-response relationship

Nonketotic hyperglycinaemia (NKH) is an inborn error of the glycine cleavage system resulting in seizures and mental retardation. Two prior reports noted an anticonvulsant effect from high-dose dextromethorphan (DM) in this disorder, although the two reported patients demonstrated widely disparate DM requirements and drug levels. We report two children with NKH who also demonstrated disparate and variable DM metabolism which markedly influenced the dose-concentration-response relationship. Levels of DM and its primary metabolite dextrorphan (DX) were utilized to guide DM therapy and exhibited patterns reflective of the extensive and poor metabolizer phenotypes for CYP2D6, the cytochrome P450 isoform responsible for DM metabolism. In the patient who appeared to represent the extensive metabolizer (EM) phenotype, treatment with the non-specific cytochrome P450 inhibitor cimetidine was required to reduce biotransformation of DM to DX and, thus, to increase DM plasma concentrations. In the patient with the apparent poor metabolizer (PM) phenotype, a change in the DM preparation to a sustained-release form and increase in the dosing interval was required to lower DM plasma concentrations. These cases demonstrate the importance of CYP2D6 phenotype in providing safe and effective DM therapy to patients with NKH.

Reduction of benzene metabolism and toxicity in mice that lack CYP2E1 expression

Transgenic CYP2E1 knockout mice (cyp2e1-/-) were used to investigate the involvement of CYP2E1 in the in vivo metabolism of benzene and in the development of benzene-induced toxicity. After benzene exposure, absence of CYP2E1 protein was confirmed by Western blot analysis of mouse liver samples. For the metabolism studies, male cyp2e1-/- and wild-type control mice were exposed to 200 ppm benzene, along with a radiolabeled tracer dose of [14C]benzene (1.0 Ci/mol) by nose-only inhalation for 6 hr. Total urinary radioactivity and all radiolabeled individual metabolites were reduced in urine of cyp2e1-/- mice compared to wild-type controls during the 48-hr period after benzene exposure. In addition, a significantly greater percentage of total urinary radioactivity could be accounted for as phenylsulfate conjugates in cyp2e1-/- mice compared to wild-type mice, indicating the importance of CYP2E1 in oxidation of phenol following benzene exposure in normal mice. For the toxicity studies, male cyp2e1-/-, wild-type, and B6C3F1 mice were exposed by whole-body inhalation to 0 ppm (control) or 200 ppm benzene, 6 hr/day for 5 days. On Day 5, blood, bone marrow, thymus, and spleen were removed for evaluation of micronuclei frequencies and tissue cellularities. No benzene-induced cytotoxicity or genotoxicity was observed in cyp2e1-/- mice. In contrast, benzene exposure resulted in severe genotoxicity and cytotoxicity in both wild-type and B6C3F1 mice. These studies conclusively demonstrate that CYP2E1 is the major determinant of in vivo benzene metabolism and benzene-induced myelotoxicity in mice.

Chronopharmacokinetics and chronopharmacodynamics of dextromethamphetamine in man

Stimulants, in particular the amphetamines, have been studied as countermeasures to fatigue induced by circadian desynchronosis and extended flight operations. To make recommendations concerning the use of dextromethamphetamine for operational tasks, its chronopharmacokinetic and chronopharmacodynamic profiles and influence on circadian rhythms as a countermeasure to performance deficits and fatigue were studied. Ten male volunteers, divided into two groups of five each, were given 30 mg/70 kg of oral dextromethamphetamine during two test sessions one week apart and were evaluated with cognitive (dichotic listening, pattern recognition, and compensatory tracking), subjective (fatigue scale), and physiologic (blood pressure) testing. Session order was counterbalanced with dextromethamphetamine administration at either 8:40 AM or 8:40 PM during session one and a crossover to the other time during session two. Subjective and cognitive testing was begun 1.5 hours before dextromethamphetamine administration and continued every half hour until 12.5 hours after administration. Blood pressure was measured immediately before behavioral testing. Serum and urine were collected at regular intervals for gas chromatography/mass spectrometer analysis of methamphetamine and one of its metabolites, amphetamine. No differences were found in the day-versus-night pharmacokinetic profile of dextromethamphetamine. Cognitive performance and subjective fatigue improved after daytime administration of dextromethamphetamine in comparison to performance before drug administration. This effect was suppressed during the circadian trough, which occurred approximately 8 hours into the night sessions (4:30 AM). No correlations were seen between serum concentration of methamphetamine and measured behavioral parameters.

Identification of urinary benzodiazepines and their metabolites: comparison of automated HPLC and GC-MS after immunoassay screening of clinical specimens

An automated high-performance liquid chromatographic method, benzodiazepines by REMEDi HS, was used to analyze benzodiazepines and their metabolites after beta-glucuronidase hydrolysis of 1-mL urine specimens from the following: 924 clinic and hospital patients whose specimens had previously been found to be presumptively positive using either EMIT or Triage immunoassay methodologies and 128 individuals whose specimens had screened negative by EMIT d.a.u.TM. REMEDi analyses did not correlate with the immunoassay results in 136 of the positive and three of the negative urine specimens. Gas chromatographic-mass spectrometric (GC-MS) confirmatory analyses were performed on these discordant specimens using 3 mL beta-glucuronidase-hydrolyzed urine followed by extraction with chloroform-isopropanol (9:1) and derivatization with N,O-bis(trimethylsilyl)trifluoroacetamide. Two benzodiazepines, flunitrazepam and clonazepam, and their 7-amino metabolites were analyzed without prior derivatization. The analyses established 87% concordance between REMEDi and GC-MS versus 13% concordance with immunoassay for the subset. GC-MS analysis of these 142 specimens demonstrated two reasons for the nonconcurrence between REMEDi and EMIT: EMIT had given either false-negative or false-positive results and EMIT had given a positive result even though the determined metabolites were below the 200-ng/mL cutoff for the immunoassay and the 80-ng/mL cutoff for REMEDi. A total of 23 specimens were found to contain only lorazepam by REMEDi and GC-MS, 15 of which had been screened by Triage. A reevaluation of these 23 specimens by EMIT d.a.u. demonstrated that 11 were positive. This finding was in contrast to previous reports that EMIT will not detect lorazepam glucuronide in urine. An unexpected finding was the REMEDi identification and subsequent GC-MS confirmation of 7-aminoflunitrazepam, a urinary metabolite of flunitrazepam that is not available in the United States and that represented illicit use by four patients. A distinct advantage of REMEDi proved to be its capability in identifying demoxepam, a major metabolite of chlordiazepoxide; GC-MS analysis could not detect this metabolite because of its thermal decomposition to nordiazepam. To further evaluate the specificity of REMEDi, we conducted GC-MS analyses in a random fashion on 55 additional nondiscordant urine specimens that were identified as either positive or negative, as well as 22 specimens identified as containing 7-aminoclonazepam by REMEDi. Concurrence was observed between the two methods for all specimens, with the exception of one apparent false positive for alpha-hydroxyalprazolam by REMEDi. The reproducibility of the REMEDi method was found to be excellent; it was assessed by comparing results of 266 specimens that were reprocessed in different batches and for known calibrators and controls also processed with each batch. Study results demonstrated that the automated REMEDi assay for urinary benzodiazepines and their metabolites was comparable with GC-MS but had distinct advantages over GC-MS because of the following reasons: simplicity of the assay, less time required for analyses, and provision of additional information concerning the parent benzodiazepine.

Antiphencyclidine monoclonal Fab fragments reverse phencyclidine-induced behavioral effects and ataxia in rats

Antiphencyclidine monoclonal antibody binding fragments (anti-PCP Fab) were studied in rats as a possible treatment for phencyclidine (PCP) overdose. Each male Sprague-Dawley rat (n = 4 per group) received an i.v. dose of 1 mg/kg of PCP followed 5 min later (as toxicity maximized) by one of three treatments in a random cross-over design. The treatments were 1 ml of saline, a nonspecific polyclonal human Fab, or a high affinity (Kd = 1.8 nM) anti-PCP monoclonal Fab. The doses of the nonspecific and anti-PCP Fab were 0.3, 1.0 and 3.0 times the mole equivalent (mol-eq) dose of PCP. Changes in locomotor activity and ataxia were the best indicators of PCP-induced behaviors among several time-dependent behavioral changes that were evaluated. PCP administration followed by saline treatment resulted in increases in locomotor activity and ataxia that declined to base line after 35 to 40 min. Anti-PCP Fab at 1.0 and 3.0 times the mol-eq dose of PCP significantly (P < .05) and rapidly reversed PCP-induced behaviors to base-line values. Although the 0.3 mol-eq dose of Fab appeared to slightly decrease the behavioral toxicity, the effects were not statistically different from controls in most cases. No significant effects on PCP-induced behaviors were observed after any dose of the nonspecific Fab. In addition, pharmacological and immunological specificity were tested further by treatment of MK-801 {(+)-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5, 10-imine-}-induced behavioral effects. MK-801 is a PCP-like, noncompetitive N-methyl-D-aspartate receptor antagonist which is structurally unrelated to PCP. The anti-PCP Fab treatment had no effect on MK-801-induced locomotor activity. These data clearly show that anti-PCP Fab is a specific PCP antagonist that can rapidly reverse PCP-induced behavioral toxicity in the rat.

Antiphencyclidine monoclonal antibody therapy significantly changes phencyclidine concentrations in brain and other tissues in rats

These studies determined how high-affinity monoclonal antiphencyclidine (PCP) antigen binding fragments of immunoglobulin G (Fab) affects PCP tissue concentrations and serum protein binding in male rats. Animals received an i.v. bolus dose of 1.0 mg/kg of PCP, followed at 2 hr when distribution was complete (but about 70% of the dose remained) by either saline (for controls) or an equimolar dose of anti-PCP Fab. This dose of PCP was chosen because it produces behavioral effects and ataxia for about 40 min. The rats were sacrificed over the next 16 hr (n = 3 per time point) and blood, brain, fat, heart, kidney, liver, lung, muscle and testis were collected. After anti-PCP Fab treatment, serum PCP concentrations increased significantly (P < .05) for the duration of the experiment. This resulted in a decrease in the PCP volume of distribution and systemic clearance to 11 and 12% of controls, respectively. Because these parameters decreased to a similar degree, the terminal elimination half-life was unaltered after Fab treatment. The percentage of unbound PCP in serum averaged 47 +/- 15% (mean +/- S.D.) in controls and 3 +/- 2% in Fab-treated animals for the duration of sampling. The area under the tissue concentration vs. time curves after anti-PCP Fab administration were decreased substantially in the brain (23% of controls), fat (24%), heart (52%), lung (74%) and testis (12%), but increased in the liver (137%). Because of anti-PCP Fab renal elimination, kidney PCP concentrations were significantly increased at all time points after Fab treatment (P < .05), which resulted in an 18-fold increase in the PCP area under the curve. These studies show anti-PCP Fab can rapidly remove PCP from the brain and maintain it in a highly bound form for a significant time.

The use of transgenic cell lines for evaluating toxic metabolites of carbamazepine

Human lymphoblastoid cell lines transgenic for human CYP450s were evaluated for the identification of toxic metabolites of the anticonvulsant drug carbamazepine (CBZ). Human CYP450 isoforms expressed by these cell lines included 1A1, 1A2, 2E1, 2A6, and 3A4. A dose-dependent inhibition of population growth from 50-200 micrograms/ml CBZ was detected by measuring cell number and respiration. The inhibition increased with the growth rate of the various lines, which correlated inversely with the presence of CYP450s, and may have been caused by CBZ itself. Cytotoxicity was observed only at the highest dose and in the line lacking transfected CYP450s. Microsomal preparations from hCYP3A4/OR cells converted CBZ into its principal oxidative metabolite, carbamazepine-10,11-epoxide (CBZ-E), at a rate of 630 pmol/min per mg protein, confirming a major role of CYP3A4 in this reaction. However, no CBZ-E (or any metabolite) was recovered from any whole-cell incubation even though hCYP3A4 cells readily converted testosterone to 6 beta-hydroxytestosterone. This suggests that differences exist between whole-cell and microsomal preparations of lymphoblastoid cells in their ability to metabolize CBZ.

GC-MS determination of amphetamine and methamphetamine in human urine for 12 hours following oral administration of dextro-methamphetamine: lack of evidence supporting the established forensic guidelines for methamphetamine confirmation

Ten human volunteers, naive to amphetamines and divided into two groups of five each, were given an oral dose of 30 mg/70 kg D-methamphetamine in one of two different paradigms: the initial dose at 0930 h or the initial dose at 2130 h. One week later, each subject was crossed over with regard to time but given the same dose. A total of 214 urine specimens were collected either prior to dosing or at each micturition for a 12-h period post dose. Specimens were analyzed on a blind basis for methamphetamine and one of its metabolites, amphetamine, by gas chromatography-mass spectrometry (GC-MS) using coinjection of extracted sample and pentafluoropropionic anhydride and selected-ion monitoring. Approximately 20% of the D-methamphetamine was recovered unchanged from the urine specimens, and 2% was recovered as amphetamine. The mean urine methamphetamine concentration in both groups reached a maximum within 4-6 h and declined thereafter. A residual amount of methamphetamine was found in some predose specimens at the crossover evaluation, reflecting that methamphetamine may be detected in urine for up to 7 days. The amphetamine concentration reached a plateau by 4-6 h. This observation coupled with the finding that all subjects excreted approximately 2% of the methamphetamine dose as amphetamine suggested a saturable process for its biotransformation. Concentrations of both methamphetamine and amphetamine tended to be higher, but were not significantly different, for night administration. Methamphetamine concentrations were consistently greater than the 500-ng/mL cutoff in most post-dosing specimens, whereas amphetamine concentrations generally did not achieve the 200-ng/mL cutoff specified by the Substance Abuse and Mental Health Services Administration (SAMHSA) guidelines for GC-MS confirmation of methamphetamine. Some specimens containing methamphetamine had no amphetamine metabolite. The current guidelines would have resulted in 90.2% of the specimens containing methamphetamine being ruled negative by confirmation following either night or day administration, whereas one subject following the initial day administration and another following night crossover administration would have been judged positive at most time intervals. These findings suggest that the current SAMHSA guidelines select for individual metabolic variations and that GC-MS confirmation of methamphetamine will result in most occasional users being ruled negative following an oral dose of methamphetamine while some will be ruled positive.

Use of a visual panel detection method for drugs of abuse: clinical and laboratory experience with children and adolescents

We evaluated the Triage panel for drugs of abuse, a visual method that simultaneously detects seven distinct drug classes in a single aliquot of urine, by use of 1214 urine specimens obtained from children and adolescent patients whose clinical findings warranted a toxicology evaluation. A total of 295 positive results were confirmed by gas chromatography-mass spectrometry. Additional toxicology investigations were not performed on specimens with negative results unless the clinical findings did not correspond with the urine Triage results. The positive predictive value of the test was found to be > 85% for detection of barbiturates, cannabinoid metabolite, cocaine metabolite, and opiates; for the benzodiazepines the positive predictive value was 77%. Positive predictive values were 53% for amphetamines and 40% for phencyclidine, although only five specimens were available for evaluation of the latter drug. Correlation between clinical findings of patients and results from the Triage test were good except for ingestion of sympathomimetic amines (because of selectivity of the antibodies used in the test for amphetamines) and in patients receiving either antianxiety or antidepressant drugs (some members of these classes of drugs or their metabolites appeared to cross-react with the benzodiazepine test). The primary advantages of the Triage test were the rapid turnaround time, the ease with which a specimen could be processed, and the ability to use rapidly provided information as part of a differential diagnosis.

Anti-phencyclidine monoclonal Fab fragments markedly alter phencyclidine pharmacokinetics in rats

The purpose of these studies was to explore the use of phencyclidine (PCP)-specific high affinity antibodies as a possible treatment for phencyclidine toxicity. High affinity (Kd = 1.8 nM) anti-PCP monoclonal Fab fragments were purified from papain digested anti-PCP immunoglobulin produced in mouse ascites. Control animals (n = 5) received an i.v. bolus dose of 1 mg/kg of PCP, along with a tracer dose of 250 microCi of [3H]PCP. Fab-treated rats (n = 5) also received this PCP dose, but at 2 hr after dosing (when PCP distribution was complete) they received an equimolar dose of anti-PCP Fab (50 mg). Within 5 min after the anti-PCP Fab administration, serum [3H]PCP concentrations increased approximately 60- to 100-fold. Fab treatment caused the [3H]PCP volume of distribution at steady state to decrease from 12.6 +/- 3.0 liters/kg (mean +/- S.D.) in control animals to 0.6 +/- 0.2 liters/kg in the Fab-treated animals (about 5% of control values). Systemic clearance changed from 66.3 +/- 16.9 to 6.8 +/- 2.8 ml/min/kg (about 10% of control values). Because both volume of distribution and systemic clearance decreased to a similar degree, the terminal elimination half-life did not change significantly (3.9 hr in controls vs. 4.9 hr in treated animals, harmonic means). Renal clearance decreased from 1.8 +/- 0.6 to 0.62 +/- 0.17 ml/min/kg after Fab treatment. The anti-PCP Fab caused the percentage of PCP recovered in urine to increase from 2.5 +/- 0.5 to 10.3 +/- 4.7%.(ABSTRACT TRUNCATED AT 250 WORDS)

Daily selenium intake estimates for residents of arsenic-endemic areas

The selenium in the diet of persons in arsenic-endemic areas, high levels of arsenic in the drinking water, was evaluated. The methodology used was that of 24-hr dietary recall. Daily selenium intakes of two rural towns in northern Mexico were found to be similar, approximating 72.9 and 60.6 micrograms. These values were similar to those of a previously arsenic-exposed area from California, Edison community. The Edison participants had a daily selenium intake of 61.8 micrograms. The possible negative effect of selenium to produce differences in reported geographical variation in disease could not be substantiated in this study. Other nutrient intakes, protein and energy were also found similar for communities. Differences were noted in vitamin A intake where one-third the daily requirement was experienced by Mexican participants compared to two-thirds the requirement being satisfied by those participants from Edison.

Health risks from contaminated water: do class and race matter?

The impact of contaminants in water on minorities and economically disadvantaged persons was reviewed. Environmental legislation governing water was summarized as background information against which relevant studies were evaluated. The majority of the available information was anecdotal or case study and did not lend itself to making quantitative comparisons or analyses. However, the data did present certain trends that led to the conclusion that inequities concerning exposure to contaminants in water may exist. The following recommendations were made: current data bases should be analyzed and new data bases created to facilitate assessments of exposure to waterborne contaminants to all populations; an analysis of populations not covered by the Safe Drinking Water Act should be undertaken; a survey should be conducted of the drinking water infrastructure and the results evaluated to identify any impacts to minorities and economically disadvantaged persons; the social, cultural and economic characteristics that influence human exposure to waterborne contaminants need to be identified; and better educational and community outreach programs need to be developed and implemented.

Disposition of a monoclonal anti-phencyclidine Fab fragment of immunoglobulin G in rats

Treatment of drug toxicity is problematic for compounds like phencyclidine (PCP) which have no known antagonists. With the advent of technology for production of large amounts of monoclonal antibody, it is now possible to explore the use of these antibodies as high affinity in vivo antagonists for treatment of PCP overdose. In the current study, the pharmacokinetics of an anti-PCP monoclonal antibody Fab (antigen binding fragment of immunoglobulin G) were determined in adult male Sprague-Dawley rats (n = 5). Each animal was cannulated and dosed with approximately 0.12 g/kg of unlabeled anti-PCP Fab fragments (Kd for PCP = 1.8 +/- 0.27 nM) along with a tracer dose of anti-PCP [3H]Fab. Blood was drawn at predetermined intervals and serum was analyzed for total radioactivity by liquid scintillation spectrometry. Serum and urine were analyzed for intact anti-PCP [3H]Fab after fractionation on a high-performance liquid chromatography molecular weight sizing column followed by quantitation by liquid scintillation spectrometry. The pharmacokinetic parameters for the [3H]Fab in rat serum were a terminal elimination T1/2 of 7.5 hr (harmonic mean), a volume of the central compartment of 0.17 +/- 0.026 liters/kg and a steady-state volume of distribution of 0.55 +/- 0.15 liters/kg (mean +/- S.D.). Systemic and renal clearances were 2.7 +/- 0.9 and 0.47 +/- 0.24 ml/min/kg, respectively. The total amount of the radioactive dose ([3H] Fab plus radioactive catabolic products) appearing in the urine was 51 +/- 11%, whereas urinary excretion of intact [3H]Fab accounted for 21 +/- 15% of the total dose. All animals tolerated the Fab infusion without adverse effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Dose- and time-dependent changes in phencyclidine metabolite covalent binding in rats and the possible role of CYP2D1

We determined whether chronic dosing with phencyclidine (PCP) could affect the in vitro function of liver microsomal enzymes in male Sprague-Dawley rats. PCP chronic dosing of rats (n = 3 per group) for 3 days with 2.5, 10 and 18 mg/kg/day caused a dose-dependent decrease (23, 36 and 53%, respectively) in the ability of the microsomal enzymes to bind covalently PCP metabolites. The 10- and 18-mg/kg/day dosing groups were significantly different from the 3-day saline-infused control group (P < .05). The results from time-dependent dosing studies indicated PCP covalent binding was significantly reduced (P < .05) in rats (n = 3 per group) infused with 18 mg/kg/day of PCP for 1, 2, 3, 4 and 10 days. Subsequently, it returned to near control values in rats infused for 20 days. In parallel with the time-dependent decreases in covalent binding, the concentrations of at least three phase I PCP mono- and dihydroxylated metabolites were also significantly reduced (P < .05) at the earlier time periods of dosing (3 and 10 days), but the rate of their formation returned to near normal values by 20 days of dosing. Total cytochrome P450 content did not differ from the control groups at any of the doses or time points. As dose- and time-dependent decreases in covalent binding suggested a specific metabolic pathway or isoenzyme was affected, we studied the affect on specific isoenzyme pathways. For these studies a series of cytochrome P450 inhibitors were used.(ABSTRACT TRUNCATED AT 250 WORDS)

Health response by questionnaire in arsenic-exposed populations

The health status of populations exposed to arsenic through drinking water was determined by a mailed questionnaire. Participants were selected from three communities located in Nevada with 1977 tap water arsenic levels of approximately 0.1 mg/l and one California community with 1977 levels around 0.39 mg/l. The questionnaire responses were obtained in 1979 from the four exposed communities and compared to those of a Wyoming community whose tap water levels of arsenic were less than 0.001 mg/l in 1979. No difference in health status for gastrointestinal, neurological, musculoskeletal, circulatory and skin disorders was found. The average number of years of consumption given by length of residence was 6-16 years. We conclude that the health status of these arsenic-exposed populations has not been adversely affected.

Effects of cocaine on canines' coronary arteries

Nine canines were anesthetized with pentobarbital and studied by both selective and semiselective coronary artery angiography following intravenous bolus doses of 1,3,5,8, or 10 mg/kg of cocaine. Catheterization was accomplished with a 5 Fr catheter over a 0.035 inch guidewire under fluoroscopic control, and angiograms were obtained by injection of a diatrizoate solution. Digital subtraction angiography (DSA) was performed prior to cocaine administration and at minutes 0.5, 1, 1.5, 3, 5, and, in some cases, minutes 10 and 15 after cocaine administration. The 1 and 3 mg/kg doses of cocaine had no effect on the coronary arteries. The 5 mg/kg dose significantly dilated the coronary arteries. The 8 mg/kg dose produced significant dilation at 30 seconds after cocaine but nonsignificant dilation of the coronary arteries at all other times. The 10 mg/kg dose produced significant dilation at 30 seconds, nonsignificant dilation at 60 seconds followed by significant constriction at 90 seconds after cocaine, which led to immediate death in most animals. The coronary dilation and constriction produced by 10 mg/kg of cocaine could be prevented by either preadministration or postadministration of naloxone, but this did not prevent subsequent death.

Detection of Helicobacter pylori by using the polymerase chain reaction

A 1.9-kb cloned fragment of chromosomal DNA randomly selected from a Helicobacter pylori cloned library was evaluated as a potential probe. The probe detected 19 of 19 H. pylori strains and yielded a specificity of 98.7% when tested against 306 other bacterial strains representing 32 different species. False-positive results with non-H. pylori strains were due to the presence of contaminating vector sequences. A polymerase chain reaction (PCR) assay was developed by using 20-base oligonucleotide primers homologous to a portion of the 1.9-kb fragment. The PCR assay amplified a 203-nucleotide-pair product which was analyzed by agarose gel electrophoresis and Southern hybridization by using a third 20-base 32P-labeled oligonucleotide complementary to a region of DNA between the primers. The PCR assay was 100% sensitive, detecting all 35 H. pylori strains tested, and did not amplify sequences in several closely related species. The assay was sensitive for as little as one copy of the cloned plasmid DNA or 100 H. pylori bacterial cells. To evaluate the PCR assay for clinical samples, gastric biopsy and aspirate specimens were tested by PCR, and the results were compared with those of microbiologic culture and histologic examination. In fresh biopsy specimens, H. pylori sequences were detected by PCR in 13 of 14 (93%) positive tissues and 0 of 19 negative tissues. In gastric aspirate specimens, 11 of 13 (85%) positive tissues were positive by PCR. H. pylori DNA was detected in 1 of 14 aspirate specimens negative by culture, histology, and PCR of the accompanying biopsy tissue. PCR is a rapid, accurate, and sensitive method for the detection of H. pylori.

Intervascular occlusion of canine renal, splenic, and vertebral arteries using electromagnetic field focusing (EFF) probe

Electromagnetic field-focusing (EFF) probe is a precision surgical and interventional tool. Use of the device produces maximum temperature in excess of 1800 degrees C by convergence of radio-frequency (RF) induced eddy currents in biological tissues. Applications of the EFF probe in angioplasty, aneurysm thrombosis, and neurosurgery have been previously reported. In the present work, the EFF probe was guided under fluoroscopic control and used to occlude renal, splenic, and vertebral arteries in dogs. The occlusion was typically accomplished with about one minute of RF power application. Histology of the treated vessel three to six weeks posttreatment showed total occlusion consisting of intimal and subintimal changes and organized thrombus in the lumen. This suggests that the EFF probe in comparison with other procedures is an inexpensive, relatively safe precision interventional tool for performing an occlusion for experimental and therapeutic purposes.

The plasma endorphin, prostaglandin and catecholamine profile of patients with fibrositis treated with cyclobenzaprine and placebo: a 5-month study

During a 5 month, double blind crossover study of the clinical effect of cyclobenzaprine on 7 patients with fibrositis, weekly measurements were done of plasma beta-endorphin (endorphin, prostaglandin E (PGE) and catecholamines). Endorphin levels were normal but varied with tender point tenderness. Mean plasma dopamine and PGE were elevated. Norepinephrine was normal to very high while epinephrine levels were continuously low to normal. We conclude that patients with fibrositis have a neurotransmitter plasma profile like other chronic pain states having stress and increased vasomotor activity with the possible exception of having low circulating epinephrine. This disparity may mark a failure of central nervous system pain modulation in fibrositis.

Furosemide-sensitive Cl transport in bovine retinal pigment epithelium

Bovine retinal pigment epithelium (RPE)-choroid explants were sealed in an Ussing chamber. Typical preparations produced a transepithelial voltage (Ve) of 12 mV (retina side positive) and had an electrical resistance (R) of 300 ohm-cm2. These values can be attributed to the RPE. Furosemide and ouabain reduced the Ve without affecting R when applied to the apical side of the RPE, but had no effect upon Ve and R when applied to the choroidal side. Acetazolamide had no effect upon Ve and R when applied to either side of the tissue. In Cl-free medium, ouabain reduced Ve without affecting R, while furosemide had no effect upon Ve and R. In Na-free medium, ouabain and furosemide had no effect upon Ve and R. Unidirectional isotope flux studies performed under open circuit conditions showed a net retina-to-choroid Cl flux that was abolished by furosemide. These results indicate that bovine RPE possesses a furosemide-sensitive Cl transport system.

Precocious retinal adhesion is affected by furosemide and ouabain

A "precocious" adhesive force develops between the neurosensory retina (NSR) and the retinal pigment epithelium (RPE) 15-30 minutes after eyes are removed from day 15 embryonic chickens and incubated at 37 degrees C. Precocious adhesion has been reported to be blocked by exposure to cold but to be unaffected by exposure to furosemide and ouabain. Since RPE transport is thought to play a major role in the adhesion between the RPE and NSR of adult mammals, and since ouabain and furosemide block RPE transport in embryonic chickens, it has been thought that precocious adhesion in embryonic chickens is not a good model for studying adhesion between the RPE and the NSR of adult mammals. We have found, however, that when steps are taken to ensure that ouabain and furosemide reach the transport sites on RPE apical membrane before precocious adhesion develops, that ouabain and furosemide do affect precocious adhesion.

Topical phenylephrine for mydriasis affects rabbit retinal pigment epithelial transport

Rabbit retinal pigment epithelium (RPE) has an alpha-1 adrenoreceptor that substantially reduces RPE short circuit current (Isc) when stimulated. Since phenylephrine is a potent alpha adrenergic agonist frequently used to obtain pupil dilation, we examined the effect of topically applied phenylephrine for pupil dilation on RPE transport. Naive black dutch-belted rabbits received either one drop of 10% phenylephrine applied at t = 0 and t = 30 min or one drop of 1% cyclopentolate applied at t = 30 min. At t = 50 min, RPE-choroid-sclera explants from these animals were sealed in an Ussing chamber. At t = 60-70 min, 1.4 X 10(-4) M epinephrine was introduced into both sides of the Ussing chamber. The change in Isc produced by epinephrine was measured. The Isc reduction in rabbits receiving phenylephrine was 26% (+/- 5% SD, n = 6). The Isc reduction in rabbits receiving cyclopentolate was 39% (+/- 6% SD, n = 5). These values are significantly different (P less than 0.02, student two-tail t-test). These results indicate that topical phenylephrine reached the RPE in vivo and prestimulated the alpha-1 adrenoreceptors.

Precision surgery with an electromagnetically induced current convergence probe application in aneurysm treatment, angioplasty, and brain tumor resection in in vivo and in vitro models

A hand-held probe, or one introduced through a catheter, rapidly produces an extremely high, tissue-vaporizing temperature in a precisely defined manner enabling surgeons or interventional radiologists to perform angioplasty, thrombose aneurysms, and vaporize tumors. The probe is operated in a near field of an inductive coil, and the current induced in the biologic tissue is converged maximally at the tip of the probe at the resonance frequency of both the inductor and the probe, producing a maximum temperature in excess of 1400 degrees C. Radio-frequency power controls the probe-tip temperature. The operation of the probe is comparable to that of a CO2 or YAG laser and is complementary to laser-surgical techniques. The low cost relative to lasers and simplicity of the device including its disposable components make the prospect of commercialization of this device promising.

Alpha-1 adrenergic receptors on rabbit retinal pigment epithelium

Retinal pigment epithelium (RPE)-choroid-sclera preparations from black, dutch-belted rabbits were sealed in an Ussing chamber. The RPE-generated trans-RPE voltage (Ve) and electrical resistance (R) were monitored. Epinephrine (an alpha and beta adrenergic agonist) reduced Ve by as much as 39% without affecting R. A response to epinephrine was noted at concentrations as low as 1.4 X 10(-7) M. Phenylephrine (an alpha adrenergic agonist) had essentially the same effect as epinephrine at identical concentrations. Clonidine (an alpha-2 adrenergic agonist) had a very slight effect but only at 10(-4) M. Isoproterenol (a beta adrenergic agonist) had no apparent effect upon Ve or R. The RPE response to epinephrine and phenylephrine was blocked by the alpha adrenergic antagonist phentolamine and by the alpha-1 adrenergic antagonist prazosin but not by the alpha-2 adrenergic antagonist yohimbine or by the beta adrenergic antagonist propranolol. Dibutyryl cyclic AMP (in the presence and absence of IBMX) and cyclic GMP (as cGMP and in the dibutyryl form) had no apparent effect upon Ve or R. These results indicate that rabbit RPE possesses an alpha-1 adrenoreceptor which, when stimulated, substantially reduces the RPE generated trans-RPE electrical current.

Initial observations of rabbit retinal pigment epithelium-choroid-sclera preparations

Retinal pigment epithelium (RPE)-choroid-sclera preparations from black dutch-belted rabbits were sealed in an Ussing chamber maintained at 37-39 degrees C. Typical preparations produced a spontaneous voltage (Ve) of 12.5 mV (retina side positive) and possessed an electrical resistance (R) of 350 ohm-cm2. Both of these values can be attributed to the RPE. Ouabain and amiloride diminished the Ve without affecting R. Ouabain was effective when applied to the apical but not to the basolateral side of the preparation, suggesting the presence of a Na-K ATPase on rabbit RPE apical membrane similar to that found in bullfrogs, embryonic chickens, cats and dogs. Dinitrophenol also reduced Ve. Digoxin, furosemide, bumetanide, ethacrynic acid and chlorothiazide had no apparent effect upon Ve and R. The lack of response to furosemide, bumetanide and ethacrynic acid strongly suggests that, unlike RPE from other species, rabbit RPE does not possess Na-dependent Cl transport and/or does not possess furosemide receptors on its apical membrane.

Digoxin cannot account for the reported association of EKG abnormalities and rhegmatogenous retinal detachment

The prevalence of cardiovascular disease (by EKG criteria) in patients with rhegmatogenous retinal detachments has been reported to be more than four times that found in age-matched controls. Adhesion between the retinal pigment epithelium (RPE) and the photoreceptors is facilitated by RPE transport. Because RPE transport is driven by a Na-K ATPase, it has been suggested that the correlation of EKG abnormalities and retinal detachment may be due to clinical use of digoxin, a Na-K ATPase inhibitor frequently given to patients with cardiovascular disease. The prevalence of EKG abnormalities in 299 consecutive patients with primary retinal detachment is about the same as that reported previously. However, 92% of these patients with EKG abnormalities did not take digoxin. Therefore, clinical use of digoxin cannot account for the reported association of EKG abnormalities and rhegmatogenous retinal detachment.

Effects of extended feeding of decocainized erythroxylon coca leaves on growth and selected organs in rats and rabbits

Erythroxylon coca leaves from the Trujillo area of Peru were extracted with methylene chloride to remove most cocaine-like alkaloids. The decocainized leaves were formulated in a honey-water vehicle and fed on a chronic basis to female rats for 32 weeks and female rabbits for 13 weeks. Rabbits fed decocainized leaves at doses of 21 or 210 mg demonstrated no significant change in growth (weight gain) when compared with those receiving vehicle. Histological findings were unremarkable except for fatty islands in the myocardium. Rats fed the decocainized leaves at doses of 1.5 and 15 mg demonstrated no significant changes in weight, whereas those receiving 150 mg had a significant decrease in weight gain when compared with control animals receiving vehicle. Necropsy findings in rats demonstrated pyometra in all groups receiving decocainized leaves as well as in some of the controls. Those rats with pyometra often exhibited endometrial metaplasia. Renal tubular calcification and proteinaceous material were consistently noted at all dose levels. Portal triaditis was also found in the livers of most rats.

Electromagnetic field focusing system in the treatment of brain tumors

The electromagnetic field focusing (EFF) probe, which is based on the principle of eddy current convergence, produces intense pinpoint heat at its point of contact with tissue. This allows cutting and vaporization of tissue and coagulation of vessels. The present experiments were conducted to study heat distribution to the surrounding tissue in brain and phantom and the effect on the brain of vaporization of intracerebral tumors in 19 rabbits. The follow-up period was as long as 47 days. The heating pattern showed a rise of temperature up to 250 degrees C at the probe tip, with minimal or no temperature increase at 2 mm and beyond. Minimal or no change was noted in the surrounding brain after tumor vaporization, indicating that this system would be safe in the vaporization of brain tumors in clinical neurosurgery.

Electromagnetic field focusing (EFF) probe--a new neurosurgical tool

The electromagnetic field focusing (EFF) probe is capable of producing well circumscribed, intense heat at the point of contact with the tissue. Experimental studies were carried out to assess this probe as a neurosurgical tool using 38 rats and 4 mice with mammary carcinoma. The study on the rats included study of the cutting, coagulating and vaporizing effect on brain tissue including study of blood brain barrier disruption and heat dissipation. The study on the mice included the study of vaporizing property of the probe on solid tumours. The probe proved to be an excellent tool for cutting, coagulating and vaporizing purposes with very minimal disruption of blood brain barrier and demonstrated well circumscribed heating pattern. The study indicates that this tool combines the beneficial effect of both the YAG and CO2 laser.

Electromagnetically induced focused heat in the treatment of surgically created aneurysm models

A hand-held radiofrequency (rf) probe of a novel design based on the principle of the induced current convergence was used to treat aneurysm models using focused hyperthermia. Aneurysms were created surgically in rats by a side-to-side anastomosis between the inferior vena cava and the abdominal aorta or by grafting a donor abdominal aorta from one rat onto the abdominal aorta of another rat. Aneurysms were treated by inserting the 0.3-mm diameter probe tip into the fundus and applying the power for brief periods (0.5-1.5 sec) using a foot pedal. Collapse of the fundus was observed as the result of the heat-induced thrombosis. Thermal distribution in the immediate vicinity of the probe as well as the heating rate were measured in a uniformly dielectric phantom and in rat vessels. The aneurysms were histologically examined immediately, three days, and three weeks after the treatment. Complete obliteration of the aneurysms and patency of the parent arteries were confirmed. Partial integrity of the vessels around the lesion was also confirmed.

Methods compared for determining glutathione peroxidase activity in blood

We compared four methods for determination of glutathione peroxidase (EC 1.11.1.9) activity, using blood samples from 52 healthy volunteers. Two methods depended on direct assay of the amount of glutathione remaining at specific time intervals; the two indirect methods involved measuring the rate of disappearance of NADPH. We assessed the precision and reproducibility of each method. One of the indirect assays proved to be far superior to the other methods. Results of each of the methods were correlated with one another. We present the normal reference intervals for glutathione peroxidase activity for all four methods.