Location and Setting of the Mars InSight Lander, Instruments, and Landing Site

Knowing precisely where a spacecraft lands on Mars is important for understanding the regional and local context, setting, and the offset between the inertial and cartographic frames. For the InSight spacecraft, the payload of geophysical and environmental sensors also particularly benefits from knowing exactly where the instruments are located. A ~30 cm/pixel image acquired from orbit after landing clearly resolves the lander and the large circular solar panels. This image was carefully georeferenced to a hierarchically generated and coregistered set of decreasing resolution orthoimages and digital elevation models to the established positive east, planetocentric coordinate system. The lander is located at 4.502384°N, 135.623447°E at an elevation of -2,613.426 m with respect to the geoid in Elysium Planitia. Instrument locations (and the magnetometer orientation) are derived by transforming from Instrument Deployment Arm, spacecraft mechanical, and site frames into the cartographic frame. A viewshed created from 1.5 m above the lander and the high-resolution orbital digital elevation model shows the lander is on a shallow regional slope down to the east that reveals crater rims on the east horizon ~400 m and 2.4 km away. A slope up to the north limits the horizon to about 50 m away where three rocks and an eolian bedform are visible on the rim of a degraded crater rim. Azimuths to rocks and craters identified in both surface panoramas and high-resolution orbital images reveal that north in the site frame and the cartographic frame are the same (within 1°).

Revision Total Knee Arthroplasty in a Patient with Bilateral Below-the-Knee Amputation: A Case Report

UPDATE

This article was updated on January 27, 2016. The byline, which had previously read "M.G. Williams, MBChB, and J. Phillips, MBBS, FRCS," now reads "M.G. Williams, MBChB, J. Phillips, MBBS, FRCS, and K. Eyres, MD, FRCS(Tr&Orth)." In addition, the name, address, and e-mail address for Dr. Eyres have been added to the address block at the end of the article.An erratum has been published: JBJS Case Connect. 2016 Mar 23;6(1):e22.

CASE

We report the case of a patient with bilateral below-the-knee amputation who had a periprosthetic fracture around a total knee arthroplasty. The fracture was managed with a revision total knee arthroplasty. We discuss the rationale for revision surgery, the surgical techniques, and the postoperative rehabilitation. Follow-up at one year demonstrated maintenance of the pretrauma functional status.

CONCLUSION

In selected patients with a periprosthetic fracture, we believe that revision of a total knee arthroplasty may be considered as an option rather than an above-the-knee amputation or an arthrodesis.

Genotyping FOXG1 Mutations in Patients with Clinical Evidence of the FOXG1 Syndrome

Rett syndrome is a well-defined neurodevelopmental disorder comprising characteristic clinical features of gait abnormalities, loss of purposeful hand movements, stereotypies, and autistic features. Mutations in the FOXG1 gene have been associated with a congenital variant of Rett syndrome. This is a report on the outcome of routine genetic testing to identify FOXG1 mutations in a patient population presenting with features of the FOXG1 syndrome, an entity thought to be distinct, but similar, to the congenital variant of Rett syndrome. We performed PCR and sequencing analysis of FOXG1 in MECP2-negative patients (n = 12) with phenotypic features of FOXG1 syndrome. FOXG1 MLPA analysis was also carried out. No mutations in FOXG1 were identified using this approach. We were unable to identify patients with features of the FOXG1 syndrome as having aberrant FOXG1 gene loci. Clinical notes are inherently subjective and may lack sufficient detail to reliably identify those with a syndromal spectrum. The results call into question the objectivity of outlining a complex syndrome according to clinical manifestations and highlight the need for a greater involvement of molecular diagnostic techniques in the diagnosis of Rett-like disorders.

Specialty Elastomer Modifiers with Isotactic Propylene Crystallinity for Polypropylene Modification

Specialty elastomers possessing isotactic propylene crystallinity are a novel class of polyolefins made possible by advances in metallocene polymerization. These polymers contain a propylene rich component endowed with isotactic crystallinity, and the balance of the composition is ethylene with other alpha olefins. Typical molecular weight of these elastomers is greater than 100,000. These polymers, when used as modifiers for toughening polypropylene (PP) homopolymers demonstrate improved impact strength to stiffness balance, enhanced low temperature toughness and improved impact to flow balance over conventional ethylene alpha-olefin modifiers.

Morphological features of the blends were determined using Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM). The detailed morphological characterization indicates that the isotactic propylene crystallinity species of the elastomers function by localizing themselves at the interface of the polypropylene matrix and the ethylene-alpha olefin component of the modifier. We believe that such a tailored localization is effective because of the simultaneous co-crystallization of the isotactic propylene crystallinity elastomers with the isotactic PP matrix, and the thermodynamic compatibility of the propylene crystallinity species with the other elastomeric components of the modifier.

Development of a sensitive bioanalytical method for determination of PNU-83757 in rat, monkey and human plasma: from LC-UV to LC-MS/MS

To support pre-clinical pharmacokinetic/toxicokinetic (PK/TK) evaluation, a sensitive bioanalytical method for determination of N-cyano-N'-(tert-pentyl)-N"-(3-pyridinyl) guanidine (PNU-83757), in rat and monkey plasma was required. Although the UV response of PNU-83757 was quite decent and the extracts using solid phase extraction (SPE) were very selective and concentrated, the best limit of quantitation (LOQ) achieved was 0.4 ng ml(-1) using 0.5 ml plasma for extraction and 2 ng ml(-1) using 0.1 ml plasma for extraction, which was insufficient for PK/TK evaluation at lower doses. When using liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometric detection (LC-APCI-MS/MS, positive ions) and SPE, a LOQ of 0.045 ng ml(-1) for PNU-83757 was reached. Quantitation was accomplished using the precursor --> product ion combinations of m/z 232 --> 162 for PNU-83757 and m/z 236 --> 166 for the internal standard, [2H(4)]PNU-83757, in the multiple reaction monitoring mode. This method has been successfully utilized for PK/TK evaluation in pre-clinical studies and proved to have sufficient sensitivity to determine plasma concentrations for a dose level as low as 1 microg kg(-1) day(-1) in the rat and monkey. Further improvement of this method by using electrospray mass spectrometric detection (LC-ESI-MS/MS, positive ions) and automated membrane SPE, gave an LOQ of 0.008 ng ml(-1), and allowed analysis of large numbers of samples to support clinical PK studies in microg dose levels.

Sequence-structure homology recognition by iterative alignment refinement and comparative modeling

Our approach to fold recognition for the fourth critical assessment of techniques for protein structure prediction (CASP4) experiment involved the use of the FUGUE sequence-structure homology recognition program (http://www-cryst.bioc.cam.ac.uk/fugue), followed by model building. We treat models as hypotheses and examine these to determine whether they explain the available data. Our method depends heavily on environment-specific substitution tables derived from our database of structural alignments of homologous proteins (HOMSTRAD, http://www-cryst.bioc.cam.ac.uk/homstrad/). FUGUE uses these tables to incorporate structural information into profiles created from HOMSTRAD alignments that are matched against a profile created for the target from multiple sequence alignment. In addition, environment-specific substitution tables are used throughout the modeling procedure and as part of the model evaluation. Annotation of sequence alignments with JOY, to reflect local structural features, proved valuable, both for modifying hypotheses, and for rejecting predictions when the expected pattern of conservation is not observed. Our stringency in rejecting incorrect predictions led us to submit a relatively small number of models, including only a low number of false positives, resulting in a high average score.

Sociotropy and autonomy: preliminary evidence for construct validity using TAT narratives

In this investigation, we evaluated the construct validity of sociotropy and autonomy as assessed by the revised Personal Style Inventory (PSI; Robins et al., 1994). Stories given to 6 cards of the Thematic Apperception Test (Murray, 1943) were coded for need for Achievement (McClelland, Atkinson, Clark, & Lowell, 1953) and need for Affiliation (Heyns, Veroff, & Atkinson, 1958). These scores were correlated with PSI Sociotropy and Autonomy, along with their component subscales. The construct validity of Sociotropy, Autonomy, and 5 of 6 component subscales were supported as hypoth sized. Consistent with past research, there was no support for the construct validity of the Perfectionism/Self-Criticism subscale of Autonomy. In addition, separate analyses by gender suggested that the construct validity of sociotropy may be greater for women than for men. The results represent an important finding in that nonquestionnaire measures of interpersonal and achievement-related concerns were found to support the validity of the PSI, a need identified by the questionnaire's authors.

An assessment of asbestos body formation in extrapulmonary sites: liver and spleen

STUDY OBJECTIVES

Asbestos bodies (ABs) form as asbestos fibers become coated by a cellular iron- and protein-rich matrix. ABs have been reported in lymph nodes and a few extrapulmonary sites, but no data exist as to their formation outside of the lung. It is not clear whether the AB found in these extrapulmonary areas have been transported as mature structures from the lung or formed at the extrapulmonary site. This study was designed to determine if ABs are produced in extrapulmonary sites. The guinea pig efficiently forms ferruginous bodies in the lung and so it was chosen as a model to test the coating efficiency of amosite asbestos fibers in lung, liver and spleen.

DESIGN

Sized amosite asbestos (5 mg) was administered either endotracheally into lung (n = 2) or directly into liver (n = 4) and spleen (n = 4) of healthy 10-week-old male guinea pigs. The lung, liver and splenic tissues were removed at 40 and 180 days post inoculation and were examined histologically for the presence of AB via light microscopy. Uncoated fibers isolated from the tissues were characterized by electron microscopy. The coating efficiency was calculated as a ratio of uncoated/coated fibers per organ.

RESULTS

The coating efficiency ratios of fibers that were collected at 40 days post-injection from the individual sites were: lung - 350:1, liver - 4200:1, and spleen - 220,000:1. At 6 months post-injection the ratios for the individual sites consisted of: lung - 176:1, liver - 11,000:1, and spleen - 1000:1.

CONCLUSION

This study indicates that AB can be formed in extrapulmonary sites and that the coating efficiency in the lung is much greater than that within the liver or spleen.

Toxicokinetics in drug development: an overview of toxicokinetic application in the development of PNU-101017, an anxiolytic drug candidate

The importance of toxicokinetics in the drug development has been identified in the last decade. The main objectives of toxicokinetics in general are to define the drug bioavailability, dose proportionality, gender differences, and species differences in pharmacokinetics and metabolism, from which the target organ toxicity can be predicted and the safety doses in the first human clinical trial can be established. Toxicokinetic studies may also serve as a tool for the toxicologic pathologist in understanding models used for predicting and assessing drug-related toxic response. Toxicokinetics/toxicodynamics are critical to investigating the toxicological mechanism and understanding the comparative toxicity between animals and humans. This report presents an overview of the application of toxicokinetics and its impact in the drug development of PNU-101017, a drug candidate for the treatment of anxioety. Serial specifically designed toxicokinetic studies identified a steep dose-response relationship between the clinical signs and PNU-101017 serum or CSF concentrations, characterized the centrally mediated respiratory depression as the toxicity leading to the lethality, and demonstrated marked species differences in the sensitivity to the toxic effects. These findings lead to a termination of PNU-101017 development due to the safety concern in humans.

Using in vitro iron deposition on asbestos to model asbestos bodies formed in human lung

Recent studies have shown that iron is an important factor in the chemical activity of asbestos and may play a key role in its biological effects. The most carcinogenic forms of asbestos, crocidolite and amosite, contain up to 27% iron by weight as part of their crystal structure. These minerals can acquire more iron after being inhaled, thereby forming asbestos bodies. Reported here is a method for depositing iron on asbestos fibers in vitro which produced iron deposits of the same form as observed on asbestos bodies removed from human lungs. Crocidolite and amosite were incubated in either FeCl(2) or FeCl(3) solutions for 2 h. To assess the effect of longer-term binding, crocidolite was incubated in FeCl(2) or FeCl(3) and amosite in FeCl(3) for 14 days. The amount of iron bound by the fibers was determined by measuring the amount remaining in the incubation solution using an iron assay with the chelator ferrozine. After iron loading had been carried out, the fibers were also examined for the presence of an increased amount of surface iron using X-ray photoelectron spectroscopy (XPS). XPS analysis showed an increased amount of surface iron on both Fe(II)- and Fe(III)-loaded crocidolite and only on Fe(III)-loaded amosite. In addition, atomic force microscopy revealed that the topography of amosite, incubated in 1 mM FeCl(3) solutions for 2 h, was very rough compared with that of the untreated fibers, further evidence of Fe(III) accumulation on the fiber surfaces. Analysis of long-term Fe(III)-loaded crocidolite and amosite using X-ray diffraction (XRD) suggested that ferrihydrite, a poorly crystallized hydrous ferric iron oxide, had formed. XRD also showed that ferrihydrite was present in amosite-core asbestos bodies taken from human lung. Auger electron spectroscopy (AES) confirmed that Fe and O were the only constituent elements present on the surface of the asbestos bodies, although H cannot be detected by AES and is presumably also present. Taken together for all samples, the data reported here suggest that Fe(II) binding may result from ion exchange, possibly with Na, on the fiber surfaces, whereas Fe(III) binding forms ferrihydrite on the fibers under the conditions used in this study. Therefore, fibers carefully loaded with Fe(III) in vitro may be a particularly appropriate and useful model for the study of chemical characteristics associated with asbestos bodies and their potential for interactions in a biosystem.

Enantiospecific determination of PNU-83894 and its major metabolite, PNU-83892, in plasma, and its application to the characterization of the enantioselective pharmacokinetics of PNU-83894 in the dog

A chiral method for the simultaneous analysis of the (+)- and (-)-enantiomers of PNU-83894 and its metabolite, PNU-83892, in plasma was developed to characterize the enantioselective pharmacokinetics of PNU-83894, a potential anticonvulsant candidate. The method involves solid-phase extraction (phenyl column) of the enantiomers from plasma followed by direct enantioselective separation on a beta-cyclodextrin HPLC chiral column and UV detection at 230 nm. The linear range for this method was found to be 12.5 ng/ml to 5.00 microg/ml and the intra- and inter-assay precision and accuracy for each enantiomer were <11% in all cases. The validity of this assay was also demonstrated by its application to the pharmacokinetic evaluation of PNU-83894 in the dog.

Asbestosis and small cell lung cancer in a clutch refabricator

OBJECTIVES

To present a case of asbestosis and small cell lung cancer caused by asbestos in a clutch refabricator.

METHODS

Exposed surfaces of used clutches similar to those refabricated in the worker's workplace were rinsed, and the filtrate analysed by analytical transmission electron microscopy. Tissue samples were also analysed by this technique.

RESULTS

Numerous chrysotile fibres of respirable dimensions and sufficient length to form ferruginous bodies (FBs) were detected from rinsed filtrates of the clutch. Bronchoalveolar lavage fluid contained many FBs, characteristic of asbestos bodies. Necropsy lung tissue showed grade 4 asbestosis and a small cell carcinoma in the right pulmonary hilum. Tissue analysis by light and analytical electron microscopy showed tissue burdens of coated and uncoated asbestos fibres greatly exceeding reported environmental concentrations (3810 FBs/g dry weight and 2,080,000 structures > or = 0.5 micron/g dry weight respectively). 72% Of the cores were identified as chrysotile.

CONCLUSIONS

Clutch refabrication may lead to exposure to asbestos of sufficient magnitude to cause asbestosis and lung cancer.

X-ray structure of human stromelysin catalytic domain complexed with nonpeptide inhibitors: implications for inhibitor selectivity

Effective inhibitors of matrix metalloproteinases (MMPs), a family of connective tissue-degrading enzymes, could be useful for the treatment of diseases such as cancer, multiple sclerosis, and arthritis. Many of the known MMP inhibitors are derived from peptide substrates, with high potency in vitro but little selectivity among MMPs and poor bioavailability. We have discovered nonpeptidic MMP inhibitors with improved properties, and report here the crystal structures of human stromelysin-1 catalytic domain (SCD) complexed with four of these inhibitors. The structures were determined and refined at resolutions ranging from 1.64 to 2.0 A. Each inhibitor binds in the active site of SCD such that a bulky diphenyl piperidine moiety penetrates a deep, predominantly hydrophobic S'1 pocket. The active site structure of the SCD is similar in all four inhibitor complexes, but differs substantially from the peptide hydroxamate complex, which has a smaller side chain bound in the S'1 pocket. The largest differences occur in the loop forming the "top" of this pocket. The occupation of these nonpeptidic inhibitors in the S'1 pocket provides a structural basis to explain their selectivity among MMPs. An analysis of the unique binding mode predicts structural modifications to design improved MMP inhibitors.

Tissue burden of asbestos in nonoccupationally exposed individuals from east Texas

BACKGROUND

The potential for asbestos exposure among members of the general population is appreciable, considering its widespread use in many products. This study examined tissue burden of asbestos in such a population.

METHODS

A group of 33 individuals who had no work history of occupational exposure to asbestos were included in the study. Tissue sections from areas adjacent to those sites sampled for digestion were found to be without ferruginous bodies (FB) or histopathology consistent with asbestos-induced changes. All individuals had 20 or less FBs per gram of digested wet lung, a number considered to reflect general population levels. Tissue analysis of uncoated fiber burden was carried out by analytical electron microscopy. There was a trend of a higher likelihood of FB and asbestos fiber content correlated with age.

RESULTS

The data are not consistent with the findings that chrysotile is readily found in lung tissue from the general population, in that none was found in 19 of the cases. It was almost as likely that one would find anthophyllite (12 of 33 cases) in this study. The commercial amphiboles (amosite and crocidolite) were occasionally found in the tissue from the general population and, when observed, were few in numbers. Twenty-six of the patients had no FBs and ten had no uncoated asbestos fibers within the limits of detectability in this study.

CONCLUSIONS

The total tissue burden of asbestos in this study is much less than earlier reported observations from other general populations.

Effects of early captopril administration after thrombolysis on regional wall motion in relation to infarct artery blood flow

OBJECTIVES

To determine whether early administration of captopril lessens infarct zone regional wall motion abnormalities when infarct artery blood flow is abnormal.

BACKGROUND

The interaction between angiotensin-converting enzyme (ACE) inhibitor therapy, ventricular function and infarct artery blood flow has not been well described.

METHODS

A total of 493 patients aged < or = 75 years with first infarctions, presenting within 4 h of symptom onset, were randomized to receive 6.25 mg captopril, increasing to 50 mg t.d.s. or a matching placebo 2.1+/-0.4 h after commencing intravenous streptokinase (1.5 x 10(6) U over 30 to 60 min). Trial therapy was stopped 48 h prior to angiography at 3 weeks, to determine regional wall motion and infarct artery flow.

RESULTS

There were no differences in ejection fractions or end-systolic volumes between patients randomized to receive captopril and those randomized to receive a placebo. Among patients with anterior infarction (n = 216), randomization to captopril resulted in fewer hypokinetic chords (40+/-13; vs. 44+/-13; p=0.028) and a trend toward fewer chords >2 SD below normal (26+/-17 vs. 30+/-17; p=0.052) in the infarct zone. In patients randomized to receive captopril who had anterior infarction and Thrombolysis in Myocardial Infarction (TIMI) 0-2, flow there were fewer hypokinetic chords (44+/-12 vs. 50+/-9; p=0.043) and a trend toward fewer chords >2 SD below normal (33+/-15 vs. 39+/-13; p=0.057). Patients receiving captopril who had anterior infarction and corrected TIMI frame counts > 27 had fewer hypokinetic chords (42+/-13 vs. 46+/-12; p=0.015) and fewer chords >2 SD below normal (27+/-17 vs. 32+/-17; p= 0.047). Captopril had no effect in patients with inferior infarction. There were 20 late cardiac deaths (median follow-up 4 years) in the captopril group and 35 in the placebo group (p=0.036).

CONCLUSIONS

Randomization to receive captopril 2 h after streptokinase improved regional wall motion at 3 weeks. The greatest benefit was seen in patients with anterior infarction particularly when infarct artery blood flow is reduced.

Lack of asbestos contamination of paraffin

OBJECTIVE

To investigate possible asbestos contamination of paraffin and migration by asbestos fibers during the tissue-embedding process.

DESIGN

Three sample categories were included in the study: (1) commercially available paraffin samples; (2) procedural control samples, which were prepared by processing the paraffin through the use of standard solvents and instruments; and (3) samples taken from areas adjacent to embedded tissue and evaluated for migration of asbestos from the tissue into the surrounding paraffin. The analysis of collected material from all samples was performed with analytical transmission electron microscopy.

RESULTS

Only one extremely small tremolite fiber was found in any of the commercially available samples of paraffin. No asbestos fibers were found either in the procedural control samples or in the samples taken adjacent to the embedded lung tissue.

CONCLUSIONS

First, it was extremely unlikely that any of the commercial paraffin samples would have skewed data due to embedded tissue. Second, the processing and instrumentation was not found to contribute asbestos material to the paraffin during the preparations. Finally, embedded tissue that contained high numbers of fibers, both uncoated fibers and asbestos bodies, did not contribute asbestos to the adjacent paraffin.

Carcinogenic implications of the lack of tremolite in UICC reference chrysotile

Using light and electron microscopy analysis, as well as electron diffraction, and energy-dispersive x-ray analysis, an aliquot of UICC chrysotile B was analyzed with special attention given to any tremolite contamination. Polarized light microscopy, with its limit of detection of approximately 1 micron when using dispersion staining, revealed chrysotile as the only fibrous asbestos component. Analytical electron microscopy at 333,000x of more than 20,000 consecutive fibers showed only the tubular morphology characteristic of chrysotile. These findings highlight that when this sample was used for exposure disease induced in animal models correlates with chrysotile-induced pathology, and does not support an explanation based on the "amphibole hypothesis." Thus, chrysotile should be considered as having the biologic ability to produce cancers, including mesotheliomas, based on the extensive use of this material as a standard reference material.

Pharmacokinetics of the individual enantiomers of cis-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]-benzamide monohydrochloride (U-54494A) in the dog

U-54494A, a racemic mixture of two enantiomers, is being developed in racemic form as an anticonvulsant drug candidate. A comparative pharmacokinetic study with intravenous and oral administration of the two individual enantiomers to the dog was conducted to evaluate the potential enantioselective pharmacokinetics of U-54494. Following i.v. administration, the (-)- and (+)-enantiomers showed no significant differences in plasma clearance (0.84 +/- 0.11 versus 0.86 +/- 0.06 l/hr/kg) and terminal elimination half-life (11.2 +/- 2.7 versus 8.0 +/- 2.6 hr) for the parent drug. However, the AUC of intact drug was two-fold lower with two-fold shorter elimination half-life following the oral administration for the (+)-enantiomer as compared to the (-)-enantiomer. Higher plasma levels of the four metabolites were also observed for the (+)-than for the (-)-enantiomer, particularly after oral administration. These results suggested that the (+)-enantiomer appeared to be more extensively metabolized by first-pass effect than the (-)-enantiomer after oral dosing, and as a result, oral bioavailability for the (+)-enantiomer is only one half of that for its antipode (12.0 +/- 1.5% versus 26 +/- 9%).

Species-dependent enantioselective pharmacokinetics of PNU-103017, a pyrone HIV protease inhibitor

PNU-103017, 4-Cyano-N-(3-(cyclopropyl(5,6,7,8,9,10-hexahydro-4-hydroxy- 2-oxo-2H-cycloocta(b) pyran-3-yl)methyl)phenyl)-benzenesulfonamide, is a selective HIV aspartyl protease inhibitor under evaluation as a potential oral treatment of Acquired Immunodeficiency Diseases. PNU-103017 is a racemic mixture of two enantiomers, designated PNU-103264 (R-) and PNU-103265 (S-). Stereoselective pharmacokinetics of the two enantiomers of PNU-103017 were observed in the dog, rat, and human after single and multiple dose administration of the racemate and were apparently species-dependent. Mean enantiomeric ratios of plasma concentrations (R-/S-) at each time point were greater than 1 in the dog, ranging from 1.22 to 3.06, but less than 1 in the rat and in the human, ranging from 0.44 to 0.80 and 0.23 to 0.73, respectively. A trend towards increased or decreased (farther from 1:1, R-/S-) enantiomeric ratio of plasma concentrations with time after each administration was also observed. The enantiomeric ratio remained unchanged after multiple dose administration in the rat, dog, and human although enzyme induction and increased plasma clearance were observed for both enantiomers.

Mutagenesis, biochemical characterization and X-ray structural analysis of point mutants of bovine chymosin

Chymosin B point mutants, A115T and G243D (chymosin A), were expressed in Escherichia coli and Trichoderma reesei respectively, characterized biochemically, crystallized and studied by X-ray analysis at 2.3 and 2.8 angstroms resolutions respectively. The three-dimensional structures showed that the mutations gave rise to local conformational changes only when compared with that of chymosin B. Kinetic analysis of the A115T mutant with a six residue synthetic peptide revealed a reduction in Km with respect to the wild type, possibly caused by the small local changes in the vicinity of S1 and S3. Although, kinetic analyses of the G243D mutant using the short substrate showed reduced catalytic activity, use of a 15 residue substrate based on residues 98-112 of kappa-casein, the natural substrate, revealed an increase in the kcat compared with chymosin B, probably a consequence of the charge introduced that may interact with the substrate between P4 and P8.

Stereospecific determination of an HIV aspartyl protease inhibitor, PNU-103017, in rat, dog and human plasma using a Pirkle-concept high-performance liquid chromatographic column

A sensitive stereospecific high-performance liquid chromatographic assay for the quantitation of the enantiomers of 4-cyano-N-(3-(cyclopropyl-(5,6,7,8,9,10-hexahydro-4-hydroxy-2-oxo-2H- cycloocta(b)pyran-3-yl)methyl)phenyl)benzenesulfonamide (PNU-103017) (I), an HIV protease inhibitor, in plasma of rat, dog and human was developed. The procedure involved an acetonitrile-aided protein precipitation followed by solid-phase extraction (SPE) of I from plasma into ethanol. Stereospecific separation was accomplished on a Pirkle-concept chiral column (Regis S,S-Whelk-01, 250x4.6 mm I.D.) with a mobile phase of absolute ethanol-0.1% acetic acid in hexane (30:70, v/v). The eluate was monitored by UV absorbance (295 nm). Linear calibration curves were obtained in the range of 0.2 to 500 microM, with a lower limit of quantitation of 0.1-0.2 microM for both enantiomers in either rat, dog or human plasma. Intra- and inter-assay precision and assay accuracy were demonstrated to be acceptable for the stereoselective pharmacokinetic analysis of I in plasma.

Development of insulin resistance in 3T3-L1 adipocytes

Insulin resistance is a manifestation of both diabetes mellitus and obesity. However, the mechanism is still not clearly identified. Herein, we describe a procedure that allows us to evaluate the development of insulin resistance in 3T3-L1 adipocytes. Under these conditions, we show that the concentration of insulin required for 50% desensitization of glucose transport activity is 100 pM; maximal desensitization could be achieved with 1 nM. This demonstrates for the first time that 3T3-L1 adipocytes develop insulin resistance in response to physiologically relevant concentrations of insulin. Glucose (or glucosamine), in addition to insulin, was required to establish desensitization. The expression of GLUT4 protein decreased by 50% with exposure to 10 nM insulin. The dose-dependent loss of GLUT4 was similar to the dose dependence for insulin-resistant transport activity. Translocation in the presence of acute insulin was apparent, but the extent of recruitment directly reflected the decrease in GLUT4 protein. GLUT4 mRNA also declined, but the ED50 was approximately 5 nM. Together, these data suggest that the loss of GLUT4 protein likely underlies the cause of desensitization. However, the loss of GLUT4 protein did not correlate with the loss in GLUT4 mRNA suggesting post-translational control of GLUT4 expression.

Occult ascending aortic rupture in the presence of an air bag

A patient presented to the emergency department after a high-speed decelerating-type motor vehicle accident. Due to activation of his air bag device, the patient was without significant obvious injury. Upon evaluation in the emergency department he was also without any radiographic or physical signs of serious injury. In the ensuing 24 hours, severe chest pain developed, and subsequent aortography demonstrated a tear of his ascending aorta just distal to the root. Although occult injury to the aorta and great vessels does occur in a small percentage of patients, it is quite rare. However, with the advent of air bags, in the absence of associated injuries, signs, and symptoms, a high index of suspicion must be entertained in decelerating-type accidents to diagnose occult injury to the aorta and great vessels.

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.