Effects of electric fields on proton transport through water chains

Molecular dynamics simulations on quantum energy surfaces are carried out to study the effects of perturbing electric fields on proton transport (PT) in protonated water chains. As an idealized model of a hydrophobic cavity in the interior of a protein the water molecules are confined into a carbon nanotube (CNT). The water chain connects a hydrated hydronium ion (H3O+) at one end of the CNT and an imidazole molecule at the other end. Without perturbing electric fields PT from the hydronium proton donor to the imidazole acceptor occurs on a picosecond time scale. External perturbations to PT are created by electric fields of varying intensities, normal to the CNT axis, generated by a neutral pair of charges on the nanotube wall. For fields above approximately 0.5 VA, the hydronium ion is effectively trapped at the CNT center, and PT blocked. Fields of comparable strength are generated inside proteins by nearby polar/charged amino acids. At lower fields the system displays a rich dynamic behavior, where the excess charge shuttles back and forth along the water chain before reaching the acceptor group on the picosecond time scale. The effects of the perturbing field on the proton movement are analyzed in terms of structural and dynamic properties of the water chain. The implications of these observations on PT in biomolecular systems and its control by external perturbing fields are discussed.

Duration of peginterferon therapy in acute hepatitis C: a randomized trial

Spontaneous resolution of acute hepatitis C virus infection cannot be predicted, and chronic evolution of the disease occurs in a majority of cases. To assess the efficacy and safety of peginterferon alpha-2b administered for 8, 12, or 24 weeks in patients with acute hepatitis C virus infection a total of 161 patients were identified with acute hepatitis C virus infection. Of these, 30 patients refused treatment but were retained in the study as a nonrandomized comparison group. Of the 131 patients who consented to treatment, 29 patients spontaneously resolved, leaving 102 patients randomly assigned to peginterferon alpha-2b (1.5 microg/kg) for 8 weeks (group A; n=34), 12 weeks (group B; n=34), and 24 weeks (group C; n=34). The primary end point was sustained virologic response. An intent-to-treat analysis was used for efficacy and safety end points. Sustained virologic response was achieved in 23/34 (67.6%), 28/34 (82.4%), and 31/34 (91.2%) of patients in groups A, B, and C, respectively; all had undetectable hepatitis C virus RNA 48 weeks after the end of therapy. Treatment for 8 or 12 weeks was effective in genotypes 2, 3, and 4, whereas genotype 1 required 24 weeks of therapy. The 8- and 12-week regimens were associated with fewer adverse events compared with the 24-week regimen. In conclusion, peginterferon alpha-2b effectively induces high sustained virologic response rates in patients with acute hepatitis C virus infection, thus preventing development of chronic hepatitis C. Duration of treatment should be further optimized based on genotype and rapid virologic response at week 4.

Integration of digital signal processing technologies with pulsed electron paramagnetic resonance imaging

The integration of modern data acquisition and digital signal processing (DSP) technologies with Fourier transform electron paramagnetic resonance (FT-EPR) imaging at radiofrequencies (RF) is described. The FT-EPR system operates at a Larmor frequency (L(f)) of 300MHz to facilitate in vivo studies. This relatively low frequency L(f), in conjunction with our approximately 10MHz signal bandwidth, enables the use of direct free induction decay time-locked subsampling (TLSS). This particular technique provides advantages by eliminating the traditional analog intermediate frequency downconversion stage along with the corresponding noise sources. TLSS also results in manageable sample rates that facilitate the design of DSP-based data acquisition and image processing platforms. More specifically, we utilize a high-speed field programmable gate array (FPGA) and a DSP processor to perform advanced real-time signal and image processing. The migration to a DSP-based configuration offers the benefits of improved EPR system performance, as well as increased adaptability to various EPR system configurations (i.e., software configurable systems instead of hardware reconfigurations). The required modifications to the FT-EPR system design are described, with focus on the addition of DSP technologies including the application-specific hardware, software, and firmware developed for the FPGA and DSP processor. The first results of using real-time DSP technologies in conjunction with direct detection bandpass sampling to implement EPR imaging at RF frequencies are presented.

A proposed curvilinearity index for quantifying airflow obstruction

BACKGROUND

Though forced expiratory volume in the first second (FEV(1)) is the primary indicator of airway obstruction, curvilinearity in the expiratory flow-volume curve is used to support the quantitative assessment of obstruction via FEV(1). Currently there is no available index to quantify a pathological contour of curvilinearity.

STUDY PURPOSE

We propose a "curvature" index (k(max)) and compare FEV(1) values to the index with a sequential sample of spirometry data.

METHODS

The hyperbolic function b(0)Q + b(1)Q V + b(2)V = 1 (in which Q = flow rate, V = volume, and b(0), b(1), and b(2) are estimated from the patient's flow-volume data) is fit to a fixed segment of the descending phase of the expiratory flow-volume curve. A previously developed biomechanical interpretation of this relationship associates the coefficient b(1) with the rate of airway-resistance-increase as exhaled volume increases. A global curvature index k(max)=b(1)/2(b(0)b(2)+b(1)) is defined to quantify the curvilinearity phenomenon. We used statistics software to determine the k(max) of spirometry data from 67 sequential patients, and to determine the relationship of k(max) to FEV(1).

RESULTS

Individual k(max) estimates appeared to correspond well with the degree of curvilinearity observed and were related in an exponential manner to FEV(1).

CONCLUSIONS

We defined a curvature index to quantify the curvilinearity phenomenon observed in the expiratory limb of flow-volume loops from patients with obstructive lung disease. This index uses data from a major segment of the flow-volume curve, and our preliminary data indicate an exponential relationship with FEV(1). This new index allows the putative association between curvilinearity and obstructive lung disease to be examined quantitatively in clinical practice and future studies.

Spectral signal-to-noise ratio and resolution assessment of 3D reconstructions

Measuring the quality of three-dimensional (3D) reconstructed biological macromolecules by transmission electron microscopy is still an open problem. In this article, we extend the applicability of the spectral signal-to-noise ratio (SSNR) to the evaluation of 3D volumes reconstructed with any reconstruction algorithm. The basis of the method is to measure the consistency between the data and a corresponding set of reprojections computed for the reconstructed 3D map. The idiosyncrasies of the reconstruction algorithm are taken explicitly into account by performing a noise-only reconstruction. This results in the definition of a 3D SSNR which provides an objective indicator of the quality of the 3D reconstruction. Furthermore, the information to build the SSNR can be used to produce a volumetric SSNR (VSSNR). Our method overcomes the need to divide the data set in two. It also provides a direct measure of the performance of the reconstruction algorithm itself; this latter information is typically not available with the standard resolution methods which are primarily focused on reproducibility alone.

Virus maturation: dynamics and mechanism of a stabilizing structural transition that leads to infectivity

For many viruses, the final stage of assembly involves structural transitions that convert an innocuous precursor particle into an infectious agent. This process -- maturation -- is controlled by proteases that trigger large-scale conformational changes. In this context, protease inhibitor antiviral drugs act by blocking maturation. Recent work has succeeded in determining the folds of representative examples of the five major proteins -- major capsid protein, scaffolding protein, portal, protease and accessory protein -- that are typically involved in capsid assembly. These data provide a framework for detailed mechanistic investigations and elucidation of mutations that affect assembly in various ways. The nature of the conformational change has been elucidated: it entails rigid-body rotations and translations of the arrayed subunits that transfer the interactions between them to different molecular surfaces, accompanied by refolding and redeployment of local motifs. Moreover, it has been possible to visualize maturation at the submolecular level in movies based on time-resolved cryo-electron microscopy.

High-performance liquid chromatography method for determination of N-glucuronidation of 4-aminobiphenyl by mouse, rat, and human liver microsomes

A simple and sensitive method for determination of the N-glucuronidation activity of mouse, rat, and human liver microsomes toward the carcinogenic arylamine 4-aminobiphenyl (4-ABP) using high-performance liquid chromatography with ultraviolet detection has been developed. The method uses chemically synthesized 4-ABP-N-glucuronide (4-ABP-G) as a standard for method validation. Validation was done with respect to specificity, linearity, precision, accuracy, and lower limits of detection. The method was specific since there were no interference peaks from the reaction matrix. The calibration curve for 4-ABP-G was linear from 50 to 5000 pmol/200 microl with R2=0.999. The newly developed method has good precision and accuracy. The intra- and interday precisions were less than 5 and 10%, respectively, and the highest values for intra- and interday accuracies were -4.6 and -12%, respectively. The lower limit of detection was 10 pmol/200 microl. The developed method was used to determine the glucuronidation activity of mouse, rat, and human liver microsomes. Human liver microsomes were the most active in 4-ABP glucuronidation (344.1 pmol/min/mg) followed by rats (30.6 pmol/min/mg) and then mice (12.3 pmol/min/mg). Human UGT1A4 supersomes were much more active than UGT1A9 (184.4 mol/min/mg versus 25.2 mol/min/mg). These results are consistent with those of earlier studies that used the radioactive [C14]UDPGA.

Dilated cardiomyopathy in Erb-b4-deficient ventricular muscle

The neuregulin receptor tyrosine kinase Erb-b4, initially linked to early cardiac development, is shown here to play a critical role in adult cardiac function. In wild-type mice, Erb-b4 protein localized to Z lines and to intercalated disks, suggesting a role in subcellular and intercellular communications of cardiomyocytes. Conditional inactivation of erb-b4 in ventricular muscle cells led to a severe dilated cardiomyopathy, characterized by thinned ventricular walls with eccentric hypertrophy, reduced contractility, and delayed conduction. This cardiac dysfunction may account for premature death in adult erb-b4-knockout mice. This study establishes a critical role for Erb-b4 in the maintenance of normal postnatal cardiac structure and function.

Association Between Functional Status and Use and Effectiveness of Beta-Blocker Prophylaxis in Elderly Survivors of Acute Myocardial Infarction

OBJECTIVES

To examine whether physical and cognitive impairments explain low use of beta-blockers in elderly patients and whether functionally impaired older adults have improved survival if a beta-blocker is prescribed at hospital discharge.

DESIGN

Cross-sectional and retrospective cohort study.

SETTING

Acute care hospitals in the United States.

PARTICIPANTS

National cohort of 45,370 elderly acute myocardial infarction survivors, with no chart-documented contraindications to beta-blocker treatment.

MEASUREMENTS

The main outcome measures were beta-blocker prescription at hospital discharge and 1-year survival.

RESULTS

Fifty percent (n=22,683) of eligible patients were prescribed a beta-blocker at discharge. Older age and functional impairments (incontinence, mobility impairment, and cognitive impairment) were independently associated with decreased use of beta-blockers. The odds ratios for prescribing a beta-blocker at hospital discharge were 0.82 (95% confidence interval (CI)=0.77-0.86), 0.63 (95% CI=0.56-0.71), and 0.40 (95% CI=0.32-0.51) for persons with one, two, and three impairments, respectively, compared with those with no impairments. In survival analysis, patients prescribed a beta-blocker were 21% less likely than nonrecipients to die within 1 year of follow-up (relative risk=0.79, P=.0001). Similar survival benefit was observed in patients with and without functional impairments.

CONCLUSION

This study shows a strong association between functional impairment and the use of beta-blockers after acute myocardial infarction in elderly patients. The results suggest that increasing use of beta-blockers in this group provides an opportunity to improve outcomes.

Effects of Cytochalasin D on Electrical Restitution and the Dynamics of Ventricular Fibrillation in Isolated Rabbit Heart

Cytochalasin D in Rabbit Ventricle.

INTRODUCTION

Cytochalasin D (cyto-D) has been used as an excitation-contraction uncoupler during optical mapping studies. However, its effects on action potential duration restitution (APDR) and dynamics during ventricular fibrillation (VF) are unclear.

METHODS AND RESULTS

Langendorff-perfused rabbit hearts (N = 6) were immersed in a tissue chamber. Transmembrane potential was recorded using glass microelectrodes. APD measured to 90% repolarization (APD90) was used to construct the APDR curve. During regular pacing at 300-msec cycle length, increasing concentrations of cyto-D resulted in progressively prolonged APD90 (131 +/- 26 msec, 171 +/- 14 msec, and 177 +/- 14 msec) and steepened maximum slope of the APDR curve (1.1 +/- 0.2, 1.3 +/- 0.2, and 1.6 +/- 0.4 for control, 5 micromoles, and 10 micromoles, respectively; P < 0.01). Resting membrane potential, AP amplitude, and maximum dV/dt did not change. Cyto-D lengthened VF cycle length and APD90, and steepened the maximum slope of the APDR curve. However, cyto-D did not significantly change the diastolic interval. The dominant frequency of pseudoelectrocardiogram progressively decreased with increasing concentrations of cyto-D (15.2 +/- 0.6 Hz, 11.1 +/- 2.4 Hz, and 9.8 +/- 3.2 Hz for control, 5 micromoles, and 10 micromoles, respectively; P < 0.01). Sustained (>1 min) VF was repeatedly inducible at baseline and with 5 or 10 micromoles of cyto-D.

CONCLUSION

Continuous perfusion of cyto-D at 5 or 10 micromoles prolonged APD90, steepened APDR slope, and reduced dominant frequency in rabbit ventricles. Cyto-D at these concentrations allowed induction of sustained VF.

Influence of a 3-day regimen of azithromycin on the disposition kinetics of cyclosporine A in stable renal transplant patients

Some macrolide antibiotics have been shown to produce significant drug-drug interactions through the inhibition of cytochrome P450 (CYP) enzymes. In renal transplant patients these interactions pose potentially serious problems for the safe administration of cyclosporine A (CSA), a substrate of CYP3A4. The effects of azithromycin on CSA disposition kinetics were evaluated in eight stable renal transplant patients. Patients had been stabilized on individualized doses of CSA which remained unchanged throughout the study. Azithromycin was administered for 3 days. Baseline measurements of CSA disposition kinetics were taken prior to azithromycin treatment (study day 2) and after 3 days (study day 5) of azithromycin treatment (500mg/day, orally). The key parameters of interest were the area under the CSA blood concentration versus time curve (AUC) measured for 24h after the morning dose of CSA on both days 2 and 5, and the C(max) values of CSA. The geometric mean ratios (GMRs) of those parameters (day 5/day 2) and their 90% confidence intervals (90% CI) were 107 (98,116) and 119 (104,136), respectively. The 7% increase in exposure level and 19% increase in peak plasma concentration are not likely to be clinically significant. It is concluded that azithromycin (500mg/dayx3 days) does not alter the disposition kinetics of CSA in a clinically significant way, and that CSA dosage adjustments are not warranted in renal transplant patients taking these two drugs together.

Simultaneous analysis of nicotine, nicotine metabolites, and tobacco alkaloids in serum or urine by tandem mass spectrometry, with clinically relevant metabolic profiles

BACKGROUND

Assessment of nicotine metabolism and disposition has become an integral part of nicotine dependency treatment programs. Serum nicotine concentrations or urine cotinine concentrations can be used to guide nicotine patch dose to achieve biological concentrations adequate to provide the patient with immediate relief from nicotine withdrawal symptoms, an important factor in nicotine withdrawal success. Absence of nicotine metabolites and anabasine can be used to document abstinence from tobacco products, an indicator of treatment success.

METHODS

The procedure was designed to quantify nicotine, cotinine, trans-3'-hydroxycotinine, anabasine, and nornicotine in human serum or urine. The technique required simple extraction of the sample with quantification by HPLC-tandem mass spectrometry.

RESULTS

The procedure for simultaneous analysis of nicotine, its metabolites, and tobacco alkaloids simultaneously quantified five different analytes. Test limit of quantification, linearity, imprecision, and accuracy were adequate for clinical evaluation of patients undergoing treatment for tobacco dependency. The test readily distinguished individuals who had no exposure to tobacco products from individuals who were either passively exposed or were abstinent past-tobacco users from those who were actively using a tobacco or nicotine product.

CONCLUSIONS

Nicotine, cotinine, trans-3'-hydroxycotinine, nornicotine, and anabasine can be simultaneously and accurately quantified in either serum or urine by HPLC-tandem mass spectrometry with imprecision <10% at physiologic concentrations and limits of quantification ranging from 0.5 to 5 micro g/L. Knowledge of serum or urine concentrations of these analytes can be used to guide nicotine replacement therapy or to assess tobacco abstinence in nicotine dependency treatment. These measurements are now an integral part of the clinical treatment and management of patients who wish to overcome tobacco dependence.

Genetic heterogeneity of small ruminant lentiviruses involves immunodominant epitope of capsid antigen and affects sensitivity of single-strain-based immunoassay

The pol and gag gene fragments of small ruminant lentivirus field isolates collected in the last decade in Italy were amplified, sequenced, and analyzed. Phylogenetic analysis revealed that the majority of ovine isolates form a distinct cluster more similar to caprine lentivirus prototypes than to the visna virus prototype. These findings confirm and extend those reported by Leroux et al. (Arch. Virol., 142:1125-1137, 1997). Moreover, we observed that a variable region of Gag, included in the fragment analyzed, corresponded to one of the three major capsid antigen epitopes, which suggests that the antibody response to this epitope may be type specific. To test this hypothesis, two recombinant peptides, derived from the Icelandic prototype K1514 and this novel genotype, were expressed and used in an enzyme-linked immunosorbent assay to screen a panel of ovine and caprine sera collected from different geographical locations in Italy. Several sera reacted in a type-specific manner, indicating that in a diagnostic setting the combination of at least these two type-specific peptides is necessary to cover a wide range of infections. Additionally, these results support the hypothesis of cross-species transmission based on the phylogenetic analysis described above. This has implications for the control and eradication of small ruminant lentivirus infections.

Functional conservation of subfamilies of putative UDP-N-acetylgalactosamine:polypeptide N-acetylgalactosaminyltransferases in Drosophila, Caenorhabditis elegans, and mammals. One subfamily composed of l(2)35Aa is essential in Drosophila

The completed fruit fly genome was found to contain up to 15 putative UDP-N-acetyl-alpha-d-galactosamine:polypeptide N-acetylgalactosaminyltransferase (GalNAc-transferase) genes. Phylogenetic analysis of the putative catalytic domains of the large GalNAc-transferase enzyme families of Drosophila melanogaster (13 available), Caenorhabditis elegans (9 genes), and mammals (12 genes) indicated that distinct subfamilies of orthologous genes are conserved in each species. In support of this hypothesis, we provide evidence that distinctive functional properties of Drosophila and human GalNAc-transferase isoforms were exhibited by evolutionarily conserved members of two subfamilies (dGalNAc-T1 (l(2)35Aa) and GalNAc-T11; dGalNAc-T2 (CG6394) and GalNAc-T7). dGalNAc-T1 and novel human GalNAc-T11 were shown to encode functional GalNAc-transferases with the same polypeptide acceptor substrate specificity, and dGalNAc-T2 was shown to encode a GalNAc-transferase with similar GalNAc glycopeptide substrate specificity as GalNAc-T7. Previous data suggested that the putative GalNAc-transferase encoded by l(2)35Aa had a lethal phenotype (Flores, C., and Engels, W. (1999) Proc. Natl. Acad. Sci. U. S. A. 96, 2964-2969), and this was substantiated by sequencing of three lethal alleles l(2)35Aa(HG8), l(2)35Aa(SF12), and l(2)35Aa(SF32). The finding that subfamilies of GalNAc-transferases with distinct catalytic functions are evolutionarily conserved stresses that GalNAc-transferase isoforms may serve unique biological functions rather than providing functional redundancy, and this is further supported by the lethal phenotype of l(2)35Aa.

Cytochrome P450 isozymes involved in the metabolism of phenol, a benzene metabolite

Benzene is an occupational and environmental toxicant. The major health concern for humans is acute myelogenous leukemia. To exert its toxic effects, benzene must be metabolized by cytochrome P450 to phenol and subsequently to catechol and hydroquinone. Previous research has implicated CYP2E1 in the metabolism of phenol. In this study the cytochrome P450 isozymes involved in the metabolism of phenol were examined in hepatic and pulmonary microsomes utilizing chemical inhibitors of CYP2E1, CYP2B, and CYP2F2 and using CYP2E1 knockout mice. CYP2E1 was found to be responsible for only approximately 50% of 20 microM phenol metabolism in the liver. This suggests another isozyme(s) is involved in hepatic phenol metabolism. In pulmonary microsomes both CYP2E1 and CYP2F2 were significantly involved.

Sex differences in cardiac catheterization: the role of physician gender

CONTEXT

Many studies indicate that women are less likely than men to undergo cardiac procedures after an acute myocardial infarction (AMI), raising concerns of sexual bias in clinical care. However, no data exist regarding the relationship between patient sex, physician sex, and use of cardiac procedures.

OBJECTIVE

To determine whether sex differences in cardiac catheterization after AMI were greater when patients were treated by male attending physicians compared with female attending physicians.

DESIGN, SETTING, AND PATIENTS

Analysis of data from the Cooperative Cardiovascular Project, a retrospective medical record review. A total of 104 >231 Medicare fee-for-service beneficiaries who were hospitalized in US acute care hospitals for an AMI between January 1994 and February 1995.

MAIN OUTCOME MEASURE

Use of cardiac catheterization within 60 days of admission, compared between the 4 groups of patient sex-physician sex combinations.

RESULTS

Women underwent fewer cardiac catheterizations than men when treated by either male physicians (38.6% vs 50.8%; P =.001) or female physicians (34.8% vs 45.8%; P =.001). Sex differences in procedure use were not greater when a patient and physician were of different sexes (P for interaction =.85). After potential confounders in multivariable analysis were accounted for, women were less likely to undergo cardiac catheterization (risk ratio, 0.90 [95% confidence interval (CI), 0.88-0.92]), regardless of the treating physician's sex. Patients treated by male physicians were more likely to undergo cardiac catheterization (risk ratio, 1.06 [95%CI, 1.02-1.10]) than those treated by female physicians, regardless of patient sex.

CONCLUSIONS

Women who have had an AMI undergo a cardiac catheterization less often than men, whether treated by a male or female physician. These results suggest that factors other than sexual bias by male physicians toward women account for sex differences in cardiac procedure use.

Bioterrorism. Implications for the occupational and environmental health nurse

1. Bioterrorism is the intentional release of a biological agent--bacterial, viral, or genetically altered--to instill fear or create chaos, massive casualities, illness, and death in humans, animals, or plants. 2. The threat of bioterrorism is real. Although every community is vulnerable, terrorists seek densely populated, highly visible targets. 3. Occupational and environmental health nurses must to be able to recognize and report signs and symptoms of an early bioweapons outbreak in their workplaces and communities. Only thorough preparedness and planning will result in effective mitigation and treatment. 4. The Bioterrorism Readiness Plan (at http://www.apic.org and http://www.CDC.gov/ncidod/hip) is a template for health care professionals to help plan a realistic response to bioterrorism. It serves as a tool for successful collaboration and communication among all disciplines and public health agencies for the best possible outcomes.

Genetic variability in the development of pulmonary tolerance to inhaled pollutants in inbred mice

After repeated exposures, many individuals develop tolerance to the adverse health effects of inhaled pollutants. Pulmonary tolerance can be characterized as the ability of the lung to withstand the adverse actions of a toxic compound after repeated exposures. To determine whether genetic background is important to the development of pulmonary tolerance to inhaled pollutants, 11 inbred strains of mice were exposed once (1x) or for 5 consecutive days (5x) to 1.0 mg/m(3) of zinc oxide (ZnO). Development of pulmonary tolerance was assessed by measuring polymorphonuclear leukocyte and protein levels in bronchoalveolar lavage fluid and comparing the responses of the 1x and 5x groups. Significant interstrain variation in polymorphonuclear leukocyte and protein responses was observed between the groups with 1x and 5x exposures, which indicates that genetic background has an important role in the development of pulmonary tolerance. The BALB/cByJ strain and the DBA/2J strain were the most tolerant and nontolerant, respectively. The CByD2F1/J offspring were uniformly nontolerant. The development of tolerance was also investigated in BALB/cByJ and DBA/2J mice after 1x and 5x exposure to ozone and aerosolized endotoxin. Discordance in the phenotypic pattern of pulmonary tolerance among strains after exposure to ZnO, ozone, and endotoxin suggested that different mechanisms may be responsible for the development of pulmonary tolerance to these agents.

Electrochromatographic separation of proteins

We have developed a modified electrochromatography system which minimizes Joule heating at electric field strengths up to 125 V/cm. A non-linear equilibrium model is described which incorporates electrophoretic mobility, hydrodynamic flow velocity, and an electrically induced concentration polarization at the surface of the stationary phase. This model is able to provide useful estimates of protein retention time and velocity in a column packed with Sephadex gel and subjected to an electric field. A correlation of electrophoretic mobility of peptide and proteins with respect to their charge, molecular mass, and asymmetry enables the selection of solute target molecules for electrochromatographic separations. Good separation of protein mixtures have been obtained.

Acute myocardial infarction in the elderly: differences by age

OBJECTIVES

We evaluated the clinical characteristics and outcomes of elderly patients hospitalized with acute myocardial infarction (AMI) to describe differences by age.

BACKGROUND

Elderly patients with AMI are perceived as a homogeneous population, though the extent by which clinical characteristics vary among elderly patients has not been well described.

METHODS

Data from 163,140 hospital admissions of Medicare beneficiaries age > or =65 years between 1994 and 1996 with AMI at U.S. hospitals were evaluated for differences in clinical characteristics and mortality across five age-based strata (in years): 65 to 69, 70 to 74, 75 to 79, 80 to 84 and > or =85.

RESULTS

Older age was associated with a greater proportion of patients with functional limitations, heart failure, prior coronary disease and renal insufficiency and a lower proportion of male and diabetic patients. Of note, the proportion of patients presenting with chest pain within 6 h of symptom onset, and with ST-segment elevation, was lower in each successive age group. Thirty-day mortality rates were higher in older age groups (65 to 69: 10.9%, 70 to 74: 14.1%, 75 to 79: 18.5%, 80 to 84: 23.2%, > or =85: 31.2%, p = 0.001 for trend). The effect of age persisted but was attenuated after adjustment for differences in patient characteristics; similar trends were observed for one-year mortality.

CONCLUSIONS

Our data indicate significant age-associated differences in clinical characteristics in elderly patients with AMI, which account for some of the age-associated differences in mortality. The practice of grouping older patients together as a single age group may obscure important age-associated differences.

Antibody responses to HIV-1 antigens are higher in HIV-1(+) intravenous drug users than in HIV-1(+) homosexuals

Immune responses to HIV-1 infection of 42 HIV-1-positive asymptomatic intravenous drug users (IVDUs) were compared with those of 135 HIV-1-infected asymptomatic homosexual men in the present study. Twenty-five HIV-1(-) individuals served as normal controls. The comparison included antibody responses to five computer-predicted epitopes of HIV-1 p17, and viral proteins gp120 and p24 as well as p17. Major immunophenotypes were also investigated. Results showed that antibody responses to the five epitopes were significantly higher in the IVDUs. A larger proportion of the IVDUs, with respect to that of homosexuals, showed positive antibody responses to p24 and p17, respectively. However, the antibody response to gp120 was similar between the two cohorts. Immunophenotyping showed that HIV-1(+) homosexuals had higher profiles in most of the major subsets than did the IVDUs, especially in the total count of lymphocytes, absolute numbers of CD3+ cells and CD8+ cells. It appeared that the HIV-1(+) IVDU cohort had higher antibody responses to most of the viral antigens, but had lower levels of lymphocyte subsets in comparison with HIV(+) homosexuals.

Recent risk rates of occupational fatalities, injuries, and illnesses in U.S. industries and their use in planning environmental controls

Cost/benefit justifications are now required for new environmental regulations. The benefit is related to the difference between the currently existing health risk rate and the rate corresponding to the proposed permissible exposure limit. The adoption of many permissible exposure limits has been delayed by the lack of supporting human data and the use of animal data instead. This has resulted in difficulties and controversies not likely to be resolved soon. Meanwhile, a review of currently existing occupational risk rates can provide a perspective for best use of available funds. Tables and text are presented summarizing published occupational risk data for 1996. Transportation incidents cause 42 percent of occupational fatalities. Proper selection and training of workers and proper work rules should be cost-effective, also especially in other listed dangerous industries. Annual risk rates per hundred workers for occupational nonfatal injuries and illness were surprisingly high: for manufacturing 10.6, and for the entire private sector, 7.4. Seven worst industries ranged from 25.8 to 30.3. The benefit from controlling such high rates is almost the same whether the final rate is 10(-3) or 10(-6). Thus, specifying a good low-cost procedure that reduces most of the initial risk can provide the lowest cost/benefit ratio, eligible for priority use of available funds.

Organ-specific differences in 8-oxoguanosine glycosylase (OGG1) repair following acute treatment with benzo[a]pyrene

The lung has been shown to be a target organ for the deleterious effects of Benzo[a]pyrene (B[a]P), regardless of the route of exposure. 8-hydroxy-2'-deoxyguanosine (oxo8dG) is a mutagenic lesion formed in DNA following exposure to B[a]P. The objective of this study was to determine the capacity of different organs to repair oxo8dG following intraperitoneal (i.p.) treatment with B[a]P. Male Spraque-Dawley rats were administered 20 mg/kg B[a]P i.p., 2 times/day for 5 days. A 26% decrease in the capacity to remove oxo8dG was observed in lung tissue at 72 hours and recovered 20% above control values at 120 hours. The capacity of the liver and kidney remained at baseline for all time points analyzed. A 7-fold increase in oxo8dG was observed in the lung at 72 hours. This study demonstrates that organ-specific differences exist in the capacity to remove oxo8dG and further demonstrates the susceptibility of lung tissue to the effects of B[a]P.

Lognormal model for determining dose-response curves from epidemiological data and for health risk assessment

A practical method is proposed for determining human dose-response curves based on reasonable assumptions and simplifications. The epidemiological data needed are the fractions of the population suffering an adverse response from exposures to two or more patterns of fluctuating concentrations of a pollutant, and the statistical parameters of each pattern. The method calculates the two parameters of the threshold type dose-response curve of the pollutant, represented by a cumulative lognormal distribution. This distribution was derived from a reasonable statistical model. The calculation does not require any arbitrary safety factors and yields central values. The dose-response parameters then may be used to calculate the health risk rate of exposure to any other fluctuating concentration pattern. Another method is proposed to select appropriate threshold limit values (TLVs) using calculations involving these parameters. Examples are given to illustrate the calculations. Results with hypothetical data gave apparently reasonable results. They showed the importance not only of the geometric mean concentration but also of the geometric standard deviations of both the concentrations and of the dose-response curve, that greatly influence the results. It is believed that results of useful accuracy should be obtained. Health risk rates are readily understood. They are useful for cost-benefit calculations. Relative rates can be used to compare the hazards of different operations and different plants. The method may make possible the development of standards specifying maximum allowable risk rates.

Cytochromes P450 involved with benzene metabolism in hepatic and pulmonary microsomes

Benzene is an occupational hazard and environmental toxicant found in cigarette smoke, gasoline, and the chemical industry. The major health concern associated with benzene exposure is leukemia. The toxic effects of benzene are dependent on its metabolism by the cytochrome P450 enzyme system. Previous research has identified CYP2E1 as the primary P450 isozyme responsible for benzene metabolism at low concentrations, whereas CYP2B1 is involved at higher concentrations. Our studies using microsomal preparations from human, mouse, and rat indicate that CYP2E1 is the P450 isozyme primarily responsible for benzene metabolism in lung and in liver. CYP2B isozymes have little involvement in benzene metabolism by either lung or liver. Our results also indicate that isozymes of the CYP2F subfamily may play a role in benzene metabolism by lung.