Biomedical subjects

D Echeverria

Publications and source records attributed to D Echeverria.

27 records · Page 2Linked to original sources

PubMed1993

Renal effects of naphtha exposure among automotive workers.

As part of a study on health effects of naphtha exposure, the association between naphtha exposure and urinary excretion of total protein, albumin, beta-N-acetyl-D-glucosaminidase (beta-NAG), and beta 2-microglobulin was assessed prospectively over 1 year among workers at an automotive plant that used naphtha to calibrate fuel injectors. Participants consisted of 248 workers who provided spot urine samples in June 1988 among whom 181 workers provided specimens again in June 1989. Naphtha air concentrations at the plant ranged from 6 to 790 mg/m3 and the length of exposure ranged from 0.8 to 7.3 years. In both 1988 and 1989, the overall distribution of the four measures of renal function appeared consistent with that of an unexposed population. In cross-sectional analyses, there were no statistically significant associations in the expected direction between cumulative or recent naphtha exposure and the measures of renal function. In longitudinal analyses, the change in beta-NAG was positively associated with the change in recent naphtha exposure (P = .009). The effect of the naphtha exposure during 1 workweek was assessed among 17 workers who provided urine samples Monday preshift, Monday postshift, and Friday postshift. No associations were found. The results of this study do not provide strong evidence of naphtha-associated renal effects at these levels of exposure.

Adult↗

PubMed1991

Acute behavioural comparisons of toluene and ethanol in human subjects.

A comparison of toluene and ethanol (EtOH) induced changes in central nervous system (CNS) function and symptoms were evaluated in two studies, and when possible the effects of toluene were expressed in EtOH equivalent units. The toluene concentrations were 0, 75, and 150 ppm, bracketing the American Conference of Governmental Industrial Hygienists threshold limit value (ACGIH TLV) of 100 ppm. The socially relevant EtOH doses were 0.00, 0.33, and 0.66 g EtOH/kg body weight, equivalent to two and four 3.5% 12 ounce beers. Forty two paid college students were used in each study. In the first study, subjects were exposed to toluene and an odour masking agent menthol (0.078 ppm) for seven hours over three days. In the second study EtOH or a placebo was administered at 1530 across three days also in the presence of menthol. Verbal and visual short term memory (Sternberg, digit span, Benton, pattern memory), perception (pattern recognition), psychomotor skill (simple reaction time, continuous performance, symbol-digit, hand-eye coordination, finger tapping, and critical tracking), manual dexterity (one hole), mood (profile on mood scales (POMS), fatigue (fatigue checklist), and verbal ability were evaluated at 0800, 1200, and 1600. Voluntary symptoms and observations of sleep were collected daily. A 3 x 3 latin square design evaluated solvent effects simultaneously controlling for learning and dose sequence. An analysis of variance and test for trend were performed on am-pm differences reflecting an eight hour workday and on pm scores for each solvent, in which subjects were their own control Intersubject variation in absorbance was monitored in breath. A 5 to 10% decrement was considered meaningful if consistent with a linear trend at p less than 0.05. At 150 ppm toluene, losses in performance were 6.0% for digit span, 12.1% for pattern recognition (latency), 5% for pattern memory (number correct), 6.5% for one hole, and 3% for critical tracking. The number of headaches and eye irritation also increased in a dose-response manner. The greatest effect was found for an increasing number of observations of sleep. A range of 2 to 7% decrements suggest the ACGIH TLV of 100 ppm toluene may be a good estimate of the biological threshold supporting a re-evaluation of the TLV. At 0.66 g EtOH/kg body weight symptoms and performance decrements were 6.6% for digit span, 9.2% for pattern recognition, 4.0% for continuous performance, 7.9% for symbol-digit, 16.5% for finger tapping, 6.2% for critical tracking, and 5.2% for the one hole test. The EtOH equivalents at 150 ppm toluene for digit span (0.56g EtOH/kg/body weight), the latency for pattern recognition (0.66 g EtOH kg body weight), and the one hole element "move" (0.37 g EtOH kg body weight) show that the first two measures would be affected at or above the 50 mg% blood alcohol concentration. This concentration is recognised as the lowest alcohol concentration associated with increased numbers of automobile accidents. The results suggest that EtOH may be a useful acute standard to compare the effects of various industrial solvents and support investigating an association between exposure to solvents and increased risk to safety in industry.

Adolescent↗

PubMed1989

Acute neurobehavioural effects of toluene.

An acute inhalation chamber study of 42 college students was performed to investigate the relation between exposure to 0, 75, and 150 ppm of toluene and changes in central nervous system function and symptoms. Paid subjects were exposed for seven hours over three days. Verbal and visual short term memory (Sternberg, digit span, Benton, pattern memory); perception (pattern recognition); psychomotor skill (simple reaction time, continuous performance, digit symbol, hand-eye coordination, finger tapping, and critical tracking); manual dexterity (one hole); mood (profile of mood scales (POMS]; fatigue (fatigue checklist); and verbal ability were evaluated at 0800, 1200, and 1600 hours. Voluntary symptoms and observations of sleep were collected daily. An analysis of variance and test for trend was performed on the difference and score for each concentration reflecting an eight hour workday where each subject was their own control. A 3 x 3 Latin square study design evaluated toluene effects simultaneously, controlling for learning across the three days and the solvent order. Intersubject variation in solvent uptake was monitored in breath and urine. A 5-10% decrement in performance was considered significant if it was consistent with a linear trend at p less than 0.05. Adverse performance at 150 ppm toluene was found at 6.0% for digit span, 12.1% for pattern recognition (latency), 5.0% for pattern memory (number correct), 6.5% for one hole, and 3.0% for critical tracking. The number of headaches and eye irritation also increased in a dose response manner. The greatest effect was found for an increasing number of observations of sleep. Overall, no clear pattern of neurobehavioural effects was found consistent with the type 1 central nervous system as classified by the World Health Organisation. Subtle acute effects, however, were found just below and above the ACGIH TLV of 100 ppm toluene, supporting the position that the guideline be lowered since the biological threshold of behavioural effects may be comparable with the TLV.

Adolescent↗

PubMed1980

Increase in the size of soluble brain adenylate cyclase with activation by guanosine 5'-(beta, gamma-imino)triphosphate.

Adenylate cyclase solubilized from bovine brain with Lubrol 12A9 or Triton X-100 can be resolved into two forms by gel filtration or sucrose density gradient centrifugation. The activity of one of these forms is not stimulatable by guanosine 5'-(beta, gamma-imino)triphosphate (Gpp(NH)p) and represents the "basal" adenylate cyclase activity. In Lubrol 12A9, this form has Mr = 330,000 (total, protein and detergent) and Mr (protein only) = 265,000. The other form of adenylate cyclase can be activated by Gpp(NH)p and has a smaller molecular weight: Mr (protein and detergent) = 293,000, Mr (protein only) = 199,000. Upon activation by Gpp(NH)p, the size of the Gpp(NH)p-responsive form of adenylate cyclase increases: Mr (protein and detergent) = 330,000, Mr (protein only) = 251,000. Similar values were obtained in Triton X-100. The kinetics of heat inactivation are different in the two forms of the enzyme. Both forms are activated about 2-fold by 5 mM MnCl2. Neither of the forms is associated with measurable low Km GTPase activity. On the basis of these studies, we propose that the catalytic unit (C) of adenylate cyclase and the guanine nucleotide regulatory unit (G/F) may exist in solution in the following rapid equilibrium: (formula: see text) We propose that activation by Gpp(NH)p stabilizes the C . G/F complex and this accounts for the greater mass of the enzyme measured after activation with Gpp(NH)p. The size of the enzyme which represents the basal activity is very similar to that of the C . G/F complex. We suggest, therefore, that the basal activity is the result of a stable association of the catalytic unit with the guanine nucleotide regulatory site.

Adenylyl Cyclases↗

PubMedDate not supplied

Behavioral effects of low-level exposure to elemental Hg among dentists.

Exposure thresholds for health effects associated with elemental mercury (Hg degree) exposure were examined by comparing behavioral test scores of 19 exposed (mean urinary Hg = 36 micrograms/l) with those of 20 unexposed dentists. Thirty-six micrograms Hg/l is 7 times greater than the 5 micrograms Hg/l mean level measured in a national sample of dentists. To improve the distinction between recent and cumulative effects, the study also evaluated porphyrin concentrations in urine, which are correlated with renal Hg content (a measure of cumulative body burden). Subjects provided an on-site spot urine sample, were administered a 1-h assessment consisting of a consent form, the Profile of Mood Scales, a symptom and medical questionnaire, and 6 behavioral tests: digit-span, symbol-digit substitution, simple reaction time, the ability to switch between tasks, vocabulary, and the One Hole Test. Multivariate regression techniques were used to evaluate dose-effects controlling for the effects of age, race, gender and alcohol consumption. A dose-effect was considered statistically significant below a p value of 0.05. Significant urinary Hg dose-effects were found for poor mental concentration, emotional lability, somatosensory irritation, and mood scores. Individual tests evaluating cognitive and motor function changed in the expected directions but were not significantly associated with urinary Hg. However, the pooled sum of rank scores for combinations of tests within domains were significantly associated with urinary Hg, providing evidence of subtle preclinical changes in behavior associated with Hg exposure. Coproporphyrin, one of three urinary porphyrins altered by mercury exposure, was significantly associated with deficits in digit span and simple reaction time.(ABSTRACT TRUNCATED AT 250 WORDS)

Affect↗

PubMedDate not supplied

Analyzing multivariate neurobehavioral outcomes in occupational studies: a comparison of approaches.

Neurobehavioral studies often employ test batteries and confront issues of multiple testing and comparability between batteries. We have organized our battery of 12 tests into areas of neurobehavioral function to reduce the number of reported results, provide greater statistical power, and improve interpretability of the results. We explored several different organizational and statistical methods of creating summary scores including a priori groupings based upon clinical experience and factor analysis. We compared the sensitivity of these summary scores to performance changes associated with exposure to styrene in the manufacture of reinforced plastics. Our results demonstrated dramatic increases in power to detect exposure related changes compared to using individual test scores. Furthermore, the various methods provided generally compatible and comparable results. We encourage other neurobehavioral investigators to pursue and refine this approach.

Adolescent↗

PubMedDate not supplied

Behavioral effects of low-level exposure to Hg0 among dental professionals: a cross-study evaluation of psychomotor effects.

A Across-study design was used to evaluate the sensitivities of five psychomotor tasks previously used to assess preclinical effects of low-level Hg0 (urinary < or =55 microg/l). Pooling dental professional subject populations from six studies conducted over the last 6 years, a larger study population was obtained with a high degree of uniformity (N = 230). The five psychomotor tests were: Intentional Hand Steadiness Test (IHST); Finger Tapping: The One-Hole Test: NES Simple Reaction Time (SRT); and Hand Tremor. Multivariate analyses were conducted following the hierarchical analysis of multiple responses (HAMR) approach. First, multiple scores of each test were combined into a single-factor (or related summary) variable and its reliability was estimated. Second. multiple regression analyses were conducted including log-transformed [Hg0]U levels, age, gender, and alcohol consumption in each model. Computed were both B and bu, the magnitudes of the log-Hg0 standardized coefficient. respectively uncorrected and corrected for dependent variable attenuation due to unreliability. Results indicated remarkable differences in the effects of relative level of Hg0 on psychomotor performance. Significant associations were found for the IHST factor (B = 0.415, p < 10(-6)), followed by finger tapping, which was relatively meager and insignificant (B 0.141, p = 0.17). The IHST results hold the greatest occupational relevance for dental professionals who rely on manual dexterity in restorative dentistry. Further, this statistical approach is recommended in future studies for condensation of multiple scores into summary scores with enhanced reliabilities useful in correcting for attenuation relationships (B(u)s) with exposure levels.

Adult↗

PubMedDate not supplied

Urinary porphyrin profiles as a biomarker of mercury exposure: studies on dentists with occupational exposure to mercury vapor.

Porphyrins are formed as intermediates in the biosynthesis of heme. In humans and other mammals, porphyrins with eight, seven, six, five, and four carboxyl groups are excreted in the urine in a well-established pattern. Mercury selectively alters porphyrin metabolism in kidney proximal tubule cells, leading to an altered urinary porphyrin excretion pattern. Previous studies in rats have shown that changes in the urinary porphyrin profile during exposure to mercury as methylmercury hydroxide are uniquely characterized by highly elevated (20- to 30-fold) levels of four- and five-carboxyl porphyrins and by the excretion of an atypical porphyrin ("precoproporphyrin"), which elutes on high performance liquid chromatography (HPLC) approximately midway between penta- and coproporphyrins. Changes in the urinary porphyrin profile are highly correlated with the dose and duration of mercury exposure and persist for up to 20 wk following cessation of mercury treatment. In the present studies, the utility of urinary porphyrin profile changes as a biomarker of mercury exposure in human subjects was evaluated. Urinary porphyrin concentrations were measured in dentists participating in the Health Screening Programs conducted during the 1991 and 1992 annual meetings of the American Dental Association and compared with urinary mercury levels measured in the same subjects. Among dentists with no detectable urinary mercury, mean concentrations of urinary porphyrins were within the established normal ranges for male human subjects. In contrast, among dentists with urinary mercury in excess of 20 micrograms/L, mean urinary concentrations of four- and five-carboxyl porphyrins as well as of precoproporphyrin were elevated three to four times those of unexposed subjects. Significant differences in urinary porphyrin concentrations remained when porphyrin concentrations in spot urine samples were adjusted for creatinine levels. These findings suggest that urinary porphyrin profiles may serve as a useful biomarker of mercury exposure in clinical or epidemiologic studies of mercury-related human health risks.

Animals↗

PubMedDate not supplied

Occupational exposure to electromagnetic fields and Alzheimer disease.

The association between occupational exposure to electromagnetic fields (EMF) and Alzheimer disease (AD) was examined. Subjects were identified from a large health maintenance organization in Seattle, Washington, and matched by age, sex, and proxy type. A complete occupational history was obtained from proxies and controls. Following the interview, two industrial hygienists (IHs) rated exposures to EMF for each job blinded to case-control status. Exposures to EMF were rated as probable intermittent exposure or probable exposure for extended periods to levels above threshold. Conditional logistic regression was used to calculate the risk of AD given EMF exposure stratified by IH. The odds ratios for ever having been exposed to EMF were 0.74 [95% confidence interval (CI) 0.29-1.92] and 0.95 (95% CI 0.27-2.43) for each IH, adjusting for age and education. No dose-response effect was noted. Agreement between the two IHs for ever having been exposed to EMF was good (kappa = 0.57, p < 0.0001). This study was unable to support an association between EMF and AD.

Adult↗