Reproductive function in relation to duty assignments among military personnel.

As a follow-up to the pilot study of semen quality of soldiers with various military assignments a larger, more complete study was conducted. Soldiers were recruited at Fort Hood, Texas. Thirty-three men were exposed to radar as part of their duty assignment in the Signal Corps, 57 men were involved with firing the 155 mm howitzer (potential lead exposure), and 103 soldiers had neither lead nor radar exposure and served as the comparison control group. Both serum and urinary follicle-stimulating hormone and luteinizing hormone and serum, salivary, and urine testosterone levels were determined in all men. A complete semen analysis was conducted on each soldier. For statistical analysis, the primary study variables were: sperm concentration, sperm/ejaculate, semen volume, percent normal morphology, percent motile, percent viable (both vital stain and hypoosmotic swelling), curvilinear velocity, straight-line velocity, linearity, sperm head length, width, area, and perimeter. Variables were adjusted for significant confounders (e.g., abstinence, sample age, race). No statistical differences (P < 0.05) were observed in any measurement. While these results are in agreement with two previous studies assessing soldiers firing the 155-mm howitzer, they contradict our previous report indicating that radar exposure caused a significant decrease in sperm numbers. A possible explanation is that the radar exposure in this study was that used in Signal Corps operations while the men in the previous study were using different radar as part of military intelligence operations. The data presented here in men firing the 155-mm howitzer combined with the results from the previous studies confirms that there are no deficits in semen quality in these men. The contradiction between the results of the radar exposure studies indicates that more data are needed to evaluate the relationship of military radar and male reproductive health.

Measuring male reproductive hormones for occupational field studies.

As part of our longitudinal study of unexposed workers, we drew blood samples and analyzed the individual endocrine profiles for 45 men. The blood collection was between 8 AM and 8 PM, and three blood samples were drawn 20 minutes apart on three occasions during the course of the study (June, October, and February). Serum concentrations of follicle-stimulating hormone, luteinizing hormone, testosterone, and prolactin were determined. A component of variance model was used to estimate variability between the 20-minute blood draws. Statistical power analysis using this component showed that three blood draws provide a marginal improvement over a single blood draw in detecting population shifts. Also, if the prospect of three blood draws reduces subject participation by 10 to 20%, the increase in power would be negated.

Inhibition of intercellular communication in human keratinocytes by fractionated asphalt fume condensates.

Asphalt fume condensate (AFC) and chromatographically separated fractions have been shown to cause cancer in mouse skin. The levels of known carcinogenic initiators in these complex mixtures, however, are considered too low to account for their carcinogenic potency. It has been proposed that AFC may contain co-carcinogenic or tumor-promoting agents in addition to carcinogenic initiators. Modulation of gap junctional intercellular communication (GJIC) has been implicated as an important effect of tumor promoters. In this study, we examined the effect of five chromatographically generated fractions of AFC on GJIC in cultured human epidermal keratinocytes (HEK). HEK cells were exposed overnight to medium containing DMSO extracts of AFC fractions. GJIC was evaluated by dye-coupling of microinjected Lucifer Yellow CH. All AFC fractions produced a concentration-dependent inhibition of GJIC. The apparent potency of each fraction correlated with its relative polarity based on HPLC elution characteristics. Cells with reduced GJIC as a result of AFC fraction exposure were found to exclude propidium iodide, suggesting that inhibition of GJIC occurred in the absence of cell killing. However, significantly reduced culture DNA content was found following the overnight exposure to the highest concentrations of AFC fractions C, D and E.

Reversible inhibition of intercellular communication among cardiac myocytes by halogenated hydrocarbons.

We examined the effect of 11 aliphatic halogenated hydrocarbons on the transfer of microinjected dye among cardiac myocytes from neonatal rats. Myocytes were suffused with increasing concentrations of halocarbon added as a 0.2% solution of dimethyl sulfoxide to M199 containing 1.8 mM Ca and 5% serum. Single cells were microinjected with the fluorescent probe Lucifer yellow (5% in 0.1 mM LiCl) and dye coupling to adjacent cells was monitored. All of the halocarbons tested exhibited a concentration-dependent inhibitory effect on intercellular communication that was reversible following washout of the compounds. Intercellular communication was blocked within 1 min of exposure to an effective concentration, and recovery of communication occurred even after 2 hr of exposure. Pretreatment of cells with SKF 525-A (25 microM) did not prevent the inhibition of intercellular communication by carbon tetrachloride suggesting an absence of P-450 involvement. EC50s were calculated for each chemical using probit analysis. A log-log comparison of the EC50s and the physicochemical properties of the chemicals demonstrated a high correlation (R2 = 0.933) between the EC50s and the octanol/water partition coefficients of the halocarbons. This suggests that incorporation of halocarbons in the membrane may block intercellular communication through modification of the immediate environment of the gap junctions. The results are in agreement with the hypothesis that inhibition of gap junctional communication is a factor in the arrhythmogenic effects of acute halocarbon exposure.

Depression of contractility in cultured cardiac myocytes from neonatal rat by carbon tetrachloride and 1,1,1-trichloroethane.

The cardiac depressant effects of carbon tetrachloride (CCl(4)) and 1,1,1-trichloroethane (CH(3)CCl(3)) were evaluated in cultured heart cells from neonatal rats. Heart cells were grown on glass coverslips and formed a confluent monolayer that beat spontaneously, rhythmically and in synchrony. Contractility was assessed by video-motion analysis. Stock solutions of CCl(4) or CH(3)CCl(3) were prepared in dimethylsulphoxide (DMSO) and aliquoted (final DMSO concentration 0.2%) into medium (M199 supplemented with 5% serum) immediately prior to perfusion across myocytes in an environmentally controlled chamber. CCl(4) and CH(3)CCl(3) had a negative chronotropic effect on myocytes by prolonging the relaxation phase of beating. Duration of the contraction phase of beating, and peak velocity of cell wall movement were not affected by these halocarbons. Beating was stopped by 2.5 mm-CCl(4) or 5 mm-CH(3)CCl(3), and washout of these compounds resulted in a resumption of beating activity. Increasing (3.6 mm) or decreasing (0.6 mm) the calcium concentration of the medium (normal = 1.8 mm) significantly affected the duration of contraction and relaxation phases of beating, but did not alter the concentration-dependent action of CCl(4). A positive chronotropic effect of isoproterenol was evident from 10(-9) to 10(-6)m, but contractility was depressed by isoproterenol concentrations greater than 10(-8)m in the presence of 750 mum-CCl(4). This study demonstrates the usefulness of cultured heart cells for assessing the cardiac depressant and sensitizing actions of halogenated hydrocarbons.

Longitudinal study of semen quality of unexposed workers. I. Study overview.

A longitudinal study of 45 men was conducted evaluating the semen quality of monthly samples collected over 9 months. The statistical variation of sperm count, semen volume, percentage of motile sperm, sperm velocity, sperm morphology, and sperm viability, assessed by both the vital stain and the hypoosmotic swelling (HOS) assay, were each evaluated using intraclass correlations and coefficients of variation. Sperm count and semen volume had large intraclass correlations (62% and 60%, respectively), indicating that if a subject has a high count or volume he will tend to continue to have high counts or volumes. On the other hand, sperm velocity had an intraclass correlation of only 16% indicating that fluctuations within a subject were nearly as large as fluctuations from subject to subject. The remaining parameters had intraclass correlations ranging from 42% to 47%. Sperm count, percent motile sperm, and semen volume each had large coefficients of variation (both between and within subjects). These variables, especially count, had relatively poor precision. Sperm velocity, percent motile sperm, percent normal morphology, the HOS assay, and the vital stain assay had lower coefficients of variation, indicating greater precision.

Ethylene glycol monomethyl ether (EGME) inhibits rat embryo ornithine decarboxylase (ODC) activity.

The effects of ethylene glycol monomethyl ether (EGME) on reproductive outcome in the rat, and on ornithine decarboxylase (ODC) activity in the rat embryo were evaluated. Dams (n = 8) were treated by gavage on gestation days 6-12 (sperm = day 0) with 0, 25, 50 or 75 mg/kg EGME in 10 ml/kg distilled water. EGME had a dose-dependent effect on reproductive outcome. Gestation length was prolonged, and the number of litters delivered and neonatal body weight were reduced. Whole embryo ODC was measured on gestation days 9, 11, 13 and 15. ODC attained maximum activity in controls on day 11, increasing by more than an order of magnitude above the activity found on day 9. On day 11, a statistically significant dose-dependent inhibition of ODC activity was observed with the maximum dose of EGME inhibiting ODC activity 60 percent. On days 13 and 15, ODC activity declined markedly from peak values, and the dose-dependent inhibition was no longer evident. The study demonstrates a correlation between the inhibition of embryonic ODC activity by EGME and the effect of EGME on reproductive outcome.