Determinants of CD4 counts among HIV-negative Ethiopians: role of body mass index, gender, cigarette smoking, khat (Catha Edulis) chewing, and possibly altitude?

To study the determinants of CD4% and CD4 counts among HIV-negative Ethiopians, and to identify factors susceptible to explain the low CD4 counts observed among Ethiopian subjects. Cohort studies among factory workers in Akaki and Wonji, Ethiopia. Clinical and laboratory examinations, including determination of HIV serological status and T-cell subsets, were performed during follow-up visits every six months. In addition, micronutrients (retinol, carotenoids, tocopherol, transferrin receptor, and selenium) plasma concentrations were determined in a subset of 38 HIV-positive and 121 HIV-negative participants. HIV-negative participants with at least one CD4 count measurement were 157 females in Akaki, 203 males in Akaki, and 712 males in Wonji. CD4 counts were independently and positively associated with body mass index (through an increase in lymphocyte counts), female gender (through an increase in CD4%), cigarette smoking (through an increase in CD4%), khat chewing (through an increase in both lymphocyte counts and CD4%), and Akaki study site (through a large increase in lymphocyte counts compensating a decrease in CD4%). Intestinal parasitic infections were not associated with CD4% or CD4 counts. Retinol, carotenoids, and alpha-tocopherol plasma concentrations decreased with HIV infection and advancing immunosuppression, but were not associated with CD4 counts among HIV-negative subjects. Low body mass index among Ethiopians may have contributed to their overall low CD4 counts. Other factors remain to be elucidated.

Application of the classic Limulus test and the quantitative kinetic chromogenic LAL method for evaluation of endotoxin concentration in indoor air.

The classic (gel-clot procedure) Limulus test (CLT) and the quantitative kinetic chromogenic LAL method (KQCL) used for the evaluation of bacterial endotoxin concentration in the indoor air of dwellings were compared. The scientific procedure included analyses of 40 air samples supplemented by the analysis of 20 sample duplicates (selected at random) which were taken during the fall season from 10 flats located in 3 towns of the Upper Silesian region (southern Poland). The particulate aerosol probes were sampled by Harvard impactor and Casella sampler. The same samples were analyzed in the Netherlands using the quantitative kinetic chromogenic LAL method, and in Poland using the classic Limulus test. Comparison of both methods revealed that the quantitative kinetic chromogenic LAL method was more precise, with better reproducibility (the coefficient of variation between analyses of the main probe and its duplicate was over two times smaller in the KQCL method than in the CLT method), fully automated in the phase of analysis and data reading, and faster and more effective than the classic Limulus test. Nevertheless, on the basis of the obtained results, the usefulness of the classic Limulus method for assessment of the degree of pollution of indoor air with bacterial endotoxin seems to be confirmed as in the majority of examined samples (21 out 40) the results obtained by both methods were of the same order of magnitude, and in the remaining 19 samples did exceed one order of magnitude. Thus, the data received by means of the classic Limulus test may be regarded as acceptable.

Contribution of 3,5,3'-tri-iodothyronine produced locally from thyroxine in several maternal tissues of the near-term pregnant rat.

3,5, 3'-Tri-iodothyronine(T3)is produced by the thyroid and locally, by monodeiodination of thyroxine (T4), in the peripheral tissues. During pregnancy the thyroid hormone status in rats is altered: plasma and tissue levels of T4 and T3 are decreased. We investigated the effects of pregnancy on the contribution of T3 produced locally in the maternal tissues by administering a continuous infusion of [125I]T4 and [131I]T3. The transport of T4 to almost all maternal organs diminished. Less T was transported from the plasma to brown adipose tissue (BAT), liver, kidney and pituitary, in contrast to the ovary where an increase was found. In BAT and brain the amount of locally produced T3 decreased, despite the known increase in deiodinase type II activity in the brain while in liver the contribution of locally produced T3 remained constant, despite a known increase in deiodinase type I activity during pregnancy. This discrepancy between deiodinase activities and locally produced T3 can be explained by an insufficient availability of T4. Thus, we conclude that in the rat a decrease in maternal T4 concentration, together with the transport of T4 to the feto-placental compartment, results indirectly in a diminished availability of T3 in the maternal organs.

Effects of marginal iodine deficiency on thyroid hormone production, distribution and transport in nonpregnant and near-term pregnant rats.

During pregnancy maternal thyroid hormones are of great importance for normal development of the central nervous system of the fetus. Iodine deficiency of the mother carl result in an impaired development of the fetal brain. In large areas of the world iodine intake is moderately low. To study the effects of marginal iodine deficiency (MID) on the production, distribution, and transport of thyroxine (T4) and 3,5,3'-tri-iodothyronine (T3) in nonpregnant and near-term pregnant rats we performed kinetic experiments (three-compartment analysis). Despite unchanged plasma T4 and T3 during MID, the production and plasma clearance rates of T4 decreased 30% (P = 0.01) in MID nonpregnant (MID-C) rats. For T3, the plasma clearance rate was increased 70% (P = 0.046), while the T3 production was more than doubled (P = 0.042) in MID-C rats. In MID near-term pregnant rats T3 production was decreased 20% (P = 0.04). Hepatic deiodinase type I activity increased during MID in both nonpregnant and pregnant rats. It appears that during MID, rats are able to maintain their euthyroid status. The pronounced increase in transport of T4 from plasma to the fast pool observed in pregnant rats on a normal iodine diet did not occur during MID. In conclusion, in rats MID affects maternal thyroid hormone metabolism, thus influencing the availability of maternal T4 for the fetus.

Maternal thyroxine and 3,5,3'-tri-iodothyronine kinetics in near-term pregnant rats at two different levels of hypothyroidism.

Thyroid hormones are extremely important for development of the fetal central nervous system. Thyroidectomy results in severe hypothyroidism. In this study two levels of maternal hypothyroidism were reached by administration of different amounts of thyroxine (T4) and 3,5,3'-tri-iodothyronine (T3) to thyroidectomized pregnant rats. We examined the production, distribution and transport of T4 and T3 by performing a kinetic experiment (three-compartment analysis) with intact and thyroidectomized near-term pregnant rats which received either very low (Tx + lowTH) or normal (Tx + TH) doses of T4 and T3. Despite administration of normal doses of thyroid hormones, plasma TSH was still elevated in the Tx + TH rats, meaning that these rats were still mildly hypothyroid. The Tx + lowTH rats were markedly hypothyroid, the plasma T4 and T3 levels being very low. In the mildly hypothyroid rats the transport of T4 from plasma to the fast pool and vice versa was decreased compared with intact near-term pregnant rats. This could imply that much less T4 is transported to the feto-placental compartment. Liver type I deiodinase was decreased, resulting in lowered plasma T3 values. In the markedly hypothyroid rats all pools and rates of transport of T4 and T3 were greatly decreased. In conclusion, even mild hypothyroidism, despite normal plasma T4 values, results in significant changes, especially in maternal T4 transport. We suggest that even mild maternal hypothyroidism will have a negative effect on the availability of maternal T4 for fetuses.

Effects of marginal iodine deficiency during pregnancy: iodide uptake by the maternal and fetal thyroid.

Iodide uptake by the thyroid is an active process. Iodine deficiency and pregnancy are known to influence thyroid hormone metabolism. The aim of this study was to clarify the effects of iodine deficiency and pregnancy on iodide uptake by the thyroid. Radioiodide was injected intravenously into nonpregnant and 19-day pregnant rats receiving a normal or marginally iodine-deficient diet. The uptake of radioiodide by the thyroid was measured continuously for 4 h. The absolute iodide uptake by the maternal and fetal thyroid glands at 24 h was calculated by means of the urinary specific activity. Pregnancy resulted in a decrease in the absolute thyroidal iodide uptake. Marginal iodine deficiency had no effect on the absolute iodide uptake by the maternal thyroid. The decreased plasma inorganic iodide was compensated by an increase in thyroidal clearance. A similar compensation was not found for the fetus; the uptake of iodide by the fetal thyroid decreased by 50% during marginal iodine deficiency. This can lead to diminished thyroid hormone production, which will have a negative effect on fetal development, especially of the brain.

Influence of various dust sampling and extraction methods on the measurement of airborne endotoxin.

The influence of various filter types and extraction conditions on the quantitation of airborne endotoxin with the Limulus amebocyte lysate test was studied by using airborne dusts sampled in a potato processing plant. Samples were collected with an apparatus designed to provide parallel samples. Data from the parallel-sampling experiment were statistically evaluated by using analysis of variance. In addition, the influence of storage conditions on the detectable endotoxin concentration was investigated by using commercially available lipopolysaccharides (LPS) and endotoxin-containing house dust extracts. The endotoxin extraction efficiency of 0.05% Tween 20 in pyrogen-free water was seven times higher than that of pyrogen-free water only. Two-times-greater amounts of endotoxin were extracted from glass fiber, Teflon, and polycarbonate filters than from cellulose ester filters. The temperature and shaking intensity during extraction were not related to the extraction efficiency. Repeated freeze (-20 degrees C)-and-thaw cycles with commercial LPS reconstituted in pyrogen-free water had a dramatic effect on the detectable endotoxin level. A 25% loss in endotoxin activity per freeze-thaw cycle was observed. Storage of LPS samples for a period of 1 year at 7 degrees C had no effect on the endotoxin level. House dust extracts showed a decrease of about 20% in the endotoxin level after they had been frozen and thawed for a second time. The use of different container materials (borosilicate glass, "soft" glass, and polypropylene) did not result in different endotoxin levels. This study indicates that the assessment of endotoxin exposure may differ considerably between groups when different sampling, extraction, and storage procedures are employed.

Thyroxine and 3,5,3'-triiodothyronine production, metabolism, and distribution in pregnant rat near term.

In the pregnant rat near term thyroxine (T4) and 3,5,3'-triiodothyronine (T3) concentrations are lower in plasma and extrathyroidal tissues, except T3 in the brain. To study the changes in T4 and T3 kinetics a bolus injection of [125I]T4 and [131I]T3 was administered to nonpregnant controls and rats 14 and 19 days pregnant. Physiological parameters of the production, interpool transport, distribution, and metabolism of T4 and T3 were estimated by means of a three-compartment model. The production and partition of T4 remained unchanged during pregnancy. The total distribution volume of T4 was enlarged. On day 19 the plasma clearance rate was doubled, and transport to the fast pool was more than tripled. The rate of production of T3 was slightly diminished. The plasma clearance rate was increased, but no changes were found in the interpool transport rates. These results suggest that in the pregnant rat near term the increased transport of T4 is responsible for the distribution of the available T4 between the maternal and the fetal compartment.

Inhibition and enhancement in the analysis of airborne endotoxin levels in various occupational environments.

Inhibition and enhancement effects on the Limulus Amebocyte Lysate (LAL) assay were studied in a series of endotoxin exposure samples from various occupational environments. Two types of analyses were performed, with various dilutions and with spiked samples. Results showed that inhibition and enhancement occurred in some samples, leading to respective underestimation and overestimation of the endotoxin concentration. When inhibition or enhancement is present, the result of this study shows that large differences in endotoxin concentration may be found, depending on the dilution at which the sample is analyzed. False conclusions about exposure levels and their potential health effects might be introduced. Results show that quality control procedures need to become standard practice when endotoxins are analyzed in occupational environments and development of a validated, generally accepted protocol should be encouraged.

A study of the relationship between airborne contaminants and environmental factors in Dutch swine confinement buildings.

A total of 171 swine confinement buildings were studied to determine the concentrations of airborne total and D50 less than or equal to micron 8.5 dust fractions, total and gram-negative bacteria, bacterial endotoxin and NH3. The concentrations of these airborne contaminants then were correlated statistically to a number of environmental factors such as feeding practices, number of animals and ventilation parameters. The results showed that airborne dust, endotoxin, bacteria and NH3 are commonly in high concentrations within the swine confinement buildings and that these are at levels where health effects have been observed in other studies. Correlation of these airborne contaminants to a number of environmental factors showed that while ventilation is an important criteria for airborne contaminants, there are a number of farming practices that significantly contribute to the levels of airborne contaminants currently found. Pearson correlations indicate a number of important criteria that the industrial hygienist should measure when faced with problems in agricultural confinement buildings.