[Prevalence and risk factors for pterygium in six rural regions of Yunnan Province]

Objective: To investigate the prevalence and risk factors of pterygium in the rural population aged 40 years and above of 12 ethnic groups in 6 regions of Yunnan Province. Methods: This was a cross-sectional study. According to the method of multistage stratified sampling, samples of the rural population aged 40 years and above were collected from 12 ethnic groups (Han, Yi, Tibetan, Lisu, Bai, Naxi, Zhuang, Miao, Dai, Jingpo, Hani, and Lahu) in six areas (Diqing, Lijiang, Wenshan, Dehong, and Pu'er) of Yunnan Province from March 2019 to November 2019. Anterior segment examination was carried out in the target population with a hand-held slit-lamp, according to which pterygium was diagnosed, while the posterior segment of the eye was assessed by direct ophthalmoscopy. A field questionnaire survey was also conducted. A two-level model was used to study the effects of the location, nationality, sex, age, occupation, outdoor activities, smoking, and alcohol consumption on the prevalence of pterygium, with the ethnic group as the high level and the individual as the low level. Results: Among 9 617 subjects, the total prevalence rate of pterygium was 22.6%, which was adjusted to 19.6% according to the age and gender data of the Statistics Bureau of Yunnan Province. There was significant difference in prevalence of pterygium among six regions after adjusting for age and sex (χ²=146.50, P<0.001). The prevalence of pterygium was the highest in Wenshan (29.4%), followed by Chuxiong (24.4%), Diqing (17.5%), Pu'er (17.5%), Dehong (15.8%), and Lijiang (15.7%) (χ²=146.50, P<0.001). The results of the single factor analysis showed that there was statistically significant difference among different groups of age, gender, nationality, location, history of smoking, drinking, eating habits, sleeping time, continuous use of eye drops, temperature, humidity, altitude, longitude, latitude, and ultraviolet ray (P<0.05). However, the results of the multivariate analysis showed that the main risk factors of pterygium were female(OR=1.357,95%CI:1.173~1.568), advanced age(OR=1.540,95%CI:1.301~1.823), location(OR=1.713,95%CI:1.000~2.667), continuous use of eye drops(OR=1.177,95%CI:1.034~1.340), and more than 40 years of alcohol drinking(OR=1.525, 95%CI: 1.108~2.099), and the protective factor was more than 40 years of smoking(OR=0.723,95%CI:0.544~0.960). Conclusions: The prevalence of pterygium varies greatly among different regions in Yunnan Province. The main factors affecting the prevalence are sex, age, region, smoking history, and drinking history.

Inhibition of calcitriol receptor binding to vitamin D response elements by uremic toxins

The genomic action of calcitriol (1,25-dihydroxy-vitamin D3) is mediated through the interaction of the calcitriol receptor (VDR) with vitamin D response elements (VDREs). Although renal failure is associated with resistance to the action of calcitriol, the mechanism of this resistance is not well understood. Therefore, we used the electrophoretic mobility shift assay to compare the ability of VDRs from normal and renal failure rats to bind to the osteocalcin gene VDRE. The results indicate that VDRs from renal failure rats have only half the DNA binding capacity as VDRs from control rats, despite identical calcitriol binding. Furthermore, incubation of normal VDRs with a uremic plasma ultrafiltrate resulted in a loss of > 50% of the binding sites for the osteocalcin VDRE. When VDRs bound to DNA as heterodimers with retinoid X receptors, the inhibitory effect of the uremic ultrafiltrate was due to a specific interaction with the VDR, not retinoid X receptors. In addition, uremic ultrafiltrate blocked calcitriol-induced reporter gene activity in transfected JEG-3 cells. Taken together, the results indicate that an inhibitory effect of a uremic toxin(s) on VDR-VDRE binding could underlie the calcitriol resistance of renal failure.

Inhibition of nuclear uptake of calcitriol receptor by uremic ultrafiltrate

The biological action of calcitriol is mediated through a hormone-receptor complex interacting with nuclear chromatin. Interaction of the calcitriol receptor (VDR) with VDR response elements produces bioactive proteins which carry out the physiological actions of calcitriol. Since biological response to calcitriol appears to be diminished in renal failure, we studied the effect of uremic toxins on the interaction of VDR with nuclear chromatin using in vitro nuclear uptake of the 3H-calcitriol labeled VDR by intestinal nuclei. We found that nuclear uptake of the labeled intestinal VDR from renal failure rats was significantly lower than that from the control animals. HPLC fractionated uremic ultrafiltrate directly inhibited nuclear uptake of the labeled VDR when the labeled VDR was incubated with 50% of the ultrafiltrate for various time intervals ranging from 15 minutes to 6 hours. Infusion of uremic ultrafiltrate to normal rats for 20 hours also produced intestinal VDR with a lower binding affinity for intestinal nuclei when compared to the controls infused with normal ultrafiltrate. The latter study suggests that uremic toxins are responsible for the decreased nuclear uptake of VDR of rats with renal failure. Although it is difficult to extrapolate these results directly to the intact cells, our findings suggest that part of the calcitriol resistance in renal failure could be explained by decreased entry of receptor into the nucleus.

Regulation of calcitriol receptor and its mRNA in normal and renal failure rats

Homologous up-regulation of calcitriol receptor (VDR) by calcitriol is believed to be a transcriptional event. In this experiment, we studied the effect of calcitriol on VDR in normal and renal failure rats. The time course of the effect of calcitriol on VDR mRNA showed a biphasic change in VDR mRNA in response to calcitriol. The concentration of intestinal VDR mRNA increased at six hours and reached peak levels approximately 15 hours after calcitriol injection. Thereafter, the mRNA began to decrease and by 48 hours the level had declined to below the control values. The VDR levels also increased, though they lagged behind the VDR mRNA, and nearly plateaued at 24 hours after calcitriol treatment. In renal failure, the concentrations of VDR were lower and the levels of VDR mRNA were higher than the respective values of normal rats, suggesting that VDR synthesis was inhibited at post-transcriptional sites. Chronic administration of calcitriol increased the VDR but lowered the VDR mRNA levels in both normal and renal failure rats. Infusion of uremic ultrafiltrate to normal rats resulted in lower VDR and higher VDR mRNA levels similar to those found in rats with renal failure. The results indicate that uremic toxins are responsible for the low VDR and high VDR mRNA in renal failure.

Effect of vitamin D metabolites on calcitriol degradative enzymes in renal failure

We have demonstrated that in renal failure calcitriol degradation is decreased and that administration of vitamin D metabolites increases the degradation. In this study, we measured intestinal 24- and 26-hydroxylase activities and the effects of chronic infusion (7 days) of vitamin D metabolites on these enzymes' activities in rats with experimental renal failure. The enzymatic activity of intestinal 24-hydroxylase, but not 26-hydroxylase, was significantly lower in renal failure rats compared to control sham operated rats. Replacement of calcitriol (3 ng/day) significantly increased 24-hydroxylase activity by 17% in rats with renal failure (P < 0.01), although the activity remained 15% lower than the controls (P < 0.01). Intestinal 26-hydroxylase activity was not lower in renal failure; however, calcitriol treatment increased the activity beyond that of normal controls. In contrast, administration of 25(OH)D3 (600 ng/day) and 24,25(OH)2D3 (1 microgram/day) reduced the conversion of calcitriol to 1,24,25(OH)3D3 by more than 50% and to 1,25,26(OH)3D3 by more than 38%, respectively. We conclude that calcitriol increased its own degradation in renal failure by increasing the enzymatic activities of both 24- and 26-hydroxylase. However, the mechanisms of increased calcitriol degradation by 25(OH)D3 and 24,25(OH)2D3 in renal failure remain unknown.

Fast gas chromatography for air monitoring: limits of detection and quantitation

Gas chromatography has the potential to be a very fast method of air monitoring in the workplace and the community. The use of "fast" gas chromatographic (GC) instrumentation and methods may allow the completion of analyses in less than 10 sec when a flame ionization detector is used and in less than 30 sec when an electron capture detector is used. In this study, the fast GC system was evaluated as an air-monitoring tool for 41 different organic vapors at concentrations as low as 0.1 ppb.

Glove permeation by semiconductor processing mixtures containing glycol-ether derivatives

Results of permeation tests of several glove materials challenged with semiconductor processing formulations containing glycolether derivatives are described. Commercial glove samples of nitrile rubber (Edmont), natural rubber (Edmont and Baxter), butyl rubber (North), PVC Baxter), a natural rubber/neoprene/nitrile blend (Pioneer), and a natural rubber/neoprene blend (Playtex) were tested according to the ASTM F739-85 permeation test method (open-loop configuration). The liquid formulations examined included a positive photoresist thinner containing 2-ethoxyethyl acetate (2-EEA), n-butyl acetate, and xylene; a positive photoresist containing 2-EEA, n-butyl acetate, xylene, polymer resins, and photoactive compounds; a negative photoresist containing 2-methoxyethanol (2-ME), xylene, and cyclized poly(isoprene); and pure 2-methoxyethyl acetate (2-MEA), which is the solvent used in a commercial electron-beam resist. With the exception of the negative photoresist, butyl rubber provided the highest level of protection against the solvent mixtures tested, with no breakthrough observed after 4 hr of continuous exposure at 25 degrees C. Nitrile rubber provided the highest level of protection against the negative photoresist and reasonably good protection against initial exposure to the other solvent mixtures. Gloves consisting of natural rubber or natural rubber blends provided less protection against the mixtures than either nitrile or butyl rubber. For most of the glove samples, permeation of the glycol-ether derivatives contained in the mixtures was faster than that predicted from the permeation of the pure solvents. Increasing the exposure temperature from 25 to 37 degrees C did not significantly affect the performance of the butyl rubber glove. For the other gloves, however, exposures at 37 degrees C resulted in decreases in breakthrough times of 25-75% and increases in steady-state permeation rates of 80-457% relative to values obtained at 25 degrees C. Repeated exposure of nitrile rubber samples resulted in shorter breakthrough times for all mixture components. In fact, exposure for as little as one-half of the nominal breakthrough time followed by air drying overnight resulted in measurable quantities of one or more of the component solvents at the inner surface of the gloves at the beginning of the next exposure. This effect was not observed with the butyl rubber samples. With the exception of the negative photoresist, heating previously exposed nitrile rubber samples at 70 degrees C for 20 hr prior to retesting reduced or eliminated the effects of residual solvents, permitting reuse of the gloves. The use of thin PVC or natural rubber gloves adjacent to the nitrile gloves provided moderate increases in permeation resistance.(ABSTRACT TRUNCATED AT 400 WORDS)