[Research on the relationship between populations' long-term exposure to fluoride in drinking water and bone fracture in China]

There are contradictory reports on the prevalence of bone fractures associated with long-term fluoride exposure from drinking water. The prevalence of bone fracture in six rural areas of China and the exposure of fluoride in drinking water was investigated. The data including medical history and demographic information, bone fractures, fluoride content in drinking water, physical activity, cigarette smoking, alcohol consumption and dietary intakes were collected. A retrospective epidemiological study by using the same design, method, quality control and the same questionnaire was conducted. A total of 8266 male and female over 50 years of age were divided into 6 groups by the fluoride concentrations in drinking water. The subjects in each group exposed to different levels of fluoride (0.25-0.34, 0.58-0.73, 1.00-1.06, 1.45-2.19, 2.62-3.58 and 4.32-7.97 mg/L) were 1363, 1407, 1370, 1574, 1051 and 1501 respectively. It has been confirmed that drinking water was the only major source of fluoride exposure in the studied populations. The total bone fracture rates were 7.41%, 6.40%, 5.11%, 6.04%, 6.09% and 7.40% in each group. Natural bone fracture rates in each group were 3.01%, 2.21%, 1.31%, 1.65%, 1.43% and 3.66% respectively. The prevalence of bone fracture and water fluoride level appeared a U-shaped relationship. The prevalence of total bone fracture and natural bone fracture in the population with fluoride 1.00-1.06 mg/L in drinking water was the lowest, compared with the groups exposed to fluoride higher than 4.32 mg/L and lower than 0.73 mg/L. The highest prevalence of hip fracture was in the group with higher water fluoride (4.32-7.97 mg/L) exposure. In general, the prevalence of hip fracture was lower and stable up to 1.06 mg/L of fluoride in drinking water, and then it appeared to rise. Based on the data collected in this investigation, it is concluded that the long-term fluoride exposure from drinking water higher than 4.32 mg/L might increase the risk of overall fractures as well as hip fractures. The risk of overall fractures and natural fractures might be lower while the water fluoride level is at 1.00-1.06 mg/L, however, no protective benefits of fluoride for the risk of hip fracture was observed.

3D-QSAR model of flavonoids binding at benzodiazepine site in GABAA receptors

With flavone as a structural template, three-dimensional quantitative structure-activity relationship (3D-QSAR) studies and ab initio calculations were performed on a series of flavonoids. A reasonable pharmacophore model was built through CoMFA, CoMSIA, and HQSAR analyses and electrostatic potential calculations. A plausible binding mode for flavonoids with GABA(A) receptors was rationalized. On the basis of the commonly recognized binding site, the specific S1 and S2 subsites relating to substituent positions were proposed. The different binding affinities could be explained according to the frontier orbitals and electrostatic potential (ESP) maps. The ESP could be used as a novel starting point for designing more selective BZ-binding-site ligands.

Effect of long-term exposure to fluoride in drinking water on risks of bone fractures

Findings on the risk of bone fractures associated with long-term fluoride exposure from drinking water have been contradictory. The purpose of this study was to determine the prevalence of bone fracture, including hip fracture, in six Chinese populations with water fluoride concentrations ranging from 0.25 to 7.97 parts per million (ppm). A total of 8266 male and female subjects > or =50 years of age were enrolled. Parameters evaluated included fluoride exposure, prevalence of bone fractures, demographics, medical history, physical activity, cigarette smoking, and alcohol consumption. The results confirmed that drinking water was the only major source of fluoride exposure in the study populations. A U-shaped pattern was detected for the relationship between the prevalence of bone fracture and water fluoride level. The prevalence of overall bone fracture was lowest in the population of 1.00-1.06 ppm fluoride in drinking water, which was significantly lower (p < 0.05) than that of the groups exposed to water fluoride levels > or =4.32 and < or =0.34 ppm. The prevalence of hip fractures was highest in the group with the highest water fluoride (4.32-7.97 ppm). The value is significantly higher than the population with 1.00-1.06 ppm water fluoride, which had the lowest prevalence rate. It is concluded that long-term fluoride exposure from drinking water containing > or =4.32 ppm increases the risk of overall fractures as well as hip fractures. Water fluoride levels at 1.00-1.06 ppm decrease the risk of overall fractures relative to negligible fluoride in water; however, there does not appear to be similar protective benefits for the risk of hip fractures.

Health effects of fluoride pollution caused by coal burning

Recently a huge amount of fluoride in coal has been released into indoor environments by the combustion of coal and fluoride pollution seems to be increasing in some rural areas in China. Combustion of coal and coal bricks is the primary source of gaseous and aerosol fluoride and these forms of fluoride can easily enter exposed food products and the human respiratory tract. Major human fluoride exposure was caused by consumption of fluoride contaminated food, such as corn, chilies and potatoes. For each diagnostic syndrome of dental fluorosis, a log-normal distribution was observed on the logarithm of urinary fluoride concentration in students in China. Urinary fluoride content was found to be a primary health indicator of the prevalence of dental fluorosis in the community. In the fluorosis areas, osteosclerosis in skeletal fluorosis patients was observed with a high prevalence. A biochemical marker of bone resorption, urinary deoxypyridinoline content was much higher in residents in China than in residents in Japan. It was suggested that bone resorption was stimulated to a greater extent in residents in China and fluoride may stimulate both bone resorption and bone formation. Renal function especially glomerular filtration rate was very sensitive to fluoride exposure. Inorganic phosphate concentrations in urine were significantly lower in the residents in fluorosis areas in China than in non-fluorosis area in China and Japan. Since airborne fluoride from the combustion of coal pollutes extensively both the living environment and food, it is necessary to reduce fluoride pollution caused by coal burning.

beta-Endorphin-containing memory-cells and mu-opioid receptors undergo transport to peripheral inflamed tissue

Immunocyte-derived beta-endorphin can activate peripheral opioid receptors on sensory neurons to inhibit pain within inflamed tissue. This study examined mu-opioid receptors (MOR) on sensory nerves and beta-endorphin (END) in activated/memory CD4(+) cells (the predominant population homing to inflamed tissue). We found an upregulation of MOR in dorsal root ganglia, an increased axonal transport of MOR in the sciatic nerve and an accumulation of MOR in peripheral nerve terminals in Freund's adjuvant-induced hindpaw inflammation. A large number of CD4(+) cells containing beta-endorphin, but very few naive cells (CD45RC(+)), were observed in inflamed tissue, suggesting that this opioid is mainly present in activated/memory cells (CD4(+)/CD45RC(-)). Taken together, our results indicate an enhanced transport of both MOR and of the endogenous ligand beta-endorphin to injured tissue. This unique simultaneous upregulation of both receptors and ligands may serve to prevent excessive and/or chronic inflammatory pain.

Brownian dynamics simulations of interaction between scorpion toxin Lq2 and potassium ion channel

The association of the scorpion toxin Lq2 and a potassium ion (K(+)) channel has been studied using the Brownian dynamics (BD) simulation method. All of the 22 available structures of Lq2 in the Brookhaven Protein Data Bank (PDB) determined by NMR were considered during the simulation, which indicated that the conformation of Lq2 affects the binding between the two proteins significantly. Among the 22 structures of Lq2, only 4 structures dock in the binding site of the K(+) channel with a high probability and favorable electrostatic interactions. From the 4 candidates of the Lq2-K(+) channel binding models, we identified a good three-dimensional model of Lq2-K(+) channel complex through triplet contact analysis, electrostatic interaction energy estimation by BD simulation and structural refinement by molecular mechanics. Lq2 locates around the extracellular mouth of the K(+) channel and contacts the K(+) channel using its beta-sheet rather than its alpha-helix. Lys27, a conserved amino acid in the scorpion toxins, plugs the pore of the K(+) channel and forms three hydrogen bonds with the conserved residues Tyr78(A-C) and two hydrophobic contacts with Gly79 of the K(+) channel. In addition, eight hydrogen-bonds are formed between residues Arg25, Cys28, Lys31, Arg34 and Tyr36 of Lq2 and residues Pro55, Tyr78, Gly79, Asp80, and Tyr82 of K(+) channel. Many of them are formed by side chains of residues of Lq2 and backbone atoms of the K(+) channel. Thirteen hydrophobic contacts exist between residues Met29, Asn30, Lys31 and Tyr36 of Lq2 and residues Pro55, Ala58, Gly79, Asp80 and Tyr82 of the K(+) channel. These favorable interactions stabilize the association between the two proteins. These observations are in good agreement with the experimental results and can explain the binding phenomena between scorpion toxins and K(+) channels at the level of molecular structure. The consistency between the BD simulation and the experimental data indicates that our three-dimensional model of Lq2-K(+) channel complex is reasonable and can be used in further biological studies such as rational design of blocking agents of K(+) channels and mutagenesis in both toxins and K(+) channels.

[Breath drive response of COPD patients with hypercapnic respiratory failure and their families]

OBJECTIVE

To investigate the breath drive response of COPD patients and their offspring and to analyze the potential heredity.

METHODS

P(0.1) and ventilatory response to hypoxia (DeltaV(E)/DeltaSaO(2)), P(0.1) response to hypoxia (DeltaP(0.1)/DeltaSaO(2)), P(0.1) response to hypercapnia (DeltaP(0.1)/DeltaP(ET)CO(2)DeltaV(E)/P(ET)CO(2)) and ventilatory response to hypercapnia (DeltaV(E)/P(ET)CO(2)) were measured in 6 COPD patients with type II respiratory failure and in 21 of their normal adult offspring.

RESULTS

(1) P(0.1) was remarkably higher among all of the COPD patients than among their offspring and normal controls. The hypoxia response (DeltaP(0.1)/DeltaSaO(2)) and DeltaP(0.1)/DeltaP(ET)CO(2) were significantly decreased among the COPD patients (P < 0.05). (2) The hypoxia response was low among 10 of the offspring of COPD patients, and was normal among the other 11. (3) The ventilatory response to hypercapnia (DeltaV(E)/DeltaP(ET)CO(2)) was significantly decreased among the COPD patients, and varied greatly among their offspring.

CONCLUSION

(1) The depression of respiratory responses to hypoxia and hypercapnia may be the reason of type II respiratory failure. (2) The depression of hypoxia response may be influenced by genetic factors.

Computer-aided design, synthesis and biological assay of p-methylsulfonamido phenylethylamine analogues

Class III antiarrhythmic agents selectively delay the effective refractory period (ERP) and increase the transmembrance action potential duration (APD). Based on our previous studies, a set of 17 methylsulfonamido phenylethylamine analogues were investigated by 3D-QSAR techniques of CoMFA and CoMSIA. The 3D-QSAR models proved a good predictive ability, and could describe the steric, electrostatic and hydrophobic requirements for recognition forces of the receptor site. According to the clues provided by this 3D-QSAR analysis, we designed and synthesized a series of new analogues of methanesulfonamido phenylethylamine (VIa-i). Pharmacological assay indicated that the effective concentrations of delaying the functional refractory period (FRP) 10ms of these new compounds have a good correlation with the 3D-QSAR predicted values. It is remarkable that the maximal percent change of delaying FRP in microM of compound VIc is much higher than that of dofetilide. The results showed that the 3D-QSAR models are reliable.

A genetic study of the depressive respiratory responses to hypoxia in chronic obstructive pulmonary disease patients with type II respiratory failure

OBJECTIVE

The depression of the ventilatory and P(0.1 )responses to hypoxia and hypercapnia may play an important role in the development of CO(2) retention in the patients with chronic obstructive pulmonary disease (COPD). The purpose of this study was to investigate if there is any linkage relationship between the depressed ventilatory and P(0.1) response phenotypes and the microsatellite markers on chromosome 6q21.1-21.2 among Chinese people.

METHODS

P(0.1) and ventilatory responses to hypoxia were measured in six COPD patients with type II respiratory failure, as well as in their 21 normal adult offsprings. Polymerase chain reaction (PCR), denaturing polyacrylamide gel electrophoresis and silver staining techniques were used to study the amplified fragment length polymorphism. Linkage analysis was done with the LINKAGE program.

RESULTS

Hypoxia response was low in 10 offsprings, and normal in the other 11 offsprings. Linkage analysis showed the maximum Lod score was 1.74(D6S276, theta = 0.10).

CONCLUSION

The depressed hypoxia response might have been influenced by genetic factors. The model was in accord with autosomal dominant inheritance. The disease-related gene was linked to D6S276 locus.

Trace element levels in drinking water and cognitive function among elderly Chinese

The relation between trace element levels in drinking water and cognitive function was investigated in a population-based study of elderly residents (n = 1,016) in rural China in 1996-1997. Cognitive function was measured using a Chinese translation of the Community Screening Interview for Dementia. A mixed effects model was used to evaluate the effect of each of the elements on cognitive function while adjusting for age, sex, and educational level. Several of the elements examined had a significant effect on cognitive function when they were assessed in a univariate context. However, after adjustment for other elements, many of these results were not significant. There was a significant quadratic effect for calcium and a significant zinc-cadmium interaction. Cognitive function increased with calcium level up to a certain point and then decreased as calcium continued to increase. Zinc showed a positive relation with cognitive function at low cadmium levels but a negative relation at high levels.

Synthesis and acetylcholinesterase inhibitory activity of huperzine A-E2020 combined compound

The synthesis of huperzine-E2020 combined compound (3) has been accomplished and the activities of 3 and the intermediates 12 and 13 to inhibit the activity of acetylcholinesterase have been measured. Conformation analyses and molecular docking studies of E2020 and the eight isomers of 12 were carried out. The results indicated that binding energies of all isomers of 12 with AChE was much lower than E2020 except for isomer RRZ, which might be the reason that the activity of 12 was lower than that of E2020. Interaction pattern of RRZ in AChE was also studied. Both binding energy and interaction pattern shows that the biological activity of RRZ might be higher than that of E2020.

[Studies on stimulating components of raw Pinellia ternata (Thunb.) (banxia)]

OBJECTIVE

To study the stimulating components of raw Pinellia ternata (Banxia).

METHODS

Used the methods of extracting with various organic solvents; x-ray fluorescence spectrometer; scanning electron microanalyzer; oxidation and reduction titrations; and ultraviolet spectrophotometry.

RESULTS

Experiments showed that calcium oxalate hydrate (C2CaO4 x H2O) was one of the stimulating components of raw Pinellia ternata, and its shape, and contents related to the stimulation of raw Pinellia ternata. After processing, the shape and contents of calcium oxalate changed, decreased respectively, and the stimulation of Pinellia ternata decreased.

CONCLUSION

The needle crystal of calcium oxalate is one of the stimulating components in raw Pinellia ternata.

[Applied anatomy of anterior ethmoid relevant to endoscopic transnasal dacryocystorhinostomy]

OBJECTIVE

This study provided clinical guidance for the endoscopic transnasal dacryocystorhinostomy.

METHOD

16 adult cadavers were studied on the applied anatomy of between anterior ethmoid and fossa of lacrimal sac and the anatomic relationship between uncinate process and medial wall of orbit.

RESULT

According to the anatomic relationship between anterior ethmoid sinus and fossa of lacrimal sac, the cells of anterior ethmoid sinus were classified into three typies, The results was that type I accounted for 31.2%, type II 50.0% type III 18.8%.

CONCLUSION

CT scans should be performed to determine the anatomic relationships between fossa of lacrimal sac and anterior ethmoid and between uncinate process and medial wall of orbit before operation for patients with different typies of obstruction of nasocrimal duct, thus the proper bony opening was located during dacryocystorhinostomy.

[The clinical study of pulmonary emphysema with pulmonary fibrosis]

OBJECTIVE

Emphysema and interstitial pulmonary fibrosis are two different diseases in clinical manifestation and pathology, but it was noticed that there were cases diagnosed as pulmonary emphysema and pulmonary fibrosis. It is necessary to study the relationship between the clinical aspects of these cases.

METHODS

11 patients with emphysema and pulmonary fibrosis were found in the past five years. Clinical symptoms, radiographic features, arterial blood-gas, lung function testing and computed tomography of the chest were analyzed.

RESULTS

These patients had a long history of cigarette-smoking. Their clinical features are those of both emphysema and pulmonary fibrosis.

CONCLUSIONS

Although emphysema and interstitial pulmonary fibrosis are two different diseases, they could coexist in some patients. Their clinical features do not like either of the two diseases. HRCT is an important method for discovering the coexistance of pulmonary emphysema and interstitial fibrosis.

Alanine-substituted peptide ligands differ greatly in their ability to activate autoreactive T-cell subsets specific for the wild-type peptide

Alanine-substituted peptide ligands (APLs) have the potential to reduce or block autoreactive T-cell activation. Most previous investigations aimed at either identification of the amino acid residue within a peptide ligand that is critical for T-cell activation or characterization of inhibitory APLs have analyzed the effects of APLs on one, or a limited number, of T-cell lines. In this study, we compared the effects of a panel of peptides on the proliferative and activation responses of one T-cell line as well as the effects of one peptide on the responses of a panel of T-cell lines. This study reveals that the T cells that comprise the T-cell population that responds to a specific peptide are heterogeneous in that an APL may fail to induce a response in some of these T cells although it is capable of inducing a response in the others. Moreover, APLs can induce T-cell activation, in terms of production of IL-2 and/or TNF-alpha, in the absence of appreciable cell proliferation. Indeed, despite being poor stimulators in proliferation assays, most APLs readily induce production of TNF-alpha. Our results demonstrate that the net outcome of APL treatment in vivo represents the sum of diverse effects, which may not be revealed completely by limited and randomly chosen in vitro assays.

[A new practical route to stereospecific synthesis of (S)-(-)-ofloxacin]

(S)-(-)-ofloxacin is one of the best fluoroquinolone agents in current clinical use. A new facile practical route with good yield and high optical purity to stereospecific synthesis of (S)-(-)-ofloxacin was described.

Synthesis and acetylcholinesterase inhibitory activity of (+/-)-14-fluorohuperzine A

The synthesis of (+/-)-14-Fluorohuperzine A has been accomplished and the ability of this agent to inhibit acetylcholinesterase has been measured. Taking into account its racemic form, this compound exhibits 62 times less potent activity than natural (-)-huperzine A.

Health effects of indoor fluoride pollution from coal burning in China

The combustion of high fluoride-content coal as an energy resource for heating, cooking, and food drying is a major exhaust emission source of suspended particulate matter and fluoride. High concentrations of these pollutants have been observed in indoor air of coal-burning families in some rural areas in China. Because airborne fluoride has serious toxicological properties, fluoride pollution in indoor air and the prevalence of fluorosis have been analyzed in a fluorosis area and a healthy nonfluorosis area in China and in a rural area in Japan. For human health, fluoride in indoor air has not only been directly inhaled by residents but also has been absorbed in stored food such as corn, chilies, and potatoes. In the fluorosis area in China, concentrations of urinary fluoride in the residents have been much higher than in the nonfluorosis area in China and in the rural area in Japan. In the fluorosis area, almost all elementary and junior high school students 10-15 years of age had dental fluorosis. Osteosclerosis in the skeletal fluorosis patients was very serious. Urinary deoxypyridinoline in rural residents in China was much higher than in rural residents in Japan. Data suggest that bone resorption was extremely stimulated in the residents in China and that fluoride may stimulate both bone resorption and bone formation. Because indoor fluoride from combustion of coal is easily absorbed in stored food and because food consumption is a main source of fluoride exposure, it is necessary to reduce airborne fluoride and food contamination to prevent serious fluorosis in China.

Molecular modeling and 3D-QSAR studies on the interaction mechanism of tripeptidyl thrombin inhibitors with human alpha-thrombin

The mechanism of inhibition of peptidyl inhibitors with thrombin was studied using molecular modeling, molecular mechanics, and CoMFA statistical analysis. A new procedure for the elucidation of binding conformations, BCSPL, is described and was employed to obtain the binding conformers of a series of 18 tripeptidyl thrombin inhibitors. Energetic studies and QSAR analysis of the BCSPL-derived conformers indicated a modest correlation between the calculated binding energies of the title compounds and their inhibitory activities to human alpha-thrombin. CoMFA analysis of the BCSPL alignment resulted in a satisfactory model of the thrombin active site.

[A monoclonal antibody-based indirect competitive inhibition enzyme-linked immunosorbent assay for detecting tetrodotoxin in puffer fish]

The homogenized tissue samples of puffer fish were extracted with boiling 0.1% acetic acid solution for 2 times, then the combined filtrate was defatted with ether ethyl for 2 times and the water phase were diluted with 0.05 mol/L PBS for ELISA determination (adjusted pH to 6.5-7.0). The results showed that the minimum detecable concentration of tetrodotoxin was 1.0 x 10(-3) mg/L (0.1 ng/assay), and the standard curve was linear between 1.0 x 10(-2) and 1.0 mg/L. The recovery rates from tetrodotoxin spiked samples of this method were 73.8%-117.4%. The accuracy of ELISA was compared with the traditional mouse bioassay system. The results showed no significant differences between the two methods (for paired-t test, P > 0.2), and significant correlations in tetrodotoxin concentration were obtained (r = 0.916).

Interactions between the ankyrin repeat-containing protein Akr1p and the pheromone response pathway in Saccharomyces cerevisiae

Akr1p, which contains six ankyrin repeats, was identified during a screen for mutations that displayed synthetic lethality with a mutant allele of the bud emergence gene BEM1. Cells from which AKR1 had been deleted were alive but misshapen at 30 degrees C and inviable at 37 degrees C. During a screen for mutants that required one or more copies of wild-type AKR1 for survival at 30 degrees C, we isolated mutations in GPA1, which encodes the G alpha subunit of the pheromone receptor-coupled G protein. (The active subunit of this G protein is G beta gamma, and G alpha plays an inhibitory role in G beta gamma-mediated signal transduction.) AKR1 could serve as a multicopy suppressor of the lethality caused by either loss of GPA1 or overexpression of STE4, which encodes the G beta subunit of this G protein, suggesting that pheromone signaling is inhibited by overexpression of Akr1p. Mutations in AKR1 displayed synthetic lethality with a weak allele of GPA1 and led to increased expression of the pheromone-inducible gene FUS1, suggesting that Akr1p normally (and not just when overexpressed) inhibits signaling. In contrast, deletion of BEM1 resulted in decreased expression of FUS1, suggesting that Bem1p normally facilitates pheromone signaling. During a screen for proteins that displayed two-hybrid interactions with Akr1p, we identified Ste4p, raising the possibility that an interaction between Akr1p and Ste4p contributes to proper regulation of the pheromone response pathway.

[A survey of T-2 toxin in wheat by an indirect enzyme-linked immunosorbent assay]

The survey of T-2 toxin in wheat randomly sampled in nine provinces was carried out, employing an indirect competitive enzyme-linked immunosorbent assay. Among 330 samples, 264 samples (80%) showed positive results. The mean concentrations was 53.3 ppb. and maximal concentration was 1122.0 ppb. It was also detected high concentration (84.5-1064.4) of T-2 toxin in human intoxication wheat samples in 1991. The investigation also showed that there existed close relationship between the level of T-2 toxin contamination and the epidemic of wheat scabby.