Durable CO2 conversion in the proton-exchange membrane system

Electrolysis that reduces carbon dioxide (CO2) to useful chemicals can, in principle, contribute to a more sustainable and carbon-neutral future1-6. However, it remains challenging to develop this into a robust process because efficient conversion typically requires alkaline conditions in which CO2 precipitates as carbonate, and this limits carbon utilization and the stability of the system7-12. Strategies such as physical washing, pulsed operation and the use of dipolar membranes can partially alleviate these problems but do not fully resolve them11,13-15. CO2 electrolysis in acid electrolyte, where carbonate does not form, has therefore been explored as an ultimately more workable solution16-18. Herein we develop a proton-exchange membrane system that reduces CO2 to formic acid at a catalyst that is derived from waste lead-acid batteries and in which a lattice carbon activation mechanism contributes. When coupling CO2 reduction with hydrogen oxidation, formic acid is produced with over 93% Faradaic efficiency. The system is compatible with start-up/shut-down processes, achieves nearly 91% single-pass conversion efficiency for CO2 at a current density of 600 mA cm-2 and cell voltage of 2.2 V and is shown to operate continuously for more than 5,200 h. We expect that this exceptional performance, enabled by the use of a robust and efficient catalyst, stable three-phase interface and durable membrane, will help advance the development of carbon-neutral technologies.

[Burden of disease and risk factors among children under 5 years in China from 1990 to 2019: a perspective of international comparison]

Based on the Global Burden of Disease study 2019, the standardized mortality rate and disability-adjusted life years (DALYs) rate of children under 5 years old were selected as evaluation indicators to compare and analyze the current situation and differences of disease burden of children under 5 years old between China and other regions from 1990 to 2019. The change trend and difference of disease burden of children under 5 years old in China were analyzed by sexes. From 1990 to 2019, the all-cause standardized mortality rate of children under 5 years old in China decreased from 1 153.81/100 000 to 160.39/100 000, and the all-cause standardized DALY rate decreased from 104 426.40/100 000 to 16 479.01/100 000. In 2019, neonatal preterm birth, congenital heart anomalies and lower respiratory infections ranked the top three disease burden of children under 5 years old in China. Except that the disease burden of neonatal preterm birth was lower than that in North America, they were much higher than that in Western Europe and North America in the same period. The burden of unintentional injury diseases, including pulmonary aspiration and foreign body in airway and drowning, was higher than that in Western Europe and North America. The standardized mortality and DALY rate of the top ten diseases and injuries in boys and girls under 5 years old in China showed a downward trend (P<0.05), and most of them were higher in boys than girls (P<0.05). From 1990 to 2019, the disease burden of children under 5 years old in China decreased significantly. However, compared other regions, it is still necessary to strengthen the prevention and control of neonatal premature birth, birth defects and unintentional injuries, and take different sex-specific interventions to improve the overall health of children.

[The clinical impact of artery-first approach combined with vascular resection and reconstruction in the treatment of pancreatic head carcinoma]

Objective: To evaluate the application of artery first, combined vascular resection and reconstruction in the treatment of pancreatic head carcinoma. Methods: The clinical data of 13 patients with pancreatic head cancer were retrospectively analyzed from February 2014 to March 2016 in the Affiliated Hospital of Xiamen University. Preoperative computed tomography of high resolution layer or magnetic resonance imaging examination demonstrated pancreatic head carcinoma, as well as close adhesion, stenosis, compression or displacement of superior mesenteric vein or portal vein wall. In the operation, the artery first approach was used and the whole arterial blood supply in the head of the pancreas was fully exposed and interdicted. Finally, en block resection and vascular resection and reconstruction was adopted. Results: 12 of 13 patients had pancreatoduodenectomy synchronously with vascular resection and reconstruction; the other patient had these two surgery sequentially. Four patients received blood vessel wedge resection, five had segmental resection combined with end to end suture, and four had segmental resection combined with artificial vascular graft reconstruction. Operation time was (327.2±65.5) minutes, and the amount of blood loss was (472.6±226.4) millilitres. One patient suffered from delayed gastric emptying, and two patients had pancreatic fistula. All patients recovered from postoperative complications by conservative treatment. No patients developed biliary fistula, gastrointestinal fistula, abdominal infection, pulmonary infection, diarrhea, hypoglycemia or other complications, and none died in perioperative period. Postoperative pathological findings confirmed the diagnosis of pancreatic ductal adenocarcinoma. Mean tumor diameter was (4.2±1.5)cm, and (3.8±1.5) metastasis were found in (13.6±2.5) resected lymph nodes. In 11 cases, the tumor cells were found in the outer membrane of blood vessels, 2 cases were found to have tumor invasion in the inner membrane, and all the resection margins were negative. All patients were followed up, and 2 patients died of liver metastasis 11 months and 18 months after operation, respectively. One patient survived with local recurrence of tumor 13 months after surgery. Other patients had no tumor recurrence and metastasis. Conclusions: The artery first approch combined vascular resection and reconstruction is safe effective and feasible in the treatment of pancreatic head carcinoma. It can improve the ablation rate of pancreatoduodenectomy.

Diamagnetic measurements based on the compensation of TF current diffusion in J-TEXT

Due to the existence both of toroidal ripples and toroidal field (TF) current diffusion, the toroidal flux changes with time when the TF current is at the flat-top. A diamagnetic measurement based on the compensation of TF current diffusion has been built in J-TEXT to solve this problem. The measurement system includes a double-loop installed in the vacuum vessel and an array of small printed circuit board (PCB) magnetic probes placed on the mid-plane of one TF coil. A model was proposed to analyze and compensate the effect of TF current diffusion. Experiment results show that the residual flux is about 1 × 10^-4 Wb after the compensation and it can meet the need of diamagnetic measurement in J-TEXT.

Adsorption of phosphate from aqueous solutions and sewage using zirconium loaded okara (ZLO): Fixed-bed column study

This study explores the potential of removing phosphorus from aqueous solutions and sewage by Zr(IV)-loaded okara (ZLO) in the fixed-bed column. Soybean residue (okara) was impregnated with 0.25M Zr(IV) solution to prepare active binding sites for phosphate. The effect of several factors, including flow rate, bed height, initial phosphorus concentration, pH and adsorbent particle size on the performance of ZLO was examined. The maximum dynamic adsorption capacity of ZLO for phosphorus was estimated to be 16.43mg/g. Breakthrough curve modeling indicated that Adams-Bohart model and Thomas model fitted the experimental data better than Yoon-Nelson model. After treatment with ZLO packed bed column, the effluent could meet the discharge standard for phosphorus in Australia. Successful desorption and regeneration were achieved with 0.2 NaOH and 0.1 HCl, respectively. The results prove that ZLO can be used as a promising phosphorus adsorbent in the dynamic adsorption system.

Osteoblastic proliferative activity of Epimedium brevicornum Maxim

The effect of the extracts of Epimedium brevicornum Maxim. was investigated on proliferative activity in vitro. The osteoblast-like UMR106 cells was employed as an osteoblast model. The EtOH extract and the n-butanol fraction from the crude extract were found to show proliferation stimulating activity. Three flavonoid compounds (icariin, epimedin B and epimedin C) were isolated from this fraction by activity-guided assay, and the effects on cell proliferation were studied. Icariin produced the most significant promoting effect on the proliferation in osteoblast-like UMR106 cells. The results suggested that E. brevicornum Maxim. extracts might have potential activity against osteoporosis, and flavonoids such as icariin might be the active constituents stimulating osteoblasts.

[Spectroscopic study on the high voltage fast pulsed discharge of nitrogen, ammonia or their mixture]

The emission spectra from the pulsed discharge plasma of nitrogen, ammonia or their mixture were measured. In the discharge of pure nitrogen gas, as the pressure increased, the discharge volume decreased and more dissociation of nitrogen molecules occurred due to the higher energy density. In the discharge of ammonia, N,N+ and NH+ were observed, but no NH2 and NH3 were detected, indicating that ammonia, which has the lower dissociation and ionization energies as compared to nitrogen, was highly dissociated. The discharge of the mixture of N2 and NH3 was also studied. The dependence of the dissociation of nitrogen on the ratio of nitrogen to ammonia was investigated by emission spectra. The optimal ratio for nitrogen dissociation was obtained. The advantage of using the mixture of nitrogen and ammonia in the synthesis of nitrides was discussed.

[Investigation on the excited state dynamics properties of hemicyanine molecules]

In this paper, the excited state dynamics properties of hemicynine were investigated by using time-resolved fluorescence and 3D fluorescence spectra techniques. The interaction of hemicyanine molecules caused formation of H-aggregates and a blue shift of the 3D fluorescence spectra in interleaving hemicyanine/arachidic acid multilayers. The peak of fluorescence was a red shift along with the time decay. The lifetime of the LB fluorescence was much shorter and the difference of beginning luminescence was less than that of the hemicyanine solution due to the stronger intermolecule interactions in the aggregates.

[Determination of puerarin in three traditional Chinese patent medicines by high performance liquid chromatography]

A simple and accurate reversed-phase high performance liquid chromatographic method to determine puerarin in three traditional Chinese patent medicines, namely "Xiao'er qingganling" tablet, "Buchang xinnaoxintong" capsulae and "Ganmao qingre" granule is described. "Xiao'er qingganling" tablet and "Buchang xinnaoxintong" capsulae were extracted with methanol in an ultrasonic bath and "Ganmao qingre" granule was extracted with water and ethanol. After being centrifuged and filtered, the samples were separated on an ODS column with a mobile phase of 100 mmol/L ammonium acetate buffer (pH 5.0)-methanol(75:25, volume ratio). The flow rate was 0.8 mL/min, and the detection wavelength was 250 nm. The calibration curve was linear in the range of 2 mg/L-20 mg/L puerarin (r = 0.9999). The average recoveries were 99.0%, 93.4% and 97.5% for "Xiao'er qingganling" tablet, "Buchang xinnaoxintong" capsulae, "Ganmao qingre" granule respectively. The average contents of puerarin in the medicines were 3.48 mg/g, 1.08 mg/g and 1.52 mg/g (sucrose), and the relative standard deviations were 1.9%, 1.4% and 1.4% respectively.

[Determination of unbound concentration of drug in drug-human serum albumin mixture by high performance frontal analysis]

A high performance frontal analysis(HPFA) method was developed to determine the unbound concentration of drugs in drug-human serum albumin (HSA) mixture under binding equilibrium. The sample was injected directly onto an internal-surface reversed-phase silica column (ISRP). The mobile phase was 67 mmol/L phosphate buffer (pH 7.4, I = 0.17 mol/L). When a large volume of sample solution under drug-HSA binding equilibrium was directly injected, the drug was eluted as a trapezoidal peak with a plateau, and the drug concentration in this region was the same as that of the unbound drug in the sample solution. The eluate of plateau region was collected and a small volume was injected onto a reversed-phase HPLC column. This HPFA-HPLC method was employed in the determination of unbound concentration in both ketoprofen (KP)-HSA and cefoperazone (CP)-HSA mixtures. The unbound concentrations of drugs obtained by using HPFA-HPLC were compared with those determined with ultrafiltration-HPLC. The effects of sample volume and flow rate of mobile phase on the plateau formation were investigated. It was found that the minimum injection volume to achieve a trapezoidal peak varied with drugs. The flow rate showed no effect on the trapezoidal peak formation. The unbound concentrations of KP and CP obtained were about the same by using HPFA-HPLC or ultrafiltration-HPLC and precisions were similar for both methods.

[Determination of bifonazole in cream by high performance liquid chromatography]

An accurate method for the determination of bifonazole in cream is described. The analytical column was packed with Hypersil ODS. The mobile phase was a mixture of 0.08 mol/L aqueous triethylamine (TEA) phosphate solution(pH 7.0)-acetonitrile-methanol (20:10:70, V/V) and the detection wavelength was 254 nm. This method is simple, accurate and can be used for the quality control of bifonazole in cream.

[HPCE determination of trimebutine maleate in rat plasma and its pharmacokinetics]

AIM

To develop a method for the determination of trimebutine maleate in rat plasma by using high performance capillary electrophoresis. The method was employed to pharmacokinetic analysis of trimebutine maleate.

METHODS

Plasma samples were deproteinized with acetonitrile (containing ephedrine hydrochloride as internal standard) and the supernatant was dried under N2 stream at 50 degrees C. The residue was dissolved with methanol-water (1:1) and injected into the capillary by siphon. The electrophoresis was performed in uncoated fused-silica capillary and the voltage was 10 kV. The running buffer was 0.03 mol.L-1 NaH2PO4(pH 6.0). The eluate was detected at 214 nm by UV detection.

RESULTS

The recovery for trimebutine maleate in rat plasma was 72.8%-87.9%. The calibration curve in plasma was linear over the range 5-200 micrograms.L-1. The limit of quantitation was 5 micrograms.L-1. The intraday relative standard deviation (n = 6) and the interday relative standard deviation (n = 18) were less than 14%. The highest concentration in plasma was observed at 30 min after ig trimebutine maleate to rats. The pharmacokinetic results were AUC0-infinity = 8 micrograms.min.mL-1, T1/2(Ke) = 173 min and Ke = 5.6 x 10(-3) min-1.

CONCLUSION

The method is accurate, sensitive and suitable for pharmacokinetic study of trimebutine maleate.

[Determination of ecdysterone in Achyranthes bidentata Bl. and its activity promoting proliferation of osteoblast-like cells]

AIM

To study the activity of ecdysterone from Achyranthes bidentata Bl. (AB) promoting proliferation of osteoblast-like (OB-like) UMR106 cells and to determine its content in AB by HPLC method.

METHODS

Ecdysterone isolated from AB was cultured with OB-like cells UMR106 together in vitro and the proliferation of OB-like cells was determined by MTT assay. The chromatographic conditions for determining ecdysterone included an ODS column (250 mm x 4.6 mm, 5 microns), a mobile phase consisting of a mixture of water-acetontrile-tetrahydrofuran (86:11:3), detection wavelength of 243 nm, and column temperature of 27 degrees C. Phenacetin was used as the internal standard.

RESULTS

The ecdysterone from AB had significant activity promoting proliferation of OB-like cells, the proliferation was promoted by 41% (n = 3). The average recovery of ecdysterone was 96.2% (RSD = 2.1%), the calibration was linear in the range of 30-300 micrograms.mL-1 (gamma = 0.9998).

CONCLUSION

Ecdysterone was screened quickly by cultivating with OB-like cells together in vitro. The HPLC method is accurate, fast and reproducible for the determination of ecdysterone in AB.

[Determination of three principal components in chuanjing tablets by using high performance liquid chromatography]

Uniform design method was employed to optimize the mobile phase of HPLC in order to determine simultaneously three principal components, theophylline, amobarbital and methylephedrine hydrochloride, in Chuanjing tablet, a compound preparation for asthma and cough. The stationary phase was ODS and the optimal mobile phase composition was V (0.015 mol/L phosphate buffer containing 0.3% triethylamine, pH 4.9): V (methanol) = 35:65. The detection was performed at 215 nm and the sensitivity was time programmed for simultaneous determination of minor and major components. Caffeine was selected as the internal standard. A baseline separation was achieved within 10 min. The linear ranges for theophylline, amobarbital and methylephedrine hydrochloride were 0.03 g/L-0.20 g/L, 7.5 mg/L-50.0 mg/L and 7.5 mg/L-50.0 mg/L, recoveries 99.7%-102.6%, 98.5%-100.2% and 98.0%-102.7%, inter-day RSDs 0.23%-1.2%, 0.35%-2.5%, 0.33%-1.6% respectively. This HPLC method is rapid and accurate, and suitable for the quality control of the preparation.

Self-Association of Poly

Poly[2-(beta-D-glucosyloxy)ethyl acrylate] (PGEA) was prepared by radical polymerization of 2-(2',3',4',6'-tetra-O-acetyl-beta-D-glucosyloxy)ethyl acrylate (AcGEA) followed by O-deacetylation. Fluorescence measurements revealed that PGEA tended to associate into aggregates in an aqueous medium. The critical aggregation concentration (cac) of PGEA in water was determined by using N-phenyl-1-naphthalamine (PNA) as a fluorescent probe. The dependence of cac on the molecular weight of PGEA and temperature was observed. A copolymer of GEA with a hydrophobic monomer, i.e., stearyl acrylate (SA), was also synthesized in order to increase the hydrophobicity of PGEA and to understand the hydrophobic effect on cac. It was found that the cac of P(GEA-co-SA) was much lower than that of PGEA, and it decreased with increasing ratio of SA in the copolymer. Size-exclusion chromatography (SEC), dynamic light scattering (DLS), and transmission electron microscopy (TEM) measurements indicated that the aggregates have hydrophobic interiors; they were spherical in shape and their sizes varied in a broad range. This phenomenon was explained in terms of a combination of hydrophobic interaction and cooperative hydrogen bonding. Copyright 2000 Academic Press.

[Isolation and identification of three steroid compounds from Mauremys mutics plastron]

OBJECTIVE

To investigate the steroids components from extract of Mauremys mutics.

METHOD

The steroid compounds were isolated by using vacuum liquid chromatography and PTLC. The structures of three compounds were determined by spectral, chromatographic and chemical analysis.

RESULTS

Three steroids were isolated from M. mutics and identified as cholesterol, elcosenoic acid cholesterol ester, cholester-4-ene-3-one.

CONCLUSION

All the three compounds were isolated from M. mutics for the first time.

Effects of beta2-microglobulin mutations on the alpha-1 helical region of H2-Ld

Beta-2 microglobulin (beta2m)has been shown to have an effect on the structural and functional constraints that facilitate proper class I antigen presentation. To date, no evidence has pinpointed the beta2m-specific amino acids that play an integral role in affecting structure in and around the peptide binding region of class I. To delineate beta2m amino acid positions that affect the alpha-1 helical region, we generated a series of mutant beta2m proteins bearing precise amino acid substitutions. The amino acid positions chosen were based upon previous results which demonstrated that human beta2m association with H2-Ld altered the structure of the alpha-1/alpha-2 super-domain. beta2m mutant proteins were used in beta2m exchange assays with cells expressing H2-Ld. Following exchange, cells were assayed to determine whether mutant beta2m association resulted in structural alteration of class I extracellular domains. The alteration in H2-Ld structure was evidenced by an increase in the binding of an antibody (34-1-2), specific for the alpha-1 helical region of H2-Ld. Results demonstrated that amino acid substitutions in beta2m positions 33 and 53 led to a dramatic increase in the reactivity of the alpha-1 domain-specific antibody 34-1-2. Identifying beta2m amino acid positions that influence the structure of the peptide binding region may allow for a better understanding of cellular immune responses that center upon class I/beta2m expression.

[Development of the lens and zonulae in the human embryo]

The embryonic development and ultrastructures of the lens and zonulae in 212 eyes of 131 human embryos were studied by light and electronic microscopy, with the finding that the capsule and zonulae appeared earlier than previously reported. The laminate structure of the capsule was observed in the 7 week embryo, and the early structures of zonulae were discernible in the 10th week on the basement membrane of the non-pigmental epithelium of the ciliary body and on the capsule, indicating that the capsule was specialized basement membrane of the lenticular epithelial cells, and the zonulae originated from the non-pigmental epithelium of the ciliary body and the capsule of lens.

[The embryonic development of iridial muscles]

Development of iridial muscles was observed in 116 fetal eyes (72 human embryos 7 weeks to full gestation). Bundles of microfilaments with local high density spots appeared in the cytoplasm of the anterior pigment epithelium early in 10 week embryos. The high density spots later grew to be the dense-bodies in the myofilaments, the original structure of the pupillary sphincter. In embryos of 4 1/2 months, blood capillaries grew into the sphincter, which was fully developed in the 6th month, and myofilaments of the dilator muscles began to appear in the cytoplasm of peripheral anterior pigment epithelium, with villous protrusions toward the stroma. Many myofilaments with scattered dense-bodies were seen in the protrusions. It was thus confirmed that both the sphincter and dilator muscles originated from the iridial anterior pigment epithelium of neuro-ectoderm; however, the former developed fully to form independent smooth muscle bundles, while the latter was less developed and remained part of the pigment epithelium (myo-epithelium). The appearance of both muscles was earlier than previously reported.

Study on antithrombogenicity of poly[beta-(acetylsalicylyloxy)ethyl methacrylate] relative to poly(hydroxyethyl methacrylate)

The antithrombogenicity of a polymer made of aspirin bound to hydroxyethyl methacrylate (HEMA), abbreviated as ASA-polymer, was compared with that of poly(hydroxyethyl methacrylate) (PHEMA). Platelet from platelet rich plasma (PRP) incubated with ASA-polymer surface exhibited noticeable decreases in adhesion and aggregation as compared to platelets incubated with PHEMA. Low molecular weight components other than aspirin, which may be released from ASA-polymer during the incubation with PRP, or contact with ASA-polymer causing denaturation of platelets without morphological changes could be responsible for the decrease of adhesion and aggregation. Both PRP and PPP exposed to ASA-polymer-coated surfaces exhibited a much smaller partial thromboplastin time (PTT) than if exposed to PHEMA-coated surfaces; the PTT of ASA-polymer was similar to that of glass exposed plasma. With respect to the in vivo antithrombogenicity, the ASA-polymer surface led to thrombus formation. This may be due to the partial hydrolysis of the acetyl groups resulting in the formation of a negatively charged surface which in turn accelerates the coagulation cascade despite its inhibitory effects on platelet adhesion and aggregation. On the other hand, neointima formed around a thrombus layer on PHEMA-coated sutures after 14 days.

Preparation, high-performance liquid chromatographic separation and characterization of hexacarboxylic porphyrinogens

A simple method for the preparation and reversed-phase high-performance liquid chromatographic separation of hexacarboxylic porphyrinogen isomers is described. Uroporphyrin I or III was partially decarboxylated in 0.5 M hydrochloric acid at 150 degrees C. Unreacted uroporphyrin and the hepta-, hexa- and pentacarboxylic porphyrins formed were esterified and then group-separated by thin-layer chromatography. After hydrolysis, the porphyrins were reduced to the corresponding porphyrinogens with 3% (w/w) sodium amalgam. The hexacarboxylic porphyrinogens were separated on an ODS-Hypersil column by elution with acetonitrile-methanol-1 M ammonium acetate, pH 5.16 (8:12:80, v/v/v) as mobile phase. Isomers were identified by high-performance liquid chromatography of the characteristic mixture of two pentacarboxylic porphyrins formed after partial decarboxylation of individual isomers. Except for the two type I isomers, resolution of the hexacarboxylic porphyrinogens was superior to that of the corresponding porphyrins.

[Embryonic development and structure of human Bruch's membrane]

A morphological study of Bruch's membrane was performed on 61 human embryonic and fetal eyes by transmission and scanning electron microscopy. The basement membrane of retinal pigment epithelium could be identified in the 5 week embryo. At the 11th week, the five components of Bruch's membrane were all discernible. The features of the five components were topographically examined by scanning electron microscopy.

High-performance liquid chromatography of porphyrins

Techniques for the analysis of porphyrins in the biomedical fields are reviewed. The emphasis is on high-performance liquid chromatography and its aspplications in: (1) the quantitative analysis of porphyrins in blood, urine and faeces; (2) qualitative porphyrin profiles in normal subjects and in the porphyrias; (3) assay of haem biosynthetic enzyme activities and (4) resolution of type isomers of porphyrins and porphyrinogens. Detection systems, quantitation methods, peak identification and sample preparation procedures are discussed.

An HPLC assay for rat liver ferrochelatase activity

A rapid, reliable, sensitive and reproducible HPLC method was developed for the assay of ferrochelatase activity in rat liver. The assay was carried out aerobically with Zn2+ and mesoporphyrin or protoporphyrin IX as substrates. Zn-porphyrins formed were extracted with dimethyl sulphoxide/methanol (30:70, v/v) containing Zn-deuteroporphyrin as the internal standard for separation and quantification by reversed-phase chromatography. The Km for mesoporphyrin was 5.9 microM, for protoporphyrin IX 8.8 microM and for zinc 6.0 microM. The specific activities were 33.1 +/- 5.0 nmol Zn-mesoporphyrin or 13.4 +/- 2.0 nmol Zn-protoporphyrin formed per hour per mg of protein for mitochondria and 12.3 +/- 2.2 nmol Zn-mesoporphyrin or 4.6 +/- 0.9 nmol Zn-protoporphyrin per hour per mg of protein for liver homogenate.

Characteristic autofluorescence for cancer diagnosis and its origin

The autofluorescence spectra of human tissues excited with the 365-nm line of pulsed xenon ion laser have been measured. The autofluorescence spectra of cancer tissues usually show characteristic peaks near 630 nm and 690 nm, which do not appear in the spectra of the corresponding normal tissues. This characteristic fluorescence can be taken as a criterion for cancer diagnosis; a consistency of 89% with the traditional biopsy method has been obtained in preliminary clinical application to the diagnosis of buccal carcinoma. Spectroscopic investigations suggest that the porphyrin compounds localized and retained in cancer tissues might be responsible for this characteristic autofluorescence.

Urinary excretion of N-nitrosamino acids and nitrate by inhabitants of high- and low-risk areas for esophageal cancer in Northern China: endogenous formation of nitrosoproline and its inhibition by vitamin C

A total of 238 samples of 24-h urine were collected from inhabitants of high-risk (Lin-xian) and low-risk (Fan-xian) areas for esophageal cancer in northern China, according to three protocols: (a) from undosed subjects; (b) from subjects who had ingested 100 mg L-proline three times a day 1 h after each meal; and (c) from subjects in Lin-xian who had ingested 100 mg ascorbic acid together with 100 mg L-proline three times a day 1 h after each meal. As an index of individual exposure to N-nitroso compounds or their precursors, ingested in food and/or formed endogenously, the levels of four urinary N-nitrosamino acids and nitrate were determined. The amounts of N-nitrosoproline, N-nitrosothiazolidine 4-carboxylic acid, N-nitrososarcosine, and nitrate excreted in the 24-h urine of undosed subjects in Lin-xian were significantly higher than those in Fan-xian, indicating a higher exposure of the inhabitants in the high-risk area to N-nitroso compounds and their precursors. Ingestion of L-proline resulted in a marked increase in urinary N-nitrosoproline levels in inhabitants from both areas, suggesting that endogenous nitrosation may occur to a larger extent when appropriate amine precursors are ingested in foods. Intake of moderate doses of ascorbic acid by high-risk subjects effectively reduced the urinary levels of N-nitrosamino acids to those found in undosed subjects in the low-risk area. If N-nitroso compounds formed in vivo are among the causative factors for esophageal cancer in this area of northern China, ascorbic acid appears to be effective in lowering the body burden of these carcinogenic compounds, thus offering a rational basis for long-term intervention studies in this area.

Studies on the hydrolysis of biocompatible acrylic polymers having aspirin-moieties

Both the homogeneous and heterogeneous hydrolysis of five new acrylic polymers having aspirin-moieties, i.e. polymers of beta-(acetylsalicylyloxy)ethyl methacrylate, beta-(acetylsalicylyloxy) propyl methacrylate,beta-(acetylsalicylyloxy) ethyl acrylate, beta-hydroxy-gamma-(acetylsalicylyloxy) propyl methacrylate, beta-hydroxy-gamma-(acetylsalicylyloxy) propyl acrylate were investigated in acidic or alkaline medium at 30 degrees C or 60 degrees C, respectively. It was observed that the chief hydrolyzed product is always aspirin with minor amount of salicylic acid.