Increased lectin-like oxidized LDL receptor-1 expression in the placentas of women with intrahepatic cholestasis during pregnancy

BACKGROUND

Intrahepatic cholestasis of pregnancy (ICP) is a reversible cholestatic liver disease of undefined etiology and pathogenesis. It is likely associated with dyslipidemia. However, the explanation for the role of dyslipidemia is not clear. We hypothesized that an increased oxidized low-density lipoprotein (oxLDL) and lectin-like oxidized LDL receptor-1 (LOX-1) may play a crucial role in the development of the disease. Thus, the aim of this study was to investigate the plasma oxLDL level and LOX-1 expression in placentas from women with ICP.

METHODOLOGY

The plasma oxLDL level and LOX-1 expression were detected in 94 intrahepatic cholestasis of pregnancy patients (ICP group) and 94 healthy pregnant women (control group). The placental LOX-lexpression was detected by Western blotting; the plasma oxLDL was measured by enzyme-linked immunosorbent assay.

RESULTS

The placental LOX-1 expression in the ICP group was higher than that in the control group (p < 0.05), whereas the plasma oxLDL did not differ significantly between the patients with ICP and healthy pregnant women.

CONCLUSIONS

LOX-1 may play a crucial role in the pathophysiological processes of ICP caused by over-apoptosis of trophocytes. Moreover, LOX-1 could be a potential target for therapeutic intervention.

[Screening of target protein interacting with lipid transfer protein AsE246 of Astragalus sinicus and expression characteristics of corresponding encoding gene]

OBJECTIVE

AsE246 was a novel nodule-specific expressed nodulin gene encoding non-specific lipid transfer protein 1 (nsLTP1) of A. sinicus. We screened and identified host plant target protein interacting with AsE246, and characterized the expression patterns of target gene under symbiotic and stress conditions.

METHODS

Yeast two-hybrid system, small-scale yeast hybridization test and real-time PCR technique were used to capture the host target protein that interacts with the bait protein AsE246, and to quantitatively analyze the temporal and spatial expression characteristics of target gene during root nodule development and nitrogen fixation process.

RESULTS

One positive clone was obtained, its cDNA insert sequence and Blast analysis showed that: the target protein was a DnaJ-like protein, thus the corresponding encoding gene was named as AsDJL1. AsDJL1 was specifically-enhancing expressed in nitrogen-fixing root nodules, and significantly increased under NaCl stress while significantly decreased under (NH4) 2SO4 stress.

CONCLUSION

This work was the first report on the isolation of proteins interacting with LTP. The work obtained some direct and convincing evidences to show the interacting gene demonstrated high similarity as AsE246 in expression patterns and functions involved. The present progress provided a basic foundation and theoretical basis to undertake any further investigation into their interaction, and regulation mechanism associated with symbiotic nitrogen fixation or response to environmental stress.

A novel HLA-DRB1*15 allelic sequence isolated from the Han population of Guangdong, China

A novel DRB1*15 allele, DRB1*1516, has been identified in a Guangdong Han individual. Its sequence was confirmed by sequencing of polymerase chain reaction products and clones. This allele differed by one nucleotide from DRB1*150101 at position 220 (G-->A), resulting in an amino acid substitution from Gly to Arg at codon 45.

Changes in HIV-1 incidence in heroin users in Guangxi Province, China

Guangxi Province, China recently experienced an outbreak of HIV-1 infection among heroin users. We studied HIV-1 incidence rates and associated risk factors for HIV-1 infection among heroin users residing in Pingxiang City. A total of 318 heroin users were followed from February 1998 through January 1999 (median follow-up: 8.1 months). Of these, 130 were prospectively followed from January through September 1999 (median follow-up: 8.3 months). HIV-1 and hepatitis C virus (HCV) incidence rates for each period were calculated. A generalized estimating equation approach was implemented to identify independent risk factors associated with HIV-1 infection across both periods. Among 318 study participants, 97.2% were men. The median age was 22 years. Approximately 60% reported sharing needles. HIV-1 prevalence at baseline was 15.4%. During the first follow-up period, HIV-1 incidence was 2.38 per 100 person years (py), and HCV incidence was 26.8 per 100 py. During the second follow-up period, HIV-1 incidence was 6.86 per 100 py, and HCV incidence was 28.9 per 100 py. After controlling for age and other factors, HCV seropositivity, history of sexually transmitted diseases, and sharing needles were independently associated with HIV-1 infection. These data suggest that HIV-1 incidence was rising over time in Pingxiang City, Guangxi Province. The high incidence of HCV heightens the importance of enhanced prevention programs to reduce injection and needle sharing among heroin users.

Degradation of green tea catechins in tea drinks

Green tea cateachins (GTC). namely (-) epicatechin (EC), (-) epicatechin gallate (ECG), (-) epigallocatechin (EGC), and (-) epigallocatechin gallate (EGCG), have been studied extensively for their wide-ranging biological activities. The goal of the present study was to examine the stability of GTC as a mixture under various processing conditions. The stability study demonstrated that GTC was stable in water at room temperature. When it was brewed at 98 degrees C for 7 h, longjing GTC degraded by 20%. When longjing GTC and pure EGCG were autoclaved at 120 degrees C for 20 min, the epimerization of EGCG to (-) gallocatechin gallate (GCG) was observed. The relatively high amount of GCG found in some tea drinks was most likely the epimerization product of EGCG during autoclaving. If other ingredients were absent, the GTC in aqueous solutions was pH-sensitive: the lower the pH, the more stable the GTC during storage. When it was added into commercially available soft drinks or sucrose solutions containing citric acid and ascorbic acid, longjing GTC exhibited varying stability irrespective of low pH value. This suggested that other ingredients used in production of tea drinks might interact with GTC and affect its stability. When canned and bottled tea drinks are produced, stored, and transported, the degradation of GTC must be taken into consideration.

[Determination of nitrite and nitrate in rat nervi ischiadicus by high performance liquid chromatography]

To study the effect of nitric oxide on the diabetic neuropathy, a quantitative method for the determination of nitrite(NO2-) and nitrate(NO3-) in rat nervi ischiadicus by high performance liquid chromatography(HPLC) with UV-VIS detection was developed. In the range of 1 mumol/L-25 mumol/L, correlation coefficient between concentration and peak area for NO2- and NO3- was more than 0.991. The minimum detection limits for both ions were 0.2 mumol/L and 0.5 mumol/L, respectively. Relative standard deviation(RSD) of inter-day and intra-day was less than 14%. The effects of different acetonitrile concentration and pH of mobile phase on separation as well as the stability of both salty ions were studied. In comparison with normal group, the levels of NO2- and NO3- for diabetic groups were lower. Measured mean values were, in turn, as follows: normal rats, (2.62 +/- 0.38) mumol/L and (24.43 +/- 5.61) mumol/L (n = 8); diabetic-controlled rats (saline-given only), (2.24 +/- 0.20) mumol/L and (17.15 +/- 7.79) mumol/L (n = 6); diabetic rats treated with bovine colostrum insulin-like growth factor(BctIGF-1) or with recombinant human insulin-like growth factor (rhIGF-1), (2.55 +/- 0.36) mumol/L and (6.12 +/- 2.14) mumol/L (n = 5) and (1.46 +/- 0.08) mumol/L and (9.95 +/- 3.34) mumol/L (n = 7), respectively.

Interaction between flavonoids and α-tocopherol in human low density lipoprotein

Oxidative modification of low density lipoprotein (LDL) may play an important role in the development of atherosclerosis. Alpha-tocopherol functions as a major antioxidant in human LDL. The present study was to test whether four natural flavonoids (kempferol, morin, myricetin, and quercetin) would protect or regenerate alpha-tocopherol in human LDL. The oxidation of LDL incubated in sodium phosphate buffer (pH 7.4, 10 mM) was initiated by addition of either 5.0 mM CuSO(4) at 37 degrees C or 1.0 mM of 2,2'-azo-bis (2-amidinopropane) dihydrochloride (AAPH) at 40 degrees C. It was found that alpha-tocopherol was completely depleted within 1 hour. Under the same experimental conditions, all four flavonoids demonstrated a dose-dependent protecting activity to alpha-tocopherol in LDL at the concentration ranging from 1 to 20microM. All flavonoids showed a varying protective activity against depletion of alpha-tocopherol in LDL, with kempherol and morin being less effective than myricetin and quercetin. The addition of flavonoids to the incubation mixture after 5 minutes demonstrated a significant regeneration of alpha-tocopherol in human LDL. The protective activity of four flavonoids to LDL is related to the number and location of hydroxyl groups in the B ring as well as the stability in sodium phosphate buffer.

Regeneration of alpha-tocopherol in human low-density lipoprotein by green tea catechin

Oxidative modification of low-density lipoproteins (LDL) may play an important role in the development of atherosclerosis. alpha-Tocopherol functions as a major antioxidant in human LDL. The present study was to test whether green tea catechins (GTC) would protect or regenerate alpha-tocopherol in human LDL. The oxidation of LDL incubated in sodium phosphate buffer (pH 7.4, 10 mM) was initiated by addition of 1.0 mM of 2,2'-azobis(2-amidinopropane) dihydrochloride at 40 degrees C. It was found that alpha-tocopherol was completely depleted within 1 h. Under the same experimental conditions, the longjing GTC extracts demonstrated a dose-dependent protective activity to alpha-tocopherol in LDL at concentrations ranging from 2 to 20 microM. Four pure epicatechin derivatives showed varying protective activity against depletion of alpha-tocopherol in LDL with (-)-epigallocatechin (EGC) and (-)-epigallocatechin gallate (EGCG) being less effective than (-)-epicatechin (EC) and (-)-epicatechin gallate (ECG). The results showed that addition of longjing GTC extracts, EC, ECG, and EGCG at 5, 10, and 15 min to the incubation mixture demonstrated a gradual regeneration of alpha-tocopherol in human LDL.

[Using polymerase chain reaction for the detection of gonorrhoea in women and children in Taiyuan]

A polymerase chain reaction (PCR) method was established for the detection of gonococcal gene in samples obtained from women and children with lower genital tract infection. The primers were used for PCR amplification derived from sequence for DNA representing part of the open reading frame (ORF) for the chromosome of N. gonorrhoea. In this study, a total number of 9204 specimens were obtained from women and children with lower genital tract infection from 1986 to 1995 in Taiyuan. The positive rate of N. gonorrhoea for Gram's stain of smears was 26.5% while the rates for culture and PCR were 12.4% and 21.0%, respectively. The results showed that PCR test was simple, rapid sensitive and specific for the detection of gonococcal gene in clinical specimens.

Inhibitory effects of jasmine green tea epicatechin isomers on free radical-induced lysis of red blood cells

Jasmine green tea is an excellent source of natural polyphenol antioxidants including mainly (-) epicatechin (EC), (-) epicatechin gallate (ECG), (-) epigallocatechin (EGC) and (-) epigallocatechin gallate (EGCG). The present study was to test our hypothesis that ingestion of jasmine tea would protect red blood cell (RBC) membrane from free radical-induced oxidation if jasmine tea epicatechin isomers could be absorbed and circulated in blood. When incubated with RBC suspension, all four epicatechin isomers purified from jasmine tea exhibited a strong protection for RBC membrane to hemolysis induced by 2,2'-azo-bis(2-amidinopropane) dihydrochloride (AAPH), an azo free radical initiator. The inhibitory effect was dose-dependent at the concentrations of 2.5 microM to 40 microM. The fatty acid analysis revealed that all four epicatechin isomers significantly prevented loss of arachidonic acid (20:4n-6) and docosahexaenoic acid (22:6n-3) in RBC incubated under the same conditions. Although the in vitro antioxidative activity of EGCG and ECG was more effective than EGC and EC, the latter two isomers were more important in vivo in scavenging free radicals. This was because only EGC and EC instead of EGCG and ECG were circulating in blood stream after a gavage-dose of 100 mg jasmine tea GTP mixture. In fact, ingestion of jasmine tea GTP extracts was associated with a significant decrease in susceptibility of RBC to hemolysis in rats.

Drug combinations and effect parameters of zidovudine, stavudine, and nevirapine in standardized drug-sensitive and resistant HIV type 1 strains

Reference strains of HIV-1 from the NIH AIDS Research and Reference Reagent Program, including wild-type IIIB, G762-3, and AZT resistant with RT 215T-->Y (G910-11/AZT); 67D-->N, 70K-->R, 215T-->F, 219K-->Q (G691-2/AZT); as well as nevirapine (NEV) resistant with 181Y-->C (N119/NEV); and 103K-->N, 181Y-->C (A17/NEV), were subjected to quantitative parametric efficacy analysis using AZT, stavudine (D4T), and nevirapine (NEV) singly or in combinations in MT4 or MT2 cells. The median-effect principle and combination index (CI) method of Chou-Talalay (see Ref. 26) have been used, which take into account both the potency (Dm value or EC50) and the shape of the dose-effect curve (m value). Under standardized assay conditions, G910-11 and G691-2 strains showed 600- and 7800-fold resistance to AZT, and N119 and A17 strains showed 3600- and 1000-fold resistance to NEV at the EC50 level, respectively. AZT-resistant strains exhibited slight cross-resistance to D4T. Computerized analysis indicates that IIIB gave sigmoidal dose-effect curves (m = 2.8, 3.4, and 3.1 for AZT, D4T, and NEV, respectively) whereas drug-resistant strains showed negative sigmoidicity toward the corresponding AZT or NEV, with m = 0.27-0.73. Therefore, the degrees of drug resistance are drastically different at classic EC50 and at therapeutically more relevant EC95 levels (ranging from severalfold to several log orders). Combinations of AZT+NEV and AZT+NEV+D4T showed synergism against IIIB, G762-3 (wild type) and A17/NEV, G910-11/AZT strains. D4T+NEV and AZT+D4T showed nearly additive or moderate antagonism. Synergism or additive effect leads to a favorable dose-reduction index (DRI). The present study on RT inhibitors provides quantitative assessment of the combinations of AZT, NEV, and D4T against HIV infections involving drug-sensitive and drug-resistant HIVs.

[Effects of thioglucoside on thyroid and iodine metabolism]

Swine, fed with fodder containing 8%-16% rape-seed meal, took 919.42-1416.02 mg of thioglucoside (glucosinolate) daily. After being fed with it for 120 consecutive days, swine's thyroid enlarged and their thyroid follicles and epithelial cells were prominently hyperplastic, lacking secretory granules and lysosome in thyroid cytoplasm, with microvilli condensed in apical cells, and a great number of vacuoles surrounding the colloid in the follicular cavity, with its secretory function vigorous and significantly increased T4 and ratio of T4 to T3, and showing hyperthyroidism. If iodine was supplied in the fodder and the antidotes were administered, the morphology and ultrastructure of the thyroid tissues in swine restored to normal, and their T4 and ratio of T4 to T3 tended to be normal, too.

Detection of genes for heat-stable enterotoxin in Escherichia coli by biotinylated ST-DNA probes

Reference strains of enterotoxigenic Escherichia coli (ETEC), non-enterotoxigenic Escherichia coli (non-ETEC), enteropathogenic Escherichia coli (EPEC), enteroinvasive Escherichia coli (EIEC), and other enteropathogenic bacteria were used to prove the reliability of BIO-ST-DNA probe hybridization. In addition, 417 strains of E. coli isolated from children with diarrheal diseases in Shanxi Children's Hospital were examined for BIO-ST-DNA probe hybridization. In the test, BIO-ST-DNA hybridization was compared with suckling mouse assay in identifying ST-ETEC. The results obtained by both methods showed no significant difference. It was found that identification of ST-ETEC using hybridization is a simple, sensitive and more practical method.

[Antihypertensive effects of atenolol and nitrendipine alone or in combination on three hypertensive models of rats]

The antihypertensive effects of atenolol (Ate) or nitrendipine (Nit) alone or in combination (Ate+Nit) were studied in conscious experimental hypertensive rats. The hypotensive effects of single ig of Ate 20 + Nit 10 mg.kg-1 were rapid and persistent in spontaneously hypertensive rats (SHR). In renovascular hypertensive rats (RVHR) and DOCA-salt hypertensive rats (DHR), Ate+Nit (6 + 3, 20 + 10, 60 + 30 mg.kg-1) given ig once a day for 10 d reduced the blood pressure in a dose-dependent manner. But Ate 20 mg.kg-1 or Nit 10 mg.kg-1 alone given ig once a day for 10 d caused no obvious reduction in blood pressure in RVHR, DHR, and SHR q = 1.32. These results revealed that the synergy is present in the antihypertensive action of Ate+Nit.

[Inhibitory effects of neferine and tetrandrine on portal vein and papillary muscle in rats]

To determine the vascular selectivity, the inhibitory effects of verapamil (Ver), neferine (Nef), and tetrandrine (Tet) on the spontaneous contractile force of portal vein and contractile force of the paced papillary muscle of left ventricle were studied in Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). The vascular selectivity was expressed by the IC50 ratio (IC50 for papillary muscle/IC50 for portal vein). The results showed that the vascular selectivity values of Ver, Nef, and Tet were 1.15, 0.32, and 0.20, respectively in WKY and 0.80, 0.24, and 0.10, respectively in SHR. It is concluded that Nef and Tet, in contrast with Ver which is devoid of selectivity for either tissue, are more liable to inhibit the myocardium than the vascular smooth muscle. In addition, the IC50 value of Tet for inhibition of the portal vein in SHR was nearly 10-fold higher than that in WKY (237 and 27 mumol.L-1, respectively). This indicates that the response of portal vein to Tet is decreased in SHR.

Comparisons of anti-human immunodeficiency virus activities, cellular transport, and plasma and intracellular pharmacokinetics of 3'-fluoro-3'-deoxythymidine and 3'-azido-3'-deoxythymidine

3'-Fluoro-3'-deoxythymidine (FLT), a candidate anti-AIDS compound in clinical trials, showed anti-human immunodeficiency virus type 1 (HIV-1) potency (50% effective concentration, 0.0052 microM) slightly better than or equal to that of 3'-azido-3'-deoxythymidine (AZT) in MT4 cells and was threefold more potent in H9 cells. There was no FLT resistance demonstrable in the AZT-resistant HIV-1 strains. Both FLT and AZT showed low cytotoxicity for MT4 cells, with selectivity indices (efficacy/toxicity ratio) of greater than 47,000 and greater than 33,000, respectively. Cellular permeation of FLT and thymidine (dThd) was greater than that of AZT, and FLT and dThd permeated the cell membranes by a carrier-mediated mechanism as well as by simple diffusion, as indicated by the existence of nitrobenzylthioinosine-5'-monophosphate-sensitive and -insensitive components. By contrast, transport of AZT into cells was by simple diffusion. The intracellular level of the triphosphate of FLT (FLTTP) in MT4 cells was two- to threefold higher than that of AZT (AZTTP) after exposure to 1.8 microM each compound for 12 h. The elimination kinetics of FLTTP and AZTTP in HIV-1-infected MT4 cells in fresh medium showed biphasic patterns, with initial half-lives of 1.03 and 1.09 h, respectively. In phytohemagglutinin-stimulated human peripheral blood lymphocytes, the FLTTP level was increased 59-fold compared with that in unstimulated cells at 12 h, was four- to sixfold higher than the level of AZTTP in stimulated cells at 12 h, and remained four- to fivefold higher during a 4-h elimination period in fresh medium and twofold higher at the end of a 12-h elimination period. Two- to eightfold more [3H]AZT than [3H]FLT was incorporated into the host cell DNA, and both [3H]AZT and [3H]FLT remained persistently incorporated for over 24 h. The incorporated [3H]AZT and [3H]FLT were alkali labile, whereas incorporated [3H]dThd was alkali stable. Pharmacokinetics of FLT in plasma of monkeys after intravenous (i.v.) administration showed that the FLT concentration in plasma declined, with a half-life of 1.19 +/- 0.1 h; the steady-state volume of distribution was 0.93 +/- 0.2 liter/kg of body weight, and total clearance was 0.56 +/- 0.15 liter/kg. Oral bioavailability of FLT was excellent and comparable to i.v. bioavailability in terms of areas under the concentration-time curves for three monkeys. Of the total dose, 41 to 61% was excreted in urine as unchanged FLT, and only 3.2 to 7.4% of the total dose was identified as glucuronide-conjugated FLT in urine 48 h after i.v. administration to monkeys. We conclude that FLT exhibits an anti-HIV-1 potency similar to that of AZT but with slightly better selectivity of effects and with higher intracellular active metabolite levels.

Differential alteration of the anti-HIV-1 effect of phosphorothioate oligonucleotide S-dC28 by AZT, interferon-alpha, and dextran sulfate

The combination of S-dC28 (a phosphorothioate oligodeoxcytidine 28 mer) with AZT, recombinant interferon alpha-A (IFN-alpha A) or dextran sulfate (DS) against replication of human immunodeficiency virus type 1 (HIV-1) were studied in MT4 cells, using both p24 core antigen and reverse transcriptase (RT) assays. Under the standardized conditions, the anti-HIV-1 dose-effect relationships of all test drugs showed sigmoidal curves with the following EC50 values: for the p24 core antigen assay, S-dC28, 0.03 microM; AZT, 0.004 microM; IFN-alpha A, 9.2 U/ml; DS, 0.26 micrograms/ml; for the RT assay, S-dC28, 0.04 microM; AZT, 0.01 microM; IFN-alpha A, 11.6 U/ml; and DS, 0.31 micrograms/ml. A computer software based on the median-effect principle and isobologram techniques were used to quantitatively analyze drug interactions by calculating the combination index (CI) where CI less than 1, = 1, and greater than 1 indicates synergism, additive effect and antagonism, respectively. For p24-ELISA, the interaction of S-dC28 and AZT in combination produced a slight antagonism on HIV-1 replicative inhibition with CI values of 1.29-1.10; for RT assays, at EC50-EC95 levels, the CI values are 1.96-1.11. For p24 core antigen assay, the combination of S-dC28 with IFN-alpha A exhibited a dose-dependent anti-HIV synergism with CI values of 1.15-0.87 at EC75-EC95 levels. The RT assays for the same combination showed a broad synergistic effect with CI values of 0.62-0.60, at EC50-EC95 levels. S-dC28 plus DS showed a nearly additive effect based on both assay methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Synergistic inhibition of human immunodeficiency virus type 1 replication in vitro by two-drug and three-drug combinations of 3'-azido-3'-deoxythymidine, phosphonoformate, and 2',3'-dideoxythymidine

The effects of 3'-azido-3'-deoxythymidine (AZT), phosphonoformate (PFA), and 2',3'-dideoxythymidine (ddT) and their combination on human immunodeficiency type 1 (HIV-1) replication were studied by measuring the HIV-1 p24 antigen expression and reverse transcriptase (RT) release in HIV-1-infected MT4 cells in vitro. RT activity was also measured in a cell-free system by using poly(rA)-oligo(dT) as the primer-template, and cell growth inhibition was measured in noninfected MT4 cells. The interactions of these two- and three-drug combinations were evaluated by the combination index (CI) method and isobologram techniques. The 50% effective concentrations (EC50s) of AZT, PFA, and ddT were 0.014 to 0.005, 9.4 to 8.8, and 8.4 to 2.5 microM, respectively, for p24 enzyme-linked immunosorbent assays (ELISAs) and 0.005 to 0.0034, 1.43 to 1.37, and 2.87 to 2.83 microM, respectively, for RT activity in vitro; for RT activity in the cell-free system, the EC50s were 0.00019 to 0.00024, 0.012 to 0.02, and 0.00074 to 0.0005 microM, for AZT-5'-triphosphate, PFA, and ddT-5'-triphosphate, respectively. AZT in combination with PFA (1:200) or ddT (1:5) as well as the combination of these three drugs (1:200:5) synergistically inhibited HIV-1 replication and RT activity in the cell-free system over a wide range of drug concentrations, with the CIs ranging from 0.5 to 0.09, in which CIs of less than 1, 1, and greater than 1 indicate synergism, additive effect, and antagonism, respectively. Three- and two-drug combinations of AZT, PFA, and ddT showed similar degrees of synergism against HIV-1 replication in p24 assays and RT release assays, whereas the combination of AZT and ddT was found to be the most selective in terms of its anti-HIV-1 effect versus cytotoxicity. Dose reduction indices calculated from both HIV-1 replication inhibition, as measured by p24 ELISA and by RT activity in the cell-free system, indicated that two- and three-drug combinations at high effect levels and the selected combination ratios allow 2- to 240-fold dose reduction over the single drug alone in terms of their anti-HIV-1 effects. The three-drug combination showed the highest dose reduction index. These finding suggest that increased efficacy and reduced toxicity may be achieved in AIDS therapy by using AZT, PFA, and ddT in two- or three-drug combinations.

Comparative evaluation of nine different methods for detecting enterotoxin of Escherichia coli

Nine different methods for detecting enterotoxin of Escherichia coli were studied and compared. We found rabbit ileal-loop test and suckling mouse assay were both quite accurate and reliable for detecting heat labile toxin (LT) and heat stable toxin (ST) of enterotoxigenic Escherichia coli (ETEC). Mouse ileal-loop test was simple, but its sensitivity and specificity were comparatively low. CHO cell-culture assay might be more sensitive and specific. LT-DNA probe was the most sensitive and specific method. In practical application, PIHT (plate immunohemolytic test), Biken's, SPA-CoA and ELISA methods are recognized as simple, rapid, sensitive and specific methods for detecting ETEC-LT. These methods can be selected for use in clinical laboratory.

[Effects of tetrandrine on hypertensive responses induced by electric stimulation and alpha-adrenoceptor agonists in pithed rats]

Tetrandrine (Tet) 5 mg.kg-1 i.v. inhibited the pressor action of norepinephrine (NE) release induced by electric stimulation (10 V, 0.5-16 Hz) of spinal cord T11-L2. However, Tet 5 mg.kg-1 ia did not obviously attenuate the hypertensive responses to NE 0.51-16.91 micrograms.kg-1 i.v., indicating that Tet did not affect the alpha 1-adrenoceptors-mediated vasoconstriction. Tet 5 mg.kg-1 ia decreased the pressor responses to NE 0.05 and 0.17 micrograms.kg-1 i.v. and markedly reduced the dose-dependent hypertensive responses to B-HT920 i.v., a selective alpha 2-adrenoceptor agonist, proving that Tet reduced alpha 2-adrenoceptors-mediated vasoconstriction.

Fluorinated sugar analogues of potential anti-HIV-1 nucleosides

In order to obtain agents with therapeutic indices superior to those of AZT, FLT, or D4T, several analogues of anti-HIV-1 nucleosides were synthesized. These include 2',3'-dideoxy-2',3' -difluoro-5-methyluridine (13), its arabino analogue 19, arabino-5-methylcytosine analogue 21, 3'-deoxy-2',3'-didehydro-2' -fluorothymidine (25), 3'-azido-2',3'-dideoxy-2'-fluoro-5-methyluridine (29), 2'-azido-3'-fluoro-2',3'-dideoxy-5-methyluridine (31), and 2'3'-dideoxy-2' -fluoro-5-methyluridine (37). These new nucleosides were screened for their activity against HIV and feline TLV in vitro. None of the compounds showed significant activity. It is interesting to note that such a small modification in the sugar moiety of active anti-HIV nucleosides (i.e., displacement of hydrogen by fluorine) almost completely inactivate the agents.

Study of the identification of enterotoxigenic Escherichia coli by LT-DNA gene hybridization

Reference strains of enterotoxigenic Escherichia coli (ETEC), non-ETEC, and other enteropathogenic bacteria were used to prove the reliability of LT-DNA gene hybridization. In the test, LT-DNA gene hybridization was compared with plate immunohemolytic test (PIHT) in identifying LT-ETEC. The results obtained by both methods showed no significant differences. 791 strains of E. coli isolated from 1,875 children with acute diarrhea in Taiyuan Children's Hospital were examined for LT-ETEC by LT-DNA gene hybridization and PIHT. 289 strains examined by LT-DNA gene hybridization were LT positive, while 205 strains examined by PIHT were LT positive. Three different assays were done: colony hybridization, PIHT and fecal direct blot hybridization on each of 74 fecal specimens from children with acute diarrhea. It was found that identification of LT-ETEC using fecal direct blot hybridization is a simple, sensitive and more practical method.

Protective effects of an adenosine deaminase inhibitor on ischemia-reperfusion injury in isolated perfused rat heart

We tested the effect of the adenosine deaminase inhibitor erythro-9-(2-hydroxy-3-nonyl)adenosine (EHNA) on ischemia-reperfusion injury in isolated perfused rat heart. In the ischemia-reperfusion group (n = 10), ventricular fibrillation occurred within 3 min of reperfusion after the 40-min ischemic period. The incidence of ventricular fibrillation was 90% with a mean duration of 3.15 +/- 0.97 (SE) min. Resting tension increased significantly. By contrast, the incidence of ventricular fibrillation after reperfusion in the EHNA-treated (5 microM) group (n = 10) was 20% (P less than 0.01), and the duration was 0.30 +/- 0.21 min (P less than 0.01). Resting tension was significantly lower and around the normal level in the EHNA-treated group (P less than 0.01). Contraction amplitude and heart rate recovered to nearly normal compared with the ischemia-reperfusion group (P less than 0.01). Coronary flow was greater in the EHNA-treated group (P less than 0.01). It is concluded that EHNA protects the heart, possibly by accumulation of adenosine that benefits the hearts and by blocking the xanthine oxidase pathway for free radical generation.

Synthesis and anti-HIV-1 activity of 2'-"up"-fluoro analogues of active anti-AIDS nucleosides 3'-azido-3'-deoxythymidine (AZT) and 2',3'-dideoxycytidine (DDC)

1-(3-Azido-2,3-dideoxy-2-fluoro-beta-D-arabinofuranosyl)thymine (6, F-AZT) and 1-(2,3-dideoxy-2-fluoro-beta-D-threopentofuranosyl)cytosine (12, F-DDC) were synthesized from the potent antiherpes virus nucleosides 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)thymine (1, FMAU) and 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-5-iodocytosine (FIAC) in the hope that introduction of a 2-"up"-fluoro substituent might potentiate the anti-HIV activity of AZT and DDC. FMAU (1) was converted in three steps into 2,3'-anhydro-1-(2-fluoro-2-deoxy-5-O-trityl-beta-D-lyxofuranosyl)thymine (4), which when treated with NaN3 followed by detritylation afforded 6. F-DDC was prepared by two methods. Tritylation of FIAC followed by treatment of the product with thiocarbonyldimidazole afforded the 5'-O-trityl-3'-O-(imidazolyl)thiocarbonyl nucleoside 9. Upon radical reduction of 9 with Bu3SnH and AIBN, 5'-O-trityl-DDC 10 was obtained. Compound 10 was detritylated to give 12, which (when obtained by this procedure) resisted crystallization, but the diacetate 12' was obtained in crystalline form. Alternatively, FAC (14) was converted into N4,O5'-dibenzoyl derivative 15, which was treated with thiocarbonyldiimidazole. Reduction of 16 with Bu3SnH/AIBN followed by debenzoylation afforded 12, which was obtained in crystalline form. F-AZT did not exhibit any significant activity against the human immunodeficiency virus (HIV) in vitro. F-DDC, however, showed activity against HIV-1, but the therapeutic index is much inferior to that of AZT.