Stopped-flow kinetic study of the reaction of ascorbic acid with peroxynitrite

A new mechanism is presented for the oxidation of ascorbate by peroxynitrite. Our mechanism involves the reaction of ascorbate both with ground-state peroxynitrous acid (HOONO) and with a reactive intermediate (HOONO*); the reactive intermediate is postulated to be formed in the decay of HOONO to form nitrate. At physiological pH, the ascorbate monoanion (AH-) is the predominant ascorbate species. The plot of the observed rate constant for peroxynitrite decay (kobs) vs AH- for the reaction of peroxynitrite with AH- shows two regions, one linear and one curved. In the linear region, which involves high AH- concentrations, the reaction is dominated by the bimolecular reaction between HOONO and AH-. At lower AH- concentrations, this bimolecular reaction slows and reactions with both HOONO and HOONO* produce the observed curvature. Analysis of the data leads to the estimation of the ratio of rate constants for the reaction of AH- with HOONO* (k2*) and the decay of HOONO to nitrate (kN), giving the value of k2*/kN = 3158 +/- 505 M-1; and of the rate constant (k2) for the reaction between AH- and HOONO, k2 = 236 +/- 14 M-1 s-1. Ascorbate displays higher selectivity for HOONO* than does methionine or 2-keto-4-thiomethylbutanoic acid, two substrates whose reactivity toward HOONO and HOONO* has previously been reported. The biological relevance of the reaction of ascorbate with peroxynitrite is discussed in terms of the rate constants and the concentrations of AH- typically found in biological systems; ascorbate may react with HOONO*, although the reaction with ground-state HOONO probably is too slow to occur in vivo.

Higher lung cancer risk for younger African-Americans with the Pro/Pro p53 genotype

A restriction fragment length polymorphism in codon 72 of the p53 gene has been implicated in lung cancer risk, although the functional significance of the polymorphism has not been determined. This association was examined in 109 lung cancer cases (67 African-American and 42 Mexican-American) and 114 controls (74 African-American and 40 Mexican-American) identified from a molecular epidemiological study of lung cancer. The susceptible Pro/Pro genotype was associated with a 1.56-fold higher risk of lung cancer in African-Americans and a 1.95-fold in Mexican-Americans, although neither estimate was statistically significant. In fact, the prevalence of the Pro/Pro genotype was only 2.5% in Mexican-American controls, compared with 20.3% for African-American controls. Patients with the susceptible genotype appeared to have earlier age at diagnosis and lower mean cigarette pack-year exposures than did patients with the Arg/Arg or Arg/Pro genotypes. Risk estimates for the susceptible genotype were 11.29 (1.1, 111.3) for patients < 53 years of age and 14.1 (1.5, 130.6) for patients who reported < 30 pack-years of smoking. The Pro/Pro genotype was not associated with elevated risk in older patients, nor with heavier smokers. If Pro/Pro is a susceptible genotype, the lower prevalence evident in Mexican-Americans may partly explain their lower rates of lung cancer.

Comparison of base inclination of ribo-AU and deoxyribo-AT polymers

The inclination angle between the base normal and the helix axis is measured for ribo-AU polymers by using flow linear dichroism (LD), and compared to measurements for deoxyribo-AT polymers under dehydrating conditions. The CD of the DNA polymers under the dehydrating conditions is not the same as the corresponding RNA polymers, which are presumed to be in the A form. However, the LD indicates that poly(dAdT)-poly(dAdT) can assume the A form in 80% 2,2,2-trifluoroethanol, although poly(dA)-poly(dT) retains B form structure in this dehydrating solvent. The inclination angles are similar for B form poly(dAdT)-poly(dAdT) and poly(dA)-poly(dT), and these parameters are also similar for A form poly(rArU)-poly(rArU) and poly(rA)-poly(rU). All inclination axes are similar.

Comparison of base inclination of ribo-GC and deoxyribo-GC polymers, and synthesis of poly(rGrC)-poly(rGrC)

The inclination angle between the base normal and the helix axis, and the axes around which the bases incline, are measured for ribo-GC polymers in buffer by using flow linear dichroism (LD), and compared to measurements for deoxyribo-GC polymers in buffer and under dehydrating conditions. A new method is designed to synthesize poly(rGrC)-poly(rGrC), which is not available commercially, in large quantities. The LD of this RNA reveals inclination angles that are similar to the B-form DNA in buffer, although the axes are different. The CD of poly(dGdC)-poly(dGdC) under the dehydrating conditions is similar to poly(rGrC)-poly(rGrC), indicating it is in the A form, and the LD gives larger inclination angles than either the B form or the corresponding RNA. Poly(dG)-poly(dC) is in the A form in buffer. Comparison among poly(rG)-poly(rC) in buffer, and poly(dG)-poly(dC) in buffer under dehydrating conditions, reveals similar inclination angles and axes, although the LD shows that the DNA has the largest inclination angles. Except for poly(rGrC)-poly(rGrC), which has a unique reduced dichroism, all the axes for G are similar, as are the axes for C.

Cell cycle arrest and inhibition of tumor cell proliferation by the p16INK4 gene mediated by an adenovirus vector

The p16INK4 (MTS1) gene has many features of a tumor suppressor gene. It maps to 9p21, a region of frequent loss of heterozygosity in a variety of tumor types. It encodes an inhibitor of cyclin-dependent kinase 4, and its homozygous deletion is common in tumor-derived cell lines. To examine its tumor suppressive function and its potential in cancer gene replacement therapy, wild-type p16INK4 was expressed in an adenovirus-derived gene delivery system and introduced into lung cancer cell lines that do not express p16INK4. Expression of the introduced p16INK4 blocked tumor cell entry into S phase of the cell cycle and inhibited tumor proliferation both in vitro and in vivo. These observations strongly support that p16INK4 is a tumor suppressor gene and is a candidate for cancer gene replacement therapy.

[Amylopsin activator in the decoction of fried malt]

From the decoction of fried malt (Fructus Hordei Germinatus) a kind of amylopsin activator was extracted and distinguished as calcium nitrate (with small amount of sodium chloride). The existence of this activator may can be explain properly why the decoction is helpful to digestion.

[Captopril in improving vascular structure and lowering blood pressure]

SHRs were given captopril 20 mg/kg/day (group A, n = 13) and 100 mg/kg/day (group B, n = 17) from intrauterus period to 16 weeks of age, then the treatment was removed. Experiments were carried out at 40 weeks. SBP, left ventricular mass/body weight ratio, wall/lumen ratio of branch III mesenteric and renal artery were determined. The perfusion pressure response to alpha 1 adrenergic agonist (phenylephrine) of resistance blood vessels in a hindquarter model in the presence of Nw-nitro-1-arginine-methyl ester (LNAME) or L-arginine were examined. Untreated SHR (n = 16) and untreated WKY (n = 17) served as controls. Both doses of captopril treatment completely prevented hypertrophy of vascular vessels to some extent comparable to that of the untreated WKY. But their SBP was still significantly higher than that of the untreated WKY. The curves of perfusion pressure responding to incremental doses of phenylephrine shifted rightward in the captopril treatment groups in a dose dependent manner. The curves of high dose group were almost identical to those of WKY, markedly different from that of the untreated SHR. Captopril decreased the over enhanced vasoconstrictor effect of LNAME in SHR. The attenuated vasoconstrictor effect by L-arginine was greatly augmented by captopril, suggesting that captopril improves the function of resistance of vessels by mediating endothelial cells. Captopril-induced alteration in vascular structure and function may be separated from its hypotensive effect. Clinically, continuing administration of captopril may be beneficial to the improvement of the vascular system in those blood pressure unresponsive patients.

A practical method for preparing peroxynitrite solutions of low ionic strength and free of hydrogen peroxide

The reaction of ozone (approximately 5% in oxygen) with sodium azide (0.02-0.2 M in water) at pH 12 and 0-4 degrees C is shown to yield concentrated, stable peroxynitrite solutions of up to 80 mM. The product of this reaction is identified based on a broad absorption spectrum with a maximum around 302 nm and by its first-order rate of decomposition (k = 0.40 +/- 0.01 s-1 at pH 7.05 and 25 degrees C). These peroxynitrite solutions can be obtained essentially free of hydrogen peroxide (detection limit 1 microM) and only traces of azide (detection limit 0.1 mM). They are low in ionic strength and have a pH of about 12 but without buffering capacity; therefore, they can be adjusted to any pH by addition of buffer. These preparations of peroxynitrite frozen at -20 degrees C show negligible decomposition for about 3 weeks of storage and follow a first-order decomposition with a halflife of about 7 days at refrigerator temperatures (approximately 5 degrees C). These preparations give reactions that are characteristic of peroxynitrite. For example, at pH 7.0, they react with L-tyrosine to give a 7.3 mol % yield of nitrotyrosine(s), and with dimethyl sulfoxide to give a 8.2 mol % yield of formaldehyde, based on starting peroxynitrite concentration.

One- and two-electron oxidations of methionine by peroxynitrite

Peroxynitrite is stable, but its acid, HOONO, either rearranges to form nitrate or oxidizes nearby biomolecules. We report here the reactions of HOONO with methionine and the methionine analog 2-keto-4-thiomethylbutanoic acid (KTBA). These oxidations proceed by two competing mechanisms. The first yields the sulfoxide; the second-order rate constants, k2, for this process for methionine and KTBA are 181 +/- 8 and 277 +/- 11 M-1.s-1, respectively, at pH 7.4 and 25 degrees C. In the second mechanism, methionine or KTBA undergoes a one-electron oxidation that ultimately gives ethylene. We propose that the one-electron oxidant is an activated form of peroxynitrous acid, HOONO*, that is formed in a steady state mechanism. The ratios of the second-order rate constants for the ethylene-producing reaction (k*2) and the first-order rate constant to produce nitric acid (kN) for methionine and KTBA, k*2/kN, are 1250 +/- 290 and 6230 +/- 1390 M-1, respectively. Both ceric and peroxydisulfate ions also oxidize KTBA to ethylene, confirming a one-electron transfer mechanism. The yields of neither MetSO nor ethylene are affected by several hydroxyl radical scavengers, suggesting that a unimolecular homolysis of HOONO to HO. and .NO2 is not involved in these reactions. HOONO* gives hydroxyl radical-like products from various substrates but displays more selectivity than does the hydroxyl radical; thus, HOONO* is incompletely trapped by typical HO. scavengers. However, a mechanism involving dissociation of HOONO* to caged radicals cannot be ruled out at this time.

An epidemiological study on the relationship of ectopic pregnancy and the use of contraceptives in Beijing--the incidence of ectopic pregnancy in the Beijing area. Beijing Collaborating Study Group for Ectopic Pregnancy

The incidence of ectopic pregnancy (EP) was studied through a 3-level monitoring network of maternal and child health care (MCH) in the entire Beijing area, including 82 hospitals, 19 MCH centers and 2 institutes for family planning. A total of 1,420 cases of EP were collected in a sample of 2.7 million women of reproductive age (15-49) during a one-year period from January 1 to December 31, 1990. The cases were confirmed by pathological examination or laparoscopy. In addition, epidemiological surveillance method was used. The results showed that the overall incidence of EP was 0.52 per thousand women of reproductive age (W = Women of reproductive age (15-49)) in the Beijing area, 0.6/1000W in the urban districts and 0.41/1000 in the rural area; 0.67/1000W married women, and 0.05/1000W in the unmarried. For married women, 0.54/1000W for those women using various contraceptive measures and 1.80/1000W for women using no contraceptives. The incidence of EP varies with different contraceptive methods. Female sterilization had the lowest incidence (0.18/1000W) and natural contraceptive measures (rhythm or withdrawal method) had the highest (2.43/1000W). It was 0.65/1000W in IUD users, 0.21/1000W in OC users and 0.57/1000W in couples using condoms or spermicides.

Lung cancer among tin miners in southeast China: silica exposure, silicosis, and cigarette smoking

The Dachang Tin Mine is an industrial facility with high rates of lung cancer compared to the resident population in Guangxi province in southern China. Historically, exposure to silica dust was very high in the 1950s, falling in recent years to levels in keeping with international standards. Radon levels in the mine are low. We report the findings of a case-control study nested into a cohort study on miners working in Dachang. Cases of lung cancer among miners incident from 1973-1989 were obtained from local comprehensive medical records covering workers employed at the mine. These were matched approximately 3 to 1 with miners randomly chosen from the district surrounding the mine within the same birth decade. Matched odds ratios of 2.42 (95% confidence limit [CL] 1.3, 4.4) for underground employment, 3.52 (95% CL 1.7, 7.5) for smoking, and 2.04 (95%) CL 1.2, 3.7) for silicosis as determined on chest film were noted. Multifactor analysis of unconditional logistic regression showed that among the risk factors for excess mortality from lung cancer only the years spent drilling underground and the cumulative smoking index (product of daily cigarette consumption and number of years smoking) were independent contributors to risk and there was no interaction observed. The presence of silicosis did not contribute to predicting risk independently of the years spent underground.

[Effects of petroleum ether extract of Peucedanum praeruptorum Dunn on rabbit trachea smooth muscles]

The contractions of isolated rabbit trachea smooth muscles by acetylcholine and potassium chloride were attenuated by petroleum ether extract of Peucedanum praeruptorum pretreatment. The dose-effect curve of acetylcholine was shifted to the right, and the maximal response was diminished. The effect was non-competitive and dose-dependent.

[Quantitative analysis of ephedrines in urine by HPLC]

Simultaneous determination of six ephedrines in urine sample has been achieved by high performance liquid chromatography on a Lichrospher RP-18 column, using methylamphetamine as internal standard. The 6 ephedrines are well separated in 25 minutes with resolution better than 1.8. This method has high recovery, selectivity and reproducibility, and the linearity is satisfactory from 1.5 micrograms/ml to 25 micrograms/ml with correlation coefficients better than 0.999.

[Studies on the pleomorphism of trachoma inclusion]

A series of trachoma inclusion color photograph is taken from the conjunctival smears of 48 trachoma cases. These smears were Giemsa-stained and stored in the slide-boxes for more than 30 years with no distinct changes in color. A description is given to the Pleomorphism of trachoma inclusion and its relation to the host cells. According to the gradual morphological changes of Chlamydia trachomatis multiplied in the infected cells, a 5-staged classification for trachoma inclusions is provided which may be benefit to understanding the pleomorphism of the trachoma inclusion and clinical laboratory diagnosis.

Quantitative analysis of the human immunodeficiency virus type 1 (HIV-1)-specific cytotoxic T lymphocyte (CTL) response at different stages of HIV-1 infection: differential CTL responses to HIV-1 and Epstein-Barr virus in late disease

Major histocompatibility complex (MHC)-restricted cytotoxic T lymphocytes (CTL) are part of the cellular immune response to human persistent virus infections. Measurements of the frequency and specificity of human immunodeficiency virus type 1 (HIV-1)-specific CTL and their variation with time may indicate their relative importance in modulating the progression of HIV-1 infection. We have used limiting dilution analysis (LDA) to derive quantitative estimates of the frequency of HIV-1-specific CTL precursors in a cross-sectional study of 23 patients at different clinical stages of HIV-1 infection and to compare these with the frequency of CTL precursors specific for another persistent virus (Epstein-Barr virus [EBV]) in the same patients. Peripheral blood mononuclear cells (PBMC) were stimulated in vitro with autologous HIV-1-infected lymphoblasts and assayed for cytotoxicity in 51Cr release assays against autologous and MHC-mismatched lymphoblastoid B cells infected with recombinant vaccinia viruses expressing the three HIV-1 structural gene products. The frequency of MHC-restricted precursors was high in asymptomatic HIV-1-infected patients (env-specific CTL precursors up to 73/10(6) PBMC; gag-specific CTL precursors up to 488/10(6) PBMC), although the relative frequency against the different structural gene products varied from patient to patient. The HIV-1-specific CTL precursor frequency was reduced in patients who had more severe (< 400/microliters) CD4+ lymphocyte depletion, while in the majority of such patients the frequency of CTL precursors against EBV was maintained at levels observed in healthy controls. Direct CTL activity in unstimulated PBMC was observed in three of nine patients but no correlation was found between the presence of an activated CTL response and the magnitude of the CTL response detected after stimulation in LDA. Thus, CTL precursors were detected against all three HIV-1 structural gene products in patients with CD4+ lymphocyte counts > 400/microliters, at frequencies that are high compared with those reported for other persistent viruses. A CTL response directed against multiple protein antigens of HIV-1 may protect the patient against epitope variation. The fact that the EBV-specific CTL precursor frequencies were maintained in advanced HIV-1 infection suggests that there may be selective impairment of the HIV-1-specific CTL response associated with disease progression.

Signal transduction in activated natural killer cells and natural killer cells inactivated with sensitive targets

We have recently demonstrated that the activation of NK cells involves a protein-kinase-C (PKC)-dependent step as well as a phosphatidylinositol (PI)-linked signal transduction system. We have also shown that when NK cells are incubated with sensitive targets for up to 6 h they lose their lytic potential and require IL-2 to regain their lytic activity. PKC is involved in many cell processes such as the transduction of hormonal signals and the machinery of cellular secretion and is activated by diacylglycerol and by a number of phorbol esters, including phorbol myristic acid (PMA). To reinforce the role of PKC in NK-cell-mediated cytotoxicity, we first showed that NK-CMC is inhibited by two agents that inhibit PKC activation, staurosporine and sphingosine. Next, we showed that antibody-dependent cellular cytotoxicity of NK-resistant targets was PKC dependent and Ca2+ dependent. Further, we showed that PMA plus ionophore alone could induce NK killing of resistant targets and that this killing was PKC and Ca2+ dependent. Finally, we contrasted the role of PKC in these activated cells to the role of PKC in cells that have been inactivated with a sensitive target, K562. We showed that PKC is not required for the IL-2-dependent reactivation of NK cells but that Ca2+ is required. To further determine what event in signal transduction is inactivated by K562, we showed that inactivated NK cells do not turnover PI in response to K562 stimulation.

[Thrombosis test in vitro of 107 cases with arteriosclerosis obliterans]

Thrombosis test in vitro of 107 cases with arteriosclerosis obliterans were measured and controlled by 36 normal persons. Of 107 cases, 13 cases belonged to ischemic phase, 47 cases nutritional disturbance phase, 47 necrosis (24 cases were first degree, 9 cases second degree, 14 third degree). Types distribution were: simple blood stasis 65 cases, blood and damp stasis 34, and 8 others. 46 patients were treated systematically by TCM-WM. The result proved that the indexes of thrombosis test in vitro of patients were much higher than that of normal persons (P less than 0.001). The relevant indexes were different in varied periods, degrees and types (P less than 0.05-0.01) and between before and after treatment (P less than 0.001). Of treated 46 cases, total effective rate was 86.96%, amputation rate was 13.04%. Formation of thrombus in vitro lowered 88.03%. The authors suggested that measurement of thrombosis test might be a accurate way to reflect the course of the disease and a basis for treatment and differentiation of symptoms.

Analysis of low-order autoregressive models for ultrasonic grain signal characterization

When testing materials nondestructively with ultrasound, the grain scattering signal provides information that may be correlated to regional microstructure variation. Second and third-order autoregressive (AR) models are used to evaluate the spectral shift in grain signals by utilizing features such as resonating frequency, maximum energy frequency, or AR coefficients. Then, Euclidean distance, based on these features, is applied to classify grain scattering characteristics. Using both computer simulated data and experimental results, the probability of correct classification is found to be about 75% for the second-order AR model and 88% for the third-order AR model, when the conditions are such that the expected shift between the center frequency of echoes is less than 4%. This implies that, by increasing the order of the AR model, the frequency information extracted from the random signal is increased, which can result in obtaining a better classification.

[Clinical analysis of 200 cases of necrotic thromboangiitis obliterans]

Two hundred cases of necrosis thromboangiitis obliterans (199 males, 1 females; age 17 approximately 63 years) were observed. The illness course averaged more than 5 years. Focuses of upper limbs were 6 cases and those of lower limbs 194 cases. 98 cases and 102 cases suffered from ulcer and gangrene respectively. 100 cases belonged to the first degree, 62 cases to the second degree, 38 cases to the third degree of III stage. 171 cases were treated by the combination of TCM and WM except 3 cases which were actively discharged and 26 cases which were to be given amputation.

RESULTS

90 cases within 171 cases were cured, 52 cases were improved obviously, 7 cases improved, 5 cases ineffective and 17 cases to be given amputation. The writers regard three principles should be followed in the treatment of necrosis thromboangiitis obliterans by the combination of TCM and WM. (1) The main importance was to improve blood circulation to remove blood stasis. (2) Controlling infection was the key point, effective antibiotics and hormone should be added besides these herbal medicines for clearing away heat and toxic materials. (3) General protecting therapy, performing various local operations on right period on the basis of improvement of blood circulation of the involved limbs, the wound could heal successfully. The writers suggest that the amputation should not be given above the level of the main artery obliterans.

[A mathematical model of age distribution of malignant tumours mortality]

There was a tendency that the mortality of malignant tumours increased with age. In order to explore the law of this tendency, the data of malignant tumours mortality from disease monitoring points in Shandong Province were mathematically analogized, and the mathematical model of age distribution of malignant tumours mortality was established by using the exponential curve, y = 10a + bx. The model was also tested and verified by using national data, to observe the universal significance of the model. The model gave a theoretical account of the law of age distribution of malignant tumours mortality from a population, and provided an initial method to predict malignant tumours mortality. The increment quantity of malignant tumours mortality in various age groups when age increased one year could be calculated by using the differential equation from the exponential curve equation, y = 10a + bx. Further, "an increment multiple constant" of the increment quantity of malignant tumours mortality could be calculated. The constant could be used as an Index for comparison in risk degree and age distribution law of malignant tumours mortality among various age groups and the same age group in different periods, and provided leads for further research of the causes of malignant tumours.

[Formation of extrinsic blood thrombosis in 102 cases of thromboangiitis obliterans]

The formation of extrinsic blood thrombosis in 102 cases of thromboangiitis obliterans and 54 healthy persons were observed with chandler method and their clinical manifestations. All the 102 patients were male, of which 13 cases were in ischemic stage, 45 cases in dystrophic stage, and 44 cases in necrotic stage. According to the differentiation of TCM, 8 belong to Yin-cold type, 50 belong to downward flowing of damp-heat type, 42 belong to blood stasis type, and 2 others. Combining method of TCM-WM was adopted to give 45 cases systemic treatment, that is, taking the promotion of blood flow to remove its stasis as the dominant factor, accompanied by intravenous drip and operation. Results showed that the length, wet weight and dry weight of extrinsic blood thrombosis were higher apparently in the cases of thromboangiitis obliterans than those in healthy persons (P less than 0.001), and there were significant differences between the values of extrinsic blood thrombosis in different stages and different degrees. After systemic treatment with TCM-WM, the values of extrinsic blood thrombosis decreased remarkably, and their symptoms and signs improved or disappeared. The clinical total effective rate was 88.89%, and the decreasing rate of the values of extrinsic blood thrombosis was 98.9%. This suggested that the high blood coagulation and extrinsic thrombosis should draw special attention and may act as an approach reflecting the severity of the disease and evaluating the effects of treatment.

Significance of seizures in very low-birthweight infants

Of 506 very low-birthweight (VLBW) infants, the authors review data on 67 identified as having seizures. 29 survivors with seizures and 305 without were followed up at the ages of one, two and five years: statistical significance of psychological and mental impairment was evaluated. Impairment was higher in the seizure group at 66 per cent (15 per cent in non-seizure group) and 43 per cent of these were considered to be severely impaired. Infants with seizures occurring for more than seven days and lasting for more than five minutes had the poorest outcome, and infants with late onset had the best outcome. Analysis showed that 40 per cent of seizures were caused by birth asphyxia, and these were strongly prognostic, correlating with mortality and impairment rates. 60 per cent of the infants who died had the same cause for both their seizures and death, and for 57 per cent of these the cause was perinatal asphyxia. The poor outlook for the VLBW infants suggests that the seizures themselves are a serious neurological insult.