Direct fluorescence analysis of genetic polymorphisms by hybridization with oligonucleotide arrays on glass supports

A simple and rapid method for the analysis of genetic polymorphisms has been developed using allele-specific oligonucleotide arrays bound to glass supports. Allele-specific oligonucleotides are covalently immobilized on glass slides in arrays of 3 mm spots. Genomic DNA is amplified by PCR using one fluorescently tagged primer oligonucleotide and one biotinylated primer oligonucleotide. The two complementary DNA strands are separated, the fluorescently tagged strand is hybridized to the support-bound oligonucleotide array, and the hybridization pattern is detected by fluorescence scanning. Multiple polymorphisms present in the PCR product may be detected in parallel. The effect of spacer length, surface density and hybridization conditions were evaluated, as was the relative efficacy of hybridization with single or double-stranded PCR products. The utility of the method was demonstrated in the parallel analysis of 5 point mutations from exon 4 of the human tyrosinase gene.

[A study on relation between effect of HB vaccination and time of the second injection]

Three kinds of hepatitis B vaccination schedule in neonates were compared. The schedule included 0, 40 day, 6 month; 0, 50 day, 6 month; 0, 60 day, 6 month; and was controlled by the 0, 30 day, 6 month schedule. The results showed that there was no statistically significant difference among three kinds of schedule, no matter who were neonates of HBs Ag-positive mother or neonates of HBsAg-negative mother. These indicated that in areas with poor condition, such as mountain, island, the second injection of hepatitis B vaccine in neonates may be completed within 30-60 days.

High density cultivation of a recombinant CD-1 cell line producing prourokinase using a Biosilon microcarrier culture system

CD-1, a genetically-engineered CHO cell line, was cultivated with a Biosilon microcarrier culture system. We successfully cultivated CD-1 cells to a very high density (over 1 x 10(7) cells/ml). Prourokinase was stably secreted at about 180 IU/10(6) cells/24 h. Experiments showed that CD-1 cells growing on Biosilon microcarriers were able to spontaneously release from the microcarriers, then reattach and proliferate on fresh microcarriers. This makes it very easy to scale up production. The microcarriers could be reused several times without affecting adhesion, proliferation and prourokinase secretion. With CM-PECC membrane radial flow chromatography and MPG chromatography, the prourokinase in conditioned medium could be purified to a specific activity of 1 x 10(5) IU/mg of protein. The purification factor was about 600 fold, and approximately 90% of the biological activity was recovered.

Activation of procarcinogens by human cytochrome P450 enzymes expressed in Escherichia coli. Simplified bacterial systems for genotoxicity assays

Bacterial assays were used to examine the activation of 14 known procarcinogens by cytochrome P450 (P450) enzymes. Human P450s 1A1, 1A2 and 3A4 were expressed in Escherichia coli with slight modification of their N-terminal sequences. Genotoxicity was measured by the induction of the SOS response in Salmonella typhimurium NM2009 (TA1535/pSK1002/pNM12), which contains a umuC regulatory sequence attached to the lacZ reporter gene. Conditions for analysis were examined using E. coli membranes and purified enzymes. Membrane fractions, fortified with NADPH-P450 reductase, were found to be useful preparations for measuring activation of the procarcinogens. Conditions of linearity were established for these assays and the systems were applied to several particular problems related to bioactivation of procarcinogens by P450s. The patterns of activation of the 14 individual chemicals were consistent with the literature developed using human liver microsomes, purified liver P450s and other approaches. The P450s expressed in bacterial membranes could be inhibited by antibodies. 7,8-Benzoflavone inhibited P450s 1A1 and 1A2 and stimulated P450 3A4 in the membranes. The contributions of P450s 1A1 and 1A2 were distinguished with some of the arylamines and 7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene. Recombinant P450 3A4 was found to be more active than P450 1A2 in the activation of aflatoxin B1 at all substrate concentrations examined.

Bufuralol hydroxylation by cytochrome P450 2D6 and 1A2 enzymes in human liver microsomes

Bufuralol 1'-hydroxylation is a prototypical reaction catalyzed by cytochrome P450 (P450) 2D6, an enzyme known to show debrisoquine/sparteine-type genetic polymorphism in humans. In the present study we further examined the roles of several human P450 enzymes, as well as P450 2D6, in the hydroxylation of (+/-)-bufuralol, using liver microsomes from several human samples and human P450 enzymes expressed in human lymphoblastoid cell lines or Escherichia coli. Kinetic analysis of bufuralol 1'-hydroxylation by liver microsomes showed that there were different Km and Vmax values in seven human samples examined; low Km values (approximately 0.05 mM) were observed in four samples (including sample HL-18), high Km values (approximately 0.25 mM) in two samples (including sample HL-67), and an intermediate Km value (approximately 0.1 mM) in one sample. Quinidine and anti-rat P450 2D1 antibody almost completely inhibited bufuralol 1'-hydroxylation in human sample HL-18 at a substrate concentration of 0.4 mM, whereas these effects were not so drastic when liver microsomes from human sample HL-67 were used. In contrast, a very low concentration (< 10 microM) of alpha-naphthoflavone or anti-human P450 1A2 antibody significantly inhibited bufuralol 1'-hydroxylation catalyzed by human sample HL-67, but not HL-18, with 0.4 mM bufuralol. When the relative contents of P450 2D6 and P450 1A2 in 20 human samples were determined, bufuralol 1'-hydroxylation in samples containing large amounts of P450 2D6 tended to be more sensitive to quinidine, whereas the P450 1A2-rich samples were highly susceptible to alpha-naphthoflavone. However, at low substrate concentrations bufuralol 1'-hydroxylation was shown to be catalyzed principally by P450 2D6, based on the inhibitory effects of anti-rat P450 2D1 antibody and quinidine, in both human samples HL-18 and HL-67. At least five other, minor, bufuralol products were formed by human liver microsomes, in addition to 1'-hydroxybufuralol. Two of them were identified as 4- and 6-hydroxybufuralol by 1H NMR spectroscopy and mass spectrometry. The formation of the 4- and 6-hydroxylated products was suggested to be catalyzed by P450 1A2, based on the results of correlation with P450 1A2 contents in 60 human samples and inhibition by anti-P450 1A2 and alpha-naphthoflavone. Purified recombinant P450 1A2 (expressed in E. coli) produced 1'-, 4-, and 6-hydroxybufuralol in a reconstituted system, although P450 2D6 (expressed in human lymphoblast cell lines) was found to catalyze only bufuralol 1'-hydroxylation.(ABSTRACT TRUNCATED AT 400 WORDS)

Expression of modified human cytochrome P450 1A1 in Escherichia coli: effects of 5' substitution, stabilization, purification, spectral characterization, and catalytic properties

Human cytochrome P450 (P450) 1A1 is primarily an extrahepatic enzyme and is important because of its roles in the activation of polycyclic hydrocarbons and other xenobiotic chemicals. Purification of active enzyme from human tissues has not been successful. We report the expression and purification of the recombinant enzyme from Escherichia coli. A full-length cDNA of human cytochrome P450 1A1 and several modified constructs were engineered into a pCW vector and used to transform E. coli cells. Little expression was observed with the native sequence and several modified constructs, but successful expression (20-25 nmol membrane-bound P450 1A1 per liter of culture) was achieved with a construct in which the Ala codon GCT was placed in the second position and the 5'-terminal codons were maximized for AT content and minimized for the potential of secondary structure formation of the mRNA transcript. alpha-Naphthoflavone was found to protect against denaturation by detergents during solubilization and was added to buffers used for purification. The recombinant P450 1A1 was purified to electrophoretic homogeneity after two ion-exchange chromatography steps in approximately 50% yield. N-Terminal amino acid sequence analysis verified the expected first 21 residues, with the exception of the terminal Met. The isolated human ferric P450 1A1 was predominantly in the high spin state, in contrast to the orthologous rat and rabbit enzymes. Recombinant P450 1A1 catalyzed 7-ethoxyresorufin O-deethylation and benzo[a]pyrene 3-hydroxylation with Km values of 0.58 and 15 microM and Vmax values of 8.3 and 2.5 nmol min-1 (nmol P450 1A1)-1, respectively. The successful expression and purification of human P450 1A1 should increase the availability of this enzyme and the generation of antibodies for further biochemical and other biological studies.

Expression of modified human cytochrome P450 2E1 in Escherichia coli, purification, and spectral and catalytic properties

Human cytochrome P450 (P450) 2E1 is of interest because of its role in the oxidation of numerous drugs and carcinogens. The purification of the protein from human liver is difficult, and we report the development of a system for relatively high-level expression in Escherichia coli. A cDNA was prepared from liver cDNA by polymerase chain reaction methods and several variants with modified 5'-termini were constructed. Analysis of seven of these indicated that the highest levels of expression were found when the first 21 codons of the native sequence were deleted and the Trp immediately following the resulting N-terminal Met was changed to Ala (GCT). Levels of 40-nmol membrane-bound P450 2E1 (liter culture)-1 were routinely recovered. The recombinant P450 2E1 was purified to electrophoretic homogeneity from the bacterial membranes in two ion-exchange steps in > 80% yield. Ferric P450 2E1 was isolated in a mixed spin state. The enzyme was active in chlorzoxazone 6-hydroxylation; the addition of human liver cytochrome b5 lowered the Km for the substrate and increased Vmax. N-Terminal amino acid sequence analysis yielded the expected first 21 residues. The expression system should facilitate the availability of human P450 2E1 and antibodies for studies of the enzyme.

High density cultivation of genetically-engineered CHO cell lines with microcarrier culture systems

Genetically-engineered CHO cell lines, r beta-13 and CLF-8B2, were cultivated with the MC-1 microcarrier culture system. The cell density could be enhanced by increasing the concentration of microcarrier. At a microcarrier concentration of 10 mg/ml, the cell density could reach 4 to 5 x 10(6) cells/ml. It was shown that these cell lines would spontaneously release from the microcarrier to attach to and proliferate on fresh microcarriers. We were thus able to scale up cultivation using a simple method, i.e. by adding fresh microcarriers and medium directly into the culture system to about 2, 4 or 8 times the original volume. Using a perfusion culture system, we have successfully cultivated CLF-8B2 cells in a 2 L bioreactor for several weeks at medium perfusion rates of 0.5 to 3 working volumes. Prourokinase was stably secreted.

Artificial neural networks in computer-assisted classification of heart sounds in patients with porcine bioprosthetic valves

The paper describes the design, training and testing of a three-layer feed-forward back-propagation neural network for the classification of bioprosthetic valve closure sounds. Forty-seven patients with a porcine bioprosthetic valve inserted in the aortic position were involved in the study. Twenty-four of them had a normal bioprosthetic valve, and the other 23 had a degenerated valve. Five features extracted from the Fourier spectra and 12 linear predictive coding (LPC) coefficients of the sounds were used separately as the input of two neural-network classifiers. The performance of the classifiers was tested using the leave-one-out method. Results show that correct classifications were 85 per cent using the spectral features, and 89 per cent using the LPC coefficients. The study confirms the potential of artificial networks for the classification of bioprosthetic valve closure sounds. Clinical use of this method, however, still requires further investigation.

[Carcinoma arising from postburn scars (report of 5 cases)]

Carcinoma arising from postburn scars is rare. We have encountered 5 patients suffering from this late complication of scars, accounting for 0.32% of 1563 admissions for late surgery after burn injuries. They were all males, with a mean age of 56 years. The mean latent period was 43.2 years, and it was apparently longer when the acute burn injury occurred earlier in life. The site of predilection was the lower extremity, and multiple biopsies of various sites of the lesion remained to be the measure of confirmation. Pathologically, they were all squamoon cell carcinoma, grade I in 4 cases and grade II in 1. Immunohistochemical staining with anti-proliferation cell nuclear antigen (PCNA) showed that PCNA positive nuclei of squamous cell carcinoma were more numerous, as compared with that in the neighboring pseudo -epitheliomatous hyperplasia (PEH) and in normal skin, denoting markedly augmented assimilation of DNA in malignant degeneration. On the contrary, the number of Langerhan's cells were smallest in cancer area, as compared with PEH and normal skin. The diagnosis, treatment and prevention of such malignant degeneration in postburn scars have been discussed.

[Long-term efficacy of hepatitis B vaccine in newborn and revaccination study]

Two-hundred and sixty-nine newborns were followed up for 4 and 5 years after completion of vaccination (10 micrograms x 3). The anti-HBs positive rates remained 82.54% and 72.03%, respectively. The low-level titer (> or = 10-99 mIU/ml) made up 44.61%, and the medium-level titer (> or = 100-99mIU/ml) 32.34%. The highest titer was 857 mIU/ml. A 10 micrograms dose of hepatitis B vaccine was given to these children. The anti-HBs level went up greatly in the first month after revaccination, but started to drop in the third month, decreased rapidly in the sixth month, and in the twelveth month the level trended to restore the level before revaccination. This paper indicated that the home-made hepatitis B vaccine was effective. Revaccination was not necessary within 5-7 years after initial vaccination. Revaccination to children whose anti-HBs level was < 10mIU/ml was beneficial but the anti-HBs persistence was short.

[Effects of ligustrazine and nitroglycerine on acute hypoxic pulmonary hypertension in anesthetized dogs]

The effects of ligustrazine and nitroglycerine on acute hypoxic pulmonary hypertension were observed in 10 anesthetized dogs. The results showed that ligustrazine (40 mg/kg) significantly reduced the hypoxic mean pulmonary artery pressure (PAPm) and pulmonary vascular resistance (PVR) the 10th and 15th minute after its injection into the right atrium, respectively. Its action was blocked by the continuous intravenous injection of methylene blue (1 mg/kg/min). It was suggested that the action of ligustrazine could be mediated by endothelium-derived relaxing factor. It was also discovered that nitroglycerine (40 micrograms/kg) could quickly decrease PAPm and PVR, indicating that nitroglycerine can be used to treat acute pulmonary hypertension and the aggravation of chronic cor pulmonale.

Comparison of time-frequency distribution techniques for analysis of simulated Doppler ultrasound signals of the femoral artery

The time-frequency distribution of the Doppler ultrasound blood flow signal is normally computed by using the short-time Fourier transform or autoregressive modeling. These two techniques require stationarity of the signal during a finite interval. This requirement imposes some limitations on the distribution estimate. In the present study, three new techniques for nonstationary signal analysis (the Choi-Williams distribution, a reduced interference distribution, and the Bessel distribution) were tested to determine their advantages and limitations for analysis of the Doppler blood flow signal of the femoral artery. For the purpose of comparison, a model stimulating the quadrature Doppler signal was developed, and the parameters of each technique were optimized based on the theoretical distribution. Distributions computed using these new techniques were assessed and compared with those computed using the short-time Fourier transform and autoregressive modeling. Three indexes, the correlation coefficient, the integrated squared error, and the normalized root-mean-squared error of the mean frequency waveform, were used to evaluate the performance of each technique. The results showed that the Bessel distribution performed the best, but the Choi-Williams distribution and autoregressive modeling are also techniques which can generate good time-frequency distributions of Doppler signals.

Measurement of fractional lipid synthesis using deuterated water (2H2O) and mass isotopomer analysis

Fractional biosynthesis of palmitate, stearate, and cholesterol was determined with deuterated water (2H2O) using mass isotopomer analysis in Hep G2 and MCA sarcoma cells in culture. The method employed differs from previous ones in that the number of deuterium atoms from 2H2O incorporated into newly synthesized molecules was determined and not assumed. After correction for background natural abundances, the isotopomer distribution due to deuterium incorporation in fatty acids and cholesterol was shown to follow a simple binomial distribution depending on the deuterium enrichment in water (p) and the maximum number of deuterium atoms incorporated per molecule (N). Under a wide range of 2H2O enrichments, N could be determined to be 17 for palmitate, 20 for stearate, and 20 for cholesterol by regression analysis or from a series of consecutive mass isotopomer ratios. The fraction derived from de novo synthesis was given by the ratio of the observed to the theoretical deuterium enrichment, which is the product (N x p). The new synthesized fraction of palmitate and stearate by Hep G2 cells for the length of the experiment was found to be 77 and 65%, respectively. These values were confirmed by experiments with [U-13C]glucose as the precursor. In MCA sarcoma cells grown in lipid-poor medium, the average values for fractional synthesis of palmitate, stearate, and cholesterol were 70, 35, and 70%, respectively. This approach should be generally applicable to the simultaneous determined of fractional synthesis of a number of compounds with either deuterium or 13C tracers. Its application is only limited by the accuracy of mass spectrometric analysis.

Expression of modified human cytochrome P450 1A2 in Escherichia coli: stabilization, purification, spectral characterization, and catalytic activities of the enzyme

A full-length human cytochrome P450 (P450) 1A2 cDNA clone and four derivatives in which the 5'-terminus was modified were inserted into the pCW vector and used to transform Escherichia coli cells. Low levels of expression were seen with most of the constructs but high expression levels (245 nmol membrane-bound P450 recovered per liter culture) were achieved when the N-terminus was MALLLAVFL, as reported earlier by Fisher et al. (C. W. Fisher, D. L. Caudle, C. Martin-Wixtrom, L. C. Quattrochi, R. H. Tukey, M. R. Waterman, and R. W. Estabrook, 1992, FASEB J. 6, 759-764). The expressed human P450 1A2 in bacterial membranes was rapidly denatured to cytochrome P420 in the presence of detergents. This denaturation was blocked by the inhibitory ligand alpha-naphthoflavone (alpha NF, 7,8-benzoflavone). Human P450 1A2 was solubilized using high concentrations of sodium cholate and Triton N-101 and could be purified to near homogeneity in high yield in two steps. alpha NF was included in the buffer in the first step and then removed in the second chromatography step along with the detergent. The purified human P450 1A2 was found to be almost completely in the high spin iron configuration, in contrast to P450 1A2 enzymes isolated from rats and rabbits. The enzyme was catalytically active toward the known substrates 7-ethoxyresorufin and phenacetin. The N-terminal appears to be blocked, as is the case for other P450s we have expressed that contain the sequence MALLLAVFL in E. coli. Previously this human P450 has only been available in limited amounts; the methods presented here should facilitate further biochemical and practical studies on this interesting enzyme.

Biosynthesis of the diterpene cis-abienol in cell-free extracts of tobacco trichomes

Biosynthesis of the hydroxylated labdane diterpene, cis-abienol, 9 alpha H-[(12Z)-labda-12,14-dien-8 alpha-ol] from geranylgeranyl pyrophosphate was observed in cell-free extracts prepared from trichome-bearing tissues of the experimental tobacco, Nicotiana tabacum L. c.v. T.I. 1068. Synthetic activity was observed with extracts of trichome glands, but not subepidermal tissue or epidermis from which glands had been removed. The activity was soluble, Mg2+ stimulated, had a pH optimum near 7.0, and was unaffected by conditions which inhibit cytochrome P450 oxygenase. These results indicate the occurrence in trichome glands of T.I. 1068, a cyclase activity which yields the cyclized hydroxylated labdanoid cis-abienol directly.

Classification of lower limb arterial stenoses from Doppler blood flow signal analysis with time-frequency representation and pattern recognition techniques

A pattern recognition system was used to classify Doppler blood flow signals for the determination of lower limb arterial stenoses. The diagnostic features were extracted from time-frequency representations of Doppler signals. Three techniques were tested to estimate time-frequency representations: the short-time Fourier transform, the autoregressive (AR) modeling, and the Bessel distribution. A boundary tracking algorithm was proposed to extract the frequency contour of the Doppler time-frequency representations. Based on the characteristics of the Doppler frequency contour, shape descriptors from an autoregressive analysis were proposed as diagnostic features. Simple algorithms were proposed to normalize these autoregressive shape descriptors. Amplitude distribution of the Doppler time-frequency representation was also found useful for stenosis classification. A total of 379 arterial segments from the aorta to the popliteal artery were classified by the pattern recognition system into three categories of diameter reduction (0-19%, 20-49%, and 50-99%). The short-time Fourier transform provided an overall accuracy of 80% (kappa = 0.38); AR modeling, 81% (kappa = 0.42); and the Bessel distribution, 82% (kappa = 0.43). All these results are better than those based on visual interpretation (accuracy = 76%, kappa = 0.29) performed by a trained technologist. The AR modeling and the Bessel distribution improved the performance of the pattern recognition system in comparison with the short-time Fourier transform. It is likely that with further improvement, the pattern recognition approach will be a useful clinical tool to quantify stenoses and to follow the disease progression with more reliability and less bias than visual interpretation as done currently in clinical practice.

A new hypothesis about the relationship between free radical reactions and hemorheological properties in vivo

This paper is concerned with a hypothesis that disturbance of free radical reactions may lead to abnormality of hemorheological properties in vivo, and so the free radicals generated in vivo may damage certain tissue cells indirectly by reducing the supply of oxygen and nutrients to these cells through slowing the circulation of blood. This hypothesis is based on the following evidence: A. We have found that the whole blood viscosity at low shear rate correlates to the lipid peroxidation in the patients suffering from certain cardio- or cerebrovascular diseases, and in dogs during liver ischemia reperfusion or hemorrhagic pancreatitis. B. Reports have shown that several alterations of hemorheological properties may take place as a result of free radical reactions, such as lipid peroxidation. For instance, lipid peroxidation may lead to decrease of deformability of red cells, increase of aggregation of red cells, formation of liquid thrombin, etc. C. We have demonstrated that some alterations of hemorheological properties involve the role of free radicals in rats suffering from intestinal ischemia/reperfusion. As evidence for this conclusion, superoxide dismutase (SOD) used as a specific scavenger of superoxide anion radical (O2-) can significantly prevent the intestinal ischemia/reperfusion induced changes of lipid peroxidation, red cell aggregation, Cassion's viscosity and whole blood viscosity at low shear rate in rats.

Signals that produce 3' termini in CYC1 mRNA of the yeast Saccharomyces cerevisiae

The cyc1-512 mutant was previously shown to contain a 38-bp deletion, 8 nucleotides upstream from the major wild-type poly(A) site, in the CYC1 gene, which encodes iso-1-cytochrome c of the yeast Saccharomyces cerevisiae. This 38-bp deletion caused a 90% reduction in the CYC1 transcripts, which were heterogeneous in size, aberrantly long, and presumably labile (K. S. Zaret and F. Sherman, Cell 28:563-573, 1982). Site-directed mutagenesis in and adjacent to the 38-bp region was used to identify signals involved in the formation and positioning of CYC1 mRNA 3' ends. In addition, combinations of various putative 3' end-forming signals were introduced by in vitro mutagenesis into the 3' region of the cyc1-512 mutant. The combined results from both studies suggest that 3' end formation in yeast cells involves signals having the following three distinct but integrated elements acting in concert: (i) the upstream element, including sequences TATATA, TAG ... TATGTA, and TTTTTATA, which function by enhancing the efficiency of downstream elements; (ii) downstream elements, such as TTAAGAAC and AAGAA, which position the poly(A) site; and (iii) the actual site of polyadenylation, which often occurs after cytidine residues that are 3' to the so-called downstream element. While the upstream element is required for efficient 3' end formation, alterations of the downstream element and poly(A) sites generally do not affect the efficiency of 3' end formation but appear to alter the positions of poly(A) sites. In addition, we have better defined the upstream elements by examining various derivatives of TATATA and TAG ... TATGTA, and we have examined the spatial requirements of the three elements by systematically introducing or deleting upstream and downstream elements and cytidine poly(A) sites.

Mechanisms of inhibition of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone bioactivation in mouse by dietary phenethyl isothiocyanate

The tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1- butanone (NNK), induces lung tumors in mice, rats, and hamsters. Phenethyl isothiocyanate (PEITC), which occurs as gluconasturtiin in cruciferous vegetables, is a potent inhibitor of NNK-induced carcinogenesis. The present study investigated the enzymatic basis for the bioactivation of NNK and the mechanisms of the inhibition of this process by dietary PEITC in mice. The apparent Km for the formation of keto aldehyde, keto alcohol, and NNK-N-oxide in lung microsomes was 4.9, 2.6, and 1.8 microM and, in liver microsomes, 5.5, 5.1, and 8.8 microM, respectively. Immunoinhibition studies suggested that cytochrome P450s (P450s) 2A1 and 2B1 or related forms are the major enzymes involved in the oxidative metabolism of NNK in mouse lung microsomes. When female A/J mice were fed diets containing 0, 1, or 3 mumol of PEITC/g of diet for 4 wk, the dietary PEITC had no significant effects on the food consumption and body weight of the mice. NNK oxidation in the lung microsomes of mice consuming the 1 or 3 mumol of PEITC/g of diet was decreased by 13 to 27% or 30 to 50%, respectively. In liver microsomes, whose NNK oxidative metabolism rates were about twice those of lung microsomes on a per mg of protein basis, the activities were decreased by 14 to 31% by the 3 mumol of PEITC/g of diet. The apparent Km remained unchanged, and the apparent Vmax decreased in the lung and liver microsomes of PEITC-fed mice, suggesting a noncompetitive nature of the inhibition. When added to the incubation mixture, PEITC decreased NNK metabolism in a concentration-dependent manner and exhibited a competitive inhibition with apparent Ki values of 51 to 93 nM. Dietary PEITC decreased the hepatic P450 content by 25%, but increased (2-fold) the O-dealkylase activities of 7-pentoxyresorufin (indicative of P450 2B1) and 7-ethoxyresorufin (indicative of P450 1A) in the liver microsomes of mice consuming the 3 mumol of PEITC/g of diet. The P450 2B level was increased in liver microsomes but slightly decreased in the lung microsomes. The p450 2E1 level was increased by dietary PEITC by 1.2- and 1.6-fold in the liver and lung microsomes, respectively. The activities of glutathione S-transferase and NAD(P)H-quinone oxidoreductase in liver and lung microsomes were not affected appreciably by the dietary PEITC treatment. The results suggest that chronic consumption of PEITC decreases the rate of metabolic activation of NNK by chemical inactivation and competitive inhibition of the enzyme(s) responsible for NNK oxidation.

M(r) 6,400 aurin tricarboxylic acid directly activates platelets

ATA is a novel anticoagulant polymeric anionic aromatic compound that inhibits von Willebrand factor binding to platelet glycoprotein Ib and thereby prevents ristocetin- and shear stress-induced platelet aggregation. To investigate its mechanism of action, ATA fractions of homogeneous M(r) have been prepared by size exclusion chromatography. ATA fractions of M(r) > or = 2,500 are most effective at inhibiting vWF-mediated platelet aggregation, and ATA of M(r) = 2,500 also inhibits thrombin-induced platelet activation. Paradoxical results were observed in studies of ATA with M(r) = 6,400. This fraction of ATA stimulates aggregation of washed platelets or platelet-rich-plasma. The dose/response of aggregation shows a bell-shaped curve with maximal aggregation at approximately 2 micrograms/ml. Platelet aggregation is associated with phosphoinositide turnover and protein kinase C- and calcium-dependent protein phosphorylation. Platelet signalling responses to ATA are inhibited by platelet pretreatment with PGI2 or dibutyryl-cyclic AMP, but are unaffected by inhibiting platelet cyclooxygenase with aspirin. These results suggest that M(r) 6,400 ATA directly activates platelet phospholipase C to initiate platelet aggregation. This effect, unique to M(r) 6,400 ATA, could potentially mitigate ATA's beneficial anti-thrombotic effect on vWF-mediated platelet responses, and should be considered when analyzing results of experiments that utilize unfractionated ATA.

Structure-activity relationships of arylalkyl isothiocyanates for the inhibition of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone metabolism and the modulation of xenobiotic-metabolizing enzymes in rats and mice

Many arylalkyl isothiocyanates are potent inhibitors of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis in rats and mice. In the mouse, 4-phenylbutyl isothiocyanate (PBITC) and 6-phenylhexyl isothiocyanate (PHITC) exhibited greater inhibition than benzyl isothiocyanate (BITC) and phenethyl isothiocyanate (PEITC). The present study was conducted to investigate the structure-activity relationships of these four arylalkyl isothiocyanates for their inhibition of NNK oxidation and effects on xenobiotic-metabolizing enzymes in rats and mice. A single dose (0.25 or 1.00 mmol/kg) of each isothiocyanate was given to F344 rats 6 or 24 h before death. The rates of NNK oxidation were decreased in microsomes from the liver, lung and nasal mucosa of rats. Generally, PEITC was more potent than BITC but less potent than PBITC and PHITC. The rates in rat liver microsomes were decreased at 6 h but recovered or increased at 24 h; the rates in rat lung microsomes were markedly decreased at both 6 and 24 h; and the rates in rat nasal mucosa microsomes were also significantly decreased. The same treatment decreased the rat liver N-nitrosodimethylamine demethylase activity dramatically and ethoxyresorufin O-dealkylase and erythromycin N-demethylase activities moderately. However, the rat liver microsomal pentoxy-resorufin O-dealkylase activity was decreased at 6 h but increased at 24 h, with PEITC showing the most marked induction. The rat liver NAD(P)H:quinone oxidoreductase activity was increased 1.4- to 3.3-fold, with PEITC being most effective; and the glutathione S-transferase activity was increased slightly. Similarly, at a single dose of 0.25 mmol/kg (5 mumol/mouse) 24 h before death, PEITC, PBITC, PHITC but not BITC, decreased NNK oxidation in mouse lung microsomes by 40-85%, with PBITC and PHITC showing greater inhibition. Furthermore, all four isothiocyanates extensively inhibited NNK oxidation in rat lung and nasal mucosa microsomes as well as mouse lung microsomes in vitro, with PEITC (IC50 of 120-300 nM) being more potent than BITC (IC50 of 500-1400 nM) but less potent than PBITC and PHITC (IC50 of 15-180 nM). PHITC was a very potent competitive inhibitor of NNK oxidation in mouse lung microsomes with apparent K(i) values of 11-16 nM. These results indicate that PBITC and PHITC are more potent inhibitors of NNK bioactivation in rats and mice than PEITC. In addition, these arylalkyl isothiocyanates could be effective in protecting against the actions of a broad spectrum of carcinogenic or toxic compounds.

[Inhibitory effect of intraventricular administration of morphine on the hyperviscosity and elevation of blood pressure induced by stress in the rat]

Experiments were performed on 99 Wistar rats. It was found that hyperviscosity and elevation of blood pressure (BP) could be induced by hanging and restraining conscious rats with their four limbs tied on a frame. These effects were unaffected by bilateral vagotomy. By intravenous injection of propranolol or phentolamine, elevation of BP could be reduced, while stress-induced hyperviscosity could only be reduced by propranolol (i.v.). Stress-induced hyperviscosity and elevation of BP could be inhibited by electroacupuncture applied to the right hind leg or microinjection of morphine into 4th ventricle of the brain. On the other hand, if opiate receptor antagonist naloxone was given into the 4th-ventricle, the stress-induced hyperviscosity and elevation of BP could no longer be inhibited by electroacupuncture. It is suggested that the hyperviscosity and elevation of BP induced by hanging and restraining are mediated by excitatory cardiovascular sympathetic outflow with the result of activation of adrenoreceptors. Activation of the opiate receptors in the hindbrain may be responsible for decrease in stress-induced hyperviscosity and elevation of BP and for the inhibitory effect of electroacupuncture of the right hind leg on stress-induced hyperviscosity and elevation of BP.