Active site topology of human cytochrome P450 2E1

Cytochrome P450 2E1 (CYP2E1), an enzyme that is induced by ethanol, plays an important role in the metabolism of various toxic and carcinogenic substances, including dialkylnitrosamines and small halocarbons. Little information is available on the active site of the enzyme. We report here the formation of aryl-iron complexes (Fe-Ar) in the reactions of human CYP2E1 with phenyldiazene, (2-naphthyl)hydrazine, and p-biphenylhydrazine. Migration of the aryl group from the iron to the porphyrin nitrogens within the intact active site produces the four possible N-arylprotoporphyrin IX regioisomers in the following ratios (NB:NA:NC:ND, where the subscript indicates the pyrrole ring): phenyl, 03:34:02:61; 2-naphthyl, 02:18:03:77; p-biphenyl, 02:52:04:42. The results indicate that the active site of human CYP2E1 is sterically unhindered directly above the iron for a distance of 10 A. It appears, furthermore, that the active site cavity is relatively open above pyrrole rings A and D but is closed above pyrrole rings B and C, a topology similar to that deduced for the rat enzyme.

Parallel algorithms and architectures based on pipelined optical buses

Optical signals have some unique properties, such as unidirectional propagation and precisely predictable path delays in waveguides, which are not shared with their electronic counterparts. By taking advantage of these unique properties, we can use optical interconnections to achieve speed improvements in single-instruction stream, multiple-data streams (SIMD) computations. We first show how optical buses can be utilized advantageously in SIMD architectures to obtain fast solutions to several computational problems, including integer addition, counting and logical XOR, sorting, and fast Fourier transforms. We then present a new implementation of the optical buses to meet the unique requirements in highperformance optical-electronic computing systems. Such an implementation allows the transmission of messages at speeds ideal for optics and, in the meantime, the processing of data at speeds ideal for electronics, dealing successfully with the speed limitation by electronics in optical-electronic computers. The primary effects of this bimodal optical bus are twofold: reduction of fiber lengths and reduction of system latency. Reduced latency is a unique advantage to an optical bimodal bus. Together, these observations make optical-bus-based architectures appear to be a promising approach to SIMD processing.

[Chemical constituents of Euphorbia hylonoma Hand. -Mazz]

Three compounds have been isolated from the root of Euphorbia hylonoma and identified as 3,3',4-tri-O- methylellagic acid, beta-sitosterol and sucrose by physicochemical and spectroscopic methods. The compound 3,3'4-tri-O-methylellagic acid is discovered in Euphorbia for the first time.

[The effect of different topical agents on pseudomonas infection of burn wound]

48 Wistar rats were scalded resulting in 15% TBSA full-thickness burn. Pseudomonas aeruginosa (10(9)/ml was inoculated to the wounds. The rats were divided into 6 groups. 5 different topical agents were separately applied to the wounds constituting 5 groups, and no drug was used in control group. Through observing the appearance of wound, the quantity of bacteria in the subeschar tissue and histo-pathological changes, we confirmed that AgSD-ZnSD-A cream was a satisfactory topical agent.

3'-end-forming signals of yeast mRNA

It was previously shown that three distinct but interdependent elements are required for 3' end formation of mRNA in the yeast Saccharomyces cerevisiae: (i) the efficiency element TATATA and related sequences, which function by enhancing the efficiency of positioning elements; (ii) positioning elements, such as TTAAGAAC and AAGAA, which position the poly(A) site; and (iii) the actual site of polyadenylation. In this study, we have shown that several A-rich sequences, including the vertebrate poly(A) signal AATAAA, are also positioning elements. Saturated mutagenesis revealed that optimum sequences of the positioning element were AATAAA and AAAAAA and that this element can tolerate various extents of replacements. However, the GATAAA sequence was completely ineffective. The major cleavage sites determined in vitro corresponded to the major poly(A) sites observed in vivo. Our findings support the assumption that some components of the basic polyadenylation machinery could have been conserved among yeasts, plants, and mammals, although 3' end formation in yeasts is clearly distinct from that of higher eukaryotes.

The sulfoxidation of the hexachlorobutadiene metabolite N-acetyl-S-(1,2,3,4,4-pentachlorobutadienyl)-L-cysteine is catalyzed by human cytochrome P450 3A enzymes

The sulfoxidation of the mercapturic acid N-acetyl-S-(1,2,3,4,4-pentachlorobuta-1,3-dienyl)-L-cysteine (N-Ac-PCBC), a urinary metabolite of the renal toxin hexachlorobutadiene (HCBD), was studied in human liver microsomes and with purified cDNA expressed human liver cytochrome P450 (P450) enzymes. N-Acetyl-S-(1,2,3,4,4-pentachlorobuta-1,3-dienyl)-L-cysteine sulfoxide (N-Ac-PCBC SO) is a major urinary metabolite of HCBD in male rats; only liver microsomes from male rats catalyze the sulfoxidation of N-Ac-PCBC. Our results presented here show that human liver microsomes from both male and female donors are capable of oxidizing N-Ac-PCBC to the corresponding sulfoxide diastereomers. The correlation of N-Ac-PCBC sulfoxidation with the rates of oxidation of P450 enzyme specific substrates suggests that only P450 3A enzymes oxidize N-Ac-PCBC. Moreover, only gestodene and troleandomycin, two selective inhibitors for P450 of the 3A family, significantly reduced the rates of N-Ac-PCBC sulfoxidation. No reduction in sulfoxidation rates was observed with inhibitors for other P450 enzymes, i.e., diethyldithiocarbamate, 4-methylpyrazole, 7,8-benzoflavone, or sulfaphenazole. Incubations of N-Ac-PCBC with purified and reconstituted recombinant P450s 1A2, 2E1, 3A4, and 3A5 resulted in sulfoxide formation only with P450s 3A4 and 3A5. In summary, these results indicate that P450 from the 3A family may sulfoxidize N-Ac-PCBC. Since these P450 enzymes account for a major fraction of the P450 in human liver and are also present in human kidney, the sulfoxidation reaction may also be expected to occur in humans exposed to HCBD.

[Cerebral lesions in AIDS: what can be expected from scintigraphy? Cerebral tomographic scintigraphy using thallium-201: a contribution to the differential diagnosis of lymphomas and infectious lesions]

CT and MRI are not consistently able to differentiate central nervous system (CNS) lymphoma from focal cerebral infection such as toxoplasmosis in the human immunodeficiency virus (HIV) involvement. In this study thallium 201 (and/or technetium-MIBI) SPECT was performed in 6 patients suffering from AIDS and CNS lesions. An index based on the ratio of thallium uptake in the lesion vs the contralateral scalp was calculated. In 4 out of 5 patients with lymphoma (3 confirmed by biopsy, 2 highly suspected on CT and resistance to antitoxoplasmosis treatment) focal lesions showed high uptake of thallium. On the other hand one markedly necrotic lymphoma and all infectious lesions did not take up thallium. This suggests a role for thallium 201 brain SPECT in the workup of focal CNS lesions in AIDS.

[The use of measuring serum soluble IL-2 receptor levels in cyclosporine-A treated lupus nephritis]

Twenty-one patients with Lupus Nephritis (LN) were treated with cyclosporine-A (CsA) for three months. Serum soluble interleukin-2 receptors (SIL-2R) were measured before and after treatment and correlated prospectively with serologic findings of LN activity. The patients had significantly higher IL-2R level before treatment (during LN flare) than after treatment (disease remission). A significant positive correlation was present between serum SIL-2R and proteinuria, and ANA as well, whereas the SIL-2R levels in LN patients were inversely correlated with serum levels of C3 and CH50. These observations suggest that serum SIL-2R level is an useful marker of disease activity in LN and may serve as a helpful adjunct in the management of this disorder.

[Assessment of effectiveness of AgSD-ZnSD-Azone cream, negative ion irradiation and "moisture burn ointment" in prevention of burn wound infection as judged by changes in LPS, TNF and ET levels]

40 Wistar rats were scalded resulting in 15% TBSA full-thickness burn. Pseudomonas aeruginosa (10(9)/ml) was seeded on the wounds. The animals were divided into 4 groups. AgSD and ZnSD (with Azone) cream was applied to the wounds in the group I. The wounds were irradiated with negative ion current in the group II. The "moisture burn ointment" was applied to the wounds in the group III. Group IV consisted of controls without any treatment. Judging by changes in levels of LPS, TNF and ET, it was shown that the best result was obtained in the group I and II. The "moisture burn ointment" group yielded the poorest results.

Chinese Confucian culture and the medical ethical tradition

The Confucian culture, rich in its contents and great in its significance, exerted on the thinking, culture and political life of ancient China immense influences, unparalleled by any other school of thought or culture. Confucian theories on morality and ethics, with 'goodness' as the core and 'rites' as the norm, served as the 'key notes' of the traditional medical ethics of China. The viewpoints of Confucianism on benevolence and material interests, on good and evil, on kindheartedness, and on character cultivation were all inherited by the medical workers and thus became prominent in Chinese traditional medical ethics. Hence, it is clear that the medical profession and Confucianism have long shared common goals in terms of ethics. Influenced by the excellent Confucian thinking and culture, a rather highly-developed system of Chinese traditional medical ethics emerged with a well-defined basic content, and the system has been followed and amended by medical professionals of all generations throughout Chinese history. This system, just to mention briefly, contains concepts such as the need: to attach great importance to the value of life; to do one's best to rescue the dying and to heal the wounded; to show concern to those who suffer from diseases; to practise medicine with honesty; to study medical skills painstakingly; to oppose a careless style of work; to comfort oneself in a dignified manner; to respect local customs and to be polite; to treat patients, noble or humble, equally, and to respect the academic achievements of others, etc. Of course, at the same time, Confucian culture has its own historical and class limitations, which exerted negative influences on traditional medical ethics. Now, if we are to keep up with the development of modern medicine, a serious topic must be addressed. That is how to retain the essence of our traditional medical ethics so as to maintain historic continuity and yet, at the same time, add on the new contents of medical ethics so as to incorporate modern features into our system. Therefore, when trying to reform medical practice in China, we are faced with the urgent need to inherit and promulgate the essence of Confucian ethics--discarding its obsolete concepts--while at the same time building up the new medical ethics that can meet the requirements of the outside world and the future.

[Escharectomy during burn shock stage contributed to controlling or alleviating infectious complication]

Among 29 patients with extensive burn, 14 received escharectomy during the shock period, and the other 15 after 96 hrs. LPS and TNF were determined before and after escharectomy 3, 7, 14 and 21 PBD. Incidence of sepsis and subeschar bacterial count were analyzed. Clinical conditions were compared. The results showed that escharectomy during burn shock stage significantly reduced infectious complications in extensively burned patients. We believe that as long as general condition of the patient allowed, early removal of eschar was beneficial in reducing the threat of sepsis.

Binding characteristics of glucocorticoid receptor in synaptic plasma membrane from rat brain

The study was carried out to identify the specific glucocorticoid membrane binding site (GCMB) on synaptic plasma membrane (SPM), and to investigate the ligand binding properties and physico-chemical characteristics of GCMB. The radioligand binding assay showed that tritiated corticosterone ([3H]B) could bind to GCMB specifically with positive cooperativity. For SPM, the binding capacity (R(zero)) was 46.67 +/- 4.62 fmol/mg protein; the dissociation constant (Kd), 97.48 +/- 18.85 nmol/L, and the Hill coefficient, 1.633 +/- 0.082. Various steroids bound with GCMB in the following rank order: RU26752, aldosterone > corticosterone, cortisol > RU26988, progesterone, R5020, triamcinolone acetonide > testosterone, estradiol > RU38486 > dexamethasone. GCMB, which could be solubilized by detergent Triton X-100, showed thermal stability, although it was susceptible to hydrolysis by trypsin and to the reducing agent, mercaptoethanol. The addition of divalent cations (Ca2+, Mg2+) was beneficial to the ligand binding. The results strongly indicate that GCMB, fulfilling the basic criteria for a receptor, constitutes a novel type of glucocorticoid receptor on neuronal membrane which is significantly different from the cytosolic glucocorticoid receptors.

[Placental ureaplasma urealyticum infection and low birth weight]

Ureaplasma urealyticum (UU) infection during pregnancy may result in poor outcome. Placentae from 116 normal healthy pregnancies were cultured for UU with a recovery rate of 28.45%. 94 cases ended by normal vaginal delivery had a UU positive rate of 29.79%. The UU positive rate of 22 placenta from cases by cesarean section was 22.73%. The 2 positive rates showed no difference of significance (P > 0.05). This result indicated that UU infection of the placenta was present before passing through the birth canal and not due to contaminant during delivery. The birth weight of the neonates with positive UU infection was on the average 2,919g, while that in the negative UU cases was 3,490g, being 571g higher than in the positive group (P < 0.01). This study showed that placental infection with UU is associated with a low birth weight.

Expression of cytochrome P450 2D6 in Escherichia coli, purification, and spectral and catalytic characterization

Cytochrome P450 (P450) 2D6 is the classic human liver debrisoquine 4-hydroxylase, the first human P450 for which genetic polymorphism was clearly demonstrated. We prepared 11 different constructs of P450 2D6, with modification at the N-terminus, for expression in Escherichia coli with the vector pCW. These varied considerably in levels of expression of apo- and holoprotein, with the best yield being obtained in a system in which much of the N-terminal hydrophobic segment was removed. Production of holoprotein was highly dependent upon the addition of delta-aminolevulinic acid and FeCl3 to cultures, even though heme production should not be limiting in this system. The expressed protein was not tightly bound to the "heavier" membrane fraction but did not appear to behave as a soluble protein either. A purification strategy was developed involving fractional centrifugation, Triton X-114 phase separation, and flavodoxin affinity chromatography, which led to recovery of apparently electrophoretically homogeneous protein in good yield. Purified P450 2D6 had the expected N-terminal amino acid sequence and catalytic activities toward debrisoquine (4-hydroxylation) and bufuralol (1'-hydroxylation). The availability of a ready source of the recombinant protein should facilitate physical as well as functional studies and antibody production for other uses.

Redundant 3' end-forming signals for the yeast CYC1 mRNA

The cyc1-512 mutation is a 38-bp deletion in the 3' untranslated region of the CYC1 gene, which encodes iso-1-cytochrome c in Saccharomyces cerevisiae. This deletion caused a 90% reduction in the levels of the CYC1 mRNA and protein because of the absence of the normal 3' end-forming signal. Although the 3' end-forming signal was not defined by previous analyses, we report that concomitant alteration by base-pair substitution of three 3' end-forming signals within and adjacent to the 38-bp region produced the same phenotype as the cyc1-512 mutation. Furthermore, these signals appear to be related to the previously identified 3' end-forming signal TATATA. A computer analysis revealed that TATATA and related sequences were present in the majority of 3' untranslated regions of yeast genes. Although TATATA may be the strongest and most frequently used signal in yeast genes, the CYC1+ gene concomitantly employed the weaker signals TT-TATA, TATGTT, and TATTTA, resulting in a strong signal.

[The characteristics of inhalation injury and pulmonary infection in burn patients and the influence on their mortality]

940 patients with thermal injury during the past 14 years were reviewed. Of them, inhalation injury was diagnosed in 75 patients, including 15 mild injury who all survived, 25 moderate injury, of whom 13 died with a mortality rate of 52.0% and 35 severe injury, of whom 31 died with a mortality rate of 88.6%. The data showed that 70% of burn that caused inhalation injury occurred in a closed space and 96% of which also caused facial injury. With the burn extent increasing, the incidence of inhalation injury and pulmonary infection rise correspondingly. The time and incidence of pulmonary infection in the patients with inhalation injury was earlier and higher than that in those without inhalation injury (P < 0.01). With similar burn area and age, the risk of death in the patients with inhalation injury was 17.2 times of the patients without inhalation injury (P < 0.001). Pulmonary infection further increased mortality of the patients (P < 0.001).

Extensive wound excision in shock stage in patients with major burns

To stop excessive plasma loss, alleviate noxious effects of devitalized tissues on the body and shorten the hospitalization time, we performed extensive escharectomy during the shock period in extensively burned patients. Group A consisted of 21 patients aged 9-45 years (26.1 +/- 7.9 years), with a mean total burn area of 63.2% +/- 18.1% TBSA, and full-thickness injury involving 35.9% +/- 19.6% TBSA. The first escharectomy was done at 24.1 +/- 13.9 hours postburn, and excision area averaged 32.3% +/- 6.7% TBSA (24%-46%). In 15 of them, Swan-Ganz catheter was introduced to monitor the hemodynamic changes. It was found that RAP, PAP, PAWP, ABP, HR, CO and CI were all stable during and after the operation. Group B consisted of 29 patients aged 11-50 years (30.4 +/- 11.7 years), in whom escharectomy was begun 4-5 days postburn. The mean healing time of the patients in group A was 33.1 days, shorter than that of group B patients (40.1 days). The duration of hemoconcentration was shorter in group A. The amount of blood transfusion was almost 700 ml less in group A during the first two weeks. Less antibiotics were used with fewer visceral complications in group A. We believe that escharectomy during the burn shock stage is feasible.

[Detection of pathogenic Entamoeba histolytica DNA in liver abscess aspirates with polymerase chain reaction]

Polymerase chain reaction (PCR) was used to diagnose amebic liver abscess by detecting pathogenic Entamoeba histolytica DNA in liver aspirates from patients with liver abscess. Oligonucleotide primers specific for gene encoding of the 30,000 molecule of pathogenic Entamoeba histolytica were used in the test. Liver aspirates from 23 cases with amebic liver abscess as evidenced by typical clinical findings or very high titres of anti-E. Histolytica antibodies with ELISA were found to be positive with PCR. Fourteen control samples (3 cases of bacterial liver abscess, 1 of liver cancer and 10 of abscess in other sites) were all negative to PCR. The results suggest that PCR is a sensitive and useful method for diagnosing amebic liver abscess.

[The damaging effect of activated human neutrophils on isolated perfused rat lungs--the role of elastase]

Human neutrophil and its elastase play an important role in the pathogenesis of various lung diseases. We investigated the damaging effect of human neutrophils stimulated with PMA (phorbol myristate acetate 10ng/ml) or calcium ionophase A23187 (2ng/ml) on isolated perfused rat lungs. The study specimens consisted of 4 groups of animals. A control, B perfused with human neutrophils, C perfused with human neutrophils stimulated with PMA, and D perfused with human neutrophils stimulated with A23187. By using the ELISA method, we found that the level of human neutrophil elastase (HNE) in perfusate increased significantly at 30min (1.68 +/- 0.79ng/ml P < 0.05) and 60min (2.35 +/- 0.87 ng/ml P < 0.01) after PMA stimulating, but the HNE in the lung lavage fluid of the same group only slightly increased and the concentration of protein in lavage fluid did not change. After stimulating with A23187, the concentration of HNE in perfusate increased markedly at 30min (4.03 +/- 1.96ng/ml P < 0.01) and maintained at high level (P < 0.01). There was a significant increase of HNE level in lung lavage fluid (2.49 +/- 0.61ng/ml) from group D rat lungs, compared with group A, B or C, and the protein as well (1.61 +/- 0.58mg/ml P < 0.05). All the results indicate that the stimulated human neutrophils can release elastase in perfused rat lung. Neutrophil stimulated with A23187 can increase pulmonary permeability and injure the lung. We suggest that the lung damage, caused by human neutrophils, may be the effect of neutrophil elastase or the synergistic effect with some other substances derived from neutrophil.

Phospholipid composition of Pneumocystis carinii carinii and effects of methylprednisolone immunosuppression on rat lung lipids

The phospholipid class composition of Pneumocystis carinii carinii freshly isolated from infected lungs generally resembled that of the host lung, suggesting that the parasite scavenges lung alveolar lipids. However, subtle quantitative differences were demonstrated, indicating that the pathogen has the metabolic capacity to de novo synthesize, or at least tailor, its lipids. The concentration of phosphatidylcholine, the major lung surfactant lipid, in the organism was lower than that in lungs of normal and immunosuppressed uninfected rats, and the concentration of phosphatidylinositol was higher. Phosphonolipids were not detected in the organism by chemical analysis and nuclear magnetic resonance spectrometry. The immunosuppressive regimen alone caused increases in both surfactant protein A and the lipid content of the whole lung. The lungs of rats that were subjected to corticosteroid immunosuppression and had heavy parasite loads had dramatically elevated surfactant protein A levels, whereas the lipid contents of these lungs were not different from lipid contents in whole lungs of immunosuppressed uninfected rats. P. carinii was found to concentrate lipids, indicating that a large amount of the lipids in the whole infected rat lung was within the parasites residing in the organ. These observations have important implications relevant to the use of corticosteroid therapy for P. carinii pneumonitis.

Expression of cytochrome P450 3A5 in Escherichia coli: effects of 5' modification, purification, spectral characterization, reconstitution conditions, and catalytic activities

Cytochrome P450 (P450) 3A5 is a human enzyme with 85% amino acid sequence identity to the more predominantly expressed P450 3A4 and has been reported to have overlapping catalytic specificity. The 5'-terminus of a P450 3A5 cDNA was modified for optimal expression in Escherichia coli using the vector pCW, by aligning the MALLLAVFL N-terminal sequence of recombinant bovine P450 17A (H. J. Barnes, M. P. Arlotto, and M. R. Waterman, (1991) Proc. Natl. Acad. Sci. USA 88, 5597-5601) to the 3A5 cDNA. Two constructs were made, differing by their identity with the modified 3A4 N-terminal sequence (E. M. J. Gillam, T. Baba, B-R. Kim, S. Ohmori, and F. P. Guengerich, (1993) Arch. Biochem. Biophys. 305, 123-131). The first modified sequence (3A5#1) was identical to recombinant P450 3A4 up to codon 15, the 3A5 sequence being introduced thereafter. In the other (3A5#2), the successful 3A4 N-terminal nucleotide sequence was attached to codon 30. The yield was greater than fourfold higher in the first construct [up to 260 nmol (liter culture)-1]. The recombinant P450 3A5 (construct 1) was purified to electrophoretic homogeneity using a variation of a three-step procedure developed previously for P450 3A4, with an overall yield of approximately 40%. Purified P450 3A5 was active in nifedipine oxidation, testosterone 6 beta-hydroxylation, aflatoxin 3 alpha-hydroxylation and 8,9-epoxidation, ethylmorphine N-demethylation, erythromycin N-demethylation, and d-benzphetamine N-demethylation. The reconstitution of nifedipine oxidation, testosterone 6 beta-hydroxylation, and the aflatoxin oxidation activities showed dependence upon the presence of cytochrome b5, divalent cations, phospholipid mixtures, glutathione, and cholate similar to that previously found for purified P450 3A4. However, rates of the N-demethylations of ethylmorphine, erythromycin, and d-benzphetamine were as high or higher for P450 3A5 than P450 3A4 and were not particularly dependent upon modifications of reconstitution systems [corrected].

[Preparation and identification of monoclonal antibody against sterigmatocystin]

Compound antigen, bovine serum albumin-sterigmatocystin (BSA-ST) or hemocyanin sterigmatocystin (H-ST) was prepared by converting ST to its hemiacetal group in ST and taking ST conjugated to BSA or H. Balb/c mice were immunized with BSA-ST, and then their spleen cells were isolated and fused with SP2/0 murine myeloma cells. A hybridoma cell strain that could stably secrete monoclonal antibody against ST (McAb-ST) was selected, and both of their ascites and serum were rich in McAb-ST induced by cells of this strain. McAb-ST was identified as Ig-Gi with a molecular weight of 168,000 kd (53,000 for heavy chain and 31,000 for light one), and with an affinity constant of H-ST reaction of 1.29 x 10(9) mol/L measured by indirect competitive enzyme-linked immunosorbent assay (IC-ELISA). Relative cross reaction of McAb-ST with ST analogues was less than 2%. The minimal 0.5 pg/25 microliters of ST can be detected with IC-ELISA using McAb-ST and ST simultaneously, with a linear range of 0.1-10 ng/ml.