Ethambutol-induced vacuolar changes and neuronal loss in rat retinal cell culture: mediation by endogenous zinc

Ethambutol is an efficacious antituberculosis agent. However, its use has been limited by the occurrence of ocular toxicity. To investigate characteristics and possible mechanisms of ethambutol ocular toxicity, we used primary rat retinal cultures as a model. Primary rat retinal cultures were obtained from newborn Sprague-Dawley rats and used for experiments after maturation (DIV > or = 10). Cytopathologic changes were examined under light and electron microscopes. Thy-1 (a membrane glycoprotein expressed by retinal ganglion neurons)-containing neurons and gamma-aminobutyric acid (GABA)-ergic neurons were identified immunocytochemically. Exposure of retinal cultures for 24-48 h to ethambutol induced cytoplasmic vacuolar changes and neuronal loss. Vacuolar changes were partially reversible with the termination of ethambutol exposure. Of neurons, Thy-1(+) ganglion neurons were more vulnerable than GABA(+) neurons. Glutamate antagonists, an antioxidant (trolox), or cycloheximide, did not attenuate either vacuolar changes or neuronal loss. A cell-permeant zinc chelator N,N,N',N'-tetrakis (2-pyridylmethyl) ethylenediamine (TPEN) markedly attenuated vacuolar degeneration and neuronal loss, while the addition of zinc augmented both. In rat retinal cultures, ethambutol induces reversible vacuolar degeneration as well as irreversible neuronal loss, more preferentially of Thy-1(+) ganglion neurons. Contrary to the current theories, ethambutol-induced retinal cytotoxicity in the present study is mediated not by excitotoxicity or zinc deficiency but by a mechanism requiring intracellular zinc. In addition, features of the ethambutol-induced cell death were not consistent with those of apoptosis.

Transducer-binding and transducer-mutations modulate photoactive-site-deprotonation in sensory rhodopsin I

Sensory rhodopsin I (SRI) is a seven-transmembrane helix retinylidene protein that mediates color-sensitive phototaxis responses through its bound transducer HtrI in the archaeon Halobacterium salinarum. Deprotonation of the Schiff base attachment site of the chromophore accompanies formation of the SRI signaling state, S(373). We measured the rate of laser flash-induced S(373) formation in the presence and absence of HtrI, and the effects of mutations in SRI or HtrI on the kinetics of this process. In the absence of HtrI, deprotonation occurs rapidly (halftime 10 micros) if the proton acceptor Asp76 is ionized (pK(a) = approximately 7), and only very slowly (halftime > 10 ms) when Asp76 is protonated. Transducer-binding, although it increases the pK(a) of Asp76 so that it is protonated throughout the range of pH studied, results in a first order, pH-independent rate of S(373) formation of approximately 300 micros. Therefore, the complexation of HtrI facilitates the proton-transfer reaction, increasing the rate approximately 50-fold at pH6. Arrhenius analysis shows that HtrI-binding accelerates the reaction primarily by an entropic effect, suggesting HtrI constrains the SRI molecule in the complex. Function-perturbing mutations in SRI and HtrI also alter the rate of S(373) formation and the lambda(max) of the parent state as assessed by laser flash-induced kinetic difference spectroscopy, and shifts to longer wavelength are correlated with slower deprotonation. The data indicate that HtrI affects electrostatic interactions of the protonated Schiff base and not only receives the signal from SRI but also optimizes the photochemical reaction process for SRI signaling.

Intrahepatic cholangiocarcinoma in Korea

We reviewed surgically treated patients with intrahepatic cholangiocarcinoma to evaluate the clinical and pathologic features of intrahepatic cholangiocarcinoma that may affect long-term survival in Korean patients with the disease. Between 1990 and 1997, 28 patients with intrahepatic cholangiocarcinoma underwent laparotomy. Resection was performed in 25 patients, and wedge resection alone in 3 patients. The liver resections consisted of right lobectomy in 5 patients, right trisegmentectomy in 1, left lobectomy in 7, extended left lobectomy in 3, hepatopancreatoduodenectomy in 2, and segmentectomy in 7. Curative resection was performed in 15 patients. Histological sections of all resected specimens were immunohistochemically stained with p53 and Ki-67 monoclonal antibodies to assess the biological behavior of the tumor cells. Cumulative survival rate and clinicopathological factors that may influence the prognosis, including biological markers (p53, Ki-67), were analyzed statistically. Patients who underwent curative resection survived significantly longer than patients who underwent noncurative resection. The median survival time of the patients who underwent curative resection was 24 months (mean, 34 +/- 8 months), with 1-, 2-, and 3-year survival rates of 66.6%, 44.4%, and 35.6%, respectively. The median survival time of the patients who underwent noncurative resection was 3 months (mean, 8 +/- 3 months), with 1- and 2-year survival rates of 26.7% and 13. 4%, respectively. Univariate analysis showed that positive regional lymph nodes correlated significantly with poor outcome (P = 0.004) and that curative resection significantly correlated with better prognosis (P = 0.001). Age, sex, tumor size, degree of cell differentiation, gross type of tumor, and p53 and Ki-67 labeling index were not significantly correlated with outcome. Our findings support the concept that aggressive liver resection, along with regional lymph node dissection, be recommended for long-term survival. The validity of molecular biologic tumor markers (p53, Ki-67) as prognostic factors has not yet been clearly demonstrated.

Precursor of pro-apoptotic cytokine modulates aminoacylation activity of tRNA synthetase

Endothelial monocyte activating polypeptide II (EMAPII) is a cytokine that is specifically induced by apoptosis. Its precursor (pro-EMAPII) has been suggested to be identical to p43, which is associated with the multi-tRNA synthetase complex. Herein, we have demonstrated that the N-terminal domain of pro-EMAPII interacts with the N-terminal extension of human cytoplasmic arginyl-tRNA synthetase (RRS) using genetic and immunoprecipitation analyses. Aminoacylation activity of RRS was enhanced about 2.5-fold by the interaction with pro-EMAPII but not with its N- or C-terminal domains alone. The N-terminal extension of RRS was not required for enzyme activity but did mediate activity stimulation by pro-EMAPII. Pro-EMAPII reduced the apparent Km of RRS to tRNA, whereas the kcat value remained unchanged. Therefore, the precursor of EMAPII is a multi-functional protein that assists aminoacylation in normal cells and releases the functional cytokine upon apoptosis.

Functional analysis of a hybrid endoglucanase of bacterial origin having a cellulose binding domain from a fungal exoglucanase

A cellulose binding domain (CBD) of an endo-beta-1,4-glucanase (Ben) from the bacterium Bacillus subtilis BSE616 was replaced with the CBD of exoglucanase I (TexI) from the fungus Trichoderma viride HK-75. The resultant hybrid enzyme Ben'-CBDTexI, comprising the catalytic domain (Ben') of Ben and the CBD (CBDTexI) of TexI, was highly expressed at 20% of the total protein in Escherichia coli. The molecular mass of the hybrid enzyme was estimated to be ca. 38 kDa by SDS-PAGE, which was in good agreement with that calculated from 305 amino acids of Ben and 42 amino acids of CBDTexI. The hybrid enzyme exhibited almost the same activity as that of the original Ben toward soluble substrates, such as cellooligosaccharides. The hybrid enzyme showed higher binding ability and hydrolysis activity toward microcrystalline cellulose (Avicel), even though the length of the CBD of TexI was four times smaller than that of Ben. The hybrid enzyme was more resistant to tryptic digestion than the original Ben. The efficient binding ability of the hybrid enzyme to Avicel permitted purification of the enzyme using an Avicel-affinity column to the extent of ca. 90% purity.

Improvement of heterologous protein productivity by controlling postinduction specific growth rate in recombinant Escherichia coli under control of the PL promoter

To develop the optimal operational strategy for the PL promoter of interferon (IFN)-gamma-producing Escherichia coli, some rational medium feeding methods, carried out just after temperature induction to control the postinduction specific growth rate (mu i), were designed. Using experimental data from various batch cultures, we correlated mu i with specific IFN-gamma production rate (qpi) to find out how mu i just after induction affected qpi. It was revealed that sustaining mu i above a certain value after induction was the key factor for high-level production of IFN-gamma. Stepwise and constant-rate medium feeding, in which the temperature induction was done simultaneously, at the late-exponential growth phase of batch culture resulted in a dramatic extension of the production period as a result of sustaining mu i after temperature induction. These methods led to the overcoming of harsh conditions after temperature induction and the improvement of IFN-gamma productivity. Finally, by both a high-cell-density culture using an exponential fed-batch culture for cell growth and constant-rate medium feeding after temperature induction for IFN-gamma production, we accomplished an increase in IFN-gamma production by 23-fold, 7.43 g/L, as compared with that of batch culture.

Molecular cloning of a Bacillus sp. KK-1 xylanase gene and characterization of the gene product

A gene encoding cellulase-free xylanase was cloned from the thermophilic bacterium Bacillus sp. KK-1 into Escherichia coli and the gene product was purified from the recombinant E. coli. This xylanase gene, designated xylY, was composed of 1,302 base pairs and encoded a polypeptide of 434 amino acids. No similarity was found between the nucleotide sequence of the xylY gene and those reported for other xylanase genes. The deduced amino acid sequence was homologous to those of cellulases belonging to the beta-glycanase family D. The purified enzyme exhibited maximum activity at 55 degrees C but also lost 70% of this activity even after incubation for 30 min at 55 degrees C. Bacillus sp. KK-1 may have acquired the xylY gene by an interspecies gene transfer during adaptation to mesophilic environment.

Suppressor mutation analysis of the sensory rhodopsin I-transducer complex: insights into the color-sensing mechanism

The molecular complex containing the phototaxis receptor sensory rhodopsin I (SRI) and transducer protein HtrI (halobacterial transducer for SRI) mediates color-sensitive phototaxis responses in the archaeon Halobacterium salinarum. One-photon excitation of the complex by orange light elicits attractant responses, while two-photon excitation (orange followed by near-UV light) elicits repellent responses in swimming cells. Several mutations in SRI and HtrI cause an unusual mutant phenotype, called orange-light-inverted signaling, in which the cell produces a repellent response to normally attractant light. We applied a selection procedure for intragenic and extragenic suppressors of orange-light-inverted mutants and identified 15 distinct second-site mutations that restore the attractant response. Two of the 3 suppressor mutations in SRI are positioned at the cytoplasmic ends of helices F and G, and 12 suppressor mutations in HtrI cluster at the cytoplasmic end of the second HtrI transmembrane helix (TM2). Nearly all suppressors invert the normally repellent response to two-photon stimulation to an attractant response when they are expressed with their suppressible mutant alleles or in an otherwise wild-type strain. The results lead to a model for control of flagellar reversal by the SRI-HtrI complex. The model invokes an equilibrium between the A (reversal-inhibiting) and R (reversal-stimulating) conformers of the signaling complex. Attractant light and repellent light shift the equilibrium toward the A and R conformers, respectively, and mutations are proposed to cause intrinsic shifts in the equilibrium in the dark form of the complex. Differences in the strength of the two-photon signal inversion and in the allele specificity of suppression are correlated, and this correlation can be explained in terms of different values of the equilibrium constant (Keq) for the conformational transition in different mutants and mutant-suppressor pairs.

Cloning and expression of a Clostridium thermocellum xylanase gene in Escherichia coli

A Clostridium thermocellum xylanase gene, designated xynX, was cloned in Escherichia coli and was categorized a novel gene as a result of the comparison of restriction patterns of the C. thermocellum xylanase genes so far reported. The xynX gene encodes a xylanase having the molecular weight of 105 kilodaltons. A number of smaller truncated proteins with activities towards 4-methylumbelliferyl-beta-D-cellobioside and xylan were also produced. The enzyme hydrolyzed xylan to xylo-oligosaccharide, indicating typical activity of endo-beta-1,4-xylanase. This endoxylanase hydrolyzed carboxymethylcellulose without notable reduction of the viscosity as an exo-beta-1,4-glucanase, even though the enzyme exhibited very low levels of activity against other soluble and insoluble cellulosic substrates.

Apoptosis-mediated immunotoxicity of polychlorinated biphenyls (PCBs) in murine splenocytes

Polychlorinated biphenyls (PCBs) exhibited immunotoxicity on antibody forming response to T-dependent antigen of sheep red blood cells, primary activation of T cells by mixed lymphocyte response, and lymphocyte proliferation induced by various mitogens. These immunosuppressions were related with the loss of lymphocyte viability which was determined by the propidium iodide method, and this death was proven to be linked with apoptosis which showed DNA fragmentation detected by the diphenylamine method and agarose gel electrophoresis. The degree of DNA fragmentation was increased in a dose- and time-dependent manner in PCB-treated splenocytes. In conclusion, it was assumed that apoptosis was attributable to the immunotoxicity of PCBs in murine splenocytes.

Adsorption of Bacillus subtilis endo-beta-1,4-glucanase to cellulosic materials

The intact and the truncated endo-beta-1,4-glucanase expressed in Bacillus megaterium by a B. subtilis gene were purified and its adsorption characteristics to cellulosic materials were investigated. The intact enzyme was purified by affinity towards insoluble cellulose and Mono-Q chromatography. The truncated enzyme was purified by gel filtration and chromatofocusing. The molecular activities of these enzymes towards the soluble substrates were identical. Optimum pH and temperature of these two types of enzyme were same, 5.5 and 60 degrees C, respectively. However, the insoluble substrate, Avicel, was hydrolyzed slowly by the intact endoglucanase while the truncated endoglucanase did not hydrolyze the Avicel. Isoelectric points of the intact and the truncated enzyme were 6.2 and 5.6, respectively. In a Sephadex column the large form of intact endoglucanase was eluted later than the small form of truncated enzyme. Only the intact enzyme was strongly adsorbed to Avicel. The practical maximum adsorption was about 20 mg/g of Avicel at pH 6.0 and 4 degrees C.

Molecular mechanism of photosignaling by archaeal sensory rhodopsins

Two sensory rhodopsins (SRI and SRII) mediate color-sensitive phototaxis responses in halobacteria. These seven-helix receptor proteins, structurally and functionally similar to animal visual pigments, couple retinal photoisomerization to receptor activation and are complexed with membrane-embedded transducer proteins (HtrI and HtrII) that modulate a cytoplasmic phosphorylation cascade controlling the flagellar motor. The Htr proteins resemble the chemotaxis transducers from Escherichia coli. The SR-Htr signaling complexes allow studies of the biophysical chemistry of signal generation and relay, from the photobiophysics of initial excitation of the receptors to the final output at the level of the flagellar motor switch, revealing fundamental principles of sensory transduction and more broadly the nature of dynamic interactions between membrane proteins. We review here recent advances that have led to new insights into the molecular mechanism of signaling by these membrane complexes.

Protonatable residues at the cytoplasmic end of transmembrane helix-2 in the signal transducer HtrI control photochemistry and function of sensory rhodopsin I

Neutral residue replacements were made of 21 acidic and basic residues within the N-terminal half of the Halobacterium salinarium signal transducer HtrI [the halobacterial transducer for sensory rhodopsin I (SRI)] by site-specific mutagenesis. The replacements are all within the region of HtrI that we previously concluded from deletion analysis to contain sites of interaction with the phototaxis receptor SRI. Immunoblotting shows plasmid expression of the htrI-sopI operon containing the mutations produces SRI and mutant HtrI in cells at near wild-type levels. Six of the HtrI mutations perturb photochemical kinetics of SRI and one reverses the phototaxis response. Substitution with neutral amino acids of Asp-86, Glu-87, and Glu-108 accelerate, and of Arg-70, Arg-84, and Arg-99 retard, the SRI photocycle. Opposite effects on photocycle rate cancel in double mutants containing one replaced acidic and one replaced basic residue. Laser flash spectroscopy shows the kinetic perturbations are due to alteration of the rate of reprotonation of the retinylidene Schiff base. All of these mutations permit normal attractant and repellent signaling. On the other hand, the substitution of Glu-56 with the isosteric glutamine converts the normally attractant effect of orange light to a repellent signal in vivo at neutral pH (inverted signaling). Low pH corrects the inversion due to Glu-56 -> Gln and the apparent pK of the inversion is increased when arginine is substituted at position 56. The results indicate that the cytoplasmic end of transmembrane helix-2 and the initial part of the cytoplasmic domain contain interaction sites with SRI. To explain these and previous results, we propose a model in which (i) the HtrI region identified here forms part of an electrostatic bonding network that extends through the SRI protein and includes its photoactive site; (ii) alteration of this network by photoisomerization-induced Schiff base deprotonation and reprotonation shifts HtrI between attractant and repellent conformations; and (iii) HtrI mutations and extracellular pH alter the equilibrium ratios of these conformations.

Enhanced effectiveness of dimethyl-4,4'-dimethoxy-5,6,5',6'-dimethylene dioxybiphenyl-2,2'-dicarboxylate in combination with garlic oil against experimental hepatic injury in rats and mice

The present study was designed to evaluate the effects of dimethyl-4,4'-dimethoxy-5,6,5',6'-dimethylene dioxybiphenyl-2,2'-dicarboxylate (PMC) in combination with garlic oil against chemical-induced hepatic injury in rats and mice. Rats insulted with carbon tetrachloride were concomitantly treated with PMC and/or garlic oil (50 and 100 mg kg-1, respectively) for four weeks. Whereas treatment of animals with garlic oil alone was ineffective in suppressing carbon tetrachloride-induced hepatotoxicity, administration of PMC in combination with garlic oil more effectively protected the liver against the carbon tetrachloride-induced insult than PMC alone, as monitored by serum aminotransferase activity. Hepatoprotective effects of the formulation were further supported by the changes in the numbers of Kupffer cells and dead hepatocytes. Although prior treatment of rats with PMC for three days failed to protect hepatotoxicity elicited by allyl alcohol, the formulation of PMC and garlic oil was capable of blocking allyl alcohol-induced hepatotoxicity by approximately 40%. To further examine the effect of the agents on lipid metabolism in the liver, hepatic triglycerides and cholesterol contents were assessed in mice after a diet containing PMC and/or garlic oil for one week followed by a single dose of carbon tetrachloride. Garlic oil appeared to be more effective in bringing hepatic lipid levels to those of control than PMC alone. Treatment of animals with PMC in combination with garlic oil synergistically improved chemical-induced impairment of hepatic triglycerides and cholesterol.(ABSTRACT TRUNCATED AT 250 WORDS)

Combination of the tod and the tol pathways in redesigning a metabolic route of Pseudomonas putida for the mineralization of a benzene, toluene, and p-xylene mixture

Construction of a hybrid strain which is capable of mineralizing components of a benzene, toluene, and p-xylene mixture simultaneously was attempted by redesigning the metabolic pathway of Pseudomonas putida. Genetic and biochemical analyses of the tod and the tol pathways revealed that dihydrodiols formed from benzene, toluene, and p-xylene by toluene dioxygenase in the tod pathway could be channeled into the tol pathway by the action of cis-p-toluate-dihydrodiol dehydrogenase, leading to complete mineralization of a benzene, toluene, and p-xylene mixture. Consequently, a hybrid strain was constructed by cloning todC1C2BA genes encoding toluene dioxygenase on RSF1010 and introducing the resulting plasmid into P. putida mt-2. The hybrid strain of P. putida TB105 was found to mineralize a benzene, toluene, and p-xylene mixture without accumulation of any metabolic intermediate.

Differential expression of rat microsomal epoxide hydrolase gene by imidazole and triazole antimycotic agents

Previous studies from this laboratory revealed that imidazole antimycotic agents, including ketoconazole and clotrimazole, induce microsomal epoxide hydrolase (mEH) and that the mEH induction involves large increases in mRNA with transcriptional activation. To establish whether these compounds elevate mEH mRNA levels in a dose-related manner and whether triazole antimycotic agents, fluconazole and itraconazole, affect mEH gene expression to similar extents, hepatic mEH mRNA levels were quantified in rats by RNA blot analyses using an mEH cDNA probe. Treatment of rats (males) with ketoconazole caused approximately 4-, 10-, and 11-fold increases in mEH mRNA levels at 24-hr posttreatment at the doses of 50, 100, and 200 mg/kg body weight, respectively, whereas mEH mRNA levels were increased approximately 18-fold at 24 hr after a single administration of clotrimazole at 50 mg/kg body weight or at greater doses, with EC50 value being noted as 20 mg/kg body weight. Fluconazole elevated mEH mRNA levels by 2-, 3-, and 6-fold at the doses of 50, 100, and 200 mg/kg body weight, respectively. However, hepatic microsomes isolated from rats treated with fluconazole for 3 days failed to exhibit significant elevation in mEH protein levels, as assessed by immunoblot analyses. No significant increase in mEH mRNA nor protein levels was observed at 1 or 3 days after treatment of rats with itraconazole (200 mg/kg body weight/day). To characterize gender-related differences in hepatic mEH gene expression in response to azole antimycotic agents, the effects of ketoconazole and clotrimazole were examined in females.(ABSTRACT TRUNCATED AT 250 WORDS)

Heavy metal toxicity testing in environmental samples

The toxicity of heavy metals in the environment depends on a number of physicochemical and biological factors. The complexity of these relationships has encouraged the use of bioassays for direct measurement of the [table: see text] impact of toxic metals on selected test species. Fish and daphnid bioassays are well accepted by the scientific and regulatory communities, but their length (48 h or more) and the considerable time and effort needed to culture the test organisms make their application to sample screening problematical. Microbial and biochemical assays based on the inhibition of bioluminescence, enzyme activity, enzyme biosynthesis, growth, respiration, and heat production are typically faster and less expensive than the traditional and fish bioassays. Some of these tests approach or equal the sensitivity of daphnids to heavy metals. Since the soil acts as a sink for airborne and waste-applied metals, the uptake of metals by plants and the associated toxic impacts are important. Growth inhibition, enzyme induction, and production of stress proteins have been considered as toxicity end points. Enzymatic tests have been developed that are specific for heavy metal toxicity. Such tests can facilitate toxicity reduction evaluations. Detection of individual metals in the environment may eventually be possible using biosensors consisting of genetically engineered microorganisms. Direct solid-phase tests for soil, sediment, or sludge toxicity, using bacterial bioluminescence or enzyme activity as end points, have been developed. Such tests may complement traditional solid-phase toxicity tests using nematodes or earthworms as indicator organisms. Based on the work reviewed, we draw the following conclusions: 1. The Microtox assay is sensitive to mercury but would fail to detect the toxicity of certain metals, such as cadmium. Among all the microbial assays reviewed, the bioassay based on growth inhibition of the alga Selenastrum capricornutum appears to give the lowest EC50s, similar to those seen for daphnid bioassays. 2. Biosensors, using genetically engineered microorganisms, offer an elegant means of detecting the presence of specific heavy metals in environmental samples. However, at the present time, they are not designed for assessing heavy metal toxicity. 3. The use of bioassays specific for heavy metal toxicity can be useful for directly assessing the bioavailability of these toxicants in environmental samples, thus avoiding the need for fractionation.+4

An interchangeable system of hairy root and cell suspension cultures ofCatharanthus roseus for indole alkaloid production

Hairy roots ofCatharanthus roseus obtained by co-cultivation of hypocotyl segments withAgrobacterium rhizogenes, and cultured in SH (Schenk and Hildebrandt) basal medium, formed two types of calli when subcultured in SH medium with 1 mg/1 α-naphthaleneacetic acid and 0.1 mg/l kinetin. One of them, a compact callus, when re-subcultured in SH basal medium gave rise to hairy roots again. A rhizogenic cell suspension culture was established from this type of callus. When cultured in SH medium with growth regulators, the rhizogenic callus produced catharanthine at a level of 41% of the level in the initial hairy roots. Upon transfer to SH basal medium, regenerated hairy roots produced this alkaloid at the original level of 1.5 mg/g dry wt. Using this cell/hairy root interchange system a new management system for hairy root culture in bioreactors has been devised and examined involving production of biomass in the form of a cell suspension in medium supplemented with growth regulators, and catharanthine production by hairy roots regenerated from these cells in medium without growth regulators.

Relationship between cell morphology and indole alkaloid production in suspension cultures of Catharanthus roseus

The relationship between the morphology and indole alkaloid production of Catharanthus roseus cells was investigated. Eleven cell lines were randomly selected from protoplast-derived clones. In each line, most of the cells maintained only one of the two shapes, either spherical or cylindrical. The cell aspect ratio (cell length/width) for most isolates was stable for more than two years of subculture. Cell division patterns of spherical and cylindrical cell isolates were different and patterns of division remained stable in each phenotype and were not considerably affected by auxin or cytokinin levels in the culture media. These observations indicate that cell morphology of our isolates is stable and probably internally determined. Production of the indole alkaloids, ajmalicine and catharanthine was significantly greater when the cell aspect ratio was more than 2.8.

Differential expression of microsomal epoxide hydrolase gene by azole heterocycles in rats

The effects of heterocycles including imidazole (IM), 1,2,4-triazole (TR) and thiazole (TH) on the expression of microsomal epoxide hydrolase (mEH) gene were examined in rats (200 mg/kg body weight/day, i.p.). Hepatic microsomes prepared from rats treated with IM for 3 days failed to exhibit an increase in mEH protein level whereas TR treatment resulted in an approximately 2- to 3-fold elevation in hepatic mEH levels relative to control, as assessed by both SDS-PAGE and immunoblot analyses. In contrast, thiazole-induced hepatic microsomes resulted in a substantial increase in mEH levels (i.e. approximately 5-fold). Slot and northern blot analyses, probed with an mEH cDNA, showed that the hepatic mEH mRNA levels in the animals treated with IM for 3 days were marginally increased by approximately 2-fold, as compared with untreated animals, whereas TR caused an approximately 8-fold increase in hepatic mEH mRNA levels after three consecutive daily treatments. TH treatment resulted in an approximately 22-fold increase in the mEH mRNA levels, demonstrating that TH is the most efficacious among these three azole heterocycles. Because TH was the most effective in increasing hepatic mEH protein and mRNA levels, the agent was chosen for further evaluation. Time course of mEH gene expression at early times after a single treatment with TH was determined and compared with that caused by pyrazine (PZ), a strong mEH inducer. Hepatic mEH mRNA levels were increased approximately 1-, 3-, 20- and 16-fold at 3, 6, 12 and 24 hr, respectively, following TH treatment, relative to control, whereas mEH mRNA levels were elevated approximately 1-, 1-, 22- and 18-fold, respectively, at the same time points after PZ treatment, as monitored by slot RNA hybridization analyses. Northern blot analyses using either total RNA or poly(A)+ RNA fractions exhibited comparable time courses in increasing mEH mRNA levels after TH or PZ treatment with maximal mRNA increases being noted at 12 hr post treatment. Although neither IM or TR failed to affect renal mEH gene expression to a notable extent, TH treatment caused 6- to 8-fold increases in kidney mEH mRNA levels, with a 2-fold increase in mEH protein detected. These results demonstrated that the azole heterocyclic compounds IM, TR and TH differentially induce mEH with TH as the most efficacious azole; and that the changes in mEH levels are primarily associated with increases in mRNA levels.

High frequency plant regeneration from anther-derived cell suspension cultures via somatic embryogenesis in Catharanthus roseus

A system for high frequency plant regeneration from cell suspension cultures in Catharanthus roseus is described. Calli were obtained from anthers cultured on Murashige and Skoog's medium supplemented with 1 mgl(-1) α-naphthaleneacetic acid and 0.1 mgl(-1) kinetin. After the second subculture on solid medium, embryogenic callus was identified and transferred to liquid medium to initiate suspension cultures. Cells dispersed finely in the medium were subcultured at 14-day intervals. Upon plating onto the basal medium, yellowish compact colonies proliferated from the cells and more than 80% of them gave rise to somatic embryos. Subsequently, plantlets developed from the embryos. Both the plantlets and the source plants showed the normal somatic chromosome number of 2n=2x=16.

Thin-film thermo-optic Ge(x)Si(1-x) Mach-Zehnder interferometer

We report on the design and fabrication of Ge(x)Si(1-x) Mach-Zehnder interferometers based on the thermo-optic effect. The modulators exhibit 8 dB of extinction with a pi-phase-shift power requirement, P(pi), of 245 mW. The 3-dB bandwidth of these thermo-optic devices is 88 kHz. Finally, we present calculations indicating the effect of various parameters on the modulation of the Mach-Zehnder interferometer.

Polymorphic reticulosis with colonic lesion--a case report

A 38-year-old man was admitted with a high fever, sore throat, and right upper quadrant pain. Nine months before his admission, he had undergone right hemicolectomy under the impression of intestinal lymphoma. But there had been no evidence of lymphoma on microscopic examination. Under the postoperative diagnosis of inflammatory bowel disease, corticosteroid therapy was tried without response. On the follow-up colonoscopic examination, an ovoid ulcer, with convergence of the surrounding mucosal folds at the descending colon and an irregularly shaped ulcer at the ileocolic anastomotic site, were found. The colonoscopic diagnosis was Behcet's colitis. After pathologic slides of biopsy and surgical specimens obtained from the palatine tonsil and colon were reviewed, the diagnosis of polymorphic reticulosis was made. The patient received anticancer chemotherapy, including cyclophophamide and glucocorticosteroid. To date, colonic involvement of polymorphic reticulosis has not been reported. Because of the similarity of the colonoscopic findings to those of Behcet's colitis, polymorphic reticulosis should be included in the differential diagnosis of inflammatory bowel disease. We assume that this is the first case of polymorphic reticulosis involving the colon with characteristic colonoscopic findings.

Synthesis of different nucleoside 5'-diphospho-sulfoquinovoses and their use for studies on sulfolipid biosynthesis in chloroplasts

6-Sulfo-alpha-D-quinovopyranosyl phosphate was reacted with different nucleoside monophosphate morpholidates to form ADP-, CDP-, GDP- and UDP-sulfoquinovose. Analytical and preparative HPLC of these nucleotides was performed on reversed-phase columns using volatile buffer systems as eluant. The isolated compounds were characterized by NMR spectroscopy (except the CDP derivative) and used for an investigation of sulfolipid biosynthesis by chloroplasts. For this purpose intact spinach chloroplasts were biosynthetically preloaded with radioactive diacylglycerol to provide a sulfoquinovosyl acceptor. When sulfosugar nucleotides were added to such prelabelled intact organelles, the background levels of sulfolipid biosynthesis did not rise. On the other hand, after osmotic shock of prelabelled chloroplasts sulfolipid labelling was significantly increased by the addition of UDP- or GDP-sulfoquinovose. The same stimulation was observed with isolated envelope membranes, and UDP-sulfoquinovose proved to be twice as active as the GDP derivative. From these results it was concluded that the final step in sulfolipid biosynthesis is catalyzed by a UDP-sulfoquinovose: 1,2-diacylglycerol 3-O-alpha-D-sulfoquinovosyltransferase. This chloroplast enzyme cannot use exogenously supplied sulfosugar nucleotides, which as membrane-impermeable compounds are expected to be formed in vivo within chloroplasts.