New strategy for the cultivation of microalgae using microencapsulation

The four species of microalgae (Dunaliella bardawil, Chlorella minutissima, Pavlova lutheri and Haematococcus pluvialis) were immobilized in Ca-alginate capsules as a basic study for the development of the economic cultivation process. Under the batch culture of aerobic conditions, the thickness of the capsule membrane and CO2 supply did not affect the growth of the immobilized microalgae, Dunaliella bardawil. Cell concentration of immobilized microalgae in the capsule was higher than those of immobilized microalgae in beads and free cells. The cell concentrations of microencapsulated Dunaliella bardawil and Haematococcus pluvialis were five times greater than that of free cells. Based on these results, microencapsulation for the culture of microalgae was an effective method for the high-density cultivation. In comparison to the immobilized cultivation on the bioreactor type, it was more effective for the cultivation in the bubble column bioreactor than that in the stirrer tank bioreactor.

Malignant obstruction of gastric outlet and duodenum: palliation with flexible covered metallic stents

PURPOSE

To assess the usefulness of flexible covered metallic stents in the palliation of malignant obstruction of the gastric outlet and duodenum.

MATERIALS AND METHODS

Twenty-four consecutive patients with malignant obstruction of the gastric outlet (n = 22) or duodenum (n = 2) underwent palliative treatment with self-expandable flexible covered metallic stents. Fourteen patients had advanced gastric carcinoma at the antrum and/or pylorus, and eight had obstruction at the anastomosis site of previous gastrojejunostomy. Complications and clinical status were investigated during the study period.

RESULTS

The technical success rate was 75% (18 of 24 patients). Twenty-one stents were placed in 18 patients by using an introducer 6 (n = 7) or 8 mm (n = 14) in diameter. The mean follow-up period was 3.4 months (range, 1 week to 9 months). Symptoms improved in 12 (67%) patients after the procedure. There was no change in symptoms in five and a decrease in one. Twelve patients died during the follow-up period (mean survival, 4.3 months). The complication rate was 25% (six of 24 patients), including stent migration (n = 5) and fracture (n = 3).

CONCLUSION

Flexible covered metallic stent placement can be useful for palliation in patients with malignant obstruction of the gastric outlet or duodenum.

Physicochemical parameters responsible for the affinity of methotrexate analogs for rat canalicular multispecific organic anion transporter (cMOAT/MRP2)

PURPOSE

Canalicular multispecific organic anion transporter (cMOAT/MRP2) is known to exhibit a broad substrate specificity toward amphiphatic organic anions, including methotrexate (MTX). The present study aims to identify the physicochemical properties of MTX derivatives that correlate with recognition specificity by cMOAT/MRP2.

METHODS

We examined the inhibitory effect of MTX and 24 analogs on the transport of [3H]-S-(2,4-dinitrophenyl)glutathione by cMOAT/MRP2. The affinity constants of these compounds were compared with their physicochemical parameters. The primary active transport of several compounds was also confirmed.

RESULTS

The affinity constants closely correlated with the octanol/water partition coefficient (clogP), and a linear combination of polar and nonpolar surface areas. The affinity for cMOAT/MRP2 also closely correlated with the molecular weight, which also showed a significant correlation with nonpolar surface area and clogP.

CONCLUSIONS

Recognition by cMOAT/MRP2 depends on a balance of dynamic surface properties between the polar and nonpolar regions of MTX analogs. The so-called "molecular weight threshold" for the cMOAT/MRP2 affinity of these compounds can be explained by their physicochemical parameters, especially their nonpolar surface areas.

Malignant esophagogastric junction obstruction: palliative treatment with an antireflux valve stent

The authors assessed the efficacy of an antireflux valve stent in the palliation of malignant esophagogastric junction (EGJ) obstruction after in vitro testing of the stent. Seventeen patients with inoperable malignant EGJ obstruction were treated. Antireflux valves, made of three polyurethane leaflets, were attached to the distal part of the stent to prevent reflux. When the flow rate of normal saline was 100 mL/sec in the forward direction, the valve fully opened at a pressure of 10 mm Hg. When the flow rate of normal saline was 0.35 mL/sec in the backward direction, the valve nearly completely closed at a pressure of 10 mm Hg. Stent placement was successful in all patients without complications. The median dysphagia score decreased significantly, from 3.0 (dysphagia to liquids) to 1.0 (dysphagia to normal solid food) (P < .0005). No patients experienced reflux symptoms. There was one case of stent migration. A valve stent that can prevent major reflux is an effective device for the palliation of malignant EGJ obstruction.

Biophysical characterization of recombinant human Bcl-2 and its interactions with an inhibitory ligand, antimycin A

Apoptosis is an essential physiological process, regulated by the family of Bcl-2-related proteins. However, the molecular mechanism by which Bcl-2 regulates apoptosis still remains elusive. Here we report the functional studies of recombinant human Bcl-2 with the deletion of 22 residues at the C-terminal membrane-anchoring region (rhBcl-2Delta22). Characterization of rhBcl-2Delta22 showed that the recombinant protein is homogeneous and monodisperse in nondenaturing solutions, stable at room temperature in the presence of a metal chelator, and an alpha-helical protein with unfolding of secondary structure at a T(m) of 62.8 degrees C. Optimal membrane pore formation by rhBcl-2Delta22 required negatively charged phospholipids. The existence of a hydrophobic groove in rhBcl-2Delta22 was demonstrated by the fluorescence enhancement of the hydrophobic ANS probe with which a pro-apoptotic Bak BH3 peptide competed. The respiratory inhibitor antimycin A also bound to the hydrophobic groove of rhBcl-2Delta22 with a K(d) of 0.82 microM. The optimal binding conformation of antimycin A was predicted from molecular docking of antimycin A with the hBcl-2 model created by homology modeling. Antimycin A selectively induces apoptosis in cells overexpressing Bcl-2, suggesting that hydrophobic groove-binding compounds may act as selective apoptotic triggers in tumor cells.

Crystallization of Clonorchis sinensis 26 kDa glutathione S-transferase and its fusion proteins with peptides of different lengths

A Clonorchis sinensis 26 kDa glutathione S-transferase (CsGST) and its fusion proteins containing 14 and 48 amino-acid peptides at the N-terminus have been crystallized using polyethylene glycol monomethylether 550 as a precipitant. Crystals of the three proteins show very similar crystal properties: they diffract to at least 2.3 A resolution and belong to the orthorhombic space group P2(1)2(1)2(1). The unit-cell parameters of CsGST crystals were a = 66.64 (1), b = 68.91 (1), c = 123.41 (2) A, which are very close to those of the crystals of the two fusion proteins. In addition, CsGST fusion proteins containing varying extents of N-terminal-extended peptides are incorporated into a crystal, indicating that the extended peptides have little effect on crystal packing. These results suggest that the crystallization system of CsGST/peptide fusion protein may be generally applicable to obtain crystals of small peptides.

Carrier-mediated hepatobiliary transport of a novel antifolate, N-[4-[(2,4-dianninopteridine-6-yl)methyl]-3,4-dihydro-2H-1,4-benzothiazin-7-yl]carbonyl-L-homoglutamic acid, in rats

The hepatic uptake and biliary excretion of a novel methotrexate derivative, N-[4-[(2,4-diamminopteridine-6-yl)methyl]-3,4-dihydro-2H-1,4-benzothiazin-7-yl]carbonyl-L-homoglutamic acid (MX-68), were examined in rats in vitro using isolated hepatocytes and bile canalicular membrane vesicles (CMVs), respectively. The uptake of MX-68 by isolated rat hepatocytes showed a saturable component (Km = 2.15 microM and Vmax = 2.34 pmol/min/mg of protein) and was inhibited by ATP-depletors and anionic compounds such as taurocholate and probenecid. [3H]MX-68 uptake was also inhibited by folate analogs such as methotrexate and 5CH3-tetrahydrofolate, but the effect of these compounds was slightly less than that of unlabeled MX-68. On replacing Na+ with choline, MX-68 uptake remained unchanged, whereas the methotrexate uptake was reduced. Uptake of MX-68 increased as the extracellular pH fell from 7.5 to 5.5. These results suggest that MX-68 is taken up via active transport systems. The uptake of MX-68 by CMVs prepared from normal rats exhibited clear ATP dependence, whereas ATP had only a minimal effect on the uptake by CMVs from Eisai-hyperbilirubinemic rats with a hereditary deficiency in canalicular multispecific organic anion transporter (cMOAT). The initial uptake rate of ATP-dependent MX-68 transport showed saturation with kinetic parameters similar to those of methotrexate. MX-68 inhibited the ATP-dependent transport of 2,4-dinitrophenyl-S-glutathione, a typical substrate for cMOAT, the inhibition constant (162 microM) being comparable with the Km of ATP-dependent MX-68 transport. These results suggest that the biliary excretion of MX-68 via the bile canalicular membrane is mediated mainly by cMOAT. In conclusion, active transport systems are involved in membrane penetration of MX-68 both at sinusoidal and canalicular sides in the liver, the latter being mainly involved with methotrexate (MTX) whereas the former differs partially from that for MTX.

Characterization of a novel cationic drug transporter in human retinal pigment epithelial cells

Retinal pigment epithelial (RPE) cells transport a variety of solutes, but the capacity of human RPE cells to transport drugs and xenobiotics is not well understood. As an initial step to address this issue, we have examined human RPE transport of verapamil. Transport of [3H]verapamil was measured in two human RPE cell lines (RPE/Hu and ARPE-19) grown to confluence on 12-well culture plates. Verapamil uptake by RPE/Hu cells was highly concentrative, reaching cell-to-medium ratios as high as 42 by 1 h. Uptake was saturable, with an apparent K(m) of 7.2 microM. Verapamil uptake decreased in the presence of metabolic inhibitors, low temperature, and organic cations, including quinidine, pyrilamine, quinacrine, and diphenhydramine. However, other organic cations, including tetraethylammonium and cimetidine failed to inhibit. Verapamil uptake was also inhibited by the cationic antiglaucoma drugs diltiazem, timolol, and propranolol. Verapamil uptake was insensitive to changes in membrane potential. However, transport was markedly altered by changes in pH. Decreasing external pH inhibited uptake, whereas efflux was stimulated. Intracellular acidification via NH4Cl prepulse also stimulated uptake. Identical findings were obtained using the commercially available cell line ARPE-19. In view of its unique specificity, the RPE cell verapamil transporter described above is a novel, heretofore undescribed, organic cation transporter, distinct from the known members of the OCT family of organic cation transporters.

Antimutagenic activity of 5alpha-cholest-7-en-3beta-ol, a new component from the starfish asterina pectinifera

From the butanol fraction of the starfish Asterina pectinifera Müler et Troschel (Asteriidae), we have isolated a new component, 5alpha-cholest-7-en-3beta-ol. Its antigenotoxic and antimutagenic activities were examined by the SOS chromotest with Escherichia coli PQ37 and by Ames test with Salmonella typhimurium TA1538, respectively. 5alpha-Cholest-7-en-3beta-ol showed potent antigenotoxic activity against the mutagens, both MNNG and NQO. For 100% of antigenotoxicity, the concentration of the compound applied against MNNG and NQO were 10 microg and 5 microg per reaction tube, respectively. Its antimutagenic activity with S. typhimurium TA1538 against the mutagen MNNG was very effective. When its concentrations were varied from 1 up to 10 microg dose per plate, the inhibition ratio of revertant CFU of TA1538 per plate was increased accordingly, from 25.2 to 99.2%. These results suggest that 5alpha-cholest-7-en-3beta-ol possesses antigenotoxic and antimutagenic activity and might be useful as a chemopreventive agent.

Transjugular liver biopsy: modified Ross transseptal needle versus quick-core biopsy needle

BACKGROUND

We evaluated the differences in sample adequacy and safety between a transseptal needle and Quick-core biopsy needle for transjugular liver biopsy.

METHODS

Eighteen consecutive patients who had a bleeding diatheses and/or ascites underwent transjugular liver biopsy using a transseptal needle (11 patients) and Quick-core biopsy needle (seven patients). The length of the specimens was measured before fixation. A pathologist reviewed histologic slides for sample adequacy and pathologic diagnoses. Clinical records were reviewed for complication.

RESULTS

In all patients, liver biopsy was successful. A total of 45 specimens were obtained, with an average of 2.5 passes per patient. The length of specimen was significantly longer with the Quick-core biopsy needle than with the transseptal needle (p<0.05). Biopsied tissue was fragmented in 17 of 25 specimens with the transseptal needle but not fragmented in any specimen with the Quick-core biopsy needle. All specimens were determined to be adequate except one with the transseptal needle. There was no early or delayed complication in any patient.

CONCLUSION

Transjugular liver biopsy is a safe and effective procedure without any significant difference in complication and adequacy when using a transseptal needle or Quick-core biopsy needle. Larger specimens can be obtained without tissue fragmentation with the Quick-core biopsy needle.

Binding and transport of methotrexate and its derivative, MX-68, across the brush-border membrane in rat kidney

Binding and transport properties of methotrexate (MTX) and its novel derivative, MX-68, were examined in brush-border membrane vesicles (BBMVs) isolated from rat kidneys. The uptake of MTX, MX-68 and folic acid by BBMVs was stimulated by an inwardly-directed H(+) gradient. Such H(+)-dependent uptake of folic acid is compatible with a previous report (Bhandari et al., Biochim Biophys Acta 1988; 937: 211). The MTX uptake exhibits saturation with a K(m) of 0.834 microM. Although the uptake of these three compounds at optimal pH depended on the osmolarity of the medium, a substantial portion of the uptake was osmolarity-insensitive. By changing the medium osmolarity, the uptake by BBMVs could be separately discriminated as osmolarity-sensitive and insensitive portions, representing transport into the intravesicular space and binding to the surface of BBMVs, respectively. For all three compounds, the binding increased in a time-dependent manner, while the amount transported reached a maximum after a relatively short incubation period. The transport of folic acid, but not its binding, exhibited an overshoot phenomenon under conditions of an inward H(+) gradient. The present results suggest that reabsorption of MTX and MX-68 in the kidney is governed by both their binding and transport mechanisms, with a similar kinetic profile to that of folic acid. The involvement of a transport system seems to make a relatively small contribution to the reabsorption of MTX assessed in BBMVs compared with MX-68 and folic acid.

Nonlinear disposition kinetics of a novel antifolate, MX-68, in rats

The excretion and tissue distribution kinetics of a novel antifolate, MX-68, were evaluated under conditions of a continuous steady-state infusion in Sprague-Dawley rats (SDRs). The biliary excretion clearance defined with respect to the hepatic concentration (CL(bile, h)) was much lower in Eisai hyperbilirubinemic rats with a hereditary deficiency in canalicular multispecific organic anion transporter than that in SDRs, suggesting the involvement of canalicular multispecific organic anion transporter in its transport across the bile canalicular membrane. The CL(bile, h) in SDRs increased as the infusion rate increased; this can be largely explained by saturation of the intracellular binding of MX-68. On the other hand, the urinary excretion clearance defined with respect to the renal concentration (CL(urine, k)) was comparable for the two strains but showed an increase and subsequent decrease as the renal concentration increased. This nonlinear profile was also found even when the CL(urine, k) was normalized by the unbound fraction in kidney. Therefore, this kinetic profile represents the saturation of both reabsorption and secretion. Reabsorption of MX-68 in kidney was supported by its saturable transport by renal brush border membrane vesicles at an inward H(+) gradient. The liver-to-plasma unbound concentration ratio decreased as the steady-state plasma concentration increased, suggesting that MX-68 is taken up by a saturable mechanism or mechanisms. Thus, the saturation of transport systems across several plasma membranes and intracellular binding in both the liver and kidney produce the nonlinear disposition of MX-68.

Involvement of ArcA and Fnr in expression of Escherichia coli thiol peroxidase gene

To explore the oxygen response regulators involved in thiol peroxidase gene (tpx) expression in Escherichia coli, we constructed a single-copy tpx-lacZ operon fusion and monitored tpx-lacZ expression in various genetic backgrounds. Expression of the tpx-lacZ fusion was increased 4-fold by aerobic growth. Anaerobic expression of tpx-lacZ in either (delta)arcA or delta(fnr) strains was 2.5-fold depressed compared with that of the wild-type strain. The results of immunoblotting experiments also demonstrated that ArcA and Fnr regulatory proteins repressed thiol peroxidase gene expression during anaerobic growth. Inspection of the tpx promoter region revealed putative binding sites for ArcA and Fnr. It thus appears that ArcA and Fnr function as repressors by blocking the binding of RNA polymerase to the tpx promoter in E. coli under anaerobic growth conditions.

Canalicular membrane transport is primarily responsible for the difference in hepatobiliary excretion of triethylmethylammonium and tributylmethylammonium in rats

Two structurally similar quaternary ammonium compounds, triethylmethylammonium (TEMA, M(r) 116) and tributylmethylammonium (TBuMA, M(r) 200) were used as model compounds to identify the unit process of hepatobiliary excretion that is responsible for markedly different biliary excretion of organic cations (OCs). Cumulative biliary excretion (in percentage of dose; i.v., 12 micromol/kg) was 0.17 for TEMA and 34.5 for TBuMA. In vivo uptake clearance into the liver was 0.686 +/- 0.020 ml/min for TEMA and 0.421 +/- 0.028 ml/min for TBuMA. When the uptake clearance was examined in an isolated hepatocyte system, comparable clearance between TEMA and TBuMA was obtained, consistent with the in vivo result. These observations suggest that uptake into the liver is not the major determinant for the difference in biliary excretion of the OCs. Coadministration of colchicine, an inhibitor of microtubule formation, had no effect on biliary excretion of the model compounds, and the primary site of subcellular distribution of the OCs appears to be the cytosol, suggesting that intracellular movement does not play a major role in the markedly different biliary excretion of the OCs. In contrast, in vivo excretion clearance across the canalicular membrane for TBuMA was 180-fold greater than that for TEMA, and in vitro efflux clearance of TBuMA was smaller than that of TEMA (p <.01), indicative of involvement of these processes in the markedly different biliary excretion of the OCs. Therefore, these data indicate that canalicular transport is primarily responsible for the markedly different biliary excretion of TEMA and TBuMA.

Kinetic profile of overall elimination of 5-methyltetrahydropteroylglutamate in rats

The in vivo biliary and urinary excretion kinetics of 5-methyltetrahydropteroylglutamate (5-CH3-H4PteGlu) were studied in rats. During infusion at various rates (48-965 nmol. h-1. kg-1), the total body clearance (CLtotal) of 5-CH3-H4PteGlu could be attributed almost entirely to the sum of the biliary and urinary (CLurine,p) excretion clearances. After a 4-h infusion at the highest rate, the 5-CH3-H4PteGlu in the liver was 10 times higher than the endogenous level, whereas its polyglutamate form did not increase, suggesting that most of the infused 5-CH3-H4PteGlu is not incorporated in the polyglutamate pool but is eliminated by excretion. The parallel increase in CLtotal and CLurine,p with the increase in infusion rate might result from saturation of reabsorption at the renal proximal tubules, since the urinary excretion clearance, defined with respect to the kidney concentration, also increased while the biliary excretion clearance, defined with respect to the liver concentration, remained almost constant. We conclude that the hepatobiliary excretion is a relatively low-affinity process with a constant clearance, whereas the renal tubular reabsorption is saturated at higher plasma 5-CH3-H4PteGlu concentration ( approximately 0.5 microM). Urinary excretion becomes the predominant elimination route for any excess 5-CH3-H4PteGlu in the body.

Cloning of a cDNA encoding a new calcium-binding protein from Dictyostelium discoideum and its developmental regulation

By employing 2D-PAGE, a protein differentially expressed during the development of Dictyostelium discoideum was discovered. The full cDNA of this protein was cloned using RT-PCR. The deduced protein is composed of 166 amino acid residues containing four EF-hand domains typical for calcium-binding proteins and was named CBP3. This protein shows little amino acid sequence homology with the other calcium-binding proteins from D. discoideum except EF-hand domains. The CBP3 mRNA was absent in vegetative amebas and accumulated maximally at 6 h of the development on filters. The mRNA level decreased thereafter and disappeared after 12 h of the development, while the protein level peaked at 8 h of development and remained constant thereafter. The mobility of CBP3 on SDS gel was shifted by treatment with EGTA, confirming the Ca2+-binding activity of the protein.

Reduced folate derivatives are endogenous substrates for cMOAT in rats

We examined the role of the canalicular multispecific organic anion transporter (cMOAT) in the biliary excretion of reduced folate derivatives in vivo and in vitro using normal [Sprague-Dawley rats (SDR)] and mutant [Eisai hyperbilirubinemic rats (EHBR)] rats whose cMOAT is hereditarily deficient. In vivo, the biliary excretion of endogenous tetrahydrofolate (H4PteGlu), 5-methyltetrahydrofolate (5-CH3-H4PteGlu), and 5,10-methylenetetrahydrofolate (5, 10-CH2-H4PteGlu) in EHBR was reduced to 8.2%, 1.9%, and 5.5% of those in SDR, respectively, whereas that of 10-formyltetrahydrofolate (10-HCO-H4PteGlu) was detected only in SDR and not in EHBR. Bile drainage caused reduction of endogenous plasma folate concentrations in SDR but not in EHBR. In vitro, significant ATP-dependent uptake of 3H-labeled 5-CH3-H4PteGlu into canalicular membrane vesicles was observed only in SDR. This ATP-dependent uptake was saturable with a Michaelis constant (Km) value of 126 microM, which was comparable with its inhibitor constant (Ki) value of 121 microM for the ATP-dependent uptake of a typical cMOAT substrate, 2,4-dinitrophenyl-S-glutathione (DNP-SG). Vice versa, DNP-SG inhibited the uptake of 5-CH3-H4PteGlu with a Ki of 35 microM, which was similar to its Km value. In addition, H4PteGlu and 5, 10-CH2-H4PteGlu also inhibited the ATP-dependent uptake of DNP-SG. These results indicate that 5-CH3-H4PteGlu and other derivatives are transported via cMOAT. Therefore, reduced folate derivatives are the first endogenous substrates for cMOAT that do not contain glutathione, glucuronide, or sulfate moieties.

Mode of action and active site of an extracellular peroxidase from Pleurotus ostreatus

The properties of the haem environment of an extracellular peroxidase from Pleurotus ostreatus were studied by electronic absorption spectroscopy. A high-spin ferric form was predominant in the native enzyme and a high-spin ferrous form in the reduced enzyme. Cyanide was readily bound to the haem iron in the native form, thereby changing the enzyme to a low-spin cyano adduct. The electronic absorption spectra of the enzyme were similar to those of lignin peroxidase from Phanerochaete chrysosporium. Compound III of the enzyme was formed after the addition of an excess of H2O2 to the native enzyme, and thereafter spontaneously reverted to the native form. The enzyme oxidized 1-(3,5-dimethoxy-4-hydroxyphenyl)-2-(2-methoxyphenoxy)-1,3-dihydroxyp ropane in the presence of H2O2 to produce 1-(3,5-dimethoxy-4-hydroxyphenyl)-2-(2-methoxyphenoxy)-1-oxo-3-hydroxypr opane , 2,6-dimethoxyhydroquinone, 2-(2-methoxyphenoxy)-3-hydroxypropanal, 2-(2-methoxyphenoxy)-3-hydroxypropanoic acid, 2,6-dimethoxy-1,4-benzoquinone and guaiacol. A similar oxidation pattern was demonstrated with a one-electron oxidant, ammonium cerium(IV)nitrate. Free radicals were detected as intermediates of the enzyme-mediated oxidation of 1-(3,5-dimethoxy-5-hydroxyphenyl)-2-(2-methoxyphenoxy)-1,3-dihydroxyp ropane and acetosyringone. These results can be explained by the mechanisms involving an initial one-electron oxidation of the lignin substructure. This radical may undergo C alpha-C beta cleavage, C alpha-oxidation and alkyl-phenyl cleavage.

Single electron transfer by an extracellular laccase from the white-rot fungus Pleurotus ostreatus

Two different bands with laccase activity were obtained after nondenaturing PAGE of the culture filtrate of Pleurotus ostreatus. Immunoblot analysis revealed that antisera raised against laccase I were not reactive to laccase II. Laccase I, which exhibited faster mobility on nondenaturing polyacrylamide gel, was purified 42.9-fold with an overall yield of 10.8%. Gel filtration and SDS-PAGE revealed that laccase I is a single polypeptide with a molecular mass of approximately 64 kDa. Laccase I contained 12.5% carbohydrate by weight and 3.9 mol copper (mol protein)-1. The absorption spectrum of laccase I showed a type 1 signal at 605 nm and EPR spectra showed that the parameters of the type 1 and type 2 Cu signals were g parallel = 2.197 and A parallel = 0.009 cm-1, and g parallel = 2.263 and A parallel = 0.0176 cm-1, respectively. The data obtained from the pH profiles suggested that two ionization groups, whose pKa values were 5.60-5.70 and 6.70-6.85, may play an important role in the active site of laccase I as the ligand of copper metal. The optimal pH and temperature for the activity of laccase I were 6.0-6.5 and 30-35 degrees C, respectively. The enzyme had affinity for various lignin-related phenolic compounds: the Km values for ferulic acid and syringic acid were 48 and 89 microM, respectively. EPR spectroscopic study of the action of laccase I on 3,5-dimethoxy-5-hydroxyacetophenone indicated that this enzyme catalyses single electron transfer with the formation of the phenoxy radical as an intermediate.

Production of gastrin-releasing peptide by a non-small cell lung carcinoma cell line adapted to serum-free and growth factor-free conditions

Gastrin-releasing peptide is an important growth-modulating factor in developing lung epithelium. It is known to be produced by small cell carcinomas of the lung, and an autocrine loop involving gastrin-releasing peptide and its receptor has been demonstrated in many small cell lung tumors. We investigated whether such an autocrine loop could also be demonstrated in non-small cell lung carcinoma, since gastrin-releasing peptide is known to stimulate human bronchial epithelial cells, from which non-small cell tumors should emerge. We report here that gastrin-releasing peptide is produced by a bronchiolo-alveolar carcinoma cell line (A549) adapted to serum-free and growth factor-free conditions. A549 cells adapted to these conditions, termed A549-R0 cells, display extensive membrane interdigitations, Golgi apparatus, and secretory-like granules, and grow as a mixture of attached colonies and floating cells. Gastrin-releasing peptide is present in the conditioned medium produced by A549-R0 cells. Colony formation of cells derived from a squamous cell carcinoma of the lung, 239T, was stimulated 9-fold by A549-R0 conditioned medium or by authentic gastrin-releasing peptide, measured in serum-free conditions. The growth stimulatory activity was inhibited by a monoclonal antibody to gastrin-releasing peptide. Transcripts for receptors for the bombesin family of peptides were also demonstrated in A549-R0 cells and 239T cells. These results demonstrate that non-small cell lung carcinomas can secrete gastrin-releasing peptide and can also respond to the peptide.

Purification and characterisation of D-glucose oxidase from white-rot fungus Pleurotus ostreatus

D-Glucose oxidase was purified 27.5-fold to apparent homogeneity with an overall yield of 23.8%, from Pleurotus ostreatus, through a purification procedure of ammonium sulphate precipitation, gel-permeation, anion-exchange and hydrophobic-interaction chromatography. The molecular mass determined by gel filtration was found to be 290 kDa. SDS/PAGE revealed that the enzyme consists of four subunits with a molecular mass of 70 kDa. The absorption spectra of the enzyme exhibit maxima at 280, 360 and 460 nm. The enzyme shows a fluorescence spectrum with an excitation maximum at 470 nm and an emission maximum at 530 nm. These results indicate that the prosthetic group of the enzyme is flavin and that the enzyme contains 4 mol flavin/mol enzyme. The enzyme is optimally active at 50 degrees C and at pH 5.5-6.0. It exhibits broad affinity for various sugars and specificity for D-glucose with Km value of 1.34 mM. 2,6-Dichloroindophenol, Wurster's blue, and 4-benzoquinone can function as electron acceptors but phenazine methosulphate cannot function as an electron acceptor. The enzyme is inhibited completely by mercuric chloride and partially by silver sulphate, sodium azide 8-hydroxyquinoline.

Purification and characterisation of an extracellular peroxidase from white-rot fungus Pleurotus ostreatus

A peroxidase was purified 98.3-fold from the culture filtrate of Pleurotus ostreatus with an overall yield of 12.4%. The molecular mass determined by gel filtration was found to be approx. 140 kDa. SDS-PAGE revealed that the enzyme consists of two identical subunits with a molecular mass of approx. 72 kDa. The pI value of this enzyme is approx. 4.3. The enzyme contains 41% carbohydrate by weight, and aspartic acid and asparagine (16.8%), and glutamic acid and glutamine (12.0%). The enzyme has the highest affinity toward synaptic acid and affinity towards various phenolic compounds containing methoxyl and p-hydroxyl groups, directly attached to the benzene ring. However, the enzyme does not react with veratryl alcohol and shows no affinity for nonphenolic compounds. The optimal reaction pH and temperature are 4.0 and 40 degrees C, respectively. The catalytic mechanism of the enzymic reaction is of the Ping-Pong type. The activity of the enzyme is competitively inhibited by high concentrations of H2O2 and its Ki value is 1.70 mM against H2O2. This enzyme contains approx. 1 mol of heme per mol of one subunit of the enzyme. The pyridine hemochrome spectrum of the enzyme indicates that the heme of P. ostreatus peroxidase is iron protoporphyrin IX. The EPR spectrum of the native peroxidase shows the presence of a high-spin ferric complex with g values at 6.102, 5.643 and 1.991.

Oral leukotriene inhibitor (MK-886) blocks allergen-induced airway responses

To elucidate the role of leukotrienes (LT) in allergic asthma in humans the effect of MK-886, an LT biosynthesis inhibitor, was evaluated on antigen-induced early (EAR) and late (LAR) asthmatic reactions and bronchial responsiveness to histamine. Eight atopic men participated in a two-part, double-blind, placebo-controlled, crossover trial. MK-886 was administered in two oral doses of 500 mg and 250 mg, 1 h before and 2 h after allergen inhalation, respectively. Biochemical effects of MK-886 were evaluated by the inhibition of urinary LTE4 excretion and calcium ionophore-stimulated LTB4 biosynthesis in whole blood ex vivo. MK-886 significantly inhibited the EAR by 58.4% (AUC0-3 h) and the LAR by 43.6% (AUC3-7 h) when compared with placebo (p < 0.01). There was no difference in PC20 histamine 30 h post allergen challenge between MK-886 and placebo (0.33 and 0.27 doubling doses, p > 0.1). MK-886 inhibited calcium ionophore-stimulated LTB4 production in whole blood (54.2 +/- 25.6%) for up to 6 h post allergen challenge. LTE4 excretion in urine was inhibited by 51.5% during the EAR by as much as 80% during the LAR. This indicates that LT play a role in allergen-induced asthmatic reactions in humans in vivo and that LT synthesis inhibitors such as MK-886 should be further explored for the treatment of asthma.

Small deletion and insertion mutations induced by the topoisomerase II inhibitor teniposide in CHO cells and comparison with sites of drug-stimulated DNA cleavage in vitro

Sixty-five teniposide-induced mutations at the hemizygous aprt locus of CHO D422 cells were analyzed by polymerase chain reaction and DNA sequencing. Most (63%) of the mutations were deletions, duplications and insertions of various sizes, with the majority being less than 20 base-pairs. The remaining mutations were base substitutions, the majority of which were transversions. A significant correspondence was found between the teniposide-induced small deletion/duplication mutations and sites of teniposide-stimulated DNA strand cleavage by topoisomerase II in vitro. In particular, sequences which were deleted in one or more of the mutants showed a much higher incidence of strong cleavage sites than sequences not involved in deletions. However, the exact positioning of the cleavage sites with respect to the deletion termini was variable. The data did not suggest any unified model to account for all the mutations, but most of the deletions and duplications could be accounted for by one of three mechanisms: (1) double-strand break repair nonhomologous end-joining; (2) replication slippage/misalignment; and (3) addition or deletion of a few nucleotides at free 3' ends left by topoisomerase II, as previously suggested for similar mutations in phage T4. There was no evidence that topoisomerase II subunit exchange was a significant mechanism of mutagenesis in this system.

DNA sequence analysis of mutations induced by melphalan in the CHO aprt locus

In previous work, we established that treatment with melphalan (L-phenylalanine mustard) produced a predominance of A.T-->T.A transversions in the Simian virus 40 (SV40)-based shuttle vector pZ189 during replication in human 293 cells. Mutations were induced with varying doses (4-12 microM) melphalan in the aprt gene of the hemizygous Chinese hamster ovary (CHO) cell line D422 to determine whether a similar mutation spectrum would be observed in an endogenous gene. DNA sequence alterations were determined for 39 spontaneous and 41 melphalan-induced independent mutant clones. Other than a predominance of transversions in both systems, the spectrum of melphalan-induced aprt mutations bears little resemblance to the spectrum observed in the supF gene of the shuttle plasmid pZ189. In aprt, mutations at G.C base pairs (bp) predominated (29 of 41 base substitutions). Significantly enhanced mutagenesis was observed at 5' G-G-C 3' and 5' G-G-C-C 3' sites in the aprt gene. Almost half of the melphalan-induced base substitutions occurred at 5' G-N-C 3' sequences, which are believed to be potential interstrand crosslink sites.

Influence of gastrointestinal site of drug delivery on the absorption characteristics of ranitidine

The absorption characteristics of ranitidine after delivery to three locations in the gastrointestinal tract were compared in an open-label study of eight healthy males. Subjects received ranitidine HCl (150 mg) for injection via a nasoenteric tube directly into their stomach, jejunum, or cecum sequentially in three separate periods (24 hr apart). Plasma samples were collected at periodic time intervals for 12 hr following each dosing and analyzed for ranitidine concentration by high-pressure liquid chromatography. Mean concentrations following cecal dosing were lower (P less than 0.05) than concentrations following gastric or jejunal dosing at each sampling time except baseline. Mean concentrations following gastric and jejunal dosing were similar except at 2 hr (gastric greater than jejunal). Mean pharmacokinetic parameters for cecal administration were different (P less than 0.05) from either the gastric or the jejunal periods with the exception of Tmax. There was no difference in any pharmacokinetic parameter after gastric or jejunal dosing. The relative bioavailability after cecal administration was less than 15% of that observed after administration into the stomach or jejunum. Additionally, Wagner-Nelson analysis indicated that the rate of ranitidine absorption was much slower following cecal administration than after gastric or jejunal dosing. Two plasma concentration peaks were observed in three of eight subjects after gastric dosing, in eight of eight subjects after jejunal dosing, and in zero of eight subjects after cecal dosing. These data demonstrate that the absorption profile of ranitidine is equivalent, in extent and duration, after delivery to the stomach or jejunum, while absorption from the cecum is significantly less.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytochrome composition and oxygen-dependent respiration-driven proton translocation in Wolinella curva, Wolinella recta, Bacteroides ureolyticus, and Bacteroides gracilis

The membrane fractions of the microaerobically grown type strains of Wolinella curva, Wolinella recta, Bacteroides ureolyticus, and Bacteroides gracilis contained membrane-bound cytochrome b, cytochrome c, and CO-binding cytochrome c. Soluble cytochrome c and CO-binding cytochrome c were also present. Although B. gracilis is oxidase negative, it possessed cytochrome c. With H2 or formate as the electron donor, proton efflux from anaerobic cells occurred upon addition of a pulse of oxygen. With formate as the electron donor, the H+/O ratios of W. curva, W. recta, B. ureolyticus, and B. gracilis were 0.75, 1.66, 2.06, and 2.04, respectively. With H2 as the electron donor, the H+/O ratios of W. curva, B. ureolyticus, and B. gracilis were 1.25, 1.97, and 2.36, respectively. Proton translocation was inhibited by the protonophore carbonylcyanide m-chlorophenylhydrazone. The results confirm that the organisms are not anaerobes but are microaerophiles capable of respiring with oxygen.

Comparison of verapamil, diltiazem, and labetalol on the bioavailability and metabolism of imipramine

Twelve healthy male subjects completed this randomized, placebo controlled, four-period crossover trial to determine the effect of verapamil, diltiazem, and labetalol on the bioavailability and metabolism of imipramine. Subjects received a 7-day course of one of four treatments; verapamil (120 mg every 8 hr), diltiazem (90 mg every 8 hr), labetalol (200 mg every 12 hr), or placebo (every 12 hr) during each study period. Imipramine (100 mg) was administered orally on the morning of day 4 of each study period. Plasma and urine samples were collected periodically over the ensuing 96 hours. Samples were assayed by HPLC for imipramine, desipramine, 2-hydroxyimipramine, and 2-hydroxydesipramine. Verapamil, diltiazem, and labetalol increased imipramine area under the plasma concentration time curve (relative bioavailability) as compared with placebo by 15%, 30%, and 53%, respectively. Verapamil and diltiazem did not demonstrate consistent changes in the formation of the measured metabolites. Labetalol caused a significant decrease in the amount of imipramine metabolized to 2-hydroxyimipramine (mean decrease: 22%) and from desipramine to 2-hydroxydesipramine (mean decrease: 8%). The molar ratios of plasma AUC of 2-hydroxyimipramine and 2-hydroxydesipramine to the parent compounds were significantly decreased. Since these metabolic processes are dependent on the cytochrome P450IID6 isozyme, these data suggest that labetalol decreases the oral clearance of imipramine by inhibiting this system. All three of these commonly used agents decreased the oral clearance of imipramine. These drug interactions could lead to elevated imipramine concentrations and have the potential for clinically important adverse events.

Wolinella recta, Wolinella curva, Bacteroides ureolyticus, and Bacteroides gracilis are microaerophiles, not anaerobes

Although the nonfermentative, asaccharolytic, putative anaerobes Wolinella curva, Wolinella recta, Bacteroides ureolyticus, and Bacteroides gracilis are phylogenetically related to the true campylobacters, the type strains of these species exhibited O2-dependent microaerophilic growth in brucella broth and on brucella agar. The optimum O2 levels for growth of these strains ranged from 4 to 14% in brucella broth and from 2 to 8% on brucella agar, when H2 was provided as the electron donor. No growth occurred under 21% O2, and scant or no growth occurred under anaerobic conditions unless fumarate or nitrate was provided as a terminal electron acceptor. Aspartate, asparagine, and malate also served as apparent electron acceptors. The organisms were catalase negative and, except for B. gracilis, oxidase positive. Catalase added to brucella broth enhanced growth. O2 uptake by all species was inhibited by cyanide and 2-heptyl-4-hydroxyquinoline N-oxide. We concluded that these organisms are not anaerobes but instead are microaerophiles, like their campylobacter relatives.

Structure of bleomycin-induced DNA double-strand breaks: predominance of blunt ends and single-base 5' extensions

In order to examine the structure of bleomycin-induced DNA double-strand breaks, defined-sequence DNA was labeled in each strand at a single restriction site and treated with bleomycin. Various double-stranded fragments resulting from bleomycin-induced double-strand breaks were isolated, denatured, and run on sequencing gels to determine the sites of cleavage in each strand. For virtually every double-strand break, the cleavage site in one strand was a pyrimidine in a G-Py sequence, reflecting a specificity similar to that of bleomycin-induced single-strand cleavage. However, the cleavage site in the complementary strand was seldom a G-Py sequence, and was usually a site where single-strand cleavage was infrequent. When the sequence at the double-strand break was G-Py-Py', the break at Py was usually accompanied by a break at the base directly opposite Py, resulting in blunt ends. When the sequence was G-Py-Pu, the break at Py was usually accompanied by a break at the base opposite Pu, resulting in single-base 5' extensions. Double-strand breaks with 3' extensions, such as would result from cleavage of two C residues in a self-complementary G-C sequence, were conspicuously absent. These data provide further evidence that bleomycin-induced double-strand breaks do not result from coincidence of independent site-specific single-strand breaks.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on the mechanism of hypoglycemia induced by intrathecal morphine: dissociation from behavioral effects, effects of tolerance and depletion of liver glycogen

To characterize further the hypoglycemic effect of intrathecally (i.t.) administered morphine, species and drug specificity, effects of morphine-induced tolerance and pentobarbital-induced anesthesia and effects on liver glycogen were studied in nonfasted animals. In rats, morphine (125 micrograms i.t.) produced the same behavioral toxicity (scratching, biting, seizures) and hypoglycemia as previously reported in mice. In mice, the glycine antagonist strychnine (5 micrograms i.t.) and the morphine metabolite morphine-3-glucuronide (2 micrograms i.t.) mimicked the behavioral, but not the hypoglycemic, effects of high-dose i.t. morphine. Kainic acid (0.1 micrograms i.t.), which caused high-frequency hindlimb movements, also did not cause hypoglycemia. Naltrexone (1 mg/kg/ s.c.) or the s.c. implantation of morphine pellets for 3 days attenuated the hypoglycemic effect, but not the behavioral effects, of morphine (40 micrograms i.t.). The hyperglycemic effect of s.c. morphine(20 mg/kg) was blocked by i.t. morphine. Anesthesia with pentobarbital (75 mg/kg i.p.) attenuated the hypoglycemic effect of morphine (40 micrograms i.t.). Morphine i.t. also caused a time- and dose-dependent decrease in liver glycogen levels and was more potent in causing glycogenolysis (30 min ED50 = 19 micrograms) than in causing hypoglycemia (30 min ED50 = 30 micrograms). It is concluded that the hypoglycemic effect of i.t. morphine appears to be independent of its behavioral effects, displays tolerance and is accompanied by hepatic glycogen depletion.

[Thin-layer chromatography of mycolic acids methanolysates of whole-cell in Mycobacterium and related bacteria]

Mycolic acid methanolysates of whole-cell in Mycobacterium and related bacteria were analysed by thin-layer chromatography. The experimental results show that five of twenty-two species, M. tuberculosis, M. bovis, M. kansasii, M. marinum and M. gastri have similar pattern of mycolates, composed of alpha-mycolates, methoxymycolates, ketomycolates and two unknown components. M. gilvum, M. phleri, M. avium, M. intracellulare, M. xenopi and M. nonchromogenicum contain alpha-mycolates, ketomycolates and wax-ester. The patterns of TLC for other tested species were different from each other. Nocardia, Rhodococcus and Corynebacterium show a relatively simple pattern which principally contain alpha-mycolates. The four genus can be differentiated. Spots of mycolic acids of nine strains Mycobacterium sp. isolated from patients in this hospital were similar to M. tuberculosis. These strains were also identified to the same result as above by traditional methods. The method is of value in the classification and identification of Mycobacterium.

Neocarzinostatin-induced DNA base release accompanied by staggered oxidative cleavage of the complementary strand

Treatment of an end-labeled DNA restriction fragment with the nonprotein chromophore of neocarzinostatin induced lesions which, after treatment with endonuclease IV or putrescine, were expressed as site-specific double-strand breaks. Analysis of the termini at cleavage sites in each strand showed that the neocarzinostatin-induced lesions consisted of an apurinic/apyrimidinic site plus a closely opposed break in the complementary strand. The break always occurred opposite the base two positions upstream from the apurinic/apyrimidinic site and had the 3'-phosphate and 5'-aldehyde termini characteristic of neocarzinostatin-induced breaks. This positioning suggests that neocarzinostatin simultaneously attacks two DNA sugars on opposite edges of the minor groove. The sequence specificity for formation of apurinic/apyrimidinic sites with closely opposed breaks reflected that of neocarzinostatin-induced mutagenesis. The potent mutagenicity of these lesions may be attributable to the presence of closely opposed damage in both DNA strands.

Effects of glucose and diabetes on binding of naloxone and dihydromorphine to opiate receptors in mouse brain

The effects of glucose and diabetes on the high-affinity lofentanil-displaceable opiate-receptor binding in mouse brain membranes were studied to determine if the attenuation of opiate actions by hyperglycemia previously observed in our laboratory was due to a modification of receptor affinity or number. With membranes from normal ICR mice, glucose (100-400 mg/dl) caused small but significant concentration-dependent decreases in receptor affinities for [3H]naloxone and [3H]dihydromorphine, both in the absence and presence of 20 mM NaCl, without changing the maximum number of binding sites. Fructose and the nonmetabolizable sugar 3-O-methylglucose had intermediate effects on naloxone affinity in the presence of NaCl that were not significantly different from control or from the effect of glucose. Similar results were obtained with brain membranes from streptozocin-induced diabetic mice. The binding affinity for [3H]naloxone in the presence of NaCl was not affected by the induction of diabetes in ICR mice via streptozocin or in spontaneously diabetic (db/db) C57BL/KsJ mice compared with their nondiabetic (m+/m+) littermates. These results indicate that the previously observed attenuation of opiate effects by glucose may be partly due to a glucose-induced decrease in opiate-receptor affinity. However, the much greater attenuation of morphine by fructose in vivo cannot be explained by this mechanism.