Effect of 5-hydroxytryptamine receptor 4 agonist mosapride on human gastric accommodation

BACKGROUND

Impaired gastric accommodation is one of the major features of functional dyspepsia. Mosapride citrate is a 5-hydroxytryptamine receptor 4 (5-HT4) agonist, which is shown to improve upper abdominal symptoms. However, effect of mosapride on gastric accommodation was not clear. We tested the hypothesis that mosapride enhances the gastric accommodation in normal individuals.

METHODS

Fourteen male healthy volunteers completed this study. Single administration of mosapride or placebo was performed randomly with more than 1-week interval. Subjects swallowed a triple-lumen polyvinyl tube with a polyethylene bag. The bag was positioned in the proximal stomach and the minimal distending pressure (MDP) was determined. The ramp distension starting from the MDP was then performed and subjects were instructed to score their perception using ordinate scales. Next the intra-bag pressure was set at MDP + 2 mmHg and a liquid meal was administered 30 min later, and the intra-bag volume was recorded for 60 min. We compared the MDP, perception scores, and the intra-bag volume changes by administering placebo and mosapride.

KEY RESULTS

Minimal distending pressure was not significantly different in subjects receiving mosapride or placebo. Treatment with mosapride had no effect on intra-bag pressures or volumes inducing first sensation or discomfort. Gastric accommodation, expressed as the difference between pre- and postmeal intra-bag volumes, and the percent change of the intra-bag volumes by the meal was significantly enhanced by mosapride compared with placebo.

CONCLUSIONS & INFERENCES

This is the first study clearly demonstrating that single administration of 5-HT4 agonist can enhance gastric accommodation in humans. (Umin.ac.jp, number UMIN000014063).

Evaluation of a low-temperature steam and formaldehyde sterilizer

We evaluated a low-temperature steam and formaldehyde (LTSF) sterilizer based on the draft European Standard prEN 14180. Microbiological tests were conducted on small and full loads using process challenge devices in five programs (P1-P5). With small loads all tests showed no growth of Bacillus stearothermophilus (ATCC7953) spores. However, positive cultures were observed with full-load tests using P5 (sterilization temperature, 50 degrees C). Our data indicated that the load influenced the efficacy of the LTSF sterilizer. Desorption tests were conducted to determine residual formaldehyde in indicator strips. The mean concentrations of formaldehyde in P1-P5 were 31.9, 56.3, 54.9, 82.2 and 180.6 microg, respectively, which are below the limits allowed by the draft Standard. Our results indicate that the LTSF sterilizer is useful for sterilization because of its excellent efficacy, short handling time, and safety.

Characterization of the functional subunit combination of nicotinic acetylcholine receptors in bovine adrenal chromaffin cells

The combination of nicotinic acetylcholine receptors (nAChRs) subunits connecting with the secretion of catecholamines in bovine adrenal chromaffin cells was pharmacologically investigated using selective agonists and antagonists for their nAChRs. The EC(50) values (microM) for the agonists that stimulate the catecholamine secretion and the rank order were as follows: nicotine (3.3)> or =1,1-dimethyl-4-phenylpiperazinium (3.5) > (E)-N-methyl-4-(3-pyridinyl)-3-butene-1-amine (14) > cytisine (23) > or =acetylcholine (25). However, because both the rank order and the EC(50) values differed considerably from those in the various subunits' combinations expressed in Xenopus oocytes or mammalian cells (e.g. alpha2beta2, alpha3beta4, alpha4beta4, etc.), we could not compare them. On the other hand, the IC(50) values (microM) for the antagonists that inhibit the secretion and the rank order were mecamylamine (0.08) > alpha-conotoxin-MII (alpha-CTX-MII) (0.71) > dihydro-beta-erythroidine (DHbetaE) (48) > alpha-bungarotoxin (alpha-BTX) (no effect). Mecamylamine is a highly selective antagonist for alpha3beta4 nAChRs, and alpha-CTX-MII and alpha-BTX are specific antagonists for alpha3beta2 and alpha7 nAChRs, respectively. DHbetaE is a selective antagonist for the alpha4beta2. It has already been shown that the mRNAs for alpha3, alpha5, alpha7 and beta4 subunits are expressed in the chromaffin cells. Therefore, the subunit combination of nAChRs associated with the catecholamine secretion from bovine adrenal chromaffin cells is suggested to be at least alpha3beta4 or alpha3beta4alpha5. Further, the results indicate that the utilization of the nicotinic agonists as selective ligands for the subunit combination of nAChRs may be not suitable for the characterization of nAChRs.

A comparative study of characteristics of current-type and conventional-type cationic bactericides

We have synthesized new polycationic bactericides, polyloxyethylene(dimethyliminio)trimethylene(dimethyliminio)ethylene dichloridel (OXD) and poly(hexamethyleneguanidine phosphate) (HEP), in order to develop more active but less skin-irritative bactericides. The effects of these bactericides on Pseudomonas aeruginosa, Escherichia coli, Serratia marcescens, Klebsiella pneumoniae, methicillin resistant Staphylococcus aureus (MRSA) and the degree of their irritations on skin were compared with those of a widely used low molecular-weight cationic bactericide, benzalkonium chloride (BAC), and a polycationic bactericide, poly[2-hydroxyethylene(dimethyliminio)methylene chloride] (2HYC). The minimum bactericidal concentration (MBC) of OXD for 10 min contact incubation was 16 microg/ml against P. aeruginosa, E. coli, S. marcescens and K. pneumoniae, and >1000 microg/ml against MRSA. The MBC of HEP for 10 min contact incubation was 16 microg/ml against P. aeruginosa, 32 microg/ml against E. coli and K. pneumoniae, and 64 microg/ml against S. marcescens and MRSA. Itch, edema, erythema, heat, injury, desquamation and keratinization caused by skin irritation were examined in 21 subjects by patch tests. Only one subject treated with OXD experienced edema, and one subject with HEP experienced keratinization. However, BAC caused itch in 3 subjects, edema in 1, erythema in 10 and desquamation in 2, indicating that the incidence of skin irritation of BAC was higher than that of OXD or HEP. OXD and HEP had sterilization ability similar to BAC, however, they were less skin-irritative than BAC. This indicates that OXD and HEP can be used as safe bactericides.

Nitric oxide donating compounds inhibit HCl-induced gastric mucosal lesions mainly via prostaglandin

Prostaglandin (PG) and nitric oxide (NO) have been known to inhibit the lesion formation induced by necrotic agents. However, no clear correlation between PG and NO has been shown in the gastroprotective action against necrotic agent-induced gastric mucosal lesions in rats. Thus, the present study was performed to clarify this correlation. Gastric mucosal lesions were induced by the oral administration of 0.6 M HCl in rats. 16,16-Dimethyl PGE2 (0.3-3 microg/kg, p.o.; dim-PGE2), sodium nitrite (0.3 and 1 mg/kg, s.c.) and sodium nitroprusside (30 and 100 microg/kg, i.v.; SNP) dose-dependently inhibited the lesion formation. Orally administered sodium nitrite or SNP (3 mg/kg) also significantly inhibited the lesion formation. The gastroprotective action by dim-PGE2 was not affected by the pre-treatment with N(G)-nitro-L-arginine methylester (10 mg/kg, i.v.). The gastroprotective effect by sodium nitrite or SNP was markedly attenuated by the pre-treatment with indomethacin (10 mg/kg, s.c.). These findings suggest that NO donating compounds inhibit the HCl-induced mucosal lesions mainly through prostaglandin, but dim-PGE2 directly inhibits the lesions without involvement of NO in rats.

Assessment of drug concentrations in tears in therapeutic drug monitoring: I. Determination of valproic acid in tears by gas chromatography/mass spectrometry with EC/NCI mode

A rapid and sensitive method for the quantitation of valproic acid in tears has been developed using gas chromatography/electron capture negative chemical ionization/mass spectrometry. Valproic acid was converted directly into its pentafluorobenzyl ester derivative without the need to perform any extraction from the biologic fluid. The concentrations in tears [C]t correlated very well with those of the free form in the plasma [Cf]p and those of the total form in the plasma [Cb+f]p. The ratios between valproic acid concentrations in tears and plasma were as follows: [C]t/[Cb+f]p = 0.10 +/- 0.02; [C]t/[Cf]p = 0.57 +/- 0.11. Ratios of [C]t/[Cb+f]p were in good agreement with previously published data.

On-line automated high-performance liquid chromatographic determination of total riboflavin phosphates using immobilized acid phosphatase as a pre-column reactor

An automated chromatographic detection system for the determination of total riboflavin phosphates using immobilized sweet potato acid phosphatase as a pre-column reactor is reported on. An immobilized enzyme reactor, incorporated in the on-line analytical system, hydrolysed riboflavin phosphates to riboflavin, and then lipophilic riboflavin was concentrated at the top of an ODS trap column. Enzymatically hydrolysed riboflavin was back-eluted from the trap column using a mobile phase containing methanol, and then subsequently chromatographed on an ODS analytical column. The effluents were monitored by UV absorption at 280 nm. The calibration graph for total riboflavin phosphates, determined by this method, was linear over the range 0.5-500 nmol/ml, with a correlation coefficient of 0.9999. The detection limit at a signal-to-noise ratio of 3 was 25 pmol/ml. The average conversion rate of riboflavin phosphates to riboflavin was estimated at 97%. The relative standard deviations of the intra- and inter-assay precision were 1.2 and 2.6%, respectively.

Effect of galanin and galanin antagonists on peristalsis in esophageal smooth muscle in the opossum

Galanin, a neuropeptide that is widely distributed in the esophageal nerves, is known to exert a neuromodulatory action in the gut. These studies examined the effect of galanin and galanin antagonists on esophageal peristalsis in anesthetized opossums in vivo. Intraluminal esophageal pressures were recorded at 1, 3, 5, 7, and 9 cm above the lower esophageal sphincter. Esophageal peristaltic contractions were induced by swallow and short- (1-s) and long-train (10-s) vagal stimulation (VS). Galanin (1 nmol/kg) inhibited the amplitude of swallow-induced peristaltic contractions and increased peristaltic velocity by enlarging the latency periods in the upper part of the esophagus and reducing them in the lower part. Galinin nearly abolished esophageal contractions caused by short-train VS at 5 Hz and inhibited the contractions at 10 Hz. Galanin increased latency periods induced by short-train VS with little change in the velocity of peristalsis and reduced the amplitude of both A (cholinergic) and B (noncholinergic) contractions due to long-train VS. However, the decrease in amplitude of B contractions was more marked. Galantide (3 nmol/kg) antagonized the inhibitory action of exogenous galanin on esophageal contractions elicited by short-train VS, but by itself galantide had no significant effect on esophageal contractions. In conclusion, exogenous galanin inhibits the amplitude of swallow-induced peristaltic contractions and converts them into nonperistaltic contractions by inhibiting both the cholinergic and noncholinergic components.

Evidence for the degradation of maleate moiety in chlorpheniramine maleate solution using a stability-indicating HPLC method

The degradation phenomenon of maleate moiety of chlorpheniramine maleate in solution has been demonstrated by means of a peculiar ion-pair HPLC method developed by the authors, which permits the simultaneous determination of chlorpheniramine and maleate. A commercial cough drug containing chlorpheniramine maleate was dissolved in water with m-hydroxybenzoic acid as an internal standard, and then kept for several days at room temperature. It was recognized that the maleate content in the drug solution had gradually decreased, whereas chlorpheniramine content had not decreased. A simple solution of maleic acid was also kept for several days at room temperature, and it was also recognized that the maleate content in the solution preserved at the same concentration as the solution of the commercial cough drug had gradually decreased, and the percent of remaining maleate reached zero. The degraded peaks on HPLC chromatogram were not detected at all by UV detector, and the disappearance of maleate was ascertained by GC-MS. No detectable example of maleate of chlorpheniramine maleate in a commercial cough syrup has suggested that maleate moiety of chlorpheniramine maleate decomposed to carbon dioxide.

Involvement of nitric oxide from nerves on diarrhea induced by castor oil in rats

Nitric oxide (NO) is involved in the mechanism of castor oil-induced diarrhea. This study was performed to elucidate the source of NO. Diarrhea was induced by oral administration of castor oil in rats. Diarrhea was significantly inhibited by the pre-treatment with a relatively selective nerve NO synthase inhibitor, 7-nitroindazole. This effect was attenuated by the treatment with L-arginine. Capsaicin-sensitive afferent nerve degeneration did not affect the diarrhea. N(G)-Nitro-L-arginine methylester significantly inhibited diarrhea even in capsaicin-pretreated rats. These data suggest, at least in part, the involvement of NO from nerves on the diarrhea induced by castor oil in rats.

Preparation and characteristics of antibacterial sepiolite containing povidone-iodine as a useful pharmaceutical product for patient care

Povidone-iodine (PVP-I), an antibacterial medicine, was infiltrated in sepiolite (SPL). The available iodine content in this new pharmaceutical product, a sepiolite preparation containing povidone-iodine (PVP-I-SPL), was retained at 98.9 and 98.3% during storage at 40 degrees C for 3 and 6 months, respectively. The effective removal of various gasses, including ammonia, hydrogen sulfide, ethylmercaptan and acetaldehyde, was achieved by use of PVP-I-SPL. Especially, the concentration of ammonia gas was reduced more than half after 30 min of exposure, suggesting that PVP-I-SPL has excellent ability to adsorb ammonia gas. The satisfactory antibacterial effect of PVP-I-SPL was also obtained by testing its minimum bactericidal concentration (MBC). No irritation reactions to the rabbit auricle or ophthalmic mucosa or to human skin were observed by the skin irritation test. The PVP-I-SPL preparation has bactericidal activity and gas-adsorbing ability; therefore, this pharmaceutical product should be useful for the prevention of infections and deodorization in hospital rooms and houses, as well as in nursing homes for elderly people.

Determination of dehydroepiandrosterone sulphate in biological samples by liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry using [7,7,16,16-2H4]-dehydroepiandrosterone sulphate as an internal standard

A method for the determination of dehydroepiandrosterone sulphate (DHEA-S) in biological samples is described. [7,7,16,16-2H4]-Dehydroepiandrosterone sulphate (2H4-DHEA-S) was synthesized and its applicability was examined as an internal standard with liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry (LC/APCI-MS). Deuterium atoms in 2H4-DHEA-S molecules were not exchanged to hydrogen atoms during the extraction procedure from biological specimens in the determination of DHEA-S with LC/MS. The calibration curve of DHEA-S was linear over the range of 2-500 ng on-column. The detection limit of DHEA-S was 0.5 ng on-column with a signal-to-noise ratio of 3. The relative standard deviations of intra- and inter-assay with 200 ng of standard sample were 3.3 and 5.0%, respectively. These results were better than a similar method reported on previously (Nakajima et al., 1996). The proposed method was successfully developed for the determination of DHEA-S in biological samples.

[Involvement of nitric oxide, which was synthesized by constitutive nitric oxide synthase, and prostaglandin on diarrhea induced by castor oil in rats]

To clarify the mechanism of castor oil-induced diarrhea, this study was performed by using rats in relation to nitric oxide (NO) and prostaglandin (PG). Castor oil induced diarrhea in all rats within 3 hr in the control group. The pretreatment of NG-nitro-L-arginine methyl ester prevented the diarrhea, and this effect was attenuated by the combined treatment of L-arginine. Amino-guanidine inhibiting inducible NO synthase had no effect on the diarrhea, but dexamethasone, an inhibitor of both inducible NO synthase and phospholipase A2 that synthesizes PGs, significantly prevented it. Indomethacin, an inhibitor of cyclooxygenase that synthesizes PGs, also significantly prevented diarrhea. Therefore, the mechanism of the preventive effect by dexamethazone on diarrhea was suggested to be the inhibition of PGs generation. From the above results, it became clear that PG and NO, especially that synthesized by constitutive NO synthase, are involved in the mechanism of diarrhea induction by castor oil in rats.

Epidemiologic analysis of Crohn disease in Japan: increased dietary intake of n-6 polyunsaturated fatty acids and animal protein relates to the increased incidence of Crohn disease in Japan

We examined the correlation between the incidence of Crohn disease and dietary change in a relatively homogeneous Japanese population. The incidence and daily intake of each dietary component were compared annually from 1966 to 1985. The univariate analysis showed that the increased incidence of Crohn disease was strongly (P < 0.001) correlated with increased dietary intake of total fat (r = 0.919). animal fat (r = 0.880), n-6 polyunsaturated fatty acids (r = 0.883), animal protein (r = 0.908), milk protein (r = 0.924), and the ratio of n-6 to n-3 fatty acid intake (r = 0.792). It was less correlated with intake of total protein (r = 0.482, P < 0.05), was not correlated with intake of fish protein (r = 0.055, P > 0.1), and was inversely correlated with intake of vegetable protein (r = -0.941, P < 0.001). The multivariate analysis showed that increased intake of animal protein was the strongest independent factor with a weaker second factor, an increased ration of n-6 to n-3 polyunsaturated fatty acids. The present study in association with reported clinical studies suggests that increased dietary intake of animal protein and n-6 polyunsaturated fatty acids with less n-3 polyunsaturated fatty acids may contribute to the development of Crohn disease.

[Quantitative analysis of chlorpheniramine maleate in cough and cold drugs by ion-pair high-performance liquid chromatography for the simultaneous determination of chlorpheniramine and maleate]

A simple, rapid and convenient chromatographic method, which permits the simultaneous determination of chlorpheniramine (CP) and maleate (MA), recently developed by the authors was applied to the analysis of chlorpheniramine maleate (CPM) in cough and cold drugs. In this method, a Capcell Pak C8 column and an isocratic mobile phase containing 15% methanol, 50 mM KH2PO4 and 5mM tetra-n-butylammonium phosphate as an ion-pair reagent were used. By using the mobile phase adjusted to pH 3.0 with orthophosphoric acid, fumaric acid, MA, CP, acetaminophen (paracetamol), caffeine, and m- and p-hydroxybenzoic acid as candidates for an internal standard were eluted separately within 17 min. Detection was carried out with UV detector at 215 nm. Under the same conditions, five other antihistamines analogous to CPM were also separated. The calibration graphs for CP and MA showed good linearity in the range of 0.5-10 nmol (0.195-3.9 micrograms) per 20 microliters injection, respectively. The proposed method was successfully applied to the simultaneous determination of CP and MA, i.e., CPM analysis, in commercial cough and cold drugs which pharmaceutical forms were tablet, granule and syrups.

High-performance liquid chromatographic determination of cholesterol and cholestanol in human serum by precolumn derivatization with 2-[2-(isocyanate)ethyl]-3-methyl-1,4-naphthoquinone combined with platinum catalyst reduction and electrochemical detection

The precolumn derivatization reagent, 2-[2-(isocyanate)ethyl]-3-methyl- 1,4-naphthoquinone (IMQ) was applied to the simultaneous determination of cholesterol and cholestanol in human serum by HPLC with electrochemical detection. The compounds extracted with hexane from human serum, to which was added 1-eicosanol as an internal standard, were reacted with IMQ in acetone and converted into the corresponding carbamic acid esters. After chromatographic separation of the derivatives, they were reduced once in a platinum catalyst reduction column connected on-line, then quantified with an electrochemical detector in the oxidation mode. The detection limits at a signal-to-noise ratio of 3 were 6.6 pg (17 fmol) and 7.4 pg (19 fmol) for cholesterol and cholestanol, respectively in a 10 microliter injection volume. This method was successfully applied to the determination of free and total cholesterol and total cholestanol in normal human serum, and the concentrations of free and total cholesterol were compared with those obtained by an enzymatic method.

Therapeutic efficacy of N-3 polyunsaturated fatty acid in experimental Crohn's disease

We investigated the therapeutic efficacy of n-3 polyunsaturated fatty acids (PUFAs) on trinitro-benzene sulfonic acid (TNBS)-induced colitis in the rats, which condition is considered an experimental Crohn's disease (CD). In rats with TNBS-induced colitis, feeding with an elemental diet (ED) plus 2% n-3 PUEA-rich perilla oil significantly suppressed plasma leukotriene (LT) B4 and ulcer index compared to that in rats fed with ED plus 2% n-6 PUFA-rich safflower oil (34.2 +/- 12.3 s 63.8 +/- 13.2 pg/ml and 8.8 +/- 12.1 vs 66.4 +/- 33.1, P < 0.01, respectively). Moreover, the plasma LTB4 and the ulcer index were significantly correlated (P < 0.05). Feeding with ED plus 2% alpha-linolenic acid (A-LA)-rich vegetable oil significantly reduced plasma LTB4 and colonic weight compared to that in rats fed with ED plus 2% eicosapentaenoic acid (EPA)/docosahexaenonic acid (DHA)-rich fish oil in this model (61.6 +/- 10.5 vs 85.0 +/- 20.9 pg/ml and 0.83 +/- 0.13 vs 0.96 +/- 0.08g, P < 0.05, respectively). This study suggested that dietary fat manipulation with perilla oil can reduce colonic damage and that this is correlated with the suppression of plasma LTB4. The therapeutic efficacy of A-LA in controlling intestinal inflammation in experimental CD may be superior to that of EPA and DHA.

A tobacco soluble protoporphyrinogen-oxidizing enzyme similar to plant peroxidases in their amino acid sequences and immunochemical reactivity

Partial amino acid sequences of a soluble protoporphyrinogen-oxidizing enzyme (PPO) purified from tobacco cultured cells were identified. The sequences of two regions of the soluble PPO corresponded to the acid/base catalysis and heme binding regions of plant peroxidases. Anti-soluble PPO IgG cross-reacted with these plant peroxidases. Thus, the soluble PPO seems to be a kind of peroxidase.

Application of the desulfurization of phenothiazines for a sensitive detection method by high-performance liquid chromatography

A simple and sensitive high-performance liquid chromatographic (HPLC) method for the determination of phenothiazine (PHE) is described. PHE is converted to diphenylamine (DIP) by desulfurization with Raney nickel catalyst. DIP is highly sensitive to electrochemical detection. The calibration graph for PHE quantification after desulfurization was linear between 0.1 and 2.0 ng per injection. The detection limit (signal-to-noise ratio = 3) of PHE after desulfurization was 10 pg, which is twenty times higher than that of the parent compound PHE. The proposed desulfurization technique was applied to other PHE-related compounds. The structural confirmation of the desulfurized product of PHE was carried out by LC-MS using atmospheric pressure chemical ionization.

Application of an electrochemical detector with a graphite electrode to liquid chromatographic determination of penicillamine and captopril in biological samples

A high-performance liquid chromatographic determination of penicillamine and captopril in rat serum, liver and kidney samples is described. An electrochemical detector with a graphite working electrode at a potential of +0.9 V vs the Ag/AgCl reference electrode is used for the detection system. Linear responses of the peak height to the amount of samples injected were obtained in a range of 0.1-500 ng on-column and 0.5-500 ng on-column for penicillamine and captopril with correlation coefficients of 0.997 and 0.995, respectively. Detection limits at a signal-to-noise ratio of 3 were 20 and 300 pg for penicillamine and captopril, respectively. The graphite electrode has a long lifetime of about 4 months with continuous use, even with the high voltage supplied. The analytical application of this method to the determination of penicillamine and captopril in biological samples was successful.

Simultaneous determination of oxidized and reduced coenzyme Q and alpha-tocopherol in biological samples by high performance liquid chromatography with platinum catalyst reduction and electrochemical detection

A convenient and sensitive high performance liquid chromatographic method with post-column platinum catalyst reduction and electrochemical detection was applied to the simultaneous determination of oxidized and reduced coenzyme Q (CoQ and CoQH2) and alpha-tocopherol (alpha-TP) in human and rat samples. After the separation of oxidized and reduced CoQ homologues (CoQ8-CoQ10 and CoQ8H2-CoQ10H2) and alpha-TP on a reversed-phase column, oxidized CoQ homologues were reduced on a platinum catalyst reduction column, and then all the reduced forms were quantified with an electrochemical detector operated in the oxidation mode (+ 0.6 V vs. Ag/AgCl). The order of elution was alpha-TP, CoQ8H2, CoQ9H2, CoQ8, CoQ10H2, CoQ9, and CoQ10 and all were well separated within 13 min. The detection limits at a signal-to-noise ratio of 3 were 20 pg for alpha-TP, 70 pg for CoQ8 and CoQ8H2, and 100 pg for CoQ9, CoQ9H2, CoQ10 and CoQ10H2. Quantitative recoveries (93-102%) from serum and tissues were obtained for all the analytes studied. This method was applied satisfactorily to the simultaneous determination of CoQ, CoQH2 and alpha-TP in biological materials.

Application of 13C NMR spectroscopy to paratope mapping for larger antigen-Fab complexes

For the purpose of engineering the antibody combining site, mapping residues that are involved in antigen binding provide us with valuable information. By use of 13C NMR spectroscopy with selectively 13C-labeled Fv fragments, we have established a general strategy to identify the residues that are perturbed upon binding of small antigen (hapten) molecules [(1990) Biochemistry 30, 6604-6610]. In the present paper, we demonstrate that this strategy can be extended to molecular structural analyses of the complexes of an Fab fragment and a larger antigen molecule such as Pseudomonas aeruginosa exotoxin A with a molecular mass of 67 kDa.

Amperometric determination of oxalate in plasma and urine by liquid chromatography with immobilized oxalate oxidase

A detection system for plasma and urinary oxalate involving a postcolumn enzymatic reaction and electrochemical detection is described. Oxalate oxidase was immobilized on AF-Tresyl Toyopearl 650 gel. The immobilized oxalate oxidase was packed into a stainless-steel column (10 x 4 mm I.D.) and used on-line as an immobilized enzyme reactor (IMER). The hydrogen peroxide produced by enzymatic reaction was detected amperometrically at a platinum electrode maintained at +0.5 V vs. Ag/AgCl. The HPLC separation of oxalate was carried out using a Capcell Pak C8 column and an isocratic mobile phase containing 80 mM KH2PO4 and 5 mM tetra-n-butylmammonium phosphate as an ion-pair reagent. The IMER was active and stable in the mobile phase employed. The plot of peak height against concentration of oxalate was linear in the range 0.1-1.6 mumol/ml with a correlation coefficient of 0.9989. The detection limit was 10 nmol/ml at a signal-to-noise ratio of 3. The within-day and between-day coefficients of variation were 5.3 and 7.9%, respectively.

Role of nitric oxide in esophageal peristalsis in the opossum

To explore the involvement of NO in normal peristalsis, the effects of inhibitors of NO synthase, including N omega-nitro-L-arginine (L-NNA) and N omega-nitro-L-arginine methyl ester (L-NAME), on esophageal peristaltic contractions induced by diverse stimuli that may involve different neuronal circuits were studied. Studies were performed in opossums. Experimental conditions in vivo included primary peristalsis (P) induced by pharyngeal stroking, short-train (1 second) electrical stimulation of the vagus nerve which caused peristaltic (S) contractions, and long-train (10 second) electrical stimulation of the vagus nerves which caused contractions at the onset of (A contractions) and after (B contractions) the stimulation period. In vitro experiments were performed on strips of esophageal circular muscle using electrical field stimulation which caused contractions at the onset of (on contractions) and after (off contractions) the stimulation period. The administration of L-NAME significantly decreased the latency period and reduced the latency gradient for P contractions, thereby increasing the velocity of peristalsis. Concomitant administration of atropine prolonged the latency period but did not restore the latency gradient. L-NAME abolished B contractions in a dose-dependent fashion. In vitro, L-NAME caused dose-dependent inhibition of off contractions and augmentation of on contractions. These studies support the hypothesis that NO may be involved in (a) both the latency period and the latency gradient, as well as in the contraction amplitude of esophageal peristalsis; and (b) esophageal B and off contractions.

Specific detection of acetyl-coenzyme A by reversed-phase ion-pair high-performance liquid chromatography with an immobilized enzyme reactor

A selective chromatographic detection system for the determination of acetyl-coenzyme A (CoA) is reported. The short-chain acyl-CoA thioesters were separated by reversed-phase ion-pair high-performance liquid chromatography (HPLC), and then acetyl-CoA was selectively detected on-line with an immobilized enzyme reactor (IMER) as a post-column reactor. Thio-CoA liberated enzymatically from acetyl-CoA was determined spectrophotometrically after reaction with Ellman's reagent in the reagent stream. The IMER with phosphotransacetylase had a substrate specificity sufficient to determine acetyl-CoA and was active and stable in the mobile phase containing methanol and the ion-pair reagent. The calibration graph was linear between 0.2 and 10 nmol, with a detection limit of 0.05 nmol. This HPLC system with detection by IMER allows the selective identification and determination of acetyl-CoA in a mixture of acetoacetyl-CoA and 3-hydroxy-3-methylglutaryl-CoA, which are difficult to separate with ion-pair HPLC.

Determination of idebenone in rat serum and brain by high-performance liquid chromatography using platinum catalyst reduction and electrochemical detection

A high-performance liquid chromatographic determination of idebenone, a new cerebral metabolism-improving agent, in rat serum and brain has been developed. After separation of idebenone on a reversed-phase column, idebenone was reduced once in a platinum catalyst reduction column connected on-line, then monitored quantitatively by electrochemical detection. A linear relationship between the peak-height ratio of idebenone to the internal standard and idebenone concentration was observed in the range 0.015-50 ng with a detection limit of 5 pg (signal-to-noise ratio = 5). This method was satisfactorily rapid and sensitive, and was successfully applied to the determination of idebenone in rat serum and brain tissues.

Role of nitric oxide in lower esophageal sphincter relaxation to swallowing

Studies were performed in the opossum to define the role of the L-arginine-nitric oxide (NO) pathway in lower esophageal sphincter (LES) relaxation to swallowing and vagal stimulation in viv and intramural nerve stimulation in vitro. In vivo, L-NAME, a water soluble NO synthase (NOS) inhibitor, caused antagonism of LES relaxation due to reflex-induced swallowing. L-NAME (20 mg/kg i.v.) reduced the amplitude of swallow induced relaxation from 88% to 28%. LES relaxation due to electrical stimulation of peripheral end of decentralized vagus nerve was also antagonized. The effects of L-NAME were reversed by L-arginine, but not by D-arginine. L-NAME treatment did not antagonize LES relaxation to intravenous administration of isoproterenol. In vitro, NO and sodium nitroprusside (SNP) caused a decrease in the sphincter tone. The relaxing effect caused by NO and SNP was not antagonized by tetrodotoxin or omega-conotoxin. Inhibitors of NO synthase, L-NMMA and L-NNA, caused slight increase in the spontaneous resting LES tone and concentration-dependent antagonism of electrical field stimulation (EFS) induced LES relaxation. L-NNA (10(-4)M) abolished EFS induced LES relaxation at low frequencies (less than 5 Hz) and antagonized the relaxation to a value 20% of the control at 20 Hz. The antagonistic action of L-NMMA and L-NNA was unaffected by D-arginine but was reversed by L-arginine. The inhibitory effect of NO, SNP, or two other putative inhibitory neurotransmitters (VIP and CGRP) on the LES was not antagonized by L-NNA. These studies show that inhibitors of NO synthase selectively antagonize LES relaxation to all three modes of intramural inhibitory nerve stimulation including physiological swallowing. These studies suggest that the L-arginine-nitric oxide pathway is involved in physiological relaxation of the LES.

Carbon-13 NMR study of switch variant anti-dansyl antibodies: antigen binding and domain-domain interactions

A 13C NMR study is reported of switch variant anti-dansyl antibodies, which possess the identical VH, VL, and CL domains in conjunction with highly homologous but not identical heavy-chain constant regions. Each of these antibodies has been selectively labeled with 13C at the carbonyl carbon of Trp, Tyr, His, or Cys residue by growing hybridoma cells in serum-free medium. Spectral assignments have been made by following the procedure described previously for the switch variant antibodies labeled with [1-13C]Met [Kato, K., Matsunaga, C., Igarashi, T., Kim, H., Odaka, A., Shimada, I., & Arata, Y. (1991) Biochemistry 30, 270-278]. On the basis of the spectral data collected for the antibodies and their proteolytic fragments, we discuss how 13C NMR spectroscopy can be used for the structural analyses of antigen binding and also of domain-domain interactions in the antibody molecule.

Role of alpha adrenoceptors in opossum internal anal sphincter

The purpose of the present investigation was to examine the role of alpha adrenoceptors in the internal anal sphincter (IAS). Studies wer performed on alpha-chloralose anesthetized opossums. Resting pressure in the IAS (IASP) was recorded using low compliant continuously perfused catheters. The effects of the alpha-1 adrenoceptor agonist phenylephrine and alpha-2 adrenoceptor agonist clonidine and their corresponding selective antagonists, prazosin and yohimbine, respectively, were examined on the resting IASP, and on rectal balloon distension (RBD)-mediated IAS relaxation. Phenylephrine caused a rise in the IASP that was blocked by prazosin and not by yohimbine. Phenylephrine had no effect on IAS relaxation caused by RBD. Clonidine on the other hand caused significant suppression of IAS relaxation in response to RBD, but caused minimal changes in the resting IASP. The suppression of IAS relaxation by clonidine was selectively antagonized by yohimbine but not by prazosin. From these studies we conclude that alpha-2 adrenoceptors exert important neuromodulatory influences on rectoanal inhibitory reflex, while alpha-1 adrenoceptors may exert modulatory effects on the resting IAS tone.

An enzymatic assay of chloramphenicol coupled with fluorescence reaction

An alternative method for the assay of chloramphenicol using an enzymatic reaction coupled with a fluorescence detection system has been developed. Chloramphenicol was enzymatically acetylated by chloramphenicol acetyltransferase in the presence of acetyl-coenzyme A (acetyl-CoA) as the acetyl-donor, after which the liberated CoA-SH was derivatized with a fluorogenic reagent, 4-(aminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole. The assay was linear over the range of 2.5-40 micrograms/ml. Analytical recoveries of chloramphenicol at concentrations of 7.5 and 22.5 micrograms/ml, added to human serum, plasma, or a slightly hemolyzed serum, were in the range of 93.3 to 106.2%. The enzymatic assay was not affected by the presence of ten other antibiotics tested.

Spectrophotometric determination of inorganic phosphate in the presence of thiol compounds

A spectrophotometric method for inorganic phosphate determination in the presence of thiol compounds is described. Thiol compounds, which interfere with the measurement of inorganic phosphate by a modification of the method of Gomori, are removed by carboxymethylation by iodoacetate prior to the formation and reduction of phosphomolybdate complex. A linear standard curve is obtained by this method, and the method is suitable for the assay of a phosphate-releasing enzyme when the measurement must be performed in the presence of thiol compounds.

An improved procedure for the histochemical demonstration of cathepsin D by the mercury-labeled pepstatin method

The desirable fixation conditions for the histochemical demonstration of cathepsin D using mercury-labeled pepstatin as an enzyme inhibitor were examined biochemically and histochemically. Four well known fixatives, namely, glutaraldehyde (GA), paraformaldehyde (PFA), glutaraldehyde with paraformaldehyde (GA-PFA) and periodate-lysine-paraformaldehyde (PLP), were applied to the prefixation of tissues prior to the reaction of the labeled inhibitor to the enzyme-active site. The effects of fixatives on cathepsin D were biochemically examined using subcellular fractionated lysosomes. Cathepsin D from rat liver lysosomes was rapidly inactivated by the fixatives containing glutaraldehyde, i.e., GA and GA-PFA, whereas the activity of cathepsin D was sufficiently maintained after fixing the enzyme in the PFA or PLP preparations. Effects of the PLP fixative on lysosomal cathepsin D in liver tissues using the mercury-labeled pepstatin method were also studied histochemically. The best result for the visualization of lysosomal cathepsin D in liver tissues was obtained using the PLP fixative with the prefixation time of three hours or more.

The appearance of a 34,000-dalton inhibitor of calpain (Ca2+-dependent cysteine proteinase) in rat liver after the administration of phenylhydrazine

A 34,000-dalton inhibitor of calpain (Ca2+-dependent cysteine proteinase) was found in the cytosol of anemic rat liver. When phenylhydrazine hydrochloride was continuously administered to rats, a 280,000-dalton calpain inhibitor that existed originally in the liver gradually disappeared within two weeks and, concomitantly, a 34,000-dalton inhibitor appeared. The purified 34,000-dalton inhibitor resembles 280,000-dalton inhibitor in that both are heat-stable proteins and do not inhibit papain and trypsin. Unlike the protomers of a 280,000-dalton inhibitor, 34,000-dalton inhibitor does not show any sign of self-association.

Electron microscopic visualization of cathepsin D using mercury-labeled pepstatin as an enzyme inhibitor

Pepstatin, a specific inhibitor of pepsin, cathepsin D (E), renin, etc., was used in a new method to demonstrate the sites of enzymes. Pepstatin (Pst) was covalently attached to glutathione (GSH), using a dicyclohexylcarbodiimide, and CH3Hg+ was then put in the residue of SH for electron microscopic observation. Pst-GS-HgCH3 thus obtained was nonisotopical, had a very low molecular weight (about 1,200 daltons), and still almost completely retained its inhibitory activity. Sections of rat liver (less than 1 mm3 thick), prefixed by glutaraldehyde, were incubated in the prepared reaction medium. Cathepsin D, located in the lysosomes, was demonstrated by this compound, but when the sections were preincubated with pepstatin, this was not the case. These results demonstrate that mercury-labeled pepstatin is a useful reagent for the histochemical staining of acid proteases for electron microscope.

The occurrence of an inhibitor of Ca2+-dependent neutral protease in rat liver

The occurrence of a novel and specific inhibitor of Ca2+-dependent neutral protease in rat liver has been demonstrated. The partially purified product is a heat-stable and acid-stable protein of an approximate molecular weight of 3x10(5), and readily inactivated by tryptic digestion. The inhibition of Ca2+-dependent protease is not a result of the binding of Ca2+ by the inhibitor.

Increase in the susceptibility of hemoglobin to proteases upon treatment with p-mercuribenzoate

Native human oxyhemoglobin, which has a rigid conformation resistant to proteases such as trypsin and subtilisin, could be hydrolyzed by these proteases at pH 7.0 after treatment with p-chloromercuribenzoate. The digestion curve of hemoglobin as a function of concentration of the mercurial was essentially parallel to the titration curve of hemoglobin with the mercurial, indicating that a relationship exists between susceptibility to proteases and modification of thiol groups of the protein. On the other hand, when myoglobin was used as a substrate, the degree of proteolysis did not increase after treatment with the mercurial. Circular dichroism measurements and gel-filtration experiments showed that the observed increase in susceptibility of hemoglobin to proteases was not due to a conformational change involving unfolding of alpha-helical structure, but was due to the dissociation of the tetrameric hemoglobin molecule into dimer and monomer after treatment with the mercurial.