Enhancement of the turnover number of thermostable malate dehydrogenase by deleting hydrogen bonds around the catalytic site

In malate dehydrogenase from Thermus flavus, substitution of Ile for Thr189, which is involved in hydrogen-bond network around a loop containing catalytic His186, caused an increase in the turnover number at room temperatures. In order to examine the effect of disruption of the hydrogen bonds on the catalytic activity, residues participating in the network were replaced by others which cannot form hydrogen bond by site-directed mutagenesis. All the mutations caused increases in the turnover number at room temperatures. This result suggests that an increase in flexibility introduced around catalytic site enhanced the catalytic activity of the malate dehydrogenase.

Conversion of a cyanhydrin compound into S-(-)-3-phenyllactic acid by enantioselective hydrolytic activity of Pseudomonas sp. BC-18

A Pseudomonas strain, named BC-18, which can convert racemic phenylacetaldehyde-cyanhydrin (3-phenyllactonitrile) enantioselectively to S-(-)-3-phenyllactic acid (S-PLA), was isolated from soil. Although PLA produced with intact cells contained the S enantiomers of approximately 75% enantiomeric excess (% e.e.), repeated crystallization gave a higher purity (99.8% e.e.) of the S configuration product. Production of S-PLA was significantly increased when 2.0% (w/v) of calcium chloride were added to the reaction mixture for precipitation of S-PLA. Chemical mutagenesis yielded a mutant strain, named BC348-9, with 16 times higher activity (40 mU/OD630), compared with that of the parent strain (2.5 mU/OD630). When the mutant strain BC348-9 was used, approximately 18 g/OD630 was produced, which is 12 times higher than that of the parent strain. The final accumulation of PLA exceeded 6.0%, 1.2 times higher than that of the parent strain.

Effects of protease inhibitors on the absorption of phenol red and fluorescein isothiocyanate dextrans from the rat intestine

The absorption enhancement effects of three types of protease inhibitors, aprotinin, bacitracin, and soybean trypsin inhibitor, on the small and large intestinal absorption of phenol red (PR) and fluorescein isothiocyanate dextrans (FDs) were examined in rats. Of these protease inhibitors, only bacitracin enhanced the absorption of PR and FDs from the rat small and large intestine. Thus, we suggest that bacitracin has not only a protease-inhibitory but also an absorption-enhancing capability. We examined the effects of various protease inhibitors on intestinal mucosal toxicity by measuring the leakage of Evans blue (EB) from the systemic circulation. Although there was a significant increase in the leakage of EB in the presence of bacitracin, it was considerably less than that in the case of polyoxyethylene 9-lauryl ether (BL-9), which was used as a positive control. Therefore, bacitracin may be a good model adjuvant for improving the intestinal absorption of poorly absorbable drugs because it did not cause serious intestinal mucosal damage, as seen in the case of BL-9.

Anti-IRS-1 monoclonal antibody, 6G5, cross-reacts to IRS-2

We previously reported the production of anti-IRS-1 monoclonal antibodies against human IRS-1 C-terminal portion. One of anti IRS-1 monoclonal antibodies, 6G5, was found to immunologically cross-react with IRS-2, which has been reported recently. The data presented here provide information arising from the use of the anti-IRS-1 MAb, 6G5; this MAb was found to be a useful reagent in studying the functional role of IRSs in the insulin-signaling system.

Studies on protein-protein interaction between copper-containing nitrite reductase and pseudoazurin from Alcaligenes faecalis S-6

Site-directed mutagenesis of a copper-containing nitrite reductase (NIR) from Alcaligenes faecalis S-6 was carried out to identify the amino acid residues involved in interaction with its redox partner, pseudoazurin, in which four positively charged residues were previously shown to be important in the interaction. Ten negatively charged residues located on the surface of NIR were replaced independently by alanine or serine. All the altered NIRs showed CD spectra and optical spectra identical to those of wild-type NIR, suggesting that all the replacements caused no gross change in the overall structure or in the environment of type 1 copper site. Kinetic analysis of electron transfer between pseudoazurin and altered NIRs revealed that the replacement of Glu-118, Glu-197, Asp-201, Glu-204, or Asp-205 by Ala caused a significant increase in the Km value for pseudoazurin compared with that of wild-type NIR. Furthermore, the simultaneous replacement of three of these residues (Glu-118, Glu-197, and Asp-201) caused a further increase in the Km value. These results suggested that the negatively charged residues are involved in electrostatic interaction with pseudoazurin. Kinetic analyses of the altered NIRs (E118A, E197A, or D201A) with altered pseudoazurins (K10A, K57A, or K77A) implicate specific pairs of the charged residues that are involved in electrostatic interaction between NIR and pseudoazurin.

Endothelin ETA and ETB receptors mediate endothelin-1-induced apamin-sensitive relaxation in the guinea pig ileum

Endothelin (ET) receptors involved in ET-1-induced responses of the longitudinal muscle of the isolated guinea pig ileum were studied. ET-1 caused concentration-dependent contractions, while ET-3 and selective ETB-receptor agonists, IRL1620 and sarafotoxin 6c (S6c), showed little or no effect. The ET-1-induced contractions were antagonized by BQ-123, an ETA-receptor antagonist, or PD142893, an ETA/ETB-receptor antagonist, indicating that the contraction is mediated by the ETA receptor. In preparations precontracted with carbachol, ET-1 elicited relaxations at lower concentrations and contractions at higher concentrations. ET-3, IRL1620 and S6c caused relaxations. These relaxations were little affected by BQ-123, but greatly antagonized by PD142893. The ET-1-induced relaxations were slightly affected by BQ-788, an ETB-receptor antagonist, but were markedly inhibited by the combination of BQ-788 and BQ-123. In ETB receptor-desensitized preparations, ET-1-induced relaxations were antagonized by BQ-123, whereas ET-3, S6c and IRL1620 showed no response. All these relaxations were abolished by apamin. These results indicate that ETA and ETB receptors mediate relaxation of the ileal smooth muscle through activation of apamin-sensitive K+ channels.

Pharmacological heterogeneity of both endothelin ETA- and ETB-receptors in the human saphenous vein

To study endothelin receptor subtypes that mediate the smooth muscle contraction of human saphenous vein, effects of some endothelin-receptor agonists and antagonists were examined. Endothelin (ET)-1 and sarafotoxin 6b (S6b) elicited potent concentration-dependent contractions with similar pD2 values and similar maximal responses. Selective ETB-receptor agonists, sarafotoxin 6c (S6c) and IRL1620 (Suc-[Glu9,Ala11,15]-endothelin-1(8-21)), also caused contractions, but their maximal responses were about one third of that of ET-1. ET-3 showed a biphasic concentration-response curve. An ETA-receptor antagonist, BQ-123 (cyclo(-D-Asp-L-Pro-D-Val-L-Leu-D-Trp-)), an ETA/ETB-receptor antagonist, PD142893 (Ac-D-Dip-Leu-Asp-Ile-Ile-Trp), or the combination of these two antagonists hardly affected the contractile effect of ET-1, while each of them markedly antagonized the effects of higher concentrations of ET-3 and S6b. Contractions induced by lower concentrations of ET-3 and S6b were resistant to these antagonists. The concentration-response curves for S6c and IRL1620 were not affected by BQ-123. The effect of IRL1620 was markedly inhibited by PD142893, while S6c-induced contractions were much more resistant to PD142893. These different sensitivities to antagonists suggested heterogeneity of both ETA- and ETB-receptors [ETA1 (sensitive to BQ-123), ETA2 (resistant to BQ-123), ETB1 (sensitive to PD142893) and ETB2 (resistant to PD142893)] in the human saphenous vein, although contractions mediated by ETB-subtypes have smaller maximal responses than those mediated by the ETA-subtypes.

[A case of rheumatoid arthritis associated with pernicious anemia and bronchiolitis obliterans organizing pneumonia]

A case of rheumateid arthritis (RA) with pernicious anemia (PA) and wandering multiple patchy densities in bilateral lung fields is reported. A 72-year-old woman was hospitalized in February 1994, because of cough. She had already advanced RA (Class IV, Stage IV). She showed macrocytic and hyperchromic anemia as follows ; red-cell count (RBC), 176 x 10(4)/microliters; hemoglobin (Hb),7.2 g/dl; hematocrit (Ht), 21.0% ; MCV, 119.3 fl; and MCH, 40.9 pg. Chest roentgenogram revealed multiple patchy densities in bilateral lung fields and there was no response to the administration of antibiotic agents. From these clinical pictures bronchiolitis obliterans organizing pneumonia (BOOP) was highly suspected. After steroid injection into the joint space, the abnormal lung shadows disappeared. Anemia had been recovering spontaneously, but recurred in July. The results of blood examination were as follows ; RBC, 162 x 10(4)/microliters; Hb, 6.7ng/dl; Ht, 19.1%; MCV, 117.9 fl; and MCH, 41.4 pg. Anti-intrinsic factor antibody was positive. The level of serum vitamin B12 was low, 76 pg/ml. Sternal bone marrow aspiration showed magaloblastic changes with hypersegmentation of granulocytes. PA was diagnosed and improvement was noted after the intramuscular administration of vitamin B12. Subjective symptoms based on RA did not change during the clinical course. It is suggested that the pathogenesis about the combination of RA, BOOP and PA is related to common immunological abnormalities in our patient. A case of RA with PA and BOOP has not been reported previously, thus this case is considered clinically valuable.

Biochemical modulation of Doxorubicin using an isoprenoid derivative, N-1379 - plasma transmembrane potential as a target site

A new isoprenoid derivative, N-1379, was evaluated as a modulating agent of doxorubicin (DOX)-induced anticancer efficacy. The level of plasma transmembrane potential, measured using DiOC6(3), correlated with cellular sensitivity to DOX in K562 myelogenous leukemia, SH101 stomach, and PH101 pancreatic cancer cells. Non-toxic N-1379 increased the cellular transmembrane potential and DOX efficacy for three cell lines. The modulation of membrane function was accompanied by increases of DOX accumulation and S/G(2)M phase population in these cells. Overexpression of a 170 kD plasma membrane glycoprotein (GP-170) was not observed in any cells examined. We suggest therefore that interaction between electronegative transmembrane potential and positive charge of DOX may be linked to intracellular DOX accumulation. N-1379 may augment DOX efficacy through its increasing effect on plasma membrane potential independently of GP-170 overexpression.

Heterogeneity of endothelin ETA receptor-mediated contractions in the rabbit saphenous vein

The involvement of endothelin ETA receptors in endothelin-1-induced contractions of the rabbit saphenous vein was studied. After desensitization of endothelin ETB receptors by pretreatment with sarafotoxin S6c, endothelin-1 and sarafotoxin S6b and a high concentration of endothelin-3 caused dose-dependent contractions. However, endothelin-1-induced contractions were much less sensitive to an endothelin ETA receptor antagonist, BQ-123 (cyclo (-D-Asp-L-Pro-D-Val-L-Leu-D-Trp-)), than sarafotoxin S6b-induced responses. The pA2 values of BQ-123 for endothelin-1- and sarafotoxin S6b-induced contractions were 5.69 and 7.65, respectively. These results suggest pharmacological heterogeneity of endothelin ETA receptors in the rabbit saphenous vein.

Ornithine decarboxylase induction during liver regeneration in IRS-1-deficient mice

We investigated the induction of ornithine decarboxylase during liver regeneration after partial hepatectomy in IRS-1-deficient mice. There were no significant differences in ODC activity or the time course of changes in ODC activity between IRS-1-deficient mice and wild-type mice. PI 3'-kinase activity showed similar increases in both groups of mice. Furthermore, ODC induction in IRS-1 transfected CHO cells was studied after stimulation by addition of FCS. The maximal ODC activity was 2.5-fold greater in IRS-1-transfected CHO cells than in control CHO cells. Our results suggest that the IRS-1 pathway may be involved in ODC induction. The absence of a difference in ODC and PI 3'-kinase activity in the regenerating liver between IRS-1-deficient mice and wild-type mice may have been related to the compensatory effects of IRS-2/pp190 [Araki et al. Nature (1994) 372, 186-190; Tobe et al. J.Biol.Chem. (1995) 270, 5698-5701].

Structure of Alcaligenes faecalis nitrite reductase and a copper site mutant, M150E, that contains zinc

The structures at 2.0 and 2.25 A resolution of native and recombinant nitrite reductase from Alcaligenes faecalis show that they are identical to each other and very similar to nitrite reductase from Achromobacter cycloclastes. The crystallographic structure of a mutant, M150E, which unlike the wild-type protein cannot be reduced by pseudoazurin, shows that the glutamate replacement for methionine binds to a metal at the type I Cu site via only one oxygen. Anomalous scattering data collected at wavelengths of 1.040 and 1.377 A reveal that the metal at the type I site is a Zn. No significant differences from the native structure other than local perturbations at the type I site are seen. A local pseudo 2-fold axis relates the two domains of different monomers which form the active site. The two residues, Asp98 and His255, believed to be involved in catalysis are related by this 2-fold. An unusual (+)-(+) charge interaction between Lys269, Glu279, and His100 helps to orient the active site Cu ligand, His100. A number of negatively charged surface residues create an electrostatic field whose shape suggests that it may serve to direct incoming negatively charged nitrite as well as to dock the electron donor partner, pseudoazurin.

DT-diaphorase as a target enzyme for biochemical modulation of mitomycin C

We studied a selective enhancement of the mitomycin C (MMC)-induced antitumor effect focusing on the intracellular metabolism by NAD(P)H:quinone oxidoreductase (DT-diaphorase, DTD). The level of cellular DTD activity related well to the degree of MMC-induced DNA total cross links and cell growth inhibition in human cancer cell lines, KB, PH101, SH101 and K562. A DTD inhibitor, dicoumarol (DIC) or flavin adenine dinucleotide (FAD), inhibited the MMC-induced DNA damage and cytotoxicity at a non-toxic concentration. The DTD-mediated MMC activation was pH-dependent, and highest at pH 6 and lowest at pH 8. Although an inverse relationship appeared to exist between DTD activity and MMC efficacy in human xenografts implanted into nude mice and 9 fresh human tumor specimens, the investigation in 3 culture cells, HEC-46, HCC-48 and HCC-50, established from those xenografts, showed that DTD activated MMC in a pH-dependent manner as well as the other cell lines. Significant tumor pH reduction from 7.1 to 6.7 by continuous glucose infusion also increased the MMC-induced tumor growth inhibition in the human tumor xenografts. Thus, we conclude that bioreductive activation by DTD in a pH-dependent manner may be of key importance in the MMC-induced antitumor effect and that an increased MMC efficacy at a reduced pH caused by hyperglycemia may be applied to clinical use as a new manipulation for a biochemical modulation of MMC.

Non-insulin-dependent diabetes mellitus complicated with idiopathic hypoparathyroidism

We report a case of non-insulin-dependent diabetes mellitus (NIDDM) complicated with idiopathic hypoparathyroidism. A 74-year-old male was hospitalized because of diplopia. He was revealed to have NIDDM. The levels of serum Ca and intact-PTH were 6.3 mg/dl and < 5 pg/ml, respectively. Brain computed tomography revealed abnormal calcification in the cerebral basal ganglia and the cerebellum. After recovery from hypocalcemia, the endogenous insulin secretion was normalized. It is suggested that the pathogenesis of NIDDM in this patient may have been related to an insulin secretory defect as a result of hypocalcemia in addition to the hereditary risk.

Two different endothelin B receptor subtypes mediate contraction of the rabbit saphenous vein

To study endothelin receptor subtypes that mediate venous smooth muscle contraction, effects of some endothelin receptor agonists and antagonists on the rabbit lateral saphenous vein were examined and compared with those on the saphenous artery. In the artery, endothelin (ET)-1 elicited concentration-dependent contractions, while selective ETB-receptor agonists, IRL1620 (Suc-[Glu9,Ala11,15]ET-1(8-21)) and sarafotoxin 6c (S6c) had almost no effect. The ET-1-induced responses shifted in parallel to the right by BQ-123 (cyclo (-D-Trp-D-Asp-Pro-D-Val-Leu-)), an ETA-receptor antagonist, or PD142893 (Ac-D-Dip-Leu-Asp-Ile-Ile-Trp), an ETA/ETB-receptor antagonist, indicating the involvement of the ETA receptor in this response. In the saphenous vein, not only ET-1 and ET-3, but also ETB-receptor agonists, IRL1620, S6c and [Glu9]sarafotoxin 6b ([Glu9]S6b), produced concentration-dependent, BQ-123-insensitive contractions. PD142893 did not affect the ET-1-induced contraction, but it shifted greatly the IRL1620-induced concentration-response curve in parallel to the right. The major components of ET-3-, S6c- and [Glu9]S6b-induced contractions were resistant to PD142893. These results indicate that two different vasoconstrictive ETB-receptor subtypes, ETB1 (sensitive to IRL1620 and PD142893) and ETB2 (insensitive to IRL1620 and PD142893), are located on the smooth muscle of the saphenous vein.

Characterization of a novel brain neutral glycosphingolipid composition in house musk shrew (Suncus murinus)

Glycosphingolipids were extracted from the brain of house musk shrew (Suncus murinus). Neutral glycosphingolipids were purified by QAE-Sephadex column chromatography followed by high-performance liquid chromatography using an Iatrobeads column. Purified glycosphingolipids were identified by high-performance thin-layer chromatography, carbohydrate analysis, fast-atom bombardment mass spectrometry and TLC immunostaining. The ganglioside pattern was almost the same as the pattern obtained for rat brain gangliosides. The brain of S. murinus, however, was unique in its neutral glycosphingolipid composition; it contained gangliotriaosylceramide and gangliotetraosylceramide as the major neutral glycosphingolipids in addition to monohexosylceramides. Mass spectroscopy analysis showed that C18:1 sphingosine and C24:0 normal fatty acids were the major ceramide constituents in the glycosphingolipis, except in the case where a slower-migrating monohexosylceramide that contained C24 h:0 hydroxy fatty acids was observed. A day after birth, monohexosylceramide contained only normal fatty acids. The amounts of hydroxy-fatty-acid-containing monohexosylceramide increased rapidly as the age of the animals increased, and the ratio of these two kinds of monohexosylceramides was reversed within five weeks. Monohexosylceramide, ganglioside, and sulfatide contents in bulbus olfactorius were almost equal in amount in contrast to the glycolipids in the cerebrum and cerebellum that contained monohexosylceramide as the major constituent. The amount of monohexosylceramide in the bulbus olfactorius was 0.3-0.4 times the values obtained for the cerebrum and cerebellum.

Histopathological reaction of calcium phosphate cement in periodontal bone defect

In this study, we evaluated the osteoconductivity of calcium phosphate cement (CPC) as compared to that of a current hydroxyapatite-based material (AP) by implanting the materials in surgically formed defects in the jaws of dogs. One month post-operation, slight inflammatory reactions were observed in tissue areas adjacent to either CPC mass or AP. Three months after operation, the CPC mass-filled defects were covered with periosteum and bone tissues. The CPC mass in the defects was partially replaced by newly formed bone. In bone defects filled with AP, most of the interparticle space was filled with connective tissues including bone tissues. Six months post-operation, the CPC mass-filled defects were covered with periosteum and new bone, and most of the CPC mass was replaced by bone. Interparticle spaces of AP were filled with connective tissues and bone tissues.

Does bacitracin have an absorption-enhancing effect in the intestine?

We studied the absorption enhancement effects of three types of protease inhibitors, aprotinin, bacitracin and soybean trypsin inhibitor, in the rat intestine. Of these protease inhibitors, bacitracin enhanced the absorption of FD-4 and phenol red from the rat small and large intestine without mucosal toxicity. Thus, it was suggested that bacitracin has not only a protease-inhibitory but also an absorption-enhancing capability.

A new type of two-dimensional thin-layer chromatography (TLC mapping) for analysis of acidic glycosphingolipid molecular species

A new approach to the analysis of acidic glycosphingolipid molecular species has been developed by using two-dimensional thin-layer chromatography: TLC mapping. TLC mapping was accomplished by use of two types of high-performance thin-layer chromatographic (HPTLC) plates. A NH2-silica gel HPTLC plate developed with chloroform:methanol:1% diethylamine (50:47:15) was used for the first-dimension chromatography. Acidic glycosphingolipids on the plate were transferred to a normal silica gel HPTLC plate by developing the plate with chloroform:methanol:ammonia (4:10:6) after the NH2 plate was placed face to face on top of the silica gel HPTLC plate. Acidic glycophingolipids on the HPTLC plate were then developed with chloroform: methanol:0.2% CaCl2 (60:40:10) for the second-dimension chromatography. The use of the TLC-mapping method allowed us to compare detailed membrane constituents, including minor molecular species with regard to acidic glycophingolipids. The method is rapid and simple and is feasible for determining acidic glycosphingolipid from biological samples.

Retrovirally transmitted gene therapy for gastric carcinoma using herpes simplex virus thymidine kinase gene

BACKGROUND

Herpes simplex thymidine kinase (HTK) is known to phosphorylate ganciclovir (GCV). Phosphorylated GCV is incorporated into genomic DNA, which leads to inhibition of cell growth and cell death in the replicating cells. Recently, much attention has been drawn to the use of retrovirally mediated gene therapy using HTK as a new therapeutic approach for brain tumors. However, little is known about this phenomenon in gastrointestinal carcinomas.

METHODS

The authors transfected the HTK gene packaged in retroviral vector into TMK-1 gastric carcinoma cells (TMK-HTK cells). Sensitivity of TMK-HTK cells to GCV was examined in vitro. Moreover, TMK-HTK cells were transduced into nude mice subcutaneously, and the effects of GCV therapy was examined at the concentration of 20 mg/kg daily for 14 days.

RESULTS

TMK-HTK cells were sensitive to GCV at the concentration of 0.1 to 100 micrograms/ml in a dose- and time-dependent manner in vitro. Moreover, 12 of 13 TMK-HTK tumors, which were transduced into nude mice subcutaneously, shrunk from the average diameter of 6.5 mm.

CONCLUSION

The results indicate that retrovirally transmitted gene therapy with GCV may provide a new therapeutic approach for treatment of gastric carcinomas.

Laparoscopic omental patch repair for perforated peptic ulcer

OBJECTIVE

The authors' initial experience with laparoscopic omental patch repair for perforated peptic ulcer is documented. Its results are compared with those of other procedures and follow-up study is reviewed.

SUMMARY BACKGROUND DATA

Since the advent of H2-antagonists, the usefulness of simple closure of a perforated peptic ulcer is increasing, and improvements in laparoscopic surgery have made possible minimally invasive surgery for perforated ulcer.

METHODS

From December 1992 to February 1994, laparoscopic omental patch repair followed by use of H2-antagonists was performed successfully in 11 patients. Fifty-five patients underwent other surgical procedures for perforated peptic ulcers (conventional open omental patch: 4, selective vagotomy in combination with antrectomy: 24, distal gastrectomy: 27).

RESULTS

The average operation time was 135 minutes. Administration of postoperative pain medication was reduced remarkably (0.9 times per patient), and all patients recovered rapidly. No serious postoperative complications were recorded. After a mean period of 11 months, the postoperative evaluation was satisfactory for all patients, and no ulcer recurrence was found.

CONCLUSIONS

In perforated peptic ulcer disease, laparoscopic omental patch repair offers a number of advantages. Because no upper abdominal incision is made, there is decreased postoperative pain, and the patient rapidly recovers with fewer and less severe complications. Although the procedure requires a surgeon with particular expertise in endoscopic suturing technique, surgeons familiar with laparoscopic cholecystectomy can readily perform it after some practice. The authors' preliminary experience suggests that this is a minimally invasive procedure for perforated peptic ulcer that offers an attractive alternative to open surgery.