Glomerular hypertrophy in preeclamptic patients with focal segmental glomerulosclerosis. A morphometric analysis

BACKGROUND

Focal segmental glomerulosclerotic lesion (FSGS lesion) is frequently observed in preeclamptic patients with nephrotic syndrome.

PATIENTS AND METHODS

We performed a morphometric analysis of renal biopsies from 20 patients with severe preeclampsia to evaluate the pathogenetic role of glomerular hypertrophy in preeclamptic nephropathy associated with FSGS lesion. We also analyzed biopsies obtained from 6 preeclamptic patients without FSGS lesion and 10 patients with isolated hematuria. Nonsclerotic glomeruli were examined.

RESULTS

The mean glomerular tuft area (GTA), the whole glomerular area (WGA), and the extracellular matrix area (EMA) were significantly and negatively correlated with the postpartum day at biopsy in preeclamptic patients with FSGS lesion who underwent renal biopsy within 40 days after delivery. The mean GTA, WGA, EMA and number of mesangial cells (MN) were significantly increased in preeclamptic patients with FSGS lesion compared with patients with isolated hematuria and compared with those without FSGS lesion when the biopsy time was matched between patients with and without FSGS lesion. The GTA and WGA were not different between preeclamptic patients without FSGS lesion and patients with isolated hematuria.

CONCLUSION

These results support the assumption that glomerular hypertrophy that develops during severe toxemic pregnancy plays an important role in the pathogenesis of FSGS lesion and is reversible about 40 days after delivery.

[Survey of the sensitivities of clinical isolates to antibacterial agents (annual report)]

Research groups were formed in 21 institutions nationwide to investigate carbapenem resistance. The activities of various antibacterial agents, principally carbapenems, were tested against clinical isolates collected from these institutions. The broth microdilution method was used to determine the minimum inhibitory concentrations (MIC) of 17 antibacterial agents for 1,241 strains of 11 bacterial species isolated at all institutions between October and December 1996. The results were as follows: Carbapenems exhibited strong antibacterial activities against MSSA and Streptococcus pneumoniae and showed low activities against MRSA. Their activities against Enterococcus faecalis were comparable to that of ampicillin and piperacillin. The carbapenems showed high activities against Haemophilis influenzae, Escherichia coli, Klebsiella pneumoniae. Enterobacter cloacae. Serratia marcescens and Bacteroides fragilis group. Their activities were greater than that exhibited by other beta-lactam antibacterial agents, but some resistant strains of Serratia marcescens were detected. The antibacterial activity of carbapenems against Pseudomonas aeruginosa was comparable to that of CAZ, and there were some resistant strains.

Contribution of peripheral chemoreception to the depression of the hypoxic ventilatory response during halothane anesthesia in cats

BACKGROUND

The effects of inhalational anesthetics on the hypoxic ventilatory response are complex. This study was designed to determine the contribution of peripheral chemoreception to the depression of hypoxic ventilatory response seen with halothane anesthesia.

METHODS

Cats were anesthetized with pentobarbital sodium and alpha-chloralose and artificially ventilated. Respiratory output was evaluated by phasic inspiratory activity of the phrenic nerve. In 12 cats, this activity was measured during inhalation of an hypoxic gas mixture with halothane, 0, 0.1, and 0.8%, with intact or denervated carotid bodies. In 10 cats, a carotid body was isolated from the systemic circulation and perfused with hypoxic Krebs-Ringer solution equilibrated with halothane, 0, 0.1, and 0.8%.

RESULTS

The hypoxic ventilatory response was depressed in a dose-dependent manner during halothane anesthesia. In carotid body perfusion studies, the response was significantly depressed only with halothane, 0.80%.

CONCLUSION

The hypoxic ventilatory response is depressed by a high dose of halothane through a peripheral effect at the carotid body.

Modulation of the remote heme site geometry of recombinant mouse neuronal nitric-oxide synthase by the N-terminal hook region

The role of two essential residues at the N-terminal hook region of neuronal nitric-oxide synthase (nNOS) in nitric-oxide synthase activity was investigated. Full-length mouse nNOS proteins containing single-point mutations of Thr-315 and Asp-314 to alanine were produced in the Escherichia coli and baculovirus-insect cell expression systems. The molecular properties of the mutant proteins were analyzed in detail by biochemical, optical, and electron paramagnetic resonance spectroscopic techniques and compared with those of the wild-type enzyme. Replacement of Asp-314 by Ala altered the geometry around the heme site and the substrate-binding pocket of the heme domain and abrogated the ability of nNOS to form catalytically active dimers. Replacement of Thr-315 by Ala reduced the protein stability and altered the geometry around the heme site, especially in the absence of bound (6R)-5,6,7, 8-tetrahydro-L-biopterin cofactor. These results suggest that Asp-314 and Thr-315 both play critical structural roles in stabilizing the heme domain and subunit interactions in mouse nNOS.

Inhibition of xanthine oxidase and xanthine dehydrogenase by nitric oxide. Nitric oxide converts reduced xanthine-oxidizing enzymes into the desulfo-type inactive form

Xanthine oxidase (XO) and xanthine dehydrogenase (XDH) were inactivated by incubation with nitric oxide under anaerobic conditions in the presence of xanthine or allopurinol. The inactivation was not pronounced in the absence of an electron donor, indicating that only the reduced enzyme form was inactivated by nitric oxide. The second-order rate constant of the reaction between reduced XO and nitric oxide was determined to be 14.8 +/- 1.4 M-1 s-1 at 25 degrees C. The inactivated enzymes lacked xanthine-dichlorophenolindophenol activity, and the oxypurinol-bound form of XO was partly protected from the inactivation. The absorption spectrum of the inactivated enzyme was not markedly different from that of the normal enzyme. The flavin and iron-sulfur centers of inactivated XO were reduced by dithionite and reoxidized readily with oxygen, and inactivated XDH retained electron transfer activities from NADH to electron acceptors, consistent with the conclusion that the flavin and iron-sulfur centers of the inactivated enzyme both remained intact. Inactivated XO reduced with 6-methylpurine showed no "very rapid" spectra, indicating that the molybdopterin moiety was damaged. Furthermore, inactivated XO reduced by dithionite showed the same slow Mo(V) spectrum as that derived from the desulfo-type enzyme. On the other hand, inactivated XO reduced by dithionite exhibited the same signals for iron-sulfur centers as the normal enzyme. Inactivated XO recovered its activity in the presence of a sulfide-generating system. It is concluded that nitric oxide reacts with an essential sulfur of the reduced molybdenum center of XO and XDH to produce desulfo-type inactive enzymes.

Cellobiose dehydrogenase from the fungi Phanerochaete chrysosporium and Humicola insolens. A flavohemoprotein from Humicola insolens contains 6-hydroxy-FAD as the dominant active cofactor

Cellobiose dehydrogenases (CDH) were purified from cellulose-grown cultures of the fungi Phanerochaete chrysosporium and Humicola insolens. The pH optimum of the cellobiose-cytochrome c oxidoreductase activity of P. chrysosporium CDH was acidic, whereas that of H. insolens CDH was neutral. The absorption spectra of the two CDHs showed them to be typical hemoproteins, but there was a small difference in the visible region. Limited proteolysis between the heme and flavin domains was performed to investigate the cofactors. There was no difference in absorption spectrum between the heme domains of P. chrysosporium and H. insolens CDHs. The midpoint potentials of heme at pH 7.0 were almost identical, and no difference in pH dependence was observed over the range of pH 3-9. The pH dependence of cellobiose oxidation by the flavin domains was similar to that of the native CDHs, indicating that the difference in the pH dependence of the catalytic activity between the two CDHs is because of the flavin domains. The absorption spectrum of the flavin domain from H. insolens CDH has absorbance maxima at 343 and 426 and a broad absorption peak at 660 nm, whereas that of P. chrysosporium CDH showed a normal flavoprotein spectrum. Flavin cofactors were extracted from the flavin domains and analyzed by high-performance liquid chromatography. The flavin cofactor from H. insolens was found to be a mixture of 60% 6-hydroxy-FAD and 40% FAD, whereas that from P. chrysosporium CDH was normal FAD. After reconstitution of the deflavo-proteins it was found that flavin domains containing 6-hydroxy-FAD were clearly active but their cellobiose oxidation rates were lower than those of flavin domains containing normal FAD. Reconstitution of flavin cofactor had no effect on the optimum pH. From these results, it is concluded that the pH dependence is not because of the flavin cofactor but is because of the protein molecule.

Gene cloning and overexpression of a geranylgeranyl diphosphate synthase of an extremely thermophilic bacterium, Thermus thermophilus

A geranylgeranyl diphosphate (GGPP) synthase gene of an extremely thermophilic bacterium, Thermus thermophilus, was cloned and sequenced. T. thermophilus GGPP synthase, overexpressed in Escherichia coli cells as a glutathione S-transferase fusion protein, was purified and characterized. The fusion protein, retaining thermostability, formed a homodimer, and showed higher specific activity than did a partially purified thermostable enzyme previously reported. Optimal reaction conditions and kinetic parameters were also examined. The deduced amino acid sequence indicated that T. thermophilus GGPP synthase was excluded from the group of bacterial type GGPP synthases and lacked the insertion amino acid residues in the first aspartate-rich motif as do archaeal and eukaryotic short-chain prenyltransferases.

Temporal changes in airway protective reflexes elicited by an endotracheal tube in surgical patients anaesthetized with sevoflurane

In order to elucidate temporal changes in airway reflex responses to prolonged tracheal intubation, 14 patients anaesthetized with sevoflurane were studied. In each spontaneously breathing patient with an endotracheal tube in place, the end-tidal concentration of sevoflurane was slowly decreased from the initial value of 1.3% until signs of airway irritation were observed. The value of end-tidal sevoflurane concentration at which the airway reflexes occurred (T(ar)) and the types of airway reflex response elicited at onset of airway reflex response were determined during the periods immediately before (presurgical period) and after surgery (post-surgical period), with an interval ranging from 2 to 7 h between the two periods. There was no significant difference in the values of T(ar) between the presurgical period (0.6 +/- 0.3%, mean +/- SD) and the post-surgical period (0.7 +/- 0.1%). There was a considerable difference in the type of airway reflexes elicited during the two different periods; the initial responses during the presurgical period were the apnoeic reflex and/or forceful expiratory efforts, whereas the initial response during the post-surgical period, in the majority of patients, was the swallowing reflex. Our results indicate that there may be adaptation mechanisms responsible for temporal changes in airway protective reflexes after prolonged endotracheal intubation in surgical patients.

Interplay between chromosomal beta-lactamase and the MexAB-OprM efflux system in intrinsic resistance to beta-lactams in Pseudomonas aeruginosa

We investigated the role of chromosomal beta-lactamase and the MexAB-OprM efflux system in intrinsic resistance to beta-lactams in Pseudomonas aeruginosa. Determination of the susceptibilities of a series of isogenic mutants with impaired production of the beta-lactamase and the efflux system to 16 beta-lactams including penicillins, cephems, oxacephems, carbapenems, and a monobactam demonstrated that the intrinsic resistance of P. aeruginosa to most of the beta-lactams is due to the interplay of both factors.

A low concentration of nitrous oxide reduces dyspnoea produced by a combination of hypercapnia and severe elastic load

We have measured how a low concentration of nitrous oxide affected respiratory sensation and ventilation. Severe dyspnoea was induced in nine normal subjects by a combination of hypercapnia and inspiratory elastic load (50 cm H2O litre-1). Subjects were asked to rate their sensation of respiratory discomfort using a visual analogue scale (VAS) while breathing either 20% nitrous oxide or 20% nitrogen gas mixture. We compared the effects of each gas mixture on respiratory sensation and ventilation using steady-state values of ventilatory variables and VAS scores obtained before, during and after inhalation of each gas mixture. Inhalation of 20% nitrous oxide reduced the sensation of respiratory discomfort from a median VAS score of 6.5 (range 5.0-8.1) before inhalation to 3.6 (2.4-5.9) during inhalation (P < 0.05). There was no significant change in minute ventilation but tidal volume increased during inhalation of 20% nitrogen did not alter VAS scores or ventilatory variables. We found that a low concentration of nitrous oxide greatly alleviated the intensity of dyspnoea without changing respiratory load compensation.

Milrinone decreases both pulmonary arterial and venous resistances in the hypoxic dog

We have studied the effect of milrinone on pulmonary vascular resistance (PVR) in dogs with hypoxic pulmonary vasoconstriction (HPV). Using a pulmonary arterial occlusion method, we measured effective pulmonary capillary pressure (Pcap) by which total PVR was partitioned into arterial (PVRa) and venous (PVRv) components. Hypoxic ventilation (FIO2 = 0.11-0.13) produced significant increases in mean pulmonary arterial pressure (PAP) and Pcap (P < 0.01) associated with increases in PVRa and PVRv (P < 0.01). During the hypoxic period, milrinone significantly decreased mean PAP and Pcap (P < 0.01), reflected in decreases in PVRa and PVRv (P < 0.01). The longitudinal distribution of PVR (PVRa/PVRv) remained unchanged throughout the experiment, indicating that HPV occurred equally in the arterial and venous segments and that milrinone-induced vasodilatation occurred equally in both segments. During hypoxia, milrinone did not produce an increase in cardiac output or a decrease in PaO2. Milrinone also produced significant decreases in mean systemic arterial pressure (P < 0.01) and systemic vascular resistance (P < 0.05) to a similar extent to the decreases in mean PAP and PVR, suggesting no selective dilating effect of milrinone on the pulmonary vasculature. These results indicate that in HPV, milrinone decreased the vascular tone of both pulmonary arterial and venous segments without increasing cardiac work or impairing pulmonary oxygenation. This suggests a potential for use in patients suffering from hypoxic pulmonary hypertension.

Effects of negative pressure assisted ventilation on dyspnoeic sensation and breathing pattern

Although negative pressure assisted ventilation with an assist-control mode may have a potential therapeutic role in the treatment of severe dyspnoea, the effects of negative pressure assisted ventilation with the assist-control mode on dyspnoea and breathing patterns have not been examined. We examined the effects of negative pressure assisted ventilation with the assist-control mode on dyspnoea and breathing patterns produced by a combination of resistive loading and hypercapnia in nine healthy subjects breathing spontaneously. Subjects were asked to rate their sensation of respiratory discomfort using a visual analogue scale. Negative pressure assisted ventilation caused a significant reduction in sensation of respiratory discomfort from a visual analogue scale score of 74 (55-91) (median (range)) before negative pressure assisted ventilation to 34 (15-53) during negative pressure assisted ventilation (p<0.01). During negative pressure assisted ventilation, there were significant changes in breathing patterns characterized by an increase in tidal volume and a decrease in respiratory frequency, while neither minute ventilation nor end-tidal carbon dioxide tension changed. Our results indicate that negative pressure assisted ventilation with the assist-control mode is effective in relief of dyspnoea and that negative pressure assisted ventilation influences the control of breathing to minimize respiratory discomfort.

Overexpression, purification, and characterization of human m-calpain and its active site mutant, m-C105S-calpain, using a baculovirus expression system

Recombinant human m-calpain was produced in a soluble form at a level of 20 mg/liter of Sf-9 cell culture by the coexpression of recombinant human m-calpain large (m80K) and small (30K) subunits using a baculovirus expression system. The expressed m-calpain was purified by sequential column chromatographies on DEAE-Toyopearl, gel-filtration, and Mono Q by the same method used to purify native m-calpain. The recombinant m-calpain had a specific activity of 691 U/mg and a Ka value (Ca2+ requirement for 50% caseinolysis activity) of 0.4 mM, which are essentially identical to those of native rabbit m-calpain. A mutant m-calpain large subunit, m-C105S-80K, where the active-site cysteine-105 is converted to serine by site-directed mutagenesis, was coexpressed with 30K in Sf-9 cells, purified, and characterized. m-C105S-calpain does not degrade casein nor an artificial tetra-peptide substrate, succinyl-Leu-Leu-Val-Tyr-MCA. Further, it shows no autolytic activity with Ca2+. This is the first report of the large-scale production of a fully active m-calpain species in the baculovirus system.

Consistency of variables in PCS and JASTRO great area database

PURPOSE

To examine whether the Patterns of Care Study (PCS) reflects the data for the major areas in Japan, the consistency of variables in the PCS and in the major area database of the Japanese Society for Therapeutic Radiology and Oncology (JASTRO) were compared.

METHODS AND PATIENTS

Patients with esophageal or uterine cervical cancer were sampled from the PCS and JASTRO databases. From the JASTRO database, 147 patients with esophageal cancer and 95 patients with uterine cervical cancer were selected according to the eligibility criteria for the PCS. From the PCS, 455 esophageal and 432 uterine cervical cancer patients were surveyed. Six items for esophageal cancer and five items for uterine cervical cancer were selected for a comparative analysis of PCS and JASTRO databases.

RESULTS

Esophageal cancer: Age (p=.0777), combination of radiation and surgery (p=.2136), and energy of the external beam (p=.6400) were consistent for PCS and JASTRO. However, the dose of the external beam for the non-surgery group showed inconsistency (p=.0467). Uterine cervical cancer: Age (p=.6301) and clinical stage (p=.8555) were consistent for the two sets of data. However, the energy of the external beam (p<.0001), dose rate of brachytherapy (p<.0001), and brachytherapy utilization by clinical stage (p<.0001) showed inconsistencies.

CONCLUSION

It appears possible that the JASTRO major area database could not account for all patients' backgrounds and factors and that both surveys might have an imbalance in the stratification of institutions including differences in equipment and staffing patterns.

Unique primary structure of a thermostable multimetal beta-galactosidase from Saccharopolyspora rectivirgula

The gene of the monomeric multimetal beta-galactosidase of Saccharopolyspora rectivirgula was cloned and sequenced. Although the enzyme could be assigned as a member of beta-galactosidases belonging to the glycosyl hydrolase family 2, it has unusual structural features for beta-galactosidase of this family; it contained a unique sequence which consists of approximately 200 amino acid residues with no similarity to known proteins. This 200-residue sequence exists as if it is inserted into a sequence homologous to the active-site domain of the Escherichia coli lacZ enzyme.

A pathway where polyprenyl diphosphate elongates in prenyltransferase. Insight into a common mechanism of chain length determination of prenyltransferases

Prenyltransferases catalyze the consecutive condensations of isopentenyl diphosphate to produce linear polyprenyl diphosphates. Each enzyme forms the final product with a specific chain length. The product specificity of an enzyme is thought to be determined by the structure around the unknown path through which the product elongates in the enzyme. To explore the path, we introduced a few mutations at the 5th, the 8th, and/or the 11th positions before the first aspartate-rich motif of geranylgeranyl-diphosphate synthase or farnesyl-diphosphate synthase. The side chains of these amino acids are situated on the same side of an alpha-helix. In geranylgeranyl-diphosphate synthase, a single mutated enzyme (F77S) mainly produces a C25 product (Ohnuma, S.-I., Hirooka, K., Hemmi, H., Ishida, C., Ohto, C., and Nishino, T. (1996) J. Biol. Chem. 271, 18831-18837). A double mutated enzyme (L74G and F77G) mainly produces a C35 compound with significant amounts of C30 and C40. A triple mutated enzyme (I71G, L74G, and F77G) mainly produces a C40 compound with C35 and C45. Mutated farnesyl-diphosphate synthases also show similar patterns. These findings indicate that the elongating product passages on a surface of the side chains of the mutated amino acids, the original bulky amino acids had blocked the elongation, and the path is conserved in prenyltransferases. Moreover, the fact that some double and triple mutated enzymes can also form small amounts of products longer than C50 indicates that the paths in these mutated enzymes can partially access the outer surface of the enzymes.

Plasma and urinary levels of adrenomedullin in chronic glomerulonephritis patients with proteinuria

In this study, we measured levels of plasma and urinary adrenomedullin (AM) in 37 patients with chronic glomerulonephritis including minimal change nephrotic syndrome, focal segmental glomerulosclerosis or membranous nephropathy that can induce severe proteinuria. Thirty-nine healthy volunteers were enrolled as controls. Plasma and urinary AM levels were measured by an AM-specific radioimmunoassay. Plasma AM concentrations were higher and urinary AM levels were lower in patients with chronic glomerulonephritis than in healthy volunteers. Patients were divided into two groups according to urinary excretion of protein for 24 h (UPro, g/day) which reflects the disease activity or glomerular damage of the glomerulonephritis (group I: Upro < 1, group II: Upro >= 1). Plasma AM levels positively and urinary AM-levels negatively correlated with the degree of proteinuria. These results suggest that plasma and urinary AM levels in patients with chronic glomerulonephritis reflect the disease activity or glomerular damage represented by the degree of proteinuria.

In-vitro and in-vivo antibacterial activities of CS-834, a new oral carbapenem

We evaluated the in-vitro and in-vivo antibacterial activities of R-95867 and CS-834, a new oral carbapenem which is an ester-type prodrug of R-95867. Against Gram-positive bacteria, R-95867 was as active or two to 256 times more active than cefpodoxime, cefdinir, cefditoren and ofloxacin, while its activity was similar to or two to eight times lower than that of imipenem. Against most Gram-negative bacteria it was as active or two to 1024 times more active than the other compounds tested. Against Helicobacter pylori it was two to 64 times more active than orally active anti-H. pylori agents, i.e. amoxycillin, clarithromycin and lansoprazole. It also showed potent bactericidal activity against Staphylococcus aureus and Escherichia coli. R-95867 induced a spherical form in E. coli and showed high affinity for PBP 2 in E. coli. Against systemic infections in mice caused by various bacteria, CS-834 showed an excellent protective effect and its in-vivo efficacy correlated well with the in-vitro activity of R-95867. These results suggest that CS-834 may be effective in the therapy of various bacterial infections.

Substrate specificity of thermostable farnesyl diphosphate synthase with alkyl group homologs of isopentenyl diphosphate

3-Alkyl group homologs of isopentenyl diphosphate were examined for the reactivity as substrates of the thermostable farnesyl diphosphate (FPP) synthase of Bacillus stearothermophilus. Even 3-n-propyl- and 3-n-butyl-but-3-enyl diphosphates, which are hardly acceptable by animal FPP synthases, are accepted by this bacterial enzyme as substrates to react with dimethylallyl- and geranyl diphosphates, yielding 7-methyl-3-n-propylocta-2,6-dienyl- and 7,11-dimethyl-3-n-propyldodeca-2,6,10-trienyl diphosphate, respectively.

Purification and characterization of wild-type and mutant "classical" nitroreductases of Salmonella typhimurium. L33R mutation greatly diminishes binding of FMN to the nitroreductase of S. typhimurium

"Classical" nitroreductase of Salmonella typhimurium is a flavoprotein that catalyzes the reduction of nitroaromatics to metabolites that are toxic, mutagenic, or carcinogenic. This enzyme represents a new class of flavin-dependent enzymes, which includes nitroreductases of Enterobacter cloacae and Escherichia coli, flavin oxidoreductase of Vibrio fischeri, and NADH oxidase of Thermus thermophilus. To investigate the structure-function relation of this class of enzymes, the gene encoding a mutant nitroreductase was cloned from S. typhimurium strain TA1538NR, and the enzymatic properties were compared with those of the wild-type. DNA sequence analysis revealed a T to G mutation in the mutant nitroreductase gene, predicting a replacement of leucine 33 with arginine. In contrast to the wild-type enzyme, the purified protein with a mutation of leucine 33 to arginine has no detectable nitroreductase activities in the standard assay conditions and easily lost FMN by dialysis or ultrafiltration. In the presence of an excess amount of FMN, however, the mutant protein exhibited a weak but measurable enzyme activity, and the substrate specificity was similar to that of the wild-type enzyme. Possible mechanisms by which the mutation greatly diminishes binding of FMN to the nitroreductase are discussed.

Tissue and subcellular distribution of mercaptopyruvate sulfurtransferase in the rat: confocal laser fluorescence and immunoelectron microscopic studies combined with biochemical analysis

In our previous study, we found that mercaptopyruvate sulfurtransferase (MST) was evolutionarily related to mitochondrial rhodanese. To elucidate the difference between MST and rhodanese, the tissue, cellular, and subcellular distribution of rat MST was determined biochemically and immunohistochemically by using anti-MST antibody raised in rabbit. In an immunohistochemical study, tetramethyl rhodamine isothiocyanate-conjugated phalloidin against F-actin and fluorescein isothiocyanate-conjugated goat anti-rabbit immunoglobulin as a secondary antibody to the anti-MST antibody were used for double fluorescent staining. They were detected by confocal laser fluorescence microscopy. In the immunoelectron microscopic study of hepatocyte and renal tubular epithelium, a postembedding immunogold method was used. Biochemical studies including western blot analyses of various tissues and subcellular fractions of the liver were also performed. MST was widely distributed in rat tissues but the cellular distribution was found to be different in each tissue. MST was predominantly localized in proximal tubular epithelium in the kidney, pericentral hepatocytes in the liver, cardiac cells in the heart, and neuroglial cells in the brain. This immunocytochemical study also found that MST was localized in both mitochondria and cytoplasm.

Functional replacement of OprJ by OprM in the MexCD-OprJ multidrug efflux system of Pseudomonas aeruginosa

For characterization of the MexCD-OprJ efflux system of Pseudomonas aeruginosa involved in resistance to fluoroquinolones and the fourth-generation cephems, we constructed mexC, mexD or oprJ mutants from the nfxB-type PAO strains by insertion mutagenesis. The gene products in the resultant mutants were examined by immunoblot assay using murine and rabbit antibodies developed against purified protein and synthetic oligopeptides. Susceptibility of the mexC (MexC- MexD- OprJ-) and mexD (MexC+ MexD- OprJ-) mutants to fluoroquinolone and the fourth-generation cephems was comparable to that of the wild-type strain PAO1. However, the oprJ mutant (MexC+ MexD+ OprJ-) was still less susceptible than PAO1, since a MexCD-OprM chimera system, which generated from a functional assist of the constitutively expressed OprM, can function in the efflux of the antimicrobial agents in the oprJ mutant. In fact, transformation of the oprJ mutant with an OprM-expression plasmid decreased the former's susceptibility to the levels exhibited by the nfxB mutant without affecting the substrate specificity of MexCD-OprJ.

Characterization of the MexC-MexD-OprJ multidrug efflux system in DeltamexA-mexB-oprM mutants of Pseudomonas aeruginosa

Expression of the multidrug efflux system MexC-MexD-OprJ in nfxB mutants of Pseudomonas aeruginosa contributes to resistance to fluoroquinolones and the "fourth-generation" cephems (cefpirome and cefozopran), but not to most beta-lactams, including the ordinary cephems (ceftazidime and cefoperazone). nfxB mutants also express a second multidrug efflux system, MexA-MexB-OprM, due to incomplete transcriptional repression of this operon by the mexR gene product. To characterize the contribution of the MexC-MexD-OprJ system to drug resistance in P. aeruginosa, a site-specific deletion method was employed to remove the mexA-mexB-oprM region from the chromosome of wild-type and nfxB strains of P. aeruginosa. Characterization of mutants lacking the mexA-mexB-oprM region clearly indicated that the MexC-MexD-OprJ efflux system is involved in resistance to the ordinary cephems as well as fluoroquinolones and the fourth-generation cephems but not to carbenicillin and aztreonam. Rabbit polyclonal antisera and murine monoclonal antibody against the components of the MexA-MexB-OprM system were prepared and used to demonstrate the reduced production of this efflux system in the nfxB mutants. Consistent with this, transcription of the mexA-mexB-oprM operon decreased in an nfxB mutant. This reduction appears to explain the hypersusceptibility of the nfxB mutant to beta-lactams, including ordinary cephems.

Inhalation anaesthetics produce asynchronous reversal of ventilation inhomogeneity and increased lung resistance in a canine model of bronchial asthma

Bronchial asthma is characterized by not only an increase in lung resistance but also inhomogeneous ventilation. We aimed to investigate how two inhalation anaesthetics, isoflurane and sevoflurane, relieve ventilation inhomogeneity and reduce lung resistance in the bronchoconstricted lung. We provoked bronchoconstriction in dogs by a continuous i.v. infusion of methacholine, then administered either isoflurane or sevoflurane. Ventilation inhomogeneity was quantified by the difference in respiratory phases between the regional alveolar pressures measured at two distinct lobes. We constructed a mathematical model that simulated our experimental results. Both anaesthetics decreased lung resistance (P < 0.01). Isoflurane significantly reduced the indices of inhomogeneity (P < 0.01). Sevoflurane exerted only a tendency to reduce uneven ventilation. Our model simulation suggested that the anaesthetics reduced ventilation inhomogeneity in preference to lung resistance when the dogs suffered from severe bronchoconstriction.

[Influence of sevoflurane on renal medullary blood flow in humans]

Proper anesthetic management is necessary to preserve renal function during anesthesia and surgery. Using ultra-sound color Doppler, we examined the influence of sevoflurane on renal medullary blood flow in 20 adult patients without renal dysfunction. After identifying an interlobar artery in the outer medulla, we measured the velocity of the arterial blood flow before induction of anesthesia, and during sevoflurane anesthesia (1 MAC, 1.5 MAC). The minimum velocity of the interlobar arterial blood flow (Vmin) during wakefulness correlated significantly with creatinine clearance measured preoperatively. We did not find any significant change in Vmin after induction of sevoflurane anesthesia, despite significant decreases in mean arterial blood pressure.

Recognition of allylic substrates in Sulfolobus acidocaldarius geranylgeranyl diphosphate synthase: analysis using mutated enzymes and artificial allylic substrates

We examined the substrate specificity of two mutated geranylgeranyl diphosphate synthases, I-9 and I-11, with respect to several artificial substrates. These mutated enzymes have replacements in the amino acid sequences from positions 170 to 173, which are thought to be a part of the putative substrate binding region. The wild-type enzyme catalyzes the condensation of IPP with a series of (2E)-3-methyl-2-alkenyl diphosphates to give products with carbon numbers between 14 and 21. On the other hand, the mutated enzymes show lower activities for artificial substrates with short alkyl chains than those of the wild-type enzyme though the carbon numbers of the products are similar to those in the case of the wild-type. The mutated enzyme I-11 never accepts artificial substrates shorter than C8. Analysis of additional mutated enzymes revealed that the characteristics of the mutated enzymes arise from a few substitutions within positions 171 to 173. These results indicate that the amino acids in the positions 171 to173 of the geranylgeranyl diphosphate synthase from Sulfolobus acidocaldarius are involved in recognition of short allylic substrates, such as dimethylallyl diphosphate, but not in recognition of the chain length of the products.

Upper airway reflexes during a combination of propofol and fentanyl anesthesia

BACKGROUND

The effects of intravenous anesthetics on airway protective reflexes have not been fully explored. The purpose of the present study was to characterize respiratory and laryngeal responses to laryngeal irritation during increasing doses of fentanyl under propofol anesthesia.

METHODS

Twenty-two female patients anesthetized with propofol and breathing through the laryngeal mask airway were randomly allocated to three groups: (1) eight patients who received cumulative total doses of 200 microg fentanyl given in the form of two doses of 50 microg and one dose of 100 microg spaced 6 min under mechanical controlled ventilation while end-tidal carbon dioxide tension (PCO2) was maintained at 38 mmHg (fentanyl-controlled ventilation group), (2) eight patients who received cumulative total doses of 200 microg fentanyl while breathing spontaneously while end-tidal PCO2 was allowed to increase spontaneously (fentanyl-spontaneous ventilation group), and (3) six spontaneously breathing patients who were anesthetized with propofol alone (propofol group). The laryngeal mucosa of each patient was stimulated by spraying the cord with distilled water, and the evoked responses were assessed by analyzing the respiratory variables and endoscopic images.

RESULTS

Before administration of fentanyl, laryngeal stimulation caused vigorous reflex responses, such as expiration reflex spasmodic panting, cough reflex, and apnea with laryngospasm. Increasing doses of fentanyl reduced the incidences of all these responses, except for apnea with laryngospasm, in a dose-related manner in both the fentanyl-controlled ventilation and the fentanyl-spontaneous ventilation groups. Detailed analysis of endoscopic images revealed several characteristics of laryngeal behavior during the airway reflex responses.

CONCLUSION

Incremental doses of fentanyl depress airway reflex responses in a dose-related manner, except for apnea with laryngospasm.

Overexpression of an archaeal geranylgeranyl diphosphate synthase in Escherichia coli cells

An archaeal geranylgeranyl diphosphate synthase was overexpressed in Escherichia coli cells as fusion proteins. These fusion proteins retained their thermostability and had higher specific activity than did a partially purified native enzyme Previously reported. We purified 24.3 mg of MBP (maltose-binding protein)-fusion protein and 5.4 mg of GST (glutathione S-transferase)-fusion protein from a one-liter culture of E. coli. The MBP-fusion proteins existed in dimer, tetramer, octamer, or dodecamer form, and their product specificities were altered according to the oligomerization. The MBP-fusion protein has protease-sensitive sites in the portion corresponding to geranylgeranyl diphosphate synthase.

Identification of genes affecting lycopene formation in Escherichia coli transformed with carotenoid biosynthetic genes: candidates for early genes in isoprenoid biosynthesis

Although isopentenyl diphosphate is a precursor of isoprenoids in Escherichia coli, the genes and enzymes involved in its biosynthesis have not been identified. Thus, we tried to isolate E. coli mutants deficient in the biosynthesis and their complementary genes by use of an artificial phenotypic screening system employing three carotenoid biosynthetic genes, crtE, crtB, and crtI. Cells were mutagenized with ethylmethanesulfonate, then transformed with a plasmid for expression of the carotenogenic genes. Mutants deficient in biosynthesis of isopentenyl diphosphate were expected to form white colonies, because they are unable to produce enough lycopene, whereas wild-type cells form red colonies. Among large numbers of red colonies, we identified 117 white colonies. Next, we transformed each mutant with an E. coli genomic library. Twenty-nine complementary genes that restore red color of host colonies were isolated. A homology search and further complementation study using subcloned genes revealed that the true complementary genes encode isopentenyl diphosphate isomerase, subunits of ATP synthase, enzymes of the Krebs cycle, some aldehyde dehydrogenases, phosphate acetyltransferase, and enzymes which relate to the biosynthesis of ubiquinones and menaquinones. Two unknown genes were also found, designated elb1 and 2, which may be involved in the early steps of isoprenoid biosynthesis.

Expression of Xenopus laevis translation initiation factor 4E (eIF-4E) by baculovirus-insect cell system

A gene encoding Xenopus laevis eIF-4E was cloned into a transfer vector, and its gene expression was attempted in cells of E. coli, yeast and insect. Effective expression of the active eIF-4E was achieved in the soluble fraction of the insect cell Sf9, which was infected with the recombinant baculovirus. Overexpression of the eIF-4E protein caused remarkable change in the shape of the cells.

Preoperative nocturnal desaturations as a risk factor for late postoperative nocturnal desaturations

Severe postoperative hypoxaemia during sleep may increase the risk of postoperative cardiovascular complications. We hypothesized that the severity of hypoxic episodes after surgery are related to the presence of preoperative sleep-disordered breathing (SDB). We tested this hypothesis in a multicentre study designed to elucidate the major risk factors for development of postoperative nocturnal desaturations. We performed overnight oximetry before operation and for one night between the second and fourth day after operation in 80 patients undergoing major surgery. We calculated oximetry variables such as oxygen desaturation index (ODI), defined as the number of oxygen desaturations exceeding 4% below baseline, percentage time spent at SpO2 < 90% (CT90, %) and lowest SpO2 value. After operation, although the change in ODI was not significant (P = 0.34), deterioration in CT90 and lowest SpO2 values were significant (P = 0.036 and P = 0.007, respectively). Multivariate analysis of possible risk factors for postoperative desaturations revealed that preoperative hypoxaemia and apnoea witnessed by others were highly correlated with postoperative hypoxaemia.

Comparison of static mechanical properties of the passive pharynx between normal children and children with sleep-disordered breathing

Collapsibility of the active pharynx, where active contraction of the upper airway muscles is evident, was previously reported to be higher in children with obstructive sleep apnea (OSA) than in those with primary snoring during sleep. Contribution of neuromuscular and anatomic factors to the increased collapsibility, however, was not estimated. We therefore evaluated collapsibility of the passive pharynx, in which upper airway muscle activities were eliminated. Our aim in the present study was to test the hypothesis that children with sleep-disordered breathing (SDB) have a structurally narrowed and a more collapsible pharynx compared with normal children. The static pressure/area relationship of the passive pharynx was endoscopically quantified in 14 children with SDB and in 13 normal children under general anesthesia with complete paralysis. The majority of children with SDB primarily closed their airways at levels of enlarged adenoids and tonsils with positive closing pressure (Pclose) (3.5+/-4.3 cm H2O), whereas half of the normal children closed their airways at the soft palate edges and the other half at the tongue bases with subatmospheric Pclose (-7.4+/-4.9 cm H2O). Cross-sectional area of the narrowest segment was significantly smaller in SDB children than in normal children. Interestingly, collapsibility of the retropalatal and retroglossal segments significantly increased in SDB children, compared with the normal subjects. We conclude that anatomic factors play a significant role in the pathogenesis of pediatric OSA and that predisposing structural abnormalities of the entire pharynx are likely to contribute to manifestation of OSA in addition to enlarged adenoids and tonsils.

Pathological changes in the formation of Helicobacter pylori-induced gastric lesions in Mongolian gerbils

We examined pathological changes in the formation of Helicobacter pylori-induced gastric lesions in Mongorian gerbils. H. pylori (NCTC11637) was orally administered once to the animals and was detected in the gastric mucosa of all gerbils given the bacteria. The number of viable H. pylori increased during the initial two weeks and thereafter reached a plateau level. The initial pathological changes were found at one week, ie, edema/congestion and a white viscous substance only in the antrum. At two weeks, superficial damage appeared in the antrum, although inflammatory cell infiltration had not occurred. Gastritis with lymphoid follicles was observed in the antrum and fundus from three weeks. At four weeks, mucosal lesions were detected as a few hemorrhagic spots in the fundus adjacent to the antrum. In the control animals, however, no pathological changes were observed even at four weeks. In the gastric mucosa infected with H. pylori, myeloperoxidase activity was negligible at two weeks, but was extremely elevated at four weeks. Similarly, neutrophil chemotactic activity was only slightly increased at two weeks, but was markedly elevated at four weeks. These results indicate that H. pylori infection induces initial pathological changes only in the antrum, but mucosal lesions occur in the fundus adjacent to the antrum. Furthermore, it is demonstrated that the initial superficial damage is generated by factors other than chemokines and neutrophil-associated factors, although mucosal inflammation may contribute to the subsequent formation of lesions and ulcers.

Subunit swapping in the Mex-extrusion pumps in Pseudomonas aeruginosa

Pseudomonas aeruginosa encodes three sets of antibiotic extrusion proteins designated as MexA,B.OprM, MexC,D-OprJ and MexE,F-OprN regulated by the nalB, nfxB and nfxC genes, respectively. MexB,D,F, OprM, J,N and MexA,C,E function as the inner membrane pumps, the outer membrane channels and the membrane fusion proteins, respectively. To investigate the possibility of subunit interchangeability, we constructed the following combinations of chimeric pumps: MexA,D-OprM/delta MexB, MexC,B-OprM/delta MexA, and MexA,B-OprJ/delta OprM. The strains producing MexA,D-OprM/delta MexB and MexC,B-OprM/delta MexA failed to restore the antibiotic resistance shown in the strains producing the natural combinations of the subunit proteins. These results suggested that the inner membrane components cannot be interchanged. In contrast, the stains producing MexA,B-OprJ/delta OprM exhibited higher resistance to several antibiotics than the mutant lacking OprM and lower resistance than the strain overexpressing OprM. This result suggests that OprJ may complement the OprM function partially. A spectrum of antibiotics, of which the minimum inhibitory concentrations were restored partially by the complementation, was the same as the spectrum to which the nalB type mutant shows resistance. We surmised from these results that the MexA/MexB unit sustains the substrate specificity of the MexA,B-OprM machinery.

Lysozyme loading and release from hydrogels carrying pendant phosphate groups

To develop a polymeric matrix for efficiently loading cationic biomolecules, polyelectrolyte hydrogels carrying pendant phosphate groups were synthesized by copolymerizing 2-methacryloyloxyethyl dihydrogen phosphate with N-isopropylacrylamide and N, N1-methylene-bis-acrylamide. The phosphate-carrying monomer yielded anionic hydrogels, which formed ionic complexes with the cationic protein, lysozyme. It was shown that the amount of complexed lysozyme reached 2.1 g g-1 dry gel, corresponding to 1.3 x 10(-3) mol phosphate group per gram lysozyme, when 40 mol% of phosphate-carrying monomer was incorporated in a hydrogel. When the hydrogel complexed with lysozyme was placed in deionized water and various KCl solutions, of varying concentrations of up to 0.5 M KCl, no lysozyme was released in deionized water, while increasing amounts of lysozyme were released as the KCl concentration increased. This confirmed that lysozyme was loaded in the hydrogel through electrostatic interactions. It was further found that the complexed lysozyme retained its enzymatic activity after being released from the hydrogel. These results suggest the use of this system for the controlled release of cationic protein drugs.

Hypercapnia enhances the development of coughing during continuous infusion of water into the pharynx

We investigated the effects of increasing CO2 ventilatory drive on the coordination of respiration and reflex swallowing elicited by continuous infusion of distilled water into the pharynx (2.5 ml/min) in 11 normal subjects. Ventilation was monitored using a pneumotachograph and swallowing was recorded by submental electromyogram. The CO2 ventilatory drive was increased by addition of external dead space, while ventilation, the frequency of swallows, and the timing of swallows in relation to the phases of the respiratory cycle were measured at steady-state conditions. We found that the CO2 ventilatory response is not influenced by continuous reflex swallowing but that hypercapnia influences the timing and frequency of these swallows. Signs of aspiration were never observed during continuous infusion of water at eucapnia, but seven of 11 subjects showed laryngeal irritation and/or pending aspiration during hypercapnia, and the incidence of laryngeal irritation was higher the greater the PCO2. Detailed analysis of laryngeal irritations consisting of single coughs in seven subjects revealed that the majority of laryngeal irritations occurred when swallows coincided with expiratory-inspiratory transition or when swallows coincided with inspiration, whereas laryngeal irritation after an expiratory swallow was never observed. These results suggest that the automatic respiratory control system is not influenced by continuous swallowing but that the coordination of swallowing and respiration may be compromised during hypercapnia.

[Regional cerebral oxygen saturation as a monitor of cerebral oxygenation and perfusion during deep hypothermic circulatory arrest and selective cerebral perfusion]

In order to evaluate cerebral oxygenation and perfusion during deep hypothermic circulatory arrest (DHCA) and selective cerebral perfusion (SCP), continuous measurement of regional cerebral oxygen saturation (rSO2) by near-infrared spectroscopy (NIRS) was performed. Two patients undergoing aortic arch surgery performed under DHCA and SCP were studied. 1) Circulatory arrest produced a continuous decrease in rSO2. Introduction of SCP increased rSO2 to even above the pre-circulatory arrest level (reperfusion hyperoxia). 2) During SCP, changes in rSO2 correlated well with the naso-pharyngeal temperature, SCP flow rate, and level of carbon-dioxide insufflation to SCP. 3) These changes in rSO2 paralleled with those of jugular venous hemoglobin saturation (SjO2) measured simultaneously, although SjO2 frequently exhibited artifacts. We conclude that rSO2 measurement may be a non-invasive and continuous measure in the evaluation of cerebral oxygenation and perfusion during DHCA and SCP.

Stimulatory effects of hepatocyte growth factor on hemopoiesis of SCF/c-kit system-deficient mice

In this study, we report that W/W mutant mice, which have severe macrocytic anemia caused by a deficit of extracellular domain in c-kit molecules and therefore die perinatally, have hemopoietic stem cells (HSCs) and mature hematolymphoid cells in the bone marrow (BM), thymus, and spleen, although there are significant decreases in cell counts. Moreover, the mitogen-induced proliferative response, mixed lymphocyte reaction, and anti-SRBC plaque formation of spleen cells in W/W mice are similar to those in age-matched +/? littermates and normal mice, suggesting that the SCF/c-kit system is necessary for cell proliferation but not essential for HSCs to differentiate. We next examine the stimulatory effects of hepatocyte growth factor (HGF) on hemopoiesis in W/W mice. HGF has a stimulatory effect on the colony formation (CFU-C) of W/W BM cells when cultured using either a methylcellulose assay (containing cytokines) or a long-term culture (LTC) assay. A similar stimulatory effect of HGF is observed in the other W or SI locus-mutant mice (W/Wv and SI/SId mice), which show less severe anemia than W/W. The numbers of nonadherent cells and cobblestone colonies significantly increase in the LTCs using their BM cells. In addition, in vivo administration of HGF shows a transient increase in the CFU-C counts in BM cells and peripheral blood cells. RBC, WBC, and platelet counts also increased. These results suggest that the SCF/c-kit system is not essential to hemopoiesis but that a compensatory system such as the HGF/c-met system functions in the SCF/c-kit system-deficient mice.

The inhibitory influence of pulmonary vagal afferents on respiratory distress induced by airway occlusion in halothane-anesthetized cats

Although the sensation of dyspnea is common, the mechanisms underlying the sensation have not been fully elucidated. Dyspnea, which is a subjective sensation induced by various respiratory and nonrespiratory stimuli, ranges in intensity from an awareness of difficulty in breathing to an incapacitating state of respiratory distress. It need not be an all or none concept when tolerable; however, intolerable dyspnea is often accompanied by some kind of escape response. In a previous study, we developed a new concept of minimum alveolar anesthetic concentration for airway occlusion (MAC-AOR). Using this model, we assessed the influence of pulmonary vagal afferents on respiratory distress induced by airway occlusion. Adult cats (n = 13) of both sexes weighing 2.7-5.6 kg (3.9 +/- 0.3 kg, mean +/- SE) were anesthetized with halothane and tracheally intubated. After determination of MAC-AOR, anesthesia was maintained with the highest concentration of halothane permitting the positive motor response identified by visual inspection or electromyogram (EMG) of the forearm, usually of the head or extremities. Twisting or jerking of the head was considered a positive response, but twitching or grimacing was not. A slight movement of the shoulder and/or the extremities was not considered positive, nor were coughing, swallowing and chewing, or rigidity recognized as the increase of tonic activity on the forearm EMG. The duration from the start of airway occlusion to the onset of the positive response (DOCCL) was considered as behavioral measures of the tolerable limit of respiratory distress. DOCCL was measured before (Control 1), during, and after (Control 2) lung expansion induced by the injection of the inhaled gas of 5 mL/kg or 10 mL/kg (LE5 or LE10) at functional residual capacity level. Subsequently, 6 of 13 cats received bilateral vagotomies, and the same procedure was repeated at the same concentration as stated above. Then, MAC-AOR after vagotomy was determined again. Before vagotomy, the values of DOCCL during lung expansion (238 +/- 30 s during LE5 and 288 +/- 24 s during LE10) were significantly longer than Control 1 (169 +/- 29 s) and Control 2 (154 +/- 29 s) values (P < 0.01). After vagotomy, the effect of lung expansion on DOCCL was totally abolished. MAC-AOR after vagotomy (1.4% +/- 0.1%) was significantly higher than that before vagotomy (1.1% +/- 0.1%) (P < 0.01). We have demonstrated that vagotomy abolishes the prolongation effect of the lung expansion on DOCCL and increases the value of MAC-AOR in this animal model. These results suggest that pulmonary vagal afferents play an important role in relief of respiratory distress developed during airway occlusion.

IMPLICATIONS

In anesthetized cats, we found that lung expansion reduces the tolerable limit to airway occlusion and vagotomy decreased minimum alveolar anesthetic concentration for airway occlusion, which suggests that pulmonary vagal afferents play an important role in relief of respiratory distress.

[Survey of the sensitivities of clinical isolates to antibacterial agents (annual report)]

Research groups were formed in 21 institutions nationwide to investigate carbapenem resistance. The activities of various antibacterial agents, principally carbapenems were tested against clinical isolates collected from these institutions. The broth microdilution method was used to determine the minimum inhibitory concentrations (MIC) of 17 antibacterial agents for 1,282 strains of 11 bacterial species isolated at all institutions between October and December 1995. The results were as follows: 1. Carbapenems exhibited strong antibacterial activities against MSSA and Streptococcus pneumoniae. Their activities against Enterococcus faecalis were comparable to that of ABPC. Carbapenems showed low activities against MRSA. 2. OFLX exhibited the greatest antibacterial activity against Haemophilus influenzae, followed by MEPM. The antibacterial activities of the other carbapenems were comparable to those of FMOX and CTM. 3. The carbapenems showed high activities against Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, and Bacteroides fragilis group. Their activities were greater than that exhibited by other beta-lactam antibacterial agents. The carbapenems also exhibited greater antibacterial activities against Serratia marcescens than the other beta-lactam antibacterial agents, but some resistant strains were detected. 4. The antibacterial activities of carbapenems against Pseudomonas aeruginosa were comparable to those of CAZ, AZT, AMK.

Functional analyses of the domain structure in the Holliday junction binding protein RuvA

BACKGROUND

Homologous recombination is crucial for genetic diversity and repairing damaged chromosomes. In Escherichia coli cells, the RuvA, RuvB and RuvC proteins participate in the processing of an important intermediate, the Holliday junction. The RuvA-RuvB protein complex facilitates branch migration of the junction, depending on ATP hydrolysis. The atomic structure of RuvA should enable critical questions to be addressed about its specific interactions with the Holliday junction and the RuvB protein.

RESULTS

The crystal structure of RuvA shows the tetrameric molecules with a fourfold axis at the center. Each subunit consists of three distinct domains, some of which contain important secondary structure elements for DNA binding. Together with the detailed structural information, the biochemical assays of various mutant RuvA proteins and domains, isolated by partial proteolysis, allowed us to define the functional roles of these domains in Holliday junction binding and the RuvB interaction.

CONCLUSIONS

The RuvA molecule is formed by four identical subunits, each with three domains, I, II and III. The locations of the putative DNA-binding motifs define an interface between the DNA and the Holliday junction. Domain III is weakly attached to the core region, comprising domains I and II; the core domains can form a tetramer in the absence of domain III. Functional analyses of the mutant proteins and the partial digestion products, including Holliday junction binding and branch-migration assays, revealed that domain III and the preceding loop are crucial for RuvB binding and branch migration, although this region is not required for the junction-DNA binding.

Brush cytology of herpes simplex virus infection in oral mucosa: use of the ThinPrep processor

Evaluation was made of oral scraping specimen using Cytobrush from 11 patients with clinical suspicious lesions for herpes simplex virus (HSV) infection. In this study, oral brush cytology prepared using an automated smear apparatus (ThinPrep method) has been applied. The smears prepared by ThinPrep are equally well suited for screening purposes, producing highly cellular specimens with well-preserved cytoplasm and nuclei. The results obtained on the 11 patients, four cytologic specimens, showed pathognomonic viral cellular changes of HSV infection. Viral isolation studies were performed on 10 of the 11 patients and ten specimens tested positive for HSV by culture. Of the ten HSV positive isolates, six were positive by either cytology or immunocytochemical staining. Of the two smears showing HSV positive cells, both smears were also confirmed by in situ hybridization (ISH) with a biotinylated clone DNA probe. Using the ICC technique, detection of HSV antigen in oral scraping smears was of great value in the diagnosis of oral HSV infection, especially in cases of equivocal lesions. Oral cytology by means of ThinPrep method obviously deserves additional trials as an adjunct in the cytology of HSV-suspected lesions.

Minimum alveolar anesthetic concentrations for airway occlusion in cats: a new concept of minimum alveolar anesthetic concentration-airway occlusion response

Minimum alveolar anesthetic concentration (MAC) is defined as an end-tidal concentration of inhaled anesthetic required to prevent purposeful movement (positive motor response) in 50% of subjects to somatic noxious stimuli. Although MAC for visceral noxious stimuli has not been well investigated, airway occlusion can be a noxious respiratory stimulus that can induce a visceral sensation of choking. In this study, MAC for airway occlusion (MAC-AOR) was determined during halothane, isoflurane, and sevoflurane anesthesia and compared with the MAC values for somatic noxious stimuli such as toe pinch (MAC-pinch) or tetanic stimulus (MAC-tetanus) in cats. Thirty-four adult cats were used. In 24 cats, the motor responses to three different stimuli (toe pinch, tetanic stimulus, and airway occlusion for 6 min) were observed during inhaled anesthesia and rated as positive or negative. The concentration of an inhaled anesthetic was changed in steps of 0.1%-0.2 vol% until the bracketing procedure (i.e., the highest concentration of inhaled anesthetic permitting a positive motor response and the lowest concentration preventing the response were determined) was completed. In 10 cats, the effect of anesthetic duration on MAC-AOR was also investigated. Each mean MAC (MAC-pinch, MAC-AOR, and MAC-tetanus, respectively) was as follows: halothane 0.99, 1.13, and 1.46; isoflurane 1.50, 1.65, and 2.22; and sevoflurane 3.07, 3.38, and 3.95. The first and last MAC-AOR values determined during 6-h halothane anesthesia were 1.10 and 1.11, respectively. In conclusion, airway occlusion can be a noxious stimulus and can induce an all-or-none type of motor response, depending on the depth of inhalational anesthesia in cats. This phenomenon can permit the introduction a new concept of MAC-AOR.

IMPLICATIONS

Airway occlusion can be a noxious visceral stimulus and induce all-or-none type of motor response in cats, depending on the depth of inhalational anesthesia. This permits the introduction of a new concept of minimum alveolar anesthetic concentration airway occlusion response.

In vivo antibacterial activity of a prodrug of NM394, a thiazetoquinoline carboxylic acid derivative

NM394 (6-fluoro-1-methyl-4-oxo-7-(1-piperazinyl)-4H-[1,3]-thiazeto [3,2-a]quinoline-3-carboxylic acid) has potent, broad-spectrum antibacterial activity in vitro, but not in vivo. To increase the bioavailability of NM394, various prodrugs were synthesized and tested. One of them, NM441, an N-(5-methyl-2-oxo-1,3-dioxol-4-yl) derivative, showed potent in vivo antibacterial activity. Using thin-layer chromatography-bioautography, we confirmed that after oral administration, NM441 was readily absorbed and hydrolyzed to NM394. Other prodrugs of NM394 were only partially metabolized to NM394. In pharmacokinetic studies in mice and monkeys, we found that the blood levels of NM394 were 7.8 and 5.9 times greater, respectively, when NM441 rather than NM394 was administered. These findings suggest that NM441 is an effective prodrug of NM394.

Emergence of a unique O3:K6 clone of Vibrio parahaemolyticus in Calcutta, India, and isolation of strains from the same clonal group from Southeast Asian travelers arriving in Japan

Active surveillance of Vibrio parahaemolyticus infection among hospitalized patients in Calcutta, India, was initiated in January 1994. The incidence of cases of V. parahaemolyticus infection suddenly increased in February 1996 and has remained high since then. One hundred thirty-four strains of V. parahaemolyticus isolated from January 1994 to August 1996 were examined for serovar, the presence of the thermostable direct hemolysin gene (tdh) and tdh-related hemolysin genes (trh1 and trh2), production of urease, and antibiogram. Strains of the O3:K6 serovar appeared for the first time in February 1996. The O3:K6 serovar strains accounted for 50 to 80% of the strains isolated during the high-incidence period (February to August 1996). All of the serovar O3:K6 strains carried the tdh gene but not the trh genes and did not produce urease. All of the isolates except two were sensitive to all of the antibiotics tested. These and the results of analysis by an arbitrarily primed PCR method indicated that the O3:K6 serovar strains belong to a unique clone. When the O3:K6 serovar strains, isolated from travelers arriving in Japan from Southeast Asian countries, were compared by the arbitrarily primed PCR method, the strains isolated between 1982 and 1993 were distinct from Calcutta O3:K6 while the strains isolated in 1995 and 1996 were indistinguishable from the Calcutta O3:K6 strains. The results suggest that this unique O3:K6 clone may have become prevalent not only in Calcutta but also in Southeast Asian countries very recently. Not only the O3:K6 strains but also the non-O3:K6, tdh-bearing strains isolated in 1996 produced thermostable direct hemolysin at high levels, and thus the level of hemolysin produced does not appear to have influenced the high incidence of serovar O3:K6 strains.