Prostaglandin E prevents indomethacin-induced gastric and intestinal damage through different EP receptor subtypes

Gastrointestinal ulcerogenic effect of indomethacin is causally related with an endogenous prostaglandin (PG) deficiency, yet the detailed mechanism remains unknown. We examined the effect of various PGE analogues specific to EP receptor subtypes on these lesions in rats and mice, and investigated which EP receptor subtype is involved in the protective action of PGE(2). Fasted or non-fasted animals were given indomethacin s.c. at 35 mg/kg for induction of gastric lesions or 10-30 mg/kg for intestinal lesions, and they were killed 4 or 24 h later, respectively. Various EP agonists were given i.v. 10 min before indomethacin. Indomethacin caused hemorrhagic lesions in both the stomach and intestine. Prior administration of 16,16-dimethyl PGE(2) (dmPGE(2)) prevented the development of damage in both tissues, and the effect in the stomach was mimicked by 17-phenyl PGE2 (EP1), while that in the small intestine was reproduced by ONO-NT-012 (EP3) and ONO-AE-329 (EP4). Butaprost (EP2) did not have any effect on either gastric or intestinal lesions induced by indomethacin. Similar to the findings in rats, indomethacin caused gastric and intestinal lesions in both wild-type and knockout mice lacking EP1 or EP3 receptors. However, the protective action of dmPGE(2) in the stomach was observed in wild-type and EP3 receptor knockout mice but not in mice lacking EP1 receptors, while that in the intestine was observed in EP1 knockout as well as wild-type mice but not in the animals lacking EP3 receptors. These results suggest that indomethacin produced damage in the stomach and intestine in a PGE(2)-sensitive manner, and exogenous PGE(2) prevents gastric and intestinal ulcerogenic response to indomethacin through different EP receptor subtypes; the protection in the stomach is mediated by EP1 receptors, while that in the intestine mediated by EP3/EP4 receptors.

Inhibition of both COX-1 and COX-2 is required for development of gastric damage in response to nonsteroidal antiinflammatory drugs

We examined the gastric ulcerogenic property of selective COX-1 and/or COX-2 inhibitors in rats, and investigated whether COX-1 inhibition is by itself sufficient for induction of gastric damage. Animals fasted for 18 h were given various COX inhibitors p.o., either alone or in combination, and they were killed 8 h later. The nonselective COX inhibitors such as indomethacin, naproxen and dicrofenac inhibited PG production, increased gastric motility, and provoked severe gastric lesions. In contrast, the selective COX-2 inhibitor rofecoxib did not induce any damage in the stomach, with no effect on the mucosal PGE(2) contents and gastric motility. Likewise, the selective COX-1 inhibitor SC-560 also did not cause gastric damage, despite causing a significant decrease in PGE(2) contents. The combined administration of SC-560 and rofecoxib, however, provoked gross damage in the gastric mucosa, in a dose-dependent manner. SC-560 also caused a marked gastric hypermotility, whereas rofecoxib had no effect on basal gastric motor activity. On the other hand, the COX-2 mRNA was expressed in the stomach after administration of SC-560, while the normal gastric mucosa expressed only COX-1 mRNA but not COX-2 mRNA. These results suggest that the gastric ulcerogenic property of conventional NSAIDs is not accounted for solely by COX-1 inhibition and requires the inhibition of both COX-1 and COX-2. The inhibition of COX-1 up-regulates the COX-2 expression, and this may counteract the deleterious influences, such as gastric hypermotility and the subsequent events, due to a PG deficiency caused by COX-1 inhibition.

Determination of intracellular and extracellular beta-lactamase activities of Pseudomonas aeruginosa after exposure to beta-lactams in vitro and in vivo

Beta-lactamase production in Pseudomonas aeruginosa was determined in in-vitro models and in rat pouch infection models after exposure to ceftazidime, imipenem, and piperacillin. Exposure of 28 P. aeruginosa strains to 1/4 minimum inhibitory concentration (MIC) of ceftazidime, imipenem, and piperacillin for 24 h enhanced intracellular beta-lactamase activities in 14, 22, and 6 strains, respectively, of the 28 clinical strains tested, and enhanced extracellular beta-lactamase activities which were not detected without exposure to antibiotics, in 7, 23, and 1 of the 28 strains, respectively. Extracellular beta-lactamase activity from P. aeruginosa S-1278, producing an inducible beta-lactamase, scarcely increased after exposure to ceftazidime and piperacillin 24 h after incubation, while the activity increased after exposure to imipenem over the range of 1/8 to 8 MIC. In the rat granuloma pouch models infected with P. aeruginosa S-1278, ceftazidime and piperacillin, after single administration (20 mg/kg) and serial administration (20 mg/kg per day x 3 days), did not enhance extracellular beta-lactamase activities. However, the activities were enhanced with single and serial administrations of imipenem, and levels over 10 mU/ml were detected until the third day. The beta-lactamase activity, similar to the activity found in rat pouches after serial administration of imipenem, inactivated various cephalosporins. In conclusion, extracellular beta-lactamase activity was detected both in vitro and in vivo after exposure to a good inducer, and extracellular beta-lactamase remained at infection site at levels that could inactivate cephalosporins.

Effect of consecutive lower-dose cisplatin in enhancement of 5-fluorouracil cytotoxicity in experimental tumor cells in vivo

It is known that cisplatin (CDDP) potentiates the cytotoxicity of 5-fluorouracil (5-FU), and that the biochemical mechanism is an increase in the intracellular reduced folate levels in the tumor cells. We investigated the effect of consecutive administration with lower-dose CDDP on intracellular accumulation of reduced folate and the activity of methionine synthase, a key enzyme in intracellular methionine synthesis. When CDDP (1 mg/kg) was administered i.p. to ascitic Yoshida sarcoma-bearing rats for 4 consecutive days, both the reduced folate levels and methionine synthase activity in the cells significantly increased, as the same as a single 5 mg/kg dose of CDDP. Furthermore, when Yoshida sarcoma-bearing rats were pre-treated with 1 mg/kg CDDP for 5 consecutive days, [14C]L-methionine incorporation into the isolated ascitic cells was significantly inhibited as compared to that in non-treated cells, suggesting that consecutive administration of lower-dose CDDP is capable of inducing the intracellular modulation of reduced folate levels and methionine synthase activity via inhibition of cellular uptake of methionine. In addition, 5-day administration of lower-dose (1 mg/kg) CDDP potentiated the antitumor effect of 5 mg/kg S-1, a new oral preparation of tegafur, given for 7 consecutive days, and this combined effect was almost similar to the antitumor effect of a combination of S-1 and a single conventional dose (5 mg/kg) of CDDP. Consecutive lower-dose CDDP also may be concluded to act as an important modulator of the enhancement of 5-FU cytotoxicity in experimental tumors.

Involvement of 5-hydroxytryptamine(1A) receptors in nicotine-induced tail tremor in rats

Involvement of the serotonergic system in tail tremor induced by repeated administration of nicotine was investigated in rats. Tail tremor induced by nicotine (0.5 mg/kg, s.c.) was suppressed by a 5-HT(1A) receptor antagonist, N-¿2-[4-(2-methoxyphenyl)-1-piperazinyl-]ethyl¿-N-(2-pyridinyl)cycloh exanecarboxamide trihydrochloride (WAY-100635; 0.3-3 mg/kg, i.p.), but not by a 5-HT(2) receptor antagonist, ketanserin (0.1-0.3 mg/kg, i.p). The 5-HT(1A) receptor agonists, buspirone (1-20 mg/kg, i.p.), gepirone (1-10 mg/kg, i.p.), tandospirone (1-10 mg/kg, i.p.) and (+/-)-8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT; 0.01-0.1 mg/kg, s.c.), enhanced the tail tremor. The enhancement of tail tremor by buspirone (10 mg/kg, i.p.) was blocked by WAY-100635 (0.3-3 mg/kg, i.p.). These findings suggest that nicotine-induced tail tremor is mediated by 5-HT(1A) receptors and that 5-HT(1A) receptor antagonists are effective in the treatment of tremor.

Bcl-2 in cell-cycle regulation of hematopoietic cells by transforming growth factor-beta1

We reported that several growth factors regulate the doubling time of hematopoietic progenitor cells by modulating the time required to pass through the G1 phase. As recent studies revealed the link between cell death and cell-cycle progression, we asked if cell death regulators such as Bcl-2 play a role in regulating the cell-cycle of hematopoietic cells by growth factors. Among growth factors, transforming growth factor-beta1 (TGF-beta1), a negative regulator of hematopoiesis, was chosen. When a large number of cells was required for analysis, we used IL-3-dependent Ba/F3 cells instead of primary hematopoietic progenitor cells because the response of Ba/F3 cells to TGF-beta1 was similar to that of primary hematopoietic progenitor cells. TGF-beta1 decelerated the cell-cycling of hematopoietic cells by inducing a delay in G1 to S phase transition, an event associated with increase in the level of Bcl-2 as well as p27, a cyclin/cyclin-dependent kinase inhibitor. In experiments using Ba/F3 cells with the potential to produce Bcl-2 in an inducible manner, Bcl-2 apparently functions upstream of p27. The effects of TGF-beta1 on Bcl-2 and p27 expression as well as cell growth were abrogated by c-kit ligand. These findings suggest that Bcl-2 plays a crucial role in regulating the cell-cycle of hematopoietic progenitor cells.

Identification of CD72 as a lymphocyte receptor for the class IV semaphorin CD100: a novel mechanism for regulating B cell signaling

We have identified the lymphocyte semaphorin CD100/Sema4D as a CD40-inducible molecule by subtractive cDNA cloning. CD100 stimulation significantly enhanced the effects of CD40 on B cell responses. Administration of soluble CD100 markedly accelerated in vivo antigen-specific antibody responses. CD100 receptors with different binding affinities were detected on renal tubular cells (K(d) = approximately 1 x 10(-9)M) and lymphocytes (K(d) = approximately 3 x 10(-7)M). Expression cloning revealed that the CD100 receptor on lymphocytes is CD72, a negative regulator of B cell responsiveness. CD72 thus represents a novel class of semaphorin receptors. CD100 stimulation induced tyrosine dephosphorylation of CD72 and dissociation of SHP-1 from CD72. Our findings indicate that CD100 plays a critical role in immune responses by the novel mechanism of turning off negative signaling by CD72.

Characterization of the protease-activated receptor-1-mediated contraction and relaxation in the rat duodenal smooth muscle

Activation of protease-activated receptor-1 (PAR-1) produces a dual action, apamin-sensitive relaxation followed by contraction, in the rat duodenal smooth muscle, which is partially dependent on activation of L-type Ca2+ channels, protein kinase C (PKC) or tyrosine kinase (TK), and resistant to tetrodotoxin. The present study further characterized the PAR-1-mediated duodenal responses. Removal of extracellular Ca2+ as well as SK&F96365 reduced the contraction due to the PAR-1 agonist TFLLR-NH2 (TFp-NH2) by 60-80% that was similar to the extent of the inhibition by nifedipine. Lowering of the extracellular Na+ concentration, but not IAA-94, a Cl- channel inhibitor, reduced both the PAR-1-mediated contraction and relaxation by about 50%. U73122, a phospholipase C (PLC) inhibitor, or wortmannin, a phosphatidyl inositol 3'-kinase (PI3K) inhibitor, significantly reduced the PAR-1-mediated contraction, but not the relaxation, by itself, as the PKC inhibitor GF109203X and the TK inhibitor genistein did. U73122 or wortmannin, like GF109203X, when applied in combination with genistein, significantly reduced the PAR-1-mediated relaxation. The relaxation was resistant to antagonists of PACAP receptors, VIP receptors and P2 purinoceptors. Thus, the PAR-1-mediated contraction is considered to be dependent on intracellular and extracellular Ca2+, the influx of the latter being induced through activation of L-type Ca2+ channels triggered by the enhanced Na+ permeability, and that PLC and PI3K, in addition to PKC and TK, are involved in the PAR-1-mediated dual responses. Furthermore, non-adrenergic, non-cholinergic nerve neurotransmitter candidates that may modulate K+ channels do not appear to contribute to the relaxation by PAR-1 activation.

Effects of long-term treatment with calcium antagonists on periarterial nerve function in the mesenteric artery of spontaneously hypertensive rats

The effect of long-term treatment with dihydropyridine calcium antagonists (amlodipine, pranidipine, nicardipine) on the periarterial nerve function was investigated in the perfused mesenteric vascular bed isolated from spontaneously hypertensive rat (SHR). Male 8-week-old SHR received amlodipine (0.01% and 0.02%) and nicardipine (0.1%) in drinking water and pranidipine (0.0035% and 0.035%) in rat chow for 7 weeks. Mean blood pressure in SHR was significantly lowered by long-term treatment with each calcium antagonist. In mesenteric vascular preparations treated with each calcium antagonist, vasoconstriction induced by periarterial nerve stimulation (PNS; 4, 8 and 12 Hz) was significantly smaller than that in non-treated SHR. The PNS (8 Hz)-evoked norepinephrine (NE) overflow in the perfusate was significantly decreased by amlodipine and pranidipine treatment, whereas nicardipine-treatment significantly enhanced the overflow of NE. In preparations with active tone produced by methoxamine and guanethidine, the PNS-induced vasodilation mediated by calcitonin gene-related peptide (CGRP)-containing (CGRPergic) vasodilator nerves was not affected by these drugs. These results suggest that long-term treatment of SHR with long-acting drugs, amlodipine and pranidipine, reduces sympathetic adrenergic nerve function but calcium antagonists have no effect on CGRPergic nerve function.

Permissive role of neutrophils in pathogenesis of indomethacin-induced gastric lesions in rats

INTRODUCTION

We examined the possible role of neutrophils in the pathogenesis of indomethacin-induced gastric lesions, in comparison with prostaglandin (PG) deficiency.

MATERIAL AND METHODS

Rats were given indomethacin (35 mg/kg, s.c.) and killed 4 hr later. Gastric motility, mucosal PGE2 levels, and myeloperoxidase (MPO) activity were measured following indomethacin. Atropine was given s.c. 30 min before administration of indomethacin, while 16, 16-dimethyl PGE2 (dmPGE2) or anti-rat neutrophil antiserum (ANS) was given i.v. 10 min or 1 hr, respectively, before indomethacin treatment.

RESULTS

Indomethacin reduced PGE2 contents in the stomach and produced hemorrhagic lesions in the stomach, with an increase of gastric motility and MPO activity. Indomethacin-induced gastric lesions were significantly prevented by dmPGE2 as well as atropine, at any time points during a 4 hr-test period. By contrast, the pretreatment of ANS did not prevent the development of gastric lesions when examined at either 1, 2 or 3 hr following indomethacin, but significantly reduced the severity of these lesions at 4 hr after indomethacin treatment. Both dmPGE2 and atropine inhibited the increase of gastric motility and MPO activity in response to indomethacin, whereas ANS prevented the increase of MPO activity, without any effect on the gastric hypermotility.

CONCLUSION

These results confirmed that indomethacin-induced gastric lesions occurred in association with gastric hypermotility, in both atropine and PG-sensitive manners, and further suggest that the neutrophil activation/migration is not sufficient by itself to induce damage in the stomach and may be implicated in the process of later extension of damage.

A new model of pulmonary superinfection with Aspergillus fumigatus and Pseudomonas aeruginosa in mice

We have produced a new model of pulmonary super-infection with Aspergillus fumigatus and Pseudomonas aeruginosa in immunosuppressed mice. Male ICR mice were given an intratracheal inoculation of 4 x 10(5) conidia of A. fumigatus in agar beads, and were immunosuppressed with 100 mg/kg subcutaneous injections of cortisone acetate on days 7, 9, 12, 14, and 16 after inoculation. Twelve days after inoculation, with the agar beads, the mice were challenged with the intranasal instillation of 2 x 10(6) CFU of P. aeruginosa. The survival rates of superinfected, A. fumigatus-alone, P. aeruginosa-alone, and non-infected mice were 50%, 30%, 90%, and 100% 14 days after pseudomonal infection (26 days after inoculation of A. fumigatus), respectively. In the superinfected mice, both A. fumigatus and P. aeruginosa were detected more than 10 days after pseudomonal infection (22 days after inoculation of A. fumigatus). Histopathological examination revealed peribronchial necrosis around A. fumigatus hyphae and inflammation by P. aeruginosa. This infection model in mice would be useful for studying the pathogenesis of superinfection.

Type II citrullinemia in an elderly patient treated with living related partial liver transplantation

A 60-year-old woman was admitted to our hospital for repeated consciousness disturbance. Blood examination showed hyperammonemia, and plasma amino acid analysis revealed a marked increase in the citrulline level. To establish a diagnosis, a percutaneous needle biopsy of the liver was performed. The determination of the urea cycle enzyme activities revealed a selective marked decrease in argininosuccinate synthetase activity, indicating the final diagnosis of type II citrullinemia. The mean survival period of this disease after the appearance of symptoms has been reported as 26.4 months, and most conservative treatments are not effective. We performed a living related partial liver transplantation. Over the subsequent 13-month follow-up, the patient's condition has remained fairly good.

Activity of interleukin 6 in the differentiation of monocytes to macrophages and dendritic cells

Peripheral blood monocytes are common precursor cells of dendritic cells (DCs) and macrophages. We have searched for factors with the potential to regulate the differentiation of monocytes to DCs and macrophages. When CD14+ monocytes are cultured with granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin (IL) 4, the CD14+CD1a- population, which consists of macrophages, was found in the serum-containing cultures but not in the serum-free cultures. Addition of IL-6 receptor-neutralizing monoclonal antibody (mAb) or gp130-neutralizing mAb to the serum-containing cultures resulted in a decreased population of CD14+CD1a- cells. An increase in the CD14+CD1a- population with reduction in CD14-CD1a+ DCs was observed with the addition of IL-6 to cultures, whereas IL-11, leukaemia inhibitory factor, oncostatin M or macrophage colony-stimulating factor did not affect the differentiation of monocytes in the presence of GM-CSF plus IL-4. This effect of IL-6 was blocked by tumour necrosis factor alpha (TNF-alpha), lipopolysaccharide (LPS), IL-1beta, CD40 ligand (CD40L) and transforming growth factor beta1 (TGF-beta1). Among these factors, TNF-alpha was most potent in interfering with the action of IL-6. These results suggest that IL-6 inhibits the differentiation of monocytes to DCs by promoting their differentiation toward macrophages, which is modulated by factors such as TNF-alpha, LPS, IL-1beta, CD40L and TGF-beta1.

The influence of controlled occlusal overload on peri-implant tissue. Part 3: A histologic study in monkeys

The influence of experimental occlusal overload on peri-implantitis in monkeys (Macaca fascicularis) has been examined to explain the pathology of the disease that develops in the tissue around osseointegrated implants. In the first article of this series, it was reported that bone resorption was not observed around implants when occlusal trauma was produced by a super-structure that was in supraocclusal contact with an excess occlusal height of approximately 100 microns, provided there was no inflammation in the peri-implant tissue. In the second part of the study, experimental inflammation was created in the peri-implant tissue, and occlusal overload was produced by a superstructure with an excess occlusal height of 100 microns. Notable bone resorption was observed around the implant with the passage of time. These results suggested that, in addition to the control of inflammation in peri-implant tissue, traumatic occlusion may play a role in bone breakdown around the implant. In the present study, while the peri-implant tissue was kept in an inflammation-free state, bone level changes around the implants were investigated when various levels of traumatic force were exerted. The supraoccluding prostheses were defined as excessively high by 100 microns, 180 microns, and 250 microns, respectively. The heights were determined with an image analysis device, and the bone responses around the implants induced by the traumatic forces were investigated. The results showed that bone resorption around implants tended to increase with 180 microns or more excessive height of the superstructure. This suggests that the threshold of excessive height of the superstructures at which peri-implant tissue breakdown may start is approximately 180 microns. It is also suggested that there is a possibility of bone resorption around the implants caused by excess occlusal trauma, even when there is no inflammation in peri-implant tissue.

Effects of L-carnitine supplementation on cardiac morbidity in hemodialyzed patients

Cardiac diseases are well known among patients on maintenance hemodialysis (HD), and carnitine deficiency may be an important factor in cardiac morbidity. We studied the effects of low-dose L-carnitine treatment (500 mg/day) on chest symptoms (dyspnea on exertion, chest pain, palpitation), cardiac function, and left ventricular (LV) mass in 9 HD patients with reduced ejection fraction (EF). After 6 months of L-carnitine treatment, most patients had at least some improvement in chest symptoms, while LVEF was increased and LV mass was decreased. Carnitine fractions increased and reached plateaus at 2-3 times the baseline levels. These results suggest that prolonged low-dose L-carnitine treatment can improve the cardiac morbidity by restoring decreased carnitine tissue levels and impaired oxidation of FFA.

The roles of prostaglandin E receptor subtypes in the cytoprotective action of prostaglandin E2 in rat stomach

AIM

To investigate the EP receptor subtype involved in the gastroprotective action of prostaglandin (PG) E2 using various EP receptor agonists in rats, and using knockout mice lacking EP1 or EP3 receptors.

METHODS

Male SD rats and C57BL/6 mice were used after an 18-h fast. Gastric lesions were induced by oral administration of HCl/ethanol (150 mM HCl in 60% ethanol). Rats were given various EP agonists i.v. 10 min before HCl/ethanol: PGE2, sulprostone (EP1/EP3 agonist), butaprost (EP2 agonist), 17-phenyl-omega-trinorPGE2 (17-phenylPGE2: EP1 agonist), ONO-NT012 (EP3 agonist) and 11-deoxyPGE1 (EP3/EP4 agonist). In a separate study, the effect of PGE2 on HCl/ethanol lesions was examined in EP1- and EP3-receptor knockout mice.

RESULTS

Gastric lesions induced by HCl/ethanol were dose dependently prevented by PGE2: this effect was mimicked by sulprostone and 17-phenylPGE2 and was significantly antagonized by ONO-AE-829, an EP1 antagonist. Neither butaprost, ONO-NT012 nor 11-deoxyPGE1 exhibited any protective activity against HCl/ethanol-induced gastric lesions. PGE2 caused an inhibition of gastric motility as well as an increase of mucosal blood flow and mucus secretion, the effects being mimicked by prostanoids activating EP1 receptors, EP2/EP3/EP4 receptors and EP4 receptors, respectively. On the other hand, although HCl/ethanol caused similar damage in both wild-type mice and knockout mice lacking EP1 or EP3 receptors, the cytoprotective action of PGE2 observed in wild-type and EP3-receptor knockout mice totally disappeared in mice lacking EP1 receptors.

CONCLUSION

The gastric cytoprotective action of PGE2 is mediated by activation of EP1 receptors. This effect may be functionally associated with inhibition of gastric motility but not with increased mucosal blood flow or mucus secretion.

Dpb11 controls the association between DNA polymerases alpha and epsilon and the autonomously replicating sequence region of budding yeast

Dpb11 is required for chromosomal DNA replication and the S-phase checkpoint in Saccharomyces cerevisiae. Here, we report detection of a physical complex containing Dpb11 and DNA polymerase epsilon (Dpb11-Polepsilon complex). During the S phase of the cell cycle, Dpb11 associated preferentially with DNA fragments containing autonomously replicating sequences (ARSs), at the same time as Polepsilon associated with these fragments. Association of Dpb11 and Polepsilon with these fragments was mutually dependent, suggesting that the Dpb11-Polepsilon complex associates with the ARS. Moreover, Dpb11 was required for the association of Polalpha-primase with the fragments. Thus, it seems likely that association of the Dpb11-Polepsilon complex with the ARS fragments is required for the association of the Polalpha-primase complex. Hydroxyurea inhibits late-origin firing in S. cerevisiae, and the checkpoint genes, RAD53 and MEC1, are involved in this inhibition. In the presence of hydroxyurea at temperatures permissive for cell growth, Polepsilon in dpb11-1 cells associated with early- and late-origin fragments. In wild-type cells, however, it associated only with early-origin fragments. This indicates that Dpb11 may also be involved in the regulation of late-origin firing. Overall, these results suggest that Dpb11 controls the association between DNA polymerases alpha and epsilon and the ARS.

Relationship among oxygenation, myoelectric activity, and lactic acid accumulation in vastus lateralis muscle during exercise with constant work rate

The purpose of this study was to determine whether oxygenation in localized working muscle depended on the muscle activity and on the lactic acidosis level. Seven healthy male subjects underwent the five 6-min cycling exercises with work rates of 50 watts (25.0 +/- 5.0% VO2max), 100 watts (36.6 +/- 6.2% VO2max), 150 watts (50.6 +/- 7.7% VO2max), 200 watts (67.8 + 6.9% VO2max), and 250 watts (82.9 +/- 7.5% VO2max) while gas exchange parameters and blood lactate concentration (BL) were measured. We also measured oxygenated hemoglobin and myoglobin concentration (oxy-Hb/Mb) with continuous-wave near infrared spectroscopy (NIR) and surface myoelectric activity with surface electrodes (EMG). The NIR probe and electrodes were positioned on the vastus lateralis muscle of the right leg. The relative change in oxy-Hb/Mb was estimated by regarding oxy-Hb/Mb in the resting condition as 100% and that obtained during thigh occlusion as 0%. The mean values of oxy-Hb/Mb and integrated EMG (iEMG) were determined from 5'30" to 6'00" at each work rate. The percentage of oxy-Hb/Mb was sustained at the first two work rates corresponding to 25.0 +/- 5.0 and 36.6 +/- 6.2% VO2max and decreased slightly at 150 watts corresponding to 50.6 +/- 7.7% VO2max, which was followed by a linear decrease at 200 and 250 watts corresponding to 67.8 +/- 6.9 and 82.9 +/- 7.5% VO2max. The iEMG, however, was increased slowly at 25.0 +/- 5.0 to 50.6 +/- 7.7% VO2max, and a rapid increment of the iEMG occurred at 67.8 +/- 6.9 and 82.9 +/- 7.5% VO2max. BL was sustained at 25.0 +/- 5.0 to 50.6 +/- 7.7% VO2max and increased linearly at 67.8 +/- 6.9 and 82.9 +/- 7.5% VO2max. There was a significant negative correlation for each subject between the percentage of oxy-Hb/Mb and iEMG (r = -0.947 to -0.993), between the percentage of oxy-Hb/Mb and BL (r = -0.890 to -0.982), and between the percentage of oxy-Hb/Mb and VO2 (r = -0.929 to -0.994) These results indicated that oxygenated hemoglobin/myoglobin concentration measured with NIR reflected the muscle activity and the lactic acidosis.

Regulatory mechanism of acid secretion in the damaged stomach: role of endogenous nitric oxide

The present article overviews the regulatory mechanism of acid secretion in the stomach after damage with taurocholate (TC), one of the bile acids. Mucosal exposure of a rat stomach to 20 mmol/L TC for 30 min caused a decrease of acid secretion with a concomitant increase in nitric oxide (NO) and prostaglandin (PG) E2 (PGE2) as well as Ca2+ in the luminal contents. Prior administration of N(G)-nitro-L-arginine methyl ester (L-NAME), as well as indomethacin, significantly attenuated the reduction of acid secretion by TC and acid secretion was even increased in the presence of L-NAME. The acid stimulatory effect of L-NAME in the damaged stomach was not mimicked by aminoguanidine and was antagonized by co-administration of L-arginine but not D-arginine. Increased NO release in the damaged stomach was suppressed by pretreatment with L-NAME or co-application of EGTA and the latter also inhibited the increase in luminal Ca2+. The enhanced acid secretory response in the presence of L-NAME was also inhibited by cimetidine, FPL-52694 (a mast cell stabilizer) or sensory deafferentation. Mucosal exposure to TC caused an increase in luminal histamine output, together with a decrease in the number of mucosal mast cells in the stomach. These changes were prevented by FPL-52694 and sensory deafferentation and were also partly suppressed by indomethacin. In addition, the acid stimulatory action of L-NAME in the damaged stomach was significantly mitigated when indomethacin was administered together with L-NAME. We conclude that: (i) damage in the stomach may activate acid a stimulatory pathway in addition to a PG-, NO- and Ca2+-dependent inhibitory mechanism, but the latter effect overcomes the former, resulting in a decrease in acid secretion; (ii) acid stimulation in the damaged stomach is mediated by histamine released from the mucosal mast cell, a process interacting with capsaicin-sensitive sensory nerves; (iii) the increase in luminal Ca2+ plays a role in increasing NO production and, hence, in regulating acid secretion; and (iv) PG may have a dual role in the regulation of acid secretion in the damaged stomach: an inhibitory effect at the parietal cell and an excitatory effect, probably through enhancing the release of mucosal histamine.

Therapeutic effects of parenteral beta-lactam antibiotics on experimental otitis media caused by penicillin-resistant Streptococcus pneumoniae in guinea-pigs

The therapeutic effects of parenteral beta-lactam antibiotics were evaluated in experimental acute otitis media caused by penicillin-resistant Streptococcus pneumoniae (PRSP) in guinea-pigs. Cefotaxime, ceftriaxone and piperacillin significantly reduced viable cell counts of PRSP in the middle ear at a dose of 50 mg/kg bd for 3 days (P < 0.01 compared with control). The therapeutic effects of cefotaxime, ceftriaxone and piperacillin were superior to those of cefotiam and ceftazidime. These therapeutic effects reflected both in vitro activity and pharmacokinetic properties of the drugs.

Protease inhibitor reduces loss of tensile strength in rat anastomosis with peritonitis

BACKGROUND

The tensile strength in intestinal anastomoses decreases postoperatively in association with degradation of the extracellular matrix, and these changes would be expected to be more intense in the presence of peritonitis.

MATERIALS AND METHODS

In this study, we investigated extracellular matrix degradation and tensile strength in a rat model of intestinal anastomosis with peritonitis. In the chemical peritonitis model, peritonitis was induced 24 h earlier with intraperitoneal HCl. A serine protease inhibitor, nafamostat mesilate (NM), was given intraperitoneally to some animals every 12 h from immediately after the operation for 3 days. Immunostaining was performed by the standard streptavidin-biotin-peroxidase method after fibronectin (Fn) and factor XIII antigen retrieval on paraformaldehyde-fixed, paraffin-embedded tissue sections.

RESULTS

In comparison with controls, administration of NM reduced the loss of tensile strength on Day 3 in a dose-dependent manner, and high-dose NM (20/mg/kg) significantly prevented the loss of tensile strength on Day 3 (P < 0. 05). In the control group, degradation of the collagen layer in the anastomosis was associated with disappearance of Fn and factor XIII staining on Day 3. The administration of NM attenuated these changes with intense immunostaining for Fn and factor XIII seen particularly between collagen fibers on both sides of the anastomosis on Day 3. In the chemical peritonitis model, administration of NM also significantly prevented the loss of tensile strength on Day 3 without disappearance of collagen fibers.

CONCLUSION

These findings suggest that NM may be clinically useful for preventing intestinal leakage, particularly when anastomoses are performed under protease-activating conditions, such as intestinal edema and inflammation.

An advantage for use of isotope labeling and NMR chemical shifts to analyze the structure of four homologous IgG-binding domains of staphylococcal protein A

Because of the complexity arising from the large molecular size and the amino acid sequence homologies of IgG-binding domains of Staphylococcal Protein A (SpA), we have introduced, a combination of stable isotope labeling and both qualitative and quantitative investigations of the structural dependence of the NMR chemical shifts for its structure analysis. In order to enable selective isotope labeling with high efficiency, a mutated low molecular weight Protein A (LPA; MWt = 27 kDa) which consists of E, D, A, B and 13 residues of the C-domain was used in this study. Amide proton chemical shifts, measured using uniformly 15N-labeled LPA and LPA labeled selectively with 15N-alanine, show that the turn between helices 1 and 2, and its tertiary interactions with helix 3, are very similar in all domains. This contradicts previous results obtained using independent structure calculations on isolated domains. The close similarity in NH and 15N chemical shifts of alanine residues in the interdomain linker suggests that the linker maintains a similar structure both in isolated domains and in the intact protein. We show that the high-field shifted methyl signal of Ala 48 is affected by the ring-current effect arising from Phe 30, and has a very similar helical environment in all four domains. Thus, helix 3 is present in all domains, as we previously reported [Kikuchi et al., J Biochem Biophys Method, 1999:38:203-208], even though it is not observed in the crystal structure [Deisenhofer J. Biochemistry 1981;20:2361-2370].

[The relationships of mononuclear leukocyte beta-adrenergic receptors to aerobic capacity and exercise-induced asthma in asthmatic children]

beta-adrenaline receptors exist on peripheral mononuclear leukocytes as well as in lung tissue. We assessed the relationships of plasma catecholamine release by exercise to aerobic capacity and to exercise-induced asthma (EIA) in asthmatic children (Study 1). We then measured mononuclear leukocyte beta-adrenergic receptor densities at rest and assessed the relationships of the number of receptors to aerobic capacity, EIA, and bronchial responsiveness to acetylcholine (Study 2). Study 1: Eleven children (9 males, 2 females; 11-16 years old) with bronchial asthma participated in this study. The subjects underwent an incremental aerobic exercise test on a cycle ergometer to determine their aerobic capacity at the lactic threshold (LT) and VO2max. Each subject underwent an EIA test of which the intensity was 175% of LT, and plasma catecholamine concentrations were measured before and after exercise. A significant negative relationship was found between the degree of EIA and % change of plasma adrenaline concentrations to rest level (p < 0.05), and a significant positive relationship was found between VO2 max/wt and % change of plasma adrenaline concentrations (p < 0.05). Study 2: Twelve asthmatic children (10 males, 2 females; 11-16 years old) participated in this study. Aerobic capacity, and degree of EIA were also measured in each subject by the same method as that used in Study. 1. The number of mononuclear leukocyte beta-adrenergic receptors at rest was determined by (-) [125I]-iodocyanopindolol binding in each subject. A significant negative relationship was found between the number of adrenergic receptors and Max. % fall in FEV1.0 (p < 0.01), and a significant positive relationship was found between the number of adrenergic receptors and VO2max/kg (p < 0.001). These results suggested that a reduced adrenaline production and a reduced number of beta-receptors contributed to the pathogenesis of EIA.