Biomedical subjects

T Kubota

Publications and source records attributed to T Kubota.

At least 199 records · Page 11Linked to original sources

PubMed2000

Surgery for gastric carcinoma in patients more than 85 years of age.

BACKGROUND: The incidence of gastric carcinoma is increasing in elderly patients. It has not been determined whether surgery improves the quality of life or prolongs survival in patients older than 85 years. This study was designed to evaluate surgery as a treatment option in patients more than 85 years of age. METHODS: The records of 18 patients aged 85 to 91 years (mean 87.3 years), who underwent surgery for gastric carcinoma between 1983 and 1997 were analysed. RESULTS: Three patients had multiple lesions. A total of 21 lesions were examined. Operative procedures included distal gastrectomy (n = 12), total gastrectomy (n = 4), proximal gastrectomy (n = 1), and laparoscopic wedge resection (n = 1). Perigastric lymphadenectomy was performed in 15 patients. No lymph node dissection was performed in three patients. Postoperative complications, including delirium, respiratory dysfunction, cardiac dysfunction, anastomotic leakage, bleeding, and ileus, occurred in 11 patients. There were two hospital deaths in patients who underwent emergency surgery. Survival was neither shortened nor prolonged by surgery as determined by life table analysis. CONCLUSIONS: Surgical treatment should not be avoided based solely on the age of the patient, and quality of life in this population may be improved by surgery. Careful patient selection should include an assessment of the will to live.

Adenocarcinoma↗

PubMed2000

MRI findings in patients with symptomatic localization-related epilepsies beginning in infancy and early childhood.

We studied MRI findings in patients with symptomatic localization-related epilepsy (S-LRE) beginning in infancy and early childhood and their relation to some clinical features. MRI findings were investigated in 183 patients with S-LRE beginning before 6 years of age. S-LRE was defined as an epileptic syndrome manifesting with only partial seizures at least for a certain period during the clinical course, having specific neuroimaging abnormalities considered to be related to epileptic seizures, moderate or severe mental retardation, or cerebral palsy. The timing of injury was divided into the following four groups; prenatal, perinatal, postnatal and unknown. It was presumed prenatal in 56 patients (31%), perinatal in 25 (14%), postnatal in 32 (18%) and unknown in 70 (38%). The median age at the onset of partial seizures was 24 months in the congenital (prenatal and unknown) group, 39 months in the perinatal group and 25 months in the postnatal group. The onset of partial seizures was later in the perinatal group than in the congenital group. There were no significant differences in the other clinical characteristics among groups except for more frequent association of cerebral palsy in the perinatal group than in the congenital group. Our study suggests that congenital (prenatal and unknown group) disorders may be most common in patients with S-LRE beginning in infancy and early childhood. The onset of partial seizures occurred later in the perinatal group.

Brain↗

PubMed2000

Immunohistochemical localization of MYOC/TIGR protein in the trabecular tissue of normal and glaucomatous eyes.

PURPOSE: To examine immunohistochemically the localization of myocilin/trabecular meshwork inducible glucocorticoid response (MYOC/TIGR) protein in the glaucomatous and normal trabecular meshworks. METHODS: Trabecular tissues were used from one eye with late-onset goniodysgenetic glaucoma, three with primary open angle glaucoma (one of which had the MYOC/TIGR gene mutation), two with exfoliation glaucoma and one without glaucoma. For light microscopic immunohistochemistry, frozen sections were stained by the avidin-biotin complex method using anti-MYOC/TIGR polyclonal antibody. For electron microscopic immunohistochemistry, the pre-embedding method using the same antibody was performed. Double immunostaining using both anti-MYOC/TIGR and anti-type VI collagen antibodies was done by the immunofluorescence method. RESULTS: With light microscopy, immunoreactivity was seen in the whole trabecular meshwork of each of the specimens. No notable differences were detected in staining among the types of glaucoma, or between the eyes with and those without the gene mutation. Under electron microscopy, immunoreaction products were observed not only in the cytoplasm of the trabecular cells but also in the extracellular matrix, where staining was associated with the long-spacing collagen, fine granular materials and possibly microfibrils. With double immunohistochemistry, MYOC/TIGR was colocalized with type VI collagen in the trabecular meshwork. CONCLUSIONS: In glaucomatous and normal trabecular meshworks, the MYOC/TIGR protein is distributed in the extracellular matrix colocalizing with type VI collagen.

Adolescent↗

PubMed2000

Analysis of the proliferative potential of tumor cells after stereotactic radiosurgery for recurrent astrocytic tumors.

We analyzed the effectiveness of stereotactic radiosurgery (SRS) for recurrent astrocytic tumors histologically. Five patients were followed by pathological examination after radiosurgery treatment of recurrent astrocytic tumors. Histological diagnoses at the time of the last operation before SRS were Daumas-Duport grade II in two patients and grade IV (glioblastoma) in three patients. No histological diagnoses at the time of SRS were identified in any patients. Contrast enhanced lesions enlarged gradually on magnetic resonance (MR) images after SRS, and local control by SRS was judged as progressive disease radiologically in all patients. Four of five patients received re-operation after SRS, and the other patient died without re-operation and underwent post-mortem examination. After SRS, Ki-67 labeling indices (LIs) of recurrent astrocytomas initially diagnosed as grade II were 2.6% and 1.1%. These LIs were relatively lower than those of the control group of patients with recurrent grade II astrocytomas that were not treated by SRS. Ki-67 LIs of three glioblastomas after SRS were 23.5%, 18.6%, and 17.8%. These LIs were significantly lower than those before SRS (2.3%, 4.5%, and 0.9%). In the autopsy case, there was a significant difference between the LI of tumor cells in the radiosurgically treated region (0.9%) and that in the untreated region (29.2%). These results suggest that the proliferative potential of malignant astrocytic tumors in the radiosurgically treated area is reduced after SRS, and that radiological enlargement of enhanced lesions on MR images is due to propagation of the residual tumor cells that were not covered by radiosurgical target volume or to radiation necrosis. SRS may be a useful therapeutic tool in multidisciplinary treatment of malignant gliomas.

Adult↗

PubMed2000

Changes in expression of mRNAs in the gerbil hippocampus following transient forebrain ischemia.

The phenomenon of delayed neuronal death in CA1 neurons following brief duration of global ischemia has eluded definitive explanation. Using a differential display technique, we examined changes in expression of mRNAs in the hippocampus following 5-min cerebral ischemia in Mongolian gerbils. Under pentobarbital anesthesia, gerbils were sacrificed by decapitation at 6 h (n = 20) and 2 days (n = 20) after ischemia, and sham-operated gerbils (n = 20) were sacrificed at 6 h after surgery. Total RNA was isolated from the hippocampal samples in each group for the differential display analysis. The mRNAs were classified into three patterns; gradual disappearance, decrease and recovery, and new appearance. Representative mRNAs in three patterns were subcloned and sequenced partly. An mRNA in the gradual disappearance pattern showed homologous with neuronal pentraxin. In situ hybridization and Northern blot analyses of neuronal pentraxin revealed the gradual disappearance pattern. An mRNA in the decrease and recovery pattern showed homologous with 14-3-3 protein gamma-subtype, and an mRNA in the new appearance pattern showed no homology in the data base. The differential display analysis is a useful technique with which to investigate changes in expression of mRNAs following transient cerebral ischemia. The novel mRNA may be involved in the treatment of cerebral ischemia. Further studies are necessary for this point.

14-3-3 Proteins↗

PubMed2000

Expression of adhesion molecules LFA-I and ICAM-I on osteoclast precursors during osteoclast differentiation and involvement of estrogen deficiency.

OBJECTIVES: Estrogen deficiency caused by the menopause or ovariectomy leads to stimulation of osteoclastogenesis. The adhesion molecules, leukocyte function-associated antigen-1 (LFA-1) and intercellular adhesion molecule-1 (ICAM-1), are necessary for osteoclast formation. In this study, the expression of LFA-1 and ICAM-1 on osteoclast precursors during osteoclast differentiation, and the involvement of ovariectomy in the expression, were investigated. METHODS: Spleen cells isolated from normal or ovariectomized (OVX) mice were co-cultured with TMS14, stromal cells derived from mouse bone marrow, in the absence or presence of 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25(OH)2D3) for 7 days. On days 3, 5 and 7 of culture, the expression of LFA-1 and ICAM-1 on osteoclast precursors was quantitated using indirect immunofluorescence and confocal laser cytometry, and, on day 7, the number of formed osteoclasts was measured by tartrate-resistant acid phosphatase (TRAP) stain. RESULTS: The level of ICAM-1 expression on osteoclast precursors gradually increased with osteoclast differentiation, whereas that of LFA-1 did not change. A high level of ICAM-1 was observed on the integrin beta 3-positive mononuclear cells. On the osteoclast precursors isolated from OVX mice, both the level of ICAM-1 expression per cell and the number of cells showing a high expression of ICAM-1 significantly increased, with an increase in the number of osteoclast-like cells. However, the level of LFA-1 did not change. CONCLUSIONS: These results indicate that the expression level of ICAM-1, but not that of LFA-1, is involved in osteoclast differentiation. Estrogen deficiency results in an increase in ICAM-1 expression on osteoclast precursors, which may be one of the mechanisms underlying bone loss following the menopause or ovariectomy.

Acid Phosphatase↗

PubMed2000

The 7alpha-methoxy substituent in cephem or oxacephem antibiotics enhances in vivo anti-Helicobacter felis activity in mice after oral administration.

The in vivo antibacterial activities of 7alpha-methoxy-cephems or 7alpha-methoxy-1-oxacephems and their demethoxy congeners after oral administration were compared in a mouse model of gastric infection with Helicobacter felis. The MICs of all four pairs of compounds with and without the 7alpha-methoxy substituent were within one two-fold dilution for H. felis and Helicobacter pylori, but the 7alpha-methoxy compounds were at least four-fold more active at bacterial eradication than their demethoxy congeners. Since these compounds are not absorbed after oral administration, they are likely to have gained direct access to the bacteria from the gastric cavity. Thus the 7alpha-methoxy substituent may enhance in vivo activity by promoting the gastric mucus permeability of the compounds or by allowing the compounds to remain longer in the gastric cavity.

Animals↗

PubMed2000

Expression and localization of inducible nitric oxide synthase in human non-pregnant and early pregnant endometrium.

The aim of the present study was to investigate the expression and distribution patterns of inducible nitric oxide synthase (iNOS) in human non-pregnant and early pregnant endometrium using Northern blot analysis, reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. Northern blot analysis revealed the expression of iNOS mRNA in human decidua and chorionic villi in the first trimester but not in the endometrium at any stage of the menstrual cycle. Nested RT-PCR, however, detected iNOS mRNA in human endometrium at all stages of the menstrual cycle. Immunohistochemical staining of the secretory endometrium using an anti-human iNOS polyclonal antibody revealed labelling specifically concentrated in glandular epithelial cells. Staining was absent in stromal cells. However, iNOS staining was positive in decidualized stromal cells in tissues obtained in the first trimester of pregnancy. Furthermore, extensive staining was observed in both syncytiotrophoblastic and cytotrophoblastic cells. The finding of a large amount of iNOS mRNA at the feto-maternal interface throughout the first trimester of pregnancy suggests that iNOS may play an important role in the maintenance of pregnancy.

Blotting, Northern↗

PubMed2000

Supplemental intraoperative oxygen augments antimicrobial and proinflammatory responses of alveolar macrophages.

BACKGROUND: The first goal was to test the hypothesis that 100% inspired oxygen maintained for approximately 8 h intraoperatively is not associated with impaired pulmonary oxygenation. The authors also tested the hypothesis that intraoperative inhalation of 100% oxygen augments proinflammatory and antimicrobial responses of alveolar macrophages during anesthesia and surgery. METHODS: The authors studied patients administered 100% oxygen (n = 30) and 30% oxygen (n = 30) during propofol-fentanyl general anesthesia. Alveolar macrophages were harvested by bronchoalveolar lavage immediately, 2, 4, and 6 h after induction of anesthesia, and at the end of surgery. The authors measured "opsonized" and "unopsonized" phagocytosis and microbicidal activity. RNA was extracted from harvested cells and cDNA was synthesized. The expression of interleukin(IL)-1beta, IL-6, IL-8, interferon-gamma (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) was measured by semiquantitative polymerase chain reaction. RESULTS: Gene expression of all proinflammatory cytokines except IL-6 increased fourfold to 20-fold over time in both groups. However, expression of TNF-alpha and IL-8, IFN-gamma, and IL-6 and IL-1beta was 2-20 times greater in patients administered 100% than in those administered 30% oxygen. Unopsonized and opsonized phagocytosis and microbicidal activity decreased progressively, with the decreases being nearly twice as great during inhalation of 30% oxygen versus 100% oxygen. CONCLUSION: Inhalation of 100% oxygen improved intraoperative decreases in phagocytic and microbicidal activity possibly because expression of proinflammatory cytokines was augmented. These data therefore suggest that intraoperative inhalation of 100% oxygen augments antimicrobial and proinflammatory responses in alveolar macrophages during anesthesia and surgery.

Anesthesia, Intravenous↗

PubMed2000

Genetic polymorphism of UDP-glucuronosyltransferase 2B7 (UGT2B7) at amino acid 268: ethnic diversity of alleles and potential clinical significance.

UGT2B7 catalyses the glucuronidation of a diverse range of drugs, environmental chemicals and endogenous compounds. Hence, coding region polymorphisms of UGT2B7 are potentially of pharmacological, toxicological and physiological significance. Two variant UGT2B7 cDNAs encoding enzymes with either His or Tyr at residue 268 have been isolated. The variants, referred to as UGT2B7*1 and UGT2B7*2, respectively, arise from a C to T transversion at nucleotide 802 of the UGT2B7 coding region. Analysis of genomic DNA from 91 unrelated Caucasians and 84 unrelated Japanese demonstrated the presence of the variant alleles encoding UGT2B7*1 and UGT2B7*2 in both populations. However, while there was an approximately equal distribution of subjects homozygous for each allele in the Caucasian population, subjects homozygous for the UGT2B7*1 allele were over 10-fold more prevalent than UGT2B7*2 homozygotes in Japanese. The frequencies of the UGT2B7*1 and UGT2B7*2 alleles were 0.511 and 0.489, respectively, in Caucasians, and 0.732 and 0.268, respectively, in Japanese. The 95% confidence intervals for the two alleles did not overlap between Caucasians and Japanese. Rates of microsomal androsterone, menthol and morphine (3-position) glucuronidation were determined for genotyped livers from Caucasian donors. Statistically significant inter-genotypic differences were not apparent for any of the three substrates. Although the UGT2B7 polymorphism characterized here is probably not associated with altered enzyme activity, the results highlight the need to consider ethnic variability in assessing the consequences of UGT polymorphisms.

Adolescent↗

PubMed2000

Leukocyte integrin-dependent and antibody-independent cytotoxicity of macrophage against allografts.

Macrophages (Mphis), but not T cells, infiltrating into the rejection site of either i.p. allografted Meth A (H-2d) fibrosarcoma cells in C57BL/6 (B6) (H-2b) mice or BALB/c (H-2d) skin onto B6 mice are cytotoxic against allografts with H-2d specificity. To determine the mechanisms of specific killing of allografts by allograft-induced Mphi (AIM), we raised approximately 5,000 rat monoclonal antibodies (mAbs) against AIM and selected three of them (R1-73, R2-40 and R1-34), each of which inhibited cytotoxic activity against allografts in a dose-dependent manner. The antigens recognized by R1-73, R2-40 and R1-34 mAbs were defined by immunoprecipitation and Western blot analyses as CD11a, CD18 and CD11b, respectively; and the allografts expressed CD54, a ligand of CD11a or CD11b, suggesting leukocyte integrin-dependent killing. Although Ab-dependent cellular cytotoxicity has been recognized as a mechanism of specific killing by Mphis, the infiltration of AIM into the rejection site of allografts far (approximately 6 days) preceded the appearance of serum IgG Ab specific for the allograft. AIM exhibiting full cytotoxic activity against allografts was also induced in the transplantation site of Fcgamma receptor knockout [(B6x129) F1] mice as well as B10.D2 (H-2 compatible with allograft) and B6-xid (X-linked immunodeficiency with B cell-specific defect) strains of mice. In the latter two strains of mice, the levels of serum IgG Ab to the allograft were negligible. Moreover, the cytotoxic activity of AIM against allografts was not affected by pretreatment of the cells with anti-mouse IgG serum, suggesting Ab-independent cytotoxicity.

Animals↗

PubMed2000

Effect of antibiotics, levofloxacin and fosfomycin, on a mouse model with Escherichia coli O157 infection.

There have been some reservations about the treatment of enterohemorrhagic Escherichia coli (EHEC) infection with antibiotics to prevent the occurrence of hemolytic uremic syndrome (HUS). However, the administration of antimicrobial agents for EHEC infection is under discussion. Therefore, we used an experimental mouse model to assess the advantage/disadvantage of two major antibiotics, levofloxacin (LVFX) and fosfomycin (FOM). Germ-free IQI mice were inoculated with EHEC O157 strain EDL931 or #7. Bacteria colonized feces at 10(9)-10(10) CFU/g, and Shiga toxins (STXs) were detected in the feces. From 1 day after infection, mice were assigned to LVFX (20 mg/kg) once daily or FOM (400 mg/kg) once daily. A significant decrease in overall mortality was observed after treatment of LVFX, with EHEC disappearing immediately from the feces of mice. FOM also reduced mortality for one strain, the STX level decreased gradually. LVFX exhibited higher therapeutic efficacy than FOM. Strain differences were observed in the model during the treatment.

Animals↗

PubMed2000

Dihydropyrimidine dehydrogenase and messenger RNA levels in gastric cancer: possible predictor for sensitivity to 5-fluorouracil.

We investigated the correlation between tumor sensitivity to 5-fluorouracil (5-FU) and enzymatic activities of thymidylate synthetase (TS) and dihydropyrimidine dehydrogenase (DPD) in human gastric cancer specimens. Forty-one patients with advanced gastric cancer gave informed consent and were enrolled in the study. Biopsy specimens of gastric cancer were obtained preoperatively through gastrofiberscopy and used to determine TS and DPD messenger RNA (mRNA) levels. TS and DPD enzyme activity and mRNA levels were also measured in resected tumor tissue samples obtained after surgical resection. TS and DPD activity were measured using the TS-binding assay and a radioenzymatic assay, respectively, while mRNA levels were measured by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR), with co-amplification of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as an internal standard. 5-FU sensitivity of resected tumor specimens was measured by the tetrazolium-based colorimetric assay (MTT assay). Both TS and DPD mRNA levels correlated well between biopsied and resected tumor specimens. A statistically significant correlation was also observed between mRNA levels in biopsied specimens and enzymatic activities in resected specimens. DPD levels significantly correlated with 5-FU sensitivity, such that high DPD activity and high DPD mRNA levels resulted in low sensitivity to 5-FU. In contrast, no correlation was observed between TS activity or TS mRNA levels and 5-FU sensitivity. We conclude that tumor DPD mRNA level, as assessed from biopsy specimens obtained by gastrofiberscopy, may be a useful indicator in predicting tumor sensitivity to 5-FU in patients with gastric cancer.

Antimetabolites, Antineoplastic↗

PubMed2000

UCN-01 (7-hydroxystaurosporine) enhances 5-fluorouracil cytotoxicity through down-regulation of thymidylate synthetase messenger RNA.

UCN-01 (7-hydroxystaurosporine) is a newly developed cell cycle inhibitor known to have several modes of action, including inhibition of cyclin-dependent kinase, induction of p21 and suppression of pRb phosphorylation. In order to test a combination therapy of UCN-01 and 5-fluorouracil (5-FU), growth inhibition of CRL 1420 (MIA PaCa-2; undifferentiated pancreatic carcinoma) by four different treatments was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. The treatments used were UCN-01 alone, 5-FU alone, 5-FU followed by UCN-01 (5-FU/UCN-01) and UCN-01 followed by 5-FU (UCN-01/5-FU). We also assessed changes in thymidylate synthetase (TS) mRNA levels, TS activity, and 5-FU incorporation by RNA (F-RNA) for each treatment. Although treatment with UCN-01 alone, 5-FU alone, and 5-FU/UCN-01 inhibited CRL 1420 growth in a concentration-dependent manner, treatment with UCN-01/5-FU inhibited the growth of CRL 1420 synergistically at less than 1 microg/ml drug concentration. The down-regulation of TS mRNA by UCN-01 resulted in stable total TS and decreased free TS, and UCN-01/ 5-FU resulted in enhanced thymidylate synthetase inhibition rate (TSIR) compared to UCN-01 alone and 5-FU/UCN-01. This increased TSIR due to UCN-01 pretreatment was accompanied by elevated F-RNA concentrations in the UCN-01/5-FU treatment. The suppression of TS mRNA and TS activity by UCN-01 may lead to higher sensitivity of tumor cells to 5-FU and may explain the synergistic antitumor effect of UCN-01/5-FU. In conclusion, low concentrations of UCN-01 (from 0.01 to 1 microg/ml) may be clinically useful, affording low cytotoxicity of UCN-01, while enhancing the antitumor effect of 5-FU.

Alkaloids↗

PubMed2000

Prevalence of human papillomavirus infection and its correlation with cervical lesions in commercial-sex workers in Japan.

OBJECTIVE: To investigate the prevalence of the human papillomavirus (HPV) infection and its correlation with cervical lesions in commercial-sex workers (CSWs) who attended a sexually transmitted disease (STD) clinic in an entertainment area in Tokyo. METHODS: Surveys were conducted on 546 prostitutes and 233 control subjects. In all subjects, HPV detection was performed by the hybrid capture method. A cervical cytological examination was performed on 247 prostitutes and 233 control subjects. RESULTS: The HPV-positive rates in the two periods of study were higher (p < 0.01) in CSWs than in the control subjects. When the cytological grades were examined according to HPV-positive rates, the proportion of cytologic Class IIIa to Class IV was significantly higher (p < 0.01) in the HPV-positive CSWs than in the HPV-negative CSWs or in the normal subjects. CONCLUSION: The high frequencies of HPV infection and cervical dysplasia in the CSWs in the present series might predict a higher risk of cervical cancer in this group of subjects.

Adolescent↗

PubMed2000

Hypokalemia-induced long QT syndrome with an underlying novel missense mutation in S4-S5 linker of KCNQ1.

Congenital long QT syndrome (LQTS) is caused by mutations in at least five genes coding for cardiac potassium or sodium channels that regulate the duration of ventricular action potentials. Acquired LQTS often is associated with drugs or metabolic abnormalities. A 47-year-old woman who presented with marked QT prolongation (QTc = 620 msec(1/2)) and repeated episodes of torsades de pointes associated with hypokalemia (2.6 mEq/L) was screened for mutations in LQTS genes using polymerase chain reaction/single-strand conformation polymorphism (PCR/SSCP). We identified a novel missense mutation in the intracellular linker of S4-S5 domains of KCNQ1, resulting in an amino acid substitution of cysteine for arginine at position 259 (R259C). Whole cell, patch clamp experiments were conducted on COS7 cells transfected with wild-type and/or R259C KCNQ1 with or without KCNE1. Functional analyses of the mutant KCNQ1 subunit on COS7 cells revealed its functional channels in the homozygous state, producing a significantly smaller current than the KCNQ1 channels and a less severe dominant-negative effect on I(Ks). The novel KCNQ1 mutation R259C is the molecular basis for I(Ks) dysfunction underlying an apparently sporadic case of hypokalemia-induced LQTS, consistent with a mild mutation likely to disclose the clinical manifestation of LQTS in a context of severe hypokalemia. Our findings suggest that gene carriers with such mild mutations might not be so rare as commonly expected in patients with acquired LQTS, and stress the importance of mutational analysis for detecting either "silent" forms of congenital LQTS or de novo mutations.

Female↗

PubMed2000

Helicobacter pylori urease suppresses bactericidal activity of peroxynitrite via carbon dioxide production.

Helicobacter pylori can produce a persistent infection in the human stomach, where chronic and active inflammation, including the infiltration of phagocytes such as neutrophils and monocytes, is induced. H. pylori may have a defense system against the antimicrobial actions of phagocytes. We studied the defense mechanism of H. pylori against host-derived peroxynitrite (ONOO(-)), a bactericidal metabolite of nitric oxide, focusing on the role of H. pylori urease, which produces CO(2) and NH(3) from urea and is known to be an essential factor for colonization. The viability of H. pylori decreased in a time-dependent manner with continuous exposure to 1 microM ONOO(-), i.e., 0.2% of the initial bacteria remained after a 5-min treatment without urea. The bactericidal action of ONOO(-) against H. pylori was significantly attenuated by the addition of 10 mM urea, the substrate for urease, whereas ONOO(-)-induced killing of a urease-deficient mutant of H. pylori or Campylobacter jejuni, another microaerophilic bacterium lacking urease, was not affected by the addition of urea. Such a protective effect of urea was potentiated by supplementation with exogenous urease, and it was almost completely nullified by 10 microM flurofamide, a specific inhibitor of urease. The bactericidal action of ONOO(-) was also suppressed by the addition of 20 mM NaHCO(3) but not by the addition of 20 mM NH(3). In addition, the nitration of L-tyrosine of H. pylori after treatment with ONOO(-) was significantly reduced by the addition of urea or NaHCO(3), as assessed by high-performance liquid chromatography with electrochemical detection. These results suggest that H. pylori-associated urease functions to produce a potent ONOO(-) scavenger, CO(2)/HCO(3)(-), that defends the bacteria from ONOO(-) cytotoxicity. The protective effect of urease may thus facilitate sustained bacterial colonization in the infected gastric mucosa.

Ammonia↗

PubMed2000

Cerebral ischemic hypoxia: discrepancy between apparent diffusion coefficients and histologic changes in rats.

PURPOSE: To compare the apparent diffusion coefficients (ADCs) and histologic changes in young rats subjected to cerebral ischemic hypoxia (IH). MATERIALS AND METHODS: Fifteen 3-week-old rats were subjected to a 30-minute IH insult (unilateral common carotid arterial ligation and exposure to 8% oxygen) and were examined at diffusion-weighted magnetic resonance imaging and light and electron microscopy on cessation of the insult (n = 5), 60 minutes after resuscitation (n = 5), or 48 hours after resuscitation (n = 5). Twelve control rats either underwent unilateral common carotid arterial ligation or were subjected to hypoxia. RESULTS: The experimental rats showed primary ADC reduction during the insult, transient ADC recovery after resuscitation, and secondary ADC reduction 48 hours after the insult. Histologic examination revealed dendritic swelling and mild swelling of the perivascular astrocytic end-feet during the primary ADC reduction phase, dark neurons and pronounced swelling of the perivascular astrocytic end-feet during the transient ADC recovery phase, and severely retracted dark neurons and extensive swelling of the astrocytic end-feet during the secondary ADC reduction phase. CONCLUSION: Transient ADC normalization after cerebral IH does not necessarily mean that histologic normalization has occurred. The transient ADC recovery phase appeared to have limited potential for neuronal salvage.

Animals↗