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Biomedical subjects

H Ohshima

Publications and source records attributed to H Ohshima.

At least 271 records · Page 15Linked to original sources
PubMed1988

Nitrosamine formation by denitrifying and non-denitrifying bacteria: implication of nitrite reductase and nitrate reductase in nitrosation catalysis.

Biochemical, microbiological and genetic studies were done to characterize the mechanism of bacterial formation of N-nitrosomorpholine (NMOR) from morpholine and nitrite at neutral pH. In Escherichia coli and Proteus morganii, the nitrosating activity was markedly induced when bacteria were cultured under anaerobiosis in minimal medium containing nitrate, while in the presence of nitrite there was no induction. However, induction of the nitrosating activity in Pseudomonas aeruginosa occurred in anaerobic cultures in the presence of either nitrate or nitrite. The nitrosation capacity was also examined in various E. coli K12 mutants whose structural gene of either nitrate reductase or nitrite reductase was deleted. Nitrosation was not linked to the three (NADH-, formate- and glucose-dependent) nitrite reductases but was directly dependent on the presence of a nitrate reductase.

Escherichia coli↗
PubMed1988

Urinary N-nitrosamino acids as an index of exposure to N-nitroso compounds.

On the basis of results from animal experiments and studies in human subjects, the amount of nitrosoproline (NPRO) excreted in 24-hr urine following ingestion of precursors (proline, nitrate) has been measured as an index of endogenous nitrosation. Several protocols of the NPRO test have been applied to human subjects, in order to study the kinetics and dietary modifiers of endogenous nitrosation, and in clinical and epidemiological studies. These studies have demonstrated that endogenous nitrosation in humans is highly complex and is influenced by factors such as gastric pH and amounts of precursors, catalysts and inhibitors. Thus, individual monitoring for nitrosation potential, rather than analyses of precursors in saliva, urine and gastric juice, is necessary in order to establish a causal relationship between endogenous nitrosation and human cancer. Results obtained after application of the NPRO test to subjects at high risk for cancers of the stomach, oesophagus, oral cavity and urinary bladder are summarized.

Environmental Monitoring↗
PubMed1988

[Tricuspid regurgitation in mitral valve prolapse studied by two-dimensional color flow mapping].

To assess the incidence of tricuspid regurgitation (TR) in mitral valve prolapse (MVP), 96 patients with MVP and 23 normal control subjects were studied. Subjects in the MVP group were further classified as a group with mitral regurgitation (MR(+) group: 61 cases), and MR(-) group (35 cases). The presence of TR in each group was studied by two-dimensional color flow mapping using a Toshiba SSH-65A apparatus. The incidence of TR was 49% in the MR(+) group and 34% in the MR(-) group, and both (35 cases). The presence of TR in each group was studied by two-dimensional color flow mapping using a Toshiba SSH-65A apparatus. The incidence of TR was 49% in the MR(+) group and 34% in the MR(-) group, and both values were statistically greater than 9% in the control group (p less than 0.001 and p less than 0.05, respectively). A female preponderance was observed only in the MR(+) group. Tricuspid valve prolapse was observed in six cases (10%) in the MR(+) group, two cases (6%) in the MR(-) group, and none in the control group. The mean tricuspid ring dimension did not differ significantly among the three groups. The female patients in MR(+) group had statistically greater measurements than the normal female subjects (p less than 0.01). In conclusion, the incidence of TR was statistically greater in female patients in the MR(+) group than in females in the other groups. It is suspected that functional or pathological changes which induce MVP are likely to progress to the tricuspid ring in female patients.

Adolescent↗
PubMed1987

Electrostatic repulsion of ion penetrable charged membranes: role of Donnan potential.

A model is proposed for the electrostatic repulsion between two ion-penetrable charged membranes in which fixed charges are uniformly distributed. This model assumes that the electric potential far inside the membrane is always equal to the Donnan potential, independent of the membrane separation. In this respect the present model completely differs from usual models for the electrostatic interaction of colloidal particles which assume that the surface potential or the surface charge density remains constant during interaction. It is shown that the rise in potential in the interacting membranes caused by their approach is greatly suppressed so that the potential in the membrane does not exceed the Donnan potential. Numerical results of the calculation of the repulsion by the non-linear Poisson-Boltzmann equation are displayed as a function of the membrane separation and an approximate formula is also derived.

Chemical Phenomena↗
PubMed1987

Volatile nitrosamine levels in common foods from Tunisia, south China and Greenland, high-risk areas for nasopharyngeal carcinoma (NPC).

On the basis of anthropological pilot studies on diet in Tunisia, south China and Greenland, food items consumed frequently by these populations at high risk for NPC were analysed for volatile nitrosamines using gas chromatography combined with a thermal energy analyzer. Relatively high levels of N-nitrosodimethylamine (NDMA), N-nitrosopyrrolidine (NPYR) and N-nitrosopiperidine (NPIP) were detected in Tunisian stewing base ("Touklia") and dried mutton preserved in olive oil ("Qaddid"). NDMA was also detected at levels ranging from trace amounts to 133 micrograms/kg in several Chinese salted and dried marine fish and in Greenland dried, unsalted fish preparations. NPYR and NPIP were also occasionally detected in several vegetables fermented in brine collected in Tunisia and China. The possible role of nitrosamines in the etiology of NPC is discussed.

China↗
PubMed1987

Origin of calcium-induced minimum in bulk compressional modulus of lipid membranes. Configurational entropy of adsorbed Ca2+.

Addition of Ca2+ to a dipalmitoylphosphatidylcholine lamellar system decreases the bulk compressional modulus (increases compressibility) of the membrane (S. Aruga, R. Kataoka and S. Mitaku, Biophys. Chem. 21 (1985) 265). The bulk modulus was reported to show a minimum value at 10 mM Ca2+ within the temperature range 20-45 degrees C. In the present report, the occurrence of this minimum in the bulk modulus is explained quantitatively as a result of fluctuation in the number of Ca2+ adsorbed onto the lipid bilayer surface. From this theory, the change in apparent molal volume of Ca2+ upon surface adsorption is estimated to be 5.7 cm3 mol-1, which appears to be a reasonable value. The number of adsorbed Ca2+ at the concentration where the bulk modulus assumes the minimum value is half of the number of allowable adsorption sites on lipid membranes. The configurational entropy of the adsorbed Ca2+ attains a maximum at the minimum point.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1987

Effects of plasma proteins on degradation properties of poly(L-lactide) microcapsules.

The degradation rate of poly(L-lactide) microcapsules in an aqueous medium was accelerated by the addition of albumin, gamma-globulins, and fibrinogen. These proteins form adsorption layers on the surface of poly(L-lactide) microcapsules. At the interface between the microcapsules and the adsorbed protein layers, the value of the electric potential is expected to increase in magnitude, i.e., become highly negative compared with that at the interface between the microcapsules and the bulk buffer solution containing no plasma protein. This potential increase causes an increase in H+ concentration at that interface, which may result in an acceleration of the hydrolytic degradation rate of poly(L-lactide) microcapsules. Also, the presence of plasma proteins can increase the solubility of poly(L-lactide), causing the poly(L-lactide) molecules to exist in an expanded form. This effect may also accelerate the degradation of poly(L-lactide) microcapsules.

Adsorption↗
PubMed1987

Tumorigenicity study in Syrian hamsters fed areca nut together with nitrite.

In order to evaluate the effect of concurrent administration of areca nut and sodium nitrite, a long-term feeding study was conducted with 120 Syrian hamsters. The animals were divided into four treatment groups, each consisting of 15 males and 15 females, and received 2 g/kg diet of sodium nitrite (group I), 20 g/kg diet of powdered areca nut (group II), 2 g/kg diet of sodium nitrite plus 20 g/kg diet of areca nut (group III) or powdered diet only (group IV) throughout their lifetime. Urine samples from all groups were analysed for N-nitrosonipecotic acid (NNIP), a major urinary metabolite of areca-nut-derived nitrosamines. NNIP was only detected in the urine of hamsters fed nitrite plus areca nut (concentration: 1.9 +/- 0.9 ng/ml urine), indicating that areca nut alkaloids underwent in vivo nitrosation to form areca-nut-specific nitrosamines. The total tumour response was not significantly elevated in groups II and III. Hamsters of group III had a markedly, but also insignificantly higher frequency of malignant tumours than those of the other groups, with a statistically significant increase in malignant lymphomas in the males. Although limited by the low number of animals per group, these results indicate that exposure to nitrite together with areca nut constituents appears to enhance the risk of developing malignancies.

Animals↗
PubMed1987

Biochemical studies on the catalysis of nitrosation by bacteria.

Biochemical and microbiological studies were conducted to characterize the mechanism of bacterial formation of N-nitrosomorpholine from morpholine and nitrite at neutral pH. Nitrosating activity was markedly induced when bacteria were cultured anaerobically in minimal culture medium containing nitrate, while the presence of cysteine or tungsten in the medium inhibited induction. Of various metals, coenzymes and inhibitors tested for their effects on in vitro nitrosation of morpholine, potassium cyanide, sodium azide, NAD(P)H and nitrate strongly inhibited nitrosation. Several mutants of Escherichia coli A10 strain were prepared in order to examine whether nitrosation activity is linked to specific loci. Niridazole-resistant mutants, which lack nitroreductase, had as much nitrosating activity as the original E. coli A10, but chlorate-resistant mutants had completely lost this activity. A good correlation was observed between nitrate reductase activity and nitrosating activity in these mutants. These results indicate that bacterial nitrosation is an enzyme-mediated reaction closely associated with molybdenoenzymes such as the nitrate reductase/formate hydrogenlyase system.

Azides↗
PubMed1987

Medroxyprogesterone acetate and sleep apnea.

Seven patients with sleep apnea DOES and one with sleep apnea DIMS were treated with medroxyprogesterone acetate (MPA). The therapeutic effect was confirmed in most of them by polysomnographic recording. A marked increase of TST was observed in two patients whose AI and/or %SAT remarkably decreased. Contrarily, three patients exhibited a considerable decrease in TST, and AI and/or %SAT were reduced remarkably in two of them with MPA. After the MPA medication a few patients complained of disturbed nocturnal sleep. A significant positive correlation was observed between the decreased rate of TST and that of the mean duration of apneas. From these results, it was considered that MPA has a mild activating action on the arousal system in the CNS, and that the action may be partly responsible for the therapeutic effects of MPA on sleep apneas.

Adult↗
PubMed1987

Treatment resistant chronic psychopathology and CT scans in schizophrenia.

In order to examine the relationship between the neuroleptic resistant chronic psychopathology and CT findings in schizophrenia, 25 schizophrenics who had been treated well and were in a stable condition were assessed for positive and negative symptoms, CT findings, medication, and the clinical course of illness. Correlational analysis showed that there was a group of patients who had comparatively small ventricles and presented treatment resistant positive symptoms, and another group of patients who had larger ventricles and lacked positive symptoms. Negative symptoms showed a tendency toward positive correlation with atrophic CT changes of cortices. Literature on CT findings and symptomatology was critically reviewed. The importance of the more chronic positive symptoms correlating to CT findings in schizophrenia were discussed.

Adolescent↗
PubMed1987

[A study of the use of methotrexate, vincristine, cis-platinum, cyclophosphamide, adriamycin, bleomycin (MVP-CAB) in metastatic transitional cell carcinoma].

Eight patients with metastatic transitional cell carcinoma of the urinary tract were treated with the MVP-CAB regimen. All of them had bidimensionally measurable lesions. The MVP-CAB regimen consisted of cyclophosphamide 500 mg/m2, methotrexate 20 mg/m2, adriamycin 20 mg/m2, bleomycin 30 mg/body, and vincristine 1 mg/body on day 1, cis-platinum 50 mg/m2 on day 2, and prednisolone 20 mg/body on days 1-3, given every 3-4 weeks. A partial response was seen in five patients, minor response in one patient and no change in two patients. The response rate was 63% (5/8). The main toxic effect of the MVP-CAB regimen was leucopenia. In 75% of the patients there was a decrease in white blood cell count by not more than 2,000/mm3, but no severe complication was noted. In addition, mild nausea, vomiting, mild anorexia, alopecia and fever were found. However, these symptoms were transient. One patient died of pulmonary fibrosis induced by bleomycin after 3 cycles.

Adult↗
PubMed1987

[Manifestation of mictional disturbance in four cases of von Recklinghausen's disease].

Four patients with neurofibromatosis (von Recklinghausen's disease) manifesting mictional disturbance are presented. They were a man aged 41 years (A) and 3 women aged 26 (B), 46 (C) and 32 (D) years, and their chief complaints included urinary retention, dysuria, urinary frequency and urinary retention. None of them had any organic obstructive disorders in the lower urinary tract. Case A who had neurofibroma at the C2 and L1-2 vertebral bodies had inactive bladder and his urinary flow rate was less than 10 ml/sec. In case B, cystometrogram was initially normal, but changed to inactive bladder type one year later and neurofibromas were found in the vertebral bodies of Th7-8 and L2. Case C, who had inactive bladder cystometrically, underwent removal of 1-acoustic neurinoma and neurinomas of cauda equina. Case D had hyperactive bladder and received resection of the neurofibroma of vertebral bodies from C6 to Th4. The finding of cystometrogram and type of urinary miction disorders suggested vertebral neurofibroma at an early stage.

Adult↗