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Biomedical subjects

H Ohshima

Publications and source records attributed to H Ohshima.

At least 307 records · Page 17Linked to original sources
PubMed1985

Stopped-flow rapid kinetics of anesthetic-induced phase transition in phospholipid vesicle membranes: nonlocalized fluctuation.

Kinetics of the gel to liquid-crystalline phase transition of dipalmitoylphosphatidylcholine vesicle membrane was studied by the stopped-flow technique with turbidity detection. The observed change in turbidity was well characterized by a single-exponential decay curve with relaxation time in the millisecond range, although the existence of a faster process than the dead-time of the stopped-flow apparatus was inferred from the amplitude analysis. Relaxation times were determined as functions of 1-hexanol concentration and temperature just below phase transition. From the analysis based on the theories of nonequilibrium relaxation, it is concluded that the phase transition induced by 1-hexanol is governed by a nonlocalized fluctuation mechanism. The anesthetic-induced nonequilibrium state is unstable rather than metastable.

Anesthetics↗
PubMed1985

Divalent cation-induced phosphatidic acid membrane fusion. Effect of ion binding and membrane surface tension.

A study was made on the correlation between the degree of membrane fusion and surface tension increase of phosphatidic acid membranes caused by divalent cations. Membrane fusion was followed by the Tb3+/dipicolinic acid assay, monitoring the fluorescent intensity for mixing of the internal aqueous contents of small unilamellar lipid vesicles. The surface tension and surface potential of monolayers made of the same lipids as used in the fusion experiments were measured as a function of divalent cation concentration. It was found that the 'threshold' concentration to induce massive vesicle membrane fusion was the same for Ca2+ and Mg2+, and that the surface tension increase in the monolayer, induced by changing divalent cation concentration from zero to a concentration which corresponds to its threshold value, inducing vesicle membrane fusion, was approximately the same: 6.3 dyn/cm for both Ca2+ and Mg2+. Both the divalent cation's threshold concentrations as well as the surface tension change corresponding to the threshold concentration for the phosphatidic acid membrane were smaller than those for the phosphatidylserine membrane. The different fusion capability of these divalent cations for phosphatidic acid and phosphatidylserine membranes is discussed in terms of the different ion binding capabilities of these ions to the membranes.

Calcium↗
PubMed1985

Identification and occurrence of two new N-nitrosamino acids in tobacco products: 3-(N-nitroso-N-methylamino)propionic acid and 4-(N-nitroso-N-methylamino)butyric acid.

Two new N-nitrosamino acids, 3-(N-nitroso-N-methylamino)propionic acid (CAS: 10478-42-9) and 4-(N-nitroso-N-methylamino)butyric acid (CAS: 61445-55-4) were isolated and identified for the first time in various types of tobacco, including snuff, chewing and pipe tobacco, cigars and cigarettes. Their levels ranged from 0.15 to 7.4 and 0 to 2.2 mg/kg of dry weight tobacco, respectively. For comparison, amounts of other N-nitrosamino acids like N-nitrosoproline (NPRO) and tobacco-specific-nitrosamines (TSNA) were determined in the same samples. The levels of N-nitrosamino acids were highly correlated with the levels of TSNA.

Chromatography, Gas↗
PubMed1985

Donnan potential and surface potential of a charged membrane.

A model is presented for the electrical potential distribution across a charged biological membrane that is in equilibrium with an electrolyte solution. We assume that a membrane has charged surface layers of thickness d on both surfaces of the membrane, where the fixed charges are distributed at a uniform density N within the layers, and that these charged layers are permeable to electrolyte ions. This model unites two different concepts, that is, the Donnan potential and the surface potential (or the Gouy-Chapman double-layer potential). Namely, the present model leads to the Donnan potential when d much greater than 1/k' (k' is the Debye-Hückel parameter of the surface charge layer) and to the surface potential as d----0, keeping the product Nd constant. The potential distribution depends significantly on the thickness d of the surface charge layer when d less than or approximately equal to 1/k'.

Cell Membrane Permeability↗
PubMed1985

Tobacco-specific and betel nut-specific N-nitroso compounds: occurrence in saliva and urine of betel quid chewers and formation in vitro by nitrosation of betel quid.

In order to evaluate exposure of betel quid chewers to N-nitroso compounds, saliva and urine samples were collected from chewers of betel quid with or without tobacco, from tobacco chewers, from cigarette smokers and from people with no such habit, and were analysed for the presence of N-nitrosamines by gas chromatography coupled with Thermal Energy Analyzer and alkaloids derived from betel nut and tobacco by capillary gas chromatography fitted with nitrogen-phosphorous selective detector. The levels of the betel nut-specific nitrosamines, N-nitrosoguvacoline and N-nitrososoguvacine (the latter being detected for the first time in saliva), ranged from 0 to 7.1 and 0 to 30.4 ng/ml, respectively. High levels of tobacco-specific nitrosamines were detected in the saliva of chewers of betel quid with tobacco and in that of chewers of tobacco, ranging from 1.6 to 59.7 (N'-nitrosonornicotine), 1.0 to 51.7 (N'-nitrosoanatabine) and 0 to 2.3 [4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone] ng/ml. Urinary concentrations of certain N-nitrosamino acids, including N-nitrosoproline, were determined as a possible index of exposure to nitroso compounds and their precursors in the study groups: no clear difference was observed. The betel nut-specific alkaloid, arecoline, was present at high levels in the saliva of betel quid chewers with or without tobacco. Nicotine and cotinine were also detected in saliva and urine of chewers of tobacco and of betel quid with tobacco. In order to assess whether N-nitroso compounds are formed in vivo in the oral cavity during chewing or in the stomach after swallowing the quids, the levels of N-nitroso compounds in betel quid extracts were determined before and after nitrosation at pH 7.4 and 2.1. The results indicate that N-nitroso compounds could easily be formed in vivo. The possible role of N-nitroso compounds in the causation of cancer of the upper alimentary tract in betel quid chewers is discussed.

Adult↗
PubMed1985

Screening of microorganisms for nitrosation catalysis at pH 7 and kinetic studies on nitrosamine formation from secondary amines by E. coli strains.

Thirty-eight strains of microorganisms isolated from infected human trachea, urine, blood and faeces were examined for their ability to form N-nitrosomorpholine from morpholine and nitrite at pH 7.25. Twenty-five bacterial strains exhibited nitrosation activity, including 18 out of 19 strains of Escherichia coli and three out of nine Pseudomonas aeruginosa, Proteus morganii, Proteus mirabilis, Klebsiella pneumoniae and Neisseria strains; E. coli A10 strain showed the highest activity. Formation of N-nitrosomorpholine was proportional to the incubation time up to 2 h and to the number of resting E. coli A10 cells; the reaction followed Michaelis-Menten kinetics. Nitrosation rate appeared to be dependent on the pKa value of several amines studied. As the nitrosation catalysis was heat-labile, our data suggest that N-nitrosation is catalysed by a bacterial enzyme(s). This reaction may lead to enhanced endogenous nitrosation in subjects suffering from an achlorhydric stomach or from chronic urinary tract infections.

Amines↗
PubMed1985

[A clinical observation of genitourinary tract tuberculosis during the last decade].

Altogether, 92 patients were diagnosed as having genitourinary tuberculosis, and were treated at our clinic from 1972 to 1981. These patients form the basis for our statistical study. The incidence of genitourinary tuberculosis among our new outpatients showed a tendency to decrease and was less than 0.4% during the last five years. The mean age of the genitourinary tuberculosis patients was 42.8, rather higher than ten years ago. Of these, 41% had a history of tuberculosis and 54% chiefly complained of bladder-related symptoms. Tubercle bacilli were detected in 87% of the patients. About 45% of the patients with urinary tuberculosis underwent nephrectomy, which was indicated principally in cases of non-functioning kidneys and severe hydronephrosis. A combination of PAS, INH, and RFP was used most often and was administered in 58 cases. Used second most often was a combination of SM, PAS, and INH (administered in 46 cases).

Adolescent↗
PubMed1985

Cell surface changes during cleavage of newt eggs: scanning electron microscopic studies.

Scanning electron microscopic studies were carried out on changes of the cell surface during the first cleavage of eggs of the newt, Cynopus (Triturus) pyrrhogaster. A dense population of elongated microvilli, which initially covered a double line indicating the initial furrow and stress marks running on each side of it, became located inside the pigmented area a little apart from its border with the unpigmented area when this borderline was established. This finding, together with data of carbon marking experiments, indicates that membrane growth occurs not only at the presumptive unpigmented surface, but also in a small portion of the presumptive pigmented area adjoining it. During cleavage within the vitelline membrane, a stable intercellular junction at the border of the pigmented and unpigmented surfaces was formed through the following successive processes: the appearance of individual lamellipodia on the borderline; contact of their apical filopodia with those of the opposite blastomere; contact of the lamellipodial bodies; and complete joining of the whole of the lamellipodia in contact. In cleavage of demembranated eggs, in which there is no chance of contact of lamellipodia of the two blastomeres, each lamellipodium persisted in an isolated state until the onset of the next division. In most cases, many strained or broken threads were seen across the space formed by opening of opposing blastomeres, at their peripheries. These threads were cytoplasmic in nature and showed cell contact. Similar threads were found stretched between blastomeres when the closed furrow was opened in medium containing EGTA.

Animals↗
PubMed1984

Monovalent cation-induced phospholipid vesicle aggregation: effect of ion binding.

Aggregation of acidic phospholipid vesicles induced by monovalent cations was studied for vesicles of small and large sizes. It was found that there were two phases in the aggregation of large acidic phospholipid vesicles. In the initial phase, observed in the range of 0.1-0.4 M monovalent salts, aggregation took place spontaneously after a change in salt concentration; in the second phase (greater than 0.4 M salt), aggregation progressed gradually with time. The order of capability for monovalent cations to induce the initial phase of aggregation of large phosphatidylserine vesicles (more than 1000 A in diameter) was Li+ greater than Na+ greater than K+ greater than TEA+. However, for the second phase of aggregation, the order was Na+ greater than Li+ greater than K+ greater than TEA+, which was the same as that to induce massive aggregation of small phosphatidylserine vesicles (250 A in diameter). A similar reversal in the order was observed in studies of the surface potential of the phosphatidylserine monolayer. In these studies, the order of the binding strength of monovalent cations was deduced from the change in surface potential produced by successive additions of MgCl2 to the subphase solution, which contained a certain level of monovalent salt initially. These measurements were carried out with monolayers that had a range of areas per molecule. The order was Na+ greater than Li+ greater than K+ for monolayers of large area (greater than 80 A2) per molecule and was Li+ greater than Na+ greater than K+ for those of small area (less than 80 A2) per molecule.(ABSTRACT TRUNCATED AT 250 WORDS)

Cations, Monovalent↗
PubMed1984

Occurrence in human urine of new sulphur-containing N-nitrosamino acids N-nitrosothiazolidine 4-carboxylic acid and its 2-methyl derivative, and their formation.

To quantitate endogenous nitrosation reactions in man, the quantity of N-nitrosoproline (NPRO) excreted in the urine after ingestion of proline and/or nitrate was estimated. When this monitoring method (NPRO test) was applied in clinical and field studies, several hitherto unidentified N-nitroso compounds were frequently detected. These were recently identified as sulphur-containing N-nitrosamino acids, N-nitrosothiazolidine 4-carboxylic acid (NTCA), and trans- and cis-isomers of N-nitroso-2-methylthiazolidine 4-carboxylic acid (NMTCA). NTCA and NMTCA were readily formed in vitro following nitrosation at acidic pH of the respective precursor, thiazolidine 4-carboxylic acid (TCA) or of 2-methylthiazolidine 4-carboxylic acid (MTCA). As the latter compounds can be formed by reaction of L-cysteine with formaldehyde or acetaldehyde, respectively, NTCA and NMTCA were also formed by reacting L-cysteine with the respective aldehyde and with nitrite at optimal pH (2.5 for NTCA and 4.5 for NMTCA). Up to 95% of NTCA and NMTCA given orally to fasted rats was recovered as such in urine and faeces within 2 days. Administration of TCA or MTCA, together with nitrite increased the urinary excretion of NTCA and NMTCA, as did co-administration of L-cysteine, nitrite, and the respective aldehyde. NTCA and NMTCA were also detected in the 24-h urine of human volunteers, and smokers tended to excrete higher levels than nonsmokers. Daily excretion levels varied, however, and a diet supplemented with ascorbic acid significantly decreased the total amount of nitrosamino acids. NTCA and NMTCA may occur in human urine as a result of (i) intake of preformed N-nitroso compounds; (ii) intake of thiazolidine 4-carboxylic acid or its 2-methyl derivative and subsequent nitrosation in vivo; (iii) endogenous two-step synthesis by the reaction of L-cysteine with the respective aldehyde and a nitrosating agent. Thus, measurement of NTCA and NMTCA together with NPRO in urine may provide an index for the exposure of human subjects to nitrosamines or their precursors, i.e., nitrosating agents, certain aldehydes, or aldehyde-generating compounds. Our data demonstrate unequivocally that N-nitroso compounds are formed in the human body, as suggested previously by Druckrey. Their relevance to human cancer at specific sites should now be investigated.

Administration, Oral↗
PubMed1984

Spontaneous disappearance of limy bile: report of a case with review of the literature.

Spontaneous disappearance of limy bile is extremely rare, and only four cases have so far been reported. This is the account of the fifth case, a 42-year-old woman, who spontaneously lost a stone incarcerated in the neck of the gallbladder and all of the limy bile, after symptoms suggestive of a transient obstructive jaundice. Various investigations including ultrasound, computed tomography, and percutaneous transhepatic cholangiography suggested spontaneous passage of the stone through the cystic duct and the papilla of Vater, followed by limy bile. Apparently the patient's gallbladder had a contracting capacity. The literature on this subject is briefly reviewed.

Adult↗
PubMed1984

Dietary phenolics and betel nut extracts as modifiers of N-nitrosation in rat and man.

Polyphenolic compounds (PPC) isolated from betel nuts and some dietary PPC were examined for their modifying effects on N-nitrosation in vitro and in vivo. The formation of N-nitrosodiethylamine (NDEA) and N-nitrosoproline (NPRO) was either enhanced or inhibited by PPC from betel nuts, depending on (1) the structure of the PPC, (2) the pH of the reaction medium, (3) the relative concentrations of nitrite and PPC, and (4) the nature of the nitrosatable amino compounds. Both catalysis and inhibition of endogenous nitrosation of proline were observed in rats, although to a lesser extent than in vitro. Caffeic and ferulic acids, as well as the PPC-containing beverages tea and coffee, exerted inhibitory effects on endogenous formation of NPRO in two human subjects. These results demonstrate that PPC can modify the yield of endogenously formed N-nitroso compounds, and may thus effect the carcinogen burden in man.

Animals↗
PubMed1984

Nitrosating properties of bis-methylthio-diiron-tetranitrosyl (Roussin's red methyl ester), a nitroso compound isolated from pickled vegetables consumed in northern China.

Bis-methylthio-diiron-tetranitrosyl (Roussin's red methyl ester, RRME), recently identified in pickled vegetables consumed in a high incidence area of oesophageal cancer in Northern China, was examined for its activity as a nitrosating agent in vivo and in vitro. Freshly synthesized RRME nitrosated secondary amines (morpholine and pyrrolidine) slowly in the presence of air; it failed to nitrosate these amines under strictly anaerobic conditions. In experiments in rats, a fresh sample of RRME was found to be a weak nitrosating agent, whereas partially decomposed RRME showed a strong nitrosating activity comparable to that of nitrite. Possible mechanisms for nitrosation by RRME are discussed.

Animals↗
PubMed1984

Presence in human urine of new sulfur-containing N-nitrosamino acids: N-nitrosothiazolidine 4-carboxylic acid and N-nitroso 2-methylthiazolidine 4-carboxylic acid.

A new type of sulfur-containing N-nitrosamino acid, N-nitrosothiazolidine 4-carboxylic acid (NTCA) and N-nitroso 2-methylthiazolidine 4-carboxylic acid (NMTCA), was isolated and identified in the urine of human subjects. Identification was based on identical chromatographic and mass spectral data for the purified urine sample and the synthesized authentic compounds. The amounts of NTCA and NMTCA excreted in 24-h urines of 15 volunteers varied from 0.9 to 35.9 micrograms/day and from 0.4 to 19.8 micrograms/day, respectively. These amounts were 2.4 and 1.6 times greater than that of N-nitrosoproline (NPRO) detected in the same urine samples. Thiazolidine 4-carboxylic acid and its 2-methyl derivative were found to be nitrosated in vitro about 250-500 and 60-300 times more rapidly than proline, respectively. In addition, NTCA and NMTCA were also readily formed by reaction of a mixture of nitrite and L-cysteine, with formaldehyde and acetaldehyde, respectively. Although their origin in human urine is unknown, preliminary results in one human volunteer have shown that some of these compounds are formed endogenously. Thus, measurement of these new sulfur-containing N-nitrosamino acids in the urine may (i) provide another index for endogenous nitrosation reactions in the human body and (ii) allow monitoring of exposure of humans to precursors such as aldehydes and nitrate/nitrite.

Chemical Phenomena↗
PubMed1984

Recent studies on N-nitroso compounds as possible etiological factors in oesophageal cancer.

Possible etiological factors involved in oesophageal cancer in various parts of the world and in certain provinces in Northern China are summarized. Evidence is accumulating that N-nitroso compounds and their precursors are involved in the disease in Northern China, as shown in a recent study: excretion of urinary N-nitrosamino acids by inhabitants living in a high- (Linxian) and in a low-risk area (Fanxian) for oesophageal cancer was compared. Linxian subjects excreted significantly more nitrate and nitrosamino acids (N-nitrosoproline, N-nitrosothiazolidine-4-carboxylic acid, N-nitrososarcosine) than those in Fanxian. When Linxian subjects were given 100 mg vitamin C three times a day (after each meal) together with proline, the level of urinary N-nitrosamino acids was reduced to that found in Fanxian. Thus, vitamin C, an efficient inhibitor of endogenous nitrosation, should now be examined in intervention trials in subjects in whom endogenous formation of N-nitroso compounds is elevated.

Africa↗