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M Ohta

Publications and source records attributed to M Ohta.

At least 937 records · Page 52Linked to original sources
PubMed1988

Characterization of the autofluorescence of rat liver plasma membranes.

The autofluorescence of isolated rat liver cell plasma membranes was characterized in vitro in relation to the autofluorescence used previously for fluorescence recovery after photobleaching (FRAP) studies. The fluorescence of membrane preparations displayed an emission pattern with a maximum at around 525 nm when excited with a 468 nm blue light. The excitation spectrum monitored at 525 nm closely resembled that of flavin compounds (riboflavin, FAD, FMN). The chloroform extract of the membrane fraction showed practically no fluorescence, whereas, both the water-soluble and water-insoluble protein fractions remaining after chloroform extraction were strongly fluorescent. The fluorescence disappeared almost completely under the effect of sodium hydrosulfite, and recovered after oxidation either by shaking in air or by adding buffered hydrogen peroxide solution. The fluorescence of the acid extract of the plasma membranes photolyzed in an alkaline medium was quite similar to that of lumiflavin obtained from the photolysis of riboflavin in an alkaline medium. The plasma membranes prepared from isolated hepatocytes (which were completely devoid of endothelial cell contamination) exhibited the same autofluorescence in the liver cell plasma membranes. The results suggest that the autofluorescence of the liver cell plasma membranes is most likely of a character similar to that of flavin, bound to hepatocyte plasma membrane proteins. This fluorescence is suitable for measuring the average lateral diffusion constant of proteins by means of FRAP methods.

Animals↗
PubMed1988

Effect of perfringolysin O on the lateral diffusion constant of membrane proteins of hepatocytes as revealed by fluorescence recovery after photobleaching.

Perfringolysin O is a thiol-activated cytolytic exotoxin the primary receptor of which is the membrane cholesterol on the cell surface. The effect of perfringolysin O was tested in various hepatocyte preparations. (i) Smears of fresh liver exposed to a mild H2O2 (1.0 mM) injury for 10 min at 37 degrees C, develop a 'peroxide-induced autofluorescence' (PIAF) on the membrane proteins. PIAF is suitable for measuring the average lateral diffusion constant (D) of the membrane proteins by means of fluorescence recovery after photobleaching technique (FRAP). Incubation for 5 min with 600 or 2000 units/ml of the perfringolysin O resulted in a significant increase (32 and 46%, respectively) of D as compared to the controls of the same age group (13-14 months). Various tests like heat denaturation of cholesterol saturation of perfringolysin O before its application as well as thiol-activation of the smears with dithiothreitol revealed that the increase of D is a specific toxin effect due mot probably to the reaction of perfringolysin O with cholesterol. (ii) Isolated hepatocytes were exposed to perfringolysin O and their viability as well as the release of two cytosolic enzymes (lactate dehydrogenase and glutamic-pyruvic transaminase) were measured; 40-60 units/ml of perfringolysin O in 30 min reduced the viability of the hepatocytes to zero and caused a release of about 70% of both cytosolic enzymes. The significance of the results is discussed from the points of view of both the toxin-effect and the FRAP method.

Animals↗
PubMed1988

Age-dependent decrease in the hepatic uptake and biliary excretion of ouabain in rats.

The biliary excretion of i.v. injected ouabain was examined in male and female Wistar-derived rats in relation to age. The hepatic uptake velocity for ouabain was also determined in isolated hepatocyte preparations obtained from male rats of various ages. Biliary recovery values of ouabain (percent of the dose) were fairly comparable for young male and female rats (3-4 month old). Recovery progressively decreased with age, the first 10-min recoveries at 24 months being about one-third those of respective young values in both sexes. A significant linear relation was demonstrated between the first 10-min recovery (Y, percent of the dose) and rat age (X, month), yielding the relations of Y = 17.75-0.43X for males and Y = 18.99-0.43X for females respectively. Similarly, the initial uptake velocity (Y, nmol/mg/min) for ouabain decreased in a linear fashion with age (X, month), yielding a significant negative correlation (Y = 0.704-0.0021X, r = -0.839, P less than 0.005, N = 21) at an ouabain concentration of 8 microM. Kinetic studies using non-linear regression analysis revealed a significantly lower Vmax value (0.533 +/- 0.041 nmol/mg/min) in old (24-29 months) rats compared to the young (4-4.5 months) value (1.193 +/- 0.105 nmol per mg/min, P less than 0.05), while the affinity constant (Km, microM) did not differ significantly between young and old animals (203.12 +/- 25.42 microM in young rats vs 283.68 +/- 28.90 microM in old rats, mean +/- SE, 0.05 less than P less than 0.1). The results of the present study suggest that the age-dependent decrease in the biliary recovery of i.v. injected ouabain in rats can be largely explained by the decrease with age in the hepatic uptake of ouabain. Furthermore, the results provide further support for our previous thesis that the decrease in the lateral mobility of hepatocyte plasma membrane proteins, as revealed by the fluorescence recovery after photobleaching technique, may play a significant role in the age-dependent decrease in the physiological function(s) of the hepatocyte plasma membrane, such as the hepatobiliary transport of ouabain.

Aging↗
PubMed1988

A comparison of pelvic retroperitoneal pneumography and computed tomography in the assessment of extramural invasion of rectal carcinoma.

Pelvic retroperitoneal pneumography (PRP) and pelvic computed tomography (CT) were performed on 33 patients with rectal carcinoma in order to compare the usefulness of the two diagnostic procedures in the preoperative assessment of local malignant extramural invasion. Six PRP-negative patients in whom no free air was visualized in the retroperitoneal space surrounding the mass, were all assessed as having extramural invasion by CT scan and all had histologic evidence of invasion. Of 27 PRP-positive patients in whom free air was seen surrounding the mass, 18 were diagnosed as having extramural invasion on CT, 15 of whom had histologic proof of invasion. In the remaining 9 PRP-positive patients, there was no evidence of extramural invasion on the CT scans, but 5 patients showed evidence of invasion histologically. PRP, when positive, had an unacceptably high rate of being false positive and was therefore unreliable in assessing extramural invasion, whereas CT was able to detect, to some extent, extramural invasion which PRP failed to demonstrate. Based on these findings, we conclude that CT is more useful than PRP in the preoperative assessment of extramural invasion of rectal carcinoma, but is of limited diagnostic value when negative.

Adult↗
PubMed1988

Intermediate filaments of hepatocytes and biliary epithelial cells in bile duct obstruction: transmission and scanning electron microscopy study.

The cytoskeletons of hepatocytes and biliary epithelial cells in bile duct ligated rate livers were investigated by transmission and scanning electron microscopy. The three dimensional organization of the intermediate filaments (IFs) of hepatocytes and biliary epithelial cells was clearly demonstrated by scanning electron microscopy. Cell borders and dilated bile canaliculi were well preserved after perfusion with detergent solution. A very dense filamentous network of IFs was seen throughout the cytoplasm, especially around the dilated bile canaliculi and at the cell borders. IFs in biliary epithelial cells were more numerous compared with hepatocytes. Morphometric analysis showed that the IFs of hepatocytes significantly (p greater than 0.001) increased in amount in bile duct ligated rats. The IFs of biliary epithelial cells showed no significant changes in bile duct ligated rats compared to controls. These results suggest that the increase in IFs in hepatocytes results from the adaptation of the hepatocytes to the stress imposed by bile duct ligation. It may be that the resulting intracanalicular pressure and back diffusion of bile induces a metaplastic change in hepatocytes so that they acquire more IFs to function like the bile duct epithelium to conduct bile flow.

Animals↗
PubMed1988

Ca2+-dependent activation of the malate-aspartate shuttle by norepinephrine and vasopressin in perfused rat liver.

The role of Ca2+ in stimulation of the malate-aspartate shuttle by norepinephrine and vasopressin was studied in perfused rat liver. Shuttle capacity was indexed by measuring the changes in both the rate of production of glucose from sorbitol and the ratio of lactate to pyruvate during the oxidation of ethanol. (T. Sugano et al. (1986) Amer. J. Physiol. 251, E385-E392). Asparagine (0.5 mM), but not alanine (0.5 mM) decreased the ethanol-induced responses. Norepinephrine and vasopressin had no effect on the ethanol-induced responses when the liver was perfused with sorbitol or glycerol. In the presence of 0.25 mM alanine, norepinephrine, vasopressin, and A23187 decreased the ethanol-induced responses that occurred with the increase of flux of Ca2+. In liver perfused with Ca2+-free medium, asparagine also decreased the ethanol-induced responses, but norepinephrine and vasopressin had no effect. Aminooxyacetate inhibited the effects of norepinephrine, A23187, and asparagine. Regardless of the presence or absence of perfusate Ca2+, the combination of glucagon and alanine had no effect on the ethanol-induced responses. Norepinephrine caused a decrease in levels of alpha-ketoglutarate, aspartate, and glutamate in hepatocytes incubated with Ca2+. The present data suggest that the redistribution of cellular Ca2+ may activate the efflux of aspartate from mitochondria in rat liver, resulting in an increase in the capacity of the malate-aspartate shuttle.

Alanine↗
PubMed1988

Oviposition pattern of Japanese quail following hypothalamic lesioning with super-absorbent polymer.

The functions of two hypothalamic areas in controlling the female reproductive cycle were investigated by the intracerebral injection of a new type of water-absorbent polymer of high capacity (super-absorbent polymer). After injection of a minute amount of the polymer into the brain tissue, bulging of the polymer produces a discrete lesion at the site of injection. Two lines (T- and J-lines) of Japanese quail were used; T-line, having a characteristic free-running oviposition pattern irrespective of the environmental 14L10D, and J-line, having a regular oviposition pattern which synchronized with 14L10D. Lesions at the preoptic area were without effect in birds of J-line, but the oviposition of T-line was changed from free-running to regular. Lesions at the posterodorsal part of the infundibular complex were without effect in T-line, but the regular oviposition pattern of J-line became free-running. These results suggest that relative dominancy between the two hypothalamic areas may determine basic pattern of oviposition through modification of the ovulation cycle.

Animals↗
PubMed1988

A possible role for the eyes in the photoperiodic response of quail.

The effects of blinding on the photoperiodic responses of male Japanese quail were investigated by measuring plasma luteinizing-hormone (LH) concentrations in intact and castrated birds. Blinded birds were still able to respond to short and long days with appropriate changes in LH levels, suggesting that the basic photoperiodic mechanisms do not require retinal photoreception. However, there were clear-cut differences between blinded and sighted birds with the LH levels being higher in blinded quail. This difference between blinded and sighted was greater in short than in long days, and was also enhanced by castration. In conclusion we propose that short day information transmitted by the eyes has an inhibitory effect for LH secretion independent from sex steroid negative feedback effects in quail.

Animals↗
PubMed1988

Production of 19-oic-11-deoxycorticosterone from 19-oxo-11-deoxycorticosterone by cytochrome P-450(11)beta and nonenzymatic production of 19-nor-11-deoxycorticosterone from 19-oic-11-deoxycorticosterone.

19-Oxo-11-deoxycorticosterone was incubated with a cytochrome P-450(11)beta-reconstituted system, and the metabolites were analyzed by high performance liquid chromatography(HPLC). The main product found after chromatography was collected and treated with diazomethane. HPLC and 1H-NMR analysis of the methylated derivative indicated that it was 19-oic-11-deoxycorticosterone methyl ester. When 19-oic-11-deoxycorticosterone was stored at -20 degrees C for 1 month, it was spontaneously converted to other steroids. Structural analysis of the main degradation product indicated that it was 19-nor-11-deoxycorticosterone. These results suggest that the conversion of 19-oxo-11-deoxycorticosterone to 19-oic-11-deoxycorticosterone occurs through the P-450(11)beta-catalyzed reaction, and that the 19-oic-11-deoxycorticosterone thus formed is nonenzymatically converted into 19-nor-11-deoxycorticosterone.

Adrenal Cortex↗
PubMed1988

Possibilities and limitations of the smearing technique for cellular studies in compact tissues: a transmission electron microscopic analysis of liver smears.

During the last decade a sophisticated biophysical technique called fluorescence recovery after photobleaching (FRAP) has become available for the measurement of lateral diffusion constants of lipids and proteins in the cell membrane. The information obtainable by this method is of great importance; however, the applicability of this method is seriously hindered by the fact that it has been elaborated mostly for isolated, individual cells. On the other hand, the use of freshly prepared cells from compact tissues for such studies is highly desirable. Therefore, a special smearing method was devised (using liver cells) for this purpose. The present paper describes (i) the method of standardization of the smearing technique, (ii) the ultrastructural features of the liver cells when studying the liver smears by means of transmission electron microscopy. The possibilities and limitations of this method are discussed. According to the observations, under well-defined conditions the structural integrity of hepatocytes is maintained in the liver smears to such an extent that they are suitable for FRAP experiments.

Animals↗
PubMed1988

Preservation of ovarian function and reproductive ability in patients with malignant ovarian tumors.

In a study designed to determine the merit of preserving ovarian function and childbearing capability in women with unilateral malignant ovarian tumors, the results of radical surgery (n = 86) and conservative surgery (n = 106) were compared. The mean length of survival was slightly but not significantly shorter following conservative surgery. There were 15 recurrences (14%) and 11 deaths among the conservative surgery group. The incidence of metastasis to the preserved ovary was high. In the most cases restoration of normal menses was fairly rapid after initial treatment, but this appeared to depend on whether or not chemotherapy was given postoperatively, the specific agents used, and the duration of their administration. Hypergonadotropic hypogonadism was the most common finding among the anovulatory patients. Sixteen women experienced a total of 27 pregnancies and 18 normal infants were born. Abortion was induced when conception occurred during a course of chemotherapy. These findings are encouraging in terms of the feasibility of preserving childbearing capability in ovarian cancer patients. However, they also underscore the necessity for close, long-term follow-up, which will be improved as new technologies become available.

Adult↗
PubMed1988

The neurotoxicity of phenobarbital and its effect in preventing pentylenetetrazole-induced maximal seizure in aging mice.

The effects of age on the neurotoxicity of phenobarbital and its anticonvulsant effect were examined in female BDF1 mice of different ages by means of a rotorod test and the pentylenetetrazole (PTZ)-induced maximal seizure, respectively. The minimal neurotoxic concentrations (MTCs) of phenobarbital in both plasma and brain evaluated by a rotorod test were 50% lower (p less than 0.05) in old (24-months-old) mice compared with the respective values in young (6-months-old) mice, while 12-months values were the highest of the three groups. Mice given some dosages of phenobarbital, particularly old (24-months-old) mice, died within the 15-min observation period after an i.p. injection of PTZ (150 mg/kg) without demonstrating a hindlimb extensor component (HLE) of maximal seizure. When these animals were classified as responders with regard to the anticonvulsant effect of phenobarbital, the minimal effective concentrations (MECs) in plasma and brain required for abolishing the PTZ-induced maximal seizure in old mice were only 10-20% those of young mice. Present results coupled with our past studies using electroshock seizure suggest that both the neurotoxicity and the efficacy of phenobarbital increase with age in mice.

Administration, Oral↗
PubMed1988

Elevation of serum pancreatic secretory trypsin inhibitor following serious injury.

Twenty-six of 31 seriously injured patients (84%) showed a marked elevation of serum pancreatic secretory trypsin inhibitor (PSTI) to more than twice the initial level within the first 2 weeks after admission. Serum PSTI rose from the second or third post-traumatic day and reached the maximum at day 5.8 on average. In uneventful cases, it returned to the level on admission within 2 weeks. The maximum serum PSTI in these patients was significantly correlated with the severity of the injury as judged at the time of admission, indicating that the elevation of serum PSTI in these patients was related to the extent of initial damage. In contrast, serum PSTI in patients with serious complications remained at high level even at 2 weeks after trauma, and it was not correlated with the initial severity of the injury.

Adult↗
PubMed1988

Dynamic response to follicle-stimulating hormone of secretion of progesterone by superfused rat ovarian granulosa cells.

Granulosa cells from immature female rats, pretreated with pregnant mare's serum gonadotropin, were cultured with microcarrier beads for 24 h, and superfused with culture medium. Progesterone was transiently released following a 10-min pulse of FSH (100 ng/ml), and there was a self-priming effect of FSH. 10-min pulses of 8-bromo-adenosine 3',5'-cyclic monophosphate (8Br-cAMP) (1 mg/ml) mimicked the effects of follicle-stimulating hormone (FSH). Continuous superfusion with FSH induced biphasic secretion of progesterone, which was composed of a parabolic (the first) and a plateau (the second) phase. By contrast, the pattern of secretion induced by continuous superfusion with 8Br-cAMP was monophasic. FSH-stimulated secretion of progesterone was rapidly inhibited by the addition of 10 microM cycloheximide (CX), but secretion recovered upon removal of this inhibitor. In the second phase, the recovery of secretion was accompanied by an overshoot of the plateau value. The present results suggest that: (1) the generation of the time-related biphasic pattern of secretion cannot be interpreted by cAMP alone; (2) FSH stimulates the secretion of progesterone by a mechanism that involves newly synthesized protein.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1988

Gluconeogenesis in perfused chicken kidney. Effects of feeding and starvation.

1. Starvation for 48 hr doubled the rate of gluconeogenesis from lactate and pyruvate in perfused chicken kidney, but did not change the rate of production of glucose from malate, succinate, or alpha-ketoglutarate. 2. Amino-oxyacetate and D-malate inhibited the production of glucose from lactate and from pyruvate by 55% in each case. Quinolinate reduced the production of glucose from lactate and from pyruvate by 50% in both fed and starved chickens, but had no effect on the production of glucose from intermediates in the citric acid cycle. 3. Starvation increased the rate of formation of mitochondrial phosphoenolpyruvate from pyruvate, but had no effect on the rate of formation of mitochondrial phosphoenolpyruvate from malate.

Animals↗
PubMed1988

Successful treatment of primary endodermal sinus tumor of the endometrium.

Endodermal sinus tumor (EST) arising in the endometrium is an extremely rare malignant neoplasm. To the authors' knowledge, this is only the second report of an EST arising in this location. The tumor was exophytic, 2.4 cm in diameter, and was located in the fundus uteri. It had infiltrated the circumambient endometrium slightly. Preoperative serum alpha-fetoprotein (AFP) levels were markedly elevated, 1580 ng/ml. The patient received a simple abdominal hysterectomy and bilateral salpingo-oophorectomy followed by combination chemotherapy consisting of vincristine, actinomycin D, and cyclophosphamide. To date, there has been no evidence of tumor recurrence, and serum AFP titers, which had returned to normal 7 weeks after surgery, continue to remain within normal limits. We believe this is the first successful treatment of a documented case of primary EST of the endometrium.

Adult↗
PubMed1988

Scanning electron microscopy of the hepatocyte cytoskeleton in human liver tissue.

Portions of eight human livers taken by wedge biopsy or needle biopsy were extracted with 0.5% Triton X-100 and then studied by scanning electron microscopy and immunoelectron microscopy. The wedge-biopsy specimens were perfused with the detergent solution. Needle-biopsy specimens were quickly frozen and cracked and then the cracked tissue was immersed in the detergent solution. The three-dimensional filament network of hepatocytes was visualized. A dense network which consisted of intermediate filaments and microfilaments was observed within the cytoplasm of hepatocytes. These filaments were better preserved in the needle biopsies which were quick-frozen and cracked before extraction than in the wedge biopsies. Variation in the amount of the cytoskeletal filaments was less prominent in the hepatocytes treated by rapid freezing. It is concluded that freeze-cracking is the most favorable method for the study of cytoskeletal pathology in various liver diseases in man.

Biopsy↗