Search PubMed⌕ Search

Biomedical subjects

F Ishibashi

Publications and source records attributed to F Ishibashi.

At least 55 records · Page 3Linked to original sources
PubMed1990

The effect of timing on gliclazide absorption and action.

In this study we tried to determine when in relation to meals gliclazide should be taken for optimum hypoglycemic action. Eight non-insulin-dependent diabetics participated in this study during hospitalization for glycemic control. After stabilization of glycemic control on gliclazide, they took a 40 mg tablet of gliclazide either 30 minutes before, immediately before, or immediately after breakfast on 3 consecutive days. We then determined serum gliclazide, glucose and IRI levels at 30-minutes intervals beginning 30 minutes before breakfast and continuing until 2 hours after breakfast. Gliclazide taken 30 minutes before breakfast increased in serum concentration before the meal-induced hyperglycemia, but that taken just before or just after breakfast was poorly absorbed and showed smaller and greatly delayed peaks. When taken 30 minutes before breakfast, gliclazide produced a peak of IRI 30 minutes after the meal; taken immediately before or after, it took twice to three times as long to produce an IRI peak. Postprandial hyperglycemia remained pronounced for a relatively long time when the drug was taken immediately before or after the meal. Based upon the experimental evidence we propose the tentative recommendation that gliclazide is best taken 30 minutes before breakfast.

Absorption↗
PubMed1989

Comparative studies on microsomal NADPH-cytochrome P-450 reductase using a monoclonal antibody: tissue distribution, specific activity and peptide mapping.

1. In order to elucidate the molecular structure and the distribution of the enzyme in different microsomes, specific antibodies have been developed against rabbit liver NADPH-cytochrome P-450 reductase. 2. The monoclonal antibody (MAb B1) against rabbit liver reductase cross-reacted well with reductases from various animal species and those from various tissues of the rabbit. 3. NADPH-cytochrome P-450 reductase from rabbit tissues such as liver, lung, adrenal gland, kidney and polymorphonuclear leukocyte were closely related in structure and antigenic properties, in addition to having similar catalytic properties. 4. No multiple forms of the reductase in the rabbit were observed in liver nor in other tissues.

Animals↗
PubMed1987

Interaction of heme with a synthetic peptide mimicking the putative heme-binding site of histidine-rich glycoprotein.

We synthesized a hexapeptide, Gly-His-His-Pro-His-Gly, previously identified as a tandem motif in the histidine-rich glycoprotein (HRG) which has multiple heme-binding sites. Binding of heme to the peptide was demonstrated by the characteristic difference spectrum showing a close resemblance to that of HRG, implying that the peptide binds heme through biaxial coordination with histidine imidazoles. Furthermore, the EPR spectra of the heme-peptide and heme-HRG complexes were almost completely identical in pattern, showing signals characteristic of the low spin iron. The results suggest that the synthetic peptide simulates the heme-binding properties of HRG and that each tandem motif in HRG serves as a unitary binding site for heme.

Binding Sites↗
PubMed1983

Effect of temperature on insulin binding and action in cultured human fibroblasts.

Insulin stimulation of glycogen synthase activity and insulin binding were measured in fibroblast monolayers at 24, 32, and 37 degrees C. Insulin stimulation of %I glycogen activity increased with increasing temperature. Maximum response was greater at 37 degrees C than at 32 degrees C, and half maximal stimulation required at 2.0 nM insulin at 37 degrees C vs. 10 nM at 32 degrees C. Insulin stimulation of glycogen synthase was greater and somewhat faster at 37 degrees C than at 32 degrees C. No insulin effect was observed at 24 degrees C. 125I-insulin binding to monolayers became maximal in 15 min at 37 degrees C, 60 min at 32 degrees C, and 120 min at 24 degrees C. However, insulin binding decreased with increasing temperature, and this decline was due to decreased numbers of receptors. Insulin binding and stimulation of glycogen synthase were comparable at 32 degrees C, with half maxima at 10 nM, indicating no evidence of "spare" receptors. The data indicate that temperature effects on insulin binding and action in fibroblasts are not directly related. The results also suggest that a rate limiting step(s) of insulin action is temperature sensitive, and that this step is not insulin binding.

Cells, Cultured↗
PubMed1982

Measurement of intracellular volume in monolayers of cultured cells.

Methods have been developed for measuring the intracellular water space (ICS) in cultured diploid fibroblast monolayers. The values obtained have been compared to similar measurements of ICS in suspended fibroblasts using an oil spin method. Markers commonly used for measurement of total water space (TWS) ([3H]H2O, [14C]urea) and extracellular space (ECS) ([3H]inulin, [14C]L-glucose, [3H]sucrose, [3H]D-mannitol) were investigated for use in cell monolayers. Monolayer incubations were terminated by rapidly rinsing the culture dishes three times with ice cold buffer. The distribution volume of the TWS marker [14C]urea plateaued at 10 to 15 min and was independent of urea concentration. [3H]H2O was not a suitable marker for measuring total water space in cell monolayers because of rapid loss of intracellular label during rinsing. Intracellular space was calculated by subtracting [3H]sucrose space (5 min) from [14C]urea space (20 min) after incubation of fibroblasts with both markers. Values obtained for ICS (mean +/- SE: microliter/10(6) cells) of fibroblasts from two cell lines measured in monolayer (1.74 +/- 0.11 and 1.60 +/- 0.10) and in suspension (1.88 +/- 0.07 and 1.78 +/- 0.11) was approximately 10% smaller than the values for cell size (2.01 and 2.22) obtained from Coulter Counter sizing. Thus, the methods developed for measurement of ICS in monolayer fibroblasts yield data comparable to those obtained with the more standard oil spin method. Furthermore, the methods can be applied to measurement of ICS in other types of adherent cells.

Body Fluids↗
PubMed1982

Glucose enhancement of insulin action: elevated glucose levels increase insulin stimulation of 2-deoxyglucose uptake in cultured human fibroblasts.

Insulin stimulation of 2-deoxyglucose uptake in cultured human skin fibroblasts has been examined in the presence of varying concentrations of extracellular glucose. When cell monolayers were preincubated in glucose-free medium, insulin stimulation of hexose transport was small. Increasing glucose levels from 2.7 to 16.7 mM in the preincubation medium enhanced insulin-stimulation 2-deoxyglucose uptake (18-65% of basal uptake). Insulin stimulation of hexose transport in the presence of glucose was the result of an increase in the Vmax without a significant change in the Km of transport. Maximum enhancement of insulin action was achieved 18-24 h after glucose exposure. After 24 h, the insulin response decreased. Glucose did not influence the concentration of insulin required for half-maximal stimulation. Growth conditions also altered the magnitude of insulin stimulation of 2-deoxyglucose uptake; the response was maximal in confluent cells (5-10 days of culture) and decreased during senescence. These data demonstrate that extracellular glucose levels influence insulin action in cultured fibroblasts. This implies that insulin responsiveness in vivo may be regulated in some systems by ambient glucose levels.

Adult↗
PubMed1981

Intravascular oxygen monitoring with a polarographic oxygen cathode.

Thin flexible oxygen cathodes coated with heparin-dispersed cellulose diacetate were prepared for an intravascular monitoring of blood pO2. The effect of the thickness of cellulose diacetate on various characteristics of the cathode, such as its sensitivity, response, residual current, moving artefact, linearity, and protection against poisoning, were measured. Coating with six to ten layers of 7.5% cellulose diacetate resulted in a high level of protection for cathode against poisoning by blood constituents, while still leaving a sufficiently rapid response. An instillation system using heparinized saline has been designed for further prevention of local blood coagulation. At the same time this system maintains a stable conductance of the salt bridge and furthermore, enables in vivo calibration of the cathode sensitivity by supplying an instillation solution of a known oxygen tension. Using this electrode system, various intravascular pO2 measurements have been carried out, and one representative result is shown. The advantages and disadvantages of this type of separated electrode system compared with the combined type electrode are also discussed in detail.

Animals↗
PubMed1981

Alloxan action on glucose metabolism in cultured fibroblasts. I. Stimulation and inhibition of glucose utilization.

The influence of alloxan on mammalian cell glucose metabolism has been investigated using human diploid fibroblastic cells in culture. When cell monolayers were exposed to D-[14C]glucose, the presence of alloxan (0.31-1.87 mM) resulted initially in a dose-dependent enhancement of total cell glucose incorporation. This was observed within 2 min and declined by 6 min. After that time, alloxan inhibited glucose incorporation. When hexose transport was examined directly using glucose analogues, alloxan neither enhanced nor inhibited the uptake of 3-O-methylglucose or 2-deoxyglucose. Alloxan exerted no effect on cell permeability or cell viability. These results suggest that alloxan may directly influence cell glucose metabolism beyond the level of phosphorylation. The dual effect of alloxan on glucose incorporation may be related to the alloxan stimulation and subsequent inhibition of glucose-induced insulin release in pancreatic islets.

Alloxan↗
PubMed1981

Alloxan action on glucose metabolism in cultured fibroblasts. II. Effects on pentose-monophosphate shunt and tricarboxylic acid pathways.

The site of action of alloxan on glucose metabolism has been investigated using cultured human fibroblasts. Analysis of cell extracts after cell monolayers were exposed to D-[U-14C]glucose indicated that the initial stimulation of glucose incorporation by alloxan was observed primarily in the nucleotide fraction (ribose) with inhibition of lactate production. The subsequent inhibition of glucose incorporation was observed in the nucleotide fraction. Assay of 14CO2 production indicated that alloxan enhanced 14CO2 formation from D-[U-14C]glucose for approximately 10 min, followed by inhibition. To probe the site of alloxan action, rates of 14CO2 formation from 1- and 6-position labeled [14C]glucose, and [U-14C]pyruvate were compared. The initial stimulation was observed mainly in D-[1-14C]glucose oxidation, whereas inhibition was measurable with the 6-position tracer and [14C]pyruvate. The results suggest that alloxan initially stimulates the pentose-monophosphate shunt and then subsequently inhibits both the pentose-monophosphate shunt and tricarboxylic acid pathways.

Alloxan↗