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Biomedical subjects

T Fushiki

Publications and source records attributed to T Fushiki.

At least 19 recordsLinked to original sources
PubMed1992

Molecular cloning and characterization of genes encoding rat pancreatic cholecystokinin (CCK)-releasing peptide (monitor peptide) and pancreatic secretory trypsin inhibitor (PSTI).

The genes encoding a rat pancreatic cholecystokinin (CCK)-releasing peptide (monitor peptide) and its structurally related peptide, rat pancreatic secretory trypsin inhibitor (PSTI), have been isolated and sequenced. The two genes share extremely high sequence similarity in the 5' flanking regions, suggesting that these regions may be responsible for the characteristic coordinate expression of the two peptides.

Amino Acid Sequence↗
PubMed1992

Monitor peptide gene expression is increased by exogenous CCK in the rat pancreas and in a rat pancreatic acinar cell line (AR4-2J).

Monitor peptide (CCK-releasing peptide) mRNA increased on the administration of CCK in rat pancreas and the AR4-2J pancreatic cell line. Subcutaneous injection of CCK into rats at 8 h intervals increased the level of monitor peptide mRNA in the pancreas. Concomitant injection of CCK antagonist CR-1409 strongly decreased it. The monitor peptide mRNA was also increased by CCK in AR4-2J cells and was decreased by the antagonist. These findings suggest that the plasma CCK induced by prolonged intake of a high protein diet may be responsible for the adaptative increase in the monitor peptide as well as exocrine proteases in the pancreas.

Amylases↗
PubMed1992

An extract of Gymnema sylvestre leaves and purified gymnemic acid inhibits glucose-stimulated gastric inhibitory peptide secretion in rats.

Gastric inhibitory peptide release into the portal vein in response to duodenal infusion of D-glucose was studied in the presence of a leaf extract of Gymnema sylvestre, purified gymnemic acid and inhibitors of some putative glucose sensors and carriers in the intestinal lumen. Intraduodenal infusion of D-glucose significantly increased the portal immunoreactive gastric inhibitory peptide concentration in a dose-dependent manner. The increase in the portal immunoreactive gastric inhibitory peptide induced by glucose was significantly depressed by concomitantly infused leaf extract of Gymnema sylvestre, purified gymnemic acid and phlorizin but not by cytochalasin B. Mannoheptulose, which inhibits glycolysis, and procaine and lidocaine, which inhibit the vagal glucoreceptor in the lumen, did not affect portal immunoreactive gastric inhibitory peptide concentrations. These results suggest that a glucose receptor, which interacts with the leaf extract of Gymnema sylvestre, purified gymnemic acid and phlorizin, exists for the release of immunoreactive gastric inhibitory peptide and that the glucose receptor for gastric inhibitory peptide release is not likely to be identical with a glucose transporter or a vagal glucoreceptor in the lumen.

3-O-Methylglucose↗
PubMed1992

Effects of chronic hypoxia on the whole-body insulin action in rats.

The effect of chronic hypoxia on the whole-body insulin action in rats was investigated. Rats were kept in a hypobaric hypoxia chamber maintained at a simulated altitude of 4000 m for 10 weeks. At the end of the experimental period, the mean body weight of the hypoxic rats was significantly lower than that of the control rats. The muscle weight to body ratio of the quadriceps muscle in hypoxic rats was larger than that in control rats, but those of the gastrocnemius, soleus, and extensor digitorum longus muscles did not differ between the control and hypoxic rats. On the other hand, the epididymal fat pads of hypoxic rats were markedly smaller than those of the control rats. The results of a euglycemic clamp experiment with infusions of 14 and 3.6 mU insulin.kg-1.min-1 indicated that the steady-state glucose infusion rate was not statistically different between hypoxic and control rats. It is suggested that chronic hypoxia did not influence the whole-body insulin action on glucose transport activity.

Adipose Tissue↗
PubMed1991

Effect of a high-protein diet on the gene expression of a trypsin-sensitive, cholecystokinin-releasing peptide (monitor peptide) in the pancreas.

The adaptation to a high protein diet of the concentration and mRNA level of a trypsin-sensitive, cholecystokinin-releasing peptide (monitor peptide), which was proposed to be the mediator of the cholecystokinin release in response to protein intake, was investigated in the rat pancreas. Adult rats were placed on one of two isocaloric diets. One group was fed a 22% casein diet (control diet) and the other a 64% casein diet (high-protein diet) for 14 days. In order to quantify the monitor peptide separately from pancreatic secretory trypsin inhibitor (PSTI-II), which is highly similar in its amino acid and mRNA nucleotide sequences to the monitor peptide but has less cholecystokinin-releasing activity, we used specific assay methods: HPLC was used for determining the monitor peptide concentration in zymogen granules and a synthetic oligonucleotide probe for determining the mRNA of the monitor peptide in the pancreas. The concentrations in the zymogen granules and the mRNA levels in the pancreas of the two peptides increased in parallel during the adaptation to the high protein diet, indicating that these two peptides were under the same control during the adaptation. The concentration and mRNA level of the monitor peptide, which were measured after 0, 3, and 14 days, increased throughout the experiment period, as did the concentration of trypsin. This suggested that the monitor peptide and trypsin may respond to similar signals during the adaptation to a high protein diet and that this apparent coordination may facilitate the adaptation of the pancreas to the diet.

Amino Acid Sequence↗
PubMed1991

Decrease in muscle glucose transporter number in chronic physical inactivity in rats.

In this study, whole body insulin action on glucose uptake and muscle glucose transporter number of rats subjected to 14 days of physical inactivity conditions was examined. Unlike other suspension and denervation models of muscle disuse, this physical inactivity model allows voluntary contractile activity with minimal stress. Minimal depression of body weight gain and significant depression of gastrocnemius muscle growth were observed compared with that of control rats after 14 days of physical inactivity. The whole body insulin sensitivity and responsiveness were determined by the euglycemic clamp technique, with 1.4, 3.6, and 14 mU insulin.kg-1.min-1 perfusion and 2-deoxy-D-[3H]glucose incorporation. The rates of glucose disposal were the same in the restrained rats as in the controls with the 1.4 and 3.6 mU insulin perfusion; however, glucose disposal significantly decreased with 14 mU insulin perfusion. 2-Deoxy-D-[3H]glucose uptake into the gastrocnemius muscle was higher in the control rats than in the physically inactive rats. Glucose transporters in the gastrocnemius and quadriceps muscles, measured by means of the D-glucose-inhibitable cytochalasin B binding assay, were significantly decreased in number in the physically inactive rats. These findings suggest that the decrease in whole body glucose uptake might in part be explained by the decreases in the total glucose transporter number in muscles.

Adrenocorticotropic Hormone↗
PubMed1990

Luminal CCK-releasing factors in the isolated vascularly perfused rat duodenojejunum.

The factors operating at the apical side of the endocrine cell releasing cholecystokinin (CCK) were investigated using the isolated vascularly perfused rat duodenojejunum. In the protease-free intestinal segment, a 30-min infusion of glucose (280 mM), oleic acid (100 mM), or triglycerides containing short- or long-chain fatty acids did not alter significantly the basal level of portal CCK-like immunoreactivity (CCK-LI), while octanoic acid (100 mM) produced a transient rise of plasma CCK-LI to approximately 250% of basal. Infusion of proteins (5% solutions of ovalbumin or casein) or of a mixture of all amino acids brought about a modest CCK secretion. In contrast, isocaloric amounts of an ovalbumin hydrolysate produced a sharp rise of portal CCK-LI to 530% of basal followed by a well-sustained plateau secretion (420% of basal) until the end of the infusion. An acid casein hydrolysate induced a slightly less pronounced CCK-LI release and was followed in decreasing order by meat, casein, and soybean peptones. Simultaneous infusion of trypsin with ovalbumin or casein hydrolysate reduced by approximately 60% the CCK release induced by peptone alone. This effect was reversed by coinfusion of soybean trypsin inhibitor (SBTI) with the trypsin-peptone mixture. Arterial infusion of tetrodotoxin (10(-6) M) or atropine (10(-5) M) had no significant effect on the trypsin-induced inhibition of peptone-mediated CCK-LI release. Administration of SBTI or camostate alone or in combination with trypsin did not alter basal CCK. Monitor peptide produced a dose-dependent transient rise of portal CCK-LI over the range from 2 to 12 micrograms.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1989

Differentiation of intestinal epithelial cell line (IEC-18) by an acid extract of rat small intestine.

A factor which may induce differentiation of intestinal epithelial cell lines in vitro was found in an acid extract of adult rat small intestine. The addition of a partially purified acetic acid extract of rat small intestine to IEC-18 cell culture dishes increased sucrase activity within 48 h. Thymidine incorporation markedly decreased within 24 h. Significant development of microvilli-like structures was observed on the acid extract-treated IEC-18 cells, compared with controls. This activity of rat acid extract was heat-stable and the apparent molecular weight of the factor was 400-800. These findings suggested that the factor may be related to the epithelial differentiation of rat small intestinal crypt cells.

Animals↗
PubMed1989

Evidence for an intraluminal mediator in rat pancreatic enzyme secretion: reconstitution of the pancreatic response with dietary protein, trypsin and the monitor peptide.

New evidence has been obtained suggesting that the "monitor" peptide is an essential intraluminal mediator in the stimulation of pancreatic enzyme secretion in response to protein intake in rats. Experiments were performed in vivo using a mixture of 50 mg of ovalbumin, alpha-lactalbumin or casein, 2 micrograms of purified protease-sensitive, cholecystokinin-releasing monitor peptide and 1 mg of porcine trypsin which was infused by cannula into the duodenum of atropine-treated rats. The small intestine had previously been washed with bicarbonate to eliminate proteases and the pancreatic juice was diverted. The amount of trypsin secreted in 2 h was comparable to that of rats in which the pancreatic juice was returned into the duodenum. However, in the presence of a monitor peptide--specific antibody which recognizes the N-terminal region of the peptide, the monitor peptide did not induce any pancreatic response. Therefore, the characteristic pattern of pancreatic enzyme secretion in response to protein intake can be reproduced by infusing only three components--dietary proteins, porcine trypsin and the purified monitor peptide.

Animals↗
PubMed1989

Two hypotheses on the feedback regulation of pancreatic enzyme secretion.

We review the mechanisms underlying the feedback regulation of pancreatic enzyme secretion in response to a meal. Pancreatic enzyme secretion in the rat and pig is known to be regulated by a negative feedback mechanism mediated by intestinal trypsin and chymotrypsin. Such a mechanism has recently been noted in humans. The presence of these enzymes in the small intestine suppresses pancreatic enzyme secretion, whereas their removal increases it. Two novel peptides have been proposed to account for the stimulation of pancreatic enzyme secretion in response to feeding trypsin inhibitor. One was assumed to be present in rat pancreatic juice and the other to be spontaneously secreted from the rat small intestine. In either case, trypsin and trypsin inhibitors do not directly interact with the luminal surface of the small intestine, but their actions are mediated by a trypsin-sensitive, cholecystokinin-releasing peptide. This is a novel explanation of the well-recognized stimulation of pancreatic enzyme secretion in response to dietary protein intake.

Cholecystokinin↗
PubMed1989

Changes in glucose transporters in muscle in response to exercise.

The mechanism underlying the increase in glucose uptake in response to muscular contraction is not known, although it has been established that the change does not require insulin. It is our hypothesis that exercise, like insulin, stimulates translocation of glucose transporters to the plasma membrane. To test this hypothesis an experiment was performed to determine whether glucose transporters are translocated from an intracellular membrane to the plasma membrane during exercise. Untrained male rats weighing approximately 250 g were exercised by treadmill running for 2 h at 25 m/min. They were killed immediately after completion of exercise, and the gastrocnemius and quadriceps muscles were quickly removed. Sedentary animals were treated in the same way. Plasma and intracellular membranes were isolated by sucrose density gradient centrifugation and cytochalasin B binding assays were performed. Exercise resulted in a redistribution of glucose transporters from the intracellular membrane to the plasma membrane. The ratio of cytochalasin B binding sites in the membrane fractions (intracellular/plasma membrane) was 3.2 +/- 0.6 in rested animals and 1.3 +/- 0.3 after exercise. The concentration of glucose transporters was increased in the plasma membrane (from 19.8 +/- 1.8 to 30.4 +/- 3.9 pmol/mg protein) and decreased in the intracellular membrane (from 20.7 +/- 3.0 to 10.8 +/- 1.1 pmol/mg protein) in response to exercise. These results suggest that at least part of the increase in glucose uptake that occurs during exercise is the result of a redistribution of glucose transporters to the plasma membrane.

Animals↗
PubMed1988

Preparation of a verifiable peptide-protein immunogen: direction-controlled conjugation of a synthetic fragment of the monitor peptide with myoglobin and application for sequence analysis.

A useful method for preparing a synthetic peptide-carrying protein for specific antibody production was established. The monitor peptide is a trypsin-sensitive cholecystokinin-releasing peptide purified from rat pancreatic juice on the basis of its stimulatory activity toward pancreatic enzyme secretion. The NH2-terminus fragment of the monitor peptide (residues 1-14) was synthesized by a solid phase method. Cysteine at the COOH terminus of the fragment was conjugated with amino groups of myoglobin using a hetero-bifunctional reagent. Sequence analysis of the fragment-myoglobin conjugate indicated that the peptide/myoglobin conjugation ratio was about 1/1 (mol/mol). Antiserum against the conjugate from a rabbit effectively abolished the stimulatory activity of the monitor peptide in the rat small intestine.

Amino Acid Sequence↗
PubMed1988

Pancreatic enzyme secretion mediated by novel peptide: monitor peptide hypothesis.

A new model is proposed for pancreatic enzyme secretion in response to food protein intake in rats. We have found a novel peptide in rat bile-pancreatic juice, which exhibits a trypsin-sensitive, cholecystokinin (CCK)-releasing activity. The amino acid sequence of the peptide purified from rat bile-pancreatic juice is very similar to that of a conservative region in pancreatic secretory trypsin inhibitor (PSTI). The peptide loses its CCK-releasing activity during trypsin digestion, but food protein intake prevents this trypsin digestion. Results of a reconstitution experiment indicate that pancreatic enzyme secretion in response to food protein intake only occurs as a result of interaction between trypsin and our purified peptide. Also, a peptide-specific antibody abolished the response. These findings lead us to hypothesize that this peptide acts as an intraduodenal mediator for CCK release in response to food protein intake.

Amino Acid Sequence↗
PubMed1988

An in vitro human muscle preparation suitable for metabolic studies. Decreased insulin stimulation of glucose transport in muscle from morbidly obese and diabetic subjects.

We have developed an in vitro muscle preparation suitable for metabolic studies with human muscle tissue and have investigated the effects of obesity and non-insulin-dependent diabetes mellitus (NIDDM) on glucose transport. Transport of 3-O-methylglucose and 2-deoxyglucose was stimulated approximately twofold by insulin in muscle from normal nonobese subjects and stimulation occurred in the normal physiological range of insulin concentrations. In contrast to insulin stimulation of 3-O-methylglucose and 2-deoxyglucose transport in muscle from normal, nonobese subjects, tissue from morbidly obese subjects, with or without NIDDM, were not responsive to insulin. Maximal 3-O-methylglucose transport was lower in muscle of obese than nonobese subjects. Morbidly obese patients, with or without NIDDM, have a severe state of insulin resistance in glucose transport. The novel in vitro human skeletal muscle preparation herein described should be useful in investigating the mechanism of this insulin resistance.

3-O-Methylglucose↗
PubMed1987

Appearance of slow-reacting and complement-requiring neutralizing antibody in cattle infected with Akabane virus.

Slow-reacting complement-requiring neutralizing (NT) antibody was detected in sera from cattle 2 weeks after infection with Akabane virus. Bovine sera obtained 3 or 4 weeks after infection contained slow-reacting noncomplement-requiring NT antibody. The slow-reacting complement-requiring NT antibody was sensitive to 2-mercaptoethanol (2-ME), whereas the slow-reacting noncomplement-requiring NT antibody was resistant to 2-ME. The initial phase may represent the IgM response and the later phase a change to IgG. A NT test was developed in which virus-serum mixtures were incubated at 4 degrees C for 48 h and then with complement at 37 degrees C for 60 min; this gave an improved sensitivity over the previous incubation at 37 degrees C for 60 min.

Animals↗
PubMed1987

Influence of neural blockages and proglumide on rat pancreatic enzyme secretion in response to intraluminal fatty acid.

Effects of neural blockages on pancreatic enzyme secretion in response to infusing fatty acid into the lumen were investigated using anesthetized rats, equipped with bile-pancreatic and duodenal cannulae, to evaluate the relative contribution of the neural and the hormonal mediations in the pancreatic response. Oleate (0.2 ml) was injected as a bolus into the rat duodenum, and the trypsin output in bile-pancreatic juice was monitored to determine the pancreatic enzyme secretion response with continuous return of bile-pancreatic juice to the intestine. When anticholinergic agents such as atropine sulfate and scopolamine were administrated, although basal level in pancreatic enzyme secretion fell, the increase of pancreatic enzyme secretion from basal level after stimulation by oleate was not significantly different from that of the control (no blockage). However, the ganglion blocker, hexamethonium, inhibited the pancreatic enzyme secretion in response to oleate by 94%. An adrenergic blocker, guanethidine, also led to as much of a decrease as the ganglion blocker-induced decrease. Adrenergic alpha- and beta-blockers partially, but not completely, inhibited the enzyme secretion. Adrenergic blockage also suppressed the basal level in pancreatic enzyme secretion. On the other hand, a specific CCK antagonist, proglumide, significantly inhibited pancreatic enzyme secretion induced by oleate in the presence of scopolamine. These observations suggest that pancreatic enzyme secretion in response to oleate is primarily mediated by CCK and that adrenergic modulation may play an important role in the CCK-mediated pancreatic enzyme secretion in response to oleate, although interpretation of these results may have some restriction related to anesthesia.

Adrenergic alpha-Antagonists↗
PubMed1986

Localization of pancreatic enzyme secretion-stimulating activity and trypsin inhibitory activity in zymogen granule of the rat pancreas.

The intracellular localization of pancreatic enzyme secretion-stimulating activity in rat pancreas was investigated. We found and purified a pancreatic enzyme secretion-stimulating peptide from rat bile/pancreatic juice. The peptide is trypsin-sensitive (showing temporary trypsin inhibitory activity), and it is hypothesized that it acts as a trypsin-sensitive mediator in the feedback regulation of diet-induced pancreatic enzyme secretion. The zymogen granule fraction was purified 5-fold by ultracentrifugation by the Percoll density gradient method. The purity of the zymogen granule fraction was determined from the specific amylase activity and electron microscopic morphology. The specific enzyme activities of amylase and trypsin and the trypsin inhibitory activity increased in parallel during the purification, and the pancreatic enzyme secretion-stimulating activity was also localized in the zymogen granule fraction. These results suggest that the pancreatic enzyme secretion-stimulating peptide originates from the acinar cells, and that it is secreted through exocytosis of zymogen granules into the small intestine, its ratio to trypsin thus remaining constant. This idea supports our hypothesis that the stimulating peptide acts as a mediator for the feedback regulation of pancreatic enzyme secretion by trypsin.

Amylases↗