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Biomedical subjects

H Tamamura

Publications and source records attributed to H Tamamura.

69 records · Page 4Linked to original sources
PubMed1990

Isolation and characterization of a tumor-derived human protein related to chromogranin A and its in vitro conversion to human pancreastatin-48.

A protein with pancreastatin-like immunoreactivity has been isolated and purified from liver metastasis of a patient with insulinoma. NH2-terminal residue analysis, in conjunction with the use of antibodies that are specific for the C-terminal amide peptide of porcine pancreastatin, identified this protein as a 186-amino-acid protein corresponding to human chromogranin A-116-301 (the fragment corresponding to the positions from 116 to 301 of human chromogranin A). Digestion of this protein with trypsin yielded a 48-amino-acid peptide with the retention of full pancreastatin activity. Serum from patient with insulinoma contains a peptide specie(s) that comigrates with the 48-amino-acid pancreastatin, suggesting that this peptide might be a physiologically important circulation form of pancreastatin in humans. A sensitive radioimmunoassay was established using antibody developed against a synthetic 29-amino-acid peptide amide of pancreastatin. Immunocytochemical staining revealed that a major population of human pancreatic islet cells were immunoreactive to the antiserum but with varying intensity of staining. Pancreastatin-like immunoreactivity was not observed in exocrine acinar cells.

Adenoma, Islet Cell↗
PubMed1990

The importance of the C-terminal amide structure of rat pancreastatin to inhibit pancreatic exocrine secretion.

A C-terminal fragment of rat pancreatatin, a 26 residue peptide amide and a fragment without a C-terminal amide were synthesized by Fmoc-based solid phase methods and their biological activities were compared. The rat C-terminal fragment inhibited pancreatic exocrine secretions produced by the intravenous injection of 2-deoxy-D-glucose (a central vagal nerve stimulation), whereas the fragment without a C-terminal amide showed no effect on pancreas. These results indicate that the C-terminal amide of this peptide is necessary to reveal its biological activity.

Animals↗
PubMed1990

Rat pancreastatin inhibits both pancreatic exocrine and endocrine secretions in rats.

Effects of synthetic rat pancreastatin C-terminal fragment on both exocrine and endocrine pancreatic functions were examined in rats, in vivo and in vitro. Pancreastatin (20, 100 pmol, 1 nmol/kg/h) significantly inhibited CCK-8-stimulated pancreatic juice flow and protein output in a dose-related manner, in vivo. The inhibitory effect on bicarbonate output was not statistically significant. Pancreastatin did not significantly inhibit basal pancreatic secretions in vivo, and did not inhibit amylase release from the dispersed acini, in vitro. Insulin release stimulated by intragastric administration of glucose (5 g/kg) was significantly inhibited by pancreastatin (1 nmol/kg/h), in vivo. Plasma glucose concentrations were increased by pancreastatin infusion, but the increase was not statistically significant. Furthermore, pancreastatin inhibited insulin release from isolated islets, in vitro. Synthetic rat C-terminal pancreastatin fragment has bioactivities on both exocrine and endocrine pancreatic functions in rats.

Amylases↗
PubMed1990

Inhibitory effect of pancreastatin on pancreatic exocrine secretions. Pancreastatin inhibits central vagal nerve stimulation.

The effects of the C-terminal fragment of rat pancreastatin on exocrine pancreatic secretions induced by several neural stimulations [IV injection of 75 or 15 mg/kg of 2-deoxy-D-glucose (central vagal nerve stimulation), injection of 2 mg of cisapride (proposed to elicit acetylcholine release from cholinergic nerve ending), and infusion of 1 or 3 mg.kg-1.h-1 of bethanechol (direct stimulation of acinar cells)] were examined in conscious rats. Rats with external bile and pancreatic fistulae were used. All the stimulations caused significant increases in pancreatic exocrine secretions. Pancreastatin at 100 pmol.kg-1.h-1 inhibited pancreatic secretions stimulated by IV injection of 2-deoxy-D-glucose but not those induced by the infusion of bethanechol or the injection of cisapride. Because these findings showed that pancreastatin inhibited pancreatic secretions induced by central vagal nerve stimulation, the effect of pancreastatin on cholecystokinin-stimulated pancreatic secretions in vagotomized rats was examined. Pancreastatin at 100 pmol.kg-1.h-1 did not inhibit pancreatic secretions stimulated by cholecystokinin octapeptide at 100 pmol.kg-1.h-1 in conscious rats after bilateral truncal vagotomy. These results suggest that pancreastatin inhibits pancreatic exocrine secretions by inhibiting vagal efferent nerve activity.

Animals↗
PubMed1990

Intraocular lesions in patients with systemic disease: findings on MR imaging.

Twenty-one intraocular lesions associated with various systemic diseases in 15 patients were studied by MR imaging. The disorders included diabetes mellitus, cardiovascular disease, Behçet disease, sarcoidosis, and ankylosing spondylitis. MR was performed on a 0.5-T system using a surface-coil technique. Ophthalmoscopic visualization of the fundus was precluded by the presence of opaque media in all cases. MR was found to be effective in demonstrating intraocular bleeding, vitreous opacity, detached lesions of the posterior pole, and eyeball deformity. Surface-coil MR is a useful adjunct in the evaluation of the eyes affected by systemic diseases, especially in patients with opaque media.

Adult↗
PubMed1989

Isolation and characterization of a tumor-derived human pancreastatin-related protein.

A protein with pancreastatin-like immunoreactivity has been isolated and purified from liver metastasis of a patient with insulinoma. NH2-terminal sequence analysis in conjunction with the use of antibodies specific for the C-terminal structure of pancreastatin identified this protein as a 186-amino acid residue protein corresponding to human chromogranin A-116-301. Using a sensitive radioimmunoassay it was found that serum from the patient with insulinoma contains two peptide species; one comigrates with the 186-amino acid residue pancreastatin and the other the 48-residue pancreastatin.

Amino Acid Sequence↗
PubMed1989

Bioactivity of human pancreastatin and its localization in pancreas.

Synthetic human pancreastatin and its C-terminal fragment were first evaluated with respect to the biological activity on the insulin secretion in the isolated rat islets. Both these pancreastatins inhibited glucose-stimulated insulin secretion at a concentration of 100 nM. The relative molar potency of human pancreastatin compared to that of porcine pancreastatin was equivalent. The pancreastatin-reactive cells were widely located in the islets of Langerhans, and not observed in exocrine acinar cells by immunocytochemistry using human pancreastatin C-terminal specific antibody. These results suggest that human pancreastatin may modulate endocrine function of the pancreas, especially insulin secretion.

Amino Acid Sequence↗
PubMed1989

Bioactivity of synthetic C-terminal fragment of rat pancreastatin on endocrine pancreas.

A C-terminal fragment of rat pancreastatin, 26-residue peptide amide was synthesized by the Fmoc-based solid phase method and its biological activity was evaluated for the first time in the conscious rat. Rat pancreastatin inhibited glucose-stimulated insulin secretion and elevated blood glucose levels in a concentration of 10 nmol/kg/h. The relative molar potency of that of porcine is equivalent. This study suggests that the synthetic rat pancreastatin has a biological activity, and may play a physiological role in the endocrine pancreas.

Animals↗
PubMed1989

High plasma pancreastatinlike immunoreactivity in a patient with malignant insulinoma.

High levels of pancreastatinlike immunoreactivity were detected in the plasma (2.9 pmol/ml, greater than 200-fold the normal level), pancreas (2.9 nmol/g wet wt, greater than 450-fold the normal level), and liver (1.6 nmol/g wet wt) of a patient with pancreatic insulinoma with metastasis to the liver by a sensitive and specific radioimmunoassay for human pancreastatin. Antiserum was produced against the C-terminal fragment of human pancreastatin-(24-52), which was synthesized according to the sequence of human chromogranin A corresponding to that of pancreastatin. With the antiserum, intense immunocytochemical staining was detected in the tumors. Sephadex G-50 gel filtration showed that the tumors and plasma contained two molecular forms of pancreastatinlike immunoreactivity--a molecular form coeluted with synthetic human pancreastatin-52 and a larger molecular form (Mr approximately 12,000-15,000). The smaller form eluted in the same position as synthetic human pancreastatin-52 on reverse-phase high-performance liquid chromatography.

Adenoma, Islet Cell↗
PubMed1989

Plasma pancreastatin-like immunoreactivity in various diseases.

Plasma pancreastatin (PST)-like immunoreactivity in normal subjects and patients with various diseases was estimated by a RIA, using antiserum raised against a synthetic C-terminal peptide of human PST deduced from the sequence of human chromogranin-A. The mean level +/- SEM was 13.2 +/- 0.6 pmol/L in normal subjects, but was significantly higher in patients with chronic renal failure (526.7 +/- 48.5). An immunoreactive form corresponding to a human PST-like sequence [human chromogranin-A-(250-301)] and a larger form were detected by gel filtration of plasma from these patients, suggesting accumulation of the larger molecular form in these patients. A significant increase in PST-like immunoreactivity was also found in patients with liver cirrhosis (20.8 +/- 3.0 pmol/L), but not in patients with noninsulin-dependent diabetes mellitus, chronic pancreatitis, or pancreatic cancer. Elevated levels were found in 16 of the 21 patients with small cell lung carcinoma examined. High levels were also found in 3 of 11 patients with islet cell tumor.

Adenoma, Islet Cell↗
PubMed1989

Comparative effects of mammalian pancreastatins on the pancreatic exocrine secretion.

We have reported that porcine pancreastatin inhibits cholecystokinin (CCK)-stimulated pancreatic exocrine secretion in conscious rats. In the present study, the effects of mammalian pancreastatins on exocrine pancreatic functions in rats were compared using synthetic pancreastatins (porcine, bovine, human, and rat). Rats were prepared with cannulae draining pure pancreatic juice and bile separately and a duodenal cannula to return bile-pancreatic juice to the intestine and with a jugular vein cannula. After 90-min basal collection of pancreatic juice, CCK-8 (100 pmol/(kg.h] was infused for 3 h with or without pancreastatins (100 pmol/(kg.h]. All pancreastatins significantly inhibited protein output at an equivalent molar potency. These results suggest that mammalian pancreastatins have the same biological activity of a comparable magnitude and exert a similar biological action on the exocrine pancreas.

Amino Acid Sequence↗
PubMed1988

Bioactivity of synthetic human pancreastatin on exocrine pancreas.

A biological activities of synthetic human pancreastatin (1-52) and its C-terminal fragment (24-52) were evaluated for the first time in the conscious rats. Both pancreastatins inhibited CCK-stimulated pancreatic secretion in a range of 20-200 pmol/kg/h with the same potency, indicating that the C-terminal portion of this peptide has a full biological activity. The relative molar potency of this substance compared to that of porcine pancreastatin was equivalent. This study suggests that human pancreastatin has the same biological activity as that of porcine, and plays a biological action in the exocrine pancreas.

Animals↗
PubMedDate not supplied

Intraocular lesions in patients with systemic disease: findings on MR imaging.

Twenty-one intraocular lesions associated with various systemic diseases in 15 patients were studied by MR imaging. The disorders included diabetes mellitus, cardiovascular disease, Behçet disease, sarcoidosis, and ankylosing spondylitis. MR was performed on a 0.5-T system using a surface-coil technique. Ophthalmoscopic visualization of the fundus was precluded by the presence of opaque media in all cases. MR was found to be effective in demonstrating intraocular bleeding, vitreous opacity, detached lesions of the posterior pole, and eyeball deformity. Surface-coil MR is a useful adjunct in the evaluation of the eyes affected by systemic diseases, especially in patients with opaque media.

Adult↗