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Biomedical subjects

T Yamamura

Publications and source records attributed to T Yamamura.

At least 307 records · Page 17Linked to original sources
PubMed1988

[Monolayer culture of pancreatic islet cells of the adult rat: effect of 2-deoxy-2-fluoroglucose].

In the present study, the culture system for preparing monolayer islet cells of the neonatal rat was applied and modified for use with the pancreas of the adult rat. In this procedure, whole pancreatic tissues were enzymatically dispersed and then cultured for 30 days in TCM 199 medium with either 5.5 mM glucose or 5.5 mM glucose plus 1 mM 2-deoxy-2-fluoroglucose. Under culture conditions without 2-deoxy-2-fluoroglucose, the responsiveness of B cells was totally abolished by day 20 of culture. The addition of 2-deoxy-2-fluoroglucose destroyed fibroblasts selectively in a period of 20 days, yielding the monolayers mostly consisting of islet cells, and the morphological characteristics were well preserved at the end of the culture study period. After culture for 20 days in medium with 2-deoxy-2-fluoroglucose, insulin secretion was raised in a dose-dependent fashion due to the increasing concentrations of glucose, leucine and 2-ketoisocaproate. The dose-response curve for insulin secretion evoked by glucose was sigmoid with a Km of 7 mM glucose, and the secretion threshold was observed at a concentration of between 2.8 and 5.5 mM glucose. The ratios of the maximum level to the basal were 6, 5 and 3 respectively for glucose, leucine and 2-ketoisocaproate. The secretory competence was preserved in the B cells on day 30 as well. Addition of epinephrine or clonidine inhibited the glucose-induced insulin secretion dose-dependently. At a concentration of 10(-7) M, both drugs produced an 80% drop in insulin secretion evoked by glucose. The inhibitory effect of epinephrine or clonidine was reversed by 3 X 10(-5) M yohimbine or 10(-5) M phentolamine, whereas 10(-5) M propranolol had little or no effect and alpha adrenergic blockade of prazosin (5 X 10(-5) M) was weak as compared to that of yohimbine. At a high concentration (10(-5) M) of phenylephrine, a marked drop of insulin secretion was observed. In summary, the present culture system facilitates the establishment of monolayers of adult rat pancreas that consist mostly of islet cells. In addition, it is certain that the response of the B cells in 2-deoxy-2-fluoroglucose to nutrient secretagogues and the adrenergic modulation of insulin secretion are well preserved for a long-term culture period of 30 days. These preparations may provide a useful tool not only for the in vitro study of the B-cell function, but also for use in implantation resource.

Animals↗
PubMed1988

Choledochal cysts. Oligoganglionosis in the narrow portion of the choledochus.

To investigate whether cystic dilation may be due to a reduction of postcholinergic cell bodies that leads to autonomic dysfunction, ganglion cell bodies were counted in five patients with choledochal cysts and five patients with normal choledochus. In the normal choledochus, the ganglion cell counts in the proximal and distal portions were 374.7 +/- 82.7/cm2 and 349.2 +/- 51.2/cm2, respectively. In cases of choledochal cysts, the ganglion cell counts in the dilated portion and narrow portions were 298.6 +/- 86.9/cm2 and 81.0 +/- 34.8/cm2, respectively. The cell ratio (narrow to dilated) was 0.271. Significant reductions of cell numbers were observed in all the choledochal cysts having various types of pancreatobiliary junctions. These findings indicate that the reduction in the number of ganglion cells in the narrow portion of the choledochal cysts supports the concept of oligoganglionosis in distal choledochus.

Adolescent↗
PubMed1988

Follow up studies on various reconstruction methods of the biliary tract including our new method (Roux Y-duodenojejunal anastomosis).

Thirty six patients with benign diseases of the biliary tract (14 patients with congenital choledochal dilatation, 15 patients with postoperative stricture and 7 patients with others) were divided into three groups: 21 patients who underwent a Roux Y (RY), 7 patients who underwent a jejunal interposition (IP) and 8 patients who underwent a side to side anastomosis between the jejunal limb of the Roux Y and the duodenum (RY-DJ). The RY-DJ was designed to decompress the Roux Y jejunal limb and to allow an inflow of bile into the duodenum. Significant complications, including cholangitis, infection, or abdominal pain, developed in 10 of the patients with RY (48 per cent), 7 of the patients with IP (100 per cent) and 1 of the patients with RY-DJ (13 per cent). None had a postoperative peptic ulcer. Simultaneous scintigraphy showed the time required for the two agents, 99mTc-IDA and 111In-DTPA, to mix at the upper jejunum, which revealed that the time taken by the patients with RY-DJ was similar to that of the patients with IP and to that of healthy controls. The time was markedly longer in the patients with RY, presumably due to a prominent stasis of the bile tracer in the Roux Y jejunal limb. Our new method (RY-DJ) for reconstruction of the extrahepatic biliary tract is more physiological and has less postoperative complications than other conventional methods.

Adolescent↗
PubMed1988

Escape phenomenon occurs by lowering cholesterol with a hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitor in patients with familial hypercholesterolemia.

3 beta-Hydroxycompactin, a hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, is a useful drug as an anticholesterolemic agent. However, in some patients with familial hypercholesterolemia, treatment was associated with a rebound in serum cholesterol concentration when the dose was increased from 10 to 40 mg/day. The rebound was more remarkable when the basal cholesterol level was lowered by cholestyramine and/or probucol. The phenomenon seems to be due to an induction of HMG-CoA reductase as seen in some animals and cultured cells.

Adult↗
PubMed1988

Serum lipid levels in elementary and junior high school children and their relationship to relative weight.

Serum lipid levels were measured in 2,626 schoolchildren ages 7 to 15 years in three elementary schools and one junior high school in a suburban area of Osaka during 1984-1985. The mean cholesterol levels increased with age in boys ages 7 to 10 years (from 156 to 177 mg/dl) and then decreased at age 13, after which the levels again increased slightly until age 15. Girls showed a similar tendency with a peak at age 10 and a minimum at age 12. Cholesterol levels were significantly lower in junior high school boys (a mean of 154-161 mg/dl for ages 13-15 years) than in girls of the same age or in boys and girls ages 10 to 12 years in the upper grades of elementary school. Cholesterol and triglyceride levels tended to be lower or the high-density lipoprotein cholesterol levels higher in elementary schools where boys and girls engaged in physical exercise than in schools where the children were not strongly encouraged to exercise. About 50% of the hypertriglyceridemic children were obese.

Adolescent↗
PubMed1988

Specular microscopy of the anterior lens capsule after endocapsular lens implantation.

Endocapsular phacoemulsification and complete in-the-bag intraocular lens (IOL) fixation was performed on 77 eyes. Specular microscopy of the anterior lens capsule was performed postoperatively, and the process of anterior capsule opacification after endocapsular cataract surgery was classified. Lens epithelial cells on the inner surface of the anterior lens capsule, facing the optical portion of the IOL, underwent a diffuse fibrosis. In more peripheral areas, where the anterior and posterior capsules were tightly adherent, the regularly proliferating lens epithelial cells retained their polygonal shape. These findings suggest the possibility of retaining the transparency of the anterior lens capsule postoperatively by refilling the capsular bag to apply internal pressure.

Aged↗
PubMed1988

Different stability of N- and C-domain of diferric ovotransferrin in urea and application to the determination of iron distribution between the two domains.

The study of guanidine-HCl or thermal denaturation of diferric ovotransferrin (Fe2Tf) has revealed a simultaneous unfolding of the two domains of the protein (Ikeda et al. (1985) FEBS Lett. 182, 305-309). In urea denaturation of Fe2Tf, however, two distinct steps of unfolding were observed in the urea concentration range from 4.5 to 9 M at pH 8.0 and 37 degrees C by measuring the residual iron-bound protein (absorbance at 465 nm) and the remaining folded structures (circular dichroism at 222 nm). From a study of urea denaturation of partially iron-saturated Tf whose iron preferentially occupied the N-domain, it was found that the first and the second steps of denaturation corresponded to those of the N-terminal (4.5-6 M urea) and C-terminal domains (over 7 M urea), respectively. The N-domain of Fe2Tf was selectively unfolded in 7 M urea and digested with trypsin to provide an iron-bound C-terminal fragment (42 kDa) in good yield (about 80% of theoretical). The kinetic analysis of the decrease in A465 of Fe2Tf in 9 M urea showed that the N-domain unfolded 3 x 10(2) times faster than the C-domain. With partially iron-saturated Tf, the decrease of A465 in 9 M urea also proceeded in a biphasic manner and the ratio, the decrement in A465 of the rapid phase/the decrement in A465 of the slow phase, gave the value of iron distribution as Fe at the N-site/Fe at the C-site.

Binding Sites↗
PubMed1988

Analysis of apolipoprotein E5 gene from a patient with hyperlipoproteinemia.

We have isolated and analyzed apolipoprotein E5 gene from a patient with hyperlipoproteinemia. Apolipoprotein E5 is a variant of apolipoprotein E with two additional units of positive charge and smaller apparent molecular weight than apolipoprotein E3, which is the major isoform of apolipoprotein E. The heterozygous gene of apolipoprotein E5/3 from the patient was cloned into lambda phage. The cloned apolipoprotein E genes were subcloned into a murine retrovirus shuttle vector and were expressed. One out of four clones expressed apolipoprotein E5. The analysis of the nucleotide sequence of the exons and exon-intron boundary regions has shown a G to A substitution in the 18th nucleotide from the 5'-end of the third exon. This single base substitution changes the amino acid residue Glu to Lys at the third position from the amino-terminus of the mature protein, and gives two additional units of positive charge to the molecule.

Apolipoproteins E↗
PubMed1988

Gallbladder dynamics and plasma cholecystokinin responses after meals, oral water, or sham feeding in healthy subjects.

To investigate the mechanisms controlling human gallbladder contraction, especially to determine the role of neural factors, the gallbladder response to various stimuli was evaluated in eight normal subjects using realtime ultrasonography. In addition, plasma cholecystokinin (CCK) levels were measured using a region-specific antibody (OAL 656). Intramuscular injections of CCK-8 and of cerulein induced mean maximal ejection fractions (EF max) of 50% +/- 6% and 58% +/- 4%, respectively. The mean EF max after ingestion of a fatty meal was 44% +/- 3%, while the EF max after a fat-restricted meal was significantly lower (17% +/- 4%). Oral water and sham feeding also significantly induced gallbladder contractions (EF max; 25% +/- 4% and 12% +/- 4% respectively) that were eliminated by premedication with atropine. The plasma CCK rose significantly after exogenous administration of CCK-8 and after ingestion of a fatty meal. The peak CCK concentration released after fatty meals was almost identical to that after exogenous CCK-8 loading. In contrast, plasma CCK levels showed no change after the fat-restricted meal, oral water and sham feeding. These findings suggest that not only CCK but also the cholinergic pathway may play important roles in the control mechanism of human gallbladder contraction.

Adult↗
PubMed1988

Electron microscopic changes of bone marrow-derived cultured mast cells after injection into the skin of genetically mast cell-deficient W/Wv mice.

Phenotypes of bone marrow-derived cultured mast cells are different from those of connective tissue-type mast cells (CTMCs) that are found in the peritoneal cavity and the skin. When cultured mast cells of WBB6F1 - +/+ mouse origin were directly injected into the skin of genetically mast cell-deficient WBB6F1 - W/Wv mice, mast cells appeared in both the dermis and the subcutaneous tissue (beneath the panniculus carnosus). In contrast to cultured mast cells, mast cells that were observed in either the dermis or the subcutaneous tissue were stained with berberine sulfate, suggesting the content of heparin. Cultured mast cells acquired the electron microscopic features of CTMC in either the dermis or the subcutaneous tissue of WBB6F1 - W/Wv mice, but the electron density of mast-cell granules was significantly higher in the dermis than in the subcutaneous tissue. Such an electron microscopic difference was also observed after the injection of purified peritoneal mast cells of WBB6F1 - +/+ mice into the skin of WBB6F1 - W/Wv mice. From the present study, we suggest that the electron density of mast-cell granules in the skin of WBB6F1 - W/Wv mice is not dependent on the type of injected mast cells but on the anatomical sites at which the injected cells are located.

Animals↗
PubMed1988

Effects of cholecystokinin octapeptide on contractile motility of guinea pig common bile duct.

Cholecystokinin octapeptide (CCK-8)-induced contraction and [3H]acetylcholine ([3H]-ACh) release from the longitudinal muscle strip of the guinea pig common bile duct were studied by a standard organ bath method and superfusion system. CCK-8 (10(-7) M) caused a biphasic contraction, a rapid phasic contraction followed by a fading tonic contraction. Hexamethonium, propranolol, and phentolamine had no effects on CCK-8-evoked contraction. Atropine or tetrodotoxin significantly reduced CCK-8-evoked initial phasic contraction and produced a rightward shift of the dose-response curve for CCK-8 (10(-10)-3 x 10(-7) M). CCK-8 provoked a significant [3H]ACh release in a dose-dependent manner, which was almost completely abolished by tetrodotoxin or Ca2+-free medium. These results suggest that CCK-8 receptors are present not only on the smooth muscle cells but also on the intramural cholinergic nerve cell bodies of the guinea pig common bile duct.

Animals↗
PubMed1988

The effects of sodium valproate on plasma somatostatin and insulin in humans.

To determine the role of gamma-aminobutyric acid (GABA) in islet tissue, sodium valproate (1600 mg/day) was administered for 6 days to 10 normal subjects and 1 patient with a somatostatinoma. Plasma valproate concentrations reached a steady state by the third day accompanied by elevation of plasma GABA concentrations. Sodium valproate administration resulted in a 40% decrease in plasma somatostatin concentrations in the normal subjects and a 63% decrease in the somatostatinoma patient, respectively, compared to the response to placebo. Plasma C-peptide concentrations did not change in any subject. Fasting blood glucose levels decreased in the somatostatinoma patient during sodium valproate administration. These results suggest that endogenous GABA may play some role in the release of somatostatin, but not in the release of insulin.

Adult↗
PubMed1988

Monolayer cultures of pancreatic islet cells from adult rats: effect of 2-deoxyglucose.

Techniques for the monolayer culture of pancreatic islet cells from adult rats and the responsiveness of B cells are described. Whole pancreatic tissue was enzymatically dispersed and then cultured for 30 days in tissue culture medium 199 containing 5.5 mmol glucose/l, with or without 1 mmol 2-deoxyglucose/l. In the absence of 2-deoxyglucose, the responsiveness of B cells diminished to almost zero by day 15 and islets degenerated. In contrast, addition of 2-deoxyglucose to the medium resulted in a selective degeneration of fibroblasts, yielding monolayers that consisted mostly of islet cells. In this stationary system in which monolayers of islet cells were maintained in medium with 2-deoxyglucose, insulin secretion from B cells on days 15 and 30 increased in a dose-dependent fashion in response to increasing concentrations of glucose, leucine and 2-ketoisocaproate. Similarly, when exposed to 16.7 mmol glucose/l, perifused B cells showed a biphasic pattern of insulin secretion on day 15. Addition of 10 mumol forskolin/l and 200 nmol 12-O-tetradecanoyl phorbol-13-acetate/l remarkably enhanced this response. Likewise, the response to 10 mmol leucine/l or 10 mmol 2-ketoisocaproate/l was biphasic. These results suggest that these monolayer cultures retain the functional properties of the adult rat pancreas, and may be useful not only as a model for the in-vitro study of B cell function, but also for implantation.

Amylases↗