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Biomedical subjects

T Kono

Publications and source records attributed to T Kono.

At least 307 records · Page 17Linked to original sources
PubMed1986

Neutral glyceride synthesis from glucose in human adipose tissue: comparison between growing and mature subjects.

Basal and insulin-stimulated neutral glyceride syntheses from glucose were studied in fat cells of different size (fat cell volume, 0.07-0.20, 0.20-0.60, 0.60-1.00, 1.00-1.50 micron3 X 10(6)) obtained from subcutaneous adipose tissues in 20 subjects aged 3 months to 67 years. In 0.07-0.20 or 0.20-0.60 micron3 X 10(6) fat cells, the basal rate of glucose conversion to neutral glyceride was significantly lower in mature (36 to 67 years old) than in growing (0 to 12 years old) subjects. In 0.60-1.00 or 1.00-1.50 micron3 X 10(6) fat cells, however, basal rate was not significantly different between the two groups. The stimulating effect of insulin on conversion of glucose to neutral glyceride was not significantly different from the basal rate in fat cells of each size taken from the mature subjects, whereas in fat cells from growing subjects, it was significantly different from the basal rate in each fat cell size category. These results indicate that when fat cell size is taken into account, not only is the rate of basal glucose conversion to neutral glyceride higher in growing subjects but also its responsiveness to exogenous insulin, and that insulin insensitivity of large fat cells, reported previously, may be influenced by age.

Adipose Tissue↗
PubMed1986

A case of adiposis dolorosa: lipid metabolism and hormone secretion.

The present report describes a 53-year-old non-obese man with adiposis dolorosa whose pain was dramatically relieved by the intravenous injection of lidocaine. The patient showed a paradoxical response of growth hormone to thyrotropin-releasing hormone. In addition, in-vitro studies on adipose tissue metabolism revealed the reduced glucose conversion to neutral glycerides in painful adipose tissue. These abnormalities may be related in some ways to the pathogenesis of this disorder.

Adipose Tissue↗
PubMed1985

Relative biological activities of Asn1-,Val5-angiotensin II, Ile5-angiotensin II and Sar1-angiotensin II in man.

Biological activities of asn1-,val5-angiotensin II (Hypertensin, Ciba, Asn1-,Val5-ANG II), ile5-angiotensin II (human angiotensin II, Ile5-ANG II) and sar1-angiotensin II (Sar1-ANG II) were compared in man. In 7 normal men 5 pmol/kg X min each of Asn1-,Val5-ANG II, Ile5-ANG II and Sar1-ANG II was infused iv from 0900 h to 0930 h at 1-week intervals. Average increments of blood pressure at the end of the infusions were 11/12, 23/20 and 36/30 mmHg, respectively (significant differences among the 3: P less than 0.001), average decrements of plasma renin activity were 0.30, 0.32 and 0.27 ng/ml X H, respectively (no significant difference among the 3), average increments of plasma aldosterone were 1.1, 2.3 and 4.4 ng/100 ml, respectively (significant difference between the former 2: P les than 0.001, between the latter 2: P less than 0.02), and durations of blood pressure rise after the cessation of these infusions (T) were 2-5 (average 5) min, 10-25 (average 20) min and 35-60 (average 40) min, respectively (significant difference between the former 2:less than P 0.01, between the latter 2: P less than 0.001). From these results it is evident that the pressor and steroidogenic actions of Ile5-ANG II are significantly stronger than those of Asn1-,Val5-ANG II and that the duration of pressor action of the former is much longer than that of the latter. Therefore, when the activities of angiotensin II (ANG II) derivatives are compared with those of ANG II in man, Ile5-ANG II--natural human ANG II--should always be used instead of Asn1-,Val5-ANG II. The pressor and steroidogenic actions and T of Sar1-ANG II are significantly stronger or longer than those of Ile5-ANG II. The reason for this is thought to be that Sar1-ANG II is bound tightly to the vascular and adrenal ANG II receptors and is not readily metabolized.

Adult↗
PubMed1985

Regional differences in carboxylesterase activity between human subcutaneous and omental adipose tissue.

Human adipose tissue was shown to contain carboxylesterase activity when measured by methylbutyrate as substrate. The enzyme has the same characteristics as carboxylesterase purified from rat epididymal adipose tissue. Like lipoprotein lipase, carboxylesterase activity was higher in large than in small fat cells. Both cell size and carboxylesterase activity were greater in human subcutaneous than in omental adipose tissue. However, the linear regression lines between the enzyme activity and cell volume in the two tissues were almost superimposable, suggesting that cell size is a determinant of enzyme activity. Although the physiological significance of adipose tissue carboxylesterase must await further clarification, it is possible that the enzyme is related to the hydrolysis of long-chain monoacylglycerols.

Adipose Tissue↗
PubMed1985

Effects of monensin on insulin processing in adipocytes. Evidence that the internalized insulin-receptor complex has some physiological activities.

In the presence of 10-100 microM monensin (a monovalent cation ionophore), a considerable amount of 125I activity of iodoinsulin accumulated in isolated rat epididymal adipocytes during a 30-min incubation. The accumulation was secondary to the action of monensin to inhibit dissociation of a certain fraction of the cellbound 125I activity. This monensin effect was reversible. The accumulation of 125I activity was ATP dependent and so was the discharge of the accumulated radioactivity. Approximately 91% of the accumulated radio-activity was precipitable with trichloroacetic acid, and at least 84% was reactive to anti-insulin antibody. Monensin at 100 microM appeared to have only mild effects on the cellular activities of glucose transport and cAMP phosphodiesterase. Nevertheless, when cells were first exposed to 10 nM insulin in the presence of 100 microM monensin and then transferred into a hormone-free buffer that contained monensin, the phosphodiesterase activity in cells remained partially activated as if cells were kept exposed to approximately 0.5 nM insulin. Under similar conditions, glucose transport activity remained partially activated as if cells were incubated with approximately 70 pM insulin. Monensin did not inhibit the reversal of the insulin effect per se. Like monensin, 20-100 microM chloroquine (a lysosomotropic inhibitor) induced a considerable accumulation of [125I] iodoinsulin. However, cells that had been exposed to insulin in the presence of chloroquine retained little hormonal effect after washing. Based on these observations and on the reported biological effects of monensin, it is suggested (a) that monensin may induce intracellular accumulation of the insulin-receptor complex by blocking the acidification of endocytic vesicles and (b) that the accumulated insulin-receptor complex may retain a weak, but significant, capacity to stimulate both glucose transport and phosphodiesterase activities.

Adenosine Triphosphate↗
PubMed1985

Agonistic activities of isoleucine8-angiotensin II in man.

In order to clarify the importance of C-terminal phenylalanine in angiotensin II (ANG II) molecule, agonistic activities of a C-terminal substituted peptide, isoleucine8-angiotensin II (Ile8-ANG II), were studied in comparison with those of sarcosine1-, isoleucine8-angiotensin II (Sar1-, Ile8-ANG II) and isoleucine5-angiotensin II (Ile5-ANG II) in 5 normal men. When infused iv at a rate of 600 pmol/kg X min for 30 min, Ile8-ANG II and Sar1-, Ile8-ANG II raised the blood pressure to the same extent (15/15 mmHg on the average), while the average blood pressure increase was 21/21 mmHg after an iv infusion of Ile5-ANG II at a rate of 5 pmol/kg X min for 30 min. Duration of the pressor action after the cessation of each infusion was 50-90, 90-120 and 10-25 min, respectively. In each case plasma renin activity (PRA) decreased and plasma aldosterone (PA) increased. When infused iv at a rate of 10 pmol/kg X min (maximum non-pressor dose) for 120 min, both Ile8-ANG II and Sar1-, Ile8-ANG II lowered PRA and increased PA gradually, but 100 mg oral captopril given immediately before these infusions caused no significant increase in PRA or no significant decrease in PA but again a decrease in PRA and an increase in PA.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Pressor activity of angiotensin II-(2-7)-hexapeptide in man.

Pressor activity and speed of metabolic degradation of angiotensin II-(2-7)-hexapeptide [ANG-(2-7)] were studied in 5 normal men. When infused iv at a rate of 72 nmol/kg X min for 7 min, ANG-(2-7) caused a very slight but statistically significant increase in blood pressure. Average blood pressure increases at 2, 5 and 7 min were 5/4, 8/10 and 8/9 mmHg, respectively, and the duration of the pressor action after the cessation of the infusion (T) was 5 min on the average. The pressor activity and T of this peptide were much less than or shorter than those of angiotensin II-(1-7)-heptapeptide [ANG-(1-7)] infused previously in the same 5 normal men at a rate of 18 nmol/kg X min, indicating that the pressor activity ratio of both the peptides in man is 1: greater than 7.2 which is similar to that of angiotensin II-(2-8)-heptapeptide (angiotensin III) and Ile5-angiotensin II (Ile5-ANG II) (1: greater than 5) and that the removal of N-terminal aspartic acid from ANG-(1-7) hastens the speed of metabolic degradation of the peptide as from Ile5-ANG II.

Adult↗
PubMed1985

Responses of patients with Bartter's syndrome to angiotensin III and angiotensin II-(3-8)-hexapeptide.

Studies were conducted to determine whether or not angiotensin III [AIII] and angiotensin II-(3-8)-hexapeptide [ANG-(3-8)] have their own specific arteriolar binding sites different from angiotensin II [AII] binding site(s) in man. Four patients with Bartter's syndrome were given asn1-,val5-AII by iv infusion at rates of 10, 20, 50 and 100 pmol/kg X min, each for 7 min. One hour later AIII was infused iv in the same 4 patients at rates of 50, 100, 250 and 500 pmol/kg X min, each for 7 min. After 100 or 150 mg/day of indomethacin treatment for 7 days, the same AII and AIII infusions were repeated. All patients showed blunted pressor responses to both AII and AIII before indomethacin and the responses were improved after indomethacin. Moreover, increment curves of blood pressure for AII were almost identical with those for AIII in individual patients both before and after indomethacin. ANG-(3-8) was infused iv in 3 normal men and 3 of the 4 patients with Bartter's syndrome at a rate of 3.500 pmol (2.838 ng)/kg X min for 15 min. Blood pressure rose in the normal men (12/12 mmHg on the average) but did not rise in the patients. These results suggest that AII, AIII and ANG-(3-8) have the same arteriolar binding sites in man.

Adolescent↗
PubMed1985

Glucose transport in adipocytes and its regulation by insulin.

Several lines of recent evidence indicate that in the absence of insulin glucose transport activity in the basal form of adipocytes is mostly associated with certain intracellular vesicles, and that the function of insulin is to translocate the glucose transport activity from the intracellular storage site to the plasma membrane. Upon sucrose density gradient centrifugation, the two subcellular structures associated with the glucose transport activity were fractionated into the plasma membrane-rich and Golgi-rich fractions. In our laboratory, the glucose transport activity in the subcellular fractions was assayed after reconstruction into egg lecithin liposomes. The apparent translocation of the glucose transport activity from the storage site to the plasma membrane was reversible, energy dependent, protein synthesis independent, almost completed in 5-10 min at 37 degrees C when the hormone concentration was 1 nM, and very slow at a low temperature (for example 15 degrees C). These results are consistent with the hypothesis that insulin regulates glucose transport activity in adipocytes by causing translocation of the glucose transport apparatus in a reversible manner, and that the translocation, or recycling, of the glucose transport apparatus is brought about by exo- and endocytosis.

Adipose Tissue↗
PubMed1984

Insulin action on glucose transport in cardiac muscle.

The mechanism of insulin action on glucose transport in rat hearts was studied. The glucose transport activity was determined after reconstitution into egg lecithin liposomes. Isolated rat hearts were perfused in the presence or absence of insulin and homogenized. The homogenate was fractionated by differential and sucrose density gradient centrifugations. Two subcellular fractions, designated as Fractions P-5 and P-6, contained glucose transport activity. Both fractions were enriched with 5'-nucleotidase (commonly known as a plasma membrane marker) and UDP-Gal:N-acetylglucosamine galactosyltransferase (known as a Golgi marker). However, only Fraction P-5 was concentrated with the insulin receptor and ouabain-sensitive p-nitrophenylphosphatase (both plasma membrane markers). The sedimentation properties of the glucose transport activity in Fraction P-6 were considerably different from those of galactosyltransferase. Insulin added to the heart before homogenization increased the glucose transport activity in Fraction P-5 approximately 1.6-fold while decreasing the activity in Fraction P-6 to approximately 62% of the control. These results are interpreted as follows. Both Fractions P-5 and P-6 are heterogeneous; nevertheless, Fraction P-5, but not Fraction P-6, may be enriched with the plasma membrane, which is assumed to be associated with glucose transport activity. Fraction P-6 may be concentrated with the Golgi apparatus; however, the latter may not be the structure (or vesicles) to which (intracellular) glucose transport activity is associated. Insulin appears to increase the glucose transport activity in rat hearts, at least in part, by inducing translocation of the glucose transport mechanism from the unidentified vesicles (in Fraction P-6) to the plasma membrane (in Fraction P-5).

Animals↗
PubMed1984

Partial characterization of the glucose transport activity in the Golgi-rich fraction of fat cells.

The glucose transport activity solubilized from the basal and plus insulin forms of the Golgi-rich fraction of adipocytes was partially characterized, and the results were compared with those of the activity obtained from the plus insulin form of the plasma membrane-rich fraction. The transport activity was determined in a cell-free, reconstituted, system. Prior to reconstitution, the activities in the three preparations were all (a) stable at 0 degrees C for at least 4 h, but not at 37 degrees C or above; (b) most stable at pH 7-9, and (c) less stable in Tes than in Tris buffer. After reconstitution, the three activities were all (d) stable at 0 degrees C, (e) most active at pH 5.5, (f) mildly stimulated by divalent cations, (g) unaffected by insulin or 1 mM of several SH-blocking agents, (h) inhibited by heavy metal ions, 10-100 mM of monovalent salts, organic solvents, several sugar isomers, and specific sugar-transport inhibitors. The rates of D-glucose uptake by the three liposome preparations were all inhibited more strongly by 2-deoxy-D-glucose or 3-O-methyl-D-glucose than by D-glucose. These data indicate that the general properties of the glucose transport activity in the Golgi-rich fraction are similar to those of the activity in the plasma membrane-rich fraction.

Adipose Tissue↗
PubMed1984

Effects of divalent cations on the regulation of insulin-sensitive glucose transport and cAMP phosphodiesterase in adipocytes. Insulin-like effects of divalent cations.

Effects of divalent cations on the regulation of glucose transport and cAMP phosphodiesterase in isolated rat epididymal adipocytes were studied. EDTA (5 mM) moderately inhibited the binding of insulin to adipocytes in Krebs-Henseleit Hepes buffer. In the same buffer, A-23187 (an ionophore specific for divalent cations; 50 microM) plus EDTA (5 mM) almost completely blocked the insulin- or hydrogen peroxide-dependent stimulation of phosphodiesterase. This inhibition was not secondary to the loss of ATP. When cells that had been treated with A-23187 plus EDTA were washed and then exposed to 1-10 mM of divalent cations, the cellular phosphodiesterase activity was elevated. Mn2+ was most stimulatory, Mg2+ was next, and Ca2+ was least effective. The stimulatory effects were enhanced by insulin. In the presence of insulin, Mn2+ at 10 mM was less stimulatory than that at 1 mM. In regular Krebs-Henseleit Hepes buffer, Mn2+ greatly stimulated phosphodiesterase if cells were first exposed to A-23187. The Mn2+-dependent stimulation was blocked by treatment of cells with 2,4-dinitrophenol. Results essentially parallel to those described above were also obtained when the rate of glucose transport was determined. The above results indicate that divalent cations mildly support the extracellular binding of insulin to its receptor, facilitate the physiological actions of insulin, and mimic the hormone actions, presumably by stimulating an intracellular enzyme.

2,4-Dinitrophenol↗
PubMed1984

Translocation hypothesis of insulin action on glucose transport.

This article reviews the experimental data that support the translocation hypothesis of insulin action on glucose transport in adipocytes. According to this hypothesis, 1) most of the glucose transport mechanism in the basal (no insulin) form of fat cells is associated with an unidentified subcellular structure (the storage site), which is separated into the Golgi-rich fraction by centrifugation, and 2) the function of insulin is to induce translocation of the glucose transport mechanism from the above storage site to the plasma membrane. This translocation of the transport mechanism is reversible, dependent on metabolic energy, and independent of protein synthesis.

Adipose Tissue↗