Effects of a new oral hypoglycaemic agent (CS-045) on metabolic abnormalities and insulin resistance in type 2 diabetes

The effects of a thiazolidinedione antidiabetic agent (CS-045) on diabetic metabolic abnormalities were studied in a double-blind clinical trial. Fourteen patients with Type 2 diabetes were selected according to study criteria. Eight were treated with oral CS-045 at 400 mg daily, and six were given placebo. A multi-step, hyperinsulinaemic, euglycaemic clamp study, with simultaneous plasma free fatty acid study, and glucagon tolerance test were performed before and after administration of drug. Following 3 months of treatment with CS-045, there were significant decreases in the mean levels of fasting plasma glucose (from 9.18 +/- 0.95 to 7.78 +/- 0.44 mmol l-1), postprandial plasma glucose (from 11.8 +/- 1.23 to 10.36 +/- 1.06 mmol l-1), and haemoglobin A1c (from 9.3 +/- 0.4 to 6.8 +/- 0.4%). Insulin sensitivity also improved (1st step: from 3.12 +/- 0.33 to 4.70 +/- 0.47 mg kg-1 min-1 (p < 0.01); 2nd step: from 5.61 +/- 0.63 to 7.54 +/- 0.58 mg kg-1 min-1 (p < 0.01); 3rd step: from 9.21 +/- 0.67 to 11.10 +/- 0.87 mg kg-1 min-1). The fasting free fatty acid level decreased significantly from 0.28 +/- 0.04 to 0.22 +/- 0.02 g l-1. The residual free fatty acid level (%) under insulin infusion clamp conditions decreased significantly from 63.7 +/- 9.7 to 45.0 +/- 9.2%. CS-045 treatment was associated with decrease in total cholesterol, total triglycerides, and increase in HDL cholesterol. Basal C-peptide immunoreactivity level decreased, but there was no change in the peak C-peptide immunoreactivity value.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult T-cell leukaemia with various abnormalities in endocrine and metabolic systems

Adult T-cell leukaemia (ATL) is a unique type of T-cell malignancy closely associated with human T-cell leukaemia virus-1 (HTLV-1). Despite frequent descriptions of hypercalcaemia, cases accompanied by diabetes insipidus or syndrome of inappropriate secretion of anti-diuretic hormone (SIADH) in ATL patients have rarely been reported. We present an unusual case of ATL with various abnormalities in his endocrine and metabolic systems involving anterior pituitary function, thyroid function, lipid metabolism and Ca metabolism. Some of these abnormalities were considered to arise from infiltration or leukaemic cells into systemic organs after elimination of the above symptoms. Clinical and haematological data showing improvement following chemotherapy are also presented.

Compartmentalized structure of the plasma membrane for receptor movements as revealed by a nanometer-level motion analysis

Movements of transferrin and alpha 2-macroglobulin receptor molecules in the plasma membrane of cultured normal rat kidney (NRK) fibroblastic cells were investigated by video-enhanced contrast optical microscopy with 1.8 nm spatial precision and 33 ms temporal resolution by labeling the receptors with the ligand-coated nanometer-sized colloidal gold particles. For both receptor species, most of the movement trajectories are of the confined diffusion type, within domains of approximately 0.25 microns2 (500-700 nm in diagonal length). Movement within the domains is random with a diffusion coefficient approximately 10(-9) cm2/s, which is consistent with that expected for free Brownian diffusion of proteins in the plasma membrane. The receptor molecules move from one domain to one of the adjacent domains at an average frequency of 0.034 s-1 (the residence time within a domain approximately 29 s), indicating that the plasma membrane is compartmentalized for diffusion of membrane receptors and that long-range diffusion is the result of successive intercompartmental jumps. The macroscopic diffusion coefficients for these two receptor molecules calculated on the basis of the compartment size and the intercompartmental jump rate are approximately 2.4 x 10(-11) cm2/s, which is consistent with those determined by averaging the long-term movements of many particles. Partial destruction of the cytoskeleton decreased the confined diffusion mode, increased the simple diffusion mode, and induced the directed diffusion (transport) mode. These results suggest that the boundaries between compartments are made of dynamically fluctuating membrane skeletons (membrane-skeleton fence model).

Insulin treatment improves relative hypersecretion of amylin to insulin in rats with non-insulin-dependent diabetes mellitus induced by neonatal streptozocin injection

The dissociated release of insulin and amylin in the hyperglycemic state has been reported. This relative hypersecretion of amylin is thought to provide an important insight into how amylin aggregates to form islet amyloid deposits in non-insulin-dependent diabetes mellitus (NIDDM). The aim of the present study was to characterize the alterations of amylin hypersecretion in NIDDM with exacerbation or amelioration of diabetic control. For this purpose, neonatally streptozocin (nSTZ) diabetic rats were treated with dexamethasone (0.25 mg/kg) or Lente insulin (3 to 5 U/kg) daily for 14 days, and responses of amylin and insulin to 16.7 mmol/L glucose or 10 mmol/L arginine were evaluated in vitro using an isolated perfused pancreas system. nSTZ rats exhibited moderate elevations of plasma glucose compared with normal rats. In the isolated perfused pancreas, the molar ratio of secreted amylin to insulin in response to 16.7 mmol/L glucose by nSTZ pancreas (1.8% +/- 0.2%) was significantly greater than that of normal rat pancreas (1.2% +/- 0.1%). Plasma glucose levels in nSTZ rats (7.3 +/- 0.4 mmol/L) increased with dexamethasone treatment (17.8 +/- 1.1 mmol/L, P < .005) and decreased with insulin treatment (5.8 +/- 0.4 mmol/L, P < .05). The secreted amylin to insulin ratio in dexamethasone-treated nSTZ rats was significantly greater than that of the controls (P < .05). Moreover, insulin-treated nSTZ rats exhibited decreased amylin to insulin molar ratios compared with saline-treated nSTZ rats (P < .05), which had the same levels as normal rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma homocysteine concentrations in Japanese patients with non-insulin-dependent diabetes mellitus: effect of parenteral methylcobalamin treatment

It has been postulated that the accumulation of homocysteine in plasma may induce arteriosclerosis. In order to explore the possible contribution of homocysteine to the occurrence of macroangiopathy in patients with non-insulin-dependent diabetes mellitus, the concentrations of total homocysteine in plasma were determined in 52 diabetic patients with clinical macroangiopathy, 84 diabetic patients without macroangiopathy, and 57 non-diabetic control subjects. The levels of total homocysteine in plasma were significantly higher in diabetic patients with macroangiopathy (10.8 +/- 3.8 nmol/ml) than in those without macroangiopathy (8.3 +/- 3.1 mmol/ml, P < 0.001) or non-diabetic subjects (7.5 +/- 2.1 nmol/ml, P < 0.001). Among all diabetic patients, multiple logistic regression analysis after adjustment for age, sex, and systolic blood pressure revealed that high levels of plasma homocysteine were significantly associated with the presence of diabetic macroangiopathy (P = 0.01). By an intramuscular injection of 1000 micrograms methylcobalamin daily for 3 weeks, the plasma levels of homocysteine in 10 diabetic patients were significantly decreased (14.7 +/- 7.5 vs. 10.2 +/- 6.0 nmol/ml, P < 0.01). Our results suggest that plasma homocysteine levels could be one of a number of independent risk factors for macroangiopathy in patients with diabetes mellitus and that they can be reduced by parenteral treatment with methylcobalamin.

Confined lateral diffusion of membrane receptors as studied by single particle tracking (nanovid microscopy). Effects of calcium-induced differentiation in cultured epithelial cells

The movements of E-cadherin, epidermal growth factor receptor, and transferrin receptor in the plasma membrane of a cultured mouse keratinocyte cell line were studied using both single particle tracking (SPT; nanovid microscopy) and fluorescence photobleaching recovery (FPR). In the SPT technique, the receptor molecules are labeled with 40 nm-phi colloidal gold particles, and their movements are followed by video-enhanced differential interference contrast microscopy at a temporal resolution of 33 ms and at a nanometer-level spatial precision. The trajectories of the receptor molecules obtained by SPT were analyzed by developing a method that is based on the plot of the mean-square displacement against time. Four characteristic types of motion were observed: (a) stationary mode, in which the microscopic diffusion coefficient is less than 4.6 x 10(-12) cm2/s; (b) simple Brownian diffusion mode; (c) directed diffusion mode, in which unidirectional movements are superimposed on random motion; and (d) confined diffusion mode, in which particles undergoing Brownian diffusion (microscopic diffusion coefficient between 4.6 x 10(-12) and 1 x 10(-9) cm2/s) are confined within a limited area, probably by the membrane-associated cytoskeleton network. Comparison of these data obtained by SPT with those obtained by FPR suggests that the plasma membrane is compartmentalized into many small domains 300-600 nm in diameter (0.04-0.24 microns2 in area), in which receptor molecules are confined in the time scale of 3-30 s, and that the long-range diffusion observed by FPR can occur by successive movements of the receptors to adjacent compartments. Calcium-induced differentiation decreases the sum of the percentages of molecules in the directed diffusion and the stationary modes outside of the cell-cell contact regions on the cell surface (which is proposed to be the percentage of E-cadherin bound to the cytoskeleton/membrane-skeleton), from approximately 60% to 8% (low- and high-calcium mediums, respectively).

Effects of cilostazol, a phosphodiesterase inhibitor, on urinary excretion of albumin and prostaglandins in non-insulin-dependent diabetic patients

Microalbuminuria is characteristic in diabetic nephropathy and is thought to be influenced by renal hemodynamics, especially by the metabolism of prostaglandins (PGs) in glomruli. To reduce urinary albumin excretion in patients with non-insulin-dependent diabetes mellitus (NIDDM), we administered 100 mg of cilostazol, a phosphodiesterase inhibitor, daily for 3 months. The urinary albumin index (UAI: microgram albumin/mg creatinine) decreased significantly after 3 months of administering cilostazol. Urinary excretions of thromboxane B2 (TXB2), a stable metabolite of thromboxane A2, decreased significantly after treatment. However, it had no effects on urinary excretions of PGE2 and 6-keto PGF1 alpha (6KF), a stable metabolite of prostacyclin. The ratio 6KF/TXB2 has been known to reflect the renal metabolism of PGs. In this study, urinary 6KF/TXB2 ratio increased significantly in parallel with a significant reduction of UAI. Cilostazol had no adverse effects on the control of blood glucose and lipids. In conclusion, cilostazol has a beneficial effect on UAI in patients with NIDDM by reducing renal production of TXB2., which increases 6KF/TXB2 ratio.

Fluorescence lifetime imaging microscopy (flimscopy). Methodology development and application to studies of endosome fusion in single cells

A new method of fluorescence microscopy for cell imaging has been developed that takes advantage of the spatial variations of fluorescence lifetimes in single cells as a source of image contrast, and thus it is named "fluorescence lifetime imaging microscopy (flimscopy)". Since time-resolved fluorescence measurements are sensitive to molecular dynamics and interactions, flimscopy allows the molecular information to be visualized in single cells. In flimscopy measurements, several (nanosecond) time-resolved fluorescence images of a sample are obtained at various delay times after pulsed laser excitation of the microscope's entire field of view. Lifetimes are calculated pixel-by-pixel from these time-resolved images, and the spatial variations of the lifetimes are then displayed in a pseudocolor format (flimscopy image). The total data acquisition time needed to obtain a flimscopy image with the diffraction-limited spatial resolution (approximately 250 nm) is decreased to just approximately 30 s for approximately 300 fluorescent molecules/micron2. This was achieved by developing a high-frequency (400 kHz) nanosecond-gating (9 ns full width at half height)-signal accumulation system. This technique allows the extent of resonance energy transfer to be visualized in single living cells, and is free from the errors due to variations in path length, light scattering, and the number of fluorophores that necessitate complex corrections in steady-state microfluorometry and fluorescence ratio imaging microscopy. Flimscopy was applied here to observe the extent of fusion of individual endosomes in single cells. Results revealed the occurrence of extensive fusion between primary endocytic vesicles and/or sorting endosomes, thereby raising the possibility that the biogenesis of sorting endosomes involves multiple fusions of primary endocytic vesicles.

Generalized resistance to thyroid hormone (GRTH) in a family: case studies

A familial case of generalized resistance to thyroid hormone (GRTH) is described. A 17-year-old man (case 1), who had been treated with methimazole under the diagnosis of Graves' disease and his 11-year old sister (case 2) visited our clinic for the evaluation of their thyroid function. They lacked the signs and symptoms of thyrotoxicosis in spite of extremely high serum thyroid hormone levels. Their plasma TSH levels were not suppressed, but in fact markedly increased after TRH loading. Their peripheral indices of thyroid hormone were within normal limits and were not influenced by exogenous T3 administration. Even 150 micrograms T3 administration for 7 days did not fully suppress the TRH-stimulated TSH level in case 2. The two patients thus were diagnosed to have GRTH. Sera from their father and another sister showed identical abnormalities.

Diazoxide infusion at excess but not at basal hyperglycemia enhances beta-cell sensitivity to glucose in vitro in neonatally streptozotocin-diabetic rats

The influence of chronic and moderate hyperglycemia vis-à-vis a 48-hour further elevation of blood glucose on beta-cell sensitivity to glucose was compared in an animal model of non-insulin-dependent diabetes. Neonatally streptozotocin-diabetic (n-STZ) rats infused with saline for 48 hours displayed moderate nonfasting hyperglycemia (mean, 11.5 +/- 1.5 mmol/L/48 h) and plasma insulin levels similar to those seen in normoglycemic, nondiabetic rats. In perfused pancreas, the insulin response to 27 mmol/L glucose was severely reduced to 1.60 +/- 0.45 pmol/min, ie, approximately 15% of the response in nondiabetic rats. A continuous infusion of diazoxide (5 mg/kg/h), which normally blocks glucose-induced insulin secretion, did not affect glucose and insulin levels in vivo, nor did it significantly affect the insulin response to glucose in vitro. In other experiments, "basal" hyperglycemia in n-STZ rats was doubled by glucose infusions for 48 hours to reach a mean of 23.8 +/- 0.6 mmol/L. Plasma insulin increased 3.2-fold. The in vitro insulin response to 27 mmol/L glucose was totally abolished, and the pancreatic insulin content was decreased by 81% relative to the content after saline. Addition of a diazoxide infusion inhibited the increase in plasma insulin by 93%. After the combined glucose and diazoxide infusion, the subsequent in vitro response to 27 mmol/L glucose was dramatically enhanced to 9.55 +/- 3.25 pmol/min, ie, the response was sixfold higher than after saline alone. This aftereffect of the diazoxide infusion was not significantly altered by an insulin infusion (2 U/d) added to the hyperglycemia plus diazoxide protocol to compensate for the insulin-lowering effect of the drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of pravastatin on serum lipids, apolipoproteins and lipoprotein (a) in patients with non-insulin dependent diabetes mellitus

In 43 patients with non-insulin dependent diabetes mellitus (NIDDM) associated with hypercholesterolemia, the effect of pravastatin, a potent HMG CoA-reductase inhibitor, on serum lipids, apolipoproteins and lipoprotein (a) was examined. After 1 to 3 months administration of 10 mg per day of pravastatin, the serum levels of total cholesterol, triglycerides and low-density lipoprotein cholesterol (LDL-C) were significantly decreased, while the serum level of high density lipoprotein cholesterol (HDL-C) was significantly increased in patients with NIDDM. The levels of apolipoproteins B (apo B) and E were significantly decreased, while apolipoprotein AI (apo A-I) was not changed by the administration of pravastatin. The atherogenic indices (LDL-C/HDL-C and apo B/apo A-I) were significantly decreased by the administration of this drug. The serum lipoprotein (a), which was increased in the diabetic patients, was not affected by the pravastatin treatment. Plasma glucose and hemoglobin A1c levels were not affected by the treatment. We concluded that pravastatin is a potentially useful agent in the treatment of hypercholesterolemia in patients with NIDDM.

Impact of uncoupling glucose stimulus from secretion on B-cell release and biosynthesis

We studied the impact of a defined degree of long-term hyperglycemia with or without blockade of attendant insulin release on subsequent B-cell secretory responsiveness and biosynthesis. Nondiabetic rats were infused for 48 h with glucose to produce marked hyperglycemia (21.3 +/- 0.5 mmol/l). Comparable levels of hyperglycemia were upheld when additions were made to this protocol. Hyperglycemia increased plasma insulin 12-fold but depressed glucose (27 mmol/l)-induced insulin secretion in vitro (isolated islets) by 67% compared with saline-infused rats. Addition of diazoxide infusion during hyperglycemia completely inhibited the hyperglycemia-induced rise in plasma insulin but enhanced glucose-induced insulin release in vitro eightfold compared with islets from rats infused with glucose alone. Addition of insulin (2 U/day) to the diazoxide plus hyperglycemia protocol inhibited the secretory response to glucose in vitro by 46% (P less than 0.05). Proinsulin biosynthesis was enhanced by 67% in islets from rats infused with glucose alone; this effect was paralleled by a similar increase in preproinsulin mRNA. Diazoxide in vivo did not affect these stimulatory effects of hyperglycemia on insulin biosynthesis; however, insulin infusion in vivo abolished the hyperglycemia-induced increase in proinsulin biosynthesis. We conclude that impairment by hyperglycemia of glucose-induced insulin secretion occurs concomitant with stimulation of biosynthesis. Uncoupling of glucose stimulus from secretion crucially affects subsequent secretory responsiveness but not biosynthesis. Insulin biosynthesis is depressed by direct or indirect effects of circulating insulin.

Development of a streak-camera-based time-resolved microscope fluorimeter and its application to studies of membrane fusion in single cells

A time-resolved microscope fluorimeter based on a synchroscan streak camera and a fast pulsed laser system has been developed to measure the fluorescence lifetime decay under the fluorescence microscope. This system allows one to measure the nanosecond fluorescence lifetimes of fluorophores in a small spot (0.8-6.3 microns diameter) in single cultured cells under a fluorescence microscope, while the cells are being viewed under a high-power objective lens. A signal acquisition time between a second and a minute was usually sufficient to obtain fluorescence decay curves with good quality for 10(3)-10(5) fluorophores localized in 1 microns 2 domain. A signal-to-noise ratio better than 30 was obtained for approximately 30,000 fluorescein-labeled band 3 molecules in a 2 microns 2 region in a single human erythrocyte ghost after signal accumulation for 30 s. The measured lifetimes for a variety of fluorescent probes attached to proteins in solution and lipids in liposomes showed a good agreement with those measured in a cuvette under standard conditions by time-correlated single photon counting. With the development of this instrument, microscope fluorimetry has become a practical, straightforward, quantitative technique for investigation of molecular processes in single cells in culture. Time-resolved microscope fluorimetry has been applied to observe fusion of liposomes in vitro and that of endosomes in single cells by monitoring resonance energy transfer. Inspection of individual liposomes and endosomes revealed the extent of fusion for each vesicle. Since the use of time-resolved microscope fluorimetry eliminates the need for subcellular fractionation or the complex correction procedures in steady-state microfluorimetry, it greatly simplifies the assay for endosome fusion in vivo. The results showed that extensive fusion of sequentially formed endosomes takes place all over the cell matrix in cultured cells. This suggests that extensive fusion with incoming endosomes takes place in many endosomal compartments, possibly sorting organelles, or that the early endosomes fuse with the preexisting network of tubular cisternae of the endosomal compartment at many points in the network. It is concluded that time-resolved microscope fluorimetry is a powerful noninvasive technique for studies of in situ biochemistry and biophysics using cells and tissues.

Multiple abnormalities in insulin responses to nonglucose nutrients in neonatally streptozotocin diabetic rats

Insulin responses to nutrient secretagogues were investigated in neonatally streptozotocin-injected (n-STZ) rats, i.e. an animal model of noninsulin-dependent diabetes. In the perfused pancreas 16 mM L-glutamine induced and 10 mM octanoate tended to induce (P less than 0.2) higher responses in n-STZ than in nondiabetic rats. Addition of 3.9 mM glucose potentiated responses to glutamine and octanoate more in n-STZ (3.3- and 3.4-fold) than in nondiabetic rats (1.5- and 1.9-fold). Conversely, the succinate derivative succinate monomethylester (Succ ME) induced lesser response in n-STZ rats (57% of that in nondiabetic rats) and coperfusion with 3.9 mM glucose increased the response less in n-STZ (1.4-fold) than in nondiabetic rats (3.8-fold). Pyruvate (20 mM) mimicked the potency of 3.9 mM glucose, i.e. pyruvate potentiated the response to Succ ME only nonsignificantly (1.2-fold) in n-STZ but markedly (4.9-fold) in nondiabetic rats. Dichloroacetate (20 mM) failed to affect the response to Succ ME together with pyruvate in n-STZ rats. To investigate the role of hyperglycemia for octanoate-induced secretion, nondiabetic rats were made hyperglycemic by 48-h glucose infusions. Octanoate-induced secretion from perfused pancreas was enhanced 3.8-fold after moderate hyperglycemia (13.2 +/- 0.6 mM) and 17-fold after marked hyperglycemia (22.7 +/- 0.6 mM). This positive association between response and degree of hyperglycemia was not found with a nonnutrient secretagogue, 3-isobutyl-1-methylxanthine. Results with glutamine and octanoate indicate that oxidation of nonglucose nutrients which normally do not regulate secretion is enhanced secondary to chronic hyperglycemia. Results with Succ ME and pyruvate suggest that early steps of oxidation of glucose are impaired in n-STZ rats.

Coupling of beta-cell desensitization by hyperglycemia to excessive stimulation and circulating insulin in glucose-infused rats

Nondiabetic rats were infused with glucose for 48 h to maintain moderate or marked hyperglycemia (mean blood glucose 13.2 +/- 0.7 or 22.8 +/- 0.3 mM, respectively). The two levels of hyperglycemia increased plasma insulin levels severalfold but decreased the insulin response to 27 mM glucose by 19 and 95%, respectively, versus saline infusion. Diazoxide (5 mg.kg-1.h-1), when continuously infused during the hyperglycemia protocols, completely inhibited the glucose-induced rise in plasma insulin levels. Diazoxide transformed beta-cell insensitivity to stimulation: glucose-induced insulin release was thus increased 318% after moderate hyperglycemia and 707% after marked hyperglycemia. These stimulatory effects of diazoxide were reversed by exogenous insulin infusion (8 or 2 U/24 h) in a dose-dependent manner. It is concluded that excessive beta-cell stimulation rather than glucotoxicity underlies hyperglycemia-induced beta-cell insensitivity. Effects of hyperinsulinemia can form part of the mechanisms whereby excessive stimulation affects beta-cell secretion.

A 48-hour lipid infusion in the rat time-dependently inhibits glucose-induced insulin secretion and B cell oxidation through a process likely coupled to fatty acid oxidation

Short- and long-term effects of hyperlipidemia with elevated FFA on insulin secretion were investigated. Male Sprague-Dawley rats were fed ad libitum and additionally infused with Intralipid 10%, 1.0 ml/h. After 3 h of Intralipid the response to 27 mM glucose in isolated perfused pancreas was enhanced by 86%, P less than 0.02. After 6 h of Intralipid enhancement had subsided. After 48 h of Intralipid glucose-induced insulin release was inhibited by 49%, from 1950 +/- 177 microU/min after saline to 1003 +/- 232 microU/min after Intralipid, P less than 0.02. Inhibition was glucose-selective since responses to other secretagogues (1 mM 3-isobutyl-1 methylxanthine, 10 mM octanoate, or 5 mM alpha-ketoisocaproic acid) were unaffected as were pancreatic contents of insulin (2284 +/- 111 mU/pancreas after saline, 2566 +/- 131 mU/pancreas after Intralipid). In isolated islets from 48 h lipid infused rats production of [14-C]CO2 from D[U-14-C]glucose was decreased (P less than 0.02) in parallel with the insulin response to 27 mM glucose. Glucose-induced secretion was partially normalized by in vitro exposure to a carnitine palmitoyl-transferase I inhibitor (Etomoxir). Effects of a 48 h lipid infusion were also tested during hyperglycemia. Rats were infused with glucose, and hyperglycemia was enhanced by dexamethasone (25 micrograms/24 h). Hyperglycemia depressed glucose-induced secretion from perfused pancreas from 2072 +/- 22 microU/min after saline + dexamethasone to 1185 +/- 155 microU/min after glucose + dexamethasone, P less than 0.01). Intralipid, added to the latter protocol, further inhibited glucose-induced secretion to 437 +/- 87 microU/min, P less than 0.005. Hyperlipidemia is concluded to be associated with short term stimulation but long term inhibition of glucose-induced insulin secretion. Evidence indicates that inhibition depends on fatty acid oxidation, is coupled to decreased glucose oxidation and operates both during normo- and hyperglycemia.

Subpopulations of endosomes generated at sequential stages in the endocytic pathway of asialoganglioside-containing ferrite ligands in rat liver

Subpopulations of endosomes generated at different stages of the endocytic pathway were isolated by a high-gradient magnetic separation followed by a Percoll density gradient centrifugation. Rat livers were perfused for 5 min with asialoganglioside (ASG)-containing ferrite particles and chased at 37 degrees C. At various times after the internalization, the endocytic vesicles containing ferrite particles were isolated by the magnetic separation. Isolated fractions contained endosomes until 15-min perfusion, after which most of the particles were transported to lysosomes. The endosomal fractions isolated after the 5- or 15-min perfusions were further analyzed by 30% Percoll density gradient centrifugation. The endosomes after 5-min perfusion showed peaks around the density of 1.05 g/ml (peak I) and 1.07 g/ml (peak Is), both of which contained asialoglycoprotein receptors. In the 15-min perfusion, another peak of endosomes (peak II) was observed at the higher density of 1.09 g/ml without the receptors, in addition to peak I. These endosomes had their own characteristic proteins. Some proteins were common in the subgroups of endosomes. These results suggest that the endosome I containing the ligands and the receptors was first produced after endocytosis and, through the endosome is, was scissioned into the endosome II containing the ligands. The endosome II was then fused with primary lysosomes for proteolytic cleavage of ligands.

Effect of galanin on arginine-stimulated pancreatic hormone release from isolated perifused rat islets

The effect of galanin on pancreatic hormone release was studied using isolated perifused rat pancreatic islets. In the presence of 100 mg/dl glucose, 10(-8) mol/L galanin significantly inhibited the basal somatostatin release compared with the perifusion without galanin, whereas there was no significant change in the basal insulin and glucagon release. However, under stimulation of 20 mmol/L arginine, 10(-8) mol/L galanin significantly enhanced glucagon release and suppressed insulin and somatostatin release. These effects disappeared immediately after cessation of galanin infusion. Additionally, 10(-8) mol/L galanin significantly enhanced the first and second phase of glucagon release stimulated by arginine, whereas arginine-stimulated insulin and somatostatin releases were significantly inhibited in both phases. In the cysteamine-treated rat islets, neither enhancement of glucagon release nor suppression of insulin release by galanin was reproducible. These findings indicate two possible explanations. First, it is suggested that the effects of galanin on insulin and glucagon release may be direct and reversed by non-specific effect of cycteamine. Secondly, it seems likely that galanin-enhanced glucagon release may be indirect and in part due to the concomitant somatostatin suppression. Galanin may have an important regulatory function on endocrine pancreas.

[Effect of press stimulation applied to back skin on gastric emptying and serum gastrin response to solid food]

We studied the effect of press stimulation applied to the back skin on gastric emptying and serum gastrin response to solid food in healthy subjects. Although gastric emptying and serum gastrin response were significantly suppressed by press stimulation of T6-9 dermatomes corresponding to the spinal levels which sympathetic outflow to the stomach arise, they were not affected by press stimulation of T10-L1 dermatomes. Plasma levels of ACTH, epinephrine and norepinephrine, which usually increase by stresses acting on the brain, did not change by press stimulation of T6-10 dermatomes. These results suggest that press stimulation applied to the back skin of T6-9 dermatomes suppress gastric emptying and gastrin response to solid food mainly through the spinal cord.

Serum fructosamine in assessment of diabetic control and relation to thyroid function

Measurement of serum fructosamine using a Roche kit is a simple and reliable method for the estimation of glycated serum proteins. The value of serum fructosamine can be affected by hyperglycemia in diabetics and an abnormal turnover rate of serum protein in patients with thyroid dysfunction. We measured the serum fructosamine level in 18 normal control subjects, 71 diabetics (8 IDDM, 63 NIDDM) and 46 non-diabetic untreated patients with thyroid dysfunction (28 hyperthyroidism, 18 hypothyroidism). The serum fructosamine level was significantly increased in the diabetics compared with the normal control subjects (3.84 +/- 0.15 mmol/l vs 2.58 +/- 0.08; mean +/- SE, P less than 0.01). The serum fructosamine level in the diabetics was positively correlated with the fasting plasma glucose and HbAlc level, showing the highest correlation with fasting plasma glucose at 2 weeks before and with the HbAlc level at 2 weeks after serum fructosamine measurement. In the patients with thyroid dysfunction, the serum fructosamine level in hyperthyroidism (2.08 +/- 0.03 mmol/l) and hypothyroidism (3.11 +/- 0.07 mmol/l) were significantly lower (P less than 0.001) and higher (P less than 0.001) than the normal control subjects (2.58 +/- 0.08 mmol/l), respectively. Furthermore, the serum fructosamine level in these patients was negatively correlated with the level of serum thyroid hormones such as T3 (P less than 0.001) and T4 (P less than 0.001). It is concluded that measurement of serum fructosamine is clinically useful for the evaluation of shorter-term glycemic control in diabetics, but its level for diabetic patients with thyroid dysfunction must be cautiously interpreted.

Saphenous vein graft patency 1 year after coronary artery bypass surgery and effects of antiplatelet therapy. Results of a Veterans Administration Cooperative Study

To determine whether antiplatelet therapies improve saphenous vein graft patency after coronary artery bypass grafting, we compared 1) aspirin (325 mg once daily), 2) aspirin (325 mg three times daily), 3) aspirin and dipyridamole (325 mg and 75 mg, respectively, three times daily), 4) sulfinpyrazone (267 mg three times daily), and 5) placebo (three times daily). Therapy with dipyridamole and sulfinpyrazone was started 48 hours before bypass graft surgery, and aspirin treatment was begun 12 hours before surgery as a single 325-mg dose. Postoperative treatment was started 6 hours after surgery and continued for 1 year. Graft patency data were obtained early (median, 9 days) and late (median, 367 days) after surgery. The early graft occlusion rate was decreased with all aspirin treatment regimens compared with that of the placebo regimen. At 1 year, in 406 patients with 1,315 grafts, the graft occlusion rate in all of the aspirin groups combined was 15.8% compared with 22.6% for the placebo group (p = 0.029). The patients taking aspirin once daily had a lower occlusion rate (13.2%) compared with the patients receiving placebo (p = 0.050). At 1 year, in the vein grafts placed to vessels less than or equal to 2.0 mm in diameter (804 distal sites), the graft occlusion rate in all of the aspirin groups was 20.1% compared with 32.3% for the placebo group (p = 0.008). In the vein grafts placed to vessels greater than 2.0 mm in diameter (511 distal sites), there was no difference in the occlusion rates between aspirin and the placebo group at 1 year (8.7% vs. 9.0%, p = 0.918).(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma sulfhydryl-containing amino acids in patients with cerebral infarction and in hypertensive subjects

It has been postulated that an accumulation of a sulfhydryl-containing amino acid, homocysteine in plasma may induce arteriosclerosis. In order to explore a possible contribution of homocysteine to the development of cerebral infarction in middle-aged and elderly patients, plasma sulfhydryl-containing amino acid profiles of 45 patients with cerebral infarction (CI) were compared with those of 45 normotensive and 45 hypertensive controls, and 20 patients with cerebral bleeding (CB), of similar ages and sex. The concentrations of both free and total homocysteine in plasma were highest in patients with CI among the 4 groups, while plasma free and total cysteinylglycine levels were similar. Although both free and total cysteine levels were also higher in patients with CI than in normotensive controls, the total homocysteine/total cysteine ratio was highest in patients with CI among the four groups. The hypertensive controls had higher plasma free and total concentrations than normotensive controls, but the levels did not differ between the 21 normotensive and 24 hypertensive CI patients. Our results suggest that high levels of plasma homocysteine in conjunction with hypertension could be one of the risk factors for arteriosclerotic CI.

[Effect of body position on gastric emptying of solid food--a study using a sulfamethizole capsule food method]

We studied the effect of body position on gastric emptying of solid food using a sulfamethizole capsule food method developed by us. Gastric emptying was significantly delayed in a supine position than in a sitting position kept for 120 minutes after ingestion of test food. These findings were observed in all of the young, middle and old aged groups. A longer sitting position after ingestion was associated with faster gastric emptying. Gastric emptying was significantly delayed in the old aged group than in the young aged group in both sitting and supine positions. Our results indicate that a postprandial sitting position is desirable for gastric digestion and emptying of solid food, especially in the old aged subjects.

[A new device for the gastric emptying test--a sulfamethizole capsule food method]

We have developed a simple but reliable method for assessing gastric emptying, a sulfamethizole capsule food method. The capsule food contains egg albumin and sulfamethizole. In saline or hydrochloride solution only a small amount of sulfamethizole, in sodium bicarbonate solution, however, a large amount of the drug was released from the capsule food. In this method, sulfamethizole concentrations in blood were measured in subjects after ingestion of 15 pieces of capsule food containing 1.0 g of sulfamethizole, and area under the curve of the blood concentrations was calculated as an index of gastric emptying. Gastric emptying of capsule food had a lag phase of 15 minutes, which was already reported in gastric emptying of radioisotope labeled solid food. Bread combined with the capsule food caused a delay in gastric emptying and a larger volume of the bread was associated with a longer gastric emptying time. In conclusion, our sulfamethizole capsule food method is useful in clinical practice to assess gastric emptying of solid food.

Improvement in early saphenous vein graft patency after coronary artery bypass surgery with antiplatelet therapy: results of a Veterans Administration Cooperative Study

To determine whether specific antiplatelet therapies improved vein graft patency after coronary artery bypass grafting (CABG) we compared (1) aspirin, 325 mg daily, (2) aspirin, 325 mg three times daily, (3) aspirin plus dipyridamole (325 mg and 75 mg, respectively, three times daily), (4) sulfinpyrazone (267 mg three times daily), and (5) placebo (three times daily). Therapy, except aspirin, was started 48 hr before CABG. When aspirin was a treatment, one 325 mg dose was given 12 hr before surgery and therapy was maintained thereafter according to the assigned regimen. Angiographic graft patency data were obtained within 60 days of surgery. Analysis of early graft patency in 555 patients (1781 grafts), revealed the following graft patency rates: aspirin daily, 93.5%; aspirin three times daily, 92.3%; aspirin and dipyridamole, 91.9%; and sulfinpyrazone, 90.2%. All aspirin-containing therapeutic regimens improved (p less than .05) graft patency compared with placebo (85.2%). Chest tube drainage measured within the first 35 hr after CABG revealed that the median loss with aspirin daily (965 ml), aspirin three times daily (1175 ml), and aspirin plus dipyridamole (1000 ml) exceeded (p less than .02) that with placebo (805 ml), while median loss with sulfinpyrazone (775 ml) did not. The reoperation rate was greater (p less than .01) in all the treatment groups that received aspirin (6.5%) compared with the two nonaspirin groups (1.7%). Overall operative mortality was 2.3%, without significant differences among treatment groups. Transient renal insufficiency occurred in 5.3% of patients taking sulfinpyrazone. Thus, early vein graft patency was improved after CABG with all aspirin-containing drug regimens.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of free and total homocysteine in human plasma by high-performance liquid chromatography with fluorescence detection

A simple, sensitive and precise method for the determination of both free and total homocysteine in human plasma is presented. The total homocysteine in plasma consists of free homocysteine (i.e. reduced plus oxidized homocysteine in the non-protein fraction of plasma) and protein-bound homocysteine. The thiol compounds in plasma, which are reduced or liberated from plasma proteins with tri-n-butylphosphine, are derivatized with a thiol-specific fluorogenic reagent, ammonium 7-fluorobenzo-2-oxa-1,3-diazole-4-sulphonate. The derivatives are separated by reversed-phase high-performance liquid chromatography. The concentrations (mean +/- S.D.) of free and total homocysteine in plasma from 35 normal subjects were 1.94 +/- 0.46 and 6.18 +/- 1.19 nmol/ml, respectively.

Hypersomatostatinemia in chronic renal failure

Plasma concentrations of somatostatin-like immunoreactivity (SLI) were determined in uremic patients on maintenance hemodialysis. Plasma SLI levels were significantly (p less than 0.001) elevated in 26 diabetic uremic patients (67.1 +/- 6.8 pg/ml, mean +/- SE) and in 24 non-diabetic uremic patients (43.5 +/- 7.2 pg/ml), when compared with 60 healthy subjects (5.0 +/- 0.7 pg/ml). Paired pooled plasma from uremic patients before and after hemodialysis was subjected to a reverse-phase octadecasilyl-silica (C-18) cartridge and then the extract was gel filtered on a Sephadex G-25 column (1.6 X 90 cm). Both elution profiles showed two peaks of SLI which coeluted with synthetic somatostatin (SS)-28 and SS-14 markers, respectively. The SS-28-like immunoreactivity (LI) peak, which was estimated by using SS-14 as a reference standard, was 3-fold larger than that for SS-14 LI. On the basis of immunoequivalency of the two components in the present assay, SS-28 LI constitutes approximately 75% of circulating somatostatin. In conclusion, plasma SLI is substantially high in uremic patients of both diabetic and non-diabetic etiology and the SS-28 is a predominant form of circulating SLI in these patients, probably, in part, for a lower clearance of this molecule.

A novel method for isolating specific endocytic vesicles using very fine ferrite particles coated with biological ligands and the high-gradient magnetic separation technique

We have developed a novel method for isolating specific endocytic vesicles using magnetic ligands and high-gradient magnetic separation. Ligands were prepared by coating extremely fine ferrite particles (10-20 nm) with bovine serum albumin and then conjugating asialoglycopeptides. These ligands were introduced into rat liver by perfusion at 16 or 37 degrees C, or by injection through the tail vein. The ligand particles were observed as electron-dense small grains in membrane-bound vesicles in Kupffer as well as parenchymal cells by electron microscopy. Livers were taken out, homogenized and lightly centrifuged. The supernatant was pumped into a separator glass tube filled with very fine ferritic stainless steel fibers and placed in a magnetic field of 0.9-2 T. Vesicles containing ferrite particles were collected with a high efficiency (ca. 70% of endocytosed magnetic ligands). About 70% of uptake appeared to be mediated by the asialoglycoprotein receptors. The captured vesicles were practically free from marker enzymes for plasma membranes, endoplasmic reticulum, and Golgi apparatus. Lysosomal enzyme activity of the vesicles increased with the time of perfusion at 37 degrees C but not at 16 degrees C. Protein composition of the captured vesicles was analyzed by one- and two-dimensional gel electrophoresis. The composition changed characteristically with time on perfusion at 16 and 37 degrees C. The present method provides a powerful tool to collect prelysosomal endocytic vesicles containing specific ligands and lysosomes fused with these specific endocytic vesicles.

Plasma somatostatin response in normal and gastrectomized subjects

The present work was undertaken to investigate a possible contribution of the stomach to plasma concentrations of somatostatin-like immunoreactivity (SLI) in humans. For this purpose, plasma SLI responses were determined in previously gastrectomized subjects during lipid-heparin induced elevation of plasma free fatty acids (FFA), which gave a consistent rise of plasma SLI in normal controls. Fasting plasma SLI levels in both the subjects with antral and total gastrectomy did not differ from the values in normal controls. Acute elevation of plasma FFA resulted in about 5-fold increase of plasma SLI above basal level in the controls. In contrast, in both the gastrectomy groups there was no significant rise in plasma SLI, despite a comparable elevation of plasma FFA levels. In conclusion, these findings demonstrate that the stomach, probably the antral region of the stomach, accounts for the most part of increase of plasma SLI when hyperfatty-acidemia is induced and suggest that following the stimulation by nutrients the stomach makes a greater contribution to plasma SLI levels than does the pancreas or extragastric intestinal tract in humans.

Effect of glibenclamide on pancreatic hormone release from isolated perifused islets of normal and cysteamine-treated rats

The effect of glibenclamide, a sulfonylurea agent, on islet hormone secretion, particularly on glucagon was studied using isolated perifused pancreatic islets of normal and cysteamine-treated rats. In normal rat islets, glibenclamide enhanced both insulin and somatostatin release in normoglycemic (50 mg/dL) and glucopenic (0 mg/dL) states, as well as under the condition of arginine stimulation. In contrast, glibenclamide stimulated glucagon release only transiently, then suppressed it in a sustaining manner in each state. In the cysteamine-treated islets, as expected, somatostatin concentrations in the perifusate remained unchanged during the infusion of arginine and/or glibenclamide. Under this condition, glibenclamide enhanced insulin release to the same extent as seen in normal islets, and again markedly inhibited glucagon release. These observations indicate that in isolated perifused rat pancreatic islets, glibenclamide suppresses glucagon secretion independently of D cell stimulation. It is concluded that glibenclamide may exert its inhibitory effect directly on A cell rather than through paracrine action of concomitant somatostatin release, and that the suppression of glucagon secretion by glibenclamide may, in part, contribute to the antidiabetogenic effect of this compound.

Changes in insulin secretion after secretin administration and the implications in diabetes mellitus

Secrepan (Eisai Co. Tokyo, Japan) was administered to 9 healthy volunteers and 36 patients with non-insulin dependent diabetes mellitus (NIDDM) to clarify the effect of secretin on the pancreatic B-cell, by determining the changes in blood of insulin (IRI). Whereas IRI in healthy subjects showed a monophasic change, reaching a peak (delta IRI = 43 +/- 7.3 microunits/ml, M +/- SE) 5 min after secretin loading and returning to the basal level in 15 min, NIDDM patients on diet therapy (delta IRI = 40.2 +/- 7.6 microunits/ml) showed no significant difference from the control group, but NIDDM patients on sulfonylurea (SU) (15.5 +/- 2.4 microunits/ml) and those on insulin therapy (5.3 +/- 1.4 microunits/ml), both showed a significant depression in responsiveness. Further, the changes in insulin secretion after atropine administration in healthy subjects and the changes in IRI response to Secrepan in vagotomized patients were also determined. As a result, data which preclude the possibility of association of the vagus nerve and cholinergic nerve with the stimulation of insulin secretion by secretin were obtained, and a direct action of secretin on the cell of islets of Langerhans was suggested. The maximum IRI response after a secretin load had a significant positive correlation with the IRI response after a 75-gm GTT and the content of C-peptide immunoreactivity in 24-hour urine. Therefore, insulin response to a secretin load can be useful in assessing endogenous insulin secretion and provides a pertinent clinical guide for the selection of an appropriate therapy for diabetes mellitus.

Clinical use of blood flowmeters

The concept of an electromagnetic flowmeter was first described by Kolin in 1936. He demonstrated that with the flowmeter which required surgical exposure of the blood vessel for probe contact but not requiring cannulation, it was possible to follow rapid flow changes and that the deflection bore a linear relationship to flow. Twenty years later a greatly improved circuitry and design was described by Denison and Spencer. Soon thereafter, a number of investigators, notably Schenk and his colleagues utilizing the square wave electromagnetic flowmeter and Cannon and his colleagues with the sine wave electromagnetic flowmeter reported on a number of experimental and clinical studies on blood flow measurements. My introduction to blood flow measurements was through Ferguson who had had a flowmeter and flowmeter probes constructed according to the design of Denison and Spencer. Our first report on flow measurements in patients with peripheral arterial disease was made in 1960. Electromagnetic flowmeters and probes available today are a vast improvement in ease of use, reliability and accuracy, thus the pertinent question is whether or not the information that can be obtained with it would warrant its routine clinical use. We started with a flowmeter constructed by following a schematic diagram and hand winding our own probes, then to the purchase of Medicon 2000, then Medicon 4000, and to our present unit, the SP2204. The advancement in instrumentation has been truly remarkable. All intraoperative blood pressure measurements are made with direct arterial puncture with 23 size needle with the hub removed and needle tip fitted to polyethylene tube connected to a strain gauge.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormalities of lipoprotein and carbohydrate metabolism in degenerative diseases of the nervous system--motor neuron disease and spinocerebellar degeneration

The levels of plasma high density lipoprotein (HDL) cholesterol and plasma triglyceride were determined in 44 patients with motor neuron disease (MND) and in 36 patients with spinocerebellar degeneration (SCD). In both groups the HDL cholesterol levels were significantly lower than those in healthy controls, whereas the plasma triglyceride levels were higher than those in the controls. Glucose levels during the oral glucose tolerance test (GTT) were significantly higher in both MND and SCD groups than in healthy controls. Immunoreactive insulin (IRI) levels during GTT were rather higher at 0 and 120 min in both MND and SCD groups than in healthy controls. Glycosylated hemoglobin levels were lower in MND than in the controls. These results indicate that both lipoprotein and carbohydrate metabolisms were impaired in MND and SCD groups. The possibility was presented that denervation might play a part in the pathogenesis of abnormalities of lipoprotein and carbohydrate metabolisms.