NANOMATRIX STRUCTURE FORMED BY GRAFT COPOLYMERIZATION OF STYRENE ONTO FRESH NATURAL RUBBER

Fresh NR was adopted to prepare rubber with a nanomatrix structure. The nanomatrix structure was formed by graft-copolymerization of styrene onto deproteinized fresh NR (fresh DPNR) in the latex stage using tert-butyl hydroperoxide/tetraethylenepentamine as an initiator. Graft-copolymer consisting of fresh DPNR and polystyrene (fresh DPNR-graft-PS) was characterized by 1H-NMR spectroscopy and transmission electron microscopy. Under a suitable condition of the graft-copolymerization, conversion and grafting efficiency of styrene was 98 and 80 mol%, respectively. Morphology of fresh DPNR-graft-PS was observed by transmission electron microscopy. The rubber particles of about 1 μm in diameter were found to be dispersed in polystyrene matrix of 10–30 nm in thickness. Tensile properties of fresh DPNR were dramatically improved by forming the nanomatrix structure, compared with DPNR.

Endothelium removal augments endothelium-independent vasodilatation in rat mesenteric vascular bed

BACKGROUND AND PURPOSE

The vascular endothelium regulates vascular tone by releasing various endothelium-derived vasoactive substances to counteract excess vascular response. We investigated whether the vascular endothelium regulates vasodilatation via released endothelium-derived contracting factors (EDCFs), by examining the effect of endothelium removal on responses to periarterial nerve stimulation (PNS) and various vasodilator agents.

EXPERIMENTAL APPROACH

The rat mesenteric vascular bed was perfused with Krebs solution. Vasodilator responses to PNS and 5 min perfusion of vasodilator agents in preparations with endothelium were compared with those in the same preparations without endothelium. The endothelium was removed by 30 s perfusion with sodium deoxycholate.

KEY RESULTS

Endothelium removal significantly augmented vasodilator responses to PNS and calcitonin gene-related peptide (CGRP), isoprenaline (beta-adrenoceptor agonist), SNP and 8-bromo-cGMP (8-Br-cGMP; cGMP analogue) but not BAY41-2272 (soluble guanylate cyclase activator). The augmentation of SNP-induced vasodilatation after denudation was much greater than that of CGRP- or isoprenaline-induced vasodilatation. In the preparations with an intact endothelium, L-NAME (nitric oxide synthase inhibitor) significantly augmented vasodilator responses to PNS and CGRP, isoprenaline, SNP and 8-Br-cGMP, but not BAY41-2272. Indomethacin (cyclooxygenase inhibitor) and seratrodast (thromboxane A(2) receptor antagonist), but not phosphoramidon (endothelin-1-converting enzyme inhibitor) or BQ-123 (selective endothelin type A receptor antagonists), significantly augmented vasodilator responses to PNS and CGRP, isoprenaline, SNP and BAY41-2272.

CONCLUSION AND IMPLICATION

These results suggest that the endothelium in rat mesenteric arteries regulates and maintains vascular tone via counteracting not only vasoconstriction through releasing endothelium-derived relaxing factors, but also vasodilatation, in part by releasing an EDCF, thromboxane A(2).

Association of soluble CD40 ligand with carotid atherosclerosis in Japanese type 1 diabetic patients

AIMS/HYPOTHESIS

It has recently been shown that the soluble form of CD40 ligand (sCD40L) interacts with CD40 on vascular cells, leading to a variety of proinflammatory responses, and that serum sCD40L levels can be a predictive marker of cardiovascular events. The aim of this study was to estimate sCD40L levels in type 1 diabetic patients to examine a possible association with carotid atherosclerosis.

SUBJECTS AND METHODS

Human sCD40L levels in serum and intima-media thickness (IMT) of carotid artery were examined in 80 Japanese type 1 diabetic patients (27 men and 53 women, age 22.8+/-3.4 years (mean+/-SD), duration of diabetes 13.2+/-6.1 years) and 20 healthy age-matched non-diabetic individuals.

RESULTS

Serum sCD40L levels were significantly (p=0.0185) higher in subjects with type 1 diabetes (2.10+/-1.33 ng/ml) compared with non-diabetic subjects (1.35+/-0.88 ng/ml). The greatest IMT (Max-IMT) and averaged IMT (Mean-IMT) were also significantly greater in patients with type 1 diabetes than in control subjects (0.73+/-0.14 vs 0.64+/-0.07 mm, p=0.0041, 0.63+/-0.09 vs 0.57+/-0.06 mm, p=0.0066, respectively). Levels of sCD40L were statistically significantly associated with Max-IMT (r=0.383, p<0.001) and Mean-IMT (r=0.275, p=0.0058). Furthermore, stepwise multivariate regression analyses demonstrated that sCD40L is a determinant of both Max- and Mean-IMT, independently of conventional risk factors.

CONCLUSIONS/INTERPRETATION

It is suggested that increased levels of serum sCD40L are associated with accelerated atherosclerotic change observed in young patients with type 1 diabetes.

Metformin or gliclazide, rather than glibenclamide, attenuate progression of carotid intima-media thickness in subjects with type 2 diabetes

AIM/HYPOTHESIS

Metformin is a well-known oral hypoglycaemic agent and has been commonly used, in combination with sulphonylurea, to treat type 2 diabetes. However, the advantageous effect of metformin plus sulphonylurea on diabetic macroangiopathy has yet to be clarified. To evaluate whether sulphonylurea or sulphonylurea plus metformin prevent diabetic macroangiopathy, we examined the progression of carotid artery intima-media thickness (IMT) as a surrogate end point.

METHODS

Subjects with type 2 diabetes were divided into three groups, receiving the following treatments: (i) glibenclamide (n=59); (ii) gliclazide (n=30); and (iii) glibenclamide + metformin (n=29). Maximum IMT and average IMT (the greatest value among 6 average values of each 3 points including greatest thickness) were measured at the beginning and end of the observation period.

RESULTS

For the follow-up period of 3 years, the annual change in average IMT of the glibenclamide plus metformin group (0.003+/-0.048 mm) was smaller than that of the glibenclamide group (0.064+/-0.045 mm) and gliclazide group (0.032+/-0.036 mm) (p<0.0001 and p=0.043 respectively). In the gliclazide group, average IMT increased during the follow-up period, but annual change in average IMT was significantly smaller than that of the glibenclamide group (p=0.005). Glibenclamide + metformin or gliclazide also attenuated the progression of maximum IMT, compared with that of glibenclamide (0.041+/-0.105, 0.044+/-0.106, 0.114+/-0.131 mm/year respectively, p=0.029 and p=0.035 respectively). Multivariable regression analysis implied that administration of metformin or gliclazide significantly and independently (p<0.05) reduces the progression of average IMT, compared with glibenclamide monotherapy.

CONCLUSIONS/INTERPRETATION

These data indicate that metformin or gliclazide, rather than glibenclamide, have a potent anti-atherogenic effect in type 2 diabetes.

Changes in blood biochemical parameters in tail-suspended rats

There have been many studies on the effects of gravity on animals and humans. In particular, weightlessness and the time course of physiological shifts in space acclimation are the most significant problems in a space environment. In a laboratory setting, tail suspension in rats has been utilized for simulation of weightlessness. We therefore utilized this technique in order to study the influence of microgravity on blood constituents in rats. It was clarified that some blood biochemical parameters were effected for the duration of suspension exposure, and they are reported here.

Carotid intima-media thickness in Japanese type 2 diabetic subjects: predictors of progression and relationship with incident coronary heart disease

OBJECTIVE

To examine carotid intima-media thickness (IMT), predictors of its progression, and its relationship with incident coronary heart disease (CHD) in type 2 diabetic Japanese patients.

RESEARCH DESIGN AND METHODS

Carotid IMT of 287 subjects with type 2 diabetes (mean age 61.6 years) without CHD or cerebrovascular disease was examined at baseline and after a mean follow-up of 3.1 years.

RESULTS

The annual progression of IMT (means +/- SEM) was 0.04+/-0.004 mm/year. Stepwise multivariate analysis demonstrated that independent risk factors for progress of IMT were the initial IMT (P<0.001), the average HbA1c level (P<0.001), and age (P = 0.001). Both the initial IMT (odds ratio [OR] 4.9, 95% CI 1.7-14.1) and a low average HDL cholesterol (OR 0.2, 0.1-0.8) were identified as predictors of incident nonfatal CHD (angina pectoris or nonfatal myocardial infarction; 3-year incidence 10.1%) after adjusting for age, sex, average HbA1c, and other risk factors.

CONCLUSIONS

The predictors of the progression of carotid IMT in Japanese type 2 diabetic subjects were its baseline thickness and the average HbA1c during the follow-up. Baseline carotid IMT and low HDL cholesterol predicted the incidence of nonfatal CHD.

Neutral taxoids from Taxus cuspidata as modulators of multidrug-resistant tumor cells

Two taxoids, taxinine NN-7 (1) and 3,11-cyclotaxinine NN-2 (2), were isolated from the neutral fraction of the EtOAc extract of a mixture of needles and young stems of Taxus cuspidata. The structures were determined by spectroscopic analysis. Both compounds showed some activity as modulators of multidrug-resistant tumor cells.

Antiplatelet drugs attenuate progression of carotid intima-media thickness in subjects with type 2 diabetes

The intima-media thickness of the carotid artery has been established as a surrogate of definite atherosclerosis in subjects with high risk of vascular events. This study was done to evaluate the effectiveness of long-term antiplatelet therapy in attenuating progression of the intima-media thickness of the carotid artery of subjects with type 2 diabetes. Subjects who had an intima-media thickness over the threshold of the normal subjects but showed no symptoms of vascular events were randomly divided into groups given antiplatelet drugs [ticlopidine (n = 34) or a small dose of aspirin (n = 40)] or no drugs (n = 74). For the follow-up period (3.0+/-0.06 years), the subjects not given antiplatelet drugs showed a significantly higher progression of intima-media thickness (0.067+/-0.009 mm/year) than those given ticlopidine (0.034+/-0.013 mm/year) or aspirin (0.033+/-0.010 mm/year). Stepwise multivariant regression analysis showed that long-term administration of ticlopidine or aspirin significantly reduced the progression of intima-media thickness of diabetic subjects by 0.041 mm/year or 0.032 mm/ year, respectively. These data indicated that despite differences of their pharmacological mechanisms, antiplatelet drugs could attenuate the progression of intima-media thickness of the carotid artery wall of asymptomatic type 2 diabetics who had early-stage carotid atherosclerosis.

[Prolonged neuromuscular blockade with vecuronium in patient with triple pregnancy treated with magnesium sulfate]

A 33 year-old parturient with triplet pregnancy underwent emergency cesarean section at 35 week of gestation under general anesthesia. The patient had received magnesium sulfate to prevent uterine contraction immediately before the cesarean section. Although serum magnesium value was not beyond therapeutic levels (3.3 mEq.l-1), the neuromuscular blocking effects with vecronium were strengthened. It was not likely that volatile anesthetic enhanced neuromuscular blockade produced by vecuronium because the onset time of vecuronium had already been faster than that in pregnant patients untreated with magnesium before she was exposed to isoflurane. In addition, it is possible that magnesium could interfere with postpartum uterine contractions because of its tocolytic properties. Magnesium sulfate therapy has several implications to anesthetic agents. We, anesthesiologists, should know about the biophysiological effects of magnesium and control the interaction between anesthetic agents and this electrolyte.

Effects of exercise on rats subjected to tail suspension

Deterioration of vital functions is observed in living organisms in microgravity. However, this deterioration can be arrested by adequate exercises. In this study, utilizing tail suspension in rats to simulate microgravity, we examined the influence of running exercise every other day on blood constituents, visceral parameters, and muscles.

Relationship between hind-limb muscle atrophy and serum enzymes in tail suspended rats

Many studies on the effects of gravity have been reported using animals or human being since the gravity influences the biological body in space. Especially suspension techniques for rat have been used as a microgravity simulation. This study is a report on the relation between serum enzymes such as CK and muscle atrophy, caused by tail suspension in rats.

Influence to organs by ten weeks tail suspension

The subject of atrophy has been the focus of interest for morphologists as well as the scientist in the space medicine. Muscle atrophy was noted to be some influence of microgravity in the space. Using tail suspension techniques, we have studied the influence of gravity to rats. In the present study, we tried to study the influence of the long term microgravity, ten weeks tail suspension.

[Retroperitoneal giant malignant fibrous histiocytoma: report of a case]

A case of histiocytoma in a 63-year-old woman with general fatigue is described. Ultrasonography and radiological examination revealed a large mass at the retroperitoneum displacing the right kidney to medial anterior abdomen. Exploration of the tumor with right kidney was done via a transperitoneal approach because the tumor had invaded the hilar fat tissue of the right kidney. The total resected weight was 3,200 g. Histological study showed malignant fibrous histiocytoma, storiform-pleomorphic type. Post-operative chemotherapy consisting of cyclophosphamide, vincristine, adriamycin, dimethyl triazeno-imidazole carboxamide (CYVADIC) was performed and the patient is doing well without any evidence of recurrence or metastasis.

Supernumerary head of biceps brachii and branching pattern of the musculocutaneus nerve in Japanese

Out of 546 upper limbs (273 cadavers), supernumerary heads of the biceps brachii were found in 75 limbs (13.7%) of 58 cadavers (21.3%). The form, origin, and insertion of the supernumerary heads, and branching pattern of the musculocutaneus nerve were studied. In addition, the dimensions of the heads were measured. In many cases, the supernumerary head arose from the humerus, between the insertion of the coracobrachialis and the upper part of the origin of the brachialis, and/or from the medial intermuscular septum. In a few cases, a supernumerary head arose from the tendon of the pectoralis major or the deltoid, or from the articular capsule, or from the crest of the greater tubercle. The supernumerary heads typically joined the common belly, or the aponeurosis of the biceps brachii. Some heads joined the belly of the long head or that of the short head. In the examination of the branching pattern of the musculocutaneus nerve, communication between the musculocutaneus nerve and the median nerve was found in 43 out of the 75 limbs (57.3%). The communicating branch ran from the musculocutaneus nerve to the median nerve in 24, from the median nerve to the musculocutaneus nerve in 12, in both directions in 5, or in another type of pattern in 2 out of 43 limbs. Sometimes a branch of the musculocutaneus nerve ran around a supernumerary head and then fused with the present trunk. The presence of a supernumerary head seemed to affect the course and branching of the musculocutaneus nerve.

Increased ketogenesis related to insulin deficiency in isolated hepatocytes from NIDDM model rats

To investigate the hepatic ketone body metabolism in NIDDM, we studied the ketone body production rates in hepatocytes from newly developed non-obese NIDDM model rats. NIDDM model rats were prepared by intraperitoneal injection of streptozotocin at 2 or 5 days of age (STZ2, STZ5 respectively). After 10-15 weeks, ketone body production rates in hepatocytes isolated from these rats were compared with those from control rats as well as ketotic rats made by intravenous injection of streptozotocin into adult rats. Basal ketone body production rates from 0.3 mM [U-14C] palmitate in hepatocytes from control, STZ 2, STZ 5 and ketotic rats were 11.7 +/- 0.98, 14.9 +/- 0.72, 16.0 +/- 0.45, 22.8 +/- 2.32 nmole.palmitate/mg.prot/hr, respectively. These rates were stimulated by 1 microgram/ml of glucagon in control, STZ 2 and STZ 5 rats (14.1 +/- 0.99, 18.6 +/- 1.36, 18.7 +/- 0.69 nmole.palmitate/mg.prot/hr, respectively), but not in ketotic rats (22.8 +/- 2.07 nmole.palmitate/mg.prot/hr). The similar effects were observed by 1 microgram/ml of epinephrine. The basal ketone body production rates were negatively correlated to both hepatic glycogen contents and plasma IRI levels. Considering these parameters together, the extent of metabolic derangement in STZ 2 and STZ 5 rats was between that in control and ketotic rats. These results indicate that the derangements of hepatic ketone body production are related to the severity of insulin deficiency and suggest that the enhanced hepatic ketogenesis contributes in part to the elevated plasma ketone body levels in non-obese NIDDM.

Hyperlipidemia and atherosclerosis in experimental insulinopenic diabetic monkeys

Chronic insulinopenic diabetes was induced by i.v. streptozotocin in the non-human primate Macaca fuscata. Five diabetic monkeys were kept for 8-19 months and nine for 24-48 months without any insulin treatment. Hyperglycemia (241 +/- 22 mg/dl, M +/- SE less than or equal to 1 year) progressed to 376 +/- 34 mg/dl (greater than 2 years) and ketosis to 3.5 mM (greater than 2 years) during the course of diabetes; this was roughly inversely proportional to hypoinsulinemia (3.4 microU/ml, 2 years). Serum cholesterol increased from 184 +/- 11 (less than or equal to 1 year) to 328 +/- 66 mg/dl (greater than 2 years) with the major increase in LDL-cholesterol (2.7-fold over control, greater than 2 years). HDL-cholesterol did not change at all throughout the experimental period. TG increased from 144 +/- 25 (less than or equal to 1 year) to 676 +/- 116 (greater than 2 years) with a major increase in the VLDL fraction (15-fold over control, greater than 2 years). Serum levels of apo B increased to 141 +/- 16 (less than or equal to 2 years) and 223 +/- 8 mg/dl (greater than 2 years) in contrast to control, 73 +/- 2. Morphologically, lipid deposition in the intima and fatty streaks have been observed in the abdominal aorta of all the diabetic monkeys with duration of more than 2 years. In six of the diabetic monkeys atheromatous changes such as intimal and medial thickening with smooth muscle cell proliferation were observed with foam cell formation. Similar atherosclerotic lesions were observed in renal and coronary arteries in at least six of these monkeys. In diabetic monkeys with duration of less than 2 years, mild atherosclerotic lesions were observed in two out of five. The results indicate that long standing insulinopenia leads to metabolic derangements characterized by hyperglycemia, ketonemia and hyperlipidemia. Elevation of LDL-cholesterol and VLDL TG with an increase of apo B is a characteristic of lipoprotein disorder. Morphologically, early to moderately advanced lesions of atherosclerosis were observed in aorta, renal and coronary arteries as a result of metabolic derangement due to insulin deficiency.

In vitro stimulation of glucose utilization by insulin in primary cultures of rat hepatocytes

The effect of glucose concentration and insulin on glucose incorporation was studied in primary cultures of rat hepatocytes. The rate of glucose incorporation into hepatocytes was proportional to the medium glucose concentration from 100 to 800 mg/dl. At 800 mg/dl glucose the rate reached a plateau. Of the glucose taken up by hepatocytes, 16 and 18% was incorporated into glycogen and lipid, respectively, and 58% into the nucleotide fraction after incubation for 4 h. In the medium, lactate was the major product found. Insulin stimulates glucose incorporation by 20-112% into all the above pathways at glucose concentrations between 100 and 800 mg/dl. The insulin effect was noted as early as 2-4 h (early effect) and up to 24 h (delayed effect). This effect of insulin was observed to be dose dependent from 5 to 200 ng/ml insulin. While the delayed insulin effect was abolished by cycloheximide, the early effect of insulin was not affected. With respect to the key enzyme activities of glucose utilization, activation of glycogen synthase (increase of I-activity/total activity) and pyruvate kinase (activation at 0.2 mM phosphoenolpyruvate) was noted 4 h after insulin addition, and these effects were not abolished by cycloheximide. These two enzymes increased in total activity after 24 h. Both glucokinase and glucose-6-phosphate dehydrogenase activities increased by 30-35% and 65-93% at 4 and 24 h, respectively. The results indicate that hepatocytes directly utilize glucose in a dose-dependent manner with respect to glucose and insulin. A major early and delayed effect of insulin appeared due to the activation and induction of the key hepatic enzymes of glucose utilization, respectively.

M. cervico-humeralis--a case report

An abnormal muscle, so-called M. cervico-humeralis, was found bilaterally in a 50-year-old Japanese male in a dissection practice at Jikei University in 1989. This is the third report of the cervico-humeral muscle in Japan, and the first case which occurred bilaterally. Both muscles were similar in shape, origin, course, and insertion. The flat and triangular-shaped muscle arose by tendinous slips from the transverse processes of the sixth and seventh cervical vertebrae (VC6 and VC7). These two tendons converged to form a single slip which passed through the brachial plexus. This single slip became a muscle running obliquely downward and laterally together with the brachial plexus and subclavian vessels to reach the medial surface of the humerus. The muscle inserted linearly by a thin flattened tendon into the lower end of the lesser tubercle and into the medial lip of the intertubercular sulcus of the humerus. The supplying nerve originated directly from the posterior cord of the brachial plexus in both muscles. The artery to the right cervico-humeral muscle arose from the axillary artery together with a branch to the subscapular muscle.

Increased plasma plant sterol levels in heterozygotes with sitosterolemia and xanthomatosis

Plasma sterol levels in a family of sitosterolemia and xanthomatosis were determined by a high performance liquid chromatography. Three affected siblings manifested marked xanthomatosis including subcutaneous soft tissues and generalized atherosclerosis. Two other siblings as well as children of the patients did not show such clinical symptoms and signs. Plasma levels of cholesterol, sitosterol, campesterol, and cholestanol in three affected subjects were 190 +/- 18.5, 25.9 +/- 11.6, 16.1 +/- 7.8, 1.84 +/- 0.92 mg/dl (mean +/- SD), respectively. Four daughters of the affected subjects, who should be considered as obligatory heterozygotes, showed moderately increased levels of these sterols (195 +/- 41.7, 1.33 +/- 0.44, 1.56 +/- 0.69, 0.80 +/- 0.28 mg/dl), which were significantly higher than those of normal subjects. Treatment with cholestyramine had little effect on the increased plasma plant sterol levels, but markedly decreased plasma cholestanol concentrations in two affected siblings. This report presents the clinical features of the patients with sitosterolemia and xanthomatosis and also demonstrates that heterozygotes with this disorder have increased plasma levels of plant sterols as well as cholestanol, and suggests that this rare disease might be inherited as an autosomal co-dominant trait in certain cases. The data also indicate that cholestyramine administration was not effective in this family for treatment of sitosterolemia.

Development of stable film test for rapid estimation of blood or plasma 3-hydroxybutyrate

A film test for the rapid detection of plasma/serum 3-hydroxybutyrate (3-OHB) has been developed. The film contains NAD, nitro blue tetrazolium, 3-OHB dehydrogenase, and diaphorase, and the surface is coated with modified biomembrane and can detect 50-1500 microM 3-OHB within 2-3 min. One drop or 50 microliters of plasma/serum or blood is applied to the film, and the violet color is read via reflectance meter after 2 min. Plasma/serum samples greater than 1500 microM 3-OHB can be measured by dilution with saline. In blood with 40% hematocrit, the color developed is 50% less than with plasma/serum, and this was adjusted in the reflectance meter. A good correlation (r = 0.99) was observed between results with automated and film methods and between visual methods and reflectance meter. In insulin-dependent diabetes mellitus, all 3 subjects with positive ketonuria (+ +), 8 of 12 subjects with mild ketonuria (+), and 7 of 25 subjects without ketonuria exhibited elevation of 3-OHB in blood greater than 200 microM. The results indicate that 3-OHB film is valuable not only in the emergency room for the differential diagnosis between ketoacidotic and nonketotic hypersomolar coma but also as a marker for insulin dependency, energy dependency on fatty acid compared with glucose, and metabolic control of diabetes.

Sex differences in blood constituents of rats following tail suspension

Tail suspension was utilized to study sex differences in the effects of hypokinesia on blood constituents of rats. Twelve male and twelve female rats were used. After four weeks of exposure to tail suspension or non-treatment, the rats were laparotomized under ether anesthesia and blood samples were obtained. Biochemical tests on the blood samples were then performed immediately. Hematocrit and serum iron were also estimated. The results were as follows: 1) The same tendencies were noted in blood constituents between male and female rats in the control group and the tail suspension group. 2) The average levels of blood albumin, creatinine, uric acid, glucose, triglyceride, serum iron and hemoglobin in the tail suspension group were lower than those in the control group, especially in male rats.

Chronically streptozocin-diabetic monkey does not closely mimic human diabetic neuropathy

In order to evaluate the value of diabetic Japanese monkeys (Macaca fuscatus) as an animal model for studying the pathogenesis of diabetic neuropathy, morphological examinations were performed on myelinated nerve fibers and endoneurial microvessels at three levels of the lower limb nerve in eight streptozocin (STZ)-diabetic monkeys with the duration of diabetes up to 36 months and in four roughly age-matched control monkeys using a computer-assisted image analyzer. Nerve fiber loss was not found, although a tendency for nerve fiber atrophy was found in diabetic monkeys. Endoneurial microvessels did not show either endothelial or pericyte proliferation or basement membrane thickening. The results suggest that chronically STZ-diabetic Japanese monkeys with the duration of diabetes up to 36 months might be useful for studying diabetic axonopathy, but do not closely mimic the nerve pathology found in human diabetic neuropathy.

Toxicity of oxidized low-density lipoprotein to cultured fibroblasts is selective for S phase of the cell cycle

Oxidized LDL (o-LDL) is toxic to a variety of cultured cells. Preliminary results suggested that susceptibility is enhanced by cell proliferation. As a step toward determining the mechanism of cytotoxicity, we chose to identify the cell cycle phase(s) during which exposure of cultured human fibroblasts to o-LDL leads to death. Cytochalasin B, which blocks cell migration and proliferation, and irradiation, which prevents mitosis but not migration, both blocked cytotoxicity. Colchicine, which arrests cells in mitosis but does not inhibit DNA synthesis, did not block cytotoxicity. Treatment of cells with hydroxyurea, which blocks cells prior to S phase, prevented cell death. Addition of o-LDL to cells immediately after S phase allowed mitosis without death. The above results coupled with results using cells synchronized by three different means indicate that cell death is selective for proliferating cells and occurs after exposure to o-LDL during S phase. Understanding the mechanism of o-LDL-induced death may have implications for tissue damage in vivo in the numerous instances of pathology in which oxidized lipoproteins or lipids are present.

Study of insulin response to oral glucose load after acute and chronic glycemic control in type 2 diabetic subjects

To investigate whether correction of fasting hyperglycemia per se improves the insulin secretion in type 2 diabetic subjects, plasma insulin response to 75 g oral glucose load has been studied after acute and chronic normalization of fasting plasma glucose levels in 7 overt type 2 diabetic subjects. For the acute normalization of elevated fasting plasma glucose levels, an artificial endocrine pancreas was employed. Although fasting plasma glucose concentrations were normalized before the oral glucose challenge, insulin response to oral glucose was not improved compared to those without normalization of fasting plasma glucose levels. After 1-3 month control of hyperglycemia, the insulin response to glucose in the subjects was significantly improved compared to those without treatments. Results indicate that chronic metabolic control is essential for the improvement of insulin response to glucose in type 2 diabetic subjects, and also suggest that the impaired insulin secretion in type 2 diabetes is not due to hyperglycemia per se, but due to the metabolic derangements which lead to chronic hyperglycemia.

Determinants in the pathways followed by the carbons of acetone in their conversion to glucose

[2-14C]Acetone was infused into rats that were fed or fasted. Each was infused with either a trace quantity of acetone or a large quantity that resulted in a blood concentration of acetone of at least 4 mM. The distribution of 14C in the carbons of glucose from each rat was determined. Two of the rats were given acetone in their drinking water and one was diabetic. Whether a rat was chronically exposed to acetone, fed or fasted, normal or diabetic, if given the trace dose, over 80% of the 14C in the glucose it formed was in carbons 1, 2, 5, and 6 of the glucose. If a rat was given the large dose, about 50% was in carbons 3 and 4. Thus, the major determinant of the pathways followed by acetone when it is metabolized is its concentration and not the prior dietary state of the animal or its previous exposure to acetone. Incorporation into carbons 1, 2, 5, and 6 occurs in the conversion of the carbons of [2-14C]lactate into glucose, whereas incorporation into carbons 3 and 4 occurs in the conversion of the carbons of [1-14C]acetate into glucose. Therefore, at high acetone concentration, the pathway that has been proposed for acetone's metabolism via acetate predominates, and via acetate there can be no net synthesis of glucose from acetone. When rats were given cyanamide and then the large dose of acetone, 74% of the 14C in the glucose they formed was in carbons 3 and 4 of the glucoses. Thus, the relative contribution of the pathway to lactate, or its metabolic equivalent, that has been proposed appears to be lessened by the administration of an aldehyde dehydrogenase inhibitor.

A suppressive role of c-kinase for the stimulation of hepatic ketogenesis by glucagon and epinephrine

The regulatory mechanism of hepatic palmitate oxidation into ketone bodies by c-kinase has been studied in isolated hepatocytes. Glucagon and epinephrine stimulated [U-14C]palmitate oxidation to ketone bodies by 60 and 25% as early as at 1 h. The stimulatory effects were almost totally prevented by the simultaneous presence of vasopressin, phorbol 12-tetradecanoate 13-acetate (TPA), or diacylglycerol (1-oleoyl-2-acetylglycerol). When hepatocytes were treated with glucagon or epinephrine, carnitine palmitoyltransferase (CPT), a key regulatory enzyme of palmitate oxidation, was activated. This hormone-induced activation of CPT was not observed in the presence of TPA. These observations suggest that c-kinase inhibits glucagon- or epinephrine-stimulated palmitate oxidation to ketone bodies, and that this inhibition may be mediated through a covalent modification of CPT.

Pathways of acetone's metabolism in the rat

Distributions of 14C were different from those of 13C in glucoses formed by livers of rats in diabetic ketosis and perfused with [2-14C]acetone and [2-13C]lactate. There was 32-73% of the 14C and 8-12% of the 13C in carbons 3 and 4 of the glucoses with the remaining 14C and 13C distributed about equally in the other carbons. Incorporations of 14C from [2-14C]acetone (14-39%) also exceeded those from [2-14C]pyruvate (8-10%) into carbons 3 and 4 of glucoses formed by hepatocytes from rats fed acetone or fasted. [2-14C]Acetone and [2-14C]pyruvate were infused into rats that were fed, fasted, given acetone in their drinking water, or in diabetic ketosis. Thirty-seven to 52% of the 14C in the glucoses formed was in their carbons 3 and 4 when the acetone was infused and 8 to 14% when the pyruvate was infused. [1,3-14C]Hydroxybutyrate was formed by the rats in diabetic ketosis given [2-14C]acetone. It is concluded that acetone is metabolized in rats to a large extent by a pathway in which lactate or its metabolic equivalent is not an intermediate and that pathway is via acetyl-CoA. via acetyl-CoA.

The nature of the pentose pathway in liver

[2-14C]Glucose, [3,4-14C]glucose, [5-14C]glucose, [4,5,6-14C]glucose, and [1-14C]ribose were perfused through livers of rats. The rats were fed or fasted and refed. In one experiment the liver perfused was regenerating and in another phenazine methosulfate was in the perfusate. Perfusion was for 30 or 90 min. Glucose from each perfusate and liver glucose-6-P and glycogen were isolated, purified, and degraded. The distributions of 14C in the carbons of the glucoses from the glycogens are similar to the distributions from the glucose 6-phosphates. The distributions of 14C are in accord with metabolism of glucose by the classical pentose pathway and not by the L-type pathway that has been proposed to function in liver.

Quantitative estimation of the pathways followed in the conversion to glycogen of glucose administered to the fasted rat

When [6-3H,6-14C]glucose was given in glucose loads to fasted rats, the average 3H/14C ratios in the glycogens deposited in their livers, relative to that in the glucoses administered, were 0.85 and 0.88. When [3-3H,3-14C]lactate was given in trace quantity along with unlabeled glucose loads, the average 3H/14C ratio in the glycogens deposited was 0.08. This indicates that a major fraction of the carbons of the glucose loads was converted to liver glycogen without first being converted to lactate. When [3-3H,6-14C]glucose was given in glucose loads, the 3H/14C ratios in the glycogens deposited averaged 0.44. This indicates that a significant amount of H bound to carbon 3, but not carbon 6, of glucose is removed within liver in the conversion of the carbons of the glucose to glycogen. This can occur in the pentose cycle and by cycling of glucose-6-P via triose phosphates: glucose----glucose-6-P----triose phosphates----glucose-6-P----glycogen. The contributions of these pathways were estimated by giving glucose loads labeled with [1-14C]glucose, [2-14C]glucose, [5-14C]glucose, and [6-14C]glucose and degrading the glucoses obtained by hydrolyzing the glycogens that deposited. Only a few per cent of the glucose carbons deposited in glycogen were deposited in liver via glucose-6-P conversion to triose phosphates. Between 4 and 9% of the glucose utilized by the liver was utilized in the pentose cycle. While these are relatively small percentages, since three NADP3H molecules are formed from each molecule of [3-3H]glucose-6-P utilized in the cycle, a major portion of the difference between the ratios obtained with [3-3H]glucose and with [6-3H]glucose is attributable to metabolism in the pentose cycle. Because 3H of [3-3H]glucose is extensively removed during the conversion of the glucose to glycogen within liver the extent of incorporation of the 3H into liver glycogen is not the measure of glucose's metabolism in other tissues before its carbons are deposited in liver glycogen. The distributions of 14C from the 14C-labeled glucoses into the carbons of the liver glycogens mean that at a minimum about 30% of the carbons of the glucose deposited in the glycogen were first converted to lactate or its metabolic equivalent.

Reciprocal changes of insulin and glucagon receptors in primary cultured hepatocytes

The specific [125I]insulin binding to primary cultured hepatocytes was significantly greater than that to freshly isolated hepatocytes. Low affinity insulin binding sites in cultured cells were 6-fold greater in number than those of freshly isolated cells without a significant change in high affinity sites. However, both sensitivity (insulin concentration for half maximum stimulation) and responsiveness (% of increase above the basal level) to insulin for the stimulation of ODC activity were similar for isolated and cultured cells indicating an important role of high affinity sites in the insulin action. On the other hand, the specific [125I]glucagon binding to cultured cells was significantly decreased. Low affinity glucagon binding sites in cultured cells decreased by about 50% in cultured cells without a significant change in high affinity sites. Both sensitivity and responsiveness to glucagon for the stimulation of ketogenesis from palmitate also decreased as compared with those of isolated cells, indicating an important role of low affinity sites in the glucagon action. These results indicate that insulin and glucagon receptors were reciprocally changed in cultured cells, as compared with isolated cells.

Development of early lesions of microangiopathy in chronically diabetic monkeys

A chronic diabetic state was produced in Macaca fuscatus , and these diabetic monkeys were kept without insulin treatment for up to 25 mo. The metabolic derangements were characterized by hyperglycemia, insulinopenia, hyperglucagonemia, ketonemia, and hyperlipidemia. Significant thickening of the capillary basement membrane of the gastrocnemius muscle was observed in the chronically diabetic monkeys, and became obvious in the course of diabetic state; 732 +/- 35 A in controls, 750 +/- 58 A in diabetic monkeys with duration of 4 mo, and 1165 +/- 112 A in those with duration of more than 11 mo. In addition to duration of the diabetic state, severity of hyperglycemia is also thought to play an important role in the capillary basement membrane thickening judging from the fact that diabetic monkeys with constant hyperglycemia showed a greater membrane thickening. Ultrastructural alterations, such as significant thickening of glomerular basement membrane and increase of mesangial matrix, were observed in kidney as well. These results indicate that diabetic microangiopathy has been produced by metabolic derangements characterized by chronic hyperglycemia, insulinopenia, and hyperlipidemia.

Ketone bodies as markers for type 1 (insulin-dependent) diabetes and their value in the monitoring of diabetic control

Serum levels of acetoacetate, 3-hydroxybutyrate and the 3-hydroxybutyrate/acetoacetate ratio were determined in Type 1 (insulin-dependent) and Type 2 (non-insulin-dependent) diabetic patients by a new sensitive method. Efforts were made to differentiate Type 1 and Type 2 diabetes by serum levels of ketone bodies and to determine whether their measurement is a useful way of monitoring diabetic control. In Type 2 diabetes, serum levels of total ketone bodies did not exceed 2.0 mmol/l even if the patients were untreated or poorly controlled. In Type 1 diabetic subjects, treated with once or twice daily injections of insulin, morning serum levels of acetoacetate, 3-hydroxybutyrate and total ketone bodies were significantly elevated by four-, ten- and sevenfold, respectively. In Type 2 diabetic subjects treated with diet or sulphonylureas, serum levels of 3-hydroxybutyrate were highest before breakfast, next highest before dinner and decreased after each meal. The changes were roughly inversely proportional to serum insulin levels. In addition, insulin treatment normalized fasting serum levels of ketone bodies better than diet or sulphonylurea treatment. Acetoacetate was also significantly increased in both types of diabetes to a lesser extent, but no apparent diurnal rhythm was observed. Determination of serum levels of ketone bodies is useful for the diagnosis of Type 1 diabetes (those with total ketone bodies greater than 2 mmol/l) and for detecting insufficient insulin therapy.

Effect of insulin on the synthesis and release of lipid peroxide by cultured hepatocytes isolated from normal and diabetic rats

Lipid peroxide content in hepatocytes isolated from ketotic diabetic rats was higher than normal, and the release of peroxide into the media was also elevated for the initial 18 h. Insulin suppressed both peroxide release and synthesis by cultured hepatocytes isolated from normal and from diabetic rats.

Insulin sensitivity in pancreatitis, liver diseases, steroid treatment and hyperthyroidism assessed by glucose, insulin and somatostatin infusion

In order to assess insulin sensitivity for glucose utilization in the other type of diabetes, insulin sensitivity tests were performed in subjects with pancreatitis, liver disease, steroid treatment and hyperthyroidism. Insulin sensitivity for glucose utilization decreased in subjects with liver disease, steroid treatment and hyperthyroidism irrespective of the presence or absence of glucose intolerance. Hyperinsulinism was associated in most of the subjects with liver disease and steroid treatment, but even in normo-insulinemic subjects, insulin insensitivity was observed. Obesity was associated with only 2 cases in both pancreatitis and liver diseases and therefore was excluded as a major cause for insulin insensitivity in subjects studied. In subjects with pancreatitis, insulin sensitivity was not significantly decreased. It is to be noted that 4 out of 5 subjects with diabetic OGTT (oral glucose tolerance test) exhibited normal insulin sensitivity. The results indicate that in pancreatitis, tissue insulin sensitivity for glucose metabolism is not altered and therefore can be used as a marker to differentiate the other type of diabetes due to pancreatitis from type 1 or 2 diabetes. Although hyperinsulinemia may be attributable to insulin insensitivity in subjects studied at least in part, steroid and thyroid hormone are thought to act directly antagonistically with insulin for glucose metabolism.

Sensitive and simplified method for the differential determination of serum levels of ketone bodies

A highly sensitive and simplified method for the differential determination of serum ketone bodies has been developed. Serum was deproteinized with perchloric acid, and acetoacetate contained in the supernate was reacted with newly synthesized p-nitrobenzene diazonium fluoroborate at 37 degrees C for 10 min. The formed hydrazo compound was converted by alkali to the more stable azo compound which has a peak absorbance at 645 nm. For the determination of 3-hydroxybutyrate, this was enzymatically converted to acetoacetate using 3-hydroxybutyrate dehydrogenase, LDH, NAD and pyruvate. Using 0.2 ml serum, acetoacetate and 3-hydroxybutyrate could be quantitated in 30 min. The described method is five times more sensitive than the enzymatic photometric method and can detect individual ketone bodies at concentrations as low as 20 mumol/l. Differential determination of serum levels of ketone bodies is clinically useful for the diagnosis of type 1 diabetes and in monitoring diabetic control.

Mechanism of adrenergic stimulation of hepatic ketogenesis

The effects of alpha- and beta-adrenergic stimulation on ketogenesis were examined in freshly isolated rat hepatocytes in order to determine which alpha- or beta-adrenergic stimulation is involved in the enhancement of ketogenesis. In the presence of 0.3 mmol/L (U-14C)-palmitate, epinephrine, norepinephrine, and phenylephrine at 500 ng/mL increased ketogenesis by 25% (16.0 +/- 0.17 v 12.8 +/- 0.13 nmol/mg protein per hour), 20% (15.3 +/- 0.28) and 20% (15.4 +/- 0.36), respectively. However, isoproterenol even at 1 microgram/mL did not stimulate ketogenesis. Phentolamine (5 micrograms/mL) almost completely abolished the effect of epinephrine on ketogenesis (13.7 +/- 0.30 v 16.0 +/- 0.17) but propranolol did not inhibit the stimulation by epinephrine (15.6 +/- 0.38 v 16.0 +/- 0.17). Trifluoperazine (10 mumol/L), presumably an inhibitor of calcium-dependent protein kinase, abolished the effect of epinephrine (13.6 +/- 0.22 v 16.0 +/- 0.17). These results indicate that catecholamines increase ketogenesis predominantly through the alpha-adrenergic system independent of cyclic AMP, and calcium-dependent protein kinase is thought to be involved in the activation of ketogenesis. On the other hand, glucagon stimulated ketogenesis with an increase of cyclic AMP, which was not inhibited by alpha- and beta-adrenergic antagonists. Alpha-adrenergic stimulation increased hepatic glycogenolysis much more at much lower concentrations when compared with ketogenesis. Stimulation of ketogenesis by catecholamines seemed to be less sensitive and responsive compared with hepatic glycogenolysis.