Eicosapentaenoic acid enhances skeletal muscle hypertrophy without altering the protein anabolic signaling pathway

This study aimed to examine the effect of eicosapentaenoic acid (EPA) on skeletal muscle hypertrophy induced by muscle overload and the associated intracellular signaling pathways. Male C57BL/6J mice were randomly assigned to oral treatment with either EPA or corn oil for 6 weeks. After 4 weeks of treatment, the gastrocnemius muscle of the right hindlimb was surgically removed to overload the plantaris and soleus muscles for 1 or 2 weeks. We examined the effect of EPA on the signaling pathway associated with protein synthesis using the soleus muscles. According to our analysis of the compensatory muscle growth, EPA administration enhanced hypertrophy of the soleus muscle but not hypertrophy of the plantaris muscle. Nevertheless, EPA administration did not enhance the expression or phosphorylation of Akt, mechanistic target of rapamycin (mTOR), or S6 kinase (S6K) in the soleus muscle. In conclusion, EPA enhances skeletal muscle hypertrophy, which can be independent of changes in the AKT-mTOR-S6K pathway.

Twenty-Four Months' Resistance and Endurance Training Improves Muscle Size and Physical Functions but Not Muscle Quality in Older Adults Requiring Long-Term Care

OBJECTIVES

To assess the effects of 24 months training on muscle quality, size, strength, and gait abilities in older adults who need long-term care.

DESIGN

Non-randomized controlled trial Setting: Kawai Rehabilitation Center and Kajinoki Medical Clinic.

PARTICIPANTS

Ten older participants who needed long-term care (age, 76.7 ± 5.6 years) were participated as training group (Tr-group) and 10 older men and women who did not require long-term care (age, 72.9 ± 6.6 years) comprised the control group (Cont-group).

INTERVENTION

Tr-group performed resistive and endurance exercises once or twice a week for 24 months.

MEASUREMENTS

Using ultrasound images, echo intensity (EI) and muscle thickness were measured in the rectus femoris and biceps femoris as an index of muscle quality and size. Physical performance was measured before and after the training; performance parameters included knee extension peak torque, 5-m normal and maximal walk test, sit-to-stand and timed up and go test.

RESULTS

After the training, there was no change in EI, while BF thickness was increased (pre; 1.82 ± 0.29 cm, 24 months; 2.14 ± 0.23 cm, p < 0.05) in Tr-group. Walk-related performances were improved after the training in Tr-group (i.e. 5-m walk test and timed up and go test). The percent change of knee extension peak torque explained the percent change of EI in the rectus femoris (regression coefficient = 1.24, R = 0.91, adjusted R2 = 0.82, p < 0.001).

CONCLUSIONS

Twenty-four months' training induced muscle hypertrophy and improved physical functions. Increased muscle quality in the rectus femoris could be a key to improved knee extension peak torque, with the potential to eventually reduce the need for long-term care in older individuals.

The Beneficial Effects of the DPP-4 Inhibitor Alogliptin on Hemoglobin A1c and Serum Lipids in Japanese Patients with Type 2 Diabetes

It has been reported that dipeptidyl peptidase-4 (DPP-4) inhibitors improve hemoglobin A1c (HbA1c) levels in diabetic patients and may also improve the serum lipids. However, few studies have examined relationship between the effects of the DPP-4 inhibitor and the pretreatment HbA1c levels in diabetic patients. Furthermore, it has been reported that prolonged treatment with DPP-4 inhibitors may make glycemic control difficult in some patients. In the present study, we investigated (1) the effect of the DPP-4 inhibitor alogliptin on HbA1c, blood glucose (BG), and serum lipid in Japanese patients with type 2 diabetes, (2) the relationship between the HbA1c levels at baseline and the effects of alogliptin, and (3) the effects of switching of the DPP-4 inhibitor to alogliptin after 12 months' administration of sitagliptin on glycemic control and serum lipids. After 6-months' treatment with alogliptin, we found reductions of HbA1c, BG, and serum total cholesterol, and LDL cholesterol levels. Pretreatment level of HbA1c was well correlated with the degree of reduction of both HbA1c and BG levels after the treatment. Also, alogliptin kept levels of HbA1c and BG reduced by sitagliptin for 12 months, and relapsing of these levels and serum lipids were not observed. This study revealed that alogliptin improved HbA1c, BG, and serum lipid profiles in type 2 diabetic patients, and the effect of alogliptin on HbA1c and BG levels was correlated with HbA1c level at pretreatment. Furthermore, long-term treatment with alogliptin did not cause relapsing of glycemic control and serum lipids.

DPP-4 Inhibitor Teneligliptin Improves Insulin Resistance and Serum Lipid Profile in Japanese Patients with Type 2 Diabetes

Dipeptidyl peptidase-4 (DPP-4) inhibitors have been reported to improve the glycemic control and blood hemoglobin A1c (HbA1c) concentrations. However, there are few reports as yet suggesting that DPP-4 inhibitors may also improve insulin resistance and the serum lipid profile in the clinical setting. This study was aimed at investigating the effect of 14-week treatment with teneligliptin (20 mg/day) on the homeostasis model assessment ratio (HOMA-R), an indicator of insulin resistance, and serum lipid profile in 9 patients with type 2 diabetes. The treatment produced a significant decrease of the blood glucose and HbA1c concentration (blood glucose: p=0.008; HbA1c: p=0.038), and also improved HOMA-R (p=0.039). Furthermore, the patients showed elevation of the serum HDL-cholesterol level (p=0.032), and a tendency towards reduction of the serum triglyceride level. The results indicate that teneligliptin acts not only to improve the blood glucose control, but also to improve the insulin resistance and serum lipid profile in Japanese type 2 diabetes patients.

Clinical effect of addition of beraprost sodium to pioglitazone treatment on the blood glucose levels in patients with type 2 diabetes mellitus

In recent years, the number of patients with type 2 diabetes mellitus caused by insulin resistance has continued to increase in Japan. Insulin resistance is considered to be closely related to the risk of cardiovascular diseases and atherosclerotic diseases, represented by arteriosclerosis obliterans (ASO). Therefore, improvement of insulin resistance is one of the important strategies in the treatment of type 2 diabetes mellitus. At present, α-glucosidase inhibitors, incretin-related drugs, and thiazolidinediones are among the most important oral hypoglycemic drugs used to improve insulin resistance. In this study, the effect of beraprost sodium, a prostaglandin I2 derivative, in the treatment of type 2 diabetes mellitus was investigated. In type 2 diabetic patients with ASO who were under treatment with pioglitazone, additional treatment with beraprost sodium exerted a significant synergistic effect in reducing the serum HbA1c levels as compared to treatment with pioglitazone alone. This result indicates that concomitant administration of pioglitazone and beraprost sodium may be useful in the treatment of diabetes -mellitus.

Acute treatment with candesartan cilexetil, an angiotensin II type 1 receptor blocker, improves insulin sensitivity in high-fructose-diet-fed rats

We aimed to determine whether acute treatment with candesartan cilexetil (CV-11974), an angiotensin II type 1 receptor blocker (ARB) can improve insulin sensitivity in high-fructose-diet (HFD)-fed rats. In vivo glucose utilization was measured by applying the euglycemic clamp technique and the expression levels of insulin-signaling molecules in skeletal muscles were examined by western blotting. A bolus injection of CV-11974 improved the glucose infusion rate (GIR) of HFD-fed rats to the level of the control rats. Furthermore, restoration of impaired tyrosine phosphorylation of insulin receptor (IR) β, Akt phosphorylation at Ser⁴⁷³ and Thr³⁰⁸, and phosphorylation of the 160-kDa Akt substrate (AS160) in the skeletal muscles of HFD-fed rats were achieved by this treatment. These results suggest that acute administration of candesartan cilexetil can increase insulin sensitivity of HFD-fed rats, which is associated with improved insulin signaling in skeletal muscles.

Combined effects of short-term calorie restriction and exercise on insulin action in normal rats

The present study examined the effect of combination of short-term calorie restriction (CR) and moderate exercise on insulin action in normal rats. Rats were divided randomly into 4 groups: ad libitum, sedentary (A-Sed); calorie restriction, sedentary (CR-Sed); ad libitum, exercise (A-Ex); and calorie restriction, exercise (CR-Ex). Rats in the exercise groups were run on a rodent treadmill. Rats in the CR groups were fed every alternate day. Oral glucose tolerance test (OGTT) showed improvements in both CR-Sed and A-Ex groups compared with the A-Sed group; no further improvement in glucose tolerance was observed in the CR-Ex group. In contrast, glucose infusion rates (GIRs) determined by the hyperinsulinemic-euglycemic clamp method indicated that the GIR of the CR and exercise combination was significantly better than that of the sole intervention of CR or exercise. There was no difference in the levels of fasting glucose, insulin, or high-molecular weight forms of adiponectin among the 4 groups. Protein expression of GLUT-4 in the skeletal muscle increased by exercise, but not by CR. Our findings indicate that the combination of exercise and CR may be effective in enhancing insulin sensitivity at the skeletal muscle in normal subjects.

Elution of residual monomers from dental composite materials

AIM

This study was designed to determine the type and amount of the monomers leached from the different particle sizes of the composite materials.

MATERIALS AND METHODS

Three different disk sizes (2, 4, 6 mm) prepared for each material group (Filtek Flow, Filtek A110, Filtek P60 and Filtek Supreme) were polymerised by LED and halogen light; the specimens were then placed in artificial saliva. The monomer release in 30 min and 24 hrs from the specimens was analyzed in HPLC calibrated for the monomer extracts before.

RESULTS

TEGDMA release was detected in all material groups after 30 min and after 24 hrs. BisGMA and BisEMA were not determined in any groups and UDMA was detected only in Filtek Supreme. Significant differences in release of TEGDMA and UDMA were obtained between the different sizes of discs. Significantly high amount of TEGDMA and UDMA monomer release was obtained in LED than Halogen groups. Lower amount of monomer release was obtained in species of 30 min than 24 hrs.

CONCLUSION

Data has revealed that the monomer release could be detected significantly high from the composite materials polymerized by a lower output curing light device; and higher elution of monomers was determined as the composite thickness has increased. Therefore, the clinical applications of composite materials and the type of curing units have very important effects on the success of restorations and in the decrease of potential side effects.

A high-fructose diet impairs Akt and PKCzeta phosphorylation and GLUT4 translocation in rat skeletal muscle

The molecular mechanism of insulin resistance induced by high-fructose feeding is not fully understood. The present study investigated the role of downstream signaling molecules of phosphatidylinositol 3-kinase (PI3K) in the insulin-stimulated skeletal muscle of high-fructose-fed rats. Rats were divided into chow-fed and fructose-fed groups. The results of the euglycemic clamp study (insulin infusion rates: 6 mU/kg BW/min) showed a significant decrease in the glucose infusion rate (GIR) and the metabolic clearance rate of glucose (MCR) in fructose-fed rats compared with chow-fed rats. In skeletal muscle removed immediately after the clamp procedure, high-fructose feeding did not alter protein levels of protein kinase B (PKB/Akt), protein kinase C zeta (PKCzeta), or glucose transporter 4 (GLUT4). However, insulin-stimulated phosphorylation of Akt and PKCzeta and GLUT4 translocation to the plasma membrane were reduced. Our findings suggest that insulin resistance in fructose-fed rats is associated with impaired Akt and PKCzeta activation and GLUT4 translocation in skeletal muscle.

Effects of continuous low-carbohydrate diet after long-term exercise on GLUT-4 protein content in rat skeletal muscle

Stimulation of AMPK and decreased glycogen levels in skeletal muscle have a deep involvement in enhanced insulin action and GLUT-4 protein content after exercise training. The present study examined the chronic effects of a continuous low-carbohydrate diet after long-term exercise on GLUT-4 protein content, glycogen content, AMPK, and insulin signaling in skeletal muscle. Rats were divided randomly into four groups: normal chow diet sedentary (N-Sed), low carbohydrate diet sedentary (L-Sed), normal chow diet exercise (N-Ex), and low carbohydrate diet exercise (L-Ex) groups. Rats in the exercise groups (N-Ex and L-Ex) were exercised by swimming for 6 hours/day in two 3-hour bouts separated by 45 minutes of rest. The 10-day exercise training resulted in a significant increase in the GLUT-4 protein content (p<0.01). Additionally, the GLUT-4 protein content in L-Ex rats was increased by 29% above that in N-Ex rats (p<0.01). Finally, the glycogen content in skeletal muscle of L-Ex rats was decreased compared with that of N-Ex rats. Taken together, we suggest that the maintenance of glycogen depletion after exercise by continuous low carbohydrate diet results in the increment of the GLUT-4 protein content in skeletal muscle.

Effects of coupling methods on galvanic corrosion behavior of commercially pure titanium with dental precious alloys

BACKGROUND

When a dissimilar couple is exposed to corrosive environment, it will normally exhibit a galvanic corrosion. The galvanic corrosion might be influenced by various factors, including type and concentration of electrolyte, surface area ratio between anode and cathode, type of coupling material, and coupling manner.

PURPOSE

The purpose of this study was to investigate and compare the galvanic corrosion behavior of commercially pure titanium when coupled with type IV Au alloy, Au-Ag-Pt alloy, and Ag-Au-Pd alloy by different coupling methods.

MATERIALS AND METHODS

Couples were prepared by a laser welding or a mechanical adhering method. Electrochemical corrosion studies were conducted in a Ringer's solution at a scanning rate of 0.1 mV/sec in a range from -250 mV to +250 mV with respect to E(OCP). Corrosion parameters (E(OCP), I(CORR), E(CORR)) were obtained.

RESULTS

It was found that (i) there was a significant difference between LWC and AJC for three couples (p<0.05), (ii) the crevice line caused all three couples more corrosive than weld joint line, (iii) for both joint, it was found that type (IV) Au alloy exhibited discoloration to some extent.

CONCLUSIONS

It is concluded that among the three couples with two different coupling methods, Ti/Ag-Au-Pd couple exhibited best corrosion resistance in a room temperature Ringer's solution.

Ca/P mol ratio of cries-affected dentin structures

BACKGROUND

A new approach called "minimum intervention" has been introduced for restoration of carious lesions to preserve tooth structure. This approach suggests that perhaps caries need not always be removed completely from deeper portions of the cavity. It is, therefore, important to characterize caries-affected dentin structures, because of the potential changes in bonding quality when using different dentinal substrates.

MATERIALS AND METHOD

Ninety teeth (30 teeth each group) were studied. The first group (CF) consisted of 30 caries-free teeth. The second group (CC) consisted of 30 teeth, for which caries-free dentin teeth was chemically demineralized. The third group (ND) consisted of 30 extracted human molars with coronal carious lesions. After all tooth samples were water-polished with grit #600 SiC paper, they were tested by surface contact angle measurements and the electron-probe microanalyzer to measure Ca/P mol ratio.

RESULTS

Contact angles were CF = 60.07 degrees ; CC = 30.8 degrees; ND = 26.11 degrees , p<0.05. Ca/P mol ratios were as follows; CF = 1.549 (+/-0.0435); CC = 1.324 (+/-0.2305); ND = 1.568 (+/-0.0523), p<0.05. Weibull analyses for Ca/P mol ratio indicated shape parameter (m) of CF was 13.3; it was 12.8 for ND and 11.8 for CC. Above the delta point (=1.65 in Ca/P ratio), for both groups m = 3.4.

CONCLUSION

Caries-affected dentin surfaces (naturally-developed and chemically created) were statistically more chemically active than caries-free dentin surface. Ca/P mol ratio of chemically created caries was less than other two groups.

Insulin-nonspecific reduction in skeletal muscle glucose transport in high-fat-fed rats

High-fat feeding diminishes insulin-stimulated glucose transport in skeletal muscle. However, conflicting results are reported regarding whether phosphatidylinositol (PI)-3 kinase-independent glucose transport is also impaired in insulin-resistant high-fat-fed rodents. The aim of the present study was to study whether non-insulin-dependent mechanisms for stimulation of glucose transport are defective in skeletal muscle from high-fat-fed rats. Rats were fed normal chow diet or high-fat diet for 4 weeks and isolated epitrochlearis muscles were used for measuring glucose transport. Insulin-stimulated glucose transport was significantly lower in rats fed the high-fat diet compared with chow-fed rats (P < .05). Hypoxia-stimulated glucose transport was also reduced in high-fat-fed rats (P < .05). Nevertheless, hypoxia-stimulated adenosine monophosphate-activated protein kinase (AMPK) phosphorylation (Thr172) level was not affected by high-fat feeding. Glucose transport by sodium nitroprusside stimulation was reduced in high-fat-fed rats (P < .05). Protein content of glucose transporter (GLUT)-4 and AMPK-alpha, and glycogen content were comparable between both groups. Our findings provide evidence that high-fat feeding can affect not only insulin but also non-insulin-stimulated glucose transport. A putative defect in common steps in glucose transport may play a role to account for impaired insulin-stimulated glucose transport in rats fed a high-fat diet.

C-peptide fragments stimulate glucose utilization in diabetic rats

Studies of C-peptide cellular effects show that not only the full-length native peptide but also specific C-terminal fragments are biologically active in in vitro systems. In the present study, the effect of five C-peptide fragments and the native peptide on whole-body glucose turnover was studied in streptozotocin diabetic rats using the insulin clamp technique. Insulin was infused intravenously at 18 pmol kg(-1) min(-1) for 90 min and blood glucose concentration was clamped at 8 and 4 mM in diabetic and non-diabetic animals. A steady state was reached during the last 30 min of the study period. Rat C-peptide II and fragments comprising residues 27-31 and 28-31 were effective in augmenting glucose turnover in diabetic rats (+100% to 150%), while no significant effects were seen for segments 1-26, 11-19 and 11-15. The metabolic clearance rate for glucose during infusion of C-peptide or fragments 27-31 and 28-31 in diabetic rats was similar to that seen in non-diabetic animals. We conclude that C-terminal tetra- and pentapeptides, but not fragments from the middle segment of C-peptide, are as effective as the full-length peptide in stimulating whole-body glucose turnover in diabetic rats.

Cinnamon extract prevents the insulin resistance induced by a high-fructose diet

The aim of this study was to determine whether cinnamon extract (CE) would improve the glucose utilization in normal male Wistar rats fed a high-fructose diet (HFD) for three weeks with or without CE added to the drinking water (300 mg/kg/day). In vivo glucose utilization was measured by the euglycemic clamp technique. Further analyses on the possible changes in insulin signaling occurring in skeletal muscle were performed afterwards by Western blotting. At 3 mU/kg/min insulin infusions, the decreased glucose infusion rate (GIR) in HFD-fed rats (60 % of controls, p < 0.01) was improved by CE administration to the same level of controls (normal chow diet) and the improving effect of CE on the GIR of HFD-fed rats was blocked by approximately 50 % by N-monometyl-L-arginine. The same tendency was found during the 30 mU/kg/min insulin infusions. There were no differences in skeletal muscle insulin receptor (IR)-beta, IR substrate (IRS)-1, or phosphatidylinositol (PI) 3-kinase protein content in any groups. However, the muscular insulin-stimulated IR-beta and IRS-1 tyrosine phosphorylation levels and IRS-1 associated with PI 3-kinase in HFD-fed rats were only 70 +/- 9 %, 76 +/- 5 %, and 72 +/- 6 % of controls (p < 0.05), respectively, and these decreases were significantly improved by CE treatment. These results suggest that early CE administration to HFD-fed rats would prevent the development of insulin resistance at least in part by enhancing insulin signaling and possibly via the NO pathway in skeletal muscle.

Mechanical properties of four methylmethacrylate-based resins for provisional fixed restorations

The use of a provisional restoration is an important phase in the treatment of the dental prosthetic patient. A good provisional restoration should satisfy the following requirements: pulpal protection, positional stability, ease in cleaning, accurate margins, wear resistance, dimensional stability, and serve as a diagnostic aid in treatment assessment and esthetics. There is a tendency for discoloration, occlusal wear, and fracture that eventually leads to unnecessary repair. Heat-processed and reinforced methacrylate-based resins have been used to improve the mechanical and physical properties of provisional restorations. Among various improvements, the interpenetrating network crosslinked PMMA (IPN) has been shown to have superior mechanical properties if manufactured through a dough compression molding process at 130 degrees C. However, there have been no published data that relate with the use of this material for fixed provisional restorations. The objective of this study was to compare four methyl methacrylate-based resins for provisional crowns and bridges with varying processing cycles, including JET [self-cure], ACRALON [heat-cured], titanium dioxide filled PMMA [heat-cured], and IPN [heat-cured denture tooth resin]. Properties studied included transverse strength, toughness, rigidity, and hardness. From the results of this study the following conclusions can be made: the IPN group may have had a lower degree of conversion as demonstrated by decreased strength, toughness, and hardness data as compared with Acralon. Increasing the polymerization cycle of unmodified Acralon resin causes a significant increase in strength.

Effects of imidapril, an angiotensin-converting enzyme inhibitor, on insulin sensitivity and responsiveness in streptozotocin-induced diabetic rats

We have studied the effect of imidapril, an angiotensin-converting enzyme inhibitor, on streptozotocin-induced diabetic rats. A sequential euglycemic hyperinsulinemic clamp procedure was used (insulin infusion rates: 3 and 30 mU/kg BW/min) in 30 diabetic rats. The rats were divided in 6 groups: a control group, a control group with N-monomethyl-L-arginine (L-NMMA, 1 mg/kg/min, a nitric oxide synthase inhibitor) infusion, a streptozotocin-induced diabetic group, a diabetic group with L-NMMA infusion, a diabetic group involving imidapril infusion (5 microg/kg/min), and a diabetic group involving simultaneous imidapril and L-NMMA infusion. Glucose concentrations were maintained around 140 mg/dl during the clamp studies. Plasma insulin levels during the 3 and 30 mU/kg BW/min insulin infusions were 30 and 400 microU/ml, respectively. Glucose infusion rates (GIR) in STZ-induced diabetic rats showed a significant decrease compared to controls. At both insulin infusion rates, imidapril-infused diabetic rats showed an increased GIR, compared with the saline infused ones. There was no significant difference in GIR between L-NMMA and saline infusion in diabetic rats. Simultaneous infusion of imidapril and L-NMMA did not significantly decrease GIR with low-dose insulin infusion, but the increase in GIR induced by imidapril with high-dose insulin infusion was impaired by 100 % by L-NMMA infusion in diabetic rats. These results suggest that imidapril may improve insulin action, in part, via nitric oxide.

The effect of nitric oxide synthase inhibitor on improved insulin action by pioglitazone in high-fructose-fed rats

The present study was performed to investigate whether nitric oxide synthase (NOS) inhibition influences the increased whole-body insulin action by pioglitazone in high-fructose-fed rats. Male Wistar rats aged 6 weeks were randomly divided into 3 groups and each group was fed one of the following diets for 3 weeks: standard chow diet (control group), high-fructose diet (fructose-fed group), and high-fructose diet plus pioglitazone (pioglitazone-treated group). The control and pioglitazone-treated groups were further divided into 2 subgroups respectively, and some rats of each subgroup were infused the NOS inhibitor, N(G)-monomethyl-l-arginine (L-NMMA), during the euglycemic clamp studies. In vivo insulin action was determined by the 2-step (3 and 30 mU/kg body weight [BW]/min low- and high-dose, respectively) hyperinsulinemic euglycemic clamp procedure in the awake condition. Glucose infusion rate (GIR) was considered as the index of insulin action. Endothelium-type NOS (eNOS) and inducible NOS (iNOS) in skeletal muscle were also measured. At the low-dose clamp, high-fructose feeding produced a marked decrease in GIR compared with the control group. Pioglitazone-treated animals showed a significant increase in GIR, reaching a similar level as the control group. However, the improved GIR was decreased to the level of the fructose-fed group by L-NMMA infusion. The GIR of the control group was not affected by L-NMMA infusion. The same tendency as the low-dose clamp was found at the high-dose clamp. In skeletal muscle, eNOS and iNOS protein content were not affected by high-fructose feeding and/or pioglitazone treatment. These results suggest that NOS inhibition can decrease the improved insulin resistance by pioglitazone in high-fructose-fed rats. Therefore, although NOS protein content is not changed by high-fructose feeding and/or pioglitazone treatment, it could be concluded that nitric oxide (NO) plays an important role in the improvement of insulin action by pioglitazone.

Hydroxyapatite/PMMA composites as bone cements

Currently PMMA is the polymer most commonly used as a bone cement for the fixation of total hip prostheses. Ideally, a bone cement material should be easy to handle, biologically compatible, nonsupporting of oral microbial growth, available in the particulate and molded forms, easy to obtain, nonallergenic, adaptable to a broad range of dental and medical applications, in possession of high compressive strength, and effective in guided tissue regenerative procedures. One of the problems associated with the conventional types of bone cement used is their unsatisfactory mechanical and exothermic reaction properties. The purpose of this in vitro study was to investigate and compare the mechanical properties (three-point bending strength, energy-to-break, and modulus of elasticity) and physical properties (setting time, water sorption, and exothermic heat) of HA/PMMA (HA group) and bovine-bone originated HA/PMMA (BB group) composites. Composites samples were fabricated by admixing method. It was found that the addition of HA and BB particles increased the water sorption. Generally 10 v/o 20 v/o HA and 0 v/o to 10 v/o BB ratio combinations had significant beneficial effects on the mechanical properties. The heat generated during polymerization was influenced by the different admixtures. More than 40 v/o HA and 40 v/o BB should be mixed into PMMA to reduce the peak temperature. Overall evaluation indicated that the BB group had better properties than the HA group.

Reinforcement of acrylic resins for provisional fixed restorations. Part III: effects of addition of titania and zirconia mixtures on some mechanical and physical properties

Acrylic resins have been used in many different applications in dentistry, especially in the fabrication of provisional fixed partial dentures. Ideally, a provisional crown and bridge material should be easy to handle and should protect teeth against physical, chemical, and thermal injuries. Some of the problems associated with this use are related to the material's poor mechanical properties. It has been demonstrated that acrylic resin can be strengthened through the addition of structural component of different size distributed in the acrylic matrix, thus forming a composite structure. The purpose of this study was to investigate the addition effects of mixtures of titania (titanium dioxide, TiO(2)) powder and zirconia (zirconium dioxide, ZrO(2)) powder being incorporated with pre-polymerized beads mixed in monomer liquid, on some mechanical and physical properties of PMMA resin. The pre-polymerized powder poly(methyl methacrylate) resin was admixed with titania and zirconia powder. A mixing ratio was controlled by volume % of 0, 1.0, 2.0, and 3.0 (samples with 0 v/o served as control groups). For using mixture of titania and zirconia, total amount of the mixture was controlled by volume % of 1.0, 2.0, and 3.0, in which titania and zirconia were mixed at the ratio 1 :1, 1 :2 and 2 :1. Prior to mechanical tests, all rectangular-shaped samples (25 mm x 2 mm x 5 mm) were stored in 37 degrees C distilled water for 7 days after polishing all six sides of samples. Samples were then subjected to the three-point bending flexion test to evaluate the bending strength as well as the modulus of elasticity. Weight gain and exothermic reaction survey were investigated as well. All data were collected and analyzed with one-way analysis of variance (ANOVA) and Sidak method (p=0.05). It was found that the addition of particles generally decreased the water absorbed by the composite system. Only 1 percent by volume concentration of 1 :1 ratio and 2 percent by volume concentration of 1 :2 and 2 :1 ratios had significantly higher strength than control group. There was significantly higher toughness (in terms of energy-to-break) for 1 percent by volume concentration of 1 :1 ratio and 2 percent by volume concentration of 2 :1 ratio than control group. There was no significant difference between control group and all percent by volume combinations in modulus of elasticity. In addition, there was no significant variations of exothermic reaction.

Initial contact angle measurements on variously treated dental/medical titanium materials

The cell attachment to bioapplicable titanium surfaces is an important parameter in the area of clinical implant dentistry and medicine. A major consideration in designing implants has been to produce surfaces that promote desirable responses in the cells and tissues contacting the implants. In this study, three titanium materials (commercially pure titanium - CPT -, Ti-6Al-4V, and TiNi) were treated mechanically, chemically, mechano-chemically, and thermally to produce concave surfaces with varying roughness. Using four media (distilled water, 1% NaCl aqueous solution, a suspension of human neutrophils, and a suspension of the MG-63 osteoblast-like cells), the initial contact angles were measured. Six readings (three drops each measured by two observers) were collected for each material and for each medium. The interclass correlation coefficients were used for the group comparisons. A one-way analysis of variance (ANOVA) and Tukey's HSD (honestly significant difference) statistical analyses were employed. It was found, for CPT, that (1) statistically, there were no significant differences among four media in contact angles, (2) the contact angle increased linearly with average roughness when the angles were higher than 45 degrees, and (3) the contact angle decreased linearly with roughness when the angle was less than 45 degrees.

Porcelain-metal bonding: part I. Effects of repeated baking process

A plurality of repeated porcelain-baking procedures are normally practiced in order to achieve the final adjustment metal-porcelain restorations. By increasing the number of baking cycles, the undesired internal strain would be built-up, causing the reduction of mechanical properties and deterioration of color characteristics. However the extensive studies on such deterioration have not been done. In this study, effects of numbers (up to 10 times) of repeated baking cycles on baking shrinkage, surface roughness, bend strength, color changes and internal microstructure were investigated when opaque, body and enamel was individually applied or when a triple-player comprising of these three porcelains was repeatedly applied. It was concluded that (1) the bend strengths increased by increasing baking cycles, (2) the average surface roughness decreased by increasing number of baking procedures, (3) changes in color characteristics was very small in the Vintage halo porcelain system, and (4) since the pores entrapped in the porcelain remained even by increasing baking cycles, it is recommended to remove the surface pores before forming the next layer when handling the high viscous opaque porcelain.

Effect of voluntary wheel-running on insulin sensitivity and responsiveness in high-fat-fed rats

The effect of voluntary wheel-running on insulin resistance was studied in high-fat-fed rats. A sequential hyperinsulinemic euglycemic clamp procedure was employed (insulin infusion rates: 3 and 30 mU/kg BW/min) in 14 high-fat-fed rats and 7 chow-fed rats under the awake condition. The high-fat-fed rats were further divided into a sedentary (n=7) and a voluntary wheel-running (n=7) groups. Blood glucose was clamped at the fasting level in each rat. Plasma insulin levels during the 3- and 30-mU/kg BW/min insulin infusions were 40-50 and 450-550 microU/ml, respectively. At both 3 and 30 mU/kg BW/min insulin infusions, high-fat-feeding showed a significant decrease in glucose infusion rate (GIR), compared with the chow-fed rats. However, decreased GIRs were restored by the 4-wk wheel-running and reached similar levels as the chow-fed rats. Therefore, it could be concluded that voluntary wheel-running prevents insulin resistance induced by high-fat feeding.

Modification by exercise training of activity and enzyme expression of hepatic branched-chain alpha-ketoacid dehydrogenase complex in streptozotocin-induced diabetic rats

The branched-chain alpha-ketoacid dehydrogenase (BCKDH) complex is the rate-limiting enzyme in the catabolism of branched-chain amino acids. In the present study, we examined the effects of exercise training on the activity and enzyme expression of the hepatic BCKDH complex in diabetic rats. The rats were prepared by intravenous injections of streptozotocin (50 mg/kg BW), and exercise training was accomplished by treadmill running for 45 min/d for 4 wk. The total and actual activities of hepatic BCKDH complex were significantly increased to approximately 160% by 4 wk of diabetes. On the other hand, diabetic rats in the trained group had the same level of activities as those in the normal rats, indicating that exercise training inhibited the diabetes-induced increase in the enzyme activities. The activity state (% active form) of the enzyme complex was about 100% in all groups and was not affected by diabetes or training. The protein amounts of the enzyme subunits (E1alpha and E2) and the abundance of mRNA for the E2 subunit, but not for the other subunits, in the liver had the same trend as the activities. These results suggest that the capacity for branched-chain amino acid catabolism in streptozotocin-induced diabetic rats is reduced by exercise training and that this modification is associated with the suppression of diabetes-induced BCKDH complex expression in the liver.

Comparison of the effects of three sulfonylureas on in vivo insulin action

To clarify the diversity in hypoglycemic actions of sulfonylureas, chronic effects of three sulfonylureas were compared on in vivo insulin-induced glucose uptake in peripheral tissues. After oral administration of glimepiride (CAS 93479-97-1), glibenclamide (CAS 10238-21-8), gliclazide (CAS 21187-98-4), or saline as control, two-step euglycemic clamp procedures were performed. During physiological hyperinsulinemia induced by 6 mU/kg/min insulin infusion, metabolic clearance rates (MCR) of glucose of the glimepiride-administered group (GP) significantly (p < 0.01) increased to 153% of the saline-administered group (SA). There was no significant statistical difference between the glibenclamide-administered group (GC), gliclazide-administered group (GZ) and SA. During 30 mU/kg/min clamps that lead to maximal insulin action, MCR of either GP or GC were significantly higher than those of SA (128% and 141%, p < 0.05 and p < 0.01, respectively). MCR of GZ were lower than those of GC (80%, p < 0.05), and showed no significant difference from those of SA. These data indicate that glimepiride activates insulin binding levels to a greater degree than the other two sulfonylureas, and that glibenclamide and glimepiride activate post-receptor binding mechanisms in peripheral tissues much more than gliclazide. These results suggest that hypoglycemic actions of sulfonylureas at the extra pancreatic levels vary with the nature of each reagent.

Effects of troglitazone and voluntary running on insulin resistance induced high fat diet in the rat

It is well known that troglitazone and voluntary running have the capacity to improve insulin resistance. The purpose of this study was to evaluate the combination effect of troglitazone and voluntary running on insulin action. Female rats aged 7 weeks were divided into high-fat diet (HF), high-fat diet + troglitazone (0.3% in diet; Tg), high-fat diet + voluntary running (for 3 wks; Tr), high-fat diet + troglitazone + voluntary running (Tg-Tr), and control (C) groups. A sequential euglycemic clamp experiment with two different insulin infusion rates of 3.0 (L-clamp) and 30.0 mU/kg BW/min (H-clamp) was performed on these rats after an overnight fast. Blood glucose concentrations were kept at fasting levels by periodic adjustment of the intravenous glucose infusion rate during the clamp experiment. Glucose infusion rates (GIRs) calculated from 60 to 90, 150 to 180 min were regarded as an index of whole body insulin action. After the clamp experiment, we determined the amount of glycogen content in the gastrocnemius muscle. Fat feeding markedly reduced GIRs in both L- and H- clamp experiments compared with C. Troglitazone treatment did not improve high-fat induced insulin resistance. In both L- and H-clamp experiments, GIRs were increased by voluntary running compared with HF, and reached the same levels as in C. GIRs of Tg-Tr were not greater than those of Tr. Glycogen content in gastrocnemius muscle showed the same trend as the results for GIRs. Therefore, the combination effect of troglitazone and voluntary running on insulin action was not found, but the effect of voluntary running was shown in fat-induced insulin resistance.

Surface characterizations of variously treated titanium materials

The attachment of cells to titanium surfaces is an important phenomenon in the area of clinical implant dentistry. A major consideration in designing implants has been to produce surfaces that promote desirable responses in the cells and tissues. To achieve these requirements, the titanium implant surface can be modified in various ways. This research was designed to elucidate the relationship between surface roughness (Ra) and contact angle (theta) of various engineered titanium surfaces of commercially pure titanium, titanium-aluminum-vanadium alloy (Ti-6Al-4V), and titanium-nickel (TiNi) alloy. The contact angle was measured using distilled water, 1% sodium chloride solution, human neutrophils, and osteoblast-like cells. Surface oxide crystallography was identified by transmission electron diffraction. It was found that: (1) there were no significant differences in contact angles among the 4 media; (2) for commercially pure titanium, a combined treatment (hydrofluoric acid/nitric acid/water --> sodium hydroxide --> oxidation) showed the lowest theta (10.51 degrees in water), while the surface treated with sulfuric acid showed the highest value (72.99 degrees in water); (3) for all commercially pure titanium samples, when theta is greater than 45 degrees, the contact angle increases linearly with Ra (hydrophobic nature) and the surface is covered with rutile-type oxide only, while the contact angle decreases linearly with Ra when theta is less than 45 degrees (hydrophilic nature) and the surface is covered with a mixture of rutile and anatase oxides; and (4) a similar trend was found on Ti-6Al-4V and TiNi surfaces.

Effects of lifestyle factors on ultrasonographically determined bone health in Japanese women

The objective of this study was to determine by ultrasonographic measurements, an inexpensive and radiation-free technique, the association between bone health and lifestyle factors among a large population of Japanese women. Two hundred and fifty-six pre-menopausal women and 585 post-menopausal women who underwent a voluntary medical check-up for osteoporosis in 1996-1997 were analyzed. There were significant positive correlations between the bone density (designated as the stiffness value) vs the weight, the height and the body mass index of the subjects only in the post-menopausal group. Negative correlations were also found between the bone density vs the age and the years since menopause. Our data using ultrasonographic technique agree well with previous studies using other devices. In both groups, subjects with current or past exercise habits had higher stiffness values. Dietary habits had no effects on the stiffness value. Smoking habits had a trend towards negative effects and alcohol consumption seemed to have a trend towards positive effects on the stiffness value in post-menopausal women, but these effects did not reach statistical significance. Positive effects of current exercise on bone density were maintained after adjustment for past exercise habits. These results support the effectiveness of exercise begun in adulthood. Having a good exercise habit is one of the most effective ways of maintaining good bone health.

Electrochemical corrosion of titanium and titanium-based alloys

STATEMENT OF PROBLEM

Two varieties of unalloyed titanium, Ti-6Al-4V and NiTi, commonly are used in medical and dental fields. Several other types of alloys for potential use in these fields have been developed, including Ti-4.5Al-3V-2Mo-2Fe and vanadium-free alloys (Ti-5Al-2.5Fe and Ti-5Al-3Mo-4Zr). The corrosion of these alloys under simulated physiologic conditions is not known. Purpose. This study compared the corrosion behaviors of 6 titanium materials through electrochemical polarization tests in 37 degrees C Ringer's solution.

MATERIAL AND METHODS

The applied voltage was potentiostatically scanned from -0.6 to 1.0 V. From polarization curves, the corrosion rate (averaged over 3 samples) for each alloy was calculated and compared with that of other alloys. Analysis of variance (ANOVA) and the Student-Newman-Keuls multiple range test were performed at a 95% overall confidence level to identify statistically significance differences in corrosion rates. Surface oxide films were identified by electron diffraction, and the electrolyte medium was analyzed by atomic absorption spectrophotometry after each alloy was tested.

RESULTS

Commercially pure titanium and Ti-5Al-2.5Fe were the most resistant to corrosion; Ti-5Al-3Mo-4Zr, Ti-6Al-4V, and NiTi were the least resistant to corrosion. NiTi exhibited pitting corrosion along with transpassivation.

CONCLUSION

Electron diffraction patterns indicated that all titanium alloys were covered mainly with rutile-type oxide (TiO(2)) after corrosion tests. The oxides that formed on Ti-5Al-2.5Fe were identified as a mixture of TiO(2) and Ti(9)O(17), and those that formed on NiTi were identified as a mixture of TiO(2) and Ni(2)Ti(4)O.

Titanium-porcelain system. Part III: effects of surface modification on bond strengths

During its development, titanium was found to be incompatible with conventional dental porcelains due to weak bond strength brought about by titanium's high yet oxidative nature. In spite of the development of new low-fusing porcelains designed for titanium application, previous studies have shown that sandblasting pre-treatment prior to porcelain application led to weakening of the metal-ceramic bonding. The aim of this study is to search for an effective alternative to sandblasting for the surface treatment of the titanium substrate in the titanium-porcelain system. The research evaluated the bond strength of 165 samples of titanium-porcelain systems divided into 11 groups. A three-point flexural bend test was conducted to measure the force required to fracture the porcelain on the titanium substrate. A correlation between the type of surface treatment and the bond strengths of each group was evaluated if it resulted to significant differences. The study found significantly differences in the energy-to-break of titanium-porcelain systems treated with hydrochloric acid and sandblasting compared with the control group. The bonds strength achieved by the titanium-porcelain system when treated with hydrochloric acid is comparable to that of conventional metal-ceramic alloy system. Hydrochloric acid treatment of the titanium substrate is a promising alternative to sandblasting for the surface treatment of the titanium substrate in the titanium-porcelain system.

Titanium-porcelain system. Part IV: some mechanistic considerations on porcelain bond strengths

The titanium-porcelain system can be considered as a double-layered structure, comprising of at least titanium substrate and porcelain body including bonding agent. Stress distribution pattern of such a double-layered structure is not necessarily same as that of a single beam under the 3-point bending testing mode. Previously tested porcelain-fired commercially pure titanium samples (n = 285) were re-evaluated. All obtained data on bond strengths and bond toughness (energy-to-break) were re-grouped in terms of c/t ratio, where c is the distance from the maximum compressive side of the beam to the calculated neutral axis and t is the thickness of titanium substrate plate thickness. It was found that (1) when the double-layered structure falls in the c < t situation, both bond strength and bond toughness are in a lower zone, which is slightly lower than the cohesive tensile strength of the porcelain, (2) when the c > t situation (with relatively thick porcelain application) is established, both bond strength and toughness are in higher zone than the porcelain itself, and (3) there is a transition zone between the above.

Nitric oxide decreases insulin resistance induced by high-fructose feeding

The effect of nitric oxide (NO) on insulin resistance was studied in high-fructose-fed rats. A sequential hyperinsulinemic euglycemic clamp procedure was employed (insulin infusion rates: 3 and 30 mU/kg BW/min) in 12 high-fructose-fed rats and 12 chow-fed rats while awake. Half of the high-fructose-fed and the chow-fed rats, respectively, were continuously given sodium nitroprusside (SNP, 3 ng/kg BW/min) during the clamp study. Blood glucose was clamped at the fasting level in each rat. Plasma insulin levels during the 3 and 30 mU/kg BW/min insulin infusions were 30 and 400 microU/ml, respectively. Metabolic clearance rate of glucose (MCR) was regarded as an index of whole body insulin action. At both 3 and 30 mU/kg BW/min insulin infusions, high-fructose feeding showed a significant decrease in MCR compared with the chow-fed rats. However, decreased MCRs were stimulated by SNP administration and reached similar levels as the chow-fed rats. SNP infusion did not influence MCRs in the chow-fed rats. Therefore it could be concluded that NO can improve insulin resistance induced by high-fructose feeding.

Exercise training prevents maturation-induced decreases in insulin receptor substrate-1 and phosphatidylinositol 3-kinase in rat skeletal muscle

We have previously reported that exercise training prevents a maturation-induced decrease in insulin sensitivity and suggested that an improvement of insulin sensitivity by exercise training was attributable, in part, to an increase in insulin-sensitive GLUT-4 on the skeletal muscle plasma membrane. In this study, we examined the effects of maturation and exercise training on the gene expression and protein content of the components of post-insulin receptor signal transduction in rat skeletal muscle. Rats aged 3 weeks were sedentary or trained by voluntary running through 4 or 27 weeks of age, and then the rats in both the sedentary and trained groups were killed and the gastrocnemius muscle was immediately removed for analysis of mRNA and protein content. The concentration of mRNA and protein for insulin receptor substrate-1 (IRS-1) in sedentary rats significantly decreased with maturation (49% and 63%, respectively, at age 27 weeks v age 4 weeks), but in trained rats they did not decrease with maturation. Although the level of phosphatidylinositol 3-kinase (PI 3-kinase) mRNA in sedentary rats was not altered with maturation, PI 3-kinase protein in sedentary rats significantly decreased with maturation (73% at 27 weeks v 4 weeks). However, PI 3-kinase protein in trained rats did not decrease with maturation. These results suggest that the prevention of maturation-induced decreases in the protein content of IRS-1 and PI 3-kinase is involved in the mechanisms responsible for the improvement of insulin sensitivity by exercise training, and exercise training may affect transcriptional regulation of the IRS-1 gene and posttranscriptional regulation of PI 3-kinase expression.

Effect of alpha/gamma phase ratio on corrosion behavior of dual-phase stainless steels

Dual-phase stainless steels have been developed in order to reduce the nickel content, which is potentially responsible to an allergic reaction when these steels are used as medical or dental applications. In this study, two different dual-phase stainless steels (2205 and Z100) were electrochemically tested to evaluate their corrosion resistance in three corrosive solutions (i.e., synthetic saliva, 0.9% NaCl solution, and Ringer solution). Particularly, an attempt was made to correlate the corrosion resistance to a metallographic parameter, which is, in this study, the alpha/gamma phase ratio. It was concluded that (1) type 2205 stainless steel exhibited excellent corrosion resistance in all three corrosion media; however 2205 stainless steel decreases its corrosion resistance by increasing chloride concentration in tested electrolytes from synthetic saliva through 0.9% NaCl solution to Ringer solution. (2) X-ray diffraction analysis indicated that the alpha/gamma phase ratio of 2205 (1.735) was higher than that of Z100 (0.905). As a result, it is suggested that by increasing the alpha/gamma phase ratio the material shows more corrosion-prone behavior when being subjected to a hostile environment containing higher chloride ion concentration.

Additive effects of estrogen deficiency and diabetes on bone mineral density in rats

We investigated the combined effects of estrogen deficiency and diabetes on bone mineral density (BMD) and bone metabolism in rats. Ten-week-old, female rats were randomly divided into four groups: controls (C), an ovariectomized group (O), a streptozotocin-induced diabetic group (S), and a combined ovariectomy and streptozotocin-induced diabetic group (OS). The BMD of the lumbar spine and the femur were measured before grouping and at 23 weeks old. At the end of the experiment, blood samples were obtained via cardiac puncture, and bone gla protein (BGP), tartrate-resistant acid phosphatase (TRAP) and 1,25-dihydroxyvitamin D levels were measured. The rats in the C, O, S, and OS groups, in that order, had higher levels of BMD of the lumbar spine and femur at 23 weeks of age. The BGP levels in the S and OS groups were significantly lower than in C and O groups. Significantly higher 1,25-dihydroxyvitamin D was observed in the O group compared with the C, S and OS groups. No differences were obtained in TRAP among four groups. Our data suggest that the combined effects of estrogen deficiency and diabetes on BMD are not synergistic or counteractive but additive.

Effects of walking on bone quality as determined by ultrasound in the elderly

In the present study, measurements of broadband ultrasound attenuation (BUA) were used as indications of bone quality in elderly residents of an old people's home. To investigate the possibility of using number of steps walked as an indicator of the role played by exercise on bone quality, we studied the relationship between BUA and the number of steps, taken as a measure of the number of impacts against the ground placing a direct mechanical stress on the bones. The subjects were 59 healthy elderly women with a mean age of 78+/-8 years who had no impairments in walking or daily life. A statistical analysis of the relationship between age, number of steps, BUA, stride length, and walking speed revealed that number of steps and BUA declined with age, and that BUA increased with a greater number of steps. Among other factors, age was found to be negatively correlated with weight (r= -0.343, P<0.01), BUA (r=-0.542, P<0.001), total number of steps (r= -0.524, P<0.001) and past exercise habits (r=-0.425, P<0.001). There were positive correlations between BUA and total number of steps (r=0.606, P<0.001), walking speed (r=0.460, P<0.001), stride length (r=0.373, P<0.01) and past exercise habits (r=0.429, P<0.001). These results show that the benefit to bone quality increases the more a person walks in daily life. The above demonstrates that degree of walking activity is positively correlated to bone quality among the elderly. These results also suggest that, when investigating the relationship between exercise and bone quality, one should look not only at distance and walking speed, but also number of steps as the number of impacts against the ground that place a direct mechanical stress on the bones. This may prove to be a useful indicator of bone quality in future use.

Water-sorption kinetics of dental polymeric resin under tensile stressing conditions

Water sorption tests were conducted on unfilled poly(methyl methacrylate) samples in distilled water at 5, 37, and 60 degrees C under three different tensile stress ratios (sigma appl/sigma ys = 0%, 5%, and 10%). Each sample was placed in a modified Hoffman open-side tubing clamp and subjected to four-point bending at pre-determined stress level for 1 day, 3 days, 1 week, 2 weeks, and 4 weeks. Water sorption was measured by weight change calculations, without accounting for any weight loss due to solubility of uncured monomer. A generalized diffusion equation can be used to express both stress-free and stress conditions; D = D0exp[-E (sigma)/kT]. It was found that the activation energy for water sorption diffusion was linearly related to applied stress ratios; i.e., E = 1.15 sigma appl/sigma ys + 10.76 (kJ/mol), with the correlation coefficient r = 0.97. Since the proportional pre-exponential constant, D0, is independent of temperature, it is speculated that the loading percentage of reinforcing filler elements in composite resin materials can be related to this constant.

Troglitazone improves insulin-stimulated glucose utilization associated with an increased muscle glycogen content in obese Zucker rats

Recent studies have demonstrated that troglitazone has the capacity to improve insulin resistance. The present study was undertaken to determine the effect of troglitazone on in vivo insulin action, the activities of the pyruvate dehydrogenase (PDH) complex and 3-hydroxyacyl-CoA dehydrogenase (3-HADH) in muscle, and muscle GLUT-4 and glycogen content in obese and lean Zucker rats. Rats were fed a normal chow diet with and without troglitazone as a food admixture (0.2%) for 3 weeks. In vivo insulin action was measured by the sequential euglycemic clamp technique at two different insulin infusion rates (6 and 30 mU/kg BW/min). At the basal (fasting) state and after the clamp studies, the activities of PDH complex and 3-HADH, and the amounts of GLUT-4 and glycogen contained in the red gastrocnemius muscles were determined. Troglitazone treatment produced a significant rise in the metabolic clearance rate of glucose (MCR) during the 6-mU/kg BW/min insulin clamp study (19.5+/-3.9 vs 9.9+/-1.5 ml/kg BW/min, mean+/-SE, P<0.05) in obese rats, but not in lean rats. Troglitazone significantly increased the muscle glycogen content after the clamp study, compared to non-treated rats, in obese rats (9.9+/-0.5 vs 6.5+/-0.4 mg/g tissue, P<0.05) and has the tendency to increase the activity state of PDH complex in obese and lean rats at the fasting state. However, no effect of the drug on muscle GLUT-4 content was found. These results indicate that troglitazone may improve insulin sensitivity associated with increased muscle glycogen content.

Rat C peptide I and II stimulate glucose utilization in STZ-induced diabetic rats

AIMS

To study the effects of physiological concentrations of rat proinsulin C peptide I and II, respectively, on whole body glucose utilization in streptozotocin diabetic and healthy rats.

METHODS

A sequential insulin clamp procedure was used (insulin infusion rates 3.0 and 30.0 mU.kg-1.min-1) in awake animals. C-peptide infusion rates were 0.05 and 0.5 nmol.kg-1.min-1. Blood glucose was clamped at 7.7 +/- 0.3 mmol/l in the diabetic rats and at 3.9 +/- 0.1 mmol/l in the healthy rats.

RESULTS

In diabetic rats infused at lower rates of C peptide and insulin, glucose utilization increased by 79-90% (p < 0.001) compared with diabetic animals infused with saline and insulin. Increasing the rate of C-peptide infusion tenfold did not elicit a statistically significant further increase in glucose utilization. C peptide I and II exerted similar effects. The metabolic clearance rate for glucose in the diabetic animals infused with C peptide was not different from that of the healthy rats. During high-dose insulin infusion (30.0 mU.kg-1.min-1) glucose utilization increased considerably and no statistically significant C-peptide effects were observed. About 85% of the increase in glucose utilization induced by C peptide could be blocked by treatment with N-monomethyl-L-arginine.

CONCLUSIONS/INTERPRETATION

Physiological concentrations of homologous C peptide stimulate whole body glucose utilization in diabetic but not in healthy rats. C peptide I and II elicit similar effects. The influence of C peptide on glucose utilization may be mediated by nitric oxide.

Insulin activation of pyruvate dehydrogenase complex is enhanced by exercise training

We studied the effects of exercise training on the activity of the pyruvate dehydrogenase (PDH) complex in rat gastrocnemius muscle (experiment 1) and the response of the complex to glucose and insulin infusion (euglycemic clamp) in trained and sedentary rats (experiment 2). In experiment 1, half of the rats were randomly allocated as sedentary animals and the other half were trained by voluntary running exercise for 8 weeks. The total activity of the PDH complex was not affected by exercise training, and the activity state (proportion of the active form) of the PDH complex was decreased from 15.0%+/-2.4% to 7.5%+/-1.1% by exercise training. The activity of 3-hydroxyacyl-coenzyme A (CoA) dehydrogenase ([3-HADH] an enzyme in beta-oxidation) was significantly higher in trained versus sedentary rats. In experiment 2, sedentary and trained rats were starved for 24 hours before performing the euglycemic clamp. Glucose and insulin infusion was performed by a euglycemic clamp (insulin infusion rate, 6 mU/kg/min) for 90 minutes. The PDH complex was inactivated to less than 1% in both sedentary and trained rats after 24 hours of starvation. The glucose infusion rate (GIR) during the euglycemic clamp was higher in trained versus sedentary rats. The euglycemic clamp resulted in activation of the PDH complex in both sedentary and trained rats, but the response of the PDH complex to the euglycemic clamp was significantly higher in trained rats (5.8%+/-0.5%) than in sedentary rats (2.9%+/-0.5%). These results suggest that exercise training promotes fatty acid oxidation in association with suppression of glucose oxidation in skeletal muscle under resting conditions, but increases the rate of carbohydrate oxidation when glucose flux into muscle cells is stimulated by insulin.

Relationship between insulin and blood pressure in Japanese obese subjects

OBJECT

The association of obesity and hypertension is well recognized. However, the nature of the relationship between increased body weight and blood pressure (BP) elevation has remained obscure.

PATIENTS AND METHODS

We evaluated BP, insulin sensitivity, insulin clearance and fasting plasma insulin concentration in 19 younger (over 40 years) and in 15 older (more than 40 years) obese subjects to determine the relationships between BP and other factors. Insulin sensitivity and clearance were determined with the euglycemic clamp technique.

RESULTS

BP was not associated with insulin sensitivity although most of the subjects showed insulin resistance. In the younger obese group, a positive correlation between diastolic BP and body mass index (kg/m2) was found (r=0.740; p=0.043). In the older obese group, systolic and diastolic BP were correlated with fasting plasma insulin levels (r=0.705; p=0.003; r=0.574; p=0.025, respectively), and systolic BP was inversely correlated with insulin clearance (r=-0.715, p=0.003).

CONCLUSION

These results suggest that insulin is an important factor in BP elevation in older obese subjects, but not in younger obese subjects.

In vitro pharmacological profile of nonpeptide CRF1 receptor antagonists, CRA1000 and CRA1001

We investigated pharmacological properties of CRA1000 (2-(N-(2-methylthio-4-isopropylphenyl)-N-ethylamino-4-(4-(3-fluoro phenyl)-1,2,3,6-tetrahydropyridin-1-yl)-6-methylpyrimidine) and CRA1001 (2-( N-(2-bromo-4-isopropylphenyl)-N-ethylamino-4-(4-(3-fluorophenyl)-1 ,2,3,6-tetrahydropyridin-1-yl)-6-methylpyrimidine), novel and selective antagonists for the corticotropin-releasing factor1 (CRF1) receptor. Both CRA1000 and CRA1001 inhibited [125I]ovine CRF binding to membranes of COS-7 cells expressing the rat CRF1 receptor with IC50 values of 30 and 38 nM, respectively, without affecting [125I]sauvagine binding to membranes of COS-7 cells expressing the rat CRF2alpha receptor. CRF elicited intracellular cyclic AMP (cAMP) accumulation in AtT-20 cells which express the CRF1 receptor but not the CRF2 receptor, and COS-7 cells expressing CRF1 or CRF2alpha receptors. The CRF-induced cAMP accumulation was inhibited by both CRA1000 and CRA1001, concentration-dependently, in AtT-20 cells and COS-7 cells expressing the CRF1 receptor, while these compounds did not attenuate the CRF response in COS-7 cells expressing the CRF2alpha receptor. CRF increased adrenocorticotropin (ACTH) secretion from AtT-20 cells, and CRA1000 and CRA1001 inhibited CRF-induced ACTH secretion, concentration-dependently, as did other CRF1 receptor antagonists. These results show that both CRA1000 and CRA1001 are potent and selective CRF1 receptor antagonists.

Physical factors affecting daily walking activities among elderly female residents of a care house

To understand the physical and other factors related to walking among the elderly residents of a Care House for the aged, the total number of steps walked were measured over a period of 1 week (Nov. 6-12. 1994) for 67 female residents (mean age 79 ± 1 years). In addition, walking speed, stride length, and the time to climb 15 steps (stair-climbing time) were measured. To understand the indirect factors such as balance and agility that may control walking, tests were conducted on the subjects' ability to stand on one leg with eyes open and closed, and jumping reaction time. Results showed a negative correlation between total number of steps and age (r=-0.543, P< 0.01), jumping reaction time (r=-0.258, p<0.05) and stair-climbing time (r=-0.501, P< 0.01).However, a positive correlation was found between total number of steps and stride length (r=0.408, P< 0.01), walking speed (r=0.419, P< 0.01), self-rated health (r= 0.390, P< 0.05) and standing on one leg with eyes closed (r=0.258, P< 0.05). The total number of steps walked and physical factors, particularly physique and balance, were also closely related. The above suggests that a walking habit among elderly persons helps to slow the decline in physical strength, which is necessary to prevent falls. It is also reflected in the person's awareness of health and may increase the opportunities for leading an active daily life.

Cloning and characterization of a short variant of the corticotropin-releasing factor receptor subtype from rat amygdala

We have identified and characterized a cDNA encoding a novel isoform of the corticotropin-releasing factor (CRF) receptor, referred to as CRF2alpha-tr, from the rat amygdala cDNA library. The nucleotide sequence of the cloned cDNA has a structure of an alternatively spliced form of the CRF2alpha receptor, which contains unspliced introns 6 and 7 in the message, and encodes a 236-amino-acid truncated protein that comprises three unique transmembrane domains. Northern blot analysis shows that the CRF2alpha-tr receptor is more strongly expressed in the rat amygdala, thalamus, and hypothalamus than the intact CRF2alpha receptor. Western blot analysis also reveals that the CRF2alpha-tr protein can be expressed in transfected COS-7 cells as well as CRF2alpha. Furthermore, this receptor binds rat/human CRF with almost the same low affinity (Kd = 12.7 nM) as the CRF2alpha and without accumulation of intracellular cAMP. Interestingly, it does not bind sauvagine or rat urocortin. These findings suggest that this truncated CRF receptor is the major isoform of CRF2alpha receptor mRNA transcripts in the amygdala and would mediate some functions of CRF pathways in the central nervous system.

Cloning and sequencing of the chromosomal DNA and cDNA encoding the mitochondrial citrate synthase of Aspergillus niger WU-2223L

The complementary DNA (cDNA) and chromosomal DNA encoding the citrate synthase (EC 4.1.3.7) gene (cit1) of Aspergillus niger WU-2223L, a citric acid-producing strain, were cloned. Synthetic oligonucleotide primers were designed according to the amino acid sequences of already known eukaryotic citrate synthases and the codon bias of A. niger genes. The 920-bp DNA fragment was amplified by polymerase chain reaction with these primers using chromosomal DNA of WU-2223L as a template, and was employed to screen a cDNA library of A. niger. One full-length cDNA clone was isolated and sequenced, within which an ORF of 1425 by encoding a protein of 475 as with a molecular weight of 52,153 Da was found. Its N-terminal region contains a typical mitochondrial-targeting motif. The predicted as sequence was 82, 68, and 65% homologous with the mitochondrial citrate synthases of Neurospora crassa, Saccharomyces cerevisiae, and pig, respectively, but it showed lower homology to bacterial citrate synthases. The full-length cDNA clone was used to screen a chromosomal library of A. niger WU-2223L, and a 7.5 kb-SalI fragment containing the corresponding chromosomal gene was isolated. Comparison of the chromosomal and cDNA sequences revealed that the cit1 gene is interrupted by six introns. In the chromosomal DNA, upstream of the coding region, a CT-rich region, but not the TATAAA or CAAT motifs, was found. Escherichia coli MOB150, a citrate synthase-deficient mutant showing a glutamate-requiring phenotype, was transformed with the plasmid pKAC-35S, which is the expression vector pKK223-3 containing the cDNA fragment encoding a putative mature protein of A. niger citrate synthase. The transformant harboring pKAC-35S showed citrate synthase activity and a glutamate-nonrequiring phenotype.

Corrosion behavior of sensitized duplex stainless steel

The present work investigates the corrosion behavior of 2205 duplex stainless steel in 0.9% NaCl solution after various heat-treatments, and compares it to that of 316L austenitic stainless steel. Both stainless steels were heat-treated at 500, 650, and 800 degrees C in air for 1 h, followed by furnace cooling. Each heat-treated sample was examined for their microstructures and Vickers micro-hardness, and subjected to the X-ray diffraction for the phase identification. Using potentiostatic polarization method, each heat-treated sample was corrosion-tested in 37 degrees C 0.9% NaCl solution to estimate its corrosion rate. It was found that simulated sensitization showed an adverse influence on both steels, indicating that corrosion rates increased by increasing the sensitization temperatures.