Mediation of Endogenous β-Endorphin in the Plasma Glucose-Lowering Action of Herbal Products Observed in Type 1-Like Diabetic Rats

Recently, there have been advances in the development of new substances effective in managing diabetic disorders. Opioid receptors couple multiple systems to result in various biological effects, although opioids are best known for analgesia. In the present review, we used our recent data to describe the advance in plasma glucose-lowering action of herbal products, especially the mediation of β-endorphin in glucose homeostasis of insulin-deficient diabetes. In type 1-like streptozotocin-induced diabetic rats, we identified many products purified from herbs that show a dose-dependent plasma glucose-lowering action. Increase in β-endorphin secretion from the adrenal gland may activate peripheral opioid μ-receptors (MOR) to enhance the expression of muscle glucose transporters and/or to reduce hepatic gluconeogenesis at the gene level, thereby leading to improved glucose utilization in peripheral tissues for amelioration of severe hyperglycemia. It has also been observed that stimulation of α(1)-adrenoceptors (α(1)-ARs) in the adrenal gland by some herbal products is responsible for the increase in β-endorphin secretion via a phospholipase C-protein kinase dependent pathway. However, an increase in β-endorphin secretion from the adrenal gland by herbal products can function via another receptor. New insights into the mediation of endogenous β-endorphin activation of peripheral MOR by herbal products for regulation of glucose homeostasis without the presence of insulin have been established. Therefore, an increase in β-endorphin secretion and/or direct stimulation of peripheral MOR via an insulin-independent action might serve as the potential target for development of a therapeutic agent or promising adjuvant in intensive plasma glucose control.

Mediation of beta-endorphin in exercise-induced improvement in insulin resistance in obese Zucker rats

BACKGROUND

Aerobic exercise including treadmill running has long been used to successfully treat and/or prevent insulin resistance and type-2 diabetes. Increase of plasma beta-endorphin is observed with exercise. The present study was designed to clarify the role of endogenous beta-endorphin in exercise-induced improvement in insulin resistance.

METHODS

We used a moderate exercise program consisting of treadmill running at 20 m/min and 0% grade for 1 h/day, 7 days/week, for 8 weeks. Plasma glucose concentration was assessed by the glucose oxidase method. The enzyme-linked immunosorbent assay was performed to quantify the plasma level of beta-endorphin-like immunoreactivity (BER). The glucose disposal rate (GDR) was measured by the hyperinsulinemic euglycemic clamp technique. Changes of the insulin signaling in isolated soleus muscle were then detected by immunoprecipitation and immunoblotting.

RESULTS

An increase of plasma BER in parallel with the reduction of plasma glucose was obtained in exercise-trained obese Zucker rats. Different from a marked reduction in sedentary obese rats, the value of insulin-stimulated GDR obtained from the exercised obese rats was reversed to near that of the sedentary lean group, eight weeks after the last period of exercise. This effect of exercise was inhibited by naloxone or naloxonazine at doses sufficient to block opioid micro-receptors. Signaling-related defects in the soleus muscle of sedentary obese Zucker rats, which impaired glucose transporter subtype 4 (GLUT 4), included decreased phosphorylation of insulin receptor substrate (IRS)-1, as well as an attenuated p85 regulatory subunit of phosphatidylinositol 3-kinase (PI3 kinase) and Akt serine phosphorylation. In contrast, exercise training failed to modify the levels of insulin receptor (IR), IRS-1, and IR tyrosine autophosphorylation in obese Zucker rats.

CONCLUSION

Enhanced insulin sensitivity via exercise training might be mediated by endogenous beta-endorphin through an increase of postreceptor insulin signaling related to the IRS-1-associated PI3-kinase step that leads to the enhancement of GLUT 4 translocation and improved glucose disposal in obese Zucker rats.

Increase of PTEN gene expression in insulin resistance

Phosphatase and tensin homologue deleted from chromosome ten (PTEN) has recently been characterized as a regulator of insulin sensitivity in the insulin target tissue. However, whether PTEN gene expression is changed in insulin resistance remains unclear. We observed that both the mRNA and protein level of PTEN in soleus muscle isolated from the obese Zucker rats (Fa/Fa) were increased compared to the age-matched lean group. Similarly, both the mRNA and protein level of PTEN in soleus muscle of the fructose-fed lean Zucker rats (Fa/Fa) showing the higher glucose-insulin index were higher than that of the regular chow fed group. These results suggest that increase of PTEN gene expression seems to be related to the development of insulin resistance.

Loperamide increases glucose ultilization in streptozotocin-induced diabetic rats

1. Loperamide has an ability to lower the plasma glucose concentration in streptozotocin (STZ)-induced diabetic rats. In the present study, we investigated the molecular mechanisms by which loperamide regulates plasma glucose concentrations in the absence of insulin. 2. Loperamide, at a dose sufficient (17.6 microg/kg) to activate mu-opioid receptors, significantly decreased plasma glucose levels in STZ-diabetic rats. The mRNA and protein levels of glucose transporter 4 (GLUT-4) in soleus muscle, detected by northern and western blotting, respectively, were increased after repeated intravenous administration of loperamide (17.6 micro g/kg) to STZ-diabetic rats over 3 days. Moreover, similar treatment with loperamide (17.6 microg/kg) for 3 days reversed the elevated mRNA and protein levels of phosphoenolpyruvate carboxykinase (PEPCK) in the liver of STZ-diabetic rats to near the levels seen in normal rats. 3. These results suggest that activation of mu-opioid receptors by loperamide can increase glucose utilization in peripheral tissues and/or reverse the higher gene expression of PEPCK to inhibit hepatic gluconeogenesis, thereby lower plasma glucose in diabetic rats lacking insulin.

Signals in the activation of opioid mu-receptors by loperamide to enhance glucose uptake into cultured C2C12 cells

In an attempt to understand the signal pathways of opioid mu-receptors for glucose metabolism, we used loperamide to investigate the glucose uptake into the myoblast C2C12 cells. Loperamide enhanced the uptake of radioactive deoxyglucose into C2C12 cells in a concentration-dependent manner that was abolished in cells pre-incubated with naloxone or naloxonazine at concentrations sufficient to block opioid mu-receptors. Pharmacological inhibition of phospholipase C (PLC) by U73122 resulted in a concentration-dependent decrease in loperamide-stimulated uptake of radioactive deoxyglucose into C2C12 cells. This inhibition of glucose uptake by U73122 was specific since the inactive congener, U73343, failed to modify loperamide-stimulated glucose uptake. Moreover, both chelerythrine and GF 109203X diminished the action of loperamide at concentrations sufficient to inhibit protein kinase C (PKC). The obtained data suggest that an activation of opioid mu-receptors in C2C12 cells by loperamide may increase glucose uptake via the PLC-PKC pathway.

Increase in adenosine A1 receptor gene expression in the liver of streptozotocin-induced diabetic rats

BACKGROUND

Adenosine A1 receptor (A1-AR) activation can lower plasma glucose in diabetic rats lacking insulin. We investigated the change in A1-AR gene expression in diabetic rats.

METHODS

The incorporation of [U-(14)C]-glucose into glycogen was carried out to evaluate the effect of N(6)-cyclopentyladenosine (CPA) on glucose utilization in vitro. The plasma glucose concentration was assessed by the glucose oxidase method. The mRNA and protein levels of A1-AR in isolated liver were detected by Western blotting analysis and Northern blotting analysis, respectively.

RESULTS

The effect of CPA, an agonist of A1-AR, on glycogen incorporation in hepatocytes isolated from streptozotocin-induced diabetic rats (STZ-diabetic rats) was more marked than that from the normal rats. However, similar glycogen synthesis was not modified by 12-O-tetradecanoylphorbol-13-acetate (TPA), an activator of protein kinase C, in the isolated hepatocytes from both the normal and the STZ-diabetic rats. A change in response at the receptor level can thus be considered. The mean level of liver mRNA transcripts encoding A1-AR was increased in STZ-diabetic rats to about 250% of that in normal rats. Exogenous insulin at a dose sufficient to normalize the plasma glucose of STZ-diabetic rats reversed the mRNA level of A1-AR in the liver after a four-day treatment. Similar results were also observed in STZ-diabetic rats that received treatment with phlorizin for four days. Moreover, the protein level of A1-AR was higher in the liver of STZ-diabetic rats than that in the normal rats. Similar treatment with exogenous insulin or phlorizin reversed the elevated protein level of A1-AR in the liver of STZ-diabetic rats to near the normal level. Therefore, correction of hyperglycemia in STZ-diabetic rats can reverse the higher gene expression of A1-AR in liver.

CONCLUSIONS

The obtained results suggest that an increase in plasma glucose is responsible for the higher gene expression of A1-AR in the liver of STZ-diabetic rats.

Release of beta-endorphin by caffeic acid to lower plasma glucose in streptozotocin-induced diabetic rats

The role of alpha 1A -adrenoceptors in the regulation of opioid secretion from the adrenal glands of streptozotocin-induced diabetic rats (STZ-diabetic rats) was examined in an attempt to determine the mechanism of plasma glucose-lowering action of caffeic acid. In agreement with a previous report, we showed that caffeic acid produced a dose-dependent lowering of the plasma glucose concentration in STZ-diabetic rats along with an increase of plasma beta-endorphin-like immunoreactivity (BER). These actions of caffeic acid were abolished by pretreatment with WB 4101 or RS 17 056 at doses sufficient to block alpha 1A -adrenoceptors. In addition, naloxone and naloxonazine at doses effective for blocking opioid micro -receptors abolished the plasma glucose-lowering action of caffeic acid. Also, unlike that in wild-type diabetic mice, caffeic acid failed to produce a plasma glucose lowering effect in opioid micro -receptor knockout diabetic mice. We observed that caffeic acid could enhance BER release from isolated rat adrenal medulla in a concentration-dependent manner; inhibitors of alpha 1A -adrenoceptors such as WB 4101 and RS 1705 abolished this action. Investigations of the signal pathways further supported that activation of alpha 1A -adrenoceptor is responsible for the stimulatory effect of caffeic acid on BER secretion from the adrenal medulla. In the presence of U73312, a specific inhibitor of phospholipase C, the caffeic acid-induced increase of BER was reduced in a concentration-dependent manner, but it was not affected by U73343, the negative control of U73312. Chelerythrine and GF 109203X also diminished the action of caffeic acid at concentrations sufficient for inhibiting protein kinase C. Moreover, bilateral adrenalectomy in STZ-diabetic rats resulted in the loss of this plasma glucose-lowering effect of caffeic acid, and there was no increase in plasma BER with caffeic acid. Therefore, beta-endorphin release from the adrenal gland appears to be responsible for the lowering of plasma glucose in STZ-diabetic rats induced by caffeic acid, through the activation of alpha 1A -adrenoceptors.

Plasma glucose-lowering effect of beta-endorphin in streptozotocin-induced diabetic rats

The effect of beta-endorphin on plasma glucose levels was investigated in streptozotocin-induced diabetic rats (STZ-diabetic rats). A dose-dependent lowering of plasma glucose was observed in the fasting STZ-diabetic rat fifteen minutes after intravenous injection of beta-endorphin. The plasma glucose-lowering effect of beta-endorphin was abolished by pretreatment with naloxone or naloxonazine at doses sufficient to block opioid mu-receptors. Also, unlike wild-type diabetic mice, beta-endorphin failed to induce its plasma glucose-lowering effect in the opioid mu-receptor knock-out diabetic mice. In isolated soleus muscle, beta-endorphin enhanced the uptake of radioactive glucose in a concentration-dependent manner. Stimulatory effects of beta-endorphin on glycogen synthesis were also seen in hepatocytes isolated from STZ-diabetic rats. The blockade of these actions by naloxone and naloxonazine indicated the mediation of opioid mu-receptors. In the presence of U73312, the specific inhibitor of phospholipase C (PLC), the uptake of radioactive glucose into isolated soleus muscle induced by beta-endorphin was reduced in a concentration-dependent manner, but it was not affected by U73343, the negative control of U73312. Moreover, chelerythrine and GF 109203X diminished the stimulatory action of beta-endorphin on the uptake of radioactive glucose at a concentration sufficient to inhibit protein kinase C (PKC). The data obtained suggest that activating opioid mu-receptors by beta-endorphin may increase glucose utilization in peripheral tissues via the PLC-PKC pathway to lower plasma glucose in diabetic rats lacking insulin.

Decrease in catechol-O-methyltransferase activity in the liver of streptozotocin-induced diabetic rats

1. The present study compared the activity of catechol- O-methyltransferase (COMT) in the liver and plasma of streptozotocin (STZ)-induced diabetic rats with that in normal rats. The activity of COMT was estimated by the metabolism of noradrenaline to metanephrine (MN), both measured by high-performance liquid chromatography with electrochemical detection. 2. Formation of MN was decreased in the liver of STZ- diabetic rats compared with normal rats. The amount of MN was also decreased in plasma obtained from STZ-diabetic rats. A Michaelis-Menten plot showed a reduction in the maximum velocity and an increase in the Km for COMT in liver samples from STZ-diabetic rats. 3. The role of hyperglycaemia in the lowering of COMT activity was then investigated using phlorizin or insulin at doses sufficient to normalize plasma glucose from STZ-diabetic rats. Both insulin and phlorizin treatment of STZ-diabetic rats for 4 days restored the activity of COMT to that seen in normal rats. Thus, correction of hyperglycaemia in STZ-diabetic rats can reverse the decrease in COMT activity. The activity of COMT is lower in STZ-diabetic rats than in normal rats mainly due to the higher plasma glucose.

Metformin-like effects of Quei Fu Di Huang Wan, a Chinese herbal mixture, on streptozotocin-induced diabetic rat

Effect on plasma glucose concentration of Quei Fu Di Huang Wan (Quei Fu DHW), the herbal mixture widely used to treat diabetic disorder in Chinese traditional medicine, was investigated in diabetic rats deficient in insulin. Changes of plasma glucose in streptozotocin-induced diabetic rats (STZ-diabetic rats) receiving repeated oral administration of Quei Fu DHW were determined. Also, the mRNA level (by Northern blotting) and protein level (by Western blotting) of phosphoenolpyruvate carboxykinase (PEPCK) in liver from STZ-diabetic rats were measured to compare differences between groups receiving repeated oral administration of Quei Fu DHW, metformin, and two active herbs (Zou Guei or Fuzei) at effective dosages. In STZ-diabetic rats, acute oral administration of Quei Fu DHW decreased the plasma glucose level significantly in a dose-dependent manner from 5 mg/kg to 26.0 mg/kg. Similar treatment with Quei Fu DHW also brought on a plasma glucose-lowering effect in normal rats, although the effectiveness was not as significant as in STZ-diabetic rats. Repeated oral treatment of Quei Fu DHW at 26 mg/kg every 8 h, three times daily for 3 days, produced a plasma glucose-lowering activity similar to that of metformin-treatment in STZ-diabetic rats. Oral administration of Zou Guei (Cinnamomi Cortex) or Fuzei (Aconiti Tuber), the individual constituent of Quei Fu DHW, at the dose of 50 mg/kg into STZ-diabetic rats for 3 days normalized hyperglycemia. Similar to the repeated treatment with Quei Fu DHW, Fuzei at the effective dose reversed the elevated mRNA and protein levels of PEPCK in liver from STZ-diabetic rats. This is consistent with findings that metformin restored the increased gene expression of PEPCK in liver from STZ-diabetic rats. However, the gene expression of PEPCK in STZ-diabetic rats was not influenced by similar treatment with Zou Guei. The present study found that oral administration of Quei Fu DHW could decrease hepatic gluconeogenesis in a way similar to metformin in lowering plasma glucose in diabetic rats lacking insulin. Thus, this preparation may be a helpful adjuvant for the treatment of diabetic disorders in clinical practice.

Plasma glucose-lowering effect of tramadol in streptozotocin-induced diabetic rats

The effect of tramadol on the plasma glucose level of streptozotocin (STZ)-induced diabetic rats was investigated. A dose-dependent lowering of plasma glucose was seen in the fasting STZ-induced diabetic rats 30 min after intravenous injection of tramadol. This effect of tramadol was abolished by pretreatment with naloxone or naloxonazine at doses sufficient to block opioid mu-receptors. However, response to tramadol was not changed in STZ-induced diabetic rats receiving p-chlorophenylalanine at a dose sufficient to deplete endogenous 5-hydroxytrptamine (5-HT). Therefore, mediation of 5-HT in this action of tramadol is ruled out. In isolated soleus muscle, tramadol enhanced the uptake of radioactive glucose in a concentration-dependent manner. The stimulatory effects of tramadol on glycogen synthesis were also seen in hepatocytes isolated from STZ-induced diabetic rats. The blockade of these actions by naloxone and naloxonazine indicated the mediation of opioid mu-receptors. The mRNA and protein levels of the subtype 4 form of glucose transporter in soleus muscle were increased after repeated treatments for 4 days with tramadol in STZ-induced diabetic rats. Moreover, similar repeated treatments with tramadol reversed the elevated mRNA and protein levels of phosphoenolpyruvate carboxykinase in the liver of STZ-induced diabetic rats. These results suggest that activation of opioid mu-receptors by tramadol can increase the utilization of glucose and/or decrease hepatic gluconeogenesis to lower plasma glucose in diabetic rats lacking insulin.

Stimulatory effect of phenylephrine on the secretion of beta-endorphin from rat adrenal medulla in vitro

In an attempt to investigate the role of alpha1-adrenoceptors in the regulation of opioid secretion from adrenal gland, phenylephrine was employed to investigate the effect on secretion of beta-endorphin-like immunoreactivity (BER) from adrenal medulla of rat in vitro. Phenylephrine enhanced the BER from isolated adrenal medulla in a concentration-dependent manner and this action was abolished by the antagonists of alpha1-adrenoceptors, prazosin and tamsulosin. Investigations of signal pathway further support that an activation of alpha1-adrenoceptors is responsible for the stimulatory effect of phenylephrine on BER secretion from adrenal medulla. In the presence of U73312, the specific inhibitor of phospholipase C (PLC), phenylephrine-induced change of BER was reduced in a concentration-dependent manner but it was not affected by U73343, the negative control of U73312. Moreover, chelerythrine and GF 109203X diminished the action of phenylephrine at concentration sufficient to inhibit protein kinase C (PKC). In conclusion, our results suggest that an activation of alpha1-adrenoceptors in adrenal medulla by phenylephrine may enhance the secretion of opioids from adrenal gland of rat via signals of PLC-PKC pathway.

Increase of opioid mu-receptor gene expression in streptozotocin-induced diabetic rats

Opioids play an important role in the regulation of glucose homeostasis. In the previous report, we showed that activation of opioid mu-receptors produced a plasma glucose lowering effect in diabetic rats lacking insulin. In the present study, we found that the response of opioid mu-receptor is more sensitive in streptozotocin-induced diabetic rats (STZ-diabetic rats) than in normal rats. Intravenous injection of loperamide, an agonist of opioid mu-receptors, induced a dose-dependent decrease of plasma glucose from 3 microg/kg to 60 microg/kg in fasting STZ-diabetic rats. However, loperamide decreased the plasma glucose of normal fasting rats at the doses of 0.3 mg/kg to 1.5 mg/kg, which were much higher than those needed to produce the same effect in diabetic rats. The plasma glucose-lowering action of loperamide at the dose effective in normal rats disappeared in opioid mu-receptor knockout mice, while the plasma glucose-lowering response to loperamide was still observed in wild-type mice. This opens the possibility of mediation through opioid mu-receptor in the plasma glucose-lowering action of loperamide. Moreover, the mRNA level of opioid mu-receptor in the liver markedly increased in STZ-diabetic rats compared to normal rats. Normalization of plasma glucose concentrations in STZ-diabetic rats with exogenous insulin or phlorizin reversed mRNA and protein levels of opioid mu-receptor in the liver after 4 days of treatment. This shows that correction of hyperglycemia in STZ-diabetic rats may reverse the higher gene expression of opioid mu-receptor. These results suggest that hyperglycemia is responsible for increase of opioid mu-receptor in STZ-diabetic rats.

Loss of plasma glucose lowering response to cold stress in opioid mu-receptor knock-out diabetic mice

Opioid mu-receptor plays an important role in the regulation of glucose homeostasis in diabetic rats lacking insulin. Opioid mu-receptor knockout mice were employed to identify the essential role of this receptor in the present study. Western blotting analysis characterized the deletion of opioid mu-receptor in liver of knockout mice as compared to that of normal (wild-type) mice. We found that the plasma glucose concentration of diabetic mice induced by intraperitoneal injection of streptozotocin was markedly decreased after exposure to cold-stress in a cold room for 1 h. However, this plasma glucose lowering response to cold-stress was disappeared in diabetic mice lacking opioid mu-receptor. The important role of opioid mu-receptor in the plasma glucose lowering response to cold stress can thus be considered. Moreover, bilateral adrenalectomy abolished this plasma glucose lowering response to cold stress in diabetic mice with opioid mu-receptor, as compared to the shamed-operated animals. Therefore, activation of opioid mu-receptor by opioid from adrenal gland appears to be responsible for the plasma glucose lowering response to cold-stress in diabetic mice with insulin deficiency.

Release of beta-endorphin by prostaglandin E2 to lower plasma glucose in streptozotocin-induced diabetic rats

In the present study, Wistar rats, which received a streptozotocin injection to induce diabetes (STZ-diabetic rats), a model similar to insulin-dependent diabetes mellitus (IDDM) or type 1 diabetes mellitus, were used to investigate the effect of prostaglandin (PG) E2 on plasma glucose. Intravenous injection of PGE2 produced a dose-dependent lowering of plasma glucose level in fasting STZ-diabetic rats after 60 min. In addition to the blockade of this hypoglycemic effect by guanethidine (a noradrenergic nerve terminal-blocking agent), prazosin at a dose effective to block alpha1-adrenoceptors abolished the action of PGE2. An increase of plasma norepinephrine (NE) was also observed in STZ-diabetic rats receiving PGE2 injections. Participation of sympathetic stimulation by PGE2 may thus be speculated. Also, the plasma glucose-lowering effect of PGE2 was also blocked by pretreatment with naloxone or naloxonazine at doses sufficient to block opioid mu-receptor. Injection of PGE2 increased plasma beta-endorphin-like immunoreactivity (BER) in STZ-diabetic rats, and this action was abolished by prazosin. Bilateral adrenalectomy resulted in the loss of this PGE2 effect, and no increase was seen in plasma BER with PGE2 in STZ-diabetic rats. Therefore, beta-endorphin from the adrenal gland appears to be responsible for the lowering of plasma glucose in STZ-diabetic rats by PGE2 through an increase of NE release to activate alpha1-adrenoceptors.

Stimulatory effect of isoferulic acid on alpha1A-adrenoceptor to increase glucose uptake into cultured myoblast C2C12 cell of mice

In an attempt to elucidate the effect of isoferulic acid on alpha1-adrenoceptor (AR), the myoblast C2C12 cells of mice were employed to investigate the change of glucose uptake in the present study. Isoferulic acid enhanced the uptake of radioactive glucose into C2C12 cells in a concentration-dependent manner, which were abolished by pretreatment with prazosin. Effect of isoferulic acid on alpha1-AR was further characterized using the displacement of [3H]YM617 binding in C2C12 cells. The radioactive glucose uptake increasing action of isoferulic acid was abolished by tamsulosin or WB 4101 at concentration sufficient to block alpha1A-adrenoceptor (alpha1A-AR) but it was not modified by chlorethylclonidine (CEC) at the concentration sufficient to abolish alpha1B-AR. An activation of alpha1A-AR by isoferulic acid in C2C12 cells can thus be considered. Pharmacological inhibition of phospholipase C (PLC) by U73312 resulted in a concentration-dependent reduction of isoferulic acid-stimulated glucose uptake in C2C12 cells. This inhibition by U73112 was specific because the inactive congener, U73343, failed to modify the action of isoferulic acid. Also, chelerythrine and GF 109203X diminished the action of isoferulic acid at concentration sufficient to inhibit the activity of protein kinase C (PKC). The obtained data suggest that an activation of alpha1A-AR by isoferulic acid may increase the glucose uptake via PLC-PKC pathway in C2C12 cells.

Modest overexpression of neuropeptide Y in the brain leads to obesity after high-sucrose feeding

Neuropeptide Y (NPY), one of the most abundant peptide transmitters in the mammalian brain, is assumed to play an important role in feeding and body weight regulation. However, there is little genetic evidence that overexpression or knockout of the NPY gene leads to altered body weight regulation. Previously, we developed NPY-overexpressing mice by using the Thy-1 promoter, which restricts NPY expression strictly within neurons in the central nervous system, but we failed to observe the obese phenotype in the heterozygote. Here we report that in the homozygous mice, overexpression of NPY leads to an obese phenotype, but only after appropriate dietary exposure. NPY-overexpressing mice exhibited significantly increased body weight gain with transiently increased food intake after 50% sucrose--loaded diet, and later they developed hyperglycemia and hyperinsulinemia without altered glucose excursion during 1 year of our observation period.

Stimulatory effect of D-ephedrine on beta3-adrenoceptors in adipose tissue of rats

The effect of ephedrine on beta3-adrenoceptos (beta3-AR) was studied in the isolated adipose tissue of Wistar rat. Incubation with D-ephedrine (0.1-10 microM) induced a concentration-dependent decrease of uptake of [14C]-deoxy-D-glucose into white adipose tissues (WAT). The inhibitory effect of D-ephedrine was potentiated by BRL 37344, the agonist of beta3-AR and concentration-dependently inhibited by SR 59230A, the selective antagonist of beta3-AR. The action of D-ephedrine on beta3-AR was further blocked by the antibodies for beta3-AR, but not the immunoglobulin. in a concentration-dependent manner. Moreover, D-ephedrine increased glycerol release from the isolated brown adipose tissues (BAT) and this action was also abolished by SR 59230A at concentration sufficient to block beta3-AR. Thus, these results suggest that D-ephedrine has the ability to activate beta3-AR both in WAT and BAT of Wistar rats in vitro.

Changes in endogenous monoamines in aged rats

1. It has been documented that ageing may alter endogenous neurotransmitters. However, these results are controversial. Thus, in the present study, cerebral cortex and plasma from male Wistar rats aged 8 weeks and 6, 12 or 24 months were used to investigate the changes in monoamines using electrochemical detection. 2. A marked decrease in L-dihydroxyphenylalanine (L-DOPA) was observed in aged rats. Like the decrease in dopamine (DA), levels of 5-hydroxytryptamine (5-HT) and 5-hydroxyindolacetic acid (5-HIAA), the major metabolite of 5-HT, in aged rats were decreased in the cerebral cortex and plasma. Plasma levels of noradrenaline and levels of adrenaline in the cerebral cortex were also decreased in aged rats. Moreover, levels of 3,4-dihydroxyphenylacetic acid (DOPAC), a metabolite of DA, in the cerebral cortex and plasma were reduced by ageing. The level of homovanillic acid (HVA) in all samples was markedly increased with ageing. 3. The ratio of DOPAC/DA and 5-HIAA/5-HT, being closely linked with the activity of monoamine oxidase, was increased in the cerebral cortex and plasma with ageing. The ratio of HVA/DOPAC, an index of the activity of catechol-O-methyltransferase, was also higher in the cerebral cortex and plasma of aged rats. 4. These data suggest that ageing may alter endogenous monoamines in both the brain and peripheral tissues.

Decrease of muscarinic M2 cholinoceptor gene expression in the heart of aged rat

It is well known that the baroreflex activity decreases with aging. However, the mechanisms of this change are still not clear. Thus, we investigated one of the parameters to see whether aging alters gene expression of muscarinic receptors in the heart of Wistar rat aged between 2 months (adult) and 24 months (aged). The mRNA level determination by Northern blot analysis for muscarinic M2 cholinoceptors in aged rat was decreased as compared to that in 2-month-old rats. Quantification of receptor protein using selective antibodies indicated that the level of muscarinic M2 cholinoceptor in the heart of 24-month-old rats was lower than that in 2-month-old animals. These results indicate the decrease of muscarinic M2 cholinoceptor in heart with aging that may contribute as one of the parameters for dysfunction in baroreflex activity.

Characterization of adenosine A1 receptor in cultured myoblast C2C12 cells of mice

In an attempt to investigate the presence of adenosine A1 receptor in cell line, we used N6-cyclopentyladenosine (CPA), an agonist of adenosine A1 receptor, to incubate with C2C12 cells in vitro. CPA increased the uptake of radioactive glucose into C2C12 cells in a concentration-dependent manner and this action was abolished by the antagonists, both 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) (1,3-dipropy1-8-cyclopentylxanthine) and 8-(p-sulfophenyl)theophylline (8-SPT), at concentrations sufficient to block adenosine A1 receptor. Northern blot analysis showed the expression of adenosine A1 receptor mRNA by C2C12 cells. Western blotting also indicated a positive correlation (r = 0.99) of antibody recognized adenosine A1 receptor with membrane protein. The presence of adenosine A1 receptor in C2C12 cells can thus be considered. In the presence of U73312 (1-[6[[(17 beta)-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H- pyrrole-2,5-dione), the specific inhibitor of phospholipase C, glucose uptake stimulated by CPA into C2C12 cells was reduced concentration-dependently while it was not modified by U73343 (1-[6[[(17 beta)-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-2,5- pyrrolidinedione), the negative control of U73312. Moreover, chelerythrine and GF 109203X (3-[1-[3-(dimethylamino)propyl]-1H-indol-3-yl]-4-(1H-indol-3- yl)-1H-pyrrole-2,5-dione) also diminished the CPA-stimulated glucose uptake at concentrations sufficient to inhibit protein kinase C. The obtained data suggest that activation of adenosine A1 receptor in C2C12 cells may increase the glucose uptake via phospholipase C-protein kinase C pathway.

Stimulation of insulin release in rats by Die-Huang-Wan, a herbal mixture used in Chinese traditional medicine

Die-Huang-Wan is a herbal mixture widely used in Chinese traditional medicine to treat diabetic disorders. We have investigated the effect of Die-Huang-Wan on plasma glucose concentration in-vivo. Die-Huang-Wan was administered orally (5.0, 15.0 or 26.0 mg kg(-1)) to three rat models. Wistar rats were used as the normal animal model, rats with insulin-resistance (induced by the repeated thrice daily injection of human long-acting insulin) were used as the non-insulin-dependent diabetic model, and streptozotocin-induced diabetic rats were used as the insulin-dependent diabetic model. In normal rats, approximately 1 h after oral administration of Die-Huang-Wan the plasma glucose concentration decreased significantly in a dose-dependent manner, from 5 to 26.0 mg kg(-1). A similar effect was observed in rats with insulin-resistance. However, this effect was not observed in streptozotocin-induced diabetic rats, even at an oral dose of 26.0 mg kg(-1). These results suggested an insulin-dependent action, a view supported by the increase of plasma insulin-like immunoreactivity in normal rats receiving Die-Huang-Wan. The results indicated that Die-Huang-Wan had an ability to stimulate the secretion of insulin and this preparation seemed helpful in improving the diabetic condition, especially hyperglycaemia in type-II diabetes.

Decrease of hypothalamic neuropeptide Y gene expression by vanadyl sulfate in streptozotocin-induced diabetic rats

In an attempt to elucidate the effect of vanadium compounds on the gene expression of neuropeptide Y (NPY), vanadyl sulfate (VOSO4) was orally administrated at the dose of 1 mg/kg body weight into streptozotocin-induced diabetic rats (STZ-diabetic rats) three times daily for 1 week. We found a marked lowering of plasma glucose with a significant decrease of food and water intake in these STZ-diabetic rats treated with VOSO4, although the weight gain was unaffected. The increase of hypothalamic NPY, both the mRNA level and peptide concentration, in STZ-diabetic rats was also reduced by this oral treatment of VOSO4. However, similar treatment of VOSO4 in normal rats failed to modify the feeding behavior and hypothalamic NPY gene expression. These data suggest that decrease of hypothalamic NPY gene expression by VOSO4 is related to the recovery of hyperphagia in diabetic rats lacking insulin.

Stimulatory effect of trans-cinnamaldehyde on norepinephrine secretion in cultured pheochromocytoma (PC-12) cells

AIM

The effect of trans-cinnamaldehyde (CNMA) on the release of norepinephrine (NE) from nerve terminal was investigated using rat pheochromocytoma 12 (PC-12) cells.

METHODS

The amount of NA released from PC-12 cells incubated with CNMA or related substances was quantified by high performance liquid chromatography (HPLC)-electrochemical detection. The lipophilic anion bisoxonol was used to monitor the effect of CNMA on the membrane potential.

RESULTS

CNMA stimulated the secretion of NE in a concentration-dependent manner from 5 mumol/L to 50 mumol/L, while the value of lactate dehydrogenase in the incubated medium was not influenced by CNMA. However, acetaldehyde, cinnamic acid, cinnamoyl chloride and cinnamamide failed to produce similar effect. The action of CNMA can thus be considered specific. The depolarizing effect of CNMA on the membrane potential was also illustrated by a concentration-dependent increase in the fluorescence of bisoxonol, a potential-sensitive dye. Saxitoxin attenuated the depolarizing action of CNMA at concentrations sufficient to block sodium channels. Besides, the effect of CNMA to depolarize the membrane potential in PC-12 cells is greater than that of 4-aminopyridine (4-AP). The action of CNMA on NE releasing depends on extracellular Ca2+ and is attenuated by 8-bromo-cAMP at concentrations sufficient to inhibit the action of cyclic AMP.

CONCLUSION

These findings suggest that CNMA can depolarize the membrane to result in a Ca(2+)-dependent and cyclic AMP-related release of NE from PC-12 cells.

Gene expression of alpha(1A)-adrenoceptor but not alpha(1B)-adrenoceptor in cultured myoblast C(2)C(12) cells of mice

Subtypes of alpha(1)-adrenoceptor (alpha(1)-AR) in the cultured myoblast C(2)C(12) cells have been examined using molecular biological identifications. Expression of the two distinct mRNAs that encode proteins of alpha(1A)- and alpha(1B)-AR was studied using reverse transcription combined with polymerase chain reaction (RT-PCR). Results of RT-PCR demonstrated a marked expression of alpha(1A)-AR in the prostate of rats. Samples from the C(2)C(12) cells under the same amount of amplification showed the expression of alpha(1A)-AR at a level slightly lower than that from the prostate of rats. Western blotting analysis using receptor subtype-specific antibody also indicated that the alpha(1A)-AR was expressed in C(2)C(12) cells as well as in prostate of rats. However, although the expression of alpha(1B)-AR was obtained in the spleen of rats, expression of alpha(1B)-AR was undetectable in the C(2)C(12) cells either the results of RT-PCR or the Western blotting analysis. The present study suggests that alpha(1A)-AR is a major subtype of alpha(1)-AR in the C(2)C(12) cell line.

Role of alpha1A-adrenoceptor in the regulation of glucose uptake into white adipocyte of rats in vitro

In an attempt to know the functional role of alpha1A-adrenoceptors in adipose tissue, white adipocytes (WAT) of Wistar rats were used to investigate the change of glucose uptake after pharmacological activation of alpha1-adrenoceptors. Methoxamine enhanced the uptake of radioactive glucose into isolated WAT in a concentration-dependent manner. Translocation of glucose transporter (GLUT4) from cytosol to membrane was also stimulated with methoxamine. Action of methoxamine to raise glucose uptake was abolished in WAT pre-incubated with the antagonists, both tamsulosin and WB 4101, at concentrations sufficient to block alpha1A-adrenoceptors. However, chlorethylclonidine (CEC). the antagonist of alpha1B-adrenoceptors, showed the inhibition of methoxamine-induced action only at a higher concentration. Even under the treatment with maximal concentration of CEC, methoxamine can produce action about 80% of the vehicle-treated control. The major role of alpha1A-adrenoceptors in the stimulation of glucose uptake by methoxamine can thus be considered. In the presence of specific inhibitor of phospholipase C (PLC), U73312, methoxamine-stimulated glucose uptake into WAT was reduced in a concentration-dependent manner and U73343, the negative control of U73312, did not affect the action of methoxamine. Moreover, chelerythrine and GF 109203X diminished the methoxamine-stimulated glucose uptake at a concentration sufficient to inhibit protein kinase C (PKC). Inhibition of phosphoinositide-3 kinase (PI-3 kinase) by LY294002 also abolished methoxamine-stimulated glucose uptake. Therefore. the obtained data suggest that an activation of alpha1A-adrenoceptors, presence in WAT, by agonist and/or neurotransmitter may increase the glucose uptake via PLC-PKC pathway and the activation of PI-3 kinase.

Activation of adenosine A1 receptors by drugs to lower plasma glucose in streptozotocin-induced diabetic rats

To examine the role of the adenosine A1 receptor in glucose regulation in the absence of insulin, the present study investigated the changes of plasma glucose in male streptozotocin-induced diabetic rats (STZ-diabetic rats) using dipyridamole to increase endogenous adenosine and N6-cyclopentyladenosine (CPA) to activate the adenosine A1 receptor. Intravenous injections of dipyridamole or CPA induced a dose-dependent decrease of plasma glucose in fasting STZ-diabetic rats. Plasma glucose lowering action of dipyridamole, like that of CPA, was inhibited in a dose-dependent manner by pre-treatment with 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) or 8-(p-sulfophenyl)theophylline (8-SPT) at which block the adenosine A1 receptors. Action of the adenosine A1 receptors can thus be considered. In isolated skeletal muscle, CPA enhanced the glucose uptake in a concentration-dependent manner. Blockade of this action by DPCPX and 8-SPT again supported the mediation of the adenosine A1 receptor. Also, CPA produced an increase of glycogen synthesis in isolated soleus muscle. Moreover, CPA decreased plasma triglyceride and cholesterol levels significantly in STZ-diabetic rats. These results suggest that activation of adenosine A1 receptors can increase glucose utilization in peripheral tissues by increasing tissue uptake and glycogen synthesis to lower plasma glucose in rats lacking insulin.

Acoustic-induced switching of the reflection wavelength in a fiber Bragg grating

Coupling between copropagating core and cladding modes was implemented by acoustic generation of lateral vibration of an etched fiber. When these coupling processes were combined with counterpropagating coupling of a core mode and a cladding mode and the Bragg reflection of a fiber grating, switching of reflection wavelength between the Bragg wavelength and cladding-mode coupling wavelengths was achieved. We report the implementation of such acoustically induced switching behaviors and explain their operation principles. The implemented results can be used for wavelength-division multiplexed add-drop filtering.

Stimulatory effect of caffeic acid on alpha1A-adrenoceptors to increase glucose uptake into cultured C2C12 cells

In an attempt to understand the antihyperglycemic action of caffeic acid, the myoblast C2C12 cells were employed to investigate the glucose uptake in the present study. Caffeic acid enhanced the uptake of radioactive glucose into C2C12 cells in a concentration-dependent manner. Similar effect of phenylephrine on the uptake of radioactive glucose was also observed in C2C12 cells. Prazosin attenuated the action of caffeic acid in a way parallel to the blockade of phenylephrine. Effect of caffeic acid on alpha1-adrenoceptors was further supported by the displacement of [3H]prazosin binding in C2C12 cells. Moreover, the glucose uptake-increasing action of phenylephrine in C2C12 cells was inhibited by the antagonists of alpha1A-adrenoceptors, both tamsulosin and WB 4101, but not by the antagonist of alpha1B-adrenoceptors, chlorethylclonidine (CEC). The presence of alpha1A-adrenoceptors in C2C12 cells can thus be considered. Similar inhibition of the action of caffeic acid was also obtained in C2C12 cells co-incubating these antagonists. An activation of alpha1A-adrenoceptors seems responsible for the action of caffeic acid in C2C12 cells. In the presence of U73312, the specific inhibitor of phospholipase C, caffeic acid-stimulated uptake of radioactive glucose into C2C12 cells was reduced in a concentration-dependent manner and it was not affected by U73343, the negative control of U73312. Moreover, chelerythrine and GF 109203X diminished the action of caffeic acid at concentrations sufficient to inhibit protein kinase C. Therefore, the obtained data suggest that an activation of alpha1A-adrenoceptors in C2C12 cells by caffeic acid may increase the glucose uptake via phospholipase C-protein kinase C pathway.

Decrease of adenosine A-1 receptor gene expression in cerebral cortex of aged rats

Changes of adenosine A-1 receptor (A1-AR) gene expression in aging were investigated in cerebral cortex using the rat aged from 2 months (adult) to 24 months (aged). Quantification of A1-AR protein level by immunoblotting analysis showed an age-related decrease of A1-AR in cerebral cortex of Wistar rats. Compared to the preparations from 2-month-old animals, the levels of A1-AR in the 6-, 12-, and 24-month-old rats were reduced by 14.3+/-5.2, 32.5+/-4.5 and 28.2+/-5.7%, respectively. Similar decrease of mRNA level in A1-AR was also obtained using Northern blotting analysis. Two representative spots of mRNA, a 3.4-kb transcript and a 5.6-kb transcript, were observed in X-ray film from cerebral cortex of rat hybridized with rat A1-AR cDNA probe. Compared to the 2 month-old rats, levels of the 5.6-kb transcript were decreased by 17.9+/-2.5, 27.4+/-3.2 and 23.1+/-2.1% in the 6-, 12- and 24-month-old rats, respectively. These results indicated an age-related decrease of A1-AR in cerebral cortex of the rat that seems responsible for the change of response to adenosine.

Less of insulin desensitization in sympathetic nerve terminals from wistar rats with insulin resistance

In an attempt to determine the effect of hyperinsulinemia on sympathetic function, release of norepinephrine (NE) from isolated aorta by insulin was measured in Wistar rats with insulin resistance. Insulin resistance was produced when the hypoglycemic action of glibenclamide at a dose of 10 mg/kg was almost abolished in rats that received daily injections of long-acting insulin for 15 days. Moreover, the stimulatory effect of insulin on glucose uptake was markedly reduced in both skeletal muscle strips and white adipocytes obtained from these rats with insulin resistance. However, the stimulatory effects of insulin at concentrations from 5 to 15 U/l on the release of NE from the aortic strip of insulin-resistant rats were not modified in the same manner but only slightly reduced compared with that of normal rats. These results suggest that insulin desensitization was produced later in sympathetic nerve terminals than in other organs in insulin-resistant rats and this may be helpful to explain the sympathetic hyperactivity associated with diabetes in clinics.

Stimulatory effect of trans-cinnamaldehyde on noradrenaline secretion in guinea-pig ileum myenteric nerve terminals

The effect of trans-cinnamaldehyde (CNMA) on the release of noradrenaline (NA) from nerve terminal was investigated using isolated ileal synaptosomes of guinea-pig. Release was determined as the amount of NA, quantified by h.p.l.c.-electrochemical detection, from samples incubated with CNMA minus that in parallel blanks treated with same volume of vehicle. CNMA stimulated the secretion of NA in a concentration-dependent manner from 5 microM to 50 microM, while the value of lactate dehydrogenase in the incubated medium was not influenced by CNMA. However, trans-cinnamic acid, cinnamoyl chloride and cinnamamide failed to produce similar effect. Specific action of CNMA can thus be considered. Guanethidine inhibited the release of NA by CNMA in a concentration- dependent manner. Saxitoxin attenuated the action of CNMA at concentrations sufficient to block sodium channels. The depolarizing effect of CNMA on the membrane potential was also illustrated by a concentration-dependent increase in the fluorescence of bisoxonol, a potential sensitive dye. The NA releasing action of CNMA was deleted by removal of calcium chloride from the bathing medium. This action of CNMA was also attenuated by Rp-cAMP at concentrations sufficient to inhibit the action of cyclic AMP. These findings suggest that CNMA can depolarize the membrane to result in a calcium-dependent and cyclic AMP-related release of NA from noradrenergic terminals.

In vitro activity of quinupristin/dalfopristin and other antibiotics against ampicillin-resistant enterococcus faecium

BACKGROUND

Enterococcus faecium constitutes approximately 10% of clinical isolates of enterococci and is noted for its antimicrobial resistance. In particular, E faecium is commonly resistant to ampicillin. The optimal treatment for severe infections caused by these multi-resistant organisms has yet to be determined.

METHODS

Enterococci tested were isolated from blood, pleural fluid and cerebrospinal fluid. Ampicillin-resistant Enterococcus faecium (AREF) was identified using the API Rapid Strep Kit system. A total of 58 isolates of AREF were enrolled in this study. Ten different antibiotics were tested, including Synercid (quinupristin/dalfopristin), teicoplanin, vancomycin, ampicillin, trimethoprim/sulfamethoxazole (TMP/SMX), ciprofloxacin, gentamicin, chloramphenicol, rifampicin and tetracycline. The agar dilution method described by the National Committee for Clinical Laboratory Standards was used to determine the minimum inhibitory concentrations (MICs) of the antibiotics tested.

RESULTS

Teicoplanin showed the best in vitro activity. Its MIC ranged from 0.25 to 2 micrograms/ml with an MIC90 of 1 microgram/ml. The MIC of vancomycin was 0.5-128 micrograms/ml with an MIC90 of 2 micrograms/ml. Three strains were vancomycin resistant, and they were the VanB phenotype. The MIC of quinupristin/dalfopristin was 0.5 to 8 micrograms/ml with an MIC90 of 2 micrograms/ml. Chloramphenicol and tetracycline showed moderate susceptibility. AREF showed high resistance to other antibiotics tested, including ciprofloxacin, gentamicin, TMP/SMX and rifampicin. High-level gentamicin resistance (MIC > 1,000 micrograms/ml) was found in 78% of AREF tested.

CONCLUSIONS

Teicoplanin showed the best in vitro activity against AREF. Clinical studies are necessary to confirm the efficacy of quinupristin/dalfopristin in vivo.

Role of adenosine in insulin-stimulated release of leptin from isolated white adipocytes of Wistar rats

Leptin, the ob gene product that can decrease caloric intake and increase energy expenditure, is functionally released by insulin from adipose tissue. Adenosine is thought to be an important regulator of the action of insulin in adipose tissue. The present study investigated the role of adenosine in the release of leptin by insulin in isolated rat white adipocytes. Release of leptin, measured by radioimmunoassay, from insulin-stimulated samples was seen after 30 min. Adenosine deaminase, at concentrations sufficient to metabolize endogenous adenosine, decreased insulin-stimulated leptin release. Also, the insulin-stimulated leptin release was completely blocked by the adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX). Mediation of endogenous adenosine in this action of insulin was further supported by the assay of adenosine released into the medium from adipocytes stimulated with insulin. In addition, activation of adenosine A1 receptors by N6-cyclopentyladenosine (CPA) induced an increase in leptin release in a concentration-dependent manner that could be blocked by antagonists, either DPCPX or 8-(p-sulfophenyl)theophylline (8-SPT). In the presence of U73312, a specific inhibitor of phospholipase C (PLC), CPA-stimulated leptin secretion from adipocytes was reduced in a concentration-dependent manner, but it was not affected by U73343, the negative control for U73312. Moreover, chelerythrine and GF 109203X diminished the CPA-stimulated leptin secretion at concentrations sufficient to inhibit protein kinase C (PKC). These results suggest that, in isolated white adipocytes, the released adenosine acts as a helper and/or a positive regulator for insulin in the release of leptin via an activation of adenosine A1 receptors that involves the PLC-PKC pathway.

Isoferulic acid as active principle from the rhizoma of Cimicifuga dahurica to lower plasma glucose in diabetic rats

Isoferulic acid extracted from the rhizome of Cimicifuga dahurica Maxim. (Ranunculaceae) has been determined to have in vivo antihyperglycemic activity. An antihyperglycemic action of isoferulic acid in spontaneously diabetic rats, similar to type I diabetes, is presented.

Changes of superoxide dismutase gene expression and activity in the brain of streptozotocin-induced diabetic rats

In an attempt to discover the changes of superoxide dismutase (SOD) in the brain of diabetic state, we investigated the level of SOD in streptozotocin-induced diabetic rats (STZ-diabetic rats) using enzyme activity assay, Northern blotting analysis of mRNA levels and Western blotting of enzyme amount. Five discrete brain regions, cerebrocortex, hypothalamus, hippocampus, the remaining non-cortex cerebrum (NCC area) and cerebellum, were examined in STZ-diabetic rats to compare with age-matched normal rats. Higher levels of Mn-SOD including the activity, mRNA expression and immunoblot of enzyme were found in all areas of the brain from STZ-diabetic rats as compared with that in Wistar rats. Except in the cerebellum, similar changes of Cu,Zn-SOD were found in the brain of STZ-diabetic rats. These results indicate an increase of SOD both gene expression and activity in the brain of STZ-diabetic rats. This alteration of SOD may be one of the important factors for the vulnerability of the brain to oxygen free radicals or may be related to the pathophysiology of diabetes.

Modeling a categorical variable allowing arbitrarily many category choices

This article discusses the modeling of a categorical variable for which subjects can select any number of categories. For c categories, the response variable consists of a cross-classification of c binary components, one pertaining to each category. Using data from a survey (Loughin, T. M. and Scherer, P. N., 1998, Biometrics, 54, 630 637) in which Kansas farmers indicated their primary sources of veterinary information, we discuss simultaneous logit modeling of the binary components of the multivariate response. The use of maximum likelihood or quasi-likelihood fitting provides chi-squared tests with degrees of freedom df = c(r - 1) for testing the independence between each of the c response components and an explanatory variable with r categories. These tests are alternatives to the weighted chi-squared test and the bootstrap test proposed by Loughin and Scherer for this hypothesis.

Investigations of the mechanism of the reduction of plasma glucose by cold-stress in streptozotocin-induced diabetic rats

Exposure to a cold environment may increase the activity of the sympathetic nervous system inducing an elevation of plasma norepinephrine and may result in hyperglycemia. In the present study, we found that a hypoglycemic effect was produced in streptozotocin-induced diabetic rats after cold-exposure at 4 degrees C for 1 h. In addition to the blockade of this hypoglycemic effect by guanethidine (a ganglion-blocking agent) and prazosin (an alpha1-adrenoceptor antagonist), an increase of plasma norepinephrine was also observed in streptozotocin-induced diabetic rats receiving this cold-stress. Participation of sympathetic hyperactivity can thus be considered. Furthermore, naloxone, in a dose (0.5 mg/kg, i.p.) sufficient to block opioid receptors, reversed this hypoglycemia. Also, an increase of plasma beta-endorphin-like immunoreactivity was observed in streptozotocin-induced diabetic rats receiving this cold-stress. Intravenous injection of beta-endorphin into streptozotocin-induced diabetic rats produced a lowering of plasma glucose. Administration of methoxamine at a dose sufficient to activate the alpha1-adrenoceptors produced hypoglycemia and a similar increase of plasma beta-endorphin-like immunoreactivity in streptozotocin-induced diabetic rats. However, plasma beta-endorphin-like immunoreactivity level was not modified by similar treatment with methoxamine or cold-stress in normoglycemic rats. Therefore, beta-endorphin appears to be responsible for the induction of hypoglycemic effects in streptozotocin-induced diabetic rats after cold exposure which is different to the response in normal rats.

Activation of opioid mu-receptor by loperamide to lower plasma glucose in streptozotocin-induced diabetic rats

We investigated the effect of loperamide, a selective agonist of opioid mu-receptor, on the plasma glucose in diabetic rats induced by an intravenous injection of streptozotocin (STZ; 60 mg/kg). Intravenous injection of loperamide induced a dose-dependent decrease of plasma glucose in fasting STZ-diabetic rats at 30 min later, but did not modify the plasma glucose level in Wistar rats. Plasma glucose lowering effect of loperamide was abolished by the pretreatment with naloxone or naloxonazine at the dose sufficient to block opioid mu-receptor. In isolated skeletal muscle, loperamide enhanced the glucose uptake into soleus muscles in a concentration-dependent manner. Blockade of this action by naloxonazine indicated the mediation of opioid mu-receptor. These results suggest that an activation of opioid mu-receptor by loperamide can increase the utilization of glucose in peripheral tissue to lower the plasma glucose in STZ-diabetic rats.

In vitro activities of macrolides against gram-positive aerobes, Haemophilus influenzae, Moraxella catarrhalis and Bacteroides fragilis in Taiwan

BACKGROUND

New macrolides with improved pharmacokinetic characteristics have been developed and introduced for clinical use in Taiwan. In order to understand the antibacterial activities of these new macrolides, we tested their in vitro activities against common pathogenic bacteria.

METHODS

Minimum inhibitory concentrations (MICs) of azithromycin, clarithromycin, dirithromycin, erythromycin and roxithromycin for clinical isolates collected from six teaching hospitals in Taiwan were determined by the agar dilution method. The tested bacteria included methicillin-sensitive and -resistant coagulase-negative staphylococci, methicillin-sensitive and -resistant Staphylococcus aureus, viridans streptococci, Streptococcus pneumoniae, Streptococcus pyogenes, Enterococcus spp, Corynebacterium spp, Haemophilus influenzae, Moraxella catarrhalis and Bacteroides fragilis.

RESULTS

High MICs were detected against most of the bacteria tested except for H influenzae and M catarrhalis. The MIC90 for viridans streptococci, S pneumoniae, S pyogenes, Enterococcus spp, S aureus (both methicillin-sensitive and -resistant), coagulase-negative staphylococci (both methicillin-sensitive and -resistant), Coryne-bacterium spp, and B fragilis were all at least 128 micrograms/ml. Wide ranges of MICs were demonstrated.

CONCLUSIONS

Most bacteria tested were highly resistant to macrolides. This result is a warning for clinicians that rational use of antibiotics, including macrolides, is mandatory.

An insulin-dependent hypoglycaemia induced by electroacupuncture at the Zhongwan (CV12) acupoint in diabetic rats

Acupuncture at the Zhongwan acupoint has been widely used in traditional Chinese medicine to relieve symptoms of diabetes mellitus. Our study investigated the effect on plasma glucose of electroacupuncture applied at the Zhongwan acupoint in rat diabetic models. Plasma concentrations of insulin, glucagon and beta-endorphin- were also determined using radioimmunoassay. A decrease in plasma glucose was observed in rats after electroacupuncture (15 Hz, 10 mA) for 30 min at the Zhongwan acupoint. This was observed in normal rats and rat models with Type II (non-insulin-dependent) diabetes mellitus. No significant effect on plasma glucose was observed in rat models with Type I (insulin-dependent) diabetes mellitus: neither the streptozotocin (STZ)-induced diabetic rats nor the genetic (BB/W) rats. Further, the hypoglycaemic action of electroacupuncture stimulation disappeared in rats with insulin-resistance induced by an injection of human long-acting insulin repeated daily to cause the loss of tolbutamide-induced hypoglycaemia. An insulin-related action can thus be hypothesised. This hypothesis is supported by an increase in plasma insulin-like immunoreactivity after electroacupuncture stimulation in normal rats. Participation of glucagon was ruled out because there was no change in plasma glucagon-like immunoreactivity resulting from electroacupuncture stimulation. In addition to an increase in plasma beta-endorphin-like immunoreactivity, the plasma glucose lowering action of electroacupuncture stimulation at Zhongwan acupoint was abolished by naloxone in a sufficient dose to block opioid receptors. Thus we suggest that electroacupuncture stimulation at the Zhongwan acupoint induces secretion of endogenous beta-endorphin which reduces plasma glucose concentration in an insulin-dependent manner.

Sympathetic hyperactivity in Wistar rats with insulin-resistance

In an attempt to know the effect of sustained hyperinsulinemia on sympathetic function, plasma norepinephrine (NE) and glucose levels were measured in Wistar rats with insulin resistance. Both the basal plasma glucose and the plasma NE levels in insulin-resistant rats were markedly higher than that obtained in normal or streptozotocin (STZ)-induced diabetic rats. Treatment with guanethidine and prazosin reversed these sympathetic hyperactive responses in insulin-resistant rats. Moreover, increase of plasma insulin in rats receiving an intraperitoneal glucose challenge test confirmed the mediation of endogenous insulin in this sympathetic hyperactivity. These results suggest an increase of sympathetic activity in insulin-resistant state that may be related to the hypertension-prone associated with diabetes mellitus in clinics.

Activity of cefepime compared with other antibiotics against gram-positive bacteria and cefuroxime-resistant gram-negative bacteria

BACKGROUND

Cefepime is a new, parenteral, fourth-generation antibiotic that is stable in the presence of Bush group 1 beta-lactamases. In vitro activity of cefepime, cefuroxime, ceftazidime, ciprofloxacin and imipenem against Gram-positive cocci and cefuroxime-resistant Gram-negative bacilli was studied.

METHODS

The agar dilution method described by the US National Committee for Clinical Laboratory Standards was used to determine the minimum inhibitory concentrations of antibiotics tested. These included cefepime, cefuroxime, ceftazidime, ciprofloxacin and imipenem. The tested clinical isolates included Gram-positive cocci (methicillin-sensitive coagulase-negative staphylococci, methicillin-resistant coagulase-negative staphylococci, methicillin-sensitive Staphylococcus aureus, methicillin-resistant S aureus, Streptococcus pyogenes, viridans streptococci, Streptococcus pneumoniae, group D enterococci) and cefuroxime-resistant Gram-negative bacilli (Escherichia coli, Klebsiella pneumoniae, Acinetobacter spp, Pseudomonas aeruginosa, Enterobacter cloacae, Serratia marcescens, Burkholderia cepacia and Xanthomonas maltophilia).

RESULTS

The activity of cefepime against most Gram-negative bacilli other than B cepacia and X maltophilia is better than that of ceftazidime. However, cefepime is less active against these Gram-negative bacilli than ciprofloxacin and imipenem. The activity of cefepime against B cepacia and X maltophilia is less than that of ceftazidime or ciprofloxacin. Among Gram-positive cocci, cefepime was active against most isolates of methicillin-sensitive staphylococci, S pyogenes, viridans streptococci and S pneumoniae. However, cefepime has poor activity against methicillin-resistant S aureus and enterococci.

CONCLUSIONS

Due to its extended spectrum of activity, cefepime has potential use as suitable empiric monotherapy for the treatment of a variety of community- and hospital-acquired infections.

Mantel-Haenszel-type inference for cumulative odds ratios with a stratified ordinal response

This article proposes a Mantel-Haenszel-type estimator of an assumed common cumulative odds ratio in a proportional odds model for an ordinal response with several 2 x c contingency tables. It is useful, for instance, for comparing two treatments on an ordinal response for data from several centers when the data are highly sparse. The estimator has behavior similar to the Mantel-Haenszel estimator of a common odds ratio for several 2 x 2 tables. It is consistent under the ordinary asymptotic framework in which the number of tables is fixed and, unlike the maximum likelihood (ML) estimator, also under sparse asymptotics in which the number of tables grows with the sample size. Simulations reveal a considerable difference between it and the ML estimator when each table has few observations. Efficiency comparisons suggest that little efficiency loss occurs compared to the ML estimator when the data are not sparse. Tests and estimators are presented for detecting and handling heterogeneity in the odds ratios, and generalizations are available for stratified r x c contingency tables.

Encoding operation and transcoding as the major loci of the frequency effect

The present study used a lexical naming task as well as a regular naming task and a lexical decision task for locating the frequency effects in lexical decision and naming. The naming of Chinese characters in the lexical naming task (pseudocharacters also presented as in the lexical decision task) involves decision processes, while they are absent in the regular naming task. Since naming a Chinese character necessarily involves lexical access, a decision component of the frequency effect in lexical decision can be isolated. This procedure will not work for alphabetic orthographies, because sublexical processes underestimate the frequency effect in the regular naming task. As a consequence, not only can a prelexical component of the frequency effect in lexical decision be estimated, but a postlexical component of the frequency effect in naming can be estimated.

Enterococcal meningitis: analysis of twelve cases

From 1986 to 1993, 12 cases of enterococcal meningitis were identified at the Veterans General Hospital, Taipei. Most of the cases were caused by Enterococcus faecalis and three cases were mixed bacterial meningitis. There were six adult and six pediatric patients. Among the adult patients, four had undergone neurosurgical procedures before onset of meningitis and the other two had severe chronic underlying diseases. In contrast, all six pediatric patients had underlying central nervous system (CNS) pathology such as meningomyelocele or hydrocephalus. Placement of CNS devices was the most important predisposing factor of enterococcal meningitis in this study series. Direct microbial invasion via CNS devices or neural tube defects was considered the most likely portal of entry in most patients. Only one patient had primary meningitis, and one other had an enterococcal infection outside the CNS. The overall mortality rate was 25%. None of the pediatric patients died. Underlying conditions were considered the most important factor influencing the prognosis of these patients.

Xanthomonas maltophilia bacteremia: an analysis of 32 cases

Thirty-two cases of Xanthomonas maltophilia bacteremia have been identified over the last two years at the Veterans General Hospital, Taipei. Among them, 27 cases (84%) were due to hospital-acquired infections, and 14 cases (44%) were polymicrobial bacteremia. One case was confirmed as prosthetic valve endocarditis and one case was complicated by recurrent attacks of ecthyma gangrenosum. Most cases had severe debilitating conditions. Twelve cases (38%) had a malignancy, 19 cases (59%) were resident in the Intensive Care Unit and 16 cases (50%) had undergone major surgery. The main predisposing factors included central venous catheterization, endotracheal intubation or tracheostomy, prior antibiotic therapy and prolonged hospitalization. Moxalactam, chloramphenicol and trimethoprim-sulfamethoxazole were the most effective agents in vitro against X. maltophilia. Twenty-two cases (69%) died during hospitalization; 13 cases (41%) were directly attributed to septicemia. Factors that adversely influenced mortality included inappropriate antimicrobial therapy and prior antibiotic treatment. Of particular interest is the fact that none of the patients who did not receive appropriate antimicrobial therapy survived. Early diagnosis and appropriate antibiotic therapy are critical for improving the prognosis of X. maltophilia infection.

The long-term modality effect: in search of differences in processing logographs and alphabetic words

The visual superiority effect (a reverse long-term modality effect) has been consistently found with Chinese logographs. For its explanation in terms of script differences, it has been believed that lexical access is more direct or quicker for Chinese logographs than for alphabetic words. It has also been believed that Chinese logographs are more unique in shape or more discriminable than alphabetic words. Finally, Chinese logographs have been considered to facilitate recall through their graphic features that classify Chinese words into categories. The results of Experiments 1-5 show that these three assumptions can be ruled out. The results of Experiments 6-10, on the other hand, support the long-term priming interpretation of the visual superiority effect, which explains (a) why the visual superiority effect can be consistently obtained for recall of Chinese words by Chinese subjects, (b) why the effect cannot be consistently obtained for recall of English words by Western subjects, (c) why the effect can be also obtained for recall of English words by Chinese subjects, (d) why the effect can be easily obtained for recall of a set of words, but not for recall of a different set of words by Chinese subjects, and (e) why the effect can be easily obtained from Chinese subjects speaking a dialect that is different from Mandarin.

Long-term effects of porcine zonae pellucidae immunocontraception on ovarian function in feral horses (Equus caballus)

Ten feral mares free-roaming in Maryland, USA, were inoculated with porcine zonae pellucidae (PZP) protein before the breeding season for three consecutive years (1988-90). Ovarian function was monitored for 51 days during the peak of the breeding season after the third annual PZP inoculation, in seven of these mares and in four untreated control mares, by means of urinary oestrone conjugates and nonspecific progesterone metabolites. None of the ten inoculated mares became pregnant in 1990, compared with 55% of 20 control mares, which included two of the four monitored for ovarian function. Three of the untreated mares demonstrated apparent normal ovarian activity, characterized by preovulatory oestrogen peaks, concurrent progesterone nadirs at ovulation, breeding activity, and luteal-phase progesterone increases after ovulation. Two of the seven monitored PZP-treated mares demonstrated ovulatory cycles that did not result in conception. One was pregnant as a result of conception in 1989 and demonstrated a normal, late-gestation, endocrine profile. The remaining four PZP-treated mares revealed no evidence of ovulation, and urinary oestrogen concentrations were significantly depressed. The experiments indicated that (i) a third consecutive annual PZP booster inoculation is greater than 90% effective in preventing pregnancies in mares and (ii) three consecutive years of PZP treatment may interfere with normal ovarian function as shown by markedly depressed oestrogen secretion.

Non-0:1 Vibrio cholerae bacteremia: a case report and literature review

We reported a case of non-0:1 group Vibrio cholerae septicemia with myelodysplatic syndrome in Taiwan. We also reviewed the other 22 reported cases of non-0:1 Vibrion cholerae septicemia found in the literature regarding its pathogenesis and treatment. The case mortality rate of these 23 cases was 47.8%. Most of them had immunocompromised diseases, particularly liver cirrhosis and hematologic malignancy. Therefore, the most important factor is the host defense. The cholera-like enterotoxin and E1-Tor-like hemolysin also play a major role, but whether the gall bladder plays a role in organ growth is still unclear. The incidence of gastroenteritis is not well understood because of the low incidence of non-0:1 V. cholerae gastroenteritis as compared with other factors such as shell-fish eating. Ampicillin as the sole antibiotic for non-0:1 V. cholerae is not efficacious. Tetracyclines or chloramphenicol is more effective for treatment.