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.

Activation of beta3-adrenoceptors by exogenous dopamine to lower glucose uptake into rat adipocytes

The effect of dopamine hydrochloride on beta3-adrenoceptors was studied in isolated adipocytes of Wistar rats using uptake of [14C]-deoxy-D-glucose (2-DG) as the indicator. Dopamine induced a concentration-dependent decrease of 2-DG uptake into adipocytes in a manner which was not modified by haloperidol at concentrations sufficient to block dopaminergic receptors. Failure of blockade was also observed in samples receiving the pretreatment with a mixture of SCH23390 and domperidone, the dopaminergic antagonists. Absence of dopaminergic receptors in rat white adipocytes was further supported by the findings that dopaminergic agonists did not modify the glucose uptake and the negative response to receptor antibodies in immunoblotting analysis. Pindolol and propranolol reversed this inhibition of dopamine in a concentration-dependent manner. However, this action of dopamine was not affected by prazosin at concentrations sufficient to block alpha-adrenoceptors. Effect of dopamine was reduced in the presence of Rp-cyclic AMPS triethylamine, the membrane-permeable antagonist of cyclic AMP (cAMP), indicating the mediation of cAMP in this inhibition. Direct effect of exogenous dopamine on beta3-adrenoceptors was identified using the antibody for beta3-adrenoceptors that reversed the inhibition of dopamine. These results suggest that dopamine can activate beta3-adrenoceptors to lower glucose uptake into rat white adipocytes which lack dopaminergic receptors.

Gene transfer via pollen-tube pathway for anti-fusarium wilt in watermelon

In order to obtain transgenic fusarium wilt resistant watermelon plants, squash DNA was introduced into the ovaries of watermelon plants via the pollen-tube pathway. The introduction of foreign genes into ovaries was accomplished using co-transformation with the CaMV35S-GUS as a marker. Transformed watermelon plants contained integrated copies of the GUS activity and the seeds of transformed progeny produced a blue color when stained with 5-bromo-4-chloro-3-indolyl glucuronide, whereas seeds from untransformed control plants did not. Of 200 transformed seedlings, ten were wilt resistant. The presence of the GUS activity in the genome of stable transgenic seedlings was confirmed by Southern blot analysis. Furthermore, the generation of random amplified polymorphic DNA (RAPD) fingerprints using primers with embedded restriction sites showed amplification products unique to these transgenic plants. Primers OPA-1 and OPA-9 gave distinct band patterns of genomic DNA using the polymerase chain reaction.

Hepatitis C viral infection is associated with fibrillary glomerulonephritis and immunotactoid glomerulopathy

The most common form of glomerular disease seen in association with hepatitis C virus (HCV) infection is membranoproliferative glomerulonephritis, with or without associated cryoglobulinemia. This study examines four cases of fibrillary glomerulonephritis and two cases of immunotactoid glomerulopathy in association with HCV infection. Findings at presentation included proteinuria, renal insufficiency, and hematuria. Renal biopsy revealed a membranoproliferative pattern of glomerular disease in five cases, and a membranous glomerulopathy with mesangial proliferative features in one. On immunofluorescence, all cases stained with IgG and C3. Electron microscopy revealed fibrils of the expected diameter, 16 to 28 nm in fibrillary glomerulonephritis and 33 to 45 nm in immunotactoid glomerulopathy. In only one case were cryoglobulins detected (at low titer and on only one of three assays). Antiviral therapy was not given in any of the six cases. Outcomes were mixed, with progression to renal failure occurring in two patients and persistent proteinuria with stable or improved renal function in three. Follow-up is not available on the sixth case. Both fibrillary glomerulonephritis and immunotactoid glomerulopathy have features that overlap with cryoglobulinemic glomerulonephritis. The relatedness of these three entities in a subset of patients with HCV infection suggests a common pathogenic mechanism of glomerular deposition of organized deposits.

The effect of stevioside on blood pressure and plasma catecholamines in spontaneously hypertensive rats

Stevioside is a sweet-tasting glycoside, composed of stevia, a diterpenic carboxylic alcohol with three glucose molecules, mainly used as a substitute for non-alcoholic sweetener. It has previously been shown to reduce blood pressure in studies in animals and human. The effect of intravenous stevioside on the blood pressure was studied in spontaneously hypertensive rats (SHR). The hypotensive effect on both systolic and diastolic blood pressure was dose-dependent for intravenous doses of 50, 100 and 200 mg/kg in conscious SHR. The maximum reductions in systolic and diastolic blood pressure were 31.4 +/- 4.2% and 40.8 +/- 5.6% (mean +/- SEM) respectively and the hypotensive effect lasted for more than 60 min with a dose of 200 mg/kg. Serum dopamine, norepinephrine and epinephrine levels were not changed significantly 60 min after intravenous injection of stevioside 100 mg/kg in anesthetized SHR. The present data show that stevioside given intravenously to conscious SHR was effective in blood pressure reduction and there was no change in serum catecholamines in anaesthetized animals with this natural compound.

An ex vivo evaluation of regulatory role of biogenic amines in rat seminal vesicle after pharmacological manipulation

We studied the neural regulation of seminal vesicles (SV) by determining the changes of intraluminal pressure of rat SV in response to an electric stimulation of the lesser splanchnic nerve (LSN). After pharmacological manipulation with neurotoxin, the contents of monoamines and their metabolites in SV were estimated. In rats receiving electric stimulation of the LSN, an increase of intraluminal pressure was obtained with a reduction of the serotonergic turnover rate in SV. An intraperitoneal injection of DSP-4 (100 mg/kg), the noradrenergic neurotoxin, into rats decreased the level of norepinephrine (NE) in SV significantly but did not influence this functional response. Also, the intraluminal pressure was lowered by an intrathecal injection of 6-OHDA (20 microg/rat) to denervate spinal monoaminergic nerves in rats although the contents of monoamines in SV were not changed. This indicates that noradrenergic neurotransmission appears unimportant in this regulation. The lowering of intraluminal pressure in rats by 6-OHDA is mainly related to an attenuation of dopaminergic neuroregulation from the decrease of turnover rate of DA. Otherwise, an intrathecal injection of 5,7-DHT (60 microg/rat) to abolish spinal serotonergic nerves did not influence the level of monoamines in SV but increased the intraluminal pressure indicating an involvement of inhibitory regulation from spinal serotonergic pathway. These results suggest that contraction by electric stimulation of the LSN in Wistar rat SV is mainly regulated by the dopaminergic nervous pathway and an inhibitory regulation of the serotonergic nervous pathway from spinal cord while the noradrenergic nervous system seems unimportant for this regulation.

Inhibition of protein kinase C translocation from cytosol to membrane by chelerythrine

Protein kinase C (PKC) is regarded as an important signal in cellular responses. Chelerythrine, the alkaloid in Zanthoxylum simulans, was recently introduced as a specific blocker of PKC phosphorylation. The present study demonstrated an inhibitory effect of chelerythrine on the translocation of PKC from cytosol to membrane using Western blotting analysis. An increase of PKC translocation from cytosol to the membrane was observed in isolated ileal synaptosomes incubated with phorbol 12-myristate 13-acetate (PMA) to reach the plateau at 30 min later. Pretreatment with chelerythrine for 20 min attenuated this action of PMA in a concentration-dependent manner and the inhibition of PKC alpha translocation was similar to that of PKC beta. An inhibitory effect of chelerythrine on the translocation of PKC is considered in addition to the inhibition of PKC phosphorylation.

Serum endothelin and atrial natriuretic peptide in cirrhotic patients with ascites and hepatorenal syndrome

BACKGROUND

The pathogenesis of cirrhotic ascites and hepatorenal syndrome remains unresolved. The involvement of both endothelin-1 and atrial natriuretic peptide have recently been suggested. This study investigated the concentrations of serum endothelin and atrial natriuretic peptide in cirrhotic patients.

METHODS

Seven healthy subjects and 31 cirrhotic patients were studied. Cirrhotic patients were divided into three groups: Group I, 16 cirrhotic patients without ascites; Group II, 10 cirrhotic patients with ascites, but without hepatorenal syndrome; and Group III, five cirrhotic patients with hepatorenal syndrome and ascites. Their sera were analyzed for endothelin-1 and atrial natriuretic peptide concentrations.

RESULTS

Cirrhotic patients with ascites, Group II and Group III, had higher plasma endothelin-1 concentrations (15.9 +/- 2.3 pg/ml and 24 +/- 2.1 pg/ml, respectively) than normal subjects and compensated cirrhotics (3.8 +/- 0.7 pg/ml and 6.4 +/- 1.1 pg/ml, respectively); p < 0.001). Atrial natriuretic peptide concentrations were also significantly higher in cirrhotic patients than in normal subjects (p < 0.025). Plasma endothelin-1 concentration had a negative correlation with creatinine clearance (r = -0.65, p < 0.001), as did atrial natriuretic peptide concentrations (r = -0.44, p = 0.012). Plasma endothelin-1 correlated significantly with atrial natriuretic peptide concentrations (r = 0.38, p = 0.035).

CONCLUSIONS

Both endothelin-1 and atrial natriuretic peptide concentrations were elevated in cirrhotic patients with ascites and hepatorenal syndrome. Endothelin-1 may have a negative impact on renal function. Our data also suggested that impaired responsiveness rather than impaired secretion of atrial natriuretic peptide is responsible for sodium retention in cirrhotic patients with ascites.

NitroG-L-arginine methyl ester decreases minimum alveolar concentration of isoflurane and reduces brain nitric oxide synthase activity in rats

BACKGROUND

Nitric Oxide (NO), an endogenous messenger produced by the enzyme nitric oxide synthase (NOS), is recently introduced to be involved in inhalational anesthesia. We have previously reported that a specific NOS inhibitor, nitroG-L-arginine methyl ester (L-NAME), reduces the value of minimum alveolar concentration (MAC) for isoflurane anesthesia in rabbits. The purpose of this study is to evaluate the effects of the NOS inhibitor, L-NAME, on isoflurane MAC and NOS activity in rats.

METHODS

Adult Wistar rats receiving isoflurane inhalation were randomly divided into two groups, with eight rats in each group. In the study group, L-NAME 30 mg/kg was given 60 min before the inhalation of isoflurane. Normal saline was given to the control group instead. The data of MAC, blood pressure (BP), and heart rate (HR) were recorded. The vital signs, such as EtCO2, PaO2, and temperature, were maintained within normal ranges. The activity of NOS in cerebellum was assessed by measuring the conversion of L-[3H] arginine to L-[3H] citrulline. All data were presented as mean +/- SD. Statistical analysis was performed using Student's t-test, where P < 0.05 was considered significant.

RESULTS

In the presence of L-NAME (30 mg/kg), the MAC for isoflurane was markedly reduced from 1.6 +/- 0.20% (study group) to 1.0 +/- 0.09% (control group) (P < 0.05). The activity of cNOS in cerebellum was 220.09 +/- 23.64 (pmol/mg protein/30 min) in the control group, and in contrast a sharp reduction as low as to 115.40 +/- 24.85 (pmol/mg protein/30 min) was seen in the study group.

CONCLUSIONS

The involvement of NO in the mechanism of isoflurane anesthesia can be demonstrated by the fact that the NOS inhibitor, L-NAME reduces the level of MAC and the cerebral NOS activity in rats.

In vivo evaluation of serotonergic agents and alpha-adrenergic blockers on premature ejaculation by inhibiting the seminal vesicle pressure response to electrical nerve stimulation

OBJECTIVE

To evaluate the effect of drugs on premature ejaculation using a rat animal model in which the seminal vesicle was electrically stimulated via its lesser splanchnic nerve and changes in the pressure response monitored.

MATERIALS AND METHODS

Male Wistar rats (aged 12-14 weeks) were injected intravenously with prazosin and serotonergic agents (serotonin, clomipramine, fluoxetine, imipramine and indatraline) at various concentrations 10 min before electrical nerve stimulation (ENS) of the lesser splanchnic nerve; the initial increase in seminal vesicle pressure in response to ENS was then compared.

RESULTS

The pressure response to ENS was reduced in the presence of prazosin or serotonergic agents. The mean (SEM) maximum inhibition values were 84.1 (8.9%) by fluoxetine at 0.1 mg/kg, 67.9 (8.7)% by prazosin at 0.1 mg/kg, 60.9 (11.0)% by serotonin at 3 mg/kg, 54.9 (4.6)% by clomipramine at 3 mg/kg, 30.0 (11.0)% by imipramine at 0.1 mg/kg, and 20.9 (4.3)% by indatraline at 0.1 mg/kg. From the concentration-response curve, the potency of prazosin was lower than that of fluoxetine, but was higher than that of serotonin or clomipramine.

CONCLUSIONS

Like serotonin, fluoxetine and clomipramine can reduce the pressure response of the seminal vesicle to ENS. Among these inhibitory agents, including prazosin, fluoxetine was the most effective and may be valuable for the clinical treatment of ejaculatory dysfunction in man.

Renal denervation prevents and reverses hyperinsulinemia-induced hypertension in rats

Experiments were performed to evaluate the role of the renal nerves in hyperinsulinemia-induced hypertension. Male Sprague-Dawley rats were made hyperinsulinemic by insulin infusion via osmotic minipumps implanted subcutaneously (3.0 mU/kg per minute for 6 weeks). Rats with vehicle infusion served as controls. Bilateral renal denervation was performed either at the beginning of or 4 weeks after insulin infusion. The systolic blood pressure was measured by the tail-cuff method twice a week. Food and water intake and urine flow were measured daily. The results showed that sustained insulin infusion significantly increased plasma insulin concentrations from 277.7+/-25.8 pmol/L to 609.9+/-22.2 and 696.7+/-23.0 pmol/L by the end of weeks 4 and 6, respectively (P<0.05). Systolic blood pressure was significantly increased from 135+/-3 to 157+/-3 and 159+/-2 mm Hg (P<0.05) at the corresponding time points. There was a significant increase in the plasma norepinephrine concentration after insulin infusion, whereas no significant changes in plasma triglyceride and glucose concentrations, water intake, urine flow, sodium excretion, sodium gain, and body weight gain were observed. Bilateral renal denervation depleted renal norepinephrine stores and prevented the development of hyperinsulinemia-induced hypertension. After hyperinsulinemia-induced hypertension had been fully established (from 134+/-2 to 157+/-2 mm Hg), bilateral renal denervation reversed the elevated systolic blood pressure to normotensive levels within 2 weeks. Transient denervated diuresis and natriuresis were observed. These results indicate that chronic hyperinsulinemia-induced hypertension requires the presence of intact renal nerves in rats.

Modification of superoxide dismutase (SOD) mRNA and activity by a transient hypoxic stress in cultured glial cells

In order to understand the role of superoxide dismutase (SOD) in response to transient hypoxia or hypoxia-reperfusion in astrocytes, the present study performed an in vitro investigation using rat glial cells in culture. Hypoxia was induced by an incubation with nitrogen gas for 10 min and that followed a further reperfusion with air for 10 min was indicating as hypoxia-normoxia. Activity of SOD was determined by the reduction of nitroblue tetrazolium (NTB). Changes of mRNA for Cu,Zn-SOD or Mn-SOD were also characterized using Northern blotting analysis. Transient hypoxia increased the activity of Mn-SOD but not that of Cu,Zn-SOD in glial cells. Expression of mRNA for SOD was also elevated in cells received hypoxia and the mRNA level for Mn-SOD raised higher than that for Cu,Zn-SOD. In cells received hypoxia-reperfusion, these changes of SOD both the activity and the mRNA level were not observed. Otherwise, the SOD protein amount, both Cu,Zn-SOD and Mn-SOD, identified by Western blotting was not changed in glial cells receiving hypoxic stress or not. The obtained results suggest that gene expression and activity of Mn-SOD in glial cells can be activated in response to the transient hypoxic stress.

Effects of nicotine on spontaneous and amphetamine-induced motor behaviors: the differences between nicotine tolerant and nontolerant rats

This study was designed to investigate the effect of nicotine on spontaneous and amphetamine (AMP)-induced motor activity in rats with or without tolerance to nicotine. Tolerance were induced by treating the rats with nicotine (0.3 mg/kg, s.c.) 2 hr before receiving challenge doses. Motor activity including locomotion and stereotypy was monitored automatically by videocamera every 15 min for 90 min. The results indicated that: (1) Nicotine increased spontaneous locomotion at 0.15 or 0.3 mg/kg (s.c.) in naive rats and at 0.6 mg/kg in tolerant rats. Nicotine also slightly affected AMP-induced locomotion at 0.15, 0.3 or 0.6 mg/kg in both naive and tolerant rats, and (2) Nicotine increased spontaneous stereotypy at 0.3 or 0.6 mg/kg in naive rats only and showed no effect on AMP-induced stereotypy in either naive or tolerant rats. Comparing the results of spontaneous motor activity between naive and tolerant rats, it revealed behavioral desensitization in locomotion at low doses (0.15 or 0.3 mg/kg) and hyperlocomotion at higher dose (0.6 mg/kg), and revealed desensitization in stereotypy at 0.3 or 0.6 mg/kg. Moreover, nicotine had temporary (at 0-15 min interval) attenuating effect on AMP-induced locomotion in naive rats but showed a potentiating effect on AMP-induced locomotion in tolerant rats. The present results indicated that acute tolerance modified the action of nicotine in both spontaneous and AMP-induced locomotion, while stereotypy was changed only in the spontaneous one but not in the AMP-induced one. In other words, acute tolerance modified the effect of nicotine on locomotion-related dopaminergic system, and it affected the stereotypy-related dopaminergic system only in the spontaneous one but not in the AMP-induced one.

Inhibition of immune cell proliferation with haloperidol and relationship of tyrosine hydroxylase expression to immune cell growth

Previous studies indicated that exogenous dopamine and its agonists directly regulated mitogen-induced immune cell proliferation. In this study, we further investigated role of endogenous dopamine in immune cell growth. Haloperidol, a general antagonist for dopamine receptors, could reduce the cell growth rate of T cell hybridoma (10I) and rat nervous pheochromocytoma cells (PC12). Tyrosine hydroxylase (TH) catalyzes the initial rate-limiting step of catecholamine biosynthesis in the nervous system. Flow cytometric analysis indicated the expression of TH in various immune cells. The presence of TH in PC12 cells was used as a control. Temporal studies indicated that the expression of TH increased during 10I cell growth. Both alpha-methyl-p-tyrosine and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine reduced TH expression and cell growth in a dose-dependent manner. These results suggest that immune T cells express TH which is correlated to cell growth, and that dopamine released from these cells may bind to the receptors to act in an autocrine or paracrine way.

Production and characterization of monoclonal antibodies against Tal1 oncoprotein

TAL1 (or SCL) oncogene functions as a transcription regulatory factor that is necessary for the early development of all hematopoietic lineages. Aberrant expression of Tall protein in T cells is the cause of T-cell acute lymphoblastic leukemia (T-ALL) in children. We generated two hybridomas that secreted monoclonal antibodies (MAbs) that reacted strongly with GST-TAL(1-210) but not with GST fusion protein in ELISA assay. These two MAbs, TWN3 and TWN60, recognized TALI oncoprotein expressed in transfected COS-1 cells by Western blotting. In addition, both MAbs were also effective in detecting TAL1 oncoprotein in leukemic cells by immunoprecipitation and immunocytochemistry. Therefore, they should be useful in the studies of Tall protein functions in both hematopoietic development and oncogenesis.

Stimulatory effect of paeoniflorin on adenosine A-1 receptors to increase the translocation of protein kinase C (PKC) and glucose transporter (GLUT 4) in isolated rat white adipocytes

In an attempt to understand the subcellular signals after activation of adenosine A-1 receptors, paeoniflorin was employed to incubate with rat white adipocytes in vitro. Translocation of protein kinase C (PKC) beta-subtype from cytosol to membrane was enhanced by an incubation with paeoniflorin in a concentration-dependent manner similar to that of porcine insulin. Also, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) inhibited this action of paeoniflorin in a concentration-related fashion and it markedly attenuated the action of paeoniflorin at a concentrations sufficient to block the action of adenosine. Moreover, chelerythrine inhibited the paeoniflorin-stimulated translocation of PKC in a way similar to that stimulated by porcine insulin. Subcellular inhibition is considered because stimulation of porcine insulin was not modified by DPCPX at concentrations sufficient to block adenosine A-1 receptors. Similar results were also observed in adipocytes regarding the translocation of glucose transporter (GLUT4) from cytosol to membrane. Thus, we found that paeoniflorin can activate adenosine A-1 receptors to increase the translocations of PKC and GLUT4, two major signals for glucose uptake, from cytosol to membrane of the white adipocytes in rats.

Stimulatory effect of octopamine on beta 3-adrenoceptors to lower the uptake of [14C]-deoxy-D-glucose into rat adipocytes in vitro

1. The effect of octopamine on beta 3-adrenoceptors has been studied in isolated adipocytes of Wistar rats using uptake of [14C]-deoxy-D-glucose as the indicator. 2. Octopamine (0.1-1 nmol 1-1) induced a concentration-dependent decrease of [14C]-deoxy-D-glucose uptake into the adipocytes and this inhibition was not influenced by haloperidol at concentrations sufficient to block dopaminergic receptors. 3. Pindolol and propranolol reversed this inhibition of octopamine in a concentration-dependent manner. The effect of octopamine was reduced in the presence of Rp-cyclic AMPS triethylamine, the membrane-permeable antagonist of cyclic AMP (cAMP), indicating the mediation of cAMP in this inhibition. 4. A direct effect of octopamine on beta 3-adrenoceptors was proved using the application of antibodies. In the presence of an antibody for beta 3-adrenoceptors, the actions of octopamine were concentration-dependently reduced in a manner similar to the decrease of BRL37344-induced inhibitions. 5. The same degree of diminished activities for octopamine as that of BRL37344, the well-known specific agonist of beta 3-adrenoceptors, was also obtained in isoprenline-desensitized adipocytes. Insulin-stimulated uptake of [14C]-deoxy-D-glucose into adipocytes was not modified by isoprenaline induced desensitization. 6. These results suggest that octopamine can activate beta 3-adrenoceptors to lower the glucose uptake through an increase of cAMP in rat white adipocytes.

Effect of dopamine on immune cell proliferation in mice

Dopamine is known as a precursor of catecholamine and one of the neurotransmitters in brain and peripheral tissues. Recent studies suggest an important role of dopamine in immune responses. In the present study, intraperitoneal administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) which lowered endogenous dopamine suppressed splenocyte proliferation in response to mitogens such as lipopolysaccharide (LPS) and concanavalin A (Con A). Moreover, intravenous injection of the specific agonists of dopamine DA-1 receptor (SKF38393) or DA-2 receptor (LY171555) into mice enhanced the splenocyte proliferation stimulated by LPS or Con A. In the in vitro cultures, dopamine, SKF38393 and LY171555 directly promoted cell proliferation to LPS or Con A. These results indicate that dopamine has an ability to regulate B- and T-cell proliferation both in vivo and in vitro.

Reduced vascular beta-adrenergic receptors and catecholamine response in rats with lead induced hypertension

Beta-adrenergic receptor-mediated relaxation of blood vessels declines in lead induced hypertension although the mechanism is unknown. We have utilized the aorta of lead hypertensive rats to investigate this problem. In an effort to elucidate the mechanism responsible for this alteration we examined plasma catecholamine levels, vascular beta-adrenergic receptor density, and cyclic adenosine monophosphate (cAMP) production in lead hypertensive rats. The density of beta-adrenergic receptors was 41% lower in the blood vessels of lead hypertensive rats compared with control rats. The corresponding apparent Kd values were not significantly different between two groups. The plasma catecholamine level was significantly higher in lead hypertensive rats compared with controls (P < 0.001). Stimulation of the vascular beta-adrenoceptor resulted in significantly lower levels of cAMP in lead hypertensive rats compared with controls (P < 0.001). The present results suggest that there is reduced beta-adrenoceptor density and diminished cAMP accumulation in blood vessels from lead hypertensive rats. Plasma catecholamine may play a role in the diminished beta-adrenoceptor and responsiveness to cAMP-mediated vascular relaxation in lead exposure.

The differential transforming activities of Tal1 oncoproteins

TAL1 (Or SCL) oncogene produces both full-length pp42 and truncated pp22 phosphoproteins in T-cell acute lymphoblastic leukemia cells. To investigate the transforming properties of these two oncoproteins, permanent transfected NIH3T3 cell lines were generated that constitutively express either pp42 or pp22. Both cell lines exhibited similar morphology as parental NIH3T3 cells. However, they showed differential anchorage independent growth in soft-agar. The clonogenicity of pp22 expressing cells was ten folds higher than that of pp42 expressing cells. This result might implicate the differential transformation potential of the two Tal1 oncoproteins.

Change of cardiac beta-adrenoceptors in lead-exposed rats

The effect of lead on cardiac beta-adrenoceptors was studied. Wistar rats used in these trials were divided into seven groups of ten animals each (A-G). Of these, groups B was given drinking water containing 0.01% lead acetate, group C 0.05%, group D 0.1%, group E 0.5%, group F 1% and group G 2% for a period of 60 days. Group A was given pure water. A radioligand-binding assay fulfilling strict criteria of receptor affinity and density was used to quantify cardiac beta-adrenoceptors. Application of a trend test indicated that both blood and heart lead levels increased significantly from group A to group G (A < G), but that beta-adrenoceptor density decreased (G < A), whereas Kd did not vary among the seven groups. Linear regression analysis showed that decrease of cardiac beta-adrenergic receptor density was closely related to elevation of blood and heart lead levels. The results show that lead exposure results in a reduction of cardiac beta-adrenoceptor density.

Myocardial protective effect of trilinolein: an antioxidant isolated from the medicinal plant Panax pseudoginseng

In a previous study we demonstrated that trilinolein, a natural plant triacylglycerol, is a novel myocardial protective agent in vivo. The mechanism probably involves an antioxidant effect. This work investigated the mechanism of myocardial protection of trilinolein to determine if inhibition of calcium influx and alteration of activity of superoxide dismutase are involved. In isolated cardiomyocytes, pretreatment with trilinolein at a low concentration of 10(-9) M effectively reduced 45Ca2+ influx stimulated by hypoxia/normoxia by 34%. In isolated perfused rat heart subjected to 60 min global hypoxemia without reperfusion, pretreatment with 10(-7) M trilinolein for 15 min reduced infarct size by 37%. Assay of superoxide dismutase-mRNA by Northern blot analysis in in vivo rat heart subjected to 30 min ischaemia and 10 min reperfusion showed pretreatment with 10(-7) M trilinolein had a synergistic action with antioxidant systems preventing the rise in superoxide dismutase-mRNA. These results reconfirm the myocardial protection of trilinolein and suggest it may be related to antioxidant activity and inhibition of 45Ca2+ influx.

Evidence of adenosine 5'-triphosphate release from nerve and P2x-purinoceptor mediated contraction during electrical stimulation of rat urinary bladder smooth muscle

PURPOSE

We provided direct evidence for the existence of purinergic innervation in the rat urinary bladder.

MATERIALS AND METHODS

The non-adrenergic non-cholinergic (NANC) innervation was studied in 4-month-old Wistar rats. Electric-field stimulation (EFS) of the detrusor muscle strips in the presence of four autonomic blockers (atropine 10(-6) M, guanethidine 10(-6) M, phentolamine 10(-6) M and propranolol 10(-6) M) showed NANC contractions accounted for about 50% of the maximum contractile response. The adenyl purines released from nerves by EFS were detected by HPLC after conversion to ethenopurines. The amount of total purine released was frequency-dependent and could be totally suppressed by tetradotoxin (10(-6) M). The amount of ATP released was significantly greater than those for ADP, AMP and adenosine (p < 0.05, n = 4). Desensitization induced by alpha, beta-MeATP (10(-6) to 10(-4) M), a P2x receptor agonist, reduced the NANC contraction. In addition, the NANC contraction was also abolished by P2 receptor blocker suramin (10(-4) to 10(-3) M) and P2x receptor blocker PPADS (10(-5) to 10(-4) M.).

CONCLUSION

The results of the present study give evidence to support purinergic nerve-mediated bladder smooth muscle contractions in the rat. Among the purine nucleotides, ATP is the dominant purinergic neurotransmitter released and P2x receptor activation is responsible for the NANC contractile response.

Effect of trilinolein on superoxide dismutase activity and left ventricular pressure in isolated rat hearts subjected to hypoxia and normoxic perfusion

Oxygen-derived free radicals have been implicated in the development of myocardial injury during hypoxia/reperfusion. Antioxidants can effectively inhibit the formation of free radicals and ameliorate the myocardial damage which may occur during hypoxia/reperfusion. Trilinolein is a triacylglycerol recently purified from the traditional Chinese medicinal plant Panax pseudo-ginseng. It has linoleic-acid residues as the only type of fatty acid residue in all three esterified positions of the triacyglycerol. It has been proposed that decreased endogenous superoxide dismutase (SOD) activity may contribute to free radical-mediated reperfusion injury of the ischemic myocardium. In the present study, when isolated rat hearts were subjected to hypoxia for 10, 30, 60 and 90 min without normoxic perfusion, a significant decrease in Mn-SOD activity was shown throughout the period of hypoxia, whereas the Cu.Zn-SOD activity was increased at 10 and 30 min but was not different from the baseline at 60 and 90 min of hypoxia. In rat hearts pretreated with 10(-7) mol/l trilinolein and subjected to 60 min of hypoxia without normoxic perfusion, Cu.Zn-SOD was augmented compared with baseline and compared with hearts subjected to 60 min of hypoxia without trilinolein, whereas Mn-SOD activity was still reduced compared with baseline, although less so than after 60 min of hypoxia without trilinolein. Pretreatment with trilinolein was associated with better preservation of left ventricular function during hypoxia and more rapid return to recovery during normoxic perfusion. This myocardial protective effect may be related to an antioxidant effect through potentiation of SOD, particularly Cu.Zn-SOD during hypoxia.