Effects of GABA on spontaneous [Ca]c dynamics and electrical properties of rat adrenal chromaffin cells

A large fraction of rat adrenal chromaffin cells (about 60%) shows spontaneous [Ca²⁺]_c oscillations and spontaneous action potentials. In the present study the effects of γ-aminobutyric acid (GABA) on the spontaneous [Ca²⁺]_c oscillations and electrical properties of rat adrenal chromaffin cells were investigated using Fura-2 [Ca²⁺]_c imaging and patch clamp techniques. GABA inhibited the spontaneous [Ca²⁺]_c oscillations in a reversible manner. The effect of GABA was mimicked by the GABA_A and GABA_C receptor agonist, muscimol, but not by the GABA_B receptor agonist, baclofen. Moreover, the effect was antagonized by the selective GABA_A receptor antagonist, bicuculline. The mode of the inhibition was all-or-none, and the threshold concentration at which the inhibition occurred varied widely (50 μM to over 1 μM) from cell to cell. GABA (100 μM) elicited a transient burst of action potentials of diminished amplitude, which was followed by arrest of action potentials. Further analysis showed that GABA (100 μM) induced inward whole-cell currents in voltage-clamp experiments and produced depolarization and membrane conductance increase in current-clamp experiments. The effects appear to be due to an increase in chloride ion conductance since the degree of GABA-induced depolarization depended on the pipette [Cl⁻]. These results suggest that GABA, acting through GABA_A receptor, may play a role in the physiological regulation of rat adrenal chromaffin cells by directly modifying the discharge of spontaneous action potentials and spontaneous [Ca²⁺]_c oscillations.     

Off-resonance saturation as a means of generating contrast with superparamagnetic nanoparticles.

This work demonstrates an alternative approach, termed off-resonance saturation (ORS), for generating contrast that is sensitive to superparamagnetic particles. This method leads to a calculated contrast that increases with superparamagnetic nanoparticle concentration. Experimental data demonstrate that in the presence of superparamagnetic particles, an off-resonance effect exists that is distinct from the magnetization transfer (MT) effect and is highly dependent on diffusion. Data show that the dependence on water diffusion becomes most significant at rates of 0.5 x 10(-9) m(2)/s and slower. We investigated the dependence of the off-resonance effect on off-resonance frequency and particle concentration. The data suggest a useful frequency offset range of 500 Hz < |Deltaomega| < 1500 Hz at 3T. This approach may be especially useful in organs and diseases in which diffusion may be altered by pathologies.     

Hab18-SPIO磁共振造影剂的制备及其实验研究

目的制备靶向人肝细胞肝癌表面抗原Hab18g的MR特异性抗体显影剂Hab18-SPIO,探讨其合成原理、制备要点及物理性状。方法利用化学交联方法,采用人肝细胞癌单抗Hab18标记SPIO,制作出靶向显影剂Hab18-SPIO。并用同样方法制备阴性抗体显影剂SED-SPIO(SED为葡萄球菌肠毒素D抗体)。使用电镜及高压液相色谱仪(HPLC)对Hab18-SPIO进行测试。结果经电镜观察和液相色谱分析证明Hab18与SPIO有效地结合在一起,通过蛋白质含量测定得到抗体与SPIO的交联率为97.5%。经电镜观察制备的靶向显影剂Hab18-SPIO粒径在50~70 nm之间,并且SPIO中颗粒较小的部分与抗体的交联较多。结论成功构建了靶向人肝细胞肝癌表面抗原Hab18g的探针,该探针具有良好的理化性质,为进一步研究早期肝癌特异性MR诊断提供了有价值的手段。     

Interactive effects of stimulation of D1 and D2 dopamine receptors on Fos expression in the lateral habenula

We have previously shown that systemic administration of non-selective dopamine agonists results in a pronounced expression of the proto-oncoprotein Fos within the lateral habenula. In the current study we examined the effects of selective D1 and D2 dopamine receptor agonists on habenular Fos expression. Rats were injected with various doses of the selective D2 agonist quinpirole (0, 0.62 or 2.5 mg/kg) either alone or in combination with various doses of the selective full D1 agonist A-77636 (0, 0.75 or 3.0 mg/kg). The selective agonists, by themselves, induced only small increases in Fos-like immunoreactivity within the lateral habenula, but combinations of the two drugs resulted in a very robust response. These findings indicate that D1 and D2 receptor agonists interact to induce Fos expression within the habenula and that the nature of this interaction differs from that reported in the striatum and the globus pallidus.     

Comparative effects of metal chelating agents on the neuronal cytotoxicity induced by copper (Cu), iron (Fe) and zinc in the hippocampus

The ability of metal chelating agents to prevent neuronal death caused by intra-hippocampal injections of cupric sulphate, ferric citrate and zinc chloride was investigated. Ammonium tetrathiomolybdate was itself toxic after injection into the hippocampus, but this toxicity was reduced by formation of a metal ion/tetrathiomolybdate complex with Cu⁺². Disodium bathocuproine disulphonate (BCDS) prevented neuronal death caused by Cu⁺², but not that induced by Fe⁺³ or Zn⁺². Desferrioxamine prevented death caused by Fe⁺³, had no significant effect of the toxicity of Zn⁺², and increased that caused by Cu⁺². Even though N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) has a higher affinity for Cu⁺² than for Zn⁺², TPEN had no effect on the toxicity of Cu⁺² while totally preventing damage caused by Fe⁺³ or Zn⁺². Ethylenediaminetetra-acetic acid (EDTA) prevented the toxicity of all three metal ions. Motor seizure activity occurred in most rats after injections of Fe⁺³; or combinations of Cu⁺² plus TPEN, or 4 nmol Fe⁺³ plus 0.1 nmol desferrioxamine. However, apart from the low dose desferrioxamine/Fe⁺³ combination, only the occasional brain contained seizure-induced neuronal loss in limbic regions outside the injected hippocampus, and these brains were not used for analysis. Seizure activity was found even with very low levels of Cu⁺² with a fixed amount of TPEN (a ratio of Cu⁺²/TPEN of 1:100), but the extent of hippocampal damage in these brains was not significantly different to that caused by injections of saline. These studies demonstrate that idiosyncratic interactions can occur between metal ions and chelating agents. Thus further investigations are needed before chelating agents can be examined for their protective properties in various neurodegenerative diseases.     

Acotiamide hydrochloride (Z-338), a novel prokinetic agent, restores delayed gastric emptying and feeding inhibition induced by restraint stress in rats

Abstract  Acotiamide hydrochloride (Z-338) is a member of new class prokinetic agents currently being developed for the treatment of functional dyspepsia (FD). DNA microarray analysis showed that acotiamide altered the expressions of stress-related genes such as γ -aminobutyric acid (GABA) receptors, GABA transporters and neuromedin U (NmU) in the medulla oblongata or hypothalamus after administration of acotiamide. Therefore, effects of acotiamide on stress-related symptoms, delayed gastric emptying and feeding inhibition, in rats were examined. Acotiamide significantly improved both delayed gastric emptying and feeding inhibition in restraint stress-induced model, but did not affect both basal gastric emptying and feeding in intact rats, indicating that acotiamide exerted effects only on gastric emptying and feeding impaired by the stress. On the other hand, mosapride showed significant acceleration of gastric emptying in intact and restraint stress-induced model, and itopride showed no effect on restraint stress-induced delayed gastric emptying. In addition, gene expression of NmU increased by restraint stress was suppressed by administration of acotiamide, while acotiamide had no effect on delayed gastric emptying induced by an intracerebroventricular administration of NmU, suggesting that the suppressive effect of acotiamide on gene expression of NmU might be important to restore delayed gastric emptying or feeding inhibition induced by restraint stress. These findings suggest that acotiamide might play an important role in regulation of stress response. As stress is considered to be a major contributing factor in the development of FD, the observed effects may be relevant for symptom improvement in FD.     

Acute Increases in Murine Tumor Echogenicity After Antivascular Ultrasound Therapy

Objective. This study was designed to determine whether the echogenicity of neoplastic tissues changed as a result of low‐intensity insonation and whether such alterations were related to an anti‐vascular effect. Methods. In 21 mice, implanted melanomas were insonated at either 1, 2, or 3 MHz using low‐intensity ultrasound (spatial‐average temporal‐average intensity, 2.1 W/cm²). B‐mode (mean gray scale) and contrast‐enhanced power Doppler (percentage area of flow) measurements were made on each tumor before and after therapy. Results. There was an increase in the echogenicity of the tumors with the increase in the frequency of the therapy beam and an accompanying decrease in tumor vascularity. Conclusions. Although the mechanisms responsible for the echogenicity change are not fully understood, it appears that an increase in the tumor mean gray scale was, at least in part, related to tissue inhomogeneities formed after disruption of the tumor neovasculature.     

高压氧治疗与血脑屏障通透性的实验研究

目的探讨常规治疗压力（0．25MPa）的高压氧增强血脑屏障开放、促进神经保护剂（神经节苷脂，GM-1）进入脑组织的作用。方法30只Wistar雄性大鼠，随机分为对照组、实验-1组、实验-2组、实验-3组、实验-4组；利用HPD 1700流体撞击仪，建立颅脑损伤动物模型，经毛细管电泳仪测定各组脑组织匀浆中GM-1相对浓度。结果各HBO治疗实验组GM-1浓度较无HBO治疗组和对照组有一定程度的提高，但对照组与各实验组、各实验组之间q检验均没有显著差异（P〉0．05）。结论常规治疗压力的高压氧无明显促进BBB通透性作用，但有增加BBB开放的趋势，促进神经保护剂进入脑组织。     

BRL 8242 (2-[2-benzimidazolyl]-amino-2-imidazoline dihydrochloride), a new inhibitor of dopamine-beta-hydroxylase with antihypertensive activity.

BRL 8242 (2-[2-benzimidazolyl]-amino-2-imidazoline dihydrochloride) was found to inhibit dopamine-beta-hydroxylase in vitro and in vivo and to have antihypertensive activity. The effect on dopamine-beta-hydroxylase in vitro was shown by inhibition of the conversion of phenylethylamine to phenylethanolamine, using enzyme extracted from rat adrenals. In vivo, BRL 8242 inhibited 3H-noradrenaline but not 3H-dopamine biosynthesis from 3H-L-dopa in rat brain. Furthermore, the compound lowered endogenous noradrenaline levels in both rat brain and heart whilst increasing the concentration of brain dopamine. In both metacorticoid hypertensive and normotensive rats, BRL 8242 lowered blood pressure. This response was dose related and correlated well with the reduction of endogenous noradrenaline in the tissues examined. It is therefore suggested that the inhibition of dopamine-beta-hydroxylase by BRL 8242 may account for its blood pressure lowering activity.     

Sensitivity of anticancer agents on human gastric cancers transplanted into nude mice

In the chemotherapy for gastric cancer, the most sensitive anticancer agent against individual tumors should be prescribed. The establishment of a sensitivity test using nude mice as anin vivo model is urgently awaited by clinicians and researchers alike. Seventy-three tumors derived from human gastric cancer were transplanted subcutaneously into nude mice and these mice were then treated intraperitoneally with anticancer agents. Mitomycin C (MMC), 5-fluorouracil (5-FU) and cyclophosphamide (CPM) were used. The doses given were 3 mg/kg of MMC, 75 mg/kg of 5-FU and 200 mg/kg of CPM. In 52 of the 73 cancers, chemosensitivity was evaluated by the microscopic changes in the tumors. The rate of positive sensitivity against gastric cancer was 44.2% in MMC, 34.6% in 5-FU and 30.8% in CPM, respectively. The sensitivity of each agent tested by this method indicated a good correlation with the clinical therapeutic effects. Our results suggest the feasibility of evaluation of the sensitivity of various agents from the microscopic changes on tumors transplanted into nude mice.