The effect of bacterial melanin on electrical activity of neurons of the substantia nigra under conditions of GABA generation

The changes in spike activity of single neurons of the compact part of the substantia nigra, evoked by nucleus caudatus stimulation under conditions of long-term registration of the single and multiple, isolated and combined actions of GABA, GABA-amide, glutamine, and ethanolamine-O-sulfate (EOS) were studied in albino rats. Inhibition of poststimulus activity under GABA action was recorded and the inhibitory effect of GABA-amide was revealed. Primary excitatory and subsequent inhibitory effects of glutamine in combination with EOS were shown. The subsequent administration of bacterial melanin, synthesized by a mutant culture of Bacillus thuringiensis (BT-M) evoked a clear-cut and prolonged excitatory reaction during all the combined actions of GABA, GABA-amide, glutamine, and EOS. Preliminary administration of BT-M abolished the inhibitory poststimulus effects of GABA, GABA-amide, and EOS, as well as glutamine-induced excitation.     

Effects of endotoxin on intestinal hemodynamics, glutamine metabolism, and function

The purpose of this study was to investigate the intestinal hemodynamics and gut glutamine metabolism during endotoxemia, and their correlation with altered intestinal absorptive capacity and permeability. Seventeen Sprague-Dawley rats were used in the study. The endotoxin group (ENDO) recieved endotoxin (10 mg/kg intraperitoneally,n=9), while the control group (CONT,n=8) received saline injection. Twelve hours later, D-xylose (0.5 g/kg) and fluorescein isothiocyanate-dextran (FITC-dextran, 750 mg/kg) were given by oral gavage. One hour later abdominal aortic (AA) blood flow, superior mesenteric venous (SMV) flow, mean arterial pressure (MAP), central venous pressure (CVP), and SMV pressure (SMVP) were also measured. The MAP, AA, and SMV blood flow decreased (P<0.05), while the CVP and SMVP increased (P<0.05) in the ENDO group as compared with the CONT group. The ENDO group showed significant decreases for both intestinal glutaminase activity and net intestinal glutamine uptake (P<0.05). The D-xylose concentration in SMV decreased significantly (P<0.05) in the ENDO group as compared with the CONT group. However, the plasma FITC-dextran concentration showed no significant difference between the groups. Endotoxin produced a hypodynamic effect in rats 12h after intraperitoneal administration in association with both a decreased intestinal glutamine metabolism and an absorptive capacity.     

Immunocytochemistry of Amino-Acids in the Rodent Pituitary Using Extremely Specific, Very High Titre Antisera

The compartmental interrelationships of the metabolically related amino-acids glutamate, GABA and glutamine and the metabolically unrelated amino-acids taurine and glycine in the rodent pituitary, were investigated by light microscopic immunocytochemistry using highly specific antisera. Glutamate-like immunoreactivity was abundant in astrocytes in the posterior pituitary. Glutamine immunoreactivity was present only at low levels in the posterior pituitary, but was abundant in astrocytes within the intermediate lobe. Other glia-like ceils in the anterior pituitary were also glutamine-immunoreactive. GABA immunoreactivity was abundant in the intermediate lobe but absent from anterior and posterior lobes. The GABA immunoreactivity mainly took the form of small punctata, the majority of which were in intimate apposition to the glutamine-immunoreactive glia. Strong taurine immunoreactivity was present in astrocytes in the posterior pituitary but only weak labelling was present in intermediate and anterior lobes of the pituitary. Specific glycine immunoreactivity was not detected in the pituitary. These results suggest that glutamate-immunoreactive astrocytes in the posterior pituitary, unlike glia in loci such as the retina, do not convert much, if any, of their glutamate content into glutamine (or if they do, it is rapidly further metabolized to another compound), whereas those astrocytes in the intermediate lobe do contain glutamine. The spatial association of GABAergic fibres with glutamine-positive astrocytes raises the possibility that astrocytes in the intermediate lobe receive a GABAergic innervation. Glutamate, glutamine and taurine (or their metabolites) may have roles as neuroactive substances regulating pituitary secretion.     

Localization of glial cell antigens in the brains of young normal mice and the dysmyelinating mutant mice, jimpy and shiverer

Tissue sections from the brains of normal, jimpy, and shiverer mice were immunostained by the peroxidase antiperoxidase method for carbonic anhydrase (CA) and the putative astrocytic "markers" glutamine synthetase (GS) and glial fibrillary acidic protein (GFAP). The cells in normal gray matter that immunostained with anti-CA and anti-GS were similar to one another in size and process elaboration. In the normal gray matter there were relatively few GFAP-positive astrocytes. When present, these cells resembled the CA- and GS-positive cells; however, the GFAP appeared to be concentrated in the astroglial processes, as distinguished from the cell bodies. Glial cell processes, immunostained for CA or GS, surrounded blood vessels and unstained neurons in the normal gray matter. The glial cells in shiverer gray matter were similar to those in the normal gray matter. When stained for GS or GFAP, the glial cells in the jimpy gray matter appeared to be somewhat hypertrophied, and when the glial cells in this mutant were stained for CA, the nuclei appeared to be swollen. It was concluded that some of the CA-positive cells in the gray matter of the normal and of each mutant mouse brain could be astrocytes. The patterns of immunostaining in the white matter emphasized the different complements of glial cells in the mutants. In the normal and shiverer mouse corpus callosum, CA, in particular, was detected only in the oligodendrocytes, their processes, and myelin. However, the data concerning the jimpy mouse suggested that the few CA-positive cells in the corpus callosum of that mutant could be astrocytes.     

谷氨酰胺对放射损伤大鼠肠粘膜组织结构及其DNA和蛋白含量的影响

目的观察谷氨酰胺对放射损伤大鼠肠粘膜组织结构及其肠粘膜上皮细胞DNA与蛋白含量的影响。方法体重(159.4±9.21)g的雄性Wistar大鼠30只,随机分为对照组(Control组)、添加谷氨酰胺照射组( GLN组)、未添加谷氨酰胺照射组(-GLN组),每组10只。以不同饲料配方喂养至第15天, GLN组和-GLN组大鼠给予9.0Gry的60Coγ全身照射。继续喂养至第20天处死全部动物,取材观察空肠粘膜光镜和电镜组织结构形态,并进行肠粘膜上皮细胞DNA、蛋白质含量的测定。结果-GLN组肠粘膜变薄、萎缩,扫描电镜可见绒毛顶端溃疡明显, GLN组肠粘膜病理改变较轻。3组肠粘膜上皮细胞DNA含量均无显著性差异,-GLN组较Control组蛋白质含量明显降低(P<0.01)。结论谷氨酰胺可减轻肠粘膜结构的急性放射损害,并对减少肠粘膜上皮细胞内蛋白质的丢失可能有积极作用。     

谷氨酰胺和重组人生长激素对门静脉高压症患者术后肠黏膜屏障功能的影响

目的研究单独或联合应用谷氨酰胺（Gln）和重组人生长激素（rhGH）对门静脉高压症患者术后肠黏膜屏障功能的影响。方法将29例肝硬化门静脉高压症接受手术治疗的患者随机分为4组：Gln组（n=6）、rhGH组（n=8）、Gln＋rhGH组（n=7）和对照组（n=8）。术后3天开始进行等氮、等热量的全胃肠外营养（TPN）支持，持续7天。对患者手术前、后的尿乳果糖／甘露醇（L／M）、十二指肠降段黏膜绒毛高度及陷窝深度进行测定。结果Gln＋rhGH组L／M升高的幅度显著小于对照组（P〈0．05），Gln和rhGH组与对照组比较差异无显著性。Gln＋rhGH组肠黏膜绒毛高度和陷窝深度均大于对照组（P〈0．05），Gln和rhGH组与对照组比较差异无显著性（P〉0．05）。Gln＋rhGH组术后绒毛高度及陷窝深度均显著大于术前（P〈0．05）；对照组术后绒毛高度小于术前（P〈0．05），陷窝深度差异无显著性（P〉0．05）；Gln和rhGH组手术前、后绒毛高度及陷窝深度差异无显著性（P〉0．05）。结论联合应用Gln和rhGH能降低门静脉高压症患者术后肠壁通透性并维护肠黏膜形态学完整性，单独应用Gln或rhGH无此作用。     

谷氨酰胺和表皮生长因子对新生鼠坏死性小肠结肠炎的影响

目的探讨谷氨酰胺(Gln)和表皮生长因子(EGF)对新生鼠坏死性小肠结肠炎(NEC)肠黏膜修复的影响。方法新生1日龄Wistar大鼠40只随机分为4组,A组(正常对照组),B组(NEC模型组),C组(NEC Gln),D组(NEC EGF Gln)。建立NEC模型,4 d后分别取近回盲段2~3 cm肠道组织固定、包埋、切片。HE染色光镜下作病理学检查,应用免疫组织化学技术检测肠黏膜增殖细胞核抗原(PCNA)的表达,TUNEL法检测肠黏膜细胞凋亡。结果B组HE染色切片见肠黏膜损伤,病理评分的中位积分为3分;C、D组损伤程度较轻,病理评分的中位积分为1分。B组PCNA阳性细胞数低于A组(P<0.01);C、D组PCNA阳性细胞数高于B组(P<0.01);且D组PCNA阳性细胞数高于C组(P<0.05)。B组肠黏膜细胞凋亡数高于A组(P<0.01);C、D组肠黏膜细胞凋亡数低于B组(P<0.01);且D组肠黏膜细胞凋亡数低于C组(P<0.05)。结论NEC新生鼠肠黏膜受损,增殖减慢,细胞凋亡数增加;补充Gln和EGF可促进NEC新生鼠肠黏膜隐窝细胞的增殖,减少肠黏膜细胞的凋亡,加快肠黏膜修复。     

谷氨酰胺∶6-磷酸-果糖酰基转移酶抑制剂细胞筛选模型的建立

目的建立己糖胺途径的关键酶谷氨酰胺∶6-磷酸-果糖酰基转移酶(glutamine∶fructose-6-phosphate amidotransferase,GFAT)抑制剂的细胞筛选模型。方法用改进的GDH法测定GFAT的活性。以速效胰岛素依赖的葡萄糖摄取观察细胞对胰岛素的反应性；用长效胰岛素诱导HIRc细胞，形成己糖胺途径过度活跃和胰岛素抵抗的细胞模型，并应用该细胞模型和GDH法筛选GFAT抑制剂。结果用25 nmol·L^-1长效胰岛素刺激HIRc细胞36 h，可明显激活己糖胺途径，使GFAT活性上升47%；同时产生胰岛素抵抗，使速效胰岛素依赖的葡萄糖摄取能力降低21%。Azaserine可明显抑制该模型中GFAT的活性。结论长效胰岛素既可过度激活HIRc细胞己糖胺途径，又可使其产生胰岛素抵抗。该模型可用于筛选GFAT抑制剂。     

Astrocytes in the damaged brain: Molecular and cellular insights into their reactive response and healing potential

Long considered merely a trophic and mechanical support to neurons, astrocytes have progressively taken the center stage as their ability to react to acute and chronic neurodegenerative situations became increasingly clear. Reactive astrogliosis starts when trigger molecules produced at the injury site drive astrocytes to leave their quiescent state and become activated. Distinctive morphological and biochemical features characterize this process (cell hypertrophy, upregulation of intermediate filaments, and increased cell proliferation). Moreover, reactive astrocytes migrate towards the injured area to constitute the glial scar, and release factors mediating the tissue inflammatory response and remodeling after lesion. A novel view of astrogliosis derives from the finding that subsets of reactive astrocytes can recapitulate stem cell/progenitor features after damage, fostering the concept of astroglia as a promising target for reparative therapies. But which biochemical/signaling pathways modulate astrogliosis with respect to both the time after injury and the type of damage? Are reactive astrocytes overall beneficial or detrimental for neuroprotection and tissue regeneration? This debate has been animating this research field for several years now, and an integrated view on the results obtained and the possible future perspectives is needed. With this Commentary article we have attempted to answer the above-mentioned questions by reviewing the current knowledge on the molecular mechanisms controlling and sustaining the reaction of astroglia to injury and its stem cell-like properties. Moreover, the cellular/molecular mechanisms supporting the detrimental or beneficial features of astrogliosis have been scrutinized to gain insights on possible pharmacological approaches to enhance astrocyte neuroprotective activities.