苜蓿根瘤菌溶磷和分泌植物生长素能力研究

对甘肃庆阳、天水、定西、武威和甘南5个不同生态区域栽培的陇东苜蓿和阿尔冈金苜蓿根瘤菌资源进行调查、分离和纯化,获得730多个分离物。分离物回接到原宿主植物检测其促生能力,筛选出29个较好的根瘤菌株,对其溶磷、分泌植物生长素能力进行了初步研究。结果表明,供试菌株都能够溶解有机磷(蛋黄卵磷脂EYPC),而不能溶解无机磷[Ca3(PO4)2];均能够分泌植物生长素(IAA),其中34.5%分泌能力较强,55.2%分泌能力中强,10.3%分泌能力较弱,分泌IAA的菌株数量比率高于禾本科根际分泌IAA菌株数量比率。

刺槐根瘤菌溶磷和分泌植物生长素特性的研究

采用溶磷圈法、钼锑抗比色法和Salkowski比色法,对分离自陕西6个区(县)的25株刺槐根瘤菌菌株进行了溶磷和分泌植物生长素(IAA)能力的定性和定量测定。在溶磷能力的定性测定中,菌株SLCH171对有机磷和无机磷的溶解能力均最强;在定量测定中,菌株SLCH171对有机磷的溶解能力最强,SLCH184对无机磷的溶解能力最强,有10株菌既能溶解无机磷又能溶解有机磷。分泌IAA测定显示,有21个菌株具有分泌IAA的能力,以SLCH184的分泌能力最强;各菌株分泌IAA能力的定量测定结果与定性测定结果基本相符。

铜胁迫对刺槐耐酸根瘤菌溶磷和分泌生长素能力的影响

以从豆科植物刺槐中分离的3株耐酸根瘤菌为研究对象,采用溶磷圈和Salkowski比色法,研究了在酸性条件下重金属铜胁迫对3株根瘤菌溶磷和分泌植物生长素IAA能力的影响。结果表明,3株耐酸刺槐根瘤菌都具有较强的溶磷和分泌IAA的能力,相对来说,溶解无机磷的能力均强于溶解有机磷的能力。铜胁迫对3株菌溶磷和分泌IAA均产生抑制,且抑制作用随着铜离子浓度的增加而增大。在相同浓度的Cu2+抑制下,菌株CHR009较其余2株菌CHR006和CHR011溶磷和分泌生长素的性能更优,对Cu2+胁迫具有更强的抗性,在重金属尾矿区植被恢复和污染土壤修复中具有潜在的应用价值。

酸性条件下Al^(3+)对苜蓿根瘤菌溶磷和分泌生长素能力的影响

采用溶磷圈和Salkowski比色法,对酸性条件下铝对耐酸性能极优的两种根瘤菌溶磷和分泌生长素能力的影响进行了研究。结果表明,两种根瘤菌都具有较强的溶磷和分泌生长素的能力,且溶解无机磷的能力更强。在铝毒胁迫下,两菌株均表现出了一定的耐受性,随着铝离子浓度的增加,铝对溶磷和分泌生长素的能力抑制作用增强,相同条件下,菌株S1007较S1002具有更好的溶磷和分泌生长素的性能。

两个杂交饲用大豆的根瘤菌生物功能与共生匹配性

杂交饲用大豆根瘤菌具有潜在的生物功能和共生匹配性,为综合评价并筛选出最具匹配性的菌株,以野生大豆与栽培大豆的杂交后代品种“蒙农S006饲用大豆”(简称S006)和品系“8-4-1棕”(简称8-4-1)为材料,在呼和浩特市和通辽市试验种植区,于分枝期对根瘤菌进行分离纯化,经BOX-PCR分类与16S rDNA扩增测序鉴定,共得到14株根瘤菌,分别予以命名,归属于中华根瘤菌属(Sinorhizobium)、根菌属(Rhizobium)和新根瘤菌属(Neorhizobium)。采用溶磷圈法、钼锑抗比色法和Salkowski比色法对所得菌株进行溶磷能力和生长素分泌能力测定,表明14株根瘤菌均具有溶磷能力和生长素分泌能力。其中,溶磷能力最强的菌株是Z8,溶磷量为4.55 mg·L^(-1);生长素分泌最高的菌株是S133,分泌量为224.16 mg·L^(-1)。在室内盆栽条件下,将所得菌株分别与试验材料进行接种,观测其共生匹配状况,以不接菌为对照。接种根瘤菌25 d后,对杂交饲用大豆地上鲜重、地上干重、株高、根瘤数、根瘤鲜重、叶片数、固氮酶活性和植株全氮含量进行测定。通过隶属函数进行综合评价,筛选出S006共生匹配效果排序前三的菌株是Z8、Z2和S134;8-4-1排序前三的菌株是Z75、S134和Z2。本研究筛选出与2个杂交饲用大豆共生匹配效果优良的菌株。后期研究中可制成根瘤菌接种菌剂,在内蒙古地区推广种植2个杂交饲用大豆时进行接种,以充分发挥优良根瘤菌的固氮作用,减少化肥施用量,为进一步深入研究提供菌种资源。

草地早熟禾根际固氮菌的生物效能

利用乙炔还原法、比色法等对草地早熟禾（Poa pratensis）根际分离得到的21个固氮菌株进行固氮酶活性、溶磷能力和分泌植物生长素性能的研究测定,在固氮酶活性测定中,21个菌株还原C2H2产生的C2H4在39.9-227.5nmol·mL-1·h-1,大于100nmol·mL-1·h-1的有14株,占所分离固氮菌株的67%;菌株的溶磷强度在13.38-58.21μg·mL-1,其中菌株N4、N16及N20溶磷能力较强;菌株N2、N4、N5、N10、N14、N16、N17及N20具有较强的分泌植物生长激素的能力。

电针对糖尿病胃轻瘫大鼠胃窦Ghrelin和GHSR蛋白及基因表达的影响

目的:探讨电针改善糖尿病胃轻瘫(DGP)大鼠胃运动的机制。方法:将48只健康SD大鼠按随机数字表法分为空白对照组、DGP模型组、电针穴位组(模型+电针穴位)、胃复安对照组(模型+胃复安灌胃)4组各12只。采用腹腔注射链脲佐菌素(STZ)配合高糖高脂饮食建立大鼠DGP模型,电针足三里、三阴交及梁门穴以观察大鼠血糖、尿糖值和胃排空率,ELISA法检测血清胰岛素(INS)、胃窦组织促生长素(Ghrelin)含量,PCR法测定胃窦部生长素促分泌激素受体基因(GHSR mRNA)表达。结果:与空白组比较,模型组大鼠血糖、尿糖值显著增高,胃排空率、血清INS水平、胃窦Ghrelin及GHSR mRNA表达降低;经电针穴位后,血糖、尿糖值降低,胃排空率、血清INS水平、胃窦Ghrelin及GHSR mRNA表达增高。结论:电针足三里等穴位可降低DGP大鼠血糖、尿糖值,促进胃排空,这可能与其调节血清INS含量、胃窦Ghrelin及GHSR mRNA表达有关。

沧州盐碱地紫花苜蓿根际促生细菌的筛选

本研究以河北省沧州黄骅市紫花苜蓿(Medicago sativa)为研究对象,对采自黄骅地区常郭乡赵子札村、羊二庄镇张八寨村及旧城镇云庄村等10个地点的紫花苜蓿根际土壤进行细菌分离纯化和培养,获得134株根际细菌。进而将其接种到紫花苜蓿植物种苗,培养60d后,比较分析了接种不同根际促生菌对植物生长的促生影响,选择了30株促生细菌优良菌株,并且对30株细菌菌株进行了溶磷能力和分泌生长素能力的测定。结果表明,菌株EF2对植物干重增重影响最为显著(P<0.05),其溶解有机磷和无机磷能力也最强;菌株LF13分泌生长素的能力最强,其对株高的影响较为明显。研究最终初步筛选出9株溶磷能力和分泌生长素能力较强并能促进紫花苜蓿显著生长的根际细菌。

Ghrelin and gastric acid secretion

Ghrelin, a novel growth hormone-releasing peptide, was originally isolated from rat and human stomach. Ghrelin has been known to increase the secretion of growth hormone (GH), food intake, and body weight gain when administered peripherally or centrally. Ghrelin is also known to stimulate the gastric motility and the secretion of gastric acid. In the previous studies, the action of ghrelin on acid secretion was shown to be as strong as that of histamine and gastrin in in-vivo experiment. In the studies, the mechanism for the action of ghrelin was also investigated. It was shown that vagotomy completely inhibited the action of ghrelin on the secretion of gastric acid suggesting that vagal nerve is involved in the mechanism for the action of ghrelin on acid secretion. As famotidine did not inhibit ghrelin-in-duced acid secretion in the study by Masuda et al, they concluded that histamine was not involved in the action of ghrelin on acid secretion. However, we have shown that famotidine completely inhibited ghrelin-induced acid secretion and histidine decarboxylase (HDC) mRNA was increased in gastric mucosa by ghrelin injection which is inhibited by vagotomy Our results indicate that histamine is involved in the action of ghrelin on acid secretion. Furthermore synergistic action of gastrin and ghrelin on gastric acid secretion was shown. Although gastrin has important roles in postprandial secretion of gastric acid, ghrelin may be related to acid secretion during fasting period or at night. However, further studies are needed to elucidate the physiological role of ghrelin in acid secretion.

Folic acid contributes to peripheral nerve injury repair by promoting Schwann cell proliferation, migration, and secretion of nerve growth factor

After peripheral nerve injury, intraperitoneal injection of folic acid improves axon quantity, increases axon density and improves electromyography results. However, the mechanisms for this remain unclear. This study explored whether folic acid promotes peripheral nerve injury repair by affecting Schwann cell function. Primary Schwann cells were obtained from rats by in vitro separation and culture. Cell proliferation, assayed using the Cell Counting Kit-8 assay, was higher in cells cultured for 72 hours with 100 mg/L folic acid compared with the control group. Cell proliferation was also higher in the 50, 100, 150, and 200 mg/L folic acid groups compared with the control group after culture for 96 hours. Proliferation was markedly higher in the 100 mg/L folic acid group compared with the 50 mg/L folic acid group and the 40 ng/L nerve growth factor group. In Transwell assays, the number of migrated Schwann cells dramatically increased after culture with 100 and 150 mg/L folic acid compared with the control group. In nerve growth factor enzyme-linked immunosorbent assays, treatment of Schwa nn cell cultures with 50, 100, and 150 mg/L folic acid increased levels of nerve growth factor in the culture medium compared with the control group at 3 days. The nerve growth factor concentration of Schwann cell cultures treated with 100 mg/L folic acid group was remarkably higher than that in the 50 and 150 mg/L folic acid groups at 3 days. Nerve growth factor concentration in the 10, 50, and 100 mg/L folic acid groups was higher than that in the control group at 7 days. The nerve growth factor concentration in the 50 mg/L folic acid group was remarkably higher than that in the 10 and 100 mg/L folic acid groups at 7 days. In vivo, 80 μg/kg folic acid was intraperitoneally administrated for 7 consecutive days after sciatic nerve injury. Immunohistochemical staining showed that the number of Schwann cells in the folic acid group was greater than that in the control group. We suggest that folic acid may play a role in improving the repair of peripheral nerve injury by promoting the proliferation and migration of Schwann cells and the secretion of nerve growth factors.

Gastric motor effects of ghrelin and growth hormone releasing peptide 6 in diabetic mice with gastroparesis

AIM:To investigate the potential therapeutic significance of ghrelin and growth hormone releasing peptide 6 (GHRP-6) in diabetic mice with gastric motility disorders. METHODS: A diabetic mouse model was established by intraperitoneal (ip) injection of alloxan. Diabetic mice were injected ip with ghrelin or GHRP-6 (20-200 μg/kg), and the effects on gastric emptying were measured after intragastric application of phenol red. The effect of atropine, NG-nitro-L-arginine methyl ester hydrochloride (L-NAME) or D-Lys3-GHRP-6 (a growth hormone secretagogue receptor (GHS-R) antagonist) on the gastroprokinetic effect of ghrelin or GHRP-6 (100 μg/kg) was also investigated. The effects of ghrelin or GHRP-6 (0.01-10 μmol/L) on spontaneous or carbachol-induced contractile amplitude were also investigated in vitro, in gastric fundic circular strips taken from diabetic mice. The presence of growth hormone secretagogue receptor 1a transcripts in the fundic strips of diabetic mice was detected by reverse transcriptase polymerase chain reaction (RT-PCR). RESULTS: We established a diabetic mouse model with delayed gastric emptying. Ghrelin and GHRP-6 accelerated gastric emptying in diabetic mice with gastroparesis. In the presence of atropine or L-NAME, which delayed gastric emptying, ghrelin and GHRP-6 (100 μg/kg) failed to accelerate gastric emptying. D-Lys3-GHRP-6 also delayed gastric emptying induced by the GHS-R agonist. Ghrelin and GHRP-6 increased the carbachol-induced contractile amplitude in gastric fundicstrips taken from diabetic mice. RT-PCR confirmed the presence of GHS-R mRNA in the strip preparations. CONCLUSION: Ghrelin and GHRP-6 increase gastric emptying in diabetic mice with gastroparesis, perhaps by activating peripheral cholinergic pathways in the enteric nervous system.

EFFECT OF PREOPERATIVE USE OF LONG-ACTING OCTREOTIDE ON GROWTH HORMONE SECRETING PITUITARY ADENOMA AND TRANSSPHENOIDAL SURGERY

Objective To investigate whether somatostatin analog octreotide long acting release (LAR) shrinks growth hormone (GH) secreting adenomas, and improves the results of subsequent transsphenoidal surgery. Methods Seventeen previously untreated active acromegalic patients with pituitary adenomas were treated with LAR (30 mg intramuscular injection every 28 days) for 3 months prior to transsphenoidal surgery. Clinical reaction, mean GH secretion, and tumor volume were measured under basal conditions and after LAR treatment. Results Presurgical treatment improved acromegaly symptoms and induced a significant reduction of GH under the 5 ng/mL limit in microadenoma (P < 0.05), while only 18.2% (2/11) in macroadenoma. Meanwhile, tumor shrinkage occurred in 58.8% (10/17) patients, with 1 case in the microadenoma group. All marked shrinkage (> 25%) occurred in the macroadenoma group. Statistical analysis showed tumor shrinkage caused by LAR was greater in macroadenoma group than that in microadenoma group (P < 0.05). During operation, adenoma was soft in 15 cases, with the exception of 2 cases in which the soft tumor was divided by fibrous septa, but all tumor removal was smooth. Conclusions A short term administration of preoperative LAR may induce a significant decrease in GH-secretion level and adenoma volume. Presurgical use of octreotide LAR improves surgical results especially in macroadenomas.

Endocrine impact of Helicobacter pylori:Focus on ghrelin and ghrelin o-acyltransferase

Ghrelin is predominantly produced by the gastric enteroendocrine cell compartment and is octanoylated by the recently discovered ghrelin o-acyltransferase （GOAT） before secretion into the bloodstream. This octanoylation is essential for many of the biological properties of ghrelin including appetite stimulation and anti-inflammatory properties as only the acylated form of ghrelin binds to the ghrelin receptor, the growth hormone secretagogue receptor （GHS-R）. Given the gastric location of ghrelin production, it is perhaps not surprising that insult to the gastric mucosa affects circulating ghrelin levels in humans. Helicobacter pylori （H. pylon） infects more than fifty percent of the world＇s population and once established within the gastric mucosa, can persist for life. Infection is associated with chronic gastritis, gastric atrophy and ulceration, reduced appetite and a lower body mass index （BMI）. The large majority of studies investigating levels of circulating ghrelin and ghrelin expression in the stomach in patients with H. pylori infection indicate that the bacterium has a negative impact on ghrelin production and/or secretion. Eradication of infection restores ghrelin, improves appetite and increases BMI in some studies, however, a causative relationship between H. pylori-associated serum ghrelin decline and food intake and obesity has not been established. Most studies measure total ghrelin in the circulation although the measurement of the ratio of acyl/total ghrelin gives a clearer indication that the ghrelin acylation process is altered during infection and atrophy. GOAT is essential for the production of biologically-active, acyl ghrelin and the impact of H. pylori on GOAT expression and activity will be highly informative in the future.

Neuroendocrine gastric carcinoma expressing somatostatin: A highly malignant, rare tumor

Poorly differentiated gastric neuroendocrine carcinomas, although rare, deserve particular attention, as they are aggressive and have an extremely poor prognosis. In this report we describe a gastric neuroendocrine carcinoma with rapidly fatal outcome. Immunohistological staining of the resected specimens revealed that the tumor was an endocrine carcinoma. The tumor disclosed intense immunoreactivity to pan-neuroendocrine markers and diffuse somatostatin immunoreactivity. There were no psammoma bodies and no demonstrable association with yon Recklinghausen＇s neurofibromatosis. In the gastrointestinal tract, neuroendocrine tumors producing predominantly somatostatin have been described only in the duodenum. To the best of our knowledge, the present report is the second case report of a neuroendocrine gastric carcinoma expressing diffusely somatostatin as the only neuroendocrine regulatory peptide.

Interferon-γ inhibits ghrelin expression and secretion via a somatostatin-mediated mechanism

AIM- To investigate if and how the proinflammatory cytokine interferon γ （IFNγ） affects ghrelin expression in mice. METHODS： The plasma concentration of ghrelin, and gastric ghrelin and somatostatin expression, were ex- amined in wild-type mice and mice infected with Helico- bacter pylori （H. pylorO. Furthermore, ghrelin expression was examined in two achlorhydric mouse models with varying degrees of gastritis due to bacterial overgrowth. To study the effect of IFNγ, alone, mice were given a subcutaneous infusion of IFNγ, for 7 d. Finally, the influ- ence of IFNγ, and somatostatin on the ghrelin promoter was characterized. RESULTS： H. py/ori infection was associated with a 50% reduction in ghrelin expression and plasma concentration. Suppression of ghrelin expression was in- versely correlated with gastric inflammation in achlorh- dyric mouse models. Subcutaneous infusion of IFNγ, suppressed fundic ghrelin mRNA expression and plasma ghrelin concentrations. Finally, we showed that the ghrelin promoter operates under the control of soma- tostatin but not under that of IFNγ. CONCLUSION： Gastric infection and inflammation is associated with increased IFNγ, expression and reduced ghrelin expression. IFNγ, does not directly control ghre- lin expression but inhibits it indirectly via somatostatin.

Ghrelin's second life:From appetite stimulator to glucose regulator

Ghrelin,a 28 amino acid peptide hormone produced by the stomach,was the first orexigenic hormone to be discovered from the periphery.The octanoyl modification at Ser3,mediated by ghrelin O-acyltransferase(GOAT),is essential for ghrelin's biological activity.Ghrelin stimulates food intake through binding to its receptor(GRLN-R) on neurons in the arcuate nucleus of the hypothalamus.Ghrelin is widely expressed throughout the body;accordingly,it is implicated in several other physiological functions,which include growth hormone release,gastric emptying,and body weight regulation.Ghrelin and GRLN-R expression are also found in the pancreas,suggesting a local physiological role.Accordingly,several recent studies now point towards an important role for ghrelin and its receptor in the regulation of blood glucose homeostasis,which is the main focus of this review.Several mechanisms of this regulation by ghrelin have been proposed,and one possibility is through the regulation of insulin secretion.Despite some controversy,most studies suggest that ghrelin exerts an inhibitory effect on insulin secretion,resulting in increased circulating glucose levels.Ghrelin may thus be a diabetogenic factor.Obesity-related type2 diabetes has become an increasingly important health problem,almost reaching epidemic proportions in the world;therefore,antagonists of the ghrelin-GOAT signaling pathway,which will tackle both energy-and glucose homeostasis,may be considered as promising new therapies for this disease.

Two synchronous somatostatinomas of the duodenum and pancreatic head in one patient

Somatostatinomas are extremely rare neuroendocrine tumors of the gastrointestinal tract,f irst described in the pancreas in 1977 and in the duodenum in 1979.They may be functional and cause somatostatinoma or inhibi-tory syndrome,but more frequently are non-functioning pancreatic endocrine tumors that produce somatostatin alone.They are usually single,malignant,large lesions,frequently associated with metastases,and generally with poor prognosis.We present the unique case of a 57-year-old woman with two synchronous non-function-ing somatostatinomas,one solid duodenal lesion and one cystic lesion within the head of the pancreas,that were successfully resected with a pylorus-preserving Whipple's procedure.No secondaries were found in the liver,or in any of the removed regional lymph nodes.The patient had an uneventful recovery,and remains well and symptom-free at 18 mo postoperatively.This is an extremely rare case of a patient with two synchro-nous somatostatinomas of the duodenum and the pancreas.The condition is discussed with reference to the literature.

The cardiovascular action of hexarelin

Hexarelin, a synthetic growth hormone-releasing peptide, can bind to and activate the growth hormone secretagogue receptor （GHSR） in the brain similar to its natural analog ghrelin. However, the peripheral distribution of GHSR in the heart and blood vessels suggests that hexarelin might have direct cardiovascular actions beyond growth hormone release and neuroendocrine effects. Furthermore, the non-GHSR CD36 had been demonstrated to be a specific cardiac receptor for hexarelin and to mediate its cardioprotective effects. When compared with ghrelin, hexarelin is chemically more stable and functionally more potent. Therefore, it may be a promising therapeutic agent for some car-diovascular conditions. In this concise review, we discuss the current evidence for the cardiovascular action of hexarelin.

STUDY ON INHIBITION OF PANCREATIC EXOCRINE SECRETION BY SOMATOSTATIN IN RATS

We used a potent and specific monoclonal antibody to somatostatin to test the physiologic inhibitory role of the tetradecapeptide somatostatin on pancreatic secretion.Somatostatin immunoneutralization increased both the total amylase and volume of pancreatic secretion.Cholecystokinin-A receptor antagonism abolished the stimulatory effect of somatostatin immunoneutralization.We conclude that somatostatin tonically inhibits pancreatic secretion in fasted rats via inhibition of the release or action of cholecystokinin.Furthermore,the source of these peptides is likely islet delta cells and intrapancreatic neurons,respectively.

Recombinant adenovirus-mediated expression of GHS-R1a in HEK 293 cells

Objective To construct the recombinant adenovirus vector carrying human growth hormone secretagogue receptor type 1a （GHS-R1a） ,for genetic transfection.Methods The full-length human GHS-R1a gene was obtained by PCR amplification and then cloned into the shuttle plasmid pAdTrack-CMV.The linearized plasmid pAdTrack-CMV-GHS-R1a was co-transformed into Escherichia coli （E.coli） BJ5183 cells along with an adenoviral backbone plasmid pAdEasy1.The HEK293 cells were then infected with adenoviruses.The expression of GHS-R1a was indicated by green fluorescent protein （GFP） ,and confirmed by Reverse Transcription Polymerase Chain Reaction （RT-PCR） and Western blot.Results Enzymatic digestion of pAdGHS-R1a yielded a large fragment （approximately 30 kb） and a small fragment （4.5 kb） ,indicating the success-ful construction of recombinant adenovirus expression vector.Expression of GFP was observed by confocal laser scanning microscopy at 24 h after infection.RT-PCR and Western blot further confirmed that GHS-R1a was efficiently expressed in 293 cells.Conclusion Recombinant adenovirus （AdGHS-R1a） is successfully constructed,and the target gene can be expressed efficiently in 293 cells,which provide a valuable tool for further studying the function of GHS-R1a.