Differential contribution of nitric oxide and cGMP to the stimulatory effects of growth hormone-releasing hormone and low-concentration somatostatin on growth hormone release from somatotrophs

There is increasing evidence that nitric oxide (NO) produced by NO synthase (NOS), and their signalling partners, guanylyl cyclase and cGMP, play a relevant role in growth hormone (GH) secretion from somatotrophs. We previously demonstrated that both GH-releasing hormone (GHRH; 10(-8) M) and low concentrations of somatostatin (10(-15) M) stimulate pig GH release in vitro, whereas a high somatostatin concentration (10(-7) M) inhibits GHRH-induced GH secretion. To ascertain the possible contribution of the NOS-NO and guanylyl cyclase-cGMP routes to these responses, cultures of pituitary cells from prepubertal female pigs were treated (30 min) with GHRH (10(-8) M) or somatostatin (10(-7) or 10(-15) M) in the absence or presence of activators or blockers of key steps of these signalling cascades, and GH release was measured. Two distinct activators of NO route, SNAP (5x10(-4) M) or L-AME (10(-3) M), similarly stimulated GH release when applied alone (with this effect being blocked by 10(-7) M somatostatin), but did not alter the stimulatory effect of GHRH or 10(-15) M somatostatin. Conversely, two NO pathway inhibitors, NAME (10(-5) M) or haemoglobin (20 microg/ml) similarly blocked GHRH- or 10(-15) M somatostatin-stimulated GH release. 8-Br-cGMP (10(-8) to 10(-4) M) strongly stimulated GH release, suggesting that cGMP may function as a subsequent step in the NO pathway in this system. Interestingly, 10(-7) M somatostatin did not inhibit the stimulatory effect of 8-Br-cGMP. Moreover, although 8-Br-cGMP did not modify the effect of GHRH, it enhanced GH release stimulated by 10(-15) M somatostatin. Accordingly, a specific guanylyl cyclase inhibitor, LY-83, 583 (10(-5) M) did not alter 10(-15) M somatostatin-induced GH release, whereas it blocked GHRH-induced GH secretion. These results demonstrate for the first time that the NOS/NO signalling pathway contributes critically to the stimulatory effects of both GHRH and low-concentration somatostatin on GH release, and that, conversely, the subsequent guanylyl cyclase/cGMP step only mediates GHRH- and not low-concentration somatostatin-induced GH secretion from somatotrophs.     

An electron microscopic study on enkephalin-like immunoreactive nerve fibers in the celiac ganglion of guinea pigs

Enkephalin-like immunoreactive nerve fibers in the celiac ganglion of guinea pigs were characterized by a high population of large granular vesicles mixed with small clear vesicles. The immunoreactive material is confined to the large granular vesicles. The immunoreactive nerve fibers formed many axo-dendritic as well as axo-somatic synapses and also formed a few synapses with presumed preganglionic axons containing numerous vesicles. The immunoreactive fibers were regarded as presynaptic at these synapses. These findings suggest that enkephalin might play a role as a neurotransmitter or neuromodulator in the ganglionic transmission of this prevertebral ganglion.     

Suppression of Leukocyte-Enhanced Cold Ischemia/Reperfusion Injury of Liver Endothelium with the Benzoquinone Antioxidant Idebenone

Objective: Despite the large body of evidence for a major role of neutrophils and oxidant stress, the exact pathogenesis of the early ischemia/reperfusion injury after cold preservation of the liver is not well understood. The potential benefit of an antioxidant on metabolic liver function during reperfusion has been demonstrated in several studies.

Materials and Methods: We describe a cold storage/reperfusion damage model with isolated perfused pig livers, where the effects of neutrophils and idebenone, a recently developed benzoquinone antioxidant were studied. The integrity of sinusoidal endothelial cells (SEC) was estimated by hyaluronic acid concentration in perfusate and the expression of endothelial constitutive nitric oxide synthase (ecNOS) after reperfusion and compared to lipid peroxidation and antioxidant content.

Results: Hyaluronic acid displayed the highest levels and ecNOS mRNA was most depressed in livers reperfused with neutrophils after 20 h cold storage; this was accompanied by an increase in lipid peroxidation (TBARS) and a breakdown of endogenous lipophilic antioxidants (-tocopherol and coenzyme Q-10). These effects were attenuated, when neutrophils were excluded from reperfusion and almost completely abolished by the addition of 200 μmol/L idebenone.

Conclusions: These data suggest that a leukocyte-mediated damage based on reactive oxygen species markedly contributes to the reperfusion injury of SEC after cold preservation of the liver. Therefore, the presence of effective antioxidants in the early reperfusion phase may be beneficial for liver graft integrity.     

The Effect of Zataria multiflora and its Constituent,Carvacrol, on Tracheal Responsiveness and Lung Pathology in Guinea Pig Model of COPD

The effects of Zataria multiflora (Z. multiflora) and its constituent, carvacrol, in guinea pigs model of chronic obstructive pulmonary disease (COPD) were examined. Animals were divided into control, COPD, COPD + drinking water containing three concentrations of extract of Z. multiflora (0.4, 0.8 and 1.6 mg/ml), COPD + drinking water containing three concentrations of carvacrol (60, 120 and 240 µg/ml) and COPD + dexamethasone (50 µg/ml). COPD was induced by exposing animals to cigarette smoke for 3 months. Emphysema as a pathological change of the lung and tracheal responsiveness were measured (n = 5 for control and COPD groups and n = 6 for another groups). Tracheal responsiveness (p < 0.05) and emphysema were significantly increased (p < 0.001) in COPD compared to the control group. Tracheal responsiveness in COPD groups treated with two higher concentrations of the Z. multiflora and three concentrations of carvacrol, and emphysema in treated with highest concentration of Z. multiflora and carvacrol were significantly improved compared to COPD group. Studied parameters were also significantly improved in the treated group with dexamethasone compared to COPD animals (p < 0.05 to p < 0.01). The results indicated a preventive effect of Z. multiflora extract and its constituent, carvacrol, on tracheal responsiveness and pathological changes of the lung. Copyright © 2015 John Wiley & Sons, Ltd.     

Characterization of cytoplasmic and membrane-associated phosphatidylinositol 4,5-biphosphate phospholipase C activities in guinea pig ventricles

Summary The phosphoinositide-specific phospholipase C (PLC) activity present in the soluble and sarcolemmal enriched membrane fraction from guinea pig hearts was characterized using phosphatidyl [³H]inositol 4,5-biphosphate (PIP₂) or phosphatidyl [³H]inositol 4-monophosphate (PIP) as substrates. The PLC activities (cytosolic and membrane associated) were specific for polyphosphoinositides (PIP₂ and PIP) since no other phospholipids were hydrolyzed at pH 7.0 under various ionic conditions. Both enzymic activities were Ca²⁺-dependent (half maximal activities were achieved around pCa 5.0). The pH, detergent (deoxycholate), divalent (Ca²⁺ and Mg²⁺), and monovalent (Na⁺ and K⁺) cation dependencies were very similar between the cytosolic and membrane-associated enzyme activities, using either PIP₂ or PIP as substrate. Hydrolysis of the polyphosphoinositides was inhibited in the presence of phosphatidylethanolamine, phosphatidylserine, or phosphatidylcholine.Under optimal conditions (pH 7.0, 1 mM Ca²⁺, 2.5 mM Mg²⁺, 100 mM Na⁺ and 0.07% deoxycholate) the specific activities of the cytosolic and membrane-associated enzymes were 19.9±0.9 and 10.1±0.9 nmol/min/mg protein, respectively, using PIP₂ as substrate. Under the same conditions these activitics were 18.1±1.0 and 8.0±0.8 nmol/min/mg protein for the cytosolic and membrane fractions, respectively, using PIP as substrate. Based on the similarity of the characteristics of these two PLC enzyme activities, it is suggested that the cytosolic and membrane-associated enzyme forms may be closely related.This work was supported by National Institutes of Health Grants HL26057 and HL22619.     

庆大霉素毒性作用对肝肾的影响及其保护的形态学研究

通过肌注庆大霉素使豚鼠出现毒性损害 ,同时以碱性成纤维细胞生长因子作为拮抗剂 ,观察庆大霉素毒性作用对肝肾的形态学影响及其碱性成纤维细胞生长因子的保护作用。结果表明 :碱性成纤维细胞生长因子对庆大霉素肾毒性有一定的保护作用     

Modulation of experimentally-induced cough by stimulation of nasal mucosa in cats and guinea pigs

We measured ventilation (VI) and arterial blood gases in Pekin ducks during acclimatization to 3800 m altitude for 1-90 days. Four experimental series were conducted over 4 years using both natural altitude and a hypobaric chamber. PaCO2 decreased to 3.5 Torr, relative to the value measured during acute hypoxia after 1 day and remained at this level for up to 90 days. However, PaO2 did not increase. Arterial pH showed an unexpected metabolic alkalosis during the first hours at altitude but after 3 days, a metabolic acidosis partially compensated the respiratory alkalosis and pHa was constant thereafter. When normoxia was restored after hypoxia, PaCO2 was 5.5 Torr less than the original normoxic control value, but PaO2 was not increased. VI showed variable changes during acclimatization but if metabolic rate was constant in our study, as reported by others, then effective parabronchial V(VP) increased during acclimatization. Increased VP tends to restore PaO2 toward normoxic levels and decreases adverse effects of gas exchange limitation, which apparently increased during acclimatization in ducks.     

Artificial liver support: future aspects

Liver transplantation and blood purification therapy, including plasmapheresis, hemodiafiltration, and bioartificial liver support, are available to treat patients with severe liver failure. The two mainstream systems developed for bioartificial liver support are extracorporeal whole-liver perfusion (ECLP) and the bioreactor system (BIS). We developed a method of plasma cross-perfusion, in which plasma is exchanged between the blood circuit of the patient and that of a hepatic function unit, that is, whole liver or a bioreactor through which immunologically free whole human blood is perfused. From the aspects of efficacy and safety, the best system of bioartificial liver support for clinical use is considered to be ECLP in cross plasma perfusion. However, a social objection about zoonosis has consistently been raised, with controversy surrounding the use of xenogeneic organs for human treatment, and this might be a final obstacle to the development of system efficacy. The combination therapy of hemodiafiltration with the administration of human serum albumin and anticoagulant factors can minimize the economic and medical resource costs through the development of transgenic livestock that secrete human pharmaceuticals systemically. It is possible that this therapy will become the most practical treatment for patients with severe hepatic failure.     

猪升主动脉几何形态与显微结构的增龄性变化

目的:探讨猪升主动脉几何形态与显微结构成分在增龄过程中的变化规律,为猪→人异种心脏移植吻合血管提供必要的形态学基础。方法:应用组织学和计算机图像分析方法,对42例1～7月龄猪升主动脉进行计量形态学研究。结果:猪升主动脉的管径、壁厚、管腔面积、管壁面积与月龄间呈高度直线正相关关系(r分别为0.98、0.98、0.99、0.99,各P值均<0.001),它们分别以1.54mm月、0.15mm/月、28.26mm~2/月和12.28mm~2/月的速率增加。管壁中胶原纤维含量随之增加(P<0.05);弹性纤维含量以2、3月龄最高,而后维持在相对恒定水平,平滑肌的含量在增龄过程中未见明显变化(P>0.05)。结论:与人类相似,猪升主动脉几何形态、显微结构成分含量与年龄密切相关。