Melatonin reduces nitric oxide synthase activity in rat hypothalamus

Abstract: In this report, rat hypothalamic nitric oxide synthase (NOS) activity is shown to be partially inhibited by physiological concentrations of the pineal hormone melatonin. In vitro studies demonstrate that 1 nM melatonin, which approximates the physiological concentration of the hormone at night, significantly inhibited NOS activity. In vivo studies show that administering melatonin or collecting the hypothalamus from animals at night, when endogenous melatonin levels are elevated, results in a significant decrease of NOS activity. Results also show that calmodulin may be involved in this process since its presence in the incubation medium prevents the inhibitory effect of melatonin on NOS activity.     

Inhibitory effects of chlorpheniramine and astemizolum on contraction of isolated rat and rabbit uteri induced by oxytocin and PGF2α

Summary The contraction of isolated rat and rabbit uteri induced by oxytocin and PGF_2α was markedly inhibited by chlorpheniramine (Chl) and astemizolum (Ast), both of which also decreased the resting tension of uteri, and their spontaneous contraction. The inhibitory effects of both drugs were dose-dependent. At high concentrations, Chl 7.4× 10^-4 mol/L and Ast 10^-4 mol/L could counteract the contraction of the uteri induced by Oxy and PGF_2α, and their spontaneous contraction as well. They decreased the resting tension to the lower level. The mechanism of their non-special relaxed action on uteri could not be completely explained only by their H₁-receptor blocking action. Whether they act by blocking calcium channel or by inhibiting calmodulin (CaM) remains to be further explored.     

Effects of Intraventricular Injection of Calmodulin Antagonist （Trifluoperazine） on Pregnancy in Rats

Injection of TFP (a specific antagonist of CaM) into the lateral ventricles of the rat brain on the fourth day of pregnancy causes marked antifertility effect in 83% of the rats (0% in the control group). Examination with the pontamone blue reaction for the implantation elucidated that the antifertitity effect was due to the blockage of implantation of the follicle. Injection of TFP into the lateral ventricles of the brain markedly reduced the concentration of CaM in hypothalamus, ovary and uterus. Serum progesterone was also reduced. However, injection glven on day 7 was ineffective to terminate the pregnancy. Injection given on certain time of pregnancy was able to reduce the cellular CaM content and to cause antifertitity. This finding demonstrated that CaM played an important rote during the course of pregnancy.     

Comparison of salivary calmodulin binding proteins in Sjögren''s syndrome and healthy individuals

Background: Reduction in salivary secretion is the hallmark of Sjögren's syndrome (SS). Calmodulin (CaM) and calmodulin binding proteins (CaMBPs) play a key role in the secretory process of saliva. Recent studies have suggested that SS‐B, an autoantibody associated with SS, is a CaMBP. This finding suggests that CaMBP may contribute to the loss of saliva in SS. To better understand the role(s) of these proteins in SS, the purpose of this study was to compare salivary CaMBPs in Sjögren's patients and controls. Methods: Saliva samples were collected from 20 patients and 20 age‐, race‐, and gender‐matched controls. CaM overlay was used to identify CaMBPs in saliva of patients and controls. Results: Higher number of salivary CaMBPs was observed among patients than controls. Conclusions: The increased number of salivary CaMBPs in SS may suggest a potential role for these proteins in the pathogenesis of the disease.     

重组人钙调素对人脐静脉内皮细胞增殖作用的影响

本文探讨外源性重组人钙调素(recombinant human calmodulin,rhCaM)对人脐静脉内皮细胞(HUVEC)增殖作用的影响。采用基因重组技术在大肠杆菌DH5α中高效表达并纯化rhCaM。将HUVEC接种于96孔培养板,加入不同浓度rhCaM,用MTT比色法检测rhCaM对HUEVC细胞增殖作用的影响。结果表明rhCaM在0.04～0.4μg/ml浓度范围内可促进HUEVC的增殖,促增殖作用随细胞培养密度的增加而减弱,也与培养基中新生小牛血清的含量密切相关。故rhCaM对HUEVC增殖具有促进作用。     

Regulation of smooth muscle actin—myosin interaction and force by calponin

Smooth muscle contraction is regulated primarily by the reversible phosphorylation of myosin triggered by an increase in sarcoplasmic free Ca²⁺ concentration ([Ca²⁺]_i). Contraction can, however, be modulated by other signal transduction pathways, one of which involves the thin filament-associated protein calponin. The h1 (basic) isoform of calponin binds to actin with high affinity and is expressed specifically in smooth muscle at a molar ratio to actin of 1: 7. Calponin inhibits (i) the actin-activated MgATPase activity of smooth muscle myosin (the cross-bridge cycling rate) via its interaction with actin, (ii) the movement of actin filaments over immobilized myosin in the in vitro motility assay, and (iii) force development or shortening velocity in permeabilized smooth muscle strips and single cells. These inhibitory effects of calponin can be alleviated by protein kinase C (PKC)-catalysed phosphorylation and restored following dephosphorylation by a type 2A phosphatase. Three physiological roles of calponin can be considered based on its in vitro functional properties: (i) maintenance of relaxation at resting [Ca²⁺]_i, (ii) energy conservation during prolonged contractions, and (iii) Ca²⁺-independent contraction mediated by phosphorylation of calponin by PKCε, a Ca²⁺-independent isoenzyme of PKC.     

Is calmodulin involved in the regulation of gap junction permeability?

The cell-to-cell channels of gap junctions mediate the direct exchange of ions and small metabolites between neighboring cells. A number of studies have shown that these channels close when the intracellular free calcium or hydrogen concentration increases, the result being cell-to-cell uncoupling. Since most of the calcium-activated biological phenomena are mediated by calmodulin (CaM), an obvious question is whether or not CaM is involved in the mechanism of cell coupling regulation. Data from the present study, showing the inhibitory effects of a calmodulin blocker on electrical uncoupling in Xenopus embryo cells, suggest a possible CaM participation in the uncoupling mechanism.     

钙调蛋白基因缺陷HIS3酵母菌株的构建和鉴定

目的：构建白念珠菌钙调蛋白基因（CMD1）缺陷HS3酵母菌体,为进一步探讨钙调蛋白基因突变对真菌生长周期及致病性的影响奠定基础。方法：首先将含cmd1::TRP1置换序列的质粒I转化二倍体酵母菌株YPH501(his3trplural）,经Soutthern印迹法筛选出含TRP1序列的菌株。其次,将含CMD1序列的质粒Ⅱ转化以上TRP1阳性菌株,进行减数分裂后选择得到TRP1阳性酵母菌株单倍体。最后,将含trp1:HIS3置换序列质粒Ⅲ转化上述TRP1阳性单倍体菌株,用不含His培养基培养得到钙调蛋白基因缺陷HIS3酵母菌株。结果：经Southern印迹法证实cmd1：TRP1基因置换克隆;减数分裂后选择得到了TRP1阳性酵母菌株单倍体;质粒Ⅲ转化单倍体后经不含His培养基培养得到CMD1缺陷HIS3菌株,接种于不含Trp倍养基上未见有菌落生长,说明质粒Ⅲ转化单倍体后已将his3TRP1转换成HIS3trp1。结论：成功构建了钙调蛋白基因缺陷HIS3酵母菌株,基因型为cmd1trp1HIS3。     

钙调蛋白在大鼠晶状体生长发育和白内障形成中作用的研究

目的 探讨钙调蛋白(CaM)活性变化在大鼠晶状体生长发育和白内障形成中的作用。方法 从大鼠脑组织中提取钙调蛋白，从牛心中提取钙调蛋白依赖型磷酸二酯酶(PDE-I)，测定不同生长发育阶段和硒性白内障大鼠晶状体中钙调蛋白的相对活性。结果 钙调蛋白相对活性随大鼠年龄增长下降，硒性白内障晶状体中钙调蛋白相对活性高于同年龄正常晶状体。结论 钙调蛋白参与晶状体的生长发育过程，钙调蛋白相对活性升高是白内障形成的原因之一。     

The effect of divalent cations on neuronal nitric oxide synthase activity.

Neuronal nitric oxide synthase (NOS I) is a Ca(2+)/calmodulin-binding enzyme that generates nitric oxide (NO*) and L-citrulline from the oxidation of L-arginine, and superoxide (O(2)*(-)) from the one-electron reduction of oxygen (O(2)). Nitric oxide in particular has been implicated in many physiological processes, including vasodilator tone, hypertension, and the development and properties of neuronal function. Unlike Ca(2+), which is tightly regulated in the cell, many other divalent cations are unfettered and can compete for the four Ca(2+) binding sites on calmodulin. The results presented in this article survey the effects of various divalent metal ions on NOS I-mediated catalysis. As in the case of Ca(2+), we demonstrate that Ni(2+), Ba(2+), and Mn(2+) can activate NOS I to metabolize L-arginine to L-citrulline and NO*, and afford O(2)*(-) in the absence of L-arginine. In contrast, Cd(2+) did not activate NOS I to produce either NO* or O(2)*(-), and the combination of Ca(2+) and either Cd(2+), Ni(2+), or Mn(2+) inhibited enzyme activity. These interactions may initiate cellular toxicity by negatively affecting NOS I activity through production of NO*, O(2)*(-) and products derived from these free radicals.