Intracellular signal transduction by the extracellular calcium-sensing receptor of Xenopus melanotrope cells

The extracellular calcium-sensing receptor (CaR) is expressed in various types of endocrine pituitary cell, but the intracellular mechanism this G protein-coupled receptor uses in these cells is not known. In the present study we investigated possible intracellular signal transduction pathway(s) utilized by the CaR of the endocrine melanotrope cells in the intermediate pituitary lobe of the South African-clawed toad Xenopus laevis. For this purpose, the effects of various pharmacological agents on CaR-evoked secretion of radiolabeled secretory peptides from cultured melanotrope cells were assessed. CaR-evoked secretion, induced by the potent CaR agonist l-phenylalanine (l-Phe), could not be inhibited by cholera toxin, nor by NPC-15437 and PMA, indicating that neither G_s/PKA nor G_q/PKC pathways are involved. However, pertussis toxin (G_i/o protein inhibitor), genistein (inhibitor of PTKs), wortmannin/LY-294002 (PI3-K inhibitor) and U-0126 (inhibitor of extracellular signal-regulated kinase, ERK) all substantially inhibited CaR-evoked secretion, indicating that the Xenopus melanotrope cell possesses a PI3-K/MAPK system that plays some role in CaR-signaling. Since no direct effect of l-Phe on ERK phosphorylation could be shown it is concluded that CaR must act primarily through another, still unknown, signaling pathway in Xenopus melanotropes. Our results indicate that the PI3-K/MAPK system has a facilitating effect on CaR-induced secretion, possibly by sensitizing the CaR.     

抗ProGRP(31-98) scFv的131I标记及生物分布研究

目的 研究抗胃泌素释放前体（ProGRP（31-98）单链抗体（scFv）的131I标记方法,并对其标记后的稳定性、免疫活性及生物分布进行分析.方法 采用氯胺T法碘化标记制备131I-anti-ProGRP（31-98）scFv,凝胶柱层析法分离纯化标记产物,利用纸层析法测定标记物的标记率、放化纯度和稳定性,采用细胞结合分析法比较131I-anti-ProGRP（31-98）scFv对小细胞肺癌细胞株NCI-H446和肺腺癌细胞株A549的免疫结合率.将131I-ProGRP（31-98）scFv注射入动物体内,研究其在实验动物体内的分布情况.结果 131I-anti-ProGRP（31-98）标记率为（93.35±0.67）％,标记产物纯化后即刻放化纯度为（98.49±1.21）％.131I-anti-ProGRP（31-98）scFv对人小细胞肺癌NCI-H446和肺腺癌A549细胞株的免疫结合率分别为（85.36±1.45）％和（21.02±2.16）％,且差异有统计学意义（P＜0.05）.131I-anti-ProGRP（31-98）scFv在实验动物体内主要通过肾脏和肝脏代谢,血液清除快.结论 131I-anti-ProGRP（31-98） scFv的标记率高,且有良好的稳定性和免疫活性,在实验动物体内主要通过肝脏和肾脏代谢,血液清除快.     

Influence of technetium-99m-labeling conditions on physico-chemical and related biological properties of an acylated poly-galactosidic macrophage targeting agent for inflammation imaging

The potential of ^99m-Tc-J001 for the investigation of inflammatory lesions via the targeting of recruited macrophages (Mφ) has already been documented in several experimental models and in human diseases. To achieve a functional imaging of inflammation via Mφ targeting, minimal labeled colloid content and high in vivo stability of ^99mTc-J001 are essential. The actual specificity of such scintigraphy is closely dependent upon the radiolabeling of only the J001 molecules available for Mφ targeting. To develop an appropriate radiopharmaceutical kit, optimization of the labeling conditions was achieved from a series of pilot formulations that were evaluated for radiolabeling efficiency and both in vitro and in vivo ^99mTc-J001 stability. Colloids were characterized using autocorrelation spectroscopy and multiangle laser-light scattering, radioactive colloid content of the formulations being deduced from biodistribution studies. This work has made possible the definition of a formulation exhibiting a radiolabeling yield >97.0%, associated with in vivo stability and minimal colloid formation, thus greatly enhancing the specificity of such macrophage scintigraphy.     

A first synthesis of 18F‐radiolabeled lapatinib: a potential tracer for positron emission tomographic imaging of ErbB1/ErbB2 tyrosine kinase activity

Fluorine‐18‐labeled lapatinib has been successfully synthesized for the first time by the reaction of a dimethylformamide solution of meta‐[¹⁸F]fluorobenzylbromide with a Boc‐protected lapatinib precursor fragment. The reaction proceeded in the presence of K₂CO₃ at 110 °C for 10 min in a microwave and was followed by Boc‐group deprotection with trifluoroacetic acid. The overall radiochemical yield of the reaction starting from the radiofluorination of the iodonium salt was 8–12% (uncorrected, n = 6) in a 140‐min synthesis time.     

Direct evidence of the temperature dependence of Gd-BOPTA transport in the intact rat liver

The aim was to study the influence of temperature on the transport of the hepatobiliary contrast agent Gadobenate dimeglumine (Gd-BOPTA). Rat livers were isolated and perfused with Gd-BOPTA at 12, 25, 30, 36 and 38 °C. After the perfusion period, biopsies were collected and the MR signal intensity was measured. Uptake and biliary excretion were quantified with radiolabeled Gd-BOPTA. MR signal intensity decreased with temperature of perfusion. This phenomenon was appropriately quantified with ¹⁵³Gd and ¹⁵³Sm labeling, in contrast to ⁶⁷Ga.     

Preparation and the kinetic stability of hyaluronan radiolabeled with In,I and C

Three different procedures for the labeling of hyaluronan (HA) with ¹¹¹In, ¹²⁵I and ¹⁴C radionuclides were compared, and the kinetic stability of radiolabeled HA under different conditions (saline, artificial gastric juice and plasma) was established. Modification of HA structure with bifunctional chelating agents (DTPA) or with the prosthetic group (tyramine or tyrosine) was essential prior ¹¹¹In and ¹²⁵I labeling. These chemical labeling techniques were fast, simple and inexpensive, and labeled agents with a high specific activity were obtained. The only disadvantage of these methods was the occurrence of unknown functional groups in the HA molecule requiring further characterization of the compound. Conversely, HA labeling with ¹⁴C by biotechnological synthesis was found to be rather expensive and time-consuming process. Although, the final product ¹⁴C-HA was identical to natural HA its low specific activity presents certain limitation for its application in biological experiments. Stability studies showed that ¹⁴C-HA and ¹²⁵I-Tm-HA were stable in all studied mediums. In the case of ¹²⁵I-Trs-HA, stability slightly decreased in rat plasma and in artificial gastric juice with increasing time. The least stable was ¹¹¹In-DTPA-HA, which degraded completely after 48 h in artificial gastric juice. Kinetic stability studies may provide primary information concerning the properties of radiolabeled HA in vitro, which is essential for the use and explanation of its behavior in biological experiments.     

Etoposide Loaded PLGA and PCL Nanoparticles II: Biodistribution and Pharmacokinetics after Radiolabeling with Tc-99m

Etoposide and nanoparticle formulations were labeled with Tc-99m and their biodistribution and pharmacokinetics were studied after intravenous administration in healthy mice and rabbits respectively. Etoposide was rapidly cleared from the body, while the disposition of nanoparticles was slower. A higher proportion of nanoparticles compared with etoposide was observed in different organs of mice. Scintigraphic images of rabbits concluded that the radioactivity shown by formulations is significantly higher after 4 and 24 h, as compared with etoposide administered in rabbits. AUC_{0 ? ∞}, clearance and MRT are better than those obtained with etoposide administration. The overall high residence of nanoparticles, compared with etoposide, signifies the advantage of PLGA and PCL nanoparticles as drug carriers for etoposide in enhancing the bioavailability and reducing the etoposide-associated toxicity.     

Preparation and quality control of the [sm]-samarium maltolate complex as a lanthanide mobilization product in rats

Development of lanthanide detoxification agents and protocols is of great importance in management of overdoses. Due to safety of maltol as a detoxifying agent in metal overloads, it can be used as a lanthanide detoxifying agent. In order to demonstrate the biodistribution of final complex, [(153)Sm]-samarium maltolate was prepared using Sm-153 chloride (radiochemical purity >99.9%; ITLC and specific activity). The stability of the labeled compound was determined in the final solution up to 24h as well as the partition coefficient. Biodistribution studies of Sm-153 chloride, [(153)Sm]-samarium maltolate were carried out in wild-type rats comparing the critical organ uptakes. Comparative study for Sm(3+) cation and the labeled compound was conducted up to 48 h, demonstrating a more rapid wash out for the labeled compound. The effective and biological half lives of 2.3 h and 2.46h were calculated for the complex. The data suggest the detoxification property of maltol formulation for lanthanide overdoses.     

血管平滑肌细胞体外摄取寡核苷酸探针的研究

目的:以99mTc标记针对c-myc和bcl-2 mRNA的寡核苷酸并检测其在血管平滑肌细胞(VSMC)中的摄取情况,初步探讨其在粥样硬化病变中的诊断价值。方法99mTc标记寡核苷酸后分别加入体外培养对数生长期及平台期猪冠状动脉VSMC,37℃条件下温育,检测不同时段摄取百分数。结果:增殖期或平台期VSMC对bcl-2探针的摄取均低于对c-myc探针的摄取。在c-myc探针组,增殖期细胞较平台期摄取高反义探针较正义探针摄取高。结论:增殖期VSMC对c-myc反义探针的摄取增高和(或)对bcl-2反义探针的摄取减少,有望成为粥样病变的早期诊断指标。     

An experimental model to study the effects of a senna extract on the blood constituent labeling and biodistribution of a radiopharmaceutical in rats

ABSTRACT Cassia angustifolia Vahl (senna) is a natural product that contains sennosides, which are active components that affect the intestinal tract and induce diarrhea. Authors have shown that senna produces DNA (deoxyribonucleic acid) lesions in Escherichia coli cultures and can act as an antifungal agent. Natural drugs can alter the labeling of blood constituents with technetium-99m (^99mTc) and can affect the biodistribution of radiopharmaceuticals. In this work, we have evaluated the influence of a senna extract on the radiolabeling of blood constituents and on the biodistribution of the radiopharmaceutical sodium pertechnetate (Na^99mTcO₄) in Wistar rats. Twelve animals were treated with senna extract for 7 days. Blood samples were withdrawn from the animals and the radiolabeling procedure was carried out. The senna extract did not modify the radiolabeling of the blood constituents. A biodistributional assay was performed by administering Na^99mTcO₄ and determining its activity in different organs and in blood. The senna extract altered the biodistribution of Na^99mTcO₄ in the thyroid, liver, pancreas, lungs and blood. These results are associated with properties of the chemical substances present in the aqueous senna extract. Although these assays were performed in animals, our findings suggest that caution should be exercised when nuclear medicine examinations using Na^99mTcO₄ are conducted in patients who are using senna extract.