Physiologic regulation and tissue localization of renal erythropoietin messenger RNA

Although erythropoietin (Epo) is produced primarily by the kidneys in response to hypoxia, the precise cell type(s) and mechanisms by which these cells regulate production are poorly understood. In the experiments we report, the kinetics of renal Epo production in response to acute hypoxia and the intrarenal localization of cellular Epo synthesis were studied at the level of Epo mRNA. Erythropoietin mRNA expression was determined by Northern blot analysis of rat kidney RNAs using a probe derived from the mouse Epo gene. Renal Epo mRNA content increased as early as 1 hour after initiation of hypoxia and continued to accumulate during 4 hours of stimulation. Discontinuation of the hypoxic stimulus resulted in rapid decay of mRNA levels. Kidney and plasma Epo levels measured by radioimmunoassay paralleled, with respective lag times, the changes in renal Epo mRNA content, suggesting that Epo production in response to acute hypoxia represents de novo synthesis and is regulated by changes in Epo mRNA. Northern blot analysis of RNAs extracted from separated glomerular and tubular tissue fractions revealed Epo mRNA in the tubular fraction, whereas glomerular tissue did not contain Epo mRNA. Thus, the site of cellular Epo synthesis is located in the renal tubule or its interstitium and not in the glomerular tuft.     

Bone marrow transplantation for patients with Philadelphia chromosome- positive acute lymphoblastic leukemia

We report the treatment outcome of allogeneic bone marrow transplantation in ten patients with Philadelphia chromosome-positive acute lymphoblastic leukemia. Six patients are alive and well for 6 to 30 months (median 19 months) after transplantation. Four patients died with transplant related complications. In view of the poor prognosis associated with this disease, marrow ablation followed by allogeneic or syngeneic marrow grafting may be the preferred treatment modality if a suitable marrow donor is available.     

Molecular basis of altered red blood cell membrane properties in Southeast Asian ovalocytosis: role of the mutant band 3 protein in band 3 oligomerization and retention by the membrane skeleton

Southeast Asian ovalocytosis (SAO) is an asymptomatic trait characterized by rigid, poorly deformable red cells that resist invasion by several strains of malaria parasites. The underlying molecular genetic defect involves simple heterozygous state for a mutant band 3 protein, which contains a deletion of amino acids 400 through 408, linked with a Lys 56-to-Glu substitution (band 3-Memphis polymorphism). To elucidate the contribution of the mutant SAO band 3 protein to increased SAO red blood cell (RBC) rigidity, we examined the participation of the mutant SAO band 3 protein in increased band 3 attachment to the skeleton and band 3 oligomerization. We found first that SAO RBC skeletons retained more band 3 than normal cells and that this increased retention preferentially involved the mutant SAO band 3 protein. Second, SAO RBCs contained a higher percentage of band 3 oligomer-ankyrin complexes than normal cells, and these oligomers were preferentially enriched by the mutant SAO protein. At the ultrastructural level, the increased oligomer formation of SAO RBCs was reflected by stacking of band 3-containing intramembrane particles (IMP) into longitudinal strands. The IMP stacking was not reversed by treating SAO RBCs in alkaline pH (pH 11), which is known to weaken ankyrin-band 3 interactions, or by removing the cytoplasmic domain of band 3 from SAO membranes with trypsin. Finally, we found that band 3 protein in intact SAO RBCs exhibited a markedly decreased rotational mobility, presumably reflecting the increased oligomerization and the membrane skeletal association of the SAO band 3 protein. We propose that the mutant SAO band 3 has an increased propensity to form oligomers, which appear as longitudinal strands of IMP and exhibit increased association with membrane skeleton. This band 3 oligomerization underlies the increase in membrane rigidity by precluding membrane skeletal extension, which is necessary for membrane deformation.     

Functional entrapment of the popliteal artery

A case of functional entrapment missed at the initial angiogram is presented. The imaging of popliteal artery entrapment syndrome and functional entrapment is discussed. The importance of appropriate imaging is emphasized. The classification of popliteal artery entrapment syndrome is discussed and it is proposed that functional entrapment is added to the existing classification in the interest of consistent reporting.     

角膜缘干细胞移植在眼科的临床应用及发展

目的:探讨角膜缘干细胞移植的应用现状及发展前景。资料来源:应用计算机检索PUBMED 2000/2007与角膜缘干细胞移植相关的文章,检索词“limbal stem cells,transplantation”,限定文献语种为“English”;同时检索万方数据库2000/2007相关文章,检索词“角膜缘干细胞,移植”,限定文献语种为中文。资料选择:共检索到相关文献180余条,选择与角膜缘干细胞的组织生物学特征、角膜缘干细胞的体外培养以及角膜缘干细胞的临床应用相关的文章。资料提炼:将初步筛选的文章进一步查找全文,排除综述和重复文献,内容相似的选择发表在权威杂志或近3年发表的文献,无论有无对照组,观察对象为人或动物均纳入。最后共纳入37篇进行综述,其中7篇研究角膜缘干细胞的组织生物学特性,8篇介绍角膜缘干细胞的体外培养,剩余22篇文章为角膜缘干细胞移植的基础和临床研究。资料综合:角膜缘干细胞移植,可以恢复正常的角膜缘屏障功能,重建眼表的完整性;而最终改善角膜的透明性和视功能。目前开展的角膜缘干细胞移植,包括自体或异体角膜缘组织移植和体外培养的角膜缘干细胞移植。自体角膜缘干细胞的移植已成为临床上较为可靠和日益成熟的治疗方法,但来源有限,且不适合双眼角膜缘病变的患者,异体角膜缘组织移植存在排斥反应,因此自体角膜缘干细胞体外培养移植术被认为是目前较理想的角膜缘干细胞移植方法,但其远期疗效需进一步临床观察。结论:目前角膜缘干细胞移植治疗严重角膜病变的研究尚处于初步阶段,自体角膜缘干细胞移植成功率是较高,自体角膜缘干细胞培养后移植治疗眼表疾病已初步获得成功,但还存在一些问题,如角膜缘干细胞生存的微环境、培养的干细胞生理、生化的免疫特性,以及黏附、增殖、分化能力等问题尚需进一步研究。     

An audit of consent refusals in clinical research at a tertiary care center in India

Background and Rationale:

Ensuring research participants’ autonomy is one of the core ethical obligations of researchers. This fundamental principle confers on every participant the right to refuse to take part in clinical research, and the measure of the number of consent refusals could be an important metric to evaluate the quality of the informed consent process. This audit examined consent refusals among Indian participants in clinical studies done at our center.

Materials and Methods:

The number of consent refusals and their reasons in 10 studies done at our center over a 5-year period were assessed. The studies were classified by the authors according to the type of participant (healthy vs patients), type of sponsor (investigator-initiated vs pharmaceutical industry), type of study (observational vs interventional), level of risk [based on the Indian Council of Medical Research (ICMR) “Ethical Guidelines for Biomedical Research on Human Participants”], available knowledge of the intervention being studied, and each patient''s disease condition.

Results:

The overall consent refusal rate was 21%. This rate was higher among patient participants [23.8% vs. healthy people (14.9%); P = 0.002], in interventional studies [33.6% vs observational studies (7.5%); P < 0.0001], in pharmaceutical industry-sponsored studies [34.7% vs investigator-initiated studies (7.2%); P < 0.0001], and in studies with greater risk (P < 0.0001). The most common reasons for consent refusals were multiple blood collections (28%), inability to comply with the study protocol (20%), and the risks involved (20%).

Conclusion:

Our audit suggests the adequacy and reasonable quality of the informed consent process using consent refusals as a metric.KEY WORDS: Autonomy, consent, India, reason, refusal, risk     

Inhibitory effect of hydroxyflutamide plus tamoxifen on oestradiol-induced growth of MCF-7 breast cancer cells

The antiandrogen flutamide has been reported to exert antiproliferative actions on breast cancer both in vitro and in vivo. Here we study the action of its active metabolite hydroxyflutamide on the oestradiol-induced growth of MCF-7 breast cancer cells. The results show that the antiandrogen inhibits the cell growth. Moreover hydroxyflutamide adds its antiproliferative effect to the action of the antioestrogen tamoxifen. The inhibitory effect is dose-dependent and it is unaffected by tamoxifen concentrations up to levels able to block oestrogen receptors completely. Dihydro-testosterone experiments parallel those on hydroxyflutamide. When the two substances are administered together, neither antagonistic nor additive effects are appreciable. Data are consistent with an androgen-like action of hydroxyflutamide on breast cancer cells. The antiproliferative effect of hydroxyflutamide, without virilizing side-effects, suggests that it is worth exploring its possible employment together with antioestrogens in the treatment of breast cancer patients.Abbreviations OH-flutamide hydroxyflutamide - E ₂ 17-oestradiol - DHT dihydrotestosterone - ER oestrogen receptor - AR androgen receptor     

Peroxidase-H2O2-halide system: Cytotoxic effect on mammalian tumor cells

Myeloperoxidase, H2O2, and a halide constitute a potent antimicrobial system. A cytotoxic effect of this system on a line of mouse ascitic lymphoma cells (LSTRA) is demonstrated here using four different assay systems: 51Cr release, trypan blue exclusion, inhibition of glucose C-1 oxidation, and loss of oncogenicity for mice. Deletion of each component of the system, preheating the peroxidase, or addition of azide, cyanide, or catalase abolished the cytotoxicity. Myeloperoxidase was effective with either chloride or iodide as the halide, while lastoperoxidase was effective with iodide but not chloride. The iodinated thyroid hormones, triiodothyronine and thyroxine, could substitute for the halide, and H2O2 could be replaced by a peroxide- generating enzyme system such as glucose and glucose oxidase or by H2O2 producing bacteria such as pneumococci or streptococci. The possibility is raised that the peroxidases of inflammatory cells and certain biologic fluids may affect tumor initiation or growth in vivo.