中国人遗传性高铁血红蛋白血症NADH-细胞色素b5还原酶基因L72P突变

目的：鉴定导致中国人遗传性高铁血红蛋白血症（ＲＣＭ）的ＮＡＤＨ－细胞色素ｂ５还原酶（ｂ５Ｒ）基因突变类型，探讨ＲＣＭ发病的分子基础。方法：逆转录－聚合酶链反应产物直接测序和ｃＤＮＡ克隆测序分析先证者的ｂ５Ｒ编码基因；限制性酶切分析其基因组ＤＮＡ。结果：发现一例ＲＣＭ患者ｂ５Ｒ基因第７２密码子存在新的错义突变（ＣＴＣ→ＣＣＣ）。结论：该突变导致ｂ５Ｒ蛋白第７２位亮氨酸被脯氨酸替换（Ｌ７２Ｐ）是该先证者致病的分子基础；进一步证实Ⅰ型ＲＣＭ患者的ｂ５Ｒ基因突变多发生在近５′端部分。     

遗传性高铁血红蛋白血症的研究进展

遗传性高铁血红蛋白血症由NADH-细胞色素b_6还原酶缺陷所致,属带染色体隐性遗传。根据临床表现和生化特点不同可将该病分为四型.I型(红细胞型)——酶缺陷只限于红细胞中,紫绀症状较轻;Ⅱ型(全身细胞型)——酶缺陷见于全身组织的体细胞,除紫钳外,尚有神经精神症状;Ⅲ型(血细胞型)——酶缺陷限于上细胞中,病人无智力障碍;N型——与Cytb_5缺陷有关.现有的研究表明:前3型酶缺陷均为22号染色体-对等位基因突变的结果.     

1例新的遗传性高铁血红蛋白血症复合杂合子基因型的鉴定

目的　从分子水平对 1例遗传性高铁血红蛋白血症患者进行确诊。方法　通过RT PCR产物直接测序 ,分析患者和正常对照b5R基因的cDNA编码序列。用PCR 限制性内切酶分析患者、其父母和正常人基因组DNA。结果　患者的一个b5R等位基因第 72位密码子 (位于外显子 3)发生了CTC→CCC突变 ,原来的亮氨酸被脯氨酸替换。患者另一个b5R等位基因第 2 0 3位密码子 (位于外显子 7)发生了TGC→TAC突变 ,原先的半胱氨酸被酪氨酸取代。结论　在中国患者确定了一个新的遗传性高铁血红蛋白血症基因型 ,即L72P/C2 0 3Y。     

中国人遗传性高铁血红蛋白血症NADH—细胞色素b5还原酶基因L …

目的：鉴定导致中国人遗传性高铁血红蛋白血症（ＲＣＭ）的ＮＡＤＨ－细胞色素ｂ５还原酶（ｂ５Ｒ）基因突变类型，探讨ＲＣＭ发病的分子基础。方法：逆转录－聚合酶链反应产物直接测序和ｃＤＮＡ克隆测定分析先证者的ｂ５Ｒ编码基因，限制性酶切分析其基因组ＤＮＡ。结果；发现一例ＲＣＭ患者ｂ５Ｒ基因第７２密码子存在新的错义突变（ＣＴＣ→ＣＣＣ）。结论：该突变导致ｂ５Ｒ蛋白第７２位亮氨酸被脯氨酸替换（Ｌ７２Ｐ）是该先证     

细胞色素b5还原酶缺陷的分子生物学研究最新进展

遗传性高铁血红蛋白血症主要由NADH-细胞色素b5还原酶(Cytb5R)缺陷引起。膜结合型和胞浆可溶型cytb5R由定位于22号染色体的同一基因编码。多种突变类型可导致该基因编码有缺陷的酶蛋白。本文就目前有关NADH-细胞色素b5还原酶蛋白特性与基因结构特点,基因突变与酶缺陷机制,以及可能建立的基因诊断方法等研究现状作一综述。     

中国人遗传性高铁血红蛋白血症二个家系所见 Cytb5R 基因 Arg~(57)→Gln 突变

目的：探明遗传性高铁血红蛋白血症ＮＡＤＨ－细胞色素ｂ５还原酶（Ｃｙｔｂ５Ｒ）缺陷的分子机制。方法：用逆转录－多聚酶链反应（ＲＴ－ＰＣＲ）方法，克隆３个遗传性高铁血红蛋白血症家系Ｃｙｔｂ５Ｒ９２１ｂｐ的ｃＤＮＡ编码序列，并用限制性酶切ＰＣＲ产物分析３个家系的基因组ＤＮＡ。结果：２个家系存在Ａｒｇ５７→Ｇｌｎ突变，３个家系均未发现Ｇｌｕ２２２→Ｇｌｙ突变。结论：Ａｒｇ５７→Ｇｌｎ突变是中国人遗传性高铁血红蛋白血症的致病原因之一。     

先天性高铁血红蛋白血症

先天性高铁血红蛋白血症临床罕见。现将我院长期误诊为先天性心脏病的先天性高铁血红蛋白血症一例报告如下。1　病例资料女 ,4 0岁。因发绀、气短 4 0年 ,咳嗽、咳痰 5年 ,加重 1周 ,于 1995年 3月 2 7日入院。患者出生后不久即被家人发现发绀 ,曾按“肺炎”治疗无改善。后长期被诊断为“先天性心脏病”。平素身体素质欠佳 ,经常感冒 ,且不易缓解 ,能胜任中等体力劳动。2 5岁结婚 ,足月顺产 2胎 ,子女均生长发育正常。否认家族中有类似病史。查体 :体温 3 7 8℃ ,脉搏 110 /ｍｉｎ ,呼吸 2 2 /ｍｉｎ ,血压 12 0 / 83ｍｍＨｇ。发育良好 ,营…     

NADH—细胞色素b5还原酶缺陷的实验室诊断进展

高铁血红蛋白含量测定、酶活力测定和电泳测定是最早用于诊断遗传性高铁血红蛋白血症的实验室方法，但对杂合子不易检出。放射免疫测定、酶联免疫测定和免疫印迹技术可对ｂ５Ｒ进行定量测定，并有助于了解ｂ５Ｒ在细胞内的分布。基因诊断技术能够检测出引起ｂｓＲ缺陷的基因突变位点，淡阐明ＲＣＭ为发病机制提供可靠的依据。     

中国人遗传性高铁血红蛋白血症研究进展

１　概述　　高铁血红蛋白血症是指血中高铁血红蛋白（ｍｅｔｈｅｍｏｇｌｏｂｉｎ）水平超过血红蛋白总量１％时的临床状态。按原因分为获得性和遗传性两大类。获得性高铁血红蛋白血症最常见,多为摄入某些氧化（还原）性药物或毒物时的一过性表现。遗传性高铁血红蛋白血症（ｈｅｒｅｄｉｔａｒｙｍｅｔｈｅｍｏｇｌｏｂｉｎｅｍｉａ,ＨＭ）绝大部分为ＮＡＤＨ细胞色素ｂ５还原酶（ＮＡＤＨｃｙｔｏｃｈｒｏｍｅｂ５ｒｅｄｕｃｔａｓｅ,ｂ５Ｒ）的遗传缺陷所致,呈常染色体隐性遗传,故又称隐性先天性高铁血红蛋白血症（ｒｅｃｅｓ…     

NADH-细胞色素b_5还原酶缺陷的实验室诊断进展

高铁血红蛋白含量测定、酶活力测定和电泳测定是最早用于诊断遗传性高铁血红蛋白血症的实验室方法，但对杂合子不易检出。放射免疫测定、酶联免疫测定和免疫印迹技术可对b5R进行定量测定，并有助于了解b5R在细胞内的分布。基因诊断技术能够检测出引起b5R缺乏的基因突变位点，为阐明RCM的发病机制提供可靠的依据。     

Plasmapheresis in severe methemoglobinemia following occupational exposure

Ferrous iron can be converted to ferric iron by oxidative stress which results in the formation of methemoglobin. Consequently, the oxygen dissociation curve is shifted to the left, which leads to tissue hypoxia and ultimately may cause death. Acquired methemoglobinemia can be due to a host of offending agents and chemicals including nitrites, local anesthetics, aniline and antimalarial drugs.There are several approaches to the management of methemoglobinemia. The first step is to stop the offending agent and initiate supportive measures. Methylene blue can be used successfully provided the patient has no evidence of glucose 6 phosphate deficiency. Hyperbaric oxygen and intravenous ascorbic acid are other treatment options.We present a case of unusually severe methemoglobinemia (82% methemoglobin) secondary to occupational exposure that failed to respond to several lines of management including methylene blue, red cell exchange, intravenous ascorbic acid, and hyperbaric oxygen. However, the patient responded swiftly to plasmapheresis started upon suspicion of concomitant thrombotic thrombocytopenic purpura, and he subsequently recovered completely.Thus, plasmapheresis may have a role in severe methemoglonbinemia unresponsive to standard treatment options.     

Life-threatening methemoglobinemia after unintentional ingestion of antifreeze admixtures containing sodium nitrite in the construction sites

Context. Construction workers are exposed to a wide variety of health hazards such as poisoning at the construction sites. Various forms of poisoning incidents in construction workers have been reported. However, studies on methemoglobinemia caused by unintentional ingestion of antifreeze admixtures containing sodium nitrite at the construction sites have not been reported yet. Objective. The aim of this study was to evaluate life-threatening methemoglobinemia after unintentional ingestion of antifreeze admixtures containing sodium nitrite at the construction sites and describe similar incidents involving ingestion of antifreeze admixtures in Korea. Materials and methods. Retrospective observational case series study on patients with methemoglobinemia after unintentional ingestion of antifreeze admixtures containing sodium nitrite admitted to the emergency department (ED) from January 1, 2010 to December 31, 2012 and cases reported to the Korea Occupational Safety and Health Agency (KOSHA) was performed. Results. Six victims were admitted to our ED. They had methemoglobin levels ranging from 32.4% to 71.5% and all of them recovered after receiving one (2 mg/kg) or two doses infusion of methylene blue. From the data of the KOSHA, six incidents that caused 27 victims were identified. Of 27 victims, five were included in the ED cases. For all incidents, antifreeze admixtures were not contained in their original containers and all new containers did not have a new label. All workers mistook antifreeze admixtures for water. Among the 28 victims included in this study, four died. Conclusion. Unintentional ingestion of antifreeze admixtures containing sodium nitrite at the construction sites can cause life-threatening methemoglobinemia. There is a need to store and label potentially hazardous materials properly to avoid unintentional ingestion at the construction sites.     

Reduction of NO-induced methemoglobinemia requires extremely high doses of ascorbic acid in vitro

The objective of the present study was to investigate the treatment of nitric oxide (NO)-induced methemoglobinemia by ascorbate and its consequences on red blood cell (RBC) glutathione in vitro. RBC were obtained from five healthy volunteers. The following experiments were carried out: (1) After methemoglobin generation by NO, ascorbate was added (2) RBC were simultaneously exposed to NO and ascorbate (3) Methemoglobin was generated by NO, ascorbate was added and incubation with NO continued. (1) After discontinuation of NO, the mean half life for methemoglobin was reduced from 195 min (controls) to 60 min (10 mM ascorbate) in a dose-dependent manner. (2) Methemoglobin formation after 3 h of NO exposure was 2.7 ± 0.3 % in controls and 1.8 ± 0.1 % with 10 mM ascorbate (p < 0.01). (3) Further methemoglobin formation was inhibited only by 10 mM ascorbate (p < 0.001). NO incubation did not affect RBC glutathione (86.5 ± 19.6 and 86.5 ± 19.6 mg/l, respectively). Treatment with 10 mM ascorbate significantly decreased glutathione (p < 0.002). In vitro, NO-induced methemoglobin formation is significantly decreased only by a high (10 mM) ascorbate concentration. Glutathione, critical for ascorbate activity, is not influenced by NO. Received: 26 November 1997 Accepted: 5 March 1998     

中国成人肝微粒体P450酶活性研究

目的观察中国成人肝微粒体细胞色素P450（CYP450）、细胞色素b5（CYb5）的含量及常见几种药物代谢酶活性水平及在性别、民族间的分布差异。方法肝组织匀浆10000&#215;g离心去除沉淀,再以100000&#215;g超速离心60min,取沉淀加PBS甘油缓冲液,充分溶解制成微粒体悬液,用Lowry法测定蛋白含量;用双光道紫外分光光度计测定CYP450和CYb5的含量及P450酶活性。结果48例成人肝微粒体CYP450和CYb5含量分别为（0．46&#177;0．07）nmol／mg和（0．44&#177;0．04）nmol／mg;男性组CYP450和CYb5含量分别为0．49&#177;0．05）nmol／mg和（0．46&#177;0．06）nmol／mg,均高于女性组的（O．41&#177;0．08）nmol／mg、（O．42&#177;0．05）nmol／mg,P〈0．05;汉族、回族和壮族3个民族P450和CYb5含量作q检验进行两两比较,各组间差异均无统计学意义（P〉0．05）。药物代谢酶NADPH细胞色素C还原酶（NR）、乙基吗啡N-脱甲基酶（EDM）、氨基比林N-脱甲基酶（ADM）、苯并芘羟化酶（BPH）和戊巴比妥侧链羟化酶（PSCH）等酶活性水平分别为（0．71&#177;0．13）nmol／（mg&#183;min）,（0．89&#177;0．18）nmol／（mg&#183;min）,（0．99&#177;0．17）nmol／（mg&#183;min）,（0．07&#177;0．01）nmol／（mg&#183;min）,（4．15土0．65）μmol／（mg&#183;min）,其中EDM活性水平女性组高于男性组（P〈0．05）,PSCH活性水平男性组高于女性组（P〈0．05）,其他各种酶活性男女之间无显著性差异;上述5种酶活性水平经q检验,汉族、回族和壮族3个民族之间差异无统计学意义（P〉0．05）。结论测定了中国成人肝微粒体CYP450、CYb5含量及NR,EDM,ADM,BPH,PSCH等酶活性水平,男性组CYP450、CYb5含量及PSCH活性高于女性组,而EDM活性水平女性组高于男性组,上述7种指标在汉族、回族和壮族之间差异均无统计学意义。     

EMLA-induced methemoglobinemia after laser-assisted hair removal procedure

This is the case of a 23-year-old female with a past medical history of ADHD and Depression who was evaluated in the emergency department for perioral cyanosis and hypoxia after application of the eutectic mixture of lidocaine and prilocaine (EMLA) local anesthetic prior to a laser-assisted hair removal procedure. This report illustrates a case of methemoglobinemia which is a rare but significant complication of topical anesthetic use.     

Electrophoretic and functional variants of NADH-methemoglobin reductase in hereditary methemoglobinemia

The electrophoretic mobility and activity of NADH-methemoglobin reductase in erythrocytes of patients with hereditary methemoglobinemia, obligatory heterozygotes, and normal subjects were examined. Six distinct electrophoretic variants were found in studies of erythrocytes from members of ten different families. Five variants (Boston Slow, Duarte, Princeton, Puerto Rico, and California) were associated with significant methemoglobinemia and moderate to marked decreases in enzymic activity. Precise correlations between levels of NADH-methemoglobin reductase activity, electrophoretic mobility, and clinical severity of methemoglobinemia, however, could not be drawn. One variant (Boston Fast) was associated with almost normal activity and very minimal methemoglobinemia. Nine members from three generations of two Italian families were found to have two bands with NADH-methemoglobin reductase activity in their erythrocytes, one with normal mobility and one with a mobility identical with that of Boston Fast. No functional or clinical impairment could be attributed to this abnormality. The observations made in this investigation were consistent with an autosomal recessive mode of inheritance of multiple alleles for NADH-methemoglobin reductase. As has been shown to be true for hemoglobin and glucose-6-phosphate dehydrogenase, multiple aberrations in the NADH-methemoglobin reductase of human erythrocytes apparently exist, some with and some without functional consequences.Two bands with NADPH-methemoglobin reductase activity with electrophoretic mobilities distinct from those of the NADH-methemoglobin reductase were found in human erythrocytes. These bands were normal in hemolysates of erythrocytes from patients with hereditary methemoglobinemia, but were absent from the hemolysate of erythrocytes deficient in NADPH-methemoglobin reductase activity. These latter erythrocytes, however, contained normal concentrations of methemoglobin and had a normal ability to reduce methemoglobin in vitro. These observations were most consistent with the thesis that the NADH-methemoglobin reductase, distinct from any NADPH-methemoglobin reductase, was the major system responsible for the reduction of methemoglobin to hemoglobin in human erythrocytes.     

分子生物学技术在神经系统遗传性疾病诊断中的应用

近20年，分子生物学技术的迅猛发展带动了一大批相关学科的深入进展，使得一些长期以来只能简单地从临床表象认识的疾病深入至分子基因水平研究，从而发现疾病的真正病因，为诊断和治疗提供了坚实的基础。由于人类基因组中数以千计的基因都表达于神经系统(中枢和外周神经系统)．