Uptake and metabolism of free cyanocobalamin by cultured human fibroblasts from controls and a patient with transcobalamin II deficiency

We have investigated the uptake and metabolism of free cyanocobalamin (CN-Cbl; vitamin B₁₂) by intact cultured human skin fibroblasts. Monolayers of control fibroblasts take up free CN-[⁵⁷Co]Cbl via a saturable, calcium-independent process that is inhibited by sulfhydryl reagents, inhibitors of protein synthesis, and inhibitors of electron transport, but not by inhibitors of glycolysis. CN-Cbl taken up in this manner is converted to active cobalamin (Cbl) coenzymes (adenosylcobalamin and methylcobalamin) and becomes associated with intracellular Cbl-dependent apoenzymes (methylmalonyl CoA mutase and homocysteine:methyltetrahydrofolate methyltransferase). Since fibroblasts from controls were also found to synthesize transcobalamin II (TC II), a plasma protein shown previously to facilitate the cellular uptake of Cbl, it seemed possible that the observed uptake of free CN-Cbl was TC II-mediated. This thesis was rejected by demonstrating that cells from a patient with complete TC II deficiency took up free CN-Cbl as well as control cells did. Finally, we propose a mechanism by which an uptake process for free Cbl might serve a function in intracellular metabolism of Cbl.     

Association analysis of Arg16Gly polymorphism of the beta2-adrenergic receptor gene in offspring from hypertensive and normotensive families

Objective: Since β2 -adrenergic receptors ( β2 AR) can influence blood pressure not only by vasodilation, but also participate in noradrenaline release from sympathetic nerve endings, we have studied whether Arg16Gly polymorphism of the β2 AR gene is associated with predisposition to essential hypertension and increased plasma noradrenaline concentration in offspring from normotensive (SN) and hypertensive parents (SH). Design and methods: The study population consisted of 105 young SN and 101 SH subjects matched for age and body mass index. Arg16Gly polymorphism of the β2 AR gene was determined by polymerase chain reaction (PCR) technique and subsequent incubation with NcoI restriction enzyme. Resulting fragments were separated using electrophoresis on a 4.2% Metaphor agarose gel. Results: SH already had significantly higher systolic BP, and a tendency to higher diastolic BP than the SN group. The frequency of Arg/Arg homozygotes was significantly increased in SH when compared to SN (25% vs 15%). Results of logistic regression analysis showed the highest relative risk for the Arg/Arg genotype and suggested a recessive action of the Arg16 variant. There was an increased diastolic BP in Arg/Arg homozygotes of the SN group ( p = 0.029). This genotype also had a tendency to increased heart rate in both groups ( p = 0.049). There was no relationship of this polymorphism with plasma noradrenaline concentration. Conclusion: Our findings suggest that genetic variability of the β2 AR gene is implicated in predisposition to essential hypertension. However, the contradictory results between individual studies indicate that the action of the β2 AR gene is indirect, through multiple intermediate phenotypes and gene interactions.     

有遗传史的原发性高血压患者子代血浆内皮素和一氧化氮浓度的比较性研究

目的 :探讨内皮素 1(ET 1)与一氧化氮 (NO)在有遗传史的原发性高血压 (EH)子代中的作用及临床意义。方法 :用ELISA方法检测有EH遗传史的患者及其子代和正常人群者及其子代血浆ET 1和NO水平 ,并将两者进行比较。结果 :①EH患者比正常人群者血浆ET 1水平明显升高 (P <0 .0 1) ,血浆NO水平也明显高于后者 (P <0 .0 1)。②有EH遗传史的血压正常的子代与正常人群的子代相比 ,血浆ET 1水平差异无显著性意义 (P >0 .0 5 ) ,而前者NO水平明显高于后者 ,差异有非常显著性意义 (P <0 .0 1)。结论 :①EH患者血浆ET 1水平明显升高 ,而在他们血压正常的子代中不增高。提示 :EH可引起机体内血浆ET 1水平增高 ,从而参与或促进EH的发展 ;但这种高ET 1水平 ,可能并无遗传性。②有EH家族史血压正常的子代中 ,血浆NO水平增高 ,提示在这些人的机体内 ,可能存在NO抵抗作用。     

Association of Alcohol or Other Drug Dependence with Alleles of the μ Opioid Receptor Gene (OPRM1)

Opioidergic neurotransmission and, specifically, the μ opioid receptor have been implicated in the reinforcing effects of a variety of drugs of abuse. Consequently, the present study examined the association of a polymorphic (CA)n repeat at the OPRM1 locus (the gene coding for the μ opioid receptor) to alcohol or drug dependence in 320 Caucasian and 108 African-American substance-dependent or control subjects. Among Caucasians, suggestion of a modest association, which could be interpreted as statistically significant ( p = 0.03), was observed between OPRMl alleles and substance (alcohol, cocaine, or opioid) dependence. Analysis by specific substance showed only a trend level association to alcohol dependence. Comparisons among African Americans yielded no evidence for association. Further studies of the association between alleles of the OPRM1 gene and substance dependence appear warranted, particularly if they use a family-based approach to control for population stratication. Phenotypes other than a broad diagnostic categorization, such as opioid antagonist effects on drinking behavior in alcoholics, may provide more consistent evidence of a role for OPRMl in behavioral variability.     

Acoustic startle reactivity during acute alcohol withdrawal in rats that differ in genetic predisposition toward alcohol drinking: effect of stimulus characteristics

BACKGROUND: We have previously reported an association between greater alcohol withdrawal magnitude after a single alcohol exposure and a genetic predisposition toward low alcohol drinking in rats selectively bred for differences in alcohol intake when acoustic startle reactivity to a tone stimulus was used to index acute alcohol withdrawal. The purpose of this study was to examine whether the quality of the acoustic startle stimulus (noise versus tone) is important for detecting a genetic relationship between alcohol withdrawal magnitude and alcohol drinking behavior. METHODS: Alcohol-naive male rats selectively bred for high alcohol intake [alcohol-preferring (P), high-alcohol-drinking (HAD)1, and HAD2] or low alcohol intake [alcohol-nonpreferring (NP), low-alcohol-drinking (LAD)1, and LAD2] received a single intragastric infusion of water or alcohol (4.0 g/20.3 ml/kg; 25% v/v), and acoustic startle test sessions were given at 14, 16, 18, 20, and 24 hr after infusion. Each test session consisted of a 5-min acclimation period followed by random presentation of various white noise stimuli (90, 100, 110, and 120 dB.) RESULTS: Line differences in acoustic startle magnitude under control conditions were present in all three pairs of selectively bred lines; P rats showed a greater startle magnitude relative to NP rats, whereas both LAD lines showed a greater startle magnitude relative to both HAD lines. During alcohol withdrawal, the P, HAD1, and HAD2 lines showed enhanced startle magnitude compared with their water-treated controls. No change in startle magnitude during alcohol withdrawal was found in the NP, LAD1, or LAD2 lines. CONCLUSIONS: In contrast to our prior findings, these results showed a genetic association between high alcohol drinking and a greater startle response magnitude to a noise stimulus during alcohol withdrawal. It seems that the genetic association between alcohol drinking and alcohol withdrawal, as assessed by the acoustic startle response, depends on the quality of the acoustic startle stimulus.     

Decreased nocturnal standard deviation of averaged NN intervals. An independent marker to identify patients at risk in the Brugada Syndrome.

AIMS: Risk-stratification of asymptomatic Brugada Syndrome (BS) patients remains a key-issue. A typical spontaneous BS-ECG pattern and ventricular tachycardia (VT)/ventricular fibrillation (VF) inducibility are two recognized risk markers. The aim of the study was to identify additional risk markers in asymptomatic BS. METHODS AND RESULTS: We have compared Holter recordings in symptomatic and in asymptomatic patients with BS. Heart rate variability (HRV), QT-interval rate-dependence and ST-segment elevation (ST-SE) were analysed. The study population included 47 BS patients (M=36, mean age=45+/-13 years) with a malignant ventricular arrhythmia in 11 cases, an unexplained syncope in 10 cases and no symptoms in the remaining 26 cases. A typical spontaneous BS-ECG was present in 21 cases and a drug-induced BS-ECG in 26 cases. A downward trend of the time domain variables of HRV was observed. During the nocturnal period, standard deviation (SD) of the 5min averaged NN intervals (SDANN) (46+/-13 vs 57+/-18ms, P=0.02) and ultra low frequency component (3287+/-2312 vs 5030+/-3270 ms(2), P=0.04) were significantly lower in symptomatic versus asymptomatic patients. In contrast, no difference was found in QT-interval rate dependence and in ST-SE. At multivariate logistic regression, VT/VF inducibility, typical spontaneous BS-ECG and a decreased nocturnal SDANN were associated with arrhythmic events (P=0.003). CONCLUSIONS: A decreased nocturnal SDANN was an independent marker of arrhythmic events in these BS patients.     

The role of mannose-binding lectin in systemic lupus erythematosus

Susceptibility to systemic lupus erythematosus (SLE) is associated with genetic, hormonal, immunological, and environmental factors. Many genes have been related with the appearance of SLE, including several loci that code different complement components and their receptors. Some genetic deficiencies of complement molecules are strongly associated with SLE, probably because these deficiencies could cause decreased clearance of apoptotic cell material. As a consequence of the apoptotic material accumulation, high levels of autoantigens can be presented inappropriately to the immune system in an inflammatory context, resulting in an imbalance on the mechanisms of immunological tolerance, immune system activation, and autoantibody production. Recent studies proposed a role to the mannose-binding lectin (MBL) in the SLE physiopathogenesis. This protein activates the complement system, and the presence of several polymorphisms at the promoter and coding regions of the MBL-2 gene determines alterations at the plasma levels of MBL. Some of these polymorphisms have been associated with SLE susceptibility, as well as with clinical and laboratory typical features of this disease, cardiovascular events, and infections. Besides, it has been described that the presence of anti-MBL autoantibodies in sera of SLE patients can influence MBL plasma levels and its functional activity.     

白细胞介素-2基因多态性与慢性乙型肝炎的相关性

目的 探讨白细胞介素-2(IL-2)基因多态性与慢性乙型肝炎的相关性,以及对HBVDNA水平的影响.方法 应用聚合酶链反应-限制性片段长度多态性分析和DNA测序的方法检测155例慢性乙型肝炎患者和170名健康对照者的IL-2基因-385T/G、+114T/G单核苷酸多态性位点基因型,血清HBV DNA测定采用荧光定量PCR技术.结果 IL-2基因+114T/G多态性在慢性乙型肝炎组和正常人群中的频率分布差异无统计学意义.IL-2基因-385T/G多态性在两组人群中的频率分布差异有统计学意义,X2=7.377,P<0.05.等位基因频率的相对风险分析发现,G等位基因携带者患慢性乙型肝炎的风险是T等位基因的1.490倍(OR=1.490,95%CI:1.085-2.046);进一步比较慢性乙型肝炎患者IL一2基因多态性与HBV DNA复制的关系,发现高水平HBVDNA(≥1×10<'3>拷贝/ml)组-385G等位基因携带者分布频率明显高于低水平HBV DNA组(<1×10<'3>拷贝/ml),X2=6.051,P=0.014,差异有统计学意义.结论 IL-2基因-385T/G多态性可能与HBV具有相关性,其中G等位基因可能是慢性乙型肝炎的遗传易感基因,携带G等位基因的个体可能更利于HBV DNA的复制.