210名广东籍人β—FBG—455G／A基因多态性分析及与血浆纤维蛋…

OBJECTIVE: To analyze the frequency of beta-fibrinogen (beta-FBG) gene G/A-455 polymorphisms in Guangdong Chinese population and the relationship between genotype and plasma fibrinogen levels. METHODS: DNA of 210 samples were analyzed by using PCR-RFLP. Turbidimetric method for the levels of plasma fibrinogen was performed in 92 samples. RESULTS: The frequency of beta-FBG G/A-455 genotype A/A was 0.038; G/G was 0.514 and G/A was 0.448. The frequency of the A-allele was 0.262. The average plasma fibrinogen level in 46 samples of genotype G/A was (2.18 +/- 0.24) g/L and in 42 samples of G/G genotype was (2.03 +/- 0.25) g/L. There was significant difference between genotype and plasma fibrinogen (P < 0.01). CONCLUSION: The frequency of beta-FBG G/A-455 A-allele in Guangdong Chinese population is higher than that in European. The plasma fibrinogen level in G/A genotype is higher than that in G/G genotype. It suggested that the beta-FBG gene expression might be associated with the genotype.     

G-455A polymorphism of the fibrinogen beta gene and deep vein thrombosis

BACKGROUND: Elevated fibrinogen levels have been linked to increased risk for deep venous thrombosis, although it is not clear whether fibrinogen is causal or rather a marker for the presence of other risk factors. A common G/A polymorphism in the gene for the fibrinogen beta-chain (FGB G-455A) is associated with elevated fibrinogen levels. The present study was designed to analyze the role of this genetic marker for deep venous thrombosis. MATERIALS AND METHODS: We performed a case-control study including 307 patients with documented deep venous thrombosis and 316 control subjects. beta-fibrinogen genotypes were determined by allele-specific polymerase chain reaction. RESULTS: GG, GA and AA genotype frequencies were similar among the patients (53.1%, 41.0, 5.9) and controls (51.6%, 42.1, 6.3; P = 0.92). Fibrinogen levels of the patients (median 3.72 g l-1; range 1.93-11.6) did not differ significantly from those of the controls (3.76; 2.17-9.99). Carriers of the homozygous AA genotype had significantly higher fibrinogen levels than noncarriers (patients: 5.32 vs. 3.59; P = 0.024; controls: 6.29 vs. 3.72; P = 0.048). CONCLUSION: Our data suggest that the fibrinogen-elevating FGB G-455A gene polymorphism is not linked to an increased risk for deep venous thrombosis.     

纤维蛋白原基因多态性与缺血性心脑血管病的关系

目的：调查健康人、心肌梗死患者及脑梗死患者的纤维蛋白原（Fg)β-455G/A、-148C/T、448G/A基因多态性频率分布、Fg分子反应性及与血浆Fg水平的关系。方法：用限制性片段长度多态性分析基因频率分布，用计算机辅助的纤维蛋白单体聚合反应分析方法和Clauss法分析血浆Fg水平。结果：等位基因－455A、－148T和448A在正常人中的频率分别是0．185，0．194及0．192；在心肌梗死患者中的频率分别是0．295，0．318及0．307；在脑梗死患者中的频率分别是0．177，0．193及0．182。心肌梗死患者中－455A、－148T和448A的频率比健康人明显升高。3个多态性位点－455G、－148C和448G或－455A、－148T和448A分别紧密连锁，符合率超过98％。心脑血管病患者的Fg功能明显增高且与Fg水平相关。3个多态性位点不同基因型组血浆Fg水平差异无显著性。结论：3对等位基因紧密连锁不平衡，不同基因型组血浆Fg水平差异无显著性，心肌梗死患者中－455A、－148T和448A的频率比健康人明显升高。提示Fgβ-455G/A、-148C/T和448G／A三种基因多态性与血浆Fg水平无关，而与心肌梗死的发病相关。心脑血管病患者不仅Fg功能明显增高，且与Fg水平相关。     

Fibrinogen is a marker for nephropathy and peripheral vascular disease in type 1 diabetes: studies of plasma fibrinogen and fibrinogen gene polymorphism in the DCCT/EDIC cohort

We examined whether plasma fibrinogen levels and the beta-fibrinogen gene G(-455)-->A polymorphism were related to microvascular or macrovascular disease in patients (n = 909) with type 1 diabetes enrolled in the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/ EDIC). Univariate regression showed that fibrinogen levels were correlated with BMI (r = 0.15; P < 0.0001), HbA(1c) (r = 0.11; P = 0.0014), total cholesterol (r = 0.17; P < 0.0001), and LDL cholesterol (r = 0.16; P < 0.0001) in all patients. In men, but not women, waist-to-hip ratio (r = 0.20; P < 0.0001) and triglycerides (r = 0.13; P = 0.0047) also became powerful predictors of fibrinogen level; in women, but not men, fibrinogen was correlated with both diastolic (r = 0.16; P = 0.0011) and systolic (r = 0.11; P = 0.0241) blood pressure. Fibrinogen was correlated with urinary albumin excretion rates in men (r = 0.13; P = 0.0033), but not in women. In both sexes, however, the development of proteinuria (albumin excretion >300 mg/24 h) was accompanied by 1.5-fold increment in plasma fibrinogen compared with patients with normal excretion or microalbuminuria. In addition, high fibrinogen levels were associated with a lower average ankle-brachial index in women (r = -0.13; P = 0.0075), but not men. Multiple regression analyses demonstrated that plasma fibrinogen was independently correlated with high albumin excretion rate in men, and with low average ankle-brachial index in women. Fibrinogen was not correlated with the severity of retinopathy. Carotid artery intima-medial thickness was not correlated with fibrinogen, and the G(-455)-->A polymorphism in the 5' promoter region of the beta-fibrinogen gene did not influence circulating fibrinogen levels. However, the presence of the more common G(-455) allele was associated with greater intima-medial thickness in the internal carotid artery (ANCOVA P = 0.045). Last, hyperfibrinogenemia in type 1 diabetes is associated with components of the insulin resistance syndrome trait cluster, and the association is influenced by sex.     

210名广东籍人β-FBG-455G/A基因多态性分析及与血浆纤维蛋白原水平的关系

目的分析中国广东籍人β纤维蛋白原Ｇ／Ａ４５５（βＦＢＧ４５５Ｇ／Ａ）基因多态性,计算各型的基因频率,测定不同基因型人血浆纤维蛋白原（ＦＢＧ）水平,探讨该基因多态性与基因表达的相关性。方法应用聚合酶链反应限制性酶切分析方法,分析２１０名广东籍人ＤＮＡ样品的βＦＢＧ４５５Ｇ／Ａ多态性,比浊法测定其中９２名血浆ＦＢＧ水平。结果βＦＢＧ４５５Ａ／Ａ纯合子８名,基因型频率为０．０３８;βＦＢＧ４５５Ｇ／Ｇ野生型１０８名,基因型频率为０．５１４;βＦＢＧ４５５Ｇ／Ａ杂合子９４名,基因型频率为０４４８。Ａ等位基因频率为０．２６２。４６名Ｇ／Ａ型血浆ＦＢＧ水平为（２．１８±０．２４）ｇ／Ｌ,４２名Ｇ／Ｇ型为（２．０３±０．２５）ｇ／Ｌ,两组比较差异有显著性（Ｐ＜０．０１）。结论中国广东籍人群中βＦＢＧ４５５Ａ等位基因频率比欧洲一些国家高（Ｐ＜０．０１）。Ｇ／Ａ型血浆ＦＢＧ水平比Ｇ／Ｇ型高（Ｐ＜０．０１）。提示该基因位点多态性与血浆ＦＢＧ的表达有一定相关。     

Chimeric mice carrying 'regional' targeted deletion of the angiotensin type 1A receptor gene. Evidence against the role for local angiotensin in the in vivo feedback regulation of renin synthesis in juxtaglomerular cells.

We have developed chimeric mice carrying 'regional' null mutation of the angiotensin type 1A (AT1A) receptor, the AT1 receptor subtype exclusively present in mouse juxtaglomerular (JG) cells. The chimeric mouse (Agtr1a -/- <--> +/+) is made up of wild-type (Agtr1a +/+) cells or cells homozygous for Agtr1a deletion (Agtr1a -/-). In the latter, the AT1A coding exon was replaced with a reporter gene, lacZ. In Agtr1a -/- <--> +/+ mice, these two clones of cells are found to be clustered and display patchy distributions in the kidney and heart. Tracking of lacZ activities in hetero- (Agtr1a +/-) and homozygous (Agtr1a -/-) deletion mutant offspring from Agtr1a -/- <--> +/+ mice revealed that the promoter activity of Agtr1a is localized in JG cells, afferent arteriolar walls, glomerular mesangial region and endothelial cells, and apical and basolateral proximal tubule membranes. The JG apparatuses of Agtr1a -/- mice are markedly enlarged with intense expression of renin mRNA and protein. In Agtr1a -/- <--> +/+ mice, these changes were proportional to the degree of chimerism. Within a given Agtr1a -/- <--> +/+ mouse, however, the degree of JG hypertrophy/hyperplasia and the expression of renin mRNA and protein were identical between Agtr1a +/+ and Agtr1a -/- cells. Thus, in the in vivo condition tested, the local interaction between angiotensin and the AT1 receptor on the JG cells has little functional contribution to the feedback regulation of JG renin synthesis.     

纤维蛋白原β—455G／A,—148C／T,448G／A基因多态性与血浆纤 …

目的调查１５６名广东汉族健康人纤维蛋白原（Ｆｇ）β－４５５Ｇ／Ａ、－１４８Ｃ／Ｔ、４４８Ｇ／Ａ基因多态性频率分布、连锁不平衡关系及与血浆Ｆｇ水平的关系。方法用限制性片段长度多态性（ＲＦＬＰ）分析方法和比浊法检测血浆Ｆｇ水平。结果等位基因Ａ＾－４５５、Ｔ－１４８和Ａ＾４４８的频率分别是为０．２７６,０．２８５及０．２７２。１５６人中３个多态性位点Ｇ＾－４５５、Ｃ＾－１４８和Ｇ＾４４８或Ａ＾－４５５、     

Genetic variation in fibrinogen; its relationship to fibrinogen levels and the risk of myocardial infarction and ischemic stroke

Summary.  Background: Confounding by common causes and reverse causation have been proposed as explanations for the association between high fibrinogen levels and cardiovascular disease. Genetic variants can alter fibrinogen characteristics and are not subject to these problems. Objectives: To determine the fibrinogen plasma levels for genotypic variants in fibrinogen-Aα (FGA Thr312Ala) and fibrinogen-Bβ (FGB − 455G/A), and whether these variants are associated with arterial thrombosis. Methods: Fibrinogen genotypes were determined in a population-based case–control study including women aged 18–50 years; 218 cases with myocardial infarction, 192 cases with ischemic stroke, and 769 healthy controls. Fibrinogen levels were determined in the control population. Results: The FGB − 455G/A variant increased plasma fibrinogen levels, whereas the FGA Thr312Ala variant lowered plasma fibrinogen levels, albeit to a modest extent. The risk of ischemic stroke was altered when the homozygote minor allele was compared with the homozygote major allele. The FGA Thr312Ala single-nucleotide polymorphism (SNP) was associated with a decrease in risk [odds ratio (OR) 0.43; 95% confidence interval (CI) 0.21–0.87], whereas the FGB − 455G/A SNP might have increased the risk (OR 1.76; 95% CI  0.7–4.03). The risk of myocardial infarction was not altered for either SNP (FGA Thr312Ala, OR 0.98, 95% CI  0.40–2.40; FGB − 455G/A, OR 0.98, 95% CI  0.40–2.40). Conclusions: With the genetic variations as markers of plasma fibrinogen levels alterations, thereby ruling out confounding and reverse causation, our results suggest that plasma fibrinogen levels could play a more pronounced role as risk factors for ischemic stroke than for myocardial infarction.     

纤维蛋白原紧密连锁不平衡基因位点BβG/A-455、C/T-148、G/A+448与缺血性脑血管病相关性分析

目的 分析纤维蛋白原(FIB)3个紧密连锁不平衡基因位点BβG/A-455、C/T-148、G/A+448基因多态性及血浆FIB水平与缺血性脑血管病的相关性.方法 以我院2010年2月至2012年2月收治的缺血性脑血管病患者89例为病例组,以同期在我院健康体检的50例为对照组,检测两组血浆FIB水平,使用多聚酶链式反应限制性片段长度多态性(PCR-RFLP)技术测定BβG/A-455、C/T-148、G/A+448基因片段.结果 缺血性脑血管病患者中,FIB基因型分布、BβA-455、T-148、A+448等位基因频率与对照组比较差异有统计学意义(P＜0.05).两组血浆FIB水平比较差异有统计学意义(P＜0.01),病例组高于对照组.A、T等位基因携带者与非携带者血浆FIB水平比较差异有统计学意义(缺血性脑血管病患者组,P＜0.01;对照组,P＜0.05),携带者高于非携带者.结论 FIB 3个紧密连锁不平衡基因位点BβG/A-455、C/T-148、G/A+448基因多态性及血浆FIB水平与缺血性脑血管病呈明显的正相关,BβG/A-455、C/T-148、G/A+448基因多态性可能是缺血性脑血管病的遗传易感因素.     

β-纤维蛋白原-455G/A基因多态性与新疆哈萨克族冠心病的关系

目的分析β纤维蛋白原(FGB)基因启动子区-455 bp位点多态性与新疆哈萨克族冠心病(CHD)的关系。方法采用聚合酶链式反应-限制性片段长度多态性分析法检测新疆哈萨克族220例CHD患者和200例正常对照者的FGB基因启动子区-455 bp位点多态性,并测定血浆纤维蛋白原(Fg)水平。结果①CHD组GA/AA基因型及A等位基因含量均高于对照组,差异有统计学意义(P均<0.05);②CHD组各基因型的Fg水平均高于对照组同种基因型,在CHD和对照组中,不同基因型Fg水平,以AA基因型为最高,GG基因型为最低,组间比较差异均有统计学意义(P<0.05)。结论β纤维蛋白原基因启动子区-455 bp位点多态性与新疆哈萨克族CHD有关,A等位基因是CHD的易感危险因素,可能通过影响Fg水平与CHD产生联系。     

A common substitution (Asn291Ser) in lipoprotein lipase is associated with increased risk of ischemic heart disease.

Lipoprotein lipase degrades triglycerides in plasma and as a byproduct produces HDL particles. Genetic variation in lipoprotein lipase may therefore affect cardiovascular risk. We tested 9,214 men and women from a general population sample and 948 patients with ischemic heart disease for the Asn291Ser substitution in lipoprotein lipase. The allele frequency in the general population was 0.024 and 0.026 for women and men, respectively. In comparison with noncarriers, female heterozygous probands had increased plasma triglycerides (delta = 0.23 mmol/liter), while HDL cholesterol was reduced in both female and male carriers (delta = 0.18 mmol/liter and delta = 0.11 mmol/liter, respectively). A similar phenotype was found in six homozygous carriers. On multiple logistic regression analysis, plasma triglycerides and HDL cholesterol were independent predictors of ischemic heart disease in both genders. On univariate analysis, odds ratios for ischemic heart disease in probands were 1.89 in women (95% CI: 1.19-3.01) and 0.90 in men (95% CI: 0.62-1.31), and on multivariate analysis were 1.98 in women (95% CI: 1.11-3.53) and 1.02 in men (95% CI: 0.65-1.60). This study demonstrates that a single common mutation in the lipoprotein lipase gene is associated with elevated plasma triglycerides and reduced HDL cholesterol levels, whereby carriers, in particular women, seem to be predisposed to ischemic heart disease. It cannot be excluded, however, that male carriers of this substitution may represent a subset of low-HDL individuals without raised triglycerides not predisposed to ischemic heart disease.     

Variable expression of familial dysbetalipoproteinemia in apolipoprotein E*2 (Lys146-->Gln) Allele carriers.

Genetic and biochemical studies were carried out in 96 relatives of six independently ascertained probands with familial dysbetalipoproteinemia (FD) carrying the APOE*2 (Lys146-->Gln) allele. Compared to noncarriers, the 40 heterozygous APOE*2 (Lys146-->Gln) allele carriers exhibited markedly increased mean levels of cholesterol and triglyceride in the very low density lipoproteins (VLDL) (1.89 +/- 0.37 vs 0.30 +/- 0.27 and 1.86 +/- 0.37 vs 0.68 +/- 0.27 mmol/liter, respectively) and plasma apolipoprotein (apo) E levels (28.1 +/- 1.6 vs 4.6 +/- 1.1 mg/dl), which is characteristic for FD. By means of a pedigree-based maximum likelihood method we calculated that carrier-status accounted for 57% and 71%, respectively, of the total variance of the ratio (VLDL + IDL)-cholesterol/plasma triglyceride and plasma apoE levels. APOE*2 (Lys146-->Gln) and APOE*3-Leiden allele carriers were found to differ significantly in: (a) plasma apoE levels, (b) in the amounts of triglycerides in the VLDL and VLDL + IDL fraction, and (c) in the amount of cholesterol in the VLDL and VLDL + IDL fraction relative to the amount of triglyceride in these fractions. In the APOE*2 (Lys146-->Gln) allele carriers the VLDL and VLDL + IDL fraction is relatively rich in triglycerides as compared with that in APOE*3-Leiden carriers. We hypothesize that these two rare mutations of apoE both lead to dominantly inherited forms of FD along different underlying metabolic defects.     

The β fibrinogen gene G-455-A polymorphism is a risk factor for Legg–Perthes disease

Summary  Legg–Perthes disease is a pediatric hip disorder characterized by avascular necrosis of the femoral head. The etiology of Legg–Perthes disease may involve repeated interruptions of the blood supply to the proximal femur. Thus, the role of thrombosis in Legg–Perthes disease is of interest. The focus of this analysis is an evaluation of the relationship between Legg–Perthes disease and the β fibrinogen gene G-455-A polymorphism in 55 cases of Legg–Perthes disease and 56 age, race, and gender-matched healthy controls. Parents of subjects completed a questionnaire about their child's lifestyle and medical history. Blood was obtained for plasma and DNA analysis. Study subjects were predominantly white (93%), male (77%) and under age 16 (70%). Cases were more likely to be exposed to passive smoke than were controls (odds ratio 5.6, 95% confidence interval 2.0–12.0). Assuming a dominant genetic model, individuals who possessed either the G/A or A/A genotype were over three times more likely to have Legg–Perthes disease compared to those without the polymorphism (odds ratio 3.4, 95% confidence interval 1.5–7.8). Separate analyzes by smoke exposure revealed that the excess risk of the G-455-A polymorphism occurred in those exposed (odds ratio 7.0) as opposed to those unexposed to passive smoke (odds ratio 1.9). Although this difference in the odds ratios is not statistically significant ( P  = 0.2), it suggests a possible interactive effect of cigarette smoke and the b fibrinogen gene G-455-A polymorphism in the risk of developing Legg–Perthes disease.     

Properties of IRT-14 (TEM-45), a newly characterized mutant of TEM-type beta-lactamases.

IRT-14 (TEM-45) is a new mutant TEM-type beta-lactamase that was isolated from clinical Escherichia coli P37 and that confers resistance to broad-spectrum penicillins with reduced sensitivity to beta-lactamase inhibitors. The MICs of amoxicillin alone and of amoxicillin combined with 2 micrograms of clavulanic acid or 2 micrograms of tazobactam per ml were 4,096, 2,048, and 1,024 micrograms/ml, respectively. The strain was susceptible to cephalosporins, aztreonam, moxalactam, and imipenem. The enzyme was purified to homogeneity, and values of the kinetic parameters Kcat, Km, and Kcat/Km were determined for different substrates. This enzyme, with a pI of 5.2, was found to have reduced affinity for broad-spectrum penicillins and cephalosporins. The values of 50% inhibitory concentrations of clavulanic acid, sulbactam, tazobactam, and brobactam are correlated with the higher KmS for substrates. The resistance of E. coli P37 to mechanism-based inactivators results from a higher level of production of the TEM-derived enzyme due to the G-to-T substitution at position 162 (G-162-->T) in the promoter region of blaTEM and from the structural modifications resulting from the Met-69-->Leu and Arg-275-->Gln substitutions that characterize IRT-14 beta-lactamase.     

Association of angiotensinogen gene T235 variant with progression of immunoglobin A nephropathy in Caucasian patients.

Genetic variability in the renin-angiotensin system may modify renal responses to injury and disease progression. We examined whether the M235T polymorphism of the angiotensinogen (AGT) gene, the insertion/deletion polymorphism of the angiotensin-converting enzyme (ACE) gene, and the A1166--> C polymorphism of the angiotensin II type 1 receptor gene may be associated with disease progression in 168 Caucasian patients with IgA nephropathy. All patients had serial measurements of their creatinine clearance, proteinuria, and blood pressure (mean+/-SD) with a follow-up of 6.1+/-4.7 yr. The genotype frequencies for each gene were consistent with Hardy-Weinberg equilibrium, and were similar to those of 100 Caucasian control subjects. We examined two primary outcomes: (a) the rate of deterioration of Ccr, and (b) the maximal level of proteinuria. We found that patients with the AGT MT (n = 79) and TT (n = 29) genotypes had a faster rate of deterioration of Ccr than those with the MM (n = 60) genotype (i.e., median values, -6.6 and -6.2 vs. -3. 0 ml/min/yr, respectively; P = 0.01 by Kruskal-Wallis test). Similarly, patients with AGT MT and TT genotypes had higher maximal values of proteinuria than those with the MM genotype (i.e., median values, 2.5 and 3.5 vs. 2.0 g/d, respectively; P < 0.02 by Kruskal-Wallis test). Neither the ACE insertion/deletion nor angiotensin II type I A1166--> C gene polymorphism was associated with disease progression or proteinuria in univariate analysis. Multivariant analysis, however, detected an interaction between the AGT and ACE gene polymorphisms with the presence of ACE/DD polymorphism adversely affecting disease progression only in patients with the AGT/MM genotype (P = 0.008). Neither of these gene polymorphisms was associated with systemic hypertension. Our results suggest that polymorphisms at the AGT and ACE gene loci are important markers for predicting progression to chronic renal failure in Caucasian patients with IgA nephropathy.     

Dominant expression of type III hyperlipoproteinemia. Pathophysiological insights derived from the structural and kinetic characteristics of ApoE-1 (Lys146-->Glu).

Type III hyperlipoproteinemia is characterized by delayed chylomicron and VLDL remnant catabolism and is associated with homozygosity for the apoE-2 allele. We have identified a kindred in which heterozygosity for an apoE mutant, apoE-1 (Lys146-->Glu), is dominantly associated with the expression of type III hyperlipoproteinemia. DNA sequence analysis of the mutant apoE gene revealed a single-point mutation that resulted in the substitution of glutamic acid (GAG) for lysine (AAG) at residue 146 in the proposed receptor-binding domain of apoE. The pathophysiological effect of this mutation was investigated in vivo by kinetic studies in the patient and six normal subjects, and in vitro by binding studies of apoE-1 (Lys146-->Glu) to LDL receptors on human fibroblasts and to heparin. The kinetic studies revealed that apoE-1 (Lys146-->Glu) was catabolized significantly slower than apoE-3 in normals (P < 0.005). In the proband, the plasma residence times of both apoEs were substantially longer and the production rate of total apoE was about two times higher than in the control subjects. ApoE-1 (Lys146-->Glu) was defective in interacting with LDL receptors, and its ability to displace LDL in an in vitro assay was reduced to 7.7% compared with apoE-3. The affinity of apoE-1 (Lys146-->Glu) to heparin was also markedly reduced compared with both apoE-2 (Arg158-->Cys) and apoE-3. These abnormal in vitro binding characteristics and the altered in vivo metabolism of apoE-1 (Lys146-->Glu) are proposed to result in the functional dominance of this mutation in the affected kindred.     

DNA sequence differences of ampD mutants of Citrobacter freundii.

Three groups of mutants with increased levels of beta-lactamase synthesis were selected from Citrobacter freundii 382010 by beta-lactam antibiotics at concentrations just above the MIC. Uninduced cultures of the hyperinducible group had 3- to 5-fold more beta-lactamase activity than the parent strain, with one mutant (termed type b) expressing 19 times the activity of the parent strain; the partially derepressed group had a relative 55-fold increase, while fully derepressed strains exhibited a 460-fold increase. Upon induction by growth in the presence of cefoxitin (32 micrograms/ml) for 2 h, the hyperinducible and derepressed groups had similar relative beta-lactamase activities of 650 and 725, respectively. Induction of beta-lactamase activity from partially derepressed mutants resulted in a relative activity of only 240. The ampD gene including its promoter region was amplified from the parent strain and the mutant strains by PCR. The sequence of ampD from the parent strain showed only three nucleotide changes from a previously published sequence, none of which resulted in a change to the deduced amino acid sequence. Hyperinducible mutant strains of type a had an amino acid change of either a tryptophan in codon 95 to an arginine (Trp-95-->Arg) (three mutants) or Ala-158-->Asp (one mutant). The hyperinducible type b strain had the change Tyr-102-->Asp. The derepressed strains had the following changes: Val-33-->Gly (one mutant), Asp-164-->Glu (one mutant), and Trp-95-->termination codon (two mutants). We infer that the amino acid changes in the hyperinducible mutants result in altered AmpD activity, whereas, in contrast, they lead to an inactive protein in derepressed mutants. No nucleotide differences were found in the ampD gene from partially derepressed strains.     

Antithrombotic effects of thrombin-induced activation of endogenous protein C in primates.

The effects on thrombosis and hemostasis of thrombin-induced activation of endogenous protein C (PC) were evaluated in baboons. Thrombosis was induced by placing into arteriovenous shunts a segment of Dacron vascular graft, which generated arterial platelet-rich thrombus, followed by an expansion region of low-shear blood flow, which in turn accumulated fibrin-rich venous-type thrombus. Thrombosis was quantified by 111In-platelet imaging and 125I-fibrinogen accumulation. Intravenous infusion of alpha-thrombin, 1-2 U/kg-min for 1 h, increased baseline activated PC levels (approximately 5 ng/ml) to 250-500 ng/ml (P < 0.01). The lower thrombin dose, which did not deplete circulating platelets, fibrinogen, or PC, reduced arterial graft platelet deposition by 48% (P < 0.05), and platelet and fibrin incorporation into venous-type thrombus by > 85% (P < 0.01). Thrombin infusion prolonged the activated partial thromboplastin clotting time, elevated fibrinopeptide A (FPA), thrombin-antithrombin III complex (T:AT III), and fibrin D-dimer plasma levels (P < 0.01), but did not affect bleeding times. Thrombin's antithrombotic effects were blocked by infusing a monoclonal antibody (HPC-4) which prevented PC activation in vivo, caused shunt occlusion, increased the consumption of platelets and fibrinogen, elevated plasma FPA and T:AT III levels, and reduced factor VIII (but not factor V) procoagulant activity (P < 0.05). We conclude that activated PC is a physiologic inhibitor of thrombosis, and that activation of endogenous PC may represent a novel and effective antithrombotic strategy.     

Familial ligand-defective apolipoprotein B. Identification of a new mutation that decreases LDL receptor binding affinity.

Detection of new ligand-defective mutations of apolipoprotein B (apoB) will enable identification of sequences involved in binding to the LDL receptor. Genomic DNA from patients attending a lipid clinic was screened by single-strand conformation polymorphism analysis for novel mutations in the putative LDL receptor-binding domain of apoB-100. A 46-yr-old woman of Celtic and Native American ancestry with primary hypercholesterolemia (total cholesterol [TC] 343 mg/dl; LDL cholesterol [LDL-C] 241 mg/dl) and pronounced peripheral vascular disease was found to be heterozygous for a novel Arg3531-->Cys mutation, caused by a C-->T transition at nucleotide 10800. One unrelated 59-yr-old man of Italian ancestry was found with the same mutation after screening 1,560 individuals. He had coronary heart disease, a TC of 310 mg/dl, and an LDL-C of 212 mg/dl. A total of eight individuals were found with the defect in the families of the two patients. They had an age- and sex-adjusted TC of 240 +/- 14 mg/dl and LDL-C of 169 +/- 10 mg/dl. This compares with eight unaffected family members with age- and sex-adjusted TC of 185 +/- 12 mg/dl and LDL-C of 124 +/- 12 mg/dl. In a dual-label fibroblast binding assay, LDL from the eight subjects with the mutation had an affinity for the LDL receptor that was 63% that of control LDL. LDL from eight unaffected family members had an affinity of 91%. By way of comparison, LDL from six patients heterozygous for the Arg3500-->Gln mutation had an affinity of 36%. The percentage mass ratio of the defective Cys3531 LDL to normal LDL was 59:41, as determined using the mAb MB19 and dynamic laser light scattering. Thus, the defective LDL had accumulated in the plasma of these patients. Using this mass ratio, it was calculated that the defective Cys3531 LDL particles bound with 27% of normal affinity. Deduced haplotypes using 10 apoB gene markers showed the Arg3531-->Cys alleles to be different in the two kindreds and indicates that the mutations arose independently. The Arg3531-->Cys mutation is the second reported cause of familial ligand-defective apoB.     

Molecular characterization of nine different types of mutants among 107 inhibitor-resistant TEM beta-lactamases from clinical isolates of Escherichia coli.

DNA-DNA hybridization and sequencing were performed to determine the molecular basis of resistance to clavulanic acid in 107 inhibitor-resistant TEM (IRT) enzymes produced by Escherichia coli clinical isolates. These beta-lactamases derived from TEM-1 enzyme focused at pI 5.2 (n = 68) or 5.4 (n = 39) and were very poorly inhibited by clavulanic acid compared with TEM-1 enzyme. Results showed that the amino acid sequences of 84 of the 107 enzymes differ from TEM-1 by one or two substitutions previously described: Arg-244-->Ser (IRT-2) in 22 strains, Met-69-->Leu (TEM-33) in 17 strains, Met-69-->Val (TEM-34) in 14 strains, Met-69-->Ile (IRT-3) in 6 strains, Met-69-->Leu associated with Asn-276-->Asp (IRT-4) in 13 strains, and Met-69-->Val associated with Asn-276-->Asp (TEM-36) in 12 strains. A new combination, Met-69-->Ile with Asn-276-->Asp, was found in 20 strains and was called IRT-8. Two IRT enzymes not previously described were characterized. The substitution Met-69-->Val associated with a novel substitution Arg-275-->Leu occurred in one strain. The combination Met-69-->Leu and Asn-276-->Asp was associated with the novel substitution Trp-165-->Arg in two strains. These two novel enzymes were called IRT-9 and IRT-10, respectively. The implication of these novel mutated positions, 165 and 275, in resistance to inactivation by clavulanate was supported by crystallographic data on the TEM-1 enzyme and results of site-directed mutagenesis. Molecular characterization of these mutants showed great diversity among the genes coding for inhibitor-resistant TEM enzymes produced by clinical E. coli isolates.