Chemokine receptor 5 (CCR5) deletion polymorphism in North Indian patients with coronary artery disease

BACKGROUND

Polymorphisms in genes coding for chemokine receptors, CCR2 and CCR5 have been studied as genetic markers of coronary artery disease (CAD). V64Ile polymorphism in CCR2 has been implicated in the manifestation of myocardial infarction in different populations, but data on association of the CCR5 deletion variant in etiology of CAD are conflicting. In the present study we tested genetic association between CCR5 Delta32 polymorphism and CAD among North Indians (Uttar Pradesh).

METHODS

Two hundred angiographically proven patients with coronary artery disease and two hundred age, sex and ethnically matched controls were genotyped for CCR5 Delta32 polymorphism by polymerase chain reaction. Genotype/allele frequencies were compared in patients and controls using the chi-square test.

RESULTS

The frequency of the heterozygote genotype in the population, including both patient and control group, was 3% and the frequency of the mutant allele Delta32 was 1.5%. CAD patients had a three times higher (4.6% vs. 1.5%) frequency of heterozygote genotype but the differences were statistically not significant. Association analysis did not achieve statistical significance, though odds ratio of 3.13 was observed for heterozygote genotype.

CONCLUSIONS

The allele frequency of the CCR5 Delta32 polymorphism in CAD patients is 2.25% and 0.75% among controls but the differences were not significant. Overall this fits well with the pattern of CCR5 Delta32 allele frequency in Indian subcontinent where it varies from 1 to 3%. The heterozygote (+/ Delta32) genotype does not seem to have any protective role against development of CAD in this population. In fact, North Indian CAD had a higher frequency of CCR5 Delta32 allele suggesting a possible susceptibility trend (odds ratio 3.08, CI 0.83-11.46, chi-square 2.167, NS).

Utility of carotid intimal medial thickness as a screening tool for evaluation of coronary artery disease in pre-transplant end stage renal disease

BACKGROUND

Coronary artery disease (CAD) is associated with a higher incidence of allograft failure and mortality in patients with end-stage renal disease (ESRD) following renal transplant.

AIM

To evaluate the efficacy of using carotid intimal medial thickness (CIMT) to predict the presence of CAD in patients with ESRD, using coronary angiography (CAG) as the gold standard.

MATERIALS AND METHODS

This prospective study enrolled consecutive patients with ESRD who underwent CAG as a part of pretransplant evaluation to rule out the presence of atherosclerotic CAD. An operator who was blinded with respect to the results of the CAG, measured carotid IMT in all patients prior to CAG and recorded it on videotape. Two independent observers blinded to the results of CAG measured carotid IMT offline to validate its predictive accuracy as a noninvasive test in predicting the presence or absence of CAD. Measurement of carotid IMT was done on USG B mode 7.5 MHZ probe [HP 5500 andover, Massachusetts]. Student's t-test was used for inter-group comparisons. Pearson correlation coefficient test was used to assess the relation between CAD and various risk factors and carotid IMT. Linear regression analysis was applied to identify independent factors determining presence of CAD. A P value < 0.05 was considered statistically significant.

RESULTS

Mean CIMT was significantly higher in those with CAD as compared to those without [0.80+/- 0.06 vs.0.70+/-0.06 mm, P< 0.0001). Patients with CIMT> 0.75 mm were older and had more incidence of diabetes(78% vs. 47%; P=0.001). Only 4/53 (7%) of patients with CIMT< 0.75 mm had CAD, vs. 38/52 (73%) in those with CIMT >0.75 mm. The sensitivity and specificity of using CIMT > 0.75 as a predictor of CAD was 90.47%and 73% and its positive and negative predictive values were 0.73 and 0.92. On multivariate analysis, only CIMT was a significant predictor of CAD.

CONCLUSION

Carotid IMT can be used to predict CAD in patients with ESRD. In the absence of other risk factors,patients with IMT< 0.75 mm may not need a pretransplant CAG.

Task Switching as a Two-Stage Decision Process

Saccades represent decisions, and the study of their latency has led to a neurally plausible model of the underlying mechanisms, LATER (Linear Approach to Threshold with Ergodic Rate), that can successfully predict reaction time behavior in simple decision tasks, with fixed instructions. However, if the instructions abruptly change, we have a more complex situation, known as task switching. Psychologists' explanations of the phenomena of task switching have so far tended to be qualitative rather than quantitative, and not intended to relate particularly clearly to existing models of decision making or to likely neural implementations. Here, we investigated task switching using a novel saccadic task: we presented the instructions by stimulus elements identical to those of the task itself, allowing us to compare decisions about instructions with decisions in the actual task. Our results support a relatively simple model consisting of two distinct LATER processes in series: the first detects the instruction, the second implements it.

Peptides and the development of double- and triple-resonance solid-state NMR of aligned samples

Peptides have been instrumental in the development of solid-state nuclear magnetic resonance (NMR) spectroscopy, and their roles in the development of solid-state NMR of aligned samples is reviewed. In particular, the roles of synthetic peptides in the development of triple-resonance methods are described. Recent developments of pulse sequences and NMR probes for triple-resonance NMR of aligned samples are presented.

TNFR2 gene polymorphism in coronary artery disease

BACKGROUND

Recently atherosclerosis and coronary artery disease (CAD) are considered to be inflammatory diseases. The genetic polymorphism in inflammatory markers has been well studied and found to be associated with development of CAD.

AIM

To study the association of biallelic polymorphism at position 196 in exon 6 of tumor necrosis factor 2 (TNFR2) gene and coronary artery disease.

SETTINGS AND DESIGN

The study design was a prospective case control study conducted at a tertiary referral center mainly catering to the north Indian population.

MATERIALS AND METHODS

One hundred and fifty angiographically proven patients with coronary artery disease and one hundred and fifty age matched controls were genotyped for TNFR2 gene by polymerase chain reaction followed by analysis of restriction fragment length polymorphism.

STATISTICAL ANALYSIS

Genotype frequencies were compared in patients and controls by Chi-square test. Binary logistic regression analysis was used to examine the relationship between genotypes and disease, incorporating other variables into the model.

RESULTS

The incidence of CAD in those with MM genotype was 65% and in those with RM genotype was 42%. Genotype frequency shows significant association of MM genotype with development of CAD (P < 0.001; odds ratio-2.585; 95% confidence interval 1.533-4.359). The association of TNFR2 genotype with CAD persisted on logistic regression analysis.

CONCLUSION

MM genotype of TNFR2 gene is associated with development of CAD and RM genotype appears to be protective.

Cellular and humoral immune responses to mycobacterial heat shock protein-65 and its human homologue in Takayasu's arteritis

Expression of heat shock protein (HSP)-65 as well as infiltration of T-cells in arterial lesions and raised levels of circulating antibodies against mycobacterial HSP65 (mHSP65) led us to the concept that mHSP65 or its human homologue (hHSP60) might be involved in the etiopathogenesis of Takayasu's arteritis (TA). Therefore, we investigated mHSP65 and hHSP60 reactive peripheral blood T-cell subsets by BrdU incorporation assay and flow cytometry as well as investigating the different isotypes of anti-mHSP65 and hHSP60 antibodies by ELISA. Eighty-four percent (22/26) of the TA patients were observed to show T-cell proliferation to mHSP65 and hHSP60 whereas only 16% (3/18) healthy controls showed such proliferation (P <0.001). Both HSPs induced proliferation of exclusively CD4+ T-cells and not CD8+ T-cells. We also observed a significantly higher prevalence of only the IgG isotype reactive to mHSP65 and hHSP60 in TA as compared to HC (mHSP65: 92% TA versus 11% HC, P <0.0001 and hHSP60: 84% versus 22%, P <0.001). Our data show a significant correlation between mHSP65 and hHSP60 reactive T-cells (CD3+: r=0.901; CD4+: r=0.968) as well as anti-mHSP65 and anti-hHSP60 IgG antibodies (r=0.814) suggesting an infection induced autoimmunity in TA, possibly induced by molecular mimicry between mHSP65 and hHSP60 or other tissue specific antigens.

Effects of aflatoxin B1 on embryo fetal development in rabbits

Aflatoxin B1 (AFB1), is a food borne mycotoxin produced by fungal species of the genera Aspergillus. To elucidate the teratogenic effects, AFB1 was dissolved in corn oil and given orally to New Zealand White rabbits during 6-18 days of gestation with the dose levels of 0.025, 0.05 and 0.1 mg/kg body weight. To assess pathomorphological features of the anomalies induced by AFB1, the fetal serial sections were histologically examined. There was no maternal mortality in any group. There was non-significant decrease in percent of live fetuses and increase in the percent resorptions and post-implantation losses at 0.1 mg/kg dose group as compared with those of controls. The mean crown to rump lengths of 0.05 and 0.1 mg/kg dose groups were significantly reduced than that of the control. The mean fetal weights were significantly reduced in 0.1 mg/kg dose group than that of other treated groups. The gross anomalies observed included wrist drop and enlarged eye socket whereas, skeletal anomalies were agenesis of caudal vertebrae, incomplete ossification of skull bones and bent metacarpals. The visceral anomalies of microphthalmia and cardiac defects were seen at 0.1 mg/kg dose group. The characteristic histological findings of fetal tissues were distortion of normal hepatic cord pattern and reduced megakaryocytes in liver, fusion of auriculo-ventricular valves, mild degenerative changes in myocardial fibers, microphthalmic eyes and lenticular degeneration. The results of this study indicated that AFB1 was found to be teratogenic in rabbits when given by oral route during gestation days 6-18 and the dose of 0.1 mg/kg could be considered as the minimum oral teratogenic dose. The histological examination of the fetal tissues indicated its importance in identifying the visceral anomalies which were otherwise not visible.

TNFR2 gene polymorphism in coronary artery disease

BACKGROUND

Recently atherosclerosis and coronary artery disease (CAD) are considered to be inflammatory diseases. The genetic polymorphism in inflammatory markers has been well studied and found to be associated with development of CAD.

AIM

To study the association of biallelic polymorphism at position 196 in exon 6 of tumor necrosis factor 2 (TNFR2) gene and coronary artery disease.

SETTINGS AND DESIGN

The study design was a prospective case control study conducted at a tertiary referral center mainly catering to the north Indian population.

MATERIALS AND METHODS

One hundred and fifty angiographically proven patients with coronary artery disease and one hundred and fifty age matched controls were genotyped for TNFR2 gene by polymerase chain reaction followed by analysis of restriction fragment length polymorphism.

STATISTICAL ANALYSIS

Genotype frequencies were compared in patients and controls by Chi-square test. Binary logistic regression analysis was used to examine the relationship between genotypes and disease, incorporating other variables into the model.

RESULTS

The incidence of CAD in those with MM genotype was 65% and in those with RM genotype was 42%. Genotype frequency shows significant association of MM genotype with development of CAD (P < 0.001; odds ratio-2.585; 95% confidence interval 1.533-4.359). The association of TNFR2 genotype with CAD persisted on logistic regression analysis.

CONCLUSION

MM genotype of TNFR2 gene is associated with development of CAD and RM genotype appears to be protective.

T1 and M1 polymorphism in glutathione S-transferase gene and coronary artery disease in North Indian population

BACKGROUND

DNA damage has been found to play an important role in atherosclerosis and coronary artery disease. Genetic polymorphisms of the genes coding for enzymes involved in the metabolism of genotoxins result in different phenotypes with respect to their ability to detoxify these agents. In the present study the contribution of the polymorphism in the glutathione S-transferase gene to the development of coronary artery disease has been investigated.

METHODS

One hundred and ninety seven angiographically proven patients with coronary artery disease and one hundred and ninety eight age-matched controls were genotyped for glutathione S- transferase polymorphism by polymerase chain reaction. Genotype frequencies were compared in patients and controls by Chi-square test. Binary logistic regression was used to examine the relationship between genotype and disease, incorporating other variables into the model.

RESULTS

GSTT1 null genotype was significantly decreased in patients with coronary artery disease. No significant association was found with GSTM1 genotypes. No such association was seen with smokers.

CONCLUSION

Null genotype of GSTT1 is protective against coronary artery disease in our population.

Interleukin-8 in Takayasu's arteritis: plasma levels and relationship with disease activity

OBJECTIVE

To investigate the plasma levels of interleukin-8 (IL-8) in Takayasu's arteritis (TA) and their relationship with disease activity.

METHODS

IL-8 levels were detected by quantitative enzyme-linked immunosorbent assay (ELISA) in the plasma of 53 TA patients, 25 age/sex-matched healthy controls and of 10 serially followed up active TA patients on immunosuppressive therapy.

RESULTS

Significantly increased levels of IL-8 were observed in TA patients (26.32 +/- 48.96 pg/ml) compared to controls (6.0 +/- 2.45 pg/ml) (p = 0.0006) and in patients with active TA (55.0 +/- 71.43 pg/ml) compared to those with an inactive disease (8.94 +/- 6.35 pg/ml) (p = 0.0001). The increased levels of the chemokine were present in 37% (20/53) of the patients compared to 8% (2/25) of the controls (p < 0.01) and in 80% (16/20) of patients with active TA compared to 12% (4/33) of those with an inactive disease (p < 0.0001). In the follow-up study, the plasma levels of IL-8 were normalized in 6/10 of the patients and the disease in 5 of these 6 patients was also observed to undergo remission.

CONCLUSION

These results suggest that IL-8 may play an important role in the pathogenesis of TA.

Anti-annexin V antibodies in Takayasu's arteritis: prevalence and relationship with disease activity

Annexin V has an important role in the regulation of apoptosis and antibodies directed against it have been shown to lead to apoptosis of vascular endothelial cells. To evaluate the role of anti-annexin V antibodies (AA5A) in Takayasu's arteritis (TA), we investigated these antibodies in the sera of 66 TA patients, 50 healthy controls and in the follow-up sera of 12 active TA patients by enzyme-linked immunosorbent assay. The AA5A-positive patients were analysed further for the presence of anti-endothelial cell antibodies (AECA) and anticardiolipin antibodies (ACLA) to determine the relationship of AA5A with these autoantibodies. AA5A were observed in 36% (24/66) of the patients versus 6% (3/50) of the controls (P<0.001) and in 53% (19/36) of patients with active TA versus 17% (5/30) of those with inactive disease (P<0.01). Levels of AA5A were also observed to be significantly higher in patients with TA compared to controls (0.557 +/- 0.362 versus 0.259 +/- 0.069; P<0.0001) and in patients with active disease compared to those with inactive disease (0.700 +/- 0.403 versus 0.385 +/- 0.205; P<0.0001). In the follow-up study, 6/12 patients who became inactive during follow-up also showed normalization of AA5A levels. AECA and ACLA were detected in 54% (13/24) and 12% (3/24) of the AA5A-positive patients, respectively. Our results show that a significant proportion of TA patients have AA5A, which exhibit an association with AECA and because they have a correlation with disease activity thus appear to be involved in the disease pathogenesis.

Absence of factor V Leiden (G1691A) mutation, FII G20210A allele in coronary artery disease in North India

BACKGROUND

Interaction between various genetic and environmental factors is associated with coronary artery diseases (CADs). Factor V Leiden mutation (FVL) and FII G20210A polymorphism are two recently described genetic factors with a propensity towards venous thrombosis, however, with a doubtful role in coronary artery disease and myocardial infarction.

AIM

Present study was conducted to assess the relationship of both these factors in coronary artery disease in population from North India.

SETTING AND DESIGN

Case control study.

MATERIAL AND METHODS

Two hundred angiographically proven coronary artery disease patients were studied to examine the association of Factor V Leiden mutation and FII G20210A mutation with coronary artery disease and myocardial infarction. Out of 200 patients, 51 had myocardial infarction. Two hundred controls were selected who were from north India and were also age and sex matched.

RESULTS AND CONCLUSIONS

Our results indicate that both these polymorphisms were totally absent in our population, therefore, these variants cannot be considered as independent risk factors or as a predictor for CAD. However, there is a need to confirm the above findings on patients from different populations from different parts of the country as there are reports which show that the incidence of Factor V Leiden varies from 1.3 % to 10%.

Interdomain interactions in hinge-bending transitions

BACKGROUND

The mechanisms that allow or constrain protein movement have not been understood. Here we study interdomain interactions in proteins to investigate hinge-bending motions.

RESULTS

We find a limited number of salt bridges and hydrogen bonds at the interdomain interface, in both the "closed" and the "open" conformations. Consistently, analysis of 222 salt bridges in an independently selected database indicates that most salt bridges form within rather than between independently folding hydrophobic units. Calculations show that these interdomain salt bridges either destabilize or only marginally stabilize the closed conformation in most proteins. In contrast, the nonpolar buried surface area between the moving parts can be extensive in the closed conformations. However, when the nonpolar buried surface area is large, we find that at the interdomain interface in the open conformation it may be as large or larger than in the closed conformation. Hence, the energetic penalty of opening the closed conformation is overcome. Consistently, a large nonpolar surface area buried in the closed interdomain interface accompanies limited opening of the domains, yielding a larger interface.

CONCLUSIONS

Short-range electrostatic interactions are largely absent between moving domains. Interdomain nonpolar buried surface area may be large in the closed conformation, but it is largely offset by the area buried in the open conformation. In such cases the opening of the domains appears to be relatively small. This may allow prediction of the extent of domain opening. Such predictions may have implications for the shape and size of the binding pockets in drug/protein design.

Building blocks, hinge-bending motions and protein topology

Here we show that the locations of molecular hinges in protein structures fall between building block elements. Building blocks are fragments of the protein chain which constitute local minima. These elements fold first. In the next step they associate through a combinatorial assembly process. While chain-linked building blocks may be expected to trial-associate first, if unstable, alternate more stable associations will take place. Hence, we would expect that molecular hinges will be at such inter-building block locations, or at the less stable, unassigned regions. On the other hand, hinge-bending motions are well known to be critical for protein function. Hence, protein folding and protein function are evolutionarily related. Further, the pathways through which proteins attain their three dimensional folds are determined by protein topology. However, at the same time the locations of the hinges, and hinge-bending motions are also an outcome of protein topology. Thus, protein folding and function appear coupled, and relate to protein topology. Here we provide some results illustrating such a relationship.

Developmental changes due to long-distance movement of a homeobox fusion transcript in tomato

Long-distance movement of RNA through the phloem is known to occur, but the functional importance of these transported RNAs has remained unclear. Grafting experiments with a naturally occurring dominant gain-of-function leaf mutation in tomato were used to demonstrate long-distance movement of mutant messenger RNA (mRNA) into wild-type scions. The stock-specific pattern of mRNA expression was graft transmissible, indicating that the mRNA accumulation pattern is inherent to the transcript and not attributable to the promoter. The translocated mRNA caused changes in leaf morphology of the wild-type scions, suggesting that the translocated RNA is functional.

Role of thrombolytic therapy for stuck prosthetic valves: a serial echocardiographic study

BACKGROUND

Thrombotic occlusion of a prosthetic valve continues to be an uncommon but serious complication. Intravenous thrombolytic therapy has been proposed as an alternative to surgical treatment, but only in critically ill patients.

METHODS AND RESULTS

Forty-one consecutive patients presenting with 48 episodes of prosthetic valve thrombosis (44 mitral and 4 aortic) were treated with thrombolytic therapy under serial echocardiographic guidance. There were 14 male and 27 female patients. The anticoagulation status was inadequate in 89.6% of episodes. Atrial fibrillation was present in 47.9% of episodes. The prostheses involved in these episodes were tilting disc in 45, bileaflet in 2, and ball and cage type in 1. The Sorin prosthetic valve was the most commonly involved. The time interval between valve replacement and thrombosis ranged from 1 month to 108 months (mean 20.4+/-20.6 months). Patients were in New York Heart Association functional class III in 47.9% and in class II in 43.9% of episodes. Thrombolytic agents used were streptokinase and urokinase in 44 and 4 episodes, respectively. The mean duration of thrombolytic therapy was 27.9+/-15.0 hours and the overall success rate was 87.5%. Patients developed peripheral embolism with almost complete recovery in 5 episodes while significant bleeding that required termination of thrombolytic therapy was observed in 2 episodes. Redo valve replacement was done in 3 episodes because these patients did not improve on thrombolytic therapy (all 3 cases were of recurrent prosthetic valve thrombosis and were found to have pannus peroperatively). Three patients died during thrombolytic therapy because of persistent heart failure. Six patients experienced a total of 13 epidoses of recurrent prosthetic valve thrombosis including index episodes (rethrombosis in 5, re-rethrombosis in 1). They were treated with repeated thrombolysis with a success rate of 76.92%. The mean duration of thrombolytic therapy in these episodes was 36.1+/-14.0 hours.

CONCLUSIONS

In patients with prosthetic valve thrombosis, intravenous thrombolysis guided by echocardiography is a safe and effective method that may expand the indications for nonsurgical treatment of prosthetic valve thrombosis. By using serial echocardiography, the duration of thrombolytic therapy can be tailored to the patient's requirement for normalization of valve hemodynamics.

Lead-induced cell death in testes of young rats

Lead is a well-documented testicular toxicant. The present work was planned to study the occurrence of germ cell death after lead administration. Young growing rats were treated with 5, 10 and 20 mg kg(-1) body weight of lead for 2 weeks. Cell death was assessed by employing in situ TUNEL staining, DNA electrophoresis and morphological examination of the tubules. The results showed that Pb induced significant numbers of germ cells to undergo apoptosis in the seminiferous tubules of rats treated with 20 mg kg(-1) body weight. However, DNA fragmentation was not detected at any of the doses. The level of lead accumulation in the testis increased in a dose-dependent manner.

Effect of endosulfan during fetal gonadal differentiation on spermatogenesis in rats

Pregnant rats were exposed to endosulfan (1 or 2 mg/kg per day) from day 12 of gestation through parturition. Male neonates were fostered to untreated dams. At 100 days of age, the male offspring were sacrificed. Exposure to endosulfan during fetal gonadal differentiation altered the process of spermatogenesis by affecting testicular lactate dehydrogenase and sorbitol dehydrogenase. Reduction in spermatid count in testis and sperm count in cauda epididymis was observed. Testis, epididymis and seminal vesicle showed significant decrease in weights in both the treated groups while no effect on prostate weight was recorded. Hence it can be suggested that endosulfan interferes in the process of spermatogenesis. The overall toxicity was dose dependent.

Sucrose export defective1 encodes a novel protein implicated in chloroplast-to-nucleus signaling

The Sucrose export defective1 (Sxd1) gene of maize was cloned and shown to encode a novel protein conserved between plants and cyanobacteria. The structure of the Sxd1 locus was determined in wild-type plants and two independent sxd1 alleles. Expression analysis demonstrated that the gene was transcribed in all green tissues, with highest levels in maturing leaf blades. In situ hybridization studies revealed high levels of Sxd1 mRNA in bundle sheath cells, with lower levels within the mesophyll. The SXD1 protein was localized to chloroplasts, in both bundle sheath and mesophyll cells. Levels of sucrose, glucose, and fructose were compared between wild-type and sxd1 plants. Mutant plants were fully capable of producing sucrose and accumulated all three sugars at concentrations above those measured in wild-type plants. Despite these increased sugar concentrations, photosynthetic gene expression was not significantly downregulated in affected areas of sxd1 leaf blades. These results are consistent with photosynthate being trapped within anthocyanin-accumulating regions of sxd1 leaves due to plasmodesmal occlusion at the bundle sheath-vascular parenchyma boundary of the minor veins. A model for SXD1 function is proposed in which the protein is involved in a chloroplast-to-nucleus signaling pathway necessary for proper late-stage differentiation of maize bundle sheath cells, including the developmentally regulated modification of plasmodesmata.

Complement and cell mediated cytotoxicity by antiendothelial cell antibodies in Takayasu's arteritis

OBJECTIVE

To study complement and cell mediated cytotoxicity by antiendothelial cell antibodies (AECA) in Takayasu's arteritis (TA).

METHODS

Complement dependent cytotoxicity (CDC) and antibody dependent cellular cytotoxicity (ADCC) of AECA positive/negative TA sera were investigated by colorimetric MTT and 51Cr release assays, respectively, using human umbilical vein endothelial cells (HUVEC) as targets.

RESULTS

Seven of 12 (58%) sera positive for IgG and/or IgM AECA exhibited CDC in comparison to none of the 13 AECA negative sera (p = 0.0052). The median value of CDC of the AECA positive group was 14% (range 13-21%) and that of the AECA negative group was 1% (p = 0.0012). Interleukin 1beta (10 U/ml) treatment of HUVEC resulted in enhancement in CDC of 6 of the 7 AECA positive cytotoxic sera, the median enhancement being 17% (range 7-29%). Tumor necrosis factor-alpha (100 U/ml) treatment of the targets resulted in a median enhancement by 36% (range 25-55%) in the CDC of 3 of these 7 sera. No sera exhibited ADCC at any of the effector:target ratios tested (10:1 to 100:1).

CONCLUSION

AECA in TA mediate CDC against endothelial cells and may have a pathogenic role in the perpetuation of vascular damage in this disease.

Point mutations and sequence variability in proteins: redistributions of preexisting populations

Here we study the effect of point mutations in proteins on the redistributions of the conformational substates. We show that regardless of the location of a mutation in the protein structure and of its type, the observed movements of the backbone recur largely at the same positions in the structures. Despite the different interactions that are disrupted and formed by the residue substitution, not only are the conformations very similar, but the regions that move are also the same, regardless of their sequential or spatial distance from the mutation. This observation leads us to conclude that, apart from some extreme cases, the details of the interactions are not critically important in determining the protein conformation or in specifying which parts of the protein would be more prone to take on different local conformations in response to changes in the sequence. This finding further illustrates why proteins manifest a robustness toward many mutational events. This nonuniform distribution of the conformer population is consistently observed in a variety of protein structural types. Topology is critically important in determining folding pathways, kinetics, building block cutting, and anatomy trees. Here we show that topology is also very important in determining which regions of the protein structure will respond to sequence changes, regardless of the sequential or spatial location of the mutation.

Beneficial effects of nicorandil versus enalapril in chronic rheumatic severe mitral regurgitation: six months follow up echocardiographic study

BACKGROUND AND AIM OF THE STUDY

It is possible that vasodilator therapy may retard left ventricular (LV) dilatation and functional deterioration in chronic mitral regurgitation (MR). The study objectives were to evaluate comparatively the efficacy of nicorandil (a new, balanced vasodilator) and enalapril therapy on LV volume, mass and function in mildly symptomatic, chronic rheumatic severe MR.

METHODS

Eighty-seven mildly symptomatic rheumatic patients with severe MR were enrolled in this prospective, randomized study. All patients underwent serial echocardiography study at entry, and again at six months. Eighty patients completed the study.

RESULTS

At six months, the nicorandil and enalapril patient groups each had a significant reduction in LV end-systolic volume index (57.4 +/- 24.8 versus 43.2 +/- 20.7 ml/m2, p = 0.003; 50.0 +/- 19.0 versus 40.4 +/- 14.2 ml/m2, p = 0.006, respectively) and LV mass index (218.0 +/- 88.0 versus 188.0 +/- 76.0 g/m2, p = 0.05; 217.2 +/- 48.0 versus 186.2 +/- 45.0 g/m2, p = 0.002 respectively). Both nicorandil and enalapril caused significant improvement in ejection fraction (63.8 +/- 7.0 versus 71.0 +/- 6.7%, p <0.0001; 63.2 +/- 6.9 versus 67.5 +/- 6.4%, p = 0.002, respectively) and a reduction in LV end-systolic stress (152.9 +/- 29.0 versus 126.0 +/- 25.0 dyne/cm2, p = 0.001; 150.0 +/- 30.2 versus 138.0 +/- 29.0 dyne/cm2, p = 0.002, respectively). However, nicorandil caused a greater reduction in absolute LV end-systolic volume index (13.3 +/- 10.1 versus 9.6 +/- 5.9 ml/m2, p = 0.02), and a greater improvement in absolute ejection fraction (7.2 +/- 4.7 versus 4.2 +/- 2.6%, p = 0.0005) than enalapril.

CONCLUSION

It is concluded that nicorandil is equivalent to enalapril in improving LV volume, mass, end-systolic stress and ejection fraction in mildly symptomatic chronic rheumatic severe mitral regurgitation over a period of six months.

A proposed structural model for amyloid fibril elongation: domain swapping forms an interdigitating beta-structure polymer

We propose a model illustrating how proteins, which differ in their overall sequences and structures, can form the propagating, twisted beta-sheet conformations, characteristic of amyloids. Some cases of amyloid formation can be explained through a "domain swapping" event, where the swapped segment is either a beta-hairpin or an unstable conformation which can partially unfold and assume a beta-hairpin structure. As in domain swapping, here the swapped beta-hairpin is at the edge of the structure, has few (if any) salt bridges and hydrogen bonds connecting it to the remainder of the structure and variable extents of buried non-polar surface areas. Additionally, in both cases the swapped piece constitutes a transient "building block" of the structure, with a high population time. Whereas in domain swapping the swapped fragment has been shown to be an alpha-helix, loop, strand or an entire domain, but so far not a beta-hairpin, despite the large number of cases in which it was already detected, here swapping may involve such a structural motif. We show how the swapping of beta-hairpins would form an interdigitated, twisted beta-sheet conformation, explaining the remarkable high stability of the protofibril in vitro. Such a swapping mechanism is attractive as it involves a universal mechanism in proteins, critical for their function, namely hinge-bending motions. Our proposal is consistent with structural superpositioning of mutational variants. While the overall r.m.s.d.s of the wild-type and mutants are small, the proposed hinge-bending region consistently shows larger deviations. These larger deviations illustrate that this region is more prone to respond to the mutational changes, regardless of their location in the sequence or in the structure. Nevertheless, above all, we stress that this proposition is hypothetical, since it is based on assumptions lacking definitive experimental support.

Plasma lipoprotein(a) levels in patients with pulmonary arterial hypertension

BACKGROUND

Pulmonary artery hypertension is a common sequelae of a variety of cardiac and lung diseases. Pathogenesis of primary and secondary pulmonary artery hypertension is still debatable.

METHODS AND RESULTS

We studied the serum lipoprotein(a) levels in patients with primary (n=27) and secondary (n=19) pulmonary artery hypertension (Eisenmenger syndrome). The results were compared with age and sex matched controls (n=46). We also studied the frequency of high levels of lipoprotein(a) (> 30 mg/dl) in pulmonary artery hypertension. Mean lipoprotein(a) levels were significantly higher in the pulmonary artery hypertension group compared to age- and sex-matched controls (31.60+/-15.49 mg/dl v. 14.66+/-14.7; p=0.0001). All patients were classified into two groups on the basis of their lipoprotein(a) levels (<30 mg/dl and >30 mg/dl). There was a higher frequency of lipoprotein(a) >30 mg/dl in patients of pulmonary artery hypertension v. controls (52% v. 24%; p= <0.001). Younger age, higher functional class, more severe congestive heart failure, shorter duration of symptoms. and more cases of hemoptysis were observed in the group with lipoprotein(a) >30 mg/dl.

CONCLUSIONS

High lipoprotein(a) may be a marker and be associated with a more adverse prognosis in severe pulmonary artery hypertension. Larger prospective studies are needed to establish lipoprotein(a) as a risk factor for the development of pulmonary artery hypertension.