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S Chakraverty

Publications and source records attributed to S Chakraverty.

At least 19 recordsLinked to original sources
PubMed2001

Association studies using novel polymorphisms in BACE1 and BACE2.

The release of amyloid-beta peptide (Abeta) from beta-amyloid precursor protein (APP) requires cleavage by beta- and gamma-secretases. Several groups have identified a candidate for the beta-site APP-cleaving enzyme, BACE1, and its homologue BACE2. We sequenced the genes for BACE1 and BACE2 and found several polymorphisms in both genes. Genotyping a large cohort of AD cases and controls has shown no association between AD and the intronic polymorphism in BACE2 while there was a weak association between the BACE1 polymorphism in exon 5 and AD in those carrying the APOE epsilon4 allele.

Aged↗
PubMed2001

Computer assisted strain-gauge plethysmography is a practical method of excluding deep venous thrombosis.

AIM: To evaluate a computed strain-gauge plethysmograph (CSGP) as a screening tool to exclude above knee deep venous thrombosis (DVT). METHODS: The first phase took place in the Radiology department. One hundred and forty-nine patients had both Doppler ultrasound and CSGP performed. Discordant results were resolved by venography where possible. The second phase took place in an acute medical admissions ward using a modified protocol. A further 173 patients had both studies performed. The results were collated and analysed. RESULTS: Phase 1. The predictive value of a negative CSGP study was 98%. There were two false-negative CSGP results (false-negative rate 5%), including one equivocal CSGP study which had deep venous thrombosis on ultrasound examination. Two patients thought to have thrombus on ultrasound proved not to have acute thrombus on venography. Phase 2. The negative predictive value of CSGP using a modified protocol was 97%. There were two definite and one possible false-negative studies (false-negative rate 4-7%). CONCLUSION: Computer strain-gauge plethysmograph can provide a simple, cheap and effective method of excluding lower limb DVT. However, its use should be rigorously assessed in each hospital in which it is used. Goddard, A. J. P., Chakraverty, S. & Wright, J. (2001). Clinical Radiology56, 30-34.

Acute Disease↗
PubMed2001

Evaluation of local invasion by oesophageal carcinoma--a prospective study of prone computed tomography scanning.

The aim of this study was to assess the value of prone computed tomography compared with the traditional supine position, in the assessment of invasion of adjacent mediastinal structures by oesophageal cancer. A prospective, single blind case-case comparative study of signs of local tumour invasion was conducted. Sixty nine consecutive patients undergoing computed tomography for preoperative staging of oesophageal carcinoma were studied. Computed tomography scanning of the thorax was performed in the standard supine followed by prone position; in 39 patients the computed tomography findings were correlated with the surgical findings. Four established radiological signs used to assess mediastinal invasion were scored in each case. Based on the radiological scoring system, there was a significant down staging in the probability of aortic invasion in 12 of the 69 cases (p<0.05). A similar improvement in accuracy was seen in the cases undergoing surgery; of the 38 cases who did not have aortic invasion at operation, 10 cases were scored as high for aortic invasion on the supine scans compared with only three on the prone position (p<0.05). Prone scanning was not of significant additional value in the assessment of major airway or pericardial invasion. Modification of the computed tomography protocol to include scanning in the prone position will improve the accuracy of the preoperative staging of patients with oesophageal malignancy and reduce the chance of overstaging disease. Especially in centres where endoscopic ultrasound is not available, our modification may reduce the chance of denying patients potentially curative operations.

Esophageal Neoplasms↗
PubMed2000

Tau polymorphisms are not associated with Alzheimer's disease.

Alzheimer's disease (AD) is one of a number of neurodegenerative conditions including frontotemporal dementia and progressive supranuclear palsy that are associated with abnormal tau protein aggregates in neurons. Mutations in the tau gene cause familial forms of frontotemporal dementia and alleles of the tau gene have been associated with risk for progressive supranuclear palsy. However, studies evaluating whether polymorphic variation in tau is associated with AD have produced conflicting results. We investigated the role of the tau exon 2 polymorphism in a large sample of AD cases and controls and found no evidence that polymorphic variation in tau is associated AD.

Aged↗
PubMed1999

Construction of a detailed physical and transcript map of the FTDP-17 candidate region on chromosome 17q21.

Frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) is an autosomal dominant condition clinically characterized by behavioral, cognitive, and motor disturbances. Until now, at least 13 different FTDP-17 families that show linkage to chromosome 17q21 have been described. To characterize the FTDP-17 candidate region, flanked by the markers D17S1789 and D17S1804, we constructed a physical map in P1 and PAC clones. A detailed transcript map was generated by positioning known genes and EST clusters to the physical map. In total, we investigated 150 STSs mapped to this region. In addition, novel transcripts were isolated by exon-trapping. We were able to localize 19 known genes and a number of ESTs to this chromosomal region. Furthermore, seven novel genes were identified for which we isolated the full-length sequence.

Base Sequence↗
PubMed1999

No association between the alpha-2 macroglobulin I1000V polymorphism and Alzheimer's disease.

Recent reports have suggested that variability in the alpha2-macroglobulin gene is a genetic risk factor for Alzheimer's disease. Here we have both tested a common polymorphism in the gene (I1000V) for association with the disease in a four-site case control study design, and tested the locus for linkage in a large series of sibpairs afflicted with late onset disease. Our results fail to show an association between this polymorphism and disease.

Age of Onset↗
PubMed1999

Carotid stenosis in the real world--can Doppler ultrasound replace angiography in a district general hospital setting?

Large trials have confirmed the benefit of carotid endarterectomy in the prevention of stroke in patients with transient ischaemic attacks and > or =70% stenosis of the ipsilateral internal carotid artery. Invasive confirmatory angiography carries some risk, but these patients can be identified by Doppler ultrasound. Non-invasive confirmatory testing with spiral computed tomographic angiography or magnetic resonance angiography is not easily available in many hospitals. In this study, criteria have been developed for use in this unit to identify significant carotid artery stenosis and enable selection for surgery after Doppler ultrasound alone, with known degrees of sensitivity, specificity and accuracy. Carotid arteriography is reserved for a minority of cases.

Blood Flow Velocity↗
PubMed1999

Stepping-table gadolinium-enhanced digital subtraction MR angiography of the aorta and lower extremity arteries: preliminary experience.

PURPOSE: To compare stepping-table digital subtraction gadolinium-enhanced magnetic resonance (MR) angiography of the distal aorta and lower extremity arteries with conventional catheter digital subtraction x-ray angiography in patients with arterio-occlusive disease. MATERIALS AND METHODS: Twenty patients underwent both conventional catheter angiography and fast three-dimensional gadolinium-enhanced MR angiography of the aorta and outflow vessels at 1.5 T; the images were acquired in three consecutive imaging locations during a single infusion of a gadolinium chelate. RESULTS: Compared with catheter angiography, according to the findings of two blinded independent reviewers, MR angiography had sensitivities of 81% and 89% and specificities of 91% and 95%, respectively, for demonstration of insignificant (< or = 50%) stenosis versus significant (51%-100%) stenosis. For demonstration of occlusion, the sensitivity and specificity were 94% and 97%, respectively, by consensus. There was good interobserver correlation between the two readers overall (kappa = 0.65 for reporting the degree of narrowing in all lesions; 0.86, for reporting of insignificant versus significant stenoses; and 0.928, for reporting of occluded versus patient segments). CONCLUSION: Stepping-table digital subtraction contrast material-enhanced MR angiography has high accuracy compared with catheter angiography in patients with arterio-occlusive disease of the aorta and outflow vessels. These preliminary study results suggest that this technique may ultimately provide a safe, noninvasive, and cost-effective alternative to catheter angiography.

Aged↗
PubMed1998

Association of missense and 5'-splice-site mutations in tau with the inherited dementia FTDP-17.

Thirteen families have been described with an autosomal dominantly inherited dementia named frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17), historically termed Pick's disease. Most FTDP-17 cases show neuronal and/or glial inclusions that stain positively with antibodies raised against the microtubule-associated protein Tau, although the Tau pathology varies considerably in both its quantity (or severity) and characteristics. Previous studies have mapped the FTDP-17 locus to a 2-centimorgan region on chromosome 17q21.11; the tau gene also lies within this region. We have now sequenced tau in FTDP-17 families and identified three missense mutations (G272V, P301L and R406W) and three mutations in the 5' splice site of exon 10. The splice-site mutations all destabilize a potential stem-loop structure which is probably involved in regulating the alternative splicing of exon10. This causes more frequent usage of the 5' splice site and an increased proportion of tau transcripts that include exon 10. The increase in exon 10+ messenger RNA will increase the proportion of Tau containing four microtubule-binding repeats, which is consistent with the neuropathology described in several families with FTDP-17.

Alternative Splicing↗
PubMed1998

Hereditary dysphasic disinhibition dementia: a frontotemporal dementia linked to 17q21-22.

OBJECTIVE: The clinical and pathologic features of hereditary dysphasic disinhibition dementia (HDDD) are described to determine whether it is a variant of known dementias. BACKGROUND: Several dementing disorders have clinical and pathologic similarities with AD, Pick's disease, and the "nonspecific" dementias. A detailed description of clinical and pathologic presentation will aid classification, but ultimately the discovery of causative gene(s) will define these disorders. METHODS: The authors performed a clinical assessment: gross and microscopic pathologic evaluation of brain tissue, genetic linkage studies, and sequence analyses. RESULTS: HDDD is an autosomal-dominant frontotemporal dementia with many similarities to Pick's disease. Salient clinical features are global dementia with disproportionate dysphasia and "frontotemporal" symptoms. A linkage between HDDD and 17q21-22 was shown, with a maximum lod score of 3.68 at zero recombination. CONCLUSIONS: Several dementias have been linked to the same region and have been termed frontotemporal dementia with parkinsonism linked to chromosome 17. These disorders may represent phenotypic variants arising from mutations within a common gene.

Adult↗
PubMed1998

Mutation, sequence analysis, and association studies of alpha-synuclein in Parkinson's disease.

A mutation within the alpha-synuclein gene on human chromosome 4 has been reported to segregate with PD in an Italian family. We screened a sample of familial cases of PD for mutation in the alpha-synuclein gene. None of the familial cases of PD carried a mutation within the alpha-synuclein gene, and no association was detected between PD and alleles of a dinucleotide repeat marker within the alpha-synuclein gene. We conclude that variation within the alpha-synuclein gene does not play a significant role in the risk for PD in our sample.

Aged↗
PubMed1997

No evidence for a schizophrenia susceptibility gene in the vicinity of IL2RB on chromosome 22.

Pulver et al. [1994a] reported modest linkage evidence for a dominantly (D) inherited "schizophrenia gene" in the vicinity of IL2RB on chromosome 22q12, and Coon et al. [1994] adduced moderate evidence under a recessive (R) model. We report here a replication study to test the hypothesis that one of these two models (or a third, intermediate (I) model) adequately describes the co-segregation of schizophrenia and chromosome 22q12 markers in an independent sample of 23 multiplex families. Altogether nine transmission models were evaluated. The models differed depending on whether the 15 family members with a diagnosis of schizophrenia spectrum disorders were considered unaffected (a "narrow" (N) definition), affected (a "wide" (W) definition), or declared "unknown" (U). The entire region between D22S268 and D22S307 is excluded (i.e., lod <-2) for models RN, RW, RU, and IW. Lod scores for the remaining models are uniformly negative; albeit, equivocal with respect to the dominant hypothesis over a small region between D22S268 and IL2RB. Nonparametric analysis under both diagnostic criteria also failed to yield any evidence for a susceptibility locus in this region of chromosome 22.

Chromosomes, Human, Pair 22↗