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Biomedical subjects

S Tyagi

Publications and source records attributed to S Tyagi.

At least 73 records · Page 4Linked to original sources
PubMed1996

Molecular beacons: probes that fluoresce upon hybridization.

We have developed novel nucleic acid probes that recognize and report the presence of specific nucleic acids in homogeneous solutions. These probes undergo a spontaneous fluorogenic conformational change when they hybridize to their targets. Only perfectly complementary targets elicit this response, as hybridization does not occur when the target contains a mismatched nucleotide or a deletion. The probes are particularly suited for monitoring the synthesis of specific nucleic acids in real time. When used in nucleic acid amplification assays, gene detection is homogeneous and sensitive, and can be carried out in a sealed tube. When introduced into living cells, these probes should enable the origin, movement, and fate of specific mRNAs to be traced.

Base Sequence↗
PubMed1996

Novel, ligation-dependent PCR assay for detection of hepatitis C in serum.

A simple, sensitive, and specific ligation-dependent PCR (LD-PCR) method for the detection of hepatitis C virus (HCV) RNA in serum is described. The assay uses two DNA capture probes for RNA isolation and two DNA hemiprobes for subsequent PCR. Each capture probe has a 3' sequence complementary to the conserved 5' untranslated region of HCV RNA and a biotin moiety at the 5' end capable of interacting with streptavidin-coated paramagnetic beads. Each hemiprobe contains a sequence complementary to the 5' untranslated region in juxtaposition to one another and a common sequence for PCR primer binding. In guanidinium thiocyanate solutions, the capture probes and the hemiprobes form a hybrid with their target, and the hybrid can be isolated from serum by the binding of the capture probes to the paramagnetic beads in the presence of a magnetic field. The hemiprobes can then be linked to each other by incubation with T4 DNA ligase to form a full probe that serves as a template for a PCR. When serial 10-fold dilutions of synthetic HCV RNA (10(7) to 10 molecules) were tested, there was a good correlation between the amount of PCR product and the initial number of RNA molecules, with a sensitivity of 100 HCV RNA molecules per reaction. Twenty-four specimens that had been tested by either a branched DNA probe (bDNA) assay (13 specimens) or a reverse transcription PCR (RT-PCR) assay (11 specimens) were also analyzed by LD-PCR. The results showed a good correlation among LD-PCR, RT-PCR, and the bDNA assay. However, both LD-PCR and RT-PCR were more sensitive than the bDNA assay when the HCV titer was low.

Base Sequence↗
PubMed1996

Balloon dilatation of inferior vena cava stenosis in Budd-Chiari syndrome.

Percutaneous balloon angioplasty was used to dilate inferior vena cava (IVC) stenosis in 12 patients with Budd Chiari syndrome. There were seven men and five women, aged 32.8 +/- 8.5 years. Angioplasty was performed using balloon 18-20 mm in diameter. In eleven (91.6%) patients, IVC could be successfully dilated. In these eleven patients, the caval diameter at the site of stenosis increased from 2.3 +/- 1.5 to 13.1 +/- 2.8 mm (p < 0.001), the mean IVC pressure decreased from 28.2 +/- 4.1 to 10.5 +/- 3.4 mmHg (p < 0.001) and the gradient across the stenosis decreased from 23.1 +/- 2.2 to 4.2 +/- 1.9 mmHg (p < 0.001). There was appreciable clinical improvement after angioplasty. On a mean followup of 10.8 (3-18) months four (36.4%) patients had restenosis which could be successfully dilated again. These results suggest that balloon dilatation of inferior vena cava stenosis is safe and effective, however, recurrence is common and needs redilatation.

Adolescent↗
PubMed1995

Calcium transport mechanism in human colonic apical membrane vesicles.

BACKGROUND & AIMS: Recent studies have shown the role of human colon in the absorption of calcium, especially in the presence of severe disease or resection of the small bowel. The aim of the current study was to explore the mechanism(s) of calcium uptake by the purified human colonic apical membrane vesicles. METHODS: Apical membrane vesicles were purified from mucosal scrapings of colons from organ donors, and 45Ca uptake was measured using a rapid filtration technique. RESULTS: The majority of the 45Ca associated with vesicles represented uptake into closed intravesicular space, whereas the remaining 45Ca uptake represented binding to the vesicles. Ca2+ uptake was found to be dependent on time, pH, temperature, and ionic strength of the incubation medium and inhibitable by ruthenium red, La3+, and ethylene glycol-bis(beta-amino-ethyl ether)-N,N,N',N'-tetraacetic acid. Experiments of the effects of membrane potential generated by K+/valinomycin or anion substitutions on Ca2+ uptake showed that the Ca2+ uptake process was potential insensitive. Calcium uptake was unaffected by outwardly directed H+, K+, and Na+ gradients. Ca2+ uptake showed saturation kinetics with no significant differences in Michaelis constant and maximum velocity values of this transporter between proximal and distal colonic segments. CONCLUSIONS: The uptake of Ca2+ by human colonic apical membranes involves predominantly a carrier-mediated transport mechanism.

Adenosine Triphosphate↗
PubMed1993

Long-term results after balloon pulmonary valvuloplasty in adults.

Percutaneous balloon pulmonary valvuloplasty for congenital pulmonary valve stenosis was performed in 40 adult patients (aged 18 to 56 years). The duration of follow-up was 24.5 +/- 11.5 months. The peak systolic pressure gradient from the right ventricle to the pulmonary artery decreased from 107 +/- 29 mm Hg to 37 +/- 25 mm Hg immediately after the procedure. On follow-up, gradient obtained either by cardiac catheterization or Doppler echocardiography was 31 +/- 13 mm Hg. In eight patients with residual gradient after valvuloplasty of > 50 mm, the mean peak systolic gradient decreased from 74.5 +/- 18.3 to 33.5 +/- 13.9 mm Hg on follow-up. Thus balloon pulmonary valvuloplasty is a safe and effective procedure for the treatment of adult patients with pulmonic stenosis; there is a tendency for high residual gradients to regress on follow-up.

Adolescent↗
PubMed1993

Balloon angioplasty for renovascular hypertension in Takayasu's arteritis.

Percutaneous transluminal renal angioplasty was performed in 54 consecutive patients with hypertension and renal artery stenosis caused by Takayasu's arteritis. Angioplasty was technically successful in 67 (89.3%) of 75 lesions attempted. In these 67 lesions, the degree of stenosis decreased from 88.3 +/- 4.8% to 23.5% +/- 13.6% (p < 0.001) after angioplasty. Following successful angioplasty there was significant improvement in hypertension (p < 0.001) within 48 hours. Patients with bilateral renal artery stenosis had higher systolic blood pressure both before balloon dilatation (p < 0.05) and after balloon dilatation before discharge (p < 0.001), compared with patients with unilateral renal artery stenosis. Three to 70 months (mean 26.4 +/- 10.3 months) after successful angioplasty, blood pressure was reduced to normal or was improved in 93% of patients. Angiographic restudy an average of 14.2 +/- 7.8 months after angioplasty showed restenosis at the same site in 7 of 52 (13.5%) lesions and fresh stenosis in one artery. All these eight lesions were successfully dilated. Further improvement in the luminal diameter was observed in 11 (21.2%) lesions. Late angiographic restudy in seven patients an average of 56.1 +/- 6.3 months after angioplasty showed no restenosis. Our results suggest that balloon angioplasty is safe and highly effective in relieving renal artery stenosis caused by Takayasu's arteritis and should be the treatment of choice for renovascular hypertension in this disease.

Adolescent↗
PubMed1992

Percutaneous transluminal angioplasty in Takayasu arteritis.

Percutaneous transluminal balloon angioplasty (PTBA) was performed in 87 patients for 111 stenotic lesions due to Takayasu arteritis. Of the lesions attempted for dilatation, 35 were in the aorta, 64 in renal arteries, 9 in subclavian, and 3 in common iliac arteries. The stenosis of aorta could be successfully dilated in 33 of 35 (94.3%) patients with fall in peak systolic pressure gradient (PSG) from 77.7 +/- 28.4 mmHg to 26.4 +/- 20.6 mmHg (P < 0.001) and increase in luminal diameter from 4.7 +/- 2.4 mm to 10.1 +/- 4.1 mm (P < 0.001). On hemodynamic and angiographic restudy in 20 patients at 3-24 months (mean 7.7 +/- 4.1 months) further fall in PSG (> or = 15 mmHg) was observed in 7 patients, no significant change in 12 patients and restenosis with increase in PSG in one patient which could be successfully redilated. Late restudy at 36-60 months (mean 43 +/- 9.4) in six patients showed continued relief of stenosis (mean PSG 8.8 +/- 7.8 mmHg). Of the 64 stenotic lesions of the renal arteries, 58 (90.6%) could be successfully dilated with decrease in stenosis from 89.1 +/- 10.1% to 29.9 +/- 14.9% (P < 0.001). Follow-up intra-arterial digital subtraction angiography in 25 patients at a mean follow-up period of 13.1 months (range 3-29 months) showed restenosis in 5/36 (13.9%) lesions which could be successfully redilated. Angioplasty was also successful in dilating 8/9 (88.9%) subclavian and all 3 common iliac artery stenosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Balloon angioplasty of native coarctation of the aorta in adolescents and young adults.

Balloon angioplasty of native coarctation of the aorta was performed in 35 consecutive adolescents and young adults, aged 14 to 37 years (mean 22.6 +/- 7.1). Twenty-eight (80%) patients had isolated discrete coarctation, six (17.1%) had tubular hypoplasia of the aortic isthmus, and one (2.9%) had hypoplasia of the post-coarctation aorta. The peak systolic pressure gradient decreased from 78.5 +/- 23.9 to 15.7 +/- 11.6 mm Hg (p less than 0.001), and the mean coarctation diameter increased from 4.7 +/- 2.4 to 13.1 +/- 2.7 mm (p less than 0.001) immediately after angioplasty. Patients with discrete-type coarctation had significantly less residual gradient than patients with long-segment tubular coarctation (12.3 +/- 10.7 vs 27.2 +/- 6.6 mm Hg, p less than 0.01). On recatheterization and angiography in 26 patients at 12.6 +/- 1.5 months after dilatation, there was no significant change in gradient (15.5 +/- 13.3 mm Hg) and diameter (13.1 +/- 1.8 mm) from the immediate post-angioplasty results. However, two patients had an increase in gradient and three had small aortic aneurysms with no change in appearance on restudy after 2 years. After 3 to 67 months' (mean 32.7 +/- 19.2) follow-up, all patients showed continued clinical improvement. Hypertension was relieved in 37.5% (12/32) and improved in 59.4% (19/32). Our experience suggests that balloon angioplasty of native aortic coarctation in adolescents and young adults is safe and highly effective with sustained improvement on intermediate-term follow-up.

Adolescent↗
PubMed1992

Balloon angioplasty of the aorta in Takayasu's arteritis: initial and long-term results.

Percutaneous transluminal balloon angioplasty for stenosis of the aorta was performed in 36 patients with Takayasu's arteritis (age range, 8 to 36 years; mean, 19.1 +/- 7.7 years). Balloon dilatation was successful in 34 patients and resulted in a decrease in the mean peak systolic pressure gradient (PSG) from 75.2 +/- 29.1 mm Hg to 24.8 +/- 19 mm Hg (p less than 0.001) and a mean increase in the diameter of the stenosed segments from 4.5 +/- 2.2 mm to 9.6 +/- 3.8 mm (p less than 0.001). Hemodynamic and angiographic restudy, which was performed in 20 patients at a mean follow-up period of 7.7 +/- 4.1 months (range, 3 to 24 months), showed a further decrease in PSG (greater than or equal to 15 mm Hg) in seven patients (from 40.0 +/- 11.2 mm Hg to 15.7 +/- 10.2 mm Hg; p less than 0.01), no significant change in PSG in 12 patients (17.1 +/- 13.6 mm Hg vs 16.6 +/- 12.7 mm Hg; p = NS), and an increase in PSG from 15 mm Hg to 85 mm Hg in one patient. The patient who showed restenosis underwent successful redilatation. Six patients who underwent late recatheterization and angiography at 36 to 60 months (mean, 43 +/- 9.4 months) show continued relief of stenosis (mean PSG, 8.8 +/- 7.8 mm Hg). Patients with short-segment (less than 4 cm) stenosis experience more relief than patients with long-segment (greater than or equal to 4 cm) stenosis (residual PSG, 18.6 +/- 8.2 mm Hg vs 40 +/- 16 mm Hg; p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Hemobilia in a child with liver abscess.

Hemobilia in children is rare and has so far been described only as a complication of blunt abdominal trauma. A case of hemobilia secondary to liver abscess treated successfully by selective arterial embolization is described. Hemobilia should be considered in any case of gastrointestinal hemorrhage before any operative intervention is undertaken.

Angiography↗
PubMed1991

Successful non-surgical embryo recovery from a goat.

Embryos from a Jamunapari goat were successfully recovered using non-surgical approach. The technique of Bessoudo et al [Theriogenology, 29 (1988) 221] was simplified and all the appliances used were fabricated indigenously. Fluid retrieval rate was 95%. Five excellent embryos (blastocysts) were recovered. The whole process of embryo collection was completed in 30 min.

Animals↗
PubMed1990

Nonrandomness in prebiotic peptide synthesis.

We have synthesized and studied the properties of phosphoanhydrides of alanine with guanosine monophosphate, uridine monophosphate, and adenosine monophosphate. This series of compounds allowed us to investigate the specificity of peptide bound formation in a reaction that could have taken place on the prebiotic earth. We asked whether the intrinsic reactivity of the amino acids, the nature of the nucleotide in the anhydride, or the complementary polynucleotide template influences the specificity of the peptide synthesis reaction. We observed that the differential reactivity of the amino acids results in nearest-neighbor preferences during the peptide synthesis, whereas the nature of the nucleotides and the presence of complementary polynucleotides had no influence on the specificity. These results suggest that some peptides would have been more abundant than others on the prebiotic earth and have implications for the study of the origins of the genetic code and protein synthesis.

Amino Acid Sequence↗
PubMed1989

Prognostic significance of pre discharge one hour electrocardiographic monitoring in patients recovering from acute myocardial infarction.

During a 15 months period, 97 patients with AMI were monitored continuously at hospital discharge for one hour. The VPCs or no VPC noted during this period of continuous monitoring were correlated with subsequent cardiac events during one year follow up. Patients with complicated VPCs had a significantly higher incidence of cardiac deaths and non-fatal re-infarctions during one year follow up (54.5%) as compared to patients with no VPCs (6.5%) (p less than .001). Patients with higher grades of VPCs had more complicated course (30.3% to 66.7% for Lown Grade II to IV) as compared to 6.5% and 20.8% for grade Lown O and I. Though, the results of this 1 hour continuous monitoring at hospital discharge are not as sensitive as with ambulatory Holter monitoring as is evident from this study where complicated VPCs were detected in 11.4% patients vs. 33% with Holter monitoring, it could be a useful tool in institutions where the facility of Holter monitoring does not exist.

Adult↗