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R Surendran

Publications and source records attributed to R Surendran.

14 recordsLinked to original sources
PubMed2006

Transabdominal modified devascularization procedure with or without esophageal stapler transection--an operation adequate for effective control of a variceal bleed. Is esophageal stapler transection necessary?

BACKGROUND: In Japan, the original Sugiura procedure reported favorable results in non-cirrhotic patients but in the West, the modified Sugiura procedure is not widely accepted because of high rebleeding, morbidity, and mortality in cirrhotics. We retrospectively analyzed the efficacy of our modified Sugiura procedure i.e., devascularization with/without esophageal transection combined with salvage endotherapy and pharmacotherapy for control of a variceal bleed. MATERIALS AND METHODS: Between January 1999 and December 2004, 912 patients with variceal bleeding were treated. Of these, 66 (7.2%) patients were subjected to surgery after failed endotherapy/propranolol. Among these 66 patients, 52 had transabdominal devascularization (16 emergency, 36 elective); 14 patients underwent devascularization with esophageal stapler transection (group I), and 38 patients had devascularization without esophageal stapler transection (group II). Another 14 patients underwent elective end-to-side proximal splenorenal shunt surgery. RESULTS: Postoperative mortality was 7.1% in group I, 10.5% in group II (P>0.05). Mortality for emergency surgery was 31.2% (5/16) but there were no deaths in the elective surgery group. Overall morbidity was 57.1% in group I and 21.0% in group II (P<0.05). The rates of variceal rebleeding were 7.1% and 7.8%; residual varices were 30.7% and 32.3%; recurrent varices were 7.6% and 5.8% following the group I and group II procedures, respectively, over a mean follow-up period of 39.9 (7-2) months. Esophageal transection-related morbidity (leak, stricture, and bleeding) was 21.4% (3/14) in group I. CONCLUSIONS: Devascularization without esophageal stapler transection is a safe and effective procedure for adequate (urgent and long-term) control of variceal bleeding with similar results and less morbidity when compared to devascularization with esophageal transection in cirrhotic patients, as well as non-cirrhotic patients.

Adult↗
PubMed2005

Effect of ursodeoxycholic acid on copper induced oxidation of low density lipoprotein.

The aim of this study was to investigate copper (Cu++) induced oxidation state of LDL isolated from obstructive jaundice (OBJ) patients with hyperlipidemia and the effect of UDCA on the same. LDL was isolated and oxidation was induced by 5 mM CuSO4 with/without UDCA at different concentrations. LDL oxidation was assessed at different time intervals in terms of conjugated dienes, hydroperoxides and 'thiobarbituric acid reacting substances' (TBARS). The change in the level of endogenous LDL alpha-tocopherol was also monitored simultaneously. The oxidisability of LDL isolated from OBJ patients was significantly higher and showed a steep increase in the level of conjugated diene formation without any lag phase. In normal samples the oxidation proceeded slowly with a lag phase. This was also evidenced by the level of formation of hydroperoxides and TBARS. The basal level of LDL alpha-tocopherol was significantly low in OBJ samples. UDCA was found to delay the oxidation of LDL in a dose dependent manner. The consumption of alpha-tocopherol was found to be minimum in the presence of UDCA. The results of this investigation show that there is a high susceptibility of LDL to oxidation in OBJ cases and this may be due to low endogenous LDL alpha-tocopherol content. UDCA minimizes LDL oxidation in dose dependent manner, which is an additional evidence for its antioxidant nature.

Adult↗
PubMed2004

Structural studies of the biomineralized species of calcified pancreatic stones in patients suffering from chronic pancreatitis.

The pancreatic stones (Pancreatic calculi) collected from patients suffering from chronic calcific pancreatitis were studied in a view to explore the constituents involved in the calcification. The calcified stones were characterized by XRD, EPR and IR spectroscopic techniques. The detailed studies indicate that these stones consist of calcium carbonate as a major component, besides phosphates and other protein content. The presence of aragonite phases in the biomineralized stones is also discussed. The EPR spectra gave an evidence of the presence of traces of manganese in different oxidation states, which is used as one of the EPR probes in the present work. The samples were sintered at different temperatures to remove all the organic matter, and their EPR spectra have been studied to obtain detailed information regarding the changes in the symmetry of these stone samples. The X-irradiated sample was also characterized by EPR and the resonance signals are attributed to freely rotating CO(2)(-) radicals. The infrared spectrum reveals the presence of many organic bands corresponding to the protein amides.

Calculi↗
PubMed1997

A 21-kDa C-terminal fragment of protein-disulfide isomerase has isomerase, chaperone, and anti-chaperone activities.

A catalyst of disulfide formation and isomerization during protein folding, protein-disulfide isomerase (PDI) has two catalytic sites housed in two domains homologous to thioredoxin, one near the N terminus and the other near the C terminus. The thioredoxin domains, by themselves, can catalyze disulfide formation, but they are unable to catalyze disulfide isomerizations (Darby, N. J. and Creighton, T. E. (1995) Biochemistry 34, 11725-11735). A 21-kDa, C-terminal fragment of PDI (amino acids 308-491), termed weePDI, comprises the C-terminal third of the molecule. The kcat for ribonuclease oxidative folding by weePDI is 0.26 +/- 0.02 min-1, 3-fold lower than the wild-type enzyme but indistinguishable from the activity of a full-length mutant of PDI in which both active site cysteines of the N-terminal thioredoxin domain have been mutated to serine. Eliminating the ability of weePDI to escape easily from covalent complexes with substrate by mutating the active site cysteine nearer the C terminus to serine has a large effect on the isomerase activity of weePDI compared with its effect on the full-length enzyme. weePDI also displays chaperone and anti-chaperone activity characteristic of the full-length molecule. As isolated, weePDI is a disulfide-linked dimer in which the single cysteine (Cys-326) outside active site cross-links two weePDI monomers. The presence of the intermolecular disulfide decreases the activity by more than 2-fold. The results imply that the functions of the core thioredoxin domains of PDI and other members of the thioredoxin superfamily might be modified quite easily by the addition of relatively small accessory domains.

Amino Acid Sequence↗
PubMed1996

Subunit structure of rod cGMP-phosphodiesterase.

The rod cGMP phosphodiesterase (PDE) is the G-protein-activated effector enzyme that regulates the level of cGMP in vertebrate photoreceptor cells. Rod cGMP PDE is generally viewed as a heterotrimeric protein composed of catalytic alpha and beta subunits ( approximately90 kDa each) and two copies of the inhibitory subunit gamma ( approximately 10 kDa). However, the possibility that rod PDE could exist as distinct isoforms, such as alphaalphagamma2 and betabetagamma2 has not been ruled out. We have studied this question using cross-linking of PDE subunits with maleimidobenzoyl-N-hydroxysuccinimide ester and para-phenyldimaleimide. The cross-linking resulted in major products with molecular mass of 100 and 150 kDa, a doublet at approximately 180-190 kDa, and a doublet at approximately 210-220 kDa. Cross-linked products were analyzed using polyclonal-specific anti-PDEalphabeta, anti-PDEalpha, anti-PDEbeta, or anti-PDEgamma antibodies. The anti-PDEalpha and anti-PDEalphabeta antibodies recognized all the cross-linked products, whereas anti-PDEbeta and anti-PDEgamma antibodies did not interact with the 150-kDa band, indicating that the composition of this band is most likely alphaalpha. Similar analysis of cross-linked products of trypsin-treated PDE preparations revealed bands that are likely formed by PDEbeta subunit. The molecular size of holo-PDE and trypsin-activated PDE were studied using analytical ultracentrifugation in order to determine if oligomerization of PDE could account for the cross-linking of identical PDE subunits. The sedimentation analysis of both holo-PDE and ta-PDE revealed homogeneous samples with molecular masses of approximately220 and approximately150 kDa, respectively. These results indicate that PDE is likely a mixture of the major species alphabetagamma2, minor species alphaalphagamma2, and possibly betabetagamma2. Our data are consistent with the detection of low PDE activity in the rd mouse, which lacks any functional PDEbeta subunit.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1995

Involvement of Neurospora mitochondrial tyrosyl-tRNA synthetase in RNA splicing. A new method for purifying the protein and characterization of physical and enzymatic properties pertinent to splicing.

The Neurospora CYT-18 protein, the mitochondrial tyrosyl-tRNA synthetase, functions in the splicing of group I introns. Here, bacterially expressed CYT-18 protein, purified by a new procedure involving polyethyleneimine precipitation to remove tightly bound nucleic acids, was used to characterize properties pertinent to RNA splicing. Analytical ultracentrifugation and other methods showed that the CYT-18 protein is an asymmetric homodimer. The measured frictional ratio, f/fo = 1.55, corresponds to an axial ratio of 10 for a prolate ellipsoid or 12 for an oblate ellipsoid. Like bacterial TyrRSs, the CYT-18 protein exhibits half-sites reactivity, each homodimer having one active site for tyrosyl adenylation and RNA splicing. The splicing activity of CYT-18 was unaffected by aminoacylation substrates at concentrations used in aminoacylation reactions, whereas the TyrRS activity was inhibited by physiological concentrations of the splicing cofactor GTP, as well as CTP or UTP, or by low concentrations of a group I intron RNA. Kinetic measurements suggest that the binding of CYT-18 to a group I intron substrate is a two-step process, with an initial biomolecular step that is close to diffusion limited (3.24 +/- 0.03 x 10(7) M-1s-1) followed by a slower conformational change (0.54 +/- 0.07 s-1). After CYT-18 binding, splicing occurs at a rate of 0.0025 s-1, within 6-fold of the rate of self-splicing of the Tetrahymena large rRNA intron in vitro. The Kd for the complex between the CYT-18 protein and a group I intron substrate, calculated from koff/kon, was < 0.3 pM, substantially lower than determined by presumed equilibrium measurements [Guo, Q., & Lambowitz, A. M. (1992) Genes Dev. 6, 1357-1372]. As a result of this tight binding, the CYT-18 protein functions stoichiometrically in in vitro splicing reactions due to its extremely slow dissociation from the excised intron RNA. The very tight binding of the CYT-18 protein to the intron RNA raises the possibility that specific mechanisms exist for dissociating the protein from the excised intron in vivo.

Cloning, Molecular↗
PubMed1994

Construction of a dimeric repressor: dissection of subunit interfaces in Lac repressor.

Formation of the lactose repressor tetramer is postulated to involve two subunit interfaces, one primarily contributing to monomer-monomer assembly to dimer and the second to dimer-dimer association to tetramer. The latter interface requires a heptad repeat of three leucines at the C-terminus of lac repressor that is presumed to form an abbreviated coiled-coil motif [Chakerian, A. E., Tesmer, V. M., Manly, S. P., Brackett, J. K., Lynch, M. J., Hoh, J. T., & Matthews, K. S. (1991) J. Biol. Chem. 266, 1371-1374; Alberti, S., Oehler, S., von Wilcken-Bergmann, B., Krämer, H., & Müller-Hill, B. (1991) New Biol. 3, 57-62; Chen, J., & Matthews, K. S. (1992) J. Biol. Chem. 267, 13843-13850]. To strengthen the dimer-dimer interface, this motif was extended by the addition of one and two leucine heptad repeat units to the C-terminus by site-specific insertion mutagenesis. The tetrameric products displayed operator and inducer affinity essentially indistinguishable from the wild-type repressor. In order to probe the effect of the elongated coiled-coil on assembly of the repressor tetramer, the other of the two postulated subunit interfaces was disrupted by introducing a point mutation (Y282D) that yields a monomeric protein in the wild-type background. Both elongated mutant repressors were able to assemble into dimeric species, apparently due to the strengthened subunit association at the C-terminal region compared to the wild-type repressor. These results further confirm the role of a coiled-coil structure in the formation of tetramer in the lac repressor.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMedDate not supplied

Groove pancreatitis.

Explore the source record for details and available documents.

Adolescent↗
PubMedDate not supplied

Predicting the composition of gallstones by infrared spectroscopy.

AIM: To determine the composition of gallstones in South India by comparing visual assessment with graphic interpretation of infrared spectra. METHODS: Infrared spectroscopy (IRS) was used in qualitative analysis of 168 gallstones from Tamilnadu, Kerala and Karnataka and compared with visual interpretation. The spectrum of cholesterol, calcium bilirubinate and calcium carbonate for each stone was correlated with visual inspection. RESULTS: Fifty four percent of gallstones were of pigment variety, 43% were of mixed and the remaining 3% were cholesterol gallstones as categorised by visual interpretation. Based on infrared spectrocopic interpretation the percentages were 58%, 39% and 2% respectively. There was a good agreement between the visual inspection and IRS in classification of gallstones (Kappa value 85%; 95% CI 77-93%). CONCLUSION: Visual inspection of gallstones can predict the composition of gallstone with good accuracy and was comparable to infrared spectroscopic interpretation.

Bilirubin↗
PubMedDate not supplied

Surgical practice in symptomatic and asymptomatic gallstone disease.

AIMS: To determine the surgical practice in individuals with symptomatic and asymptomatic gallstone disease using a questionnaire survey. METHODS: A questionnaire was sent to 724 patients with gallstone disease. Details of symptoms, duration of illness, nature of treatment including surgery, color of gallstones retrieved and postoperative follow-up particulars were obtained. RESULTS: The study group included 225 (54%) men; there was a rising trend of prevalence of gallstones in men with increasing age (p<0.05). A third of the patients (142 [34%]) were symptomatic. The mean duration of symptoms was 12.1 months. One hundred and ninety seven patients (48%), including 90 asymptomatic ones, underwent cholecystectomy. Most patients (92.5% of those symptomatic and 76.6% of those asymptomatic) underwent cholecystectomy within one year of diagnosis. Eight asymptomatic patients underwent surgery 3 years or more after diagnosis. The predominant color of stones retrieved was black or brown (57%) or mixed (39%). CONCLUSIONS: A majority of patients with gallstone disease had cholecystectomy within one year of diagnosis. Black or brown pigment stones were the dominant types of gallstones.

Bile Pigments↗
PubMedDate not supplied

Acquired volvulus following Nissen fundoplication.

Nissen fundoplication is the procedure of choice for the management of gastroesophageal reflux disease. We report a case of acquired gastric volvulus following open fundoplication. The mechanism of formation and correction of the volvulus is discussed.

Adult↗