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P Roychowdhury

Publications and source records attributed to P Roychowdhury.

13 recordsLinked to original sources
PubMed2006

Fabrication and evaluation of porous 2,3-dialdehydecellulose membrane as a potential biodegradable tissue-engineering scaffold.

A simple, novel method to produce porous 2,3-dialdehydecellulose (DAC) membranes as a potential tissue-engineering scaffold has been developed from methylolcellulose by the simultaneous water-induced phase separation and sodium chloride salt leaching techniques, followed by oxidation with sodium periodate in water. Membrane pores increased in size with increasing weight or particle size of the sodium chloride salt. The porosity of the membrane was not affected by the salt particle size, but it increased with an increase in the salt weight to 60%. At higher salt weight percentages, no significant change in the membrane porosity was observed. The oxidation step had no effect on the membrane porosity or pore size. All membranes with a porosity value ranging between 87 and 93% showed interconnected porous structures. The use of these membranes as a potential tissue-engineering scaffold was evaluated with the use of human neonatal skin fibroblast cells. Confocal microscopy showed cell attachment and spreading on these membranes. Immunohistochemical tests revealed the presence of collagen type III and fibronectin, indicating that the cells were viable and formed the extracellular matrix. In conclusion, the DAC membrane supports cell adhesion and proliferation and hence shows potential to be used as a tissue-engineering scaffold.

Absorbable Implants↗
PubMed2005

21-deoxycortisone (17alpha-hydroxy-4-pregnene-3,11,20-trione).

The title compound, C21H28O4, a synthetic glucocorticoid, crystallizes with a single molecule in the asymmetric unit. Ring A is almost in a half-chair conformation, rings B and C are almost in chair conformations, and ring D is between a twist and a 13beta-envelope conformation. The A/B ring junction is quasi-trans, whereas the B/C and C/D ring junctions both approach trans characteristics. The molecule as a whole is slightly convex towards the beta side, with an angle of 9.60 (2) degrees between the C10-C19 and C13-C18 vectors. Molecular-packing and hydrogen-bonding (both intra- and intermolecular) interactions play a major role in the structural association of the compound.

Cortisone↗
PubMed2005

Alteration of blood pressure among the donors in a blood donation camp.

Anxiety can alter the cardiovascular parameters. In the present study, among the normotensive donors, the effect of anxiety on alteration of blood pressure and heart rate was assessed. Blood pressure and pulse rate were recorded in the volunteers just before blood donation and the results were compared with the blood pressure and heart rate recorded previously (one week before the camp) in the same population. There was a rise of both systolic and diastolic blood pressure with a significant increase in pulse rate just before blood donation. As the donors had previous experience of blood donation; the mental stress just before blood donation can be regarded as known stress -- which caused increase in norepinephrine secretion leading to peripheral vasoconstrictions and rise in diastolic blood pressure. Anxiety through sympathetic stimulation increased the heart rate, cardiac output and systolic blood pressure.

Adolescent↗
PubMed2002

Homology modelling of the ligand binding domain of mineralocorticoid receptor: close structural kinship with glucocorticoid receptor ligand binding domain and their similar binding mode with DOC (de-oxy corticosterone).

Mineralocorticoids play a major role in regulating sodium and potassium homeostasis and also contribute to the control of blood pressure and in some physiological disorders. The physiological effects of this class of corticosteroids are mediated by ligand-induced nuclear transcription factor, the mineralocorticoid receptor(MR) / glucocorticoid receptor(GR), a member of the steroid / nuclear receptor superfamily. Although the MR interacts with both glucocorticoids and mineralocorticoids, the GR interacts specifically with glucocorticoids. The three dimensional structure of progesterone complexed to its receptor revealed in X-ray diffraction method is utilised to develop a homology model of human mineralocorticoid receptor ligand binding domain (hMR LBD) in a similar fashion as mouse GR LBD was developed previously. The secondary structure of hMR LBD contains eleven helices, eight turns and four sheets. This receptor contains a long helix, H9, with thirty four residues. The 12-residue C-terminal extension (residues 973-984) of hMR LBD, which is essential for hormone binding, is tightly fixed in position by an antiparallel b-sheet interaction. The three dimensional model reveals two polar sites located at the extremities of the elongated hydrophobic ligand-binding pocket (LBP). De-oxy corticosterone (DOC) is docked to the LBs of both hMR LBD and mGR LBD. The difference accessible surface area (DASA) study revealed the interaction zones of both the receptors in complex with DOC. Observations relating to the native and complex proteins revealed a close structural kinship between hMR LBD and mGR LBD.

Amino Acid Sequence↗
PubMed2001

Homology modelling of the ligand-binding domain of glucocorticoid receptor: binding site interactions with cortisol and corticosterone.

Glucocorticoids are involved in the growth, development and homeostasis of a number of tissues. The physiological effects of this class of lipophilic steroids are mediated by ligand-inducible nuclear transcription factor, the glucocorticoid receptor/mineralocorticoid receptor, a member of the steroid/nuclear receptor superfamily. The glucocorticoid receptor interacts specifically with glucocorticoids, whereas the mineralocorticoid receptor interacts with both glucocorticoids and mineralocorticoids. The molecular structure of progesterone complexed to its receptor obtained from X-ray crystal structure analysis is used to build up a homology model of mouse glucocorticoid receptor ligand-binding domain (mGR LBD). The secondary structure of mGR LBD contains 11 helices, nine turns and four sheets. The mGR LBD contains a long helix, H9, with 30 residues, and exhibits slight deformation when the receptor protein binds with its cognate ligands. The mGR LBD has a 12-residue C-terminal extension (residues 772-783) that is essential for hormone binding. This extension is tightly fixed in position by an antiparallel beta-sheet interaction between amino acids 680-682 (S3) and 775-777 (S4). The three-dimensional model reveals two polar sites located at the extremities of the elongated hydrophobic ligand-binding pocket. Cortisol and corticosterone are docked to this ligand-binding pocket. The difference accessible surface area study revealed the steroid-binding region of mGR LBD.

Amino Acid Sequence↗
PubMed1997

Chemical analysis of sound and carious enamel of permanent tooth.

Enamel consists mainly of inorganic material (96%) and only a small amount of organic substance and water (4%). The inorganic material is similar to apatite. The originally found apatite mineral remains basically unchanged except at the surface in contact with the oral tissues, where diffusion processes operate. Enamel reflects the trace element environment present in the tissue fluids at the time of tissue development. These are variations of types and concentration of inorganic elements found in permanent and deciduous enamel. Variations are also seen in sound and carious enamel.

Dental Caries↗
PubMed1993

X-ray analyses of aspartic proteinases. V. Structure and refinement at 2.0 A resolution of the aspartic proteinase from Mucor pusillus.

The structure of mucor pusillus pepsin (EC 3.4.23.6), the aspartic proteinase from Mucor pusillus, has been refined to a crystallographic R-factor of 16.2% at 2.0 A resolution. The positions of 2638 protein atoms, 221 solvent atoms and a sulphate ion have been determined with an estimated root-mean-square (r.m.s.) error of 0.15 to 0.20 A. In the final model, the r.m.s. deviation from ideality for bond distances is 0.022 A, and for angle distances it is 0.050 A. Comparison of the overall three-dimensional structure with other aspartic proteinases shows that mucor pusillus pepsin is as distant from the other fungal enzymes as it is from those of mammalian origin. Analysis of a rigid body shift of residues 190 to 302 shows that mucor pusillus pepsin displays one of the largest shifts relative to other aspartic proteinases (14.4 degrees relative to endothiapepsin) and that changes have occurred at the interface between the two rigid bodies to accommodate this large shift. A new sequence alignment has been obtained on the basis of the three-dimensional structure, enabling the positions of large insertions to be identified. Analysis of secondary structure shows the beta-sheet to be well conserved whereas alpha-helical elements are more variable. A new alpha-helix hN4 is formed by a six-residue insertion between positions 131 and 132. Most insertions occur in loop regions: -5 to 1 (five residues relative to porcine pepsin): 115 to 116 (six residues); 186 to 187 (four residues); 263 to 264 (seven residues); 278 to 279 (four residues); and 326 to 332 (six residues). The active site residues are highly conserved in mucor pusillus pepsin; r.m.s. difference with rhizopuspepsin is 0.37 A for 25 C alpha atom pairs. However, residue 303, which is generally conserved as an aspartate, is changed to an asparagine in mucor pusillus pepsin, possibly influencing pH optimum. Substantial changes have occurred in the substrate binding cleft in the region of S1 and S3 due to the insertion between 115 and 116 and the rearrangement of loop 9-13. Residue Asn219 necessitates a shift in position of substrate main-chain atoms to maintain hydrogen bonding pattern. Invariant residues Asp11 and Tyr14 have undergone a major change in conformation apparently due to localized changes in molecular structure. Both these residues have been implicated in zymogen stability and activation.

Amino Acid Sequence↗
PubMed1989

Structure of strychnine hydrochloride sesquihydrate.

C21H23N2O2+.Cl-.1.5H2O, Mr = 397.90, monoclinic, P2(1), a = 7.617 (1), b = 32.463 (2), c = 7.849 (1) A, beta = 90.40 (2) degrees, V = 1940.8 (4) A3 Z = 4, Dm = 1.39, Dx = 1.36 g cm-3, lambda (Cu K alpha) = 1.5418 A, mu = 19.724 cm-1, F(000) = 844, final R = 0.047 for 3368 observed reflections. Strychnine hydrochloride is a naturally occurring alkaloid in its protonated form. One of the N atoms accepts the proton from hydrochloric acid changing its hybridization to sp3. The indole N atom is sp2 hybridized with its lone-pair electron involved in conjugation with the carbonyl group. The hydrogen bonds form a complex zigzag network which stabilizes the structure.

Chemical Phenomena↗
PubMed1985

Molecular structure of troponin C from chicken skeletal muscle at 3-angstrom resolution.

The x-ray structure of chicken skeletal muscle troponin C (TnC), the Ca2+-binding subunit of the troponin complex, shows that the protein is about 70 angstroms long with an unusual dumbbell shape. The carboxyl and amino domains are separated by a single long alpha helix of about nine turns. Only the two high-affinity Ca2+-Mg2+ sites of the COOH-domain are occupied by metal ions resulting in conformational differences between the COOH- and NH2-domains. These differences are probably important in the triggering of muscle contraction by TnC. Also the structure of TnC is relevant in understanding the function of other calcium-regulated proteins, in particular that of calmodulin because of its strong similarity in amino acid sequence.

Animals↗
PubMedDate not supplied

Multiple myeloma presenting as acute pancreatitis.

Acute pancreatitis is a very uncommon presenting feature of multiple myeloma. We report an elderly non-alcoholic man presenting with acute abdominal pain and rapidly progressing renal failure. Investigations revealed lytic lesions in the vertebrae and skull, M band on urine electrophoresis, and radiological and biochemical evidence of acute pancreatitis. The patient died despite conservative management of the pancreatitis.

Acute Disease↗