PubMed Health⌕ Search

Biomedical subjects

K Rajagopalan

Publications and source records attributed to K Rajagopalan.

At least 19 recordsLinked to original sources
PubMed2006

Hospitalisation risks in the treatment of schizophrenia in a Medicaid population: comparison of antipsychotic medications.

This study used administrative claims data to compare the relative risks for hospitalisation among patients with schizophrenia within a US Medicaid programme receiving atypical and typical antipsychotics. The newer atypical antipsychotics may be better tolerated among mentally ill patients receiving public assistance (Medicaid) who are less functional than other mentally ill populations. Risperidone, olanzapine, quetiapine and ziprasidone were compared with each other and to typical antipsychotics as a single category. Cox proportional hazard estimates, adjusted for differences in patient characteristics, showed numerically lower risks for each of the atypicals in comparison with the typicals, with that for quetiapine being statistically significant (HR: 0.672, p = 0.0413). There were no statistically significant differences among atypical pairs. This study provides evidence that risk for hospitalisation among Medicaid patients with schizophrenia may be lower with atypical antipsychotics, particularly quetiapine.

Adult↗
PubMed2002

Hirschsprung's disease associated with Ondine's curse.

This is a case report of a very rare combination of congenital aganglionosis of the intestine (Hirschsprung's disease) and congenital central hypoventilation syndrome-CCHS- (Ondine's curse). The combination is also called Haddad syndrome. In about 50% of the cases of CCHS there is associated Hirschsprung's disease. There are only about 48 cases reported worldwide. The disease has a very high mortality especially in the settings of a developing country.

Fatal Outcome↗
PubMed2000

Insights into molybdenum cofactor deficiency provided by the crystal structure of the molybdenum cofactor biosynthesis protein MoaC.

BACKGROUND: The molybdenum cofactor (Moco) is an essential component of a large family of enzymes involved in important transformations in carbon, nitrogen and sulfur metabolism. The Moco biosynthetic pathway is evolutionarily conserved and found in archaea, eubacteria and eukaryotes. In humans, genetic deficiencies of enzymes involved in this pathway trigger an autosomal recessive and usually deadly disease with severe neurological symptoms. The MoaC protein, together with the MoaA protein, is involved in the first step of Moco biosynthesis. RESULTS: MoaC from Escherichia coli has been expressed and purified to homogeneity and its crystal structure determined at 2 A resolution. The enzyme is organized into a tightly packed hexamer with 32 symmetry. The monomer consists of an antiparallel, four-stranded beta sheet packed against two long alpha helices, and its fold belongs to the ferredoxin-like family. Analysis of structural and biochemical data strongly suggests that the active site is located at the interface of two monomers in a pocket that contains several strictly conserved residues. CONCLUSIONS: Asp128 in the putative active site appears to be important for catalysis as its replacement with alanine almost completely abolishes protein activity. The structure of the Asp128-->Ala variant reveals substantial conformational changes in an adjacent loop. In the human MoaC ortholog, substitution of Thr182 with proline causes Moco deficiency, and the corresponding substitution in MoaC severely compromises activity. This residue is located near the N-terminal end of helix alpha4 at an interface between two monomers. The MoaC structure provides a framework for the analysis of additional dysfunctional mutations in the corresponding human gene.

Amino Acid Sequence↗
PubMed1999

Analysis of the steroid binding domain of rat steroid 5alpha-reductase (isozyme-1): the steroid D-ring binding domain of 5alpha-reductase.

We have previously shown that the photoactive 4-azasteroid, [1,2 3H]N-4(benzylbenzoyl)-3-oxo-4-aza-4-methyl-5alpha-androst an-17beta-carboxamide is an effective probe of rat steroid 5alpha-reductase (isozyme-1) (5alphaR-1). In the current investigation, PEG-fractionated (6.5%) detergent-solubilized preparations containing 5alphaR-1 activity were ultraviolet (UV)-photolyzed with [3H]-4MABP and subsequently purified by 8.75% preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The fractions corresponding to the radioactive peak following the dye front were analyzed by 10% sodium dodecyl sulfate-polyacrylamide gel electrophoresis and showed the presence of a single, labeled, 26 KDa protein band, the apparent molecular weight of 5alphaR-1. TCA precipitation of the labeled fractions, followed by long-term digestion of the TCA pellet with chymotrypsin and high-performance liquid chromatography analysis, indicated that the majority of the radioactivity eluted with a peak retention time of 55-56 min. Rechromatography of this fraction using a modified gradient (elution 54-55 min), followed by sequence analysis, yielded a single N-terminal tetrapeptide with the sequence, -L-E-G-F-, corresponding to residues 15-18 of the 5alphaR-1 sequence. Site-directed mutagenesis studies indicated that mutant F18L showed an approximately 12-fold increase in the Km for testosterone, whereas the Km for reduced nicotinomide adenine dinucleotide phosphate remained virtually unaltered.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1999

Orientation of GTP and ADP within their respective binding sites in glutamate dehydrogenase.

Previous studies have identified the guanine and adenine binding domains of the GTP and ADP binding sites of GDH. In this study the peptide sequences within or near to the terminal phosphate-binding domains of the GTP and ADP binding sites of bovine liver glutamate dehydrogenase (GDH) were identified using photoaffinity labeling with the benzophenone nucleotide derivatives, [gamma-32P]GTPgammaBP and [gamma-32P]ATPgammaBP. Without activating light, GTPgammaBP exhibited inhibiting effects on the GDH reaction similar to GTP; ATPgammaBP, as expected, produced activating effects similar to those of ADP. Photoinsertion into GDH by both probes exhibited saturation effects in agreement with the respective kinetic effects. Specificity of labeling was supported by specific and effective reduction of photoinsertion of [gamma-32P]GTPgammaBP and [gamma-32P]ATPgammaBP into GDH by GTP and ADP, respectively. Using a combination of immobilized Fe3+-chelate affinity chromatography and reversed-phase HPLC, photolabeled peptides located within or near the phosphate-binding domains of the GTP and ADP sites were isolated. Sequence analysis showed that GTPgammaBP primarily modified a peptide near the middle of the GDH sequence, Asn135-Lys143 and Glu290-Lys295. However, ATPgammaBP modified a single peptide corresponding to the sequence Met411-Arg419 near the C-terminal domain. Using these results and the data from the previously identified base-binding domain peptides the orientation of GTP and ADP within their respective binding sites in the catalytic cleft of GDH is proposed and explained on the basis of a proposed three-dimensional schematic model structure derived from the bacterial enzyme.

Adenosine Diphosphate↗
PubMed1997

Site-specific photobiotinylation of immunoglobulins, fragments and light chain dimers.

Herein we report a new method to rapidly photoinsert biotin into a specific and highly conserved site on the Ig structure using a mild photochemical activation step. This site resides in the Fv fragment and involves invariant residues which provide base stacking interactions to the purine ring of ATP (Rajagopalan et al. (1996) Proc. Natl. Acad. Sci. USA 93, 6019-6024). Biotin was coupled to either the phosphate or the ribose of the 8-azidopurine nucleotide or nucleoside photoaffinity probe and shown to insert into the affinity site efficiently. Several monoclonal and polyclonal antibodies, as well as enzymatic and recombinant antibody fragments and light chain dimers were photoaffinity biotinylated and used in ELISA, FACS and Western blots. The selectivity of this site-specific biotinylation method also allows for biotinylation of antibodies in culture supernatants and immune sera without prior purification. Because the biotinylation takes place under physiological conditions and within a short time period, photobiotinylation would be the preferred method for antibodies which are easily damaged by classical non-site specific random biotinylation chemistry.

Animals↗
PubMed1996

Novel unconventional binding site in the variable region of immunoglobulins.

The variable immunoglobulin (Ig) domains contain hypervariable regions that are involved in the formation of the antigen binding site. Besides the canonical antigen binding site, so-called unconventional sites also reside in the variable region that bind bacterial and viral proteins. Docking to these unconventional sites does not typically interfere with antigen binding, which suggests that these sites may be a part of the biological functions of Igs. Herein, a novel unconventional binding site is described. The site is detected with 8-azidopurine nucleotide photoaffinity probes that label antibodies efficiently and under mild conditions. Tryptic peptides were isolated from photolabeled monoclonal antibodies and aligned with the variable antibody domains of heavy and light chains. The structure of a variable Ig fragment was used to model the binding of the purine nucleotide to invariant residues in a hydrophobic pocket of the Ig molecule at a location distant from the antigen binding site. Monoclonal and polyclonal antibodies were biotinylated with the photoaffinity linker and used in fluorescence-activated cell sorter and ELISA analyses. The data support the utility of this site for tethering diagnostic and therapeutic agents to the variable Ig fragment region without impairing the structural and functional integrity of antibodies.

Affinity Labels↗
PubMed1996

Right ventricular blood flow during left ventricular support in an experimental porcine model.

BACKGROUND: Right ventricular blood flow may be adversely affected during left ventricular assist device (LVAD) use leading to right ventricular (RV) ischemia and RV dysfunction. This study characterized normal RV blood flow responses to LVAD operation. METHODS: Seven Yorkshire pigs weighing 74.4 +/- 3.4 kg underwent right coronary artery blood flow measurements with an ultrasonic flow probe and injection of radiolabeled microspheres. A Thoratec LVAD was used in either synchronous or asynchronous modes and RV loading was increased using a pulmonary artery snare. RESULTS: The RV blood flow was compared between three regions that differed in proximity to the right coronary artery: proximal segment, mid-RV, and distal. The right ventricular distal flow was 0.93 +/- 0.07 mL x min-1 x g-1 compared with 0.74 +/- 0.06 mL x min-1 x g-1 at right ventricular proximal flow during control measurements (p = 0.0001). This difference was maintained during LVAD operation in either synchronous or asynchronous modes and also during pulmonary artery constriction. CONCLUSIONS: Global RV flow is not adversely affected by LVAD use. A flow gradient occurs along the right coronary artery with the distal vascular bed having relatively less reserve, which may be more susceptible to ischemia in patients with preexisting coronary disease or RV distention during LVAD use.

Animals↗
PubMed1996

Photoaffinity labeling of rat steroid 5 alpha-reductase (isozyme-1) by a benzophenone derivative of a 4-methyl-4-azasteroid.

[1,2-3H]N-4(Benzylbenzoyl)-3-oxo-4-aza-4-methyl-5 alpha-androstane-17 beta-carboxamide ([3H]-4MABP) has been synthesized as a photoaffinity probe of the steroid-binding domain of rat steroid 5 alpha-reductase isozyme-1 (5 alpha R-1). Reversible binding of the probe to 5 alpha R-1 in microsomal preparations yielded a reversible dissociation constant (Kd) of -3 nM, whereas inhibition experiments indicated that the probe had a 50% inhibition concentration of 4.4 nM and was a competitive inhibitor of the enzyme (Ki approximately 3 nM) with respect to testosterone. SDS-PAGE analysis of microsomal, detergent-solubilized, and (6.5%) polyethylene glycol-precipitated fractions of 5 alpha R-I photolyzed with [3H]4MABP in the presence of NADPH showed that the radioactivity was incorporated into a single protein band with a mass of 26 kDa (apparent molecular weight of 5 alpha R-1). UV photolysis was accompanied by an irreversible loss in enzyme activity, consistent with its covalent modification. Increasing the time of UV irradiation and concentration of [3H]4MABP indicated that the half-life and apparent Kd for its photo insertion were approximately 3 min and 7.5 nM, respectively. Photolysis in the presence of a 20-fold excess of N,N-diethyl-4-aza-4-methyl-3-oxo-5 alpha-androstane-17 beta-carboxamide or the 3-carboxysteroid SKF-105111 resulted in partial protection of 5 alpha R-1 from the probe, whereas minimal incorporation of radioactivity was observed in the absence of NADPH or in the presence of NADP+. The results indicate that [3H]4MABP is an effective probe of the steroid (D-ring) binding domain of 5 alpha R-1.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1994

Does septal position affect right ventricular function during left ventricular assist in an experimental porcine model?

Right ventricular (RV) failure has been a major problem with patients supported by left ventricular (LV) assist devices (LVADs). To assess the importance of interventricular septal (IVS) position as a mechanism of RV failure, 7 Yorkshire pigs underwent implantation of a Thoratec LVAD. RV function was assessed before and during LVAD operation under differing conditions: (1) with an LV intraventricular latex balloon inflated or deflated to alter IVS position and (2) with and without pulmonary artery (PA) constriction to assess the effect of changes in afterload. RV stroke work, RV dP/dt, and RV end-diastolic length did not change significantly with LVAD operation or with changing afterload conditions. Septal shift was documented as a change in LV shape index (LVSI) calculated using echocardiography. LVSI decreased by 11% when the LVAD was turned on, indicating leftward shifting of the IVS (P = .01). During LVAD support and increased RV afterload, the LVSI decreased by 14.8% (P = .02). RV cardiac output decreased somewhat during LVAD support. However, RV output was worst when the septal position was normalized using the inflated intraventricular balloon during increased RV afterload (P = .05). Unloading by the LVAD of the left ventricle results in a leftward shift of the interventricular septum, which does not appear to adversely affect RV function. However, during conditions of increased RV afterload, septal shifting may be beneficial to RV function.

Animals↗
PubMed1993

Synthesis and application of bidentate photoaffinity cross-linking reagents. Nucleotide photoaffinity probes with two photoactive groups.

Two "targeted bidentate" photoaffinity cross-linking reagents, the monoanhydride of 8-N3ADP with N-(4-(benzoyl)phenylmethyl)phosphoramide ([gamma-32P]8-N3ATP gamma BP) and the monoanhydride of 8-N3GDP with N-(4-(benzoyl)phenylmethyl)-phosphoramide ([gamma-32P]8-N3GTP gamma BP), were developed for studying the inter- and intramolecular interactions of nucleotide-binding proteins. Experiments using these bidentate reagents with two photoactive groups led to specific cross-linking: [gamma-32P]8-N3GTP gamma BP and [gamma-32P]8-N3ATP gamma BP showed intersubunit cross-linking of glutamate dehydrogenase and [gamma-32P]8-N3GTP gamma BP appeared to cross-link the alpha- and beta-subunits of tubulin. The non-azido "monodentate" versions of these reagents, the monoanhydride of ADP with N-(4-(benzoyl)phenylmethyl)-phosphoramide ([gamma-32P]ATP gamma BP) and the monoanhydride of GDP with N-(4-(benzoyl)phenylmethyl)-phosphoramide ([gamma-32P]GTP gamma BP), were also synthesized and characterized. The ability of these monodentate reagents with one photoactive group to serve as photoaffinity probes was established by photolabeling specifically the exchangeable GTP-binding domain of tubulin with [gamma-32P]GTP gamma BP and the ATP-binding domain of purified adenylate kinase and several nucleotide-binding proteins in human brain homogenate with [gamma-32P]ATP gamma BP.

Adenosine Triphosphate↗
PubMed1993

Photoaffinity labeling of ribulose-1,5-bisphosphate carboxylase/oxygenase activase with ATP gamma-benzophenone. Identification of the ATP gamma-phosphate binding domain.

The phosphate-binding domain of the ATP-binding site of tobacco Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase) activase was elucidated by photo-affinity labeling with a monoanhydride of ADP with N-(4-(benzoyl)phenylmethyl)phosphoramide ([gamma-32P]ATP gamma BP). Covalent incorporation of [gamma-32P]ATP gamma BP into the 42-kDa Rubisco activase subunit was dependent upon irradiation with ultraviolet light. Photolabelling of Rubisco activase with ATP gamma BP exhibited saturation kinetics; the apparent Kd for photolabeling was 5 microM. Two lines of evidence showed that ATP gamma BP modified Rubisco activase at the ATP-binding domain. First, physiological concentrations of ATP and ADP afforded complete protection against photolabeling of Rubisco activase by ATP gamma BP. Second, photolysis of Rubisco activase in the presence of ATP gamma BP decreased both the ATPase and the Rubisco activating activities. Inactivation of enzyme activity was dependent on ATP gamma BP concentration and could be prevented by including ADP during photolabeling. The region of Rubisco activase that was modified by ATP gamma BP was identified by isolating photolabeled peptides. Sequence analysis showed that ATP gamma BP modified Rubisco activase in two distinct regions; one region, S117-A136, is adjacent to the P-loop and the other region, V223-T234, exhibits homology to a region of adenylate kinase that ligates the essential metal ion. Photolabeling of these two regions of Rubisco activase was consistent with modification of the ATP gamma-phosphate-binding domain of Rubisco activase with ATP gamma BP.

Adenosine Diphosphate↗
PubMed1992

Critical anatomic dimensions for intrathoracic circulatory assist devices.

The design of totally implantable circulatory support devices must account for the anatomical constraints of the body cavity. To aid development of an implantable electrohydraulic ventricular assist device (EVAD), thoracic anatomical measurements and fit trials were performed. Various dimensions of the thoracic cavity were measured in 19 preserved and fresh cadavers. The mean left ventricle apex to chest wall distance was 2.7 +/- 0.2 cm. The mean sagittal radius of curvature at the fifth rib was 11.1 +/- 0.4 cm, and the transverse radius at the fifth rib was 9.4 +/- 0.3 cm. The mean sternal length was 18.9 +/- 1.2 cm. Using these measurements a model measuring 17.5 x 10.5 x 3.8 cm was designed. This model was placed in the chest of 11 patients undergoing open heart surgery. In one patient there was significant lung compression and in another hypotension suggesting great vessel compression. Finally, 1 of 11 patients had a short sternum and a small thorax, and the device did not fit. In conclusion, thoracic measurements may be used in the design of circulatory support devices. The model fit adequately in 73% of patient trials.

Adult↗
PubMed1989

Serum antibodies to defined carbohydrate antigens during the course of treated leprosy.

Sequential monitoring of 724 sera for antibodies to a neoantigen based on phenolic glycolipid-I (PGL-I) and native lipoarabinomannan (LAM) in 90 leprosy patients undergoing therapy in San Francisco was conducted. Untreated lepromatous patients frequently (91%) had significant antibodies to both moieties. Antibodies were less frequently found in tuberculoid patients (74% to neoantigen and 37% to LAM). In the first 3 years of treatment, average serum antibodies to both moieties fell significantly. Antibodies to LAM fell during each of the first 4 years of therapy, but decreasing antibody levels to the PGL-I neoantigen did not appear to fall consistently after the third year of treatment. A wide variation in the rate of fall of serum antibodies was noted. Sequential changes in the amounts of serum antibodies to the neoantigen and LAM in general paralleled one another but were at times discrepant. Both in San Francisco and Malaysia, skin-smear negative, long-term treated, lepromatous leprosy patients frequently harbored significant antibodies to both PGL-I and LAM.

Antibodies, Bacterial↗
PubMed1988

An immunohistochemical and morphological study of amyloidosis complicating leprosy in Malaysian patients.

Congo red screening of tissue blocks from 37 consecutive autopsies on leprosy patients revealed 7 cases of systemic amyloidosis, indicating a prevalence rate of 19%. 5 were males and 2 females. All were ethnic Chinese. Their ages ranged from 52 to 85 years with a mean of 69 years. Six had lepromatous leprosy while the remaining 1 had tuberculoid leprosy. In all 7 cases, the amyloid was AA in type, being permanganate-sensitive and immunoreactive with anti-human AA protein antiserum. Hepatic deposition was limited to blood vessels, a pattern typical of AA (secondary) amyloidosis. With regard to renal involvement, 4 showed a predominantly vascular pattern of infiltration while 3 exhibited the more ominous glomerular pattern. Three died of chronic renal failure and 2 of congestive cardiac failure attributable to renal and cardiac amyloidosis respectively. One patient succumbed to septicaemia and the remaining 1 to acute myocardial infarction. AA amyloidosis remains a serious and significant complication of leprosy among Malaysians.

Aged↗