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H Roy

Publications and source records attributed to H Roy.

At least 19 recordsLinked to original sources
PubMed2005

Periadventitial angiopoietin-1 gene transfer induces angiogenesis in rabbit carotid arteries.

This study was performed to evaluate angiogenic responses of angiopoietin-1 (Ang1) in vivo after adenovirus-mediated gene transfer in the periadventitial space of the rabbit carotid arteries using a collar technique. Adenoviruses encoding LacZ and vascular endothelial growth factor (VEGF) receptor-1-Ig fusion protein (VEGF-R1-Ig) adenoviruses were used as controls. Increased neovessel formation was seen in adventitia of the Ang1 transduced arteries 7 days after the gene transfer. Neovessels in the Ang1 transduced arteries were large in size and well perfused. Ang1 binds to Tie2 (tyrosine kinase with immunoglobulin and epidermal growth factor homology domain) receptors, which were expressed in the endothelium of the neovessels. When VEGF-R1-Ig was used with Ang1, it resulted in a decrease in the number of neovessels, which implies that VEGF-A or some other VEGF-R1 ligand(s) play a crucial role in angiogenesis occurring in response to Ang1. There were no significant differences in the total number of capillaries in the adventitia of the VEGF-R1-Ig transduced arteries as compared to LacZ controls. Neointima formation was not increased in the Ang1 transduced arteries as compared to the controls. We conclude that in the periadventitial space Ang1 shows angiogenic activity and is a potentially useful factor for the induction of therapeutic vascular growth in vivo.

Adenoviridae↗
PubMed2005

VEGF-A, VEGF-D and VEGF-D(DeltaNDeltaC) induced intimal hyperplasia in carotid arteries.

BACKGROUND: The role of vascular endothelial growth factors (VEGFs) in intimal hyperplasia and atherogenesis remains unknown. Several studies have suggested that some members of the VEGF family reduce intimal hyperplasia, but others have proposed that VEGFs accelerate restenosis and atherosclerosis. This investigation conducted a comparative study with adenoviruses encoding different VEGFs in a rabbit carotid artery collar model of intimal hyperplasia in order to analyze the role of VEGFs in the formation of intimal hyperplasia. MATERIALS AND METHODS: Intimal hyperplasia was induced in the carotid arteries of cholesterol fed New Zealand White rabbits using a silastic collar. Adenoviral vectors encoding VEGF-A, VEGF-B, VEGF-C, VEGF-C(DeltaNDeltaC), VEGF-D and VEGF-D(DeltaNDeltaC) were delivered to the adventitia using the collar as a gene delivery device. Adeno-LacZ was used as a control. RESULTS: A significant (P < 0.01) increase in the intima/media ratio was observed in the arteries transduced with VEGF-A, VEGF-D and VEGF-D(DeltaNDeltaC). There was a significant increase in the number of proliferating cells in the adventitia, media and intima of the VEGF-A, VEGF-D and the VEGF-D(DeltaNDeltaC) transduced arteries. The majority of medial smooth muscle cells in these arteries had a synthetic phenotype. The presence of matrix metalloproteinase-2 (MMP-2) and MMP-9 in the VEGF-A, VEGF-D and the VEGF-D(DeltaNDeltaC) transduced arteries was significantly increased. A significant positive correlation was observed between adventitial angiogenesis and intimal hyperplasia. CONCLUSIONS: Adventitial delivery of adenoviruses encoding VEGF-A, VEGF-D and VEGF-D(DeltaNDeltaC) increased intimal hyperplasia in the rabbit collar model. Adventitial angiogenesis correlated positively with the intimal hyperplasia. These results indicated that efficient adventitial production of VEGF-A, VEGF-D and VEGF-D(DeltaNDeltaC) can cause thickening of the inner layer of the artery in rabbits.

Animals↗
PubMed2001

Crystallization and preliminary X-ray diffraction data of the second and archaebacterial-type aspartyl-tRNA synthetase from Thermus thermophilus.

The archaebacterial-type aspartyl-tRNA synthetase (AspRS2) from the thermophilic eubacterium Thermus thermophilus was crystallized using the hanging-drop vapour-diffusion method. Crystals grew at pH 9.5 in the presence of PEG 8000 and NaCl. A native diffraction data set has been collected at 2.5 A resolution using synchrotron radiation and cryocooling. Crystals belong to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 57.3, b = 121.9, c = 166.9 A and V(M) = 3.03 A(3) Da(-1). There is one dimer of M(r) 96 000 per asymmetric unit. A molecular-replacement analysis gave solutions for the rotation and translation functions.

Archaea↗
PubMed2000

The heterotrimeric Thermus thermophilus Asp-tRNA(Asn) amidotransferase can also generate Gln-tRNA(Gln).

Thermus thermophilus strain HB8 is known to have a heterodimeric aspartyl-tRNA(Asn) amidotransferase (Asp-AdT) capable of forming Asn-tRNA(Asn) [Becker, H.D. and Kern, D. (1998) Proc. Natl. Acad. Sci. USA 95, 12832-12837]. Here we show that, like other bacteria, T. thermophilus possesses the canonical set of amidotransferase (AdT) genes (gatA, gatB and gatC). We cloned and sequenced these genes, and constructed an artificial operon for overexpression in Escherichia coli of the thermophilic holoenzyme. The overproduced T. thermophilus AdT can generate Gln-tRNA(Gln) as well as Asn-tRNA(Asn). Thus, the T. thermophilus tRNA-dependent AdT is a dual-specific Asp/Glu-AdT resembling other bacterial AdTs. In addition, we observed that removal of the 44 carboxy-terminal amino acids of the GatA subunit only inhibits the Asp-AdT activity, leaving the Glu-AdT activity of the mutant AdT unaltered; this shows that Asp-AdT and Glu-AdT activities can be mechanistically separated.

Amino Acid Sequence↗
PubMed2000

Thermus thermophilus contains an eubacterial and an archaebacterial aspartyl-tRNA synthetase.

Thermus thermophilus possesses two aspartyl-tRNA synthetases (AspRSs), AspRS1 and AspRS2, encoded by distinct genes. Alignment of the protein sequences with AspRSs of other origins reveals that AspRS1 possesses the structural features of eubacterial AspRSs, whereas AspRS2 is structurally related to the archaebacterial AspRSs. The structural dissimilarity between the two thermophilic AspRSs is correlated with functional divergences. AspRS1 aspartylates tRNA(Asp) whereas AspRS2 aspartylates tRNA(Asp), and tRNA(Asn) with similar efficiencies. Since Asp bound on tRNA(Asn) is converted into Asn by a tRNA-dependent aspartate amidotransferase, AspRS2 is involved in Asn-tRNA(Asn) formation. These properties relate functionally AspRS2 to archaebacterial AspRSs. The structural basis of the dual specificity of T. thermophilus tRNA(Asn) was investigated by comparing its sequence with those of tRNA(Asp) and tRNA(Asn) of strict specificity. It is shown that the thermophilic tRNA(Asn) contains the elements defining asparagine identity in Escherichia coli, part of which being also the major elements of aspartate identity, whereas minor elements of this identity are missing. The structural context that permits expression of aspartate and asparagine identities by tRNA(Asn) and how AspRS2 accommodates tRNA(Asp) and tRNA(Asn) will be discussed. This work establishes a distinct structure-function relationship of eubacterial and archaebacterial AspRSs. The structural and functional properties of the two thermophilic AspRSs will be discussed in the context of the modern and primitive pathways of tRNA aspartylation and asparaginylation and related to the phylogenetic connexion of T. thermophilus to eubacteria and archaebacteria.

Acylation↗
PubMed2000

Fat and carbohydrate balances during adaptation to a high-fat.

BACKGROUND: Dietary fat contents are highly variable. Failure to compensate for the positive fat balance that occurs during the shift to a high-fat, low-carbohydrate diet by increasing energy expenditure or by decreasing food intake may result in the gain of fat mass. OBJECTIVE: The objective of this study was to investigate the time course of fat oxidation during adaptation to an isoenergetic high-fat, low-carbohydrate diet. DESIGN: After a 5-d control diet, dietary fat was increased from 37% of energy to 50% of energy for 4 d in 6 healthy, young lean men. Respiratory quotient and substrate macronutrient oxidation and balance were measured in a respiratory chamber. Fasting concentrations of insulin, glucose, and triacylglycerol; maximal oxygen consumption (f1.gif" BORDER="0">O(2)max) during treadmill exercise; and free-living energy expenditure were determined. Body fat was measured by dual-energy X-ray absorptiometry and visceral adipose tissue by computerized tomography. RESULTS: Compared with the baseline diet, the high-fat, low-carbohydrate diet resulted in positive fat and protein balances and a negative carbohydrate balance. Insulin concentration and the postabsorptive respiratory quotient were positively correlated with the fat balance during the high-fat, low-carbohydrate diet, whereas f1.gif" BORDER="0">O(2)max during treadmill exercise was negatively related to fat balance. With use of stepwise regression, f1.gif" BORDER="0">O(2)max was the best predictor of fat balance. There was a negative correlation between fat balance and carbohydrate balance (r(2) = 0.88). CONCLUSION: Both baseline insulin concentration and f1.gif" BORDER="0">O(2)max during treadmill exercise predict fat balance during the shift to a high-fat diet under isoenergetic conditions.

Adipose Tissue↗
PubMed2000

Concurrent physical activity increases fat oxidation during the shift to a high-fat diet.

BACKGROUND: It takes several days to adapt to a high-fat diet. In an earlier study, we observed a large degree of interindividual variation in the capacity to adapt to a high-fat diet. We hypothesized that concurrent physical activity would accelerate fat oxidation during an isoenergetic high-fat diet. OBJECTIVE: The objective of this study was to determine the effect of increased physical activity on the ability of young healthy men to increase fat oxidation during the shift to a high-fat diet. DESIGN: Six young healthy men participated in a randomized, single-blind crossover study. The volunteers consumed a diet contributing 37% of energy as fat, 14% as protein, and 49% as carbohydrate for 4 d. Energy expenditure and macronutrient balance were then measured in a respiration chamber as the energy content of the isoenergetic diet was changed to 50% fat, 14% protein, and 36% carbohydrate. Treadmill walking, as the physical activity, was used to increase total daily energy expenditure to 1.8 times the resting metabolic rate during 1 of 2 stays in the metabolic chamber. Total daily energy expenditure was maintained at 1.4 times the resting metabolic rate for the other stay. RESULTS: Energy balance was not significantly different between the 2 conditions. The 24-h respiratory quotient decreased more rapidly and to a greater extent under conditions of increased energy expenditure. Further, there was a decrease in the interindividual variability in the response of the respiratory quotient to a high-fat diet with increased energy expenditure (physical activity). Cumulative carbohydrate and protein balances were greater under conditions of increased physical activity. Conversely, cumulative fat balance was greater under sedentary conditions. CONCLUSION: Concurrent physical activity increases fat oxidation during the shift to a high-fat diet.

Adaptation, Physiological↗
PubMed1999

tRNA glycylation system from Thermus thermophilus. tRNAGly identity and functional interrelation with the glycylation systems from other phylae.

The systems of tRNA glycylation belong to the most complex aminoacylation systems since neither the oligomeric structure of glycyl-tRNA synthetases (GlyRS) nor the discriminator bases in tRNAGly are conserved in the phylae. To better understand the structure-function relationship in glycylation systems of various origins and the functional peculiarities related to their structural divergences, the elements in tRNA conferring its glycine identity in Thermus thermophilus were characterized and compared to those of other systems. Thermophilic identity is conferred by the G1-C72, C2-G71, G3-C70, and C50-G64 pairs together with the G10, U16, C35, and C36 single residues. In contrast to most other aminoacylation systems, the discriminator base is not directly involved in identity. Transplantation of these elements in tRNAAsp and tRNAPhe converts specificity toward glycine albeit conservation of nucleotide 73. Analysis of the functional interrelation of the identity elements shows coupling in synthetase recognition of the elements from anticodon and G10 whereas those from acceptor arm are recognized independently. Despite nondirect implication in identity, the discriminator base contributes cooperatively with C36 in specificity of glycylation. The link between the structural heterogeneity and the functional divergence of the glycylation systems and the phylogenic interrelation of these systems were approached by comparing the ability of GlyRSs of various phylae to glycylate heterologous tRNAGly. Dimeric GlyRSs from mammalian and archaebacteria acylate efficiently only eukaryotic and archaebacterial tRNAGly with a discriminatory A73, whereas tetrameric Escherichia coli GlyRS acylates only eubacterial tRNAGly with a discriminatory U73. In contrast, dimeric yeast GlyRS acylates efficiently both eukaryotic and archaebacterial tRNAGly as well as peculiar prokaryotic isoacceptors. Species specificity is lost with the dimeric GlyRS from Thermus thermophilus that acylates efficiently eubacterial, archaebacterial, and eukaryotic tRNAGly. These features are discussed in the context of the evolution of the glycylation systems and the phylogenic interrelation of the organisms.

Acylation↗
PubMed1994

Chemoprevention of azoxymethane-induced colonic carcinogenesis by supplemental dietary ursodeoxycholic acid.

The present studies were conducted at the Universities of Chicago and Arizona to examine and compare the effects of supplemental dietary ursodeoxycholic acid to cholic acid, a known tumor promoter, and to piroxicam, a known chemopreventive agent, in the azoxymethane (AOM) model of experimental colonic carcinogenesis. Male Fischer 344 rats were utilized in these experiments. All animals were fed a basal diet (AIN-76) supplemented with 0.2% or 0.4% cholic acid, 0.2% or 0.4% ursodeoxycholic acid, 0.2% ursodeoxycholic acid plus 0.2% cholic acid, or 75 ppm piroxicam. Rats were given s.c. injections once a week for 2 weeks with AOM (15 mg/kg body wt/week) or vehicle (saline) after being fed their respective diets for 2 weeks. The rats in each group were then maintained on their respective diets for approximately 28 weeks; after sacrifice, their colons were removed and examined macroscopically and microscopically for the presence of tumors. The results of these studies demonstrated that none of the control rats fed the various diets injected with AOM-vehicle developed tumors. In groups receiving AOM, the addition of cholic acid (0.4%) caused a significant increase in the incidence of tumors. In contrast, the addition of 0.2% ursodeoxycholic acid did not promote AOM-induced colonic tumors, and when it was added to a promoting dose of cholic acid (0.2%), 0.2% ursodeoxycholic acid prevented enhancement of tumor promotion. At higher doses (0.4%), supplemental dietary ursodeoxycholic acid significantly reduced the incidence of colon tumors and cancers. Moreover, the tumor suppressive effects of 0.4% ursodeoxycholic acid exceeded that of dietary piroxicam. Our results further emphasize the important role of bile salts in modulating colonic tumor development. These studies also demonstrate for the first time that supplemental dietary ursodeoxycholic acid is a chemopreventive agent in the AOM model of experimental colonic carcinogenesis.

Animals↗
PubMed1993

Assembly of in vitro synthesized large subunits into ribulose-bisphosphate carboxylase/oxygenase. Formation and discharge of an L8-like species.

Ribulose-bisphosphate carboxylase/oxygenase (Rubisco) from higher plants consists of eight approximately 53-kDa large subunits and eight approximately 14-kDa small subunits. Cytosolic ribosomes synthesize the small subunits as precursors, which enter the chloroplast, undergo proteolytic processing, and assemble with large subunits. Large subunits, synthesized in the chloroplast, first form a complex with the chloroplast chaperonin 60 (Cpn60(14)). In the presence of ATP, large subunits dissociate from Cpn60(14) and assemble into Rubisco. We now describe partial characterization of a new species, Z, containing radiotracer-labeled, newly synthesized pea Rubisco large subunits. Rubisco assembly occurs in low salt in the presence of small subunits and ATP. As with Rubisco assembly, the formation of Z is ATP-dependent and is inhibited by high chloride. Once formed, Z is stable except in high chloride. Z does not appear to interact directly with small subunits. However, after Z formation, Rubisco assembly occurs in an ATP-independent reaction that requires KCl and small subunits. These results are consistent with the hypothesis that Z is a large subunit containing structure that can contribute large subunits to Rubisco under appropriate conditions. Z shares some physical characteristics with reported cyanobacterial L8 core particles. However, formation of Rubisco from Z in the absence of ATP and the presence of small subunits appears to require conditions that otherwise destabilize Z.

Adenosine Triphosphate↗
PubMed1992

Theory of chaperonin action: inertial model for enhancement of prokaryotic Rubisco assembly.

We have performed a computational simulation of the aggregation and chaperonin-dependent reconstitution of dimeric prokaryotic ribulose bisphosphate carboxylase/oxygenase (Rubisco), based on the data of P. Goloubinoff et al. (1989, Nature 342, 884-889) and P. V. Viitanen et al. (1990, Biochemistry 29, 5665-5671). The aggregation is simulated by a set of 12 differential equations representing the aggregation of the Rubisco folding intermediate, Rubisco-I, with itself and with aggregates of Rubisco-I, leading up to dodecamers. Four rate constants, applying to forward or reverse steps in the aggregation process, were included. Optimal values for these constants were determined using the ellipsoid algorithm as implemented by one of us (Ecker, J.G. & Kupferschmid, M., 1988, Introduction to Operations Research, Wiley, New York, pp. 315-322). Intensive exploration of simpler aggregation models did not identify an alternative that could simulate the data as well as this one. The activity of the chaperonin in this system was simulated by using this aggregation model, combined with a model similar to that proposed by Goloubinoff et al. (1989). The model assumes that the chaperonin can bind the folding intermediate rapidly, and that the chaperonin complex releases the Rubisco molecule slowly, permitting time for its spontaneous folding while interacting with the chaperonin. This is followed by self-association of the folded Rubisco monomer to yield the active dimeric Rubisco. A modification of the model that simulates temperature effects was also constructed. The most important results we obtained indicate that the chaperonin-dependent reconstitution of Rubisco can be simulated adequately without invoking any catalysis of folding by the chaperonin. In addition, the simulations predict values for the association rate constant of Rubisco-I with the chaperonin, and other variables, that are subject to experimental verification.

Chaperonins↗
PubMed1992

Synthesis and assembly of large subunits into ribulose bisphosphate carboxylase/oxygenase in chloroplast extracts.

We have developed a new system for the in vitro synthesis of large subunits and their assembly into ribulose bisphosphate carboxylase oxygenase (Rubisco) holoenzyme in extracts of higher plant chloroplasts. This differs from previously described Rubisco assembly systems because the translation of the large subunits occurs in chloroplast extracts as opposed to isolated intact chloroplasts, and the subsequent assembly of large subunits into holoenzyme is completely dependent upon added small subunits. Amino acid incorporation in this system displayed the characteristics previously reported for chloroplast-based translation systems. Incorporation was sensitive to chloramphenicol or RNase but resistant to cycloheximide, required magnesium, and was stimulated by nucleotides. The primary product of this system was the large subunit of Rubisco. However, several lower molecular weight polypeptides were formed. These were structurally related to the Rubisco large subunit. The initiation inhibitor aurintricarboxylic acid (ATA) decreased the amount of lower molecular weight products accumulated. The accumulation of completed large subunits was only marginally reduced in the presence of ATA. The incorporation of newly synthesized large subunits into Rubisco holoenzyme occurred under conditions previously identified as optimal for the assembly of in organello-synthesized large subunits and required the addition of purified small subunits.

Journal Article↗
PubMed1991

An update on the use of drugs for common eye problems in older patients.

Common ophthalmic disorders occurring in older adults often can be managed in the primary care setting with appropriate medication. This review focuses on pharmacologic intervention for dry eye, allergy, glaucoma, inflammatory disease, and infection, as well as diagnostic agents for dilation. Discussed are the selection, proper administration, dosage forms, and side effects of ophthalmic agents.

Aged↗