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Biomedical subjects

R Roy

Publications and source records attributed to R Roy.

At least 235 records · Page 13Linked to original sources
PubMed1994

A chalcone glycoside from Clerodendron phlomidis.

A new chalcone glycoside, together with pectolinarigenin, 7-hydroxyflavone and 7-hydroxyflavanone 7-O-glucoside have been isolated from the flowers and leaves of Clerodendron phlomidis. The structure of the chalcone glycoside has been established as 4,2',4'-trihydroxy-6'-methoxychalcone 4,4'-D-diglucoside by spectroscopic and degradative methods.

Carbohydrate Sequence↗
PubMed1994

Effects of methane metabolism on nitrification and nitrous oxide production in polluted freshwater sediment.

We report the effect of CH(4) and of CH(4) oxidation on nitrification in freshwater sediment from Hamilton Harbour, Ontario, Canada, a highly polluted ecosystem. Aerobic slurry experiments showed a high potential for aerobic N(2)O production in some sites. It was suppressed by C(2)H(2), correlated to NO(3) production, and stimulated by NH(4) concentration, supporting the hypothesis of a nitrification-dependent source for this N(2)O production. Diluted sediment slurries supplemented with CH(4) (1 to 24 muM) showed earlier and enhanced nitrification and N(2)O production compared with unsupplemented slurries (</=1 muM CH(4)). This suggests that nitrification by methanotrophs may be significant in freshwater sediment under certain conditions. Suppression of nitrification was observed at CH(4) concentrations of 84 muM and greater, possibly through competition for O(2) between methanotrophs and NH(4) -oxidizing bacteria and/or competition for mineral N between these two groups of organisms. In Hamilton Harbour sediment, the very high CH(4) concentrations (1.02 to 6.83 mM) which exist would probably suppress nitrification and favor NH(4) accumulation in the pore water. Indeed, NH(4) concentrations in Hamilton Harbour sediment are higher than those found in other lakes. We conclude that the impact of CH(4) metabolism on N cycling processes in freshwater ecosystems should be given more attention.

Journal Article↗
PubMed1994

Regulation of lysyl oxidase expression in lung fibroblasts by transforming growth factor-beta 1 and prostaglandin E2.

The regulation of lysyl oxidase produced by cultured, lipid-enriched, neonatal rat lung fibroblasts was explored. The presence of 40 pM of transforming growth factor-beta 1 (TGF-beta 1) in overnight cultures increased levels of enzyme secreted into the medium by 1.6-fold while steady-state levels of lysyl oxidase mRNA increased similarly. In contrast, incubation of these cultures with 100 nM of prostaglandin E2 (PGE2) reduced enzyme activity levels by 40 to 50% although steady-state mRNA was not changed. Consistent with the effect of PGE2, the presence of indomethacin stimulated levels of secreted enzyme activity. When present in cultures simultaneously with TGF-beta 1, PGE2 prevented the stimulation beyond control levels seen with TGF-beta 1 alone. Densitometry of protein bands immunoprecipitated by antibody to lysyl oxidase indicated that the degree of conversion of the 50 kD proenzyme to the 29 kD enzyme was not significantly altered by TGF-beta 1 or PGE2. However, the net accumulation of all forms of lysyl oxidase protein was increased by TGF-beta 1 and decreased by PGE2. These results indicate that TGF-beta 1 and specific prostaglandin(s) exert opposing effects on the expression of lysyl oxidase in these lung fibroblasts.

Animals↗
PubMed1994

High efficiency of muscle regeneration after human myoblast clone transplantation in SCID mice.

SCID mouse tibialis anterior muscles were first irradiated to prevent regeneration by host myoblasts and injected with notexin to damage the muscle fibers and trigger regeneration. The muscles were then injected with roughly 5 million human myoblasts. 1 mo later, 16-33% of the normal number of muscle fibers were present in the injected muscle, because of incomplete regeneration. However, > 90% of these muscle fibers contained human dystrophin. Some newly formed muscle fibers had an accumulation of human dystrophin and desmin on a part of their membrane. Such accumulations have been demonstrated at neuromuscular junctions before suggesting that the new muscle fibers are innervated and functional. The same pool of clones of human myoblasts produced only < or = 4% of muscle fibers containing human dystrophin when injected in nude mice muscles. Several of the human myoblasts did not fuse and remained in interstitial space or tightly associated with muscle fibers suggesting that some of them have formed satellite cells. Moreover, cultures of 98% pure human myoblasts were obtained from transplanted SCID muscles. In some mice where the muscle regeneration was not complete, the muscle fibers containing human dystrophin also expressed uniformly HLA class 1, confirming that the fibers are of human origin. The presence of hybrid muscle fibers containing human dystrophin and mouse MHC was also demonstrated following transplantation. These results establish that in absence of an immune reaction, transplanted human myoblasts participate to the muscle regeneration with a high degree of efficacy even if the animals were killed only 1 mo after the transplantation.

Animals↗
PubMed1993

Effects of transforming growth factor beta and interleukin-1 beta on expression of cyclooxygenase 1 and 2 and phospholipase A2 mRNA in lung fibroblasts and endothelial cells in culture.

Experiments were conducted to determine the roles of the rate limiting enzymes, cyclooxygenase 1 and 2 (COX1 and COX2) and cytoplasmic phospholipase A2 (PLA2), in transforming growth factor beta (TGF-beta) and interleukin-1 (IL-1 beta) activated prostaglandin synthesis. Results show that TGF-beta increases steady state levels of COX1 mRNA in both human embryo lung fibroblasts (IMR90) and calf pulmonary artery endothelial cells (BPAEC). Temporal experiments show that TGF-beta increases, within 2hrs, a 5.5kb COX1 in IMR90 and the 2.7kb COX1 mRNA in BPAEC. IL-1 beta increases COX1 mRNA only in IMR-90, not BPAEC. COX2 mRNA, under basal conditions, is not detected in BPAEC and is expressed only marginally in IMR90. TGF-beta or IL-1 beta have no effect on expression of COX2 gene in either cell type. IL-1 beta increases steady state levels of PLA2 mRNA in both IMR90 and BPAEC while TGF-beta increases expression of the PLA2 gene only in BPAEC. Time experiments with TGF-beta show induction of PLA2 mRNA within 1hr, peaking at 4hrs. PG synthesis in response to the cytokines was determined in IMR90 and BPAEC to further assess the significance of the above results. TGF-beta increases the synthesis of prostacyclin in BPAEC in a time related fashion peaking at 8hrs at 13 fold above basal. To focus on the action of COX1 and bypass the action of PLA2, exogenous arachidonic acid was used as substrate for PG synthesis. In these experiments IL-1 beta increases PGE2 synthesis 8 fold in IMR90 while IL-1 beta and TGF-beta added simultaneously increases PGE2 synthesis 25 fold. These results in sum illustrate that the cytokines, TGF-beta and IL-1 beta, regulate both COX1 and PLA2 mRNA levels. Furthermore, this regulation appears coordinated to bring about elevation of prostaglandin synthesis.

6-Ketoprostaglandin F1 alpha↗
PubMed1993

Repair of 8-hydroxyguanine in DNA by mammalian N-methylpurine-DNA glycosylase.

8-Hydroxyguanine is one of the major base lesions implicated in mutagenesis induced by ionizing radiation and radiomimetic agents. This lesion appears to be repaired by human cells via multiple pathways including the one that involves a base glycosylase. Mouse N-methylpurine-DNA glycosylase, responsible for the removal of N-alkylpurines in DNA that are induced by simple monofunctional alkylating agents, also releases 8-hydroxyguanine from DNA in vitro and in vivo in Escherichia coli. The human N-methylpurine-DNA glycosylase, with a lower preference for N-alkylguanine than the mouse protein, removes the oxidized base less efficiently than the mouse protein. The recombinant mammalian glycosylases can rescue E. coli lacking MutM (Fpg) protein, the DNA glycosylase that is primarily responsible for removing 8-hydroxyguanine from the bacterial DNA.

Animals↗