Biomedical subjects

Isabelle Hardy

Publications and source records attributed to Isabelle Hardy.

6 recordsLinked to original sources

PubMed2006

Altered DNA damage response in Caenorhabditis elegans with impaired poly(ADP-ribose) glycohydrolases genes expression.

Poly(ADP-ribosyl)ation is one of the first cellular responses induced by DNA damage. Poly(ADP-ribose) is rapidly synthesized by nick-sensor poly(ADP-ribose) polymerases, which facilitate DNA repair enzymes to process DNA damage. ADP-ribose polymers are rapidly catabolized into free ADP-ribose units by poly(ADP-ribose) glycohydrolase (PARG). The metabolism of poly(ADP-ribose) is a well-defined biochemical process for which a physiological role in animals is just beginning to emerge. Two Caenorhabditis elegans PARGs, PME-3 and PME-4, have been cloned by our group. The pme-3 gene encodes an enzyme of 89kDa having less than 18% overall identity with human PARG but 42% identity with the PARG signature motif. The pme-4 gene codes for a PARG of 55kDa with approximately 22% overall identity with human PARG and 40% identity with the PARG signature motif. Two alternatively spliced forms of PME-3 were identified with an SL1 splice leader on both forms of the mRNA and were found to be expressed throughout the worm's life cycle. Similarly, pme-4 was shown to be expressed in all developmental stages of the worm. Recombinant enzymes that were expressed in bacteria displayed a PARG activity that may partly account for the PARG activity measured in the total worm extract. Reporter gene analysis of pme-3 and pme-4 using a GFP fusion construct showed that pme-3 and pme-4 are mainly expressed in nerve cells. PME-3 was shown to be nuclear while PME-4 localized to the cytoplasm. Worms with pme-3 and pme-4 expression knocked-down by RNAi showed a significant sensitivity toward ionizing radiations. Taken together, these data provide evidence for a physiological role for PARGs in DNA damage response and survival. It also shows that PARGs are evolutionarily conserved enzymes and that they are part of an ancient cellular response to DNA damage.

Amino Acid Sequence↗

PubMed2006

Orbital decompression: cadaver study.

BACKGROUND: Patients with Graves' ophthalmopathy may need surgical treatment to alleviate ophthalmologic complications. The degree of reduction in proptosis following surgical intervention remains difficult to predict. OBJECTIVES: To elaborate a human model using cadaver orbits to study surgical management of Graves' ophthalmopathy. To evaluate quantitatively the contribution of each orbital wall decompression and their combinations in reduction in proptosis. To improve the ability to predict the degree of proptosis reduction according to the wall(s) chosen for decompression. METHODS: Artificial exophthalmos was created in 12 cadavers' orbits by injecting a polysaccharide gel in the peribulbar and retrobulbar tissues. Proptosis reduction was measured following successive orbital decompression. RESULTS: Decompression of one wall produced a nonstatistical significant reduction in proptosis. The combination of the medial and lateral walls significantly reduced the proptosis by a mean of 4.2 mm. Three-wall decompression gave a mean significant reduction of 6.6 mm, and when combined with the advancement of the lateral wall, it reduced proptosis by 12.5 mm. CONCLUSIONS: We created an experimental model for research and didactic purposes for surgical mangement of Graves' ophthalmopathy. With this model, to obtain 5 mm or more of proptosis reduction, three-wall decompression is required. Advancement of the lateral wall achieved a further reduction in proptosis. For a proptosis reduction of less than 5 mm, decompression of the medial and lateral walls is appropriate.

Cadaver↗

PubMed2005

Intralesional injection of Tisseel fibrin glue for resection of lymphangiomas and other thin-walled orbital cysts.

PURPOSE: Surgical removal of orbital lymphangiomas is often difficult because the capsule of these lesions is fragile, and, once violated, it tends to collapse, making identification of residual tumor difficult and dissection often incomplete. A surgical technique combining partial controlled decompression of the lesion with intralesional injection of Tisseel fibrin glue is evaluated to determine its effectiveness in resecting the lesion and preventing recurrences. METHODS: This is a retrospective interventional case series. Three young patients, two with lymphangiomas and one with congenital hydrocystoma, underwent surgical resection of their thin-walled cystic lesions of the orbit with the use of intralesional injection of Tisseel fibrin glue. Resolution of the signs and symptoms, complications of the surgery, and recurrence of bleeding are the parameters studied. RESULTS: All 3 patients had improvement of their signs and symptoms. None had complications related to the surgery, and no recurrence of bleeding occurred during the follow-up period. CONCLUSIONS: Our study suggests that this surgical technique with intralesional injection of Tisseel fibrin glue is an effective treatment modality for the resection of lymphangiomas and other orbital thin-walled cystic lesions.

Blood Loss, Surgical↗

PubMed2005

Topoisomerase I amino acid substitutions, Gly185Arg and Asp325Glu, confer camptothecin resistance in Leishmania donovani.

The antitumor compound camptothecin (CPT) is also recognized for its specific activity against Leishmania donovani topoisomerase I (Topo-I). In consequence, defining CPT resistance mechanisms represents an important strategic tool in the acquisition of a better understanding of its mode of action. In the present study, we selected a single highly resistant L. donovani strain termed LdRCPT.160 by stepwise exposure to CPT. Gene sequencing revealed two single nucleotide mutations in the LdRCPT.160 LdTOP1A gene, resulting in two amino acid substitutions (Gly185Arg and Asp325Glu) in the protein. Moreover, these two substitutions observed in the LdTOP1A protein were correlated with a decreased Topo-I DNA relaxation activity in these resistant parasites. Nevertheless, there was no change in the LdTOP1A gene expression level. Interestingly, transfection studies of the LdRCPT.160 LdTOP1A gene in its wild-type counterpart showed that it induced CPT resistance. Site-directed mutagenesis studies demonstrated that, despite a substantial level of resistance conferred by the Gly185Arg and Asp325Glu substitutions separately, both were essential to reach a high-resistance phenotype. Of interest, the amino acid substitutions observed in LdRCPT.160 LdTOP1A protein occurred near the amino acids previously predicted to interact with CPT, providing new insight into the mechanism of CPT molecular action.

Amino Acid Substitution↗

PubMed2004

Thyroid-associated orbitopathy: a clinicopathologic and therapeutic review.

PURPOSE OF REVIEW: To review the literature related to thyroid-associated orbitopathy and to emphasize recent developments in its pathophysiology, diagnosis, and therapy. Current therapeutic trends and controversies are discussed. RECENT FINDINGS: Expression of thyroid stimulating hormone receptor is highest in the fat and connective tissue of patients with thyroid-associated orbitopathy, where fibroblasts have the potential for adipogenesis. Electrophysiology can now detect subclinical optic neuropathy, and somatostatin-receptor scintigraphy can help justify immunomodulation. Other than steroids, radiotherapy can control inflammation, but its use is controversial. Current trends in orbital decompression are to camouflage incisions and to limit strabismus with balanced decompression, deep lateral wall techniques, fat removal, and onlay implants. Proptosis reductions of 0.9 to 12.5mm are possible by the use of various algorithms. Before or after decompression, botulinum toxin can correct strabismus, intraocular pressure elevation, and retraction. The latter is now also treated with full-thickness blepharotomy. SUMMARY: As knowledge of the pathophysiology of thyroid-associated orbitopathy grows, there is a slow movement from nonspecific and invasive measures to more directed treatments causing less morbidity.

Graves Disease↗

PubMed2002

Divergent evolution of hemagglutinin and neuraminidase genes in recent influenza A:H3N2 viruses isolated in Canada.

Limited information is available concerning the molecular drift of the influenza neuraminidase (NA) genes. We report on the genetic variability of the NA gene from 31 influenza A:H3N2 viruses isolated in the Province of Québec (Canada) during the last three flu seasons (1997-2000). Amino acid substitutions within the NA protein were observed at rates of 1.01% and 0.45% between strains of the 1997-1998 and 1998-1999 seasons and between those of the 1998-1999 and 1999-2000 seasons, respectively. In most strains (28/31), amino acid changes occurred within at least one of four codons (197, 339, 370, and 401) previously implicated as antigenic sites. The 8 functional and 10 framework residues that compose the catalytic site of the NA enzyme were completely conserved over the study period. All isolates contained the seven conserved asparagine-linked glycosylation sites found in the NA of the progenitor A/Hong Kong/8/68 strain. In addition, most strains (30/31) had an eighth potential glycosylation site at position 329, whereas a ninth one was found at position 93 in 16 strains. The NA of all strains in this study was related to that of the vaccine strain A/Beijing/353/89, whereas the HA genes of these strains were related to the A/Beijing/32/92 vaccine strain. Thus, it appears that recent influenza strains continue to evolve from a reassortant produced during the cocirculation of the two above variants. Interestingly, some strains whose HA genes were closely related showed significant differences in their NA genes and conversely. This study confirms the importance of analyzing both the NA and the HA genes to assess the evolution of recent influenza epidemic strains.

Canada↗