Biomedical subjects

Y Boucher

Publications and source records attributed to Y Boucher.

At least 19 recordsLinked to original sources

PubMed2002

Solid stress facilitates spheroid formation: potential involvement of hyaluronan.

When neoplastic cells grow in confined spaces in vivo, they exert a finite force on the surrounding tissue resulting in the generation of solid stress. By growing multicellular spheroids in agarose gels of defined mechanical properties, we have recently shown that solid stress inhibits the growth of spheroids and that this growth-inhibiting stress ranges from 45 to 120 mmHg. Here we show that solid stress facilitates the formation of spheroids in the highly metastatic Dunning R3327 rat prostate carcinoma AT3.1 cells, which predominantly do not grow as spheroids in free suspension. The maximum size and the growth rate of the resulting spheroids decreased with increasing stress. Relieving solid stress by enzymatic digestion of gels resulted in gradual loss of spheroidal morphology in 8 days. In contrast, the low metastatic variant AT2.1 cells, which grow as spheroids in free suspension as well as in the gels, maintained their spheroidal morphology even after stress removal. Histological examination revealed that most cells in AT2.1 spheroids are in close apposition whereas a regular matrix separates the cells in the AT3.1 gel spheroids. Staining with the hyaluronan binding protein revealed that the matrix between AT3.1 cells in agarose contained hyaluronan, while AT3.1 cells had negligible or no hyaluronan when grown in free suspension. Hyaluronan was found to be present in both free suspensions and agarose gel spheroids of AT2.1. We suggest that cell-cell adhesion may be adequate for spheroid formation, whereas solid stress may be required to form spheroids when cell-matrix adhesion is predominant. These findings have significant implications for tumour growth, invasion and metastasis.

Animals↗

PubMed2002

Radiographic evaluation of the prevalence and technical quality of root canal treatment in a French subpopulation.

AIM: This study was undertaken to examine the prevalence and technical quality of root fillings and the periapical status of endodontically treated teeth in a French subpopulation. METHODOLOGY: Full-mouth periapical radiographs were obtained from 208 consecutive adult patients seeking care within the dental service provided by the Hôtel-Dieu in Paris. The occurrence and technical quality of root fillings were assessed for each root according to the position and the density of the obturation. The periapical status was evaluated using the Periapical Index Scoring System. The type of coronal restoration and the presence of posts were also noted. RESULTS: Of the 8743 roots included in the survey, 23% were root-filled. An acceptable standard of treatment was found in 21% of roots with 16% of these cases associated with signs of periapical disease. In roots with unacceptable root-fillings, 27% had periapical pathology. A post was seen in 26% of the root-filled canals, with 29% of these cases associated with periapical pathology. An intracoronal restoration existed in 30% of the filled roots, of which 22% exhibited a periapical lesion. An extra-coronal restoration was present in 60% of the filled roots, of which 24% had radiographic signs of periapical pathology. The remaining 10% of filled roots that had no coronal restoration were associated with periapical pathology in 33% of cases. At least one periapical lesion was seen in 63% of the patients. CONCLUSION: The results demonstrate a high prevalence of root-filled teeth and poor technical quality of treatment. Roots presenting with acceptable root fillings were associated with a lower prevalence of periapical pathology (P < 0.001). Posts in roots were associated with periapical pathology significantly more than in roots without posts (P < 0.001).

Adolescent↗

PubMed2002

Effects of excitatory amino acid receptor antagonists on pulpal blood flow of the rat mandibular incisor.

Pulpal blood flow (PBF) changes have been monitored by laser Doppler flowmetry on rat mandibular incisors. Electrical stimulation (10 sec, 50 microA, 2 ms, 20 Hz) of one incisor induced a blood flow decrease followed by a blood flow increase. The effect of intravenous administration of antagonists of ionotropic glutamate receptors (iGluRs) and antagonists of metabotropic glutamate receptors (mGluRs) was compared with that of those obtained from animals treated with the vehicle alone. No long-term effect on basal PBF was observed, except a remaining increase of 34.5% (p < 0.05, n = 5) for ketamine (10 mg/kg), an iGluR antagonist, and of 37% (p < 0.05, n = 5) for MCPG (7.5 mg/kg), an mGluR antagonist. In animals treated with iGluR antagonists, acute changes in PBF after stimulation were not significantly different from those observed with vehicle. In animals treated with mGluR antagonists, the blood flow decrease was significantly enhanced in amplitude and duration for MCPG (7.5 mg/kg), respectively, +73% and +92% (p < 0.05, n = 5). These results suggest that Group I mGluRs participate in the regulation of the immediate pulpal blood flow decrease induced by electrical stimulation of the lower incisor in the rat.

Analysis of Variance↗

PubMed2001

LYVE-1 is not restricted to the lymph vessels: expression in normal liver blood sinusoids and down-regulation in human liver cancer and cirrhosis.

Lymphatic vessel endothelial hyaluronan receptor (LYVE)-1 is thought to be restricted to lymph vessels and has been used as such to show that tumor lymphangiogenesis occurs on overexpression of lymphangiogenic factors in mouse tumor models. However, these studies have not yet been corroborated in human tumors. Here we show, first, that LYVE-1 is not exclusive to the lymph vessels. Indeed, LYVE-1 is also present in normal hepatic blood sinusoidal endothelial cells in mice and humans. Surprisingly, LYVE-1 is absent from the angiogenic blood vessels of human liver tumors and only weakly present in the microcirculation of regenerative hepatic nodules in cirrhosis, though both vessels are largely derived from the liver sinusoids. Second, we propose a novel approach to identify lymphatics in human and murine liver. By combining LYVE-1 and Prox 1 (a transcription factor) immunohistochemistry, we demonstrate that lymphatics are abundant in cirrhosis. In contrast, in human hepatocellular carcinoma and liver metastases, they are restricted to the tumor margin and surrounding liver. The absence of intratumor lymphatics in hepatocellular carcinomas and liver metastases may impair molecular and cellular transport in these tumors. Finally, the presence of LYVE-1 in liver sinusoidal endothelia suggests that LYVE-1 has functions beyond the lymph vascular system.

Animals↗

PubMed2001

Role of tumor-host interactions in interstitial diffusion of macromolecules: cranial vs. subcutaneous tumors.

The large size of many novel therapeutics impairs their transport through the tumor extracellular matrix and thus limits their therapeutic effectiveness. We propose that extracellular matrix composition, structure, and distribution determine the transport properties in tumors. Furthermore, because the characteristics of the extracellular matrix largely depend on the tumor-host interactions, we postulate that diffusion of macromolecules will vary with tumor type as well as anatomical location. Diffusion coefficients of macromolecules and liposomes in tumors growing in cranial windows (CWs) and dorsal chambers (DCs) were measured by fluorescence recovery after photobleaching. For the same tumor types, diffusion of large molecules was significantly faster in CW than in DC tumors. The greater diffusional hindrance in DC tumors was correlated with higher levels of collagen type I and its organization into fibrils. For molecules with diameters comparable to the interfibrillar space the diffusion was 5- to 10-fold slower in DC than in CW tumors. The slower diffusion in DC tumors was associated with a higher density of host stromal cells that synthesize and organize collagen type I. Our results point to the necessity of developing site-specific drug carriers to improve the delivery of molecular medicine to solid tumors.

Animals↗

PubMed2001

Vascular endothelial growth factor receptor-2-blocking antibody potentiates radiation-induced long-term control of human tumor xenografts.

Antiangiogenic therapy can enhance radiation-induced tumor growth inhibition. However, the effects of combined antiangiogenic and radiation therapy on long-term tumor control and normal tissue response have not been reported. We treated mice bearing two different human tumor xenografts with anti-vascular endothelial growth factor receptor-2 antibody (DC101) and five dose fractions of local radiation and followed them for at least 6 months. DC101 significantly decreased the dose of radiation necessary to control 50% of tumors locally. The decrease was 1.7- and 1.3-fold for the moderately radiosensitive small cell lung carcinoma 54A and the highly radioresistant glioblastoma multiforme U87, respectively. In contrast to tumors, no increase in skin radiation reaction by the antibody was detected. Surprisingly, 44% of mice bearing 54A tumor developed clear ascites after DC101 treatment at its highest dose; this was fatal to 20% of mice. This adverse effect was seen only in mice that received whole-body irradiation 1 day before tumor implantation. The encouraging results on two human tumor xenografts suggest that vascular endothelial growth factor receptor-2 blockade merits further investigation to assess its potential as an enhancer of radiation therapy in the clinic.

Angiogenesis Inhibitors↗

PubMed2001

Decorin inhibits endothelial migration and tube-like structure formation: role of thrombospondin-1.

Interactions between endothelial cell receptors and the extracellular matrix (ECM) play a critical, yet poorly understood role in angiogenesis. Based on the anti-adhesive role of decorin, we hypothesized that decorin binding to ECM molecules such as thrombospondin-1 (TSP-1) plays a regulatory role in endothelial tube-like structure (TLS) formation. To test this hypothesis, endothelial cells were plated on TSP-1, decorin, or mixed substrates of TSP-1 plus decorin. TLS formation was induced by applying type I collagen on the confluent endothelial monolayer. Cartilage decorin inhibited the formation of TLSs in a concentration-dependent manner. On substrates of high decorin concentrations (2.5 and 5.0 microg/cm(2)) the reduction in TLSs was due either to a reduction in the number of adhering cells or to decreased cell migration. At low decorin concentrations (0.05 and 0.25 microg/cm(2)) the reduction in TLSs was independent of the number of attached cells. Time-lapse video microscopy revealed that decorin substrates facilitated homotypic aggregation and isolated cord formation at the expense of endothelial migration and TLS formation. Consistent with the reduced migration, endothelial cells formed fewer vinculin-positive focal adhesions and actin-stress fibers on decorin substrates. Endothelial migration and TLS formation were also significantly inhibited by skin decorin and the protein core of cartilage decorin. The inhibition of TLS formation by the protein core of cartilage decorin was potentiated by TSP-1. These findings suggest that decorin alone or in combination with TSP-1 interferes with the activation of endothelial cell receptors by ECM molecules, thus blocking intracellular signals that induce cytoskeletal reorganization, migration, and TLS formation.

Cartilage↗

PubMed2001

Effects of BP 2-94, a selective H(3)-receptor agonist, on blood flow and vascular permeability of the rat mandibular incisor pulp.

Pulpal blood-flow changes were monitored by laser Doppler flowmetry after electrical stimulation of the mandibular incisor. Stimuli of 10 s (50 microA, 2 ms, 20 Hz) were applied to the incisors of untreated animals and longer stimulations (5 min) were applied in animals treated with the alpha-blocker phenoxybenzamine. Changes in vascular permeability in the dental pulp were measured by Evans blue extravasation following resection of the superior cervical ganglion. In these groups, a selective agonist of H(3) receptors, BP2-94 (1.5 and 15 mg/kg), and an H(3)-antagonist ciproxifan (1 mg/kg) were administered. The effects of these drugs were compared with those obtained from animals treated only with the vehicle (methylcellulose 1%). Basal pulpal blood-flow was not affected significantly by BP2-94 or ciproxifan. The vasoconstriction induced in the group of intact rats by electrical stimulation of 10 s is decreased in amplitude and duration at the higher dose of BP2-94 by 58 and 40%, respectively (P<0.05, n=5). In the sympathectomized animals, plasma extravasation was significantly increased at 15 mg/kg BP2-94 (+100%, P<0.01, n=5). These results suggest that H(3) receptors may participate in the regulation of changes in vessel contraction and permeability provoked by electrical stimulation of the dental pulp. However, the non-selective effects of the H(3) agonists reacting on adrenergic sites and H(1) receptors could explain a part of the results.

Animals↗

PubMed2001

Microbial genomes: dealing with diversity.

We have now complete genome sequences of several pairs of closely related prokaryotes (conspecific strains or congeneric species). Surprisingly, even strains of the same species can differ by as much as 20% in gene content. Conceptual and methodological approaches for dealing with such diversity are now being developed, and should transform microbial genomics.

Evolution, Molecular↗

PubMed2001

Bacterial origin for the isoprenoid biosynthesis enzyme HMG-CoA reductase of the archaeal orders Thermoplasmatales and Archaeoglobales.

The enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase or HMGR) fulfills an essential role in archaea, as it is required for the synthesis of isoprenoid ethers, the main component of archaeal cell membranes. There are two clearly homologous but structurally different classes of the enzyme, one found mainly in eukaryotes and archaea (class 1), and the other found in bacteria (class 2). This feature facilitated the identification of several cases of interdomain lateral gene transfer (LGT), in particular, the bacterial origin for the HMGR gene from the archaeon Archaeoglobus fulgidus. In order to investigate if this LGT event was recent and limited in its scope or had a broad and long-term impact on the recipient and its related lineages, the HMGR gene was amplified and sequenced from a variety of archaea. The survey covered close relatives of A. fulgidus, the only archaeon known prior to this study to possess a bacterial-like HMGR; representatives of each main euryarchaeal group were also inspected. All culturable members of the archaeal group Archaeoglobales were found to display an HMGR very similar to the enzyme of the bacterium Pseudomonas mevalonii. Surprisingly, two species of the genus Thermoplasma also harbor an HMGR of bacterial origin highly similar to the enzymes found in the Archaeoglobales. Phylogenetic analyses of the HMGR gene and comparisons to reference phylogenies from other genes confirm a common bacterial origin for the HMGRs of Thermoplasmatales and Archaeoglobales. The most likely explanation of these results includes an initial bacteria-to-archaea transfer, followed by a another event between archaea. Their presence in two divergent archaeal lineages suggests an important adaptive role for these laterally transferred genes.

Archaeoglobales↗

PubMed2000

Anti-Vascular endothelial growth factor treatment augments tumor radiation response under normoxic or hypoxic conditions.

Recent studies in experimental animals have shown that combining antiangiogenic therapy with radiation can enhance tumor response. Whether this enhancement is mainly attributable to angiogenesis inhibition, endothelial cell radiosensitivity, tumor cell apoptosis, or a decrease in the number of hypoxic cells (improved oxygenation) is not known. We designed this study to discern the role of tumor oxygenation. We chose an anti-vascular endothelial growth factor (anti-VEGF) monoclonal antibody (mAb) which has a known target, human VEGF. We also measured interstitial fluid pressure (IFP) to test the hypothesis that the decreased vascular permeability induced by the anti-VEGF mAb can lower IFP. The effect of anti-VEGF mAb on vascular density, partial oxygen tension (pO2), and apoptosis was also measured. Athymic NCr/Sed nu/nu mice bearing 6-mm xenograft of the human glioblastoma multiforme (U87), or colon adenocarcinoma (LS174T) were treated with anti-VEGF mAb injected i.p. on alternate days for a total of six injections at a dosage of 100 microg/injection/mouse. For combined anti-VEGF and radiation, single radiation doses were given under normal blood flow (20 and 30 Gy) or clamped hypoxic conditions (30 and 40 Gy) 24 h after the sixth injection of mAb. The inhibition of the growth of U87 and LS174T tumors by the anti-VEGF mAb was associated with a significant reduction in tumor vascular density and a relatively small increase in the number of apoptotic cells. Compared with size-matched controls, IFP decreased by 74% in LS174T, and 73% in U87 in mice treated with anti-VEGF mAb. After antibody treatment PO2 increased significantly in U87, but did not change in LS174T tumors. Combined treatment induced in U87 tumors a tumor-growth delay (TGD) which was greater than additive; in LS174T except for the 40-Gy hypoxic group, the effect was only additive. In both U87 and LS174T the TGD induced by the antibody was independent of oxygen levels in the tumor at the time of radiation. The fact that the increase in TGD occurred under both normoxic and hypoxic conditions suggests that anti-VEGF mAb treatment can compensate for the resistance to radiation induced by hypoxia.

Adenocarcinoma↗

PubMed2000

Oncotic pressure in solid tumors is elevated.

Oncotic and hydrostatic pressure differences control the movement of fluid and large molecules across the microvascular wall of normal and tumor tissues. Recent studies have shown that the interstitial fluid pressure in tumors is elevated and is approximately equal to the microvascular pressure. Whereas oncotic pressure in blood plasma of various species is known, no data are available on the oncotic pressure in the interstitial space of tumors. We hypothesize that because of the leaky nature of tumor vessels, oncotic pressure in tumor interstitium should be close to that in plasma. To this end, we first developed a chronic wick method for the direct measurement of oncotic pressures in the interstitial fluid of tumors grown in mice. We found interstitial oncotic pressures in four human tumor xenografts to be higher than in s.c. tissue and comparable to that in plasma [rhabdomyosarcoma (RD), 24.2+/-4.7; squamous cell carcinoma (FaDu), 19.9+/-1.9; small cell lung carcinoma (54A), 21.1+/-2.8; colon adenocarcinoma (LIS174T), 16.7+/-3.0 mm Hg; s.c. tissue, 8.2+/-2.3; plasma, 20.0+/-1.6 mm Hg]. These results support our hypothesis that the oncotic pressure difference across the tumor microvascular wall is low. The high oncotic pressure in tumors is consistent with the elevated interstitial fluid pressure, and it contributes to the suboptimal delivery of large therapeutic agents to neoplastic cells.

Animals↗

PubMed2000

Odorant and pheromone binding by aphrodisin, a hamster aphrodisiac protein.

Aphrodisin is a soluble glycoprotein of hamster vaginal discharges, which stimulates male copulatory behavior. Natural aphrodisin was purified and its post-translational modifications characterized by MALDI-MS peptide mapping. To evaluate its ability to bind small volatile ligands, the aphrodisiac protein was expressed in the yeast Pichia pastoris as two major isoforms differing in their glycosylation degree, but close in conformation to the natural protein. Dimeric recombinant aphrodisins were equally able to efficiently bind odors (2-isobutyl-3-methoxypyrazine and methyl thiobutyrate) and a pheromone (dimethyl disulfide), suggesting that they could act as pheromone carriers instead of, or in addition to, direct vomeronasal neuron receptor activators.

Animals↗

PubMed2000

Utilization of gutta-percha for retrograde root fillings.

Just as gutta-percha used with a root canal sealer is a recommended material for orthograde root fillings, it could similarly be the material of choice for retrograde fillings. Unfortunately, clinical accessibility and visibility do not always facilitate such a technique. The aim of this article is to present a new technique which enables retrograde fillings to be achieved with gutta-percha and a sealer. After the apex had been resected, a hole was drilled perpendicular to the plane of section of the apex about 1 mm coronally. The bucco-lingual depth required to reach the main canal was calculated. The cavity was then dried, coated with the sealer, and obturated with gutta-percha in accordance with thermo-mechanical compaction techniques. After excess filling material had been removed, the gutta-percha was cold burnished and the angles of the root were smoothed. Clinical cases illustrating healing of the periapical tissues are shown.

Apicoectomy↗

PubMed2000

The role of lateral gene transfer in the evolution of isoprenoid biosynthesis pathways.

Lateral gene transfer (LGT) is a major force in microbial genome evolution. Here, we present an overview of lateral transfers affecting genes involved in isopentenyl diphosphate (IPP) synthesis. Two alternative metabolic pathways can synthesize this universal precursor of isoprenoids, the 1-deoxy-D-xylulose 5-phosphate (DOXP) pathway and the mevalonate (MVA) pathway. We have surveyed recent genomic data and the biochemical literature to determine the distribution of the genes composing these pathways within the bacterial domain. The scattered distribution observed is incompatible with a simple scheme of vertical transmission. LGT (among and between bacteria, archaea and eukaryotes) more parsimoniously explains many features of this pattern. This alternative scenario is supported by phylogenetic analyses, which unambiguously confirm several cases of lateral transfer. Available biochemical data allow the formulation of hypotheses about selective pressures favouring transfer. The phylogenetic diversity of the organisms involved and the range of possible causes and effects of these transfer events make the IPP biosynthetic pathways an ideal system for studying the evolutionary role of LGT.

Amino Acid Sequence↗

PubMed2000

Persistent pain related to root canal filling and apical fenestration: a case report.

Endodontic treatments may give rise to persistent pain whose origin is sometimes difficult to determine. Although it is unusual, pain may occur due to apical fenestrations following endodontic treatment. If this occurs, the solution is surgical intervention. This surgical procedure consists of raising a flap to expose the fenestration, followed by curettage of any overextended canal filling materials that may be potentially irritating to the underlying mucosa, remodeling of the apex, and its repositioning below the level of the cortical bone. A case is described that illustrates this clinical situation. The case also demonstrates information that can be obtained from tomodensitometric films.

Apicoectomy↗

PubMed1999

Taxane-induced apoptosis decompresses blood vessels and lowers interstitial fluid pressure in solid tumors: clinical implications.

Elevated tumor interstitial fluid pressure (IFP) is partly responsible for the poor penetration and distribution of therapeutic agents in solid tumors. The etiology of tumor interstitial hypertension is poorly understood. We have postulated that the solid stress generated by tumor cells growing in a confined space compresses blood vessels and increases tumor microvascular pressure and IFP. To test the hypothesis that neoplastic cell loss would decompress blood vessels and lower IFP, we induced apoptosis in tumors with paclitaxel and docetaxel. Taxanes inhibited the growth of the murine mammary carcinoma (MCa-IV) and of the human soft tissue sarcoma (HSTS-26T). Taxanes induced apoptosis and reduced the density of intact neoplastic cells in both MCa-IV and HSTS-26T. To determine whether neoplastic cell loss decompressed blood vessels, we measured the diameter of tumor vessels in HSTS-26T tumors implanted in transparent dorsal skin fold chambers. At 48 and 96 h after paclitaxel, the diameter of tumor vessels was significantly increased. The increase in vascular diameters was associated with reductions in microvascular pressure and IFP. The changes in neoplastic cell density and IFP were also correlated. In the human glioblastoma U87, which is resistant to paclitaxel, the IFP and cellular density were not modified by paclitaxel treatment. Collectively, these results support the hypothesis that solid stress generated by neoplastic cell proliferation increases vascular resistance and IFP. The increase in vessel diameter induced by paclitaxel and docetaxel suggests that taxanes could improve tumor response by increasing the vascular surface area for delivery of therapeutic agents.

Animals↗

PubMed1999

Enhancement of fluid filtration across tumor vessels: implication for delivery of macromolecules.

Cancer therapies using genes and other macromolecules might realize their full clinical potential if they could be delivered to tumor tissue in optimal quantities. Unfortunately, the compromised circulation within tumors poses a formidable resistance to adequate and uniform penetration of these agents. Previously, we have proposed elevated interstitial fluid pressure (IFP) as a major physiological barrier to delivery of macromolecules. Here we postulate that modulation of tumor microvascular pressure (MVP) and associated changes in IFP would enhance macromolecular delivery into a solid tumor. To test our hypothesis, we altered tumor MVP by either periodic injection or continuous infusion of angiotensin II (AII) and measured the resulting changes in IFP and uptake of macromolecules. We used the nicotinyl hydrazine derivative of human polyclonal IgG (HYNIC-IgG) as a nonspecific macromolecule and CC49 antibody as a specific macromolecule. We found that both chronic and periodic modulation of tumor MVP enhances transvascular fluid filtration, leading to a 40% increase in total uptake of the specific antibody within 4 hr of its administration. Conversely, neither continuous nor periodic infusion of AII induced any increase in uptake of nonspecific antibodies. Strategies to improve delivery of macromolecules and limitations of this approach are identified.

Animals↗