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G Perrin

Publications and source records attributed to G Perrin.

At least 19 recordsLinked to original sources
PubMed2006

Interferometric coupling of the Keck telescopes with single-mode fibers.

Here we report successful interferometric coupling of two large telescopes with single-mode fibers. Interference fringes were obtained in the 2- to 2.3-micrometer wavelength range on the star 107 Herculis by using the two Keck 10-meter telescopes, each feeding their common interferometric focus with 300 meters of single-mode fibers. This experiment demonstrates the potential of fibers for future kilometric arrays of telescopes and is the first step toward the 'OHANA (Optical Hawaiian Array for Nanoradian Astronomy) interferometer at the Mauna Kea observatory in Hawaii. It opens the way to sensitive optical imagers with resolutions below 1 milli-arc second. Our experimental setup can be directly extended to large telescopes separated by many hundreds of meters.

Journal Article↗
PubMed2005

Effects of PEEP on oxygenation and respiratory mechanics during one-lung ventilation.

BACKGROUND: One-lung ventilation-related hypoxaemia (OLV-RH) can occur in patients with healthy lungs. In this case, PEEP frequently improves oxygenation. The aim of this study was to determine, in a healthy lung model of OLV, whether the increase in PEEP improved oxygenation and whether the mechanisms involved include both inspiratory lung recruitment and an end-expiratory lung volume increase. Since inhaled nitric oxide (iNO) may have a synergistic effect on oxygenation in the case of PEEP-induced recruitment, their association was also tested. METHODS: Twenty pigs were studied during open-chest, left OLV. Arterial blood gases and haemodynamic variables were measured at different levels of PEEP (0, 5, 10 and 15 cm H(2)O) applied in random order with or without iNO 4 p.p.m. Pressure-volume curves were measured at each level of PEEP. RESULTS: PEEP(5) and PEEP(10) improved Pa(O(2))/FI(O(2)) ratio (P<0.005) and shunt (P<0.005) regardless of the presence of iNO. PEEP(15) improved oxygenation and shunt only when it was associated with iNO (P<0.001). Whereas PEEP(5), PEEP(10) and PEEP(15) were associated with a significant increase in end-expiratory volume (P<0.001), only PEEP(5) and PEEP(10) were associated with continuous lung volume recruitment (P<0.01). Moreover, PEEP(15) induced a significant decrease in linear compliance (P<0.001). CONCLUSIONS: In a healthy porcine lung model of OLV-RH, moderate PEEP can improve oxygenation. This effect implies both expiratory and inspiratory pulmonary recruitment. Co-administration of 4 p.p.m. iNO was ineffective.

Animals↗
PubMed2005

Clinical and histological correlations in prolactinomas, with special reference to bromocriptine resistance.

BACKGROUND: Prolactinomas usually exhibit a benign course and can be safely and effectively managed by dopamine agonists (DA). However, some are locally invasive and may show resistance to DA therapy, and the management of such cases remains controversial. The aim of the present study was to determine whether histological features and markers of cell proliferation correlated to the clinical behaviour of prolactinomas and with DA resistance. METHOD: This retrospective study included 74 cases (36 men and 38 women) who had monohormonal prolactinomas removed by transsphenoidal surgery. The prolactinomas were categorized on the basis of tumour size (48 macroadenomas), invasion of the cavernous sinus (n = 31), and resistance to bromocriptine (BRC) therapy (n = 14). Group 1 consisted of non-invasive microprolactinomas (n = 24), group 2 of non-invasive macroprolactinomas (n = 19), group 3 of invasive non-BRC-resistant tumours (n = 19), and group 4 of invasive BRC-resistant tumours (n = 12). The later group included one case of carcinoma with bone and lung metastases. Seven additional parameters were studied, these being age, sex, basal prolactin (PRL) levels, the Ki-67 and PCNA labelling indices (LI), mitotic count, and cellular atypia. FINDINGS: Age and preoperative PRL levels did not correlate to the histological parameters studied. Tumour size and invasion were related to cellular atypia and the Ki-67 LI. BRC-resistant tumours were more frequently invasive (12/14) than BRC-responsive tumours (11/30; p = 0.002) and were more frequent in men than in women (33 versus 5%; p = 0.003). BRC-resistant tumours had a higher Ki-67 LI and mitotic count (4.2+/-2.0% and 4+/-1, respectively) than other tumours (0.7+/-0.2% and 1+/-0, respectively; p<0.05). The strongest correlations with tumoural staging were seen with male sex and high mitotic activity. Six out of the 12 invasive BRC-resistant macroprolactinomas, including the PRL secreting carcinoma, exhibited histological features of aggressiveness (a mitotic count >/=3 [i.e. in the fourth quartile] and/or a high Ki-67 LI and cellular atypia). CONCLUSIONS: In this surgical retrospective series, histological signs of aggressiveness are present in 50% of invasive and BRC-resistant prolactinomas, which are more frequent in men than in women. This fits with the behaviour of BRC-resistant prolactinomas, which can continue to grow despite DA treatment. These findings justify the long-term follow up of these tumours, and the use of surgery and/or radiotherapy if there is concern about the control of tumour growth.

Adult↗
PubMed2005

[Endovascular treatment of isthmic aortic rupture: use of second generation stent grafts].

OBJECTIVE: Prospective analysis of endovascular management of traumatic isthmic rupture with second generation stent grafts. STUDY DESIGN: Prospective analysis and follow-up. PATIENTS: Ten consecutive multiple injured patients presenting an acute isthmic traumatic rupture who underwent an endovascular repair with second generation stent grafts. METHODS AND RESULTS: The aortic injury was diagnosed by spiral computed tomography scan. The appropriate time to repair was decided according to multidisciplinary decision after analysis of associated injuries status and mediastinal lesions evolution. Endovascular repair was successfully completed in all patients under general anaesthesia without requirement of haemodynamic manipulations. Despite a prolonged length of stay related to associated injuries, all patients were discharged from hospital without migration of devices or complication related to the endovascular procedure. After a 20 months follow-up (range 6 - 38 months), all patients were alive with a satisfactory CT scan analysis. CONCLUSION: The immediate availability of the second generation of stents-grafts allowed the endovascular treatment of isthmic rupture without haemodynamic manipulations or massive heparinization. The analysis of this selected series reinforces the interest of this non-invasive technique for anaesthetists especially in polytraumatized patients.

Adult↗
PubMed2004

The building blocks of planets within the 'terrestrial' region of protoplanetary disks.

Our Solar System was formed from a cloud of gas and dust. Most of the dust mass is contained in amorphous silicates, yet crystalline silicates are abundant throughout the Solar System, reflecting the thermal and chemical alteration of solids during planet formation. (Even primitive bodies such as comets contain crystalline silicates.) Little is known about the evolution of the dust that forms Earth-like planets. Here we report spatially resolved detections and compositional analyses of these building blocks in the innermost two astronomical units of three proto-planetary disks. We find the dust in these regions to be highly crystallized, more so than any other dust observed in young stars until now. In addition, the outer region of one star has equal amounts of pyroxene and olivine, whereas the inner regions are dominated by olivine. The spectral shape of the inner-disk spectra shows surprising similarity with Solar System comets. Radial-mixing models naturally explain this resemblance as well as the gradient in chemical composition. Our observations imply that silicates crystallize before any terrestrial planets are formed, consistent with the composition of meteorites in the Solar System.

Journal Article↗
PubMed2004

The central dusty torus in the active nucleus of NGC 1068.

Active galactic nuclei (AGNs) display many energetic phenomena--broad emission lines, X-rays, relativistic jets, radio lobes--originating from matter falling onto a supermassive black hole. It is widely accepted that orientation effects play a major role in explaining the observational appearance of AGNs. Seen from certain directions, circum-nuclear dust clouds would block our view of the central powerhouse. Indirect evidence suggests that the dust clouds form a parsec-sized torus-shaped distribution. This explanation, however, remains unproved, as even the largest telescopes have not been able to resolve the dust structures. Here we report interferometric mid-infrared observations that spatially resolve these structures in the galaxy NGC 1068. The observations reveal warm (320 K) dust in a structure 2.1 parsec thick and 3.4 parsec in diameter, surrounding a smaller hot structure. As such a configuration of dust clouds would collapse in a time much shorter than the active phase of the AGN, this observation requires a continual input of kinetic energy to the cloud system from a source coexistent with the AGN.

Journal Article↗
PubMed2003

Transpedicular screwing of the seventh cervical vertebra: anatomical considerations and surgical technique.

The purpose of this study was first to assess the feasibility of C7 transpedicular screwing with a morphological study and secondly to evaluate the safety of such a surgical technique when guided only by posterior landmarks. Eighteen C7 vertebrae, harvested from fresh human cadavers, were included in this study. First the morphometry of C7 pedicle was performed on computed tomography with multiplanar reconstructions. Results of this quantitative anatomy were compared with the literature data. Secondly 30 pedicle screws, whose placement was guided only by anatomical features on the posterior face of the dorsal arch, were inserted in 15 C7 vertebrae. A second computed tomographic examination was done after the surgical procedure to check the screw placement in both planes. The average pedicular width was 6+/-1.2 mm and the average height was 5.8+/-1.1 mm. The pedicle angulation in the transverse plane was 33.3 degrees +/-6.6 degrees, the pedicle angulation in the sagittal plane was 4.3 degrees +/-4.5 degrees downward with reference to the lower endplate of C7. The average distance from the entry point of transpedicular screwing to the anterior cortex of the vertebral body was 29+/-3 mm. Concerning the safety of transpedicular screwing, 63% of screws were found entirely inside the pedicle without any violation of the pedicle cortex. Most of pedicle violations were observed in the transverse plane. No grade II violation of the pedicle was observed. Dimensions of the C7 pedicle are amply compatible with transpedicular fixation using 3.5 mm screws. Such a surgical technique seems to be an interesting option when posterior fixation of C7 is required. Nevertheless morphological guidelines appeared not to be sufficient to ensure safe transpedicular screwing. Laminoforaminotomy is strongly recommended, although it has not been evaluated in this study.

Aged↗
PubMed2002

[Technical aspects and surgical strategy for removal of corticotroph pituitary adenoma].

The development of transsphenoidal microsurgery and the refinement of endocrinological and radiological diagnostic procedures have afforded therapeutic options appropriate for each individual case in patients with pituitary-dependent hypercortisolism. Compared with other secreting pituitary tumors, the corticotroph adenoma seems to be the most biologically active tumor. Clinical evidence of hypercortisolism mainly occurs at an early stage of tumor growth when the tumor is very small, below the detection threshold of modern imaging techniques. While the treatment of large tumors remains difficult due to the non-discrete boundary lines of the tumor and extension or invasion, surgical removal of very tiny tumors requires reliable preoperative or peroperative identification in order to achieve total tumor resection for clinical remission and pituitary preservation to prevent hypopituitarism. We reviewed all the current surgical techniques or clever surgical procedures used to achieve both goals with the lowest complication rate. We report here the state-of-the-art of surgical management of corticotroph pituitary adenoma focusing on preoperative radiological and biological data required for performing guided intrasellar surgical exploration and reliable tumor identification. Different technical aspects of the nasosphenoidal approaches are reported as well as the modified transdiaphragmatic or transtubercular transcisternal approaches to tumors in a suprasellar localization or lying along the pituitary stalk. The advantages of minimally invasive surgical techniques such as intrasellar endoscopic surgery are discussed. Adapted surgical techniques for second transnasal surgery indicated for recurrent tumors are described. Guidelines are given for peroperative tumor identification with macroscopic assessment or histological control with frozen section biopsies. Different techniques for tumor removal are discussed from selective microadenomectomy to enlarged pituitary resection and total hypophysectomy. Methods for preoperative guidance of total tumor removal are proposed including histological or biological assessment of normal adjacent pituitary tissue. the strategy of surgical intrasellar exploration and tumor resection is outlined using a set of algorithms. The first is devoted to positive preoperative documentation of the tumor. The second is proposed for the surgical scenario where there is no preoperative MRI evidence of the tumor. Special strategies are discussed for ectopic adenoma or multiple tumors. Revision surgical management after surgical failure or tumor recurrence is described. Special guidelines for surgical treatment of large clinically silent corticotroph macroadenomas are given with emphasis on the high risk of recurrence in comparison with other silent pituitary tumors such as gonadotroph or immunonegative adenomas.

ACTH Syndrome, Ectopic↗
PubMed2002

[Corticotroph microadenomas of the pituitary stalk. Diagnostic and therapeutic difficulties].

Thirteen percent of the pituitary adenomas in our series have been corticotroph adenomas. Most have been microadenomas located in the adenohypophysis, more often laterally than posteromedially. In a few rare cases, the corticotroph cells of the pars tuberalis gave rise to an adenoma. Only 16 cases of pituitary stalk adenomas have been published to date. We report here three new cases among a series of 150 patients who underwent surgery for corticotroph adenomas (2% incidence as in the literature). There was no difference in the clinical or biological presentation of intrasellar and pituitary stalk adenomas. This location must be systematically searched on the MRI, but a negative exploration cannot excluded the diagnosis of pituitary stalk adenoma like in intrasellar ones. Two anatomical entities seems to be separated. Some stalk adenomas developed preferentially in the supradiaphragmatic space (one in our series) and are accessible for selective resection. Others develop within the pituitary stalk itself and sometimes in the pars distalis (two patients in our series) which requires section of the pituitary stalk with hypophysectomy if the lower limit is not clearly seen during surgery. The subfrontal or pterional access is the approach of choice for suprasellar tumors. These approaches remain controversial for pituitary stalk adenomas because of the poor visibility of the pituitary stalk and the floor of the third ventricle. The transnasosphenoidal approach with extension to the sphenoidal planum and opening of the optochiasmatic cisterna appears to be the best alternative for surgical removal of these adenomas.

Adenoma↗
PubMed2002

[Cushing's disease and corticotrophic adenoma: results of pituitary microsurgery].

Between November 1994 and June 2001, 194 patients with Cushing's disease underwent transsphenoidal surgery: 167 patients had adenomectomy, 14 had ante hypophysectomy, 5 had subtotal hypophysectomy, 4 had hemihypophysectomy 4 had central hypophysectomy. Complications occurred in 18 patients (9.3%), including 4 deaths (three were apparently not related to surgery). Remission of disease was achieved in 162 of 190 (85.3%) patients analyzed. Surgical failures were associated with lack of pituitary adenoma, size of the tumor and invasiveness. Among patients with confirmed adenomas, the rate of remission was significantly higher (p<0.01) in patients with microadenomas (92.6%) than in patients with macroadenomas (66.7%). Reoperation in 6 failures was followed by remission in 4 cases. The overall remission rate was 87.4%. In the 162 patients with immediate success, duration of follow-up was 10.0 +/- 5.9 years (m +/- DS; median=10.0). Recurrence of the disease occurred in 24 (14.8%) of 162 patients at a mean 4.8 years (range: 0.8-12.0 years). Our longest sustained remission is 25.6 years. Actuarial analysis indicates that the probability of a patient remaining well 12 years after surgery is 80.0%. It is 86.2% in microadenomas versus 52.5% in macroadenomas and 94.5% in the patients with postoperative hypocortisolism versus 59.2% in the others.

Adenoma↗
PubMed2001

Melanoma patients respond to a cytotoxic T lymphocyte-defined self-peptide with diverse and nonoverlapping T-cell receptor repertoires.

HLA-A2+ melanoma patients develop naturally a strong CD8+ T cell response to a self-peptide derived from Melan-A. Here, we have used HLA-A2/peptide tetramers to isolate Melan-A-specific T cells from tumor-infiltrated lymph nodes of two HLA-A2+ melanoma patients and analyzed their TCR beta chain V segment and complementarity determining region 3 length and sequence. We found a broad diversity in Melan-A-specific immune T-cell receptor (TCR) repertoires in terms of both TCR beta chain variable gene segment usage and clonal composition. In addition, immune TCR repertoires selected in the patients were not overlapping. In contrast to previously characterized CD8+ T-cell responses to viral infections, this study provides evidence against usage of highly restricted TCR repertoire in the natural response to a self-differentiation tumor antigen.

Amino Acid Sequence↗
PubMed2001

Survival of Listeria monocytogenes during manufacture, ripening and storage of soft lactic cheese made from raw goat milk.

Soft lactic cheeses were manufactured with raw goat milk inoculated with Listeria monocytogenes. The physico-chemical and microbiological characteristics of curds and cheeses were determined after each processing step as well as during ripening and refrigerated storage. The fate of Listeria monocytogenes was evaluated by enumeration on PALCAM agar and by a qualitative detection after a double selective enrichment procedure. The results showed that the physico-chemical and microbiological characteristics of lactic cheeses caused a decrease of Listeria monocytogenes counts. However, this decrease did not lead to the complete disappearance of the pathogen and Listeria monocytogenes was able to survive in soft lactic cheeses made with raw goat milk.

Animals↗
PubMed2001

[Should silent corticotroph-cell adenoma be classified as a non-functional pituitary adenoma?].

A 45-year-old man underwent surgery for a silent corticotroph-cell pituitary adenoma which developed in 9 months. The tumor was termed silent because it exhibited increased corticotropic secretion without clinical signs of hypercorticism. This classes it as a non-functional adenoma. The non-functional group includes different types of adenomas such as gonadotroph and other silent thyreotroph and somatotroph adenomas with variable proliferative potential. Silent corticotroph-cell adenoma is considered as an aggressive tumor. In contrast, gonadotroph adenomas usually grow slowly and postoperative tumor remnants can remain stable for years. Because of this variability in tumor growth, the therapeutic decision is difficult if there is a postoperative remnant. No precise guidelines can be established. We suggest that non-functional pituitary adenomas should be considered separately, according to the histological type. This classification is essential for improving knowledge and specifying indications for radiotherapy.

Adenoma↗
PubMed2000

Variability and immunogenicity of caprine arthritis-encephalitis virus surface glycoprotein.

The complete surface glycoprotein (SU) nucleotide sequences of three French isolates of caprine arthritis-encephalitis virus (CAEV) were determined and compared with those of previously described isolates: three American isolates and one French isolate. Phylogenetic analyses revealed the existence of four distinct and roughly equidistant evolutionary CAEV subtypes. Four conserved and five variable domains were identified in the SU. The fine specificities of antibodies produced against these domains during natural infection were examined using a pepscan analysis. Nine immunogenic segments were delineated throughout the conserved and variable domains of SU, two of them corresponding to conserved immunodominant epitopes. Antigenic determinants which may be involved in the immunopathogenic process induced by CAEV were identified. These results also provide sensitive and specific antigen peptides for the serological detection and differentiation of CAEV and visna/maedi virus infections.

Amino Acid Sequence↗
PubMed2000

[Prolactinoma in man: clinical and histological characteristics].

Prolactinoma usually occurs a small intrasellar tumor in women or as a large tumor in men. To determine whether the predominance of macroprolactinomas in men is due to a delay in diagnosis as has been suggested, or whether there is a sex-related difference in growth rate we conducted a retrospective study in 45 men and 51 women with prolactinomas. Preoperative prolactin level (PRL) was 2,789 573 ng/ml and mean tumor size was 26 2 mm. Prolactin levels and tumor size were significantly higher in women (292 74 ng/ml and 10 1 mm; p<0.01). There was no correlation with age at diagnosis or duration of symptoms. Giant tumors were only observed in men (n=8). Frequency of resistance to bromocriptine (30% vs 5%, p<0.01) and invasive tumors (52% vs 27%, p<0.001) were significantly higher in men than in women. Likewise, proliferation rate was higher for the prolactinomas in men (Ki-67: 2.6 1.1% positive nuclei vs 0.4 0.2%; p=0.08; PCNA: 5.0 2.3% vs 3.7 1.1%). In conclusion, prolactinomas in men are more aggressive than in women. They grow rapidly, often invade the cavernous sinus and are resistant to bromocriptine; proliferation rates can be increased.

Adolescent↗
PubMed1999

CD95 (Fas/Apo-1) as a receptor governing astrocyte apoptotic or inflammatory responses: a key role in brain inflammation?

Astrocytes are a major cellular component of the brain that are capable of intense proliferation and metabolic activity during diverse inflammatory brain diseases (such as multiple sclerosis, Alzheimer's dementia, tumor, HIV encephalitis, or prion disease). In this biological process, called reactive gliosis, astrocyte apoptosis is frequently observed and could be an important mechanism of regulation. However, the factors responsible for apoptosis in human astrocytes are poorly defined. Here, we report that short term cultured astrocytes derived from different brain regions express significant levels of CD95 at their surface. Only late passage astrocytes are sensitive to CD95 ligation using either CD95 mAb or recombinant CD95 ligand. Blocking experiments using caspase inhibitors with different specificities (DEVD-CHO, z-VAD-fmk, and YVAD-cmk), an enzymatic activity assay, and immunoblotting show that CPP32/caspase-3 play a prominent role in CD95-induced astrocyte death. In contrast, early passage astrocytes are totally resistant to death, but a significant increase in astrocytic IL-8 secretion (p < 0.001, by Wilcoxon's test for paired samples) is observed after CD95 triggering. Production of IL-8 contributes to the resistance of astrocytes to CD95 ligation. Furthermore, in the presence of IFN-gamma, resistant astrocytes became sensitive to CD95-mediated death. These data suggest that microenvironmental factors can influence the consequences of CD95 ligation on astrocytes. Therefore, we propose that CD95 expressed by human astrocytes plays a pivotal role in the regulation of astrocyte life and death and may be a key factor in inflammatory processes in the brain, such as reactive gliosis.

Adjuvants, Immunologic↗
PubMed1999

Astrocytoma infiltrating lymphocytes include major T cell clonal expansions confined to the CD8 subset.

Anaplastic astrocytoma and glioblastoma are frequent and malignant brain tumors that are infiltrated by T lymphocytes. Whether these cells result from non-specific inflammation following blood-brain barrier disruption or an antigen-driven specific immune response is unknown. In this study, an in-depth characterization of TCR diversity in tumor and blood RNA biopsies was performed in a series of 16 patients with malignant astrocytoma. Whilst there was no obvious restriction of the AV and BV gene segment usage, complementarity-determining region 3 size analysis and sequencing of amplified TCR transcripts revealed multiple T cell oligoclonal expansions in all astrocytomas analyzed. Unique T cell clones were present in different adjacent areas of a given tumor, but never detected in the blood. Quantification of the number of TCR clonal transcripts per microg of tumor RNA indicated that certain T cell clonal expansions may represent at least 300 cells/10(6) tumor cells. Furthermore, we demonstrated that the in vivo expanded clones were almost exclusively confined to the CD8(+) subset. Overall, these data suggest that spontaneous antigen-driven immune responses may be elicited against human astrocytoma despite the immunosuppressive microenvironment generated by the brain and the tumor itself. However, the ultimate failure of the immune system to control tumor growth could be the consequence of a deficient CD4 T(h) component of the response. This observation could have important consequences for the development of immunotherapies for astrocytoma patients.

Adult↗