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Biomedical subjects

D Boucher

Publications and source records attributed to D Boucher.

At least 19 recordsLinked to original sources
PubMed2001

Quantitative analysis of desmosterol, cholesterol and cholesterol sulfate in semen by high-performance liquid chromatography.

A simple, rapid and accurate method to separate and quantify cholesterol, desmosterol and cholesterol sulfate in human spermatozoa and seminal plasma (SP) is described. This high-performance liquid chromatographic procedure is based on reversed-phase chromatography on a Inertsil ODS2 5 microm silica column with a binary gradient of mixtures of chloroform-methanol and chloroform-methanol-water as the mobile phase at a flow-rate of 0.25 ml/min. Sterols are separated with good resolution and high reproducibility. The eluted sterols are quantified using a light-scattering (mass) detector. As little as 64, 64 and 68 pmol of cholesterol, desmosterol and cholesterol sulfate, respectively, can be quantified under these conditions. Cholesterol is the predominant sterol both in spermatozoa (107+/-7 nmol/10(8) spermatozoa) and SP (0.83+/-0.10 micromol/ml) whereas the concentrations of desmosterol were 38+/-6 nmol/10(8) in spermatozoa and 0.18+/-0.02 micromol/ml in SP. Cholesterol sulfate represents about 6% of total cholesterol in the spermatozoa and SP. In conclusion, this method offers interesting perspectives for the quantitative analysis of these sterols not only in semen, but also in other biological samples.

Cholesterol↗
PubMed2001

Differential binding regulation of microtubule-associated proteins MAP1A, MAP1B, and MAP2 by tubulin polyglutamylation.

The major neuronal post-translational modification of tubulin, polyglutamylation, can act as a molecular potentiometer to modulate microtubule-associated proteins (MAPs) binding as a function of the polyglutamyl chain length. The relative affinity of Tau, MAP2, and kinesin has been shown to be optimal for tubulin modified by approximately 3 glutamyl units. Using blot overlay assays, we have tested the ability of polyglutamylation to modulate the interaction of two other structural MAPs, MAP1A and MAP1B, with tubulin. MAP1A and MAP2 display distinct behavior in terms of tubulin binding; they do not compete with each other, even when the polyglutamyl chains of tubulin are removed, indicating that they have distinct binding sites on tubulin. Binding of MAP1A and MAP1B to tubulin is also controlled by polyglutamylation and, although the modulation of MAP1B binding resembles that of MAP2, we found that polyglutamylation can exert a different mode of regulation toward MAP1A. Interestingly, although the affinity of the other MAPs tested so far decreases sharply for tubulins carrying long polyglutamyl chains, the affinity of MAP1A for these tubulins is maintained at a significant level. This differential regulation exerted by polyglutamylation toward different MAPs might facilitate their selective recruitment into distinct microtubule populations, hence modulating their functional properties.

Animals↗
PubMed2001

Mid-infrared trace gas detection using continuous-wave difference frequency generation in periodically poled RbTiOAsO4.

A tunable mid-infrared continuous-wave (cw) spectroscopic source in the 3.4-4.5 micrometers region is reported, based on difference frequency generation (DFG) in a quasi-phase-matched periodically poled RbTiOAsO4 (PPRTA) crystal. DFG power levels of 10 microW were generated at approximately 4 micrometers in a 20-mm long PPRTA crystal by mixing two cw single-frequency Ti:Al2O3 lasers operating near 713 nm and 871 nm, respectively, using a laser pump power of 300 mW. A quasi-phase-matched infrared wavelength-tuning bandwidth (FWHM) of ~ 12 cm-1 and a temperature tuning rate of 1.02 cm-1/degree C were achieved. Experimental details regarding the feasibility of trace gas detection based on absorption spectroscopy of CO2 in ambient air using this DFG radiation source are also described.

Aluminum Oxide↗
PubMed2001

Membrane fluidity and lipid content of human spermatozoa selected by swim-up method.

In this work, we examined whether spermatozoa (spz) from normospermic fertile patients and selected by a swim-up (S-U) procedure had a particular membrane fluidity related to their maturity and their lipid content as compared with the sperm cells from the whole ejaculate (total sperm). Swim-up selected sperm had a reduced cytoplasmic space as revealed by a lower creatine kinase (CK) activity compared with total sperm (2 +/- 1 vs. 12 +/- 5 mUI/10(7) spz, p < 0.05). The cholesterol (Chol) and total phospholipid (PL) contents were significantly lower in S-U selected sperm than in total sperm (0.72 +/- 0.08 vs. 1.20 +/- 0.30 nmol/10(6) spz for Chol and 1.77 +/- 0.17 vs. 2.78 +/- 0.50 nmol/10(6) spz for PL, p < 0.05) and such a decrease was observed for the three major membrane PL: phosphatidylethanolamine (PE), phosphatidylcholine (PC) and sphingomyelin (SM). However, these decreases were not associated with a change in either Chol/PL or PC/(PC + PE) molar ratios. Membrane fluidity estimated by fluorescence polarization remained comparable between the S-U sperm fraction and total sperm (fluorescence polarization anisotropy, r, which is inversely proportional to the fluidity: 0.235 +/- 0.006 vs. 0.230 +/- 0.005). The sperm membrane fluidity obtained in normospermic patients was compared with abnormospermic ones (oligoasthenoteratospermia). In abnormospermic patients, the membrane fluidity was decreased in migrated spermatozoa compared with total sperm (anisotropy: 0.210 +/- 0.010 vs. 0.250 +/- 0.013, p < 0.01). Our data suggest that the S-U method selected a subpopulation of mature spermatozoa characterised by a low content of Chol and PL, likely related to a reduced membrane area. The fact that Chol/PL and PC/(PC + PE) molar ratios were unchanged shows a maintenance of the membrane quality. This was confirmed by the fluorescence anisotropy measurement showing no difference in plasma membrane fluidity between S-U selected sperm and total sperm. In abnormal semen the migrated spermatozoa had a lower fluidity compared with total sperm suggesting a defective sperm function. These results bring new elements characterizing the S-U selected spermatozoa.

Chromatography, High Pressure Liquid↗
PubMed2001

Transitional cell carcinoma of the endometrium associated with a benign ovarian Brenner tumor: a case report.

Transitional cell carcinomas (TCCs) of the endometrium are rare, and only 10 cases have been described to date. We report the case of a 46-year-old woman who developed both a TCC of the endometrium and a benign ovarian Brenner tumor. Such an association has not yet been reported in the literature. Immunohistochemical studies of the uterine tumor showed cytokeratin 7 positivity and cytokeratin 20 negative staining, which was consistent with a Müllerian derivation. Human papilloma virus (HPV) immunostaining as well as polymerase chain reaction (PCR) analysis using primers for HPV types 6, 11, 16, and 18 failed to detect viral DNA. The coexistence of a TCC of the endometrium and an ovarian Brenner tumor might be coincidental but raises the possibility of a field effect, as seen with multifocal endometrioid tumors or multiple urinary tract TCCs.

Brenner Tumor↗
PubMed2001

Diffuse hepatic intravascular carcinomatous embolization resulting in fatal liver failure: a clinicopathologic study of 4 cases.

The authors report four cases in which patients died of acute or fulminant hepatic failure resulting from massive intravascular metastatic carcinomatous embolization, a rarely reported manifestation of metastatic disease. Neoplasms were high grade carcinomas. Tumor emboli were present within portal branches ranging 0.12-2.9 mm in diameter and were free floating or attached to the vascular wall, with or without varying degrees of superimposed organization. In one case, intravascular tumor necrosis was prominent and appeared as granular casts with superimposed dystrophic calcification and/or entrapped foamy histiocytes. There were associated geographical areas of parenchymal (4 cases) and tumor (1 case) ischemic necrosis with a multifocal and regional topographic distribution. An associated predominant pattern of intrasinusoidal tumor infiltration (with or without fibrosis) was present in 3 cases, whereas the fourth case had underlying micronodular cirrhosis, providing ancillary evidence for preexisting altered intrahepatic microcirculation. The literature on fatal hepatic failure resulting from neoplasia is reviewed with a reassessment of its pathobiological significance.

Acute Disease↗
PubMed2000

Compression of femtosecond laser pulses in thin one-dimensional photonic crystals.

We demonstrate experimentally the effect of compression of femtosecond laser pulses in thin (a few micrometers) one-dimensional photonic crystal. We show that the compression effect is reasonably described by the linear dispersion properties of the photonic crystal itself and the quadratic dispersion approximation cannot be efficiently used for the description of interaction of the femtosecond laser pulses with the thin photonic crystal. For given parameters of the femtosecond pulse it leads to the existence of the optimal dimension of the photonic crystal from the point of view of the compression efficiency. Due to the wide spectral width of the femtosecond laser pulses the high-order dispersion effects play an important role in pulse propagation in photonic crystals and as a result the pulse compression occurs for both positive and negative signs of chirp of the incoming femtosecond pulses.

Journal Article↗
PubMed2000

Mycophenolate mofetil, an alternative to cyclosporine A for long-term immunosuppression in kidney transplantation?

BACKGROUND: Mycophenolate-mofetil (MMF) is a nonnephrotoxic immunosuppressant most often used in combination with cyclosporine A (CsA) and prednisone (Pred). This study reports the outcome of 17 adult renal recipients whose immunosuppressive regimen was changed from CsA-Pred to MMF-Pred because of CsA nephrotoxicity. METHODS: CsA nephrotoxicity was diagnosed in all patients based on suggestive histopathological lesions on a renal biopsy. Sixteen patients had deteriorating graft function and 1 had isolated persistent proteinuria. Immunosuppressive therapy was changed 57+/-32 months posttransplant. RESULTS: After replacement of CsA by MMF, a reduction in serum creatinine was observed in all patients (mean 26+/-17%). This reduction was maintained 20+/-8 months after the change in therapy without any episodes of acute rejection. Serum lipids and blood pressure also decreased significantly. CONCLUSION: This study demonstrates that MMF-Pred can be an effective long-term immunosuppressive treatment alternative for renal transplant patients experiencing CsA nephrotoxicity. Such treatment may result in improved graft function, and better control of hypertension and hyperlipidemia.

Adult↗
PubMed2000

Hurricane disturbance and tropical tree species diversity.

The debate over the maintenance of high diversity of tree species in tropical forests centers on the role of tree-fall gaps as a primary source of disturbance. Using a 10-year data series accumulated since Hurricane Joan struck the Caribbean coast of Nicaragua in 1988, we examined the pattern of species accumulation over time and with increased sampling of individuals. Our analysis shows that the pattern after a hurricane differs from the pattern after a simple tree-fall disturbance, and we conclude that pioneers are limited in large disturbances and thus do not suppress other species the way they do in smaller disturbances.

Climate↗
PubMed2000

Separation and quantification of cholesterol and major phospholipid classes in human semen by high-performance liquid chromatography and light-scattering detection.

A high-performance liquid chromatographic method coupled with light-scattering detection for the separate and accurate quantification of cholesterol and main phospholipid classes was applied to human spermatozoa and seminal plasma (SP). This method is based on normal-phase chromatography with silica gel as stationary phase and a ternary gradient with hexane, mixtures of chloroform-methanol and water as mobile phase. Lipids are separated with a good resolution and a high reproducibility. About 5 x 10(6) spermatozoa or 25 microl of seminal plasma are sufficient to accurate quantitative analysis of phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylinositol (PI), phosphatidycholine (PC), sphingomyelin (SM) and cholesterol. PC is the predominant phospholipid class in spermatozoa (102+/-8 nmol/10(8) spermatozoa) whereas SM is the major in the SP (163+/-6 nmol/ml). Both in spermatozoa and SP, PI is the minor class of the phospholipids (12+/-1 nmol/10(8) spermatozoa and 24+/-2 nmol/ml). In conclusion, this method offers interesting perspectives for analysis of sperm lipid composition in semen samples with low quantities of spermatozoa.

Cholesterol↗
PubMed2000

Discussion.

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Journal Article↗
PubMed2000

Discussion.

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Journal Article↗
PubMed2000

Membrane fluidity predicts the outcome of cryopreservation of human spermatozoa.

Semen cryopreservation is an important procedure in the treatment of human infertility. However, the ability of spermatozoa to survive freeze/thaw processes varies between patients. Cryopreservation-induced stress may result in membrane injury with consequent loss of sperm motility and viability. We investigated the relationship between the physico-chemical state of the human sperm membranes and their tolerance to cryopreservation. Conventional characteristics of 20 semen samples were analysed before and after cryopreservation as well as their membrane fluidity assessed by measuring the fluorescence polarization anisotropy, which is inversely proportional to the fluidity. Correlation between fluidity and post-thaw recoveries of motile and viable spermatozoa were examined. Results showed that membrane anisotropy markedly varies between patients. In cryopreserved spermatozoa, anisotropy values were significantly higher than in fresh spermatozoa. Furthermore, recovery of motile and viable spermatozoa after freeze/thaw was strongly correlated with anisotropy of fresh spermatozoa (P < 0.05). The higher the membrane fluidity was before freezing, the better was the response of spermatozoa to cryopreservation. The results indicate that the freeze/thaw process results in a rigidifying effect on the sperm membrane and suggest that sperm adaptability to freeze/thaw-induced stress could be dependent on their initial membrane fluidity. The latter finding has practical implications for predicting the response of spermatozoa following freezing and thawing and for improving the recovery of viable spermatozoa.

Cell Membrane↗
PubMed2000

Sex chromosome mosaicism in males carrying Y chromosome long arm deletions.

Microdeletions of the long arm of the Y chromosome (Yq) are a common cause of male infertility. Since large structural rearrangements of the Y chromosome are commonly associated with a 45,XO/46,XY chromosomal mosaicism, we studied whether submicroscopic Yq deletions could also be associated with the development of 45,XO cell lines. We studied blood samples from 14 infertile men carrying a Yq microdeletion as revealed by polymerase chain reaction (PCR). Patients were divided into two groups: group 1 (n = 6), in which karyotype analysis demonstrated a 45,X/46,XY mosaicism, and group 2 (n = 8) with apparently a normal 46,XY karyotype. 45,XO cells were identified by fluorescence in-situ hybridization (FISH) using X and Y centromeric probes. Lymphocytes from 11 fertile men were studied as controls. In addition, sperm cells were studied in three oligozoospermic patients in group 2. Our results showed that large and submicroscopic Yq deletions were associated with significantly increased percentages of 45,XO cells in lymphocytes and of sperm cells nullisomic for gonosomes, especially for the Y chromosome. Moreover, two isodicentric Y chromosomes, classified as normal by cytogenetic methods, were detected. Therefore, Yq microdeletions may be associated with Y chromosomal instability leading to the formation of 45,XO cell lines.

Adult↗
PubMed2000

Prostasomes inhibit the NADPH oxidase activity of human neutrophils.

Prostasomes are particular lipid vesicles secreted by the prostate in human semen and involved in several physiological functions such as the improvement of sperm motility or immunomodulation. We have previously shown that they reduced the overall reactive oxygen species (ROS) production of seminal polymorphonuclear neutrophils (PMN). The present study was conducted to define the mechanism by which prostasomes inhibit the ROS production of blood and seminal PMN. The luminol chemiluminescence measuring total ROS production of blood PMN stimulated by either a phorbol ester (PMA) or a chemoattractant peptide, formyl-Met-Leu-Phe (fMLP) was significantly inhibited by prostasomes. The NADPH oxidase activity of the PMN was measured by 2-methyl-6-(p-methoxyphenyl)-3,7-dihydroimidazo[1, 2-a]pyrazin-3-one (MCLA) chemiluminescence. Prostasomes inhibited the NADPH oxidase activity of blood or seminal PMN and increased the lag-phase of the enzyme after PMA stimulation. Prostasomes also inhibited significantly the NADPH oxidase activity of fMLP stimulated blood PMN, but the inhibition was not significant for seminal PMN. The lipid composition of blood PMN was analysed and compared to the lipid composition of prostasomes. This showed that prostasomes had a high cholesterol:phospholipid molar ratio and a high proportion of sphingomyelin. Together with the fact that prostasomes can rigidify the plasma membrane of blood PMN, these results led us to postulate that prostasomes inhibit the NADPH oxidase activity of PMN by lipid transfer from the prostasomes to the plasma membrane of the PMN.

Cholesterol↗
PubMed2000

Discussion

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Journal Article↗