Search PubMed⌕ Search

Biomedical subjects

A Laurent

Publications and source records attributed to A Laurent.

At least 55 records · Page 3Linked to original sources
PubMed1999

Stimulation of bone marrow cells and bone formation by nacre: in vivo and in vitro studies.

There is frequently a loss of vertebral bone due to disease or aging. Nacre (mother of pearl from the oyster Pinctada maxima) stimulates bone cell differentiation and bone formation in vitro and in vivo. Experimental bone defects were prepared in the vertebrae of sheep and used to test the suitability of nacre as an injectable osteogenic biomaterial for treating vertebral bone loss. Twenty-one cavities were prepared in the first four upper lumbar vertebrae of 11 sheep and filled with nacre powder. The lumbar vertebrae were removed after 1 to 12 weeks, embedded undecalcified in methacrylate, and processed for histological studies. The nacre slowly dissolved and the experimental cavities contained a large active cell population. By 12 weeks, the experimental cavity was occupied by newly matured bone trabeculae in contact with or adjacent to the dissolving nacre. The functional new bone trabeculae were covered with osteoid lined with osteoblasts, indicating continuing bone formation. The in vitro study on rat bone marrow explants cultured with a water-soluble extract of the nacre organic matrix also resulted in the stimulation of osteogenic bone marrow cells with enhanced alkaline phosphatase activity. Thus, both the in vivo and in vitro findings suggest that nacre contains one or more signal molecules capable of activating osteogenic bone marrow cells.

Alkaline Phosphatase↗
PubMed1999

Analysis in the rat of 4-hydroxynonenal metabolites excreted in bile: evidence of enterohepatic circulation of these byproducts of lipid peroxidation.

4-Hydroxynonenal (HNE) is a cytotoxic product resulting from the lipid peroxidation of membrane polyunsaturated fatty acids. In vitro, metabolism mainly leads to the corresponding alcohol (DHN), carboxylic acid (HNA), and the glutathione conjugate, whereas in vivo, mercapturic acid conjugates of HNE, DHN, HNA, and HNA-lactone and, more recently, dicarboxylic acids and related mercapturate conjugates were identified in urine of rats. In the study presented here, the identity of the HNE biotransformation products in the bile of rats following a single iv administration of [4-(3)H]HNE and the potential for enterohepatic recycling of HNE metabolites were investigated. The identity of metabolites was assessed by comparison of their HPLC retention times with those of the corresponding synthesized standards and by mass spectrometry analysis. Five metabolites were present in the bile; two of them corresponded to HNE- and DHN-glutathione conjugates. Two others metabolites were identified as DHN- and HNA-lactone mercapturic acid conjugates. The fifth metabolite was isolated but remained unidentified. As previously observed for urinary elimination, the kinetic excretion of biliary metabolites exhibited a rapid metabolism of HNE in rats. Within 4 h of injection, the bile accounted for 19.5% (+/-2.8%) of the injected radioactivity, whereas only 3% was found in the feces within 48 h [Alary, J., et al. (1995) Chem. Res. Toxicol. 8, 34-39]. The extent of HNE enterohepatic recycling was estimated utilizing a modified version of the linked rat model in three animals. All rat recipients were found to have measurable levels of HNE metabolites in bile, confirming that HNE is likely to undergo enterohepatic recirculation in the rat. The extent of recycling was approximatly 7. 7% of the total dose in this model. Two unknown metabolites were present in the bile of recipient rats and not found in the bile of donors rats, suggesting that intestinal microflora and/or intestinal mucosa could biotransform HNE-related compounds before or during the reabsorption process.

Aldehydes↗
PubMed1999

Calcium- and ADP-magnesium-induced respiratory uncoupling in isolated cardiac mitochondria: influence of cyclosporin A.

This study was designed to determine the effect of calcium and ADP-Mg on the oxidative phosphorylation in isolated cardiac mitochondria. The influence of cyclosporin A was also evaluated. The mitochondria were extracted from rat ventricles. Their oxidative phosphorylations were determined in two respiration media with different free Ca2+ concentrations. Respiration was determined with palmitoylcarnitine and either ADP or ADP-Mg. With elevated free Ca2+ concentrations and ADP-Mg, the transition state III to state IV respiration did not occurred. The ADP:O ratio was reduced. The phenomenon was not observed in the other experimental conditions (low free Ca2+ concentration with either ADP- or ADP-Mg or elevated free Ca2+ concentration with ADP-). Uncoupling was allied with a constant AMP production, which maintained an elevated ADP level in the respiration medium and prevented the return to state IV respiration. It was also observed in a respiration medium devoid of free Ca2+ when the mitochondria were pre-loaded with Ca2+. Uncoupling was inhibited by cyclosporin A. Furthermore, the Krebs cycle intermediates released from 14C-palmitoylcarnitine oxidation revealed that succinate was increased by elevated free Ca2+ and ADP-Mg. Succinate is a FAD-linked substrate with low respiration efficiency. Its accumulation could account for the decreased ADP:O ratio. The Ca2+- and ADP-Mg-induced uncoupling might be partly responsible for the mechanical abnormalities observed during low-flow ischemia.

Adenosine Diphosphate↗
PubMed1999

Effect of indinavir on the single-dose pharmacokinetics of theophylline in healthy subjects.

The effect of multiple doses of indinavir on the pharmacokinetics of a single dose of theophylline was investigated in 16 healthy male subjects using a randomized, double-blind, placebo-controlled, parallel-group study design. On days 1 and 7, all of the subjects received a single oral 250 mg dose of theophylline. From days 2 to 7, the subjects received orally administered 800 mg doses of indinavir or a matched placebo every 8 hours. On day 7, theophylline and indinavir (or a placebo) were coadministered. The geometric mean AUC(0-24 h) of theophylline increased 18% when coadministered with indinavir compared to when theophylline was administered alone. This small increase in AUC(0-24 h), although considered statistically significant, did not meet the prespecified criterion for clinical significance. The geometric mean Cmax of theophylline, when coadministered with indinavir, was within 8% of theophylline when administered alone. The mean tmax (+/- SD) value for theophylline, when coadministered with indinavir (0.9 +/- 0.5 h), was comparable to that observed for theophylline alone (1.0 +/- 0.5 h). In conclusion, the administration of multiple doses of indinavir followed by a single dose of theophylline did not appear to result in a clinically significant pharmacokinetic interaction for theophylline.

Administration, Oral↗
PubMed1999

Thrombosis of angiographic catheters in humans: experimental study.

One of the major problems in the use of catheters is their thrombogenicity since the embolization of clots near the central nervous system or the coronary arteries can cause permanent damage. Catheter thrombogenicity was evaluated in humans during angiographic procedures by their tendency to become occluded. Characterization of catheters was achieved using roughness measurements, FTIR with ATR, DSC and ESCA. The catheters were 5 commercially available catheters, made mainly of polyethylene, Pebax or polyamide sterilized and ready for clinical use. Thirty-one patients due to have an angiographic procedure and with normal blood and hemodynamic parameters were included in the study. The 50 cm catheter test sample was inserted through an introducer into the femoral artery at the beginning of an angiographic procedure. The outcoming blood flow rate (BFR) was continuously monitored by a special computerized device for 15 min or until the total amount of blood reached 30 ml. The angiographic procedure was then normally resumed. DSC and FTIR showed results consistent with the expected composition of catheters. ESCA results showed very high Si/C ratios and could not be explained in all instances. Occlusion of the catheters occurred in 44% of the cases and the average time to obtain occlusion was 8.5 min (3-15 min). Values of the decrease rate of BFR in ml/min2 allowed separation of the catheters into 3 groups of low, medium and high thrombogenicity. However, occlusion occurred at least one time for each type of catheter. Blood volume and BFR curves vs. time allowed the determination of 3 main types of thrombotic behavior: type I shows no significant reduction of BFR; type II shows a progressive decrease in flow rate; type III is much less frequent and shows an abrupt decrease of BFR either quickly followed by a compensatory increase and resuming of a steady flow or by abrupt occlusion. In type II curves the pattern of occlusion follows a classical diffusion model because the Peclet number is greater than 1 and then the classical Higbie solution for diffusion could be used. The most thrombogenic material was the smoothest. There was no correlation between surface chemical composition and thrombogenicity. However, catheters that were based on PE appeared less thrombogenic than PA catheters in this study.

Angiography↗
PubMed1998

Single-fraction stereotactic radiotherapy: a dose-response analysis of arteriovenous malformation obliteration.

PURPOSE: Stereotactic radiotherapy delivered in a high-dose single fraction is an effective technique to obliterate intracranial arteriovenous malformations (AVM). To attempt to analyze the relationships between dose, volume, and obliteration rates, we studied a group of patients treated using single-isocenter treatment plans. METHODS AND MATERIALS: From May 1986 to December 1989, 100 consecutive patients with angiographically proven AVM had stereotactic radiotherapy delivered as a high-dose single fraction using a single-isocenter technique. Distribution according to Spetzler-Martin grade was as follows: 79 grade 1-3, three grade 4, 0 grade 5, and 18 grade 6. The target volume was spheroid in 74 cases, ellipsoid in 11, and large and irregular in 15. The targeted volume of the nidus was estimated using two-dimensional stereotactic angiographic data and, calculated as an ovoid-shaped lesion, was 1900 +/- 230 mm3 (median 968 mm3; range 62-11, 250 mm3). The mean minimum target dose (Dmin) was 19 +/- 0.6 Gy (median 20 Gy; range: 3-31.5). The mean volume within the isodose which corresponded to the minimum target dose was 2500 +/- 300 mm3 (median 1200 mm3; range 75-14 900 mm3). The mean maximum dose (Dmax) was 34.5 +/- 0.5 Gy (median 35 Gy; range 15-45). The mean angiographic follow-up was 42 +/- 2.3 months (median 37.5; range 7-117). RESULTS: The absolute obliteration rate was 51%. The 5-year actuarial obliteration rate was 62.5 +/- 7%. After univariate analysis, AVM obliteration was influenced by previous surgery (p = 0.0007), Dmin by steps of 5 Gy (p = 0.005), targeted volume of the nidus (< or = 968 mm3 vs. >968 mm3; p = 0.015), and grade according to Spetzler-Martin (grade 1-3 vs. grade 4-6; p = 0.011). After multivariate analysis, the independent factors influencing AVM obliteration were the Dmin [relative risk (RR) 1.9; 95% confidence interval (CI) 1.4-2.5; p < 0.0001] and grade distribution according to Spetzler-Martin (RR 1.4; 95% CI 1.1-1.7; p = 0.010). Delayed complications were observed in eight patients. The 5-year actuarial rate of delayed complications was 7.4%. CONCLUSION: After stereotactic radiotherapy delivered in a single high dose using a single-isocenter technique, the success rate for complete obliteration is independently correlated to Dmin but does not seem to be influenced by Dmax and the targeted volume of the nidus.

Adolescent↗
PubMed1998

Insulin-like 4 (INSL4) gene expression in human embryonic and trophoblastic tissues.

Polypeptide growth factors play an important role in the regulation of human embryonic development. Insulin-like 4 gene (INSL4) is a member of the insulin family, which includes insulin, IGF-I, IGF-II, relaxin, and INSL3. Using RT-PCR, we previously found abundant INSL4 mRNA in the human placenta. In this study, we examined the chronology and spatial expression of this gene in sections of human placenta and conceptus by means of in situ hybridization. Expression of the IGF-II gene was studied as a positive control. INSL4 distribution was tissue- and cell-specific. Indeed, INSL4 mRNA was most abundant in syncytiotrophoblast cells. In fetal tissues, INSL4 mRNA was identified in the perichondrium of all four limbs, vertebrae, and ribs. Moreover, INSL4 mRNA was abundant in interbone ligaments. These findings indicate that the INSL4 gene may play an important role in trophoblast development and regulation of bone formation. IGF-II mRNA, in agreement with the literature, are mainly located in the mesodermal core in the villous trophoblast and in most embryonic tissues.

Gene Expression Regulation, Developmental↗
PubMed1998

Materials and biomaterials for interventional radiology.

Devices used in interventional radiology have significantly developed in the past few years. In order to understand the trends of this development, we analyzed how new interventional devices are progressively incorporating materials having original physical properties, and how developers are today progressively turning towards biomaterials, with respect to the new regulatory environment, and the requirements of biocompatibility.

Animals↗
PubMed1998

A 5-year follow-up study of suicide attempts among French adolescents.

PURPOSE: The social, medical, and psychological outcomes of 552 adolescents hospitalized subsequent to an attempted suicide were assessed after an average 5-year follow-up period. METHODS: Evaluation took place by means of mailed questionnaires completed by the adolescents, their parents, and the general practitioner. Using regression analysis, responses were compared with those of a comparison group (n = 273). RESULTS: In the suicidal group, the mean annual mortality rate was seven-fold greater than in the general population of the same age. Education level was lower, and the consumption of alcohol, psychiatric hospitalizations, and contacts with the criminal justice system were more frequent than in the control group. No other variables explored were significantly different between the two groups. CONCLUSIONS: The results of this study carried out on a large sample of French suicidal adolescents tend to confirm results of previous studies performed in other countries. They show that the prognosis for the suicidal adolescent group is less favorable than that of the comparison group.

Adolescent↗
PubMed1998

The INSL4 gene maps close to WI-5527 at 9p24.1-->p23.3 clustered with two relaxin genes and outside the critical region for the monosomy 9p syndrome.

The insulin like growth factor 4 (INSL4) gene belongs to the insulin gene superfamily and has been mapped by fluorescent in situ hybridization to 9p24. Expression of INSL4, of unknown function, has been recently detected in the perichondrium and ligaments of the human embryo. Here we have mapped INSL4 within the framework of a partial YAC contig covering the distal part of 9p to find out whether this gene lies within the critical region defined for the monosomy 9p syndrome. The gene was also located using a human-rodent radiation hybrid panel. INSL4 was found to be distal to the del(9p) critical region and excluded as a candidate for the syndrome. In addition, the positions of two relaxin genes (RLN1, RLN2) that belong to the same superfamily as INSL4 and which have also been mapped to chromosome 9, were refined. We have shown that the three genes are clustered in the same region.

Animals↗
PubMed1998

[Sugar diabetes. Update elements].

The various types of diabetes mellitus are now more precisely classified according to their etiopathogenies. Therefore, type 1 (autoimmune or not), type 2, gestational diabetes, as well as MODY (Maturity Onset-Diabetes of the Young) and secondary diabetes are considered as separate entities. Any type of diabetes brings its set of complications. Biological chemistry is directed to define the etiopathogenic characteristics of the various types of diabetes and to assess the severity of metabolic and functional disturbances. Diagnostic criteria in term of glycemia have also been reviewed to asses diabetes and glucose intolerance.

Blood Glucose↗
PubMed1997

Evidence for the polyclonal nature of focal nodular hyperplasia of the liver by the study of X-chromosome inactivation.

Focal nodular hyperplasia (FNH) of the liver is a benign tumor commonly considered as a reactive disorder related to a pre-existing vascular malformation. However, the pathogenesis of this lesion has been recently discussed. To determine whether FNH is a polyclonal or a clonal lesion, we investigated the inactivation pattern of the X chromosome, using molecular genetic analysis of the DNA methylation pattern at a polymorphic site on the human androgen receptor gene (HUMARA). Fifteen FNH were studied, and results were compared with those obtained from 7 hepatic adenomas (HA) and 2 hepatocellular carcinomas (HCC). DNA was extracted from both lesional and nonlesional livers, fixed, and paraffin-embedded. To assess the methylation pattern, we used a quantitative fluorescent polymerase chain reaction (PCR) procedure that allows for the accurate measurement of the peak intensities of each allele. Three patients were noninformative because they were homozygous at the HUMARA locus. According to the threshold for monoclonality established by a titration curve, all FNH showed a random pattern of X-chromosome inactivation consistent with a polyclonal lesion. In contrast, all but 1 hepatic adenoma and all hepatocellular carcinomas were clonal, as shown by the nonrandom pattern of X-chromosome inactivation observed in these cases. In conclusion, these results suggest that FNH should be considered as a reactive disorder rather than as a tumoral proliferation. Discordant results recently observed in the literature could be at least in part explained by methodological differences in the PCR procedure.

Adenoma↗
PubMed1997

[Apropos of families where parents are battered by their children].

Although the reported prevalence rate of children who assault their parents is high, ranging from 0.6 to 16%, publications dealing with this subject are rare. Based upon data from the literature and a personal experience the family structure of such aggressive parents-children relationships are described in an attempt to define causative mechanisms. This may help to early recognition and prevention of this type of familial violence.

Adolescent↗
PubMed1997

Psychological assessment of patients with idiopathic pruritus ani.

BACKGROUND: The purpose of this study was to compare psychological profiles in 17 patients suffering from idiopathic pruritus ani with a control group of 28 patients showing secondary pruritus ani. METHODS: The two groups completed the Mini-Mult personality test and results were compared using chi 2 test and analysis of variance. RESULTS: The mean hypomania and depression scale scores were greater and smaller respectively in the idiopathic pruritus ani group. Nevertheless, the percentage of abnormal psychological profiles was not significantly different between the two groups. CONCLUSIONS: It seems arbitrary to systematically ascribe psychogenic aetiologies to idiopathic pruritus ani even though psychological factors may be present in individual patients.

Adult↗
PubMed1997

Identification of pro-EPIL and EPIL peptides translated from insulin-like 4 (INSL4) mRNA in human placenta.

Recently, a new member of the insulin gene superfamily termed insulin-like 4 (INSL4) was identified in the human placenta and uterus. The present study investigated whether placenta translates INSL4 mRNA into a putative peptide named early placenta insulin-like (EPIL). Among antibodies elicited against the C chain of pro-EPIL, one antibody (AB7381) was specifically directed against the C chain 59-88 portion, and among those elicited against the A and B chains of EPIL, one antibody (Ab1661) was directed against the A chain 115-139 and the B chain 23-52 portions. Immunohistochemistry based on antibody 7381 to pro-EPIL and antibody 1661 to EPIL demonstrated that the cytotrophoblast from early placenta preferentially expresses the pro-EPIL peptide, whereas the EPIL peptide is expressed by both the cytotrophoblast and the syncytiotrophoblast. At term, the pro-EPIL peptide was detected in villous cytotrophoblast cells, whereas the EPIL peptide was not detected. Moreover, in vitro experiments performed on term placenta showed that the steady state levels of INLS-4 mRNA in the cytotrophoblast are 10 times (one log unit) lower than in the differentiated villous syncytiotrophoblast cells. Taken together, these findings reveal that expression of EPIL peptides in the villous cytotrophoblast is different from that displayed by the syncytiotrophoblast. Finally, these data are the first demonstration that INSL4 mRNA are translated into pro-EPIL and EPIL peptides.

Amino Acid Sequence↗
PubMed1997

[Evaluation of impaction on bone nail and bone plate of the pertrochanteric fracture].

PURPOSE OF THE STUDY: Impaction in pertrochanteric fracture sites is a well known phenomenon; the screw-plate system is designed to stabilise the fracture. Although easier to use, the risk with the nail-plate system is postoperative penetration of the nail into the joint. The present study was conducted to determine the exact conditions of the impaction, and to identify possible ways to improve the nail-plate system. MATERIAL-METHOD: The study included 129 cases of pertrochanteric fracture, excluding sub-trochanteric fractures. All fractures were fixed with a 130 degrees angulated nail-plate. In all cases, consolidation was uneventful after 8 to a 12 weeks. The anatomical type of fracture, i.e. stable or unstable, was determined according to the size of the intermediary fragment, including the trochanter minor. The displacement was measured as the difference between the length of the nail and the length of the femoral head and neck measured along the axis of the femoral neck. The parameters examined were: fracture stability degree, bony mineralisation (Singh Index), nail length, femoral neck, length nail position in the femoral head, and above all, fracture reduction. All these parameters were computerised and compared using Stat View statistics software. RESULTS: Impaction was observed in 43 per cent of cases. Among these, 25 per cent were rated as slight (1 to 5 mm), 18 per cent as moderate (over 5 mm) and 9 per cent as marked (10 to 25 mm). Impaction was associated with demineralisation of the bone tissue (p = 0.001). The anatomical classification of the fracture was not a determining factor (p = 0.19), as marked displacements were also recorded in stable fractures. A posterior and inferior position of the intramedullary nail in the femoral head is one of displacement determining factors (p = 0.004, two-sided 1 test). Valgus over-correction is the most important factor, especially when it is associated with bony demineralisation (p = 0.02) and an inadequately centred intramedullary pin (p = 0.02). Shorter the femoral neck, and shorter the nail, greater was the frequency of nail articular penetration. DISCUSSION: The risk of articular penetration therefore reaches 15 per cent in petrochanteric fractures repaired with a nail plate, set at an angle of 130 degrees. A short neck, a cervicodiaphyseal angle superior to 140 degrees, and demineralisation are the three determining parameters. Stable or unstable fracture has in fact little effect on displacement incidence, and therefore does not, on its own, warrant the use of a prosthesis in comminuted fractures. The authors compared their results to literature on progressive sliding system: the incidence of complications associated with this type of fracture treatment is identical, but the determining parameters are different. CONCLUSION: The study shows that the nail-plate is efficient and provides simple and solid fracture fixation. However, this osteosynthesis material needs to be modified in order to improve its fixation in the femoral head.

Adult↗
PubMed1997

Cerebral arteriovenous malformations: the value of radiologic parameters in predicting response to radiosurgery.

PURPOSE: To define the morphological patterns of cerebral arteriovenous malformations (AVMs) that influence their response to radiosurgery at 2 years. METHODS: We retrospectively reviewed the yearly MR and angiographic follow-up studies in 102 patients who had radiosurgical treatment for cerebral AVMs between 1990 and 1992. Parameters studied were maximum length and volume of the nidus, position relative to the midline, anatomic structures involved, sectional anatomic location (depth within the brain tissue), angioarchitecture, and Spetzler and Martin grading. Statistical analysis determined their influence on treatment results at 2 years. RESULTS: Parameters that correlated with obliteration at 2 years were maximum length less than 25 mm, small volume, sectional location deep within brain tissue, and plexiform angioarchitecture. Ventricular and paraventricular locations correlated with nonobliteration at 2 years. CONCLUSION: This study highlights the role of two new morphological parameters in predicting the efficiency of radiosurgery in the treatment of cerebral AVMs: depth within the parenchyma and angioarchitecture. It also emphasizes the usefulness of sectional imaging in the work-up before radiosurgery.

Adolescent↗