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J Benoit

Publications and source records attributed to J Benoit.

At least 73 records · Page 4Linked to original sources
PubMed1990

Temporal relationship between ERG components and geniculate unit activity in rabbit.

The purpose of this study was to examine if there is an ERG component (alpha-wave, b-wave, oscillatory potentials) which can be used to account for the intraretinal processing time. To address this issue, ERGs and LGN unit responses were recorded simultaneously from anesthetized and paralyzed rabbits. A gradual decrease in the intensity of the light stimulus yields a progressive increase in the latency of the LGN unit response. A similar, highly correlated (r = 0.91 +/- 013), latency shift was also noted for one oscillatory potential (OP2). In comparison, correlation coefficients of r = 0.63 +/- 0.27 and r = 0.70 +/- 0.29 were obtained for the alpha- and b-wave respectively. Furthermore, in 77.6% of the cells examined, OP2 preceded LGN unit activity while the b-wave preceded LGN activity in only 17.8% of the cases. Our results suggest that, of all the retinal potentials considered, the peak time of OP2 better reflects the primary visual processes and the intraretinal time taken for visual processing.

Animals↗
PubMed1990

The oscillatory potentials in response to stimuli of photopic intensities delivered in dark-adaptation: an explanation for the conditioning flash effect.

Previous studies reported that the oscillatory potentials (OPs) evoked to the first flash of a series were always smaller than those produced by the later flashes. This conditioning flash effect (CFE) was suggested to arise from rod inhibition of cone-mediated OPs. We investigated this CFE with the use of two stimulus intensities: 10 cd sec m-2 and 1 cd sec m-2. While the highest intensity did yield the previously reported CFE, the dimmest intensity did not. Our results further indicated that with the brightest stimulus, there is a significant increase in the interpeak interval of the OPs, while dimmest stimuli failed to reveal a similar marked increase. We also noted a significant correlation between the frequency domain of the OPs (as estimated with the interpeak interval) and the amplitude of the OPs (individual or collective: SOPs). Our results would also suggest that the observed CFE could result from a cone inhibition of rod-mediated OPs.

Adaptation, Ocular↗
PubMed1990

Vidarabine-loaded nanoparticles: a physicochemical study.

The chemical reaction of vidarabine (VIDA) with isohexyl cyanoacrylate nanoparticles in a pH-dependent fashion occurs only in the presence of dioctylsulfosuccinate (DOSS). The formation of an ion pair with DOSS allows a better contact of VIDA with the monomer during the polymerization process taking place in micelles. On the basis of molecular weight profiles of the polymer, determined by gel permeation chromatography (GPC), it is proposed that VIDA induces the polymerization of cyanoacrylic monomers through a zwitterionic pathway. This mechanism allows the covalent linkage of the drug with the polymer, which is consistent with NMR experiments. The present study illustrates the need for physicochemical studies in the design of new colloidal drug delivery formulations.

Chemical Phenomena↗
PubMed1990

[Synovial osteochondromatosis of the knee and synovial chondrosarcoma. Report of 2 cases].

The possible transformation of synovial osteochondromatosis into chondrosarcoma is rarely reported in the literature, as well as the coexistence of the two entities. The authors have observed two such cases. The first one was discovered by arthroscopy in the course of a synovial osteochondromatosis associated with a posterior tumour proved secondarily as being a chondrosarcoma. On the contrary, the second case presented as a destroying tumour invading the entire joint and proved secondarily as being a benign osteochondromatosis. Cartilaginous masses very important may lead to bone destruction in the course of benign osteochondromatosis. However, in such cases, the possibility of an associated or a secondary chondrosarcoma must be looked for using radiology, arthroscopy and microscope examination.

Chondromatosis, Synovial↗
PubMed1990

[Early reoperation for infection in orthopedic surgery of the leg (arthroplasties and hip surgical procedures excluded)].

The authors report 32 cases of post-operative infections reoperated before the first month of which 12 articular fractures of the tibia. 6 tibial osteotomies of valgisation, 6 tibial diaphyseal fractures, 2 fractures of the lower extremity of the femur, 2 bimalleolar fractures, 1 serious knee sprain, 1 patellar fracture, 1 calcaneum fracture and an arthroscopic arthrolysis of the knee. Twelve of them had an articular infection. Globally, they have obtained 22 satisfactory results (very good or good) and 10 non satisfactory results out of which 2 deaths and 1 amputation. The bad results were due either to a particularly aggressive germ (streptococcus and gas gangrene), or to an articular infection insufficiently controlled: 5 out of the 10 arthrites on infected articular fractures have had a non satisfactory result. As for metaphyseal infections, a simple cleaning has given 4 very good results out of 6, the 2 excluded being very serious and special cases. For the 6 diaphyseal leg infections after osteosynthesis, the early reoperation has not avoided a secundary graft in a picture of infected pseudoarthrosis. In view of this series, the authors propose to adapt the cleaning operation to the localisation and to the presence or not of an articular infection.

Adolescent↗
PubMed1989

The diagnostic use of the second oscillatory potential in clinical electroretinography.

Of all the electroretinogram (ERG) components (a-wave, b-wave, and oscillatory potentials) only one oscillatory potential, OP2, was found to be significantly correlated with the absolute intensity of the flash stimulus (i.e., the intensity of the stimulus irrespective of the state of retinal adaptation). Our finding was further confirmed in single cell recordings of lateral geniculate unit activity in rabbits in which peak time of OP2 was found to correlate better with the geniculate activity. For these reasons we have identified OP2 as the "intensity coding" oscillatory potential of the ERG. In order to investigate if this new feature could have some clinical significance, we examined photopic ERGs recorded from patients affected with various retinopathies. In most instances the peak time of OP2 paralleled that of the b-wave, that is, in the ERG with delayed b-wave the peak time of OP2 was also delayed, while in ERGs with normal b-wave peak time the peak time of OP2 was also normal. However, in some conditions (especially in cone-rod diseases) a delayed OP2 was found in ERGs with normal b-wave peak times.

Adult↗
PubMed1989

Methotrexate diffusion from acrylic cement. Local chemotherapy for bone tumours.

We investigated the possible use of acrylic cement containing chemotherapeutic drugs in the treatment of malignant lesions in bone. The diffusion of methotrexate (MTX) from methylpolymethacrylate implants was studied in vitro: polymerisation of the cement did not destroy the drug; liberation began immediately and about 10% was released by 18 hours. Some release continued for as long as six months. In vivo experiments on rats with induced osteosarcoma showed that MTX in cement had both local and general effects which were dependent on the dosage. A series of 17 large dogs with spontaneous osteosarcoma were then treated by local resection and cement containing MTX. General chemotherapeutic effects were detectable from 2 hours to 5 days, survival was increased and local recurrence was reduced, but there were four cases of delayed wound healing. Preliminary studies in human patients confirm the possibility that this method of local chemotherapy could be a useful addition to the treatment of malignant tumours of bone.

Animals↗
PubMed1989

[Beta-2 microglobulin and amyloid osteoarthropathy in patients undergoing chronic hemodialysis].

The incidence of beta-2 microglobulin amyloidosis was assessed in two populations of chronic hemodialysis patients. Out of 34 patients who underwent biopsy during orthopedic surgery (33 cases) or autopsy (1 case), 26 had amyloid deposits which fixed anti-beta microglobulin serum. Out of 55 unselected patients treated for over months at the dialysis centre, 14 (25%) had clinical symptoms suggesting amyloidosis and out of 43 patients who had a systematic radiological skeletal survey, 23 (53%) had bone deposits. The plasma beta microglobulin concentrations (about 20 times the normal value) we not significantly different whether or not the patients had histological proven amyloidosis, clinically or radiologically probable amyloidosis, no detectable amyloidosis. However, the duration of hemodialysis was longer in those with proven or highly probable amyloidosis. The finding illustrate the indirect role of elevation of beta-2 microglobulin in the genesis of this pathology and also the necessity of lowering its concentration in order to avoid the long term complications of osteoarticular deposits, the functional consequences of which may be very serious.

Adult↗
PubMed1989

[Osteonecrosis of the femur head in patients with renal transplant. Apropos of 82 surgically treated hips].

Fifty-six renal transplanted patients having an average age of 33 years have been operated on for necrosis of the femoral head from 1973 to 1988. They totalise 85 cephalic necrosis due to the therapeutic peaks of corticotherapy. The femoral condyles were affected by the necrosis in 21 patients, and the humeral head in 16 patients. 82 surgical operations of first intention and 18 resumptions leading to 100 the total number of operations. The 26 drilling gave place to 11 by arthroplasty. The good results of the drillings only concern the infraradiological stages and the MRI allows to detect the non symptomatic stages 0. The 33 intermediate prosthesis did not lead to septic complications but 9 cotiloidal alterations of which 4 important with a resumption by total prosthesis. 36 total prosthesis were realized out of which 13 for resumption. Two early and two late suppurations after septicemia complicated the evolution. If at stage 0 or 1 the drilling seems to remain a reliable indication, the total prosthesis is the only possible solution for invalidating stages IV, the intermediate prosthesis seems to be able to keep a place in the intermediate stages.

Adolescent↗
PubMed1988

[Joint complications in patients with chronic renal failure hemodialyzed for over 10 years. 40 cases].

A retrospective study of 40 patients with chronic renal failure who underwent haemodialysis for more than 10 years (mean: 153 months) showed that 18 patients (45 p. 100) had arthralgia in the shoulders, hands, wrists and knees, 13 (32 p. 100) had carpal tunnel syndrome requiring surgery, and 20 (50 p. 100) were found to have bone cavities in the humeral head, external supra-acetabular region, carpus and patella. Aluminium overload was present in 47 p. 100 of the patients, and amyloid deposits were found in 10 of the 12 patient operated upon for carpal tunnel syndrome. This study confirms the frequency in patients under long-term haemodialysis of an articular pathological entity consisting of arthralgia, carpal tunnel syndrome, juxta-articular bone cavities and amyloid deposits which are now known to be made of beta 2-microglobulin. The initial lesion seems to affect the synovial membrane; it appears to be facilitated by age and is often associated with aluminium overload. The mechanism(s) responsible for amyloid deposits remain (s) to be elucidated.

Adolescent↗
PubMed1988

Comparative effects of four surfactants on growth, contraction and adhesion of cultured human fibroblasts.

A range of surfactants, including the anionic sodium dodecyl sulfate, the cationic cetyltrimethylammonium bromide and the non-ionics octylphenoxy polyethoxyethanol (Triton X100) and polyoxyethylene 20 sorbitan monoleate (Tween 80) was studied for effects on proliferation, contractibility and attachment of cultured human fibroblasts. Only ionic surfactants exhibited a stimulatory effect on fibroblast proliferation, whereas all the surfactants tested increased the contraction of collagen gels containing fibroblasts, with the greatest effect from the non-ionic surfactants. This activity was not correlated with an increase of cell population or cell attachment within the collagenous matrix. The activity of the surfactants was seen only at levels close to their LD50 values and in a narrow range of concentrations. Thus, we consider that they are the result of the so-called hormesis phenomenon.

Adult↗
PubMed1988

Effects of cyclic adenosine monophosphate on human chorionic gonadotropin and estradiol output by cultured human placental cells.

We have previously shown that adenosine-3',5'-cyclic monophosphate (cAMP) inhibits basal estradiol output in human trophoblast cells. The objective of this study was to investigate further the effect of 8-bromo-cAMP on the conversion of C19 androgens to estradiol by placental cells. Trophoblast cells were prepared from human term placenta and maintained in monolayer culture. On days 3 and 4 of culture, these cells were treated with dehydroepiandrosterone sulfate, androstenedione, or testosterone with or without the concomitant presence of 8-Br-cAMP. 8-Br-cAMP markedly enhanced human chorionic gonadotropin secretion into the culture medium. On the other hand, the concomitant addition of 8-Br-cAMP with the androgen precursors led to an inhibition of estradiol output. The concentrations of androstenedione and dehydroepiandrosterone in the culture medium after treatment with dehydroepiandrosterone sulfate were elevated by the concomitant presence of 8-Br-cAMP. From these results we conclude that 8-Br-cAMP enhances human chorionic gonadotropin output in human term placental cells, whereas the presence of 8-Br-cAMP in cells given androgen precursors inhibits estradiol output, probably at the level of aromatization.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1988

Differential effects of 8-bromo-cyclic AMP on human chorionic gonadotropin (hCG), progesterone and estrogen production by term placental cells.

The present study examined the effects of a cAMP analog on the output of hCG and progesterone (P) in human term trophoblast cells in culture, as well as the conversion of androstenedione and testosterone to estradiol--17 beta and estrone by these cells. The levels of hCG and P in the culture medium increased throughout the four-day culture period. Addition of 8-bromo-adenosine-3',5'-monophosphate (8-Br-cAMP), forskolin or cholera toxin (but not 8-Br-cGMP) stimulated hCG and P production by the cultivated placental cells. In contrast, the presence of 8-Br-cAMP for 2 days significantly decreased basal estradiol-17 beta output, as well as conversion of androstenedione to estradiol-17 beta; the conversion of androstenedione to estrone was not affected. 8-Br-cAMP attenuated the conversion of testosterone to both estradiol-17 beta and estrone. These results further support the view that cAMP could have both stimulatory and inhibitory actions on placental hormonogenesis.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1986

Amniostat-FLM: an initial clinical trial with both vaginal pool and amniocentesis samples.

Amniostat-FLM, a new rapid slide agglutination test, was compared with thin-layer chromatography as a method for detecting phosphatidylglycerol in amniotic fluid. This is the first reported use of Amniostat-FLM to evaluate vaginal pool and contaminated vaginal pool amniotic fluid. One hundred one of 161 amniotic fluid samples were collected from the vaginal pool. Thirty-nine of these were contaminated. Vaginal pool amniotic fluid, whether contaminated or not, did not adversely effect the ease of performance, reliability, or interpretation of Amniostat-FLM. This test seems ideally suited to institutions where 24-hour availability of thin-layer chromatography is not available. In institutions where it is available, Amniostat-FLM could be used as a screening test. Amniostat-FLM was found to be significantly less sensitive when compared with thin-layer chromatography in detecting the presence of phosphatidylglycerol. At our institution the screening of amniotic fluid samples with Amniostat-FLM before use of thin-layer chromatography was only cost effective at greater than or equal to 34 weeks of gestation.

Agglutination Tests↗