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Biomedical subjects

M Bonnet

Publications and source records attributed to M Bonnet.

At least 19 recordsLinked to original sources
PubMed1992

Prognostic value of new retinal tears associated with the development of postoperative proliferative vitreoretinopathy.

We prospectively evaluated for the presence of new retinal tears 60 eyes of 60 patients who developed recurrent retinal detachment complicated by proliferative vitreoretinopathy (PVR) after surgery for primary rhegmatogenous retinal detachment. New retinal tears associated with the development or recurrence of postoperative PVR were disclosed in 27 eyes (45%). New tears were categorized into two distinct groups: (1) peripheral new tears and (2) posterior new tears. Peripheral new tears were disclosed in 11 eyes. They were invariably located at the posterior edge of the vitreous base and showed a prevalence in the inferior quadrants. The prognosis for permanent retinal reattachment after reoperation was not influenced by the presence of peripheral new tears. Posterior new tears were disclosed in 19 eyes. They were located in the mid-periphery or close to the posterior pole. They were more frequent in grade D PVR (57.7%) compared with grade C PVR (11.7%) (P less than 0.01). Posterior new tears were associated with a poor prognosis. In grade D PVR the anatomic success rate following repeated surgery was only 13.3% (2/15 eyes), whereas all eyes with grade D PVR and no posterior new tears were successfully reattached (P less than 0.001). Failures to reattach the retina were related to recurrent PVR. It is concluded that the development of posterior new tears in postoperative PVR reflects a severe and active PVR process.

Adolescent↗
PubMed1992

Dantrolene inhibits halothane-induced membrane reorganization. A study using 31P-NMR and differential scanning calorimetry.

The action of the relaxing agent dantrolene on dipalmitoylphosphatidylcholine (DPPC) model membranes in the presence and absence of the general anesthetic halothane has been investigated by DSC and 31P-NMR. Dantrolene has a weak effect on both the thermodynamic and NMR parameters of the pure model membrane. When halothane is present in the system, the relaxing agent acts to counterbalance the strong anesthetic-induced membrane perturbation. This is reflected in DSC experiments by a change of the enthalpy variation (delta H) and of the main gel-to-fluid phase transition temperature (Tc) towards the values of the pure lipid system. The amount of halothane-induced small tumbling vesicles, as detected by 31P-NMR by the superposition of an isotropic line on a lamellar-type powder spectrum, is considerably reduced upon dantrolene addition. This means that the relaxing agent "cures" the membrane de-structuring action promoted by halothane. Membranes first treated with dantrolene are also protected from the halothane perturbation. So, the relaxing agent is both "curative" and "preventative" against halothane. The optimum effect is obtained for 1 dantrolene molecule per ca 34 halothane molecules. The mechanisms of action were discussed in relation to membrane fluidity.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1992

In vitro and in vivo intraleukocytic accumulation of azithromycin (CP-62, 993) and its influence on ex vivo leukocyte chemiluminescence.

The accumulation of azithromycin in phagocytic cells was studied both in vitro by using a radiolabelled drug and a bioassay and in vivo for 12 volunteers receiving 1.5 g (total dose) orally within 3 days. In vitro, neutrophils and unfractionated blood leukocytes accumulated azithromycin up to 160-fold the extracellular concentration within 1 h at 37 degrees C but less than 3-fold at 4 degrees C. Dead cells accumulated up to 30-fold azithromycin, whereas NaF-treated cells accumulated up to 60-fold arithromycin. The mean efflux from preloaded cells was at most 31.0% +/- 10.6% (standard error of the mean) of the cell-associated concentration within 4 h of incubation at 37 degrees C in drug-free buffer. In vivo, the azithromycin concentration was 45.2 +/- 6.1 mg/liter of intracellular fluid at 2 h after the third dose and 36.6 +/- 8.3 mg/liter at 1 week thereafter. The corresponding concentrations in serum were 0.2 +/- 0.1 (2 h) and less than 0.05 (1 week). The luminol-enhanced chemiluminescence response induced by phorbol myristate acetate, opsonized zymosan, and two opsonized strains of Haemophilus influenzae (a type b capsulated strain and a noncapsulated strain) was also studied ex vivo by using the blood leukocytes from the 12 test volunteers and 4 control volunteers at 2 and 6 h after the third oral dose of azithromycin and at 2, 4, and 7 days thereafter. Azithromycin did not influence this response despite high levels of cellular accumulation.

Adult↗
PubMed1992

[C2F6 in the treatment of retinal detachment associated to PVR: therapeutic trial].

We conducted a clinical trial on C2F6 as a retinal tamponade in the management of retinal detachment with proliferative vitreoretinopathy. Twenty seven eyes of 27 consecutive patients were enrolled in the study. Permanent retinal reattachment was achieved in 21 eyes (78%). The anatomic success rate was 85% in eyes with grade B PVR (17/20 eyes), and 57% in eyes with grade C and D PVR (4/7 eyes). The success rate was as high as that achieved in a previous series of eyes managed with the use of C3F8 combined with the same surgical technique. C2F6 shares the advantages of C3F8 in the management of retinal detachments complicated by proliferative vitreoretinopathy. However its absorption is more rapid as compared to C3F8. This is an advantage with regard to the postoperative disadvantages of gas tamponade. Further clinical use on a larger series of patients is required to confirmed the preliminary results.

Cryosurgery↗
PubMed1992

[Incidence of signs indicating psoriatic rheumatism in radiological involvement of fingers and toes. Apropos of 193 cases of psoriatic arthropathy].

On the basis of 193 cases of psoriatic arthropathy, the authors sought the incidence and rapidity of onset of signs suggestive of this type of rheumatic disorder when there are radiological lesions of the fingers and toes. They conclude that when such radiological lesions exist, signs suggestive of psoriatic arthropathy are frequent (90%), early (85% of cases of psoriatic arthropathy present for less than 5 years) and predominantly involve the distal parts of the fingers and toes (85.5%). The authors consider that the signs which distinguish psoriatic arthropathy from rheumatoid arthritis are due to an extrasynovial process of enthesopathic origin.

Adolescent↗
PubMed1992

[Late macular pseudo-hole after surgical peeling of a premacular membrane].

We present three clinical cases showing a pseudo macular hole that developed late after an uneventful surgical removal of an epiretinal membrane. The pseudo macular hole developed 3 to 19 months postoperatively. The macular changes seen in all cases showed stricking differences when compared with pseudo macular holes associated with epiretinal membranes. A hypothesis is suggested for the pathogenesis.

Diagnosis, Differential↗
PubMed1991

Halothane-induced membrane reorganization monitored by DSC, freeze fracture electron microscopy and 31P-NMR techniques.

The effect of the volatile anaesthetic halothane on the structure and dynamics of lipid multilayers (dimyristoyl- and dipalmitoylphosphatidylcholine, DM- and DP-PC, aqueous dispersions) was studied using Differential Scanning Calorimetry (DSC), Freeze Fracture Electron Microscopy and solid state phosphorus-31 Nuclear Magnetic Resonance (31P-NMR). The action of the drug depends upon the halothane-to-lipid molar ratio, Ri, and temperature. With DPPC lipids, three main regions can be distinguished: i) 0 less than Ri less than 0.7, ii) 0.7 less than Ri less than 2 and iii) Ri greater than 2. As Ri increases in the first region, a linear decrease in the main gel-to-fluid phase transition temperature (Tc), a broadening in the DSC transition peak and a lowering in the enthalpy variation (delta H), are observed. A minimum in delta H is reached at Ri = 0.7. In this region, 31P-NMR spectra indicate that the multibilayer structure is maintained. In the second region, Tc still decreases with the same slope, but delta H increases up to a plateau value for Ri = 2. In the lipid fluid phase, an isotropic NMR line appears superimposed on the powder pattern that corresponds to a lamellar phase. For Ri greater than 2, Tc and delta H remain almost constant. At values of temperature that are greater than Tc, a growing isotropic line occurs in 31P-NMR spectra. This means a new supramolecular structure made of lipids and halothane is stabilized. This structure has been characterized as small vesicles of about 400 A to 600 A diameter by Freeze Fracture electron microscopy observations. With DMPC and low ratios (Ri less than or equal to 2), DSC and NMR results are similar to those obtained for DPPC. However, the minimum delta H is reached at Ri = 0.2 and the decrease in Tc is faster than for DPPC when Ri increases from 0. For Ri greater than 2, while Tc and delta H remain constant as in the case of DPPC, 31P-NMR spectra of DMPC systems show a superimposition of an isotropic line and two powder patterns, which correspond to small tumbling vesicles, a possible hexagonal phase and a lamellar phase respectively. Halothane, thus acts on model membranes in two different steps: at low Ri the bilayer is disturbed but keeps its structure. Whereas for higher drug concentrations, a new organization of lipids seems to be stabilized for T greater than Tc.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1991

Serous macular detachment associated with optic nerve pits.

Between September 1972 and March 1989, we examined 25 eyes of 24 patients exhibiting optic nerve-head pits associated with serous macular detachment. We followed 21 patients for a period of 1-15 years (mean, 62 months). Various treatment modalities were applied, depending on the time of initial examination. Five eyes underwent no treatment and three eyes underwent two distinct treatment modalities. Photocoagulation treatment was performed in ten eyes. Argon laser photocoagulation was combined with intravitreal injection of pure SF6 in eight eyes and of C3F8 in three. Intravitreal injection of pure C3F8 without photocoagulation was carried out in two eyes. The results of biomicroscopy of the vitreous gel and of fluorescein angiography and the responses to the various treatment modalities support the hypothesis that the mechanism underlying serous macular detachment complicating optic nerve-head pits is traction retinal detachment combined with a rhegmatogenous component in the roof of the optic pit.

Adolescent↗
PubMed1991

Management of retinal detachment after penetrating eye injury.

Between December 1981 and April 1989 the authors operated on 61 eyes presenting with retinal detachment after penetrating eye injury. Air or expanding gases were used for retinal tamponade. The follow-up between complete gas absorption and last examination ranged from 8 months to 8 years (mean, 29 months). Retinal reattachment was achieved in 50 eyes (81.9%). Anatomic success was achieved by a single operation in 43 eyes (70.5%). A postoperative visual acuity of 20/40 or better was achieved in 46% of the eyes. The factors found to influence the postoperative outcome adversely include (1) association of severe blunt trauma (P less than 0.05), (2) anterior proliferative vitreoretinopathy (PVR) involving two or more quadrants (P less than 0.01), and (2) retinotomies (P less than 0.007).

Adolescent↗
PubMed1991

Changes in electromyographic responses to muscle stretch, related to the programming of movement parameters.

Three experiments are reported that used the advance information paradigm which consists of providing subjects with either no or partial information about an upcoming movement. Subjects moved handles to control the vertical displacements of CRT beams, to point to eight targets. The illumination of different combinations of these targets prior to movement execution provided advance information about which hand, movement direction, or movement extent would be required. Reaction time (RT), integrated EMG activity in the forearm extensor and flexor muscles, and M1, M2, and M3 components of the stretch reflex responses triggered in these muscles were analysed as a function of the precued movement parameter. Compared to the no-information condition, RT decreased in all precue conditions; however, the reduction was greater when direction than when hand was precued, and greater when hand than extent was precued. The EMG activity of forearm muscles increased during the preparatory period in all precue conditions, but generally did not differ among them. An overall facilitation of the stretch reflex components was observed in all precue conditions. This facilitation: (1) was greater for flexor than extensor muscles, (2) was similar regardless of the degree of extent precued, (3) differed for the M2 and M3 components depending on whether the responding hand precued was ipsilateral or contralateral. When the precued movement direction was considered, similar changes in the M3 component were found in extensor and flexor muscles. M3 was facilitated when the muscle was precued as an agonist and was inhibited when it was precued as an antagonist. Collectively these data provide support for a motor programming conception of movement organization.

Adolescent↗
PubMed1991

[Papillary hyperfluorescence caused by traction of the vitreous body].

We present 4 clinical cases showing late dye leakage on the optic disc related to vitreous traction. Optic disc dye leakage disappeared following posterior vitreous detachment in one patient, delamination of the posterior hyaloid in two patients and segmentation of the posterior vitreous surface in one patient. Vitreous traction should be added to the previously described causes of optic disc dye leakage.

Adult↗
PubMed1991

[Spontaneous course of retinal detachment with macular hole in patients with severe myopia].

We followed-up without any treatment 17 eyes of 14 highly myopic patients affected by a retinal detachment confined to the posterior pole. The follow-up ranged from 3 to 92 months (mean follow-up: 4 years). The retinal detachment remained unchanged in 12 eyes (70.5%), spontaneously reattached in 3 eyes (17.6%), and progressed to the periphery in 2 eyes (11.7%). At the end of the follow-up period, 68.7% of eyes retained useful visual acuity. From these data we conclude that 1) immediate surgical management is probably unnecessary in a number of myopic eyes with retinal detachment confined to the posterior pole and 2) such detachments likely are traction retinal detachments rather than rhegmatogenous retinal detachments due to a macular hole.

Adult↗
PubMed1990

CNV, stretch reflex and reaction time correlates of preparation for movement direction and force.

Ten human subjects were tested in a pre-cued choice reaction time (RT) paradigm in which the warning stimulus gave a varying amount of prior information regarding the direction (flexion or extension) or force level (weak or strong) for an impending right forearm movement. During the preparatory period (PP), either CNV was monitored from 8 scalp leads, or elbow stretch reflexes were tested at selected times using mechanical torque steps as stimuli. Mean RTs increased as the amount of prior information decreased. The locus of maximal rate of increase of scalp negativity migrated from the frontal lobe to the parietal lobe during the PP, under all conditions. Using laplacian derivations, it was found that the CNV at Cz did not distinguish among the different information conditions, whereas the CNV over the somatosensory arm area was greatest when direction information was given in advance. The CNV over the arm motor region was greatest when force information was available. The last 100 msec of the PP was characterized by the development of current sources over the premotor region for full information, and over the somatosensory region for the other conditions. This coincided with the appearance of very large late stretch reflexes or triggered reactions in the prepared agonist for full information, indicating that the intended movement had been fully processed by this time and awaited only a sensory trigger. The data support a parametric model of motor preparation, with direction and force being processed by at least partially independent networks.

Adolescent↗
PubMed1990

Influence of teicoplanin and vancomycin on degranulation by polymorphonuclear leucocytes stimulated by various agonists: an in-vitro study.

The interaction between vancomycin and teicoplanin (50 and 100 mg/l) on human neutrophils was studied using fMLP- and A23187-induced degranulation of elastase, beta-glucuronidase and vitamin B12-binding-protein. Each of these proteins is a marker of a different population of granules. fMLP-induced degranulation of beta-glucuronidase was significantly impaired by pre-incubating the neutrophils with teicoplanin (without affecting cell viability) although the inhibition was at most 23% at 100 mg/l, a concentration not achieved in the serum of patients after normal doses. Calcium ionophore-induced degranulation of beta-glucuronidase and elastase were slightly impaired (Student two-tailed; P less than 0.1) by both glycopeptides (beta-glucuronidase) and teicoplanin only (elastase). Again, inhibition remained below 25%. Vancomycin and teicoplanin at high concentrations, seldom achieved in patients, can moderately impair neutrophil degranulation.

Anti-Bacterial Agents↗
PubMed1990

[Retinal detachment and massive vitreoretinal proliferation: clinical study of 60 cases].

Perfluoropropane gas as an adjunct to vitreoretinal microsurgery in the management of proliferative vitreoretinopathy. Pure perfluoropropane gas was used as an adjunct to vitreoretinal microsurgery in 60 eyes of 60 patients with rhegmatogenous retinal detachment complicated by proliferative vitreoretinopathy. 0.3 ml to 1.8 ml (average 0.9 ml) of pure perfluoropropane gas were used. The surgical procedure included a vitrectomy and a scleral buckling procedure in all patients. The follow-up after complete gas absorption ranges from 6 months to 3 years in the successful eyes. Total retinal reattachment was achieved in 41 eyes (68.3%). The anatomical success rate was 88% (22/25 eyes) in grade C1-C2 PVR cases, 68.7% (11/16 eyes) in grade C3-D1 PVR cases, and 42% (8/19 eyes) in grade D2-D3 PVR cases. Visual acuity of 0.1 or better was achieved in 80% of eyes with grade C PVR and 61% of eyes with grade D PVR. Visual acuity of 0.4 or better was achieved in 26.9% of eyes with grade C PVR. Macular changes were revealed by fluorescein angiography in 53% of successful eyes. We recommend the use of C3F8 rather than SF6 in the management of rhegmatogenous retinal detachment complicated by PVR. In our experience the anatomical success rate achieved with C3F8 is approximately the same as that achieved with SF6. However permanent retinal reattachment was achieved with a single operation in 87.8% of successful eyes of the present series of patients manages with C3F8 as compared to only 12% of successful eyes of a previous series of patients managed with SF6.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗