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P Menei

Publications and source records attributed to P Menei.

At least 19 recordsLinked to original sources
PubMed1998

NGF release from poly(D,L-lactide-co-glycolide) microspheres. Effect of some formulation parameters on encapsulated NGF stability.

Poly(d,l-lactide-co-glycolide) (PLGA 37.5/25 and 25/50) biodegradable microparticles, which allow the locally delivery of a precise amount of a drug by stereotactic injection in the brain, were prepared by a W/O/W emulsion solvent evaporation/extraction method which had been previously optimized. The aim of this work was to study the influence of two formulation parameters (the presence of NaCl in the dispersing phase and the type of PLGA) on the NGF release profiles and NGF stability during microencapsulation. A honey-comb-like structure characterized the internal morphology of the microspheres. The initial burst was attributed to the rapid penetration of the release medium inside the matrix through a network of pores and to the desorption of weakly adsorbed protein from the surface of the internal cavities. The non-release fraction of the encapsulated protein observed after twelve weeks of incubation was accounted for firstly by the adsorption of the released protein on the degrading microparticles and secondly by the entanglement of the encapsulated protein in the polymer chains. The use of sodium chloride in the dispersing phase of the double emulsion markedly reduced the burst effect by making the microparticle morphology more compact. Unfortunately, it induced in parallel a pronounced NGF denaturation. Finally, it appeared that microparticles made from a hydrophilic uncapped PLGA 37.5/25 in the absence of salt, allowed the release of intact NGF at least during the first 24 h as determined by both ELISA and a PC12 cell-based bioassay.

Animals↗
PubMed1998

Schwann cells genetically modified to secrete human BDNF promote enhanced axonal regrowth across transected adult rat spinal cord.

The infusion of BDNF and NT-3 into Schwann cell (SC) grafts promotes regeneration of brainstem neurones into the grafts placed in adult rat spinal cord transected at T8 (Xu et al., 1995b). Here, we compared normal SCs with SCs genetically modified to secrete human BDNF, grafted as trails 5 mm long in the cord distal to a transection site and also deposited in the transection site, for their ability to stimulate supraspinal axonal regeneration beyond the injury. SCs were infected with the replication-deficient retroviral vector pL(hBDNF)RNL encoding the human preproBDNF cDNA. The amounts of BDNF secreted (as detected by ELISA) were 23 and 5 ng/24 h per 106 cells for infected and normal SCs, respectively. Biological activity of the secreted BDNF was confirmed by retinal ganglion cell bioassay. The adult rat spinal cord was transected at T8. The use of Hoechst prelabelled SCs demonstrated that trails were maintained for a month. In controls, no SCs were grafted. One month after grafting, axons were present in SC trails. More 5-HT-positive and some DbetaH-positive fibres were observed in the infected vs. normal SC trails. When Fast Blue was injected 5 mm below the transection site (at the end of the trail), as many as 135 retrogradely labelled neurones could be found in the brainstem, mostly in the reticular and raphe nuclei (normal SCs, up to 22, mostly in vestibular nuclei). Numerous neurones were labelled in the ventral hypothalamus (normal SCs, 0). Also, following Fast Blue injection, a mean of 138 labelled cells was present in dorsal root ganglia (normal SCs, 46) and spinal cord (39 vs. 32) rostral to the transection. No labelled spinal neurones rostral to the transection were seen when SCs were not transplanted. Thus, the transplantation of SCs secreting increased amounts of BDNF improved the regenerative response across a transection site in the thoracic cord. Moreover, the enhanced regeneration observed with infected SCs may be specific as the largest response was from neurones known to express trkB.

Adult↗
PubMed1997

[Intradural lumbar disk hernias. Apropos of 6 cases and review of the literature].

Transdural discal hernia is a rare complication of lumbar discal pathology. In this paper, we report five cases of transdural herniated disc and one intraradicular discal hernia. In the literature review, we found 97 cases since the first case described by Walter Dandy in 1942. The main risk in this exceptional location of discal hernia is to miss an intradural discal piece leading to a poor result. MRI or CT scan with intrathecal contrast can show an intradural lesion but they usually fail to indicate its precise nature.

Adult↗
PubMed1996

Effect of stereotactic implantation of biodegradable 5-fluorouracil-loaded microspheres in healthy and C6 glioma-bearing rats.

OBJECTIVE: Poly(lactic acid-co-glycolic acid) (PLAGA) microspheres are promising systems for interstitial chemotherapy of brain tumors. They can be readily implanted by stereotaxy and are biocompatible with the brain, in which they are totally biodegraded within 2 months. 5-Fluorouracil (5-FU) was selected for encapsulation, because this hydrophilic and antimetabolic drug is not directly neurotoxic and does not readily cross the blood-brain barrier. Also, its anticancer activity may be improved by sustained administration. Furthermore, it is a potent radiosensitizer. METHODS: To study their fate and toxicity, two types of 5-FU-loaded PLAGA microspheres were implanted in healthy rats by stereotaxy. One type presented a fast in vitro release profile (FR), and the second exhibited a slow in vitro release pattern (SR) (100% of the encapsulated 5-FU is released within 72 hours and 18 days, respectively). Periodically, rats were killed for microscopic examination. The efficacy of these microspheres on rat glioma was then evaluated. Seven days after stereotactic implantation of C6 malignant glioma cells in the brain, the rats were treated by intratumoral injection of 5-FU solution, blank microspheres, or 5-FU-loaded microspheres (FR and SR types). The mortality of these treated groups was compared by the log-rank test with that of an untreated group. RESULTS: After implantation of two types of 5-FU-loaded PLAGA microspheres, no sign of clinical or histological toxicity was observed. Entrapped 5-FU crystals were observed until Days 12 and 20 postimplantation within FR and SR microspheres, respectively, which suggests a longer releasing period in vivo than in vitro. In the therapeutic evaluation, only intratumoral implantation of SR-type 5-FU-loaded microspheres significantly decreased the mortality (P = 0.017). CONCLUSION: 5-FU-loaded PLAGA microspheres were implanted in rat brains without evident toxicity. Histological examination suggested a longer sustained delivery period in vivo than in vitro. Intratumoral implantation of SR-type 5-FU-loaded microspheres decreased the mortality of C6 tumor-bearing rats. This effect can be related to the local and the sustained delivery of the drug, because 5-FU administered systemically is ineffective against brain tumors.

Animals↗
PubMed1995

Preparation and characterization of 5-fluorouracil-loaded microparticles as biodegradable anticancer drug carriers.

To provide a device releasing 5-fluorouracil in a controlled manner and injectable into the brain by stereotaxy, biodegradable poly ((+/-)-lactide-co-glycolide) (PLAGA) microparticles were prepared by an emulsion-extraction process. Although the solubility profile of the drug was not suitable for its encapsulation by the aforementioned method, careful choice of process variables allowed significant drug loading, reaching 30%. Thus, the size of the 5-fluorouracil crystals, the organic phase/aqueous phase ratio, the theoretical drug loading and the microparticle size played a predominant role. The microsphere size was adjusted to 20-40 microns by selecting the appropriate PLAGA and polyvinylalcohol concentrations, and the stirring rate of the initial emulsion. It was shown that the microparticle structure depended directly on the experimental conditions governing the precipitation rate of the coating material: two types of microparticles, I and II, were characterized. The morphology of the particles influenced the 5-fluorouracil-release patterns, as did other process parameters, such as the 5-fluorouracil crystal size and the PLAGA concentration. It was possible to sustain the 5-fluorouracil release over 18 days.

Biocompatible Materials↗
PubMed1995

[Transpetrosal approaches to the clivus. Surgical anatomy, challenges and limitations].

Radical excision of skull base tumors is a real challenge for neurosurgeons. The need to preserve the nerves and the vessels in the area lead us to use lateral approaches, if the lesion lies lateral to the cavernous portion of the carotid artery and behind the petrous apex. Lateral approaches are classified into two groups: ventrolateral approaches (in front of the cochlea) and dorsolateral approaches (with or without resection of the bony labyrinth). The three surgical approaches studied were the subtemporal preauricular infratemporal, the subtemporal anterior transpetrosal, and the combined supra and infratentorial presigmoid approach. The approaches were performed on adult cadaver heads fixed in formolin. The technique, the exposure, the modifications and extensions, as well as the problems of reconstruction are discussed.

Dissection↗
PubMed1995

[Infection after long lasting procedure in neurosurgery].

A retrospective study was performed to appreciate the frequency of infectious complications following long duration neurosurgical procedure with or without antibiotic prophylaxis. Among the 6,702 surgical procedures studied 87 lasted more than 6 hours. The frequency of wound infections of those 87 patients was 13.8% whereas it was only 1.43% for the whole group. There was no significant statistical difference between patients who were treated with antibiotics and those who were not. The high frequency of infection by Klebsiella (25% of the identified germs) was caused by a contamination of the intensive care unit. Duration of the surgical procedure, synthetic material and repetitive procedures are important points to analyse when comparing the different publications. If any antibiotic prophylaxis is to be used, it must be adapted to the microbial environment of each care unit.

Anti-Bacterial Agents↗
PubMed1994

Vertebral hemangioma. Spontaneous spinal canal remodeling after fracture.

STUDY DESIGN: The patient in this report had a fracture of a hemangiomatous vertebra with a fragment protruded into the canal and without neurological signs. There was a 12 month follow-up. RESULTS: After conservative treatment, there were no neurologic signs, a good fusion, and natural remodeling of the spinal canal. CONCLUSIONS: The risk of a hemangiomatous vertebra fracture with a fragment retropulsed into the spinal canal and without neurologic signs is low. Also, a remodeling of the spinal canal can occur, as after a burst fracture.

Aged↗
PubMed1994

Fate and biocompatibility of three types of microspheres implanted into the brain.

The implantation of polymer devices in the brain that release neuroactive drugs locally and in a controlled manner is gaining increasing interest. The fates and tissue reactions of poly(epsilon-caprolactone), ethylcellulose, and polystyrene microspheres, prepared by the solvent evaporation method, radiosterilized by gamma-irradiation, and stereotactically implanted in rat brain have been studied by routine staining and immunohistochemistry. During the first few days after implantation, a nonspecific astrocytic brain tissue reaction was observed along with a macrophagous-microglial cell reaction typically found following any damage in the central nervous system, except in the presence of certain foreign body giant cells. Nine months into the experiment, microspheres appeared to be engulfed by histiocytic cells. The microsphere cluster was surrounded by a sheath composed of collagen and astrocytic cells. No necrosis was observed, suggesting the absence of toxicity. In some animals, however, an hydrocephalus developed as a result of obstruction of the medial ventricle by some microspheres.

Animals↗
PubMed1994

Drug targeting into the central nervous system by stereotactic implantation of biodegradable microspheres.

Controlled drug release in the central nervous system through an implantable polymeric vector has been developed in recent years. For this purpose, different polymeric devices composed primarily of synthetic biocompatible and biodegradable polymers have been investigated. The first polymeric devices developed were macroscopic implants (monolithic devices), which required open surgery for implantation. Microencapsulation methods, however, allow the production of microparticles or nanoparticles loaded with neuroactive drugs. Because of their size, these micro- or nanoparticles may be easily implanted by stereotaxy in discrete, precise, and functional areas of the brain without causing damage to the surrounding tissue. Presently, this method is most frequently applied in the fields of neuro-oncology and neurodegenerative diseases, but neurologically, the potential applications of drug targeting by stereotactic implantation of drug-loaded particles are legion.

Biodegradation, Environmental↗
PubMed1994

[Epidural hematoma. Myth and reality, based on 3 exemplary cases].

The acute epidural hematoma is a real surgical emergency with a good outcome if the operation is performed in reasonable delays. In 1994, too many young patients eventually died or were left with major disabilities, because of an unacceptable and almost always avoidable loss of time. We do emphasize some rules which have to be followed to avoid catastrophic events.

Accidents, Traffic↗
PubMed1994

[Malignant astrocytoma of the cerebellum. Apropos of 10 cases. Review of the literature].

While reviewing a series of 138 cerebellar tumors operated upon between 1978 and 1991, the authors could only find 2 glioblastomas and 8 anaplastic astrocytomas, occurring in 4 children (3 to 14 years old) and 6 adults (23 to 48 years old). These 10 cases represent 2% of the all malignant gliomas population observed during the same period of time. Clinically speaking, nothing makes these tumors different from other cerebellar ones. However, with an heterogenous image and an irregular contrast enhancement, the CT (scan) appearance can lead to the diagnosis. 7 lesions develop within the cerebellar vermis (vermis cerebelli) and 3 develop within the cerebellar hemisphere. Total surgical resection is performed in 9 cases and subtotal resection in 1 case (because of the extension to the floor of the fourth ventricle). Adjunctive radiotherapy on their posterior cranial fossa is achieved in 8 cases. The 2 patients with a glioblastoma present with a recurrence of their tumor at 15 months and 6 years respectively, and eventually died. Out of the patients with an anaplastic astrocytoma, 4 are still alive without recurrence and with a median follow-up of 7 years. The pathogenesis of such lesions is discussed. An aggressive therapeutic management is suggested because of the possible prolonged survival rate.

Adolescent↗
PubMed1994

Are the calcium antagonists really useful in cerebral aneurysmal surgery? A retrospective study.

From 1983 to 1990, 234 patients with one or several cerebral arterial aneurysms were surgically treated in our department. Since 1983, we have been performing surgery as early as possible. As soon as the subarachnoid hemorrhage diagnosis is confirmed by computed tomography (or if unconfirmed, by lumbar puncture), we assume that each patient may have an aneurysm. Between 1987 and 1990, 111 patients were treated by vascular volume expansion (maintenance of central venous pressure above 5 cm H2O with 4% albumin or Ringer-lactate or, if necessary, with 20% albumin), which we supplemented with calcium antagonists (nimodipine in 60 patients and nicardipine in 51 patients). Two months after being discharged, each patient is examined by a neurosurgeon and, on the same day, is subjected to a neuropsychological evaluation and a computed tomographic scan of the brain. A few months after this consultation, a working-position/family-activities questionnaire is issued to the patient. All of the results studied on the basis of postoperative mortality, second-month computed tomographic scan ischemia, neuropsychological evaluation, and return to work show no significant difference between the groups with or without calcium antagonists or between the nimodipine and nicardipine subgroups.

Activities of Daily Living↗
PubMed1993

Invasive character of an intradural spinal meningioma in early childhood.

The authors report the case of a 2-year-old baby girl with an intradural meningotheliomatous meningioma of the cauda equina which recurred three times. Despite four operative procedures and localized radiotherapy, the lesion kept on growing to reach the retroperitoneal space. Extensive laminectomy and associated radiotherapy were probably responsible for a spinal dislocation which had to be operated on. The child was left paraplegic with major bladder dysfunction after all procedures. This is the first reported case of well-documented "malignant" evolution of a spinal meningioma.

Female↗
PubMed1993

Biodegradation and brain tissue reaction to poly(D,L-lactide-co-glycolide) microspheres.

The therapeutic application of neuroactive molecules in neuroscience is limited, due to the problems posed by the administration of these drugs (peripheral metabolism, systemic effect and passage of the blood-brain barrier). One solution is the implantation in the brain of biodegradable polymer devices with controlled release of a neuroactive drug. The biodegradation and tissue reaction of the copolymer poly(D,L-lactide-co-glycolide) microspheres prepared by the solvent evaporation method, radiosterilized and stereotactically implanted in the rat brain were studied by routine staining, immunohistochemistry and transmission electronic microscopy. The brain tissue reaction observed was a non-specific astrocytic proliferation and a macrophagous-microglial cell reaction, typically found following damage to the central nervous system. Some foreign-body giant cells were observed and the inflammatory and macrophagous reaction decreased dramatically after 1 month and almost ended after 2 months when the microspheres were totally biodegraded. The copolymer poly(D,L-lactide-co-glycolide) microspheres may be considered biocompatible to the brain tissue.

Animals↗