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Jacques Penderis

Publications and source records attributed to Jacques Penderis.

5 recordsLinked to original sources
PubMed2003

Impaired remyelination and depletion of oligodendrocyte progenitors does not occur following repeated episodes of focal demyelination in the rat central nervous system.

It has been hypothesized that the progressive failure of remyelination in chronic multiple sclerosis is, in part, the consequence of repeated episodes of demyelination at the same site, eventually depleting oligodendrocyte progenitor cells (OPCs) and exhausting the remyelinating capacity. We investigated the effect of previous focal, ethidium bromide-induced demyelination of brain stem white matter (with intervening recovery) on the efficiency of the remyelination process during second and third subsequent episodes of demyelination, and the OPC response during a second episode of demyelination. Previous focal demyelinating lesions followed by recovery did not result in any retardation of the remyelination process, nor did they alter the proportion of Schwann cell versus oligodendrocyte remyelination. The OPC response during remyelination was quantified by in situ hybridization using a probe to platelet-derived growth factor-alpha receptor (PDGF alpha R), an OPC-expressed mRNA. Following recovery from focal, toxin-induced CNS demyelination, the OPC density returned to levels equivalent to those in normal white matter. Further more, there was no depletion of OPCs following repeated episodes of focal, toxin-induced CNS demyelination at the same site. These results indicate that repeated CNS demyelination, which has the opportunity to repair in the intervening period, is not characterized by impaired remyelination or depletion of OPCs.

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PubMed2002

The age-related decrease in CNS remyelination efficiency is attributable to an impairment of both oligodendrocyte progenitor recruitment and differentiation.

The age-associated decrease in the efficiency of CNS remyelination has clear implications for recovery from demyelinating diseases such as multiple sclerosis (MS) that may last for several decades. Developing strategies to reverse the age-associated decline requires the identification of how the regenerative process is impaired. We addressed whether remyelination becomes slower because of an impairment of recruitment of oligodendrocyte progenitors (OPs) or, as is the case in some MS lesions, an impairment of OP differentiation into remyelinating oligodendrocytes. The OP response during remyelination of focal, toxin-induced CNS demyelination in young and old rats was compared by in situ hybridization using probes to two OP-expressed mRNA species: platelet-derived growth factor-alpha receptor and the OP transcription factor myelin transcription factor 1 (MyT1). We found that the expression patterns for the two OP markers are very similar and reveal a delay in the colonization of the demyelinated focus with OPs in the old animals compared with the young animals. By comparing the mRNA expression pattern of MyT1 with that of the myelin proteins myelin basic protein and Gtx, we found that in the old animals there is also a delay in OP differentiation that increases with longer survival times. These results indicate that the age-associated decrease in remyelination efficiency occurs because of an impairment of OP recruitment and the subsequent differentiation of the OPs into remyelinating oligodendrocytes, and that strategies aimed at ameliorating the age-associated decline in remyelination efficiency will therefore need to promote both components of the regenerative process.

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PubMedDate not supplied

Intraventricular tension pneumocephalus as a complication of transfrontal craniectomy: a case report.

OBJECTIVE: To report the diagnosis and surgical treatment of a case of intraventricular tension pneumocephalus in a dog after a transfrontal craniectomy for removal of a falx cerebri meningioma. STUDY DESIGN: Case report. ANIMAL: A 12-year-old spayed English springer spaniel. RESULTS: Intraventricular air and a fistula between the craniectomy site and ventricular system were identified by magnetic resonance imaging. Prompt repair of the dural defect using prosthetic dura mater resulted in immediate regression of the neurological signs and cerebral spinal fluid rhinorrhea. Magnetic resonance imaging repeated 8 weeks after surgery showed complete resolution of pneumocephalus. CONCLUSIONS AND CLINICAL RELEVANCE: Tension pneumocephalus is an uncommon but life-threatening complication of craniectomy that requires urgent diagnosis and treatment.

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