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Biomedical subjects

M Wassef

Publications and source records attributed to M Wassef.

At least 109 records · Page 6Linked to original sources
PubMed1991

Cerebellar development: afferent organization and Purkinje cell heterogeneity.

Olivo- and spinocerebellar maps in the adult cerebellum of small rodents are discontinuous, with sharp boundaries. Cortical Purkinje cells constitute a heterogeneous population, organized into parasagittal, mutually exclusive compartments. The boundaries of the intrinsic cortical compartments and those of the projectional maps are congruent. During development; (i) The incoming olivary fibres, once they penetrate in the cerebellar parenchyma, are attracted toward their ultimate terminal fields, without passing through a stage of random dispersion. (ii) Migrating Purkinje cells and inferior olivary neurons begin, asynchronously, to express cellular markers in an independent manner, giving rise to a transient compartmentation of the cerebellar cortex and the inferior olivary complex respectively. In both instances, the biochemical heterogeneity disappears during the first postnatal week, simultaneously with the acquisition of adult-like cerebellar maps. (iii) The formation of the maps is an early event, prior to the establishment of the synaptology of the cerebellar cortical circuitry. Moreover, the organization of the spinocerebellar projection in adult mutant mice does not depend on the presence of granule cells (staggerer) but on the presence of normal Purkinje cells (weaver), indicating that synaptogenesis with their target neurons is not involved in the process of map formation. The matching of region specific chemical labels between incoming afferent fibres and heterogeneous sets of Purkinje cells is the most appealing mechanism for the formation of cerebellar maps.

Afferent Pathways↗
PubMed1991

Induction of a mesencephalic phenotype in the 2-day-old chick prosencephalon is preceded by the early expression of the homeobox gene en.

The homeobox gene en, homologous to the gene en-grailed of Drosophila, is expressed in the metencephalic-mesencephalic segment of the vertebrate neural tube. Using quail-chick chimeras, an antibody against en proteins, and cytoarchitectonic techniques, we demonstrate that metencephalon transplanted to prosencephalon, at E2, maintains a high level of en proteins and its presumptive cerebellar fate. The ectopic metencephalon induces in the contiguous host prosencephalon the expression of en and, subsequently, a mesencephalic phenotype. These related genetic and phenotypic expressions indicate that the transcriptional regulatory en gene is involved in cerebellar and mesencephalic cyto-differentiation. The expression of en can also be induced in chick prosencephalon by a mammalian metencephalic graft, indicating that the factors regulating the transcription of en are phylogenetically well conserved.

Animals↗
PubMed1990

Expression of compartmentation antigen zebrin I in cerebellar transplants.

The mammalian cerebellum is divided into multiple parasagittal compartments as defined by the organization of afferent and efferent projections and by the pattern of expression of several biochemical markers. One such marker is the antigen zebrin I, a 120 kD polypeptide of unknown function that is expressed differentially by a subset of Purkinje cells. Zebrin I+ Purkinje cells are grouped into an array of 14 parasagittal bands interposed by zebrin I- compartments. This Purkinje cell compartmentation corresponds to compartments in the olivocerebellar projection. The afferent axon compartments are present prior to the expression of the mature zebrin I phenotype, thus raising the possibility that differential afferent input regulates the zebrin I phenotype of the target of that input. Lesion studies in the neonate preclude a role for afferent inputs in the regulation of zebrin I expression postnatally, but a prenatal role in commitment still remains open. To explore this possibility, cerebellar anlagen were dissected from embryos at embryonic days 12-15, that is, prior to any contact with afferents, and transplanted ectopically into adult hosts. In the first series of experiments, the grafts were placed into the anterior chamber of the eye, and in the second series, into cavities prepared in the neocortex. Grafts were allowed to mature and then were immunoperoxidase or immunofluorescence stained for zebrin I immunoreactivity. Zebrin I was expressed by grafted Purkinje cells in cortico and in oculo. Double-labelling experiments confirmed that both the zebrin I+ and the zebrin I- phenotypes were present. The zebrin I immunoreactivity revealed that the zebrin I+ Purkinje cells resemble those in situ with an extensive dendritic arborization that extends through the molecular layer perpendicular to the long axes of the folia. In conclusion, the present data suggest that afferent input does not play a role in the determination of the zebrin I phenotype of Purkinje cells.

Animals↗
PubMed1990

Antibodies to HIV-1 nef(p27): prevalence, significance, and relationship to seroconversion.

A sensitive and specific enzyme-linked immunoassay for antibodies to the human immunodeficiency virus type 1 (HIV-1) nef gene product, p27, has been developed using recombinant Escherichia coli-derived protein from the LAV-1-Bru sequence. Of 92 HIV-1 infected hemophiliacs, 72 (78%) produced anti-nef antibodies in this assay; the early appearance of anti-nef prior to full seroconversion was a rare event in this population, occurring in only one subject (approximately 1%). Anti-nef antibodies were not detected in any of 500 sera from 98 repeatedly HIV seronegative subjects who had been exposed to sexually transmitted modes of HIV infection (45 subjects) or through blood products (53 subjects). There was no significant association of titer or anti-nef antibody with protection from disease in HIV infection (p = 0.1). Although the nef protein is relatively immunogenic in natural infection, this study cannot confirm the previously reported high prevalence of anti-nef antibodies prior to seroconversion, nor the finding of anti-nef antibodies in HIV seronegative but exposed subjects.

Cohort Studies↗
PubMed1990

[Tubulo-papillary tumor of the kidney. Apropos of a case].

Tubulopapillary tumors represent a particular group of the renal tumors. Beyond their characteristic histological features, these tumors can be distinguished from the other renal tumors by the frequency of stage I on histology and by a more favorable prognosis.

Adenocarcinoma, Papillary↗
PubMed1989

Proximal trajectory of the brachium conjunctivum in rat fetuses and its early association with the parabrachial nucleus. A study combining in vitro HRP anterograde axonal tracing and immunocytochemistry.

The proximal course of the developing brachium conjunctivum (BC) in the rat described from embryonic day 16 (E16) to one day postnatal (P1). Axons of the cerebellar deep nuclear neurons entering this bundle were identified by anterograde axonal tracing after in vitro horseradish peroxidase (HRP) injections in the cerebellar plate. At all ages, the main ascending limb of the BC can be followed from its emergence, dorsal to the cerebellar plate where it assumes an almost vertical course, up to its decussation. Close to the ventricle at E16, the decussating fibers are progressively displaced ventrally probably because of the fusion, on the midline, of bilaterally produced raphe neurons. In E16 and E17 embryos, labeled BC fibers extend beyond the decussation in the caudal part of the red nucleus. Decussating BC axons, in some E16 early embryos, end with large and complicated growth cones, as described previously in 'decision regions' for chick embryo motoneurons. Growth cones were never observed in this region in older embryos. In addition to the main ascending limb of the BC, we also traced its ipsilateral descending limb and the cerebello-olivary projections. In parallel, the development of a nucleus immunoreactive for the vitamin D-dependent calcium-binding protein (CaBP) is reported. By E16, its neurons migrate rostrally and settle in the region where the BC is demonstrated by tracing experiments. At E17 and thereafter this isthmic nucleus is composed of a shell of CaBP-immunoreactive neurons ensheathing an immunonegative cylinder. Between E17 and birth, in spite of the profound modifications of the isthmic region, this CaBP-immunoreactive nucleus remains in close proximity to the BC. This nucleus is identified as the marginal nucleus of the BC or parabrachial nucleus, by double-labeling experiments combining the visualization of the retrogradely labeled axons and neurons of the deep cerebellar nuclei inside the CaBP immunofluorescently labeled parabrachial nucleus. Subsequently the deep cerebellar neurons translocate caudoventrally moving away from the parabrachial nucleus inside which their axons become visible. This pattern of migration could indicate that a few neurons of the deep nuclei remain ectopic, wedged between the restiform body and the BC while receiving an appropriate Purkinje cell (PC) projection.

Animals↗
PubMed1989

[Rectal malacoplakia. Contribution of x-ray computed tomography and endorectal echography].

The authors report about the observation of a case of malacoplakia with rectal involvement. They lay stress on the usefulness of computed tomography and of rectal echography, which allow assessing extension within the rectal wall and, as the case may be, into the lymph nodes. These examinations also allowed following up the disease, the signs of which abated with antibiotic treatment.

Adolescent↗
PubMed1989

Middle ear adenoma. A tumor displaying mucinous and neuroendocrine differentiation.

Middle ear adenoma (MEA) is a distinctive, rare entity that appears to be derived from the lining epithelium of the middle ear mucosa. We report four cases of MEA displaying the typical histologic growth pattern. Two distinct tumor cell immunophenotypes were identified in all cases; the first type exhibited positivity with anti-epithelial membrane antigen and anti-keratin antibodies, and the second type showed immunoreactivity with anti-keratin, anti-vimentin, and anti-neuron-specific enolase antibodies. Ultrastructural studies revealed bidirectional mucinous and neuroendocrine differentiation, demonstrated by the presence of two distinct cell types containing apically located mucous granules and basally concentrated neuroendocrine granules, respectively. The presence of neuroendocrine differentiation was supported by the immunohistochemical detection of vasoactive intestinal polypeptide in the tumor cells in one case and neuron-specific enolase in three cases. These findings suggest that the potential for mixed mucinous/neuroendocrine differentiation described in other endodermally derived tumors also exists in middle ear mucosa. We also believe that the rare lesions diagnosed as primary carcinoid tumors of the middle ear might in fact be MEA with predominant or only neuroendocrine differentiation. The clinical course of our four cases and our review of the pertinent literature confirm the benign nature of MEA and indicate that these tumors should be treated by complete local excision without additional therapy.

Adenoma↗
PubMed1988

[Extracranial meningioma. Apropos of 7 cases; pathogenic, diagnostic and therapeutic problems].

Meningioma is a benign tumor developing in the meningeal layers. Extracranial meningiomas, seven cases of which are reviewed, are often revealed by ENT signs. In the majority of cases they originate from the cranium and histologic diagnosis (particularly of fresh specimens) is often difficult. A CT scan is the examination of choice for assessing possible extension of these tumors. Treatment often involves the combined efforts of a neurosurgical and an otorhinolaryngologic team.

Adolescent↗
PubMed1987

Neuron-specific enolase and malignant lymphomas (23 cases).

The immunoreactivity of polyclonal antiserum to neuron-specific enolase (NSE) has been investigated. Twenty-three cases of malignant lymphoma (ML) were studied and compared with previously published reports. In our study 11 out of 23 cases showed strong or weak NSE positivity; any type of ML could be positive or negative even among B or T cell ML. This study indicated that polyclonal NSE is not a specific marker; it might be an inconstant marker of ML with no apparent correlation between reactivity and morphology or phenotype.

Antibodies, Monoclonal↗
PubMed1987

Subfascial lifting.

The authors demonstrate by anatomical dissection that inaccuracies made by classical anatomists have worried plastic surgeons for many years. They demonstrate that continuity between the parotid fascia and the fibrous platysma has not been recognized. In addition, anatomists in the past have not been aware that the platysma is a unique type of fasciomuscular layer because in contrast to conventional anatomical opinions, the platysma has no bony attachment to the mandible.

Face↗
PubMed1987

Superficial fascial and muscular layers in the face and neck: a histological study.

The author emphasizes and clarifies some disputed anatomical points based on topographical histological studies of the superficial muscular and fibrous layers of the face and neck, made in 8 cadavers, 6 human fetuses, 3 monkeys, and 42 surgical specimens. The findings in this anatomical study should make certain plastic surgical operations of the face more understandable, especially the rhytidectomy as it is done today.

Adult↗
PubMed1987

Cerebellar mutations affecting the postnatal survival of Purkinje cells in the mouse disclose a longitudinal pattern of differentially sensitive cells.

The pattern of surviving Purkinje cells (PCs) was investigated in three cerebellar mutant mice with severe postnatal PC death. Two of these mutations, nervous (nr) and Purkinje cell degeneration (pcd) mutations are already well characterized. The third mutation is a new one, which appeared spontaneously in DW/J-Pas mice and was called tambaleante (tbl). PCs were identified by immunocytochemistry using an antibody against vitamin D-dependent calcium-binding protein which labels all the PCs in adult control mice. In each of the three mutations, surviving PCs are arranged according to a different and reproducible pattern which is symmetric relative to the midline. In NR and young PCD mutants, PCs are closely packed in broad sagittal bands. In TBL, they are more loosely arranged in a rather patchy pattern. In PCD and in TBL mutants the death of resistant PCs is only shortly delayed but in NR there is little change in the number of surviving PCs after 3 months. The differential sensitivity of subsets of PCs to the effect of nr, pcd, and tbl mutations is topographically determined. These results provide a new evidence of the PC heterogeneity which has been previously demonstrated by histochemical and immunohistochemical techniques. Moreover, in the anterior vermis of control mice, three thin sagittal bands of PCs are labeled by the Q113 monoclonal antibody. Similarly, in the anterior lobe of the NR cerebellum, the thin longitudinal strips of missing PCs coincide with the absence of Q113 immunoreactivity: in this region the nr mutation affects specifically the survival of Q113 positive cells. However, other clusters of Q113 immunoreactive PCs do survive in NR mice suggesting that susceptibility to the nr mutation and Q113 positivity are two independent markers of the underlying PC compartmentalization.

Animals↗
PubMed1987

[Tympanic and jugular paragangliomas. I. Clinical symptomatology and evaluation of extension. Apropos of 25 cases].

Based on a review of 25 cases of tympanic and jugular paragangliomas treated and followed up in the Lariboisière hospital, Paris between 1978 and 1986, clinical aspects and extension of these tumors are studied. The often long delay in making the diagnosis is related to lack of knowledge of presenting symptomatology, frequent discordance between functional and physical symptomatology exists, but remarkable progress has been made in assessment of extension of tumors using new imaging techniques, particularly angiography, which can also guide the preoperative embolization and surgical procedures.

Adult↗
PubMed1987

[Tympanic and jugular paragangliomas. II. Angiographic, surgical and irradiation treatment. Results. Indications. Apropos of 25 cases].

Results of treatment are reviewed in 25 cases of tympanic and jugular paragangliomas treated and followed up in the Lariboisière hospital, Paris between 1978 and 1986. Therapy has been transformed by the use of embolization but its non-negligible neurologic accident risks, whatever the carotid artery territory involved, justify prior weighing of indications for its application. New surgical technics allow more extensive exeresis, but intrapetrous extension to the nerve compartment of the jugular foramen and the anterior pericarotid region still raises difficult surgical problems and appears to be the principal reason for failure of treatment. Radiotherapy is very effective and applicable for inoperable forms, as a complement to incomplete surgical removal and for recurrences.

Cerebral Angiography↗
PubMed1987

[Fibrous dysplasia and ossifying fibroma of the base of the skull. Apropos of 6 cases].

The authors report 6 cases of fibrous dysplasia (F.D.) of the base of the skull and review the literature. They confirm the impossibility of histological differentiation between ossifying fibroma and monostic dysplasia with cranio-facial sites. They stress the value of CAT scan in the assessment of spread and that of dynamic isotope scan in the differential diagnosis with plaque-shaped hyperostotic meningioma, in the diagnosis of polyostotic forms and in postoperative surveillance. They stress the risk of visual sensorial impairment: visual by stenosis of the optic canals and auditory by stenosis of the E.A.M. Operative indications are influenced by this risk, thereby explaining the need for prolonged surveillance.

Adolescent↗
PubMed1987

[Olfactory esthesioneuroma. Clinical, histological and therapeutic aspects; apropos of 6 cases].

On the basis of 6 cases, the authors review the clinical, histological and therapeutic aspects of olfactory esthesioneuromas. These rare tumours, showing varying rates and degrees of progression from one patient to another, generally have a severe prognosis. Diagnosis is based upon precise histological criteria which may be clarified by electromicroscopic data. In difficult cases it may be useful to seek the aid of immuno-histochemical techniques in order to demonstrate the presence in tumour cells of specific neuronal enolase and the labelling of such cells by anti-protein S-100 antibodies. The treatment of choice would appear to be radio-surgical completed by chemotherapy similar to that used in neuroblastomas.

Adolescent↗