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M Wassef

Publications and source records attributed to M Wassef.

At least 19 recordsLinked to original sources
PubMed1992

Development of the olivocerebellar projection in the rat: I. Transient biochemical compartmentation of the inferior olive.

In the present study the early phases of the development of the inferior olive were examined by using immunocytochemical techniques. We observed that, from embryonic day 16 onward, antibodies against the calcium binding proteins parvalbumin and calbindin and the calcitonin gene related peptide stain partially overlapping territories of the inferior olive. This staining delimits a biochemical zonation of the inferior olive which is combinatory and transient. We have previously observed a biochemical parcellation of the cerebellar Purkinje cells which, like that of the inferior olive, is first observed at E16, involves the combined expression of marker proteins and is also transient. In order to know whether the biochemical compartmentations of the cerebellum and inferior olive arise independently, the time course of the development of the olivocerebellar projection was studied by anterograde and retrograde in vitro axonal tracing by using the fluorescent carbocyanine dye DiI. The olivocerebellar axons were found to reach the limit of the cerebellar plate at E16 and to enter it at E17. Even at this age the great majority of the climbing fibers are tightly fasciculated, which minimizes their interactions with the PC clusters. These observations indicate that the topographical heterogeneity of Purkinje cells and inferior olive neurons arise independently. The transient biochemical individualization of subgroups of neurons during development could contribute to recognition mechanisms.

Animals↗
PubMed1992

Development of the olivocerebellar projection in the rat: II. Matching of the developmental compartmentations of the cerebellum and inferior olive through the projection map.

A transient biochemical parcellation has been observed by immunocytochemical methods, during the perinatal development of both the inferior olive and the cerebellum. In the present study, we sought a relationship between this developmental compartmentation and the organization of the olivocerebellar projection. In the inferior olive, a transient parvalbumin immunoreactivity restricted to the dorsal cap of the medial accessory olive is observed around birth. The climbing fiber projection of the dorsal cap was identified in the cerebellum of newborn rats based on its parvalbumin immunoreactivity. The pattern of this projection, restricted to lobules IX and X of the vermis, and to the flocculus, is indistinguishable from that of the adult medial accessory olive, which was previously described from axonal tracing experiments. The parvalbumin immunoreactive climbing fibers were followed between birth and postnatal day 7. In the caudal vermis, Purkinje cell subpopulations can be identified between embryonic day 20 and postnatal day three, on the basis of their differential immunostaining with an antibody directed against a specific peptide, PEP 19. In lobule X, the parvalbumin immunoreactive climbing fibers form two sagittal bands on each side of the midline, one medial and one lateral. The medial parvalbumin immunoreactive climbing fiber band is coextensive with a PEP 19 negative Purkinje cell cluster, indicating a clear relationship between the biochemical parcellations of the cerebellum and inferior olive.

Animals↗
PubMed1992

Relationship between Wnt-1 and En-2 expression domains during early development of normal and ectopic met-mesencephalon.

Grafting a met-mesencephalic portion of neural tube from a 9.5-day mouse embryo into the prosencephalon of a 2-day chick embryo results in the induction of chick En-2 (ChickEn) expression in cells in contact with the graft (Martinez et al., 1991). In this paper we investigate the possibility of Wnt-1 being one of the factors involved in En-2 induction. Since Wnt-1 and En-2 expression patterns have been described as diverging during development of the met-mesencephalic region, we first compared Wnt-1 and En-2 expression in this domain by in situ hybridization in mouse embryos after embryonic day 8.5. A ring of Wnt-1-expressing cells is detected encircling the neural tube in the met-mesencephalic region at least until day 12.5. This ring consistently overlapped with the En-2 expression domain, and corresponds to the position of this latter gene's maximal expression. We subsequently studied ChickEn ectopic induction in chick embryos grafted with various portions of met-mesencephalon. When the graft originated from the level of the Wnt-1-positive ring, ChickEn induction was observed in 71% of embryos, and in these cases correlated with Wnt-1 expression in the grafted tissue. In contrast, this percentage dropped significantly when the graft was taken from more rostral or caudal parts of the mesencephalic vesicle. Taken together, these results are compatible with a prolonged role of Wnt-1 in the specification and/or development of the met-mesencephalic region, and show that Wnt-1 could be directly or indirectly involved in the regulation of En-2 expression around the Wnt-1-positive ring during this time. We also provide data on the position of the Wnt-1-positive ring relative to anatomical boundaries in the neural tube, which suggest a more general role for the Wnt-1 protein as a positional signal involved in organizing the met-mesencephalic domain.

Animals↗
PubMed1992

[Atherosclerosis of an arterialized venous graft. Reduction by rigid external support].

Vein grafts undergo early intimal thickening and accelerated atherosclerosis. To assess the role of increased wall stress and distension in the pathogenic responses, 11 New Zealand white rabbits underwent interposition of an autologous jugular vein graft in the left common carotid artery. To relieve wall stress and reduce distension, the half proximal part of the vein was wrapped with a polytetrafluoroethylene graft (i.d. 4 mm). Animals were fed 1% cholesterol for 8 weeks. Vein graft and carotid artery were perfusion fixed with Karnovsky solution at 100 mmHg. They were stained with Sudan IV, and 5-microns cross sections were stained with hematoxylin-eosin and orcein. The internal diameter was reduced by 46 +/- 10% in wrapped vein graft segments as compared with unwrapped ones. The percentage of luminal surface covered by sudanophilic lesions (%AS) was assessed by automatic planimetry. Results (mean +/- SD) were as follows. [table: see text]. Abundant foam cells were found in the intima of unwrapped veins, whereas they were absent or rare in wrapped segments. We concluded that atherosclerotic lesions could be prevented in vein grafts by reducing wall stress and distension.

Adaptation, Physiological↗
PubMed1992

[Cervico-cephalic hemangiomas and vascular malformations. Histopathological appearance and classification].

We present the histological and clinicopathological classification of hemangiomas and vascular malformations, such as was produced by the work of the study group on hemangiomas and vascular malformations of Lariboisière hospital. These lesions can first be classified according to the presence (phasic hemangioma of infants and pyogenic granuloma) or absence (malformations) of active cell proliferation. The malformations are classified according to their histological architecture and to the histological structure of the vessels they are composed of: capillary (hemangioma simplex, telangiectasias, etc.), capillary and/or venous (capillarovenous and cavernous malformations), arterial, venous and capillary (arteriovenous malformations). The classification of lymphatic malformations follows the same principles. The distinctive histological features of the various lesions are illustrated and briefly described.

Arteriovenous Malformations↗
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↗
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

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

[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↗