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S Louryan

Publications and source records attributed to S Louryan.

65 records · Page 4Linked to original sources
PubMedDate not supplied

Cytochemical identification of HSP110 during early mouse facial development.

Apoptotic cell death constitutes a common phenomenon observed during development. This process plays an important role in the regulation of cell populations and in early differentiation of embryonic organs. Several teratologic situations are considered as resulting in a dramatic increase of the apoptotic process. In mammalian cells, heat shock proteins (HSPs), expressed or increased in response to various stresses, act as molecular chaperones in physiological conditions. In order to determine specific histochemical markers of apoptotic cells in normal craniofacial development, we observed the expression of stress proteins (HSPs) 70, 86, and 110. The apoptotic pattern of mesectodermal cell death areas was confirmed using both nuclear staining (Feulgen) and specific labeling of DNA fragmentation (TUNEL). These areas are localized in the proximal parts of the first and second visceral arches. They are located in mesectodermal and ganglionic cells. Apoptotic mesectodermal populations strongly express HSP110, as shown by the cytochemical identification of HSP110 and by double staining HSP110-TUNEL, suggesting that this protein could be considered as a new marker for apoptotic embryonic cells, and could be used in further teratologic studies to better quantify induced cell death.

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PubMedDate not supplied

Correlation of HSP110 expression with all-trans retinoic acid-induced apoptosis.

In a previous study, we observed the strong expression of a stress protein of the HSP100/Clp family (HSP110) in apoptotic mesectodermal cells during early mouse facial development. In the present study, we describe the strong expression of the same HSP110 in mesectodermal cells undergoing apoptosis after all-trans retinoic acid (RA) administration. We used a teratological model known to increase cell deaths mainly in the first and second branchial arches during mammalian cephalogenesis: the treatment of E9 mouse embryos with all-trans RA, which results in craniofacial malformations comparable to those that characterize mandibulofacial dysostosis in man. Pregnant NMRI mice were treated with 60 mg/kg body weight of all-trans RA, given orally on day 9 of gestation; embryos were taken 4, 12 or 24 hr after RA administration. The apoptotic pattern of RA-induced cell deaths was confirmed using the dUTP biotin nick-end labeling (TUNEL) method and transmission electron microscopy (TEM). HSP110 expression was detected using an immunohistochemical approach. The increase in the number of TUNEL-positive cells and HSP110-positive cells after all-trans RA administration was quantified in the first branchial arch using a computerized method. Twelve hours after RA administration, the increase in the number of HSP110-positive cells is greater than the increase in the number of TUNEL-positive cells. Twenty-four hours after RA administration, only TUNEL-positive cells remain strong in number. We suggest that HSP110 expression could represent a biochemical event of apoptotic cell death induced by RA, associated with early stages of the apoptotic process. In order to find out if HSP110 expression resulted from neosynthesis, we performed in situ hybridization, which demonstrated that the expression of HSP110 occurred at the level of mRNA.

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PubMedDate not supplied

[Head formation in the vertebrates: facts and hypotheses].

One of the most important features of vertebrates is that, as craniates, they have a head. They present some developmental similarities with the cephalochordates, which constitute a brother group of the vertebrates. The amphioxus has a rudimentary brain vesicle, with a frontal single eye. The vertebrates differ by formation of a "new" skull, largely developed from neural crest and placodic cells. At the light of common literature, we discuss here a possible scenario in which an enlargement of the primary neural induction process gives rise to an extension of the forebrain, followed by increased neural crest cell migration.

Animals↗
PubMedDate not supplied

[The teratogenicity of 13-cis-retinoic acid on the mandibular-otic anlagen of the mouse embryo: a histological and histochemical approach].

Oral administration of 400 mg/kg of 13-cis retinoic acid to 9 day pregnant mice gives rise to important maxillofacial malformations. The first manifestation of teratogenic effect is an increase of density of cell death arising in the dorsal part of the first two branchial arches at day 9.5. These two arches become hypoplastic at days 10 and 11, and the preskeletal anlagen appear too late in comparison to control embryos. Meckel's cartilage is too curvilinear and medially situated. Pre-ossicular and pre-mandibular blastemata develop with spatial distortions which are well analyzable at days 16 and 17. They give some arguments to discuss several features of normal early development of this area.

Abnormalities, Drug-Induced↗
PubMedDate not supplied

[An in toto study of the cholinesterase activity in the visceral cranium of the mouse embryo].

In toto analysis of cholinesterase activity in the cephalic extremity of 9- to 14-day old mouse embryo permits to define four different stages. Stage 1 corresponds to activity in the cephalic neural crest-derived cells. Stage 2 is characterized by activity in the proximal part of both first branchial arches and in the oculomotor blastemata. Stage 3 corresponds to a decrease of the activity, which appears in the area of fusion of several facial processes. Stage 4 corresponds to activity in nervous and muscular blastemata. Cholinesterase activity is thus chronologically varying and implies several differentiating cell populations.

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