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Title: Hamster thecal cells express muscle characteristics

Contraction of the follicular wall about the time of ovulation appears to be a coordinated event; however, the cells that mediate it remain poorly studied. We examined the theca externa cells in the wall of hamster follicles for the presence of a functional actomyosin system, both in developing follicles and in culture. We used a monoclonal antibody (HHF35) that recognizes the alpha and gamma isoelectric variants of actin normally found in muscle, but not the beta variant associated with non-muscle sources, to evaluate large preovulatory follicles for actin content and composition. Antibody staining of sectioned ovaries showed intense circumferential reactivity in the outermost wall of developing follicles. Immunoblots from two-dimensional gels of theca externa lysates demonstrated the presence of the two muscle-specific isozymes of actin. Immunofluorescence of cultured follicular cells pulse-labeled with (3H) thymidine (for autoradiographic detection of DNA replication) revealed the presence, in many dividing cells, of actin filaments aligned primarily along the longitudinal axis of the cells. In cultures exposed to the calcium ionophore A23187 (10(-4) M) for varying periods (5 min to 1 h), contraction of many individual muscle-actin-positive cells was observed. Immunofluorescence of these cells, fixed immediately after ionophore-induced contraction, revealed compaction of the actin filaments.more » Our findings demonstrate that the cells of the theca externa contain muscle actins from an early stage and that these cells are capable of contraction even while proliferating in subconfluent cultures. They suggest that follicular growth may include a naturally occurring developmental sequence in which a contractile cell type proliferates in the differentiated state.« less
Authors:
; ;
Publication Date:
OSTI Identifier:
6499879
Resource Type:
Journal Article
Resource Relation:
Journal Name: Biol. Reprod.; (United States); Journal Volume: 39:1
Research Org:
Washington State Univ., Pullman (USA)
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; ACTIN; BIOSYNTHESIS; ANIMAL CELLS; CELL PROLIFERATION; MUSCLES; CONTRACTION; AUTORADIOGRAPHY; CELL CULTURES; DNA REPLICATION; FLUORESCENCE; HAMSTERS; MONOCLONAL ANTIBODIES; OVARIES; THYMIDINE; TRITIUM COMPOUNDS; TWO-DIMENSIONAL ELECTROPHORESIS; ANIMALS; ANTIBODIES; AZINES; BODY; ELECTROPHORESIS; FEMALE GENITALS; GONADS; HETEROCYCLIC COMPOUNDS; LABELLED COMPOUNDS; LUMINESCENCE; MAMMALS; NUCLEIC ACID REPLICATION; NUCLEOSIDES; NUCLEOTIDES; ORGANIC COMPOUNDS; ORGANIC NITROGEN COMPOUNDS; ORGANS; PROTEINS; PYRIMIDINES; RIBOSIDES; RODENTS; SYNTHESIS; VERTEBRATES 550201* -- Biochemistry-- Tracer Techniques