Jacqueline Weinman

Regulation by thyroid hormones of terminal differentiation in the skeletal dorsal muscle. I: Neonate mouse

Changes both in the ATPase myofibrillar profile and in the electrophoretic pattern of myosin isoforms were examined in the mouse dorsal skeletal muscle (longissimus) during postnatal development. In the newborn, only type II C and a few type I fibers were present; differentiation into type II A and II B fibers took place during the 3 weeks following birth. During the same period, a transition from three neonatal isomyosins to four adult isoforms was observed. The two phenomena were related to a marked increase in the serum thyroid hormones levels. Hypothyroidism and hyperthyroidism experiments were performed. Hypothyroidism produced by propylthiouracil treatment of pregnant females and thiourea injections of the litters was shown to induce a complete inhibition of postnatal muscular differentiation. Hyperthyroidism produced by triiodothyronine treatment of the neonate mice significantly accelerated the myosin transition and the switch in the myofibrillar pattern. Our results suggest a primordial role for thyroid hormones in directly regulating the appearance of myosin and fiber adult types and in modulating directly or indirectly the disappearance of the neonatal types.

Immunocytochemical and biochemical evidence for the presence of calmodulin in bull sperm flagellum isolation and characterization of sperm calmodulin

Upon fluorescent staining with a goat antibody anti-ram testis calmodulin, washed bull sperm appears to contain calmodulin in the acrosome, in the post acrosomal region, in the neck region probably associated with the implantation plates and thin laminated fibers, and in a sheath around the upper part of the flagellum. Heads and midpieces + tails were separated by elutriation of sonicated sperm. Immunofluorescent labeling of fragments confirms the presence of calmodulin in implantation plates, where sonication disrupted heads from midpieces, and in a sheath around the midpiece and the upper part of the principal piece. These results were confirmed by electrophoretic and radioenzymatic assays of calmodulin in the fragments, using calmodulin-deficient Ca2+/calmodulin-dependent myosin light chain kinase. Small but significant amounts (approx. 3 micrograms per 10 (10) sperm) are found in midpieces + tails vs. approx. 280 micrograms in the same number of heads. These results are in agreement with a recent report from Jones et al. (1980) Proc. Natl. Acad. Sci. U.S.A. 77, 2772-2776. Sperm calmodulin was purified from a whole sperm 1 M KCl extract and found to exhibit the same characteristics as other mammalian calmodulins isolated so far in terms of ultraviolet absorption spectrum and amino acid composition, including one residue of epsilon-N-trimethyllysine. Its behavior upon SDS-polyacrylamide gel electrophoresis was dependent on the presence or absence of Ca2+. The high performance liquid chromatography tryptic peptide maps were similar, if not identical, to mammalian calmodulin maps (Autric et al. (1980) Biochim. Biophys. Acta 631, 139-147). Sperm calmodulin is therefore probably identical to the somatic cell protein.

Annexins in rat enterocyte and hepatocyte: an immunogold electron-microscope study.

In the present study, immunogold labeling of ultrathin sections of rat small intestine and liver has been used to obtain insights into the ultrastructural localization and possible functions of annexins. In enterocytes, annexins II, IV, and VI are found at the periphery of the core of each microvillus and of the rootlets, but are absent from the interrootlet space. Annexins II, IV, and VI are also observed close to the interdigitated plasma membrane. In hepatocytes, only annexin VI is found to be concentrated within the microvilli in the bile canaliculi, on the inner face of the sinusoidal cell surface, particularly in the space of Disse, and all along the plasma membrane. Annexin VI is also detected in mitochondria of enterocytes and hepatocytes. These localizations are in agreement with the concept of a close calcium-dependent association of annexins with membranes and cytoskeletal proteins, particularly with actin. Moreover, they support the hypothesis of an involvement of annexins in exocytotic and endocytotic processes, which take place in epithelial cells.

Annexin expressions are temporally and spatially regulated during rat hepatocyte differentiation

Annexin (Anx) 1, 2, 5, and 6 expressions were determined at the transcriptional and translational levels in the rat hepatocytes from gestational day 15 to postnatal day 17. Dramatic shifts were observed in Anx 1 and 2 levels, which peaked at day 1 and gestational day 20, respectively, and reached low levels thereafter. However, Anx 5 and 6 rates were more constant. Prenatal administration of dexamethasone (dex) resulted in a decrease of Anx 1 mRNA levels, and a strong increase in Anx 2 mRNA contents. In adult hepatocytes cultured in the presence of EGF or HGF, Anx 1 and 2 expressions resumed. By immunohistochemistry, Anx 1 was detected only in the cytoplasm of hepatocytes of 1‐ to 3‐day‐old rats, Anx 2 and 6 both exhibited a redistribution from the cytoplasm toward the plasma membrane, and Anx 5 was present in the nucleus, cytoplasm, and plasma membrane. Thus, Anx 1, 2, 5, and 6 have individual modes of expression and localization in the differentiating hepatocytes, where they might play unique roles at well defined phases of liver ontogeny.

Changes in calmodulin level after fertilization and during first cleavage in the egg of the urodelan amphibian Pleurodeles waltlii

We report three significant calmodulin rises related to Pleurodeles waltlii egg fertilization and following developmental events. These elevations are correlated to the major obvious Ca2+-dependent events: Na+-H+ exchange, activation of NAD kinase, triggering of cortical reaction, resumption of meiotic division II, initiation of DNA synthesis and regulation of cell division. Therefore, it is suggested that alterations in calmodulin level in fertilized egg may be part of the Ca2+-dependent regulatory mechanisms which turn on metabolisms, initiate development and govern cell cleavages.

Synthesis and infrared spectra of some 3α-hydroxy Δ5-steroids

Abstract A generally applicable method for the preparation of 3 α-hydroxy Δ 5 -steroids is used to obtain 3 α-hydroxyandrost-5-ene, 3α-hydroxypregn-5-ene, 3 α-hydroxypregn-5-ene-20-one and their corresponding acetates. The infrared spectra of these compounds and of 3 α-hydroxycholest-5-ene and 3 α-hydroxyandrost-5-ene-17-one, known steroids, are measured in the range of 3700–3900 cm −1 and the characteristic group frequencies reported.

Calmodulin in rat enterocyte: an immunogold electron-microscope study

Immunogold labeling of ultrathin sections of the epithelium of rat small intestine has been used to obtain insights into the ultrastructural localization and possible function of calmodulin in the enterocyte. Calmodulin is found mainly overlying the periphery of the microvillous core, in agreement with the location of the 110-kDa calmodulin complex. Extremely small amounts of calmodulin can be detected along the interdigitating basolateral membrane. This immunogold electron-microscope study suggests that calmodulin plays an important role in regulating the mechanochemical activity of myosin I but not in processes associated with the basolateral membrane of rat enterocyte.

Calmodulin during development and metamorphosis in urodelan amphibians

Calmodulin isolated and purified to homogeneity from young larvae is very similar to that obtained from adult Pleurodeles waltlii and these proteins are almost identical to previously described vertebrate calmodulins. During P. waltlii development, an increase in total individual calmodulin content is observed after the heart beating stage. In dorsal axial muscle, calmodulin level which is very high at the beginning of larval life (premetamorphosis) decreases strikingly in the first part of prometamorphosis. Such an evolution is observed in Ambystoma mexicanum too. Then, a significant increase occurs during metamorphosis. In contrast, calmodulin level in P. waltlii cardiac ventricular muscle increases continuously from hatching to the end of metamorphic climax. Thyroxine treatment which promotes precocious metamorphosis in P. waltlii and experimental metamorphosis in neotenic A. mexicanum, induces a rapid and significant increase in muscle calmodulin concentration.

Sulfuric acid hydrolysis of 3β-hydroxy-5α, 6α-epoxyandrostane

Abstract 3β -hydroxy-5α, 6α-epoxyandrostane was subjected to sulfuric acid hydrolysis. A careful chromatography of the resulting product was carried out, yielding 3β, 5α, 6β-trihydroxyandrostane and 3β, 5α-dihydroxyandrostane-6-one. Chemical properties and the infrared spectra of these compounds and their corresponding acetates, provided proof for the structures.