The steroid hormone levels and receptors of steroid hormone receptors in rat muscles during physical exertion

It is shown that the testosterone content in skeletal muscles of female albino rats is 2-fold decreased, while the estradiol content-1.5-fold increased and progesteron content showed no changes after systematic physical exercises. The pharmacokinetic investigations showed that androgen half-life in the organism decreased from 8 to 5 h under physical exercises. The amount of androgen receptors in cytosol of skeletal muscles increases from 1.34 +/- 0.08 to 1.71 +/- 0.10 fmol/mg per 1 mg of protein. Kd is 0.40 +/- 0.03 and 0.48 +/- 0.08 nM, respectively. Sensitivity of the organism to hormonal signal play an important role in the metabolism regulation in skeletal muscles along with the hormonal content change during the organism adaptation to physical exercises.     

Callus growth and plant regeneration in diverse cultivars of cucumber (Cucumis sativus L.)

The growth and differentiation of callus tissues derived from cotyledons of ten cultivars ofCucumis sativus L. were investigated. Cotyledonary explants from all ten cultivars formed callus tissue on Murashige and Skoog (MS) medium supplemented with 0.5 M 2,4-dichlorophenoxyacetic acid and 5 M 6-benzylaminopurine. Fresh weight of the callus tissues averaged 1 to 8 g per flask after five weeks of culture. Shoot development was achieved in three cultivars, Hukchinju, Manchoonchoungjang and Seoul, on MS medium supplemented with 0.5 M -naphthaleneacetic acid and 5 M 6-benzylaminopurine. Reducing the 6-benzylaminopurine concentration to 0.01 M resulted in root formation on callus tissues and on shoots transferred to this medium. All cultivars gave the same response in tests of root formation, but shoot regeneration from callus culture of cucumber cotyledons was dependent on genotype with cultivar Manchoonchoungjang exhibiting the best shoot differentiation capability among the genotypes examined. Examination of mitotic metaphase from the regenerants revealed that all were tetraploid.     

Highly permeable contacts and electrical characteristics of the tissue of the normal liver and hepatomas. III. Absence of an effect of the tumor promoter phenobarbital on intercellular contacts in the mouse liver

The effect of phenobarbital--a specific promoter of hepatocarcinogenesis--on electrical parameters of mouse liver cells in vitro has been investigated using the conventional microelectrode technique. No alterations were found in cell membrane potentials, input resistances and electrical coupling coefficients measured either immediately after a short-term incubation of isolated livers in the presence of phenobarbital, or after a long-term treatment of the animals per os with the promoter for several weeks.     

Ultrastructural characteristics of the simple eyes of the louse Pediculus humanus corporis

The simple eye of the human louse consists of two apparatuses: dioptric and light sensitive. The dioptric apparatus contains only a biconvex lens, which represents local thickening of the cuticle. The eye lacks the crystal cone (Semper cells) and special pigment cells. The light sensitive part of the eye contains about 130 photoreceptor cells. Each photoreceptor has rhabdomere which consists of numerous microvilli. The pigment granules are located only in the photoreceptor cells.     

Role of bacterial γ-glutamyltranspeptidase as a novel virulence factor in bone-resorbing pathogenesis

Mammalian γ-glutamyltranspeptidase (GGT) has been identified as a bone-resorbing factor. Since GGT of Bacillus subtilis exhibits similarity in their primary structure and enzymatic characteristics with mammalian GGTs, the bone-resorbing activity of bacterial GGT was examined in this study. Osteoclastogenesis was performed in a co-culture system of mouse calvaria-derived osteoblasts and bone marrow cells. A conditioned medium from GGT-overproducing B. subtilis culture showed significantly higher activity of osteoclast formation than a conditioned medium from wild-type B. subtilis culture. Recombinant GGT (rGGT) of wild-type B. subtilis and an enzymatic activity-defected rGGT of B. subtilis 2288 mutant were expressed in Escherichia coli and purified using His tag. Both purified rGGTs induced similar levels of osteoclastogenesis, suggesting that B. subtilis GGT possesses virulent bone-resorbing activity and its activity is probably independent of its enzymatic activity. Furthermore, a recombinant protein of B. subtilis GGT heavy subunit (Bs rGGT/H) showed strong activity of osteoclastogenesis while the light subunit failed to show strong activity, suggesting that the bone-resorbing activity is mainly located at the heavy subunit. More importantly, the GGT enzymatic activity may not be required for this virulence activity since the light subunit contains the catalytic pocket. In addition, B. subtilis rGGT stimulated mRNA expressions of receptor activator of nuclear factor kappa-B ligand (RANKL) and cyclooxygenase-2 (COX-2), while an osteoprotegerin inhibited the osteoclast formation induced by Bs rGGT/H. This is the first demonstration that bacterial GGT itself is sufficient to act as a bone-resorbing virulence factor via RANKL-dependent pathway. Therefore, it can be hypothesized that GGT of periodontopathic bacteria may play an important role as a virulence factor in bone destruction.     

Human CEACAM1-LF regulates lipid storage in HepG2 cells via fatty acid transporter CD36

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is expressed in the liver and secreted as biliary glycoprotein 1 (BGP1) via bile canaliculi (BCs). CEACAM1-LF is a 72 amino acid cytoplasmic domain mRNA splice isoform with two immunoreceptor tyrosine-based inhibitory motifs (ITIMs). Ceacam1^−/− or Ser503Ala transgenic mice have been shown to develop insulin resistance and nonalcoholic fatty liver disease; however, the role of the human equivalent residue, Ser508, in lipid dysregulation is unknown. Human HepG2 hepatocytes that express CEACAM1 and form BC in vitro were compared with CEACAM1^−/− cells and CEACAM1^−/− cells expressing Ser508Ala null or Ser508Asp phosphorylation mimic mutations or to phosphorylation null mutations in the tyrosine ITIMs known to be phosphorylated by the tyrosine kinase Src. CEACAM1^−/− cells and the Ser508Asp and Tyr520Phe mutants strongly retained lipids, while Ser508Ala and Tyr493Phe mutants had low lipid levels compared with wild-type cells, indicating that the ITIM mutants phenocopied the Ser508 mutants. We found that the fatty acid transporter CD36 was upregulated in the S508A mutant, coexpressed in BCs with CEACAM1, co-IPed with CEACAM1 and Src, and when downregulated via RNAi, an increase in lipid droplet content was observed. Nuclear translocation of CD36 associated kinase LKB1 was increased sevenfold in the S508A mutant versus CEACAM1^−/− cells and correlated with increased activation of CD36-associated kinase AMPK in CEACAM1^−/− cells. Thus, while CEACAM1^−/− HepG2 cells upregulate lipid storage similar to Ceacam1^−/− in murine liver, the null mutation Ser508Ala led to decreased lipid storage, emphasizing evolutionary changes between the CEACAM1 genes in mouse and humans.     

Growth hormone attenuation of epidermal growth factor-induced mitogenesis

Growth hormone (GH) has previously been reported to influence the adipose conversion of 3T3-F442A murine fibroblasts, partly by causing these cells to exit the cell cycle and to become unresponsive to serum-stimulated mitogenesis. To better understand this process, quiescent fibroblasts were treated with fully stimulatory doses (50 nM) of epidermal growth factor (EGF) in the presence or absence of pituitary human GH (hGH) or the phorbol ester phorbol 12-myristate 13-acetate (PMA), which is known to down-regulate EGF receptor activity. EGF-induced DNA synthesis was attenuated by hGH in a dose-dependent manner with an ED₅₀ of approximately 0.1 nM and a maximally effective dose of 10–30 nM. This effect appeared to be the result of inhibition of DNA synthesis and exclusive of a time shift in the initiation of the S phase of the cell cycle. Additionally, insulin-like growth factor-1 (IGF-1), which can act as an important in vivo mediator of GH, failed to mimic the anti-mitogenic effects of GH. The ability of hGH to antagonize EGF-stimulated mitogenesis did not appear to be due to the down-regulation of EGF receptor mass or to pronounced changes in EGF-induced tyrosine kinase activity. Furthermore, when GH was administered at various times after EGF addition, GH continued to be effective at inhibiting EGF-induced DNA synthesis for up to 9 hr after EGF treatment. Modulation of EGF-induced cell cycle progression was further evidenced by the ability of GH to promote a marked decrease in the EGF-induced expression of D cyclins. In comparison, PMA inhibited EGF-induced DNA synthesis for up to 18 hr after EGF addition and also down-regulated EGF receptor mass and activity; these observations suggest that the mechanism of GH action is largely distinct from that of PMA. We conclude that GH can selectively and dose-dependently modulate EGF receptor-mediated DNA synthesis exclusive of any rapid or extensive effects on EGF receptor mass or tyrosine kinase activity. Furthermore, the capacity of GH to attenuate EGF-induced mitogenesis, even when administered 9 hr after EGF addition, and the GH modulation of EGF-induced expression of D cyclins, suggest that there are GH-induced effects on systems involved in the transition of these fibroblasts through the G₁ phase of the cell cycle. In sum, these data support a specific interaction of this somatotropic hormone/cytokine with EGF in the control of cell cycle progression in 3T3-F442A fibroblasts. J. Cell. Physiol. 173:44–53, 1997. © 1997 Wiley-Liss, Inc.