[Membrane testosterone receptors in cultured vascular smooth muscle cells].

Objective: To determine the presence of membrane testosterone receptors in cultured vascular smooth muscle cells (VSMC), and investigate their relationship with classical intracellular androgen receptors (iAR).

Methods: VSMCs were cultured from the thoracic aorta of male Sprague-Dawley rats by the explant method. Subconfluent VSMCs were incubated with serum-free medium for 24 h to obtain quiescent non-dividing cells, and then treated with the indicated agents.

[Testosterone at physiological level inhibits PGF2alpha-induced increase in intracellular Ca2+ in cultured vascular smooth muscle cells].

Objective: To explore the acute effects of testosterone at the physiological level on PGF2alpha-induced increase in intracellular Ca2+ in cultured vascular smooth muscle cells (VSMCs).

Methods: VSMCs from the thoracic aorta of male Sprague-Dawley rats were cultured using the explant method. The subconfluent VSMCs were incubated with serum-free medium for 24 hours to obtain quiescent non-dividing cells and then treated with the indicated agents.

Epidermal growth factor induces changes of interaction between epidermal growth factor receptor and actin in intact cells.

The epidermal growth factor receptor (EGFR) is a cytoskeleton-binding protein. Although purified EGFR can interact with actins in vitro and normally at least 10% of EGFR exist in the insoluble cytoskeleton fraction of A431 cells, interaction of cytosolic EGFR with actin can only be visualized by fluorescence resonance energy transfer when epidermal growth factor presents in the cell medium. Results indicate that the correct orientation between EGFR and actin is important in the signal transduction process.

Two domains of the epidermal growth factor receptor are involved in cytoskeletal interactions.

Epidermal growth factor receptor can interact directly with F-actin through an actin-binding domain. In the present study, a mutant EGFR, lacking a previously identified actin-binding domain (ABD 1), was still able to bind elements of the cytoskeleton. A second EGFR actin-binding domain (ABD 2) was identified in the region of the receptor that includes Tyr-1148 by a yeast two-hybrid assay.

Overexpression of the gene for transmembrane 4 superfamily member 4 accelerates liver damage in rats treated with CCl4.

Background/aims: Transmembrane 4 superfamily member 4 (TM4SF4) is up-regulated in regenerating liver after partial hepatectomy in rats, but the in vivo functions of this protein are still largely unknown. Therefore, we investigated the role of TM4SF4 during liver injury.

Methods: Expression of TM4SF4 was analyzed by RT-PCR and Western blotting in normal and CCl4-injured rats.

cDNA cloning, functional expression and cellular localization of rat liver mitochondrial electron-transfer flavoprotein-ubiquinone oxidoreductase protein.

A membrane-bound protein was purified from rat liver mitochondria. After being digested with V8 protease, two peptides containing identical 14 amino acid residue sequences were obtained. Using the 14 amino acid peptide derived DNA sequence as gene specific primer, the cDNA of correspondent gene 5'-terminal and 3'-terminal were obtained by RACE technique.

[Regulation of androgen receptor mRNA expression by testosterone in cultured vascular smooth muscle cells].

Objective: To investigate the effects of testosterone exposure on androgen receptor (AR) mRNA expression in cultured vascular smooth muscle cells (VSMCs).

Methods: VSMCs were cultured from the thoracic aorta of male SD rats using explant method. The total RNA was extracted by one-step guanidine isothiocyanate method and subjected to Northern blotting analysis for determining AR mRNA level.

Homologous up-regulation of androgen receptor expression by androgen in vascular smooth muscle cells.

Objective: Androgens play an important role in the arterial vascular system, and androgen receptors (AR) have been identified in vascular smooth muscle cells (VSMCs). This study examined the effects of testosterone exposure on AR gene expression in cultured rat aortic smooth muscle cells.

Methods: Changes in AR protein and messenger RNA (mRNA) levels after androgen exposure were determined using immunoblotting and Northern blotting analysis respectively.

[Testosterone regulation of androgen receptor protein expression in cultured vascular smooth muscle cells].

Objective: To investigate the effects of testosterone exposure on androgen receptor (AR) protein expression in vascular smooth muscle cells (VSMC) and the possible mechanisms mediating the effects.

Methods: VSMC were cultured from thoracic aorta of male Sprague-Dawley rats by using the explant method. Cytoplasmic and nuclear extracts were prepared by means of cell lysis and high salt extraction respectively, and subjected to western blotting analysis for determination of AR protein level.

Functional expression and processing of rat choline dehydrogenase precursor.

Choline dehydrogenase (CHDH, EC 1.1.99.

Mitochondria and Apoptosis.

Apoptosis is an important biological process it plays critical role in cell growth differentiation as well as the response toward outside stimulus. Recently it was found that the mitochondrial transmembrane potential and mitochondrial permeability transition have a remarkable role in the process of apoptosis. Hypothesis of a permeability transition pore complex located in the mitochondrial membranes was postulated and had got extensive interest.

Synthesis of Human Proinsulin C-peptide and Preparation of Specific Antibody to It.

A HPLC and CE pure human proinsulin C-peptide was synthesized by solid-phase method and TSK column purification. Its amino acid sequence and MS were consistent with theoretical values. In comparison with the formly reported chemical synthesis of C-peptide, this method has the advantage of simplicity and higher overall yield (41%).

Dimerization A Key Mechanism of Receptor Tyrosine Kinase Activation.

Receptor tyrosine kinase superfamily includes a group of growth factor receptors with intrinsic tyrosine kinase activity which share similar molecular structure. Their ligand-induced activation is mediated primarily by the receptor dimerization. It was proposed that ligand-induced homo- or hetero- dimerization is essential for the activation of receptor kinase however, the mechanisms of receptor dimerization are different.

Activation mechanism of solubilized epidermal growth factor receptor tyrosine kinase.

Dimerization of epidermal growth factor receptor (EGFR) leads to the activation of its tyrosine kinase. To elucidate whether dimerization is responsible for activation of the intracellular tyrosine kinase domain or just plays a role in the stabilization of the active form, the activated status of wild-type EGFR moiety in the heterodimer with kinase activity-deficient mutant receptors was investigated. The kinase activity of the wild-type EGFR was partially activated by EGF in the heterodimer with intracellular domain deletion (sEGFR) or ATP binding-deficient mutant (K721A) EGFRs, while the wild-type EGFR in the heterodimer of wild-type and phosphate transfer activity-deficient mutant receptor D813N could be fully activated.

Studies on the Denaturation and Conformation of Choline Dehydrogenase.

The substrate choline was able to improve the pH stability of choline dehydrogenase (CDH). It was found that during the thermal denaturation there were an increase of beta-structure and a decrease of the alpha-helix content. Changes in beta-structure were attributed to beta-turn and 3(10)-helix.

Interaction of the Apolipoprotein A-I Model Peptides with Liposomes.

Two amphiphilic peptides, Amp1 and Amp2, were synthesized according to the sequence of the lipid-binding domain in apolipoprotein. Amp2 has a Val residue substituted for the Lys at the 4th position of Amp1. Intrinsic fluorescence spectra, peptide-induced leakage of calcein-laoded liposomes, quenching of tryptophan fluorescene by iodide and acrylamide, circular dichroism spectra, and measurement of the membrane penetration depth of tryptophan residue with spin-labeled phospholipids indicate unexceptionally that Amp1 interacted more strongly with the lipid bilayer than Amp2.

Studies on the Spectral Properties of Choline Dehydrogenase.

The addition of the substrate didn't show any influence on the intrinsic emission spectra of purified CDH, which had a maximum at 335 nm. On the other hand, the 520 nm fluorescence of CDH increased after the addition of substrate. The secondary structure of solubilized CDH was examined by Fourier-transform infrared spectroscopy.

Kinetic Properties of Choline Dehydrogenase.

The kinetic behavior of purified CDH had been investigated by steady-state initial velocity studies and inhibition studies with products. Variations in the concentration of one substrate led to changes in the K(m) and V(max) for the other substrate. The product betaine aldehyde was a noncompetitive inhibitor with respect to choline, whereas it competed with PMS.

Interaction of Apolipoprotein Model Peptides with Liposomes: A High Performance Liquid Chromatography Study.

The apparent partition constants of two amphiphilic peptides, Amp1 and Amp2, for partitioning into phosphatidylglycerol/phosphatidylcholine bilayer were measured using size-exclusion high performance liquid chromatograph. The exposed amino groups of vesicle-bound peptides were studied by TNBS assay. It was proposed that their N-terminals were exposed to the aqueous phase, and that the main explanation for the stronger interaction of Amp1 with lipid bilayer compared with Amp2 was its stronger lipid binding ability, though Amp1 was also buried deeper in the lipid membrane.

The Protection of Choline Dehydrogenase by Its Substrate.

Choline dehydrogenase, an enzyme bound to the mitochondrial inner membrane, plays an important role in the mitochondrial respiratory chain. The purified enzyme is different from the membrane bound enzyme in some properties. The inactivation effects of temperature and SDS on choline dehydrogenase were studied.

Influence of Lipid Composition on the Interaction of Apolipoprotein Model Peptides with Liposomes.

Two amphiphilic peptides, Ampl and Amp2, were synthesized according to the sequence of the lipid-binding domain in apoliporotein. Amp2 has a Val residue substituted for the Lys at the 4th position of Ampl. Interaction between Ampl / Amp2 and liposomes with different lipid compositions were compared by studying the blue shifts of the intrinsic fluorescence emission maxima, the peptide-induced lipsome leakage and the quenching of tryptophan fluorescence by acrylamide.