Flavonoids inhibit the expression of heat shock proteins

Cells exposed to several forms of stress, such as heat shock, transiently synthesize a group of proteins called heat shock proteins (hsps). Although many stressors other than heat shock are known to induce hsps, inhibitors of hsp expression have never been reported. Here we show that quercetin and several other flavonoids inhibit the synthesis of hsps induced by heat shock in two human cell lines, Hela cells and COLO320 DM cells. Quercetin inhibited the induction of hsp70 at the level of mRNA accumulation. This is the first report to describe the inhibition of hsp expression by reagents.     

Structure of cDNA clones for the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase from a fern (Asplenium cataractarum rosenstock,aspleniaceae), and its comparison with those of various seed plants

We isolated the small subunit of ribulose-1, 5-bisphosphate carboxylase/oxygenase (RuBisCO SSu) from a fern,Asplenium cataractarum and determined its 34 N-terminal amino acid sequence. We obtained a cDNA clone that contains the entire coding region of the SSu from the same fern species, using synthetic oligonucleotide probes derived from the above amino acid sequence. It contains a 525 bp open reading frame capable of coding for a polypeptide with 174 amino acids, 31 bp 5′-and 206 bp 3′-noncoding regions. It was also elucidated that the precursor to the SSu contains a transit peptide of 53 amino acid residues and a mature protein of 121 residues. We compared the deduced amino acid sequence of the fern SSu with those of 11 other vascular plant species (including gymnosperms, monocots and dicots). As low as 55% homology was observed between those of a fern and seed plants. Constancy of the amino acid substitution rate in RuBisCO SSu was supported by our relative rate test. Amino acid substitution rate per year per site for RuBisCO SSu was calculated to be 0.81×10⁻⁹ assuming that the separation between pteridophytes and seed plants arose 380 million years ago.     

Immunocytochemical studies on the pituitary pars distalis of the Japanese long-fingered bat,Miniopterus schreibersii fuliginosus

Summary Immunocytochemical studies were performed to describe the characteristics of cell types and their distribution in the pars distalis of Japanese long-fingered bat, Miniopterus schreibersii fuliginosus, collected at various stages of the reproductive cycle. Six distinct cell types have been identified in the pars distalis by the unlabeled immunoperoxidase technique and by the ABC method. Growth hormone (GH) and prolactin (PRL) cells were immunostained with antisera against chicken GH and ovine PRL. The GH-immunoreactive cells were round or oval orangeophilic cells distributed throughout the pars distalis with prominent aggregation in the posterolateral region. The PRL cells were pleomorphic carminophilic cells that occurred in small groups within the central and dorsocaudal regions of the pars distalis. They were sparsely distributed in the central region of the pars distalis in the hibernating bats, but increased significantly in the pregnant and lactating bats. The adrenocorticotropic (ACTH) cells were large round or polygonal amphophilic cells in the rostroventral and ventrolateral regions of the pars distalis. The thyrotropic (TSH) cells were small rounded or polygonal and distributed mainly in the ventrolateral region of the pars distalis. Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) cells were identified immunocytochemically with antisera against the specific beta subunits of ovine LH and rat FSH. There were two populations of LH and FSH cells, one aggregated in the zona tuberalis and the other scattered singly throughout the rest of the pars distalis. The aggregated cells were immunoreactive with both antisera directed to LH and FSH, while scattered cells were reactive solely with antiserum to either LH or FSH and exhibited seasonal variations. In females, the proportional volume of the pars distalis occupied by LH cells was significantly reduced during pregnancy and lactation. No evidence of involution was observed in pars distalis cells except for PRL cells in males or females during hibernation.     

Ultrastructure of the kidney of a South American caecilian,Typhlonectes compressicaudus (Amphibia,Gymnophiona)

Summary The ultrastructure of the distal nephron, the collecting duct and the Wolffian duct was studied in a South American caecilian, Typhlonectes compressicaudus (Amphibia, Gymnophiona) by transmission and scanning electron microscopy (TEM, SEM). The distal tubule (DT) is made up of one type of cell that has a well-developed membrane labyrinth established both by interdigitating processes and by interlocking ramifications. The processes contain large mitochondria, the ramifications do not. The tight junction is shallow and elongated by a meandering course. The connecting tubule (CNT) is composed of CNT cells proper and intercalated cells, both of which are cuboidal in shape. The CNT cells are characterized by many lateral interlocking folds. The intercalated cells have a dark cytoplasm densely filled with mitochondria. Their apical cell membrane is typically amplified by microplicae beneath which a layer of globular particles (studs) is found. The collecting duct (CD) is composed of principal cells and intercalated cells, again both cuboidal in shape. The CD epithelium is characterized by dilated intercellular spaces, which are often filled with lateral microfolds projecting from adjacent principal cells. The apical membrane is covered by a prominent glycocalyx. The intercalated cells in the CD are similar to those in the CNT. The Wolffian duct (WD) has a tall pseudostratified epithelium established by WD cells proper, intercalated cells and basal cells. The WD cells contain irregular-shaped dense granules located beneath the apical cell membrane. The intercalated cells of the WD have a dark cytoplasm with many mitochondria; their nuclei display a dense chromatin pattern.Research fellow of the Alexander von Humboldt Foundation     

Microfibrils are a major component of the mesangial matrix in the glomerulus of the rat kidney

Summary Certain secretory cells in the hypophysial pars tuberalis of the Djungarian hamster display marked circannual structural alterations. The present investigation deals with the immunohistochemical properties of this cell group. A distinct TSH-like immunoreactivity was found in secretory cells of this type in the pars tuberalis of animals exposed to long photoperiods, whereas under short photoperiods the TSH-like immunoreactivity was nearly absent. In the pars distalis, the number and distribution of TSH-positive cells did not differ significantly between animals maintained under long and under short photoperiods. LH-and FSH-positive cells could not be detected in the pars tuberalis, but they are clearly present in the pars distalis of both groups of hamsters. Our immunocytochemical results suggest that photoperiodic stimuli influence the secretory activity of TSH-like immunoreactive cells in the pars tuberalis. A connection with the neuroendrocrine-thyroid axis is discussed.The study was supported by the Deutsche Forschungsgemeinschaft (Wi 558/3-1, Pe 134/2-4)     

Biochemical switching device realizing McCulloch-Pitts type equation

We analyzed cyclic enzyme systems, one of the best candidates for biochemical switching devices, especially focusing on their control mode against external perturbations. Since these systems have the reliability of ON-OFF types of operation (McCulloch-Pitts' neuronic equation), we shall present here the mechanical difference between these systems and electronic switching circuit, especially on the mnemonic mechanism of biochemical switching devices.     

Effects of medicinal plant extracts from Chinese herbal medicines on the mutagenic activity of benzo[a]pyrene

The effects of medicinal plants on the mutagenicity of benzo[a]pyrene were studied with Salmonella typhimurium tester strains. The chosen medicinal plants are very frequently used as Chinese herbal medicines. Each medicinal plant was extracted with hot water, which is similar to the method used in Chinese medicinal treatment. Cinnamomi cortex, Rhei rhizoma, Scutellariae radix and Rehmanniae radix were found to decrease the mutagenic activity of benzo[a]pyrene. Atractylodis rhizoma also reduced the mutagenicity of benzo[a]pyrene, but this was not certain, because it showed a killing effect on the cell survival test. Bupleuri radix and Aurantii nobilis pericarpium had an enhancing effect, but then neither of these extracts is itself mutagenic. Each medicinal plant extract showed a different effect on the mutagenicity of benzo[a]pyrene. These effects were classified into 5 types: (I) decreasing effect, (II) killing effect, (III) enhancing effect, (IV) enhancing and decreasing effect and (V) inactive.     

Cloning and characterization of porcine brain cofilin cDNA. Cofilin contains the nuclear transport signal sequence

Cofilin is a widely distributed, pH-sensitive, actin-modulating protein with an apparent molecular mass of 21 kDa, which forms intranuclear and/or cytoplasmic actin/cofilin rods in cultured fibroblastic cells under specific conditions. In this study, a cDNA library from porcine brain mRNA was constructed, and full-length brain cofilin cDNA clones were isolated by screening with oligonucleotide probes. The deduced amino acid sequence of cofilin is 166 residues long and contains a sequence of Lys-Lys-Arg-Lys-Lys which is very similar to the nuclear transport signal sequence (Pro-Lys-Lys-Lys-Arg-Lys-Val) of SV40 large T antigen. The sequence may act as a signal capable of inducing nuclear accumulation of cofilin in cells exposed to heat shock or dimethyl sulfoxide. The cofilin sequence contains a hexapeptide (Asp-Ala-Ile-Lys-Lys-Lys) identical to the amino-terminal sequence (residues 2-7) of muscle and nonmuscle tropomyosin. Cofilin also has in the carboxyl-terminal portion a region homologous to the sequence shared by gelsolin, fragmin, and Acanthamoeba profilin. Furthermore, the overall amino acid sequence of cofilin shows weak homology with the rod portion of myosin and suggests a high alpha-helical content.     

Purification and characterization of kinesin from bovine adrenal medulla

Kinesin was purified from bovine adrenal medulla. The sedimentation coefficient was 8.8 S. Sedimentation equilibrium ultracentrifugation studies showed the molecular weight of kinesin to be 300,000. The calculated axial ratio was 1:16. The Stokes radius was estimated to be 8.9 nm by gel filtration. Circular dichroism showed the alpha-helix content to be about 50%. Purified kinesin preparation contained a major polypeptide with a molecular weight of 120,000 and minor ones with molecular weights of 71,000, 68,000, and 65,000. Bovine adrenal kinesin had an ATPase activity which was stimulated severalfold by microtubules to a specific activity of about 0.1 mumol/min.mg. Kinesin molecules adsorbed to a glass slide promoted the movement of microtubules on the glass surface at a rate of about 0.5 micron/s. Immunostaining of EBTr (bovine embryonic trachea fibroblast) cells and bovine adrenal chromaffin cells in interphase with an affinity-purified antibody against the major polypeptide of kinesin showed that some kinesin was located on microtubules and the rest distributed throughout the cytoplasm in a diffuse manner. EBTr cells in mitotic phase gave a staining pattern showing that kinesin was present throughout the cytoplasm with higher concentration in the region of mitotic apparatus.