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.     

Monoclonal antibodies to mouse complement receptor type 1 (CR1). Their use in a distribution study showing that mouse erythrocytes and platelets are CR1-negative

mAb to murine C receptor type 1 (CR1) were produced and three of them were characterized. One antibody, designated as 8C12, immunoprecipitated a protein of 190,000 Mr from a detergent extract of surface-labeled spleen cells and stained spleen B but not T lymphocytes in fluorescent flow cytometry. It inhibited both CR1-mediated rosette formation and the cofactor activity of CR1 for factor I-mediated cleavage of C3b, suggesting that it recognizes the ligand-binding site of CR1. The two other antibodies, designated as 7G6 and 7E9, recognized different epitopes from that recognized by 8C12, and they cross-reacted with a protein of 150,000 Mr that is present in a spleen extract. The distribution of CR1 in murine hemopoietic cells was studied by binding experiments with radiolabeled 8C12 and fluorescent flow cytometry. When CR1 was not detected by 8C12 alone, the two other antibodies were used in combination with 8C12 to confirm the negative results. Almost all B lymphocytes from the spleen, lymph nodes, and peripheral blood were CR1 positive. Most of the Thy-1-positive lymphocytes from these tissues were CR1 negative. Thymus lymphocytes were also CR1 negative. Peritoneal macrophages and chemotactic factor stimulated but not unstimulated peripheral blood granulocytes were CR1 positive. In contrast to human E, mouse E were CR1 negative. This pattern of distribution was consistent with previous results obtained by rosette assays. Although mouse platelets cause immune adherence hemagglutination with C3b-bearing SRBC, they are CR1 negative. Three other lines of evidence also indicated that platelets are CR1 negative. First, no band of CR1 was demonstrated by immunoprecipitation with 8C12 of an extract of surface-labeled platelets. Second, 8C12, which inhibited rosette formation by lymphocytes, alone or in combination with 7G6 and 7E9, did not inhibit immune adherence between platelets and C3b-bearing SRBC. Third, polyclonal rabbit IgG prepared from anti-mouse CR1 antiserum did not inhibit immune adherence by platelets. These results strongly suggest that the C3b-binding factor(s) on mouse platelets is different from CR1 and that processing of C3b-bearing immune complexes in mouse blood may be mediated by a new and as yet unidentified C3b-binding factor(s).     

Cytokinetic effects of carboplatin and cisplatin on a human ovarian cancer cell line

The cytokinetic effects of carboplatin(CBDCA) on a human ovarian cancer cell line(KF-1) were examined by means of cell survival rate and flow cytometry in comparison with cisplatin(CDDP). CBDCA and CDDP exhibited dose dependent cytotoxicity on KF-1, and CBDCA showed compatible cell growth inhibition to that of 15 times concentration of CDDP in comparison with IC50 of 72 hrs after drug addition. From the analysis of cell cycle, CBDCA and CDDP inhibited cell cycle progression at G2 + M phase. CBDCA exhibited G2 + M phase block to that of 15 to 20 times the concentration of CDDP. We suggested that CBDCA had potential therapeutic activity against ovarian cancer, but should be evaluated carefully in the clinical use.