Kinetics of the reconstitution of hemoglobin from semihemoglobins α and β with heme

Kinetics of the reconstitution of hemoglobin from semihemoglobins and with hemin dicyanide have been investigated using three kinds of stopped-flow technique (Soret absorption, fluorescence quenching of tryptophan, and Soret CD). The semihemoglobins and are occupied by heme in the and chains, respectively, the other chain being heme-free. Based on the kinetic results, the following scheme for the reconstitution is proposed; First, hemin dicyanide enters the pocket-like site of the apo chains. Second, in semihemoglobin , the CN-ligand in the fifth coordination position of iron is replaced by the imidazole ring of the proximal His immediately after the heme insertion. In contrast, semihemoglobin changes its conformation after the heme insertion, and this is followed by the ligand replacement. Finally, the partial structure changes induced by the ligand replacement propagate onto the whole molecule and the final conformation is attained. The results indicate that semihemoglobin retains a more rigid and organized structure, and more closely approaches its final structure than does semihemoglobin . Correspondence to: Y. Kawamura-Konishi     

Influence of the surface potential on the Michaelis constant of membrane-bound enzymes: effect of membrane solubilization

We have purified from a membrane fraction of bovine brain a calmodulin-binding protein (calspectin) that shares a number of properties with erythrocyte spectrin: It has a heterodimeric structure with M_r 240 000 and 235 000 and binds to (dimeric form) or crosslinks (tetrameric form) F-actin. We show that calspectin (tetramer) is capable of inducing the polymerization of G-actin to actin filaments by increasing nucleation under conditions where actin alone polymerizes at a much slower rate. Thus, brain calspectin behaves in the same manner as erythrocyte spectrin, supporting the idea that, in conjunction with actin oligomers it comprises the cytoskeletal meshwork underlying the cytoplasmic surface of the nerve cell.     

Induction of a neutral protease from rat intestine by a dietary manipulation

The activity of a neutral protease is increased in soluble fractions from the intestine of rats after a shift from a protein-free to a casein mash and an injection of triiodothyronine. The increased activity is prevented by the administration of cycloheximide. The time curve of the response of the protease activity in intestine is similar to that of liver DNA synthesis after a shift to 50% casein and triiodothyronine.     

Chromosome studies in the mammalian subfamily Antilopinae

The karyology was studied in nine species of Antilopinae and evaluated with regard to cytotaxonomic relations within the subfamily. Karyotypes of three of these species were previously undescribed. Chromosomes were examined by conventional staining methods, G-, C-, and T-banding techniques, and by autoradiography. Evolutionary differentiation of karyotypes in this group is characterized by extensive Robertsonian fusions and a particular translocation between the X chromosome and an autosome. With comparison of Giemsa-banding patterns a taxonomy has been constructed which differs most markedly from the classical taxonomy in two aspects: the blackbuck, Antilope cervicapra, shows a strong karyotypic affinity to gazelles of the subgenus Nanger; Thomson's gazelle, Gazella thomsoni, lacks the numerous Robertsonian fusions and the X-autosome translocation common to other members of Gazella studied to date. Cases of intraspecific polymorphism of chromosome morphology and number are presented.     

Dystrophin in rod spherules; submembranous dense regions facing bipolar cell processes

 It is known that the retina contains the protein dystrophin in the ribbon synapse, but the ultrastructural analysis is not yet fully elucidated. Our previous study reported that dystrophin is localized under the rod cell membranes in rat retinas. In the present study, we have investigated the relationship between dystrophin-rich regions of rod cell membranes and other neuronal processes in mouse retinas with a monoclonal antibody raised against the human dystrophin C-terminus. Immunoblotting, immunofluorescence stainings, and immunoelectron microscopy were employed. Immunoblotting analysis indicated that mouse retinas possessed some of the dystrophin isoforms of approximately 260 kDa, 140 kDa, and 70 kDa molecular weight. Confocal images showed a punctate appearance in the outer plexiform layer, as previously described. Immunoelectron microscopy showed that dystrophin immunoreactive products were always observed at submembranous dense regions of the rod spherule abutting bipolar processes. These results suggest that retinal dystrophin may be closely involved in signal transmission from rods to bipolar cells. Accepted: 7 May 1997     

The Electrophoretical Analysis of Esterase and Catalase and Its Use in Taxonomical Studies of Mycobacteria

The zymogram patterns of esterases and catalases of mycobacterial strains were studied using the thin layer agar electrophoresis. Though there were some variations, Mycobacterium hominis, M. bovis, M. kansasii, M. fortuitum, M. runyonii, M. avium, M. phlei and M. smegmatis seemed to show species-specific patterns consisting of 2 to 6 esterase bands and one or more catalase bands. The patterns of scotochromogens and nonchromogens were rather variable.     

Comparison of neuronal responses in primate inferior-temporal cortex and feed-forward deep neural network model with regard to information processing of faces

Journal of Computational Neuroscience - Feed-forward deep neural networks have better performance in object categorization tasks than other models of computer vision. To understand the relationship...