Stereospecificity for oligosaccharides of two receptor sites in a labellar sugar receptor of the fleshfly.

Responses of a single sugar receptor to oligosaccharides, such as turanose, palatinose, cellobiose, trehalose, maltotriose, melezitose, and raffinose, were depressed almost completely after 3 min treatment with 0·5 mM p-chloromercuribenzoate (PCMB). In the same preparation, responses to d-glucose were depressed in the same manner, but those to d-fructose were hardly affected after PCMB treatment. This may indicate that these oligosaccharides do not react with a furanose site but react only with a pyranose site. The stereospecificity for these oligosaccharides of the sugar receptor are discussed.The response to 4 M d-mannose, a very weak stimulative sugar, was almost completely depressed after PCMB treatment, which suggests that a stimulative fraction of d-mannose reacts with the pyranose site in spite of its inhibitory effect on fructose stimulation.     

Visualization of intracellular ice crystals formed in very rapidly frozen cells at −27 °C

Tumor cells of an ascites sarcoma of rat were primarily frozen very rapidly with the original host ascitic fluid at ?27 °C by the spraying method. Frozen specimens were fractured and replicated at about ?100 °C under vacuum by a special spray-sandwich method for freeze-etching, and the morphological appearance of ice crystals formed in and around the frozen cells were observed by electron microscopy.The cells cooled very rapidly at ?27 °C actually froze intracellularly, and intracellular ice crystals ranged from 0.03 to 0.5 μm in grain size due to the initial freezing rate of the specimens. In the cells having granulous intracellular ice crystals less than 0.05 μm in grain size, cytoplasmic organelles seemed to maintain their original structures.We suggested in our previous report that these tumor cells, frozen very rapidly at temperatures above ?30 °C, survived intracellular freezing as long as they remained translucent, and optically no ice crystals appeared within them, as seen in intact unfrozen cells. It may therefore be concluded that the tumor cells frozen very rapidly at temperatures near ?30 °C actually freeze intracellularly and probably maintain their viability as long as the size of individual intracellular ice-crystals is kept smaller than 0.05 μm, although the exact critical size of innocuous intracellular ice crystals is uncertain.     

Human hepatocytes and aging: a cytophotometrical analysis in 35 sudden-death cases.

Alterations in the nuclear and cellular size of human hepatocytes occurring with age, and particularly in senescence, were studied by microphotometry. The material studied was obtained in 35 cases of sudden death, involving 17 males and 18 females ranging in age from 16 to 100 years. Cells of the peripheral zones of hepatic lobules were analyzed. The following results were obtained: 1. The mean nuclear area of hepatocytes remained relatively constant in subjects under 60 years of age but showed an increase in those over 60, this increase being associated with a greater standard deviation. 2. Volumetric analysis showed that the modal value included between 61 and 100% (mean 86%) of the cell nuclei examined and did not increase with age. This cell population was presumed to consist of diploid cells, the size of which remained constant. 3. An increase in mean nuclear area was due to the appearance of cells with larger nuclei which probably were the result of polyploidization. 4. Hepatocyte size increased with age. Analysis of the nucleus-to-cell sizes showed that the increase in cell size with age was more significant than the increase in nuclear size. 5. Cellular enlargement was more closely correlated with decrease in gross liver weight than with nuclear enlargement.     

Expression of cell adhesion molecule,Gicerin/CD146 during the formation of heart and in the cardiac hypertrophy

Molecular and Cellular Biochemistry - Gicerin/CD146 is a cell adhesion molecule which belongs to the immunoglobulin (Ig) superfamily. We have reported the existence of gicerin/CD146 in the nervous...     

Late Quaternary Environmental and Human Impacts on the Mitochondrial DNA Diversity of Four Commensal Rodents in Myanmar

Journal of Mammalian Evolution - We addressed the spatiotemporal characteristics of four commensal rodent species occurring in Myanmar in comparison with other areas of the Indo-Malayan region. We...     

Identification and Dynamics of Arabidopsis Adaptor Protein-2 Complex and Its Involvement in Floral Organ Development

The adaptor protein-2 (AP-2) complex is a heterotetramer involved in clathrin-mediated endocytosis of cargo proteins from the plasma membrane in animal cells. The homologous genes of AP-2 subunits are present in the genomes of plants; however, their identities and roles in endocytic pathways are not clearly defined in plants. Here, we reveal the molecular composition of the AP-2 complex of Arabidopsis thaliana and its dynamics on the plasma membrane. We identified all of the α-, β-, σ-, and μ-subunits of the AP-2 complex and detected a weak interaction of the AP-2 complex with clathrin heavy chain. The μ-subunit protein fused to green fluorescent protein (AP2M-GFP) was localized to the plasma membrane and to the cytoplasm. Live-cell imaging using a variable-angle epifluorescence microscope revealed that AP2M-GFP transiently forms punctate structures on the plasma membrane. Homozygous ap2m mutant plants exhibited abnormal floral structures, including reduced stamen elongation and delayed anther dehiscence, which led to a failure of pollination and a subsequent reduction of fertility. Our study provides a molecular basis for understanding AP-2–dependent endocytic pathways in plants and their roles in floral organ development and plant reproduction.     

Fluorescent-Based Methods for Gene Knockdown and Functional Cardiac Imaging in Zebrafish

A notable advantage of zebrafish as a model organism is the ease of gene knockdown using morpholino antisense oligonucleotide (MO). However, zebrafish morphants injected with MO for a target protein often show heterogeneous phenotypes, despite controlling the injection volume of the MO solution in all embryos. We developed a method for estimating the quantity of MO injected into each living morphant, based on the co-injection of a control MO labeled with the fluorophore lissamine. By applying this method for knockdown of cardiac troponin T (tnnt2a) in zebrafish, we could efficiently select the partial tnnt2a-depleted zebrafish with a decreased heart rate and impairment of cardiac contraction. To investigate cardiac impairment of the tnnt2a morphant, we performed fluorescent cardiac imaging using Bodipy-ceramide. Cardiac image analysis showed moderate reduction of tnnt2a impaired diastolic distensibility and decreased contraction and relaxation velocities. To the best of our knowledge, this is the first report to analyze the role of tnnt2a in cardiac function in tnnt2a-depleted living animals. Our combinatorial approach can be applied for analyzing the molecular function of any protein associated with human cardiac diseases.     

Inactivation of Rabbit Liver Carbonyl Reductase by Phenylglyoxal and 2,3,4-Trinitrobenzenesulfonate Sodium

The chemical modifications of rabbit liver carbonyl reductase (RLCR) with phenylglyoxal (PGO) and 2,3,4-trinitrobenzenesulfonate sodium (TNBS), which are respective chemical modifiers of arginine and lysine residues, were examined. RLCR was rapidly inactivated by these modifiers. Kinetic data for the inactivation demonstrated that each one of arginine and lysine residues is essential for catalytic activity of the enzyme. Furthermore, based on the protective effects of NADP +, NAD + and their constituents against the inactivation of RLCR by PGO and TNBS, we propose the possibility that the functional arginine and lysine residues are located in the coenzyme-binding domain of RLCR and interact with the 2′-phosphate group of NADPH.