A Theoretical Model of Jigsaw-Puzzle Pattern Formation by Plant Leaf Epidermal Cells

Plant leaf epidermal cells exhibit a jigsaw puzzle–like pattern that is generated by interdigitation of the cell wall during leaf development. The contribution of two ROP GTPases, ROP2 and ROP6, to the cytoskeletal dynamics that regulate epidermal cell wall interdigitation has already been examined; however, how interactions between these molecules result in pattern formation remains to be elucidated. Here, we propose a simple interface equation model that incorporates both the cell wall remodeling activity of ROP GTPases and the diffusible signaling molecules by which they are regulated. This model successfully reproduces pattern formation observed in vivo, and explains the counterintuitive experimental results of decreased cellulose production and increased thickness. Our model also reproduces the dynamics of three-way cell wall junctions. Therefore, this model provides a possible mechanism for cell wall interdigitation formation in vivo.     

Embigin/basigin subgroup of the immunoglobulin superfamily: Different modes of expression during mouse embryogenesis and correlated expression with carbohydrate antigenic markers

Embigin and basigin are highly glycosylated transmembrane glycoproteins with two immunoglobulin domains and form a subgroup in the immunoglobulin superfamily. Previous studies have demonstrated the functional significance of these molecules. In the present study, in situ hybridization analysis of their expression was performed during mouse embryogenesis. Embigin was strongly expressed in the endoderm during early postimplantation embryogenesis, and in the somite stage in the gut and visceral endoderm. Embryonic ectoderm and its derivative tissues weakly to moderately expressed this molecule. From day 10 to 15 of gestation, no embigin signal was detected. Basigin was more broadly expressed. During the organogenesis period, basigin was expressed in various epithelial tissues, brain ventricles, the spinal cord and dorsal root ganglion. The modes of expression of these two proteins throughout the egg cylinder stage correlated with the expression of the carbohydrate markers that they carry; embigin with Dolichos biflorus agglutinin binding sites and basigin with Le^x antigen and more closely with fucosyltransferase IV, which forms the antigenic epitope. These findings imply that proteins with specific carbohydrate epitopes play roles in early postimplantation embryogenesis.     

Chemical Composition of the Cell Walls of Clostridium botulinum Type A

Cell walls were isolated by sonic disruption of log-phase cells of Clostridium botulinum type A strain 190L and purified by treatment with sodium dodecyl sulfate (SDS) followed by digestion with proteases. Electron microscopy revealed that the cell walls thus obtained were free of both cytoplasmic membrane and cytoplasmic fragments. The purified cell wall contained 8.7% total nitrogen, 15.0% total hexosamines, 22.4% reducing groups, 8.3% carbohydrate, and 3.1% glucose. The content of total phosphorus was very low (0.02%), and therefore it was expected that teichoic acid might be absent in the cell wall. The wall peptidoglycan contained glutamic acid, alanine, diaminopimelic acid, glucosamine and muramic acid in the molar ratios of 1.00:1.85:0:85:1.06:0.67. A low amount of galactosamine was also present, but no other amino acids were found in significant quantities. The SDS-treated cell walls were not attacked by lysozyme, but after extraction with hot formamide they were completely dissolved by the enzyme and released reducing groups. The lysozyme digest was separated into two constituents, the saccharide moiety and the peptide moiety on Sephadex G-50.     

Problems of Acyl Migration in Lipase-Catalyzed Enantioselecttve Transformation of Meso-1,3-Diol Systems

In the enantioselective hydrolysis of the di-O-acetyl derivatives of meso-1,3-diol catalyzed by lipases, racemization of the monoacetate products occurs due to non-enzymatic general base-catalyzed acyl migration. The rate of acyl migration increases with increase of pH and buffer concentration. A mechanism of the migration has been proposed to proceed through a six-member ring transition that accounts for the experimental results. The acyl migration, however, was not observed in the enantioselective transesterification of meso-1,3-diols in neutral organic solvents.     

Specific refractoriness of adenylate cyclase in skin to epinephrine,prostaglandin E,histamine and AMP

The cyclic AMP level in pig skin (epidermis) increases markedly after incubation with epinephrine, prostaglandin E, histamine or adenosine 5′-monophosphate. This increase is transient and “spiking” is the consistent response to these four stimulators. The “spiking” is due to a non-responsiveness or refractoriness which develops within minutes and is specific to any one stimulating hormone but not to the others. The addition of inhibitors of protein syntheses did not prevent the development of the refractoriness. Adenylate cyclase and phosphodiesterase activities measured in skin homogenates prepared from skin samples taken before, during and after the “spiking” did not change significantly. The hormone-induced refractoriness in this skin system appears to be due to a specific, localized loss of function of the adenylate cyclase system.     

Differences in rapid eye movement sleep behavior disorder manifestation between synucleinopathies and tauopathies

Rapid eye movement sleep behavior disorder (RBD) frequently occurs in synucleinopathies including multiple system atrophy, Parkinson’s disease, and dementia with Lewy bodies despite the clinical course of RBD being different between these disorders. Comparatively, the existence of RBD symptoms is relatively rare in patients with progressive supranuclear palsy, a tauopathy showing atypical parkinsonism compared with Parkinson’s disease. Moreover, in patients with Alzheimer’s disease, which is another tauopathy, RBD symptoms are less frequent than dementia with Lewy bodies, although both disorders share commonalities in terms of the existence of cortical dementia. Thus, RBD is thought to be relatively specific to synucleinopathies.

     

Thy-1 inhibits mitogen-induced Ca2+ oscillation in ras-transformed mouse fibroblasts.

Cell surface glycoprotein Thy-1 functions as a transformation suppressor in v-ras-transformed NIH/3T3 cells [Sugimoto et al., (1991) Cancer Res. 51, 99-104.]. In order to understand the mechanism of action of Thy-1, we examined the effect of Thy-1 expression on mitogen-induced Ca2+ oscillation which was correlated with v-ras-transformation [Fu et al., (1991) FEBS Lett. 281, 263-266.]. Forced expression of Thy-1 in v-ras-transformed cells inhibited mitogen-induced Ca2+ oscillation. Although v-Ras-free, Thy-1-positive NIH/3T3 cells (major population) did not show Ca2+ oscillation, whereas in Thy-1-negative NIH/3T3 cells (less than 1% of the population) Ca2+ oscillation was observed. Finally, replacement of the carboxyl-half of Thy-1 with that of CD4 abolished the inhibitory effect of Thy-1. These results suggest that Thy-1 directly or indirectly participates in the negative regulation of Ca2+ response by inhibiting Ca2+ oscillation.