Immunohistochemical localization of type II and type I collagens in articular cartilage of the femoral head of dexamethasone-treated rats

The immunohistochemical localization of type II and type I collagens was examined in the articular cartilage of the femoral head of growing rats injected systemically with 5 mg kg−1 dexamethasone for 2 weeks every other day. The intensities of immunostaining for type II collagen, measured by microphotometry, was highest in the flattened cell layer and high in the hypertrophic cell layer, moderate in the proliferative cell and transitional cell layers and low in the superficial layer. After dexamethasone administration, the intensities decreased markedly in the flattened cell layer and slightly in the hypertrophic cell layer, although the decreases in other layers were negligible. The staining intensities for type I collagen were highest in the flattened cell layer, low in the superficial and transitional cell layers and very low in the proliferative and hypertrophic cell layers. After dexamethasone administration, the intensities increased markedly in the flattened cell layer and slightly in the superficial and proliferative cell layers, but did not change in the transitional and hypertrophic cell layers. Thus, dexamethasone administration caused a decrease in type II collagen and an increase in type I collagen in the matrix of the surface portion of articular cartilage. The composition of isoforms of collagen in the matrix changed after the steroid administration. The results strongly suggest that the shift in collagen composition from type II to type I predominance is a cause of the degeneration of the articular cartilage after glucocorticoid administration. This revised version was published online in November 2006 with corrections to the Cover Date.     

Polymorphism of axillary bud galls induced by Rhopalomyia longitubifex (Diptera: Cecidomyiidae) on Artemisia princeps and A. montana (Asteraceae) in Japan and Korea, with designation of new synonyms

In the past, Rhopalomyia longitubifex, Rhopalomyia shinjii, and Rhopalomyia sp. (Diptera: Cecidomyiidae) have been regarded as independent species based on differences in the sizes and shapes of axillary bud galls induced on Artemisia montana (Asteraceae) in Japan and A. princeps in Japan and Korea. However, comparison of morphological features and molecular sequencing data indicate that these Rhopalomyia gall midges are identical and that the differences in gall shape are polymorphisms, although the measurements of gall height and diameter overlap slightly. This finding suggests that although galls have frequently been regarded as extensions of the phenotype of a species, differences in gall shape may not always be reliable for identifying gall‐inducing cecidomyiids. The older name, R. longitubifex, is applied to these gall midges, and the names that were applied to this species on later occasions are revised or synonymized. The mature and immature stages of R. longitubifex are redescribed and information on the distribution, host range, and gall size of this species is provided. We also discuss the role of gall polymorphism in the early stages of speciation.     

Resurrection of Rabdophaga salicivora Shinji (Diptera: Cecidomyiidae), a Japanese gall midge formerly misidentified as a North American species, Rabdophaga rigidae (Osten Sacken), with observations on the phylogenetic relationships of its populations in Japan and the Russian Far East

Intercontinental biotic connections between Eurasia and North America are common in many gall midge genera (Diptera: Cecidomyiidae), but only a few species have been recorded from both continents. In Japan, four gall midge species had been previously considered to be identical to North American species, but three of these cases have already been disproved. We examined the remaining species, Rabdophaga rigidae, which had been originally described from Japan as Rabdophaga salicivora in 1938, later recorded from the Russian Far East in 1967, and synonymized with a North American species, R. rigidae, in 1982. Morphological features and partial sequence data of the mtDNA cytochrome oxidase subunit I (COI) region suggested that the Japanese species is a distinct species and is identical to the species recorded from the Russian Far East. We therefore apply the original name, R. salicivora, to the Japanese and the Russian species. In addition, on the basis of a molecular phylogenetic analysis, we conclude that R. salicivora possibly came to the Japanese Archipelago through the Korean Peninsula and established itself first in the southern parts of Japan. Then, it expanded its distribution range to northern parts of Honshu, but could not reach Hokkaido, probably because of the Tsugaru Strait between Honshu and Hokkaido.     

The role of aquaporin 3 in the movement of water and cryoprotectants in mouse morulae

The permeability to water and cryoprotectants of the plasma membrane is crucial to the successful cryopreservation of embryos. Previously, we have shown in mouse morulae that water and glycerol move across the plasma membrane by facilitated diffusion, and we have suggested that aquaporin 3 plays an important role in their movement. In the present study, we clarify the contribution of aquaporin 3 to the movement of water and various cryoprotectants in mouse morulae by measuring the Arrhenius activation energies for permeability to cryoprotectants and water, through artificial expression of aquaporin 3 using Aqp3 cRNA in mouse oocytes, and by suppressing the expression of aquaporin 3 in morulae by injecting double-stranded RNA of Aqp3 at the one-cell zygote stage. The results show that aquaporin 3 plays an important role in the facilitated diffusion of water, glycerol, and ethylene glycol, but not of acetamide and dimethylsulfoxide. On the other hand, in a propylene glycol solution, aquaporin 3 in morulae transported neither propylene glycol nor water by facilitated diffusion, probably because of strong water-solute interactions. These results provide important information for understanding the permeability of the plasma membrane of the mouse embryo.     

Monomeric A beta and metals reduce their cytotoxicities to each other

The present study has examined the effect of metals, such as iron and copper on the cytotoxicity of amyloid beta protein 1-40 (Abeta40). First, we showed that monomeric Abeta40 has stronger cytotoxicity than various type of aggregated Abeta40. Next we showed the addition of metals into the monomeric Abeta40 reduced the cytotoxicity of either monomeric Abeta40 or metals (iron and copper) although the addition of metals into monomeric Abeta40 resulted in a marked increase of aggregated form of Abeta40, which composed of beta-sheeted Abeta40 and Abeta40 aggregation not characterized by beta-sheet fibrils (coagrated Abeta40). Taken together, the metals and monomeric Abeta40 affect on each other and cause the reduction of their cell toxicity.     

Alteration of the kinetics of type I procollagen synthesis in human osteosarcoma cells by 1,25-dihydroxyvitamin D3

The kinetics of type I procollagen synthesis in a human osteosarcoma cell line, MG 63, were investigated after treatment with 1,25-dihydroxyvitamin D₃ (1,25-(OH)₂ D₃), a hormonal inducer of phenotypic differentiation. Pulse label and chase experiments demonstrated greatly enhanced production and more rapid reduction of intracellular procollagen molecules in the 1,25-(OH)₂ D₃–treated cells as compared to the nontreated case. After a chase for 1 h, labeled procollagen was reduced by nine-tenths in 1,25-(OH)₂ D₃–treated cells, while half of the radioactivity still remained in nontreated cells. The expression rate of type I collagen, which was examined by pulse label experiment, was elevated in association with an increase in the mRNA coding for the type I collagen α1 chain by 1,25-(OH)₂ D₃ treatment. However, the amount of intracellular procollagen present after 4 h continuous labeling was almost the same, independent of the 1,25-(OH)₂ D₃ treatment. Thus, we conclude that strage of the molecule was not affected. The results therefore suggest an increase in both the synthesis and secretion of type I collagen. The 1,25-(OH)₂ D₃ treatment was also found to induce the α subunit of prolyl 4-hydroxylase and to be associated with an elevated level of hydroxyproline in the procollagen. Moreover, gelatinase B–resistant procollagen molecules, indicative of intracellular procollagen molecules in the stable triple helical form, were detected only in the 1,25-(OH)₂ D₃–treated cells. These data suggest more efficient proline hydroxylation is involved in rapid secretion of procollagen after hormone administration. The present evidence points to posttranslational control of procollagen synthesis. J. Cell. Biochem. 65:542–549. © 1997 Wiley-Liss Inc.