Strategy for preparation of hybrid polymer hydrogels using silica nanoparticles as multifunctional crosslinking points.

Novel hybrid polymer hydrogels were prepared in a facile manner by simple mixing of a water-soluble copolymer having trimethoxysilyl side chains with silica nanoparticles used as multiple crosslinkers.

Saponin-induced release of single cells from filaments and rhizoid differentiation in Spirogyra.

Some species of Spirogyra living in streams can anchor to the substratum by differentiating a rhizoid from a terminal cell of a filament. Rhizoid differentiation occurs in the light but not in the dark. When a filament of Spirogyra sp. competent for rhizoid differentiation was incubated in a medium containing 0.1% saponin, terminal cells were released one by one, forming single cells. Single cells effectively differentiated to be rhizoids when saponin in the incubation medium was removed. The single-cell system developed in the present study seems suitable for analysis of gene expression during rhizoid differentiation of Spirogyra.

Synthesis of a callosic substance during rhizoid differentiation in Spirogyra.

Spirogyra living in running water is anchored to the substratum by rhizoids that form at the ends of the filaments. A new terminal cell differentiates into a rhizoid cell if the filament is injured. The mode of growth changes from diffuse to tip growth when rhizoid differentiation begins. In this study, we found that a callosic substance was synthesized during rhizoid differentiation. Decreasing the cell turgor, lowering extracellular Ca2+ or adding Gd3+, all inhibited the commencement of rhizoid differentiation as well as synthesis of the callose-like substance at the tip of the terminal cell. A callosic substance was also synthesized during formation of the conjugation tube.

Rhizoid differentiation in Spirogyra: position sensing by terminal cells.

Some species of Spirogyra anchor themselves to the substrate by differentiating rhizoids. A rhizoid is differentiated only from the terminal cell, suggesting that this cell can recognize its terminal position in a filament. In the present study, we have analyzed the mechanism for position sensing by the terminal cell. When a filament is cut, a new cell occupies the terminal position, and three phenomena are induced: (1) the cell wall of the cut cell detaches from the new terminal cell; (2) adhesive material is secreted by the terminal cell; and (3) the terminal cell begins to differentiate a rhizoid via tip growth. All of these phenomena were inhibited by adding sorbitol to the external medium, suggesting that turgor pressure is involved in position sensing by the terminal cell. The inhibition by sorbitol was reversible. Upon cutting a filament, the distal end of a new terminal cell became convex. However, when a filament was cut in the presence of sorbitol, the distal end of a new terminal cell became less convex. Either treatment with Gd(3+) or decrease in extracellular Ca(2+) resulted in inhibition of all these phenomena, suggesting possible involvement of stretch-activated ion channel in position sensing by terminal cells.

National regulations for diagnostics in health surveillance, therapy and compensation of hand-transmitted vibration injury in Japan.

OBJECTIVES: During the period of technological innovation and rapid economic development, portable power tools were introduced on a large scale in Japan. Vibration disease from the operation of those tools and its prevention and therapy became urgent social problems in the 1970s. This paper aims to introduce national regulations in Japan for diagnostics in the health surveillance, certification, therapy and compensation of vibration disease and evaluates them in the present perspective. METHOD: Relevant laws, regulations and administrative directives were described in chronological order. Effect of those laws, regulations and directives were evaluated by statistics. RESULTS: Relevant regulations were established in 1947 and were revised in the 1960s and 1970s. According to those regulations, administrative directives were issued. Relevant vibration-disease statistics improved from the 1970s to 1990s. The annual ratio of workers examined was 95% to 100% in national forests (NFs), 47.3% in 1980 and 40.8% in 1990 in private industry (PI). The number of workers certified in NFs was 1,796 from 1971-1975, with a decrease to nine from 1991-1995, while in PI there were 9,783 from 1976-1980, decreasing to 2,331 from 1991-1995. However, in the construction industry the number increased again in the 1990s. The top four workers certified by the type of tool from 1994-1997 were operators of rock drills, chainsaws, pick hammers and concrete vibrators. The annual number of workers under treatment (at highest level) was 3,605 (1982; NFs) and 13,501 (1987; PI), with a decrease to 3,481 (1997; NFs) and 8,958 (1997; PI). Regulations for compensation covered 3,670 workers from 1965 to 1997 (NFs) and 22,723 from 1976 to 1997 (PI) in medical treatment benefits, and 189 (NFs) and 15,448 (PI) in disability benefits during the same term. CONCLUSION: The national regulations developed in Japan since 1965 for health surveillance, certification, therapy and compensation of hand-transmitted vibration disease have proven effective for prevention and compensation of vibration disease in many industries, but unsolved problems remain in the construction industry.