Observation of internal structure of biological sample was carried out with newly developed 3-Dimensional Internal Structure Microscope (3D-ISM). A true colored 3-dimensional image of the sample with high resolution and high quality was obtained with this system compared with those image available with X-Ray CT, MRI or microtome used. The internal structure of a sample was obtained by observing each sliced side after each slicing, while the slicing and observing procedure was proceeded continuously. After repeatedly slicing a sample, the digital image data of the sectional views were transferred to a computer, where 3-dimensional image of the internal structure of the sample was reconstructed. This report describes the observation and the measurement of the biological sample with a developed device.

抄録全体を表示

This article is intended to summarize the state-of-the art of cryopreservation of biological organs by raising eight questions to be answered. Brief answers and comments are given to each of the questions. Although they never are sufficient for complete understanding of the phenomena occurring in cryopreservation, they might be useful for letting us know better what we should do next.

抄録全体を表示

The purpose of this study is to evaluate whether the thermophysical properties of cells reflect the freezing process, and can be used as indices of cryopreservation. Medaka embryo (Oryzias latipes) was selected as the biological material for this study. The effective thermal conductivity of Medaka embryos was measured using the self-heated thermistor technique developed by Balasubramaniam and Bowman (1977). The test chamber (8×8×12 mm) was covered with insulating material, and a thermistor bead of 2.5 mm in diameter installed in the bottom. The effective thermal conductivity was measured at 6, 0, -4, -10, -15 and -20℃ with a cooling rate of 1℃/min, and the viability of the embryos was evaluated by the hatching rate. The effective thermal conductivity is closely correlated with the hatching rate, increasing as the their hatching rate decreased. Thus the thermophysical properties of biological materials can be used as indices with which to evaluate the freezing process.

抄録全体を表示

The change of moisture distribution profile in a grain of rice during boilling was observed by NMR T2 imaging. The 2-D T2 images were taken over a series of rice grain samples which were boiled for predetermined minutes and quenched. A real time observation was done using a 1-D CPMG T2 imaging method. The rise of moisture profile was shown to be much faster than that predicted by a simulation where Fickian diffusion was associated with the reaction of starch gelatinization. This discrepancy suggested that moisture diffusivity and /or starch gelatinization rate used in the simulation were wrong, and there is a need for more appropriate measurements.

抄録全体を表示

Tulip bulbs require a low temperature period to activate dormancy breaking. To elucidate factors on dormancy breaking induced by low temperatures, changes in dynamic states of water in tulip bulb tissues were non-destructively determined by proton density and spin-lattice relaxation times (T_1) images using MRI. The low temperature treatment increased signal intensity of mobile water in the inner part of the scale parenchyma tissue whereas no mobile water was observed in noncooled bulb scales. On the contrary, water mobility in the epidermal system containing aquiferous (water storage) tissue of the scale was higher in the noncooled bulb while no signal was observed in the precooled bulbs. Furthermore, the long fraction of spin-spin relaxation time (T_2) increased to about 75% in the scale parenchyma tissue in the precooled bulb, while it remained about 60% in the noncooled ones. Although no difference in total amounts of water content was observed in the whole bulbs stored at both temperatures, a significant increase of water content in the inner part of the scale parenchyma tissue was observed in the precooled bulb. Further, the respiration rate of the whole precooled bulbs during the storage period was suppressed to as low as half that of the noncooled bulbs. And the sugar accumulation of the precooled bulb scales was twice that of the noncooled bulbsn. Therefore, water status detected by NMR suggested that water migration from the aquiferous tissue of epidermal system to the inner part of the scale parenchyma occurs through higher osmotic pressure (Ψ_π) resulting from higher sugar accumulation during cold storage. When the precooled bulbs were transferred to 20 ℃, the treatment resulted in a threefold increase in respiration as compared with noncooled bulbs. These results suggest an effect of water redistribution in scale parenchyma tissue during cold storage. In succession, higher water production resulting from higher respiration in the precooled bulbs when transferred to ambient temperatures encouraged metabolic activity. These synergistic effects in water status would lead to rapid growth of the flower stalk after planting.

抄録全体を表示

Since a serious incidence of food poisoning by Escherichia coli O157 happened in 1996, the importance for hygienic control of fruits and vegetables has become to be recognized. This short review describes the actual situation and problems about sterilization methods of fruits and vegetables in low temperature distribution processes. It also mentions the sanitation manual of radish sprouts cultivation which is based on HACCP system. This manual is enacted for safety security of the water cultivated vagetables.

抄録全体を表示

Metabolism is based on enzyme reactions. The rate of enzyme reaction is regulated by the diffusion of substrate governed by the viscosity of water. Xenon gas in water has great ability for the formation of structured water as a result of hydrophobic hydration. As spin-lattice relaxation time T_1 of protons in water has a close relationship with viscosity, the change in viscosity of structured water was examined through T_1. Xenon gas was applied to barley coleoptiles and broccoli. The rate of protoplasmic streaming in coleoptile cells decreased as intracellular water became structured. The structured water was also confirmed to be effective for the suppression of respiration of broccoli.

抄録全体を表示

Water is known to have two amorphous solid states at low temperatures. Connecting these two amorphous states and the high-temperature liquid state, Poole et al. proposed a new physical picture for water: the liquid-liquid phase transition hypothesis. Presently, available experimental data and simulation results are consistent with this hypothesis. However, the nature of liquid water is not elucidated unambiguously.

抄録全体を表示

Ice structure was quantitativly described in the freezing of food. The moving speed of freezing front plays a key role in the determination of ice structure. Supercooling was proved to give a very fine structure of ice although the process was uncontrollable. On the contrary, pressure-shift freezing also gave a fine ice structure in the controlled process. In the freezing of living cell, water permeabillity of plasma mambrane is very important in the freeze-induced osmotic dehydration process. Dielectric measurement was proved to be effective for the measurement of water permeability of plasma membrane. Water pemeability of plant cell membrane was lower, in general, than that of animal cells, which seems to explain the poor freezing tolerance of plant cells. Effects of ice structure were discussed on the quality of frozen food and the drying rate in freeze drying. Progressive freeze concentation was proposed to be an economical alternative to suspension crystallization method in freeze concentration.

抄録全体を表示