The feasibility of being able to conduct noninvasive measurement of HbAlc concentration based on photoacoustic spectroscopy was studied. A spheroid-type signal-detecting cell was newly developed to improve the sensitivity of the detecting cell. The cell was appropriately designed so that the positions of two focal points of the cell corresponded to those of a detecting microphone and a photoacoustic source under the skin, respectively. This cell was able to improve the Q-value eightfold that of a conventional Helmholtz-type cell. The signal-to-noise ratio of the total system was improved to 48 dB, which may be sufficient to detect the photoacoustic signal generated from a deep skin layer. The performance of the system developed was evaluated by conducting measurement experiments on HbAlc concentration using a phantom that consisted of a swine skin tissue and an HbAlc solution. In the experiments, the concentration of HbAlc was determined from photoacoustic signals using dualwavelength spectroscopy. It was shown that the HbAlc concentration was measured by our photoacoustic system with an accuracy of 3%.

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Suturing using needle and thread is one of the basic operations in surgical operations. Suture knot making is very difficult in a distance equal to that of the surgeon's working space, such as during laparoscopic surgery. To cope with this difficulty, several methods have been proposed, however they are not suitable for replacing the present suturing work done using needle and thread. This research proposes a new method where the threads are closed together at first, and then a heating device is used to melt and weld the ends of the threads together. This knot-making method is named the “weld method.”This report explains part of process for developing a surgical instrument that can make knots by means of the weld method during laparoscopic surgery. The author developed a prototype instrument that has a thread-knotting function, a forceps function and a thread cutting function within the 5 mm shaft diameter of the instrument. The thread diameter applied was about 0.2 mm. Thread shrinking length due to heating was about 5 mm. Heating conditions were researched to determine the sufficient tensile strength of the knot without scorching considering the limited space on the tip of 5 mm instrument shaft. It was shown that the tensile strength of welded knot has a practical value in the case of using thread with a diameter of about 0.2 mm, and that the welding method can be applied not only to nylon thread, but also to absorbable synthetic thread.

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There is increasing interest in the use of magnetic stimulation as a modality for clinical examination and therapy. It is desirable that the eddy current density produced by a change in the strength of a magnetic field should be greater than the excitability threshold of the muscles or nerves to be stimulated. Magnetic stimulation for clinical use has two advantages over electrical stimulation: 1) It can be carried out non-invasively without the need for skin-surface electrodes, and 2) the removal of the patient's clothing is not required. However, effective magnetic stimulation requires the input of a high current into the stimulation coil. The requisite equipment is therefore large and costly. It is necessary to develop magnetic stimulators that are more efficient in stimulating tissues and more convenient to use than those presently available. The eddy current waveform differs from the rectangular current waveform common in electrical applications. Basic studies on the effects of magnetic stimulation on threshold values and other aspects of eddy current waveforms have not been conducted. In this study, the authors attempted to measure the strength-duration curve (S-D curve) of eddy currents on the sural muscle of the bullfrog and propose a new S-D curve formula for eddy currents in place of Weiss's equation for rectangular current waveforms.

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Control of the total cholesterol level in the body plays an important role for preventing life-style related diseases. Currently, the measurement of cholesterol levels in clinical institutions is carried out using an absorption photometer with an enzymatic reaction. However, the conventional method is troublesome due to the necessity of going to a hospital for invasive blood collection and using the enzyme reaction through many procedures. On the contrary, about 11 percent of the body's cholesterol is found in the skin at the same rate as in the blood, according to the United States Federal Drug Administration. Therefore, we focus on a simple and noninvasive measurement for cholesterol using a molecularly imprinted self assembled monolayer (SAM) . A gold electrode was immersed in an ethanol solution containing cholesterol and stearylmercaptan, and then washed in ethanol in order to extract the cholesterol as a template molecule. The extraction of cholesterol molecules creates shape-complementary cavities on the SAM, and the detection of electro-inactive cholesterol is achieved using an electrochemical method with potassium ferrocyanide as the redox marker. The change in the oxidation peak current (I) shows a linear relationship with the cholesterol concentration. The change of I is related to the cavity concentration for the masstransport of the redox marker on the molecularly imprinted SAM. When the cholesterol-sensitive SAM recognizes cholesterol, I decreases due to marker diffusion rejection to the gold electrode surface. On the contrary, when the SAM extracts cholesterol, the marker diffuses to the electrode surface and 1 increases. The sensing properties of the molecularly imprinted SAM, such as sensitivity, selectivity, and reproducibility, have been examined, and it has been applied for simple and speedy electrochemical sensor development.

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An electrical cell-substrate impedance sensing (ECIS) system was developed by our collaborator, Giaever and Keese, some 10 years ago (Nature '93) to detect the nanometer order changes in cell-to-cell and cell-to-substrate distances of cultured cells on an electrode. The ECIS system has been applied widely for the analysis of cell responses to chemical (e.g., histamine) and mechanical (e.g., shear stress) stimulation. Although the significance of resistance parameters has been well established, the relationship between electrical capacitance and cell motion has not yet been sufficiently discussed. In this study, we analyzed the relationship between the electrical impedance and cell-to-cell and/or cell-to-substrate distance using a physical model with an insulator board, punched cylindrical holes and electrode. The insulator board and holes are supposed to be the cell itself and cell-to-cell distance, respectively. We investigated the influence of the changes of the cell-to-cell distance (hole size) (A) and cell-to-substrate (insulator-electrode) distance (h) on the electrical impedance. We measured the impedance over the frequency range from 20 Hz to 1 MHz. In practical application of the ECIS, 4 kHz is commonly used to detect the impedance change. Accordingly, we also investigated the impedance changes for various values of A and h at 4 kHz. When A was reduced, serial resistance R_s was remarkably increased, while parallel capacitance C_p was decreased and series capacitance C_s changed only slightly. The vector impedance loci increased greatly when A was reduced from 2.0 mm to 1.0 mm with h of 2.0 mm. On the other hand, when h was reduced, C_p increased, and C_s significantly decreased and parallel resistance R_p, R_s decreased only slightly. Since, resistance increases mainly with a decrease in A, and the capacitance decreases mainly with a decrease in h, it is suitable to evaluate the change in A using R_p, and that in h using C_s. In other words, the polarization impedance of electrode Z_p changes significantly, especially in the low-frequency band, when A or h changes, even if the electrode area is fixed. In conclusion, the ECIS system offers a useful method to separately detect cell-to-cell and cell-to-substrate distances.

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