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Biomedical subjects

Y Mitamura

Publications and source records attributed to Y Mitamura.

59 records · Page 4Linked to original sources
PubMedDate not supplied

Monocyte chemotactic protein-1 in the vitreous of patients with proliferative diabetic retinopathy.

PURPOSE: To investigate the correlation between monocyte chemotactic protein-1 (MCP-1) levels in the vitreous and clinical findings in eyes with proliferative diabetic retinopathy (PDR). METHODS: We assayed MCP-1 levels by ELISA in vitreous samples of 88 consecutive patients with PDR (52 eyes) and macular holes or idiopathic epimacular membrane (controls, 36 eyes). RESULTS: The level of MCP-1 in the vitreous was 2,097.5 +/- 1,099.4 pg/ml (mean +/- SD) in PDR, and 504.3 +/- 405.6 pg/ml in the controls. In PDR eyes, multivariate regression analysis revealed a significant association between MCP-1 levels in the vitreous and the degree of proliferative membrane, and a significant negative association between MCP-1 levels and the extent of preoperative retinal photocoagulation. CONCLUSION: The results suggest that MCP-1 may play a role in the development of the proliferative phase of PDR.

Adult↗
PubMedDate not supplied

The valvo-pump. An axial, nonpulsatile blood pump.

The valvo-pump, an axial, nonpulsatile blood pump implanted at the heart valve position while preserving diseased heart muscle, has several advantages over an artificial heart replacement, including 1) a good anatomic fit to the natural heart, 2) less blood contacting surface, and 3) ease of implantation. The housing for the pump is a tube, 37 mm in diameter (maximum) and 33 mm in length. Within the housing there is an impeller with either 10 vanes (33 mm in diameter) or 5 vanes (22 mm in diameter). The impeller is connected to a samarium-cobalt-rare-earth magnet direct current (DC) brushless motor measuring 23.8 mm in diameter and 30.2 mm in length. Sealing is achieved by means of a magnetic fluid seal. A guiding wheel with 4 vanes is located behind the impeller. The pump was studied on a hydraulic mock circulatory system to evaluate its performance characteristics. A pump flow of 6.9 L/min was obtained at a pump differential pressure of 48 mmHg, and flow of 3.1 L/min was obtained at 58 mmHg. The valvo-pump can be made feasible by developing a small, high-output, power motor and an endurable seal, as well as by optimizing the impeller design.

Electric Power Supplies↗
PubMedDate not supplied

A transcutaneous optical information transmission system for implantable motor-driven artificial hearts.

Precise regulation of output voltage (motor voltage) and monitoring of the implanted pump were obtained with a transcutaneous energy transmission system. Information on both motor voltage and pump stroke is transmitted through the skin by frequency-modulated infrared pulses using a light emitting diode and a phototransistor. The motor voltage is compared with the nominal value, and the duty cycle of the primary pulse is regulated according to the error signal. Infrared pulses up to 100 KHz were transmitted through porcine muscle up to 1 cm thick. Both the pump stroke and motor voltage signals were transferred across the muscle without interference. The output voltage was kept almost constant for the change in tissue gap of 3-8 mm and of 0-10 mm in radial displacement. The system developed is useful for implantable artificial hearts.

Electric Conductivity↗
PubMedDate not supplied

Modification of the frictional surfaces of artificial joints.

To overcome the wear problems associated with artificial joint materials, new surface structures with regular patterning were designed and fabricated. The lubrication properties were studied to evaluate the wear of the frictional surfaces. The surface structure was a pattern of "dents" with a diameter of 0.2-1.0 mm and a pitch of 0.6-2.0 mm. The pattern was fabricated on the stainless steel (SUS) surface by a photochemical etching technique with 3 microns depth, and on an ultrahigh molecular weight polyethylene (UHMWPE) surface by mechanical processes. The time dependent changes of frictional force between SUS and UHMWPE were measured, and the surface morphologic changes were observed. The patterned surface showed lower frictional force than the smooth non-patterned surface, and less wear occurred on the patterned sample than on the sample without a pattern. There were optimum sizes for the diameter and the pitch of the pattern. These results demonstrated that lubrication properties could be improved by patterning of the frictional surfaces. The surface patterning was effective in preventing wear of the frictional surface, and the life of an artificial joint could be extended by such patterning.

Biomechanical Phenomena↗