Biomedical subjects

Masatoshi Ishikawa

Publications and source records attributed to Masatoshi Ishikawa.

7 recordsLinked to original sources

PubMed2006

A physical model for galvanotaxis of Paramecium cell.

We propose a qualitative physical model of galvanotaxis of Paramecium cells using a bottom-up approach to link the microscopic ciliary motion and the macroscopic behavior of the cells. From the characteristic pattern of ciliary motion called the Ludloff phenomenon, the torque that orients the cell toward the cathode is derived mathematically. Dynamical equations of motion are derived and their stability is discussed. In numerical simulations using our model, cells exhibit realistic behavior, such as U-turns, like real cells.

Animals↗

PubMed2005

Localization of ADAMTS13 to the stellate cells of human liver.

Although the chromosomal localization (9q34) of the gene encoding the human form of ADAMTS13 (a disintegrin-like and metalloproteinase with thrombospondin type-1 motifs 13) and its exclusive expression in the liver have been established, the cells that produce this enzyme are yet to be determined. We investigated the expression of ADAMTS13 mRNA and protein in fresh frozen specimens obtained during liver biopsies of 8 patients with liver diseases. In situ hybridizations to localize ADAMTS13 mRNA showed positive signals exclusively in perisinusoidal cells with irregularly elongated dendritic processes extending between hepatocytes. Furthermore, ADAMTS13 was detected immunohistochemically in perisinusoidal cells, whereas no staining was observed in hepatocytes. The positive cells varied in shape from unipolar to dendritic with irregularly elongated cytoplasmic processes, features common to hepatic stellate cells (HSCs). Double-labeling experiments revealed that the ADAMTS13-positive cells also expressed alpha-smooth muscle actin, confirming that these cells were activated HSCs. These results suggest that HSCs may be major cells producing ADAMTS13 in human liver.

ADAM Proteins↗

PubMed2005

Decreased activity of plasma ADAMTS13 may contribute to the development of liver disturbance and multiorgan failure in patients with alcoholic hepatitis.

BACKGROUND: The pathogenesis of alcoholic hepatitis (AH) remains unclear and the prognosis of severe alcoholic hepatitis (SAH) is very poor. Deficiency of von Willebrand factor (VWF)-cleaving protease (VWF-CP/ADAMTS13) results in an increase of the plasma unusually large VWF multimer and leads to platelet clumping, which causes microcirculatory disturbance and finally multiorgan failure. The aim of this study was to explore the potential role of ADAMTS13 on the development of liver disturbance and multiorgan failure in AH. METHODS: The activity of plasma ADAMTS13 and its clinical correlation were determined in 14 patients with AH, 4 with SAH (Maddrey score, mean 62), and 10 with alcoholic liver cirrhosis (LC). RESULTS: The activity of the plasma ADAMTS13 significantly decreased in patients with AH (mean 59%, p < 0.001), SAH (17%, p < 0.001) and LC (76%, p < 0.02) as compared with the healthy subjects (102%, n = 60). The activity was markedly lower in SAH than in AH (p < 0.02) and LC (p < 0.02). In three nonsurvivors with SAH who had multiorgan failure, it was extremely low (4.5%, 5.0%, and 16.0%, respectively), but in a survivor with SAH it remained mild decrease (44%). In AH, the protease activity increased at the recovery stage (42% --> 75%, p < 0.05). In the univariate analysis, the activity correlated with 10 clinical variables including functional liver capacity, inflammation signs, renal function, and platelet count in patients with AH and SAH. Among these, multivariate analysis showed that serum total bilirubin and C-reactive protein independently correlated with the protease activity. CONCLUSION: The activity of plasma ADAMTS13 markedly decreased in SAH in addition to AH. The activity was closely related to hyperbilirubinemia and inflammation signs, and was extremely low in nonsurvivors with SAH and multiorgan failure. The marked decrease of plasma ADAMTS13 may, in part, contribute to not only the progression of liver disturbance in AH, but also the development of multiorgan failure in SAH through microcirculatory disturbance.

ADAM Proteins↗

PubMed2004

Onset of ischemic colitis following use of electrical muscle stimulation (EMS) exercise equipment.

Our patient was a 71-year-old man who presented with lower abdominal pain, and bloody and white mucosal stools. He purchased by mail-order an electrical muscle stimulation (EMS) device, which he strapped onto his lower abdomen, and for 2 consecutive days he underwent muscle stimulation comprising 600 contractions at 2.40 mA and 1.20 V over a 10 minute period. He experienced the onset of lower abdominal pain immediately following muscle stimulation on the second day, and then passed stools containing blood and white mucus. The cause was thought to be electrical and mechanical stimulation of the lower abdomen by the EMS equipment, either inducing colonic or vascular spasm, or dislodging thrombi associated with atrial fibrillation or atherosclerosis. This is the first known report of ischemic colitis associated with the use of EMS exercise equipment. We report this case in the belief that this condition is likely to become more common with increasing use of such devices.

Aged↗

PubMed2002

Simple integration technique to realize parallel optical interconnects: implementation of a pluggable two-dimensional optical data link.

An assembly technique is presented to realize pluggable or fully integrated optoelectronic systems based on image relays. A method to visually align and assemble optoelectronic chips or fiber bundles to half of a relay is explained. To validate this technique, two-dimensional arrays of vertical-cavity surface-emitting lasers and photodetectors and a fiber image guide have been integrated to gradient index lenses with simple optomechanical parts. Although the connection of these modules was realized with +/-0.5 mm lateral tolerances, parallel optical interconnects were successfully achieved at 10 MHz. The lateral misalignment between chips was on average 20 microm and at worst 60 microm.

Journal Article↗

PubMed2002

Installing magnetic keepers using LASER welding.

Magnetic overdenture attachments can provide useful denture retention. A technique is proposed that involves installing the magnetic keeper in the overdenture abutment coping using laser welding. Compared with the conventional cast-to technique, the new technique provides a suitable contour to the abutment coping with the magnetic keeper and ensures proper mounting in the abutment coping, installing the magnetic keeper easily and effectively.

Dental Abutments↗

PubMed2002

Complete denture with a removable palatal lift prosthesis: a case report and clinical evaluation.

The palatal lift prosthesis is used to alleviate rhinopharyngeal closure dysfunction. It is generally problematical to use in edentulous patients, because the palatal lift prosthesis requires secure retention of the denture base and is difficult for the patient to retain while eating. This article describes the fabrication of a complete denture with a removable palatal lift prosthesis and a clinical evaluation of the denture's stability. A sprue pin and tube were used as a connecting attachment between the removable palatal lift prosthesis and the denture base. The force required for lifting the soft palate and the denture's stability were measured in the clinical evaluation. The prosthesis required an average retentive force of 0.26 N for each 1 mm of soft palate lift. The force required to dislodge the denture was measured with and without the palatal lift prosthesis in place. The force required to dislodge the conventional complete dentures of five healthy individuals was also measured as a reference. The denture was 24.4% less stable when the palatal lift prosthesis was in place and was generally easier to dislodge than were conventional dentures. This denture with a removable palatal lift prosthesis is useful for patients with dysfunction of the soft palate involving hypernasal speech who have difficulty in retaining the prosthesis while eating.

Adult↗