Differences in laser-Doppler indices between skin-surface measurement sites in subjects with diabetes.

This study performed laser-Doppler flowmetry (LDF) measurements with the aim of identifying differences in diabetes-induced microcirculatory-blood-flow (MBF) responses between the following skin surface measurement sites: an acupoint around the wrist, an acupoint around the ankle, and a nearby nonacupoint around the ankle. The 67 study subjects were assigned to diabetic, prediabetic, and healthy groups according to the results of oral glucose tolerance tests. Beat-to-beat and spectral analyses were applied to the LDF waveform to obtain the foot delay time (FDT), the flow rise time (FRT), and the relative energy contributions (RECs) in five frequency bands. FRT and FDT were significantly shorter and the RECs of the endothelial-, neural-, and myogenic-related frequency bands were significantly smaller in the diabetic group than in the control group at the acupoint around the ankle, but there were no such prominent differences at the other sites. The acupoint around the ankle was better than the nearby nonacupoint and the acupoint around the wrist for distinguishing the age-matched diabetic, prediabetic, and healthy subjects. These findings imply that when monitoring diabetes-induced MBF responses, the measurement locations should be chosen carefully in order to minimize interference effects and to improve the ability to distinguish subjects with different conditions.

Changes in the spectral index of skin-surface laser Doppler signals of nude mice following the injection of CT26 tumor cells.

This study investigated microcirculatory-blood-flow responses in nude mice following the injection of CT26 tumor cells by analyzing the frequency content of skin blood-flow signals recorded on the skin surface. CT26 cells were injected subcutaneously (10^4/100 µl) into the right back flank of each 7-week-old mouse. Three-minute laser Doppler flowmetry (LDF) signals were measured in 60 nude mice. The data sequences were obtained at 1, 2, and 3 weeks after injecting CT26 cells. Mouse tissue samples were cut into sections and examined microscopically to determine the condition of cancer metastasis. Spectral analysis performed after 1 week revealed a significant decrease in the relative energy contribution of the endothelium-related frequency band, and significant increases in those of the myogenic and respiration-related frequency bands of the LDF signals in the metastasis group (n=12). To the best of our knowledge, this is the first study demonstrating the feasibility of evaluating metastasis in animal subjects based on changes in noninvasively measured LDF parameters. Changes in the LDF spectral indexes can be attributed to differences in the microcirculatory regulatory activities. The present measurements performed on the skin surface provide a noninvasive and real-time method for evaluating the microcirculatory responses induced by implanting CT26 tumor cells.

Characteristics of beat-to-beat photoplethysmography waveform indexes in subjects with metabolic syndrome.

UNLABELLED: Metabolic syndrome (MetS) increases the risk of the subsequent development of cardiovascular disease. This study aimed to determine if the harmonic indexes of finger photoplethysmography (PPG) waveforms can be used to discriminate different arterial pulse transmission conditions between MetS and healthy subjects. Three-minute PPG signals were obtained in 65 subjects, who were assigned to 3 age-matched groups (MS, with no less than three MetS factors; pre-MS, with one or two MetS factors; CONTROL: with no MetS factor). FDT (foot delay time) and amplitude proportions (Cn) and their standard deviations (SDn) and coefficients of variations (CVn) were calculated for harmonics 1 to 10 of the PPG waveform. FDT was smaller in MS than in CONTROL. C1 and C2 values were significantly smaller, whereas C4-C9 values were significantly or appeared to be larger in MS than in pre-MS. Most of the SDn and CVn values were largest in MS. This study is the first to demonstrate that harmonic-analysis indexes of the beat-to-beat PPG waveform can provide information about MetS-induced changes in the arterial pulse transmission and cardiovascular regulatory activities. The present findings may therefore be useful in developing a noninvasive and easy-to-perform technique that could improve the early detection of cardiovascular diseases.