Shigeru Ichioka

High-intensity static magnetic fields modulate skin microcirculation and temperature in vivo

We investigated the acute effect of static magnetic fields of up to 8 T on skin blood flow and body temperature in anesthetized rats. These variables were measured prior to, during, and following exposure to a magnetic field in a superconducting magnet with a horizontal bore. The dorsal skin was transversely incised for 1 cm to make a subcutaneous pocket. Probes of a laser Doppler flowmeter and a thermistor were inserted into the pocket and positioned at mid-dorsum to measure skin blood flow and temperature. Another thermistor probe was put into the rectum to monitor rectal temperature. After baseline measurement outside the magnet, the rat was inserted into the bore for 20 min so that mid-dorsum was exactly positioned at the center, where the magnetic field was nearly homogeneous. Post-exposure changes were then recorded for 20 min outside the bore. Sham-exposed animals were submitted to exactly the same conditions, except that the superconducting magnet was not energized. Skin blood flow and temperature decreased significantly during magnetic field exposure and recovered after removal of the animal from the magnet. The rectal temperature showed a tendency to decrease while the animal was in the magnet. The microcirculatory and thermal reactions in the present study were consistent and agreed with some of the predictions based on mathematical simulations and model experiments.

Biological effects of static magnetic fields on the microcirculatory blood flow in vivo: a preliminary report

There have been few studies of the effect of static magnetic fields on microcirculatory haemodynamics in vivo. The rat skinfold transparent chamber technique was used, which provides an excellent means of observing and quantifying direct in vivo microvascular haemodynamic responses to static magnetic fields up to 8 T. An intravital videomicroscope was used to measure the changes in blood flow before and after exposure to a magnetic field for 20 min in a horizontal type superconducting magnet with a bore 100 mm in diameter and 700 mm long. After exposure, microcirculatory blood flow showed an initial increase for about 5 min followed by a gradual decrease and a return to the control value. It is hypothesised that these changes represent rebound hyperaemia following reduced blood flow during exposure.

Vascular wall energetics in arterioles during nitric oxide-dependent and -independent vasodilation.

The objective of this study was to evaluate whether the nitric oxide (NO) released from vascular endothelial cells would decrease vessel wall oxygen consumption by decreasing the energy expenditure of mechanical work by vascular smooth muscle. The oxygen consumption rate of arteriolar walls in rat cremaster muscle was determined in vivo during NO-dependent and -independent vasodilation on the basis of the intra- and perivascular oxygen tension (Po2) measured by phosphorescence quenching laser microscopy. NO-dependent vasodilation was induced by increased NO production due to increased blood flow, whereas NO-independent vasodilation was induced by topical administration of papaverine. The energy efficiency of vessel walls was evaluated by the variable ratio of circumferential wall stress (amount of mechanical work) to vessel wall oxygen consumption rate (energy cost) in the arteriole between normal and vasodilated conditions. NO-dependent and -independent dilation increased arteriolar diameters by 13 and 17%, respectively, relative to the values under normal condition. Vessel wall oxygen consumption decreased significantly during both NO-dependent and -independent vasodilation compared with that under normal condition. However, vessel wall oxygen consumption during NO-independent vasodilation was significantly lower than that during NO-dependent vasodilation. On the other hand, there was no significant difference between the energy efficiency of vessel walls during NO-dependent and -independent vasodilation, suggesting the decrease in vessel wall oxygen consumption produced by NO to be related to reduced mechanical work of vascular smooth muscle.

AN EXPERIMENTAL COMPARISON OF HYDROCOLLOID AND ALGINATE DRESSINGS, AND THE EFFECT OF CALCIUM IONS ON THE BEHAVIOUR OF ALGINATE GEL

Gel-forming dressings, which absorb the wound exudate to form a non-adherent gel, accelerate wound healing in a moist environment. The most commonly used of these dressings are calcium alginate and hydrocolloid membranes. This study was designed to evaluate the physical properties of these dressings, including fluid retaining ability, gel formation, and the dissolution process to clarify the mechanisms that promote healing. A simple immersion method was used for measurement. This technique was useful for the quantitative assessment of gel-forming dressings and may help to evaluate potential application of these dressings. A comparative analysis showed that alginate dressings remained gelled longer than hydrocolloid dressings. This result was consistent with previously reported clinical features of these dressings. The absence of calcium in wound fluid induced rapid resolution of alginate gel while the presence of a certain concentration of calcium prevented degradation of the gel for as long as one month.

Arterioles' contribution to oxygen supply to the skeletal muscles at rest

We tested the hypothesis that oxygen is supplied to the resting skeletal muscle by arterioles rather than by capillaries. This hypothesis was evaluated in rats and rabbits by combining different approaches (1) determination of the intravascular oxygen tension (PO2) in arterioles of different diameters, (2) measurement of the perfused capillary number in response to changes in tissue PO2, and (3) estimation of the optimum capillary number to provide oxygen efficiently to the surrounding tissue. The intravascular PO2 values of arterioles along the vessels decreased downstream, suggesting that a significant amount of oxygen diffuses from the arterioles to the surrounding tissue. The perfused capillary number decreased as the tissue PO2 level was elevated, and this mutual relationship displayed a nonlinear correlation. The results suggest that a boundary PO2 level affecting the capillary recruitment exists for tissue PO2 of less than 40xa0mmHg with the capillary blood-flow stops above that PO2 level. At a high PO2 level, therefore, the oxygen is supplied from the arterioles. Furthermore, an estimation of optimum capillary number reveals that the capillary arrangement is constructed to achieve sufficient oxygen supply to the muscle during exercise, rather than at rest. These results suggest that oxygen is supplied from arterioles to the resting skeletal muscle, whereas the oxygen is supplied from the capillaries during exercise.

Nonlinear regulation of capillary perfusion in relation to ambient pO2 changes in skeletal muscle

To study the process of O2 transport to tissue, we investigated how capillary perfusion is controlled in response to changes in tissue O2 levels in skeletal muscle. Capillary red blood cell (RBC) velocity and perfused capillary recruitment were measured in rabbit tenuissimus muscle at various ambient oxygen tensions (pO2) by intravital microscopy. Both RBC velocity and capillary recruitment significantly decreased as the pO2 level of the suffusate was increased, and the relationship between capillary perfusion, calculated from the velocity and recruitment data, and the pO2 level of the suffusate clearly yielded a nonlinear correlation that fitted a sigmoidal curve. Capillary perfusion dramatically decreases or increases above or below a suffusate pO2 level of around 40xa0Torr, where the O2 dissociation curve of hemoglobin changes slope. These findings support the hypothesis that microvasculature possesses an intrinsic, effective flow-control mechanism by sensing the metabolic demands of tissue, intimately related to the O2 saturation of hemoglobin.

A case of cystic dermal duct tumor corresponding to poroid hidradenoma.

A case of dermal duct tumor on the back of a 61‐year‐old male, representing a cystic lesion, is reported. Such cystic dermal duct tumors seem to be considered poroid hidradenomas according to the recently suggested classification of poromas. Poroid hidradenoma is rarely mentioned in the literature, and no description of its clinical features has yet been published. Carcinoembryonic antigen (CEA) immunostaining was positive in the tumor cells adjacent to the cystic space. We suppose that these CEA‐positive cells were associated with cyst formation in our case.

Ultrasonographic Demonstration of a Skin Metastasis of Adenocarcinoma

A case of skin metastasis of adenocarcinoma on the back of a 69‐year‐old female was reported. The ultrasound appearance of the tumor indicated a malignant lesion prior to the detection of a primary lung carcinoma.

Dual-beam laser illuminator of fluorescence microscope for in vivo microcirculation studies.

A new fluorescence intravital microscope of long working distance (39 mm) has been developed for the observation of microcirculation in a wide visual field by designing a simple epi-illumination technique with dual laser beams. Cross-illumination, in which a pair of laser beams is symmetrically placed on either side of the objective such that they intersect at the focal plane of the objective, was employed to produce uniform distribution of the incident light in the object plane. In vitro experiments using a fluorescein isothiocyanate dextran (FITC-dextran; molecular weight=70 000) solution of known concentration confirmed uniform tracer excitation in a wide visual field (approximately 30 mm2), and a linear correlation between fluorescence intensity and tracer concentration (r=0.999), ranging between 5μmol l−1 and 25μmol l−1. In vivo observations in the microcirculation of a hamster cheek pouch indicated that the present technique had the advantage of high contrast compared with the image obtained by bright-field transillumination. This microscope illuminator may prove useful for the evaluation of vascular permeability under physiological and inflammatory conditions, with sufficient quantitative reliability to determine tracer concentrations in all parts of the microvascular network. Furthermore, a long working distance in this technique could have considerable advantages for the application to nail-fold capillaroscopy in humans.