Long-term observation of pial microcirculatory parameters using an implanted cranial window method in the rat.

The aim of this study was to confirm whether our improved closed cranial window (CCW) method could be used for long-term microscopical observation of pial microcirculation intravitally in the rat. We investigated chronological changes in three microcirculatory parameters: permeability of blood-brain barrier, leukocyte behavior, and plasma velocities in the pial venules, immediately after implantation (control group) and at one and four weeks after implantation in different age-matched rats (implanted group). No extravasation of sodium fluorescein from pial venules was confirmed in any observation period. The number of endothelial-adhering leukocytes in the implanted group kept within the physiological range, being similar to those of the control group. The velocities of fluorescent microspheres flowing in pial venules showed no noticeable changes between the two groups. These findings suggest that our CCW method allows long-term observation of the pial microcirculation without any pathophysiological changes in the evaluated parameters up to four weeks after the implantation.

Role of blood flow on RF exposure induced skin temperature elevations in rabbit ears.

In this in vivo study, we measured local temperature changes in rabbit pinnae, which were evoked by radiofrequency (RF) exposure for 20 min at localized SAR levels of 0 (sham exposure), 2.3, 10.0, and 34.3 W/kg over 1.0 g rabbit ear tissue. The effects of RF exposures on skin temperature were measured under normal blood flow and without blood flow in the ear. The results showed: (1) physiological blood flow clearly modified RF induced thermal elevation in the pinna as blood flow significantly suppressed temperature increases even at 34.3 W/kg; (2) under normal blood flow conditions, exposures at 2.3 and 10.0 W/kg, approximating existing safety limits for the general public (2 W/kg) and occupational exposure (10 W/kg), did not induce significant temperature rises in the rabbit ear. However, 2.3 W/kg induced local skin temperature elevation under no blood flow conditions. Our results demonstrate that the physiological effects of blood flow should be considered when extrapolating modeling data to living animals, and particular caution is needed when interpreting the results of modeling studies that do not include blood flow.

Anti-atherosclerotic effects of tamoxifen in cholesterol-fed ovariectomized rabbits.

It has been indicated that the anti-estrogen agent, tamoxifen, developed for the treatment of breast cancer, may act on the vascular system as an estrogen agonist. However, to our knowledge few reports suggest that tamoxifen exerts anti-atherogenic actions. In the present study, we evaluated the anti-atherosclerotic effects of tamoxifen in ovariectomized cholesterol-fed rabbits. Ovariectomized rabbits were fed a 1% cholesterol diet and divided into 4 groups: control group (C, n=5); estrogen treatment (E, n=6); low-dose tamoxifen treatment (0.5 mg/kg) (LT, n=6); and high-dose tamoxifen (1.0 mg/kg) (HT, n=7). After 6 weeks, both Oil red O-positive areas on the intimal surfaces of aortae and the ratios of intimal to medial areas (I/M ratios) measured from cross-sections of aortae were significantly lower in groups E, LT and HT compared with group C. Although there were no significant differences in serum NOx (NO2 and NO3) levels among the 4 groups, NOx levels were slightly higher in groups E, LT and HT than group C. Acetylcholine (ACh) was administered to all animals, and the responses of ear arteriole diameters were compared among the 4 groups. While ear arteriole diameters were significantly decreased in group C, no significant changes were observed in groups E, LT or HT following ACh administration. Ratios of ear arteriole diameters after to before ACh administration were significantly greater in groups E, LT and HT compared to group C. These findings suggest that tamoxifen exerts anti-atherosclerotic effects, and that these effects are attributed to the maintenance of vascular endothelial function.

Enriched levels of erythropoietin in human umbilical cord blood stimulate hematopoietic progenitor cells.

Human umbilical cord blood (CB) is a recognized source of hematopoietic tissues for transplantation, the treatment of malignancies and gene therapy, among other potential clinical applications. A rich network of hematopoietic cytokines and growth factors possessing stimulatory effects on primitive hematopoietic stem/progenitor cells further characterizes fetal CB. To better elucidate these complex interactions and properties, we compared the hematopoietic activities of CB and normal human peripheral blood (PB), by examining growth/survival of normal hematopoietic progenitors and erythropoietin-dependent UT-7/EPO cells. Colony-forming activity assays of normal bone marrow (BM) BFU-E and CFU-GM showed that CB significantly enhanced progenitor cell growth in comparison to PB. Apoptosis was determined by enumerating APO 2.7 mAb stained cells using flow cytometry. UT-7/EPO cell cultures subjected to PB exhibited a four-fold higher rate of apoptosis than CB exposed cultures, indicating that CB markedly suppressed apoptosis in this human leukemic cell line. Immunoprecipitation of UT-7/EPO cell lysates and immunodetection of the anti-phosphotyrosine Ab (4G10), revealed that CB induced tyrosine phosphorylation of three proteins, with approximate molecular masses of 160, 117.5 and 80 kDa. The 80 kDa protein corresponds to the previously reported molecular mass for the Epo receptor, suggesting that erythropoietin is enriched in CB compared with adult PB.

Inhibitory effects of 1,4-DHP antagonists on synaptic GABA release modulated by BAY-K 8644 in mechanically dissociated rat substantia innominata.

The effects of dihydropyridine (1,4-DHP) agonist and antagonists on miniature inhibitory postsynaptic currents (mIPSCs) were investigated in mechanically dissociated rat substantia innominata neurons attached to native GABAergic presynaptic nerve terminals, namely 'synaptic bouton preparation', using nystatin perforated patch recording mode under voltage-clamp conditions. BAY-K 8644 (BAY-K), an L-type Ca(2+) channel agonist, reversibly and concentration dependently facilitated the GABAergic mIPSC frequency without altering the distribution of current amplitudes. Removal of extracellular Ca(2+) completely suppressed the facilitatory effect of BAY-K on mIPSC frequency. The facilitatory effect of BAY-K on mIPSC frequency was maintained even in the presence of selective N-, P- and Q-type Ca(2+) channel antagonists, such as 3 x 10(-6) M omega-conotoxin-GVIA (omega-CgTX-GVIA), 3 x 10(-8) M omega-agatoxin-IVA (omega-AgTX-IVA) and 3 x 10(-6)M omega-conotoxin-MVIIC (omega-CmTX-MVIIC). However, nicardipine (3 x 10(-6) M) and nimodipine (3 x 10(-6) M), 1,4-DHP antagonists, significantly inhibited the mIPSC frequency enhanced by BAY-K by 37 +/- 5 and 42 +/- 6%, respectively. These results suggest the possible existence of L-type Ca(2+) channels in GABAergic presynaptic nerve terminals.