Pontine parabrachial neurons have been suggested to play a regulatory role in both respiratory and sleep cycle control. Encouraged by the finding that microinjections of the cholinergic agonist carbachol into the medial pontine reticular formation (mPRF) of the cat produced respiratory changes paralleling those observed during rapid eye movement (REM) sleep (Neurosci. Lett., 102 (1989) 211–216), this study tested the hypothesis that cholinergic mechanisms in the mPRF can also cause state-dependent changes in the discharge of parabrachial neurons. This paper describes extracellular recordings of parabrachial neurons during REM sleep and during the carbachol-induced REM sleep-like state (DCarb). Cells which were activated (REM-on) or inactivated (REM-off) during REM maintained these same state-dependent firing patterns during the DCarb state. These results support the hypothesis that cholinergic mechanisms in the mPRF can cause state-dependent changes in the discharge of parabrachial neurons. 相似文献
We studied whether a flow-independent increase of luminal wall shear stress (WSS) could dilate hamster arterioles in vivo
and which endothelial mediators are potentially involved. To this end the plasma viscosity was elevated by exchanging blood
for dextran-erythrocyte solution thereby augmenting WSS. Diameters of small and large arterioles as well as red blood cell
velocities were measured before and after exchange of blood for solutions of identical haematocrit containing either high-
(HMWD) or low-molecular weight dextran (LMWD). The potential role of endothelial autacoids was investigated by local application
of the NO-synthase inhibitor NG-nitro-L-arginine (L-NNA), the inhibitor of cyclooxygenase, indomethacin (3 μM), or the K+-channel blocker, tetrabutylammonium (TBA, 0.1 mM) to assess the potential effects of EDHF. HMWD (n = 11 animals) increased plasma viscosity by 64 ± 3% and dilated arterioles of all branching orders (A1–A4) significantly
[by 24 ± 3% (A1–A2) and 32 ± 3% (A3–A4)]. This dilation compensated fully for the calculated initial increase of WSS. LMWD
(n = 6) did not affect plasma viscosity or arteriolar diameters. Tissue treatment with L-NNA (30–300 μM, n = 12) substantially diminished the HMWD-induced dilation in small arterioles (A3–A4; to 13 ± 3%; P<0.05) and virtually abolished it in large ones (A1–A2). Consequently, the calculated WSS increased significantly in these
arterioles (by 31 ± 5%). TBA combined with L-NNA (n = 4) did not reduce further the remaining dilation. Indomethacin (n = 6) had no effect on HMWD-induced dilation. We conclude that an increase of WSS induces a mainly NO-mediated arteriolar
dilation. This dilation occurs in all arteriolar branching orders and is of sufficient magnitude to compensate for the initial
WSS-increase. Thus, any elevations of WSS fulfil the requirement for a signal to change diameter along the arteriolar tree
in a coordinated manner. The fully compensating dilation which we observed indicates that WSS is a controlled variable. It
does, however, raise questions as to its role as a continuous endothelial stimulus.
Received: 2 August 1996 / Received after revision: 24 February 1997 / Accepted: 14 April 1997 相似文献
Summary Vibrational wave propagation was tested in vivo on the tibial bone of both legs of 56 female volunteers. The impact was produced
by a hammer with a force strain gauge and the response was monitored by two accelerometers. The peak amplitude of the accelerations,
the velocity of the acceleration wave propagation and damping were analysed for comparison among the different age groups.
The results showed significant negative correlations between age and the peak amplitude of acceleration, and the velocity
of acceleration wave propagation (p<0.01). The damping time of the acceleration wave also had a negative correlation with age. These findings suggested that
age differences were related to the differences in the mechanical properties of bone. With reduction of bone mineral density,
the velocity of the vibrational wave propagation would decrease, with simultaneous increase in impedance. In addition, wave
absorption would be accelerated. It is suggested that this method could be used as an indicator of bone density. The method
could also be developed to provide an index to monitor the progress of osteoporosis.
Visiting research assistant from the Department of Sport Medicine, Chengdu College of Physical Education, Chengdu, People's
Republic of China
Visiting research assistant from Seoul National University, Seoul, South Korea 相似文献
Cloud point temperatures (Tcp) and crystallization temperatures (Tl/s) were measured at different constant shear rates for the ternary system tetrahydronaphthalene/poly(ethylene oxide)/oligo(dimethyl siloxane‐b‐ethylene oxide) using a rheo‐optical device and in the case of Tl/s additionally a viscometer. This system enables for the first time a joint investigation of both transitions with a given mixture. Shear favors the homogeneous liquid state and the formation of crystals. Tcp (liquid/liquid demixing, UCST) shifts to lower and Tl/s (liquid/solid, segregation of PEO) to higher temperatures by several degrees as the shear rate, , is increased up to 500 s?1. The normalized shift in Tcp fits well into previous results for high molecular weight blends, oligomer mixtures, polymer solutions in single solvents and low molecular weight mixtures. A phase separated near critical blend was examined 1 K below its Tcp by means of a shear cell (Linkam) in the quiescent state and under shear with respect to its morphology. Upon an increase in one observes a transition from the co‐continuous structures existing in the quiescent state via deformed and oriented particles to string like morphologies. Finally, at sufficiently high shear rates the mixture becomes homogeneous and structures can no longer be seen under the microscope. The morphologies developing after the secession of shear are pointing to pronounced influences of the flow history of the system on the final structure of two phase blends.
Equilibrium phase diagram of the system THN/COP/PEO at the indicated temperatures as obtained from turbidimetric titration. The curve for 42 °C indicates the compositions under which the mixtures segregate the first solid PEO particles upon cooling. The curves for the higher temperatures denote the demixing of the homogeneous system into two liquid phases. 相似文献
Ruchkin and Johnson (1991) claim that the mode of responding used by Rösler & Heil (1991) may have camouflaged effects of a negative slow wave that Ruckin et al. (1988) had found to be related to the difficulty of mental calculation problems. This criticism is addressed by three arguments which support the interpretation of Rösler and Heil (1991). According to this view, the negative slow wave in question is more likely related to unspecific processing factors, such as effort and event expectation, than to specific processing demands such as these induced by mental arithmetic. 相似文献
As a means for assessing cardiac function, electrical field plethysmography (EFP) has been shown to have some features quite
different from electrical impedance plethysmography (EIP). Here the two techniques are compared by using the two systems simultaneously
on a subject and also with independent use in different electrode configurations. The results conform with the view that EIP
is related primarily to volumetric changes of the aorta, whereas EFP is affected predominantly by changes in cardiac dimensions
and orientation. Because of this difference, the standard time differential formula used for EIP is not applicable for the
computation of cardiac output from the EFP waveforms. An alternative method of computation based on the amplitude of the EFP
waveform is suggested. 相似文献