Adrenergic and myogenic regulation of viscoelasticity in the vascular bed of the human forearm.

This study tested the hypothesis that the compliance (C) and viscoelasticity (K) of the forearm vascular bed are controlled by myogenic and/or α-adrenergic receptor (αAR) activation. Heart rate (HR) and waveforms of brachial artery blood pressure (Finometer) and forearm blood flow (Doppler ultrasound) were measured in baseline conditions and during infusion of noradrenaline (NA; αAR agonist), with and without phentolamine (αAR antagonist; n = 10; 6 men and 4 women). These baseline and αAR-agonist-based measures were repeated when the arm was positioned above or below the heart to modify the myogenic stimulus. A lumped Windkessel model was used to quantify the values of forearm C and K in each set of conditions. Baseline forearm C was inversely, and K directly, related to the myogenic load (P < 0.001). Compared with saline infusion, C was increased, but K was unaffected, with phentolanine, but only in the 'above' position. Compliance was reduced (P < 0.001) and K increased (P = 0.06) with NA infusion (main effects of NA) across arm positions; phentolamine minimized these NA-induced changes in C and K for both arm positions. Examination of conditions with and without NA infusion at similar forearm intravascular pressures indicated that the NA-induced changes in C and K were due largely to the concurrent changes in blood pressure. Therefore, within the range of arm positions used, it was concluded that vascular stiffness and vessel wall viscoelastic properties are acutely affected by myogenic stimuli. Additionally, forearm vascular compliance is sensitive to baseline levels of αAR activation when transmural pressure is low.

Storage of light in atomic vapor.

We report an experiment in which a light pulse is effectively decelerated and trapped in a vapor of Rb atoms, stored for a controlled period of time, and then released on demand. We accomplish this "storage of light" by dynamically reducing the group velocity of the light pulse to zero, so that the coherent excitation of the light is reversibly mapped into a Zeeman (spin) coherence of the Rb vapor.

Angle-tuned type II external-cavity frequency doubling without temperature stabilization.

We report frequency doubling of a low-power cw diode laser at 1064 nm in an external ring cavity by use of an angle-tuned KTP type II crystal. We demonstrate a new setup that requires no temperature stabilization of the crystal. An intracavity lambda/2 plate rotates the polarization of the fundamental after each cavity round trip by 90 degrees; this provides the two eigenpolarizations of the crystal required for a type II nonlinear process. As a result, it is possible to maintain the resonance condition by use of a standard locking circuit.

D2 dopamine receptor involvement in the rough-and-tumble play behavior of juvenile rats.

By using dorsal contacts and pinning to quantify play behavior in juvenile rats, it was found that the D2 agonist, quinpirole, reduced both measures of play at doses greater than 0.05 mg/kg. Eticlopride, a D2 antagonist, also reduced both measures of play and blocked the reduction caused by quinpirole. The effect of quinpirole on play was largely unaffected by concurrent administration of either a D1 agonist (SKF 38393) or a D1 antagonist (SCH 23390), suggesting that D1 and D2 receptors are functionally independent with respect to play behavior. Quinpirole also reduced overall activity, suggesting that the effects on play may not be selective to neural circuitry responsible for play behavior. Although low doses of quinpirole (0.001--0.03 mg/kg) had a tendency to increase pinning, this effect was not very robust. These data suggest that D2 dopamine receptors may not have a major role in the control of play behavior in juvenile rats.

Familial isolated pulmonary hypoplasia: a case report, suggesting autosomal recessive inheritance.

The exceptional observation of a healthy couple with two girls and a boy suffering from pulmonary hypoplasia and two normal children is reported. The affected infants died 1, 2 and 20 h after birth respectively. No other malformations were found. Histological findings suggest that the underdevelopment of the lungs has its origin at a more proximal level than the terminal bronchioles. Autosomal recessive inheritance is suggested.

Effects of alpha-2 adrenoceptor antagonists on rough-and-tumble play in juvenile rats: evidence for a site of action independent of non-adrenoceptor imidazoline binding sites.

The pharmacological specificity of alpha-2 adrenoceptor involvement in the modulation of rough-and-tumble play behavior was assessed in juvenile rats. The alpha-2 adrenoceptor antagonists idazoxan and RX821002 both increased the frequency of pinning in individually housed rats that were given a brief opportunity to play. Dorsal contacts, a measure of play solicitation, were not consistently affected by these compounds. Since RX821002 shows little affinity for non-adrenoceptor imidazoline binding sites, it is likely that the facilitation of play following administration of these two compounds is due to blockade of alpha-2 receptors. The effect of RX821002 and idazoxan is unlikely to be an artifact associated with using rats that are reared in isolation, as RX821002 also increased pinning, as well as dorsal contacts, in group-housed rats that were isolated for a short period (4h) before the play session. The alpha-1 adrenoceptor antagonist prazosin, which also binds to alpha-2B receptors, reduced the frequency of both pinning and dorsal contacts. There was a strong trend for St 587, a centrally active alpha-1 agonist, to attenuate the effect of prazosin on play. While this leaves open the possibility that prazosin may be reducing play through alpha-1 blockade, antagonist activity at alpha-2B receptors cannot be ruled out. From these data, we conclude that the facilitation of play following idazoxan and RX821002 is likely due to blockade of alpha-2A adrenoceptors. These findings add further support for a specific role of alpha-adrenoceptors in the modulation of playfulness in the juvenile rat.