Application of local heat induces capillary recruitment in the Pallid bat wing

Abstract

Skin blood flow increases in response to local heat due to sensorineural and nitric oxide (NO)-mediated dilation. It has been previously demonstrated that arteriolar dilation is inhibited with NO synthase (NOS) blockade. Flow, nonetheless, increases with local heat. This implies that the previously unexamined nonarteriolar responses play a significant role in modulating flow. We thus hypothesized that local heating induces capillary recruitment. We heated a portion (3 cm2) of the Pallid bat wing from 25 degrees C to 37 degrees C for 20 min, and measured changes in terminal feed arteriole (approximately 25 microm) diameter and blood velocity to calculate blood flow (n = 8). Arteriolar dilation was reduced with NOS and sensorineural blockade using a 1% (wt/vol) NG-nitro-L-arginine methyl ester (L-NAME) and 2% (wt/vol) lidocaine solution (n = 8). We also measured changes in the number of perfused capillaries, and the time precapillary sphincters were open with (n = 8) and without (n = 8) NOS plus sensorineural blockade. With heat, the total number of perfused capillaries increased 92.7 +/- 17.9% (P = 0.011), and a similar increase occurred despite NOS plus sensorineural blockade 114.4 +/- 30.0% (P = 0.014). Blockade eliminated arteriolar dilation (-4.5 +/- 2.1%). With heat, the percent time precapillary sphincters remained open increased 32.3 +/- 6.0% (P = 0.0006), and this increase occurred despite NOS plus sensorineural blockade (34.1 +/- 5.8%, P = 0.0004). With heat, arteriolar blood flow increased (187.2 +/- 28.5%, P = 0.00003), which was significantly attenuated with NOS plus sensorineural blockade (88.6 +/- 37.2%, P = 0.04). Thus, capillary recruitment is a fundamental microvascular response to local heat, independent of arteriolar dilation and the well-documented sensorineural and NOS mechanisms mediating the response to local heat.

Venomotion modulates lymphatic pumping in the bat wing

“…Bat wing preparations have been used to make fundamental advancements in the understanding of vascular innervation (54), the myogenic response (4, 15), shear-induced dilation (13,51), arteriolar and venular vasomotion (3,47,53), and capillary recruitment (52). Most vascular responses have been shown to be similar to more common animal models such as the hamster cheek pouch, rat mesentery, and cremaster muscle, although bat wing responses are often more robust (13,15).…”

“…Experimental procedures and animal care were performed in compliance with protocols approved by the Texas A&M University Institutional Animal Care and Use Committee. With a few notable exceptions, experimental procedures were similar to those employed by Widmer et al (51,52). Briefly, Pallid bats were maintained in a colony for over two years before experimentation.…”

“…Because the bats were wild-caught, their ages were unknown. Bats were trained to participate in experiments without anesthesia, lying asleep in a plastic box with their wing extended outside of the box (51,52). Following an established schedule, no bats in the colony were used for experimentation more than once per week, and no experiment lasted more than six hours.…”

“…The resulting image had a resolution of 700 ϫ 480 pixels as displayed on screen. Video was recorded for at least 5 min to ensure a stable baseline (51,52). The size of the captured video image was large enough for a venule and its paired lymphatic microvessel to be simultaneously visualized, ensuring that all venular and lymphatic motion can be captured simultaneously.…”

Kann die Modulation des Reperfusionsschadens das Operationsergebnis in der Plastischen Chirurgie verbessern?

“…1) würden wir die maximale Ischämiezeit, bis zu der eine Replantation erfolgversprechend ist, auf 7 Stunden festlegen, bei ausreichender Kühlung auch noch auf bis zu 10 stoffmonoxid-System eine Rolle spielt, ist bislang nicht eindeutig geklärt [18]. Die Kälteapplikation hingegen ist geeignet, den Zelltod durch Verringerung insbesondere des Sauerstoffbedarfs zeitlich hinauszuzögern und damit dem Gewebe die Möglich-keit zur "Erholung" zu geben, zugleich wird jedoch auch die Perfusion über eine Vasokonstriktion vermindert.…”