Cutaneous and subcutaneous blood flow during general anaesthesia

The vasodilator effect of anaesthetic agents on cutaneous vessels has often been investigated. In contrast, although subcutaneous tissue is concerned with metabolism and thermoregulation, the effects of anaesthesia on subcutaneous blood flow have not been well documented. The purpose of this study was to determine the magnitude of changes in cutaneous and subcutaneous blood flow during general anaesthesia in Man. Anaesthesia was induced with flunitrazepam in 15 patients before facial plastic surgery. Blood flow was estimated using heat thermal clearance (HC). Two HC sensors in different areas allowed the measurement of superficial and deep HC. Systolic (SABP), diastolic (DABP) and mean arterial blood pressure (MABP), heart rate (HR), and rectal and mean skin temperature were also recorded. After induction of anaesthesia, HR increased significantly (p less than 0.05) whereas SABP, DABP and MABP remained unchanged. The rectal-toe temperature gradient fell from 6.3 +/- 4.1 degrees C to 3.4 +/- 1.1 degrees C (p less than 0.01) suggesting a reduction in vasomotor tone. Superficial HC increased from 0.37 +/- 0.06 to 0.42 +/- 0.08 W.m-1.degrees C-1 (p less than 0.05) whereas deep HC decreased from 0.33 +/- 0.07 to 0.31 +/- 0.09 W.m-1.degrees C-1 (NS) and returned to the control value thereafter. Rectal temperature and mean skin temperature were unchanged. The changes in deep HC are similar to those previously observed in muscle during induction of anaesthesia. Our results show that anaesthesia mainly affects cutaneous blood flow, without any significant change in subcutaneous blood flow during the early phase of anaesthesia in human beings.     

Effects of intraarterial, intravenous, and intraluminal neurotensin on canine ileal sodium and water absorption and blood flow

Neurotensin is a regulatory peptide which is found primarily in the ileum and is secreted into the blood and lumen. The physiologic effects of neurotensin are uncertain but in certain pathologic states neurotensin increases to levels which can have effects on many organs. The effects of intravenous, intraarterial and intraluminal neurotensin (0.075-7.5 micrograms/min) on fed canine ileal sodium and water fluxes, potassium secretion, and blood flows were studied. Intravenous and intraarterial infusion of neurotensin increased net sodium, potassium, and water secretion, due to increased secretory fluxes, and increased hematocrits. Intraarterial neurotensin was not more effective than intravenous neurotensin except for stimulating potassium secretion. Neurotensin increased potassium secretion at 0.075 micrograms/min IA, increased sodium and water secretion at 0.75 micrograms/min IA and IV, and increased hematocrit at 7.5 micrograms/min IA and and IV. Total and absorptive site blood flows and arterial and venous pressures were not changed. Intraluminal neurotensin had no effects at any infusion rate. Neurotensin can increase potassium secretion at physiologic levels by a local effect and can increase sodium and water secretion at high physiological-pathological levels through a hormonal mechanism. The secretion is not dependent on cardiovascular changes.     

Effects of atropine and guanethidine on canine intestinal absorption and blood flow

The possibility of tonic autonomic control over intestinal Na and H₂O absorption and whether the cardiovascular system was involved was tested by administration of atropine or guanethidine. ³H₂O and ²²Na in saline perfused through the lumen were used to calculate unidirectional fluxes and total and absorptive site blood flow in canine ileum. Both atropine and guanethidine had qualitatively similar effects on absorption and blood flow with atropine being quantitatively greater. Net Na and H₂O absorption were not increased significantly but their absorptive and secretory unidirectional fluxes were increased significantly. Total blood flow was not affected but absorptive site blood flow was increased and resistance decreased. The absorptive site blood flow was correlated with the absorptive Na fluxes similarly in all groups. The secretory fluxes of Na and H₂O were correlated with estimated capillary pressure when all three groups were considered together. It was concluded that there is tonic cholinergic control over intestinal absorption which is mediated, in part, through cardiovascular effects. The findings were consistent with tonic parasympathetic activity having primarily a direct effect on gut absorption and blood flow but tonic sympathetic activity primarily modulating the direct effects of other regulatory mechanisms.     

Cutaneous blood flow and sweat rate responses to exogenous administration of acetylcholine and methacholine.

The aim of this study was to evaluate cutaneous vasodilation and sweating responses to exogenous administration of acetylcholine (ACh) and methacholine (MCh), which have different sensitivities to endogenous cholinesterase. Four intradermal microdialysis probes were placed in dorsal forearm skin: two sites were perfused with ACh (1 x 10(-7)-1 M) and the other two with the same molar concentrations of MCh. Sweat rate (SR) and cutaneous blood flow were simultaneously assessed directly over each microdialysis membrane. Dose-response curves were constructed, and the effective concentration of the drug resulting in 50% of the maximal response (EC(50)) was identified. For SR and cutaneous vascular conductance (CVC), there were no significant differences in EC(50) between sites receiving the same drug: -1.52 +/- 0.18 and -1.19 +/- 0.09 log-molar concentration of ACh at distal and proximal sites, respectively, and -2.35 +/- 0.24 and -2.42 +/- 0.23 log-molar concentration of MCh at distal and proximal sites, respectively, for SR (P > 0.05) and -3.87 +/- 0.32 and -3.97 +/- 0.27 log-molar concentration of ACh at distal and proximal sites, respectively, and -4.78 +/- 0.17 and -4.46 +/- 0.16 log-molar concentration of MCh at distal and proximal sites, respectively, for CVC (P > 0.05). However, the EC(50) for CVC and SR was significantly lower at the MCh than at the ACh sites. A second procedure was performed to confirm that differences in responses between ACh and MCh could be attributed to different cholinesterase sensitivities. Similarly, four microdialysis membranes were placed in dorsal forearm skin: two sites were perfused with ACh and other two with MCh. However, one of each of the ACh and MCh sites was also perfused with 10 microM neostigmine (an acetylcholinesterase inhibitor). Neostigmine at the ACh site induced a leftward shift (i.e., lower EC(50)) of the SR and CVC dose-response curves compared with the site treated with ACh alone, resulting in no difference in the EC(50) for SR and CVC between the ACh + neostigmine and the MCh site. These results suggest that elevations in SR and CVC occur earlier with MCh than with ACh treatment because of differences in cholinesterase susceptibility between these drugs.     

Nuclear-mitochondrial discordance and gene flow in a recent radiation of toads

Natural hybridization among recently diverged species has traditionally been viewed as a homogenizing force, but recent research has revealed a possible role for interspecific gene flow in facilitating species radiations. Natural hybridization can actually contribute to radiations by introducing novel genes or reshuffling existing genetic variation among diverging species. Species that have been affected by natural hybridization often demonstrate patterns of discordance between phylogenies generated using nuclear and mitochondrial markers. We used Amplified Fragment Length Polymorphism (AFLP) data in conjunction with mitochondrial DNA in order to examine patterns of gene flow and nuclear-mitochondrial discordance in the Anaxyrus americanus group, a recent radiation of North American toads. We found high levels of gene flow between putative species, particularly in species pairs sharing similar male advertisement calls that occur in close geographic proximity, suggesting that prezygotic reproductive isolating mechanisms and isolation by distance are the primary determinants of gene flow and genetic differentiation among these species. Additionally, phylogenies generated using AFLP and mitochondrial data were markedly discordant, likely due to recent and/or ongoing natural hybridization events between sympatric populations. Our results indicate that the putative species in the A. americanus group have experienced high levels of gene flow, and suggest that their North American radiation could have been facilitated by the introduction of beneficial genetic variation from admixture between divergent populations coming into secondary contact after glacial retreats.     

Seawater drinking restores water balance in dehydrated harp seals

The purpose of this study was to answer the question of whether dehydrated harp seals (Phoca groenlandica) are able to obtain a net gain of water from the intake of seawater. Following 24 h of fasting, three subadult female harp seals were dehydrated by intravenous administration of the osmotic diuretic, mannitol. After another 24 h of fasting, the seals were given 1,000 ml seawater via a stomach tube. Urine and blood were collected for measurement of osmolality and osmolytes, while total body water (TBW) was determined by injections of tritiated water. In all seals, the maximum urinary concentrations of Na⁺ and Cl⁻ were higher than in seawater, reaching 540 and 620 mM, respectively, compared to 444 and 535 mM in seawater. In another experiment, the seals were given ad lib access to seawater for 48 h after mannitol-induced hyper-osmotic dehydration. In animals without access to seawater, the mean blood osmolality increased from 331 to 363 mOsm kg⁻¹ during dehydration. In contrast, the blood osmolality, hematocrit and TBW returned to normal when the seals were permitted ad lib access to seawater after dehydration. In conclusion, this study shows that harp seals have the capacity to gain net water from mariposa (voluntarily drinking seawater) and are able to restore water balance after profound dehydration by drinking seawater.     

Inhibition of vasopressin secretion when dehydrated rats drink water

The present study determined whether vasopressin (VP) secretion is inhibited by an oropharyngeal signal associated with swallowing fluids when dehydrated rats drink water, as it is when dehydrated dogs are used as experimental subjects (Thrasher, TN, Keil LC, and Ramsay DJ. Am J Physiol Regul Integr Comp Physiol 253: R509-R515, 1987). VP levels in systemic plasma (pVP) fell rapidly when rats drank water after overnight water deprivation. Systemic plasma Na+ concentration (pNa) also fell, but that change likely contributed little to the early inhibition of VP secretion. In contrast, consumption of water by dehydrated rats with an open gastric fistula had no effect on pVP, nor did consumption of isotonic saline by dehydrated rats; in neither case was pNa affected by fluid consumption. These findings provide no evidence that the act of drinking inhibits VP secretion in dehydrated rats. Thus some post-gastric effect of the ingested water seems to be responsible for the inhibitory signal. These results are consistent with previous suggestions that an early inhibitory stimulus for VP secretion in rats is provided by post-gastric visceral osmo- or Na+ receptors that sense the composition of the ingested fluid.     

Inhibition of thirst when dehydrated rats drink water or saline

The present experiments sought to identify the physiological signals that inhibit thirst when dehydrated rats drink water or NaCl solution. Rats were deprived of drinking fluid but not food overnight. When allowed to drink again, the dehydrated animals consumed water or saline (0.05 M, 0.10 M, 0.15 M, or 0.20 M NaCl solution) almost continuously for 5-8 min before stopping. The volumes consumed were similar regardless of which fluid they ingested, but blood analyses indicated that increased plasma osmolality and decreased plasma volume, or both, still remained when drinking terminated. These results suggest that the composition of the ingested fluid is less significant than its volume in providing an early signal that inhibits thirst and fluid consumption by dehydrated rats. Analyses of the gastrointestinal tracts revealed that the cumulative volume in the stomach and small intestine correlated highly with the amount consumed regardless of which fluid was ingested. These and other results suggest that the volume of fluid ingested by dehydrated rats is sensed by stretch receptors detecting distension of the stomach and small intestine, which provide an early inhibitory stimulus of thirst.     

Cutaneous evaporimetry. IX. Cutaneous water loss in old age

The cutaneous water loss (CWL) were investigated in 15 old human subjects by Evaporimeter Ep-1. The mean value of the CWL resulted 11,9 +/- 4,3 g/h. This result is significantly lower compared with the value of normal people equal to 17, 5 +/- 4,0 g/h as reported in foregoing notes.     

Cutaneous evaporimetry. VII. Cutaneous water loss in Basedow's disease

The cutaneous water loss was investigated in 12 patients affected with Basedow's disease by Evaporimeter Ep-1. The mean value of the CWL resulted 49,8 +/- 18,2 g/h. This result is significantly higher compared with the value of normal somali people equal to 25,24 +/- 14,6 g/h.     

Cutaneous and subcutaneous blood flow measurement in rabbit's ear by epicutaneous diffusion of xenon 133. Influence of the arteriovenous anastomosis]

The cutaneous and subcutaneous blood flow measurement by a diffusible inert gas concerns theorically capillary nutritional flow. In clinical routine, where pathological openning of arteriovenous anastomosis is suspected, the blood flows measured by Xenon technic are often increased. The function of the shunts are displayed on the epuration curve obtained on a region where there are numerous: rabbit's ear.     

Root pressurization affects growth-induced water potentials and growth in dehydrated maize leaves

Profiles of water potential (Psi w) were measured from the soil to the tips of growing leaves of maize (Zea mays L.) when pressure (P) was applied to the soil/root system. At moderately low soil Psi w, leaf elongation was somewhat inhibited, large tensions existed in the xylem, and Psi w were slightly lower in the elongating leaf tissues than in the xylem, i.e. a growth-induced Psi w was present but small. With P, the tension was relieved, enlarging the difference in Psi w between the xylem and the elongating tissues, i.e. enlarging the growth-induced Psi w, which is critical for growth. Guttation occurred, confirming the high Psi w of the xylem, and the mature leaf tissue rehydrated. Water uptake increased and met the requirements of transpiration. Leaf elongation recovered to control rates. Under more severe conditions at lower soil Psi w, P induced only a brief elongation and the growth-induced Psi w responded only slightly. Guttation did not occur, water flow did not meet the requirements of transpiration, and the mature leaf tissues did not rehydrate. A rewatering experiment indicated that a low conductance existed in the severely dehydrated soil, which limited water delivery to the root and shoot. Therefore, the initial growth inhibition appeared to be hydraulic because the enlargement of the growth-induced Psi w by P together with rehydration of the mature leaf tissue were essential for growth recovery. In more severe conditions, P was ineffective because the soil could not supply water at the required rate, and metabolic factors began to contribute to the inhibition.     

Cutaneous blood supply of the penis

Twelve male cadaver specimens were injected with a latex solution to define the cutaneous blood supply of the penis. The cutaneous blood supply of the penile shaft is derived solely from a pair of axial arteries running in the dartos layer. Additional deep perforating arteries from the dorsal penile artery and corporal vessels supply the glans and subcoronal region. An understanding of this anatomy allows one to develop safely a variety of penile skin flaps for difficult reconstructive problems.     

Cutaneous blood vessels in scent pigs

The purpose of this study was to systematically provide anatomic data for flap research in plastic surgery on the cutaneous blood vessels. Seven scent pigs used in this study were killed anesthetically, and their carotid vessels were intubated and injected with a black liquid rubber. Twenty-four hours later, the integument of the scent pig was removed, and the perforating points of the cutaneous vessels were recorded. The different-sized pieces of integument became transparent. Part of this transparent skin tissue was cut into cross-sectional strips. There were three types of the cutaneous vascular source, the same as in humans. Six division levels of vessels in the skin were identified, which formed five vascular plexuses and two systems (the perforating vessel system and the cutaneous vessel system). There were two sets of vein systems: the concomitant vein and the oscillating vein; the latter can be divided into regular and irregular types. The structures of the perforating vessel system and the cutaneous vessel system were the morphological basis for choosing flaps. Two anatomic points have been emphasized: the preserved vascular plexus in thin flaps (not the subcutaneous vascular network reported previously) and the dependency of vascular structure on its location. Otherwise, this study has also provided two new kinds of flaps used in experimental study: the arterial loop flap and the intermuscular septal perforator flap. Although there were differences as well as similarities in skin vasculature between humans and the scent pig, the scent pig is still suitable for flap research.