First phase microcirculatory reaction to mechanical skin irritation: a three layer model of a compliant vascular tree

Mechanical skin irritation creates vasodilatation in the line of a stroke and in the surrounding tissue. To obtain further insight on underlying physiological mechanisms we developed a model of the vascular network comprised of three layers, where the first and the last one have a tree structure. They represent the arterial and the venous system, respectively. Both are connected via an intermediate zone representing the core of the microcirculation, which is described by means of a compliant compartment model. Irritation induces change in compliance of vessels situated at the entrance of the intermediate zone. Thus the model describes flow and pressure behavior due to mechanical skin irritation.     

Somatotopic representation of climbing fiber projections from limb cutaneous afferents to the paramedian lobule of the cat cerebellum

Climbing fiber projections to the cerebellar paramedian lobule were investigated electrophysiologically by stimulation of bilateral superficial radial nerve (SR) and superficial peroneal nerve (SP) in the cat anesthetized with pentobarbitone. In the medial zone of the paramedian lobule, short latency climbing fiber responses to stimulation of the ipsilateral SR were recorded rostrally from the top caudal part of the intermediate folia and short latency responses to stimulation of the ipsilateral SP were obtained caudally from the bottom caudal part of the folia. In the central zone, long latency responses to stimulation of the bilateral SR and SP were obtained. "Four limbs area" in which these responses were recorded was 1.0-1.2 mm in width. Short latency responses to stimulation of the ipsilateral SR were observed rostrally from this area, and short and long latency responses to stimulation of the ipsilateral SP were distributed caudally from this area. In the lateral zone, short and long latency responses to stimulation of the ipsilateral SR were recorded rostrally from the rostral part of the intermediate folia, and long latency responses to stimulation of the ipsilateral SP were observed caudally from the caudal part of the folia. In the most lateral zone, short and long latency responses to stimulation of the ipsilateral SR were obtained rostrally from the rostral part of the intermediate folia, and long latency responses to stimulation of ipsilateral SP were recorded only in the bottom caudal part of the folia caudally from the caudal part of the folia.     

Developmental changes in audiogenic epilepsy and myoclonus in KM rats

The reaction to a single sound stimulation (a bell) applied daily and the time of the first appearance of myoclonus were recorded in Krushinsky-Molodkina (KM) rats of different ages (30, 60, and 150-200 days). The audiogenic seizures in adult animals were of short latency and always resulted in tonic convulsions, which were stable in their patten. In contrast, in young animals (in particular, in 30-day-old rats), the seizures were less pronounced and unstable. The daily sound stimulation produced a gradual development of myoclonic seizures in young and adult rats. In old rats, the stable myoclonus appeared on the 17th day of stimulation, and in 30-day-old animals the myoclonus was recorded on the 26th day. In 60-day-old rats the myoclonus appeared for the first time on the 20th day of stimulation. It is suggested that these age differences can be explained by the btain immaturity (in particular, of neurotransmitter system) in young animals.     

Facial Skin Coloration Affects Perceived Health of Human Faces

Numerous researchers have examined the effects of skin condition, including texture and color, on the perception of health, age, and attractiveness in human faces. They have focused on facial color distribution, homogeneity of pigmentation, or skin quality. We here investigate the role of overall skin color in determining perceptions of health from faces by allowing participants to manipulate the skin portions of color-calibrated Caucasian face photographs along CIELab color axes. To enhance healthy appearance, participants increased skin redness (a*), providing additional support for previous findings that skin blood color enhances the healthy appearance of faces. Participants also increased skin yellowness (b*) and lightness (L*), suggesting a role for high carotenoid and low melanin coloration in the healthy appearance of faces. The color preferences described here resemble the red and yellow color cues to health displayed by many species of nonhuman animals.     

Leave the fat, skip the bolster: thinking outside the box in lower third nasal reconstruction

Defects of the lower third of the nose often present especially challenging reconstructive dilemmas. The surrounding skin to match is often thick, sebaceous, and sun damaged, none of which characterizes the historically ideal periauricular donor skin for grafting. The surrounding nasal skin is quite stiff, precluding very small local flaps. To avoid the "misplaced patch" appearance of most classic full-thickness grafts to this area or the depressed scar of an elliptical excision, many surgeons turn to larger local or regional flaps. These provide not only skin color and texture match but also the necessary several millimeters of subcutaneous fat necessary for proper tip aesthetics. Many defects of the lower third are small, making many surgeons reluctant to employ these larger flaps with their long scars and potential to twist or distort delicate tip or ala anatomy. The author has sought a means to transport skin and subcutaneous fat for lower third nasal defects outside of flaps. On the basis of the superiority of nasolabial fold scars and a vast positive experience in the literature utilizing skin and fat composite grafts with no bolsters, the author applied these techniques to 33 lower third nasal defects in 29 patients. Of 33 grafts varying in size from 4 mm circular to 17 mm x 16 mm and retaining 1 to 5 mm of fat, no grafts were lost. Four grafts developed a 30 percent area or less of central necrosis resulting in localized depression. Three of these four grafts were in active smokers and the fourth graft was in a former smoker. Aside from these four grafts and one with considerable excess fat early in the series, contour was good to excellent. Hypopigmentation is still common but improves with time. Easily performed composite grafts effectively carry the necessary fat for aesthetic reconstruction and do not risk long scars on the nose and twisting of the tip and ala that can result from flaps. Revisions are infrequent and extremely simple when indicated.     

An Analysis of Field Potentials During Different Tailflip Behaviours in Crayfish

Crayfish tailflips have been intensively studied to reveal the decision-making processes and neural organisation underlying a stereotyped escape behaviour. Three behaviours mediated by different neural pathways have been well described: medial giant, lateral giant and non-giant tailflips. It has proved difficult to distinguish between the three without invasive or restrictive experimental manipulation. We report unambiguous differences between the signals generated by the crayfish Cherax destructor during the three types of tailflip when recorded by bath electrodes placed in the holding aquarium. Using our ability to distinguish between the different behaviours in freely moving animals we examined the relationship between the type of tailflip evoked by stimulation to different parts of the body. The transition zone between medial and lateral giant tailflips is the thoracic-abdominal border but it is not absolute and some stimuli produce responses that cannot be unambiguously assigned to either behavioural category. We examined the latency between stimulation at different points down the length of the body and the appearance of the electrical signal accompanying escape for both medial and lateral tailflips. We used two methods to estimate the proportion of the latency accounted for by giant fibre conduction velocity. The results support current views of the differences between the activation sites of the two giant fibre systems and suggest why stimulation in the transition zone results in ambiguous outcomes.     

The latency difference of the tibial and sural nerve sep: Peripheral versus central factors

The latency of the cortical SEP (CSEP) following stimulation of the posterior tibial nerve is nearly always shorter than the latency of the CSEP evoked by stimulation of the sural nerve. Till now this fact was believed to be due mainly to different conduction velocities within the peripheral nerves owing to the muscle afferents of the posterior tibial nerve. The surprising discovery that the lumbar and cervical SEPs exhibit much shorter time lags than the CSEPs led to the experiments described in this paper: during the registration of the peripheral sciatic nerve action potentials only slight differences in the conduction velocities were observed. Thereupon a topographical analysis was performed during which the minimum latency of the sural nerve CSEP was not measured at the usual C′_z electrode position but was found to be shifted to a more occipital and ipsilateral point.From these results it was concluded that, for the main part, the latency difference of the CSEPs results from ‘central factors’, which had already been postulated for the median nerve CSEP by Burke and coworkers.     

Stimulation of regional lymphatic and blood flow by epicutaneous oxazolone.

The application of the epicutaneous antigen oxazolone results in persistent induration and erythema; however, the relative changes in lymph and blood flow in the inflammatory skin are largely unknown. To define the contribution of lymph and blood flow to the clinical appearance of cutaneous inflammation, we studied the sheep ear after the application of oxazolone. As a model for the study of these changes, the sheep ear had several experimental advantages: 1) a simplified superficial vascular network, 2) defined lymphatic drainage, and 3) an avascular and alymphatic cartilaginous barrier. Lymph flow was continuously monitored by cannulation of the prescapular efferent lymph duct. Blood flow, as reflected by cutaneous erythema, was noninvasively measured by use of a visible-spectrum spectrophotometer. The application of the epicutaneous oxazolone resulted in increased ear thickness for >7 days. The lymph flow from the oxazolone-stimulated ear peaked between 24 and 48 h after oxazolone stimulation. Spectrophotometric evaluation indicated that the cutaneous erythema peaked 72-96 h after application of oxazolone. Corrosion casting and scanning electron microscopy of the microcirculation at 96 h after antigen stimulation demonstrated significant dilatation of the superficial vascular network. These results suggest a biphasic response to oxazolone stimulation: 1) an early increase in vascular permeability associated with increased lymph flow and 2) a subsequent increase in relative blood flow associated with a dilated inflammatory microcirculation.     

Effects of very-long-range forces on filament formation in india ink particle preparations in water

The expected diffusion phase of a drop of india ink layered on water is interrupted by the appearance of straight 0.5-mm-diameter filaments of carbon particles when two experimental conditions are imposed. First, the water is derived from ice melted near a lead mass and, second, the ink suspension is inserted into space surrounding a cylindrical vessel of chipped ice containing calcium chloride. Equilibrium between the phases, respectively diffuse and filamentary can be disturbed by placing objects in this space to the left-hand side of the ice-containing vessel. When a thin film of oil-on-water is so placed the filament disappears within 15 s. Its disappearance is prevented by the solution of a prostaglandin in the same oil. Reasons are discussed for viewing the observations as indirectly derived from a coherent air flow surrounding the ice-calcium mixture, a coherence induced in turn in its contained gas molecules by a force described by Casimir. The observations can then be seen as macroscopic quantal in nature.     

Improving limb flexion in FES gait using the flexion withdrawal response for the spinal cord injured person

In the restoration of gait for paraplegics using functional electrical stimulation, the method most commonly used to produce hip flexion for the swing phase of gait has been the elicitation of the flexion withdrawal response. Several problems have been noted with the response: there is a decrease in the magnitude of the hip flexion to repeated stimuli (habituation); long latency; and inhibition of the response when stimulated bilaterally. These have been characterized and methods for overcoming the problems tested. Results show that increasing stimulation frequency reduces latency. Habituation can be reduced in some subjects by multiplexing two sites of stimulation. Habituation can further be reduced by applying single high-intensity pulses and this has been used in a one-step-ahead controller for regulating hip flexion angle. Inhibition due to bilateral stimulation had been significantly reduced by altering the timing of the stimulation to the two legs.     

Development of the hypothalamic-cortical interrelations in the ontogeny of the cat

Under chloralose narcosis, employing the evoked potentials method, studies have been made on the projection of the posterior hypothalamus to the frontal cortex in 1-30 days old kittens. The animals were divided into 3 age groups: 1-9, 10-19 and 20-30 days. Studies of the EPs in different points of pericruciate zone showed that these potentials are observed in all the investigated points from the first days of postnatal life. The latent period of responses in the youngest animals varied from 40 to 80 ms, exhibiting insignificant fluctuations depending on the cortical zone investigated. From the very beginning of postnatal life, in the same cortical zone the EPs may be observed in response to stimulation of the ischiadic nerve as well. In older animals, the latent period of the EPs decreases in all the points, the decrease being most significant near the crucial fissure. To the 30th day of postnatal life, the EPs in this zone with respect to their latency and configuration became quite similar to those in adult animals. In the third age period, the latency varies from 6 to 10 ms in the focus of maximum activity; with the removal of the recording electrode from this zone the latent period of the hypothalamo-cortical responses increases up to 30-40 ms. Overlapping of the EPs in response to central and peripheral stimulation was observed at all age periods.     

Postnatal development of the splenic white pulp in the golden hamster Mesocricetus auratus. I. The periarterial lymphoid sheath (PALS)

The histological organization of the periarterial lymphoid sheath (PALS) was studied during the postnatal life of the golden hamster Mesocricetus auratus with special interest in the cell components occurring in each of their regions. Our results suggest a role of the cell components defining the splenic microenvironment at each developmental stage in governing the developmental process. This process can be temporarily and histologically divide into three stages: 1. At birth, a few lymphocytes and lymphoblasts surrounding the central artery define primitive PALS. 2. A second period is determined on the 2nd day by the appearance of a marginal sinus which bounds the two splenic compartments, white and red pulp. The PALS increases circumferentially around the central artery defined by the pattern of reticular cells and fibres. 3. Between the 4th and 10th days, the PALS reaches its definitive organization, except for the absence of primary and secondary lymphoid follicles, defining an inner and outer region. The marginal zone appears on the 6th day.     

Visualization and Analysis of Blood Flow and Oxygen Consumption in Hepatic Microcirculation: Application to an Acute Hepatitis Model

There is a considerable discrepancy between oxygen supply and demand in the liver because hepatic oxygen consumption is relatively high but about 70% of the hepatic blood supply is poorly oxygenated portal vein blood derived from the gastrointestinal tract and spleen. Oxygen is delivered to hepatocytes by blood flowing from a terminal branch of the portal vein to a central venule via sinusoids, and this makes an oxygen gradient in hepatic lobules. The oxygen gradient is an important physical parameter that involves the expression of enzymes upstream and downstream in hepatic microcirculation, but the lack of techniques for measuring oxygen consumption in the hepatic microcirculation has delayed the elucidation of mechanisms relating to oxygen metabolism in liver. We therefore used FITC-labeled erythrocytes to visualize the hepatic microcirculation and used laser-assisted phosphorimetry to measure the partial pressure of oxygen in the microvessels there. Noncontact and continuous optical measurement can quantify blood flow velocities, vessel diameters, and oxygen gradients related to oxygen consumption in the liver. In an acute hepatitis model we made by administering acetaminophen to mice we observed increased oxygen pressure in both portal and central venules but a decreased oxygen gradient in the sinusoids, indicating that hepatocyte necrosis in the pericentral zone could shift the oxygen pressure up and affect enzyme expression in the periportal zone. In conclusion, our optical methods for measuring hepatic hemodynamics and oxygen consumption can reveal mechanisms related to hepatic disease.     

Salivation pattern of Rhodnius prolixus (Reduviidae; Triatominae) in mouse skin

The objective of this work was to study the pattern of salivation of triatomines during feeding in mouse skin. Rhodnius prolixus was fed with a solution of the dye acridine orange or fluorescein. The saliva was efficiently labelled with acridine orange, probably due to the difference in pH between the salivary gland (6.0) and the hemolymph (6.5-7.0). This procedure was not effective at labelling the saliva of Triatoma infestans, however, fluorescent labelling of R. prolixus saliva allowed us to demonstrate that salivation occurs during entire feeding process. The saliva is released soon after the bite. In the probing phase, saliva is pumped continuously in the host skin, including around the blood vessels. During the engorgement phase, saliva is observed in a bolus within the blood vessel and some of it is sucked up by the insect, together with blood. The frequency of saliva emission inside the vessels was low (0.51+/-0.18 Hz). The saliva deposition in the microcirculation is continuous and modulated by the frequency of the cibarial pump because, when functioning at high frequency, cibarial pump sucks almost all saliva to the insect gut. This mechanism would determine the quantity of saliva deposited in the microcirculation as necessary, and consequently minimizing the host's immune response to salivary antigens.     

Description of and treatment to inhibit the rejection of human split-thickness skin grafts by congenitally athymic (nude) rats

Gradual rejection of topically engrafted human split-thickness skin grafts (HSTSG) occurred in greater than 90% of congenitally athymic (nude) rats between 21 and 42 days of grafting. Engraftment and rejection of HSTSG is accompanied by a partial restoration of some cell-mediated immune components, the mixed lymphocyte response and lysis of human target cells. Histologic features of the rejection process were those seen in a host-versus-graft reaction. Immunofluorescent analysis of skin undergoing rejection demonstrated IgG at the basement membrane zone in most grafts. Nude rats rejecting HSTSG had circulating IgG which bound to the basement membrane zone and blood vessels of human skin. Nude rats treated with cyclosporine injections for 21 days had an enhanced survival of HSTSG, 120 or more days.     

Fiberoptic laser-doppler anemometer microscope applied to the cerebral microcirculation in rats

We have applied our developed fiber-optic laser-Doppler anemometer microscope (FLDAM) for the study of the cerebral microcirculation in the rat. The red cell velocity in single pial microvessels was successfully measured through a closed cranial window for the vessel diameter range from 7.8 to 230 μm. The temporal resolution of the FLDAM was sufficiently high to detect the pulsation in the arterioles. Arterio-venous distributions of the temporal mean red cell velocity and wall shear rate are also described.     

Pulsatile pressure and flow in the skeletal muscle microcirculation

Although blood flow in the microcirculation of the rat skeletal muscle has negligible inertia forces with very low Reynolds number and Womersley parameter, time-dependent pressure and flow variations can be observed. Such phenomena include, for example, arterial flow overshoot following a step arterial pressure, a gradual arterial pressure reduction for a step flow, or hysteresis between pressure and flow when a pulsatile pressure is applied. Arterial and venous flows do not follow the same time course during such transients. A theoretical analysis is presented for these phenomena using a microvessel with distensible viscoelastic walls and purely viscous flow subject to time variant arterial pressures. The results indicate that the vessel distensibility plays an important role in such time-dependent microvascular flow and the effects are of central physiological importance during normal muscle perfusion. In-vivo whole organ pressure-flow data in the dilated rat gracilis muscle agree in the time course with the theoretical predictions. Hemodynamic impedances of the skeletal muscle microcirculation are investigated for small arterial and venous pressure amplitudes superimposed on an initial steady flow and pressure drop along the vessel.     

Muscle flaps' triphasic microcirculatory response to sympathectomy and denervation.

Whether sympathectomy and somatic denervation in muscle flaps increased microcirculatory flow in the short or long term, thus producing an effect similar to the delay phenomenon, which increases survival in transferred skin flaps, was determined. The rat cremaster muscle flap model was used for in vivo microscopy. In the left cremasters of 30 Sprague-Dawley rats, the genitofemoral nerve was divided and the proximal vessels were stripped of their adventitia. The muscle was not elevated. In each rat, the contralateral cremaster served as the control. The rats were assigned to one of five groups: no delay before observation, a 24-hour delay, a 48-hour delay, a 7-day delay, or a 14-day delay. After the delay, red blood cell velocity, vessel diameters, number of functional capillaries, and leukocyte-endothelial interactions were measured. Microvessel response to topical vasoactive substances was measured. Immediately after denervation, red blood cell velocity increased transiently (71 percent; p = 0.006). Main arterioles dilated (20 percent; p = 0.02) at 24 hours, and capillary perfusion increased 36 percent (p = 0.001) at 2 weeks. The microvessels had hyperactive responses to all vasoactive agents 2 weeks after denervation. These findings indicate that proximal sympathectomy with somatic denervation leads to a triphasic, dynamic response in the peripheral microcirculation of the cremaster muscle flap. An initial acute hyperadrenergic phase was followed by a nonadrenergic phase, with significant vasodilatation, and a sensitized phase, with increased capillary perfusion and hyperresponsiveness to vasoactive substances. This study shows that with minimal access to the cremaster muscle flap neurovascular pedicle and without changing the blood supply to the flap, significant hemodynamic improvements can be made in the peripheral microcirculation.     

Impact of fresh fruit smoothie consumption on apparent health of Asian faces

Skin carotenoid coloration has been proposed as a valid cue to health in humans, reflecting fruit and vegetable intake, and enhancing apparent health. Supplementation with a carotenoid-rich fruit and vegetable smoothie affects skin color, but it is not known if this skin color change enhances healthy appearance. In three experiments, we examine the effects of skin color change induced by supplementation with a carotenoid-rich fruit smoothie (25 mg carotenoids/d) on the apparent health of Malaysian Chinese faces. In experiment 1, observers were asked to identify the healthier looking of pairs of photographs of the same subject taken pre- and post-supplementation (or pre- and post-placebo), choosing the pre-supplementation (or pre-placebo) images. When confounding due to facial expression was eliminated in experiment 2, observers showed no preference for unmodified pre-supplementation photograph or the same image with skin color manipulated to simulate a level of smoothie-induced color change associated with 4 weeks of supplementation. In experiment 3, observers manipulated the skin color of face photographs along the smoothie-induced color change axis to optimize healthy appearance. Observers chose to induce a color change approximately equivalent to one third of the change induced by daily consumption of our carotenoid rich smoothie. This suggests that the skin color change induced by the supplementation enhanced apparent facial health, however the dose and duration of the supplementation overshot the optimal healthy-looking color of Malaysian Chinese skin. This suggests that there is an optimal carotenoid color for healthy appearance, and that this optimal level may be constrained by preferences for averageness, by the association between very yellow skin and ill health, or by negative health impacts of very high doses of carotenoids.