Tension decrease during skin stretching in undermined versus not undermined skin: an experimental study in piglets

In a controlled study using 15 piglets, the efficacy of skin stretching using a skin stretching device was tested by quantifying the tension decrease during skin stretching in undermined and not undermined wounds. The viability of the skin margins was examined in both situations. Thirty standardized wounds was created: around 15 wounds on one flank, the surrounding skin was undermined; whereas around the 15 wounds on the opposite flank, the surrounding skin was not undermined. The force required to close the 9 x 9 cm defect was measured at the beginning, after undermining, and after 30 minutes of skin stretching. Also examined was the wound healing after 1 day and 1 week. A tension decrease of 3.02 N (13.6 percent reduction of the total force that is required to close the wound at the beginning) was seen due to undermining the surrounding skin. Skin stretching for 30 minutes without undermining the skin showed a tension decrease of 6.10 N (26.5 percent). Therefore, the tension decrease due to skin stretching was twice as high in comparison with undermining the skin margins alone. This has been statistically proven to be significant (-d (difference) = 3.08, 95 percent confidence interval = 2.16; 4.00, p < 0.001). When the undermined skin of the wound was stretched for 30 minutes, we measured a total tension decrease of 7.60 N (34.1 percent). There was a statistically significant but small difference in total tension decrease as a result of undermining combined with skin stretching in comparison with skin stretching without undermining (-d = 1.51, 95 percent confidence interval = 0.77; 2.23, p < 0.001). Undermining the surrounding skin involved cutting musculocutaneous perforating vessels. Looking at the viability of the skin, seven wounds, all found in the undermined group, showed skin necrosis after 1 week. Excessive seroma formation was seen in all wounds around which the skin was undermined. In the not undermined wounds, there were no problems in wound healing. In conclusion, skin stretching for only 30 minutes using a skin stretching device significantly reduces wound closing tension. The additional advantage of skin stretching over that of undermining alone is clearly shown. Undermining the wound margins before skin stretching gives a small additional tension decrease but has well-known complications, such as skin-edge necrosis and seroma formation.     

Rapid alignment of collagen fibers in the dermis of undermined and not undermined skin stretched with a skin-stretching device

A controlled, quantitative histochemical study was performed in five piglets to establish changes in undermined and not undermined stretched skin. The skin was stretched with a stretching device for 30 minutes to close a large skin defect. On each flank of the piglet, at a standard position, 9 x 9-cm wounds were created under general anesthesia. On one flank, the surrounding skin was undermined cranially and caudally over a 10-centimeter area. Sections of skin biopsies obtained during stretching were stained with picrosirius red and studied with routine light microscopy and polarized light microscopy in combination with image analysis. The length of collagen fibers was analyzed as a parameter of changes in the dermis resulting from skin stretching. This newly developed quantitative method appeared to be valid, specific, and reproducible, allowing for objective determination of changes in the length of the fibers in the plain of the sections. Changes in the orientation of collagen fibers in the dermis as a result of skin stretching were thereby determined. Epidermal thickness did not change significantly under the influence of stretching forces in both undermined and not undermined skin. However, the orientation of the collagen fibers changed significantly as a result of skin stretching. In undermined wounds, parallel alignment and elongation of the fibers in the plane of the sections was already observed after 15 minutes of stretching. The fibers became aligned in the direction of the stretching force, perpendicular to the wound margin. After 30 minutes of stretching, the mean major axes of the collagen fibers were longest in the plane of the sections (p < 0.001). This meant that elongation and parallel alignment of the collagen fibers had occurred. Stretching of not undermined skin for 15 minutes resulted in significantly stronger parallel alignment in the plane of the sections as compared with undermined skin. This was less well defined after 30 minutes of stretching in not undermined skin. It is concluded that skin stretching with a skin-stretching device for 30 minutes results in significant histomorphological changes of collagen fibers in the dermis of both undermined and not undermined skin. The fibers realign rapidly as a result of stretching forces and become aligned in the direction of the stretching force, perpendicular to the wound margin. These dynamic changes in collagen fibers explain the significantly decreased wound closing tension resulting from skin stretching and explain how skin stretches beyond its inherent extensibility.     

Forehead skin microcirculation during tilt table testing and lower body negative pressure

Noninvasive skin microcirculation measurements based on a new Near Infrared sensor technique (NIR/Fa. Silicon Sensor GmbH; Berlin) were embeded in a tilt table experiment for simulation of acute effects of weightlessness (HDT -6 degrees) and active standing with the Russian Tschibis-LBNP device. The phenomenon of orthostatic intolerance depends on complex interactions among functional characteristics of central and peripheral cardiovascular control. The purpose of this study was to assess the blood volume and flow motion changes as well as pulsatile spectral pattern during orthostatic and antiorthostatic stress.     

Substance P and microcirculation during stress

The experiments have been made on rats with the use of animals' immobilization on the back during 1 or 24 h as a stressor. Intravital study of the microcirculation in the rat mesentery has shown that P substance in a concentration of 7 X 10(-8) M aggravated the disturbances caused by the immobilization, while antiserum to P substance with an activity of 150 ng SP/equiv. normalized the microcirculation. The action of P substance and antiserum was similar as regards disturbances of vascular permeability for colloid carbon particles. It is concluded that P substance participates in the mechanisms of microcirculatory and vascular permeability disturbances during stress.     

High-intensity static magnetic fields modulate skin microcirculation and temperature in vivo

We investigated the acute effect of static magnetic fields of up to 8 T on skin blood flow and body temperature in anesthetized rats. These variables were measured prior to, during, and following exposure to a magnetic field in a superconducting magnet with a horizontal bore. The dorsal skin was transversely incised for 1 cm to make a subcutaneous pocket. Probes of a laser Doppler flowmeter and a thermistor were inserted into the pocket and positioned at mid-dorsum to measure skin blood flow and temperature. Another thermistor probe was put into the rectum to monitor rectal temperature. After baseline measurement outside the magnet, the rat was inserted into the bore for 20 min so that mid-dorsum was exactly positioned at the center, where the magnetic field was nearly homogeneous. Post-exposure changes were then recorded for 20 min outside the bore. Sham-exposed animals were submitted to exactly the same conditions, except that the superconducting magnet was not energized. Skin blood flow and temperature decreased significantly during magnetic field exposure and recovered after removal of the animal from the magnet. The rectal temperature showed a tendency to decrease while the animal was in the magnet. The microcirculatory and thermal reactions in the present study were consistent and agreed with some of the predictions based on mathematical simulations and model experiments.     

Oxygenation of unsaturated fatty acids in seeds during storage

Seeds of Cichorium intybus L., Crepis thomsonii Babc, and Crepis vesicaria L, were stored from 4 to 8 years at 5°C and then for 18 months under a variety of conditions. Oxygenated acids in Cichorium intybus oil increased from approximately 1% initially to 3% in the first storage period and to 17% while stored at room temperature during the second period. The corresponding levels at these three stages for Crepis thomsonii were 2, 6 and 18%. By gas chromatography (GC) and GC-mass spectrometry, the major oxygenated acids formed during storage were identified as hydroxy acids with conjugated unsaturation and 9,10-epoxy acids. In Crepis vesicaria seed, oil of which contained 53% vernolic (12,13-epoxy-9-octadecenoic) acid originally, approximately 2% of 9,10-epoxides were formed during the storage at room temperature. Levels of hydroxy acids with conjugated unsaturation in this species were 0.3% initially, 2% after 5 years at 5°C, and 9% after 18 months at room temperature. Primary substrates from which oxygenated acids were formed in the three species were crepenynic and linoleic acids, and the almost exclusive formation of 9,10-epoxide from linoleic acid indicated enzymatic involvement.     

Myocytes Oxygenation and High Energy Phosphate Levels during Hypoxia

Decrease of ambient oxygen level has been used in myocytes culture experiments in examining the responsiveness to stress secondary to hypoxia. However, none of these studies measure the myocytes oxygenation levels resulting in ambiguity as to whether there is insufficient oxygen delivery. This study examined the hypothesis that at a basal myocardial work state, adequate myocyte oxygenation would be maintained until extremely low arterial pO₂ levels were reached. Myocyte pO₂ values in normal dogs were calculated from the myocardial deoxymyoglobin (Mb- δ) levels using ¹H-spectroscopy (MRS) and were normalized to Mb-δ obtained after complete LAD occlusion. During Protocol 1 (n = 6), Mb-δ was measured during sequential reductions of the oxygen fraction of inspired gas (FIO₂) from 40, 21, 15, 10, and 5%, while in protocol 2 (n = 10) Mb-δ was measured at FIO₂ of 3%. Protocol 3 (n = 9) evaluated time course of Mb-δ during prolonged exposure to FIO₂ of 5%. Myocardial blood flow (MBF) was measured with microspheres and high energy phosphate (HEP) levels were determined with ³¹P-MRS. MVO₂ progressively increased in response to the progressive reduction of FIO₂ that is accompanied by increased LV pressure, heart rate, and MBF. Mb-δ was undetectable during FIO₂ values of 21, 15, 10, and 5%. However, FIO₂ of 3% or prolonged exposure to FIO₂ of 5% caused progressive increases of Mb-δ which were associated with decreases of PCr, ATP and the PCr/ATP ratio, as well as increases of inorganic phosphate. The intracellular PO₂ values for 20% reductions of PCr and ATP were approximately 7.4 and 1.9 mmHg, respectively. These data demonstrate that in the in vivo system over a wide range of FIO₂ and arterial pO₂ levels, the myocyte pO₂ values remain well above the K_m value with respect to cytochrome oxidase, and oxygen availability does not limit mitochondrial oxidative phosphorylation at 5% FIO₂.     

The effect of stretching on formation of myofibroblasts in mouse skin

Summary Wound contraction results from the contractile activity of modified fibroblasts, termed myofibroblasts, which are present in the granulation tissue of the healing wound. This study examines the relative role of mechanical tension (stretching) and wound healing as events capable of stimulating the formation of myofibroblasts in mouse skin. The skin of hairless mice was subjected to mechanical stretching and to a small incisional wound either separately or in combination. Animals were killed at intervals between 1 and 6 days and the dermis examined with the electron microscope. Stretching alone produced little evidence of inflammation at any time interval but cells with the ultrastructural characteristics of myofibroblasts were present at 4 days and abundant at 6 days. Skin that had been both stretched and wounded showed a marked inflammatory response and also contained myofibroblasts, but they were less frequent than in the skin subjected to stretching alone. Very few myofibroblasts were evident in skin that had only been wounded. It is suggested that the effect of mechanical tension alone may initiate formation of myofibroblasts in a tissue.     

Restoration of microcirculation in the brain during ischemia

The work shows that, after slinging two carotids in rats, the blood pressure in the circle of Willis decreases to approximately 40 mm Hg. The developing ischemia is accompanied by a mass adhesion of leukocytes to the walls of the brain venules and smallest veins. In two hours after slinging, the blood pressure in the vessels of the circle of Willis decreases to 16-20 mm Hg. The rate of adhesion increases abruptly. In these vessels the leukocyte conglomerates are formed which results in complete occlusion of the vessels and the death of animals. These processes are shown to be reversible. The insertion of 4.0-4.5 ml of plasmosubstituent polyglucin into the vessels of the circle of Willis "washes away" the leukocyte conglomerates as well as a part of adhered leukocytes and restores the blood flow in the venules and smallest veins for 10-15 min.     

Study of skin microcirculation by epicutaneous diffusion of 133 xenon]

The diffusion of radioactive inert gas xenon 133 through the epidermis in man was studied by compartimental model with a constant speed injection. From this we deduce the cutaneous and subcutaneous flow.     

Blood extraction from lancet wounds using vacuum combined with skin stretching.

Key factors and practical limits of blood extraction from lancet wounds on body sites other than the finger were determined by testing a large number of conditions. During these tests, the pain associated with lancing alternate body sites was rated as less painful than a fingerstick 98% of the time. Vacuum combined with skin stretching was effective in extracting an adequate volume of blood from the forearm for glucose testing, up to an average of 16 microl in 30 s. The amount of blood extracted increases with the application of heat or vacuum before lancing, the level of vacuum, the depth of lancing, the time of collection, and the amount of skin stretching. Vacuum and skin stretching led to significant increases, up to fivefold in the perfusion of blood in the skin as measured by laser Doppler. Our observations suggest that vacuum combined with skin stretching increases blood extraction at alternate sites by increasing the lancet wound opening, increasing the blood available for extraction by vasodilatation, and reducing the venous return of blood through capillaries.     

Orientation and stretching of DNA chains during pulsed field gel electrophoresis

The quantitative analysis of the decay of birefringence accompanying gel electrophoresis leads to the characterization of two phenomena respectively attributed to alignment of the tube and to overstretching of the chain in its tube. The major contribution to the molecular orientation is given by the overstretching which relaxes according to a stretched exponential law. The other process, slow, is characterized by a reptation time and a mean orientation factor in good agreement with the biased reptation model without overstretching.