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One of the most important functions of skin is thermoregulation. The alterations in the patterns of blood flow in skin is one of the main physiological processes responsible for thermoregulatory control. The mechanisms governing the thermoregulatory control of cutaneous blood flow are mainly neural and chemical in nature. At present, there is a lack of studies in the literature looking at the relationship between reinnervation and the blood flow pattern of skin grafts.The present study uses Laser Doppler flowmetry and the immunohistochemical stains protein gene product 9.5, calcitonin gene-related peptide and substance P to identify nerve fibres, and antibodies to CD31 and von Willebrand factor to identify endothelial tissues. The aim of the present study was to investigate the patterns of blood flow and nerve tissue regeneration in split-skin grafts up to 15 years following the original procedure. Thirty-two split-skin grafts were studied and these were placed into two groups based on the nature of the bed of excision: group I consisted of patients who underwent tangential excision and split-skin grafting (n=17), and group II consisted of patients with split-skin grafts placed onto fascial beds (n=15). Each subpopulation of patients was further divided into three groups based on the length of time following grafting: one to three years, four to six years and seven to 15 years. These divisions were arbitrarily chosen and called A1, A2 and A3, respectively. In the Laser Doppler flowmetry arm of the study, the grafts were assessed at various stages after heating, cooling and further reheating.The Laser Doppler flowmetry studies showed that, on subjecting the skin grafts in both groups I and II to heating and cooling followed by reheating, the overall response of the blood flow to changes in the temperature was slower.The immunohistochemical analysis showed that in all graft types and graft ages, protein gene product 9.5, calcitonin gene-related peptide and substance P stains demonstrated a relative lack of the presence of nerve fibres in the split-skin grafts compared with the control (‘normal’ skin). However, von Willebrand factor and CD31 immunological staining demonstrated that vessels were present in the split-skin grafts, with no significant difference in size or quantity from the control samples.It was found that the blood flow in the split-skin graft in response to thermal challenge, although present, was slower than that of normal skin, a finding which was independent of the age of the skin graft. It is thought that this was related to a lack of regeneration of nerve fibres and, hence, a deficiency in the neurally mediated reflexes of the blood vessels within the split-skin grafts.

Background: There is a paucity of reports in the literature examining the pattern of sensory and autonomic neural recovery of myocutaneous microvascular flaps and skin grafts to the lower limbs after a prolonged period of time.Objectives: To investigate the recovery of sensation and autonomic nerve activity in long-standing split-skin grafts applied to fascial beds and in myocutaneous microvascular flaps.Methods: The patients were divided into two groups: group a consisted of patients with a split-skin graft applied to a fascial bed (n=11) and group B consisted of patients with free microvascular flaps (n=4). Patients in both groups underwent various clinical subjective and objective tests, including the measurement of electrical resistance and thermal sensory analysis. Laser Doppler flowmetry was used to investigate the blood flow patterns.Results: Patients in both groups showed significantly reduced sensory modalities. However, the findings of both the electrical resistance and laser Doppler flowmetry were significantly different among the patients in group a compared with controls. In contrast, electrical resistance and laser Doppler flowmetry test results were similar in group B and controls.Conclusions: Both split-skin grafts applied to fascial beds and microvascular flaps on the lower limb had poor sensory recovery. However, after 15 years, the microvascular flaps regained the ability to sweat and some degree of thermoregulatory function. This may imply that the long-standing myocutaneous free flaps regained some aspects of their autonomic innervation, whereas the split-skin grafts had not.

Diffraction experiments with holographic gratings recorded in SiO2 nanoparticle-polymer composites have been carried out with slow neutrons. The influence of parameters such as nanoparticle concentration, grating thickness, and grating spacing on the neutron-optical properties of such materials has been tested. Decay of the grating structure along the sample depth due to disturbance of the recording process becomes an issue at grating thicknesses of about 100 microns and larger. This limits the achievable diffraction efficiency for neutrons. As a solution to this problem, the Pendellösung interference effect in holographic gratings has been exploited to reach a diffraction efficiency of 83% for very cold neutrons. [ABSTRACT FROM AUTHOR]