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Effects of hypobaric pressure on human skin: implications for cryogen spray cooling (part II) 总被引:1,自引:0,他引:1
BACKGROUND AND OBJECTIVES: Clinical results have demonstrated that dark purple port wine stain (PWS) birthmarks respond favorably to laser induced photothermolysis after the first three to five treatments. Nevertheless, complete blanching is rarely achieved and the lesions stabilize at a red-pink color. In a feasibility study (Part I), we showed that local hypobaric pressure on PWS human skin prior to laser irradiation induced significant lesion blanching. The objective of the present study (Part II) is to investigate the effects of hypobaric pressures on the efficiency of cryogen spray cooling (CSC), a technique that assists laser therapy of PWS and other dermatoses. STUDY DESIGN/MATERIALS AND METHODS: Experiments were carried out within a suction cup and vacuum chamber to study the effect of hypobaric pressure on the: (1) interaction of cryogen sprays with human skin; (2) spray atomization; and (3) thermal response of a model skin phantom. A high-speed camera was used to acquire digital images of spray impingement on in vivo human skin and spray cones generated at different hypobaric pressures. Subsequently, liquid cryogen was sprayed onto a skin phantom at atmospheric and 17, 34, 51, and 68 kPa (5, 10, 15, and 20 in Hg) hypobaric pressures. A fast-response temperature sensor measured sub-surface phantom temperature as a function of time. Measurements were used to solve an inverse heat conduction problem to calculate surface temperatures, heat flux, and overall heat extraction at the skin phantom surface. RESULTS: Under hypobaric pressures, cryogen spurts did not produce skin indentation and only minimal frost formation. Sprays also showed shorter jet lengths and better atomization. Lower minimum surface temperatures and higher overall heat extraction from skin phantoms were reached. CONCLUSIONS: The combined effects of hypobaric pressure result in more efficient cryogen evaporation that enhances heat extraction and, therefore, improves the epidermal protection provided by CSC. 相似文献
995.
BACKGROUND AND OBJECTIVES: Two wavelengths, 585 and 595 nm, are currently common options for treating vascular malformations such as port-wine stains (PWS). Controversy exists as to which wavelength induces greater photothermal damage to the blood vessels and subsequent resolution of the malformations. STUDY DESIGN/MATERIALS AND METHODS: We irradiated normal, human skin in vivo at 585 and 595 nm wavelengths using fluences of 10-30 J/cm(2) with a 1.5 millisecond laser pulse. The level of purpura, total vascular damage, maximum coagulation depth (MCD), and perivascular damage were quantified by gross observation and histological analysis. RESULTS: Results demonstrated that 585 nm light caused greater purpura, vascular damage, maximum coagulation depth, and perivascular damage than 595 nm. Purpura showed a positive correlation with total vascular damage to a certain extent beyond which the total vascular damage did not change. For equivalent purpura, 585 and 595 nm produced no statistically significant difference in vascular damage. The difference in the laser-induced vascular damage between 585 and 595 nm, although statistically significant, was no more than 50%. CONCLUSIONS: The bathochromic (red) shift and formation of met-hemoglobin, which reduces the 585 nm light absorption and increases that of 595 nm compared to native oxy-hemoglobin, play a considerable role in creating more parity in vascular damage between the two wavelengths than would be expected based on their respective "native" absorption coefficients alone. 相似文献
996.
Hislop JN Caunt CJ Sedgley KR Kelly E Mundell S Green LD McArdle CA 《Journal of molecular endocrinology》2005,35(1):177-189
Activation of seven-transmembrane receptors is typically followed by desensitization and arrestin-dependent internalization via vesicles that are pinched off by a dynamin collar. Arrestins also scaffold Src, which mediates dynamin-dependent internalization of beta2-adrenergic receptors. Type I mammalian gonadotropin-releasing hormone receptors (GnRHRs) do not rapidly desensitize or internalize (characteristics attributed to their unique lack of C-terminal tails) whereas non-mammalian GnRHRs (that have C-terminal tails) are rapidly internalized and desensitized. Moreover, internalization of Xenopus (X) GnRHRs is dynamin-dependent whereas that of human (h) GnRHRs is not, raising the possibility that binding of arrestin to the C-terminal tails of GnRHRs targets them to the dynamin-dependent internalization pathway. To test this we have compared wild-type GnRHRs with chimeric receptors (XGnRHR C-terminal tail added to the hGnRHR alone (h.XtGnRHR) or with exchange of the third intracellular loops (h.Xl.XtGnRHR)). We show that adding the XGnRHR C-terminal tail facilitates arrestin- and dynamin-dependent internalization as well as arrestin/green fluorescent protein translocation, but Src (or mitogen-activated protein kinase/extracellular-signal-regulated kinase kinase) inhibition does not slow internalization, and h.XtGnRHR internalization is slower than that of the hGnRHR. Moreover, arrestin expression increased XGnRHR internalization even when dynamin was inhibited and h.Xl.XtGnRHR underwent rapid arrestin-dependent internalization without signaling to G(q/11). Thus, although the C-terminal tail can direct GnRHRs for arrestin- and dynamin-dependent internalization, this effect is not dependent on Src activation and arrestin can also facilitate dynamin-independent internalization. 相似文献
997.
Gaya DR Stuart RC McKee RF Going JJ Davidson R Stanley AJ 《European journal of gastroenterology & hepatology》2005,17(12):1425-1428
According to the published medical literature to date, prophylactic gastrectomy undertaken in the context of carriage of a germline truncating E-cadherin mutation and an appropriate positive family history will lead to the discovery of occult foci of adenocarcinoma in all gastrectomy specimens. We describe the first published case of a patient whose prophylactic gastrectomy in this setting failed to reveal any dysplastic or malignant foci. Furthermore the patient's nephew, who was found to carry an identical E-cadherin mutation on family screening and also underwent prophylactic gastrectomy, was shown to have multi-focal diffuse adenocarcinoma after analysis of the gastrectomy specimen. Both patients were also found to have penetrant genetic haemochromatosis. Within this case, we discuss the clinical manifestations and penetrance of germline E-cadherin mutations and the difficult decisions facing both clinicians and families with this mutation. We also speculate on how these patients' undiagnosed genetic haemochromatosis may have influenced the pathology encountered. 相似文献
998.
Micheva-Viteva S Pacchia AL Ron Y Peltz SW Dougherty JP 《Antimicrobial agents and chemotherapy》2005,49(12):5185-5188
Human immunodeficiency virus type 1 (HIV-1) is not eliminated from patients even after years of antiretroviral therapy, apparently due to the presence of latently infected cells. Here we describe the development of a cell-based system of latency that can be used for high-throughput screening aimed at novel drug discovery to eradicate HIV-1 infection. 相似文献
999.
We present a case study of a truck driver with sinus node dysfunction diagnosed with the help of an implantable loop recorder more than 18 months after implantation. This case emphasizes that cardiogenic syncope may be very infrequent and its diagnosis can be elusive despite extensive testing. 相似文献
1000.
Humberd CM Murray CK Stuart SK Reeb BA Hospenthal DR 《The American journal of tropical medicine and hygiene》2005,73(5):962-963
The currently accepted gold standard for enumeration of leptospires is tabulation of organisms using a Petroff-Hausser counting chamber and dark-field microscopy, a technically demanding, time-consuming technique. Quantification of leptospires with a Coulter counter produced reliable and reproducible counts, comparable to the counting chamber. This experiment demonstrates that the faster, less technically demanding Coulter counter may be an alternative to determine numbers of leptospires. 相似文献