Dental resin curing blue light induces vasoconstriction through release of hydrogen peroxide.

Dental resin curing blue light (BL) is frequently used during treatments in dental clinics. However, little is known about the influence of BL irradiation on pulpal blood vessels. The aim of the present study was to investigate the mechanism of effect of BL irradiation on vascular tone. Rat aorta (RA) rings were irradiated with a BL source in organ baths, and the responses were recorded isometrically. Effect of BL irradiation on phenylephrine (PE) -precontraction and acetylcholine (ACh) -induced relaxation after PE -precontraction were obtained and compared in BL -irradiated and control RA rings. Effect of 20 min preincubation with catalase (enzyme that breaks down hydrogene peroxide, 1200 u/ml) on PE -precontraced and BL-irradiated rings was also evaluated. Total oxidative stress (TOS) and total antioxidant capacity (TAC) in BL-irradiated and control RA preparations were measured with special assay kits and spectrophotometry. BL slightly decreased ACh -induced endothelium -dependent relaxations in PE (1 µM) -precontracted RA rings (n = 6, p > 0.05 vs. control). BL induced marked contraction 23.88 + 3.10% of PE (maximum contraction) in isolated RA ring segments precontracted with PE (p < 0.05 vs. control). The contractile effect of BL was inhibited by 1200 u/ml catalase (n = 6, p < 0.05 vs. control). BL irradiation increased the level of TOS in RA rings (n = 6, p < 0.05 vs. control). TAC levels were similar in BL-irradiated and control preparations. These results suggest that BL induces contraction in RA, and the mechanism of this effect may to be through release of hydrogen peroxide.

Síndrome de vasoconstricción cerebral reversible de evolución mortal / Fulminant reversible cerebral vasoconstriction syndrome

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Experimental and numerical investigation on the transient vascular thermal response to multi-pulse Nd:YAG laser.

BACKGROUND AND OBJECTIVE: Port wine stains (PWS) are congenital vascular malformations that progressively darken and thicken with age. Laser therapy is currently the most effective way in clinical practice for PWS. A 1,064 nm Nd:YAG laser in the near-infrared band can achieve a deeper treatment depth compared to the current widely adopted pulsed dye laser. However, because of its relatively weak absorption by blood, single-pulse Nd:YAG laser requires high energy density to cause effective vessel damage, but may inflict undesirable burning to surrounding collagen. Multi-pulse laser has great potential in clinical treatment because it needs less energy density for each pulse. This paper presented an experimental and theoretical study of the transient thermal effects of low-energy multi-pulse Nd:YAG laser on blood vessels. STUDY DESIGN/MATERIALS AND METHODS: In vivo experiments were performed on dorsal skin chamber. By using a high speed camera (up to 2,000 fps), the complete and dynamic thermal response of blood vessels during laser irradiation and between pulse intervals was obtained. In vitro experiment in capillary tubes and Numerical simulations by two-scale heat transfer model were also conducted to further explore the in vivo experimental findings. RESULTS: The complete and dynamic response of blood vessels were obtained, including vessel dilation, thrombus formation, partial vessel constriction, thread-like constriction, cavitation and bubbles, and hemorrhage. Thread-like constriction is the desirable treatment end point, which will only occur after thrombus completely occludes the vessel lumen. Cavitation can cause hemorrhage when thrombus fails to occlude the vessel lumen. In vitro experiment found that vessel constriction was due to the constriction of thrombus induced by laser irradiation. Theoretical investigation revealed that the mechanism for the effective reduction of energy density by multi-pulse Nd:YAG laser was due to enhanced light absorption of the blood with thrombus formation. CONCLUSIONS: For multi-pulse treatment, laser parameters are recommended as repetition rate of 10 Hz and pulse number of 10. The incident energy in each pulse should be strong enough to induce blood coagulation through seven or eight pulses and should be lower than the threshold of blood cavitation. Lasers Surg. Med. 49:852-865, 2017. © 2017 Wiley Periodicals, Inc.

Influence of electroacupuncture on thermal changes in a soft tissue defect.

This study investigated thermal changes in the skin at locations where soft tissue defects existed and acupuncture needles stimulated by using bipolar electroacupuncture (EA) had been inserted. Under general anesthesia (GA), experimental defects were made at the dorsum site of five New Zealand rabbits. Bipolar EA was used for 20 minutes to stimulate the experimental defects, and the skin temperature was monitored at the sites where the acupuncture needles had been inserted and the soft tissue defects existed. The initial thermography of those defects had the same trend as that of the negative pole of EA stimulation at the first acupoint. Skin thermography during the first 3 minutes of bipolar EA indicated a centrifugal vasoconstriction and a vasodilatation at the negative and positive poles, respectively. After that, the thermal change in soft tissue undergoing EA stimulation was not modified by a different EA polarity. The local temperature at the defect and its surroundings under both positive and negative electric loads was increased by 0.2-0.3 °C for vasodilatation. This study indicates that EA influences sympathetic modulation of soft tissue defects and that selective sympathetic modulation caused by bipolar EA is responsible for the clinical perception.

Miniature electrical stimulator for hemorrhage control.

Noncompressible hemorrhage is currently the most common cause of preventable death in battlefield and in civilian trauma injuries. Tourniquets, specialized wound dressings, and hemorrhage-inhibiting biomaterials are not sufficiently effective in arrest of noncompressible hemorrhage and often cause collateral tissue damage. An effective, easy-to-use, portable device is needed to reduce blood loss in trauma patients immediately following injury and to maintain hemorrhage control up to several hours-until the injured is evacuated to a medical facility. We developed a miniature electrical stimulator to induce vascular constriction and, thereby, reduce hemorrhage. Vasoconstriction of the rat femoral arteries and veins was studied with pulse durations in the range of 1 µs to 10 ms and repetition rate of 10 Hz. Pulse amplitude of 20 V, duration of 1 ms, and repetition rate of 10 Hz were found sufficient to induce rapid constriction down to 31 ± 2% of the initial diameter, which could be maintained throughout a two-hour treatment. Within one minute following treatment termination the artery dilated back to 88 ± 3% of the initial diameter, providing rapid restoration of blood perfusion. Histology indicated no damage to the vessel wall and endothelium seven days after stimulation. The same treatment reduced the blood loss following complete femoral artery resection by 68 ± 11%, compared to untreated vessels. Very low power consumption during stimulation (<10 mW per 1.6 mm electrode) allows miniaturization of the stimulator for portable battery-powered operation in the field to control the blood loss following vascular trauma.

Direct, acute effects of Klotho and FGF23 on vascular smooth muscle and endothelium.

Chronic kidney disease (CKD) is regarded as a state of Klotho deficiency and FGF23 excess. In patients with CKD a strong association has been found between increased serum FGF23 and mortality risk, possibly via enhanced atherosclerosis, vascular stiffness, and vascular calcification. The aim of this study was to examine the hypothesis that soluble Klotho and FGF23 exert direct, rapid effects on the vessel wall. We used three in vitro models: mouse aorta rings, human umbilical vein endothelial cells, and human vascular smooth muscle cells (HVSMC). Increasing medium concentrations of soluble Klotho and FGF23 both stimulated aorta contractions and increased ROS production in HVSMC. Klotho partially reverted FGF23 induced vasoconstriction, induced relaxation on phosphate preconstricted aorta and enhanced endothelial NO production in HUVEC. Thus Klotho increased both ROS production in HVSMC and NO production in endothelium. FGF23 induced contraction in phosphate preconstricted vessels and increased ROS production. Phosphate, Klotho and FGF23 together induced no change in vascular tone despite increased ROS production. Moreover, the three compounds combined inhibited relaxation despite increased NO production, probably owing to the concomitant increase in ROS production. In conclusion, although phosphate, soluble Klotho and FGF23 separately stimulate aorta contraction, Klotho mitigates the effects of phosphate and FGF23 on contractility via increased NO production, thereby protecting the vessel to some extent against potentially noxious effects of high phosphate or FGF23 concentrations. This novel observation is in line with the theory that Klotho deficiency is deleterious whereas Klotho sufficiency is protective against the negative effects of phosphate and FGF23 which are additive.

The effect of fluence rate on the acute response of vessel diameter and red blood cell velocity during topical 5-aminolevulinic acid photodynamic therapy.

BACKGROUND: In a previous study it is shown that for topically applied ALA-PDT, PpIX concentration correlates with vascular changes including vasoconstriction and/or vascular leakage of small vessels and arterioles in the mouse epidermis and dermis. In this study we report on vascular responses induced by ALA-PDT for different fluence rates, including both changes in vessel diameter and dynamics in RBC velocity in arterioles, imaged using intra-vital confocal microscopy in skinfold chambers in hairless mice. Our interest is in the dynamics of vascular changes in the early stages of illumination. METHODS: We have determined the total PDT dose to be relatively low, 13 J cm(-2), and fluence rates of 26, 65 and 130 mW cm(-2) were investigated. Local vascular effects occurred very soon after the start of the therapeutic illumination in ALA-PDT. RESULTS: In this study, we did not find a significant difference between fluence rates. Arterioles were particularly sensitive to vasoconstriction during low dose PDT, often resulting in complete vasoconstriction. When we observed complete vasoconstriction, this coincided with changes in RBC velocity. CONCLUSION: Since the therapeutic effects of PDT are dependent on a fine balance between the need for oxygen during illumination and disruption of the vasculature, the results of the present study add to our understanding of acute vascular effects during ALA-PDT and aid our efforts to optimize PDT using porphyrin pre-cursors.

Topical hexylaminolevulinate and aminolevulinic acid photodynamic therapy: complete arteriole vasoconstriction occurs frequently and depends on protoporphyrin IX concentration in vessel wall.

Vascular responses to photodynamic therapy (PDT) may influence the availability of oxygen during PDT and the extent of tumor destruction after PDT. However, for topical PDT vascular effects are largely unknown. Arteriole and venule diameters were measured before and after hexylaminolevulinate (HAL) and aminolevulinic acid (ALA) PDT and related to the protoporphyrin IX (PpIX) concentration in the vessel wall. A mouse skin fold chamber model and an intravital confocal microscope allowed direct imaging of the subcutaneous vessels underlying the treated area. In both HAL and ALA groups over 60% of arterioles constricted completely, while venules generally did not respond, except for two larger veins that constricted partially. Arteriole vasoconstriction strongly correlated with PpIX fluorescence intensity in the arteriole wall. Total PpIX fluorescence intensity was significantly higher for HAL than ALA for the whole area that was imaged but not for the arteriole walls. In conclusion, complete arteriole vasoconstriction occurs frequently in both HAL and ALA based topical PDT, especially when relatively high PpIX concentrations in arteriole walls are reached. Vasoconstriction will likely influence PDT effect and should be considered in studies on topical HAL and ALA-PDT. Also, our results may redefine the vasculature as a potential secondary target for topical PDT.

Effects of chronic exposure to radiofrequency electromagnetic fields on energy balance in developing rats.

The effects of radiofrequency electromagnetic fields (RF-EMF) on the control of body energy balance in developing organisms have not been studied, despite the involvement of energy status in vital physiological functions. We examined the effects of chronic RF-EMF exposure (900 MHz, 1 V m(-1)) on the main functions involved in body energy homeostasis (feeding behaviour, sleep and thermoregulatory processes). Thirteen juvenile male Wistar rats were exposed to continuous RF-EMF for 5 weeks at 24 °C of air temperature (T a) and compared with 11 non-exposed animals. Hence, at the beginning of the 6th week of exposure, the functions were recorded at T a of 24 °C and then at 31 °C. We showed that the frequency of rapid eye movement sleep episodes was greater in the RF-EMF-exposed group, independently of T a (+42.1 % at 24 °C and +31.6 % at 31 °C). The other effects of RF-EMF exposure on several sleep parameters were dependent on T a. At 31 °C, RF-EMF-exposed animals had a significantly lower subcutaneous tail temperature (-1.21 °C) than controls at all sleep stages; this suggested peripheral vasoconstriction, which was confirmed in an experiment with the vasodilatator prazosin. Exposure to RF-EMF also increased daytime food intake (+0.22 g h(-1)). Most of the observed effects of RF-EMF exposure were dependent on T a. Exposure to RF-EMF appears to modify the functioning of vasomotor tone by acting peripherally through α-adrenoceptors. The elicited vasoconstriction may restrict body cooling, whereas energy intake increases. Our results show that RF-EMF exposure can induce energy-saving processes without strongly disturbing the overall sleep pattern.

Low-level-laser irradiation induces photorelaxation in coronary arteries and overcomes vasospasm of internal thoracic arteries.

BACKGROUND AND OBJECTIVE: As low-level laser irradiation (LLLI) seems to induce vasodilation besides many other known biological effects, LLLI has been increasingly used in therapy of medical conditions with various irradiation parameters. The aim of this study was to investigate the effect of LLLI on photorelaxation of human coronary and internal thoracic arteries (ITA). MATERIALS AND METHODS: Thirty vessel segments of ITA used for routine coronary artery bypass grafting as well as left anterior descending coronary arteries (LAD) of patients undergoing cardiac transplantation were cut into 4-mm rings stored in a modified Krebs-Henseleit solution and evaluated in a myograph. Both types of vessel segments were irradiated by a semiconductor non-thermal GaAs diode laser operating at a wavelength of 680 nm. After precontraction with thromboxane agonist U44619, respective relaxation responses were evaluated and compared to pharmacological dilatation induced by substance P. RESULTS: Mean pharmacological vasodilation by substance P was 22.6 ± 3.3%, 12.8 ± 1.4%, and 20.4 ± 3.2% in macroscopic healthy LAD, LAD with atheromatous plaque, and ITA, respectively. Average photorelaxation induced by LLLI was 16.5 ± 2.0%, 1.9 ± 1.7%, and 6.8 ± 4.7%, accordingly. Vasodilatatory responses induced either by substance P or administration of LLLI were significantly decreased in LAD with atheromatous plaque (P < 0.0001). Vasospasms of ITA segments occurring during experiments could be abandoned when LLLI was administered. CONCLUSION: Macroscopic healthy LAD exposed to LLLI revealed significant photorelaxation. With the administration of LLLI, 73% of the maximal obtainable effect by an endothelium-dependent vasodilator could be reached. Furthermore, LLLI has the potential to overcome vasospasms of ITA.

Thermally-mediated ultrasound-induced contraction of equine muscular arteries in vitro and an investigation of the associated cellular mechanisms.

We have previously shown that MHz frequency ultrasound causes contraction of the carotid artery in vitro. We now extend this investigation to equine mesenteric arteries and investigate the cellular mechanisms. In vitro exposure of the large lateral cecal mesenteric artery to 4-min periods of 3.2 MHz continuous wave ultrasound at acoustic powers up to 145 mW induced reversible repeatable contraction. The magnitude of the response was linearly dependent on acoustic power and, at 145 mW, the mean increase in wall stress was 0.020 ± 0.017 mN/mm(2) (n = 34). These results are consistent with our previous study and the effect was hypothesised to be thermally mediated. A 2°C temperature rise produced an increase in intracellular calcium, measured by Fluo-4 fluorescence. Inhibition of the inward-rectifier potassium ion channel with BaCl(2) (4 µM) increased the response to ultrasound by 55% ± 49%, indicating a similar electrophysiologic basis to the response to mild hyperthermia. In small mesenteric arteries (0.5-1.0 mm diameter) mounted in a perfusion myograph, neither ultrasound exposure nor heating produced measureable vasoconstriction or a rise in intracellular calcium and we conclude that temperature-sensitive channels are absent or inactive in these small vessels. It, therefore, appears that response of blood vessels to ultrasound depends not only on the thermal properties of the vessels and surrounding tissues but also on the electrophysiology of the smooth muscle cells.

[Molecular-cellular mechanisms of light radiation and weak magnetic fields on the blood status and microcirculation system (at therapeutic doses) with using modern magnetolaser equipment (review of the literature)].

This review covers the molecular-cellular mechanisms of therapeutic action of light and magnetic field on blood components, blood vessels and the microcirculation system. Noted the role of the magnetic field as a trigger of vasodilation/vasoconstriction, depending on the initial vascular tone. Discussed the importance of NO-dependent effects of magnetic field on the microcirculatory response and angiogenesis.

Effect of laser irradiation on adrenoreactivity of pial arterial vessels in rats.

Experiments on WKY and SHR rats showed that low-intensity laser irradiation reduced the tone of pial arterial vessels thereby potentiating the subsequent constrictor effect of norepinephrine. Irradiation in the red region of the spectrum produced a more pronounced effect in the blue region. The observed effects were less pronounced in SHR rats compared to normotensive WKY rats.

Concomitant trastuzumab with thoracic radiotherapy: a morphological and functional study.

BACKGROUND: The purpose of this study is to elucidate if there is an additive or supra-additive toxic effects of radiotherapy (RT) and trastuzumab (T) on vascular structures when used concomitantly. METHODS: Female Wistar albino rats were treated with either 8 or 15 Gy of thoracic RT. T was applied i.p. with a dose of 6 mg/kg 2 h before RT. Four rats in each arm were killed at 6th h, 21st and 70th days after irradiation and thoracic aorta of each animal was dissected for electron microscopy. In addition, functional studies for evaluating the relaxation and contraction were carried out 21 days after RT. RESULTS: Only 15-Gy RT dose groups showed significant difference in terms of functional deterioration as more contraction than the others (P < 0.05) without any difference between RT and RT + T. However, T produced additional deficit in relaxation when added to RT, which was considered near significant (P: 0.0502). Electron microscopy showed endothelial and subendotelial damage signs in 15-Gy dose groups. T + 15-Gy arm showed more pronounced endothelial cell damage than 15-Gy RT-only arm, 70 days after RT. CONCLUSION: T and high-dose RT may lead to vascular damage that seems at least additive.

Dynamic retinal vessel response to flicker in age-related macular degeneration patients before and after vascular endothelial growth factor inhibitor injection.

PURPOSE: Retinal vessel responses to flickering light are different in various systemic and ocular diseases and can be improved after successful therapy. We investigated retinal vessel response to flickering light in age-related macular degeneration (AMD) patients before and after treatment with a single intravitreal bevacizumab (Avastin(®) ) injection. METHODS: In 10 patients with exudative AMD [age: median (1.quartile; 3.quartile) 76.0 (73.5; 80.0) years], retinal vessel reactions were examined by Dynamic Vessel Analyser (DVA) before and 3 months after a single intravitreal application of bevacizumab (1.25 mg). A baseline measurement was followed by three consecutive monochromatic flicker stimulations (530-600 nm, 12.5 Hz, 20 seconds). Temporal retinal vessel reaction was analysed and compared with the reaction in healthy controls. RESULTS: Mean arterial dilation at the end of flicker was not different in all groups. For veins this parameter amounted to: pre-treatment, 2.6 (1.7; 3.9)%; post-treatment, 2.9 (2.4; 4.0)%; control, 4.3 (3.2; 5.7)%; significant: pre-treatment - control (Dunnett's procedure, p < 0.05). Maximal dilation occurred in arteries at: pre-treatment, 17.5 (14.8; 32.5) seconds; post-treatment, 18.0 (16.6; 30.6) seconds; control, 14.5 (10.8; 17.3) seconds. Both AMD groups were slower (p < 0.05): in veins at 17.0 (14.5; 20.0) seconds, 12.8 (8.6; 14.8) seconds and 18.5 (17.1; 19.9) seconds, respectively; significant post-treatment - control (p < 0.05). In the post-treatment AMD group arterial constriction after stimulation occurred more slowly compared with the control group (p < 0.05). CONCLUSION: Dynamic retinal arterial and venous reactions to flickering light are altered in AMD compared with controls. Three months after a single injection of a vascular endothelial growth factor inhibitor, the investigated retinal dynamic vascular parameters were not altered in our study.

Permanent occlusion of feeding arteries and draining veins in solid mouse tumors by vascular targeted photodynamic therapy (VTP) with Tookad.

BACKGROUND: Antiangiogenic and anti-vascular therapies present intriguing alternatives to cancer therapy. However, despite promising preclinical results and significant delays in tumor progression, none have demonstrated long-term curative features to date. Here, we show that a single treatment session of Tookad-based vascular targeted photodynamic therapy (VTP) promotes permanent arrest of tumor blood supply by rapid occlusion of the tumor feeding arteries (FA) and draining veins (DV), leading to tumor necrosis and eradication within 24-48 h. METHODOLOGY/PRINCIPAL FINDINGS: A mouse earlobe MADB106 tumor model was subjected to Tookad-VTP and monitored by three complementary, non-invasive online imaging techniques: Fluorescent intravital microscopy, Dynamic Light Scattering Imaging and photosensitized MRI. Tookad-VTP led to prompt tumor FA vasodilatation (a mean volume increase of 70%) with a transient increase (60%) in blood-flow rate. Rapid vasoconstriction, simultaneous blood clotting, vessel permeabilization and a sharp decline in the flow rates then followed, culminating in FA occlusion at 63.2 sec+/-1.5SEM. This blockage was deemed irreversible after 10 minutes of VTP treatment. A decrease in DV blood flow was demonstrated, with a slight lag from FA response, accompanied by frequent changes in flow direction before reaching a complete standstill. In contrast, neighboring, healthy tissue vessels of similar sizes remained intact and functional after Tookad-VTP. CONCLUSION/SIGNIFICANCE: Tookad-VTP selectively targets the tumor feeding and draining vessels. To the best of our knowledge, this is the first mono-therapeutic modality that primarily aims at the larger tumor vessels and leads to high cure rates, both in the preclinical and clinical arenas.

Renin-Angiotensin system suppression mitigates experimental radiation pneumonitis.

PURPOSE: To find the mitigators of pneumonitis induced by moderate doses of thoracic radiation (10-15 Gy). METHODS AND MATERIALS: Unanesthetized WAG/RijCmcr female rats received a single dose of X-irradiation (10, 12, or 15 Gy at 1.615 Gy/min) to the thorax. Captopril (an angiotensin-converting enzyme inhibitor) or losartan (an angiotensin receptor blocker) was administered in the drinking water after irradiation. Pulmonary structure and function were assessed after 8 weeks in randomly selected rats by evaluating the breathing rate, ex vivo vascular reactivity, and histopathologic findings. Survival analysis was undertaken on all animals, except those scheduled for death. RESULTS: Survival after a dose of 10 Gy to the thorax was not different from that of unirradiated rats for

Pulsed electrical stimulation for control of vasculature: temporary vasoconstriction and permanent thrombosis.

A variety of medical procedures is aimed to selectively compromise or destroy vascular function. Such procedures include cancer therapies, treatments of cutaneous vascular disorders, and temporary hemostasis during surgery. Currently, technologies such as lasers, cryosurgery and radio frequency coagulation, produce significant collateral damage due to the thermal nature of these interactions and corresponding heat exchange with surrounding tissues. We describe a non-thermal method of inducing temporary vasoconstriction and permanent thrombosis using short pulse (microseconds) electrical stimulation. The current density required for vasoconstriction increases with decreasing pulse duration approximately as t(-0.25). The threshold of electroporation has a steeper dependence on pulse duration-exceeding t(-0.5). At pulse durations shorter than 5 micros, damage threshold exceeds the vasoconstriction threshold, thus allowing for temporary hemostasis without direct damage to surrounding tissue. With a pulse repetition rate of 0.1 Hz, vasoconstriction is achieved approximately 1 min after the beginning of treatment in both arteries and veins. Thrombosis occurs at higher electric fields, and its threshold increases with vessel diameter. Histology demonstrated a lack of tissue damage during vasoconstriction, but vascular endothelium was damaged during thrombosis. The temperature increase does not exceed 0.1 degrees C during these treatments.

In vivo assessment of pigmentary and vascular compartments changes in UVA exposed skin by reflectance-mode confocal microscopy.

Exposure of the skin to ultraviolet A (UVA) results in various biological responses, skin-colour changes being among the major ones. Although intense research has been performed on UVA-induced pigmentation and vascular changes, the process of skin-colour changes after UVA irradiation remains unclear. For a better understanding of the UVA tanning mechanism, we here performed a human study in 27 healthy volunteers with skin phototype (SPT) II to VI. After a single UVA exposure to inner forearm, the skin sites were imaged using reflectance-mode confocal microscopy (RCM), for analysis of melanin and vascular changes. Punch biopsies were also taken from the UVA-exposed or non-exposed sites for histological examination. Skin sections were stained with Fontana-Masson and evaluated by a sensitive tyrosinase assay for comparison with RCM images. Furthermore, the effect of blood flow on skin-colour changes was evaluated visually after administration of an intradermal anesthesia of lidocaine with or without epinephrine. Our RCM analysis showed dendritic melanocytes and a different melanin distribution in the epidermal layer, clearly visible 1 week after the UVA exposure in subjects of SPT V which were supported by histological examination. However, no melanin distribution pattern changes were apparent immediately after the exposure, while RCM images showed accelerated capillary flow patterns. The restriction of this UVA induced-accelerated blood flow by epinephrine inhibited partially or completely the immediate pigment darkening and delayed tanning. These in vivo studies confirmed that vascular change is an important factor for the development of the immediate pigment darkening and delayed tanning.

Development of photolabile caged analogs of endothelin-1.

Photoactivable caged analogs of endothelin-1 (ET-1) were obtained after derivatization with the photolabile 4,5-dimethoxynitrobenzyl (DMNB) group. This was achieved by the incorporation of N-alpha-Fmoc caged building blocks of Lys, Asp, Glu and Tyr during the solid phase peptide synthesis step. The C-terminal carboxylic function was also derivatized. However, difficulties were encountered with the introduction of the Asp and Glu photoactivable building blocks. As a matter of fact, formation of an aminosuccinyl derivative, through cyclization of the Asp(ODMNB) residue, and the formation of a pyrrolidone ring from the Glu(ODMNB) residue were highly favored by the electronic properties of the photocleavable function. ET-1 analogs were also tested in the ET(A) and ET(B) paradigms and specific pharmacological profiles were obtained for each peptide.