Intramolecular sensitization of americium luminescence in solution: shining light on short-lived forbidden 5f transitions.

The photophysical properties and solution thermodynamics of water soluble trivalent americium (Am(III)) complexes formed with multidentate chromophore-bearing ligands, 3,4,3-LI(1,2-HOPO), Enterobactin, and 5-LIO(Me-3,2-HOPO), were investigated. The three chelators were shown to act as antenna chromophores for Am(III), generating sensitized luminescence emission from the metal upon complexation, with very short lifetimes ranging from 33 to 42 ns and low luminescence quantum yields (10(-3) to 10(-2)%), characteristic of Near Infra-Red emitters in similar systems. The specific emission peak of Am(III) assigned to the (5)D1 → (7)F1 f-f transition was exploited to characterize the high proton-independent stability of the complex formed with the most efficient sensitizer 3,4,3-LI(1,2-HOPO), with a log ß110 = 20.4 ± 0.2 value. In addition, the optical and solution thermodynamic features of these Am(III) complexes, combined with density functional theory calculations, were used to probe the influence of electronic structure on coordination properties across the f-element series and to gain insight into ligand field effects.

Aging hands: a technique of hand rejuvenation by laser resurfacing and autologous fat transfer.

Hands are a primary target for actinic damage and premature aging. Until recently, very little could be done to successfully erase the various signs of photoaging. This article presents a simple technique, combining fat transfer and laser resurfacing, to safely and effectively rejuvenate hands and erase the signs of aging.

Laser abrasion for cosmetic and medical treatment of facial actinic damage.

Previous studies have shown the carbon dioxide (CO2) laser to be effective in the treatment of actinic cheilitis. After CO2 laser abrasion, normal skin and marked cosmetic improvement of the lip were noted. In our study, twenty-three patients were treated with CO2 laser abrasions for cosmetic improvement of facial lines and actinic changes. Pre- and postoperative histopathologic examinations were made on two patients. Preoperative examination of specimens from actinically damaged skin showed atypical keratinocytes in the basal layer of the epidermis, with overlying dense compact orthokeratosis and parakeratosis. Abundant solar elastosis was seen in the papillary dermis. Postoperative histologic specimens showed a normal-appearing epidermis with fibrosis in the papillary dermis and minimal solar elastosis (about four weeks after laser treatment). At present, various modalities are available for the regeneration of the aged skin, including chemical peels and dermabrasion. Significantly fewer complications were noted with CO2 laser abrasion than with these methods. Thus, CO2 laser abrasion can be useful in the cosmetic and medical treatment of the aged skin. Marked clinical and histologic improvement has been demonstrated.

Carbon dioxide laser blepharoplasty: conjunctival temperature during surgery.

Eight patients underwent carbon dioxide (CO2) laser blepharoplasty. The temperature of the upper eyelid conjunctiva was monitored and recorded during laser surgery. A minimal increase in temperature was noted. This study confirms the absence of thermal injury at a distal site from the laser application and the safety of the laser procedure.

Ultrastructural characteristics of keloid fibroblasts.

Myofibroblasts abound in granulation tissue, where they play an important role in the healing process. We evaluated the characteristics of fibroblasts in ten patients with keloids, a disorder of skin wound repair. Keloid lesions uniformly exhibited numerous fibroblasts with prominent Golgi complexes and abundant rough endoplasmic reticulum. Although rare fibroblasts exhibited a convoluted nucleus and tangled microfilaments, none could be characterized as myofibroblast, as defined by cytoplasmic myofilaments and cell to cell junctions. We conclude that fibroblast density and activity are increased in keloids, but true myofibroblasts are not a component of these lesions.

Regulation of collagen gene expression in cutaneous diseases with dermal fibrosis: evidence for pretranslational control.

Dermal fibrosis, characterized by collagen accumulation, is the hallmark of several cutaneous diseases. To examine the mechanisms of collagen deposition in fibrotic skin diseases, fibroblast cultures were established from the skin of patients with progressive systemic sclerosis, morphea, scleredema, familial cutaneous collagenoma, connective tissue nevi of the collagen type, or keloids; these patients served as prototypes of fibrotic skin diseases with varying clinical features and potentially different etiologic factors. Collagen production was assayed by the synthesis of [3H]hydroxyproline, and types I and III procollagen messenger RNA (mRNA) levels were determined by dot blot hybridizations using human type I and type III procollagen-specific cDNA probes. The collagen production in fibroblast cultures from the fibrotic diseases was increased up to 6-fold over the controls, and a relatively good correlation between the collagen production and type I collagen mRNA levels was noted. The type I/III procollagen mRNA ratio in control fibroblast cultures was 5.9 +/- 1.6 (mean +/- SD). The corresponding ratio in keloid cell culture was markedly increased, while slightly decreased values were noted in the case of morphea and familial cutaneous collagenoma; the values in other cultures were within the normal range. The results suggest that procollagen production in fibroblast cultures derived from fibrotic skin diseases reflects elevated levels of the corresponding procollagen mRNA. The increased mRNA abundance, suggesting pretranslational control, may result from enhanced transcriptional activity of the corresponding gene or alternatively reflects increased stability of the mRNA molecule.

Preliminary report: a new technique of enterotomy closure using Nd:YAG laser welding compared to suture repair.

This study compared the histology and tensile strength of Nd:YAG laser welded and sutured small bowel enterotomies in Sprague-Dawley rats. Enterotomies (0.5 cm long) were either welded with the Nd:YAG laser (1 W and 10.6 sec pulses) or repaired with interrupted, simple 6-O silk sutures. Group I consisted of seven animals; five with enterotomies repaired by laser welding and two repaired by suturing. Group II consisted of eight animals with each having both laser and suture repairs. Animals were killed and specimens were removed and examined at 1 day, and at 1, 2, and 3 weeks postoperatively to compare the progression of healing. On macroscopic examination the laser welded enterotomies were closed 84% of the time and only 23% had adhesion formation while 90% of sutured repairs were closed and 100% had adhesion formation. Histologic examination of both suture and laser welded enterotomies demonstrated active healing at 1 week with minimal collagen bridging the enterotomies. At 2 and 3 weeks the sutured enterotomies had granulomatous reaction around the sutures while the laser welded enterotomies had minimal inflammatory response and near normal small bowel histology. The tensile strength of the 3-week specimens from both the suture and laser welded enterotomies were 50% of normal bowel. These findings suggest that the laser welding of small bowel enterotomies is comparable in closure and tensile strength to suture repair. The time required to repair the enterotomy is significantly decreased, the procedure is easily performed, and there is a marked decrease in adhesion formation following laser repair.

Biostimulation of wound healing by lasers: experimental approaches in animal models and in fibroblast cultures.

Recent evidence suggests that low-energy lasers, such as an He-Ne laser, might stimulate wound healing. In this review we are summarizing our recent observations indicating that low-energy lasers enhance collagen gene expression both in skin fibroblast cultures in vitro, as well as in animal models of wound healing in vivo.

Biostimulation of wound healing in vivo by a helium-neon laser.

Clinical observations have suggested that low-energy lasers might stimulate wound healing. To understand the mechanism of the biostimulation, we previously examined the effects of low-energy lasers on collagen production by human skin fibroblasts and reported an increase of collagen synthesis in vitro. To examine the effects of low-energy lasers in vivo, hairless mice were experimentally wounded, sutured, and subjected to laser irradiation by a helium-neon laser with a power output of 1.56 mW and an energy fluence of 1.22 Joules/cm2. Experimental wounds were subjected to laser treatment every other day for 2 months; control wounds remained untreated. Specimens from the wounds were then examined for histological findings, tensile strength, and total collagen content. Results demonstrated a considerable improvement in the tensile strength of the laser-irradiated wounds at 1 and 2 weeks. Furthermore, the total collagen content was significantly increased at 2 months when compared with control wounds. These results suggest a beneficial effect of the helium-neon laser on wound healing in vivo.

Laser modulation of human immune system: inhibition of lymphocyte proliferation by a gallium-arsenide laser at low energy.

Cultured human lymphocytes were subjected to irradiation with a gallium-arsenide laser at energy fluence varying from 2.17 to 651 mJ/cm2, and the cell proliferation was assessed by [3H]thymidine incorporation. Both mitogenic proliferation in response to phytohemagglutinin and spontaneous cell proliferation were markedly inhibited by the laser irradiation at energy fluence as low as 10.85 mJ/cm2. Similarly, the functional response of cells to antigen stimulation in a one-way mixed-lymphocyte reaction was also diminished as a result of laser irradiation. The results indicate that laser irradiation at low energy can interfere with immune system in vitro, and similar modulation could potentially occur in human subjects exposed to laser irradiation in vivo.

Large vessel sealing with the argon laser.

This study compared the histology, biochemistry, and tensile strength of laser-welded and sutured canine venotomies, arteriotomies, and arteriovenous fistulas. Twelve animals had bilateral femoral vessels studied, with one repair (control) closed with interrupted 6-0 polypropylene sutures, and the contralateral repair (experimental) welded with the argon laser. Specimens were examined at weekly intervals from 1 to 4 weeks (four animals for each type of repair), and were evaluated histologically by hematoxylin and eosin, elastin, and trichrome stains; biochemically by the formation of [3H]hydroxyproline as an index of collagen synthesis; and mechanically by tensile strength determinations. At removal, all experimental closures were patent without hematomas, aneurysms, or luminal dilatation. Histologic and biochemical examination and tensile strength determinations suggest that laser welding may be an alternative to sutures for repair of large-diameter venotomies, arteriotomies, and arteriovenous fistulas, as healing is comparable to that seen with suture repairs up to 4 weeks postoperatively.

Use of lasers for closure of cutaneous wounds: experience with Nd:YAG, argon and CO2 lasers.

The concept of tissue fusion by laser has been recently established. In this study, we have examined the skin welding by laser and tested the efficacy of four different lasers for this application. The results attest to the feasibility of the procedure and suggest that laser welding may represent an alternative for closure of cutaneous wounds.

Comparison of laser-welded and sutured arteriotomies.

We compared the histologic features, tensile strength, and collagen synthesis of laser-welded and sutured arteriotomies. Four bilateral canine femoral or carotid arteries, 2 cm long, were studied at one through four weeks postoperatively, with one vessel (control) closed with interrupted 6-0 polypropylene sutures and the contralateral vessel (experimental) welded with an argon laser (0.5 W [1417 J/cm2], four-minute exposure per 1-cm length of incision). Histologic examination revealed that laser-welded arteriotomies had less inflammatory reaction, more normal collagen and elastin reorientation, and similar endothelial continuity when compared with the control, sutured wounds. The tensile strength of the one- and two-week laser-welded specimens was less than that of sutured wounds and became approximately equal to sutured repairs at three and four weeks. There were no significant differences in the rate of collagen synthesis. There was no evidence of abnormal healing in the laser-welded specimens, suggesting that argon laser welding may be an alternative to suture repair of arteriotomies.

Laser welding: an alternative method of venous repair.

This study compared the histology, biochemistry, tensile strength, and extensibility of Nd:YAG laser-welded and sutured venotomies. Two-centimeter-length bilateral canine femoral or jugular venotomies were evaluated with one vessel (control) closed with interrupted 6-0 polypropylene sutures, and the contralateral vessel (experimental) welded with the Nd:YAG laser (1 W power and 30- to 40-sec exposure). Specimens were removed and examined immediately after fashioning (t0) and at 1, 4, or 5 weeks post-operatively to compare the progression of healing. Histologic examination of the 4- and 5-week sutured wounds had granulomatous reaction around the sutures with areas of excessive collagen accumulation. In contrast, the laser-welded wounds had minimal inflammatory response, near normal collagen content, and minimal residual disorientation and break in the elastic fiber continuity. The rate of collagen synthesis in laser-welded wounds was approximately twice that of sutured wounds at 1, 4, and 5 weeks, and correlated with increased tensile strengths of lasered wounds. The extensibility of the 5-week specimens was 0.19 for sutured and 0.29 for laser-welded wounds as compared to 0.29 for normal vein. These preliminary data suggest that laser welding of venotomies may have several advantages over conventional suture techniques.

Laser welding of venotomies.

We investigated the histologic and biochemical effects of carbon dioxide and neodymium (Nd)-YAG laser welding on the healing of venotomies. Ten canine femoral venotomies 2 cm in length were approximated and welded with 10 600-nm wavelength, 1-W power over 20 to 25 s for CO2 laser, and 1060-nm wavelength, 1-W power over 30 to 40 s for Nd-YAG laser. On removal at one to three weeks, all veins (4/4 welded by CO2 and 6/6 by Nd-YAG) were patent without hematomas. Histologic and biochemical analyses of the venous tissues demonstrated active healing at the venotomy sites. We conclude that the CO2 and Nd-YAG lasers can be used successfully to weld venotomies and may provide an alternative to conventional suture techniques for repair of vascular lesions.

Demonstration of elevated type I and type III procollagen mRNA levels in cutaneous wounds treated with helium-neon laser. Proposed mechanism for enhanced wound healing.

To assess laser modulation of wound healing, full-thickness cutaneous wounds were produced in the backs of pigs, and subjected to treatment with helium-neon laser. For comparison, some wounds were treated with non-laser energy source (a tungsten light) or left untreated as controls. Type I and type III procollagen mRNA levels were determined in the wounds by molecular hybridization with cDNA probes. The results indicated that type I and type III mRNA levels were markedly increased at days 17 and 28 of the healing in wounds treated with He-Ne laser, when compared to control or tungsten light-treated wounds. The results suggest that helium-neon laser stimulates wound healing by enhancing procollagen gene expression. These observations may have relevance to previous clinical studies suggesting that helium-neon laser stimulates wound healing.

Laser welding of large diameter arteries and veins.

Based on our preliminary studies and the results of this study, we conclude that argon laser welding of 4-8 mm internal diameter veins, arteries, and arteriovenous fistulas may have several potential advantages compared to conventional suture techniques. The benefits of laser repairs may include improved mechanical properties, and absence of the foreign body response related to sutures. Laser welding is sterile, nontactile and possibly time conserving, and the wounds heal rapidly without aneurysms or excess tissue proliferation.

Skin closure by Nd:YAG laser welding.

Skin incisions 6 mm in length were made on the backs of hairless mice. Control wounds were closed with interrupted 5-0 Prolene sutures, and experimental wounds were approximated and closed by laser welding using a Nd:YAG laser. The wounds were examined daily, and specimens were excised at weekly intervals for histopathologic study, transmission electron microscopy, tensile strength determination, and type I collagen-specific messenger ribonucleic acid measurements. The laser-welded wounds demonstrated rapid healing. Histologic study showed a functional scar tissue at day 7 and a minimal residue of the original wound at day 14. Tensile strength of the control and experimental wounds was similar at all time points. The levels of collagen-specific messenger ribonucleic acid were significantly higher in the sutured group in comparison with the laser group or with normal control skin. This study suggests that laser welding might have advantages over suturing, since the former is sterile and nontactile, does not require introduction of foreign material into the wound, and provides subjectively improved cosmetic results.

Biological effects of laser welding on vascular healing.

The feasibility of welding thin-walled microvessels by laser has been established. This report summarizes our experience using laser welding to repair thick-walled, high-pressure, 4 to 8-mm canine arteries using CO2, Nd:YAG, and argon lasers. The CO2 laser did not produce seals that could withstand arterial pressure. Nd:YAG laser welds were initially successful, but the majority failed within 20 to 40 minutes. The argon laser uniformly sealed 2-cm-length arteriotomies that healed rapidly within 4 to 6 weeks and had less foreign body response compared to sutured controls. Laser welding may represent an alternative for repair of small- and large-diameter vessels with several advantages compared to conventional suture techniques.