Photodynamic Inactivation of the Single Crayfish Nerve Cell: Dynamics of Electrophysiological Responses and Comparison of Photosensitisers

. The study of single neuron response to photodynamic effect provides a means for the study of the dynamics of cytotoxic events leading to cell death and allows comparison of the phototoxicity of different photosensitisers. Isolated crayfish stretch receptor neurons were photosensitised for 30 min, then irradiated with a He-Ne laser (632.8 nm; 0.3 W/cm²) until irreversible firing cessation. The dynamics of neuron firing frequency were continuously recorded throughout. The following photosensitisers were studied: methylene blue, janus green B, protoporphyrin IX, chlorins e ₆ and p ₆, haematoporphyrin derivative (Photoheme) and sulphonated aluminium phthalocyanine (Photosens). Nerve cells were found to be insensitive to either He-Ne laser irradiation or photosensitisation alone, but very vulnerable to the photodynamic effect: neurons changed firing rate and died at nanomolar concentrations of photosensitisers. The dynamics of neuron responses was found to depend on photosensitiser type and concentration. The current approach provides a means of evaluation of initial threshold cell membrane alteration and cytotoxic events leading to cell death. The dependence of firing acceleration rate and neuron lifetime on photosensitiser concentration additionally allowed comparison of efficiencies of different photosensitisers. Photosens, Photoheme and chlorin p ₆ were found to be the most potent photosensitisers: neurons responded to their photodynamic effects at concentrations as low as 1–5 nM. Paper received 23 February 1998; accepted following revision 7 December 1998.     

Hexose Transporter Expression and Function in Mouse Small Intestine: Role of Diurnal Rhythm

Background  Expression and function of hexose transporters vary diurnally in rat small intestine; however, this subject remains unexplored in mice. Aim  The aim of the study was to investigate the diurnal expression and function of hexose transporters SGLT1, GLUT2, and GLUT5 in mouse small bowel. Methods  Twenty-four c57bl6 mice maintained in a 12-h light/dark room (6 am–6 pm) were sacrificed at 9 am, 3 pm, 9 pm, and 3 am (n = 6 each). In duodenal, jejunal, and ileal mucosa, total cellular mRNA and protein levels were quantitated by real-time PCR and semiquantitative Western blotting, respectively. The everted sleeve technique measured transporter-mediated glucose uptake at 9 am and 9 pm. Results  mRNA expression of SGLT1, GLUT2, and GLUT5 varied diurnally in all three intestinal segments (p ≤ 0.03). SGLT1, GLUT2, and GLUT5 protein levels varied diurnally in duodenum and jejunum (p < 0.05) but not in ileum. Transporter-mediated glucose uptake was greater at 9 pm than 9 am (p ≤ 0.04) in all three segments. V _max was greater in duodenum (10 vs 6 nmol/cm/s) and jejunum (8 vs 5 nmol/cm/s) at 9 pm compared to 9 am (p = 0.01); K _m remained unchanged. Summary  mRNA levels of intestinal hexose transporters varied diurnally. Protein levels peaked 6–12 h later during dark cycle when >70% of food intake occurred; glucose transport followed a similar pattern with increased uptake at 9 pm. Conclusion  Hexose transporter expression and function vary diurnally with nocturnal feeding patterns of mice. Presented in part at Academic Surgical Congress in Phoenix, Arizona (Feb 7, 2007) and published in abstract form in Journal of Surgical Research (2007;137:255–256). This work was supported in part by the National Institutes of Health (Grant DK 39337-MGS).     

Diffusing Fibre Tip for the Minimally Invasive Treatment of Liver Tumours by Interstitial Laser Coagulation (ILC): An Experimental Ex Vivo Study

A newly developed diffusing laser applicator was examined for interstitial laser coagulation (ILC) of liver tumours. The applicator consisted of a matted quartz core and a quartz glass dome, also matted on its inner surface and sealed to the fibre. The applicator provided a homogeneous light intensity distribution over an active length of about 20 mm. Lesions were created in an ex-vivo porcine liver model using a Nd-YAG laser comparing the new diffusing tip with a Ringmode^?-ITT applicator in order to find optimal laser parameters and damage thresholds. The lesions were investigated using macroscopic size measurement, volume calculation and histological examination (H&E, NADPH-dehydrogenase). The damage threshold of the diffusing tip was 6 W at 14 min exposure time whereas the Ringmode^?-ITT applicator had its limit at 5 W and 12 min exposure. Comparing various exposure times showed that treatment over a time of more than 840 s did not significantly increase the lesion volume. At 5 W and 720 s the mean lesion volume was 6.9±1.1 cm³ with the diffusing tip and 6.3±0.6 cm³ with the Ringmode^?-ITT applicator, both having a slight ellipsoidal shape. Hence, the created lesions were not significantly different for both applicators when the same laser parameters were applied. On the other hand, the new diffusing tip had a higher damage threshold and was therefore capable of producing maximal coagulation volumes of up to 7.9±0.5 cm³ at 5 W and 20 min. The experiments showed that lesions with a dimension of 31×22 mm can be achieved with the diffusing applicator which seem suitably sized for treating small human liver metastases in a single laser session. Paper received 25 April 1997; accepted after revision 13 March 1998.     

Extravascular perivenous fibrin support leads to aneurysmal degeneration and intimal hyperplasia in arterialized vein grafts in the rat

Background and aims  External support of vein grafts by fibrin glue possibly prevents overdistension, vascular remodeling, and neointimal hyperplasia. Previous animal models of neointimal hyperplasia showed conflicting results. Here, long-term effects of external fibrin glue support were studied in a new rat model of jugular vein to abdominal aorta transposition. Materials and methods and methods  In male Wistar rats (250–300 g) right jugular vein (1.0–1.5 cm) was transposed to the infrarenal aorta. Fibrin glue (0.25 ml) covered the vein before releasing the vascular clamps (n = 6). Control vein grafts were exposed directly to blood pressure. After 16 weeks vein grafts were pressure-fixed for histology. Intima thickness, luminal and intimal area were measured by planimetry and elastic fibers demonstrated by Elastica van Giesson staining. Results  Intimal thickness (74.04 ± 6.7 μm vs 1245 ± 187 μm, control vs fibrin treatment; p < 0.001), intimal area (2517.16 ± 355 mm² vs 18424 ± 4927 mm², control vs fibrin treatment; p < 0.05) and luminal area (2184.75 ± 347 mm² vs 7231.85 ± 1782 mm², control vs fibrin treatment; p < 0.05) were significantly increased, elastic fibers in the vessel wall were diminished and the vessel wall infiltrated by mononuclear cells in fibrin glue supported veins. Conclusion  External support of vein grafts by fibrin glue leads to aneurysmal degeneration and intimal hyperplasia, thereby possibly jeopardizing long-term graft patency.     

Interstitial Laser Photocoagulation with Four Cylindrical Diffusing Fibre Tips: Importance of Mutual Fibre Distance

. Simultaneous application of multiple fibres could increase the volume of coagulation produced with interstitial laser photocoagulation (ILP) for solid tumours. To take full advantage of the presumed synergistic thermal effect between the fibres, the optimal combination of laser power and distance between the fibres was investigated. Four fibres with a cylindrical diffusing tip of 2 cm length were used, coupled to an optical beamsplitter for Nd:YAG light (four channels, maximal variation 9.5%, transmission >85%). The distance between the fibres was 1, 1.5, 2, 2.5 , 3 or 4 cm with a power output of either 4, 5, 6 or 7 W/fibre; energy per fibre was constant at 1800 J by adjusting exposure time. After laser application, dimensions of the coagulated lesions were measured. The optimal mutual fibre distance was 2 cm ( p<0.01) at all power levels. This resulted in lesions with a mean (SD) volume of 44.5 (2.1) cm³ and a largest diameter of 5.1 (0.4) cm at 7 W/fibre. Smaller distances between the fibres resulted in smaller lesions with central carbonisation, whereas larger distances resulted in four separate zones of coagulation. It was concluded that simultaneous application of four interstitial fibres may result in a considerable increase of volume of coagulation. Fibre position and mutual fibre distance determines whether synergism of the coagulative effect occurs. Paper received 14 July 1998; accepted following revision 18 January 1999     

Evaluation of carbon dioxide laser irradiation associated with calcium hydroxide in the treatment of dentinal hypersensitivity. A preliminary study

Attempts have been made to treat dentinal hypersensitivity by sealing exposed dentinal tubules, and the carbon dioxide (CO₂) laser has been shown to have a sealing effect on dentinal surfaces. The purpose of this study was to analyze the morphological ultra-structure and temperature change after CO₂ laser irradiation of dentin. Fourteen human third molars were selected and cleaned. An area was delimited, and the samples were randomly divided into seven groups: Group 1 (G1): control; G2, calcium hydroxide paste (CA) + CO₂ laser (L) (0.5 W/63,69 W/cm²); G3, CA + L (1 W/125,38 W/cm²); G4, CA + L (1.5 W/191,08 W/cm²); G5, L (0.5 W); G6, L (1 W); G7, L (1.5 W). All irradiation was performed in unfocused mode. The electron micrographs were analyzed by three observers. For temperature analysis, a thermocouple was used. Data were subjected to statistical analysis. The Kruskal–Wallis non-parametric test showed statistical differences between the groups (P < 0.05). For the two by two comparisons, all groups treated with calcium hydroxide paste presented significantly higher mean scores. In the groups treated by CO₂ laser only, fusion, re-crystallization, cracks and carbonization were observed. A change of 1 ± 5°C was noted in the temperature. Under the limitation of an in vitro study, and with the protocols used, we concluded that CO₂ laser is safe to use for the establishment of partial fusion and re-solidification of the dentinal surface.     

Impaired endothelium-dependent and neurogenic relaxation of corpus cavernosum from diabetic rats: improvement with L-arginine

This study describes the relaxant response to acetylcholine, electrical field stimulation and sodium nitroprusside after contraction by phenylephrine (10⁻⁵ M) in corpus cavernosum from control and diabetic rats. The response to acetylcholine (10⁻⁹–10⁻³ M) and electrical field stimulation (0.5–64 Hz) is decreased and can be restored by the addition of nitric oxide synthatase substrate, l-arginine(10⁻⁵ M). The response to sodium nitroprusside is not changed in diabetic rats compared to control rats. NADPH-diaphorase staining was enhanced in a diabetic preparation compared to control preparations. The findings suggest a role for the depletion of l-arginine in diabetes mellitus. The enhanced NADPH-diaphorase staining may be due to a deficiency of NOS substrate l-arginine in the endothelium and nerves of diabetic tissues. Received: 27 April 1999 / Accepted: 19 August 1999     

Laser-induced fluorescence: III. Quantitative analysis of atherosclerotic plaque content

Background and Objective: Laser-induced fluorescence (LF) spectroscopic analysis of the chemical composition of atherosclerotic plaque was examined. Study Design/Materials and Methods: The intima of 18 dog aortas was injected with chemical compounds found in atherosclerotic plaque. Spectra were recorded in air prior to and after injection of collagens I, III and IV, elastin, cholesterol, triglyceride, and β-nicotinamide adenine dinucleotide (NADH). Results: Significant changes in LF intensity were detected after injection of collagens I and III, cholesterol and elastin in thoracic aorta (P < 0.001), but not with triglyceride or NADH. Minor changes were detected in abdominal aorta. Multiple regression analysis of LF intensity ratios demonstrated a clear correlation with the quantity of injected collagens I (R² = 0.90–0.99) and III (R² = 0.84–1.0), cholesterol (R² = 0.72–0.76), and triglyceride (R² = 0.68–0.80) in both thoracic and abdominal aorta. The correlation between LF and atherosclerotic plaque composition was confirmed in a rooster model of atherosclerosis where multiple regression analysis predicted the measured aortic cholesterol (R² = 0.78) and triglyceride content (R² = 0.96). Conclusions: (1) Fluorescence spectra recorded from dog aorta were significantly altered by injection of collagens I and III, cholesterol, and elastin. (2) LF may allow quantitative assessment of plaque chemical content. © 1995 Wiley-Liss, Inc.     

Disinfection of the Optical Fibre of a Nd-YAP Laser Used in Dental Care

In order to set up a disinfection protocol, the tip of the optical fibre of an Nd-YAP laser, λ=1.34 μm, was contaminated in vitro with: Mycobacterium smegmatis (CIP 7326), Candida albicans (ATCC 2091), Bacillus stearothermophilus (ATCC 7953) or Streptococcus sanguis (ATCC 10556). It was then treated with various biocidal solutions, Septinol^? V, glutaraldehyde 2%, ethanol 95° and NaOCl 6%, using one of two protocols: 10 s of contact, or 5 s of contact followed by 5 s of wiping. The latter technique proved to be the most effective. Whatever the biocidal solution used, all the bacteria adhering to the fibre were eliminated. The protocol was checked in vivo in the canals of 10 teeth presenting root canal infections. No bacteria withstood the treatment with Septinol^? V. This treatment does not alter the qualities and performance of the fibre as far as light transmission is concerned. Paper received 8 February 1997; accepted after revision 17 March 1998.     

Evaluation of the Third Generation Photosensitiser SC102 in Two Animal Models

. SC102, a poly(ethylene glycol) (PEG-2000) derivative of the second generation photosensitiser temoporfin (Foscan), was evaluated for photodynamic activity utilising two standard animal models: the rabbit, inoculated with the cottontail rabbit papilloma virus (CRPV) and the healthy canine larynx. Optimal drug dose and drug–light interval (DLI) were determined in a series of pharmacokinetic experiments using SC102 administered intravenously at doses of 3 and 30 mg/kg in our standard CRPV rabbit model. Plasma pharmacokinetics in the rabbit showed an elimination half-life of 121±20 h. Peak tumour concentration occurred at 144 h for the 3 mg/kg group and at 240 h for the 30 mg/kg group. The disposition ratio of SC102 between tumour to healthy tissue, at peak tumour levels, was approximately 4 to 1 for both dose levels. Skin tolerance to increasing 652 nm wavelength fluences was excellent. Even in those rabbits given a 30 mg/kg SC102 dose, no significant damage to the skin was observed, even when a fluence of 160 J/cm² was applied at the optimal drug–light interval of 10 days. Tumour efficacy of SC102 PDT was evaluated in rabbits previously inoculated with CRPV. One time photoactivation of a single 30 mg/kg dose of SC102 at a DLI of 10 days using a fluence of 100 J/cm² achieved a complete tumour clearance rate of 35%. Two-time photoactivation on days 6 and 10 after single administration of the same dose in a separate group of rabbits, using a fluence of 75 J/cm² on both occasions, yielded an improved cure rate of 58%. Evaluation of normal tissue tolerance to SC102 PDT was also investigated in the healthy dog larynx model 10 days after an intravenous dose of 30 mg/kg SC102. A fluence of 200 J was determined to be the maximum tolerated dose at which time there was a 4:1 ratio of SC102 between laryngeal mucosa and muscle. The photophysical and pharmacokinetic profiles of SC102 show significant differences from those of Foscan from which it is derived. In these preliminary in vivo experiments we have demonstrated the outstanding tolerance of normal tissues to SC102 PDT using high fluences. We have also shown tumour efficacy with light doses readily achievable in the clinical setting. Disposition of SC102 in the skin is low and photosensitivity risk may disappear within the drug–light interval. Based on these conclusions we believe SC102 PDT may have potential utility as an adjunct to surgical resection of tumours necessitating wide field exposure of normal tissue to activating light. Paper received 15 January 1999; accepted after revision 6 October 1999.     

Effect of diode laser on enzymatic activity of parotid glands of diabetic rats

The aim of this study was to evaluate the effect of laser irradiation (LI) on enzymatic activities of amylase, catalase and peroxidase in the parotid glands (PG) of diabetic and non-diabetic rats. Ninety-six female rats were divided into eight groups: D0; D5; D10; D20 and C0; C5; C10; C20, respectively. Diabetes was induced by administration of streptozotocin and confirmed later by the glycemia results. Twenty-nine (29) days after the induction, the PGs of groups D5 and C5; D10 and C10; D20 and C20, were irradiated with 5 J/cm², 10 J/cm² and 20 J/cm² of laser diode (660 nm/100 mW) respectively. On the following day, the rats were euthanized and the enzymatic activity in the PGs was measured. Diabetic rats that had not been irradiated (group D0) showed higher catalase activity (P < 0.05) than those in group C0 (0.14 ± 0.02 U/mg protein and 0.10 ± 0.03 U/mg protein, respectively). However, laser irradiation of 5 J/cm² and 20 J/cm² decreased the catalase activity of the diabetic groups (D5 and D20) to non-diabetic values (P > 0.05). Based on the results of this study, LI decreased catalase activity in the PGs of diabetic rats.     

Intracellular Localisation of Hypericin in Human Glioblastoma and Carcinoma Cell Lines

Hypericin, a natural polycyclic quinone extracted from Hypericum perforatum, has been recently shown to be a powerful sensitiser for photodynamic therapy (PDT). However, its intracellular localisation remains unclear and contradictory. In the present work we compared the intracellular localisation of hypericin in three cultured cell lines (adenocarcinoma cells WiDr, carcinoma cells NHIK 3025 and glioblastoma cells D54Mg) with the distribution of fluorescent probes specific to lysosomes (LysoTracker Blue DND-22), mitochondria (MitoTracker Green FM) and endoplasmic reticulum (ERTracker Blue-White DPX). It was shown that the hypericin staining pattern was different compared to the intracellular distribution of mitochondria or lysosomes. Hypericin was concentrated in the perinucleolar cytoplasmic area mainly on one side of the nucleus – the region rich in endoplasmic reticulum and Golgi. Sometimes nuclear envelope was also stained. Plasma membrane was not stained but the dye was often accumulated in the intercellular space between the tightly contacting WiDr cells in colonies. Hypericin concentrations of 10 μM or less were not toxic for WiDr cells in the dark. Orange light (λ_max≈600 nm; 6 mW/cm²) killed the cells stained with 1 μM hypericin with LD₅₀∼ 1J/cm². Paper received 21 November 2000; accepted after revision 28 February 2001.     

Effects of Different Wavelengths of Low Level Laser Irradiation on Murine Immunological Activity and Intracellular Ca<Superscript>2+</Superscript> in Human Lymphocytes and Cultured Cortical Neurogliocytes

. The purpose of this study was to determine the wavelength-response effects of low level laser irradiation (LLLI) on immunocompetence of mice in vivo and intracellular free calcium ([Ca²⁺]_i) in human lymphocytes and cultured cortical neurogliocytes (CCN) in vitro. Mice were first immune compromised by cyclophosphamide (CTX) injection, and the immunological activities including the production of interleukin 2 (IL-2), the murine mixed lymphocyte reaction (MLR), the mitogenic response of murine thymocytes (MRT), the proliferation of murine bone marrow cells (BMC) and the natural killer (NK) cells activity, were investigated after intravascular low level laser irradiation (ILLLI) (1 mW, 1.1×10⁴ J/cm²) at wavelengths of 532 nm, 632.8 nm, 650 nm and 1520 nm, respectively. In addition, using Ca²⁺ sensitive indicator Fura-2 AM with the Spex AR-CM-MIC cation measurement system ([Ca²⁺]_i) in single human lymphocytes and CCN were measured after LLLI (7.5 J/cm²) at wavelengths of 532 nm, 632.8 nm, 650 nm, 810 nm and 1300 nm, respectively. Results showed that the ILLLI at wavelengths of 532 nm, 632.8 nm and 650 nm, produced a significant increase in the proliferation of BMC and the NK activity. The production of IL-2 was greatly promoted after irradiation at 632.8 nm and 650 nm. After irradiation at 532 nm and 650 nm, the murine MLR was evidently enhanced, and MRT was dramatically increased only after irradiation at 632.8 nm. In contrast, no significant effects were found on the above mentioned indexes by irradiation at 1520 nm in comparison to the control. In addition, [Ca²⁺]_i in single human lymphocytes and CCN were increased after LLLI at wavelengths of 532 nm, 632.8 nm and 650 nm, respectively, whereas they were not significantly affected by the wavelengths of 810 nm and 1300 nm. Our results indicated that LLLI could induce significant and different effects on the immunological activities of the mice and cause an increase in [Ca²⁺]_i in single human lymphocytes and CCN. Furthermore, these effects are dependent on the wavelengths, for example, more positive effects produced by the wavelengths of 532 nm, 632.8 nm and 652 nm than those produced by the wavelengths of 810 nm, 1300 nm and 1520 nm. Paper received 18 October 1999; accepted after revision 24 February 2000.     

Post-acute response of 9L gliosarcoma to Photofrin™-mediated PDT in athymic nude mice

The objective of this study is to measure the chronic responses of 9L glioma and normal brain to photodynamic therapy (PDT). Tumor size, proliferation activity of glioma cells, and vascular endothelial growth factor (VEGF) expression in both the tumor area and the brain adjacent to tumor (BAT) were observed 7 days after clinically relevant doses of PDT treatment. 9L Gliosarcoma cells were implanted into the brain of 20 athymic nude mice. Fifteen mice were injected intraperitoneally with Photofrin™ at a dose of 2 mg/kg on day 6 after tumor implantation and were treated with laser at different optical doses of 40 J/cm² (n = 5), 80 J/cm² (n = 5), and 120 J/cm² (n = 5) at 24 h after Photofrin injection, respectively. The remaining five tumor-bearing mice served as a tumor-only control. All animals were killed 14 days after tumor implantation. Hematoxylin and eosin and immunostaining were performed to assess tumor volume, VEGF expression in the tumor and the BAT, as well as Ki67 expression in the tumor area. The tumor volume of the mice receiving 80 or 120 J/cm² group was significantly smaller than the control group (p < 0.01). VEGF immunoreactivity in the BAT was significantly increased in the 120 J/cm² PDT-treated mice (p < 0.001), compared with the immunoreactivity seen in untreated mice and those receiving Photofrin and lower optical doses. No significant differences were detected in the proliferation of glioma cells and VEGF expression in the tumor area between these groups. These data indicate that PDT can shrink tumor, especially at the high light dose, and that PDT induces expression of VEGF in the BAT, which is associated with tumor recurrence. Therefore, PDT combined with anti-angiogenic agents may be an effective treatment strategy for glioma.     

Firing Inhibition Processes in the Response Dynamics of Isolated Crayfish Nerve Cell to the Photodynamic Effect of Sulphonated Aluminium Phthalocyanine: Participation of Free Radicals and Ca2+

. Chemical modifications allows the enhancement or attenuation of the cell response to photodynamic effect and provides information on the mechanisms of this effect. Isolated crayfish neurons were incubated for 30 min with 10⁻⁷ M Photosens (AlPcS _n ) and irradiated by He-Ne laser (632.8 nm, 0.3 W/cm²). Such treatment caused firing inhibition until it was irreversibly abolished. The antioxidants homocarnosine, DABCO or ascorbate, pro-oxidant, FeSO₄ or a mixture of FeSO₄ and ascorbate; Ca²⁺ modulators, CdCl₂, verapamil, EDTA, dantrolene, caffeine, theophylline, or a threefold CaCl₂ concentration were used to modify neuron response (firing inhibition and abolition). Homocarnosine, CdCl₂, DABCO, dantrolene, and caffeine or theophylline added 30–90 min before irradiation, increased neuron lifetime under the photodynamic effect of Photosens whereas FeSO₄/ascorbate, EDTA, threefold Ca²⁺ concentration or caffeine (added 5 min before irradiation) decreased neuron lifetime. It is concluded that, free radical processes and Ca²⁺ participate in the Photosens-induced photodynamic inhibition and subsequent irreversible abolition of neuron firing. Paper received 28 April 1999;accepted after revision 4 October 1999.     

Effect of Helium-Neon (He-Ne) Laser Irradiation on Dog Neoplasm Cells in Culture

The effects of laser light on the cellular proliferation have been extensively characterised. Low-power laser sources, such as the helium–neon (He-Ne) laser irradiation with a wavelength of 632.8 nm, have been found to produce photobiological and photodamaging effects with evidence of interference with cell proliferation functions. The present study has investigated the in vitro effect of He-Ne laser irradiation on the proliferative action of dog tumour cells in culture. Dose–response studies showed that repeated He-Ne irradiation (irradiance 12.8 mW/cm²) once a day for 4 consecutive days in a dose range between 0.13 and 2.08 J/cm² significantly increased with increasing energy density up to a laser dose of 0.26 J/cm², whereas at >1.04 J/cm², the cell proliferation decreased with increasing energy densities. It is concluded that the application of He-Ne laser irradiation at energy densities ranging from 0.13 J/cm² to 2.08 J/cm² produced different effects on cell proliferation in dog tumour cells in culture. Paper received for publication 27 June 1997; accepted following revision 6 February 1998.     

Laser Resistance of Endotracheal Tubes I: Experimental Results of a Compound Tube in Comparison to a Metallic Tube

Laser-induced ignition of endotracheal tubes is a serious problem in CO₂ laser surgery of the upper aerodigestive tract. A new tube built of composite materials with a foam at its surface is protected by vaporisation of water from the wet foam. This tube and a flexible metallic tube of stainless steel were tested experimentally against the radiation of various lasers such as CO₂, holmium/YAG, Nd/YAG, Nd/YAG frequency doubled in KD*P, argon and excimer. At laser power densities of 10³ W/cm², the shaft of the metallic tube was damaged within seconds whereas the compound tube was stable for more than 2 min; the damage threshold of the new tube was found to be at 3.2×10⁶ W/cm². While the compound tube was found to be sufficiently laser resistant, the metallic tube was found to exhibit functional damage, in particular the PVC inflation conduits inside of the tube were destroyed. Received for publication 13 June 1997; accepted following revision 16 February 1998     

Laser-Activated Solid Protein Solder for Nerve Repair: In Vitro Studies of Tensile Strength and Solder/Tissue Temperature

. Laser-activated solid protein solder strips have been developed for peripheral nerve repair. Indocyanine green dye added to the solder strongly absorbs diode wavelengths (∼800 nm) and causes localised heating and coagulation of the albumin protein solder. The protein strengthens the tissue join, particularly during the acute healing phase postoperative, while shielding the underlying axons from excessive thermal damage. In this investigation of the solid protein solder technique for nerve repair, the effect of laser irradiance on weld strength and solder and tissue temperature were studied. The tensile strength of repaired nerves rose steadily with increased irradiance reaching a maximum of 105±10 N/cm² at 12.7 W/cm². At higher irradiances, tensile strength fell. The maximum temperature reached at the solder surface and at the solder/nerve interface, measured using a non-contact fibre optic radiometer and thermocouple, respectively, also rose steadily with laser irradiance. At 12.7 W/cm², the temperatures reached at the surface and at the interface were 88±5°C and 71±4°C, respectively. This in vitro investigation demonstrates the feasibility of the laser-activated solid protein solder strips for peripheral nerve repair. The laser irradiance and the corresponding solder surface temperature for optimal tensile strength have been identified. Paper received 20 May 1998; accepted following revision 17 February 1999.     

Factors associated with hernia and bulge formation at the donor site of the pedicled TRAM flap

The purpose of this study was to evaluate the correlation between risk factors and hernia or bulge formation at the donor site of the transverse rectus abdominis myocutaneous (TRAM) flap. A retrospective study was conducted between September 2005 and December 2008 in 206 patients who underwent breast reconstruction with pedicled TRAM flap. Eight (3.9%) of these patients had abdominal wall hernia and 26 (12.6%) had abdominal bulging. The incidence of hernia was significantly higher (P < 0.05) among patients with body mass index (BMI) ≥ 30 kg/m² (hernia incidence, 15.0%) than that among patients with BMI <30 kg/m² (hernia incidence, 3.2%), while the incidence of abdominal bulge was significantly lower (P < 0.05) among patients with BMI ≥ 30 kg/m² (abdominal bulge incidence, 5.0%) than that among patients with BMI ≥ 30 kg/m² (abdominal bulge incidence, 19.1%). Therefore, obesity was identified as a risk factor for abdominal wall hernia. It was also found that the use of mesh to reinforce the abdominal wall significantly reduced (P < 0.025) the incidence of hernia (use of mesh (hernia incidence, 2.5%) versus non-mesh (hernia incidence, 5.9%)) and abdominal bulge (use of mesh (abdominal bulge incidence, 9.9%) versus non-mesh (abdominal bulge incidence, 17.3%)) among the patients.     

Effectiveness of various thermal ablation techniques for the treatment of nodular thyroid disease—comparison of laser-induced thermotherapy and bipolar radiofrequency ablation

Alternative minimally invasive treatment options such as radiofrequency ablation (RFA) or laser-induced thermotherapy (LITT) are at present under investigation for achieving a nonsurgical targeted cytoreduction in benign and malignant thyroid lesions. So far, studies have not been able to show a secure advantage for neither LITT nor RFA. The aim of this study was to compare the two ablation procedures in terms of their effectiveness. Thermal lesions were induced in porcine thyroid glands either by LITT or bipolar RFA ex vivo (n = 110 each) and in vivo (n = 10 each) using power settings between 10 and 20 W. Temperature spread during application was documented in 5- and 10-mm distance of the applicator. Postinterventional lesion diameters were measured and lesion size was calculated. Furthermore, enzyme histochemical analysis of the thyroid tissue was performed in vivo. Lesion volumes induced by LITT ranged between 0.74 ± 0.18 cm³ (10 W) and 3.80 ± 0.41 cm³ (20 W) with a maximum of 5.13 ± 0.16 cm³ at 18 W. The inducible lesion volumes by RFA were between 2.43 ± 0.68 cm³ (10 W) and 0.91 ± 0.71 cm³ (20 W) with a maximum of 2.80 ± 0.85 cm³ at 14 W. The maximum temperatures were 112.9 ± 9.2°C (LITT) and 61.6 ± 13.9°C (RFA) at a distance of 5 mm and 73.2 ± 6.7°C (LITT) and 53.5 ± 8.6°C (RFA) at a distance of 10 mm. The histochemical analysis demonstrates a complete loss of NADPH dehydrogenase activity in thermal lesions as a sign of irreversible cell damage both for LITT and RFA. This study is the first to compare the effectiveness of laser-induced thermotherapy and radiofrequency ablation of thyroid tissue. LITT as well as RFA are suitable for singular thyroid nodules and induces reproducible clinically relevant lesions in an appropriate application time. The maximum inducible lesion volumes by LITT are significantly larger than by RFA with the devices used herein.