The current study was designed to investigate the effect of pulsed laser irradiation upon conduction latency in the frog sciatic nerve (Rana temporaria) in vitro. Dissected nerves (n = 40) were mounted in an experimental trough at room temperature and irradiated using a GaAlAs laser diode (820 nm, 5 kHz, 70 mW) with 2.38 J or 3.57 J (total delivered energy). In both laser groups there was an increase in negative peak latency following laser irradiation (0.032 ± 0.01 ms with 2.38 J; 0.018 ± 0.01 ms with 3.57 J); this increase was significant with 2.38 J (p < 0.01, ANOVA). An additional study (n=10) showed a significant increase in temperature of the dissected nerve following irradiation with 3.57 J (maximum increase = 0.46 ± 0.13°C: p < 0.01, ANOVA) compared to control group temperature (maximum increase = 0.12 ± 0.03°C). The results of the current study have shown that laser mediated changes in nerve conduction latency are demonstrable in vitro; thus previously reported in vivo findings may be attributable, at least in part, to a direct neurophysiological effect.
A study on the stimulative and inhibitory effects of low incident power densities of argon laser energy on wound healing in rats was undertaken. Our results were calculated at 80% of wound closure relative to control showed acceleration in healing days and size reduction were 22.9% and 41.9%, respectively, at the maximum stimulative dose of approximately 19 J/cm2, and 8 J/cm2 and -8.7% -14.8% at the optimum inhibitory dose of approximately 130 J/cm2 for an elliptical (0.39 cm2) wound size with 3 times/week treatment schedule in 27 weeks old rats; doses of approximately 80 J/cm2 showed zero bioactivation. Statistical analysis with the student’s t-test revealed significant differences between irradiated and unirradiated control wounds with dose variations up to 60 J/cm2 and insignificant differences at higher doses. Wound acceleration was dose-dependent, increasing with the incident dose until it reached maximum, whereafter the stimulation effect disappeared and inhibition increased up to the maximum dose of around 130 J/cm2. Calculated skin reflection losses in the region of 70% required higher dosages to detect this phenomenon. There was no appreciable temperature rise up to doses of 150 J/cm2 for a power density of 80 mW/cm2. Reduced effectiveness of wound shape and size were also noted at the higher inhibitory doses.
Population I Leydig cells of the central part of the Albino rat testicle showed signs of increased but nonspecific activity in the entire series of experimental animals compared with sham irradiated controls (n = 30 in each group) after anterior pituitary stimulation with low incident energy levels of the HeNe laser at 632.8 nm with an incident power at the pituitary calculated as 2.75 ± 0.25 mW. The authors conclude that LLLT applied to the pituitary in the rat model at the parameters used in the present study may have an effect on testosterone production. Further quantitative and qualitative work is required to assess the significance of the increase in activity of type I Leydig cells and their morphological changes following LLLT applied transdurally to the pituitary gland.
With the report on promising therapeutic effects of nitrogen laser to treat tuberculous lung cavities, studies were carried out to examine the in vitro effects of the laser over a wide range of microbes, namely Candida albicans, Staph. aureus, Esch. coli, Proteus vulgaris, S. typhi and multidrug resistant Klebsiella aerogenes, Pseudomonas aeruginosa and Mycobacterium fortuitum. The nitorogen laser with tightly focused, partially focused and unfocused reflected beams with energy densities of 228 J/cm2, 17.1J/cm2 and 5.4 J/cm2, respectively were found to inhibit the growth of the above organisms lawned over solid nutrient media. This is the first report to document the wide spectrum inhibition of microorganisms exposed to nitrogen laser in vitro.
The efficacy of HeNe laser therapy for pain attenuation in patients with herpes zoster (HZ) was evaluated in 33 patients. (8 males, 25 females with an average age of 50 years). The HeNe laser was applied with a noncontact scanning technique for 10 to 15 min per session. If necessary, subsequent laser therapy with a GaAlAs diode laser was used. Pain scores (PS) were obtained and evaluated at one month after the onset of HZ rash and at the end of laser therapy. At one month assessment, the HeNe laser therapy resulted in no pain (PS: 0) in 9 patients and slight pain (PS: 1-4) in 16 patients. At the final evaiuation, there was no pain in 20 patients and slight pain in 12 patients. No side effect associated with this treatment were identified. Our results suggest that the HeNe laser therapy promotes wound healing and reduces HZ pain and possibly the incidence of postherpetic neuralgia.
Two bilateral 6.0 mm round skin defects were made on 60 DDY strain mice. The mice were divided into four groups and treated with low incident doses of laser energy at different wavelengths for 15 days: (a) Group I- Control; (b) Group II - 830 nm wavelength; (c) Group III - 680 nm wavelength; and (d) Group IV - 632.8 nm wavelength. For the treatment groups, only the right skin defect was irradiated. The rate of healing was assessed by examination through a monitor microscope, measurement of skin defect area and histological examination. No significant difference was observed between the four groups by macroscopic examination. The area of skin defect of the treated groups was significantly smaller than that of the control groups (p < 0.05) from the 1st-13th day after irradiation. For both irradiated and non-irradiated skin defects of treatment groups, Group III was smaller than Group II (p < 0.05) and Group IV was smaller than Group II (p < 0.05) Histological examination of the tissue skin defect showed greater proliferation of connective tissue and blood vessels in the dermis in treated groups than in control.