Evaluation of vitamin D plasma levels after mild exposure to the sun with photoprotection

Abstract: Background: Most of the organism's vitamin D (VD) is obtained through the cutaneous synthesis after exposure to the sun's UVB radiation. Sunscreens are indicated for the prevention of actinic damage to the skin, however, there are few clinical trials assessing the synthesis of cutaneous VD in real-life situations of sun exposure with ordinary clothing and usual photoprotection. Objectives: To evaluate the synthesis of VD with suberythemal sun exposure in healthy adults using topical photoprotection (SPF 30). Methods: Quasi-experimental study, conducted at Rio de Janeiro (Brazil), during winter, with 95 healthy adults who had 25-OH-VD checked twice, 24 hours apart, and were exposed to the sun (UVB=20 mJ/cm2), according to a randomized grouping: SC - use of SPF 30 on the face, neck and chest (n=64), NO - no sunscreens (n=10), CO - confined from sun exposure for 24h (n=21). The groups were matched according to the propensity score related to gender, age, phototype, body mass index, glycosylated hemoglobin and baseline levels of VD. The outcome evaluated was the variation (ΔVD) in serum level of 25-OH-VD (ng/ml) between the groups. Results: A statistically significant difference was identified between CO and SC groups [median (p25-p75)]: ΔVD =1.4 (-0.3-3.6) vs. 5.5 (4.8-6.6); p<0.01. There was no difference between SC and NO groups: 5.4 (3.1-6.1) vs. 4.1 (2.5-6.0); p=0.17. Study limitations: Laboratory analysis technique (chemiluminescence) with great variability, loss of food intake standardatization, unbalanced groups. Conclusions: Suberythemal sun exposure with sunscreen (SPF 30) provides similar vitamin D serum variation than without photoprotection in healthy adults.

Lesión cutánea por radiación en angioplastía coronaria compleja / Cutaneous radiation injury after failed percutaneous coronary angioplasty

Resumen: Las lesiones cutáneas por radiación (LCR) son una complicación infrecuente, con un estimado de 3.600 casos de lesiones mayores reportados en la actualidad. Presentamos un caso de lesión eritematosa mayor por radiación posterior a angioplastía coronaria fallida y en segundo tiempo angioplastía coronaria con rotablación.

Abstract: Cutaneous radiation injuries are an infrequent complication, with an estimated 3.600 cases of major injuries reported up to now. We present a case of a major erythematous lesion induced by radiation after failed coronary angioplasty and consecutive coronary rotablation.

Prevalence of dermatological complaints in patients undergoing treatment for breast cancer

Abstract: BACKGROUND: Internal malignancies such as breast cancer, as well as their treatment can often result in skin changes. OBJECTIVE: To assess the prevalence of dermatological complaints in patients who are undergoing oncological treatment for breast cancer in a hospital in Tubarão, Santa Catarina, Brazil. METHODS: Observational, cross-sectional study, from October 2015 to February 2016 in which 152 patients with the diagnosis of breast cancer, undergoing treatment with chemotherapy, radiotherapy, hormone therapy and/or surgery, were interviewed and completed a research protocol developed by the author. RESULTS: The treatment of breast cancer was associated with dermatological complaints in 94.1% of the interviewed, being with hair loss the most frequent, present in 79.6% of the sample, followed by nail changes (56%). Patients with lighter skin phototypes (I, II and III) had a lower risk (p=0.045) of developing skin changes when compared to darker phototypes. Radiation therapy (p=0.011) and oncological surgery (pFisher=0.004) were statistically significant when related to skin changes. STUDY LIMITATIONS: Inherent to the design of the study, as well as recall bias. CONCLUSIONS: It was found that most patients diagnosed with breast cancer showed dermatologic manifestations during the proposed cancer treatment. Patients undergoing radiotherapy and surgery showed skin changes with greater statistical significance.

Global and gene-specific DNA methylation and hydroxymethylation in human skin exposed and not exposed to sun radiation

Abstract: Background: epigenomes can be influenced by environmental factors leading to the development of diseases. Objective: To investigate the influence of sun exposure on global DNA methylation and hydroxymethylation status and at specific sites of the miR-9-1, miR-9-3 and MTHFR genes in skin samples of subjects with no history of skin diseases. Methods: Skin samples were obtained by punch on sun-exposed and sun-protected arm areas from 24 corpses of 16-89 years of age. Genomic DNA was extracted from skin samples that were ranked according to Fitzpatrick's criteria as light, moderate, and dark brown. Global DNA methylation and hydroxymethylation and DNA methylation analyses at specific sites were performed using ELISA and MSP, respectively. Results: No significant differences in global DNA methylation and hydroxymethylation levels were found among the skin areas, skin types, or age. However, gender-related differences were detected, where women showed higher methylation levels. Global DNA methylation levels were higher than hydroxymethylation levels, and the levels of these DNA modifications correlated in skin tissue. For specific sites, no differences among the areas were detected. Additional analyses showed no differences in the methylation status when age, gender, and skin type were considered; however, the methylation status of the miR-9-1 gene seems to be gender related. Study limitations: there was no separation of dermis and epidermis and low sample size. Conclusion: sun exposure does not induce changes in the DNA methylation and hydroxymethylation status or in miR-9-1, miR-9-3 and MTHFR genes for the studied skin types.

Photoprotective effect of verbascoside from Buddleja cordata in SKH-1 mice exposed to acute and chronic UV-B radiation / Efecto fotoprotector del verbascósido de Buddleja cordata en ratones SKH-1 expuestos de forma aguda y crónica a laradiación UV-B

Ultraviolet radiation (UVR) is involved in both sunburn and the development of skin cancer, which has a high incidence worldwide. Strategies to reduce these effects include the use of photoprotective substances. The aim of this work was to investigate the photoprotective effect of verbascoside isolated from the methanolic extract of Buddleja cordata (BCME) in SKH-1 mice exposed to acute and chronic UV-B radiation. The mouse dorsal area was evaluated macroscopically and microscopically for diagnosis; verbascoside penetration into mouse skin was investigated in vivo by the tape stripping method. After acute UV-B exposure, 100 percent of irradiated mice that had been protected with verbascoside showed no signs of sunburn or of inflammatory processes. After chronic exposure, 100 percent of unprotected mice showed skin carcinomas; in contrast, in mice topically treated with either BCME or verbascoside, the presence of lesions was decreased by 90 percent. These results prove that verbascoside penetrates through the skin of mice and suggest that verbascoside and BCME may potentially prevent photodamage on mice’s skin after acute and chronic UVR exposure.

La radiación ultravioleta (RUV) provoca quemaduras solares y el desarrollo de cáncer de piel. El objetivo de este trabajo fue investigar el efecto fotoprotector del verbascósido obtenido del extracto metanólico de Buddleja cordata (EMBC) en ratones SKH-1 expuestos a RUV-B de manera aguda y crónica. El diagnóstico histológico se llevó a cabo en la piel de la zona dorsal de los ratones. La penetración del verbascósido fue cuantificada mediante la técnica de la cinta adhesiva. En el experimento agudo, el 100 por ciento de los ratones protegidos con verbascósido no evidenciaron signos de quemadura ni procesos inflamatorios. En el experimento crónico los ratones sin protección e irradiados presentaron carcinomas cutáneos. En contraste en los ratones protegidos con EMBC o verbascósido las lesiones disminuyeron un 90 por ciento en ambos grupos. El verbascósido penetró en la piel del ratón. Los resultados sugieren que el EMBC y el verbascósido previenen el fotodaño en la piel de ratones expuestos de forma aguda o crónica a la RUV.

Lower energy and pulse stacking. A safer alternative for skin tightening using fractional CO2 laser

PURPOSE : To evaluate the effect of different energies and stacking in skin shrinkage. METHODS : Three decreasing settings of a fractional CO2 laser were applied to the abdomen of Twenty five Wistar rats divided into three groups. Group I (n=5) was histologically evaluated for microthermal zones dimensions. Groups II and III (n=10 each) were macroscopic evaluated with freeware ImageJ for area contraction immediately and after 30 and 60 days. RESULTS : No statistical significance was found within microthermal zone histological dimensions (Group I) in all settings studied. (Ablation depth: 76.90 to 97.18µm; Coagulation depth: 186.01 to 219.84 µm). In Group II, macroscopic evaluation showed that all settings cause significant immediate skin contraction. The highest setting cause significant more intense tightening effect initially, contracting skin area from 258.65 to 179.09 mm2. The same pattern was observed in Group III. At 30 and 60 days, the lowest setting significantly sustained contraction. CONCLUSION : Lower fractional CO2 laser energies associated to pulse stacking could cause consistent and long lasting tissue contraction in rats.

Action of AlGaInP laser and high frequency generator in cutaneous wound healing. A comparative study

ABSTRACT PURPOSE: To evaluate in a macroscopic, histological and histomorphometric manner the healing process of cutaneous wounds in mice. METHODS: The sample consisted of 40 male mice and was divided in four groups: 1st group (control, n=10), 2nd group (High Frequency Generator - HF, the maximum amplitude range, 120s, n=10), 3rd group (AlGaInP Laser 660 nm, 30mW power, 5 J/cm2, applying scan mode, 120s, n=10) and 4thgroup (AlGaInP Laser 660 nm, 30 mW power, 8 J/cm2, applying scan mode, n=10). The surgical incision was made with an 8 mm diameter punch perpendicularly to the back of the animal. The statistical analysis was achieved by the statistical test One Way Anova post hoc Tukey Test and significance at p<0.05 in GraphPad Prism program. RESULTS: It was observed that in the acute phase the AlGaInP Laser at 5 J/cm2 provided a greater stimulus to healing, and both lasers were effective in the remodeling phase. CONCLUSION: The AlGaInP lasers from 5 J/cm2 to 8 J/cm2 showed better biomodulatory results in the acute and remodeling phases respectively, however, the HF was less effective than the laser, providing significant benefits only in the acute phase of tissue repair.

Reconstructive dosimetry for cutaneous radiation syndrome

According to the International Atomic Energy Agency (IAEA), a relatively significant number of radiological accidents have occurred in recent years mainly because of the practices referred to as potentially high-risk activities, such as radiotherapy, large irradiators and industrial radiography, especially in gammagraphy assays. In some instances, severe injuries have occurred in exposed persons due to high radiation doses. In industrial radiography, 80 cases involving a total of 120 radiation workers, 110 members of the public including 12 deaths have been recorded up to 2014. Radiological accidents in industrial practices in Brazil have mainly resulted in development of cutaneous radiation syndrome (CRS) in hands and fingers. Brazilian data include 5 serious cases related to industrial gammagraphy, affecting 7 radiation workers and 19 members of the public; however, none of them were fatal. Some methods of reconstructive dosimetry have been used to estimate the radiation dose to assist in prescribing medical treatment. The type and development of cutaneous manifestations in the exposed areas of a person is the first achievable gross dose estimation. This review article presents the state-of-the-art reconstructive dosimetry methods enabling estimation of local radiation doses and provides guidelines for medical handling of the exposed individuals. The review also presents the Chilean and Brazilian radiological accident cases to highlight the importance of reconstructive dosimetry.

Daño y respuesta celular en piel por exposición prolongada a radiación UV / Cell response and skin damage by prolonged exposure to UV radiation

La piel es uno de los órganos importantes que con mayor frecuencia sufre estrés oxidativo por la radiación ultravioleta (UV), proveniente de la radiación solar, por su longitud de onda se clasifica en: UVA, UVB, y UVC. La UVB es la que mayor daño biológico produce en la piel causando estrés oxidativo, el cual se da por una excesiva producción de Especies Reactivas del Oxígeno (ERO's) y su corrección está mediado por diferentes mecanismos enzimáticos endógenos como: Superóxido Dismutasa (SOD), Glutatión Peroxidasa (GPX), Catalasa y sistemas exógenos no enzimáticos como la vitamina E y la vitamina C. Los ERO's causan daños como oxidación de proteínas, ADN y lípidos, dando como consecuencia múltiples fenómenos inflamatorios, cáncer, inmunosupresión, daños celulares y estructurales. Para la realización de este artículo se hizo una revisión sistemática en bases de datos bibliográficas (PubMed/MEDLINE, Science) y a través de internet en revistas públicas, se definieron criterios de inclusión y exclusión (afecciones de la piel provocadas por la exposición de luz UV, ERO´s, antioxidantes) y un conjunto de variables para analizar las características de los artículos seleccionados como Respuesta celular en piel producida por exposiciones a la luz solar. Es importante estar actualizado en estos mecanismos, por el aumento del número de personas que se exponen a diario a la luz solar

The skin is one of the most important organs can undergo oxidative stress by ultraviolet radiation (UV), this come from solar ultraviolet radiation and is classified by its wavelength: UVA, UVB, and UVC. It is UV-B that causes greater biological damage to the skin causing oxidative stress, which occurs by excessive production of reactive oxygen species (ROS's) and its correction is mediated by different mechanisms such as endogenous enzyme; Superoxidedismutase (SOD), glutathione peroxidase (GPX), catalase and exogenous systems non-enzymatic include vitamin E, vitamin C. The ROS's cause oxidative damage to proteins, DNA, and lipids, giving due multiple inflammatory phenomena, cancer, immunosuppression and structural and damage cells. We performed a systematic review in bibliographic databases (PubMed / MEDLINE, Science) and through internet in public journals, Inclusion and exclusion criteria (skin disorder caused by exposure to UV light, ROS's, antioxidants) and a set of variables were defined to analyze the characteristics of selected items as skin cell response by exposure to sunlight. It is Important to be updated on these mechanisms by increasing the number of people who are exposed daily to sunlight

Low-level laser therapy modulates musculoskeletal loss in a skin burn model in rats

PURPOSE: To investigate the effectiveness of low-level laser therapy (LLLT) on gastrocnemius muscle morphology and Myod imunoexpression in a model of dorsal burn in rats. METHODS: Sixteen male Wistar rats were distributed into two groups: control group (CG): rats submitted to scald burn injury without treatment and laser treated group (LG): rats submitted to scald burn injury and treated with laser therapy. Fourteen days post-surgery, gastrocnemius muscle was evaluated being the specimens stained with HE and morphometric data was evaluated. MyoD expression was assessed by immunohistochemistry. RESULTS: The results showed that laser treated animals presented more organized tissue morphology compared to the non-treated animals, with a higher number of nucleus in the fibers. Also, the cross sectional area of the fibers and the MyoD immunoexpression in the laser treated groups was higher. CONCLUSION: Low-level laser therapy had positive effects on gastrocnemius muscle, improving tissue muscle morphology, increasing cross sectional area and MyoD immunoexpression. .

Phototherapy promotes healing of cutaneous wounds in undernourished rats

BACKGROUND: Various studies have shown that phototherapy promotes the healing of cutaneous wounds. OBJECTIVE: To investigate the effect of phototherapy on healing of cutaneous wounds in nourished and undernourished rats. METHODS: Forty rats, 20 nourished plus 20 others rendered marasmus with undernourishment, were assigned to four equal groups: nourished sham, nourished Light Emitting Diode treated, undernourished sham and undernourished Light Emitting Diode treated. In the two treated groups, two 8-mm punch wounds made on the dorsum of each rat were irradiated three times per week with 3 J/cm2 sq cm of combined 660 and 890nm light; wounds in the other groups were not irradiated. Wounds were evaluated with digital photography and image analysis, either on day 7 or day 14, with biopsies obtained on day 14 for histological studies. RESULTS: Undernourishment retarded the mean healing rate of the undernourished sham wounds (p < 0.01), but not the undernourished Light emission diode treated wounds, which healed significantly faster (p < 0.001) and as fast as the two nourished groups. Histological analysis showed a smaller percentage of collagen in the undernourished sham group compared with the three other groups, thus confirming our photographic image analysis data. CONCLUSION: Phototherapy reverses the adverse healing effects of undernourishment. Similar beneficial effects may be achieved in patients with poor nutritional status. .

Biomodulation effects of LED and therapeutic ultrasound combined with semipermeable dressing in the repair process of cutaneous lesions in rats

PURPOSE: To compare the biomodulatory effects of LED and ultrasound combined with semipermeable dressing in the repair of cutaneous lesions. METHODS: Eighty-four Wistar rats were submitted to surgical injury (2.5 cm) and divided into four groups (n=21): Group I (control), Group II (LED therapy, LED), Group III (LED therapy + dressing, LED+D) and Group IV (ultrasound + dressing, US+D). At seven, 14 and 21 days, the animals were euthanized, and the specimens of interest removed for histological analysis. RESULTS: Histological and histomorphometric analysis revealed a greater percent wound regression in animals receiving the dressing (group III: 55.97; group IV: 53.06), as well as a greater reduction in the inflammatory infiltrate (group III: 29.14; group IV: 31.71) since day 7. A later effect, with progression of the tissue repair process only after 14 and 21 days, was observed in the LED group intense fibroblast proliferation and greater collagen fiber production and organization were seen in the LED+D and US+D groups compared to the other groups. CONCLUSION: LED combined with a dressing was more effective at accelerating in the repair of cutaneous lesions. .

Effects of low-power light therapy on wound healing: LASER x LED

Several studies demonstrate the benefits of low-power light therapy on wound healing. However, the use of LED as a therapeutic resource remains controversial. There are questions regarding the equality or not of biological effects promoted by LED and LASER. One objective of this review was to determine the biological effects that support the use of LED on wound healing. Another objective was to identify LED´s parameters for the treatment of wounds. The biological effects and parameters of LED will be compared to those of LASER. Literature was obtained from online databases such as Medline, PubMed, Science Direct and Scielo. The search was restricted to studies published in English and Portuguese from 1992 to 2012. Sixty-eight studies in vitro and in animals were analyzed. LED and LASER promote similar biological effects, such as decrease of inflammatory cells, increased fibroblast proliferation, stimulation of angiogenesis, granulation tissue formation and increased synthesis of collagen. The irradiation parameters are also similar between LED and LASER. The biological effects are dependent on irradiation parameters, mainly wavelength and dose. This review elucidates the importance of defining parameters for the use of light devices.

Fractional Erbium laser in the treatment of photoaging: randomized comparative, clinical and histopathological study of ablative (2940nm) vs. non-ablative (1540nm) methods after 3 months

BACKGROUND: Fractional non-ablative lasers keep the epidermis intact, while fractional ablative lasers remove it, making them theoretically more effective. OBJECTIVES: To evaluate the clinical and histological alterations induced by fractional photothermolysis for treating photoaging, comparing the possible equivalence of multiple sessions of 1540nm Erbium, to one session of 2940nm Erbium. METHODS: Eighteen patients (mean age 55.9) completed the treatment with three sessions of 1540nm fractional Erbium laser on one side of the face (50 mJ/mB, 15ms, 2 passes), and one session of 2940nm on the other side (5mJ/mB, 0.25ms, 2 passes). Biopsies were performed before and 3 months after treatment. Clinical, histological and morphometric evaluations were carried out. RESULTS: All patients presented clinical improvement with no statistically significant difference (p> 0.05) between the treated sides. Histopathology revealed a new organization of collagen and elastic fibers, accompanied by edema, which was more evident with the 2940nm laser. This finding was confirmed by morphometry, which showed a decrease in collagen density for both treatments, with a statistical significance for the 2940nm laser (p > 0.001). CONCLUSIONS: Three 1540nm sessions were clinically equivalent to one 2940nm session. The edema probably contributed to the positive results after three months, togheter with the new collagen and elastic fibers organization. The greater edema after the 2940nm session indicates that dermal remodeling takes longer than with 1540nm. It is possible that this histological superiority relates to a more prolonged effect, but a cohort longer than three months is needed to confirm that supposition. .

Evaluación de los efectos del LED en el tejido dérmico de ratones / The effect of application of red LED on the dermis of rats

Diodos Emisores de la Luz- Light Emitting Diodes (LED) son fuentes de luz que están siendo introducidos en los tratamientos del envejecimiento. El objetivo del estudio fue evaluar los efectos del LED rojo en la dermis de ratones wistar. Se trata de un estudio experimental controlado y randomizado, fueron utilizados 20 ratones wistar divididos en cinco grupos. Los grupos fueron: G1 en donde se aplicó 10 sesiones de diez minutos de fototerapia por LED. El G2 con 20 sesiones de 10minutos, el G3 con 10 sesiones de 20 minutos, el G4 con 20 sesiones de 20 minutos y el G5 fue el grupo control. Después de las aplicaciones se recolectó el material biológico de la zona, siendo realizado el análisis histológico de las áreas que recibieron las aplicaciones, sometiéndolas a las coloraciones de HE, tricómico de Masson y Verhoeef. Fue observada la presencia de micro vasos dérmicos con resultados significativos entre el G2 y el G5. Con relación a la presencia de mastocitos hubo resultados significativos entre el G1 y el G3. El análisis de las fibras elásticas presentó resultados significativos en los grupos G1, G2, G3, G4 en comparación al grupo control (G5). La evaluación de los efectos del LED en las fibras colágenos, los grupos tratados comparados al grupo control no presentaron ninguna diferencia significativa.

The Light-Emitting Diodes Light Emitting Diodes (LED) are a source of light wich are being introduced into the treatment of aging process. This study evaluate the effect of application of red LED on the dermis of Wistar rats. Twenty Wistar rats were used in this randomized controlled experimental study. Those rats were divided randomly into five groups. The G1 group underwent ten sessions of phototherapy by LED lasting ten minutes each. The G-2, 20 sessions of 10 minutes, the G-3, 20 minutes, the fourth group, 20 sessions of 20 minutes and the G-5 group was the control group. After the application, the biological material was collected and the histological analysis of the areas that suffered application were done, being subjected to HE staining, and Masson trichrome & Verhoeff. It was observed the presence of dermal microvascular, with significant results among G2 and G5 groups. Regarding the presence of mast cells, significant results were observed among G1 and G3 groups, however, that was not the case with the G5. By analyzing the elastic fibers, significant results were observed among G1, G2, G3, G4 groups, but the same results weren’t observed in the fifth group. Regarding the assessment of the effects of LED on the collagen fibers, the treated groups, when compared to the control group, showed no significant difference.

Determinación de la influencia de la altitud en el índice de protección natural (IPN) de la piel y el factor de protección solar requerido (SPF) / Determination of the influence of altitude on the contents of natural protection (IPN) skin and sun protection factor required (SPF)

Se evalúa la influencia de la altitud sobre el Índice de Protección Natural (IPN) y el Factor de Protección Solar requerido (SPF) comparando niños de Mucuchies, Mérida, Venezuela (3100 m.s.n.m.) y Palmarito, Mérida, Venezuela (5 m.s.n.m.), utilizando el equipo Sun Protection Diagnostic SP 37®. Según el análisis de los resultados a través de estadísticas descriptivas, se evidencia que el IPN y el SPF son variables dependientes de la altitud de la localidad en que se encuentran los niños, ya que en las localidades más altas los rayos solares inciden de forma más directa que en las más bajas.

It is evaluated the effect of altitude on Natural Protection Index (IPN) and the required Sun Protection Factor (SPF) comparing children Mucuchies, Merida, Venezuela (3100 m) and Palmarito, Merida, Venezuela (5 m) using Sun Protection Diagnostic SP37® equipment. According to the analysis of results through descriptive statistics, it appears that the IPN and the SPF are variable dependent on the altitude of the locality in which children are, as in the most high solar rays more directly than in the lowest.

Experimental model of cutaneous radiation injury in rabbits

PURPOSE: To describe an experimental model of cutaneous radiation injury in rabbits. METHODS: On this study eight six-month-old New Zealand male rabbits, with an average weight of 2.5kg were used. They were distributed in four groups (n=2 per group). The control group did not receive radiotherapy and the others received one radiotherapy session of 2000, 3000 and 4500 cGy, respectively. Photographic analysis and histopathological evaluation of the irradiated areas were carried out. RESULTS: After 30 days, the animals from the control group had all their hair grown. In spite of that, the animals from group 2000 cGy had a 60-day alopecia and from group 3000 cGy, a 90-day alopecia. After the 30th day, the 3000cGy group demonstrated 90-day cutaneous radiation injuries, graded 3 and 4. One of the animals from group 4500 cGy died on the 7th day with visceral necrosis. The other from the same group had total skin necrosis. A progressive reduction of glands and blood vessels count and an increase on collagen deposition was observed. CONCLUSION: The proposed experimental model is reproductable. This study suggests that the dosage 4500cGy is excessive and the 3000 cGy is the most effective for this experimental model of cutaneous radiation injury in rabbits.

morphological study of the effects of X-rays on the melanocytes of the skin, under light microscope

To observe the effects of x-irradiation on the melanocytes of the skin under light microscope. A prospective experimental study. The study was carried out at Department of Anatomy, Basic Medical Sciences Institute, Jinnah Postgraduate Medical Centre Karachi from 2008 to 2009. Thirty animals were taken and were divided in to two groups. Each group was further subdivided into three subgroups containing five animals each according to the time of sacrifice i.e. 48 hours, 15[th] day and 45[th] day respectively. A single whole body x-irradiation in a dose of 5 Gy was given. Animals were sacrificed under ether anesthesia after completion of their respective periods. Tissues were processed and 4-5 micron thick paraffin embedded sections were cut and stained with Masson's Fontana stain. Insignificant [P>0.05] decrease in number of melanocytes was obtained when compared to control in group B1 animals. In group B2, increase in size and number of melanocytes was noted with long dendritic processes and large amount of melanin seen scattered between the layers of epidermis was present and results were moderately significant [P<0.01] in case of face and abdomen and significant [P<0.05] in case of back. In group B3 Size and number of melanocytes were also increased with large amount of melanin scattered between the layers of epidermis. The results obtained were highly significant [P<0.001] in case of face and moderately significant [P<0.01] in case of abdomen and back. X-irradiated skin of face, abdomen and back of the guinea pig depicted increased number and size of melanocytes with long dendritic processes and large amount of melanin scattered between the layers of epidermis