RESUMO
PURPOSE: Today, the long-term effects of partial exposure of cholinesterase on the kidney continue to be a research topic. In this study, we aimed to histopathologically investigate the possible effect of acute toxicity due to fenthion, an organophosphate (OP) compound, on the kidneys. METHODS: In all, 21 rats were randomly divided into three groups. Experimental group was each administered intraperitoneal 0.8 g/kg fenthion within physiologic serum. Sham group was only administered intraperitoneal physiologic serum. The control group continued normal nutrition with no procedure performed. After 24 h, all rats were sacrificed by cervical dislocation. Half of the recipient kidney tissues were examined histopathologically and the other half biochemically. RESULTS: No histopathological findings were found in the control group. Rats in the experimental group were observed to have epithelial cell disorganization in tubules, moderate epithelial cell loss, and degeneration. Again, expansion of tubules, vacuolization of tubular epithelial cells, and tubular structure approaching atrophy were observed, with cells approaching apoptosis and common hemorrhage noted although rats in the sham group were observed to have mild tubular degeneration. CONCLUSIONS: It should not be forgotten that one of the causes of systemic complaints linked to acute toxicity exposed to the OP compound of fenthion may be cellular injury to glomerular and tubular structures in the kidneys.
Assuntos
Injúria Renal Aguda/patologia , Inibidores da Colinesterase/toxicidade , Fention/toxicidade , Túbulos Renais/patologia , Intoxicação por Organofosfatos/patologia , Injúria Renal Aguda/induzido quimicamente , Animais , Modelos Animais de Doenças , Feminino , Humanos , Túbulos Renais/efeitos dos fármacos , Intoxicação por Organofosfatos/etiologia , Ratos , Ratos WistarRESUMO
The effect of the electromagnetic field (EMF) established when cell phones are in use on human health, and particularly the head, has been the subject of major scientific research. Phones are usually carried near the lumbar region when not in use, and the kidneys will also inevitably be affected by such fields. We investigated the effects on the kidneys of female rats exposed to a continuous 900-megahertz (MHz) EMF for 1 h daily in mid-late adolescence. Control, sham, and EMF groups were established. The EMF was applied to the application group rats daily on postnatal days 35-59. A pseudo-megahertz effect was applied to sham group rats. All animals were euthanized on postnatal day 60. Right kidney tissues were subjected to routine procedures. Malondialdehyde, total antioxidant status, and total oxidant status (TOS) were investigated in left kidneys, and the oxidative stress index (OSI) was also calculated from these. Histopathological analysis revealed no pathology in either the control or sham groups. However, findings including hemorrhage in glomerulus, vacuolization and irregularity in the proximal and distal tubular epithelium, diffuse glomerular degeneration and edema, occasional degeneration in Bowman capsules, hemorrhage in the medullary region, disturbed nucleus location and morphology, and tubular edema in the cortex were observed in the EMF groups. TOS and OSI values were lower in the EMF group (9.4316 ± 1.0211 and 0.8461 ± 0.0826, respectively) and the sham group (8.2171 ± 0.6437 and 0.7358 ± 0.0545, respectively) than in the control group (11.1522 ± 1.3389 and 1.0085 ± 0.1174, respectively) ( p < 0.05). In conclusion, exposure to a continuous 900-MHz EMF for 1 h daily during middle and late adolescence may cause various changes in the female rat kidney at postnatal day 60.
Assuntos
Campos Eletromagnéticos/efeitos adversos , Rim/efeitos da radiação , Fatores Etários , Animais , Antioxidantes/metabolismo , Feminino , Marcação In Situ das Extremidades Cortadas , Rim/metabolismo , Rim/patologia , Malondialdeído/metabolismo , Estresse Oxidativo/efeitos da radiação , Ratos , Ratos Sprague-DawleyRESUMO
The growing spread of mobile phone use is raising concerns about the effect on human health of the electromagnetic field (EMF) these devices emit. The purpose of this study was to investigate the effects on rat pup heart tissue of prenatal exposure to a 900 megahertz (MHz) EMF. For this purpose, pregnant rats were divided into experimental and control groups. Experimental group rats were exposed to a 900 MHz EMF (1 h/d) on days 13-21 of pregnancy. Measurements were performed with rats inside the exposure box in order to determine the distribution of EMF intensity. Our measurements showed that pregnant experimental group rats were exposed to a mean electrical field intensity of 13.77 V/m inside the box (0.50 W/m(2)). This study continued with male rat pups obtained from both groups. Pups were sacrificed on postnatal day 21, and the heart tissues were extracted. Malondialdehyde, superoxide dismutase and catalase values were significantly higher in the experimental group rats, while glutathione values were lower. Light microscopy revealed irregularities in heart muscle fibers and apoptotic changes in the experimental group. Electron microscopy revealed crista loss and swelling in the mitochondria, degeneration in myofibrils and structural impairments in Z bands. Our study results suggest that exposure to EMF in the prenatal period causes oxidative stress and histopathological changes in male rat pup heart tissue.
Assuntos
Telefone Celular , Campos Eletromagnéticos/efeitos adversos , Coração/efeitos da radiação , Efeitos Tardios da Exposição Pré-Natal/patologia , Animais , Animais Recém-Nascidos , Apoptose , Catalase/metabolismo , Feminino , Glutationa/metabolismo , Masculino , Malondialdeído/metabolismo , Microscopia Eletrônica , Microscopia Eletrônica de Transmissão , Gravidez , Ratos , Ratos Sprague-Dawley , Superóxido Dismutase/metabolismoRESUMO
As the use of plastic-containing materials in our daily lives becomes increasingly common, exposure to nanoplastics accordingly becomes inevitable. Micro and nanoplastics released from large amounts of plastic waste constitute a serious environmental problem. Therefore, this study aimed to examine the effects of polystyrene nanoplastic (PS-NP) on the hippocampus. MATERIAL AND METHOD: Thirty Wistar albino rats, 15 male and 15 female, aged 6-8 weeks, were used in the research. These were randomly divided into three groups of five males and five females each. A five-minute open field test was applied to all rats on the first and last days of the study. Three groups of rats (Control, NP1 and NP2) received the standard chow and water. Additionally, rats in the first neoplastic group (NP1) received 25 mg/kg PS-NP and rats in the second nanoplastic group (NP2) received 50 mg/kg PS-NP, at the same time each day by oral gavage. The rats were sacrificed under deep anesthesia at the end of four weeks. The hippocampi were removed and subjected to histopathological and biochemical analyses. RESULTS: Green fluorescent dots were detected in the hippocampi of both dose groups receiving nanoplastics (NPs) administered orally to female and male rats. Histopathological examination revealed neuronal degeneration in the hippocampi of male and female rats from both dose groups. However, while no significant difference was observed among the groups in terms of changes in antioxidant enzyme values and open-field test data in male rats, significant differences in peroxidase (POD) and glutathione S-transferase (GST) values and fecal boli and grooming numbers were determined in female rats exposed to NPs. In conclusion, exposure to NP substances extend as far as the hippocampus, causing neuronal damage and behavioral problems.
Assuntos
Antioxidantes , Microplásticos , Animais , Feminino , Masculino , Ratos , Antioxidantes/farmacologia , Hipocampo/metabolismo , Microplásticos/toxicidade , Plásticos/farmacologia , Poliestirenos/toxicidade , Poliestirenos/metabolismo , Ratos WistarRESUMO
OBJECTIVES: Spermatogenesis, in which cell regeneration continues, can be affected by environmental, chemical, psychological factors or various diseases. There is conflicting information in the literature about the effect of isotretinoin, which is widely used in acne treatment, on testes and spermatogenesis. Therefore, we planned a rat study to evaluate the long-term efficacy of oral isotretinoin on testicular tissues and spermatogenesis. MATERIALS AND METHODS: The Group 1 (n = 6) 7.5 mg/kg/day and the Group 2 (n = 6) received isotretinoin at a dose of 30 mg/kg/day dissolved in sunflower oil, the Sham Group (n = 6) received only sunflower oil by gavage, and the control group (n = 6) received standard feed and water for four weeks. After the 4th week, all animals were fed with standard feed and water and followed for the next four weeks. At the end of the 8th week, all animals were sacrificed under deep anesthesia. Seminiferous tubule diameters, epithelial thickness, apoptotic index, sperm number and motility recorded Results: Sperm count, motility, vitality, diameter of seminiferous tubule and germinal epithelium thickness were decreased and apoptotic index increased in the groups received isotretinoin. There was no significant difference between the groups in terms of testosterone levels. CONCLUSIONS: We consider that further comprehensive studies, including human clinical trials, should be conducted to examine the negative effects of isotretinoin on spermatogenesis in the long term especially when there is a need using isotretinoin in men for various reasons and to eliminate the contradictions in the literature in this regard.
Assuntos
Isotretinoína , Sêmen , Humanos , Masculino , Ratos , Animais , Isotretinoína/efeitos adversos , Óleo de Girassol/farmacologia , Espermatogênese , Testículo , Água/farmacologiaRESUMO
OBJECTIVE: The aim of this study was to examine the changes on the Purkinje cells in the cerebella of male rat pups born to pregnant dams that were exposed to an electromagnetic field in the prenatal period. METHODS: The first stage of the study involved 12 Sprague-Dawley rats, 6 male and 6 female, weighing between 180 and 250 g. The female rats in the experimental group were exposed to a 900-MHz electromagnetic field for 1 h at the same time every day, and no procedure was performed on the control group. Following pregnancy, six male pups from each group were divided into experimental and control groups without any procedure on the pups. After 2 months, they were sacrificed and their cerebella were removed. Histopathologically, following routine processing and fixation procedures, the cerebella were embedded in the tissue blocks. The sections taken from these blocks were stained with cresyl violet. The Purkinje cells in the cerebella were then counted on sections using the optical dissector method on an image analysis system. RESULTS: The estimation of number of the Purkinje cells in the groups revealed more cells in rats in the control group than in the experimental group. Histopathologically, Purkinje cells exhibited a normal morphological structure in the control group, while the cells in the experimental group showed damage. CONCLUSIONS: It might be asserted that the exposure of mothers to an electromagnetic field in the prenatal period may affect the development of Purkinje cells in the pup cerebella.
Assuntos
Campos Eletromagnéticos , Células de Purkinje , Gravidez , Feminino , Masculino , Ratos , Animais , Campos Eletromagnéticos/efeitos adversos , Ratos Sprague-Dawley , VitaminasRESUMO
The purpose of this study was to investigate the 60-day-old male rat testis following exposure to continuous 900-megahertz (MHz) electromagnetic field (EMF) throughout the adolescent period using histopathological and biochemical analysis methods. Twenty-four Sprague Dawley rats aged 21 days were randomly and equally (n = 8) divided into three groups. No procedure was performed on the control group rats. The sham group rats were held in an EMF-cage without exposure to EMF. The EMF group rats were exposed to continuous 900-MHz EMF for 1 h each day inside the EMF-cage during adolescence. On postnatal day 60 the testes were extracted and divided into right and left halves. The right half was used for histopathological evaluation and the left half for biochemical analyses. Our results show that changes may occur in morphology and oxidative stress biomarkers in the rat testis following exposure to continuous 900-MHz EMF throughout the adolescent period.
Assuntos
Campos Eletromagnéticos , Testículo , Animais , Biomarcadores/metabolismo , Catalase/metabolismo , Masculino , Malondialdeído/metabolismo , Microscopia Eletrônica de Transmissão , Estresse Oxidativo , Ratos Sprague-Dawley , Superóxido Dismutase/metabolismo , Testículo/metabolismo , Testículo/patologia , Testículo/ultraestruturaRESUMO
The aim of this study was to evaluate the efficacy of low-level 940 nm laser therapy with energy intensities of 5, 10 and 20 J/cm2 on bone healing in an animal model. A total of 48 female adult Wistar rats underwent surgery to create bone defects in the right tibias. Low-level laser therapy (LLLT) was applied immediately after surgery and on post-operative days 2, 4, 6, 8, 10 and 12 in three study groups with energy intensities of 5 J/cm2, 10 J/cm2 and 20 J/cm2 using a 940 nm Gallium-Aluminium-Arsenide (Ga-Al-As) laser, while one control group underwent only the tibia defect surgery. All animals were sacrificed 4 or 8 weeks post-surgery. Fibroblasts, osteoblasts, osteocytes, osteoclasts and newly formed vessels were evaluated by a histological examination. No significant change was observed in the number of osteocytes, osteoblasts, osteoclasts and newly formed vessels at either time period across all laser groups. Although LLLT with the 10 J/cm2 energy density increased fibroblast activity at the 4th week in comparison with the 5 and 20 J/cm2 groups, no significant change was observed between the laser groups and the control group. These results indicate that low-level 940 nm laser with different energy intensities may not have marked effects on the bone healing process in both phases of bone formation.
Assuntos
Regeneração Óssea/efeitos da radiação , Lasers Semicondutores/uso terapêutico , Terapia com Luz de Baixa Intensidade/métodos , Cicatrização/efeitos da radiação , Animais , Relação Dose-Resposta à Radiação , Feminino , Fibroblastos/efeitos da radiação , Osteoblastos/efeitos da radiação , Osteoclastos/efeitos da radiação , Osteogênese/efeitos da radiação , Ratos Wistar , Valores de Referência , Reprodutibilidade dos Testes , Tíbia/patologia , Tíbia/efeitos da radiação , Fatores de Tempo , Resultado do TratamentoRESUMO
SUMMARY OBJECTIVE: The aim of this study was to examine the changes on the Purkinje cells in the cerebella of male rat pups born to pregnant dams that were exposed to an electromagnetic field in the prenatal period. METHODS: The first stage of the study involved 12 Sprague-Dawley rats, 6 male and 6 female, weighing between 180 and 250 g. The female rats in the experimental group were exposed to a 900-MHz electromagnetic field for 1 h at the same time every day, and no procedure was performed on the control group. Following pregnancy, six male pups from each group were divided into experimental and control groups without any procedure on the pups. After 2 months, they were sacrificed and their cerebella were removed. Histopathologically, following routine processing and fixation procedures, the cerebella were embedded in the tissue blocks. The sections taken from these blocks were stained with cresyl violet. The Purkinje cells in the cerebella were then counted on sections using the optical dissector method on an image analysis system. RESULTS: The estimation of number of the Purkinje cells in the groups revealed more cells in rats in the control group than in the experimental group. Histopathologically, Purkinje cells exhibited a normal morphological structure in the control group, while the cells in the experimental group showed damage. CONCLUSIONS: It might be asserted that the exposure of mothers to an electromagnetic field in the prenatal period may affect the development of Purkinje cells in the pup cerebella.
RESUMO
The effects on human health of electromagnetic field (EMF) have begun to be seriously questioned with the entry into daily life of devices establishing EMF, such as cell phones, wireless fidelity, and masts. Recent studies have reported that exposure to EMF, particularly during pregnancy, affects the developing embryo/fetus. The aim of this study was therefore to examine the effects of exposure to continuous 900-Megahertz (MHz) EMF applied in the prenatal period on ovarian follicle development and oocyte differentiation. Six pregnant Sprague Dawley rats were divided equally into a non-exposed control group (CNGr) and a group (EMFGr) exposed to continuous 900-MHz EMF for 1 h daily, at the same time every day, on days 13-21 of pregnancy. New groups were established from pups obtained from both groups after birth. One group consisting of female pups from CNGr rats was adopted as newborn CNGr (New-CNGr, n = 6), and another group consisting of female pups from EMFGr rats was adopted as newborn EMFGr (New-EMFGr, n = 6). No procedure was performed on New-CNGr or New-EMFGr rats. All rat pups were sacrificed on the postnatal 34th day, and their ovarian tissues were removed. Follicle count, histological injury scoring and morphological assessment with apoptotic index criteria were performed with sections obtained following routine histological tissue preparation. Follicle count results revealed a statistically significant decrease in primordial and tertiary follicle numbers in New-EMFGr compared to New-CNGr (p < 0.05), while atretic follicle numbers and apoptotic index levels increased significantly (p < 0.05). Histopathological examination revealed severe follicle degeneration, vasocongestion, a low level of increased stromal fibrotic tissue and cytoplasmic vacuolization in granulosa cell in New-EMFGr. Prenatal exposure to continuous 900-MHz EMF for 1 h each day from days 13-21 led to a decrease in ovarian follicle reservoirs in female rat pups at the beginning of the prepubertal period.
Assuntos
Campos Eletromagnéticos/efeitos adversos , Folículo Ovariano/patologia , Folículo Ovariano/efeitos da radiação , Reserva Ovariana/efeitos da radiação , Efeitos Tardios da Exposição Pré-Natal/etiologia , Efeitos Tardios da Exposição Pré-Natal/patologia , Envelhecimento/patologia , Envelhecimento/efeitos da radiação , Animais , Relação Dose-Resposta à Radiação , Feminino , Micro-Ondas/efeitos adversos , Folículo Ovariano/fisiopatologia , Gravidez , Efeitos Tardios da Exposição Pré-Natal/fisiopatologia , Doses de Radiação , Ratos , Ratos Sprague-DawleyRESUMO
The central nervous system (CNS) begins developing in the intrauterine period, a process that continues until adulthood. Contact with chemical substances, drugs or environmental agents such as electromagnetic field (EMF) during adolescence therefore has the potential to disturb the development of the morphological architecture of components of the CNS (such as the hippocampus). The hippocampus is essential to such diverse functions as memory acquisition and integration and spatial maneuvering. EMF can result in severe damage to both the morphology of the hippocampus and its principal functions during adolescence. Although children and adolescents undergo greater exposure to EMF than adults, the information currently available regarding the effects of exposure to EMF during this period is as yet insufficient. This study investigated the 60-day-old male rat hippocampus following exposure to 900 megahertz (MHz) EMF throughout the adolescent period using stereological, histopathological and biochemical analysis techniques. Eighteen male Sprague Dawley rats aged 21days were assigned into control, sham and EMF groups on a random basis. No procedure was performed on the control group rats. The EMF group (EMFGr) was exposed to a 900-MHz EMF for 1h daily from beginning to end of adolescence. The sham group rats were held in the EMF cage but were not exposed to EMF. All rats were sacrificed at 60days of age. Their brains were extracted and halved. The left hemispheres were set aside for biochemical analyses and the right hemispheres were subjected to stereological and histopathological evaluation. Histopathological examination revealed increased numbers of pyknotic neurons with black or dark blue cytoplasm on EMFGr slides stained with cresyl violet. Stereological analyses revealed fewer pyramidal neurons in EMFGr than in the other two groups. Biochemical analyses showed an increase in malondialdehyde and glutathione levels, but a decrease in catalase levels in EMFGr. Our results indicate that oxidative stress-related morphological damage and pyramidal neuron loss may be observed in the rat hippocampus following exposure to 900-MHz EMF throughout the adolescent period.
Assuntos
Campos Eletromagnéticos/efeitos adversos , Hipocampo/anatomia & histologia , Hipocampo/efeitos da radiação , Células Piramidais/efeitos da radiação , Animais , Peso Corporal , Encéfalo/citologia , Encéfalo/crescimento & desenvolvimento , Encéfalo/efeitos da radiação , Catalase/metabolismo , Contagem de Células , Telefone Celular , Citoplasma/efeitos da radiação , Citoplasma/ultraestrutura , Glutationa/metabolismo , Hipocampo/citologia , Peroxidação de Lipídeos/efeitos da radiação , Masculino , Malondialdeído/metabolismo , Tamanho do Órgão , Estresse Oxidativo/efeitos da radiação , Ratos , Ratos Sprague-DawleyRESUMO
Large numbers of people are unknowingly exposed to electromagnetic fields (EMF) from wireless devices. Evidence exists for altered cerebellar development in association with prenatal exposure to EMF. However, insufficient information is still available regarding the effects of exposure to 900 megahertz (MHz) EMF during the prenatal period on subsequent postnatal cerebellar development. This study was planned to investigate the 32-day-old female rat pup cerebellum following exposure to 900MHz EMF during the prenatal period using stereological and histopathological evaluation methods. Pregnant rats were divided into control, sham and EMF groups. Pregnant EMF group (PEMFG) rats were exposed to 900MHz EMF for 1h inside an EMF cage during days 13-21 of pregnancy. Pregnant sham group (PSG) rats were also placed inside the EMF cage during days 13-21 of pregnancy for 1h, but were not exposed to any EMF. No procedure was performed on the pregnant control group (PCG) rats. Newborn control group (CG) rats were obtained from the PCG mothers, newborn sham group (SG) rats from the PSG and newborn EMF group (EMFG) rats from the PEMFG rats. The cerebellums of the newborn female rats were extracted on postnatal day 32. The number of Purkinje cells was estimated stereologically, and histopathological evaluations were also performed on cerebellar sections. Total Purkinje cell numbers calculated using stereological analysis were significantly lower in EMFG compared to CG (p<0.05) and SG (p<0.05). Additionally, some pathological changes such as pyknotic neurons with dark cytoplasm were observed in EMFG sections under light microscopy. In conclusion, our study results show that prenatal exposure to EMF affects the development of Purkinje cells in the female rat cerebellum and that the consequences of this pathological effect persist after the postnatal period.
Assuntos
Cerebelo/patologia , Cerebelo/efeitos da radiação , Campos Eletromagnéticos/efeitos adversos , Exposição Materna/efeitos adversos , Neurônios/patologia , Neurônios/efeitos da radiação , Fatores Etários , Animais , Contagem de Células/métodos , Feminino , Gravidez , Efeitos Tardios da Exposição Pré-Natal/etiologia , Efeitos Tardios da Exposição Pré-Natal/patologia , Células de Purkinje/patologia , Células de Purkinje/efeitos da radiação , Ratos , Ratos Sprague-DawleyRESUMO
BACKGROUND/AIM: To determine what effect a 900-MHz electromagnetic field (EMF) applied in the prenatal period would have on the liver in the postnatal period. MATERIALS AND METHODS: At the start of the study, adult pregnant rats were divided into two groups, control and experimental. The experimental group was exposed to a 900-MHz EMF for 1 h daily during days 13-21 of pregnancy. After birth, no procedure was performed on either mothers or pups. Male rat pups (n = 6) from the control group mothers (CGMR) and male rat pups (n = 6) from the experimental group mothers (EGMR) were sacrificed on postnatal day 21. RESULTS: Biochemical analyses showed that malondialdehyde and superoxide dismutase values increased and glutathione levels decreased in the EGMR pups. Marked hydropic degeneration in the parenchyma, particularly in pericentral regions, was observed in light microscopic examination of EGMR sections stained with hematoxylin and eosin. Examinations under transmission electron microscope revealed vacuolization in the mitochondria, expansion in the endoplasmic reticulum, and necrotic hepatocytes. CONCLUSION: The study results show that a 900-MHz EMF applied in the prenatal period caused oxidative stress and pathological alterations in the liver in the postnatal period.
Assuntos
Campos Eletromagnéticos/efeitos adversos , Glutationa/metabolismo , Fígado , Malondialdeído/metabolismo , Superóxido Dismutase/metabolismo , Animais , Feminino , Fígado/patologia , Fígado/efeitos da radiação , Masculino , Estresse Oxidativo/efeitos da radiação , Gravidez , Efeitos Tardios da Exposição Pré-Natal/etiologia , Ratos , Ratos Sprague-Dawley , Fatores de TempoRESUMO
The aim of this study was to investigate the effect of exposure to a 900-MHz electromagnetic field (EMF) in the prenatal term on the 21-old-day rat testicle. Pregnant rats were divided into control (CG) and EMF (EMFG) groups. EMFG was exposed to 900-MHz EMF during days 13-21 of pregnancy. Newborn CG rats were obtained from the CG and newborn EMFG (NEMFG) rats from the EMFG. Testicles were extracted at postnatal day 21. Lipid peroxidation and DNA oxidation levels, apoptotic index and histopathological damage scores were compared. NEMFG rats exhibited irregularities in seminiferous tubule basal membrane and epithelium, immature germ cells in the lumen, and a decreased diameter in seminiferous tubules and thickness of epithelium. Apoptotic index, lipid peroxidation and DNA oxidation were higher in NEMFG rats than in NCG. 21-day-old rat testicles exposed to 900-MHz EMF in the prenatal term may be adversely affected, and this effect persists after birth.
Assuntos
Campos Eletromagnéticos/efeitos adversos , Efeitos Tardios da Exposição Pré-Natal , Testículo/patologia , Animais , Apoptose , DNA/metabolismo , Feminino , Peroxidação de Lipídeos , Masculino , Oxirredução , Gravidez , Ratos , Ratos Sprague-DawleyRESUMO
Abstract The aim of this study was to evaluate the efficacy of low-level 940 nm laser therapy with energy intensities of 5, 10 and 20 J/cm2 on bone healing in an animal model. A total of 48 female adult Wistar rats underwent surgery to create bone defects in the right tibias. Low-level laser therapy (LLLT) was applied immediately after surgery and on post-operative days 2, 4, 6, 8, 10 and 12 in three study groups with energy intensities of 5 J/cm2, 10 J/cm2 and 20 J/cm2 using a 940 nm Gallium-Aluminium-Arsenide (Ga-Al-As) laser, while one control group underwent only the tibia defect surgery. All animals were sacrificed 4 or 8 weeks post-surgery. Fibroblasts, osteoblasts, osteocytes, osteoclasts and newly formed vessels were evaluated by a histological examination. No significant change was observed in the number of osteocytes, osteoblasts, osteoclasts and newly formed vessels at either time period across all laser groups. Although LLLT with the 10 J/cm2 energy density increased fibroblast activity at the 4th week in comparison with the 5 and 20 J/cm2 groups, no significant change was observed between the laser groups and the control group. These results indicate that low-level 940 nm laser with different energy intensities may not have marked effects on the bone healing process in both phases of bone formation.