2012 Vol. 25, No. 2
2012, 25(2): 125-132. doi: 10.3967/0895-3988.2012.02.001
Objective To explore the associations between sugar-sweetened beverage (SSB) consumption and obesity as well as obesity-related cardiometabolic disorders among children in China.Methods A total of 6974 (boys 3558,girls 3412) children aged 6-13 years participated in the study.Each partcipant's height,weight,waist circumference,fasting glucose,triglycerides,total cholesterol,highdensity lipoprotein cholesterol,and low-density lipoprotein cholesterol were measured.The type of beverage consumption was determined using a self-administered questionnaire.Results SSBs were consumed regularly by 46.1％ of the children.The prevalence [adjusted odds ratio (95％ confidence internal (CI)] of obesity was 7.6％ [as the reference group (ref.)],10.1％ [1.36(1.07,1.74)],and 11.6％ [1.46(1.21,1.75)],among children who regularly drank milk,other beverages and SSBs,respectively.Regularly drinking SSBs elevated the likelihood of abdominal obesity [adjusted odds ratio (95％ CI):1.36 (1.17,1.59)].The prevalence [adjusted odds ratio (95％ CI)] of obesity among children who regularly drank sports/caloric beverages,carbonated beverages,sweet tea,and plant protein beverages was 16.8％ [2.00(1.31,3.07)],12.7％ [1.52(1.23,1.88)],11.5％ [1.52(1.18,1.95)],and 10.4％ [1.41(1.03,1.94)],respectively,which was higher than that of regular milk drinkers [7.6 ％ (ref.)].The prevalence [adjusted odds ratio (95％ CI)] of abdominal obesity among children who regularly drank sweet tea,fruit/vegetable juices,and carbonated beverages was 17.7％ [1.55(1.26,1.90)],16.2％[1.36(1.09,1.70)],and 15.3％ [1.24(1.03,1.50)],respectively,which was much higher than that of regular milk drinkers [12.8％ (ref.)].Conclusions Regular SSB consumption was positively related to obesity and abdominal obesity.This relationship should be investigated further using a longitudinal study design.
2012, 25(2): 133-140. doi: 10.3967/0895-3988.2012.02.002
Objective To explore the association of sleep duration with obesity among children in urban areas of China.Methods A total of 6 576 children (3 293 boys and 3 283 girls) aged 7-11 years were randomly selected from 36 primary schools in 6 metropolitan cities in China.A 7-day Physical Activity Recall was used to assess the sleep duration and physical activity level.The height,weight,waist circumference (WC)and percentage of body fat (％BF,as determined by bioelectrical impedance analysis technique) were measured by following the standardized operation procedures.The information on demography,lifestyle and eating habits was collected with a self-administered questionnaire from participants and their parents.Results The average sleep duration per night in the children was 9.7 h with the decreasing trends along with the increase of age (P＜0.05).The sleep duration was negatively associated with body mass index (BMI) and WC in both boys and girls after adjustment for confounders (β value -0.23 and -0.82 for boys,-0.24 and -0.91 for girls,respectively,P＜0.01).However,no significant association of sleep duration with ％BF was found.Children who slept less than 9.0 h per night had a higher risk for overweight and obesity (0R=1.29,95％ CI:1.01,1.64) and abdominal obesity (OR=1.38,95％ CI:1.04,1.83) as compared with those who slept for 10.0-10.9 h.Conclusions Short sleep duration is associated with obesity.It is important to ensure adequate sleep duration of children and foster their healthy lifestyle at an early stage of life.
Visceral Fat Area, Waist Circumference and Metabolic Risk Factors in Abdominally Obese Chinese Adults
2012, 25(2): 141-148. doi: 10.3967/0895-3988.2012.02.003
Objective To examine the association of visceral adiposity as measured by VFA and WC with lipid and glucose metabolic biomarkers in abdominally obese Chinese adults,and to assess whether WC could be an indicator of visceral fat.Methods WC and VFA were measured in 155 overweight and obese adults.A fasting blood sample was collected from participant (n=118) whose VFA ≥100 cm2 for analyses of lipid and glucose profile.The relationship between VFA and WC and biomarkers was investigated.Results WC and VFA were significantly interrelated.The coincidence rate of abdominal obesity determined by Japanese VFA and Chinese WC criteria increased across age quartiles in women from 51.7％ to 96.2％.A large WC was associated significantly with low HDL-cholesterol concentration (P＜0.01)and the association was weakened by additional control of VFA.WC and VFA were positively associated with glucose,hemoglobin A1c and insulin concentrations (P＜0.05 except for the association of VFA with insulin:P＜0.01),and all the associations were not significant by additional control of either WC or VFA.As WC quartiles increased,significant stepwise increments in triglyceride,glucose,hemoglobin A1c and insulin and descent in HDL-cholesterol were observed.However,triglyceride and HDL-cholesterol were not significantly different when compared across VFA quartiles.Conclusion Higher visceral fat was associated with an adverse lipid and glucose profile.WC can be a moderate predictor for visceral fat and provides a feasible measurement to estimate glucose metabolic risks.Further studies are warranted to establish age-specific WC cutoffs.
A Survey of Urolithiasis in Young Children Fed Infant Formula Contaminated with Melamine in Two Townships of Gansu, China
2012, 25(2): 149-155. doi: 10.3967/0895-3988.2012.02.004
Objective To determine the prevalence of urolithiasis in young children fed infant formula (IF) contaminated with melamine,and the association between IF consumption and urolithiasis.Design A total of 2 733 children ≤3 years of age on September 1,2008 in two townships of Gansu Province,China were studied.Cases of urolithiasis were diagnosed by ultrasonography.Milk product consumption was determined by their caregivers.Remaining IF samples were tested for melamine and cyanuric acid.Results Of 2 733 eligible children in the two townships,2 186 (80％) were enrolled in our study.Overall,16.6％ (362) of 2 186 children had urolithiasis.The prevalence was 24.6％ in children exclusively fed Sanlu brand IF,9.7％ in those fed other IF,and 8.5％ in those fed exclusively on other milk products.For children exclusively breast-fed,no urolithiasis was found (P＜0.05).The prevalence of urolithiasis was 11.4％ in children fed 400 g of Sanlu IF,rising to 37.5％ in children fed over 25 600 g.Of 48 Sanlu IF samples,91.7％ contained melamine (median=1 800 ppm; range=45-4 700) and 66.7％ contained cyanuric acid (median=1.2 ppm; range=0.4-6.3).Melamine was also detected in 22.2％ of 36 other brand IF (median=27.5 ppm,range=4-50).Conclusions Urolithiasis was associated with melamine-contaminated IF.Although one product caused most morbidity,other milk products may have also contributed to the outbreak.
Association of Catalase Genotype with Oxidative Stress in the Predication of Colorectal Cancer: Modification by Epidemiological Factors
2012, 25(2): 156-162. doi: 10.3967/0895-3988.2012.02.005
Objective This paper aims to assess the interaction between common variations in catalase (CAT)polymorphic gene and environmental factors for antioxidant defense enzyme in modulating individual susceptibility to colorectal cancer (CRC).Methods A case-control study with 880 colorectal cancer cases and 848 controls was conducted to investigate whether variations in the catalase (CAT) gene,one of the genes involved in scavenging oxidative stress,influenced susceptibility to CRC.Results The interaction between life style and genotypes as well as with their effects on colorectal cancer was deduced from the present study.Significant difference (P=0.01) was identified in the distribution of CAT genotype between the colorectal cancer cases and the controls.The CRC cases had significantly lower mean activity than the controls (P＜0.01).Correlation analyses revealed statistically significant correlations between CAT activity and CAT genotype (P＜0.01).Conclusion The risk of CRC was associated with smoking,low vegetable consumption,high pork and poultry consumptions,and low or high BMI.This is the first study reporting an association of polymorphism CAT-21A＞T with colorectal cancer.Low CAT activity was associated with an increased risk of CRC; however,no evidence was found to support an association between CAT-21A＞T polymorphism and CRC risk.
2012, 25(2): 163-166. doi: 10.3967/0895-3988.2012.02.006
Objective To examine Clonorchis sinensis infection in China and evaluate the effectiveness of efforts to prevent and control it,two nationwide surveys were undertaken in 31 provinces,autonomous regions,and municipalities (PAMs) during 1988-92 (the 1990 survey) and during 2001-04 (the 2003 survey),Methods During the period 2001-04,two sampling methods were applied.The first method repeated the stratified cluster random sampling used in the 1990 survey; the second method applied two-characteristic stratified cluster random sampling in 27 PAMs-the 2003 endemic area (EA) survey.The Kato-Katz thick smear method was used for the nationwide survey.Results The infection rates of Clonorchis sinensis in the 1990 and 2003 surveys were 0.311％ and 0.579％,respectively.The infection rate was 2.40％ in the 2003 EA survey,and it was estimated that 12.49 million people in China were infected with Clonorchis sinensis.Conclusion The 2003 survey showed that the standardized infection rate of Clonorchis sinensis increased by 74.85％ compared with the 1990 survey.The infection rate in males was higher than in females; the infection rate among people eating raw fish or eating out frequently was higher than among those who did not.
2012, 25(2): 167-171. doi: 10.3967/0895-3988.2012.02.007
Objective To quantitatively evaluate the contamination area and risk of a live pathogen during tissue homogenization by either ultrasonic processor or tissue disperser.Methods A recombinant Herpes Simplex Virus (rHSV) containing GFP gene was used as the index virus,and fresh liver tissue from healthy mice was used as simulated specimen.After 10％ liver homogenate was mixed with rHSV (100 TCID50/0.1 mL) in a 5 mL tube,the stability of rHSV in liver homogenate and influences of an ultrasonic processor and a tissue disperser on viral infectivity were determined by GFP expressions in cell cultures.The contaminating areas of live viruses during homogenization were evaluated by a cell culture-based sedimentary.The contamination radii were counted by measurement of the distance between the operator and the farthest GFP positive well.Results The infectivity of rHSV in 10％ liver homogenate maintained almost unchanged after it was incubated at room temperature for 30 min.Treatment with an ultrasonic processor clearly dropped down the virus infectivity,while a disperser not.Obvious spills and slashes of live viruses were observed in processes of homogenization with those two apparatuses,The contamination radii are positively related with sample volume,output energy of operator and handling time.Conclusion Homogenizing infectious samples with an ultrasonic processor and a tissue disperser at commonly used conditions caused obvious spills and splashes of live viruses,which possesses high risk to induce Laboratory acquired infections (LAIs).
2012, 25(2): 172-181. doi: 10.3967/0895-3988.2012.02.008
Objective To investigate the cytotoxic mechanism of cadmium (Cd) on cerebral cortical neurons.Methods The primary cultures of rat cerebral cortical neurons were treated with different concentrations of cadmium acetate (0,5,10,and 20 μmol/L),and then the cell viability,apoptosis,ultrastructure,intracellular [Ca2+],and reactive oxygen species (ROS) levels,mitochondrial membrane potential (Δψ),activities of catalase (CAT) and superoxide dismutase (SOD) were measured.Results A progressive loss in cell viability and an increased number of apoptotic cells were observed.In addition,Cd-induced apoptotic morphological changes in cerebral cortical neurons were also demonstrated by Hoechst 33258 staining.Meanwhile,ultrastructural changes were distortion of mitochondrial cristae and an unusual arrangement.Simultaneously,elevation of intracellular [Ca2+] and ROS levels,depletion of △ψ were revealed in a dose-dependent manner during the exposure.Moreover,CAT and SOD activities in the living cells increased significantly.Conclusion Exposure of cortical neurons to different doses of Cd led to cellular death,mediated by an apoptotic mechanism,and the apoptotic death induced by oxidative stress may be a potential reason.And the disorder of intracellular homeostasis caused by oxidative stress and mitochondrial dysfunction may be a trigger for apoptosis in cortical neurons.
Relationship between Cognition Function and Hippocampus Structure after Long-term Microwave Exposure
2012, 25(2): 182-188. doi: 10.3967/0895-3988.2012.02.009
Objective To analyze the effects of long-term microwave exposure on hippocampal structure and function in the rat.Methods Experiments were performed on 184 male Wistar rats (three exposure groups and a sham group).Microwaves were applied daily for 6 min over 1 month at average power densities of 2.5,5,and 10 mW/cm2.Learning and memory abilities were assessed by Morris water maze.High performance liquid chromatography was used to detect neurotransmitter concentrations in the hippocampus.Hippocampal structures were observed by histopathological analysis.Results Following long-term microwave exposure there was a significant decrease in learning and memory activity in the 7 d,14 d,and 1 m in all three microwave exposure groups.Neurotransmitter concentrations of four amino acids (glutamate,aspartic acid,glycine,and gamma-aminobutyric acid) in hippocampus were increased in the 2.5 and 5 mW/cm2 groups and decreased in the 10 mW/cm2 group.There was evidence of neuronal degeneration and enlarged perivascular spaces in the hippocampus in the microwave exposure groups.Further,mitochondria became swollen and cristae were disordered.The rough endoplasmic reticulum exhibited sacculated distension and there was a decrease in the quantity of synaptic vesicles.Conclusion These data suggest that the hippocampus can be injured by long-term microwave exposure,which might result in impairment of cognitive function due to neurotransmitter disruption.
2012, 25(2): 189-196. doi: 10.3967/0895-3988.2012.02.010
Objective To investigate the toxic effects of n-hexane on the Ganod of female mice.Methods n-Hexane was administered to four groups of mice by inhalation at doses of 0,3.0,15.1,and 75.8 mL/m3 respectivelyfor five weeks.Each group consisted of 10 mice,of which half were injected in first with 10 IU of pregnant mare serum gonadotrophin (PMSG) on the 33rd days,and then with 10 IU of human chorionic gonadotrophin (HCG) 48 hrs later.After the treatment,mouse sera were sampled and ovulating hormone (LH),follicle-stimulating hormone (FSH),estradiol (E2),and progesterone (P4) levelswere measured by electrochemiluminescence immunoassays (ECLIA).In each group,the right ovaries of the non-super-ovulated mice were stained with hematoxylin and eosin while ovaries on the left side were prepared with the TUNEL method in order to detect apoptotic cells.Results The duration of the diestrus stage decreased significantly (P＜0.05) in the 75.8 mL/m3 group.All super-ovulated mice in each treatment group produced fewer eggs than those in the control group (P＜0.05).The number of follicles in ovaries in the 75.8 mL/m3 group was smaller compared with the control group (P＜0.05).The serum P4 levels in each treatment group were lower than those in the control group (F=6.196,P＜0.01).The cell apoptotic rate in the 75.8 mL/m3 group was higher (P＜0.05).Conclusion n-Hexane may have directly mediated via alterations hormone secretion and promoted granulosal cell apoptotic,which may be one of the important mechanisms for n-hexane induced mouse ovary impairment.
Altered Expression of Matrix Metalloproteinases and Tight Junction Proteins in Rats following PEMF-Induced BBB Permeability Change
2012, 25(2): 197-202. doi: 10.3967/0895-3988.2012.02.011
Objective To investigate the expression of occludin,ZO-1,MMP-2,and MMP-9 in cerebral microvasculature following Pulse Electromagnetic Field (PEMF) induced BBB permeability change.Methods Sprague-Dawley rats were randomized into PEMF and sham exposed groups (n=8).After exposure to PEMF at 0.5,1,3,6,and 12 h,BBB permeability was measured by Evans-Blue extravasation.The expression of occludin,ZO-1,MMP-2,and MMP-9 were detected by real-time quantitative reverse transcriptase PCR and western blotting.MMP-2 and MMP-9 activity were detected by EnzChek gelatinase assay.Results Compared with the sham group,PEMF exposure led to increased permeability of the BBB to EB,which was prolonged after exposure.BBB permeability became progressively more severe,and recovered at 6 h.The gene and protein expression of occludin and ZO-1 were significantly decreased,while MMP-2 and MMP-9 expression were significantly increased after exposure to PEMF.All levels of expression recovered 12 h following PEMF.Conclusion Changes to BBB permeability were related to the alteration expression of tight junction proteins and matrix metalloproteinase after exposure to PEMF.
Construction and Secretory Expression of β-Galactosidase Gene from Lactobacillus Bulgaricus in Lactococcus Lactis
2012, 25(2): 203-209. doi: 10.3967/0895-3988.2012.02.012
Objective This study is to examine the secretion effects of β-galactosidase in Lactococcus lactis.Methods The usp45 and β-galactosidase genes were cloned and inserted into plasmid pMG36e to obtain the recombinant plasmid pMG36e-usp-lacZ.This recombinant plasmid was transformed into both Escherichia coli DH5α and L.lactis MG1363.The enzyme activity,gene sequencing,SDS-PAGE and hereditary stability were assessed and studied.Results The lacZ gene inserted into plasmids pMG36e-usp-lacZ was 99.37％ similar to the GenBank sequence,and SDS-PAGE revealed an evident idio-strap at 116 KDa between L.lactis MG1363/pMG36eusp-lacZ in both supernatant and cell samples.β-Galactosidase activity measured 0.225 U/mL in L.lactis pMG36e-usp-lacZ transformants,and its secretion rate was 10％.The plasmid pMG36e-usp-lacZ appeared more stable in MG1363.Conclusion The authors concluded that these new recombinant bacteria well expressed and secreted β-galactosidase,indicating that the β-galactosidase expression system was successfully constructed,and this might provide a new solution for management of lactose intolerance specifically and promote the use of gene-modified organisms as part of the food-grade plasmid in general.
Inhibitory Effect of Extracellular Polysaccharide EPS-II from Pseudoalteromonas on Candida adhesion to Cornea in vitro
2012, 25(2): 210-215. doi: 10.3967/0895-3988.2012.02.013
Objective Fungal keratitis (FK) is a vision-threatening infection,whose treatment requires more effective and safer anti-fungal agent exploitation urgently.With this aim,we focused on the effect of an extracellular polysaccharide on fungal adhesion to human corneal epithelial cells.Methods We performed the cytotoxicity assays of the extracellular polysaccharide EPS-Ⅱ from an antarctic bacterium Pseudoaltermonas and evaluated its inhibitory effect on Candida albicans cells'adherence to human corneal epithelial cells (HCECs).Results EPS-Ⅱ,which displayed minor cytotoxicity but also promoted proliferation of HCECs,could inhibit the adherence of yeast cells to HCECs in a dose-dependent manner.EPS-Ⅱ could also suppress the subsequent P13K/AKT signaling pathway,and thereby decrease the expression of early inflammatory cytokines.Conclusions Extracellular polysaccharide EPS-Ⅱ was suggested as a new natural agent for attenuating FK.
2012, 25(2): 216-223. doi: 10.3967/0895-3988.2012.02.014
Objective To investigate the toxic effect of sodium fluoride (NaF) on the nematode Caenorhabditis elegans (C.elegans).Methods Adult C.elegans were exposed to different concentrations of NaF (0.038 mmol/L,0.38 mmol/L,and 3.8 mmol/L) for 24 h.To assess the physiological effects of NaF,the brood size,life span,head thrashes,and body bend frequency were examined.Reactive oxygen species (ROS) and cell apoptosis were detected as parameters of biochemical response.The gene expressions were determined by real-time polymerase chain reaction (PCR) to assess the molecular-level response.Results At the physiological level,the brood size of C.elegans exposed to 0.038 mmol/L,0.38 mmol/L,and 3.8 mmol/L concentrations of NaF were reduced by 6％,26％,and 28％ respectively in comparison with the control group.The maximum life spans of C.e/elegans exposed to 0.038 mmol/L,0.38 mmol/L,and 3.8 mmol/L concentrations of NaF were reduced by 3 days and 5 days,respectively.Head thrashes and body bend frequency both decreased with increasing concentrations of NaF.At the biochemical level,the production of ROS and the incidence of cell apoptosis increased with increasing concentrations of NaF(P＜0.05).At the molecular level,different concentrations of NaF exposure raised the expression of stress-related genes,such as hsp16.1,sod-3,ctl-2,dhs-28,gst-1,and cep-1.Conclusion NaF exposure could induce multiple biological toxicities to C.elegans in a concentration-dependent manner.These toxicities may be relevant to the oxidative stress induced by increased ROS production and accumulation in C.elegans.
Laboratory Evaluation of the Molluscicidal Activity of Pulsatilla Chinensis (Bunge) Regel Saponins against the Snail Oncomelania Hupensis
2012, 25(2): 224-229. doi: 10.3967/0895-3988.2012.02.015
Objective To observe the toxicity of Pulsatilla chinensis (Bunge) Regel saponins (PRS) against Oncomelania hupensis (0.hupensis).Methods O.hupensis snails were exposed to 40％ and 80％ of 24 h LC50 of PRS for 24 h,and then choline esterase (CHE),alanine aminotransferase (ALT),alkaline phosphatase (ALP),lactate dehydrogenase (LDH) activities in cephalopodium and liver of snails were determined.Niclosamide (NIC) was used as the reference molluscicide.Zebra fish lethality test was evaluated to non-target aquatic species of PRS.Results The molluscicidal activity of PRS (LC50 at 24 h:0.48 mg/L) was similar to that of NIC (LC50 at 24 h:0.16 mg/L).Significant alterations about CHE,ALP,and ALT activities both in the cephalopodium and the liver of snails were observed when O.hupensis was exposed to 40％ and 80％ LC50 of PRS or NIC for 24 h.PRS and NIC could not affect LDH activity in the cephalopodium and the liver.Lower toxicity to fish of PRS was observed up to the highest concentration tested than NIC.Conclusion PRS,as compared with the reference molluscicide NIC,is thought to be used for the control of harmful vector snails safely.
Inactivation of Resistant Mycobacteria mucogenicum in Water: Chlorine Resistance and Mechanism Analysis*
2012, 25(2): 230-237. doi: 10.3967/0895-3988.2012.02.016
Objective To better understand the mechanism of chlorine resistance of mycobacteria and evaluate the efficiency of various disinfection processes.Methods Inactivation experiments of one strain Mycobacteria mucogenicum,isolated from a drinking water distribution system in South China were conducted with various chlorine disinfectants.Inactivation efficiency and disinfectant residual,as well as the formation of organic chloramines,were measured during the experiments.Results This strain of M.mucogenicum showed high resistance to chlorine.The CT values of 99.9％ inactivation by free chlorine,monochloramine and chlorine dioxide were detected as 29.6±1.46,170±6.16,and 10.9±1.55 min·(mg/L) respectively,indicating that chlorine dioxide exhibited significantly higher efficiency than free chlorine and monochloramine.It was also found that M.mucogenicum reacted with chlorine disinfectants more slowly than S.aureus,but consumed more chlorine disinfectants during longer time of contact.Lipid analysis of the cell construction revealed that 95.7％ of cell membrane lipid of M.mucogenicum was composed of saturated long chain fatty acids.Saturated fatty acids were regarded as more stable and more hydrophilic which enabled the cell membrane to prevent the diffusion of chlorine.Conclusion It was concluded that different compositions of cell membrane might endow M.mucogenicum with a higher chlorine resistance.
Effects of Echinacoside on Histio-central Levels of Active Mass in Middle Cerebral Artery Occlusion Rats*
2012, 25(2): 238-244. doi: 10.3967/0895-3988.2012.02.017
Objective To investigate the effects of echinacoside on the extracellular striatal levels of norepinephrine (NE),dopamine (DA),homovanillic acid (HVA),3,4-dihydroxyphenylethanoid acid (DOPAC),5-hydroxyindoleacetic acid (HIAA),and 5-hydroxytryptamine(5-HT) in middle cerebral artery occlusion (MCAO rats.Methods The middle cerebral artery was occluded in male Sprague-Dawley rats.Three days later microdialysis probes were placed into the right striatum of MCAO rat brains and the brains were perfused with Ringer's solution at a rate of 1.5 μL/min.Cerebral microdialysates were collected every 30 minutes from awake and freely moving rats before assaying for NE,DA,HVA,DOPAC,HIAA,and 5-HT levels by reverse phase HPLC with electrochemistry.Results Three days after MCAO,the extracellular striatal levels of NE,DA,DOPAC,HIAA,HVA,and 5-HT of the MCAO rats increased significantly (at least P＜0.05 vs.control).However,simultaneous treatment with echinacoside (30.0 or 15.0 mg/kg) attenuated these increases (at least P＜0.05 vs.non-treated model rats).Conclusion These results imply that echinacoside may protect striatal dopa minergic neurons from the injury induced by MCAO and may help prevent and treat cerebral ischemic diseases.
2012, 25(2): 245-249. doi: 10.3967/0895-3988.2012.01.012
Objective This paper aims to evaluate the genotoxicity in peripheral blood lymphocytes of rats after exposure to sunlight at different time points of day in a tropical region of Brazil (5°S,42°W).Materials and Methods Thirty Wistar-Hannover rats,three months old,were randomly divided into three groups of 10 animals each:Group Ⅰ [control,without exposure to ultraviolet (UV) radiation],Group Ⅱ (exposed to sunlight during 08:00 a.m.to 10:00 a.m.),and Group Ⅲ (exposed to sunlight during 10:00 a.m.to 12:00 a.m.).After a week of exposure,peripheral blood samples were taken from the tail of these animals to prepare smears on two slides per animal.In 24 h after exposure to sunlight in Group Ⅲ,a new collection was obtained to observe the repair activity.The alkaline comet assay was used in this study to evaluate the genotoxic activity of sunlight (P＜0.05).Results There was no statistical difference between Group Ⅰ and Ⅱ (P=0.672).On the other hand,the exposure to sunlight in Group Ⅲ showed genotoxic action in comparison to the other groups (P＜0.0001).Also,there was no significant repair in Group Ⅲ R (P=0.407).Conclusion This study has shown a genotoxic potential of sunlight (UVA-B) in lymphocytes of mammals from 10:00 a.m.to 12:00 a.m.,due to a higher intensity of UV in this tropical region.