Development of a new cerebral ischemia reperfusion model of Mongolian gerbils and standardized evaluation system

Background:The Mongolian gerbil is an excellent laboratory animal for preparing the cerebral ischemia model due to its inherent deficiency in the circle of Willis.However,the low incidence and unpredictability of symptoms are caused by numerous complex variant types of the circle.Additionally,the lack of an evaluation system for the cer-ebral ischemia/reperfusion(I/R)model of gerbils has shackled the application of this model.Methods:We created a symptom-oriented principle and detailed neurobehavioral scoring criteria.At different time points of reperfusion,we analyzed the alteration in locomotion by rotarod test and grip force score,infarct volume by triphenyltetrazo-lium chloride(TTC)staining,neuron loss using Nissl staining,and histological charac-teristics using hematoxylin-eosin(H&E)straining.Results:With a successful model rate of 56%,32 of the 57 gerbils operated by our method harbored typical features of cerebral I/R injury,and the mortality rate in the male gerbils was significantly higher than that in the female gerbils.The suc-cessfully prepared I/R gerbils demonstrated a significant reduction in motility and grip strength at 1 day after reperfusion;formed obvious infarction;exhibited typi-cal pathological features,such as tissue edema,neuronal atrophy and death,and vacuolated structures;and were partially recovered with the extension of reperfu-sion time.Conclusion:This study developed a new method for the unilateral common carotid artery ligation I/R model of gerbil and established a standardized evaluation system for this model,which could provide a new cerebral I/R model of gerbils with more practical applications.

Temporal and spatial distribution characteristics in the natural plague foci of Chinese Mongolian gerbils based on spatial autocorrelation

Background:The nest flea index of Meriones unguiculatus is a critical indicator for the prevention and control of plague,which can be used not only to detect the spatial and temporal distributions of Meriones unguiculatus,but also to reveal its cluster rule.This research detected the temporal and spatial distribution characteristics of the plague natural foci of Mongolian gerbils by body flea index from 2005 to 2014,in order to predict plague outbreaks.Methods:Global spatial autocorrelation was used to describe the entire spatial distribution pattern of the body flea index in the natural plague foci of typical Chinese Mongolian gerbils.Cluster and outlier analysis and hot spot analysis were also used to detect the intensity of clusters based on geographic information system methods.The quantity of M.unguiculatus nest fleas in the sentinel surveillance sites from 2005 to 2014 and host density data of the study area from 2005 to 2010 used in this study were provided by Chinese Center for Disease Control and Prevention.Results:The epidemic focus regions of the Mongolian gerbils remain the same as the hot spot regions relating to the body flea index.High clustering areas possess a similar pattern as the distribution pattern of the body flea index indicating that the transmission risk of plague is relatively high.In terms of time series,the area of the epidemic focus gradually increased from 2005 to 2007,declined rapidly in 2008 and 2009,and then decreased slowly and began trending towards stability from 2009 to 2014.For the spatial change,the epidemic focus regions began moving northward from the southwest epidemic focus of the Mongolian gerbils from 2005 to 2007,and then moved from north to south in 2007 and 2008.Conclusions:The body flea index of Chinese gerbil foci reveals significant spatial and temporal aggregation characteristics through the employing of spatial autocorrelation.The diversity of temporary and spatial distribution is mainly affected by seasonal variation,the human activity and natural factors.

Impairment of cellular and humoral immunity in overweight Mongolian gerbils (Meriones unguiculatus)

Animal immunity is usually impaired in obesity.We know little about the effect of being overweight or obese on the immune function of wild rodents.The present study is aimed to test the hypothesis that immunity is suppressed in overweight Mongolian gerbils(Meriones unguiculatus).In the study,16 overweight(body mass:90.8-127.6 g)and 16 lean gerbils(body mass:60.5-77.7 g)were randomly selected from a total of 174 male gerbils(body mass range:55.8-144.7 g).Half of the overweight and lean males were injected with sterile saline;the others were immunochallenged(IC)with phytohaemagglutinin and keyhole limpet hemocyanin to assess cellular and humoral immunity,respectively.Body fat mass,wet and dry spleen mass,leukocyte counts,blood glucose levels and serum leptin levels were significantly higher in the overweight gerbils than in the lean gerbils.However,phytohemagglutinin response indicative of cellular immunity and immunoglobulin G concentrations was significantly lower in the IC overweight gerbils than in the IC lean gerbils.These results indicate that cellular and humoral immunity are impaired in the overweight gerbils.Excessive body fat mass,higher leukocyte counts and serum leptin levels imply that overweight gerbils are in a low grade inflammatory state.

Tyrosinase (Tyr) Gene Mutation in Albino Mongolian Gerbil (Meriones unguiculatus)

Tyrosinase is encoded by the Tyr (c or albino) locus and is the key enzyme in pigment biosynthesis. Loss of function of this enzyme caused by gene mutation results in albinism. Most cases of albinism are caused by missense mutations of tyrosinase. Albino mutations in Tyr have been identified in various animals, including human, mouse, rat, rabbit, cattle, cat, and ferret, but not in gerbil. We created two new gerbil strains: MON/Num/a (inbred agouti phenotype) and MON/Num/c (albino phenotype). Here, we report that four nucleotide substitutions in the Tyr gene caused two missense mutations in amino acids in the albino gerbil: a G-to-A mutation at position 204 in exon 1 caused R77H, and A-to-G at position 1392 and G-to-T at position 1393 in exon 5 caused Q473R. The substitution at position 1408 in exon 5 was silent. These missense mutations are conserved in all albino phenotypes we tested. Therefore, we suggest that these mutations are responsible for albinism in gerbil.

Role of transient receptor potential vanilloid-1 in behavioral thermoregulation of the Mongolian gerbil Meriones unguiculatus

Ambient temperature considerably affects the physiology and behavior of mammals.Thermosensory and thermoregulatory abilities play an important role in the response to changing ambient temperature in endotherms.However,the molecular mechanisms of behavioral thermoregulation remain poorly understood.Transient receptor potential vanilloid-1(TRPV1)is activated by changes in ambient temperature and is involved in acute thermoregulation.Here,we aimed to determine whether TRPV1 is involved in behavioral thermoregulation in wild rodents by conducting 2 experiments.In the first,42 adult Mongolian gerbils(Meriones unguiculatus;14 per treatment)were randomly assigned to 3 housing temperatures(4,23,and 36℃for 4 weeks.In the second,20 gerbils(10 per treatment)were randomly injected with capsaicin(TRPV1 agonist)or AMG517(TRPV1 antagonist).The results showed a significant decrease in food intake and non-shivering thermogenesis in the gerbils housed at 36℃.Additionally,there was a significant increase in the preference of gerbils housed at 4℃ to low temperatures.The expression of TRPV1 protein in the brown adipose tissue(BAT)and liver was significantly positively correlated with that of protein kinase A(PKA).The expression of TRPV1 and PKA proteins in the BAT was positively correlated with the temperature preference of the gerbils.The gerbils injected with capsaicin preferred significantly lower temperatures than the control group gerbils.These findings suggest that TRPV1 and PKA are involved in behavioral thermoregulation in Mongolian gerbils.

Effects of levonorgestrel-quinestrol(EP-1)treatment on Mongolian gerbil wild populations:a case study

Rodent pest population outbreaks occur frequently in grassland ecosystems in northern China.The Mongolian gerbil(Meriones unguiculatus)is a dominant pest rodent which is distributed across the semi-desert grasslands of Inner Mongolia,China.In 2009,we studied the contraceptive effect of levonorgestrel-quinestrol(EP-1),concentration 50 ppm,on a wild Mongolian gerbil population.The one-off contraceptive treatment was compared with a control group using a semi-monthly live trapping method in the Ordos Semi-desert Grassland Region of Inner Mongolia.The results show that juveniles were not recruited in spring in the treatment group.Ratios of juveniles in the control and treatment groups showed significant semi-monthly differences from spring to summer(one-way ANOVA,F_(2,14)=7.53,P<0.05).Between both groups,annual fluctuations of juvenile and total population densities were significantly different respectively(F_(2,14)=4.64,P<0.05;F_(2,18)=7.72,P<0.05).The contraceptive EP-1 delayed the normal reproductive pattern of Mongolian gerbil populations.This suppressed birth rates of gerbil populations,reduced their densities,and changed their age structures.The period of EP-1 baiting should be extended but it could be an ideal method for controlling Mongolian gerbil populations during each breeding season.