Baclofen is cytoprotective to cerebral ischemia in gerbils

The release of the neurotransmitter, glutamate, and the activation of receptor operated calcium channels, may increase the degree of damage in ischemic brain tissue. Inhibition of excitatory neurotransmitters should therefore result in cytoprotection of ischemic brain tissue. In this study we evaluated the effect of baclofen, an inhibitor of presynaptic glutamate release, on ischemic gerbil cortex, hippocampus (CA 1 and CA4), striatum and thalamus. Histological evaluation was done in a blind manner in 4 groups (total 36 animals): a control group (9 animals) and three groups (27 animals) with varying doses of baclofen. For cerebral ischemia, we used single episode of five minutes of arterial occlusion of the carotid arteries. Baclofen in doses of 0, 25, 50, and 100 mg/kg were given to different groups five minutes prior to ischemic insult. This was followed by intraperitoneal injections given 24 and 48 hours after the initial insult. Statistically significant histological cytoprotection was demonstrated. Doses of 25 mg/kg appeared to demonstrate significant protection of the cortex (p=0.0002), the CA1 and CA4 regions of the hippocampus (p=0.0004 and 0.0001) respectively. At a dose of 50 mg/kg, significant cytoprotection was demonstrated at the hippocampus (CA1 and CA4 regions), in particular at the CA4 region (p=0.0029). The 100 mg/kg dose appeared to have most significant protection at the CA1 and CA4 regions of the hippocampus (both p=0.0001), striatum (p=0.0011), and the thalamus (p=0.0008). All statistical comparisons were done using non-parametric tests (Mann-Whitney U test). Our study demonstrates that baclofen is cytoprotective to ischemic neuronal cells, especially in the hippocampus. Clinically this may be beneficial to those patients with strokes or head injuries.     

长爪沙鼠的贮食行为与其个性和代谢水平之间的关系

贮食行为是动物应对食物资源的季节性和不可预测性变化的一种适应性生存策略。在群居性贮食动物中,同胎个体常表现出不同的贮食水平,而关于贮食行为与动物的个性和代谢水平之间的关系尚缺乏研究。本文以长爪沙鼠（Meriones unguiculatus）为对象,在筛选出具有高贮食和低贮食行为特征个体的基础上,比较了两组动物的个性特征（勇敢行为和探索能力）、静止代谢率、血清甲状腺激素水平、贮食期间的运动距离和贮食后的平均每日代谢率等。结果发现：高、低贮食长爪沙鼠的数量各占49%（22/45）和47%（21/45）,两组动物之间的个性特征、静止代谢率和血清甲状腺激素均没有显著差异。在贮食期间高贮食个体的运动距离显著高于低贮食个体,且在停止贮食后,高贮食个体的平均每日代谢率显著低于低贮食个体。这些结果表明,在室内条件下,长爪沙鼠的贮食量高低与个性和静止代谢率无关,但高贮食个体会在停止贮食后降低其总能量消耗,以补偿贮食过程中的高能量代价。     

Annual cycles of four flea species in the central Negev desert

Bionomics of fleas (Siphonaptera) parasitizing rodent hosts, mostly the gerbil Gerbillus dasyurus (Wagner) and the jird Meriones crassus Sundevall (Gerbillidae), were investigated in the central Negev desert of Israel. Populations were sampled weekly (by Sherman trapping of hosts) from August 2000 to July 2001. Among 1055 fleas of nine species captured, four species predominated (94%). Two species of Pulicidae, Xenopsylla dipodilli Smit and X. ramesis (Rothschild), reproduced perennially, whereas adults of Nosopsyllus iranus theodori Smit (Ceratophyllidae) and Stenoponia tripectinata medialis Jordan (Hystrichopsyllidae) occurred only in cool months (October-March). During their main activity season on the most infested host species (estimated from > 300 trap-nights/month), prevalence of these four flea species reached 40-70%, 20-30%, 100% and 50-70%, respectively, with infestation intensities of 2-2.7, 7-12, 2-3.5 and 2.5-7 fleas per infested rodent, respectively. Xenopsylla dipodilli oviposition peaked during autumn with parous rate > 80% by September-October. During December-April, the majority of X. dipodilli females were immature and/or nulliparous (defined as having mature ovaries but no follicular relics). In contrast, X. ramesis had two reproductive peaks, in mid-spring and autumn, evidenced by the influx of immature females in late spring and summer (30-40%) and in winter (20-30%) after maximal parous rates: 80-100% in March-April and 95-100% in October-November. Nosopsyllus iranus theodori and Stenoponia tripectinata medialis adults occurred only during cool months. At the beginning of activity, during October-November, the sex ratio of N. i. theodori was strongly biased to females (86%) that were immature and/or nulliparous. In winter, adult females were 52-65% parous and 10-32% immature. In March, as the adult population of N. i. theodori declined, 78% of females were parous and 12% immature. Seasonal activity of S. t. medialis (November-March) was shorter than for the other three species; females were predominantly nulliparous in November (80%), after which the proportion of parous females increased gradually to 84% in February. Two females of S. t. medialis collected in March were mature but nulliparous, suggesting that this species of flea might 'oversummer' (as pupae or teneral adults) in the cocooned stage.     

Profiling and identification of eubacteria in the stomach of Mongolian gerbils with and without Helicobacter pylori infection

Background. Mongolian gerbils are frequently used to study Helicobacter pylori‐induced gastritis and its consequences. The presence of an indigenous bacterial flora with suppressive effect on H. pylori may cause difficulties with establishing this experimental model. Aim. The aim of the present study was to determine bacterial profiles in the stomach of Mongolian gerbils with and without (controls) H. pylori infection. Methods. Gastric tissue from H. pylori ATCC 43504 and CCUG 17874 infected and control animals were subjected to microbial culturing and histology. In addition, gastric mucosal samples from H. pylori ATCC 43504 infected and control animals were analyzed for bacterial profiling by temporal temperature gradient gel electrophoresis (TTGE), cloning and pyrosequencing of 16S rDNA variable V3 region derived PCR amplicons. Results. Oral administration of H. pylori ATCC 43504, but not CCUG 17874, induced colonization and gastric inflammation in the stomach of Mongolian gerbils. Temporal temperature gradient gel electrophoresis (TTGE) and partial 16S rDNA pyrosequencing revealed the presence of DNA representing a mixed bacterial flora in the stomach of both H. pylori ATCC 43504 infected and control animals. In both cases, lactobacilli appeared to be dominant. Conclusion. These findings suggest that indigenous bacteria, particularly lactobacilli, may have an impact on the colonization and growth of H. pylori strains in the stomach of Mongolian gerbils.     

Effects of diet quality on phenotypic flexibility of organ size and digestive function in Mongolian gerbils (Meriones unguiculatus)

In the context of evolution and ecology, there is a trade-off between the benefits of processing food through a digestive system with specific phenotypic attributes and the cost of maintaining and carrying the digestive system. In this study, we tested the hypothesis that digestive modulations at several levels can match each other to meet the energy and nutrient demands of Mongolian gerbils, a small granivorous rodent species, by acclimating them to a high-quality diet diluted with alfalfa powder. Mongolian gerbils on the diluted diet maintained metabolizable energy intake by an integrated processing response (IPR), which included increases in dry matter intake, gut capacity and rate of digesta passage after 2-weeks of acclimation. Down-regulation of hydrolytic enzyme activity in the intestinal brush-border membrane supported the adaptive modulation hypothesis. The absence of up-modulation of summed enzyme hydrolytic capacity on the diluted diet indicated that greater mass of small intestine on a high-fibre diet is not a direct indicator of digestive or absorptive capacity. Changes in mass of vital organs and carcass suggested that the amount of energy allocated to various organs and hence physiological functions was regulated in response to diet shift.     

Identification of Helicobacter pylori strain cagPAI+ and cagPAI- Antigens by IgG antibodies from sera of experimentally colonized meriones unguiculatus (Mongolian gerbils)

Background: Mongolian gerbils that are experimentally infected with Helicobacter pylori develop a chronic inflammation that is similar to natural infections in humans. The aim of this study was to compare the antigens of H. pylori cagPAI+ and cagPAI? strains that are expressed during Meriones unguiculatus colonization. Materials and Methods: We identified H. pylori cagPAI+ and cagPAI? strain antigens via Western blotting of samples from Mongolian gerbils that were subjected to unique, mixed, and sequential bacterial infections. Results: The antigens from the J99/CG3 (cagPAI+) strain had a lower molecular weight than the antigens from the 251F/CG3 (cagPAI?) strain. There were fewer identified antigens in the single unique infections compared with the mixed and sequential infections. The number of recognized antigens that had a frequency of recognition >60% was higher for the simultaneous and sequential infection groups compared with the single infection group. A 57‐kDa antigen was present in >60% of the samples and four of the five experimental groups. Antigens specific to each bacterial strain were identified; the 190‐ and 158‐kDa antigens appear to be specific for cagPAI?, and the 70‐kDa antigen appears to be specific for cagPAI+. Conclusions: In this study, we identified antigens that are common and specific to the H. pylori cagPAI+ and cagPAI? strains.     

Gastric and duodenum microflora analysis after long-term Helicobacter pylori infection in Mongolian Gerbils

Background: Long‐term Helicobacter pylori infection leads to chronic gastritis, peptic ulcer, and gastric malignancies. Indigenous microflora in alimentary tract maintains a colonization barrier against pathogenic microorganisms. This study is aimed to observe the gastric and duodenum microflora alteration after H. pylori infection in Mongolian Gerbils model. Materials and Methods: A total of 18 Mongolian gerbils were randomly divided into two groups: control group and H. pylori group that were given H. pylori NCTC J99 strain intragastrically. After 12 weeks, H. pylori colonization was identified by rapid urease tests and bacterial culture. Indigenous microorganisms in stomach and duodenum were analyzed by culture method. Histopathologic examination of gastric and duodenum mucosa was also performed. Results: Three of eight gerbils had positive H. pylori colonization. After H. pylori infection, Enterococcus spp. and Staphylococcus aureus showed occurrences in stomach and duodenum. Lactobacillus spp. showed a down trend in stomach. The levels and localizations of Bifidobacterium spp., Bacteroides spp., and total aerobes were also modified. Bacteroides spp. significantly increased in H. pylori positive gerbils. No Enterobacteriaceae were detected. Positive colonization gerbils showed a higher histopathologic score of gastritis and a similar score of duodenitis. Conclusions: Long‐term H. pylori colonization affected the distribution and numbers of indigenous microflora in stomach and duodenum. Successful colonization caused a more severe gastritis. Gastric microenvironment may be unfit for lactobacilli fertility after long‐term H. pylori infection, while enterococci, S. aureus, bifidobacteria, and bacteroides showed their adaptations.     

Social stress decreases marking behavior independently of testosterone in Mongolian gerbils

This study examined the endogenous androgen regulation of the marking behavior in Mongolian gerbils (Meriones unguiculatus). In the first experiment, developmental changes of fecal testosterone levels, ventral gland growth, and the marking frequency of male gerbils were investigated. From 9 weeks of age, marking frequency increased with increases in fecal testosterone levels and ventral gland size. The ventral gland size and marking frequency were significantly correlated to the fecal testosterone level. In the second experiment, we hypothesized that reduction in the marking frequency of subordinate males after social confrontations was controlled by a decrease in the circulating testosterone level, and we followed changes in marking frequency, endocrine status, and ventral gland size after social confrontations in which two adult male gerbils established their social ranks by fighting. As expected, marking frequency and ventral gland size were significantly related to social rank, that is, marking frequency was higher among dominant gerbils and lower among subordinates. In addition, fecal corticosterone levels among subordinates were higher than those of dominant animals. However, neither the fecal and plasma testosterone levels, nor testis size, differed between dominant and subordinate gerbils. These results revealed that endogenous androgen played a role in regulating marking behavior and ventral gland size during the developmental stage and that the reductions in marking frequency and ventral gland size occurring in subordinate males after social confrontations were not directly regulated by androgen changes.     

链脲佐菌素诱导长爪沙鼠Ⅰ型糖尿病模型的实验研究

目的探讨链脲佐菌素(STZ)诱导长爪沙鼠Ⅰ型糖尿病模型的可能性,并观察模型动物早期肾脏损害情况。方法雄性长爪沙鼠96只,随机分为正常对照组(NC组)、模型组1(DM1组)、模型组2(DM2组),DM1及DM2组沙鼠分别一次性腹腔注射100 mg/kg、200 mg/kg STZ,NC组注射等量柠檬酸盐缓冲溶液。注射STZ后1、2、4、6周末,分别监测沙鼠一般情况,血糖、胰岛素等血清学指标和尿液指标,并处死沙鼠进行胰腺和肾脏组织的病理学检查。结果注射STZ 24 h后,DM2组及DM1组部分沙鼠逐渐出现典型的"三多一少"症状,随着病程的发展,DM2组沙鼠持续高血糖,DM1组沙鼠血糖值与NC组差异有显著性(P0.05),但有下降趋势;DM2组沙鼠胰岛素显著性降低(P0.05),其他血清学指标及尿液指标均显著性升高(P0.05),DM1组沙鼠各指标差异无显著性。DM2组沙鼠及DM1组少数沙鼠胰腺组织中可见胰岛β细胞减少、空泡样变性等变化,DM2组沙鼠肾脏组织中出现肾小球基质增多,毛细血管襻扩张等病变,DM1组沙鼠肾脏组织未见明显变化。结论 STZ 200 mg/kg可成功诱导长爪沙鼠Ⅰ型糖尿病模型,在病程早期沙鼠肾脏结构和功能已经发生改变。