Differential susceptibility to Brugia pahangi infection in Mongolian gerbils (Meriones unguiculatus) of different coat colour

The influence of intraspecific host variables on the response to parasitic infections is an important aspect of host-parasite relationships, yet little is known about this aspect of filariasis for lack of a model. This study presents coat colour mutants of the Mongolian gerbil (Meriones unguiculatus) as potential new models for research into the effects of host genetic variation on response to filarial infection. Peak level of microfilaraemia, eosinophil response, body weight and degree of splenomegaly in gerbils infected with Brugia pahangi varied with agouti, albino, and black coat colour. These results suggested that coat colour-related genes might influence host immune response to developmental stages of the parasite and eosinophil-mediated reaction might cause host damage.     

Phonotactic responses to vocalization in adult Mongolian gerbils (Meriones unguiculatus)

Mongolian gerbils have a rich repertoire of vocalization, with at least 13 distinct types of calls observed in a single colony. The purpose of this study was to compare the communicative value of these different call types in a standardized setting. Phonotactic behavior toward vocalizations delivered from loudspeakers was quantified by means of an eight-arm radial maze. Animals were observed to stay near the sound source for longer period of time when short bent-upward frequency-modulated (bUFM) calls, which are observed during seemingly friendly contact, were presented, while animals stayed significantly longer away from the speaker when arched FM (AFM) calls, which are produced by animals under severe physical stress, were presented. Our data show that an 8-arm radial maze can be used to study the function of Mongolian gerbil vocalization and suggest that both bUFM and AFM calls have communicative purposes, increasing the probability that recipient conspecifics approach or escape from the sound source, respectively.     

Brugia pahangi: infections and their effect on the lymphatic system of Mongolian jirds (Meriones unguiculatus)

Brugia pahangi has been found to be primarily a lymphatic-dwelling parasite in jirds when infections are induced by the subcutaneous injection of infective larvae or by allowing infected Aedes aegypti to feed.Migration to the regional lymphatics occurred as early as 1–4 days. Although some injected larvae remained in the skin for as long as 30 days and some became localized in the heart, lungs, pleural cavity, or peritoneal cavity, about three-fourths of the recovered filariae were found in the regional lymphatics. In contrast, when larvae were injected peritoneally they remained largely in the peritoneal cavity for at least 30 days.The relevant lymphatics and their drainage patterns in jirds have been described.The major pathological changes noted in jirds involved the regional lymphatic vessels and nodes, which were severely affected when they contained dead worms. Pulmonary granulomas due to dead microfilariae and occasionally to dead larvae or adult worms were noted.Observations are included on the susceptibility and course of B. pahangi infections in jirds.     

Induction of host resistance to Brugia pahangi in jirds (Meriones unguiculatus) protected by chemoprophylaxis

Jirds were given a chemoprophylactic inoculation of flubendazole (FMBZ) and then five injections of infective larvae of Brugia pahangi whilst still protected by the FMBZ. When the drug was thought to be non-effective the jirds (and controls) were given a challenge infection of B. pahangi larvae. By comparison with control jirds the treated-infected-challenged jirds had 40% fewer adult worms. The control treated-challenged jirds contained mostly sterile female worms showing that they were still partially protected by FMBZ but worms numbers were not significantly reduced as compared with untreated controls.     

长爪沙鼠的遗传多样性分析

利用17个微卫星DNA标记对Z:ZCLA长爪沙鼠封闭群、野生群和近交系进行遗传多样性分析, 评估群体内的遗传变异和群体间的遗传分化。结果表明：在Z:ZCLA封闭群和野生群中共有9个微卫星DNA标记获得稳定的结果, 分别为AF200940、AF200941、AF200942、AF200945、AF200946、AF200947、D11Mit128、PKC和 SCN, 共检测到41个等位基因, 每个基因的等位基因数从1～7不等, 片段大小在120～283 bp之间, 所有位点的平均期望杂合度(He)和多态信息含量(PIC)值分别为0.5032和0.4656, Z:ZCLA封闭群和野生群9个微卫星位点平均有效等位基因数分别为2.78和2.89, 平均基因杂合度分别为0.3704和 0.3893, 平均多态信息含量分别为0.3256和0.3344, 两个群体都表现为中度多态, Z:ZCLA封闭群较野生群稍低; 在3个近交系中共有8个位点获得稳定的扩增结果, 分别为AF200941、AF200942、AF200945、AF200946、AF200947、D11Mit128、PKC和 SCN, 共检测到11个等位基因, 片段大小在140~241 bp之间, 其中5个位点在群体内表现为单态纯合, 3个位点在群体内表现为单态杂合, 所有位点在群体内和群体间均呈单态性, 表明这3个长爪沙鼠品系基本符合近交系的要求, 微卫星标记技术适用于近交系长爪沙鼠的遗传检测。     

多巴胺对长爪沙鼠 贮食行为的影响

长爪沙鼠的贮食行为具有高低二型性。禁食诱导的贮食行为可能与中脑多巴胺系统（Dopamine,DA）有关,但尚乏证据。本文通过Fos标记相关脑区的活性,酪氨酸羟化酶（TH）标记DA神经元,以免疫组化方法观察高贮食组沙鼠腹腔注射DA拮抗剂haloperidol （1 mg/kg）和对低贮食组沙鼠腹腔注射DA激动剂apomorphine（0.3 mg/kg）的行为和神经变化,验证中枢DA对贮食行为的调节。结果显示,haloperidol抑制了禁食诱导的沙鼠的贮食行为,这种抑制刺激了伏隔核和尾壳核Fos-ir阳性细胞表达,但却降低了黑质区Fos-ir和Fos-ir/TH-ir的细胞表达。Apomorphine增加了禁食诱导的沙鼠的贮食行为,且降低伏隔核和尾壳核Fos-ir阳性细胞表达。这些结果表明,中脑DA系统参与调节了禁食条件下长爪沙鼠的贮食行为。     

Benign testicular hyperplasia in Mongolian gerbils (Meriones unguiculatus)

At necropy, 20 out of 35 Mongolian gerbils (Meriones unguiculatus) with prolonged infertility at 12-30 weeks of age were found to have spontaneous hyperplasia in both seminiferous and epididymal tubules. This high incidence of hyperplasia in young gerbils is indication of possible congenital lesions and suggests the possibility of using these animals as a useful model for the further study of male infertility.     

长爪沙鼠种群繁殖的季节性特征

长爪沙鼠是分布于我国北方典型和荒漠草原及农牧交错区的优势鼠种之一。2000 年10 月至2004 年10 月通过标志重捕法研究了栖息于内蒙古农牧交错区草地生境的种群动态。对其不同季节出生群性成熟特征和种群性成熟比率、繁殖个体比例、个体月补充率等繁殖参数的季节特征研究显示:冬季和春季出生的个体性成熟较夏季出生的个体快,尤雌鼠表现突出,其3 个季节出生群的性成熟时间分别为4. 6 ± 0.2、4. 4 ± 0.8 和7.7 ± 0.4月龄。种群性成熟比率、繁殖个体比例和个体补充率月间差异显著,季节消长明显,即春季最高,秋季(9 ～10月间)最低。结果还显示,种群性成熟比率与气温和降水负相关。长爪沙鼠喜栖于植被稀疏、低矮的干燥沙质土壤环境。从初春到夏末,随降水和气温增加其栖息生境的植被由低矮稀疏变得高而稠密,土壤湿度和粘性亦随之提高,地面种子库因发芽贮量减少,适宜生境的减少可能加剧了社群竞争,抑制了种群的繁殖表现。长爪沙鼠种群繁殖的季节变化反映了其生活史对策中适应高纬度气候和食物的季节波动的重要特征。     

Indicators for post-surgery recovery in Mongolian gerbils (Meriones unguiculatus)

Telemetric investigations of various parameters are widely used to estimate an animal's state. However, the implantation of the transmitters includes anaesthesia and surgery and has short and longer lasting impacts on the studied object. The aim of the present paper was to evaluate these effects in Mongolian gerbils, namely the hypothermia caused by the anaesthetic and the enduring disturbance of daily rhythmicity until complete recovery. The surgery associated with the implantation of the transmitters differed both in severity and type of anaesthesia. Whereas normal values of body temperature were restored within hours, restoration of daily rhythm required several days, depending on the severity of the surgical procedure. Also, the sensitivity of the body temperature to activity changes was different until the rhythms were re-established. A method based on the rhythm magnitude and shape was proposed to estimate the time until complete recovery of the animals.     

禁食时间对雌性长爪沙鼠免疫功能的影响

动物的免疫系统是防御细菌、病毒等病原体侵害的重要途径,对其生存很重要,而食物短缺是影响动物免疫的重要因素。前期研究发现,禁食3天可抑制雌性长爪沙鼠T细胞介导的免疫功能,而禁食时长可能在影响动物免疫中起重要作用。为此,本实验主要测定不同的禁食时间如何影响雌性长爪沙鼠的免疫功能,该问题的解决有助于理解它们在野外面临食物短缺时的生存状况。将55只成年雌鼠随机分为8组,分别禁食1 d、2 d 、3 d和自由取食,每种处理又分别注射磷酸缓冲液和植物血凝素（PHA）。结果发现,随禁食时间的延长,PHA反应（指示T细胞介导的免疫功能）逐渐受到抑制,胸腺和脾脏逐渐萎缩,表明禁食时间对长爪沙鼠的免疫功能影响显著。同样,随饥饿时间增加,长爪沙鼠的体脂、血糖和血清瘦素水平逐渐下降,并且与PHA反应呈正相关,但白细胞总数和皮质酮水平不受禁食时间的影响。结果表明,禁食时间长短能显著影响雌性长爪沙鼠的免疫功能,随禁食时间的延长,长爪沙鼠T细胞介导的免疫功能逐渐受抑制,这可能与体脂和葡萄糖含量下降有关,血清瘦素逐渐降低也可能是其免疫受抑制的原因。     

Effect of different photoperiods on gonadal maintenance and development in Mongolian gerbils (Meriones unguiculatus)

The role of photoperiod in adult testicular maintenance and body weight and juvenile development was assessed in male Mongolian gerbils (Meriones unguiculatus). Gerbils were raised on a 14L (14 hr of light) photoperiod. In the first study, adult gerbils with functional testes were transferred to thirteen different photoperiods (0L, 2L, 4L, 6L, 8L, 10L, 12L, 14L, 16L, 18L, 20L, 22L, or 24L) and body weights and testicular size were measured every week for 10 weeks. Body weights were similar in all groups. Testicular regression had occurred in animals housed on 0L, 2L, 4L, 6L, 8L, and 24L by week 10. In the second study, 14L-born prepubertal gerbils were transferred to thirteen different photoperiods as in the first study. Body weights and testicular development were examined for 10 weeks. At the end of 10 weeks the body weights of animals in all groups except 24L were similar to those of adults. Animals in 24L had a lower body weight gain. Exposure to 0L, 2L, and 24L inhibited testicular development and testes weights were significantly different from those of the other groups. These results demonstrate that maintenance of body weight in adult gerbils appears to be independent of photoperiodic signal. Exposure to very long (24L) and short photoperiods (< 10 hr) causes testicular regression in adult gerbils. Moreover, different photoperiods experienced in early life can influence prepubertal testis growth and body weight gain.     

雷公藤制剂对雄性长爪沙鼠繁殖功能的影响

为了检测雷公藤制剂对长爪沙鼠繁殖功能的影响,根据预实验结果,将40只雄性长爪沙鼠分为40 mg/kg连续用药4周组(n=16)、100 mg/kg一次给药组(n=10)和1%CMC灌胃对照组(n=14)处理,6周后剖检,比较睾丸、附睾的脏器系数、精子密度、精子活力、精子形态和繁殖率等指标.结果表明40 mg/kg连续用药组鼠的睾丸、附睾脏器系数与对照组比较差异显著;精子密度、精子活力和活精子百分率显著下降;精子畸形率显著上升;繁殖率显著下降(df=1,P<0.05).100 mg/kg一次给药组除附睾脏器系数显著下降、精子畸形率显著上升外,其它指标与对照组无明显差异.该药对长爪沙鼠连续作用4周后不育效果明显,并且具有致畸性,在药物有效范围内,高浓度一次性给药方式不如较低浓度连续多次给药效果显著.     

Determination of halothane ED-50 in Mongolian gerbils (Meriones unguiculatus)

The effective dose-50 (ED-50) for halothane anesthesia was studied in 45 male Mongolian gerbils at age 12 weeks. Close control of circadian variation and animal temperature was maintained. Regression analysis for the percent of animals moving in response to a standard stimulus revealed an ED-50 of 1.32 volumes %, a concentration that approximates the ED-50 of the rat.     

Improving the productivity of breeding colonies of Mongolian gerbils (Meriones unguiculatus)

The productivity of breeding colonies of Mongolian gerbils can be substantially enhanced by using as breeding stock only the 40% of females that exhibit vaginal opening before reaching 25 days of age. Early-maturing females are more likely to breed successfully on first pairing. The lifetime fecundity of early-maturing females is more than twice that of their late-maturing sisters. In those cases in which early-maturing females fail to breed with the first male with which they are paired, they (but not late-maturing females) can be mated with a second male with a high probability of success. Two-thirds of the early-maturing females that failed to reproduce following a first pairing became pregnant following a second. Only 11% of late-maturing females did so.     

Infectivity of cryopreserved Giardia cysts for Mongolian gerbils (Meriones unguiculatus)

Although Giardia species trophozoites have been cryopreserved successfully, no report on the successful cryopreservation of cysts could be found. Using infectivity to Mongolian gerbils (Meriones unguiculatus) as a measure of cyst viability, we tested the viability of 4 strains of Giardia cysts that had been cryopreserved for 1-67 wk. Cysts were frozen in either Keister's medium or physiological saline, both containing 5% or 7.5% dimethylsulfoxide as the cryoprotectant. Viability of cryopreserved cysts was dependent upon the number of cysts inoculated, the length of time cysts were held at 4 C before cryopreservation, and the cryopreserving medium. Infection was established in gerbils by inoculating them with cysts that had been cryopreserved for up to 67 wk, cysts that had been held for less than 30 days before cryopreservation, and cysts frozen in Keister's medium. Saline appears to be unsuitable as a freezing medium for the cryopreservation of Giardia cysts.     

Increased susceptibility to infection with Brugia pahangi in aged female jirds (Meriones unguiculatus)

Female Mongolian jirds, Meriones unguiculatus, from 5 age groups of 2, 12, 16, 21, and 28 months, were infected with Brugia pahangi. Infections were followed for 125 days by weekly bleedings beginning 55 days postinoculation. Jirds were then killed and adult parasites recovered. Results showed a significant shortening of the prepatent period in the 12-, 21-, and 28-month-old groups. The proportion of gravid female worms did not vary significantly among the 5 groups. Similarly, the ratio of females to male worms showed little variation from group to group. Microfilaremia data for the 5 infection groups show an age-associated increase in numbers of circulating microfilariae. Some individuals in the 28-month group demonstrated 1,500 to 3,000 microfilariae per 0.25 ml peripheral blood, a level that was not approached by young females.     

剥夺食物对雄性长爪沙鼠贮食行为的影响

禁食导致一些啮齿动物的贮食量增加,但禁食处理后雄性长爪沙鼠贮食行为的变化则不一致。每天禁食22 h,长爪沙鼠的一些个体表现出高水平的贮食行为(禁食贮食组),而另一些个体则没有表现出贮食行为(禁食无贮食组)。延长禁食(22 h)持续的时间(连续重复3 d 和20 d)和增加禁食时间(禁食48 h),都没有使禁食无贮食组的动物表现出贮食行为。同样在自由取食条件下,长爪沙鼠的贮食行为也表现为二型性。在自由取食和禁食条件下,贮食量与体重、体脂含量和瘦素的浓度之间无明显相关关系。研究结果表明,禁食是诱导雄性长爪沙鼠贮食行为发生的一个重要条件,但增加禁食的程度并不改变其贮食行为的表现。     

Intraperitoneal versus subcutaneous telemetry devices in young Mongolian gerbils (Meriones unguiculatus)

Radiotelemetry has become a very popular biotelemetric tool for measuring physiological parameters such as heart rate, blood pressure, body temperature and muscle activity, as well as general behavioural activity in undisturbed, freely moving animals. In most studies using this technique, adult subjects are used. However, sometimes an ontogenetic approach is required to clarify whether changes in one parameter are preceeded or followed by changes in another parameter. Tracking physiological changes in young, developing individuals could explain given states of these animals as adults. Implanting telemetry devices can be done subcutaneously and intraperitoneally, the former method posing less of a challenge on the animal and its recovery from surgery. Because telemetry will be used in weanling gerbils during subsequent studies, we needed to investigate whether subcutaneous implantation of telemetric devices is preferable to intraperitoneal surgery with respect to animal welfare. This is a technical paper describing anaesthetic and surgical techniques in detail during a pre-trial involving subcutaneous (n=10, aged 21-29 days) and intraperitoneal (n=10, aged 19-34 days) implantation of dummy telemetry transmitters (1.9 cm3, 3.6 g after shortening of leads) in weanling gerbils, Meriones unguiculatus. Body weight was measured and analysed over four-day intervals. Optimizing anaesthetic dosages was a first step in this pilot trial. This occurred during the first few subcutaneous implantations. Three animals died while anaesthetized during the subcutaneous procedure but none post-surgery. All animals survived anaesthesia during the intraperitoneal implantation, but two died in the first three days post-surgery. In the former method, the tension on the dermal sutures caused by the presence of the transmitters was too great, resulting in the animals opening the sutures by chewing them. The animals died during the latter procedure probably due to strangulation of the intestine by the excess lead that was coiled in the abdomen. Furthermore, placement of the exposed negative lead of the transmitter on the underlying muscle had to be done on the m. pectoralis transversus in order for it to stay in place as the animal developed. This paper showed that the implantation of a telemetric device in weanling gerbils is feasible and is best executed through the intraperitoneal technique.