长爪沙鼠产后发育中线粒体产能

本文通过产后1日龄到3O日龄长爪沙鼠肝脏和棕色脂肪组织的线粒体研究揭示,肝线粒体在出生后的呼吸速率、氧化磷酸化作用以及细胞色素氧化酶活力均达到恒定水平。肝线粒体蛋白质量随胎后发育日龄而增加,直至2O日龄左右,琥珀酸氧化酶活力在此时也增加到近于恒定,因此肝线粒体产能发育随日龄增长到2O日龄右。这可能是长爪沙鼠体温调节发育的细胞机制之一。从棕色脂肪线粒体的细胞色素氧化酶和琥珀酸氧化酶活力的变化,显示棕色脂肪组织在长爪沙鼠新生幼仔阶段产热中所起的重要作用。     

The transmission of an avian filarioid Cardiofilaria nilesi to the jird, Meriones unguiculatus

This paper reports the experimental transmission of a bird parasite into jirds. Infective larvae of Cardiofilaria nilesi obtained from laboratory colonized Coquillettidia crassipes mosquitoes which had fed on an infected chicken were inoculated subcutaneously into jirds. The number of larvae per jird varied from 10 to 228. Microfilaraemia appeared 22 to 89 days after inoculation of the infective larvae. Experiments were carried out with 24 jirds through six generations extending over a period of 22 months and 17 produced patent infections. At present 8 infected jirds are being maintained in the laboratory; their patent periods ranging from 6 to 13 months. However, the longest patent period observed was about thirteen months. The percentage of adults recovered in autopsied jirds ranged from 0 to 40 with an average of 16. The chicken showed a microfilarial periodicity with the peak microfilarial density around 2200 hours. However, in jirds there was a change in sub-periodicity. This model in the jird may be very useful for the screening of filaricides and in immunological work.     

长爪沙鼠作为动物模型感染卫氏并殖吸虫的实验观察

本实验首次用卫氏并殖吸虫囊蚴感染长爪沙鼠,探讨其作为研究卫氏并殖吸虫动物模型的可能性。结果显示：被感染的１８只沙鼠全部检获到发育的大型童虫,回收率为６．７％～９０％。童虫分布范围广泛,不仅腹腔、胸腔、肝、肺等组织中检获到大量童虫,并在２只沙鼠脑组织中亦发现童虫,所有童虫的生殖系统已发育达到性成熟前期。这表明沙鼠体内自然遗传属性及内在生态环境是适合卫氏并殖吸虫的生长发育。如对实验的沙鼠接种适量的卫氏并殖吸虫囊蚴,有可能提高沙鼠的存活时间,使童虫发育为成虫并产卵,从而使沙鼠这个实验动物成为一个适宜的卫氏并殖吸虫动物模型是有可能的。     

Dipetalonema viteae: Effects of hypo- and hyperthermic stress on microfilaremia in the Mongolian jird, Meriones unguiculatus

The effects of thermal stress on the numbers of circulating microfilariae of the filariid parasite, Dipetalonema viteae, in its host, the Mongolian jird, Meriones unguiculatus, was determined. The microfilaremia of each animal was allowed to stabilize, and the effects of stress were measured from this level. The ambient temperature was raised or lowered in 5C increments and maintained at each increment for a 24-hr period. Deep core body temperature of the jirds was recorded by the use of telemetry transmitters placed in the abdominal cavity. The transmitter signals were recorded on a Dynograph recorder. Blood samples were drawn at 0, 12, and 24 hr exposure to each ambient temperature, and microfilariae counted. Microfilaremial levels were then compared to numbers circulating prior to thermal stress. Both hypothermia and hyperthermia in the jird resulted in increased numbers of microfilariae in the peripheral blood. It is speculated that these fluctuations are changes in the percentage of the total microfilarial pool, and represent fluctuations of larvae being driven out of tissue and deep circulatory channels.     

Cone visual pigments in two marsupial species: the fat-tailed dunnart (Sminthopsis crassicaudata) and the honey possum (Tarsipes rostratus)

Uniquely for non-primate mammals, three classes of cone photoreceptors have been previously identified by microspectrophotometry in two marsupial species: the polyprotodont fat-tailed dunnart (Sminthopsis crassicaudata) and the diprotodont honey possum (Tarsipes rostratus). This report focuses on the genetic basis for these three pigments. Two cone pigments were amplified from retinal cDNA of both species and identified by phylogenetics as members of the short wavelength-sensitive 1 (SWS1) and long wavelength-sensitive (LWS) opsin classes. In vitro expression of the two sequences from the fat-tailed dunnart confirmed the peak absorbances at 363 nm in the UV for the SWS1 pigment and 533 nm for the LWS pigment. No additional expressed cone opsin sequences that could account for the middle wavelength cones could be amplified. However, amplification from the fat-tailed dunnart genomic DNA with RH1 (rod) opsin primer pairs identified two genes with identical coding regions but sequence differences in introns 2 and 3. Uniquely therefore for a mammal, the fat-tailed dunnart has two copies of an RH1 opsin gene. This raises the possibility that the middle wavelength cones express a rod rather than a cone pigment.     

Effects of dehydration and heat stress on food intake and dry matter digestibility in East African ruminants

Comparative investigations were made between wild and domestic ruminants from arid and semi-arid regions and those species from non-arid areas in an attempt to evaluate the adaptations of these ruminants in terms of the effects of heat stress and dehydration on food intake and digestibility. The effect of (a) an intermittent heat load (a daily light cycle of 12 h at 22 degrees C and 12 h at 40 degrees C) compared to 22 degrees C throughout the day and (b) dehydration level of 15% weight loss, with and without the heat load, on the intake and digestibility of a poor quality hay was investigated in the Grant's gazelle, Oryx, the domestic Turkana goats, fat-tailed sheep, zebu cattle, Thomson's gazelle and wildebeest. The intermittent heat load with water available ad libitum depressed the food intake of zebu cattle and Turkana goats by more than 40%. It had no significant effect on the food intake of the other species. The Thomson's and Grants gazelle, oryx, wildebeest and fat-tailed sheep appear well adapted to withstanding a periodic heat load. Dehydration at 22 degrees C caused a marked depression on food intake of all the species investigated. Dehydration together with a heat load caused no further reduction in the food intake by the Grants's gazelle, oryx, and goats but it did cause a further reduction in the intake in the other species. The small non-domestic ruminants (i.e. Grant's and Thomson's gazelle) appear much more digestive efficient than any of their domestic counterpart.     

Visual pigments and retinoids in the Mongolian jird

The visual cells, visual pigments and major retinoids of the Mongolian jird (Meriones unguiculatus) were examined. Light and electron microscope analyses show that these jirds had mainly rod photoreceptors. Octylglucoside extracts prepared from their retinas contained only rhodopsin with a maximum absorption at 497 nm and a concentration of 0.51 nmol per retina. Employing a standard method of high performance liquid chromatography (HPLC), the pigment epithelium from each eye was found to possess 0.52 nmol of retinyl palmitate (the most abundant form of retinyl ester) along with a small amount of retinol (0.02 nmol). Most of the retinoids in the body of these animals are stored in the liver, in the form of retinyl palmitate (1228.80 nmol per gram liver). As the Mongolian jird is small, inexpensive and readily available, this animal is a mammalian species suitable for the research of the biochemistry of retinoids and vision.     

Characterization of two whey protein genes in the Australian dasyurid marsupial, the stripe-faced dunnart (Sminthopsis macroura)

We report the first isolation and sequencing of genomic BAC clones containing the marsupial milk protein genes Whey Acidic Protein (WAP) and Early Lactation Protein (ELP). The stripe-faced dunnart WAPgene sequence contained five exons, the middle three of which code for the WAPmotifs and four disulphide core domains which characterize WAP. The dunnart ELPgene sequence contained three exons encoding a protein with a Kunitz motif common to serine protease inhibitors. Fluorescence in situ hybridization located the WAPgene to chromosome 1p in the stripe-faced dunnart, and the ELPgene to 2q. Northern blot analysis of lactating mammary tissue of the closely related fat-tailed dunnart has shown asynchronous expression of these milk protein genes. ELPwas expressed at only the earlier phase of lactation and WAPonly at the later phase of lactation, in contrast to beta-lactoglobulin (BLG) and alpha-lactalbumin (ALA) genes, which were expressed in both phases of lactation. This asynchronous expression during the lactation cycle in the fat-tailed dunnart is similar to other marsupials and it probably represents a pattern that is ancestral to Australian marsupials.     

Monogamy as a Rule Rather than Exception in Nocturnal Lemurs: the Case of the Fat-tailed Dwarf Lemur, Cheirogaleus medius

According to present hypotheses on the evolution of life history traits and social systems in Malagasy lemurs, nocturnality and infant parking are associated with a solitary lifestyle and a polygynous mating system. However, theoretically extreme seasonality of reproduction could limit the number of females that can be monopolized by a given male and thus hinder the evolution of polygyny. The aim of this ongoing study is to test these contrasting expectations by looking at the social and mating system of the fat-tailed dwarf lemur Cheirogaleus medius . This species hibernates for up to 7 mo, so that time for breeding and raising offspring is extremely limited.
A mark-recapture study in western Madagascar was combined with observations and radio-tracking of 36 individuals during the rainy seasons from 1995 to 1998. According to these data, fat-tailed dwarf lemurs live in permanent sleeping groups consisting of a male and a female (n = 8) or one male and two females (n = 1). One or two offspring from the previous year were frequently observed to sleep together with an adult pair. Members of each sleeping group were the exclusive users of their nest holes and home ranges. During the birth season, males and females took turns at baby-sitting their offspring. Females without paternal help were unable to raise their offspring successfully. Since females did not exhibit oestrus synchrony, the ultimate selective factor favouring pair-living could be obligate paternal investment. The results, together with the lack of sexual size dimorphism and relatively small testis size, suggest that the fat-tailed dwarf lemur lives in family groups with a monogamous mating system. A review of the mating systems of nocturnal lemurs shows that monogamy appears to be the rule rather the exception.     

Phase Contrast Imaging Reveals Low Lung Volumes and Surface Areas in the Developing Marsupial

Marsupials are born with immature lungs when compared to eutherian mammals and rely, to various extents, on cutaneous gas exchange in order to meet metabolic requirements. Indeed, the fat-tailed dunnart is born with lungs in the canalicular stage of development and relies almost entirely on the skin for gas exchange at birth; consequently undergoing the majority of lung development in air. Plane radiographs and computed tomography data sets were acquired using phase contrast imaging with a synchrotron radiation source for two marsupial species, the fat-tailed dunnart and the larger tammar wallaby, during the first weeks of postnatal life. Phase contrast imaging revealed that only two lung sacs contain air after the first hour of life in the fat-tailed dunnart. While the lung of the tammar wallaby was comparatively more developed, both species demonstrated massive increases in air sac number and architectural complexity during the postnatal period. In addition, both the tammar wallaby and fat-tailed dunnart had lower lung volumes and parenchymal surface areas than were expected from morphometrically determined allometric equations relating these variables to body mass during the neonatal period. However, lung volume is predicted to scale with mass as expected after the neonatal marsupial reaches a body mass of ∼1 g and no longer relies on the skin for gas exchange. Decreased lung volume in the marsupial neonate further supports the maxim that cutaneous gas exchange occurs in the marsupial neonate because the respiratory apparatus is not yet capable of meeting the gas exchange requirements of the newborn.     

A new nematode species, Physaloptera musayevi sp. n., from the Lybian jird Meriones libycus and the social vole Microtus socialis in the Gobustan area of Azerbaijan Republic

Nematodes belonging to the genus Physaloptera Rudolphi, 1819 were obtained from the Lybian jird Meriones libycus and the social vole Microtus socialis in the Gobustan area as a result of helminthological research. These nematodes significantly differed from other species of the genus in morphological and morphometric characters. In the present paper, they are described as the new species Physaloptera musayevi sp. n.     

Endoparasites of fat-tailed mouse opossums (Thylamys: Didelphidae) from northwestern Argentina and southern Bolivia, with the description of a new species of tapeworm

The parasite fauna of 2 species of fat-tailed mouse opossums from northwestern Argentina is herein presented. Five species of helminths were found, i.e., Pterygodermatites kozeki, Hoineffia simplispicula, Oligacanthorhynchus sp., and a new species of tapeworm, Mathevotaenia sanmartini n. sp. (Cyclophyllidea: Anoplocephalidae). The new species is characterized by a calyciform scolex, relatively few testes (32), and a long cirrus sac; it occurs in fat-tailed mouse opossums at localities above 4,000 m. Those characters make it different from 6 species known to occur in marsupials from the New World, and from other species occurring in armadillos and bats. Didelphoxyuris thylamisis, H. simplicispicula, and Oligacanthorhynchus sp. appear to occur in marmosas from the Yungas region. In contrast, both P. kozeki and M. sanmartini n. sp. appear to occur exclusively in the Puna.     

Experimental infection and adaptation of Rodentolepis nana to the Mongolian jird Meriones unguiculatus

A mouse-derived strain of Rodentolepis ( = Hymenolepis) nana was transferred to the Mongolian jird Meriones unguiculatus. It was found that M. unguiculatus has low susceptibility to R. nana mouse isolates. Likewise, adaptation of the parasite to jird hosts, in the absence of dexamethasone treatment, was not demonstrable, at least during ten-passage trials. Nevertheless, the parasite was able to establish, grow and develop to gravid adults in M. unguiculatus treated daily with dexamethasone. Prepatent periods in dexamethasone-treated jirds in ten-passage series ranged from 10 to 17 days post-infection (DPI), the average being 12 days, and the patent periods lasted from 18 to 30 DPI, with an average of 25 days. The population pattern of faecal egg output in immunosuppressed jirds suggests that under a daily dexamethasone treatment protocol, the parasite is able to maintain egg production as long as treatment is sustained.     

Brugia malayi,Brugia pahangi, and Brugia patei: Pulmonary pathology in jirds, Meriones unguiculatus

The chronological development of pulmonary lesions due to subperiodic Brugia malayi and related species was studied in the jird, Meriones unguiculatus. Major pathologic changes included (1) granulomas induced by larvae and adults, (2) obstructive endarteritis, and (3) chronic interstitial inflammation with degenerating microfilariae. The majority of pulmonary granulomas were initiated near the time of the final molt, about 30 days postinoculation, followed by involution and formation of residual vascular lesions over the next several months. A minority of granulomas arose about sexually mature adult worms and showed a characteristic sequence of development along the length of these worms. Ultrastructural observations suggested that within granulomas internal structures of the worm underwent an autolytic-like disintegration, while the cuticle remained intact. A material, presumably of parasitic origin, then appeared between the cuticle and adherent epitheloid and giant cells and was subsequently phagocytized by these cells. Obstructive endarteritis appeared to peak at about the time of the final molt, and became largely fibrotic by 125 days postinoculation; electron microscopy of the subintimal infiltrates revealed a variety of cells including inflammatory cells and others interpreted as modfied cells of vascular origin (smooth muscle cells and two types of endothelial cells).Parasitological data suggested that both larvae and adults migrated to the lungs and that mating occurred here, rather than in peripheral sites of development. In terms of development, reproduction and survival, the pulmonary arteries of the male jird offered a suitable alternative for the localization of these primarily lymphatic filariae; our results thus suggest that the pulmonary localization of these worms should not be considered indicative of an aberrant mode of development. The failure of female jirds to develop detectable peripheral microfilaremia was associated with a high rate of infertility among female worms, rather than pulmonary sequestration or destruction of microfilariae.     

Brugia malayi: detection of parasite antigen in sera from infected jirds

Sera from Brugia malayi-infected jirds were demonstrated to contain a heat-stable, 95- to 105-kDa parasite antigen by immunoblot with rabbit antibody to the parasite and with a monoclonal antibody that binds to phosphorylcholine. This antigen is a major component of B. malayi adult worm excretory/secretory antigen, and it is present in lavage fluid obtained from ip-infected animals. The antigen was detected by enzyme immunoassay in all sera collected from jirds 9-54 weeks after sc injection with 100 or 300 infective larvae (L3). Parasite antigen titers were higher in animals infected with the higher L3 dose. Antiphosphorylcholine antibodies were present in jird sera for the first 12 weeks after larval injection, but thereafter, antibody titers decreased to undetectable levels. Parasite antigen was not detected by immunoblot or enzyme immunoassay in sera from 21 human subjects with B. malayi microfilaremia. Antigen may be cleared from human sera by antiphosphorylcholine antibodies, which were present in all sera tested. The practical significance of B. malayi antigen detection in the jird is that it provides a sensitive means of noninvasively monitoring the status of infection in this important experimental filariasis model.     

In vitro chemotaxis of Brugia pahangi infective larvae to the sera and hemolymph of mammals and lower animals

The jird (Mongolian gerbil) is a highly susceptible experimental host for the lymphatic filarial nematode, Brugia pahangi. The chemotactic activity of serum from this host for B. pahangi infective larvae was compared in vitro to that of sera or hemolymph of a wide variety of other organisms including mammals, reptiles, fishes and invertebrates. The range of the Chemotactic Index (CI) was from 96.0 for the jird to 56.2 for a snail. An average of CI of saline control was 4.5. Significant chemotactic activity was present in many organisms, especially mammals, but was not closely related to either the phylogenetic position of the organism and to its known susceptibility as definitive host for B. pahangi. Migratory response was diminished in a consistent way by serial dilution of sera of humans, jirds and fetal bovine serum. Pre-incubation of larvae in fetal bovine serum inhibited migration, especially towards the sera of humans. Inhibition could be reversed by rinsing larvae in saline, longer rinse periods resulting in greater recovery of CI. These results are the first to suggest the activity of the specific amphid chemoreceptors in the chemotaxis of the infective larvae of B. pahangi.     

Calibration of a burrow count index for the Indian desert jird, Meriones hurrianae

Population estimates, often difficult to acquire, warrantee the use of an index as an economical substitute for rapid assessments of populations. We estimated population size of the little known social, semi-fossorial Indian desert jird (Meriones hurrianae) in Kachchh, Gujarat, India under closed population capture-mark-recapture (CMR) framework to calibrate a burrow count index for the species. A total of 147 individuals were trapped in 16 colonies using baited Sherman traps and the number of burrow entrances at each colony was recorded. Data from colonies with low number of captures were pooled to estimate capture probability using Huggins heterogeneity models with gender, site, body weight and age category as covariates in Program MARK. Colony sizes ranged from 2 to 46 individuals. The number of burrow entrances was calibrated against CMR-based population estimates using least squares regression (n = 16, adjusted R ² = 0.96, t = 18.18, P < 0.001). The index was further validated using Jackknife (JK) analysis where JK-predicted population estimates strongly correlated with CMR estimates (r = 0.96, P < 0.001). In habitats and climatic conditions similar to Kachchh and within the range of colony sizes sampled, our calibrated index can be a valuable and effective tool for large scale surveys of the desert jird, which occupies a keystone trophic level in the semi-arid ecosystem.     

Pollen dispersal in sugar beet production fields

Pollen-mediated gene flow has important implications for biodiversity conservation and for breeders and farmers’ activities. In sugar beet production fields, a few sugar beet bolters can produce pollen as well as be fertilized by wild and weed beet. Since the crop, the wild beets, and the weed beets are the same species and intercross freely, the question of pollen flow is an important issue to determine the potential dispersal of transgenes from field to field and to wild habitats. We report here an experiment to describe pollen dispersal from a small herbicide-resistant sugar beet source towards male sterile target plants located along radiating lines up to 1,200 m away. Individual dispersal functions were inferred from statistical analyses and compared. Pollen limitation, as expected in root-production fields, was confirmed at all the distances from the pollen source. The number of resistant seeds produced by bait plants best fitted a fat-tailed probability distribution curve of pollen grains (power–law) dependent on the distance from the pollen source. A literature survey confirmed that power–law function could fit in most cases. The b coefficient was lower than 2. The number of fertilized flowers by background (herbicide-susceptible) pollen grains was uniform across the whole field. Airborne pollen had a fertilization impact equivalent to that of one adjacent bolter. The individual dispersal function from different pollen sources can be integrated to provide the pollen cloud composition for a given target plant, thus allowing modeling of gene flow in a field, inter-fields in a small region, and also in seed-production area. Long-distance pollen flow is not negligible and could play an important role in rapid transgene dispersal from crop to wild and weed beets in the landscape. The removing of any bolting, herbicide-resistant sugar beet should be compulsory to prevent the occurrence of herbicide-resistant weed beet, thus preventing gene flow to wild populations and preserving the sustainable utility of the resistant varieties. Whether such a goal is attainable remains an open question and certainly would be worth a large scale experimental study.     

The development of brood capsules and protoscolices in secondary hydatid cysts of Echinococcus granulosus. A histological study.

Using the Mongolian jird (Meriones unguiculatus) as a laboratory host for the cystic stage of the British horse strain of Echinococcus granulosus, the mode of development of brood capsules and protoscolices was studied histologically. The successive stages in development in secondary hydatid cysts are described and shown to correspond closely with previous observations on primary hydatid cysts. The usefulness of this experimental model for future ultrastructural studies is emphasized.     

Cephalic morphology of the honey possum,Tarsipes rostratus (Marsupialia: Tarsipedidae); an obligate nectarivore

The sharply tapering skull of the honey possum is delicately constructed and has only a few, minute teeth; its mandible is reduced to a thin, flexible rod. The mandibular fossa has been diplaced caudally to the caudomedial corner of the squamosal. Head skeletons of the feathertail glider and western pygmy-possum, omnivores that are closely related to the honey possum, bear greater resemblance to the distantly related carnivorous fat-tailed dunnart than to the honey possum. Selected muscles associated with the jaws, hyoid, and tongue of these four mouse-sized (9–22 g) marsupials are described for the first time. The honey possum is characterized by a greatly reduced temporalis that is almost completely hidden by the eye. Its digastric consists of a single belly that inserts onto the caudal margin of the mylohyoid. The lateral pterygoid is relatively long as it extends caudally to insert onto the elongated mandible. The stylohyoid originates high up on the caudal surface of the tympanic bulla; it curves around the caudal and ventral surfaces of the bulla to reach the basihyoid. The insertion of the genioglossus is restricted to the caudal quarter of the tongue. Homologous muscles of the feathertail glider and western pygmy-possum are more similar to those of the fat-tailed dunnart. In addition to the very different musculoskeletal system, the honey possum has an unusual tongue that tapers to a fine point. © 1995 Wiley-Liss, Inc.