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PubMed2005

Differential gene expression in yellow-necked mice Apodemus flavicollis (Rodentia, Mammalia) with and without B chromosomes.

Most B chromosomes are heavily heterochromatic, promoting the general idea that they are genetically inert. The B chromosomes of Apodemus flavicollis are euchromatic and show a high degree of homology with the A chromosomes. The euchromatic nature of B chromosomes in A. flavicollis suggests that they may carry active genes and have transcriptional activity. We applied the differential display reverse transcription-polymerase chain reaction (DD RT-PCR) in order to analyze and compare gene expression in animals possessing B chromosomes and animals without B chromosomes. After a second and third round of amplification, three cDNA fragments were differentially expressed in +B mice compared with 0B animals. These cDNAs were Chaperonin containing TCP-1, subunit 6b (zeta) (CCT6B), Fragile histidine triad gene (FHIT) and hypothetical gene XP transcript. The differential expression pattern was confirmed by Real Time RT-PCR. We suggest that altered expression of these important genes is due to the presence of B chromosomes. In elevating the expression of these genes, B chromosomes of A. flavicollis affect some of the crucial processes in the cell. The significance of these effects and the nature of B chromosomes of A. flavicollis are discussed in the context of the data presented.

Acid Anhydride Hydrolases↗
PubMed2004

Cadmium and lead concentrations in Gallegoides arfaai (Cestoda: Anoplocephalidae) and Apodemus sylvaticus (Rodentia: Muridae) from Spain.

Information on parasites of vertebrates living in terrestrial ecosystems as sentinels for heavy metal environmental pollution is scarce. The aim of the present study was to assess the concentration of cadmium and lead using the model Apodemus sylvaticus/Gallegoides arfaai in order to test the potential suitability of G. arfaai as a sentinel organism for lead and cadmium under natural field conditions. Samples of 15 A. sylvaticus as well as whole specimens of G. arfaai were analysed for both elements by inductively coupled plasma mass spectrometry. The level of cadmium in G. arfaai was always much lower than in the tissues of A. sylvaticus. Contrarily, values for lead in G. arfaai were found to be 6, 20 and 24-fold higher than in the kidney, liver and muscle of A. sylvaticus. We propose the model A. sylvaticus/G. arfaai as a promising bioindication system to evaluate environmental lead exposure in terrestrial habitats, especially for non-urban areas.

Animals↗
PubMed2005

Two new species of Eimeria Schneider 1875 (Apicomplexa: Eimeriidae) from the broad-toothed field mouse, Apodemus mystacinus Danford and Alston 1877 (Rodentia: Muridae) from Jordan.

Coprological examination of 40 Apodemus mystacinus Danford and Alston 1877 from Jordan revealed oocysts of three species of genus Eimeria. Two species are described as new. Eimeria zuhairamri sp. n. has broadly ellipsoidal oocysts 29.6 (27.0-34.0) x 23.3 (22.0-25.0) mum with distinctly granulated wall and oocyst residuum. Endogenous development occurs in jejunum and ileum. Eimeria alorani sp. n. has oocysts 26.9 (23.0-29.0) x 19.3 (18.0-22.0) mum with smooth wall and absent residuum. Endogenous development is confined to the caecum. The third species, developing in jejunum, has oocysts morphologically indistinguishable from Eimeria uptoni. The identity of E. uptoni and the taxonomy of Eimeria of Apodemus are discussed.

Animals↗
PubMed2005

Ultrastructure of the spermatozoon of Raillietina (Raillietina) baeri (Cyclophyllidea, Davaineidae) an intestinal parasite of the multimammate rat, Mastomys huberti (Rodentia, Muridae).

The mature Raillietina (Raillietina) baeri spermatozoon exhibits an apical cone of electron-dense material about 2.5 microm long and 0.5 microm wide and two helicoidal crest-like bodies roughly 100-125 nm thick. The latter are of different lengths, spiralized and stand in an angle of about 50 degrees with the spermatozoon axis. The axoneme is of the 9 + "1" pattern and does not reach the posterior extremity of the gamete. The nucleus is an electron-dense cord coiled in a spiral around the axoneme. The cytoplasm exhibits a posterior densification and contains few small electron-dense granules in regions I, II and V of the spermatozoon. In regions III and IV, it is divided into irregular compartments by walls of electron-dense material. The cortical microtubules are spiralized and make an angle of 40-50 degrees to the spermatozoon axis. In this work, we describe, for the first time, a spermatozoon of a davaineidaean cestode parasitic of mammals. This has enabled us to show a wide apical cone, which has never been described before in a cyclophyllidean species the spermatozoon of which has two crest-like bodies.

Animals↗
PubMed2006

Endogenous development, pathogenicity and host specificity of Eimeria cahirinensis Couch, Blaustein, Duszynski, Shenbrot and Nevo, 1997 (Apicomplexa: Eimeriidae) from Acomys dimidiatus (Cretzschmar 1826) (Rodentia: Muridae) from the Near East.

Eimeria cahirinensis Couch et al. 1997 was found in faecal samples of Acomys dimidiatus from three different localities in the Near East. Twenty-two of 104 (21%) A. dimidiatus trapped on both the south- and north-facing slopes of "Evolution Canyon", Lower Nahal Oren, Mt. Carmel, Israel in August 2001 and 2002 were infected with E. cahirinensis. Oocysts were also obtained from a single individual of A. dimidiatus trapped in Wadi Ramm, Jordan in the summer of 1999. Laboratory-reared spiny mice (Acomys spp.) were inoculated to determine the prepatent and patent period, sporulation time, site of infection, immunogenicity, pathogenicity, pathology and morphology of endogenous stages of E. cahirinensis. Both asexual and sexual stages were localised in the apical part of duodenal and jejunal villi. An experimental inoculation of representatives of several rodent genera revealed the host range of E. cahirinensis to be limited to the genus Acomys.

Animals↗
PubMed2006

Distribution of L1-retroposons on the giant sex chromosomes of Microtus cabrerae (Arvicolidae, Rodentia): functional and evolutionary implications.

Long interspersed nuclear elements (L1 or LINE-1) are the most abundant and active retroposons in the mammalian genome. Traditionally, the bulk of L1 sequences have been explained by the 'selfish DNA' hypothesis; however, recently it has been also argued that L1s could play an important role in genome and gene organizations. The non-random chromosomal distribution of these retroelements is a striking feature considered to reflect this functionality. In the present study we have cloned and analyzed three different L1 fragments from the genome of the rodent Microtus cabrerae. In addition, we have examined the chromosomal distribution of this L1 in several species of Microtus, a very interesting group owing to the presence in some species of enlarged ('giant') sex chromosomes. Interestingly, in all species analyzed, L1-retroposons have preferentially accumulated on both the giant- and the normal-sized sex chromosomes compared with the autosomes. Also we have demonstrated that L1-retroposons are not similarly distributed among the heterochromatic blocks of the giant sex chromosomes in M. cabrerae and M. agrestis, which suggest that L1 retroposition and amplification over the sex heterochromatin have been different and independent processes in each species. Finally, we proposed that the main factors responsible for the L1 distribution on the mammalian sex chromosomes are the heterochromatic nature of the Y chromosome and the possible role of L1 sequences during the X-inactivation process.

Animals↗
PubMed2006

Cytogenetics of a new cytotype of African Mus (subgenus Nannomys) minutoides (Rodentia, Muridae) from Kenya: C- and G- banding and distribution of (TTAGGG)n telomeric sequences.

We present the results of a cytogenetic study on Mus (Nannomys) minutoides from Kenya by means of C- and G- banding and in-situ fluorescence hybridization (FISH) to localize the telomeric sequences. The karyotype is characterized by the occurrence of several Rb chromosomes Rb(1.X), Rb(1.Y). Rb(2.17), Rb(3.13), Rb(4.10), Rb(5.11), Rb(6.7), Rb(8.12), not previously described for this species. This finding suggests a high level of chromosomal diversification, which means it is possible to consider this cytotype as a new, well-differentiated, chromosomal lineage within the subgenus. The C-banding of the metaphases illustrated conspicuous blocks of centromeric heterochromatin at the paracentromeric regions of all telocentric chromosomes. Centromeric heterochromatin is not visible on all biarmed chromosomes. Following hybridization with telomeric probes, bright interstitial telomeric sequence (ITS) fluorescence signals are evident at the pericentromeric area of all Rb chromosomes, with the exception of Rb(2.17). Considering the localization of the C-positive heterochromatin and of the telomeric sequences, the events leading to the Kenyan cytotype from an all-telocentric condition probably included two steps: first, fusion without loss of heterochromatin and pericentromeric telomeric sequences; second, the reduction of the C-positive satellite DNA followed by the amplification of telomeric sequences in the C-negative paracentromeric region of Rb chromosomes. The presence of a single Rb(2.17) without ITS indicates possible variations of this mechanism.

Animals↗
PubMedDate not supplied

Accelerated molecular evolution in Microtus (Rodentia) as assessed via complete mitochondrial genome sequences.

Microtus is one of the most taxonomically diverse mammalian genera, including over 60 extant species. These rodents have evolved rapidly, as the genus originated less than 2 million years ago. If these numbers are taken at face value, then an average of 30 microtine speciation events have occurred every million years. One explanation for the rapid rate of cladogenesis in Microtus could be the karyotypic differentiation exhibited across the genus: diploid numbers range from 17 to 64. Despite the striking chromosomal variability within Microtus, phenotypic variation is unremarkable. To determine whether nucleotide substitution rates are also elevated in voles, we sequenced the entire mitochondrial DNA (mtDNA) genome of the Eurasian sibling vole (Microtus rossiaemeridionalis). We compared this genome to another previously sequenced vole mtDNA genome (Microtus kikuchii) and performed pairwise sequence comparisons with the mtDNA genomes of ten additional mammalian genera. We found that microtine mtDNA genomes are evolving more rapidly than any other mammalian lineage we sampled, as gauged by the rate of nucleotide substitution across the entire mtDNA genome as well as at each individual protein-coding gene. Additionally, we compared substitution rates within the cytochrome b gene to seven other rodent genera and found that Microtus mtDNA is evolving fastest. The root cause of accelerated evolution in Microtus remains uncertain, but merits further investigation.

Animals↗
PubMed2006

Characterization of the satellite DNA Msat-160 from the species Chionomys nivalis (Rodentia, Arvicolinae).

The satellite DNA Msat-160 has been previously characterized in several species of the genus Microtus. Here we present the characterization of Msat-160 from Chionomys nivalis, a species with a very primitive karyotype. As in other Microtus species analyzed, C. nivalis Msat-160 is AT rich, has a monomer length of 160 bp, is undermethylated and is mainly located in all the pericentromeric heterochromatin of all autosomes and the X chromosome, but is completely absent from the Y chromosome. Hence, our results support the hypothesis that Msat-160 was initially distributed in the pericentromeric heterochromatin of all autosomes and the X chromosome. The taxonomic status of the genus Chionomys in relation to the genus Microtus is a very interesting issue, so we constructed phylogenetic dendrograms using Msat-160 sequences from several Microtus species. Although the results were not informative about this issue, the presence of Msat-160 in C. nivalis and Microtus species suggested that both genera are closely related and that this satellite DNA was present in the common ancestor. Studies of Msat-160 in different arvicoline species could help to determine the origin of this satellite and, perhaps, to establish the phylogenetic relationships of some arvicoline groups.

Animals↗
PubMed2006

The origin of an unusual sex chromosome constitution in Acomys sp. (Rodentia, Muridae) from Tanzania.

This paper describes a case which presents an evident variation from the "standard" XX/XY sex chromosomal constitution in a rodent, Acomys sp. This species known to be found in three localities of East Africa has only recently been separated from A. spinosissimus, its closest relative. In our study, five specimens of Acomys sp. and eight specimens of A. spinosissimus were live-trapped in five localities. Comparisons between the two taxa assed by G-banding show a complete homology in the chromosomal shape and banding pattern for 29 pairs of chromosomes corresponding to the complete autosomal set of A. spinosissimus. However, while all the A. spinosissimus analysed have 2n = 60 and a XY-XX system, in Acomys sp. males and females constitute mosaics for sex chromosomes in the bone marrow cells. Females (2n = 59, 60) have an excess (97%) of aneuploid cells with one single giant X chromosome, and males (2n = 60, 61) show X0/XY cells occurring in somatic tissues and XY cells in the germinal lineage. In addition, an odd heterochromatic submetacentric chromosome was identified in all the cells examined in two males and a female of Acomys sp. Since this chromosome was not related to sex determination and it is not present in all the analysed specimens, it can be considered as a B chromosome. Finally, the in situ fluorescence hybridisation (FISH) with telomeric probes showed a very intense interstitial telomeric signal (ITS) at the medial part on the long heterochromatic arm of the X chromosome. This could be due to recent chromosomal rearrangement.

Animals↗
PubMed1990

A comparative electron microscopic analysis of mechanoreceptors in the hard palate of the mouse (Mus musculus; Rodentia) and the musk shrew (Suncus murinus; Insectivora).

These mechanoreceptors were studied with particular regard to their type and the distribution. In both species they were concentrated in the crests of transverse palatine rugae. In the mouse, Meissner corpuscles, glomerular corpuscles, and Merkel cell nerve endings were seen in every palatine ruga, though the first antemolar ruga also contained simple and atypical lamellated corpuscles. In contrast, the palatine rugae of the musk shrew contained only simple corpuscles and Merkel cell nerve endings. Meissner corpuscles in the mouse palate were frequently aggregated to form a palisade-like, huge corpuscle. Anterior intermolar rugae especially contained a larger number of such huge corpuscles. Simple corpuscles in the palate of the musk shrew were more densely distributed in the anterior than in the posterior rugae. In both species Merkel cell nerve endings were localized within epithelial downgrowths of the rugal crest. These downgrowths tended to increase in number anteroposteriorly.

Animals↗
PubMed1987

Transcriptional activity of constitutive heterochromatin in the mammal Microtus agrestis (Rodentia, Cricetidae).

Two cytological approaches were applied to the analysis of genetic activity in euchromatin and heterochromatin in the European field vole Microtus agrestis. The first is based on the transcriptional activity of prematurely condensed chromosomes, the second on in situ hybridization of labeled cellular RNA to metaphase chromosomes. The results show that in cultivated fibroblasts, the transcriptional activity of constitutive heterochromatin is in the same order of magnitude as that of euchromatin; its chromosomal pattern is nonrandom. It is concluded that--as has already been shown for insects and amphibians--also in mammals, constitutive heterochromatin is transcribed in its decondensed state but is genetically inactive when forming chromocenters at interphase.

Animals↗
PubMed1991

Nesting and digging behavior in three species of Calomys (Rodentia; Cricetidae).

Two sets of behaviors relevant for the construction of shelters, nest building and digging, were studied in three con-generic species of South American cricetid rodents. Significant differences were observed among the three species in both sets of behaviors, but not between sexes within the same species. Calomys musculinus built the largest nests, C. laucha showed the highest number of digging bouts and the shortest digging latency, and C. venustus scored low in both nesting and digging behaviors. In general, these observations are consistent with the few, anecdotal records of the shelters used by these species in the field. The low nesting and digging scores of C. venustus are correlated with that species' low thermal conductance, but the marked differences in the nesting and digging scores of C. musculinus and C. laucha cannot be accounted for by differences in their basal metabolic rates or thermal conductances.

Animals↗
PubMed1985

Comparative hematology and coagulation: studies on rodentia (rats).

Blood from adult male Wistar rats clotted rapidly in glass or siliconized tubes; the clots retracted and did not lyse. The serum prothrombin, plasma prothrombin and activated partial thromboplastin times were shorter than those of normal humans. In contrast, the thrombin and reptilase times were longer than those of normal human plasma, due apparently to the presence of a low-grade thrombin inhibitor in rat plasma. Coagulation factors, X, VIIIR:vW and IX assayed lower in rat than human plasma, while factors VIII:C and anti-thrombin III were higher. Values for other coagulation factors (II, V, VII, XI, XII and Fletcher) fell within the human range. Platelets were small and numerous. They aggregated well with ADP but poorly or not at all with collagen, ristocetin, thrombin, epinephrine, arachidonic acid and pig or bovine plasmas. Leukocytes numbered 4-8 X 10(3) cells/mm3, a near human range and were predominantly lymphocytic. Erythrocytes were small (MCV = 56-60 fl) and numerous (5.5-6.4 X 10(6) cells/mm3).

Animals↗