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PubMed2003

Age-related patterns of fertility in captive populations of birds and mammals.

We have analyzed birth records from the International Species Inventory System database of zoo animals to describe patterns of fertility as a function of age in birds and mammals. Unlike age at death, fertility in captive populations is partly controlled by animal keepers depending on availability of space and potential mates and on the aims of captive propagation programs. Thus, fertility records must be considered carefully to avoid potential age-specific biases. The zoo data suggest that fertility declines from a peak at young adult ages in most species. The rate of decline in reproductive function is correlated with the rate of somatic aging, indicated by the increase in mortality rate with age, and with the age at peak fertility. Over the sample as a whole, these patterns do not differ systematically between the sexes, nor do they differ between birds and mammals. While it is clear that the demographic consequences of aging of the reproductive system follow a different course than the aging of somatic tissue, the rates of each are correlated either through functional connections or through parallel evolutionary responses to common selective factors.

Aging↗
PubMedDate not supplied

Comparative aging and life histories in mammals.

A comparative assessment of aging and longevity in mammals has four uses in aging research. These are: (1) hypothesis formulation and evaluation, (2) investigating the generality of putative aging mechanisms, (3) isolating key physiological factors influencing aging rate, and (4) allowing the most appropriate choice of animal models for particular research questions. The first use requires detailed information on a wide variety of species, and I will examine general patterns of aging in a sample of over 600 species of mammals. The second use requires the selection of several models as distantly related to one another as feasible. The third use is best served by evaluating species or populations as closely related to one another as possible, assuming that they differ substantially in aging rate. The fourth use requires a logic of animal model selection, as well detailed information about a wide range of species. Specific examples of each use will be given.

Aging↗
PubMed1999

Evolving functions of apolipoprotein AIV: from birds to mammals.

Apolipoprotein (apo) AIV is a serum protein that displays particularly vivid dynamics regarding its distribution among the various plasma lipoprotein and nonlipoprotein fractions. This article discusses two main aspects. First, the general functional properties of apo AIV as a highly mobile and versatile apolipoprotein, delineated in mammalian species, are described. Second, the implications of the fact that not only mammals, but also the chicken, express apo AIV are highlighted. Given the differences in certain lipid metabolic pathways between mammals and birds, the structure and functions of apo AIV may have evolved into distinct functions in different amniotes.

Animals↗
PubMed2003

Fungal diseases in small mammals: therapeutic trends and zoonotic considerations.

As medical knowledge continues to expand, the division between animal and human diseases continues to decrease. The popularity of small mammals in lieu of the increased numbers of immunocompromised individuals will require increasingly broader understandings of zoonotic disease. The vast amount of animal research in areas of human disease requires diligent study to stay abreast of emerging diagnostics and therapeutics. The core requirements of skin scrapings, fungal culture, and microscopy for the diagnosis of small mammal fungal disease, however, are unchanged.

Animals↗
PubMed2003

Oral biology and disorders of tusked mammals.

Tusked mammals can be terrestrial or aquatic. Many of these magnificent animals are kept in captivity all over the world. Functions of tusks vary as much as the species in which they occur. Dental anomalies and disorders of tusks and the rest of the dentition in these mammals were discussed, with an emphasis on the elephant. The tusk anatomy, with its large, conically-shaped pulp, makes it an ideal tooth for partial pulpectomy treatment in trauma cases where the pulp is exposed. Surgical techniques for tusks have been developed and were discussed. Oral tumors occur, but are rare.

Animals↗
PubMed2000

The plasma membrane transformation facilitates pregnancy in both reptiles and mammals.

Mechanisms of placentation are very diverse in mammals and range from types in which the uterine epithelium is breached by the implanting blastocyst to those where the epithelium remains intact. Despite these differences in mechanisms, the initial response of the plasma membrane of uterine epithelial cells is remarkably similar across mammalian species which has led to the term 'plasma membrane transformation' to encapsulate the concept of a common beginning to implantation. Membrane phenomena similar to those of mammals have now been observed in some viviparous lizards at the ultrastructural level during early pregnancy, and we propose extending the concept of 'plasma membrane transformation' to lizards with live birth.

Animals↗
PubMed2001

Cold adaptive thermogenesis in small mammals from different geographical zones of China.

The mechanisms of thermogenesis and thermoregulation were studied in the tree shrew (Tupaia belangeri) and greater vole (Eothenomys miletus) of the subtropical region, and Brandt's vole (Microtus brandti), Mongolian gerbil (Meriones unguiculatus), Daurian ground squirrel (Spermophilus dauricus) and plateau pika (Ochotona curzoniae) of the northern temperate zone. Resting metabolic rate (RMR) and non-shivering thermogenesis (NST) increased significantly in T. belangeri, E. miletus, M. brandti and M. unguiculatus after cold acclimation (4 degrees C) for 4 weeks. In T. belangeri, the increase in RMR and thermogenesis at liver cellular level were responsible for enhancing the capacity of enduring cold stress, and homeothermia was simultaneously extended. Stable body temperature in M. brandti, E. miletus, M. unguiculatus and O. curzoniae was maintained mainly through increase in NST, brown adipose tissue (BAT) mass and its mitochondrial protein content, and the upregulation of uncoupling protein (UCP1) mRNA, as well as enhancement of the activity of cytochrome C oxidase, alpha-glycerophosphate oxidase and T(4) 5'-deiodinase in BAT mitochondria. The RMR in O. curzoniae and euthermic S. dauricus was not changed, while NST significantly increased during cold exposure; the former maintained their stable body temperature and mass, while body temperature in the latter declined by 4.8 degrees C. The serum T(3) concentration or ratio of T(3)/T(4) in all the species was enhanced after cold acclimation. Results indicated that: (1) the adaptive mechanisms of T. belangeri residing in the subtropical region to cold are primarily by increasing RMR and secondly by increasing NST, and the mechanisms of thermogenesis are similar to those in tropical mammals; (2) in small mammals residing in northern regions, the adaptation to cold is chiefly to increase NST; (3) the mechanism of cold-induced thermogenesis in E. miletus residing in subtropical and high mountain regions is similar to that in the north; (4) a low RMR in warm environments and peak RMR and NST in cold environments enabled M. unguiculatus to tolerate a semi-desert climate; (5) O. curzoniae has unusually high RMR and high NST, acting mainly via increasing NST to adapt to extreme cold of the Qinghai-Tibet Plateau; (6) the adaptation of euthermic S. dauricus to cold is due to an increase in NST and a relaxed homeothermia; and lastly (7) the thyroid hormone is involved in the regulation of cold adaptive thermogenesis in all the species studied.

Adaptation, Physiological↗
PubMed1999

Identification of Ebola virus sequences present as RNA or DNA in organs of terrestrial small mammals of the Central African Republic.

The life cycle of the Ebola (EBO) virus remains enigmatic. We tested for EBO virus in the organs of 242 small mammals captured during ecological studies in the Central African Republic. EBO virus glycoprotein or polymerase gene sequences were detected by reverse transcription PCR in RNA extracts of the organs of seven animals and by PCR in DNA extract of one animal. Neither live virus nor virus antigen was detected in any organ sample. Direct sequencing of amplicons identified the virus as being of the Zaire/Gabon subtype. Virus-like nucleocapsids were observed by electron microscopy in the cytoplasm of the spleen cells of one animal. The animals belonged to two genera of rodents (Muridae; Mus setulosus, Praomys sp1 and P. sp2) and one species of shrew (Soricidae; Sylvisorex ollula). These preliminary results provide evidence that common terrestrial small mammals living in peripheral forest areas have been in contact with the EBO virus and demonstrate the persistence of EBO virus RNA and DNA in the organs of the animals. Our findings should lead to better targeting of research into the life cycle of the EBO virus.

Animals↗
PubMed2003

Functional analysis of chicken Sox2 enhancers highlights an array of diverse regulatory elements that are conserved in mammals.

Sox2 expression marks neural and sensory primordia at various stages of development. A 50 kb genomic region of chicken Sox2 was isolated and scanned for enhancer activity utilizing embryo electroporation, resulting in identification of a battery of enhancers. Although Sox2 expression in the early embryonic CNS appears uniform, it is actually pieced together by five separate enhancers with distinct spatio-temporal specificities, including the one activated by the neural induction signals emanating from Hensen's node. Enhancers for Sox2 expression in the lens and nasal/otic placodes and in the neural crest were also determined. These functionally identified Sox2 enhancers exactly correspond to the extragenic sequence blocks conspicuously conserved between chicken and mammals, which are not discernible by sequence comparison among mammals.

Animals↗
PubMed1976

Salmonellosis in wild mammals.

One thousand two hundred and sixty-nine freeliving, wild mammals, representative of 16 species from estates in Berkshire, Oxfordshire and Surrey, were examined for the presence of salmonellas. Salmonella typhimurium was isolated from 1 and S. dublin from 7 house mice (Mus musculus). There were no isolations from the other species examined. It was concluded that the house-mice infected with S. dublin acquired the organism from experimentally infected cattle. The wild mammal population does not at present appear to constitute a reservior for infection of domestic animals.

Animals↗
PubMed1995

Arrangement and number of intralaryngeal ganglia and ganglionic neurons: comparative study of five species of mammals.

The arrangement and number of intralaryngeal ganglia and their neurons in five mammals (dog, rat, guinea pig, rabbit and cat) were examined morphologically. Intralaryngeal ganglions were situated mainly in branches of the internal branch of superior laryngeal nerve (Int-SLN), dorsal and/or dorsolateral to the posterior cricoarytenoid muscle, and around the inferior laryngeal nerve in dogs, rats, guinea pigs and cats, but they were identified at the branching out point of the Int-SLN exclusively in rabbits. The ganglion of each animal was spindle-shaped, with a surrounding fibrous capsule, and it contained many ganglionic neurons, vessels and connective tissue cells. The ganglionic neuron was oval-shaped and had a round nucleus: the diameter was smaller (20-25 microns) in the rat than in the other mammals (25-30 microns). More than 80 per cent of ganglionic neurons occurred in the supraglottis of all the animals except the rat. In the rat, this value was approximately 40 per cent.

Animals↗
PubMed2003

The molecular evidence of Babesia microti infection in small mammals collected in Slovenia.

In Europe, the zoonotic cycle of Babesia microti has not been determined so far. Recently, B. microti was detected in Ixodes ricinus ticks in Slovenia by using molecular methods. In order to investigate the mammalian hosts of B. microti in Slovenia we collected 261 small mammals representing 11 species. They were tested for the presence of babesial parasites with a PCR assay based on the nuclear small subunit rRNA gene (nss-rDNA). The bank vole (Clethrionomys glareolus) and yellow-necked mouse (Apodemus flavicollis) were infected with B. microti. The prevalence rate was 15.9% for C. glareolus and 11.8% for A. flavicollis. Nucleotide sequences of amplified portions of B. microti nss-rDNA from C. glareolus and A. flavicollis were indistinguishable from each other and identical with those previously described in I. ricinus ticks collected in Slovenia. The results of this study represent molecular evidence of B. microti in small mammals in Europe.

Animals↗
PubMed2004

Is sex-biased ectoparasitism related to sexual size dimorphism in small mammals of Central Europe?

Sexual size dimorphism (SSD) in mammals reveals the extent of sexual selection, which may in turn explain why males are often more infected by parasites than females and that parasites may contribute to the association between SSD and male-biased mortality. Here, we investigated the relationship between SSD in small mammals of Central Europe and the differences in sex infection by fleas. A comparative analysis was conducted for 10 species of rodents and insectivores. We found that males harbour higher flea species richness than females and that the abundance of fleas is higher in males than in females. This difference is not related to male-biased density. However, contrary to our hypothesis, we found that an increase in SSD is not related to an increase in male infection by fleas compared with female infection. We discuss our results in term of sex-differences in immunocompetence and/or sex-differences in behaviour.

Animals↗
PubMed2002

Assessment of risks of brodifacoum to non-target birds and mammals in New Zealand.

The risks to non-target birds and other wildlife from the use of vertebrate pesticides, including anticoagulant rodenticides, are determined to a significant extent by species' intrinsic susceptibility, and the toxicokinetics of the compounds used. Brodifacoum is highly toxic to birds and mammals. The acute toxicity of brodifacoum to birds in New Zealand varies from <1 mg/kg in pukeko (Porphyrio p. melanotus), the native swamp hen, to >20 mg/kg in the paradise shelduck (Tadorna variegata). Like other second-generation anticoagulants brodifacoum is strongly bound to vitamin K epoxide reductase and will persist, apparently for at least 6 months, in organs and tissue containing this enzyme, e.g., liver, kidney, and pancreas. The unique toxicokinetics of this class of compound exacerbates the risk of primary and secondary poisoning of non-target species. Vertebrate pest control programmes in New Zealand using bait containing brodifacoum have resulted in the primary and secondary poisoning and sub-lethal contamination of non-target species. These include native raptors, such as the Australasian harrier (Circus approximans) and morepork (Ninox novaeseelandiae), other native birds such as the pukeko, weka (Gallirallus australis), southern black-backed gull (Larus dominicanus), and kiwi (Apteryx spp.), and introduced mammals, including game animals. There are increasing numbers of reports worldwide of wildlife contamination and toxicosis after the use of second-generation anticoagulants. All pest control activities require careful risk-benefit assessment in view of their potential to cause adverse environmental impact. Monitoring of wildlife for pesticide residues will provide data that can be used to reduce the risk of anticoagulant bioaccumulation and mortality in non-target species.

4-Hydroxycoumarins↗
PubMed2004

Features of the uncoupling effect of fatty acids in liver mitochondria of mammals with different body weight.

In the presence of oligomycin, EGTA, and magnesium ions, the protonophore uncoupling activity of palmitate (V(Pal)) is determined as the ratio of the acceleration of respiration with palmitate to its concentration. Under these conditions, V(Pal) in liver mitochondria of one-month-old rats with the body weight of 50 g is 1.46-fold higher than in liver mitochondria of adult rats with the body weight of 250 g, whereas the uncoupling activity of FCCP does not depend on the age of the animals. The difference in V(Pal) is mainly due to its component insensitive to carboxyatractylate and glutamate (V(Ins)). This value is 2.9-fold higher in mitochondria of one-month-old rats than in those of adult rats. The protonophore activity of palmitate is similar in liver mitochondria of four-day-old and adult rats. In liver mitochondria of adult mammals (mouse, rat, guinea pig, rabbit), V(Pal) decreases with increase in the body weight of the animals. In double logarithmic coordinates, the dependence of the V(Pal) value on the body weight is linear with slope angle tangent of -0.18. The V(Pal) value is mainly contributed by its component V(Ins). In the presence of calcium ions, palmitate induces the nonspecific permeability of the inner membrane of liver mitochondria (pore opening). This Ca2+-dependent uncoupling effect of palmitate is less pronounced in mitochondria of one-month-old rats than in those of adult rats. In mitochondria of adult animals (mice, rats, and guinea pigs), the Ca2+-dependent uncoupling activity of palmitate is virtually the same. It is concluded that the protonophore uncoupling effect of palmitate in liver mitochondria of mammals, unlike its Ca2+-dependent effect, is associated with thermogenesis at rest and also with production of additional heat on cooling of the animals.

Animals↗
PubMedDate not supplied

Basal metabolic rate and energetics of reproduction in therian mammals.

Traditionally, the fact that reproduction in eutherian (= placental) mammals tends towards prolonged intrauterine development and short lactation has been interpreted as an evolutionary advance over the metatherian (= marsupial) short gestation and prolonged lactation. However, it has recently been postulated that marsupial reproduction involves low initial energy investment and may be advantageous by minimizing energy loss if conditions necessitate early termination. Moreover, because marsupials have basal metabolic rates (BMRs) 30% lower than those of most eutherians, it has been suggested that daily and total energy expenditures during reproduction may also be lower. We have now tested the predictions that low BMR is maintained during reproduction and that initial investment is lower in marsupials. Using indirect calorimetry, we have made the first longitudinal measurements of energy expenditure during reproduction for a marsupial and for two eutherian species with low BMRs. We find that initial investment is lowest in a eutherian and total energetic expenditures were greatest for the marsupial. We also find that, relative to BMR, all three species have increased mean maternal resting metabolic rates (RMRs) during both gestation and lactation; this is the first evidence that mammals with low BMRs can substantially elevate metabolism for prolonged periods during gestation and lactation.

Animals↗
PubMed2001

Parallel adaptive radiations in two major clades of placental mammals.

Higher level relationships among placental mammals, as well as the historical biogeography and morphological diversification of this group, remain unclear. Here we analyse independent molecular data sets, having aligned lengths of DNA of 5,708 and 2,947 base pairs, respectively, for all orders of placental mammals. Phylogenetic analyses resolve placental orders into four groups: Xenarthra, Afrotheria, Laurasiatheria, and Euarchonta plus Glires. The first three groups are consistently monophyletic with different methods of analysis. Euarchonta plus Glires is monophyletic or paraphyletic depending on the phylogenetic method. A unique nine-base-pair deletion in exon 11 of the BRCA1 gene provides additional support for the monophyly of Afrotheria, which includes proboscideans, sirenians, hyracoids, tubulidentates, macroscelideans, chrysochlorids and tenrecids. Laurasiatheria contains cetartiodactyls, perissodactyls, carnivores, pangolins, bats and eulipotyphlan insectivores. Parallel adaptive radiations have occurred within Laurasiatheria and Afrotheria. In each group, there are aquatic, ungulate and insectivore-like forms.

Animals↗