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At least 649 records · Page 36Linked to original sources
PubMed1995

The evolution of the type I interferon gene family in mammals.

A phylogenetic analysis of mammalian type I interferon (IFN) genes showed: (1) that the three main subfamilies of these genes in mammals (IFN-beta, IFN-alpha, and IFN-omega) diverged after the divergence of birds and mammals but before radiation of the eutherian orders and (2) that IFN-beta diverged first. Although apparent cases of interlocus recombination among mouse IFN-alpha genes were identified, the hypothesis that coding regions of IFN-alpha genes have been homogenized within species by interlocus recombination was not supported. Flanking regions as well as coding regions of IFN-alpha were more similar within human and mouse than between these species; and reconstruction of the pattern of nucleotide substitution in IFN-alpha coding regions of four mammalian species by the maximum parsimony method suggested that parallel substitutions have occurred far more frequently between species than within species. Therefore, it seems likely that IFN-alpha genes have duplicated independently within different eutherian orders. In general, type I IFN genes are subject to purifying selection, which in the case of IFN-alpha and IFN-beta is strongest in the putative receptor-binding domains. However, analysis of the pattern of nucleotide substitution among IFN-omega genes suggested that positive Darwinian selection may have acted in some cases to diversify members of this subfamily at the amino acid level.

Amino Acid Sequence↗
PubMed1978

Ultrastructure of capillaries in the conduction system of the heart in various mammals.

The capillaries in the atrioventricular node and atriventricular bundle of the heart (mammals) were investigated by thin sections and freeze-etch replicas. Fenestrated endothelial cells were found to occur in all mammals examined in this study. These fenestrations (500 +/- 50 A diameter) are bridged by a diaphragm and occur in relatively small sieve areas. In contrast to the AV-node and AV-bundle, the non-specialized myocardium is supplied by continuous capillaries. The presence of the fenestrated capillary in the conduction system of the heart may serve to increase both permeability and passive transport capacity.

Animals↗
PubMed1975

Isolation of Emmonsia crescens Emmons et Jellison 1960 from small mammals in Bulgaria.

Authors examined a total of 3849 specimens of mammals included in 36 species from different region of Bulgaria. Adiaspiromycosis was detected microscopically in 18 mammals species. Strains of Emmonsia crescens Emmons et Jellison 1960 was isolated from 6 species--Apodemus flavicollis, Apodemus sylvaticus, Clethrionomys glareolus, Microtus arvalis, Musmusculus and Rattus norvegicus.

Animals↗
PubMed1991

Species variation in organellar location and activity of L-pipecolic acid oxidation in mammals.

The oxidation of L-pipecolic acid to alpha-aminoadipic acid was studied in eight species of mammals using an assay system more sensitive than those previously employed. After percoll-gradient fractionation, activity was localized to the mitochondrial-enriched fractions in tissues from rabbit, guinea pig, pig, dog, and sheep, with guinea pig kidney cortex showing greatest specific activity. These results contrast with the peroxisomal oxidation of L-pipecolic acid observed in macaques and man (Mihalik and Rhead 1989; Mihalik et al. 1989). Rats and mice had undetectable levels of both peroxisomal and mitochondrial L-pipecolic acid oxidation. In the rat, peroxisomal oxidation activity was not induced by feeding with either clofibrate or clofibrate and L-pipecolic acid. Thus, among mammals, both the ability to oxidize L-pipecolic acid and the organellar location of this oxidation is species dependent.

Animals↗
PubMed1989

Critical evaluation of polychlorinated biphenyl toxicity in terrestrial and marine mammals: increasing impact of non-ortho and mono-ortho coplanar polychlorinated biphenyls from land to ocean.

Residues of potentially toxic non-ortho chlorine substituted coplanar 3,3',4,4'-tetra-,3,3',4,4',5-penta-, 3,3',4,4',5,5'-hexachlorobiphenyl and their mono- and di-ortho analogs 2,3',4,4',5-penta, 2,3,3',4,4'-penta-, 2,3,3',4,4',5-hexa- and 2,2',3,3',4,4'-hexa-, 2,2',3,4,4',5-hexachlorobiphenyl) were determined in humans, dogs, cats (terrestrial), a finless porpoise (Neophocoena phocoenoides--coastal), Dall's porpoises (Phocoenoides dalli, dalli), Baird's beaked whales (Berardius bairdii) and killer whales (Orcinus orca--open ocean). Among the coplanar polychlorinated biphenyl (PCB) congeners, the concentration of the di-ortho congeners was the highest and the non-ortho congeners was the lowest. However, all three coplanar PCBs occurred at significantly higher levels than toxic polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). The relative bioconcentration and metabolic capacity of terrestrial and marine mammals to these chemicals, suggest that the toxic threat of coplanar PCBs increases from land to ocean, but the reverse is true for PCDDs and PCDFs. The toxic threat of coplanar PCBs to higher aquatic predators such as cetaceans was principally assessed by 2,3,7,8-T4CDD Toxic Equivalent Analysis which is based on the induction of arylhydrocarbon hydroxylase (AHH) and ethoxyresorufin O-deethylase (EROD). Analysis indicates, in particular, that the bioaccumulation of toxic 3,3',4,4',5-penta- and 2,3,3',4,4'-pentachlorobiphenyls in carnivorous marine mammals is a cause for considerable concern.

Animals↗
PubMed1979

Enamel structure in some therapsids and mesozoic mammals.

The distribution of enamel tubules, the shapes and arrangements of prisms, and the orientation of crystals in ground sections from several therapsids and mesozoic mammals have been investigated by conventional and polarizing microscopy. Along each of three separate phylogenetic lines which evolved occluding teeth, there was a progressive increase in the numbers of enamel tubules. In the investigation, the arcade-shaped prisms typical of recent mammals were first seen in material from the Cretaceous period. All the enamels investigated from the Triassic contained columns of crystals, which were deduced as hexagonal. The inner ends of the crystals within each column deviated towards the center of the column. It is concluded that the existence of an interprismatic region provides the most important distinction between prismatic enamels and the hexagonal columns of crystals in the Triassic material.

Animals↗
PubMed1996

Phosphatidate phosphatases of mammals, yeast, and higher plants.

Phosphatidate phosphatase (EC 3.1.3.4) catalyzes the hydrolysis of phosphatidate to yield sn-1,2-diacylglycerol and inorganic phosphate. In mammalian systems, forms of phosphatidate phosphatase involved in glycerolipid synthesis and signal transduction have been identified. Forms of the enzyme involved in signal transduction have been purified and partially characterized. In yeast, phosphatidate phosphatases associated with the endoplasmic reticulum and mitochondria have also been purified and partially characterized. Information on phosphatidate phosphatases from mammals and yeast is useful in characterizing the enzyme from plant systems. This review examines progress on the characterization of phosphatidate phosphatases from mammals, yeast, and higher plants. The purification and characterization of the phosphatidate phosphatase involved in glycerolipid synthesis in developing oilseeds may lead to the identification of the encoding gene. Increasing our understanding of the enzymes of lipid synthesis in developing seeds will aid in the development of biotechnological strategies for seed oil modification.

Animals↗
PubMed2000

Small mammal trapping in tropical montane forests of the upper Nilgiris, southern India: an evaluation of capture-recapture models in estimating abundance.

Capture-mark-recapture was used to study small mammal populations in tropical montane forests in southern India. Eleven plots in six montane forest patches were sampled from February-October, 1994. Six species were captured, including four rodents and two shrews. PROGRAM CAPTURE was used to derive estimates of density of the most abundant species in the study area, Rattus rattus Linnaeus. The coefficient of variation of the density estimate was used as an index of precision. The coefficient of variation decreased exponentially with increasing capture probability and with an increase in trapping duration. The coefficient of variation and the capture probability were not correlated with estimates of density. The density estimate increased with trapping duration, as did trap mortality. The latter may have been due to the trend of increased mortality with recaptures of the same individual, which in turn may have been due to weight loss over consecutive captures. Estimates of density derived using four estimators were different for 2, 3, 4 and 5 days of trapping. The coefficient of variation was highest for the generalized removal estimate and lowest for Darroch's estimate. The models and estimators could not be applied to more than one species, and for this species, only in select habitats in a few seasons. Therefore, models of density estimation developed for temperate areas may not be suitable for tropical habitats due to low densities of small mammals in these habitats.

Animals↗
PubMedDate not supplied

Alaskan marine mammal tissue archival project.

A project to establish an archive of Alaskan marine mammal tissues was conceived in 1987 to be a part of the National Biomonitoring Specimen Bank (NBSB). Protocols and field collection of marine mammals, long-term storage, and analysis are summarized in this paper. Instrumental neutron activation analysis has been used for an initial evaluation of trace element content in samples of northern fur seal (Callorhinus ursinus) from the Pribilof Islands. The findings agree with previously observed trace element levels in northern fur seals. The archived specimens can be used in future studies when comparison of past and present pollution levels are needed.

Alaska↗
PubMed2003

Thiamine triphosphate and thiamine triphosphatase activities: from bacteria to mammals.

In most organisms, the main form of thiamine is the coenzyme thiamine diphosphate. Thiamine triphosphate (ThTP) is also found in low amounts in most vertebrate tissues and can phosphorylate certain proteins. Here we show that ThTP exists not only in vertebrates but is present in bacteria, fungi, plants and invertebrates. Unexpectedly, we found that in Escherichia coli as well as in Arabidopsis thaliana, ThTP was synthesized only under particular circumstances such as hypoxia (E. coli) or withering (A. thaliana). In mammalian tissues, ThTP concentrations are regulated by a specific thiamine triphosphatase that we have recently characterized. This enzyme was found only in mammals. In other organisms, ThTP can be hydrolyzed by unspecific phosphohydrolases. The occurrence of ThTP from prokaryotes to mammals suggests that it may have a basic role in cell metabolism or cell signaling. A decreased content may contribute to the symptoms observed during thiamine deficiency.

Amino Acid Sequence↗
PubMed2004

The first haramiyoid mammal from Asia.

A lower molar of a haramiyoid mammal is described from the Toutunhe Formation of Liuhuanggou near Urumqi in the southern Junggar Basin, Xinjiang, China. It is referred to Eleutherodon sp., otherwise exclusively known from the Upper Bathonian of England. It is the first record of the order Haramiyida from Asia and the first Mesozoic mammal described from the southern Junggar Basin. Apart from the English specimens of Eleutherodon and Staffia from the Upper Jurassic of East Africa, it is the geologically youngest haramiyoid known. It is the first vertebrate taxon from the Toutunhe Formation that is probably not endemic and lends some support to the dating of the Formation as late Middle Jurassic, probably Bathonian.

Animals↗
PubMed1997

Cooperative care of young in mammals.

The provision of care to non-offspring in animal societies has attracted substantial scientific attention because of its apparent contradiction to the concept of individual selection. In mammals such cooperative care of alien young has been described for both non-breeding and breeding females. I first review the types of non-offspring care that are known from mammals and then discuss the actual and potential fitness benefits and costs for the donors and recipients of this cooperative behaviour. For many species, however, quantitative analysis is still missing. Non-offspring care provided by non-breeding individuals may best be explained by indirect fitness benefits due to improved reproduction of a related breeder under environmental conditions in which successful direct reproduction is not possible. Cooperative care of young among breeding females is also directed preferentially to non-descendant kin and may have evolved due to mutualistic benefits. Our current knowledge of mammalian cooperative care of the young raises questions that must be answered in order to fully understand the evolution of social behaviour.

Altruism↗
PubMed1998

The story of the internal carotid artery of mammals: from Galen to sudden infant death syndrome.

Some anatomical aspects of the blood supply of the brains of mammals have been examined to illuminate their functions. A fundamental explanation of sudden infant death syndrome (cot death) is suggested following experimental observations. Speculative contributions have been made to comparative physiological ideas concerning mammals of pronograde and erect habitus, their vascular pressure adaptations and temperature management. Neuro- and interventional radiologists may make some significant future applications of these ideas. Of immediate practical interest is the possibility of influencing the well-being of human embryos' neural tube development in utero by a comprehensive study of their temperature environment.

Adaptation, Physiological↗
PubMed2004

The decline of isochores in mammals: an assessment of the GC content variation along the mammalian phylogeny.

Whether isochores, the large-scale variation of the GC content in mammalian genomes, are being maintained has recently been questioned. It has been suggested that GC-rich isochores originated in the ancestral amniote genome but that whatever force gave rise to them is no longer effective and that isochores are now disappearing from mammalian genomes. Here we investigated the evolution of the GC content of 41 coding genes in 6 to 66 species of mammals by estimating the ancestral GC content using a method which allows for different rates of substitution between sites. We found a highly significant decrease in the GC content during early mammalian evolution, as well as a weaker but still significant decrease in the GC content of GC-rich genes later in at least three groups of mammals: primates, rodents, and carnivores. These results are of interest because they confirm the recently suggested disappearance of GC-rich isochores in some mammalian genomes, and more importantly, they suggest that this disappearance started very early in mammalian evolution.

Animals↗
PubMed2006

Preliminary assessment of the impact of microRNA-mediated regulation on coding sequence evolution in mammals.

Despite prior claims to the contrary, several lines of evidence suggest that selection acts on synonymous mutations in mammals. What might be the mechanisms for such selection? Here I attempt to quantify the constraints on the evolution of the coding sequence resulting from regulation of mRNA by microRNAs (miRNAs) that antisense-bind to the coding region of mRNAs. I employ a set of genes recently experimentally verified to be the target of a miRNA, all with putative antisense pairing domains within the coding sequence. Although very small ( approximately 22 nucleotides), 2 of 13 pairing domains show evidence of significantly slow sequence evolution. This, along with evidence that these genes are regulated by the miRNA under consideration, provides the first good candidate domains for intra-CDS pairing of a miRNA in mammals. When analyzed en masse, the putative pairing domains have a significantly reduced rate of synonymous evolution (approximately 35% lower than null). However, given the size and rarity of pairing domains within the coding sequence, the effects that such constraint has on estimates of the mutation rate are small enough to be ignored (probably less than 1% reduction). The pairing sites also have low Ka values and the selection on the synonymous sites is unlikely to lead to misleading reports of localized high Ka/Ks ratios.

3' Untranslated Regions↗
PubMed2003

The influence of climate on the basal metabolic rate of small mammals: a slow-fast metabolic continuum.

The influence of climate (mean annual rainfall, rainfall variability, ambient temperature, T(a)) on the basal metabolic rate (BMR) of 267 small mammals (<1 kg) from six zoogeographical zones was investigated using conventional and phylogenetically independent data (linear contrasts). All climate variables varied between zones, as did BMR and body temperature ( T(b)), but not thermal conductance. Holarctic zones were more seasonal and colder, but rainfall was less variable, than non-Holarctic zones. In general, the BMR was most strongly influenced by body mass, followed by T(a) and the rainfall variables. However, there was significant variation in the strength of these relationships between zones. BMR and T(b) increased with latitude, and mass-independent BMR and T(b) were positively correlated. The latter relationship offers evidence of a slow-fast metabolic continuum in small mammals. The fast end of the continuum (high BMR) is associated with the highest latitudes where BMR is most strongly influenced by T(a) and mean annual rainfall (i.e. mean productivity). The slow end of the continuum (low BMR) is associated with the semi-tropics, low productivity zones, and climatically unpredictable zones, such as deserts. Here rainfall variability has the strongest influence on BMR after body size. The implications of a slow-fast metabolic continuum are discussed in terms of various models associated with the evolution of BMR, such as the aerobic capacity models and the "energetic definition of fitness" models.

Acclimatization↗
PubMed2005

Occurrence and molecular characterization of Cryptosporidium spp. in mammals and reptiles at the Lisbon Zoo.

The presence of Cryptosporidium parasites in mammals and reptiles kept at the Lisbon Zoo was investigated. A total of 274 stool samples were collected from 100 mammals and 29 reptiles. The species and genotype of the isolates identified by light microscopy were determined by nested PCR and sequence analysis of a fragment of the small subunit rRNA gene. Cryptosporidium oocysts were found in one black wildebeest (Connochaetes gnou), one Prairie bison (Bison bison bison) and in one Indian star tortoise (Geochelone elegans). The PCR and sequence analysis of these three isolates showed that those excreted by the Prairie bison were Cryptosporidium mouse genotype, those from the black wildebeest were from a new Cryptosporidium genotype and those infecting the Indian star tortoise were Cryptosporidium tortoise genotype. The present work reports a new Cryptosporidium genotype in a black wildebeest and the first finding of the Cryptosporidium mouse genotype in a ruminant.

Animals↗
PubMed2005

Box-modeling of 15N/14N in mammals.

The 15N/14N signature of animal proteins is now commonly used to understand their physiology and quantify the flows of nutrient in trophic webs. These studies assume that animals are predictably 15N-enriched relative to their food, but the isotopic mechanism which accounts for this enrichment remains unknown. We developed a box model of the nitrogen isotope cycle in mammals in order to predict the 15N/14N ratios of body reservoirs as a function of time, N intake and body mass. Results of modeling show that a combination of kinetic isotope fractionation during the N transfer between amines and equilibrium fractionation related to the reversible conversion of N-amine into ammonia is required to account for the well-established approximately 4 per thousand 15N-enrichment of body proteins relative to the diet. This isotopic enrichment observed in proteins is due to the partial recycling of 15N-enriched urea and the urinary excretion of a fraction of the strongly 15N-depleted ammonia reservoir. For a given body mass and diet delta15N, the isotopic compositions are mainly controlled by the N intake. Increase of the urea turnover combined with a decrease of the N intake lead to calculate a delta15N increase of the proteins, in agreement with the observed increase of collagen delta15N of herbivorous animals with aridity. We further show that the low delta15N collagen values of cave bears cannot be attributed to the dormancy periods as it is commonly thought, but inversely to the hyperphagia behavior. This model highlights the need for experimental investigations performed with large mammals in order to improve our understanding of natural variations of delta15N collagen.

Animals↗