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At least 685 records · Page 38Linked to original sources
PubMed1994

Mouse erythroid cells express multiple putative RNA helicase genes exhibiting high sequence conservation from yeast to mammals.

RNA secondary structure is a critical determinant of RNA function in ribosome assembly, pre-mRNA splicing, mRNA translation and RNA stability. The 'DEAD/H' family of putative RNA helicases may help regulate these processes by utilizing intrinsic RNA-dependent ATPase activity to catalyze conformational changes in RNA secondary structure. To investigate the repertoire of DEAD/H box proteins expressed in mammals, we used PCR techniques to clone from mouse erythroleukemia (MEL) cells three new DEAD box cDNAs with high similarity to known yeast (Saccharomyces cerevisiae) genes. mDEAD2 and mDEAD3 (mouse DEAD box proteins) are > 95% identical to mouse PL10 but exhibit differential tissue-specific expression patterns; mDEAD2 and mDEAD3 are also approx. 70% identical (at the aa level) to yeast DED1 and DBP1 proteins. Members of this DEAD box subclass contain C-terminal domains with high content of Arg, Ser, Gly and Phe, reminiscent of the RS domain in several Drosophila and mammalian splicing factors. mDEAD5 belongs to a second class related to translation initiation factors from yeast (TIF1/TIF2) and mammals (eIF-4A); this class contains a novel conserved peptide motif not found in other DEAD box proteins. Northern blotting shows that mDEAD5 is differentially expressed in testis vs. somatic tissues. Thus, mouse erythroid cells produce two highly conserved families of putative RNA helicases likely to play important roles in RNA metabolism and gene expression.

Amino Acid Sequence↗
PubMed1989

The gluconeogenicity of fatty acids in mammals.

Although excess glucose can be readily converted to fatty acids in mammals, most textbooks state that glucose cannot be formed from fatty acids. Whilst this remains largely true, several pathways have now been discovered in mammals in which fatty acids are potentially gluconeogenic.

Animals↗
PubMed2004

Osmotic stress of salmon stimulates upregulation of a cold inducible RNA binding protein (CIRP) similar to that of mammals and amphibians.

Salmon are subjected to hyperosmotic stress during transition from freshwater to the marine environment. A variety of mechanisms have evolved to allow movement of the animal from a hydrating to a dehydrating environment. Using differential assay of mRNA expression, a 1.3 kb transcript was found to be upregulated in branchial lamellae of salmon exposed to hyperosmotic conditions. The transcript contains an open reading frame of 618 nt coding for a 205 amino acid protein with a molecular mass of 21.5 kDa. The putative protein, dubbed salmon glycine-rich RNA binding protein (SGRP), possesses a high degree of identity (>70%) with the cold inducible RNA binding proteins (CIRP) of mammals and amphibians and contains the canonical features of these proteins including a single RNA recognition motif (RRM), high glycine content and conserved flanking motifs. SGRP mRNA was observed to increase in response to hyperosmotic stress of branchial tissue with maximum levels of expression after 48 h of exposure. Transcript also was observed in liver, kidney and heart but was not upregulated significantly by osmotic stress in these tissues. Exposure of isolated lamellae to heat stress and sodium arsenite, known inducers of hsps, did not stimulate accumulation of SGRP transcript. Similarly, inhibition of protein synthesis with cycloheximide and the MAPK and MEK signal transduction pathways with SB202190 and PD98059 failed to alter expression of the gene. Of significance was the absence of an increase in expression of SGRP in response to cold stress (DeltaT = 5 and 12 degrees C for 12 and 24 h). The findings of this research suggest that ectothermic salmon inhabiting boreal waters possess a protein analogous to the CIRPs currently identified in mammals and amphibians. In contrast to the function of CIRPs, SGRP appears to have a more prominent role in adaptation to hyperosmotic conditions rather than cold stress.

Amino Acid Sequence↗
PubMed2004

Scaling the amplitudes of the circadian pattern of resting oxygen consumption, body temperature and heart rate in mammals.

We questioned whether the amplitudes of the circadian pattern of body temperature (T(b)), oxygen consumption (V (O(2))) and heart rate (HR) changed systematically among species of different body weight (W). Because bodies of large mass have a greater heat capacitance than those of smaller mass, if the relative amplitude (i.e., amplitude/mean value) of metabolic rate was constant, one would expect the T(b) oscillation to decrease with the increase in the species W. We compiled data of T(b), V (O(2)) and HR from a literature survey of over 200 studies that investigated the circadian pattern of these parameters. Monotremata, Marsupials and Chiroptera, were excluded because of their characteristically low metabolic rate and T(b). The peak-trough ratios of V (O(2)) (42 species) and HR (35 species) averaged, respectively, 1.57+/-0.08, and 1.35+/-0.07, and were independent of W. The daily high values of T(b) did not change, while the daily low T(b) values slightly increased, with the species W; hence, the high-low T(b) difference (57 species) decreased with W (3.3 degrees C.W(-0.13)). However, the decrease in T(b) amplitude with W was much less than expected from physical principles, and the high-low T(b) ratio remained significantly above unity even in the largest mammals. Thus, it appears that in mammals, despite the huge differences in physical characteristics, the amplitude of the circadian pattern is a fixed (for V (O(2)) and HR), or almost fixed (for T(b)), fraction of the 24-h mean value. Presumably, the amplitudes of the oscillations are controlled parameters of physiological significance.

Animals↗
PubMed2005

Scaling the daily oscillations of breathing frequency and skin temperature in mammals.

Among mammals, the peak-trough difference (PTD) of the circadian pattern of body temperature (T(b)) drops very little with the increase in body mass (W), despite the large increase in heat capacitance and thermal inertia. We asked whether this might be contributed by systematic differences in the circadian pattern of breathing frequency (f) and skin temperature (Tskin), which are parts of the control mechanisms of heat loss. Measurements had been conducted on animals of eight species, chosen to cover a four-fold range in W, while resting and awake. The oscillation of f preceded that of T(b) in 7 of the 8 species, and its acrophase did not correlate with W. The daily mean and PTD of f scaled with W in a similar manner (respectively, W(-)(23) and W(-)(0.29)), the PTD averaging about 20% of the daily mean. The circadian oscillations of Tskin, measured in specimens of five species at three locations (abdomen, ear and thigh), were in phase with T(b). Neither the PTD nor the acrophase of Tskin changed systematically with W. The differences between T(b) and Tskin (means, peaks and troughs) decreased significantly with W; on average, the T(b)-Tskin difference scaled to W(-)(0.19). In conclusion, the relative amplitudes and the acrophase of Tskin and f did not show systematic inter-species differences. The progressive increase of Tskin with W could be a factor in maintaining the PTD of T(b) within a narrow range among mammals of very different size.

Animals↗
PubMed2006

Risk assessment of metals and organic pollutants for herbivorous and carnivorous small mammal food chains in a polluted floodplain (Biesbosch, The Netherlands).

A risk assessment was made for a carnivorous and a herbivorous food chain in a heavily polluted natural estuary (Biesbosch), by determining the most critical pollutants and the food chain most at risk. Exposure of food chains to metals, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) was assessed by analyzing dietary concentrations, internal concentrations, and biomarkers of exposure. Common shrew (Sorex araneus) and bank vole (Clethrionomys glareolus) were selected as representative small mammal species for the carnivorous and herbivorous food chain, respectively, and earthworms (Lumbricus rubellus) and snails (Cepaea nemoralis) as representative prey species for the carnivorous food chain. Metals contributed most to the total risk for small mammals and earthworms. PCBs, but not PAHs, contributed to the overall risk for S. araneus at regularly flooded locations. The carnivorous food chain appeared most at risk given the higher exposure levels and bioaccumulating potency found for contaminants in S. araneus.

Animals↗
PubMed2005

Comparative genomics of the Hlx homeobox gene and protein: conservation of structure and expression from fish to mammals.

Hlx is a homeobox transcription factor gene that is expressed in intestinal and hepatic mesenchyme of the developing mouse embryo and is essential for normal intestinal and hepatic development. Because of the morphological and molecular similarities in the development of the digestive system across species, we hypothesized that the Hlx gene and protein sequences and expression patterns would be conserved among vertebrates. Comparison of the Hlx gene orthologues of human, chimpanzee, mouse, rat, pufferfish (Fugu) and zebrafish demonstrates that these six genes share an identical organization with four exons and three introns. Comparison of the inferred Hlx protein sequences from these and three additional species (chick, Spanish ribbed newt and rainbow trout) reveals significant sequence identity, with identical homeodomains. The expression of Hlx in the mesenchyme of developing chick embryos is highly similar to that of mouse. Fugu Hlx is expressed in a tissue-specific manner that is similar though not identical to that of mouse, suggesting a conservation of Hlx function between mammals and birds. The mammalian and fish Hlx genes share a putative 5' upstream enhancer as well as an inverted repeat containing CCAAT boxes on opposite strands that we have previously shown to be important for mouse Hlx gene expression. These results suggest that the function of Hlx and the mechanisms regulating its expression are highly conserved in mammals, birds, amphibians and fish.

Amino Acid Sequence↗
PubMed2006

Maximum running speed limitations on terrestrial mammals: a theoretical approach.

Here we study maximum running speed (MRS) limitations on a previously proposed model of energetic and muscle-tendon unit functions on running mammals. In the present work the MRS and some anatomical or physiological limitations are estimated for mammals with body mass between 1.5 and 300 kg. The MRS variations with body mass are discussed and compared with results of previous experimental and observational studies. The tendon strength seems to be the most relevant limitation, but leg extensor muscle mass and metabolic costs could be relevant also. The physiological maximum muscle speed seems to be less important in the body mass range studied here.

Animals↗
PubMed2006

Acute phase response in zebrafish upon Aeromonas salmonicida and Staphylococcus aureus infection: striking similarities and obvious differences with mammals.

Zebrafish has emerged as a valuable model for immunological studies. However, little is known about the overall picture of its immune response to infectious pathogens. Here we present the first systematic study of its immune response to Aeromonas salmonicida and Staphylococcus aureus, a Gram-negative and a Gram-positive bacteria, respectively. Genes induced upon infection were identified with suppression subtractive hybridization, with many of them encoding acute phase proteins (APPs). When compared with mammals, striking similarities and obvious differences have been observed. Both similar APPs (SAA, hepcidin and haptoglobin, etc.) and a similar system for the induction of APPs (which involves the TLRs, pro-inflammatory cytokines and C/EBPs) were identified, implying evolutionary conserved mechanisms among fish and mammals. Some novel APPs were also discovered, suggesting different immune strategies adopted by fish species. Among which, LECT2 was induced by up to 1000-fold upon infection, shedding new lights on the function of this gene. Our results constitute the first demonstration of a similar while different immune response in zebrafish and open new avenues for the investigation of evolutionary conserved and fish specific mechanisms of innate immunity.

Acute-Phase Reaction↗
PubMed2006

Prescribed burning in a Eucalyptus woodland suppresses fruiting of hypogeous fungi, an important food source for mammals.

Fruit bodies of hypogeous fungi are an important food source for many small mammals and are consumed by larger mammals as well. A controversial hypothesis that prescribed burning increases fruiting of certain hypogeous fungi based on observations in Tasmania was tested in the Australian Capital Territory to determine if it applied in a quite different habitat. Ten pairs of plots, burnt and nonburnt, were established at each of two sites prescribe-burnt in May 1999. When sampled in early July, after autumn rains had initiated the fungal fruiting season, species richness and numbers of fruit bodies on the burnt plots were extremely low: most plots produced none at all. Both species richness and fruit body numbers were simultaneously high on nonburnt plots. One of the sites was resampled a year after the initial sampling. At that time species richness and fruit body abundance were still significantly less on burnt plots than on nonburnt, but a strong trend towards fungal recovery on the burnt plots was evident. This was particularly so when numbers of fruit bodies of one species, the hypogeous agaric Dermocybe globuliformis, were removed from the analysis. This species strongly dominated the nonburnt plots but was absent from burnt plots in both years. The trend towards recovery of fruit body abundance in the burnt plots one year after the burn was much more pronounced with exclusion of the Dermocybe data. The Tasmanian-based hypothesis was based mostly on the fruiting of two fire-adapted species in the Mesophelliaceae. Neither species occurred on our plots. Accordingly, the results and conclusions of the Tasmanian study cannot be extrapolated to other habitats without extensive additional study. Implications for management of habitat for fungi and the animals that rely on the fungi as a food source are discussed.

Animals↗
PubMed2004

Comparative analysis of melanin-concentrating hormone structure and activity in fishes and mammals.

A comparative analysis of the structure of the melanin-concentrating hormone (MCH) precursor reveals that this sequence has been subjected to a higher selection pressure in mammals than in teleosts, suggesting that the structural constraints have not been the same throughout the vertebrate lineage. In contrast, the MCH peptide sequence has been very well conserved in all species. A sensitive and reproducible eel skin assay was developed and allowed us to define the structural features needed for a full MCH bioactivity. It was shown that the minimal structure carrying the critical residues was the same in fishes and in mammals. A pharmacological approach confirmed that MCH receptor activation decreased the cAMP levels in the fish skin, but this effect appeared to be independent from a Galphai protein. We propose that one of the intracellular signaling pathways of the MCH receptor in fish skin is the activation of one or several cellular phosphodiesterases.

Amino Acid Sequence↗
PubMed2006

Evolution of the placenta in eutherian mammals.

We review recent advances in our understanding of placental evolution with particular focus on the interhaemal barrier. It seems likely that the non-invasive, epitheliochorial placentation of living eutherians is a derived state. However, there is disagreement on whether the last common ancestor of eutherian mammals had an endotheliochorial placenta or a haemochorial one. Research has been stimulated by improved understanding of the relations between the orders of mammals provided by molecular phylogenetics. In part, the uncertainties arise from doubt about how to root the mammalian tree. Resolution of this issue will require improved taxon sampling in molecular analyses. At the same time, we need to foster research in comparative placentation on relevant taxa, particularly at the ultrastructural level. Only then can we ensure that information available about the placenta is adequate to capitalise on future advances in molecular phylogenetics. Examples are given of recent findings that could benefit cladistic analysis of placental evolution.

Animals↗
PubMed2005

Radiocaesium (137Cs) in marine mammals from Svalbard, the Barents Sea and the North Greenland Sea.

Specific activities of the anthropogenic radionuclide, 137Cs, were determined in marine mammals from Svalbard and the Barents and North Greenland Seas. Muscle samples were collected from 12 polar bears, 15 ringed seals, 10 hooded seals, 7 bearded seals, 14 harp seals, one walrus, one white whale and one blue whale in the period 2000-2003. The mean concentrations (+/-SD) of 137Cs were: 0.72+/-0.62 Bq/kg wet weight (w.w.) for polar bears; 0.49+/-0.07 Bq/kg w.w. for ringed seals; 0.25+/-0.10 Bq/kg w.w. for hooded seals; 0.22+/-0.11 Bq/kg w.w. for bearded seals; 0.36+/-0.13 Bq/kg w.w. for harp seals; 0.67 Bq/kg w.w. for the white whale sample; 0.24 Bq/kg w.w. for the blue whale; and below detection limit for the walrus. Significant differences in 137Cs specific activities between some of the species were found. Ringed seals had higher specific activities than the other seal species in the study. Bearded seals and hooded seals had similar values, which were both significantly lower than the harp seal values. The results in the present study are consistent with previous reported results, indicating low specific activities of 137Cs in Arctic marine mammals in the Barents Sea and Greenland Sea region during the last 20 years. The species specific differences found may be explained by varying diet or movement and distribution patterns between species. No age related patterns were found in specific activities for the two species (polar bears and hooded seals) for which sufficient data was available. Concentration factors (CF) of 137Cs from seawater were determined for polar bears, ringed, bearded, harp and hooded seals. Mean CF values ranged from 79+/-32 (SD) for bearded seals sampled in 2002 to 244+/-36 (SD) for ringed seals sampled in 2003 these CF values are higher than those reported for fish and benthic organisms in the literature, suggesting bioaccumulation of 137Cs in the marine ecosystem.

Age Factors↗
PubMed2004

Are BMP-15 and GDF-9 primary determinants of ovulation quota in mammals?

How do mammals control the number of eggs that are ovulated during the estrous and menstrual cycles? Our understanding of this fundamental process has grown in recent years as a result of intense efforts to identify and characterize the genes that control the ovulation quota. An increasing body of evidence shows that two oocyte-specific factors, bone morphogenetic protein-15 (BMP-15) and growth and differentiation factor-9 (GDF-9), play crucial roles in determining folliculogenesis, ovulation rate and litter size in sheep and mice. In this article, we review recent advances on the physiological, cellular and molecular roles of BMP-15 and GDF-9, which, potentially, link these oocyte-secreted factors to the species-specific determination of ovulation quota and litter size in mammals.

Animals↗
PubMed2004

L1 (LINE-1) retrotransposon diversity differs dramatically between mammals and fish.

L1 retrotransposons replicate (amplify) by copying (reverse transcribing) their RNA transcript into genomic DNA. The evolutionary history of L1 in mammals has been unique. In mice and humans approximately 80 million years of L1 evolution and replication produced a single evolutionary lineage of L1 elements while generating approximately 20% of the genomic mass in each species. By contrast, zebrafish contain >30 distinct L1 lineages that have generated approximately one-tenth as much DNA. We contend that, by becoming far more permissive of interspersed repeated DNA than other organisms, mammals are conducive to competition between L1 families for replicative dominance, and that this competition, perhaps for the host factors required for L1 replication, results in a single L1 lineage.

Animals↗
PubMed2005

Gene duplication and complex circadian clocks in mammals.

The circadian clock arose early in the evolution of life to enable organisms to adapt to the cycle of day and night. Recently, the extent and importance of circadian regulation of behaviour and physiology has come to be more fully realized. Core molecular cogs of circadian oscillators appear to have been largely conserved between such diverse organisms as Drosophila melanogaster and mammals. However, gene duplication events have produced multiple copies of many clock genes in mammals. Recent studies suggest that genome duplication has lead to increased circadian complexity and local tissue regulation. This has important implications for temporal regulation of behaviour via multiple clocks in the central nervous system, and also extends to the local physiology of major body organs and tissues.

Animals↗
PubMed2003

Natural phospholipase A(2) myotoxin inhibitor proteins from snakes, mammals and plants.

A renewed interest in the phenomenon of inter- and intra-species resistance towards the toxicity of snake venoms, coupled with the search for new strategies for treatment of snake envenomations, has prompted the discovery of proteins which neutralize the major toxic components of these venoms. Among these emerging groups of proteins are inhibitors of toxic phospholipases A2 (PLA2s), many of which exhibit a wide range of toxic effects including muscle-tissue damage, neurotoxicity, and inflammation. These proteins have been isolated from both venomous and non-venomous snakes, mammals, and most recently from medicinal plant extracts. The snake blood-derived inhibitors have been grouped into three major classes, alpha, beta, and gamma, based on common structural motifs found in other proteins with diverse physiological properties. In mammals, DM64, an anti-myotoxic protein isolated from opossum serum, belongs to the immunoglobulin super gene family and is homologous to human alpha1B-glycoprotein and DM43, a metalloproteinase inhibitor from the same organism. In plants, a short note is made of WSG, a newly described anti-toxic-PLA2 glycoprotein isolated from Withania somnifera (Ashwaganda), a medicinal plant whose aqueous extracts neutralize the PLA2 activity of the Naja naja venom. The implications of these new groups of PLA2 toxin inhibitors in the context of our current understanding of snake biology as well as in the development of novel therapeutic reagents in the treatment of snake envenomations worldwide are discussed.

Animals↗
PubMed2005

The ribonuclease A superfamily of mammals and birds: identifying new members and tracing evolutionary histories.

The RNase A superfamily has been important in biochemical, structural, and evolutionary studies and is believed to be the sole vertebrate-specific enzyme family. To understand the origin and diversification of the superfamily, we here determine its entire repertoire in the sequenced genomes of human, mouse, rat, and chicken. We report a previously unnoticed gene cluster in mouse chromosome 10 and a number of new genes, including mammalian RNases 11-13, which are close relatives of the recently identified RNases 9 and 10. Gene expression data imply male-reproductive functions for RNases 9-13, although their sequences suggest the lack of ribonucleolytic activities. In contrast to the presence of 13-20 functional genes in mammals, chicken has only 3 RNase genes, which are evolutionarily close to mammalian RNase 5, like other nonmammalian RNases. This and other evidence suggests that the RNase A superfamily originated from an RNase 5-like gene and expanded in mammals. Together with the fact that multiple lineages of the superfamily, including RNases 2, 3, 5, and 7, have antipathogenic activities, we suggest that the superfamily started off as a host-defense mechanism in vertebrates. Consistent with this hypothesis, all members of the superfamily exhibit high rates of amino acid substitution as is commonly observed in immunity genes.

Amino Acid Sequence↗