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PubMed2005

Almost all about citrulline in mammals.

Citrulline (Cit, C6H13N3O3), which is a ubiquitous amino acid in mammals, is strongly related to arginine. Citrulline metabolism in mammals is divided into two fields: free citrulline and citrullinated proteins. Free citrulline metabolism involves three key enzymes: NO synthase (NOS) and ornithine carbamoyltransferase (OCT) which produce citrulline, and argininosuccinate synthetase (ASS) that converts it into argininosuccinate. The tissue distribution of these enzymes distinguishes three "orthogonal" metabolic pathways for citrulline. Firstly, in the liver, citrulline is locally synthesized by OCT and metabolized by ASS for urea production. Secondly, in most of the tissues producing NO, citrulline is recycled into arginine via ASS to increase arginine availability for NO production. Thirdly, citrulline is synthesized in the gut from glutamine (with OCT), released into the blood and converted back into arginine in the kidneys (by ASS); in this pathway, circulating citrulline is in fact a masked form of arginine to avoid liver captation. Each of these pathways has related pathologies and, even more interestingly, citrulline could potentially be used to monitor or treat some of these pathologies. Citrulline has long been administered in the treatment of inherited urea cycle disorders, and recent studies suggest that citrulline may be used to control the production of NO. Recently, citrulline was demonstrated as a potentially useful marker of short bowel function in a wide range of pathologies. One of the most promising research directions deals with the administration of citrulline as a more efficient alternative to arginine, especially against underlying splanchnic sequestration of amino acids. Protein citrullination results from post-translational modification of arginine; that occurs mainly in keratinization-related proteins and myelins, and insufficiencies in this citrullination occur in some auto-immune diseases such as rheumatoid arthritis, psoriasis or multiple sclerosis.

Animals↗
PubMed2006

Comparative genome maps of the pangolin, hedgehog, sloth, anteater and human revealed by cross-species chromosome painting: further insight into the ancestral karyotype and genome evolution of eutherian mammals.

To better understand the evolution of genome organization of eutherian mammals, comparative maps based on chromosome painting have been constructed between human and representative species of three eutherian orders: Xenarthra, Pholidota, and Eulipotyphla, as well as between representative species of the Carnivora and Pholidota. These maps demonstrate the conservation of such syntenic segment associations as HSA3/21, 4/8, 7/16, 12/22, 14/15 and 16/19 in Eulipotyphla, Pholidota and Xenarthra and thus further consolidate the notion that they form part of the ancestral karyotype of the eutherian mammals. Our study has revealed many potential ancestral syntenic associations of human chromosomal segments that serve to link the families as well as orders within the major superordinial eutherian clades defined by molecular markers. The HSA2/8 and 7/10 associations could be the cytogenetic signatures that unite the Xenarthrans, while the HSA1/19p could be a putative signature that links the Afrotheria and Xenarthra. But caution is required in the interpretation of apparently shared syntenic associations as detailed analyses also show examples of apparent convergent evolution that differ in breakpoints and extent of the involved segments.

Animals↗
PubMed2006

Centrin isoforms in mammals. Relation to calmodulin.

In mammals, three calmodulin (CaM) genes code for 100% identical proteins. In these species, four centrin (Cetn) genes have been reported to exist. They are examined in this paper. While the gene for Cetn 1 contains no introns and appears to be derived from Cetn 2 by retroposition, a gene product for Cetn 1 is expressed. Cetn 2, 3, and 4 represent bona fide genes. The major difference between the members of the CaM and the Cetn subfamilies is the presence (usually) in Cetn of an approximately 23 amino acids long (but occasionally much longer) protruding amino acid end. In all members of these two subgroups, four EF hand motifs (in this paper taken as loops containing 12 amino acids) are separated by 24, 25 and 24 amino acids (each a helix-loop-helix) positioned between motifs 1and 2, 2 and 3, and 3 and 4, respectively. This rule applies not only to CaM and Cetn in mammals but also to these two subfamilies in simpler eukaryotes such as Saccharomyces cerevisiae and Giardia lamblia. The various mRNA products can be identified most readily by their characteristic 3' UTRs. While CaM is an ancient molecule that is expressed in all cells and is ubiquitous within these cells and interacts therein with almost 100 different proteins, many of which display the IQ or related binding motifs, the distribution and function of Cetn (an equally ancient molecule) is restricted mostly to basal bodies (e.g. in rods of the retina), axonemes, flagella, cilia and centrosomes. Are these two subclasses of calcium carriers (each molecule possessing four EF hands which possibly interact with different association constants)-if they are both present within a cell-randomly chosen for their service to the specific proteins with which they interact?

Amino Acid Sequence↗
PubMed2005

AKINbeta3, a plant specific SnRK1 protein, is lacking domains present in yeast and mammals non-catalytic beta-subunits.

The SNF1/AMPK/SnRK1 heterotrimeric kinase complex is involved in the adaptation of cellular metabolism in response to diverse stresses in yeast, mammals and plants. Following a model proposed in yeast, the kinase targets are likely to bind the complex via the non-catalytic beta-subunits. These proteins currently identified in yeast, mammals and plants present a common structure with two conserved interacting domains named Kinase Interacting Sequence (KIS) and Association with SNF1 Complex (ASC), and a highly variable N-terminal domain. In this paper we describe the characterisation of AKINbeta3, a novel protein related to AKINbeta subunits of Arabidopsis thaliana, containing a truncated KIS domain and no N-terminal extension. Interestingly the missing region of the KIS domain corresponds to the glycogen-binding domain (beta-GBD) identified in the mammalian AMPKbeta1. In spite of its unusual features, AKINbeta3 complements the yeast sip1Deltasip2Deltagal83Delta mutant. Moreover, interactions between AKINbeta3 and other AKIN complex subunits from A. thaliana were detected by two-hybrid experiments and in vitro binding assays. Taken together these data demonstrate that AKINbeta3 is a beta-type subunit. A search for beta-type subunits revealed the existence of beta3-type proteins in other plant species. Furthermore, we suggest that the AKINbeta3-type subunits could be plant specific since no related sequences have been found in any of the other completely sequenced genomes. These data suggest the existence of novel SnRK1 complexes including AKINbeta3-type subunits, involved in several functions among which some could be plant specific.

Amino Acid Sequence↗
PubMed1988

Screening of preduodenal lipases in several mammals.

The tissular localization of preduodenal lipases was studied from the tongue to the pyloric portion of the stomach in 11 mammals. Lipolytic activities were clearly differentiated from those of pancreas. All lipase activities show an acidic pH optimum, except the gastric enzyme from hog. For every mammal tested, preduodenal lipase activity was associated mainly with only a single tissue located either in tongue, or in the pharyngeal area, or in the stomach. Resistance to acidic pH medium allows the classification of lipase activities into three groups. These results are related to the dietary habits and zoologic classification of the different animal species.

Animals↗
PubMed1993

Towards a molecular resolution of the ordinal phylogeny of the eutherian mammals.

Reconstructing the evolutionary relationships among the orders of eutherian mammals entails the identification of a single true phylogenetic tree out of approximately 10(19) possible ones. The morphological and paleontological legacy to the field consists of numerous contradictory trees that are mostly devoid of binary resolution. With the introduction of molecular methodologies, several superordinal relationships have been identified, and in several instances a complete taxonomic revision was indicated. In this review, I present a summary of the phylogenetic affinities of the eutherian orders as revealed by molecular studies, and outline the differences between the molecular phylogenetic schemes and the phylogenetic trees produced through the use of morphological data. Questions of monophyly or paraphyly of the eutherian orders are also discussed. It is estimated that all but 10(9) of the 10(19) possible phylogenetic trees have been ruled out by molecular analysis, and that DNA and protein sequences with their potential to supply millions of phylogenetically useful characters will resolve the phylogeny of the orders of mammals into a consistently bifurcating tree in the not-so-distant future.

Animals↗
PubMedDate not supplied

Isolation of Leishmania species from wild mammals in French Guiana.

Between 1981 and 1987, 486 wild mammals collected from 13 sites in French Guiana were examined for Leishmania. Eleven of 31 two-toed sloths, Choloepus didactylus, were infected, 4 of the isolates being identified as L. braziliensis guyanensis. This species was also found in 2 Didelphis marsupialis and 2 Proechimys sp. L. mexicana amazonensis was isolated from 3 Proechimys sp., 2 of which were P. cuvieri. The role of these mammals in the life cycles of the 2 anthropotropic species of Leishmania encountered in French Guiana is discussed.

Animals↗
PubMed1993

Development of the National Marine Mammal Tissue Bank.

The National Marine Mammal Tissue Bank (NMMTB) has been established as part of a comprehensive effort to obtain reliable information on contaminant levels in marine mammal tissues. A four component program consisting of the NMMTB, stranding networks, monitoring and quality assurance has been developed. The development and current status of the NMMTB and its relationship to the other three components will be described.

Animals↗
PubMed1994

Chlorinated hydrocarbon contaminants in arctic marine mammals.

By 1976, the presence of chlorinated hydrocarbon contaminants (CHCs) had been demonstrated in fur seal (Callorhinus ursinus), ringed seal (Phoca hispida), hooded seal (Cystophora cristata), bearded seal (Erignathus barbatus), walrus (Obdobenus rosmarus divergens), beluga (Delphinapterus leucas), porpoise (Phocoena phocoena) and polar bear (Ursus maritimus) in various parts of the Arctic. In spite of this early interest, very little subsequent research on contaminants in Arctic marine mammals was undertaken until the mid-1980s. Since that time, there has been an explosion of interest, resulting in a much expanded data base on contaminants in Arctic marine mammals. Except in the Russian Arctic, data have now been obtained on the temporospatial distribution of PCBs and other contaminants in ringed seal, beluga and polar bear. Contaminants in narwhal (Monodon monoceros) have also now been measured. On a fat weight basis, the sum of DDT-related compounds (S-DDT) and PCB levels are lowest in walrus (< 0.1 microgram/g), followed by ringed seal, (0.1-1 microgram/g range). Levels are an order of magnitude higher in beluga and narwhal (1-10 micrograms/g range). It appears that metabolism and excretion of S-DDT and PCBs may be less efficient in cetaceans, leading to greater biomagnification. Polar bears have similar levels of PCBs as cetaceans (1-10 micrograms/g), but with a much simpler congener pattern. DDE levels are lowest in polar bear, indicating rapid metabolism. Effects of age and sex on residue levels are found for all species where this was measured. Among cetaceans and ringed seal, sexually mature females have lower levels than males due to lactation. Although PCB levels in adult male polar bears are about twice as high as females, there is only a trivial age effect in either sex apart from an initial decrease from birth to sexual maturity (age 0-5). Comparison of levels of S-DDT and PCBs in Arctic beluga and ringed seal with those in beluga in the Gulf of St. Lawrence and ringed seal in the Baltic Sea, indicate that overall contamination of the Arctic marine ecosystem is 10-50 times less than the most highly contaminated areas in the northern hemisphere temperate latitude marine environment. Geographic distribution of residue levels in polar bears indicates a gradual increase from Alaska east to Svalbard, except PCB levels are significantly higher in eastern Greenland and Svalbard. Information on temporal trends is somewhat contradictory.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

A review of heavy metal and organochlorine levels in marine mammals in Australia.

Study of toxic contaminants in marine mammal specimens collected around Australia is currently uncoordinated and piecemeal. Most states collect samples but there is little or no financial support for their analysis. This study combines data, published or unpublished, from 13 sources. Heavy metals have been analysed in about 676 specimens; over 400 were for mercury levels in P. macrocephalus taken at a whaling station. The remaining samples were mostly from toothed whales, a few baleen whales (< 20), pinnipeds (41) and dugongs (49). The most consistently analysed metals were lead, mercury and cadmium. Liver and kidney lead levels ranged from < 1-3 ppm; levels in bone were 0-418 ppm, with most less than 10 ppm. Mercury levels in a large sample of P. macrocephalus muscle were < 12.2 ppm. Mercury levels in the small number of samples from other species were 0.51-143 ppm (kidney), 1.52-479 ppm (liver) and < 0.1-36 ppm (muscle). Cadmium levels in liver (0-52 ppm) and kidney (0-106 ppm) were extremely variable. Levels greater than 10 ppm were recorded in many species and were especially high in Hydrurga leptonyx, Dugong dugon, Mesoplodon layardii and Pseudorca crassidens. Adult Tursiops truncatus inhabiting the inshore gulfs of South Australia had considerably higher levels of cadmium compared with other regions. Information on organochlorine levels is sparse (approximately 39 specimens) and suggest low levels when compared to other parts of the world. Total DDT was highest (28.4 ppm) in a neonatal Orcinus orca. Some high levels of DDT were recorded in Tursiops truncatus, Delphinus delphis and Arctocephalus pusillus doriferus. PCBs ranged from < 0.05 to 3.87 ppm. A comprehensive pathological assessment of marine mammals is needed in order to evaluate the effects of toxic contaminants.

Animals↗
PubMed1996

Ecological hazard assessment of dioxins: hazards to organisms at different levels of aquatic food webs (fish-eating birds and mammals, fish and invertebrates).

An ecological hazard assessment was performed for 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin in the aquatic environment, taking into account four different classes of species which differ with respect to their positions in aquatic food webs: invertebrates, fish, birds preying on aquatic organisms, and mammals preying on aquatic organisms. The most sensitive toxicological endpoints for each class were selected from the literature. These endpoints were extrapolated to no effect concentrations (NECs) in water with a two-level food chain model as indicator for secondary poisoning. From the results it is concluded that fish-eating birds and mammals experience larger hazards from dioxins and related compounds than fish. The limited data available appear to indicate that invertebrates are rather insensitive to dioxins. The study indicates that assessment of secondary poisoning affects environmental quality criteria setting and risk assessment.

Animals↗
PubMed1994

The ecotoxicological significance of cadmium intake and residues in terrestrial small mammals.

Little is known about the ecotoxicological hazard of cadmium to wild small mammals. This paper reviewed laboratory and field studies to determine: (i) intake and residue lowest-observable-adverse-effect-levels (LOAELs) for the ecologically important parameters of reproduction and development; (ii) whether these LOAELs are exceeded by wild small mammals on contaminated habitats and what adverse effects result; and (iii) which species may be at most risk from cadmium. The intake LOAEL in laboratory rodents was 3.5-7.5 mg kg-1 body wt day-1 and the residue LOAEL, based on cellular damage in the kidney, was a renal cadmium concentration of 105 mg kg-1 dry wt. On contaminated habitats, these LOAELs are exceeded by common shrews Sorex araneus but not by wild rodents. However, there is little evidence of adverse cadmium-mediated effects in common shrews and this species may be tolerant to cadmium exposure. Large cadmium concentrations in body organs may simply reflect an ability to store cadmium in a nontoxic, metallothionein-bound state. In contrast, studies suggest that microtine voles may be sensitive to cadmium and, despite their relatively low cadmium intake and accumulated residues, may suffer adverse effects. The need to establish dose-residue-effect relationships for intakes and residues which are appropriate for wild species and also based on ecologically important parameters is discussed.

Animals↗
PubMed1979

Yersinia enterocolitica among small wild mammals in France.

A survey of Yersinia enterocolitica was made in two French areas (Indre and Alsace) in several components of the terrestrial ecosystem. Y. enterocolitica has been isolated from several habitats and from numerous species of small mammals. The trap line method enabled us to estimate the density of the two abundant small mammal species, Microtus arvalis and Apodemus sylvaticus, and the densities of Y. enterocolitica carriers. The frequency of isolation was high when temperatures were low, but did not seem to be in direct relationship with animal densities. Infectious lesions were never found in spleens or intestines of 1893 captured animals. Samples of fresh water, fresh-water fish, soil and earthworms were occasionally collected. A total of 163 strains were isolated. Of these, 99 were of biochemical type 1; 20 different 0 serogroups were found.

Animals↗
PubMed1995

The organization of neocortex in mammals: are species differences really so different?

By examining a variety of mammals, it is possible to determine common features of cortical organization, and from these infer homologies across species. Such analysis also enables differences in the organization of the neocortex to be identified. Species differ in the amount of cortex that is devoted to a particular sensory system, in the size and configuration of a cortical field, in the number of cortical fields, and in the pattern of connections of homologous fields. It is suggested that the plan of organization that is retained is the result of homologous developmental events, and that modifications to this plan are generated by a limited set of mechanisms. These types of changes to the common network might account for the sensory and behavioural diversity that is observed in extant mammals.

Animals↗
PubMedDate not supplied

The action of FMRFamide (Phe-Met-Arg-Phe-NH2) and related peptides on mammals.

First purified 11 years ago from clam ganglia, FMRFamide (Phe-Met-Arg-Phe-NH2) was quickly demonstrated to be cardioactive in several molluscan species. Subsequent discovery that FMRFamide, or FMRFamide-related peptides (FaRPs), were present in mammalian central nervous system and gastrointestinal tract prompted investigations into the effect of FMRFamide on mammals. FMRFamide has now been shown to be cardioexcitatory in mammals, to inhibit morphine-induced antinociception, and to block morphine-, defeat-, and deprivation-induced feeding. It also inhibits colonic propulsive motility, induces behavioral effects when administered intrathecally, and has been reported to have amnesic effects in rodents. A proposal has arisen that a FMRFamide-like substance is an endogenous opioid antagonist and has stimulated a search for such a substance. However, FMRFamide has only weak affinity for opioid receptors and not all the actions of FMRFamide appear to be explained by actions at opioid receptors. Alternative mechanisms have been proposed which suggest that FMRFamide acts as a neuromodulator.

Animals↗
PubMed1988

Iron-binding properties and amino acid composition of marsupial transferrins: comparison with eutherian mammals and other vertebrates.

1. Some physicochemical properties of transferrin from three marsupials, viz a possum (Trachosurus vulpecula), a kangaroo (Macropus fuliginosus) and the quokka (Setonix brachyurus) were studied and compared with those of transferrins from mammalian and non-mammalian vertebrate species. 2. The molecular weight of the marsupial transferrins fell within the range of 76,000-79,000 daltons. 3. The marsupial transferrins were similar to the transferrins of eutherian mammals with respect to optical spectral properties, iron binding capacity and the pH-dependence of iron binding, and iron release mediated by 2,3-DPG. 4. The amino acid compositions of the marsupial transferrins were compared with each other and with the transferrins from the other vertebrate species. The compositions of the marsupial transferrin were closely related to each other, and also showed similarities with transferrins from eutherian mammals and chicken ovotransferrin.

Amino Acids↗
PubMed1988

Thyroid function in a lizard, a tortoise and a crocodile, compared with mammals.

1. Thyroid activity was examined in the lizard, Trachydosaurus rugosus, the tortoise Chelodina longicollis and the crocodile, Crocodylus johnstoni, acclimated to 20-22 degrees C and 30-32 degrees C. Thyroidal uptake and release of 125I, plasma concentrations of T3 and T4 were measured as was resting oxygen consumption (at 30 degrees C) before and after both thyroidectomy and thyroxine injections. 2. All three species showed 125I uptake at both temperatures and showed no thyroidal release of 125I at 20-22 degrees C but exhibited thyroidal release of 125I (and presumably hormone secretion) at 30-32 degrees C. 3. Plasma concentrations of thyroxine ranged from 0.55 nM to 3.24 nM and triiodothyronine from 0.14 nM to 0.51 nM. 4. Neither thyroidectomy nor thyroxine injections had any effect on metabolic rate in 20-22 degrees C acclimated lizards. Thyroidectomy resulted in a significant decrease in metabolic rate in 30-32 degrees C acclimated lizards and tortoises and thyroxine injections resulted in significant increases in metabolism in 30-32 degrees C acclimated lizards, tortoises and crocodiles. 5. A comparison of thyroid parameters in reptiles and mammals concluded that although the reptilian thyroid is active at high temperatures it is still considerably less active than it is in mammals.

Alligators and Crocodiles↗
PubMed1992

The roles of intracellular buffers and bone mineral in the regulation of acid-base balance in mammals.

1. Regulation of intracellular and extracellular pH may conflict in their requirements for movement of acid or base. 2. Cells make a positive or a negative contribution to 'tissue buffering' of extracellular fluid (ECF), depending on their internal buffer value, on the tightness of their internal pH control by membrane mechanisms, and on the nature of the acid-base disturbance. 3. A role is suggested for electrogenic Na-HCO3 co-transport in some of the ion shifts that occur in acid-base disturbances. 4. The time course of 'tissue buffering' in nephrectomized mammals in hypercapnia is variable, and it is far from clear in intact, unanaesthetized mammals. 5. Buffering of ECF by Ca salts of bone mineral in acidosis can only be substantial if accompanied by Ca excretion; the release of HCO3 with Na and K is more significant. 6. The relative importance of cells and of bone mineral in the buffering of ECF is unclear.

Acid-Base Equilibrium↗