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At least 73 records · Page 4Linked to original sources
PubMed2000

Prolonged fasting increases the response of the renin-angiotensin-aldosterone system, but not vasopressin levels, in postweaned northern elephant seal pups.

The 8- to 12-week postweaning fast exhibited by northern elephant seal pups (Mirounga angustirostris) occurs without any apparent deleterious effects on fluid and electrolyte homeostasis. However, during the fast the role of vasopressin (AVP) has been shown to be inconclusive and the involvement of the renin-angiotensin-aldosterone system (RAAS) has yet to be examined. To examine the effects of prolonged fasting on these osmoregulatory hormones, 15 postweaned pups were serially blood-sampled during the first 49 days of their fast. Fasting did not induce significant changes in ionic or osmotic concentrations, suggesting electrolyte homeostasis. Total proteins were reduced by day 21 of fasting and remained depressed, suggesting a lack of dehydration. Aldosterone and plasma renin activity exhibited a correlated, linear increase over the first 49 days of the fast, suggesting an active RAAS. Aldosterone exhibited a parabolic trend over the fast with a peak at day 35, suggesting a shift in the sensitivity of the kidney to aldosterone later in the fast. AVP was elevated at day 49 only, but concentrations were relatively low. RAAS was modified during the postweaning fast in pups and appears to play a significant role in the regulation of electrolyte and, most likely, water homeostasis during this period.

Aldosterone↗
PubMed2000

Cutaneous heat flux models do not reliably predict metabolic rates of marine mammals.

Heat flux models have been used to predict metabolic rates of marine mammals, generally by estimating conductive heat transfer through their blubber layer. Recently, Kvadsheim et al. (1997) found that such models tend to overestimate metabolic rates, and that such errors probably result from the asymmetrical distribution of blubber. This problem may be avoided if reliable estimates of heat flux through the skin of the animals are obtained by using models that combine calculations of conductive heat flux through the skin and fur, and convective heat flux from the surface of the animal to the environment. We evaluated this approach based on simultaneous measurements of metabolic rates and of input parameters necessary for heat flux calculations, as obtained from four harp seals (Phoca groenlandica) resting in cold water. Heat flux estimates were made using two free convection models (double-flat-plate and cylindrical geometry) and one forced convection model (single-flat-plate geometry). We found that heat flux estimates generally underestimated metabolic rates, on average by 26-58%, and that small variations in input parameters caused large variations in these estimates. We conclude that cutaneous heat flux models are too inaccurate and sensitive to small errors in input parameters to provide reliable estimates of metabolic rates of marine mammals.

Animals↗
PubMed2002

Presence and regulation of metallothioneins in peripheral blood leukocytes of grey seals.

Heavy metal residues have been reported at high levels in marine mammals. Although the immunotoxicity of these contaminants has been demonstrated in laboratory models, evaluation of their potential immunotoxicity for human and wildlife species is complicated by variables that modulate the immune response and the immunotoxic effects of xenobiotics under field conditions. Metallothioneins (MT) modulate the bioavaibility of physiological cations and the toxicity of heavy metals. Moreover, these proteins have been demonstrated to modulate immune functions. In the present study, we demonstrated a rapid and sustained increase of transcripts of the two major isoforms of MT (MT-1 and MT-2) in grey seal peripheral blood leukocytes (PBL) exposed in vitro to Zn. This increase in mRNA corresponds to an increase of MT proteins in PBL. However, we demonstrated a high heterogeneity among the three major PBL subpopulations (granulocytes, lymphocytes and monocytes). Monocytes appear to be the most sensitive cells to Zn or Cd exposure. Intracellular MT levels in PBL subpopulations were dependent not only on the duration of exposure and the concentration, but also on the metal species. Cd was more potent than Zn as an inducer of MT in lymphocytes but not in monocytes. Moreover, grey seal peripheral blood lymphocytes are less sensitive to Cd exposure than human lymphocytes. This noninvasive approach helps to better assess the risk of heavy metal exposure by considering the potential role of MT as modulators of immune response.

Animals↗
PubMed1993

Dolphin and porpoise morbilliviruses are genetically distinct from phocine distemper virus.

The morbilliviruses recently isolated from two cetacean species in the North and Mediterranean Seas have been shown to differ from phocine distemper virus isolated from European seals using monoclonal antibodies. We have identified a "universal" morbillivirus primer set, based on highly conserved regions of the morbillivirus phosphoprotein (P) gene and used this to amplify a region surrounding the RNA editing site from all known members of the group. Sequence analysis of this region of the gene shows that the dolphin and porpoise viruses are related but quite different from all other members of the group, forming a distinct lineage more closely related to the ruminant morbilliviruses than to the carnivore viruses.

Animals↗
PubMed1997

Molecular characterization and baculovirus expression of the glycoprotein B of a seal herpesvirus (phocid herpesvirus-1).

A glycoprotein B (gB) gene homologue was identified in a 5.4-kb BamHl genomic fragment of the phocid herpesvirus type-1 (PhHV-1) which represents a widespread and important pathogen of pinnipeds. Sequence analysis revealed a gB-specific open-reading frame comprising 881 amino acids. Phylogenetic analysis gave evidence for a close evolutionary relationship between PhHV-1 and members of the Varicellovirus genus of the alpha-Herpesvirinae and canid herpesvirus in particular. In PhHV-1-infected Crandell feline kidney cells gB is expressed as a 113-kDa glycosylated molecule which is proteolytically cleaved into at least two fragments of 67 and 53-59 kDa apparently forming disulfide-linked heterodimers of 140 kDa. Cell surface expression of PhHV-1 gB was confirmed by FACS analysis. Thus, synthesis and processing of the gB protein of PhHV-1 follows a pattern also observed in other Varicelloviruses. Since the gB protein of herpesviruses, expressed in the baculovirus system, has been shown to be a suitable target for vaccine design, we used this system for expression of PhHV-1 gB. Recombinant (rec) baculovirus-expressed gB was identified as a 105-kDa glycosylated molecule. Proteolytic cleavage into fragments of 62 and 52 kDa was markedly delayed compared to wild-type (wt) gB. Wt and rec gB harbored endoglycosidase H (precursor)- as well as N-glycosidase F-sensitive N-glycans (proteolytic fragments). Baculovirus-expressed gB appeared to be antigenically authentic, since it was recognized in radioimmunoprecipitation and immune peroxidase monolayer assays by PhHV-1-neutralizing seal sera and by gB-specific neutralizing murine monoclonal antibodies. Furthermore, PhHV-1-neutralizing antibodies were induced in mice following immunization with baculovirus-expressed gB, indicating its suitability for incorporation in a candidate vaccine for seals.

Amino Acid Sequence↗
PubMed1988

Capillary configuration in contracted muscles: comparative aspects.

We compared the degree of orientation (anisotropy) of capillaries in skeletal muscles of animals with large differences in oxygen needs and/or tolerance to hypoxia (mammals of different size; reptiles; birds; mammals native to high altitude; diving mammals). In terrestrial mammals, we found a substantial increase in capillary tortuosity with fiber shortening, in muscles with large differences in capillary density (capillary counts/fiber mm2 in transverse sections ranging 450-4350). There was no systematic difference in muscle capillary tortuosity with body size (mouse to pony), or with adaptation to high altitude (deer mice) or to prolonged periods of anoxia (Harbor seals), when account was taken of sarcomere length. A substantial increase in capillary tortuosity was also found in contracted skeletal muscles of the alligator with remarkably low capillary density (capillary counts/fiber mm2 in transverse sections, 120-280). On the contrary, we found that in pigeon pectoralis, a highly aerobic muscle with large capillary density and a large number of capillary anastomoses running perpendicular to the muscle fiber axis, the decrease in capillary anisotropy with decreasing sarcomere length was smaller than in other muscles. Our results indicate that 1) sarcomere length at which samples are fixed needs to be taken into account when capillary counts in transverse sections are compared between muscles and/or after different experimental conditions, and 2) muscle capillary tortuosity is a consequence of fiber shortening, rather than an indicator of the O2 requirements of the tissue.

Alligators and Crocodiles↗
PubMed1992

The complete mitochondrial DNA sequence of the harbor seal, Phoca vitulina.

The nucleotide sequence of the mitochondrial DNA (mtDNA) of the harbor seal, Phoca vitulina, was determined. The total length of the molecule was 16,826 bp. The organization of the coding regions of the molecule conforms with that of other mammals, but the control region is unusually long. A considerable portion of the control region is made up of short repeats with the motif GTACAC particularly frequent. The two rRNA genes and the 13 peptide-coding genes of the harbor seal, fin whale, cow, human, mouse, and rat were compared and the relationships between the different species assessed. At ordinal level the 12S rRNA gene and 7 out of the 13 peptide-coding genes yielded a congruent topological tree of the mtDNA relationship between the seal, cow, whale, human, and the rodents. In this tree the whale and the cow join first, and this clade is most closely related to the seal.

Amino Acid Sequence↗
PubMed1995

A molecular view of pinniped relationships with particular emphasis on the true seals.

Phylogenetic analysis of conservative nucleotide substitutions in 18 complete sequences of the mitochondrial cytochrome b gene of Phocidae (true seals), Odobenidae (walruses), and Otariidae (sea lions and fur seals), plus three ursid and three felid sequences, identified the pinnipeds as monophyletic with Otariidae and Odobenidae on a common evolutionary branch. Analysis of total nucleotide differences separated the evolutionary lineages of northern and southern phocids. Both lineages are distinct from the most ancestral phocid genus, Monachus (monk seals), represented by the Hawaiian monk seal. The inclusion of the Hawaiian monk seal in the subfamily Monachinae makes the subfamily paraphyletic. Among the northern phocids, the hooded seal (genus Cystophora, chromosome number 2n = 34) is sister taxon to the Phoca complex. The Phoca complex, which is characterized by the chromosome number 2n = 32, includes genus Phoca and the monotypic genus Halichoerus (grey seal). The comparison does not support a generic distinction of Halichoerus within the Phoca complex. The present data suggest that Cystophora and Phoca separated > or = 6 million years ago. Among the southern phocids the close molecular relationship of the Weddell and leopard seals relative to their morphological distinction exemplifies rapid adaptation to different ecological niches. This result stands in contrast to the limited morphological differentiation relative to the pronounced molecular distinctions that may occur within the Phoca complex.

Animals↗
PubMed1993

Distribution patterns of polychlorinated biphenyl congeners in harbor seal (Phoca vitulina) tissues: statistical analysis.

Tissue samples from five harbor seals (Phoca vitulina) have been analyzed for coplanar and other polychlorinated biphenyl (CB) congeners, in order to measure variations in levels and patterns of the CBs. Blubber samples contained the highest levels of CBs in all animals; kidney and liver were relatively high-level tissues. CB-153 and CB-138 were the most abundant CB congeners in all samples analyzed. Variations in the patterns of CB congeners in tissues were studied by principal component analyses and multivariate analysis of variance. The CB congener patterns in seals from different geographical regions had distinctly different patterns, whereas the patterns appeared quite similar in tissues within each seal. Based on multivariate analysis of variance, it was, however, possible to detect some systematic variation of the principal components with individual seals and with tissue type within the seals. The assessment of differences in CB congener patterns was possible by comparison to results obtained by repeated analyses of a quality control sample. The calculated dioxin toxic equivalents of the CB congeners followed the levels of the CB congeners, with the highest levels being found in the blubber samples.

Animals↗
PubMed1996

Chromosome survey of seals in the Baltic Sea in 1988-1992.

The populations of grey seals (Halichoerus grypus) and ringed seals (Phoca hispida botnica) in the Baltic Sea have decreased very much, especially during the last decades. Environmental pollution has been seen as an important cause. As top predators, the seals accumulate pollutants from their environment. High concentrations of chlorinated hydrocarbons and heavy metals have been found in seals from the Baltic Sea. In the present study the possible mutagenic effects of environmental pollutants on the seals have been studied by screening cultured lymphocytes for chromosome aberrations. Blood samples were taken from grey seal pups before weaning in March-April, and from adult ringed seals at the end of April during 1988-1992. Blood cells were cultured for 48 h for screening for chromosome aberrations, and for 61 h with bromodeoxyuridine for the study of sister chromatid exchange (SCE). The types of aberrations found were chromosome and chromatid breaks, gaps, and fragmentations. More complicated rearrangements were rare. Blood samples from a total of 47 grey seal pups and from ten adult ringed seals were analysed. The mean frequency of cells with chromosome aberrations from the grey seals was 5.7% (SD +/-5.3). The median was 4, because the distribution was skewed with some animals having a considerably higher frequency of aberrations than the average. Some cells with several aberrations and fragmentation of the chromosomes were observed among the lymphocytes from these animals. The frequencies of SCEs were not markedly higher than those normally found in humans. The frequencies of aberrations found in the adult ringed seals were lower than those found in the grey seal pups. The chromosome aberrations are probably caused by chemical pollutants.

Animals↗
PubMed1995

Contaminant levels in harbor seals from the northeastern United States.

The concentrations of polychlorinated biphenyls (PCBs), organochlorine pesticides, polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzofurans (PCDF), polychlorinated dibenzo-p-dioxins (PCDD), and mercury (Hg) were determined in blubber and liver tissues of harbor seals (Phoca vitulina) collected along the northeast coast of the U.S. Average PCB concentrations in seal blubber (sum of congeners) were 12.0 micrograms/g (wet weight) with a range of 7.30 to 24.3 micrograms/g in 1980 and 6.66 micrograms/g (wet weight) with a range of 2.61 to 11.3 micrograms/g in 1990-1992. Comparisons between blubber data from this study and previous work indicated that the concentration of PCBs along the northeast coast of the U.S. may have decreased over the past twenty years. The average p,p'-DDE concentrations in seal blubber were 10.9 micrograms/g (wet weight) in 1980 with a range of 6.95 to 21.9 micrograms/g and 4.12 micrograms/g (wet weight) with a range of 1.83 to 7.84 micrograms/g in 1990-1992. Only trace amounts of PCDFs and PCDDs were found in a few blubber samples; levels in most tissues were below detection (3-5 pg/g) (wet weight). Trace amounts (< 30 ng/g) of phenanthracene, anthracene, and alkylated MW-178 compounds were found in some seal samples; all other PAH compounds were below the detection level (5-15 ng/g). Toxic equivalents (TEQ) of selected coplanar and mono-ortho PCB congeners and relative toxic equivalents (RTE) (pg total TEQ/microgram total PCB) were calculated, using recently proposed dioxin toxic equivalent factors (Ahlborg et al. 1994). The TEQs ranged from 41 to 315, and the RTEs ranged from 2.25 to 16.3.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1996

Bioaccumulation of vanadium and other trace metals in livers of Alaskan cetaceans and pinnipeds.

Concentrations for 38 elements are routinely measured in the marine mammal liver tissues archived in the National Biomonitoring Specimen Bank (NBSB). Results show that hepatic concentrations of vanadium, selenium, silver, cadmium, and mercury are positively correlated with age for beluga whales (Delphinapterus leucas) and of vanadium, selenium, cadmium, and mercury with length for ringed seals (Phoca hispada). Many researchers have reported linear correlations of hepatic selenium, cadmium, and mercury with marine mammal age; however, there is only one other report of a linear correlation of hepatic vanadium with marine mammal age. Vanadium levels are at or below detection limits (< or = 0.01 micrograms/g) in liver tissues of U.S. east coast marine mammals from the NBSB but are present at levels ranging from 0.02 to 1.2 micrograms/g of wet weight in the tissues of Alaskan marine mammals. Although only three bearded seal (Eriganthus barbatus) and three bow-head whale (Balaena mysticetus) liver samples have been analyzed, hepatic vanadium levels also increased with animal size for these species. The presence of relatively high levels of vanadium in the livers of these Alaskan animals may reflect a unique dietary source of vanadium, a unique geochemical source of vanadium, or anthropogenic input to the Alaskan marine environment.

Aging↗
PubMed1995

Patterns of chlorinated biphenyl congeners in harbor seals (Phoca vitulina) and in their food: statistical analysis.

Patterns of chlorinated biphenyl (CB) congeners have been compared in two groups of samples, namely blood samples from harbor seals (Phoca vitulina) and muscle tissue samples in the fish with which the seals were fed. The data originate from a Dutch controlled feeding study, performed in 1981 and 1983. The seals were living in captivity in two separate groups, and the fish samples were plaice (Pleuronectes platessa) from the Dutch part of the Wadden sea and mackerel (Scomber scombrus) from the Atlantic ocean. The levels of CB congeners were different in the two types of fish. The CB congener patterns of these four "matrices" were compared by analysis of principal components, and were found to be different in the two groups of harbor seals, which were fed the different types of fish. The corresponding CB congener patterns of the two groups of fish were also different. There was no indication for a relatively larger impact of biotransformation due to induction of isoforms of the cytochrome P450-system at the higher absolute CB congener levels in the Wadden sea group of seals compared to the Atlantic group of seals. The differentiation between the CB congener patterns in the two groups of seals in the Dutch study can be ascribed solely to different CB congener patterns in their food. The difference between CB congener patterns in the seals and in their diet can be explained by the structure-related biotransformation of the CB congeners in the harbor seal.

Animals↗
PubMed1993

Mercury and major essential elements in seals, penguins, and other representative fauna of the Antarctic.

Concentrations of total Hg and major essential elements, Ca, Mg, Na, and K, were measured in the muscle, liver, and kidney of three species of seals, crabeater seal (Lobodon carcinophagus), leopard seal (Hydrurga leptonyx), and Weddell seal (Leptonychotes weddelli) collected in the Antarctic. The muscle and liver of three species of penguins, i.e., gentoo penguin (Pygoscelis papua), Adelie penguin (P. adeliae), chinstrap penguin (P. antarctica), and other representative fauna were also analyzed for the elements. Distinct inter-tissue differences in the metal concentration were observed; liver had the greatest concentrations of Hg, kidney showed maximum concentration of Ca and Na, while muscle was characterized by the greatest content of Mg and K. Inter-specimen differentiation of concentrations among the same species was distinctly visualized for Hg but not for the major essential elements. The Hg concentration in the seals analyzed are in keeping with those reported previously by other authors. Such comparison for Ca, Mg, Na, and K was impossible because of the lack of available literature data for their concentrations in marine seals. Numerous significant correlations were observed between concentrations of the several metals analyzed. There was no correlation between Hg, which is a non-essential element and both Zn and Cd which are essential and non-essential elements, respectively in the liver or kidney of seals. However, there were significant correlations between concentration of Zn and the sum of molar concentrations of Hg+Cd in kidney (r = 0.82) and liver (r = 0.76). The results suggest that several control mechanisms operate to maintain physiologically required levels that decreases any effect of heavy metal toxicants such as Hg and Cd.

Animals↗
PubMed1981

Disaccharidase-deficient animals have normal ultrastructure of intestinal brush border membranes.

The intestinal disaccharidases, lactase, sucrase-isomaltase complex, and glucoamylase are proteins intimately associated with the brush-border membrane of the epithelial cell. These three enzyme activities are found in the intestine of the adult rat; lactase and glucoamylase activities are primarily associated with the intestine of the infant rat. Only glucoamylase and isomaltase activities are detected in the intestine of the California sea lion, Zalophus californianus. The activities of these enzymes are detected only in villus cells, and not in crypt cells. We have carried out electron microscopic studies of negatively stained brush-border preparations of intestinal crypt and villus cells; from the intestine of the 10-day-old rat and from that of the California sea lion. The density of the knob-like structures protruding from the brush-border membranes was not significantly different in any of these preparations. The diameter of the knobs on the preparations from crypt cells was smaller than the diameters of the knobs found on membranes prepared from the other sources. These data are discussed in terms of the relationship between the presence of knob structures and disaccharides activities associated with the brush-border membranes.

Animals↗
PubMed1977

Fine structure of seminiferous tubules in antarctic seals.

The fine structure of seminiferous tubules from 5 crabeater, 2 leopard and 2 Ross seals showed that during the nonbreeding season the tubules were essentially similar in possessing spermatogenic and Sertoli cells. However, the tubules of leopard and Ross seals had more primary and secondary spermatocytes and spermatids than the crabeater seals. In general, the tubules were devoid of spermatozoa. The spermatids showed stages of maturation such as Golgi phase of acrosome formation, acrosomal cap formation and condensation of nuclei. Some spermatids degenerated in tubules. Both maturing and degenerating spermatids were closely associated with Sertoli cells. Junctional complexes with plaques of filaments were observed between Sertoli cells and the spermatogenic cells. Sertoli cells, irregular and polygonal, contained highly convoluted nuclei, strands of rough endoplasmic reticulum, smooth endoplasmic reticulum, Golgi complexes, small mitochondria, variable amounts of lipid droplets, lysosomes, lipofuscin granules and highly plicated plasma membranes. In brief, the spermatogenic activity had practically ceased in the testes and the animals probably secreted low levels of testosterone during the nonbreeding season.

Animals↗