Showing papers on "Beluga published in 1998"
TL;DR: The reduced proliferation of beluga cells exposed in vitro to mixtures of organochlorines at concentrations in the range of those observed in tissues of St. Lawrence belugas might provide a basis to support the hypothesis that contaminants induce immunosuppression in these animals.
Abstract: The effects of in vitro exposure to different organochlorines were evaluated on immune functions of beluga whale peripheral blood leukocytes and splenocytes. The effects of different concentrations of four different congeners of PCBs (138, 153, 180, and 169) as well as two DDT metabolites (p,p'-DDT and p,p'-DDE) were evaluated on phagocytosis and cell proliferation. The effects of dioxins and mixtures of organochlorines were also evaluated on cell proliferation. The different compounds tested had no marked effect on phagocytosis. PCB 138 and p,p'-DDT, but not PCB 153, PCB 180, PCB 169, and p,p'-DDE, reduced significantly the proliferative response of beluga splenocytes cultured either with or without phytohemagglutinin A (PHA). Proliferation of beluga splenocytes was not markedly affected by exposure to 5 ppm of PCB 138, 153, 180, and 169 separately. Exposure to a mixture of congeners 138, 153, and 180 (5 ppm each) significantly reduced splenocytes proliferation, but not the mixture of congeners 138, 153, 180, and 169 (5 ppm each). TCDD did not affect cell proliferation in our study. The reduced proliferation of beluga cells exposed in vitro to mixtures of organochlorines at concentrations in the range of those observed in tissues of St. Lawrence belugas might provide a basis to support the hypothesis that contaminants induce immunosuppression in these animals.
107 citations
TL;DR: In this paper, the authors measured masked hearing thresholds of a beluga whale at the Vancouver Aquarium and found that the masked signal was a typical beluga vocalization; the masking noise included two types of icebreaker noise and naturally occurring icecracking noise.
Abstract: An experiment is presented that measured masked hearing thresholds of a beluga whale at the Vancouver Aquarium. The masked signal was a typical beluga vocalization; the masking noise included two types of icebreaker noise and naturally occurring icecracking noise. Thresholds were measured behaviorally in a go/no-go paradigm. Results were that bubbler system noise exhibited the strongest masking effect with a critical noise-to-signal ratio of 15.4 dB. Propeller cavitation noise completely masked the vocalization for noise-to-signal ratios greater than 18.0 dB. Natural icecracking noise showed the least interference with a threshold at 29.0 dB. A psychophysical analysis indicated that the whale did not have a consistent decision bias.
67 citations
TL;DR: Data are consistent with an important role for the DRB1 locus in the cellular immune response of beluga, and the ratio of nonsynonymous to synonymous substitutions is similar to that among primate alleles, arguing against a reduction in the balancing selection pressure in the marine environment.
Abstract: The variation at loci with similarity to DRB class II major histocompatibility complex loci was assessed in 313 beluga collected from 13 sampling locations across North America, and 11 narwhal collected in the Canadian high Arctic. Variation was assessed by amplification of exon 2, which codes for the peptide binding region, via the polymerase chain reaction, followed by either cloning and DNA sequencing or single-stranded conformation polymorphism analysis. Two DRB loci were identified in beluga: DRB1, a polymorphic locus, and, DRB2, a monomorphic locus. Eight alleles representing five distinct lineages (based on sequence similarity) were found at the beluga DRB1 locus. Although the relative number of alleles is low when compared with terrestrial mammals, the amino acid variation found among the lineages is moderate. At the DRB1 locus, the average number of nonsynonymous substitutions per site is greater than the average number of synonymous substitutions per site (0.0806 : 0.0207, respectively;P<0.01). Most of the 31 amino acid substitutions do not conserve the physiochemical properties of the residue, and 21 of these are located at positions implicated as forming pockets responsible for the selective binding of foreign peptide side chains. Only DRB1 variation was examined in 11 narwhal, revealing a low amount of variation. These data are consistent with an important role for the DRB1 locus in the cellular immune response of beluga. In addition, the ratio of nonsynonymous to synonymous substitutions is similar to that among primate alleles, arguing against a reduction in the balancing selection pressure in the marine environment. Two hypotheses may explain the modest amount of Mhc variation when compared with terrestrial mammals: small population sizes at speciation or a reduced neutral substitution rate in cetaceans.
58 citations
Journal Article•
30 citations
13 citations
Journal Article•
TL;DR: A method for the determination of mortality profiles for beluga whales (Delphinapterus leucas), based on growth layers in mandibular bone, as opposed to teeth, which is consistent with an expected catastrophic profile.
2 citations