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PubMed1978

How much is secondary structure responsible for resistance of double-stranded RNA to pancreatic ribonuclease A?

1. Double-stranded f2 sus11 or Qbeta RNAs, resistant to bovine pancreatic RNAase A in 0.15 M NaCl/0.015 M sodium citrate (SSC), are quickly and completely degraded at 10-fold lower ionic strength (0.1 X SSC) under otherwise similar conditions. At this ionic strength the secondary structure of double-stranded RNA is maintained, as judged by the following: (a) the unchanged resistance of double-stranded RNA and DNA, under similar low ionic strength conditions, to nuclease S1 from Aspergillus oryzae, in contrast with the sensitivity of the corresponding denatured nucleic acids to this enzyme, specific for single-stranded RNA and DNA; (b) the co-operative pattern of the thermal-transition profile of double-stranded RNA (with a Tm of 89 degrees C) in 0.1 X SSC. 2. Whereas in SSC bovine seminal RNAase (RNAase BS-1) and whale pancreatic RNAase show an activity on double-stranded RNA significantly higher than that of RNAase A, in 0.1 X SSC the activity of the latter enzyme on this substrate becomes distinctly higher than that of RNAase BS-1, and similar to that of whale RNAase. 3. From these results it is deduced that the secondary structure is probably not the only nor the most important variable in determining the susceptibility double-stranded RNA to ribonuclease. Other factors, such as the effect of ionic strength on the enzyme and/or the binding of enzyme to nucleic acids, may play an important role in the process of double-stranded RNA degradation by ribonucleases specific for single-stranded RNA.

Aspergillus oryzae↗
PubMed1979

Complete amino acid sequence of the myoglobin from the Pacific spotted dolphin, Stenella attenuata graffmani.

The complete amino acid sequence of the major component myoglobin from the Pacific spotted dolphin, Stenella attenuata graffmani, was determined by the automated Edman degradation of several large peptides obtained by specific cleavage of the protein. The acetimidated apomyoglobin was selectively cleaved at its two methionyl residues with cyanogen bromide and at its three arginyl residues by trypsin. By subjecting four of these peptides and the apomyoglobin to automated Edman degradation, over 80% of the primary structure of the protein was obtained. The remainder of the covalent structure was determined by the sequence analysis of peptides that resulted from further digestion of the central cyanogen bromide fragment. This fragment was cleaved at its glutamyl residues with staphylococcal protease and its lysyl residues with trypsin. The action of trypsin was restricted to the lysyl residues by chemical modification of the single arginyl residue of the fragment with 1,2-cyclohexanedione. The primary structure of this myoglobin proved to be identical with that from the Atlantic bottlenosed dolphin and Pacific common dolphin but differs from the myoglobins of the killer whale and pilot whale at two positions. The above sequence identities and differences reflect the close taxonomic relationship of these five species of Cetacea.

Amino Acid Sequence↗
PubMed1990

Heme methyl hyperfine shift pattern as a probe for determining the orientation of the functionally relevant proximal histidyl imidazole with respect to the heme in hemoproteins.

Heme methyl 1H and 13C resonances of met-cyano form of myoglobin from the shark, Geleorhinus japonicus (GJMbCN), have been assigned via 1H-13C heteronuclear shift correlated spectroscopy (COSY) connectivities and their hyperfine shifts were compared with those of the corresponding resonances of some hemoproteins. Variation of the heme methyl 1H hyperfine shift pattern correlates well with the angle (phi) between the projection of the proximal histidyl imidazole plane onto the heme plane and the NII-Fe-NIV vector. The alteration of the interaction of the heme peripheral side-chains and/or the iron-bound ligand with the surrounding amino acid residues cannot account for large differences in the shifts of the corresponding heme methyl resonances between GJMbCN and sperm whale MbCN. Since the heme methyl 1H shifts for GJMbCN fall in between those of the corresponding resonances for sperm whale Mb and Aplysia limacina Mb in which the phi values have been reported to be 19 degrees and 29 degrees, respectively, the phi value in GJMb is estimated to be slightly larger than 19 degrees.

Animals↗
PubMed1995

Formate binding to ferric wild type and mutant myoglobins thermodynamic and X-ray crystallographic study.

The X-ray crystal structure of the formate derivative of ferric loggerhead sea turtle (Caretta caretta) Mb has been determined at 2.0 A resolution (R = 0.164) by difference Fourier techniques. Formate, sitting in the central part of the heme distal site, is coordinated to the heme iron as unidentate ligand, through the O1 oxygen atom, and is hydrogen bonded to the distal His64(E7) NE2 atom through O2. Thermodynamics for formate binding to ferric loggerhead sea turtle Mb, sperm whale Mb, Aplysia limacina Mb, as well as to the VR and VRS mutants of sperm whale Mb were obtained between pH 4.5 and 8.5, at 20.0 degrees C. These results, representing the first structure of a ferric hemoprotein:formate complex solved by X-ray crystallography, outline the role of amino acid residues at positions E7, F8 and E10 in modulating ligand binding properties of oxygen carrying proteins.

Animals↗
PubMed1991

Proton nuclear magnetic resonance study of the solution distal histidine orientation in monomeric Chironomus thummi thummi cyanomet hemoglobins. Dynamic stability of the heme pocket as monitored by labile proton exchange.

The 1H nuclear magnetic resonance spectral characteristics of the cyano-Met form of Chironomus thummi thummi monomeric hemoglobins I, III and IV in 1H2O solvent are reported. A set of four exchangeable hyperfine-shifted resonances is found for each of the two heme-insertion isomers in the hyperfine-shifted region downfield of ten parts per million. An analysis of relaxation, exchange rates and nuclear Overhauser effects leads to assignments for all these resonances to histidine F8 and the side-chains of histidine E7 and arginine FG3. It is evident that in aqueous solution, the side-chain from histidine E7 does not occupy two orientations, as found for the solid state, rather the histidine E7 side-chain adopts a conformation similar to that of sperm whale myoglobin or hemoglobin A, oriented into the heme pocket and in contact with the bound ligand. Evidence is presented to show that the allosteric transition in the Chironomus thummi thummi hemoglobins arises from the "trans effect". An analysis of the exchange with bulk solvent of the assigned histidine E7 labile proton confirms that the group is completely buried within the heme pocket in a manner similar to that found for sperm whale cyano-Met myoglobin, and that the transient exposure to solvent is no more likely than in mammalian myoglobins with the "normal" distal histidine orientation. Finally, a comparison of solvent access to the heme pocket of the three monomeric C. thummi thummi hemoglobins, as measured from proton exchange rates of heme pocket protons, is made and correlated to binding studies with the diffusible small molecules such as O2.

Animals↗
PubMed1989

Antigenic and molecular characterization of subtype H13 hemagglutinin of influenza virus.

Influenza A viruses with subtype H13 hemagglutinin display an unusual host range. Although common in shorebirds, they are very rare or absent in wild ducks; additionally, H13 viruses have been isolated from a whale. To study the molecular basis for this host range, we have determined the complete nucleotide sequences of the hemagglutinin genes of three H13 influenza viruses from different species or geographical areas: A/gull/Maryland/77, A/gull/Astrachan (USSR)/84, and A/pilot whale/Maine/84. Based on the deduced amino acid sequences, H13 hemagglutinin shares the basic structure of other type A hemagglutinin subtypes such as H3, but has clearly diverged from other completely sequenced subtypes. Unique features of H13 hemagglutinin include the occurrence, near the receptor binding pocket, of residues Arg/Lys-227 and Trp-229 (H3 numbering); the significance of these are unknown. The sequence of the HA1-HA2 cleavage site resembles those of avirulent avian influenza viruses. The whale H13 hemagglutinin is similar to those from gulls, supporting the hypothesis that influenza viruses from avian sources can enter marine mammal populations but are probably not permanently maintained there. Antigenic analysis using a panel of monoclonal antibodies suggests that, like other subtypes, H13 viruses are heterogeneous, with different antigenic variants predominating in the eastern versus the western hemispheres.

Amino Acid Sequence↗
PubMed1995

Presence of airborne contaminants in the wildlife of northern Québec.

As part of the environmental impact studies of the Great Whale and the Nottaway-Broadback-Rupert (NBR) hydroelectric projects, Hydro-Québec collected data on the occurrence and levels of several contaminants present in wildlife from both regions between 1989 and 1991. The analyses performed included metals (mercury, arsenic, selenium, cadmium, lead, nickel and copper), polychlorinated biphenyls (PCBs as arochlors or the sum of 20-40 congeners) and organochlorine pesticides such as hexachlorobenzene (HCB), DDT, DDE, hexachlorocyclohexane (HCH), chlordane, mirex and dieldrin. Species sampled included fish (freshwater and marine), birds (waterfowl, gull and ptarmigan), terrestrial mammals (marten, mink and hare) and marine mammals (freshwater and marine seals, belugas). Most laboratory analyses were carried out on both muscle and liver tissues, but some were conducted on other tissues as well: feathers, eggs and blubber. The results indicate that numerous airborne contaminants were present in the wildlife of both the Great Whale and the NBR study areas and that their level of contamination was similar to that of other northern environments. Total mercury in muscle was high in piscivorous fish, birds and mammals (terrestrial and marine). We observed significant levels of cadmium and lead in the livers of some herbivorous terrestrial animals, such as ptarmigans and hares. Among the organochlorine contaminants analyzed, levels of PCBs and DDE in piscivorous birds (mergansers and loons) and in marine mammals (seals and belugas) were high. For some contaminants, such as mercury, cadmium, lead, PCBs and DDE, the levels observed in some species or tissues could be considered worrisome with regard to public health, if those species or tissues constitute an important part of traditional native diets.

Air Pollutants↗
PubMed1988

The mechanism of reaction of nitrosyl with met- and oxymyoglobin: an ESR study.

In this ESR work we have studied the pentacoordinate symmetry in horse, whale and sperm-whale myoglobin (Mb) in different physical states such as solution and powder. Experiments were performed in which the following parameters were varied: the sample temperature, pH, reaction time with NO, and NO concentration. The results enabled us to explain the NO reaction mechanism in the oxy and met forms of myoglobin. The study of powder samples at different degrees of hydration allowed us to identify the diamagnetic intermediate species existent in the reaction of NO with met-Mb proposed in the literature. The results presented explain adequately the pH effect and temperature dependence observed in the ESR spectra obtained using the met-Mb sample solutions from Sigma Chemical Co., which consist of a mixture (13%) of Mb-O2.

Electron Spin Resonance Spectroscopy↗
PubMed1985

Denaturation thermodynamics of chicken cardiac metmyoglobin.

The unfolding at pH 8 of chicken cardiac aquometmyoglobin was examined as a function of temperature and concentration of guanidinium chloride using the two-state model. The isothermal unfolding data at 25 degrees C were fitted to Tanford's transfer model and the binding model of Aune and Tanford. The estimates obtained for delta GD were virtually identical, viz., 8.3 +/- 0.3 kcal mol-1. The chicken metmyoglobin is thus some 5.3 kcal mol-1 less stable than that of sperm whale metmyoglobin. The unfolding parameters alpha and delta n were decreased 20% from those of mammalian myoglobins thus far examined, suggesting nonidentity of native conformations. The apparent enthalpy change on unfolding was dependent on both temperature and denaturant concentration. The decreases in the isothermal unfolding parameters from those of sperm whale are principally assigned to three of the 46 sequence changes.

Animals↗
PubMed1992

A comparative study on ceramide composition of cetacean brain gangliosides.

1. Ceramide composition and N-glycolylneuraminic acid content of gangliosides from gray and white matters and myelin of cerebrum and cerebellum were analyzed in eight species belonging to the suborder Odontoceti and two species to Mystacoceti. 2. The most characteristic feature was high contents of C20:0 (10-40%) and C24 species (5-40%). 3. Content of hydroxy fatty acid of C24 species was higher in cerebellum (5-20%) than cerebrum (0-3%). 4. Major component of long-chain base was dC18:1 (70-90%). 5. N-glycolylneuraminic acid was found in sperm whale, Dall's porpoise and killer whale (0.1-1.7%).

Animals↗
PubMed2004

Organochlorine pesticides and polychlorinated biphenyls in California sea lions.

Concentrations of polychlorinated biphenyls (PCBs), DDTs, chlordanes, HCHs, hexachlorobenzene (HCB), dieldrin, heptachlor epoxide, tris(4-chlorophenyl)methane (TCPMe), and tris(4-chlorophenyl)methanol (TCPMOH) were measured in the blubber of California sea lions (Zalophus californianus) collected in 2000. DDTs were the most predominant contaminants, followed by PCBs, chlordanes, TCPMe, HCHs, TCPMOH, dieldrin, and heptachlor epoxide. Concentrations of PCBs and DDTs varied from a few microg/g to several hundreds of microg/g on a lipid weight basis. Concentrations of DDTs have declined by an order of magnitude over the last three decades in California sea lions; nevertheless, the measured concentrations of PCBs and DDTs in California sea lions are still some of the highest values reported for marine mammals in recent years. Concentrations of organochlorines were highly correlated with one another. Concentrations of PCBs and DDTs in the blubber of gray whale, humpback whale, northern elephant seal, and harbor seal, and in the adipose fat of sea otter, were lower than the levels found in California sea lions, and were in the range of a few to several microg/g on a lipid weight basis.

Adipose Tissue↗
PubMed2004

Probing the free radicals formed in the metmyoglobin-hydrogen peroxide reaction.

The reaction between metmyoglobin and hydrogen peroxide results in the two-electron reduction of H2O2 by the protein, with concomitant formation of a ferryl-oxo heme and a protein-centered free radical. Sperm whale metmyoglobin, which contains three tyrosine residues (Tyr-103, Tyr-146, and Tyr-151) and two tryptophan residues (Trp-7 and Trp-14), forms a tryptophanyl radical at residue 14 that reacts with O2 to form a peroxyl radical and also forms distinct tyrosyl radicals at Tyr-103 and Tyr-151. Horse metmyoglobin, which lacks Tyr-151 of the sperm whale protein, forms an oxygen-reactive tryptophanyl radical and also a phenoxyl radical at Tyr-103. Human metmyoglobin, in addition to the tyrosine and tryptophan radicals formed on horse metmyoglobin, also forms a Cys-110-centered thiyl radical that can also form a peroxyl radical. The tryptophanyl radicals react both with molecular oxygen and with the spin trap 3,5-dibromo-4-nitrosobenzenesulfonic acid (DBNBS). The spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) traps the Tyr-103 radicals and the Cys-110 thiyl radical of human myoglobin, and 2-methyl-2-nitrosopropane (MNP) traps all of the tyrosyl radicals. When excess H2O2 is used, DBNBS traps only a tyrosyl radical on horse myoglobin, but the detection of peroxyl radicals and the loss of tryptophan fluorescence support tryptophan oxidation under those conditions. Kinetic analysis of the formation of the various free radicals suggests that tryptophanyl radical and tyrosyl radical formation are independent events, and that formation of the Cys-110 thiyl radical on human myoglobin occurs via oxidation of the thiol group by the Tyr-103 phenoxyl radical. Peptide mapping studies of the radical adducts and direct EPR studies at low temperature and room temperature support the conclusions of the EPR spin trapping studies.

Animals↗
PubMed1990

X-ray crystal structure of a recombinant human myoglobin mutant at 2.8 A resolution.

We have grown crystals in trigonal space group P3(2)21 of a mutant human myoglobin, aquomet form, in which lysine at position 45 has been replaced by arginine and cysteine at position 110 has been replaced by alanine. Suitable crystals of native recombinant human myoglobin have not been obtained. We have used the molecular replacement method to determine the X-ray crystal structure of the mutant at 2.8 A resolution. At the present stage of refinement, the crystallographic R-value for the model, with tightly restrained stereochemistry, is 0.158 for 5.0 to 2.8 A data. As expected, the overall structure is quite similar to the sperm whale myoglobin structure. Arginine 45 adopts a well-ordered conformation similar to that found in aquomet sperm whale myoglobin.

Humans↗
PubMed1984

Proton nuclear magnetic resonance investigation of the heme cavity structure of liver fluke (Dicrocoelium dendriticum) methemoglobin.

The 1H nuclear magnetic resonance characteristics of met-cyano and met-aquo hemoglobin from the sheep bile duct parasite Dicrocoelium dendriticum have been compared to those of other monomeric hemoglobins and myoglobins. By varying temperature and pH, it was found that the studied material is a mixture of several isozymes differing slightly in their structural features around the heme cavity. The heme in-plane rhombic asymmetry, as indicated by the spread of the heme methyl hyperfine shifts, is intermediate between that of sperm whale myoglobin and leghemoglobin. The proximal histidine is present and its dynamic properties, as probed by the exchange of the ring NH with bulk solvent protons, point towards a cavity more stable than those of sperm whale myoglobin and leghemoglobin. In the met-cyano form, an exchangeable proton was detected close to the iron center that was tentatively assigned to an arginine residue located three amino acid residues closer to the C terminus than the proximal histidine. The transition from the met-aquo form to the met-hydroxy form occurring at pH 8.1 and previously detected by optical methods was observed. Furthermore, consideration of the mean heme methyl hyperfine shift average indicates that the iron remains six-co-ordinate down to below pH 4.5 irrespective of an acid-transition (pK approximately 5) in the protein. However, the presence of a "pseudo" six-co-ordinate (i.e. high-spin, in-plane, five-co-ordinate) iron at pH values below the acid-transition pK cannot be excluded on the basis of the presently available data. The pH dependence of several resonances in both the met-cyano and met-aquo forms of the protein reflect a pK value compatible with the titration of a heme propionate.

Animals↗
PubMed1999

Spatial and temporal trends and effects of contaminants in the Canadian Arctic marine ecosystem: a review.

Recent studies have added substantially to our knowledge of spatial and temporal trends of persistent organic pollutants and heavy metals in the Canadian Arctic marine ecosystem. This paper reviews the current state of knowledge of contaminants in marine biota in the Canadian Arctic and where possible, discusses biological effects. The geographic coverage of information on contaminants such as persistent organochlorines (OCs) (PCBs, DDT- and chlordane-related compounds, hexachlorocyclohexanes, toxaphene) and heavy metals (mercury, selenium, cadmium, lead) in tissues of marine mammal and sea birds is relatively complete. All major beluga, ringed seal and polar bear stocks along with several major sea bird colonies have been sampled and analysed for OC and heavy metal contaminants. Studies on contaminants in walrus are limited to Foxe Basin and northern Québec stocks, while migratory harp seals have only been studied recently at one location. Contaminant measurements in bearded seal, harbour seal, bowhead whale and killer whale tissues from the Canadian Arctic are very limited or non-existent. Many of the temporal trend data for contaminants in Canadian Arctic biota are confounded by changes in analytical methodology, as well as by variability due to age/size, or to dietary and population shifts. Despite this, studies of OCs in ringed seal blubber at Holman Island and in sea birds at Prince Leopold Island in Lancaster Sound show declining concentrations of PCBs and DDT-related compounds from the 1970s to 1980s then a levelling off during the 1980s and early 1990s. For other OCs, such as chlordane, HCH and toxaphene, limited data for the 1980s to early 1990s suggests few significant declines in concentrations in marine mammals or sea birds. Temporal trend studies of heavy metals in ringed seals and beluga found higher mean concentrations of mercury in more recent (1993/1994) samples than in earlier collections (1981-1984 in eastern Arctic, 1972-1973 in western Arctic) for both species. Rates of accumulation of mercury are also higher in present day animals than 10-20 years ago. Cadmium concentrations in the same animals (eastern Arctic only) showed no change over a 10-year period. No temporal trend data are available for metals in sea birds or polar bears. There have been major advances in knowledge of specific biomarkers in Canadian Arctic biota over the past few years. The species with the most significant risk of exposure to PCBs and OC pesticides may be the polar bear which, based on comparison with EROD activity in other marine mammals (beluga, ringed seal), appears to have elevated CYP1A-mediated activity. The MFO enzyme data for polar bear, beluga and seals suggest that even the relatively low levels of contaminants present in Arctic animals may not be without biological effects, especially during years of poor feeding.

Animals↗
PubMed2003

Levels and trends of polybrominated diphenylethers and other brominated flame retardants in wildlife.

In this paper, we review the available data for polybrominated diphenylethers (PBDEs) and other flame retardants in wildlife, with the exception of fishes from Europe and North America which are covered in more detail elsewhere. More data are available for PBDEs than for other compounds, and these show that some of these compounds have become widely distributed in the environment, being found in samples from Europe, Australia, Azerbaijan, North America and the Arctic. Most available data relate to birds and their eggs and marine mammals, but the results of two food web studies are also included. The detection of PBDEs in pelagic marine mammals which feed in deep offshore waters, including baleen whales, indicate that these compounds have found their way into deep-water, oceanic food webs as well as the coastal/shallow sea examples described in detail. In the North Sea study, the most marked increase in lipid-normalised concentrations of six BDE congeners occurred during transfer from predatory fish to marine mammals. In the St. Lawrence Estuary study, marked differences in the ratios observed between species suggested that some fish species may be able to metabolise BDE99.A number of time trend studies have also been conducted, notably in guillemot eggs from Sweden (1969-2000), beluga whales from the Canadian Arctic (1982-1997 and 1989-2001) and from the St. Lawrence Estuary (1988-1999), and ringed seals from the Canadian Arctic (1981-2000). In the temperate latitudes, from these and other studies (e.g. in dated sediment cores), PBDE concentrations began to rise earlier than in those from high latitudes, in line with data for production and use. These trends have now slowed in many cases. Declines could be expected in Europe for many congeners following the cessation of manufacture and use of the penta-mix formulation in the EU, though these are not yet apparent in environmental samples. In Arctic biota, however, the rapidly rising concentrations seen currently in Canada could be expected to continue for some time, reflecting continued production and use of the penta-mix formulation in North America (>95% of the world total) and the impact of long-range atmospheric transport.

Animals↗
PubMed2000

Tryptophanyl contributions to apomyoglobin fluorescence resolved by site-directed mutagenesis.

The individual emission properties of the two tryptophanyl residues of sperm-whale apomyoglobin have been resolved by examining the fluorescence variations induced by denaturants, i.e., acid and guanidine, on apomyoglobin mutants W7F and W14F. The fluorescence changes have been correlated to the conformational transitions undergone by apomyoglobin on increasing denaturant concentration. The results indicate that the fluorescence decrease, observed for sperm-whale apomyoglobin on going from pH 8.0 to pH 6.0, cannot be ascribed to the formation of a charge transfer complex between a nearby histidine residue and W14 as reported in earlier papers but rather to minor structural changes affecting the microenvironments of both residues. The formation of the acidic partly folded state around pH 4.0 determines an increase of the fluorescence yield and a small red shift (5 nm) of W7 due to removal of sterically interacting K79, which is able to attenuate the emission of this residue in the native state. The fluorescence intensity of the other residue, i.e., W14, is not affected by the acidic transition. Guanidine denaturation experiments revealed an increase of fluorescence yield of W14 upon the intermediate formation, whereas the fluorescence of the other residue remained constant. The results suggest that the unfolding pathway may be different depending on the chemical nature of the denaturant used.

Animals↗
PubMed2001

An insight into the epidemiology of dolphin morbillivirus worldwide.

Serum samples from 288 cetaceans representing 25 species and originating from 11 different countries were collected between 1995 and 1999 and examined for the presence of dolphin morbillivirus (DMV)-specific antibodies by an indirect ELISA (iELISA) (N = 267) or a plaque reduction assay (N = 21). A total of 35 odontocetes were seropositive: three harbour porpoises (Phocoena phocoena) and a common dolphin (Delphinus delphis) from the Northeastern (NE) Atlantic, a bottlenose dolphin (Tursiops truncatus) from Kent (England), three striped dolphins (Stenella coeruleoalba), two Risso's dolphins (Grampus griseus) and a bottlenose dolphin from the Mediterranean Sea, one common dolphin from the Southwest (SW) Indian Ocean, three Fraser's dolphins (Lagenodelphis hosei) from the SW Atlantic, 18 long-finned pilot whales (Globicephala melas) and a bottlenose dolphin from the SW Pacific as well as a captive bottlenose dolphin (Tursiops aduncus) originally from Taiwan. The presence of morbillivirus antibodies in 17 of these animals was further examined in other iELISAs and virus neutralization tests. Our results indicate that DMV infects cetaceans worldwide. This is the first report of DMV-seropositive animals from the SW Indian, SW Atlantic and West Pacific Oceans. Prevalence of DMV-seropositives was 85.7% in 21 pilot whales from the SW Pacific and both sexually mature and immature individuals were infected. This indicates that DMV is endemic in these animals. The same situation may occur among Fraser's dolphins from the SW Atlantic. The prevalence of DMV-seropositives was 5.26% and 5.36% in 19 common dolphins and 56 harbour porpoise from the NE Atlantic, respectively, and 18.75% in 16 striped dolphins from the Mediterranean. Prevalence varied significantly with sexual maturity in harbour porpoises and striped dolphins; all DMV-seropositives being mature animals. The prevalence of seropositive harbour porpoise and striped dolphins appeared to have decreased since previous studies. These data suggest that DMV is not endemic within these populations, that they are losing their humoral immunity against the virus and that they may be vulnerable to new epidemics.

Animal Diseases↗