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Biomedical subjects

A S Blix

Publications and source records attributed to A S Blix.

At least 19 recordsLinked to original sources
PubMed2005

Isolation and partial characterization of a parapoxvirus isolated from a skin lesion of a Weddell seal.

A solitary skin lesion was found on the neck of a Weddell seal (Leptonychotes weddellii), chemically immobilized in Queen Maud Land (70 degrees 09'S, 05 degrees 22'E) Antarctica 2001. The lesion was elevated and 3cm in diameter, consisting of partly fresh and partly necrotic tissue, and proliferative papilloma-like structures were seen. Electron microscopy on a biopsy from the lesion revealed typical parapoxvirus particles. Polymerase chain reaction (PCR; B2L gene) generated amplicons of approximately 594 base pairs, comparable to Orf-virus, the prototype parapoxvirus. A comparison of these B2L PCR amplicon DNA sequences with corresponding sequences from other parapoxviruses, showed that the Weddell seal virus resembled isolates from grey seal (Halichoerus grypus) and harbour seal (Phoca vitulina) more than parapoxvirus from red deer (Cervus elaphus), sheep, cattle and Japanese serows (Capricornis crispus). It is thus concluded that the Weddell seal parapoxvirus belong to the tentative seal parapoxvirus species. Since parapox and orthopoxviruses may cause similar clinical diseases, we suggest that the term sealpox should be restricted to the clinical disease, whereas seal parapoxvirus should be used when caused by a parapoxvirus, rather than the general term "sealpox virus". This is the first verified case of parapoxvirus infection in a Weddell seal, and also the first report of any such infections in the Antarctic.

Animals↗
PubMed2004

Click sounds produced by cod (Gadus morhua).

Conspicuous sonic click sounds were recorded in the presence of cod (Gadus morhua), together with either harp seals (Pagophilus groenlandicus), hooded seals (Cystophora cristata) or a human diver in a pool. Similar sounds were never recorded in the presence of salmon (Salmo salar) together with either seal species, or from either seal or fish species when kept separately in the pool. It is concluded that cod was the source of these sounds and that the clicks were produced only when cod were approached by a swimming predatorlike body. The analyzed click sounds (n = 377) had the following characteristics (overall averages +/- S.D.): peak frequency = 5.95 +/- 2.22 kHz; peak-to-peak duration = 0.70 +/- 0.45 ms; sound pressure level (received level) = 153.2 +/- 7.0 dB re 1 microPa at 1 m. At present the mechanism and purpose of these clicks is not known. However, the circumstances under which they were recorded and some observations on the behavior of the seals both suggest that the clicks could have a predator startling function.

Animal Communication↗
PubMed2000

On the direction and velocity of blood flow in the extradural intravertebral vein of harp seals (Phoca groenlandica) during simulated diving.

Ronald et al. (1977) suggested that blood flow in the caudal/lumbar sections of the extradural intravertebral vein (EIV) of seals changes direction from running towards the head before diving, to the opposite during diving. The possible advantage would be that the oxygen-depleted venous effluent from the brain is routed via the EIV to the posterior parts of the hepatic sinuses and the inferior caval vein and, hence, is prevented from mixing with the more oxygen-rich venous blood in their anterior parts. We have re-examined this hypothesis by use of Doppler flowmetry. A catheter-tip flow probe was introduced into the EIV of two similar-sized juvenile harp seals, and flow direction and rate determined before, during and after simulated dives lasting for 5 min, at three positions (caudal, lumbar and thoracic) along the EIV. Regardless of probe position, blood was mainly flowing towards the head in 11 of 13 experiments prior to diving, in 8 of 13 experiments during diving and in 11 of 13 experiments during recovery after diving (and away from the head in the remaining experiments). Flow direction was most variable in the caudal position. Mean blood velocity in the EIV was substantially lower during diving (0.10 +/- 0.22 cm s-1 (n=5) in thoracic position) than in the pre-dive (3.98 +/- 3.32 cm s-1 [n=5]) and post-dive (5.75 +/- 4.07 cm s-1 [n=5]) situations. Thus, the direction and rate of flow in the EIV was variable, particularly during diving, as is to be expected in a system of anastomosing, valveless veins. We conclude that the hypothesis of Ronald et al. (1977) most likely is false.

Animals↗
PubMed2000

Seasonal changes in heart rate and food intake in reindeer (Rangifer tarandus tarandus).

This study tested the hypothesis that the annual cycle in heart rate (HR) in reindeer is, at least in part, a consequence of seasonal fluctuation in voluntary-food intake. Heart rate and daily dry matter voluntary-food intake (DDMVFI) were recorded in two captive female reindeer (Rangifer tarandus tarandus) from April 1995 to August 1996. Heart rate was measured continuously in each animal for 20-24 h for 7 days each month using Polar(R) Sport Testers (PST); DDMVFI was measured in each animal daily for 17 months. Modal daily heart rate (MDHR) and DDMVFI fluctuated seasonally in close synchrony, both reaching maxima in July and minima in January. The relationship between HR and DDMVFI was investigated experimentally by manipulating the level of feeding in a stepwise manner in May, when appetite was low and in August, when DDMVFI was close to maximum. Heart rate showed stepwise changes in close synchrony with the changes in levels of feeding. These results suggest that the seasonal increase in HR in summer is a consequence of increased food intake and, likewise, decreased HR in winter is a consequence of reduced food intake. The observed relationship between food intake and HR presumably reflects changes in cardiac output and/or the rate of flow of blood to the gastrointestinal tract which are influenced by meal size.

Adaptation, Physiological↗
PubMed2000

Chitinolytic bacteria in the minke whale forestomach.

Minke whales consume large amounts of pelagic crustaceans. Digestion of the prey is initiated by indigenous bacteria in a rumen-like forestomach system. A major structural component of the crustacean exoskeleton is chitin, the beta-1,4-linked polymer of N-acetyl-D-glucosamine. The exoskeletons appear to dissolve completely in the non-glandular forestomach. Bacteria in the forestomach fluid of six krill-eating minke whales were enumerated and isolated using an anaerobic habitat-simulating culture medium. Median viable population densities ranged between 6.0 x 10(6) and 9.9 x 10(9) bacterial cells per mL forestomach fluid. Bacterial isolates (n = 44) cultured from the forestomach fluid of one minke whale mainly resembled strains of Eubacterium (25%), Streptococcus (18%), Clostridium (14%), and Bacteroides (11%). As much as 12% of the bacterial isolates were chitinolytic, while beta-N-acetylglucosaminidase activity was demonstrated in 54% of the isolates, and utilisation of N-acetyl-D-glucosamine was observed in 73%. The chitinolytic isolates resembled strains of Bacteroides, Bacteroidaceae, Clostridium, and Streptococcus. Scanning and transmission electron microscopy of partly digested krill from the minke whale forestomach revealed bacteria close to and inside the chitinous exoskeleton. The bacterial chitinase may act on the chitinous crustacean exoskeletons, thereby allowing other bacteria access to the nutritious soft inner tissues of the prey, and thus initiating its degradation and fermentation.

Animals↗
PubMed2000

Panting in reindeer (Rangifer tarandus).

Two winter-insulated Norwegian reindeer (Rangifer tarandus tarandus) were exposed to air temperatures of 10, 20, 30, and 38 degrees C while standing at rest in a climatic chamber. The direction of airflow through nose and mouth, and the total and the nasal minute volumes, respectively, were determined during both closed- and open-mouth panting. The animals alternated between closed- and open-mouth panting, but the proportion of open-mouth panting increased with increasing heat load. The shifts from closed- to open-mouth panting were abrupt and always associated with a rise in respiratory frequency and respiratory minute volume. During open-mouth panting, the direction of airflow was bidirectional in both nose and mouth, but only 2.4 +/- (SD) 1.1% of the air was routed through the nose. Estimates suggest that the potential for selective brain cooling is markedly reduced during open-mouth panting in reindeer as a consequence of this airflow pattern.

Animals↗
PubMed2000

Simulations of the effect of currently used grenade harpoons for the killing of whales using a pig-model.

Physical model experiments, as well as simulations of the effects of grenade harpooning on anaesthetized pigs fully immersed in water suggest that the shock effect of the blast from the currently used grenades is relatively minor. Also the animals are not stunned to death, but loose consciousness and subsequently die from hemorrhage. Survival time is therefore very short if the animals are hit in the thorax, and is likely to be further reduced if the charge which is currently used is increased, or, even better, if shrapnel (fragment scattering) grenades are used instead of blast grenades.

Animals↗
PubMed1999

The effect of body fat on basal metabolic rate in adult harp seals (Phoca groenlandica).

Three adult harp seals (Phoca groenlandica) were fed different daily amounts of capelin (Mallotus villosus), and their body composition determined by use of the tritiated water method at different levels of fattening. Basal metabolic rate (BMR) was measured after 5 days of fasting by indirect calorimetry, and was on average 1.1 W.kg-1 when 45% of body mass (BM) was fat and 2.3 W.kg-1 when body fat was reduced to 13% of BM. This suggests that body fat contributes little to BMR in these animals. It follows, that predictions of BMR on the basis of BM is questionable in seals, in which body fat may change seasonally between 20 and 60% of BM.

Adipose Tissue↗
PubMed1998

Effects of adrenergic and cholinergic drugs on splenic arteries and veins from hooded seals (Cystophora cristata).

Isolated ring preparations of arteries and veins from hooded seal spleens were subjected in vitro to adrenaline (A), noradrenaline (NA), isoprenaline (Iso), and acetylcholine (ACh), alone or in combination with the blockers phentolamine (Phe), propranolol (Pro), and atropine (Atr). Both arteries and veins constricted in response to A (the estimated effective dose required for half-maximal response (ED50) was 3.3 and 0.2 microM, for arteries and veins, respectively) and NA (estimated ED50 was 1.5 and 0.6 microM, for arteries and veins, respectively), but these effects were abolished when the drugs were given in combination with the alpha-adrenoceptor blocker Phe. The responses of arteries and veins to ACh and the beta-adrenoceptor agonist Iso were minor and inconsistent, and were completely abolished when combined with their respective blockers (Atr and Pro, respectively). The ED50 for both A and NA are quite high in relation to normal plasma levels of A and NA in seals. This implies that these vessels (and, hence, the supply of blood to the spleen) primarily are subjected to neurogenic, rather than humoral physiological control.

Adrenergic Agents↗
PubMed1998

Rapid brain cooling in diving ducks.

Hypothermia may limit asphyxic damages to the brain, and many small homeotherms have been shown to use anapyrexic strategies when exposed to asphyxic conditions. Larger homeotherms do not seem to use the same strategy, but could save oxygen and prevent hypoxic brain damage by employing selective brain cooling (SBC) in connection with asphyxia. To test the hypothesis that selective brain cooling may take place in connection with asphyxia, we have recorded brain [hypothalamic (THyp)] and body [colonic (TC)] temperatures and heart rates in four Pekin ducks during 5-min simulated (head submersion) diving in cold water (10 degrees C). Diving resulted in a drop in THyp (3.1 +/- 1.4 degrees C) that continued into the recovery period (P < 0.001). Restricting heat loss from the buccal cavity and eyes during diving compromised brain cooling in an additive manner. TC was not influenced by diving. Control cooling of the head with crushed ice during a 5-min period of undisturbed breathing had no effect on THyp. Warm water (35 degrees C) markedly reduced brain cooling, and dive capacity was reduced by approximately 14% (P < 0.05) compared with diving in water at 10 degrees C. The data suggest that SBC is used in ducks during diving, and we propose that this mechanism may enable the bird to save oxygen for prolonged aerobic submergence and to protect the brain from asphyxic damages.

Animals↗
PubMed1997

Volume capacity and contraction control of the seal spleen.

Volume changes in the spleens of hooded seals (Cystophora cristata) and harp seals (Phoca groenlandica) were measured plethysmographically in vitro in response to epinephrine, norepinephrine, isoprenaline, phentolamine, and acetylcholine. Dilated spleens contracted forcefully within 1-3 min of alpha-adrenoceptor activation with 1.0-5.0 micrograms epinephrine/kg body mass, whereas stimulation of beta-adrenoceptors and cholinergic receptors had little effect. The mass of dilated hooded seal spleens corresponded to 2-4% (n = 7) of body mass, with volume (V; ml) relating to body mass (M; kg) as follows: V = 12.0M + 910 (r2 = 0.96, n = 4). Thus the spleen of a 250-kg hooded seal maximally expels 3.9 liters, or 13%, of its estimated total blood volume. Average hematocrit in splenic venous outflow from dilated spleens was 90 +/- 3% (n = 3) in hooded seals and 85% (n = 2) in harp seals. From these data we have estimated that the aerobic diving limit of a 250-kg hooded seal increases only 105 s, at the most, if complete emptying of the spleen occurs during diving, while the corresponding estimate for a 112-kg harp seal is 80 s.

Animals↗
PubMed1995

Pineal and thyroid functions in newborn seals.

Daily variations of pineal and plasma melatonin and plasma thyroid hormones were measured in harp seals (Phoca groenlandica), grey seals (Halichoerus grypus), and hooded seals (Cystophora cristata), ranging in age from newborn to 14 days. In newborn harp seals the mean mass of the pineal gland was 273 mg (+/- 45 SEM, n = 11), containing 49 ng (median) melatonin. In newborn, 4- and 10-day-old grey seals, the pineal mass was similar, weighing on average 337 mg (+/- 74, n = 6) and containing 90 ng melatonin. Two newborn hooded seal pups had pineals weighing 520 and 1289 mg, with 254 and 7600 ng melatonin, respectively. There were no day-night differences in the pineal contents of melatonin or in the number of pineal beta-adrenergic receptors measured in newborn harp seals, and, in newborn, 4- and 10-day-old grey seals, there were no day-night or age differences in pineal melatonin content. Plasma melatonin levels were 10 times higher in newborn seals than in two 10-day-old grey seals and one 14-day-old harp seal pup. In all seal pups, the levels exhibited a 24-hr rhythmicity, with increasing night- and decreasing daytime concentrations. Plasma levels of thyroxine (T4) and triiodothyronine (T3) were generally higher in newborn seals than in 10- and 14-day-old seals or in adult females. There was no apparent 24-hr rhythmicity, but the thyroid hormone levels generally declined throughout each sampling sequence. High pineal and thyroid activities may play a thermoregulatory role in newborn seals, but the results do not indicate a stimulatory action of melatonin in the peripheral conversion of T4 to T3. It is speculated that the large and active pineal gland, particularly in newborn seals, may be related to aspects of their diving habit.

Aging↗
PubMed1995

Daily energy expenditure in free living minke whales.

Six minke whales (Balaenoptera acutorostrata) were instrumented with VHF-radio transmitters and four with sonic speed-depth transmitters off the west coast of northern Norway and Svalbard and followed within view for up to 24 h. During such periods their respiratory rate was continuously recorded and their energy expenditure estimated according to Folkow & Blix (1992) at different swimming speeds and types of activity. We found that cost of swimming is remarkably low in these large animals and that their estimated daily energy expenditure on average only amounts to 80 kJ kg-1 day-1.

Animals↗
PubMed1994

Digestibility of krill (Euphausia superba and Thysanoessa sp.) in minke whales (Balaenoptera acutorostrata) and crabeater seals (Lobodon carcinophagus).

Apparent digestible efficiency (% DE) was studied by use of dietary Mn as an inert marker, in minke whales (Balaenoptera acutorostrata) and crabeater seals (Lobodon carcinophagus) which had been eating krill. Median % DE in minke whales (n5) eating krill of the genus Thysanoessa sp. (energy density (ED) 23.8 kJ/g) was 93 (range 87-93). Median % DE in crabeater seals (n6) eating krill of the species Euphausia superba (ED 20.8 kJ/g) was 84 (range 79-85), which is significantly lower than the % DE of krill in minke whales (P = 0.008). Since the chemical composition in E. superba and in Thysanoessa sp. is similar, it is suggested that the complex multi-stomached system of minke whales, which contains both chitinase (EC 3.2.1.14)-producing as well as several other types of bacteria, is superior to the single-stomached system of crabeater seals with regard to krill digestion. It is worth noting, however, that the % DE of krill in the crabeater seal is still very high.

Animals↗
PubMed1993

In vitro digestibility of different prey species of minke whales (Balaenoptera acutorostrata).

Information on diet composition, daily energy expenditure, energy storage and the utilization of energy in the prey are important factors when evaluating the food consumption of minke whales (Balaenoptera acutorostrata) during their summer stay in northern waters. The purpose of the present study was in this context to obtain information on the digestible energy (DE) of different prey selected by minke whales. An in vitro three-stage digestion technique, simulating the different compartments of the digestive system, has been developed. The initial step simulated the anaerobic microbial fermentation of substrate in the forestomach. The next stage included the addition of pepsin (EC 3.4.23.1)-HCl, simulating ventricle enzymic decomposition, and finally, in the third step, fresh extract from duodenal contents was used to simulate enzymic intestinal degradation of the remaining components of the food. The inoculum was normally obtained from animals which had recently eaten the prey to be tested. In such tests we obtained a dry matter disappearance (DMD) and a DE for herring (Clupea harengus) of 80.4 (SD 5.0)% (n 18) and 92.1 (SD 3.7)% (n 16) respectively, and a DMD of krill (Thysanoessa sp.) of 83.4 (SD 4.9)% (n 6). The DMD of krill was reduced to 73.8 (SD 7.3)% (n 8) while the DE was 70.6 (SD 10.4)% (n 7) when inoculum from whales which had recently eaten cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) was used. These results indicate a high digestibility of the most common species of prey in these animals, and also that the whales have little difficulty in changing from one prey species to another.

Animals↗
PubMed1993

Seasonal changes in the adherent microflora of the rumen in high-arctic Svalbard reindeer.

Seasonal changes in bacterial colonization of the epithelial tissue were examined in the rumen of high-arctic Svalbard reindeer. Samples of tissue were collected from eight sites in the rumen of reindeer during summer and winter and bacterial colonization was examined using scanning and transmission electron microscopy. At two of these sites, colonization by adherent bacteria was estimated to cover approximately 30% of the ruminal epithelium in specimens collected from reindeer during summer. Bacteria at these sites resembled Ruminococcus sp. and were surrounded by large amounts of glycocalyx. In winter specimens, less than 10% of the epithelial surface was covered by adherent bacteria. Those bacteria that did colonize the epithelial surface were smaller and had virtually no glycocalyx on their surface. Bacteria attached to plant cell wall material in summer samples of reindeer ingesta contained large intracellular glycogen deposits, whereas feed particle-associated bacteria in ingesta collected in winter contained no intracellular glycogen. These data demonstrate that the ruminal bacterial population responds to seasonal changes in feed intake and quality. It is yet to be determined if these bacterial changes enhance the ability of Svalbard reindeer to survive in the hostile environment of the high Arctic.

Animals↗
PubMed1992

Water flux and early signs of entrance into phase III of fasting in grey seal pups.

Body water loss and turnover rate were measured in fasting newly weaned grey seal (Halichoerus grypus) pups without access to water for 52 days, by use of bolus injections of deuterated water. Total body water (N) was 41.8 +/- 2.3 (SD)% of total body weight at day 3 and 44.5 +/- 5.9 (SD)% at day 51 of fasting (P greater than 0.05), while the water content of body core decreased from 73 to 61% over the same period. The average water efflux rate in the same period was 362 +/- 17 (SD) ml d-1, the reduction in N over the same period contributing 35% to this end. The biological half-time of deuterated water was 38.2 +/- 3.3 (SD) d. Plasma osmolality increased from a stable level of 329 +/- 11 (SD) mosmol kg-1 to 445 +/- 11 (SD) mosmol kg-1 after day 38 of fasting. Plasma urea was the major contributor to this increase, in spite of a steadily decreasing urine urea concentration (Nordøy et al. 1990) throughout the entire experimental period. It is concluded that grey seal pups endure 52 d of fasting without intake of water with a minor dehydration of body core, while they become hyperosmotic due to increased catabolism of protein after 38 d when sparing of the insulating blubber layer in preparation for life in cold water seems to occur.

Animals↗