Adrenal histostructure in the postnatal ontogeny of the Greenland seal, Pagophilus groenlandica Erxleben, 1777 (Phocidae)]

Histological structure of adrenal gland is studied in four age groups of the harp seal: in adults, in two juvenile groups (6 and 1-1.5 months), and in newborns (1-1.5 days). Development of the adrenal gland in this species is analogous to that of terrestrial mammals, but also has some peculiarities of its own. Differentiation of the definitive cortex occur in the prenatal development. In the newborns it is, though weakly developed, clearly differentiated into arched, fascicle and reticular zones. The foetal cortex is discovered in newborns, which further develops in juveniles and is present (without any signs of involution and degeneration) in adults. Adrenal gland persistence was previously known in horses only, but in that case the foetal cortex was partly degenerated in adults. Chromaffin cells undergo differentiation in embryonic development, as newborns already possess two types of such cells. The final differentiation ends in juvenile of 1.5 months old.     

Seasonal energetics of northern phocid seals

The metabolic rate of harp (Pagophilus groenlandicus), harbor (Phoca vitulina), and ringed seals (Pusa hispida) was measured at various temperatures in air and water to estimate basal metabolic rates (BMRs) in these species. The basal rate and body composition of three harp seals were also measured throughout the year to examine the extent to which they vary seasonally. Marine mammalian carnivores generally have BMRs that are over three times the rates expected from body mass in mammals generally, both as a response to a cold-water distribution and to carnivorous food habits with the basal rates of terrestrial carnivores averaging about 1.8 times the mean of mammals. Phocid seals, however, have basal rates of metabolism that are 30% lower than other marine carnivores. Captive seals undergo profound changes in body mass and food consumption throughout the year, and after accounting for changes in body mass, the lowest rate of food intake occurs in summer. Contrary to earlier observations, harp seals also have lower basal rates during summer than during winter, but the variation in BMR, relative to mass expectations, was not associated with changes in the size of fat deposits. The summer reduction in energy expenditure and food consumption correlated with a reduction in BMR. That is, changes in BMR account for a significant portion of the seasonal variation in energy expenditure in the harp seal. Changes in body mass of harp seals throughout the year were due not only to changes in the size of body fat deposits, but also to changes in lean body mass. These results suggest that bioenergetics models used to predict prey consumption by seals should include time-variant energy requirements.     

Histological development of the equine fetal adrenal gland.

The horse fetal adrenal gland was shown to begin to increase in weight from about the end of the 4th month of pregnancy when the fetus has a crown-rump length of about 20 cm. Growth then proceeds steadily to term but, in contrast to the adult horse, the medulla remains thicker than the cortex throughout fetal life. The cortex also becomes established around 20 cm crown-rump length and at the same time the glomerular and fascicular zones become distinguishable. In contrast the reticular zone is not differentiated until around 50 cm crown-rump length. In the fetal adrenal cortex, the fascicular zone is less prominent than in the adult horse although counts of cell nuclei in the cortical region indicate hypertrophy of the fascicular cells during the last third of gestation.     

ADRENOCORTICAL FUNCTION IN PINNIPED HYPONATREMIA

Potentially fatal sodium imbalance occurs in captive and free-ranging pinnipeds and is associated with a variety of stressors. We sought to determine the role of adrenal hormones, principally aldosterone, in the development of this condition. To induce hyponatremia, two ringed seals, Phoca hispida , were maintained in fresh water and fed a low-sodium diet; as controls, two other ringed seals were held in salt water and received a salt-supplemented diet. After 3–6 mo, adrenocorticotropic hormone (ACTH) was used to assess adrenocortical function. In normonatremic control seals, ACTH produced a 2-j-fold increase in circulating cortisol and a 7-fold increase in aldosterone. One of the experimental seals maintained normal plasma sodium levels, and ACTH elicited an exaggerated aldosterone response. The other salt-deprived seal became hypo-natremic, and ACTH had little effect on plasma aldosterone levels. An ACTH stimulation test performed on a spontaneously hyponatremic harp seal, P. groenlandica , which had been maintained in a salt-rich environment, failed to elicit cortisol or aldosterone secretion from the adrenal cortex. This study demonstrated the unusual sensitivity of the seal's zona glomerulosa to central stimulation, providing a mechanism through which the stress response might exhaust adrenal hormone reserves or desensitize the cortex to other physiological stimuli.     

Detection of Cryptosporidium sp. in two new seal species, Phoca vitulina and Cystophora cristata, and a novel Cryptosporidium genotype in a third seal species, Pagophilus groenlandicus, from the Gulf of Maine

Data on the geographic distribution and host specificity of Cryptosporidium spp. are critical for developing an understanding of likely transmission patterns in nature. During a molecular-based survey of fecal samples from 293 terrestrial and aquatic animals in Maine, USA, we detected Cryptosporidium sp. in 11 harbor seals (Phoca vitulina), 1 hooded seal (Cystophora cristata), and 1 harp seal (Pagophilus groenlandicus). None of the terrestrial or freshwater mammal fecal samples or bird samples tested positive for Cryptosporidium sp. However, the sequencing results of the small subunit (ssu) rRNA gene indicate that the seals were infected with an undescribed species of Cryptosporidium , previously isolated only from ringed seals (Phoca hispida) in northern Quebec, Canada. In addition, the Cryptosporidium sp. detected in the harp seal is significantly different from the previously observed Cryptosporidium sp. in other seals. We confirmed the genetic distinctiveness of this Cryptosporidium genotype and the identity of the other Cryptosporidium sp. seal ssu rRNA sequences by using data from the 70-kDa heat shock protein gene. Based on phylogenetic reconstructions of both genes, it seems that either Cryptosporidium canis or C. felis are sister species to the seal associated Cryptosporidium spp. Our findings extend the range of " Cryptosporidium sp. seal" well south of the 55th parallel, add other species to the list of seals affected by Cryptosporidium sp., and highlight the presence of unrecognized population and potentially species level variation in Cryptosporidium.     

Morphometric and histological studies on the adrenal glands of the camel Camelus dromedarius

The adrenal gland of the camel consists of an outer cortex and an inner medulla. The general disposition of the cortex and medulla, however, differs occasionally from that of other mammals. Extensions of medulla could reach as far as the periphery of the cortex. Islet of medullary tissue may be found in sections of the cortex and cortical tissue consisting of all zones of the cortex may occur around arteries or nerves in the medulla. The medulla may be separated from the cortex by connective tissue especially in old camels. The arrangement of noradrenaline-secreting cells is different from that in other ruminants; they are found in groups scattered between the adrenaline-secreting cells. Bundles of smooth muscle occur in venules at the corticomedullary interface. Accessory adrenal glands are found embedded in the renal fat. They are similar in structure to the adrenal gland. The adrenal cortex forms 74% of the volume of the gland and the ratio of the cortex to medulla is 4:1. The zona glomerulosa, fasciculata and reticularis constitute about 13%, 53%, and 29% by volume of the cortex, respectively.     

DIET OF WEANED PUPS AND SEASONAL VARIATIONS IN BODY CONDITION OF JUVENILE BARENTS SEA HARP SEALS PHOCA GROENLANDICA

Data on blubber depth, body condition, and diet were collected from young of year and juvenile harp seals ( Phoca groenlandica ) in the Barents Sea in the periods February-April and June-October 1990–1997. Harp seal pups feed independently shortly after weaning. In the southern parts of the Barents Sea the diet of harp seal pups consisted mainly of euphausiids ("krill") Thysanoessa sp. and amphipods of the genus Parathemisto . The change in body condition of harp seal pups between weaning (mid-March) and June indicated that considerable amounts of blubber energy, deposited during suckling, were mobilized. This suggests that the early food intake of weaned pups was insufficient to meet the energy requirements. The pattern of low spring and earlysummer body condition, followed by a subsequent rapid improvement in condition during late summer and autumn appeared to occur not only among pups-of-the-year, but also in one- and two-year old harp seals.     

Impact of diazepam on pineal-adrenal axis in an avian model

Diazepam, a benzodiazepine derivative, better known as a melatonin blocker in mammals, was injected into pigeons at a dose of 3 mg/kg body weight/day for 1 h, 1 day, 7 days and 15 days. This was done to investigate whether diazepam-induced changes in the pineal gland were reflected in the functioning of the adrenal gland. The results indicated that diazepam caused inhibition of pineal function and the degree of inhibition was very much time dependent. In addition, the pineal gland was unable to modulate the adrenomedullary hormonal titre yet it considerably influenced the physiology of the adrenal cortex.     

Monoclonal antibody to alkaline phosphatase from the intestinal mucosa of the harp seal, Phoca groenlandica.

1. Hybridoma secreting a monoclonal antibody APP.1 to the harp seal alkaline phosphatase (A1Ph) was obtained by fusing murine myeloma Sp 2/0 cells with the splenocytes of BALB/c mice immunized with purified isozyme K. 2. The antibody has no effect on the enzyme activity and shows a high affinity for harp seal A1Ph (KD = 8.5 x 10(-10) M). The antibody has similar affinities for the AlPh of harp seal, fur seal, common seal and deer. 3. The antibody APP.1 was coupled to Sepharose and employed in chromatographic purification of the harp seal intestinal AlPh. Alkaline phosphatase isolated on this immunosorbent has a spec. act. of 20,800 units per mg of protein. 4. The antibody-enzyme complex gives an excellent immunocytochemical labeling of tissue sections, cell cultures and smears.     

Influence of pinealectomy on the mitotic activity of regenerating adrenal cortex in rats

There is some evidence that the pineal gland may influence the proliferation of both normal and neoplastic cells. The adrenal cortex has very high capacity for regeneration. Therefore, the effects of pinealectomy on the mitotic activity of regenerating adrenal cortex of rats were studied on the second, seventh and twelfth days following the enucleation of adrenals. Pinealectomy caused a significant decrease in the mitotic index of regenerating adrenal cortex after 2 and 12 days in comparison to sham operated controls.     

An immunohistochemical study of the adrenal medulla of the ox

Summary The adrenal medulla of ox was studied by an indirect immunofluorescent technique using anti-ox chromaffin granule serum. The serum had a weak cross reaction with ox brain stem and splenic nerve. There was a species cross reaction with sheep, pig and horse. Immunoelectrophoresis showed five components in the serum against ox adrenal lysates. The whole adrenal medulla of ox was found to fluoresce by the immunofluorescent technique but not the cortex. The adrenals of sheep, pig and horse behaved similarly using the anti-ox serum. A serum prepared against ox chromogranin-A, the most abundant soluble protein of the chromaffin granules, was also used for immunofluorescence. Again both the adrenaline and noradrenaline storing cells fluoresced, but not the cortex.     

Brucellosis in ringed seals and harp seals from Canada. lforbes@em.agr.ca

A novel Brucella sp. was isolated from lymph nodes of four ringed seals (Phoca hispida) collected near Pangnirtung (Baffin Island, Canada) in January and February 1995 and in one harp seal (Phoca groenlandica) collected near the Magdalen Islands (Gulf of St. Lawrence, Canada) in March 1996. Bacteriological characteristics were the same for all five isolates. The colonies were typical of Brucella spp., but took 2 to 5 days longer than the traditional species to appear on primary isolation media. Biotyping results did not match any of the known biovars of Brucella, but were similar to isolates of the genus Brucella previously reported from marine mammals inhabiting other areas of the northern hemisphere. This is the first confirmed report of brucellosis in marine mammals from Canada, and the first report of this organism in ringed and harp seals.     

Seroprevalence of Toxoplasma gondii in Canadian pinnipeds

Sera (n = 328) collected from phocids (1995-97) from the east coast of Canada, including harp seals (Phoca groenlandica), hooded seals (Cystophora cristata), grey seals (Halichoerus grypus), and harbor seals (Phoca vitulina), were diluted 1:25, 1:50, and 1:500 and tested by a modified agglutination test for antibodies to Toxoplasma gondii. Titers equal to or greater than 1:25 were considered evidence of exposure. Grey seal (11/122, 9%), harbor seal (3/34, 9%), and hooded seal (1/60, 2%) had titers of 1:25 and 1:50. Harp seals (n = 112) were seronegative. Probable maternal antibody transfer was observed in one harbor and one grey seal pup at 10 and 14 day of age, respectively. Transmission of T gondii in the marine environment is not understood. The discovery of T. gondii in marine mammals might indicate natural infections unknown because of lack of study or might indicate recent contamination of the marine environment from the terrestrial environment by natural or anthropogenic activities.     

The effects of climate change on harp seals (Pagophilus groenlandicus)

Harp seals (Pagophilus groenlandicus) have evolved life history strategies to exploit seasonal sea ice as a breeding platform. As such, individuals are prepared to deal with fluctuations in the quantity and quality of ice in their breeding areas. It remains unclear, however, how shifts in climate may affect seal populations. The present study assesses the effects of climate change on harp seals through three linked analyses. First, we tested the effects of short-term climate variability on young-of-the year harp seal mortality using a linear regression of sea ice cover in the Gulf of St. Lawrence against stranding rates of dead harp seals in the region during 1992 to 2010. A similar regression of stranding rates and North Atlantic Oscillation (NAO) index values was also conducted. These analyses revealed negative correlations between both ice cover and NAO conditions and seal mortality, indicating that lighter ice cover and lower NAO values result in higher mortality. A retrospective cross-correlation analysis of NAO conditions and sea ice cover from 1978 to 2011 revealed that NAO-related changes in sea ice may have contributed to the depletion of seals on the east coast of Canada during 1950 to 1972, and to their recovery during 1973 to 2000. This historical retrospective also reveals opposite links between neonatal mortality in harp seals in the Northeast Atlantic and NAO phase. Finally, an assessment of the long-term trends in sea ice cover in the breeding regions of harp seals across the entire North Atlantic during 1979 through 2011 using multiple linear regression models and mixed effects linear regression models revealed that sea ice cover in all harp seal breeding regions has been declining by as much as 6 percent per decade over the time series of available satellite data.     

Summer feeding ecology of harp seals (Phoca groenlandica) in relation to arctic cod (Boreogadus saida) in the Canadian high arctic

Summary The diet and feeding behaviour of harp seals, Phoca groenlandica, was examined in two high arctic locations. Fish otoliths were used to evaluate dietary composition and aspects of the population dynamics of the major prey species, arctic cod, Boreogadus saida. Harp seals, primarily adults, arrive in the high arctic in mid to late June and depart by early October. Their migration is undertaken specifically for feeding. Harp seals feed intensively on arctic cod, often occurring in dense multispecies aggregations in late summer. The average weight of harp seal stomach contents was high; glutted individuals contained as much as 6% of their body weight in food. Although arctic cod declined in abundance between years, size of cod ingested was similar between areas and years, and overlapped completely with cod taken by other marine mammals. Age/size segregation of arctic cod may account for poor representation of fish <3 years old in the seal diet. Widespread reproductive failure of arctic cod could have a profound influence on the energy balance of adult harp seals since there does not appear to be an alternate food source of equivalent energy value and abundance in arctic waters. Increasing harp seal populations will likely result in increased competition with a host of arctic cod predators, particularly ringed seals.     

DIGESTIBILITY OF CRUSTACEANS and CAPELIN IN HARP SEALS (PHOCA GROENLANDICA)

Gross energy intake (GEI), apparent digestible efficiency (%DE), and body-mass change were studied both in recently weaned and in subadult harp seals fed capelin ( Mallotus villosus ) and crustaceans ( Parathemisto libellula and Thysanoessa sp.) ad lib. The median %DE of Parathemisto libellula (with a wet-weight energy density (ED) of 3.9 kJ/g) and Thysanoessa sp. (ED: 2.3 kJ/g) was 81% and 83%, respectively, while the median %DE of capelin (ED: 8.6 kJ/g) was 94% and 93% for subadult harp seals and one harp seal pup, respectively. No correlation between age and %DE was obtained (P > 0.05). Despite ad lib. access to the food, the harp seal pups were unable to maintain body mass while on a crustacean diet, and it is therefore suggested that harp seal pups most likely must supplement their crustacean diets with fish to maintain growth.     

Differential changes of fat-soluble vitamins and pollutants during lactation in northern elephant seal mother-pup pairs

We investigated the changes of vitamins A and E as well as PCBs and DDTs during lactation in northern elephant seal (Mirounga angustirostris) mother-pup pairs. On average, milk vitamin A concentrations were 6 times higher during late lactation than during early lactation, a pattern that differs dramatically from terrestrial mammals. Vitamin A concentrations also significantly increased in the inner blubber throughout lactation, whereas they remained constant in the outer blubber. Similar dynamics were observed for PCBs and DDTs in maternal blubber and milk. Blubber appears to be an important storage site for vitamin A and organochlorines in seals and a direct transfer of those molecules to the mammary gland may occur. The dynamics of vitamin A, PCBs and DDTs differed from those of vitamin E. There was a significant drop in milk vitamin E concentrations between early and late lactation, which is the usual pattern observed in terrestrial mammals. The dynamics of vitamin E in the blubber layers also differed from those of vitamin A, suggesting different mechanisms of mobilization and transfer into the milk.     

Adrenal renin: a possible local regulator of aldosterone production

Extrarenal renin has been identified in a number of tissues, including the brain, the submaxillary gland, uterus, ovary, vascular endothelium, testes, pituitary gland, and the adrenal cortex. In some tissues, including the adrenal cortex, all of the components of the renin-angiotensin system have been identified; however, no specific physiologic role has been clearly demonstrated for these extrarenal renin-angiotensin systems. We have studied the role of the renin-angiotensin system in the adrenal cortex of the rat and have found that renin is localized and synthesized in the zona glomerulosa cells. Its production can be influenced by alterations in electrolyte balance, as well as the genetic background of the rat. In adrenal capsular explant cultures, a converting enzyme inhibitor can lower angiotensin II production and reduce the stimulation of aldosterone by potassium, suggesting that this system is involved in the aldosterone response to potassium. In addition to rat adrenals, renin has been identified in human adrenal tissue and human adrenal tumors, including aldosteronomas, and a patient with hypertension has been reported to have an adrenal tumor that appeared to be secreting renin into the circulation.     

Steroidogenic characteristics of the adrenal cortex of the mare studied by electron microscopy

The three concentric zones of the horse adrenal cortex (zonae glomerulosa, fasciculata and reticularis) showed marked interpenetration and exhibited a different relative development according to their position in the gland. Whereas the three cortical zones each had a specific histological structure, the ultrastructure of their cells showed a certain qualitative homogeneity. The differences corresponded essentially to the relative abundance of the constituents which are generally considered typical of steroidogeneous cells: mitochondria with vesicular cristae, smooth endoplasmic reticulum and lipid droplets. Their importance increased progressively from the zona glomerulosa to the zona reticularis. In this zone, the presence of gap and septate-like cell junctions, and mitochondria with vesicular cristae in close proximity to a smooth endoplasmic reticulum with numerous dilated tubules, suggested that steroidogenesis may be the most active. Ultrastructural findings were indicative of only quantitative differences between the steroidogenic capacities of the three zones of the mare adrenal cortex.