Physiology of the endocrine, cardiorespiratory and nervous systems in pinnipeds: Integrative approach and biomedical considerations

Thesis (Ph.D.) University of Alaska Fairbanks, 1997This thesis explored several aspects of the hormonal and cardiovascular physiology in pinnipeds (seals and sea lions). Plasma concentrations of the vasoactive hormones angiotensin II (Ang II), arginine vasopressin (AVP, the antidiuretic hormone) and atrial natriuretic peptide (ANP) were studied in six species of seals and sea lions. Resting levels of AVP, ANP and Ang II in these pinnipeds were similar to those reported for other vertebrate species, including humans. Age-related differences were found in the concentrations of these hormones in seals and sea lions. Geographic differences in hormone concentrations were found in Steller sea lions and harbor seals. To address the endocrine and cardiovascular responses to breath-holding (apnea) in marine mammals, heart rates and plasma levels of Ang II, AVP and ANP were studied in Weddell seal (Leptonychotes weddellii) and northern elephant seal (Mirounga angustirostris) pups during periods of spontaneous breathing (eupnea) and apnea. Ang II, AVP, and ANP, as well as the autonomic nervous system, were found to contribute differently to the control of heart rate in seal pups, depending whether the respiratory system was in eupnea or apnea. Because of changes in seals of different ages, it appeared that the integration of cardiorespiratory and hormonal function is not fully mature at birth, but develops post-natally, probably simultaneously to the development of diving behavior. These studies also suggested that the factors affecting cardiorespiratory function, including hormones, may differ by species. Plasma concentrations of AVP, ANP and Ang II were measured during food limitation and fasting in captive Steller sea lions (Eumetopias jubatus) and compared to levels in free-ranging conspecifics. The results suggest that Steller sea lions have a remarkable capacity to maintain hydrosmotic and endocrine balance during short-term food limitation and fasting. Hormonal studies did not provide conclusive evidence that Steller sea lions in Alaskan waters are currently affected by long-term food limitation

Challenges to reduce the ‘10/90 gap’: mental health research in Latin American and Caribbean countries

Razzouk D, Gallo C, Olifson S, Zorzetto R, Fiestas F, Poletti G, Mazzotti G, Levav I, Mari JJ. Challenges to reduce the ‘10/90 gap’: mental health research in Latin American and Caribbean countries

Scaling matters: incorporating body composition into Weddell seal seasonal oxygen store comparisons reveals maintenance of aerobic capacities

Adult Weddell seals (Leptonychotes weddellii) haul-out on the ice in October/November (austral spring) for the breeding season and reduce foraging activities for ~4 months until their molt in the austral fall (January/February). After these periods, animals are at their leanest and resume actively foraging for the austral winter. In mammals, decreased exercise and hypoxia exposure typically lead to decreased production of O2-carrying proteins and muscle wasting, while endurance training increases aerobic potential. To test whether similar effects were present in marine mammals, this study compared the physiology of 53 post-molt female Weddell seals in the austral fall to 47 pre-breeding females during the spring in McMurdo Sound, Antarctica. Once body mass and condition (lipid) were controlled for, there were no seasonal changes in total body oxygen (TBO2) stores. Within each season, hematocrit and hemoglobin values were negatively correlated with animal size, and larger animals had lower mass-specific TBO2 stores. But because larger seals had lower mass-specific metabolic rates, their calculated aerobic dive limit was similar to smaller seals. Indicators of muscular efficiency, myosin heavy chain composition, myoglobin concentrations, and aerobic enzyme activities (citrate synthase and β-hydroxyacyl CoA dehydrogenase) were likewise maintained across the year. The preservation of aerobic capacity is likely critical to foraging capabilities, so that following the molt Weddell seals can rapidly regain body mass at the start of winter foraging. In contrast, muscle lactate dehydrogenase activity, a marker of anaerobic metabolism, exhibited seasonal plasticity in this diving top predator and was lowest after the summer period of reduced activity

Plasma arginine vasotocin and angiotensin II concentrations during saline acclimation in birds with salt glands

Pekin ducks (Anas platyrhynchos), Canada geese (Branta canadensis) and Glaucous-winged gulls (Larus glaucescens) responded differently during acclimation to saline equivalent to full strength sea water. All species were in hydrosmotic balance until they were given 375 mM NaCl. When the birds drank 75 mM NaCl ducks transiently decreased plasma sodium concentration ([Na⁺][formula omitted]) and osmolality (Osm[formula omitted]) and increased cloacal Na⁺ excretion; geese transiently increased hematocrit (Hct), suggesting transient extracellular dehydration; and gulls increased Osm[formula omitted] (but not Hct), suggesting that their Osm[formula omitted] had been below normal when fresh water was offered. During acclimation to moderately concentrated saline, all species progressively increased plasma arginine vasotocin levels ([AVT][formula omitted]) (without concomitant increase in Osm[formula omitted]) and decreased plasma angiotensin II concentration ([Ang II][formula omitted]) without parallel changes in Hct. Following acclimation to 300 mM NaCl total body water (TBW) was increased in ducks and geese, but acclimation to 375 mM NaCl did not affect TBW in gulls. When they drank 450 mM NaCl, ducks and geese decreased body mass and increased Hct, plasma electrolyte and osmotic concentrations, [AVT][formula omitted] and [Ang II][formula omitted], indicating they were dehydrated. In contrast, saline acclimated gulls did not increase [Ang II][formula omitted] and increased [AVT][formula omitted] less than ducks or geese. Initial [AVT][formula omitted] was not significantly correlated with sex in either ducks or geese. Female ducks increased [Ang II[formula omitted] and Osm[formula omitted] less than males during exposure to 450 mM NaCl, while female geese increased [Ang II][formula omitted] more than males. Salt gland NaCl secretion and renal water retention counterbalanced NaCl ingested in low to moderately concentrated saline in ducks, geese and gulls, but not in ducks and geese drinking saline equivalent to sea water. Gulls likely maintained simultaneous, concerted function of kidneys and salt glands during high salt intake, while cloacal excretion may have decreased in the Anatidae. Based on their relative salt secreting efficiencies, plasma ionic concentrations, Osm[formula omitted] and Hct increased much more in ducks than in geese when they drank 450 mM NaCl, and remained unchanged in gulls drinking 375 mM NaCl. Release of AVT and Ang II in birds with salt glands appears to be controlled by a complicated interrelationship between volume and tonicity (threshold for release varies among species), and these (and possibly other) hormones may affect salt gland and kidney function to maintain salt and water balance.Science, Faculty ofZoology, Department ofGraduat

Superoxide radical production in response to environmental hypoxia in cultured shirimp

Markers of oxidative stress in response to hypoxia and reoxygenation were assessed in Pacific white shrimp (Litopenaeus vannamei). Adult shrimp were either exposed to hypoxia (1 mg O2/L) for 6, 12, or 24 h followed by 1-h reoxygenation, or exposed to hypoxia for 24 h followed by 1- to 6-h reoxygenation. In all cases, shrimp maintained at constant normoxia were used as controls. Spectrophotometric techniques were applied to analyze lactate concentration, superoxide radical (O2[dot above]-) production, lipid peroxidation (TBARS), and antioxidant capacity status in muscle, hepatopancreas, and gill samples. Results indicate differences among tissues, even under control conditions. O2[dot above]- production and TBARS levels were higher in hepatopancreas than in gill or muscle. No effect of exposure to hypoxia was found. However, reoxygenation following exposure to hypoxia was found to affect the oxidative metabolism of muscle and hepatopancreas from cultured shrimp. Lactate concentration and O2[dot above]- production increased while antioxidant capacity decreased in hepatopancreas and muscle in the first hours of reoxygenation. This could translate into tissue damage, which may significantly jeopardize the commercial aquaculture product

Aging and exercise affect the level of protein acetylation and SIRT1 activity in cerebellum of male rats

Abstract Aging is associated with a gradual decline in cognitive and motor functions, the result of complex biochemical processes including pre-and posttranslational modifications of proteins. Sirtuins are NAD ? dependent protein deacetylases. These enzymes modulate the aging process by lysine deacetylation, which alters the activity and stability of proteins. Exercise can increase mean life-span and improve quality of life. Data from our laboratories revealed that 4 weeks of treadmill running improves performance in the Morris Maze test for young (4 months, old) but not old (30 months, old) male rats, and the exercise could not prevent the age-associated loss in muscle strength assessed by a gripping test. The positive correlation between protein acetylation and the gripping test suggests that the age-dependent decrease in relative activity of SIRT1 in the cerebellum impairs motor function. Similarly to the acetylation level of total proteins, the acetylation of a 9 -tubulin is also increased with aging, while the effect of exercise training was not found to be significant. Moreover, the protein content of nicotinamide phosphoribosyltransferase, one of the key enzymes of NAD biosynthesis, decreased in the young exercise group. These data suggest that aging results in decreased specific activity of SIRT1 in cerebellum, which could lead to increased acetylation of protein residues, including a 9-tubulin, that interfere with motor function