Changes in pituitary, ovarian, and testicular activity in harbour seals (Phoca vitulina) in relation to season and sexual maturity

1999 ◽  
Vol 77 (2) ◽  
pp. 211-221 ◽  
Author(s):  
K J Gardiner ◽  
I L Boyd ◽  
B K Follett ◽  
P A Racey ◽  
P JH Reijnders
Keyword(s):  
Seasonal Changes ◽  
Time Course ◽  
Phoca Vitulina ◽  
Late Gestation ◽  
Progesterone Concentration ◽  
Plasma Progesterone ◽  
Photoperiodic Control ◽  
Harbour Seals ◽  
Significant Difference ◽  
Time Of Year

This study examined pituitary sensitivity to exogenous gonadotrophin-releasing hormone (GnRH) in relation to time of year and changes in plasma progesterone, testosterone, luteinising hormone (LH), and follicle-stimulating hormone (FSH) concentrations during the annual cycle of adult and juvenile harbour seals (Phoca vitulina vitulina). There was no significant difference in seasonal changes in reproductive hormone levels between six captive individuals and seals caught from the wild (n = 80). Based on results from both the captive and the wild individuals, the plasma progesterone concentration was elevated in late gestation, whereas it declined at the equivalent time in nonpregnant females. The progesterone concentration was also elevated during the phase of delayed implantation, but there was no difference between pregnant and nonpregnant seals. In captive seals given exogenous GnRH, the LH concentration peaked 10-20 min after injection of GnRH, and the magnitude of the LH response depended upon the dose up to ~120 ng·kg-1. FSH did not respond to GnRH in the time course of the experiment. Pituitary sensitivity to GnRH was greatest in the summer and autumn and lowest in the winter and spring. Seasonal changes in pituitary sensitivity were apparent in both adults and juveniles. There was evidence that three of the four juvenile seals attained puberty during the study. We conclude that the seasonal patterns of pituitary sensitivity and plasma hormone concentration in harbour seals are consistent with a reproductive cycle under photoperiodic control and with the general mechanisms underlying photoperiodic control of seasonal reproduction in higher vertebrates.

The effect of weather conditions on harbour seal (Phoca vitulina) haulout behaviour in the Moray Firth, northeast Scotland

1996 ◽  
Vol 74 (10) ◽  
pp. 1806-1811 ◽  
Author(s):  
Kate Grellier ◽  
Paul M. Thompson ◽  
Heather M. Corpe
Keyword(s):  
Significant Relationship ◽  
Seasonal Changes ◽  
Negative Relationship ◽  
Weather Conditions ◽  
Phoca Vitulina ◽  
Effect Of Temperature ◽  
Harbour Seals ◽  
Moray Firth ◽  
A Site ◽  
The Relationship

Abundance data from a 6-year study (1988–1993) of harbour seals (Phoca vitulina) were used to control for seasonal changes in haulout behaviour and assess the effect of temperature and other weather conditions on haulout numbers at a site in Scotland. A significant relationship between Julian day and haulout numbers was consistent between years. In some years, there was also a significant relationship between ambient temperature and haulout numbers, but examination of the residuals around the relationship between haulout numbers and Julian day revealed no evidence for a consistent effect of temperature, wind speed, or wind-chill adjusted temperatures. A weak negative relationship between haulout numbers and both precipitation and cloud cover did exist, but these variables explained little of the variation in seal numbers.

Energy requirements for maintenance and growth of captive harbour seals, Phoca vitulina

1990 ◽  
Vol 68 (3) ◽  
pp. 423-426 ◽  
Author(s):  
Nina Hedlund Markussen ◽  
Morten Ryg ◽  
Nils Are Øritsland
Keyword(s):  
Body Weight ◽  
Energy Requirement ◽  
Phoca Vitulina ◽  
Metabolizable Energy ◽  
Age Classes ◽  
Maintenance Requirement ◽  
Harbour Seals ◽  
Significant Difference ◽  
Gross Energy ◽  
Ad Libitum

Four captive harbour seals were fed with herring both at restricted and at ad libitum levels during 1985 to 1988. The maintenance requirement, calculated from the x-intercept of the regression, was 194 ± 71 kcal∙kg body weight−0.75∙day−1. Assuming that metabolizable energy is 82.8% of gross energy, the maintenance requirement is 161 kcal∙kg body weight−0.75∙day−1. There was no significant difference in maintenance requirement between individuals or between age classes, and neither was there any significant difference between seasons. The gross energy requirement of growth was 909 kcal/100 g.

Increasing feed intake in late gestation does not affect plasma progesterone concentration in the sow

2004 ◽  
Vol 62 (9) ◽  
pp. 1618-1626 ◽  
Author(s):  
Helen Margaret Miller ◽  
George Robert Foxcroft ◽  
Frank Xavier Aherne
Keyword(s):  
Feed Intake ◽  
Late Gestation ◽  
Progesterone Concentration ◽  
Plasma Progesterone

Correlates of seasonal changes in metabolism in Atlantic harbour seals (Phoca vitulina concolor)

1998 ◽  
Vol 76 (8) ◽  
pp. 1520-1528 ◽  
Author(s):  
D A Rosen ◽  
D Renouf
Keyword(s):  
Energy Expenditure ◽  
Metabolic Rate ◽  
Total Energy ◽  
Energy Intake ◽  
Body Mass ◽  
Seasonal Changes ◽  
Energy Use ◽  
Phoca Vitulina ◽  
Harbour Seals ◽  
Gross Energy

This study tested the hypothesis that seasonal variation in resting metabolic rate (RMR) was more closely related to changes in total energy use than to energy intake. It also quantified the extent to which variation in metabolism contributed to changes in total energy expenditure. RMR, gross energy intake, and body mass and composition were measured in six captive Atlantic harbour seals (Phoca vitulina concolor) over 16 months. Gross energy intake during the year (across all seals) averaged 25.4 ± 4.1 MJ/d (mean ± SD). The energy used by the seals Eused a composite measure of energy expenditure from ingested energy and tissue catabolism) averaged 19.2 ± 3.4 MJ/d. RMR averaged 11.2 ± 1.5 MJ/d during the year, while mass-corrected metabolism declined with age. The seals displayed significant changes in both absolute and mass-corrected metabolism during the year. Overall, Eused was a stronger predictor of changes in metabolism than either gross energy intake or body mass. Mass-corrected metabolic rate was more closely related to Eused than was absolute metabolism. Energy changes in metabolism during the year (range = 6.9 ± 1.9 MJ/d) were minor compared with those in Eused (27.8 ± 7.3 MJ/d). These results suggest that seasonal changes in metabolism were a response to, or facilitated by, concurrent changes in Eused but were not the cause of variation in Eused. Rather, variation in both RMR and Eused was the result of changes in other bioenergetic components of the seals' energy budget, such as activity.

PROGESTERONE CONCENTRATION IN THE PERIPHERAL PLASMA OF PREGNANT GOATS

1972 ◽  
Vol 53 (3) ◽  
pp. 447-452 ◽  
Author(s):  
G. IRVING ◽  
D. E. JONES ◽  
A. KNIFTON
Keyword(s):  
Cord Blood ◽  
Venous Blood ◽  
Progesterone Concentration ◽  
Plasma Progesterone ◽  
Peripheral Plasma ◽  
Significant Difference ◽  
Competitive Protein Binding ◽  
The Mean ◽  
Serial Samples ◽  
Twin Pregnancies

SUMMARY Plasma progesterone concentration was measured by a competitive protein-binding method in serial samples of jugular venous blood from 21 pregnant goats, 11 with twin and 10 with single foetuses. Progesterone levels in twin pregnancies were significantly greater than in singletons. The mean progesterone concentration (ng/ml plasma) in the twin pregnancies was greatest during the 3rd month of gestation (10·7 ± 0·4 (s.e.m.)) and in the singletons during the 4th month (7·8 ± 0·2 (s.e.m.)). There was a significant decrease in mean progesterone concentration in the last month of pregnancy due to a steady decline in the last 7 days before parturition. The mean progesterone concentrations at parturition in five twin and eight single pregnancies were 2·2 ± 0·4 and 1·5 ± 0·2 (s.e.m.) ng/ml plasma respectively; there was no significant difference between these values. In cord blood from nine kids immediately after delivery the progesterone concentration was 0·9 ± 0·1 ng/ml.

DIFFERENCE IN CONCENTRATION OF PROGESTERONE IN PLASMA BETWEEN PREGNANT AND NON-PREGNANT QUOKKAS (SETONIX BRACHYURUS)

1980 ◽  
Vol 84 (1) ◽  
pp. 153-158 ◽  
Author(s):  
M. H. CAKE ◽  
F. J. OWEN ◽  
S. D. BRADSHAW
Keyword(s):  
Luteal Phase ◽  
Oestrous Cycle ◽  
Progesterone Concentration ◽  
Plasma Progesterone ◽  
Peripheral Plasma ◽  
Early Stages ◽  
Significant Difference ◽  
Early Peak

The plasma progesterone concentrations during pregnancy and the oestrous cycle of the quokka were measured daily after each had been initiated by the removal of pouch young. Progesterone levels ranged from 0·6 ng/ml in the early stages of the oestrous cycle to about 2·5 ng/ml at the peak of the luteal phase. There was no significant difference between pregnant and non-pregnant states before the removal of the pouch young nor in the latter half of the cycle. However, the plasma progesterone concentration on days 3–4 after removal of the pouch young was significantly greater in pregnant animals when compared with nonpregnant animals at the same stage and also when compared with the levels before removal of young. This early peak in the concentration of progesterone in peripheral plasma is discussed in relation to the development of the previously dormant blastocyst.

Effects of plane of nutrition and season of birth on the age and body weight at puberty of British Friesian heifers

1981 ◽  
Vol 33 (3) ◽  
pp. 273-279 ◽  
Author(s):  
W. Little ◽  
C. B. Mallinson ◽  
Diana N. Gibbons ◽  
G. J. Rowlands
Keyword(s):  
Body Weight ◽  
Weight Gain ◽  
Treatment Group ◽  
Live Weight ◽  
Seasonal Effects ◽  
Season Of Birth ◽  
Progesterone Concentration ◽  
Plasma Progesterone ◽  
Significant Difference ◽  
Ad Libitum

ABSTRACT1. Four groups of British Friesian heifers born in April (no. = 30), July (no. = 29), October (no. = 30) 1977 and January 1978 (no. =27) were allocated to one of six treatments (planes of nutrition) at a mean age of 91 days. From 91 to 365 days of age heifers on treatments 1 to 5 were given individually, according to body weight, a proprietary pellet to 126 days of age, and thereafter a diet of dried lucerne and barley. Heifers on treatments 1 and 2 were fed at the same rate whereas heifers on treatments 3 to 5 were fed at successively higher rates. Heifers on treatment 6 were fed ad libitum the proprietary pellets to 126 days of age and thereafter a 'barley beef diet. Mean live-weight gains between 91 and 365 days of age for treatments 1 and 2 combined and 3 to 6, respectively, were 0·58, 0·68, 0·75, 0·82 and 1·06 kg/day.2. Plasma progesterone concentrations were determined twice weekly in each animal. Puberty was assumed to have occurred 2 days before the start of the first period in which the progesterone concentration exceeded 1μg/1 for at least 10 days.3. There was no significant difference between treatments in mean body weight at puberty (242 kg), but age at puberty (347, 305, 288, 301 and 239 days for treatments 1 and 2 combined and 3 to 6, respectively) was inversely related to rate of live-weight gain between 91 and 365 days of age. However, within each treatment group the fastest growing heifers reached puberty at the same age but at a heavier body weight than the slowest growing heifers.4. There were significant seasonal effects on age and body weight at puberty. The most rapidly reared animals (treatment 6) born in January and April were, on average, 52 days younger and 54 kg lighter at puberty than those born in July and October, but the effects of season of birth in other treatments were different.5. There was no significant difference between treatments in the number of conceptions (mean 0·67) achieved at first service by an Aberdeen Angus bull introduced when the heifers were 350 days of age.

THE EFFECTS OF DEXAMETHASONE AND INDOMETHACIN ON THE OUTCOME OF PREGNANCY IN THE RABBIT

1975 ◽  
Vol 64 (2) ◽  
pp. 363-370 ◽  
Author(s):  
J. R. G. CHALLIS ◽  
I. J. DAVIES ◽  
K. J. RYAN
Keyword(s):  
Late Pregnancy ◽  
Late Gestation ◽  
Premature Delivery ◽  
Progesterone Concentration ◽  
Dexamethasone Treatment ◽  
Similar Time ◽  
Plasma Progesterone ◽  
Peripheral Plasma ◽  
Prostaglandin F ◽  
Length Of Gestation

SUMMARY Pregnant rabbits were treated with indomethacin (8–10 mg/kg/day) or dexamethasone (1·2–1·8 mg/kg/day) during late gestation. The effects of these treatments on the concentrations of progesterone and prostaglandin F (PGF) in the peripheral plasma, and the outcome of gestation were studied. Treatment with indomethacin significantly prolonged the length of gestation (P < 0·01) compared with control, untreated animals. In these treated animals, the plasma progesterone levels declined at a similar time to that in control rabbits but the increase in systemic PGF normally seen during late pregnancy was reduced. Dexamethasone treatment reliably induced premature delivery within 3–6 days. The plasma progesterone concentration fell rapidly during the first 24 h of dexamethasone administration, but in no animal was this associated with a significant increase in the plasma levels of PGF. These results are consistent with the suggestion that prostaglandins are involved in the normal initiation of parturition in the rabbit. They do not support the hypothesis that the effect of dexamethasone on the length of gestation is mediated through an increase in the production of prostaglandin F.

Time Course of Simulator Sickness in Asian Military Pilots

2020 ◽  
Vol 91 (11) ◽  
pp. 892-896
Author(s):  
Janine En Qi Loi ◽  
Magdalene Li Ling Lee ◽  
Benjamin Boon Chuan Tan ◽  
Brian See
Keyword(s):  
Air Force ◽  
Time Course ◽  
Simulator Training ◽  
Simulator Sickness ◽  
Time Points ◽  
True Prevalence ◽  
Subjective Scale ◽  
Significant Difference ◽  
Simulator Sickness Questionnaire ◽  
Military Pilots

INTRODUCTION: This study sought to determine the incidence, severity, and time-course of simulator sickness (SS) among Asian military pilots following flight simulator training.METHODS: A survey was conducted on Republic of Singapore Air Force pilots undergoing simulator training. Each subject completed a questionnaire immediately after (0H), and at the 3-h (3H) and 6-h (6H) marks. The questionnaire included the simulator sickness questionnaire (SSQ) and a subjective scale to rate their confidence to fly.RESULTS: In this study, 258 pilots with a median age of 31.50 yr (range, 2155 yr) and mean age of 32.61 6.56 yr participated. The prevalence of SS was 48.1% at 0H, 30.8% at 3H, and 16.4% at 6H. Based on a threshold of an SSQ score >10, the prevalence of operationally significant SS was 33.3% at 0H, 13.2% at 3H, and 8.1% at 6H. The most frequent symptoms were fatigue (38.1%), eye strain (29.0%), and fullness of head (19.9%). There was no significant difference in mean scores between rotary and fixed wing pilots. Older, more experienced pilots had greater scores at 0H, but this association did not persist. A correlation was found between SSQ score and self-reported confidence.DISCUSSION: To our knowledge, this study is the first to report the prevalence of operationally significant SS in Asian military pilots over serial time points. Most pilots with SS are able to subjectively judge their fitness to fly. Sensitivity analysis suggests the true prevalence of SS symptoms at 3H and 6H to be closer to 23.8% and 12.0%, respectively.Loi JEQ, Lee MLL, Tan BBC, See B. Time course of simulator sickness in Asian military pilots. Aerosp Med Hum Perform. 2020; 91(11):892896.

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