title: Ultradian, circadian and seasonal rhythms in cortisol secretion and adrenal responsiveness to ACTH and yarding in unrestrained red deer (Cervus elaphus) stags

authors: Ingram, J.R.

abstract: Seasonal changes in the activity and responsiveness of the adrenal gland in red deer (Cervus elaphus) stags were quantified by measuring 24 h endogenous cortisol secretory profiles and plasma cortisol responses to either administration of exogenous ACTH or a standardised stressor during November (period of velvet growth), February (pre-rut), April (mid-rut) and July (post-rut) (southern hemisphere) using a remote blood sampling device (DracPac). Ultradian rhythms in the concentration of plasma cortisol were observed resulting from the episodic secretion of cortisol from the adrenal cortex at a mean rate of 0.8 pulses/h. Circadian rhythms in plasma cortisol concentrations were also found in 11 out of the 20 complete 24 h profiles (mean amplitude, 3.8+/-1.4 ng/ml). Seasonal rhythms in mean 24 h plasma cortisol concentrations and cortisol pulse parameters were also observed. Mean 24 h plasma cortisol concentrations were higher in November (12.5+/-1.0 ng/ml) than in February (6.3+/-1.0 ng/ml), April (4.0+/-1.0 ng/ml) or July (4.2+/-1. 0 ng/ml). Cortisol pulse height, nadir and amplitude were all significantly higher in November than at other times of the year (P<0.01). Peak cortisol concentrations following infusion of ACTH(1-24) (0.04 IU kg(-1)) were higher (P<0.05) in November (55.8+/-2.7 ng/ml) and lower (P<0.001) in April (33.7+/-1.8 ng/ml) than those in February and July (48.7+/-2.0 ng/ml and 45.4+/-2.0 ng/ml respectively). The area under the cortisol response curve was significantly smaller (P<0.05) in April (266.6+/-15.3 ng/ml/190 min) than at other times of the year (February, 366.1+/-15.3 ng/ml/190 min; July, 340.7+/-15.3 ng/ml/190 min and November, 387.8+/-21.2 ng/ml/190 min). These data demonstrate that the adrenal gland of the red deer stag exhibits ultradian, circadian and seasonal rhythms in activity, and that its responsiveness to ACTH varies with season. November, a period of reproductive quiescence in the southern hemisphere, with new antler growth and rapid weight gain, is associated with higher mean plasma cortisol concentrations and a greater responsiveness to exogenous ACTH. In contrast, the breeding season is associated with lower adrenal activity and responsiveness.

text: Ultradian, circadian and seasonal rhythms in cortisol secretion and adrenal responsiveness to ACTH and yarding in unrestrained red deer (Cervus elaphus) stags Seasonal changes in the activity and responsiveness of the adrenal gland in red deer (Cervus elaphus) stags were quantified by measuring 24 h endogenous cortisol secretory profiles and plasma cortisol responses to either administration of exogenous ACTH or a standardised stressor during November (period of velvet growth), February (pre-rut), April (mid-rut) and July (post-rut) (southern hemisphere) using a remote blood sampling device (DracPac). Ultradian rhythms in the concentration of plasma cortisol were observed resulting from the episodic secretion of cortisol from the adrenal cortex at a mean rate of 0.8 pulses/h. Circadian rhythms in plasma cortisol concentrations were also found in 11 out of the 20 complete 24 h profiles (mean amplitude, 3.8+/-1.4 ng/ml). Seasonal rhythms in mean 24 h plasma cortisol concentrations and cortisol pulse parameters were also observed. Mean 24 h plasma cortisol concentrations were higher in November (12.5+/-1.0 ng/ml) than in February (6.3+/-1.0 ng/ml), April (4.0+/-1.0 ng/ml) or July (4.2+/-1. 0 ng/ml). Cortisol pulse height, nadir and amplitude were all significantly higher in November than at other times of the year (P<0.01). Peak cortisol concentrations following infusion of ACTH(1-24) (0.04 IU kg(-1)) were higher (P<0.05) in November (55.8+/-2.7 ng/ml) and lower (P<0.001) in April (33.7+/-1.8 ng/ml) than those in February and July (48.7+/-2.0 ng/ml and 45.4+/-2.0 ng/ml respectively). The area under the cortisol response curve was significantly smaller (P<0.05) in April (266.6+/-15.3 ng/ml/190 min) than at other times of the year (February, 366.1+/-15.3 ng/ml/190 min; July, 340.7+/-15.3 ng/ml/190 min and November, 387.8+/-21.2 ng/ml/190 min). These data demonstrate that the adrenal gland of the red deer stag exhibits ultradian, circadian and seasonal rhythms in activity, and that its responsiveness to ACTH varies with season. November, a period of reproductive quiescence in the southern hemisphere, with new antler growth and rapid weight gain, is associated with higher mean plasma cortisol concentrations and a greater responsiveness to exogenous ACTH. In contrast, the breeding season is associated with lower adrenal activity and responsiveness.

year: 1999

title: Testing the infrequent purchases model using direct measurement of hidden consumption from food stocks

authors: Gibson, John

subjects: food consumption

abstract: Survey reports of zero expenditure result from either genuine non-consumption, or purchases undertaken too infrequently to observe during a survey, with hidden consumption from stocks. Infrequent purchase models rely on untested hypotheses to distinguish these types of zeros. We test such models with data from an unusual survey where food stocks are measured at the start and end of the survey reference period. Parameter estimates using these direct measures of hidden consumption out of stocks are compared with estimates from infrequent purchase models that attempt to recover this hidden consumption. The results suggest considerable bias when using the infrequent purchase models.

text: Testing the infrequent purchases model using direct measurement of hidden consumption from food stocks Survey reports of zero expenditure result from either genuine non-consumption, or purchases undertaken too infrequently to observe during a survey, with hidden consumption from stocks. Infrequent purchase models rely on untested hypotheses to distinguish these types of zeros. We test such models with data from an unusual survey where food stocks are measured at the start and end of the survey reference period. Parameter estimates using these direct measures of hidden consumption out of stocks are compared with estimates from infrequent purchase models that attempt to recover this hidden consumption. The results suggest considerable bias when using the infrequent purchase models.

year: 2012

title: Te Arawa– Kaitaki of Te Arawa Lakes

authors: Curtis, Sir Toby

abstract: The Te Arawa Lakes Trust has embarked on a project to develop a Te Arawa Cultural Values Framework, in regard to the 14 lakes located in our tribal region. There are a host of positives that we believe can accrue as an outcome of this exercise. Already the calibre of people acknowledged for their cultural expertise have added a lot by their attendance. Their presence and contribution injected a level of enthusiasm and confidence in the compilation of the final draft. It is hoped that distribution among the wider community will elicit constructive feedback.

text: Te Arawa– Kaitaki of Te Arawa Lakes The Te Arawa Lakes Trust has embarked on a project to develop a Te Arawa Cultural Values Framework, in regard to the 14 lakes located in our tribal region. There are a host of positives that we believe can accrue as an outcome of this exercise. Already the calibre of people acknowledged for their cultural expertise have added a lot by their attendance. Their presence and contribution injected a level of enthusiasm and confidence in the compilation of the final draft. It is hoped that distribution among the wider community will elicit constructive feedback.

year: 2015