scholarly journals Can concentrations of steroid hormones in brown bear hair reveal age class?

2018 ◽  
Vol 6 (1) ◽  
Author(s):  
Marc Cattet ◽  
Gordon B Stenhouse ◽  
John Boulanger ◽  
David M Janz ◽  
Luciene Kapronczai ◽  
...  
Keyword(s):  
Steroid Hormones ◽  
Brown Bear ◽  
Age Class

scholarly journals Individual Variation in Predatory Behavior, Scavenging and Seasonal Prey Availability as Potential Drivers of Coexistence between Wolves and Bears

Diversity ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 356
Author(s):  
Andrés Ordiz ◽  
Cyril Milleret ◽  
Antonio Uzal ◽  
Barbara Zimmermann ◽  
Petter Wabakken ◽  
...  
Keyword(s):  
Prey Availability ◽  
Interspecific Interactions ◽  
Brown Bear ◽  
Predatory Behavior ◽  
Early Summer ◽  
Gray Wolf ◽  
Apex Predators ◽  
Main Prey ◽  
Large Carnivore ◽  
Age Class

Several large carnivore populations are recovering former ranges, and it is important to understand interspecific interactions between overlapping species. In Scandinavia, recent research has reported that brown bear presence influences gray wolf habitat selection and kill rates. Here, we characterized the temporal use of a common prey resource by sympatric wolves and bears and described individual and seasonal variation in their direct and/or indirect interactions. Most bear–wolf interactions were indirect, via bear scavenging of wolf kills. Bears used >50% of wolf kills, whereas we did not record any wolf visit at bear kills. Adult and subadult bears visited wolf kills, but female bears with cubs of the year, the most vulnerable age class to conspecifics and other predators, did not. Wolf and bear kill rates peaked in early summer, when both targeted neonate moose calves, which coincided with a reduction in bear scavenging rate. Some bears were highly predatory and some did not kill any calf. Individual and age-class variation (in bear predation and scavenging patterns) and seasonality (in bear scavenging patterns and main prey availability of both wolves and bears) could mediate coexistence of these apex predators. Similar processes likely occur in other ecosystems with varying carnivore assemblages.

Ultrastructural Cytopiasmic Changes of Adrenal Cortex During Pregnancy

1969 ◽  
Vol 27 ◽  
pp. 298-299
Author(s):  
T. M. Murad ◽  
Karen Israel ◽  
Jack C. Geer
Keyword(s):  
Adrenal Gland ◽  
Steroid Hormones ◽  
Adrenal Cortex ◽  
Lipid Droplets ◽  
Plasma Cholesterol ◽  
Adrenal Steroids ◽  
Dynamic Changes ◽  
Cortical Cells ◽  
Acetyl Coenzyme A ◽  
Adrenal Cortical Cells

Adrenal steroids are normally synthesized from acetyl coenzyme A via cholesterol. Cholesterol is also shown to enter the adrenal gland and to be localized in the lipid droplets of the adrenal cortical cells. Both pregnenolone and progesterone act as intermediates in the conversion of cholesterol into steroid hormones. During pregnancy an increased level of plasma cholesterol is known to be associated with an increase of the adrenal corticoid and progesterone. The present study is designed to demonstrate whether the adrenal cortical cells show any dynamic changes during pregnancy.

Smooth endoplasmic reticulum in perfusion and immersion-fixed Leydig cells

1990 ◽  
Vol 48 (3) ◽  
pp. 82-83
Author(s):  
R.T.F. Bernard ◽  
R.H.M. Cross
Keyword(s):  
Endoplasmic Reticulum ◽  
Electron Microscope ◽  
Steroid Hormones ◽  
Transmission Electron Microscope ◽  
Leydig Cells ◽  
Smooth Endoplasmic Reticulum ◽  
Random Mixture ◽  
Transmission Electron

Smooth endoplasmic reticulum (SER) is involved in the biosynthesis of steroid hormones, and changes in the organisation and abundance of this organelle are regularly used as indicators of changes in the level of steroidogenesis. SER is typically arranged as a meshwork of anastomosing tubules which, with the transmission electron microscope, appear as a random mixture of cross, oblique and longitudinal sections. Less commonly the SER appears as swollen vesicles and it is generally suggested that this is an artefact caused during immersion fixation or during immersion of poorly-perfused tissue.During a previous study of the Leydig cells of a seasonally reproducing bat, in which tissue was fixed by immersion, we noted that tubular SER and vesicular SER often occured in adjacent cells and sometimes in the same cell, and that the abundance of the two types of SER changed seasonally. We came to doubt the widelyheld dogma that vesicular SER was an artefact of immersion fixation and set out to test the hypothesis that the method of fixation does not modify the ultrastructure of the SER.

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