Skip header and navigation

5 records – page 1 of 1.

The effects of season and sex upon the morphology and material properties of keratin in the Svalbard rock ptarmigan (Lagopus muta hyperborea).

https://arctichealth.org/en/permalink/ahliterature261829
Source
J Therm Biol. 2014 Aug;44:126-30
Publication Type
Article
Date
Aug-2014
Author
John J Lees
Lars P Folkow
Robert L Nudds
Jonathan R Codd
Source
J Therm Biol. 2014 Aug;44:126-30
Date
Aug-2014
Language
English
Publication Type
Article
Keywords
Acclimatization
Animals
Female
Galliformes - anatomy & histology - metabolism - physiology
Hoof and Claw - anatomy & histology - metabolism
Keratins - metabolism
Male
Seasons
Sex Factors
Abstract
The material properties and morphologies of the modified integumentary organs of birds (the keratinous bills, claws and feathers) have evolved to withstand the variety of mechanical stresses imposed by their interaction with the environment. These stresses are likely to vary temporally in seasonal environments and may also differ between the sexes as a result of behavioural dimorphism. Here we investigate the morphology and material properties of the claws of male and female Svalbard ptarmigan (Lagopus muta hyperborea) during the summer and winter using nanoindentation. Despite differences in locomotor demands between the sexes and pronounced seasonal differences in environmental conditions, like ground substrate, ambient temperature and day length, there was no significant difference in Young?s modulus or hardness between the seasons for each sex. However, when comparing males and females, female claws were significantly harder than those of males and both sexes had significantly wider claws during winter. We propose that wider claws may follow winter claw moulting as the claws are regrown and form an important part of the ptarmigan?s snowshoe-like foot that is an adaptation to locomotion on snow. Future work focusing on growth rates and more broad measures of material properties in both captive and wild birds is required to determine the extent of seasonal and sex differences in the material properties of their keratinous structures.
PubMed ID
25086983 View in PubMed
Less detail

No oxygen? No problem! Intrinsic brain tolerance to hypoxia in vertebrates.

https://arctichealth.org/en/permalink/ahliterature258916
Source
J Exp Biol. 2014 Apr 1;217(Pt 7):1024-39
Publication Type
Article
Date
Apr-1-2014
Author
John Larson
Kelly L Drew
Lars P Folkow
Sarah L Milton
Thomas J Park
Source
J Exp Biol. 2014 Apr 1;217(Pt 7):1024-39
Date
Apr-1-2014
Language
English
Publication Type
Article
Keywords
Adaptation, Physiological
Animals
Anoxia - genetics - metabolism
Brain - physiology
Diving - physiology
Ecosystem
Hibernation
Mole Rats - physiology
Sciuridae - physiology
Seals, Earless - physiology
Turtles - physiology
Whales - physiology
Abstract
Many vertebrates are challenged by either chronic or acute episodes of low oxygen availability in their natural environments. Brain function is especially vulnerable to the effects of hypoxia and can be irreversibly impaired by even brief periods of low oxygen supply. This review describes recent research on physiological mechanisms that have evolved in certain vertebrate species to cope with brain hypoxia. Four model systems are considered: freshwater turtles that can survive for months trapped in frozen-over lakes, arctic ground squirrels that respire at extremely low rates during winter hibernation, seals and whales that undertake breath-hold dives lasting minutes to hours, and naked mole-rats that live in crowded burrows completely underground for their entire lives. These species exhibit remarkable specializations of brain physiology that adapt them for acute or chronic episodes of hypoxia. These specializations may be reactive in nature, involving modifications to the catastrophic sequelae of oxygen deprivation that occur in non-tolerant species, or preparatory in nature, preventing the activation of those sequelae altogether. Better understanding of the mechanisms used by these hypoxia-tolerant vertebrates will increase appreciation of how nervous systems are adapted for life in specific ecological niches as well as inform advances in therapy for neurological conditions such as stroke and epilepsy.
PubMed ID
24671961 View in PubMed
Less detail

Seasonal variation in the thermal responses to changing environmental temperature in the world's northernmost landbird.

https://arctichealth.org/en/permalink/ahliterature286983
Source
J Exp Biol. 2017 Nov 07;
Publication Type
Article
Date
Nov-07-2017
Author
Andreas Nord
Lars P Folkow
Source
J Exp Biol. 2017 Nov 07;
Date
Nov-07-2017
Language
English
Publication Type
Article
Abstract
Arctic homeotherms counter challenges at high latitudes using a combination of seasonal adjustments in pelage/plumage, fat deposition, and intricate thermoregulatory adaptations. However, there are still gaps in our understanding of their thermal responses to cold, particularly in Arctic birds. Here, we have studied the potential use of local heterothermy (i.e., tissue cooling that can contribute to significantly lower heat loss rate) in Svalbard ptarmigan (Lagopus muta hyperborea) - the world's northernmost landbird. We exposed birds kept under simulated Svalbard photoperiod to low ambient temperatures (Ta; between 0 and -30°C) during three seasons (early winter, late winter, summer), whilst recording resting metabolic rate (RMR), core temperature (Tc) and several cutaneous temperatures. Leg skin temperature varied the most, but still only by up to ~15°C, whereas body trunk skin temperature changed
PubMed ID
29113988 View in PubMed
Less detail

Seasonal variation in the thermal responses to changing environmental temperature in the world's northernmost land bird.

https://arctichealth.org/en/permalink/ahliterature297759
Source
J Exp Biol. 2018 01 10; 221(Pt 1):
Publication Type
Journal Article
Research Support, Non-U.S. Gov't
Date
01-10-2018
Author
Andreas Nord
Lars P Folkow
Author Affiliation
Department of Biology, Section for Evolutionary Ecology, Lund University, SE-223 62 Lund, Sweden andreas.nord@biol.lu.se.
Source
J Exp Biol. 2018 01 10; 221(Pt 1):
Date
01-10-2018
Language
English
Publication Type
Journal Article
Research Support, Non-U.S. Gov't
Keywords
Acclimatization
Animals
Arctic Regions
Body Temperature Regulation
Cold Temperature
Galliformes - physiology
Male
Seasons
Svalbard
Thermogenesis
Abstract
Arctic homeotherms counter challenges at high latitudes using a combination of seasonal adjustments in pelage/plumage, fat deposition and intricate thermoregulatory adaptations. However, there are still gaps in our understanding of their thermal responses to cold, particularly in Arctic birds. Here, we have studied the potential use of local heterothermy (i.e. tissue cooling that can contribute to significantly lower heat loss rate) in Svalbard ptarmigan (Lagopus muta hyperborea) - the world's northernmost land bird. We exposed birds kept under simulated Svalbard photoperiod to low ambient temperatures (Ta; between 0 and -30°C) during three seasons (early winter, late winter, summer), whilst recording resting metabolic rate (RMR), core temperature (Tc) and several cutaneous temperatures. Leg skin temperature varied the most, but still only by up to ~15°C, whereas body trunk skin temperature changed
PubMed ID
29113988 View in PubMed
Less detail

Why Rudolph's nose is red: observational study.

https://arctichealth.org/en/permalink/ahliterature117982
Source
BMJ. 2012;345:e8311
Publication Type
Article
Date
2012
Author
Can Ince
Anne-Marije van Kuijen
Dan M J Milstein
Koray Yürük
Lars P Folkow
Wytske J Fokkens
Arnoldus S Blix
Author Affiliation
Department of Intensive Care Medicine, Erasmus Medical Center, Erasmus University Rotterdam, 's-Gravendijkwal 230, PO Box 2040, 3000 CA Rotterdam, Netherlands. c.ince@erasmusmc.nl
Source
BMJ. 2012;345:e8311
Date
2012
Language
English
Publication Type
Article
Keywords
Adult
Anatomy, Comparative
Animals
Cold Temperature
Color
Erythrocytes - physiology
Female
Humans
Male
Microcirculation
Microscopy, Video
Microvessels - anatomy & histology - pathology
Nasal Mucosa - blood supply - physiology
Nasal Polyps - pathology
Reindeer - anatomy & histology - physiology
Statistics, nonparametric
Turbinates - blood supply - physiology
Young Adult
Abstract
To characterise the functional morphology of the nasal microcirculation in humans in comparison with reindeer as a means of testing the hypothesis that the luminous red nose of Rudolph, one of the most well known reindeer pulling Santa Claus's sleigh, is due to the presence of a highly dense and rich nasal microcirculation.
Observational study.
Tromsø, Norway (near the North Pole), and Amsterdam, the Netherlands.
Five healthy human volunteers, two adult reindeer, and a patient with grade 3 nasal polyposis.
Architecture of the microvasculature of the nasal septal mucosa and head of the inferior turbinates, kinetics of red blood cells, and real time reactivity of the microcirculation to topical medicines.
Similarities between human and reindeer nasal microcirculation were uncovered. Hairpin-like capillaries in the reindeers' nasal septal mucosa were rich in red blood cells, with a perfused vessel density of 20 (SD 0.7) mm/mm(2). Scattered crypt or gland-like structures surrounded by capillaries containing flowing red blood cells were found in human and reindeer noses. In a healthy volunteer, nasal microvascular reactivity was demonstrated by the application of a local anaesthetic with vasoconstrictor activity, which resulted in direct cessation of capillary blood flow. Abnormal microvasculature was observed in the patient with nasal polyposis.
The nasal microcirculation of reindeer is richly vascularised, with a vascular density 25% higher than that in humans. These results highlight the intrinsic physiological properties of Rudolph's legendary luminous red nose, which help to protect it from freezing during sleigh rides and to regulate the temperature of the reindeer's brain, factors essential for flying reindeer pulling Santa Claus's sleigh under extreme temperatures.
Notes
Cites: Am J Physiol. 1985 Nov;249(5 Pt 2):R617-234061681
Cites: J Physiol. 1983 Jul;340:445-546887057
Cites: ORL J Otorhinolaryngol Relat Spec. 1997 Jan-Feb;59(1):50-69104750
Cites: Rhinology. 1997 Mar;35(1):22-79200259
Cites: Am J Rhinol. 1999 Jan-Feb;13(1):1-610088021
Cites: Nat Med. 1999 Oct;5(10):1209-1210502828
Cites: Crit Care. 2005;9 Suppl 4:S13-916168069
Cites: Clin Otolaryngol. 2005 Aug;30(4):373-516209686
Cites: Crit Care. 2005;9(6):R601-616280059
Cites: Med Biol Eng Comput. 2008 Jul;46(7):659-7018427850
Cites: N Engl J Med. 2009 Feb 12;360(7):e919213676
Cites: Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2010 Jan;109(1):91-720123381
Cites: Acta Vet Scand. 2011;53:4221707976
Cites: J Exp Biol. 2011 Nov 15;214(Pt 22):3850-622031750
Cites: Am J Physiol Regul Integr Comp Physiol. 2000 Oct;279(4):R1190-511003983
Cites: Rhinology. 2001 Mar;39(1):13-611340689
Cites: Lancet. 2001 Nov 17;358(9294):1698-911728549
Cites: Lancet. 2002 Nov 2;360(9343):1395-612423989
Cites: Crit Care Med. 2004 Sep;32(9):1825-3115343008
Cites: Microvasc Res. 1989 Sep;38(2):175-852796763
PubMed ID
23247980 View in PubMed
Less detail