Augmenting Trait-Dependent Diversification Estimations with Fossil Evidence: A Case Study Using Osmoregulatory Neurovasculature

2018 ◽  
Vol 91 (3) ◽  
pp. 148-157 ◽  
Author(s):  
Haley D. O’Brien
Keyword(s):  
Brain Cooling ◽  
Selective Brain Cooling ◽  
Evaporative Water ◽  
Large Mammal ◽  
Paleontological Data ◽  
Extinction Rates ◽  
State Dependent ◽  
Key Innovation ◽  
Sister Clade ◽  
Binary Character

When comparative neuromorphological studies are extended into evolutionary contexts, traits of interest are often linked to diversification patterns. Features demonstrably associated with increases in diversification rates and the infiltration or occupation of novel niche spaces are often termed “key innovations.” Within the past decade, phylogenetically informed methods have been developed to test key innovation hypotheses and evaluate the influence these traits have had in shaping modern faunas. This is primarily accomplished by estimating state-dependent speciation and extinction rates. These methods have important caveats and guidelines related to both calculation and interpretation, which are necessary to understand in cases of discrete (qualitative) character analysis, as can be common when studying the evolution of neuromorphology. In such studies, inclusion of additional characters, acknowledgement of character codistribution, and addition of sister clade comparison should be explored to ensure model accuracy. Even so, phylogenies provide a survivor-only examination of character evolution, and paleontological contexts may be necessary to replicate and confirm results. Here, I review these issues in the context of selective brain cooling – a neurovascular-mediated osmoregulatory physiology that dampens hypothalamic responses to heat stress and reduces evaporative water loss in large-bodied mammals. This binary character provides an example of the interplay between sample size, evenness, and character codistribution. Moreover, it allows for an opportunity to compare phylogenetically constrained results with paleontological data, augmenting survivor-only analyses with observable extinction patterns. This trait- dependent diversification example indicates that selective brain cooling is significantly associated with the generation of modern large-mammal faunas. Importantly, paleontological data validate phylogenetic patterns and demonstrate how suites of characters worked in concert to establish the large-mammal communities of today.

Selective Brain Cooling in the Horse during Exercise

1994 ◽  
pp. 189-193 ◽  
Author(s):  
F. F. McConaghy ◽  
J. R. S. Hales ◽  
D. R. Hodgson
Keyword(s):  
Brain Cooling ◽  
Selective Brain Cooling

Efficacy of Selective Brain Cooling Using a Nasopharyngeal Method in Piglets

2015 ◽  
Vol 24 (1) ◽  
pp. 140-149 ◽  
Author(s):  
Mohammad Fazel Bakhsheshi ◽  
Errol E. Stewart ◽  
Joo Ho Tai ◽  
Laura Morrison ◽  
Lynn Keenliside ◽  
...  
Keyword(s):  
Brain Cooling ◽  
Selective Brain Cooling

Panting in reindeer (Rangifer tarandus)

2000 ◽  
Vol 279 (4) ◽  
pp. R1190-R1195 ◽  
Author(s):  
Øyvind Aas-Hansen ◽  
Lars P. Folkow ◽  
Arnoldus Schytte Blix
Keyword(s):  
Heat Load ◽  
Rangifer Tarandus ◽  
Minute Volume ◽  
Respiratory Frequency ◽  
Brain Cooling ◽  
Climatic Chamber ◽  
Selective Brain Cooling ◽  
Open Mouth ◽  
Rangifer Tarandus Tarandus ◽  
Air Temperatures

Two winter-insulated Norwegian reindeer ( Rangifer tarandus tarandus) were exposed to air temperatures of 10, 20, 30, and 38°C while standing at rest in a climatic chamber. The direction of airflow through nose and mouth, and the total and the nasal minute volumes, respectively, were determined during both closed- and open-mouth panting. The animals alternated between closed- and open-mouth panting, but the proportion of open-mouth panting increased with increasing heat load. The shifts from closed- to open-mouth panting were abrupt and always associated with a rise in respiratory frequency and respiratory minute volume. During open-mouth panting, the direction of airflow was bidirectional in both nose and mouth, but only 2.4 ± (SD) 1.1% of the air was routed through the nose. Estimates suggest that the potential for selective brain cooling is markedly reduced during open-mouth panting in reindeer as a consequence of this airflow pattern.

Selective brain cooling is affected by wearing headgear during exercise

1993 ◽  
Vol 74 (3) ◽  
pp. 1229-1233 ◽  
Author(s):  
W. Rasch ◽  
M. Cabanac
Keyword(s):  
Heat Loss ◽  
Cycle Ergometer ◽  
Tympanic Temperature ◽  
Esophageal Temperature ◽  
Brain Cooling ◽  
Selective Brain Cooling ◽  
Exercise Load ◽  
Convective Heat Loss ◽  
The Face ◽  
Skin Temperatures

The purpose of this work is to relate the concept of selective brain cooling (SBC) during exercise to heat loss from the head while either bare or covered. During hyperthermia, SBC is considered to occur if tympanic temperature (Tty) is lower than esophageal temperature (Tes). In experiment I the head heat loss was measured with and without headgear. Each of four subjects took part in three sessions of exercise on a cycle ergometer. The face was cooled to simulate outdoor conditions. The first session (no headgear) served as control for the two following sessions in which a headband and a woolen cap were worn. Evaporative and radiative-convective heat loss were monitored from the head. Wearing a cap significantly reduced the heat loss from the head compared with the control condition. During the headband session the heat loss was not significantly lower than the control values. Tty, Tes, and head skin temperatures (T(sk)) were also recorded. Tty was significantly lower (-0.55 +/- 0.15 degrees C) than Tes at the end of exercise (150-W exercise load) when no headgear was worn. During headgear sessions, Tty was no longer significantly lower than Tes, either during the headband (-0.15 +/- 0.31 degrees C) or during the cap session (-0.30 +/- 0.13 degrees C). In experiment II the influence of wearing headgear on temperature regulation was studied. Hand skin blood flow, hand T(sk), and heat loss from the hand were recorded in addition to the variables monitored in experiment I. Wearing headgear elevated Tty and peripheral vasomotor responses, whereas Tes evolved in the opposite direction.(ABSTRACT TRUNCATED AT 250 WORDS)

Rectal temperature measurement results in artifactual evidence of selective brain cooling

2001 ◽  
Vol 281 (1) ◽  
pp. R108-R114 ◽  
Author(s):  
Shane K. Maloney ◽  
Andrea Fuller ◽  
Graham Mitchell ◽  
Duncan Mitchell
Keyword(s):  
Rectal Temperature ◽  
Brain Temperature ◽  
Brain Cooling ◽  
Selective Brain Cooling ◽  
Blood Temperature ◽  
Arterial Blood ◽  
The Status ◽  
Conscious Sheep ◽  
Surrogate Measures ◽  
Arterial Blood Temperature

Selective brain cooling (SBC) is defined as a brain temperature cooler than the temperature of arterial blood from the trunk. Surrogate measures of arterial blood temperature have been used in many published studies on SBC. The use of a surrogate for arterial blood temperature has the potential to confound proper identification of SBC. We have measured brain, carotid blood, and rectal temperatures in conscious sheep exposed to 40, 22, and 5°C. Rectal temperature was consistently higher than arterial blood temperature. Brain temperature was consistently cooler than rectal temperature during all exposures. Brain temperature only fell below carotid blood temperature during the final few hours of 40°C exposure and not at all during the 5°C exposure. Consequently, using rectal temperature as a surrogate for arterial blood temperature does not provide a reliable indication of the status of the SBC effector. We also show that rapid suppression of SBC can result if the animals are disturbed.

A novel, simple, efficient and selective brain cooling method

Resuscitation ◽  
2015 ◽  
Vol 96 ◽  
pp. 34-35
Author(s):  
Mohammad Fazel Bakhsheshi ◽  
Laura Morrison ◽  
Lynn Keenliside ◽  
Ting-Yim Lee
Keyword(s):  
Brain Cooling ◽  
Selective Brain Cooling ◽  
Cooling Method
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