The Rise of Endothermy

2019 ◽  
pp. 337-422
Author(s):  
Georg F. Striedter ◽  
R. Glenn Northcutt
Keyword(s):  
Cerebellar Cortex ◽  
Mass Extinction ◽  
Olfactory System ◽  
Convergent Evolution ◽  
Brain Size ◽  
Reciprocal Connections ◽  
Left And Right ◽  
Excellent Color ◽  
The Brain ◽  
Commissural Connections

Mammals and birds exhibit many examples of convergent evolution, including endothermy and related traits that helped them survive the end-Cretaceous mass extinction. The subsequent diversification of both lineages was accompanied by multiple expansions in relative and (often) absolute brain size. Examples of convergent evolution in the brain include complex folding of the cerebellar cortex, complex auditory circuits, and highly laminar areas within the telencephalon. Of course, birds and mammals also diverged in numerous respects. In particular, early mammals (but not birds!) shifted into a nocturnal niche, which was accompanied by an expansion of the olfactory system and the evolution of highly light-sensitive eyes. In the process, early mammals became “color-blind,” but excellent color vision re-evolved in some diurnal lineages, notably platyrrhine primates. Mammalian brains are also unusual for having strong reciprocal connections between thalamus and dorsal pallium (i.e., neocortex) and extensive commissural connections between the left and right neocortex.

scholarly journals Odour character differences for enantiomers correlate with molecular flexibility

2008 ◽  
Vol 6 (30) ◽  
pp. 75-86 ◽  
Author(s):  
Jennifer C Brookes ◽  
A.P Horsfield ◽  
A.M Stoneham
Keyword(s):  
Small Molecules ◽  
Olfactory System ◽  
Membered Ring ◽  
Structural Flexibility ◽  
Important Class ◽  
Separate Factor ◽  
Extensive Class ◽  
Left And Right ◽  
The Brain ◽  
Card Model

The olfactory system sensitively discerns scents from many small molecules as the brain analyses signals from nasal receptors. These receptors are selective to some degree, though the mechanism for selectivity is still controversial. Enantiomers, chiral pairs of left- and right-handed structures, are an important class of molecules in assessing proposed mechanisms. We show that there is a correlation between molecular (structural) flexibility and whether or not the left- and right-handed enantiomers smell the same. In particular, for the fairly extensive class of enantiomers with six-membered ring flexibility, enantiomers do not smell the same. There are, of course, significant experimental uncertainties, which we discuss here. We discuss models of receptor selectivity, both those based on shape and those where discrimination is based on other factors, such as electron affinity, proton affinity or vibration frequencies. The differences in scent of these enantiomers appear to be consistent with simple generalizations of a ‘swipe card’ model in which, while the shape must be good enough, critical information for actuation is a separate factor.

Advantages of Complementary Stereo Images as Viewed with the Low-Temperature Field-Emission SEM

1992 ◽  
Vol 50 (2) ◽  
pp. 1314-1315
Author(s):  
William P. Wergin ◽  
Eric F. Erbe
Keyword(s):  
Fold Increase ◽  
Horizontal Displacement ◽  
Three Dimensions ◽  
Stereo Image ◽  
Stereo Pair ◽  
Sem Micrograph ◽  
Left And Right ◽  
The Common ◽  
The Brain ◽  
Pair Analysis

The eye-brain complex allows those of us with normal vision to perceive and evaluate our surroundings in three-dimensions (3-D). The principle factor that makes this possible is parallax - the horizontal displacement of objects that results from the independent views that the left and right eyes detect and simultaneously transmit to the brain for superimposition. The common SEM micrograph is a 2-D representation of a 3-D specimen. Depriving the brain of the 3-D view can lead to erroneous conclusions about the relative sizes, positions and convergence of structures within a specimen. In addition, Walter has suggested that the stereo image contains information equivalent to a two-fold increase in magnification over that found in a 2-D image. Because of these factors, stereo pair analysis should be routinely employed when studying specimens.Imaging complementary faces of a fractured specimen is a second method by which the topography of a specimen can be more accurately evaluated.

scholarly journals Molecular evolutionary analysis of human primary microcephaly genes

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Nashaiman Pervaiz ◽  
Hongen Kang ◽  
Yiming Bao ◽  
Amir Ali Abbasi
Keyword(s):  
Evolutionary History ◽  
Genetic Basis ◽  
Brain Size ◽  
Primate Species ◽  
Evolutionary Analysis ◽  
Australopithecus Afarensis ◽  
Primary Microcephaly ◽  
Modern Humans ◽  
History Of ◽  
The Brain

Abstract Background There has been a rapid increase in the brain size relative to body size during mammalian evolutionary history. In particular, the enlarged and globular brain is the most distinctive anatomical feature of modern humans that set us apart from other extinct and extant primate species. Genetic basis of large brain size in modern humans has largely remained enigmatic. Genes associated with the pathological reduction of brain size (primary microcephaly-MCPH) have the characteristics and functions to be considered ideal candidates to unravel the genetic basis of evolutionary enlargement of human brain size. For instance, the brain size of microcephaly patients is similar to the brain size of Pan troglodyte and the very early hominids like the Sahelanthropus tchadensis and Australopithecus afarensis. Results The present study investigates the molecular evolutionary history of subset of autosomal recessive primary microcephaly (MCPH) genes; CEP135, ZNF335, PHC1, SASS6, CDK6, MFSD2A, CIT, and KIF14 across 48 mammalian species. Codon based substitutions site analysis indicated that ZNF335, SASS6, CIT, and KIF14 have experienced positive selection in eutherian evolutionary history. Estimation of divergent selection pressure revealed that almost all of the MCPH genes analyzed in the present study have maintained their functions throughout the history of placental mammals. Contrary to our expectations, human-specific adoptive evolution was not detected for any of the MCPH genes analyzed in the present study. Conclusion Based on these data it can be inferred that protein-coding sequence of MCPH genes might not be the sole determinant of increase in relative brain size during primate evolutionary history.

scholarly journals Effects of Brain Size on Adult Neurogenesis in Shrews

2021 ◽  
Vol 22 (14) ◽  
pp. 7664
Author(s):  
Katarzyna Bartkowska ◽  
Krzysztof Turlejski ◽  
Beata Tepper ◽  
Leszek Rychlik ◽  
Peter Vogel ◽  
...  
Keyword(s):  
Adult Neurogenesis ◽  
Subventricular Zone ◽  
Molecular Mechanisms ◽  
Brain Size ◽  
Hippocampal Formation ◽  
Small Animals ◽  
Suncus Murinus ◽  
The Brain ◽  
Neomys Fodiens ◽  
Migratory Stream

Shrews are small animals found in many different habitats. Like other mammals, adult neurogenesis occurs in the subventricular zone of the lateral ventricle (SVZ) and the dentate gyrus (DG) of the hippocampal formation. We asked whether the number of new generated cells in shrews depends on their brain size. We examined Crocidura russula and Neomys fodiens, weighing 10–22 g, and Crocidura olivieri and Suncus murinus that weigh three times more. We found that the density of proliferated cells in the SVZ was approximately at the same level in all species. These cells migrated from the SVZ through the rostral migratory stream to the olfactory bulb (OB). In this pathway, a low level of neurogenesis occurred in C. olivieri compared to three other species of shrews. In the DG, the rate of adult neurogenesis was regulated differently. Specifically, the lowest density of newly generated neurons was observed in C. russula, which had a substantial number of new neurons in the OB compared with C. olivieri. We suggest that the number of newly generated neurons in an adult shrew’s brain is independent of the brain size, and molecular mechanisms of neurogenesis appeared to be different in two neurogenic structures.

THE METABOLISM OF NORMAL BRAIN AND HUMAN GLIOMAS IN RELATION TO CELL TYPE AND DENSITY

1955 ◽  
Vol 33 (3) ◽  
pp. 395-403 ◽  
Author(s):  
Irving H. Heller ◽  
K. A. C. Elliott
Keyword(s):  
Cerebral Cortex ◽  
White Matter ◽  
Brain Tumors ◽  
Corpus Callosum ◽  
Oxygen Uptake ◽  
Glial Cells ◽  
Cerebellar Cortex ◽  
Unit Weight ◽  
Uptake Rates ◽  
The Brain

Per unit weight, cerebral and cerebellar cortex respire much more actively than corpus callosum. The rate per cell nucleus is highest in cerebral cortex, lower in corpus callosum, and still lower in cerebellar cortex. The oxygen uptake rates of the brain tumors studied, with the exception of an oligodendroglioma, were about the same as that of white matter on the weight basis but lower than that of cerebral cortex or white matter on the cell basis. In agreement with previous work, an oligodendroglioma respired much more actively than the other tumors. The rates of glycolysis of the brain tumors per unit weight were low but, relative to their respiration rate, glycolysis was higher than in normal gray or white matter. Consideration of the figures obtained leads to the following tentative conclusions: Glial cells of corpus callosum respire more actively than the neurons of the cerebellar cortex. Neurons of the cerebral cortex respire on the average much more actively than neurons of the cerebellar cortex or glial cells. Considerably more than 70% of the oxygen uptake by cerebral cortex is due to neurons. The oxygen uptake rates of normal oligodendroglia and astrocytes are probably about the same as the rates found per nucleus in an oligodendroglioma and in astrocytomas; oligodendroglia respire much more actively than astrocytes.

scholarly journals The Hammer and the Nail: Biomechanics of Striking and Struck Canadian University Football Players

2021 ◽  
Author(s):  
Jeffrey S. Brooks ◽  
Adam Redgrift ◽  
Allen A. Champagne ◽  
James P. Dickey
Keyword(s):  
College Football ◽  
Head Impact ◽  
Football Players ◽  
Video Footage ◽  
Impact Location ◽  
Rule Changes ◽  
Left And Right ◽  
The Brain

AbstractThis study sought to evaluate head accelerations in both players involved in a football collision. Players on two opposing Canadian university teams were equipped with helmet mounted sensors during one game per season, for two consecutive seasons. A total of 276 collisions between 58 instrumented players were identified via video and cross-referenced with sensor timestamps. Player involvement (striking and struck), impact type (block or tackle), head impact location (front, back, left and right), and play type were recorded from video footage. While struck players did not experience significantly different linear or rotational accelerations between any play types, striking players had the highest linear and rotational head accelerations during kickoff plays (p ≤ .03). Striking players also experienced greater linear and rotational head accelerations than struck players during kickoff plays (p = .001). However, struck players experienced greater linear and rotational accelerations than striking players during kick return plays (p ≤ .008). Other studies have established that the more severe the head impact, the greater risk for injury to the brain. This paper’s results highlight that kickoff play rule changes, as implemented in American college football, would decrease head impact exposure of Canadian university football athletes and make the game safer.

The brain of the tree pangolin (Manis tricuspis ). II. The olfactory system

2018 ◽  
Vol 526 (16) ◽  
pp. 2548-2569 ◽  
Author(s):  
Aminu Imam ◽  
Adhil Bhagwandin ◽  
Moyosore S. Ajao ◽  
Muhammed A. Spocter ◽  
Amadi O. Ihunwo ◽  
...  
Keyword(s):  
Olfactory System ◽  
The Brain

On the anatomic relation of choroid plexus to brain: a comparative study

1980 ◽  
Vol 238 (1) ◽  
pp. R76-R81 ◽  
Author(s):  
H. F. Cserr ◽  
M. Bundgaard ◽  
J. K. Ashby ◽  
M. Murray
Keyword(s):  
Choroid Plexus ◽  
Brain Volume ◽  
Brain Size ◽  
Ventricular Volume ◽  
Brain Weight ◽  
Air Breathing ◽  
Original Proposal ◽  
Adaptive Value ◽  
Choroid Plexuses ◽  
The Brain

The size of choroid plexuses and cerebral ventricles relative to brain varies widely among vertebrates. The functional significance of this variability has attracted little attention since Herrick's original proposal that large choroid plexuses might enhance oxygen delivery to the brain and therefore be of adaptive value in the transition of vertebrates from water to air breathing. We compared choroid plexus and brain weight or ventricular and brain volume in 40 species from nine vertebrate groups. Both choroid plexus weight and ventricular volume were unrelated to brain size. Plexus weight ranged from 0 to 5.2% of brain weight and ventricular volume from 0.9 to 132% of brain volume. Amid this diversity the dipnoans, chondrosteans, holosteans, amphibians, and crossopterygian examined in this study are exceptional in uniformly having large plexuses. The adaptive significance of large choroid plexuses may lie in the presence of specific homeostatic mechanisms and their role in the response to the increases in PCO2 that accompany the transition to air breathing.

scholarly journals Cuttlefish use stereopsis to strike at prey

2020 ◽  
Vol 6 (2) ◽  
pp. eaay6036 ◽  
Author(s):  
R. C. Feord ◽  
M. E. Sumner ◽  
S. Pusdekar ◽  
L. Kalra ◽  
P. T. Gonzalez-Bellido ◽  
...  
Keyword(s):  
Information Processing ◽  
Visual Information ◽  
Convergent Evolution ◽  
Visual Fields ◽  
Three Dimensional ◽  
Visual Information Processing ◽  
Depth Information ◽  
Cephalopod Species ◽  
Left And Right

The camera-type eyes of vertebrates and cephalopods exhibit remarkable convergence, but it is currently unknown whether the mechanisms for visual information processing in these brains, which exhibit wildly disparate architecture, are also shared. To investigate stereopsis in a cephalopod species, we affixed “anaglyph” glasses to cuttlefish and used a three-dimensional perception paradigm. We show that (i) cuttlefish have also evolved stereopsis (i.e., the ability to extract depth information from the disparity between left and right visual fields); (ii) when stereopsis information is intact, the time and distance covered before striking at a target are shorter; (iii) stereopsis in cuttlefish works differently to vertebrates, as cuttlefish can extract stereopsis cues from anticorrelated stimuli. These findings demonstrate that although there is convergent evolution in depth computation, cuttlefish stereopsis is likely afforded by a different algorithm than in humans, and not just a different implementation.

Longitudinal Brain Size Measurements in App/Ps1 Transgenic Mice

2010 ◽  
Vol 4 ◽  
pp. MRI.S5885 ◽  
Author(s):  
Trevor J. Vincent ◽  
Jonathan D. Thiessen ◽  
Laryssa M. Kurjewicz ◽  
Shelley L. Germscheid ◽  
Allan J. Turner ◽  
...  
Keyword(s):  
Brain Size ◽  
Three Dimensional ◽  
Gene Mutations ◽  
Mutant Form ◽  
Swedish Mutation ◽  
Significant Difference ◽  
Lateral Width ◽  
Resolution Imaging ◽  
Or Gene ◽  
The Brain

There appear to be species differences among the effects of gene mutations related to familial Alzheimer's disease on the brain during aging. To gain a better understanding of the effects of the Swedish mutation of amyloid precursor protein and the mutant form of human presenilin 1 on mice, commercially available mice from Jackson Laboratory were studied. Three dimensional T2*-weighted imaging was used to monitor the size of brains of APP/PS1 mice monthly, from 6 to 13 months of age. No significant difference was measured in the size of the medial-lateral width, dorsal-ventral height, rostral-caudal length or the volume of the APPSwe/ PS1 mouse brain. Faster and higher-resolution imaging methods are needed to accurately determine if small volume or shape changes occur in mouse brains with age or gene mutations.

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