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G Baron

Publications and source records attributed to G Baron.

At least 55 records · Page 3Linked to original sources
PubMed1984

Comparison of accessory olfactory bulb volumes in the common tree shrew (Tupaia glis).

The volume size of the accessory olfactory bulb (AOB) of 40 common tree shrews (Tupaia glis) was compared with regard to differences between left and right sides, males and females, and animals born in the wild and those born and raised in captivity. There were no statistically significant differences between the two sides and the two sexes, but a significant reduction of the AOB from wild to captive animals was apparent. This reduction was more pronounced in females than in males and somewhat more pronounced in the inner granular layer (layer 6) than in the other measured components (layers 1 + 2, layers 3-5). No well-founded explanation for this reduction could be given.

Animals↗
PubMed1984

Comparison of brain structure volumes in insectivora and primates. IV. Non-cortical visual structures.

The relative size of the eyes, optic nerves, chiasms and tracts, and of the dorsal nucleus of the lateral geniculate body is distinctly larger in Primates than in (theoretically) isoponderous Insectivora. Within Insectivora, the relative size is lowest in moles, medium in shrews and hedgehog-like tenrecs, and largest in hedgehogs. Within Primates, all relative sizes are on the average larger in simians than in prosimians: the eyes to a small degree, the lateral geniculate bodies moderately and the optic nerves considerably larger. The ratio between eyes and optic nerves is large in night-active primates and distinctly smaller in day-active forms, with no overlap. The only night-active simian (Aotus trivirgatus) is in line with night-active prosimians. The relative size of the non-cortical visual structures in man is in line with that of day-active simians, whereas two of the great apes (orang-utan and gorilla) are relatively low. The size of the visual structures appears to depend mainly on functional requirements and is not, or is distinctly less, related to differences in the evolutionary level. The size of the visual structures of tree-shrews (Scandentia) shows special features which are not found in Insectivora and Primates and is compatible with their separation from these orders.

Animals↗
PubMed1984

Comparison of brain structure volumes in insectivora and primates. V. Area striata (AS).

Volumes of the area striata (area 17, Brodmann) were measured in 44 species of Primates and Scandentia and some of its laminar components in 25 species. The relative size (expressed by size indices) is on the average distinctly larger in simians than in isoponderous prosimians. The average dimensions of increase are 2.5 times for total area striata (ASV), 3.4 times for white matter (ASW), 2.35 times for grey matter (ASG), 1.9 times for lamina 1 (ASG 1) and 2.4 times for laminae 2-6 (ASG 2-6). The high increase of the white matter and the low increase of lamina 1 both correspond to similar results on the total neocortex (Frahm et al., 1982). The molecular layer (ASG 1) is on the average about 12% of the total area striata grey (ASG). The visual cortex thus has a narrower molecular layer than the neocortex as a whole, in which an average of 14% was found. The size indices of man are within the simian range and generally slightly above the simian average. Tree shrews have relatively small visual cortices, but reach into the lower part of the prosimian range. For Insectivora, ASG volumes were estimated from CGL volumes. According to these estimates, the relative ASG size is about 1/90 in shrews, about 1/40 in tenrecs and about 1/10 in hedgehogs that of isoponderous prosimians. In the European hedgehog, the area striata is about 12% of the total neocortex, a value similarly to that found in area measurements by Brodmann (1913). The relative size of the area striata is discussed with regard to functional, ecoethological and phylogenetic considerations. With increasing body weight, the increase in the visual structures, both cortical and non-cortical, is weak when compared with other brain parts and body organs (strongly negative allometry).

Animals↗
PubMed1983

Conditions necessary to the establishment of mating dominance by the male hamster.

We tested whether establishment of a dominance hierarchy among four males will ensure the dominant male preferential mating access to a single female. Establishment of the dominance hierarchy in the absence of a female did not result in any competitive mating advantage for the dominant male in terms of mating priority or total number of intromissions. However, establishment of the dominance hierarchy in the presence of a female, with interactions between the males and female occurring throughout the 4-day estrous cycle prior to the female becoming receptive resulted in the dominant male having a clear mating priority. Under these conditions the dominant male achieved more intromissions than the three subordinate males combined. Thus, male dominance status can affect mating success; however, it appears that interaction with the female as well as with other males prior to the onset of receptivity by the female is essential for assurance of a clear mating priority.

Animals↗
PubMed1983

Comparison of brain structure volumes in Insectivora and Primates. III. Main olfactory bulb (MOB).

Volumes of the main olfactory bulb (MOB) in 76 species of Insectivora, Scandentia, Primates and Macroscelidea, and some of the laminar components in 34 species were measured. No statistically significant differences were found (1) between the two sides in the 162 individuals and (2) between males and females in the 19 species in which both sexes were examined. In interspecific comparisons the relative size (expressed by size indices) shows a definite tendency to decrease from Insectivora through prosimians and simians to man. The average indices were 100-64-10-3.6, respectively. Scandentia and Macroscelidea have the highest average MOB indices (135 and 166). The relative MOB size is discussed in relation to feeding and social behaviour. It was shown that MOB development is largely linked to dietary adaptations but that its importance in feeding behaviour is paralleled by a similar importance in social behaviour. Within each dietary type, MOB development is associated with the different characteristics of the occupied niche. Among Insectivora, ground-dwelling species occupy the upper, and semiaquatic species the lower positions in the size scale for the MOB. Among Primates, in closely related species, the nocturnal species have in general better developed MOBs than the diurnal species. The composition of the MOB is relatively stable, i.e. the laminar components (layers 1 + 2, 3, and 4-6) show no clear change in their percentage size from well developed to strongly reduced MOBs. Only in the diurnal simians are layers 4-6 relatively small. This corresponds with the general observation (obtained from light-microscopy) that the granular layer (layer 6) is reduced and decomposed in higher Primates, and especially in man.

Animals↗
PubMed1982

Infection of organotypic cultures of spinal cord and dorsal root ganglia with Trypanosoma cruzi.

Although the involvement of the nervous system in Chagas' disease is well described, the mechanism of the neuronal destruction is unclear. Immunologic, toxic mechanisms and direct invasion have been advocated. Organotypic cultures of spinal cord and dorsal root ganglion derived from Swiss outbred mice were infected with the Brazil strain of Trypanosoma cruzi. Light microscopic and ultrastructural studies were performed at regular intervals. It was found that trypomastigotes were rapidly taken up by glial and other supporting cells. Neurons were rarely parasitized and demyelination was not evident. Loss of several cytoskeletal components was seen. Dendrites were swollen and axons lost their normal filamentous structures but synaptic membranes remained intact. Mitochondrial swelling was evident even in nonparasitized neurons from infected cultures. By 7-10 days of infection the majority of neurons lost their typical morphology and were eventually destroyed by mechanisms other than direct parasite invasion. Organotypic cultures exposed to T. cruzi-conditioned medium exhibited no change in morphology. Since neurons were found only rarely to be parasitized, it is suggested that neuronal destruction is an indirect result of the parasitism of supporting cells such as glial cells and macrophages.

Animals↗
PubMed1982

Comparison of brain structure volumes in Insectivora and Primates. II. Accessory olfactory bulb (AOB).

A total of 134 individuals from 75 species were investigated with regard to existence and size of the accessory olfactory bulb (AOB). Based on volume measurements the AOB and its three measured components do not show any uniform trend in size changes from lower Insectivora through higher Primates. The investigated structures are in most prosimians clearly larger than in low Insectivora, in most New World simians clearly smaller, and in Old World simians absent. Even within narrowly related groups there may exist strong differences in size and structural differentiation. In AOBs of large relative size, the inner granular layer (layer 6) is relatively larger than in AOBs of small relative size. The variability in size is especially large in those individuals and species with a relatively small AOB. No differences were found between the AOBs (1) of the two sides within the same individual (brain) and (2) between the two sexes within the same species. There is no interdependency in size between MOB (main olfactory bulb) and AOB. The relative size of the AOB is discussed in relation to various ecological and behavioural considerations. No clear relations could be found between the size of the AOB and dietary specialization. A comparison of the relative size of the AOB with activity cycle, sexual behaviour and the use of pheromones in various species of Primates supports the suggestion that the vomeronasal system may be involved in sexual and/or social interaction.

Animals↗
PubMed1981

New and revised data on volumes of brain structures in insectivores and primates.

More than 2,000 data on volumetric measurements of 42 structures in a variety of up to 76 species (28 insectivores, 21 prosimians, 27 simians) are given. All volumes measured in serial sections were converted to fresh volumes of a brain having a standard size within a given species. The date are available to all scientists for comparison and analysis. To allow critical evaluation, details on fixation and preparation, on determination of fresh brain weights and volumes of brain parts and on intraspecific variability are given.

Animals↗
PubMed1981

[Ecological niches and morphometric development of visual centers in primates].

Volumes of the lateral geniculate body and the tractus opticus from 12 species of Prosimians and 10 species of Simians were examined. The progression indices of the lateral geniculate Body do not differ significantly neither between Prosimians and Simians nor between diurnal and nocturnal Primates. Therefore, they cannot be considered as a criterion for phylogenetic development or for eco-ethological adaptations such as activity cycles. The progression indices of the tractus opticus, however, are higher in diurnal than in nocturnal Primates. The two-groups discriminant function based on the progression indices of the lateral geniculate body and the optic tract serves to establish a line which separates nocturnal from diurnal Primates. The lack of any correspondance in the progression of these two brain structures may be explained by the differential development of magnocellular and parvocellular layers of the lateral geniculate body.

Animals↗
PubMed1980

Brain center correlations among Chiroptera.

Correlations between progression indices of five categories of nuclei and brain centers indicate that Megachiroptera rely primarily on vision and olfaction while Microchiroptera rely primarily on audition. Among Microchiroptera, some rely more heavily on olfaction than on vision as a secondary sense, and vice-versa. There may have been compensatory effects, in the course of evolution, regarding the choice of the primary and secondary information channels.

Animals↗
PubMed1979

Quantitative changes in the fundamental structural pattern of the diencephalon among primates and insectivores.

The volumes of the main components of the diencephalon from 10 basal insectivores, 12 prosimians, and 15 simians including man were compared. The comparison of the percentage composition within the diencephalon shows that the thalamus and the subthalamus increase whereas the epithalamus and the hypothalamus decrease in relative size among primates. The allometric analysis reveals that, in spite of a relative reduction, the epithalamus and the hypothalamus are also progressive structures. However, their allometric size increase, being especially accentuated in earlier phyletic phases, is small in comparison to that of the thalamus and the subthalamus. These latter two components are characterized by a continuous phylogenetic growth from the basal insectivores to the simians. The correlation analysis shows that the strongest correlations and, in many cases, that isometric size increase exist between structures which belong to the same functional system. These findings indicate the existence of at least two major developmental gradients in the quantitative development of the diencephalon, a neencephalic and a limbic one.

Animals↗
PubMed1977

[Eco-ethological significance of the allometric development of the two visual systems in chiroptera].

Volumes of the rostral colliculus and the nuclei of the geniculate body were examined in 19 species of Chiroptera belonging to 8 families characterized by different eco-ethological adaptations. These volumes were compared to those of Basal Insectivores using the allometry formula. The data were expressed in terms of progression indices which estimate how many times a given brain center is greater than that of a Basal Insectivore of the same body weight. According to the progression indices of the rostral colliculus, Chiroptera separate into two groups: the Megachiroptera which have a mean index of 331 and the Microchiroptera with a mean index of 188. On the other hand, mean indices of the lateral geniculate body distinguish between three groups : the Megachiroptera (mean 869); the frugivorous and nectarivorous Microchiroptera (mean 293); the insect-eating, blood sucking, and fish eating Microchiroptera (mean 135). The results indicate that the two anatomically and structurally distinct elements belong to two functionally different visual systems which have evolved somewhat independently. The relation between allometric development of these visual centers and the eco-ethological adaptations of the species examined reveals, to a certain extent, the relative importance of the different functional aspects of vision.

Adaptation, Biological↗