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G Baron

Publications and source records attributed to G Baron.

At least 37 records · Page 2Linked to original sources
PubMed1999

Encephalization, adaptation and evolution of chiroptera: A statistical analysis with further evidence for bat monophyly.

As part of a large-scale study on brain morphometrics and adaptations in mammals, we addressed the problem of chiropteran evolution. A specific statistical framework was designed to test which of two competing hypotheses (bat monophyly vs. diphyly) is more strongly supported by quantitative brain data. Our analyses, based on 120 species, revealed that megabats and microbats were more closely related to each other than to primates, and illustrated the convergent adaptations of the brain of bats to similar trophic (i.e. feeding related) niches. Ecologically-corrected characters were then used to derive a new phylogeny which also supports the chiropteran clade. The monophyletic origin of bats is the preferred hypothesis to explain brain quantitative evolution in chiropterans and primates.

Adaptation, Physiological↗
PubMed1994

Residence time distribution in a packed bed bioreactor containing porous glass particles: influence of the presence of immobilized cells.

An experimental investigation of the liquid phase residence time distribution (RTD) in a packed bed bioreactor containing porous glass particles is presented. For Re < 1, intraparticle forced convection is negligible and only diffusion, characterized by an effective diffusion coefficient, must be considered to describe the mass transfer process between the extraparticle and the intraparticle fluid phase. For Re > 1, the mass transfer rate becomes dependent on the liquid flow rate, indicating the existence of intraparticle convection. A model including axially dispersed flow for the external fluid phase and an 'apparent' effective diffusivity that combines diffusion and convection, predicts experimental RTD data satisfactorily. Yeast cells immobilized inside the porous glass beads did not affect the mass transfer rate at low biomass loading. At high biomass loading (0.02 g yeast cells g-1 carrier), the mass transfer rate between the extraparticle and intraparticle fluid phase was significantly decreased. Comparison of the RTD data from experiments performed in the presence and absence of cells in the external fluid phase revealed that the mass transfer rate is influenced by the cells immobilized inside the porous particles and not by the cells present in the external fluid phase.

Biotechnology↗
PubMed1994

Allometric comparison of brain and main brain subdivisions in birds.

The brain weights and volumes of the main brain subdivisions: telencephalon, diencephalon, mesencephalic tegmentum, optic tectum, cerebellum and myelencephalon were measured in 8 species of Phasianoidea (Galliformes) and in 20 species of birds belonging to 13 orders. The sizes of these structures were compared using allometry formulae calculated for each structure from the 8 Phasianoidea. Encephalization and the relative size of the main brain subdivisions are expressed by size indices. Higher encephalization indices are obtained in species which are either highly telencephalized as in Psittaciformes or with a large cerebellum as in Sphenisciformes. The brainstem components: diencephalon, mesencephalic tegmentum and myelencephalon appear to be more conservative in their size variation than the telencephalon, cerebellum and optic tectum. The size of the cerebellum appears to be related to flight abilities. The size of the optic tectum is related to the importance of vision in foraging within the Charadriiformes. In tactile-feeding Charadriiformes and filter-feeding Anseriformes, the optic tectum is relatively small.

Animals↗
PubMed1993

Growth kinetics of gel-immobilized yeast cells studied by on-line microscopy.

A 'microscope reactor' was used to study on-line the dynamics of gel immobilized cell systems. The applicability of the reactor is demonstrated by a study of the growth kinetics of Saccharomyces cerevisiae entrapped in 2% calcium alginate. The specific growth rates of single immobilized cells and free cells were measured. The growth of a microcolony in Ca-alginate was followed and the specific growth rate of the cells in the microcolony determined. A simple growth model was used to estimate the cell volume fraction of the yeast cells in the microcolony. As internal and external mass transfer limitations can be neglected and immobilized cell growth rates were found to be identical to those of free cells, one may conclude that immobilization does not influence cell growth under our experimental conditions.

Alginates↗
PubMed1993

The ontogenic development of sensorimotor reflexes and spontaneous locomotion in the Mongolian gerbil (Meriones unguiculatus).

Most behavioral studies on the ontogeny of sensorimotor reflexes and locomotion were done in quadrupedal species with equally developed forelimbs (FL) and hindlimbs (HL). In contrast, the Mongolian gerbil has long and strong HL but relatively small FL, indicating their differential use for locomotion. We have used the gerbil to study the ontogeny of a number of reflexes and locomotor acts to see if their sequence of appearance, their maturation, as well as their intensity of expression, differed from some other mammals. The following sequence was observed: forward FL hopping, FL grasp, forward HL hopping, surface body righting, chin tactile placing, lateral FL hopping, lateral HL hopping, medial FL hopping, medial HL hopping, visual placing, air body righting, and FL and HL tactile placing. When comparing FL and HL, a given reflex does not necessarily appear earlier in the limb that expresses it more strongly. The results are discussed in relation to the development of the central nervous system, the limb, and the locomotor behavior.

Animals↗
PubMed1990

A rapid two-step purification of rat liver fetal thymidine kinase.

The fetal isoenzyme of thymidine kinase was purified to apparent homogeneity from cytosols of rat fetuses liver. A two-step purification including anion exchange chromatography and affinity chromatography was developed. The purified enzyme appears as oligomeric with a relative molecular weight of 71 kDa. In denaturing media its molecular weight was 24 kDa, and its pHi 8.3.

Animals↗
PubMed1990

Comparison of brain structure volumes in Insectivora and primates. IX. Trigeminal complex.

Volumes of the trigeminal complex (TR) were measured in 30 species of Insectivora, 3 species of Scandentia, 18 species of prosimians, 26 species of non-human simians and in man. The relative size showed a definite tendency to decrease from 159 in Insectivora to 56 in simians (expressed as size indices). The difference in the development of the TR between Insectivora and Primates is explained by differences in the role of their oro-facial region in exploratory behavior. The largest size was found in semiaquatic Insectivora (average 283). In semiaquatic forms, the reduction of the olfactory centers is compensated by an increase in TR size. The extremely long vibrissae innervated by the trigeminal nerve seem to have a teletactile function in detecting vibrations in the water produced by potential prey.

Animals↗
PubMed1989

Comparative morphology and morphometry of the nasal fossae of four species of North American shrews (Soricinae).

The present study compares the morphology of the nasal conchae and the relative development (i.e., surface area and neurosensory cell number) of the olfactory epithelium between four species of shrews occupying different ecotopes (Blarina brevicauda, Sorex cinereus, S. fumeus, S. palustris). The number of olfactory cells was corrected for split cell error. Data were analyzed by using size indices based on the allometric method. The convoluted shape of the maxilloturbinal in Blarina, with large respiratory epithelial surface area, could not be related with certainty to the subterranean ecotope. From the comparison between Soricinae and Crocidurinae, one major difference concerned the shape and attachment of ectoturbinal 3. Differences in the relative development of the olfactory organ are discussed with regard to differences in the use of chemical signals. The semi-fossorial B. brevicauda, with the more developed olfactory organ, is reported to possess more scent-glands and to manifest active scent-marking behaviors and fecal deposits associated with territoriality. The two terrestrial species, S. cinereus and S. fumeus, have olfactory epithelia showing an intermediate development. Published accounts of fewer scent-glands and a lack of active scent-marking behavior indicate a lesser use of olfactory communication in these two species where mutual avoidance seems the rule. Indication of an even more reduced use of olfactory signals in social interactions by the semiaquatic S. palustris is suggested by its least-developed olfactory epithelium. The comparison between Soricinae and Crocidurinae supports a relationship between the development of the olfactory organ and the relative use of olfactory communication known to occur in social interactions.

Animals↗
PubMed1989

[An uncommon form of thymidine kinase in breast cancers].

An unusual form of thymidine kinase has been found in cytosols from breast cancers. It differs from the adult and fetal isoenzymes of thymidine kinase in so far as its activity could not be isolated from that of thymidylate kinase. Following sucrose density gradients, electrofocusing, ion exchange chromatography or molecular sieving, both activities appeared as a single peak. These facts suggest that they could be attributed to a single multifunctional protein.

Breast Neoplasms↗
PubMed1988

Cross-sectional growth and decline of human stature and brain weight in 19th-century Germany.

A new six-parameter two-phase nonlinear growth and decline model is fitted to cross-sectional data on human stature and brain weight obtained from autopsies in Germany at the end of the 19th century. Brain growth may have ended at a total age of approximately seven years, much younger than estimated in previous studies. Earlier statistical approaches may not have pinpointed the beginning of the plateau. The decline of stature was slight and is weakly significant. The decline of brain weight was stronger but occurred mostly after sixty years of age. Secular increase may have been unimportant from 1820 to 1900.

Adolescent↗
PubMed1988

Comparison of brain structure volumes in insectivora and primates. VIII. Vestibular complex.

Volumes of the vestibular complex (VC) and its four main components (medial, inferior, lateral and superior nuclei; VM, VI, VL and VS) were measured in 28 species of Insectivora, 3 species of Scandentia, 18 species of prosimians, 26 species of non-human simians and in man. The relative size showed a definite tendency to increase 2-4.5 times from Insectivora through simians (expressed by size indices). The highest increase was found in VS, the lowest in VI and, in Pongidae and man, also in VL. The differences are discussed with respect to differences in the locomotory behavior of the various taxonomic groups and to differences in the fiber connections and thus different functions of the various nuclei. Species which exploit a 3-dimensional environment and execute fast and complicated head and body movements have a larger VC than closely related species confined to the ground or which are less skilled leapers. The great increase of the VS may be related to the predominant role of vision in primates, particularly in simians.

Animals↗
PubMed1987

Number of mitral cells and the bulb volume in the aging human olfactory bulb: a quantitative morphological study.

The present study documents the morphological changes in the aging human olfactory bulb. Eight bulb pairs from white females between the ages of 25 and 102 years were used. The number of mitral cells in layers IV and III was determined for each bulb and corrected for split cell error. Counts were made on 10-micron thick Nissl-stained sections at 250-micron intervals. The mean number of mitral cells per olfactory bulb at age 25 was estimated from linear regression to be 50,935; at age 60, 32,718; and at age 95, 14,501. The average loss over the time interval studied was 520 mitral cells per year. The volume of each bulb layer, except layer IV, was determined. The difference in the volume of each layer within individuals with age and the total volume with age was not significant (P less than 0.11). The estimated mean bulb volume was found to be 50.02, 43.35, and 36.68 mm3 at ages 25, 60, and 95 years, respectively. The estimated reduction in bulb volume per year increase of age was 0.19 mm3. The ratio of mitral cells to bulb volume for layer III decreased by 19.4 units for every year increase in age. No significant difference was found between the left and the right bulbs in regard to the number of mitral cells and the bulb volume. Histologically, the glomerular layer thickness as well as the mitral cell size and concentration per unit area decreased with age. The intrabulbar anterior olfactory nucleus was discontinuous, highly variable in size, and presumably variable even in neuronal numbers.

Adult↗
PubMed1987

Comparison of brain structure volumes in Insectivora and primates. VI. Paleocortical components.

Volumes of the main structures of the 'paleocortical complex' were measured in 2 species of Macroscelidea, 39 species of Insectivora, 3 species of Scandentia, 18 species of prosimians, 26 species of nonhuman simians and man. Changes in the relative size from Insectivora through man (expressed by size indices) showed a definite tendency to decrease in the lateral olfactory tract (TRL), its nucleus (NTO), and in the olfactory cortices (RB, PRPI, TOL) and to increase in the anterior commissure (COA) and substantia innominata (SIN). The reduction in the olfactory cortices is strongest for the retrobulbar region (RB, = anterior olfactory nucleus in Anglo-American terminology), and least for the olfactory tubercle (TOL). In prosimians, the reduction clearly parallels that of the main olfactory bulb (BOL); in simians and especially in man, the indices of PRPI and TOL are clearly larger than those of BOL. Possible reasons for these growing deviations were discussed: (1) increasing difficulties in clearly homologizing and delineating the olfactory cortices in the microsmatic simians, and (2) non-olfactory functional influences.

Animals↗
PubMed1987

Comparison of brain structure volumes in Insectivora and primates. VII. Amygdaloid components.

Volumes of the amygdaloid complex (AMY) and some subdivisions were measured in 2 species of Macroscelidea, 39 species of Insectivora, 3 species of Scandentia, 18 species of prosimians, 26 species of simians and man. Changes in the relative size from Insectivora through man (expressed by size indices) showed a definite tendency to increase in the cortico-basolateral subdivision (LAM) and more or less constant relations in the centromedial subdivision (MAM), except for the nucleus tractus olfactorii lateralis (NTO), which becomes distinctly reduced. The reduction of NTO is even stronger than that of the main olfactory bulb (BOL), which in simians and man is small but distinct, whereas NTO is hardly recognizable in most of these forms. In the LAM group the size increase of the large-celled part of the basal nucleus (MCB) is less than that of the small-celled components (including the lateral nucleus). The differences between LAM and MAM groups are discussed with regard to the predominant fiber connections, which in MAM are stronger with conservative brains parts (brainstem), and in LAM with progressive brain parts (e.g. neocortex).

Amygdala↗
PubMed1985

Volume comparisons in the cerebellar complex of primates. I. Ventral pons.

Volumes of the ventral pons (VPo) were measured in 82 brains of primates, Scandentia, and Insectivora, and the relative size of the VPo was expressed by size indices. The reference line was through the prosimian average; the mean index of prosimians was set at 1. The taxonomic groups arranged in a sequence of ascending mean VPo indices were: Insectivora (0.04), prosimians (1.00), monkeys (2.55), apes (4.48) and man (9.44). Thus, the VPo of man is more than 9 times larger than that of isoponderous average prosimians, and more than 230 times larger than that of isoponderous "basal' insectivores. The indices may reflect trends and extent of VPo evolution in primate phylogeny.

Animals↗
PubMed1985

Volume comparisons in the cerebellar complex of primates. II. Cerebellar nuclei.

Volumes of medial, interposed, and lateral cerebellar nuclei (MCN, ICN, and LCN) were measured in Insectivora, Scandentia, and Primates, including man. The relative size of the nuclei was expressed in size indices. Insectivora had by far the smallest cerebellar nuclei. The simians, in general, had larger cerebellar nuclei than the prosimians, but there was considerable overlap. From Insectivora to man, the MCN was the least progressive and the LCN the most progressive. The indices are expected to reflect the relative size of the three longitudinal zones of the cerebellum (vermis/MCN, pars intermedius/ICN, hemisphere/LCN). They, together with those of the ventral pons and cerebellum (part I), are discussed in relation to the predominant locomotor pattern of a species, and with reference to evolutionary trends in primate phylogeny.

Animals↗