Biomedical subjects

G Rehkämper

Publications and source records attributed to G Rehkämper.

26 records · Page 2Linked to original sources

PubMed1991

Quantitative development of brain and brain structures in birds (galliformes and passeriformes) compared to that in mammals (insectivores and primates).

The brain weight and brain structure volumes of galliform and passeriform birds were calculated and related to body weight. The total brains and 14 brain regions were investigated in order to calculate factors by which these structures in passeriforms exceed those in galliforms in size. The larger passeriform brains have larger telencephala, especially ventral hyperstriata and neostriata. The enlargement of total brain and telencephalon resembles that in primates, compared to insectivores, within mammals. The enlargement of the ventral hyperstriata + neostriata in passeriforms is fundamentally similar to that of the isocortex in mammals: it reflects an expansion of multimodal integrational capacities, as the ventral hyperstriatum and neostriatum are occupied exclusively or primarily by multimodal integrational areas as is the isocortex.

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PubMed1988

Allometric comparison of brain weight and brain structure volumes in different breeds of the domestic pigeon, Columba livia f.d. (fantails, homing pigeons, strassers).

In three breeds of domestic pigeons (fantails, homing pigeons, and strassers) the volumes of fresh, i.e. unfixed tissue of 14 brain structures were determined (telencephalon, diencephalon, nervus opticus, tectum, cerebellum, tegmentum and hyperstriatum accessorium, hyperstriatum ventrale, neostriatum, paleostriatum, hippocampus, septum, regio praepiriformis, bulbus olfactorius). Allometric comparisons that take into account differences in body weight and size were made among these three breeds. The tectum, hippocampus, paleostriatum and especially the neostriatum and olfactory bulb are remarkably larger in homing pigeons. These data are discussed in a functional context, in which the homing ability of homing pigeons is considered.

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PubMed1987

Fine structure of the ganglion of Cephalodiscus gracilis (Pterobranchia, Hemichordata).

The ganglion of Cephalodiscus gracilis M'Intosh 1882 is entirely intraepithelial and located in the dorsal epidermis immediately behind the tentacular apparatus that is formed by the mesosome (collar). A characteristic feature of the ganglion is a well-developed neuropile in which different types of nerve fibres can be discerned, many of which contain small granules with electron-dense contents. There are no glia-like cells in association with these fibres. Only slender basal processes of epidermal epithelial cells traverse the neuropile. In the depth of the epithelium the neuropile borders the epidermal basal lamina; apically it is covered by a layer of cell bodies, the majority of which belong to what appear to be ordinary ciliated epidermal cells. Besides these epidermal cells the perikarya of two additional types of cells, which are considered to be neurons, can be discerned. One type is characterised by many rough endoplasmic reticulum cisterns and mitochondria, the other by abundant small, electron-dense granules. The nuclei of these cells are comparatively pale and contain a prominent nucleolus. The neuron cell bodies do not form a distinct layer; but they are loosely distributed somewhat deeper than those of the ordinary epidermal cells. They probably send off an apical process to the epidermal surface and a basally directed one into the neuropile. The ganglion has been compared to the nervous systems in cnidarians, some spiralians, and especially other hemichordates, echinoderms, and chordates; it is found to be of primitive rather than degenerate nature. Furthermore, the possible functional significance of its close connection to the food-capturing tentacular apparatus is discussed.

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PubMed1986

The brain of Geogale aurita Milne-Edwards and Grandidier 1872 (Tenrecidae, Insectivora).

Macromorphology, composition, and encephalization of the brain of Geogale aurita, a small Madagascan tenrec, were studied. The relative brain size (encephalization) seems to be lower in Geogale than in the Tenrecinae (spiny or bristled tenrecs) which so far have been found to be at the bottom of the encephalization scale of extant mammalian species. Conservative features found in brain macromorphology are e.g. a minute corpus callosum and an uncovered tectum, and such found in brain composition are e.g. an extremely small neocortex and a large medulla oblongata. In all these brain characteristics, Geogale approaches more to the Tenrecinae than to the Oryzorictinae. However, including Geogale in the Tenrecinae would distinctly widen the range of variation of these characters in this subfamily. Therefore, a classification of Geogale in a specific subfamily would be more appropriate.

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PubMed1985

A quantitative approach to cytoarchitectonics. X. The areal pattern of the neostriatum in the domestic pigeon, Columba livia f.d. A cyto- and myeloarchitectonical study.

The areal pattern of the neostriatum of the domestic pigeon, Columba livia f.d., is described in detail. The map was completed with the help of cyto- and myeloarchitectonical studies during which both qualitative and quantitative methods were applied. The map is divided into 16 areas which are characterized in this paper. Most of these areas can be interpreted as being not only structural but also functional units. The areas Ne 1, Ne 7, and Ne 12 represent primary projection fields. The areas Ne 2, Ne 4, Ne 5, Ne 9, Ne 13, and Ne 14 can be regarded as associative areas, closely connected with the primary areas. The areas Ne 6, Ne 11, Ne 15, and Ne 16 are described with regard to a possible integrative function.

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PubMed1984

A quantitative approach to cytoarchitectonics. IX. The areal pattern of the hyperstriatum ventrale in the domestic pigeon, Columba livia f.d.

A map of the areal pattern of the hyperstriatum ventrale in the domestic pigeon (Columba livia f.d.) is proposed. This map is based mainly on the distribution of the grey level index which has been characterized using an automatic image analyzer. Twelve areas are described. They are classified into two groups (Hvm 1-6, Hvl 1-6) which are defined by a different range of grey level indices. Three of these areas show topographic relationships to primary projection areas in the neighbouring neostriatum (Nucleus basalis, Ectostriatum, Feld L), and connections are in part well known. Therefore, these areas are assumed to be associative in function. The function of the other areas remains an open question.

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PubMed1979

A quantitative approach to cytoarchitectonics. V. The areal pattern of the cortex of microcebus murinus (E. Geoffroy 1828), (Lemuridae, primates).

The boundaries of iso- and allocortical areas of Microcebus murinus were analyzed with an automatic quantitative procedure using an image analyzer. The results are summarized in a cortical map and compared with a previous study of Microcebus murinus (Clark, 1931) and Galago demidovii (Zilles et al., 1979). A surprising correspondence could be observed between Microcebus and Galago with respect to the cortical areal pattern and the cytoarchitectonic structure of the various areas, including their position and extension, although both species are grouped into different suborders.

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PubMed1979

A quantitative approach to cytoarchitectonics. IV. The areal pattern of the cortex of Galago demidovii (e. Geoffroy, 1796), (lorisidae, primates).

The boundaries of neo- and allocortical areas of Galago demidovii are analyzed with an automatic quantitative procedure using an image analyzer. The results are summarized in a cortical map and compared with a cortical map of Tupaia. Galago shows a highly differentiated temporal lobe and no homogeneous peristriate area comparable to the classical concept of Brodmann's Area 19. Primary motor, somatosensory, auditory, and visual areas are delineated and shown to be surrounded by distinct secondary areas.

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