Early formation of a GFAP-positive cell population in the ventricular zone during chicken brain development.

It is believed that neurons are generated near the surface of the embryonic cerebral ventricles, whereas glial cell proliferation occurs at sites distant to the ventricles. There is still uncertainty concerning the developmental stages when glial and neuronal cell lines diverge in the proliferative zone. The purpose of this study was to determine whether at early stages of chicken brain development during neurogenesis, cells from the astrocytic lineage are present in relevant amounts, where they are located in the neural tube, and to what extent brain regional differences exist. In this report, we demonstrate that specific markers for astrocytes [glial fibrillary acidic protein (GFAP) and glutamate-aspartate transporter (GLAST)] are expressed and translated during early neurogenesis in the developing chicken embryo at day 4 in the investigated brain regions. Between days 4 and 7, GFAP expression declines, and increases again after day 7. This profile is not entirely paralleled by GLAST expression, suggesting a later acquisition of this functional glial property. Comparison of different brain regions revealed that caudal parts of the developing chicken central nervous system are delayed in development with respect to the switch from neuronal to glial genesis. In conclusion, we show that gliogenesis occurs much earlier in the embryonic chicken brain than hitherto assumed.

First single movement of turkey embryos.

UNLABELLED: The purpose of the study was to characterize the first contraction of an isolated muscle in turkey embryo. The space of time of the contraction since beginning of incubation, topography, morphogenesis and histology of the concerned muscle and its mechanical counterpart are described. MATERIAL AND METHODS: From the 3rd day of incubation on until the 6th day the embryos were continuously watched through a cellophane window in the eggshell. The installing of the window followed a certain time schedule to reveal the influence of the experimental conditions. For histology the embryos were fixed in Bouin's fluid, then completely cut in serial sections of 5 microm thickness and stained according to Masson-Goldner's trichrome procedure plus resorcin-fuchsin. Wire frame 3D reconstructions were performed to reveal the topography of the region. RESULTS: A paired muscle 1 mm long and 0.1 mm broad, derived by fusion of the four occipital myomeres, is responsible for the first individual contraction. The contraction produces a stretching in the neck region. The muscle named M. occipitalis primordialis consists of four end-to-end connected groups of mononucleated muscle cells; insofar it looks like early muscle in fishes and amphibians. The muscle contains two types of cells according to the cell nuclei. The elastic rod-shaped notochord represents an endoskeleton. Immediately after contraction it brings the body of the embryo back into its former shape. In the neck region the diameter of the notochord is less and, therefore, the elasticity of notochord is higher than further caudal. The floor plate may prevent damage of the neural tube during excursion of the notochord. The floor plate is flanked by two floor plate posts, which have a filamentous content like the floor plate. Their function may be fastening of floor plate and protection of nerve tissue. The passive pulse movements in the occipital region for 2 days before first contraction are considered to be of importance in orientation and extent of the consecutive active reactions. CONCLUSION: Vital observation accompanying serial section examination showed to be a suitable approach to biomechanical investigations in embryology. It allowed even after nearly 180 years of intensive morphological studies of avian embryos to find a new, up till now not described muscle.

Evolving rule-based systems in two medical domains using genetic programming.

OBJECTIVE: To demonstrate and compare the application of different genetic programming (GP) based intelligent methodologies for the construction of rule-based systems in two medical domains: the diagnosis of aphasia's subtypes and the classification of pap-smear examinations. MATERIAL: Past data representing (a) successful diagnosis of aphasia's subtypes from collaborating medical experts through a free interview per patient, and (b) correctly classified smears (images of cells) by cyto-technologists, previously stained using the Papanicolaou method. METHODS: Initially a hybrid approach is proposed, which combines standard genetic programming and heuristic hierarchical crisp rule-base construction. Then, genetic programming for the production of crisp rule based systems is attempted. Finally, another hybrid intelligent model is composed by a grammar driven genetic programming system for the generation of fuzzy rule-based systems. RESULTS: Results denote the effectiveness of the proposed systems, while they are also compared for their efficiency, accuracy and comprehensibility, to those of an inductive machine learning approach as well as to those of a standard genetic programming symbolic expression approach. CONCLUSION: The proposed GP-based intelligent methodologies are able to produce accurate and comprehensible results for medical experts performing competitive to other intelligent approaches. The aim of the authors was the production of accurate but also sensible decision rules that could potentially help medical doctors to extract conclusions, even at the expense of a higher classification score achievement.

Microwave dielectric measurements and tissue characteristics of the human brain: potential in localizing intracranial tissues.

This study describes the measurements of dielectric properties in the microwave range to differentiate various human central nervous structures. Using a vector network analyser transmission and reflection coefficients were measured from 500 MHz to 18 GHz in four human formalin fixed human brains. The positions of the electrodes were marked, and the tissue was histologically stained to visualize the myelo- and the cytoarchitecture as well as the nerve fibre orientation at the electrodes. The profiles of the transmission coefficients showed a characteristic minimum peak. In order to describe this peak, a mathematical function was fitted. Parameters derived from digital image processing were used to characterize the myelo- and cytoarchitecure of the tissue at the electrodes. A multiple regression model, with the frequency at the transmission peak minimum as a dependent variable and two tissue characteristics at the two electrodes as independent variables, showed a multiple regression coefficient of 0.765. A neural network model was able to estimate the frequency at the transmission peak minimum from the tissue characteristics at the electrode. The measurements of dielectric properties are well suited to differentiate distinct intracerebral structures. The method could be used for online monitoring of the needle's position during a stereotactic intervention in neurosurgery.