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H Van der Loos

Publications and source records attributed to H Van der Loos.

53 records · Page 3Linked to original sources
PubMed1980

Early lesions of mouse vibrissal follicles:: their influence on dendrite orientation in the cortical barrelfield.

There is a statistically significant order in the tangential orientation of stellate cell dendrites, both spiny and smooth, in layer IV of the barrelfield of the mouse parietal cortex. Neurones situated in a barrel side have most of their dendrites oriented towards the barrel hollow; those situated in the hollow preferentially orient their dendrites parallel to the long axis of the barrel. A quantitative measure of the orientation of individual dendrites in barrelfields of 60-day old mice was obtained using a semi-automatic computer-microscope and a minicomputer. In the same manner, the dendrite orientation of layer IV stellate cells was determined in barrelfields, whose (cytoarchitectonic) pattern had been experimentally altered through lesions of the middle row of the mystacial vibrissal follicles at birth. The dendrites of these cells are oriented in harmony with the novel parcellation of the cortex. Consequently, for cells in the altered areas of the barrelfields, the dendrite orientation is different from that of cells with identical positions in a normal field (see Fig. 8). We tentatively interpret these findings as an adaptation of dendrite orientation to an altered pattern of thalamic input to layer IV that, in turn, is a consequence of the peripheral manipulation.

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PubMed1980

Two useful techniques in three-dimensional electron microscopy: quarter-micron serial sectioning and stereoscopy.

Quarter-micron serial sectioning is a technique useful for 3-D analyses in which light microscopical resolution is not sufficient and the maximal resolution of the electron microscope is not necessary. We propose that the technique described here is advantageous for many current electron microscopic studies in which ultrathin sections are commonly used. In particular, the sections are sturdier; they yield high-contrast images; they contain, per section, more information about the third dimension, information that can be retrieved through stereoscopy; and, when it comes to 3-D reconstruction from serial sections, less sections are needed to reconstruct tissue elements contained in a bloc of a given size. Compared to thicker sections, quarter-micron sections yield images of acceptable readability.

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PubMed1980

[A new concept about the morphogenesis of the prosencephalon in mammals (author's transl)].

The development of the prosencephalon of the mouse has been studied from the 8th to the 13th day post-conception, and some details of mammalian prosencephalic morphogenesis have thus been elucidated. The temporal pattern of development has been analysed in serial semithin coronal sections, and the prosencephalon reconstructed at different ages. The morphological differentiation of the cerebral hemispheres is dependent on a combination of cell proliferation and cell death. Necrosis thins the prosencephalic walls in certain regions (lamina terminalis and "choroid plate"). It is around the lamina terminalis, the choroid plate, and the zone of fusion of the walls of the dorsal and ventral telodiencephalic sulci that the prosencephalic vesicle develops. Thus, the olfactory bulbs are formed rostrally and the lateral ventricles laterally. The fusion between the telencephalic and diencephalic walls occurs at the ependymal surfaces of the dorsal and ventral telodiencephalic sulci, and not at their pial surfaces. The limits between the lateral ventricles and the 3rd ventricle are constituted rostrally by the lamina terminalis, dorsally and ventrally by a region where the corpus striatum mediale and the "choroid plate" meet, and caudalli by the fusion of the ependymal surfaces of the dorsal and ventral telodiencephalic sulci.

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PubMed1979

Tangential orientation and spatial order in dendrites of cat auditory cortex: a computer microscope study of Golgi-impregnated material.

In the tangential plane (parallel to the pial surface) dendrites in the primary auditory cortex (A1) of cat were found to exhibit preferentially oriented growth. This was shown by means of a computer microscope study of Golgi-Cox stained neurons as seen in 100 micrometers and 300 micrometers thick tangential sections. Two techniques were used to represent the 3-dimensional structure of dendrites: the "dendritic stick" and the "dendritic trumpet". The former dismembers a dendrite into its individual segments; the latter considers a dendrite as an entity and represents it by its centroid, its moments and the spatial dispersionof its branches. Both statistical and Fourier analyses of the data show that within the tangential plane there is a significant and consistent orientation of the dendritic sticks in a dorso-ventral direction which seems correlated with the cortical isofrequency contours observed in electrophysiological maps of the A1 region. The dendritic trumpet analyses also show a distinctly non-random vertical distribution of pyramidal cell basal dendrites but not of stellate cell dendrites.

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PubMed1977

Development of the barrels and barrel field in the somatosensory cortex of the mouse.

Barrels of the PMBSF of the mouse somatosensory cortex become apparent in Nissl-stained tangential sections simultaneously, on the fourth postnatal day. At this time they are miniatures of those in the adult and are situated in the deepest sublamina of the trilaminar cortical plate. An early barrel appears as a patch of decreased cell density: the prospective hollow of the barrel. Septa become noticeable during the sixth postnatal day. From that period to adulthood, the relative contribution of the PMBSF to the total cortical surface area increases -- an increase that goes against one's expectation: the barrel related periphery matures very early and so does the central, lateral region of the cortex. Barrel growth parallel to the pial surface is greater along the major axes than along the minor axes. By using the barrels to identify prospective layer IV in immature cortex, we could determine that layers V and VI attain their adult height during the sixth postnatal day -- an age when prospective layers I-IV are only half their adult height. The onset of barrel formation coincides with the moment after which injury to the pertinent somatosensory periphery (the vibrissal papillae) no longer causes profound alterations in barrel morphology.

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PubMed1973

Somatosensory cortex: structural alterations following early injury to sense organs.

In mouse somatosensory cortex there are discrete cytoarchitectonic units, called "barrels." Each barrel is related to one sensory vibrissa on the muzzle. Individual vibrissae were carefully injured at birth; 12 to 43 days later, the corresponding barrels proved to be absent. Evidently the sensory periphery has an important influence on the structure of the somatosensory cortex.

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PubMed1970

The structural organization of layer IV in the somatosensory region (SI) of mouse cerebral cortex. The description of a cortical field composed of discrete cytoarchitectonic units.

This article traces the author's personal history in neuroanatomical studies of the cerebral cortex including his father's pioneering studies using electrophysiology and early neuroanatomical methods. By providing the background context for the observations reported in the original heavily cited Brain Research article, the author describes how his methods of investigation with celloidin embedded material prepared with the Golgi method and Nissl staining revealed for the first time the “barrel fields” of the mouse cerebral cortex that are activated by stimulation of the facial vibrissae (whiskers). The original article reviewed the series of studies published on the murine cortical field in what later was termed a Brain Research Review. Those original observations opened an entire field of cortical organization and function that has remained an active and fertile field of neuroscience investigation.

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PubMedDate not supplied

Selective breeding for variations in patterns of mystacial vibrissae of mice. Bilaterally symmetrical strains derived from ICR stock.

The establishment of certain patterns of mystacial vibrissae in mice has been the aim of an extensive breeding program carried on in this laboratory since 1977. In a companion paper we have reported on variations in this pattern in an outbred population of ICR mice. Starting with 21 ICR animals we bred, mostly by brother-sister mating, for 13 bilaterally symmetric patterns of mystacial vibrissae characterized by the presence (or absence) of supernumerary whiskers (SWs). The strains are classified as follows: I, a mouse strain with the standard pattern; II, eight strains bred for the occurrence of SWs at a given site or sites; and III, four mouse strains bred for a maximal number of SWs in different regions of the whiskerpad. Commonly, SWs occur in regions that coincide with the zones of mergence between the three facial processes except for two class II strains in which we bred for SWs in the "straddler" row of vibrissae, and for one class III strain, in which we cultivated the tendency (that appeared late in our program) to have SWs at the crest of a facial process. For classes I and II we analyzed the results for about 18 generations in terms of "improvement," meaning an increase in the percentages of animals with the desired phenotype together with a decreased frequency of undesired SWs. For class III, success in breeding meant the increase of the mean number of the desired SWs. All results led to the same conclusion: there is a genetic basis for the occurrence of SWs. The side preference of a particular SW is not strain dependent. It disappears in those class I and II strains in which almost 100% of animals obtained the desired phenotype. The increase in number of SWs in one zone of mergence does not depend on the presence of SWs in the other. Where tested, we almost always found a representation of an SW in a topologically equivalent location within the "barrelfield" area of the somatosensory cerebral cortex. Except for some diseases early in the breeding program, and some side effects of inbreeding that were eliminated, the population was without obvious defects. Where tested, there was no correlation between the occurrence of SWs and sex. The observed variations in pattern of mystacial vibrissae and their genetic background led us to propose a morphogenetic model for the formation of the pattern of mystacial vibrissae.

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PubMedDate not supplied

Variation in pattern of mystacial vibrissae in mice. A quantitative study of ICR stock and several inbred strains.

We report on the variation in the pattern of mystacial vibrissae in ICR mice, of which one-half of the about 600 animals investigated showed one or more supernumerary whiskers (SWs). The SWs and their follicles--in all respects identical to the units of the standard pattern except for their smaller size--occurred at a restricted number of sites. In addition, a limited number of mice from two BALB/c strains were analyzed. Half of them also had one or more SWs, but mainly at one site. Mice of the C3H/HeJ and DBA/2J(a) strains were virtually without SWs, whereas animals from the NMRI strain were standard without exception. Nearly all animals of the C57BL/6J strain lacked between 1 and 4 vibrissae, always from one or two of the same adjacent sites. There was a slight overall predominance for the left side of the face to bear SWs and there was no clear-cut association with sex; the entire population was without obvious defects. The sites where extra or lacking whiskers occur are associated with the lines of fusion between the medial and the lateral nasal fold, and between the latter and the maxillary arch. Where tested, we always found a topologic equivalency between the pattern of the whisker follicles and the contralateral pattern of the "barrels"--multineuronal units in layer IV of the parietal cerebral cortex--whether the pattern was standard, "enriched," or lacking in elements. The data presented in this paper provided a basis for several studies carried out subsequently on animals that are the offspring of those characterized here, studies suggesting that the occurrence of supernumerary and of lacking whiskers has a genetic basis.

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