Biomedical subjects

E Welker

Publications and source records attributed to E Welker.

60 records · Page 4Linked to original sources

PubMed1985

A magnetic device to stimulate selected whiskers of freely moving or restrained small rodents: its application in a deoxyglucose study.

After receiving an intraperitoneal injection of [14C]2-deoxy-D-glucose (2-DG), a total of 28 mice which had pieces of metal wire glued to certain whiskers (all others were clipped) were exposed to magnetic field bursts. The stimulated whiskers were B1 (freely moving mice, set I) or whiskers C1-3 and E1 (restrained mice, set II) on the left side. In set I, stimulated mice were compared with animals of various control groups. Autoradiography demonstrated an activation of columnar shape overlying the presumed corresponding barrel contralateral to stimulation; in a part of the ipsilateral barrelfield, 2-DG uptake was depressed significantly. In the subnuclei caudalis and interpolaris of the trigeminal brainstem complex a spot of activation was observed ipsilaterally but there was no depression contralaterally. Whereas several animals of the control groups showed some aspects of these responses, they were consistent only in stimulated mice. In set II, animals received stimulation with different intensities. 2-DG uptake was higher in barrels C1-3 than in E1. It increased with increasing intensity. The same observations were made in two nuclei of termination. The device we describe here can be used to study stimulus-specific responses at various levels of the somatosensory pathway.

Animals↗

PubMed1983

Tectal connections in Python reticulatus.

The origins of the axons terminating in the mesencephalic tectum in Python reticulatus were examined by unilateral tectal injections of horseradish peroxidase. Retrogradely labeled cells were observed bilaterally throughout the spinal cord in all subdivisions of the trigeminal system, with the exception of nucleus principalis, which showed labeled cells only on the ipsilateral side. Labeling of the reticular formation occurred bilaterally in nucleus reticularis inferior magnocellularis, nucleus reticularis lateralis, nucleus reticularis, and the mesencephalic reticular formation. The tectum also receives bilateral projections from the dorsal tegmental field, the nucleus of the lateral lemniscus, and nucleus isthmi, and ipsilateral projections from nucleus profundus mesencephali. A few labeled cells were found ipsilaterally in the locus coeruleus and in nuclei vestibulares ventrolateralis and ventromedialis. In the diencephalon labeled cells were observed ipsilaterally in nucleus ventrolateralis thalami, nucleus ventromedialis thalami, nucleus suprapeduncularis, and in the dorsal and ventral lateral geniculate nuclei. Bilateral labeling was observed in nucleus periventricularis hypothalami. Furthermore, labeling was ipsilaterally present in the ventral telencephalic areas. The tectum in Python reticulatus receives a wide variety of afferent connections which confirm the role of the tectum as an integration center of visual and exteroceptive information.

Afferent Pathways↗

PubMed1981

Telencephalic projections to the eye in Python reticulatus.

The afferent connections of the eye of Python reticulatus have been studied with HRP, Nuclear yellow and Granular blue. It appeared that in this snake the eye receives afferent connections from basal telencephalic areas both ipsi- and contralaterally. Following experiments in which Granular blue was injected into one eye and Nuclear yellow into the other eye no double labeling occurred.

Afferent Pathways↗

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.

Animals↗

PubMedDate not supplied

Stimulation of the lateral hypothalamus provokes the initiation of robust long-term potentiation of the thalamo-cortical input to the barrel field of the adult, freely moving rat.

Long-term potentiation in the thalamo-cortical input to the somatosensory cortex barrel field has been reported to be inducible in vitro only during a narrow critical period of the first postnatal week. Here we explored whether this is due to inability of adult synapses to express LTP or lack of appropriate conditions for LTP induction in slice preparations. We recorded thalamo-cortical field potentials (FPs) from the barrel field of chronically prepared adult rats. In the first series, several parameters of conditioning tetanization of thalamus (T) have been tried. Statistically significant LTP of 135-150% relative to the baseline was observed only in rare cases (3/18) so that the mean changes were not statistically significant. In the second series, five trains of 100 Hz stimulation of T were paired with a "reinforcing" stimulation of the lateral hypothalamus (LH). In most cases (9/13) thalamo-cortical FPs were potentiated. The mean post-tetanic amplitude was 238 +/- 42% (+/- SEM) relative to the baseline (n = 13). The potentiation persisted for > > 1 hr and typically even further increased when tested 24-48 hr later. LTP magnitude strongly correlated with the initial paired-pulse ratio (PPR, coefficient of correlation r = 0.98) so that LTP magnitude was larger (333 +/- 107, n = 6) in cases with PPR > 1.3. The mean PPR tended to decrease after LTP (from 2.05 to 1.65). Altogether the results suggest that LTP is inducible in the thalamo-cortical input to the barrel field of normal adult rats. The dependence of LTP magnitude upon the initial PPR suggests that inputs with low initial release probability undergo larger LTP. Together with the tendency to a decrease in the PPR this suggests an involvement of presynaptic mechanisms in the maintenance of neocortical LTP.

Animals↗

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.

Animals↗