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Biomedical subjects

B Fritzsch

Publications and source records attributed to B Fritzsch.

122 records · Page 7Linked to original sources
PubMed1983

The electroreceptive ampullary organs of urodeles.

The system of lateral-line organs in urodeles was examined by the use of various light- and electron-microscopical techniques. The results show that, in addition to the well-known mechanoreceptive neuromast organs, a second type of receptor can be identified. This second type of organ was presumably seen by earlier workers, but they seemingly failed to point out the distinction between the two organs. The presently described organs are anatomically similar to the ampullary organs of various anamniotic species such as Brachiopterygii, sturgeons, lungfish, and silurids. In all these species the ampullary organs display only one afferent fiber but no efferent innervation and are situated around an ampullary enlargement in or below the epidermis as in urodeles. All ampullary receptors including those of urodeles are very sensitive to weak electrical fields. Similar to the situation in teleosts, the ampullae of urodeles show numerous microvilli but no kinocilia. All other nonteleostean ampullary receptors appear to possess only kinocilia as apical specializations but no microvilli. Current evidence suggests that the electroreceptive ampullary organs are as phylogenetically old as all other vertebrate sensory systems; they are now known to be relatively common among anamniotic vertebrates. Since all ampullary receptors share many common characteristics, it is assumed that they were derived from one phylogenetic precursor but have evolved certain peculiarities in each species not shared by other ampullary receptors.

Animals↗
PubMed1983

The development of the retinopetal nucleus olfacto-retinalis of two cichlid fish as revealed by horseradish peroxidase.

Adult patterns and the development of the nucleus of origin of centrifugal innervation of the retina, the nucleus olfacto-retinalis (NOR), were studied with horseradish peroxidase in 2 cichlid fish species. In the adults large and small cells within the nuclear boundaries can be distinguished by their cytoarchitecture and their HRP-labelling. The NOR is already formed at hatching (5.5 days post-spawning) but cannot be filled by HRP injections into one eye until 2 days later. The number of labelled neurons increases steadily until adult cell density is reached. Later larval stages show that the NOR neurons also increase in size. The two cell types found in the adult can first be distinguished at around 30 days post-spawning. Early unilateral enucleation reduces the density of the small cells in the contralateral NOR. In spite of different environmental constraints on the growth of the larvae, the NOR develops in a similar way in both species but always somewhat later in the substrate-spawner than in the mouth-brooder. The centrifugal innervation of bird (isthmo-optic nucleus, ION) and fish (NOR) retinae starts at comparable developmental stages of the retina, but no cell death as found in the developing ION in birds occurs in the developing NOR in fish. It is suggested that this is due to the constant adjustment of the NOR to the ever increasing cell numbers in the fish retina. The NOR is thus the only known centrifugally projecting nucleus in vertebrates which lacks extensive degenerating patterns during early development. The known LH-RH immunoreactivity, the two cell types, the early development, and the projection to the retina of the NOR in cichlid fish resemble closely characteristics of the ganglion of the terminalis nerve of other piscine species.

Animals↗
PubMed1981

Efferent neurons to the labyrinth of Salamandra salamandra as revealed by retrograde transport of horseradish peroxidase.

Application of horseradish peroxidase to the severed VIIIth nerve of Salamandra salamandra resulted in heavy bilateral labeling of neurons of the medullary reticular formation. These neurons closely resemble the Mauthner neuron in their widespread dendritic ramification. In most preparations axon collaterals are seen to leave the medulla via the contralateral VIIIth nerve. It is suggested that these neurons are labyrinthine efferents.

Animals↗
PubMed1981

Pretectal neurons project to the salamander retina.

Injection of horseradish peroxidase solution into the eye of some european salamander species labeled retrogradely pretectal neurons. These neurons lie near the commissura posterior and extend their dendrites into the visual pretectal neuropil. On the average, each animal contained 28 labeled cells. Their distribution is bilaterally with a slight preference to the contralateral pretectum. As in other vertebrates these retrogradely labeled pretectal cells may be considered as efferents to the salamander retina.

Animals↗
PubMed1981

The pattern of lateral-line afferents in urodeles. A horseradish-peroxidase study.

The organization of posterior and anterior afferents of the lateral-line system was studied in several species of urodeles by means of transganglionic transport of horseradish peroxidase. The afferents of each lateral-line nerve form distinct fascicles in the medullary alar plate. Each of the two branches of the anterior lateral-line nerve is organized in two long and one short fascicles. The posterior lateral-line afferents form only two long fascicles. Each ordinary neuromast is supplied by only two afferents, which run in the two ventral medullary fiber bundles. It is suggested that afferents to hair cells displaying one type of polarity form together one bundle, but those contacting hair cells polarized in the opposite way form the second ventral bundle of one lateral-line branch. Thus, the lateral-line afferents may be organized in a directotopic fashion. The short dorsal fascicle formed only by the anterior lateral-line afferents receives fibers exclusively from small pit organs. Each pit organ is supplied by only one afferent. Anatomically, these pit organs resemble in many respects the electroreceptive ampullary organs of certain fish. Neurons labeled retrogradely via the anterior lateral-line nerve afferents have been attributed to the nervus trigeminus or facialis. In addition to the posterior lateral-line afferents, only few centrifugally projecting neurons were labeled. These neurons are discussed as efferents to the posterior lateral-line neuromasts.

Afferent Pathways↗
PubMed1981

Development of retinofugal neuropil areas in the brain of the alpine newt, Triturus alpestris.

The development of the retinofugal projection areas of the brain has been studied in larvae of Triturus alpestris by means of anterograde transported horseradish peroxidase. The optic tract establishes contacts with the optic tectum prior to the onset of robust terminal formation in the diencephalon. The tectum becomes covered by the retinofugal projection in a rostro-caudal direction. The basal optic neuropil develops synchronously with the oculomotor neurons. Their dendrites extend into this neuropil area. A small amount of uncrossed label occurs long before metamorphosis. Around metamorphotic climax this ipsilateral label increases but does not attain the adult pattern even three monts postmetamorphosis. The data are compared with the onset of visual induced behaviour.

Animals↗
PubMed1981

Transneuronal vestibular afferent influence on the nodular molecular layer synaptogenesis.

The effect of vestibular afferent deprivation on the synaptogenesis of the nodular molecular layer has been studied quantitatively. No detectable effect on the time sequence of the development of the molecular layer and the external granular layer was found. Only around hatching a significantly reduced synaptic profile density was found in otocyst-deprived chickens on both halves of the nodulus. This effect can most easily be explained by the assumption of an anterograde transient transneuronal influence of vestibular afferents on the ability of parallel fibers to form synapses.

Animals↗
PubMed1980

Retinal projections in European Salamandridae.

The retinal projections to the brain were studied in three species of European Salamandridae using anterograde transport of horseradish peroxidase and autoradiography. The results obtained were basically identical for all species and confirmed earlir findings on the fiber supply to the preoptic nucleus and the basal optic neuropil. In the anterior thalamus projections to three distinct terminal fields are clearly visible: (i) the diffusely stained corpus geniculatum thalamicum, (ii) the neuropil of Bellonci, pars lateralis, and (iii) a dorsomedial terminal field, the neuropil of Bellonci, pars medialis. Caudal to these terminal fields is an almost terminal-free region, the lateral neuropil. In the posterior thalamus a medial terminal field, the uncinate field, and a laterally located terminal field, the posterior thalamic neuropil, are distinguishable. The tectum opticum displays as many as four dense layers of retinofugal fibers and terminals in the rostral part and, in addition, a more densely stained strip of neuropil running from rostral to caudal over the tectum. The extent of ipsilateral fibers is greater than previously reported in other urodele species. They supply the medial and the lateral parts of the neuropoil of Bellonci, the uncinate field, and reach the tectum opticum via the medial optic tract. Further, they form terminals in the innermost optic fiber layer throughout the rostral half of the ipsilateral tectum. A small proportion of ipsilateral fibers contributes very sparsely to all other thalamic terminal fields, leaving only the caudal part of the tectum and several layers of the rostral tectum completely free of a direct retinofugal fiber supply.

Animals↗
PubMed1979

Observations on degenerative changes of Purkinje cells during early development in mice and in normal and otocyst-deprived chickens.

The cerebellar noduli of 18 neonatal mice and 13 young chickens were studied by light and electron microscopy. Beginning with postnatal day 10 in mice and incubation day 17 in chickens some Purkinje cells of the nodulus show degenerative changes. The nuclei and cytoplasm of these cells are darker than the neighbouring tissue due to an accumulation of large amounts of ribosomelike particles and an increased stainability of the cytoplasm. Mitochondria and endoplasmic reticulum undergo a moderate swelling, the Golgi apparatus hypertrophies whereas the somata and nuclei atrophy. The percentage of degenerating Purkinje cells reaches a peak of about 45% around postnatal day 14 in mice and the 4th day after hatching in chickens. In 26 otocyst-deprived chickens a smaller proportion of Purkinje cells with degenerative changes is found. The way in which the otocyst removal influences the neonatal Purkinje cell degeneration is not clear.

Animals↗
PubMedDate not supplied

Neuroanatomical evidence for electroreception in lampreys.

The patterns of the anterior lateral-line afferents of Lampetra fluviatilis as revealed by transganglionic transport of horseradish peroxidase are described. The afferents form two roots in entering the rhombencephalon. Fibers of the dorsalmost root can be traced to a short dorsal fascicle which runs along the dorsal nucleus. The ventral roots form two fascicles adjacent to the nucleus intermedius. Comparison with urodeles indicates that lampreys, like urodeles and other anamniotic vertebrates are electroreceptive.

Afferent Pathways↗
PubMedDate not supplied

A simple, reliable and inexpensive silver stain for nerve fibers in bleached skin.

A procedure for silver staining is described which leads to the selective and reliable impregnation of nerve fibers in bleached skin of vertebrates and invertebrates. In combination with osmium, the protocol enhances the staining of secondary sensory cells of mechanosensory and electrosensory organs so that the innervation pattern of each organ and the number of sensory cells per organ can easily be evaluated. The technique can be also used for staining nerve fibers in whole embryos.

Animals↗