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T Voigt

Publications and source records attributed to T Voigt.

At least 37 records · Page 2Linked to original sources
PubMed1992

Modulation of connexon densities in gap junctions of horizontal cell perikarya and axon terminals in fish retina: effects of light/dark cycles, interruption of the optic nerve and application of dopamine.

In the fish retina, connexon densities of gap junctions in the outer horizontal cells are modulated in response to different light or dark adaptation times and wavelengths. We have examined whether the connexon density is a suitable parameter of gap junction coupling under in situ conditions. Short-term light adaptation evoked low connexon densities, regardless of whether white or red light was used. Short-term dark adaptation evoked high connexon densities; this was more pronounced in the axon terminal than in perikaryal gap junctions. Under a 12 h red light/12 h dark cycle, a significant difference in connexon densities between the light and the dark period could be established in the gap junctions of the perikarya and axon terminals. Under a white light/dark cycle, only the gap junctions of axon terminals showed a significant difference. Crushing of the optic nerve resulted in an increase in connexon densities; this was more pronounced in axon terminals than in perikarya. Dopamine injected into the right eye of white-light-adapted animals had no effect. However, dopamine prevented the effect of optic-nerve crushing on connexon density. The reaction of axon-terminal gap junctions to different conditions thus resembles that of perikaryal gap junctions, but is more intense. Axon terminals are therefore thought to play an important role in the adaptation process.

Adaptation, Physiological↗
PubMed1991

Serotoninergic innervation of the ferret cerebral cortex. I. Adult pattern.

We have investigated the serotoninergic innervation of the adult ferret cerebral cortex with immunohistochemical techniques. Distribution pattern of serotoninergic fibers in the ferret neocortex is characterized by a decrease in the density of fibers as one moves from the pial surface towards the white matter. Throughout the entire cerebral cortex, the serotoninergic fibers are very dense within the supragranular layers, especially within layer 1. In contrast, granular and infragranular layers exhibit only a sparse innervation. Although this general pattern of innervation is roughly the same in all cortical areas, significant variations in the fiber density are apparent in different regions. Areas 17, 1, 6, and 8 (primary visual cortex, presumptive somatosensory cortex, presumptive motor cortex, and prefrontal cortex, respectively) are described in more detail to illustrate the diversity of the serotoninergic innervation patterns. The density of innervation is highest in areas 1 and 6, intermediate in area 8, and lowest in area 17. It is noteworthy that while areas 1, 6, and 8 show a marked decrease in fiber density at the boundary between layer 3 and 4, the less strongly innervated area 17 shows a change in density in the transition from layer 2 to layer 3. The types of fibers found within the ferret cortex are similar to those described in other mammalian species. The bulk of the innervation is made by very fine fusiform axons with small ovoid varicosities. In addition to this fiber type, axons with thick round varicosities and some smooth nonvaricose axons were found. The latter types occur in very small numbers within the supragranular layers and mostly in more anterior cortical regions. While the general innervation pattern and the fiber types are similar to those described in the cat cerebral cortex, the pericellular baskets found in the cat cortex (Mulligan and Törk, J Comp Neurol 270:86-110, 1988) are not seen in the ferret.

Animals↗
PubMed1991

Serotoninergic innervation of the ferret cerebral cortex. II. Postnatal development.

We have investigated the serotoninergic innervation of the ferret cortex from the day of birth to adulthood with immunohistochemical techniques. Due to the premature birth of ferrets, this period spans the entire generation of cells located within the upper cortical layers and their subsequent migration to their final positions. Already at birth, serotoninergic fibers innervate the developing cortex. This innervation is most dense within the marginal zone, the subplate region, and the lower portion of the cortical plate. As long as cell migration continues, serotoninergic fibers enter the expanding portions of the cortex. Only the region just below the marginal zone where newly arriving cells are added to the cortical plate is not innervated by the ingrowing fibers. When the bulk of cell migration ceases, during the third postnatal week, this gap disappears and the fibers gradually form a continuous innervation from the pia to the ventricle. As the cortex matures, the serotoninergic fibers become successively confined to the upper layers, to generate the adult pattern. In the adult ferret cortex, the highest innervation density is found within layers 1, 2, and 3, with a much sparser innervation within the lower layers (Voigt and de Lima, J. Comp. Neurol. 314:403-414, 1991). The dense innervation in the deep cortical layers is only transient, virtually disappearing toward adulthood. These results suggest that serotoninergic axons innervate cortical layers as soon as newly arriving cells reach their final positions within the cortex. This early innervation lends support to the idea that serotonin may play a role during development of the cerebral cortex.

Aging↗
PubMed1991

Ambient air pollution and respiratory disease.

OBJECTIVE: To review the literature on ambient air pollution and respiratory disease, and to consider the criteria for defining causation. DATA SOURCES: Medical and scientific journals indexed by Medline, conferences, proceedings and monographs. STUDY SELECTION: Two kinds of study were selected--(i) controlled clinical trials which have exposed normal or asthmatic subjects and/or patients with chronic obstructive airways disease to sulphur dioxide, nitrogen dioxide or ozone; and (ii) epidemiological studies which have investigated the chronic toxicity of these pollutants, acid aerosols and polycyclic aromatic hydrocarbons. DATA EXTRACTION AND SYNTHESIS: Experimental studies were tabulated under the headings "Design", "Subjects", "Pollutant concentration", "Duration of exposure", "Outcome measures" and "Conclusions". Epidemiological studies were summarised and compared in an attempt to reconcile conflicting results. (The experimental and epidemiological evidence has been used by regulatory bodies to develop ambient air quality guidelines.) CONCLUSIONS: At the present state of knowledge, it is not possible to conclude that air pollution can cause respiratory disease de novo, but levels marginally above current guidelines certainly have adverse effects on individuals with pre-existing chronic lung disease.

Air Pollutants↗
PubMed1991

Large and rapid changes of myofibrillar total calcium during the cardiac cycle. Electron probe microanalysis of voltage-clamped guinea-pig ventricular myocytes.

At 36 degrees C and 2 mM [Ca2+]o, single guinea-pig ventricular myocytes were voltage clamped with patch electrodes. When paired pulsing had potentiated the contraction to the maximum, the cells were shock-frozen for electron probe microanalysis (EPMA). Shock-freezing was timed at the end of diastole (-80 mV) or at different times during systole (+5 mV). The same paired-pulse protocol was applied to another group of myocytes from which contraction was recorded and [Ca2+]i was estimated by microfluospectroscopy (50 microMNa-Indo-1). In potentiated cells, during the first pulse, contraction peaked within 128 +/- 25 ms after start of depolarization. [Ca2+]i peaked within 25 ms to 890 /+- 220 nM (mean +/- SEM) and fell within 100 ms to about 450 nM. sigma Camyo, the total calcium concentration in the overlapping myofilaments (A-band), was measured by EPMA in 17 potentiated myocytes. During diastole, sigma Camyo was 2.6 +/- 0.4 mmol/kg dry weight (dw), which can be converted to 0.65 mM (mmoles per liter myofibrillar space). Since [Ca2+]i was 180 nM, we estimate that 99.97% of total calcium is bound. A time-course for systolic sigma Camyo was determined by shock-freezing 13 cells at different times after start of depolarization to +5 mV. sigma Camyo was 5.5 +/- 0.3 mmol/kg dw (1.4 mM) after 15-25 ms, 4.6 +/- 0.5 mmol/kg dw (1.1 mM) after 30-45 ms, and 3.1 mmol/kg dw (0.8 mM) after 60-120 ms. The fast time-course of sigma Camyo suggests that calcium binds to and unbinds from troponin C at a fast rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Morphology of the cells within the inferior temporal gyrus that project to the prefrontal cortex in the macaque monkey.

The primate neocortex possesses an extraordinary degree of regional specialization. Virtually all cortical functions are dependent upon a complex system of reciprocal connections between related cortical regions that allow for distributed information processing. Although some aspects of the organization of these corticocortical projections are understood, little is known about the morphology and afferents to the cells of origin of long corticocortical projections in primates. We combined intracellular injection of Lucifer Yellow (LY) in fixed tissue with in vivo retrograde transport of fast blue to study the dendritic morphology of neurons within the inferior temporal gyrus (ITG) and the superior temporal sulcus (STS) that furnish corticocortical projections to the prefrontal cortex. The fast blue retrogradely labeled cells formed two clearly defined bands within the inferior temporal cortex: a supragranular band that corresponded to layer III, and an infragranular band that corresponded to layers V and VI. After Lucifer Yellow intracellular filling, these retrogradely labeled cells projecting to the prefrontal cortex were found to be morphologically very heterogeneous. Although all filled cells had spiny dendrites, they presented a wide range of cell body sizes and dendritic tree morphologies. In layer III, the majority of cells were typical pyramids of various sizes. In layers V-VI, numerous typical pyramidal cells were present. In addition, significant numbers of modified pyramidal forms were found, including vertical and horizontal fusiform cells, asymmetrical pyramids and multipolar cells. The entire dendritic arbor of individual subtypes in layers III, V, and VI was restricted to a few cortical layers, but as a group these cells had dendrites spanning the whole cortical depth. We suggest that corticocortically projecting cells are distinct from subcortically projecting cells and consist of a defined set of morphological and functional subgroups, each of which is driven by a distinct set of afferents and likely possesses different response properties.

Animals↗
PubMed1990

[Differential diagnosis of non-thrombotic insufficiency of the conductive veins].

The differential diagnosis of the non-thrombotic insufficiency of conducting veins is in general possible by anamnesis and clinical angiological examination, even if non-vascular diseases are taken into consideration. In other patients, particularly in isolated insufficiency of the conducting veins, in addition to this non-invasive and, if the occasion arises, invasive angiological methods must be used.

Diagnosis, Differential↗
PubMed1990

Retrograde transneuronal transport of wheat-germ agglutinin to the retina from visual cortex in the cat.

Injections of peroxidase-conjugated wheat-germ agglutinin (WGA-HRP) were made into areas 17 or 18 of cats. After survivals of 3-7 days, foci of HRP-labeled ganglion cells were found at the appropriate topographic locations in the retinas. The labeling was interpreted as resulting from retrograde transneuronal transport through the lateral geniculate nucleus. This phenomenon offers a new and simple technique for the study of retinotopic maps in visual cortex.

Animals↗
PubMed1990

[Effect of smoking on hemostasis and hemorheology in pregnancy].

We found in normal and pathologic pregnant women who were discordant for smoking impaired haemostaseological and haemorheological parameters. Cigarette smoking provokes an increase of thrombocytes, a hyperfibrinolysis, a haemoconcentration and a decreased deformability of erythrocytes.

Blood Coagulation Tests↗
PubMed1989

Development of glial cells in the cerebral wall of ferrets: direct tracing of their transformation from radial glia into astrocytes.

Coronal sections of the cerebral wall from developing ferrets (newborn to adult) were double-stained with antibodies to vimentin and glial fibrillary acidic protein (GFAP). At birth, the dominant glial population was radial glia and these cells labeled only for vimentin. A small population of immature astrocytes in the cortical plate was double labeled for GFAP and vimentin. In successive days, the number of vimentin-positive radial glia gradually decreased and they disappeared entirely at about 21 days. During this same period, the double-stained astrocytes increased in number and were distributed throughout the cortical plate and intermediate zone. After 6 weeks of age the astrocytes were mostly confined to the developing white matter. Around this time they gradually lost their vimentin staining, and in the adult no vimentin-positive elements were seen except at the ependymal surface. In newborn ferrets single radial glial cells were also visualized by applying the carbocyanine dye DiI onto the pial surface of fixed brains. While most radial glia extended from the ventricular zone to the pial surface, a substantial fraction of them had lost their contact to the ventricular zone. Their somata were displaced into the subventricular zone and lower portion of the intermediate zone. The possibility that radial glia transform into astrocytes was directly tested by injecting fluorescent dyes under the pial surface of newborn ferrets at a time when virtually no GFAP-positive astrocytes are present. The tracer, which was taken up in the upper portion of the cortical plate, stained the radial glial cell somata in the ventricular zone in a similar way as the dye DiI did in the fixed brains. As the radial glial cells disappeared at successively longer survival times, the tracer was ultimately found within newly formed GFAP-positive astrocytes. These results provide strong support for the hypothesis that radial glia cells are the immature form of astrocytes (Choi and Lapham: Brain Res. 148:295-311, '78; Schmechel and Rakic: Anat. Embryol. (Berl.) 156:115-152, '79), and also show that, at least in the ferret cortex, the transformation is accompanied by a change in the expression of intermediate filament protein.

Aging↗
PubMed1988

Morphological and immunocytochemical observations on the visual callosal projections in the cat.

The connections between the left and right 17-18 border regions of the cat's visual cortex were labeled by axonal transport of peroxidase-conjugated wheat-germ agglutinin (WGA-HRP) and examined by light and electron microscopy. The cells of origin of the pathway were further characterized by transport of fluorescent microspheres ("beads") followed by in vitro injection of cells with Lucifer Yellow, and by beads transport followed by immunocytochemistry with antibodies to gamma-aminobutyric acid (GABA). The cells of origin of the callosal pathway were located in the lower part of layer 2/3, the upper part of layer 4, and layer 6. In layers 2/3 and 6, they were pyramidal cells; in layer 4 they were star pyramids or spiny stellate cells. None of them were spinefree or sparsely spinous cells, and none were GABA-positive. The axon terminals of the callosal pathway formed type 1 (asymmetric) synapses, and most of them contacted dendritic spines. Both the cells of origin and the terminals were arranged in patches. The findings suggest that the direct action of the callosal pathway is excitatory. The callosal system appears to represent only a subset of the cell types that have intrinsic horizontal projections within areas 17 or 18.

Animals↗
PubMed1988

Ocular dominance and disparity coding in cat visual cortex.

The orientation selectivity, ocular dominance, and binocular disparity tuning of 272 cells in areas 17 and 18 of barbiturate-anesthetized, paralyzed cats were studied with automated, quantitative techniques. Disparity was varied along the axis orthogonal to each cell's best orientation. Binocular correspondence was established by means of a reference electrode positioned at the boundary of lamina A and A1 in the area centralis representation of the lateral geniculate nucleus. Measures were derived that expressed each cell's disparity sensitivity and best disparity and the shape and slope of its tuning curve. Cells were found that corresponded to categories described by previous authors ("disparity-insensitive," "tuned excitatory," "near," and "far" cells), but many others had intermediate response patterns, or patterns that were difficult to categorize. Quantitative analysis suggested that the various types belong to a continuum. No relationship could be established between a cell's best orientation and its ocular dominance or any aspect of its disparity tuning. There was no relationship between a cell's ocular dominance and its sensitivity to disparity. Ocular dominance and best disparity were related. As reported by others, cells with best disparities close to zero (the fixation plane) tended to have balanced ocularity, while cells with best disparities in the near or far range had a broad distribution of ocular dominance. Among cells with receptive fields near the vertical meridian, those preferring far disparities tended to be dominated by the contralateral eye, and those preferring near disparities by the ipsilateral eye. It is suggested that this relationship follows from the geometry of near and far images and the pattern of decussation in the visual pathway. There was a significant grouping of cells with similar best disparities along tangential electrode tracks. We believe that this grouping is due to the columnar organization for ocular dominance and the relationship between ocular dominance and best disparity. No evidence was found for a columnar segregation of disparity-sensitive and disparity-insensitive cells.

Animals↗
PubMed1988

Pharmacological modulation of the rod pathway in the cat retina.

1. In the intact cat eye, the responses of ganglion cells to light stimulation were recorded extracellularly and the actions of iontophoretically applied 2-amino-4-phosphonobutyrate (APB), a potent agonist at ON-bipolars, and of strychnine, a glycine antagonist, were investigated. 2. Under light-adapted conditions, the activity of ON-center ganglion cells is decreased by APB but is increased by strychnine. APB and strychnine act independently of one another. 3. The activity of light-adapted OFF-center ganglion cells is increased by APB and by strychnine. The light response remains clearly modulated. Strychnine blocks the action of simultaneously applied APB. The results are in agreement with the action of a push-pull mechanism, according to which ON-cone-bipolars provide a glycinergic input into OFF-center ganglion cells. 4. Under dark-adapted conditions, APB blocks the light responses of both ON-center and OFF-center ganglion cells. The discharge rate of ON-center ganglion cells is completely suppressed; OFF-center ganglion cells show a high maintained discharge. 5. Strychnine blocks the scotopic light response of OFF-center ganglion cells and blocks the action of simultaneously applied APB. The light response of ON-center ganglion cells is hardly affected by strychnine. 6. The effects of strychnine on OFF-center ganglion cells are in agreement with the hypothesis that the glycinergic AII amacrine cells modulate the activity of the scotopic OFF-channel. 7. Intravitreally applied APB abolished the scotopic b-wave of the electroretinogram at concentrations of 100 microM. 8. Our data suggest that as in rabbit (10) the rod bipolars in cat retina are depolarizing (ON) bipolar cells.

Aminobutyrates↗
PubMed1987

Dopaminergic innervation of A II amacrine cells in mammalian retina.

Dopaminergic amacrine cells were stained in cat, rat, and rabbit retina using an antibody against tyrosine hydroxylase (TH). Following intraocular injection of DAPI (4,6,diamidino-2-phenylindole), subsequent retinal whole-mount preparations revealed that the dopaminergic fiber plexus formed rings around amacrine cell bodies. Intracellular injection of Lucifer yellow (LY) into A II amacrine cells confirmed that this rod-related, bistratified interneuron has its cell body within the dopaminergic rings. Using a photooxidation process, LY was transformed into an electron-dense reaction product, enabling ultrastructural examination of LY-injected A II amacrine cells. In retinae counterstained with an antibody against TH, it was possible to show synapses from TH-positive fibers onto these cells. The dopaminergic plexus was further investigated by injecting single dopaminergic cells with LY and thus revealing their branching pattern. The present results emphasize the role of dopamine in modulating the rod pathway in mammalian retina.

Animals↗
PubMed1987

Morphological and immunocytochemical identification of indoleamine-accumulating neurons in the cat retina.

The type and distribution of indoleamine-accumulating neurons were studied in the cat retina. The neurons were characterized by their capacity to take up an exogenous indoleamine, 5,6-dihydroxytryptamine, which could then be visualized using formaldehyde-induced fluorescence. Under direct microscopic control, intracellular injection of Lucifer yellow into the labeled cells revealed that the indoleamine-accumulating neurons comprise 2 distinct morphological types of amacrine cell and 1 class of ganglion cell. The dendritic morphology and retinal distribution of these cells were studied in detail. The proportion of retinal cells that accumulate 5-HT was measured using 5-HT (5-hydroxytryptamine) preloading in vitro and immunocytochemistry with an anti-5-HT antibody. Only 1 type of amacrine cell showed uptake of 5-HT at a concentration of 10(-7) M. Cells containing endogenous 5-HT were not detected by immunocytochemistry.

5,6-Dihydroxytryptamine↗
PubMed1987

[New aspects in the therapy of thrombosis and prevention of recurrence in pregnancy].

Therapy of phlebothrombosis during pregnancy general is carried out with heparin, in which case the initial hospital treatment may be continued later on with subcutaneous applications of heparin in the out-patient department. Regular clinical and apparative controls are performed during pregnancy within. Low dose heparin is injected up to the optimal dicumarol blood level (beginning with the 2nd day post partum) immediately pre-, intra- and postpartelly. - Coagulation analyses in 11 patients with former phlebothrombosis during pregnancy revealed no antithrombin III-deficiency, but hints to insufficient fibrinolysis in four cases.

Blood Coagulation Tests↗
PubMed1987

[Rheologic studies in intrauterine retardation and pregnancy-induced hypertension].

Hemorheological investigations were done in 23 pregnant women with intrauterine growth retardation, 23 patients with pregnancy induced hypertension and 21 healthy pregnant women, of whom 10 regularly smoked. The rigidity of red cells was disturbed and the hematocrit was elevated by smoking. The same disturbances could be observed in women with intrauterine growth retardation. In addition, the erythrocyte aggregation was significantly elevated in patients with hypotrophic newborns at term. Pregnancy induced hypertension was associated with disturbances in all rheological parameters. Placental perfusion was significantly prolonged in all pathologic pregnancies.

Erythrocyte Aggregation↗