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Biomedical subjects

F H Güldner

Publications and source records attributed to F H Güldner.

At least 19 recordsLinked to original sources
PubMed1997

Structural plasticity of optic synapses in the rat suprachiasmatic nucleus: adaptation to long-term influence of light and darkness.

Synapses of optic afferents (optic synapses) in the suprachiasmatic nucleus of hooded rats were morphometrically evaluated after exposing the animals to 12 h, 14 days, 2 months, and 8 months of constant light (light rats) and darkness (dark rats). Compared with dark rats, optic synapses from light rats have larger boutons with larger mitochondria, more clear vesicles, fewer dense-core vesicles and front-line vesicles, smaller presynaptic dense projections, a smaller amount of postsynaptic density material, a smaller relative number of Gray-type I (asymmetric) junctions, a greater relative number of Gray-type II (symmetric) junctions, as well as more and larger mitochondria in the postsynaptic dendrites. Junctions of optic synapses are mostly straight, but the small number of positively curved contacts are more flattened in light rats than in dark rats. An age-related increase in the size of presynaptic dense projections was also observed. There are no changes in the sizes of clear and dense-core vesicles, in the size of synaptic junctions and their numerical density in area, and in the unspecific contact area between pre- and postsynaptic elements. The changes in optic boutons are characteristic for activated and relatively disused synapses with a slow, tonic firing rate. It appears that (1) the amount of postsynaptic density material is proportional to the strength of Gray-type I synapses, and that (2) some excitatory optic synapses become inhibitory after long-term activity, whereas some inhibitory synapses turn into excitatory contacts after long-term disuse.

Adaptation, Physiological↗
PubMed1996

Complex synaptic arrangements in the rat suprachiasmatic nucleus: a possible basis for the "Zeitgeber" and non-synaptic synchronization of neuronal activity.

A special type of complex synaptic arrangement occurs in the ventro-lateral portion of the rat suprachiasmatic nucleus. These arrangements are polycentric, with about equal numbers of pre- and postsynaptic elements. Because of an incomplete astroglial covering, these synaptic complexes are connected with each other and form a continuous reticulum or sponge-like system throughout the ventro-lateral region of the nucleus. In two partially reconstructed complex synaptic arrangements, boutons from retinal afferents could be seen to make up the majority of presynaptic elements. They form asymmetric and symmetric synaptic appositions with dendritic elements. Non-optic axo-dendritic synapses of unknown origin with asymmetric and symmetric appositions and dendro-dendritic synapses with symmetric appositions are also seen in complex synaptic arrangements. Within complex synaptic arrangements, dendrites often run in bundles, with some dendrites spiralling around others. Membranes of neighbouring dendrites are closely apposed. These interdendritic appositions are possibly ephapses and may, together with intersomatic contacts, mediate non-synaptic synchronization of neuronal activity in the suprachiasmatic nucleus, as described by other authors. The activity of optic and non-optic synapses in complex synaptic arrangements over a 24 h period may also produce an integrated response that influences the circadian rhythm of neuronal activity in this nucleus.

Animals↗
PubMed1994

Structural differences between optic synapses in the suprachiasmatic nucleus of hooded and albino rats.

Synapses of retinal afferents (optic synapses) in the suprachiasmatic nucleus (SCN) were morphometrically compared between hooded and albino rats. Optic synapses from albino rats show larger boutons with larger mitochondria, synaptic appositions with less postsynaptic density material, relatively more symmetric (presumably inhibitory) contacts, and relatively less asymmetric (presumably excitatory) contacts, compared with hooded rats. There are no differences in the numbers of clear and dense core vesicles, the size of synaptic appositions, and their numerical density in area of micrograph. Possible differences in activity and/or metabolism between optic synapses from hooded and albino rats are discussed.

Albinism, Oculocutaneous↗
PubMed1994

Communication between the facial and auriculotemporal nerves.

The communication between the auriculotemporal and the facial nerves, i.e. the communicating auriculotemporal nerves (CATN), was studied in 55 facial sides from Thai cadavers. CATN only joined the temporofacial (upper) division of the facial nerve. CATN patterns were classified as follows: (1) the facial nerve was joined by 1 CATN (20.7%), (2) by 2 separate CATN branches (60.4%), (3) by 3 separate CATNs (15.1%); (4) several CATNs ran parallel to the zygomatic and buccal nerves to the muscles of facial expression (3.8%). The 4 types of CATN pattern showed further variations according to the site of union with the facial nerve. The superficial temporal artery was crossed by CATN branches anteriorly in 47.1%, posteriorly in 18.9%, and anteriorly and posteriorly in 34.0% of the cases. The facial nerve branches that were joined by CATNs were observed to supply the upper muscles of facial expression, i.e. frontalis, orbicularis oculi and zygomaticus major. Some offshoots from CATNs were seen to innervate orbicularis oculi. On the basis of our results we suggest that CATNs may convey proprioceptive impulses from orbicularis oculi.

Cranial Nerves↗
PubMed1990

Golgi-like demonstration of "dark" neurons with an argyrophil III method for experimental neuropathology.

A silver method is proposed for the selective, well-contrasted and reproducible demonstration of "dark" neurons in frozen, vibratome and paraffin sections cut at a thickness of 5 to 200 microns from aldehyde-fixed brains. The Golgi-like staining of the dendrites enables assorting of "dark" neurons according to characteristic neuron classifications. The staining procedure includes an esterification with 1-propanol, a treatment with diluted acetic acid and development. The esterification strongly increases the argyrophilia of both "dark" neurons and mitochondria. Unwanted co-staining of mitochondria is suppressed by the acetic acid treatment, while a special developer is used to render the staining controllable. The applicability of the method to experimental neuropathology is demonstrated by Golgi-like staining of "dark" neurons in rat brains exposed, before transcardial perfusion-fixation and delayed autopsy, to various pathological conditions including ischemia, hypoglycemia, trauma, status epilepticus, deafferentation and poisoning with kainic acid, colchicine and sodium azide, respectively.

Animals↗
PubMed1988

Plasticity of postsynaptic density material in optic synapses of the suprachiasmatic nucleus in the senescent rat.

Optic synapses in the suprachiasmatic nucleus were studied in senescent rats after 2 weeks of constant light influence (light rats) or darkness (dark rats). The amount of postsynaptic density material was significantly greater in dark rats compared with light rats. Dark rats also showed a higher percentage of asymmetric synapses than light rats. The sizes of synaptic appositions and boutons were also compared. The phenomena observed may indicate supersensitivity and a higher number of excitatory synapses in dark rats and subsensitivity and lower number of excitatory synapses in light rats.

Aging↗
PubMed1985

Structural plasticity of developing optic synapses under different lighting conditions.

Four-month-old male hooded rats were reared from birth under constant light and darkness conditions. Changes in the amount of postsynaptic density material in the optic synapses in the suprachiasmatic nucleus of these rats were compared with animals maintained under routine light-dark (12 h) cycles. The thickness of postsynaptic density material was found to be significantly greater in dark-reared rats relative to light-reared animals. The plasticity of this structure may have functional implications in the sensitivity of postsynaptic response. There was no significant difference in the lengths of the synaptic apposition and the size of boutons.

Animals↗
PubMed1985

Activity dependent plasticity of postsynaptic density structure in the ventral cochlear nucleus of the rat.

Young adult male rats were anaesthetised with urethane and exposed to either 24 h of silence or 24 h of repetitive 77 dB tones in a sound-proofed anechoic chamber. The influence of these two conditions on the ultrastructure of the synaptic appositions made by auditory afferents in the anterior ventral cochlear nucleus (end bulbs of Held) was compared. Both the cross-sectional area and the mean thickness of the postsynaptic density (PSD) in the rats exposed to tones were significantly reduced when compared with rats maintained in silence. Similarly, the degree of curvature of the apposition was significantly reduced. The results of these experiments provide further evidence that the postsynaptic density material is a plastic structure significantly influenced by the amount of activity in the presynaptic element.

Acoustic Stimulation↗
PubMed1984

The maturation of post-synaptic densities in chicken forebrain.

During normal post-hatch development and maturation in chicken forebrain there was a doubling in the average thickness of the post-synaptic densities (PSDs) in isolated synaptosomes, but no change in the average length of synaptic junctions. In the same period the concentration of the major post-synaptic density protein ( mPSDp ) in membranes prepared from the synaptosomes increased 3-5-fold. We suggest that immature synapses have a basic PSD framework which contains little or no mPSDp and that, during development, specific components such as the mPSDp are progressively incorporated into it. We suggest that the thickness of the PSD is proportional to the amount of mPSDp it contains.

Animals↗
PubMed1984

"Seamless" endothelial cells of blood capillaries.

The distribution and number of seamless endothelial cells (SE) were studied in various organs and tissues of rats, rabbits and humans (1) by light microscopy after silver impregnation of the endothelial cell boundaries, (2) by electron microscopy, and (3) in three-dimensional reconstructions of duodenal villi and renal glomeruli. Since SE are situated mostly at branching points, the number of SE is roughly correlated to the number of branchings in the capillary system concerned. SE make up about 50% of all endothelial cells in the renal glomerulum and duodenal villi, and about 30% in the cerebral cortex. However, they rarely occur in bradytrophic tissues. SE have been found exclusively in net capillaries (true capillaries). They seem to be absent in most arterio-venous capillaries (capillary parts of thoroughfare channels), in the capillaries of endocrine glands, as well as in the sinusoidal systems of heart muscle, liver, spleen and bone marrow. It is concluded that SE are developed when tube formation is confined to a single endothelial cell. SE are intercalated most frequently in those capillaries that develop lastly in the terminal vascular bed. The seamless segments are canalized by fusion of intraendothelial vacuoles with pre-existing vascular walls. The existence of SE, confirming the dual structural design of capillary systems, may be used as a detector for net capillaries.

Adipose Tissue↗
PubMed1984

Suprachiasmatic nucleus: numbers of synaptic appositions and various types of synapses. A morphometric study on male and female rats.

The suprachiasmatic nucleus (SCN) of male rats was estimated contain 16 X 10(6) synaptic appositions (unilaterally) or 250 X 10(6) appositions in 1 mm3 tissue of the nucleus with an average of 1404 appositions per neuron. There are significantly fewer synaptic appositions in the suprachiasmatic nucleus of female rats (15 X 10(6) per SCN or 236 X 10(6) in 1 mm3 tissue of SCN with 1264 appositions per neuron on an average). Additionally, numbers of various types of synapses (axo-somatic, invaginated, dendrodendritic and optic) are estimated.

Animals↗
PubMed1983

Asymmetric distribution of catecholamine-containing neuronal perikarya in the upper cervical spinal cord of rat.

Hitherto undescribed catecholamine-containing neuronal perikarya (CCNP) were demonstrated in the white and grey matter of the rat cervical spinal cord. In the white matter they were mainly located in the dorsal part of the lateral funiculus; the number of CCNP in the left lateral funiculus was significantly higher than that in the right and they also extended further caudally. After colchicine treatment, a greater number of CCNP were visible on both sides, the left side again containing more CCNP than the right. In addition, CCNP in colchicine-treated animals were observed further caudally than in untreated animals. In contrast, no lateralization was apparent in the grey matter CCNP.

Animals↗
PubMed1983

Numbers of neurons and astroglial cells in the suprachiasmatic nucleus of male and female rats.

The suprachiasmatic nucleus (SCN) of male and female rats contains about 180,000 neurons per mm3 tissue. As the volume of the SCN (unilaterally) does not exceed 0.064 mm3 in the present preparation it is assumed to contain between 11,000 and 12,000 neurons. The astroglia: neuron ratio is approximately 1:3. The number of neurons and glial cells were obtained by a new approach measuring the areal density of the nuclei on micrographs and their mean volume from three-dimensionally reconstructed nuclei in serial thick sections. Neuronal nuclei tend to be smaller in SCN of male rats, but contain relatively more nucleoli than neuronal nuclei in SCN of female rats.

Animals↗
PubMed1981

Identification and morphometric evaluation of the synapses of optic nerve afferents in the optic tectum of the axolotl (Ambystoma mexicanum).

Ther terminals of retinal afferents in the tectum of the axolotl have been identified ultrastructurally using techniques of horseradish peroxidase-filling and degeneration. The mitochondria in filled structures show a characteristic electron-lucent matrix. After both eyes have been removed, terminals with light mitochondria disappear from the area known to receive an optic input. In this area the presence of light mitochondria is almost always diagnostic of the retinal origin of a bouton. The synapses are similar to those assumed to be of retinal origin in other vertebrates. Detailed morphometric analysis has been carried out on identified optic synapses in the optic tectum of the axolotl.

Ambystoma mexicanum↗
PubMed1980

Constant occurrence of an ipsilateral retino-tectal projection in the axolotl (Ambystoma mexicanum) revealed by horseradish peroxidase tracing.

Cut optic nerves were filled orthogradely with horseradish peroxidase (HRP) to reveal contralateral and ipsilateral retino-tectal projections in the axolotl, by light and electron microscopy. The ipsilateral projection is small but consistently present. It is concentrated in the rostral tectum particularly the dorsomedial and ventrolateral areas. The results are compared with findings in other vertebrates.

Ambystoma mexicanum↗
PubMed1980

Increase in postsynaptic density material in optic target neurons of the rat suprachiasmatic nucleus after bilateral enucleation.

During and after degeneration of the optic nerve afferents in the rat suprachiasmatic nucleus (SCN) postsynaptic density (PD) material is added to existing symmetrical and asymmetrical appositions of non-optic synapses on optic target neurons. If the correlation between thickness of the postsynaptic density and excitatory or inhibitory function of a synapse holds in this nucleus, the change in morphology of synapses could mean that some inhibitory synapses turn into excitatory contacts.

Animals↗