Biomedical subjects

A Seiger

Publications and source records attributed to A Seiger.

At least 127 records · Page 7Linked to original sources

PubMed1984

Intraocular grafting of cultured brain tissue: growth, vascularization and neuron survival in locus coeruleus and cortex cerebri.

Locus coeruleus and cortex cerebri from embryonic (ED 17) and newborn rats were kept 4 days in tissue culture under conditions maintaining organotypic features and then transplanted to the anterior chamber of the eye of adult rats. Vascularization from the host iris was delayed in pre-cultured grafts as compared to directly grafted material. In spite of this, several morphological parameters developed normally. Thus, pre-cultured grafts grew considerably in oculo. Falck-Hillarp histochemistry showed that grafts of cortex cerebri received an adrenergic innervation from the host iris and that locus coeruleus grafts contained central adrenergic neurons capable of innervating a sympathetically denervated host iris. The successful combination of tissue culture and intraocular transplantation should permit the selective advantages of both techniques to be applied to the same tissue pieces, generating new information unobtainable by either method alone.

Animals↗

PubMed1984

Appearance and distribution of neurofilament immunoreactivity in iris nerves.

We have used antiserum raised against neurofilament (NF) protein and indirect immunofluorescence techniques to visualize neuronal structures in rodent, cat, and cow irides. In the adult rat iris a large population of nerve fibers with a nonautonomic distribution show NF-like immunoreactivity. In whole mounts, smooth fluorescent fibers were seen in a fine-meshed plexus from the sphincter margin to the ciliary processes. Superimposed, a sparse pattern of thick meandering axon bundles were seen. Electroblotting and peroxidase immunochemical staining techniques unequivocally showed the presence of all three NF polypeptides in the adult rat iris. Adult mouse irides showed a somewhat sparser pattern of NF-positive nerves than that of the rat. Adult guinea pig irides contained irregular NF-positives fibers and few axon bundles. In cryostat-sectioned cat iris numerous irregularly distributed individual fibers were found, whereas in similarly sectioned cow iris thick NF-positive axon bundles were more numerous. By embryonic day 18 numerous sparse NF-positive axons were seen, and the subsequent gradual increase in both axons in bundles and fine-meshed plexuses of individual fibers produced an appearance similar to that in the adult by 6 days of postnatal age. One week after grafting of irides to the anterior eye chamber, most NF-positive nerves had disappeared from the iris grafts. Sympathetic and parasympathetic denervation of the irides did not influence the distribution of the NF-positive iris nerves. Five days after electrothermal lesion of the trigeminal nerve just distal to its ganglion a large proportion of the NF-positive nerves had disappeared from the iris. All perikarya in the parasympathetic ciliary and most perikarya in the superior cervical sympathetic and in the trigeminal sensory ganglion showed NF immunoreactivity. The present report shows a way to visualize nonautonomic nerve populations in stretch-prepared as well as sectioned irides by immunofluorescence techniques using an antiserum to neurofilament protein.

Animals↗

PubMed1984

Degree of hyperinnervation of area dentata by locus coeruleus in the presence of septum or entorhinal cortex as studied by sequential intraocular triple transplantation.

In situ area dentata receives a sparse noradrenergic innervation from locus coeruleus. Embryonic area dentata co-transplanted with locus coeruleus to the anterior eye chamber receives an abundant ingrowth of nerves from the noradrenergic neurons of the locus graft. We sought to identify restrictive forces acting on coeruleo-dentate axons by arranging for the innervation of area dentata transplants by either entorhinal cortex or septal nuclei transplants prior to locus coeruleus transplantation. The noradrenergic hyperinnervation was not inhibited when locus coeruleus transplants were placed on the opposite side of area dentata from the entorhinal or septal transplant. Noradrenergic innervation of area dentata was restricted when the locus coeruleus transplant was placed in contact with the septal transplant. This inhibitory interaction seemed to take place between the septal and locus coeruleus transplants rather than in the area dentata neuropil. This type of interaction points towards one means by which axonal growth may be inhibited during development or in the adult.

Animals↗

PubMed1984

Enkephalin immunoreactivity in iris nerves: distribution in normal and grafted irides, persistence and enhanced fluorescence after denervations.

The morphology and distribution of nerve fibers showing enkephalin-like immunoreactivity was studied in rat and mouse iris whole mounts. In adult rat, a relatively dense network of varicose fibers was seen throughout the iris. Individual, long, usually smooth fibers were observed running together with non-fluorescent fibers in bundles. Positive nerve fibers were also seen in the ciliary body and the choroid membrane. The fluorescence intensity was normally low. No enkephalin-positive fibers were detected in adult mouse iris. Extirpation or lesioning either one or all the three ganglia known to supply the rat iris with nerve fibers, the superior cervical, the ciliary and the trigeminal ganglia, caused no detectable decrease in amount of enkephalin-positive fibers. However, in irides grafted to the anterior eye chamber of adult recipients, no enkephalin-positive fibers could be observed 2-12 days postoperatively, strongly suggesting that degeneration of these fibers had occurred. When iris grafts were left longer in the eye, nerve fibers with enkephalin-like immunoreactivity reappeared. An increased fluorescence intensity was observed both in the ipsilateral and contralateral iris following extirpation or lesioning all three ganglia and in the ipsilateral iris after extirpation of the ciliary ganglion. Three days after a systemic injection of capsaicin, which causes a permanent disappearance of substance P fibers, the same phenomenon was often observed. This raises the possibility of an interaction between the enkephalin-positive and the substance P fiber systems in the iris.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1984

Ultrastructural and histochemical studies of the rat iris: identified neuronal inputs and supportive glia.

A detailed ultrastructural description was made of the rat iris with special emphasis on nerve fibre populations and their supportive glial cells. The location and identity of different autonomic (sympathetic and parasympathetic) and sensory nerves was further studied by monoamine histofluorescence, acetylcholinesterase histochemistry, immunohistochemistry for substance P and neurofilament, and Linder's silver staining. Schwann cells were defined with immunohistochemical techniques using antiserum to glial fibrillary acidic protein. By correlation of these morphological techniques, the relative proportion of different neuronal inputs and their glial constituents in various parts of the rat iris could be determined. The sympathetic and parasympathetic unmyelinated fibres showed the well-known preferential localization in the posterior part, approaching the smooth muscle cells and chromatophores in the dilator muscle. Larger arterioles in the anterior loose stroma of the iris were in close proximity to sympathetic fibres as indicated by monoamine histofluorescence. Sensory trigeminal nerves were visualized both with Linder's silver staining and neurofilament immunohistochemistry. Large myelinated axon bundles in the anterior part of the iris were clearly seen, and thin unmyelinated fibres were scattered throughout the anterior and posterior parts. Unmyelinated substance P-containing fibres were scattered preferentially in the anterior part of the iris, without close association with blood vessels. Distribution of supportive cells, indicated by means of immunofluorescence with antiserum against glial fibrillary acidic protein, appeared largely similar to that of neurofilament-positive nerve fibres. In the sphincter muscle, cholinesterase-positive nerve fibres were densely packed and adrenergic fibres as well as sensory, neurofilament- and substance P-containing fibres were sparse but distributed throughout the muscle. Accompanying glial cells positive for glial fibrillary acidic protein were also found.

Acetylcholinesterase↗

PubMed1984

Ultrastructural and histochemical evidence for differentiation of intraocular locus coeruleus grafts and invasion of the host iris by central neurites and glia.

Intraocular grafts of dorso-lateral pons, including the noradrenaline-containing cell group locus coeruleus, have been studied with ultrastructural and histochemical techniques. Also, the invasion of neuronal and glial constituents from the grafts into the iris of the host animal is described. In mature brain grafts, aggregates of locus coeruleus neurons were easily discernible with monoamine histofluorescence. These cells had an ultrastructural appearance very similar to that in situ. Numerous somatic spines were frequently associated with synaptic specializations, and monoamine-containing vesicles could be found scattered in the cytoplasm of the locus coeruleus cells. Large neurons of the nucleus tractus mesencephalici nervi trigemini were also found. These cells were neurofilament-immunoreactive just as in situ, and were ultrastructurally characterized by size, distribution of the granular endoplasmic reticulum and abundant large terminals in synaptic contact with their somata and processes. All grafts showed a vigorous astroglial proliferation, evidenced both with immunohistochemistry of glial fibrillary acidic protein and electron microscopy. The astroglial cells were more numerous, larger and with more processes than in adult in situ counterparts. At the attachment site of the brain stem grafts, the iris dilator plate was entirely changed ultrastructurally by a vigorous invasion of neuronal and astrocytic processes. The normal, loose connective tissue stroma of the iris was replaced by layers of almost exclusively central nerve fibres and astrocytes respectively. Monoamine histofluorescence demonstrated an extreme adrenergic hyperinnervation of the iris at the attachment site of the graft, compared to the normal sympathetic ground plexus, whereas neurofilament immunohistochemistry did not visualize any substantial ingrowth of such positive central nerve fibres. Immunohistochemistry of glial fibrillary acidic protein strongly supported the ultrastructural evaluation, showing profound astroglial invasion deep into the iris stroma. Electron microscopic identification of central nerve fibres in the iris showed numerous adrenergic locus coeruleus fibres with small dense-core vesicles. Also, bundles of thin, central, unmyelinated axons were found deep in the iris as well as occasional dendrites. Both large dense-cored and small clear vesicles were encountered in the iris fibres of brain graft origin. Axo-dendritic synaptic specializations formed by locus coeruleus-derived adrenergic fibres were found in the iris.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1984

Neonatal cerebellectomy alters ethanol-induced sleep time of short sleep but not long sleep mice.

The effects of neonatal cerebellectomy on ethanol-induced sleep times in long sleep (LS) and short sleep (SS) mice were investigated. Cerebellectomy did not alter the ethanol sensitivity of LS animals for loss of righting reflex. In contrast, SS mice became more sensitive to alcohol after cerebellectomy. Even so, large differences were still observed between the alcohol-induced sleep times of cerebellectomized LS and SS mice. The data indicate that, while the cerebellum must have a prominant influence on alcohol sleep time in SS animals, this brain structure is not solely responsible for the observed differences in righting reflex sensitivity to ethanol in these two mouse lines. We postulate the existence of noncerebellar central neurons with differential sensitivities to the depressant effects of ethanol in LS and SS mice.

Animals↗

PubMed1984

Neurofilament and glial fibrillary acid protein-related immunoreactivity in rodent enteric nervous system.

Using antisera raised against neurofilaments and the glial fibrillary acidic protein (GFAP) we have examined the appearance and distribution of neurofilament- and GFAP-like immunoreactivity in the enteric nervous system of rat, mouse and guinea-pig. In whole mounts of the external circular and longitudinal muscle layers, including the myenteric plexus, a high number of neurofilament-positive perikarya were visualized both in the ganglia and in the circularly running interconnecting strands in all three species. These cells were large, usually with eccentrically placed nuclei and single, relatively thick neurofilament-positive processes. In addition, in guinea-pig myenteric plexus a small number of cells with multiple processes could be seen. Both in the longitudinal and circular interconnecting strands a large number of thin, smooth, neurofilament-positive fibres were observed. This regular network of ganglia and strands was superimposed on a sparse system of thin, usually individual neurofilament-positive fibres in the underlying circular muscle layer. Cryostat sections revealed neurofilament-positive cell bodies in the submucous plexus, whereas fibres showing neurofilament-like immunoreactivity were observed in all layers of the gut wall, with the exception of the epithelium. In whole mounts including rat and mouse myenteric plexus, a large number of cells and fibres showing GFAP-like immunoreactivity were visualized. The GFAP-positive cells were smaller and more numerous than the neurofilament-positive ones. They were present both within the ganglia and in the interconnecting strands. Several short fluorescent processes could frequently be seen emanating from the cell body. Both the strands and the ganglia contained a high number of thin, GFAP-positive fibres. Fluorescent fibres and cells were also observed in the circular muscle layer. In sections of rat and mouse small intestine, cells were observed throughout the gut wall, with the exception of the epithelium. Double labelling experiments clearly showed that neurofilament- and GFAP-positive cells represented separate cell populations. Furthermore, GFAP-positive cells and fibres outlined the neurofilament-positive perikarya. It is thus likely that the GFAP-positive cells represent enteric glial cells. The pre- and postnatal development of neurofilament- and GFAP-like immunoreactivity was studied in whole mounts from rat embryos and pups. Furthermore, the presence of neurofilament and GFAP-positive fibres was observed in whole mount preparations of rat and mouse mesenterium.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1984

Structural and functional impairment of adrenergic input to intraocular cerebellar grafts during thyroid hormone deficiency.

Embryonic cerebellae were transplanted to the anterior eye chamber of normal and thyroidectomized adult rats and were left in the eye to mature for 5 weeks. The cerebellar grafts received adrenergic innervation from the sympathetic ground plexus of the host iris. The density of adrenergic fibers innervating the grafts was reduced by approximately 50% in all thyroidectomized groups, without any effect on the fluorescence intensity or the morphology of individual nerve fibers. The reduction in adrenergic ingrowth was entirely prevented in grafts raised in similarly thyroidectomized recipients, which were substituted daily with thyroxine (100 micrograms/kg, SC). Electrophysiologically, there was no difference between the groups in terms of spontaneous firing rate of Purkinje neurons, recorded extracellularly from cerebellar grafts. However, there was a 10-fold decrease in the potency of catecholamines to inhibit the spontaneous neuronal activity in thyroidectomized hosts as compared to controls when applied either locally by micropressure ejection or by superfusion. Similar to the observed histologic changes in catecholamine innervation, the abnormal responsiveness of hypothyroid cerebellar neurons to locally applied catecholamines could be prevented by daily substitution with thyroxine in these animals. It is thus concluded that there is both structural and functional impairment of the adrenergic innervation of intraocular cerebellar grafts that underwent development under conditions of thyroid hormone deficiency.

Adrenergic Fibers↗

PubMed1984

Chronic lead exposure of the developing brain: electrophysiological abnormalities of cerebellar Purkinje neurons.

This manuscript reviews our recent research concerning electrophysiological effects of chronic low-level lead exposure on developing brain. We found that, although growth, survival and histological organization of in oculo cerebellar grafts appear normal after perinatal exposure to blood lead levels of 450 to 550 micrograms/liter, the physiological activity of Purkinje neurons in these lead-treated grafts is abnormally low after discontinuation of lead treatment. On the other hand, chronic low-level lead exposure postnatally via systemic injections or perinatally via the drinking water did not alter in situ cerebellar Purkinje cell activity. Moderate systemic doses (2 mg/kg) did cause a persistent slowing of Purkinje neuron firing rates; however, this effect was much smaller than in intraocular cerebellar grafts. The slowing may be mediated by lead actions on various transmitter systems. We have found that chronic lead induces catecholaminergic neurons to hyperinnervate target areas. Perhaps this hyperinnervation is initiated by the postsynaptic lead-induced blockade of the electrophysiological effects of norepinephrine which we have previously observed in the cerebellum in situ and in cerebellar grafts in oculo.

Action Potentials↗

PubMed1984

Glial fibrillary acidic protein-like immunoreactivity in the iris: development, distribution, and reactive changes following transplantation.

Using immunohistochemistry with antisera raised against the glial fibrillary acidic protein (GFA), we have studied the appearance and distribution of GFA-like immunoreactivity in whole mounts of rodent iris and in sectioned cat and cow iris. In the adult rat iris, a dense plexus of GFA-positive fibers was seen in both the dilator plate and the sphincter. The fluorescent fibers formed large meandering bundles and a dense irregular network of thinner fibers. In the sphincter, mainly thinner fibers were seen. Thin fibers were also seen winding around blood vessels in the dilator plate. In adult mouse iris, the GFA-positive fibers had a quite different distribution with a few radially oriented fiber bundles superimposed on a more regular network of thinner fibers. Adult guinea pig irides showed still another pattern of GFA-positive fibers with a low number of bundles and thinner fibers forming a sparse irregular network. In thicker fiber bundles of all three rodent species, as well as at branching sites of the thinner fibers, negative or weakly fluorescent swellings surrounded by GFA-like immunoreactivity were present. These structures probably represent the cellular origin of the GFA-positive fibers. Thick, strongly fluorescent fiber bundles, as well as numerous thinner fibers, were seen in sections of cat and cow iris. Prenatally, fibers were visualized at embryonic day 18 in the rat. In these irides as well as in irides from 21-day-old embryos and 1-day-old pups, most fibers were organized in a gradually increasing system of thin meandering fiber bundles that showed limited branching. At postnatal day 6, a more mature network of thinner fibers had developed between the now more numerous fiber bundles. No obvious increase or decrease in the amount of GFA-positive fibers was seen in irides grafted to the anterior eye chamber of adult rat recipients examined 1 and 6 days after grafting. However, in these irides, as well as in the host irides, strongly fluorescent spider-like cells with short branching processes and a negative nucleus were seen. These cells were more numerous and more strongly fluorescent in grafted irides as compared to recipient irides and in the 6-day iris grafts as compared to the 2-day grafts. In all probability, the GFA-positive fibers and cells forming a network in adult irides from different species and in embryonic and grafted rat irides represent Schwann cells and their processes. The cellular origin of the spider-like cells in the iris grafts is less clear.

Animals↗

PubMed1983

The neurological mutation staggerer is expressed in embryonic cerebellar transplants matured in the anterior eye chamber of normal mice.

Transplantation of embryonic day 11 cerebellar anlage to the anterior eye chamber of wildtype recipient mice was used to investigate the intrinsic character of the cerebellar mutation staggerer. One phenotypic expression of the staggerer gene in vivo is a postnatal degeneration of cerebellar granule cells. After 43 days of in oculo development cerebellar buds from homozygous staggerer embryos similarly develop into nervous tissues lacking granule cells. On the other hand, transplants of wildtype cerebellar anlagen contain a large population of granule cells. Both the staggerer and wildtype cerebellar transplants had a survival of large neurons, characteristic of Purkinje, Golgi and deep nuclei cells.

Animals↗

PubMed1983

The level of nerve growth factor (NGF) as a function of innervation. A correlation radio-immunoassay and bioassay study of the rat iris.

A two-site radio-immunoassay for beta NGF demonstrated 5-10 pg of NGF in the normal, adult rat iris. Ciliarectomy or sympathectomy did not significantly alter the amount of NGF after 10 days. However, denervation including all sensory axons (stereotactic lesion distal to the trigeminal ganglion) increased the level to about 100 pg of NGF. Total denervation resulting from homologous transplantation of the iris gave a similar increase after only 2 days. Fibre outgrowth responses evoked by corresponding iris explants in an NGF bioassay supported the results and suggested in addition that sympathetic denervation may cause a moderate transient increase in NGF after 3 days. It seems that sensory nerves in particular influence the level of NGF in a terminal field, either by a high capacity for uptake and removal of NGF or by exerting a negative feed-back on the production or processing of this growth factor.

Animals↗

PubMed1983

Cerebellar role in the differential ethanol sensitivity of long sleep and short sleep mice.

Two lines of mice have been selectively bred for differential sleep time responses to ethanol. Long sleep (LS) mice sleep over an order of magnitude longer than short sleep (SS) mice. We have found that these behavioral sensitivities are also reflected in the responsiveness of cerebellar Purkinje neurons in those two mouse lines in situ and in intraocular cerebellar brain grafts. The differential sensitivity of Purkinje cells to the depressant effects of ethanol appears to be an intrinsic property of the cerebellum and shows a high genetic correlation with the hypnotic effects of this drug as measured by sleep time. Sleep time studies of neonatally cerebellectomized LS and SS mice indicate that the cerebellum is not the primary determinant of the sensitivity of these mice to the soporific effects of ethanol. The sleep time of SS, but not LS mice, was altered by cerebellectomy suggesting that the cerebellum has different influences on the ethanol-induced loss of righting reflex in these two mouse lines.

Animals↗

PubMed1983

Trophic effects of brain areas on the developing cerebral cortex: I. Growth and histological organization of intraocular grafts.

Trophic interactions during development of brain regions were examined in rats using intraocular grafts of central nervous tissue. The increase in volume of transplanted fetal parietal cerebral cortex, as measured through the cornea, was markedly augmented by the presence of several different previously grafted CNS areas such as locus coeruleus, tectum, or cerebral cortex. DNA measurements and histological examinations suggested that this increased volume was due both to hyperplasia and hypertrophy. Previous grafts of iris, in contrast, did not significantly alter the final size of subsequently grafted cortex pieces. Contact between the two transplants was found to be critical in eliciting the trophic response. Growth-stimulated cortical grafts had a better organized cyto-architecture with larger neurons, including typical pyramidal cells, more neuropil, a lower cell density, and a more organotypic distribution of the cell bodies than non-stimulated controls. The experiments thus demonstrate a profound effect of adjacent neural tissue on development of neocortex. It is concluded that trophic interactions upon brain development can be revealed by sequential intraocular grafting.

Animals↗

PubMed1983

Survival and growth of neurons with enkephalin-like immunoreactivity in fetal brain areas grafted to the anterior chamber of the eye.

Areas of fetal rat brain and spinal cord known to contain enkephalin-like immunoreactive cell bodies and/or terminal fields were transplanted to the anterior chamber of the eye of adult rats. Enkephalin-like immunoreactive neurons survive and produce an enkephalin-like immunoreactive fiber network within grafts of spinal cord, ventral medulla oblongata, ventrolateral pons, tectum, locus coeruleus, substantia nigra and the areas containing columna fornicis and globus pallidus. Although single intraocular grafts of neocortex do not apparently contain enkephalin-like immunoreactive fibers, such grafts contain a variable amount of sparsely distributed enkephalin-like fibers when sequentially grafted in oculo with either locus coeruleus or spinal cord. Combinations of locus coeruleus and globus pallidus contained a rich enkephalin fiber network in the locus coeruleus part and a sparse innervation of the globus pallidus part. We conclude that enkephalin-like immunoreactive neurons in small areas of fetal rat brain can be successfully transplanted to the anterior chamber of the eye. They are able to survive and develop to maturity in complete isolation from the rest of the brain. In general, the enkephalin-like immunoreactive fiber density in the various single grafts approximated that of their brain counterparts in situ. Fiber formation can be reinitiated in mature enkephalin-like immunoreactive neurons by addition of new brain target areas. Thus, the technique permits establishment of isolated, defined enkephalin systems and pathways accessible to functional analysis.

Animals↗

PubMed1983

Modulatory interactions between enkephalin and catecholamines: anatomical and physiological substrates.

The anatomical and electrophysiological basis of enkephalin-catecholamine interactions was studied in the central nervous system of the Sprague-Dawley rat. Sections of fetal rat brain were treated alternatively with antibodies raised against enkephalin or tyrosine hydroxylase (EC 1.14.16.2). Enkephalinergic fibers were found to innervate almost all brain areas known to contain catecholamine cell bodies or terminal fields. The possible electrophysiological correlates of such an overlap in enkephalin and catecholamine terminal fields was investigated in frontal neocortex. Parenteral administration of antipsychotic agents known to block catecholamine receptors, such as spiroperidol, alpha-flupenthixol, and (+)-butaclamol, reversibly antagonized enkephalin-induced depressions of neuronal activity. The biochemically inactive isomers of these antipsychotics, beta-flupenthixol and (-)-butaclamol, manifested no such activity. Unilateral lesions of the catecholaminergic projections to frontal cortex produced by interstitial injection of 6-hydroxydopamine resulted in an ipsilateral decrease in enkephalin efficacy and in an elimination of the antagonisms of enkephalin depressions by antipsychotic agents. It is hypothesized that catecholamines may act as modulators to augment responsiveness to peptides such as enkephalins.

Animals↗

PubMed1983

Enkephalin-like immunofluorescence in nerves of the rat iris following systemic capsaicin injection.

A network of nerve fibers with an enkephalin-like immunoreactivity was demonstrated in rat iris whole mounts. Systemic administration of capsaicin in doses which caused partial (5 mg/kg) or complete (50 mg/kg) disappearance of substance P-containing fibers in the iris did not cause degeneration of enkephalin-positive nerve fibers. The enkephalin-immunoreactive network seemed intact also after a capsaicin dose of 250 mg/kg. In fact, the fluorescence intensity of the nerve fibers showing enkephalin-immunoreactivity was often increased three days after a capsaicin injection in a dose of 50 mg/kg. The mechanism behind this effect of capsaicin remains to be elucidated, but could be due either to a direct effect on the enkephalin-positive nerves or involve the disappearance of substance P nerves and/or a simultaneous inflammatory response. However, an increased fluorescence intensity of the enkephalin-immunoreactive fibers was sometimes seen also without capsaicin treatment.

Animals↗