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Biomedical subjects

A Seiger

Publications and source records attributed to A Seiger.

At least 181 records · Page 10Linked to original sources
PubMed1977

Pineal serotonin metabolism in non-innervated perinatal glands before and after intraocular maturation: supersensitivity of adrenoceptors that have never been innervated.

Transplantations were made of fetal pineal glands (crown-rump length, CRL, 19-30 mm) or pineal glands from adult male rats to the anterior chamber of the eye of the rat. Studies were performed with regard to the importance of the age of the donor animal (and thereby the degree of maturation and innervation of the gland to be transplanted) for the possible development of denervation supersensitivity. The transplants were cultured in a medium containing 14C-serotonin. Increased production of 14C-N-acetylserotonin (NAcS) was used as the main criterion for beta-adrenergic stimulation. 4 experimental groups were obtained by transplanting fetal or adult pineals to intact or sympathetically denervated eyes. In all 4 groups beta1-stimulation (KWD 2033 10(-6) M) increased 14C-NAcS formation. The response to beta-stimulation was significantly higher in denervated fetal pineal transplants than in innervated fetal transplants and thus demonstrating beta-receptor supersensitivity. It was concluded that a) the ability to respond to beta-adrenoreceptor stimulation with increased 14C-NAcS formation develops between the 18th and 20th day of gestation, b) transplants derived from fetal as well as from adult rats can respond to beta-adrenergic stimulation, c) this sensitivity also develops in oculo in transplants that at the time of transplantation lacked the capacity to increase their 14C-NAcS formation in response to treatment with beta-agonist, d) denervation supersensitivity occurs in fetal transplants that became mature in sympathetically denervated eyes.

Animals↗
PubMed1977

Growth of locus coeruleus neurons in oculo independent of simultaneously present adrenergic and cholinergic nerves in the iris.

Fetal brain tissue pieces containing locus coeruleus (LC) neurons were grafted to the anterior eye chamber alone or together with other grafts (irides, sympathetic ganglia or additional LC) in the presence of the sympathetic and parasympathetic part of the autonomic ground plexus of the iris. Specimens were analyzed with quantitative fluorescence microscopy and uptake of [3H]metaraminol. LC neurons were shown to grow independently of the simultaneous presence of sympathetic fibers in oculo in the following three experimental situations: 1. Fetal LC grafted to normal eyes, analyzed after cessation of the production of the halo of fluorescent fibres on the host irides. 2. Maturated LC neurons in which growth is reinitiated by addition of an iris transplant which becomes completely innervated. 3. Fetal LC neurons placed on or opposite to iris transplants that in turn were introduced into the eye chamber 1 month before. All LC grafts produced halos of fluorescent fibres on both host irides and iris transplants in a restricted zone. Fetal LC grafts produced fluorescent nerve fibres on host irides independent of the removal of the parasympathetic fibres in the irides. Fetal LC grafts were not significantly inhibited in their fibre production on irides where maturated LC grafts had already formed a halo of densely packed fluorescent fibres. When two fetal LC grafts were introduced simultaneously into the same eye chamber both were able to produce fluorescent fibres together on the host iris. Sympathetic ganglion transplants formed normal looking adrenergic plexuses on host irides that were already carrying LC grafts with halos of fluorescent fibres. In conclusion, the fibre production of LC neurons in oculo is independent of the presence of sympathetic, and probably also parasympathetic, and maturated central NA nerves.

Adrenergic Fibers↗
PubMed1976

Brain tissue transplanted to the anterior chamber of the eye. 4. Drug-modulated transmitter release in central monoamine nerve terminals lacking normal postsynaptic receptors.

Small pieces of fetal rat brain selected to contain a high number of noradrenaline (NA), dopamine (DA), or 5-hydroxytryptamine (5-HT) neuroblasts were transplanted to the anterior chamber of the eye of adult rats. The sympathetic ground plexus of the host iris was removed by superior cervical ganglionectomy so that transmitter mechanisms of the different central monoamine fibers innervating the iris could be selectively studied after intraocular maturation. Such irides, containing NA, DA, or 5-HT nerve terminals were incubated with radiolabelled transmitters and then stimulated by an electrical field while superfused, to investigate the spontaneous and stimulation-induced release of amine, both in drug-free buffer and buffer containing drugs acting on monoamine receptors. The central monoamine neurons of all three types were able to take up exogenous amines and release them upon stimulation by an electrical field, in much the same way as corresponding nerves in situ in slices of cerebral cortex (NA, 5-HT) or olfactory tubercle (DA). The alpha-adrenergic receptor blocking agent phentolamine increased the stimulation-induced release of 3H-NA from central NA fibers on the iris significantly. The dopamine receptor stimulating agent apomorphine decreased the stimulation-induced release of 3H-DA from central DA fibers on the iris. Pimozide, a DA receptor blocking drug tended to increase the 3H-DA release. The 5-HT receptor stimulating agent ergocornine tended to reduce the stimulation-induced release of 3H-5-HT from central 5-HT fibers on the iris. It was concluded that all three types of central monoamine nerve fibers develop essentially normal transmitter storage and release mechanisms also in an environment completely devoid of normal postsynaptic receptors. The drug experiments add strong support to the view that there are presynaptic monoamine receptors ("autoreceptors") able to modulate transmitter release present on the monoamine nerve terminals.

Animals↗
PubMed1976

Beating intraocular hearts: light-controlled rate by autonomic innervation from host iris.

The sympathetic adrenergic ground plexus of the rat iris is able to innervate whole embryonic hearts transplanted to the anterior eye chamber. The transplants beat continuously from the time of transplantation and for at least five months, initially at 150-200 beats/min, and later approximately 250 beats/min. From seven days postoperatively onwards increased light to the eye produced deceleration while decreased light produced acceleration of the transplants. The rate changes coincided with changes in pupil diameter. Topical atropine reduced the light dependent rate variations of the transplants, especically the dramatic decrease in rate at white light. Waking stress caused a large rate increase. The "waking-effect" was strongly reduced by sympathetic decentralization and completely abolished by propranolol. The high rate seen in red light was decreased to the low rate of white light by decentralization. Isoprenaline restored red light rate levels in the decentralized transplant. The intraocular heart thus receives a dual functional autonomic input from the host iris and becomes a sensitive monitor of an autonomic nervous activity that can easily be varied at will in a physiological way by changing the light influx to the eye.

Adaptation, Physiological↗
PubMed1976

N-acetyltransferase and hydroxyindole-O-methyltransferase activity in intraocular pineal transplants: diurnal thythm as evidence for functional sympathetic adrenergic innervation.

Immature rat pineal grafts were transplanted bilaterally to the anterior eye chamber of adult male rats. The transplants matured and became sympathetically innervated from the host iris and synthesized 5-hydroxytryptamine as revealed by fluorescence histochemistry. Transplants were used to investigate whether the newly formed nerve terminals were functional and thus could induce a rhythm in pineal N-acetyltransferase (NAT) enzyme activity and hydroxyindole-O-methyl transferase (HIOMT) enzyme activity. The in situ pineal glands from the recipient animals exhibited NAT and HIOMT levels and diurnal variations of enzyme activities no different from control rats without transplants. Sympathetically innervated transplants showed lower NAT enzyme activity than the in situ pineals but did yield a highly significant increase in darkness NAT activity as compared to light NAT activity (20:1). Sympathetically denervated transplants showed a much smaller rise in darkness NAT enzyme activity as compared to light values (1.8:1) but the rhythm was still statistically significant (p less then 0.01). Sympathetically innervated transplants had a higher HIOMT activity in darkness than in light (2.7:1)9 The HIOMT activity of the sympathetically denervated grafts was invariably low. Protein contents of transplants were found to be significantly lower than in situ pineal protein content but failed to show a diurnal variation.

Acetylserotonin O-Methyltransferase↗
PubMed1976

Locus coeruleus: fibre growth regulation in oculo.

Locus coeruleus (LC) neurons from fetal and young rats survived homotransplantation to the anterior eye chamber. The outgrowth of LC fibres on sympathetically denervated host irides could be quantified precisely using Falck-Hillarp fluorescence histochemistry and [3H]metaraminol uptake. Fetal LC neurons survive better than postnatal ones and produced fibres for one month in oculo: by then )0-50% of the area of the host iris was innervated. After intraocular maturation of the CNS graft the fibre amount on the iris remained constant. Introduction of an iris graft contacting a mature LC graft immediately stimulated the LC to a complete (100%) reinnervation of the iris graft without any change of the restricted innervated area already formed on the host iris. The outgrowth of LC fibres on irides was not influenced by the presence or absence of sympathetic or parasympathetic nerves or by nerve growth factor or its antiserum. We conclude that an iris transplant offers a specific growth stimulus for the LC graft and that this stimulus is not present in the normal host iris. The nature of this stimulus is unknown but may involve the sensory denervation of the iris graft.

Animals↗
PubMed1975

Brain tissue transplanted to the anterior chamber of the eye: 3. Substitution of lacking central noradrenaline input by host iris sympathetic fibers in the isolated cerebral cortex developed in oculo.

Fetal parietal cerebral cortex was homologously transplanted to the anterior chambers of the eyes of adult rats. The transplants got vascularized, proliferated, as measured by in vivo stereoscopic inspections, and differentiated into brain tissue similar to cortex cerebri in situ and survived for long times, greater than 41/2 months. Fibers from the intact sympathetic adrenergic ground plexus of the iris were able to innervate the transplants in an organotypic way regarding fluorescence morphology, pattern of distribution of the nerve terminals and, to a certain extent, density of innervation, the only variable parameter being density of innervation. Thus, in unpretreated or MAO inhibited transplants only rather few to scattered terminals could be found, while after preincubation in 10(-5)M alpha-methyl-noradrenaline the number of visible terminals was normal or slightly less than normal, as compared to cortex cerebri in situ. When superior cervical ganglia (SCG) were transplanted together with fetal cortex tissue to sympathetically denervated eyes the ingrowth in the cortex tissue was similar to that after single cortex transplantation combined with 5 day old SCG, while a marked hyperinnervation was encountered when combined with adult SCG. It is concluded that the developing cortex cerebri, deprived of its normal CNS source of adrenergic nerves, is able to receive sympathetic adrenergic nerves from the iris in an organotypic way upon transplantation to the anterior chamber of the eye.

Animals↗
PubMed1975

Formation of a functional adrenergic input to intraocular cerebellar grafts: ingrowth of inhibitory sympathetic fibers.

The intraocular transplantation technique was used to study the ingrowth of peripheral sympathetic adrenergic nerves from the iris into transplants of fetal rat cerebellum, and the possible function of these nerves. The transplants, grown in oculo for one-half to eight months, were analyzed by fluorescence histochemistry and electrophysiological techniques. Peripheral sympathetic adrenergic fibers from the iris were able to grow into the cerebellar transplants and arborize in a pattern similar to that in situ, appearing in all three cortical layers and the noncortical areas of the transplants. The density of visible nerves without pretreatment and after preincubation in 10(-6) or 10(-5) M alpha-methylnorepinephrine was comparable to mature rat cerebellum. The spontaneous discharge of the Purkinje cells in oculo was inhibited by microiontophoresis of norepinephrine (NE) and amphetamine in sympathetically innervated, as well as sympathectomized transplants denervated by ganglionectomy. The NE response was blocked by the adrenergic beta-receptor blocker MJ-1999. GABA also inhibited the Purkinje cell activity while glutamate accelerated the discharge. Parenteral amphetamine inhibited Purkinje cell activity in sympathetically innervated transplants, but was ineffective in denervated transplants. The Purkinje cell spontaneous activity was inhibited by electrical stimulation of the NE fiber input through the cervical sympathetic trunk. This inhibition could be antagonized by parenteral reserpine or the beta-adrenergic antagonist propranolol. The responses of the Purkinje cells within the transplants to drugs and transmitters mimic those of the adult rat in situ. In view of the fluorescence histochemical evidence for an ingrowth of peripheral sympathetic adrenergic fibers into the cerebellar transplants, and the results of stimulating the sympathetic trunk, it is suggested that peripheral adrenergic fibers may be able to establish functional connections with the Purkinje cells similar to the cerebellar adrenergic synapses normally formed in situ by fibers from the locus coeruleus.

Amphetamine↗
PubMed1975

Brain tissue transplanted to the anterior chanber of the eye: 2. Fluorescence histochemistry of immature catecholamine- and 5-hydroxytryptamine neurons innervating the rat vas deferens.

Small pieces of the wall of the rat vas deferens were homologously transplanted to the anterior chamber of the eye together with small pieces of embryonic brain stem containing either developing noradrenaline (NA) cells of the locus coeruleus or 5-hydroxytryptamine (5-HT) neurons of the developing raphe system. The eyes of the recipients were sympathetically denervated. The double transplants became rapidly vascularized from the host iris. After 3 1/2 months the irides, together with their two transplants were analyzed by Falck-Hillarp fluorescent microscopy. Both the NA and the 5-HT neurons had survived and matured in the eye. Fluorescent varicose nerve terminals of the NA and 5-HT type respectively were found in all three potential receptor areas, i.e. within the CNS transplants, in the host irides and in the vas deferens transplants. In the latter, the newly formed monoamine nerve terminals arborized mainly within a well developed smooth muscle layer. The density of such new fibres was higher than or similar to that of the normally present sympathetic plexus in areas of the transplant close to the CNS transplant and lower in areas at a distance from the CNS transplant. It is concluded that immature central NA and 5-HT fibres are able to grow simultaneously into different types of sympathetically denervated smooth muscle tissues to form networks of fibres in the receptor organs resembling the normal sympathetic innervation.

Animals↗