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Biomedical subjects

L Olson

Publications and source records attributed to L Olson.

At least 451 records · Page 25Linked to original sources
PubMed1977

Mnoaminergic reinnervation of the transected spinal cord by homologous fetal brain grafts.

It was shown that immature noradrenaline (NA) containing cells from locus coeruleus and 5-hydroxytryptamine (5-HT) containing cells from the raphé nuclei could survive homologous transplantation to adult spinal cords that were adrenergically denervated by a transverse lesion. Fully viable transplants were found at all postoperative time studied (0.5-4 months) and both NA and 5-HT cell bodies were found to produce a network of nerve terminals in the gray matter and axons in the white matter that reached cranially and caudally at least 10 mm from the cell bodies. The nerve fibers had a normal varicose appearance. It was concluded that NA and 5-HT axons can grow in adult lesioned white matter.

Animals↗
PubMed1977

Electrophysiology and cytology of hippocampal formation transplants in the anterior chamber of the eye. I. Intrinsic organization.

Pieces of the immature hippocampal formation were transplanted to the anterior chamber of adult rat eyes. The transplants survived, became vascularized from the host irides, and proliferated extensively in proportion to the age of the donor fetus. These transplants mature and develop an adult organization in oculo. This maturation proceeds unimpaired in the absence of gyrus dentatus or after superior cervical ganglionectomy.

Animals↗
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

On spinal noradrenaline receptor supersensitivity: correlation between nerve terminal densities and flexor reflexes various times after intracisternal 6-hydroxydopamine.

The noradrenaline (NA)-dependent hindlimb flexor reflex that can be elicited by pinching the foot of acutely spinalized rats given nialamide-DOPA or clonidine was evaluated different time intervals (14 days-6 months) after intracisternal injections of 6-OH-dopamine (6-OH-DA) and correlated to the degree of bulbospinal catecholamine (CA) denervation as seen by Falck-Hillarp fluorescence histochemistry. Six and 14 days after 6-OH-DA, when almost all NA nerve terminals of the spinal cord had degenerated, the NA receptors where supersensitive to stimulation with clonidine as evidenced by an increased flexor reflex. This supersensitivity gradually disappeared as new nerve terminals were formed in the grey matter of the spinal cord during the following 3-6 months. The supersensitivity phenomenon 14 days after 6-OH-DA could also be demonstrated by L-DOPA given to animals pretreated with 100 mg/kg nialamide. Using this relatively low dose of nialamide, almost no reflex response was seen in the control group. Using a higher degree of monoaminoxidase inhibition (nialamide 200 mg/kg) also non-supersensitive, NA receptors became maximally stimulated. Therefore, 6-OH-DA treated rats now showed a weaker reflex than controls, the reflex response being directly correlated to the number of nerve terminals present that could form NA from the precursor. Using 5,6-dihydroxytryptamine, which selectively destroys 5-hydroxytryptamine (5-HT) nerves, it was shown that the flexor reflex changes were specifically related to the NA nerves and unchanged by the simultaneous presence or absence of 5-HT nerve terminals. This was further supported by the finding of a correlation between amount of nerve terminals and flexor reflex responses in individual animals, especially at longer survival times both in the clonidine and the nialamide-DOPA experiments.

Animals↗
PubMed1976

Fluorescence-microscopical demonstration of a population of gastro-intestinal nerve fibres with a selective affinity for quinacrine.

A population of nerve fibres in the gastro-intestinal tract of mice showing a high affinity for quinacrine was revealed by fluorescence microscopy. Similar results were obtained in rats and guinea pigs. Whole-mounts of sheets of the smooth muscle layer following incubation in 10(-6)-10(-7) M quinacrine for 15-60 min revealed fine fluorescent varicose nerve fibers in the myenteric plexus of Auerbach both around nerve cell bodies and in the interconnecting strands. Many fibers were also present between the strands of the plexus, especially running parallel to the circular muscle layer. Such fibers were not seen in similarly quinacrine-incubated irides. A proportion of the cell bodies in Auerbach's plexus also showed quinacrine accumulation. These cells were apparently smaller neurons, sometimes with fluorescent processes. Intraperitoneal injections of quinacrine failed to demonstrate nerve fibers, but some cell bodies in Auerbach's plexus were positive. Subsequent paraformaldehyde treatment for monoamine visualization showed persistent adrenergic nerve terminals in the intestine and iris. These nerves seemed to be fewer and had a more yellow fluorescence than normally. The identity of the quinacrine-positive fibers is discussed with respect to recent suggestions that "purinergic", substance P, enkephalin, and somatosin-containing nerves, in addition to adrenergic and cholinergic nerves, are present in the gut wall.

Animals↗
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↗