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Biomedical subjects

E Mugnaini

Publications and source records attributed to E Mugnaini.

At least 127 records · Page 7Linked to original sources
PubMed1975

The structural basis for electrotonic coupling in the avian ciliary ganglion. A study with thin sectioning and freeze-fracturing.

Each "ciliary" neurone in the ciliary ganglion of adult birds receives its innervation from a single myelinated fibre of the oculomotor nerve by means of a dual mode of synaptic action, electrical and chemical. The preganglionic fibre branches repeatedly around the postganglionic axon but the extra-cellular compartment is large. The preterminal fibres, most of which are unmyelinated, end with large boutons on the axon hillock, a few on short dendrites and on the portion of the perikaryon of the ciliary neurone from which the axon emerges. This synaptic apparatus is enveloped by a glial sheath, mainly consisting of satellite cell bodies and loose myelin lamellae. The nonsynaptic portion of the ciliary perikaryon is covered by a sheath consisting mainly of compact myelin. The ciliary neurone has an initial axon segment like that of C.N.S. neurones. The area of each neurone apposed to boutons measures about 16,000 mum2. Approximately 9 percent is specialized for chemical transmission and 0.17 percent for electrical transmission. Each neurone has about 280,000 gap junctional particles. Assuming that each particle represents one channel, the electrical resistance provided by these junctions is estimated to be of the order of 100 k omega. The electrical coupling between the preganglionic fibre and the ciliary neurone may therefore be of resistive nature.

Animals↗
PubMed1975

Nerve growth factor induces volume increase and enhances tyrosine hydroxylase synthesis in chemically axotomized sympathetic ganglia of newborn rats.

Concomitant daily treatment of newborn rats for a 2-week to 1-month period with 10 mug/g of body weight of nerve growth factor and 100 mug/g of body weight of 6-hydroxydopamine produces in the cell bodies of adrenergic neurons the characteristic effects of the growth factor but in the nerve terminals the characteristic effects of 6-hydroxydopamine. The dual opposite effects result in a striking volume increase of sympathetic ganglia which far exceeds that produced by nerve growth factor alone. The selective induction of tyrosine hydroxylase [L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating), EC 1.14.16.2] in these chemically axotomized adrenergic neurons is even more pronounced than that produced by nerve growth factor alone in intact neurons.

Animals↗
PubMed1975

Light and electron microscopic studies on the excessive growth of sympathetic ganglia in rats injected daily from birth with 6-OHDA and NGF.

Concomitatn daily treatment of rats immediately after birth with NGF and 6-OHDA for a period of 2-4 weeks, results in a volume increase of sympathetic ganglia of thirty times that of controls and 2.3 that of NGF treated littermates, at three weeks of age. Studies at the light, fluorescent and electron-microscope, showed that this overall enlargement is due to increase in size and number of sympathetic neurons and, to an even higher extent, to profuse production and branching of collaterals from postganglionic adrenergic nerve fibers. These axonal collaterals find accomodation inside the ganglia where they displace nerve cells and build a thick fibrillar capsule around the same ganglia. The survival in excellent conditions of sympathetic nerve cells treated with NGF but prevented by 6-OHDA from establishing anatomical and functional connections with their end organs, suggests that the growth factor find access to its target cells through the plasms membrane which envelops the cell perikarya. The extraordinary production of collaterals by chemically axotomized sympathetic fibers, brings to light growth potentialities of these fibers which materialize only upon disconnection of their endings from peripheral tissues. These results uncover a new facet of the interaction between nerve fibers and innervated tissues.

Animals↗
PubMed1974

Adrenergic innervation of the parasympathetic ciliary ganglion in the chick.

The chick ciliary ganglion receives a nonvascular symathetic innervation in addition to the well-known cholinergic one; fluorescent, varicose adrenergic fibers form pericelluar baskets. Adrenergic fibes were identified electron microscopically in ganglia fixed with potassium permanganate. The fibers degenerate after injection of 6-hydroxydopamine. No true synaptic relationships involving adrenergic varicosities and ganglion cells or cholinergic terminals were demonstrable. The distribution of the adrenergic fibers suggests a kind of "distance à synapse" with the choroidal cells or with the preganglionic fibers (or both). The adrenergic innervation might provide a modulation of the cholinergic transmission.

Animals↗
PubMed1972

Synaptic transmission at single glomeruli in the turtle cerebellum.

We have recorded from the granular layer of the turtle cerebellum extracellular unitary potentials that appear to reflect pre- and postsynaptic events at the synapse between a single swelling of a mossy fiber and the dendritic tips of several granule cells. The presynaptic component is an all-or-none potential. It can be directly activated by spinal stimulation and is unaltered by repetitive activity or by high concentrations of magnesium. The postsynaptic component is a graded potential. It follows the presynaptic component by approximately 1 millisecond and is depressed by repetitive activity and by high concentrations of magnesium. The recording of large potentials produced by the flow of postsynaptic current within a single glomerulus suggests powerful transmission. Electron micrographs demonstrate large cerebellar glomeruli in the turtle and a substantial accumulation of mitochondria in the dendritic tips of granule cells.

Action Potentials↗
PubMedDate not supplied

Two-color immunohistochemistry for dopamine and GABA neurons in rat substantia nigra and zona incerta.

Dopaminergic and GABAergic neurons were visualized in the same section of rat substantia nigra (SN) and zona incerta (ZI) by a two-color double immunoperoxidase procedure or by double immunofluorescence. Rabbit antiserum to tyrosine hydroxylase (TH) and sheep antiserum to glutamic acid decarboxylase (GAD), markers for catecholaminergic and GABAergic neurons, respectively, were used as primary antisera. These techniques rely on species difference of primary antisera and non-crossreactivity of linking antisera. In normal and colchicine pretreated rats, SN pars compacta (SNC), SN pars lateralis (SNL), and ZI pars medialis (area A13) contained high densities of TH-positive neurons. Relatively few TH-positive cells were scattered in SN pars reticulata (SNR) and ZI pars lateralis (ZIL). In normal rats, GAD-positive boutons were more numerous throughout SNR and ZIL than in SNC, SNL, and area A13. In colchicine pretreated rats, the majority of neurons in SNR and ZIL and few neurons in SNC, SNL, and area A13 were GAD-positive and TH-negative. This study suggests a dichotomy of both SN and ZI into a predominantly dopaminergic and a predominantly GABAergic part.

Animals↗