Biomedical subjects

Z Henderson

Publications and source records attributed to Z Henderson.

At least 55 records · Page 3Linked to original sources

PubMed1989

Lamellar bodies are markers of cholinergic neurons in ferret nucleus basalis.

Lamellar bodies are composed of stacks of closely-packed, ribosome-free cisterns which are in continuity with the rough endoplasmic reticulum. In the ferret nucleus basalis stained for choline acetyltransferase it was shown, by correlating light with electron microscopy, that only the cholinergic cells there possess lamellar bodies. The significance of lamellar bodies in the cholinergic neurons of the nucleus basalis is not known, but these structures may reflect a peculiar aspect of the functioning of the cholinergic cells which will need to be investigated further.

Acetylcholinesterase↗

PubMed1989

Acetylcholinesterase on the dendrites of central cholinergic neurons: an electron microscopical study in the ferret.

A combination of choline acetyltransferase immunohistochemistry and acetylcholinesterase histochemistry was used to characterize the ultrastructural distribution of acetylcholinesterase in identified cholinergic and non-cholinergic neurons in the ferret brain. Previous studies have shown that most of the cholinergic input to the brain arises from choline acetyltransferase-positive neurons found in the neostriatum, basal forebrain and dorsolateral pontine tegmentum. In all these cells intense staining for acetylcholinesterase was localized within the cisternae of the rough endoplasmic reticulum, in the nuclear envelope and Golgi apparatus, and along the plasma membranes of the soma and dendrites. In contrast, the distribution of acetylcholinesterase in non-cholinergic neurons was restricted mainly to the cisternae of the endoplasmic reticulum and the nuclear envelope. Since previous studies have associated high levels of acetylcholinesterase staining with non-cholinergic neurons in the locus coeruleus and substantia nigra zona compacta, these areas were examined as well. The ultrastructural localization of acetylcholinesterase in the principal locus coeruleus neurons was as observed in typical non-cholinergic neurons. On the other hand, the distribution of acetylcholinesterase in the principal cells of the zona compacta of the substantia nigra was more like that found in cholinergic neurons. In conclusion, the subcellular distribution of acetylcholinesterase in the principal cholinergic neurons of the brain follows a characteristic pattern which, with one exception, is different from that of acetylcholinesterase-positive non-cholinergic neurons.

Acetylcholinesterase↗

PubMed1988

The effects of N-acetylaspartylglutamate and distribution of N-acetylaspartylglutamate-like immunoreactivity in the rat somatosensory thalamus.

The ventrobasal thalamus and adjacent regions were stained for the presence of N-acetylaspartylglutamate-like immunoreactivity. Immunoreactive axonal terminals were observed in this area and also in certain non-specific thalamic nuclei, the reticular thalamic nucleus and the lateral geniculate nucleus. Stained somata were found in the habenula, centrolateral thalamic nucleus and reticular thalamic nucleus. Iontophoretically applied N-acetylaspartylglutamate had variable, although predominantly inhibitory, actions on ventrobasal thalamus neurons. These results indicate that N-acetylaspartylglutamate is unlikely to be the neurotransmitter of ascending somatosensory afferents, but do not rule out the possibility that it has some other neurotransmitter or neuromodulator role in the ventrobasal thalamus.

Action Potentials↗

PubMed1988

Development of ganglion cell topography in ferret retina.

The adult ferret has approximately 90,000 retinal ganglion cells, arranged in a prominent area centralis and visual streak. The role of differential cell generation, cell death, and retinal growth in the control of adult retinal ganglion cell number and distribution was evaluated by examining basic aspects of retinogenesis, including growth in retinal area, developmental changes in the number, size, and distribution of retinal ganglion cells (identification aided by retrograde transport of HRP), and the incidence of degenerating cells in the ganglion cell layer. Retinal development in the ferret was also compared to retinal development in the cat (which has an even more differentiated area centralis) to determine what alterations of developmental parameters are most closely associated with this species difference in adult morphology. The area of the retina increases linearly from birth (12 mm2) to postnatal day 24 (54 mm2), reaching an eventual adult value of 64 mm2. Ganglion cell numbers peak at 155,000 (approximately twice the adult number) on postnatal day 3, and fall to adult numbers by postnatal day 6. The remaining cells of the ganglion cell layer, principally displaced amacrine cells, reach their peak number on postnatal day 10 (approximately 280,000), falling to 200,000 by adulthood. Degenerating cells are abundant in the ganglion cell layer in the immediate postnatal period. A difference in the incidence of degenerating cells in the presumptive area centralis versus that in the retinal periphery was not observed postnatally, though there were other striking spatial nonuniformities, suggesting that differential cell loss might contribute to other features of retinal topographic organization. Ganglion cell density is virtually uniform across the retina at birth. Cell density is first reduced in the dorsal retina, resulting in a dorsal-to-ventral gradient in cell density that persists until day 10, when ganglion cell number has stabilized. By postnatal day 24, an area centralis and visual streak has emerged, but not of adult magnitude. Because ganglion cell number has stabilized long before the area centralis and visual streak emerge, we conclude that differential retinal growth is the principal mechanism producing this feature of retinal topography. Comparison with the cat suggests that the proportionately greater nonuniform growth of the cat's eye accounts for the greater differentiation of its area centralis.

Algorithms↗

PubMed1987

Overlap in the distribution of cholinergic and catecholaminergic neurons in the upper brainstem of the ferret.

The distribution of catecholaminergic and cholinergic neurons in the upper brainstem of the ferret were mapped by staining immunohistochemically two adjacent series of sections of brainstem for tyrosine hydroxylase and choline acetyltransferase, respectively. As in other species, large numbers of tyrosine-hydroxylase-positive neurons are localized in the ventral tegmental area (A10), the substantia nigra (A9), and in A8. Tyrosine-hydroxylase-positive neurons in the dorsolateral pontine tegmentum (A4, A6, and A7--the locus coeruleus complex) of the ferret are rather diffusely distributed, as has been observed in other carnivore species such as the cat and the dog, but unlike the cat, these cells in the ferret display a relative uniformity in size and morphology. Choline-acetyltransferase-positive neurons which extend in the ferret's pedunculopontine tegmental nucleus and ventral parabrachial area (Ch5) are relatively large cells that stain intensely for choline acetyltransferase, and their dendrites form prominent bundles in regions where unstained fibre tracts are prevalent. Choline-acetyltransferase-positive neurons distributed in the laterodorsal tegmental nucleus (Ch6) are smaller than the cholinergic cells of Ch5, and they stain less intensely for choline acetyltransferase. Rostrally, there is little overlap between the catecholaminergic cell groups A8, A9, and A10 and the cholinergic cell groups of Ch5 and Ch6. Caudally, the Ch5 neurons extend some considerable extent into the locus coeruleus complex. In the region of overlap, no cells with staining for both tyrosine hydroxylase and choline acetyltransferase were observed, as was ascertained with a double staining method employing a combination of tyrosine hydroxylase immunofluorescence and choline acetyltransferase peroxidase-antiperoxidase immunohistochemistry. In conclusion, the ferret has a typically carnivore pattern for the distribution of catecholaminergic cells in the upper brainstem, and there is a significant overlap between the catecholaminergic and cholinergic cell groups in the dorsolateral pontine tegmentum.

Animals↗

PubMed1987

Source of cholinergic input to ferret visual cortex.

The source of cholinergic input to ferret visual cortex was investigated with a combination of retrograde transport of horseradish peroxidase and choline acetyltransferase immunohistochemistry. Cholinergic projections to ferret visual cortex arise from basal forebrain cells in the septum, diagonal and nucleus basalis magnocellularis; the largest contribution comes from cells in the caudal part of the nucleus basalis magnocellularis. There is no discernible source in the brainstem.

Afferent Pathways↗

PubMed1987

A small proportion of cholinergic neurones in the nucleus basalis magnocellularis of ferret appear to stain positively for tyrosine hydroxylase.

The immunofluorescence and peroxidase-antiperoxidase methods for immunohistochemistry were used to show that a small number of neurones in the nucleus basalis magnocellularis of ferret stain positively for what appears to be tyrosine hydroxylase, a marker for catecholaminergic neurones. With a double immunocytochemical staining method, it was confirmed that the tyrosine hydroxylase-like immunoreactivity is localized in neurones that also stain strongly for choline acetyltransferase.

Animals↗

PubMed1987

Does the substantia nigra have a cholinergic innervation?

We have studied the distribution of choline acetyltransferase-containing fibres in ferret substantia nigra using immunohistochemistry at the light microscopical level. Positive staining for choline acetyltransferase was not observed in any nigral cell bodies, but was found in a network of fine-calibre, varicose axons, more densely distributed in the zona compacta than the zona reticulata.

Acetylcholinesterase↗

PubMed1987

Cholinergic innervation of ferret visual system.

The distribution of acetylcholinesterase and choline acetyltransferase in primary visual areas of adult pigmented ferret was determined with cholinesterase histochemistry and choline acetyltransferase immunohistochemistry. In all visual areas the distribution of acetylcholinesterase in the neuropil closely matches that of choline acetyltransferase. In the cerebral cortex acetylcholinesterase and choline acetyltransferase are associated with axons found in every cortical layer and in the white matter. Area 17, identified by Nissl architectonics and cytochrome oxidase histochemistry, is distinguished by having a relatively low density of choline acetyltransferase- and acetylcholinesterase-stained axons in layer IV. Certain cortical non-pyramidal cell types show moderate staining for acetylcholinesterase after relatively long incubations, but no choline acetyltransferase-positive cells are observed in the cortex. In the lateral geniculate nucleus and superior colliculus the levels of choline acetyltransferase and acetylcholinesterase are considerably higher than in cerebral cortex, and choline acetyltransferase-stained axons there display prominent varicosities. The distribution of choline acetyltransferase and acetylcholinesterase in the neuropil of lateral geniculate nucleus and superior colliculus of ferret shows marked laminar variation. For instance, in the lateral geniculate nucleus, the levels of acetylcholinesterase and choline acetyltransferase in the "On" sublaminae of laminae A and A1 are higher than the "Off" sublaminae. In the superficial layers of the superior colliculus the levels of choline acetyltransferase and acetylcholinesterase are highest in the stratum zonale and lowest in the stratum opticum; in the intermediate gray layer of the superior colliculus acetylcholinesterase- and choline acetyltransferase-stained fibres are distributed into dense patches. As in cortex, choline acetyltransferase-positive cell bodies are not found in the lateral geniculate nucleus or superior colliculus, and acetylcholinesterase-stained cell bodies are visible only after long incubations. Cell bodies staining positively for choline acetyltransferase are found in a satellite of the superior colliculus, the parabigeminal nucleus.

Acetylcholinesterase↗

PubMed1987

Retinal decussation patterns in pigmented and albino ferrets.

The decussation patterns of retinal ganglion cells in adult pigmented and albino ferrets were determined from the distribution of cells labelled after large unilateral injections of horseradish peroxidase into the visual pathway, involving the lateral geniculate nucleus and fibres of passage to the superior colliculus. About 6000 retinal ganglion cells project ipsilaterally in pigmented ferrets compared with only about 1500 in albino ferrets. In both strains, the vast majority of these cells (99 and 87% in pigmented and albino animals, respectively) are located in the temporal crescent, although we describe one albino ferret in which an aberrant uncrossed projection arises from nasal retina. In pigmented ferrets, there is a sharp nasotemporal division that runs through the area centralis; a small proportion of the ganglion cells in temporal crescent (less than 10%) does project contralaterally. In albinos, however, the majority of cells in temporal retina project contralaterally. There is no clear nasotemporal division in the albino retina; the density of uncrossed ganglion cells is reduced throughout temporal crescent and at no location exceeds the comparable density of the crossed projection. The peak density within the reduced uncrossed projection is also displaced away from the area centralis into temporal retina. Analysis of cell type on the basis of soma size indicates that whereas large horseradish peroxidase injections into the visual pathway of pigmented ferrets label all types of ganglion cell in the crossed projection, injections restricted to the superior colliculus label only those ganglion cells with large or small somata. The distribution of cell sizes in the crossed projection from temporal retina is biased towards small cells in the pigmented ferret but in albinos resembles that seen in the crossed projection from nasal retina. Thus the adult pigmented ferret has both a well developed nasotemporal division in which decussation lines are obvious in the crossed and uncrossed pathways and also, unlike rodents but like cats, a class of ganglion cell that does not project to the superior colliculus. The albino mutation both reduces the uncrossed projection throughout temporal retina, although the reduction is greatest close to the area centralis, and also commensurately increases the crossed projection from temporal retina.

Albinism↗

PubMed1986

Organization of the visual pathways in the newborn kitten.

We have used retrograde and anterograde transport to examine the major visual pathways in newborn kittens. Retinal projections from both eyes to the dorsal lateral geniculate nucleus (dLGN) and superior colliculus (SC) are present and topographically organized. The dLGN projects topographically to areas 17 and 18 and receives reciprocal projections from cells in layer VI of areas 17, 18, 19 and suprasylvian cortex on the same side of the brain. Area 19 also has a sparse thalamic input but probably not from the dLGN. The laminar distribution of [3H]proline transported from dLGN to area 17 was quantified: label was spread through all layers, with a minimum at the border of layers I/II. Layer I was always labelled less heavily than IV. These results are critically compared with those based on other tracing techniques. Cells of layer V in areas 17, 18, 19 and the suprasylvian cortex project topographically to the superficial layers of the ipsilateral SC. Area 19 and the lateral suprasylvian cortex also send a crossed projection to restricted parts of the opposite SC. Thus these visual projections are not only present and topographically ordered on the day of birth, but, unlike certain highly exuberant interhemispheric and cortico-cortical projections, they are qualitatively remarkably mature, some days before the onset of visual activity. The major subcortical projections to and from the visual cortex appear to be constructed without the benefit of visual experience and much of the activity-dependent plasticity of cortical cells may well involve only local modulation of synaptic input.

Animals↗

PubMed1985

Distribution of ganglion cells in the retina of adult pigmented ferret.

The retinal ganglion cell distribution in adult pigmented ferret was mapped in Nissl-stained retinas and in retinas back-filled with HRP after large bilateral injections of the enzyme into the brain. In common with other carnivores the ferret has an area of peak cell density equivalent to the area centralis and a prominent visual streak of high cell density extending horizontally across the retina. The maximum ganglion cell densities for the retinas were estimated to be 3500-5200 cells/mm2 in Nissl-stained, dehydrated retinas and 3300-4300 cells/mm2 in HRP-labelled, undehydrated retinas. Three cell types were distinguished in the HRP-labelled retinas and they appear to correspond to alpha-, beta- and gamma-cell types of cat retina. However, unlike in cat, the retinal ganglion cells of the ferret do not consistently fall into 3 distinct groups with respect to cell size, nor is there a tendency for the cells in the area centralis to be smaller than those in the peripheral retina. Estimates for the total number of ganglion cells of 82,000 and 88,000 were obtained from Nissl-stained retinas, and of 74,000, 75,000 and 78,000 from HRP-labelled retinas.

Animals↗

PubMed1984

Ultrastructural localization of acetylcholinesterase in substantia nigra: a comparison between rat and guinea pig.

The distribution and ultrastructural localization of acetylcholinesterase (AChE) was examined in the substantia nigra of rat and guinea pig. Although the pars compacta, in both species, is clearly defined when stained with thionin, there is an apparent discrepancy in the distribution of AChE at the light microscope level. In the rat substantia nigra the enzyme appears to be concentrated mainly in the pars compacta, whereas in the guinea pig the AChE seems homogeneous throughout the entire substantia nigra. Ultrastructural studies, however, reveal a close correspondence in the morphology of rat and guinea pig substantia nigra. The subcellular localization of AChE is also similar. The between-species discrepancy seen with the light microscope was attributed to relative differences in level of intensity of staining for AChE. In both rat and guinea pig, the enzyme is localized in two types of neuron and in the extracellular space. The ultrastructural distribution of AChE is discussed with reference to neurochemical studies on its release from nigral neurons.

Acetylcholinesterase↗

PubMed1984

Cholinergic synapses in the rat brain: a correlated light and electron microscopic immunohistochemical study employing a monoclonal antibody against choline acetyltransferase.

Using a monoclonal antibody to choline acetyltransferase, immunoreactive synaptic boutons were identified in the neostriatum, cingulate cortex, basolateral nucleus of the amygdala, hippocampus and interpeduncular nucleus of the rat. The synapses were generally symmetrical although some asymmetrical membrane specializations were observed. Postsynaptic targets included perikarya, dendritic shafts and dendritic spines.

Acetylcholine↗

PubMed1984

A non-cholinergic function for acetylcholinesterase in the substantia nigra: behavioural evidence.

Acetylcholinesterase is released from substantia nigra neurons, independently of cholinergic transmission. In an attempt to discover the functional significance of this phenomenon, the behavioural effects of injecting acetylcholinesterase into one substantia nigra of the rat were investigated. Following a single injection of the enzyme, intraperitoneal amphetamine evoked circling behaviour in a direction away from the side of injection. Purified acetylcholinesterase with a similar electrophoretic mobility to the endogenous secreted form, was far more potent in eliciting circling than much higher activities of commercial enzyme, consisting of several molecular species of acetylcholinesterase. Similar infusions of butyrylcholinesterase did not induce circling. Depending upon the amount of enzyme initially given, the behavioural effects of a single injection of acetylcholinesterase persisted for up to thirty days. During this period apomorphine, administered systemically, induced transient circling towards the acetylcholinesterase-treated side. It is concluded that secreted acetylcholinesterase has a functional significance within the substantia nigra, independent of cholinergic transmission. This released enzyme could exert long-term changes in the activity of the nigrostriatal system, involving modification of dopamine striatal receptors.

Acetylcholine↗

PubMed1984

Binocular interaction in the fetal cat regulates the size of the ganglion cell population.

During fetal development of the cat's visual system there is a marked overproliferation of optic nerve axons. In utero binocular interaction contributes to the severity of fiber loss since removal of an eye during gestation attenuates axon loss in the remaining optic nerve. The purpose of the present study was to determine whether this reduced loss of optic nerve fibers is due to a failure of retraction by supernumerary axon branches or to a reduction in ganglion cell death. To resolve this issue, we compared the number of ganglion cells and optic nerve fibers in adult cats which had one eye removed at known gestational ages. Retinal ganglion cells were backfilled with horseradish peroxidase and counts were made from retinal wholemounts. The axon complement was assessed with an electron microscopic assay. In the retinas of a normal cat we estimated 151,000 and 152,000 ganglion cells. The optic nerves of two other normal cats contained approximately 158,000 and 159,000 axons. In comparison, an animal enucleated on embryonic day 42 had 180,000 ganglion cells and 178,000 optic nerve fibers, while in an animal enucleated on embryonic day 51 the corresponding estimates were 182,000 and 190,000. The close agreement between cell and fiber counts indicates that axonal bifurcation does not contribute appreciably to the axon surplus in the optic nerve of prenatally enucleated cats. These results demonstrate that prenatal binocular interaction regulates the size of the mature retinal ganglion cell population.

Animals↗

PubMed1983

Postnatal changes in retinal ganglion cell and optic axon populations in the pigmented rat.

The number of ganglion cells in the retina of the postnatal rat has been examined. We estimated both the number of axons in the optic nerve and the number of cells which can be retrogradely labelled with horseradish peroxidase from injections into the brain. In the retina of the newborn rat there are at least twice as many ganglion cells as in the adult rat. By retrograde labelling of the ganglion cells and following transection of their axons 24-48 hrs later we can find no evidence that ganglion cells withdraw their axon without degeneration of the patent cell body. We have found that the excess ganglion cells are lost over the first ten postnatal days and during this period we observe pyknotic nuclei in the ganglion cell layer. From our estimates of the total number of neurones in the ganglion cell layer and the number of ganglion cells found at different ages we conclude that the migration of amacrine cells into the ganglion cell layer occurs in the first five postnatal days.

Age Factors↗

PubMed1982

An anatomical investigation of projections from lateral geniculate nucleus to visual cortical areas 17 and 18 in newborn kitten.

The presence of projections from the lateral geniculate nucleus to visual cortical areas 17 and 18 in newborn kitten was examined using the method of retrograde axonal transport. An injection of either horseradish peroxidase (HRP) or horseradish peroxidase conjugated to wheat germ agglutinin (HRP-WGA) was made into area 17 on one side of the brain and area 18 on the other side. The results were not unlike those from experiments on adults. Area 17 injections label a relatively high proportion of cells in laminae A and A1 and the distribution of sizes of labelled cells is almost the same as that for the total cell population. Area 18 injections label only a small percentage of the total cell population in laminae A and A1 and most of the labelled cells are large. Cells in the C layers are labelled after an injection into either area 17 or 18. It was concluded that the formation of organized thalamocortical projections in the kitten does not rely on visual experience as the projections are already present at birth.

Animals↗