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P M Field

Publications and source records attributed to P M Field.

At least 19 recordsLinked to original sources
PubMed1992

Monoclonal antibodies reveal molecular differences between terminal fields in the rat dentate gyrus.

We have derived a number of monoclonal antibodies which detect molecular differences correlating with the afferent inputs to the molecular layer of the adult rat hippocampal dentate gyrus. One group, dubbed OM-1 to OM-4, strongly stain the outer zone of the molecular layer, which receives its major innervation from the ipsilateral entorhinal cortex. A second group, IM-1 and IM-2, show a complementary pattern and preferentially stain the inner molecular layer, which receives inputs from the ipsilateral and contralateral hippocampus. These antigens are not, however, restricted to these layers, being found outside the hippocampus in several other areas of neuropil in the adult brain. In the developing brain the IM-1 antigen appears ubiquitously from the earliest age studied, embryonic day 12. Within the dentate gyrus, its restriction to the inner terminal field of the molecular layer only occurs during the second postnatal week. In contrast, OM staining appears only sparsely and late in the prenatal brain, appearing in developing cortical white matter between embryonic days 18 and 20. The outer dentate molecular layer becomes OM-positive from birth onwards, corresponding to the time of arrival of entorhinal axons during the first postnatal week. These two groups of monoclonal antibodies recognize a number of different glycoproteins. Ultrastructural immunohistochemistry shows they are cell surface molecules, and as such may be involved in the recognition events required for the establishment of specific patterns of neuronal connectivity.

Animals↗
PubMed1991

Selective innervation of embryonic hippocampal transplants by adult host dentate granule cell axons.

Fragments containing different cytoarchitectonic fields were dissected out of late embryonic rat hippocampal primordia and transplanted into the hippocampus or septum of adult syngeneic hosts. Field CA3 transplants contained clusters of large, angular (pyramidal) cell bodies surrounded by a radiating corona of dendrites. These cells stained selectively with our monoclonal antibody Py, and a proportion were labelled by [3H]thymidine administered on the 15th day of embryonic life. Field CA1 transplants contained smaller, angular, Py-negative cells, which formed elongated laminae rather than globular clusters. The ability of the host dentate granule cells to project to the transplants was examined by (1) the Timm stain for mossy fibres, (2) electron microscopy of Golgi-impregnated CA3 pyramidal neurons in the transplants, and (3) quantitative electron microscopic assessment of the proportions of large mossy fibre terminals in the synaptic population of the transplants. The Timm stain showed that CA3 transplants received a projection from host dentate granule cells when the transplants were placed in direct contact with the axons in the host mossy fibre pathway. As in the normal host field CA3, the ingrowing mossy fibres terminated selectively on the juxtacellular regions of the dendritic tree and ignored the major part of the dendrites in the radiating corona. The electron micrographs showed that within this territory the host mossy fibres formed synaptic terminals with all the complex features typical of normal mossy fibres, and were presynaptic to complex spines arising from the juxtacellular region of Golgi-impregnated donor CA3 pyramidal cells. The quantitative electron microscopic study demonstrated that the mossy fibre-innervated juxtacellular regions of the field CA3 transplants had up to 20% of the normal density of mossy fibre synapses found in the stratum lucidum of field CA3 in situ. CA3 transplants which were placed in the septum, remote from the host mossy fibres, had either trivial numbers of mossy fibre synapses or none. This confirmed that the abundant mossy fibre terminals in the intrahippocampal CA3 transplants were of host origin, and not due to donor dentate granule cells inadvertently included in the grafts. The selectivity of the host dentate projection for field CA3 transplants was demonstrated by the observation that CA1 transplants in the same locations received only slight mossy fibre projections in the Timm stain, and in electron micrographs their synaptic population had only insignificant numbers of large mossy fibre terminals.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Synapse formation in the adult brain after lesions and after transplantation of embryonic tissue.

Some years ago it was demonstrated that when the adult rat septal nuclei are partially deafferented the remaining afferent fibres form new connections. The conclusion that new synaptic connections form in the adult central nervous system (CNS) was greeted initially with much scepticism, later with over-enthusiasm and unwarranted generalisation to all lesion situations, together with even less warranted attribution of various beneficial functional properties. Today, as the pendulum swings into a more reasonable position, some of the original observations, which at the time attracted little attention, have become more interesting. (1) The observation that in the normal septal nuclei the ratio of spine to shaft synapses is extraordinarily constant (to an accuracy better than 1%) from one animal to another. How could such almost crystalline rigidity of structure be produced in normal development and maintained in the face of major lesion-induced changes in connectivity? (2) The observation that synaptic re-occupation by sprouting axons restores exactly the normal number of synapses, presumably indicating that the neurones have a fixed number (as well as spine/shaft distribution) of postsynaptic sites. Thus, the septal lesion paradigm is as strong a method for investigating synaptic rigidity as for investigating plasticity. In the intervening years, the use of embryo to adult transplantation has made it obvious that considerable reconstruction of adult brain synaptology is possible, and that many of the normal rules of connectivity are maintained (most prominently for the 'point-to-point' axonal systems). What could lead to further fruitful investigation is the extent to which the observations (e.g. relating to hierarchies of axonal preference, the need for denervation, and the involvement of glial cells) in partially deafferented adult systems, such as the septal nuclei, are retained, or modified, in face of the ingrowing fibres from embryonic transplants.

Animals↗
PubMed1989

Fetal medial habenula transplants: innervation of the rat interpeduncular nucleus.

The effects of donor age and site of placement on the survival of fetal medial habenula (MH) transplants into adult rats hosts were examined. The innervation of the interpeduncular nucleus (IPN) in such cases was also examined. Explants of MH consisting of the medial-dorsal lip of the third ventricle were held in vitro for 1-2 days. Colloidal gold conjugated to wheat germ agglutinin was added for the last 18 hours to label the cells. Four of 16 cases with E19 derived transplants contained donor neurons. Markedly larger transplants were present in 95% of 20 cases with E16 derived transplants. Sites in the ventral midbrain were successful, while limited or no survival occurred at sites more remote from IPN. Retrograde labeling of transplant neurons was present in each case studied with HRP injection into host IPN. Colloidal gold-labeled macrophages, some oriented capillaries and GFAP-positive processes marked the donor-host interface. In EM the interface was evident only by the difference in tissue elements in the transplant versus host. Numerous synapses of Gray types I and II were present in the transplant. Excellent survival of MH neurons, donor/host interfaces, innervation of IPN by the transplant and fine structure in and around the transplants, all suggest that such preparations are suitable for further experimental analysis of the habenulo-interpeduncular system.

Animals↗
PubMed1988

Use of colloidal gold complexes of wheat germ agglutinin as a label for neural cells.

We have made stable complexes between wheat germ agglutinin and either 5 or 10 nm particles of colloidal gold. These complexes were phagocytosed by neuronal and glial cells in embryonic rat hippocampal cultures and the incorporated gold gave intense, low-background staining in the light microscope either directly, for the most heavily labelled cells, or after intensification by physical development of silver. Cells were labelled in a punctate fashion over perikarya and processes. In the electron microscope, particles of gold were observed in lysosomal vesicles, frequently in an aggregated form. Gold complex incorporated into cells in culture was retained by those cells over periods up to 20 days. Embryonic hippocampal cells were labelled in suspension culture by incorporation of wheat germ agglutinin-gold complexes and transplanted into the brains of syngeneic adult host rats. Grafted neurons and glia were observed in the electron microscope to retain high levels of gold label over periods up to 30 days. Receipt of synaptic connections by transplanted neurones was observed. Complexes of wheat germ agglutinin with 10 nm gold particles were injected unilaterally into field CA3 of the hippocampus of adult rats. Specific retrograde transport of gold was observed in the light and electron microscopes to pyramidal and hilar neurones of the contralateral hippocampus and to neurones of the medial septal nucleus. Colloidal gold-wheat germ agglutinin complexes appear to be useful cellular markers that can be visualized at both light and electron microscope levels.

Animals↗
PubMed1986

A software package for the manipulation, display and analysis of electron and light microscope data.

Quantitative light and electron microscopy is an expanding field which has found applications in many biological disciplines. Computer-enhanced data-acquisition has led to increased speed and accuracy, and combined with computational analysis, stereological parameters can be quickly derived and spatial hypotheses can be easily tested. A software package is described, which controls the manipulation, display and analysis of two-dimensional microscope data. Features include alignment of specimens, rotations, translations, deletions, recoding, perimeter and area measurement, point-counts, tests of dispersion and tests of spatial distributions. The programme is graphics-orientated and supports various point-plot modes and histograms. It includes linear and non-linear curve-fitting options and has been specifically designed to encourage new analysis procedures, which automatically benefit from existing graphics options.

Data Collection↗
PubMed1985

The density of reinnervation of adult rat superior cervical sympathetic ganglionic neurons is limited by the number of available postsynaptic sites.

The adult rat superior cervical ganglion has about 27,000 neurons and is innervated by about 9000 preganglionic axons which make a total of nearly 11 million synapses. Surgical removal of the upper part of the ganglion, reducing the number of neurons to about 20%, causes an overall reduction of the number of synapses to about 30%, but has no effect on the numbers of preganglionic axons. Thus, a 5-fold increase in the axon/neuron ratio causes an increase of only about 50% in the number of synapses per cell. Axotomy followed by regeneration of the preganglionic axons causes no further increase in the number of synapses per cell, even though the average number of synapses per axon is reduced to about one-quarter of the normal. This suggests that the ganglionic neurons can only accept a limited number of synapses, and that in the normal situation there is only possibility for a relatively minor increase before this limit is reached. This study is complementary to a previous one in which the numbers of preganglionic axons were surgically reduced and it was found that, when allowed to regenerate into an entire denervated ganglion, the remaining axons could not increase their numbers of synapses. Thus, in the normal rat superior cervical sympathetic ganglion the total number of synapses is such that while the preganglionic axons are probably expressing close to their full synaptogenic potential, the ganglionic neurons express only about two-thirds of their ability to receive synapses.

Animals↗
PubMed1983

Relative slowness of heterotypic synaptogenesis in the septal nuclei.

The dorsolateral quadrant of the lateral septal nucleus receives a bilateral projection from the fimbria. When the fimbria of one side is cut, the axons of the remaining fimbria take over its synaptic sites preferentially, but when both fimbrias are cut the sites are reinnervated by non-fimbrial axons. To explore the basis of this preference, the present study plots the time courses of the appearance and disappearance of degenerating synapses, and the loss and recovery of non-degenerating synapses after ipsi-, contra- and bi-lateral fimbrial lesions. A preliminary investigation showed that at any time after these three lesions there was no change in the numerical density per unit area of 'control' structures such as shaft synapses (which do not degenerate) and neuronal perikarya (which neither shrink nor degenerate). This indicates that the changes in the numerical density of fimbrial (spine) synapses can be used as a measure of the processes of deafferentation and reinnervation without the danger of the numerical data being distorted by shrinkage. In the sampled area, the ipsilateral fimbrial axons account for about 45% of the synapses and the contralateral fimbrial axons for 25%. The number of degenerating synapses appearing at any one time underestimates the loss of non-degenerating synapses by about one-third, and a photographic simulation of degeneration suggests that a major factor in this discrepancy is the difficulty in recognizing degenerating synapses. Our main finding is that there is a major delay in the rate of removal of degeneration, and in the rate of reinnervation, after bilateral as opposed to unilateral lesions. This delay cannot be accounted for in any simple way by the greater amounts of degeneration. Thus after unilateral lesions, which cause the turnover of 25% (contralateral) or 45% (ipsilateral) of the synapses, 50% of the degeneration is removed in 1-2 days after the peak, whereas after bilateral lesions, which affect 70% of the synapses, it takes 20 days for 50% of the degeneration to be removed. That the synaptic changes after bilateral lesions involve a qualitatively different mechanism is also suggested by the observations of a much greater proportional increase in the multiple synapse index, and a decreased astroglial response.

Afferent Pathways↗
PubMed1983

Neurological mapping using an electron microscope/microprocessor data acquisition system.

Quantitative electron microscopy is used widely in many neurobiological laboratories but can be greatly enhanced by the computer storage, display and analysis of features or boundaries observed under the microscope. An interactive system is described, in which a microprocessor and microcomputer combination controls the data acquisition and display; more detailed analysis can be carried out on a mainframe computer. The performance of this system is examined and it is shown to be a cheap and effective solution, capable of expansion in many directions.

Animals↗
PubMed1979

Decentralization of the superior cervical ganglion in neonates impairs the development of the innervation of the iris. A quantitative ultrastructural study.

The superior cervical sympathetic ganglion was decentralized unilaterally by section of the preganglionic chain in 2- or 4-day-old rats. Twenty-one days post-operatively the dilator muscle of the iris was examined electron microscopically. Quantitative estimates demonstrated that there was a reduction both in the numbers of axon bundles and of individual axons in the iris innervated by the deafferented ganglion as compared with its fellow of the contralateral control side.

Animals↗
PubMed1979

Muscarinic receptors in the central nervous system of the rat. I. Technique for autoradiographic localization of the binding of [3H]propylbenzilylcholine mustard and its distribution in the forebrain.

[3H]Propylbenzilylcholine mustard ([3H]PrBCM) is a synthetic, potent muscarinic antagonist, which binds specifically and irreversibly by means of a covalent linkage to muscarinic receptors. Ten micrometer coronal cryostat sections taken through unfixed rat brain at the level of the maximum extent of the caudate nucleus were mounted on glass slides and incubated with 2.4 nM [3H]PrBCM at 30 degrees C for 25 min. They showed a total binding of 3250 pmol/g protein, of which 2130 pmol/g protein was sensitive to pretreatment with 10-6 M atropine. The specific (atropine-sensitive) binding was saturable. Saturation was reached at 15 min, with a rate constant of 1.3 x 106 M-1 sec-1. Binding was unaffected by drugs acting at nicotinic receptors (D-tubocurarine, hexamethonium), or by physostigmine, but was inhibited by muscarinic drugs (pilocarpine, oxotremorine, 3-quinuclidinylbenzilate). Postfixation for 15 min in Carnoy's fixative reduced the specific binding by 10% and the non-specific by 50%. Prefixation (i.e. before incubation with [3H]PrBCM) with any fixatives containing formaldehyde largely prevented specific binding, but a range of concentrations of glutaraldehyde (2% to 0.05%) caused only small reductions in specific binding (e.g. 0.1% glutaraldehyde caused only a 6% reduction). Clear, regionally specific patterns of localization of specific label in light microscope autoradiographs could be obtained from cryostat sections prefixed with 0.1% glutaraldehyde, incubated with 2.4 nM [3H]PrBCM for 15 min at 30 degrees C, and postfixed for 15 min in Carnoy's solution. Of the 105 forebrain areas studied 12 had grain counts between 6 and 9 times the non-specific level and a further 30 had counts 4 to 6 times non-specific. The higher grain counts were in the external plexiform layer of the olfactory bulb, anterior olfactory nucleus, olfactory tubercle, pyriform cortex, stratum radiatum of the hippocampus, stratum moleculare of the dentate gyrus, lateral amygdaloid nucleus, cortico-amygdaloid transition zone, anteroventral thalamic nucleus, hypothalamic supraoptic nucleus, caudate-putamen, nucleus accumbens, and in laminae 3 and 6 of the neocortex (parietal region). There were high grain densities over the choroid plexus the lateral but not the third or fourth ventricles.

Animals↗
PubMed1979

Muscarinic receptors in the central nervous system of the rat. II. Distribution of binding of [3H]propylbenzilylcholine mustard in the midbrain and hindbrain.

The distribution of muscarinic receptors has been studied in the rat midbrain and hindbrain by counting silver grains in light microscope autoradiographs of the specific (atropine-sensitive) binding of [3H]propylbenzilylcholine mustard in cryostat sections. Of the 78 areas studied 6 had grain counts between 6 and 9 times the nonspecific level ("high"), and a further 15 had counts 4-6 times non-specific ("intermediate"). The basilar pontine nuclei and the ventral nuclei of the lateral lemniscus had high counts. Among the cranial nerve motor nuclei the facial and hypoglossal nuclei had high counts and the motor trigeminal nucleus and nucleus ambiguus had medium counts. The interpeduncular nucleus as a whole had low counts but there were two bands of intense staining on each side around the entry zone of the bundles of afferent cholinergic fibres from the habenula. Intermediate levels of binding occurred over the inferior colliculus and the superficial and intermediate grey layers of the superior colliculus. The molecular layer of the vestibulocerebellar vermis was distinctly labelled.

Animals↗
PubMed1979

Muscarinic receptofs in the central nervous system of the rat. III. Postnatal development of binding of [3H]propylbenzilylcholine mustard.

The postnatal development of muscarinic receptors has been studied in 7 selected areas from the brains of 1-17-day-old rats by counting silver grains in light microscope autoradiographs of the specific (atropine-sensitive) binding of [3H]propylbenzilylcholine mustard in cryostat sections. A major part of the adult receptor density is present at 1 day of age, a time when only a small fraction of the adult number of synapses has yet been formed. Of the areas studied the hypoglossal nucleus is the most precocious in muscarinic receptor development, and the dentate gyrus the latest (associated with the late development of the dentate granule cells). The pattern of receptor distribution changes with development. The caudate-putamen first develops receptor in patches, beginning at the lateral (ventricular) surface. The pontine nuclei develop receptor in a medial to lateral sequence. The maturation of the adult laminar pattern of the olfactory bulb depends on the alignment of cells (especially the mitral cells). The neocortex initially has uniform labelling throughout its depth, and later the labelling in layer 4 becomes relatively less dense (probably associated with the ingrowth of afferent fibres). The hippocampal formation first develops receptor evenly over the pyramidal cell dendrites; later receptor appears over the newly formed dentate stratum moleculare and becomes much reduced over the hippocampal stratum lucidum and stratum lacunosum-moleculare (probably associated with the ingrowth of afferent fibres from the dentate gyrus and entorhinal area). In the cerebellum muscarinic receptor is found only in the lobules which receive the primary vestibular afferents. In the neonate it is present in the granular layer, but this later disappears and is replaced by the adult pattern of labelling in the molecular layer.

Aging↗
PubMed1979

Muscarinic receptors in the central nervous system of the rat. IV. A comparison of the effects of axotomy and deafferentation on the binding of [3H]propylbenzilylcholine mustard and associated synaptic changes in the hypoglossal and pontine nuclei.

The reaction of axotomy has been studied in the rat hypoglossal nucleus by quantitative electron microscopical counts of numbers of synapses and by changes in muscarinic receptors assessed by counting silver grains in light microscope autoradiographs of the specific (atropine-sensitive) binding of [3H]propylbenzilylcholine mustard in cryostat sections. For the first 5 days after unilateral peripheral hypoglossal nerve axotomy the muscarinic ligand binding falls to 50% of control levels and then shows no further fall for up to 30 days. Synapse numbers decrease progressively over the first 10 days after operation, by which time they reach 50% of normal. Thus receptor changes reach completion at a time when synapse loss is still continuing. Later, both muscarinic ligand binding and synapse numbers recover to an extent which depends at least in part on the effectiveness of the peripheral nerve regeneration, suggesting that both the receptor and synapse changes may be dependent upon neuromuscular contacts. The reactions of muscarinic receptors to axotomy and deafferentation have been studied in the rat basilar pontine nuclei. Cerebellectomy, which causes axotomy of the pontine neurones and also removes their postsynaptic targets (the granule cells), causes no change in pontine muscarinic receptor over the first week after operation. This differs from the rapid fall in hypoglossal muscarinic receptors induced by axotomy. At longer survivals after cerebellectomy there is a partial loss of pontine muscarinic receptors associated with atrophy of the pontine neurones. Destruction of the neocortical afferents causes a loss of at least half of the synapses in the pontine neuropil. However, the light microscopic autoradiographic study revealed no obvious changes in the dentisy or distribution of the pontine muscarinic receptors from 4 days to more than 6 months after operation.

Afferent Pathways↗
PubMed1978

Electron microscope autoradiographic evidence for specific transneuronal transport in the mouse accessory olfactory bulb.

The distribution of radioactive material was examined autoradiographically 8 h after application of [3H] proline to the vomeronasal organ in mice. Labelled material was transported along the axons of the vomeronasal nerves to their terminals in the glomerular layer of the accessory olfactory bulb (AOB). A lesser but consistent amount of radioactivity was found in the external plexiform layer (EPL) of the AOB. Electron microscopic autoradiography was used to determine which of the components of the EPL contained this labelled material. The method of proportional grain counts showed that the highest concentration of silver grains lay over the mitral cell dendrites, which are the elements immediately postsynaptic to the vomeronasal nerve axons. However, a fairly high proportion of grains also lay over the peripheral processes of granule cells. By application of a method of 'crossfire analysis' (which is explained in detail) it was possible to show that the observed grain distribution is best explained by the assumption that the radioactive material is confined to mitral cells, and the labelling over granule cell processes is due to crossfire from these sources. Im one animal at 5 days after [3H]proline administration label was found to have extended from mitral cells to granule cells, suggesting that the transsynaptically transported radioactive material, which was confined to the mitral cells at 8 h, may have become further redistributed at longer survivals. In a control experiment, [3H]proline was applied directly to the surface of the AOB. This gave rise to a completely different distribution of radioactivity in the EPL: radioactive material was present in all tissue components.

Animals↗