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R J Morris

Publications and source records attributed to R J Morris.

At least 163 records · Page 9Linked to original sources
PubMed1988

Stopped-flow cryoenzymological investigation of the pre-steady-state kinetics of hydrolysis of Leu-Gly-NHNH-Dns by leucine aminopeptidase.

Stopped-flow fluorescence experiments have been carried out to study the steady-state kinetics of hydrolysis of Leu-Gly-NHNH-Dns [Dns = 5-(dimethylamino)naphthalene-1-sulfonyl] by porcine kidney cytosol leucine aminopeptidase (LAP) in 50% v/v methanol/buffer solution at ambient temperature and the pre-steady-state kinetics of this reaction in the -35 to 0 degrees C temperature range. Experiments have been carried out on LAP species containing Mg(II), Mn(II), Cu(II), Ni(II), Zn(II), and no metal ion at the regulatory metal binding site. At ambient temperatures, the stopped-flow fluorescence changes observed on hydrolysis of the substrate have been used to measure the steady-state kinetic parameters kcat and KM. The results show that 50% v/v methanol lowers the values of kcat from 2- to 12-fold compared to the reactions in the absence of methanol for all of the metallo-LAP, but that the values of KM are essentially unaffected. The pre-steady-state reactions carried out under nonturnover conditions at -35 degrees C reveal a new relaxation for LAP species with Ni(II), Cu(II), and Zn(II) in the regulatory site. The value of kobsd for this relaxation reaches a plateau at high substrate concentrations, and the magnitude of its fluorescence change at a fixed concentration of substrate is proportional to the enzyme concentration. Thus, this relaxation corresponds to the production and decay of a new enzyme-substrate intermediate not observed at higher temperatures whose fluorescence differs from that of the succeeding intermediate that is normally seen above -26 degrees C.

Algorithms↗
PubMed1988

Long-chain alkanediols: biological markers for cyanobacterial contributions to sediments.

One significant family of sedimentary lipids of widespread occurrence are series of C28-C32 alkanediols and hydroxyketones. The recognition of the same series of alkanediols as major lipid components of a field population of the cyanobacterium Aphanizomenon flos-aquae leads us to propose that these lipids are markers for cyanobacterial inputs to sediments. The frequency of occurrence of the alkanediols in sedimentary environments supports the recent finding that cyanobacteria are major contributors to the aquatic biomass.

Cyanobacteria↗
PubMed1988

Two distinct phases and mechanisms of axonal growth shown by primary vestibular fibres in the brain, demonstrated by parvalbumin immunohistochemistry.

Antibodies to parvalbumin label intensely a small number of non-overlapping fibre systems in embryonic rat brain. All are in hindbrain--the oculomotor and trochlear motor fibres, the acoustic and vestibular fibres of the VIIIth nerve, and an unidentified group of fibres which ascend under the dorsal surface in caudal medulla. Of these, the vestibular fibres are the first to acquire parvalbumin immunoreactivity, and we have used this property to follow the growth of their axons in the brain. This occurs in two phases. In the first, occurring at embryonic days 12-14, the axons grow in small groups or fascicles under the pial surface to their most distant terminal zones rostrally in the cerebellum and caudally in the descending vestibular nuclei. This growth is directed towards the two sites where germinal neuroepithelium is expanding over the medullary velum in forming the cerebellum and lateral recess of the IVth ventricle. In a second stage, commencing at E15, individual collaterals branch from these fascicles to arborize amongst their presumptive synaptic targets (cells of the vestibular nuclei and vestibulocerebellum) located in the sub-ventricular and ventricular layers. In this phase the axons follow a radial route, at right angles to their original subpial course, possibly by growing along radial glial processes. The target cells then migrate to their final position with the vestibular axons maintaining contact with them. The vestibular fibres are the first axons to enter the cerebellum, but from E15 onwards their fascicles are joined by increasing numbers of non-vestibular fibres following the same course. These other axons, and the movement of cells to form the deep cerebellar nuclei, separate the fascicles of vestibular fibres so that their course into the cerebellum becomes very diffuse. Thus this single set of axons grow, not only in two distinct phases, but also follow distinctly different substrates for growth in each. Furthermore, they then appear to act as pioneer fibres guiding the entry or egress of later-developing axons to or from the cerebellum.

Animals↗
PubMed1988

Emergency presentation of corneal graft patients.

One hundred and forty-two patients with corneal grafts made 205 visits to the Accident and Emergency Department of Moorfields Eye Hospital during a twelve-month period. One-third of cases showed a graft rejection episode while another third had a problem directly related to the graft. The figures emphasise the need for continuing patient education so that graft problems may be dealt with promptly.

Corneal Transplantation↗
PubMed1988

Evidence of high-frequency acoustic emissions from the white-beaked dolphin (Lagenorhynchus albirostris).

Recordings of the signals from a school of white-beaked dolphins show that the frequency of their acoustic emissions extends to at least 305 kHz. These signals were detected by a sector scanning sonar used as a passive listening device of high bearing and time resolution. The records contain three types of signal, one of high intensity, one of a variable high repetition rate, and another showing a time-varying effect. Acoustic signals radiated by dolphins have been recorded and studied over a long period of time by many investigators. The purpose of this letter is to report evidence that acoustic emissions from white-beaked dolphins have significant energy at frequencies around 305 kHz, about one octave higher than previously observed. The observations discussed here were made aboard the fisheries research vessel CLIONE in the Wellbank flat area of the southern North Sea on 13 June 1970 between 1040 and 1110 h. When the dolphin signals were observed, the transmitter of the sector-scanning sonar in use was turned off, and the system was utilized as a passive listening device of high bearing and time resolution.

Animals↗
PubMed1988

Epithelial stem cells in vivo.

Cellular topography within the highly polarized surface epithelia can be used to identify the location of the stem cells. In some instances, this can be quite precise and allows the characteristics of stem cells to be studied. Our current knowledge of the stem cell population in murine epidermis and small intestinal crypts is reviewed. In the epidermis, the stem cells would appear to make up about 10% of the basal layer and are distributed towards the centre of the basal layer component of the epidermal proliferative unit. These cells have a long cell cycle and are probably the same cells that retain both tritiated thymidine and radioactively labelled carcinogens for long periods of time. This label retention permits the labelling of the putative stem cell compartment. Over recent years, there has been an accumulation of information indicating various types of heterogeneity within the basal layer, much of which can be interpreted in relation to cellular hierarchies. In the small intestine, cell positions can be fairly precisely identified and the stem cell zone identified. Complex modelling of a wide range of cell kinetic experiments suggests that each crypt contains between 4 and 16 steady state functional stem cells. Radiobiological experiments suggest that up to 32 cells may be capable of clonal regeneration. The repopulation of the clonogenic cell compartment has been determined and the doubling time measured to be 19.7 h. Such studies should throw further light on the behaviour of stem cells and identify the timing of periods of increased and decreased cell proliferation (activation and suppression of controls).

Animals↗
PubMed1987

A new medium for primary cultures of adult murine epidermal cells: application to experimental carcinogenesis.

A culture medium has been formulated to support the long-term proliferation and differentiation of normal murine epidermal cells in primary cultures. This formulation is based upon MCDB-151 modified by the addition of 1.2 mM Ca2+, 1% fetal bovine serum (FBS) or 0.1% purified bovine serum albumin (BSA), trace elements, and growth supplements. For 4-12 weeks, the cultures demonstrate desmosomes, keratin fibers, basal proliferation, and stratification characteristic of keratinocytes. The addition of 12-O-tetradecanoylphorbol-13-acetate (TPA) resulted in approximately 70% cellular detachment, but with continued treatment, the remaining cells proliferated to confluence and stratified. This culture medium has application to a number of studies related to skin carcinogenesis in the murine model system that have not previously been possible.

Animals↗
PubMed1987

Sequential expression of OX2 and Thy-1 glycoproteins on the neuronal surface during development. An immunohistochemical study of rat cerebellum.

The related neuronal surface glycoproteins, Thy-1 and OX2, are shown here to have a reciprocal pattern of expression during development in rat cerebellum. OX2 appears at axonogenesis, on neuronal cell bodies and their axons. Immunohistochemical staining for this molecule then gradually wanes, and over the same period the cells acquire their first, weak staining for Thy-1. Intense Thy-1 expression occurs during the period of dendritic growth.

Animals↗
PubMed1986

Migration of host astrocytes into superior cervical sympathetic ganglia autografted into the septal nuclei or choroid fissure of adult rats.

Adult astrocytes and their processes, identified by glial fibrillary acidic protein immunohistochemistry and by electron microscopy, migrate into superior cervical ganglia auto-transplanted into the choroid fissure or septal nuclei of adult rats. Migration routes were along the blood vessels, and along the Schwann cell bundles of the transplant. Ultrastructurally, astrocytic processes could be seen to lie in direct contact with Schwann cell processes within the basal lamina enwrapping the Schwann cell and its associated axons. Around the region of the host/transplant interface, the astrocytes were transformed into flattened cells with many short, irregular, fringe-like processes, but within the depths of the transplant mass they resumed a more stellate configuration. Glial fibrillary acidic protein immunoreactivity was present within the intrinsic satellite and Schwann cells of the grafted ganglia, but at a much lower level than in the host astrocytes. It is concluded that reactive astrocytes from adult host central nervous system migrate into peripheral ganglionic transplants, where they differentiate and establish organized arrangements with the ganglionic elements.

Animals↗
PubMed1986

Brotizolam, a triazolothienodiazepine, in insomnia.

Sixty-three outpatients with chronic insomnia were treated for 3 weeks under double-blind conditions with either brotizolam (n = 29) at a dose of 0.25 mg or 0.5 mg or placebo (n = 34). A 3-day placebo period preceded and followed the double-blind treatment phase. Brotizolam consistently produced significantly more sleep improvement than placebo but also more adverse effects. In those patients switched abruptly from brotizolam to placebo, rebound insomnia was observed, being most marked at the first post-brotizolam placebo night.

Adult↗
PubMed1986

Structural microheterogeneity of the muscarinic cholinergic receptor is not related to functional diversity identified by differences in affinity for pirenzepine.

The muscarinic receptor for acetylcholine shows a diversity in ligand binding properties and effector mechanisms which have suggested the existence of two subtypes (M1 and M2), to which the selective antagonist pirenzepine binds with markedly different affinities. The receptor from rat brain, covalently labelled with the alkylating antagonist tritiated propylbenzilylcholine mustard, displays a structural microheterogeneity on electrophoresis, covering the region of apparent molecular weight 66,000-76,000, with dominant components at 68,000 and 73,000. Selective inhibition by pirenzepine of labelling of the M1 receptor with tritiated mustard has been analysed on fluorographs of sodium dodecyl sulphate-polyacrylamide gels and shown to cause a uniform reduction in radioactive labelling of the broad receptor peak, rather than selectively inhibiting either the high- or low-molecular-weight regions of the band. It is further shown that although this receptor microheterogeneity is found for each of four brain regions studied, it is not found for the heart receptor, which gives a discrete labelled band of apparent molecular weight 72,000. It is therefore suggested that the structural microheterogeneity is the result of tissue-specific, posttranslational modification of the molecule, such as glycosylation, and is not directly related to the functional diversity of the receptor.

Animals↗
PubMed1986

Evidence that a slowly cycling subpopulation of adult murine epidermal cells retains carcinogen.

The distribution and persistence of radioactively labeled benzo(a)pyrene [B(a)P] in the skin of adult female SENCAR mice were investigated by autoradiography of epidermal whole mounts and cross-sections at intervals following a single initiating application of 200 nmol of either [3H]B(a)P (2 mCi) or [14C]B(a)P (23 muCi). One day after treatment, the entire thickness of the skin was labeled; the grain density was greatest over hair follicles, sebaceous glands, and interfollicular epidermis. At 1 and 2 weeks, decreases in the nuclear grain density were consistent with the overall pattern of epidermal renewal. One month after treatment, carcinogen label-retaining cells made up approximately 2% of the interfollicular basal cells. They were also present in the hair follicles, approximately 4 and 5% of basal cells in the infundibulum and external root sheath, respectively. They were rare in the germ region and dermal papilla. Carcinogen label-retaining cells were compared with slowly cycling [3H]thymidine label-retaining cells and "maturing" basal cells, two distinct proliferative subsets of adult murine epidermis. Carcinogen label-retaining cells were found to have characteristics of the slowly cycling cells: (a) most of the carcinogen labeled nuclei were found in the central regions of the epidermal proliferative units; (b) treatment of the carcinogen label-retaining cells with 2 micrograms of 12-O-tetradecanoylphorbol-13-acetate elicited labeled mitoses within 1 day, and a general decrease in grain density over basal nuclei. In contrast, maturing basal cells 4 days after a single injection of [3H]thymidine were found at the periphery of the epidermal proliferative units. Within 1 day after treatment with 2 micrograms of 12-O-tetradecanoylphorbol-13-acetate, maturing basal cells were displaced to the suprabasal layers. Double isotope-double emulsion autoradiographs demonstrated doubly labeled cells 1 month after continuous labeling with [3H]thymidine and [14C]B(a)P and provide evidence that the radioactive carcinogen is retained by the slowly cycling [3H]thymidine label-retaining cells. These observations suggest that a slowly cycling population of epidermal cells may be relevant to the initiation phase of two-stage carcinogenesis.

Animals↗
PubMed1985

Early stages of Purkinje cell maturation demonstrated by Thy-1 immunohistochemistry on postnatal rat cerebellum.

The cell surface glycoprotein, Thy-1, is present on Purkinje cells at birth, so allowing Thy-1 immunohistochemistry to demonstrate the final stage of migration and the transition to dendritic growth of these cells. In the most caudal lobule of the cerebellar cortex of the newborn rat, migrating Purkinje cells are found. These have a prominent process (up to 50 micron long) from which fine filopodia project, presumably sensing the environment in front of the cell. These cells are orientated tangentially, at right angles to the radial orientation they assume for dendritic growth. Strong Thy-1 labelling is found not only on their surface, but also on a cytoplasmic cap above the presumed leading pole of the nucleus. More rostrally in the cerebellar cortex, Purkinje cells arrive up to 3 days before birth and are quiescent until the postnatal development of their dendritic tree. At birth and during early postnatal periods a rounded cell is found with little cytoplasm; Thy-1 staining labels its surface and the fine processes which emanate from it. Such cells coexist with other Thy-1-positive Purkinje cells with more developed surface orientated processes. Even as early as the day of birth these fine processes cross the molecular layer and contact the lower level of the external granule layer. Orientated dendritic growth appears to occur by a selective thickening of these processes and a massive apical protrusion of intensely Thy-1-positive cytoplasm. The whole of the Purkinje cell surface membrane exhibits high levels of Thy-1 throughout dendritic growth and synaptogenesis, and cytoplasmic antigen is prominent during the period of greatest growth. Thy-1 is also found on the neurons of the deep cerebellar nuclei, and is seen transiently on Golgi interneurons. High levels of the antigen are present on blood vessels and choroid plexus at birth but are lost from these structures over the first 2 postnatal weeks.

Animals↗
PubMed1985

Late emergence of Thy-1 on climbing fibres demonstrates a gradient of maturation from the fissures to the folial convexities in developing rat cerebellum.

In the third week of postnatal life, Thy-1 staining of Purkinje cells starts to decrease, first in the depths of the fissures and then progressively, over the next 10 weeks, up the walls of the fissures to the convexities of the folia. This is accompanied by a far more striking appearance of high levels of Thy-1 on a network of fibres whose distribution strongly suggests they are climbing fibres. They acquire the antigen in the same topographical gradient of maturation, and at the same time, as Purkinje cells lose it. That these are climbing fibres was confirmed by destroying the inferior olive with 3-acetylpyridine, which also eliminated the intense Thy-1 staining in the cerebellum. At a stage (18 days) when only some climbing fibres in the molecular layer are seen to be Thy-1-positive, only a proportion of inferior olivary neurons are Thy-1-positive with intense antigen labelling over the Nissl substance. The possibility that Thy-1 also appears on mossy fibres, and at relatively low levels on parallel fibres, is discussed.

Afferent Pathways↗
PubMed1985

Specific patterns of fibre outgrowth from transplants to host mice hippocampi, shown immunohistochemically by the use of allelic forms of Thy-1.

Foetal mouse hippocampal primordia from mice homozygous for the Thy-1.1 allele were transplanted into the hippocampal region of adult histocompatible mice, homozygous for the Thy-1.2 allele. After survival periods of two months to one year the transplants consisted of a discrete tissue mass, well fused with the host, and distinguished from it by an intense Thy-1.1 immunoreactivity of the neuropil. The host hippocampus was entirely negative for Thy-1.1 immunoreactivity except for well defined projections arising from the transplant. These projections had three different patterns of distribution in the host: (1) a mossy-fibre-like distribution (to the stratum lucidum of field CA3); (2) a fimbria-like distribution (to the stratum oriens and stratum radiatum of fields CA1 and CA3), and (3) a commissural/association-like distribution (to the inner stratum moleculare of the dentate gyrus). Analysis of the position of the transplants and their component cell types indicated that, for each of the three distribution patterns, three conditions had to be fulfilled: (1) the transplant had to contain the appropriate type of cell (granule cells for mossy fibre projections, and larger pyramid-like cells for the other two); (2) the transplant neurons giving rise to the projection had to lie in direct contact with the host field to be innervated, and (3) the terminal field had to be specifically denervated. Thus, for three fibre systems the patterns of transplant-to-host projections observe rules of organization comparable to those of the normal hippocampal circuitry. This implies that in the adult host brain there remain (or there can be elicited) the molecular cues capable of establishing patterns of neuronal connectivity comparable to those formed during normal development.

Animals↗
PubMed1985

Solitary magnocellular neurons in the homozygous Brattleboro rat have vasopressin and glycopeptide immunoreactivity.

A small but distinctive population (about 1 in 600) of magnocellular neurosecretory neurons in homozygous Brattleboro rats are immunoreactive for vasopressin, and a similar number for the carboxy-terminal glycopeptide of the vasopressin prohormone. These solitary cells are found in all animals and in all parts of the magnocellular system, but not in the suprachiasmatic or other hypothalamic nuclei. The majority of the solitary cells do not differ morphologically from the remainder of the magnocellular neurons. The immunoreactivity is markedly denser in the Nissl bodies than in the Golgi region. Serial sections show that the vasopressin and glycopeptide immunoreactive material is co-localized in the same cells, and that these cells are not immunoreactive for oxytocin. A published sequence for the Brattleboro vasopression gene mutation indicates a base-deletion upstream from the glycopeptide-encoding portion, and implies a frameshift that would cause translation of incorrect protein continuing into the poly-A tail of the mRNA. Although this could apply to the majority of the Brattleboro presumptive vasopressin neurons, the co-localization in our solitary cells of material immunoreactive with antibodies to both the amino- and carboxy-terminals of the vasopressin prohormone suggest that in these cases an additional mechanism may be operating.

Animals↗
PubMed1985

A neutralising monoclonal antibody against a paramyxovirus reacts with a brain antigen.

A monoclonal antibody against simian virus (SV5) HN glycoprotein which specifically neutralises the virus cross-reacts in immunofluorescence with an antigen in the cytoplasm of Purkinje cells of adult rat brain. After fixation in acetic acid-ethanol a cross-reaction is also seen with a myelin component. Cross-reaction of this antibody with human brain was also observed on section using immunofluorescence and in tissue extracts using ELISA and radioimmune assays. Monoclonal antibodies against other viruses, against another epitope on the same virus polypeptide and against another SV5 polypeptide of the same isotype were all negative in these tests.

Animals↗