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Biomedical subjects

R Hawkes

Publications and source records attributed to R Hawkes.

At least 91 records · Page 5Linked to original sources
PubMed1987

Neuronal maturation in the normal and hypothyroid rat cerebellar cortex studied with monoclonal antibody MIT-23.

By immunocytochemistry we have studied the expression of the mitochondria-associated polypeptide MIT-23 during the postnatal development of the normal and hypothyroid rat cerebellar cortex, in afferent fibers, and also in neurons of the cerebellar nuclei. The glial cells are never immunoreactive. In all neurons of the cerebellar cortex, MIT-23 expression always occurs after the final mitosis and migration are complete, and persists throughout adult life. Almost all MIT-23 expression begins postnatally. A few Purkinje cells are already immunoreactive at birth and the rest begin expression during the following two days. Immunoreactive Golgi and granule cells are found from postnatal day 4 (P4), basket cells from P10, and stellate cells from P16. Purkinje cells from different anteroposterior regions of the vermis express different levels of MIT-23 with higher staining intensities in lobules I to IV. These differences appear early in development and are retained in the adult. MIT-23 expression in the hypothyroid cerebellar cortex differs from that in control animals only in minor ways. However, sections immunoperoxidase-stained with anti-MIT-23 antibody reveal that, in addition to previously reported alterations in cerebellar development due to a shortage of thyroid hormones, Purkinje cell axonal development is slowed down in the hypothyroid condition, and occasional Purkinje cells in normal and especially in hypothyroid animals have their somata and or dendrites in ectopic locations. Analysis of these cells reveals a preferential direction of dendritic trunk growth in the direction of the molecular layer. Furthermore, secondary branching of ectopic dendrites is confined exclusively to the developing molecular layer, as in normal Purkinje cells, thus suggesting that neither the mature nor immature granule cell environment is sufficient to sustain normal dendritic development.

Animals↗
PubMed1987

Antigenic map of the rat cerebellar cortex: the distribution of parasagittal bands as revealed by monoclonal anti-Purkinje cell antibody mabQ113.

Both anatomical and physiological mapping methods have revealed that the mammalian cerebellar cortex consists of a family of parasagittal bands of cells, each band with its own pattern of afferent and efferent axons. Monoclonal antibody mabQ113 recognizes an unknown polypeptide antigen that is confined to a subset of rat cerebellar Purkinje cells. Immunoreactive cells are arranged into parasagittal bands extending throughout the vermis and hemispheres. Expression of the Q113 epitope by individual Purkinje cells may not be all-or-nothing, since the bands tend to be more strongly stained in the vermis than the hemispheres. The band display is symmetrical about the midline and reproducible from individual to individual. Whole-mount immunocytochemistry and serial reconstruction reveal a median band of mabQ113+ Purkinje cells adjacent to the midline (P1+) and six other positive bands disposed symmetrically at either side (P2+ to P7+). Bands are distinct throughout most of the cortex but tend to fuse ventrally and caudally. There are two sources of interindividual differences. Firstly, most animals express supernumerary "satellite" bands in the vermis. Satellite bands are usually only one cell wide, are not bilaterally symmetrical, and differ in position and number from individual to individual. Secondly, the precise position of an individual band can differ, perhaps according to the variable cortical lobulation, for example, the position of P4+ in lobules VIII/IX and P6+ in lobule VII. While a scheme of parasagittal bands is a good description of the vermian organization, the distribution of mabQ113+ and mabQ113- Purkinje cells in the hemispheres may be better described as a checkerboard of antigenic patches.

Animals↗
PubMed1987

Monoclonal antibodies reveal the global organization of the cerebellar cortex.

Electrophysiological mapping of the rat cerebellar cortex has revealed an elaborate functional somatotopy that tract tracing procedures have shown to correlate with specific patterns of afferent and efferent connectivity that encompass the cerebellum as a whole. In contrast, most anatomical and biochemical procedures suggest that the cerebellar cortex is remarkably uniform. To unmask covert molecular heterogeneity underlying the functional map, it is appropriate to use monoclonal antibody technology to search for antigenic epitopes whose cerebellar distribution reflects or encodes the positional information. Given that no preconditions can be set on the biochemical nature of the putative epitopes, a shotgun approach to immunization and screening is required. The construction of monoclonal antibodies and screening for specificities that reveal positional information is discussed with examples from an anti-cerebellar antibody library.

Antibodies, Monoclonal↗
PubMed1987

The development of differential mabQ113-immunoreactivity in the rat habenular complex.

Monoclonal antibody mabQ113 selectively labels a subset of Purkinje cells which are arranged in parasagittal bands throughout the vermis and hemispheres of the rat cerebellar cortex. No other cerebellar cell types are immunoreactive. By contrast, in the remainder of the brain the mabQ113 epitope is located primarily in glial cells. In general, the glial immunoreactivity is not differentially distributed. An exception is that mabQ113 densely and uniformly stains the lateral habenula (LHb) but gives no labelling of the medial habenula (MHb). During cerebellar development, the mabQ113 epitope is expressed in three stages. Before postnatal day 7 (P7) all Purkinje cells are negative. Secondly, all Purkinje cells become mabQ113+ between P7 and P12. The parasagittal bands are created between P12 and P30 by selective suppression of epitope expression. To explore whether epitope suppression is also responsible for differential staining patterns in other brain regions the ontogenic development of mabQ113 immunoreactivity has been mapped in the habenular complex. Neither the MHb nor the LHb express the mabQ113 epitope prenatally. P1 is the first age at which the LHb is stained. During the next few days the intensity of staining within the LHb steadily increases until the adult pattern is attained at P6. At no time is there expression of the mabQ113 antigen in the MHb. This also confirms that the two classes of habenular astrocytes, mabQ113-/GFAP+ and mabQ113+/GFAP+, are intrinsically different throughout postnatal life.

Animals↗
PubMed1987

Anti-CNS antibodies in neurological and psychiatric disorders.

To investigate the possibility that anti-CNS antibodies may play a pathogenic role in a number of neurological and psychiatric disorders, a population study was undertaken. Serum samples were obtained from a total of 257 adults and were screened against sodium dodecyl sulphate polyacrylamide gel electrophoretic blots of various normal, necropsy-derived adult human brain regions. The incidence of IgG immunoreactive banding in the total sample was 30%. Within the diagnostic groups the incidence of banding was: controls 32%, schizophrenia 28%, mental retardation 27%, cerebellar ataxia 33%, Parkinson's disease 22%, myasthenia gravis 45% and epilepsy 31%. The differences are not statistically significant. There was no significant difference in the numbers and locations of bands between the various diagnostic groups and the controls. The overall incidence of immunoreactivity corresponding to the high molecular weight subunit of neurofilaments was only 6%, thus not confirming a previously reported incidence of 95%. The similarity between the diagnostic and the control sera suggests that caution should be exerted in interpreting the pathogenic significance of anti-CNS immunoreactive banding on Western blots.

Adult↗
PubMed1986

A monoclonal antibody to mammalian neurofilament protein stains somata and dendrites in gymnotid fish.

Monoclonal antibody N210 (mabN210) recognizes the 210 kdalton neurofilament protein in mammals and gives characteristic immunocytochemical staining of neurofilament-rich processes. For example, in the cerebellum it recognizes myelinated axons and the calyx formed by basket cell axon collaterals. The distribution of mabN210 immunoreactivity was studied in the gymnotid brain (Apteronotus albifrons). In contrast to the mammalian distribution, mabN210 immunoreactivity was not found in most axons of the gymnotid brain. Instead, deposits of reaction product were present in the somata and dendrites of most neurons and were especially dense in those neurons with extensive dendritic trees, the Purkinje cells, pyramidal cells of the electrosensory lateral line lobe, the crest cells of the nucleus medialis and the pyramidal cells of the tectum. Electrosensory lateral line lobe pyramidal cells are known to contain few, if any, neurofilaments in their dendrites. Western blots of whole gymnotid brain proteins demonstrated that mabN210 recognizes two polypeptides apparent molecular weights 60 and 19 kdaltons. These proteins are thus antigenically similar to neurofilament protein and their expression in the gymnotid brain may be related to the peculiar dendritic branching pattern of Purkinje cells and similar cell types.

Afferent Pathways↗
PubMed1986

A survey of MabQ113 immunoreactivity in the adult rat brain: differential staining of the lateral and medial habenular nuclei.

Monoclonal antibody mabQ113 recognizes a polypeptide antigen which, in rat cerebellum, is confined exclusively to a subset of Purkinje cells which are organized into parasagittal bands. In this report we have explored the distribution of mabQ113 immunoreactivity in some other regions of the rat brain. The most interesting result was a dramatic differential staining of the habenular complex in which mabQ113 densely and uniformly stained the lateral habenula but did not stain the medial habenula. Within the lateral habenula reaction product is localized primarily in the cellular processes of astrocytes but there is also staining of neighboring neuronal dendritic and axonal profiles. The afferent and efferent tracts of the habenular nuclei are not immunoreactive and there was no systematic difference in staining between the afferent and efferent nuclear groups of the two habenular nuclei. The pattern of mabQ113 immunoreactivity in rat brain is distinct from previously described biochemical differentiation markers of the two nuclei and thus may serve as a useful probe to study habenular anatomy, development and function.

Afferent Pathways↗
PubMed1986

Immunocytochemical demonstration of topographic ordering of Purkinje cell axon terminals in the fastigial nuclei of the rat.

We have used a monoclonal antibody, mabQ113, which selectively stains a subset of cerebellar Purkinje cells, to study the topography of the corticonuclear projection of the median vermis to the fastigial nuclei in the rat. The fastigial projection zone contains both mabQ113+ and mabQ113- Purkinje cells grouped into parasagittal bands. The immunoreactivity extends throughout the Purkinje cell including the axon terminals and thus it is possible to investigate the topographic distribution of mabQ113+ terminals. In the fastigial nuclei the target cells receiving mabQ113+ axon terminals are concentrated in the caudal pole. In the rostral pole, cells receive anti-GAD+ terminals but not mabQ113+ terminals. There is no gradient in anti-GAD staining. Double-labelling experiments with mabQ113, anti-GAD, and an antisynaptic antibody mabQ155 suggest that there is little or no mixing of mabQ113+ and mabQ113- Purkinje cell terminals on the same target neuron.

Animals↗
PubMed1986

Selective suppression of neurofilament antigen expression in the hypothyroid rat cerebral cortex.

As an integral component of the cytoskeleton neurofilaments play a central role in the establishment and maintenance of neuronal form. In particular, high neurofilament concentrations are characteristic of many classes of axons in the central nervous system. Isolated neurofilaments from rat brain consist of 3 distinct polypeptides with apparent molecular weights 210K, 160K and 68K. A murine monoclonal antibody, mabN210, has been produced which specifically recognizes an epitope associated with the high molecular weight subunit and this antibody has been used to explore the regulation of neurofilament expression during brain development. It has been shown that in the rat cerebellar cortex, the expression of mabN210-immunoreactivity in basket cell axons is severely suppressed in hypothyroidism while neurofilament antigen expression in other cerebellar axons seems not to require thyroid hormones. In view of the well-known cortical deficits in hypothyroidism, these studies have now been extended to include the developing rat cerebral cortex and selected cortical afferent and efferent axons. In hypothyroid rats there is a marked suppression of mabN210-immunoreactivity in the cerebral cortex and corpus callosum and, to a lesser extent, there is a reduction in staining in the internal capsule. By contrast, hypothyroidism did not reduce mabN210-immunoreactivity in the lateral olfactory tract or the stria medullaris. In rats, serum thyroid hormone starts to rise to adult levels on postnatal day 4. It appears that axons that have attained their mature distribution prior to the onset of thyroid hormone expression are not affected by hypothyroidism whereas mabN210-immunoreactivity is suppressed in those axonal tracts that reach a mature distribution after P4.

Afferent Pathways↗
PubMed1985

Monoclonal antibodies reveal sagittal banding in the rodent cerebellar cortex.

We have produced two monoclonal antibodies against polypeptide-associated antigens of developing rat cerebellum. One antibody recognizes an antigen associated with synaptic vesicles and another binds to a polypeptide which is restricted to the cytoplasm of a subset of cerebellar Purkinje cells. Both antibodies reveal the biochemical differentiation of the rodent cerebellar cortex into antigenically distinct sagittal zones.

Animals↗
PubMed1985

Selective staining of a subset of Purkinje cells in the human cerebellum with monoclonal antibody mabQ113.

MabQ113 is a monoclonal antibody raised against rat cerebellum which selectively strains Purkinje cells. Likewise, in mabQ113-immunoperoxidase stained sections of human cerebellum, deposits of reaction product are found only in the Purkinje cells. The dendritic arborizations, cell body, and axonal processes are immunoreactive. In rat, mabQ113 reveals a series of parasagittal antigenic bands which run throughout the cerebellar cortex. The staining distribution in human cerebellar cortex likewise reveals heterogenous staining but the pattern is a complex one and seems to be unlike the parasagittal banding found in the rat. In a number of human diseases Purkinje cell degeneration is not uniform throughout the vermis and cerebellar hemispheres. It is possible that mabQ113+ and mabQ113- subsets of Purkinje cells may respond differentially to various pathological conditions.

Animals↗
PubMed1985

Basket cell development in the normal and hypothyroid rat cerebellar cortex studied with a monoclonal anti-neurofilament antibody.

We have used a monoclonal antibody against an antigenic determinant of the 210-kdalton neurofilament protein to study basket cell maturation in rat cerebellar cortex. Neurofilament immunoreactivity first appears in basket cells at postnatal day 12 and mature axonal "pinceaux" are present at postnatal day 17. There are large differences in the rate of maturation from lobe to lobe which do not fully correspond to the rate of Purkinje cell differentiation. In hypothyroid rats the expression of the neurofilament antigen by basket cells is almost completely suppressed.

Animals↗
PubMed1984

Thermodynamic stability and point mutations of bacteriophage T4 lysozyme.

The thermodynamics of melting of bacteriophage T4 lysozyme and four of its mutants have been measured by van't Hoff methods. The effect of pH has been explored and utilized to obtain the dependence of the enthalpy on temperature as suggested by Privalov and co-workers. The enthalpy change is a steep linear function of temperature. delta Cp is large and constant within experimental error. Changes in delta Hu are as large as 30% for a single point mutation. Changes in enthalpy are largely compensated by changes in entropy. Changes in stability, as measured by the free energy of unfolding, are smaller than those of delta H, but are very large in a relative sense, since delta G is very much smaller than delta H. Origins of the destabilization caused by mutations are discussed.

Amino Acid Sequence↗
PubMed1984

18B1: an axon-specific antigen associated with many proteins.

We describe an antigen, 18B1, defined by a monoclonal antibody. Immunoperoxidase staining of brain sections shows that 18B1 is selectively associated with neurofilament-rich axons. Antibody staining of sodium dodecyl sulphate-gel blots, on the other hand, shows that 18B1 is associated with a large number of proteins, none of which are structural components of brain neurofilaments. The antigen is sensitive to a variety of proteases but is not degraded by various glycosidases, suggesting that 18B1 is probably an amino acid sequence. Its association with neurofilament-rich axons together with its absence from neurofilaments themselves suggests that it may be involved in mediating interactions between neurofilaments and the proteins that bear it.

Animals↗
PubMed1982

MIT-23: a mitochondrial marker for terminal neuronal differentiation defined by a monoclonal antibody.

We describe a monoclonal antibody directed against a neuron-specific mitochondrial protein from rat brain. On protein blots the antibody recognizes a single polypeptide of apparent molecular weight of 23,000. By solid-phase immunoassay the antigen was detected in nonneural tissues. Within neurons, the antibody stains cytoplasmic granules that immunoelectron microscopy shows are mitochondria, hence the designation MIT-23. Immunocytochemical staining of the cerebellar cortex showed that MIT-23 occurs in all the neuronal types but is absent from glial and other nonneuronal cells. During neonatal development of the cerebellum, MIT-23 appears in neurons after their final cell division or migration is completed, suggesting that specific proteins associated with mitochondria participate in neuronal maturation.

Animals↗