Sensitization of central trigeminovascular neurons: blockade by intravenous naproxen infusion.

We have previously observed that migraine attacks impervious to triptan therapy were readily terminated by subsequent i.v. administration of the non-steroidal anti-inflammatory drug (NSAID) ketorolac. Since such attacks were associated with periorbital allodynia--a symptom of central sensitization--we examined whether infusion of the NSAID naproxen can block sensitization of central trigeminovascular neurons in the medullary dorsal horn, using in vivo single-unit recording in the rat. Topical exposure of the cerebral dura to inflammatory soup (IS) for 5 min resulted in a short-term burst of activity (<8 min) and a long-lasting (>120 min) neuronal hyper-responsiveness to stimulation of the dura and periorbital skin (group 1). Infusion of naproxen (1 mg/kg) 2 h after IS (group 1) brought all measures of neuronal responsiveness back to the baseline values recorded prior to IS, and depressed ongoing spontaneous activity well below baseline. When given preemptively 1 h before IS (group 2), naproxen blocked the short-term burst of activity and every long-term measure of neuronal hyper-responsiveness that was studied in the central neurons. The same preemptive treatment, however, failed to block IS-induced short-term bursts of activity in C-unit meningeal nociceptors (group 3). The results suggest that parenteral administration of naproxen, unlike triptan therapy, can exert direct inhibition over central trigeminovascular neurons in the dorsal horn. Though impractical as a routine migraine therapy, parenteral NSAID administration should be useful as a non-narcotic rescue therapy for migraine in the setting of the emergency department.

p21 controls patterning but not homologous recombination in RPE development.

p21/WAF1/CIP1/MDA6 is a key cell cycle regulator. Cell cycle regulation is an important part of development, differentiation, DNA repair and apoptosis. Following DNA damage, p53 dependent expression of p21 results in a rapid cell cycle arrest. p21 also appears to be important for the development of melanocytes, promoting their differentiation and melanogenesis. Here, we examine the effect of p21 deficiency on the development of another pigmented tissue, the retinal pigment epithelium. The murine mutation pink-eyed unstable (p(un)) spontaneously reverts to a wild-type allele by homologous recombination. In a retinal pigment epithelium cell this results in pigmentation, which can be observed in the adult eye. The clonal expansion of such cells during development has provided insight into the pattern of retinal pigment epithelium development. In contrast to previous results with Atm, p53 and Gadd45, p(un) reversion events in p21 deficient mice did not show any significant change. These results suggest that p21 does not play any role in maintaining overall genomic stability by regulating homologous recombination frequencies during development. However, the absence of p21 caused a distinct change in the positions of the reversion events within the retinal pigment epithelium. Those events that would normally arrest to produce single cell events continued to proliferate uncovering a cell cycle dysregulation phenotype. It is likely that p21 is involved in controlling the developmental pattern of the retinal pigment. We also found a C57BL/6J specific p21 dependent ocular defect in retinal folding, similar to those reported in the absence of p53.

Susceptibility of proliferating cells to benzo[a]pyrene-induced homologous recombination in mice.

The pink-eyed unstable mutation, p(un), is the result of a 70 kb tandem duplication within the murine pink-eyed, p, gene. Deletion of one copy of the duplicated region by homologous deletion/recombination occurs spontaneously in embryos and results in pigmented spots in the fur and eye. Such deletion events are inducible by a variety of DNA damaging agents, as we have observed previously with both fur- and eye-spot assays. Here we describe a study of the effect of exposure to benzo[a]pyrene (B[a]P) at different times of development on reversion induction in the eye. Previously we, among others, have reported that the retinal pigment epithelium (RPE) displays a position effect variegation phenotype in the pattern of pink-eyed unstable reversions. Following an acute exposure to B[a]P or X-rays on the tenth day of gestation an increased frequency of reversion events was detected in a distinct region of the adult RPE. Examining exposure at different times of eye development reveals that both B[a]P and X-rays result in an increased frequency of reversion events, though the increase was only significant following B[a]P exposure, similar to our previous report limited to exposure on the tenth day of gestation. Examination of B[a]P-exposed RPE in the present study revealed distinct regions where the induced events lie and that the positions of these regions are found at increasing distances from the optic nerve the later the time of exposure. This position effect directly reflects the previously observed developmental pattern of the RPE, namely that cells in the regions most distal from the optic nerve are proliferating most vigorously. The numbers and positions of RPE cells displaying the transformed (pigmented) phenotype strongly advocate the proposal that dividing cells are at highest risk to deletions induced by carcinogens.

Benzo(a)pyrene and X-rays induce reversions of the pink-eyed unstable mutation in the retinal pigment epithelium of mice.

The pink-eyed unstable (p(un)) mutation is the result of a 70kb tandem duplication within the murine p gene. Homologous deletion/recombination of the locus to wild-type occurs spontaneously in embryos and results in pigmented spots in the fur and eye that persist for life. Such deletion events are also inducible by a variety of DNA damaging agents, as we have observed previously with the fur spot assay. Here, we describe the use of the retinal pigment epithelium (RPE) of the eye to detect reversion events induced with two differently acting agents. Benzo(a)pyrene (B(a)P) induces a high frequency, and X-ray exposure a more modest increase, of p(un) reversion in both the fur and the eye. The eye-spot assay requires fewer mice for significant results than the fur spot assay. Previous work had elucidated the cell proliferation pattern in the RPE and a position effect variegation phenotype in the pattern of p(un) reversions, which we have confirmed. Acute exposure to B(a)P or X-rays resulted in an increased frequency of reversion events. The majority of the spontaneous reversions lie toward the periphery of the RPE whereas induced events are found more centrally, closer to the optic nerve head. The induced distribution corresponds to the major sites of cell proliferation in the RPE at the time of exposure, and further advocates the proposal that dividing cells are at highest risk to develop deletions.

Phototransduction in transgenic mice after targeted deletion of the rod transducin alpha -subunit.

Retinal photoreceptors use the heterotrimeric G protein transducin to couple rhodopsin to a biochemical cascade that underlies the electrical photoresponse. Several isoforms of each transducin subunit are present in the retina. Although rods and cones seem to contain distinct transducin subunits, it is not known whether phototransduction in a given cell type depends strictly on a single form of each subunit. To approach this question, we have deleted the gene for the rod transducin alpha-subunit in mice. In hemizygous knockout mice, there was a small reduction in retinal transducin alpha-subunit content but retinal morphology and the physiology of single rods were largely normal. In homozygous knockout mice, a mild retinal degeneration occurred with age. Rod-driven components were absent from the electroretinogram, whereas cone-driven components were retained. Every photoreceptor examined by single-cell recording failed to respond to flashes, with one exception. The solitary responsive cell was insensitive, as expected for a cone, but had a rod-like spectral sensitivity and flash response kinetics that were slow, even for rods. These results indicate that most if not all rods use a single transducin type in phototransduction.

Morphological, physiological, and biochemical changes in rhodopsin knockout mice.

Mutations in rod opsin, the visual pigment protein of rod photoreceptors, account for approximately 15% of all inherited human retinal degenerations. However, the physiological and molecular events underlying the disease process are not well understood. One approach to this question has been to study transgenic mice expressing opsin genes containing defined mutations. A caveat of this approach is that even the overexpression of normal opsin leads to photoreceptor cell degeneration. To overcome the problem, we have reduced or eliminated endogenous rod opsin content by targeted gene disruption. Retinas in mice lacking both opsin alleles initially developed normally, except that rod outer segments failed to form. Within months of birth, photoreceptor cells degenerated completely. Retinas from mice with a single copy of the opsin gene developed normally, and rods elaborated outer segments of normal size but with half the normal complement of rhodopsin. Photoreceptor cells in these retinas also degenerated but did so over a much slower time course. Physiological and biochemical experiments showed that rods from mice with a single opsin gene were approximately 50% less sensitive to light, had accelerated flash-response kinetics, and contained approximately 50% more phosducin than wild-type controls.

Differentiation of engrafted multipotent neural progenitors towards replacement of missing granule neurons in meander tail cerebellum may help determine the locus of mutant gene action.

Previously we observed that stable clones of multipotent neural progenitor cells, initially isolated and propagated from the external granular layer of newborn wild-type mouse cerebellum, could participate appropriately in cerebellar development when reimplanted into the external granular layer of normal mice. Donor cells could reintegrate and differentiate into neurons (including granule cells) and/or glia consistent with their site of engraftment. These findings suggested that progenitors might be useful for cellular replacement in models of aberrant neural development or neurodegeneration. We tested this hypothesis by implanting clonally related multipotent progenitors into the external granular layer of newborn meander tail mice (gene symbol=mea). mea is an autosomal recessive mutation characterized principally by the failure of granule cells to develop in the cerebellar anterior lobe; the mechanism is unknown. We report that approximately 75% of progenitors transplanted into the granuloprival anterior lobe of neonatal mea mutants differentiated into granule cells, partially replacing or augmenting that largely absent neuronal population in the internal granular layer of the mature meander tail anterior lobe. (The ostensibly 'normal' meander tail posterior lobe also benefited from repletion of a more subtle granule cell deficiency.) Donor-derived neurons were well-integrated within the neuropil, suggesting that these progenitors' developmental programs for granule cell differentiation were unperturbed. These observations permitted several conclusions. (1) That exogenous progenitors could survive transplantation into affected regions of neonatal meander tail cerebellum and differentiate into the deficient cell type suggested that the microenvironment was not inimical to granule cell development. Rather it suggested that mea's deleterious action is intrinsic to the external granular layer cell. (Any cell-extrinsic actions--albeit unlikely--had to be restricted to readily circumventable prenatal events.) This study, therefore, offers a paradigm for using progenitors to help determine the site of action of other mutant genes or to test hypotheses regarding the pathophysiology underlying other anomalies. (2) In the regions most deficient in neurons, a neuronal phenotype was pursued in preference to other potential cell types, suggesting a 'push' of undifferentiated, multipotent progenitors towards compensation for granule cell dearth. These data suggested that progenitors with the potential for multiple fates might differentiate towards repletion of deficient cell types, a possible developmental mechanism with therapeutic implications. Neural progenitors (donor or endogenous) might enable cell replacement in some developmental or degenerative diseases--most obviously in cases where a defect is intrinsic to the diseased cell, but also, under certain circumstances, when extrinsic pathologic forces may exist.

ERG abnormalities in relation to histopathologic findings in vitiligo mutant mice.

The vitiligo, mivit, mutation has several prenatal and perinatal effects on development of the retinal pigment epithelium, and later, leads to extensive, progressive degeneration of photoreceptor cells in the neural retina of homozygous affected mice. The aim of the present study was to determine by functional criteria how early can abnormalities be detected in the neural retina. Electroretinograms (ERGs) were correlated with histopathological findings in the same animals. Congenic homozygous mutants, heterozygotes, and homozygous wild-type mice were studied at 2, 3, 6, 24 and 56 weeks of age, the same animals being tested serially at the three older time points. The nontested eye of each animal was embedded in Epon and sectioned at 1 micron for light microscopic study. ERG recordings from vitiligo homozygotes differed from heterozygous and wild-type mice, but the latter two groups did not differ from each other. As early as two weeks of age, homozygous mutants showed a significant reduction of rod dominated maximum ERG a-wave and b-wave amplitude. ERG b-wave sensitivity (sigma) was significantly reduced, and ERG implicit times were delayed for homozygous mutants at 3 (a-wave) and 6 (b-wave) weeks of age. This is the first study to report reduced and delayed ERG a-waves and b-waves in this animal model, like the early functional abnormalities in human retinitis pigmentosa, and also the first to show short and disoriented rod outer segments, beginning retinal separation from the pigment epithelium, and a few macrophage-like cells already present in the subretinal space at 2 weeks of age (in three of four homozygous mutant eyes examined). Given these early functional and structural abnormalities in the neural retina, it remains to be determined whether the mi gene targets the retinal pigment epithelial cell, the photoreceptor cell, or both.

Mapping and retinal phenotype of the hugger mutation in the mouse.

Hugger, hug, is a recessively expressed mutation in mice that features mildly abnormal locomotion, not yet explained, and a unique combination of developmental and degenerative retinal abnormalities. Analysis with the efficient MEV linkage testing stock established that hug is on mouse Chr 19 about 14 cM from th centromere, between the microsatellite markers D19Mit28 and D19Mit14. An abnormal retinal phenotype was recognized on the day of birth, when some retinal ganglion cells already lie in abnormal positions in the inner plexiform layer. By postnatal day 18 the number of neurons is reduced in all three cellular layers of the retina. Rod photoreceptor cells develop only rudimentory outer segments, and by 9 months of age, about 75% of the photoreceptor cells have completely disappeared. Similar photoreceptor cell abnormalities are seen in prph2 (formerly rds) homozygotes, which lack the peripherin/rds protein of the rod outer segments, but a mating of the respective homozygotes yielded normal progeny. Rom1, which codes for an outer segment protein similar to peripherin/rds, maps to a more proximal position on Chr 19.

Phagosome number and distribution in retinal pigment epithelial cells of vitiligo mutant mice.

The vitiligo mutant mouse has a disorder affecting the interaction of retinal pigment epithelium (RPE) and photoreceptor cells of the neural retina. Among the phenotypic features are patches of hyper- and hypopigmentation in the embryonic RPE, increased RPE cell production neonatally, and a later onset of progressive photoreceptor cell degeneration that continues for more than one year until all photoreceptor cells are gone. Failure of RPE microvilli to intertwine with rod outer segments (ROS) at any age, the accumulation of ROS membranous fragments in the subretinal space, and a relatively early retinal separation from the RPE suggested analysis of whether RPE phagocytosis might be impaired. Post-natal day 23 (P23) and P36 mutant and congenic control wild-type mice were kept in darkness overnight and eyes were examined by light and transmission electron microscopy 0.5 hr before, 1.5 hr after and 10.5 hr after lights turned on at 0700 hr. At these ages ROS have not yet degenerated, though they are shorter than normal and somewhat misoriented. The number of phagosomes per RPE cell was markedly reduced in mutants compared to controls at both ages and all time points. Nonetheless, the highest counts were obtained 1.5 hr after the lights turned on in mutant and control specimens. In the mutant eyes, the proportion of phagosomes in the microvillous zone of the RPE cells was consistently lower than in any other cellular compartment. Phagosome distribution in the apical and basal zones of the RPE cell cytoplasm was within normal limits. Macrophage-like cells become numerous in the subretinal space at older ages, but were already present at P23 and P36, and contained phagosomes in their cytoplasm. The hypothesis is proposed that binding of ROS to RPE cells might be defective in vitiligo mice, in contrast to the rdy rat, where the work of others indicates that binding is normal and the subsequent ingestion of phagosomes is impaired.

Pigment epithelial and retinal phenotypes in the vitiligo mivit, mutant mouse.

PURPOSE: To describe the abnormal phenotype in retinal pigment epithelium (RPE) and neural retina of vitiligo mutant mice from embryonic stages to old age. METHODS: Eyes of wild-type controls and congenic vitiligo mutants were examined by light and electron microscopy from embryonic day (E) 12 to 2 years of age. The amount and distribution of pigment in the RPE was studied in wholemounts. RESULTS: Earliest phenotypic expression of mivit is seen in the RPE, which is abnormally multilayered dorsally at E12 to E13, and contains both hyperpigmented and hypopigmented patches. Postnatally, most RPE cells have abnormally short, compact, apical microvilli not containing melanosomes and not interdigitating with rod outer segments (ROS). Rod outer segments begin to degenerate relatively late, at approximately postnatal day (P) 30, and fragments accumulate in the subretinal space; photoreceptor nuclei decrease in number progressively from approximately P60 to P500. Retinal detachment, more prominent than in most other retinal degenerations, begins as ROS break up. Additional unusual events are the appearance of macrophage-like cells in the subretinal space by P21 to P60 and extensive shedding of photoreceptor nuclei across the external limiting membrane and into the subretinal space from approximately P180 to P500. Photoreceptor cell degeneration follows a radial gradient, more severe centrally, and is more advanced superiorly than inferiorly. By 2 years, almost all rod and cone cells are gone, and the residual neural retina is invaded by heavily pigmented cells. CONCLUSIONS: The initial ocular target of the mivit gene is the RPE, which is abnormal for many weeks before photoreceptor cells differentiate and become demonstrably affected. The authors hypothesize that the slowly progressive photoreceptor cell degeneration is secondary to abnormal function of the RPE. This mutation serves to refocus attention on critical influences of the RPE on function and maintenance of photoreceptor cells.

Increased cell genesis in retinal pigment epithelium of perinatal vitiligo mutant mice.

PURPOSE: To compare cell proliferation in vitiligo and control mouse retinal pigment epithelium (RPE) perinatally. METHODS: C57BL/6J-mivit/mivit mice and congenic +/+ controls were injected once with bromodeoxyuridine 1 hour before they were killed between embryonic day 18 and postnatal day 8. Wholemounts of Carnoy-fixed posterior eyecups, minus lens and neural retina, were stained immunohistochemically to detect DNA synthesis (bromodeoxyuridine incorporation) and mitotic cells (R3 antibody binding). Cells were counted in carefully controlled sampling sites, and total RPE area and face-view cell areas were calculated. Retinal pigment epithelial cell heights were measured on light and electron micrographs. RESULTS: Total surface areas of the mutant and control RPE monolayer were similar (I.E., RPE wholemount area was normal), but cell number was approximately doubled in the mutant RPE. By postnatal day 6, mutant cells had approximately 70% the face-view area as controls, but their heights were increased approximately 80%, so that cell volumes were near normal despite the higher packing density. Regional differences in cell size in the control RPE were absent in the mutant specimens. The mutant RPE showed an increased bromodeoxyuridine labeling index, as well as an absolute increase in the number of cells engaged in DNA synthesis and in mitosis. CONCLUSIONS: Cell genesis in the vitiligo RPE is quantitatively abnormal perinatally, well before the neural retina has been recognized to display functional or morphologic defects. Cells are being generated at an abnormally high rate, so that twice the normal number of cells are packed into a RPE of normal total area.

Chondrodysplasia and neurological abnormalities in ATF-2-deficient mice.

Activating transcription factor-2 (ATF-2) is a basic region leucine zipper protein whose DNA target sequence is the widely distributed cAMP response element (CRE). We report here that mice carrying a germline mutation in ATF-2 demonstrated unique actions of ATF-2 not duplicated by other ATF/CREB family members. Mutant mice had decreased postnatal viability and growth, with a defect in endochondral ossification at epiphyseal plates similar to human hypochondroplasia. The animals had ataxic gait, hyperactivity and decreased hearing. In the brain, there were reduced numbers of cerebellar Purkinje cells, atrophic vestibular sense organs and enlarged ventricles. Unlike CREB alpha/delta-deficient mice whose main defect is in long-term potentiation, the widespread abnormalities in ATF-2 mutant mice demonstrate its absolute requirement for skeletal and central nervous system development, and for maximal induction of select genes with CRE sites, such as E-selectin.

Mode of spread to and within the central nervous system after oral infection of neonatal mice with the DA strain of Theiler's murine encephalomyelitis virus.

Theiler's murine encephalomyelitis virus is a neurotropic enterovirus known to cause biphasic neural disease after intracerebral inoculation into adult mice. The present study characterizes a neonatal mouse model with a high disease incidence for the study of the acute phase of the pathogenesis of the DA strain of Theiler's murine encephalomyelitis virus after oral infection. The route of viral spread to and within the central nervous system (CNS) was determined by examining the kinetics of viral replication in various organs and by performing histopathological analysis. Viral antigen was detected widely in the neonatal CNS, mainly in the gray matter, and it was asymmetrical and multifocal in its distribution, with considerable variation in lesion distribution from animal to animal. Necrotizing lesions appeared to expand by direct extension from infected cells to their close neighbors, with a general disregard of neuroanatomical boundaries. The diencephalon showed particular susceptibility to viral infection. Other areas of the CNS, including the cerebellum and dentate gyrus of the hippocampus, were consistently spared. Neurons with axons extending peripherally to other organs or receiving direct input from the peripheral nervous system were not preferentially affected. The kinetics of viral replication in the liver, spleen, and CNS and the histopathological findings indicate that viral entry to the CNS is via a direct hematogenous route in orally infected neonatal mice and that the disease then progresses within the CNS mainly by direct extension from initial foci.

Protein and lipid composition of radial component-enriched CNS myelin.

The radial component is a junctional complex that is believed to stabilize the apposition of myelin membranes in the internode of CNS myelin. Based on our previous finding that the radial component of compact myelin retains its structure in tissue treated with the detergent Triton X-100, we have attempted to isolate the junctional complex from spinal cord myelin treated with this detergent. Using 0.5% Triton X-100, our procedures yielded a fraction of isolated myelin that was enriched in well-preserved radial component. This fraction that contained morphologically well-defined radial component was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting, and TLC, and was found to be significantly and consistently enriched in the 21.5-kDa and 17-kDa isoforms of myelin basic protein, and in cerebrosides, hydroxy sulfatide, and sphingomyelin. In addition, the myelin-associated enzyme 2',3'-cyclic nucleotide 3'-phosphodiesterase, tubulin, and actin tended to be resistant to Triton extraction. The fraction of isolated myelin that contained radial component was deficient in proteolipid protein and DM-20, the 18.5- and 14-kDa isoforms of myelin basic proteins, and in the major phospholipids, phosphatidylethanolamine, phosphatidylcholine, and phosphatidylserine. Our data indicate that the radial component can be isolated and that certain myelin and cytoskeletal proteins and lipids are closely associated with it.

A leucine-to-proline mutation in the putative first transmembrane domain of the 22-kDa peripheral myelin protein in the trembler-J mouse.

Peripheral myelin protein PMP-22 is a potential growth-regulating myelin protein that is expressed by Schwann cells and predominantly localized in compact peripheral myelin. A point mutation in the Pmp-22 gene of inbred trembler (Tr) mice was identified and proposed to be responsible for the Tr phenotype, which is characterized by paralysis of the limbs as well as tremors and transient seizures. In support of this hypothesis, we now report the fine mapping of the Pmp-22 gene to the immediate vicinity of the Tr locus on mouse chromosome 11. Furthermore, we have found a second point mutation in the Pmp-22 gene of trembler-J (TrJ) mice, which results in the substitution of a leucine residue by a proline residue in the putative first transmembrane region of the PMP-22 polypeptide. Tr and TrJ were previously mapped genetically as possible allelic mutations giving rise to similar, but not identical, phenotypes. This finding is consistent with the discovery of two different mutations in physicochemically similar domains of the PMP-22 protein. Our results strengthen the hypothesis that mutations in the Pmp-22 gene can lead to heterogeneous forms of peripheral neuropathies and offer clues toward possible explanations for the dominant inheritance of these disorders.

Trembler mouse carries a point mutation in a myelin gene.

The autosomal dominant trembler mutation (Tr), maps to mouse chromosome 11 (ref. 2) and manifests as a Schwann-cell defect characterized by severe hypomyelination and continuing Schwann-cell proliferation throughout life. Affected animals move clumsily and develop tremor and transient seizures at a young age. We have recently described a potentially growth-regulating myelin protein, peripheral myelin protein-22 (PMP-22; refs 7, 8), which is expressed by Schwann cells and found in peripheral myelin. We now report the assignment of the gene for PMP-22 to mouse chromosome 11. Cloning and sequencing of PMP-22 complementary DNAs from inbred Tr mice reveals a point mutation that substitutes an aspartic acid residue for a glycine in a putative membrane-associated domain of the PMP-22 protein. Our results identify the PMP-22 gene as a likely candidate for the mouse trembler locus and will encourage the search for mutations in the corresponding human gene in pedigrees with hypertrophic neuropathies such as Charcot-Marie-Tooth and Dejerine-Sottas diseases (hereditary motor and sensory neuropathies I and III).

Radial component of CNS myelin: junctional subunit structure and supramolecular assembly.

The radial component is a structural specialization within CNS myelin that is believed to stabilize the apposition of membranes in the internode. Previous observations on thin sections and freeze-fracture replicas show that this junctional complex consists of linear, particulate strands that run parallel to the nerve fibre axis and radially through the myelin sheath, but details on its molecular organization are lacking. The objective of our current study was to gain further insight into its arrangement and composition by examining its fine-structure and incidence in: myelin with known deficits in protein composition (e.g., shiverer, transgenic shiverer, myelin deficient and jimpy mutant mice); isolated CNS myelin, which has been shown by X-ray diffraction to be more stable than intact CNS myelin; and human white matter, in which this junctional complex has not yet been described. Our results confirm the localization and general appearance of the radial component as previously reported. In addition, we found that: (1) the radial component occurs abundantly in human CNS myelin where it has a complex subunit structure; (2) the constituent junctional unit of this structure is organized as a pair of globular domains (each approximately 40 A diameter) at the extracellular apposition which is linked by approximately 15 A diameter filaments extending through the bilayer to approximately 25 A globular domains in the adjacent cytoplasmic apposition; (3) the radial component is present with apparently normal structure in the sparse, compact myelin of murine mutants containing either different amounts of MBP or no PLP which indicates that neither of these proteins is necessary for junctional integrity; (4) the radial component is present in purified CNS myelin membranes which may account for the stability of these membranes; and (5) the radial component is structurally resistant to Triton, which suggests a method for its further biochemical characterization. Finally, from an analysis of images from tilted transverse and longitudinal sections, we have reconstructed a model of its three-dimensional, supramolecular organization.

Adherence of cells to myelin basic protein. I. Adherence of red and white blood cells from patients with multiple sclerosis to myelin basic protein.

Red blood cells (RBC) and white blood cells (WBC) of patients with multiple sclerosis (MS) show decreased adherence to myelin basic protein (MBP) immobilized on plastic surfaces compared to the binding of cells from patients with other neurological diseases (OND), or such other autoimmune diseases as psoriasis (PS), and to that of healthy controls (HC). No similar phenomenon occurred to basic and non-basic type proteins other than MBP, for example, to histone (HIS), lysozyme (LYS) and ovalbumin (OVA). Thus, decreased adherence of RBC and WBC in MS patients to MBP appears to be a unique feature of the disease if compared with OND or PS.