Localization of mRNA for low density lipoprotein receptor and a cholesterol synthetic enzyme in rabbit nervous system by in situ hybridization.

The low density lipoprotein receptor and one of its ligands, apoprotein E, are known to be synthesized in the central nervous system. In the current study, we used in situ hybridization to localize the receptor mRNA in selected neurons and glia throughout the nervous system of 9-day-old rabbits. Particularly high levels were found in sensory ganglia, sensory nuclei, and motor-related nuclei. The same regions contained high levels of mRNA for 3-hydroxy-3-methylglutaryl-coenzyme A synthase, a regulated enzyme in cholesterol biosynthesis. The distribution of low density lipoprotein receptor mRNA was similar in mature and immature rabbits. The data suggest that certain cells in the nervous system have high requirements for cholesterol, which they satisfy through cholesterol synthesis and through receptor-mediated uptake of cholesterol-carrying lipoproteins. The latter originate in astrocytes which synthesize and secrete apoprotein E. These data suggest that the nervous system of mammals contains an active system for continuous redistribution and recycling of cholesterol that is physically distinct from the lipoprotein transport system in plasma.

Substance P-like immunoreactivity in the trigeminal sensory nuclei of an infrared-sensitive snake, Agkistrodon blomhoffi.

With the peroxidase-antiperoxidase immunohistochemical method we ascertained the presence of substance P-like immunoreactivity (SPLI) in fibers and cell bodies of the trigeminal sensory system of the pit viper, Agkistrodon blomhoffi. There are a few SPLI fibers each in the principal sensory nucleus and the main neuropil of the lateral descending nucleus (i.e., the infrared sensory nucleus); a moderate number in the descending nucleus; and a large number in the caudal subnucleus, the medial edges of the interpolar subnucleus, and the marginal neuropil of the lateral descending nucleus. About 30% of the cell bodies in the ophthalmic and maxillo-mandibular ganglia show SPLI, and of the two craniocervical ganglia, the proximal ganglion has many more cells with SPLI than the distal ganglion. The SPLI distribution in the common trigeminal sensory system is similar to that of mammals, and suggests that the function of this system is also similar. In the infrared that the function of this system is also similar. In the infrared sensory system, the differing distribution in the main and marginal neuropils suggests separate functions for these two structures in the system.

Noradrenergic neurons with divergent projections to the motor trigeminal nucleus and the spinal cord: a double retrograde neuronal labeling study.

Double retrograde axonal tracing was combined with the indirect immunofluorescence antibody method to determine whether noradrenergic neurons have divergent projections to the motor nucleus of the trigeminal nerve and the spinal cord. Rhodamine-labeled microspheres were injected into the motor trigeminal nucleus and True Blue was deposited into lumbar segments of the spinal cord. After a 10-18-day survival period, brainstem sections were processed for immunofluorescence staining of noradrenergic neurons using antibodies to rat dopamine-beta-hydroxylase. Rhodamine-labeled noradrenergic neurons were observed ipsilaterally throughout the A5 and A7 groups; the contralateral A5 and A7 groups contained few rhodamine-labeled cells. A few rhodamine-labeled noradrenergic neurons were observed in the locus coeruleus and subcoeruleus. True Blue-labeled noradrenergic neurons were identified in the A5 and A7 groups, in the ventral part of the locus coeruleus and in the subcoeruleus. Double retrogradely labeled noradrenergic neurons were observed in the A5 and A7 groups but not in the locus coeruleus and subcoeruleus. Of the total number of rhodamine-labeled noradrenergic cells, a large percentage also contained True Blue: 54% in the caudal A5 group, 59% in the rostral A5 group, and 72% in the A7 group. Of the total number of True Blue-labeled noradrenergic neurons, the percentage of double retrogradely labeled cells was 33% in the caudal A5 group, 46% in the rostral A5 group, and 56% in the A7 group. The findings of this study provide the first anatomic evidence for the existence of a prominent population of noradrenergic cells in the A5 and A7 groups with divergent projections to the motor trigeminal nucleus and the spinal cord. We propose that this subpopulation of noradrenergic neurons in the A5 and A7 groups influences motoneurons at multiple levels of the neuraxis.

Cerebral arterial innervation by nerve fibers containing calcitonin gene-related peptide (CGRP): I. Distribution and origin of CGRP perivascular innervation in the rat.

The origin, density and distribution of calcitonin gene-related peptide (CGRP) immunoreactivity in cerebral perivascular nerves and the trigeminal ganglion of rats were examined in this study. CGRP immunoreactive axons were abundant on the walls of the rostral circulation of the major cerebral arteries in the circle of Willis. The fibers form a grid- or meshwork of longitudinal and circumferential axons studded with numerous varicose swellings. The density of CGRP fibers was particularly high at the bifurcation of major arteries. A few CGRP fibers cross the midline to innervate arteries on the contralateral side of the arterial tree. The arteries of the caudal circulation were sparsely innervated by CGRP fibers. In the trigeminal ganglion, about 30% of the ganglion cells had CGRP immunoreactivity. The cell size of most (75%) of CGRP neurons was less than 30 micron in diameter. There was no significant difference in staining density between small and large CGRP neurons. Unilateral transection of the maxillary and mandibular divisions of the trigeminal nerve caused a substantial decrease of CGRP immunoreactivity in the ipsilateral dorsal two-thirds of the trigeminal nucleus and cervical spinal cord but did not noticeably change the diameter of the vascular lumen or the densities of CGRP fibers in the walls of the cerebral arteries. In contrast, unilateral transection that included the ophthalmic division eliminated CGRP fibers on the ipsilateral cerebral arteries and eliminated CGRP immunoreactivity throughout the trigeminal nucleus in the brainstem and rostral cervical cord. In addition, these lesions caused a significant reduction in the diameter of the denervated arteries. The present study demonstrates that CGRP, a putative neurotransmitter/neuromodulator, is especially abundant in the rostral cerebral circulation and is derived from the ipsilateral ophthalmic division of the trigeminal nerve. In addition, the loss of CGRP perivascular nerves is associated with a reduction of the arterial lumen. This suggests that CGRP is a strong candidate as a nerve-derived trophic factor at trigeminal terminals and provides additional evidence that CGRP is a component in the trigeminovascular system influencing vascular diameter.

Calcitonin gene-related peptide-immunoreactive nerve fibers in mandibular periosteum of rat: evidence for primary afferent origin.

Peptidergic neurons may play a role in the local regulation of bone mineralization. The neuropeptide vasoactive intestinal peptide (VIP) increases bone resorption in vitro, while calcitonin gene-related peptide (CGRP) has been shown to inhibit bone resorption in vitro. We have previously reported that sympathetic nerves with VIP-immunoreactivity innervate bone and periosteum. In the present study we sought to determine if CGRP fibers, like VIP fibers, exist in periosteum and what their origin might be. In whole-mount preparations of mandibular periosteum from rat, CGRP- and VIP-immunoreactive (IR) nerve fibers were present as networks within the periosteum. In preparations using two-color immunofluorescence, most CGRP-IR fibers were also immunoreactive for substance P (SP). In rats in which the subperiosteal space subjacent to the mandibular molars was injected with Fast blue or Fluoro-gold, retrogradely labeled cells were seen in ipsilateral trigeminal ganglia, superior cervical ganglia, and nodose ganglia. Individual cells labeled with both CGRP immunoreactivity and retrograde tracer were seen only in the mandibular portion of the trigeminal ganglion. These data suggest that CGRP-IR nerve fibers in periosteum may be of primary afferent origin. Given the reported effects of CGRP on bone mineralization, the present results suggest that primary afferent nerves containing CGRP and SP, as well as sympathetic nerves containing VIP, may play a role in focal bone remodeling.

[Biochemical and immunocytochemical study of the axonal domain of mature and immature microtubules]. / Etude biochimique et immunocytochimique du domaine axonal des microtubules matures et immatures.

The axonal domain of microtubules was analyzed using biochemistry and immunocytochemistry. High resolution isofocusing was used to study the cold-labile and cold-stable fractions of various samples: thalamus, optic nerve, sciatic nerve, brachial plexus and trigeminal nerve. The cold-labile fraction from the thalamus, i.e. from a central nervous system cell population contains 20 well-resolved isotypes as the axonal fraction from the central nervous system. The cold-stable fraction from the peripheral nervous system contains only 18 isotypes. All the cold-stable fractions are characterized by an important relative quantity of isotypes 7-9, with specific patterns tissue dependent. The cold-labile fractions are specific in both the central and peripheral nervous system. Immunocytochemistry using anti-tubulin and anti-MAP2 specific antibodies was used in PEG semi-thin sections of the embryonic tectal plate at stage E10. In the axonal profiles, cold-stable fragments of microtubules were observed. The perikaryon of the young neurons, both migrating and post-migratory, contains MAP2 as the cold-labile fractions of microtubules of the axonal process. These results suggest that; tubulin is involved in the cold-stability of the axonal domain, but this role seems tissue dependent; MAP2 is a marker of neuronal differentiation; in the growing axonal process, cold-stable fragments are present and the cold-labile pool of microtubules contain a transiently expressed protein, MAP2.

44-kDal bone phosphoprotein (osteopontin) antigenicity at ectopic sites in newborn rats: kidney and nervous tissues.

Previous immunohistochemical data have shown that the 44-kDal bone phosphoprotein (44K BPP, also called sialoprotein I or oestopontin) recently isolated in our laboratory was synthesized by osteoblasts and osteocytes and was expressed early during differentiation of bone-forming cells. We report here the presence of 44K BPP antigenicity at certain ectopic sites, namely, the proximal-convoluted tubule of the kidney, neurons, sensory and secretory cells in the internal ear. To insure specificity and reproducibility, different immunohistochemical methods were used and affinity-purified antibodies against two separate preparations of pure 44K BPP were tested. In the cells of the proximal-convoluted tubule, 44K BPP immunoreactivity was observed within apical endocytotic vacuoles and within lysosomes. This staining thus correlates with the degradation of the 44K BPP epitope which we previously demonstrated to occur in serum. On the other hand, in the neurons of the acoustic ganglion and the sensory cells of the macula, 44K BPP immunoreactivity was associated with the Golgi apparatus indicating synthesis and secretion by these cells. The finding that the 44K BPP (or a structurally related molecule) is synthesized by neurons and neuroepithelial cells deserves further investigation with respect to a possible embryologic relationship between neuroectodermal cells and the precursors of some bone forming-cells of the skull.

A survey of neurological mutant mice. II. Lipid composition of myelinated tissue in possible myelin mutants.

The lipids of white matter and peripheral nerve from neurological mutant mice with possible myelin abnormalities were analyzed by thin-layer chromatography and quantitated by densitometry. Eight mutants had major abnormalities in the central nervous system (CNS) and/or peripheral nervous system (PNS) tissues examined (optic nerve, and trigeminal and sciatic nerves). In the optic nerve of axJ/axJ, there were increases of 20-30% in the levels of the major phospholipids; peripheral nerve was normal. In bc3J/bc3J CNS, the major phospholipids and cholesterol were increased by 25-40%; the PNS was normal. In myd/myd CNS, there were increases of about 20% in the levels of both forms of cerebrosides and in the major phospholipids; in the PNS the lipids were normal. ot/ot CNS had 20-40% reductions of all the glycolipids and minor alterations in some of the phospholipids and cholesterol; the PNS had 20% losses of both forms of cerebrosides. In the PNS of ji/ji, there were decreases of 10-40% among the glycolipids and of 15-25% in three of the major phospholipids; the CNS was virtually normal. In the PNS of dtJ/dtJ, vb/vb and wr/wr, almost all lipids were significantly decreased. The CNS of dtJ/dtJ and vb/vb were normal; wr/wr had minor reductions of certain glycolipids and phospholipids. Six mutants had relatively minor lipid abnormalities in their myelinated tissues. In cr/cr PNS, there were elevated levels of the cerebrosides and major phospholipids; the CNS was virtually normal. In db/db CNS and PNS, there were reduced levels of the nonhydroxy forms of cerebroside and sulfatide. The major change in htr/htr was the elevation of all the glycolipids in the CNS. In the CNS of Lc/+, nonhydroxy cerebroside was reduced. In shm/shm PNS, nonhydroxy sulfatide was elevated and there were small decreases in some of the phospholipids. wl/wl CNS showed decreases among most of the glycolipids. Mutants homozygous for du, mto, spa and tg had virtually normal lipid levels in both the optic and peripheral nerves. Cholesterol ester, lysophospholipids and other unusual lipid species were not detected in any of the mutants. The plasmalogen forms of ethanolamine and choline phosphatides were at normal levels in all mutants that otherwise had significant alterations among their lipids. Although many alterations in lipid composition were found in these mutants, the changes were moderate compared to the classical myelin mutants and indicate that none of the mutants are severely myelin-deficient.(ABSTRACT TRUNCATED AT 400 WORDS)

A survey of neurological mutant mice. I. Lipid composition of myelinated tissue in known myelin mutants.

The lipids of white matter and peripheral nerve from mutant mice with known myelin deficiencies were analyzed by one- and two-dimensional high-performance thin-layer chromatography and quantitated by densitometry. In optic nerve, the mutants jp/Y, jpmsd/Y, qk/qk, shi/shi and shimld/shimld, which have severe central nervous system (CNS) myelin deficiency, had a common pattern of lipid loss: cerebrosides and sulfatides (hydroxy and nonhydroxy forms) were generally reduced by 70-95% or more; most phospholipids were diminished by 15-55%, and cholesterol was reduced by 35-60%. Only in the CNS of jp/Y and jpmsd/Y did cholesterol ester accumulate. In peripheral nerve, the lipid composition varied markedly among these mutants. In jp/Y there was no change, while in jpmsd/Y there was a 5-15% loss among the phospholipids and cholesterol. Homozygous qk had reductions of 75-85% in the nonhydroxy forms of cerebroside and sulfatide, a 130% increase in hydroxy sulfatide, and a 55% loss of sphingomyelin. In shi/shi and shimld/shimld homozygotes, the glycolipids were altered by +/- 20%, most phospholipids and cholesterol were reduced by 5-15%, and sphingomyelin was reduced by 40%. Tr and TrJ showed 35-90% reductions in most lipid classes of the peripheral nervous system; CNS lipid composition was normal. Homozygous twi had a uniform loss of most lipid classes in both optic (generally 10-20%) and trigeminal nerves (generally 40-55%); cerebrosides did not accumulate in these tissues. dy/dy had a 10-20% reduction of cerebrosides in trigeminal nerve trunk. The CNS of dy homozygotes had 10-35% increases in specific classes of glycolipids and phospholipids, and in cholesterol. None of the mutants showed detectable levels of lysophospholipids or other unusual lipid species. The fractions of ethanolamine and choline phosphatides in the plasmalogen form were close to normal in all mutants.

Nerve fibers surrounding intracranial and extracranial vessels from human and other species contain dynorphin-like immunoreactivity.

Dynorphin B(20-32) was visualized by immunohistochemistry in guinea-pig and rat perivascular nerve fibers and was measured by radioimmunoassay within the walls of feline, canine, bovine and human cephalic and systemic arteries and veins. Canine vessels contained the highest levels. When human blood vessels or trigeminal ganglia were subjected to reverse-phase high-performance liquid chromatography, dynorphin immunoreactivity exhibited a retention time identical to that of synthetic dynorphin B. No differences in dynorphin-like immunoreactivity were measurable between feline systemic arteries and veins, or between cephalic and systemic vessels. The highest amounts were present in leptomeninges devoid of large pial arteries. Relatively high levels were also measured in feline and human trigeminal ganglia and feline superior cervical and sphenopalatine ganglia, three sources of projecting perivascular axons. Levels did not diminish, however, in ipsilateral feline cephalic vessels following either unilateral trigeminal or superior cervical ganglionectomies. Hence, dynorphin-containing fibers may project from parasympathetic cell bodies or perhaps from intrinsic brain sources. Previously published reports indicate that the kappa agonist dynorphin does not modify vessel tone when added in vitro but does inhibit release of neurotransmitters from afferent and sympathetic axons via prejunctional receptors. These observations suggest a pharmacological role for dynorphin on sensory and autonomic functions of the vasculature.

Substance P-like immunoreactive fibers in the trigeminal sensory nuclei of the pit viper, Trimeresurus flavoviridis.

Substance P-like immunoreactive nerve fibres were located in the trigeminal sensory system of the infrared-sensitive snake, Trimeresurus flavoviridis, using the immunohistochemical method. There are two trigeminal sensory systems in the medulla of this animal: the descending nucleus and the lateral descending nucleus. The descending nucleus is equivalent to the trigeminal spinal nucleus in other vertebrates, and the lateral descending nucleus is a special trigeminal sensory nucleus belonging to the infrared sensory system. In the present study we determined that the lateral descending nucleus is completely ensheathed by large numbers of substance P-like immunoreactive fibers. The distribution of these fibers seems to be similar to that of the thin vagal unmyelinated fibers, rather than to that of the thick trigeminal myelinated fibers. More substance P-like immunoreactive nerve fibers were observed in the lateral descending tract than in the descending tract. Almost no dense substance P-like immunoreactive fibers were found in these tracts rostral to the lateral descending nucleus or rostral to the subnucleus caudalis of the descending nucleus. The substance P-like immunoreactive fibers in the lateral descending tract extended to those of Lissauer's tract of the spinal cord, and the substance P-like immunoreactive fibers surrounding the Lissauer's tract were similar in appearance to those of the lateral descending nucleus. This nucleus seems to have developed from the elements existing in Lissauer's tract, and also to have a similar modulating function. The primary nucleus of the infrared sensory system is the most substance P-like immunoreactive nucleus in the trigeminal sensory system of this animal. Even in the trigeminal sensory system, substance P-like immunoreactive fibers seem not to be related solely to the nociceptive sensation.

Immunocytochemical localization of 5'-nucleotidase in myelinated peripheral nerves from the rat.

In sciatic and trigeminal nerves from the rat, 5'-nucleotidase immunostaining was observed on the surfaces of the myelinated fibers and in the membranes encircling the outermost loops of the myelin sheaths, the paranodal loops, and perhaps the inner loops, but neither in the compact myelin nor in the axoplasm. These results, which were consistent with previous biochemical data regarding sciatic nerve, suggest that the function of 5'-nucleotidase in myelinated fibers in the peripheral nervous system may be to promote diffusion of adenosine between the glial and neuronal compartments.

Comparison of the distribution of Na+,K+-ATPase and myelin-associated glycoprotein (MAG) in the optic nerve, spinal cord and trigeminal ganglion of shiverer (shi/shi) and control (+/+) mice.

Na+,K+ ATPase and myelin-associated glycoprotein (MAG) were studied by immunocytochemistry on paraffin sections of the spinal cord, optic nerve and trigeminal ganglion of adult control (+/+) and CNS myelin-deficient shiverer (shi/shi) mice. Immunostaining for Na+, K+-ATPase outlined the periphery of nerve fibers in the spinal cord white matter, optic nerve and trigeminal ganglion of +/+ and shi/shi mice. Immunostaining for Na+,K+-ATPase appeared somewhat denser in the optic nerve and spinal cord lateral funiculi of shi/shi than in +/+ mice. In addition, immunostaining for Na+,K+-ATPase was demonstrated at the plasmalemma of presumed satellite cells situated at the periphery of ganglion cell bodies in the trigeminal ganglion of both species of mice. Immunostaining for MAG was localized along the periphery of nerve fibers in the spinal cord funiculi (with little immunostaining within gray horns), optic nerve and trigeminal ganglion of both +/+ and shi/shi mice. The major differences between shi/shi and +/+ mice were that the number of MAG-immunostained nerve fibers was greatly reduced in the spinal cord funiculi and the density of immunostaining was slightly increased in the optic nerve of shi/shi mice. The numbers of MAG-immunostained nerve fibers in trigeminal ganglion were similar in both species. Also, the cytoplasm of some oligodendrocyte-like cells was found densely immunostained for MAG in the spinal cord and optic nerve of shi/shi mice, but not of +/+ mice. This light microscopic study provides evidence that the defective shiverer gene leads to a decrease in MAG deposition and to aggregations of MAG-like material within perikarya of oligodendrocyte-like cells in regions of the CNS.

Trigeminal origin of beta-preprotachykinin products in feline pial blood vessels.

A specific and sensitive radioimmunoassay measured the presence of immunoreactive neurokinin A within feline and human pial arteries. Immunoreactivity exhibited a retention time identical to that of synthetic peptide when acid extracts from feline and human blood vessels were subjected to reverse-phase high-performance liquid chromatography. As shown previously for substance P, levels of immunoreactive neurokinin A decreased significantly in the vessels from the ipsilateral rostral circle of Willis 19-24 days following unilateral trigeminal ganglionectomy. Hence, trigeminal projections to cerebral blood vessels contain both products of beta-preprotachykinin mRNA.

Insulin receptors in the peripheral nervous system: a structural and functional analysis.

Although the brain is known to contain specific insulin receptors, there is no information on whether these receptors are also present in the peripheral nervous system (PNS). The present studies sought to provide this information by characterizing insulin binding in bovine autonomic (superior cervical) and sensory (trigeminal) ganglia. It was found that both ganglia contain specific, high-affinity receptors for insulin. Like insulin receptors in other tissue, these receptors could be solubilized and purified on wheat germ agarose columns and were found to have tyrosine-specific kinase activity. SDS-PAGE and autoradiography revealed that the apparent molecular weight (Mr) of the PNS insulin receptor was approximately 133 kDa which is similar to the Mr of hepatic receptors, but is approximately 10 kDa larger than the insulin receptor found in the brain. Because the vasculature of autonomic and sensory ganglia is fenestrated, it is possible that PNS insulin receptors are exposed to blood-borne insulin.

A quantitative correlation of substance P-, calcitonin gene-related peptide- and cholecystokinin-like immunoreactivity with retrogradely labeled trigeminal ganglion cells innervating the eye.

To evaluate the intraganglionic organization of ocular sensory neurons in the guinea pig, we studied the retrograde axonal transport from the eye to the trigeminal ganglion of cholera toxin B subunit and then applied immunohistochemistry for substance P, calcitonin gene-related peptide and cholecystokinin. Retrogradely labeled cells were observed only in the anteromedial portion of the ipsilateral ganglion. We observed no somatotopical organization to trigeminal neurons containing any of these three peptides, either for cells projecting to the eye or for the ganglion as a whole. The relative proportion of neurons immunoreactive for each of these three peptides was similar among the population of neurons retrogradely labeled with cholera toxin B and among the population of neurons without direct projections to the eye.

Detection of bovine herpesvirus type 1 RNA in trigeminal ganglia of latently infected rabbits by in situ hybridization.

At times after conjunctival inoculation with bovine herpesvirus type 1 (BHV-1), representing the acute and latent phases of infection, rabbit trigeminal ganglia were examined for the presence of BHV-1 nucleic acids by in situ hybridization using a 3H-labelled BHV-1 DNA probe. During the acute phase of virus infection, both BHV-1 DNA and RNA were detected in ganglionic neurons and occasionally in adjacent satellite cells. However, during the latent phase of infection only viral RNA was detectable in involved neurons. Viral RNA appeared restricted to the nucleus of latently infected cells and was present in varying amounts in individual cells. These results indicate that the BHV-1 genome is transcriptionally active in ganglionic neurons during latent infection.

Novel monoclonal antibodies provide evidence for the in situ existence of a nonphosphorylated form of the largest neurofilament subunit.

We have obtained five monoclonal antibodies to the Mr 200,000 neurofilament component (NF200) after immunization with polypeptides purified from enzymatically dephosphorylated bovine neurofilaments. In immunoblots of untreated neurofilament protein and protein from filaments exposed to phosphatase, these antibodies recognize nonphosphorylated or dephosphorylated, but not phosphorylated, forms of NF200. The epitopes recognized by these new monoclonal antibodies reside in the carboxyterminal domain of the NF200 polypeptide as defined by immunoreaction with limited chymotryptic fragments. Immunohistochemical studies of bovine cerebellum, spinal cord, trigeminal ganglion, and trigeminal nerve with these new monoclonal antibodies demonstrate immunoreactivity primarily in neuronal perikarya; axons and dendrites are weakly or infrequently immunostained. After enzymatic dephosphorylation of these tissues, a more extensive distribution of immunoreactivity is seen, especially in axons and dendrites. Immunostaining of cultured rat sympathetic neurons is restricted to cell bodies. These data provide evidence for the in situ existence of NF200 epitopes that are not phosphorylated in some classes of neurons or regions of a neuron, but are modified by phosphorylation in other neurons or neuronal domains. These new monoclonal antibodies are distinctly different from those in a large library (over 100) raised to, and specific for, phosphorylated neurofilament proteins. They are novel tools for probing neurofilament distribution, metabolism, structure, and possibly function.

Small basic proteins of myelin from central and peripheral nervous systems are encoded by the same gene.

Peripheral nervous system (PNS) and central nervous system (CNS) rodent myelins, which are produced by different cell types, share common morphological and functional characteristics although their major integral membrane proteins are completely different. Both types of myelin however, contain sets of four myelin basic proteins (MBPs), which share similar immunochemical and electrophoretic properties. We have isolated and characterized cDNA clones corresponding to the rat mRNAs encoding the small MBPs (SMBPs) found in both CNS and PNS myelin. Sequence analysis of these clones indicate that SMBPs in both divisions of the nervous system are encoded by the same nucleotide sequences, which suggests that they are the products of the same gene expressed in both oligodendrocyte and Schwann cells. In dot-blot hybridization experiments with the CNS SMBP cDNA as a probe, it was shown that there is a 20-fold higher level of MBP mRNA in a CNS myelin fraction than in total brainstem mRNA. It also was found that in optic and sciatic nerves, which contain oligodendrocytes and Schwann cells respectively, there are higher levels (4-fold and 2-fold, respectively) of MBP mRNA than in brainstem. Blot-hybridization experiments showed that a probe derived from the coding region of the rat SMBP cDNA hybridizes to an homologous mRNA (approximately equal to 2.6 kilobases) present in human optic nerve, which is not detectable with a probe derived from the 3' untranslated region. This conservation of coding-region sequences is in accord with the highly homologous amino acid sequences reported for the MBPs in the two species.

Herpes simplex virus immediate-early protein ICP4 in murine models of latency.

Herpes simplex virus-1 (HSV) infection of trigeminal and dorsal root ganglia was established in mice via corneal scarification and footpad injection, respectively. Trigeminal and dorsal root ganglia were removed during the acute and latent stages of infection and processed for the immediate-early HSV polypeptide ICP4 (VP175) using both a monoclonal reagent and polyclonal antiserum and the avidin biotin complex immunoperoxidase method. ICP4 (VP175) antigen was readily detected during the acute infection of both dorsal and trigeminal ganglia, but not during latency. This antigen could again be detected by reactivation of the latent virus by explanation and organ culture. The detection of ICP4 (VP175) during latency in a rabbit model but not in a murine model may correlate with biologic differences in each system (e.g., rabbits spontaneously reactivate). Alternatively, the discrepancy could reflect viral strain characteristics or may imply that ICP4 (VP175) need not be constitutively expressed (at detectable levels) in all models of latent infection.