Neuromyelitis optica unique area postrema lesions: nausea, vomiting, and pathogenic implications.

OBJECTIVE: To characterize the neuropathologic features of neuromyelitis optica (NMO) at the medullary floor of the fourth ventricle and area postrema. Aquaporin-4 (AQP4) autoimmunity targets this region, resulting in intractable nausea associated with vomiting or hiccups in NMO. METHODS: This neuropathologic study was performed on archival brainstem tissue from 15 patients with NMO, 5 patients with multiple sclerosis (MS), and 8 neurologically normal subjects. Logistic regression was used to evaluate whether the presence of lesions at this level increased the odds of a patient with NMO having an episode of nausea/vomiting. RESULTS: Six patients with NMO (40%), but no patients with MS or normal controls, exhibited unilateral or bilateral lesions involving the area postrema and the medullary floor of the fourth ventricle. These lesions were characterized by tissue rarefaction, blood vessel thickening, no obvious neuronal or axonal pathology, and preservation of myelin in the subependymal medullary tegmentum. AQP4 immunoreactivity was lost or markedly reduced in all 6 cases, with moderate to marked perivascular and parenchymal lymphocytic inflammatory infiltrates, prominent microglial activation, and in 3 cases, eosinophils. Complement deposition in astrocytes, macrophages, and/or perivascularly, and a prominent astroglial reaction were also present. The odds of nausea/vomiting being documented clinically was 16-fold greater in NMO cases with area postrema lesions (95% confidence interval 1.43-437, p = 0.02). CONCLUSIONS: These neuropathologic findings suggest the area postrema may be a selective target of the disease process in NMO, and are compatible with clinical reports of nausea and vomiting preceding episodes of optic neuritis and transverse myelitis or being the heralding symptom of NMO.

Immunological aspects of axon injury in multiple sclerosis.

The role of immune-mediated axonal injury in the induction of nonremitting functional deficits associated with multiple sclerosis is an area of active research that promises to substantially alter our understanding of the pathogenesis of this disease and modify or change our therapeutic focus. This review summarizes the current state of research regarding changes in axonal function during demyelination, provides evidence of axonal dysmorphia and degeneration associated with demyelination, and identifies the cellular and molecular effectors of immune-mediated axonal injury. Finally, a unifying hypothesis that links neuronal stress associated with demyelination-induced axonal dysfunction to immune recognition and immunopathology is provided in an effort to shape future experimentation.

NGF signaling from clathrin-coated vesicles: evidence that signaling endosomes serve as a platform for the Ras-MAPK pathway.

The target-derived neurotrophic factor "nerve growth factor" (NGF) signals through TrkA to promote the survival, differentiation, and maintenance of neurons. How the NGF signal in axon terminals is conveyed to the cell body is unknown. The "signaling endosome hypothesis" envisions that NGF-TrkA complexes are internalized at the axon terminal and retrogradely transported to the cell body. Following NGF treatment, we found that clathrin-coated vesicles contained NGF bound to TrkA together with activated signaling proteins of the Ras-MAP kinase pathway. Evidence that these vesicles could signal was their ability in vitro to activate Elk, a downstream target of Erk1/2. Our results point to the existence of a population of signaling endosomes derived from clathrin-coated membranes in NGF-treated cells.

Infusion of nerve growth factor (NGF) into kitten visual cortex increases immunoreactivity for NGF, NGF receptors, and choline acetyltransferase in basal forebrain without affecting ocular dominance plasticity or column development.

Intracerebroventricular or intracortical administration of nerve growth factor (NGF) has been shown to block or attenuate visual cortical plasticity in the rat. In cats and ferrets, the effects of exogenous NGF on development and plasticity of visual cortex have been reported to be small or nonexistent. To determine whether locally delivered NGF affects ocular dominance column formation or the plasticity produced by monocular deprivation in cats at the height of the critical period, we infused recombinant human NGF into the primary visual cortex of kittens using an implanted cannula minipump. NGF had no effect on the normal developmental segregation of geniculocortical afferents into ocular dominance columns as determined both physiologically and anatomically. The plasticity of binocular visual cortical responses induced by monocular deprivation was also normal in regions of immunohistochemically detectable NGF infusion, as measured using intrinsic signal optical imaging and single-unit electrophysiology. Immunohistochemical analysis of the basal forebrain regions of the same animals demonstrated that the NGF infused into cortex was biologically active, producing an increase in the number of NGF-, TrkA-, p75(NTR)-, and choline acetyltransferase-positive neurons in basal forebrain nuclei in the hemisphere ipsilateral to the NGF minipump compared to the contralateral basal forebrain neurons. We conclude that NGF delivered locally to axon terminals of cholinergic basal forebrain neurons resulted in increases in protein expression at the cell body through retrograde signaling.

Failed retrograde transport of NGF in a mouse model of Down's syndrome: reversal of cholinergic neurodegenerative phenotypes following NGF infusion.

Age-related degeneration of basal forebrain cholinergic neurons (BFCNs) contributes to cognitive decline in Alzheimer's disease and Down's syndrome. With aging, the partial trisomy 16 (Ts65Dn) mouse model of Down's syndrome exhibited reductions in BFCN size and number and regressive changes in the hippocampal terminal fields of these neurons with respect to diploid controls. The changes were associated with significantly impaired retrograde transport of nerve growth factor (NGF) from the hippocampus to the basal forebrain. Intracerebroventricular NGF infusion reversed well established abnormalities in BFCN size and number and restored the deficit in cholinergic innervation. The findings are evidence that even BFCNs chronically deprived of endogenous NGF respond to an intervention that compensates for defective retrograde transport. We suggest that age-related cholinergic neurodegeneration may be a treatable disorder of failed retrograde NGF signaling.

Nerve growth factor signaling, neuroprotection, and neural repair.

Nerve growth factor (NGF) was discovered 50 years ago as a molecule that promoted the survival and differentiation of sensory and sympathetic neurons. Its roles in neural development have been characterized extensively, but recent findings point to an unexpected diversity of NGF actions and indicate that developmental effects are only one aspect of the biology of NGF. This article considers expanded roles for NGF that are associated with the dynamically regulated production of NGF and its receptors that begins in development, extends throughout adult life and aging, and involves a surprising variety of neurons, glia, and nonneural cells. Particular attention is given to a growing body of evidence that suggests that among other roles, endogenous NGF signaling subserves neuroprotective and repair functions. The analysis points to many interesting unanswered questions and to the potential for continuing research on NGF to substantially enhance our understanding of the mechanisms and treatment of neurological disorders.

Pathobiologic findings in DCIS of the breast: morphologic features, angiogenesis, HER-2/neu and hormone receptors.

With the increasing incidence of ductal carcinoma in situ (DCIS) of the breast and its relationship to invasive breast carcinoma, it is important to understand the biology of this entity. We report on a hospital-based survey of 219 case subjects with DCIS of the breast without associated invasive carcinoma diagnosed between 1982 and 1994. The cases of DCIS were analyzed for architectural type, size, nuclear grade, necrosis, calcification, periductal fibrosis, neovascularization, estrogen receptor (ER), progesterone receptor (PR), and HER-2/neu expression. Periductal neovascularization was associated with tumor size, microcalcifications, periductal fibrosis, and HER-2/neu overexpression. Expression of ER and PR was observed in 60 and 62% of the cases, respectively, and HER-2/neu overexpression in 28% of the cases. ER and PR expression were both inversely associated with comedo histology and nuclear grade. HER-2/neu overexpression was positively associated with comedo histology, high nuclear grade, and periductal neovascularization and was inversely correlated with both ER and PR expression. High nuclear grade was positively associated with comedocarcinoma, necrosis, microcalcification, and periductal fibrosis. The role of these molecular/pathologic markers in the biology of DCIS and their potential clinical implications are discussed.

NGF signals through TrkA to increase clathrin at the plasma membrane and enhance clathrin-mediated membrane trafficking.

Neurotrophin (NT) signals may be moved from axon terminals to neuron cell bodies via signaling endosomes-organelles in which NTs continue to be bound to their activated receptors. Suggesting that clathrin-coated membranes serve as one source of signaling endosomes, in earlier studies we showed that nerve growth factor (NGF) treatment increased clathrin at the plasma membrane and resulted in colocalization of clathrin with TrkA, the receptor tyrosine kinase for NGF. Strikingly, however, we also noted that most clathrin puncta at the surface of NGF-treated cells did not colocalize with TrkA, raising the possibility that NGF induces a general increase in clathrin-coated membrane formation. To explore this possibility further, we examined the distribution of clathrin in NGF- and BDNF-treated cells. NGF signaling in PC12 cells robustly redistributed the adaptor protein AP2 and the clathrin heavy chain (CHC) to surface membranes. Using confocal and epifluorescence microscopy, as well as biochemical assays, we showed the redistribution of clathrin to be attributable to the activation of TrkA. Significantly, NGF signaled through TrkA to induce an increase in clathrin-mediated membrane trafficking, as revealed in the increased endocytosis of transferrin. In that BDNF treatment increased AP2 and clathrin at the surface membranes of hippocampal neurons, these findings may represent a physiologically significant response to NTs. We conclude that NT signaling increases clathrin-coated membrane formation and clathrin-mediated membrane trafficking and speculate that this effect contributes to their trophic actions via the increased internalization of receptors and other proteins that are present in clathrin-coated membranes.

The molecular biology of breast cancer: accelerating clinical applications.

Recent advances in basic science have led to a better understanding of the molecular events important in the pathogenesis of breast cancer. Very little of this new knowledge, however, has had a significant impact on improving the diagnosis and therapy of breast cancer. We review many of the molecular events important in the pathogenesis of breast cancer, including inherited abnormalities in BRCA-1 and BRCA-2, p53, ATM, and PTEN and sporadic alterations in growth factors and their receptors, signal transduction, cell cycle control, DNA repair, cell death, angiogenesis, and invasion and metastasis. We suggest ways to speed up clinical applications of the new molecular knowledge base through the use of preclinical disease models, development of high throughput sample analysis and infrastructure programs to facilitate translational research, implementation of practice guidelines, and development of regional oncology networks. Only through the implementation of such a deliberate, multifaceted strategy will the gap between the research laboratory and the clinic be closed.

Nerve growth factor and the neurotrophic factor hypothesis.

The discovery of nerve growth factor (NGF) over 40 years ago led to the formulation of the "Neurotrophic Factor Hypothesis". This hypothesis states that developing neurons compete with each other for a limited supply of a neurotrophic factor (NTF) provided by the target tissue. Successful competitors survive; unsuccessful ones die. Subsequent research on NTFs has shown that NTF expression and actions are considerably more complex and diverse than initially predicted. Even for NGF, different regulatory patterns are seen for different neuronal populations. As would be predicted by the "Neurotrophic Factor Hypothesis", NGF levels critically regulate basal forebrain cholinergic neuron size and neurochemical differentiation. In contrast, the level of trkA, the NGF receptor, regulates these properties in caudate-putamen cholinergic neurons. Understanding NTF regulation and actions on neurons has led to their use in clinical trials of human neurological diseases. NTFs may emerge as important therapies to prevent neuronal dysfunction and death.

Characterization and cloning of lgp110, a lysosomal membrane glycoprotein from mouse and rat cells.

lgp110 is a heavily glycosylated intrinsic protein of lysosomal membranes. Initially defined by monoclonal antibodies against mouse liver lysosomes, it consists of a 45-kilodalton core polypeptide with O-linked and 17 asparagine-linked oligosaccharide side chains in mouse cells. Sialic acid residues make the mature protein extremely acidic, with an isoelectric point of between 2 and 4 in both normal tissues and most cultured cell lines. Partial sequencing of mouse lgp110 allowed oligonucleotide probes to be constructed for the screening of several mouse cDNA libraries. A partial cDNA clone for mouse lgp110 was found and used for additional library screening, generating a cDNA clone covering all of the coding sequence of mature rat lgp110 as well as genomic clones covering most of the mouse gene. These new clones bring to seven the number of lysosomal membrane proteins whose amino acid sequences can be deduced, and two distinct but highly similar groups (designated lgp-A and lgp-B) can now be defined. Sequence comparisons suggest that differences within each group reflect species variations of the same protein and that lgp-A and lgp-B probably diverged from a common ancestor prior to the evolup4f1ary divergence of birds and mammals. Individual cells and individual lysosomes possess both lgp-A and lgp-B, suggesting that these two proteins have different functions. Mouse lgp110 is encoded by at least seven exons; intron positions suggest that the two homologous ectodomains of each lgp arose through gene duplication.

Derived protein sequence, oligosaccharides, and membrane insertion of the 120-kDa lysosomal membrane glycoprotein (lgp120): identification of a highly conserved family of lysosomal membrane glycoproteins.

The 120-kDa lysosomal membrane glycoprotein (lgp120) is an acidic, heavily glycosylated membrane protein enriched in the lysosomal membrane. To determine the basis for its selective transport to and stability in lysosomes, we have investigated the structure of lgp120. By using an oligonucleotide probe corresponding to the amino terminus of rat lgp120, we isolated and characterized cDNA clones containing the entire coding region. The deduced amino acid sequence demonstrates that lgp120 contains a putative signal peptide, 18 sites for N-linked glycosylation, a single membrane-spanning segment, and a short (11 amino acid) cytosolic tail. The sequence suggests a distinct domain organization, with two luminal glycosylated regions separated by a nonglycosylated proline-rich region. Proteolysis in detergent showed that the protein was not intrinsically resistant to exogenous or endogenous proteases. The N-linked oligosaccharides on lgp120, tetraantennary structures with two lactosamine repeats on one of the branches, were not different from those of glycoproteins on the plasma membrane. lgp120 was similar in its domain organization and portions of its amino acid sequence to the avian 100-kDa lysosomal membrane protein LEP100 [Fambrough, D. M., Takeyasu, K., Lippincott-Schwartz, J., Siegel, N. R. & Somerville, D. (1988) J. Cell Biol. 106, 61-67], and to a distinct 110-kDa lysosomal membrane protein (lgp110) that colocalizes with lgp120. The similarities between lysosomal membrane glycoproteins from diverse species, coupled with the fact that at least two distinct lysosomal membrane glycoproteins are expressed in a single species, indicate the existence of a conserved family of glycoproteins enriched in the lysosomal membrane.

Characterization of intestinal brush border cytoskeletal proteins of normal and neoplastic human epithelial cells. A comparison with the avian brush border.

The elaborate cytoskeletal matrix underlying the intestinal epithelial cell brush border (BB) is the hallmark of a mature enterocyte. As such, alterations in this structure are potentially useful as markers aiding in the recognition of subtle defects in cell maturation, such as those accompanying dysplasia and neoplasia. For exploration of this hypothesis, the BB components of human ileal and colonic enterocytes have been compared structurally and biochemically with the well-characterized avian BB, and alterations in the BB cytoskeleton in various states of dysplasia and neoplasia have been identified. Ultrastructural analysis of isolated human ileal BBs indicate that the human BB is structurally homologous to BBs isolated from chicken and other mammalian sources. Like other mammalian BBs (eg, from rat) the terminal web cytoskeleton of the human BB is less extensive than that in the avian BB. Immunochemical analysis of isolated human BBs indicates that the major proteins of the avian microvillar actin bundle, villin, fimbrin, and the 110-kd subunit of the 110K-calmodulin complex, are all present in the human BB. The terminal web protein myosin is also present. Unlike the terminal web of the avian BB, which contains a BB-specific isoform of spectrin, TW 260/240, the human BB contains the more widely distributed spectrin isoform, fodrin. In addition, the human BB contains multiple proteins immunoreactive with antibodies to protein 4.1, a spectrin/actin binding protein that is absent from the avian BB. Immunolocalization studies examining the distribution of the BB-specific microvillar protein, villin, in human colonic mucosa indicate that the localization of this protein is disrupted in certain dysplastic and neoplastic states. Thus, both the expression and/or distribution of BB-specific proteins such as villin may be useful markers for defects in the differentiation state of the enterocyte.

Developmental theory and adolescent sexual behavior.

Although substantial research exists regarding adolescent sexual behavior, there is no unifying framework. In this article, a developmental framework is applied to the subject of adolescent sexual behavior.

Mechanisms of cytoskeletal regulation: modulation of membrane affinity in avian brush border and erythrocyte spectrins.

The spectrins isolated from chicken erythrocytes and chicken intestinal brush border, TW260/240, share a common alpha subunit and a tissue-specific beta subunit. The ability of these related proteins to bind human erythrocyte inside out vesicles (IOVs) and human erythrocyte ankyrin in vitro have been quantitatively compared with human erythrocyte spectrin. Chicken erythrocyte spectrin binds human IOVs and human ankyrin with affinities nearly identical to that for human erythrocyte spectrin. TW260/240 does not significantly bind to either IOVs or ankyrin. These results demonstrate a remarkable tissue preservation of ankyrin-binding capacity, even between diverse species, and confirm the role of the avian beta-spectrins in modulating this functionality. Avian brush border spectrin may represent a unique spectrin which serves primarily as a filament cross-linker and which does not interact strongly with membrane-associated proteins.