Alpha 6 beta 4 integrin and newly deposited laminin-1 and laminin-5 form the adhesion mechanism of gastric carcinoma. Continuous expression of laminins but not that of collagen VII is preserved in invasive parts of the carcinomas: implications for acquisition of the invading phenotype

We studied the expression and distribution of different laminin chains, the alpha 6 beta 4 integrin and type VII collagen, i.e., components of the epithelial adhesion complex, in gastric carcinomas and in suggested preneoplastic stages of this malignancy. Intestinal-type gastric carcinomas showed strong reactivity for laminin alpha 1, alpha 3, beta 1, and beta 3 chains, the components of laminin-1 and -5, at the interface between malignant cells and tumor stroma. The reactivities were continuous throughout the carcinomas, even in structures invading through the smooth muscle layers of the gastric wall. The expression of different laminin chains was accompanied by strong polarized reactivity for the alpha 6 beta 4 integrin, which is a receptor for both laminin-1 and laminin-5. Collagen type VII was only occasionally present at sites showing reactivity for laminin-5 and was totally absent from the cell islands invading through the gastric wall. Intestinalized gastric epithelium showed a similar expression pattern of laminins and the alpha 6 beta 4 integrin as the gastric carcinomas. Our results suggest that gastric carcinomas use the alpha 6 beta 4 integrin and newly deposited laminin-1 and -5, accompanied by the disappearance of type VII collagen, as their mechanism of adhesion during the invasion through surrounding tissues. Unlike in previous studies, the reactivity for the laminin-5 protein was not restricted to the invading cells but surrounded the malignant glandular structures throughout the tumor. Our results also show that both intestinal-type gastric carcinoma, and intestinal metaplasia mimic the gastric surface epithelium in the expression pattern of laminins and the beta 4 integrin subunit. This supports previous studies proposing a pathogenetic sequence from intestinal metaplasia to gastric carcinoma.     

Characterization of dp6troglycan-laminin interaction in peripheral nerve

Dystoroglycan is encoded by a single gene and cleaved into two proteins, alpha and beta-dystroglycan, by posttranslational processing. The 120kDa peripheral nerve isoform of alpha-dystroglycan binds laminin-2 comprised of the alpha 2, beta 1, and gamma 1 chains. In congenital muscular dystrophy and dy mice deficient in laminin alpha 2 chain, peripheral myelination is disturbed, suggesting a role for the dystroglycan- laminin interaction in peripheral myelinogenesis. To begin to test this hypothesis, we have characterized the dystroglycan-laminin interaction in peripheral nerve. We demonstrate that (1) alpha-dystroglycan is an extracellular peripheral membrane glycoprotein that links beta-dystroglycan in the Schwann cell outer membrane with laminin-2 in the endoneurial basal lamina, and (2) dystrophin homologues Dp116 and utrophin are cytoskeletal proteins of the Schwann cell cytoplasm. We also present data that suggest a role for glycosylation of alpha-dystroglycan in the interaction with laminin.     

Corrective gene transfer of keratinocytes from patients with junctional epidermolysis bullosa restores assembly of hemidesmosomes in reconstructed epithelia

Herlitz junctional epidermolysis bullosa (H-JEB) provides a promising model for somatic gene therapy of heritable mechano-bullous disorders. This genodermatosis is caused by the lack of laminin-5 that results in absence of hemidesmosomes (HD) and defective adhesion of squamous epithelia. To establish whether re-expression of laminin-5 can restore assembly of the dermal-epidermal attachment structures lacking in the H-JEB skin, we corrected the genetic mutation hindering expression of the beta 3 chain of laminin-5 in human H-JEB keratinocytes by transfer of a laminin beta 3 transgene. The transduced keratinocytes synthesized a recombinant beta 3 polypeptide that assembled with the endogenous laminin alpha 3 and gamma 2 chains into a biologically active laminin-5 that was secreted, processed and deposited into the extracellular matrix. Re-expression of laminin-5 induced cell spreading, nucleation of hemidesmosomal-like structures and enhanced adhesion to the culture substrate. Organotypic cultures performed with the transduced keratinocytes, reconstituted epidermis closely adhering to the mesenchyme and presenting mature hemidesmosomes, bridging the cytoplasmic intermediate filaments of the basal cells to the anchoring filaments of the basement membrane. Our results provide the first evidence of phenotypic reversion of JEB keratinocytes by somatic gene therapy and demonstrate that genetic treatment of the mild forms of skin blistering diseases and other inherited extracellular matrix pathologies is a realistic goal.     

Quantitative analysis of Na+ and Ca2+ current contributions on spike initiation in the newt olfactory receptor cell

The developmental localization patterns of collagen type IV alpha1-5 chains, laminin-1, laminin-5, and laminin alpha2 chain were analyzed in the embryonic mouse eye using isoform specific antibodies and immunofluorescence microscopy. Laminin-1 isoform and alpha1-2(IV) were ubiquitously expressed along the ocular surface basement membranes at a very early stage of eye development. Alpha3-5(IV) were first detected at later stages of development, and exhibited a variable distribution pattern along the ocular surface basement membrane. In contrast, expression of the laminin alpha2 chain was restricted to the conjunctival basement membrane, and was first detected during the same developmental period in which keratin K4-positive, differentiated conjunctival epithelial cells were observed. Although laminin-5 was uniformly expressed along the adult ocular surface basement membrane, during embryogenesis it was first incorporated into the conjunctival basement membrane structure. These data suggest that some of the laminin isoforms, including laminin alpha2 and laminin-5, may play a role in the formation of a conjunctival-type basement membrane. The temporal relationship between the localization of these molecules to the conjunctival basement membrane and the appearance of differentiated conjunctival epithelial cells suggests a role for external influence on the differentiation pathways of ocular surface epithelium.     

Laminin-1 and laminin-2 G-domain synthetic peptides bind syndecan-1 and are involved in acinar formation of a human submandibular gland cell line

The culture of human submandibular gland (HSG) cells on laminin-1 induces acinar differentiation. We identified a site on laminin involved in acinar differentiation using synthetic peptides derived from the C-terminal G-domain of the laminin alpha1 and alpha2 chains. The alpha1 chain peptide AG73 (RKRLQVQLSIRT) decreases the size of acini formed on laminin-1. Cells cultured with either AG73 or the homologous alpha2 chain peptide MG73 (KNRLTIELEVRT) form structures that appear acinar-like, but the cell nuclei are not polarized to the basal surface and no lumen formation occurs, indicating that additional sites on laminin are required for complete differentiation. The G-domain of laminin-1 contains both integrin and heparin binding sites, and anti-beta1-integrin antibodies disrupt acinar formation. Cell adhesion to the peptides and to E3, an elastase digest fragment of laminin-1 containing AG73, is specific, since other laminin peptides or EDTA do not compete the binding. Heparin and heparan sulfate decrease cell adhesion to AG73 and MG73 but anti-beta1-integrin antibodies have no effect. Treating the cell surface with heparitinase inhibits adhesion to both AG73 and MG73. We isolated cell surface ligands using both peptide affinity chromatography and laminin-1 affinity chromatography. Treating the material bound to the affinity columns with heparitinase and chondroitinase enriches for a core protein identified as syndecan-1 by Western blot analysis, thus identifying a syndecan-1 binding site in the globular domain of laminin-1 and laminin-2. In summary, multiple interactions between laminin and HSG cells contribute to acinar differentiation, involving both beta1-integrins and syndecan-1.     

Laminin 5 can promote assembly of the lamina densa in the skin equivalent model

Skin equivalents were prepared by culturing human keratinocytes on the surface of type I collagen gel contracted by human skin fibroblasts (dermal equivalents) and by raising the gel to an air-liquid interface. A stratified squamous epithelium was formed with a well-differentiated cornified layer at the top of keratinocyte layers within 7 days after plating of the keratinocytes on the dermal equivalents. Although major basement membrane components such as collagens IV and VII and laminin 5 were detected immunohistochemically at the dermal-epidermal junction, a lamina densa was rarely observed by electron microscopy even in 14-day skin equivalents. When laminin 5 (1, 5 or 20 microg/ml) was added to the culture medium on day 7 through day 14, types IV and VII collagens at the dermal-epidermal junction stained more strongly by immunohistochemistry compared with the control. Patches of lamina densa were present along the epidermal-dermal junction, and vesicles containing electron-opaque sheets approximately 0.6 microm in diameter that reacted with anti-collagen IV antibody were also observed in basal keratinocytes in 14-day skin equivalents by electron microscopy. Morphometric analysis showed that the total length of lamina densa along the dermal-epidermal junction as well as in the vesicles increased up to 180%, 230% or 520% of control cultures by the addition of laminin 5 (1, 5 or 20 microg/ml, respectively). These results suggest that laminin 5 accelerates formation of the lamina densa along the dermal-epidermal junction of the skin equivalents, depending on the concentration of laminin 5 supplemented exogenously.     

Intestinal epithelial restitution. Involvement of specific laminin isoforms and integrin laminin receptors in wound closure of a transformed model epithelium

Disruptions in the mucosal lining of the gastrointestinal tract reseal by epithelial cell migration, a process termed restitution. We examined the involvement of laminin isoforms and their integrin receptors in restitution using the intestinal epithelial cell line T84. T84 cells express primarily laminins 5, 6, and 7 as indicated by immunostaining using laminin subunit-specific monoclonal antibodies (MAbs). A MAb (BM2) specific for the laminin alpha 3 subunit, a component of laminins 5, 6, and 7, completely inhibited the closure of mechanical wounds in T84 monolayers. Confocal microscopy using MAbs BM2 (laminin alpha 3 subunit) and 6F12 (laminin beta 3 subunit) revealed that laminin-5 is deposited in a basal matrix that extends into the wound. The MAbs 4E10 (laminin beta 1 subunit) and C4 (laminin beta 2 subunit) stained the lateral membranes between T84 cells. This staining was enhanced in cells adjoining wounds. Because T84 cells stained faintly with MAbs 4C7 (laminin alpha 1 subunit) and with MAbs 4F11 and 1B4 (laminin alpha 2 subunit), we suggest that expression of laminins 6 and 7 is enhanced in response to wounding. The alpha 3 beta 1 integrin and the alpha 6-containing integrins function in wound closure because MAbs specific for the beta 1 integrin subunit (MAb13), the alpha 3 subunit (IVA5), and the alpha 6 subunit (2B7) potently inhibited T84 migration into wounds. Immunofluorescence using UMA9, a beta 4-integrin-specific MAb, revealed that alpha 6 beta 4 integrin exists in a Triton-X-100-insoluble structure at the basal surface and that the staining of this structure is enhanced in cells adjoining wounds. In addition, a Triton-X-100-soluble pool of alpha 6 beta 4, as well as alpha 3 beta 1 and presumably alpha 6 beta 1, was found along lateral surfaces of T84 cells. On flattened cells adjoining wounds, staining for these integrins was distributed diffusely, suggesting a redistribution that accompanies cell migration. Taken together, these data suggest that wound-induced epithelial cell migration is a finely tuned process that is dependent upon the regulated function and localization of specific laminins and their integrin receptors.     

Developmental expression of laminin beta 2 in rat retina. Further support for a role in rod morphogenesis

PURPOSE: The authors previously hypothesized that laminin beta 2 (S-laminin) plays a role in directing photoreceptor development. The aim of this study was to examine the temporal and spatial expression pattern of beta 2 laminins in rat retina to test this hypothesis. METHODS: Retinas from Sprague-Dawley rats were harvested on embryonic days (E) 14, 16, and 21, as well as on postnatal days (P) 2, 5, and 10. Cryostat sections were probed with antibodies directed against beta 2 laminin, laminin-1 (alpha 1-beta 1-gamma 1), and von Willebrand factor. RESULTS: At the onset of rod photoreceptor birth (E14), laminin beta 2 surrounds the cells of the retinal pigmented epithelium (RPE) and is present on the apical surface of the retinal neuroepithelium. At E16, laminin beta 2 persists on the apical surface of the neuroepithelium and the subjacent apical surface of the RPE. At birth, laminin beta 2 fills the matrix between the juxtaposed surfaces of the RPE and neuroepithelium; moreover, laminin beta 2 immunoreactivity penetrates the neural retina. Throughout postnatal development, laminin beta 2 immunoreactivity surrounds maturing inner and outer segments. Laminin beta 2 also is found in association with blood vessels in the neural retina itself, as well as with choroidal blood vessels; in both places, it is co-localized with an endothelial marker, von Willebrand factor, and laminin-1. CONCLUSIONS: The spatial and temporal expression of laminin beta 2 is consistent with its hypothesized role in rod development. Laminin beta 2 is in a unique position to interact with mitotically active cells (in early retinal development), uncommitted progenitors (in late embryonic development), developing rods (in early postnatal development), and mature outer segments (throughout adulthood). Together with our earlier functional data, these data support our hypothesis that this molecule is an important component of the interphotoreceptor matrix.     

Spatiotemporal patterns of expression of extracellular matrix molecules in the developing and adult rat olfactory system

Using immunocytochemical methods, we have examined extensively the spatial and temporal patterns of expression of three extracellular matrix molecules-laminin, fibronectin, and type IV collagen-in the embryonic, postnatal (days 2 and 11) and adult rat olfactory system. The study started at embryonic day 14 when olfactory fibres and their associated migrating cells course through the nasal mesenchyme. From embryonic day 14 to the adult, a sheet-like pattern of labelling for laminin, fibronectin and type IV collagen was observed along the basal surface of the olfactory epithelium and around the telencephalon. This type of labelling was continuous around the telencephalic vesicle, whereas it appeared disrupted in the basal lamina of the olfactory epithelium to permit exit of the olfactory axons and their associated migrating cells into the mesenchyme. From embryonic day 14 to day 20, punctate labelling for the three molecules studied was observed along the mesenchymal olfactory pathway, the ventral part of the olfactory bulb, the olfactory nerve layer and the presumptive glomerular layer, respectively. By embryonic day 17, the punctate labelling initially detected in the mesenchymal olfactory pathway was replaced by a sheet-like pattern related to the mature basal lamina surrounding the olfactory axon fascicles. Punctate labelling for laminin and type IV collagen persisted in the olfactory nerve layer and around the glomeruli through adult life whereas that of fibronectin declined and disappeared by postnatal day 2. The spatiotemporal distribution of the punctate pattern for laminin, fibronectin and type IV collagen observed in the embryonic olfactory system suggests a role in delineating the pathway for olfactory axon elongation. The continuous expression of laminin and type IV collagen in the adult olfactory bulb may be related to the regenerative activity and high plasticity of the olfactory system.     

Safety and the car size effect: a fundamental explanation

Primordial germ cells (PGCs) are described from the gonad of c. 2 cm juvenile Branchiostoma virginiae; early oocytes (c. 10 microm) and enlarging, previtellogenic oocytes (c. 35 microm) are described from the ovary of c. 5 cm adults. The germinal epithelium of the juvenile gonad and adult ovary is composed of both germinal and somatic cells. In the juvenile, somatic cells retain contact with the basal lamina of the germinal epithelium though their perikarya may be displaced towards the lumen; the germinal epithelium is, therefore, a simple but pseudostratified epithelium. In the adult ovary, somatic cells may lose contact with the basal lamina and the epithelium appears to become stratified. PGCs and oocytes are identified as germ cells by the presence of nuage. PGCs and oocytes are polarised epithelial cells. They rest on a basal lamina, extend apically towards a lumen, form adhering junctions with neighbouring cells, and exhibit apical-basal polarity. PGCs and early oocytes have an apical flagellum with an associated basal body, accessory centriole, and one or more striated rootlet fibres. The flagellum is surrounded by a collar of microvilli. Once oocytes begin to enlarge and bulge basally into the connective tissue layer, the flagellum is lost, but the basal bodies and ciliary rootlets are present at the apex of 35 microm oocytes. Similarities of the oogenic pattern in cephalochordates and echinoderms indicate that the establishment of egg polarity in deuterostomes is influenced by the polarity of the germinal epithelium.     

Differential localization of laminin chains in bovine follicles

The composition of a basal lamina markedly affects its ability to filter material and affects the fate of adjacent epithelial cells. Therefore, basal laminae differ in composition with tissue development, and between different tissues in the body. Laminins are a component of basal laminae and consist of one alpha, one beta and one gamma chain, of which there are at least five, three and two isoforms, respectively. This is the first study to immunolocalize a range of these individual laminin chains (alpha 1, alpha 2, beta 1, beta 2, gamma 1) in ovarian follicles. Frozen sections of bovine ovaries (n = 6) were immunostained using specific antisera to laminin chains and factor VIII-related antigen (to identify endothelial cells). Secondary antisera were labelled with one of two different fluorochromes (DTAF and Cy3), and dual localization of laminin chains and factor VIII-related antigen was performed. The alpha 1, beta 2 and gamma 1 chains were consistently localized to the follicular basal lamina in all healthy follicles. Staining was less intense in the atretic antral follicles. Conversely, alpha 2 and beta 1 were rarely present in the follicular basal laminae of healthy antral follicles. Two of nine healthy antral follicles observed stained weakly for alpha 2 in their basal lamina, and beta 1 was present at low concentrations in growing preantral follicles. In atretic antral follicles, the follicular basal lamina stained positively for alpha 1, alpha 2, and beta 2 but no beta 1 was detected and the gamma 1 staining was less intense than in healthy follicles. Antisera to Englebreth Holm-Swarm tumour laminin stained basal laminae of all follicles. In the theca of antral follicles, beta 1 and beta 2 chains were both present in the vasculature. Staining for the gamma 1 chain was present in the thecal vasculature and generally throughout the theca of healthy and atretic antral follicles. Therefore, the composition of the follicular basal lamina alters during development and atresia, and potentially plays a role in the changing identity of the granulosa cells and the accumulation of antral follicular fluid.     

Secular trend in body height since the Neolithic period

Rat mesangial cells express two unique isoforms of laminin which can be modulated by culture medium composition. To define further the nature of laminin expressed by cultured rat mesangial cells, synthesis of individual laminin chains, as well as their trimeric association, was examined. Based on data from Northern analysis of mRNA expression, immunoblots, immunofluorescence staining and radioimmunoprecipitation of biosynthetically labeled proteins, mesangial cells express laminin beta1, beta2, and gamma1 chains. Mesangial cells do not express laminin alpha1 or alpha2. MC produce a unique alpha chain, designated alpha'm. These laminin chains assemble into two major isoforms. One contains alpha'mbeta1gamma1, co-precipitates with entactin and is assembled into the fibrillar extracellular matrix. The second isoform contains alpha'mbeta2 and a presumed gamma chain that migrates in gel slightly ahead of gamma1. The beta2-containing isoform is concentrated in punctate sites on the cell surface. In addition, mesangial cells display different phenotypes when plated on laminin-1 (alpha1beta1gamma1), as compared to purified beta2. An LRE-containing peptide of laminin beta2 serves as an attachment site for mesangial cells and is sufficient to induce the phenotype observed with intact beta2. These data suggest that laminin isoform expression plays an important role in mesangial cell phenotype and function.     

Laminin-alpha1-chain sequence Leu-Gln-Val-Gln-Leu-Ser-Ile-Arg (LQVQLSIR) enhances murine melanoma cell metastases

We earlier screened overlapping synthetic peptides from the globular domain of the laminin alpha1 chain to identify active sites for cell attachment. We report here that one of the active cell-adhesion peptides, AG-73 (Arg-Lys-Arg-Leu-Gln-Val-Gln-Leu-Ser-Ile-Arg-Thr; RKRLQVQLSIRT) causes B16F10 murine melanoma cells to metastasize to the liver, a site not normally colonized by these cells. Increases in liver metastases and in lung colonization are observed in immune-deficient beige/nude/xid and in C57Bl/6 mice with this peptide. This metastatic activity was observed with i.v. and with i.p. peptide injections, regardless of tumor cell or of peptide-injection times. In vitro, the AG-73 peptide enhances tumor cell adhesion, migration, invasion, and gelatinase production, and blocks laminin-1-mediated cell migration. AG-73 was found to significantly inhibit cell adhesion to a proteolytic laminin-1 fragment, E3, containing the AG-73 sequence. Cell attachment to AG-73, the E3 fragment, and laminin-1 involved cation-dependent receptors. We report that a laminin peptide has the novel and unexpected activity of causing B16F10 melanoma cells, a lung selected cell line, to metastasize to the liver. The minimal active sequence of AG-73, LQVQLSIR, could be one of the most important biologically active sites of laminin-1, especially in promotion of the malignant phenotype. Activation of the malignant phenotype by this peptide provides a significant new model for understanding metastatic mechanisms.     

Increased 3-nitrotyrosine and oxidative damage in mice with a human copper/zinc superoxide dismutase mutation

The structural and functional barrier preventing the free advancement of microbial plaque subgingivally along the tooth surface is formed by the junctional epithelial (JE) cells directly attached to the tooth (DAT cells). The mechanism leading to degeneration of the DAT cells is not known. In the present study we examined the possible role of short chain fatty acids (SCFAs) on epithelial cells by making use of 2 epithelial cell cultures (HaCaT and ERM) and an explant culture model of human JE. The SCFAs butyrate and propionate were used in concentrations found in human plaque and gingival crevicular fluid (0.25-16.0 mM). The SCFAs had no effect on primary cell adhesion nor on the epithelial attachment apparatus (EAA). By contrast, even 0.25 mM of butyrate significantly retarded epithelial cell growth. Similar effects with propionate were first observed at concentrations higher than 1.0 mM. The retardation of epithelial cell growth was found to be due to inhibition of cell division. Furthermore, after butyrate treatment dense accumulations of intermediate filaments and cytoplasmic vacuolization were characteristically seen in cells adjacent to cells of normal appearance. This suggests that some cells of the growing epithelial cell population are more sensitive to the SCFAs than others, and agrees with previous reports on the DAT cells of periodontally-involved teeth in vivo. The results suggest that SCFAs are microbial factors that play a role in the initiation and progression of periodontal pocket formation by impairing epithelial cell function rather than having a direct effect on the EAA.     

Laminin localization in enterocytic basement membrane of rat small bowel grafts. A light and electron microscopic study

In vitro laminins stimulate numerous biological effects, such as cell migration, proliferation, attachment and differentiation. In vitro laminins influence immunocompetent cells and in vivo possibly play an important role in graft rejection. To establish how laminins could be involved in the regulation of acute rejection of small bowel allografts (with and without immunosuppression), we investigated laminin distribution in rat small bowel allografts four days after transplantation, i.e., before the onset of histological signs of rejection, using antibodies against alpha1, beta1, gamma1 chain of laminin-1. In immunosuppressed allografts, the ultrastructure of the enterocytic basement membrane appeared normal, but no laminin staining was seen in this membrane, although basement membranes of intramural blood vessels and muscle cells were normally stained. In non-operated immunosuppressed rats, laminin staining was clearly reduced in the enterocytic basement membrane, demonstrating that cyclosporin A is able to affect this membrane. Since only rats in which laminin is altered survive, this laminin alteration in the enterocytic basement membrane presumably plays an important role in overcoming the acute rejection.     

Association of ecto-5'-nucleotidase with specific cell types in the adult and developing rat olfactory organ

A unique feature of the olfactory epithelium is its ability to give rise to new sensory neurons throughout life and also following injury. Cells at the basal side of the epithelium serve as neurogenic progenitor cells. The enzyme ecto-5'-nucleotidase is expressed at the surface of developing nerve cells and is regarded as a marker of neural development. To study the expression pattern of the enzyme, we analyzed its distribution in the adult and developing rat olfactory organ. Labeling is restricted to specific cell types and varies between the epithelia investigated. At the basal side of the olfactory epithelium, activity of 5'-nucleotidase is associated specifically with the dark/horizontal basal cells. Neither the light/globose basal cells, which are the immediate precursors of the sensory receptor cells, nor subsets of potentially immature olfactory receptor cells are labeled. On the other hand, microvillar cells dispersed at the lumenal side of the epithelium contain 5'-nucleotidase activity. The enzyme is also present at the inner lining of the ducts of Bowman's glands as they traverse the epithelium. Within the respiratory epithelium, activity of 5'-nucleotidase is associated with basal cells as well as with the epithelial surface. During development, 5'-nucleotidase is initially limited to the respiratory epithelium, including its basal cells. Dark/horizontal basal cells of the olfactory epithelium, which are positive for 5'-nucleotidase, first appear at the border of the respiratory epithelium, suggesting that they might originate from immigrating basal cells of the respiratory epithelium. Within the vomeronasal organ, labeling is largely restricted to the receptor-free epithelium. Although the functional role of 5'-nucleotidase in the olfactory system needs to be further defined, the distribution of the enzyme can be used successfully as a marker for defined cell types.     

Fitting Weibull duration models with random effects

The interstitial space of the thyroid gland of adult marmosets contains, like the stroma of other organs, cells and intercellular substance (matrix), blood vessels (predominantly capillaries), lymph vessels and unmyelinated nerves. It is demarcated from the follicular epithelium, the capillaries and Schwann cells by a basal lamina (BL). The perifollicular BL shows thickenings of up to 3 microns over long distances or a multilayered arrangement. These thickened segments exhibit numerous epithelial processes and ridges; in other words, the contour of the basal cell membrane is very irregular in these areas. Indentations of capillaries into the epithelium are rarely observed. The endothelium is only slightly porous. Lymph capillaries occur in large numbers. They originate freely in the interstitial space, show gaps or unspecific contacts between the thin endothelial cells; a basal lamina is missing. Bundles of 10-nm thick filaments (anchor filaments) extend to the endothelial cells of the lymph capillaries. Thin and very long (up to 8 microns) plate-like processes surround the capillaries or run parallel to the outer contour of the follicles. They originate at the poles of oval, fibroblast-like cells. Since these cells are FXIII- and C3bi-positive, they can be considered as dendritic cells. They obviously play a role in the frequently-observed autoimmune diseases of this species. In addition, monocytes and all transitional forms including macrophages, fibrocytes and lymphocytes as well as numerous mast cells occur. In the region of the BL, integrins of the beta 1-group (alpha 6) can be demonstrated immunohistologically in addition to the usual components (collagen type IV, laminin and heparan sulfate-proteoglycan). Of the fibrillar collagens type I does not occur, type III occurs only in small amounts, whereas types V and VI are observed in large amounts. The presented findings may serve as basis for more extensive experiments on these primates.     

A motoneuron-selective stop signal in the synaptic protein S-laminin

Motor axons preferentially reinnervate original synaptic sites on denervated muscle fibers. We have shown that components of synaptic basal lamina direct this selectivity, and we identified a protein, s-laminin, that is concentrated in synaptic basal lamina. Here, we report that a recombinant s-laminin fragment inhibits neurite outgrowth promoted by laminin. A tripeptide sequence in this fragment, Leu-Arg-Glu (LRE), contributes to this inhibition and is itself sufficient to inhibit outgrowth. LRE-mediated inhibition is selective for motoneuron-like cells and is observed in mixtures with several, but not all, outgrowth-promoting substrates. Growth cones extending on laminin stop for up to several hours upon contacting deposits of the s-laminin fragment. Thus, LRE may serve as a cell type-selective and context-dependent target-derived signal that plays a role in synapse formation.