Structure and assembly of hemidesmosomes

The hemidesmosome is a complex junction containing many proteins. The keratin cytoskeleton attaches to its cytoplasmic plaque, while its transmembrane elements interact with components of the extracellular matrix. Hemidesmosome assembly involves recruitment of alpha 6 beta 4 integrin heterodimers, as well as cytoskeletal elements and cytoskeleton-associated proteins to the cell surface. In our cell culture models, these phenomena appear to be triggered by laminin-5 in the extracellular matrix. Cell interaction with laminin-5 apparently induces both phosphorylation and dephosphorylation of subunits of alpha 6 beta 4 integrin. There is emerging evidence that such events are necessary for subsequent cytoskeleton anchorage to the hemidesmosome cytoplasmic plaque. Once assembled, the hemidesmosome plays an essential role in maintaining firm epithelial adhesion to the basement membrane, with hemidesmosome disruption being a hallmark of certain devastating blistering diseases. However, the hemidesmosome is more than just a stable anchor, as it may also be the site of signal transduction, mediated by its alpha 6 beta 4 integrin component. This review discusses our current knowledge of the structure and assembly of the hemidesmosome.

Processing of laminin-5 and its functional consequences: role of plasmin and tissue-type plasminogen activator

The laminin-5 component of the extracellular matrices of certain cultured cells such as the rat epithelial cell line 804G and the human breast epithelial cell MCF-10A is capable of nucleating assembly of cell- matrix adhesive devices called hemidesmosomes when other cells are plated upon them. These matrices also impede cell motility. In contrast, cells plated onto the laminin-5-rich matrices of pp126 epithelial cells fail to assemble hemidesmosomes and are motile. To understand these contradictory phenomena, we have compared the forms of heterotrimeric laminin-5 secreted by 804G and MCF-10A cells with those secreted by pp126 cells, using a panel of laminin-5 subunit-specific antibodies. The alpha3 subunit of laminin-5 secreted by pp126 cells migrates at 190 kD, whereas that secreted by 804G and MCF-10A cells migrates at 160 kD. The pp126 cell 190-kD alpha3 chain of laminin-5 can be specifically proteolyzed by plasmin to a 160-kD species at enzyme concentrations that do not apparently effect the laminin-5 beta and gamma chains. After plasmin treatment, pp126 cell laminin-5 not only impedes cell motility but also becomes competent to nucleate assembly of hemidesmosomes. The possibility that plasmin may play an important role in processing laminin-5 subunits is supported by immunofluorescence analyses that demonstrate colocalization of laminin-5 and plasminogen in the extracellular matrix of MCF-10A and pp126 cells. Whereas tissue-type plasminogen activator (tPA), which converts plasminogen to plasmin, codistributes with laminin-5 in MCF-10A matrix, tPA is not present in pp126 extracellular matrix. Treatment of pp126 laminin-5-rich extracellular matrix with exogenous tPA results in proteolysis of the laminin-5 alpha3 chain from 190 to 160 kD. In addition, plasminogen and tPA bind laminin-5 in vitro. In summary, we provide evidence that laminin-5 is a multifunctional protein that can act under certain circumstances as a motility and at other times as an adhesive factor. In cells in culture, this functional conversion appears dependent upon and is regulated by tPA and plasminogen.

In vitro dentinal penetration by tracers used in microleakage studies

Many microleakage studies, in their methodology, employ different tracers which may penetrate around restorative materials to varying extents due to their physical or chemical characteristics. The present series of in vitro studies were designed to compare the ability of freshly obtained microleakage tracers to enter cut dentinal tubules. Tracers selected were 5% eosin, 2% methylene blue, 50% silver nitrate and Indian ink all buffered, where necessary, to a range of pH 6.9-7.2. The solution of Indian ink was further investigated by particle size analysis to determine the range of particle sizes within the solution. Particles ranged from < 1 micron to 600 microns. Buffered and unbuffered solutions of the tracers were applied for 1 h to open cavities, devoid of a smear layer, prepared in 42 premolars. Specimens were sectioned longitudinally through the cavities either with or without water coolant. Penetration into dentinal tubules by the tracer resulted in an area of stained dentine and this area was subsequently measured using image analysis. The results demonstrated that there were few statistically significant differences between the areas of dentinal penetration associated with each tracer. Neither the tracer used, its pH nor sectioning technique had a predictably significant effect on dentinal penetration. Indian ink was observed to be capable of entering dentinal tubules.

Computed tomographic evaluation of dinosaur egg shell integrity

The purpose of this study was to determine whether computed tomography (CT) could be used to identify hatching holes in partially embedded dinosaur eggs. One Faveololithus and two Dendroolithus eggs were examined using a fourth generation CT scanner. The eggs were partially embedded in a fossilized sediment matrix, with the exposed portion of the shell appearing intact. In CT images of all three eggs, the shells appeared hyperdense relative to the matrix. Hatching holes were visible as large gaps in the embedded portion of the shell, with inwardly displaced shell fragments. It was concluded that CT is an effective technique for nondestructively assessing dinosaur egg shell integrity.

Imidazoline receptor proteins are regulated in platelet-precursor MEG-01 cells by agonists and antagonists

The I1-imidazoline receptor is a novel brainstem modulator of sympathetic outflow that is elevated on platelets and in brains of depressed patients. A positive correlation has been reported (accompanying manuscript) between plasma norepinephrine (NE) concentrations and the densities (Bmax) of platelet I1 binding sites (I1 sites). I1-candidate proteins of 33 kDa and 85 kDa are now identified on Western blots probed with anti-imidazoline receptor antiserum (IRBP antiserum), that correlate with Bmax values for I1 sites. Furthermore, a human megakaryoblastoma cell line (MEG-01) has been used to study the regulation of these proteins on megakaryocytic cells, while bovine adrenal chromaffin cells provide a standard I1 cell type for comparison. Both the 33 kDa and 85 kDa IRBP-immunoreactive bands were enriched in plasma membrane fractions. IRBP antiserum did not cross-react with I2 imidazoline binding sites located on platelet mitochondrial membranes. The 85 kDa band was enhanced under conditions lacking fetal bovine serum (FBS) from the culture medium 6 h prior to harvesting. Conversely, 33 kDa protein was enhanced on MEG-01 cells grown in the presence of 10% FBS; suggesting that a precursor (85 kDa) and product (33 kDa) relationship might be induced by serum. The 85 kDa band was robustly up-regulated in response to imidazoline receptor-sensitive ligands; moxonidine, idazoxan and agmatine (10 microM each for 6 h). NE also up-regulated the 85 kDa IRBP-immunoreactive protein on MEG-01 membranes, but to a lesser extent. Idazoxan, an imidazoline alpha 2-antagonist, off-set its induction of 85 kDa protein by reducing the 33 kDa band. Yohimbine, a non-imidazoline alpha 2-antagonist, was ineffective alone, or in combination with moxonidine (up to 40 microM), but yohimbine blocked NE's induction of the 85 kDa band. Therefore, a rise in either plasma NE and/or endogenous I-site ligands (i.e. agmatine) could explain an elevation of imidazoline receptors observed in depression.

Laminin-5 and modulation of keratin cytoskeleton arrangement in FG pancreatic carcinoma cells: involvement of IFAP300 and evidence that laminin-5/cell interactions correlate with a dephosphorylation of alpha 6A integrin

Under normal culture conditions, epithelial cells of the FG line, derived from a pancreatic tumor, characteristically grow in mounds and fail to flatten efficiently onto their substrate. In such cells, keratin intermediate filaments (IFs) are concentrated in the perinuclear region. Furthermore, the IF associated protein, IFAP300, primarily localizes along these keratin bundles. Additionally, alpha 6 beta 4 integrin heterodimers localize in streaks or spots towards the edges of cells while alpha 3 beta 1 integrin is predominantly at cell-cell surfaces. Neither show any obvious interaction with IF. Remarkably, upon plating FG cells into medium containing soluble rat laminin-5, FG cells rapidly adhere and spread onto their substrate. Moreover, FG cells "capture" rat laminin-5 and place it basally in circles or arcs at areas of cell-substrate interaction. Double label immunofluorescence microscopy reveals colocalization of IFAP300 as well as alpha 6 beta 4 and alpha 3 beta 1 integrin with the polarized laminin-5. Concomitantly, alpha 6 integrin undergoes dephosphorylation on serine residue 1041. Laminin-5-induced rapid adhesion can be blocked by antibodies against the alpha 3 integrin subunit. In contrast, while alpha 6 integrin antibodies do not block laminin-5-induced rapid adhesion, they prevent FG cells from assuming an epithelial-like morphology. Keratin IF bundles associate with IFAP300-alpha 6 beta 4/alpha 3 beta 1 integrin complexes along the cell-substratum-attached surface of FG cells coincubated in laminin-5-containing medium. Coprecipitation results suggest that in these complexes, IFAP300 may associate with the alpha 6 beta 4 integrin heterodimer. Based on our results and published evidence that IFAP300 binds keratin in vitro [Skalli et al., 1994; J. Cell Biol. 125:159-170], we propose that laminin-5/FG cell interaction results in a novel integrin dephosphorylation event, which subsequently induces IFAP300 association with alpha 6 beta 4 integrin. IFAP300 then mediates the interaction of IFs with the cell surface via the alpha 6 beta 4 integrin heterodimer.

Use of psychotropic medication in Oklahoma: a statewide survey

Analysis of statewide survey data revealed that 22.5% of individuals with mental retardation who were served by the Oklahoma mental retardation system were receiving antipsychotic medication. Anxiolytic medications were prescribed for 9.3%, and antidepressants were prescribed for 5.9%. Higher levels of medication use were found in institutional settings and Intermediate Care Facility settings.

Coating of titanium alloy with soluble laminin-5 promotes cell attachment and hemidesmosome assembly in gingival epithelial cells: potential application to dental implants

The formation of a biological seal around the transmucosal portion of dental implants may be crucial for the long-term success of these therapies. Data to date suggest that the gingival epithelium attaches to dental implants through the formation of hemidesmosomes. Biochemical and genetic data indicate that the laminin isoform, laminin-5, a component of basement membranes, plays a crucial role in the assembly and maintenance of hemidesmosomes. We report the use of soluble laminin-5 as a biological coating of titanium-alloy to promote cell attachment of the gingival epithelial cell line, IHGK. Monoclonal antibodies reactive with laminin-5 depleted the coating solution of all cell attachment activity and blocked cell attachment to laminin-5-coated disks. Immunodepletion with antibodies to fibronectin had no effect. Finally, we demonstrate that IHGK cells assembled hemidesmosomes within 24 h of attachment to laminin-5-coated titanium alloy but not to the titanium alloy alone. These results suggest that soluble laminin-5 may have clinical applications as a dental implant coating to promote the formation of a biological seal.

When do sphenoidal electrodes yield additional data to that obtained with antero-temporal electrodes?

The advantage of using sphenoidal (SE) over antero-temporal electrodes (ATE) remains controversial among epileptologists. Yet, in a recently published study of 17 patients with seizures of antero-temporal origin (Kanner et al., 1995), we demonstrated that SE placed under fluoroscopic guidance (FPSE), in order to insure that their recording tips are positioned immediately below the foramen ovale (FO), yielded a significant advantage over SE placed with the standard blind method of insertion (BPSE), in both interictal and ictal recordings. This study was done to test the following hypothesis: FPSE advantage over BPSE and ATE resides in the recording of epileptiform activity with a restricted electric field. We compared spike voltages at FPSE, BPSE and ATE in sets of 5 randomly selected spikes per interictal focus, recorded in the course of separate monitoring studies with BPSE and FPSE. We represented the voltage differences as ratios, VATE/FPSE and VATE/BPSE and calculated a mean ratio for each spike set. The spikes' voltage was almost identical at BPSE and at ATE (mean VATE/BPSE = 0.94), while it was significantly higher at FPSE than at ATE (mean VATE/FPSE = 0.66; P < 0.001, t test). A significantly narrower electric field contour was found among interictal foci in which FPSE yielded additional data during interictal (P < 0.001) and ictal (P = 0.016) recordings. Conversely, VATE/FPSE did not differ from VATE/BPSE among interictal foci where FPSE failed to yield any advantage over BPSE in either interictal (P = 0.240), or ictal (P = 0.311) recordings. These findings prove that SE yield additional localizing data when recording epileptiform activity with a restricted field, provided that its recording tip is positioned below the FO. When distant from FO, SE can be expected to yield comparable data to that obtained with ATE.

The role of laminin-5 and its receptors in mammary epithelial cell branching morphogenesis

In vivo, normal mammary epithelial cells utilize hemidesmosome attachment devices to adhere to stroma. However, analyses of a potential role for hemidesmosomes and their components in mammary epithelial tissue morphogenesis have never been attempted. MCF-10A cells are a spontaneously immortalized line derived from mammary epithelium and possess a number of characteristics of normal mammary epithelial cells including expression of hemidesmosomal associated proteins such as the two bullous pemphigoid antigens, alpha 6 beta 4 integrin and its ligand laminin-5. More importantly, MCF-10A cells readily assemble mature hemidesmosomes when plated onto uncoated substrates. When maintained on matrigel, like their normal breast epithelial cell counterparts, MCF-10A cells undergo a branching morphogenesis and assemble hemidesmosomes at sites of cell-matrigel interaction. Function blocking antibodies specific for human laminin-5 and the alpha subunits of its two known receptors (alpha 3 beta 1 and alpha 6 beta 4 integrin) not only inhibit hemidesmosome assembly by MCF-10A cells but also impede branching morphogenesis induced by matrigel. Our results imply that the hemidesmosome, in particular those subunits comprising its laminin-5/integrin 'backbone', play an important role in morphogenetic events. We discuss these results in light of recent evidence that hemidesmosomes are sites involved in signal transduction.

Laminin-5 and modulation of keratin cytoskeleton arrangement in FG pancreatic carcinoma cells: involvement of IFAP300 and evidence that laminin-5/cell interactions correlate with a dephosphorylation of alpha 6A integrin

Under normal culture conditions, epithelial cells of the FG line, derived from a pancreatic tumor, characteristically grow in mounds and fail to flatten efficiently onto their substrate. In such cells, keratin intermediate filaments (IFs) are concentrated in the perinuclear region. Furthermore, the IF associated protein, IFAP300, primarily localizes along these keratin bundles. Additionally, alpha 6 beta 4 integrin heterodimers localize in streaks or spots towards the edges of cells while alpha 3 beta 1 integrin is predominantly at cell-cell surfaces. Neither show any obvious interaction with IF. Remarkably, upon plating FG cells into medium containing soluble rat laminin-5, FG cells rapidly adhere and spread onto their substrate. Moreover, FG cells "capture" rat laminin-5 and place it basally in circles or arcs at areas of cell-substrate interaction. Double label immunofluorescence microscopy reveals colocalization of IFAP300 as well as alpha 6 beta 4 and alpha 3 beta 1 integrin with the polarized laminin-5. Concomitantly, alpha 6 integrin undergoes dephosphorylation on serine residue 1041. Laminin-5-induced rapid adhesion can be blocked by antibodies against the alpha 3 integrin subunit. In contrast, while alpha 6 integrin antibodies do not block laminin-5-induced rapid adhesion, they prevent FG cells from assuming an epithelial-like morphology. Keratin IF bundles associate with IFAP300-alpha 6 beta 4/alpha 3 beta 1 integrin complexes along the cell-substratum-attached surface of FG cells coincubated in laminin-5-containing medium. Coprecipitation results suggest that in these complexes, IFAP300 may associate with the alpha 6 beta 4 integrin heterodimer. Based on our results and published evidence that IFAP300 binds keratin in vitro [Skalli et al., 1994; J. Cell Biol. 125:159-170], we propose that laminin-5/FG cell interaction results in a novel integrin dephosphorylation event, which subsequently induces IFAP300 association with alpha 6 beta 4 integrin. IFAP300 then mediates the interaction of IFs with the cell surface via the alpha 6 beta 4 integrin heterodimer.

Morphogenetic effects of soluble laminin-5 on cultured epithelial cells and tissue explants

The rat cell line 804G assembles an extracellular matrix which induces not only the rapid adhesion and spreading of epithelial cells but also the assembly of a cell-matrix attachment device called the hemidesmosome. The major component of this matrix is laminin-5. We have purified rat laminin-5 from medium conditioned by 804G cells. Epithelial cells which are co-incubated with medium supplemented with soluble laminin-5 adhere and spread rapidly. Furthermore, human carcinoma cells undergo a dramatic morphologic change in the presence of laminin-5 and form orderly arrays resembling epithelial sheets. Soluble rat laminin-5 is selectively incorporated into an insoluble matrix of epithelial cells in vitro, since rat-specific laminin-5 antibodies stain cell-substrate contacts. Addition of medium containing soluble laminin-5 to explanted, human corneal rims induces assembly of hemidesmosomes, important cell-matrix attachment devices. Furthermore, rat-specific laminin-5 antibodies stain areas of contact between corneal epithelium and basement membrane, indicating that rat laminin-5 from the medium is incorporated into basement membrane. We discuss the use of laminin-5 as a medium supplement for the culture of both epithelial cells and epithelial tissue explants.

Laminin-5 and hemidesmosomes: role of the alpha 3 chain subunit in hemidesmosome stability and assembly

Hemidesmosomes are complex macromolecular structures which integrate elements of the extracellular matrix and the cytoskeleton of epithelial cells. To characterize cell-matrix interactions in the hemidesmosome, we have made use of 804G cells which possess the unusual ability to assemble hemidesmosomes in vitro. During the course of our studies, we have raised a set of monoclonal antibodies against rat laminin-5, the major structural element comprising 804G matrix. One of these, termed CM6, recognizes the 150 kDa alpha chain of rat laminin-5 and binds the globular (G) domain of intact laminin-5 molecules as determined by rotary shadowing. CM6 antibodies perturb formed hemidesmosomes in 804G cells. In particular, within 1 hour of incubation of 804G cells with CM6 antibodies, colocalization of laminin-5 and alpha 6 beta 4 integrin is lost and by 2 hours, staining generated by hemidesmosomal antibodies appears primarily cytoplasmic in the perinuclear zone. Ultrastructurally, CM6 antibodies first appear to induce detachment of hemidesmosomes from the underlying matrix. Next, portions of the basal cell surface invaginate to form vesicles whose cytoplasmic-facing surface is coated with hemidesmosomes still associated with keratin intermediate filaments. Anchoring filaments extend into the inside compartment of the vesicles. We have also studied the impact of CM6 antibodies on a model system in which the matrix of 804G cells induces de novo assembly of hemidesmosomes in human keratinocytes. This process involves the plasma membrane reorganization of the hemidesmosome associated integrin alpha 6 beta 4 as well as a redistribution of other hemidesmosome components such as the 230 kDa bullous pemphigoid antigen. Pretreatment of 804G matrix with CM6 antibodies blocks such plasma membrane reorganization of hemidesmosome components and inhibits hemidesmosome formation. Our studies indicate a crucial role for the G domain of the alpha chain of laminin-5 in both nucleation of hemidesmosome assembly as well as maintenance of hemidesmosome structural integrity.

Botulinum toxin--a possible new treatment for axillary hyperhidrosis

The inhibitory action of botulinum toxin is not limited to the neuromuscular junction. The toxin also blocks the autonomic cholinergic fibres, including the sympathetic fibres to sweat glands. We have previously demonstrated that the toxin produces localized anhidrosis. To determine the dosage, pattern and duration of the anhidrotic effect of botulinum toxin and to test the efficacy of axillary injections, we further studied seven healthy volunteers. Two individuals had subcutaneous injections of botulinum toxin (20 mouse units, Dysport-Porton Products) in the dorsum of the hand. Five healthy volunteers had 15-50U of botulinum toxin A (Botox) injected in one axilla. A circular area of complete anhidrosis on the dorsum of the hand was evident on day 2 and persisted for 11 months. By day 3, two of the axillae (injected with 50 U each) were totally dry and in one (injected with 30 U) the sweating was substantially reduced. The effect persisted for 6-8 months before wearing off. No effect was appreciated in two axillae (injected with 15 and 20 U). No significant side-effects were encountered. Subcutaneous injections of botulinum toxin causes chemodenervation of the sweat glands. In normal individuals axillary sweating can be abolished by 50 U of botulinum toxin A (Botox). The results offer a possible novel treatment for severe cases of axillary hyperhidrosis.

Changes in expression of monoclonal antibody epitopes on laminin-5r induced by cell contact

Laminin-5r is a basement membrane component that promotes rapid adhesion and hemidesmosome formation in epithelial cells. We raised monoclonal antibodies and identified their corresponding epitopes on the constituent chains of laminin-5r by western blotting. Using a combination of immunoprecipitation and ELISA assays, we determined that these epitopes are differentially exposed on two forms of the laminin-5r heterotrimer: soluble (passively adsorbed onto plastic) and cell-associated. Antibody 5C5 epitope is exposed on the cell-associated form, but not the soluble/passively adsorbed form of laminin-5r. Epitopes reactive with antibodies CM6, FM3, and TR1 are also preferentially exposed on cell-associated laminin-5r, such that reactivity of these antibodies with the cell-associated form is fourfold higher than with the soluble/passively adsorbed form in ELISA assays. Incubation of passively adsorbed laminin-5r with the human epithelial cell line SCC12 induced exposure of 5C5 and CM6, FM3, or TR1 epitopes. These data suggest that cells actively modify laminin-5r, perhaps during matrix assembly, and that the 5C5 epitope may serve as a marker for assembled laminin-5r matrix.

Desmosomes and hemidesmosomes: structure and function of molecular components

Desmosomes and hemidesmosomes are the major cell surface attachment sites for intermediate filaments at cell-cell and cell-substrate contacts, respectively. The transmembrane molecules of the desmosome belong to the cadherin family of calcium-dependent adhesion molecules, whereas those in the hemidesmosome include the integrin class of cell matrix receptors. In each junction, the cytoplasmic domains of certain transmembrane junction components contain unusually long carboxy-terminal tails not found in those family members involved in linkage of actin to the cell surface. These domains are thought to be important for the regulation of junction assembly and specific attachment of intermediate filaments via associated adapter proteins. Recent developments have suggested the exciting possibility that these junctions, in addition to playing an important structural function in tissue integrity, are both acceptors and affectors of cell signaling pathways. Many desmosomal and hemidesmosomal constituents are phosphoproteins and in certain cases the function of specific phosphorylation sites in regulating protein-protein interactions is being uncovered. In addition, a more active role in transmitting signals that control morphogenesis during development and possibly even regulate cell growth and differentiation are being defined for cytoplasmic and membrane components of these junctions.

Pityrosporum ovale (Malassezia furfur) as the causative agent of seborrhoeic dermatitis: new treatment options

Several studies indicate that Pityrosporum ovale plays an important role in seborrhoeic dermatitis. Many of these are treatment studies which describe the effectiveness of antimycotics, paralleled by a reduction in the number of P. ovale colonies and then recolonization, leading to a recurrence of seborrhoeic dermatitis. In this study 20 patients with seborrhoeic dermatitis of the scalp were treated with terbinafine (Lamisil) 1% solution once daily for 4 weeks. Eleven of 18 patients (61%) were cured and they were still free of lesions 2 weeks after stopping treatment. No side-effects related to treatment were seen. There was also a significant reduction in the number of P. ovale colonies. This may explain both the good clinical effect and the observation that all patients who were cleared of P. ovale were still free of lesions 2 weeks after stopping treatment.

Effect of a high-protein meal on gabapentin pharmacokinetics

The anticonvulsant gabapentin is transported across biological membranes via the L-amino acid transport system (System-L). Absorption of gabapentin is saturable, and in-vitro data have previously demonstrated that both L-leucine and L-phenylalanine may compete with the intestinal transport of gabapentin. The purpose of this study therefore was to determine whether a high-protein meal would interfere with gabapentin absorption. Ten healthy volunteers received in a randomized, cross-over design, a single 600-mg dose of gabapentin in the fasting state and after a high-protein meal consisting of 80 gm total protein (4.1 g phenylalanine, 8.2 g leucine and 4.2 g isoleucine), 52 g carbohydrate, and 9 g fat. Plasma gabapentin concentrations were measured by HPLC at baseline, 0.25, 0.5, 0.75, 1, 1.5, 2, 2.5, 3, 3.5, 4, 5, 6, 8, 12, 24, 30 h. Calculated pharmacokinetic parameters included Cmax' Tmax' AUC and T1/2. In addition, a pharmacodynamic assessment (using visual analog scales) of gabapentin-related adverse effects was performed at 2 h post drug ingestion and was compared between study phases. Statistical analysis included Student's t-test for paired data, with significance assigned at P < 0.05. Cmax was significantly increased by 36% (3.87 +/- 1.15 vs 5.28 +/- .97 micrograms/ml, P = 0.002), and Tmax tended to be shorter (3.9 +/- 1.8 vs 2.8 +/- .35 h, P = 0.10), after the high-protein meal. Although AUC was increased by 11%, this did not achieve statistical significance. Despite significantly higher plasma concentrations at 2 h, subjects reported significantly fewer adverse effects after the high-protein meal. Potential mechanisms to explain these unexpected findings may be that the large amino acid load delivered with the high-protein meal enhanced gabapentin absorption via trans-stimulation, the process by which acutely increased intestinal luminal amino acid concentrations result in an acute up regulation in System-L activity. Conversely, the decrease in perceived adverse CNS effects of gabapentin following the high-protein meal may reflect CNS competition for System-L transport.

Expression of hemidesmosomes and component proteins is lost by invasive breast cancer cells

Hemidesmosomes are multiprotein structures that attach basal cells of stratified epithelia to basement membranes. Although normal human breast epithelia are not stratified, we observed expression of electron-dense hemidesmosomes and hemidesmosome protein components by breast epithelial and myoepithelial cells at the basal lamina in vivo. Primary cultured normal human breast epithelial cells also contained hemidesmosomes and component proteins, and could be used as a model for hemidesmosome assembly and regulation. In these cultured cells, hemidesmosome proteins were expressed and localized basally in an unvaried temporal pattern, and electron-dense hemidesmosomes were not seen until the final protein was localized to the cell base. In addition, rate of localization was influenced by confluence, doubling time, and extracellular matrix. Invasive breast cancer cells did not express hemidesmosomes or most of the component proteins in vivo. In carcinoma in situ, cells away from the basement membrane lacked hemidesmosomes and hemidesmosome proteins, and cells at the basement membrane exhibited abnormalities of hemidesmosome protein expression. Primary human malignant breast cells in culture exhibited a mix of hemidesmosome phenotypes. These data suggest that hemidesmosomes may be important subcellular structures in determining the cytoarchitecture of the breast epithelium. Further, their downregulation may influence cytoarchitecture remodeling closely linked with cell cycle, motility, and extracellular matrix interactions; and their loss in carcinoma may be associated with loss of normal cytoarchitecture.

Rapid spreading and mature hemidesmosome formation in HaCaT keratinocytes induced by incubation with soluble laminin-5r

HaCaT cells, an immortalized keratinocyte line, incubated in plastic wells in the presence of conditioned medium from 804G cells adhered and spread rapidly in less than 30 min. In contrast, cells plated in fibroblast or keratinocyte conditioned medium adhered poorly and remained rounded at 30 min. Immunodepletion of 804G conditioned medium with polyclonal antisera to laminin-5r, but not control antisera, abolished rapid cell spreading. Electron microscopy of HaCaT cells spread by incubation in 804G conditioned medium, but not control medium, revealed mature hemidesmosomes after 24 h. Rapid spreading was also observed in wells precoated with 804G conditioned medium or 804G cell-deposited matrix, but not with fibronectin, vitronectin, or laminin-1. Immunoblotting of 804G conditioned medium with anti-laminin-5r antibodies unveiled polypeptides of 150, 140, 135, and 100 kDa, identical by electrophoretic mobility to immunoreactive polypeptides in 804G deposited matrix. Our results suggest that addition of laminin-5r in a soluble form is sufficient to promote rapid spreading and hemidesmosome assembly in keratinocytes. The mechanism of soluble laminin-5r action may include efficient surface "priming" for cell adhesion. Soluble laminin-5r may have a physiologic role in morphogenesis and repair of the epidermis and may be of use for therapeutic applications.

Family functioning: a correlate of diabetic control?

Poor diabetic control was found in nearly 50% of adolescents attending two paediatric clinics. Adolescents with well and poorly controlled diabetes differed in reported parental involvement in their diabetic regime. There was little association between glycaemic control and family functioning using the McMaster Family Assessment Device (FAD) whether rated by adolescent or a parent. Neither did sufferers with diabetes differ from families of matched community controls according to the FAD overall though the families of well controlled diabetics were more likely than the other two groups to score themselves in the unhealthy range on the subscale of global functioning.