Direct Detection Constraints on Dark Photons with the CDEX-10 Experiment at the China Jinping Underground Laboratory.

We report constraints on the dark photon effective kinetic mixing parameter (κ) with data taken from two p-type point-contact germanium detectors of the CDEX-10 experiment at the China Jinping Underground Laboratory. The 90% confidence level upper limits on κ of solar dark photon from 205.4 kg-day exposure are derived, probing new parameter space with masses (m_{V}) from 10 to 300 eV/c^{2} in direct detection experiments. Considering dark photon as the cosmological dark matter, limits at 90% confidence level with m_{V} from 0.1 to 4.0 keV/c^{2} are set from 449.6 kg-day data, with a minimum of κ=1.3×10^{-15} at m_{V}=200 eV/c^{2}.

[Impact of cessation of antiviral therapy at delivery on postpartum liver function in mothers with chronic hepatitis B virus infection].

Objective: To investigate the impact of immediate cessation of antiviral therapy on postpartum liver function and the factors influencing postpartum abnormality in mothers with chronic hepatitis B virus infection. Methods: A retrospective cohort study was conducted. One hundred eighty-eight pregnant women with HBV DNA level > 2×106 IU/ml were enrolled from June 2014 to June 2018. Demographic information and clinical data of liver function and HBV DNA load during gravidity, intrapartum and postpartum period were collected. According to the antiviral treatment recommendations during pregnancy, the women were divided into three groups, namely, tenofovir (TDF), telbivudine (LdT) and control group. Liver function abnormalities among the three groups were compared within 6 months after delivery, and the factors influencing abnormal liver function were analyzed by unconditional logistic regression. Results: Of the 188 cases, 72 cases were in the TDF group, 80 cases in the LdT group, and 36 cases in the control group. Pregnant women in the TDF and LdT groups received oral TDF (300 mg/d) and LdT (600 mg/d) from 28 ± 4 weeks of gestation till delivery. Among the 188 patients, 30 (16.0%) had abnormal postpartum liver function abnormality. The incidence of postpartum liver function abnormality [alanine aminotransferase (ALT) > 2 × upper limit of normal (ULN)] in the TDF, LdT, and control groups was 19.4%, 12.5%, and 16.7%, respectively. The postpartum peak levels of ALT (median, range) in the three groups were 34.5 (12.0-946.0) U/L, 37.5 (12.0-733.8) U/L, and 39.0 (7.0-513.0) U/L, respectively. There was no significant difference between the two indexes among the three groups (P > 0.05). There was no statistically significant difference in the degree of postpartum liver function abnormalities between the three groups (P = 0.944). Most of the liver function abnormalities were mild to moderate (2 × ULN≤ALT < 10 × ULN), and usually resolved spontaneously or by treatment. Univariate and multivariate analysis showed that baseline ALT level during pregnancy was an independent factor associated with postpartum liver function abnormality (OR = 1.031, CI 95%: 1.005-1.058; χ(2) = 5.340, P = 0.021), whereas age, antiviral therapy, HBeAg-positivity, baseline HBV DNA levels, gravidity, parity, preterm delivery and delivery mode were not significantly associated with postpartum liver function abnormality. Conclusion: Cessation of antiviral therapy after delivery did not significantly increase the risk of postpartum liver function abnormality in pregnant women with chronic HBV infection. The ALT level during pregnancy is a factor influencing postpartum liver function abnormality.

MiR-589-5p is a potential prognostic marker of hepatocellular carcinoma and regulates tumor cell growth by targeting MIG-6.

MicroRNAs (miRNAs) are small noncoding RNAs approximately with 22 nucleotides. Accumulating evidence indicates that microRNAs are involved in carcinogenesis and tumor progression. Some recent investigations have also reported that several microRNAs could act as biomarkers in cancer diagnosis and prognosis. MicroRNA-589-5p (miR-589-5p) is a less studied microRNA, in this study, we explored its roles in hepatocellular carcinoma (HCC). We analyzed miR-589-5p expression in HCC tissues by sequencing data and proved the expression in liver cancer cell lines by quantitative real-time PCR (qRT-PCR). We studied the effect of miR-589-5p on the growth of liver cancer cells by MTT assay, colony formation and flow cytometry, and identified its target gene by luciferase reporter assay. We found that miR-589-5p was commonly overexpressed in HCC specimens. High expression of miR-589-5p was a risk factor for HCC patient (Hazard ratio [HR] = 1.434; 95% confidence intervals [CI] = 1.006-2.044; p = 0.046). We also found miR-589-5p had higher expression in hepatocarcinoma cell lines HepG2 and HuH-7 than did in normal hepatocyte Lo-2. We identified that suppression of miR-589-5p inhibited cell proliferation and cell cycle progression by loss-of-function studies. Furthermore, we found mitogen-inducible gene 6 (MIG-6) to be a target of miR-589-5p. Our study demonstrated that miR-589-5p facilitated the growth of liver cancer cells by targeting MIG-6 and could be a prognosis biomarker for HCC. Suppression of miR-589-5p may be a feasible approach for inhibiting HCC progress.

Thy-1 supports adhesion of mouse thymocytes to thymic epithelial cells through a Ca2(+)-independent mechanism.

The aim of this study was to explore whether Thy-1, like other members of the Ig-like superfamily (e.g., CD2 and neural cell adhesion molecule), participates in cell-cell adhesion. This was investigated by measuring the binding of Thy-1+ probe cells (thymocytes or AKR1 T lymphoma cells) to Thy-1- cloned mouse thymic epithelial (MTE) cells using a quantitative cell adhesion assay. The results were as follows: (a) the thymo-epithelial cell interaction was found to be inhibitable (by 25-40%) by soluble Thy-1 molecules purified from phosphatidylinositol-specific phospholipase C-treated mouse thymocytes as well as by Fab' fragments of a Thy-1-specific mAb; (b) the binding of the Thy-1- AKR1 (Thy-1-d) mutant to MTE cells was found to be reduced (by 50%) as compared with that of the wild type T lymphoma; (c) the Thy-1-mediated adhesion pathway did not require Ca2+ and promoted the initial thymo-epithelial binding measured at 4 degrees C. These data provide the first direct evidence of an adhesive function of Thy-1 and suggest that this molecule, in addition to its T cell triggering properties, might play a role during the early T cell maturation by promoting thymocyte adhesion to thymic stroma.

Thy-1 triggers mouse thymocyte apoptosis through a bcl-2-resistant mechanism.

Programmed cell death plays an important role during thymocyte development, since a vast majority (97%) of mouse cortical thymocytes die in thymus, whereas only 3% of these cells are rescued from cell death and positively selected. Although it seems well established that thymocyte fate depends upon appropriate surface-expressed T cell receptor, little is known about the molecular mechanism(s) responsible for the massive thymocyte elimination that occurs in the thymus. We report here that Thy-1 is capable of triggering mouse thymocyte death in vitro through a bcl-2-resistant mechanism. We have previously shown that Thy-1 is involved in mouse thymocyte adhesion to thymic stroma through interaction with an epithelial cell ligand. To examine the Thy-1 signaling function in thymocytes, we have mimicked its interaction with stromal cells by culturing mouse thymocytes onto tissue culture plates coated with monoclonal antibodies (mAb) directed at distinct Thy-1 epitope regions. mAb recognizing determinants in a defined Thy-1 structural domain, but not others, were found to induce marked thymocyte apoptosis as evidenced by morphological and biochemical data. Use of a quantitative DNA dot blot assay indicated that Thy-1-mediated thymocyte apoptosis was not blocked by RNA or protein synthesis inhibitors, EGTA, or by cyclosporin A, and differed, therefore, from "activation-driven cell death". Moreover, Thy-1(+)-transfected, but not wild-type AKR1 (Thy-1-d) thymoma cells underwent apoptosis after ligation with apoptosis-inducing, Thy-1-specific mAb. In contrast to thymocytes, the latter event was inhibitable by RNA and protein synthesis inhibitors, an indication that thymocytes, but not thymoma cells, contain the molecular components necessary for Thy-1-driven apoptosis. We further showed that Thy-1-triggered thymocyte death is a developmentally regulated process operative in fetal thymocytes from day 17 of gestation, but not in peripheral T cells. Indeed, the target of apoptosis by anti-Thy-1 was found to reside mainly within the CD4+8+3- and CD4+8+3lo double positive immature thymocyte subsets. Finally, it is of major interest that Thy-1-mediated apoptosis, which was found to be readily detectable in thymocytes from bcl-2-transgenic mice, represents a thus far unique experimental system for studying bcl-2-resistant thymocyte death mechanism(s).

Biosynthesis, membrane association, and release of N-CAM-120, a phosphatidylinositol-linked form of the neural cell adhesion molecule.

The neural cell adhesion molecule (N-CAM) of rodents comprises three distinct proteins of Mr 180,000, 140,000, and 120,000 (designated N-CAM-180, -140, and -120). They are expressed in different proportions by different tissues and cell types. but the individual contribution of each form to cell adhesion is presently unknown. Previous studies have shown that the two N-CAM species of higher relative molecular mass span the membrane whereas N-CAM-120 lacks a transmembrane domain and can be released from the cell surface by phosphatidylinositol-specific phospholipase C. In this report, we provided evidence that N-CAM-120 contained covalently bound phosphatidylinositol and studied N-CAM-120 from its biosynthesis to its membrane insertion and finally to its release from the cell surface. Evidence was presented showing that the lipid tail of N-CAM-120 contained ethanolamine as is the case for other lipid-linked molecules. The phospholipid anchor was attached to the protein during the first minutes after completion of the polypeptide chain. This process took place in the endoplasmic reticulum as judged from endoglycosidase H digestion experiments. Immediately after a 2-min pulse with [35S]methionine, we detected also a short-lived precursor that had not yet acquired the lipid tail. Pulse-chase studies established that N-CAM-120 was transported to the cell surface from which it was slowly released into the extracellular milieu. The molecules recovered in the incubation medium appeared to have lost all of their bound fatty acid but only around half of the ethanolamine. Upon fractionation of brain tissue, approximately 75% of N-CAM-120 was recovered with a membrane fraction and approximately 25% in a membrane-free supernatant. A small proportion (approximately 6%) was found to be resistant to extraction by non-ionic detergent. A major posttranslational modification of N-CAM is polysialylation. Our results showed that also N-CAM-120 was polysialylated in the young postnatal brain and released in this form from cultured cerebellar cells. The presence of N-CAM in a form that can be released from the cell surface and accumulates in the extracellular fluid suggests a novel mechanism by which N-CAM-mediated adhesion may be modulated.

Impact of strain rate on the hardness and elastic modulus of human tooth enamel.

Human tooth enamel is a natural biocomposite consisting of mineral units surrounded by a soft protein shell. The mechanical behaviors of enamel are closely associated with its structure. In this paper, the strain-rate dependent mechanical properties of enamel were investigated with nanoindentation techniques. Five constant strain rates (0.01s-1, 0.03s-1, 0.05s-1, 0.1s-1, 0.3s-1) were used in this study. Results showed that the hardness and elastic modulus of enamel increased with increasing strain rate. These results indicate that the variation of hardness under different stain rates is associated with creep behavior of organic matrix in enamel. And indentation creep rate sensitivity of human enamel was measured with a value of 0.062. Moreover, the elastic module of enamel is dependent upon strain rate. Such rate dependence originates from the organic matrix which is sensitive to the strain rate. This behavior may be important in explaining the excellent toughness and energy absorption abilities of natural tooth structure.

Thymocytes in Thy-1-/- mice show augmented TCR signaling and impaired differentiation.

Thy-1, a single variable-like immunoglobulin superfamily domain anchored in the plasma membrane by a glycosyl phosphaditylinositol tail [1], is a major surface glycoprotein in adult mammalian neurons and rodent thymocytes [2]; the function of Thy-1 has remained enigmatic since its discovery [3]. Studies in vitro have implicated Thy-1 in homotypic and heterotypic cell-cell interactions [2,4]. Ligation of Thy-1 initiates transmembrane signaling pathways that lead to diverse physiological outcomes in different cells [2,5-7]. In rodents, Thy-1 is highly expressed on the surface of CD4+CD8+ double-positive immature thymocytes and downregulated in mature T cells. Here, we report that thymocytes from Thy-1-/- mice [8] had altered cell-cell contacts, and hyperresponsiveness to T-cell receptor (TCR) triggering as demonstrated by the heightened activation of p56lck, phosphorylation of TCR subunits, Ca2+ fluxes and cell proliferation. Thy-1-/- thymocytes exhibited impaired maturation from the double positive to single positive stage of thymocyte development, possibly due to inappropriate negative selection, and were prone to T lymphomas in aged mice. These observations indicate that Thy-1 negatively regulates TCR-mediated signaling and controls activation thresholds during thymocyte differentiation.

Membrane rafts and signaling by the multichain immune recognition receptors.

The recent recognition of the presence of rafts in the plasma membrane and of their involvement in cell signaling has strongly stimulated the search for their function in receptor-mediated signal transduction in lymphocytes. Recent progress suggests that a general feature of membrane rafts is to serve as platforms wherein the signaling cascades triggered through different multichain immune recognition receptors (e.g. the TCR, BCR and FcepsilonRI) are initiated and organized.

A user's guide for characterizing plasma membrane subdomains in living cells by spot variation fluorescence correlation spectroscopy.

Due to the intrinsic molecular Brownian agitation within plasma membrane and the vast diversity of membrane components, it is expected that the plasma membrane organization is highly heterogeneous with the formation of local complex multicomponent assemblies of lipids and proteins on different time scales. Still, deciphering this lateral organization on living cells and on the appropriate length and temporal scales has been challenging but is crucial to advance our knowledge on the biological function of the plasma membrane. Among the methodological developments based on biophotonics, the spot variation FCS (svFCS), a fluorescent correlation spectroscopy (FCS)-based method, has allowed the significant progress in the characterization of cell membrane lateral organization at the suboptical level, including to providing compelling evidence for the in vivo existence of lipid-dependent nanodomains. The aim of this chapter is to serve as a guide for setting and applying the svFCS methodology to study the plasma membrane of both adherent and nonadherent cell types.

On the thickness and nanomechanical properties of salivary pellicle formed on tooth enamel.

OBJECTIVE: To determine the thickness and nanomechanical properties of salivary pellicle formed on tooth enamel. METHODS: In vitro adsorption experiments were conducted by immersing enamel samples in centrifuged saliva for 1min, and then the nanomechanical properties of the salivary pellicle/tooth enamel system were measured firstly using nanoindentation based on a continuous stiffness measurement technique. Finally, a model was proposed to obtain the thickness and the intrinsic nanohardness of this biofilm. RESULTS: The composite nanohardness of salivary pellicle/tooth enamel system varied with indentation depth. The model can describe the experimental date at both shallow and deep indentation depths very well. The fitted average thickness of salivary pellicle was about 17nm, which was in good accord with the scanning probe microscopy experimental results. The intrinsic hardness of salivary pellicle and tooth enamel was about 0.52Gpa and 4.88Gpa respectively, which was consistent with previous studies. CONCLUSIONS: It was convenient to extract intrinsic hardness and thickness of salivary pellicle from the indentation curve according to the model. Moreover, this model was applicable to plasticity-dominated behaviour of the soft film/hard substrate system. CLINICAL SIGNIFICANCE: The research results may be helpful to extend the understanding of our lubricating and anti-caries behaviours of salivary pellicle and to the oral hygiene industry for diagnose oral diseases.

Biochemical properties of brain somatostatin receptors.

The physical properties of brain and pituitary somatostatin receptors were characterized using photocrosslinking techniques. Somatostatin receptors in rat corpus striatum and anterior pituitary membranes were covalently bound to the non-reducible somatostatin analog, [125I]CGP 23996, using the crosslinking agent n-hydroxysuccinimidyl-4-azidobenzoate and ultraviolet light. In striatal membranes, a protein of 60,000 mol. wt was labeled by [125I]CGP 23996. The binding was potently inhibited by somatostatin analogs but not by other biologically active peptides. The labeling of the 60,000 mol. wt protein by [125I]CGP 23996 was diminished by guanine triphosphate gamma thiol, which is consistent with the labeling of a somatostatin receptor coupled to guanine triphosphate binding proteins. The migration of the [125I]CGP 23996 labeled 60,000 mol. wt protein in native sodium dodecyl sulfate-gels was not affected by the reducing agent dithiothreitol, indicating that there is a general lack of disulfide bridges in the striatal somatostatin receptor. The striatal somatostatin receptor was solubilized with the detergent 3-[(3-cholamidopropyl)-dimethylaminoio]-1-propanesulfonate and specifically bound to the lectin wheat germ agglutinin, suggesting that the striatal somatostatin receptor is a glycoprotein. [125I]CGP 23996 also labeled a 60,000 mol. wt protein in anterior pituitary membranes. The characteristics of [125I]CGP 23996 binding to anterior pituitary membranes were consistent with the labeling of a somatostatin receptor. Interestingly, a comparison of the [125I]CGP 23996 labeled material from striatal and anterior pituitary membranes by two-dimensional polyacrylamide gel electrophoresis revealed the presence of several striatal somatostatin receptors of varying charge (pI values between 6 and 6.5) but only a single pituitary receptor. These findings indicate that physical differences may exist between subtypes of somatostatin receptors.

Biochemical properties of somatostatin receptors.

Somatostatin (SRIF) induces its biological actions by binding to and stimulating membrane-associated receptors. To investigate the molecular mechanisms by which SRIF induces its biological effects, we have characterized the biochemical properties of SRIF receptors. SRIF receptors can be solubilized in an active form with the detergent CHAPS and can be detected with the high-affinity SRIF analog [125I]MK 678. The pharmacological characteristics of solubilized SRIF receptors from brain are similar to the receptors in membranes, suggesting that the solubilized receptors retain their biological activity. Solubilized SRIF receptors appear to be tightly associated with GTP-binding proteins, since analogs of GTP can greatly reduce agonist labeling of the solubilized SRIF receptor. The solubilized SRIF receptor migrates as a mass of approximately 400 kd and is a glycoprotein since it can specifically interact with lectin columns. The solubilization of the SRIF receptor has allowed for its purification by affinity chromatography. The purified SRIF receptor migrates as a mass of 60 kd in denaturing gels. Using affinity chromatography, the receptor can be purified to near homogeneity. Present studies are directed toward sequencing and cloning cDNA encoding the SRIF receptor in order to further characterize its physical properties and expression.

Thy-1 functions as a recognition/signaling molecule during mouse T lymphocyte development.

Thy-1 is a prototype of mammalian glycosyl phosphatidylinositol (GPI)-anchored molecules and belongs to the Ig superfamily. This cell surface glycoprotein is expressed on mouse T lymphocytes, neurons and hematopoietic stem cells. Despite detailed structural studies, little is known about the physiological role(s) of Thy-1. We discuss here our results on the role of Thy-1 in immature T lymphocytes during intrathymic maturation. It was observed that Thy-1-mediated adhesion of mouse thymocytes to thymic stromal cells occurs through interaction with an unknown ligand. The interaction occurs by a Ca(2+)-independent mechanism and does not require TCR/CD3 surface expression. To evaluate the signal transduction upon Thy-1 ligation in immature thymocytes, we cultured mouse thymocytes with monoclonal antibodies specific for Thy-1, immobilized onto the tissue culture plates. Monoclonal antibodies directed at determinants located in a defined epitope domain, but not others, triggered marked physiological cell death (apoptosis) of immature thymocytes, as evidenced by morphological and biochemical data. This apoptosis is independent of the cell surface expression of TCR/CD3. It is a developmentally regulated process since the period in which thymocytes are sensitive to Thy-1-dependent apoptosis corresponds to the developmental "window" during which massive death of immature thymocytes takes place within the thymus. Therefore, we propose that Thy-1 could function as a cell survival/death regulator in mouse T lymphocyte development.

[Treatment of myelodysplastic syndrome by combined traditional Chinese medicine and Western medicine therapy].

50 cases were treated with Myelodysplastic Syndrome (MDS) by combined TCM-WM therapy. They were classified into RA 17 cases, RAS 6, RAEB 19, CMML 1 and RAEBT 7. The patients were divided into two groups, one with RA and RAS receiving treatment of hemopoietic and immune drugs plus Chinese medicinal herbs, the other with RAEB, CMML and RAEBT receiving treatment of LD Ara-c and LD Hom chemotherapy plus medicinal herbs. The effective rates were 47.83% and 62.96% respectively, the total effective rate being 56%. 6 cases (RAEB 4, RA 1, RAS 1) were treated with all-trans retinoic acid used as an inducer of differentiation, 2 of them were effective. 11 patients with MDS who had transformed into acute leukemia were treated by LD Ara-c and combined TCM-WM chemotherapy, the remission rate was 54.55% and the survival period was 9-27 months after remission. In some cases low dose chemotherapy resulted in hemocytopenia, bone marrow inhibition, infection, mild nausea and anorexia.

Spectral dependence of spin photocurrent and current-induced spin polarization in an InGaAs/InAlAs two-dimensional electron gas.

The converse effects of spin photocurrent and current induced spin polarization are experimentally demonstrated in a two-dimensional electron gas system with Rashba spin splitting. Their consistency with the strength of the Rashba coupling as measured for the same system from beating of the Shubnikov-de Haas oscillations reveals a unified picture for the spin photocurrent, current-induced spin-polarization, and spin-orbit coupling. In addition, the observed spectral inversion of the spin photocurrent indicates a system with dominating structure inversion asymmetry.

Purification of a putative brain somatostatin receptor.

The brain somatostatin (somatotropin release-inhibiting factor; SRIF) receptor was purified by affinity chromatographic techniques. A protein of 60 kDa could be purified from rat brain. The protein was eluted from a [D-Trp8]SRIF affinity column with either sodium acetate (pH 5.5) or free [D-Trp8]SRIF. The binding of the protein to the affinity column was prevented by free [D-Trp8]SRIF or the stable SRIF analogue SMS 201-996 but not by the inactive somatostatin 28-(1-14). The purified receptor could be covalently labeled by the 125I-labeled SRIF analogue CGP 23996. Excess [D-Trp8]SRIF blocked the binding of 125I-labeled CGP 23996 to the purified receptor, but somatostatin 28-(1-14) did not affect the binding. A 60-kDa protein was also purified from the anterior pituitary cell line AtT-20, which has a high expression of SRIF receptors. In contrast, no 60-kDa protein could be purified from CHO cells, which have no detectable SRIF receptors. These findings present evidence for the purification of the SRIF receptor.

Intrahepatic transfusion-transmitted virus detected by in situ hybridization in patients with liver diseases.

Transfusion-transmitted virus (TTV) has been identified from patients with post-transfusion hepatitis of unknown aetiology, but the clinical relevance remains unclear. The aim of this study was to evaluate TTV in liver. We studied 15 patients with hepatitis non-A-E and 44 with hepatitis B virus (HBV). The nested polymerase chain reaction (PCR) with primers corresponding to the conserved region of the published TTV genome was employed to amplify TTV fragments in serum, and in situ hybridization was used to detect TTV in biopsied liver specimens. TTV DNA was detected in serum from six (40%) of 15 patients with hepatitis of unknown aetiology and from 16 (36.4%) of 44 patients with chronic hepatitis B, respectively. The intrahepatic viral fragment was detected in 17 (77.3%) of 22 patients with TTV in serum. There was no statistical difference in the prevalence of TTV infection between the two groups (hepatitis non-A-E 40% vs HBV 25%, P > 0.75). When patients in both groups, with and without TTV, were compared, no differences were found in serum alanine aminotransferase (ALT) levels (hepatitis non-A-E: 131.5 +/- 66.6 vs 244.2 +/- 257.4, P=0.955; HBV: 240.1 +/- 418.9 vs 214.6 +/- 276.7 U l(-1), P=0.761) or histological activity index (grade) score (hepatitis non-A-E: 6.4 +/- 5.5 vs 5.6 +/- 5.9, P=0.689; HBV: 5.6 +/- 3.7 vs 5.5 +/- 3.7, P=0.345). HBV DNA levels in patients with and without TTV co-infection did not differ significantly (300 +/- 776.4 microg ml(-1) vs 97.1 +/- 160.5 microg ml(-1), P=0.980). Hence, TTV does exist in liver, but plays no role in hepatitis or aggravation of liver damage when co-infected with HBV.

Sulfated glycans directly interact with mouse Thy-1 and negatively regulate Thy-1-mediated adhesion of thymocytes to thymic epithelial cells.

Thy-1 is a major brain cell surface glycoprotein of adult mammal species also expressed in rodent thymus. Despite extensive studies, the function(s) of this molecule has remained so far ill defined. We have recently shown that Thy-1 was involved in the adhesion of mouse thymocytes to thymic epithelium through a specific interaction with a heterophilic ligand(s) expressed on the epithelial cell surface. In the present study, we aimed at evaluating the interaction of sulfated glycans with mouse Thy-1, as well as its consequence on Thy-1-mediated thymic lympho-epithelial cell interaction. It was shown that 125I-labeled Thy-1 directly bound to immobilized heparin. Sulfated glycans such as pentosan sulfate, dextran sulfate, and fucoidan were found to strongly inhibit the binding of Thy-1 to heparin. In contrast, chondroitin sulfate, keratan sulfate, and heparan sulfate were not inhibitory. Sulfated glycans (e.g., pentosan sulfate, assayed at a concentration of 50 micrograms/ml) completely blocked the Thy-1-dependent adhesion of T cells to a mouse thymic epithelial cell monolayer. To explore the mechanism of this inhibition, we compared the ability of T cell to adhere to mouse thymic epithelial cell monolayer or to sulfated glycans. Our results suggest that sulfated glycans bind to a Thy-1 site distinct from that with which this molecule interacts with its heterophilic ligand. Moreover, sulfate glycans could modulate the binding of rat mAb directed at spatially distinct Thy-1 epitopes. The present results identified a potential mechanism regulating Thy-1-mediated lympho-epithelial cell adhesion.

Phosphatidylinositol is involved in the membrane attachment of NCAM-120, the smallest component of the neural cell adhesion molecule.

The rodent neural cell adhesion molecule (NCAM) consists of three glycoproteins with Mr of 180,000, 140,000 and 120,000. The Mr 120,000 protein (NCAM-120) has been shown to exist in membrane-bound and soluble forms but the nature of its membrane association and release has remained obscure. We show here that phosphatidylinositol-specific phospholipase C (PI-PLC), but not a phospholipase C of different specificity, releases a substantial proportion of NCAM-120 from brain membranes and solubilizes almost quantitatively NCAM-120 present at the surface of C6 astroglial cells. The PI-PLC effect was highly selective since only one other protein species was detectably released from C6 cells. These results suggest that NCAM-120 is held in the membrane by covalently bound phosphatidylinositol or a closely related lipid in a way similar to several other surface proteins from eukaryotic cells. The presence of NCAM in a form which can be released from the cell surface by a highly selective mechanism raises additional possibilities for modulation and control of cell--cell adhesion.