Effect Of Sialic Acid Research Articles

Role and Mechanism of Sialic Acid in Alleviating Acute Lung Injury through In Vivo and In Vitro Models.

Excessive inflammatory reactions are the most important pathological injury factor in acute lung injury (ALI). Our recent study found that sialic acid had an anti-colitis effect. In this study, the effect of sialic acid (SA) on acute lung inflammation was investigated. A lipopolysaccharide (LPS)-induced ALI animal model and LPS-stimulated HUVEC cell model were used to evaluate the anti-inflammatory effect of SA and study its molecular mechanisms. Compared with the LPS group, the lung index of the SA group decreased from 0.79 ± 0.05% to 0.58 ± 0.06% (LPS + 50 SA) and 0.62 ± 0.02% (LPS + 100 SA), with p < 0.01, suggesting that SA could improve the pulmonary edema of mice and alleviate LPS-induced lung injury. Transcriptome research identified 26 upregulated genes and 25 downregulated genes involved in the protection of SA against ALI. These genes are mainly related to the MAPK and NF-κB signaling pathways. Our study also proved that SA markedly downregulated the expression of inflammatory factors and blocked the JNK/p38/PPAR-γ/NF-κB pathway. Meanwhile, SA treatment also upregulated the expression of HO-1 and NQO1 in ALI mice. In vitro, SA obviously repressed the expressions of inflammatory cytokines and the JNK/p38-NF-κB/AP-1 pathway. SA also regulated the expression of oxidative stress-related genes through the Nrf2 pathway. Taken together, SA exhibits a protective role by modulating the anti-inflammatory and anti-oxidation pathways in ALI, and it may be a promising candidate for functional foods to prevent ALI.

Reduced Anticancer Potency of Carboplatin in the Presence of Sialic Acid in SH-SY5Y Cells

Background: Neuroblastoma (NB) is the most common solid childhood tumor with aggressive behavior and a high mortality rate. Multiple therapeutic approaches have been developed and applied to treat neuroblastoma, but resistance to therapies is inevitable, leading to treatment failure and cancer relapse. Therefore, perceiving the mechanisms of reduced drug sensitivity seems appropriate and promising in NB treatment to determine synergistic effects strategies like combination therapy. Objectives: The present study aimed to investigate the modulation effect of the therapeutic efficacy of carboplatin (a chemotherapeutic agent) by co-administration of sialic acid (an alpha-keto acid sugar with a 9-carbon backbone located at the outermost end of N-linked and O-linked carbohydrate chains and in lipid-associated glycoconjugates showing aberrant expression in tumor cells caused tumor-genesis) in NB cells. Methods: In the present study, the effects of sialic acid, carboplatin, and Sia-Carbo (sialic acid in combination with carboplatin) were evaluated on viability and apoptosis using the determination of EC50 and IC50. Also, the capability of metastasis and apoptosis were assessed using real-time PCR. Moreover, the expression of MRP-1 encoded by ABCC1 (as a target for therapeutic suppression in high-risk neuroblastoma) was studied in different treatment groups. Conclusions: Regarding IC50 increasing carboplatin in the presence of sialic acid, the results showed that sialic acid treatment significantly modulated carboplatin's effect on cell apoptosis and induced ABCC1 expression. These findings show that sialic acid metabolic engineering can be a good approach to neuroblastoma therapy. It was suggested that targeting aberrant sialylation in combination with carboplatin exerts more profound apoptotic and anticancer effects on the neuroblastoma SH-SY5Y cell line than carboplatin monotherapy.

Effects of oral sialic acid on gut development, liver function and gut microbiota in mice.

Sialic acid (N-acetylneuraminic acid), a 9-carbon monosaccharide, has been widely studied in immunology, oncology and neurology. However, the effects of sialic acid on organ and intestinal development, liver function and gut microbiota were rarely studied. In this study, we found that oral sialic acid tended to increase the relative weight of liver and decreased the serum aspartate aminotransferase (GPT) activity. In addition, sialic acid treatment markedly reduced gut villus length, depth, the ratio of villus length/depth (L/D), areas, width and the number of goblet cells. Furthermore, gut microbes were changed in response to oral sialic acid, such as Staphylococcus lentus, Corynebacterium stationis, Corynebacterium urealyticum, Jeotgalibaca sp_PTS2502, Ignatzschineria indica, Sporosarcina pasteurii, Sporosarcina sp_HW10C2, Facklamia tabacinasalis, Oblitimonas alkaliphila, Erysipelatoclostridium ramosum, Blautia sp_YL58, Bacteroids thetaiotaomicron, Morganella morganii, Clostridioides difficile, Helicobacter tryphlonius, Clostridium sp_Clone47, Alistipes finegoldii, [pseudomonas]_geniculata and Pseudomonas parafulva at the species level. In conclusion, oral sialic acid altered the intestinal pathological state and microbial compositions, and the effect of sialic acid on host health should be further studied.

The Effect of Sialic Acid on the Expression of miR-218, NF-kB, MMP-9, and TIMP-1.

Sialic acid (N-acetylneuraminic acid, NANA) is found at all cell surfaces of vertebrates. Although it is widely accepted that sialic acid is an essential substrate for brain development via a significant role in nerve transfers, structure of glycosides, and synaptogenesis phenomena, there are some reports on the elevated levels of sialic acid and prevalence of neurodegeneration. Matrix metalloproteases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs) are involved in neuroinflammation disorders and produced by many cell types, including activated T cells, macrophages, neurons, astrocytes, and microglial cells. It can be hypothesized that sialic acid may have a potentially critical role in regulation of a wide range of uncovered neurodegeneration factors as its downstream targets. In this study, for the first time, we aimed to analyze the possible effect of the sialic acid solution exposure in the human C118 cell line, which was derived from a human brain astrocytoma (glial cells), on the expression patterns of miR-218, NF-kB, MMP-9, and TIMP-1. For MMP-9, protein levels were studied too. Half maximal inhibitory concentration (IC50) value of NANA was obtained by MTT assay. Glial cell line was treated with sialic acid (300, 500, and 1000µg/ml) for 24h to investigate the effects of this ligand on the expression of miR-218, NF-kB, MMP-9, and TIMP-1 genes. Protein levels were checked by Western blotting, and by using zymography, the gelatinolytic activity of MMP-9 secreted into conditioned media was assayed. At 300µM, 500µM, and 1000µM sialic acid treatments, the expression of miR-218 was downregulated; subsequently, the NF-kB, MMP-9, and TIMP-1 genes as well as their protein expressions were upregulated. More interestingly, the enzyme activity of secreted MMP-9 was upregulated too (p-values ≤ 0.05). This study could demonstrate the significant effect of sialic acid on miR-218, NF-kB, MMP-9 , and TIMP-1 expressions in gene and protein levels and also the levels of enzyme activity of secreted MMP-9. Therefore, provided information indicates the novel idea of a possible linkage between sialic acid species and regulation of these neuroinflammation genes in Glial cell line.

Abstract B63: Bittersweet symphony: How tumor-associated glycan structures orchestrate immune evasion

Abstract The tumor microenvironment is immune suppressive, allowing tumor cells to escape from immune attack. By relieving this immune suppression, immune cells might be able to effectively eliminate the tumor. Therefore, a detailed understanding on how tumor cells induce an immunosuppressive tumor microenvironment is required. Glycosylation is the most abundant post-translational modification of proteins. It is highly diverse on a cellular level and strongly affected by oncogenesis. Tumor cells generally display an aberrant glycosylation profile and this is now well accepted as a new hallmark of cancer. Overexpression of glycan structures containing sialic acids (Sia) is frequently observed on tumors. Glycan structures can be recognized by lectin receptors expressed on immune cells, whereby sialic acids specifically bind to the Siglec receptor family. The majority of Siglec receptors has an immunoreceptor tyrosine-based inhibition motif and therefore, sialylated glycan structures are known to suppress ongoing immune responses. Hence, we hypothesize that tumor cells overexpress sialylated glycan structures in order to communicate with the immune system and to dampen immune attack. We have previously demonstrated that a genetically engineered Sialow glycovariant of the mouse melanoma B16 model displayed delayed growth in vivo compared to wild-type B16 Siahigh tumors (1). Moreover, higher frequencies of IFNγ-producing effector T-cells were detected in B16 Sialow tumors. This was paralleled by a 50% reduction in FoxP3+CD4+ regulatory T-cell frequencies in Sialow tumors (1), together indicating that tumor-associated sialic acids indeed play, indeed, a crucial role in suppressing the anti-tumor immune response. To check whether the inhibitory effect of sialic acids on the effector T cell response is tumor type specific, we investigated the role of sialic acids in a mouse colorectal cancer model (MC38). With the use of Crispr-Cas9 we successfully knocked out the N-acylneuraminate cytidylyltransferase (CMAS) gene, which is responsible for the sialylation pathway and thus the generation of sialylated glycans on the cell surface. In contrast to the B16 Sialow tumors, the Sianeg MC38 CMAS KO tumors displayed an increased tumor growth in vivo compared to the Siahigh MC38 Mock tumors. Moreover, less viable leukocytes could be recovered from the Sianeg MC38 CMAS KO tumors compared to the Siahigh MC38 Mock tumors. With the use of mass spectrometry, we analyzed the complete glycosylation profile of our Sianeg MC38 CMAS KO and Siahigh MC38 Mock cells and observed, in addition to the absence of sialylation, an increase in LacNAc (Galβ1-4GlcNAc) structures on the Sianeg MC38 CMAS KO cells. This glycan structure is a ligand for carbohydrate-binding Galectin receptors. Galectins are well known for their potential to induce leukocyte apoptosis after binding specific glycoproteins on the leukocyte surface. Using qPCR we observed higher mRNA levels of Galectin-1 in our MC38 CMAS KO cells. The enhanced production of Galectin-1 and the elevated expression of LacNAc together suggest that MC38 CMAS KO cells are able to recruit Galectin-1, thereby facilitating the enhanced immune suppression in these tumors. Currently, we are confirming the role of Galectins in our MC38 CMAS KO tumors. In conclusion, tumor cells alter their glycosylation profile and based on our data, we propose that tumor cells use these glycan structures as a mechanism to influence antitumor immunity and that this phenomenon might be tumor-type specific. Their immune inhibitory nature and their tumor-specific expression identifies tumor-associated glycans as potent candidates for future immune checkpoint blockade therapy. Reference: 1. Perdicchio M. et al. Tumor sialylation impedes T cell mediated anti-tumor responses while promoting tumor associated-regulatory T cells. Oncotarget 2016;7(8):8771-8. Citation Format: Lenneke A.M. Cornelissen, Athanasios Blanas, Joost C. Van der Horst, Laura Kruijssen, Yvette Van Kooyk, Sandra J. Van Vliet. Bittersweet symphony: How tumor-associated glycan structures orchestrate immune evasion [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr B63.

Cell surface sialic acid inhibits Cx43 gap junction functions in constructed Hela cancer cells involving in sialylated N-cadherin

Numerous studies have shown that changes in the glycan structures of cells correlate with tumorigenesis, however, a casual link between the altered glycan structures and the abnormal GJIC in cancer cells is rarely studied. In this paper, we investigated the effects of sialic acid on the Cx43 gap junction functions, and clarified its potential mechanisms thereby. Sialidase significantly increased Cx43 gap junction functions in constructed Cx43-Hela cells along with down-regulation of cell surface sialic acid, which is dramatically reversed by sialidase inhibitor NeuAc2en. Further study indicated that sialidase failed to affect Cx43 at either protein or phosphorylation level, instead, it induced a considerable fraction of Triton X-100 insoluble, as compared with the untreated cells. We also found that sialidase treatment reduced the N-cadherin glycosylation and enhanced both Cx43-ZO-1 interaction and N-cadherin-ZO-1 association. Moreover, sialidase promoted the cell-cell adhesion with elevating N-cadherin binding to β-catenin, accompanied by increasing colocalization of Cx43 with microtubules at the cell periphery. Based on live cell microscopy, with the FARP technology in the Cx43-EGFP-Hela cells, we found that Cx43 in the plague recovered more quickly in sialidase treatment group, indicating that sialidase could promote the Cx43 traffic to the plague. Overall, these studies indicate cell surface sialic acid on cancer cells may suppress Cx43 gap junction functions via inhibiting Cx43 traffic to the plague involving in sialylated N-cadherin, a process that likely underlies the intimate association between abnormal GJIC and glycosylation on cancer development.

Isoform‐specific effects of sialic acid on voltage‐dependent Na+ channel gating: functional sialic acids are localized to the S5‐S6 loop of domain I

The isoform specific role of sialic acid in human voltage-gated sodium channel gating was investigated through expression and chimeric analysis of two human isoforms, Na(v1.4) (hSkM1), and Na(v1.5) (hH1) in Chinese hamster ovary (CHO) cell lines. Immunoblot analyses indicate that both hSkM1 and hH1 are glycosylated and that hSkM1 is more glycosylated than hH1. Four sets of voltage-dependent parameters, the voltage of half-activation (V(a)), the voltage of half-inactivation (V(i)), the time constants for fast inactivation (tau(h)), and the time constants for recovery from inactivation (tau(rec)), were measured for hSkM1 and hH1 expressed in two CHO cell lines, Pro5 and Lec2, to determine the effect of changing sialylation on channel gating under conditions of full (Pro5) or reduced (Lec2) sialylation. For all parameters measured, hSkM1 gating showed a consistent 11-15 mV depolarizing shift under conditions of reduced sialylation, while hH1 showed no significant change in any gating parameter. Shifts in channel V(a) with changing external [Ca2+] indicated that sialylation of hSkM1, but not hH1, directly contributes to a negative surface potential. Functional analysis of two chimeras, hSkM1P1 and hH1P1, indicated that the responsible sialic acids are localized to the hSkM1 S5-S6 loop of domain I. When hSkM1 IS5-S6 was replaced by the analogous hH1 loop (hSkM1P1), changing sialylation had no significant effect on any voltage-dependent parameter. Conversely, when hSkM1 IS5-S6 was added to hH1 (hH1P1), all four parameters shifted by 6-7 mV in the depolarized direction under conditions of reduced sialylation. In summary, the gating of two human sodium channel isoforms show very different dependencies on sialic acid, with hSkM1 gating uniformly altered by sialic acid levels through an apparent electrostatic mechanism, while hH1 gating is unaffected by changing sialylation. Sialic acid-dependent gating can be removed or created by replacing or inserting hSkM1 IS5-S6, respectively, indicating that the functionally relevant sialic acid residues are localized to the first domain of the channel.

Inhibition of in vitro fertilization of mouse gametes by sulfated sialic acid polymers.

The effect of sialic acid (N-acetyl neuraminic acid), sialic acid dimer, sialic acid polymers (colominic acid) and sulfated colominic acid on the activity of hyaluronidase, on the dispersion of cumulus cells by mouse sperm and on in vitro mouse fertilization (sperm penetration of zona pellucida) were evaluated. Bovine testicular hyaluronidase activity was significantly inhibited by colominic acid and sulfated colominic acid, but not by sialic acid and its dimer. The dispersion of cumulus cells from eggs by mouse sperm was also inhibited by colominic acid and sulfated colominic acid. In vitro fertilization of mouse gametes was inhibited by sulfated colominic acid. The IC50 value of sulfated colominic acid-induced inhibition of fertilization was 0.3 mg/ml (ca. 0.9 mM). The value changed from 0.9 mM for cumulus-surrounded egg to 1.5 mM for cumulus free-egg. On the other hand, colominic acid showed little or no inhibitory effect on mouse in vitro fertilization at 0.5 mg/ml (ca. 1.6 mM). This antifertility activity by sulfated colominic acid did not appear to be due to an effect on sperm motility or on the oocytes. These results suggest that (1) the cumulus cells surrounding the eggs were dispersed by sperm hyaluronidase, (2) hyaluronidase was inhibited by colominic acid and by sulfated colominic acid, (3) sulfated colominic acid inhibits sperm penetration of zona pellucida by the inhibition of hyaluronidase and/or some enzymes required for mouse gametes fertilization.

Sialylation of the Sialic Acid Binding Lectin Sialoadhesin Regulates Its Ability to Mediate Cell Adhesion

The macrophage-specific cell surface receptor sialoadhesin, which is a member of the newly recognized family of sialic acid binding lectins called siglecs, binds glycoprotein and glycolipid ligands containing a2-3–linked sialic acid on the surface of several leukocyte subsets. Recently, the sialic acid binding activity of the siglec CD22 has been demonstrated to be regulated by sialylation of the CD22 receptor molecule. In the present work, we show that desialylation of in vivo macrophage sialylconjugates enhances sialoadhesin-mediated lectin activity. Herein, we show that receptor sialylation of soluble sialoadhesin inhibits its binding to Jurkat cell ligands, and that charge-dependent repulsion alone cannot explain this inhibition. Furthermore, we show that the inhibitory effect of sialic acid is partially dependent on the presence of an intact exocyclic side chain. These results, in conjunction with previous findings, suggest that sialylation of siglecs by specific glycosyltransferases may be a common mechanism by which siglec-mediated adhesion is regulated.

Minor influence of sialic acid on conformation of a membrane-bound oligosaccharide recognition site.

Wideline 2H NMR spectroscopy was used to assess the conformational and orientational effects of N-acetylneuraminic acid (NeuAc) (sialic acid) as a component of a particular oligosaccharide chain at a bilayer membrane surface. For this purpose, three glycosphingolipids, sharing a neutral core tetrasaccharide and differing only in the number of sialic acid residues, were compared. The starting compound was GD1A, which has terminal sialic acid attached to the second and fourth sugars of its neutral tetrasaccharide core. GD1A was probe-labeled in a non-perturbing fashion on both of these sialic acid residues and on its single GalNAc residue by replacement of -COCH3 with -COCD3 giving [(d3NeuAc)2,d3-GalNAc]GA1a. This represents the most complex glycolipid to have been studied by 2H NMR spectroscopy at a bilayer membrane surface. The sialic acid residue on the fourth sugar from the membrane was subsequently removed to produce the glycolipid [d3NeuAc,d3GalNAc]GM1, deuterated at the two remaining amino sugars. The neutral glycolipid [d3GalNAc]asialo-GM1 was then generated by removal of the second sialic acid residue, leaving an uncharged species deuterated at one (internal) oligosaccharide chain site (GalNAc). The effect of sialic acid was futher examined by selective deuteration of GM1 and asialo-GM1 at C6 of the terminal Gal residue, giving [d2Gal]GM1 and [d2Gal]asialo-GM1. Spectra of the three glycosphingolipids were compared at 7.7 mol % in unsoncicated fluid bilayers of 1-palmitoyl-2-oleoylphosphatidylcholine containing 23 mol % cholesterol. For liposomes suspend in buffered salt solutions with 2 mM Ca2+, 2H NMR spectra demonstrated the presence of well defined average conformation for each oligosaccharide chain. This preferred average conformation persisted over a wide temperature range, consistent with there being a single major oligosaccharide conformer in each case. Spectral features arising from both deuterated amino sugar (GalNAc) of asialo-GM1 could be identified, little changed, in spectra of GM1 and GD1A. Similarly, deuterons in the terminal Gal residue of asialo-Gm1 produced the same spectrum seen for this residue in GM1. Our findings indicate that certain major conformational and orientational features of this complex oligosaccharide recognition site are preserved, within maximum angular deviation + or -5 degrees or less upon addition or removal of a sialic acid residue.

Sialic acid and oxidizability of low density lipoprotein subfractions of hyperlipidemic patients

Objectives: Low density lipoprotein (LDL) does not constitute an homogenous fraction and it is known that the heavy LDL subfraction is potentially more atherogenic than the light one. Because concentration of LDL. subfractions tend to be different in hyperlipidemias, it was verified whether these subfractions can also differ in sialic acid and neutral sugar content, as well as their resistance to oxidation. Design and Methods: Two subfractions of low density lipoprotein (light LDL, density 1.019–1.034 g/mL and heavy LDL, density 1.034–1.063 g/mL) were isolated from the plasma of 17 patients with hypercholesterolemia, 11 with combined hyperlipidemia, 7 with hypertriglyceridemia, and 19 normolipidemic subjects. The content of sialic acids and neutral sugars of apo B was determined, respectively, by the periodate-thiobarbituric acid method and by reaction with phenol. The oxidation of LDL subfractions was determined by exposure to 5 μM copper (II) followed by the measurement of lipid hydroperoxides production by high performance liquid chromatography with electrochemical detection. Results: The study groups did not differ in the neutral sugar content of LDL subfractions. However, compared to normolipidemic subjects, the sialic acid concentration of both LDL subfractions was lower in patients with hypercholesterolemia and hypertriglyceridemia and higher in those with combined hyperlipidemia ( p < 0.05). In the hypercholesterolemia and combined hyperlipidemia groups, the lipid hydroperoxide content (μM) of heavy LDL was higher than in normolipidemic subjects ( p < 0.05). Conclusions: The heavy LDL subfraction was more susceptible to oxidation in the patients with combined hyperlipidemia compared to controls and the other hyperlipidemic groups. The effect of sialic acids on heavy LDL oxidizability seems to vary according to the type of hyperlipidemia.

Effect of sialic acid on glycation-induced fluorescence of albumin.

The aims of this study were to determine whether in vitro nonenzymatic glycation of proteins by sialic acid (sialylation) induces the generation of fluorescence, and whether the presence of this keto sugar may affect the generation of fluorescence induced by other sugars. Incubation of bovine serum albumin (BSA; 1.5 mM) with sugars (50 mM in 0.2 M phosphate buffer, pH 7.4, at 37 degrees C) resulted in a time-dependent increase of formaldehyde release (moles/moles of protein). On the 17th day of incubation, the value was 0.53 +/- 0.06, 0.78 +/- 0.15 and 1.23 +/- 0.18 for sialic acid, fructose and glucose respectively, compared with 0.37 +/- 0.05 for BSA. The fluorescence intensity (arbitrary units/mg protein) was higher after 17 days of incubation with fructose (16.9 +/- 1.8) than with glucose (12.7 +/- 1.3), while no significant increase was noted with sialic acid compared with BSA (3.8 +/- 0.4). Fluorescence intensity increase by incubation with glucose (50 mM) was significantly reduced by sialic acid (20 mM) after both 10 (P < 0.001) and 14 (P < 0.001) days of incubation, while inhibition was weaker after 14 (P < 0.05) than after 10 (P < 0.001) days when fructose (50 mM) was used as the glycating agent. This indicates that sialic acid can be potentially used to limit the damage from adverse glycation-induced processes.

Effects of Sialic Acid and Sialoglycoconjugates on Cytosolic Phospholipases A 2 from Bovine Brain

Two forms of Ca 2+-independent cytosolic phospholipases A 2 were separated by Sephadex G-75 column chromatography. N-Acetylneuraminic acid, gangliosides, and sialoglycoproteins inhibited both phospholipases A 2 in a concentration dependent manner, but colominic acid, poly(2,8-N-acetylneuraminic acid), had no effect on enzymic activities. Interactions between phospholipases A 2 and sialoglycoconjugates may be involved in the translocation of phospholipases A 2 from cytosol to plasma membrane during receptor stimulation.

Sialic acid in fibrinogen: effects of sialic acid on fibrinogen-fibrin conversion by thrombin and properties of asialofibrin clot.

The final stage in a series of blood coagulating reactions is fibrinogen-fibrin conversion by thrombin. This reaction consists of fibrinopeptide A and fibrinopeptide B release, polymerization of fibrin monomer, and stabilized fibrin formation by factor XIII. The latter two reactions require calcium. In the present study there was no difference in the rate of thrombin-induced fibrinopeptide release between fibrinogen and asialofibrinogen where sialic acid in the terminal end of carbohydrate moiety of fibrinogen was removed by neuraminidase, but turbidity associated with asialofibrin clot formation was increased more rapidly. In asialo-derivatives, the dissolution time of the clots in high concentrated urea solution tended to be shortened and rigidity as a gel tended to be decreased. In measurement by thromboelastography there was no difference in the reaction time (r) between fibrinogen and asialofibrinogen, but the maximum amplitude (ma) was obviously decreased in asialofibrinogen. Furthermore, when the rate of cross-link formation between gamma chains by F-XIII was compared, the production of gamma-dimer in the same reaction time was found to be lower and formation of stabilized fibrin tended to be retarded in asialofibrinogen. Sialic acid in fibrinogen thus may clearly influence the polymerization of fibrin-monomer and the formation of cross-linked fibrin in a series of reactions for fibrinogen-fibrin conversion. This may be consistent with the theory that fibrinogen sialic acid residues are low affinity calcium-binding sites and influence fibrin assembly.

Biochemical and biological properties of urinary follicle-stimulating hormone (FSH) from the rhesus monkey (Macaca mulatta).

Follicle-stimulating hormone (FSH) is routinely used for the induction of superovulation in women. Homologous gonadotropin preparations that could be used for reproductive studies in macaques would have valuable research applications. Accordingly, we set out to characterize the physical and biological characteristics of urinary FSH (UFSH) in the ovariectomized rhesus monkey. In urine from 7 monkeys, concentrations of bioactive FSH ranged from 16 to 57 μg/1, relative to cynFSH-RPI (NIDDK). UFSH was contrasted to pituitary FSH (PFSH) by non-reducing SDS-polyacrylamide gel electrophoresis (PAGE), native disc PAGE, and FPLC chromatofocusing. The apparent molecular weights of UFSH and PFSH are similar (approximately 35 kD); however, UFSH is more negatively charged and demonstrates a lower overall isoelectric (pl) range than PFSH. The bioactivity of UFSH was assessed by the stimulation of aromatase activity in cultured Sertoli cells and by induction of follicular maturation in hamsters. Two fractions of pituitary FSH, which differed in isoelectric properties, were obtained by chromatofocusing. The in vivo biological activity of FSH-A (acidic, pl 3.8-4.6) and UFSH (pl 3.5-4.5) were similar, but greater than FSH-B (basic, pl 4.6-5.5). These results support the hypothesis that heavily sialylated, low pl FSH expresses high in vivo bioactivity. This may reflect the well-known effect of sialic acid in prolonging the circulating half-life of glycoproteins. Thus, the quality and quantity of FSH present in ovariectomized rhesus monkey urine indicates that this may be a useful source for the preparation of enriched hormone preparations. © 1992 Wiley-Liss, Inc.

Effect of sialic acid on the electrophoretic mobility of mouse splenic lymphocytes

AbstractThe effect of sialic acid on the electrophoretic mobility (surface charge) of mouse splenic lymphocytes was investigated. On treatment of whole spleen and T cells with neuraminidase, their electrophoretic mobilities decreased to one‐half of the initial values. Calculation of the surface charge from the electrophoretic mobility of lymphocytes before and after treatment with the enzyme indicated that one‐half of the negative surface charge, which determines the electrophoretic mobility, was due to neuraminidase‐sensitive sialic acid in mouse lymphocytes. However, the calculated decrease in the surface charge did not coincide with the amount of sialic acid released from the cell membrane on the enzyme treatment of lymphocytes.

The myocardial cell surface, its histochemistry, and the effect of sialic acid and calcium removal on its stucture and cellular ionic exchange.

HomeCirculation ResearchVol. 41, No. 5The myocardial cell surface, its histochemistry, and the effect of sialic acid and calcium removal on its stucture and cellular ionic exchange. Free AccessAbstractPDF/EPUBAboutView PDFSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyRedditDiggEmail Jump toFree AccessAbstractPDF/EPUBThe myocardial cell surface, its histochemistry, and the effect of sialic acid and calcium removal on its stucture and cellular ionic exchange. J S Frank, G A Langer, L M Nudd and K Seraydarian J S FrankJ S Frank Search for more papers by this author , G A LangerG A Langer Search for more papers by this author , L M NuddL M Nudd Search for more papers by this author and K SeraydarianK Seraydarian Search for more papers by this author Originally published1 Nov 1977https://doi.org/10.1161/01.RES.41.5.702Circulation Research. 1977;41:702–714 Previous Back to top Next FiguresReferencesRelatedDetails November 1, 1977Vol 41, Issue 5Article InformationMetrics Copyright © 1977 by American Heart Associationhttps://doi.org/10.1161/01.RES.41.5.702 Originally publishedNovember 1, 1977 PDF download Advertisement

Sialic acid and the social behaviour of cells.

Summary1. It is suggested that specific carbohydrate side‐chains of membrane glycoproteins are the sites for cell recognition or adhesion when the terminal sugar, sialic acid, is absent.2. It is suggested that sialic acid plays a ‘protective’ or ‘blocking’ role in cell interactions so that addition of sialic acid to asialo side‐chains converts them to forms inactive for recognition. This principle of ‘blocking’ by sialic acid has been observed in other situations as in covering tumour antigens and in protecting glycoproteins from uptake by the liver. It is here extended to cell‐cell adhesions.3. It is to be expected that specific ‘protective’ actions of sialic acid in membrane‐bound glycoproteins will be difficult to detect. As a charged residue, sialic acid is likely to have a strong influence both on the glycoproteins on which it is borne and on their interactions with each other at the cell surface. Removal of sialic acid by enzymes could therefore perturb the structure of the cell surface in several ways and so obscure the ‘protective’ effects of sialic acid. Sialic acid is therefore suggested to have a structural role also.4. Evidence is assembled in favour of a model in which sialysation of specific adhesive receptors affects the social behaviour of cells. This may be an effect associated with growing cells since the contact properties of mitotic cells (and populations rich in dividing cells) are decreased by the increased sialysation of receptors. One of the factors associated with malignant behaviour could be that adhesive receptors are permanently blocked by sialic acid.5. A schematic representation of some of the points is given in Fig. 4.

Effect of sialic acid, kerato sulfate and neuraminidase on the growth of solid Ehrlich ascites tumor

The effect of sialic acid, keratosulfate and neuraminidase on the growth of solid Ehrlich ascites tumor has been investigated. Various concentrations of test materials were given subcutaneously into the back of ddN mice, followed by tumor inoculation. On the 8 th day after tumor inoculation, average tumor weights in experimental groups were compated with those in controlgroups, which were given isotonic saline. 2% keratosulfate and 0.2% sialic acid accelerated the growth of tumors to some extent, while 2% sialic acid had a tendency to inhibit it. Neuraminidase solution tested so far had no significant effect on the tumor growth.

Kinetic localization of contractile calcium in rabbit myocardium.

Kinetic localization of contractile calcium in rabbit myocardium.