Sugar specific cellular lectins of Phallusia mamillata hemocytes: purification, characterization and evidence for cell surface localization

Cellular lectins (CLs) of Phallusia mamillata were demonstrated in protein preparations obtained by salt fractionation from hemocytes sonicated in a suitable medium. Since the lectins from the precipitated fraction bind sugars containing D-galactosyl groups, they were purified by affinity chromatography on Sepharose. SDS-PAGE under reducing conditions showed that CLs are formed of two components of apparent MWs approximately 36,900 and 35,090 and thus differ from serum lectins (SLs) (MW about 62,200). The "shrinkage" observed when SLs were examined under nonreducing conditions suggest the presence of intrachain disulphide bonds which can affect the molecular structure of the SLs. CL-SL differences were also revealed by the nonidentity reaction of the immuno-precipitate in immunodiffusion using an anti-SL immune serum. The capacity of hemocytes to form rosettes or clumps with erythrocytes demonstrated that they possess alpha-lactose specific CLs on their surfaces.     

Histamine release induced by glucose (mannose)-specific lectins isolated from Brazilian beans. Comparison with concanavalin A

The histamine releasing properties of glucose (mannose)-specific lectins isolated from Brazilian beans was examined. TheCanavalia brasiliensis, Dioclea rostrata, andDioclea virgata lectins induced histamine release in rat peritoneal mast cells similar to concanavalin A. Less potency and efficacy was observed forCanavalia maritima, Dioclea guianensis, andDioclea violacea while very low activities were seen for the lectins fromDioclea grandiflora, Canavalia bonariensis, andCratylia floribunda.The histamine releasing effect was quenched by higher doses ofD. virgata lectin similar to what was reported for concanavalin A. This effect was abrogated by increasing the concentration of calcium in the incubating medium. As these above proteins have sites that bind calcium, higher doses of the lectins might withdraw the calcium which is essential for the mast cell secretion.     

Reactivity of lectins with feline erythrocytes

Blood groups A, B and AB of cats (not related to human blood groups) are defined serologically with feline antisera. Five cats were blood typed and used in this study. Three cats were type B; two were type A. Two per cent suspensions of red blood cells (RBCs) from each cat were prepared and used in agglutination tests with 11 commercial lectins. Lectins are carbohydrate-binding proteins of non-immune origin. Most of these lectins agglutinated either all or none of the five samples of RBCs. However, wheat germ lectin (WGL) strongly agglutinated feline type B RBCs, but did not agglutinate type A RBCs. Thus WGL may be useful in feline blood typing, especially because the naturally occurring anti-B isoagglutinin is of low incidence and low titre.     

Characteristics of the histamine release from hamster cheek pouch mast cells stimulated by lectins from Brazilian beans and concanavalin A

We have characterized the histamine releasing effects of lectins extracted from Brazilian beans, in comparison to concanavalin A, in hamster cheek pouch cell suspensions containing mast cells. The lectins fromDioclea virgata, Canavalia brasiliensis, andDioclea rostrata induce histamine release in a similar manner to concanavalin A, but appear to differ in potency and efficacy. The effects depended on the temperature, pH, and metabolic energy, demonstrating the non-cytotoxic nature of the histamine release. It is suggested that the lectins studied act by the same mechanism as concanavalin A (interacting with sugars in the antibodies bound to the mast cells), since high concentrations of glucose inhibit the histamine release. The lectins at high concentrations quench the histamine release. This suppression is reversed by increasing calcium concentration, suggesting that the lectins bind to the calcium that is essential for the secretion, thereby confirming and extending our previous data using the lectin fromDioclea virgata in rat peritoneal mast cells.accepted by W. Lorenz     

Reactivity of seed lectins with blood-typed canine erythrocytes

Extracts from 117 species of plant seeds were examined for lectin activity against a panel of blood-typed canine red calls. Seed extracts were tested with unmodified and enzyme-treated red cells. Some (53) reacted with either unmodified or enzyme-treated red cells, some (7) were haemolytic, and some (57) did not react. No lectins were found to exhibit canine blood group specificity. Lectin reactivity for canine red cells is compared to reactivity for human red cells.     

高温致神经管缺陷过程中凝集素受体变化的实验动物研究

妊娠金黄地鼠随机分为实验组和对照组,前者于受精后第８天置４２℃水浴中持续２０ｍｉｎ,后者置３７℃水浴中持续２０ｍｉｎ。分别于高温后８、１２、２４、４８ｈ剖腹取胎,石蜡包埋,连续切片。应用生物素标记的花生凝集素、刀豆凝集素、麦胚凝集和荆豆凝集素为分子探针作亲合细胞化学染色,对各期鼠胚神经上皮及其基膜、脊索和神经管周围间充质中相应受体糖基进行定性、定位和半定量观察。结果显示,正常胚胎神经上皮及其周围组     

On the possible role of endogenous lectins in early animal development

Summary In this review I have tried to summarize the information available on the lectins of developing embryos. The emerging evidence indicates that during fertilization carbohydrate-binding proteins play a role in sperm adhesion and in the reorganization of the extracellular matrix of the fertilized egg. Results also indicate that in adult tissues lectins participate in cell recognition and adhesion, and that several galactose-binding lectins function as receptors for laminin and, in principle could also interact with polylactosamine groups of other extracellular matrix glycoproteins. Since in developing embryos lectins are located at the cell surface, and colocalize with extracellular matrix glycoproteins, they could play a role in transitory adhesive interactions and in the segregation of organ primordia. On the basis of experiments in cultured cell lines, it has been suggested that lectins are involved in lysosomal and nuclear glycoprotein transport. These carbohydrate-binding proteins could also regulate development by modulating these processes in the embryo. Since galactose-binding lectins are mitogenic, and are present in high concentration in the chick yolk sac, these proteins could be released into the embryonic circulation, bind to cells expressing appropriate receptors, and act as growth regulators, by modulating cell division of specific cell lineages.     

In vitro release of heparin from silica xerogels.

Heparin, a powerful anticoagulant used for the prophylaxis of both surgical and medical thrombosis, was incorporated into a silica xerogel matrix during polycondensation of organic silicate. The influence of various chemical sol-gel parameters (the properties of reaction precursors, catalyst and final moisture content of the gel and heparin concentration) was studied. The release of heparin from the gel was according to zero order during the dissolution period and the release rate of heparin was proportional to the drug load in the concentration range between 6.8 and 13.6 wt%. It was found that the catalyst used for the preparation of the gel, the final moisture content and the chemical modification of silica xerogel network have an influence on the release rate of heparin. The released heparin from all the different xerogels studied retained about 90% of its biological activity.     

In vitro stimulation of plasminogen activator release from vein walls by adrenaline.

The effect of adrenaline on plasminogen activator release was studied in vitro in human vein biopsy specimens, in which the fibrinolytic activity was determined according to the fibrin slide technique. The tissue slides were covered with a thin fibrin film containing 10(-9) and 10(-7) M adrenaline and exposed for 30 to 60 minutes. In both concentrations highly significant (p less than 0.001) enhancement of fibrinolytic activity was shown, and the enhancement of fibrinolysis was most pronounced during the first 30 minutes of exposure. Stimulation of fibrinolysis was maximal after exposure to the physiological concentration of 10(-9) M, while no further increase was seen using the pharmacological concentration. These results show that adrenaline has a stimulant effect on tissue fibrinolysis in vitro, and this effect may account for the direct stimulation of fibrinolysis by adrenaline in vivo.     

Reactivity of purified lectins with blood typed canine erythrocytes

Agglutination tests were performed with 40 commercially available lectins and a panel of blood typed canine erythrocytes. Erythrocytes were obtained from 17 dogs (two poodles, two black labradors, five greyhounds and eight beagles). The erythrocytes expressed various combinations of dog erythrocyte antigens (DEA) 1.1, 1.2 or null, 4 and 7. Lectin reactivity with untreated, ficin treated, and neuraminidase-treated cells was determined. No correlation between lectin reactivity and the canine blood group antigens expressed on the red cell test panel was found. Results suggest that some canine erythrocytes may be differentiated from others on the basis of reactivity with Phytolacca americana and Glycine max lectins.     

In vitro phagocytosis of Giardia duodenalis cysts by hemocytes of the Asian freshwater clam Corbicula fluminea

Hemocytes of the Asian freshwater clam Corbicula fluminea, phagocytosed in vitro infectious Giardia duodenalis cysts. After 15, 30, 60, 90, and 120 min of incubation an average of 22%, 32%, 43%, 54%, and 72% of the cysts were phagocytosed by 22%, 55%, 63%, 81%, and 86% of the hemocytes, respectively. The number of hemocytes showing phagocytosis and the mean number of cysts ingested per hemocyte increased␣significantly over time (P < 0.01); the numbers of nonphagocytosed cysts significantly decreased (P < 0.02). Extrapolation reveals that C. fluminea can retain by phagocytosis an average of 1.6 × 10⁶ G. duodenalis cysts/ml hemolymph. The phagocytic capacity of C. fluminea hemocytes indicates the applicability of this freshwater benthic bivalve for bioindication of contamination of waste waters and agricultural drainage with Giardia cysts. Received: 28 March 1997 / Accepted: 6 June 1997     

红毛毡提取物体外抗肿瘤的实验研究

目的：探讨红毛毡提取物的体外抗癌作用。方法：用MTT法检测红毛毡提取物对13种肿瘤细胞株体外生长的抑制作用。结果：红毛毡提取物对所试肿瘤细胞株的体外生长均具有较强的抑制作用,其中对急性T细胞白血病细胞Jurkat、人肾癌细胞OS-RC-2、人慢性髓质白血病细胞K562、人肺癌细胞A549和人乳腺导管癌细胞MDA-MB-435s的作用强,半数抑制浓度（IC50）分别为9．25±3．68、10．75±2．40、10．90±3．74、11．21±3．07和12．66±1．19μg·ml^-1,其次是对人食管癌细胞Eca-109、人胰腺癌细胞PANC-1、人黑色素瘤细胞A375、人肝癌细胞QGY-7703和人胃癌细胞SGC-7901,半数抑制浓度（IC50）分别为14．36±2．26、15．36±6．73、15．48±1．98、17．21±10．32和19．01±5．95μg·ml^-1。结论：红毛毡提取物具有广谱抗肿瘤作用。     

Inhibition of IgE and compound 48/80-induced histamine release by lectins.

Lectins from Ricinus communis and Glycine max, as well as wheat germ agglutinin and concanavalin A, caused a dose-dependent release of histamine from mast cells present in the mixed peritoneal cells from the rat. In addition, histamine release in an IgE-mediated and a compound 48/80-mediated reaction was inhibited in cells which had been pretreated with these lectins. With concanavalin A and the R. communis lectin both effect were prevented by the addition of the appropriate monosaccharides to the incubations. However, the lectin-induced histamine release and the lectin-induced inhibition of subsequent IgE-mediated histamine release could be dissociated: thus L-rhamnose, a hexose not ordinarily found on mammalian cell membranes, a specifically inhibited histamine release which was caused by the lectin from R. communis without affecting the inhibition of IgE-mediated histamine release. Conversely, D-fucose, which also is not a constituent of cell membrane glycolipids or glycoproteins prevented the inhibition of IgE-mediated histamine release by this lectin without affecting the lectin-induced histamine release. Furthermore, the nominally galactose-specific lectins from Sophora japonica and Ulex europeus inhibited IgE-mediated histamine release while causing little if any histamine release themselves. High concentrations of the lectin from Lotus tetragonolobus failed to cause histamine release or to affect the IgE-mediated histamine release reaction. Based on the known structural specificity of these lectins and the amounts of the lectins which were required to demonstrate an effect, it was concluded that D-galactose, alpha-linked, intrachain D-glucose (or mannose), and N-acetylglucosamine residues but probably not N-acetyl-galactosamine or L-fucose residues in the glycolipids or glycoproteins of the mast cell membrane can play a role in the initiation of histamine release and in the desensitization of the cells to subsequent histamine release-inducing stimuli.     

In vitro effects of adrenomedullin and calcitonin gene related peptide on the release of serotonin and amino acids from rat dorsal spinal cord

Adrenomedullin (AM) and calcitonin gene-related peptide (CGRP) are structurally related, interact with each others receptors and show overlapping biological activities. Immunoreactivity (IR) and mRNAs along with binding sites for both CGRP and adrenomedullin have been shown in the rat spinal cord. CGRP mediates the transmission of nociceptive information at the spinal cord level and both peptides has shown to induces c-fos expression and accumulation of cAMP in spinal cells. In this study, HPLC methods were used to investigate the effects of AM and CGRP on the basal and K⁺-evoked release of serotonin, glutamate (Glu), aspartate (Asp), glycine (Gly) and γ amino butyric acid (GABA) from the slices prepared from the rat spinal cord. Neither CGRP (10⁻⁷ and 10⁻⁶ M) nor AM (10⁻⁷ and 10⁻⁶ M) had significant effects on the basal release of serotonin and the amino acids tested in this study. However, CGRP produced statistically significant increases in the K⁺-evoked release of Asp and Glu, whereas AM failed to do so. Neither AM nor CGRP (10⁻⁷ and 10⁻⁶ M) showed any significant effects on the K⁺-evoked release of serotonin, GABA and Gly. Present data suggest that the stimulatory effects of CGRP on the release of Asp and Glu were exerted by distinct types of CGRP receptors.     

In vitro histamine and serotonin release studies in atopic dermatitis.

6 patients suffering from severe atopic dermatitis with high serum IgE were investigated. 3 of the patients had elevated plasma histamine levels (1.5-2.0 ng/ml). Compared to 9 nonatopic normal volunteers, the patient showed increased in vitro histamine release from peripheral leukocytes after stimulation with iothalamate and methacholine: while there was no significant histamine release at a methacholine concentration of 10(-4) M in normals, 4 of the patients with atopic dermatitis showed measurable histamine release under these conditions in vitro. The uptake of radiolabeled serotonin by platelets in vitro was decreased in 2 of the patients. There was no significant difference in serotonin release induced in vitro by different concentrations of thrombin, epinephrine and methacholine; 2 patients showed an increased platelet release reaction after iodipamide stimulation. It is concluded that a general tendency to release vasoactive mediators, even after 'nonimmunologic' stimulation, might play a role in the pathogenesis of atopic dermatitis.     

In vitro binding of parasites (Bonamia ostreae) and latex particles by hemocytes of susceptible and insusceptible oysters

Bonamia ostreae is a protozoan parasite that has caused severe losses in the flat oyster (Ostrea edulis) industry in Europe. The cupped oyster (Crassostrea gigas), recently introduced and cultured in Europe, is not infected by the disease. In vitro tests were conducted to determine whether there was a difference in the ability of hemocytes from each species to recognize and bind inert foreign particles (fluorescent latex beads) and purified, infective B. ostreae. The results indicated no difference in their ability to bind latex beads, but C. gigas were able to bind more B. ostreae than were O. edulis. The relative inability of the O. edulis hemocytes to recognize the parasite is discussed as a possible factor in flat oyster susceptibility.