Biological and biochemical properties of Phaseolus vulgaris isolectins

Exposure of the rat small intestine to raw kidney beans results in reorganization of absorptive cell microvilli

BACKGROUND/AIMS

A single exposure to raw kidney beans (RKB) results in vesiculation, shortening, and then regrowth of microvilli in the rat small intestine. This study investigated changes that occur in the structure of microvilli 2-10 hours after RKB exposure.

METHODS

Circumferences of microvilli from absorptive cells obtained sequentially after challenge with RKB or chow were assigned to one of three groups: small, intermediate, or large. The distribution and concentration of actin in intact mucosae or isolated epithelial sheets were determined by confocal laser scanning microscopy, immunocytochemistry, and immunoblot analysis with specific probes.

RESULTS

Six hours after exposure to RKB, most microvilli were large, abnormal in shape, and contained significantly more actin filaments than large microvilli from control rats. In addition, the fluorescence intensity of F-actin increased within injured microvilli without changes in the total intracellular actin concentration. By 8-10 hours after challenge with RKB, some microvilli remained larger than those of control rats but had resumed their normal shape and contained fewer actin filaments than at 6 hours.

CONCLUSIONS

Exposure of the rat small intestine to RKB results in enlargement of absorptive cell microvilli and reorganization of membrane and core actin filaments without changes in intracellular actin concentration. Enlarged microvilli are rapidly repaired.

Isolation of an immunosuppressive lectin from Phaseolus vulgaris L. cv Cacahuate using stroma

An immunosuppressive lectin was isolated from seed of Phaseolus vulgaris cv Cacahuate using physically entrapped stroma. The lectin was found to be a 94 kDa tetrameric protein. When 50 micrograms, of this lectin were administered intraperitoneally 2 days before the immunization with sheep red blood cells, humoral response against the immunogen was completely inhibited. Other properties of the protein are discussed.

Purification and characterization of novel lectins from Great Northern bean, Phaseolus vulgaris L

Two lectins, GNL-1 and 2, were isolated from extracts of Great Northern bean powder through fractionation with ammonium sulfate, ion-exchange chromatographies on CM- and DEAE-celluloses, and gel filtration chromatography on Sephacryl S-200 HR. These lectins were shown to be homogenous by gel electrophoresis, gel filtration, and isoelectric focusing. The lectins (GNL-1 and 2) have molecular masses of 175 and 145 kDa on gel filtration, respectively. They yield three bands having the respective same molecular masses on SDS-PAGE (GNL-1; alpha-subunit of 34.5 kDa, beta of 37.0, and gamma of 39.0: GNL-2; alpha' of 34.5 kDa, beta' of 37.0, and gamma' of 39.0). Two lectins are shown to be glycoproteins and the carbohydrate contents of GNL-1 and 2 are 5.1 and 4.5%, respectively. The isoelectric points are 5.5 and 5.1 and the extinction coefficients (A 1cm 1%) at 280 nm are 11.37 and 11.45, respectively. These lectins are nonspecific in agglutination for rabbit and any types of human erythrocytes. Inhibition study shows no specificity against mono and disaccharides. On the other hand, binding assay of horseradish peroxidase-glycoproteins to the bands electroblotted onto PVDF membrane reveals that all of the subunits can bind to sugar moieties in fetuin, asialofetuin, and porcine thyroglobulin specifically. Moreover, assay of mitogenic activity shows that GNL-1 is a strong mitogen, but GNL-2 is lack of the activity.

Study of renal tubular glycoconjugates in tubulointerstitial damage using conjugated lectins

Changes in the glycoconjugates of renal tubules associated with tubular damage were studied by lectin histochemistry, and their possible significance was determined. The excretion of various saccharides in tubular casts may also serve as markers of renal tubular damage. Renal tissues from 55 cases with various glomerular diseases including ten controls were studied. The patients were divided into two groups: one with tubulointerstitial lesions (TILs) (30 cases), and the other without (15 cases). Our results showed a wide spectrum of changes, predominantly in the disease group with TILs. The brush border of the proximal tubules showed significantly increased staining with Triticum vulgaris (WGA) and decreased staining with Canavalia ensiformis (Con A) lectins in both disease groups. The distal tubules revealed a significant increase in the apical and a decrease in the basal staining with Arachis hypogaea (PNA) and WGA lectins, respectively, in cases with TILs. The significant decrease in the basal domain staining was also seen with WGA lectin in cortical ducts. The vulnerability of various segments of the tubules in the process of TILs was clearly demonstrable. It appeared that the distal tubules were the most vulnerable anatomical segments around which the TILs began and later spread to involve other segments of tubules.

Comparative investigations on the amino-acid sequences of different isolectins from the sponge Axinella polypoides (Schmidt)

The sponge Axinella polypoides contains four different D-galactose binding lectins and one, termed lectin IV, which is specific for hexuronic acids. Only the D-galactose binding lectins were investigated in this study. The complete amino-acid sequence of lectin I, the main component in the crude extract was determined. Lectin I is a homodimer and each subunit comprises 144 amino acids with a M(r) of 15,847 +/- 10, as calculated from the sequence data and determined by mass spectrometry. Each subunit contains one intrachain disulfide bridge between positions 4 and 46. Of lectin II, only the first 49 amino acids of the NH2-terminal end were analysed. This part has 29 amino acids in common with lectin I, including a cysteine residue at position 4, also suggesting an intrachain loop in a identical position as in lectin I. The molecular mass of its subunit is 16,235 +/- 10 Da. Only the first 15 NH2-terminal amino acids of lectins III and V could be sequenced. Lectin V was identical to lectin II in all positions, whereas lectin III showed only 5 residues identical to lectins I or II. Thus, lectins I, II and III are derived from three different genes, whereas lectin V may either be a proteolytic cleavage product, or result from different splicing events or may be derived also from a separate gene. Neither of the four lectins showed any similarity to known lectin sequences of animal or plant origin.

Purification and some properties of proliferation suppressing factor from human lung adenocarcinoma PC-8

Extracts by 3 M KCl from a human lung adenocarcinoma cell line, PC-8, suppressed the proliferation of phytohemagglutinin activated lymphocytes. The proliferation suppressing factor (PSF) was purified from the extracts by ammonium sulfate precipitation, gel filtration and ion exchange chromatography. The purified PSF had a molecular weight of 50 kDa by SDS-PAGE and was acid- and heat-labile. Since the PSF also suppressed the proliferation of three established human cell lines, it is unlikely that the PSF hinders the interaction between lymphocytes and mitogens.

Repair of microvilli in the rat small intestine after damage with lectins contained in the red kidney bean

That microvilli of intestinal absorptive cells in the duodenum and jejunum are disrupted by acute challenge with lectins contained in raw kidney beans (RKB) was shown nearly 10 yr ago by light microscopy. However, the precise morphologic damage produced by RKB has not been characterized, and it is not known whether microvilli, once damaged, undergo repair. We have examined these issues by challenging rats with suspensions of 300 mg of RKB, boiled beans, or standard laboratory chow by orogastric lavage. Microvillus length was measured in electron micrographs from 6 to 20 h after challenge. Epithelial cell migration was determined by autoradiography after injection of [3H]thymidine. After challenge with RKB, microvilli (a) showed extensive vesiculation along the length of villi 2-4 h after challenge; (b) were reduced significantly in length along the entire villus 6 h after challenge; and (c) were near normal in length by 20 h after challenge. Microvillus length was also reduced significantly 6 h after challenge with boiled beans. The rate of cell migration was not accelerated by treatment with RKB. These data suggest that damage to microvilli caused by 300 mg of RKB is self-limited and reversible; microvilli once damaged by RKB are repaired. Repair of microvilli is due to intrinsic reparative processes rather than accelerated replacement of damaged cells. We speculate that microvilli may be repeatedly damaged and repaired after ingestion of dietary lectins.

Mitogenic lectins bind to the antigen receptor on human lymphocytes

The specificity of interactions between mitogenic and non-mitogenic lectins and disulfide-linked cell surface receptors on human lymphocytes was explored. Lysates (Nonidet-P40) of surface-radioiodinated tonsil lymphocytes and T lymphoblastoid cells (HPB-ALL) were absorbed with lectin-agarose derivatives (or bovine serum albumin, BSA-agarose) or immunoprecipitated with appropriate monoclonal antibodies (mAb). Lectin eluates and solubilized immunoprecipitates were analyzed by two-dimensional (nonreduced/reduced) sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Radiolabeled polypeptides were visualized by autoradiography. Among the various lectin-binding polypeptides, two disulfide-linked heterodimers (II and III) and two apparent homodimers (I and IV) are bound by pea lectin, concanavalin A and lentil lectin on tonsil lymphocytes; II, III and IV are bound both leukoagglutinating (L)- and erythroagglutinating (E)-phytohemagglutinins from Phaseolus vulgaris (PHA). Pokeweed mitogen recognizes only II and III. These molecules are weakly bound by peanut agglutinin, soybean agglutinin, Ulex europaeus agglutinin-I, Dolichos biflorus agglutinin, Vicia villosa agglutinin and Sophora japonica agglutinin, but are not bound by Helix pomatia agglutinin or BSA-agarose. Heterodimer II (82-88 kDa), comprised of 50-55-kDa and 40-43-kDa subunits, probably represents the alpha/beta T cell antigen receptor (TcR alpha/beta). Heterodimer III (64-72 kDa), comprised of 41-kDa and 37-kDa subunits, may represent TcR gamma. The homodimers, I (120-130 kDa) and IV (55-61 kDa), comprised of 55-60-kDa and 30-kDa polypeptides, respectively, have apparently not been previously described. Evidence that H1-2D4, a mAb directed against the antigen receptor on HPB-ALL cells, and E-PHA interact with a common molecule includes: (a) immunoprecipitation of TcR with H1-2D4 from the glycopeptide fraction specifically eluted from insolubilized lectin with N-acetylgalactosamine; and (b) adsorption of TcR from a solubilized H1-2D4 immunoprecipitate by E-PHA-agarose. Recognition of CD3 by E-PHA is indicated by immunoprecipitation of CD3 protein by UCHT1 from the glycopeptide fraction specifically eluted from E-PHA. The results are consistent with the view that mitogenic lectins interact with certain disulfide-linked molecules on human lymphocytes, including the TcR alpha/beta and perhaps TcR gamma; while some nonmitogenic lectins also recognize these receptors, the interaction is of low affinity.

Purification and characterization of a lectin from Phaseolus acutifolius var. latifolius

The lectin from Phaseolus acutifolius var. latifolius has been purified to homogeneity by affinity chromatography using stroma-sephadex, gel filtration and electrofocusing. The purified lectin consists of four subunits of 21 Kd molecular mass each one with 7.4% w/w total carbohydrate. Red cells of human and animal species, are agglutinated but are not inhibited by a series of sugars. Mitogenicity and immunosuppressive activities were demonstrated. Agglutination requires magnesium and calcium ions.

An economic anterograde axonal tracing method using Phaseolus vulgaris agglutinin (PHA) P-form

Phaseolus vulgaris leucoagglutinin (PHA-L) has been demonstrated to be an excellent neuroanatomical anterograde tracer. So far there are relatively few applications of this technique, mainly due to the cost of the lectin. Instead of PHA-L, we have successfully used PHA-P, which is a crude and inexpensive form of PHA-L. The sensitivity of the present method, examined in the rat striatonigral pathway, is as high as that of the conventional method. Furthermore, a large amount of PHA-P, injected into the cat eye, demonstrated the retinofugal projection in detail.

Interaction between the CD45 antigen and phytohemagglutinin. Inhibitory effect on the lectin-induced T cell proliferation by anti-CD45 monoclonal antibody

Immunoprecipitation studies from 125I-labeled T cells, previously activated with the lectin phytohemagglutinin (PHA) from Phaseolus vulgaris, showed a preferential association between the CD45 glycoprotein family containing members of 220, 205, 190 and 180 kDa, and a protein of 33 kDa. This 33-kDa protein, with an identical molecular mass as PHA, was not associated with other highly expressed molecules such as class I histocompatibility antigens (HLA-A,B,C), transferrin receptor, CDw44 and CD11a. Further immunoprecipitation analysis from peripheral blood lymphocytes incubated with 125I-labeled PHA confirmed the identification of the CD45-associated 33-kDa protein as the lectin PHA. These results prompted us to analyze the possible involvement of the CD45 molecules in the T cell activation process induced by PHA. Thus, two monoclonal antibodies specific for CD45 antigens were able to inhibit the T cell proliferation induced by the lectin. This inhibitory ability was exerted by affecting both the interleukin 2 production and the interleukin 2 receptor expression.

Separation of isolectins by high-performance hydrophobic interaction chromatography

High-performance hydrophobic interaction chromatography (HP-HIC) was found to be an effective method for the separation of lectins into isolectin fractions. All of the purified lectins used in this study, Phaseolus vulgaris haemagglutinin (PHA), wheat germ agglutinin (WGA), Ricinus communis agglutinin (RCA), and Arachis hypogaea agglutinin (AHA), were prepared by affinity chromatography. HP-HIC was performed on a column (15 X 2.1 cm) of TSK gel Phenyl-5PW at room temperature. The lectin sample, dissolved in 1.0 or 0.5 M ammonium sulphate in phosphate buffered saline (pH 7.4) (PBS), was applied to the column and eluted with a linear gradient from 1.0 or 0.5 M ammonium sulphate in PBS to 0 M ammonium sulphate in PBS at a flow-rate of 4 ml/min. In the case of RCA, addition of glycerol to the elution buffer resulted in sharper isolectin peaks. PHA, WGA, RCA, and AHA were rapidly separated into 5, 5, 4, and 6 isolectins, respectively.

An assay for leukoagglutinating lectins using suspension cultured mouse lymphoma cells (BW5147) stained with neutral red

A sensitive and rapid assay for leukoagglutinating lectins has been developed. This assay utilizes neutral red-stained mouse lymphoma cells from the suspension cultured cell line BW5147. The agglutination of the stained cells can be monitored visually in a manner similar to that for conventional assays for erythroagglutinating lectins using erythrocytes. The activity of lekoagglutinating lectins that are not capable of agglutinating erythrocytes can be quantified by this assay. The utility of the assay was demonstrated using leukoagglutinating and erythroagglutinating lectins from the seeds of Phaseolus vulgaris and Maackia amurensis.

Evidence that mannosyl residues are involved in human immunodeficiency virus type 1 (HIV-1) pathogenesis

The Human Immunodeficiency Virus (HIV), the causative agent of AIDS, is thought to bind to T4+ (CD4+) target cells through the heavily glycosylated gp120 envelope glycoprotein. Plant lectins bind glycoproteins through noncovalent interaction with specific hexose residues; therefore, lectins were evaluated for their ability to inactivate HIV in vitro. The mannose-specific lectins concanavalin-A and succinyl concanavalin-A completely inactivated HIV while lentil lectin, wheat germ agglutinin, and phytohemagglutinin-P substantially inactivated HIV. BS-II, Vicia villosa (hairy vetch), and Ptilota plumosa (red marine algae) failed to alter the infectibility of HIV. Neither simple stearic hindrance, viral aggregation, nor lectin-cell interactions served to explain this phenomenon. Glycoprotein glycosylation was evaluated by differential lectin binding as well as molecular weight changes in gp120 when virus was produced in the presence of swainsonine, a glycosylation inhibitor. Lentil lectin bound gp120 better than concanavalin-A, suggesting the majority of glycosylation sites are fucosylated. The apparent molecular weight of gp120 was reduced by swainsonine, although HIV infectivity and concanavalin-A inactivation were retained. Thus, at least some N-glycosylation sites are complex-type glycoproteins but regions external to the (GlcNAc)2(Man)3 "core" pentasaccharide region are not required for HIV infectivity. It appears that the site or sites involved are nonfucosylated, high mannose and/or biantennary, nonsialylated, N-glycosylated regions of gp120 or gp41. Alternatively, they may be in close approximation to such carbohydrate regions.

Stimulation of 2',3'-cyclic nucleotide 3'-phosphodiesterase in human lymphocytes by Robinia pseudoacacia lectin

2',3'-Cyclic nucleotide 3'-phosphodiesterase (CNP) activity was studied in human peripheral blood lymphocytes. Incubation of human lymphocytes with optimum mitogenic concentrations of Robinia pseudoacacia lectin produced an increase in CNP activity. This increase was not detected before 24 h of incubation. Furthermore, whereas unfractionated lymphocytes exhibited activation of CNP, this was not observed in B and T cell subpopulations.

The relationship between metal ion content and mitogenicity of PHA-L4 isolectin as determined by agarose electrophoresis

The lectin (PHA) from Phaseolus vulgaris is a tetrameric metalloprotein which exists as 5 different isolectins. An agarose electrophoretic assay is described that can distinguish between metallized and demetallized PHA. The assay has been employed for the analysis of 5 different preparations of the isolectin PHA-L4, and the preparations have subsequently been tested for their ability to induce lymphocyte transformation. A reverse correlation was found between the relative amount of irreversibly demetallized isolectin, as determined by agarose electrophoresis and the mitogenic activity of the preparation. The degree of irreversible demetallization seemed to be dependent on the preparation method used. One method gave 25% and another 100% demetallization of the isolectins. The assay was found to be a rapid and simple way to test the relative amount of mitogenically active lectin present in a preparation.

Regulation of processing of a plant glycoprotein in the Golgi complex: A comparative study usingXenopus oocytes

The synthesis of phytohemagglutinin (PHA), the major seed lectin ofPhaseolus vulgaris, was investigated inXenopus oocytes injected with RNA isolated from developing bean cotyledons. As is the case for normal PHA, oocyte-synthesized PHA polypeptides were found to contain two asparagine-linked oligosaccharide chains, one of which was of the high-mannose type and the other one of the Golgi-modified type, being largely resistant to endo-β-N-acetylglucosaminidase H digestion and containing fucose. The modified oligosaccharide chain of oocyte-synthesized PHA appeared to be much larger and more heterogeneous with respect to the modified chain normally present on PHA. When the oocytes were injected with purified mRNA for PHA, isolated by hybrid-selection using a PHA complementary-DNA clone, the results were the same as those obtained by injecting total cotyledonary RNA. On the whole, these results indicate that plant glycoproteins are directed to the Golgi complex even when synthesized in an animal cell, and that correct sorting of the oligosaccharide chains to be processed is independent of the cell-type in which protein synthesis occurs. The form of processing is however cell-type specific.

Binding of isolectins from red kidney bean (Phaseolus vulgaris) to purified rat brush-border membranes

Ingestion of red kidney bean phytohemagglutinin causes impaired growth and intestinal malabsorption, and facilitates bacterial colonization in the small intestine of weanling rats. We have studied interactions of the highly purified phytohemagglutinin erythroagglutinating (E4) and mitogenic (L4) isolectins with microvillous membrane vesicles prepared from rat small intestines. E4 and L4 were radioiodinated with 125I by the chloramine-T technique. E4 and L4 isolectins both bound to microvillous membrane vesicles. Binding was saturable and reversible. Each mg of membrane protein bound 744 +/- 86 micrograms E4 and 213 +/- 21 micrograms L4. The apparent Ka for E4 and L4 binding was 2.5 x 10(-6) and 13.0 x 10(-6) M-1, respectively. Binding of each 125I-labelled isolectin was abolished by 100-fold excess of unlabelled isolectin. In each case binding also was inhibited by appropriate oligosaccharide inhibitors, indicating that isolectin-microvillous membrane interactions were mediated by carbohydrate recognition. Patterns of saccharide inhibition of isolectin binding were different for E4 and L4. Competitive binding experiments demonstrated mutual noncompetitive inhibition of E4 and L4 binding consistent with steric hindrance. Therefore, E4 and L4 each bound to its own set of receptors. Based on the known saccharide specificities of E4 and L4, these data indicate that there are differences in expression of complex asparagine-linked biantennary and tri- or tetraantennary oligosaccharides at the microvillous surface. The data also provide the possibility that direct interactions of one or more phytohemagglutinin isolectins with intestinal mucosa in vivo may contribute to the antinutritional effects associated with ingestion of crude red kidney beans.

A one-step procedure for isolation and resolution of the Phaseolus vulgaris isolectins by affinity chromatography

A new fast-working one-step method for the resolution of the Phaseolus vulgaris isolectins is described which requires inexpensive materials.

Molecular analysis of a phytohemagglutinin-defective cultivar of Phaseolus vulgaris L

The seeds of Phaseolus vulgaris cv. Pinto III are known to lack detectable amounts of phytohemagglutinin (PHA) and to accumulate very reduced levels of PHA mRNA compared with normal cultivars. Using PHA complementary-DNA clones and monospecific antibodies we analyzed cv. Pinto III genomic DNA and cotyledonary proteins synthesized both in vitro and in vivo. We detected genomic DNA sequences that hybridize with complementary-DNA clones for the two different classes of PHA polypeptides (PHA-E and PHA-L), at levels comparable to a normal bean cultivar. This indicates that the cv. Pinto III phenotype is not the result of a large deletion of the PHA structural genes. Messenger RNA isolated from cv. Pinto III developing cotyledons synthesizes in vitro very small amounts of a protein which is recognized by antibodies specific for PHA, and gives, on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, a single band with molecular weight similar but not identical to that of PHA-L polypeptides. This protein is also synthesized in vivo at a very reduced level, less than 1% compared with PHA in normal cultivars, and has mitogenic activity comparable to that of the PHA-L subunit, while it shows very weak erythroagglutinating activity. The initial steps in the synthesis and processing of this protein are identical to those already identified for PHA polypeptides. The cv. Pinto III protein could be either a PHA-L polypeptide whose synthesis is not affected by the mutation or a PHA-like lectin present normally at low levels in P. vulgaris.

Intestinal microbial flora after feeding phytohemagglutinin lectins (Phaseolus vulgaris) to rats

Incorporation of purified phytohemagglutinin (PHA) lectins derived from red kidney beans (Phaseolus vulgaris) in the diet of weanling rats will cause growth failure, malabsorption of nutrients, and bacterial overgrowth in the small intestine. These effects are not caused by feeding a similar quantity of PHA to germfree rats. To define the morphological and bacterial changes on the mucosal surfaces of the jejunum, ileum, and cecum in greater detail, we pair fed two groups of weanling rats isocaloric, isonitrogenous diets with or without 0.5% PHA protein. On the jejunal surfaces of control rats, the mucous layer was a confluent covering with sparsely scattered bacteria and protozoa. In PHA-treated rats, the mucous layer was thin and discontinuous, and the microvillous surface of the tissue was extensively populated by bacterial cells of two distinct morphotypes--a gram-negative rod and a gram-positive coccobacillus. In all PHA-treated animals, these bacteria formed adherent monospecific or mixed adherent microcolonies on the tissue surface. Tissue damage was observed in PHA-exposed jejunal tissue as evidenced by vesiculation of the microvillous plasma membrane and by damage to the brush border membrane. On the ileal surfaces of control rats, there was a thick mucous layer within which small numbers of bacteria and protozoa were seen. Segmented filamentous bacteria were anchored in the tissue surface. In PHA-treated rats, the ileal surface was only incompletely covered by a mucous layer, and the overlying mucosal surface was extensively covered by large numbers of protozoan cells (predominantly Hexamita muris). Most of the ileal surfaces not covered by the mucous layer were occupied and virtually occluded by an overgrowth of these protozoan cells with occasional cells of Giardia muris and the tissue-associated segmented bacillus. In the ceca of control rats, the mucosa was incompletely covered by a discontinuous mucous layer and colonized by an unnamed Spirillum sp., other bacteria, and occasional protozoa. The cecal surfaces of PHA-treated rats retained most of their incomplete overlying mucous layer, which was heavily colonized by the same type of Spirillum sp. seen in untreated animals; intestinal crypts were colonized. These descriptive morphological studies demonstrate that exposure to purified PHA in the diet caused characteristic changes in the microbial ecology of the small intestine. The changes in microbial flora contributed to the malabsorption of nutrients in the small intestines of PHA-fed animals.

Intrinsic projections of the retrohippocampal region in the rat brain. I. The subicular complex

The intrahippocampal projections of the subicular complex were studied in the rat with the aid of the anterogradely transported lectin Phaseolus vulgaris leucoagglutinin (PHA-L). After iontophoretic injections of the lectin into the subiculum proper, presubiculum, or the parasubiculum, axons and terminal processes immunoreactive for PHA-L were traced to their respective terminal fields within the hippocampal region. After subicular injections PHA-L-stained axons could be followed both in a caudal and a rostral direction. The caudally directed fibers course around or within the angular bundle to enter layers VI and V of the medial entorhinal area (MEA). Many fibers penetrate through these layers to terminate in layer IV of the medial and the lateral entorhinal area, which contains a major terminal field of this projection. At more ventral levels, all layers of the entorhinal area are innervated by cells located in the subiculum. Other retrohippocampal projections of the subiculum proper include the deep and the outer two layers of the presubiculum and the medial sector of the parasubiculum, in addition to a massive projection which terminates in the retrosplenial cortex. The rostrally directed projections from the subiculum form a dense innervation of strata lacunosum, radiatum, oriens, and of individual pyramidal cells in the regio superior of the Ammon's horn. All these projections of the subiculum are exclusively ipsilateral. After injections of PHA-L into layers II and III of the presubiculum, both ipsi- and contralateral projections were traced to the outer three layers of the medial entorhinal area; the lateral entorhinal area apparently receives no innervation from the presubiculum. The innervation of layer III is very dense while in layer II and deep layer I, restricted zones of innervation are found. The fibers reach these layers via the deep layers of the MEA and through the molecular layer after first coursing around the parasubiculum. In addition, a minor projection from the presubiculum to the pyramidal cell layer of the subiculum and to the molecular layer of the hippocampal formation was found. PHA-L injections into the parasubiculum labeled fibers that form a dense innervation of layer II in the MEA and the medial part of the lateral EA, and of the most medial sector of layer III in the MEA. Layer I and the superficial part of layer II of the contralateral MEA also contain a dense terminal network after PHA-L injections into the parasubiculum.(ABSTRACT TRUNCATED AT 400 WORDS)

Lectin histochemistry of human placenta

The human placenta was studied histochemically using 23 fluorescein-isothiocyanate-labeled lectins. Distinct patterns of staining, as well as some differences between first-trimester and term placenta, were discerned. Eleven lectins (HPA, VVA, BPA, HAA, SBA, PNA, GSA-I, MPA, RCA-I, RCA-II, and UEA-I) did not react with the trophoblast. Two lectins (LCA and PEA) reacted with the trophoblast of first-trimester placenta but not with the trophoblast of third-trimester placenta. The remaining ten lectins (ConA, Suc.ConA, WGA, GSA-II, LAA, STA, DBA, LBA, PHA-E, and PHA-L) reacted with the trophoblast of both first- and third-trimester placenta, and two of these lectins (ConA and Suc.ConA) reacted preferentially with the syncytiotrophoblast. Five lectins (LAA, STA, DBA, GSA-II, and LBA) reacted with nuclei of the cytotrophoblast. The nuclei of some stromal and syncytiotrophoblastic cells were also reactive. Eighteen lectins reacted with the trophoblastic basement membrane, and all reacted with Hofbauer cells and the stroma of the villi. Lectin binding was influenced by the mode of fixation and tissue processing. These data show that some lectins can be used to identify components of the placental villi (e.g., basement, membrane) to characterize differences between the first- and third-trimester trophoblast, and to distinguish the cytotrophoblast from the syncytiotrophoblast.

Phytohemagglutinin-induced diarrheal disease

A purified plant lectin, phytohemagglutinin (PHA), or crude red kidney bean (RKB) from which it was derived, when incorporated as 1% of dietary protein into a purified casein protein diet caused weanling rats to fail to grow or lose weight in comparison to control animals pair fed an isonitrogenous, isocaloric diet. Feeding PHA was observed to cause diarrhea: fecal wet and dry weights were increased within 2 days after starting the diet. Increased fecal weight was caused by increased dry weight as well as by an increased fecal water content. On reversion to a normal casein diet, rapid amelioration of the antinutritional effects of PHA occurred with resumption of normal growth rate. Specific binding of PHA to the microvillus region of the small intestinal epithelium was demonstrated using rabbit anti-PHA and fluorescein-labeled goat anti-rabbit immunoglobin. PHA binding was observed after chronic intake in the diet or when applied to normal tissue in vitro. Loss of PHA binding to the intestine was observed to occur within 48 hr on reversion to a control casein diet. No significant morphological damage to the microvilli or the mucosal villus architecture was observed to accompany PHA adherence under these experimental conditions. Antinutritional and antiabsorptive effects of dietary PHA were associated with diarrhea. PHA adhered to the microvillus membrane of the small intestinal villus surface during the diarrheal state.(ABSTRACT TRUNCATED AT 250 WORDS)

Mitogenic and mitogenically defective phytohemagglutinin isolectins stimulate T-cell growth factor (interleukin 2) production and response in fresh and cultured human T lymphocytes

L4-PHA (L4) and E4-PHA (E4) lectins isolated from Phaseolus vulgaris have different mitogenic properties. The mechanisms of the differences in mitogenic behavior were sought in the interaction of lectin, lymphocyte subsets, and T-cell growt factor (TCGF) also known as interleukin 2 (IL-2). TCGF activity in culture supernatants ( L4S ; E4S ) from L4- and E4-stimulated, freshly isolated lymphocytes was assayed as stimulation of DNA synthesis in TCGF-dependent continuous T-cell cultures (CTC). E4S contained less TCGF than did L4S . Addition of partially purified TCGF does not increase the stimulation of fresh lymphocytes by L4 or E4. L4 and E4 equally stimulate both helper (OKT4+) and suppressor (OKT8+) cells. The ability of L4 to further stimulate CTC is slowly lost (15 greater than 30 greater than 45 days). It is concluded that production of TCGF is not rate limiting in E4 and L4 stimulation of lymphocytes. The growth of CTC, which requires the presence of TCGF, remains sensitive to, but not dependent on, L4 for at least 30 days.

Biosynthesis and processing of phytohemagglutinin in developing bean cotyledons

Phytohemagglutinin (PHA) is a family of tetrameric isolectins which accumulate in the protein bodies of developing Phaseolus vulgaris cotyledons. Each tetramer contains erythroagglutinating (E) or lymphocyte-mitogenic (L) subunits, or a combination of both. The subunits have Mr around 33000, E being slightly larger than L. Phytohemagglutinin is a glycoprotein, and its carbohydrate moiety contains N-acetylglucosamine, mannose, fucose and xylose, indicating that this protein has complex oligosaccharide sidechains. Several steps in the biosynthesis and in the cotranslational and post-translational processing of the glycopolypeptides of PHA have been identified. The polypeptides of PHA are synthesized by polysomes attached to the endoplasmic reticulum. The glycosylation of the polypeptides is a cotranslational process, in which each PHA polypeptide usually acquires two oligosaccharide sidechains. The oligosaccharides of PHA isolated from the endoplasmic reticulum are susceptible to digestion with alpha-mannosidase and endo-beta-N-acetylglucosaminidase H indicating that they are of the high-mannose type. In the presence of tunicamycin two unglycosylated polypeptides of PHA are synthesized, indicating that the differences in Mr between the E and L subunits of PHA are not due to differences in glycosylation alone. Transport of PHA to the protein bodies is mediated by the Golgi apparatus where at least part of the oligosaccharide chains of PHA are modified [ Chrispeels , M. J. (1983) Planta ( Berl .) 157, 454-461, and 158, 140-151]. The modified oligosaccharide chains of PHA are then gradually trimmed to a smaller size when the protein is already in the protein bodies. This processing results in an increase in the mobility of the PHA subunits in denaturing polyacrylamide gels.

Detection and characterization of a lectin from non-seed tissue ofPhaseolus vulgaris

The distribution of lectin in various tissues ofPhaseolus vulgaris L. (cv. red) has been investigated using a sensitive solid-phase enzyme immunoassay. Roots, leaves and stems from 3- to 4-week-old plants were screened for their lectin content; low levels could be detected in all organs, with a relative distribution of 37% in roots, 20% in leaves and 43% in stems. The lectin from stemsleaves and roots was then isolated from 5- to 6-week-old plants using extraction, salt fractionation and affinity chromatography on immobilized porcine thyroglobulin. A comparative study of the seed lectin and the lectin isolated from 5- to 6-week-old plants was made using hemagglutination, inhibition of hemagglutination, immunodiffusion, polyacrylamide and agarose electrophoresis. The results showed that lectin isolated from the different tissues was immunologically identical and exhibited the same subunit structure and similar isolectin composition as the seed lectin.

Morphological details of the projection from the presubiculum to the entorhinal area as shown with the novel PHA-L immunohistochemical tracing method in the rat

Iontophoretic injections of the lectin, phaseolus vulgaris leucoagglutinin (PHA-L) were made into the presubiculum of rats. The anterogradely transported lectin was visualized by using an anti-PHA-L antibody in combination with immunohistochemistry. The PHA-L tracing method revealed morphological details of the projection of the presubiculum to the ipsi- and contralateral medial entorhinal area usually not seen with other anterograde transport techniques. Fine varicose fibers form a dense terminal plexus in the deep parts of layer III. In layer II and deep layer I, the fibers form column-like axonal bundles, terminating in patches in the deep part of layer I. Some fibers reach the outer three layers of the entorhinal area (EA) from collaterals of axons running in the molecular layer, while a majority enter from the deep layers.

Bean lectins IV: genetic variation in the non-denatured structure of lectins from different Phaseolus vulgaris L. cultivars

Variation in the native conformation of bean lectins was examined using electrophoresis of non-denatured total protein extracts and purified albumin and globulin lectin. The observed variation was related to the genetic variation reported previously for lectin polypeptide composition as revealed by two-dimensional isoelectricfocusing-sodium dodecyl sulfate polyacrylamide gel electrophoresis (IEF-SDS/PAGE). When eleven cultivars with different IEF-SDS/PAGE lectin polypeptide compositions were compared, eight had unique non-denatured lectin patterns and three had identical patterns. For some cultivars differences in non-denatured lectin patterns were observed between the purified albumin and globulin lectin preparations.

Phaseolus vulgaris phytohemagglutinin contains high-mannose and modified oligosaccharide chains

Phytohemagglutinin, the major lectin in the seeds of the common bean Phaseolus vulgaris L., was isolated by affinity chromatography from cotyledons of nearly mature seeds and from developing cotyledons labeled with [(3)H]glucosamine, [(3)H]mannose or [(3)H]fucose. The protein was subjected to exhaustive proteolysis and the carbohydrate composition of the resulting glycopeptides examined. Two classes of oligosaccharide side-chains were found. The sidechains of the first class are of the high-mannose type, containing two residues of N-acetylglucosamine and 8 or 9 mannose residues. The sidechains of the second class are of the modified type containing N-acetylglucosamine, mannose, fucose, xylose in molar ratios of 2:3.8:0.6:0.5. Two-dimensional gel electrophoresis shows that phytohemagglutinin can be fractionated into seven different glycosylated polypeptides, and that each one contains at least one modified oligosaccharide chain. The results indicate that most glycosylated polypeptides probably contain one chain of each class. The carbohydrate composition of the two types of chains is similar to that found in other plant glycoproteins, but this is the first report of a plant glycoprotein with both highmannose and modified oligosaccharides on the same polypeptide chain.

Fractionation of glycoproteins according to lectin affinity and molecular size using a high-performance liquid chromatography system with sequentially coupled columns

The lectin phytohaemagglutinin was coupled to porous silica (10 micron) and used as adsorbent in a high-performance liquid affinity column sequentially coupled to a TSK-G 3000SW gel permeation column. This system was used for high-speed separation/analysis of human serum glycoproteins according to their lectin affinity and molecular size. Serum samples could be resolved in at least six different peaks representing glycoproteins exhibiting different molecular weights but with a carbohydrate content compatible with the specificity of phytohaemagglutinin.

An anterograde neuroanatomical tracing method that shows the detailed morphology of neurons, their axons and terminals: immunohistochemical localization of an axonally transported plant lectin, Phaseolus vulgaris leucoagglutinin (PHA-L)

A new neuroanatomical method for tracing connections in the central nervous system based on the anterograde axonal transport of the kidney bean lectin, Phaseolus vulgaris-leucoagglutinin (PHA-L) is described. The method, for which a detailed protocol is presented, offers several advantages over present techniques. First, when the lectin is delivered iontophoretically, PHA-L injection sites as small as 50-200 micron in diameter can be produced, and are clearly demarcated since the neurons within the labeled zone are completely filled. Second, many morphological features of such filled neurons are clearly demonstrated including their cell bodies, axons, dendritic arbors and even dendritic spines. Third, there is some evidence to suggest that only the neurons at the injection site that are filled transport demonstrable amounts of the tracer, raising the possibility that the effective injection site can be defined quite precisely. Fourth, even with the most restricted injections, the morphology of the labeled axons and axon terminals is clearly demonstrated; this includes boutons en passant, fine collateral branches, and various terminal specializations, all of which can be visualized as well as in the best rapid Golgi preparations. Fifth, when introduced iontophoretically, PHA-L appears to be transported preferentially in the anterograde direction; only rarely is it transported retrogradely. Sixth, PHA-L does not appear to be taken up and transported effectively by fibers of passage. Seventh, there is no discernible degradation of the transported PHA-L with survival times of up to 17 days. Finally, since the transported marker can be demonstrated with either peroxidase or fluorescent antibody techniques, it may be used in conjunction with other neuroanatomical methods. For example, double anterograde labeling experiments can be done using the autoradiographic method along with immunoperoxidase localization of PHA-L, and the retrogradely transported fluorescent dyes can be visualized in the same tissue sections as PHA-L localized with immunofluorescence techniques.

Dry beans of Phaseolus. A review. Part 2. Chemical composition: carbohydrates, fiber, minerals, vitamins, and lipids

Beans of Phaseolus are an important food crop both economically and nutritionally, and are cultivated and consumed worldwide. With ever rising costs of meats and fresh fruits and vegetables, dry beans are expected to contribute more to the human nutrition in coming years. Traditionally, they have been referred to as "poor man's meat" and have contributed significantly to the diets of many people of several countries in Asia, Africa, Middle East, and South America. In recent years, a renewed interest in bean research in Western European countries and the U.S. is evident. In this review, certain biochemical, technological, nutritional, and toxicological aspects are discussed and the limitations and problems associated with dry beans of Phaseolus as human food are addressed.

Dry beans of Phaseolus: a review. Part 3

Beans of Phaseolus are important food crops both economically and nutritionally, and are cultivated and consumed world wide. With ever rising costs of meats, fresh fruits, and vegetables, dry beans are expected to contribute more to the human nutrition in coming years. Traditionally, they have been referred to as "poor man's meat" and have contributed significantly to the diets of many people of several countries in Asia, Africa, the Middle East, and South America. In recent years, a renewed interest in bean research in Western European countries and the U.S. is evident. In this review, certain biochemical, technological, nutritional, and toxicological aspects are discussed and the limitations and problems associated with dry beans of Phaseolus as human food are addressed.