Appearance of peanut agglutinin in the blood circulation after peanut ingestion promotes endothelial secretion of metastasis-promoting cytokines.

Peanut agglutinin (PNA) is a carbohydrate-binding protein in peanuts that accounts for ~0.15% peanut weight. PNA is highly resistant to cooking and digestion and is rapidly detectable in the blood after peanut consumption. Our previous studies have shown that circulating PNA mimics the actions of endogenous galactoside-binding protein galectin-3 by interaction with tumour cell-associated MUC1 and promotes circulating tumour cell metastatic spreading. The present study shows that circulating PNA interacts with micro- as well as macro-vascular endothelial cells and induces endothelial secretion of cytokines MCP-1 (CCL2) and IL-6 in vitro and in vivo. The increased secretion of these cytokines autocrinely/paracrinely enhances the expression of endothelial cell surface adhesion molecules including integrins, VCAM and selectin, leading to increased tumour cell-endothelial adhesion and endothelial tubule formation. Binding of PNA to endothelial surface MCAM (CD146), via N-linked glycans, and subsequent activation of PI3K-AKT-PREAS40 signalling is here shown responsible for PNA-induced secretion of MCP-1 and IL-6 by vascular endothelium. Thus, in addition to its influence on promoting tumour cell spreading by interaction with tumour cell-associated MUC1, circulating PNA might also influence metastasis by enhancing the secretion of metastasis-promoting MCP-1 and IL-6 from the vascular endothelium.

Effect of human tubal fluid medium and hyperactivation inducers on stallion sperm capacitation and hyperactivation.

Conventional in vitro fertilization has not yet been implemented in the equine species. One of the main reasons has been the inability to develop a culture medium and incubation conditions supporting high levels of stallion sperm capacitation and hyperactivation in vitro. Although different culture media have been used for this purpose, human tubal fluid (HTF) medium, widely used in the manipulation of human and mice gametes, has not been reported so far in stallion sperm culture. The first part of this study aimed to compare HTF and Whitten's media on different stallion sperm quality and capacitation variables. Additionally, the effect of procaine, aminopyridine and caffeine in both media was evaluated on sperm motility parameters at different incubation times. Integrity and destabilization of the plasma membrane were evaluated by merocyanine 540/SYTOX Green (MC540), mitochondrial membrane potential (∆Ψm) using tetramethylrhodamine methyl ester perchlorate (TMRM), acrosome membrane integrity by PNA/FITC and tyrosine phosphorylation by P-tyrosine mouse mAb conjugated to Alexa Fluor® by flow cytometry. Motility parameters were evaluated using the integrated semen analysis system (ISAS®). We found no differences between Whitten's and HTF media and incubation time in terms of sperm viability, uninduced acrosome membrane damage or mitochondrial membrane potential at 30- and 120-min incubation. Membrane fluidity (MC540) increased in both media at 30- and 120-min incubation compared to noncapacitating conditions. Similarly, tyrosine phosphorylation increased in both media in capacitating conditions at 2- and 4-hr incubation compared to noncapacitating conditions. Although procaine showed the best result in terms of sperm hyperactivated motility in both media, aminopyridine also showed parameters consistent with the hyperactivation including an increase in curvilinear velocity and decrease in straightness. In conclusion, HTF medium and aminopyridine equally support capacitation-related parameters in stallion sperm.

In vitro infectivity and differential gene expression of Leishmania infantum metacyclic promastigotes: negative selection with peanut agglutinin in culture versus isolation from the stomodeal valve of Phlebotomus perniciosus.

BACKGROUND: Leishmania infantum is the protozoan parasite responsible for zoonotic visceral leishmaniasis in the Mediterranean basin. A recent outbreak in humans has been reported in this area. The life cycle of the parasite is digenetic. The promastigote stage develops within the gut of phlebotomine sand flies, whereas amastigotes survive and multiply within phagolysosomes of mammalian host phagocytes. The major vector of L. infantum in Spain is Phlebotomus perniciosus. The axenic culture model of promastigotes is generally used because it is able to mimic the conditions of the natural environment (i.e. the sand fly vector gut). However, infectivity decreases with culture passages and infection of laboratory animals is frequently required. Enrichment of the stationary phase population in highly infective metacyclic promastigotes is achieved by negative selection with peanut agglutinin (PNA), which is possible only in certain Leishmania species such as L. major and L. infantum. In this study, in vitro infectivity and differential gene expression of cultured PNA-negative promastigotes (Pro-PNA(-)) and metacyclic promastigotes isolated from the sand fly anterior thoracic midgut (Pro-Pper) have been compared. RESULTS: In vitro infectivity is about 30 % higher in terms of rate of infected cells and number of amastigotes per infected cell in Pro-Pper than in Pro-PNA(-). This finding is in agreement with up-regulation of a leishmanolysin gene (gp63) and genes involved in biosynthesis of glycosylinositolphospholipids (GIPL), lipophosphoglycan (LPG) and proteophosphoglycan (PPG) in Pro-Pper. In addition, differences between Pro-Pper and Pro-PNA(-) in genes involved in important cellular processes (e.g. signaling and regulation of gene expression) have been found. CONCLUSIONS: Pro-Pper are significantly more infective than peanut lectin non-agglutinating ones. Therefore, negative selection with PNA is an appropriate method for isolating metacyclic promastigotes in stationary phase of axenic culture but it does not allow reaching the in vitro infectivity levels of Pro-Pper. Indeed, GIPL, LPG and PPG biosynthetic genes together with a gp63 gene are up-regulated in Pro-Pper and interestingly, the correlation coefficient between both transcriptomes in terms of transcript abundance is R (2) = 0.68. This means that the correlation is sufficiently high to consider that both samples are physiologically comparable (i.e. the experiment was correctly designed and performed) and sufficiently low to conclude that important differences in transcript abundance have been found. Therefore, the implications of axenic culture should be evaluated case-by-case in each experimental design even when the stationary phase population in culture is enriched in metacyclic promastigotes by negative selection with PNA.

The antitumor activity of PNA modified vinblastine cationic liposomes on Lewis lung tumor cells: In vitro and in vivo evaluation.

Non-small cell lung cancer (NSCLC) is one of the frequently-occurring disease in the world, and the treatment effects are usually unsatisfactory. Vinblastine is an anti-microtubule drug in clinic. In this study, a nanostructured liposome was designed and prepared for treating NSCLC. In the liposomes, peanut agglutinin (PNA) was modified on the liposomal surface, 3-(N-(N',N'-dimethylaminoethane)carbamoyl) cholesterol was used as cationic materials, and vinblastine was encapsulated in the aqueous core of liposomes, respectively. The PNA modified vinblastine cationic liposomes were approximately 100 nm in size with a positive potential. In vitro results showed that the targeting liposomes could significantly enhance cellular uptake, selectively accumulate in LLT cells, and dramatically initiate apoptosis via activating pro-apoptotic proteins and apoptotic enzymes, thus leading to the strongest antitumor efficacy to LLT cells. In vivo results demonstrated that the targeting liposomes could display a prolonged circulation time in the blood, accumulate more drug in tumor location, and induce most of tumor cells apoptosis. As a result, a robust overall antitumor efficacy in tumor-bearing mice was observed subsequently. In conclusion, the chemotherapy using the PNA modified vinblastine cationic liposomes could provide a potential strategy for treating non-small cell lung cancer.

Peanut agglutinin appearance in the blood circulation after peanut ingestion mimics the action of endogenous galectin-3 to promote metastasis by interaction with cancer-associated MUC1.

Peanut agglutinin (PNA), which accounts for ~0.15% of the weight of the common peanut, is a carbohydrate-binding protein that binds the oncofoetal Thomsen-Friedenreich (TF) disaccharide (galactoseß1,3N-acetylgalactosamineα-) that is overexpressed by ~90% of human cancers. Previous studies have shown that PNA is highly resistant to cooking and digestion and rapidly enters the human blood circulation after peanut ingestion. This study investigates the hypothesis that PNA appearance in the circulation after peanut ingestion may mimic the actions of endogenous TF-binding human galectin-3 in metastasis promotion. It shows that PNA at concentrations similar to those found in blood circulation after peanut ingestion increases cancer cell heterotypic adhesion to the blood vascular endothelium and enhances the formation of tumour cell homotypic aggregates, two important steps in the metastasis cascade, and enhances metastasis in a mouse metastasis model. These effects of PNA are shown to result from its interaction with the cancer-associated TF disaccharide on the transmembrane mucin protein MUC1, causing MUC1 cell surface polarization that reveals underlying cell surface adhesion molecules. Thus, PNA appearance in the blood circulation after peanut ingestion mimics the actions of endogenous galectin-3 and promotes cancer cell metastatic spread by interaction with cancer-associated TF/MUC1. As metastasis accounts for the majority of cancer-associated fatality, regular consumption of peanuts by cancer patients would therefore be expected to have an adverse effect on cancer survival.

In vitro and in vivo antitumor effects of Peanut agglutinin through induction of apoptotic and autophagic cell death.

In this study we unravel the mechanism underlying the antitumorigenic effects of Peanut agglutinin (PNA) isolated from Arachis hypogea in Dalton's lymphoma (DL) bearing mice and elucidated the mechanism in vitro in HeLa cells. In vivo PNA administration at 1 and 2 mg/kg body weight reduced DL proliferation with increase in autophagic and apoptotic characteristics. In vitro data showed that PNA at 0.1-100 µg/ml dose exhibit selective antiproliferative activity on various cancer cell lines without displaying cytotoxic effect on normal cells. However, heat denatured PNA failed to show any antiproliferative activity. Moreover, PNA was found to induce autophagic and apoptotic cell death in HeLa cells. Exponential increase in reactive oxygen species (ROS) was proved to be the master signal for promoting PNA induced cell death in HeLa cells. Interestingly, when HeLa cells were pre-exposed with N-acetylcysteine (NAC) and followed to PNA treatment, there was sharp decline in autophagy, apoptosis and a concomitant abrogation of antiproliferative potential. PNA at lower doses was also seen to inflict senescence. Hence, this common culinary item derived molecule whose discovery dates back to late 1970s was for the first time evaluated mechanistically in vivo and in vitro as a novel naturally occurring therapeutic agent against cancer.

Probing bacterial-toxin inhibition with synthetic glycopolymers prepared by tandem post-polymerization modification: role of linker length and carbohydrate density.

Probing the depths: A tandem post-polymerization modification strategy was used to systematically probe the multivalent inhibition of a bacterial toxin as a function of linker length (see scheme), carbohydrate density, and glycopolymer chain length. Guided by structural-biology information, the binding-pocket depth of the toxin was probed and used as a means to specifically improve inhibition of the toxin by the glycopolymer.

Affinity of anti-insulin-like growth factor Ι receptor antibody binding to the receptor altered by plant lectins.

The binding ability of anti-insulin-like growth factor Ι receptor (IGF-ΙR) single-chain variable fragments (scFvs) to IGF-IR was measured in the presence of plant lectins. Combinations of concanavalin A (Con A), wheat germ agglutinin (WGA), or peanut agglutinin (PNA) and 1H7 or 3B7 anti-IGF-ΙR scFv/phage antibodies that were previously produced and characterized were used. WGA inhibited binding of both scFvs proteins to the receptor. PNA slightly enhanced the binding of 1H7 scFv and phage antibody to the receptor. Con A led to enhancement of 3B7 scFv-binding but had no effect in a test of phage antibodies and determination of kinetic parameters. The effect of lectins differed for scFvs and phage antibodies, implying that affinity altered by lectins is dependent upon the molecular structure of the antibodies. Results indicated that animal lectins may affect the affinity of therapeutic antibodies targeting cell membrane receptors in vivo.

Lectins influence chondrogenesis and osteogenesis in limb bud mesenchymal cells.

The role of cell surface glycoproteins in cell behavior can be characterized by their interactions with plant lectins. This study was designed to identify the effects of lectins on chondrogenesis and osteogenesis in limb bud mesenchymal cells in vitro. Limb bud mesenchymal cells from mouse embryos were cultured in high-density micromass culture. Wheat germ agglutinin (WGA), concanavalin A (ConA), peanut agglutinin (PNA), Dolichos biflorus agglutinin (DBA) and Ricinus communis agglutinin (RCA) were added separately to the culture media. Cells were cultured for 5 or 9 days, and cell viability was assayed by neutral red on day 5. The micromasses were stained with alcian blue, alizarin red S and Von Kossa stains, and alkaline phosphatase assays were also done. Dolichos biflorus agglutinin induced an increase in chondrogenesis, calcium precipitation and proteoglycan production. ConA and PNA did not affect chondrocyte differentiation but induced chondrocytes to produce more proteoglycan. Wheat germ agglutinin reduced chondrification and ossification but induced mesenchymal cells to store lipid droplets. Ricinus communis agglutinin 1 was toxic and significantly reduced cell survival. In conclusion, DBA was the most effective inducer of ossification and chondrification. Wheat germ agglutinin induced adipogenesis instead. These assays showed that lectins play important roles in limb bud development.

Growth-inhibiting extracellular matrix proteins also inhibit electrical activity by reducing calcium and increasing potassium conductances.

Inhibitionof neurite sprouting and electrical activity by extracellular matrix (ECM) glycoproteins was studied during neurite regeneration by using anterior pagoda (AP) neurons of the leech. Adult isolated neurons were plated in culture inside ganglion capsules, which among many ECM proteins, contain a group of inhibitory peanut lectin- (PNA) binding glycoproteins. These proteins inhibit neurite production and contribute to the formation of a bipolar outgrowth pattern by AP neurons. Addition of PNA lectin to the culture medium to block the inhibitory effects of ECM glycoproteins induced an increase of neurite sprouting, the loss of the bipolar pattern, and also an increase in the amplitude and duration of action potentials evoked by intracellular current injection. PNA lectin had independent effects on neurite sprouting and electrical activity, since there was no correlation between the total neurite length and the amplitude of the action potentials. Moreover, action potentials were increased by the presence of PNA lectin even in neurons that did not grow. The changes induced by PNA lectin on the active conductances underlying the action potentials were estimated by quantitative model simulations. We predict that the increases in the amplitude and duration of the action potential induced by PNA lectin were due to an increase in a calcium conductance and a reduction in the delayed rectifier potassium conductance. Our results suggest that inhibitory ECM glycoproteins may use independent signaling pathways to inhibit neurite sprouting and electrical activity. These proteins affect the action potential by changing the proportion of inward and outward active conductances.

A rapid assay of the sialidase activity in species of the Bacteroides fragilis group by using peanut lectin hemagglutination.

In this study, a novel, simple and rapid hemagglutination assay by using a peanut lectin to detect a neuraminidase activity in strains of the Bacteroides fragilis group was developed. One hundred and fourteen species of the B. fragilis group isolated from children with and without diarrhea and 15 reference strains were evaluated. Neuraminidase production was determined by using the method above described and its inhibition was observed by using galactose. The neuraminidase production was observed in 54 (84.37%) diarrhea and in 43 (86%) non-diarrhea strains. HA titers were ranged from 2 to 32. This neuraminidase assays based on PNA hemagglutination is highly sensitive, reproducible and could be used as a tool to detect the sialidase activity in anaerobic bacteria, particularly, in species of the B. fragilis group.

Lipopolysaccharide and lipoteichoic acid induce different innate immune responses in bovine mammary epithelial cells.

The objective of the present study was to characterize the innate immune responses induced by in vitro stimulation of bovine primary mammary epithelial cells (bMEC) using gram-negative lipopolysaccharide (LPS) and gram-positive lipoteichoic acid (LTA) bacterial cell wall components. Quantitative real-time PCR (qRT-PCR) was employed to examine the mRNA expression of a panel of 22 cytokines, chemokines, beta-defensins and components of the Toll-Like Receptor signaling pathway. Stimulation of bMEC with LPS for 24h elicited a marked increase in mRNA expression for IL-1beta, IL-8, TNFalpha, CXCL6 and beta-defensin while members of the Toll-Like Receptor pathway, although present, were largely unaffected. Surprisingly, stimulation of these cells with LTA for 24 h did not significantly alter the expression of these genes. A time course of the expression of IL-1beta, IL-8, TNFalpha, CXCL6 and beta-defensin was subsequently performed. The mRNA levels of all genes increased rapidly after stimulation for 2-4 h with both LPS and LTA but only the former treatment resulted in sustained responses. In contrast, the increased gene expression for LTA stimulated cells returned to resting levels after 8-16 h with the exception of beta-defensin, which remained up-regulated. The limited and unsustained cytokine response to LTA may explain why mastitis caused by gram-positive bacteria has greater potential for chronic intra-mammary infection than gram-negative infection. It was concluded that bovine mammary epithelial cells have a strong but differential capacity to mount innate immune responses to bacterial cell wall components.

Neuraminidase production by Erysipelothrix rhusiopathiae.

In order to characterise neuraminidase activity by Erysipelothrix, 85 isolates of Erysipelothrix spp. from a variety of sources including human clinical, marine and terrestrial animals, and the environment were investigated for neuraminidase production. Neuraminidase activity was detected by a peanut lectin haemagglutination method. The effects of media, incubation conditions and pH on the production and activity of neuraminidase were also investigated. Enzyme activity was detected only in the supernatants of the isolates of Erysipelothrix rhusiopathiae which had been incubated in cooked meat broth and Todd Hewitt broth supplemented with horse serum after 16 and 36 h incubation at 37 degrees C. The maximum titres were reached at 40 h in cooked meat broth and 56 h in Todd Hewitt broth supplemented with horse serum. All 58 isolates and the type strain (ATCC 19414) of E. rhusiopathiae produced detectable neuraminidase activity with titres between 10 and 320. The optimal pH for the enzyme activity varied among the isolates with a pH between 6.0 and 7.0 covering the highest enzyme activity of the most. There was no statistically significant difference in the level of neuraminidase activity between isolates from different sources (p > 0.05). Neuraminidase activity was not detected in the non-pathogenic Erysipelothrix spp. such as E. tonsillarum. Neuraminidase was detected only in E. rhusiopathiae suggesting its possible role as a virulence factor. Enzyme production and activity were medium and pH dependent. The peanut lectin haemagglutination assay is a simple, rapid and sensitive method and is particularly useful for the analysis of multiple samples.

Intradermal exposure of BALB/c strain mice to peanut protein elicits a type 2 cytokine response.

There is a growing need for the development of methods to characterize the allergenic properties of novel proteins, particularly those expressed by transgenic crop plants. Hence, there is considerable interest in the development of suitable animal models for this purpose. The production of specific IgE antibody has been reported following sensitization with food allergen via oral or systemic (intraperitoneal) routes of exposure. We have characterized cytokine profiles induced by intradermal treatment of BALB/c strain mice with a purified peanut allergen, Arachis hypogea lectin. Mice were exposed to peanut lectin by intradermal administration and the cytokine responses in the lymph node draining the site of exposure analyzed at the secreted protein level by enyzme-linked immunosorbent assay (ELISA) and cytokine mRNA level by ribonuclease protection assay (RPA). Exposure to peanut lectin, under conditions that induced robust IgE antibody titers, was found to be associated with a T helper 2 (Th2)-type cytokine expression profile at both the mRNA and secreted protein levels. Culture of naïve lymph node cells with peanut lectin failed to stimulate marked proliferation or cytokine production, confirming this protein is not mitogenic for mouse lymphocytes. Furthermore, the expression of Th2 cytokines was associated with the effector/memory CD62L- cell population. Similar treatment with a non-allergenic protein, potato acid phosphatase, failed to induce Th2 cytokine expression. These data demonstrate that exposure of mice to peanut allergen results in the selective stimulation of a Th2-type response.

The influence of dietary lectins on the cell proliferation of human breast cancer cell lines in vitro.

BACKGROUND: Lectins, carbohydrate proteins, bind non-covalently to glycoconjugate of normal and malignant cells. If used in cell culture, they can influence cellular proliferation. In this study the in vitro effects of six dietary lectins on the cell proliferation of human breast cancer cell lines were investigated. MATERIALS AND METHODS: Cell proliferation was assessed by a colorimetric XTT-based assay kit. Lectin binding was characterized by lectin histochemistry. RESULTS: WGA considerably influenced the cell growth of all tested cell lines (MCF-7, T 47D, HBL 100, BT 20), whereas the effects of PHA-L, SBA and HPA were smaller, began at higher concentrations and were restricted to three cell lines (MCF-7, T 47D and HBL 100 for PHA-L; MCF-7, T 47D and BT 20 for SBA, respectively) and to one cell line (HBL 100 for HPA). STA and PNA had no effect at all. CONCLUSION: The present data suggested that some dietary lectins can inhibit cell growth of human breast cancer cells in vitro. These findings would argue for a protective effect of these plant lectins for breast cancer.

Localization and characterization of phenamil-sensitive Na+ influx in isolated rainbow trout gill epithelial cells.

Percoll density-gradient separation, combined with peanut lectin agglutinin (PNA) binding and magnetic bead separation, was used to separate dispersed fish gill cells into sub-populations. Functional characterization of each of the sub-populations was performed to determine which displayed acid-activated phenamil- and bafilomycin-sensitive Na(+) uptake. Analysis of the mechanism(s) of (22)Na(+) influx was performed in control and acid-activated (addition of 10 mmoll(-1) proprionic acid) cells using a variety of Na(+) transport inhibitors (ouabain, phenamil, HOE-694 and bumetanide) and a V-type ATPase inhibitor (bafilomycin). We found that cells migrating to a 1.03-1.05 g ml(-1) Percoll interface [pavement cells (PVCs)] possessed the lowest rates of Na(+) uptake and that influx was unchanged during either bafilomycin (10 nmoll(-1)) treatment or internal acidification with addition of proprionic acid (10 mmoll(-1)). Mitochondria-rich (MR) cells that migrated to the 1.05-1.09 g ml(-1) interface of the Percoll gradient demonstrated acidification-activated bafilomycin and phenamil-sensitive Na(+) influx. Further separation of the MR fraction into PNA(+) and PNA(-) fractions using magnetic separation demonstrated that only the PNA(-) cells (alpha-MR cells) demonstrated phenamil-and bafilomycin-sensitive acid-activated (22)Na(+) uptake. We confirm the coupling of a V-type H(+)-ATPase with phenamil-sensitive Na(+) uptake activity and conclude that high-density alpha-MR cells function in branchial Na(+) uptake in freshwater fish.

Enhanced expression of a peanut agglutinin reactive O linked oligosaccharide on fibronectins from the synovial fluid of patients with rheumatic disease: quantitation, domain localization, and functional significance.

OBJECTIVE: To characterize the domain localization, quantitation, and functional binding consequences of an O linked oligosaccharide expressed on synovial fluid (SF) fibronectin (Fn). METHODS: Identification and localization of the O linked oligosaccharide was performed by limited digestion of isolated SF Fn with a series of proteolytic enzymes followed by Western blotting with peroxidase labeled peanut agglutinin. Binding affinity to denatured collagen was performed utilizing a solid phase gelatin-binding assay. Quantitation was performed by measuring purified Fn in an antibody-lectin sandwich binding assay. RESULTS: A desialyated O linked oligosaccharide was identified on the C-terminal 18 kDa segment of the SF Fn collagen-binding domain. These SF collagen-binding Fn fragments were more basic and had higher gelatin-binding affinities than corresponding plasma fibronectin fragments. Expression of this O linked oligosaccharide was highest on Fn isolated from osteoarthritic SF, followed by Fn isolated from rheumatoid arthritis SF, and finally normal human plasma. CONCLUSION: Fn isolated from SF have glycosylation alterations that may influence their biologic properties in the diseased joint.

Effects of wheat germ agglutinin and concanavalin A on the accumulation of glycosaminoglycans in pericellular matrix of human dermal fibroblasts. A comparison with insulin.

The effect of insulin, wheat germ agglutinin (WGA), peanut agglutinin (PNA) and concanavalin A (ConA) on [3H]glucosamine incorporation into pericellular glycosaminoglycans (GAGs) was investigated in two lines of cultured human dermal fibroblasts. Insulin and WGA stimulated [3H]glucosamine incorporation into hyaluronic acid (HA) and heparan sulphate (HS) without any alteration of chondroitin sulphate (CS) and dermatan sulphate (DS) contents. ConA increased [3H]glucosamine incorporation into HS, CS and DS, but had no effect on [3Hglucosamine incorporation into HA. PNA affected neither the content, nor the composition of GAGs. In contrast to PNA, ConA and WGA stimulated glycolysis and demonstrated an evident antiproliferative effect on dermal fibroblasts. Thus, both the insulin-like action of WGA and ConA on cultured dermal fibroblasts and the differences between the effects of lectins on modulation of GAGs synthesis appear to be determined by their chemical structure.

Distribution of S- and M-cones in normal and experimentally detached cat retina.

The lectin peanut agglutinin (PNA) and antibodies to short (S)- and medium to long wavelength (M/L)-sensitive cones were utilized in order to define the relative distributions of the two spectral types of cone across the domestic cat's retina. These values, in turn, were compared to those from retinas that had been experimentally detached from the retinal pigment epithelium. The pattern of cone distribution in the normal cat's retina is established by the preponderance of M-cones that constitute between 80% and 90% of all cones. Their peak density of over 26,000 cells/mm(2) resides at the area centralis. Though M-cone density decreases smoothly to the ora serrata where they have densities as low as 2,200 cells/mm(2), the density decrease along the nasotemporal axis is slower,creating a horizontal region of higher cone density. S-cones constitute between 10% and 20% of all cones, the number being quite variable even between individual animals of similar age. The highest S-cone densities are found in three distinct locations: at the superior far periphery near the ora serrata, immediately at the area centralis itself, and in a broad zone comprising the central and lower half of the inferior hemiretina. S-cones in the cat retina do not form a regular geometrical array at any eccentricity. As for the detached cat retina, the density of labeled S-cone outer segments (OS) decreases rapidly as early as 1 day postdetachment and continues decreasing to day 28 when the density of cones labeling with anti-S opsin has dropped to less than 10% of normal. This response points to a profound difference between rods and cones; essentially all rods, including those without OS, continue to express their opsin even in long-term detachments. The implications of these results for visual recovery after retinal reattachment are discussed.

Systemic effect of peanut agglutinin following intravenous infusion into rats.

BACKGROUND: Ingested peanut agglutinin stimulates colonic proliferation in humans. In rats, ingested peanut agglutinin stimulates hormone release and proliferation in the small and large intestines. Peanut agglutinin is absorbed into the circulation but little is known about the systemic effect of this lectin. Therefore, we studied the effect of intravenous peanut agglutinin on hormone release and intestinal growth. METHOD: Six rats per group received peanut agglutinin infusion at 0, 2, 20 or 200 microg/rat/day for 6 days via the right jugular vein. Organ weights were measured, pancreatic enzymes, DNA, RNA and protein levels were analysed. Plasma hormones were measured by radioimmunoassay. All tissues were examined histologically. Small intestinal and colonic proliferation rates were estimated by metaphase arrest. RESULTS: High-dose peanut agglutinin significantly reduced the wet weight of the stomach by 7% (P < 0.05) and large intestine by 10% (P < 0.05). Peanut agglutinin dose-dependently released enteroglucagon; low-, medium- and high-dose by 64%, 126% (P < 0.01) and 180% (P < 0.01), respectively, and glucagon-like peptide-1 by 127% (P < 0.01), 169% (P < 0.01) and 315% (P < 0.001), respectively. Peanut agglutinin had no effect on cholesystokinin, gastrin or insulin levels. Peanut agglutinin, low-, medium- and high-dose stimulated proliferation in the mid colon by 42% (P < 0.01), 30% and 38%, respectively. Only high-dose peanut agglutinin stimulated proliferation in the distal colon by 54% (P < 0.01). No histological changes were evident in any tissue. CONCLUSION: Intravenous peanut agglutinin released hormones and stimulated colonic proliferation. Proliferation of the small intestine seen after ingestion of peanut agglutinin in previous studies appears to require luminal contact between enterocytes and the lectin. Possible clinical applications include reversal of atrophy during total parenteral nutrition, anastomotic healing after surgery and restoration of mucosa integrity in colitis.