Electron-cytochemical study of carbohydrate components of the surface membrane of cultured neurons of the edible snail Helix pomatia

An electron-cytochemical study of the structure and topography of carbohydrate determinants of the surface membrane of CNS neurons of the edible snailHelix pomatia cultured in vitro was carried out by means of a set of colloidal goldlabeled lectins. An analysis of binding of lectins having different specificity to carbohydrate determinants shows the inhomogeneity of the carbohydrate pool of the membrane of the body of nerve cells having a different mediator nature. It was established that monoaminergic and peptidergic neurons equally bind lectins PNA, RCA, and WGA and do not demonstrate binding with PVA and LPA. Here HPA, a product of the albumen gland of the edible snailH. pomatia, marks only the membrane of peptidergic neurons. A conclusion is made about the absence of terminal residues of sialic acid on the membrane of many types of the snail neurons, which may be due to characteristics of its molecular structure. It is suggested also that the differences in the carbohydrate composition of the glycocalyx of different types of cells can serve as the basis for the formation of specific connections between different types of neurons of the developing brain.A. A. Bogomolets Institute of Physiology, Ukrainian Academy of Sciences, Kiev. Translated from Neirofiziologiya, Vol. 24, No. 3, pp. 291–298, May–June, 1992.     

Cell type-specific binding of Ricinus lectin to murine cerebellar cell surfaces in vitro

Summary The binding of several plant lectins, Concanavalin A (ConA), Lens culinarisA (LCA), wheat germ agglutinin (WGA), and Ricinus communis agglutinin 120 (RCA120) to cell surfaces of developing mouse cerebellar cells was assayed by the use of fluorescein isothiocyanate (FITC)-conjugated compounds. Freshly dissociated, live single-cell suspensions from 6-day-old mouse cerebellum contain 93% ConA, 99% LCA, 98% WGA, and 59% RCA 120-positive cells with ring fluorescence. Of the RCA 120-positive cells, 4% express a high and 55% a lower or very low number of lectin receptors. Flow cytometric analysis of fluorescent lectin binding yields results qualitatively similar to those obtained by scoring positive and negative cells in the fluorescence microscope.In monolayer cultures of 6-day-old mouse cerebellum practically all cells express receptors for ConA, LCA, and WGA, whereas RCA 120 binding sites are absent from neurons with small cell bodies (granule, basket and stellate cells) and present in large number on neurons with large cell bodies (Purkinje and possibly Golgi Type-II cells) and fibroblasts. RCA 120 receptors are weakly expressed on astro-and oligodendroglia. Cell type-specific expression of RCA 120 receptors is constant throughout all ages studied (embryonic day 13 to postnatal day 9). At early embryonic ages the proportion of highly fluorescent neurons with large cell bodies is significantly increased.     

Effect on fertilization and localized binding of lectins in the ascidian Phallusia mammillata

The effect of concanavalin A (conA), fucose-binding protein (FBP), Ricinus communis agglutinin (RCA), and wheat germ agglutinin (WGA) on fertilization of the ascidian Phallusia mammillata was investigated. ConA, FBP, and RCA had no influence on fertilization and did not bind to the chorion or sperm, as determined with FITC-conjugated conA and by electron microscopy with gold-labelled FBP. WGA (100 μg/ml) prevented fertilization of eggs by sperms in concentrations which gave 100% fertilization in controls (2 × 10⁷ sperm/ml). N-Acetyl-glucosamine (50 mM) abolished the effect of WGA, whereas an excess (100 mM) of this competitive sugar alone did not affect fertilization. FITC-conjugated and gold-labelled WGA revealed binding sites on the chorion, but not on follicle cells nor sperms. Electron microscopy showed that WGA gold-markers are bound to the fibrillar network forming the outer layer of the chorion and indicate that WGA inhibits fertilization by interfering with sperm binding to the chorion. Binding of WGA to the chorion may either mask sperm binding receptors or cause chorion resistance to sperm enzymes.     

Lectin binding to injured corneal endothelium mimics patterns observed during development

Fluorochrome conjugated lectins were used to observe cell surface changes in the corneal endothelium during wound repair in the adult rat and during normal fetal development. Fluorescence microscopy of non-injured adult corneal endothelia incubated in wheat-germ agglutinin (WGA), Concanavalin A (Con A), and Ricinus communis agglutinin I (RCA), revealed that these lectins bound to cell surfaces. Conversely, binding was not observed for either Griffonia simplicifolia I (GS-I), soybean agglutinin (SBA) or Ulex europaeus agglutinin (UEA). Twenty-four hours after a circular freeze injury, endothelial cells surrounding the wound demonstrated decreased binding for WGA and Con A, whereas, RCA binding appeared reduced but centrally clustered on the apical cell surface. Furthermore, SBA now bound to endothelial cells adjacent to the wound area, but not to cells near the tissue periphery. Neither GS-I nor UEA exhibited any binding to injured tissue. By 48 h post-injury, the wound area repopulates and endothelial cells begin reestablishing the monolayer. These cells now exhibit increased binding for WGA, especially along regions of cell-to-cell contact, whereas, Con A, RCA and SBA binding patterns remain unchanged. Seventy-two hours after injury, the monolayer is well organized with WGA, Con A and RCA binding patterns becoming similar to those observed for non-injured tissue. However, at this time, SBA binding decreases dramatically. By 1 week post-injury, binding patterns for WGA, ConA and RCA closely resemble their non-injured counterparts while SBA continues to demonstrate low levels of binding. In early stages of its development, the endothelium actively proliferates and morphologically resembles adult tissue during wound repair.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cellular heterogeneity in normal human urothelium: Quantitative studies of lectin binding

Summary A panel of 10 FITC-labelled lectins (MPA, PNA, ConA, DBA, SBA, RCA-120, WGA, UEA, GS-I, GS-II) was applied to cryosections of seven specimens of normal urothelium. Seven of the lectins (MPA, ConA, RCA, WGA, UEA, GS-I and GS-II) showed a pattern of increasing fluorescence intensity from basal to superficial cells of the urothelium whereas PNA, DBA and SBA showed more uniform binding throughout the urothelium. Urothelial cell suspensions labelled with FITC-lectins were studied by flow cytometry to quantify the variation in binding to different cells types. Three cellular subpopulations were identified in normal urothelium on the basis of their optical properties. Fluorescence intensity due to specific lectin binding was then measured separately for each subpopulation. Although there was some variation among individual cases, a general pattern emerged in this small series. WGA, RCA, and GS-II bind in large quantities to all urothelial cells while PNA, SBA, ConA and DBA show little binding. MPA, RCA, UEA and GS-I showed the most marked increase in fluorescence intensity from basal to superficial cells as observed microscopically and quantified by flow cytometry.     

Lectin binding to injured corneal endothelium mimics patterns observed during development

Summary Fluorochrome conjugated lectins were used to observe cell surface changes in the corneal endothelium during wound repair in the adult rat and during normal fetal development. Fluorescence microscopy of non-injured adult corneal endothelia incubated in wheat-germ agglutinin (WGA), Concanavalin A (Con A), and Ricinus communis agglutinin I (RCA), revealed that these lectins bound to cell surfaces. Conversely, binding was not observed for either Griffonia simplicifolia I (GS-I), soybean agglutinin (SBA) or Ulex europaeus agglutinin (UEA). Twenty-four hours after a circular freeze injury, endothelial cells surrounding the wound demonstrated decreased binding for WGA and Con A, whereas, RCA binding appeared reduced but centrally clustered on the apical cell surface. Furthermore, SBA now bound to endothelial cells adjacent to the wound area, but not to cells near the tissue periphery. Neither GS-I nor UEA exhibited any binding to injured tissue. By 48 h post-injury, the wound area repopulates and endothelial cells begin reestablishing the monolayer. These cells now exhibit increased binding for WGA, especially along regions of cell-to-cell contact, whereas, Con A, RCA and SBA binding patterns remain unchanged. Seventy-two hours after injury, the monolayer is well organized with WGA, Con A and RCA binding patterns becoming similar to those observed for non-injured tissue. However, at this time, SBA binding decreases dramatically. By 1 week post-injury, binding patterns for WGA, ConA and RCA closely resemble their non-injured counterparts while SBA continues to demonstrate low levels of binding. In early stages of its development, the endothelium actively proliferates and morphologically resembles adult tissue during wound repair. The 16-day fetal tissue is mitotically active, does not exhibit a well defined monolayer, and demonstrates weak fluorescence binding for WGA, Con A and RCA. Conversely, SBA binding is readily detected on many cell surfaces. By 19 days in utero, the endothelial monolayers becomes organized and cell proliferation greatly diminishes. WGA, Con A and RCA now exhibit binding similar to that seen in the adult tissue. SBA binding is not detected at this time. Thus, changes in lectin binding during wound repair of the adult rat corneal endothelium mimic changes in lectin binding seen during the development of the tissue.Supported by grant EY-06435 from The National Institutes of Health     

The Effect of Concanavalin A on Membrane Potential and Intracellular pH during Activation In Vitro of Tobacco Pollen Grains

We studied the effects of short-term (5–10 min) treatment of Nicotiana tabacum L. pollen grains with concanavalin A (ConA) on their activation (changes in the membrane potential and intracellular pH) and germination in vitro. ConA (10–1000 g/ml) induced plasma membrane hyperpolarization in the vegetative cell and enhanced pollen grain germination. These effects depended on ConA concentration and were interrelated: the value of the membrane potential was negatively correlated with the number of pollen grains germinated for 1 h of their incubation (r = –0.96). In addition, ConA (100 g/ml) increased the intracellular pH value by 0.3 unit. All these effects of ConA are determined by its specific interaction with carbohydrate determinants because a competitive sugar methyl--mannopyranoside (0.1 M) completely blocked ConA effects. The data obtained presume that the specific receptors are present on the surface of pollen grains, evidently on their plasma membrane, and their interaction with lectins has a functional significance for pollen grain activation and germination.     

Differences in lectin binding patterns of normal human endometrium between proliferative and secretory phases

Lectin binding patterns in normal human endometrium were examined by light and electron microscopy using seven different lectins (ConA, WGA, RCA, PNA, UEA-1, DBA, and SBA). For light microscopic observations, criteria based on the incidence and intensity of cells positive for the lectin staining were adopted to evaluate the different staining patterns of the proliferative and secretory endometria obtained by the avidin-biotin-peroxidase complex (ABC) technique. At the light microscopic level, ConA, WGA, and RCA stained endometrial glandular cells in both phases. The number of PNA-positive cells with the binding sites entirely limited to the apical surface tended to be reduced slightly in the secretory phase. UEA-1 weakly stained the apical surface of glandular cells in the proliferative phase but not in the secretory phase. Among the lectins used in this study, DBA and SBA displayed remarkable changes between the phases. That is, in the proliferative phase they produced only a faint or slight positive stain at the apical surface, but the incidence and intensity of DBA- and the SBA-positive glandular cells increased in the secretory phase. By electron microscopy, the reaction product of ConA was observed in the plasma membrane, endoplasmic reticulum, nuclear envelope, and the Golgi apparatus, and the binding sites of RCA and DBA were observed in the plasma and Golgi membranes. Between both phases, the reactivity of ConA and RCA showed almost no change. However, the secretory endometrial cells containing the DBA-positive Golgi apparatus were markedly increased in number compared with the proliferative ones bearing the lectin-positive organelles.(ABSTRACT TRUNCATED AT 250 WORDS)     

Characterization of carbohydrates of adult Echinococcus granulosus by lectin-binding analysis

The identification of lectin-binding structures in adult worms of Echinococcus granulosus was carried out by lectin fluorescence; the distribution of carbohydrates in parasite glycoconjugates was also studied by lectin blotting. The lectins with the most ample recognition pattern were ConA, WGA, and PNA. ConA showed widespread reactivity in tegument and parenchyma components, including the reproductive system, suggesting that mannose is a highly expressed component of the adult glycans. Although reproductive structures appeared to be rich in N-acetyl-D-glucosamine (GlcNAc)-N-acetyl neuraminic acid (NeuAc) and galactose (Gal) as demonstrated by their strong reactivity with WGA and PNA, respectively, some differences were observed in their labeling patterns. This was very clear in the case of the vagina, which only reacted with WGA. Furthermore, WGA and ConA both had reactivity with the excretory canals. RCA, the other Gal binding lectin used, only reacted with the tegument, suggesting that widespread PNA reactivity with the reproductive system is related to the presence of the D-Gal-beta-(1,3)D-GalNAc terminal structure. UEA I failed to bind to any parasite tissues as determined by lectin fluorescence, whereas DBA and SBA showed a very faint staining of the tegument. However, in transferred glycans, N-acetyl-D-galactosamine (GalNAc) and fucose (Fuc) containing glycoproteins were distinctly detected.     

138 Molecular Evolution of Glutamine Synthetase In Protists

The binding of fluorescein isothiocyanate (FITC) conjugated lectins to gametes of Aglaothamnion byssoides Itono during the fertilization was studied by the use of confocal microscope. The physiological effects of lectins and carbohydrates on gamete binding were also examined. Three lectins, concanavalin A (ConA), Soybean agglutinin (SBA) and wheat germ agglutinin (WGA) bound to the surface of spermatia, but each lectin labeled different region of the spermatium. SBA bound only to the spermatial appendages but ConA bound to the whole spermatial surface except spermatial appendages. WGA labeled narrow region which connects spermatial body and appendages. During fertilization, ConA and WGA specific substances on the spermatial surface moved towards the area contacting with trichogyne and accumulated on the surface of fertilization canal. Spermatial binding to trichogynes was inhibited by pre-incubation of spermatia with SBA, while trichogyne receptors were blocked by the complementary carbohydrate, N-acetyl-D-galactosamine. WGA and its complementary carbohydrate had little effect on gamete binding. For searching the step of sexual isolation, crossing experiment was performed between Aglaothamnion byssoides and twelve other red algal species. Results showed that the gamete recognition was genus-specific: the gametes bound freely with their partners of the same genus. When two species from same genus were crossed, sexual isolation occurs gradually during the fertilization process. Therefore, sexual isolation in red algae appears to be determined by multi-step process and gamete binding is the initial step.     

Lectin staining of cultured CNS microglia.

Carbohydrate binding proteins, known as lectins, bind to specific sugar groups on most membranes. We used fluorescent and light microscopy to study the interaction of various lectins with the membranes of microglia cultured from neonatal rat or fetal mouse cerebral cortices. Microglia stained intensely with GS-1, RCA, WGA, and ConA and slightly with DBA, UEA, BPA, and SBA. No staining was seen with GS-2, MPA, or PNA. Staining was specific for microglia in the mixed glial cultures and was dose dependent. In addition, microglial lectin binding could be reduced or blocked by competitive inhibition using specific sugars. Treatment of the microglia with agents such as dimethylsulfoxide (DMSO), interleukin-1 (IL-1), interferon (IFN), or lipopolysaccharide (LPS) did not eliminate lectin staining, although the degree of staining was altered. Positive staining of the microglia was also associated with a functional change for at least one lectin, i.e., ConA. Superoxide anion production by microglia was increased in the presence of ConA. Overall, binding of the lectins GS-1, RCA, WGA, and ConA can be used as an identifying tool for microglia in glial cultures, but intensity of staining varies depending on their functional state.     

137 Gamete Recognition and Sexual Isolation in a Red Alga,Aglaothamnion Byssoides (Rhdophyta)

The binding of fluorescein isothiocyanate (FITC) conjugated lectins to gametes of Aglaothamnion byssoides Itono during the fertilization was studied by the use of confocal microscope. The physiological effects of lectins and carbohydrates on gamete binding were also examined. Three lectins, concanavalin A (ConA), Soybean agglutinin (SBA) and wheat germ agglutinin (WGA) bound to the surface of spermatia, but each lectin labeled different region of the spermatium. SBA bound only to the spermatial appendages but ConA bound to the whole spermatial surface except spermatial appendages. WGA labeled narrow region which connects spermatial body and appendages. During fertilization, ConA and WGA specific substances on the spermatial surface moved towards the area contacting with trichogyne and accumulated on the surface of fertilization canal. Spermatial binding to trichogynes was inhibited by pre‐incubation of spermatia with SBA, while trichogyne receptors were blocked by the complementary carbohydrate, N‐acetyl‐D‐galactosamine. WGA and its complementary carbohydrate had little effect on gamete binding. For searching the step of sexual isolation, crossing experiment was performed between Aglaothamnion byssoides and twelve other red algal species. Results showed that the gamete recognition was genus‐specific: the gametes bound freely with their partners of the same genus. When two species from same genus were crossed, sexual isolation occurs gradually during the fertilization process. Therefore, sexual isolation in red algae appears to be determined by multi‐step process and gamete binding is the initial step.     

Distribution of glycoconjugates on the plasma membrane and on membranes of the open-canalicular system in human platelets. A cytochemical study

Distribution of carbohydrate moieties in the membrane system of the human blood platelet was studied by electron microscopy employing lectins as a probe. Glutaraldehyde-fixed platelets were treated with biotinylated-lectins (ConA, RCA, WGA, PNA, SBA, DBA and UEA-1) and labeled with horseradish peroxidase-conjugated avidin. Among the lectins used, ConA bound uniformly to the plasma membrane as well as to the membrane of the open-canalicular system (OCS). Other lectins showed more or less reduced binding on the OCS membrane compared with that on the plasma membrane, indicating that there exist regional differences in the distribution pattern of glycoconjugates in the membrane system of the platelet. The relationship of the distribution pattern of the glycoconjugates with the distribution of the major platelet glycoproteins GPIb and GPIIbIIIa is discussed.     

Distribution of glycoconjugates on the plasma membrane and on membranes of the open-canalicular system in human platelets

Summary Distribution of carbohydrate moieties in the membrane system of the human blood platelet was studied by electron microscopy employing lectins as a probe. Glutaraldehyde-fixed platelets were treated with biotinylatedlectins (ConA, RCA, WGA, PNA, SBA, DBA and UEA-1) and labeled with horseradish peroxidase-conjugated avidin. Among the lectins used, ConA bound uniformly to the plasma membrane as well as to the membrane of the opencanalicular system (OCS). Other lectins showed more or less reduced binding on the OCS membrane compared with that on the plasma membrane, indicating that there exist regional differences in the distribution pattern of glycoconjugates in the membrane system of the platelet. The relationship of the distribution pattern of the glycoconjugates with the distribution of the major platelet glycoproteins GPIb and GPIIbIIIa is discussed.     

Lectin-mediated agglutination of preimplantation mouse embryos

Plant lectins were used to monitor qualitative changes in carbohydrate-containing receptors during preimplantation mouse development. Beginning at the morula stage, an age-related decline was observed in agglutination of early mouse embryos by concanavalin A (ConA). In contrast, wheat germ agglutinin (WGA) and Ricinus communis agglutinin (RCA) agglutinated embryos strongly throughout preimplantation development.     

Differential effects of lectins mediating erythrocyte attachment and ingestion by macrophages

Lectin-mediated interaction of erythrocytes and macrophages was brought about in two steps. Step I involved macrophage treatment with lectin, and step II is the incubation of lectin-treated macrophages with mouse erythrocytes. The extent and nature of lectin-mediated macrophage erythrocyte interaction was studied using concanavalin A (ConA), wheat germ (WGA), soybean (SBA) and waxbean (WBA) agglutinins. The parameters affecting the interaction were studied in detail with the first two lectins.Under comparable conditions of lectin interaction with macrophages (step I), WGA mediates rosette formation involving interaction with several times the number of erythrocytes than those interacting with ConA-treated macrophages. The interaction mediated by WGA reaches, at 37 °C, a saturation value after 30 min of step II, whereas that mediated by ConA is still linear and exhibits half the amount of attached erythrocytes at 60 min. ConA-mediated attachment of erythrocytes is highly temperature-dependent being at 37 °C twice that observed at 24 °C. The temperature dependence of attachment is not affected by changes of either ConA concentration (5–40 μg/ml) or the temperature in step I. An optimum is observed, however, when the temperature of incubation in step I ranges between 14–18 °C. WGA-mediated attachment of erythrocytes is markedly less temperature-sensitive, exhibiting 70% of optimal attachment already at 8 °C. Only when the attachment phase follows incubation with a low concentration of WGA (2 μg/ml) high temperature sensitivity is exhibited. At 37 °C, however, the number of attached erythrocytes is the same for macrophages treated with WGA at concentrations of 2, 5, 10 and 40 μg/ml.ConA-mediated erythrocyte-macrophage interaction does not lead to erythrophagocytosis. When mediated by WGA, the attachment step is followed by a temperature-dependent ingestion step, i.e. 10% and 50% of the erythrocytes that attach to macrophages during the 60 min incubation at 24 °C and 37 °C, respectively, are ingested. There is a lag period of 10–20 min between attachment and ingestion implicating involvement of additional cellular processes preceding engulfment. Electron microscope images of areas of interaction of attached erythrocytes with macrophages indicate a significantly tighter binding (a thinner gap at membrane-membrane apposition areas) in the case of WGA-mediated rosette formation as compared with that established in ConA-mediated rosettes. Attachment via WGA is followed by a rapid change in the relative position of the attached erythrocytes on the macrophage, from a primary attachment at the distal peripheral regions of the cell, to a perinuclear position. In contrast, erythrocytes attached via ConA remain at the primary attachment point (at 37 °C) for extended periods. This differential behaviour does not stem from effects of ConA on macrophages, since when yeast cells were attached to ConA treated macrophages, the yeast cells showed the same movement as that exhibited by erythrocyte when attached via WGA.The different interaction patterns of erythrocytes with macrophages coated with ConA and WGA can be fitted into the following working hypothesis: the number of WGA-binding sites on the plasma membrane of macrophages is at least three times that of ConA-binding sites. Stable cell-cell interactions involve multibridge formation at the contact area of the two cells and this involves a delicate balance between number of lectin-receptor conjugates and their aggregation state within the membrane phase. A certain amount of clustering is a prerequisite for attachment, while a high degree of clustering reduces the chance of fruitful interactions. The engulfment step depends on the ability of membrane areas adjacent to primary contact area to establish additional stable bridges in the entire circumference of the attached cell. ConA-receptor conjugates appear to be less abundant and more aggregated within the membrane plane, preventing the completion of fruitful circumferential interaction of the adjacent membrane. WGA-receptor conjugates, being more abundant and apparently less aggregated are available at membrane areas needed for cell enclosure and provide the additional bridging without which engulfment does not take place. Change in relative position of attached erythrocytes seems to be a step in the manifold events occurring from attachment to ingestion.     

Changing levels of uv light and carcinogen-induced unscheduled DNA synthesis in mouse oocytes during meiotic maturation.

The effects of cytochalasin B (CB) and colchicine on the lectin-mediated agglutination of dissociated cells from chick embryos at the early primitive streak stage were studied. Cells incubated in the absence of the above-mentioned drugs were agglutinable with concanavalin A (ConA), wheat germ agglutinin (WGA), and Ricinus communis agglutinin (RCA). A pre-incubation with neuraminidase was required to render the cells agglutinable with soybean agglutinin (SBA). This treatment had no appreciable effect on the agglutinability of the cells with the other three lectins. Treatment with the drug colchicine had no appreciable effect on the extent of agglutination with any of the above-mentioned lectins. Cells treated with CB dissolved in dimethylsulfoxide (DMSO) in saline, exhibited a reduced lectin-mediated agglutinability. However, a similar decline in agglutinability was observed in controls incubated in saline containing DMSO alone. It is suggested that structures sensitive to colchicine and CB do not play a major role in the control of surface lectin receptors in early embryonic cells.     

Protein microarrays to study carbohydrate-recognition events

In order to expand areas in which protein microarrays can be used to solve important biological problems, we have investigated ways in which the technique can be employed for functional glycomics. Initially, our protein microarrays were used for the rapid identification of carbohydrate-binding proteins using trifunctional carbohydrate probes and fluorescent dye-labeled polysaccharides. Glycan probes were selectively bound to the corresponding lectins immobilized on the solid surface. In addition, these microarrays were also employed for profiling of carbohydrates on Jurkat T-cell surfaces. These cells adhered to ConA, RCA(120), SNA and WGA, indicating expression of alpha-Man, Gal, NeuNAcalpha2,6Gal and GlcNAc residues on their surfaces. Furthermore, we determined binding affinities between WGA and carbohydrates by measuring IC(50) values of GlcNAc that inhibited 50% of trivalent GlcNAc binding to WGA immobilized on the solid surface. All the experiments show that protein microarrays can be used to study carbohydrate-recognition events in the field of glycomics.     

Characteristics of chloride-dependent effects of acetylcholine and neutral aminoacids on neurons of the snail (Achatina)

The response was investigated of neurons composing the cerebral ganglia inAchatina fulica (the Giant African snail) to application of acetylcholine (ACh), gamma-aminobutyric acid (GABA), and glycine (Gly). Chloride-dependent currents induced by these transmitters in 1 1/2-month old siblings were inhibited by dibutyryl-cAMP and strychnine. Inhibition of ACh response produced 10^–8 M GABA was mimicked by application of dibutyryl-cAMP and isobutylmethylxanthine. Complete cross-desensitization was characteristic of both GABA- and Bly-induced response, but this effect did not occur when ACh and GABA (or Gly) were applied. A conclusion was reached on the basis of the pharmacological relationship between GABA- and Gly-induced response that these amino acids act on a single receptor — channel complex in the neurons of infant snails, whereas ACh-, GABA-, and Gly-induced chloride currents were not so related in cells of 4 year-oldAchatina.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 1, pp. 35–43, January–February, 1991.     

Solid state fermentation and fractionation of oat straw by Basidiomycetes

Summary Seventee white-rot and brown-rot fungi were screened for their ability to fractionate the lignocellulose structure of oat straw through the preferential attack of lignin or cellulose. Fermentations were carried out under solid-state conditions with 25 g quantities of straw. The fermented straw was analyzed for weight loss, Klason lignin loss and cellulase digestion. All the fungi attacked both lignin and carbohydrate fractions causing 3–28% weight losses and 26–34 g/100 g enzymatic digestibility. Polyporus tulipiferae, Phanerochaete chrysosporium and Polyporus sp. were tested for the effects of various nitrogen, phosphate and carbon levels, incubation temperatures and incubation time. The three fungi had different responses to these factors.