Fluorescent and Ferritin Labelling of Cuticle Surface Carbohydrates of Caenorhabditis elegans and Panagrellus redivivus

Caenorhabditis elegans and Panagrellus redivivus were investigated for surface carbohydrates using fluorescent-labelled and ferritin-labelled lectins. Rhodamine-labelled Concanavalin A was specifically located in the cephalic region of both species. Rhodamine-labelled wheat germ agglutinin was located over the entire cuticle of P. redivivus but was absent on C. elegans. Rhodamine-labelled peanut agglutinin and Limax flavus agglutinin did not label nematodes of either species. Galactose and sialic acid were not detected on either species, whereas mannose-glucose residues were specifically localized in the head areas of both species. No detectable N-acetylglucosamine occurred on C. elegans, but it was evenly distributed over the cuticle surface of P. redivivus.     

Surface antigens of Biomphalaria glabrata (Gastropoda) hemocytes: functional heterogeneity in cell subpopulations recognized by a monoclonal antibody

A hemocyte surface membrane marker (BGH₁) has been identified using hemocyte-specific monoclonal antibodies (mABs) generated by somatic cell fusion methods. The BGH₁ epitope was expressed on a subpopulation of circulating, glass-adherent blood cells from two strains of the snail, Biomphalaria glabrata. Approximately 40% of the circulating hemocytes from the PR albino (M-line) B. glabrata strain were BGH₁^?, compared to a prevalence of 10% BGH₁⁺ cells in the 10-R2 snail strain. When hemocytes were firmly attached and spread on a glass surface, BGH₁⁺ cells were morphologically distinguishable from BGH₁^? cells by their ovoid shape and the presence of short, thin filopodial projections along the ectoplasmic border. In contrast, BGH₁^? hemocytes were more pleomorphic and possessed long, spike-like filopodia. Moreover, the BGH₁ epitope was trypsin-resistant and retained its antigenic reactivity with probe mABs following fixation with paraformaldehyde or paraformaldehyde/MeOH. Fixation with glutaraldehyde, however, significantly reduced mAB binding to the BGH₁ surface epitope. There was no apparent age-dependent expression of the BGH₁ determinant since circulating hemocyte populations in very young (1–2 mm) to adult (10–12 mm) snails were composed of both BGH₁⁺ and BGH₁^? subpopulations. Quantitative shifts in the prevalence of epitope-bearing hemocytes between the smallest snail size class (1–2 mm) and the larger snails (3–4 and 10–12 mm) are believed to be due to a differential production and/or release of BGH₁^? hemocytes within the blood circulation rather than a gradual age-related change in the expression of surface antigens on individual cells. Experiments designed to assess the in vitro phagocytic capability and lysosomal acid phosphatase (APase) activity of mAB-reactive hemocytes revealed that BGH₁⁺ cells, when compared to those lacking the surface marker, were significantly reduced in both their phagocytic and APase-producing activities. Since the PR albino strain of B. glabrata possesses a higher proportion of BGH₁^? hemocytes and a lower total concentration of circulating cells than do snails of the 10-R2 strain, PR albino snails are thus potentially reduced in their natural capacity to mount cellular reactions against foreign materials.     

Calcium at the surface of cardiac plasma membrane vesicles: Cation binding,surface charge screening,and Na−Ca exchange

Summary Calcium binding and Na–Ca exchange activity were measured in isolated cardiac plasma membrane vesicles under various ionic conditions. A model was developed to describe the Ca binding characteristics of cardiac sarcolemmal vesicles using the Gouy-Chapman theory of the diffuse double layer with specific cation binding to phospholipid carboxyl and phosphate groups. The surface association constants used for Ca, Na, K and H binding to both of these groups were 7, 0.63, 0.3 and 3800m ^–1, respectively. This model allows the estimation of surface [Ca] under any specific ionic conditions. The effects of the divalent screening cation, dimethonium, on Ca binding and Na–Ca exchange were compared. Dimethonium had no significant effect on Ca binding at high ionic strength (150mm KCl), but strongly depressed Ca binding at low ionic strength. Dimethonium had no significant effect on Na–Ca exchange (Na-inside dependent Ca influx) at either high or low ionic strength. These results suggest that the Ca sites of the Na–Ca exchanger are in a physical environment where they are either not exposed to or not sensitive to surface [Ca].     

Impact de l'échantillonnage sur la mésure des nucléotides adényliques (ATP,ADP, AMP) du microplancton

The influence of sampling and sample treatment upon adenylic nucleotide (ATP, ADP, AMP) content of microplankton is studied. Changes in light conditions during nigh-sampling and extracting do not induce significant variations, in the adenylic nucleotide content of microplankton or in energy charge values.The contribution of zooplankton (size up to 200 µm) to microplankton adenosine values can be neglected for inshore surface waters and traditional sample volumes (about one liter). This result can been explained by the low density of zooplankton in such a small sample volume and by differences in efficiency of the extracting method used.

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Impact de l'échantillonnage sur la mésure des nucléotides adényliques (ATP, ADP, AMP) du microplancton

     

A new pollen type,C-banded and fluorochrome counterstained chromosomes,and evolution inGuatteria and related genera (Annonaceae)

Guatteria, Guatteriopsis, Guatteriella andHeteropetalum share the same conspicuous pollen type which is new for theSpermatophyta. It is zonoaperturate with a folded aperture region and an extremely reduced exine. First chromosome counts and karyotype analyses forGuatteriopsis (4 species investigated) andGuatteriella (1 species) are identical with those ofGuatteria (19 species seen): 2n = 28. The genome is characterized by diploidization and partly telocentric chromosomes. Sequentially Giemsa C- and fluorochrome banded chromosomes and interphase nuclei are described. The cuticular folding pattern is distinct forHeteropetalum only. Growth forms and ecology are reported for many species. The evolutionary pattern of theGuatteria group is discussed and compared with other genera and families.     

Vergleichende Mikromorphologie der Narbenoberflächen bei den Angiospermen; Zusammenhänge mit Pollenoberflächen bei heterostylen Sippen

Stigmatic surfaces of about 250 species from more than 100 families were examined by scanning electron microscopy. There are five main groups which differ by the amount of secretion, the morphology of the surface and the distribution of receptive cells. The types of stigmatic surfaces are often remarkably constant on the family level.Ericaceae andLiliaceae are examples for very heterogenous families. Particular interest was paid to heteromorphic (heterostylous and cleistogamous) species. In most heterostylous species there is a close morphological correlation between the stigmatic surface and the sculpture of compatible pollen. Heterostyly was established for the genusGoniolimon. The dimorphism of plants with chasmogamous and cleistogamous flowers is a phenomenon which is not comparable to the polymorphism of heterostylous forms.

     

Three classes of signalling molecules on B-cell membranes

The question of whether surface immunoglobulin and Ia molecules have a signalling function in helper T cell-dependent activation of B cells has been evaluated. Two sources of B cells have been used, one a purified population of hapten-binding B cells, the other a B-cell lymphoma, CH12, with known antigen specificity. Evidence is presented that both immunoglobulin and Ia molecules are receptors actively involved in the initial activation of resting B cells. Nevertheless, the requirements for ligand binding to either receptor can be bypassed under appropriate conditions, and the implications of this result for the function of these molecules is discussed. With respect to B-cell Ia, the authors present data that demonstrate two distinct functions of this molecule, one as a restricting element for T-cell activation, the second as a signalling receptor for B-cell excitation. On the CH12 surface, the I-A molecule fulfills the former function, but T-cell interactions with I-A fail to result in B-cell stimulation, suggesting that B-cell Ia may limit helper T cell-B cell interactions. We suggest that the binding of antigen surface immunoglobulin and binding of helper T-cell receptors to the appropriate Ia molecule(s) results in the activation of genes that encode for a third class of membrane B-cell receptors, those that bind B-cell stimulating factors.     

Cell surface changes in preimplantation mouse embryos during compaction investigated using FITC conjugated lectins after proteolytic enzyme treatment

Summary Fluorescein-conjugated lectins were used to examine the reappearance of glycoproteins on the surface of 8-cell mouse embryos after treatment with proteolytic enzymes. Embryos were decompacted in calcium free medium, treated with various proteases and the process of recompaction monitored. The most effective enzymes in delaying recompaction were subtilopeptidase A and proteinase K at 1 mg/ml; the initiation of recompaction was delayed by about 5 h and 90% recompaction by 14–18 h. Papain and -chymotrypsin were only effective in the absence of calcium. The reappearance of receptors for fluorescein-conjugated Con-A, MPA, RCA-I, FBP, BSL-II and DBA was examined photometrically at 0,8–10 and 17–18 h after proteinase K treatment. There was an increase in binding of MPA, RCA-I, FBP and BSL-II in control embryos during the period of the experiment, between approx. 61 and 80 h post coitum in which embryos passed from the 8-cell stage to the 16–32 cell stage. Con-A binding remained the same and that of DBA decreased. By the time that 50% of enzyme treated embryos had recompacted (8–10 h) binding of Con-A was similar to control embryos. Binding of FBP had almost reached control levels while that of BSL-II, DBA, RCA-I and MPA had reached 60–85% of control levels. When embryos were fully compact (17–18 h) Con-A, FBP and DBA were bound in equal or slightly greater amounts to enzyme treated as to control embryos, and receptors for BSL-II, MPA and RCA-I had recovered almost to control levels. The results clearly show that the recovery of glycoproteins on the surface of 8–16 cell embryos parallels recompaction, providing further evidence for the role of these molecules in compaction.