The plasma membrane of the Funaria caulonema tip cell: morphology and distribution of particle rosettes,and the kinetics of cellulose synthesis

Freeze-fracturing of Funaria hygrometrica caulonema cells leads to a cleavage within the plasma membrane. The extraplasmatic and the plasmatic fracture faces differ in their particle density. The plasmatic fracture face in caulonema tip cells or in tip cells of side branches, but never in other caulonema cells, is further characterized by the occurrence of particle rosettes. The highest density of rosettes is found at the cell apex but decreases steeply toward the cell base. The shape of the rosettes varies remarkably; 20% of them are found in an incomplete, presumably disintegrating or aggregating state. The complete rosette has a diameter of about 25 nm and consists of five to six particles. The size of the single particles varies between 4 nm to 10 nm. The rosettes are thought to posses cellulose-synthase activity. It is assumed that one rosette produces one elementary fibril; rough calculations, considering the number of rosettes and the estimated amount of cellulose produced in the tip region, indicate that an elementary fibrillar length of 900 nm is formed in 1 min by one rosette. The consequence of the kinetics on the life-time of the rosettes and the cellulose-synthase activity are discussed.Abbreviations EF extraplasmatic fracture face - PF plasmatic fracture face     

Plasma-membrane rosettes involved in localized wall thickening during xylem vessel formation of Lepidium sativum L.

Developing xylem vessel elements in roots of cress, Lepidium sativum L., were freeze-fractured after rapid freezing in nitrogen slush (without cryoprotection). With the double-replica technique, both the plasmatic fracture face (PF) and the extraplasmatic fracture face (EF) of the plasma membrane were exposed. The EF revealed abundant, but rather indistinct terminal globules; whereas the PF showed numerous rosettes. Terminal globules and rosettes were localized, restricted to regions of secondary wall thickening only, and showed comparale frequencies per m², supporting the assumption that they are part of the same synthase complex. The abundance of rosettes in regions of high cellulose production supports their postulated involvement in cellulose microfibril formation. With up to 191 rosettes per m², the rosettes appear to be too densely arranged to be directly aligned on individual microtubules. This favors the channelling hypothesis of synthase movement in the plasma membrane.Abbreviations EF extraplasmatic fracture face - PF plasmatic fracture face     

Arrays of plasma-membrane “rosettes” involved in cellulose microfibril formation of Spirogyra

The cell-wall structure and plasma-membrane particle arrangement during cell wall formation of the filamentous chlorophycean alga Spirogyra sp. was investigated with the freeze-fracture technique. The cell wall consists of a thick outer slime layer and a multilayered inner wall with ribbon-like microfibrils. This inner wall shows three differing orientations of microfibrils: random orientation on its outside, followed by axial bundles of parallel microfibrils, and several internal layers of bands of mostly five to six parallel associated microfibrils with transverse to oblique orientation. The extraplasmatic fracture face of the plasma membrane shows microfibril imprints, relatively few particles, and “terminal complexes” arranged in a hexagonal package at the end of the imprint of a microfibril band. The plasmatic fracture face of the plasma membrane is rich in particles. In places, it reveals hexagonal arrays of “rosettes”. These rosettes are best demonstrable with the double-replica technique. These findings on rosette arrays of the zygnematacean alga Spirogyra are compared in detail with the published data on the desmidiacean algae Micrasterias and Closterium.     

Coelomocytes of earthworms: the T-cell-like rosette.

The coelomocytes forming spontaneous rosettes with sheep red blood cells (SRBC) were studied under various experimental conditions in lumbricus terrestris. The percentage of rosettes did vary with the pH, increased with the incubation period and remained constant at 4°C and at room temperature. The viability of the coelomocytes was a prerequisite for the formation of rosettes.The phenomenon was found to be stable, repeatable, and specific, thus suggesting rosettes are probably not an artefact.The coelomocytes forming rosettes were basophilic, nongranulated, and nonadhering cells with a large nucleus and little cytoplasm closely resembling vertebrate T-lymphocytes. The adhering cells did not form rosette.These results suggest that the coelomocytes forming rosettes could well be the evolutionary precursors or analogs of immunocyte rosettes forming cells of the vertebrates. Whether or not the coelomocyte receptors for the SRBC are similar to those of the T-cells of the vertebrate remains to be established.     

The effect of thyroparathyroidectomy, parathyroid hormone and calcitonin on plasma strontium in rats

The effect of thyroparathyroidectomy (TPTX) on the plasmatic Sr concentrations in rats previously supplemented with this element, has been studied, as well as its effect on the treatment of TPTX rats with hormonal combinations and, finally, the one presenting hormonal excess or defect of the phosphocalcium metabolism regulating hormones: parathormone (PTH) and calcitonin (CT). Twenty four hours after TPTX, the plasmatic Sr concentrations show a pattern similar to those of Ca and Mg and contrary to Pi. The subsequent evolution is different, as the plasmatic concentrations increase, probably due to the maintenance of Sr supplementation. The administration of this element to TPTX rats and the treatment with a hormonal combination with two of the following hormones: PTH, CT and T4 antagonize the hormonal effect on the restoration of the plasmatic concentrations of the elements analyzed. The PTH excess and defect (TPTX treated with CT + T4) show plasmatic increases in Sr; the CT excess provokes decreases while the defect (administration of PTH + T4) causes increases. The T4 administration reproduces the CT effects, but inconsistently. These results suggest that CT may be the hormone that plays a regulating role in the plasmatic Sr concentrations.     

Morphological differences in the interactions between human mononuclear cells and coated or uncoated sheep red blood cells

Summary Enriched preparations of E, EA and EAC rosettes formed by human peripheral blood mononuclear cells were freeze-etched and examined electron-microscopically. In E rosettes only lymphocytes were involved, whereas in EA and EAC rosettes lymphocytes and mononuclear phagocytes participated as rosette-forming cells. In EA and EAC rosettes, cytoplasmic extensions of the rosette forming cell were seen to penetrate the sheep red blood cell, whereas E rosettes showed a broad zone of adherence without penetration. None of the three types of rosettes showed an interspace between the membranes. Unlike E rosettes, EA and EAC rosettes showed polarity in the adherence of sheep red blood cells. These observations made by freeze-etch electron microscopy indicate distinct morphological differences between rosettes formed with coated or uncoated erythrocytes.The authors wish to thank Prof. Dr. A. Cats, Dr. P.C.J. van Breda Vriesman and Dr. J.C.H. de Man for helpful discussion and criticism; the assistance of Miss R. Kleinjan and Mrs. A.C. Scheurkogel-van Efferen is gratefully acknowledged. This work was supported in part by a grant of the Praeventiefonds     

Plasma-membrane rosettes in root hairs of Equisetum hyemale

Particle arrangement in the plasma membrane during cell wall formation was investigated by means of the double-replica technique in root hairs of Equisetum hyemale. Particle density in the protoplasmic fracture face of the plasma membrane was higher than in the extraplasmic fracture face. Apart from randomly distributed particles, particle rosettes were visible in the PF face of the plasma membrane. The rosettes consisted of six particles arranged in a circle and had an outer diameter of approx. 26 nm. No gradient in the number of rosettes was found, which agrees with micrifibril deposition taking place over the whole hair. The particle rosettes were found individually, which might indicate that they spin out thin microfibrils as found in higher-plant cell walls. Indeed microfibril width in these walls, measured in shadowed preparations, is 8.5±1.5 nm. It is suggested that the rosettes are involved in microfibril synthesis. Non-turgid cells lacked microfibril imprints in the plasma membrane and no particle rosettes were present on their PF face. Fixation with glutaraldehyde caused, probably as a result of plasmolysis, the microfibril imprints to disappear together with the particle rosettes. The PF face of the plasma membrane of non-turgid hairs sometimes showed domains in which the intramembrane particles were aggregated in a hexagonal pattern. Microfibril orientation during deposition will be discussed.Abbreviations EF extraplasmic fracture face - PF protoplasmic fracture face     

Resource sharing among ramets in the clonal herb,Fragaria chiloensis

Summary The herbaceous perennial, Fragaria chiloensis, reproduces vegetatively on coastal sand dunes in California by growth of stolons that bear rosettes. Movement of water and photosynthates through stolons integrates water and carbon metabolism of rosettes both before and after they root. New, unrooted rosettes import sufficient water and nitrogen to maintain levels near those of established rosettes; yet support of an unrooted rosette did not decrease growth of a connected, rooted sibling given abundant light, water, and soil nutrients. Under such conditions strings of unrooted rosettes with the associated stolon appeared self-sufficient for carbon; shade and drought induced import of photosynthates. New rosettes produced and maintained a limited root mass upon contact with dry sand, which could increase probability of establishment. Rooting did not induce senescence of stolons. Connection between two established rosettes prevented death by drought and shade, even when neither rosette could have survived singly. Results suggest that physiological integration of connected rosettes may increase total growth of clones of F. chiloensis through sharing of resources among ramets, especially when resource availability is changeable or patchy.     

A controlled cycle of tetrahydrocannabinol smoking: T and B cell rosette formation.

T and B cell rosettes were serially determined before, during, and after a four week cycle of tetrahydrocannabinol (THC) smoking in 10 hospitalized subjects. The early T cell rosettes were significantly fewer during the period of THC smoking and tended to return toward baseline after smoking, whereas no changes were seen in the seven simultaneously studied controls. Both the THC smokers and controls showed no change in their normal values for WBC, % lymphocytes, B cell rosettes (complement receptor) and late T cell rosettes. The data suggest that T cells, present in nearly normal numbers in the smokers, had reduced capacities to form early rosettes during and directly related to THC smoking. While the immunological significance of reduced early rosette formation is unclear, the data suggest that further immunological study of marijuana smokers would be indicated.     

Spatial structure-mediated indirect effects of an aquatic plant, Trapa japonica, on interaction between a leaf beetle, Galerucella nipponensis, and a water strider, Gerris nepalensis

The spatial structure-mediated indirect effects of an aquatic host plant, Trapa japonica (Trapaceae), on survival of a leaf beetle, Galerucella nipponensis (Coleoptera: Chrysomelidae), with regard to predation by a water strider, Gerris nepalensis (Hemiptera: Gerridae), were investigated in an irrigation pond and under indoor conditions. Beetle density, particularly in the first-instar stage of the larvae, became extremely low in the second generation in the pond, even though food resources were abundant. The biological check method, which excludes natural enemies by caging, suggested that a causal factor of the low density was predation by Gerris nepalensis in midsummer and thereafter. Normally growing rosettes extend their leaves horizontally on the water surface. However, some rosettes of T. japonica grew leaves vertically in the later seasons, and such overgrown rosettes were distributed patchily in the ponds. Beetle density was higher on the latter rosettes than on the former ones. The indoor experiment showed that the water strider can feed on the eggs of beetles on normally grown rosettes but not on the overgrown rosettes. Furthermore, female adults of Galerucella nipponensis preferred the overgrown rosettes over the normally grown rosettes for oviposition when water striders were present. These facts suggest that the spatial structure-mediated indirect effects of the host plant modify the interaction between herbivore and predator. Received: November 22, 2001 / Accepted: February 26, 2002     

Proportion of lymphocytes forming E, EA, and EAC rosettes following treatment with human interferon preparations in vitro

The proportion of lymphocytes forming E, EA, and EAC rosettes after treatment with human interferon preparations in vitro was measured. While interferon increased the percentage of lymphocytes forming E rosettes, the percentage of cells forming EA rosettes was diminished. The proportion of lymphocytes forming EAC rosettes was not altered to any major extent by interferon treatment. The same effects were observed when fibroblast interferon, purified to homogeneity with regard to molecular weight, was used.     

Morphometric ultrastructural evaluation of human peripheral blood T lymphocyte subpopulations isolated on the basis of their affinity for sheep red blood cells

The present investigation were undertaken to compare on the basis of ultrastructural morphometric analysis human T lymphocyte subfractions forming rosettes with sheep red blood cells (SRBC). The following T lymphocyte subfractions were obtained: ARFC (active rosettes), T1RFC (rosettes after 1 h at 4 degrees C) and T2RFC (rosettes after 2 h at 4 degrees C). Analysis of the mean cell and nuclei volumes of lymphocyte subfractions led to the separation of two cell groups differing in volume in each donor: a cell group consisting of large cells (T1RFC) and group of small cells (ARFC and T2RFC).     

Visualization of particle complexes in the plasma membrane of Micrasterias denticulata associated with the formation of cellulose fibrils in primary and secondary cell walls

Highly ordered arrays of intramembrane particles are observed in freeze- fractured plasma membranes of the green alga Micrasterias denticulata during the synthesis of the secondary cell wall. The observable architecture of the complex consists primarily of a precise hexagonal array of from 3 to 175 rosettes, consisting of 6 particles each, which fracture with the P-face. The complexes are observed at the ends of impressions of cellulose fibrils. The distance between rows of rosettes is equal to the center-to-center distance between parallel cellulose fibrils of the secondary wall. Correlation of the structure of the complex with the pattern of deposition indicates that the size of a given fibril is proportional to the number of rosettes engaged in its formation. Vesicles containing hexagonal arrays of rosettes are found in the cytoplasm and can be observed in the process of fusing with the plasma membrane, suggesting that the complexes are first assembled in the cytoplasm and then incorporated into the plasma membrane, where they become active in fibril formation. Single rosettes appear to be responsible for the synthesis of microfibrils during primary wall growth. Similar rosettes have now been detected in a green alga, in fern protonemata, and in higher plant cells. This structure, therefore, probably represents a significant component of the cellulose synthesizing mechanism in a large variety of plant cells.     

Numbers of rosette formine cells in human peripheral blood.

Thymus-derived (T-cell) and “bursal” derived (B-cell) lymphocytes in human peripheral blood were quantitated by assaying percentages of cells forming erythrocyte rosettes. T-cell rosettes were formed with neuraminidase treated sheep erythrocytes. B-cell rosettes were formed with complement coated sheep erythrocytes. Large differences in the percentages of T-rosette forming cells were noted depending on the method used to assay these cells. When rosette forming cells (RFC) and non-RFC were counted concurrently the percentage of T-cell rosettes were 53–75% whereas methods involving the separate counting of RFC and total cells gave T-cell RFC percentages of 23–40%. These differences were due to the “co-rosetting” of non-RFC into the T-cell rosette clusters. This occurred because of the gentleness required to resuspend the fragile T-cell rosettes. “Co-rosetting” was demonstrated by forming stable complement receptor rosettes with complement-coated human erythrocytes and resuspending them either gently or vigorously. Significantly higher percentages of rosettes were noted with gentle cell suspension than with vigorous resuspension. The percentages of rosette forming T-cells in human peripheral blood are therefore lower than previously estimated.     

Sympodial construction of Fibonacci-type leaf rosettes in Pinguicula moranensis (Lentibulariaceae)

BACKGROUND AND AIMS: The leaf rosettes of the carnivorous Pinguicula moranensis follow a spiral phyllotaxis approaching a Fibonacci pattern while the stalked flowers arise from extra-axillary sites between the leaves. The organization of this rosette has been discussed by various authors, with various results. The aim of the present study was to clarify the development of the flowering rosettes of this species. METHODS: The formation of the rosettes is shown with the aid of scanning electron microscopy. KEY RESULTS AND CONCLUSIONS: The scanning electron micrographs show that each flower terminates an article (sympodial unit). The leaves of consecutive articles of such sympodially constructed rosettes are arranged along a spiral Fibonacci pattern (with divergence angles around 137 degrees). This results from homodromy of leaf initiation in consecutive articles with the first leaf (prophyll) of a new article inserted in an obliquely transverse position next to the floral scape that terminates the former article. Sympodial construction of flowering shoots and leaf rosettes is also known from Aloe, Gunnera and Philodendron. As a by-product of this study, the unidirectional development of the Pinguicula flower is confirmed and discussed.     

Particle rosettes and microtubular ridges on the plasma membrane of Chara

We have examined the plasma membrane of cortical and internodal cells of Chara globularis var. capillacea (Thuill.) Zanev. using rapid-freezing and freeze-fracturing techniques. The non-etched image of the protoplasmic face reveals particle rosettes, and also reveals ridges which can be correlated with cortical microtubules. Since both rosettes and microtubular ridges can thus be viewed simultaneously, we have looked for a spatial relationship between them, but have found them to be essentially independent. We have found that the density of particle rosettes is a function of age and of type of cell. Groups of pits may represent the complementary exoplasmic component of the rosettes.     

Plasmodium falciparum malaria: rosettes are disrupted by quinine, artemisinin, mefloquine, primaquine, pyrimethamine, chloroquine and proguanil.

An assay was developed measuring the disruption of rosettes between Plasmodium falciparuminfected (trophozoites) and uninfected erythrocytes by the antimalarial drugs quinine, artemisinin mefloquine, primaquine, pyrimethamine, chloroquine and proguanil. At 4 hr incubation rosettes were disrupted by all the drugs in a dose dependent manner. Artemisinin and quinine were the most effective anti-malarials at disrupting rosettes at their therapeutic concentrations with South African RSA 14, 15, 17 and The Gambian FCR-3 P. falciparum strains. The least effective drugs were proguanil and chloroquine. A combination of artemisinin and mefloquine was more effective than each drug alone. The combinations of pyrimethamine or primaquine, with quinine disrupted more rosettes than quinine alone. Quinine may be an effective drug in the treatment of severe malaria because the drug efficiently reduces the number of rosettes.     

The cost of reproduction in Senecio keniodendron,a giant rosette species of Mt. Kenya

Summary A three year study of Senecio keniodendron (Compositae), a giant rosette species of the alpine zone of Mt. Kenya, demonstrated that individuals which reproduce are more likely to die, and less likely to reproduce in the future if they do survive, than are vegetative individuals of the same size. However, if an individual reproduces, survives and reproduces again, then it produces more seeds during the second reproductive episode than does a plant of the same height reproducing for the first time, because reproduction is followed by production of lateral rosettes, increasing the number of potentially-reproductive rosettes per plant.Slow-growing rosettes are less likely to reproduce than fast-growing rosettes. For rosettes which do reproduce, rosette size and rate of leaf production, measured before reproduction begins, are good predictors of fecundity.     

Interaction of antigen-specific T cell factors with unique "receptors" on the surface of mast cells: demonstration in vitro by an indirect rosetting technique

Picryl (trinitrophenyl) chloride (PCL) contact sensitization of mice induces T cells that release an antigen-binding T cell factor (PCLF) that plays an important role in the initiation of contact sensitivity responses, in part via activation of mast cells. The current study employs an in vitro indirect rosette assay to demonstrate that PCLF can interact with the mast cell surface. Sheep red blood cells (SRBC) were hapten conjugated with trinitrophenyl (TNP), dinitrophenyl (DNP), or oxazolone (OX). When TNP-conjugated SRBC were coated with PCLF, monoclonal anti-DNP IgE, or anti-DNP IgG1, they produced 40 to 50% rosettes with purified normal mouse peritoneal mast cells. Analogous antigen-binding factors, from lymphoid cells of OX and dinitrofluorobenzene contact-sensitized mice, gave similar mast cell rosetting levels with OX-SRBC and DNP-SRBC, respectively. PCLF demonstrated a high degree of hapten specificity in that it formed rosettes with TNP-SRBC but not with DNP-SRBC, unlike IgE and IgG1, or DNPF, which formed rosettes with either SRBC type. Similarly, soluble TNP-BSA could inhibit PCLF rosette-forming capacity, but soluble DNP-BSA could not. In addition to mouse mast cells, PCLF formed rosettes with rat basophil leukemia cells, mouse peritoneal exudate macrophages, mouse alveolar macrophages, and J 774 cultured mouse macrophages; it did not form rosettes with rat mast cells, rat alveolar macrophages, or mouse spleen cells. Thus, PCLF-formed rosettes were antigen specific, relatively species specific, and mast cell/macrophage specific. PCLF-mediated rosette-forming activity could be detected in the presence of nanogram quantities of PCLF. More than 10 times greater IgE was needed to produce IgE-mediated rosettes. Reduction and alkylation eliminated the rosetting activity of IgE, but the rosetting activity of PCLF was not affected. PCLF, but not IgE rosette-forming activity, could be removed by and eluted from affinity columns linked with a monoclonal antibody specific for T cell-derived antigen-binding factors, whereas PCLF rosetting activity was not retained by an anti-immunoglobulin affinity column. Preincubation of mast cells with rat myeloma IgE or mouse monoclonal IgE of various specificities blocked IgE rosettes but not PCLF-induced rosettes. Other immunoglobulin isotypes likewise did not block PCLF rosettes. However, PCLF rosettes could be blocked by preincubation of mast cells with OX factor (OXF),and OXF-mediated rosettes could be blocked similarly by PCLF. These results suggest that the antigen-binding T cell factor PCLF interacts with a unique receptor on the surface of mouse mast cells.     

Membrane markers of the lymphocytes of human peripheral blood: techniques of study and normal values in adults]

Peripheral blood lymphocytes from normal subjects were evaluated for their cell surface markers. Normal values were determined in females and males for T-cells (E rosettes and active E rosettes) and for B cells (surface immunoglobulins, EA rosettes and EAC rosettes). Means expressed in percentage and in absolute number per cubic millimeter +/- standard error in normal subjects males and females.