Dermatologically active sesquiterpene lactones in trichomes ofParthenium hysterophorus L. (Compositae)

Summary Scanning electron microscopy of the leaf surface, phyllaries and achene-complex ofParthenium hysterophorus L. showed the presence of 4 types of glandular and non-glandular trichomes. Chemical analysis established the presence of sesquiterpene lactones in the trichomes that cause eczematous dermatitis.Acknowledgments. We thank Dr.Garry Cole, University of Texas, for the use of the AMR-1000 Scanning electron microscope andJudy Stevenson for technical assistance. The work at the University of Texas was supported by the National Science Foundation (Grant No. BMS 71-01088) and the Robert A. Welch Foundation (Grant No. F-130).     

Inhibition of insect larval growth by phenolics in glandular trichomes of tomato leaves

Summary We have found that the foliar tetracellular glandular trichomes (tetrads) of the tomato plant,Lycopersicon esculentum Mill., contribute significantly to the antibiotic effect of the leaf against the fruitwormHeliothis zea (Boddie), as measured by reduction in larval growth. This effect is attributable to phenolic compounds localized within the tetrads. We have found that the cellular fluid of the tetrads is particularly rich in the flavonol glycoside rutin, accompanied by lesser amounts of other phenolics.Acknowledgments. Supported by CFMTAB grant No. 21, and USDA-SEA grant No. 5901-0269. We thank Shell Development Company of Modesto, California, for supplying eggs ofH. zea, J. S. Rolston for preparation of the figures, and B. C. Campbell for the SEM photograph in fig. 1.     

Insect anti-juvenile hormone and juvenile hormone activity from plants in the genusNama

Summary The insect anti-juvenile hormones precocene I and II (7-methoxy-2,2-dimethyl-2H-1-benzopyran and 6,7-dimethoxy-2,2-dimethyl-2H-1-benzopyran) were identified in three of nineNama (Hydrophyllaceae) species. Precocene I occurred inN. lobbii while precocene II occurred inN. hispidum, N. lobbii andN. sandwicense. N. hispidum contained the highest concentration (ca 0.5% dry weight) of precocene II, which was found in the leaves, stems, seed capsules, corolla, glandular trichomes, and seeds. In addition to the anti-juvenile hormone, insect juvenile hormone activity was detected in the organosoluble extracts ofN. rothrockii andN. sandwicense. N. sandwicense is the first plant discovered to contain compounds with both anti- and juvenile hormone activity.     

Trichomes as models for studying plant cell differentiation

Trichomes, originating from epidermal cells, are present on nearly all terrestrial plants. They exist in diverse forms, are readily accessible, and serve as an excellent model system for analyzing the molecular mechanisms in plant cell differentiation, including cell fate choices, cell cycle control, and cell morphogenesis. In Arabidopsis, two regulatory models have been identified that function in parallel in trichome formation; the activator–inhibitor model and the activator–depletion model. Cotton fiber, a similar unicellular structure, is controlled by some functional homologues of Arabidopsis trichome-patterning genes. Multicellular trichomes, as in tobacco and tomato, may form through a distinct pathway from unicellular trichomes. Recent research has shown that cell cycle control participates in trichome formation. In this review, we summarize the molecular mechanisms involved in the formation of unicellular and multicellular trichomes, and discuss the integration of the cell cycle in its initiation and morphogenesis.     

Scanning electron microscopy of cells from hydroxyurea-arrested blastulae ofXenopus laevis

Summary Cells fromXenopus embryos blocked at the blastula stage by treatment with hydroxyurea have been isolated and cultured in vitro. The morphology of these cells has been compared with that of cells from normal embryos using scanning electron microscopy. Cells from such hydroxyurea-blocked embryos do not show the features, or changes in features, in culture shown by cells from normal embryos.Acknowledgments. We wish to thank Mr C. Veltkamp for his help with the electron microscopy, and Mrs J. Clumpus for technical assistance.     

Estimation of nonspecific lectin-mediated staining of glutaraldehyde-fixed cells

Summary Lectin-mediated stainings are widely used for the visualization of carbohydrate-carrying cellular components using the electron microscope. The use of glutarladehyde-fixed cells for these stainings introduces the possibility of low nonspecific lectin-trapping by the glutaraldehyde which coats the cells. This trapping was estimated by means of peroxidase-binding to human leukocytes,Tetrahymena pyriformis andEscherichia coli cells and was shown to be prevented by rinsing the glutaraldehyde-fixed cells in an amino acid solution before exposure to the lectin.     

The choroid in the eye of the eel (Anguilla anguilla)

Summary By means of light and scanning electron microscopy evidence of the existence of a normally organized choroid in the eye of the eel,Anguilla anguilla, is presented.     

Ultrastructural autoradiographic study of the intracellular fixation of3H-acrolein

Summary The fixation of³H acrolein inDunaliella bioculata was followed by means of quantitative autoradiography electron microscopy. A fixation was observed mostly in the nucleus where aldehyde linkage remained stable at least for 48 hours.     

Characterization of polyphenol-containing dense cells

Summary Dense cells ofRubus chamaemorus L. (cloudberry) root meristems have been characterized by histochemical staining reactions at light and electron microscope levels. Presence of polyphenolic compounds in the cellular matrix contribute to the density of the dense cells.This research was supported by an operating grant from Agriculture Canada.     

Physiological role of apyrene spermatozoa ofBombyx mori

Summary Observation by electron and phase-contrast microscopy demonstrated that inBombyx mori the dissociation of eupyrene bundles, apparently through digestion of the prostatic secretion or an endopeptidase, was promoted by the vigorously flagellating movement of apyrene spermatozoa in the spermatophore.     

Über die Struktur pflanzlicher Karotinkriställchen

Summary Crystals of carotene in plant cells (carrot root, corona ofNarcissus etc.) have been attributed to the orthorhombic or the hexagonal system. However, an optical investigation showed that they have a lower symmetry. In the case of the crystals in the corona ofNarcissus, the structural identity with synthetic-carotene is proved by X-ray and electron diffraction analysis. Although the geometry of the electron diffraction patterns is almost indistinguishable from hexagonal, its reflections can be identified with those from the planes of the monoclinic lattice of-carotene. The face of the plate-shaped crystals corresponds to (102).     

La vitellogenesi inArbacia lixula eSphaerechinus granularis (Echin. Echin.)

Summary The researches carried out both under the light and electron microscopes permitted us to ascertain that, in EchinodermataArbacia lixula andSphaerechinus granularis, yolk globules form by aggregation of ribonucleoproteic particles. It appears that the globules themselves in the first stage of their formation show such physico-chemical conditions as to condition the precipitation of silver in the method used to reveal Golgi apparatus.     

White leaf disease ofCynodon dactylon Pers., a mycoplasmal disease in India

Summary White leaf disease of Bermuda grass (Cynodon dactylon Pers.) has been reported from a few countries to be caused by a mycoplasma-like organism. We have tried to observe the causal agent in white leaf diseased plants ofC. dactylon collected near Varanasi. Both tetracycline treatment and electron microscopy have revealed the presence of mycoplasma-like bodies in phloem cells of the diseased plants.     

Heterogeneous ferritin in the blood of two species of Tyrrhenian limpets,Patella coerulea L. andPatella lusitanica G.

Summary The hemolymph ofPatella is yellow and contains 30–300 μg/ml of iron. Ferritin was found to be uniquely abundant in the hemolymph, and was identified by electron microscopy and electrophoresis. Electrophoretically it appears to be heterogeneous, with an individually variable number of components with very similar mobilities. Ferritin in the blood of limpets might relate to the turnover of radular denticles.     

Feinstruktur von Pilzzellen. II. Endogene Konidienbildung beiPenicillium cyclopium

Summary On investigation by electron microscope of the phialides of a strain ofPenicillium cyclopium endogenous layed proconidia could often be observed.     

Studies on peripheral neurons and neurohaemal tissue in the thorax of the stick insect (Carausius morosus)

Summary The distribution of peripheral neurosecretory and non-neurosecretory neurons, and transverse nerve neurohaemal swellings, is described in the thorax ofCarausius morosus. The electrical activity of the isolated transverse nerves has been recorded.We are grateful to the Science Research Concil for financial support, and to Dr Sue Fifield and Steven Irving for methylene blue and electron microscope preparations.     

Ultrastructure of muscle spindles in C57BL/6Jdy 2J/dy 2J dystrophic mice

Summary The sensory organs of skeletal muscles, the muscle spindles, were examined using electron microscopy indy ^2J/dy ^2J dystrophic mice. Despite widespread damage to the extrafusal (skeletomotor) fibres the intrafusal (spindle) fibres appeared normal and seemed resistant to the aetiological factors for murine dystrophy.This work was supported by grants from the Medical Research Council and the Science Research Council of Great Britain.     

Three-dimensional structure of annexins

Annexins constitute a family of structurally related calcium- and phospholipid-binding proteins whose molecular structure has been investigated in detail in the crystalline and membrane-bound form. Their polypeptide chain is folded into four or eight α-helical domains of similar structure with a central hydrophilic pore. Bound to phospholipid membranes, the four-domain arrangement of the annexin molecule is conserved. A peripheral binding mode has been well documented by electron microscopy and a variety of other techniques.     

The elegans of spindle assembly

The Caenorhabditis elegans one-cell embryo is a powerful system in which to study microtubule organization because this large cell assembles both meiotic and mitotic spindles within the same cytoplasm over the course of 1 h in a stereotypical manner. The fertilized oocyte assembles two consecutive acentrosomal meiotic spindles that function to reduce the replicated maternal diploid set of chromosomes to a single-copy haploid set. The resulting maternal DNA then unites with the paternal DNA to form a zygotic diploid complement, around which a centrosome-based mitotic spindle forms. The early C. elegans embryo is amenable to live-cell imaging and electron tomography, permitting a detailed structural comparison of the meiotic and mitotic modes of spindle assembly.     

Effect of prostaglandins on skin tumorigenesis

Summary Concomitant administration of prostaglandins E₂ (PGE₂) and F₂ a(PGF₂ a) with a carcinogen, 3-methylcholanthrene (MCA) to mice for 2 months markedly enhanced the occurrence of squamous cell carcinomas. Only epidermal cell hyperplasia occurred in mice treated with MCA alone by that time. Radioactivity measurements and electron microscopic autoradiography revealed that prostaglandins stimulate DNA, RNA and protein synthesis in neoplastic cells. These findings indicate that PGE₂ and PGF₂ a can act as cocarcinogens on skin tumorigenesis.