Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Migration of root-knot larvae (Meloidogyne incognita) into the primary root tissues of red clover (Trifolium pratense, cult. “Kenland”) was accompanied by separation and subsequent compression of cells in front of and along the path of the penetrating nematode. The protoplasts of the parenchymatous cortical cells did not respond to the presence of the penetrating larvae. However, as the nematode approached the differentiating vascular tissue, the cytoplasmic density of the pericyclic and meristematic cells increased. This increased density was accompanied by an alteration in the morphological features of the nucleus. In addition to these changes, two different types of extracellular material were observed during penetration. A homogeneous substance appeared in and around the external opening of the amphid; and an electron dense material was found along the middle lamellae of the separating plant cells and between the cuticle of the nematode and the cell walls of the host.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1615-6102
    Keywords: Low temperature scanning electron microscopy ; Freezesubstitution ; Cell wall ; Plant pathology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Electron microscopy (EM) has greatly helped to elucidate our understanding of bacterial structure and function. However, several recent studies have cautioned investigators about artifacts that result from the use of conventional EM preparation procedures. To avoid these problems, the use of low temperature scanning electron microscopy (LTSEM) was evaluated for examining frozen, fully hydrated specimens. Spinach leaves (Spinacia oleracea L. cv. New Jersey), which were naturally infected or inoculated with bacteria, were used as the experimental material. 1 cm segments of the infected leaves were plunge frozen in liquid nitrogen, transferred to a cryochamber for sputter coating and then moved onto a cryostage in an SEM. After observation, some of the frozen, hydrated leaf segments were transferred onto agar medium to determine whether preparation for LTSEM was nondestructive to the bacteria. The other tissue segments were chemically fixed by freeze-substitution. The results indicated that after cryopreparation and observation in the LTSEM: (i) viable bacteria, which were recovered from the leaf sample, could be cultured on agar medium for subsequent study, and (ii) the frozen samples could be freeze substituted and embedded so that transmission electron microscopic (TEM) observations could be carried out on the same specimen. In conclusion, frozen, hydrated leaf tissue infected with bacteria can be observed using LTSEM and then can be either processed for TEM observation to obtain further structural details or recovered to culture the pathogenic bacteria for supplementary studies.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Light microscopic observations dating back to 1892 have established that sieve elements of papilionaceous legumes contain a unique type of slime body. This large, compact crystalline type of P-protein has also been observed in sieve elements in recent electron microscopic investigations but its formation and possible relationship to other P-protein structures have not been examined. The present fine structural study describes its development in hypocotyl tissue of 4-day old seedlings of soybean (Glycine max L.). Preceding the formation of a P-protein body, a young sieve element possesses large numbers of ribosomes, abundant vesiculate ER and numerous dictyosomes surrounded by vesicles. A finely granular material accumulates among these components, then condenses into electron opaque masses. Scattered bundles of tubules appear within these masses, then aggregate, and next align longitudinally in the sieve element. By a further transformation, the tubules are converted into an electron opaque crystalline P-protein body. This body continues to grow by aggregation and transformation of additional tubules, and at maturity may be as long as 15–30 microns. The main body, which is square in cross section, tapers toward the ends and is terminated by sinuous “tails”. Eventually this crystal disperses into a mass of fine striated fibers that fills the lumen of the mature sieve element. Attention is directed to similarities between the bundles of tubules and previously described “extruded nucleoli”. Factors possibly involved in the structural variations and transformations described above are also discussed.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 76 (1973), S. 249-260 
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Woronin bodies are cytoplasmic organelles which commonly lie near the septa in ascomycetous fungi. Although these organelles were observed nearly 100 years ago, little is known about their origin and development. The present ultrastructural investigation describes the ontogeny of Woronin bodies inFusarium oxysporum f. sp.lycopersici [Sacc.] Snyd. and Hans. In this fungus, Woronin bodies are produced by microbodies. Development of the Woronin body begins with the appearance of electron dense material within the microbody. This material aggregates adjacent to the membrane of the microbody and condenses into a single paracrystalline inclusion. Following its formation, the inclusion is gradually extruded and is eventually separated from the parent organelle by an exocytotic mechanism. After the separation, the paracrystalline inclusion is found at the septal pore. Although many recent electron microscopic studies have used various terms to designate these membrane bound organelles, inFusarium these inclusions are believed to correspond to the Woronin bodies initially described by light microscopists.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Carrot sticks that were prepared with a sharp culinary knife exhibited a whitish translucent appearance on the surface. This condition was not readily apparent with carrot sticks sliced with a razor sharp blade. Scanning electron microscopic examination of the translucent tissue revealed that the knife tended to shear, separate and compress the cells and tissues of the root. Dehydration of the large mass of exposed cells probably was responsible for the appearance of the whitish translucent tissue. Development of this condition is undesirable because consumers associate this with aged or nonfresh carrot sticks.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Morphology and distribution of the relatively less well known organelles of plants have been studied with the electron microscope in tissues fixed in glutaraldehyde and postfixed in osmium tetroxide. An organelle comparable morphologically to the animal microbody and similar to the plant microbody isolated by Mollenhauer et al. (1966) has been encountered in a variety of plant species and tissues, and has been studied particularly in bean and radish roots, oat coleoptiles, and tobacco roots, stems and callus. The organelle has variable shape and is 0.5 to 1.5 μ in the greatest diameter. It has a single bounding membrane, a granular to fibrillar matrix of variable electron density, and an intimate association with one or two cisternae of rough endoplasmic reticulum (ER). Microbodies are easily the most common and generally distributed of the less well characterized organelles of plant cells. It seems very probable that they contain the enzymes characteristic of animal lysosomes (containing hydrolases) or animal microbodies (containing catalase and certain oxidases). Spherosomes are also possible sites of enzyme activity but are not as common or as widely distributed as microbodies. For this reason it appears likely that the particles designated as “plant lysosomes”, “spherosomes”, “peroxisomes”, etc., in some of the cytochemical and biochemical studies on enzyme localization will prove to be microbodies. Variations in the morphology and ER associations of microbodies in tissues of bean and radish are described and discussed. “Crystal-containing bodies” (CCBs) are interpreted as a specialized type of microbody characteristic of metabolically less active cells. Stages in the formation of CCBs from microbodies of typical appearance are illustrated for Avena. The general occurrence of microbodies in meristematic and differentiating cells and their close association with the ER suggest that they may play active roles in cellular metabolism. The alterations in their morphology and numbers that are observed in certain differentiating cells suggest further that the enzyme complements and metabolic roles of microbodies might change during cellular differentiation. If so, microbodies could be the functional equivalent of both microbodies and lysosomes of animal cells.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 0730-2312
    Keywords: Spirodela ; thylakoids ; atrazine ; diuron ; chloroplast ; ultrastructure ; 32,000-dalton protein ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Cultivation of Spirodela oligorrhiza (Kurtz) Hegelm on a sublethal dose of atrazine results in a higher linolenic to linoleic acid ratio in the thylakoid membrane lipids, less starch, more osmiophilic globules, and a reduced stroma lamellar system. Also, the grana become randomly oriented and contain more numerous and elongated lamellae. These alterations in the lipid composition and ultrastructure of the chloroplast resemble those previously observed in triazine-resistant weed biotypes and in chloroplasts developed under low light. Thylakoid membranes from atrazine-adapted plants revealed an additional high-affinity binding constant for [14C]-diuron but the number of diuron binding sites actually decreased by 20 times compared to controls. The 32,000-dalton membrane protein of the chloroplast is synthesized actively, but its breakdown appears decreased compared to control plants. The adaptive reorganization of thylakoid components may be a compensatory mechanism for maintenance of a functional interaction of the proteins and lipids of the photosystem II complex.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...