An unusual archegonium with persistent ventral canal cell inPhyscomitrium cyathicarpumMitt. — an ultrastructural study

1982 ◽  
Vol 12 (2) ◽  
pp. 293-295 ◽  
Author(s):  
Manohar Lal ◽  
Gavinder Kaur ◽  
Eklavya Chauhan
Keyword(s):  
Ultrastructural Study ◽  
Canal Cell ◽  
Ventral Canal

Elektronenmikroskopische Untersuchungen über die Eizellbildung und Eizellreifung des Lebermooses Sphaerocarpus donnellii Aust.

1965 ◽  
Vol 20 (8) ◽  
pp. 795-801 ◽  
Author(s):  
Lothar Diers
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Phase Contrast ◽  
Lipid Droplets ◽  
Unit Membrane ◽  
Light Phase ◽  
Lamellar System ◽  
Small Bodies ◽  
Canal Cell ◽  
Ventral Canal

The formation and maturation of the egg of the liverwort, Sphaerocarpus donnellii, was investigated by light, phase contrast and particularly by electron microscopy. The division of the central cell into the egg and the ventral canal cell, and the maturation of the egg, is completed within four days. All stages of this formation and maturation were examined under the electron microscope after fixation in KMnO4 or OsO4. — In the maturing egg there always occur the endoplasmic reticulum, well recognisable plastids with a poorly developed lamellar system, numerous mitochondria and dictyosomes, a rising number of lipid droplets, unknown small bodies limited by a unit membrane, and numerous ribosomes. During maturation the nucleus considerably enlarges and forms evaginations into the cytoplasm. Starch is increasingly deposited in the plastids. A degeneration of plastids has not been found.

Sexual reproduction of mountain hemlock (Tsuga mertensiana)

1975 ◽  
Vol 53 (17) ◽  
pp. 1811-1826 ◽  
Author(s):  
John N. Owens ◽  
Marje Molder
Keyword(s):  
Cell Walls ◽  
Pollen Tubes ◽  
Linear Tetrad ◽  
Form Complex ◽  
Male Gametes ◽  
Canal Cell ◽  
Micropylar Canal ◽  
Tsuga Mertensiana ◽  
Mother Cells ◽  
Ventral Canal

Meiosis of pollen mother cells begins in October of the year in which cones are initiated. They reach pachytene then become dormant until the next March. Meiosis is complete and the winged pollen mature by mid-June. Meiosis of the megaspore mother cell occurs in May, forming a linear tetrad of megaspores. The female gametophyte undergoes free nuclear division at pollination in mid-June. No pollination drop is present; rather, the pollen adheres to the sticky, splayed edge of the micropyle, where it germinates and pollen tubes grow toward the nucellus. The nucellus elongates into the micropylar canal, forming a nucellar beak, which makes contact with the pollen tubes. Several pollen tubes penetrate the nucellus.At the time of fertilization early in August, each ovule contains two to four aichegonia each having two to four neck cells in one tier. Pollen tubes penetrate the neck cells and two male gametes are formed. The ventral canal cell breaks down and fusion occurs in the center of the archegonium. Four free nuclei form and migrate to the base of the archegonium. cell walls form, and a 16-celled proembryo develops. Both simple and cleavage polyembryony occur. Rosette cells divide but do not form complex embryos. The embryo and seed are mature in October and the cones dry and open during October and November. Mature cones averaged 70 seeds, of which 46% were filled.Reproduction in mountain hemlock (Tsuga mertensiana (Bong.) Carr.) is similar to that in other species of Tsuga except for the presence of winged pollen. Any attempt to place the species in the genus Picea or place it as a hybrid midway between Picea and Tsuga is unfounded based on all of the more-conservative reproductive and embryological characteristics.

scholarly journals Female gametophyte development and embryogenesis in Taxus baccata L.

2014 ◽  
Vol 65 (1-2) ◽  
pp. 135-139 ◽  
Author(s):  
Vladimir B. Brukhin ◽  
Peter V. Bozhkov
Keyword(s):  
Early Embryo ◽  
Temperate Climate ◽  
Taxus Baccata ◽  
Linear Tetrad ◽  
Canal Cell ◽  
Nuclear Stage ◽  
Female Gametophyte Development ◽  
Ventral Canal ◽  
Embryonic Region ◽  
Suspensor Cells

Crassinucellate ovules are initiated in <em>Taxus</em>, directly from the shoot apex. The rudimentary pollen chamber is formed in the nucellus. A linear tetrad of megaspores with a functional chalazal megaspore is formed. A free-nuclear stage is charac-teristic at the beginning of megagametophyte development. Archegonia without ventral canal cell are solitary or in complexes. The embryo has a very long suspensor even after maturation. Two types of polyembryony have been revealed: i) embryogenic redifferentiation of suspensor cells and ii) cleavage of embryonic region in the early embryo. In the northern temperate climate of St. Petersburg one month delay in development of reproductive structures has been noted.

On the cytological features of fertilisation and related phenomena in Pinus silvestris , L

1898 ◽  
Vol 63 (389-400) ◽  
pp. 400-401
Keyword(s):  
Pinus Silvestris ◽  
Wall Formation ◽  
Canal Cell ◽  
Cytological Features ◽  
Ventral Canal ◽  
Complete Account

This paper gives a fairly complete account of the minute cytological details of the act of fertilisation and of the processes surrounding from the formation of the ventral canal cell up to the period of cl wall formation at the base of the egg. As the oosphere nucleus, after separation of the nucleus of the ventral canal cell, moves rapidly back towards the centre of the e it increases greatly in size, as described by Strasburger. Ts increase in size is shown to be due to the appearance in the nucleus of a peculiar metaplasmic substance, which fills up the nucleus, and owing to its attraction for stains, ultimately obscures the chromatin.

Tumor Diagnosis

1982 ◽  
Vol 40 ◽  
pp. 262-265
Author(s):  
Bruce Mackay
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Differential Diagnosis ◽  
Light Microscopy ◽  
Clinical Examination ◽  
Ultrastructural Study ◽  
Diagnostic Procedures ◽  
Specific Diagnosis ◽  
Transmission Electron ◽  
Microscopic Diagnosis

The broadest application of transmission electron microscopy (EM) in diagnostic medicine is the identification of tumors that cannot be classified by routine light microscopy. EM is useful in the evaluation of approximately 10% of human neoplasms, but the extent of its contribution varies considerably. It may provide a specific diagnosis that can not be reached by other means, but in contrast, the information obtained from ultrastructural study of some 10% of tumors does not significantly add to that available from light microscopy. Most cases fall somewhere between these two extremes: EM may correct a light microscopic diagnosis, or serve to narrow a differential diagnosis by excluding some of the possibilities considered by light microscopy. It is particularly important to correlate the EM findings with data from light microscopy, clinical examination, and other diagnostic procedures.

Further Observations on the Virus of Epizootic Diarrhea of Infant Mice. An Electron Microscopic Study

1967 ◽  
Vol 25 ◽  
pp. 110-111
Author(s):  
W. G. Banfield ◽  
G. Kasnic ◽  
J. H. Blackwell
Keyword(s):  
Electron Microscope ◽  
Infected Cell ◽  
Microscopic Study ◽  
Intestinal Epithelium ◽  
Ultrastructural Study ◽  
Osmium Tetroxide ◽  
Lead Citrate ◽  
Electron Microscopic ◽  
Virus Particles ◽  
Infected Cells

An ultrastructural study of the intestinal epithelium of mice infected with the agent of epizootic diarrhea of infant mice (EDIM virus) was first performed by Adams and Kraft. We have extended their observations and have found developmental forms of the virus and associated structures not reported by them.Three-day-old NLM strain mice were infected with EDIM virus and killed 48 to 168 hours later. Specimens of bowel were fixed in glutaraldehyde, post fixed in osmium tetroxide and embedded in epon. Sections were stained with uranyl magnesium acetate followed by lead citrate and examined in an updated RCA EMU-3F electron microscope.The cells containing virus particles (infected) are at the tips of the villi and occur throughout the intestine from duodenum through colon. All developmental forms of the virus are present from 48 to 168 hours after infection. Figure 1 is of cells without virus particles and figure 2 is of an infected cell. The nucleus and cytoplasm of the infected cells appear clearer than the cells without virus particles.

Glycogen in guinea pig neutrophils: Ultrastructural study of neutrophils at the intradermal site of BCG injection

1983 ◽  
Vol 41 ◽  
pp. 726-727
Author(s):  
Corazon D. Bucana
Keyword(s):  
Bone Marrow ◽  
Guinea Pig ◽  
Electron Density ◽  
Peritoneal Cavity ◽  
Ultrastructural Study ◽  
Guinea Pigs ◽  
Random Distribution ◽  
Glycogen Content ◽  
Polymorphonuclear Neutrophils ◽  
Ultrastructural Studies

In the circulating blood of man and guinea pigs, glycogen occurs primarily in polymorphonuclear neutrophils and platelets. The amount of glycogen in neutrophils increases with time after the cells leave the bone marrow, and the distribution of glycogen in neutrophils changes from an apparently random distribution to large clumps when these cells move out of the circulation to the site of inflammation in the peritoneal cavity. The objective of this study was to further investigate changes in glycogen content and distribution in neutrophils. I chose an intradermal site because it allows study of neutrophils at various stages of extravasation.Initially, osmium ferrocyanide and osmium ferricyanide were used to fix glycogen in the neutrophils for ultrastructural studies. My findings confirmed previous reports that showed that glycogen is well preserved by both these fixatives and that osmium ferricyanide protects glycogen from solubilization by uranyl acetate.I found that osmium ferrocyanide similarly protected glycogen. My studies showed, however, that the electron density of mitochondria and other cytoplasmic organelles was lower in samples fixed with osmium ferrocyanide than in samples fixed with osmium ferricyanide.

An ultrastructural study of vegetative incompatibility in plants

1978 ◽  
Vol 36 (2) ◽  
pp. 436-437
Author(s):  
Randy Moore
Keyword(s):  
Ultrastructural Study ◽  
Cell Walls ◽  
Growth And Development ◽  
Solanum Pennellii ◽  
Initial Product ◽  
Basic Aspect ◽  
Tissue Interactions ◽  
Graft Interface ◽  
Antigen Antibody ◽  
Standard Fixation

Cell and tissue interactions are a basic aspect of eukaryotic growth and development. While cell-to-cell interactions involving recognition and incompatibility have been studied extensively in animals, there is no known antigen-antibody reaction in plants and the recognition mechanisms operating in plant grafts have been virtually neglected.An ultrastructural study of the Sedum telephoides/Solanum pennellii graft was undertaken to define possible mechanisms of plant graft incompatibility. Grafts were surgically dissected from greenhouse grown plants at various times over 1-4 weeks and prepared for EM employing variations in the standard fixation and embedding procedure. Stock and scion adhere within 6 days after grafting. Following progressive cell senescence in both Sedum and Solanum, the graft interface appears as a band of 8-11 crushed cells after 2 weeks (Fig. 1, I). Trapped between the buckled cell walls are densely staining cytoplasmic remnants and residual starch grains, an initial product of wound reactions in plants.

Golgi Apparatus and Melanogenesis: Ultrastructural Study of a Human Cellular Blue Nevus (Melanocytoma)

1973 ◽  
Vol 31 ◽  
pp. 380-381
Author(s):  
S.R. Allegra
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Ultrastructural Study ◽  
The Other ◽  
Blue Nevus ◽  
Normal Complement ◽  
Golgi Vesicles ◽  
Golgi System ◽  
The Subject ◽  
Cellular Blue Nevus

The respective roles of the ribo somes, endoplasmic reticulum, Golgi apparatus and perhaps nucleus in the synthesis and maturation of melanosomes is still the subject of some controversy. While the early melanosomes (premelanosomes) have been frequently demonstrated to originate as Golgi vesicles, it is undeniable that these structures can be formed in cells in which Golgi system is not found. This report was prompted by the findings in an essentially amelanotic human cellular blue nevus (melanocytoma) of two distinct lines of melanocytes one of which was devoid of any trace of Golgi apparatus while the other had normal complement of this organelle.

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