Raul Dodsworth Machado

On the fine structure of the electrocyte of Electrophorus electricus L.

SummaryThe general ultrastructure of the electrocyte, the basic unit of the electric organs of Electrophorus electricus, is analyzed. Presented herein are detailed observations of the syncytial surface, its fibrillar coat, invaginations of the plasma membrane and synaptic terminals. Using Thiérys method glycogen granules were identified in the syncytial cytoplasm and inside the synaptic terminals, their size and structure being compatible with the muscular origin of the electric organs, to which the filamentous meshwork found in the cytoplasm may be related. Among the perinuclear-organelles, are dense bodies with crystalline patterns. The mitochondrial matrix contains dense granules, their size and structure varying according to the organ to which they belong and to the fixation method used.

Ultrastructure of Eucalyptus grandis × Eucalyptus urophylla. I. Shoots Cultivated in Vitro in Multiplication and Elongation‐Rooting Media

Structural changes of the leaf blade of Eucalyptus grandis × Eucalyptus urophylla shoots from multiplication and elongation‐rooting (E‐R) steps of in vitro cultures were analyzed by electron microscopy and morphometry. Normal and hyperhydric shoots were produced in a multiplication medium, while only normal plants were transferred to an E‐R medium. In both plant types, the wax deposit and cuticle layers were thin, indicating that they did not play the main role in avoiding water loss. In contrast to normal shoots, the hyperhydric types were characterized by a decline in the number of stomata on the adaxial surface and an enlargement of palisade cells. At the ultrastructural level, the hyperhydric shoots showed chloroplasts with small grana, absence of starch grains, and a higher density of rough endoplasmic reticulum, indicating that their metabolic activity is higher than in normal shoots. In E‐R‐medium‐derived plants, the stomata were sometimes localized in protrusions and were unable to close. However, they were not ultrastructurally altered. In palisade cells of E‐R‐medium‐produced leaves, the peroxisomes increased in number and size; this increase was related to chloroplast enlargement. These observations were thought to be involved in the higher photosynthetic capacity and the increase in metabolic activity required for leaf expansion during root formation. The adaptation of E. \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

A scanning electron microscope study of normal and vitrified leaves from Datura insignis plantlets cultured in vitro

grandis\times E

An electron microscopic investigation of the surface coat of the electrocyte of Electrophorus electricus

\end{document} . urophylla to multiplication and E‐R steps of in vitro cultures leads to ultrastructural changes, indicating that the metabolic activity of hyperhydric and rooted plants was higher than in normal plantlets produced in multiplication medium.

Localization of actin in the electrocyte of Electrophorus electricus L.

SummaryThe localization of (Na+-K+) ATPase in the intact electrocyte of the electric organ of Electrophorus electricus (L.) and its subcellular fractions was investigated by biochemical and cytochemical methods. The distribution of AChE activity in the subcellular fractions was also comparatively analysed with this enzyme serving as a marker of the innervated membranes of the electrocyte. After application of cytochemical method of Farquhar and Palade to glutaraldehyde-fixed tissue, reaction was observed only at the membranes of vesicles localized at the periphery of the electrocyte. Previously fixed electrocytes, incubated in Ernsts medium showed reaction only at the vesicles whereas in unfixed tissue reaction also appeared at other membranes (surface and invaginations) of the anterior and posterior faces. This reaction was significantly inhibited in the presence of ouabain or in the absence of K+. Inhibition of Na+-K+-ATPase by glutaraldehyde fixation was also confirmed by biochemical analysis.

Staining of microtubules of the electrocyte ofElectrophorus electricus L. by alcian blue and lanthanum

The surface anatomy of normal and vitreous leaves of plantlets obtained from Datura insignis Barb Rodr nodal segment cultures was compared using scanning electron microscopy. Normal and vitrified leaves are similar in several ways. They are both amphistomatic, and have similar distributions of glandular and non-glandular trichomes. Stomata have similar length, diameter and distribution in normal and vitreous plants. Immature stomata, which have closed pores, and plugged stomata, which contain an amorphous material between their guard cells, occur in both normal and vitrified leaves. Normal and vitreous leaves differ in the frequency of normal and abnormal stomata. Normal stomata have kidney-shaped guard cells and resemble closely those found in field-grown plants, whereas abnormal stomata have deformed guard cells. Normal stomata represent approximately 80% of the total number of stomata in normal leaves, but only 7% of the total number of stomata in vitreous leaves. Abnormal stomata represent 90% of the total number in vitreous leaves. The deformation of guard cells could possibly be a mechanical impediment to stomatal function.

Calcium binding to electroplax membranes from Electrophorus electricus.

The leaf blade of Eugenia sulcata Spring ex Mart, is examined with special attention to the epidermis, using light and electron microscopy (transmission and scanning). The anticlinal walls of the adaxial epidermis are wavy and the external periclinal walls do not have a uniform thickness on account of internal projections. Transmission electron microscopy shows in this wall three distinct layers. Scanning electron microscopy demonstrates that the outer surface of the abaxial epidermis does not exhibit striations. Number and arrangement of subsidiary cells permit the stomata to be classified in the anomostaurocytic type; according to the unequal thickening of guard cells they can be considered graminoid. The leaf blade is dorsiventral and includes subepidermic secretory cavities.

Cytochemistry and freeze-fracture of membranes isolated from the electrocyte of Electrophorus electricus (L.).

SummaryThe surface coat of the electrocyte of the main electric organ of Electrophorus electricus was studied using cytochemical methods (periodic acid-silver methenamine, periodic acid-chromic acid-silver methenamine, periodic acid-thiosemicarbazide-silver proteinate, Concanavalin A — horseradish peroxidase, ruthenium red, Alcian-blue lanthanum nitrate, colloidal iron hydroxide and cationized ferritin). The surface of the electrocyte presents perpendicularly oriented tubular invaginations of the cell membrane. The fibrous coat 50–100 nm thick, penetrates into the lumen of the invaginations. It is also observed in the synaptic clefts existent in the posterior face of the electrocyte. The coating of the surface membrane gives a positive reaction with all techniques used. Binding of colloidal iron hydroxide particles was observed only in the outer layer of the coat. With the Alcian-blue lanthanum nitrate technique, microtubules were observed in the cytoplasm of the electrocyte.The results indicate that the surface coat of the electrocyte contains mucopolysaccharides, glycoproteins, acid mucopolysaccharides and anionic sites detected at low (colloidal iron hydroxyde) and neutral (cationized ferritin) pH.