Use of nitrogen mustard N-oxide for the fixation of electron microscopic tissues

Nitrogen mustard N-oxide was tried for the fixation of tissue for electron microscopy. A fixative consisting of 1% nitrogen mustard N-oxide, 1% glutaraldehyde and 1% paraformaldehyde buffered at pH 7.4 followed by 1% OsO4 buffered at pH 7.4 was found useful for the tissues examined: thyroid, anterior pituitary, adrenal gland and oviduct of mice. If the tissues are fixed and the sections are stained with uranyl acetate and lead acetate doubly, the follicle colloid, colloid droplets, and secretory granules containing thyroglobulin in the thyroid become higher in electron density. The cisterna of the maturing face of the Golgi apparatus, secretory granules, ribosomes, nucleolus and chromatin in the cells examined are extremely electron dense. Tubular elements of smooth endoplasmic reticulum in the adrenal cortical cell and microtubules in all the cells examined are also well preserved. The fixative containing nitrogen mustard N-oxide is useful also for cytochemistry. Using tissue fixed by this method and stained en bloc by uranyl acetate, the noradrenaline and adrenaline cells in the adrenal medulla are clearly distinguished by light microscopy.

Freeze-fracture images of the zonula occludens in the mouse oviduct epithelium

Freeze-fracture images of zonulae occludentes of the oviduct epithelium of adult mice were observed in the electron microscope. The structure of zonulae occludentes varies depending on the types of oviduct epithelial cells. Those between two secretory cells consist of 5--14 (9.2 +/- 2.0) strands interposed between the luminal and the lateral plasma membrane. The strands run irregularly making well developed anastomoses with one another. The tight junction between two ciliated cells consists of 4--14 (8.5 +/- 2.3) strands. Among them the upper 3--9 strands are unique in shape. The strands run regularly, compactly and parallel to the luminal surface and to each other with a few anastomoses. The distance between the adjacent strands is about 40 nm. Under this characteristic part several strands are very loosely distributed and run irregularly. The pattern of the strands in the zonula occludens between a secretory cell and a ciliated one resembles that between adjacent ciliated cells. The junction consists of 4--13 (8.3 +/- 2.0) strands. The characteristically dense and parallel arrangement of the strands demonstrated in this study is presumed to be related to the ciliary movement. All the zonulae occludentes in the mouse oviduct epithelium are "very tight" in type. No large gap junctions are seen in the mouse oviduct epithelium.

Some observations on ciliogenesis in the oviduct epithelium of the mouse

Ciliogenesis in the epithelium of the oviduct ampulla of 5-9 day-old mice has been investigated by electron microscopy. As reported by many investigators, fibrous granules, deuterosomes, and procentrioles are important for ciliogenesis. After injection of colchicine, fibrous granules disappear, while numerous coated vesicles and lysosome-like dense bodies appear in the same region, and the formation of deuterosomes and procentrioles is impeded. In the ciliogenic cell, the Golgi apparatus, consisting of numerous vesicles, is very well developed, and a large number of microtubules are distributed between the supranuclear and apical cytoplasm. In addition to these, many small vesicles, some of which are fused with the plasma membrane, occur in the apical cytoplasm. These vesicles, which may be derived from the Golgi apparatus, are considered to be necessary for the apical plasma membrane, because the protrusion of cilia requires additional plasma-membrane substance during their differentiation and development. The microtubules, some of which are connected with these vesicles, might play some role in the movement of these vesicles from the Golgi field to the apical cytoplasm. When colchicine is administered to suckling mice, formation of microtubules is blocked in the upper part of the ciliated cell, and the apical vesicles disappear. This also indicates that the microtubules bring the vesicles from the Golgi field to the apical region of the cell.

Electron-microscopic studies on the development and aging of the oviduct epithelium of mice

The fine structure of the oviduct epithelium of the newborn to the old mouse was studied with an electron microscope. Just after birth, epithelial cells lining the ampulla of the mouse oviduct are simple columnar in shape and of one type in fine structure. They contain numerous free ribosomes, an extremely poor rough endoplasmic reticulum, and a small Golgi complex. In the 3-day-old mouse, the epithelial cells are differentiated neither into ciliated nor secretory cells, and are characterized by the appearance of many autolysosomes and a solitary cilium. The ciliary cells differentiates 5 days after birth. Ciliogenesis is frequently observed at 5-10 days. The important role of the fibrous granules for ciliogenesis and that of the Golgi apparatus for membranogenesis of the cilia are described and discussed. The secretory cell having mucous secretory materials is differentiated at 23 days. In the epithelial cell lining the ampulla of the aged (22 to 24-month-old) mouse oviduct, large autolysosomes and vacuoles 2-6 micrometer in diameter occur in the ciliated cell, though cilia and other cell organelles are well preserved. In the old mouse the secretory granules almost disappear and the rough endoplasmic reticulum is strikingly dilated in the secretory cell. No features showing the transformation between the secretory cell and the ciliary one are seen in the mouse oviduct.

Kinetics of protein synthesis and release in the STH-cell of the mouse anterior pituitary as revealed by electron microscopic autoradiography of 3H-amino acids

In order to investigate the kinetics of the synthesis and release of the secretory protein in the STH-secreting cell of the pituitary anterior lobe, studies were made using the electron microscopic autoradiography of 3H-amino acids. Each mouse received an intravenous injection of 2.8 mCi of 3H-amino acids consisting of equal amounts of 3H-leucine, 3H-tyrosine, 3H-lysine, 3H-histidine and 3H-glycine. The animal was sacrificed at 3, 5, 15 and 30 min, 1, 2, 4, 8 and 24 hrs after the injection. Although the whole silver grains are very few 3 min after the injection, half of the grains are recognized over the r-ER (47.1%); the Golgi apparatus already shows a few grains (5.9%). Total silver grains over the STH-cell increase in number with the lapse of time; the ratio of the grain number over the r-ER to the total grains over the whole cell decreases gradually, while the ratio of the grain number over the Golgi apparatus increases to reach a peak about 30 min after the injection (40.1%) and then decreases gradually. The ratio of the number of labelled granules to that of total granules increases slowly until 24 hrs after the injection (3 min: 0%, 5 min: 0.8%, 30 min: 3.9%, 2 hrs: 5.0%, 8 hrs: 8.0%, 24 hrs: 12.3%). It is concluded that the turnover in synthesis and release of exportable protein in the mouse STH-cell is very slow as compared with that of the thyroid and parathyroid cell.

Inhibition of photophosphorylation by ATP and the role of magnesium in photophosphorylation

ATP and pyrophosphate at high concentration (greater than 1 mM) inhibited photophosphorylation of isolated spinach chloroplasts in the normal salt medium and did not cause stimulation of electron transport. The inhibition of photophosphorylation by ATP or pyrophosphate was shown to be abolished by the addition of excess MgCl2, ADP and phosphate. It has been demonstrated that the rates of photophosphorylation in the absence and presence of ATP or pyrophosphate are determined similarly by the concentrations of magnesium-ADP (Mg - ADP-) and magnesiumphosphate (Mg - Pi) complexes. It is highly probable that Mg - ADP- and Mg - Pi, but not free ADP and free phosphate, are the active form of the substrates of photophosphorylation. This is in support of the view that ATP inhibits photophosphorylation by decreasing the concentration of Mg2+ which is available for the formation of the complex with ADP and phosphate.