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Biomedical subjects

A J DALTON

Publications and source records attributed to A J DALTON.

At least 19 recordsLinked to original sources
PubMed1962

Speculations based on the morphology of the Golgi systems in several types of proteinsecreting cells.

Electron microscopical observations on the relationship of the Golgi region to other intracellular organelles in certain protein-secreting cells have substantiated and extended existing hypotheses. In micrographs of several cell types, the juxtanuclear Golgi regions were observed to be closely associated with nuclear "pores." The "transition elements" of the ergastoplasmic membranes possess "blebs" which may represent a transport process facilitating the movement of intracisternal contents into the Golgi zone. A "blebbing" process of this nature may be one source of the small variety of Golgi vesicles. Zymogen granules of different densities were observed and their significance was postulated. Light Golgi vacuoles were observed. It is suggested that these vacuoles represent accumulations of relatively fluid material segregated from the secretory product in these cell types. These hypotheses from inferential evidence are discussed and extended.

Animals↗
PubMed1959

An association between mitochondria and the endoplasmic reticulum in cells of the pseudobranch gland of a teleost.

An elaborate and apparently unique specialization of the endoplasmic reticulum having the form of tubules and a precise orientation with respect to the mitochondria has been described for the specific cell of the pseudobranch gland. The tubules also are concentrated near the vascular border of the cell where they show continuity with the plasma membrane and open directly against the basement membrane. On the other side of the basement membrane, the endothelial cells of the sinusoid show openings or discontinuities characteristically associated with secretory cells. The pseudobranch gland is presumed to have carbonic anhydrase as one of its primary products, if not its only one, and the elaborate ultrastructure is thought to be associated with the special problems of secreting this enzyme.

Animals↗
PubMed1959

Spermiogenesis in Lumbricus herculeus; an electron microscope study.

Small pieces of the sperm sacs of Lumbricus herculeus were fixed for 4 hours in chrome-osmium, embedded in methacrylate, sectioned with a Porter-Blum microtome, and studied with a R.C.A. EMU-2C electron microscope. Each spermatid of a group developing synchronously is attached by a cytoplasmic strand to a common nutrient protoplasmic mass. This mass contains mitochondria and yolk bodies but is anucleate. The proximal centriole, that is, the centriole nearer the nucleus, is at first associated with a small peg which becomes firmly attached to the nuclear membrane. Later these two bodies become separated during the development of the middle-piece which is differentiated in the usual manner from a nebenkern formed by the fusion of 6 or 7 mitochondria. The acrosome develops in relation to the dictyosome (Golgi body), itself composed of 8 or more individual flattened sacs and situated in the cytoplasm opposite the point of attachment of the spermatid to the nutrient mass. Soon after its formation, the acrosome becomes incorporated into a cytoplasmic appendage or acrosome carrier. The carrier moves from its original position, along the lateral border of the elongating nucleus, to the distal margin of the nucleus where the acrosome is deposited. No evidence was found of a centriole located at the point of junction between nucleus and acrosome as suggested by earlier workers.

Acrosome↗
PubMed1957

A cytological study of the albuminsecreting cells of the hen oviduct.

1. The electron and light microscope have been employed in a cytological study of the albumin-secreting cells of the hen oviduct and of fractions of this tissue obtained after homogenization and differential centrifugation. 2. These studies confirm the observation that in this tissue material corresponding to liver "microsomes" in amino acid-incorporating ability and ribonucleic acid content sediments in relatively low centrifugal fields. 3. The electron microscope studies suggest that the protein secretion of the gland is formed in intimate association with the ergastoplasm.

Amino Acids↗