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Biomedical subjects

D DANON

Publications and source records attributed to D DANON.

At least 19 recordsLinked to original sources
PubMed1964

ELECTRON MICROSCOPY OF IN VITRO ENDOCYTOSIS OF T2 PHAGE BY CELLS FROM RABBIT PERITONEAL EXUDATE.

Macrophages from rabbit peritoneal exudate cells incubated in vitro with T(2) bacteriophage from 10 up to 120 minutes show phage particles adsorbed to cell membranes, in the process of being engulfed by means of rhopheocytosis, micropinocytosis, and phagocytosis, and localized within dense vacuoles, semi-dense vacuoles, and clear vacuoles of the cytoplasm. The electronmicrographs suggest that newly formed endocytic vacuoles containing phage particles fuse with one another and also fuse with dense bodies of the cytoplasm as they migrate towards the cell interior, thus yielding larger vacuoles of varying densities containing higher concentrations of phage. The polymorphonuclear cells present in a small proportion in the peritoneal exudate cells also endocytosed phage particles. The T(2) particles are found in large cytoplasmic vacuoles surrounded by an electron-opaque material presumably derived from cytoplasmic granules. No disintegration of T(2) phage within the macrophage following incubations up to 120 minutes could be demonstrated; however, disrupted phage particles were noted within cytoplasmic vacuoles of polymorphonuclear leucocytes after 15 minutes' incubation.

Animals↗
PubMed1964

ALTERATIONS IN POLYRIBOSOMES DURING ERYTHROID CELL MATURATION.

This communication presents a morphological study of the changes in ribosome content and organization which occur during the maturation of erythroid cells of the phenylhydrazine-treated rabbit. Electron micrographs of thin sectioned nucleated and non-nucleated erythroid cells have been subjected to a quantitative analysis of the distribution of ribosomes as polyribosomes of various sizes and as single ribosomes. The ribosomes of nucleated erythroid cells of marrow are virtually all arranged in the polyribosome configuration consisting of clusters of 2 to 6 individual ribosomes. These cells are the most active in the erythroid series in protein biosynthesis. During maturation to the non-nucleated reticulocyte stage, found in the circulating blood, there is a decrease in protein synthesizing capacity, a fall in total ribosome content, and, more significantly, a decrease in the number and size of polyribosomes. Maturation to the ribosome-free erythrocyte, either under in vitro or in vivo conditions, entails a further decrease in protein synthesis which correlates with a progressive disaggregation of the biosynthetically active polyribosomes into smaller clusters and inactive single ribosomes. Possible models which may account for the stability of the polyribosome and for the mechanism of polyribosome dissociation are discussed.

Animals↗
PubMed1963

The use of shadow-casting technique for measurement of the width of elongated particles.

A method is described for the estimation of the true width of fibrillar or rod-like structures from electron micrographs of metal-shadowed preparations. The method is based on variations in the image width as a function of the angle (beta) between the long axis of the fibril and the direction of the shadow in the plane of the preparation. The image width when beta = 0 degrees practically represents the real width of the elongated particle but is often indistinguishable from the background. The fibril image width is conveniently measured at beta values between 15 degrees and 90 degrees . The true width is obtained by plotting the image width versus sin beta and extrapolating to beta = 0 degrees . Latex spheres are sprayed with the fibrils or rods to indicate the direction of shadow. Tobacco mosaic virus (TMV) was used as a model structure because of its known constant diameter of 150 A (5). The width (in the case of TMV equal to the diameter) found by the present method was 150 A +/- 8 A.

Electrons↗
PubMed1963

A RAPID MICRO METHOD FOR RECORDING RED CELL OSMOTIC FRAGILITY BY CONTINUOUS DECREASE OF SALT CONCENTRATION.

A single volume of 0.075 ml. of a 1 in 10 dilution of whole blood in isotonic NaCl solution is introduced into a container cell, two walls of which are made of a dialysing membrane. The container cell is introduced into a test tube of distilled water, placed in an instrument which is essentially a colorimeter with a recorder, between the source of light and the photoelectric cell. Dialysis through the membrane results in a continuous decrease in the salt concentration of the medium surrounding the erythrocytes. The measurement of the degree of haemolysis is based on the increasing transparency of the erythrocyte suspension while haemolysis takes place. Recording this increasing light transmission as a function of time, i.e., as a function of decreasing salt concentration, yields the osmotic fragility curve. The automatically recorded curve is obtained in less than 10 minutes.

Erythrocytes↗