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Biomedical subjects

A Engel

Publications and source records attributed to A Engel.

At least 325 records · Page 18Linked to original sources
PubMed1978

Radiation exposure and recognition of electron microscopic images of protamine at high resolution.

The effect of radiation exposure on visual recognition of individual macromolecules of the protein protamine was examined using high resolution electron microscopy in scanning transmission, fixed beam transmission, dark field and bright field, and recording of images on plates or via video imaging systems including image intensifiers and digital image storage. Loss of recognition of protamine, including its 5 A substructure, followed approximately three-hit kinetics with a Do on the exponential portion of the curve of about 470 e/A2. In spite of the inevitable chemical damage at high doses, virtually all molecules in orientations that exhibited the characteristic protamine structure could still be recognized in dark field scanning transmission or fixed beam bright field at 100-200 e/A2. Recognition fell from 30 to 6% when doses were increased from 1000 to 2000 e/A2 in fixed beam dark field. Exposure rates, varied over seven orders of magnitude from 0.15 e/A2-s to 3 X 10(6) e/A2-s, had no effect at all on the recognition of structures.

Animals↗
PubMed1978

Molecular weight determination by scanning transmission electron microscopy.

A scanning transmission electron microscope is employed to determine the mass of biological macromolecules. Elastically scattered electrons are collected by an annular detector that is capable of counting single electrons. Off-line processing of these dark field micrographs stored on a magnetic tape is accomplished by a mini-computer. It allows the number of electrons scattered by spherical or filamentous proteins to be evaluated. The calibration factor relating the number of scattered electrons to the mass of the protein is derived from scattering theory and is experimentally determined from biological macromolecules of known mass. Mass-loss kinetics of biological specimens due to the electron beam are measured for various protein structures. The application of this method is illustrated by determination of the mass of an oligometric protein (major phage T4 head protein) and the mass per unit length of a filamentous protein aggregate (F-pili). The unique possibilities of this new technique as well as its limitations are discussed.

Bacterial Proteins↗
PubMed1977

[The descendants of 47, XYY subjects. Apropos of a family].

Having come across a family where the wife of a father who had 47 XYY chromosomes had 5 pregnancies, of which 3 were pathological (one case of anencephaly and spina bifida, one early abortion, one stillborn girl) the authors reviewed the literature concerning the lineage of parents with 47 XYY chromosomes. We have details of a total of 34 subjects who had this caryotype. 10 of them were sterile (30 per cent) and 10 (30 per cent) had a pathological lineage. Only 14 subjects (40 percent) gave rise to a line of normal descendants. The authors discuss the mechanism by which this caryotype (47 XYY) might be transmitted. They point out that so far only few cases have been published and conclude that it is important that many details about this subject should be published so that worthwhile genetic counselling will later be able to be carried out.

Abortion, Spontaneous↗