Biomedical subjects
Publications and source records attributed to V Elings.
Reproducible images of uncoated DNA in the atomic force microscope (AFM) have been obtained by imaging plasmid DNA on mica in n-propanol. Specially sharpened AFM tips give images with reproducible features several nanometers in size along the DNA. Plasmids can be dissected in propanol by increasing the force applied by the AFM tip at selected locations.
In skeletal muscle the activation of phosphorylase b is catalyzed by phosphorylase kinase. Both enzymes occur in vivo as part of a multienzyme complex. The two enzymes have been imaged by atomic force microscopy and the results compared to those previously found by scanning tunneling microscopy. Scanning tunneling microscopy and atomic force microscopy have been used to view complexes between the activating enzyme phosphorylase kinase and its substrate phosphorylase b. Changes in the size and shape of phosphorylase kinase were observed when it bound phosphorylase b.
The high resolution of the scanning tunneling microscope (STM) makes it a potentially important tool for the study of biomaterials. Biological materials can be imaged with the STM by a procedure in which fluid, nonconductive biomaterials are replaced by rigid and highly conductive freeze-fracture replicas. The three-dimensional contours of the ripple phase of dimyristoylphosphatidylcholine bilayers were imaged with unprecedented resolution with commercial STMs and standard freeze-fracture techniques. Details of the ripple amplitude, asymmetry, and configuration unobtainable by electron microscopy or x-ray diffraction can be observed relatively easily with the STM.
Scanning probe microscopes derived from the scanning tunnelling microscope (STM) offer new ways to examine surfaces of biological samples and technologically important materials. The surfaces of conductive and semiconductive samples can readily be imaged with the STM. Unfortunately, most surfaces are not conductive. Three alternative approaches were used in our laboratory to image such surfaces. 1. Crystals of an amino acid were imaged with the atomic force microscope (AFM) to molecular resolution with a force of order 10(-8) N. However, it appears that for most biological systems to be imaged, the atomic force microscope should be able to operate at forces at least one and perhaps several orders of magnitude smaller. The substitution of optical detection of the cantilever bending for the measurement by electron tunnelling improved the reliability of the instrument considerably. 2. Conductive replicas of non-conductive surfaces enabled the imaging of biological surfaces with an STM with a lateral resolution comparable to that of the transmission electron microscope. Unlike the transmission electron microscope, the STM also measures the heights of the features. 3. The scanning ion conductance microscope scans a micropipette with an opening diameter of 0.04-0.1 micron at constant ionic conductance over a surface covered with a conducting solution (e.g., the surface of plant leaves in saline solution).
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The end diastolic volume and systolic ejection fraction have gained increasing acceptance as important indicators of ventricular performance. Time consuming calculations and lack of computer facilities have hindered the emergence of these calculations as a routine part of cardiac catheterization studies. The introduction of the programmable hand calculator has provided means for rapid analysis of ventricular volume data in an efficient and inexpensive manner. In this paper the step-by-step procedure for programming the hand calculator is given, as well as instructions for entering raw data and obtaining final calculations. Programs are given for both single plane and biplane cine angiographic studies.