Thomas L. Hayes

STRUCTURE AND HOMOGENEITY OF THE LOW-DENSITY SERUM LIPOPROTEINS

Although human serum lipoproteins have been studied intensively over the past decade, we still lack complete information concerning the chemical composition and structure of these macromolecules. One difficulty with regard to such studies is the wide range of lipoprotein classes that exist as part of the total blood lipoprotein spectra. It might be estimated, for instance, that in a typical serum lipoprotein distribution (as shown schematically in FIGURE 1 for a normal 45-year-old male) there might easily be the order of 100 lipoprotein classes, each of which could be distinguished from the others by physical or chemical means or by some combination of analytical methodologies now available. In this presentation we shall examine variations in composition that occur within each broad lipoprotein group and consider further the evidence for homogeneity of lipoproteins isolated within one narrow Sf band. There is evidence that the larger low-density lipoproteins, particularly those above Sr 100, may be lipoprotein complexes of limited stability. Furthermore, these macromolecular units present in the blood stream may be in a state of constant transformation, possibly reflecting a relationship to the breakdown and transport of all classes of lipids within the blood compartment. Considering this, we shall present evidence bearing on a hypothesis of a lipoprotein complex model for these very large low-density lipoproteins.

Low-temperature X-ray microanalysis of the differentiating vascular tissue in root tips of Lemna minor L

The fracture faces of bulk‐frozen tissue offer a number of advantages for the analysis of diffusible elements. They are easy to prepare, remain uncontaminated, and, unlike most frozen‐hydrated sections, can be shown to exist in a fully hydrated state throughout examination and analysis. Root tips of Lemna minor briefly treated with a polymeric cryoprotectant are quench frozen in melting nitrogen. Fractures are prepared using the AMRAY Biochamber, lightly etched if necessary to reveal surface detail and carbon coated while maintaining the specimen at 110 K. The frozen‐hydrated fracture faces are analysed at 110 K using the P/B ratio method which is less sensitive to changes in surface geometry and variations in beam current. The method has been used to investigate the distribution of seven elements (Na+, Mg++, P, S, Cl−, K+ and Ca++) in the developing vascular tissue of the root tip. The microprobe can measure relative elemental ratios at the cellular level and the results from this present study reveal important variations in different parts of the root. The younger, more actively dividing cells, appear to have a slightly higher concentration of diffusible ions in comparison to the somewhat older tissues which have begun to differentiate into what are presumed to be functional vascular elements.

The rotifer jaw: A scanning and transmission electron microscope study: I. The trophi of Philodina acuticornis odiosa

The trophi of the rotifer Philodina acuticornis odiosa have been studied by a variety of morphological techniques designed to elucidate the complex structure and function of this unusual hard tissue. The scanning electron microscope has been found to be valuable in supplementing observations on thin sections in addition to providing a unique three-dimensional impression of the entire trophi. In contrast to classical concepts, the jaws appear to be composed of intimately associated, essentially fused, components rather than distinct and separate parts which articulate together. Histochemical evidence suggests that the substance of the jaw is composed of acid mucopolysaccharide material and that a mineralized component, probably calcium, may reside in dense granules peripheral to the main body of the jaws.

The rotifer jaw: A scanning and transmission electron microscope study: II. The trophi of Asplanchna sieboldi

Trophi of the monogonont rotifer Asplanchna is a hollow structure coated internally by a cellular lining. This lining is continuous (through openings in the trophi) with cells which invest the external, more basal, aspects of the jaw. These highly filamentous lining cells are the sites of contact for muscle fibers which control jaw movement. Desmosomes and hemidesmosomes are responsible for the attachment of muscles to lining cells and lining cells to jaw, respectively. Both transmission and scanning electron microscopy confirm that the various components of the trophi are fused together and lack joint-like connections.

Effects of Total Body Irradiation upon Lipoprotein Metabolism

Author(s): Hewitt, John E.; Hayes, Thomas L.; Gofman, John W.; Jones, Hardin B.; Pierce, Frank T..

Correlation of scanning electron microscope and light microscope images of individual cells in human blood and blood clots.

Abstract Blood and bone marrow were examined with conventional light microscopy techniques of staining. The same preparations were then also examined in the scanning electron microscope. The individual cells photographed in the light microscope were imaged in the scanning electron microscope using the secondary electron mode. The surface features revealed in the scanning electron micrographs were found to be distinctive for the different types of leukocytes identified by conventional light microscopy staining methods. The microarchitecture of human whole blood clots as imaged with the scanning electron microscope is also presented.

The Examination of Cystolithic Hairs ot Cannabis and other Plants by means of the Scanning Electron Microscope

A number of plants similar in appearance to marijuana (Cannabis sativa) were examined using the scanning electron microscope. This information may be of assistance in identifying marijuana in routine investigations using the optical microscope.

Low-temperature scanning electron microscope analysis of the portland cement paste early hydration

Abstract The use of the frozen hydrated scanning electron microscopy (FHSEM) in the study of cement paste is described. This technique permits analysis of the fractured surface of cement paste in a fully hydrated state with water present as ice in a low temperature scanning electron microscope. At 110 K the paste has a substantial increase in mechanical strength, because water is converted from liquid to a solid state, and this permits the use of bulk specimens at very early hydration. Some preliminary results for 1 hour hydration are presented and future applications of this technique are discussed.

A determination of lipoprotein molecular weight by use the electron microscope

A determination of the molecular weight of the S~ 6-8 class human serum lipoprotein was carried out by direct particle count in the electron microscope. The methods for the isolation and viewing of the lipoprotein are described. The results suggest that a dimerization occurs during the procedures used in preparation for electron microscopy.

Low temperature scanning electron microscope studies of mouse small intestine

Etched frozen hydrated specimens of mouse small intestine have been examined with low temperature scanning electron microscopy as a preliminary to X‐ray microanalysis. Recognizable images have been obtained of most of the known histological features of the gut. Nuclear and cytoplasmic details were often seen. Ice crystal damage was evident, although the degree of artefact depended on the cell type being examined and also varied from cell to cell or within cells.