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Biomedical subjects

S F JACKSON

Publications and source records attributed to S F JACKSON.

12 recordsLinked to original sources
PubMed1958

Fine structure and function in Stentor polymorphous.

The fine structure of the ciliate Stentor has been studied by means of the electron microscope and the results have been correlated with observations made on the living organism by means of light microscopy; special reference has been made to structural features which may be responsible for contraction and extension in Stentor. Descriptions have been given of the structure of the macronucleus, the vacuolated cytoplasm, mitochondria and the pellicle; a detailed study has also been made of the adoral membranelles. About 250 membranelles encircle the peristomal cap and each is composed of 3 rows of cilia, with 20 to 25 cilia in each row; a fibrillar root system connected with the membranelles depends into the endoplasm for about 20 micro and each is essentially in the shape of a fan, the terminal ends of each root bifurcating to connect to neighbouring roots. The membranelles thus form a cohesive unit and this morphological arrangement may have a bearing on the motion and coordination of the whole system. Two structural features extending throughout the length of the animal have been identified per cortical stripe in the body wall of Stentor; first, km fibres lying just beneath the pellicle are composed of stacks of fibrillar sheets and are identical with the birefringent fibres observed in the living animal. The individual fibrils of the sheets are in turn connected to the kinetosomes of the body cilia; thus the km fibres are homologous to kinetodesmata. Secondly, M bands lie beneath the km fibres and form an interconnected system in contact with the surrounding vacuolated cytoplasm; the thickness of the M bands is greatest at the base of a contracted animal. The contractile and extensile properties of these organelles have been discussed in the light of experimental results and theoretical considerations.

Animals↗
PubMed1957

Studies on the biosynthesis of collagen. I. The growth of fowl osteoblasts and the formation of collagen in tissue culture.

1. A tissue culture method was devised in which suspensions of osteoblasts, obtained directly from frontal bones of fowl embryos, were grown in a fluid, fibrin-free medium. 2. Maximum growth of the tissue, as measured by dry weight, with the formation of collagen protein, based on the estimation of hydroxyproline, was obtained in periods of up to 6 days. 3. Appreciable amounts of protein-bound hydroxyproline were formed during the first 24 hour growth period, but electron microscopy of portions of the same cultures failed to demonstrate the presence of any typical collagen fibrils. 4. The subsequent formation of many characteristic collagen fibrils was not associated with a significant rise in the mean hydroxyproline content of the tissue. 5. The cytoplasmic granules of the osteoblasts stained intensely with the P.A.S. technique when the collagen fibrils were being formed. 6. It is suggested that collagen-forming cells synthesise and secrete a hydroxyproline-rich precursor of protein or large peptide nature, which subsequently becomes directly transformed into typical collagen fibrils.

Cells, Cultured↗
PubMed1957

Studies on the biosynthesis of collagen. II. The conversion of 14C-L-proline to 14C-hydroxyproline by fowl osteoblasts in tissue culture.

1. Fowl osteoblasts grown in bulk tissue cultures in the presence of (14)C-(L)-proline incorporated this amino acid into peptide linkage. A significant amount of the incorporated radioactivity was found in the hydroxyproline, glutamic acid, and aspartic acid fractions of the cultures. 2. The rate of formation of protein-bound (14)C-hydroxyproline from (14)C-(L)-proline was maximal in cultures grown for 15 hours and fell exponentially with the increasing age of the cultures. 3. (14)C-(L)-glutamic acid was incorporated by the osteoblast cultures, but no significant amount was converted to hydroxyproline.

Amino Acids↗