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A cytochemical analysis was undertaken of C cells of thyroid glands obtained from sixteen young oogs and five human s t ill - b o r n neonates. Tissues were fixed in selective liquid fixatives (N e lly 's , Carnoy s, glutaraldehyde-picric-acetic acid, glutaraldehyde-potassium dichromatesodium sulphate and formol-saline) or fixed in formalin vapour a f t e r freeze drying. Cryostat sections and some of the above fixatives were used for enzyme demonstration. Simple and conjugated proteins in the cytoplasm of canine C cells were studied by numerous cytochemical reactions. Acetylatiun, methylation, benzoylation, nitrosation, acid hydrolysis and aldehyde blockade as well as enzyme hydrolysis were employed to evaluate the aldehyde fuchsin, colloidal iron, toluidine blue and periodic acid-Schiff staining reactions in canine C cells. I have confirmed that the cytoplasm of canine C cells contains an abundance of acidic protein groups which are due to side-chain carboxyls. Mild acid hydrolysis, amongst other reactions, may result in peptide hydrolysis at the aspartyl group, which hydrolysis contributes to the anionic charge in the C cell cytoplasm. Basic proteins are not readily stained in the canine C c e l l . Bisulphide groups are numerous and their oxidation adds to the negative charge of the C cell cytoplasm. I found that the positive aldehyde fuchsin and colloidal iron reactions are not attributa ole to mucosubstances such as sulphomucms, sialomucins or acidic mucopolysaccharides, but seem to be imparted by an acidic protein unconjugated to polysaccharide. A positive aldehyde fuchsin reaction probably depends on both disulphidc and carboxyl groups within C c e lls . A positive colloidal iron reaction in canine C cells requires the presence of carboxyl groups but an increased number of these groups does not enhance the staining reaction. The conditions required generally for s ilv e r binding and more specifically for the Grimelius s ilv e r impregnation in canine C cells were evaluated by oxidation and various other cytochemical procecures. I found that the argyrophilia of thyroid C colls depends upon an exogenous reducing agent and upon pH, optimal impregnation occurring at a s lig h tly acid pH. Oxidation preceding s ilv e r impregnation by the Grimelius method, reduces the a f f i n i t y of structures in the cell for s ilv e r n itr a te . Indirect evidence supports the view that argyrophilia in the C cells depends upon disulphide groups. I t is suggested that s ilv e r nitrate and disulphide groups react in C cells to form silv e r nercaptide which produces the argyrophilia. The presence of C cel s was demonstrated in human neonates by means of cytochemical methods known to demonstrate C cells in dogs. C cells were found predominantly in the posterior region and upper pole of both lobes where they were found scattered in clusters of six to eight cells per high power f i e l d Two morphological forms of normal human C cells were observed - an ovoid cell and one with cytoplasmic processes. By demonstrating oxidative enzymes and masked metachromasia, three categories of e p ith e lia l cells have been shown in the neonatal thyroid gland : A ( f o l l i c u i a r ) , C and AC (intermediate) c e lls . The l a t t e r may be homologous with the oxyphil cells observed in normal and pathological adult thyroid glands. The c lin ic a l applications in which I have useo the results of the above studies are outlined in the la s t section of the dissertation.

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The distribution of photosystem I (PS I) and photosystem II (PS II) in a primitive green alga Tetraselmis subcordiformis, which belongs to Prasinophyceae and does not have grana in its chloroplast, was studied by immunoelectron microscopy. Two PS I antibodies were used: one against a PS I component of maize, the other against the 60 and 62 KDa PS I reaction centre proteins of the cyanobacterium Synechococcus elongatus. Both antibodies showed that 76-78% of the labelling is on the appressed thylakoid membranes and only 22-24% is located on the unappressed membranes. Use of antiserum against cp-47 of PS II from S. elongatus also gives 76% of the labelling on appressed thylakoid membranes and 24% on unappressed thylakoid membranes. Cytochemical detection of PS I activity by the photooxidation of 3,3$ sp prime$-diaminobenzidine and of PS II activity by the photoreduction of distyryl nitroblue tetrazolium chloride also revealed that PS I and PS II activities exist on both types of thylakoid membranes. Therefore, our results indicate that the distribution of PS I and PS II in green algae may differ from that in higher plants.

Includes bibliographical references (leaves 195-202). / xi, 205 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Scaevola spinescens is an Australian native plant, found widely in the arid to semi-arid regions of South Australia and through into most other states. Aboriginal people of Hawker in South Australia have traditionally used it as a natural medicine to treat a variety of symptoms. The thesis aims to extract, isolate and determine the structure of organic compounds from Scaevola spinescens. / Thesis (Ph.D.)--Adelaide University, Dept. of Chemistry, 2001

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