Carbohydrate localization

Abstract: The histology and carbohydrate histochemistry of ten teleostean esophagi were compared. Structurally, the four layers of a typical vertebrate digestive tract were consistently present. The epithelium was always stratified and in all but one species (Ictalurus nebulosus) contained taste buds. Esophageal mucous cells were not the typical goblet cells seen in other vertebrates but appeared to be of six different types, pairs of which were associated with particular families. In esocids, poorly developed mucous acini and serous monogranular cells were present. In all species, the subepithelial connective tissue was not divided into definitive lamina propriae and submucosae due to the absence of muscularis mucosae. Variably present in this connective tissue region were argentophilic fibers and in esocids only, randomly dispersed striated muscle fibers. The arrangement of the muscularis was reverse to that of the general vertebrate plan. In mucous cells, three general types of epithelial mucosubstances were identified and in broad terms were recognized as sulfomucins, sialomucins and neutral mucosubstances. Morphological differences were accompanied by differences in carbohydrate localization, each esophageal epithelium containing at least two different mucosubstances. However, the mucosubstances identified in each mucous cell had a profile of characteristics different in some respects from any other. Thus teleostean esophagi appear to perform an integrated diversity of functions as reflected by their complex morphology and carbohydrate histochemistry.

Abstract: The role and distribution of the Golgi apparatus has been compared in hymenial and subhymenial cells ofCoprinus cinereus using conventional electron microscopic and carbohydrate localization techniques. Basidia at early interphase II of meiosis possessed numerous single Golgi cisternae. Golgi vesicles may contain fibrous granular material similar to basidial and basidiospore walls. Vesicles similar in size and apparently in content to those on cisternae accumulated at the growing apex of the young basidiospore. Golgi vesicles were also found in cystidia but appeared to be absent in other cells studied. Pseudoparaphyses, cystidia and subhymenial cells contained large deposits of glycogen which were removed enzymatically in light microscope preparations, but carbohydrate staining persisted in the cytoplasm of basidia, cystidia and basidiospores at the probably sites of Golgi vesicles and cisternae after enzymatic digestion. Septal pore caps of subhymenial cells were surrounded by a fibrillar cytoplasmic zone devoid of cell organelles except ribosomes. The periodic acid-silver hexamine and silver protein techniques for ultrastructural localization of carbohydrates were compared; the latter gave specific results with the controls used. Carbohydrates were localized in certain wall layers of the immature basidiospore and in the contents of Golgi vesicles. Staining also occurred in glycogen, plasma membrane and lomasomes. In the septal pore apparatus staining occurred only in the septal wall and a region in the septal pore swelling probably containing fibrils. The wall of the pseudoparaphyses stained more than the basidial wall. The results suggest that carbohydrates accumulate in Golgi vesicles attached to cisternae, that changes in vesicle contents occur during migration to the basidiospore, and that these vesicles may transport polysaccharides and mucopolysaccharides to the developing basidiospore wall.

Abstract: The congeners Gyrodactylus salaris and G. derjavini are specific ectoparasites of Atlantic salmon Salmo salar and brown trout S. trutta, respectively. To elucidate the involvement of lectin-carbohydrate interactions in this host specificity, carbohydrates on the tegument of the two species and the corresponding lectin activity of their hosts have been studied. Carbohydrate composition on the tegument differed significantly between the two gyrodactylids. Three of four commercially available peroxidase-labelled lectins with primary affinity towards D-mannoside, D-GalNAc and L-fucose bound more strongly to G. derjavini than to G. salaris. Lectins with an affinity towards D-mannoside and D-GalNAc bound significantly stronger to the cephalic lobes on G. derjavini compared to the tegument and sheaths of the hamuli. One brown trout strain and three different salmon strains were tested for lectin activity in skin and plasma. Two Baltic salmon strains and one strain from the Atlantic region were included. Brown trout differed significantly from the salmon strains when skin samples were tested for D-GalNAc activity. Lectins binding to other carbohydrates showed trends for similar host differences. The implications of carbohydrate-lectin interactions for host specificity in gyrodactylids are discussed.

Abstract: Hamamelitol is an unusual branched-chain sugar alcohol previously suggested to function as a leaf compatible solute. In this study, we have examined the leaf metabolism and intracelluiar compartmentalization of hamamelitol and other soluble sugars during long-term water stress treatment of Hedera helix (English ivy). Total leaf hamamelitol content was relatively low in greenhouse control plants, but increased 2-fold during water stress treatment to levels approaching those observed in field-grown plants (6–7 μmol g−1 fresh weight). Using density gradient fractionation with non-aqueous solvents, we showed that hamamelitol occurs primarily in the cytoplasm and vacuoles of leaf mesophyll cells. During water stress treatment most of the increase in leaf hamamelitol occurred in the mesophyll cytoplasm, compensating osmotically for a decrease in cytoplasmic sucrose concentration. The maximum concentration of cytoplasmic hamamelitol was 155 mol m−3 and occurred in field-grown plants. Labelling experiments showed that hamamelitol is slowly synthesized from 14CO2 in leaves of H. helix, but is very long-lived (estimated t1/2 of 4 years). Together, these data indicate that hamamelitol probably functions during long-term stress conditions as an osmotically active, compatible solute in plant leaves. We suggest that the signal for enhanced accumulation of hamamelitol during the water stress treatment was initiated by decreased plant growth and increased leaf sucrose hydrolysis.