β-Mannosidosis, an inherited glycoprotein metabolic disorder so far identified only in the caprine species, is characterized by deficiency of β-mannosidase, oligosaccharide accumulation and excretion, neurovisceral cytoplasmic lysosomal storage vacuoles and central nervous system myelin and axonal lesions. In this investigation, transmission electron microscopy was used to study peripheral nerve elements in the gingiva of five affected goats and a control animal. Merkel and Schwann cells were vacuolated. Accumulations of dense bodies distended Merkel cell end plates and free-ending axons in the prickle cell layer as well as Pacinian corpuscle axons, and myelinated, unmyelinated, and demyelinated axons in the lamina propria. Unlike central nervous system myelin paucity, loss of peripheral nerve myelin was exclusively related to axonal dense body accumulation and enlargement. The identification of these lesions may facilitate detection of β-mannosidosis in man and other species.

ABSTRACT Interactions between fungal and algal components of Usnea cavernosa Tuck, were demonstrated with transmission and scanning electron microscopy. Cells were observed in very close associations, and both intrawall and intracellular haustoria were evident. In addition, a previously unreported type of interaction was discovered which consisted of an extracellular hyphal sheath with distinctive protuberances which penetrated into the algal cell wall. Internal environmental factors which may bear on the types of cellular interactions were evaluated by dividing the lichen thalius into three artificial regions using spatial and temporal criteria. Fungal hyphae in the various internal anatomical zones (e.g., cortex, medulla, central cord) demonstrated differences in cell wall structure and extracellular material produced.

Polysaccharides (1,2-glycols), identified by a cytochemical stain at the ultrastructural level, were found in storage droplets of algal cells and cytoplasm of both the medullary hyphae and hyphae of the chondroid central cord of Usnea cavernosa Tuck. The intercellular matrix of the chondroid cen- tral cord contained no polysaccharides stainable with the method employed. High concentration of 1,2-glycol polysaccharides noted in the hyphal cyto- plasm of the chondroid central cord may suggest a possible function of the cord as a storage tissue for a readily converted energy source.