The intraepidermal innervation of the snout skin of the opossum has been studied with the light and electron microscope. Numerous large nerve fibers loose their myelin sheath in the superficial dermis and pass into the epidermis. The basement membranes of the epidermis and Schwann cell become continuous at the point of entry of the neurite into the epidermis. Within the epidermis, the neurite is associated with a specialized secretory epidermal cell, termed a Merkel cell. This cell has many secretory granules apposed to the neurite. The Merkel cells are epidermal cells since they have desmosomes between them and adjacent epidermal cells. The neurite in the stratum spinosum is enveloped by Schwann cells in a manner analogous to the Schwann cell investment of unmyelinated neurites. In the upper stratum spinosum the nerve fiber evidences changes which can be interpreted as degenerative. The Merkel cell-neurite complex is interpreted as representing a sensory receptor unit.

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PubMedDate not supplied

The effect of spontaneous diabetes mellitus on fatty acid oxidation, beta-hydroxybutyrate dehydrogenase activity and respiratory coupling of hepatic mitochondria in the guinea-pig (Cavia porcellus).

1. The purpose of this study was to determine whether hepatic mitochondria of guinea-pigs with spontaneous diabetes mellitus differ from those of non-diabetic guinea-pigs in the oxidation of fatty acids, the activity of beta-hydroxybutyrate dehydrogenase, or respiration-linked oxidative phosphorylation. During the course of the study, a third group of animals (referred to as the unclassified group) was discovered which, on the basis of the clinical chemistry and histological changes in the pancreas, appeared to be in a pre-diabetic or post-diabetic state. 2. No differences in the respiratory control ratios were found between any of the three groups. Fatty-acid oxidation in hepatic mitochondria was greater in both the unclassified and diabetic groups than in the non-diabetic group. Beta-Hydroxybutyrate dehydrogenase activity, however, was increased only in the diabetic group. These findings suggest that increased fatty acid oxidation is probably an intermediate change in the development of or the recovery from diabetes mellitus, whereas the activity of beta-hydroxybutyrate dehydrogenase is affected only in more advanced stages.

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