David N. Menton

Structure and organization of mammalian stratum corneum.

The structure of horny cells and their spatial relationship in the stratum corneum of several mammals, including man, have been studied by the combined use of Nomarski differential interference microscopy, transmission electron microscopy, and scanning electron microscopy. In the body skin of these mammals the horny cells and cells in the stratum granulosum are organized in neatly stacked vertical columns. The cells in each stack interdigitate at their edges with the cells in adjacent stacks by means of a steplike shallow depression which encircles the superficial aspect of each cell, thus maintaining contiguity and uniform thicknesss for the stratum corneum as a whole. The columned stack arrangement is quite likely responsible for the hexagonal shape of the individual cell. In the palmar and plantar skin of the mammals studied, the horny cells of the stratum corneum apparently lack a specific organization as well as the hexagonal shape. The horny cells from all areas are characterized by abundant villous-like processes which are consistent in size, shape, and distribution with attachment sites of desmosomes.

Parathyroid hormone-induced changes of the brush border topography and cytoskeleton in cultured renal proximal tubular cells

SummaryIn order to examine the possibility of parathyroid hormone-mediated ultrastructural rearrangements in target epithelium, isolated canine renal proximal tubular cells were grown on a collagen-coated semipermeable membrane in a defined medium. Scanning and transmission electron microscopy of these monolayers revealed abundant microvilli. Exposure of the proximal tubular cells to parathyroid hormone resulted in a biphasic changes involving: (1) dramatic shortening and rarefaction of microvilli within 1 min; and (2) recovery of microvillar topography after 5 min. A similar shortening of microvilli was observed following exposure to ionomycin, whereas incubation with cyclic AMP resulted in an elongation of microvilli. Parathyroid hormone stimulated cyclic AMP production and increased cytoplasmic free calcium concentration in cultured proximal tubular cells. Pretreatment of cells with a calmodulin inhibitor abolished the effect of parathyroid hormone on brush border topography. Shortening of microvilli was associated with a disappearance of microvillar core filaments. Staining of F-actin with fluoresceinphalloidin showed that parathyroid hormone resulted in fragmentation of stress fibers. It is concluded that parathyroid hormoneinduced cell activation involves cytoplasmic-free calcium, calmodulin, and the cytoskeleton.

High-voltage galvanic stimulation on wound healing in guinea pigs: Longer-term effects

The purpose of this investigation was to determine the effects of high-voltage stimulation (HVS) on wound tensile strength properties and wound closure (histology). Eighteen mature guinea pigs with full-thickness incisions were treated with HVS for 45 minutes daily for 2 weeks; 9 animals were studied after the 14 days of treatment and the remaining 9 were studied 2 weeks later. Five animals (10 wounds) served as controls at each time period. After 2 or 4 weeks, treated and untreated skin was harvested, tested to failure, and prepared for histological examination. Two-week-treated and control wounds had comparable values for peak force to failure, elongation, and energy absorbed to failure. Epithelialization was more advanced in treated animals at 14 days (p < .05). There was a trend (p = .068) toward stronger wounds in 4-week-treated animals (maximum load to failure), but not differences were observed between controls and treated groups for elongation or energy absorbed to failure. Dermal healing appeared to be more advanced in treated animals at 30 days. Although peak force to failure was almost 500g higher for treated guinea pigs after 2 weeks of treatment and more than 700g higher than controls after 4 weeks, mean data were highly variable, so the hypothesis that HVS augments wound strength could not be accepted. It is difficult, however, not to assign clinical significance to the findings.

Scanning electron microscopy of human placental villi from early and late in gestation

Human placental villi from term placentas and from 10 to 14 week placentas were examined in the scanning electron microscope (SEM) after critical point drying. When prepared by this method, the syncytial surface appears covered with slender microvilli similar to those seen in transmission electron micrographs. We find no support in our observations for the suggestion that the trophoblastic surface is a mosaic of microvillous and nonmicrovillous areas or that substantial areas lack microvilli. In addition, the villi often show circumferentially oriented furrows. SEMs of the early placentas showed numerous syncytial sprouts, most of which represent stages in the formation of new free or terminal villi.

Toadfish saccular hair cell bundle has a preferred orientation in the otolithic membrane

The macula of the saccule of the toadfish, Opsanus tau, is covered by an otolithic membrane containing sockets into which the stereocilia and kinocilia of the hair cells project. We have found that the hair cell bundle has a distinct eccentric orientation within this space of the otolithic socket. Although the sockets of the otolithic membrane are irregular in shape, all kinocilia are located closet to the same border of the sockets. Since the socket is a fluid or gel filled space through which the hair cell bundle moves, this orientation may have some significance for transduction since it leaves a larger space in the on direction for stereociliary movement.