Modulation of Ca2+ levels in keratinocytes by all-trans retinoic acid.

Human epidermal keratinocytes, that have been growth-arrested by removal of epidermal growth factor from the culture medium, are stimulated to proliferate by all-trans retinoic acid (RA). The same treatment inhibits the onset of differentiated features and reduces cell-substrate adhesion. In the present study we show that the same treatment results in a decrease in total cell-associated Ca2+ as measured by changes in the amount of 45Ca2+ bound to cells at equilibrium following RA treatment and by a decrease in intracellular free Ca2+ levels as measured with the Ca(2+)-sensitive dye, Indo-1. The alterations in Ca2+ levels were evident within an hour after RA treatment, were in the range of 30-35% and occurred over the same RA concentration range that stimulated proliferation (i.e., 0.25-1.0 micrograms/ml). When the extracellular Ca2+ concentration was elevated from the normal level of 0.15-1.4 mM, intracellular free Ca2+ increased by a factor of 2 while total cell-associated Ca2+ increased approximately 6-fold. Even under conditions of high extracellular Ca2+, RA was able to reduce cell-associated and intracellular free Ca2+. These data indicate that RA has the capacity to lower Ca2+ levels in keratinocytes concomitantly with its effects on biological behavior.     

In situ saphenous vein bypass grafts: angiographic evaluation and interventional repair of complications

In situ saphenous vein grafts are being used with increasing frequency for bypass procedures involving the femoral and popliteal arteries. Complications of these procedures include anastomotic stenoses and persistent arteriovenous fistulae that may result in failure of the graft. Balloon angioplasty and embolotherapy with detachable balloons were employed successfully in three or four recent cases of patients with complications from in situ grafts. Tailored angiography is essential for evaluating in situ grafts, and interventional techniques are extremely useful for managing complications.     

The effects of antioxidant supplementation during Percoll preparation on human sperm DNA integrity

The integrity of sperm DNA is crucial for the maintenance of genetic health. A major source of damage is reactive oxygen species (ROS) generation; therefore, antioxidants may afford protection to sperm DNA. The objectives of the study were, first, to measure the effects of antioxidant supplementation in vitro on endogenous DNA damage in spermatozoa using the single cell gel electrophoresis (comet) assay and, second, to assess the effect of antioxidant supplementation given prior to X-ray irradiation on induced DNA damage. Spermatozoa from 150 patients were prepared by Percoll centrifugation in the presence of ascorbic acid (300, 600 microM), alpha tocopherol (30, 60 microM), urate (200, 400 microM), or acetyl cysteine (5, 10 microM). DNA damage was induced by 30 Gy X-irradiation. DNA strand breakage was measured using the comet assay. Sperm DNA was protected from DNA damage by ascorbic acid (600 microM), alpha tocopherol (30 and 60 microM) and urate (400 microM). These antioxidants provided protection from subsequent DNA damage by X-ray irradiation. In contrast, acetyl cysteine or ascorbate and alpha tocopherol together induced further DNA damage. Supplementation in vitro with the antioxidants ascorbate, urate and alpha tocopherol separately has beneficial effects for sperm DNA integrity.      

Matrix metalloproteinase expression in basal cell carcinoma: relationship between enzyme profile and collagen fragmentation pattern

Matrix metalloproteinases (MMPs) with collagenolytic and gelatinolytic activities are up-regulated in basal cell carcinoma. In the present study we demonstrate that the major collagenolytic enzyme detected is MMP-1 (interstitial collagenase) while gelatinolytic enzymes include both MMP-2 (72-kDa gelatinase A) and MMP-9 (92-kDa gelatinase B). Significant fractions of all three enzymes are present as active forms. In spite of the fact that high levels of gelatinolytic enzymes are present, the major fragmentation products resulting from digestion of intact type I collagen are the 1/4 and 3/4 fragments (products of MMP-1-mediated digestion). Thus, it appears that the gelatinolytic enzymes are not capable of degrading the collagen fragments as rapidly as they are produced. Since previous studies have demonstrated that interaction of interstitial fibroblasts with high molecular weight fragments of type I collagen leads to increased MMP production, the present results suggest a mechanism underlying altered function of stromal elements in the connective tissue adjacent to the growing neoplasm.     

Effects of all-trans retinoic acid and Ca++ on human skin in organ culture.

In this study, we have established an organ culture model of human skin and examined the effects of both all-trans retinoic acid (RA) and extracellular Ca++ on the epidermal and dermal components of the organ-cultured skin. Our data show that while organ cultures maintained in serum-free, growth factor-free culture medium containing 0.15 mM Ca++ degenerated rapidly, those treated with concentrations of RA that have been shown previously to stimulate fibroblast and keratinocyte proliferation in monolayer culture (J Invest Dermatol 1989, 93:449; 1990, 94:717; Am J Pathol 1990, 136:1275) demonstrated a healthy appearance for up to 12 days. Degeneration of the control cultures was characterized by separation of the epidermis from the underlying dermis, progressive cell necrosis leading to a complete absence of viable cells from both the dermal and epidermal compartments, disintegration and fibrillation of the dermal connective tissue, and a cessation of protein synthesis. RA-treated organ cultures contained large numbers of healthy-appearing cells in both the epidermal and dermal compartments. One or several layers of viable basal cells in the epidermis could be seen at least through day 12. However, the upper layers of the epidermis frequently separated from the cells in the basal layer. The dermal connective tissue was histologically well-preserved. Furthermore, the level of protein synthesis was higher in the RA-treated cultures than in the control cultures. In addition to treating organ cultures with RA, other cultures were exposed to serum-free, growth factor-free culture medium containing 1.4 mM Ca++. The presence of the elevated Ca++ concentration also preserved cellular and connective tissue structures in the dermal and epidermal compartments. In comparison to RA there was better preservation of the overall epidermal structure. The upper layers of epidermal cells did not separate from the basal cells, and the various stages of epithelial differentiation could be seen. Histologically, the dermis was well-preserved in the presence of elevated extracellular Ca++. Specimens treated with a combination of Ca++ and RA demonstrated features consistent with the features induced by each treatment separately. This included an expanded basal layer of epithelial cells and a prominent keratotic layer with a fairly orderly pattern of differentiation. The tendency of the upper epidermis to separate from the basal cells was partially mitigated. Taken together, these data indicate that both RA and extracellular Ca++ act to prevent the degeneration of human skin in organ culture but probably do so through different mechanisms.