A procedure is described which allows primary cultures of rat keratinocytes grown at the liquid-air interface to develop and maintain multilayered strata and to produce highly keratinized sheets morphologically similar to those seen in epidermis in situ. Various substrata were tested and compared as to their ability to support growth and stratification of keratinocytes. It was found that when cultured on plastic surfaces, keratinocytes adhered tightly to the substratum and produced a confluent monolayer that later stratified to two to three layers. Cells plated on Vitrogen 100 collagen failed to reach confluence and, in addition, exhibited the "clustering" phenomenon and deterioration of collagen after 3 to 4 d of growth. Significantly better attachment and spreading were observed for cells grown on rat-tail collagen as compared with plastic and Vitrogen 100 collagen. The best results, including maximal and uniform stratification, were seen in cells grown on a mixture of rat-tail and Vitrogen 100 collagens. The system that was developed in the present study offers a model for use in the study of epidermal toxicity from topically applied environmental chemicals.

Arsenic produces a variety of stress responses in mammalian cells, including metabolic abnormalities accompanied by growth inhibition and eventually apoptosis. Morphological alterations in cells exposed to arsenic often suggest underlying disruption of cytoskeletal structural elements responsible for cellular integrity, shape, and locomotion. However, specifics of the ultrastructural changes produced by arsenic remain poorly understood. Various tissues and organs differ in their sensitivity to arsenic, with the liver and skin being the most studied. Characteristic skin pathology related to arsenic exposure ranges from hyperkeratotic lesions to squamous-cell carcinomas. However, molecular events in the arsenic-exposed skin still remain to be elucidated. Although mutagenicity of arsenic has not been unequivocally established, recent evidence supports the view that oncogenic mutations do occur, and that only selected enzymes related to DNA replication and repair are affected by arsenic. Sensitivity of the mitotic spindle to arsenic, particularly its organic compounds, underlies the well-documented chromosomal aberrations in arsenic-exposed populations. Arsenite-induced stress at the molecular level shares many features with the heat shock response. This includes the differential sensitivity of the stress signal pathway elements to the magnitude of the stress, stressor-specific activation of the response elements, and the protective role of the heat shock response. Oxidative stress, the central component of heat shock response, is typical of arsenic-related effects that are, in fact, regarded as the chemical paradigm of heat stress. Similar to heat stress, arsenite induces heat shock proteins (HSPs) of various sizes. The signal cascade triggered by arsenite-like heat stress induces the activity of the mitogen-activated protein (MAP) kinases, extracellular regulated kinase (ERK), c-jun terminal kinase (JNK), and p38. Through the JNK and p38 pathways, arsenite activates the immediate early genes c-fos, c-jun, and egr-1, usually activated by various growth factors, cytokines, differentiation signals, and DNA-damaging agents. Like other oxygen radical-producing stressors, arsenic induces nitric oxide production at the level of transcriptional activation along with induction of poly(ADP)-ribosylation, NAD depletion, DNA strand breaks, and formation of micronuclei. This review presents an overview of current research on molecular aspects of arsenic stress with an emphasis on the tissue-specific events in humans. It deals with current progress on the understanding of the signal transduction pathways and mechanisms underlying the sensitivity of various species, organs, and tissues to arsenic.

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The percutaneous access device (PAD) is used to connect an external drive unit to the Kantrowitz CardioVad (KCV), a cardiac assist device for the treatment of chronic heart failure. The PAD conveys pneumatic power from a drive unit to the implanted blood pump and an electrocardiogram signal from the myocardium to the drive unit. The device-tissue interface of the PAD is precoated with autologous fibroblasts cultured from a skin sample of the intended recipient. This preparation demonstrated long-term stability in animals and was adopted for use in patients receiving the KCV. The KCV is activated intermittently, and the drive unit may be connected and disconnected by the patient, which subjects the PAD to frequent manipulation.To date, the PAD has been implanted in nine patients ranging in age from 41 to 74 years. Implant times ranged from 2 to 458 days, for a total of 1082 days, of which 557 days were in an outpatient setting. Two patients experienced episodes of infection that did not originate from the PAD-tissue interface.This feasibility study demonstrated that (1) the PAD is stable and infection resistant in long-term ambulatory patients, (2) the PAD withstood the challenge of daily manipulation (the KCV is turned on and off electively), and (3) PADs can be replaced, if necessary.