Oxidative Stress and Skin Cancer: An Overview

Skin is the largest body organ that serves as an important environmental interface providing a protective envelope that is crucial for homeostasis. On the other hand, it is a major target for toxic insult by a broad spectrum of physical and chemical agents that are capable of altering its structure and function. There are a large number of dietary contaminants and drugs can manifest their toxicity in skin. These environmental toxicants or their metabolites are inherent oxidants and/or directly or indirectly drive the production of a variety of reactive oxidants also known as reactive oxygen species. These are short-lived entities that are continuously generated at low levels during the course of normal aerobic metabolism. These are believed to activate proliferative and cell survival signaling that can alter apoptotic pathways that may be involved in the pathogenesis of a number of skin disorders. The skin possesses an array of antioxidant defense mechanisms that interact with toxicants to obviate their deleterious effect. The “antioxidant power” of a food is an expression of its capability both to defend the human organism from the action of the free radicals and to prevent degenerative disorders. Plants like olive trees have their own built-in protection against the oxidative damage of the sun, and these built-in protectors function as cell protectors in our own body. Although many antioxidants have shown substantive efficacy in cell culture systems and in animal models of oxidant injury, unequivocal confirmation of their beneficial effects in human populations has proven elusive.     

Pain-elicited aggression in the squirrel monkey: An implicit avoidance contingency

Squirrel monkeys were given either forward pairings of a bite-tube CS and shock US or backward pairings of these stimuli. Backward pairings produced stronger control of biting by the bite tube alone than did forward pairings. In a second experiment, subjects received backward pairings of US and CS with either a fixed ITI or a random ITI. Conditioned biting was obtained only when trials were presented with a fixed ITI. The magnitude of unconditioned biting was also significantly greater with the fixed ITI. It was argued that these results demonstrate that conditioning in this situation depends upon the degree to which biting predicts a relatively long shock-free period. When trials occur randomly in time, biting predicts no definite shock-free period; hence, it is not learned.     

Infant and Toddler Child-Care Quality and Stability in Relation to Proximal and Distal Academic and Social Outcomes

This study considered the quality and stability of infant and toddler nonparental child care from 6 to 36 months in relation to language, social, and academic skills measured proximally at 36 months and distally at kindergarten. Quality was measured separately as caregiver–child verbal interactions and caregiver sensitivity, and stability was measured as having fewer sequential child-care caregivers. This longitudinal examination involved a subsample (N = 1,055) from the Family Life Project, a representative sample of families living in rural counties in the United States. Structural equation modeling revealed that children who experienced more positive caregiver–child verbal interactions had higher 36-month language skills, which indirectly led to higher kindergarten academic and social skills. Children who experienced more caregiver stability had higher kindergarten social skills.