Caspase-3-dependent and -independent apoptosis in focal brain ischemia.

Background: Although extensive caspase-3 activation has been demonstrated in experimental brain ischemia produced in neonatal rat, the role this caspase plays in the focal ischemia of adult brain is not clear, as the levels of caspase-3 in adult rat brain are extremely low. This raises the question whether caspase-3 synthesis and activation are essential for execution of the apoptotic program and DNA fragmentation in permanent brain ischemia, a condition that impairs cellular protein synthesis.

Materials And Methods: Rat middle cerebral artery was permanently occluded and histochemical detection of procaspase-3, active caspase-3 and DFF 40/CAD and apoptotic morphology analysis were performed at 6, 24, 48, and 72 hours after occlusion.

Tyrosine levels regulate the melanogenic response to alpha-melanocyte-stimulating hormone in human melanocytes: implications for pigmentation and proliferation.

Melanocyte-stimulating hormone (alpha-MSH) increases cytosolic levels of cAMP as well as tyrosinase activity in murine melanocytes. These activities depend upon the presence of melanin precursors and may differ in human melanocytes. In this study, we demonstrate that high levels of tyrosine (3.

Activation of a cAMP pathway and induction of melanogenesis correlate with association of p16(INK4) and p27(KIP1) to CDKs, loss of E2F-binding activity, and premature senescence of human melanocytes.

There is strong evidence that the senescent phenotype, whether induced by telomere shortening, oxidative damage, or oncogenic stimuli, is an important tumor suppressive mechanism. The melanocyte is a cell of neural crest origin that produces the pigment melanin and can develop into malignant melanomas. To understand how malignant cells escape senescence, it is first crucial to define what genes control senescence in the normal cell.

Intrahepatic cholestatic syndromes: pathogenesis, clinical features and management.

Intrahepatic cholestasis is characterized by a decrease in bile flow in the absence of overt bile duct obstruction, resulting in the accumulation of bile constituents in the liver and blood. Various etiological factors have been incriminated including drugs, total parenteral nutrition, sepsis, pregnancy, graft-versus-host disease and systemic disorders such as sarcoidosis, amyloidosis and Hodgkin's disease. The pathogenesis of cholestasis is unclear and several mechanisms have been hypothesized, without convincing evidence that any of these play a role in clinical cholestasis.

Aging in epidermal melanocytes: cell cycle genes and melanins.

With aging, melanocytes become unevenly distributed in the epidermis. In light skin individuals, hypopigmentation is found in association with focal hyperpigmentation (lentigo senilis). Apparently this results from progressive loss of active melanocytes and focal increase in melanocyte proliferation and/or aggregation.