The use of lasers for decorative tattoo removal.

As the incidence of tattoo placement continues to increase, so does the demand for tattoo removal, with more than 10 million people in the US alone with a tattoo. Used in an appropriate clinical setting, Q-switched lasers provide relatively efficacious clearance of decorative tattoo pigment with minimal side-effects. We present our clinical experience along with literature findings on decorative tattoo removal and the important issues practitioners should consider in the management of tattoos.

The use of lasers in the pediatric population.

Over the past 2 decades, there have been numerous advances in laser therapy of birth-marks in the pediatric population. Concerns regarding efficacy, overall benefit, and side-effects linger. We present our opinion, based upon decades of clinical experience, on the role of lasers to treat port wine stains, superficial hemangiomas, and café au lait macules in children.

Effects of Hg2+ on cytosolic Ca2+ in isolated skate hepatocytes.

Hg2+ is an environmental pollutant that adversely affects a range of cellular functions, including those that regulate free cytosolic Ca2+ (Ca(i)2+). To investigate the mechanism of Hg(2+)-induced Ca(i)2+ signaling, we examined the effects of Hg2+ on Ca(i)2+ in isolated skate hepatocytes, and developed a method to assess cytosolic Hg2+ (Hgi2+) in these cells as well. At lower concentrations (1-5 microM), Hg2+ induced little detectable change in Ca(i)2+. At higher concentrations (10 microM-1 mM), Hg2+ induced a dose-dependent, progressive increase in Ca(i)2+, which occurred even in Ca(2+)-free medium. Pretreatment of hepatocytes with the membrane-impermeant Hg2+ chelator glutathione (GSH) blocked the Hg(2+)-induced Ca(i)2+ increase, whereas addition of GSH after exposure to Hg2+ slowed but did not prevent further increases in Ca(i)2+. Pretreatment with the membrane-permeant Hg2+ chelator dithiothreitol (DTT) also blocked Hg(2+)-induced increases in Ca(i)2+. Unlike GSH, however, addition of DTT after Hg2+ significantly decreased Ca(i)2+, returning it to near-baseline levels. Thapsigargin induced a sustained increase in Ca(i)2+, but subsequent addition of Hg2+ resulted in a further, progressive Ca(i)2+ increase. We also describe the use of the fluorescent dye BTC-5N to measure Hgi2+, and with it found that Hgi2+ reaches nanomolar levels within minutes of extracellular application, but that these measurable levels of Hgi2+ do not precede elevations in Ca(i)2+. Hg2+ did not irreversibly damage the hepatocytes over this time period (< 5 min), as determined both by propidium iodide permeability and light microscopic appearance. Together, these findings suggest: (i) Hg2+ increases Ca(i)2+ in skate hepatocytes; (ii) Hg2+ must enter the hepatocytes for this Ca(i)2+ increase to occur; (iii) this increase is mediated by release of Ca2+ from endogenous stores that are distinct from the thapsigargin-sensitive Ca2+ stores; and (iv) this increase occurs in association with measureable levels of Hg2+ in the cytosol. Adverse cellular effects of Hg2+ may be mediated by changes in Ca(i)2+ that result from intracellular accumulation of this toxic metal.

Characterization and function of ATP receptors on hepatocytes from the little skate Raja erinacea.

Hormonal regulation of hepatocytes, via cytosolic Ca2+ signaling, is well established in higher life forms but has not been investigated in elasmobranchs. We therefore examined Ca2+ signaling in hepatocytes isolated from the little skate, Raja erinacea. In hepatocyte populations, ATP induced a rapid, biphasic increase in Ca2+, as it does in mammalian hepatocytes. Other hormones that act on mammalian hepatocytes, such as vasopressin, angiotensin, and phenylephrine, induced no such Ca2+ increase. The initial phase of the ATP-induced Ca2+ increase was seen even in Ca(2+)-free medium, whereas the late sustained phase of the increase was not. Similar dose-response curves were obtained by stimulation with ATP, ADP, UTP, and 2-methylthio-ATP. In contrast, AMP, adenosine, beta, gamma-methyl-ATP, CTP, and GTP induced little or no Ca2+ increase. In single hepatocytes, ATP, ADP, UTP, and 2-methylthio-ATP each induced a sustained increase in Ca2+ at high concentrations, but at low concentrations induced Ca2+ oscillations. A maximal concentration of ATP (100 microM) caused a marked, transient increase in bile flow in the isolated perfused skate liver, whereas 100 microM adenosine had no such effect. These findings demonstrate that skate hepatocytes possess P2 nucleotide receptors that link to intracellular plus extracellular Ca2+ mobilization, which in turn regulates bile secretion. The broad specificity of the response to ATP and related compounds suggests either that multiple types of P2 receptors are expressed by skate hepatocytes or else that these cells possess a single primitive nucleotide receptor from which other P2 subtypes subsequently evolved.