Owing to higher diagnostic performance, (68)Ga-DOTA-TOC PET/CT (or alternative (68)Ga-labeled somatostatin analogues) should replace (111)In-pentetreotide in the investigation of MEN1 patients.

Terminal differentiation is a key element in the maintenance of tissue homeostasis in the epidermis. We show here that methotrexate (MTX) induces differentiation of human epidermal keratinocytes in vitro. MTX inhibits proliferation of keratinocytes and also induces several markers of differentiation: a change in cell morphology, a marked increase in cell size, an increase in the proportion of cells that express involucrin, and an increase in the amount of cornifled envelope protein. These effects of MTX are dose-and exposure-timedependent and become irreversible after 24 hr, approximately one population doubling time. These effects of MTX cannot be attributed to cytotoxicity since keratinocytes not only remain viable but also actively synthesize proteins. MTX causes reproducible changes in the SDS/PAGE profiles of newly synthesized proteins and, in particular, increases the amount of involucrin synthesis. Thymidine completely prevents these effects of MTX, suggesting that they are caused by a depletion of thymine deoxyribonucleotides. The effect of MTX on keratinocytes may provide a model for studying the relationship between deoxyribonucleotide metabolism and differentiation in normal cells. In addition, the ability of MTX to induce differentiation in keratinocytes suggests a mechanism to explain its therapeutic action in psoriasis.

A mathematical concept known as Parrondo's paradox motivated the development of several novel computational models of chemical systems in which thermal cycling was explored. In these kinetics systems we compared the rates of formation of product under cycling temperature and steady-sate conditions. We found that a greater concentration of product was predicted under oscillating temperature conditions. Our computational models of thermal cycling suggest new applications in chemical and chemical engineering systems.

The release of lipoteichoic acid (LTA) and teichoic acid (TA) from a Streptococcus pneumoniae type 3 strain during exposure to ceftriaxone, meropenem, rifampin, rifabutin, quinupristin-dalfopristin, and trovafloxacin in tryptic soy broth was monitored by a newly developed enzyme-linked immunosorbent assay. At a concentration of 10 μg/ml, a rapid and intense release of LTA and TA occurred during exposure to ceftriaxone (3,248 ± 1,688 ng/ml at 3 h and 3,827 ± 2,133 ng/ml at 12 h) and meropenem (2,464 ± 1,081 ng/ml at 3 h and 2,900 ± 1,364 ng/ml at 12 h). Three hours after exposure to rifampin, rifabutin, quinupristin-dalfopristin, and trovafloxacin, mean LTA and TA concentrations of less than 460 ng/ml were observed (for each group,P < 0.01 versus the concentrations after exposure to ceftriaxone). After 12 h of treatment, the LTA and TA concentrations were 463 ± 126 ng/ml after exposure to rifampin, 669 ± 303 ng/ml after exposure to rifabutin, and 1,236 ± 772 ng/ml after exposure to quinupristin-dalfopristin (for each group,P < 0.05 versus the concentrations after exposure to ceftriaxone) and 1,745 ± 1,185 ng/ml after exposure to trovafloxacin (P = 0.12 versus the concentration after exposure to ceftriaxone). At 10 μg/ml, bactericidal antibacterial agents that do not primarily affect cell wall synthesis reduced the amount of LTA and TA released during their cidal action againstS. pneumoniae in comparison with the amount released after exposure to β-lactams. Larger quantities of LTA and TA were released after treatment with low concentrations (1× the MIC and 1× the minimum bactericidal concentration) than after no treatment for all antibacterial agents except the rifamycins. This does not support the concept of using a low first antibiotic dose to prevent the release of proinflammatory cell wall components.

Thymidine phosphorylase/platelet-derived endothelial cell growth factor (TPase/PD-ECGF) is a catabolic enzyme that has been shown to be chemotactic for endothelial cells in vitro and angiogenic in vivo. TPase/PD-ECGF expression is increased in a variety of tumors. In the skin, TPase is active in normal keratinocytes in vitro and in vivo. Our objective was to study the expression and localization of TPase/PD-ECGF by immunohistochemical analysis in normal skin and cutaneous tumors and to correlate this information with enzymatic activity of TPase. TPase/PD-ECGF expression was observed in keratinocytes with intense staining of the infundibulum of hair follicles but no staining of hair bulbs. Expression localized primarily to the nucleus of keratinocytes in the basal layer but was more intense and cytoplasrmic in suprabasal keratinocytes. Increased expression of TPase/PD-ECGF in differentiated cells was confirmed by in vitro studies of TPase activity. In cutaneous tumors, there was positive staining for TPase/ PD-ECGF in squamous cell carcinomas (10/10), eccrine poromas (3/4), eccrine syringomas (4/4), trichoepitheliomas (1/3), and tumors of the follicular infundibulum (2/3) and melanomas (5/8). There was no staining of any intradermal nevi (0/2), basal cell carcinomas (0/10) or Merkel cell carcinoma (0/1). We conclude TPase/PD-ECGF is found throughout the epidermis and its expression increases with differentiation of keratinocytes. In cutaneous tumors, expression of TPase/PD-ECGF may be linked to the cell of origin of the tumor as well as the tumor's degree of differentiation.

The antiviral activity of the fraudulent nucleoside arabinosyladenine (ara-A) against herpes simplex virus (HSV) type 1 was increased nearly 20-fold by the adenosine deaminase inhibitor, coformycin. The combination of ara-A plus coformycin was 90 times more potent in blocking HSV replication than was arabinosylhypoxanthine (ara-H). In suspension culture both drugs were more active than they were in monolayer culture. Deoxyribonucleic acid (DNA) synthesis also was inhibited by the nucleosides. Depending upon the species of DNA examined, ara-A was 8 to 15 times more active in the presence of coformycin, and the combination was 35 to 70 times more potent than ara-H. Both drugs inhibited total DNA synthesis to the same extent in uninfected and HSVinfected KB cells. In contrast, viral DNA synthesis was three to six times more susceptible to inhibition than was cellular DNA synthesis. Inhibition of viral DNA synthesis was more pronounced in suspension culture than in monolayer culture. However, the method of cell propagation did not alter the degree to which the drugs inhibited DNA synthesis in uninfected KB cells. An index has been derived to quantitate the extent of the selective inhibition of viral or cellular DNA synthesis. Fifty percent inhibitory concentrations of a drug were calculated for uninfected KB DNA synthesis and viral DNA synthesis and expressed as a ratio. The logarithm of this ratio was termed the selective index and was positive ifviral DNA synthesis was inhibited preferentially or negative if uninfected KB DNA synthesis was more strongly inhibited. Data from experiments performed in monolayer culture gave positive selective index values of 0.3, 0.5, and 0.4 for ara-A plus coformycin, ara-A, and ara-H, respectively. Values of 0.7 and 0.6 were obtained from suspension culture data for ara-A plus coformycin and ara-H, respectively. Considered collectively, the data presented in this communication establish that coformycin increased the potency of ara-A but did not increase its selectivity.

No abstract

Disorders in which there is toxic buildup of circulating substrate may be treated by furnishing an enzyme reservoir capable of metabolically processing the excess substrate. The epidermal keratinocyte is a potential site for such a reservoir. In this study, we explore the capacity of genetically modified keratinocytes to metabolize extracellular substrate in a culture model that resembles in vivo epidermal architecture. Keratinocytes from adenosine deaminase (ADA)-deficient patients were transduced with a retroviral vector encoding the human ADA gene and the capacity of this tissue to deaminate deoxyadenosine (dAdo) in vitro was measured. The results show that at a substrate concentration of 10 microM, ADA-corrected keratinocytes deaminate dAdo at a rate of 0.38 nmol/min.10(6) cells. These results indicate that keratinocytes process extracellular substrate at rates that suggest complete substrate conversion in a single pass. This study provides a strong indication that the epidermis, the largest and most accessible tissue of the body, is a valuable site for designing clinically relevant gene therapies.