Protein tyrosine phosphatases are involved in LH/chorionic gonadotropin and 8Br-cAMP regulation of steroidogenesis and StAR protein levels in MA-10 Leydig cells.

The LH signal transduction pathway features the activation of protein tyrosine phosphatases (PTPs) as one of the components of a cascade that includes other well characterized events such as cAMP-dependent protein kinase A (PKA) activation. Moreover, the action of PTPs is required to increase the rate-limiting step in steroid biosynthesis, namely the cAMP-regulated transfer of cholesterol to the inner mitochondrial membrane. Since both PKA activity and steroidogenic acute regulatory (StAR) protein induction are obligatory steps in this transfer of cholesterol, the present study was performed to investigate the role of PTPs in the regulation of PKA activity and StAR expression in response to LH/chorionic gonadotropin (CG) and 8Br-cAMP in MA-10 cells. While the exposure of MA-10 cells to the PTP inhibitor, phenylarsine oxide (PAO), did not modify PKA activity, it partially inhibited the effect of human CG and cAMP analog on StAR protein levels. Time-course studies demonstrated that PAO inhibited cAMP induction of StAR protein and mRNA. At 30 min, the effect on cAMP-stimulated StAR protein levels was a 35% inhibition, progressing to up to 90% inhibition at 120 min of stimulation. The maximal inhibitory effect on cAMP-induced StAR mRNA level was obtained at 60 min (85%). In summary, these results demonstrate that inhibition of PTP activity affected both StAR protein and mRNA synthesis and suggest that the activity of hormone-regulated PTPs is a requirement in the LH signaling cascade that results in the up-regulation of StAR protein and, subsequently, increased steroid synthesis.

Pulpal temperature changes during low-power hard-tissue CO2 laser procedures.

Thermal insult to pulpal tissue is recognized as a major limitation to the use of lasers for dental hard-tissue procedures. This study examined thermal changes at the level of the dental pulp in human molar teeth irradiated with a CO2 dental laser using a pulsed mode of operation. Sectioned molar teeth were exposed, in vitro, to CO2 laser radiation. The laser parameters were those used clinically for laser desensitization and laser-enhanced fluoride treatment. Fissure regions and root surfaces were irradiated. For settings which might reasonably be used clinically, the temperature rise was not of a magnitude which would be expected to cause pulpal inflammation or necrosis. With regard to thermal properties of tooth structure, times taken to reach the maximum temperature reduced, and times taken to cool to baseline increased with increasing laser exposures.

Established antimicrobial susceptibility testing methods with a new twist--points to consider and a glimpse of the future.

The developments seen in these systems allow speculation about future trends in antimicrobial susceptibility testing methods. Microbiology system manufacturers seem to be heeding the call of all industry, for greater automation, enhanced data management capabilities and increased flexibility (see Table 2 below). [table: see text] Cost seems to be less of an issue. This may be due to the decrease in the availability of medical technologists and the need to find systems with better throughput and increased productivity. Increased automation, data management capabilities, and walkaway technology may justify the additional cost of some of these systems. The computer software package provided with these systems is becoming increasingly important with the focus on quality assurance and utilization. Computer generated data analysis gives the microbiologist the tools to educate physicians through the use of selective reporting functions, antibiograms, cost analysis and drug effectiveness comparisons. Each of the four systems is unique and will probably find a niche among the various markets that exist in the United States, European and other specialized markets. The lack of automation in the ALAMAR system may be its selling point in those areas where automation is not affordable, but new ways are being sought for ease of interpretation of results. BIOMIC and CATHRA systems may be more beneficial to those microbiologists who do not want to stop doing traditional Bauer-Kirby or agar dilution methods, but require computer enhancements. ALADIN, may fill a niche to which other walkaway systems have not adapted, but because of its expense, will face more demands than the other three systems covered in this review.