Experimental design affects social behavior outcomes in adult zebrafish developmentally exposed to lead.

Lead (Pb(2+)) affects neuronal and endocrine systems that influence social interactions. By providing potential hiding locations, spatial heterogeneity may affect Pb(2+)-induced behavioral outcomes. Therefore, a test chamber was designed into which a refuge could be inserted. The refuge allowed test subjects to escape from the mirror image that stimulated agonistic interactions. Behaviors with a mirror were compared with baseline activity patterns without a mirror. Adult (12-month old) male and female zebrafish, exposed to Pb(2+) (0-10 µM) as embryos (2-24 hours post fertilization), were tested individually for 5 min in each chamber design within 2 h of feeding. Behaviors were evaluated for % time in mirror zone, distance traveled (=activity level), and attacks on the mirror image. When there was no refuge, significant concentration-dependent increases occurred in male % time in mirror zone, activity level, and number of attacks. Increases in these variables were less pronounced in females. When there was a refuge, there were significant differences for males only in activity level and attacks at the higher developmental exposure concentrations; % time in mirror zone followed a similar pattern and level as without refuge. Females displayed Pb(2+)-induced behavioral changes only for attacks on mirror. Since the presence of refuges that is, environmental enrichment, reduced Pb(2+)-induced agonistic behavior in both sexes, experimental spatial design can be considered an important factor when interpreting behavioral outcomes.

Developmental lead exposure causes startle response deficits in zebrafish.

Lead (Pb(2+)) exposure continues to be an important concern for fish populations. Research is required to assess the long-term behavioral effects of low-level concentrations of Pb(2+) and the physiological mechanisms that control those behaviors. Newly fertilized zebrafish embryos (<2h post fertilization; hpf) were exposed to one of three concentrations of lead (as PbCl(2)): 0, 10, or 30 nM until 24 hpf. (1) Response to a mechanosensory stimulus: Individual larvae (168 hpf) were tested for response to a directional, mechanical stimulus. The tap frequency was adjusted to either 1 or 4 taps/s. Startle response was recorded at 1000 fps. Larvae responded in a concentration-dependent pattern for latency to reaction, maximum turn velocity, time to reach V(max) and escape time. With increasing exposure concentrations, a larger number of larvae failed to respond to even the initial tap and, for those that did respond, ceased responding earlier than control larvae. These differences were more pronounced at a frequency of 4 taps/s. (2) Response to a visual stimulus: Fish, exposed as embryos (2-24 hpf) to Pb(2+) (0-10 µM) were tested as adults under low light conditions (≈ 60 µW/m(2)) for visual responses to a rotating black bar. Visual responses were significantly degraded at Pb(2+) concentrations of 30 nM. These data suggest that zebrafish are viable models for short- and long-term sensorimotor deficits induced by acute, low-level developmental Pb(2+) exposures.

Total cost and operating room time comparison of rotator cuff repair techniques at low, intermediate, and high volume centers: mini-open versus all-arthroscopic.

BACKGROUND: The objective of this study was to determine mean cost and operative time differences between mini-open and all-arthroscopic rotator cuff repair techniques at surgical centers of low, intermediate, and high annual rotator cuff repair volume. METHODS: The 2006 New York State Ambulatory Surgery Database (NY-SASD) was utilized. It represents 100% of all outpatient procedures performed in hospital-affiliated and freestanding surgical centers, containing 10,658,923 patients for 2006 alone. Only patients who had an arthroscopic acromioplasty and either open or arthroscopic rotator cuff repair were included, leaving 5,224 patients for the study. These were divided into 2 groups: the mini-open group (1,334) and the all-arthroscopic group (3,890). Surgical center volume data were divided into 3 groups: low volume (<75 rotator cuff repairs per year), intermediate volume (75-199 rotator cuff repairs per year), and high volume (200+ rotator cuff repairs per year). RESULTS: Patient age and gender were normally distributed within the 2 groups with no significant differences between them (P = .82 and P = .31, respectively). Operative time was significantly shorter in the mini-open group (103 minutes) compared to the all-arthroscopic group (113 minutes), P < .00001. Surgical charges were also significantly less in the mini-open group ($7,841) compared to the all-arthroscopic group ($8,985), P < .00001. Regardless of the repair method, high volume surgical centers were significantly more expensive when compared to low and intermediate volume centers, P < .00001. CONCLUSION: The mini-open rotator cuff repair technique requires significantly less operative time and is significantly less expensive than the all-arthroscopic repair. Regardless of the repair technique, high volume surgical centers cost significantly more than low and intermediate volume surgical centers.

Developmental selenomethionine and methylmercury exposures affect zebrafish learning.

Methylmercury (MeHg) is a ubiquitous environmental pollutant and has been shown to affect learning in vertebrates following relatively low exposures. Zebrafish were used to model long-term learning deficits after developmental MeHg exposure. Selenomethionine (SeMet) co-exposure was used to evaluate its role in neuroprotection. Embryos were exposed from 2 to 24h post fertilization to (1) MeHg without SeMet, (2) SeMet without MeHg and (3) in combination of MeHg and SeMet. In case (1), the levels of MeHg were 0.00, 0.01, 0.03, 0.06, 0.10, and 0.30 microM. In case (2), the levels of SeMet were 0.00. 0.03, 0.06, 0.10, and 0.30 microM. In case (3), co-exposure levels of (MeHg, SeMet) were (0.03, 0.03), (0.03, 0.06), (0.03, 0.10), (0.03, 0.30), (0.10, 0.03), (0.10, 0.06), (0.10, 0.10), and (0.10, 0.30) microM. Learning functions were tested in individual adults, 4 months after developmental exposure using a spatial alternation paradigm with food delivery on alternating sides of the aquarium. Low levels of MeHg (<0.1 microM) exposure delayed learning in treated fish; fish exposed to higher MeHg levels were unable to learn the task; SeMet co-exposure did not prevent this deficit. These data are consistent with findings in laboratory rodents. The dorsal and lateral telencephalon are the primary brain regions in fish involved in spatial learning and memory. Adult telencephalon cell body density decreased significantly at all MeHg exposures >0.01 microM MeHg. SeMet co-exposure ameliorated but did not prevent changes in telencephalon cell body density. In summary, MeHg affected both learning and brain structure, but SeMet only partially reversed the latter.