Characterization of Train-Induced Vibration and its Effect on Fecal Corticosterone Metabolites in Mice.

Excessive environmental vibrations can have deleterious effects on animal health and experimental results, but they remain poorly understood in the animal laboratory setting. The aims of this study were to characterize train-associated vibration in a rodent vivarium and to assess the effects of this vibration on the reproductive success and fecal corticosterone metabolite levels of mice. An instrumented cage, featuring a high-sensitivity microphone and accelerometer, was used to characterize the vibrations and sound in a vivarium that is near an active railroad. The vibrations caused by the passing trains are 3 times larger in amplitude than are the ambient facility vibrations, whereas most of the associated sound was below the audible range for mice. Mice housed in the room closest to the railroad tracks had pregnancy rates that were 50% to 60% lower than those of mice of the same strains but bred in other parts of the facility. To verify the effect of the train vibrations, we used a custom-built electromagnetic shaker to simulate the train-induced vibrations in a controlled environment. Fecal pellets were collected from male and female mice that were exposed to the simulated vibrations and from unexposed control animals. Analysis of the fecal samples revealed that vibrations similar to those produced by a passing train can increase the levels of fecal corticosterone metabolites in female mice. These increases warrant attention to the effects of vibration on mice and, consequently, on reproduction and experimental outcomes.

A water soluble additive to suppress respirable dust from concrete-cutting chainsaws: a case study.

Respirable dust is of particular concern in the construction industry because it contains crystalline silica. Respirable forms of silica are a severe health threat because they heighten the risk of numerous respirable diseases. Concrete cutting, a common work practice in the construction industry, is a major contributor to dust generation. No studies have been found that focus on the dust suppression of concrete-cutting chainsaws, presumably because, during normal operation water is supplied continuously and copiously to the dust generation points. However, there is a desire to better understand dust creation at low water flow rates. In this case study, a water-soluble surfactant additive was used in the chainsaw's water supply. Cutting was performed on a free-standing concrete wall in a covered outdoor lab with a hand-held, gas-powered, concrete-cutting chainsaw. Air was sampled at the operator's lapel, and around the concrete wall to simulate nearby personnel. Two additive concentrations were tested (2.0% and 0.2%), across a range of fluid flow rates (0.38-3.8 Lpm [0.1-1.0 gpm] at 0.38 Lpm [0.1 gpm] increments). Results indicate that when a lower concentration of additive is used exposure levels increase. However, all exposure levels, once adjusted for 3 hours of continuous cutting in an 8-hour work shift, are below the Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) of 5 mg/m(3). Estimates were made using trend lines to predict the fluid flow rates that would cause respirable dust exposure to exceed both the OSHA PEL and the American Conference of Governmental Industrial Hygienists (ACGIH®) threshold limit value (TLV).

The dynamic shear moduli of whale blubber.

BACKGROUND: Blubber is a thick adipose tissue located beneath the dermas. Its viscoelastic properties affect whale tracking tag design, hydrodynamics, and acoustical properties that can be used to study animal behavior and avoid ship strikes. OBJECTIVE: Measure the dynamic shear storage and loss moduli for whale blubber at distances below the dermas for several species. Also, measure the non-collagen and collagen protein content to explore a correlation to viscoelastic properties. METHODS: Blubber samples were obtained from whale strandings (humpback, sperm, and two gray) in the Pacific Northwest. Shear moduli were measured at oscillation frequencies of 0.31 Hz to 25 Hz using a rotational rheometer. Protein content was measured using a staining protocol. RESULTS: Storage modulus and loss modulus variation with frequency was very consistent across all samples tested. Log-linear and extended polynomials respectively had R-squared values of at least 0.96. Variation of both moduli with depth was fit reasonably well by fourth-order polynomials. Protein content trends varied with species. CONCLUSIONS: The samples used in this study were necrotic tissue, however the variation with frequency and to a lesser extent depth was very consistent and may have a broader applicability. Protein content was not found to correlate to moduli values.