Age matching animal models to humans--theoretical considerations.

Biomedical animal models predict clinical efficacy with varying degrees of success. An important feature of in vivo modeling is matching the age of the animals used in preclinical research to the age of peak incidence for a disease state in humans. However, growth and development are highly variable between mammalian species, and age matching is always based on assumptions about the nature of development. We propose that researchers commonly make the assumption that developmental sequences are highly conserved between mammalian species--an assumption that we argue is often incorrect. We instead argue that development is often a modular process. Consideration of the modular nature of development highlights the difficulty in matching animal ages to human ages in a one-to-one scalar manner. We illustrate this with a discussion of the problem of age matching rodents to humans for neuroprotection experiments, and argue that researchers should pay deliberate attention to the modularity of developmental processes in order to optimally match ages between species in biomedical research.

Hydrogen sulfide as a therapeutic target for inflammation.

INTRODUCTION: The view of hydrogen sulfide has changed from a toxic by-product to a crucial signaling molecule, with enormous potential as a pharmacological target for diseases ranging from heart disease to sepsis. Despite this progression of ideas, there is still a large amount that is unknown about this gaseous signaling molecule. Hydrogen sulfide has been implicated as a tissue protectant in many pathological conditions, the mechanisms of tissue protection is a point of controversy, particularly distinguishing the direct actions from the indirect downstream effects of hydrogen sulfide. This point of controversy is particularly pertinent in inflammation research. AREAS COVERED: Current research into the pathways in which hydrogen sulfide can act as a pro-inflammatory molecule and as an anti-inflammatory molecule. EXPERT OPINION: How controversies regarding hydrogen sulfide may have occurred is discussed. Addressed are the direct and indirect pathways of hydrogen sulfide on inflammation, the effects of different concentrations of hydrogen sulfide and how the effects of hydrogen sulfide on the immune system vary with different delivery mechanisms. Furthermore, there is a discussion on what key gaps exist in current knowledge and must be addressed before hydrogen sulfide can be considered a valid pharmacological target.

Neuroprotective effect of hydroxypropyl-ß-cyclodextrin in hypoxia-ischemia.

Neonatal cerebral ischemic injury is a common and debilitating pathology for which there is currently no known purely pharmacological treatments that are effective when delivered immediately after injury. Cyclodextrins are cyclic oligosaccharides that can remove cholesterol from cell membranes and thereby affect receptor function. Cyclodextrins have previously been shown to be neuroprotective in vitro. We showed that hydroxypropyl-ß-cyclodextrin is neuroprotective in rats in vivo when delivered by intraperitoneal injection 30 min following hypoxia-ischemia, when assessed 15 days after surgery. A single dose of 1 g/kg hydroxypropyl-ß-cyclodextrin reduced brain infarction size by 28.57% compared with control (P<0.001). We also report that the same compound reduces neuronal excitability in hippocampal slices and propose that hydroxypropyl-ß-cyclodextrin is neuroprotective by reducing excitotoxicity in the delayed phase of brain damage.

Characterization of a rat hypoxia-ischemia model where duration of hypoxia is determined by seizure activity.

Perinatal and early childhood asphyxia is common, debilitating and has few efficacious treatments. A hypoxia ischemia (HI) rat model that involves a unilateral ligation of the common carotid artery followed by a 60 min period of 8% oxygen hypoxia is often used to test proposed treatments. However, this HI protocol produces inconsistent infarction volumes due to the variability of individual rats to compensate for the ligated artery and hypoxia. Therefore, this HI model is problematic for experiments that prevent measurement of infarction volume, such as those that require analysis of homogenised brain tissue. We therefore aimed to find a simple and non-invasive predictor of infarction volume. Observations made prior, during and following HI in p26 rats showed that weight change 24 h following surgery was a strong predictor of infarction volume. The occurrence of a tonic clonic seizure during hypoxia was highly correlated with success of inducing an infarction, and for this reason we assessed whether ceasing the hypoxia for each rat following a tonic clonic seizure would produce a more consistent infarction volume. Using this procedure, infarction volumes measured at 3 and 15 days after surgery were significantly less variable, resulting in considerable improvements in statistical power compared with the original model.