A rapid, valid and inexpensive assay for measuring epiphyseal plates in mouse tibia

Comparison of Toxicities among Different Bumped Kinase Inhibitor Analogs for Treatment of Cryptosporidiosis

Recent advances on the development of bumped kinase inhibitors for treatment of cryptosporidiosis have focused on the 5-aminopyrazole-4-carboxamide scaffold, due to analogs that have less hERG inhibition, superior efficacy, and strong in vitro safety profiles. Three compounds, BKI-1770, -1841, and -1708, showed strong efficacy in C. parvum infected mice. Both BKI-1770 and BKI-1841 had efficacy in the C. parvum newborn calf model, reducing diarrhea and oocyst excretion. However, both compounds caused hyperflexion of the limbs seen as dropped pasterns. Toxicity experiments in rats and calves dosed with BKI-1770 showed enlargement of the epiphyseal growth plate at doses only slightly higher than the efficacious dose. Mice were used as a screen to check for bone toxicity, by changes to the tibia epiphyseal growth plate, or neurological causes, by use of a locomotor activity box. These results showed neurological effects from both BKI-1770 and BKI-1841 and bone toxicity in mice from BKI-1770, indicating one or both effects may be contributing to toxicity. However, BKI-1708 remains a viable treatment candidate for further evaluation as it showed no signs of bone toxicity or neurological effects in mice.

Animal models to explore the effects of glucocorticoids on skeletal growth and structure

Glucocorticoids (GCs) are effective for the treatment of many chronic conditions, but their use is associated with frequent and wide-ranging adverse effects including osteoporosis and growth retardation. The mechanisms that underlie the undesirable effects of GCs on skeletal development are unclear, and there is no proven effective treatment to combat them. An in vivo model that investigates the development and progression of GC-induced changes in bone is, therefore, important and a well-characterized pre-clinical model is vital for the evaluation of new interventions. Currently, there is no established animal model to investigate GC effects on skeletal development and there are pros and cons to consider with the different protocols used to induce osteoporosis and growth retardation. This review will summarize the literature and highlight the models and techniques employed in experimental studies to date.

The salmonid myostatin gene family: a novel model for investigating mechanisms that influence duplicate gene fate

BACKGROUND

Most fishes possess two paralogs for myostatin, a muscle growth inhibitor, while salmonids are presumed to have four: mstn1a, mstn1b, mstn2a and mstn2b, a pseudogene. The mechanisms responsible for preserving these duplicates as well as the depth of mstn2b nonfunctionalization within the family remain unknown. We therefore characterized several genomic clones in order to better define species and gene phylogenies.

RESULTS

Gene organization and sequence conservation was particularly evident among paralog groupings and within salmonid subfamilies. All mstn2b sequences included in-frame stop codons, confirming its nonfunctionalization across taxa, although the indels and polymorphisms responsible often differed. For example, the specific indels within the Onchorhynchus tshawytscha and O. nerka genes were remarkably similar and differed equally from other mstn2b orthologs. A phylogenetic analysis weakly established a mstn2b clade including only these species, which coupled with a shared 51 base pair deletion might suggest a history involving hybridization or a shared phylogenetic history. Furthermore, mstn2 introns all lacked conserved splice site motifs, suggesting that the tissue-specific processing of mstn2a transcripts, but not those of mstn2b, is due to alternative cis regulation and is likely a common feature in salmonids. It also suggests that limited transcript processing may have contributed to mstn2b nonfunctionalization.

CONCLUSIONS

Previous studies revealed divergence within gene promoters while the current studies provide evidence for relaxed or positive selection in some coding sequence lineages. These results together suggest that the salmonid myostatin gene family is a novel resource for investigating mechanisms that regulate duplicate gene fate as paralog specific differences in gene expression, transcript processing and protein structure are all suggestive of active divergence.

Endocrine actions of myostatin: systemic regulation of the IGF and IGF binding protein axis

Myostatin's inhibitory actions on striated muscle growth are believed to be directly mediated by locally produced myostatin and possibly by IGF binding proteins (IGFBPs). We therefore measured skeletal muscle, heart, and liver expression, in neonates and adults, and circulating levels of various IGF axis components (IGF-I, IGFBP-1 to IGFBP-3, and acid labile subunit) in wild-type and mstn-/- mice. Compared with wild type, differences in muscle expression were tissue specific, although IGF-I receptor expression was higher in all mstn-/- neonatal tissues and in adult gastrocnemius. Liver expression of several components also differed between genotype as IGF-I receptor, IGFBP-3 and IGFBP-5 expression was higher in mstn-/- neonates and IGF-I and IGFBP-3 in adults. Circulating IGF-I levels were also higher in mstn-/- adults, whereas IGFBP-1 and IGFBP-2 levels were lower. Comparing IGF-I:IGFBP molar ratios suggested that the relative IGF-binding capacity was potentially lower in mstn-/- mice, and thus, total and "free" IGF-I levels may be elevated. This in turn may increase negative feedback control on GH, because mstn-/- liver weights were lower. Bone growth was similar in both genotypes, suggesting that changes in circulating IGF-I may be more important to muscle, whose mass is enhanced in mstn-/- mice, than to bone. Myostatin receptors, but not myostatin itself, are expressed in the liver. Changes in hepatic production of circulating IGF axis components could therefore result from the loss of endocrine myostatin. Thus, myostatin may inhibit striated muscle growth directly at the cellular level and indirectly through systemic effects on the IGF axis.