Morphometric Parameters of Peripheral Nerves in Calves Correlated with Conduction Velocity

Background

Peripheral nerve injuries are the most frequent neurologic disorder in cattle. So far, no physiologic values have been established for the motor nerve conduction velocity (mNCV) in this precocial species.

Objectives

The electrophysiologic and morphometric reference values of peripheral nerves in calves were determined. It was hypothesized that these parameters would correlate to the high degree of maturity in the first days of life in this species compared to other species.

Animals

Twenty‐six healthy calves were used in this study.

Methods

The mNCV of the radial and the sciatic/common peroneal nerve was measured in all 26 calves. Nerve biopsies from a group of 6 calves were taken to correlate the obtained electrophysiologic data with morphological parameters.

Results

The mean mNCV of the radial nerve was 48.3 ± 10.6 m/s, whereas the mean mNCV of the sciatic/peroneal nerve was with 83.8 ± 5.9 m/s significantly faster (P < .0001). The average fiber diameter was 8.40 ± 2.80 μm (range, 1.98–17.90 μm) and the average g‐ratio was 0.61 ± 0.04 SD.

Conclusion and Clinical Importance

The established reference values for mNCV in calves correlate well with the evaluated morphometric parameters. Attributable to their comparably fast mNCV and high fiber diameters, juvenile calves appear to be much more mature individuals than other mammals. Electrophysiologic characterization of peripheral nerve injury now is feasible in this species.     

Knockout of GPR56 gene inhibits maturation of oligodendrocyte progenitor cells

AIM：To explore the effect of G-protein-coupled protein 56 (GPR56) gene knockout on axonal myelination and the maturation of oligodendrocyte progenitor cells (OPCs) in the corpus callosum of mouse brain. METHODS：Thirty-six GPR56+/- and GPR56-/- mice were selected and divided into GPR56+/- group and GPR56-/- group (18 mice in each group). According to the postnatal days, the mice in each group were further divided into P7, P14, P21 and P28 subgroups. Myelin formation in the corpus callosum of P14, P21 and P28 GPR56+/- and GPR56-/- mice was observed by FluoroMyelin staining. The number of myelinated axons and thickness of myelin sheaths were measured by electron microscopy. The numbers of platelet-derived growth factor alpha receptor-positive (PDGF-aR+) and proteolipid protein-positive (PLP+) cells in the corpus callosum of GPR56+/- and GPR56-/- mice were compared by the methods of immunofluorescence and in situ hybridization. GPR56+/- and GPR56-/- OPCs were cultured using P1 GPR56+/- and GPR56-/- mouse brain cortex and induced differentiation and maturation in vitro. The percentage of GPR56+/- and GPR56-/- O4+ cells in pro-oligodendroblast, immature oligodendrocyte and mature oligodendrocyte stages was compared by O4 immunostaining. RESULTS：The myelin formation was obviously reduced in the corpus callosum of P14, P21 and P28 GPR56-/- mice as compared with GPR56+/- mice. The number of myelinated axons was obviously reduced and the g-ratio value was increased significantly in the corpus callosum of P28 GPR56-/- mice. No significant difference of the PDGF-aR+ cell number in the corpus callosum between P7 d GPR56+/- and GPR56-/- mouse brains was observed. The number of PLP+ cells was significantly decreased in the corpus callosum of P28 GPR56-/- mice as compared with GPR56+/- mice. The percentage of GPR56-/- O4+ cells in pro-oligodendroblast stages was obviously higher than that of GPR56+/- O4+ cells. On the contrary, the percentages of GPR56-/- O4+ cells in immature oligodendrocyte and mature oligodendrocyte stages were significantly reduced. CONCLUSION:GPR56 may be involved in axonal myelination and OPCs maturation in the corpus callosum of mouse brain.