Search

Spinal circuitry produces the rhythm and patterning of locomotion. However, both descending and sensory inputs are required to initiate and adapt locomotion to the environment. Spinal cord injury (SCI) disrupts descending controls of the spinal cord, producing paralysis. Epidural stimulation (ES) is a promising clinical therapy for motor control recovery and is capable of reactivating the lumbar spinal locomotor networks, yet little is known about the effects of ES on locomotor neurons. Previously, we found that both sensory afferent pathways and serotonin exert mixed excitatory and inhibitory actions on lumbar interneurons involved in the generation of the locomotor rhythm, identified by the transcription factor Shox2. However, after chronic complete SCI, sensory afferent inputs to Shox2 interneurons become almost exclusively excitatory and Shox2 interneurons are supersensitive to serotonin. Here, we investigated the effects of ES on these SCI-induced changes. Inhibitory input from sensory pathways to Shox2 interneurons was maintained and serotonin supersensitivity was not observed in SCI mice that received daily sub-motor threshold ES. Interestingly, the effects of ES were maintained for at least three weeks after the ES was discontinued. In contrast, the effects of ES were not observed in Shox2 interneurons from mice that received ES after the establishment of the SCI-induced changes. Our results demonstrate mechanistic actions of ES at the level of identified spinal locomotor circuit neurons and the effectiveness of early treatment with ES on preservation of spinal locomotor circuitry after SCI, suggesting possible therapeutic benefits prior to the onset of motor rehabilitation.

Cryptosporidium, a waterborne enteric parasite, is a frequent cause of diarrheal disease outbreaks worldwide. Thus far, the few antigens shown to be important for attachment to and invasion of the host cell by Cryptosporidium are all mucin-like glycoproteins. In order to investigate other antigens that could be important for Cryptosporidium host-parasite interactions, the Cryptosporidium genome databases were mined for other mucin-like genes. A single locus of seven small mucin sequences was identified on chromosome 2 (CpMuc1 to -7). Reverse transcriptase PCR analysis demonstrated that all seven CpMucs were expressed throughout intracellular development. CpMuc4 and CpMuc5 were selected for further investigation because of the significant sequence divergence between Cryptosporidium parvum and C. hominis alleles. Rabbit anti-CpMuc5 and -CpMuc4 antibodies identified several polypeptides in C. parvum lysates, suggestive of proteolytic processing of the mucins. All polypeptides were larger than the predicted molecular weight, which is suggestive of posttranslational processing, most likely O-glycosylation. In immunofluorescence assays, both anti-CpMuc4 and -CpMuc5 antibodies reacted with the apical region of sporozoites and revealed surface-exposed epitopes. The antigens were not shed during excystation but did partition into the aqueous phase of Triton X-114 extractions. Consistent with a role in attachment and invasion, CpMuc4 and CpMuc5 could be detected binding to fixed Caco-2A cells, and anti-CpMuc4 peptide antibodies inhibited Cryptosporidium infection in vitro. Sequencing of CpMuc4 and CpMuc5 from C. hominis clinical isolates identified several polymorphic alleles. The data suggest that these antigens are integral for Cryptosporidium infection in vitro and may be potential vaccine candidates.