Short-term observations of the regenerative potential of injured proximal sensory nerves crossed with distal motor nerves

Motor nerves and sensory nerves conduct signals in different directions and function in different ways.In the surgical treatment of peripheral nerve injuries,the best prognosis is obtained by keeping the motor and sensory nerves separated and repairing the nerves using the suture method.However,the clinical consequences of connections between sensory and motor nerves currently remain unknown.In this study,we analyzed the anatomical structure of the rat femoral nerve,and observed the motor and sensory branches of the femoral nerve in the quadriceps femoris.After ligation of the nerves,the proximal end of the sensory nerve was connected with the distal end of the motor nerve,followed by observation of the changes in the newly-formed regenerated nerve fibers.Acetylcholinesterase staining was used to distinguish between the myelinated and unmyelinated motor and sensory nerves.Denervated muscle and newly formed nerves were compared in terms of morphology,electrophysiology and histochemistry.At 8 weeks after connection,no motor nerve fibers were observed on either side of the nerve conduit and the number of nerve fibers increased at the proximal end.The proportion of newly-formed motor and sensory fibers was different on both sides of the conduit.The area occupied by autonomic nerves in the proximal regenerative nerve was limited,but no distinct myelin sheath was visible in the distal nerve.These results confirm that sensory and motor nerves cannot be effectively connected.Moreover,the change of target organ at the distal end affects the type of nerves at the proximal end.

Effect of bifidobacterium on defensin-5 expression in intestinal injury of preweaning rats

AIM:To investigate the protective effect of bifidobacterium in endotoxin-induced intestinal injury in preweaning rats.METHODS:Preweaning rats were randomly divided into three groups(n =40 for each):a control group(groupC),a model group(group E) and a treatment group(group T).Both groups E and T were intraperitoneally injected with lipopolysaccharide(LPS) at a dose of 5 mg/kg(5 mg/L in normal saline),and group T was intragastrically administrated with bifidobacterium suspension(2.0 × 109 CFU/m L,0.5 m L each time,twice a day,until the end of the experiment) 7 d before LPS administration.Group C was intraperitoneally injected with normal saline.After intraperitoneal injection and intragastric administration,the rats were placed back to the initial cage to receive breast feeding.The rats were killed at 2,6,12,24 or 72 h,respectively,after endotoxin or physiological saline injection to collect serum and ileal tissue samples.Myeloperoxidase(MPO) contents in serum and ileum were detected at different times,and expression of ileal defensin-5 m RNA was evaluated by reverse transcription-polymerase chain reaction.RESULTS:Serum and ileal MPO contents in group E were significantly higher than those in group C(serum contents:107.50 ± 17.70 vs 157.14 ± 24.67,P < 0.05; ileal contents:1.03 ± 0.21 vs 1.57 ± 0.33,P < 0.05),which peaked at 12 h and 6 h,respectively.MPO contents in group T were significantly lower than those in group E(serum contents:114.38 ± 24.56 vs 145.25 ± 23.62,P < 0.05; ileal contents:1.25 ± 0.24 vs 1.57 ± 0.33,P < 0.05).The expression of defensin-5 m RNA in group E was significantly higher than that in group C(0.953 ± 0.238 vs 0.631 ± 0.146,P < 0.05),which peaked at 2 h,and then decreased gradually.The expression of defensin-5 m RNA in group T was significantly lower than that in group E(0.487 ± 0.149 vs 0.758 ± 0.160,P < 0.05) apparently in 24 h.The expression of defensin-5 m RNA at 2 h in group T was significantly higher than that in group C(0.824 ± 0.158 vs 0.631 ± 0.146,P < 0.05).CONCLUSION:MPO and defensin-5 m RNA increase in preweaning rats with LPS-induced intestinal injury.Bifidobacterium protects the gut by inhibiting MPOactivity,not by increasing defensin-5 secretion.