Histological observation on acellular nerve grafts co-cultured with Schwann cells for repairing defects of the sciatic nerve

BACKGROUND： Animal experiments and clinical studies about tissue engineering method applied to repair nerve injury mainly focus on seeking ideal artificial nerve grafts, nerve conduit and seed cells. Autologous nerve, allogeneic nerve and xenogeneic nerve are used to bridge nerve defects, it is one of the methods to promote the repair of nerve injury by culturing and growing Schwann cells, which can secrete various neurotrophic factor activities, in the grafts. OBJECTIVE ： To observe the effect of acellular nerve grafts co-cultured with Schwann cells in repairing defects of sciatic nerve. DESIGN： An observational comparative study.SETTING： Tissue Engineering Laboratory of China Medical University.MATERIALS： The experiment was carried out in the Tissue Engineering Laboratory of China Medical University between April 2004 and April 2005. Forty neonatal Sprague-Dawley rats of 5-8 days （either males or females） and 24 male Wistar rats of 180-220 g were provided by the experimental animal center of China Medical University. METHODS： ① Culture of Schwann cells： The bilateral sciatic nerves and branchial plexus were isolated from the 40 neonatal SD rats. The sciatic nerves were enzymatically digested with collagenase and dispase, isolatd, purified and cultured with the method of speed-difference adhersion, and identified with the SABC immunohistochemical method. ② Model establishment： In vitro Schwann cells were microinjected into 10-mm long acellular nerve grafts repairing a surgically created gap in the rat sciatic nerve. According to the different grafted methods, the animals were randomly divided into three groups： autografts （n=8）, acellular nerve grafts （n=8）, or acellular nerve grafts with Schwann cells （n=8）. ③ The regenerated nerve fiber number and average diameter of myeline sheath after culture were statistically anlayzed. MAIN OUTCOME MEASURES： ① The regenerated nerve ultrastructure, total number and density of myelinated nerve fibers, and the thickness of myeline sheath were observed under electron microscope. ② The images were processed with the Mias-1000 imaging analytical system to calculate the number of myelinated nerve fibers, and the thickness of myeline sheath. RESULTS： All the 24 Wistar rats were involved in the analysis of results. ① Results observed under transmission electron microscope： The regenerated myelinated nerve fibers in the group of acellular nerve grafts with Schwann cells were more even than those in the group of acellular nerve grafts, the number of myelinated nerve fibers and thickness of myelin sheath were close to those in the allografts group （P 〉 0.05）, but significantly different from those in the group of acellular nerve grafts （P 〈 0.05）. ② Results observed under scanning electron microscope： A great amount of Schwann cells with two polars were observed in the group of grafts with Schwann cells, the feature of cultured Schwann cells showed shoulder by shoulder, head to head. ③ The number of myelinated nerve fibers and thickness of myelin sheath analyzed by Mias-1000 imaging system in the group of acellular nerve grafts with Schwann cells were close to those in the autografts group （P 〉 0.05）, but significantly different from those in the group of acellular nerve grafts （P 〈 0.05）.CONCLUSION： Host axonal regeneration is significantly increased after implant of acellular nerve grafts. Acellular nerve grafts with Schwann cells offers a novel approach for repairing the gap of nerve defect.

Histological Observation of Chicken Skin

In this study, histological characteristics of the skin of adult lsa laying hens were observed. The results show that chicken skin is composed of epider- mis, dermis and hypodermis. The epidermis of chicken skin is thin, consisting of basal cells, spiny cells, transitional cells and horny cells. Specifically, there are few spiny cells scattered between the stratum basale and the transitional layer, without forming a layer; only 1 -2 layers of cells can be observed in the transitional layer. The derails is divided into superficial dermis and deep derufis. Moreover, deep dermis consists of dermal dense layer, dermal loose layer and elastic fibrous layer. There is no smooth muscle in pteryla within the dermal dense layer. The loose layer of deep dermis is developed, which is much much thicker than the dense layer. This study laid the foundation for in-depth investigation of the histological structure of poultry skin.

Histological Features of Parotid Gland of Albino Rats Exposed to. Smokeless Tobacco

Smokeless tobacco is very common personal habit of people living in various areas of Asia which is an alarming sign for the development of different oral diseases in such people. The aim of present study was to investigate effects of smokeless tobacco on parofid glands of the Aalbano rats by using various percentages of the smokeless tobacco. The rats were divided into three different groups, control group （A） no smokeless tobacco, experimental group （B） 5% smokeless tobacco and experimental group （C） 10% of smokeless tobacco with different feeds required according parameters. Weekly weight gain and partid gland were analyzed through student P test and histological structures were recorded through HE stain and Retculin stain. The results showed that as compared to control group body, weight of the rats was decreased in groups B and C having smokeless tobacco percentage in the diet. Weight of parotid gland as compared to control group was decreased in groups B and C with diet of smokeless tobacco. Further, histological observation under HE stain showed that parofid gland of group B showed mild narrowing of ductal lumen, collapse of vessels and stromal was also increased, in group C parenchyrnal tissues with loss of acini found damaged and glandular dystrop and lymphatic infiltration were determined moderate to severe. Meanwhile, reticulin stain showed that vascular collapses were shown because of increasing in stromal glandular atrophy in group C as compared to control group. In conclusion, this study showed that smokeless tobacco caused serious injuries in the tissue level in parotid gland with high percentage of smokeless tobacco which highlight health hazards on its consumption.

Animal Experiment of Viscose Carbon Fiber Based C/C Composites Applied in Bone Fracture Intramedullary Fixation

The animal experiment of viscose carbon fiber based C/C composites applied in bone defection intramedullary fixation was carried out in New Zealand white rabbits.The histological observation on the 100th day after surgical operation indicated that the experimental animals recovered well and the bone defect area was reconstructed by new bone trabecula.Immunohistochemical observation of leukocyte common antigen and macrophage suggested that intramedullary fixation materials did not induct any chronic toxicity reactions such as inflammatory reactions,macrophage reactions and formation of granulation tissue.The tissue compatibility of this material was excellent.Meanwhile,the impurity element species and the biological toxic element content of viscose fiber based C/C composites were determined by atomic fluorescence analyzer and inductively coupled plasma atomic emission spectrometry.The results reveal that there are few biological toxic elements in the viscose fiber based C/C composites and it can satisfy the constituent demands of surgical implants.