Germ-free ( GF) pigs are a special and adaptable experimental animal model for biomedical studies and animal productions, which are negative for bacteria, viruses, yeast and fungi tested by current microbiological examination. GF pigs were initially used in cleanse of epidemic diseases in animal production and in a bid to study the relationship be-tween animal disease and intestinal flora.Because of the similarities to humans in anatomy, physiology and hematology, and the clear microbiological background, GF pigs have been playing an important role in detecting the relationship between intestinal flora with growth and the development of diseases in medical biology, and also providing a special medical animal model for intestinal flora targeted prevention, diagnosis and treatment for update technology research in the clinic.This pa-per reviews the characteristics, advancements and research tendency of GF piglets.

Objective To compare the transfection rate of AAV2-EGFP and AAV2/1-EGFP to human skin fibroblast(HFB).Methods Two recombinant adeno-associated viruses(AAV) encoding enhanced green fluorescent protein(EGFP) were constructed and transfected to HFB at multiple of infection MOI ranging from 104 to 106.Twenty-four hours after the infection,the expression rates of EGFP on cultured HFB were assessed by flow cytometry and the transfected cells were observed under fluorescence microscope.The killing effect of the virus on the infected cells was assayed by MTT.Results The transfection efficiency of AAV2-EGFP was increased as MOI increased.When MOI was 104,the transfection efficiency of AAV2-EGFP was 7.68%?1.18%;When MOI was 105,that was 52.12%?1.59%;When MOI was 106,that showed no significant increase.However,the transfection efficiency of AAV2/1-EGFP showed no obvious changes at any MOI.Conclusion AAV2 is more efficient than AAV2/1 in transfecting HFB,but neither AAV has a high transfection efficiency.

Objective To investigate the xenotransplantation model of fetal pig skin precursor tissue and its development after transplantaion. Methods Porcine skin precursor tissue was obtained from the embryo of gestation day 56 (E56), and made into microskin or stamp skin graft. The microskin was transplanted to the dorsal wound in BALB/c nude mice, then covered with human corpse skin. The stamp skin graft was imbedded subcutaneously into the back of nude mice, and microskin was injected subcutaneously into the auricles of nude mice. Their growth and development were observed and they were examined by HE staining at 6th and 12th week after transplantation respectively. Two-sample t test was used to analyze the size of newly grown skin tissue. Results Porcine skin precursor tissue graft in three models above survived and continued growth after transplantation, and growth ability of the dorsal wound transplantation model was significantly stronger than that of the auricle model. Epidermis and hypodermis were detected in newly grown skin tissues. Hair follicles, a few of sebaceous glands, but no sweat glands were observed in auricle model, while many sebaceous glands and sweat glands were observed in the dorsal wound model. Conclusion Transplantation of microskin to dorsal wound is the optimal model of investigating the xenotransplantation of fetal pig skin precursor tissue and its development after transplantion.

Objective To establish the background information of physiological parameters for germ?free ( GF ) Taihu piglets. Methods In this study we selected 25 days old GF Taihu piglets and 4 conventional ( CV) littermates, the male and female ratio was 1∶3, to measure the normal clinical values of hematology and serum biochemistry, immunoglobu?lin concentration and main organ coefficients. The analysis of relative growths of main organ weight to body weight was con?ducted in the Taihu GF and CV pigs by allometric scaling model. Results (1) Twelve hematological parameters and 8 blood biochemical parameters in the GF piglets were significantly lower than those in CV pigs (P<0?05). (2) The aver?age body weight, IgM concentration of GF pigs and CV pigs had significant difference ( P <0?05 ) , and no mesenteric lymph nodes were found in the GF pigs. (3) The gut weight had the largest allometric association with body weight in the GF pigs, while spleen weight has the largest allometric association with body weight in the CV pigs. Both the weight of heart and stomach in CV and GF pigs had a negative allometric association with body weight (allometric coefficient b<1), respectively. Conclusions Different microbe control grades affect the body weight, hematology and serum biochemistry, expression of immunoglobulin and development of main organs in laboratory pigs.

Avicel is made of a mixture of microcrystalline cellulose (MCC) and carboxymethyl cellulose (CMC), and used for virus plaque assay. The avicel in common use is produced by FMC Biopolymer. Due to the relatively fixed proportion of MCC and CMC, avicel in common use is not suitable for plaque determination experiment of all types of viruses. In this study, we evaluated the effect of avicel made of different proportions of MCC and CMC on virus plaque assay, and developed an improved avicel virus plaque assay featured with simple and convenient operation, good practicability and high stability. To generate avicel overlays with different proportions of MCC and CMC, twelve different 2×avicel solutions were prepared. Their overall viscosity and bottom viscosity were measured to evaluate the ease of operation. The results showed that most of the 2×avicel solutions (except the 4.8% MCC+1.4% CMC and 4.8% MCC+1.0% CMC group) were easy to absorb and prepare nutrient overlap than 2×CMC solution. In order to find the best scheme to detect the titer of porcine epidemic diarrhea virus (PEDV), these avicel overlay solutions with different proportion of MCC and CMC were used as a replacement in the standard plaque assay. By comparing the size, clarity, stability and titer accuracy of virus plaque, we identified that 0.6% MCC and 0.7% CMC was the most preferable composition of avicel overlay for PEDV plaque assay. In conclusion, we developed an improved virus plaque assay based on avicel, which may facilitate the research of virus etiology, antiviral drugs and vaccines.
Animals ; Carboxymethylcellulose Sodium/chemistry* ; Cellulose/chemistry* ; Swine