2012 Vol. 33, No. 1

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Animal models are essential for the development of new anti-infectious drugs. Although some bacterial infection models have been established in rodents, small primate models are rare. Here, we report on two bacterial infection models established in tree shrew (Tupaia belangeri chinensis). A burnt skin infection model was induced by dropping 5×106 CFU of Staphylococcus aureus on the surface of a wound after a third degree burn. This dose of S. aureus caused persistent infection for 7 days and obvious inflammatory response was observed 4 days after inoculation. A Dacron graft infection model, 2×106 CFU of Pseudomonas aeruginosa also caused persistent infection for 6 days, with large amounts of pus observed 3 days after inoculation. These models were used to evaluate the efficacy of levofloxacin (LEV) and cefoperazone (CPZ), which reduced the viable bacteria in skin to 4log10 and 5log10 CFU/100 mg tissue, respectively. The number of bacteria in graft was significantly reduced by 4log10 CFU/mL treatment compared to the untreated group (P<0.05). These results suggest that two bacterial infection models were successfully established in tree shrew using P. aeruginosa and S. aureus. In addition, tree shrew was susceptible to P. aeruginosa and S. aureus, thus making it an ideal bacterial infection animal model for the evaluation of new antimicrobials.
Tupaia belangeri are small mammals with a squirrel-like appearance; they were formerly classified under the primates order despite the lack of derived features characteristic of primates. Given that T. belangeri are easy to raise, cheap to maintain, and have a small body size, a high reproductive rate, and close affinity to primates, these animals would be used as an alternative to primates in biomedical research. Three-month old T. belangeri chineses were infected with enterovirus 71 (EV71) via three different routes, namely, oral administration, nasal dripping, and tail intravenous injection, to study the infection in infant T. belangeri and find a feasible scheme to make them an ideal animal model of EV71 in place of primates. Daily activities were regularly observed, body temperatures were measured, and blood tests were conducted. Blood and fecal samples were regularly collected. The infection was examined via the neutralizing antibody test, reverse transcription polymerase chain reaction (RT-PCR), Real-Time PCR, and pathological analysis. The temperature, as well as the white blood cell count and the number of lymphocytes, increased four days after infection. Virus loads were determined in all three groups, and the peak appeared on, before, or after the tenth day, respectively. Thus, oral administration proved to be the best route. The highest serum antibody titer obtained was 1:16. Acute paralysis with urinary retention manifested after about two weeks, and pathological changes were observed in the brain, heart, lung, spleen, kidney, and other tissues. In conclusion, T. belangeri chineses can infected with EV71 via oral administration, nasal dripping, and tail intravenous injection. Therefore, T. belangeri are potential EV71 animal models for further studies on the mechanism of pathogenesis or vaccine evaluation.
The clinical use of morphine to reduce pain is limited because of its drug tolerance, dependence and addiction. In the present study, the tree shrews (Tupaia belangeri chinensis) developed morphine tolerance and chronic morphine dependence by morphine injections with increasing doses (5, 10, 15, 20 mg/kg body weight for 7 days). Meanwhile, the naloxone (1.25 mg/kg body weight)-induced conditioned place aversion (CPA) and the withdrawal symptom were also found. The tree shrew model of chronic morphine dependence can be used to investigate the withdrawal symptoms and to select potential withdrawal symptoms reducing drugs in the future.
The tree shrew may be an important experimental animal for disease models in humans. The effects of some extenders and momamines on sperm cryopreservation will provide helpful data for experimentation of strains and conservation of genetic resources in tree shrews. Epididymal sperm were surgically harvested from male tree shrews captured around Kunming, China and sperm motility, acrosome integrity and fertility were assessed during cryopreservation. In Experiment 1 eight extenders (TTE, TCG, TCF, TTG, BWW, BTS, DM, and SR) supplemented with 0.4 mol/L DMSO were used to dilute the sperm: only TTE, DM and SR showed no differences in motility and acrosome integrity compared to fresh controls after equilibration. After freezing and thawing, sperm in any extender showed lower motility than fresh control and sperm in DM showed higher motility than other groups. However, BWW produced the lowest motility. For acrosome intergrity, TTE and DM showed higher than BWW, BTS and SR after equilibration. The parameter in DM was higher than other groups (except TTE) after thawing. In Experiment 2 four penetrating cryoprotectant agents (CPA) [dimethyl-formamide (DF), formamide (F), dimethylacetamide (DA), and acetamide (A)] at 0.2 mol/L, 0.4 mol/L, 0.8 mol/L, and 1.2 mol/L, respectively were added to the DM extender. Motility showed no difference among CPA groups and non-CPA group (control) after equilibration, but all thawed sperm showed lower values in motility and acrosome intergrity than pre-freezing groups. However, sperm in 0.8 mol/L DF and 0.4 mol/L DMSO showed higher values in both parameters than that in other CPA groups (P>0.05). In Experiment 3 the fertilization rate of oocytes inseminated with 0.4mol/L DMSO (50%) were higher than that with 0.8mol/L DF (16%). In conclusion, non-ion extenders supplemented with egg yolk may be better for sperm cryopreservation in tree shrews and cryoprotectant effects of monoamines agents should be further studied in this species.
The tree shrew (Tupaia belangeri chinensis) is a small non-rodent mammal, which is a relatively new experimental animal in medicine due to its close evolutionary relationship to primates and its rapid propagation. Sperm characteristics and cryopreservation in the tree shrew were the main contents of our spermatological research. Epididymal sperm were surgically harvested from male tree shrews captured from the Kunming area. The rate of testis weight to body weight was (1.05±0.07)%, volume of both testis was (1.12±0.10) mL, total sperm from epididymis and vas deferens were 2.2?8.8×107, and sperm motility and acrosome integrity were (68.8±3.9)% and (90.0±2.1)%, respectively. Sperm ultrastructure of the tree shrew was examined by scanning electron microscopy and transmission electron microscopy. Tree shrew sperm had a round or oval shaped head of approximately 6.65×5.82 μm, and midpiece, principal piece, tail, and total sperm lengths were 13.39, 52.35, 65.74, and 73.05 μm, respectively. The mitochondria in the midpiece consisted of approximately 48 gyres and had a 9+9+2 axonemal pattern. After freezing and thawing, sperm showed partly intact acrosomes and plasma membrane defects, and sperm breakages, twists, and swellings were found. The tree shrew had similar ultrastructure with other mammalians except for the mitochondria number and the sperm size. Ultrastructural alteration is still the main cause resulting in poor sperm after cryopreservation.
The objective of this study was to set up a rhesus monkey model of polycystic ovary syndrome (PCOS), which is globally prevalent among reproductive-aged human women, and to understand the reproductive traits of PCOS female monkeys. Six adult female rhesus monkeys aged 6?10 a, were divided into a PCOS group and a control group. The PCOS group were given two cycles of subcutaneous injections of propionic acid testosterone (PAT), 3.5 mg/kg body weight, on day 1, day 3, and day 5 of the menstrual cycle, respectively, and then given muscle injections of human chorionic gonadotropin (HCG), 350 IU/kg body wtight, on day 7, day 9, and day 11, respectively. Results showed that high levels of serum LH and T [(5.35±0.17) IU/L and (7.58±0.14) ng/mL, respectively], and a high ratio value of LH/FSH (5.35/1.30=4.12) were observed in the PCOS group. No significant differences were found in serum FSH, E2, and P in the PCOS group compared with those of the control. Polycystic ovaries in the PCOS monkeys were recorded by live ultrasound. The blastocysts rates of the PCOS vs. the control were 23.53% vs. 66.67%, and there was a significant difference between the two groups. This study shows that PAT coupled with HCG can induce PCOS in rhesus monkeys in the short term. The reproductive features of PCOS monkeys were similar to those of PCOS patients.
To investigate the characteristics of rhesus monkey embryonic stem cells and to promote their clinical application, the differentiation and proliferation of rosettes neural stem cells from GFP marked rhesus monkey embryonic stem cells were studied The results showed that: 1) A stable and high-efficient neural differentiation system was established. More than 95% of the embryonic stem cells were differentiated into neural stem cells on the 12th days of differentiation; 2) the rosettes neural stem cells differentiated from the rhesus monkey embryonic stem cells could maintain their rosettes-shape by proliferating with bFGF/EGF; 3) the neural stem cells could differentiate into neurons after transplanted into the rhesus monkey brain. In conclusion, the rosettes neural stem cells differentiated from rhesus monkey embryonic stem cells could maintain their characteristics after proliferation with bFGF/EGF and they could survive and differentiate into neurons after transplanted into the rhesus monkey brain, which strongly supports the clinical application of neural stem cells in the future.
Nonhuman primates are critical resources for biomedical research. Rhesus macaque is a popularly used laboratory nonhuman primate that share many characteristics with humans. However, rhesus macaques are the natural host of two exogenous retroviruses, SRV (simian type D retrovirus) and STLV (simian T lymphotropic virus). SRV and STLV may introduce potentially significant confounding factors into the study of AIDS model. Moreover, B virus (ceropithecine herpesvirus 1) is likely to harm not only rhesus macaque but also humans in experiments involving rhesus macaque. Yunnan province has large-scale breeding colonies of Chinese rhesus macaque. Therefore there is an urgent need for SPF Chinese rhesus macaque colonies. Here we investigated SRV, STLV and BV infections in 411 Chinese rhesus macaque by PCR technique. The results showed that the prevalence of SRV, STLV and BV among Chinese rhesus macaque breeding colony was 19.71% (81/411), 13.38% (55/411) and 23.11% (95/411), respectively. Comparison of viruses infection in different age-groups and male/female of Chinese rhesus macaque was also analyzed. This study will contribute to establishment of SPF Chinese rhesus macaque breeding colony.
Breast cancer is a common malignant tumor. It is essential to develop suitable animal models for discovering novel preventive and therapeutic approaches. Tree shrews (Tupaia belangeri chinensis) have a closer evolutionary relationship with humans than do rodents, which have been widely used in laboratory research. Spontaneous breast tumors were identified in tree shrews in 1960s; however, no detailed studies about tree shrew breast tumors have been conducted to date. Here, we characterized a spontaneous breast tumor from tree shrews by Haematoxylin Eosin (H&E) staining. This tumor was identified as a papillary tumor. Immunohistochemical staining (IHC) for progesterone receptor (PR), Ki-67 and cleaved caspase-3 showed that tumor cells were positive for PR, highly proliferative, and less apoptotic compared to normal breast epithelial cells. Thus, the spontaneous tumor of tree shrew is very close to human papillary tumors in terms of morphology and pathology and we concluded that tree shrew may be a suitable animal model for breast cancer research.
The tree shrews, as an ideal animal model receiving extensive attentions to human disease research, demands essential research tools, in particular cellular markers and monoclonal antibodies for immunological studies. In this paper, a 1 365 bp of the full-length CD4 cDNA encoding sequence was cloned from total RNA in peripheral blood of tree shrews, the sequence completes two unknown fragment gaps of tree shrews predicted CD4 cDNA in the GenBank database, and its molecular characteristics were analyzed compared with other mammals by using biology software such as Clustal W2.0 and so forth. The results showed that the extracellular and intracellular domains of tree shrews CD4 amino acid sequence are conserved. The tree shrews CD4 amino acid sequence showed a close genetic relationship with Homo sapiens and Macaca mulatta. Most regions of the tree shrews CD4 molecule surface showed positive charges as humans. However, compared with CD4 extracellular domain D1 of human, CD4 D1 surface of tree shrews showed more negative charges, and more two N-glycosylation sites, which may affect antibody binding. This study provides a theoretical basis for the preparation and functional studies of CD4 monoclonal antibody.
Interferons (IFNs) represent proteins with antiviral activities that are secreted from cells in response to a variety of stimuli. In addition to antiviral, antibacterial and anti-parasitic host-defense functions they are now also recognized as crucial regulators of cell proliferation, differentiation, survival and death as well as activators of specialized cell functions particularly in the immune system and play important roles in infectious and inflammatory diseases, autoimmunity and cancer. Tree shrews (Tupaia belangeri) were found to be susceptible to several human viruses and therefore are widely regarded as good models for analyzing mechanism of human diseases. In this report, we have forecasted the interferon family members of tree shrew from its genome mainly using the methods like Blast (whole genome shotgun sequence) and gene prediction. Our data show that tree shrew interferon system includes: type I IFN: α (five subtypes), β, ω, κ, ε, δ; type II IFN: γ; type III IFN: λ1, λ2/3. Furthermore, the predicted structures of α and λ have similar character with those of other mammals. However, there are some differences in cysteine position and N-glycosylation numbers between human and Tree shrew IFNs. These results provide fundamental basis for further molecular cloning and function analysis of tree shrew IFNs in future.
Much attention has been payed to tree shrews for their close phylogenetic relationship with primates, small size, and short reproductive cycle. Especially, they are considered as excellent experiential animals for medicine or/and disease research. A nucleotide sequence encoding neuropeptide Y(NPY) precursor has been cloned from the cDNA library of Tupaia belangeri chinensis. Sequence alignment revealed that the sequence homology with primate NPY was up to 96.9%. The phylogenetic analysis based on NPY precursor sequence revealed that the tree shrew has a close relationship with primates.
To explore pathological alteration of T2DM in cynomolgus monkeys, gene expression profiles of peripheral blood leukocytes from spontaneous and diet-induced T2DM models was analyzed using quantitative real-time PCR. Among 36 T2DM associated genes tested, 19 genes (including G6PC, CCR2B, CTLA4) displayed a similar expression pattern in both spontaneous and diet-induced T2DM models and were significantly up-regulated or down-regulated compared to controls. Interestingly, expression abundance of all up-regulated genes in the diet-induced T2DM was stronger, although not significantly, than spontaneous models, indicating diet-induced T2DM in monkeys should be a reliable research model for changes in gene expression. The characteristic gene expression pattern obtained here may be useful for the clinical diagnosis of T2DM.
To investigate a simple and effective intraocular xenotransplant technique of rhesus monkey neural progenitor cells to rats, mechanical injury was induced in the rat’s right retina. And the GFP-labeled rhesus monkey neural progenitor cells suspension was slowly injected into the vitreous space of the right injured and left control eye. Confocal image suggested that the xenografted cells survived in both the injured and control eye, meanwhile the cells integrated in the injured right retina. The results demonstrated that intravitreal xenotransplant could be adopted as a simple and reliable method.
We showed that rhesus monkeys (Macaca mulatta) can develop a morphine dependence. Rhesus monkeys successfully established a conditioned place preference (CPP) induced by morphine treatment and this preference lasted for at least (36.3±1.3) months. This animal model may be useful for research into addiction in humans.
Depression is a common neuropsychiatric disorder, marked by depressed mood for at least two weeks. The World Health Organization predicts that depression will be the number one leading cause of disease and injury burden by 2030. Clinical treatment faces at least three serious obstacles. First, the disease mechanism is not fully understood and thus there are no effective ways to predict and prevent depression and no biological method of diagnosis. Second, available antidepressants are based on monoamine mechanisms that commonly have a long delay of action and possibly cause a higher risk of suicide. Third, no other antidepressant mechanisms are available, with fast action and few side effects. Unfortunately, several decades of research based on rodent models of depression have not been successful in resolving these problems, at least partially due to the huge differences in brain function between rodents and people. Tree shrews are the closest sister to primates, and brain functions in these species are closer to those of humans. In this review, we discuss a tree shrew model of depression with social defeat etiology and aspects of construct, face and predicted validity of an animal model. Although a tree shrew model of depression has long been ignored and not fully established, its similarities to those aspects of depression in humans may open a new avenue to address this human condition.
TRIM5-cyclophilin A (TRIMCyp) fusion gene is an unusual TRIM5 locus. At present, this fusion phenomenon has been found in the representative species which contain owl monkey (Aotus trivirgatus) of Aotus genus that belongs to New World monkeys and Old World monkeys such as Northern pig-tailed macaque (M. leonina), Sunda pig-tailed macaque(M. nemestrina), Crab-eating macaque (M. fascicularis), Indian rhesus macaque (M. mulatta) and Assam macaque (M. assamensis), etc. But the fusion mode and transcription splicing pattern of TRIMCyp fusion gene are different between New World and Old World monkeys. The TRIMCyp fusion gene of New World monkeys is formed by inserting a CypA pseudogene cDNA sequence into the region between exon 7 and exon 8 of the TRIM5 locus through retrotransposition. However the TRIMCyp fusion gene of Old World monkeys results from the retrotransposition of a CypA pseudogene cDNA into 3' terminal or 3'-UTR of TRIM5 gene. The distributions, genotypes, expression and restricting activities against different retroviruses of TRIMCyp were different across species of primates. Moreover, most of the researches focused on the TRIMCyp fusion gene of owl monkey and pig-tailed macaque and found that they may play very important roles in restricting HIV-1 replication and determine the susceptibility to HIV-1 infection. It was reported that the TRIMCyp protein of owl monkey could inhibit HIV-1 infection in a similar way as TRIM5α, but TRIMCyp protein of pig-tailed monkey loss the restricting activity to HIV-1 infection. Here we reviewed the distributions, genotypes and restriction mechanism for inhibiting retroviruses replication of TRIMCyp fusion gene in primates.
With the accomplishment of genome sequencing of human, chimpanzee and other primates, there has been a great amount of primate genome information accumulated. Primate comparative genomics has become a new research field at current genome era. In this article, we reviewed recent progress in phylogeny, genome structure and gene expression of human and nonhuman primates, and we elaborated the major biological differences among human, chimpanzee and other non-human primate species, which is informative in revealing the mechanism of human evolution.