Duplication of the lantibiotic structural gene in M-type 49 group A streptococcus strains producing streptococcin A-M49.

Streptococcin A-M49 is produced by certain strains of M-type 49 group A streptococci. The structural gene for streptococcin A-M49 was cloned after hybridization with a probe containing the scnA lantibiotic structural gene. Sequence analysis revealed a duplication of the scnA gene; each gene (scnA' and scnA") encoded a 51-amino-acid prepeptide.     

Effect of sesamol on radiation-induced cytotoxicity in Swiss albino mice

The radio-protective ability of sesamol (SM) at various doses viz., 0, 10, 25, 40, 50, 70 and 100 mg/kg bw, administered intraperitoneally 30 min prior to 9.5 Gy whole-body γ-irradiation was studied in Swiss albino mice. Radiation toxicity and mortality were observed during a period of 30 days and the percentage mortality was calculated. SM pretreatment with 50 mg/kg bw was found to be the most effective dose in maintaining body weight and in reducing the percentage mortality, while 100 mg/kg bw was found to be more effective in maintaining the spleen index and in stimulation of endogenous spleen colony-forming units. Pretreatment with SM (50 mg/kg bw) in mice irradiated with 15 Gy significantly reduced dead, inflammatory, mitotic and goblet cells in irradiated jejunum. SM at 50 mg/kg bw also increased crypt cells, maintained villus height, and prevented mucosal erosion. Nuclear enlargement in epithelial cells was found less in SM-treated mice compared with the irradiated control. The radiation-induced decrease in endogenous antioxidant enzymes (GSH, GST, catalase) and the increase in lipid peroxidation were also reduced by pretreatment with SM [50 and 100 mg/kg bw] at all monitored post-irradiation intervals. There was no protection at a dose less than 25 mg/kg bw.     

Inhibition of adriamycin-induced micronuclei by desferrioxamine in Swiss albino mice

Swiss albino male mice, 6–8 weeks old, were treated i.p. with different doses of desferrioxamine dissolved in water for 7 days. Some of the mice in each group were injected i.p. with adriamycin (15 mg/kg) and killed after 30 or 24, 48 and 72 h. The femoral cells of mice in different groups were collected and studied. Desferrioxamine treatment failed to affect the incidence of micronuclei at doses of 125–250 mg/kg/day. Pretreatment with desferrioxamine was found to provide significant protection against adriamycin-induced micronuclei without interfering with its cytotoxic potential.     

Effect of sesamol on radiation-induced cytotoxicity in Swiss albino mice

The radio-protective ability of sesamol (SM) at various doses viz., 0, 10, 25, 40, 50, 70 and 100mg/kg bw, administered intraperitoneally 30min prior to 9.5Gy whole-body gamma-irradiation was studied in Swiss albino mice. Radiation toxicity and mortality were observed during a period of 30 days and the percentage mortality was calculated. SM pretreatment with 50mg/kg bw was found to be the most effective dose in maintaining body weight and in reducing the percentage mortality, while 100mg/kg bw was found to be more effective in maintaining the spleen index and in stimulation of endogenous spleen colony-forming units. Pretreatment with SM (50mg/kg bw) in mice irradiated with 15Gy significantly reduced dead, inflammatory, mitotic and goblet cells in irradiated jejunum. SM at 50mg/kg bw also increased crypt cells, maintained villus height, and prevented mucosal erosion. Nuclear enlargement in epithelial cells was found less in SM-treated mice compared with the irradiated control. The radiation-induced decrease in endogenous antioxidant enzymes (GSH, GST, catalase) and the increase in lipid peroxidation were also reduced by pretreatment with SM [50 and 100mg/kg bw] at all monitored post-irradiation intervals. There was no protection at a dose less than 25mg/kg bw.     

Effects of split fast neutron doses on the liver cells of albino Swiss mice

The effect of neutron doses from a D-T compact neutron generator on the liver cells of adult male and female albino Swiss mice was investigated. Fast neutrons (14.5 MeV) were delivered to the whole body in a single dose or in two, four, six or eight equal doses separated by 3-day intervals. The lowest dose, 100 rem, was given for an exposure time of 6 hours and was then steadily raised to 912 rem for an exposure time of 48 hours. During exposure the neutron flux was controlled by the activation foil technique. Animals were killed for testing after each irradiation. Histological examination of the hepatocytes in the light microscope showed marked degenerative changes only after the longer irradiation periods (24, 36 and 48 h). Electron microscopy showed cytological (cytoplasmic and nuclear) changes in the hepatocytes after only 12 hours' irradiation. Densitometric scans of electron micrographs of control and 12 h-irradiated livers indicated that the control hepatocyte interphase nucleus contains approximately 72% heterochromatin, while the irradiated nucleus contains only 64% heterochromatin.     

Immunological properties of an L-form of a group A beta hemolytic streptococcus

Antisera were prepared by injecting several groups of rabbits with antigen preparations of the parent streptococcus and its derived L-form. Serum was obtained from each rabbit by cardiac puncture prior to and at intervals after injection of the organisms. To measure the immune response of all animals a modified latex agglutination test was used. This test was found to be specific and easily reproducible. Animals immunized intravenously with the heat-killed streptococci and those immunized intramuscularly with the L-form produced the highest level of antibodies against their respective antigen preparations. Lancefield extracts of the streptococcus reacted with the streptococcal antisera but not with antisera to the L-form. In the antisera to the L-form we found specific antibodies which could not be adsorbed with the parent streptococcus.A portion of this study formed part of a thesis submitted by Sister M. B. Muellenberg to the University of South Dakota, Vermillion, S.D. in partial fulfillment for the requirement for the degree of Master of Arts.     

Tissue specific and variable collagen proliferation in Swiss albino mice treated with clenbuterol

Chronic administration of clenbuterol, a beta-adrenoceptor agonist (2 mg/kg body weight/day for 30 days) to mice resulted in an increased body mass. Measurement of dry tissue mass suggested a protein anabolic effect in the gastrocnemius and heart. Quantitative estimation of collagen content, a non-contractile element as calculated from hydroxyproline assay revealed its proliferation in the gastrocnemius, cardiac ventricle, intestine and to some extent also in the kidney. Clenbuterol did not induce collagen proliferation in non-muscle tissues such as the lungs and liver. Histopathological examination of sections from treated ventricles showed an extensive collagen infiltration in the subendocardium and at myonecrosis sites.     

Occurrence of priapism after transient right MCAO in Swiss albino mice

Introduction: There are few reports about sexual problems in animal models after stroke. The aim of this paper is to report the occurrence of priapism after right MCAO in Swiss albino mice. In addition, we compared neurological score and apoptosis between the priapism-affected and unaffected mice.

Methods: Swiss albino mice were subjected to 45?min’ MCAO and 7?days’ reperfusion. Mice were observed before MCAO, then daily for 7?days to assess priapism. Neurological status and apoptosis (TUNEL assay) were assessed and compared in priapism and non-priapism mice.

Results: The results showed that the incidence of priapism after MCAO in Swiss albino mice were 65%. Priapism was detectable often at day 2 after stroke. Priapism-affected group had more severe behavioural deficits after stroke compared to non-priapism stroke mice.

Conclusion: Priapism after right MCAO is not rare in albino mice and could be considered as a marker of stroke severity. Further studies are needed to assess the incidence of priapism after stroke in other animal species used for stroke studies such as rat.     

Genetic regulation of host responses to group A streptococcus in mice.

The group A streptococci (GAS, Streptococcus pyogenes) are important human pathogens which can cause a variety of diseases, ranging from mild infections to very severe invasive diseases. In recent years, evidence has been accumulated that host genetic factors have a major influence on the outcome of streptococcal infections. Variability in the degree of susceptibility of different inbred mouse strains to infection with GAS has demonstrated that the host genetic background largely determines the susceptibility of mice to this pathogen. This information is particularly useful for studying the immune mechanisms underlying disease susceptibility in mice, and provides an entry point for the identification of host defence loci. This paper reviews the recent advances in the characterisation of pathogenic mechanisms associated with the development of GAS-induced septic shock in the mouse model and outlines the current knowledge regarding the genetic control of immune responses to Group A streptococcus in mice.     

M41型A群链球菌的Ⅰ型胶原样蛋白与人低密度脂蛋白的相互作用

【目的】检测M41型A群链球菌(GAS)ATCC12373中Ⅰ型胶原样蛋白(Scl1)与人低密度脂蛋白(LDL)的相互作用。【方法】克隆了M41型GAS ATCC12373的Ⅰ型胶原样蛋白(Scl1)及其V区(Scl1-V)基因,并表达、纯化重组蛋白rScl1(C176)和rScl1-V(C176V)。通过重组蛋白与人血浆的亲和色谱层析、Western blot及酶联免疫吸附试验(ELISA)检测C176、C176V与LDL的相互作用;通过GAS与LDL的ELISA试验和人血浆与GAS的共孵育试验,检测GAS与LDL的相互作用。【结果】结果证明C176和C176V可以与LDL特异性结合;表达Scl1的M41型GAS可以与LDL相结合。【结论】M41型GAS的Scl1可以与LDL特异性结合。     

T-lymphocyte mediated injury of beta cells in dual-aetiology diabetes mellitus in Swiss albino mouse.

Earlier we had described a dual aetiology diabetes mellitus (DADM) in mice injected with a sub-diabetogenic dose of streptozotocin (SD-SZN) and afterwards infected with coxsackie B3 virus (CBV). Further experiments were conducted to understand the mechanism of diabetogenesis. In in vitro stimulation and proliferation tests, the splenic lymphocytes (SLC) of mice given either SD-SZN or CBV infection showed lower responses to two T cell mitogens than those of control mice, indicating an immunosuppressive effect. Unexpectedly, SLC of mice given both SD-SZN and CBV showed enhanced response, indicating immunoactivation; they were not stimulated to proliferation in response to CBV antigen, indicating that the immunoactivation was not directed against CBV, but against streptozotocin or cellular elements. When mice were depleted of T cells by injecting with anti-thymocyte serum, the diabetogenic effect of SD-SZN and CBV infection was abrogated, without diminishing the replication of virus in the pancreas. Thus beta cell injury in DADM appears to be T cell-mediated.     

Mutagenic profiles of carbazole in the male germ cells of Swiss albino mice

Mutagenic effect of carbazole was evaluated by employing dominant lethal mutation and sperm head abnormality assays in male Swiss albino mice. For the dominant lethal mutation assay, adult male mice were treated for five consecutive days either with 30 or 60 mg/kg body weight (b.w.) of carbazole by single intraperitoneal (i.p.) injection. For the sperm head abnormality assay mice were treated with 50, 100, 150, 200 and 300 mg/kg b.w as a single i.p. injection. Treatment of adult male mice with carbazole resulted in induction of dominant lethal mutation and abnormal sperm heads. The results show that carbazole is mutagenic in male germ cells of mice.     

Tuftsin augments antitumor efficacy of liposomized etoposide against fibrosarcoma in Swiss albino mice

Anticancer drugs are generally plagued by toxic manifestations at doses necessary for control of various forms of cancer. Incorporating such drugs into liposomes not only reduces toxicity but also enhances the therapeutic index. Some antioxidants and potent immunomodulators have also been shown to impart significant antitumor activity presumably by nonspecific activation of the host immune system. In the present study, we evaluated augmentation of the antitumor activity of etoposide (ETP) by the immunomodulator tuftsin in Swiss albino mice with fibrosarcoma. The efficacies of the free form of ETP, liposomized ETP (Lip-ETP), and tuftsin-bearing liposomized ETP (Tuft-Lip-ETP) formulations were evaluated on the basis of tumor regression, effect on expression level of p53wt and p53mut, and survival of the treated animals. Tuft-Lip-ETP, when administered at a dosage of 10 mg/kg body weight/day for five days, significantly reduced tumor volume, delayed tumor growth, and also up-regulated the expression of p53wt. In contrast, although Lip-ETP delayed tumor growth, it did not decrease tumor size. The results of the present study suggest that tuftsin incorporation in drug-loaded liposomes is a promising treatment strategy for various forms of cancers, including fibrosarcoma.