Transmission modes of Pneumocystis carinii among rats observed by karyotype analysis.

To observe the transmission patterns of karyotype of Pneumocystis carinii (Pc) by rat colonies, three strains of rats, Sprague-Dawley(SD), Wistar(W) and Fisher(F) from various animal vendors, were suppressed of their immunity by injection of methyl prednisolone. They were kept for 5 to 13 weeks in 3 different animal rooms, A, B, and C. The purified organisms were prepared in low melting point agarose gel by embedded lysis method for pulsed field gel electrophoresis. Field inversion gel electrophoresis showed 2 patterns of the karyotype of Pc. The rooms A and C contained SD rats from the source P, and also the room A was used for F and W rats. However, Pc from all of the SD and F rats in the room A showed same karyotypes, the pattern I. The SD rats from different vendors, M and S, were reared in the room B, and shared the same Pc karyotypes, the pattern II. The rats of W strain were from the vendor M, and immune-suppressed in the animal room A. Five weeks after the experiment, the Pc showed the karyotype pattern II but the pattern became mixed with the type I after 7 to 8 weeks. The findings revealed that the animals born and reared in the same animal quarter harbored Pc with same karyotypes. If the animals were kept under immune-suppression in the same room with heavily infected hosts, they could be infected by Pc from their neighbors. The present experimental findings suggest that Pc is transmitted among rats through the air.     

Karyotypes of Pneumocystis carinii from Korean rats.

Molecular karyotyping was applied to Pneumocystis carinii(Pc) from two strains of experimental rats, Sprague Dawley(SD) and Fisher(F), in Korea. Field inversion gel electrophoresis and contour clamped homogeneous electric field electrophoresis resolved 15 chromosomal bands from the Pc. The size of the bands was estimated 270kb to 684kb from SD rats, and 273kb to 713 kb from F rats. The bands of 283 kb from SD rats and of 273 kb from F rats stained more brightly suggesting duplicated bands. Total number of chromosomes was at least 16, and total genomic size was estimated 7 x 10(6) bp. All of the bands from F rats hybridized to the probe of repeated DNA sequences of Pc and the band of 448 kb size was proved to contain rDNA sequences, but Pc. chromosome bands from SD rats showed no reactions to the probes. The 2 different karyotypes of P. carinii from 2 strains of rats were maintained consistently for 2 years.     

Comparison of glycogen store in two strains of rat and guinea-pig under fed and fasted conditions

Glycogen content in the liver, skeletal muscle and heart has been determined in Sprague-Dawley (SD) and Wistar (W) rats and in tricoloured (T) and albino Dunkin Hartley (DH) guinea-pigs. The 12-week-old animals were studied under non-fasted or control conditions (N) and after 48 hr of fast (F48). Hepatic glycogen was higher in DH guinea-pigs (95.6 +/- 3.8 mg g-1) than in W (77.2 +/- 5.3 mg g-1) and SD (80.2 +/- 2.3 mg g-1) rats under N conditions. Mean values for the two strains were slightly higher in guinea-pigs than in rats. After fasting, hepatic glycogen was almost exhausted in the two species but was higher in W (1.5 +/- 0.08 mg g-1) and T (1.5 +/- 0.2 mg g-1) than in SD and DH (0.6 +/- 0.1 mg g-1). The content of glycogen in the anterior muscles of the thigh was comparable in the two strains of rat and guinea-pig, but was twice as high in the guinea-pigs (DH:15.1 +/- 0.6; T: 16.4 +/- 0.7 mg g-1) as in the rats (SD: 8.1 +/- 0.2; W: 7.1 +/- 0.5 mg g-1) under N conditions. In F48 animals, muscular glycogen decreased by 41-46% (rats) and 38-39% (guinea-pigs). Hepatic and extra-liver glycogen stores were calculated and found higher in the guinea-pigs than in the rats. The total utilization during fasting was larger in the guinea-pigs (6140 mg/kg body wt) than in the rats (4500 mg/kg body wt).(ABSTRACT TRUNCATED AT 250 WORDS)     

Kinetic profile of influenza virus infection in three rat strains

Influenza is a respiratory tract disease of viral origin that can cause major epidemics in humans. The influenza virus infects and damages epithelial cells of the respiratory tract and causes pneumonia. Lung lesions of mice infected with influenza virus resembles those seen in humans with influenza, and can result in severe and even fatal pneumonia. In contrast, experimental infection of rats with the virus induces a milder form of the disease, with no mortality. The purpose of the study reported here was to determine the time course of influenza infection and lung injury in Brown Norway (BN), Fischer-344 (F344), and Sprague-Dawley (SD) rats to ascertain whether genetic background impacts susceptibility to infection and host responses. Rats of each strain were inoculated intranasally with 10,000 plaque-forming units of rat-adapted influenza virus (RAIV), and lungs were assessed at postinoculation hour (PIH) 2, 24, 48, 72, and 144 for viral titer, inflammatory cells, pro-inflammatory cytokines, and biochemical indicators of lung edema (protein) and injury (lactate dehydrogenase [LD] activity). Virus titer peaked at PIH 24, and was 100-fold higher in the F344 and SD, compared with the BN strain. Alveolar macrophages, LD activity, and total protein concentration were higher in the BN rats, whereas neutrophil numbers and interleukin 6 and tumor necrosis factor-alpha activities were greatest in the bronchoalveolar lavage fluid of F344 and SD rats. The results indicate that F344 and SD rats respond in similar manner to viral infection, whereas viral replication was more limited in BN rats and was associated with a different profile of pulmonary cells.     

Immunologic comparisons of Pneumocystis carinii strains obtained from rats, ferrets, and mice using convalescent sera from the same sources.

Pneumocystis carinii (Pc) infections were developed in animals immunosuppressed by dexamethasone treatment either from activation of latent infection (ferret) or trans-tracheal inoculation of Pc obtained from infected lungs of the homologous species (rat, mouse). Convalescent antisera were obtained by stopping dexamethasone treatment after 2-4 wk and allowing 5-8 wk for recovery. Parasites from infected lungs were purified by differential filtration, solubilized in loading buffer, subjected to sodium dodecyl sulfate- polyacrylamide gel electrophoresis, and blotted to polyvinylidene fluoride sheets for Western analysis. Antisera from each animal species were reacted on Western blots of antigens from rat, ferret, and mouse. Each combination of antigen and antibody from the same species of animal showed reaction with 5 or more bands of Pc antigen. Convalescent mouse antibody did not react with rat or ferret antigens. Convalescent rat antibody reacted with a mouse antigen at about 66 kDa but not with ferret antigen, and convalescent ferret antibody showed minimal, probably non-specific reactions with both rat and mouse antigens. Variations in reactions indicate antigenic differences in Pc strains infecting these animals.     

The cotton rat (Sigmodon hispidus) is a permissive small animal model of human metapneumovirus infection, pathogenesis, and protective immunity

Human metapneumovirus (hMPV) is a newly described paramyxovirus that is an important cause of acute respiratory tract disease. We undertook to develop a small animal model of hMPV infection, pathogenesis, and protection. Hamsters, guinea pigs, cotton rats, and nine inbred strains of mice were inoculated intranasally with hMPV. The animals were sacrificed, and nasal and lung tissue virus yields were determined by plaque titration. None of the animals exhibited respiratory symptoms. The quantity of virus present in the nasal tissue ranged from 4.6 x 10(2) PFU/gram tissue (C3H mice) to greater than 10(5) PFU/gram (hamster). The amount of virus in the lungs was considerably less than in nasal tissue in each species tested, ranging from undetectable (<5 PFU/g; guinea pigs) to 1.8 x 10(5) PFU/gram (cotton rat). The peak virus titer in cotton rat lungs occurred on day 4 postinfection. hMPV-infected cotton rat lungs examined on day 4 postinfection exhibited histopathological changes consisting of peribronchial inflammatory infiltrates. Immunohistochemical staining detected virus only at the luminal surfaces of respiratory epithelial cells throughout the respiratory tract. hMPV-infected cotton rats mounted virus-neutralizing antibody responses and were partially protected against virus shedding and lung pathology on subsequent rechallenge with hMPV. Viral antigen was undetectable in the lungs on challenge of previously infected animals. This study demonstrates that the cotton rat is a permissive small animal model of hMPV infection that exhibits lung histopathology associated with infection and that primary infection protected animals against subsequent infection. This model will allow further in vivo studies of hMPV pathogenesis and evaluation of vaccine candidates.     

Bacterial infection (Legionella pneumophila) stimulates fever, metabolic rate and brown adipose tissue activity in the guinea pig

The objective of this study was to assess whether bacterial infection stimulates oxygen consumption and brown adipose tissue (BAT) activity. Guinea pigs infected with Legionella pneumophila showed marked fever and a significant (33%) increase in resting oxygen consumption (VO2), 24h after infection. At this time, food intake and body weight were normal and the in vitro thermogenic activity of BAT taken from infected animals was elevated by 64% above that of control guinea pigs. VO2 and BAT activity fell to control values by 48h as infected animals became moribund and over this period food intake was markedly reduced.     

Epizootiological studies of Salmonella typhimurium infection in guinea pigs

In two natural outbreaks of S. typhimurium infection in guinea pigs, frequent isolations of the organism from the conjunctiva and cervical lymph nodes and high incidences of the conjunctivitis and abscess formation in the cervical lymph nodes were shown, suggesting more importance of the conjunctiva as infection route than oral route. These features in salmonellosis of guinea pigs were tried to reproduce in experimental infections by conjunctival and oral inoculations of 10(2) and 10(6) cells of 4 different strains of S. typhimurium and also by contact infection simulating natural conditions. As the results, it was demonstrated that guinea pigs were more susceptible to the conjunctival infection than the oral infection, because higher infection rates and more frequent incidence of abscess formation in the cervical lymph nodes as well as conjunctivitis were produced by the conjunctival inoculation than the oral inoculation of the organism. Main localization sites of the organism were the cervical lymph nodes, conjunctiva and upper respiratory tract in conjunctivally inoculated guinea pigs but more widely distributed in orally infected ones. These findings were common in animals infected with 4 different strains of S. typhimurium and also in contact infection. Thus the conjunctiva was regarded as an important route of S. typhimurium in guinea pigs.     

Attempts to establish experimental Cyclospora cayetanensis infection in laboratory animals

Attempts were made to develop an animal model for Cyclospora cayetanensis to identify a practical laboratory host for studying human cyclosporiasis. Oocysts collected from stool of infected humans in the United States, Haiti, Guatemala, Peru, and Nepal were held in potassium dichromate solution to allow development of sporozoites. The following animal types were inoculated: 9 strains of mice, including adult and neonatal immunocompetent and immune-deficient inbred and outbred strains, rats, sandrats, chickens, ducks, rabbits, jirds, hamsters, ferrets, pigs, dogs, owl monkeys, rhesus monkeys, and cynomolgus monkeys. Most animals were inoculated by gavage, although some of the primates were fed oocysts on food items. The animals were examined for signs of infection, particularly diarrhea, and stool samples were examined for 4-6 wk after inoculation. None of the animals developed patent infections or signs of infection. We conclude that none of the animals tested is susceptible to infection with C. cayetanensis.     

Genetic mapping of lymphocytic choriomeningitis virus pathogenicity: virulence in guinea pigs is associated with the L RNA segment.

The Armstrong CA 1371 (ARM) and WE strains of lymphocytic choriomeningitis virus (LCMV) differ in the ability to produce disease in adult guinea pigs. Infection with the ARM strain is not lethal, even at high virus doses (greater than 10,000 PFU), whereas the WE strain causes 100% mortality even at low doses (less than 10 PFU). To determine the genetic basis of this virulence, intertypic reassortants were made between the ARM and WE strains of LCMV. The two reassortants with the genotypes WE/ARM (L segment of WE and S segment of ARM) and ARM/WE (L segment of ARM and S segment of WE) were tested for their pathogenicity in guinea pigs. The ARM/WE reassortant was avirulent like the ARM/ARM parental strain. Minimal viral replication was observed in organs of guinea pigs inoculated with 10(2) or 10(5) PFU of ARM/ARM or ARM/WE, and all animals survived. In contrast, the WE/ARM reassortant was highly virulent like the WE/WE parental strain and killed all of the infected animals. High levels of viral replication were observed in guinea pigs infected with the latter two strains. In contrast to these in vivo observations, both the parental strains and the ARM/WE or WE/ARM reassortants had similar growth potential in cultured guinea pig fibroblasts. Thus, the L RNA segment of LCMV WE is important for viral replication in vivo and is associated with fatal acute disease after infection of adult guinea pigs.     

Rat strains differ in antibody response to natural Haemophilus species infection

Antibody response to Haemophilus species in rat strains was monitored by enzyme-linked immunosorbent assay (ELISA) using antigens of two Haemophilus strains and a Pasteurella pneumotropica strain. Five rat strains from a breeding colony naturally infected by Haemophilus were significantly different in ELISA antibody activity and in the number of seropositive animals. BN and RP rats were (relatively) high and low responders, respectively and BUF, LEW and WAG rats were intermediate. In a second study, five rat strains were exposed to Haemophilus-infected rats, and, after six weeks, were also significantly different in ELISA antibody activity and in numbers of seropositive animals. Here, BN and LEW rats were (relatively) high and low responders, respectively, and BD IX, F344 and WKY rats were intermediate.     

Infectivity of Trichinella sp. isolated from Crocodylus niloticus to the indigenous Zimbabwean pig (Mukota).

An experimental infection of the indigenous Zimbabwean pig (Mukota) with a Trichinella sp. derived from crocodile (Crocodylus niloticus) was performed. The same larval isolates of Trichinella were infected to rats as a control. The muscles of both pigs and rats were found to be heavily infected with the first-stage larvae. The present study constitutes the first report of a successful experimental infection of the pig with Trichinella sp. originating from crocodile.     

Effects of an anesthetic mixture of medetomidine,midazolam, and butorphanol in rats—strain difference and antagonism by atipamezole

An anesthetic mixture of medetomidine (MED), midazolam (MID), and butorphanol (BUT) has been used in laboratory animals. We previously reported that this anesthetic mixture produced closely similar anesthetic effects in BALB/c and C57BL/6J strains. We also demonstrated the efficacy of atipamezole (ATI), an antagonist of MED that produced quick recovery from anesthesia in mice. Anesthetics have various anesthetic effects among animal strains. However, the differences in the effects of anesthetic mixtures in rats are unclear. In the present study, we first examined effects of the abovementioned anesthetic mixture using three different rat strains: Wistar (WST), Sprague-Dawley (SD), and Fischer 344 (F344). Second, we examined how different dosages and optimum injection timing of ATI affected recovery from anesthesia in rats. We used the anesthetic score to measure anesthetic duration and a pulse oximeter to monitor vital signs. We found no significant differences in anesthetic duration among the three different strains. However, recovery from anesthesia in the SD strain took significantly longer than in the other strains. The antagonistic effects of ATI (0.15 mg/kg and 0.75 mg/kg) were equivalent when administered at 30 min after anesthetic mixture administration. The antagonistic effects of ATI 0.75 mg/kg were stronger than those of ATI 0.15 mg/kg at 10 min after anesthetic mixture administration. This anesthetic mixture is a useful drug that can induce similar anesthetic effects in three different strains and has an antagonist, ATI, that makes rats quickly recover from anesthesia. These results may contribute to the welfare of laboratory animals.     

Nude rat (F344/N-rnu) tuberculosis

As many mononuclear cells from Mycobacterium tuberculosis-infected lung tissues are not available for fluorescence-activated cell sorter (FACS) analysis and the tuberculin test is not feasible in a mouse tuberculosis model, we attempted to develop a rat tuberculosis model. We have previously reported that rat tuberculosis is associated with granulomas that lack central necrosis. In order to develop a better animal model of tuberculosis in immunocompromised humans (tuberculosis associated with HIV infection or tuberculosis of the elderly), we infected F344/N-rnu nude rats with M. tuberculosis via the airborne route. The animals developed pulmonary granulomas with central necrosis encapsulated by dense collagen fibres, closely resembling those of human tuberculosis. The nude rats died of disseminated tuberculosis by the 85th day after aerosol infection, while F344 wild-type rats did not. Interestingly, T-cells that were reactive with anti-CD4 antibody and anti-CD8 antibody, indicating the presence of remnant thymus, were observed in the infected lung tissues of the nude rats. Therefore, T-cell precursors may be present in nude rats. The nude rat tuberculosis model mimics tuberculosis in immunocompromised humans and may provide a suitable model for immunological studies in vivo.     

The pig as an intermediate host for Taiwan Taenia infection

Eggs (1000-100,000/animal) of Taiwan Taenia were inoculated per os into 14 Small-Ear-Miniature (SEM), 19 Landrace-Small-Ear-Miniature (L-SEM), and 5 Duroc-Yorkshire-Landrace (DYL) pigs. These animals were sacrificed 7-107 days after infection. Thirty-four pigs were found to be infected with Taiwan Taenia cysticerci and the infection rates of SEM, L-SEM, and DYL were 86%, 89% and 100% respectively. The cysticerci recovery rates of SEM, L-SEM and DYL pigs were 27.2%, 1.7% and 0.27% respectively. Cysticerci were recovered only from the livers and none were found in muscles, viscera or other parts of the carcasses. More cysticerci were located in the liver parenchyma (71%) than on the liver surface (29%). Taiwan Taenia cysticerci were smaller than those of classical T. saginata or T. solium. Moreover, Taiwan Taenia cysticerci had 2 rows of rudimentary hooklets on the scolex. The results of this study indicate that young pigs are good intermediate hosts for Taiwan Taenia and that the SEM pig is a satisfactory host for experimental studies with this tapeworm. These results were similar to other studies with different geographic strains of the T. saginata-like tapeworm in the Far East. These strains appear to be the same and possibly a new species.     

Trypanosoma cruzi: blood parasitism kinetics and their correlation with heart parasitism intensity during long-term infection of Beagle dogs

The goals of the present study were to evaluate the kinetics of blood parasitism by examination of fresh blood, blood culture (BC) and PCR assays and their correlation with heart parasitism during two years of infection in Beagle dogs inoculated with the Be-78, Y and ABC Trypanosoma cruzi strains. Our results showed that the parasite or its kDNA is easily detected during the acute phase in all infected animals. On the other hand, a reduced number of positive tests were verified during the chronic phase of the infection. The frequency of positive tests was correlated with T. cruzi strain. The percentage of positive BC and blood PCR performed in samples from animals inoculated with Be-78 and ABC strains were similar and significantly larger in relation to animals infected with the Y strain.Comparison of the positivity of PCR tests performed using blood and heart tissue samples obtained two years after infection showed two different patterns associated with the inoculated T. cruzi strain: (1) high PCR positivity for both blood and tissue was observed in animals infected with Be-78 or ABC strains; (2) lower and higher PCR positivity for the blood and tissue, respectively, was detected in animals infected with Y strains. These data suggest that the sensitivity of BC and blood PCR was T. cruzi strain dependent and, in contrast, the heart tissue PCR revealed higher sensitivity regardless of the parasite stock.     

Genetic association of crown rust resistance gene Pc68, storage protein loci, and resistance gene analogues in oats

Segregating F(3) families, derived from a cross between oat cultivar Swan and the putative single gene line PC68, were used to determine the association of seed storage protein loci and resistance gene analogues (RGAs) with the crown rust resistance gene Pc68. SDS-PAGE analysis detected three avenin loci, AveX, AveY, and AveZ, closely linked to Pc68. Their diagnostic alleles are linked in coupling to Pc68 and were also detected in three additional lines carrying Pc68. Another protein locus was linked in repulsion to Pc68. In complementary studies, three wheat RGA clones (W2, W4, and W10) detected restriction fragment length polymorphisms (RFLPs) between homozygous resistant and homozygous susceptible F(3) DNA bulks. Four oat homologues of W2 were cloned and sequenced. RFLPs detected with two of them were mapped using F(3) and F(4) populations. Clone 18 detected a locus, Orga2, linked in repulsion to Pc68. Clone 22 detected several RFLPs including Orga1 (the closest locus to Pc68) and three RGA loci (Orga22-2, Orga22-3, and Orga22-4) loosely linked to Pc68. The diagnostic RFLPs linked in coupling to Pc68 were detected by clone 22 in three additional oat lines carrying Pc68 and have potential utility in investigating and improving crown rust resistance of oat.     

Strain differences in in vitro rat hepatocyte unscheduled DNA synthesis (UDS): effect of UV is independent of strain while increased sensitivity is apparent using Fischer-344 instead of Sprague-Dawley rats

The unscheduled DNA synthesis (UDS) assay measures DNA repair following in vitro treatment of rat primary hepatocytes. This report compares the UDS response of primary hepatocytes from 2 widely used rat strains, the Fischer-344 (F344) and Sprague-Dawley (SD) strains. Ultraviolet (UV) light and 5 known genotoxic chemicals were evaluated in each strain in parallel experiments. The chemicals tested were 2-acetylaminofluorene (2-AAF), 4-aminobiphenyl (4-AB), benzidine, dimethylnitrosamine (DMN) and N-propyl-N'-nitro-N-nitrosoguanidine (PNNG). Four of these compounds (2-AAF, 4-AB, benzidine and DMN) require metabolic activation. Benzidine and PNNG were both negative using SD rat hepatocytes, but were weakly positive using F344 rat hepatocytes. In the first of 2 experiments, 4-AB was inconclusive in SD hepatocytes, but strongly positive in F344 cells. In the second experiment, 4-AB was positive in hepatocytes from both strains. 2-AAF was more strongly positive in F344 cells than in SD cells. DMN and UV light induced positive dose responses with little or no differences between strains. It is concluded that hepatocytes from F344 rats may be more sensitive, qualitatively and quantitatively, than hepatocytes from SD rats as indicators of UDS. This difference is not due to intrinsic differences in DNA repair mechanisms but is probably due to differences in drug-metabolizing enzymes between these strains. Thus, for routine screening, F344 rats are preferable for measurement of the in vitro UDS-inducing potential of compounds.     

Reproductive disorders in female rats infected with sialodacryoadenitis virus.

Effects of sialodacryoadenitis virus infection on the reproduction of Wistar and Sprague-Dawley (SD) rats were studied. Estrous cycle was considerably out of order in about 40% of infected rats of both strains, starting on days 4 to 20 postinfection and persisting for 2 to 12 days. Of Wistar and SD dams infected on day 0 of gestation about 30% and 10% of the fetuses were found dead, while only 4 and 3% of non-infected dams. In severely diseased Wistar and SD dams infected on day 15 of gestation, the offspring showed death rates of 57% and 13%, respectively, because of inadequate nursing.     

The epidemiological investigation of Trichinella infection in brown rats (Rattus norvegicus) and domestic pigs in Croatia suggests that rats are not a reservoir at the farm level

Whether the brown rat (Rattus norvegicus) is a reservoir of Trichinella spp. infection or merely an accidental host, which may be vector of Trichinella spp., continues to be debated. We estimated the prevalence of Trichinella sp. infection in brown rat populations and in domestic pigs in 2 villages in Croatia, where Trichinella sp. infection in pigs has been endemic in the past 10 yr. Trichinella spiralis larvae, identified by a multiplex polymerase chain reaction analyses, were the only species detected in both rats and pigs. In 2001 and 2002, 2,287 rats were collected on 60 farms with different levels of sanitation and with, or without, T. spiralis-infected pigs. The prevalence of infection in rats ranged from 0.2 to 10.7%. Infected rats were detected only on farms with T. spiralis-positive pigs and low sanitation or formerly with low sanitation (P = 0.007, Fisher's exact test), yet no infected rat was detected on farms with T. spiralis-negative pigs. The finding that no infected rat was found on farms with T. spiralis-negative pigs suggests that, in the investigated area, the brown rat is not a reservoir but only a victim of improper pig slaughtering.