Uninfected Rats Research Articles

Bacterial dissemination, rather than translocation, mediates hypermetabolic response in endotoxemic rats.

To study the pathogenesis of the host response during bacterial translocation, a rat model was designed for prolonged follow-up after injury. A prospective, controlled animal study. Animal laboratory. Young male Wistar rats. Antibiotic decontamination of rats was performed 4 days before intragastric inoculation with a selected Escherichia coli strain (10(10) bacteria/kg of body weight). Two days later, the rats received a lipopolysaccharide injection or not (control group) and were observed for 3 days. They were then killed. A reference group (pair-fed healthy animals) was studied in parallel. During observations, urinary total nitrogen loss and 3-methylhistidine excretion were determined daily. When the rats were killed, mesenteric lymph nodes (MLNs), spleen, and liver were aseptically removed and cultured. Colonies identified as translocated E. coli were counted in each organ. Intracellular amino acid free pools were measured in extensor digitorum longus and anterior tibialis. Endotoxin induces bacterial translocation of bacteria from gut lumen to MLNs (100% vs. 59% in the lipopolysaccharide-untreated control group; p < .05) and dissemination to spleen and liver (65% and 45% of positive cultures after endotoxemia, respectively, vs. 6% and 12% in the control groups). No translocation occurred in the reference group. Evidence for the hypermetabolic response was seen in lipopolysaccharide-treated and infected rats, but protein catabolism was more closely related to the occurrence of bacterial dissemination to spleen and liver than to translocation alone (e.g., the cumulative 3-methylhistidine excretion during the observation period was 4.07+/-0.18 micromol in uninfected rats, 4.48+/-0.29 in rats with positive MLN cultures alone and 6.17+/-0.30 in MLN, spleen, or liver infected rats; 1 vs. 2, NS; 3 vs. 1, and 3 vs. 2, p < .05). Gut barrier failure is associated with a deep excessive catabolic response in the host. The mechanism by which the metabolic state affects the resistance to infection apparently involves amino acid metabolism.

Persistent Neonatal Borna Disease Virus (BDV) Infection of the Brain Causes Chronic Emotional Abnormalities in Adult Rats

Neonatal Borna disease virus (BDV) brain infection results in selective developmental damage to the hippocampal dentate gyrus and the cerebellum. When mature, neonatally BDV-infected rats show extreme locomotor hyperactivity and reduced freezing behavior in novel environments. Traditional interpretation of both of these behavioral abnormalities would suggest decreased anxiety in infected rats compared to normal animals. However, it also possible that the locomotor hyperactivity in infected rats reflects higher rather than reduced anxiety, and is the result of increased escape responses to aversive stimuli. The present experiments were undertaken to test a hypothesis about elevated anxiety in neonatally BDV-infected adult Lewis rats by studying their species-specific fear-related responses. Compared to normal subjects, BDV-infected rats exhibited locomotor hyperactivity and elevated defecation in a highly aversive, brightly lit open field. As expected, in a less aversive, dimly lit open field, uninfected controls increased ambulation, whereas infected rats significantly decreased locomotor activity and defecation. Unlike uninfected rats, BDV-infected rats exhibited an attenuated freezing response immediately after loud auditory stimuli. On the contrary, immediate freezing responses following footshock were comparable in the two groups of animals indicating an intact ability to freeze in BDV-infected rats. Despite a decreased baseline startle responsiveness, BDV-infected rats demonstrated increased sensitization of the startle response by preceding footshocks, suggesting a tendency toward elevated escape responses. Compared to normal subjects, BDV-infected rats showed decreased conditional freezing and elevated conditional defecation response in the context previously paired with aversive stimulation indicating sparing of an autonomic component of fear conditioning. The findings indicate that neonatally BDV-infected adult rats are hyperreactive to aversive stimuli, possibly as a result of chronic emotional abnormalities.

INHIBITION OF CYTOMEGALOVIRUS IN VITRO AND IN VIVO BY THE EXPERIMENTAL IMMUNOSUPPRESSIVE AGENT LEFLUNOMIDE

825 Despite progress in antiviral chemotherapy, cytomegalovirus (CMV) continues to complicate the clinical course of many allograft recipients. Enhancement of viral activity by requisite immune suppression frequently engages the clinician in a struggle to balance graft preservation with control of CMV disease. Leflunomide, an inhibitor of protein tryrosine kinase activity and pyrimidine synthesis, is an experimental immunosuppressive agent with demonstrated effectiveness against acute and chronic rejection in animal models. We have recently discovered that the active metabolite of this agent, A77 1726, inhibits the production of multiple isolates of human CMV in both human fibroblasts and endothelial cells in vitro. Viral plaque assays demonstrated a consistent dose-dependent reduction of virus yield over a range of concentrations equivalent to those which inhibit in vitro immune activation. Unlike anti-CMV drugs currently in use, A77 1726 has no effect upon viral DNA synthesis, as demonstrated by CMV-specific DNA dot blot analysis and direct biochemical assay of viral DNA polymerase activity. Rather, as indicated by transmission electron microscopy, this agent appears to act at the level of virion assembly by interfering with nucleocapsid tegumentation, possibly by inhibition of tegument protein phosphorylation. Likely as a consequence of this unique mechanism of action, A77 1726 is equally effective against drug-resistant isolates. To determine the effectiveness of leflunomide in the control of viral load in vivo, groups of immunodeficient nude rats were inoculated with rat CMV (RCMV, Maastricht strain, 105 plaque-forming units/animal, IP) and treated with either leflunomide (15 mg/kg/day for 14 days), ganciclovir (10 mg/kg/day for 5 days), or drug-free vehicle. Experiments also included uninfected control animals. Following euthanization at 14 days post-inoculation, viral infection was confirmed by histologic observation of typical cytomegalic ductal epithelium in salivary glands, and further verified by immunohistochemical detection of RCMV antigens in multiple tissues. Plaque assay of tissue homogenates prepared from salivary gland, spleen, and lung demonstrated 75-99% reduction in virus yield in organs harvested from leflunomide-treated animals, and 85-99% reduction in those harvested from ganciclovir-treated animals. No virus was ever recovered from uninfected control rats. Thus in addition to its in vitro antiviral activity, leflunomide is capable of reducing viral load in vivo. These findings imply that leflunomide, an effective immunosuppressive agent, shows potential to concurrently attenuate a major complication of immunosuppression, CMV disease, by a novel mechanism of antiviral activity.

Developmental brain injury associated with abnormal play behavior in neonatally Borna disease virus-infected Lewis rats: a model of autism

Play behavior, nonsocial exploratory activity, and nonplay social interaction were observed in male juvenile Lewis rats with brain developmental injury following neonatal infection with Borna disease virus (BDV). These behaviors were tested using the `intruder-resident' paradigm, with social isolation of residents for six days prior to testing. Four experimental pairings of infected (BDV) and uninfected (NL) rats were studied as follows: NL–NL; NL–BDV; BDV–NL; and BDV–BDV (the first member is the resident, the second member is the intruder). Observation of social activities was carried out for 10 min on two consecutive days. Nonsocial exploratory activity (e.g. ambulation and rearing) was similar in BDV and NL residents. Duration of nonplay social investigation (e.g. sniffing, approach, and follow) was higher in BDV residents as compared to NL residents when tested on the first test day. On the second day, all rats showed similar level of nonplay social interaction. When confronted with NL intruders, NL residents exhibited significantly more play behavior compared to the NL–BDV, BDV–NL and BDV–BDV pairs, when play behavior was measured by the number of `pins'. Moreover, irrespective of a type of intruder, NL residents demonstrated higher play soliciting behavior than BDV residents, indicating attenuated readiness to play in BDV-infected rats. The number of pins and play solicitations in BDV–NL pairs significantly increased over the two days of testing, while play activity in NL–BDV pairs declined on the second test day. This pattern suggests that the degree of social reinforcement on the first day of testing affected the level of play on the second day. These data demonstrate deficits in play behavior and other social interactions following BDV-associated developmental brain injury, thus supporting the value of the neonatally BDV-infected rat as an animal model of autism.

Effect of Water Extract Of Tetrapleura Tetraptera (Aidon) On Haematological And Biochemical Parameters in Rats infected With Trypanosoma Brucei

This study investigated whether water extract of Tetrapleura tetraptere has trypanocidal effect against T.brucei in laboratory rats. Studies also examined its effect on the weight, haematological parameters as well as the blood chemical analyses of the infected animals. Results showed that oral administration of the water extract to the infected rats significantly reduced the parasite load, also weight loss was significantly lower in the infected and treated rats than the untreated ones. These positive observations were accompanied by reduced leukocytosis, improved state of anaemia and increased packed cell volume, all of which are indices of recovery from the state of cell toxicity arising from parasitemia. The tolerance of the extract by the animal was evaluated by the determination of the blood chemistries. Results revealed that there was no significant difference in the concentrations of the blood glucose, total protein, uric acid and unconjugated bilirubin in the uninfected but treated rats compared with the "neat" rats which were neither infected nor treated. However, conjugated bilirubin and creatinine values were significantly increased. It was also observed that when the infected animals were treated with the extract, the blood levels of total protein, uric acid, creatinine and unconjugated bilirubin decreased slightly, but consistently, as against the untreated rats. These observations indicate the beneficial effects of the plant extract and suggest that the T. tetraptera may contain active substance(s) which could have therapeutic effect against trypanosome infection. Nigerian Quarterly Journal of Hospital Medicine Vol. 9, No. 1 (1999) pp. 66-70

Reactions from rat gastric mucosa during one year of Helicobacter pylori infection.

The aim of the present study was to investigate responses from the gastric mucosa of rats during long-term H. pylori infection. Twenty-four Sprague-Dawley rats were inoculated with a mouse-adapted strain of human H. pylori (vacA+, cagA+), 16 uninfected rats served as controls. Three to six rats from each group were killed two weeks or two, six, or 12 months later. At sacrifice, blood was sampled and the gastric mucosa was taken for bacterial culture, histology, immunocytochemistry and in situ hybridization. H. pylori colonized the antrum in 23/24 inoculated rats; with time the density of bacteria increased. The inflammation in the antral mucosa was mild to moderate and was dominated by infiltration of lymphocytes and macrophages. Serum H. pylori-specific IgG2a was significantly increased in the infected rats. The frequency of epithelial cell apoptosis was significantly increased in the early months of infection. The mucosal expression of trefoil peptide mRNA remained unchanged. We conclude that after one year of H. pylori infection in rats, the mucosal responses were rather mild, indicating that the animals may adapt to the infection by mechanisms which remain to be identified.

Changes of splenocyte IFN-gamma mRNA synthesis in rats infected with Paragonimus westermani.

Changes in the expression level of splenocyte IFN-gamma mRNA of Sprague-Dawley (SD) rats infected with Paragonimus westermani were analyzed by competitive reverse transcription-polymerase chain reaction (RT-PCR) followed by southern blot. The template RNA was extracted from the splenocytes of rats infected with 20 metacercariae of P. westermani. The products of competitive RT-PCR were subjected to southern blot and enhanced chemiluminescence (ECL), and analyzed with a densitometer. In comparison with that of uninfected control rat splenocytes (value of 1), the levels of mRNA expression of IFN-gamma had changed to 0.747 at 1 week post infection (PI), 0.00175 at 2 week PI, 0.0217 at 3 week PI, 0.194 at 4 week PI and then to 0.537 at 5 week PI. The level at 7 week PI had returned to 1.25, comparable with that of uninfected rats. These results show that, when infected with P. westermani, the levels of IFN-gamma mRNA of SD rat splenocytes were remarkably reduced by more than 500 times at 2 week PI and restored to normal level at 7 week PI.

Evidence That the Factor Used by the Tapeworm, Hymenolepis diminuta, to Direct the Foraging of Its Intermediate Host, Tribolium confusum, Is a Volatile Attractant

We have previously demonstrated that flour beetles, Tribolium confusum, are more attracted to the feces from rats with patent Hymenolepis diminuta infections than to feces from uninfected rats. The objective of this study was to determine if this effect is due to a volatile attractant. Volatile substances emitted by feces from H. diminuta-infected rats or from uninfected controls were collected by aspirating fresh rat feces, while trapping the volatiles on Porapak Q (a solid adsorbant). The volatiles were eluted from the Porapak Q with diethyl ether, and the relative attractancy of the volatiles to prestarved beetles was assessed by bioassay. More beetles were attracted to volatiles of feces from infected rats than to volatiles of feces from uninfected controls (P< or =0.0001). The magnitude of the response varied with the time in the bioassay test arena and also the concentration of the volatiles (P< or =0.0232). When the volatiles we re concentrated by aspirating more boli over a longer period of time, the beetles responded more quickly and in greater numbers to the volatiles of feces from infected rats. The experiments presented here provide the first indication that a tapeworm (H. diminuta) can enhance its chances of transmission by directing the foraging of its intermediate host (T. confusum) through the use of attractive, volatile material released from the feces of its definitive host.

Characterizations of Pneumocystis carinii and rat lung lipids: glyceryl ethers and fatty alcohols

Pneumocystis carinii carinii and rat lung phospholipids contained 3–6% 1-alkyl-2-acyl glycerols composed of the glyceryl ether species, 1-O-octadecyl glycerol (batyl alcohol), 1-O-octadec-9-enyl glycerol (selachyl alcohol), 1-O-hexadecyl glycerol (chimyl alcohol), and 1-O-hexadec-9-enyl glycerol. Of the major phospholipid classes, phosphatidylinositol (PI) and phosphatidylserine contained the highest percentage of alkyl acyl glycerols. Methylprednisolone treatment caused an increase in alkyl acyl PI of rat lung lipids from 12% to 45%. As the PI concentration in lung phospholipids increases in rats treated with methylprednisolone, the increase in alkyl acyl PI was substantial; the proportions of alkyl acyl phosphatidylethanolamine and alkyl acyl lyso phosphatidylcholine (PC) also increased. Pneumocystis phospholipids contained higher proportions of alkyl acyl PC than the phospholipids of the lungs from normal and immunosuppressed uninfected rats. The glyceryl ether compositions of P. carinii carinii PC and lyso PC were similar, which suggests that lyso PC in the organism is derived by phospholipase A2 action on PC. This was not the case for PC and lyso PC of the lung controls. Analysis of the free fatty alcohols, precursors of glyceryl ethers identified only saturated species in P. carinii carinii and rat lung controls. Thus, the introduction of a double bond in the alcohol moiety of glyceryl ethers occurs after formation of the ether linkage between fatty alcohol and the glyceryl backbone.—Kaneshiro, E. S., Z. Guo, D. Sul, K. A. Kallam, K. Jayasimhulu, and D. H. Beach. Characterization of Pneumocystis carinii and rat lung lipids: glyceryl ethers and fatty alcohols. J. Lipid. Res. 1998. 39: 1907–1917.

OXYBUTYNIN DECREASES RENAL PELVIC PRESSURES IN NORMAL AND INFECTED RAT URINARY TRACT

Since abnormally elevated renal pelvic pressures may contribute to renal damage, we examined whether an anticholinergic agent could decrease elevated renal pelvic pressures. We have previously demonstrated in a rat model that renal pelvic pressures rise physiologically during normal bladder filling and high urinary flows; these pressures rise to abnormal levels during acute urinary tract infection (UTI). In these studies we investigated the effects of oxybutynin on the in vivo rat urinary tract. Simultaneous bladder and renal pelvic pressures were measured with and without oxybutynin at low (<2 ml./kg./hr.), moderate (2-10), high (10-20), and very high (>20) urinary flows while the rat bladder filled and emptied spontaneously. Although minimal differences were found between bladder filling pressures with and without oxybutynin, at higher urinary flows the renal pelvic pressure in oxybutynin treated rats was significantly lower than in nontreated animals. Indeed, when rats with urinary tract infection were treated with oxybutynin, their renal pelvic pressures were lower than those in uninfected rats. We conclude that oxybutynin affects rat upper urinary collecting system pressures, and is capable of decreasing abnormally elevated renal pelvic pressures due to urinary tract infection to normal or subnormal levels.

Oxybutynin decreases renal pelvic pressures in normal and infected rat urinary tract.

Since abnormally elevated renal pelvic pressures may contribute to renal damage, we examined whether an anticholinergic agent could decrease elevated renal pelvic pressures. We have previously demonstrated in a rat model that renal pelvic pressures rise physiologically during normal bladder filling and high urinary flows; these pressures rise to abnormal levels during acute urinary tract infection (UTI). In these studies we investigated the effects of oxybutynin on the in vivo rat urinary tract. Simultaneous bladder and renal pelvic pressures were measured with and without oxybutynin at low (<2 ml./kg./hr.), moderate (2-10), high (10-20), and very high (>20) urinary flows while the rat bladder filled and emptied spontaneously. Although minimal differences were found between bladder filling pressures with and without oxybutynin, at higher urinary flows the renal pelvic pressure in oxybutynin treated rats was significantly lower than in nontreated animals. Indeed, when rats with urinary tract infection were treated with oxybutynin, their renal pelvic pressures were lower than those in uninfected rats. We conclude that oxybutynin affects rat upper urinary collecting system pressures, and is capable of decreasing abnormally elevated renal pelvic pressures due to urinary tract infection to normal or subnormal levels.

Suppression of proliferative cholangitis in a rat model with direct adenovirus-mediated retinoblastoma gene transfer to the biliary tract.

Proliferative cholangitis (PC) associated with hepatolithiasis develops the stricture of main bile ducts, and is the main cause of residual and/or recurrent stones after repeated treatments for hepatolithiasis. The aim of this study was to inhibit PC using the cytostatic gene therapy with direct adenovirus-mediated retinoblastoma (Rb) gene transfer to the biliary tract. PC was induced by introducing a fine nylon thread into the bile duct in a rat model. The adenovirus vector encoding a nonphosphorylatable, constitutively active form of retinoblastoma gene product (AdRb) was administered directly into the biliary tract. The adenovirus vector encoding beta-galactosidase (AdlacZ) was also given as a control. The bile duct wall thickness and 5'-bromodeoxyuridine (BrdU) labeling index were compared among uninfected, AdlacZ-infected, and AdRb-infected PC rats. The Rb expression in the bile duct was detected using reverse-transcription polymerase chain reaction (RT-PCR) and immunohistochemical study. AdRb-infected bile ducts showed inhibition of the epithelial and fibrous tissue proliferation and the peribiliary gland hyperplasia, resulting in a significant reduction of wall thickness compared with uninfected and AdlacZ-infected ones. The BrdU labeling index was 4.87% +/- 3.06% in the AdRb-infected bile ducts, while those of uninfected and AdlacZ-infected ones were 15.48% +/- 4.61% and 11.72% +/- 1.23%, respectively (P < .05). In conclusion, our cytostatic gene therapy approach using direct Rb gene transfer into the biliary tract suppressed PC in a rat model and may offer an effective therapeutic option for reducing recurrences following treatments against hepatolithiasis.

Activity of flour beetles (Tribolium confusum) in the presence of feces from rats infected with rat tapeworm (Hymenolepis diminuta)

We studied the attraction of flour beetles (Tribolium confusum) to feces from rats infected with the rat tapeworm, Hymenolepis diminuta. Beetles were either fed or fasted prior to each trial. During trials, beetles were tested singly or in groups and offered a choice (i) between natural baits made from fecal pellets from infected and uninfected rats or (ii) between artificial baits made from feces of uninfected rats and differing only in the presence or absence of tapeworm tissue. Fasted beetles had a strong nonspecific attraction to baits, while fed beetles tended to avoid baits. Fasted beetles also exhibited a greater ability to discriminate between control and infective baits, sometimes preferring infective baits but at other times avoiding them. Experiments with artificial baits show that at least some of the signals which beetles respond to are of parasite origin. The results suggest that the foraging behavior of beetles in the presence of rat feces is more complex than previously thought and includes the phenomena of attraction to and avoidance of feces from infected rats in situations whose parameters have yet to be identified conclusively.

Hymenolepis diminuta Fractions but Not Previous Tapeworm Infection Stimulate Intestinal Myoelectric Alterations In vivo in the Rat

Infection of rats with the enteric, lumen-dwelling tapeworm Hymenolepis diminuta causes electric changes in host intestinal smooth muscle and decreased luminal transit. The mechanisms that stimulate host intestinal alterations during this nontissue invasive infection may include the tapeworm's biomass, its diurnal migratory behavior, a host immune-mediated response, or direct parasite stimulation of host motor activity. In vivo intestinal myoelectric activity was monitored to evaluate the following: (1) that reinfection with H. diminuta is influenced by host immune regulation and (2) that administration of tapeworm fractions to never-before-infected rats initiates an alteration of enteric smooth muscle activity. To address the first hypothesis, we determined that altered intestinal myoelectric activity patterns were no different and did not occur earlier in a second infection with H. diminuta than in a primary infection. The lack of either a change in myoelectric pattern or an earlier onset of intestinal myoelectric changes indicates that tapeworm-induced myoelectric activity is not anamnestically stimulated by host immunomodulatory mechanisms. Consistent with the second hypothesis, administration of either H. diminuta carcass homogenate or tegument-enriched fractions directly into the intestinal lumen of tapeworm-naive rats initiated myoelectric patterns previously characteristic of chronic H. diminuta infection. Additionally, the appearance of characteristic nonmigrating myoelectric patterns in uninfected rats administered tapeworm fractions indicates that a substance from H. diminuta acts as the triggering signal molecule for intestinal myoelectric alterations. These findings also indicate that neither the tapeworm's biomass nor its diurnal movement is required for initiation of H. diminuta-altered myoelectric patterns. We have shown that H. diminuta possess a signal molecule(s) that alters host enteric electric activity, and we suggest that these alterations may play an important role in the symbiotic rat-tapeworm interrelationship.

The spatial and temporal concentrations of choline in the lumen contents of the small intestine of uninfected and Hymenolepis diminuta infected rats

The spatial and temporal concentrations of free choline in the lumen of the small intestine of the uninfected and Hymenolepis diminuta-infected rat were investigated. In the unfed infected or uninfected rat, the choline concentrations ranged from ∼500 μM in the duodenum to ∼20 μM in the posterior ileum, with some segments in infected rats containing significantly higher choline levels than in uninfected rats. Following feeding, choline levels were significantly elevated to approximately 3 mM by 6 h, although these concentrations fell rapidly in transit down the intestine. By 12 h the choline levels were similar to those in the unfed rat. An initial small shift in the worm biomass toward the duodenum after feeding was followed by a redistribution of biomass along the length of the small intestine. The worm biomass, however, had little or no effect on the choline levels. The high concentrations of free choline observed in the anterior regions of the intestine are postulated to be predominantly determined by nutritional intake while the concentrations in the posterior region may in part be determined by blood choline levels. The high levels of choline indicate that choline is not limiting to support growth of the worms.

Hymenolepis diminuta:Mucosal Mastocytosis and Intestinal Smooth Muscle Hypertrophy Occur in Tapeworm-Infected Rats

Dwinell, M. B., Wise, R. M., Bass, P., and Oaks, J. A. 1998.Hymenolepis diminuta:Mucosal mastocytosis and intestinal smooth muscle hypertrophy occur in tapeworm-infected rats.Experimental Parasitology89,92–102. The mechanisms mediating motility changes during noninvasive tapeworm infection have not been characterized. In contrast, host intestinal motility changes during invasive nematode infection are mediated by mucosal mast cells (MMC). The purpose of this study was to examine and the correlate onset of myoelectric alterations 8 days after initial tapeworm infection with changes in intestinal morphology, MMC numbers, and MMC secretory activity. Segments of the small intestine, the tapeworms normal habitat, along with stomach, colon, and bladder were taken from tapeworm-infected and control rats. Tissues were fixed and stained to identify MMC and for morphologic measurement. Tapeworm-infected and uninfected rats with chronically implanted intestinal electrodes were treated with ketotifen, a mast cell stabilizer, andin vivomyoelectric activity monitored. In tapeworm-infected rats, the muscularis externa, on day 20 postinfection, and crypts of Lieberkuhn, on day 26 postinfection, from the entire small intestine appeared thickened or deeper, respectively. Increased muscularis thickness was due to smooth muscle hypertrophy in both the circular and the longitudinal muscle layers. Mucosal mastocytosis was first observed on day 26 postinfection and occurred only in the ileum of tapeworm-infected rats. Pharmacologic stabilization of mast cells with ketotifen did not prevent onset of enteric myoelectric alterations during tapeworm infection. Stomach, colon, and bladder MMC numbers and tissue dimensions were not different betweenHymenolepis diminuta-infected rats and uninfected controls. Initiation of myoelectric alterations 8 days after infection precedes and may be a contributing factor to the onset of both smooth muscle hypertrophy and mucosal mastocytosis. Taken together, our data indicate that mast cells are not an initiating factor nor chronic stimulus maintaining intestinal myoelectric alterations duringH. diminutainfection.

Suppression of Rat Bone Marrow Cells by Friend Murine Leukemia Virus Envelope Proteins

In a retroviral rat model, we have investigated the nontransforming effects of murine leukemia virus FB29 on the bone marrow. Upon intraperitoneal inoculation with murine leukemia virus FB29 of either neonatal or adult rats, bone marrow cells became massively infected within the first 12 days postinoculation. In neonatally inoculated rats, a persistent productive bone marrow infection was established, whereas in rats inoculated as adults, no infected bone marrow cells could be detected beyond 12 days postinoculation. Retroviral infection was most likely cleared by an antiviral immune response (Heinet al.,1995,Virology211, 408–417). Exposure to virus irreversibly decreased numbers of bone marrow cells staining with monoclonal antibody OX7 by 10–30%. Reduction of OX7+bone marrow cells by 20% was also observedin vitro,after bone marrow cells from uninfected adult rats had been co-incubated with virus. FB29-envelope proteins were sufficient alone to reduce numbers of OX7+bone marrow cells, bothin vivoandin vitro.According to results on incorporation of propidium iodide, decreased numbers of OX7+cells were due to cell death. By flow cytometric analyses OX7+bone marrow cells as well as monocytes/macrophages were identified to be major target cells for infection with FB29 within the bone marrow. Thus, the mechanism(s) responsible for death of OX7+bone marrow cells might be due to direct toxicity of viral envelope proteins and/or to interactions of viral envelope proteins with cells of the monocytic lineage.

Urine-associated horizontal transmission of Seoul virus among rats.

To understand the mode of transmission of Seoul type hantavirus in Wistar rats, we examined the shedding of the virus and antibody production in infected rats. When 1-day-old rats were inoculated with KI-83-262 strain of Seoul virus, the S segment of the viral genome was detected in lungs, clots, urine, saliva, submaxillary glands, rectums, and kidneys by nested reverse transcriptase PCR. On the other hand, when 8-week-old rats were infected with the virus, viral genome was detected only in the lungs and rectum. In uninfected newborn rats intranasally administered urine from infected newborn rats, four of six rats shed the virus into their urine. In addition, three of eight rats kept in same cage with infected animals also shed the virus into urine. Moreover, the virus genome was detected in the urine of urban rats (Rattus norvegicus) in an enzootic focus. These findings suggest that the urine containing virus from infected rats is an actual source of Seoul virus infection.

Fasting hyperglycaemia and impaired oral glucose tolerance in acute Trypanosoma brucei infection of rats

Trypanosoma brucei (Federe strain) produced all acute infection in rats given 10(6) parasites intraperitoneally. Parasitaemia, which first appeared at 2 days post-infection (pi), was heavy from day 5 until death at 8 to 12 days pi. The fasting tail-blood glucose (FBG) concentrations in the infected rats increased significantly (P<0.05) from 2.73+/-0.14 mmol/l on day 0 pi to 6.21+/-0.16 mmol/l and 5.93+/-0.33 mmol/l on days 5 and 8, respectively. However, the values had decreased in most of the rats on day 11 pi, at which time 4 out of 12 had less than 0.5 mmol/l. The mean FBG showed a quadratic relationship with the duration of infection and the fitted curve had a high goodness of fit (r2=0.98). Oral glucose tolerance was impaired in the infected rats on days 5, 8 and 11 pi. Tail-blood glucose concentration was determined 2 h after the intake of glucose (1.0 g/kg). The mean percentage increases in blood glucose from the FBG concentrations were significantly (P<0.05) higher in the infected than in uninfected rats. There was a positive correlation (r=1.0) between the mean percentage increases and the duration of infection. It seems probable, therefore, that the delivery of glucose into the tissues was reduced, with other metabolic implications likely to affect the pathogenesis of the disease.

A Rat Model of Chronic Helicobacter pylori Infection: Studies of Epithelial Cell Turnover and Gastric Ulcer Healing

Background: Our aim was to infect rats with Helicobacter pylori and to study the effects of the infection on the gastric mucosa in normal and in ulcer-operated rats. Methods: A mouse-adapted H. pylori (cagA-, VacA-) strain was inoculated into 23 rats. Another 20 uninfected rats served as controls. Two months later a gastric ulcer was induced in some rats. The animals were killed 3, 6, or 15 days after the ulcer operation. Tissues were taken for histology and for culture of H. pylori. Serum antibodies were determined. Results: All inoculated rats were infected by H. pylori after 2 months, mainly in the antrum. In these rats a mild to moderate chronic inflammation and a significantly increased frequency of apoptotic cells were observed in the antrum and in the ulcer margin, the ulcer healing was delayed, and the serum level of H. pylori-specific Ig was increased. Conclusions: H. pylori infection in rats was successful and was accompanied by a mild to moderate mucosal inflammation. Gastric ulcer healing was delayed in infected rats, probably due to the inflammation and the increased apoptosis in epithelium.