Altered immunoglobulin isotype profile and anti-immature worm surface immunoglobulins in mice harboring a praziquantel-resistant Schistosoma mansoni isolate

After placement in mice of PZQ-sensitive and -insensitive S. mansoni isolates obtained from villagers responding and not responding to PZQ, parasitological criteria reflecting their biological development and also the host anti-immature worm immunoglobulin isotypes were examined 8 and 10 weeks post infection. Hepatic granuloma diameter, hepatic histopathological changes and immunolocalization of IgG and IgM on the surface of PZQ-sensitive and -resistant worms were also examined 10 weeks post infection. Data showed that parasitological criteria were not significantly different between mice infected with the PZQ-sensitive and -insensitive S. mansoni isolates. As regards serum immunoglobulins, in mice infected with the PZQ-insensitive S. mansoni isolate, IgG and IgG1 were significantly (p<0.05) lower 8 and 10 weeks post infection, respectively (1.41+/-0.07 and 1.08+/-0.10 and 1.35+/-0.06 and 1.09+/-0.07) than in mice infected with the PZQ-sensitive S. mansoni isolate (1.73+/-0.15 and 1.38+/-0.10 and 1.73+/-0.17 and 1.54+0.21) after the same observation periods. IgM level was nearly the same while IgE was lower than that recorded in mice infected with the PZQ-sensitive S. mansoni isolate. IgG immunofluorescence was also lower (60%+/-6.78) on the surface of resistant worms than that of sensitive worms (66.6%+/-5.27); meanwhile, hepatic granuloma diameter was significantly larger (296.5+/-3.0 vs 283.6+/-4.0) in mice infected with the PZQ-insensitive S. mansoni isolate with higher percentage of intact eggs. Differences in the immunogenic make up of PZQ-sensitive and -insensitive S. mansoni isolates qualitatively and/or quantitatively favoring a certain Th cell subpopulation response could be the underlying reason for such differences recorded in the host immunoglobulin isotype response and also the egg-induced hepatic histopathological changes.     

Comparative studies on animal models for <Emphasis Type="Italic">Opisthorchis viverrini</Emphasis> infection: host interaction through susceptibility and pathology

Syrian hamsters and gerbils are animal models for Opisthorchis viverrini infection. In both models, the parasites develop into adults with different pathologies of the hepatobiliary system. However, no comparative pathological studies have yet been completed. We therefore investigated host interaction through the susceptibility and pathological changes of Syrian hamsters and gerbils infected with 50 O. viverrini metacercariae for 30, 60, and 90 days post-infection. Animals were sacrificed at each time point for comparative study. Susceptibility and infectivity were investigated through worm burden. Parasite morphology and reproductive organs were stained with carmine and observed under light microscopy. Reproductive organs and eggs per worm were counted to confirm worm maturity. Bile acid components of both animal groups were analyzed by thin-layer chromatography. The results showed that infection in gerbils was of greater severity than in Syrian hamsters by observation of bile obstruction, enlargement of the gallbladder and common bile duct, and generation of fibrosis and cirrhosis. The worm burden of infected gerbils was lower than that observed in Syrian hamsters. Infectivity in both Syrian hamsters and gerbils was 100% with infection by 50 metacercariae; whereas with 10 metacercariae, the infectivity in gerbils was zero to very low, but still 100% in Syrian hamsters. The largest body size of worms, and the largest ovary and testes areas, was correlated with eggs per gram of feces and eggs per worm. The bile acid components cholic acid and chenodeoxycholic acid were undetectable in gerbils. The present study suggests that although Syrian hamsters, usually the host selection for an animal model, are susceptible to O. viverrini infection, infected gerbils produce worms that mature more rapidly, have larger body sizes, and more fully developed reproductive organs; this may be caused by the difference in bile acid components.     

The effect of BCG-vaccine upon experimental visceral leishmaniasis in hamsters

Stimulation with Bacillus Calmette-Guerin (BCG) vaccine has been reported to enhance resistance of mice against Leishmania donovani infection. Such infection is usually lethal in hamsters, thus providing a more stringent animal model to assess the effect of BCG upon visceral leishmaniasis. Animals receive two IP injections (2-8 X 10(7) BCG) pre or post IC challenge with 4 X 10(6) amastigotes. Controls received BCG alone (with no infection) or were untreated (NT). Pretreated animals exhibited significantly fewer (P less than 0.05) hepatic or splenic amastigotes than NT animals at days 7, 14, and 28 post challenge, but most BCG treated hamsters died earlier than NT. Post treated hamsters showed no significant reduction in parasite burdens, or in median time to death as compared to NT group. Hamsters which received BCG but were not infected appeared healthy during the study. The reason for increased susceptibility of BCG-treated hamsters to disease is not clear, but observed pathologic complications of L. donovani infected hamsters appear to be exacerbated by BCG stimulation.     

Extrinsic incubation periods for horizontal and vertical transmission of West Nile virus by Culex pipiens pipiens (Diptera: Culicidae)

Culex pipiens pipiens L. (Diptera: Culicidae), infected per os from a membrane feeder, transmitted West Nile virus (family Flaviviridae, genus Flavivirus, WNV) at 26 degrees C horizontally during feeding to hamsters and suckling mice and vertically to F1 progeny during egg deposition. Horizontal transmission rates increased with extrinsic incubation, with 75-100% of the females transmitting on days 16 through 25 postinfection (pi). No females deposited eggs infected with WNV after the first bloodmeal on 3-8 d pi. Females vertically transmitted WNV during egg laying after their second, third, and fourth bloodmeals on days 13-33 pi. The vertical transmission rate was 4.7%. The vertical minimal infection rate was 0.52 infected F1 specimens/1,000 specimens tested from females feeding during their second and later bloodmeals on hamsters or suckling mice. The sequence of horizontal and vertical transmission is reported. A female may transmit WNV 1) horizontally to a host during feeding and subsequently vertically to her offspring during egg laying, 2) vertically to her offspring during oviposition without prior horizontal transmission to a host, and 3) horizontally to a host without vertically transmitting the virus. These two means of transmission by Cx. p. pipiens contribute to the relatively high minimum infection rates that are reached in late summer and to the survival of virus during winter and initiation of amplification in the spring in the northeastern United States.     

Spectrum and age-related incidence of spontaneous tumours in a colony of Han:AURA hamsters.

One-hundred-and-forty-four male and 184 female untreated Syrian golden hamsters (strain Han:AURA) were kept for life under standard laboratory conditions. They were examined with regard to spontaneously occurring tumours in relation to their survival periods. The mean survival rate of the males was 106 +/- 26 weeks and that of the females 97 +/- 20 weeks. Tumours were found in 71% of males and 67% of females. Adenomas and carcinomas of the adrenal glands were the most frequently observed tumours in both sexes (male: 66%; female: 38%) and in the early stages of life. Malignant lymphoma (8%), adenomas and carcinomas of pancreatic islet-cells (8%) and papillomatous benign and malignant squamous cell tumours of the forestomach (7%) showed relatively high incidences in males, whilst in females, leiomyoma (10%) and endometrial adenocarcinoma (7%) of the uterus and adenomas and carcinomas in the pars distalis of the pituitary gland (9%) occurred frequently.     

The suppression of rejection of Nippostrongylus brasiliensis in lactating rats: the nature of the immunological defect

Lactating female rats infected with 3000 third-stage larvae of Nippostrongylus brasiliensis showed significant increases in worm fecundity and total worm burdens when compared with infected nulliparous controls. Statistically significant differences were recorded for each of the three periods of infection, although these differences were of greatest magnitude during Period 3 (16–30 days of infection).

Immune mesenteric lymph node cells (100 × 10⁶), obtained from nulliparous female donors on Day 15 of a primary infection, were transferred syngeneically to lactating female recipients. The transferred cells invariably caused suppression of worm fecundity, reduction in the number of eggs per uterus in gravid female worms and rejection of a substantial proportion of worms by Day 10 of a challenge infection in the lactating recipients. The results of this study showed that immune cells were functional in lactating female recipients and that transfer of immune cells repaired the deficit in the rejection mechanism.

Mesenteric lymph node cells (100 × 10⁶), obtained from lactating female donors on Day 15 of a primary infection, were transferred syngeneically to nulliparous female recipients. The transferred cells caused suppression of worm fecundity, reduction in the number of eggs per uterus in gravid female worms and rejection of the majority of parasites by Day 10 of a challenge infection in the nulliparous recipients. Clearly, potentially immune lymphoid cells were present in the mesenteric nodes of lactating females at the time that the rejection mechanism was severely impaired.

Mesenteric lymph node cells obtained from infected lactating donors were substantially less effective in lactating recipients than in nulliparous recipients. These cells caused the expulsion of 51 per cent of worms by Day 10 in lactating recipients, whereas they caused expulsion of 99 per cent of worms in nulliparous recipients.

These observations suggest that the inductive processes of the immune response occur normally, but that differentiation of induced cells to effector cells is impaired in lactating animals.

     

Effects of sex and age on the susceptibility of C57BL/6J mice to infection with <Emphasis Type="Italic">Brachylaima cribbi</Emphasis> and the course of infection in NOD SCID mice

The C57BL/6J strain of Mus musculus is susceptible to the terrestrial trematode Brachylaima cribbi. The duration of infection in these mice is generally 9-12 weeks with a peak excretion of eggs at 4 weeks post-infection (wpi). The effects of age and sex on the course of infection were investigated by comparing infections in male and female mice aged 8 or 28 weeks at the time of infection. There were no significant differences in the susceptibility of the adolescent mice of either sex or older male mice. However, older, mature female mice were significantly more resistant to B. cribbi infection than older mature males and adolescent females with reduced worm burden, fecundity and egg fertility. In comparison with young males, all three parameters were again reduced but this was only significant statistically for reduced egg fertility. It is likely that mature female sex hormones influence resistance to B. cribbi infection. The susceptibility of immunodeficient NOD SCID mice was evaluated and compared with C57BL/6J mice. NOD SCID mice were susceptible to B. cribbi infection with the infection persisting with a relatively unchanged worm burden for the life of the mouse with the longest surviving mice being 31 wpi. The life-span of B. cribbi is therefore at least 31 weeks. There were no significant differences in egg excretion, worm burden or fecundity among NOD SCID mice at 4, 8 or 18 wpi. As the infection progressed in NOD SCID mice, the location of worms in the small intestine moved from the anterior third in the early stages of the infection to the mid- to posterior intestine in the later stages. Comparison of the infection in NOD SCID mice with C57BL/6J mice indicates that the expulsion of worms in the latter is mediated by an immune response.     

Western equine encephalomyelitis virus infection affects the life table characteristics of Culex tarsalis (Diptera: Culicidae)

The life table attributes of Culex tarsalis Coquillett females infected experimentally by feeding on 4 and 6 log10 plaque-forming units (PFU) of western equine encephalomyelitis virus (WEEV) per milliliter of heparinized chicken blood were compared with an uninfected control group. Females continually were offered 10% sucrose and an oviposition substrate and daily a blood meal through a biomembrane feeder. Mortality (dead females) and fecundity (female eggs per female) were monitored daily until all females died. Overall, 94% of 198 females in the two virus-infected groups were positive for WEEV at death when tested by plaque assay; the average body virus titer at death did not differ between groups. WEEV infection significantly altered the life table characteristics of Cx. tarsalis. Life expectancy at infection in days (ex), reproductive effort in female eggs per female per generation (Ro), and generation time (T) in days for the infected cohorts were significantly lower than for the uninfected controls, whereas the reproductive rate (rc) in female eggs per female per day was higher for infected than uninfected cohorts. In agreement with the WEEV infection data that showed similar body titers, there were few differences between the life table parameters for the 4 and 6 log10 PFU treatment groups. Greatest differences were observed for survivorship between days 17-40 when virus titers in infected dying females were greatest. Our data extend recent studies that indicate mosquito infection with encephalitis viruses has a cost of reduced life expectancy and fitness.     

An RNA Viral Infection of Hamster Testes and Uteri Resulting in Orchitis and Effects on Fertility and Reproduction

A pantropic, attenuated RNA virus [TC83 strain of Venezuelan encephalitis (VE) virus] grew in hamster testes after intratesticular inoculation. Virus did not grow in testes after subcutaneous injection nor in uninoculated testes after unilateral testicular injection. Although viremia disappeared within 6 days when virus-neutralizing antibodies appeared in serum, viral growth in testes continued for 2-3 weeks after intratesticular inoculation. Virus also persisted for 12 days in testes of hamsters immunized 4 weeks previous to intratesticular inoculation. Thus, there seemed to be a barrier between germinal epithelium and blood to early virus-neutralizing antibodies which developed within 2-4 weeks of infection. Cytonecrosis, inflammation, depression in the number of germinal cells, atrophy, fibrosis and eventual sterility occurred with viral growth in testes of normal hamsters, but no histopathology other than atrophy and aspermia was seen in epididymides. Similar changes occurred in testes of some previously immunized hamsters. Virus antigen was found in diploid, but not haploid germinal cells, and virus (either attenuated or virulent VE) did not adsorb to or grow in sperm maintained in vitro. Males with infected testes and virus in the epididymis remained fertile for about 2 weeks after inoculation. Virus was only occasionally transferred to the uterus-vagina of normal females by copulation with males with infected testes, and only rarely did such females become infected. Usually, pregnancy developed and progressed normally, and no convincing transfer of virus to progeny occurred. In normal female hamsters inoculated intrauterinely or subcutaneously, virus did not reach higher concentrations in uteri than in blood, virus disappeared concurrently in both and no histopathology developed in uteri. However, infection of females by intrauterine inoculation of attenuated VE virus 2 hours before mating prevented pregnancy whereas intrauterine inoculation of saline or an adenovirus did not.     

Effect of stevioside on growth and reproduction

The effect on growth and reproduction in hamsters of stevioside, which is extracted from stevia leaves (Stevia rebaudiana Bertoni) and is currently used as a non-caloric sweetener, was investigated. Four groups of 20 one-month-old hamsters (10 males and 10 females) were daily force-fed with stevioside (0.0, 0.5, 1.0 and 2.5 g/kg body wt/day, respectively). No abnormalities were found in growth and fertility in both sexes. All males mated females efficiently and successfully. Females showed normal 4-day oestrus cycles and became pregnant after mating. Each female was mated and allowed to bear three litters during the period of experiment. The duration of pregnancy, number of fetuses, as well as number of young delivered each time from females in the experimental groups were not significantly different from those in the control group. The young F1 and F2 hamsters continuously receiving stevioside via drinking water until one month old and daily force-fed afterwards at the same doses as their parents showed normal growth and fertility. Histological examinations of reproductive tissues from all three generations revealed no evidence of abnormality which could be linked to the effects of consuming stevioside. We conclude that stevioside at a dose as high as 2.5 g/kg body wt/day affects neither growth nor reproduction in hamsters.     

Effectiveness of synthetic trioxolane OZ78 against Schistosoma japonicum in mice and rabbits

Antischistosomal activities of a synthetic peroxide OZ78 (an ozonide carboxylic acid) against Schistosoma japonicum have been studied in mice and rabbits. Among 132 mice used, 30 of them were infected with 80-100 S. japonicum cercariae for collection of juvenile and adult schistosomes applied in in vitro tests. The remaining 102 mice were infected with 40 schistosome cercariae used for experimental treatment. Other 13 rabbits infected each with 200 schistosome cercariae were treated orally with OZ78 42 days post-infection. Most treated mice and rabbits were sacrificed 4 weeks post-treatment to collect residual schistosomes for evaluation of the drug efficacy. OZ78 and its sodium salt (OZ78-Na salt) 10-60 μg/mL alone exhibited no in vitro effect against day 14, day 21 schistosomula, and day 35 adult schistosomes. But OZ78 and OZ78-Na salt 10 and 20 μg/mL together with hemin 80 μg/mL showed decrease in worm motor activity and severe damage to the worm tegument and intestine, and all worms died within 3 days post-incubation. After infected mice were treated orally with OZ78 at a single dose of 400 mg/kg for 1 day, 34.9% of the worms shifted to the liver. Three and 7 days post-treatment, 100% of the worms were recovered from the liver. Fourteen days post-treatment, 92.3% of the worms still remained in the liver and 7.7% of the worms returned back to the mesenteric veins. Male and female worms shifted to the liver revealed in apparent shrinkage, degeneration of worm body, depigmentation in gut, and disappearance of ova in the uterus of some female worms. Meanwhile, dead worm and dead worm fragments were found in the liver tissues. In mice infected with various stages of schistosomes and treated orally with single OZ78 400 mg/kg, moderate or potential effect of the drug against day 0 (3-h-old worm), day 7, day 14, and day 21 juvenile worms and day 28, day 35 as well as day 42 adult worms were observed, the differences of total or female worm burdens between each treated group and control group were statistically significant (P?相似文献   

Schistosoma japonicum-infected hamsters (Mesocricetus auratus) used as a model in experimental chemotherapy with praziquantel, artemether, and OZ compounds

The purpose of the study is to better understand the antischistosomal properties of artemether, praziquantel, and ozonide (OZ) compounds (synthetic trioxolanes, secondary ozonides) in hamster (Mesocricetus auratus) model. A total of 230 male hamsters infected each with 100 Schistosoma japonicum cercariae were used in the study. Groups of five to ten hamsters were treated orally with artemether, praziquantel, and OZ78 or OZ277 7-35 days post-infection at single doses of 50, 100, 150, or 200 mg/kg. Untreated but infected hamsters in each batch of test served as the control. All treated hamsters were sacrificed 4 weeks post-treatment for collection of residual worms using perfusion technique. Nonparametric method (Mann-Whitney test) was used to analyze the data. In groups of five hamsters treated with artemether 7, 14, 21, 28, and 35 days post-infection at single doses of 150 and 200 mg/kg, the difference of mean worm burden between each treated group and control group was statistically significant (P<0.01). Apart from individual group, no difference in mean worm burden between each two groups of them was seen (P>0.05). Further test with various single doses of 50-200 mg/kg confirmed the similar susceptibility of 7-day-old juvenile and 35-day-old adult schistosomes to artemether. After administration of praziquantel 100 mg/kg to groups of five hamsters 7, 21, and 35 days post-infection, higher worm burden reduction of 95.5% was seen in the group with 35-day-old adult schistosomes while in the groups with 7- and 21-day-old juvenile schistosomes, poor efficacy was seen with mean worm burden reductions of 36.6% and 35.6%. In the same batch of hamster treated with praziquantel 200 mg/kg, the moderate effect of the drug against 7- and 21-day-old worms was seen, but their mean worm burden was significantly higher than that of the group with adult schistosomes. In comparison of artemether and praziquantel against various stages of schistosomes, the results further demonstrated that artemether possessed similar effect against juvenile and adult schistosomes in hamsters, while praziquantel was more effective against adult schistosomes than the juvenile ones in the same host. Finally, after administration of OZ78 and OZ277 to the groups of four to six hamsters with 14- and 35-day-old schistosomes at a single dose of 200 mg/kg, promising effect against juvenile and adult schistosome was observed with the mean worm burden and female worm burden reductions of 69.6-94.2% and 64.2-100% as well as 73.3-80.7% and 68.3-81.1%, respectively. The results indicate that in hamster model, praziquantel exhibits higher effect against adult schistosomes than the juvenile ones, while artemether and OZ compound display similar effect against both juvenile and adult schistosomes.     

Cellular mechanisms involved in the increased contraction of portal veins from Schistosoma mansoni-infected mice

We previously reported that portal veins from mice infected with male Schistosoma mansoni exhibited an increased reactivity to 5-hydroxytryptamine (5-HT). Here, we extended our observations to mice infected by both male and female worms and we further investigated another constrictor agent and the mechanism(s) responsible for the enhanced maximal contraction ( E(max)). Bisexual infection increased the E(max) of 5-HT (from 0.66+/-0.06 mN.s to 1.56+/-0.38 mN.s), in a similar way to the unisexual (male) infection. Infection with male worms increased portal vein reactivity to acetylcholine, as revealed by a higher E(max) (1.03+/-0.2 mN.s) in relation to non-infected control animals ( E(max)= 0.54+/-0.08 mN.s). Sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase (SERCA) inhibition with 100 nM thapsigargin reduced the E(max) of 5-HT by 35% in both tissues, discharging a deficiency of SERCA pump in infected animals. In contrast, the number of voltage-dependent Ca(2+) channels (L-type) was higher in portal veins from infected than non-infected control mice. Inhibition of Ca(2+)-activated chloride channels (Cl(Ca)) with 10 micro M niflumic acid reduced the E(max) of 5-HT in portal veins more from infected than non-infected animals (remaining tension = 60.9+/-2.2% and 70.4+/-2.3%, respectively). Histopathological analysis revealed an increased content of collagen and elastin in portal veins from male S. mansoni-infected mice, compatible with an increased intraluminal pressure. In conclusion, male S. mansoni altered portal vein physiology, increasing the E(max) of two vasoconstrictors, possibly by increasing membrane depolarisation through a more effective opening of Cl(Ca) channels, with calcium entering through L-type Ca(2+) channels.     

Single- or mixed-sex Schistosoma japonicum infections of intermediate host snails in hilly areas of Anhui,China

Schistosomiasis japonicum is one of the most serious communicable diseases, and the transmission of the parasite is dependent of its complex life cycle on which many factors can have an impact. Multiple infections comprising both male and female schistosome within snail intermediate hosts, for example, would facilitate parasite transmission. However, no research on Schistosoma japonicum communities in field-collected Oncomelania hupensis hupensis in relation to schistosome sex has been reported. Therefore, snail survey was performed in a hilly region of Anhui, China, and single- or mixed-sex schistosome infections of snails were detected with final host mouse infection. A total of 8,563 snails were sampled in the field, and 67 were identified with schistosome infections. Of these infected snails, 46 were selected for final host infection. From this, 21 snails were infected with female schistosome, 23 with males and 2 with both males and females. More worms were recovered for snails with mixed-sex infections than with single-sex infection and for snails with male schistosome infection than with female infection (P?<?0.001). The observed frequency of mixed-sex infections of snails was significantly higher than would be expected if randomly distributed (P?<?0.01). The ratio male/female of schistosome infections in snails was nearly equal and up to 95.65 % (44/46) of infected snails were single-sex infection. Schistosome infections in snails collected from the hilly area of Anhui Province were not randomly distributed but over-dispersed.     

Morphometric dimensions of Syrian golden hamster pancreas of both sexes.

The morphometric dimensions of the various structures of the pancreas of adult Syrian golden hamsters, of both sexes, were evaluated using stereological methods. The average body mass of the animals used was 133.8 +/- 2.45 g and 140.6 +/- 7.98 g for the males and females, respectively, and the pancreatic mass, 389.9 +/- 14.88 and 409.7 +/- 21.42 mg, respectively. The analysis of variance of the obtained data showed that: a) the acini, intercalated ducts and stroma did not present statistically significant differences in any of the dimensions evaluated, with the exception of the nucleus volume of the acinar cells which was 8.5% larger in the female (P < 0.05); b) the excretory ducts exhibited surface density, total external surface, surface-to-volume ratio, and absolute cell number, 18%, 33%, 14%, and 44%, respectively, larger in the females (P < 0.05); and c) the pancreatic islets of the females exhibited volume density, total volume and absolute cell number, 20%, 27% and 27%, respectively, larger than those of the males (P < 0.05).     

Animal models for Opisthorchis viverrini infection

We investigated the utility of various animal models for the study of opisthorchiasis in humans and its common sequel of cholangiocarcinoma (CCA). Rats, mice, gerbils, and hamsters were infected with Opisthorchis viverrini metacercariae. Worms from the infected animal hosts were recovered from livers and counts made of eggs per gram of feces. Worms were observed in and recovered from hamsters and gerbils but not rats and mice. The recovered worms from the infected gerbils were larger and more physiologically developed than those from the infected hamsters. The results suggest that gerbils are more susceptible to infection by Opisthorchis viverrini and thus more suitable for modeling opisthorchiasis and its connection to CCA.     

Hypothalamic sites of progestin action on aggression and sexual behavior in female Syrian hamsters

The effects of intracranial implants of the synthetic progestin, promegestone (R5020), on aggression and sexual behavior were examined in female Syrian hamsters. Ovariectomized female hamsters showed high levels of aggression and no lordosis towards stimulus male and female hamsters, both prior to and after estradiol benzoate treatment. Forty-six hr after estradiol treatment (10 micrograms SC), 10% crystalline promegestone was applied bilaterally (27 ga cannulae) to the ventromedial hypothalamus. When tested 5-7 hr later, these animals had a significant reduction in the rate of attacks towards females, with no lordosis responding to a male. In contrast, promegestone in the caudal anterior hypothalamus activated low levels of lordosis, yet these females maintained high levels of aggression towards stimulus females. Females receiving promegestone in the rostral anterior hypothalamus, and control females receiving intracranial cholesterol, maintained high levels of aggression and no lordosis. Estradiol treatment alone enhanced pelvic movements in response to experimenter-applied perineal stimulation in a majority of females (18/22 compared with 4/22 prior to estradiol injection), with intracranial treatments having no further effect. These results indicate that progestins act on aggression and sexual behavior in female Syrian hamsters at different hypothalamic loci.     

Regulation of primary Strongyloides ratti infections in mice: a role for interleukin-5.

C57BL/6 mice genetically deficient in interleukin-5 (IL-5-/-) and normal C57BL/6 (IL-5+/+) mice were infected with larvae of a homogonic strain of the nematode Strongyloides ratti. In primary infections both male and female IL-5-/- mice released two to four times more eggs and larvae than IL-5+/+ mice. IL-5-/- mice harboured about 60% more intestinal worms, which were more fecund, than IL-5+/+ mice. The duration of the infection was similar in normal and IL-5-deficient mice. Both IL-5-/- and IL-5+/+ mice resisted a secondary infection. IL5-/- mice lost more weight during the infection than normal mice and took longer to regain their initial weight after expelling the worms. The number of eosinophils increased in the bone marrow, peritoneal cavity and small intestine of IL-5+/+ mice, but not IL-5-/- mice, following infection. No significant differences between infected IL-5+/+ and IL-5-/- mice in mast cells or other leucocytes were observed in the peritoneal cavity. Thus, IL-5 functions to protect the host in a primary infection of S. ratti by limiting the number and fecundity of worms establishing in the small intestine. This protection is correlated with elevated blood and tissue eosinophilia which occurs in normal mice but not in IL-5-/- mice.     

Characterization of Persistent Modoc Viral Infections in Syrian Hamsters

Adult Syrian hamsters were readily infected by intranasal inoculation with Modoc virus. Viremias were detected 2 to 6 days after infection and peak viremia titers (10^6.2 plaque-forming units/ml of blood) occurred 4 days postinoculation. All infected animals developed neutralizing and hemagglutination-inhibiting antibodies by 7 days, and complement-fixing antibodies by 14 days postinoculation. High titers of antibodies persisted for at least 4 months. Modoc virus was recovered from throat swabs at 7 days postinoculation, but not at 14 days or later. Urine samples were positive for virus throughout a 12-week observation period. Isolation of virus from lungs and kidneys of one and three animals, respectively, at 151 to 221 days after inoculation confirmed chronic infection. Viral isolations were made only when organs were cultivated in vitro and were unsuccessful by tests on 10% homogenates of the organs. Horizontal viral transmission of virus by infected hamsters that were viruric was demonstrated in only 1 of 27 normal hamsters that were cocaged for 4 weeks under crowded conditions. General failure to obtain horizontal viral transmission may relate to rapid inactivation of virus in excreted urine. Vertical viral transmission was not demonstrated from five chronically infected female hamsters to their 34 offspring. However, if primary infection occurred during pregnancy, the progeny were either stillborn or died shortly after birth, and thus appeared to represent transplacental viral transmission.     

Immunity toLitomosoides carinii inMastomys natalensis

NaiveMastomys natalensis, Litomosoides carinii-infectedM. natalensis at a postpatent stage of the infection andL. carinii-infectedM. natalensis treated chemotherapeutically with furazolidone (FUR), FUR and diethylcarbamazine (FUR/DEC) or amoscanate (AMOS) were challenged by either injection or implantation of 40 third stage larvae (L3, s.c.), 40 fourth stage larvae (L4, 16 days old, i.p.), 20 and 20 preadult worms (36 days old, i.p.), 12 adult worms (i.p.) or 6×10⁶ microfilariae/kg (i.v.).Microfilaraemia in animals challenged at a postpatent stage (independent of the kind of challenge), was either totally suppressed or at least greatly reduced. Necropsy of L3-challenged animals showed that neither the length of the worms nor their content of morphologically intact, intrauterine stages was affected.Infected, treated animals challenged with developing stages (L3, L4 and preadult worms) showed reduced levels of microfilaraemia (by up to 75%). Dissection of AMOS-treated, L3-challenged animals showed that both the developmental rate and the fertility of the worms were affected.Microfilaraemia was also reduced after implantation of adult worms into treated animals. This was independent of the interval between treatment and challenge (44–150 days) except in animals challenged 10 days after AMOS-treatment, which showed no difference from naive controls.However, infected, treatedM. natalensis, cotton rats and gerbils did not develop immunity against intravenously injected blood microfilariae.