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 approximately 500 microM in the duodenum to approximately 20 microM 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 the growth of the worms.     

Hymenolepis diminuta: effect on the oxidation-reduction potential in the mammalian gastrointestinal canal.

The oxidation-reduction potential (Eh) of the small intestine of uninfected and parasitized (ten 16-day-old Hymenolepis diminuta) rats has been determined under three different types of experimental conditions. On an ad lib. feeding regime at 10.00 hr there were highly significant (P < 0.001) differences between the intestinal Eh of uninfected and parasitized rats in every region of the small intestine. While the entire uninfected gut displayed relatively strong reducing tendencies (?28 to ?195 mV), in the parasitized gut the Eh was predominantly positive (+75 to ?76 mV) and reflected worm biomass distribution. Changes in intestinal Eh were also measured over a period of 6 hr after the feeding of a 1-g glucose meal. The Eh in uninfected animals increased from ?232 to +118 mV; in parasitized animals from ?31 to +189 mV. While the changes were greater in the former group, those of the latter reflected the changing worm biomass distribution. The most positive regional Eh value was always associated with the maximum % worm biomass distribution. Third, using surgical intestinal-loop preparations there were significantly (P < 0.05) higher positive Eh values in parasitized (+185 mV) than in uninfected (+128 mV) rats; in both animal groups the Eh of the duodenal-jejunal loops were more positive than that of the ileal loops (P < 0.05).The results are discussed in terms of the close inter-relationship between intestinal pH, Eh, the microflora and luminal pO₂ tensions.     

Effect of size of Trichinella spiralis (Nematode) infections on glucose and ion transport in the rat intestine

An in vivo perfusion technique, using 3 intestinal loops representing the anterior, mid and posterior regions of the rat small intestine, was used to determine intestinal glucose uptake 5 days after infection with Trichinella spiralis. At high levels of infection (3,000 and 6,000 larvae/rat) net glucose absorption by the intestinal mucosa was significantly impaired in all regions of the small intestine when compared to uninfected controls. At low levels of infection (50 larvae/rat) glucose uptake by the mucosa was significantly enhanced in all 3 regions of the small intestine. Intermediate levels of infections (200-1,000 larvae/rat) also enhanced glucose uptake, but only in the anterior regions of the small intestine. When washings from the small intestine of rats infected with 50 larvae/rat were added to the perfusion fluid used on uninfected rats, glucose uptake was also significantly enhanced. These results suggest that at low levels of infection the intestinal lumen contains a metabolite which may affect the mucosal transport of glucose and the related fluxes of H2O, Na+, Cl-, and K+, in the rat intestine. Luminal [H+] and pCO2 decreased from the proximal to distal regions of the small intestine following perfusion; pO2 was significantly decreased in the proximal and distal regions.     

Intestinal immunity suppresses carrying capacity of rats for the model tapeworm, Hymenolepis diminuta

Hymenolepis diminuta is a parasitic tapeworm of the rat small intestine and is recognized as a useful model for the analysis of cestode-host interactions. In this study, we analyzed factors affecting the biomass of the tapeworm through use of rat strains carrying genetic mutations, namely X-linked severe combined immunodeficiency (xscid; T, B and NK cells deficiency), nude (rnu; T cell deficiency), and mast cell deficient rats. The worm biomass of F344-xscid rats after infection with 5 cysticercoids was much larger than control F344 rats from 3 to 8?weeks. The biomass of F344-rnu rats was also larger than the controls, but was intermediate between F344-xscid and control rats. These observations demonstrated that host immunity can control the maximal tapeworm biomass, i.e., carrying capacity, of the rat small intestine. Both T cell and other immune cells (B and NK cells) have roles in determining the carrying capacity of tapeworms. Total worm biomass and worm numbers in mast cell deficient rats (WsRC-Ws/Ws) were not significantly different from control WsRC-+/+ rats after 3 and 6?weeks of primary infection. Mast cell deficient rats displayed reinfection resistance for worm biomass but not worm expulsion. These findings suggest that the mast cell has a role for controlling the biomass of this tapeworm in reinfection alone, but does not affect the rate of worm expulsion. Overall, our findings indicate that the mast cell is not a major effector cell for the control of the carrying capacity of tapeworms. The identity of the major effector cell remains unknown.     

Effects of fungal endophytes on the seed and seedling biology of Lolium perenne and Festuca arundinacea

Summary Many grasses are infected by endophytic fungi that grow intercellularly in leaves, stems, and flowers and are transmitted maternally by hyphal growth into ovules and seeds. The seed biology and seedling growth of endophyte-infected and uninfected perennial ryegrass (Lolium perenne) and tall fescue (Festuca arundinacea) were investigated under controlled environmental conditions. The percentage of filled seeds produced by infected tall fescue was over twice of uninfected tall fescue; infected and uninfected perennial reegrass had similar percentages. Weights of seeds from infected and uninfected plants were similar in both species. Seeds from infected plants of both species exhibited a higher rate of germination than seeds from uninfected plants. Shoot growth in the greenhouse was compared by making three sequential harvests of above-ground plant parts from infected and uninfected plants of both species. Infected perennial ryegrass plants produced significantly more biomass and tillers than uninfected plants after 6 and 10 weeks of growth and significantly more biomass after 14 weeks of growth. Infected tall fescue plants produced significantly more biomass and tillers than uninfected plants after 10 and 14 weeks of growth. The physiological mechanism of enhancement of growth is not known. The results of this study suggest that infected plants may have a selective advantage in populations with uninfected members.     

Effect of level of infection with Nippostrongylus brasiliensis on intestinal absorption of hexoses in rats

Transfer of glucose and galactose in vitro from the mucosal to serosal side of the entire small intestine was significantly reduced in male rats 10 days after infection with 100 or more larvae. Transfer of hexoses across the mucosa into the gut tissue by the entire intestine was generally not significantly affected by infection but transfer from the tissue to serosal fluid was significantly reduced, the reductions occurring throughout the intestine, and the metabolism of glucose significantly increased, the increases occurring in the distal two-thirds of the intestine. Females showed a reduction in serosal glucose transfer at an infection level of 50 larvae whereas males did not and the uninfected distal third of the intestine showed the same response to infection as the infected proximal third. The length of the intestine increased significantly at infection levels of 100 or more larvae.     

Strongyloides ratti: Mast cell and goblet cell responses in the small intestine of infected rats

Kinetics of intestinal mast cells and goblet cells were examined in relation to worm localization at various sites in the small intestine of rats infected with 3000 filariform (stage 3) larvae of Strongyloides ratti. The most marked intestinal mastocytosis was observed on Day 20 at the anterior site of the small intestine where the majority of the worms had concentrated. The number of mast cells in the posterior small intestine increased in parallel with the posterior shift of parasites at the later stage of the infection. In contrast to the intestinal mast cell response, the number of goblet cells was not significantly affected by the infection. These results strongly suggest that intestinal mastocytosis is closely related to the presence of the worms and that mast cells may play an important role for the expulsion of S. ratti.     

CHOLINE AND ACETYLCHOLINE IN RATS: EFFECT OF DIETARY CHOLINE

Abstract– The concentration of free choline in peripheral tissues (duodenum, heart, kidney, liver, stomach and plasma) of rats was found to be related to the amount of free choline in the diet. Under steady-state conditions, the concentration of free choline in plasma varied from a minimum of approx 6 nmol/ml (in rats fed a choline-deficient diet) to a maximum value not exceeding 21 nmol/ml. The concentration of plasma choline was elevated above 21 nmol/ml for a short time after parenteral administration of choline chloride or one of its precursors (CDP choline or phosphorylcholine), but was not affected by stress, endocrine manipulations, drug treatments or the time of day when rats were killed. The metabolism of intravenously administered [methyl-³H] choline was accelerated in peripheral tissues (except plasma) of choline-deficient rats, indicating that free choline is not preserved during choline deficiency by a reduction in its rate of turnover. Furthermore, the decrease in concentration of plasma choline that occurred in rats fed a choline-deficient diet was prevented by addition of deanol (dimethylaminoethanol) to the diet. These results indicate that free choline in peripheral tissues of rats is derived from both free choline in the diet, and from precursors of choline present within the diet. In contrast to the effects in peripheral tissues, the concentration of free choline in brain was not reduced by dietary deprivation of free choline; however, the increase in free choline that occurred when rats were decapitated was reduced in brains by deficiency of choline, suggesting a decrease in the concentration of esterified forms of cerebral choline. The concentration of acetylcholine was not reduced in the brain, duodenum, heart, kidney or stomach of 21-week old rats raised from birth on a choline-deficient diet, in the duodenum of rats given a choline-deficient diet for 1, 5 or 11 days, or in brains of rats deprived of free choline for 1 or 11 days. However, the rate of in vivo synthesis of ACh from [methyl-³H]choline was accelerated in cholinergic tissues that were depleted of free choline (i.e. duodenum, heart and stomach).     

Animal Models for Echinostoma malayanum Infection: Worm Recovery and Some Pathology

Echinostomes are intestinal trematodes that infect a wide range of vertebrate hosts, including humans, in their adult stage and also parasitize numerous invertebrate and cold-blooded vertebrate hosts in their larval stages. The purpose of this study was to compare Echinostoma malayanum parasite growth, including worm recovery, body size of adult worms, eggs per worm, eggs per gram of feces, and pathological changes in the small intestine of experimental animals. In this study, 6-8-week-old male hamsters, rats, mice, and gerbils were infected with echinostome metacercariae and then sacrificed at day 60 post-infection. The small intestine and feces of each infected animal were collected and then processed for analysis. The results showed that worm recovery, eggs per worm, and eggs per gram of feces from all infected hamsters were higher compared with infected rats and mice. However, in infected gerbils, no parasites were observed in the small intestine, and there were no parasite eggs in the feces. The volume of eggs per gram of feces and eggs per worm were related to parasite size. The results of histopathological changes in the small intestine of infected groups showed abnormal villi and goblet cells, as evidenced by short villi and an increase in the number and size of goblet cells compared with the normal control group.     

Histological examination ofBorrelia burgdorferi infections in unfedIxodes ricinus nymphs

Borrelia burgdorferi, the agent of Lyme borreliosis, is vectored in Europe byIxodes ricinus. In unfed ticks, the spirochaete resides primarily in the midgut, but a low percentage (5.5%; 4/73) of naturally infected ticks may present a systemic infection involving organs such as the salivary glands and central ganglion (Burgdorferet al., 1983). In this study, we examined 79 unfed nymphs collected in two sites in Switzerland (Neuchatel and Aarberg), and 35 unfed nymphs which were fed as uninfected larvae on 3 infectedApodemus sylvaticus mice. Dieterle silver staining was used to visualize the spirochaetes in the ticks. Of the unfed field-collected nymphs, 21/79 (27%) were infected of which 2/21 (10%) had systemic infections. Taking account of the site of collection, we observed that 0/12 ticks from Neuchatel were systemically infected whereas 2/9 (22%) from Aarberg had a disseminated infection. Out of the 35 unfed nymphs examined after an infectious blood meal on rodents, 14 (40%) were infected and 2 (14%) had a disseminated infection. A total of 4/35 (11%) unfed infected nymphs presented a systemic infection which represents a higher percentage than previously described. The presence of spirochaetes in salivary glands of systemically infected ticks before the initiation of feeding may reduce the time delay generally recorded for the tick-borne transmission ofB. burgdorferi.     

Mucosal mast cell responses in the small intestine of rats infected with Echinostoma hortense

Mucosal mast cell (MMC) responses and worm recovery rates in rats infected with Echinostoma hortense were investigated from day 3 to day 56 post-infection (p.i.). Experimental infected group showed apparently higher number of MMC in each part of the small intestine than that of the control group. The number of MMC in the duodenum increased gradually after the infection and reached a peak on day 35 p.i. Thereafter, the number of MMC continued to decrease at a slow pace. The kinetics of MMC responses in the upper and lower jejunum were similar to that of the duodenum, but the number of MMC in the jejunum was lower. The worm recovery rate decreased with respect to time of which it was markedly reduced on day 49 and 56 p.i. The duration in which a high number of MMC appeared was similar to that in which a low rate in worm recovery was recorded. These results indicate that intestinal mastocytosis may play an important role in the expulsion of E. hortense.     

Effects of anti-allergic drugs on intestinal mastocytosis and worm expulsion of rats infected with Neodiplostomum seoulense

The effects of anti-allergic drugs on intestinal mastocytosis and the expulsion of Neodiplostomum seoulense were observed in Sprague-Dawley rats, after oral infection with 500 metacercariae. The drugs used were hydroxyzine (a histamine receptor H1 blocker), cimetidine (a H2 blocker), cyclosporin-A (a helper T-cell suppressant), and prednisolone (a T- and B-cell suppressant). Infected, but untreated controls, and uninfected controls, were prepared. Worm recovery rate and intestinal mastocytosis were measured on weeks 1, 2, 3, 5, and 7 post-infection. Compared with the infected controls, worm expulsion was significantly (P < 0.05) delayed in hydroxyzine- and cimetidine-treated rats, despite mastocytosis being equally marked in the duodenum of all three groups. In the cyclosporin-A- and prednisolone-treated groups, mastocytosis was suppressed, but worm expulsion was only slightly delayed, without statistical significance. Our results suggest that binding of histamine to its receptors on intestinal smooth muscles is more important in terms of the expulsion of N. seoulense from rats than the levels of histamine alone, or mastocytosis.     

The relationship of abnormal mucosal microtopography with distribution of Trichostrongylus colubriformis in the small intestines of lambs

The relationship of abnormal mucosal microtopography with distribution of Trichostrongylus colubriformis in the small intestines of lambs. International Journal for Parasitology4: 153–163. The distribution of T. colubriformis was studied by counting worms in sequential 1-m segments from the guts of 14 infected lambs. Mucosal morphology was described at corresponding 1-m intervals and compared with similar samples from uninfected controls. A mean of 90 per cent of worms was recovered in the first 6 metres of gut. Maximum worm counts occurred in the first (eight lambs) second (three lambs) or third (three lambs) metre. Less than 0·8 per cent of worms were found in the abomasa of five lambs. Flat mucosae or abnormal surface patterns were seen frequently in the anterior small intestine of infected lambs. Degree of mucosal abnormality was positively associated with magnitude of worm numbers/m, and negatively correlated with distance of the sample from the pylorus, by analysis of partial correlation of worm numbers/m, mucosal type score, and distance from the pylorus. Mucosae from areas with > 4000 worms/m tended to have significantly shorter villi than intestine of control lambs. Factors influencing worm distribution and pattern of establishment are discussed, as is the association of extreme villus atrophy with poor performance by infected lambs.     

Experimental infection of the rabbit tick,<Emphasis Type="Italic"> Haemaphysalis leporispalustris</Emphasis>, with the bacterium<Emphasis Type="Italic"> Rickettsia rickettsii</Emphasis>, and comparative biology of infected and uninfected tick lineages

The present study consisted of two experiments that evaluated experimental infections of Haemaphysalis leporispalustris ticks by a Brazilian strain of Rickettsia rickettsii, and their effect on tick biology. In experiment I, ticks were exposed to R. rickettsii during the larval, nymphal or adult stages by feeding on rabbits (Oryctolagus cuniculus) needle-inoculated with R. rickettsii, and thereafter reared on uninfected rabbits for the entire next tick generation. Regardless of the tick stage that acquired the infection, all subsequent tick stages were shown to be infected by PCR (infection rates varying from 1.3 to 41.7%), and were able to transmit R. rickettsii to uninfected rabbits, as demonstrated by rabbit seroconversion, guinea pig inoculation with rabbit blood, and PCR on rabbit blood. In Experiment II, ticks were exposed to R. rickettsii during the larval stage by feeding on rabbits co-infested with R. rickettsii-infected adult ticks, and thereafter reared on uninfected rabbits until the next generation of larvae. Again, all subsequent tick stages were shown to be infected by PCR (infection rates varying from 3.0 to 40.0%), and were able to transmit R. rickettsii to uninfected rabbits. Thus, it was demonstrated that larvae, nymphs, and adults of H. leporispalustris were able to acquire and maintain the R. rickettsii infection by transstadial and transovarial transmissions within the tick population, with active transmission of the bacterium to susceptible rabbits by all parasitic stages. Analyses of biological parameters of uninfected and R. rickettsii-infected tick lineages were performed in order to evaluate possible deleterious effects of R. rickettsii to the infected tick lineages. Surprisingly, all but one of the four R. rickettsii-experimental groups of the present study showed overall better biological performance than their sibling uninfected control ticks. Results of the present study showed that H. leporispalustris could support infection by a high virulent strain of R. rickettsii for at least two generations, in which infected tick lineages tended to have better performance than uninfected ticks. Our results support a possible role of H. leporispalustris in the enzootic maintenance of R. rickettsii in Latin America, as previously suggested by earlier works.     

Impact of the fungus Balansia henningsiana on Panicum agrostoides: frequency of infection,plant growth and reproduction,and resistance to pests

Summary The impact of the systemic fungus Balansia henningsiana (Clavicipitaceae) on the grass Panicum agrostoides was examined in field and greenhouse studies comparing infected and uninfected plants. Approximately one-half of all plants in three populations located in southern Indiana were infected. In field samples and greenhouse studies infected plants were significantly heavier than uninfected plants and produced significantly more tillers. Infection tended to suppress flowering but occasional asymptomatic tillers on infected plants produced healthy inflorescences. Although infected plants produced fewer inflorescences than uninfected plants as a proportion of total tillers, absolute numbers of inflorescences were similar in the two groups. Because other grasses infected by different species of Balansia and related fungi often are more resistant to insect damage, pest damage was quantified in one population. No differences between infected and uninfected plants were detected in levels of herbivory but infected plants had significantly less damage by the common leaf spot fungus Alternaria triticina. The results suggest that there is no selective disadvantage for plants infected by B. henningsiana.     

Transfer of Eimeria nieschulzi using extraintestinal tissue

The issue of extraintestinal infection by Eimeria nieschulzi in the rat was addressed by transferring various tissues from infected to uninfected rats by mouth. All 6 rats receiving liver, spleen, or small intestine from rats killed at 3 or 8 hr postinoculation (PI), and all 5 rats receiving spleen and small intestine from rats killed 8 days PI, showed infections. Rats receiving tissues from rats killed at 8 days PI showed infections 24 hr later, indicating that fourth-generation merozoites were transferred. This is the first demonstration of an extraintestinal rodent eimerian.     

Kinetics of ingested host immunoglobulin G in hemolymph and whole body homogenates during nymphal development of Dermacentor variabilis and Ixodes scapularis ticks (Acari: Ixodidae)

Patterns in the utilization of host immunoglobulin G (IgG) during nymphal development differed between Dermacentor varibilis (Say) and Ixodes scapularis Say ticks. In unfed nymphs of D. variabilis, host IgG was readily detectable in both hemolymph and whole body homogenates. In unfed nymphs of I. scapularis, host IgG was absent in hemolymph and at very low concentrations in whole body homogenates. Host IgG in unfed nymphs was undoubtedly the remnants of IgG acquired during the larval bloodmeal that persisted through metamorphosis to the nymphal stage. In both tick species, host IgG crossed the midgut into the hemocoel during the latter phases of engorgement. Concentrations of host IgG in I. scapularis declined considerably after replete nymphs molted to the adult stage. In contrast, concentrations of host IgG in D. variabilis remained elevated throughout metamorphosis to the adult stage. When larval D. variabilis were fed on a rat, then 2 months later as nymphs on a rabbit, the rat IgG (“old IgG”) present in unfed nymphs was totally replaced by rabbit IgG (“new IgG”) within 2 d of nymphs attaching to the rabbit. Presumably, the old IgG acquired from a previous bloodmeal was secreted via saliva into the new host. This revised version was published online in July 2006 with corrections to the Cover Date.     

Some influences of population density on Hymenolepis diminuta in rats.

When measured 56 days postinfection the length, wet weight and dry weight of Hymenolepis diminuta were all found to decrease with increasing number of cysticercoids given up to 20. The mean position of the worms in 10, 12 and 20 worm infections is significantly posterior to that of 1, 2 and 5 worm infections and the worms are attached over a wider area of the intestine. Egg production by the worms was followed up to day 56 postinfection; the number of eggs produced per worm and even per rat decreased with increasing population density. Thus the best way to get most eggs and to maintain the parasite in the laboratory is to have rats infected with only one tapeworm. Rats given 1-20 cysticercoids showed a mean recovery of 100-65%, while rats given 40-200 cysticercoids showed a mean recovery ranging from 13 to 2%. In addition to 'normal' worms, defined as worms greater than 10 mm, small, most probably destrobilated, worms were found. In the 50 and 100 cysticercoid infections, worm recoveries were, respectively, 8% 'normal', 16% small, and 2% 'normal', 5% small. From the significantly lower recovery from heavy infections it is concluded that a deleterious factor is operating during the 8 weeks after the infection.     

Nicotine Exposure Does not Alter Plasma to Brain Choline Transfer

Acute and chronic nicotine exposure in rats is associated with an increase in brain acetylcholine (ACh) transmission. The acquisition of choline for neuronal ACh synthesis occurs primarily via two pathways; first, free choline is transported from the blood across the blood-brain barrier (BBB) and/or second, from synaptic choline generated by either hydrolysis of non-bound ACh or membrane phosphatidylcholine catabolism. To determine if nicotine-induced cholinergic demand is associated with increased choline transport rates into brain, we measured BBB choline transport in naïve and S-(−) nicotine exposed rats (acute and chronic, 4.5 mg/kg/d for 1, 14, 21 and 28 d; osmotic minipumps) using the in situ rat brain perfusion technique. No significant changes in choline uptake after acute or chronic nicotine exposure were observed in whole brain or cortex. Of considerable interest was a significant decrease in regional brain choline uptake measured in the hippocampus after chronic nicotine exposure (28 d). Our data suggest that the increased ACh transmission observed after nicotine exposure does not correlate with increased blood-to-brain transfer of choline. Considering these data and previous literature reports, we propose that the additional free choline required under conditions of nicotine exposure (for ACh synthesis) is primarily recruited from membrane phospholipid metabolism.     

Studies on the involvement of prostaglandins and their precursors in the rejection of Nippostrongylus brasiliensis from the rat

In vitro incubation of 6-day Nippo-strongylus brasiliensis in the presence of PGE₁ at 1000 ng/ml and PGE₂ at 500–10,000 ng/ml of medium did not affect worm motility nor in vivo survival of worms implanted into the small intestine of recipient rats. The intraduodenal injection of 250 and 500 μg PGE₁ or PGE₂ did not lead to expulsion of worms from infected rats. An in vitro exposure to precursor fatty acids of PGE₁ and PGE₂, dihomo-γ-linolenic acid and arachidonic acid, respectively, at concentrations of 1000–15,000 ng/ml of medium also failed to inhibit worm motility and in vivo worm survival. These results are at variance with some earlier reports and do not suggest that prostaglandins are directly involved in the immune rejection of N. brasiliensis. No prostaglandins could be demonstrated in worm homogenates.