Susceptibility to coccidiosis: effect of strain of mouse on reproduction of Eimeria vermiformis

The reproduction of Eimeria vermiformis in different strains of phenotypically normal mice and in mice with various immunological characteristics or defects was compared. In some strains of phenotypically normal mice there were marked differences in oocyst production, both in terms of numbers and in the duration of patency, allowing the strains to be classified as resistant or susceptible to infection with E. vermiformis. These differences were apparent only in primary infections; both types of strain were equally resistant to reinfection. Amongst the strains of mice with immunological deficiencies, reproduction of the parasite was greatest in the athymic (nu/nu) mutants and these mice were completely susceptible to reinfection. Strains of mice with lowered or defective antibody production, or with defective neutrophils and low NK cell activity (bg/bg) were more susceptible than the relevant controls to primary infection but all developed substantial immunity to reinfection. Asplenic (Dh/+) mutants were remarkably resistant to infection.

Coccidiosis: characterization of antibody responses to infection with Eimeria nieschulzi

The antibody responses of rats to infection with the intestinal intracellular protozoan parasite Eimeria nieschulzi were examined by a sensitive radio-immunoassay with a soluble preparation of sporulated oocysts as antigen. Specific antibodies of the IgM, IgG1, IgG2a and IgG2b isotypes were found in the blood circulation and IgA antibodies were detected in the bile and in intestinal washings. The IgM response was rapid, its peak was relatively brief and it was not recalled by the reinoculation of oocysts. There were some differences between the responses in the different subclasses of IgG but they all reached a peak between 20-30 days after the initiation of the primary infection and there was an anamnestic response to a challenge inoculation of oocysts. IgA antibodies to E. nieschulzi antigen in the bile and in intestinal washings increased and decreased after both primary and secondary inocula. Antibodies of all isotypes tested were virtually absent in the blood circulation of infected athymic rats. These findings are discussed with reference to antibody responses to other parasitic infections and to the role of antibodies in immunity to coccidiosis.

Ecdysteroids in adults of the nematode, Dirofilaria immitis

Adult males and females of the dog heartworm, Dirofilaria immitis, were extracted separately and, following separation of the free and conjugated ecdysteroid fractions, the conjugates were hydrolysed enzymically. Both the ecdysteroids released by hydrolysis of the conjugates and the free hormones were further purified and analysed by a combination of radioimmunoassay, thin-layer chromatography and high-performance liquid chromatography monitoring fractions by radioimmunoassay, and by gas-liquid chromatography/mass spectrometry (selected ion monitoring). Both males and females contained free and conjugated ecdysteroids. Evidence was obtained for the presence of ecdysone, 20-hydroxyecdysone, 20,26-dihydroxyecdysone and possibly ponasterone A. The possible parallel between ecdysteroid endocrinology in nematodes and insects is discussed.

Antibodies to coccidia: detection by the enzyme-linked immunosorbent assay (ELISA)

The ELISA test was used for the detection of antibodies to coccidia in the serum and/or egg yolk of chickens infected with Eimeria acervulina, E. maxima or E. tenella and in the serum of rats infected with E. nieschulzi. Antigens prepared from different developmental stages of the parasite were tested and the cross-reaction between different species of Eimeria were examined. The variability in cross-reactivity of different species and the advantages and possible applications of the test are discussed.

Identification of the 22-phosphate esters of ecdysone, 2-deoxyecdysone, 20-hydroxyecdysone and 2-deoxy-20-hydroxyecdysone from newly laid eggs of the desert locust, Schistocerca gregaria

The four major ecdysteroid (insect moulting hormone) conjugates present in the newly laid eggs of the desert locust, Schistocera gregaria, have been purified by reversed-phase and anion-exchange high-performance liquid chromatography. The steroid moieties were identified as ecdysone, 2-deoxyecdysone, 20-hydroxyecdysone and 2-deoxy-20-hydroxyecdysone. Phosphate analysis of acid-hydrolysed samples showed a steroid:phosphate ratio of approx. 1:1 for all four compounds. The intact conjugates were identified as ecdysone 22-phosphate, 2-deoxyecdysone 22-phosphate, 20-hydroxyecdysone 22-phosphate and 2-deoxy-20-hydroxyecdysone 22-phosphate by fast atom bombardment mass spectrometry and 1H, 13C and 31P n.m.r. The significance of ecdysteroid phosphates as a source of free hormone during embryogenesis is discussed.

A functional homologue of mammalian secretory component exists in chickens

The existence of a molecule in chickens homologous to the secretory component of mammals has long been in dispute. An intravenous injection of [14C]fucose was given to chickens as a marker for newly synthesized glycoproteins and then unlabeled human IgA was injected intravenously half an hour later. It was shown that the human IgA subsequently appeared in the bile of the chickens combined with a [14C]fucose-labeled molecule; the chicken IgA in these bile samples was similarly labeled. Radiolabeled human secretory IgA was not transported in large amounts across the chicken liver in vivo and neither was purified chicken bile IgA. These results indicate that a molecule exists in chickens which behaves in a manner analogous to mammalian secretory component.

Invasion of chicken caecal and intestinal lamina propria by crypt epithelial cells infected with coccidia

The development of second generation schizonts of Eimeria necatrix and E. tenella was studied with the electron microscope. Invasion of the crypt epithelial cells by merozoites of the first generation schizonts caused changes in the morphology of the infected cells and stimulated their migration into the lamina propria through breaks which appeared in the basement membrane of the crypts. Second generation schizonts developed in the lamina propria within these crypt cells whose epithelial origin was confirmed by their interconnection by desmosomes and tight junctions and by their possession of characteristic microvilli. A comparison is made between this invasion of the lamina propria by parasitized cells and invasion of connective tissue by malignant epithelial cells; the possible mechanisms involved are discussed.

Mucosal transport of Eimeria tenella in the cecum of the chicken

A study of the early life history of Eimeria tenella with the electron microscope confirmed that sporozoites do not directly enter the enterocytes of the crypts, in which they develop, but are carried there by host cells. However, these cells are not macrophages, as previously thought, but intraepithelial lymphocytes. The evidence presented demonstrates that sporozoites first penetrate surface enterocytes and then enter intraepithelial lymphocytes that leave the epithelium, pass through the lamina propria and enter the crypts.

The biotransformation of 17 alpha-ethynyl[3H]estradiol in the rat: irreversible binding and biliary metabolites

1. The irreversible binding of metabolites of 17 alpha-ethynyl[6,7-3H]estradiol ([3H]EE2) to intracellular proteins, and the biliary metabolites of [3H]EE2, were studied in male rats. 2. Very low levels of irreversible binding to hepatic microsomal and soluble proteins were observed. 3. Approx. 75% of the radiolabelled material excreted in bile was present as beta-glucuronides and arylsulphate esters. 4. The compounds liberated from the biliary conjugates by enzymic hydrolysis consisted of EE2, 2-hydroxy-EE2, 16-hydroxy-EE2, 2-methoxy-EE2, 2-hydroxymestranol and at least three additional metabolites not fully identified. 2-Methoxy-EE2 was the principal metabolite. 5. EE2 and all its identified metabolites were excreted as both beta-glucuronides and arylsulphate esters. The glucuronide fraction contained a greater proportion of EE2, a lower proportion of 2-methoxy-EE2 and a lower ratio of 2-methoxy-EE2 to 2-hydroxymestranol than the arylsulphate fraction.

Coccidiosis: T-lymphocyte-dependent effects of infection with Eimeria nieschulzi in rats

The intestinal pathology caused by infection with Eimeria nieschulzi was investigated and comparisons were made between the effects in athymic nude (rnu/rnu) rats and their heterozygous (rnu/+) litter-mates. Most of the changes noted, i.e. increase in gut weight, partial villous atrophy and increased numbers of mast, goblet and pyroninophilic cells were shown to be largely or wholely thymus dependent. The numbers of intraepithelial lymphocytes were decreased in both groups during the period of study. The peripheral blood leucocyte response was similar in both groups of rats during a primary infection but differed after a challenge inoculum, indicating that the secondary type of response which occurred in the rnu/+ rats was thymus dependent, as is resistance to reinfection.

Immunity to coccidia in chickens: adoptive transfer with peripheral blood lymphocytes and spleen cells

Suspensions of cells prepared from the caecal tonsils and spleen, and the peripheral blood lymphocytes of chickens immune to Eimeria maxima, were tested for their ability to transfer resistance to syngeneic recipients. The intravenous injection of approximately 6 x 10(8) spleen cells or peripheral blood lymphocytes caused a significant reduction of oocyst production by the challenged recipients, in comparison with controls which were uninjected or given cells from birds susceptible to E. maxima. Peripheral blood lymphocytes appeared to be most effective when obtained 10-15 days after a primary, or 3-10 days after a secondary inoculation of oocysts. The peripheral blood lymphocytes which participate in the early response to challenge of immune birds were not found to be protective. When given intraperitoneally, greater numbers of spleen cells were required to reduce oocyst production, and small numbers of caecal tonsil cells were ineffective. The ability of the various cell suspensions to transfer antibody and cell-mediated responses was monitored with 'marker' antigens. There was some indication that both types of response were involved in protection.

The origin of IgA in chicken bile: its rapid active transport from blood

In the chicken, there are two bile ducts, one draining the left lobe of the liver directly into the duodenum and the other draining the right lobe via the gall bladder. Cannulation of these ducts enabled us to collect bile in unanesthetized birds and to compare the IgA concentrations of the hepatic bile, gall bladder bile and blood serum. Bile from the cystic and hepatic ducts of the same bird contained similar amounts of IgA (1.7 mg/ml), roughly 10 times as much as in serum, but considerably less than that found in the concentrated bile collected by aspiration from the gall bladder (8 mg/ml). Ligation of the two bile ducts resulted in a three to fourfold increase in the concentration of IgA in serum suggesting that IgA is normally removed from serum by the biliary route. This was confirmed by a substantial recovery of i.v. injected, radiolabeled monoclonal dimeric human IgA in the bile corresponding to a rapid active clearance from the blood circulation; negligible amounts of monomeric human IgA, similarly injected, were recovered from the bile.

Presence of a complete endothelial barrier between lymph and lymphoid tissue in the lumbar lymph nodes of the duck (Anas platyrhynchos)

The ultrastructure of the lumbar lymph nodes of the domestic duck is described and compared with published accounts of mammalian lymph nodes. The barrier to cell migration between lymphoid tissue and lymph is more formidable in the duck than in the mammal. In the duck the lymphatic endothelium lining the lymph spaces is continuous and bonded with desmosomes whereas in the mammal it is unbonded and fenestrated. In both types of node there are filtering zones and areas of dense lymphatic tissue but their topographical organisation differs. There is no cortex or medulla in the duck lymph node and filtration occurs in extensive lymphatic spaces traversed by numerous trabeculae to which are attached rounded phagocytic macrophages. Dense lymphoid tissue is scattered throughout the node, suspended by trabeculae or attached to the capsule and there are blood vessels analogous to the post capillary venules of mammalian nodes where lymphocytes migrate between blood and lymphoid tissue.

Coccidiosis: localization of lymphoblasts in the infected small intestine

Peripheral blood lymphocytes of chickens and thoracic duct lymphocytes and mesenteric lymph node cells of rats, were labelled with 125I-deoxyuridine and injected intravenously into chickens or rats respectively. Sixteen to 18 h later the intestines of coccidia infected animals contained more radioactivity than those of uninfected controls. This result was obtained with cell suspensions from both infected and normal donors indicating that, as with nematode infected rodents, the increased homing of the cells to parasitised gut was not antigen specific. In chickens the stimulus which causes the increased homing of cells to the intestine was induced within hours of parasite inoculation. This reflects the rapid response of this host, previously described with other parameters, and which may be characteristic of birds.

Basophils and eosinophils in three strains of rats and in athymic (nude) rats following infection with the nematodes Nippostrongylus brasiliensis or Trichinella spiralis

A previous report showed that infection with the nematode Nippostrongylus brasiliensis stimulates a basophilia as well as an eosinophilia in the blood of August rats. The present study shows that blood levels of basophils and eosinophils were increased in two other rat strains, one inbred and one outbred, after infection with N. brasiliensis, and infection of two inbred rat strains with Trichinella spiralis also stimulated a basophilia as well as an eosinophilia. No increase occurred in basophils or eosinophils in athymic (nude) rats infected with N. brasiliensis, although both these cell types were found in the blood of control, specific pathogen free, nude rats in numbers comparable to those in specific pathogen free, heterozygote controls of the same strain. Rat basophils usually have few granules and in blood smears often appear as if they were partly degranulated. Basophils from uninfected nude rats contained more negative than positive staining granules compared with basophils from parasitized heterozygotes. The possession of small numbers of granules which vary in their reaction to stains of the Romanowski type is a normal feature of rat basophils in blood smears. Consequently rat basophils differ in these respects from those of other species.

Utilization of a glycol-stabilized liquid NAD for the measurement of three enzymes on the GEMSAEC

Some analytical parameters have been investigated for a recently described stabilized liquid coenzyme technology in which water-free NAD is dissolved in 1,2 propanediol. Correlation for 108 specimens assayed for AST, ALT and LD with a reference method in which glycol-based NAD was absent was greater than or equal to 0.998 with near identical reproducibility over a period of at least 107 days. Mean recovery of exogenous serum enzymes in this linear kinetic assay is 103%. With the option of mixing only the volume of reagent needed for the enzymatic assay, waste can be eliminated as compared to more costly preparations stabilized by lyophilization. Hazards from an impure water supply are avoided since no reconstituting volume is required.

Intestinal mast cell response in rats and chickens to coccidiosis, with some properties of chicken mast cells

The response of intestinal mast cells to infection with coccidian protozoa in rats and chickens was compared with the well-known increase in the numbers of these cells which follows helminth infections. In <i>Eimeria</i>-infected chickens and rats given a moderate primary infection, there was an initial fall in the numbers of intestinal mast cells, small and insignificant in the rats, but more marked in the chickens. This was followed, towards the end of infection, by a return to (chicken) or an increase above (rat) normal levels. In birds given a large challenge inoculum of oocysts there was, within hours of dosing, an initial increase in numbers followed by a return to normal by day 2 and this response was similar in both immunised and susceptible birds. This rapid recruitment of cells was not seen in immune rats similarly challenged: in this species numbers were not increased until day 2 at the earliest. A marked increase in vascular leakage after the large challenge inoculum was apparent only in immunised birds. Thus this could not be correlated with the increase in numbers of mast cells which occurred equally in both immune and susceptible and was probably related to the invasion of host cells by the parasite. The mast cells of chickens are not degranulated by polymyxin B or compound 48/80, both of which affect rat mast cells. In the rat, connective tissue and intestinal mast cells differ in various ways including their dye-binding properties, but this was not seen with chicken mast cells.

Immunity to coccidiosis: T-lymphocyte- or B-lymphocyte-deficient animals

Comparisons were made between infections with Eimeria spp. in normal animals and in animals with functional deficiencies in either T-lymphocytes (athymic nude rats) or B-lymphocytes (bursectomized chickens). Approximately three times more oocysts of E. nieschulzi were passed during a primary infection in the nu/nu rats, and in contrast to the nu/+ rats, they were completely susceptible to reinfection. Nu/nu rats did not produce agglutinating antibodies to sporozoites, and injections of serum from immunized nu/+ rats caused a reduction of oocyst production during a primary infection in both nu/nu and nu/+ rats. In chickens, oocyst production in primary infections with E. maxima or with E. acervulina was increased 1.5 to 2-fold in the bursectomised (BX) groups, and the clinical effects of infection with E. maxima were greater than in controls. The BX birds were slightly more susceptible than the controls to challenge inoculations of oocysts, but nevertheless, they were very substantially immune. Tests for the functioning of B- and T-lymphocytes indicated that in the BX birds there was a severe deficiency of B-cell function, but near-normal T-cell function. The results show that T-lymphocytes are essential for immunity and that, although they may function partly as helper cells for immunoglobulin production, their major effect is exerted via some other mechanism.