Pink salmon (Oncorhynchus gorbuscha) migratory energetics: response to migratory difficulty and comparisons with sockeye salmon (Oncorhynchus nerka)

Pink salmon (Oncorhynchus gorbuscha) are generally considered weak upriver migrants relative to sockeye salmon (Oncorhynchus nerka), though this assertion is largely anecdotal. To assess energy-use patterns during migration, we collected pink salmon from two major Fraser River stocks (Weaver and Seton in British Columbia, Canada) in 1999 at three times and locations: (1) at the start of freshwater migration, (2) at the end of migration before spawning, and (3) immediately after spawning. We calculated the energy content of somatic and reproductive tissues, recorded several body measurements, and conducted both intraspecific (between pink stocks) and interspecific analyses with co-migrating Fraser River sockeye salmon collected during the same season. We found that between pink salmon stocks, there were no significant energetic or morphological differences either at river entry or upon arrival at spawning areas regardless of the level of migratory difficulty encountered. When compared with sockeye salmon, however, we found that pink salmon began upriver migration with significantly smaller somatic energy reserves but made up for this deficiency by minimizing absolute transport and activity costs, presumably by seeking out migratory paths of least resistance. This energetic efficiency comes at a cost to reproductive output: relative to sockeye salmon, pink salmon diverted less absolute energy to egg production, producing smaller ovaries and fewer eggs. We speculate that fundamental differences in behaviour shape the migratory energetic tactics employed by pink salmon.

Excess post-exercise oxygen consumption in adult sockeye (Oncorhynchus nerka) and coho (O. kisutch) salmon following critical speed swimming

The present study measured the excess post-exercise oxygen cost (EPOC) following tests at critical swimming speed (Ucrit) in three stocks of adult, wild, Pacific salmon (Oncorhynchus sp.) and used EPOC to estimate the time required to return to their routine level of oxygen consumption (recovery time) and the total oxygen cost of swimming to Ucrit. Following exhaustion at Ucrit, recovery time was 42-78 min, depending upon the fish stock. The recovery times are several-fold shorter than previously reported for juvenile, hatchery-raised salmonids. EPOC varied fivefold among the fish stocks, being greatest for Gates Creek sockeye salmon (O. nerka), which was the salmon stock that had the longest in-river migration, experienced the warmest temperature and achieved the highest maximum oxygen consumption compared with the other salmon stocks that were studied. EPOC was related to Ucrit, which in turn was directly influenced by ambient test temperature. The non-aerobic cost of swimming to Ucrit was estimated to add an additional 21.4-50.5% to the oxygen consumption measured at Ucrit. While these non-aerobic contributions to swimming did not affect the minimum cost of transport, they were up to three times higher than the value used previously for an energetic model of salmon migration in the Fraser River, BC, Canada. As such, the underestimate of non-aerobic swimming costs may require a reevaluation of the importance of how in-river barriers like rapids and bypass facilities at dams, and year-to-year changes in river flows and temperatures, affect energy use and hence migration success.

The effect of temperature on swimming performance and oxygen consumption in adult sockeye (Oncorhynchus nerka) and coho (O. kisutch) salmon stocks

Our knowledge of the swimming capabilities and metabolic rates of adult salmon, and particularly the influence of temperature on them, is extremely limited, and yet this information is critical to understanding the remarkable upstream migrations that these fish can make. To remedy this situation, we examined the effects of temperature on swimming performance and metabolic rates of 107 adult fish taken from three stocks of sockeye salmon Oncorhynchus nerka and one stock of coho salmon O. kisutch at various field and laboratory locations, using large, portable, swim tunnels. The salmon stocks were selected because of differences in their ambient water temperature (ranging from 5 degrees C to 20 degrees C) and the total distance of their in-river migrations (ranging from approximately 100 km for coastal stocks to approximately 1100 km for interior stocks). As anticipated, differences in routine metabolic rate observed among salmon stocks were largely explained by an exponential dependence on ambient water temperature. However, the relationship between water temperature and maximum oxygen consumption (MO2max), i.e. the MO2 measured at the critical swimming speed (Ucrit), revealed temperature optima for MO2max that were stock-specific. These temperature optima were very similar to the average ambient water temperatures for the natal stream of a given stock. Furthermore, at a comparable water temperature, the salmon stocks that experienced a long and energetically costly in-river migration were characterized by a higher MO2max, a higher scope for activity, a higher Ucrit and, in some cases, a higher cost of transport, relative to the coastal salmon stocks that experience a short in-river migration. We conclude that high-caliber respirometry can be performed in a field setting and that stock-specific differences in swimming performance of adult salmon may be important for understanding upstream migration energetics and abilities.

Infectivity of Cryptosporidium parvum oocysts following cryopreservation

This study was undertaken to investigate the cryopreservation of Cryptosporidium parvum oocysts. Oocysts purified from mouse feces were suspended in distilled water, 10% glycerin, and 2.5% potassium dichromate. They were stored at -20 C and -80 C for 2, 7, and 30 days, respectively. In addition to the purified oocysts, the feces of C. parvum-infected mice were preserved under the same conditions described above. Purified and fecal oocysts were thawed at 4 C, and their viability was assessed by a nucleic acid stain, excystation test, tissue culture infectivity test, and infectivity to immunosuppressed adult mice. Oocysts purified from fecal material prior to cryopreservation lost most of their viability and all of their infectivity for tissue culture and mice. However, when oocysts were cryopreserved in feces, between 11.7 and 34.0% were judged to be viable and retained their infectivity for mice when stored at -20 C (but not -80 C) for 2, 7, and 30 days. Clearly, fecal material provides a cryoprotective environment for C. parvum oocysts stored at -20 C for at least 30 days.

Infection of immunosuppressed C57BL/6N adult mice with a single oocyst of Cryptosporidium parvum

The present study was designed to determine the minimum number of Cryptosporidium parvum oocysts capable of producing patent infections in immunosuppressed C57BL/6N adult mice. Sixty-four female mice were divided into 6 groups of 8 mice each, except group 1 that contained 24 mice. Mice in groups 1-3 were immunosuppressed with dexamethasone and inoculated with 1, 5, and 10 oocysts per mouse, respectively. The accuracy of the inoculum size was microscopically confirmed. Mice in groups 4-6 served as controls: they received either only oocyst inoculation (group 4), or immunosuppression (group 5), or no treatments (group 6). Fecal oocyst shedding was monitored daily for each mouse using an indirect immunofluorescent assay. Parasite colonization in the terminal ileum of each mouse was evaluated histologically. Four of 24 mice in group 1 developed patent infections, with a prepatent period of approximately 6 days. All mice in groups 2 and 3 developed patent infections, with prepatent periods ranging from 4 to 7 days. Mice in groups 4-6 remained uninfected. Parasite colonization was observed in the terminal ilea of all mice in groups 1-3 that shed fecal oocysts. The present study experimentally demonstrates that a single viable oocyst can induce patent C. parvum infections in immunosuppressed C57BL/6N adult mice and indicates that this mouse model could be used for the parasite genotype or isolate cloning.

Season- and size-dependent risk taking in juvenile coho salmon: experimental evaluation of asset protection

Using juvenile coho salmon, Oncorhynchus kisutch, we tested predictions arising from dynamic optimization models of foraging under predation risk. Coho juveniles from two size groups raised in the laboratory were individually fed varying food rations. Their willingness to risk predation was measured as the time to resume foraging after presentation of a predator model. Small fish (mean weight 1.5 g) resumed feeding earlier than larger fish (3.5 g) as predicted by dynamic models under summer photoperiod but not under autumn photoperiod. Contrary to predictions, larger fish did not increase risk taking and small fish decreased risk taking between summer and autumn treatments. Food ration significantly influenced time to resume feeding only in small coho. A simple mechanistic model we proposed to explain feeding motivation under risk as a function of body size and prior growth rate was not sufficient to explain observed variation in risk taking. This study suggests that coho salmon use photoperiod and their own body size as cues for long-term, state-dependent adjustments of feeding behaviour. The lower risk taking of larger fish is probably an example of asset protection, whereby larger animals accept less predation risk to protect their greater accumulated fitness value. The decrease of risk taking in small fish in the autumn was possibly caused by a switch of life history trajectory towards delayed smolting. Copyright 1999 The Association for the Study of Animal Behaviour.

A role for host phosphoinositide 3-kinase and cytoskeletal remodeling during Cryptosporidium parvum infection

Cryptosporidium parvum preferentially infects epithelial cells lining the intestinal mucosa of mammalian hosts. Parasite development and propagation occurs within a unique intracellular but extracytoplasmic parasitophorous vacuole at the apical surface of infected cells. Parasite-induced host cell signaling events and subsequent cytoskeletal remodeling were investigated by using cultured bovine fallopian tube epithelial (BFTE) cells inoculated with C. parvum sporozoites. Indirect-immunofluorescence microscopy detected host tyrosine phosphorylation within 30 s of inoculation. At >30 min postinoculation, actin aggregates were detected at the site of parasite attachment by fluorescein isothiocyanate-conjugated phalloidin staining as well as by indirect immunolabeling with monoclonal anti-actin. The actin-binding protein villin was also detected in focal aggregates at the site of attachment. Host cytoskeletal rearrangement persisted for the duration of the parasitophorous vacuole and contributed to the formation of long, branched microvilli clustered around the cryptosporidial vacuole. The phosphoinositide 3-kinase inhibitor wortmannin significantly inhibited (P < 0.05) C. parvum infection when BFTE cells were pretreated for 60 min at 37 degreesC prior to inoculation. Similarly, treatment of BFTE cells with the protein kinase inhibitors genistein and staurosporine and the cytoskeletally acting compounds 1-(5-iodonaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazapine, cytochalasin D, and 2,3-butanedione monoxime significantly inhibited (P < 0.05) in vitro infection at 24 h postinoculation. These findings demonstrate a prominent role for phosphoinositide 3-kinase activity during the early C. parvum infection process and suggest that manipulation of host signaling pathways results in actin rearrangement at the site of sporozoite attachment.

Actin-dependent motility in Cryptosporidium parvum sporozoites

The present study investigated the role of actin polymerization and myosin motor protein activity in the gliding motility of Cryptosporidium parvum sporozoites. Short motility trails were detected using an indirect immunofluorescent assay (IFA) with a polyclonal antisporozoite antibody following incubation of sporozoites on poly-L-lysine-coated glass slides. Sporozoite motility was blocked following exposure to cytochalasin D, a myosin light-chain kinase inhibitor 1-(5-iodonaphthalene-1-sulfonyl)-1H-hexhydro-1,4-diazapin e, and the myosin ATPase inhibitor 2,3-butanedione monoxime. Sporozoites were observed to form rounded, blunt-ended shapes when exposed to these same inhibitors. Incubation of purified oocysts with these compounds did not significantly inhibit in vitro excystation or subsequent infectivity in cultured epithelial cells. Indirect IFA revealed a uniform distribution of actin protein throughout the body of the sporozoite; immunoelectron microscopy confirmed a diffuse intracellular pattern of gold particles in excysted sporozoites. Collectively, these findings show that sporozoite motility is dependent upon an intact actin-myosin motor system, and the dynamic interaction of F-actin and myosin motor proteins has a further role in maintaining the structural integrity of excysted sporozoites. Further, in vitro excystation and infectivity of C. parvum occurs in the absence of dynamic sporozoite locomotion.

Synergistic anticryptosporidial potential of the combination alpha-1-antitrypsin and paromomycin

The combined effect of the serine protease inhibitor alpha-1-antitrypsin (AAT) and the aminoglycoside paromomycin on Cryptosporidium parvum infection in vitro was investigated. AAT and paromomycin were mixed with C. parvum oocysts as either single or combined treatments and used to inoculate epithelial cell cultures. Single- and combined-treatment groups had significantly lower (P < 0.01) parasite numbers than untreated controls. The mean fractional inhibitory concentration indices suggested significant synergistic activity.

Antagonistic effect of human alpha-1-antitrypsin on excystation of Cryptosporidium parvum oocysts

This study evaluated the effects of the human serine protease inhibitor alpha-1-antitrypsin (AAT) on in vitro excystation and infectivity of Cryptosporidium parvum. Excystation was monitored at 37 C in RPMI medium in the presence of 0, 100, 500, or 1,000 micrograms/ml AAT. AAT significantly inhibited (P < 0.05) excystation of bleach-decontaminated oocysts in a concentration-dependent manner at incubation intervals from 15 to 90 min but did not alter the excystation dynamics of unbleached oocysts. Bleach-treated oocysts, suspended in RPMI containing 0, 1, 10, 100, 500, or 1,000 micrograms/ml AAT, were used to inoculate bovine fallopian tube epithelial (BFTE) cell monolayers. Alternately, sporozoites, excysted at 37 degrees C and collected by filtration, were used to inoculate BFTE cells under the same conditions. The mean number of parasites counted in AAT-treated, oocyst-inoculated cells was significantly less (P < 0.01) than control mean values at 24 and 48 hr post-inoculation (PI); longer PI intervals (72-96 hr) exhibited a decreased inhibitory effect. AAT did not inhibit parasite infection when cultures were inoculated with C. parvum sporozoites. The findings of this study show that the anticryptosporidial potential of AAT is primarily associated with an antagonistic effect on oocyst excystation.

Adapting Eimeria tenella to grow in primary chicken kidney cells following repeated passages between cell culture and chickens

The present study was undertaken to adapt a field isolate (F0) of Eimeria tenella to grow in primary chicken kidney cells (PCKCs) by selecting for characteristics of the parasite rather than modifying the culture and/or environmental conditions. Fourteen generations (F1 to F14) of E. tenella were produced following repeated passages between PCKCs and chickens. Although F1 yielded only a 28% increase in oocysts, in PCKCs compared with F0, F2 to F5 produced from 259% to 277% more oocysts, respectively. There was no significant increase in the percentage of oocysts produced in PCKCs by F6 to F14 compared with F5. Generations F1 to F14 demonstrated a greater propensity for multiple infections within the same host cell than did F0. For example, it was not uncommon to observe two, three, and occasionally four oocysts within a single PCKC. Chickens inoculated with F0 oocysts generally experienced greater pathogenesis by day 7 postinoculation than chickens inoculated with F14 oocysts as measured by decreased body weights, increased cecal lesions, and a higher mortality rate.

Protease activity associated with excystation of Cryptosporidium parvum oocysts

A Cryptosporidium parvum homogenate (CPH), prepared from partially excysted oocysts, was examined for proteolytic activity capable of hydrolyzing azocasein. Protease activity, measured at pH 7.0, was not detected in fresh oocysts but increased progressively with incubation at 37 C. Activity peaked after 60 min incubation but progressively decreased with extended incubation intervals. Cryptosporidial protease activity was significantly inhibited (P < 0.01) by the serine protease inhibitors phenylmethylsulfonyl fluoride (PMSF), diisopropyl fluorophosphate (DIFP), aprotinin, alpha-1-antitrypsin (AAT), and the cysteine protease inhibitor L-trans-epoxysuccinyl-leucylamido-(4-guanidino)-butane (E-64). No single inhibitor completely blocked CPH-associated protease activity; however, the combination of PMSF and E-64 inhibited > 95% of the azocasein hydrolysis measured in untreated control samples. The same group of inhibitors was further evaluated for their ability to inhibit excystation of C. parvum oocysts. PMSF, DIFP, aprotinin, and AAT significantly inhibited (P < 0.05) oocyst excystation at 15-, 30-, and 60-min incubation intervals; E-64 had no significant inhibitory effect on excystation. The results of this study demonstrate proteolytic activity during peak periods of excystation. Further, cryptosporidial protease activity was sensitive to both serine and cysteine protease inhibitors, but only serine protease inhibitors significantly inhibited oocyst excystation. These findings provide preliminary evidence of cryptosporidial proteases of both serine and cysteine protease classes and suggest that serine protease(s) are functionally associated with excystation.

Primary and secondary infections with Cryptosporidium parvum in immunosuppressed adult mice

The present study was undertaken to determine if infection of immunocompetent adult C57BL/6N mice with Cryptosporidium parvum would render them more resistant to a challenge infection following immunosuppression with dexamethasone (DEX). Fecal oocyst shedding and parasite colonization of the terminal ilea were greater in immunosuppressed mice than in nonimmunosuppressed mice. Secondary infections with C. parvum resulted in decreased oocyst shedding and reduced parasite colonization compared with primary infections. Flow cytometry revealed fewer splenic B cells but more splenic total T, CD4+ T, CD8+ T cells and macrophages in immunosuppressed mice than in nonimmunosuppressed mice. The CD4+ to CD8+ T cell ratios and blastogenic responses to lipopolysaccharide (LPS), but not to concanavalin A, were decreased in immunosuppressed mice compared with nonimmunosuppressed mice. Blastogenic responses to LPS and percentages of splenic total B cells and macrophages were increased in secondary infections compared to primary infections. Enhanced susceptibility to C. parvum infection in immunosuppressed mice revealed DEX-mediated effects on both cell-mediated and humoral immunity. Our results suggest that increased resistance in immunosuppressed mice to secondary infections with C. parvum may involve increases in B cells and macrophages.

Efficacy of serine protease inhibitors against Cryptosporidium parvum infection in a bovine fallopian tube epithelial cell culture system

The anticryptosporidial potential of the protease inhibitors alpha-1-antitrypsin (AAT), antipain, aprotinin, leupeptin, methoxysuccinyl-ala-ala-pro-valine chloromethylketone (MAAPVCK), soybean trypsin inhibitor (SBTI), and phenylmethylsulfonyl fluoride (PMSF) was evaluated in a bovine fallopian tube epithelial (BFTE) cell culture system. Protease inhibitor concentrations of 5, 10, 50, 100, and 500 micrograms/ ml (PMSF at 1, 2, and 3 mM) in RPMI medium were mixed with Cryptosporidium parvum oocysts and used to inoculate BFTE cell monolayers. At 24 hr postinoculation (candlejar/37 C), cells were rinsed with RPMI medium, fixed in methanol, and stained with Giemsa. Parasites were enumerated in cell monolayers by brightfield microscopy. The mean number of parasites counted in each protease inhibitor treatment group was expressed as a percentage of the mean number of parasites counted in an infection control group. Leupeptin and SBTI reduced parasite numbers to 40-50% of the control mean at 500 micrograms/ml: AAT, antipain, and aprotinin reduced parasite numbers to 10-15% at the same concentration. PMSF reduced parasite numbers to 40% of the control mean at 3 mM. MAAPVCK did not significantly inhibit cryptosporidial infection. These findings suggest that a protease component of C. parvum may be essential for host cell infection.

Interaction of the human serine protease inhibitor alpha-1-antitrypsin with Cryptosporidium parvum

The protozoan parasite Cryptosporidium parvum was studied for interaction with a human serine protease inhibitor (serpin), alpha-1-antitrypsin (AAT). A C. parvum homogenate (CPH) prepared from oocysts was incubated with purified human AAT and complexes formed between the serpin and CPH were detected using an enzyme-linked immunosorbent assay (ELISA). The optical density read at 450 nm of AAT:CPH reactivity was significantly increased (P < 0.001) relative to CPH in the absence of AAT treatment. Additionally, ELISA reactivity was blocked by incubating AAT with a cognate target enzyme, porcine pancreatic elastase (PPE), prior to treatment of the CPH. Incubation of a partially excysted sample of C. parvum with AAT (37 C x 60 min) demonstrated preferential fluorescence labeling of sporozoites by indirect immunofluorescence assay; AAT complexes were not detected on intact oocysts. Localization of AAT interactions with C. parvum sporozoites was visualized by transmission immunoelectron microscopy. Collectively, these data suggest that C. parvum sporozoites express a protease-like component that is recognized by human AAT. The ability to block ELISA reactivity with PPE suggests that the AAT interactions we detected are functionally similar to the serpin-enzyme complex AAT forms with a protease target.

Infectivity of preserved Cryptosporidium parvum oocysts for immunosuppressed adult mice

The present study was undertaken to determine the infectivity of Cryptosporidium parvum oocysts for immunosuppressed adult C57BL/6N mice after the oocysts had been stored from 1-48 months at 4 degrees C in 2.5% potassium dichromate. All mice inoculated with oocysts 1-18 months old developed patent infections, while mice inoculated with older oocysts remained uninfected. The prepatent period was extended from 2 to 6 or 7 days as the storage time for oocysts increased. The finding that C. parvum oocysts remain infective for mice for at least 18 months offers important economic and time-saving advantages for investigators who frequently require large numbers of oocysts that must be painstakingly purified from calf manure.

Complete development of Cryptosporidium parvum in bovine fallopian tube epithelial cells

Cryptosporidium parvum is a coccidian parasite responsible for causing protracted and life-threatening diarrheal illness in immunocompromised humans, especially patients with AIDS. The lack of medications effective in treating people suffering from cryptosporidiosis has prompted the development of in vivo and in vitro models for this disease. This study is the first to demonstrate that C. parvum can complete its entire life cycle (from sporozoite to infective oocyst) in a primary culture of bovine fallopian tube epithelial (BFTE) cells. Scanning and transmission electron photomicrographs were used to detail the ultrastructure of individual parasitic stages. Successful infections were produced by inoculating cell cultures with either oocysts or purified sporozoites. Infection of BFTE cells with C. parvum close paralleled in vivo infections with regard to host cell location and chronology of parasite development. Infecting BFTE cells with sporulated oocysts provided a reproducible and quantitative cultivation system with significantly (P < or = 0.001) higher infection rates than in Madin-Darby canine kidney cells. Oocysts produced in BFTE cells were infective for immunosuppressed adult C57BL/6N mice. Cultivation of C. parvum in BFTE cells will facilitate the study of interactions between parasites and host cells as well as provide a reliable system for evaluating anticryptosporidial compound efficacy.

Increasing the yield of Eimeria tenella oocysts in primary chicken kidney cells

The present study was undertaken to increase the yield of Eimeria tenella oocysts in primary chicken kidney cells (PCKCs) using a comparatively inexpensive cell-culture system. PCKCs growing on coverslips positioned on the bottoms of individual wells in 24-well tissue-culture plates were infected with sporozoites of E. tenella. The effects of changing the culture medium (RPMI 1640), medium pH, serum type, and serum concentration in the wells were determined by counting newly produced oocysts at 7 days postinoculation. There were significantly more (P < 0.01) oocysts produced when the medium was supplemented with 10% fetal bovine serum (FBS) and changed either daily or every other day compared with not changing the medium. When the same medium was changed daily, significantly more (P < 0.05) oocysts were produced at pH 7.4 than at pH 8.0 but not at pH 6.0. If the medium was changed daily, significantly more (P < 0.05) oocysts were produced when medium was supplemented with 10% FBS only rather than 5% and 10% chicken serum. The cell-culture system described in this study offers a convenient and efficient method for investigating the biological, biochemical, and immunological relationships between E. tenella and the host cell.

Effects of dehydroepiandrosterone in immunosuppressed adult mice infected with Cryptosporidium parvum

Cryptosporidiosis is a diarrheal disease in humans and other animals caused by the coccidian parasite, Cryptosporidium parvum. This study was undertaken to determine the effectiveness of dehydroepiandrosterone (DHEA) in reducing C. parvum infections in immunosuppressed adult C57BL/6N mice and to identify the immunomodulatory effects of DHEA that result in increased resistance to cryptosporidiosis. Dexamethasone-immunosuppressed mice were readily infected with C. parvum following orogastric intubation with 10(6) oocysts/mouse. DHEA treatment of these mice significantly reduced (P < 0.01) both fecal oocyst shedding and parasite colonization of the ilea. Immunosuppressed mice treated with DHEA had more splenic total T cells, CD4+ T cells, and CD8+ T cells than immunosuppressed mice that were not treated, but the differences were not always significant. Moreover, nonimmunosuppressed mice treated with DHEA had significantly more (P < 0.05) splenic total T cells, CD4+ T cells, and total B cells than nonimmunosuppressed mice that did not receive DHEA. Of particular interest was the significantly larger (P < 0.05) number of CD8+ T cells in immunosuppressed, C. parvum-infected, DHEA-treated mice compared with the same mice that were not treated. Up-regulation of the immune system by exogenous DHEA may be useful in the treatment and palliation of cryptosporidiosis.

Therapeutic efficacy of paromomycin in immunosuppressed adult mice infected with Cryptosporidium parvum

The intent of this study was to evaluate the therapeutic efficacy of paromomycin in immunosuppressed adult C57BL/6N mice infected with Cryptosporidium parvum. Seven groups of 10 mice/group were used. Groups 1, 2, and 7 served as normal, toxicity, and placebo controls, respectively. Groups 2-7 were immunosuppressed with dexamethasone phosphate administered ad libitum in drinking water. Groups 3-7 were infected with C. parvum on day 7 postimmunosuppression. Groups 3-6 were treated by administering paromomycin per os for 10 consecutive days, beginning on day 10 postinfection, at dosage levels of 0.25, 0.5, 1, and 2 g/kg/day, respectively. Paromomycin was judged to be nontoxic at the dosage levels used. Groups 1 and 2 remained uninfected while groups 3-7 began shedding oocysts by day 3 postinfection. Paromomycin was therapeutically effective against C. parvum at 1 and 2 g/kg/day as determined by significant reductions in fecal oocyst shedding (P < 0.01), parasite colonization (P < 0.05), and villus atrophy (P < 0.05) in the ilea and terminal ilea of infected mice. We conclude that paromomycin may be useful in the treatment and palliation of cryptosporidiosis.

Patent gut infections in immunosuppressed adult C57BL/6N mice following intraperitoneal injection of Cryptosporidium parvum oocysts

Two experiments were conducted to determine if intraperitoneal (i.p.) and/or subcutaneous (s.c.) injection of Cryptosporidium parvum oocysts could produce patent gut infections in dexamethasone (DEX) or dexamethasone phosphate (DEXp)-immunosuppressed adult female C57BL/6N mice. The results from experiment 1 were suggestive but did not unequivocally demonstrate that i.p. injection of oocysts could produce patent gut infections in these mice. In experiment 2, all mice were individually caged, immunosuppressed with DEXp (groups 1 and 2) or DEX (groups 3 and 4), and administered C. parvum oocysts either by orogastric intubation (groups 1 and 3), i.p. (group 2), or s.c. (group 4). All but 1 mouse in groups 1 and 3 began shedding oocysts in their feces on day 3 post-infection (PI). Mice in these 2 groups continued to shed oocysts until they were killed on day 17 PI. Mice administered oocysts s.c. did not shed oocysts. In group 2, 1 mouse died, 1 failed to shed oocysts, and 1 began shedding oocysts on day 3 PI. The remaining 5 mice started shedding oocysts on either days 8, 10, or 14 PI and continued to shed oocysts until they were killed. We conclude that immunosuppressed adult C57BL/6N mice administered oocysts i.p. can develop patent gut infections with C. parvum.

The immunosuppressive effects of dexamethasone administered in drinking water to C57BL/6N mice infected with Cryptosporidium parvum

The feasibility of immunosuppressing adult C57BL/6N mice by using dexamethasone in drinking water to sustain infections with Cryptosporidium parvum was investigated. An ethanol-soluble formulation of dexamethasone (DEX) was compared with a water-soluble (phosphated) formulation (DEXp). DEX or DEXp was provided for mice ad libitum in drinking water at dosages of 10, 33, and 100 micrograms/ml. DEX was also administered to mice by intraperitoneal injection at 125 micrograms/mouse/day. All mice were inoculated intragastrically with 10(6) C. parvum oocysts/mouse on day 14 postimmunosuppression. Mice immunosuppressed through drinking water exhibited increased signs of toxicity compared with mice intraperitoneally injected with DEX. Moreover, mice receiving DEX in drinking water were less active and died significantly sooner (P < 0.05) than mice receiving DEXp at the same dosages. Immunosuppressed mice began shedding oocysts 3 days postinfection and continued to shed until they either died or were killed. Beginning on day 12 postinfection, mice receiving DEX or DEXp in drinking water shed significantly more oocysts (P < 0.05) than mice immunosuppressed via intraperitoneal injection. Immunosuppressing mice through drinking water was comparatively simple, less traumatic than injection, and efficient with regard to time and labor.

Effects of dehydroepiandrosterone in immunosuppressed rats infected with Cryptosporidium parvum

Cryptosporidium parvum is a coccidian parasite that causes diarrheal disease in animals and humans. Severe cryptosporidial infections were noted in young adult rats immunosuppressed with the glucocorticosteroid dexamethasone (DEX). B-cell and T-cell responses to the mitogens lipopolysaccharide and concanavalin A, respectively, were depressed in the DEX-treated rats. In addition, DEX treatment suppressed serum IgG levels, in vitro IgG production, and natural killer cell activities. Previous results have shown that DEX-immunosuppressed rats treated with dehydroepiandrosterone (DHEA) exhibit significant reductions in cryptosporidiosis as determined by monitoring oocyst shedding in the feces and parasite colonization of the small intestine. Results from this study indicated that B- and T-cell responses to their respective mitogens, serum IgG levels, and in vitro IgG production were greater in DHEA-treated immunosuppressed rats than in untreated DEX-immunosuppressed rats infected with C. parvum. Similar results were demonstrated in DHEA-treated versus normal control rats infected with C. parvum. These results suggest that the effects of DHEA in reducing cryptosporidiosis are the result of a potentiation of the immune system in the immunosuppressed rats.

Complete development of Cryptosporidium parvum in a human endometrial carcinoma cell line

Sporozoites of Cryptosporidium parvum, excysted from oocysts isolated from calves, were applied to monolayers of the human endometrial carcinoma cell line RL95-2. Cells were grown as monolayers in 24-well plates at concentrations ranging from 5 x 10(4) to 1 x 10(5) RL95-2 cells per well. At 1 or 7 days postculturing, C. parvum sporozoites (ranging from 1 x 10(5) to 2 x 10(5) were added to the monolayers of RL95-2 cells. The cells were fixed and stained to estimate the extent of parasite colonization. Light microscopy and electron microscopy confirmed the development and replication of C. parvum within the RL95-2 cells. A standardized and reproducible in vitro culture system for C. parvum is necessary to evaluate therapies against cryptosporidiosis.

Growth of hybridoma cells and antibody production in agamma calf serum

An agamma calf serum (ACS) was compared to fetal bovine serum (FBS) and calf serum supplemented growth media for both murine and human fusion partners and derived hybridoma cells. The variables analyzed were cloning efficiencies, growth characteristics, and MAb production levels. Cultures were established in each serum source, and supernatants were kept for analysis. For cloning efficiencies, the results indicate that although there is no clear advantage in the performance of FBS-supplemented medium, ACS-supplemented RPMI 1640 medium can be used to clone hybridomas and the fusion partners. When analyzed for MAb production in the various sera, the hybridoma cell lines used in this study appeared to produce up to twice as much immunoglobulin when grown in ACS as when grown in supplemented medium. IgG- and IgM-secreting hybridoma cultures should be checked independently for antibody production. Six out of eight murine and human hybridoma cell lines produced higher levels of MAbs when grown in ACS.

The phototoxic effect of erythrosin B on third-stage larvae of gastrointestinal nematodes in sheep

The phototoxic effect of erythrosin B on the infective third-stage larvae (L3) of naturally acquired mixed populations of ovine gastrointestinal nematodes was investigated. This xanthene dye was phototoxic when administered orally to parasitized lambs or applied directly to feces containing nematode ova. Phototoxicity was assessed by the lack of motility (non-swimming) exhibited by the L3 following their collection by Baermannization from cultured feces and exposure to fluorescent light for 360 min. When lambs were administered erythrosin B orally at dosages of O (control), 40, 60 and 80 mg dye kg-1 body weight daily for 10 consecutive days, the percentages of non-swimming L3 were 16%, 46%, 55% and 62%, respectively. However, erythrosin B phototoxicity did not persist after administration of the dye was discontinued and the percentage of non-swimming L3 declined to a level similar to that of the untreated controls within 2 days. The highest percentage of non-swimming L3 was observed when erythrosin B was added directly to feces containing nematode ova. A dose-response curve was evident from the successively higher percentages of non-swimming L3 with increasing concentrations of erythrosin B. Xanthene dyes have the potential to control parasites acquired by livestock on pasture by inducing a phototoxic reaction in the infective L3.

Dehydroepiandrosterone-induced reduction of Cryptosporidium parvum infections in aged Syrian golden hamsters

Cryptosporidiosis, a parasitic disorder caused by Cryptosporidium parvum, is frequently a fulminating and life-threatening disease in immunocompromised hosts. The immune status of the host plays a critical role in determining the length and severity of the disease. Dehydroepiandrosterone (DHEA) is an immunomodulator that has been demonstrated to upregulate immune parameters. Ten aged (20-24 mo) Syrian golden hamsters were treated with DHEA for 7 days prior to intragastric inoculation with 1 x 10(6) C. parvum oocysts. An additional 10 aged hamsters were infected similarly but retained as untreated controls. The untreated hamsters presented with generalized infections as determined by oocyst shedding in the feces and parasite colonization of the small intestine. Hamsters treated with DHEA exhibited a significant reduction in cryptosporidial infection when compared to untreated hamsters. These results suggest that DHEA may be an effective prophylactic agent for cryptosporidiosis in immunocompromised patients.

Comparison of the host ranges and antigenicity of Cryptosporidium parvum and Cryptosporidium wrairi from guinea pigs

Oocysts of a Cryptosporidium isolate from guinea pigs were not infectious for adult mice, but were infectious for two of three newborn calves and for suckling mice. However, oocysts isolated from calves or mice infected with guinea pig Cryptosporidium were not infectious for guinea pigs. Four isolates of C. parvum from calves were incapable of infecting weanling guinea pigs. Microscopic examination of tissue from the colon and cecum of suckling guinea pigs inoculated with C. parvum revealed sparse infection of some pups. These host range studies and previously described differences in 125I-labeled oocyst surface protein profiles between Cryptosporidium sp. from guinea pigs and C. parvum suggest they are distinct species. We propose the name Cryptosporidium wrairi be retained. Studies with monoclonal antibodies indicate that C. wrairi and C. parvum are antigenically related.

Experimental Cryptosporidium parvum infections in immunosuppressed adult mice

Five strains of adult mice were immunosuppressed with the synthetic glucocorticosteroid dexamethasone (DEX), administered either orally or intraperitoneally. The strains of mice used were C57BL/6N, DBA/2N, CBA, C3H/HeN, and BALB/cAnN. All mice were evaluated for susceptibility to Cryptosporidium parvum after intragastric inoculation with 10(6) oocysts per mouse. The DBA/2N, CBA, C3H/HeN, and BALB/cAnN mice given 0.25 micrograms of DEX per g per day orally (the dose and route previously used to infect rats with C. parvum) failed to develop chronic infections. However, the C57BL/6N mice sustained light infections during the entire 28-day experiment. The five strains of mice were also administered DEX intraperitoneally at concentrations ranging from 62.5 to 500 micrograms/day. Only the C57BL/6N mice given DEX at 125 micrograms/day developed chronic infections which persisted over 10 weeks, suggesting that the genetic background of the mouse plays a role in determining susceptibility to cryptosporidosis following immunosuppression with DEX. We believe that the C57BL/6N mouse model will prove to be superior to other animal models for evaluating potential anticryptosporidial agents, as well as for elucidating the immunological defects that allow C. parvum to establish chronic infections, because of cost effectiveness and ease in maintenance, breeding, and handling. We also evaluated the C3H/HeJ/beige mouse (lacks natural killer cell activity) and the C57BL/6N mouse maintained on a low-protein diet to induce immunosuppression. Neither of these mice exhibited heavy cryptosporidial infections.

Cryptosporidium parvum: experimental infections in aged Syrian golden hamsters

Young (8-12 weeks) and aged (20-24 months) Syrian golden hamsters were intragastrically inoculated with Cryptosporidium parvum oocysts to compare the susceptibility to cryptosporidiosis between these two age groups. Oocyst shedding was significantly more intense in the aged than in the young hamsters. Moreover, parasite colonization of the small intestine was observed in the aged but not the young hamsters. Splenocytes from aged hamsters exhibited significantly lower T, B, and natural killer cell activities than did those from young hamsters. These studies suggest that susceptibility to cryptosporidial infections may be greater in aged individuals than has been previously realized.

Effectiveness of dehydroepiandrosterone in reduction of cryptosporidial activity in immunosuppressed rats

The aim of this study was to evaluate the efficacy of the immunomodulator dehydroepiandrosterone in the treatment of cryptosporidiosis in glucocorticoid-induced immunosuppressed rats. A significant reduction in cryptosporidial activity occurred in treated versus untreated rats as assessed by oocyst shedding intensities and examination of parasite colonization in the small intestine.

Production and partial characterization of monoclonal antibodies specific for the gamonts of Eimeria tenella

Thirteen hybridomas secreting monoclonal antibodies (Mabs) specific for the sexual stages (gamonts) of Eimeria tenella were produced by fusing spleen cells of gamont-immunized RBF/Dn mice with FOX-NY myeloma cells. A Mab subisotype profile revealed 1 IgG2a and 12 IgG1. All Mabs demonstrated a similar binding pattern when incubated with parasitic gamonts as determined by the indirect fluorescent antibody test. Ascitic fluid containing Mab (GD9 (IgG1) was produced and used to immunize chicks passively per os. There was a 34% decrease (P less than 0.05) in oocyst output from immunized chicks when compared to control chicks. Passively immunized chicks also had reduced cecal lesion scores when compared to control chicks. These results suggest that Mab GD9 partially inhibited the fertilization process of E. tenella.

Effects of dexamethasone and dehydroepiandrosterone in immunosuppressed rats infected with Cryptosporidium parvum

Treatment of rats immunosuppressed with dexamethasone and inoculated with Cryptosporidium parvum oocysts were treated with dehydroepiandrosterone. A significant reduction in cryptosporidial activity was observed as determined by oocyst shedding and colonization of host tissue by parasites. Dexamethasone treatment alone resulted in decreases in T-, B- and natural killer (NK) cell responses and antibody production that, with the exception of NK-cell activity, were all reversed after administration of dehydroepiandrosterone.

Hemolytic properties of lytic peptides active against the sporozoites of Cryptosporidium parvum

Cryptosporidium parvum is a protozoan parasite that causes mildto-severe diarrheal disease in animals and humans. There are currently no effective chemotherapeutic agents available for the treatment of cryptosporidiosis. Recently, small, naturally occurring antimicrobial lytic peptides with anti-protozoal activities have been described. In the present study, we compare the in vitro anti-cryptosporidial activities of synthetic lytic peptides and their corresponding hemolytic activities after a 30 min incubation at 37 degrees C. Sporozoite viability was assessed microscopically by the uptake of the vital dyes fluorescein diacetate (FDA) and propidium iodide (PI). Hemolysis was assessed spectrophotometrically by the release of soluble hemoglobulin. The most active peptide, Hecate-1, reduced sporozoite viability by 85.5% with a corresponding hemolytic activity of 21.5% at a concentration of 10 microM.

Cryptosporidial infections in SCID mice reconstituted with human or murine lymphocytes

Severe combined immunodeficient (SCID) mice were experimentally infected with Cryptosporidium parvum. Adoptive transfer of BALB/c thymocytes, spleen and bone marrow cells resulted in functional immunologic reconstitution followed by complete eradication of the cryptosporidial infection. Additional SCID mice were injected with human blood peripheral blood lymphocytes and were subsequently infected with C. parvum. The latter mice (SCID-hu-PBL) were at least partially reconstituted with human lymphoid tissues, as evidenced by flow cytometric identification of human cell populations in the SCID mouse spleens and the response of these cells to the T-cell mitogen phytohemagglutinin. The SCID-hu-PBL mice did not resolve the cryptosporidial infections, although a transient reduction in parasitemia was noted 4-6 wk post-reconstitution.

Chronic Cryptosporidium parvum infections in congenitally immunodeficient SCID and nude mice

Severe combined immune deficient (SCID) and athymic National Institutes of Health (NIH)-III (bg/nu/xid) mice were evaluated for susceptibility to Cryptosporidium parvum infections as neonates and as adults after challenge with inocula of 5 x 10(4) and 1 x 10(6) oocysts/mouse, respectively. SCID and NIH-III nude mice developed chronic infections that persisted over 12 weeks. Cryptosporidial organisms were observed in the small and large intestines of all mice. Colonization of the gallbladder and hepatobiliary duct epithelium occurred in a majority of the NIH-III nude mice and a smaller number of the SCID mice. Severe infections in both mouse strains were associated with clinical deterioration followed by death. Signs in these mice included dehydration, icterus, and emaciation. Deaths apparently resulted from hepatic dysfunction. Control mice experienced transient infections with no clinical signs. Immunodeficient mice should prove useful in studies of disease pathogenesis and in evaluating potential anticryptosporidial agents.

A model for demonstrating the adhesion of Actinobacillus seminis to epithelial cells

The objective of this study was to demonstrate that a field isolate of Actinobacillus seminis (As8C) will adhere to epithelial cells and that this adhesion can be inhibited by pretreating the bacteria with mouse serum containing polyclonal antibodies (PoAbs) prepared against this isolate. An indirect fluorescent antibody test, transmission electron microscopy, and phase-contrast microscopy confirmed the adhesion of As8C to an established culture of bovine kidney epithelial cells (BKECs). In a bacterial adhesion assay, 40 As8C were estimated to adhere to each BKEC after 60 min. Using a bacterial inhibition assay, PoAbs diluted 10(-2) or 10(-3) inhibited the adhesion of As8C to BKECs by approximately 90%. Bacterial inhibition decreased to about 50% when the PoAbs were diluted to 10(-4). There was less than 10% inhibition of adhesion of As8C to BKECs when higher dilutions of PoAbs were used. The inhibition of As8C adhesion to BKECs was less than 20% following pretreatment of BKECs with 10(-2) to 10(-5) dilutions of PoAbs. Moreover, pretreatment of As8C with a 10(-2) dilution of PoAbs did not appear to adversely affect bacterial growth on agar. It is likely that the PoAbs interrupted the adhesion of As8C to BKECs by sterically interfering with a bacterial adhesin-epithelial cell receptor interaction.

Immunofluorescent microscopical visualization of trails left by gliding Cryptosporidium parvum sporozoites

Cryptosporidium parvum sporozoites that exhibited gliding motility in vitro were examined by immunofluorescence with anticryptosporidial monoclonal antibodies (Mabs) for surface antigen deposition on poly-L-lysine-coated glass microscope slides. The Mabs that revealed trails are specific for an immunodominant 23-kDa antigen previously localized to the sporozoite surface.

In vitro activities of lytic peptides against the sporozoites of Cryptosporidium parvum

Cryptosporidium parvum is a protozoan parasite that causes mild to severe diarrheal disease in animals and humans. There are currently no effective chemotherapeutic agents available for the treatment of cryptosporidiosis. Recent studies have described small, naturally occurring antimicrobial lytic peptides with antiprotozoal activities. In the present study, the anticryptosporidial activities of three synthetic lytic peptides were determined in an in vitro sporozoite susceptibility assay. Sporozoite viability was assessed microscopically by the uptake of the vital dyes fluorescein diacetate and propidium iodide. Sporozoite viability was reduced by 93.5% following a 60-min exposure to 10 microM Hecate-1 at 37 degrees C. Shiva-10 reduced sporozoite viability by approximately 74.0% after a 60-min exposure at 100 microM and 37 degrees C. The cecropin-b analog SB-37 reduced sporozoite viability by 6.0% following a 60-min exposure at 100 microM and 37 degrees C. A control peptide showed no anticryptosporidial activity.

Effect of oxamisole on immune parameters of mice infected with murine hepatitis

The effects of Oxamisole, 2,3,5,6,7,8-hexahydro-2-phenyl-8,8- dimethoxyimidazo[1,2a]pyridine on immune parameters of mice infected with murine hepatitis were investigated. Young Swiss Webster mice were injected intraperitoneally (i.p.) with the Friend-Braunsteiner strain of murine hepatitis virus and with various doses of Oxamisole at 48 h pre- 24 h pre-, and 4 h post-virus exposure. Antiviral activity was seen in the drug-treated mice which was approximated on the basis of 21-day survival frequency and hepatic discoloration, SGOT and SGPT levels and amount of infectious virus recoverable from the liver. On day 4 post-viral exposure, splenic cells from some of the drug- and placebo-treated cells of infected mice injected with Oxamisole, 25 mg/kg/day, produced significantly more interleukin-1 and interleukin-2 than cells of infected mice treated with saline only. Similarly, mice treated with 25 mg/kg/day of this compound had cells with significantly increased antibody-dependent cell-mediated cytotoxicity as compared with placebo treated animals. However, cells from mice treated with Oxamisole did not demonstrate altered natural killer cell activity. It is concluded that Oxamisole, when administered to mice infected with murine hepatitis virus, has antiviral properties which possibly are mediated through the immunomodulatory effects of this compound on the immune system.

Cultural and biochemical characterization of Actinobacillus and Actinobacillus-like species from ram lambs with epididymitis

Cellular, colonial, cultural, and biochemical characteristics of 25 field strains of gram-negative pleomorphic bacilli from rams with epididymitis were compared with Actinobacillus actinomycetemcomitans American Type Culture Collection (ATCC) strain 29522 and Actinobacillus seminis ATCC strain 15768. Three field strains were identified as A. actinomycetemcomitans, 15 as A. seminis, and 2 as Haemophilus agni; however, 5 strains (3 in group A and 2 in group B) were not identified as species in the genera Actinobacillus, Haemophilus, or Pasteurella based on the taxonomic criteria in Bergey's manual of systematic bacteriology. The 5 Actinobacillus-like organisms in groups A and B were predominantly gram-negative coccobacilli and exhibited less pleomorphism than the 2 Actinobacillus species. The colonial morphologies of groups A and B were similar to the 2 Actinobacillus species but were smaller in diameter and had a pale yellow color. Groups A and B, like the actinobacilli, were facultative anaerobic and capnophilic, did not grow on MacConkey agar, and were catalase-positive and oxidase-positive. Group A reduced nitrate but group B did not. The A. seminis strains utilized ornithine, and group A utilized arginine; but group B did not utilize either ornithine or arginine. All strains failed to utilize lysine or tryptophane. All strains produced acid but no gas from glucose, and the utilization of other carbohydrates varied markedly both between and within the 5 groups of bacteria.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison and partial characterization of the protein profiles and outer membrane antigens of Actinobacillus species isolated from ram lambs with epididymitis

Three monoclonal antibodies (LG17, LG30, LG33) were used in the indirect fluorescent antibody test, the ELISA, and the immunoelectrotransfer blot technique to identify group-specific and strain-specific epitopes on the outer membranes of Actinobacillus seminis, A actinomycetemcomitans, and 17 field isolates of Actinobacillus spp. The field isolates had been obtained by bacteriologic culture of specimens from ram lambs with epididymitis. Only antibody LG33 consistently had specificity for an outer membrane epitope shared by most of the bacterial isolates tested. Staining of polyacrylamide gels with periodic acid-Schiff reagent, Sudan black B, and Coomassie brilliant blue R250 indicated that target antigens for antibodies LG17 and LG33 contained carbohydrate and lipoprotein components, respectively. The chemical composition of the LG30 target antigen was not determined because of its instability after exposure to sodium dodecyl sulfate. Discontinuous-gradient polyacrylamide gel electrophoresis in sodium dodecyl sulfate and spectrophotometric scans of the gels were used to analyze n-octyl-beta-D-glucopyranoside protein extracts from A seminis, A actinomycetemcomitans, and 13 representative field isolates of Actinobacillus spp. Bacterial isolates could be grouped according to their protein profiles. The first group consisted of A seminis, A actinomycetemcomitans, and 7 field isolates of Actinobacillus spp, all of which shared common protein bands with molecular masses of approximately 94 kilodaltons (kD), 64 kD, 60 kD, 52 kD, 44 kD, and 26 kD. The second group was composed of 6 field isolates, each with unique protein profiles; isolates had relatively few protein bands in common. These data suggested that members of the genus Actinobacillus cultured from ram lambs with epididymitis probably include a number of various strains.