Biomedical subjects

P C Allen

Publications and source records attributed to P C Allen.

At least 19 recordsLinked to original sources

PubMed1998

Dietary modulation of avian coccidiosis.

During the past several years, our laboratory has been investigating the anticoccidial activities of various natural products that have potential use as dietary supplements for coccidiosis control. Sources of fats containing high concentrations of n-3 fatty acids such as menhaden oil and flaxseed oil and flaxseed, when added to starter rations and fed to chicks from one day of age, effectively reduce lesions caused by the caecal parasite Eimeria tenella, but not lesions caused by Eimeria maxima. Our results are consistent with reports of effects of diets high in n-3 fatty acids on other protozoan parasites which suggest that the state of oxidative stress induced by these diets in the cells of both host and parasites is responsible for their parasitic actions. Artemisinin, a naturally occurring (Artemisia annua) endoperoxide and effective antimalarial significantly lowers lesions from E. tenella when given at low levels as a feed additive. The mechanism of its action is also considered to involve induction of oxidative stress. Diets supplemented with 8 p.p.m. gamma-tocopherol (abundant in flaxseeds) or with 1% of the spice tumeric, reduce mid-small intestinal lesion scores and improve weight gains during E. maxima infections. These compounds may exert their anticoccidial activity because they are effective antioxidants. Betaine, a choline analogue found in high concentrations in sugar beets, improves nutrient utilisation by animals under stress. When provided as a dietary supplement at a level of 0.15% it has enhanced the anticoccidial activity of the ionophore, salinomycin. Betaine may act as an osmoprotectant whereby it improves the integrity and function of the infected intestinal mucosa. In in vivo studies, betaine plus salinomycin significantly inhibit invasion of both E. tenella and E. acervulina. However, subsequent development of E. acervulina is inhibited more effectively with this combination treatment than development of E. tenella.

Animals↗

PubMed1998

Effects of dietary supplementation with n-3 fatty acid ethyl esters on coccidiosis in chickens.

The ethyl esters of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids were added to a broiler starter diet singly or in combination [as bulk purified ethyl ester concentrate from menhaden oil (n3FAC)] in quantities similar to those found in a diet supplemented with 5% menhaden oil (MO). Diets were fed to chickens from 1 d of age through 3 wk of age. At 2 wk of age, the chickens were infected with Eimeria tenella, Eimeria acervulina, or Eimeria maxima. At 6 d postinfection (PI), the effects of the diets were assessed on weight gains, plasma carotenoids, gross lesion scores, and histological parasite scores in gut cross sections, or oocyst output. Significant ameliorating effects of diet on lesion scores and parasite scores were only seen in E. tenella infections and were only produced by the n3FAC and MO supplements. These two supplements, which contained higher molar concentrations of double bonds than the other supplements, also significantly reduced plasma carotenoids in uninfected chickens, indicating that they promoted a state of oxidative stress. These results are consistent with previous reports on the interaction of coccidiosis with dietary n-3 fatty acids and strengthen the hypotheses that dietary-induced oxidative stress is an effective deterrent against cecal coccidiosis in chickens.

Animals↗

PubMed1997

The effect of high n-3 fatty acids diets on the ultrastructural development of Eimeria tenella.

A study of development of Eimeria tenella in chickens fed high n-3 fatty acids (n-3FA) diets showed ultrastructural degeneration of both asexual and sexual parasite stages. Abnormal shedding of asexual and sexual parasite developmental stages into the cecal lumen was also observed. Ultrastructural degeneration was characterized by cytoplasmic vacuolization, chromatin condensation within the nucleus, a lack of parasitophorous vacuole delineation, and, in some cases, a complete loss of parasite ultrastructural organization. The results of this study indicate that diets high in n-3FA may be useful in the control of avian coccidia.

Animal Feed↗

PubMed1997

Effects of combined treatment with recombinant bovine somatotropin and immunization with live oocysts on performance of broiler chicks raised in coccidia-seeded floor pens.

In our laboratory, preliminary studies have indicated that recombinant bovine somatotropin (rbST) can stimulate protective immunity against coccidia infection. A floor pen trial on coccidia-seeded litter was run to further test its activity as an adjuvant during immunization of chicks with a live oocyst vaccine. Five hundred day-old male broiler strain chicks were randomly assigned to five experimental Treatments: 1, medicated controls; 2, unimmunized, not treated with rbST; 3, unimmunized, rbST-treated; 4, immunized, not treated with rbST; 5, immunized, rbST-treated. Each treatment consisted of four pens of 25 chicks each. At the end of the growout period (7 wk), the chicks in Treatment 1 (medicated controls) had the highest mean BW, but mean BW of chickens in Treatment 3 (rbST treatment only) were not significantly less. On the other hand, the mean weights of chicks in Treatments 4 (immunized only) and 5 (immunized plus rbST) were significantly reduced, and not different from those of the untreated chickens (Treatment 2). However, when challenged at 3 wk, the chicks in Treatment 5 had a mean combined total lesion score that was significantly lower than that from Treatment 3, indicating that they had developed a higher degree of specific immunity, but of the expense of weight gain. The results suggest that rbST has a potential for use as an adjuvant with live oocyst vaccination, but that the ratio between rbST dose and numbers of oocysts in the live vaccine needs to be carefully controlled.

Animals↗

PubMed1997

Nitric oxide production during Eimeria tenella infections in chickens.

The objective of this study was to gather evidence for production of nitric oxide (NO) during a primary infection with the protozoan parasite Eimeria tenella, which carries out its life cycle in the ceca of chickens. Relationships of plasma levels of NO2(-)+NO3-, stable metabolites of NO, with parasite dose and with time after infection were examined, as well as effects of administration of aminoguanidine, an inhibitor of induced nitric oxide synthase (iNOS). Inoculation with 5 x 10(4) and 1 x 10(6) but not 1 x 10(3) oocysts per chick caused significant (P < or = 0.05) increases in micromolar concentrations of plasma NO3(-)+NO3- when measured at 7 d postinoculation (PI). In chickens inoculated with 5 x 10(4) oocysts, significant (P < or = 0.05) increases in plasma NO2(-)+NO3- were seen at 5 and 7 but not 3 d PI. Daily intraperitoneal administration of 1.25 mg per chick aminoguanidine during the period of infection did not lower the increases in plasma NO2(-)+NO3- seen at 5 and 7 d PI, and did not affect the degree of colonization of the cecal tissue by the parasite. However, administration of aminoguanidine did alter the gross appearance of the ceca, which were less swollen and filled with blood at 5 and 7 d PI as compared with ceca from untreated chickens. Hemorrhage is a major pathological manifestation of E. tenella infections, associated with the disruption of the cecal mucosa by the developing parasite. The results of this experiment are consistent with the hypothesis that an aminoguanidine-inhibitable NO synthase, perhaps in the vascular endothelium of the cecal blood vessels, may contribute to hemorrhage by causing vasodilation.

Animals↗

PubMed1997

Production of free radical species during Eimeria maxima infections in chickens.

Five experiments were conducted to investigate the production of nitric oxide (NO) and superoxide anion (O2-) during infections of chickens with the coccidial parasite, Eimeria maxima, in order to assess the importance of these free radical species in the pathogenesis of the infections. Nitric oxide production was estimated by analyzing NO2(-)+NO3-, stable metabolites of NO, in the plasma and intestinal mucosa. The potential for O2- production was estimated from activities of beta-nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in mucosal homogenates. Levels of NO2(-)+NO3- reached maximum values at about 6 d postinoculation, a time when mucosal damage was high and oocysts were being shed. The activity of NADPH oxidase in infected mucosa was also increased. Thus, at that time, there was a potential for oxidative destruction of mucosal tissue from these free radicals and their reaction products. Levels of NO2(-)+NO3- did not increase in a stepwise manner with increasing infective dose, suggesting that production of NO may be regulated post-transcriptionally by other factors elaborated by the immune response to infection, or may be controlled by substrate limitations. A comparison of two E. maxima strains indicated that the virulence of a strain was not directly related to NO production. Increased production of O2- due to increased NADPH oxidase activity during infection may cause a reduction in levels of carotenoid pigments that is unrelated to malabsorption.

Animals↗

PubMed1997

Interaction of dietary flaxseed with coccidia infections in chickens.

Two experiments were conducted to determine effects of diets containing n-3 fatty acids (n-3FA) from whole as well as ground flaxseed on the performance of broilers during coccidia infections. Diets were fed from 1 d of age through 3 wk of age. Chickens were infected with coccidia at 2 wk of age and the effects of infection assessed at 6 d postinfection. The first experiment contrasted effects of several high n-3FA-containing diets, including one supplemented with whole flaxseed, on infections with Eimeria tenella or Eimeria maxima. Infected chickens that consumed the flaxseed-supplemented diet had the lowest weight gains, but they were not significantly different from gains of infected chickens on the control diet. Diets supplemented with 5% menhaden oil or 15% flaxseed significantly reduced lesions caused by E. tenella, but had no effect on lesions caused by E. maxima. In a second experiment, diets supplemented with 5 or 10% ground flaxseed were assessed for effects on the performance of broilers infected with three dose levels (500, 5,000, or 50,000 oocysts) of E. maxima. Neither flaxseed diet protected weight gain during infection with 50,000 oocysts. However, a 5% flax diet protected weight gains in chickens infected with 500 or 5,000 oocysts. Diets supplemented with 5 or 10% ground flaxseed exacerbated lesions in chickens infected with 5,000 or 50,000 E. maxima oocysts compared to the control diet. Thus, diets containing high amounts of n-3 fatty acids do not affect the development of all Eimeria sp. in the same manner. The oxidative stress produced by these diets may more adversely affect development of E. tenella, which infects the relatively oxygen-poor ceca, whereas it does not affect development of E. maxima which parasitizes the middle portion of the small intestine.

Animals↗

PubMed1997

Assessment of recombinant bovine somatotropin as an immunomodulator during avian coccidiosis: immunization with living oocysts.

Coccidiosis, a disease of great economic importance to the poultry industry, is generally controlled prophylactically by additions of anticoccidial drugs to the feed. However, increasing development of drug-resistant coccidia species has stimulated searches for alternative control methods, one of which is vaccination. As part of this effort, recombinant bovine growth hormone (rbST) was tested as a possible immune stimulator in combination with live oocyst vaccination. At a dose of 0.045 mg per chick, given by s.c. injection at 1 d of age, rbST did not improve immunity developed by immunization with 500 or 2,500 oocysts of Eimeria maxima as judged by weight gain and lesion scores. At a single dose of 0.09 mg per chick given at 1 d of age in combination with IMMUCOX, rbST provided some protection against challenge infection with Eimeria tenella but not Eimeria acervulina as judged by reduction in lesion scores. Treatment with 0.09 mg rbST per chick alone at 1 and 3 d of age was protective against challenge with E. tenella but not E. acervulina or E. maxima as judged by reduction in lesion scores. These results strongly indicate that rbST can act as an immune modulator in chickens infected with coccidia, and provide a basis for further investigations of its use as a vaccine adjuvant.

Adjuvants, Immunologic↗

PubMed1997

Effects of components of Artemisia annua on coccidia infections in chickens.

Four experiments were run to test the anticoccidial activity of dried Artemisia annua leaves and several of their chemical constituents for possible use as prophylactic feed additives. When fed over a period of 3 wk at a level of 5%, a dried leaf supplement of A. annua provided significant protection against lesions due to Eimeria tenella but not Eimeria acervulina or Eimeria maxima. When fed over a period of 5 wk at a level of 1% to chicks undergoing immunization with a live vaccine, it provided significant protection in partially immunized chicks against E. acervulina and E. tenella lesions from a dual species challenge infection. It also afforded lower mean lesion scores in challenged chicks immunized over a period of 5 wk. Artemisinin, an antimalarial component of A. annua, was present at a level of 0.034% in the dried leaf preparation. A 5% supplement thus afforded about 17 ppm artemisin. When the pure compound was fed at that level for a period of 3 wk, it protected weight gains and significantly reduced lesion scores attributable to E. tenella but not E. acervulina. Other components of A. annua, camphor and 1,8-cineole, at 119 ppm also protected weight gains, and reduced E. tenella lesion scores. Camphor reduced E. acervulina lesions. Artemisinin fed for 4 wk at levels of 2, 8.5, and 17 ppm significantly reduced oocyst output from separate E. acervulina and E. tenella infections and a dual species infection. Pure artemisinin thus appears to be effective against at least two coccidia species when used as a feed additive, and its activity may depend, in part, on the length of time it is administered before a challenge infection.

Analysis of Variance↗

PubMed1997

The effect of inhibitors of inducible nitric oxide synthase on chronic colitis in the rhesus monkey.

GI inflammation is associated with an increase in nitric oxide production and expression of the inducible isoform of nitric oxide synthase (iNOS). Using a spontaneous model of chronic colonic inflammation in rhesus monkeys, which shares morphological and clinical features with ulcerative colitis, we assessed the therapeutic benefit of administration of iNOS inhibitors. Sixteen colitic rhesus monkeys underwent an endoscopy procedure before commencement of the trial, and biopsies from three sites of the colon and plasma were collected. Monkeys were randomly assigned to three treatment groups and were administered by oral bolus 60 mg/kg/day L-N 6-(1-Iminoethyl) lysine, 60 mg/kg/day aminoguanidine or a placebo (0.9% NaCl) twice daily. Monkeys were sacrificed after 10 days, coIonic tissue from multiple sites was dissected and processed for histological and biochemical analysis. In rhesus colitis, diarrhea was characterized by a significant increase in fecal water content and daily fecal output. iNOS was localized immunohistochemically in plasma cells and neutrophils in the colonic mucosa and lamina propria, paralleled by enhanced iNOS gene expression determined by reverse-transcriptase polymerase chain reaction. Only L-N 6-(1-iminoethyl) lysine administration resulted in a significant reduction in systemic nitric oxide production, and neither of the iNOS inhibitors significantly reduced the histological inflammatory score nor ameliorated diarrheal symptoms. From these findings, we conclude that in this chronic, spontaneous model of colonic inflammation, administering iNOS inhibitors with this treatment regimen did not provide any major therapeutic benefit.

Administration, Oral↗

PubMed1996

Diets high in n-3 fatty acids reduce cecal lesion scores in chickens infected with Eimeria tenella.

Four experiments were run in which diets incorporating various levels of n-3 fatty acids (n-3FA) from fish (menhaden) oil or flax seed were tested for their abilities to reduce the severity of Eimeria tenella infections in young broiler chicks. The diets were fed from 1 d of age through 3 wk of age. Chickens were infected at 2 wk of age. Diets consisting of broiler starter ration supplemented with 2.5 to 10% fish oil, 10% flax seed oil, or 10% linseed oil significantly decreased cecal lesions and maintained weight gains as compared to unsupplemented diets. Light micrographs of ceca from chickens that consumed high n-3FA diets showed reduced parasite invasion and development. Short-term feeding of diets high in n-3FA to young chicks may be a practical method for reducing production losses from cecal coccidiosis.

Animals↗

PubMed1996

Association of lowered plasma carotenoids with protection against cecal coccidiosis by diets high in n-3 fatty acids.

A series of four experiments was run to assess the effectiveness of diets containing high amounts of n-3 fatty acids in reducing the pathological effects of cecal coccidiosis in chickens caused by Eimeria tenella. To determine whether the dietary effects were related to development of oxidative stress, plasma samples were analyzed for tocopherols and carotenoids. Plasma vitamin E (alpha-tocopherol) values were not consistent between experiments. Total plasma carotenoids, however, were significantly decreased by 2.5 to 20% diet supplementation with fish oil in several experiments. These decreases coincided with significant reductions in lesion scores. Under the experimental conditions, total plasma carotenoid concentrations may serve as a sensitive indicator for oxidative stress, which may be a factor in reducing cecal lesions in E. tenella infections.

Animals↗

PubMed1995

Comparison of 16S rRNA sequences of segmented filamentous bacteria isolated from mice, rats, and chickens and proposal of "Candidatus Arthromitus".

Segmented filamentous bacteria (SFB) are nonpathogenic bacteria that are commonly found attached to the intestinal walls of many animals. Until now, these bacteria have not been cultured in vitro. Recently, a 16S rRNA sequence analysis revealed that SFB isolated from mice represent a distinct subline within the Clostridium subphylum of the gram-positive bacteria. Since SFB isolated from mice, rats, and chickens are known to be host specific, we investigated the phylogenetic relationships among SFB obtained from these three hosts. Total DNAs from the intestinal floras of chickens and rats were used as templates for PCR amplification of 16S rRNA genes. PCR products were cloned and screened by a dot blot hybridization procedure to identify homologous sequences that cross-reacted with mouse SFB-specific oligonucleotide probes. A phylogenetic analysis of these 16S ribosomal DNA sequences revealed that SFB isolated from these three hosts form a natural group, which is peripherally related to the genus Clostridium sensu stricto (group I Clostridium). The SFB obtained from chickens, rats, and mice had closely related, albeit different, 16S rRNA gene sequences. The observed levels of 16S rRNA sequence divergence, ca. 1.5 to 3%, together with host specificity, suggest that SFB isolated from mice, rats, and chickens represent different species and that coevolution of the SFB and their hosts occurred. "Candidatus Arthromitus" is proposed as the provisional generic name for this group of organisms.

Animals↗

PubMed1993

Effects of formaldehyde fumigation of housing on carotenoid pigmentation in three breeds of chickens.

Three breeds of chickens (two broiler breeds, A and B, and one layer breed, C) were raised from 1 day to 3 wk of age in either standard housing or housing additionally fumigated with formaldehyde. Groups of chicks from each breed in both housings received either regular poultry starter ration or this ration supplemented with marigold meal. At 3 wk of age, chicks of all three breeds had higher (111, 113, and 115%) mean body weights when raised in fumigated housing. There was no significant effect of supplemental carotenoids on body weight. Chicks of all three breeds raised in fumigated housing had significantly higher plasma carotenoid concentrations when fed either regular or supplemented feed, and, with the exception of Breed A on regular feed, also had significantly increased skin carotenoid values. No significant differences among breeds in plasma or skin carotenoid values were seen in chicks fed regular ration. However, significant differences were seen among groups of chicks fed supplemental carotenoids. The layer breed, C, had the highest percentage increase in carotenoid pigmentation when fed the carotenoid-supplemented diet in fumigated housing.

Animal Feed↗

PubMed1993

Effect of atherogenic diet on chicken plasma lipids and lipoproteins.

Adult male White Leghorn chickens were used in an experimental model system to study atherogenesis, and the effects of an atherogenic diet on plasma lipoprotein composition including carotenoids were determined. This model also included treatment with diazepam, a drug known to reduce formation of atherogenic plaques. After 6 wk consumption of a high-cholesterol, high-triglyceride diet, chickens had mean total plasma cholesterol, triglyceride, and carotenoid concentrations that were significantly increased over those from chicks that consumed the standard diet. Diazepam treatment had no significant effect on whole plasma concentrations of these lipids. Total body weight gain was unaffected by diet, but liver weight expressed as percentage of body weight was significantly increased in chickens that consumed the atherogenic diet. High density lipoprotein (HDL) and low density lipoprotein (LDL) fractions were isolated from plasma samples by ultracentrifugation. The atherogenic diet increased the carotenoid, cholesterol, and protein content of the LDL fractions but not the HDL fractions.

Animals↗

PubMed1992

Effect of coccidiosis on the distribution of dietary lutein in the chick.

A series of experiments was run to determine whether the distribution of dietary carotenoids in chick plasma and tissue was dependent upon a saturable carrier, and to observe how infection with Eimeria acervulina affected this distribution. Broiler (Hubbard x Hubbard) and Sex Sal (Rhode Island Red x White Rock) chicks were fed a white corn and soybean meal-based diet supplemented with varying levels of a commercial lutein concentrate. Plasma, small intestine, and liver were analyzed for lutein. In the first experiment, mean plasma values in control broiler chicks increased linearly from 0 to 200 ppm supplementation. Mean plasma values of infected chicks were decreased an average of 71% as compared with controls, and reached a plateau between 100 and 200 ppm dietary lutein. In the second experiment, plasma, small intestinal, and liver lutein levels in broiler chicks reached a plateau between 200 and 500 ppm. In the third experiment, plasma and liver values in Sex Sal chicks leveled off between 250 and 500 ppm whereas levels in the small intestine increased linearly. Infection of the Sex Sal chicks at 3 wk of age with E. acervulina caused plasma lutein levels to be reduced about 88%, small intestinal levels 76%, and liver levels 72%. Supplementation with 500 ppm resulted in higher proportions of lutein in tissues. Infection with E. acervulina shifted the ratios to even higher proportions in the tissues at all supplementation levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Long segmented filamentous organisms in broiler chicks: possible relationship to reduced serum carotenoids.

Over the past several years, broiler-flocks at the author's laboratory have exhibited low serum carotenoid levels. This phenomenon has not been related to exceptionally low carotenoids in the feed or to known protozoan or viral infections. However, long segmented filamentous organisms (LSFO) have been identified in the pale chicks. An inverse correlation between LSFO counts and serum carotenoid levels was not observed, but prevention of LSFO infection consistently resulted in higher carotenoid values. Young chicks were very susceptible to naturally acquired LSFO infection, but the organisms decreased in number with time and became very difficult to find by the time the chicks were 7 wk old. Segments of LSFO containing endospores were detected in mucosal smears. This observation, along with the extreme ease of natural infection, suggests that LSFO are transmitted by dust-borne spores. Transmission can be prevented by fumigation of housing with formaldehyde vapors.

Animals↗

PubMed1992

Comparative study of long, segmented, filamentous organisms in chickens and mice.

No transmission of long, segmented, filamentous organisms (LSFO) from a laboratory mouse strain (Mus musculus) to a domestic broiler chicken strain (Gallus domesticus) occurred by oral dosing with mouse mucosal and fecal preparations, even in hydrocortisone-treated chicks. Transmission of chicken LSFO to laboratory mice was attempted, but the results were confounded by the mice having been already infected with LSFO. However, the morphologic characteristics of the LSFO in the dosed mice suggested that transmission of chick LSFO did not occur. Mouse LSFO, as detected in carbol thionin-stained mucosal smears, are generally wider, longer, and have slightly different morphologic characteristics than chicken LSFO. The results of these studies suggest that the LSFO in mice and chickens may be two distinct species.

Animals↗