Biomedical subjects

R Fayer

Publications and source records attributed to R Fayer.

At least 109 records · Page 6Linked to original sources

PubMed1992

Cryptosporidiosis: Pathogenesis and immunology.

Cryptosporidium parvum is an increasingly recognized agent of intestinal infection in normal and immunocompromised humans, and in many other animals. The intraepithelial cell infection results in villous atrophy, mild submucosal inflammation, reduction of brush-border enzymes and a characteristic persistent watery diarrhea. The infection is self-limiting in immunocompetent hosts, probably because of specific acquired immunity; specific serum and secretory antibody responses develop that may be required for clearance and protection against reinfection. Passive milk antibody, especially i f in high titers, may be partially protective but severe, persistent infection in athymic rodents and humans with AIDS demonstrate that T cells are essential for controlling the infection. Specific anti-bodies and lymphocyte extracts have been tested in cases of cryptosporidiosis but the interpretation of the results remains controversial. Here, Shu-Xian Zu, Guo-Dong Fang, Ronald Foyer and Richard Guerrant emphasize that effective treatment and prevention remain dependent on advances in our understanding of the host cell-parasite relationship.

Journal Article↗

PubMed1992

Colostrum from cows immunized with Eimeria acervulina antigens reduces parasite development in vivo and in vitro.

Experiments were undertaken to determine whether passive immunization utilizing hyperimmune bovine colostrum (HBC) specific for Eimeria acervulina (EA) antigens conferred protection against coccidiosis in chickens. The HBC was produced by immunizing three pregnant, nonmilking Jersey cows with EA antigens administered via one intramuscular injection followed by three intramammary infusions at approximately 10, 8, 6, and 4 wk before parturition. One cow was immunized with sporozoites (SZ), the second with merozoites (MZ), and the third with recombinant merozoite antigen (rMZ). A fourth cow, unimmunized, provided normal colostrum (NC) for control purposes. Colostral whey from each cow was tested by ELISA for antibody against SZ, MZ, and rMZ antigens. In all immunized cows, antiparasite titers were elevated above those of the control. Antibodies from MZ- and rMZ-immunized cows recognized both MZ and rMZ antigen. Separate groups of 2-wk-old chickens received two oral doses of anti-SZ, -MZ, or -rMZ HBC or NC or PBS daily from 1 day before through 6 days after oral inoculation (DAI) with EA oocysts. Feces from each group were examined for oocysts. Intestines were examined for lesions 6 DAI. Histologic sections of duodenum were examined for asexual stages and gametocytes utilizing monoclonal antibody and fluorescence microscopy. In Experiments 1 and 2, oocyst production was reduced in all HBC-treated groups, except one treated with rMZ HBC, compared with PBS- or NC-treated groups. In Experiment 2, the severity of lesions was significantly reduced in all HBC-treated groups compared with those that received NC or PBS. Significantly fewer developmental stages were found in histological sections from all chickens treated with anti-SZ and anti-rMZ HBC than from controls. Anti-SZ HBC significantly reduced the number of intracellular SZ found 24 h after their inoculation into cultures of primary chicken kidney cells. These results suggest that HBC specific for certain EA antigens can inhibit parasite development and reduce severity of parasite-related gut lesions.

Animals↗

PubMed1992

Activity of sulfadimethoxine against cryptosporidiosis in dairy calves.

Of 13 neonatal calves inoculated orally with 1.5 x 10(6) oocysts of Cryptosporidium parvum, 7 in group A were fed 5-g boluses of sulfadimethoxine for 21 consecutive days beginning 1 day before infection, and 6 calves in group B were untreated controls. Calves in group A had diarrhea for 6-18 days (mean = 11 days); those in group B had diarrhea for 4-14 days (mean = 8.7 days). The severity of diarrhea, based on a daily numerical scoring system, was similar for both groups. Calves in group A shed an average of 18 x 10(6) oocysts/ml of feces for 3.9 days; those in group B shed an average of 2.4 x 10(6) oocysts/ml of feces for 5.3 days. By 28 days of age, calves in group A vs. group B gained an average of 8.9 kg vs. 15.7 kg. These findings indicate that sulfadimethoxine did not significantly reduce the number of days or severity of diarrhea, or the number of oocysts or patent period, nor did it improve weight gains.

Administration, Oral↗

PubMed1991

Bovine sarcocystosis: How parasites negatively affect growth.

Growth, though genetically encoded, is markedly influenced in healthy animals by the interaction of hormonal and nutritional factors. The uptake and use of nutrients by specific tissues is regulated by a priority system that modulates physiological processes. Nutritional, hormonal and immunological consequences of parasitism often lead to partitioning of nutrients away from growth. In this article, Ron Foyer and Ted Elsosser use a bovine sarcocystosis model to show that changes in plasma concentrations of insulin-like growth factor-I (IGF-I), growth hormone (GH) and somotostotin (SSN), as well as the host's immunological response to the parasite via cytokine interactions with the endocrine system, are modulators of perturbed growth.

Journal Article↗

PubMed1991

Identification of a 15-kilodalton surface glycoprotein on sporozoites of Cryptosporidium parvum.

An immunoglobulin A monoclonal antibody (MAb5C3) was developed against a 15-kDa surface glycoprotein (GP15) of Cryptosporidium parvum sporozoites. Indirect immunofluorescence and colloidal gold immunoelectron microscopy revealed that the antibody reacted with both the sporozoite and merozoite surface plasma membranes. On Western immunoblots, MAb5C3 binding was found to be strongly inhibited when 200 mM N-acetylglucosamine was used as a competing sugar. N-Acetylgalactosamine inhibited binding of the antibody only slightly, whereas glucose, mannose, and galactose failed to inhibit binding. MAb5C3 was found to recognize a similar 15-kDa epitope associated with a Cryptosporidium sp. isolated from guinea pigs. However, MAb5C3 failed to react with any proteins or glycoproteins associated with C. baileyi from chickens, Cryptosporidium sp. (= bovine C. muris) from cattle, C. serpentis from a rat snake, bradyzoites of Besnoitia darlingi from an opossum, sporozoite/oocyst extracts of Caryospora bigenetica from an eastern diamondback rattlesnake, sporozoites of Eimeria nieschulzi and E. papillata from rats and mice, or tachyzoites of Toxoplasma gondii (RH strain). When hybridoma supernatants containing MAb5C3 were administered orally to suckling mice experimentally infected with C. parvum, a 75% reduction in developmental stages was seen histologically at 72 h postinfection and a 67.5% reduction in mean oocyst output was found at 6 days postinfection.

Animals↗

PubMed1991

Tumor necrosis factor-alpha affects growth hormone secretion by a direct pituitary interaction.

Administration of 50, 250, and 1,250 ng/kg iv of recombinant bovine tumor necrosis factor-alpha (RBTNF) did not affect basal plasma concentrations of growth hormone (GH) or thyroid-stimulating hormone in male calves. However, when administered 30 min before challenge with 1 microgram/kg iv of thyrotropin-releasing hormone (TRH), 250 ng/kg of RBTNF increased the subsequent incremental GH response. At 1,250 ng/kg of RBTNF, GH response to TRH was significantly blunted. For each dose of RBTNF administered, the incremental change in plasma thyroid-stimulating hormone following TRH was not significantly different from control. To examine direct effects of RBTNF on pituitary function, fresh bovine pituitaries were sliced into 1-mm cubes and incubated with 0 or 10(-8), 10(-9), or 10(-10) M RBTNF. Additional cultures were treated with 10(-8) or 10(-9) M GH-releasing factor or 10(-8) M TRH and 0 or 10(-8) M RBTNF. Media GH increased in cultures with 10(-10) M RBTNF and declined linearly as RBTNF concentration increased. RBTNF blocked GH release from GH-releasing factor- and TRH-challenged pituitary slices. Membranes prepared from homogenized bovine pituitaries had specific saturable binding characteristics for monomeric 125I-RBTNF. Membranes treated with 4 M MgCl2 for 10 min and washed free of Mg2+ produced Scatchard plots fit to a two-site model (high affinity site Kd = 6.6 nM), while Scatchards of non-Mg(2+)-treated membranes fit a single site (Kd = 8.9 nM). Polyacrylamide gel electrophoresis separation of 125I-RBTNF cross-linked pituitary membranes showed specific binding of monomeric 125I-RBTNF to protein components ranging in molecular weight from 19,000 to 77,000. The data suggest that RBTNF has modulatory effects on the regulation of GH secretion acting directly at the pituitary through specific receptors.

Analysis of Variance↗

PubMed1991

Tumor necrosis factor as a potential mediator of acute metabolic and hormonal responses to endotoxemia in calves.

The effects of coliform endotoxin (E) and recombinant bovine tumor necrosis factor alpha (TNF) were compared with respect to clinical signs of disease and changes in plasma metabolite and pituitary and pancreatic hormone concentrations in calves. In addition, changes in plasma TNF concentration during each challenge exposure were quantitated by use of radioimmunoassay. Healthy Holstein bull calves with mean body weight of 90 kg were each given, in order, on different days, saline solution (5.0 ml, IV, day 1, n = 4), E (type 055:B5, 1.0 micrograms/kg of body weight IV, day 2, n = 4) and TNF (5.0 micrograms/kg IV, day 9, n = 3). Jugular venous blood samples, rectal temperature reading, and PCV were obtained at hourly intervals before (2 hours) and after challenge exposure. The PCV increased (P less than 0.05) after E and TNF administrations for the first 5 hours, then returned to normal in calves given E, but decreased and remained low in calves given TNF through 24 hours. Plasma triglyceride and nonesterified free fatty acids concentrations were increased through 10 hours (P less than 0.05) after E administration, whereas triglyceride and nonesterified free fatty acids concentrations were not significantly affected by TNF administration. Increase in blood glucose concentration at 1 hour after administration of E and TNF was followed by prolonged hypoglycemia that lasted through 6 hours. Changes in plasma insulin concentration paralleled the observed changes in glucose concentration, initially increased at 2 hours after E and TNF (P less than 0.05) administrations, but then tended to decrease below control values thereafter.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗

PubMed1991

Immunohistologic examination of monoclonal antibodies generated against Eimeria bovis sporozoites for reactivity to meronts and sexual stages of E bovis and other eimerian parasites.

Seven monoclonal antibodies (MAB) generated against sporozoites of Eimeria bovis were tested for reactivity against immature and mature first-generation meronts, sexual stages, and oocysts in tissues from experimentally infected calves by use of an avidin-biotin peroxidase complex (ABPC) immunohistologic test. Three of the 7 MAB reacted in the ABPC test. One of these, MAB-4FB4, reacted only with mature E bovis meronts. The other 2 MAB, MAB-2AE7 and MAB-4AD7, reacted with all the developmental stages of E bovis tested. Asexual stages and sexual stages of E tenella from chickens and E papillata from mice also were examined in the ABPC test. Monoclonal antibodies MAB-2AE7 and MAB-4AD7 reacted with all stages of these eimerian protozoa. None of the other 5 MAB reacted with these parasites. Results of this study suggested that antigens are shared among the asexual and sexual stages of several diverse Eimeria species.

Animals↗

PubMed1991

Studies on cryopreservation of Cryptosporidium parvum.

Neonatal BALB/c mice received oocysts or sporozoites of Cryptosporidium parvum pretreated by a variety of cryopreservation protocols. Histologic sections of infected and control mice were examined to determine if pretreated organisms established infection in the intestine. Sporozoites were inoculated rectally, oocysts orally. Freshly excysted sporozoites were frozen in Hanks' balanced salt solution (HBSS) containing dimethylsulfoxide (DMSO) or glycerol at concentrations of 5%, 10%, or 15% at cooling rates of -1 C and -10 C per min. Other sporozoites were frozen to -70 C in the absence of cryoprotectant without controlled reduction of temperature, others placed in HBSS with 10% DMSO but not subjected to freezing, whereas others were placed in vitrification media containing 5.5 M propylene glycol, 6.5 M glycerol, or 8 M ethylene glycol for 1 min before resuspension in fresh HBSS and inoculation into mice. Intact oocysts were frozen without controlled reduction of temperature directly to -70 C in HBSS containing no cryoprotectant or in HBSS that contained 10% DMSO. Others were cooled at -0.3 C per min from 4 C to -70 C in HBSS with 5% or 10% DMSO. Still others were cooled at a rate of -1 C per min until reaching -40 C and then cooled at -10 C per min until reaching -70 C in HBSS with 7.5% DMSO. Oocysts and sporozoites not exposed to cryoprotectants were inoculated into mice orally and rectally, respectively, for control purposes. Only unfrozen oocysts and sporozoites not exposed to cryoprotectant, and some of the unfrozen oocysts and sporozoites exposed to 10% DMSO, successfully established infections in mice.

Animals↗

PubMed1991

Immunogold labeling of stages of Cryptosporidium parvum recognized by immunoglobulins in hyperimmune bovine colostrum.

Ultrathin sections of mouse ileum infected with Cryptosporidium parvum were stained by immunogold techniques. Sections first were stained with polyvalent antibodies in whey from hyperimmune bovine colostrum (HBC), then stained by secondary antibodies in rabbit antibovine IgA, IgM, IgG1, and IgG2, and lastly labeled by goat anti-rabbit gold conjugate. Examination of the immunostained specimens by electron microscopy revealed that each bovine immunoglobulin isotype in the whey recognized antigens in meronts, merozoites, microgametocytes, microgametes, and macrogamonts. Based on these findings it is hypothesized that antigens in all stages of C. parvum provide targets of opportunity for the antiparasitic activity of HBC whey antibodies thereby accounting for its efficacy as an immunotherapeutic agent.

Animals↗

PubMed1990

Cessation of Cryptosporidium-associated diarrhea in an acquired immunodeficiency syndrome patient after treatment with hyperimmune bovine colostrum.

Cryptosporidium is a parasite of the human gastrointestinal tract that can cause life-threatening diarrhea in immunodeficient patients. Although more than 80 agents have been tried with occasional anecdotal success, treatment remains primarily limited to hydration. A 38-yr-old homosexual man with antibody to human immunodeficiency virus and Cryptosporidium-related diarrhea is described. The patient excreted 6-12 L of stool per day for at least 3 mo, 2 of them spent in the hospital. Trials with more than 6 antidiarrheal medications were ineffective. The patient received bovine colostrum hyperimmune to Cryptosporidium by direct duodenal infusion. During infusion, the patient's fecal output decreased to less than 2 L per day, and 48 h after treatment, stools were formed and oocysts to Cryptosporidium were absent. The patient remained asymptomatic for 3 mo. Hyperimmune bovine colostrum offers an exciting new therapy for cryptosporidiosis; controlled trials to establish efficacy should be undertaken and the active factor(s) characterized.

Acquired Immunodeficiency Syndrome↗

PubMed1990

Extraintestinal stages of Eimeria bovis in calves and attempts to induce relapse of clinical disease.

Monoclonal antibodies to all life cycle stages of Eimeria bovis were used in an avidin-biotin immunoperoxidase test to examine extraintestinal tissues from experimentally infected calves for developmental stages of the parasite. First-generation meronts of Eimeria bovis were found in the mesenteric lymph nodes (MLNs) of three of four calves examined during the first 18 days of primary experimental infection. No extraintestinal stages were found in the MLNs of two calves examined 69 days after a primary infection or in five calves examined 6 months after a challenge infection. Tissue homogenates of liver, spleen, and MLNs from immune calves were not infectious for nonimmune recipient calves following oral or intraperitoneal inoculation indicating that infectious stages were not present in these extraintestinal tissues at the time of inoculations. Relapse of clinical coccidiosis and reoccurrence of oocyst shedding were not seen in E. bovis immune calves that were stressed by being put on a 16-week corticosteroid treatment program.

Adrenal Cortex Hormones↗

PubMed1990

Plasma and tissue concentrations and molecular forms of somatostatin in calves infected with Sarcocystis cruzi.

The effects of parasitic infection on plasma and tissue content of immunoreactive somatostatin (SRIF) were studied in 4-mo old male calves inoculated with the protozoan Sarcocystis cruzi. Because feed intake significantly decreased (70%) in infected calves around day 28 postinfection (pi), concomitant with the asexual replication of S. cruzi and outward expression of clinical signs, the relative contributions of infection and associated reduction in nutrition on plasma SRIF were evaluated. Treatment groups were: noninfected ad libitum fed (C), infected (250,000 S. cruzi oocysts per os) ad libitum fed (I) and noninfected calves pairfed to the level of intake of each infected calf (PF). Mean plasma concentrations of SRIF (pg/ml) on day 30 pi were: C, 224 +/- 22; I, 742 +/- 150; PF, 246 +/- 31 (effect of infection P less than .05). In another study, SRIF was measured in plasma and in pancreatic, duodenal, jejunal and ileal tissue extracts from normal and S. cruzi infected calves. Plasma and tissue samples were collected on day 42 pi. Mean plasma SRIF were 2.5 times higher in infected than control calves. Plasma insulin and insulin-like growth factor 1 was lower in infected v control calves (P less than .02). Plasma glucagon was similar between groups. Duodenal (P less than .05) and jejunal (P less than .02) SRIF content was higher in infected than control calves. Chromatography of tissue extracts on Sephadex G-50 revealed that the increase in SRIF was accounted for, in part, by molecular forms larger than cyclic SRIF-14. Data suggest that peripheral SRIF is increased in calves during S. cruzi infection. The increase in SRIF is not solely related to plane of nutrition. Altered levels of gut SRIF(s) may be associated with perturbed metabolic regulation in parasitized animals through direct effects on the gut.

Animals↗

PubMed1990

Radioimmunoassay for bovine tumor necrosis factor: concentrations and circulating molecular forms in bovine plasma.

Antisera against recombinant bovine tumor necrosis factor (rbTNF) were produced in rabbits immunized with rbTNF in Freund's complete adjuvant (F314) and used in a double antibody radioimmunoassay to measure plasma TNF. Assay standards were rbTNF. Iodination of rbTNF and chromatography on G-50 Sephadex with 50 mM EDTA, 0.1% BSA, 0.05 M phosphate buffer, pH 7.5 resulted in labelled rbTNF which was greater than 97% TCA precipitable (specific activity of 37.5 microCi/micrograms). F314 (1:80,000 dilution) bound 21% of 125I-rbTNF in a non-equilibrium assay at 4 C. Separation of bound and free 125I-rbTNF was accomplished by precipitation with goat anti-rabbit IgG prepared with 6% polyethyleneglycol (mw = 8000). Minimum detectable TNF was 4 pg/assay tube. Matrix effects of plasma were minimal. Recovery of rbTNF from plasma was linearly (recovered TNF = .932 * added TNF = .12; r = .99). Displacement curves of increasing amounts of plasma from calves challenged with endotoxin to effect an increase in endogenous TNF were parallel to the rbTNF standard curve. F314 failed to crossreact with any other cytokines tested except human TNF (less than 1%). Neither recombinant nor native bovine TNF significantly interacted with antisera for TNF of human or murine origin. Plasma TNF was acutely elevated in calves infused with endotoxin. Changes in plasma TNF were determined in samples from calves with chronic parasitic infection. Endogenous plasma TNF existed as a monomer with a molecular weight of 17,000, and was not bound to any plasma carrier protein. These data indicate that a specific RIA for bTNF capable of detecting changes in in vivo TNF levels has been established.

Animals↗

PubMed1990

Kinetics of Cryptosporidium parvum sporozoite neutralization by monoclonal antibodies, immune bovine serum, and immune bovine colostrum.

Monoclonal antibodies, immune bovine serum, and immune bovine colostral whey neutralized infectivity of Cryptosporidium parvum sporozoites for mice in a time-dependent manner. Immune colostral whey neutralized sporozoites more rapidly and completely than immune serum, monoclonal antibody (MAb) 18.44, or a combination of MAb 18.44 and MAb 17.41. Mice were partially protected against oral challenge with C. parvum oocytes when treated with immune colostral whey, MAb 17.41, or a combination of MAb 17.41 and MAb 18.44.

Animals↗

PubMed1990

Immunotherapeutic efficacy of bovine colostral immunoglobulins from a hyperimmunized cow against cryptosporidiosis in neonatal mice.

Infection with Cryptosporidium parvum, a ubiquitous protozoan parasite of virtually all mammals, can cause mild to severe diarrhea in immunocompetent hosts and life-threatening diarrhea in immunocompromised hosts. Passive immunotherapy of experimentally infected animals and naturally infected humans with hyperimmune bovine colostrum has been reported to be efficacious, whereas chemotherapy has not. In this study, the efficacy of specific immunoglobulin isotypes purified from bovine colostrum from a cow hyperimmunized with Cryptosporidium parvum was assessed in neonatal BALB/c mice. Mice were orally infected with oocysts and treated with whole whey immunoglobulin G1 (IgG1), IgG2, IgA, or IgM at six intervals from 22 to 66 h postinfection. In histologic sections of intestine examined at 72 h postinfection, the reduction in number of intestinal stages in treated mice versus untreated controls was very highly significant (P less than 0.0001). The greatest reduction in parasite number was found in mice treated with IgG1, IgA, or whey.

Animals↗

PubMed1990

Cryptosporidium parvum (Apicomplexa: Cryptosporidiidae) oocyst and sporozoite antigens recognized by bovine colostral antibodies.

Colostral whey from seven hyperimmunized and two control cows (hyperimmune bovine colostrum) was examined by Western immunoblotting for the presence of antibody against oocysts and sporozoites of Cryptosporidium parvum, using rabbit anti-bovine immunoglobulin A (IgA), IgG1, IgG2, and IgM antibodies, followed by a horseradish peroxidase goat anti-rabbit polyvalent antibody. Although considerable variation was found in binding activity between cows on different immunization protocols, IgA and IgG1 in whey recognized a greater variety of C. parvum antigens than did IgG2 and IgM. A band at 9 to 10 kilodaltons appeared unique in that it was recognized only by IgA.

Animals↗

PubMed1990

Continuous in vitro cultivation of Sarcocystis cruzi.

Sporozoites of Sarcocystis cruzi were inoculated onto monolayer cultures of bovine pulmonary artery endothelial (CPA) cells. Sporozoites entered the cells, formed large and small multinucleate schizonts, and produced large numbers of merozoites. Continuous cultivation from the original sporozoite inoculum has been maintained for more than 1,320 days by subinoculating merozoites onto new cultures of CPA cells. During this time, the capacity to produce both types of schizonts was preserved, and schizogony was the only form of reproduction that was observed.

Animals↗