Juliane Rieger

Improved Cell Line IPEC-J2, Characterized as a Model for Porcine Jejunal Epithelium

Cell lines matching the source epithelium are indispensable for investigating porcine intestinal transport and barrier properties on a subcellular or molecular level and furthermore help to reduce animal usage. The porcine jejunal cell line IPEC-J2 is established as an in vitro model for porcine infection studies but exhibits atypically high transepithelial resistances (TER) and only low active transport rates so that the effect of nutritional factors cannot be reliably investigated. This study aimed to properly remodel IPEC-J2 and then to re-characterize these cells regarding epithelial architecture, expression of barrier-relevant tight junction (TJ) proteins, adequate TER and transport function, and reaction to secretagogues. For this, IPEC-J2 monolayers were cultured on permeable supports, either under conventional (fetal bovine serum, FBS) or species-specific (porcine serum, PS) conditions. Porcine jejunal mucosa was analyzed for comparison. Main results were that under PS conditions (IPEC-J2/PS), compared to conventional FBS culture (IPEC-J2/FBS), the cell height increased 6-fold while the cell diameter was reduced by 50%. The apical cell membrane of IPEC-J2/PS exhibited typical microvilli. Most importantly, PS caused a one order of magnitude reduction of TER and of trans- and paracellular resistance, and a 2-fold increase in secretory response to forskolin when compared to FBS condition. TJ ultrastructure and appearance of TJ proteins changed dramatically in IPEC-J2/PS. Most parameters measured under PS conditions were much closer to those of typical pig jejunocytes than ever reported since the cell line’s initial establishment in 1989. In conclusion, IPEC-J2, if cultured under defined species-specific conditions, forms a suitable model for investigating porcine paracellular intestinal barrier function.

Effect of Dietary Zinc Oxide on Morphological Characteristics, Mucin Composition and Gene Expression in the Colon of Weaned Piglets

The trace element zinc is often used in the diet of weaned piglets, as high doses have resulted in positive effects on intestinal health. However, the majority of previous studies evaluated zinc supplementations for a short period only and focused on the small intestine. The hypothesis of the present study was that low, medium and high levels of dietary zinc (57, 164 and 2,425 mg Zn/kg from zinc oxide) would affect colonic morphology and innate host defense mechanisms across 4 weeks post-weaning. Histological examinations were conducted regarding the colonic morphology and neutral, acidic, sialylated and sulphated mucins. The mRNA expression levels of mucin (MUC) 1, 2, 13, 20, toll-like receptor (TLR) 2, 4, interleukin (IL)-1β, 8, 10, interferon-γ (IFN-γ) and transforming growth factor-β (TGF-β) were also measured. The colonic crypt area increased in an age-depending manner, and the greatest area was found with medium concentration of dietary zinc. With the high concentration of dietary zinc, the number of goblet cells containing mixed neutral-acidic mucins and total mucins increased. Sialomucin containing goblet cells increased age-dependently. The expression of MUC2 increased with age and reached the highest level at 47 days of age. The expression levels of TLR2 and 4 decreased with age. The mRNA expression of TLR4 and the pro-inflammatory cytokine IL-8 were down-regulated with high dietary zinc treatment, while piglets fed with medium dietary zinc had the highest expression. It is concluded that dietary zinc level had a clear impact on colonic morphology, mucin profiles and immunological traits in piglets after weaning. Those changes might support local defense mechanisms and affect colonic physiology and contribute to the reported reduction of post-weaning diarrhea.

Effect of dietary zinc oxide on jejunal morphological and immunological characteristics in weaned piglets

The aim of this study was to evaluate age-related changes and the effect of dietary Zn concentration on morphological and immunological characteristics in the gastrointestinal tract of piglets. A total of 96 purebred Landrace piglets were weaned at the age of 26 ± 1 d, and randomly allocated into 3 treatment groups fed with low (57 mg Zn/kg), medium (164 mg Zn/kg), and high (2425 mg Zn/kg) dietary Zn (ZnO). Piglets (4 males and 4 females per treatment group) were killed at 33 ± 1, 40 ± 1, 47 ± 1, and 54 ± 1 d of age. In the jejunum, villus height, crypt depth, and the number of goblet cells producing neutral, acidic, sulfated, and sialylated mucins were measured. Intraepithelial lymphocytes were characterized by flow cytometry and the gene expression of mucin 2 (MUC2), mucin 20 (MUC20), β-defensin 3, and trefoil factor 3 (TFF3) was determined by reverse transcription quantitative PCR. Villus height and crypt depth in the jejunum showed age related differences (P < 0.01), whereas the dietary concentrations of Zn had no effect. The mucin types were modified mainly by age, and dietary Zn had no effect in the proximal jejunum. In the distal jejunum, age and Zn had effects on the mucin types. The abundance of sulfomucins decreased (P < 0.001) and sialomucins increased with age (P < 0.001), while high dietary ZnO reduced the sulfomucins (P < 0.001) and increased the sialomucins (P < 0.05) in the crypts. The phenotypes of lymphocytes in the epithelium of the proximal jejunum showed relatively constant percentages of T-cells, as well as natural killer cells. High dietary Zn treatment led to a reduced abundance of CD8(+) γδ T-cells (P < 0.05). The apportionment of different cytotoxic T-cell was age dependent. Although the percentage of CD4(-)CD8β(+) increased (P < 0.01), the relative amount of CD4(+)CD8β(+) decreased with age (P < 0.05). The expression of MUC2 and MUC20 was not influenced by age or dietary Zn concentration. High Zn intakes resulted in a reduced gene expression of β-defensin 3 (P < 0.05), but did not affect the expression of TFF3. It is concluded that Zn in the form of ZnO appears to have specific effects on the innate and adaptive gut associated immune system of piglets. These might contribute to the positive effects of Zn on the prevention of postweaning diarrhea.

Antiviral effects of a probiotic Enterococcus faecium strain against transmissible gastroenteritis coronavirus

The enteropathogenic coronavirus transmissible gastroenteritis virus (TGEV) causes severe disease in young piglets. We have studied the protective effects of the probiotic Enterococcus faecium NCIMB 10415 (E. faecium), which is approved as a feed additive in the European Union, against TGEV infection. E. faecium was added to swine testicle (ST) cells before, concomitantly with, or after TGEV infection. Viability assays revealed that E. faecium led to a dose-dependent rescue of viability of TGEV-infected cells reaching nearly to complete protection. Virus yields of the E. faecium–treated cultures were reduced by up to three log10 units. Western blot analysis of purified TGEV revealed that the levels of all viral structural proteins were reduced after E. faecium treatment. Using transmission electron microscopy, we observed attachment of TGEV particles to the surface of E. faecium which might be a means to trap virus and to prevent infection. Increased production of nitric oxide in the cells treated with E. faecium and elevated expression of interleukin 6 and 8 pointed to stimulated cellular defense as a mechanism to fight TGEV infection.

Porcine intestinal mast cells. Evaluation of different fixatives for histochemical staining techniques considering tissue shrinkage.

Staining of mast cells (MCs), including porcine ones, is critically dependent upon the fixation and staining technique. In the pig, mucosal and submucosal MCs do not stain or stain only faintly after formalin fixation. Some fixation methods are particularly recommended for MC staining, for example the fixation with Carnoy or lead salts. Zinc salt fixation (ZSF) has been reported to work excellently for the preservation of fixation-sensitive antigens. The aim of this study was to establish a reliable histological method for counting of MCs in the porcine intestinum. For this purpose, different tissue fixation and staining methods that also allow potential subsequent immunohistochemical investigations were evaluated in the porcine mucosa, as well as submucosa of small and large intestine. Tissues were fixed in Carnoy, lead acetate, lead nitrate, Zamboni and ZSF and stained subsequently with either polychromatic methylene blue, alcian blue or toluidine blue. For the first time our study reveals that ZSF, a heavy metal fixative, preserves metachromatic staining of porcine MCs. Zamboni fixation was not suitable for histochemical visualization of MCs in the pig intestine. All other tested fixatives were suitable. Alcian blue and toluidine blue co-stained intestinal goblet cells which made a prima facie identification of MCs difficult. The polychromatic methylene blue proved to be the optimal staining. In order to compare MC counting results of the different fixation methods, tissue shrinkage was taken into account. As even the same fixation caused shrinkagedifferences between tissue from small and large intestine, different factors for each single fixation and intestinal localization had to be calculated. Tissue shrinkage varied between 19% and 57%, the highest tissue shrinkage was found after fixation with ZSF in the large intestine, the lowest one in the small intestine after lead acetate fixation. Our study emphasizes that MC counting results from data using different fixation techniques can only be compared if the respective studyimmanent shrinkage factor has been determined and quantification results are adjusted accordingly.

Dietary Enterococcus faecium NCIMB 10415 and Zinc Oxide Stimulate Immune Reactions to Trivalent Influenza Vaccination in Pigs but Do Not Affect Virological Response upon Challenge Infection

Swine influenza viruses (SIV) regularly cause significant disease in pigs worldwide. Since there is no causative treatment of SIV, we tested if probiotic Enterococcus (E.) faecium NCIMB 10415 or zinc (Zn) oxide as feed supplements provide beneficial effects upon SIV infection in piglets. Seventy-two weaned piglets were fed three different diets containing either E. faecium or different levels of Zn (2500 ppm, Znhigh; 50 ppm, Znlow). Half of the piglets were vaccinated intramuscularly (VAC) twice with an inactivated trivalent SIV vaccine, while all piglets were then infected intranasally with H3N2 SIV. Significantly higher weekly weight gains were observed in the E. faecium group before virus infection, and piglets in Znhigh and E. faecium groups gained weight after infection while those in the control group (Znlow) lost weight. Using ELISA, we found significantly higher H3N2-specific antibody levels in the E. faecium+VAC group 2 days before and at the day of challenge infection as well as at 4 and 6 days after challenge infection. Higher hemagglutination inhibition (HI) titers were also observed in the Znhigh+VAC and E. faecium+VAC groups at 0, 1 and 4 days after infection. However, there were no significant differences in virus shedding and lung lesions between the dietary groups. Using flow cytometry analysis significantly higher activated T helper cells and cytotoxic T lymphocyte percentages in the PBMCs were detected in the Znhigh and E. faecium groups at single time points after infection compared to the Znlow control group, but no prolonged effect was found. In the BAL cells no influence of dietary supplementation on immune cell percentages could be detected. Our results suggest that feeding high doses of zinc oxide and particularly E. faecium could beneficially influence humoral immune responses after vaccination and recovery from SIV infection, but not affect virus shedding and lung pathology.

Enhancement of immunohistochemical detection of Salmonella in tissues of experimentally infected pigs

Salmonella Typhimurium is one of the main pathogens compromising porcine and human health as well as food safety, because it is a prevailing source of foodborne infections due to contaminated pork. A prominent problem in the management of this bacteriosis is the number of subclinically infected carrier pigs. As very little is known concerning the mechanisms allowing Salmonella to persist in pigs, the objective of this study was to develop an immunohistochemical approach for the detection of salmonellae in tissue of pigs experimentally infected with Salmonella Typhimurium. Samples were obtained from a challenge trial in which piglets of the German Landrace were intragastrically infected with Salmonella enterica serovar Typhimurium DT104 (1.4-2.1×1010 CFU). Piglets were sacrificed on days 2 and 28 post infection. Tissue samples of jejunum, ileum, colon, ileocecal mesenteric lymph nodes (Lnn. ileocolici), and tonsils (Tonsilla veli palatini) were fixed in Zamboni’s fixative and paraffin-embedded. Different immunohistochemical staining protocols were evaluated. Salmonella was detected in varying amounts in the tissues. Brown iron-containing pigments in the lymph nodes interfered with the identification of Salmonella if DAB was used as a staining reagent. Detergents like Triton X-100 or Saponin enhanced the sensitivity. It seems advisable not to use a detection system with brown staining for bacteria in an experimental setup involving intestinal damage including haemorrhage. The use of detergents appears to result in a higher sensitivity in the immunohistochemical detection of salmonellae.

Effects of high levels of dietary zinc oxide on ex vivo epithelial histamine response and investigations on histamine receptor action in the proximal colon of weaned piglets

The aim of the study was to identify the effect of high dietary zinc oxide (ZnO) levels on the histamine-induced secretory-type response and histamine metabolism in the porcine proximal colon. After weaning at d 26, 3 diets with low (LZn), normal (NZn), and high (HZn) concentrations of zinc (57, 164, or 2,425 mg/kg) were fed to a total of 120 piglets. Digesta and tissue samples were taken from the ascending colon after 7 ± 1, 14 ± 1, 21 ± 1, and 28 ± 1 d. Partially stripped tissue was mounted in Ussing chambers, and histamine was applied either to the serosal or mucosal compartments. Tissue was pretreated with or without aminoguanidine and amodiaquine to block the histamine-degrading enzymes diamine oxidase (DAO) and histamine -methyltransferase (HMT), respectively. Gene expression and catalytic activity of DAO and HMT in the tissue were analyzed. The numbers of mast cells were determined in tissue samples, and histamine concentration was measured in the colon digesta. Colon tissue from another 12 piglets was used for functional studies on histamine H and H receptors by using the neuronal conduction blocker tetrodotoxin (TTX) and the H and H receptor blocker chloropyramine and famotidine, respectively. After serosal histamine application to colonic tissue in Ussing chambers, the change of short-circuit current (Δ) was not affected by pretreatment and was not different between Zn feeding groups. The Δ after mucosal histamine application was numerically lower ( = 0.168) in HZn compared to LZn and NZn pigs. Mast cell numbers increased from 32 to 46 d of life ( < 0.05). Further studies elucidated that the serosal histamine response was partly inhibited by chloropyramine or famotidine ( < 0.01). The response to mucosal histamine tended to be decreased when chloropyramine but not famotidine was applied from either the serosal or the mucosal side ( = 0.055). Tetrodotoxin alone or in combination with chloropyramine resulted in a similar reduction in the mucosal histamine response ( < 0.01). In conclusion, the present study could not identify marked changes in colonic histamine metabolism on dietary ZnO oversupplementation. For the first time, however, H receptors were functionally identified in the pig colon that are localized either on neurons or on cells that activate secretion via neurons. Luminal histamine can elicit a secretory-type response via these receptors.

BERLIN: The Veterinary Collection of the Institute of Veterinary Anatomy, Department of Veterinary Medicine, Freie Universität Berlin

The Institute of Veterinary Anatomy at the Department of Veterinary Medicine, Freie Universitat Berlin, houses several veterinary collections, ranging from various sections with a historical background to sections showcasing veterinary plastinates, which have only been produced in recent years. For example, the Gurlt collection of the institute, which was founded by the veterinary anatomist Ernst Friedrich Gurlt (1794–1882), showcases unique preserved skeletons as well as wet specimens of malformations of domestic animals. The Ziegler collection comprises more than 160 wax models, which were used for teaching during the nineteenth and twentieth centuries and are mainly based on drawings of the anatomist Wilhelm His (1831–1904). The collection of wax models consists of 48 models, mainly heads of dogs, horses, and cattle, which were produced between 1975 and 1995. Moreover, the institute houses 42 corrosion cast specimens, which for a large part have been produced from the mid-1970s until today. Also, approximately 40 anatomical models that can be taken apart and are made of gypsum and wood, originating from various epochs of twentieth-century Germany, are on display. The institute also houses a comprehensive collection of large-format wall charts, originating from the years before 1945 and from the years between 1949 and 1985, which were almost exclusively custom-made.