Biomedical subjects

Wim Van den Broeck

Publications and source records attributed to Wim Van den Broeck.

9 recordsLinked to original sources

PubMed2006

Anatomy and nomenclature of murine lymph nodes: Descriptive study and nomenclatory standardization in BALB/cAnNCrl mice.

Murine lymph nodes are intensively studied but often assigned incorrectly in scientific papers. In BALB/cAnNCrl mice, we characterized a total of 22 different lymph nodes. Peripheral nodes were situated in the head and neck region (mandibular, accessory mandibular, superficial parotid, cranial deep cervical nodes), and at the forelimb (proper axillary, accessory axillary nodes) and hindlimb (subiliac, sciatic, popliteal nodes). Intrathoracic lymph nodes included the cranial mediastinal, tracheobronchal and caudal mediastinal nodes. Abdominal lymph nodes were associated with the gastrointestinal tract (gastric, pancreaticoduodenal, jejunal, colic, caudal mesenteric nodes) or were located along the major intra-abdominal blood vessels (renal, lumbar aortic, lateral iliac, medial iliac and external iliac nodes). Comparative and nomenclative aspects of murine lymph nodes are discussed. The position of the lymph nodes of BALB/cAnNCrl mice is summarized and illustrated in an anatomical chart containing proposals for both an official nomenclature according to the Nomina Anatomica Veterinaria and English terms.

Animals↗

PubMed2005

Association of Flavobacterium psychrophilum strains with intestinal explants of rainbow trout Oncorhynchus mykiss.

Flavobacterium psychrophilum is an important pathogen in rainbow trout Oncorhynchus mykiss. The portal of entry for F. psychrophilum is not well known. In this study, the role of the intestine as a colonization site for F. psychrophilum was determined. For this purpose, the ability of a high (Dubois) and a low (99/10A) virulence strain of F. psychrophilum to adhere to intestinal explants of rainbow trout was evaluated. After incubation, samples of the gut were examined bacteriologically, histologically and by electron microscopy. The number of gut-associated F. psychrophilum bacteria was significantly higher for the Dubois than for the 99/10A strain. Histological samples clearly showed numerous bacteria of the high virulence strain associated with the intestinal tissue as opposed to only a few bacteria of the low virulence strain. Additionally, extensive exfoliation of intestinal epithelium was noted after incubation with the high virulence strain, but less with the low virulence strain. These findings were confirmed using scanning electron microscopy and suggest that the intestinal epithelium might represent an important site for colonization of the F. psychrophilum strain and may act as a portal of entry for high virulence F. psychrophilum.

Animals↗

PubMed2002

Oral immunisation of pigs with fimbrial antigens of enterotoxigenic E. coli: an interesting model to study mucosal immune mechanisms.

The intestinal mucosal immune system can discriminate actively between harmful pathogenic agents and harmless food antigens resulting in different immune responses namely IgA production and oral tolerance, respectively. Recently, a pig model has been developed for studying intestinal mucosal immune responses in which F4 fimbrial antigens of enterotoxigenic Escherichia coli (F4 ETEC) are used as oral antigens. A unique feature of this model is that soluble F4 antigens can be administered to pigs which have a receptor for this fimbriae (F4R(+)) on their small intestinal villous enterocytes and pigs which do not have this receptor (F4R(-)). Oral administration of F4 to the F4R(+) pigs results in an intestinal mucosal immune response that completely protects the pigs against a challenge infection. In F4R(-) pigs such an intestinal mucosal immune response does not occur. However, a priming of the systemic immune system can be seen similar to the priming in pigs fed with the same dose of a food antigen, suggesting that F4 in F4R(-) pigs behaves as a food antigen. The fact that different mucosal immune responses can be induced with soluble F4, makes it an interesting model to study mucosal immune mechanisms in the pig.

Administration, Oral↗

PubMed2002

Immunohistochemical detection of androgen receptors in the canine uterus throughout the estrus cycle.

Serum androgen levels in the bitch increase during proestrus and remain elevated until metestrus. To find out whether androgens can have a direct impact on the canine uterus, androgen receptors (AR) were identified immunohistochemically in uterine tissue. Androgen receptor distribution in the uterine horns, body and cervix was described during different cycle stages, during pregnancy and in the postpartum period. Nuclear staining for AR was observed in cells of the surface epithelium, glandular ducts, basal glands and stroma of the endometrium, and in myometrial smooth muscle cells. In addition, cytoplasmic staining was observed in epithelial cells from proestrus to early metestrus, when the cells were secretory active, and in stroma cells during pregnancy, suggesting a role for androgens in decidualization. During pregnancy and in the postpartum period nuclear staining for AR was nearly absent. During the estrus cycle stroma cells stained with higher intensities for AR than epithelial cells, supporting the idea that stroma cells mediate some effects of steroid hormones on epithelial cells in the genital tract. In contrast with earlier findings on estrogen receptor-alpha and progesterone receptors, no significant changes in androgen receptor expression were observed during the estrus cycle. Few correlations were found between the staining for AR and serum levels of the sex steroids. The present findings suggest that there is a basal expression of AR in the canine uterus throughout the estrus cycle that may not be influenced by sex steroid hormones.

Androgens↗

PubMed2002

F4 receptor-independent priming of the systemic immune system of pigs by low oral doses of F4 fimbriae.

Oral administration of F4 fimbriae of Escherichia coli induces intestinal mucosal immune responses in F4 receptor-positive (F4R(+)) pigs, but not in F4R(-) pigs. We examined whether F4 fimbriae in F4R(-) animals behave like a food antigen and can induce oral tolerance. Therefore, F4R(+) and F4R(-) pigs were fed 2mg of F4 and challenged i.m. to evaluate the effect of oral F4 on the systemic immune system. As control antigen, two different oral doses (2 and 600 mg) of OVA were used. Thirty days after the i.m. OVA challenge, the OVA-specific serum IgG titre in 600 mg-fed pigs was lower than that in non-fed animals, indicating that tolerance was induced. Conversely, in the 2mg-fed pigs a rapid increase of OVA-specific IgG with higher titres than those in non-fed pigs was seen following challenge, indicating a priming of the systemic immune system. A similar priming was seen in both F4-fed F4R(-) and F4R(+) pigs. Upon challenge, non-fed pigs displayed a primary immune response with a slow increase of F4-specific serum IgG, whereas F4-fed F4R(-) and F4R(+) pigs showed secondary responses with a rapid increase of serum IgG. This was expected in F4R(+) pigs, as in these animals oral F4 induces F4-specific antibody-secreting cells in the spleen, suggesting a priming of the systemic immune system. However, also the F4-fed F4R(-) pigs displayed a secondary response, despite the failure to detect a response upon oral F4 administration. These findings suggest that the F4 antigen, at a dose of 2 mg, behaves like a common food antigen in F4R(-) pigs, namely it induces a systemic priming.

Animals↗

PubMed2002

Immunolocalization of sex steroid hormone receptors in canine vaginal and vulvar tissue and their relation to sex steroid hormone concentrations.

The aim of this immunohistochemical study was to describe the cellular distribution of the estrogen receptor-alpha (ERalpha), progesterone receptor (PR) and androgen receptor (AR) in canine vaginal and vulvar tissue. Samples were taken from dogs in different stages of the estrous cycle. Nuclear staining for ERalpha, PR and AR was observed in surface epithelium, stromal and smooth muscle cells. Receptors were also expressed in vulvar skin. Cytoplasmic staining for AR was observed in basal and parabasal cell layers of vulvar and vaginal epithelium. For all three receptors, staining intensity was generally higher in stromal cells compared with epithelial cells, suggesting that stromal cells may be more receptive to steroid hormone action. Therefore, as in other tissues of the female genital tract, stromal-epithelial interactions induced by sex steroid hormones may be of importance in canine vaginal and vulvar tissues. No cyclic changes in receptor immunostaining were observed. Significant positive correlations were found between receptor immunostaining in some vaginal and vulvar cell groups and the serum concentrations of estradiol-17beta and testosterone, but not with the serum progesterone concentration. Significant negative correlations were found between ERalpha immunostaining in epithelial and stromal cells of the vagina and the serum estradiol-17beta concentration, suggesting a negative feedback mechanism between estradiol-17beta and its receptor. Both cell types play a role in the differentiation of vaginal epithelium, under the influence of estradiol-17beta.

Animals↗

PubMedDate not supplied

Segmenting two-phoneme syllables: developmental differences in relation with early reading skills.

This study explored developmental differences in children's segmentation skills of VC and CV syllables (e.g., /af/ and /fa/) in relation to their early reading abilities. To this end, we followed a subgroup of Dutch speaking prereaders who participated in, and replicated the segmentation task in first grade, at the outset of phonics reading instruction. Reading abilities were assessed after 6 and 9 months. First, we confirmed that VCs offer an easier context to isolate phonemes than CVs. Second, matching analyses showed that this development from VC to CV segmentation posed comparatively increasing difficulties for poor segmenters. Third, this qualitatively different development was reflected in early reading performance. Our data emphasize the importance of phonetic factors and instruction-based experiences in phonological development.

Awareness↗

PubMedDate not supplied

The misconception of the regression-based discrepancy operationalization in the definition and research of learning disabilities.

In this article, I argue that the regression-based discrepancy method used in the diagnosis of learning disabilities is invalid because it is inconsistent with the underlying underachievement concept of which it is intended to be the operationalization. I mathematically demonstrate that the regression-based discrepancy method largely reflects achievement-specific determinants, thereby defeating its own object of describing aptitude-achievement discrepancies. The implications for research examining the role of intelligence in learning disabilities are outlined.

Aptitude Tests↗

PubMedDate not supplied

Will the real discrepant learning disability please stand up?

Willson and Reynolds (in this issue) challenged my thesis that the regression-based discrepancy method (RDM) is not a valid tool to detect aptitude-achievement discrepancies. In this response, I show that the statistical and theoretical counterarguments of Willson and Reynolds are based on a misreading of the statistical models presented. Furthermore, I demonstrate that the regression adjustment, which is largest for lower correlations, is the direct source of the lack of validity of the RDM procedure. Nevertheless, RDM can be considered a valid method to measure an achievement component that is unrelated to intelligence.

Child↗