Biomedical subjects

L Van Nassauw

Publications and source records attributed to L Van Nassauw.

At least 19 recordsLinked to original sources

PubMed2006

Acute distal colitis impairs gastric emptying in rats via an extrinsic neuronal reflex pathway involving the pelvic nerve.

BACKGROUND AND AIMS: Patients with inflammatory bowel disease often present with abnormal gut motility away from the inflammatory site. We studied remote motility disturbances and their pathophysiology in a rat model of colitis. METHODS: Colitis was induced 72 h prior to experiments using trinitrobenzene sulphate (TNBS) instillation. Inflammation was verified using histology and myeloperoxidase (MPO) measurements. To assess gut motility, we determined gastric emptying, distal front and geometric centre (GC) of intestinal transit 30 min after intragastric administration of a semiliquid Evans blue solution. The effects of hexamethonium (20 mg/kg), capsaicin (125 mg/kg) and pelvic nerve section on colitis induced motility changes were evaluated. c-Fos expression was studied in the pelvic nerve dorsal root ganglion (DRG) S1. RESULTS: Colitis reduced gastric emptying from 38.4 (3.6)% in controls to 22.7 (4.4)% in TNBS treated rats in the absence of local gastric inflammation. Colitis had no effect on the distal front or on the geometric centre of small intestinal transit. Hexamethonium reduced gastric emptying in controls to 26.3 (4.1)% but restored it to 35.8 (4.4)% in TNBS treated rats. Capsaicin significantly impaired gastric emptying in controls from 33.1 (5.2)% to 9.5 (3.3)% while this effect was less pronounced in TNBS treated rats (from 19.2 (2.3)% to 11.5 (3.8)%; NS). In TNBS treated rats, pelvic nerve section completely restored gastric emptying from 19.8 (5.3)% to 52.5 (6.3)% without any effect on gastric emptying in control rats. TNBS colitis induced de novo c-Fos expression in the DRG S1. CONCLUSIONS: Experimental colitis in rats delays gastric emptying via a neuronal pathway involving pelvic afferent nerve hyperactivity.

Acute Disease↗

PubMed2004

In vitro activation of murine DRG neurons by CGRP-mediated mucosal mast cell degranulation.

Upregulation of CGRP-immunoreactive (IR) primary afferent nerve fibers accompanied by mastocytosis is characteristic for the Schistosoma mansoni-infected murine ileum. These mucosal mast cells (MMC) and CGRP-IR fibers, which originate from dorsal root (DRG) and nodose ganglia, are found in close apposition. We examined interactions between primary cultured MMC and CGRP-IR DRG neurons in vitro by confocal recording of intracellular Ca(2+) concentration ([Ca(2+)](i)). The degranulatory EC(50) for the mast cell secretagogue compound 48/80 (C48/80; 10 microg/ml) and the neuropeptides CGRP (2.10(-8) M) and substance P (SP; 3.10(-8) M) were determined by measurement of extracellular release of the granule chymase, mouse mast cell protease-1. Application of C48/80 (10 microg/ml) and CGRP and SP (both 10(-7) M) to Fluo-4-loaded MMC induced a transient rise in [Ca(2+)](i) after a lag time, indicative of mast cell degranulation and/or secretion. The CGRP response could be completely blocked by pertussis toxin (2 microg/ml), indicating involvement of G(i) proteins. Application of MMC juice, obtained by C48/80 degranulation of MMC, to Fluo-4-loaded DRG neurons induced in all neurons a rise in [Ca(2+)](i), indicative of activation. Degranulation of MMC by C48/80 in culture dishes containing Fluo-4-loaded DRG neurons also caused activation of the DRG neurons. In conclusion, these results demonstrate a bidirectional cross-talk between cultured MMC and CGRP-IR DRG neurons in vitro. This indicates that such a communication may be the functional relevance for the close apposition between MMC and CGRP-IR nerve fibers in vivo.

Animals↗

PubMed2003

Effects of Schistosoma mansoni infection on somatostatin and somatostatin receptor 2A expression in mouse ileum.

Intestinal schistosomiasis is accompanied by motility-related dysfunctions but the underlying mechanisms are not well-known. Therefore, the presence and effects on intestinal contractility of somatostatin (SOM) and its receptor, SSTR2A, were investigated in the ileum of normal and infected mice. The distribution of SOM and SSTR2A was visualized using immunocytochemistry. Radioimmunoassay combined with oogram studies was performed to determine SOM levels and contractility measurements were determined in organ bath experiments. Schistosomiasis resulted in a significant decrease in somatostatin-positive endocrine cells, whereas the number of somatostatin-immunoreactive (IR) neuronal cell bodies did not change. From 8 weeks postinfection onwards, an increase was noted in somatostatin-IR nerve fibres in both villi and granulomas. The staining intensity for SSTR2A, expressed in somatostatin-negative myenteric cholinergic neurones, increased during infection suggesting an upregulation of this receptor. SOM levels were negatively correlated with the number of eggs during the acute phase, and were elevated during the chronic phase. Pharmacological experiments revealed that schistosomiasis diminished the inhibitory effect of SOM on neurogenic contractions. We can conclude that schistosomiasis influences the distribution and expression levels of SOM and SSTR2A in the murine ileum, which might explain the changed motility pattern.

Adrenergic Fibers↗

PubMed2001

Role of reactive nitrogen species in neuronal cell damage during intestinal schistosomiasis.

Free radicals are known to be involved in the host reaction during Schistosoma mansoni-induced inflammation in the liver and the intestine. In the present study, the influence of reactive nitrogen species (RNS) on the enteric neurons of infected ileum of mice was investigated. Cryosections and whole-mounts of the ileum of control, and 8- and 15-week-infected mice were processed for immunohistochemical localization of 3-nitrotyrosine, a biomarker of RNS, and of active caspase-3, a key executioner of apoptosis. An antibody directed against protein gene product 9.5 or S100 protein was used as a marker for neurons or enteroglial cells. In infected mice, but not in control animals, 3-nitrotyrosine was detected in parasite eggs and, as revealed by double immunolabelling, in some neuronal and enteroglial cells. Quantitative analysis of whole-mounts showed that the percentage of 3-nitrotyrosine-immunoreactive neurons significantly increased with time in both the submucous and myenteric plexus. Caspase-3 immunoreactivity was predominantly found in parasite eggs in infected mice. Immunoreactive enteric neurons were occasionally observed. The results indicate that inflammation-induced RNS are present in the ileum of S. mansoni-infected mice, and participate in the elimination of the schistosome eggs causing damage in a significant number of enteric neurons. However, neuronal cell death appears to be a rare phenomenon in the schistosome-infected mouse ileum.

Animals↗

PubMed2000

Avian junctional endoblast has strong embryo-inducing and -dominating potencies.

In the present study, we demonstrate that quail junctional endoblast fragments have powerful embryo-inducing potencies when placed on the deep side of the upper layer (UL) of the anti-sickle region of unincubated chicken blastoderms. Moreover, in most cases the inducing potencies of the autochthonous Rauber's sickle-endophyll complex were inhibited at distance. Also, junctional endoblast still in situ in an early streak embryo strongly inhibits the inducing capacities of a Rauber's sickle - endophyll complex apposed on the deep side of the upper layer of the cranial part of the area pellucida. So junctional endoblast, besides embryo inducing potencies also seems to dominate and to inhibit at distance the gastrulation potencies of an ectopically placed or autochthonous Rauber's sickle - endophyll complex.

Animals↗

PubMed2000

Localisation of epidermal growth factor receptor in the quail ovary.

The present study focuses on the distribution of EGFR in the follicular and stromal compartments of the Japanese quail (Coturnix coturnix japonica) ovary, using immunohistochemical methods and a histological ligand binding assay. EGFR was predominantly present in granulosa cells during each stage of the folliculogenesis. Furthermore, EGFR was also detected in thecal cells and in oocytes. In some cells of the vascular endothelium, of the ovarian smooth muscle, and of the surface epithelium, the presence of EGFR was detected as well. The presence of EGFR allows to formulate the hypothesis that EGFR-ligands are involved in the autocrine and/or paracrine regulation of oocyte maturation and of folliculogenesis in the quail, and possibly in all birds.

Animals↗

PubMed1999

Distribution of apoptosis-related proteins in the quail ovary during folliculogenesis: BCL-2, BAX and CPP32.

It is suggested that follicular apoptosis is driven by the status of the BCL-2: BAX rheostat, and that CPP32 is a key effector of granulosa cell death. In the present study, we have immunohistochemically localized two BCL-2 family members, BCL-2 and BAX, and one caspase, CPP32, in the quail ovary during folliculogenesis. BCL-2 was predominantly found in the granulosa cells of developing follicles. BAX was detected in some follicular cells of atretic follicles, and in the nucleus of some prelampbrush oocytes. Expression of CPP32 was detected in leukocytes and in follicular cells of atretic follicles. Immunostaining was also found in interstitial cells, in surface epithelial and vascular endothelial cells, and in some thecal cells of post-ovulatory follicles. In the granulosa cells of non-growing and small prehierarchal follicles, a weak immunostaining was observed. We can conclude that in the avian ovary, BAX and CPP32 are involved in atresia. The present results support the BCL-2: BAX rheostat hypothesis.

Animals↗

PubMed1998

Histochemical demonstration of apoptotic cells in the chicken embryo using annexin V.

This study describes the use of biotinylated annexin V for the histochemical detection of apoptotic cells in cultured chicken embryos during gastrulation. This method is based on the Ca2+-dependent binding of annexin V to phosphatidylserine, a negatively charged phospholipid, located at the inner leaflet of the cell membrane in living cells. However, in the early stages of apoptosis, phosphatidylserine is translocated to the outer layer of the cell membrane and can then be recognized by annexin V. Applying this method in cultured chicken embryos during gastrulation, we obtained labelling of apoptotic cells in the three germ layers. In the epiblast and mesoblast, labelling was predominantly present in the region lateral to the primitive streak. At the level of the germinal crescent, labelled cells were also found in the epiblast. Labelled cells in the deep layer, which is a heterogeneous tissue layer composed of endophyll, sickle endoblast and definitive endoblast, were rather scarce. The distribution of cells, as observed in this study after labelling with annexin V in light microscopy and confocal laser scanning microscopy, is consistent with distributions reported by other authors using other approaches and with our previous observations made with the TUNEL technique and by electron microscopy after fixation in a tannic acid-based fixative. The main advantages of this method over other more sophisticated methods is its easiness and rapidity of execution and the fact that both early and late stages of apoptosis are detected.

Animals↗

PubMed1998

Induction of (pre) gastrulation and/or (pre) neurulation by subgerminal ooplasm and Rauber's sickle in cultured anti-sickle regions of avian unincubated blastoderms.

Rauber's sickle fragments from unincubated quail blastoderms, associated or not with chicken central subgerminal ooplasm, were placed on the deep side of the upper layer (UL) of the isolated anti-sickle region of unincubated chicken blastoderms and cultured in vitro. When only a Rauber's sickle fragment was placed, we observed always a pronounced thickening of the UL (pregastrulation) in the immediate neighbourhood. Some times a primitive streak (PS) developed. When the Rauber's sickle fragment was "sandwiched" between the UL and a central subgerminal ooplasmic mass [containing the nucleus of Pander (1817)], always a (pre)neural plate accompanied by endophyll developed, not or well associated with a primitive streak. In the latter case a complete miniature embryo developed. De novo formation of endophyll was observed. As it contained quail nuclei it was derived from Rauber's sickle cells which colonized the subgerminal ooplasm. Our experiments indicate that the uncommitted upper layer (UL) of the anti-sickle of unincubated blastoderms constitutes an excellent reactor tissue for inductions. The thickening induced in the UL of the anti-sickle region by Rauber's sickle initiates (pre)gastrulation and the thickening induced by endophyll initiates (pre)neurulation. In the beginning, pregastrulation and preneurulation seem to be independent phenomena. It is only later, when both become correctly linked at the right place and time, that a normal embryo will develop.

Animals↗

PubMed1996

Immunohistochemical localization of transforming growth factor-beta 1 beta 2 during folliculogenesis in the quail ovary.

Immunohistochemical methods were used to show the presence and distribution of transforming growth factor-beta 1 and beta 2 during folliculogenesis in quail ovarian tissues. The results indicated that both transforming growth factor-beta subtypes are present. Immunolabelling for transforming growth factor-beta 1 demonstrated that prelampbrush oocytes are immunoreactive in the Balbiani complex, and developing and pre-ovulatory oocytes in the zona radiata. Immunolabelling was also associated with granulosa cells. The number of stained granulosa cells decreased during folliculogenesis. In the pre-ovulatory follicles, immunolabelling was found predominantly in the theca interna. Immunolabelling for transforming growth factor-beta 2 was associated with the zona radiata of developing and pre-ovulatory follicles, and with stromal interstitial cells. Moderate immunoreactivity was found in the Balbiani complex of prelampbrush oocytes. Weak immunolabelling was localized in the granulosa cells of prelampbrush follicles, and in a few cells of the theca interna of pre-ovulatory follicles. The immunolocalization of transforming growth factor-beta 1 and -beta 2 in the quail ovary supports their autocrine and/or paracrine role in avian ovarian processes.

Animals↗

PubMed1996

Localization of apoptotic cells by direct immunogold detection of digoxigenin-labeled genomic DNA in semithin sections.

In this study, which correlates apoptosis with avian ovarian physiology, we modified an in situ DNA nick end-labeling method using immunogold reagents to detect apoptotic cells in semithin sections of quail ovaries embedded in glycol methacrylate resin. Special attention was paid to the prevention of background staining. The results are comparable with those of the ApopTag peroxidase kit in paraffin-embedded ovaries.

Animals↗

PubMed1995

Immunohistochemical localization of epidermal growth factor in the ovary of the adult Japanese quail.

The present study focuses on the immunohistochemical localization of epidermal growth factor in the ovary of the adult Japanese quail. Immunoreactivity was predominantly found in the smooth muscle cells of blood vessels and of chordae, in granulosa cells of pre-lampbrush follicles, in interstitial cells, in the Balbiani complex of pre-lampbrush oocytes, and in ganglia. In developing follicles, immunoreactivity was also detected in some granulosa and thecal cells, in the zona radiata, and especially in cell clusters localized in the thecal periphery. The number of immunostained cells in the granulosa decreased during folliculogenesis, and increased after ovulation. In the ooplasm of oocytes, immunoreactivity was shifted from the Balbiani complex to the zona radiata during development. These observations support the hypothesis that epidermal growth factors acts primarily on less differentiated follicles. It is also suggested that epidermal growth factor can modulate ovarian contractility. Finally, in one ovary, we detected immunostained bodies in the ooplasm of small developing oocytes.

Animals↗

PubMed1995

Persistence after hypothalamectomy of a tamoxifen-like effect in the ovary of quail embryos exposed cyclically in ovo to low incubation temperatures.

Three days old quail embryos were hypothalamectomized in ovo by the decapitation technique according to Callebaut (1993). Half of these embryos was exposed to day cyclically repeated prolonged low subnormal incubation temperatures (25 degrees C). The other half of these decapitated embryos was normally continuously incubated. As is the case for not decapitated embryos the ovaries of the first group presented a tamoxifen like effect: cortical rim atrophy with proportional hypertrophy of the medulla and a pronounced decrease in the number of oogonia and oocytes. By contrast the ovaries of the second group of decapitated embryos presented a normal aspect without sterilization of the ovigerous sex cords. It was concluded that: 1. the hypophysis, the hypothalamus or other prosencephalic tissues play no intermediary role in the establishment of a tamoxifen like effect in the ovary; 2. the early embryonic development of the quail ovary during the considered period takes place without the intervention of the hypothalamus.

Animals↗

PubMed1993

Microinjection of antifibronectin antibodies in the chicken blastoderm: inhibition of mesoblast cell migration but not of cell ingression at the primitive streak.

The involvement of fibronectin in adhesion and migration of individual mesoblast cells during chicken gastrulation was examined after microinjection of functional and nonfunctional antifibronectin antibodies in the blastoderm during the period of rapid migration of mesoblast cells. The injection of affinity-purified polyclonal antihuman fibronectin antibody (total IgG or Fab fragment) or of monoclonal antichicken cellular fibronectin caused a thickening of the primitive streak, which was composed of loosely connected cells. This effect was most evident at the level of Hensen's node, and very few mesoblast cells were observed migrating in the space between upper layer and deep layer. The obvious explanation of this effect was that the de-epithelialization of upper layer cells persisted in the presence of antibodies, but ingressed cells failed to emigrate from the primitive streak. Immunostaining of microinjected antibodies showed binding to the basement membrane, to the cell surface of mesoblast cells that had migrated before microinjection occurred, and to the cell surface of deep layer cells. Cells that ingressed and detached in the course of reincubation of the embryo possessed little immunolabelling along their cell surface. The results suggest that the failure of ingressed cells to emigrate from the primitive streak and to form mesoblast was due (1) to alterations in adhesion between newly ingressed primitive streak cells, which had the ability to detach but possessed relatively little fibronectin along their cell surfaces and a small number of cell protrusions, and (2) probably to a lack of adhesion of detached cells to the basement membrane, which was blocked by the presence of antifibronectin antibodies. We conclude that the presence of fibronectin in the basement membrane is required for emigration of ingressed cells and migration of mesoblast cells to occur. Once migration has commenced, fibronectin is also deposited along the cell surface of migrating cells, a factor that may increase their mutual adhesion.

Animals↗

PubMed1993

In vitro study of the contractility of the wall of the preovulatory follicle in the Japanese quail.

In the present study, we examined in vitro the potassium-induced contractions of isolated parts of the wall of the quail preovulatory follicle through use of an electromagnetic force-length transducer system. We studied longitudinal and transverse strips of the whole wall, of the theca, and of the outer layer (tunica albuginea and surface epithelium). It was observed that force development and shortening of strips of the whole wall and those of the theca are similar. Statistical analysis of maximal isometric force, peak shortening length, and percentage of reduction of follicular volume showed that the orientation of strips is without importance. Results from different orientations were pooled, and the different layers were compared statistically. The general result of this analysis was that the contractile activity of the outer layer was significantly lower than the performance of either the whole wall or the theca. We concluded that contraction of the follicular wall is mainly dependent on the contractile activity of the theca externa. This contractile system is comparable to that of mammals. We suggest that the main function of the theca externa during ovulation is to maintain a constant intrafollicular pressure.

Animals↗

PubMed1992

Smooth muscle cells in the walls of ovarian follicles in the Japanese quail.

The walls of pre-ovulatory follicles of the Japanese quail were examined at the ultrastructural level for the presence of cells displaying the typical morphological features of smooth muscle cells. These characteristics were found in the cells of the chordae, the tunica albuginea, and the theca externa. Small, elongated cells, containing microfilaments, were observed in the theca of prelampbrush follicles localized in the ovarian cortex. These thecal cells were considered as the putative precursors of the thecal smooth muscle cells of the pre-ovulatory follicle. The difference between the smooth muscle cells of the pre-ovulatory follicle and those in the wall of the most recent post-ovulatory follicle is the contracted state of the latter, which is most evident in the cells of the theca externa. It can be concluded that the cells of the theca externa are smooth muscle cells which are mainly contracted during the ovulatory process. A comparison was made with other vertebrate species.

Animals↗

PubMed1992

Immunolocalization of smooth muscle-like cells in the quail ovary.

We localized alpha-smooth muscle actin (alpha-SMA) in the quail ovary, using the peroxidase-anti-peroxidase technique. Special attention was paid to the influence of fixation on the immunoreactivity of the antigen. The immunostaining of alpha-SMA largely depended on the nature of the fixative. The antigen could most successfully be localized in ovaries fixed in Carnoy's fluid. We also localized alpha-SMA and desmin in semi-thin glycol methacrylate sections of the pre-ovulatory follicle, using the immunogold-silver staining method. The sections were pretreated with Lugol's iodine or sodium metaperiodate to enhance the immunoreactivity. alpha-SMA was demonstrated in the cells of the chordae, the tunica albuginea, and the theca externa of each follicle. These structures were inter-connected, forming an ovarian suspensory apparatus. The thecal cells of prelampbrush follicles also expressed alpha-SMA. In the wall of the pre-ovulatory follicle, desmin was found in the cells of the chordae and the tunica albuginea, and in a few cells of the theca externa. In the theca interna, desmin, and sometimes alpha-SMA, was observed in cells adjacent to the endothelium of sinusoids, which are probably pericytes. Our results support the hypothesis that in birds the ovarian follicles possess a thecal contractile system, that is presumably involved in the ovulatory process.

Actins↗

PubMed1991

Structural and immunohistochemical aspects of the postovulatory follicle in Japanese quail.

In the present study, we searched for the presence of granulosa lipid spheres, of lacunae, and of the smooth-muscle markers desmin and alpha-smooth-muscle actin, in the wall of the POF1 of the quail ovary. Lacunae, using the labelled yolk technique, were visible as large cavities in the POF1 wall. The immunohistochemical localization of desmin was similar to that observed in preovulatory follicles. A similar distribution was observed using an anti-alpha-smooth-muscle actin antiserum, but the cells of the theca externa were also positively stained. The general conclusion was that the studied structures were similarly localized in the follicle wall, before and during the day after ovulation, but that they are more obvious in the POF, due to its general contracted state.

Animals↗