Biomedical subjects

S Sys

Publications and source records attributed to S Sys.

6 recordsLinked to original sources

PubMed2002

A stereologic evaluation of glucagon-like peptide-1 (GLP-1) mucosal cells in the small intestine of the developing pig.

Studies that investigate possible developmental changes in gastrointestinal hormones in the pig are sparse and contradictory. Therefore, a quantitative morphological study using stereologic methods on paraffin sections of the different small intestinal regions (cranial and caudal duodenum, jejunum and ileum) of the developing pig (second half of the gestation, neonatal and weaning period) has been conducted. The sections were processed for GLP-1-immunohistochemistry. During the investigated time span, the volume of GLP-1-IR cells increased approximately 40-fold in both the jejunum and ileum, notwithstanding a decrease of their volume density. The ileal small intestinal segment contained the highest volume density of GLP-1-IR cells. In contrast, GLP-1-IR cells were only occasionally encountered in the duodenum. The development-related changes of the investigated parameters coincide with dietary changes and the regional differences are in accordance with functional reports that point to GLP-1 as a gastrointestinal hormone that ediates the 'ileal brake' and stimulates glucose-dependent pancreatic insulin secretion.

Animals↗

PubMed2001

Stereologic description of the changing expression of constitutive nitric oxide synthase and heme oxygenase in the enteric plexuses of the pig small intestine during development.

The similarities between heme oxygenase-2 (HO-2) and nitric oxide synthase (nNOS) and the transient expression of nNOS during development led us to investigate whether both systems are similarly affected by changes that occur during development and by regional differences along the small intestine. By combining NADPH diaphorase histochemistry and HO-2 immunohistochemistry on whole-mount preparations and by using stereologic methods, a qualitative and quantitative description of HO-2 and nNOS expression was obtained. Examinations were carried out on the small intestine of fetal, 1-2-day and 5-6-week-old pigs. In all age groups, three enteric plexuses were distinguished. The presence of HO-2-immunoreactive (HO-2-IR) and NADPH diaphorase-positive neurons corresponded to earlier morphological and physiological reports. Nevertheless, the total number of nitrergic neurons remained constant or decreased in the enteric plexuses, whereas the total number of HO-2-IR neurons displayed an overall increase. Changing concentrations of glucocorticoids, target-derived signals, presynaptic input, and an effect of HO-2 activity on nNOS synthesis are likely to play roles in the observed developmental changes. The numerical density of HO-2-IR neurons remained relatively constant along the intestinal tract; in contrast, the nitrergic neurons were most numerous in the inner submucous and myenteric plexus in the duodenum and ileum, respectively. It is believed that the duodenal nitrergic neurons in the inner submucous plexus could be involved in the regulation of duodenal secretion processes, whereas the region-dependent density in the myenteric plexus possibly forms the morphological basis for a regionally different participation of NO in the relaxation of the small intestine.

Age Factors↗

PubMed2001

Developmental changes in heme-oxygenase-2 and bNOS expression in enteric neurons in the pig duodenum.

There exists much parallelism between carbon monoxide- and nitric oxide-generating systems. Therefore, we wondered whether developmental and functional differences along the duodenum similarly affect, part of them, namely, heme oxygenase-2-(HO-2) and neural isoform of nitric oxide synthase- (nNOS) expressing neurons. By applying NADPH diaphorase histochemistry and HO-2 immunohistochemistry on whole-mount preparations and by using stereologic methods, a qualitative and quantitative description of HO-2 and nNOS expression was obtained. Examinations were carried out on the duodenum of fetal, neonatal and weaned pigs. At all ages, three enteric plexuses were readily distinguished. The presence of both enzymes fits in with other morphological and physiological reports. However, the expression of both enzymes significantly changed during development. The number of HO-2-IR neurons increased approximately 20-fold in the inner submucous and almost doubled in the myenteric plexus. In addition, the number of nNOS-expressing neurons displayed a significant decrease in the outer submucous plexus after weaning. High levels of glucocorticoids may cause the perinatally increased HO-2 expression, whereas an influence on nNOS expression is doubtful. Therefore, it seems that notwithstanding the high similarity between both systems, their expression is regulated differently in the pig duodenum.

Animals↗

PubMed2001

Phosphorylation-dependent alteration in myofilament ca2+ sensitivity but normal mitochondrial function in septic heart.

The subcellular mechanisms responsible for myocardial depression during sepsis remain unclear. Recent data suggest a role for impaired energy generation and utilization, resulting in altered contractile function. Here, we studied the energetic and mechanical properties of skinned fibers isolated from rabbit ventricle in a nonlethal but hypotensive model of endotoxemia. Thirty-six hours after lipopolysaccharide (LPS) injection (in the presence of altered myocardial contractility), mitochondrial respiration, coupling between oxidation and phosphorylation, and creatine kinase function were similar in preparations from endotoxemic (LPS) and control animals. The maximal Ca2+-activated force was similar in LPS and control preparations. However, the Ca2+ concentration corresponding to half-maximal force (pCa50, where pCa = -log10[Ca2+]) was 5.55 +/- 0.01 (n = 11) in LPS fibers versus 5.61 +/- 0.01 (n = 10) in control fibers (p < 0.01). Both protein kinase A (PKA) and alkaline phosphatase treatment led to the disappearance in the difference between control and LPS pCa50 values. Incubation of control fibers with the nitric oxide donor S-nitroso-N-acetylpenicillamine (SNAP) did not change the Ca2+ sensitivity after subsequent skinning, whereas isoproterenol decreased pCa50 from 5.62 +/- 0.01 to 5.55 +/- 0.01 (p < 0.01). These data suggest that during sepsis, cardiac mitochondrial and creatine kinase systems remain unaltered, whereas protein phosphorylation decreases myofibrillar Ca2+ sensitivity and may contribute to the depression of cardiac contractility.

Actin Cytoskeleton↗

PubMed1998

Nitric oxide synthase expression in enteric neurons during development in the pig duodenum.

The expression of the constitutive neural isoform of nitric oxide synthase (bNOS) is dynamic and thus forms an ideal parameter to evaluate whether development and region affect the enteric nervous system. By applying NADPH-diaphorase histochemistry on whole-mount preparations of the myenteric and submucosal plexuses and by using the 'unbiased counting frame', a qualitative and quantitative description of bNOS-expression in enteric neurons in the pig duodenum in various developmental stage and region was obtained. Examinations were carried out on the oral and aboral duodenum of fetal pigs from the second half of gestation, of 1-2-day-old pigs and of 6-8-week-old pigs. In the pig duodenum, three enteric plexuses were readily distinguished: the inner submucous, the outer submucous and the myenteric plexuses. All three plexuses already harboured, to different degrees, bNOS-expressing neurons at midgestation. Although the enteric nervous system was present at midgestation, the enteric neurons had not yet reached their adult phenotype and morphology. During gestation, the number of inner submucous bNOS-expressing neurons increased approximately 50-fold, whereas after birth that number fell to about 10% of the prenatal value. During further postnatal development it returned to prenatal values. In addition, the number of bNOS-expressing myenteric neurons doubled postnatally. These changes favour a role for NO in mediating the development of enteric neurons and point to a greater necessity for inhibitory innervation in the adult pig as compared with the fetal pig. Furthermore, the number of bNOS-expressing outer submucosal and myenteric neurons was significantly higher in the oral duodenal segment compared with the aboral duodenal segment. This regional difference suggests that the oral duodenal segment is more prominently involved in the regulation of NO-mediated gastrointestinal processes than the aboral one. The developmentally and regionally dependent bNOS-expression can be explained by shifts and differences in the balanced system of hormones, presynaptic input and target-derived signals that affects neurotransmitter expression.

Age Factors↗

PubMed1998

Optimal parameters for transurethral intravesical electrostimulation determined in an experiment in the rat.

OBJECTIVE: Parameters of current for transurethral intravesical electrostimulation (IVES) are studied in the rat to determine the settings which elicit optimal detrusor contractions. Action mechanisms related to the induction of detrusor contractions upon ives are also investigated. METHODS: In 24 female Wistar rats transurethral IVES was performed using 95 combinations of different pulse durations and frequencies. The reference electrode was positioned in the bladder, in the urethra, or on the abdominal wall. RESULTS AND CONCLUSIONS: The optimal detrusor contractions are induced in the rat with a current of 10 Hz frequency and 20 ms pulse duration. A mathematical correlation is found between frequency and pulse duration which permits to determine the best combination. Evidence for the existence of local factors inducing detrusor contractions by IVES is given. The detrusor contractions proved independent of the position of the reference electrode.

Animals↗