Quantitative analysis of the neurons from the myenteric plexus in the ileum of rats submitted to severe protein deficiency

Association between jejunal remodeling in fasting rats and hypersensitivity of intestinal afferent nerves to mechanical stimulation

Remodeling of Intestinal properties and hypersensitivity of intestinal afferents to mechanical stimulation were previously demonstrated in a fasting rat model. Other studies investigated the association between mechanical and histological remodeling during fasting. This study aimed to further explore the relationship between the jejunal remodeling and intestinal afferent hypersensitivity by combining afferent nerve recordings with histological and mechanical data. Eight male Sprague Dawley rats had no access to food for 7 days (Fasting group). Seven male rats served as controls (Control group). Jejunal segments were studied in vitro in an organ bath for analysis of afferent signaling and for analysis of mechanical and histomorphological parameters. Correlation analyses were done to analyze association between nerve activity (spike rate increase ratio, SRIR) at distension levels of 20, 40 and 80 cmH2O and mechanical stress and histomorphological changes of the jejunal segments. Compared with the Control group, the main findings in jejunal segments in the Fasting group were (1) Most histomorphometry parameters were reduced (P < 0.05-P < 0.001), (2) SRIR values were higher (P < 0.001), (3) The relative numbers of intermuscular and submucosal neurons were increased (P < 0.05-P < 0.01), and (4) SRIR was negatively correlated with intestinal wall thickness, circumferential muscle layer thickness and positively correlated with the inner residual strain, the number of neurons, and the mechanical stress. In conclusion, the fasting-induced histomorphological remodeling (reduced wall thickness and increased relative number of neurons) and biomechanical remodeling (residual strain changes and high stress level) of the intestine in fasting rats were associated with hypersensitivity of intestinal afferents. Afferent hypersensitivity appears to be dependent on stress rather than on strain.

Perinatal exposure to low doses of glyphosate-based herbicide combined with a high-fat diet in adulthood causes changes in the jejunums of mice

AIM

Exposure to pesticides and consumption of high-fat diets are widespread in society. Reports have shown that exposure to glyphosate and a high-fat diet can cause gastrointestinal disorders and increase susceptibility to obesity. Thus, this study evaluated the impacts of perinatal exposure to glyphosate followed by consumption of a high-fat diet in adulthood on the histology and morphometry of jejunums and enteric nervous system of C57BL/6 mice.

MATERIAL AND METHODS

After mating, 20 C57BL/6 female mice were separated into a control group (CG) and a glyphosate group (GLY) that received water with 0.5% glyphosate. After the lactation period, some male offspring were randomly separated into CG-SD and GLY-SD (standard diet) groups or CG-HD and GLY-HD (high-fat diet) groups. After 12 weeks, jejunum samples were collected and submitted to histological analysis.

KEY FINDINGS

Indirect exposure to glyphosate changed the morphometry of the intestinal wall, increased the proportion of intraepithelial lymphocytes (IELs) and goblet cells, and altered the area occupied by collagen fibers. The hyperlipidemic diet hypertrophied the jejunal total wall, total muscular and submucosal layers, decreased IELs, and increased the proportion of goblet cells. GLY-HD mice had shallower crypts, shorter villi, and less goblet cells and IELs than mice from GLY-SD group. GLY-HD also showed an increased number of neurons in myenteric and submucosal plexuses. Groups exposed to glyphosate and/or fed a high-fat diet had atrophied submucosal neurons.

SIGNIFICANCE

This study suggests that perinatal glyphosate exposure combined with a high-fat diet in adulthood increases the risk of jejunum inflammation and dysfunction.

Enteric neuroplasticity in seawater-adapted European eel (Anguilla anguilla)

European eels live most of their lives in freshwater until spawning migration to the Sargasso Sea. During seawater adaptation, eels modify their physiology, and their digestive system adapts to the new environment, drinking salt water to compensate for the continuous water loss. In that period, eels stop feeding until spawning. Thus, the eel represents a unique model to understand the adaptive changes of the enteric nervous system (ENS) to modified salinity and starvation. To this purpose, we assessed and compared the enteric neuronal density in the cranial portion of the intestine of freshwater eels (control), lagoon eels captured in brackish water before their migration to the Sargasso Sea (T0), and starved seawater eels hormonally induced to sexual maturity (T18; 18 weeks of starvation and treatment with standardized carp pituitary extract). Furthermore, we analyzed the modification of intestinal neuronal density of hormonally untreated eels during prolonged starvation (10 weeks) in seawater and freshwater. The density of myenteric (MP) and submucosal plexus (SMP) HuC/D-immunoreactive (Hu-IR) neurons was assessed in wholemount preparations and cryosections. The number of MP and SMP HuC/D-IR neurons progressively increased from the freshwater to the salty water habitat (control > T0 > T18; P < 0.05). Compared with freshwater eels, the number of MP and SMP HuC/D-IR neurons significantly increased (P < 0.05) in the intestine of starved untreated salt water eels. In conclusion, high salinity evokes enteric neuroplasticity as indicated by the increasing number of HuC/D-IR MP and SMP neurons, a mechanism likely contributing to maintaining the body homeostasis of this fish in extreme conditions.

Characterization of the myenteric neuronal population and subpopulation of the duodenum of adult wistar rat fed with hypoproteic chow

The effects of severe protein malnutrition (4%) on myenteric neurons of Wistar rat duodenum, in relation to a standard 22%-protein diet for rodents, were assessed in this study. Segments of the duodenum from 10 rats from each nutritional group were submitted to the elaboration of whole mounts - 5 stained with Giemsa to determine the total population of myenteric neurons and the others stained by a histochemical method to detect nervous cells through the NADPH-diaphorase enzyme activity for studying the subpopulation of nitrergic neurons. The area of 100 neurons per animal, totalizing 2,000 neurons, were randomly measured by using the Image Pro-Plus®software. Malnourished rats presented 34.38% lower body weight and 10.60% duodenum length reduction when compared to the control group. Quantitative analysis demonstrated no significant differences between control and malnourished group by using Giemsa; however, as the organ reduction was not followed by an increase inversely proportional to the density of neurons, the condition imposed suggests the loss of neurons from the total population. Nevertheless, through NADPH-d histochemistry, there was a neuronal density increase for the malnourished group. There was no significant difference between the groups for both techniques with respect to the morphometric analysis of the body cell.

Atrophy and neuron loss: effects of a protein-deficient diet on sympathetic neurons

Protein deficiency is one of the biggest public health problems in the world, accounting for about 30-40% of hospital admissions in developing countries. Nutritional deficiencies lead to alterations in the peripheral nervous system and in the digestive system. Most studies have focused on the effects of protein-deficient diets on the enteric neurons, but not on sympathetic ganglia, which supply extrinsic sympathetic input to the digestive system. Hence, in this study, we investigated whether a protein-restricted diet would affect the quantitative structure of rat coeliac ganglion neurons. Five male Wistar rats (undernourished group) were given a pre- and postnatal hypoproteinic diet receiving 5% casein, whereas the nourished group (n = 5) was fed with 20% casein (normoproteinic diet). Blood tests were carried out on the animals, e.g., glucose, leptin, and triglyceride plasma concentrations. The main structural findings in this study were that a protein-deficient diet (5% casein) caused coeliac ganglion (78%) and coeliac ganglion neurons (24%) to atrophy and led to neuron loss (63%). Therefore, the fall in the total number of coeliac ganglion neurons in protein-restricted rats contrasts strongly with no neuron losses previously described for the enteric neurons of animals subjected to similar protein-restriction diets. Discrepancies between our figures and the data for enteric neurons (using very similar protein-restriction protocols) may be attributable to the counting method used. In light of this, further systematic investigations comparing 2-D and 3-D quantitative methods are warranted to provide even more advanced data on the effects that a protein-deficient diet may exert on sympathetic neurons. (c) 2009 Wiley-Liss, Inc.