Histochemical study of intestinal mucins after administration of silver nanoparticles in Sprague-Dawley rats.

To investigate the effects of silver nanoparticles on the histological structure and properties of the mucosubstances in the intestinal mucosa, Sprague-Dawley rats were divided into four groups (10 rats in each group): vehicle control, low-dose group (30 mg/kg), middle-dose group (300 mg/kg), and high-dose group (1,000 mg/kg), and administered silver nanoparticles (60 nm) for 28 days, following OECD test guideline 407 and using GLP. The control sections contained no silver nanoparticles; however, the treated samples showed luminal and surface particles and the tissue also contained silver nanoparticles. A dose-dependent increased accumulation of silver nanoparticles was observed in the lamina propria in both the small and large intestine, and also in the tip of the upper villi in the ileum and protruding surface of the fold in the colon. The silver nanoparticle-treated rats exhibited higher numbers of goblet cells that had released their mucus granules than the controls, resulting in more mucus materials in the crypt lumen and ileal lumen. Moreover, cell shedding at the tip of the villi was frequent. Lower amounts of neutral and acidic mucins were found in the goblet cells in the silver nanoparticle-treated rats, plus the amount of sialomucins was increased, while the amount of sulfomucins was decreased. In particular, in the colon of the silver nanoparticle-treated rats, sialyated mucins were detected in the lamina propria, the connective tissue under the epithelia. Therefore, the present results suggest that silver nanoparticles induce the discharge of mucus granules and an abnormal mucus composition in the goblet cells in the intestines.

Changes of glycoconjugate expression in nasal respiratory mucosa of rats exposed to welding fumes.

To investigate the effects of welding fumes on the glycoconjugates in nasal respiratory mucosa, male Sprague-Dawley rats were exposed to manual metal arc stainless steel (MMA-SS) welding fumes at a concentration of 56-76 mg/m(3) total suspended particulate for 2 h/day in an inhalation chamber for 90 days. During the exposure period, the experimental animals were sacrificed after 2 h and 15, 30, 60, and 90 days of exposure; then sections were examined using lectin histochemistry. Some remarkable changes, such as destroyed cilia, desquamation and mucification of epithelial cells, and destruction of nasal septal glands, were seen in the welding fume-exposed groups. Specific changes in the lectin binding patterns were also observed in the welding fume-exposed rats. The Ricinus communis agglutinin-I (RCA-I) staining of the cilia and columnar cells increased slightly when compared with the unexposed rats. The RCA-I and Ulex europaeus agglutinin-I (UEA-I) staining of the goblet cells also increased as the exposure continued. The mucigenous epithelial cells reacted with Bandeiraea simplicifolia lectin-I (BSL-I), RCA-I, and succinylated wheat germ agglutinin A (sWGA) after 15 days of exposure, which was not visible in the control group. The dorsal septal glands exhibited an affinity with peanut agglutinin (PNA), BSL-I, and RCA-I, which was also not visible in the control group. The affinity for Dolichos biflorus agglutinin (DBA), soybean agglutinin (SBA), PNA, sWGA, BSL-I, and UEA-I in the ventral septal glands of the welding fume-exposed groups tended to increase, whereas the concanavalin A (Con A) reactivity in the dorsal septal glands decreased slightly. In conclusion, it was assumed that the changes in the glycoconjugate residues in the nasal respiratory mucosa of the welding fume-exposed rats represented important components of defense mechanisms against the toxicants in the welding fumes.

Effects of repeated welding fumes exposure on the histological structure and mucins of nasal respiratory mucosa in rats.

To investigate the effects of welding fumes on the histological structure and properties of mucins of the nasal respiratory mucosa, Sprague-Dawley rats were exposed to manual metal arc-stainless steel (MMA-SS) welding fumes at a concentration of 56-76 mg/m3 total suspended particulates for 2 h per day in an inhalation chamber for 90 days. Experimental animals were sacrificed at 2 h, 15, 30, 60 and 90 days after exposure. Loss of cilia, desquamation of epithelial cells, mucigenous epithelial cells and destruction of nasal septal glands were observed frequently in the welding fumes-exposed groups. These changes became more severe as the exposure continued. The amount of neutral mucins in goblet cells in the welding fumes-exposed group had a tendency to increase, the amount of sulfomucins decreased, while the sialomucins increased as the exposure continued. Mucinogenic epithelial cells, not visible in the control group, contained minimal to small amounts of neutral mucins. In the dorsal septal glands, neutral mucins not visible in the control group appeared, and neutral mucins in the ventral septal glands increased slightly. These results indicate that the observed changes in the properties of mucins due to inhalation of welding fumes may play roles in protection against toxicants.

Effects of electroacupuncture with different frequencies on spinal ionotropic glutamate receptor expression in complete Freund's adjuvant-injected rat.

We investigated expressional changes of spinal glutamate receptors by electroacupuncture (EA) in an inflammatory animal model. Inflammation was induced by an intraplantar injection of complete Freund's adjuvant (CFA) into the hindpaw of male Sprague-Dawley rats. Bilateral EA stimulation at 2, 15 and 120 Hz was applied at those acupoints corresponding to Zusanli and Sanyinjiao in man using needles with 3-day intervals for 30 days. Paw edema and mechanical thresholds were measured by a water displacement plethysmometer and Analgesy-Meter, respectively. Edema and mechanical sensitivity of the hindpaw induced by CFA-injection were strongly inhibited by EA stimulation. At 30 days after CFA-injection, effects of EA on ionotropic glutamate receptor (NR-1, NR-2A, GluR-1 and GluR-2/3) expression in association with c-fos and calcitonin gene-related peptide (CGRP) expression were observed in the dorsal horn of the spinal cord using immunohistochemistry. The number of c-fos-like immunostained cells was decreased significantly in the superficial laminae of the dorsal horn by 2Hz EA, but CGRP expression also showed a marked decrease in the same region using the other types of EA stimulation. N-methyl-D-aspartate receptor (NR-1 and NR-2A) expression was attenuated in all regions of the dorsal horn by all types of EA. Of the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor (GluR-1 and -2/3), only GluR-1 expression was prevented by EA treatment in the superficial laminae and the neck of the dorsal horn. It is concluded that EA treatment can attenuate inflammatory edema and mechanical thresholds in CFA-injected rats through modulating expression of ionotropic glutamate receptors, and especially N-methyl-D-aspartate receptors, in the dorsal horn of the spinal cord.

Glycoconjugates of the gastric mucosa in cold-treated chipmunks.

During seasonal hibernation, there is reduced gastrointestinal activity, but relatively little is known of the physiology involved. In the present experimental study, male Korean chipmunks (Tamias sibiricus barberi) were maintained in cold conditions (6 degrees C) for 3, 5 or 9 months to mimic conditions occurring during seasonal hibernation. Changes in the composition of glycoconjugates (Gcs) of the gastric mucosa were determined after cold-treatment. Cold-treated chipmunks, in comparison with warm control animals, revealed a thinner layer of Gcs on the free surface gastric epithelium with reduced depth of their pits. Cold-treated chipmunks showed similar staining patterns and lectin affinity for Gcs as compared with warm control animals. After long-term cold treatment, reduction in the amounts of Gcs were more severe in gastric pit epithelium and glandular mucous cells than in the free surface gastric epithelium. A significant reduction in immunostaining of nitric oxide synthase (NOS) was also observed in chipmunks after long-term cold-treatment. The changes in Gcs and NOS staining patterns may be interpreted in relation with a continued but reduced functioning of the gastric mucosa throughout hibernation. However, the findings in the present experimental model for hibernation, which shows significant changes in Gcs and NOS staining patterns, need to be demonstrated during seasonal hibernation in the wild.