Masako Yajima

Non‐neuronal release of ACh plays a key role in secretory response to luminal propionate in rat colon

Non‐technical summary ACh is the best characterized neurotransmitter that is synthesized in cholinergic neurons in the brain and gut wall. In the gut, acetylcholine is released from the nerve endings in response to luminal stimuli and regulates the movement of gut contents via stimulating muscle contraction and epithelial ion secretion. We show that acetylcholine is synthesized in colonic epithelial cells and released on the serosal side by luminal chemical stimulation of the short chain fatty acid propionate and causes chloride secretion. These results suggest that non‐neuronal release of acetylcholine in response to luminal stimuli plays a role in colonic chloride secretion.

Bacterial Translocation in Neonatal Rats: The Relation Between Intestinal Flora, Translocated Bacteria, and Influence of Milk

Background A high incidence of bacterial translocation in neonates results not only from immaturity of host-defense functions, but also from the dominant colonization of aerobic bacteria in the intestine. Bacterial colonization develops differently among breast-fed, formula-fed, premature, and full-term infants. The purpose of this study was to examine the incidence of bacterial translocation and to identify the translocated bacterial species, relating these findings to the intestinal microflora and to the type of feeding in neonatal rats. Methods Animals were divided into three groups: breast-fed normal pups (MR group), formula-fed pups fed via an intragastric cannula implanted esophageally (AR group), and breast-fed pups after the removal of the cannula (Sham group). Artificial rearing was achieved using a machine feeding system. Culture and identification of the bacteria in the intestine, mesenteric lymph nodes, liver, portal blood, and lungs were made using a simplified version of Mitsuokas method. Results At 14 days of age, the dominant bacteria in the feces of the MR and Sham Groups were Enterobacteriaceae, Lactobacillus, and Enterococcus, but Enterobacteriaceae and Clostridium were significantly more common in the AR group than in the MR group. The dominant bacteria in the mesenteric lymph nodes were Enterobacteriaceae, Lactobacillus, and Staphylococcus. The extent of systemic bacterial translocation decreased earlier in the Sham group than in the AR group. Conclusions The frequency with which species of bacteria were cultured from mesenteric lymph nodes and other peripheral sites did not mirror the composition of the intestinal flora. Among the translocated bacteria, Staphylococcus may be especially hard to recognize and difficult for the host-defense systems to destroy. Breast-feeding inhibited systemic bacterial translocation in the suckling period of the rat.

Intestinal Adherent Bacteria and Bacterial Translocation in Breast-Fed and Formula-Fed Rats in Relation to Susceptibility to Infection

The barrier function of the intestinal mucosa is immature in the newborn mammal, and is strengthened by breast milk. We investigated this effect of breast milk by comparing the susceptibility to infection assessed in terms of adherent bacterial colonization of the intestinal tissue (AdC) and bacterial translocation (BT) between breast-fed and formula-fed newborn rats. Three-day-old rat pups were assigned to one of three groups: mother-reared (MR), pseudo-cannulated (sham), and artificially reared (AR). AR rats were infused with formula through an intragastric cannula, under the control of a computer-regulated pumping machine. MR and sham rat pups were reared with their respective dams and received breast milk until weaning in a specially designed cage. In 10-d-old rats, there was no significant difference in the fecal or cecal flora between the AR and MR groups, whereas the AdC and the BT to the liver were greater in the AR than MR group. Enterobacteriaceae, Streptococcus and/or Enterococcus, and Staphylococcus were dominantly detected as microorganisms in AdC flora and BT. The AdC flora did not directly reflect the bacterial colonization flora. These findings suggest that AR rat pups mature normally, although there is a greater colonization of Enterobacteriaceae and BT in AR than MR pups. Consequently, the intestinal barrier function of the pups reared by artificial feeding may become susceptible to BT, and AdC may be more indicative than bacterial colonization of the susceptibility to BT.

The G-protein on cholesterol-rich membrane microdomains mediates mucosal sensing of short- chain fatty acid and secretory response in rat colon

Aim:  Short‐chain fatty acids (SCFA) stimulate colonic contraction and secretion, which are mediated by an enteric reflex via a mucosal sensing and cholinergic mechanisms. The involvement of G‐protein signal transduction was examined in the secretory response to luminal propionate sensing in rat distal colon.

Reactivity of Secretory IgA Antibodies in Breast Milk from 107 Japanese Mothers to 20 Environmental Antigens

The secretory IgA (sIgA) antibody response to 20 environmental antigens, including microorganisms, toxins, food, and inhaled allergens, was evaluated in the breast milk from 107 Japanese mothers 1–10 days after delivery. Specific sIgA antibody responses were detected in most milk samples against almost all of the antigens tested, although there was a wide variation in the specific sIgA antibody profiles of each individual’s milk. With regard to twelve bacterial antigens, highly specific sIgA antibody responses were detected against Escherichia coli, Yersiniaenterocolitica, and Pseudomonasaeruginosa. With regard to eight nonbacterial antigens, highly specific sIgA antibody responses were detected against rotavirus, cholera, and pertussis toxins. Similar sIgA antibody profiles were obtained when the 107 milk specimens were divided into colostrum (milk 1–5 days after delivery, n = 36) and transitional milk (milk 6–10 days after delivery, n = 71). This study provides information on the possible protective role of human milk sIgA antibodies and will serve as a baseline for future studies.

Reduced Thymic Size and Numbers of Splenic CD4+ and CD8+ Cells in Artificially Reared Mouse Pups

The effect of early nutrition on the development of the immune tissue and T cells of mouse pups was examined. Newborn mice were divided into three experimental groups: mother-reared (MR) pups, pups that were fed on a milk substitute from the first day (AR-0), and the third day (AR-2), using a hand-feeding system. The average thymic size of the AR-2 pups was respectively significantly larger and smaller than that of the AR-0 and MR pups. In contrast, the splenic sizes of the AR-0 and AR-2 pups were greater than that of the MR pups. The numbers of CD4+CD8− and CD4−CD8+ cells in the spleen of the MR pups were significantly higher than those in the AR-0 pups. These results indicate that early nutrition affected the sizes of the thymus and spleen and the composition of CD4+CD8− or CD4−CD8+ T cells in the spleen.

Long-Term Oral Feeding of Lutein-Fortified Milk Increases Voluntary Running Distance in Rats

To evaluate the effects of lutein-fortified milk administration on running exercise, a voluntary wheel-running model was performed in rats. Four-week-old F344 rats were administered test milk (10 mL/kg) daily following a 4-h fasting period, and their running distances were measured each day for a 9-week period. Total weekly running distance significantly increased from the sixth week until the end of the test period in lutein-supplemented rats (lutein-fortified milk administered) compared with control rats (vehicle administered). This increase was not apparent in rats administered lutein alone. In the lutein-fortified-milk exercise group compared with the sedentary control group, carnitine palitroyltransferase 1 (CPT-1), total AMP-activated protein kinase (tAMPK), and phosphorylated AMP-activated protein kinase (pAMPK) contents were significantly increased in the gastrocnemius muscle, with a concomitant decrease in triglyceride and total cholesterol levels in the blood and liver. Furthermore, the lutein level in blood of lutein-administered rats significantly decreased with exercise. These results suggest that lutein-fortified milk may enhance the effect of exercise by effective utilization of lipids when combined with voluntary running.

Non-neuronal, but atropine-sensitive ileal contractile responses to short-chain fatty acids : age-dependent desensitization and restoration under inflammatory conditions in mice

Intestinal epithelial cells sense short‐chain fatty acids (SCFAs) to secrete non‐neuronal acetylcholine (ACh). However, the roles of luminal SCFAs and epithelial ACh under normal and pathological conditions remain unknown. We examined ileal contractile responses to SCFAs at different ages and their mucosal cholinergic alterations under inflammatory conditions. Ileal contractile responses to SCFAs in 1‐day‐old pups to 7‐week‐old mice were compared using an isotonic transducer, and responses to an intraperitoneal injection of lipopolysaccharide (LPS) were analyzed in 7‐week‐old mice. The mRNA expression levels of a SCFA activate free fatty acid receptor, acetylcholinesterase (AChE), choline acetyltransferase (Chat), and choline transporter‐like protein 4 (CTL4) were measured using real‐time quantitative RT‐PCR. AChE was analyzed by histochemical and optical enzymatic assays. Atropine‐sensitive ileal contractile responses to SCFAs occurred in all 1‐day‐old pups, but were frequently desensitized after the weaning period. These contractile responses were not inhibited by tetrodotoxin and did not appear when the mucosal layer had been scraped off. Contractile desensitization in 7‐week‐old mice was abolished in the presence of the AChE inhibitor, eserine, which was consistent with increased AChE activity after weaning. Ileal contractions to SCFAs in adult mice were restored by LPS, which significantly increased the epithelial mRNA expression of Chat and CTL4. Atropine‐sensitive ileal contractile responses to SCFAs constitutively occur in the newborn period, and are desensitized during developmental stages following the up‐regulated expression of AChE in the villous mucosa, but are restored under inflammatory conditions possibly via the release of epithelial ACh.