Light exposure influences the diurnal oscillation of gut microbiota in mice

The gut microbiota exhibit diurnal compositional and functional oscillations that influence the host homeostasis. However, the upstream factors that affect the microbial oscillations remain elusive. Here, we focused on the potential impact of light exposure, the main factor that affects the host circadian oscillation, on the diurnal oscillations of intestinal microflora to explore the upstream factor that governs the fluctuations of the gut microbes. The gut microbiota of the mice that were underwent regular light/dark (LD) cycles exhibited a robust rhythm at both compositional and functional level, in all parts of the intestine. Comparably, constant darkness (Dark-Dark, DD) led to the loss of the rhythmic oscillations in almost all parts of the intestine. Additionally, the abundance of Clostridia in DD conditions was dramatically enhanced in the small intestine. Our data indicated light exposure is the upstream factor that governs the regular diurnal fluctuations of gut microbiota in vivo.

High-dose preoperative radiotherapy does not alter the strength of unilaterally irradiated colon anastomoses in rats

PURPOSE

We studied the influence of preoperative radiotherapy on the strength of colon anastomoses in rats. We compared a conventional (2 Gy/fraction; 1 fraction/day; 5 days/week; cumulative doses of 40.0, 60.0, and 80.0 Gy) and a hyperfractionated schedule (1.6 Gy/fraction, 2 fractions/day, 5 days/week, cumulative doses of 41.6, 60.8, and 80.0 Gy). We compared unilaterally with bilaterally irradiated anastomoses for two conventional radiation schedules.

METHODS AND MATERIALS

The rectosigmoid was always irradiated. Depending on the experiment, the cecum was irradiated or not. A side-to-side anastomosis between rectosigmoid and cecum was constructed the day following the last irradiation. The strength of the anastomosis was evaluated by means of a bursting pressure (BP) measurement after 10 days. A control group and a sham-treated group were carried out.

RESULTS

Compared to controls, the strength of unilaterally irradiated anastomoses was not altered and BP values were independent of the radiation schedule and of the cumulative dose. In case of bilaterally irradiated colon anastomoses, anastomotic strength was significantly reduced at 80 Gy, but not at 40 Gy.

CONCLUSIONS

After high doses of preoperative radiotherapy, colon anastomoses in rats can be safely constructed if only one anastomotic segment is irradiated. The strength of bilaterally irradiated colon anastomoses is dose-dependent.

Epithelial cell nodules developing in the cecum of irradiated mice. Some comparisons with jejunal nodules

A method for producing macroscopic epithelial nodules was developed in order to investigate the properties of epithelial stem cells in the large intestine of mice. The cecum was exteriorized and exposed to various doses of X-ray radiation. Numbers of nodules subsequently developing were counted and plotted against radiation dose. From the logarithmic regression line, the susceptibility to irradiation of nodule-forming stem cells (NFSC) was determined. The susceptibility of cecal NFSC was comparable to the value reported for jejunal NFSC. Mice of (C57BL/6 x DS) F1-Pgk-1b/Pgk-1a that carried X-chromosome inactivation mosaicism for the phosphoglycerate kinase gene were used for examination of nodule clonality. Most cecal nodules contained only 1 type of phosphoglycerate kinase, suggesting a monoclonal origin of the nodules. Histochemical studies showed the presence of absorptive epithelial, goblet and entero-endocrine cells in 17-day-old nodules, implying multipotentiality of the NFSC. In spite of these similarities between cecal and jejunal NFSC, the macroscopic appearance of cecal nodules was quite different from that of jejunal nodules. Only crypt-like structures were observed in the former, whereas both crypt-like and villus-like structures were present in the latter. A comparison between cecal and jejunal nodules may be useful for understanding the morphogenesis of the intestinal mucosa.

Adjuvant postoperative radiation therapy for colorectal carcinoma above the peritoneal reflection. II. Antimesenteric wall ascending and descending colon and cecum

From 1970 to 1981, 50 patients had curative surgery for carcinoma of the cecum, ascending, or descending colon and were Stage greater than or equal to B2. In 15 cases, the lesion originated on the antimesenteric (posterolateral) bowel wall. Of seven cases (with minimum three-year follow-up) not receiving adjuvant postoperative regional irradiation, four recurred in the tumor bed/abdominal wall versus 0/3 irradiated patients. Similarly, the five-year survival was improved in the irradiated group (2/3) versus only 2/9 in the unirradiated group. Patients with transmural extension of right or left colon cancers originating on the anti mesenteric (posterolateral) bowel wall may have a high incidence of postoperative regional failure which may be decreased by adjuvant postoperative regional irradiation.

Inhibition of artificial and spontaneous lung metastases by preirradiation of abdomen--II. Target organ and mechanism

We have previously reported that irradiation of the abdomen of mice before i.v. injection of both immunogenic and nonimmunogenic tumour cells is capable of suppressing their ability to form metastatic lung nodules in a time and dose-dependent fashion. Experiments with segmental exposure indicated the target organ to be located in the ventral half of the abdomen. The effect has now been shown positively to depend upon irradiation of the caecum, and can be abolished either by shielding the caecum from irradiation or by surgically removing it prior to irradiation. Further experiments have shown that the effect cannot be elicited in germ-free mice and that its magnitude is markedly reduced in animals given gut-sterilizing antibiotics. Split-dose irradiation only slightly reduced the magnitude of suppression, provided both doses were given within the time window of effectiveness of single doses. Tumour-growth retardation was observed and spontaneous lung metastases were also suppressed when tumour-bearing mice received abdominal irradiation 7 days after tumour cell transplantation into the leg. However, abdominal irradiation did not significantly reduce subsequent tumour transplantability by the s.c. or i.p. routes. The experimental data are consistent with a mechanism by which transmigration of enteric bacteria across the radiation-damaged mucous membrane of the caecum effectively results in an endogenous infusion of endotoxin.