Effects of radiation upon gastrointestinal motility

Abstract

neural and chemical control. Myogenic control refers to the electrical activity generated by the smooth muscle of the gut. Electrical control activity (ECA) [1][2][3][4] is the omnipresent rhythmic depolarization of the cell membranes of the smooth muscle of the small intestine. With neural or chemical stimulation, membrane depolarization exceeds an excitation threshold and a contraction results. The electrical correlate of a contraction is called electrical response activity (ERA) [1][2][3][4] . These bursts of electrical response activity have a 1:1 relationship with contractions. Because ERA occurs only during the depolarization phase of the ECA cycle, the frequency of contractions is limited to and determined by the frequency of ECA. Neural and chemical stimulation may not be present during each depolarization of ECA, and thus contractions then do not occur at the maximum possible frequency (Figure 1). Recordings of gastrointestinal motility can either be made with devices that record physical contractions (manometry catheter or strain gauges) or motility can be implied from electrical activity or transit times.Single dose (938 Gy) in a canine model disrupted normal electrical patterns [5] . Jejunal myoelectric activity decreased in frequency, duration and length of migration o f E R A p o s t p r a n d i a l l y. E C A wa s i r r e g u l a r w i t h nonuniform morphology and occasionally migrated in an orad direction. ECA was occasionally uncoupled; coupling is a phenomenon in which corresponding ECAs recorded from different areas maintain a consistent time shift [6] . In spite of these functional abnormalities, the histology was minimally altered. These changes in electrical activity suggest a profound change in the physiology of the smooth muscle as well as the nerves controlling the muscle.Gastrointestinal smooth muscle contractile activity can also be influenced by extrinsic autonomic (parasympathetic and sympathetic) from the CNS and the intrinsic neurons of the enteric ner vous system. The stomach, small intestine and proximal colon derive their parasympathetic innervation through the vagus nerve which contains both afferent and efferent fibers. Relative to the intrinsic enteric neurons, the efferent potion of the vagus is really quite small; however, each vagal efferent fiber may influence about 2000 enteric neurons [7,8] . The sensory component of the vagus nerve is much greater. Sensory fibers account for 80% of all vagal fibers [9] . Vagal afferents detect both the mechanical and chemical stimulation of the small intestine and relay this information centrally for processing. Sympathetic innervation of the intestine arises from the thoracic and lumbar spinal nerves. These ������ ��������� ������ ��������� Effects of radiation upon gastrointestinal motility AbstractWhether due to therapeutic or belligerent exposure, the gastrointestinal effects of irradiation produce symptoms dreaded by a majority of the population. Nausea, vomiting, diarrhea and abdominal cramping are hallmarks of the prodromal ph...

Localized Intestinal Radiation and Liquid Diet Enhance Survival and Permit Evaluation of Long-Term Intestinal Responses to High Dose Radiation in Mice

“…In these models, liquid diet feeding before and after surgery dramatically improved survival [36]. Since radiation is known to alter gut motility [37], [38], and the segment radiation method involves bowel handling and radiation, we believe that ileus was the likely cause of death/need for euthanasia in segment-radiated mice fed with normal chow. We did not study tissue histology in these animals due to the limited number studied under this protocol.…”

2013 Dade W. Moeller Lecture

“…2), and might also cause cognitive impairment (Raber et al 2004, Acevedo et al 2008). (Baker et al 2011) Lower-body doses this high would result in severe prodromal emesis and diarrhea (Anno et al 1995, Otterson et al 1996), but would probably not cause acute gastrointestinal lethality (Fig 2). However, lower-body doses this high would exceed renal tolerance (Fig.…”

Microbial influences on the small intestinal response to radiation injury

“…Ionizing radiation causes a wide diversity of functional disorders in the small intestine, including altered motility [32,33], disrupted absorption of carbohydrates [34], amino acids and bile acids [35], and a more thrombophilic endothelium due to the induction of inflammatory cell adhesion to the endothelium [36] and increased expression of endothelial von Willebrand factor [37]. …”