The Acute Radiation Syndrome - the Importance of the Gastro-intestinal Injury in the Catabolism and Distribution of Serum-albumin

Gastrointestinal Function

This chapter describes the normal biochemical processes of intestinal secretion, digestion, and absorption. The digestive system is composed of the gastrointestinal (GI) tract, or the alimentary canal, salivary glands, the liver, and the exocrine pancreas. The principal functions of the gastrointestinal tract are to digest and absorb ingested nutrients, and to excrete waste products of digestion. Most nutrients are ingested in a form that is either too complex for absorption or insoluble, and therefore, indigestible or incapable of being digested. Within the GI tract, much of these substances are solubilized and further degraded enzymatically to simple molecules, sufficiently small in size, and in a form that permits absorption across the mucosal epithelium. This chapter explains in detail the mechanisms of salivary secretions, compositions of saliva, and the functions of saliva. The chapter also elaborates properties of bile as well as the synthesis of bile acids. The chapter explores the pathogenesis of the important gastrointestinal diseases of domestic animals, and the biochemical basis for their diagnosis and treatment. The chapter concludes with a discussion on disturbances of gastrointestinal function such as vomition, acute diarrheas, malabsorption, bacterial overgrowth, and ulcerative colitis.

The metabolic effects of abdominal irradiation in man with and without dietary therapy with an elemental diet

The metabolic effects of abdominal radiotherapy were assessed in patients with pelvic neoplasms, and the effects of supplementation of the diet with an 'elemental' diet assessed. Therapeutic irradiation led to significant mean weight losses of 1.4 kg in control patients and 1.0 kg in patients receiving 'elemental' diet supplements. Irradiation was associated with small falls in plasma potassium and calcium concentrations in both groups. In the 'elemental' group there was a small increase in circulating alanine and insulin concentrations and a fall in glycerol and ketone body concentrations, but all variables remained within or close to normal basal reference ranges. Plasma albumin fell slightly but significantly in the 'elemental' diet group from 44 +/- 1 to 42 +/- 1 g/litre during treatment. Is is concluded that modern radiotherapy is no more than a modest catabolic stimulus. Long-term dietary supplementation with 'elemental' diets in ill subjects did not produce adverse effects.

Gastrointestinal Function

This chapter discusses the functions of gastrointestinal tract. The principal functions of the gastrointestinal tract are assimilation of nutrients and excretion of the waste products of digestion. Within the gastrointestinal tract, these substances are solubilized and degraded enzymatically to simple molecules, sufficiently small in size and in a form that permits absorption across the mucosal epithelium. The distribution of the different types of secretory cells in the salivary glands varies among species. The mandibular and sublingual glands are mixed salivary glands containing both mucous and serous types of cells, and produce a viscous secretion that contains large amounts of mucus. The cytoplasm of the secretory cells contains numerous zymogen granules that vary in size and number depending on the activity of the gland. These granules contain the precursors of the hydrolytic enzymes responsible for digestion of the major dietary components. The cells of the terminal ducts probably secrete the bicarbonate ion responsible for neutralizing hydrochloric acid that enters the duodenum from the stomach.