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Results for “Digestive System Physiological Phenomena”

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At least 19 recordsLinked to original sources
PubMed1992

Renal, respiratory and ionic regulation in Atlantic salmon (Salmo salar L.) kelts following transfer from fresh water to seawater.

Atlantic salmon may return to the sea after spawning in fresh water. These fish, known as kelts, reportedly show a limited ability to hypoosmoregulate. However, this study shows that fresh-water-adapted kelts exposed to seawater demonstrate rapid adaptation (within 48 h) in osmoregulatory parameters to values characteristics of seawater-adapted salmonids. The urine flow rate falls from 1.2 to 0.2 ml.kg-1.h-1 within 24 h. Over the same period, urine osmolality increases from 48 mosmol.kg-1 to become isosmotic with the plasma, and Mg2+ secretion by the kidney tubules elevates the urine concentration from 0.5 to 100 mmol.l-1. As is characteristic for marine teleosts, kelts drink seawater and process the ingested water in the gut to replace body water lost by osmosis to the hyperosmotic medium. Seawater exposure causes a marked hypoxia, arterial oxygen tension falling by 43% within minutes and persisting for at least 4 days at this low level. This is associated with large changes in blood pH and acid-base balance. The physiological mechanisms involved in adaptation to a hyperosmotic external medium are discussed, and the osmoregulatory capacity of kelts is compared with that of salmon at other stages of the life cycle.

Adaptation, Physiological↗
PubMed1991

Autologous perfusion of an isolated rabbit gastrointestinal tract.

Most perfusion techniques rely on mechanical means to provide blood flow to the isolated organ for maintaining its physiological conditions. The approach usually requires a complicated mechanical system with the associated problems of blood type matching and prevention of blood cell damage. This paper describes a gastrointestinal tract perfusion technique that uses the rabbit's own cardiopulmonary system as the autologous blood supply source. The technique allows for the removal of the complete intestinal loop from the abdominal cavity of the rabbit, and maintains its blood circulation through silastic tubing connections of the catheterized portal vein and cranial and caudal mesenteric arteries. An alternative perfusion site that uses the aorta as the arterial blood supply and the vena cava as the venous return also is described. The isolated perfused GI tract may then be placed in a separate test environment for controlled experiments. For an acute animal test, the approach was found to be a convenient alternative to conventional approaches.

Animals↗
PubMed1992

Humoral induction of pyloric rhythmic output in lobster stomatogastric ganglion: in vivo and in vitro studies.

In the lobster Jasus lalandii, 14 neurones of the stomatogastric ganglion (STG) are organized in a network that produces rhythmic pyloric outputs. In vitro experiments have shown that the STG neurones receive, via the stomatogastric nerve (stn), neuromodulatory inputs that influence the expression of the bursting properties of the neurones and the ability of the network to produce its rhythmic output. In contrast to these in vitro observations, in vivo transection of the stn does not abolish the pyloric rhythm. Rhythmic output can be recorded by electromyography immediately after stn transection and for up to 2 years afterwards. We have shown that, under these experimental conditions, the STG appears to be isolated from any neuronal input that might account for the maintenance of the rhythmic output. Experiments carried out in the 2 days after stn transection showed that an in vitro preparation of the isolated STG was unable to produce any rhythmic output, but blood serum added to the system could restore the pyloric output. These results suggest strongly that the pyloric network receives neural and humoral modulatory influences in parallel and that each type of influence alone is able to maintain the bursting capability of the pyloric neurones.

Animals↗
PubMed1992

The role of the gastrointestinal tract in the development of burn sepsis.

Conceptualization of the gastrointestinal tract as the "motor" that drives sepsis and multiple-system organ failure has only recently been appreciated. Most of the investigation into the pathophysiology of gut-derived sepsis involves using animal models; however, some of the findings are already being corroborated in human studies. The gastrointestinal tract is a dynamic organ whose function as a front-line defense against infection needs to be appreciated. The development of lethal sepsis is a function of the microbial load and virulence, the status of the gastrointestinal barrier, and the magnitude of the host defense response. In assuming care of a critically ill patient, we must be judicious in the use of antibiotics in order to prevent intestinal overgrowth of potential pathogens. Providing proper nutrition by an enteral route (when possible) not only satisfies caloric needs but regulates the microflora and maintains the integrity of the mucosal barrier. Burn patients should receive enteral nutrition early, the first day if possible. This not only will protect the intestinal mucosa but also will blunt the hypermetabolic response following thermal injury. Lastly, the patient should not receive an excessive amount of narcotic or sedative, for these drugs have an inhibitory effect on gastrointestinal motility, encouraging bacterial overgrowth. In the near future, new therapeutic modalities may soon become available to protect and treat the compromised gastrointestinal barrier. These modalities may include, but certainly are not limited to, the use of glutamine and xanthine oxidase inhibitors to prevent stress-related injury to the gastrointestinal mucosa.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Physiological changes due to age. Pharmacodynamic changes of drug action and implications for therapy.

The elderly respond differently to drugs than do younger people. Their physiological response is much more variable, and predictability of drug action is much less certain. When all non-pharmacological factors and age-associated pharmacokinetics are taken into account, there is still no full explanation of the potentially altered drug action and increased drug toxicity observed in the elderly. It is only relatively recently that age-associated physiological changes (primary age changes), their interplay with age-associated pathophysiological changes (secondary age changes) and environmental changes (tertiary age changes) have been studied with regard to the effect of those changes on the pharmacodynamics of drug action. In general, age-associated pharmacodynamic changes, i.e. changes in the type, intensity and duration of drug action, have been associated with changes in receptor function (e.g. altered receptor number and affinity, altered second messenger function, altered cell response), changes in the homeostatic mechanisms, and reduced reserve capacity. It is important to realise that these changes, which can differ greatly among patients, may be responsible for an increased incidence of adverse drug reactions and therapeutic failure. They may also mandate a higher dose in some circumstances, as some organs become less responsive to drug action with age.

Adult↗
PubMed1991

[Gastrointestinal flora and health in man and animal].

A balanced and stable gastro-intestinal microflora is of vital importance for the optimum function of the gastro-intestinal tract and consequently for the health of man and animals. The gastro-intestinal microflora is a very complex ecosystem, the current knowledge of which is still very limited. It is obvious that the intestinal flora has a protective function (prevention of infection). In addition it has a positive effect on nutrition (digestion, effects on physiology, production of vitamins). Changes in diet, stress, the use of antibiotics and excessive hygiene all bring about changes in the micro-biological ecosystem and consequently changes in health conditions. Knowledge about the microbial ecology of the intestine is also of importance in the prevention of zoonoses. Recently, increasing attention is being paid to the development of methods to influence the composition of the gastro-intestinal microflora in man and animals by probiotics (dried cells or fermented food). These concepts will be dealt with in the present paper and, in addition some of the possible uses will be discussed.

Animal Nutritional Physiological Phenomena↗
PubMed1978

Prostaglandins; their biological and pharmacological role.

The biological and pharmacological roles of prostaglandin system are reviewed. The most recent and important finding is the isolation and characterization of endoperoxides, thromboxanes and prostacyclin. In many respect they seem to be even more effective than the original prostaglandins and could explain many actions previously attributed to prostaglandins. Prostaglandins, endoperoxides, thromboxanes, and prostacyclin seem to have important physiological and pathophysiological roles, e.g. in the cardiovascular, gastro-intestinal and reproductive systems, the skin, and the central nervous system, as well as in inflammatory, immunological and metabolic reactions. Thus, prostaglandin-like substances, their analogues, prostaglandin antagonists, and the drugs that affect prostaglandin synthesis present good prospects for the treatment of many diseases affecting these systems. The mode of action of most anti-inflammatory and analgesic drugs can be explained by actions on the prostaglandin system. New potent and selective regulators of the prostaglandin system are being investigated and more indications are being found for using existing drugs. Although the field is generally promising, there are many contradictory findings. This calls for a cautious interpretation of the many interesting observations.

Animals↗
PubMedDate not supplied

[Prostaglandins. Various clinical, physiological and chemical aspects].

The prostaglandins (PTGs) are compounds derived of the essential lipids of diet. The name was received by isolation of the prostate, however, subsequent investigations demonstrate its existence in all tissues investigated, in every species of animals studied and in the mariner choral Plexaura homamalla, that is important fountain of PTGs for investigation. For its localization, action's mechanisms and diverse effects in apparatus and systems they promise to be potent therapeutic arms in diverse diseases. The literature relationed to PTGs is extense, there exist excellent reviews about it.

Calcium↗