Analogue computer model of the human cardiovascular control system

A simplified analogue computer model of the human cardiovascular control system is developed in this paper. This model can be adjusted to reproduce the response of a subject to a submaximal work-load. The validity of the model is evaluated and suggestions for its further development are included.     

Dietary control and the stomach

Signals for meal termination are traced to the stomach rather than duodenum or mouth when rats eat familiar food. Two types of signal occur, one measuring amount of nutrient independent of volume or dilution, the other gastric distention. The signals concerning the second ascend the vagus. Nutrient content is measured by some product of the digestive breakdown of the nutrient. The nutrient signals have to be calibrated through a process of learning. The gastric signals generated by food with a novel flavor are disregarded and oropharyngeal cues assume control instead. Finally, evidence against the role of cholecystokinin and bombesin in satiety is presented.     

On the peripheral bladder control system of the dog and urodynamics:In vivo characterisation and hybrid computer simulation

A quantitative model of the peripheral bladder control system of the dog is developed. This model is based on the experimental characterisation of the detrusor muscle and the urethra in 25 female dogs. Intravesical pressure, urinary flow and bladder volume were simultaneously recorded during electrical bladder stimulation, and, from these data, a dynamic model of the bladder control system has been deduced. A general equation for predicting urinary flow patterns is developed, and the hybrid computer EAI-690 is used to simulate the evacuation of the bladder. The effect of different parameters of the system on the micturition pattern is investigated in detail. This work may have interesting clinical applications: for example, in the development of adequate techniques for the evacuation of the paraplegic bladder. Also, the experimental procedures elaborated in this study could be applied in the diagnosis of bladder function and urethral obstruction. Indeed, we have been able to characterise the detrusor muscle and the urethra independently using clinically accessible variables.     

Model to simulate the gastric electrical control and response activity on the stomach wall and on the abdominal surface

A new physical model to simulate the gastric electrical activity (ECA and ERA) as picked up at points on the stomach wall and on the abdominal surface is proposed. In this model the part of the stomach where the electrical activity originates and propagates is represented by a truncated cone of finite length; the electrical potential representing the electrical activity of the cell is generated by a distal movement of an annular band polarised by electric dipoles which are oriented perpendicularly to the surface of the cone. The model reproduces not only the spatial and temporal organisation of the gastric electrical activity (ECA and ERA) but also its morphological characteristics (waveform, amplitude, frequency, phase lag) as obtained by experimentsin vivo. This model also reproduces the morphological characteristics of the signal as picked up, by experimentsin vivo on the abdominal surface in man.     

The role of the stomach receptors in gastric secretion

Summary Experiments on dogs showed that single abundant feeding produces less secretion than if the same quantity of food is subdivided into numerous feedings. Inhibition of stomach secretion is reflexive and is connected with the stimulation of mechanoceptors of the stomach. Both conditioned and unconditioned secretions of salivary glands are inhibited.Presented by Prof. V. N. Chernigovsky. Active member of the AM S, USSR     

Primary gastric choriocarcinoma in a dog

Primary gastric choriocarcinoma (PGC) is a rare neoplasm to date only reported in humans. This report describes a canine gastric tumour with microscopical, histochemical and immunohistochemical features of PGC. The tumour diffusely infiltrated the submucosa and muscularis propria of the pylorus and anterior duodenum, and metastasized to the gastric lymph node. Immunohistochemically, the neoplastic cells displayed aberrant expression of beta-catenin and E-cadherin, but normal expression of the adenomatous polyposis coli (APC) protein. Expression of the oncogenes c-myc and Ras was also increased. These observations suggest that this canine PGC had synchronous activation of both the Wnt/beta-catenin and Ras signalling pathways of carcinogenesis.     

Metabolism of the acutely ischemic dog heart. I. Construction of a computer model.

Construction of a computer model of glycolysis, the Krebs cycle, and related metabolism in acutely ischemic dog heart, involving 122 metabolites, 65 enzymes, and 406 chemical reactions, is described. A previous model of the same metabolism in normal-flow rat heart was modified to fit ischemic dog heart experimental data to within experimental error. The result resembles other models of ischemic heart preparations, implying common underlying mechanisms. The principal change made was reduction of enzyme amounts, consistent with the generally slower metabolism of large animals, suggesting that differing enzyme amounts are a major component of interspecies metabolic difference. Glycolytic intermediates oscillate, asynchronously and with large changes in level; pyridine nucleotides become highly reduced; pH falls, but mitochondria stay alkaline relative to cytoplasm even after oxidative phosphorylation stops.