Physiological studies of exocrine pancreatic secretion in conscious rats. 7th communication: short-term kinetics of adaptation of digestive enzymes to different nutritional stimuli.

In conscious rats provided with appropriate indwelling catheters the kinetic period of adaptation (short-term adaptation) of digestive enzymes was investigated in response to a rapid change of diet and to intraduodenal infusions of different food components. Flow-rate and total protein concentration of pancreatic juice were measured. Enzyme-separation by PAA-Gel-Electrophoresis and quantitative analysis of amylases I and II, lipase, chymotrypsins I and II and trypsin were performed. The specific enzymatic activity was characterized by the enzyme fraction in percent of total protein. Rapid "change of diet" in rats, previously adapted for two weeks to a certain diet, caused increasing and decreasing concentrations of the corresponding enzymes respectively. The kinetic of this adaptation could well be described by exponential functions. Intraduodenal perfusion of starch, soy-bean oil or amino acids revealed similar changes in enzyme secretion as seen in the dietary experiments; i. e. intraduodenaL perfusion of starch caused mainly an increase in amylase secretion, soy-bean oil in lipase secretion and amino acids in the secretion of proteases. The kinetics could be described as a definite transfer function to a rectangular stimulus. The time lag between the duodenal "stimulation" and "response" in pancreatic enzyme secretion was only a few hours. After a period of rapid change in enzyme secretion during the initial 5 hours, the secretion rises more slowly to reach steady-state level after 18-22 hours. The results of this study allow a more detailed formal description of the kinetics of pancreatic short-term adaptation to nutritional stimuli without clarifying the involved mechanisms.

Failure of secretin to prevent or ameliorate cerulein-induced pancreatitis in the rat.

Infusion of supramaximal concentrations of the synthetic pancreozymin analog cerulein induces acute edematous pancreatitis in the rat. Vacuolization and necrosis of acinar cells is paralleled by an almost complete reduction of pancreatic secretion from the cannulated duct. Preinfusion or coinfusion of synthetic secretin slightly increases pancreatic volume and protein secretion. This effect is only transient, and is always overcome by the actions of cerulein. Secretin does not prevent or improve the cellular destruction of the acinar cells. The results suggest that secretin has no beneficial effect on hormone-induced pancreatitis.

Physiological studies of exocrine pancreatic secretion in conscious rats. 6th communication: steady-state adaptation to different food composition.

In conscious rats provided with appropriate indwelling catheters the steady-state adaptation of digestive enzymes in pancreatic juice is investigated in relation to different food composition. Six isocaloric diets with different composition of carbohydrates (5-70%), proteins (10-57%) and fat (0-38%) are applied for two weeks before operation and also afterwards. The parameters determined are: flow-rate and total protein concentration of pancreatic juice, enzyme-separation by PAA-Gel-Electrophoresis and quantitative analysis of amylases I and II, lipase, chymotrypsins I and II and trypsin. The specific enzymatic activity, characterized by the enzyme fraction in per cent of total protein can be described best as a linear function of the corresponding nutrient portion (%) in the food. (Coefficient of linear regression mostly r = 0.98%). The regression lines for the sum of both amylases and all proteases are parallel to each other (y = 0.45x + b). Lipase activity is also linearly increasing with fat in food having a much smaller slope (y = 0.16x + b). The regression lines (y = ax + b) intersect with the ordinate at different points (section b), characterizing the "basal" secretion of pancreatic enzymes without any substrate in food. b (in %) for amylase I = 3.14, amylase II = 0.7 !, total proteases = 12.5 and lipase = 13.6. The regularity of inherent laws governing adaptation of pancreatic enzyme production and secretion to food composition allow to predict the prospective enzymatic secretion pattern for any given food composition.

An additional secretory protein in the rat pancreas.

An additional protein in rat pancreatic juice has been observed, which is present in healthy rats after pancreatic duct cannulation or in rats in which experimental pancreatitis has been induced by either cerulein or taurocholate. The protein appears 1/2-1 day after surgery or onset of pancreatitis, is present for the following 3-4 days and disappears afterwards. It is found in pancreatic homogenate or in zymogen granules from rats with pancreatitis, but not in normal rats. It does not seem to be related to the recently described 'pancreatic stone protein'. We would like to refer to this protein as 'pancreatitis-associated protein'.

Physiological studies of exocrine pancreatic secretion in conscious rats. 5. Communication: circadian rhythms of flow rate and composition of pancreatic juice.

1. In conscious rats provided with indwelling pancreatic and biliary catheters, the circadian variations of flow rate, electrolyte- and protein concentrations are followed. 2. Individual enzymes are separated by Polyacrylamid-Gelelectrophoresis and quantitatively determined by photometry after evaluation of the coloured bands. 3.) Volume flow rate increases towards the evening and reaches maximal values in the early morning hours (2-4 a. m.). 4. A similar nocturnal maximum can be observed for the concentrations and elimination rates of total protein, potassium and bicarbonate, while the concentration of sodium is fairly constant and only slightly decreasing in very high flow rates. 5. Typical circadian variations can be observed for the individual enzyme fractions: at night, the part of amylase is higher and the amount of chymotrypsinogen is lower, together with the increased nocturnal protein elimination. At day time these relations are inversed. 6. This rhythm is also existing in fasting animals, although with reduced basal values and smaller amplitude of variation. 7. In fasting animals the relative part of amylase is smaller compared with that of chymotrypsinogen, probably in relation to the reduced elimination of total protein. 8. The circadian variations of exocrine pancreatic secretion may be primarily inaugurated by hormonal action of hormones, whose release is controlled by nervous centers in the brain.

Exteriorized lymphatico-venous shunts in conscious rats.

Surgical techniques for establishing fistulas of the hepatic and intestinal lymphatics and thoracic duct in conscious rats are described. Continuous recirculation of the lymph into the vena cava inferior is performed by a device which measures flow velocity before returning the lymph to the animal through a permanent venous catheter. Clotting is prevented in all cases by constant infusion of an anticoagulant solution (containing heparin or Na-citrate) into the top of the indwelling catheter.

[Studies on the precorneal tear film. First communication: an optical system for demonstrating tear film without fluorescein (author's transl)]. / Studien über den präkornealen Tränenfilm (PKTF). 1. Mitteilung. Ein optisches Verfahren zur Darstellung des Tränenfilms ohne Fluoreszein.

Tear film is usually studied by using fluorescein. An optical system is described which despenses with the use of fluorescein. It mainly consists in an equal diffuse illumination of the cornea, provided through an opaque truncated cone that is illuminated from behind. The cone is situated as close as possible to the front of the eye. The cornea and its surface can be observed through a hole at the narrow end of the cone. Interferences in the lipid layer of the tear film are recognizable as "colors of thin layers". The physical background to interferences in thin, convex layers is discussed. Break-ups are visualized by using a supplementary "Schlieren" method.

[Critical review of our knowledge and presentation of a new working hypothesis concerning the stability of the precorneal tear film (PCTF) (author's transl)]. / Kritische Ubersicht über unsere Kenntnisse und Vorstellung einer neuen Arbeitshypothese über die Stabilität des präkornealen Tränenfilms (PKTF).

1. The paper reviews critically our present knowledge and experimental findings concerning the structure, formation and stability of the PCTF. 2. A new hypothesis, which contradicts Holly's concept, is put forward to explain the rupture of the PCTF (formation of dry spots). 3. Special chapters deal with tear secretion and drainage, and finally with the function of the eyelids (blinking), especially in relation to the formation and preservation of a stable preocular tear film.

Physiological studies of exocrine pancreatic secretion in conscious rats. 4. Communication. Effects of anesthesia on flow rate and composition of pancreatic juice.

1. In conscious rats provided with indwelling pancreatic and biliary catheters, the influence of anesthesia was investigated. 2. Ether was applied in concentrations of 4, 6 and 8 Vol % by an evaporator and Na-pentobarbital injected intravenously (30 mg/kg b. w.) 3. Flow rate, electrolytes (ion-selective electrodes and flame photometry), total protein concentration and the amount of several different individual enzyme fractions were determined quantitatively by electrophoresis. 4. During ether anesthesia flow rate and total protein concentration are decreased by about 50% of the control. A certain constant basal flow is established. Na+-Concentration is increased (+15%) and K+-concentration is diminished by about 30-35%. Characteristic changes in the enzyme spectrum are induced. 5. Changes due to pentobarbital anesthesia are as follows: reduction of the mean flow rate (30-35%) with large fluctuations. Corresponding variations of the K+-concentration. Diminution of the protein content without typical changes in the individual enzyme fractions.

Physiological studies of exocrine pancreatic secretion in conscious rats. 3. Communication. Separation and determination of enzymes by gel-electrophoresis.

1. A method is described for the electrophoretic separation and following quantitative determination of the different protein fractions of pancreatic juice. 2. A polyacrylamide (PAA) gel-electrophoresis is performed in two systems: one anionic at pH = 9.0 with 7.5% PAA and a cationic one at pH = 5.0 with 10% PAA. 3. After about two hours of separation using a current of 3 and 4 mA respectively, the gels are stained with Amido-black 10B after fixation of the proteins with acetic acid. 4. The colour in excess is removed with acetic acid. 5. The coloured bands are isolated by cutting. 6. Evaluation of the colour by NaOH and determination of the colour intensity by photometry. 7. Evaluation of the colour extinction as relative percentages of the different protein and enzyme fractions. (Extinction of total dye = 100%) 8. There are at least 13 bands in the cationic system and about 7 additional ones in the anionic system distinctly separated, 12 of them could be identified using enzymatic methods. 9. Evidence is given that the colour intensity has a linear relationship to enzyme activity. 10. The validity of the presented method is discussed and compared with other electrophoretic methods.

[The effect of desoxycholate on the electrolyte and water absorption in the terminal ileum. Studies in conscious rats (author's transl)]. / Die Wirkung von Desoxycholat auf die Elektrolyt- und Wasserabsorption im terminalen Ileum. Perfusionsversuche an der wachen Ratte.

With an in vivo perfusion technique the influence of 10(-3) mol/l desoxycholate (DC) on the net electrolyte and volume absorption are studied in the terminal ileum of unanesthetized rats. Control experiments are performed in the same animal. The following data are observed: 1. There is a highly significant decrease in net Cl- absorption (p less than 0.002). 2. The Na+ and volume absorption is diminished or reversed into secretion. 3. The K+ secretion is enhanced (P less than 0.01). The sodium-water equivalent is reduced caused by alteration of the Na+ as well as the water permeability.

Influence of feeding fructose on fructose and glucose absorption in rat jejunum and ileum.

The influence of feeding isocaloric diets containing either 65% of fructose (F 65) on 65% of glucose (G 65) were studied on the uptake of both sugars in segments of rat proximal jejunum and distal ileum. The hexose absorption was compared to that obtained in animals receiving isocaloric amounts of a diet containing 30% of glucose (G 30). Feeding fructose (F 65) for 3 days resulted in a 2.5-fold increase of fructose uptake in the jejunum and a 40% increase in the ileum as compared to group G 30. When fructose (F 65) was administered instead of G 65 the uptake of fructose was enhanced by 75% in the jejunum and 35% in the ileum. Stimulation of glucose absorption in segments of the proximal and distal small intestine by diets F 65 and G 65 was nearly identical as compared to the values of group G 30. The stimulation of the uptake of fructose induced by fructose feeding parallels an adaptive increase in the activity of enzymes involved in fructose metabolism in the mucosa of the small intestine.

Physiological studies of exocrine pancreatic secretion in conscious rats. 2. Communication: recovery of the animals after operation.

1. In conscious rats provided with indwelling pancreatic and biliary catheters, the postoperative recovery period is investigated. 2. Immediately after operation, serum amylase and lipase concentrations are highly elevated, declining afterwards rapidly and normalizing within 4 days. 3. Food intake, protein secretion and flow rate of the pancreatic juice show an increasing pattern during the first 4-5 days after operation. 4. The amount of secreted protein is a logarithmic function of the amount of food ingested. 5. The spectrum of secreted enzymes shows typical changes after operation, the total sum of relative enzyme fractions remaining constant. 6. The recovery period of rats provided with a pancreatic fistula -- as described previously -- lasts 4-5 days.

Physiological studies of exocrine pancreatic secretion in conscious rats. 1. Communication: surgical methods and registration techniques.

1. Two surgical methods are described to derive bile and pancreatic juice separately by indwelling catheters in rats. 2. The secretes are always recirculated into the animals duodenum, the indwelling catheters forming an extracorporal loop. 3. The experiments are performed in the conscious animal. 4. The flow rate of the secretes is measured by drop-counting with resetting after a definite number of drops (staircase registration). 5. By interposed flow-through transducers several parameters can be determined f. i. by ion-selective-electrodes and microphotometers. 6. Additional analytic measurements can be carried out in samples. 7. There is a time-shift between the recorded curves corresponding to several different flow-through transducers placed one after the other in the extracorporal circuit of flow. This time shift is variable due to the dead spaces of the system and the actual flow-rate. The theoretical aspects of this general problem are discussed in detail. 8. Sampling of pancreatic juice causes immediately a pronounced increase of flow rate and the amount of protein secreted. Therefore, volumes taken must be given back quantitatively into the animals duodenum in order to avoid a disturbance of the normal secretion pattern.

Psychophysical measurements concerning the range of visual perception.

Two adjacent semicircular testfields of luminances l and L + delta L, were presented on an adapting field of luminance LU. In earlier experiments, it was found that the just noticeable difference of brightness (jnd) delta L, can be described by delta L = delta Ls + bLc (Lingelbach and haberich 1977). For foveal observations and LU values within the photopic range, delta Ls and b are power functions of LU. In this study, these investigations area continued for scotopic background luminances and extrafoveal conditions (6 degrees and 12 degrees temporal). The following results area obtained: 1. Under scotopic conditions of background luminance, LU, the jnd's for foveal observations are nearly independent of LU. delta L is dependent on the luminance L and can be expressed by the same curve for different levels of LU. 2. For extrafoveal conditions, the results can be described in the same way as for the fovea. The jnd is found to be delta L = delta Ls + bLc. In the total range of LU investigated (0.001 less than or equal to LU less than or equal to 100 cd/m2), the parameters delta Ls and b are power functions of LU. c increases with log L from about 1.1--1.5. 3. The sum of jnd-steps as separate "units of sensation" form a "dynamic characteristic" for each adaptational level. It is different for fovea and periphery. 4. The Fechner scaling of brightness, which corresponds to the sum of jnd-steps up to each adaptational luminance LU ("static characteristic"), shows an unexpected similarity to the Stevens power function.

[The effect of unconjugated bile salts on the intestinal absorption of electrolytes and water in the proximal jejunum. Studies in conscious rats (author's transl)]. / Die Wirkung unkonjugierter Gallensäuren auf die Elektrolyt- und Wasserabsorption im proximalen Jejunum. Perfusionsversuche an der wachen Ratte.

With an in vivo-perfusion-technique the influence of unconjugated bile salts (cholate, desoxycholate) on the net electrolyte and volume absorption is studied in the jejunum of conscious rats. The applied doses correspond to physiological concentrations in the intestine of rats. Control experiments were performed in the same animal. Cholate and desoxycholate diminish the net electrolyte and volume absorption resp. cause a net secretion. The effects are largely reversible. The extent of net volume absorption depends on the applied dose of each bile salt. The possible mode of action of unconjugated bile salts on the electrolyte and water absorption in the small intestine is discussed.

Intestinal absorption under the influence of vasopressin: studies in unanaesthetised rats.

Experiments were carried out in different segments of the intestine of unanaesthetised rats to assess the effect of vasopressin on intestinal absorptive processes. The following data were observed. (1) Within a physiological range of doses (Aziz, 1969), ADH diminished the net sodium absorption mainly by reducing the unidirectional sodium influx, whereas the behaviour of the efflux was not uniform. (2) The unidirectional volume fluxes showed the same behaviour as did the sodium fluxes. (3) ADH produced an oral-aboral gradient (jejunum greater than ileum greater than colon). (4) ADH did not significantly change the transfer of actively transported sugars; it did influence, however, passively transported substances. (5) During the intravenous application of ADH, a substance was secreted into the perfusion solution which diminished the absorption of volume and electrolytes. (6) Cyclic AMP acted on intestinal absorption in the same way as did ADH. In view of these results two mutually independent transport pathways for sodium and water are supposed, one of which is influenced by ADH or cAMP. Based on a two membrane model, an ADH mechanism is discussed: the permeability of the luminal membrane system is enhanced in the presence of vasopressin.