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Biomedical subjects

E Simon

Publications and source records attributed to E Simon.

At least 163 records · Page 9Linked to original sources
PubMed1986

Independent osmoregulatory control of central and systemic angiotensin II concentrations in dogs.

In 14 dogs angiotensin (ANG II)-like immunoreactivity was analyzed in simultaneously collected samples of cerebrospinal fluid (CSF) from the anterior part of the third cerebral ventricle and of plasma. Plasma and CSF ANG II were not different in euhydrated conscious dogs (29.3 +/- 2.7 and 30.8 +/- 2.8 pg X ml-1, means +/- SE). During anesthesia CSF ANG II was not significantly altered, but plasma ANG II was more than doubled in comparison with conscious animals. In conscious dogs 24 h of dehydration with sodium-rich food significantly increased ANG II concentration in the plasma (to 59.8 +/- 16.5 pg X ml-1) and CSF (to 71.8 +/- 20.1 pg X ml-1). Subsequent rehydration by drinking caused no consistent changes in plasma ANG II within 90 min but reduced CSF ANG II significantly. Salt loading by infusion of 5% saline in seven conscious dogs produced a small but consistent decrease in plasma ANG II by 20%, on average, whereas CSF ANG II rose in five animals. The directions of changes in concentration of central ANG II compared with plasma ANG II suggest that central endogenous ANG II may function as a central osmoregulatory mediator independent from systemic ANG II.

Angiotensin II↗
PubMed1986

[Methodological and experimental studies of jet ventilation--indications and limits of the procedure].

Results of experimental and methodical investigations of so-called "Injector-Ventilation" or jet ventilation verify procedures' safety regarding ventilation and anaesthesia management. Classification of jet ventilation permits delimitation to IPPV and different methods of HFV. Resulting from considerations, especially based on reported insignificancy of "Venturi-Effect" under clinical conditions, authors suggest use of unitary term "Normo-Frequent Jet Ventilation" (NFJV).

Anesthesia, Inhalation↗
PubMed1986

[Normofrequent jet ventilation (N20/02 mixture). I. Anesthesiologic principles and experiences using the jet ventilation method].

Report on normo-frequent jet ventilation using N2O/O2 mixture for endolaryngeal and tracheal diagnostic and surgical procedures. Presentation of a system of flexible and rigid sounds. Choice of sounds and driving pressures permits adaptation to different physiological and pathological conditions. Possible methodical complications and their prophylaxis are pointed out. Cardiac arrhythmias occur caused by manipulations only and independent of jet ventilation. Therefore authors recommend continuous ECG monitoring during endolaryngeal manipulations under general anaesthesia too.

Anesthesia, Inhalation↗
PubMed1986

[Critical evaluation of jet ventilation from the viewpoint of the endoscopist].

Endoscopists' clinical experiences using jet ventilation (N2O/O2 mixture) for microlaryngoscopy, endolaryngeal microsurgery and tracheobronchoscopy of adults, children and (small) infants are advantageous. Especially authors accentuate: Improved clearness of laryngeal area; overcoming intubation obstacles; extraordinary variability of sounds' arrangement. Authors observed no complications caused by this method. A "symptom of absent sharpness" (microscope) refers to dignity of epithelial alterations at vocal cords. The hygienic molestation of endoscopist by gas backflow is disadvantageous; on the other hand the same backflow essentially excludes a potentially risk of aspiration.

Adult↗
PubMed1985

Control of plasma angiotensin II in a bird with salt glands (Anas platyrhynchos).

A radioimmunoassay was developed for the measurement of avian angiotensin II (1Asp-5Val-AII) in the blood plasma. This assay was used to investigate the relationship between body fluid parameters and plasma levels of AII in the Pekin duck, an avian species employing salt glands, besides the kidneys, for NaCl excretion in case of chronic salt stress. A plasma AII concentration of 35.3 +/- 3.9 pg X ml-1 (mean +/- SE) was found in normally hydrated, freshwater-adapted (FW) ducks with a plasma osmolality of 294.9 +/- 0.9 milliosmoles (mOsm) X kg-1. In saltwater-adapted (SW) ducks with a plasma osmolality of 312 +/- 1.5 mOsm X kg-1 and functioning salt glands, a plasma AII level of 102.6 +/- 9.3 pg X ml-1 was found and plasma AII was positively correlated with plasma osmolality (r = 0.601; n = 47; 2P less than 0.001). Intravenous infusion of AII at different rates resulted in a strictly linear relationship between the log values of the AII plasma concentrations and the infusion rates, indicating a plasma clearance rate for AII of 119 ml X min-1 X kg-1 when taking into consideration endogenous AII formation. Experiments designed to produce physiological changes in body fluid and plasma volume and tonicity in FW and SW ducks by appropriate salt and/or water loading indicate that although both parameters may contribute to the control of plasma AII, volume is the dominant stimulus.

Adaptation, Physiological↗
PubMed1985

Arginine vasotocin and glomerular filtration rate in saltwater-acclimated ducks.

We examined the relationship between whole kidney glomerular filtration rate (GRF) and the plasma concentration of immunoreactive arginine vasotocin (AVT), the avian antidiuretic hormone, in saltwater-acclimated ducks. During steady-state diuresis, driven by infusion of sodium chloride solutions, transient reductions of [14C]inulin clearance (3 ml X min-1 X kg-1) occurred when plasma AVT concentrations were roughly doubled by systemic injection of synthetic AVT or after stimulation of endogenous AVT release by perfusion of the third ventricle with hypertonic artificial cerebrospinal fluid (CSF). Transient increases in GFR occurred when plasma AVT was reduced during inhibition of its endogenous release by hypotonic ventricle perfusion. GFR also increased after injection of AVT antiserum but returned to control values within 30 min, while plasma AVT concentration remained very low for at least 1 day. During antidiuresis evoked by infusion of strongly hypertonic saline, GFR values estimated from plasma disappearance curves of [125I]iothalamate were not different from the GFR values estimated subsequently with the same method in the same ducks made diuretic by hypotonic saline infusions, although AVT concentrations were depressed during the latter as compared with the former infusion. Factors other than AVT must be important for the control of GFR during sustained osmotic stress.

Adaptation, Physiological↗
PubMed1985

Contribution of individual superficial nephron segments to ammonium handling in chronic metabolic acidosis in the rat. Evidence for ammonia disequilibrium in the renal cortex.

Ammonia entry along surface nephron segments of rats was studied with micropuncture techniques under control and chronic metabolic acidosis conditions. Tubule fluid was collected successively from sites at the end and beginning of the distal tubule and at the end of the proximal tubule of the same nephron. During chronic metabolic acidosis, ammonium excretion doubled. As anticipated, the ammonium concentration (TFNH+4) was significantly higher in proximal tubule fluid during acidosis, and ammonium delivery to end proximal sites increased from 19.4 +/- 2.3 to 34.0 +/- 3.2 pmol/min (P less than 0.001). Although chronic acidosis did not affect TFNH+4 at the beginning of the distal tubule, ammonium delivery to the end of the distal tubule increased from 5.72 +/- 0.97 to 9.88 +/- 0.97 pmol/min. In both control and acidotic groups ammonium delivery was lower (P less than 0.001) to end distal sites than to end proximal sites, indicating net loss in the intervening segment. This loss was greater during chronic metabolic acidosis (23.9 +/- 3.3 vs. 13.6 +/- 2.0 pmol/min in controls, P less than 0.025). In both groups net entry of ammonia, in similar amounts, occurred along the distal tubule (P less than 0.05). In situ pH averaged 6.80 +/- 0.05 at end proximal tubule sites and fell to 6.54 +/- 0.08 at the beginning of the distal tubule (P less than 0.005). Chronic metabolic acidosis did not affect these measurements. The calculated free ammonia at the end of the proximal tubule rose from 9.3 +/- 2.2 to 21 +/- 9 microM (P less than 0.005) during chronic metabolic acidosis, and was also higher at beginning distal sites during acidosis (8.8 +/- 2.4 vs. 2.7 +/- 0.7 microM in controls, P less than 0.05). In both groups ammonia values for the beginning distal tubule fluid were lower than for end proximal tubule fluid. Thus, loss of ammonium in the loop segment is enhanced by chronic metabolic acidosis. Distal entry of ammonia is markedly less than along the proximal tubule and does not change in chronic metabolic acidosis, and ammonia permeabilities for the proximal and distal segments of surface nephrons seem different.

Acidosis↗
PubMed1984

A comparison between total body thermosensitivity and local thermosensitivity in mammals and birds.

We have investigated how total body thermosensitivity in various mammalian and avian species (mouse, rat, golden hamster, guinea pig, rabbit, dog, goat, pigeon, duck, goose) is related to their respective local thermosensitivities in the hypothalamus, spinal cord and skin. Local and total thermosensitivities were determined by measuring the relationship between the response of one thermoregulatory effector, metabolic heat production, and the appropriate temperature. Local cooling was performed with chronically implanted, water perfused thermodes, and local thermosensitivities were estimated by relating the maximum activation of metabolic heat production to the induced decreases in local temperature. Total body cooling was achieved by means of chronically implanted intravascular heat exchangers or with thermodes inserted into the lower intestinal tract, and total body thermosensitivity was assessed by relating the rise in metabolic heat production to the induced fall in core temperature. These analyses plus previous estimations derived from the literature show total body thermosensitivity in the different species to range from -4.0 to -12.0 W X kg-1 . C-1. We also measured rabbit spinal cord thermosensitivity and guinea pig hypothalamic and spinal cord thermosensitivity; values for local thermosensitivity in other species were derived from the literature. In all species, local thermosensitivities determined as cold sensitivities in the described way were smaller than the corresponding total body core sensitivities. We conclude that thermosensitive structures outside of the investigated thermosensitive areas contribute a major input to the controller of body temperature, particularly in avian species in which hypothalamic thermosensitivity is lacking.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Plasma and cerebrospinal fluid vasopressin and osmolality in relation to thirst.

Conscious dogs chronically implanted with a device for cerebrospinal fluid (CSF) sampling from the anterior 3rd ventricle were submitted to 24 h dehydration. During rehydration by drinking the total water intake ( TWI ) after 16 min was determined in 8 and after 90 min in 14 experiments. Samples were simultaneously drawn to determine the osmolalities (Posm, CSFosm ) and AVP concentrations (PAVP, CSFavp ) of plasma and CSF. After 24 h dehydration all of these parameters were significantly elevated in comparison to euhydrated dogs investigated on 19 occasions. In 8 experiments 60% of the final TWI had been ingested within the first 16 min with no changes of Posm, CSFosm and CSFAVP , but a significant decrease of PAVP at this time. TWI per kg body weight ( TWI X kg-1) after 90 min was significantly correlated with the osmolalities and AVP levels in plasma and CSF prior to rehydration. The decreases of Posm, CSFosm and PAVP, but not of CSFAVP , were significantly correlated with TWI X kg-1. The results indicate that PAVP and CSFAVP are subject to long term control by body fluid tonicity exhibiting a feedback relationship to water intake. In addition, PAVP but not CSFAVP seems to be under short term, possibly nonosmotic, control during water intake.

Animals↗
PubMed1984

Blood volume changes and arginine vasotocin (AVT) blood concentration in conscious fresh water and salt water adapted ducks.

Blood volume changes consisting in the removal and reinfusion respectively, of 10% of the estimated blood volume (23.2 ml on average) were induced to determine their effects on the blood concentration of arginine vasotocin (AVT), the antidiuretic hormone (ADH) of birds, in fresh water adapted ducks (water ducks) with blood osmolalities and ADH concentrations similar to those of normally hydrated mammals, and in salt water adapted ducks (salt ducks) with chronically elevated blood osmolalities and ADH concentrations. The investigations were carried out in steady state conditions, when infusion of 1 ml . min-1 of isotonic saline was matched by the excretion in water ducks and when infusion of 0.4 ml . min-1 of 1,000 mosmolal saline was matched by the salt gland excretion in the salt ducks. After blood removal, AVT blood concentration (mean +/- SE) increased from 6.5 +/- 0.4 to 8.4 +/- 0.6 pg . ml-1 in water ducks and from 18.1 +/- 1.6 to 22.6 +/- 1.9 pg . ml-1 in salt ducks. The respective blood osmolalities of 297.4 +/- 1.4 and 318.6 +/- 3.3 mOsm . kg-1 did not change. Reinfusion of the blood after steady-state conditions had been reattained decreased blood AVT from 7.9 +/- 0.7 to 6.7 +/- 0.5 pg . ml-1 in water ducks. In the salt ducks AVT concentration had already returned to the control level before blood reinfusion which induced no further reduction. The blood osmolalities remained unchanged in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1984

Response of rat pancreatic proteases to dietary proteins, their hydrolysates and soybean trypsin inhibitor.

The present study was designed to determine whether the adaptation of pancreatic trypsin and chymotrypsin activities to dietary protein level can be attributed to the presence in the diet of the specific peptide bonds that are substrates for these enzymes. In addition, the effect of feeding soybean trypsin inhibitor (SBTI) was tested since this compound is known to stimulate synthesis of pancreatic proteases. For 3 weeks, rats were fed a diet containing 10, 20 or 30% protein as lactalbumin (control); lactalbumin predigested by trypsin, chymotrypsin or pancreatin; a mixture of amino acids; or lactalbumin supplemented with SBTI. At the end of the experiment, the activities of trypsin, chymotrypsin and amylase were determined in the rats' pancreatic homogenates. Trypsin and chymotrypsin activities at each protein level were exactly the same whether predigested lactalbumin or lactalbumin was fed. The 20 and 30% amino acid mixtures, however, produced a decrease in activities of both proteases. SBTI doubled the activities of both proteases at all three levels of protein. Amylase activity was maximal at 20% level of protein. It is concluded that adaptation of pancreatic proteases to dietary protein level is induced by small peptides that are digestion products of dietary protein. Induction of pancreatic trypsin or chymotrypsin therefore does not require the presence of substrate for these enzymes in the intestine. Dietary SBTI produced a considerable increase in pancreatic proteases compared to that produced by proteins or peptides. It is suggested that the increases in pancreatic proteases caused either by protein-rich diets or SBTI are mediated by two distinct mechanisms.

Amylases↗
PubMed1984

The effect of feeding soybean trypsin inhibitor and repeated injections of cholecystokinin on rat pancreas.

The effects of dietary soybean trypsin inhibitor (SBTI, Kunitz type) or repeated i.p. injections of 95% pure cholecystokinin (CCK-39) on rat pancreas were investigated in a 10-day experiment. SBTI and CKK -39 induced similar increases in pancreatic weight, which led to both cellular hypertrophy and hyperplasia. Trypsin and chymotrypsin activity increased with an increase in pancreatic weight. Amylase activity increased only after CCK-39 injection, whereas lipase activity was not affected by either SBTI or CCK-39 treatment. After both treatments, insulin content showed only a slight tendency to increase, whereas glucagon content was not different from controls. The results indicate that SBTI and CCK-39 mainly exert their effects on the exocrine pancreas in a similar but not identical manner. It is therefore suggested that SBTI is not only a potent stimulator of the secretion of CCK activity but also of other unidentified gastrointestinal factor(s).

Amylases↗