Development of a special catheterbag to enable artificial organ evaluation in conscious, unrestrained pigs: technical note.

Pigs are widely used as models for a variety of human diseases, because many of their physiological functions closely resemble those of humans. However, information on instrumentation techniques is still scarce. In particular, experiments in conscious pigs focused on extracorporeal circuits are connected to a variety of methodical problems with respect to the handling of the animals. Usually, pigs are placed in restraint-slings during the application of an extracorporeal system. However, this method of restraint may lead to excessive mental distress even in trained animals. The latter might influence the results and certainly affects principles of animal welfare. Our own experiences with instrumented, conscious, but unrestrained dogs encouraged us to modify methods used for the fixation of in-dwelling central venous catheters in dogs with special regard to the species specific behaviour and phenotype of pigs. A cord retractable leash (CRL) was used for maintaining a safe distance between the animal and the outer ends of the catheters. To prevent dehiscences of the required fixation sutures a new catheter bag (CB) was designed to counteract tension forces caused by the CRL's spring-mechanism. The combination of both the CRL and CB enabled us to conduct safe experiments with conscious, unrestrained pigs. We alleviated the mental distress these animals were exposed to in comparison to former methods based on restraint of the animals.

Dose dependency of fermentation and the extent of renal excretion of palatinit (isomalt) in rats with respect to its energy value.

The impact of dose-dependent caloric salvage by microbial fermentation processes in the lower gut and the extent of renal excretion for the overall energetic availability of the alternative bulk sweetener Palatinit were investigated in rats. To evaluate the extent of dose-dependent fermentation a conventional and a germ-free rat model were used and fecal excretions of Palatinit after intragastric application were compared. Because of the lack of bacterial colonization in the gastrointestinal tract in germ-free rat the difference in fecal excretion of Palatinit between germ-free and conventional rat is mainly due to bacterial fermentation. To determine the amount of renal excretion of Palatinit the urine was collected. The experiments were conducted using different amounts of Palatinit (300 and 1,200 mg/kg body weight = mg/kg b.w.). Fecal excretions of Palatinit and its monomers (sorbitol and mannitol) were measured by high-performance liquid chromatography (HPLC) and for the determination of renal excretions a gas chromatography system was used. After the application of 300 mg/kg b.w. Palatinit only the breakdown product sorbitol could be recovered in the feces of germ-free rats (29% of the applied dose). No intact Palatinit could be found. In contrast, neither Palatinit nor the breakdown products sorbitol or mannitol could be detected in the feces of conventional rats after application of the same dose. After the application of the higher dose only small amounts of intact Palatinit were found in the feces of germ-free rats (average 12%). There was no intact measurable Palatinit in the feces of conventional rats. The fecal excretions of sorbitol and mannitol in the feces of the germ-free rats were 55% and 39%; in conventional rats only 21% sorbitol was excreted. Only traces of Palatinit, sorbitol or mannitol were found in the urine of conventional and germ-free rats after application of the low as well as the high dose. In conclusion, this study clearly shows the dose dependency of fermentation and therefore the dose dependency of the energetic (i.e., caloric) availability of this disaccharide sugar alcohol. In the calculation of the energy value of Palatinit the renal excretion of Palatinit and its monomers can be neglected.

A method for estimating the available energy of incompletely digested carbohydrates in rats.

We developed a method to estimate the available energy from carbohydrates that are unavailable or partially unavailable through direct digestion and absorption. Radiolabeled bacterial and plant cellulose and polydextrose were administered orally to germfree and conventional rats. Label in breath, feces, intestinal contents and carcass were determined with excellent total recovery of the administered label. Comparison of these measurements in germfree and conventional rats was used to calculate the energy directly available by digestion and that available only after fermentation. Although the method overestimates available energy because of the more efficient digestive metabolism of the germfree rat, it provides a reliable, maximum energy value based upon fewer assumptions than previous methods. In conventional rats, 65% of the administered cellulose and 54% of the administered polydextrose were recovered in feces. In conventional rats, appreciable amounts of cellulose were fermented and an available energy value of 3.5 kJ/g was calculated. Calculation of the total availability of polydextrose, taking into account the direct absorption of small amounts of monomers present and the efficiency of fermentation, indicates an available energy value of 4.7 kJ/g.

Prevention of catheter-related infections by a new, catheter-restricted antibiotic filling technique.

Catheter-related infections pose a hazard to both humans and laboratory animals. The aim of this study was to develop a technique preventing bacterial colonization of intravascular catheters. In 27 dogs a total of 70 catheters were implanted. On an average catheters were used for 207 days. Three protocols were compared: (1) flushing the catheters with a heparinized solution; (2) filling only the catheter lumen with alpha-chymotrypsin solution (225 units/ml); (3) filling only the catheter lumen with a solution containing a mixture of the aminoglycoside antibiotic gentamicin (20 mg/ml) and chymotrypsin (225 units/ml). Catheter fillings were always withdrawn before catheter use. Catheter exit sites were all treated with povidone iodine ointment once a day. Body temperatures and weights were recorded, bacteriological and electron microscopical examinations of catheters performed. Without gentamicin filling all catheters were colonized after a few weeks. The dogs showed clinical signs of chronic bacteraemia. Gentamicin filling eradicated colonization. No further bacteraemia was observed. We conclude that filling only the catheter lumen with a concentrated solution of chymotrypsin and gentamicin, combined with measures to prevent infections via the subcutaneous catheter tunnel, is an effective and safe technique to prevent catheter-related infections.

[A simple method for 14CO2 measurement in metabolic experiments]. / Eine einfache Methode zur 14CO2-Messung bei Stoffwechselversuchen.

The determination of the fate of a compound following administration can be performed using the disposition method with 14C-labeled substances, which also allow the measurement of metabolism with CO2 as an expired end product. To substitute the laborious CO2-collection in washing bottles as carbonate a simple instrumentation was built for continuous 14CO2-measurement. The air from the metabolic cage is led in thin layer through a chamber fitted to a foot-monitor, the output of which is online for computation. The instrument is sensitive and calibration is easy.

[Metabolism of 14C-labeled urea in conventional and bacteria-free guinea pigs]. / Stoffwechsel von 14C-markiertem Harnstoff bei konventionellen und bakterienfreien Meerschweinchen.

This report deals with the utilization of 14C-labeled urea in antibiotically decontaminated, bacteria-free guinea pigs using intragastric resp. intraperitoneal administration route. With conventional animals 52% of the intragastrically administered 14C dose can be demonstrated in the exhaled air, 1.2% in organs and 41% in the urine. 1.8% were found in intestinal and faecal contents. In bacteria-free animals 29% of the activity appeared in the exhaled air, 52% in urine and 2% remain in the intestinal tract, feces and animal body. Intraperitoneal administration of 14C urea revealed 17% resp. 14% in the exhaled air, 72% resp. 66% in urine and 2% resp. 3% in intestinal tract, feces and animal body in conventional resp. bacteria-free guinea pigs.

[Leukocyte agglutination test for the determination of microbial burden]. / Leukozyten-Agglomerationstest zur Feststellung mikrobieller Belastung.

Transfer of laboratory animals from the breeder to the experimental unit includes in most cases a change of the microbial environment even under SPF-conditions. Many experimental treatments may also disturb the balance between host and microbial load and provoke infections. With the aim to detect such undesired effects in the course of the experiment the suitability of the leukergy test was investigated. SPF-rats, endotoxin-treated rats, and conventionalized germ-free rats were checked for leukocyte agglomeration, and the findings were compared with total leukocyte number, blood picture, endotoxin content in the blood and body temperature. A rise of leukergy from 10 to more than 20% was recorded in endotoxin-treated and conventionalized rats.

[Modification of the teratogenesis of actinomycin D and cyclophosphamide by a Mycoplasma pulmonis infection in rats]. / Modifikation der Teratogenese von Actinomycin-D und Cyclophosphamid durch eine Mycoplasma pulmonis-Infektion bei der Ratte.

In the present investigation experiments have been made on the modification of the teratogenesis by a Mycoplasma pulmonis infection in rats. Substances with known teratogenic effects (Actinomycin D, Cyclophosphamide) were used. Groups of artificially infected pregnant rats were compared with pregnant rats from the SPF unit. The present study has shown that in the group of artificially infected animals no significant increase of the teratogenic effects by Actinomycin was found. In the Cyclophosphamide-treated groups more and more serious malformations have been observed in relation to dose and day of treatment.

Intestinal accumulation of urea in germ-free animals--a factor in caecal enlargement.

To examine the connection between caecal size and urea concentration in the caecal contents urease inhibition was tested in conventional animals and urea and urease were administered to germ-free rats and mice. Administration of alloxan and barbituric acid and immunization with urease led to slightly larger caeca in conventional animals. Neomycin treatment caused a clear enlargement of the caecum. In germ-free animals urease administration led to a reduction in the caecal size, whereas urea in the drinking water caused enlargement. The urea concentration and the urease activity in the caecal contents correlated well with the caecal weights.

[Sterilization of drinking water using peracetic acid]. / Tränkwassersterilisation mit Peressigsäure.

The efficiency of peracetic acid on drinking-water conservation and sterilization was investigated. It was determined in watering experiments that a starting concentration of 0.01-0.02% peracetic acid was required in order to guarantee the sterility of water and water-bottle for a duration of one week. As the applied peracetic acid concentration could be reduced by addition of organic substances such as saliva and stomach content, the possibility of peracetic acid resorption by the animal is negligible.