Pleurodesis with polidocanol in pigs. An experimental study.

Polidocanol was instilled in five pleural cavities of three pigs. Adhesions formed in all. Adhesion distribution varied from covering a minor part to most of the lung, depending on the amount of polidocanol. One control cavity treated with sodium chloride was unaffected. Microscopy showed fibrous bridges between the pleural layers and mild submesothelial fibrosis and inflammation.

Lymphatic clearance of synovial fluid in conscious pigs: the aminoterminal propeptide of type III procollagen.

The aminoterminal propeptide of type III procollagen (PIIINP) in serum is employed as a direct marker of fibrillogenesis. The balance between local fibrillogenesis and serum PIIINP is governed by the transport and possible degradation en route from tissue to circulation. In conscious pigs, we investigated the transport of PIIINP from the knee cavity into the circulation after intra-articular injection of radiolabelled PIIINP followed by sequential sampling of thoracic duct lymph, serum and urine. Clearance from the joint space was evaluated by external detection of 131I-HSA, used as co-tracer. Lymph samples were gel filtrated to assess possible lymphatic degradation of the intact PIIINP. 125I-PIIINP and 131I-HSA were found in thoracic duct lymph within 20 min of the intra-articular injection. Both isotopes had a biphasic appearance, with the first peak after 60 min and a larger peak after 150 min. During the 6 h observational period 18% of the injected PIIINP was found in the lymph. Gel chromatography of lymph showed the fast formation of a small fraction with a lower MW than that of PIIINP, which suggests that some degradation of PIIINP may occur through the lymphatics. The half-life of the joint clearance of HSA by bulk flow was assessed to be 8.3 h. The clearance of PIIINP from the joint was estimated to be equal to that of HSA, which indicates that PIIINP leaves the joint space by bulk flow as has been proposed for HSA.(ABSTRACT TRUNCATED AT 250 WORDS)

Fate of circulating amino-terminal propeptide of type III procollagen in conscious pigs.

The amino-terminal propeptide of type III procollagen (PIIINP, M(r) 42,000) is a promising marker for the formation of type III collagen of granulation tissue in experimental and clinical studies. The disposal kinetics of circulating PIIINP is, however, almost unknown. In conscious pigs with a thoracic duct-venous shunt, 125I-labeled PIIINP was injected intravenously. The initial distribution volume was 2.2 liters, which was 1.7 times the plasma volume (P < 0.01). The disappearance curve was three-phased, with an initial steep decline (t1/2 58 min), followed by two slower phases (t1/2 239 min and 289 h). Consecutive gel filtrations showed that the initial slope of the plasma disappearance curve corresponded to the plasma clearance of the intact PIIINP. The initial plasma clearance was 26.5 ml plasma/min, whereas the urinary clearance was 8.7 ml plasma/min (P < 0.01). The other components of the plasma disappearance curve originated from the formation and disappearance of a high and a low molecular weight (MW) fraction as part of the degradation of PIIINP. The high MW fraction (approximately M(r) 90,000) was similar to a previously described, but not further characterized, PIIINP immunoreactive component. The existence of the low MW fraction (approximately M(r) 20,000) has not been reported before. The lymphatic recirculation of intact PIIINP was rapid, and the lymph-serum ratio was almost constant within 1 h of injection. We conclude that the t1/2 of circulating PIIINP is 58 min, that PIIINP escapes the circulation very quickly, and that the degradation of PIIINP includes at least two intermediary steps.

Histomorphological evaluation of wound healing of rabbit oviduct after microsurgical reanastomosis with the use of autologous fibrin adhesive, human fibrin adhesive or poly-glycolic acid suture.

The morphology of the healing process of microsurgical reanastomosis of the rabbit oviduct with the use of fibrin adhesive, autologous and heterologous, and conventional sutures is described. Both oviducts in 48 rabbits were cut and reanastomosis were performed. The rabbits were killed at different intervals after the operations, ranging from 2 h to 28 days, and the anastomoses were evaluated by histomorphological examination. The autologous fibrin adhesive was absorbed after a week and an uncomplicated healing was observed. Heterologous fibrin adhesive caused a granulomatous inflammation interpreted as an immune reaction of the host to the foreign protein, and conventional suturing resulted in severe tissue damage with an intensive inflammatory reaction.

Multiple oral administration of a ketoprofen-dextran ester prodrug in pigs: assessment of gastrointestinal bioavailability by deconvolution.

Deconvolution has been applied to estimate the in vivo dissolution/release process of ketoprofen from a ketoprofen-dextran ester prodrug in pigs. The prodrug was given to three pigs at intervals of 12 hr and in seven doses corresponding to 4 mg ketoprofen/kg body weight. Frequent blood sampling was carried out at the first, third, and seventh intervals. Plasma steady-state concentrations of ketoprofen following the prodrug administration were between 2 and 4 micrograms/ml. The reference consisted of a single p.o. dose of parent ketoprofen (4 mg/kg body weight). For each pig the response following the multiple dosing was deconvolved with the reference response using an algebraic deconvolution procedure adopted from the literature. The obtained cumulated in vivo dissolution/release profiles revealed similar release rates for the three pigs and similar extents of release (59, 70, and 65%). The mean in vivo dissolution/release times (MDT) were calculated to be 5.4, 6.1, and 5.7 hr, respectively. In conclusion, following administration of the dextran prodrug the plasma concentration curves and the dissolution/release profiles are uniform, with small interindividual variations.

Purification of porcine aminoterminal propeptide of type III procollagen from lymph and use for lymphatic clearance studies in pigs.

To investigate the lymphatic transport of the aminoterminal propeptide of type III procollagen (PIIINP) we established a thoracic duct-venous shunt in 6 pigs. Porcine PIIINP was purified, characterised, and compared with human PIIINP to ensure the suitability of the radioimmunoassay of human PIIINP for measurements in pigs. SDS-PAGE and radioimmunoinhibition assays show human and porcine PIIINP to be similar, thus indicating that the assay of human PIIINP is also reliable for determinations on pig serum and lymph. Intact PIIINP, as identified by gel filtration, accounted for 60% and 40% of the total PIIINP immunoreactivity in lymph and serum, respectively. The higher amount of total immunoreactivity and proportion of intact PIIINP in lymph compared with serum support the hypothesis that intact PIIINP is transported from peripheral tissue into the circulation by lymph. Two days after the shunt was established, the lymph was collected quantitatively hour-by-hour for 24 h. The flow was higher during the light periods than in the dark (p less than 0.01). The PIIINP concentration varied inversely with the flow, being higher in the dark hours (p less than 0.03). However, the total collected amount of PIIINP in lymph did not differ during the light and dark periods. Serum PIIINP remained unchanged over the 24 h. The lymphatic clearance of total PIIINP immunoreactive components was 6.2 ml serum/min and the lymphatic clearance of intact PIIINP was 9.1 ml serum/min, equal to 7 and 10 times the plasma volume/24 h, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiovascular effects of pregnanolone emulsion: an experimental study in artificially ventilated dogs.

The acute cardiovascular effects of pregnanolone emulsion, a new steroid preparation for intravenous anaesthesia, were investigated in artificially ventilated dogs. The anaesthetic was administered as repeated intravenous bolus injections, doubling the dosage with each injection. The plasma concentration of pregnanolone, and the haemodynamic, respiratory and metabolic variables were determined after each injection. Cardiac output and heart rate increased from the first bolus dose of the anaesthetic (0.5 mg/kg), which produced anaesthesia lasting 10 to 15 min. Both continued to increase after administration of 1.0, 2.0 and 4 mg/kg, whereas reductions of systemic arterial pressure and estimated myocardial contractility were observed only at the two highest dosages. A decrease in vascular resistance was calculated in the systemic circulation, whereas vascular resistance increased in the pulmonary circulation. A state of circulatory shock followed administration 8, 16 and 32 mg/kg of the anaesthetic.

Electrical potential difference across the stomach wall and gastric morphology in anaesthetized pigs after intravenous administration of cytotoxic drugs.

Nausea and vomiting are frequent side-effects of cancer chemotherapy. To investigate whether such therapy has an acute toxic effect on the gastric mucosa, cyclophosphamide, epirubicin and fluorouracil were administered intravenously to anaesthetized pigs. Gastric mucosal function was evaluated by continuous measurements of the gastric transmucosal electrical potential difference (PD) and the intragastric pH by using a newly developed microelectrode principle. After sacrifice, gastric histology was examined. During chemotherapy a significant decline in gastric PD was observed two hours after drug infusion, indicating a hampered gastric mucosal function. Apart from a slight hyperemia, gastric histology was normal. In this animal model a change in gastric mucosal function developed at the same time after chemotherapy as the gastric side-effects in humans.

Bioavailability of ketoprofen from orally administered ketoprofen-dextran ester prodrugs in the pig.

The bioavailability of ketoprofen after oral administration of aqueous solutions of various ketoprofen-dextran ester prodrugs in pigs was assessed. Conjugates derived from dextran fractions in the molecular weight range 10,000-500,000 were employed. Compared to the administration of an oral solution of an equivalent dose of parent ketoprofen, the average absorption fractions for the different prodrugs ranged from 100 to 67%. Relatively small inter-individual variation of ketoprofen bioavailability was observed. Apparently, the molecular size of the employed dextran transport group only has a minor influence on the pharmacokinetic parameters. The ketoprofen plasma profiles for all the administered prodrugs exhibited a characteristic lag time of ketoprofen appearance in the blood (2-3 h). Quite similar results were obtained from identical experiments carried out in the pig, employing naproxen-dextran esters. Thus, the present study adds support to a more versatile application of the dextran ester prodrug approach to providing selective colon delivery of drugs possessing a carboxylic acid functional group.

Stability of ketoprofen-dextran ester prodrugs in homogenates of various segments of the pig GI tract.

Initial velocities of ketoprofen formation from ketoprofen-dextran ester prodrugs incubated in homogenates of various segments of the pig GI-tract were determined. Enzyme-mediated drug release was found in caecum and colon homogenates with their contents, whereas release rates in the stomach, duodenum, jejunum and ileum homogenates were comparable to those determined in pure buffer solutions of identical pH. In colon homogenates adjusted to various pH values between 6.0 and 7.9, little variation in release rates was observed. However, the contribution of enzyme-catalyzed drug regeneration to the overall initial velocity of ketoprofen formation increased significantly as a function of decreasing pH. The presence of several antibiotics and betamethasone in colon homogenates did not affect the drug activation process, whereas the addition of various enzyme inhibitors slowed down the ketoprofen release rates. During incubation in colon homogenates the average molecular weight of the dextran esters decreased. The drug release may therefore involve an initial fragmentation of the drug-liganded dextran chains carried out by dextranases secreted from the microflora which reside in the pig's large bowel.

External thoracic duct-venous shunt in conscious pigs for long term studies of connective tissue metabolites in lymph.

An experimental animal model for lymph studies is described. Thoracic duct-venous shunt was established in 12 pigs. Shunt patency averaged 5.5 days. The composition of connective tissue metabolites in lymph and serum were investigated during a standardized surgical operation (thoracotomy) under general anesthesia. We measured the carboxyterminal propeptide of type I procollagen (PICP), the aminoterminal propeptide of type III procollagen (PIIINP) hyaluronan (HA) and total protein. During surgery/anesthesia lymph PICP (p less than 0.04), lymph PIIINP (p less than 0.03) and serum PIIINP (p less than 0.01) and serum PIIINP (p less than 0.03) increased. The changes may be explained by the inactive physical state of the animals. HA showed wide variations, with a tendency like PIIINP. In conscious animals the lymph/serum ratio of PIIINP and HA were 10 and 35, respectively, indicating that lymph is a major route of tissue clearance for these components. The lymph/serum ratio of PICP was 1.0 in conscious pigs, indicating a direct release into the circulation. Total protein in lymph decreased (p less than 0.04) during surgery/anesthesia, whereas no changes were observed in serum. Pigs can be used instead of dogs and sheep in studies on lymph. The effect of surgery/anesthesia must be taken into consideration.

Autologous fibrin sealant in reconstructive rabbit oviduct microsurgery.

A simple method for preparing concentrated fibrinogen for use in a tissue adhesive system is described. Approximately 75% to 80% of the plasma fibrinogen can be separated and concentrated within 45 to 60 minutes from a small blood sample collected from the patient before the operation. Autologous fibrinogen prepared by this method was evaluated in reconstructive microsurgery of the rabbit oviduct.

Macromolecular prodrugs. XVI. Colon-targeted delivery--comparison of the rate of release of naproxen from dextran ester prodrugs in homogenates of various segments of the pig gastrointestinal (GI) tract.

We have determined initial rates of naproxen formation from dextran-naproxen ester prodrugs incubated in homogenates of various segments of the pig GI tract. Drug liberation proceeded 15-17 times faster in cecum and colon homogenates than in aqueous pH 7.4 buffer or homogenates of the small intestine. The degree of conjugate substitution did not affect the liberation rates, whereas enhanced drug activation was observed with decreasing molecular size of the carrier dextran. During incubation in colon homogenates the average molecular weight of the dextran prodrugs decreased. The mechanism of drug activation from the prodrugs may therefore involve an initial depolymerization step of the dextran chains by dextranases secreted from bacteria in the pig colon. The generated small fragments then serve as substrates for esterases and other hydrolases.

Macromolecular prodrugs. XV. Colon-targeted delivery--bioavailability of naproxen from orally administered dextran-naproxen ester prodrugs varying in molecular size in the pig.

The bioavailability of naproxen after oral administration of aqueous solutions of various dextran-naproxen ester prodrugs in pigs was determined. The dextran prodrugs employed ranged in molecular weight from 10,000 to 500,000. As calculated relative to an equivalent oral dose of parent naproxen, the absorption fractions of all the derivatives were close to 100%. Only small interindividual variation of naproxen bioavailability was observed. The naproxen plasma profiles for all the administered prodrugs exhibited a characteristic lag time of naproxen appearance in the blood (2-3 hr). Compared to administration of the prodrugs alone, coadministration of excess of the parent dextran further delayed the absorption of naproxen from the GI tract. The results of the present study demonstrate the potential of dextran prodrugs for colon site-specific delivery of drugs containing a carboxylic acid functional group.

Simultaneous sampling of portal, hepatic and systemic blood during intragastric loading and tracer infusion in conscious pigs.

A surgical model for catheterization at multiple sites has been developed for use in long-term metabolic studies. For blood sampling, catheters were inserted into the portal and hepatic veins and the common carotid artery. The hepatic vein catheter was inserted from the margin of a liver lobe and led through the venous system, until the tip was close to the bifurcation with the inferior vena cava. A new technique was developed to ensure correct placement of the hepatic vein catheter using the specific extraction of indocyanin-green over the liver during surgery. Gastrostomy was performed using a Pezzer catheter. Catheters in the artery and hepatic and portal veins were patent for blood withdrawal for up to 4 weeks, and thus allowed repeated metabolic studies. Studies were performed in conscious animals familiar with the experimental situation.

Strength of implanted carbon fibers. Studies of the lumbar spine in goats.

The L3-4 supraspinous and interspinous ligaments in 10 goats were replaced with carbon fibers stabilized with silk-suture seizing. The implants were removed after 3 weeks in 5 animals and after 3 months in the other 5. The maximum traction strength of nonimplanted slings was 157 +/- 9 kg (M +/- SD). After implantation, the strength was reduced to 136 +/- 17 kg, and after 3 months to 107 +/- 9 kg. However, the maximum strength of the spinous processes was 71 +/- 19 kg, which was less than the strength of 3-month implants. We concluded that the carbon fiber sling stabilized with silk sutures could be used for replacement of the interspinous ligament.

Influence of drainage conditions on mucosal bladder damage by indwelling catheters. II. Histological study.

A previous study demonstrated a strong but short-lasting suction through the catheter eyes by a hydro-dynamically generated negative pressure fluctuation terminating bladder evacuation in some frequently occurring circumstances of indwelling catheter drainage. This report regards the biological effect. Fifteen successive evacuations on such drainage conditions in each of 4 anesthetized pigs were followed by cystectomy and histological examination. All bladders presented small swollen areas, histologically showing localized mucosal elevations dominated by edema of lamina propria and submucosa, occasionally with urothelial thinning or defects. Drainage with suction prevented in 3 animals caused normal bladders. The changes were similar to those following hydro-statical suction and much like those of the "polypoid cystitis" so commonly occurring with indwelling catheters. This suggests both types of suction by ordinary drainage as a major pathogenetic factor in the latter condition. The clinical significance and the occurrence during regimes of straight drainage or intermittent clamping are discussed.

Acute appendicitis in the rabbit. An experimental study.

With the purpose of devising an experimental model of acute appendicitis, the vermiform appendix in five rabbits was lightly compressed with a specially designed metal clamp, and in five others it was firmly ligated proximally. Based on these experiments, a final model was evolved, with a firm ligature midway on the vermiform process. This model was tested in 15 rabbits and proved to be reliable in provoking acute inflammation in one part, while the rest of the appendix remained unaffected. The literature is reviewed.

Implantation of a pressure cuff around the subphrenic oesophagus.

The possibility of implanting a pressure cuff around the subphrenic oesophagus as a barrier to reflux was tested in six pigs. The oesophagus tolerated cuff pressures from 48 to 95 cmH2O, corresponding to intra-oesophageal pressures from 27 to 75 cmH2O. The pigs with the perioesophageal cuff swallowed a solid diet without difficulty. However, dysphagia occurred in pigs kept alive for more than a month and the main reason was malfunction of the device because of surrounding fibrosis. This problem should be solved before implantation of the device in humans is attempted.