Henning Peter Olesen

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.

Salicylate- and Aspirin-Induced Uncoupling of Oxidative Phosphorylation in Mitochondria Isolated from the Mucosal Membrane of the Stomach

The hypothesis that the damaging effect on the stomach mucosa of salicylic acid and its derivatives is ascribable to an uncoupling of oxidative phosphorylation has been investigated by testing of mitochondria isolated from the corpus gland area of mini-pig gastric mucosa. Mitochondria, influenced by salicylate or acetylsalicylate (0.7-5.6 mmol/l), demonstrated increased respiration rate, decreased respiratory control ratio, and decreased P/O ratio when tested in vitro. Uncoupling of oxidative phosphorylation occurred at a salicylate concentration between 3.5 and 5.6 mmol/l.

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.

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

Abstract. 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 radiola‐belled 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. Whereas the fractional amount of PIIINP in lymph and blood was lower than that of HSA, in urine the fractional amount of PIIINP was substantially higher than that of HSA. This may be the outcome of a more rapid irreversible degradation of PIIINP than of HSA.

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.

The Influence of Acetylsalicylic Acid (Aspirin) on Gastric Mucosal Content of Energy-Rich Phosphate Bonds

The mucosal content of adenosine triphosphate, adenosine diphosphate and adenosine monophosphate in mini-pig corpus gland area and in pyloric gland area was examined after aspirin ingestion in acute experiments and after ingestion for several weeks. Ingestion of aspirin led to a statistically significant decrease of adenine nucleotide content in corpus gland and in pyloric gland area. An inverse correlation between the pH of the aspirin suspensions and the size of the decrease was established in the short-time experiments. In non-affected pyloric gland area mucosa and adenine nucleotide content was significantly lower than in the corpus gland area. Pyloric mucosa was more susceptible to aspirin-induced lowering of adenine nucleotide content than was the corpus mucosa. Prolonged aspirin ingestion led to statistically significant reductions of adenine nucleotide pool. The findings explain the decrease in mucous secretion and in acid secretion demonstrated in several studies. The finding of lower and more susceptible adenine nucleotide pool in the pyloric area might be the explanation for the preponderant occurrence of aspirin ulcerations in this region.

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)

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.

Reconstructive Microsurgery of the Rabbit Oviduct Using Serosal Microsutures and Fibrin Sealant

Microsurgical reconstruction of the rabbit oviduct was undertaken utilizing either: A: fibrin sealant in a thick layer applied to two or three serosa microsutures (20 rabbits), B: fibrin sealant only (20 rabbits), and C: microsutures only (20 rabbits). The pregnancy rates and the patency rates of the oviducts showed no significant differences between the three groups. However, the formation of adhesions at the site of re‐anastomosis was significantly lower and the total duration of surgery significantly shortened when fibrin sealant was employed. It is concluded that fibrin sealant combined with serosa microsutures certainly is the most convenient method in human tubal microsurgery seeing that this method maintains a higher tensil strength at the site of reanastomosis as compared to group B and avoid the risk of mucosal lesions as compared to group C. out using a clamp to approximate the tube ends, and instead to place two or three microsutures in the serosal layer before covering the anastomosis by fibrin sealant. Moreover, the risk of spontaneous rupture of the anastomosis between the 2nd and the 4th day after surgery, as with fibrin adhesive alone, would certainly be minimized. Accordingly the present investigation was initiated in the hope of achieving the same high pregnancy and oviduct patency rates and the same low formation of adhesions and short operation time as for anastomosis with fibrin sealant alone when compared with anastomosis by PGA microsutures.

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.