Biomedical subjects

A Tümer

Publications and source records attributed to A Tümer.

5 recordsLinked to original sources

PubMed1998

In vivo degradation and release kinetics of chloramphenicol-loaded poly(D,L)-lactide sponges.

Poly(d,l)-lactide (PDLLA) homopolymer, with an average molecular weight of 20,000 daltons, was produced by the ring-opening polymerization of d,l-lactide in the presence of SnCl(2).2H(2)O as the catalyst. The PDLLA sponges loaded with chloramphenicol were prepared by a solvent evaporation technique. The drug loadings achieved were 14.84 and 25.23 mg for the PDLLA sponges with 35 and 70 mg total weights, respectively. These sponges were implanted in Wistar rats, and in vivo degradation, drug release, and tissue reactions were followed. The PDLLA sponges carrying no drug degraded with time linearly. Almost 80% of the sponges were degraded in about 180 days. While the drug-loaded PDLLA sponges were degraded much faster in 4 weeks (about 35% of the matrix was degraded), then the degradation slowed down significantly. Drug release from the sponges was parallel to the degradation. Almost 60% of the loaded drug released in 4 weeks. There were no acute inflammatory reactions in the initial period, either for the plain or for the drug-loaded PDLLA sponges. Macrophages and multinuclear giant cells start to appear after 7 days of implantation. The fibroblastic activity also started after the same period. After that, there were decreases in the number of some cells (neutrophils, lymphocytes, and macrophages), while multinuclear giant cells and fibroblastic activities gradually increased. Granulation tissue started at about 1 month, and new connective tissue was gradually formed until 180 days of implantation. There were significant numbers of inflammatory cells after 60 days, which were replaced by fibroblasts after 180 days. There was almost no significant neovascularization after 180 days, but implant fragmentation gradually increased (which slows the degradation) with time. It was concluded that this novel drug release sponge may be safely and effectively used as an active soft tissue-filling material.

Animals↗

PubMed1983

Fate of cholesterol-rich liposomes after subcutaneous injection into rats.

The fate of small (30-60 nm) and large (about 400 nm diameter) liposomes composed of phosphatidylcholine or sphingomyelin and equimolar cholesterol and containing quenched carboxyfluorescein and 111In-labelled bleomycin after footpad injection of rats was investigated. Judging from the values of latent carboxyfluorescein in the plasma, phosphatidylcholine and sphingomyelin small liposomes entered the blood circulation intact, presumably via the lymphatics to reach 3 h after injection a peak of 16.9 and 23.1% of the dose per total blood, respectively. Of the 111In radioactivity given in phosphatidylcholine liposomes, about 32% was recovered in the liver. Hepatic uptake of 111In for sphingomyelin liposomes was lower (about 9%) reflecting their slower rate of clearance. No latent carboxyfluorescein could be detected in the blood after injection with phosphatidylcholine or sphingomyelin large liposomes and levels of 111In in the liver (and spleen) were very low. A proportionally much greater amount of liposomal 111In was intercepted by the popliteal and to a lesser extent, the lumbar lymph nodes. Such uptake was significantly higher (e.g. 463%) for small than for large (e.g. 195% per g popliteal nodes) liposomes. After foot pad injection of large liposomes into Walker 256 tumour-bearing rats, localization of 111In in the popliteal nodes was similar to that seen with control animals. However, 111In localization in the lumbar nodes was augmented more than 5-fold. These results suggest that large liposomes as used in this study, characterized by efficient drug entrapment, inability to reach the liver and spleen and improved localization in the lymph nodes of tumour-bearing animals may be preferable to vesicles of small size for the local treatment of lymphatic metastases.

Animals↗

PubMed1983

Spontaneous contractions and stretch-evoked responses of isolated lymph nodes.

In this study the spontaneous activities of prescapular lymph nodes, which were isolated from calves, goats and sheep and mesenteric lymph nodes of guinea-pigs were recorded and analysed in the frequency domain. Stretch-evoked contractions of the mesenteric lymph nodes were also recorded and their frequency characteristics analysed. The preparations were placed in a Krebs solution which was kept at 37 degrees C and bubbled continuously with a mixture of 95% O2 and 5% CO2. The tension changes occurring in the lymph nodes were recorded. The patterns obtained were initially transformed into numerical values which were then used to obtain autocorrelation functions and power spectra, according to the time series analysis method. A passive stretch of 100 s duration was applied to the mesenteric lymph nodes and the responses were examined using the transient response-frequency characteristics method. It was observed that prescapular and mesenteric lymph nodes had spontaneous activities due to the contractions of the smooth muscles within the nodes. A frequency analysis of these contractions indicated that at least three contractile components were responsible for the contractions; these components contract within the frequency bands of 0.01-0.04 Hz, 0.05-0.07 Hz and 0.09-0.14 Hz respectively. It was also observed that the spontaneous activities could be regulated and synchronized by stretch. It is suggested that these contractions of the lymph nodes play an essential role in lymph propulsion within the nodes.

Animals↗

PubMedDate not supplied

Decrease in the placental transfer of chloramphenicol when administered in albumin microspheres into rats.

Chloramphenicol is an antibiotic which can pass across the human placenta and has teratogenic effects in the foetus. When this antibiotic is entrapped in albumin microspheres and administered to pregnant rats intravenously its placental transport is significantly lowered when compared with that of free drug. Drug modifications such as entrapment are suggested as an alternative way to prevent harmful effects of drugs in case of consumption during pregnancy.

Animals↗

PubMedDate not supplied

Effect of encapsulation of chloramphenicol in albumin microspheres on its in vitro transfer across the human placenta.

The possibility of reducing drug transfer across the placenta was tested in two of our previous studies. The aim of those studies was to demonstrate an alternative method of drug application during pregnancy which we think would yield a dual benefit, i.e. protecting the foetus from the harmful effects of drugs while curing the mother. The present study was planned as a continuation of the testing of the same idea and we tried to see the effect of albumin microsphere encapsulation of chloramphenicol on its transfer across the human placenta in vitro. Microspheres containing chloramphenicol were prepared according to the method previously described. The mean per cent encapsulation of chloramphenicol in albumin microspheres was found to be 42 +/- 4.3 per cent (n = 5) and the mean size of the albumin microspheres was 3.08 +/- 0.6 mm. In vitro stability of the drug-carrying microspheres was measured by dialysing them at 37 degrees C for 24 h. Chloramphenicol was released from the microspheres gradually leaving about 50 per cent of the entrapped drug in the microspheres after 1.5 h. About 20 per cent of the chloramphenicol was retained in the microspheres at 24 h postincubation. The persistence of the antibacterial effect of the released chloramphenicol is confirmed by antibiogramme tests. In the perfusions the initial free drug concentration was kept at 100 mg/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Albumins↗