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Biomedical subjects

H Schott

Publications and source records attributed to H Schott.

At least 73 records · Page 4Linked to original sources
PubMed1988

[The osteocutaneous outer arm flap. A new concept in microsurgical mandibular reconstructions].

The authors present five cases where the OCLAF technique was adapted to reconstruct large mandibular defects. Some significant advantages made us think about the possibility of the OCLAF as an acceptable alternative in that specific case. These are the ease and safety of the dissection, the respect of a bony vascularisation, a very valuable pedicle size, and a remarkable mobility of the skin paddle to the underlying bone. Of course we had to face some minor disadvantages: the microsurgical procedure, the donor site scar, the absence of cancellous bone in the transfer and the weakening of the bone shaft at the donor site. Nevertheless we think the OCLAF is to be considered whenever large mandibular defects have to be reconstructed with vascularized bone.

Adult↗
PubMed1987

Swelling studies of gelatin. II: Effect of additives.

Interactions between gelatin and six cationic, anionic, and nonionic drugs or excipients were investigated through their effects on initial swelling rate and equilibrium swelling of gelatin. Short rectangular strips of Type B gelatin containing the additives were immersed in buffer solutions of pH 7.0 at 20 degrees C. Their weight gain due to uptake of buffer solution and their weight loss due to leaching of the additive and of gelatin were determined as a function of time. During preparation of the strips, methyprylon and dicloxacillin sodium crystallized, while octoxynol 9 separated as small droplets in the gelatin matrix. Up to 7% of gelatin leached into the buffer solution during 96 h of immersion from strips of plain gelatin and strips containing five additives. The sixth additive, cetylpyridinium chloride, tripled the amount of gelatin leached while most of this additive remained in the gelatin strip. The other five additives were largely or completely extracted by the buffer solution. Potassium chloride underwent the fastest leaching, being completely dissolved within the first half hour. Octoxynol 9 was extracted most slowly because the swelling solution formed a viscous liquid crystalline phase inside the gelatin. Swelling followed second-order kinetics. Initial swelling rates and equilibrium swelling were calculated with a linearized function. Cetylpyridinium chloride, dodecylammonium chloride, and methyprylon reduced the initial swelling rate of gelatin while dicloxacillin sodium increased it. Octoxynol 9 and potassium chloride left it unchanged. Cetylpyridinium chloride and dodecylammonium chloride reduced the equilibrium swelling of gelatin substantially. Dicloxacillin sodium and octoxynol 9 increased it substantially, while potassium chloride and methyprylon increased it slightly. The extensive interaction of the cetylpyridinium ion with gelatin may result in reduced bioavailability.

Cetylpyridinium↗
PubMed1987

[Liposomes as carriers of lipophilic cytosine arabinoside and fluorodeoxyuridine derivatives. Their cytostatic effect and possibilities of tumor cell specific therapy].

A method of preparation for large volumes of sterile, homogenous bilayer liposomes as carriers of lipophilic cytostatic prodrugs is described. Liposomes in the size range of 60 to 120 nanometers are produced through the dialysis of lipid/prodrug/detergent micelles by means of a capillary dialysis system. The cytostatic effect of cytosine arabinoside (ara-C) prodrug liposomes against L1210 leukemia showed to be superior to free ara-C treatment in respect to drug dosage and treatment schedule. Fluorodeoxyuridine (FUdR) prodrug-liposomes were active against various solid tumors, although with less pronounced effects, but at 20-60 times lower drug concentrations as compared to free FUdR. To further improve the cytostatic effect of such prodrug-containing liposomes, methods for the linkage of tumor-cell-specific antibodies to the liposomes are discussed. The targeted delivery of cytostatic drugs by such means might improve their antitumor effects and reduce the untoward toxic side-effects.

Animals↗
PubMed1987

[Not Available].

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History, Modern 1601-↗
PubMed1987

[Liver damage in hormone therapy of prostate cancer].

The behaviour of the transaminases under contra-sexual initial treatment of the carcinoma of the prostate gland with Cytonal in contrast to Turisteron was compared. In these cases under the Cytonal therapy as an expression of the hepatotoxic side effects a double as high serum activity of the transaminase ALAT could be proved compared with the serum activity of the patients treated with Turisteron. Due to the good tolerability and the only insignificant hepatotoxic reactions Turisteron is well suited for the long-term treatment of the carcinoma of the prostate gland.

Aged↗
PubMed1986

Treatment of murine L1210 lymphoid leukemia and melanoma B16 with lipophilic cytosine arabinoside prodrugs incorporated into unilamellar liposomes.

Lipophilic prodrugs of I-beta-D-arabinofuranosyl cytosine (Ara-C), namely N4- and 5'-oleyl-I-beta-D-arabinofuranosyl cytosine (N4-oleyl-ara-C, 5'-oleyl-ara-C) and N4-palmitoyl-I-beta-D-arabinofuranosyl cytosine (N4-palm-ara-C) were incorporated into liposomes of various lipid compositions. The phospholipid vesicles were prepared by controlled dialysis of lipid/prodrug/detergent micelles yielding homogeneous and stable unilamellar liposomes. The liposome size ranged from 70 to 120 nm depending on the lipid composition and the amounts of prodrug incorporated. Depending on the total amount of micellized Ara-C prodrugs, a maximal incorporation rate of 250 micrograms prodrug per mg egg phosphatidylcholine was achieved. The incorporation efficiency was in the range of 85 to 97%. The in vivo antitumor activity of the liposome preparations against L1210 lymphoid leukemia was clearly superior by factors of 2-8 depending on the therapy schedule and route of drug application. The treatment of melanoma B16 with free Ara-C as well as with the prodrug-liposomes exhibit rather weak antitumor activity. Drug application by means of prodrug-liposomes yields equal or higher tumor-inhibitory effects at drug concentrations which were 2-4 times lower than those of free Ara-C. Although drug tolerance and myelosuppression studies with Swiss albino mice revealed that the prodrug-liposomes were 5-10 times more toxic than free Ara-C, a substantial improvement of efficiency could be observed. The incorporation of the ara-C prodrugs into liposomes provides protection against fast degradation and systemic elimination which might be an explanation for the improved antitumor effect of these preparations.

Animals↗
PubMed1986

Swelling studies of gelatin. I: Gelatin without additives.

The swelling rate and the equilibrium swelling of gelatin (type B) were studied by casting warm gelatin solutions into films, cutting them into short rectangular strips after gelation, drying them, and measuring the weight gain on immersion in buffer solutions as a function of time. The process variables investigated included concentration of the gelatin casting solutions, the thickness, drying conditions, age and residual moisture content of the film strips, the chemical nature and concentration of the buffers in the swelling solutions, and the temperature of these solutions at a constant pH of 7.0 (1.9 pH units above the isoionic point). The swelling kinetics followed a second-order equation. The initial swelling rate and the equilibrium swelling of the amorphous portion of the gelatin strips (which was somewhat smaller than the total observed swelling) were calculated from a linearized form of the rate equation. Of the factors investigated, the equilibrium swelling was increased most strongly when the temperature of the swelling solution was raised from 20 to 25 degrees C. Strip thickness was the predominant factor governing the rate of swelling, which was inversely proportional to the thickness. Conditions leading to slower drying and longer storage times promoted more extensive crystallization, thereby increasing the density of the gelatin strips and reducing their swelling rate.

Acetates↗
PubMed1986

[Not Available].

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Austria↗
PubMed1985

5'-O-Palmitoyl- and 3',5'-O-dipalmitoyl-5-fluoro-2'-deoxyuridine--novel lipophilic analogues of 5'-fluoro-2'-deoxyuridine: synthesis, incorporation into liposomes and preliminary biological results.

5'-O-palmitoyl- and 3',5'-O-dipalmitoyl-5-fluoro-2'-deoxyuridine were prepared by the reaction of 5-fluoro-2'-deoxyuridine in dimethylacetamide with palmitic acid chloride. The incorporation of the synthesized prodrugs into liposomes composed of egg phosphatidylcholine/stearylamine/cholesterol/alpha-tocopherol at a molar ratio of 10:1:2:0.05 was nearly quantitative; homogeneous bilayer vesicles (75 nm diameter) were obtained. Preliminary tolerance studies revealed that the prodrug-liposome preparations are about 20-60 times more toxic than the parent drug. The prodrugs incorporated into liposomes were 10 to 30 times more active against murine colon 38 carcinoma compared to the free drug. In comparison to the administration of the prodrugs in peanut oil the liposomal preparations seem to exert improved effects and represent a valuable drug delivery system for parenteral applications.

Animals↗
PubMed1985

Effect of nonionic surfactants on aqueous primidone suspensions.

The following interactions between the soluble surfactant, octoxynol 9, and the very slightly soluble, finely powdered drug, primidone, in aqueous suspension were investigated: adsorption/desorption of the surfactant, micellar solubilization of the drug, and deflocculation of its particles. The last effect, measured by the sedimentation volume of the suspensions, was also investigated for other octoxynols. The adsorption of octoxynol 9 on solid primidone was proportional to the equilibrium surfactant concentration up to the critical micelle concentration. It leveled off at higher concentrations, reaching saturation at completion of a close-packed surfactant monolayer. The adsorption was essentially completely reversible. The solubility of primidone in water was very slight; its micellar solubilization was even less extensive. The sedimentation volume of primidone suspensions decreased with increasing equilibrium concentration of octoxynol 9 and began to level off at the critical micelle concentration of 0.018%. At about twice that concentration, the sedimentation volume became almost constant, but reached its lowest value only at less than or equal to 0.5%. Slow rotation of suspensions prior to sedimentation promoted flocculation and higher sedimentation volumes between 0.01 and 0.03% octoxynol 9. Octoxynols with higher hydrophilic-lipophilic balance than octoxynol 9 produced considerably larger sedimentation volumes at comparable concentrations, due to a lower surface activity and a lesser tendency to adsorb on primidone.

Micelles↗
PubMed1985

Shifts in the apparent ionization constant of the carboxylic acid groups of gelatin.

Titration data of Type B gelatin were used to investigate shifts of the apparent ionization constant of the carboxylic acid groups caused by changes in the degree of ionization or net molecular charge and in ionic strength. The intrinsic ionization constant was estimated by comparison between titrations in water and in 0.10 molal NaCl. This estimated value of the carboxylic acid groups of gelatin was comparable to those reported for the carboxylic acid groups of poly(acrylic acid) and of a polyampholyte based on methacrylic acid. Neighboring cationic groups of the gelatin molecule assist in the removal of the proton from a carboxylic acid group by electrostatic repulsion while neighboring carboxylate ions hinder the ionization by electrostatic attraction of the proton. These interactions result in a negative or positive electrostatic free energy of ionization, respectively. This excess free energy was calculated by two analogous procedures, from the difference between the apparent and intrinsic ionization constants, and from the slope of a plot of the apparent ionization constant versus net molecular charge. These two methods of calculation gave comparable values for gelatin. Maximum values for the electrostatic free energy of ionization, determined at nearly complete ionization, were of the same order of magnitude for gelatin and for the synthetic polyampholyte. They were an order of magnitude larger for poly(acrylic acid) due to the lack of cationic groups. Addition of 0.10 molal NaCl shifted the apparent ionization constant of the carboxylic acid groups of gelatin toward their intrinsic ionization constant and reduced the absolute value of the electrostatic free energy of ionization compared to its values in water at comparable degrees of ionization.

Carboxylic Acids↗
PubMed1984

Single-step elongation of oligodeoxynucleotides using terminal deoxynucleotidyl transferase.

Procedures for the stepwise addition of one or more deoxyribonucleotide residues to the 3' end of an oligodeoxyribonucleoside phosphate acceptor using commercially available terminal deoxynucleotidyl transferase is described. 2-80 nmol of acceptors with a chain length of four, five or nine monomer units were elongated with a single 2'-deoxyribonucleoside 5'-triphosphate in yields of 20-30%. The monomers carried no protecting groups and were used both radioactively labelled and unlabelled. The elongated oligodeoxynucleoside phosphates were isolated by reverse-phase (Nucleosil C18) high-performance liquid chromatography or paper chromatography. The isolated products were sequenced by the fingerprint method. Advantages and disadvantages of this new methodology for the enzymatic synthesis of defined oligodeoxynucleotides are discussed.

Base Sequence↗