Activator proteins and topology of lysosomal sphingolipid catabolism.

The lysosomal degradation of several sphingolipids by acid hydrolases is dependent on small non-enzymic cofactors, called sphingolipid activator proteins some of which have been identified as sphingolipid binding proteins. This review summarizes the information available on the structure, function, biosynthesis, gene organization and pathobiochemistry of the known sphingolipid activator proteins. It also offers models for their mode of action and for the topology of lysosomal digestion of glycolipids.

The organization of the gene for the human cerebroside sulfate activator protein.

The organization of 14 exons covering 97% of the cDNA sequence of human cerebroside sulfate activator protein precursor has been determined from two overlapping EMBL-4 human genomic clones extending over 17 kb. All exons and exon/intron splice junctions and five introns were sequenced. Exon 8 consists of only 9 bp and is involved in alternative splicing which generates three different mRNAs of cerebroside sulfate activator precursor.

The erythrocyte-perfused "working heart" model: hemodynamic and metabolic performance in comparison to crystalloid perfused hearts.

A brief period of ischemia was used to evaluate an erythrocyte-enriched Krebs-Henseleit (KH) buffer (n=8) compared to KH only (n=8) in an isolated working rabbit heart. Experimental protocol was as follows: preischemic baseline, 5 min of global ischemia followed by 45 min of reperfusion. Preischemic heart rate was identical, coronary flow was significantly lower (2.7 versus 5.6 mL/min/g wet wt, p<0.01), the other hemodynamic and biochemical values were significantly higher in erythrocyte-perfused hearts: aortic flow 23.5 versus 12.0, p<0.01; cardiac output 26.2 versus 17.6, p<0.01; all in mL/min/g wet wt; dp/dt max 1286 versus 997 mmHg/s, p<0.01; myocardial oxygen consumption 3.5 versus 2.3 micromol/min/g wet wt, p<0.05. During early reperfusion, in the erythrocyte-perfused hearts, coronary flow further increased (p<0.003), the other hemodynamic parameters returned to baseline values in both groups. High-energy phosphates showed significantly higher values (ATP 2.0+/-0.1 versus 1.3+/-0.1, p<0.05; CrP 2.0+/-0.2 versus 1.6+/-0.1, p<0.05 all in micromol/g wct wt), water content was significantly lower (81% versus 74%, p<0.05) in erythrocyte-perfused hearts. It can be concluded that the erythrocyte-perfused working heart model provides excellent oxygenation, leading to superior hemodynamic and metabolic performance. Additionally, in the erythrocyte-perfused hearts preservation of coronary flow reserve underlines the physiological competency of this preparation.

[Phenytoin and phenytoin derivatives for local administration]. / Phenytoin und Phenytoinderivate zur lokalen Applikation.

A well known side effect of the long-term therapy with phenytoin is gum hyperplasia. 1-Acyl compounds and esters of the p-hydroxymetabolite with aliphatic and aromatic carboxylic acids were synthesized as potential prodrugs for therapeutic use if the neoformation of connective tissue is intended. The compounds were characterized by there physico-chemical constants and the absorption was proofed by a buccal test.

[Pharmaceutical and biopharmaceutical evaluation of acetylaminonitropropoxybenzolum (Falimint). 8. Biotransformation of the active agents]. / Zur pharmazeutischen und biopharmazeutischen Begutachtung von Acetylaminonitropropoxybenzolum (Falimint). 8. Mitteilung: Biotransformation des Wirkstoffes.

Two metabolites of Falimint which have not been elucidated till now were demonstrated to be the glucuronides of 2-acetamino-4-nitro-phenol and 2-amino-4-nitro-phenol. A further metabolite was found by isolation with adsorption resins and identified to be the sulfuric acid conjugate of 2-amino-4-nitro-phenol.

[Pharmaceutical and biopharmaceutical evaluation of acetylaminonitropropoxybenzolum (Falimint). 3: Polarographic analysis and determination of active agents]. / Zur pharmazeutischen und biopharmazeutischen Begutachtung von Acetylaminonitropropoxybenzolum (Falimint).

According to its aromatic nitro group acetylaminonitropropoxybenzene (Falimint) can be determined polarographically. The typical behavior of the nitro group becomes evident by the elektrochemical reduction. The investigation has shown two phases of reduction with pH-depended half-wave-potential shifts, so that a two-step mechanism is conceivable. Using direct current polarography the substance is determined in a concentration range from 1 to 100 micrograms/ml. Low elektroaktive background signals within the potential range the four-electron reduction step are the basis for the determination of the active agent in saliva, urine and blood plasma without any extracting procedures. It is possible to identify the substance by means of oscilloand square-wave-polarography. The resulting polarogrammes are typically for the p-nitrophenyl structure. Further a new quantitativ polarographic method, named sample-DC-polarography on the stationary mercury electrode is discussed for the determination of Falimint in blood plasma without any steps of separation and cleaning in the concentration range of 0,1-3,0 micrograms/ml.

[The pharmaceutical and biopharmaceutical assessment of acetylaminonitropropoxybenzene (Falimint). 6. Quantitative composition of metabolites]. / Zur pharmazeutischen und biopharmazeutischen Begutachtung von Acetylaminonitropropoxybenzolum (Falimint). 6. Mitteilung: Quantitative Zusammensetzung der Metaboliten.

Substances appearing in the metabolism of Falimint were analyzed quantitatively. The composition of metabolites is remarkable constant in various persons and dosages. The concentration of metabolites in urine accumulates after 2 h. Within 6 h the bulk of metabolites is eliminated.

[Drug permeation through artificial lipoid membranes. 20. The effectiveness of multiple-lamellar liposomes for evaluating drug transport]. / Arzneimittelpermeation durch künstliche Lipoidmembranen. 20. Mitteilung: Eignung multilamellarer Liposomen zur Beurteilung des Arzneistofftransportes.

The use of stable liposomes for distribution experiments with some drugs is described. Great differences between distribution coefficients liposomes/water and n-octanol/water were found.

[Drug permeation through synthetic lipid membranes. Part 10: The effects of diffusion layers on the permeation process (author's transl)]. / Arzneimittelpermeation durch künstliche Lipoidmembranen. 10. Mitteilung: Einfluss von Diffusionsschichten auf den Permeationsprozess.

Two different processes take their courses during the permeation of substances through lipid membranes. The substance must pass across the diffusion layers on the membranes and also across the lipid barrier proper. The effects of these two processes on the permeation vary with the kind of the membrane and of the substance as well as with the diffusion layer thickness which is determined by the intensity of movement. Correlations have been established which permit to calculate diffusion layers, membrane permeation coefficients, and also diffusion coefficients in the diffusion layers. Thus have been provided the prerequisites for the comparison of results obtained on using different model parameters.

[Drug permeation through artificial lipid membranes. 17. The mechanism of ion pair transport]. / Arzneimittelpermeation durch künstliche Lipoidmembranen. 17. Mitteilung: Zum Mechanismus der lonenpaarpermeation.

The transport of ionized drugs across lipoid membranes can be increased considerable by lipophilic counter ions. This is caused by an increased lipophilicity of the ion pair which is formed between the ionized drugs and the lipophilic counterion. Caused by their very strong solubility in the membrane the lipophilic counterions accumulate and act like a carrier for the ionized drugs. Then the necessary compensation of the charges can take place by protons or other suitable ions of the used solution.

[Preparation of a cytostatic-containing bone cement]. / Zur Herstellung eines cytostaticahaltigen Knochenzementes.

Local application of cytostatic during therapy of tumors in bones is desirable. In these cases the drugs had to be incorporated in bone glue. Liberation, stability and side-effects have been estimated using methotrexate and doxorubicin (Adriblastin) in vitro. The liberation were determined in combination with auxiliary substances and even solidity of the bone glue was maintained.

[Pharmaceutic and biopharmaceutic evaluation of acetylaminonitropropoxybenzene (Falimint). A Biotransformation of the active agent]. / Zur pharmazeutischen und biopharmazeutischen Begutachtung von Acetylaminonitropropoxybenzolum (Falimint). 4. Mitteilung: Biotransformation des Wirkstoffes.

2-Acetamino-4-nitropropoxybenzene is metabolized almost completely. Till now in urine of man seven components have been detected. The main way of metabolism is the oxidation of the propoxy group to a carboxyl group. Also the deacetylated compound of this acid has been found to a certain extent. A further metabolite is supposed to be oxidized in the side chain in another way. In a higher extent dealkylation to 2-acetamino-4-nitrophenol takes place which is eliminated probably in conjugation with glucuronic acid. Free 2-acetamino-4-nitrophenol and 2-amino-4-nitrophenol respectively are only detectable in traces. Deacetylation of 2-amino-4-nitropropoxybenzene takes place only in a very small extent. Till now metabolites with reduced nitro group haven't been found.

[Drug transport through artificial lipoid membranes. 22. Amplitude of ultrasonicated liposomes as a model system for investigations of drug transport]. / Arzneimitteltransport durch künstliche Lipoidmembranen. 22. Mitteilung: Eignung ultraschallbehandelter Liposomen als Modellsystem für Transportuntersuchungen mit Arzneistoffen.

The use of sonicated liposomes for the characterization of the transport behaviour of basic drugs is described. The rate of permeation depends mostly on the lipophilic character of the drugs.

[Dissolution processes and surface alteration. 4. Determination of the "effective" surface]. / Auflösungsprozesse und Oberflächenänderung. 4. Mitteilung: Bestimmung der "effektiven" Oberfläche.

A method is described for measuring the "effective" surface of a drug by means of dissolution parameters using the Paddle-model or a resorption-model respectively. The obtained values were compared with the specific surface which was determined by BET-technique. The "effective" surfaces obtained by means of the dissolution parameters are smaller than those determined BET-technique.

[Drug permeation through synthetic lipid membranes. Part 13: The effects of tensides on the permeation of ionized drugs (author's transl)]. / Arzneimittelpermeation durch künstliche Lipoidmembranen. 13. Mitteilung: Einfluss von Tensiden auf die Permeation ionisierter Arzneistoffe.

The permeation of substances present in the ionized form is most markedly affected by tensides containing ions of opposite sign. These tensides produce a considerable increase in permeation. The effect of micelle formation will become evident only if the transport of the free drug through the membrane is more rapid than the release of the drug from the micelles. If the concentrations of nonionic tensides are less than the critical micelle concentration, a permeation increase occurs which is presumably caused by a reduction of the surface tension of the membrane.

[Drug transport through artificial lipoid membranes. 21. Ion pair transport with alkyl salicylic acids]. / Arzneimitteltransport durch künstliche Lipoidmembranen. 21. Mitteilung: Ionenpaartransport mit Alkylsalicylsüren.

Using hexylsalicylic acid it was demonstrated that alkylated derivatives of salicylic acid are able to increase partition and transport of ionized basic drugs across lipophilic membranes. The influence of different donor concentrations on the relation of transport was studied by means of pholedrine in combination with hexylsalicylic acid. In order to explain the mechanism of the ion-pair-transport experiments were carried out which show beside the mentioned increase of transport the occurrence of a countertransport of protons and lithium-ions, respectively. The lipophilic counterion hexylsalicylate acts inside of this mechanism as a carrier for the ionized drugs.

[A new experimental design for the in vitro evaluation of drug absorption in topical forms. 1. Design and model calculation]. / Eine neue Versuchsanordnung zur in-vitro-Beurteilung der Wirkstoffresorption aus topischen Arzneiformen. 1. Mitteilung: Versuchsanordnung und Modellrechnungen.

An in-vitro model is presented which consists on several membrane Layers. The penetration of drugs from the ointment bases into these membrane Layers is observed. By combination of different membranes this system can be varied. In model calculations the resulting conditions are demonstrated.

[Possibilities for the in vitro evaluation of bioavailability. 5. Compact peroral agents with basic drugs]. / Möglichkeiten zur in-vitro-Beurteilung der Bioverfügbarkeit. 5. Mitteilung: Untersuchung von festen Peroralia mit basischen Wirkstoffen.

Lipophilic, basic drugs can be transported across lipoid-membrane even if the part of the substance being not ionized in the solution is very low. Therefore the resorption model can be used for the control of drugs containing the substances as salts. In the case of 4 substances no differences could be found concerning half transport time between the aqueous solutions and the drugs.

Influence of ion-pair-formation on the pharmacokinetic properties of drugs. Part 3: Influence of hexylsalicylic acid on the pharmacokinetics of pholedrine.

Based on previous in vitro studies it could be shown that ion-pair-formation with the lipophilic hexylsalicylic acid (1) influences the pharmacokinetics of the hydrophilic drug pholedrine (2) which is ionized in all physiological media. After oral combination with 1 an increase of the AUC of 2 could be observed. This finding is due both to the increase of the absorption of 2 and to the decrease of the elimination of 2. After i.v. application the high biotransformation rate of 2 prevents an influence of 1.

[Improvement of the solubility behavior of problem drugs. 9. In vitro absorption studies using melting solidification products of iomeglamic acid]. / Beiträge zur Verbesserung des Auflösungsverhaltens von Problemarzneistoffen. 9. Mitteilung: In-vitro-Resorptionsuntersuchungen mit lomeglamsäure-Schmelzerstarrungsprodukten.

By means of the absorption apparatus according to Fürst and Neubert the solid dispersions of the iomeglamic acid were studied with regard to their in vitro absorption properties. All products showed better half lives of transport in relation to the pure compound. This was in correlation to the solubility parameters.