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Biomedical subjects

E Pop

Publications and source records attributed to E Pop.

At least 55 records · Page 3Linked to original sources
PubMed1989

Brain-specific chemical delivery systems for beta-lactam antibiotics. Synthesis and properties of some dihydropyridine and dihydroiosquinoline derivatives of benzylpenicillin.

Six chemical delivery systems (CDS) were synthesized for benzylpenicillin in order to improve its transport across the blood-brain barrier. The CDS's were based on a dihydropyridine----quaternary pyridinium ion redox system, analogous to the naturally occurring NADH----NAD+ system. Two different types of CDS's were prepared: benzylpenicillin esters of diols in which the other hydroxyl group is esterified by dihydrotrigonelline and benzylpenicillin esters of amino alcohols in which the amine group is acylated by dihydrotrigonelline, or by 1,2-dihydro-2-methyl-4-isoquinolinecarboxylic acid. Lipophilicities of the CDS's were proved to be much higher than those of benzylpenicillin by using Rm values as lipophilicity indexes. Upon oxidation, all of the CDS's gave the quaternary ion forms. Kinetic studies in buffer (pH profiles) indicated that the quaternary salts released benzylpenicillin in pH range of 5-9 via hydrolysis. The CDS's in acidic media yielded as the major reaction product 6-hydroxy-1,4,5,6-tetrahydropyridines as a result of water addition, while in basic conditions benzylpenicillin was released. The water addition reaction was dependent on the CDS's structure, being more prevalent in the case of the "amide-esters". The dihydroisoquinoline CDS was rather stable in the pH range 5-8.

Blood-Brain Barrier↗
PubMed1989

Brain-specific chemical delivery systems for beta-lactam antibiotics. In vitro and in vivo studies of some dihydropyridine and dihydroisoquinoline derivatives of benzylpenicillin in rats.

Four chemical delivery systems (CDS's) based on a dihydropyridine----quaternary pyridinium salt redox system were used for the brain delivery of benzylpenicillin (BP). CDS's 5 and 9 are diesters of C1 and C2 diols in which one hydroxyl group is esterified by the benzylpenicillin-3-carboxylic group and the other by dihydrotrigonelline. CDS's 13a and 17 are benzylpenicillin esters of amino alcohols in which the amine group is acylated by dihydro-trigonelline (13a) or by 1,2-dihydro-2-methyl-4-isoquinolinecarboxylic acid (17). In vitro relative stability studies showed that both CDS's and quaternary pyridinium salts were quite unstable in rat and rabbit blood or brain but much more stable in dog or human blood. Kinetic studies performed in rat brain homogenate demonstrated the facile enzymatic oxidation of the CDS's to the corresponding quaternary salts. Hydrolysis of the CDS's and the quaternary salts resulted in the release of benzylpenicillin. In biological media CDS 13a also yielded a water addition product, the 6-hydroxy-1,4,5,6-tetrahydropyridine derivative. In vivo distribution studies were carried out in rats. After iv administration of equimolar doses of BP and CDS's, brain benzylpenicillin levels were found to be substantially higher and more prolonged in case of 5 and 9 than of BP itself. However, administration of 13a and 17 resulted in lower brain benzylpenicillin levels due to the water addition reaction and a nonspecific brain delivery, respectively. The remarkable increase of BP levels as well as the prolonged effect after the administration of 5 and 9 is a result of an improved penetration through the blood-brain barrier of the lipophilic CDS's and a "lock-in" effect of the corresponding quaternary salts generated in situ.

Animals↗
PubMed1989

Chemical delivery systems for some penicillinase-resistant semisynthetic penicillins.

Chemical delivery systems (CDS's) based on a dihydropyridine----quaternary pyridinium ion redox system analogous to the naturally occurring NADH----NAD+ system were synthesized for a group of staphylococcal penicillinase resistant penicillins, including methicillin, oxacillin, cloxacillin, and dicloxacillin, in order to improve their penetration of the central nervous system (CNS). The CDS's are penicillin monoesters of gem-diols in which the other hydroxyl group is esterified by the dihydrotrigonelline carrier. The CDS's were found to be much more lipopholic than the parent drugs by comparing their log k' values used as lipophilicity indexes. A study of the chemical oxidation of the CDS's performed by a UV spectrophotometric method showed relatively slow reaction. Stability studies were performed in buffers and different animal tissues for both the CDS's and the quaternary salt type derivatives. These studies showed that the CDS's were oxidized to the quaternary salt forms at neutral and basic pH and added water at lower pH. The quaternary salts released the parent drugs both in buffers and in vitro. A preliminary in vivo distribution study in the rat and rabbit demonstrated blood-brain barrier (BBB) penetration by the CDS, whereas no drug was detected by administering the drug itself.

Animals↗
PubMed1989

Chemical delivery systems for drugs containing an amino group: synthesis and properties of some pyridine derivatives of desipramine.

Seven chemical delivery systems (CDS) based on a dihydropyridine<-->quaternary pyridinium salt type redox system and analogous to the naturally occurring NADH<-->NAD+ coenzyme system were applied in the case of the antidepressant drug desipramine. The pyridine moiety-containing carriers were linked to the amino function of desipramine either as amides or substituted carbamates. Lipophilic properties were expressed in terms of chromatographic Rm values. Oxidative stability of the dihydropyridine forms of the CDSs were determined in vitro. The amide type derivatives were stable toward hydrolysis in buffers and in biological fluids, whereas the carbamates released the parent drug in a very efficient manner. In a behavioral despair test, the CDSs did not show improved activity when compared to desipramine. In vivo distribution studies of one of the CDS did not show more efficient delivery of the desipramine into the rat brain but did show a prolonged presence at a constant level.

Animals↗
PubMedDate not supplied

[A method for the determination of corroding factors of amalgams by electrical measurements].

The study describes a method for the determination of corrosion kinetics of amalgams from the buccal cavity by measuring initial and evolutive electrical potentials in parallel with an evaluation of clinical factors. It also deals with factors which might be improved in this connection. The method was applied experimentally in 125 cases with restoration therapy with silver amalgam, and a digital milivoltmeter for direct current was used, of 0.2% precision class with silver chloride electrodes to which two probes have been adapted. The values determined varied between--320 and--82 milivolts. The advantages as compared with previously used methods are the following: an electrical measurement of resistance to corrosion of amalgams, and improvement of factors which influence corrosion.

Corrosion↗
PubMedDate not supplied

[Possibilities for orthodontic treatment in adults].

Following a discussion on the controversial opinions concerning the orthodontial treatment in adults, as well as on the fact that in many cases the orthodontial treatments in adults are much shorter than in children, the authors present data on eight cases reflecting the possibilities of orthodontial therapy in adults. The authors stress the necessity that the orthodontist should recognize the limitations of such therapy in adults, increasing in this way the possibilities for a successful therapy.

Adult↗
PubMedDate not supplied

[Philosophy of prevention in stomatology].

The authors make an analysis of the concept of prevention as applied to the field of stomatology, and also discuss the prophylactic strategies, and the means for action. A series of aspects are discussed, including: the why of preventive practice? What is preventive practice? The philosophy of prevention; which are the facilities and the necessary equipment?

Dental Prophylaxis↗
PubMedDate not supplied

[Passivity of certain disinfectant substances in the presence of acrylic resins].

On the basis of data published in the specialized literature the authors have experimented the effects of five substances currently used for the disinfection of prostheses. These included: Denclen (a British product), Super Quick's (made in the FRG), and Leodent also a West German product), as well as two general disinfectants of the buccal cavity: perogen and bromocet, on the acrylic resins used for the dental prostheses: Superpont (made in Czechoslovakia) and Romacryl (a Romanian product). The study showed that these substances, both the special ones and the general disinfectants are not completely passive when in contact with the acrylic prostheses. They should be used with care, and in accordance with the indications concerning concentration and duration of application.

Acrylic Resins↗