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Biomedical subjects

A Georgopoulos

Publications and source records attributed to A Georgopoulos.

At least 127 records · Page 7Linked to original sources
PubMed1982

[Pyrazine-1,4-dioxides fused to heterocycles / 2nd comm.: Synthesis and antibacterial activity of substituted pyrido[2,3-b]pyrazine-1,4-dioxides (author's transl)].

The position selective synthesis of substituted pyrido[2,3-b]-pyrazine-1,4-dioxides is reported. Compound 3g was subjected to a series of screening-tests for antibacterial activity and compared to therapeutical standards. The range of antibacterial activity mainly comprises enterobacteriaceae, above all E. coli, Klebsiella, Proteus and Shigella strains. Activity against gram-positive organisms and Serratia is much weaker and completely lacking with Pseudomonas. Therapeutic activity in septicaemic infections of the mouse is very good, especially in the case of E. coli infection with an ED50 of 13 mg/kg mouse for s.c. application. With p.o. application 3g shows activity comparable to nalidixic acid and nitrofurantoin in the experimental acute pyelonephritis in the mouse. The activity of 3g, however, is clearly inferior to that of gentamicin.

Animals↗
PubMed1981

In vitro activity of naftifine, a new antifungal agent.

Naftifine exhibits an interesting in vitro spectrum of activity against dermatophytes (38 strains; minimal inhibitory concentration [MIC] range 0.1 to 0.2 microgram/ml), aspergilli (6 strains; MIC range, 0.8 to 12.5 microgram/ml), Sporothrix schenckii (2 strains; MICs, 0.8 and 1.5 microgram/ml), and yeasts of the genus Candida (77 strains; MIC range, 1.5 to greater than 100 microgram/ml). Its degree of efficacy is unaffected by the organism density in the test medium, and it is primarily fungicidal against dermatophytes as well as yeasts. Its in vitro efficacy is pH dependent and rises with increasing pH values.

Allylamine↗
PubMed1981

In vivo antimycotic activity of naftifine.

Naftifine, a new antifungal agent belonging chemically to the allylamines, was tested for its in vivo activity after topical application against guinea pig skin infections caused by Trichophyton mentagrophytes, T. mentagrophytes var. quinckeanum, or Microsporum racemosum. Compared with standard compounds, naftifine proved to be highly effective mycologically and clinically after topical application in the above models.

Animals↗
PubMed1980

Composition of fluids from diffusion chambers implanted in the soft tissue and kidneys of rabbits.

The fluids from diffusion chambers implanted in soft tissue and kidneys of rabbits were analysed for total protein, albumin, enzymes, ions, glucose, creatinine, urea, uric acid, bilirubin and cholesterol. These date were compared with the corresponding values in plasma. Our data for chamber fluid are in good agreement with data reported for interstitial fluids. The composition of the kidney chamber fluid is nearly constant from three to ten weeks after implantation. The low urea, uric acid and creatinine concentrations indicate that the chamber is not located in the urine collecting area of the kidney. Three days after subcutaneous implantation of chambers, the fluid contains less protein than plasma but has an equal concentration of ions, thus meeting the principal requirements for interstitial fluid. There are indications that the healing process lasts up to ten days after the surgical implantation. In order to examine the permeability of the diffusion chambers, the equilibration half-life times of antibiotics and substances of high and low molecular weights were determined in vitro.

Animals↗
PubMed1980

A diffusion chamber technique for measuring concentrations of antibiotics in interstitial fluid.

A method for collecting soft tissue interstitial fluid in experimental animals for the measurement of antibiotic concentrations is described. Diffusion chambers with permeable membranes of 0.45 micron porosity were implanted subcutaneously for four days in order to determine simultaneous concentrations of ampicillin and clindamycin in serum and chamber fluid after perioral administration in rabbits and of oxytetracycline after intravenous injection in dogs. The results are discussed in view of findings from other investigators using different types of tissue cages.

Ampicillin↗
PubMed1980

Measurements of antimicrobial drug concentrations in renal interstitial fluid using the diffusion chamber technique.

A technique is described to obtain renal interstitial fluid (RIF) from rabbits after implantation of diffusion chambers with permeable membranes of 0.45 mu porosity in both kidneys. Pharmacokinetic studies were conducted two to three weeks after implantation. No difference in gentamicin concentrations, as measured microbiologically, was seen between RIF withdrawn from the left and right kidney chambers at the same points in time. Simultaneous drug concentrations were determined in RIF and serum of rabbits after oral administration of ampicillin or nalidixic acid and after intramuscular injection of gentamicin. Ampicillin concentrations in RIF peaked at two hours with about one fourth of the peak concentration measured in serum at one hour. These curves crossed at 3.45 hours. In RIF, the maximum concentration of gentamicin found at two hours was again approximately one fourth of the serum peak level determined at half an hour. The gentamicin curves crossed at 3.15 hours. No levels of nalidixic acid could be detected microbiologically in serum and RIF. In collected urine, however, concentrations of this drug could be measured for several sampling periods. Our results show that this diffusion chamber technique can be useful in the pharmacokinetic examination of drugs, also with respect to their distribution in the kidneys.

Ampicillin↗
PubMed1980

Concentrations of various antibiotics in serum and fluids accumulated in diffusion chambers implanted in various sites in rabbits.

Diffusion chambers with Millipore membranes were implanted in soft tissue, kidneys, and peritoneal and pleural cavities of rabbits. Single doses of azlocillin, cefazolin, and gentamicin were injected intramuscularly and ampicillin was administered orally 2--5 weeks after implantation. The concentrations of the respective drugs in simultaneously collected samples of fluid from each diffusion chamber were measured and compared with concentrations found at the same time in serum. All chambers were tolerated well, and the method proved to be effective for collecting data on the distribution of drugs throughout the body.

Ampicillin↗
PubMed1978

Nonspecific resistance to bacterial infections. Enhancement by ubiquinone-8.

A lipid fraction from Escherichia coli was extracted with apolar solvents and was found to protect mice from a number of experimental bacterial infections. The benzoquinone, ubiquinone-8, was isolated from this extract by high pressure liquid chromatography and identified as such by nuclear magnetic resonance and mass spectrometry. At a dose of 25 mg/kg this substance was found to provide complete protection against otherwise lethal infections with gram-negative and gram-positive bacteria in mice. Treatment was most effective when given intravenously 24 h before infection. In comparative studies, ubiquinone-8 had a clearly higher activity than ubiquinones-4, Q6, and Q10. A highly significant increase in the clearance rate of bacteria from the blood by the spleen and the liver of treated animals, correlated well with the protective effect of ubiquinone-8. The compound stimulated the ability of mouse macrophages to incorporate sheep erythrocytes and significantly increased the number of antibody-producing cells in spleens of mice.

Animals↗
PubMed1978

A simple micro agar diffusion method for the determination of antibiotic concentrations in blood and other body fluids.

A micro agar diffusion method to determine antibiotic levels in only 0.02 ml of serum is described. With this technique, standard curves for Ampicillin, Penicillin G, Gentamicin, Tetracycline HCl and Amphotericin B were calculated. The method displays a good reproducibility with an error of less than 10%. To compare this technique with a conventional macro agar diffusion method fixed antibiotic concentrations in rabbit serum were examined. Corresponding results were obtained indicating the equivalence of this method, which thus proved to be suitable to determine antibiotic levels in small volumes of body fluids.

Amphotericin B↗
PubMed1975

Antimicrobial activities of 81.723 hfu, a new pleuromutilin derivative.

The new pleuromutilin derivative 81.723 hfu is extremely active against gram-positive organisms such as streptococci, staphylococci, and against mycoplasmas. A number of Shigella, Klebsiella, and Escherichia coli strains were also found to be quite susceptible to this new agent, whereas other gram-negative organisms like Pseudomonas aeruginosa, Proteus species, and Alcaligenes faecalis proved to be naturally resistant to 81.723 hfu. The new compound acts bacteriostatically. Bactericidal effects have been observed only at concentrations which are 100-fold higher than the minimal inhibitory concentrations. The new antibiotic is well tolerated in all animal species tested so far and has been successfully used in the treatment of experimental infections with gram-positive organisms and with mycoplasmas in mice and rats. Resistance against this new compound arose gradually in all microorganisms investigated. It is noteworthy that the rate at which resistance against 81.723 hfu emerged in mycoplasmas (Mycoplasma gallisepticum and Mycoplasma hyorhinis) was significantly slower than the corresponding rate at which resistance against tylosin tartrate appeared. Mycoplasma strains which became insensitive to 81.723 hfu were also resistant to tylosin tartrate, whereas mycoplasmas which developed resistance against tylosin tartrate, although less sensitive to 81.723 hfu than wild-type strains, were still eliminated by this drug. In a strain of Klebsiella pneumoniae, complete cross-resistance was observed between the pleuromutilin derivative on one hand and lincomycin and erythromycin on the other. Modest degrees of cross-resistance were also observed with chloramphenicol. However, it appears unlikely that the latter phenomenon is sufficiently pronounced to affect treatment with either antibiotic.

Agaricales↗
PubMed1975

Posterior parietal association cortex of the monkey: command functions for operations within extrapersonal space.

Experiments were made on the posterior parietal association cortical areas 5 and in 17 hemispheres of 11 monkeys, 6 M. mulatta and 5 M. arctoides. The electrical signs of the activity of single cortical cells were recorded with microelectrodes in waking animals as they carried out certain behavioral acts in response to a series of sensory cues. The behavioral paradigms were one for detection alone, and a second for detection plus projection of the arm to contact a stationary or moving target placed at arm's length. Of the 125 microelectrode penetrations made, 1,451 neurons were identified in terms of the correlation of their activity with the behavioral acts and their sensitivity or lack of it to sensory stimuli delivered passively; 180 were studied quantitatively. The locations of cortical neurons were identified in serial sections; 94 penetrations and 1,058 neurons were located with certainty. About two-thirds of the neurons of area 5 were activated by passive rotation of the limbs at their joints; of these, 82% were related to single, contralateral joints, 10% to two or more contralateral joints, 6% to ipsilateral, and 2% to joints on both sides of the body. A few of the latter were active during complex bodily postures. A large proportion of area 5 neurons were relatively insensitive to passive joint rotations, as compared with similar neurons of the postcentral gyrus, but were driven to high rates of discharge when the same joint was rotated during an active movement of the animal...

Animals↗
PubMed1975

[Intravaginal infection of the rat with Trichomonas vaginalis and Candida albicans. An experimental model for chemotherapy (author's transl)].

Ovariectomised and oestrogen premedicated rats were infected intravaginally, with first C. albicans and then with T. vaginalis. Under these conditions infections with T. vaginalis could be established with more reliability than when using axenically-cultivated T. vaginalis alone. This mode of infection is easily reproduced, and it allows the performance of chemotherapeutic tests on small groups of laboratory animals. Such tests were carried out with Metronidazole, Tinidazole and Nifuratel.

Animals↗