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Biomedical subjects

G Moreno

Publications and source records attributed to G Moreno.

At least 73 records · Page 4Linked to original sources
PubMed1990

Factors influencing the distribution pattern of porphyrins in cell membranes.

The mechanism of the sensitizer-membrane interactions has been studied by following the distribution properties of selected porphyrins, including haematoporphyrin (HP) and protoporphyrin (PP), into unilamellar liposomes of dipalmitoyl phosphatidylcholine (DPPC). The endomembrane distribution of HP and PP has been checked as a function of the membrane fluidity and composition by fluorescence polarization and quenching techniques. At porphyrin concentrations below 0.5 microM, HP and PP exclusively localize in the inner phospholipid monolayer; at higher concentrations, the outer monolayer also becomes populated. The porphyrin binding sites in liposomes, however, are different for HP and PP: HP preferentially distributes into water-accessible lipid regions, while PP localizes in the most hydrophobic loci of the lipid matrix. A porphyrin redistribution occurs when the fluidity properties of the liposomes are changed by addition of cholesterol or cardiolipin. In DPPC-cholesterol vesicles, all HP molecules dissolve in DPPC-rich regions while all PP molecules partition in cholesterol-rich environments. In DPPC-cardiolipin vesicles both porphyrins preferentially localize in regions accessible to the external medium. The effect of the nature of the carrier on porphyrin distribution in membranes has been studied by following the uptake and photosensitization properties of free and DPPC-incorporated PP and HP with rat liver mitochondria. The porphyrin photosensitizing efficiency has been checked by following the impairment of the respiratory function of mitochondria upon irradiation. Liposome-bound HP is less active than aqueous HP in determining membrane photodamage in mitochondria. On the contrary, aqueous PP is a very poor sensitizer as compared to a DPPC liposome-entrapped drug.(ABSTRACT TRUNCATED AT 250 WORDS)

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1990

Carrier thiols are targets of Photofrin II photosensitization of isolated rat liver mitochondria.

To gain further insight into the ability of Photofrin II to photosensitize mitochondrial translocators, and to ascertain whether mitochondrial thiols are specific targets of Photofrin II, the activity of phosphate carrier was measured in isolated rat liver mitochondria irradiated with 365 nm light in the presence of Photofrin II. Photodynamic treatment decreased the maximum rate of phosphate uptake, without changing the phosphate affinity for its own carrier. The ability of the thiol reagent mersalyl (an inhibitor of phosphate, dicarboxylate and oxodicarboxylate carriers) to protect these carriers against Photofrin II photosensitization was also tested. Protection was observed, indicating the involvement of carrier thiols in mitochondrial photosensitization.

Animals↗
PubMed1990

Uptake and photodynamic efficiency of hematoporphyrin, hydroxyethylvinyldeuteroporphyrin and hematoporphyrin derivative (Photofrin II): a study with isolated mitochondria.

The uptake of Photofrin II (PFII), hematoporphyrin (Hp) and hydroxyethylvinyldeuteroporphyrin (HVD) by isolated mitochondria was studied using the high performance liquid chromatography (HPLC) technique. The various PFII components show a high affinity for mitochondria. At 5.75 micrograms/ml PFII, their ratio of incorporation was found to be very similar, except for Hp which is about two times less incorporated. These results were reproduced with pure Hp and pure HVD. The uptake of Hp and HVD increases with concentration but, while that of Hp reaches a plateau, the uptake of HVD continues to increase. At a high porphyrin concentration (approximately 10(-5) M), the loss of respiratory control is obtained with the same light dose for Hp and PFII. Taking into account the uptake and the known photophysical parameters of the various porphyrins, the photodynamic efficiency of HVD seems equivalent to that of Hp. The present results and known data on cell photoinactivation suggest that the activity of these porphyrins is mainly dependent on their incorporation.

Animals↗
PubMed1989

Haematoporphyrin derivative (Photofrin II) photosensitization of isolated mitochondria: inhibition of ADP/ATP translocator.

To gain further insight into the mechanism by which irradiation of mitochondria in the presence of haematoporphyrin derivative (Photofrin II) (PF II) causes impairment of mitochondrial oxidative phosphorylation, the rate of ADP/ATP exchange via the ADP/ATP translocator was measured fluorometrically is isolated rat liver mitochondria. In accord with noncompetitive inhibition, PF II photosensitization decreases the maximum rate of exchange Vmax (20.8 and 9.6 nmol ATP effluxed min-1 x mg protein in the control and after 2 min irradiation, respectively) without changing the ADP affinity for the carrier (Km = 5 microM in both cases). Comparison of the rate of oxygen uptake by mitochondria stimulated by either ADP or by the uncoupler carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP) confirms that the adenine nucleotide carrier is a major target of photodynamic action which causes oxidative phosphorylation impairment.

Adenosine Triphosphatases↗
PubMed1989

Promising new drugs in the treatment of tuberculosis and mycobacteriosis.

The aims of this work were to investigate the possible effect of several antimicrobial agents alone and in combinations against 190 clinical isolates of Mycobacterium tuberculosis and 30 isolates of Mycobacterium avium, 30 Mycobacterium fortuitum and 30 Mycobacterium chelonei. The susceptibility was determined in Müller-Hinton agar and Middlebrook 7H 10 agar. For interpretation of the results the minimum inhibitory concentration (MIC) was determined and for the combinations of antimicrobials we used the Fractional Inhibitory Concentration Index (FIC). The possible clinical efficacy was determined by the Inhibitory Quotient. The synergistic effect of several combinations of these compounds was demonstrated.

Anti-Bacterial Agents↗
PubMed1989

[Eco-epidemiology of visceral and cutaneous leishmaniasis in the Yemen Arab Republic. I. Presence, in sympatric condition, of Leishmania infantum and Leishmania donovani complexes].

In complement to a previous survey, the authors proceed to the analysis of strains isolated from visceral human and canine leishmaniasis. Finally, among eight human strains isolated and identified with an enzymatic method, seven belong to the Leishmania donovani complex and one to the L. infantum complex. The L. donovani complex is represented by the MON-31 and MON-83 zymodem. The first one is also present in Saudi Arabia and Ethiopia. The second one, corresponding to a small variant, pleads for an intrafocal polymorphism phenomenon which was until now unknown in the L. donovani complex. The L. infantum complex is observed: 1) in sympatria with L. donovani in mountainous areas; 2) alone in the Tihama coastal plain. As for human cutaneous leishmaniasis present in the same focuses it is caused by L. tropica MON-71 and not by the above mentioned complexes.

Animals↗
PubMed1988

Growth of melanocytes in a skin equivalent model in vitro.

We have developed a pigmented human skin equivalent by inserting a punch biopsy of human infant foreskin as a source of epidermis into a collagen lattice (dermal equivalent). Using a conventional epidermal culture medium and stimulation with UVB irradiation or 8-MOP + UVA treatment, melanocytes were found to grow out from the biopsy with the epidermal sheet. In this newly formed epidermis, melanocytes and keratinocytes were maintained in an architectural relationship similar to that present in vivo and melanocyte outgrowth could be quantitatively evaluated. Consequently, this pigmented human skin equivalent is a useful model for investigating the biology and photobiology of human skin pigmentation.

Child↗
PubMed1988

Autoradiographic study of the effects of psoralen and ultraviolet light on DNA, RNA and protein synthesis in cultured keratinocytes and psoriatic skin.

DNA, RNA and protein synthesis were studied by autoradiography in cultured keratinocytes, immediately, 24 and 48 h after 8-methoxypsoralen and ultraviolet light, (PUVA) treatment. Using the same technique, the immediate and long-term effects of PUVA therapy on DNA, RNA and protein synthesis were analysed in skin biopsies from psoriatic patients. In the cultures, immediately after irradiation, DNA and RNA syntheses were similarly inhibited in a dose-dependent manner, while protein synthesis was slightly affected only for the highest dose. After 24 h, RNA synthesis recovered whereas DNA synthesis was more severely inhibited suggesting that other cell components may be damaged by PUVA. In patients, DNA and RNA syntheses decreased immediately after PUVA sessions. During all the sessions until the psoriatic plaques had cleared, an impairment of DNA synthesis was observed in comparison with the synthesis in involved and uninvolved skin before treatment. These results suggest that the therapeutic efficiency of PUVA is based on the inhibition of DNA replication due to direct effects on nucleic acids but also to photoreactions with other cell components.

Animals↗
PubMed1987

Photosensitivity of DNA replication and respiration to haematoporphyrin derivative (photofrin II) in mammalian CV-1 cells.

DNA synthesis, as well as respiration, has been studied in CV-1 cells incubated with 5 or 25 micrograms/cm3 haematoporphyrin derivative Photofrin II (PF II) for 1, 24 or 48 h and then irradiated with various doses of UVA light (365 nm). The impairments of DNA synthesis increased with the duration of incubation with the porphyrin, its concentration and the dose of irradiation. The cellular consumption of oxygen is also inhibited by the treatment, but less severely. In the case of the higher PF II concentration (25 micrograms/cm3), the impairment of DNA synthesis after illumination seems to be mainly due to 3HTdR transport inhibition. This effect can be related to plasma membrane damage as shown by lactate dehydrogenase leakage. At 5 micrograms/cm3 PF II, DNA synthesis inhibition is observed even after short exposure to PF II and light without 3HTdR transport impairment. In that case, DNA and/or mitochondrial photodamage may explain the inhibition.

Animals↗
PubMed1986

Hematoporphyrin derivative (Photofrin II) photosensitization of isolated mitochondria: impairment of anion translocation.

Isolated mitochondria have been incubated in the presence of 6 micrograms/ml hematoporphyrin derivative (Photofrin II), and irradiated at lambda = 365 nm. After 2 min irradiation (30 W/m2), a congruent to 50% inhibition of citric cycle intermediates transport is observed with a rather similar photosensitivity for the succinate, citrate or oxaloacetate carriers.

Animals↗
PubMed1986

4-Thiouridine photosensitized RNA-protein crosslinking in mammalian cells.

Monkey kidney cells (CV-1) cultivated in the presence of 0.1 mM 4-thiouridine (S4U) and subsequently illuminated at 365 nm exhibit a marked RNA synthesis inhibition. Maximal effect (approximately 40%) was obtained for a 4 h S4U incubation and a 45 KJ/m2 dose. Under these conditions up to 20% of total cellular RNA is retained at the interphase during phenol-chloroform extraction. The fraction of RNA crosslinked to proteins amounts to 50% of the 3H-uridine labeled RNA synthesized during S4U incorporation and less than 10% for the control samples. This strongly suggests that S4U incorporated within the RNA chains acts as a photoaffinity probe. The data above provide the basis of a method for studying in vivo RNA-protein interactions under non destructive conditions.

Animals↗
PubMed1986

Photosensitization of mammalian cells by psoralens and porphyrins.

Because of the ability of photosensitizers to induce specific photochemical reactions in vivo, leading to cell injury and death, many such molecules have been considered as therapeutic agents. Among them two classes of sensitizers, i.e. furocoumarins (psoralens) and porphyrins, are currently used for the photochemotherapy of various skin diseases and malignant lesions. Different types of cell responses can result according to the intracellular localization of the photosensitizer and to the nature of the photochemistry induced by the chromophore which absorbs photons. In this review, the cytological aspects of photosensitization by psoralens and porphyrins will be discussed.

Animals↗
PubMed1986

Oxic and anoxic photodamage triggered at the subcellular level by the synergistic action of haematoporphyrin derivative and nitroimidazoles.

A first attempt to impair a biological function by the synergistic effects of HpD and nitroimidazoles (metronidazole or misonidazole) under anaerobic conditions is reported. A function tightly linked to a membrane has been chosen as model and the Ca2+ movements through the inner mitochondrial membrane have been studied. When isolated mitochondria (1 mg/cm3) are irradiated in oxic condition with 25 micrograms/cm3 HpD and 1 mmol dm-3 nitroimidazole in the medium, Ca2+ uptake is stopped after 15 s of irradiation. When irradiated in anoxic conditions with 25 micrograms/cm3 HpD alone, addition of ATP triggers a normal Ca2+ uptake even after 10 min of irradiation. In contrast Ca2+ uptake is stopped by 1 min irradiation after addition of 1 mmol dm-3 misonidazole to HpD and by 2 min irradiation after addition of 1 mmol dm-3 metronidazole. Thus, under these experimental conditions, the enhancement ratio of the HpD action (defined as the ratio of the durations of irradiation necessary to obtain the cessation of Ca2+ uptake before and after addition of a component other than HpD) is of the order of 40, 10 and 5 for oxygen, misonidazole and metronidazole, respectively. Misonidazole is still efficient at a concentration of 0.1 mmol dm-3.

Adenosine Triphosphate↗