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Biomedical subjects

P Tulkens

Publications and source records attributed to P Tulkens.

At least 19 recordsLinked to original sources
PubMed1990

Renal tissue injury and proliferative response after successive treatments with anticancer platinum derivatives and tobramycin.

The administration of anticancer platinum derivatives such as cisplatin, or aminoglycoside antibiotics is frequently associated with tubular necrosis which can eventually lead to acute renal failure. Previously, we have shown that renal tissue injury induced by these drugs elicits a process of tissue repair involving the stimulation of cell proliferation. The present study was undertaken to examine the morphological alterations and the proliferative response resulting from tobramycin administration to animals previously challenged with the platinum derivatives cisplatin and carboplatin. Female Sprague-Dawley rats were treated i.p. with cisplatin (8 mg/kg delivered in four daily injections) or carboplatin (40 mg/kg given in one injection) and sacrificed 21 or 60 days after drug administration. Tobramycin was administered i.p. twice a day at a daily dose of 10 mg/kg over the ten days preceding sacrifice. At 1 h before sacrifice, each animal received i.p. 200 microCi of [3H] thymidine for the measurement of DNA synthesis and cell proliferation (determined by histoautoradiography). Successive treatments with cisplatin and tobramycin appeared to produce an increase in the severity of histopathological alterations such as tubular necrosis and cystic degeneration. Moreover, cisplatin pretreatment dramatically increased the severity of tobramycin-induced lysosomal phospholipidosis. Histopathological alterations were followed by an important proliferative response partly associated with tubular regeneration but also due to fibroblastic proliferation which led to peritubular fibrosis. Surprisingly, the additive effect of cisplatin and tobramycin on renal injury became particularly striking with increasing time intervals between treatments. In contrast, successive treatments with carboplatin and tobramycin did not cause significative changes of the degree of renal injury, compared with either drug given alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Effects of gentamicin on the renal uptake of endogenous and exogenous protein in conscious rats.

To study the effect of gentamicin on the renal uptake of proteins, Sprague-Dawley female rats were intravenously injected with solutions containing unlabeled human beta 2-microglobulin (beta 2-m), retinol-binding protein, and increasing amounts of gentamicin (from 0.063 up to 31.5 mg/kg). The concentrations of human proteins and that of endogenous beta 2-m, albumin, and IgG in the urine collected during the 2 hr following the injection were determined by immunoassays. Gentamicin transiently increased the urinary excretion of rat and human beta 2-m in a dose-dependent manner. The mean relative increase of rat beta 2-m excretion ranged from 2 at a gentamicin dose of 0.06 mg/kg up to 500 at a gentamicin dose of 31.5 mg/kg. By contrast, the urinary excretion of other proteins was only increased by a factor of 2 to 5 at the highest dose of gentamicin. The relative increase of the urinary excretion of proteins was positively correlated with the fractional reabsorption of the proteins by the rat kidney. The inhibitory effect of gentamicin on the renal uptake of protein was very similar to that observed in rats injected with polycationic proteins like lysozyme and cytochrome C. These observations, combined with the fact that gentamicin, like proteins, enters the tubular cell by adsorptive endocytosis, strongly suggest that this drug competes with proteins for common binding sites on the apical tubular membrane and for subsequent endocytosis. Furthermore, the iv injection of large amounts of gentamicin and polycationic proteins induces a lysosomal enzymuria which very likely is a manifestation of an increased exocytosis.

Animals↗
PubMed1984

Interactions of aminoglycoside antibiotics with negatively charged lipid layers. Biochemical and conformational studies.

Previous studies [Laurent et al., Biochem. Pharmac. 31, 3861 (1982)] have demonstrated that aminoglycoside antibiotics bind to negatively charged phospholipid bilayers and inhibit the activity of lysosomal phospholipases. This inhibition also occurs in vivo in animal and man. It is considered to be an early and significant step in the development of aminoglycoside-induced nephrotoxicity. The binding of 6 aminoglycosides in current clinical use (dibekacin, gentamicin, tobramycin, kanamycin A, amikacin and streptomycin) to phosphatidylinositol has been studied by gel filtration technique and by conformational analysis. Variation of the phosphatidylinositol content from 0 to 27% of total phospholipids causes a cooperative increase in aminoglycoside binding. At fixed phosphatidylinositol concentration, the binding of the different aminoglycosides is related to the number of aminogroups carried by the drug (viz., gentamicin greater than kanamycin A greater than streptomycin) and is largely, but not entirely dependent upon electrostatic interactions. Conformational analysis of the interaction of aminoglycosides with phosphatidylinositol monolayers was made by a step-wise computation approach. We first have taken into account the Vander Waals, torsional and electrostatic energies and we have calculated the hydrophobic and hydrophilic centers of each molecule. Assembly was then computed by successive association of one molecule of drug and up to 4 molecules of phosphatidylinositol. The calculated interaction energies varied from -8.5 kcal/mol (gentamicin) to -4.9 kcal/mol (amikacin) and -3.9 kcal/mol (streptomycin).(ABSTRACT TRUNCATED AT 250 WORDS)

Aminoglycosides↗
PubMed1984

In vitro inhibition of lysosomal phospholipases by aminoglycoside antibiotics: a comparative study.

Aminoglycosides induce an early and characteristic phospholipidosis in the lysosomes of kidney tubular cells. Inhibition of lysosomal phospholipase activity by gentamicin has been demonstrated in vivo and in vitro. Ten aminoglycosides have been examined for their potency in inhibiting phospholipases A1 and A2. Similar IC50's and IC90's (concentrations causing 50 and 90% inhibition) were found for sisomicin, dibekacin, gentamicin, tobramycin, kanamycin B and netilmicin. Kanamycin A, HABA-dibekacin and amikacin showed increasingly higher IC's. Thus, both the number and the position of amino groups are important. Streptomycin had little effect on phosphatidylcholine hydrolysis. Kinetic studies with gentamicin suggest a competitive type of inhibition. This approach may help for the in vitro screening of less toxic aminoglycosides.

Aminoglycosides↗
PubMed1984

A 2'guanidyl derivative of gentamicin (S86451) with reduced nephrotoxicity studies at low and medium dose levels in the rat.

The nephrotoxic potential of S86451 (2'guanidyl, 2'deamino gentamicin C1) has been investigated in Sprague-Dawley rats at 10 and 25 mg/kg, in comparison with gentamicin at 4 and 10 mg/kg. The criteria were (i) the severity of the lysosomal phospholipidosis, as assessed by both biochemical and morphological investigations; (ii) the degree of tubular regeneration, a consequence of the aminoglycoside-induced focal necrosis measured by 3H-thymidine incorporation into kidney cortex DNA. S86451 was found at least 2-5 times less toxic than gentamicin. Thus, this compound should be a safer antibiotic than gentamicin in combating organisms with a similar sensitivity to either drug.

Animals↗
PubMed1984

Tubular regeneration in rat kidney cortex during treatment with gentamicin at a low dose.

Tissue injury induced in rat kidney cortex by gentamicin at a low dose (10 mg/kg) has been studied by measuring subsequent regeneration after treatment for 4, 7, and 14 days. Cell proliferation was demonstrated by the incorporation of [3H]-thymidine into kidney cortex DNA. In treated animals, the specific radioactivity of DNA increased up to 4.6 times the mean value found in the controls. Autoradiography showed labelling of nuclei in proximal tubular cells. Electron microscopy showed that a subpopulation of tubular cells, devoid of myeloid bodies, which are characteristic of gentamicin intoxication, is also poorer in peroxisomes, and therefore may belong to less differentiated, regenerating cells. It is concluded that a low dose of gentamicin induces measurable tissue regeneration.

Animals↗
PubMed1984

Gentamicin-induced stimulation of DNA synthesis in rat kidney. Comparison between in vivo and in vitro models.

We have performed combined in vivo and in vitro measurements of thymidine uptake into kidney cortex DNA of animals treated with gentamicin for 7 days at 10 or 20 mg/kg daily (BID). Labelled thymidine is taken up by cortex fragments in vitro (90 min incubation) and incorporated into DNA; treatment of the animals with gentamicin results in a significant dose-dependent enhancement of this in vitro thymidine incorporation; labelled cells are found primarily in the proximal tubules and interstitium; there is an excellent correlation (r : 0.983, n = 15) between the changes of incorporation measured in vivo and in vitro as demonstrated by the sequential use of [3H]thymidine (in vivo) and [14C]thymidine (in vitro) within the same animals.

Animals↗
PubMed1983

Gentamicin nephrotoxicity in cadmium, lead and mercury pretreated rats.

The effect of a previous chronic exposure to cadmium, lead or inorganic mercury on the nephrotoxic potential of gentamicin was investigated in female Sprague-Dawley rats. A daily dose of 10 mg gentamicin/kg body weight/day was administered for 21 days to rats having a renal load of 168 micrograms Cd, 35 micrograms Pb or 129 micrograms Hg/g whole kidney. Urine analysis suggests an attenuation of the nephrotoxic potential of gentamicin while a microscopical examination of kidneys indicates a superimposition of the effects of the metals and the antibiotics. The only clear interaction observed consists in a reduction of gentamicin accumulation in the cortex of cadmium-treated animals. It is concluded that none of the metal pretreatments potentiates the nephrotoxic effects of gentamicin.

Amino Acids↗
PubMed1983

Comparative nephrotoxicity of four aminoglycosides: biochemical and ultrastructural modifications of lysosomes.

In 1982, aminoglycosides still are widely prescribed and considered indispensable for the treatment of severe gram-negative infections. All the aminoglycosides are nephrotoxic, but both experimental works and clinical investigations indicate that they do not all have the same nephrotoxic potential. Within the renal tubular cell in several animal species and in man, the initial and the most extensive changes are those that occur in the lysosomes. We compared the effects of gentamicin, tobramycin, netilmicin and, amikacin on (a) lysosomal structural latency, (b) the activity of several enzymes, either lysosomal or those contained in the proximal tubular cell brush border, and (c) the accumulation of myeloid bodies in the lysosomes. From our results, it appears that gentamicin is the aminoglycoside that induces the greatest number of lysosomal changes whereas amikacin induces the least, with the effects of netilmicin and tobramycin quite close to those of amikacin. Other works comparing the nephrotoxicity of aminoglycosides reveal the same high nephrotoxic potential of gentamicin.

Amikacin↗
PubMed1979

Cellular toxicity of gentamicin.

Subconjunctival injections of gentamicin induced a lysosomal storage process within the conjunctival fibroblasts in rats, rabbits, and humans. Under electron microscopy, the accumulated substance was composed of a granular material and pleomorphic lamellar structures, corresponding to the presence of complex lipids. In animals, the other ocular tissues as well as the cells reached through the bloodstream remained unaffected, except the proximal convoluted tubules of the kidneys, where important lesions were evident. Although human kidneys were not examined in our study, we believe they might present similar alterations.

Animals↗
PubMed1979

Fate of plasma membrane during endocytosis. I. Uptake and processing of anti-plasma membrane and control immunoglobulins by cultured fibroblasts.

The uptake and processing by cultured rat embryo fibroblasts of control rabbit immunoglobulins (C IgG) or IgG directed against plasma membrane constituents (anti-PM IgG), and labeled with fluorescein (F) or with radioactive acetate (A), have been investigated by cell fractionation and immunological techniques. Both F and A anti-PM IgGs become bound to the cell surface, by a process that is slow, but largely temperature-independent. In the presence of an excess of high-affinity antibodies, binding reaches an absolute limit which corresponds to extensive coating of the plasma membrane. The anti-PM IgGs remain attached to the membrane for at least several days, even at 37 degrees C, with no significant transfer to lysosomes or degradation. In contrast, C IgGs are handled very differently by the fibroblasts, and their fate is strikingly affected by the type of labeling used. AC IgG is taken up slowly, at a rate proportional to its concentration, and is subsequently broken down in what appears to be lysosomes. Part of the AC IgG also binds to the plasma membrane. FC IgG is taken up many times faster than AC IgG, though with the same strict linearity as a function of concentration. Most of the FC IgG taken up is stored in cytoplasmic granules which behave like lysosomes. For reasons that are not understood, only about half of the stored FC IgG can be broken down. Cells exposed simulatnaously to AC IgG and FC IgG, or to A anti-PM IgG and FC IgG, handle each type of IgG in its characteristic fashion. Kinetic analysis of these results indicates that Ac IgG could be taken up by fluid endocytosis, but that FC IgG must be interiorized by a selective mechanism, presumably adsorptive in nature. That anti-PM antibodies remain stably bound to the plasma membrane and do not interfere with the uptake of FC IgG is interpreted to indicate either that two distinct membrane domains are involved in the two phenomena, or that membrane patches coated with anti-PM IgG participate in endocytosis, and are recycled back to the cell surface after delivering their contents intracellularly.

Animals↗
PubMed1979

Fate of plasma membrane during endocytosis. II. Evidence for recycling (shuttle) of plasma membrane constituents.

Cultured rat embryo fibroblasts were first allowed to store for 24 h fluorescein-labeled goat immunoglobulins directed against rabbit immunoglobulins (F anti-R IgG), and were subsequently exposed for 24 h to [(3)H]acetylated rabbit immunoglobulins known to bind to the cell membrane either specifically (anti-plasma membrane IgG: A anti-PM IgG) or unspecifically (contol IgG: AC IgG). As a result of immunological interaction between the two antibodies (no effect was found if the cells had been preloaded with control goat FC IgG), a substantial portion of the stored F anti-R IgG was unloaded from its intracellular storage site, appearing in the medium in the form of soluble immune complexes with rabbit A IgG. Part of the unloaded F anti-R IgG also was recovered in association with the plasma membrane, but only when A anti-PM IgG was used. In addition, significant reverse translocation of AC IgG from plasma membrane to lysosomes or some related intracellular storage compartment was also observed. With A anti-PM IgG, this translocation was less marked and affecte at the same time the plasma membrane marker 5'- nucleotidase. Cells that had stored horseradish peroxidase (HRP) simultaneously with F anti-R IgG did not unload HRP when exposed to A anti-PM IgG. These results support strongly, though not unequivocally, the concept that plasma membrane patches interiorized by endocytosis are recycled, or shuttled, back to the cell surface. In the framework of this concept, recycling antibody-coated membrane is taken to serve as vehicle for the selective intracellular capture and extracellular discharge of immunologically bound F anti-R IgG. The alternative explanation of regurgitation triggered off by immune complexes is considered less likely in view of the lack of HRP unloading.

Animals↗