Biomedical subjects

D Beauchamp

Publications and source records attributed to D Beauchamp.

At least 55 records · Page 3Linked to original sources

PubMed1995

Calculation and number processing in mild Alzheimer's disease.

Calculation and number processing abilities in 17 patients suffering from a mild form of dementia of Alzheimer's type (DAT) were studied by means of a standardized multitask assessment battery, the EC301 (Deloche et al., 1994). Patients were selected from a larger sample by using a specific visuo-perceptive task to control the confounding effects of deficits in analysing digit serial order. Language and memory skills were evaluated by means of standardized testing procedures. The EC301 overall score showed impaired performance in 12 cases. Calculation and number processing scores were highly correlated with Mini-Mental State Examination and language performance. However, multiple single-case analyses indicated heterogeneous patterns of preserved/impaired abilities with respect to the three cognitive areas under investigation (calculation, memory, and language) and to the different components of the calculation and number processing system.

Aged↗

PubMed1995

Lymphoid tissues targeting of liposome-encapsulated 2',3'-dideoxyinosine.

OBJECTIVE: To improve the pharmacokinetics and lymphoid tissues targeting of 2',3'-dideoxyinosine (ddI) by encapsulation in liposomes. METHODS: The pharmacokinetics and tissue distribution of free and liposome-encapsulated ddI were determined in C57BL/6 mice following intravenous and subcutaneous administration of a single bolus dose (3 mg ddI/kg). RESULTS: Intravenous administration of liposome-encapsulated ddI greatly reduced the systemic clearance of the anti-HIV agent. The elimination plasma half-life of ddI incorporated in 112 and 83 nm liposomes was 46 and 14 times higher than that of the free drug, respectively. The tissue distribution profile of liposomal lipids clearly showed that the use of liposomes allows efficient targeting of lymph nodes and macrophage-rich tissues (spleen and liver) for at least 24 h following intravenous injection. In contrast, the accumulation of liposomes in these tissues was much lower following subcutaneous administration. CONCLUSION: Incorporation of ddI in liposomes greatly improved the pharmacokinetics of the anti-HIV agent after intravenous injection. The use of liposomes could represent a convenient approach to targeting lymphoid tissues. Strategies aimed at improving drug retention within liposomes should further enhance and prolong drug delivery to lymphoid organs.

Animals↗

PubMed1995

Encapsulation of foscarnet in liposomes modifies drug intracellular accumulation, in vitro anti-HIV-1 activity, tissue distribution and pharmacokinetics.

OBJECTIVE: To improve the in vitro anti-HIV-1 activity, intracellular accumulation in macrophages and in vivo pharmacokinetics and tissue distribution of foscarnet (trisodium phosphonoformate; PFA) by encapsulation in liposomes. METHODS: The accumulation of free and liposome-encapsulated PFA was determined in monocyte-macrophage RAW 264.7 cells and human premonocytoid U937 cells. The antiviral activity was evaluated in U937 cells infected with HIV-1IIIB. Tissue distribution and pharmacokinetics of free and liposomal PFA were determined in female Sprague-Dawley rats following the administration of an intravenous bolus dose (10 mg PFA/kg). RESULTS: The entrapment of PFA in liposomes resulted in a higher drug accumulation in both U937 and RAW 264.7 cells. A slightly greater efficacy against HIV-1IIIB replication into U937 cells was observed upon encapsulation of PFA into liposomes. Improved pharmacokinetics was observed upon entrapment of PFA in liposomes. Much higher drug levels were found in plasma for the liposomal formulation. The systemic clearance of the liposomal drug was 77 times lower than that of free drug. The encapsulation of PFA in liposomes greatly enhanced the drug accumulation in organs of the reticuloendothelial system. CONCLUSION: The encapsulation of PFA in liposomes modified the tissue distribution and plasma pharmacokinetics of the antiviral agent, resulting in a marked improvement of drug accumulation in organs involved in HIV immunopathogenesis and in a greater PFA bioavailability. The antiviral activity of liposomal PFA was slightly greater than that of free drug in HIV-1IIIB-infected U937 cells.

Animals↗

PubMed1995

Liposomal encapsulation of foscarnet protects against hypocalcemia induced by free foscarnet.

Hypocalcemia and an increase in creatinine level are the most important serious effects associated with foscarnet (PFA) therapy. In an animal model, we have explored the potential protective role of liposome-encapsulated foscarnet (LE-PFA) on these metabolic abnormalities. PFA administered as one bolus injection (0.5 or 1.0 g/kg) caused significant rapid decreases (approximately 20%) in the levels of calcium and phosphorus in serum within a few minutes and up to 30 min after injection. LE-PFA did not induce any of these changes, while peak levels in serum and the half-life of this formulation were much higher than those of the free drug. PFA administered for 2 weeks (340 or 500 mg/kg/day) resulted in no changes in creatinine or blood urea nitrogen levels in serum at the low-dosage level, but at the higher-dosage level, the creatinine level in serum increased by day 5 posttreatment. Furthermore, there was no increase in the creatinine or blood urea nitrogen level after 2 weeks of treatment with LE-PFA at a dosage of 35 mg/kg/day. When the pharmacokinetics of both free PFA and LE-PFA were compared, the plasma half-life of the encapsulated drug was approximately four times longer than that of the free drug. In addition, the systemic clearance of LE-PFA was approximately one-fifth of that of the free drug. In conclusion, free PFA causes hypocalcemia and hypophosphatemia and increases the creatinine level in serum, whereas the LE form of this drug seems to protect against the abnormal changes in calcium and phosphorus levels caused by the free drug. By preventing hypocalcemia and increasing its half-life, LE-PFA can be used at lower doses and at longer intervals. Clinical investigations of these formulations may be worthwhile.

Animals↗

PubMed1995

[Is it still possible to reduce the incidence of nephrotoxicity of aminoglycosides?].

Aminoglycosides are still widely used alone or in combination with a beta-lactam antibiotic for the treatment of severe Gram negative infection. Oto- and nephrotoxicity are the major side effects associated with the use of these drugs. Although several risk factors associated with aminoglycoside nephrotoxicity have been identified, only few therapeutic approaches were suggested to reduce the incidence of their toxicity in patients. The single daily injection is the only approach actually used to reduce the renal toxicity of aminoglycosides in patients. However, the relationship between the nephrotoxicity of aminoglycosides and the time of the day these drugs should be given has never been explored in patients. Data obtained in laboratory animals indicated that temporal variations can be detected in the renal toxicity of aminoglycosides: the nephrotoxicity was observed during the rest period of the animals while no toxicity was found at other times of the day. Other studies suggested also that food intake can modulate the temporal variations in the nephrotoxicity of aminoglycosides. A better knowledge of the risk factors associated with the renal toxicity of aminoglycosides, a reduction in the number of daily injections of aminoglycosides, administration of aminoglycosides at the time of the lowest toxicity of the drug in patients submitted to an appropriate diet are the most interesting approaches to reduce the incidence of the renal toxicity of these agents.

Aminoglycosides↗

PubMed1994

Potentiation of gentamicin nephrotoxicity in the rat by infusion of aprotinin.

The present study was undertaken to examine a possible effect of aprotinin, a 6.5-kDa polypeptide with an inhibitory effect on proteolysis, on aminoglycoside nephrotoxicity. Experimental animals (female Sprague-Dawley rats, 175-200 g body wt) were treated for 4 days with 40 mg/kg gentamicin given ip at 12-hr intervals. Aprotinin (40,000 kIU per animal) was infused i.v. over a period of 8 days, using subcutaneously implanted miniosmotic pumps. In protocol A, infusion pumps were placed 4 days before starting gentamicin treatment. In protocol B, pumps were implanted 15-18 hr prior to first gentamicin administration. In addition to rats exposed to both gentamicin and aprotinin (GAP), animals were treated with gentamicin ip+saline i.v. (G), saline ip+aprotinin i.v. (AP), or received only saline by both routes of administration (C). All rats were terminated 4 days after the end of gentamicin dosing. One hour before sacrifice, 200 microCi of [3H]thymidine was given ip to each animal in order to monitor cell turnover in renal tissue. The kidneys were analyzed with respect to (i) histopathological alterations and renal dysfunction, (ii) aminoglycoside tissue accumulation, and (iii) tubular regeneration (measurement of cell proliferation). In animals receiving aprotinin alone, histological examination of renal cortex on paraffin sections disclosed mild tubular injury with focal cell necrosis. In plastic-embedded tissue, proximal tubule epithelium was characterized by the presence of numerous inclusions densely stained with toluidine blue. At the ultrastructural level, these inclusions appeared filled with amorphous electron-dense material. In gentamicin-treated animals, cortical drug accumulation reached values higher than 0.3 mg/g renal tissue, but a significant 30-40% decrease of gentamicin accumulation was noted in GAP groups, compared to G groups. Histological examination of renal cortex (paraffin sections) revealed the development of acute tubular necrosis in both G and GAP groups. Tubular injury was accompanied by mild renal dysfunction, as shown by the level of serum creatinine which was increased almost 3-fold in the G group, compared to C and AP groups. Aprotinin infusion produced a further increase of serum creatinine, particularly in protocol A where it was 72% higher for the GAP group than for the G group. In both G and GAP groups, postnecrotic tubular regeneration was evidenced by determining the rate of DNA synthesis and the frequency of S-phase cells in renal cortex. Both methods gave consistent results and showed a 8- to 13-fold increase of cell proliferation in groups receiving gentamicin alone, compared to C groups.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1994

Nephrotoxicity of low doses of tobramycin in rats: effect of the time of administration.

The circadian and the circannual variations of the nephrotoxicity of tobramycin were studied in female Sprague-Dawley rats. Animals were maintained on a light-dark period of 14/10 hrs (light on: 06h00 to 20h00). They were injected once daily for 4 and 10 days with saline or tobramycin at a dose of 40 mg/kg/day i.p. at either 08h00, 14h00, 20h00 and 02h00, in April 1991, July 91, October 91, January 92. In April 91, tobramycin injected at 14h00 during 10 days induced a significant increase of [3H]-thymidine incorporation into DNA of renal cortex as compared to other groups (p < 0.01): toxicity was highest at 14h00 and lowest at 02h00. No temporal change was observed in the renal cortical accumulation of tobramycin, and in serum creatinine after the 4 or 10 days of treatment. In experiments done in April, July and October 1991 and in January 1992, no circannual variation was found in tobramycin cortical levels but peaks of toxicity were observed at 02h00 in April and October 1991 and at 14h00 in July 1991 and January 1992. There was no linear correlation between the toxicity and the tobramycin accumulation in the renal cortex (r = 0.21). The data suggest that the circadian changes in tobramycin toxicity are due to temporal changes in the susceptibility of renal cells to tobramycin.

Animals↗

PubMed1994

Comparison of cellular accumulation, tissue distribution, and anti-HIV activity of free and liposomal 2',3'-dideoxycytidine.

We have investigated the cellular accumulation, tissue distribution, and antihuman immunodeficiency virus activity of free dideoxycytidine (ddC) and liposomal ddC (L-ddC). We have found that L-ddC was more efficiently taken up than its free form by RAW 264.7 cells (a monocyte-macrophage cell line) (p < 0.01) while a comparable uptake was seen in U937 cells (a promonocytic cell line). In the rat, L-ddC accumulated preferentially in liver and spleen when injected intravenously (p < 0.01), and mostly in spleen when given intraperitoneally (p < 0.01). In contrast, free ddC was rapidly eliminated out of the body. Liposomal ddC showed a similar anti-HIV activity in comparison with free ddC in U937 cells. Given the fact that encapsulation of ddC in liposomes does not affect its anti-HIV activity but enhances its in vitro cellular accumulation and its in vivo distribution in reticuloendothelial system (RES) tissues, we conclude that ddC in liposomal formulation is a promising anti-HIV agent with a targeted action on the RES, which is considered a reservoir for dissemination of virus to other cells, tissues, and organs.

Animals↗

PubMed1994

Azithromycin uptake and intracellular accumulation by Toxoplasma gondii-infected macrophages.

The uptake of azithromycin and erythromycin was measured in RAW 264.7 mouse macrophages infected with Toxoplasma gondii to determine whether the activity of macrolides could be correlated with their degree of host cell penetration. Uptake was expressed as the ratio of the intracellular (I) to the extracellular (E) concentrations. After infection, the intracellular accumulation of macrolides was equivalent to that measured in uninfected cells and azithromycin reached an I/E ratio of 105.8 +/- 8.0 in infected macrophages incubated with 20 mg/L of drug. The release of azithromycin from macrophages previously exposed to the drug was enhanced by exposure to Micrococcus luteus and phorbol myristate acetate but not after infection with T. gondii. Azithromycin accumulates readily and remains inside T. gondii-infected macrophages thereby interfering with the growth of the parasite which was confirmed by growth-inhibition experiments and by electron microscopy.

Animals↗

PubMed1994

Antiviral efficacy, intracellular uptake and pharmacokinetics of free and liposome-encapsulated 2',3'-dideoxyinosine.

OBJECTIVE: To evaluate the effect of liposome encapsulation on the in vitro antiviral efficacy, intracellular uptake and in vivo pharmacokinetics of 2',3'-dideoxyinosine (ddl). METHODS: The accumulation of free and liposome-encapsulated ddl was determined in murine monocyte-macrophage RAW 264.7 cells and human premonocytoid U937 cells. The antiviral efficacy was evaluated in U937 cells infected with HIVIIIB. Tissue distribution and pharmacokinetics of free and liposomal ddl were determined in female Sprague-Dawley rats following the administration of a single intravenous bolus dose (3 mg ddl/kg). RESULTS: The entrapment of ddl in liposomes results in a lower drug accumulation in both U937 and RAW 264.7 cells. A lower antiviral efficacy against HIVIIIB replication in U937 cells was observed on encapsulation of ddl in liposomes. Improved pharmacokinetics were observed on entrapment of ddl in liposomes. Higher drug levels were found in plasma for the liposomal formulation. The systemic clearance of the liposomal drug was 120 times lower than that of free drug. Liposome encapsulation of ddl greatly enhanced the drug accumulation in organs of the reticuloendothelial system. CONCLUSION: The encapsulation of ddl in liposomes modified the tissue distribution and plasma pharmacokinetics of the antiviral agent resulting in a marked improvement of drug biodisponibility. The antiviral efficacy of liposomal ddl was lower than that of free drug in HIVIIIB-infected U937 cells.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1994

Temporal changes of pharmacokinetics, nephrotoxicity, and subcellular distribution of tobramycin in rats.

The present study was designed to determine the temporal changes in tobramycin nephrotoxicity during the dark and the light periods of the day and to look for the mechanisms of such changes. Female Sprague-Dawley rats (9 to 11 weeks old) were housed in a 14-h-light-10-h-dark cycle (lights on 0600 to 2000 h). A bolus of tobramycin (60 mg/kg of body weight) was intravenously injected into a first group of 15 rats, at either 1400 or 0200 h. Six blood samples were taken from each rat, 30 to 210 min after the bolus injection. The total clearance of the drug was reduced during the rest period (1400 h) of rats compared with the activity period (0200 h) (P = 0.0007). Another group of 99 rats was given intraperitoneally a single dose of tobramycin (40 mg/kg), and renal cortices were collected 2 to 222 h after injection. The cortical drug levels were always higher in animals injected at 1400 h than in those injected at 0200 h. A last group of 32 rats was used in the studies of tobramycin (30 mg/kg/day, once daily for 10 days, intraperitoneally) nephrotoxicity and subcellular distribution. Weight gain in the rats receiving tobramycin (both 1400 and 0200 h) was significantly (P = 0.028) less than that in the controls. Nephrotoxicity, indicated by the incorporation of [3H]thymidine into cortical DNA and urinary excretion of N-acetyl-beta-D-glucosaminidase, was significantly higher in animals treated at 1400 h than in those treated at 0200 h. No difference in the subcellular distribution of tobramycin was observed. The data indicate that the reduction in the clearance of tobramycin during the rest period is in part responsible for the higher nephrotoxicity in rats.

Acetylglucosamine↗

PubMed1994

Subcellular distribution of daptomycin given alone or with tobramycin in renal proximal tubular cells.

Previous studies in experimental animals showed that daptomycin, a lipopeptide antibiotic, protects against aminoglycoside nephrotoxicity (C. A. Wood, H. C. Finkbeiner, S. J. Kohlhepp, P. W. Kohnen, and D. N. Gilbert, Antimicrob. Agents Chemother. 33:1280-1285, 1989; D. Beauchamp, M. Pellerin, P. Gourde, M. Pettigrew, and M. G. Bergeron, Antimicrob. Agents Chemother. 34:139-147, 1990). In order to better understand the mechanism involved in this protective effect, the subcellular distribution of daptomycin was investigated in the proximal tubular cells of animals treated with daptomycin alone or in combination with tobramycin. A first group of female Sprague-Dawley rats received a single intravenous injection of daptomycin at a dose of 100 mg/kg of body weight and were killed at 10 min, 1 h, or 24 h after the injection. Other groups of rats were treated during 10 days with saline (NaCl, 0.9%), tobramycin at dosages of 20 mg/kg/12 h, daptomycin at dosages of 10 mg/kg/12 h, or the combination tobramycin-daptomycin at the same dosages. At the time of sacrifice, the renal cortex of the right kidney of each animal was dissected, and small blocks of tissue were fixed, dehydrated, and embedded in Araldite 502 epoxy resin. The subcellular distribution of daptomycin and tobramycin was determined on ultrathin sections by immunogold labeling. Ten minutes after the injection of daptomycin alone, gold particles were seen over the brush border membrane and on the membranes of the endocytic vacuoles of proximal tubular cells. One hour after the injection, a similar distribution was seen and numerous gold particles were found over the lysosomes of proximal tubular cells. The results suggest that daptomycin might protect against aminoglycoside nephrotoxicity by interfering with the interaction between the aminoglycoside and phospholipids inside the lysosomes of proximal tubular cells.

Animals↗

PubMed1994

Daptomycin may attenuate experimental tobramycin nephrotoxicity by electrostatic complexation to tobramycin.

The lipopeptidic antibiotic daptomycin is reported to reduce experimental tobramycin nephrotoxicity (D. Beauchamp, M. Pellerin, P. Gourde, M. Pettigrew and M. G. Bergeron, Antimicrob. Agents Chemother. 34:139-147, 1990; C. A. Wood, H. C. Finkbeiner, S. J. Kohlhepp, P. W. Kohnen, and D. C. Gilbert, Antimicrob. Agents Chemother. 33:1280-1285, 1989). In an attempt to explain these results, the in vivo and in vitro interactions between daptomycin and tobramycin were studied. Tobramycin alone and preincubated with negatively charged phospholipid bilayers (liposomes) was dialyzed against increasing concentrations of daptomycin in buffer at pH 5.4. A significant drop in the concentration of tobramycin was observed when daptomycin was added to the opposite half cells. Furthermore, daptomycin induced a concentration-dependent release of lipid-bound tobramycin. Gold labeling experiments showed that daptomycin could be incorporated into phospholipid layers. Female Sprague-Dawley rats were treated with daptomycin alone, with tobramycin alone, or with the combination over 2 to 10 days. Levels of daptomycin and tobramycin in serum were similar in all groups. The levels of tobramycin in the renal cortex increased significantly with time and, on day 10, reached values of 654 +/- 122 and 844 +/- 298 micrograms/g of tissue (mean +/- standard deviation; not significant) in animals treated with tobramycin and the combination of daptomycin-tobramycin, respectively. No significant difference was observed in the levels of tobramycin in the kidneys between animals treated with tobramycin or the daptomycin-tobramycin combination at any time. By contrast, daptomycin levels were significantly higher in the renal cortexes of animals treated with daptomycin-tobramycin in comparison with those in the renal cortexes of animals treated with daptomycin alone on days 6,8, and 10 (P < 0.01). For immunogold labeling studies, animals were killed 4 h after a single injection of daptomycin alone or daptomycin in combination with tobramycin. Daptomycin was found throughout the matrixes of the lysosomes of proximal tubular cells of animals treated with daptomycin alone. In animals treated with the combination of daptomycin and tobramycin, daptomycin was associated with intralysosomal myeloid bodies. Our results suggest that daptomycin might attenuate experimental aminoglycoside nephrotoxicity by interacting with the aminoglycoside, perhaps electrostatically, and thereby protecting intracellular targets of toxicity.

Animals↗

PubMed1994

Ceftriaxone protects against tobramycin nephrotoxicity.

The effect of ceftriaxone on tobramycin-induced nephrotoxicity was investigated. Female Sprague-Dawley rats were treated during 4 and 10 days with saline (NaCl, 0.9%), ceftriaxone at a dose of 100 mg/kg of body weight/12 h subcutaneously, tobramycin at doses of 40 and 60 mg/kg/12 h intraperitoneally, or the combination ceftriaxone-tobramycin. Creatinine levels in serum were significantly higher in animals treated with tobramycin alone given at 60 mg/kg/12 h during 10 days, compared with control animals (P < 0.01) or animals receiving the combination tobramycin-ceftriaxone (P < 0.01). After 10 days of treatment, ceftriaxone did not accumulate in renal tissue but did reduce the renal intracortical accumulation of tobramycin (P < 0.05). Tobramycin given alone at either 40 or 60 mg/kg/12 h induced a significant inhibition of sphingomyelinase activity compared with control animals (P < 0.05). However, this enzyme activity was significantly less inhibited when tobramycin was injected in combination with ceftriaxone (P < 0.05). Ceftriaxone alone had no effect on the activity of this enzyme. The [3H]thymidine incorporation into the DNA of renal cortex was also significantly lower in animals treated with tobramycin-ceftriaxone compared with animals receiving tobramycin alone (P < 0.05). The 24-h urinary excretion of beta-galactosidase was significantly reduced in animals treated with the combination tobramycin-ceftriaxone compared with the administration of tobramycin alone at 40 and 60 mg/kg/12 h after 5 and 10 days (P < 0.05). Histologically, ceftriazone induced very few cellular alterations and reduced considerably the presence of typical signs of tobramycin nephrotoxicity. This investigation demonstrated that ceftriaxone protects animals against tobramycin-induced nephrotoxicity.

Animals↗

PubMed1994

Attenuation by daptomycin of gentamicin-induced experimental nephrotoxicity.

Previously, daptomycin was shown to reduce tobramycin nephrotoxicity in vivo (D. Beauchamp, M. Pellerin, P. Gourde, M. Pettigrew, and M. G. Bergeron, Antimicrob. Agents Chemother. 34:139-147, 1990; C. A. Wood, H. C. Finkbeiner, S. J. Kohlhepp, P. W. Kohnen, and D. C. Gilbert, Antimicrob. Agents Chemother. 33:1280-1285, 1989). Female Sprague-Dawley rats were treated with saline (NaCl, 0.9%), daptomycin (10 mg/kg of body weight every 12 h, subcutaneously), gentamicin (30 mg/kg/12 h, intraperitoneally) or with a combination of daptomycin plus gentamicin over a 10-day period. Animals were killed 4, 10, and 20 days after the end of treatment. Four days after the end of drug administration, gentamicin and daptomycin levels in the renal cortices of animals treated with the combination of daptomycin and gentamicin were significantly higher than in those of rats given gentamicin or daptomycin alone (P < 0.01). Despite the higher cortical concentrations of gentamicin, rats given the combination of gentamicin and daptomycin had less reduction in renal cortex sphingomyelinase activity, less evidence of regeneration of cellular cortical cells ([3H]thymidine incorporation into cortex DNA), lower creatinine concentration in serum, and less histopathologic evidence of injury than rats given gentamicin alone. By immunogold technique, both daptomycin and gentamicin were localized to the lysosomes of proximal tubular cells, regardless of whether animals received the drugs alone or in combination. Interestingly, myeloid body formation occurred in both those animals given gentamicin alone and those given daptomycin plus gentamicin. No significant changes were observed for all groups between 10 and 20 days after the end of therapy, suggesting that the toxicity of gentamicin was not delayed by the concomitant injection of daptomycin. The results confirm that daptomycin can attenuate experimental gentamicin nephrotoxicity.

Animals↗

PubMed1994

L-651,392, a potent leukotriene inhibitor, controls inflammatory process in Escherichia coli pyelonephritis.

In this study, the relationship between leukotrienes, peritubular cell infiltration with polymorphonuclear cells (PMNs) and renal tubular damage was investigated in a rat model of acute ascending pyelonephritis. Infection was induced by the injection of 10(5) CFU of Escherichia coli into the bladder and occlusion of the left ureter for 24 h. Treatment of infected animals was started 24 h after the induction of pyelonephritis with either hydrocortisone (25 mg/kg of body weight per day), the leukotriene inhibitor L-651,392 (10 mg/kg/day), or the vehicle of L-651,392 and was maintained for 5 days. At the end of treatment, the animals were killed, serum was collected, and both kidneys were removed for colony counts and histopathology. Renal function was evaluated by the measurement of blood urea nitrogen levels and creatinine clearance. The numbers of PMNs and mononuclear cells (MNs) in the cortex and medulla were recorded for all groups on plastic sections done from the left kidney. Infection alone (vehicle of L-651,392) resulted in intensive interstitial infiltration and a severe tubular destruction in the cortex. Treatment with hydrocortisone did not prevent PMN migration and tissue damage. By contrast, treatment with L-651,392 resulted in a significant reduction in PMNs (P < 0.001 in comparisons with all other groups) and greater preservation of the tubular structure despite identical bacterial counts than in the group receiving hydrocortisone. We conclude that L-651,392 prevents inflammatory cells from reaching the site of infection and protects the kidney from tubular damage associated with inflammation during pyelonephritis. Inhibitors of leukotrienes should be further investigated for their potential benefit as adjuvants to antibiotherapy in the treatment of pyelonephritis.

Animals↗

PubMed1993

Pharmacodynamics of antibiotics in fibrin clots.

Fibrin is an integral component of intravascular thrombus, surgical wounds, haematomas, vegetations and foreign bodies which predispose to infection. The tropism that many pathogens have for fibrin may favour bacterial growth and lead to infection. To improve our understanding of the pharmacodynamic interaction between antibiotics and pathogens infecting fibrin clots, this review will: define the role of fibrin as a protective environment for microorganisms; give an historical perspective of in-vitro and in-vivo fibrin clots; describe the pharmacodynamic model of infected fibrin clots; review pharmacodynamic determinants of outcome; and discuss intramicrobial pharmacokinetics. Fibrin clots are hard to penetrate following antibiotic administration and there is a major gradient of concentration from the surface to the core of the clots which has great influence on bacterial growth and lysis. Resistance can develop and morphological and structural changes in bacteria may vary within the different regions of the clot.

Animals↗

PubMed1993

Increased renal uptake of gentamicin in endotoxemic rats receiving concomitant thromboxane A2 antagonist therapy.

This report describes the effects of endotoxin and a thromboxane receptor antagonist, L-655,240, on kidney function and the intrarenal pharmacokinetics of aminoglycosides. The rationale for these studies was that thromboxane antagonists may eventually be used in combination with aminoglycosides in patients with gram-negative sepsis and endotoxemia. As aminoglycosides are nephrotoxic and endotoxin has already been shown to increase the renal uptake of gentamicin, we investigated the possibility that thromboxane antagonists might interfere with the nephrotoxic potential of both substances. A decrease in the volume of distribution and an increase in the intracortical concentration of gentamicin were observed in animals given endotoxin. Compared with animals given endotoxin alone, those which received endotoxin plus L-655,240 had significant accumulation of gentamicin in the renal cortex and medulla, as determined by the area under the concentration-time curve, and a significant reduction in the total clearance of the antibiotic (P < 0.05). This difference in uptake could not be attributed to hypotension or changes in the glomerular filtration rate or renal plasma flow. L-655,240 alone did not modify gentamicin pharmacokinetics but did decrease p-aminohippuric acid secretion. Thromboxane antagonists in the context of endotoxemia increase intrarenal uptake of aminoglycosides. If these compounds are to be used as therapeutic agents when endotoxin is present, their influence on renal handling of nephrotoxic drugs needs to be considered. Multiple-dosing regimens deserve investigation.

Animals↗