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N Gerber

Publications and source records attributed to N Gerber.

At least 19 recordsLinked to original sources
PubMed2000

Receptor-binding conformation of the "ELR" motif of IL-8: X-ray structure of the L5C/H33C variant at 2.35 A resolution.

The "ELR" (Glu-Leu-Arg) tripeptide sequence near the N-terminus of interleukin-8 (IL-8) contributes a large part of the receptor binding free energy. Prior X-ray and nuclear magnetic resonance (NMR) structures of IL-8 have shown this region of the molecule to be highly mobile. We reasoned that a hydrophobic interaction between the leucine and the neighboring beta-turn might exist in the receptor binding conformation of the N-terminus. To test this hypothesis, we mutated two residues to cysteine and connected the N-terminus to the beta-turn. The mutant retains receptor binding affinity reasonably close to wild type and allows the characterization of a high-affinity conformation that may be useful in the design of small IL-8 mimics. The L5C/H33C mutant is refined to R-values of R = 20.6% and Rfree = 27.7% at 2.35 A resolution. Other receptor binding determinants reside in the "N-loop" found after "ELR" and preceding the first beta-strand. All available structures of IL-8 have been found with one of two distinct N-loop conformations. One of these is relevant for receptor binding, based on NMR results with receptor peptides. The other conformation obscures the receptor-peptide binding surface and may have an undetermined but necessarily different function.

Amino Acid Motifs↗
PubMed2000

Single- and multiple-dose pharmacokinetics of ziprasidone under non-fasting conditions in healthy male volunteers.

AIMS: To evaluate the pharmacokinetics and tolerability of single and multiple oral doses of ziprasidone in healthy male volunteers, and to determine the influence of ziprasidone on serum prolactin levels. METHODS: Single and multiple doses of ziprasidone were given orally (as two divided daily doses), at fixed dosages of 10 and 40 mg day(-1), and using titrated regimens of 40-80 and 40-120 mg day(-1), for 14 days. All dosages were taken immediately after food. The study adopted a randomized, double-blind, placebo-controlled design. Prolactin response, sedative properties, tolerability, and extrapyramidal symptoms were also investigated. RESULTS: Steady-state exposure to ziprasidone was attained after 1 day of dosing. Mean Cmax and AUC(0,12 h) increased with increasing dose, with apparent dose-proportionality between the 20 and 60 mg dose levels. Trough-to-peak ratios at steady state ranged from 2 to 5. Accumulation ratios for the fixed-dose regimens were 1.49 and 1.48 at the 5 and 20 mg dose levels, respectively. Ziprasidone was associated with transient prolactin elevation but levels of prolactin returned to baseline within the dosing interval at steady state. There was a marginal, transient increase in serum prolactin levels which was not dose-related at the 80 and 120 mg day(-1) doses, and which was noted to attenuate with chronic dosing. Ziprasidone was generally well tolerated. The most frequent side-effect was mild or moderate headache. A minority of patients suffered first-dose postural hypotension. Ziprasidone was also associated with a mild sedative effect that became less pronounced as treatment continued. There were no drug-related changes in electrocardiogram or clinical laboratory variables that were of clinical importance. CONCLUSIONS: Ziprasidone is characterized by a predictable pharmacokinetic profile resulting in symptoms that reflect its pharmacological action.

Adolescent↗
PubMed2000

Ziprasidone and the activity of cytochrome P450 2D6 in healthy extensive metabolizers.

AIMS: To determine whether ziprasidone alters the metabolizing activity of the 2D6 isoenzyme of cytochrome P450 (CYP2D6). METHODS: Twenty-four healthy young subjects aged 18-45 years were screened for CYP2D6 metabolizing activity and shown to be extensive metabolizers of dextromethorphan. These subjects were then randomized to receive a single dose of ziprasidone 80 mg, paroxetine 20 mg or placebo, 2 h before receiving a dose of dextromethorphan. Urine samples for the determination of dextromethorphan concentrations were collected over the 8 h period following dextromethorphan dosing, and used for the determination of dextromethorphan/dextrorphan ratios. Blood samples were collected immediately before and up to 10 h after the administration of ziprasidone or paroxetine, and used to derive pharmacokinetic parameters of ziprasidone and paroxetine. RESULTS: There were no statistically significant changes in the urinary dextromethorphan/dextrorphan ratio in the ziprasidone group or the placebo group. By contrast, there was a 10-fold increase in the urinary dextromethorphan/dextrorphan ratio in the paroxetine group and this differed significantly from those in the ziprasidone and placebo groups (P = 0.0001). CONCLUSIONS: The findings of this study suggest that ziprasidone does not inhibit the clearance of drugs metabolized by CYP2D6.

Adolescent↗
PubMed2000

The effects of ziprasidone on steady-state lithium levels and renal clearance of lithium.

AIMS: To assess the potential of ziprasidone to alter the renal clearance and steady-state serum levels of lithium. METHODS: Healthy subjects who had stable serum lithium levels during the first 7 days of treatment with lithium 900 mg day(-1), given as two divided daily doses, were randomized to receive concomitant treatment with either ziprasidone, 40 mg day(-1), given as two divided daily doses, on days 9-11 followed by 80 mg day(-1), given as two divided daily doses on days 12-15 (n = 12), or placebo twice daily (n = 13). Ziprasidone or placebo was administered 2 h before each dose of lithium. RESULTS: Ziprasidone administration was associated with a 0.07 mmol l(-1) (13%) mean increase in steady-state serum lithium levels compared with a mean increase of 0.06 mmol l(-1) (10%) with placebo. Mean renal clearance of lithium decreased by 0.09 l h(-1) (5%) in the ziprasidone group and by 0.14 l h(-1) (9%) in the placebo group. None of these differences between the two groups was statistically or clinically significant. CONCLUSIONS: Ziprasidone does not alter steady-state serum lithium concentrations or renal clearance of lithium.

Adult↗
PubMed1999

Quantitation and mapping of aflatoxin B1-induced DNA damage in genomic DNA using aflatoxin B1-8,9-epoxide and microsomal activation systems.

Aflatoxin B1 (AFB1) is a mutagenic and carcinogenic mycotoxin which may play a role in the etiology of human liver cancer. In vitro studies have shown that AFB1 adducts form primarily at the N7 position of guanine. Using quantitative PCR (QPCR) and ligation-mediated PCR (LMPCR), we have mapped total AFB1 adducts in genomic DNA treated with AFB1-8,9-epoxide and in hepatocytes exposed to AFB1 activated by rat liver microsomes or human liver and enterocyte microsomal preparations. The p53 gene-specific adduct frequencies in DNA, modified in cells with 40-400 microM AFB1, were 0.07-0.74 adducts per kilobase (kb). In vitro modification with 0. 1-4 ng AFB1-8,9-epoxide per microgram DNA produced 0.03-0.58 lesions per kb. The adduct patterns obtained with the epoxide and the different microsomal systems were virtually identical indicating that adducts form with a similar sequence-specificity in vitro and in vivo. The lesions were detected exclusively at guanines with a preference towards GpG and methylated CpG sequences. The methods utilizing QPCR and LMPCR thus provide means to assess gene-specific and sequence-specific AFB1 damage. The results also prove that microsomally-mediated damage is a suitable method for avoiding manipulations with very unstable DNA-reactive metabolites and that this damage can be detected by QPCR and LMPCR.

Aflatoxin B1↗
PubMed1999

A novel cytochrome P450 3A isoenzyme in rat intestinal microsomes.

PCR with several pairs of primers facilitates screening for new isoenzymes among highly homologous cytochrome P450s (CYPs). Combinations of two pairs of primers, which amplify N- and C-terminal coding sequences of either CYP3A1/CYP3A23 or CYP3A2 detected the presence of a previously unrecognized CYP3A in enterocyte microsomes isolated from rats. PCR, Northern blot, and immunoblotting with specific antibodies indicated that this isoenzyme is clearly distinguishable from CYP3A1, 3A23 or 3A2. Sequencing of a 285 bp coding fragment of this gene revealed 97% similarity with rat olfactory CYP3A9 (P450olf3).

Animals↗
PubMed1999

Gallium nitrate suppresses the production of nitric oxide and liver damage in a murine model of LPS-induced septic shock.

The efficacy of gallium (Ga) nitrate was examined in a murine model of sepsis. Male Balb/c mice (6-8 weeks) were randomized into 3 groups: 1) vehicle-treated controls 2) mice with sepsis induced by treatment with 0.3 mg i.v. of Propionibacterium acnes followed one week later by 0.01 microg lipopolysaccharide (LPS) and 10 mg of D-galactosamine (GalN) 3) mice with sepsis injected with 45 mg/kg s.c. of gallium nitrate (calculated as elemental Ga) 24 hours prior to LPS/GalN. Two hours after LPS/GalN or vehicle, plasma concentrations of tumor necrosis factor (TNF-alpha) in groups 1, 2 and 3 were 54+/-31 (n=6), 21,390+/-5139 (n=4), and 21,909+/-943 (n=5) pg/ml, respectively. After 6 hours, plasma concentrations of gamma interferon (IFN-gamma) were <10 (n=8), 4771+/-1078 (n=6), and 1622+/-531 (n=15) pg/ml, respectively, and of nitrate/nitrite (products of nitric oxide) were 64+/-8 (n=7), 146+/-18 (n=8), and 57+/-8 (n=15) microM. At 18 hours, serum chemistries were; SGOT 171+/-46 (n=13), 10,986+/-3062 (n=7), and 1078+/-549 (n=8) IU/L; SGPT 165+/-59, 17,214+/-4340, and 2088+/-1097 IU/L; and total bilirubin 0.2+/-0.0, 0.9+/-0.4, and 0.2+/-0.0 mg/dl for groups 1, 2, and 3 respectively. Blinded histologic evaluation of livers at 18 hours revealed inflammatory infiltrate scores (x [range], 0=none, 1=minimal, 2=mild, 3=moderate, and 4=severe) of 0.1 [0-1] (n=8), 3.0 [2-4] (n=15), and 2.0 [0-3] (n=10), and necrosis scores of 0.0, 2.8 [0-4], and 0.9 [0-4]. Although Ga did not affect production of TNF-alpha, it ameliorated hepatocellular injury and protected against necrosis. Based on this model of sepsis, Ga may have a role in treating the human disease.

Animals↗
PubMed1998

Metabolism of the human immunodeficiency virus protease inhibitors indinavir and ritonavir by human intestinal microsomes and expressed cytochrome P4503A4/3A5: mechanism-based inactivation of cytochrome P4503A by ritonavir.

Both ritonavir and indinavir were readily metabolized by human intestinal microsomes. Comparison of the patterns of metabolites in incubations with enterocyte microsomes and expressed cytochrome P450 (CYP) isozymes and immunoinhibition and chemical inhibition studies showed the essential role of the CYP3A subfamily in the metabolism of both protease inhibitors by the small intestine. Ritonavir was similarly biotransformed by microsomes containing expressed CYP3A4 or CYP3A5 isozymes (KM = 0.05-0.07 microM, Vmax = 1-1.4 nmol/min/nmol CYP). In contrast, both the patterns of metabolites and the enzyme kinetic parameters for the metabolism of indinavir by expressed CYP3A5 (KM = 0.21 microM, Vmax = 0.24 nmol/min/nmol CYP) and CYP3A4 (KM = 0.04 microM, Vmax = 0.68 nmol/min/nmol CYP) were different. The biotransformation of both indinavir and ritonavir in human enterocyte microsomes was characterized by very low KM values (0.2-0.4 microM for indinavir and <0.1 microM for ritonavir). The Vmax for indinavir metabolism was greater in enterocyte (163 +/- 35 pmol/min/mg protein) than in liver (68 +/- 44 pmol/min/mg protein) microsomes. The metabolism of ritonavir in liver and enterocyte microsomes was associated with inactivation of CYP3A. The initial Vmax for ritonavir metabolism by enterocyte microsomes was 89 +/- 59 pmol/min/mg protein. The apparent inactivation rate constants for intestinal CYP3A and expressed CYP3A4 were 0.078 and 0.135 min-1, respectively. Metabolic inactivation of CYP3A by ritonavir explains the improved bioavailability and pharmacokinetics of ritonavir and the sustained elevation of blood levels of other, concomitantly administered, substrates of CYP3A.

Anti-HIV Agents↗
PubMed1998

Nitric oxide synthase structure and electron transfer.

The nitric oxide synthases (NOS), although unrelated to the cytochromes P450 in terms of sequence, exhibit spectroscopic and catalytic properties strongly reminiscent of those of the P450 system. One important difference is the requirement of the NOS enzymes for tetrahydrobiopterin. The biopterin cofactor is shown by chemical studies to bind close to pyrrole ring D of the prosthetic heme group, a position confirmed recently for inducible NOS and endothelial NOS by crystal structures. The only plausible role so far for the tetrahydrobiopterin is as a transient electron donor for the activation of molecular oxygen. NADPH-derived electrons are provided to the heme by the NOS flavin domain, but the biopterin may be required to provide an electron at a faster rate than that supported by the flavin groups. Chimeras in which the reductase domains of the isoforms have been exchanged indicate that the overall rate of catalytic turnover is directly governed by the ability of the flavin domain to deliver electrons. Electron transfer from the flavin to the heme domain, and within the flavin and heme domains, is thus a critical determinant of the catalytic turnover of NOS.

Animals↗
PubMed1997

Effect of gallium nitrate on experimental autoimmune uveitis.

Gallium nitrate (GN) has been shown to inhibit T cell-mediated inflammatory disease. The purpose of our study was to test the effect of gallium nitrate (GN) on experimental autoimmune uveitis (EAU). Experimental autoimmune uveitis was induced in male Lewis rats immunized with retinal S-antigen. Rats received subcutaneous injections of GN or saline one day prior to immunization and 1, 4, 7, 10, 13, 16, and 19 days after immunization. Ocular inflammation was graded clinically and histologically by masked observers, and in vitro assays of cell-mediated and humoral immunity were performed. GN significantly inhibited the development of EAU graded clinically (P = 0.001) and histologically (P = 0.002). Treatment with GN also resulted in a small (30-41%) decrease in the lymphocyte responses to retinal S-Antigen and a small (12-37%) reduction in antibody production to S-antigen. These data show that GN suppresses the development of EAU, and inhibits both lymphocyte proliferative responses to antigen and antibody production.

Animals↗
PubMed1997

Gallium nitrate suppresses lupus in MRL/lpr mice.

Gallium (Ga) nitrate, a drug which prevents a variety of experimental autoimmune diseases, was investigated in a murine model of systemic lupus erythematosus (SLE). In one experiment, female MRL/Mp lpr/lpr (MRL/lpr) mice were randomized into 2 groups of 6: 1) vehicle (trisodium citrate) and 2) Ga. Subcutaneous injections began at 3 weeks of age and continued weekly until the mice were euthanized a week after the thirteenth injection. The loading dose of Ga (calculated as elemental Ga) was 45 mg/kg, followed by 15 mg/kg/week. In another experiment (n = 18) with 3 males and 3 females per group, mice received 1) vehicle, 2) Ga x 1 (one 45 mg/kg dose), and 3) Ga x 13. In the experiment with 12 mice, axillary lymph nodes from Ga-treated mice were significantly smaller than those from vehicle-treated mice (91+/-42 and 360+/-358 mg respectively, mean+/-SD), and spleens as well as lymph nodes from the former showed significantly less lymphoid infiltrate. In the experiment with 18 mice, prescapular lymph nodes weighed 312+/-98, 217+/-52, and 42+/-34 mg, and spleens weighed 732+/-492, 409+/-164, and 192+/-93 mg in the groups which received vehicle, Ga x 1, and Ga x 13 respectively. Control mice had significantly more lymphoid infiltrates in the lungs, spleen, and lymph nodes and, unlike Ga x 13 mice, exhibited glomerulitis and renal vasculitis. Within groups, females developed more severe disease than males. The Ga x 13 group had increased percentages of CD4-bearing and CD8-bearing lymphocytes in lymph nodes and increased CD4-bearing lymphocytes in the spleen, with an increased proliferative response to mitogen stimulation in vitro in lymph nodes, although not in the spleen. The Ga x 13 group also gained less weight and developed osteosclerosis. Although preliminary, our findings suggest that clinical trials with Ga in SLE are merited.

Animals↗
PubMed1997

Metabolism of rifabutin in human enterocyte and liver microsomes: kinetic parameters, identification of enzyme systems, and drug interactions with macrolides and antifungal agents.

Biotransformation of rifabutin, an antibiotic used for treatment of tuberculosis in patients infected with the human immunodeficiency virus (HIV), and its interactions with some macrolide and antifungal agents were studied in human intestinal and liver microsomes. Both liver and enterocyte microsomes metabolized rifabutin to 25-O-deacetylrifabutin, 27-O-demethylrifabutin, and 20-, 31-, and 32-hydroxyrifabutin. The same products (except 25-O-deacetylrifabutin) were formed by microsomes from lymphoblastoid cells that contained expressed CYP3A4. The apparent Michaelis-Menten constant (Km); approximately 10 to 12 mumol/L) and maximal velocity (Vmax; approximately 100 pmol/min/mg of protein) values for CYP-mediated metabolism were similar in liver and enterocyte microsomes. Deacetylation of rifabutin (Km approximately 16 to 20 mumol/L and Vmax approximately 50 to 100 pmol/min/mg of protein) was catalyzed by microsomal cholinesterase. Clarithromycin, ketoconazole, and fluconazole inhibited CYP-mediated metabolism of rifabutin in enterocyte microsomes equally or more potently than in liver microsomes but had no effect on cholinesterase activity. Azithromycin did not inhibit in vitro metabolism of rifabutin. This study provides evidence that CYP3A4 and cholinesterase are major enzymes that biotransform rifabutin in humans and that intestinal CYP3A4 contributes significantly to rifabutin presystemic first-pass metabolism and drug interactions with macrolide and antifungal agents.

Acetylation↗
PubMed1997

A small and painful puzzle.

This case of osteoid osteoma is reported for two reasons. First, for its rarity and unusual location (it was diagnosed very late) and second because it demonstrates that the history of a painful condition leads to the correct diagnosis, and although clinical investigations may provide corroboratory evidence, they are certainly no substitute. A 23-year-old student experienced spontaneous nightly pain in the distal phalanx of his right hallux. The pain increased over 2 years but with a good response to non-steroidal anti-inflammatory medication. After 9 months X-rays showed a cystic lucency. The patient was seen by a number of consultants, but the diagnosis of osteoid osteoma was delayed. After surgery the diagnosis was confirmed histologically and the pain has not recurred.

Adult↗
PubMed1997

Effect of sertraline on protein binding of warfarin.

The effect of sertraline on the plasma protein binding of warfarin was investigated in a nonblinded randomised placebo-controlled parallel trial in 12 healthy male volunteers. The study participants received single doses of warfarin before administration of sertraline or placebo and again after sertraline or placebo had been administered for 22 days. Treatment with sertraline for 26 days increased the area under the mean prothrombin time vs time curve by 145 sec *h (7.9%), compared with a decrease of 17 sec *h (-1.0%) in the placebo group. Although statistically significant (p = 0.02), this difference was not felt to be clinically meaningful. There appeared to be a slight delay in the normalisation of the prothrombin time in the sertraline-treated group after the second dose of warfarin, which also would not be expected to be clinically significant. After 22 days, a statistically significant (p = 0.02) increase in unbound warfarin was observed in the sertraline group compared with the placebo-treated individuals. Neither the change in prothrombin time nor the change in plasma protein binding were considered to have any clinical relevance; however, good clinical practice dictates that prothrombin time should be monitored in patients treated concurrently with warfarin and sertraline to ensure that the integrity of coagulation response is maintained. The metabolism of warfarin is principally mediated by the cytochrome P450 (CYP) isoenzyme CYP2C9/10. Thus, sertraline appears to have a minimal effect on the CYP2C9/10 isoenzyme.

1-Naphthylamine↗
PubMed1997

Isolation and identification of major urinary metabolites of rifabutin in rats and humans.

The antimycobacterial drug rifabutin is extensively metabolized in humans and laboratory animals. About 40% of the dose is excreted in urine as unchanged drug, and lipophilic (extractable with 1-chlorobutane) and polar metabolites. Polar metabolites accounted for 59.1 +/- 2.5% and 88.8 +/- 4.4% of radioactivity in urine collected over 96 hr after intravenous administration of 25 and 1 mg/kg of [14C]rifabutin to Sprague-Dawley rats, respectively. After 48 hr, all urinary radioactivity consisted of polar metabolites. The most abundant polar metabolite, identified by electrospray ionization-MS, collision-induced dissociation-MS, and comparison of HPLC retention times with the synthetic standard, was N-isobutyl-4-hydroxy-piperidine. Lipophilic metabolites accounted for <20% of urinary radioactivity. Major lipophilic metabolites, 25-O-deacetyl-rifabutin, 27-O-demethyl-rifabutin, 31-hydroxy-rifabutin, 32-hydroxy-rifabutin, and 20-hydroxy-rifabutin were isolated from both human and rat urine by HPLC and identified by electrospray ionization-MS, collision-induced dissociation-MS, and NMR spectrometry. In addition, two metabolites formed by the oxidation of the N-isobutyl-piperidyl group of rifabutin were found in the urine of rats, but not humans.

Adolescent↗
PubMed1996

Prevention of murine cardiac allograft rejection with gallium nitrate. Comparison with anti-CD4 monoclonal antibody.

Gallium nitrate (GN) was evaluated for its ability to interfere with a cute rejection of DBA/2-->C57BL/6 heterotopic cardiac allografts, in comparison with the depleting anti-CD4 mAb, GK1.5. The administration of GN for 30 days (s.c. 30 mg/kg elemental gallium on days 0 and 3, 10 mg/kg every third day) resulted in >60-day graft survival in 78% (25 of 32) of the graft recipients, whereas 2 perioperative injections of anti-CD4 monoclonal antibody (mAb) resulted in >60-day graft survival in 58% (24 of 41) of the graft recipients. Serum gallium levels peaked at about 2000 ng/ml after 2-3 weeks of treatment and decreased to about 300 ng/ml by day 60, a level that was maintained for at least 30 more days. During the early posttransplant period, 25% of GN-treated grafts, but not anti-CD4 mAb-treated grafts, exhibited an unusual, transient reduction in graft impulse strength, suggesting a transient rejection response. Macroscopically, the long-surviving (>60 days) grafts from either treatment group exhibited none of the features of rejecting allografts. Histologically, they exhibited minor edema and rare epicardial inflammation but no tissue necrosis. However, there were vascular changes in allografts from GN-treated mice, including altered endothelial morphology, associated with moderate intimal hyperplasia and mild perivascular leukocytic infiltration. Allografts from anti-CD4 mAb-treated mice exhibited prominent neointimal hyperplasia associated with endothelial morphologic changes and prominent vascular and perivascular leukocytic infiltration. In general, both GN and anti-CD4 mAb promoted long-term allograft survival, but these allografts displayed the histopathologic signs of ongoing inflammation and chronic allograft rejection.

Animals↗