Co-pyrolysis of chicken feathers and macadamia nut shells, a promising strategy to create nitrogen-enriched electrode materials for supercapacitor applications

Global food waste emits substantial quantities of nitrogen to the environment (6.3 Mtons annually), chicken feather (CF) waste is a major contributor to this. Pyrolysis, in particular co-pyrolysis of nitrogen-rich and lignocellulosic waste streams is a promising strategy to improve the extent of pyrolytic nitrogen retention by incorporating nitrogen in its solid biochar structure. As such, this biochar can serve as a precursor for nitrogen-enriched activated carbons for application in supercapacitors. Therefore, this study investigates the co-pyrolysis of CF with macadamia nut shells (MNS) to create nitrogen-rich activated carbons. Co-pyrolysis increased nitrogen retention during pyrolysis from 9 % to 18 % compared to CF mono-pyrolysis, while the porosity was maintained. After removing undesirable inorganic impurities by dilute acid washing, this led to a specific capacitance of 21F/g using a scan rate of 20 mV/s. Finally, cycling stability tests demonstrated good stability with 73 % capacitance retention after 10 000 cycles.

Cooling reverses pathological bifurcations to spontaneous firing caused by mild traumatic injury

Mild traumatic injury can modify the key sodium (Na⁺) current underlying the excitability of neurons. It causes the activation and inactivation properties of this current to become shifted to more negative trans-membrane voltages. This so-called coupled left shift (CLS) leads to a chronic influx of Na⁺ into the cell that eventually causes spontaneous or "ectopic" firing along the axon, even in the absence of stimuli. The bifurcations underlying this enhanced excitability have been worked out in full ionic models of this effect. Here, we present computational evidence that increased temperature T can exacerbate this pathological state. Conversely, and perhaps of clinical relevance, mild cooling is shown to move the naturally quiescent cell further away from the threshold of ectopic behavior. The origin of this stabilization-by-cooling effect is analyzed by knocking in and knocking out, one at a time, various processes thought to be T-dependent. The T-dependence of the Na⁺ current, quantified by its Q _10-Na factor, has the biggest impact on the threshold, followed by Q _10-pump of the sodium-potassium exchanger. Below the ectopic boundary, the steady state for the gating variables and the resting potential are not modified by temperature, since our model separately tallies the Na⁺ and K⁺ ions including their separate leaks through the pump. When only the gating kinetics are considered, cooling is detrimental, but in the full T-dependent model, it is beneficial because the other processes dominate. Cooling decreases the pump's activity, and since the pump hyperpolarizes, less hyperpolarization should lead to more excitability and ectopic behavior. But actually the opposite happens in the full model because decreased pump activity leads to smaller gradients of Na⁺ and K⁺, which in turn decreases the driving force of the Na⁺ current.

Nav Channels in Damaged Membranes

Sick excitable cells (ie, Nav channel-expressing cells injured by trauma, ischemia, inflammatory, and other conditions) typically exhibit "acquired sodium channelopathies" which, we argue, reflect bleb-damaged membranes rendering their Nav channels "leaky." The situation is excitotoxic because untreated Nav leak exacerbates bleb damage. Fast Nav inactivation (a voltage-independent process) is so tightly coupled, kinetically speaking, to the inherently voltage-dependent process of fast activation that when bleb damage accelerates and thus left-shifts macroscopic fast activation, fast inactivation accelerates to the same extent. The coupled g(V) and availability(V) processes and their window conductance regions consequently left-shift by the same number of millivolts. These damage-induced hyperpolarizing shifts, whose magnitude increases with damage intensity, are called coupled left shift (CLS). Based on past work and modeling, we discuss how to test for Nav-CLS, emphasizing the virtue of sawtooth ramp clamp. We explain that it is the inherent mechanosensitivity of Nav activation that underlies Nav-CLS. Using modeling of excitability, we show the known process of Nav-CLS is sufficient to predict a wide variety of "sick excitable cell" phenomena, from hyperexcitability through to depolarizing block. When living cells are mimicked by inclusion of pumps, mild Nav-CLS produces a wide array of burst phenomena and subthreshold oscillations. Dynamical analysis of mild damage scenarios shows how these phenomena reflect changes in spike thresholds as the pumps try to counteract the leaky Nav channels. Smart Nav inhibitors designed for sick excitable cells would target bleb-damaged membrane, buying time for cell-mediated removal or repair of Nav-bearing membrane that has become bleb-damaged (ie, detached from the cytoskeleton).

Molecular Dynamics Studies of Defects in Si

The efficacy of three modern empirical potentials in the molecular dynamic simulation of the configurations, energies and mobility of dislocation cores and their excitations is assessed in the light of recent literature. The results are found to be inconsistent both between different potentials and with experimental evidence. It is argued that the discrepancies are rooted in the limited databases which have been used in the construction of empirical potentials. The reason for the discrepancies is demonstrated by comparing empirical and density functional calculations of the generalized stacking fault energy.

Laryngeal squamous cell carcinoma in a 13 year-old child associated with human papillomaviruses 16 and 18: a case report and review of the literature

Squamous cell carcinoma (SCC) of the larynx is extremely rare in adolescents and typically has an aggressive nature. The mechanism of laryngeal oncogenesis is complex and little is known about the role that human papillomavirus (HPV) plays in SCC in adolescents. We report a case of invasive laryngeal SCC that co-expressed HPV DNA subtypes 16 and 18 in a 13 year-old boy. Detection of HPV DNA types 6, 11, 16, 18, 31, 33, and 51 was performed by in situ hybridization, with confirmation by polymerase chain reaction. Immunohistochemical staining with p16 and HPV 16/18 revealed diffusely positive staining in the tumor cells. Coinfection by HPV DNA types 16 and 18 has not been previously reported, but our case suggests that HPV is a risk factor in developing laryngeal SCC in children and adolescents. Future studies evaluating HPV in the pathogenesis of these lesions is recommended to determine its prognostic significance.

Quantification of in vivo replicative capacity of HIV-1 in different compartments of infected cells

Based on a mathematical model, we analyze the dynamics of CD4+ cells, actively, latently, persistently, and defectively infected cells and plasma virus after initiation of antiretroviral therapy in 14 HIV-1-infected asymptomatic patients. By simultaneous fitting of our model to clinical data of plasma HIV-1 RNA, peripheral blood mononuclear cell (PBMC)-gag RNA, proviral DNA, and CD4+ cell counts, we estimate kinetic parameters to determine the basic reproductive rate (R0) of the virus in different infected cell compartments as a measure of the replicative capacity of the virus in vivo. We find that the basic reproductive rate is larger than 1 before treatment only in actively infected cells (mean R0(act) approximately 2.46) indicating that only in this compartment the virus can maintain an ongoing infection. In latently and persistently infected cells the basic reproductive rate is considerably smaller (R0(lat) approximately 0.03 and R0(pers) approximately 0.008, respectively) indicating that these compartments contribute little to the total basic reproductive rate and cannot maintain an ongoing infection in absence of actively infected cells.

Low metabolic rate in scorpions: implications for population biomass and cannibalism

Scorpions are abundant in arid areas, where their population biomass may exceed that of vertebrates. Since scorpions are predators of small arthropods and feed infrequently across multi-year lifespans, a parsimonious explanation for their observed, anomalously high biomass may be a depressed metabolic rate (MR). We tested the hypothesis that scorpion MR is significantly depressed compared with that of other arthropods, and we also measured the temperature-dependence of the MR of scorpions to quantify the interaction between large seasonal variations in desert temperatures and MR and, thus, long-term metabolic expenditure. Scorpion MR increased markedly with temperature (mean Q(10)=2.97) with considerable inter-individual variation. At 25 degrees C, the MRs of scorpions from two genera were less than 24 % of those of typical terrestrial arthropods (spiders, mites, solpugids and insects) of the same mass. It is likely, therefore, that the low MR of scorpions contributes to their high biomass in arid areas. The combination of high biomass and high production efficiency associated with low MR may also favor a density-dependent ‘transgenerational energy storage’ strategy, whereby juveniles are harvested by cannibalistic adults that may be closely related to their juvenile prey.

Rigorous solution for the elasticity of diluted gaussian spring networks

We present a rigorous solution of the elasticity of the diluted Gaussian spring networks (DGSNs) at zero temperature. We show that the deformation of a diluted DGSN is homogeneous provided that the displacements of the particles on the boundary are homogeneous. It follows that at zero temperature the nonvanishing elastic stiffness coefficients are proportional to the hydrostatic pressure in both two and three dimensions. Follows a rigorous proof of the equivalence of the elasticity of the DGSN and the conductance of the random resistor network at zero temperature.

Residual HIV-RNA levels persist for up to 2.5 years in peripheral blood mononuclear cells of patients on potent antiretroviral therapy

The long-term response of 10 asymptomatic, antiretroviral therapy-naive HIV-1-infected patients to potent combination antiretroviral therapy was characterized by monitoring levels of HIV-1 RNA in plasma, peripheral blood mononuclear cells (PBMC), and lymphoid tissue using highly sensitive HIV-1 RNA assays. Although plasma viral loads were continuously suppressed to levels below 50 HIV-1 RNA copies/ml for up to 2.5 years (60-128 weeks), HIV-1 RNA was still detectable at very low levels (1 to 49 HIV-1 RNA copies/ml) in 25% of the samples. In corresponding PBMC specimens, residual HIV-RNA was detectable in as much as 91% of samples tested (1 to 420 HIV-1 RNA copies/microg total RNA). Similarly, HIV-1 RNA levels in lymphoid tissue also remained detectable at a high frequency (86%). A highly significant correlation was demonstrated between therapy-induced change in PBMC HIV-1 RNA levels and change in plasma HIV-1 RNA levels (r2 = 0.69; p = 0.003). These findings support the concept that measurement of HIV-1 RNA in the easily accessible PBMC compartment is relevant for evaluating the potency of current and future antiretroviral therapies.

Covalent attachment of hybridizable oligonucleotides to glass supports

A simple, rapid, and efficient method for the covalent binding of oligonucleotides to solid glass supports was developed. Glass slides were derivatized with aminophenyl or aminopropyl silanes and 5'-succinylated target oligonucleotides were attached by carbodiimide-mediated coupling. Approximately 40 to 50% of the applied target oligonucleotides covalently bound to the derivatized glass. Hybridizations with radioactively labeled oligonucleotide probes showed that up to 90% of the attached oligonucleotides were available for hybridization. This system can conveniently be applied for studies on hybridization and detection of nucleic acids.

Effects of ambient oxygen tension on flight performance, metabolism, and water loss of the honeybee

Although the metabolic rate of resting insects is relatively insensitive to atmospheric O2 tensions, metabolic rates during flight increase by 20- to 100-fold above resting levels. In this study we test whether O2 delivery limits metabolic rate during unladen hovering flight of the honeybee, Apis mellifera. Below 10 kPa PO2, wing-stroke frequency decreased, and at 5 kPa, bees could not fly. However, for PO2's ranging from 39 to 10 kPa, metabolic rate and wing-stroke frequency were unaffected by PO2. Evaporative water loss rates increased by 40% at the lowest O2 tensions, which suggests that flying honeybees compensated for decreasing ambient PO2 by modulating convective ventilatory flow. Under normal sea-level conditions, O2 delivery does not limit flight metabolic rate in unladen, hovering honeybees and does not limit maximal metabolic rate. At altitudes above 3,000 m, the convective component of O2 delivery may, however, limit flight metabolic rate and flight capacity in honeybees.

Energy metabolism, enzymatic flux capacities, and metabolic flux rates in flying honeybees

Honeybees rely primarily on the oxidation of hexose sugars to provide the energy required for flight. Measurement of VCO2 (equal to VO2, because VCO2/VO2 = 1.0 during carbohydrate oxidation) during flight allowed estimation of steady-state flux rates through pathways of flight muscle energy metabolism. Comparison of Vmax values for flight muscle hexokinase, phosphofructokinase, citrate synthase, and cytochrome c oxidase with rates of carbon and O2 flux during flight reveal that these enzymes operate closer to Vmax in the flight muscles of flying honeybees than in other muscles previously studied. Possible mechanistic and evolutionary implications of these findings are discussed.

Pharmacokinetics of antimicrobial agents in anuric patients during continuous venovenous haemofiltration

BACKGROUND

The optimal drug dosing in anuric patients undergoing continuous haemofiltration is a difficult task. More pharmacokinetic data is needed to derive practical guidelines for dosage adjustments.

METHODS

Drug elimination of various antimicrobial agents (amikacin, amoxycillin, ceftazidime, ciprofloxacin, flucloxacillin, imipenem, netilmicin, penicillin G, piperacillin, sulphamethoxazole, tobramycin, vancomycin) was studied in 24 patients with acute renal failure treated by pump-assisted continuous venovenous haemofiltration (CVVH). Concentrations of serial blood and ultrafiltrate samples were determined by HPLC or by fluorescence polarization immunoassay. Total body clearance (CL) and haemofilter clearance (CLf) rates were determined by standard model-independent equations. Data from published literature on fractions not bound to proteins (fu), non-renal drug clearance fractions (Qo), and normal clearance values (CLn) were used to derive a pharmacokinetic model, taking into account drug removal by ultrafiltration and by non-renal clearance.

RESULTS

A total of 37 treatment periods was studied. Blood flow through the haemofilters was 100 ml/min resulting in an average ultrafiltrate flow rate (UFR) of 13.2 +/- 4.6 (range 3.2-22.1) ml/min. Acceptable correlations of calculated and measured haemofilter clearances and total body clearances were obtained.

CONCLUSIONS

Total body clearance in anuric patients during CVVH is predictable from drug properties, which are generally known. The individual dosage requirements may be calculated by multiplying Qo + fu.UFR/CLn with the dose considered appropriate in the absence of renal impairment.

Penetration of cefuroxime into the cerebrospinal fluid of patients with traumatic brain injury

Cefuroxime levels were measured in cerebrospinal fluid (CSF) and serum of four patients with traumatic brain injury following the implantation of intraventricular catheters. The levels ranged from 0.15 to 2.03 micrograms/mL in CSF and from 1.8 to 66.9 micrograms/mL in serum. No ventriculostomy related infections were detected.

Monitoring of co-trimoxazole concentrations in serum during treatment of pneumocystis carinii pneumonia

The purpose of this prospective randomized open trial was to investigate the impact of monitoring concentrations in serum on the efficacy and side effects of high-dose co-trimoxazole therapy. Forty consecutive patients with microscopically confirmed Pneumocystis carinii pneumonia were enrolled. Therapy was started with 5 and 25 mg of trimethoprim and sulfamethoxazole, respectively, per kg of body weight given every 6 h for 2 days and continued every 8 h either with (group A) or without (group B) monitoring and dose adjustments according to sulfamethoxazole levels in serum (target, 150 to 200 micrograms/ml) for a total of 21 days. Only 7 of 19 patients (83%). Patients who were treated for the full period and patients for whom co-trimoxazole was prematurely stopped had similar concentrations of sulfamethoxazole (157 +/- 52 versus 155 +/- 47 micrograms/ml) and trimethoprim (5.0 +/- 1.4 versus 5.6 +/- 1.0 microgram/ml). Concentrations of sulfamethoxazole and trimethoprim in group A (158 +/- 39 and 5.6 +/- 1.8 micrograms/ml, respectively) did not differ from those in group B (153 +/- 57 and 5.1 +/- 1.6 micrograms/ml, respectively), and the average daily maintenance doses for groups A (75.4 mg/kg plus 15.1 mg/kg) and B (76.4 mg/kg plus 15.3 mg/kg) were nearly identical. Although the average sulfamethoxazole concentrations were maintained within the target zone in the monitoring group (day 5, 160 +/- 44 micrograms/ml; day 10, 160 +/- 41 micrograms/ml; day 15, 168 +/- micrograms/ml; and day 21, 157 +/- 95 micrograms/ml), only 28% of the individual sulfamethoxazole levels were within the target range of 150 to 200 micrograms/ml after the dose adjustments (32% in group B without intervention). Response rates were similar in both groups. Complete response or improvement was observed in 18 of 19 (group A) and 19 of 21 (group B) patients. The method used for monitoring sulfamethoxazole levels with subsequent dose adjustment did not allow us to reliably achieve the target concentrations and did not significantly alter the incidence of side effects or the efficacy of the therapy.

The scid mouse as an experimental model for the evaluation of anti-Pneumocystis carinii therapy

The usefulness of scid mice bearing endogenous Pneumocystis carinii infection as a model for experimental chemotherapy was examined using standard compounds known to be effective against P. carinii. Trimethoprim/sulphamethoxazole was able to reduce pulmonary P. carinii cysts in a dose-dependent manner within the dose range studied (10/50 to 100/500 TMP/SMX mg/kg/d, bd, po, 5 days per week for 30 treatments). However, alterations in associated symptoms of infection (reduced body weight, increased lung weight, increased blood leucocytes and erythrocytes), was apparently not linearly dose-dependent. Blood and lung lavage fluid levels of sulphamethoxazole one hour post administration of trimethoprim/sulphamethoxazole was dose-dependent, but not linear with dose, and was apparently correlated to cyst reduction; trimethoprim was below the limit of detection at this time. Treatment of mice with 100/500 mg/kg/day trimethoprim/sulphamethoxazole required 2 weeks (bd for 10 days of treatment) before changes in indices of infection became significant. Pentamidine (20 mg/kg, sc, three times per week for 3 weeks) was nearly as effective as high-dose trimethoprim/sulphamethoxazole in reducing cysts, whereas lower doses were ineffective. Despite being unable to reduce pulmonary P. carinii infection, even low doses of pentamidine (6 or 2 mg/kg, sc, three times per week for 3 weeks) were able to reduce lung weights and blood leucocyte levels. This model of pulmonary P. carinii infections is amenable to chemotherapeutic intervention in an apparently dose-dependent fashion, and can be used to evaluate the capacity of compounds to eradicate P. carinii and resolve signs of infection.

Levels of dapsone and pyrimethamine in serum during once-weekly dosing for prophylaxis of Pneumocystis carinii pneumonia and toxoplasmic encephalitis

Concentrations of dapsone, monoacetyldapsone, and pyrimethamine were determined in 36 serum samples from human immunodeficiency virus-infected patients on prophylaxis with once-weekly administration of dapsone-pyrimethamine (200 mg of dapsone-75 mg of pyrimethamine). During day 1 after ingestion, median levels of 1,038 ng of dapsone per ml and 356 ng of pyrimethamine per ml were found. During days 6 to 7, the dapsone level fell to < 20 ng/ml in five of nine serum samples, but the pyrimethamine level remained elevated (125 ng/ml). Concurrent, but separately ingested, didanosine administration did not seem to decrease the drug concentrations.

Variability of serum concentrations of trimethoprim and sulfamethoxazole during high dose therapy

Serum kinetics of trimethoprim and sulfamethoxazole were studied in 23 patients during oral and i.v. treatment of Pneumocystis carinii pneumonia. Daily doses of 15-22 mg/kg trimethoprim and 75-110 mg/kg sulfamethoxazole were given every 6 h. Despite administration of a loading dose of twice the regular dose, serum trough concentrations continuously rose from 12 h to 96 h by 63% for trimethoprim and 102% for sulfamethoxazole. After 4-6 days mean trough concentrations of trimethoprim and sulfamethoxazole were 7.7 +/- 3.0 and 198 +/- 74 mg/l, with individual values of < 4.6 and < 103 mg/l in two patients and > 11.4 and > 307 mg/l in two others. Patients treated orally or i.v. had similar serum levels. However, large interindividual variability was observed despite weight-specific dosing. Administration of a loading dose did not prevent accumulation of serum levels of trimethoprim and sulfamethoxazole over several days of treatment.

A method for the quantification of intracellular zidovudine nucleotides

An assay to quantify the phosphorylation products of zidovudine (AZT) in peripheral blood mononuclear cells (PBMC) was developed. Extracts of PBMC were separated by high-performance liquid chromatography. Eluted AZT mono- (MP), di- (DP), and triphosphate (TP) were collected in separate portions. Treatment with alkaline phosphatase yielded equimolar amounts of AZT, which after solid-phase enrichment were assayed by radioimmunoassay. Detection limit was 0.1 pmol/10(6) PBMC for each nucleotide. Recoveries of 102%-118% were observed. AZT nucleotides were measured in samples from three patients receiving 250 mg of AZT every 12 h. Intracellular concentrations of AZT-MP after 1-2 h ranged from 0.9 to 1.4 pmol/10(6) PBMC and then declined to 0.3-1.1 pmol/10(6) PBMC after 4 h. AZT-DP and AZT-TP reached concentrations of 0.3-0.5 pmol/10(6) PBMC after 1-2 h and could not be detected after 4 h in any of the three patients. Duplicate determinations deviated by less than 20%.

Interactive effects of thyroxine and experimental location on running endurance, tissue masses, and enzyme activities in captive versus field-active lizards (Sceloporus undulatus)

This study investigates the effects of exogenous thyroxine (T4) on running endurance, tissue masses, and the activities of citrate synthase (CS), pyruvate kinase (PK), cytosolic alpha-glycerophosphate dehydrogenase (alpha-GPDH), and beta-hydroxyacyl Coenzyme A dehydrogenase (HOAD) in Sceloporus undulatus (eastern fence lizard). The enzymes were assayed to indicate maximal catabolic activities that support exercise. Parallel experiments were done on captive and field-active groups to determine whether responses in captive studies adequately predict responses in nature. Exogenous T4 was administered via intraperitoneal pellets. The effect of T4 on running endurance was dependent on the location of the experiment (P = 0.040) such that stamina was increased by T4 only in field-active lizards. At lower levels of biological organization, interactivity between T4 and experimental location was evident but less prevalent than at the level of the whole animal, and some location effects occurred independent of T4 treatment. Heart and kidney masses were significantly greater and total hind leg muscle mass was less in captive than in field-active lizards. Thyroxine reduced liver mass in both locations and kidney mass only in captive lizards. Mass-specific CS and alpha-GPDH in gastrocnemius muscle (mixed fiber type) and HOAD in heart were lower in captive than in field-active lizards; PK in heart and liver and alpha-GPDH in heart were higher in captive lizards. Thyroxine increased CS in liver and HOAD in heart, decreased alpha-GPDH in liver in both locations, and decreased alpha-GPDH in gastrocnemius only in captive lizards. The effects of T4 differed significantly between experimental locations in gastrocnemius muscle (T4 decreased PK only in captive lizards) and in liver (T4 increased PK in field-active lizards and decreased PK in captive lizards). The mechanistic basis of differences in stamina between captive and field-active and between placebo and T4-treated lizards is largely unexplained by the factors measured here, thus illustrating the uncertainty of predicting organismal performance from lower level measurements. Nonetheless, T4 has now been shown to have greater physiological activity in field-active than in captive Sceloporus with regard to resting and total daily metabolic rates and running endurance. The results of this study further confirm that endocrine experiments on captive animals may not predict responses in nature. Further efforts to clarify the physiological significance of seasonal variations in levels of thyroid hormones will have to involve, at least in part, invasive studies on field-active lizards.

Long-term accuracy of fluorescence polarization immunoassays for gentamicin, tobramycin, netilmicin and vancomycin

External quality control was performed during six years to determine the accuracy over time of the Abbott TDx fluorescence polarization system for assaying antibiotics. Unknown spiked serum samples of gentamicin, tobramycin, netilmicin and vancomycin were provided monthly by the British national external quality assessment scheme. Comparison of the 209 assay results with the target concentrations showed good correlations in all four assays. No significant deviations from linearity, from slope 1.0, and from intercept 0.0 were detected by regression analysis. Relative deviations were less than 10% and less than 15% for 78% and 90% of all specimens, respectively. On an average the same calibration curves could be used over a period of 19 weeks. Fluorescence polarization immunoassays provided rapid and reliable results over the entire study period.

Identification of fluorescent glycopeptide derivatives by two consecutive high pressure liquid chromatographic procedures

Reversed phase high pressure liquid chromatography (HPLC) was used to separate individual components of the complex glycopeptide antibiotic teicoplanin in microgram quantities with gradient elution. Each of eight different fractions was then subjected to a specific and highly sensitive HPLC method, which has been developed for the determination of teicoplanin concentrations in biological specimens. This analytical procedure includes precolumn derivatization with fluorescamine and isocratic elution. The fluorescent teicoplanin derivatives were identified by comparing their retention times in both HPLC procedures. Derivatization resulted in increased hydrophobicity and improved chromatographic separation, but the order of elution of the different compounds was not changed. The antimicrobial activity of the individual underivatized fractions correlated with their respective contents of total teicoplanin A2, whereas the pseudo-aglycone A3 appeared less active. Similar techniques have the potential to be applied to other complex glycopeptide antibiotics.

[Are cephalosporins more active than penicillin G in poisoning with the deadly Amanita?]

High dose penicillin-G has been found empirically to be effective against liver cell damage in amanita mushroom poisoning. We have recently found that betalactam antibiotics inhibit eukaryotic DNA polymerase-alpha, penicillins being more active than cephalosporins, and this may explain the antagonistic effect of penicillin-G against amanitin toxicity. Preliminary experiments in liver cell cultures and in mice are summarized, as well as first clinical experience pointing to the possibility that cephalosporins may be more effective against amanita mushroom toxicity than penicillin-G.

Determination of teicoplanin concentrations in serum by high-pressure liquid chromatography

An isocratic reversed-phase high-pressure liquid chromatographic method for the determination of six components of the teicoplanin complex in biological fluid was developed. By using fluorescence detection after precolumn derivatization with fluorescamine, the assay is specific and highly sensitive, with reproducibility studies yielding coefficients of variation ranging from 1.5 to 8.5% (at 5 to 80 micrograms/ml). Response was linear from 2.5 to 80 micrograms/ml (r = 0.999); the recovery from spiked human serum was 76%. An external quality control was performed to compare this high-pressure liquid chromatographic method (H) with a standard microbiological assay (M); no significant deviation from slope = 1 and intercept = 0 was found by regression analysis (H = 1.03M - 0.45; n = 15).

Ciprofloxacin-induced hematuria

We used ciprofloxacin, a quinolone-derivative, to treat a lung infection due to Pseudomonas aeruginosa in an adult cystic fibrosis patient. On three different occasions the use of ciprofloxacin was associated with the development of an asymptomatic hematuria with red blood cell casts. The mechanism responsible for this hematuria is presently unknown, but clinicians should be aware of this potential adverse effect of ciprofloxacin.

Effect of standard breakfast on drug absorption and multiple-dose pharmacokinetics of ciprofloxacin

Ciprofloxacin was administered to 10 volunteers, who received seven oral doses of 250 mg each at 12-h intervals. Volunteers alternately fasted (F) or received a standard breakfast (B) before the morning dose. Pharmacokinetic parameters were derived from high-pressure liquid chromatography data from samples taken after the first and seventh doses and were analyzed in addition for differences caused by food intake. A significant (P less than 0.05) influence of the standard breakfast on the time to the peak was observed. Peak levels (+/- standard deviation) after the first and seventh doses averaged F (fasting): 1.35 +/- 0.17, B (breakfast): 1.02 +/- 0.28 micrograms/ml, and F: 1.41 +/- 0.32, B: 1.17 +/- 0.5 micrograms/ml, respectively. Mean trough concentrations after the first and seventh doses were F: 0.10 +/- 0.03, B: 0.14 +/- 0.03 micrograms/ml, and F: 0.16 +/- 0.05, B: 0.14 +/- 0.04 microgram/ml, respectively. As with the peak, trough concentrations were not affected significantly by food intake or by accumulation over the study period. Breakfast equally did not affect the terminal half-lives, which averaged F: 3.97 +/- 0.67, B: 4.35 +/- 0.88 h after the first dose and F: 4.64 +/- 0.91, B: 3.72 +/- 0.84 h after the seventh dose. Twelve-hour urinary recovery measured by high-pressure liquid chromatography averaged F: 31, B: 30% for the first dose and, in spite of a possible carry-over from the sixth dose, decreased to F: 25, B: 28% after the seventh dosing interval. When measured by bioassay, an increase of urinary recovery between the first dose (F: 38, B: 38%) and the seventh dose (F: 45, B: 45%) was observed. These differences suggest induction of drug metabolism with repeated doses. Ciprofloxacin was well tolerated by the volunteers.

Comparison of high-pressure liquid chromatography and bioassay for determination of ciprofloxacin in serum and urine

Ciprofloxacin was given orally to 10 healthy volunteers for seven consecutive doses of 250 mg every 12 h. Serum and urine samples were collected at distinct times between 0 and 96 h and analyzed both by high-pressure liquid chromatography and by a microbiological assay. The detection limits were 0.006 and 0.03 microgram/ml, respectively. For each method, imprecision coefficients of variation were less than 6.1% at various concentrations in serum and urine. The means +/- standard deviations of the absolute values of the relative differences between the two methods were 9.3 +/- 6.8% (n = 225) for serum samples and 58.5 +/- 50.4% (n = 70) for urine samples. Comparison of the concentrations in serum measured with high-pressure liquid chromatography and bioassay by regression analysis yielded a slope which was not significantly different from 1.0 (99.9% confidence limits: 0.984 less than slope less than 1.035). In urine, however, the bioassay results were markedly higher than the high-pressure liquid chromatography values (1.327 less than slope less than 1.698), which indicates the presence of antimicrobially active metabolites. The cumulative 12-h urinary recovery after the first and seventh doses averaged 30.2 +/- 8.5 and 26.4 +/- 4.6%, respectively, by high-pressure liquid chromatography, whereas with bioassay 38.2 +/- 5.9 and 45.5 +/- 5.9% activity was recovered. Protein binding appeared to be neither concentration nor pH dependent and averaged 21.9 +/- 4.1%.

Variability of ceftriaxone pharmacokinetics in hospitalized patients with severe infections

The pharmacokinetic behavior of ceftriaxone was studied in 60 patients with severe community- or hospital-acquired infections. Serum concentrations one to three hours after a 30-minute intravenous infusion appeared to be dose related. The mean two-hour levels were 110, 138, and 146 mg/liter, and trough values averaged 54.9, 28.5, and 16.1 mg/liter after doses of 1.0, 2.0, and 3.0 g, respectively. At 24 hours, values were at least 10 mg/liter in all but seven patients. The serum half-life of ceftriaxone in all patients and for all dosage regimens varied from 3.5 to 59.4 hours. In patients with normal renal function (serum creatinine 1.30 mg/dl or less) the mean half-life was 8.2 hours. In patients with moderate (creatinine 1.34 to 1.83 mg/dl) and severe (creatinine 2.40 mg/dl or greater) renal insufficiency, the mean serum half-lives were 12.8 and 12.4 hours, respectively. In six patients who had severe renal failure and concomitant hepatic dysfunction, half-lives ranged from 23.7 to 59.4 hours. Single daily doses of 2.0 g of ceftriaxone produced adequate serum concentrations. Dose reductions are recommended in patients with both renal and hepatic dysfunction.