Layered double hydroxides for phosphorus recovery from acidified and non-acidified dewatered sludge

Phosphate, which contains the essential element phosphorous (P), is a necessary fertilizer for agriculture, but the current phosphate deposits are running out and alternative sources are needed. Sludge obtained from wastewater treatment plants contains high concentrations of phosphorus and represents an alternative, sustainable source. In this study, sludge obtained from a wastewater treatment plant with biological and chemical phosphorus removal was acidified (pH = 3, 4, 5 and 6) to release orthophosphate followed by sequestration of the orthophosphate by a zinc aluminum layered double hydroxide (Zn₂Al-LDH). Sulfuric acid (H₂SO₄), nitric acid (HNO₃), and hydrochloric acid (HCl) was tested, which showed that only sulfate anions compete with phosphate and results in reduced phosphate recovery (25-35%). The orthophosphate concentration in the liquid phase increased from 20% (raw sludge) to 75% of the total phosphorus concentration at a pH of 3, which enhanced the phosphate uptake by the ZnAl-LDH from 1.7 ± 0.2% to 60.3 ± 0.6%. During acidification, the competing anion carbonate is degassed as CO₂, which further improved the phosphate uptake. PXRD showed the intercalation of carbonate in the LDH in the raw sludge at pH = 8, whereas orthophosphate was intercalated at lower pH values. ²⁷Al MAS NMR spectroscopy and powder X-ray diffraction (PXRD) proved preservation of the LDH at all pH values. Furthermore, about a fourth of the Al is present as an amorphous aluminum phosphate (AlPO₄) upon exposure to phosphate at low pH (pH = 3 and 5) based on ²⁷Al MAS NMR spectroscopy. At a pH of 6 about a third of the P is present as brushite (CaHPO₄·2H₂O).

Irreversible fouling of membrane bioreactors due to formation of a non-biofilm gel layer

Extra-cellular polymeric substances (EPS), known to contribute to fouling in membrane bio-reactors (MBRs), are generally divided into bound and free EPS. The free EPS are able to form a gel layer on the membrane active surface. The mechanisms involved in formation of such layer and its effects on performance of the MBR membranes were studied. The free EPS, extracted by centrifugation and microfiltration, contained a significant amount of humic-like substances. Under static contact to the membrane, adsorption of humic-like substances to the membrane occurred and could be explained by conventional adsorption kinetics. Due to static adsorption, surface roughness of the membrane declined significantly, indicating that adsorbed matters to the membrane filled the cavities of the membrane surface. Filtration of the free EPS caused 50% water flux decline. The fouling resistance linearly increased with the amount of the humic-like substances retained during filtration as predicted by gel growth theory. A low pressure backwash could re-establish the water flux only up to 70%.

Novel assays to assess the functional capacity of the classical, the alternative and the lectin pathways of the complement system

Deficiencies in many of the complement proteins and their regulatory molecules have been described and a variety of diseases, such as recurrent infections, systemic lupus erythematosus (SLE) and renal diseases, may be linked to deficiency in the complement system. Screening for complement defects is therefore of great importance. In this study, we present novel improved enzyme-linked immunosorbent assays for the functional assessment of the three individual pathways of the complement system. The method is applicable at high serum concentrations and we demonstrate that it minimizes both false negative as well as false positive results. In particular, for the functional mannose-binding lectin activity it represents an improvement on the existing assays. In this respect, the present assays represent novel improved diagnostic protocols for patients with suspected immunodeficiencies related to the complement system.

Ontogeny of dextromethorphan O- and N-demethylation in the first year of life

The exponential increase in the number of drugs used to treat infant and childhood illnesses necessitates an understanding of the ontogeny of drug biotransformation for the development of safe and effective therapies. Healthy infants received an oral dose (0.3 mg/kg) of dextromethorphan (DM) at 0.5, 1, 2, 4, 6, and 12 months of age. DM and its major metabolites were measured in urine. CYP2D6 genotype was determined by polymerase chain reaction-restriction fragment length polymorphism. Genotyping data indicated a strong correlation between CYP2D6 genotype and DM O-demethylation (beta=-0.638; 95% CI: -0.745, -0.532; P<0.001). CYP2D6 activity was detectable and concordant with genotype by 2 weeks of age, showed no relationship with gestational age, and did not change with post natal age up to 1 year. In contrast, DM N-demethylation developed significantly more slowly over the first year of life. Genotype and the temporal acquisition of drug biotransformation are critical determinants of a drug response in infants.

Pharmacokinetics of naratriptan in adolescent subjects with a history of migraine

Naratriptan is a novel 5-HT1 agonist developed to treat acute migraine. The study objective was to characterize the pharmacokinetics of oral naratriptan in adolescent migraine patients outside a migraine attack. Subjects received a single 2.5 mg naratriptan tablet. Serial serum samples for naratriptan concentrations were collected over 24 hours. Blood pressure, pulse rate, and 12-lead ECG were recorded at baseline and at regular intervals after dosing. Seven patients--3 males and 4 females, 12 to 16 years of age--received drug and completed the study. The geometric mean and 95% confidence interval maximum concentration (Cmax) was 8.0 ng/mL (5.9-10.7), elimination half-life (t1/2) was 4.9 hours (4.5-5.4), area under the concentration-time curve (AUC) was 74.6 ng.h/mL (56.6-98.2), and apparent total clearance (Cl/F) was 558.8 mL/min (424.3-735.9). The median time to maximal concentration (tmax) was 4 hours, with a range of 1.5 to 4. Blood pressure, pulse rate, and ECG parameters did not change significantly from baseline. No serious adverse events or subject withdrawal after drug administration occurred. Oral naratriptan pharmacokinetic parameters in adolescents were similar to values reported in adults. Naratriptan doses for adolescents older than 12 years of age would be expected to be similar to adult doses.

Increased tacrolimus levels in a pediatric renal transplant patient attributed to chronic diarrhea

Tacrolimus is an immunosuppressant used to prevent rejection of transplanted organs. It is metabolized in both the gut and the liver by the cytochrome P450 (CYP) 3A4 enzyme system and is a substrate for the P-glycoprotein (P-gp) drug efflux pump. As CYP3A4 enzymes and P-gp are present at differing concentrations throughout the gastrointestinal tract, the bioavailability of tacrolimus may be influenced by changes in gastrointestinal transit time in addition to changes in hepatic metabolism. We report the case of a pediatric renal transplant patient who experienced a three-fold increase in serum tacrolimus concentrations during an episode of gastroenteritis with chronic diarrhea.

Chromium and zinc concentrations in pediatric patients receiving long-term parenteral nutrition

Serum, urine, and parenteral nutrition (PN) chromium and zinc concentrations in pediatric patients receiving long-term PN were studied. Serum, urine, and PN chromium and zinc concentrations were measured at baseline and four to six months later in four infants (less than 1 year old) and seven children (1-12 years old) receiving long-term PN. In the children, serum, urine, and PN solution zinc concentrations were measured monthly after the amino acid product was changed from a standard to a pediatric product with monthly dosages of 0, 20, 30, and 40 mg of cysteine hydrochloride per gram of amino acids. The mean +/- S.D. baseline serum chromium concentration was 4.9+/-1.9 microg/L (normal value, <0.3 microg/L); the urine chromium concentration ranged from 3.4 to 32.2 microg/L. The mean +/- S.D. prescribed chromium dosage was 0.18+/-0.05 microg/kg/day, and the dosage delivered in PN solutions was 0.41+/-0.23 microg/ kg/day. At baseline, the mean +/- S.D. serum zinc concentration was 1383+/-472 microg/L (normal range, 430 to 940 microg/L), and the prescribed and delivered zinc dosages were 177+/-10 and 238+/-145 microg/kg/ day, respectively. With 20, 30, and 40 mg of cysteine per gram of amino acids, the mean +/- S.D. serum zinc concentration was 1728+/-782, 1664+/-349, and 1685+/-268 microg/L, respectively, and the actual zinc dosages delivered were 209+/-10, 270+/-148, and 322+/-194 microg/kg/day, respectively. Serum and urine chromium concentrations were abnormally high in infants and children receiving PN solutions supplemented with normal doses of these trace elements; an escalating dosage of cysteine in the children tended to increase serum and urine zinc concentrations.

Cysteine supplementation results in normalization of plasma taurine concentrations in children receiving home parenteral nutrition

We evaluated plasma sulfur amino acid concentrations in children with short gut syndrome receiving home parenteral nutrition (n = 6). Cysteine HCl addition to solutions formulated with a pediatric amino acid product will increase plasma taurine concentrations to within the normal reference range.

The clinical pharmacology of loop diuretics in the pediatric patient

The loop diuretics furosemide and bumetanide are frequently employed in the pediatric population for the management of fluid overload in both acute and chronic disease states. They act mainly by inhibiting sodium reabsorption in the nephron at the thick ascending limb of Henle's loop. Important pharmacokinetic differences between adults and infants include a reduced clearance and prolonged half-life, that may cause accumulation of these agents to potentially toxic levels if dosing intervals are not adjusted. Unfortunately, little is known about the time required for maturation of loop diuretic elimination in older infants, children, and adolescents. Similar to adults, limited pharmacodynamic evidence in neonates suggests that a maximally efficient diuretic dose exists. Increasing the diuretic dose beyond this maximum does not offer further benefit, but may increase the risk of toxicity. Common problems encountered in the pediatric patient as well as in adults are loop diuretic tolerance and resistance. Loop diuretic dosing strategies aimed at overcoming these phenomena include administration by continuous infusion, coadministration with albumin, and coadministration with metolazone or thiazides. This article reviews the pharmacology, pharmacokinetics, and pharmacodynamics of furosemide and bumetanide in pediatric patients. A better understanding of the clinical pharmacology of the loop diuretics should aid clinicians in the development of dosing regimens aimed at producing adequate diuresis without promoting excessive diuretic tolerance.

New-onset juvenile dermatomyositis: comparisons with a healthy cohort and children with juvenile rheumatoid arthritis

OBJECTIVE

To determine, in a case-control study, if patients with new-onset juvenile dermatomyositis (juvenile DM) have increased symptoms prior to onset, exposure to certain environmental conditions, frequency of familial autoimmune diseases, or antibody titers, compared with 2 control groups.

METHODS

A structured interview with the families of 80 children with juvenile DM, 40 children with juvenile rheumatoid arthritis (JRA), or 23 healthy children, from the same geographic area as the children with juvenile DM, was conducted. All children's sera were tested for antibody to Toxoplasma gondii, herpes simplex virus (HSV), or coxsackievirus B (CVB).

RESULTS

A high proportion of children with juvenile DM had constitutional symptoms 3 months before the disease-onset date (P = 0.013 versus control children). Children with JRA had more relatives with rheumatoid arthritis (P = 0.0001) and pernicious anemia (P = 0.003) than did children with juvenile DM or healthy children. Among children < or =7 years of age, elevated enteroviral titers were more frequent in those with juvenile DM (81%) and in healthy controls (90%) than in those with JRA (64%), suggesting a common environmental exposure. Titers to T gondii, HSV, or CVB 1-6 were normal.

CONCLUSION

Frequencies of familial autoimmune disease, exposure to environmental factors, or elevated antibody titers to T gondii, HSV, or CVB are not increased in juvenile DM. Children with juvenile DM do have symptoms of illness 3 months before the disease-onset date, and young patients have elevated enteroviral titers, as do young geographic controls.

Transdermal fentanyl administration in children and adolescents with sickle cell pain crisis

PURPOSE

The purpose of this study was to determine the dose-concentration relationship and clinical effect of transdermal fentanyl (TF) in patients with sickle cell pain crisis (SCPC).

PATIENTS AND METHODS

Ten patients aged 9-16 years were studied. Patients initially received a TF dose of 25 (n = 7) or 50 (n = 3) micrograms/h if morphine use was > 2.5 mg/h. Supplemental morphine usage via patient-controlled analgesia (PCA), sedation status, pain status, respiratory rate, pulse rate, oxygen saturation, and blood pressure were monitored.

RESULTS

The average TF dose was 0.77 +/- 0.37 micrograms/kg/h on day 1 and 1.17 +/- 0.46 micrograms/kg/h on day 2. Fentanyl concentrations measured at 24 and 48 h were 0.60 +/- 0.31 and 1.18 +/- 0.44 ng/ml, respectively. A significant relationship existed between TF dose and fentanyl concentration (r2 = 0.56, p < 0.01). There was no difference in any of the clinical monitoring parameters between day 1 and day 2. However, 7 of 10 patients reported subjective improvement in pain control over that achieved with PCA alone. No adverse effects were noted.

CONCLUSIONS

Improved understanding of the dose-effect relationship for TF in children and adolescents is necessary before adequate pain control can be achieved with this delivery system.

Pharmacokinetics of vincristine in children and adolescents with acute lymphocytic leukemia

We studied the pharmacokinetics of vincristine in children with acute lymphocytic leukemia by means of a specific high-performance liquid chromatographic assay with ultraviolet and electrochemical detection and a limited sampling strategy. Our objectives were to characterize the disposition of vincristine in pediatric patients, to determine clinical, demographic, or biochemical variables related to variability in vincristine pharmacokinetic parameters, and to assess the relationship between pharmacokinetic parameters and vincristine neurotoxicity. Plasma samples were collected at 5 and 30 minutes, and 1, 3, and 24 hours after a rapid intravenous injection during 3 minutes. Vincristine-induced neurotoxicity was retrospectively evaluated by chart review. Pharmacokinetic studies were completed for 64 doses in 54 children between 2 months and 18 years of age (median, 4.3 years), including 2-month-old monozygous twin girls. Vincristine clearance, estimated by Bayesian methods, was highly variable, with a mean (SD) clearance of 19.9 (14.9) ml/min per kilogram or 482 (342) ml/min per square meter. Mean clearance for all subjects was faster than in published studies of adults, which may be related in part to the greater specificity of the assay used in our study, as well as to age-related differences in drug disposition. Vincristine-associated neurotoxicity was frequent but mild and was not predicted by vincristine systemic exposure; however, neurotoxicity may have been underestimated. Clearance in one patient who received concomitant treatment with pentobarbital exceeded the 75th percentile for all patients, and four of five patients receiving concomitant histamine2 antagonists had clearances below the 25th percentile for all subjects, suggesting that drugs that induce or inhibit hepatic cytochrome P-450 enzymes may affect vincristine disposition. Further studies are needed to identify the factors responsible for interpatient variability in vincristine disposition and to develop improved dosing guidelines.

Parenteral nutrition associated with increased infection rate in children with cancer

BACKGROUND

Recent meta-analyses of published controlled studies concluded that adult patients with cancer randomly assigned to receive parenteral nutrition had higher rates of infectious complications than control subjects.

METHODS

The infection risk associated with parenteral nutrition was assessed in 310 pediatric patients with cancer. These patients had central venous access devices (CVAD), Hickman/Broviac (H/B) catheters, or implantable subcutaneous ports in place for the delivery of chemotherapy and supportive care.

RESULTS

The median duration of CVAD placement was 363 days; a total of 450 patient years (i.e., the sum of the total years of catheters experienced from all patients studied) were examined. Overall, the infection rate was 0.06 infections/100 days. During the period of parenteral nutrition administration, the rate increased to 0.5 infections/100 days. Among patients who received parenteral nutrition, there were no significant differences in any clinical parameter between the patients who developed an infection and those who did not. When evaluating the entire study population, infection was more likely to occur in patients who had acute nonlymphocytic leukemia (P < 0.01) or H/B catheters (P < 0.01), or who received parenteral nutrition (P < 0.02); there was no relationship between infection and catheter duration, days hospitalized, or days neutropenic (absolute neutrophil count < 0.5 x 10(9)/l). Only CVAD type and parenteral nutrition retained significance in a multivariate Cox proportional hazards model. After adjustment for diagnosis and CVAD type, the risk of infection was 2.4-fold greater in patients given parenteral nutrition (95% confidence interval 1.5 to 3.9; P < 0.001).

CONCLUSION

These data confirm that administration of parenteral nutrition is associated with an increased risk of infection in children who have CVAD in place for cancer therapy.

Plasma amino acids in patients with acute nonlymphocytic leukemia receiving parenteral nutrition

OBJECTIVE

To assess the effect of parenteral amino acid solutions on plasma amino acid concentrations in patients with acute nonlymphocytic leukemia (ANLL) receiving parenteral nutrition (PN).

DESIGN

Ten patients were studied at diagnosis, on the morning PN was started, and three times during PN therapy coinciding with the sequential administration of three different amino acid solutions (Aminosyn, FreAmine HBC, and TrophAmine). The order of amino acid solution administration in each patient was by a randomized, block design.

RESULTS

The patients were undergoing identical intensive induction therapy. There was no significant difference in the number of days they received PN or the amount of protein or calories received during the three PN study periods. At diagnosis, phenylalanine and glutamic acid concentrations were elevated compared with previously published normal values and remained elevated at all observation times. During PN, asparagine, aspartic acid, and tyrosine concentrations were significantly lower with all three amino acid solutions compared with their concentrations at diagnosis. Glycine and threonine concentrations were also significantly lower with FreAmine HBC and TrophAmine administration and cysteine concentrations were significantly lower with FreAmine HBC administration than at the time of diagnosis. Aminosyn was associated with plasma amino acid concentrations most similar to those measured at diagnosis.

CONCLUSIONS

These results indicate that most amino acid concentrations fall within the normal range at diagnosis in the ANLL patients studied. Plasma concentrations for certain amino acids can be influenced by the amino acid solution used in PN. Further understanding of the derangements in amino acid metabolism and the influence of parenterally administered amino acid solutions on plasma amino acid concentrations may lead to improvements in the nutritional support of cancer patients.

Urinary nitrogen constituents in the postsurgical preterm neonate receiving parenteral nutrition

Minimal information is available defining urinary nitrogen constituents in preterm neonates receiving parenteral nutrition (PN). The study objective was to evaluate 24-hour urine collections for total urinary nitrogen (TUN), urinary urea nitrogen (UUN), and the nitrogen content in creatinine, ammonia, free amino acids, protein, hippuric acid, and uric acid at baseline (days 1 to 2 of PN and days 1 to 3 after surgery) and 7 days later in eight preterm, postsurgical neonates. Calculation of undetermined nitrogen was also completed. Comparisons with historic, normal data were made for each urinary nitrogen constituent. At baseline, PN provided 59 +/- 10 nonprotein kcal/kg.day-1 and 430 +/- 54 mg/kg.day-1. At day 7, PN provided 106 +/- 23 nonprotein kcal/kg.day-1 and 432 +/- 30 mg/kg.day-1. TUN, UUN, and protein nitrogen decreased significantly from baseline at day 7 (p < .05). The percentages of TUN as amino acids, creatinine, and uric acid nitrogen were calculated. Percent amino acid nitrogen (6.0 +/- 2.3% vs 8.4 +/- 1.5%, p < .05), percent creatinine nitrogen (1.6 +/- 0.5% vs 2.9 +/- 0.8%, p < .001) and percent uric acid nitrogen (1.7 +/- 0.9% vs 3.6 +/- 2.1%, p < .05) increased significantly at day 7. The observed urinary free amino acid nitrogen fraction represented a higher percentage of TUN both at baseline and at day 7 when compared with term neonatal reference data, whereas creatinine nitrogen, uric acid nitrogen, and protein nitrogen represented a lower percentage of TUN. However, amino acid and creatinine nitrogen as a percentage of TUN were similar to levels in milk formula-fed preterm infants.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of moderate hypothermia during elective craniotomy

Use of moderate hypothermia as an adjunct to elective craniotomy is described in 21 patients. Systemic hypothermia to 32 degrees C was induced by cooling blankets at a mean cooling rate of 1.6 degrees C/min. Patients were rewarmed at the same rate prior to closure of wounds. There were no hypothermia-related complications and the method increased brain relaxation. The rationale for use of this therapy in elective craniotomy and severe head injury is reviewed.

Increased teniposide clearance with concomitant anticonvulsant therapy

PURPOSE

A possible pharmacokinetic interaction between teniposide and anticonvulsant medications was evaluated in pediatric patients.

PATIENTS AND METHODS

The systemic clearance of teniposide was determined in six pediatric patients with acute lymphocytic leukemia receiving concomitant therapy with anticonvulsants. Clearance was then compared with a control group of patients treated with the same protocol therapy and matched for age at diagnosis, sex, and race but not receiving anticonvulsants or other agents known to induce hepatic metabolism or alter protein binding of drugs. Eight blood samples were obtained during and after 4-hour infusions of teniposide, and plasma concentrations were measured by a specific high-performance liquid chromatography (HPLC) assay. A two-compartment model was fitted to each subject's data.

RESULTS

The mean systemic clearance (range) for the six anticonvulsant-treated patients studied during 22 courses of therapy was 32 mL/min/m2 (range, 21 to 54 mL/min/m2), significantly higher (P less than .001) than the mean value of 13 mL/min/m2 (range, 7 to 17 mL/min/m2) for the control patients studied during 26 courses of therapy. Clearance estimates for control patients were similar to previously published values for pediatric patients.

CONCLUSION

These data indicate that the systemic clearance of teniposide is consistently increased two- to three-fold by concomitant phenobarbital or phenytoin therapy. The consequent substantial reduction in systemic exposure may reduce teniposide's efficacy.

Age-related differences in hepatic drug clearance in children: studies with lorazepam and antipyrine

The disposition of intravenous antipyrine and lorazepam, administered as model substrates for hepatic oxidative metabolism and conjugation, was evaluated in 50 children (mean age, 7.8 years; range, 2.3 to 17.8 years) with acute lymphocytic leukemia in complete remission and compared with a group of ten healthy adults. Antipyrine clearance normalized to body weight was significantly greater in children than in adults (0.91 versus 0.59 ml/min/kg; p = 0.012), but was not different when normalized to body surface area. In contrast, lorazepam total clearance (CL) and unbound clearance (CLu) normalized to body weight were not significantly different between children and adults but were smaller in children when normalized to body surface area (CL = 31.9 versus 40.6 ml/min/m2, p = 0.036; CLu = 352 versus 485 ml/min/m2, p = 0.010). The mean lorazepam fraction unbound in children was 0.087, which was not different from adult volunteers (0.084). This study has identified significant differences between children and adults in the disposition of these two compounds, with higher milliliter per minute per kilogram clearance for antipyrine but not lorazepam.

Toxicities of parenteral nutrition in the critically ill patient

Critically ill patients have unique nutritional substrate requirements. Although important advances have been made in understanding these requirements in the face of pathophysiologic and biochemical alterations induced by stress or trauma, nutrition-associated toxicities still occur. The importance of these toxicities to the critically ill patients cannot be over-stated. Many of these toxicities can be avoided by conservative use of selected nutrition substrates in specific subsets of the critically ill population. Practitioners must continue to anticipate and recognize parenteral nutrition-associated toxicities, however, as well as delineate any toxicity from the progression or exacerbation of disease.

Correlation of the percent of positive Chlamydia trachomatis direct fluorescent antibody detection tests with the adequacy of specimen collection

Chlamydia trachomatis is an obligate, intracellular parasite infecting the columnar and transitional cells lining the endocervix, uterus, fallopian tubes, rectum, urethra, and epididymis. We determined if the percent of specimens positive for C. trachomatis in the Microtrak Direct Specimen Test depended on the quality of specimens obtained. Female genital slides (649) were evaluated by the direct fluorescent antibody (DFA) test for the presence and numbers of (a) C. trachomatis elementary bodies and (b) columnar, transitional and squamous epithelial cells, and polymorphonuclear neutrophils (PMNs). Only 138 (21.3%) of the 649 slides were considered to be adequately taken, that is, containing columnar/transitional cells either alone or in conjunction with squamous cells and/or PMNs. Of the 138 adequate slides, 10 (7.2%) were C. trachomatis positive. However, 511 (78.7%) of the 649 slides were judged inadequate; 395 contained only squamous cells and/or PMNs, 19 were too thick to determine cell types, 46 contained only cell debris, and 51 contained neither cells nor debris. Only four (0.78%) of 511 were C. trachomatis positive. Thus adequate specimens containing columnar/transitional cells for C. trachomatis detection had a tenfold increase in the percent of positive results compared to inadequately collected specimens. By using the DFA test, one has the advantage of determining the adequacy of the specimens obtained as well as the presence of chlamydiae.