Challenges in diagnosis and management of neutropenia upon exposure to immune-checkpoint inhibitors: meta-analysis of a rare immune-related adverse side effect.

BACKGROUND: Cancer immunotherapy via immune-checkpoint inhibition (ICI) by antibodies against cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and cell death protein 1 (PD-1) have significantly improved the outcome of metastasized melanoma and of a rapidly increasing number of other cancer types. The anti-tumor effect is often accompanied by immune-related adverse events (irAE). Hematological irAE, specifically neutropenia, are rarely observed. However, neutropenia is associated with high morbidity and mortality due to infection complications. Thus, early detection and treatment is crucial. METHODS: We present the clinical course of two patients with severe neutropenia after ICI therapy and demonstrate the difficulty of the diagnosis when a comedication of metamizole, a well-known analgesic drug used to treat cancer pain, is present. Further, we provide a comprehensive descriptive and statistical analysis of published data on diagnostics, treatment and infection complication in patients with at least grade 4 neutropenia by a systematic database search. RESULTS: Finally, 34 patients were analyzed, including the two case reports from our cohort. The median onset of neutropenia was 10.5 weeks after first ICI administration (interquartile range: 6 weeks). In 76% (N = 26), a normalization of the neutrophil count was achieved after a median duration of neutropenia of 13 days. In a subsample of 22 patients with detailed data, the infection rate was 13%, proven by positive blood culture in 3 cases, but 68% (N = 15) presented with fever > 38 °C. Treatment regime differed relevantly, but mainly included G-CSF and intravenous corticosteroids. Death was reported in 14 patients (41%), 3 of whom (9%) were associated with hematological irAE but only two directly associated with neutropenia. CONCLUSION: With an increasing number of cancer patients eligible to ICI therapy, the incidence of severe hematological toxicities may rise substantially over the next years. Clinicians working in the field of cancer immune therapies should be aware of neutropenia as irAE to provide immediate treatment.

Magic angle effect plays a major role in both T1rho and T2 relaxation in articular cartilage.

PURPOSE: To investigate the effect of sample orientation on T1rho and T2 values of articular cartilage in histologically confirmed normal and abnormal regions using a whole-body 3T scanner. MATERIALS AND METHODS: Eight human cadaveric patellae were evaluated using a 2D CPMG sequence for T2 measurement as well as a 2D spin-locking prepared spiral sequence and a 3D magnetization-prepared angle-modulated partitioned-k-space spoiled gradient echo snapshots (3D MAPSS) sequence for T1rho measurement. Each sample was imaged at six angles from 0° to 100° relative to the B0 field. T2 and T1rho values were measured for three regions (medial, apex and lateral) with three layers (10% superficial, 60% middle, 30% deep). Multiple histopathologically confirmed normal and abnormal regions were used to evaluate the angular dependence of T2 and T1rho relaxation in articular cartilage. RESULTS: Our study demonstrated a strong magic angle effect for T1rho and T2 relaxation in articular cartilage, especially in the deeper layers of cartilage. On average, T2 values were increased by 231.8% (72.2% for superficial, 237.6% for middle, and 187.9% for deep layers) while T1rho values were increased by 92% (31.7% for superficial, 69% for middle, and 140% for deep layers) near the magic angle. Both normal and abnormal cartilage showed similar T1rho and T2 magic angle effect. CONCLUSIONS: Changes in T1rho and T2 values due to the magic angle effect can be several times more than that caused by degeneration, and this may significantly complicate the clinical application of T1rho and T2 as an early surrogate marker for degeneration.

[Establishment of a living biobank : Improved guidance of precision cancer care with in vitro and in vivo cancer models]. / Etablierung einer Living Biobank : Bessere Steuerung der Präzisionsonkologie durch In-vitro- und In-vivo-Krebsmodelle.

BACKGROUND: Precision oncology is a clinical approach aimed towards tailoring treatment strategies for patients based on the genetic profile of each patient's cancer. The integration of a living biobank, consisting of patient-derived tumor organoids and PDXs, with next generation sequencing approaches and high-throughput drug screening help to guide clinical decision-making and clinical trial development. METHODS: Tumor organoids derived from fresh tumor samples were used for in vitro and in vivo high-throughput drug testing. RESULTS: Over a period of two years we established 56 in vitro tumor organoids and 19 in vivo xenografts from 18 different solid tumor types. Tumor morphology and molecular profiles show good concordance between the in vitro and in vivo models compared to their native tumor. High-throughput drug screening (up to 160 drugs) has been tested on eight tumor organoid lines. Seven of them underwent an additional combination drug screen. We nominated several targeted small molecules and novel combinations that have been validated in corresponding xenograft models. CONCLUSION: This precision medicine approach outlines the integration of genomic data with drug screening from personalized preclinical cancer models to guide precision cancer care. It also fuels next generation research and has been implemented for clinical trial development.

UTE bi-component analysis of T2* relaxation in articular cartilage.

OBJECTIVES: To determine T2* relaxation in articular cartilage using ultrashort echo time (UTE) imaging and bi-component analysis, with an emphasis on the deep radial and calcified cartilage. METHODS: Ten patellar samples were imaged using two-dimensional (2D) UTE and Car-Purcell-Meiboom-Gill (CPMG) sequences. UTE images were fitted with a bi-component model to calculate T2* and relative fractions. CPMG images were fitted with a single-component model to calculate T2. The high signal line above the subchondral bone was regarded as the deep radial and calcified cartilage. Depth and orientation dependence of T2*, fraction and T2 were analyzed with histopathology and polarized light microscopy (PLM), confirming normal regions of articular cartilage. An interleaved multi-echo UTE acquisition scheme was proposed for in vivo applications (n = 5). RESULTS: The short T2* values remained relatively constant across the cartilage depth while the long T2* values and long T2* fractions tended to increase from subchondral bone to the superficial cartilage. Long T2*s and T2s showed significant magic angle effect for all layers of cartilage from the medial to lateral facets, while the short T2* values and T2* fractions are insensitive to the magic angle effect. The deep radial and calcified cartilage showed a mean short T2* of 0.80 ± 0.05 ms and short T2* fraction of 39.93 ± 3.05% in vitro, and a mean short T2* of 0.93 ± 0.58 ms and short T2* fraction of 35.03 ± 4.09% in vivo. CONCLUSION: UTE bi-component analysis can characterize the short and long T2* values and fractions across the cartilage depth, including the deep radial and calcified cartilage. The short T2* values and T2* fractions are magic angle insensitive.

Baseline mutational profiles of patients with carcinoma of unknown primary origin enrolled in the CUPISCO study.

BACKGROUND: Patients with unfavorable carcinoma of unknown primary origin (CUP) have an extremely poor prognosis of ∼1 year or less, stressing the need for more tailored treatments, which are currently being tested in clinical trials. CUPISCO (NCT03498521) was a phase II randomized study of targeted therapy/cancer immunotherapy versus platinum-based chemotherapy in patients with previously untreated, unfavorable CUP, defined as per the European Society for Medical Oncology guidelines. We present a preliminary, descriptive molecular analysis of 464 patients with stringently diagnosed, unfavorable CUP enrolled in the CUPISCO study. MATERIALS AND METHODS: Genomic profiling was carried out on formalin-fixed, paraffin-embedded tissue to detect genomic alterations and assess tumor mutational burden and microsatellite instability. RESULTS: Overall, ∼32% of patients carried a potentially targetable genomic alteration, including PIK3CA, FGFR2, ERBB2, BRAFV600E, EGFR, MET, NTRK1, ROS1, and ALK. Using hierarchical clustering of co-mutational profiles, 10 clusters were identified with specific genomic alteration co-occurrences, with some mirroring defined tumor entities. CONCLUSIONS: Results reveal the molecular heterogeneity of patients with unfavorable CUP and suggest that genomic profiling may be used as part of informed decision-making to identify the potential primary tumor and targeted treatment options. Whether stringently diagnosed patients with unfavorable CUP benefit from targeted therapies in a similar manner to those with matched known primaries will be a key learning from CUPISCO.

Comparison of cartilage histopathology assessment systems on human knee joints at all stages of osteoarthritis development.

OBJECTIVE: To compare the MANKIN and OARSI cartilage histopathology assessment systems using human articular cartilage from a large number of donors across the adult age spectrum representing all levels of cartilage degradation. DESIGN: Human knees (n=125 from 65 donors; age range 23-92) were obtained from tissue banks. All cartilage surfaces were macroscopically graded. Osteochondral slabs representing the entire central regions of both femoral condyles, tibial plateaus, and the patella were processed for histology and Safranin O - Fast Green staining. Slides representing normal, aged, and osteoarthritis (OA) tissue were scanned and electronic images were scored online by five observers. Statistical analysis was performed for inter- and intra-observer variability, reproducibility and reliability. RESULTS: The inter-observer variability among five observers for the MANKIN system showed a similar good Intra-class correlation coefficient (ICC>0.81) as for the OARSI system (ICC>0.78). Repeat scoring by three of the five readers showed very good agreement (ICC>0.94). Both systems showed a high reproducibility among four of the five readers as indicated by the Spearman's rho value. For the MANKIN system, the surface represented by lesion depth was the parameter where all readers showed an excellent agreement. Other parameters such as cellularity, Safranin O staining intensity and tidemark had greater inter-reader disagreement. CONCLUSION: Both scoring systems were reliable but appeared too complex and time consuming for assessment of lesion severity, the major parameter determined in standardized scoring systems. To rapidly and reproducibly assess severity of cartilage degradation, we propose to develop a simplified system for lesion volume.

Targeted therapies and checkpoint inhibitors in sarcoma.

Sarcomas are defined as a group of mesenchymal malignancies with over 100 heterogeneous subtypes. As a rare and difficult to diagnose entity, micrometastasis is already present at the time of diagnosis in many cases. Current treatment practice of sarcomas consists mainly of surgery, (neo)adjuvant chemo- and/or radiotherapy. Although the past decade has shown that particular genetic abnormalities can promote the development of sarcomas, such as translocations, gain-of-function mutations, amplifications or tumor suppressor gene losses, these insights have not led to established alternative treatment strategies so far. Novel therapeutic concepts with immunotherapy at its forefront have experienced some remarkable success in different solid tumors while their impact in sarcoma remains limited. In this review, the most common immunotherapy strategies in sarcomas, such as immune checkpoint inhibitors, targeted therapy and cytokine therapy are concisely discussed. The programmed cell death (PD)-1/PD-1L axis and apoptosis-inducing cytokines, such as TNF-related apoptosis-inducing ligand (TRAIL), have not yielded the same success like in other solid tumors. However, in certain sarcoma subtypes, e.g. liposarcoma or undifferentiated pleomorphic sarcoma, encouraging results in some cases when employing immune checkpoint inhibitors in combination with other treatment options were found. Moreover, newer strategies such as the targeted therapy against the ancient cytokine macrophage migration inhibitory factor (MIF) may represent an interesting approach worth investigation in the future.

Macroscopic and histopathologic analysis of human knee menisci in aging and osteoarthritis.

OBJECTIVE: Meniscus lesions following trauma or associated with osteoarthritis (OA) have been described, yet meniscus aging has not been systematically analyzed. The objectives of this study were to (1) establish standardized protocols for representative macroscopic and microscopic analysis, (2) improve existing scoring systems, and (3) apply these techniques to a large number of human menisci. DESIGN: Medial and lateral menisci from 107 human knees were obtained and cut in two different planes (triangle/cross section and transverse/horizontal section as well) in three separate locations (middle portion, anterior and posterior horns). All sections included vascular and avascular regions and were graded for (1) surface integrity, (2) cellularity, (3) matrix/fiber organization and collagen alignment, and (4) Safranin-O staining intensity. The cartilage in all knee compartments was also scored. RESULTS: The new macroscopic and microscopic grading systems showed high inter-reader and intra-reader intraclass correlation coefficients. The major age-related changes in menisci in joints with no or minimal OA included increased Safranin-O staining intensity, decreased cell density, the appearance of acellular zones, and evidence of mucoid degeneration with some loss of collagen fiber organization. The earliest meniscus changes occurred predominantly along the inner rim. Menisci from OA joints showed severe fibrocartilaginous separation of the matrix, extensive fraying, tears and calcification. Abnormal cell arrangements included decreased cellularity, diffuse hypercellularity along with cellular hypertrophy and abnormal cell clusters. In general, the anterior horns of both medial and lateral menisci were less affected by age and OA. CONCLUSIONS: New standardized protocols and new validated grading systems allowed us to conduct a more systematic evaluation of changes in aging and OA menisci at a macroscopic and microscopic level. Several meniscus abnormalities appear to be specific to aging in the absence of significant OA. With aging the meniscal surface can be intact but abnormal matrix organization and cellularity were observed within the meniscal substance. The increased Safranin-O staining appears to represent a shift from fibroblastic to chondrocytic phenotype during aging and early degeneration.

Surface properties of sediments from two Argentinean reservoirs and the rate of phosphate release.

This article reports the surface properties (electrophoretic mobility, surface charge and specific surface area (SSA)), and phosphate release rates of sediments from two Argentinean reservoirs. Even though sediments are a heterogeneous mixture of minerals with different charging behavior, electrophoresis reveals that all sediment particles are negatively charged in the pH range 3-9. Iron and aluminum oxides, which usually carry a net positive charge at low pH, seem to be forming aggregates with negatively charged minerals and/or carrying a net negative charge due to the presence of organic matter. The phosphate release rate increased by increasing pH and temperature, and depended linearly on the SSA of the sediments. These data, together with the high activation energy of the process, indicate that the rate-controlling process is a chemical reaction occurring at the solid-water interface, and not a diffusion process. The rate-controlling step seems to be the breaking of bonds between phosphate and surface groups, breaking that should be preceded by one or more deprotonation steps at the surface and favored by electrostatic repulsion between the negative charge surface and the phosphate anion.

Gene therapy--phase I trial for primary untreated head and neck squamous cell cancer (HNSCC) UICC stage II-IV with a single intratumoral injection of hIL-2 plasmids formulated in DOTMA/Chol.

Recombinant IL-2 protein has shown many immunostimulatory effects in a variety of human tumors. However, the clinical use of rIL-2 is limited by common and serious side effects after systemic administration. IL-2 expression plasmids may circumvent these drawbacks, producing high local IL-2 concentrations that cause limited or no systemic side effects. Due to the superficial growth of squamous cell carcinoma of the head and neck (HNSCC) are readily accessible for direct intratumoral injection and therefore an optimal target for such a gene therapy approach. There has been evidence for local and systemic activation of immune cells by peritumoral injections of IL-2 in patients with advanced HNSCC (Whiteside et al. 1993; Cortesina et al. 1994; De Stefani et al. 1996). We now perform a placebo-controlled, dose-rising study of the safety and tolerability of a single intratumoral injection of hIL-2 plasmid at four dose levels formulated in DOTMA/Chol in patients with primary untreated head and neck squamous cell cancer (HNSCC) TNM stage II-IV. The patients will be monitored for the occurrence of any adverse reactions to the given medication. In addition, we will determine whether the intratumoral administration of the plasmid induces and or enhances tumor-specific host responses at the immunological and or clinical level.

Cardiac output determination in children: equivalence of the transpulmonary thermodilution method to the direct Fick principle.

OBJECTIVE: To show the equivalence of the transpulmonary thermodilution method to the direct Fick principle in children. DESIGN: Prospective single-centre study. SETTING: A 16-bed paediatric cardiac ICU and a cardiac catheterisation laboratory at an university affiliated centre for paediatric cardiology and congenital heart disease. PATIENTS: We consecutively investigated 18 patients (mean age 12.1 +/- 6.4 years) during cardiac catheterisation and after corrective cardiac operation. METHODS AND RESULTS: We prospectively defined limits of equivalence for cardiac index (CI) for both methods of +/- 0.25 l/min x m(2). We measured oxygen consumption for determination of CI by Fick as the clinical "gold standard" and performed a set of three transpulmonary thermodilution measurements. The mean CI(Fick) was 2.88 +/- 1.07 l/min x m(2) (range 1.10-4.62 l/min x m(2)) and CI(TPID)was 2.85 +/- 1.03 l/min x m(2)(range 1.02-4.49 l/min x m(2)). The mean difference between CI(Fick) and CI(TPID)was 0.030 +/- 0.168 l/min x m(2), and limits of agreement -0.306 to 0.366 l/min x m(2)(90% confidence interval -0.040 to 0.099 l/min x m(2)). The regression equation was : CI(Fick)=1.0244 x CI(TPID)-0.040, r(2) = 0.976, P < 0.0001. The intraclass coefficient of reliability for three repeated measurements of CI(TPID) was 0.97, the corresponding lower limit of the 95% confidence interval was 0.94. CONCLUSION: We demonstrated the equivalence of CI measurement by transpulmonary thermodilution and the Fick principle in children. This new method may improve hemodynamic monitoring and management in seriously ill children.

Travel-related vector-borne virus infections in Germany.

Laboratory diagnosis of imported, vector-borne virus diseases during a 22-month-period in Munich, Germany, is summarized. IN 13/317 Germans returning from the Mediterranean with suspected sandfly fever, acute sandfly fever, serotype Toscana, was confirmed serologically: 84.6% of the infections were acquired in Italy. Of 249 German tourists with febrile disease returning from the tropics, acute infection with dengue virus was diagnosed serologically in 26 (10.4%): most infections were acquired in Thailand (57.7%). In a seroepidemiological study of 670 German aid workers who had spent two years in the tropics, 49 (7.3%) were positive for antibodies to dengue, 9 (1.3%) to chikungunya, and 1 (0.1%) to Sindbis virus. Of 17 Middle Eastern patients with suspected viral haemorrhagic fever, genomic Crimean-Congo haemorrhagic fever virus RNA was amplified in 4 (23.5%) by semi-nested reverse transcriptase polymerase chain reaction, and confirmed by molecular characterization of nucleic acid. With the increase in travel to and from endemic areas, imported vector-borne virus infections are increasingly important in Germany.

Action and binding of the endothelin antagonist bosentan on astrocytes of cultured rat central nervous system. Electrophysiological and autoradiographic studies.

Our autoradiographic studies demonstrate that astrocytes in explant cultures of rat central nervous system possess binding sites for the first orally active, mixed, nonpeptide endothelin receptor antagonist [3H] bosentan. Binding of [3H]bosentan was inhibited by unlabelled bosentan and endothelin-1 at high concentrations, suggesting specific binding of the antagonist. Electrophysiological studies have revealed that bosentan reversibly blocked the depolarizations by endothelin but not by angiotensin II, indicating that the antagonist specifically antagonizes the action of endothelin on the glial membrane. This is consistent with biochemical studies from other laboratories demonstrating that bosentan did not interfere with binding of angiotensin II. The availability of bosentan, a potent and selective endothelin receptor antagonist should help to elucidate the role of endothelin on astrocyte function.

Treatment of acute nonlymphoblastic leukemia in adults with daunorubicin-DNA complex: a preliminary report.

Forty-four adult patients under 60 years of age with acute nonlymphoblastic leukemia were randomized for induction treatment with one of the following three regimens: R 1 = courses of daunorubicin on day 1 + ARA-C on days 1--5; R 2 = courses of daunorubicin on days 1 and 2 + ARA-C on days 4--8; R 3 = courses of daunorubicin-DNA complex on days 1--2 + ARA-C on days 4--8. Out of 14 patients, 9 went into remission on R 1, 6 out of 14 on R 2, and 8 out of 16 on R 3. The preliminary results suggest that daunorubicin-DNA complex has the same efficacy for inducing remission as daunorubicin alone, if the same time intervals and dosages are used.

Study of human serum albumin-TiO(2) nanocrystalline electrodes interaction by impedance electrochemical spectroscopy.

The adsorption of human serum albumin (HSA) onto nanocrystalline TiO(2) electrodes was studied by electrochemical impedance spectroscopy (EIS) in function of pH and electrode potential. The characterization and physico-chemical properties of the TiO(2) electrode were investigated by scanning electron microscopy (SEM), UV-photoelectron spectroscopy (UPS), cyclic voltammetry and capacitance measurements. The impedance response of the particulate TiO(2) electrode/protein interface was fitted using an equivalent circuit model to describe the adsorption process. The adsorbed protein layer, which is formed as soon as the protein is injected into the solution and becomes in contact with the electrode, was investigated as a function of electrode potential and solution pH. The measurements were performed under pseudo-steady-state and steady-state conditions, which gave information about the different states of the system. With the pseudo-steady state measurements, it was possible to determine two rate constants of the protein adsorption process, which correspond to two different states of the protein. The shortest one was associated with the first contact between the protein and the substrate and the second relaxation time, with the protein suffering an structural rearrangement due to the interaction with the TiO(2) electrode. It was detected that at sufficiently long times (approx. 1 h, where the system was under steady state conditions), a quasi-reversible protein adsorption mechanism was established. The measurements performed as a function of frequency under steady-state conditions, an equivalent circuit with a Warburg element gave the better fitting to data taken at -0.585 V closer to the oxide flat band potential and it was associated with protein diffusion. Experimental results obtained at only one frequency as a function of potential could be fitted to a model that takes into account non-specific and probable specific protein adsorption, which renders to be potential- and pH-dependent. Low capacity values were obtained in the whole potential range, which were measured in the presence and in the absence of the protein layer. The capacity dependence on potential and pH were associated with the generation of surface states on TiO(2). A surface state concentration of 4.1x10(18) cm(-2) was obtained by relating the parallel capacitance with oxide surface states arising from the protein-oxide interaction.

MHC-class I antigen expression on micrometastases in bone marrow of patients with head and neck squamous cell cancer.

Although squamous cell carcinoma of the head and neck region very rarely metastasize to the skeleton, epithelial cells have been found in bone marrow aspirates of these patients. This observation reflects the general spread of the disease, indicating a poor clinical prognosis with a much higher risk of developing local or distant recurrences. In a first attempt to characterize the phenotypic properties, the expression of the major histo-compatibility complex (MHC) class I antigens on bone marrow micrometastases was assessed. It has been shown that the down-regulation of these molecules is a potential mechanism to escape from HLA class I restricted lysis by cytotoxic T-cells. The significance of reduced MHC class I expression might be relevant for the survival of residual metastatic cells in the bone marrow of patients with squamous cell carcinoma of the head and neck region. Bone marrow aspirates were screened for individual disseminated epithelial cells using the immunoalkaline phosphatase technique with monoclonal antibodies to the epithelial differentiation marker cytokeratin 19 (CK19), as described previously. Specimens containing CK19-positive cells were colabelled with the monoclonal antibody W6/32. The loss of MHC expression is not related to the tumor stage but clearly to the degree of differentiation: 6 out of 7 patients with low-grade SCCHN, but only 3 out of 13 patients with medium-grade SCCHN showed a complete loss of MHC class I molecules. This finding could indicate the reduced prognosis of undifferentiated SCCHN. The lack of MHC class I expression could encourage the survival of residual tumor cells in the bone marrow of patients with SCCHN that evade immunosurveillance.

The significance of Tenascin-C serum level as tumor marker in squamous cell carcinoma of the head and neck.

BACKGROUND: Tenascin, an extracellular matrix glycoprotein, is transiently present in embryonic tissue, in benign granulation tissue, but also in several highly anaplastic tumors like fibrosarcoma, melanoma and squamous cell carcinoma of the skin. This study was performed to validate elevated Tenascin serum levels as a possible marker for head and neck squamous cell carcinomas (HNSCC). PATIENTS AND METHODS: Tenascin serum levels were evaluated in patients with primary (n = 92) and with recurrent (n = 28) HNSCC. Patients with benign, non inflammatory ear, nose and throat diseases (n = 16) served as the control. The Tenascin serum levels were measured by ELISA (Aventis). RESULTS: Serum Tenascin concentrations of patients with benign ENT diseases ranged between 0.37 and 2.19 micrograms/ml (n = 16, mean +/- SD: 1.23 +/- 0.59 micrograms/ml), of patients with HNSCC (primary diagnosis) between 0.05 and 8.75 micrograms/ml (n = 92, mean +/- SD: 1.81 (1.36 micrograms/ml) and of patients with recurrent HNSCC between 0.53 and 10.0 micrograms/ml (n = 28, mean +/- SD: 2.78 +/- 2.2 micrograms/ml). CONCLUSION: We found a significant elevation of Tenascin serum levels only in patients with higher tumor stages (T4/UICC4) (p < 0.01/p < 0.1) or recurrent disease compared to Tenascin serum levels in healthy controls. Thereby Tenascin serum levels cannot be used clinically as a routine serum marker for the control of head and neck cancer. Further investigations are necessary to evaluate whether the measurement of Tenascin levels as tumor markers could offer additional information to the clinical outcome of patients with HNSCC.

Differential scanning potentiometry: surface charge development and apparent dissociation constants of natural humic acids.

Humic acids (HA) are the main components of soil organic matter which can form complexes with metal ions and other soil and/or water contaminants. Here, we focus on their acid-base properties. HA were extracted from two different soils (Tipic Ustifluvent and Entic Haplustoll) with different vegetation. In this study we use a simple method, differential scanning potentiometry (DSP), to determine HA buffer capacity distribution, apparent dissociation constant values and surface charge development.

Surface-charging behavior of Zn-Cr layered double hydroxide.

A Zn-Cr layered double hydroxide (LDH) having the formula Zn(2)Cr(OH)(6)Cl(0.7)(CO(3))(0.15)2.1H(2)O was synthesized and characterized by powder X-ray diffraction, infrared spectroscopy, acid-base potentiometric titration, mass titration, electrophoretic mobility, and modeling of the electrical double layer. Adsorption of alizarin was also performed in order to show some particular features of the HDL. Net hydroxyl adsorption, which increases with increasing pH and decreasing supporting electrolyte concentration, takes place above pH 5. The electrophoretic mobility of the particles was always positive and it decreased when the pH was higher than 9. An isoelectric point of 12 could be estimated by extrapolating the data. The modified MUSIC model was used to estimate deprotonation constants of surface groups and different adsorption models were compared. Good fit of hydroxyl adsorption and electrophoresis could be achieved by considering both OH(-)/Cl(-) exchange at structural sites and proton desorption from surface hydroxyl groups. The modeling, in agreement with alizarin adsorption, indicates that most of the structural positive charge of the LDH is screened at the surface by exchanged anions and negatively charged surface groups. It also suggests that only structural charge sites initially neutralized by chloride ions are active for anion exchange. The remaining sites are blocked by carbonate and do not participate in the exchange.