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Retroviral vectors are powerful tools in clinical gene therapy as they integrate permanently into the target cell genome and thus guarantee long-term expression of transgenes. Therefore, they belong to the most frequently used application platforms in clinical gene therapy involving a broad range of different target cells and tissues. However, stable genomic integration of retroviral vectors can be oncogenic, as reported in several animal models and in clinical trials. In particular, γ-retroviral vectors, which derive from naturally mutagenic γ-retroviruses, integrate semirandomly into the host genome with regard to the target sequence, but have a preference for regions of active transcription and regulatory elements of transcriptionally active genes. The integration can result in overexpression of adjacent genes or disruption of ‘target’ gene expression. Moreover, γ-retroviral integration can cause modified transcripts and proteins through alternative or aberrant splicing or through premature termination of transcription.
Initially, the event of insertional mutagenesis and subsequent induction of leukemia by the genotoxicity of a γ-retroviral vector was described in a mouse model after genetic modification of hematopoietic stem cells (HSCs). Vector-related activation and overexpression of the oncogene ecotropic viral integration site-1 (Evi1) fostered clonal outgrowth and leukemogenesis. Additional genotoxic events of γ-retroviral vectors were observed in clinical HSC gene therapy trials for X-linked severe combined immune deficiency (SCID-X1), chronic granulomatous disease (X-CGD), and Wiskott-Aldrich Syndrome (WAS). But, genotoxicity induced by γ-retroviral vectors has never been described in clinical gene therapy trials involving adoptive transfer of genetically modified mature T lymphocytes. This fact is surprising, since T cells are long-lived and have a high capacity of self-renewal.
In a previous study, the susceptibility towards oncogenic transformation of mature T cells and HSCs after genetic modification was compared. It could be demonstrated that T-cell receptor (TCR)-polyclonal mature T cells are far less prone to transformation after γ-retroviral transfer of (proto-)oncogenes in vivo than HSCs. Additional experiments revealed that TCR-oligoclonal (OT-I and P14) mature T cells are transformable in the same setting and give rise to mature T-cell lymphomas (MTCLs).
In the present thesis, the susceptibility of mature T cells towards insertional mutagenesis was investigated. Within the first part of the thesis, retroviral integration sites (RISs) from 33 murine MTCLs were retrieved and subsequently analyzed in terms of integration pattern, detection of common integration sites (CIS) and gene ontology (GO). As these bioinformatic results demonstrated that insertional mutagenesis most likely contributed to mature T-cell lymphomagenesis, the susceptibility of mature T cells was directly assessed in a mouse model. Therefore, murine TCR-oligoclonal OT-I T cells were transduced with an enhanced green fluorescent protein (EGFP) encoding γ-retroviral vector and gene-modified T cells were transplanted into RAG1-/- mice. After 16 months, including one round of serial transplantation, a case of MTCL emerged. Tumor cells were characterized by CD3, CD8, TCR and ICOS expression. Integration site analysis via ligation-mediated polymerase chain reaction (LM-PCR) revealed a proviral insertion in the Janus kinase 1 (Jak1) gene. Subsequent overexpression of Jak1 could be demonstrated on transcriptional and protein level. Furthermore, T-cell lymphoma cells were characterized by an activated Jak/STAT-pathway as signal transducer and activator of transcription 3 (STAT3) was highly phosphorylated. The overexpression of Jak1 was causally implicated in tumor growth promotion as specific pharmacological inhibition of Jak1 using Ruxolitinib significantly prolonged survival of mice transplanted with these Jak1-activated tumor cells. A concluding systematic metaanalysis of available gene expression data on human mature T-cell lymphomas/leukemias confirmed the relevance of Jak/STAT overexpression in sporadic human T-cell tumorigenesis.
This was the first reported case of an insertional mutagenesis event in mature T cells in vivo. Thus, the results obtained in this thesis underline the importance of long-term monitoring of genetically modified T cells in vivo and the evaluation of vector toxicology and safety in T-cell based gene therapies. In particular, the transduction of T cells with a recombinant TCR or CAR (chimeric antigen receptor) bears a risk enhancement, as normal T-cell homeostasis is perturbed besides the general risk of insertional mutagenesis.
Ribosome biogenesis is best understood in the yeast Saccharomyces cerevisiae. In human or mammalian ribosome biogenesis, it has been shown that basic principles are conserved to yeast, but additional features have been reported. Our understanding about the interplay between proteins and RNA in human ribosome biogenesis is far from complete.
The present study focused on the analysis of the human ribosome biogenesis co-factors PWP2, EMG1 and Exportin 5 (XPO5) to understand the degree of conservation of ribosome biogenesis. The proteins were characterized in respect to their localization and interaction partners. For the early 90S co-factor, PWP2, it was possible to pull down and identify the human UTP-B complex with MALDI mass spectrometry. Besides the orthologues of the members of this complex known in yeast (TBL3, WDR3, WDR36, UTP6, UTP18), the human UTP-B complex is not only conserved from yeast to humans, but contains also additional components, like the DEAD-box RNA helicase DDX21, which lacks a yeast orthologue. DDX21 was localized to the nucleus, assembled to the native UTP-B complex and co-precipitated also with other UTP-B complex members, presumably extending the functions of this complex in ribosome biogenesis.
This phenomenon was also observed for the 90S co-factor EMG1, an RNA methyltransferase, whose mutant form causes the Bowen-Conradi syndrome, if aspartic acid is mutated to glycine at position 86. This study revealed that the mutant, EMG1-D86G, clearly lost its nucleolar localization and co-precipitated to histones for unknown reasons.
A participation of the nuclear export receptor XPO5 in human ribosome biogenesis was shown in this study. Pulldown analysis, sucrose density gradients and UV crosslinking and analysis of cDNAs of XPO5 revealed the involvement of XPO5 in pre-60S subunit maturation. Moreover, besides the known pre-miRNAs and tRNAs as substrates for nuclear export, XPO5 crosslinked to snoRNAs. XPO5 was further demonstrated to interact with the miRNA Let-7a, which has an important regulatory function for MYC, a transcription factor required for ribosome biogenesis.
All results support a role of these proteins in human ribosome biogenesis and therefore it seems that the biogenesis of ribosomes in human cells requires additional components, like DDX21 and XPO5.
In this thesis, Hanbury-Brown-Twiss (HBT) interferometry is used together with the Ultrarelativistic Quantum Molecular Dynamics (UrQMD) to analyse the time and space structure of heavy-ion collisions.
The first chapter after the introduction gives an overview of the different types of models used in the field of heavy-ion collisions and a introduction of the UrQMD model in more detail. The next chapter explains the basics of Hanbury-Brown-Twiss correlations, including azimuthally sensitive HBT (asHBT).
Results section:
4. Charged Multiplicities from UrQMD
5. Formation time via HBT from pp collisions at LHC
6. HBT analysis of Pb+Pb collisions at LHC energies
7. HBT scaling with particle multiplicity
8. Compressibility from event-by-event HBT
9. Tilt in non-central collisions
10. Shape analysis of strongly-interacting systems
11. Measuring a twisted emission geometry
This thesis covers the standard integrated HBT analyses, extracting the Pratt-Bertsch radii, at LHC energies. The analyses at these energies showed a too soft expansion in UrQMD probably related to the absence of a partonic phase in UrQMD. The most promising results in this thesis at these energies are the restriction of the formation time to a value smaller than 0.8 fm/c and furthermore, the results from the asHBT analyses. In simulations of non-central heavy-ion collisions at energies of Elab= 6, 8 and 30 AGeV the validity of the formulae to calculate the tilt angle via asHBT has been checked numerically, even for the case of non-Gaussian, flowing sources. On this basis has been developed and test in the course of this thesis that allows to measure a scale dependent tilt angle experimentally. The signal should be strongest at FAIR energies.
Structural determinants for substrate specificity of the promiscuous multidrug efflux pump AcrB
(2013)
Opportunistic Gram-negative pathogens such as Escherichia coli, Klebsiella pneumoniae, Acinetobacter Baumanii and Pseudomonas aeruginosa are becoming more and more multiresistant against many commonly available antibiotics [39, 40]. An important resistance mechanism of Gram-negative bacteria is the efflux of noxious compounds by tripartite systems [39, 41-44]. The best studied and most clinically relevant tripartite system is the AcrA-AcrB-TolC system of Escherichia coli, where substrate recognition and energy transduction takes place in the inner membrane protein AcrB. AcrB has a remarkably huge substrate spectrum and can recognize structurally diverse molecules, such as hexan in contrast to erythromycin, as its substrates [45]. Therefore, overproduction of the tripartite system can render a Gram-negative pathogen resistant against multiple antibiotics at once. The mechanisms of how AcrB is able to recognize such an enormous spectrum of molecules as substrates, without compromising its specificity (e.g. by neglecting essential compounds like lipids or gluclose as its susbtates), remained puzzling. Structural insight into substrate specificity was so far limited to two co-crystal structures of AcrB, where minocycline and doxorubicin, respectively, were identified bound to an internal binding pocket of AcrB. This binding pocket is particularly deeply buried into internal parts of the T monomer of AcrB and was, therefore, denoted deep binding pocket (DBP). Analysis of several AcrB co-crystal structures with substrate molecules bound to the DBP [4, 23, 25] indicated that the substrate promiscuity involved multisite binding modes within the DBP. Multisite binding modes, where different substrate molecules can bind to slightly different positions and orientations to the same binding pocket, is a common feature of multidrug recognizing proteins such as QacR or BmrR [27-29]. Nevertheless, AcrB's substrate spectrum is much broader than substrate spectra of most other multidrug recognizing proteins. Therefore, it is likely that additional mechanisms are involved in mediating the observed high substrate promiscuity of AcrB. In our recently published high-resolution AcrB/doxorubicin co-crystal structure (pdb entry: 4DX7 [23]) we were able to identify two additional substrate binding pockets in the L monomer of AcrB: i) the access pocket (AP), with an opening towards the periplasm, and ii) a putative binding site in a groove between transmembrane helices 8 and 9 (TM8/TM9 groove), accessible from the lipid layer of the inner membrane. Both binding pockets are likely to be access sites for substrates towards AcrB. Furthermore, each of the binding pockets are possibly specialized to recognize a specific subset of the entire substrate spectrum of AcrB, i.e. highly hydrophobic substrates (e.g. n-dodecyl-ß-d-maltoside or sodium dodecylsulfate) might access AcrB towards the TM8/TM9 groove and water soluble substrates (e.g. berberine) might access AcrB towards the AP. Since substrates will accumulate in the membrane or the periplasm according to their hydrophilic or hydrophobic nature, substrates will be "pre-selected" by the medium, rather than by the protein itself, and guided to their appropriate access site. This process is proposed to be called "medium- mediated pre-selection". The AcrB/doxorubicin co-crystal structure (pdb entry: 4DX7 [23]) furthermore revealed that the AP and DBP are in next neighborhood to each other and are separated by a switch loop. This switch loop adopts distinct conformations in the L, T and O monomers. Specific switch loop conformations are strongly involved in coordinating the selective occupation of both binding pockets, the AP and the DBP. The conformation of the switch loop in the L monomer (L-switch loop) opens the AP and closes the DBP, whereas the conformation of the switch loop in the T monomer (T-switch Loop) opens the DBP and closes the AP. An analysis of all asymmetric AcrB structures indicated that the L-switch loop is able to adopt multiple distinct conformations, whereas the conformation of T-switch loop remained largely congruent in all crystal structures. Moreover, each distinct switch loop conformation, observed in co-crystal structures of AcrB with occupied AP [4, 23], was perfectly adapted to the bound substrate molecule. Therefore, the putatively flexible switch loop is likely to act as an adaptive module and mediates a high binding pocket plasticity without altering the global protein structure. This binding mode is called adaptor-mediated binding mechanism, where an flexible adaptive module (like the switch loop) is able to adapt the surface shape of an binding pocket to different substrate molecules. Furthermore, structural and biochemical analyses of an AcrB G616N variant, revealed the involvement of specific switch loop conformations in the substrate specificity of AcrB. A substitution of G616, located on the switch loop, to N616 was able to alter the conformation of the switch loop exclusively in the L monomers of AcrB, whereas the switch loop conformations in T and O monomers remained congruent to the conformations observed in crystal structures of wildtype AcrB. Moreover, cells producing the AcrB G616N and MexB, both bearing the G616N amino acid substitution, exhibited a reduced resistance against certain substrates, whereas the resistance against most other substrates remained on the level of wildtype AcrB. Correlations of the phenotypes with minimal projection areas, a novel 2-spatiodimensional parameter which approximates the size of a substrate molecule, revealed that AcrB variants with a G616N substitution have a reduced efflux activity for exclusively large substrate molecules. The rejection of large substrates is most likely connected with altered L-switch loop conformations....
Autophagie ist ein evolutionär stark konservierter Degradationsmechanismus für geschädigte Proteine bis hin zu ganzen Organellen eukaryotischer Zellen. Dabei umhüllt eine Doppelmembran, bisher unbekannten Ursprungs, das zu degradierende Material und bildet das Autophagosom. Dies fusioniert später mit Lysosomen, wodurch dessen Inhalt proteolytisch zersetzt und die Bestandteile der Zelle wieder zur Verfügung gestellt werden kann.
In dieser Abeit wurde der Fokus auf den mitochondrialen Abbau über Autophagie (Mitophagie) und dessen Funktion als ein mitochondrialer Qualitätsmechanismus gesetzt. Als Zellmodell wurden primäre humane Endothelzellen der Nabelschnurvene (HUVEC) verwendet. Diese zeichenen sich durch einen Übergang von einer mitotischen, jungen in eine lange postmitotische, seneszente Phase während der Kultiverungszeit aus. Dabei durchlaufen sie einer zelluläre und mitochondriale Morphologieänderung. , wodurch sich die Möglichkeit bot , die Autophagie unter verschiedenen Parametern zu betrachten.
So wird generell eine Abnahme des autophagosomalen / lysosomalen Weges mit dem Alter beschrieben und die Abhängigkeit der Mitophagie von der mitochondrialen Länge.
Mitophagie ist unter normalen Kultivierungsbedingungen ein mikroskopisch selten zu beobachtender Vorgang. Daher wurde ein mitochondriales Schädigungsystem etabliert, welches die photosensibiliesierende Wirkung des Farbstoffs MitoTracker Red Cmx Ros (MTR) nutzt, um Mitochondrien gezielt oxidativ zu schädigen und die Mitophagie zu aktivieren.
Mitotische HUVEC zeigten 2 h – 8 h nach oxidativer Schädigung eine mitochondriale Fragmentierung größtenteils begleitet von einem Verlust des Membranpotentials. Über einen Zeitraum von 72h-120h kam es zur Regeneration des mitochondrialen Netzwerks durch Neusynthese mitochondrialer Biomoleküle. Entgegen der rescue Hypothese konnten oxidativ geschädigte Mitochondrien nicht durch eine Fusion mit funktional intakten Mitochondrien gerettet werden und wurden über den autophagosomalen / lysosomalen Weg abgebaut, gekennzeichnet durch die Ubiquitin-Ligase Parkin vermittelte Markierung und finaler Kolokalisation mit den autophagosomalen und lysosomalen Markerproteinen LC3B und LAMP-2A. Auf mRNA- und Proteinebene zeigte sich in diesem Zeitraum eine erhöhte Expression autophagie-relevanter Gene (ATGs) ATG5, ATG12 und LC3B.
Der Vergleich von mitotischen mit postmitotischen HUVEC nach oxidativer Schädigung wies zwei grundlegende Unterschiede auf.
Zum einem behielten, in Gegensatz zu jungen Zellen, die Mitochondrien alter HUVEC ihre Morphologie und ihr Membranpotential bei. Diese erhöhte Widerstandfähigkeit gegenüber oxidativem Stress konnte auf die erhöhte Expression der mitochondrial lokalisierten Serin / Threonin Kinase PINK1 zurückgeführt werden, ein Schlüsselgen in Parkinson.
Die PINK1-Transkription stand invers zu der Expression der mitochondrialen Teilungsfaktoren Fis1- und Drp1, welche in postmitotischen HUVEC stark vermindert war.
Andererseits wiesen alte Zellen eine verminderte Degradationsfähigkeit geschädigter Mitochondrien auf. Dieser Umstand war durch eine verminderte lysosomale Azidität bedingt. Eine externe ATP-Zugabe förderte die Azidität der Lysosomen alter Zellen und die Fusion mit Autophagosomen, wodurch Mitochondrien und ihre geringere ATP-Produktion im Alter als ein Faktor der Autophagie ermittelt weden konnte.
Die Autophagierate steht in Verbindung mit der Lebensspanne von Zellen bis hin zu ganzen Organismen. Durch die Überexpression autophagie-relevanter GFP-Fusions-Proteine ATG5, ATG12 und LC3B, welche nach oxidativer Schädigung in ihrer Expression verstärkt wurden, förderten die Mitophagie und wurden stabil in junge HUVEC exprimiert. Diese Überexpressionen bewirkten eine verbesserte mitochondriale Qualität, veranschaulicht durch ein erhöhtes Membranpotential und die ATP-Bereitstellung, einer besseren mtDNA Integrität und sie verlängerten die Lebensspanne signifikant, wobei die Produktion von reaktiven Sauerstoffspezien (ROS), entgegen der von Harman aufgestellten Alterungstheorie, keine Verminderung zeigte. Dennoch wiesen sie einen erhöhten Gehalt oxidativ modifizierter Proteine auf, welche letztendlich auf die erhöhten Autophagosomenanzahl zurückgeführt werden konnte, in denen höchstwahrscheinlich das oxidativ geschädigte Material gelagert wird.
In dieser Arbeit kann gezeigt werden, dass Mitochondrien nach oxidativer Schädigung eine Teilung vollziehen und geschädigte Mitochondrien selektiv über Autophagie abgebaut werden. Dabei fungiert Mitophagie als ein mitochondrialer Qualitätmechanismus und steht unmittelbar mit der Lebensspanne in Verbindung.
In der vorliegenden Arbeit konnte gezeigt werden, dass bestimmte neuronale microRNAs im Rückenmark und in den Spinalganglien konstitutiv exprimiert und nach peripherer Entzündung mit Formalin oder Zymosan differenziell reguliert werden. Bei der SNI-induzierten Neuropathie konnte indessen keine signifikante Regulation der untersuchten microRNAs nachgewiesen werden. Aufgrund der Lokalisation in den Neuronen der Schmerz-verarbeitenden Laminae I und II des Dorsalhorns des Rückenmarks und angesichts der Regulation in entzündlich stimulierten Neuronen und Mikroglia wurde der Fokus der Arbeit auf die Untersuchung von microRNA-124a gelegt. Anhand von Expressionsanalysen konnte gezeigt werden, dass eine periphere entzündliche Stimulation mit Formalin oder Zymosan microRNA-124a im Rückenmark inhibiert, die Expression pro-inflammatorischer und pro-nozizeptiver Gene hiernach ermöglicht und ein vermehrtes Schmerzverhalten bewirkt. Die funktionelle Relevanz von microRNA-124a wurde in vivo mittels intravenöser Applikation von microRNA-124a-Modulatoren bei einem Modell für entzündliche Schmerzen, dem Formalin-Modell untersucht. Dabei führte die Hemmung von microRNA-124a zu einem verstärkten Schmerzverhalten, welches mit einer Hochregulation verschiedener Entzündungsmarker einherging. Die Überexpression von microRNA-124a dagegen antagonisierte die Hochregulation entzündlicher Mediatoren und führte zu einer Schmerzhemmung. Darüber hinaus konnte in der vorliegenden Arbeit der antinozizeptive Effekt von microRNA-124a mit der Regulation der Epigenetik-regulierenden Targets MeCP2, HDAC5 und MYST2 assoziiert werden und u.a. über die Hemmung des neuromodulierenden, pro-inflammatorischen Peptids BDNF verifiziert werden. Die spezielle Darreichung von microRNA-124a könnte demzufolge einen vielversprechenden Ansatz zur Therapie chronisch-entzündlicher Schmerzen liefern. Zukünftig werden weitere Studien notwendig sein um die eindeutige Funktion, die individuelle Wirkung sowie die therapeutische Relevanz von microRNA-124a zu analysieren. Darüber hinaus müssten Dosis-Wirkungs-Beziehungen und Nebenwirkungsprofile für microRNA-124a erstellt werden, um potenzielle Risiken, Chancen und Vorteile der microRNA-Modulation hinsichtlich einer humanen Schmerztherapie bewerten zu können.
Metallorganische Netzwerke (engl. metal-organic frameworks, MOFs) sind eine neuartige Klasse mikro/mesoporöser Materialien, für die eine Vielzahl von möglichen Anwendungen demonstriert werden konnte. Das Ziel dieser Arbeit besteht in der Synthese von MOF Mikro/Nanopartikeln sowie der Herstellung von sogenannten Oberflächen-deponierten MOFs (engl. surface-attached metal-organic frameworks, SURMOFs). MOF Partikel mit kontrollierbarer Morphologie und Größe wurden unter milden Bedingungen synthetisiert. Um MOFs als Sensoren, intelligente Membrane, oder in nanotechnologischen Bauelementen verwenden zu können, ist die Integration auf der jeweiligen Oberfläche wichtig. Daher beschäftigt sich der Großteil dieser Arbeit mit der kontrollierten Abscheidung von SURMOFs auf verschiedenartigen Trägermaterialien. Etliche interessante Eigenschaften (z.B. die Fluoreszenz in Abhängigkeit von der Gegenwart von Gastmolekülen und die dynamische Gasadsorptionskapazität) der SURMOFs wurden untersucht.
This research was conducted in the Rwenzori Region of the Western Branch, East African Rift System (EARS). The EARS is a tectonic structure extending over a length of more than 3000 km from the Afar Triple Junction, in Ethiopia, to Lake Malawi in the south. The Western Rift System is a roughly NE to ENE trending sector of the EARS, which runs along the western boundary of Uganda and the neighboring Democratic Republic of Congo (D.R.C). It stretches 2100 km from Nimule, NW on Uganda-Sudan border, extending to Lake Malawi in the SE of Africa. The unusual uplift of the Rwenzori Mountains within an extensional regime and the mechanisms associated with the high frequency of seismic activity in the region was hardly understood and therefore, had remained a subject of contention that needed to be critically addressed in detail. To my knowledge, this was probably the first study to be performed and documented in great depth within the domains of seismic noise variation, seismic anisotropy and b value analyses beneath the Rwenzori Region. After about six years of operation (2006-2012), the seismology group of the RIFTLINK Research Project (www.riftlink.org) acquired a vast amount of high-quality, digital data that were collected using a seismic network of well calibrated seismic equipment. The project was divided into two phases. Phase I, that operated between February 2006 - September 2007, consisted of thirty-two temporary seismic stations, which were selectively spread out in the Rwenzori Region on the Ugandan side, to detect and record extremely weak as well as strong naturally occurring earthquakes. The seismic equipment used included EDL and REFTEK digitizers, which were coupled with Güralp and MARK sensors respectively (REFTEKS: only short-period MARK sensors, EDLs: short-period MARK plus few broadband Güralp Sensors). Exactly 22375 earthquakes were recorded. The data were processed using the SEISAN software package. About 14413 earthquakes were carefully localized using the velocity model of Bram (1975) that implements a Vp=Vs ratio fixed at 1.74. Phase II, that extended between 2009-2012 consisted of thirty-two seismic stations, which were spread out around the Rwenzori Mountains, both on the Ugandan side and the neighboring D.R.C. Only Taurus digitizers that were coupled with Trillium sensors were used in the D.R.C. On the Ugandan side however, both EDL and Taurus digitizers, which were coupled with Trillium and Güralp sensors were used. ...
Calcium-deficiency rickets (CDR) is a metabolic bone disease in children that is characterized by impaired mineralization and severe bone deformities. As CDR is often an endemic phenomenon that is almost exclusively restricted to tropical areas, environmental conditions are currently considered to be a possible predisposing factor for the CDR. Apart from a lack of macronutrients and micronutrients, an oversupply of potentially toxic elements (PTEs) in the soil-plant pathway of the CDR areas is thought to be involved in the aetiology of CDR. This study is the first to comprehensively analyze the impact of the environment on Ca deficiency and the resulting CDR.
To analyze the impact of the environment on CDR in developing countries, a rural region near Kaduna City, northern Nigeria, was chosen as a study area. From this area, cases of CDR have been reported since the early 2000s with a prevalence rate of 5%. Within this study area, 11 study sites, including areas with a high CDR prevalence (HR), a low CDR prevalence (LR) and no CDR prevalence (NR), were visited. In these HR, LR and NR study sites, the bedrock was investigated and the types of parent materials were identified. Local farmers were interviewed to determine the type and intensity of the land use. The soil types were determined along toposequences. The soil textures as well as the clay mineral fractions were determined. The pH values were measured, and the contents of organic carbon (OC) were determined. The potential cation-exchange capacity (CECpot) and the base saturation (BS) were analyzed. Furthermore, the total and plant-available macronutrient, micronutrient and PTE concentrations were measured in the soils. The drinking water was analyzed for pH values and the concentrations of Ca, Se and F were measured. The maize was analyzed for the Ca, Mg, K and P, Se and phytic acid (PA) contents.
The field and laboratory analyses on the bedrock showed that the HR, LR and NR study sites near Kaduna City, northern Nigeria, were underlain by Older Granites. A direct link between the distribution of the bedrock, the parent materials and the prevalence of CDR was not found. Interviews with the local farmers showed that the land use in the Kaduna study area is dominated by the cultivation of cash crops and food crops. Field analyzes on the soil types in the Kaduna study area showed that the distribution of the soil types is highly dependent on the topography and the distribution of the parent materials. In near vicinity to the inselbergs, Lixisols had developed on grus slope deposits. In the lower pediment and plain positions, Acrisols had developed on grus slope deposits and pisolite slope deposits. In the upper plains, Plinthosols had developed on pisolite slope deposits and in the river valleys, Fluvisols had developed on river deposits. Such soil types and soil type distributions are typical for granite-underlain areas in the northern guinea savanna of West Africa. Similarly, the physical soil conditions were representative for the soils of the northern guinea savanna: sandy topsoils, clayey subsoils and relatively high contents of kaolinite clay minerals in the clay fractions. With regard to the geochemical composition, no significant difference was found between the soils of the Kaduna study area and the soils of other granite-underlain areas in West Africa. Only the concentrations of P were considerably low in the soils of the Kaduna study area. However, P deficiency is a typical phenomenon in West African savanna soils and is not restricted to CDR areas. The micronutrient concentrations in the soils were low, but not critically low. Laboratory analyses on the amounts of PTEs showed that compared to worldwide background levels and international critical limits the PTE concentrations were very low in the soils of the Kaduna study area. In the drinking water, neither a significant lack of macronutrients and micronutrients, nor a noticeable oversupply of PTEs was found. The maize in the HR, LR and NR study sites contained normal contents of Mg, K and P, low contents of Ca and Se as well as slightly elevated concentrations of PA compared to West African food composition tables. Comparisons between the mineral contents of traditional and modern maize cultivars showed that the traditional maize cultivars contained significantly higher contents of Ca and noticeably lower concentrations of PA than the modern maize cultivars.
A direct link between the environmental conditions and the CDR in the Kaduna study area was considered unlikely, as neither a statistically significant lack of macronutrients and micronutrients, nor a statistically significant oversupply of PTEs was found in the environment of this area. Instead, the results indicated that the nutrition rather than the environmental conditions that impacts the prevalence of CDR.