Molecular characterization of a spontaneously generated new allele at a VNTR locus: no exchange of flanking DNA sequence

Variable-number tandem-repeat (VNTR) DNA markers are contributing new power to human genetic studies because their hypervariable nature allows individualization at the DNA level. The practical value of VNTR markers has been well established for genetic linkage mapping, forensic biology, paternity testing, and monitoring of bone marrow transplants. A popular hypothesis attributes generation of variability at VNTR loci to unequal exchange between homologous chromosomes at meiosis. Contrary to the prediction of this hypothesis, we report here the finding that a newly generated VNTR allele is parental for closely spaced flanking markers; the new allele was generated by loss of one repeat unit, without exchange of flanking DNA sequences. These results are consistent with sister chromatid exchange and polymerase slippage or deletion, as well as with some models for gene conversion.     

Amyloid β Oligomeric Species Present in the Lag Phase of Amyloid Formation

Alzheimer’s disease (AD)-associated amyloid β peptide (Aβ) is one of the main actors in AD pathogenesis. Aβ is characterized by its high tendency to self-associate, leading to the generation of oligomers and amyloid fibrils. The elucidation of pathways and intermediates is crucial for the understanding of protein assembly mechanisms in general and in conjunction with neurodegenerative diseases, e.g., for the identification of new therapeutic targets. Our study focused on Aβ42 and its oligomeric assemblies in the lag phase of amyloid formation, as studied by sedimentation velocity (SV) centrifugation. The assembly state of Aβ during the lag phase, the time required by an Aβ solution to reach the exponential growth phase of aggregation, was characterized by a dominant monomer fraction below 1 S and a population of oligomeric species between 4 and 16 S. From the oligomer population, two major species close to a 12-mer and an 18-mer with a globular shape were identified. The recurrence of these two species at different initial concentrations and experimental conditions as the smallest assemblies present in solution supports the existence of distinct, energetically favored assemblies in solution. The sizes of the two species suggest an Aβ42 aggregation pathway that is based on a basic hexameric building block. The study demonstrates the potential of SV analysis for the evaluation of protein aggregation pathways.     

Deoxynivalenol (DON)- und Zearalenon (ZEA)-Gehalte in Weizen, Roggen und Triticale: Ergebnisse aus der Besonderen Ernteermittlung (BEE) 2001 und 2002

Deoxynivalenol and Zearalenone contents were determined in wheat, rye and triticale samples which were representative of the 2001 and 2002 harvests in Germany. The frequency of DON and ZEA detection and the mean levels of these toxins were higher in wheat, rye and triticale in 2002 in comparison to 2001. The influence of varieties and preceding crop on DON contents in wheat and triticale is presented.

Presented at the 25th Mykotoxin-Workshop in Giessen, Germany, May 19–21, 2003     

Lack of association between glucocorticoid use and presence of the metabolic syndrome in patients with rheumatoid arthritis: a cross-sectional study

Lupus nephritis is a major contributor to morbidity and mortality in systemic lupus erythematosus, but little is known about the pathogenic processes that underlie the progressive decay in renal function. A common finding in lupus nephritis is thickening of glomerular basement membranes associated with immune complex deposition. It has been speculated that alterations in the synthesis or degradation of membrane components might contribute to such changes, and thereby to initiation and progression of nephritis through facilitation of immune complex deposition. Matrix metalloproteinases (MMPs) are enzymes that are intimately involved in the turnover of major glomerular basement membrane constituents, including collagen IV and laminins. Alterations in the expression and activity of MMPs have been described in a number of renal diseases, suggesting their relevance to the pathogenesis of various glomerulopathies. The same is true for their natural inhibitors, the tissue inhibitor of metalloproteinase family. Recent data from our group have identified an increase in proteolytic activity within the glomerulus coinciding with the development of proteinuria in the mouse model of systemic lupus erythematosus. (NXB × NZW)F₁ Here we review current understanding of MMP/tissue inhibitor of metalloproteinase function within the kidney, and discuss their possible involvement in the development and progression of lupus nephritis.     

Human monoclonal antibody homodimers. Effect of valency on in vitro and in vivo antibacterial activity.

Human IgG1 mAb dimers specific for either group B streptococci or Escherichia coli K1 bacteria were formed using chemical cross-linkers. The effect of antibody valency on biologic efficacy was investigated by comparing the IgG dimers against the corresponding IgG monomers. Binding activity and relative avidity were assessed using Ag binding and competition ELISA, and functional activity was analyzed using opsonophagocytic assays. These in vitro assays revealed that the dimers were greater than or equal to 50-fold more active than the monomers. A neonatal rat infection model showed the in vivo protective efficacy of the dimers was greater than or equal to 20-fold greater than that of the monomers. Enhancing the activity of mAb by chemical cross-linking may be a useful strategy for salvaging low affinity IgG mAb that possess poor functional properties.     

Delimiting the frequency of paternal leakage of mitochondrial DNA in chinook salmon

We analyzed embryos of a wild-return hatchery population of chinook salmon for the presence of paternal mtDNA. None of the 10,082 offspring examined revealed paternally transmitted DNA, delimiting the maximum frequency of paternal leakage in this system to 0.03% (power of 0.95) and 0.05% (power of 0.99).     

Lost in the zygote: the dilution of paternal mtDNA upon fertilization

The mechanisms by which paternal inheritance of mitochondrial DNA (mtDNA) (paternal leakage) and, subsequently, recombination of mtDNA are prevented vary in a species-specific manner with one mechanism in common: paternally derived mtDNA is assumed to be vastly outnumbered by maternal mtDNA in the zygote. To date, this dilution effect has only been described for two mammalian species, human and mouse. Here, we estimate the mtDNA content of chinook salmon oocytes to evaluate the dilution effect operating in another vertebrate; the first such study outside a mammalian system. Employing real-time PCR, we determined the mtDNA content of chinook salmon oocytes to be 3.2 x 10(9)+/-1.0 x 10(9), and recently, we determined the mtDNA content of chinook salmon sperm to be 5.73+/-2.28 per gamete. Accordingly, the ratio of paternal-to-maternal mtDNA if paternal leakage occurs is estimated to be 1:5.5 x 10(8). This contribution of paternal mtDNA to the overall mtDNA pool in salmon zygotes is three to five orders of magnitude smaller than those revealed for the mammalian system, strongly suggesting that paternal inheritance of mtDNA per offspring will be much less likely in this system than in mammals.     

Concurrent evolution of ancient sister lakes and sister species: the freshwater gastropod genus <Emphasis Type="Italic">Radix</Emphasis> in lakes Ohrid and Prespa

Ancient sister lakes are considered to be ancient lakes lying in close geographic proximity, sharing a related origin and significant time of co-existence, usually having hydrological connection as well as a balanced degree of faunal overlap and distinctness. A paradigm for studying sister lake relationships are the ancient lakes Ohrid and Prespa in the Balkans, which are characterized by high degrees of endemicity. Three general patterns of endemic species can be distinguished for these lakes: (1) taxa that are endemic to either lake, with no close relatives in the respective sister lake, (2) closely related but distinct endemic taxa in both lakes (sister species) and (3) shared endemic taxa occurring in both lakes. In the present paper, two endemic freshwater pulmonate gastropod species, Radix relicta (Lake Ohrid) and R. pinteri (Lake Prespa), are used to study the evolution of presumed sister species based on biogeographical and comparative DNA data from world-wide Radix taxa. Phylogenetic, phylogeographical and parametric bootstrap analyses all suggest a sister group relationship of R. relicta and R. pinteri (pattern 2 of endemic diversity). Sister to these two taxa is the widespread R. ampla, which does not occur in the vicinity of lakes Ohrid and Prespa. The southern feeder spring complexes of Lake Ohrid are inhabited by another lineage (Radix sp. 1), which resembles Radix relicta in morphology/anatomy. For Lake Prespa, the widespread R. auricularia was reported in addition to the endemic R. pinteri. Comparative phylogenetic data favour a western Adriatic zoogeographical affinity of lakes Ohrid and Prespa over an Aegean-Anatolian faunal connection. The status of lakes Ohrid and Prespa as sister lakes is evaluated in the light of current knowledge on gastropod speciation and endemism in these hotspots of biodiversity.