Dopamine D4 receptor polymorphism and idiopathic Parkinson's disease

Patients with idiopathic Parkinson's disease (IPD) are described as having markedly decreased novelty seeking characteristics. Since recent publications suggest an association between the dopamine D4 receptor polymorphism and novelty seeking, we investigated this polymorphism in a group of 122 patients with IPD and 127 healthy control subjects. We found similar allele and genotype frequencies in both groups and no association with the age of onset of symptoms. Therefore, the dopamine D4 receptor polymorphism does not confer genetic susceptibility to IPD and cannot explain the decreased novelty seeking in IPD patients.     

Systematic investigations on the reactivity of oxazolinium salts

The termination reaction of the cationic polymerization of 2-phenyl- and 2-nonyl-2-oxazolines was examined by reacting the corresponding model oxazolinium salts having tosylate and trifluoromethansulfonate counterions with various nucleophiles. The reaction was monitored by ¹H NMR spectroscopy. Piperidine and KOH react with the oxazolinium salts very fast and quantitatively. In the case of piperidine, the use of a double molar amount of piperidine is necessary to achieve complete conversion. The addition of piperidine, pyridine, 4-dimethylaminopyridine and morpholine takes place in position 5 of the oxazolinium ring, whereas water and KOH add in position 2. The rate of the termination reaction depends on the electron density of the nucleophile which can be correlated with the pK_a value. With CF₃SO as counterion the addition of nucleophiles in position 5 is distinctly faster, whereas the addition of water in position 2 is much slower than with TsO^? as counterion. The ring-opening of the nonyl oxazolinium ion is slower than that of the phenyl oxazolinium ion.     

Sequence variation and size ranges of CAG repeats in the Machado-Joseph disease, spinocerebellar ataxia type 1 and androgen receptor genes

A subgroup of trinucleotide repeat diseases result from abnormalexpansions of CAG repeats which are translated into polyglutaminestretches. As yet there is little understanding of how the polyglutaminesfunction either normally, or when expanded. We have investigatedthese sequences in the Machado-Joseph disease, androgen receptorand spinocerebellar ataxia type 1 genes in humans and otherprimates. None of the 748 normal chromosomes that were examinedhad more than 34 uninterrupted gluta-mine codons in the Machado-Josephdisease gene. Similarly, no normal alleles with more than 39uninterrupted glutamine codons have been reported for the otherdisease genes associated with polyglutamine expansions. Sequenceanalyses of the repeats in primates revealed shorter polyglutaminestretches in some of the non-human primates at all three lociand marked diversions from the expected polyglutamines in theorang-utan Machado-Joseph gene and in the marmoset spinocerebellarataxia type 1 gene. These data suggest that conservation ofthese polyglutamine stretches may not always be necessary fornormal gene function.     

The myelin basic protein-specific T cell repertoire in (transgenic) Lewis rat/SCID mouse chimeras: preferential Vβ8.2 T cell receptor usage depends on an intact Lewis thymic microenvironment

In the Lewis rat, myelin basic protein (MBP)-specific, encephalitogenic T cells preferentially recognize sequence 68–88, and use the Vβ8.2 gene to encode their T cell receptors. To analyze the structural prerequisites for the development of the MBP-specific T cell repertoire, we reconstituted severe-combined immunodeficient (SCID) mice with fetal (embryonic day 15–16) Lewis rat lymphoid tissue, and then isolated MBP-specific T cell lines from the adult chimeras after immunization. Two types of chimera were constructed: SCID mice reconstituted with rat fetal liver cells only, allowing T cell maturation within a chimeric SCID thymus consisting of mouse thymic epithelium and rat interdigitating dendritic cells, and SCID mice reconstituted with rat fetal liver cells and rat fetal thymus grafts, allowing T cell maturation within the chimeric SCID and the intact Lewis rat thymic microenvironment. Without exception, the T cell lines isolated from MBP-immunized SCID chimeras were restricted by MHC class II of the Lewis rat (RT1.B¹), and none by I-A^d of the SCID mouse. Most of the T cell lines recognized the immunodominant MBP epitope 68–88. In striking contrast to intact Lewis rats, in SCID mice reconstituted by rat fetal liver only, MBP-specific T cell clones used a seemingly random repertoire of Vβ genes without a bias for Vβ8.2. In chimeras containing fetal Lewis liver plus fetal thymus grafted under the kidney capsule, however, dominant utilization of Vβ8.2 was restored. The migration of liver-derived stem cells through rat thymus grafts was documented by combining fetal tissues from wild-type and transgenic Lewis rats. The results confirm that the recognition of the immunodominant epitope 68–88 by MBP-specific encephalitogenic T cells is a genetically determined feature of the Lewis rat T cell repertoire. They further suggest that the formation of the repertoire requires T cell differentiation in a syngeneic thymic microenvironment.     

Enhancement of death-receptor induced caspase-8-activation in the death-inducing signalling complex by uncoupling of oxidative phosphorylation

Signalling through the death receptor CD95 induces apoptosis by formation of a signalling complex at the cell membrane and subsequent caspase-8 and caspase-3-activation. Treatment of Jurkat T cells with protonophores across the mitochondrial membrane such as 2,4-dinitrophenol (DNP) enhances the death-inducing capacity of CD95. In this study, we show that this enhancement is due to the specific acceleration of caspase-8-processing and activation at the CD95-receptor. DNP-treatment did not affect NF-kappaB-induction by CD95. Immunoprecipitation experiments showed that the amounts of the adapter FADD/MORT1 and pro-caspase-8 at the CD95-receptor were not altered by DNP. Subcellular fractionation studies revealed that the amount of mature caspase-8 but not pro-caspase at the membrane was increased following CD95-stimulation in the presence of DNP. As a consequence of caspase-activation, c-FLIP-levels in the cytosol decreased. In Jurkat cells overexpressing c-FLIPS, DNP was still able to enhance caspase-activation. The enhancing capacity of DNP was seen in some cell lines (Jurkat, CEM and HeLa) but not in SKW6 cells and was also found in mitogen-stimulated human T cells. Furthermore, the enhancement extended to TRAIL-induced caspase-activation. Thus, a mechanism exists by which caspase-8-activation can be accelerated at death receptors and this mechanism can be triggered by targeting mitochondrial oxidative phosphorylation.     

Sleep and memory consolidation: The role of electrophysiological neuroimaging

Summary Memory consolidation involves a complex series of molecular, cellular and network-level processes that take place on time scales from millisecond to months. Evidence from a wide range of experimental observations supports the hypothesis that parts of these processes occur during sleep when the brain is not engaged in processing and encoding incoming information. Indeed, sleep seems to be favorable for brain plasticity. Experience-dependent cortical plasticity observed during sleep has been hypothesized to be part of the global process of memory consolidation. Thus, studying task-dependent, regionally specific reactivation of neuronal assemblies during posttraining sleep may make important contributions to elucidating the role of sleep in memory trace processing. A new methodology – low-resolution brain electromagnetic tomography (LORETA) – offers the possibility of localizing electrical activity produced by cortical neuronal generators under normal (undisturbed) sleeping conditions. The high time resolution of brain electrical data can be exploited to produce neuroimages for specific EEG spectral frequency bands (e.g. delta, theta, or spindle bands). This makes it possible to investigate, dependent on the type of memory, when – in which sleep stages (S2 sleep, SWS, REM sleep) – and where – in which cortical brain regions (primary sensory cortex, higher association cortex) – experience-dependent reactivation occurs.     

Light controlled solubility change of polymers: Copolymers of N,N-dimethylacrylamide and 4-phenylazophenyl acrylate

Copolymers of N,N-dimethylacrylamide (DMA) and 4-phenylazophenyl acrylate (PAPA) have been prepared by free-radical copolymerization in dioxane (DMAP-x). The molecular weights of the copolymers show a strong decrease with increasing azobenzene content due to the retardation effect of the azobenzene group. An analogous decrease in molecular weight was found with a number of polymers of DMA which were polymerized in the presence of the non-polymerizable model 4-phenylazophenyl propionate (PAPP). We were able to induce a lower critical solution temperature (LCST) above a certain content of azobenzene moieties in the copolymers (DMAP-x) in contrast to the good water solubility of poly(DMA). Due to the reversible photoisomerization and the concomitant change in the dipole moment of the azobenzene moieties, the LCST depends not only on the content of azobenzene but also on the degree of isomerization. A difference in the LCST up to 20°C was found for dark adapted polymer solutions (0% Z-isomer) and polymer solutions in the photostationary state (ca. 85% Z-isomer). Within this temperature range the polymer can be precipitated by irradiation with light.     

Characterization of a population of small macrophages in induced sputum of patients with chronic obstructive pulmonary disease and healthy volunteers

The inflammatory process in chronic obstructive pulmonary disease (COPD) is active mainly in the airways, but little is known about the properties of the inflammatory cells in this compartment. We have studied leucocytes in induced sputum of COPD patients compared to controls in order to uncover what types of macrophages might be involved in the disease. Sputum induction was performed by inhalation of nebulized sodium chloride solution. Leucocytes were isolated and stained with specific monoclonal antibodies for analysis in flow cytometry. Flow cytometry analysis revealed that a major portion of CD14+ macrophages in COPD has lower forward scatter, i.e. they are small macrophages. While in control donors these small macrophages accounted for 6.9% of all macrophages, the percentage of these cells in COPD was 45.7%. CD14 and HLA-DR expression was high on these small sputum macrophages while the large sputum macrophages expressed only low levels of these surface molecules, both in control donors and COPD patients. Small sputum macrophages of both control donors and COPD patients showed higher levels of constitutive tumour necrosis factor (TNF) compared to the large macrophages. TNF was inducible by lipopolysaccharide (LPS) preferentially in the small sputum macrophages in the control donors but there was no further induction in COPD patients. These data show that the small sputum macrophages are a major macrophage population in COPD and that these cells exhibit features of highly active inflammatory cells and may therefore be instrumental in airway inflammation in COPD.