New Developments in Cholinergic Imaging in Alzheimer and Lewy Body Disorders

PURPOSE OF REVIEW

This paper aims to review novel trends in cholinergic neuroimaging in Alzheimer and Lewy body parkinsonian disorders.

RECENT FINDINGS

The spectrum of cholinergic imaging is expanding with the availability of spatially more precise radioligands that allow assessment of previously less recognized subcortical and cortical structures with more dense cholinergic innervation. In addition, advances in MRI techniques now allow quantitative structural or functional assessment of both the cholinergic forebrain and the pedunculopontine nucleus, which may serve as non-invasive prognostic predictors. Multimodal imaging approaches, such as PET-MRI or multiligand PET offer new insights into the dynamic and interactive roles of the cholinergic system at both local and larger-scale neural network levels.

SUMMARY

Our understanding of the heterogeneous roles of the cholinergic system in age-related diseases is evolving. Multimodal imaging approaches that provide complimentary views of the cholinergic system will be necessary to shed light on the impact of cholinergic degeneration on regional and large-scale neural networks that underpin clinical symptom manifestation in neurodegeneration.

Recent advances in cholinergic imaging and cognitive decline-Revisiting the cholinergic hypothesis of dementia

PURPOSE OF REVIEW

Although the cholinergic hypothesis of dementia provided a successful paradigm for the development of new drugs for dementia, this hypothesis has waned in popularity. Cholinergic brain imaging may provide novel insights into the viability of this hypothesis.

RECENT FINDINGS

Cholinergic receptor and forebrain volumetric studies suggest an important role of the cholinergic system in maintaining brain network integrity that may deteriorate with cognitive decline in Alzheimer disease (AD) and Lewy body disorders (LBD). Bidirectional changes in regional receptor expression may suggest the presence of compensatory responses to neurodegenerative injury. Cholinergic system changes are more complex in LBD because of additional subcortical degenerations compared to AD. Cholinergic-dopaminergic interactions affect attentional, verbal learning and executive functions, and impairments in these two transmitter systems may jointly increase the risk of dementia in Parkinson disease.

SUMMARY

The cholinergic hypothesis is evolving from a primary focus on memory toward expanded cognitive functions modulated by regionally more complex and interactive brain networks. Cholinergic network adaptation may serve as a novel research target in neurodegeneration.

Association of Cardinal Motor Symptoms with Region-Specific Dopamine Transporter Activity in Mild to Moderate Parkinson's Disease

OBJECTIVE

To investigate the relationship between measures of the cardinal motor features and the degree of nigrostriatal dopaminergic denervation in patients with mild to moderate Parkinson's disease (PD).

METHODS

PD patients (Hoehn and Yahr stages I-III, n = 27) underwent ¹¹C-β-CFT dopamine transporter (DAT) positron emission tomography. Clinical examination included the Unified PD Rating Scale (UPDRS) motor examination with sub-scores for the cardinal motor features of PD, grooved pegboard, and finger- and foot-tapping scores. Postural sway was also assessed. Patients on dopaminergic drugs were studied in the "off" state.

RESULTS

Lower total striatal DAT binding was associated with higher UPDRS motor scores, slower performance on the grooved pegboard, and higher variability of postural sway. UPDRS subscale scores for rigidity and tremor, and foot- and finger tapping did not significantly correlate with striatal DAT binding. Thalamic DAT binding correlated with finger-tapping (r = 0.532, p = 0.005) and foot-tapping scores (r = 0.474, p = 0.017). Regional striatal analysis showed that ventral striatal DAT binding robustly correlated with UPDRS total motor (r = -0.507, p = 0.007) and grooved pegboard (r = -0.567, p = 0.002) performance. Posturography analysis showed increased sway variability with decreased posterior putamen DAT activity (r = -0.475, p = 0.019).

CONCLUSION

These findings indicate that the nigrostriatal dopaminergic model of PD has limited correlations with the motor features of this disorder. Although nigrostriatal patterns of denervation may explain some of these findings, a more comprehensive model of parkinsonian motor impairments likely involves extra-striatal dopaminergic and non-dopaminergic mechanisms.

Advances in Therapeutic Options for Gait and Balance in Parkinson's Disease

There is a need to explore non-dopaminergic approaches to treating balance and gait problems in PD. There is emerging evidence on the role of cholinergic denervation of the PPN-thalamus system and falls in PD. Preliminary clinical trial data suggest that the subgroup of PD patients with frequent falls may be suitable candidates for future cholinergic augmentation clinical trials. Recent controlled clinical trials using methylphenidate have been unable to confirm earlier reports of improved gait in PD. Although progressive deterioration of axial motor symptoms occur with DBS of the STN or GPi, new preliminary research suggests that other surgical stimulation sites, such as the PPN, may have a potential benefit on gait and balance impairments in PD. Ongoing vigorous exercise and physical fitness should be highly encouraged to patients with PD who are at risk of physical deconditioning and fear of falling but effective anti-fall physical therapy interventions remain an unmet clinical need.

Forty-two novel COL7A1 mutations and the role of a frequent single nucleotide polymorphism in the MMP1 promoter in modulation of disease severity in a large European dystrophic epidermolysis bullosa cohort

BACKGROUND

Dystrophic epidermolysis bullosa (DEB) is a severe genetic skin blistering disorder caused by mutations in the gene COL7A1, encoding collagen VII. Recently, the MMP1 promoter single nucleotide polymorphism (SNP) rs1799750, designated as 1G 2G, was shown to be involved in modulation of disease severity in patients with recessive DEB (RDEB), and was proposed as a genetic modifier.

OBJECTIVES

To identify the molecular basis of DEB in 103 individuals and to replicate the results of the MMP1 promoter SNP analysis in an independent patient group, as verification is necessary in such a rare and heterogeneous disorder.

METHODS

To determine the molecular basis of the disease, we performed COL7A1 mutation screening, reverse transcription-polymerase chain reaction (PCR) and real-time quantitative PCR. The status of the MMP1 SNP was analysed by PCR and restriction enzyme digestion and verified by sequencing.

RESULTS

We disclosed 42 novel COL7A1 mutations, including the first large genomic deletion of 4 kb affecting only the COL7A1 gene, and three apparently silent mutations affecting splicing. Even though the frequency of the high-risk allele was increased in patients with RDEB, no statistically significant correlation between disease severity and genotype could be made. Also, no correlation was observed with development of squamous cell carcinoma, a severe complication of DEB.

CONCLUSIONS

Taken together, the results suggest that the MMP1 SNP is not the sole disease modifier in different forms of DEB, and other genetic and environmental factors contribute to the clinical phenotype.

Introduction of diagnosis-related groups in Germany: evaluation of impact on in-patient care in a dermatological setting

BACKGROUND

German diagnosis-related groups (G-DRG) have been introduced in Germany as a reimbursement system for in-patient care. The aim of this study was to report data-based experiences from the introduction process and to evaluate the impact on in-patient dermatology.

METHODS

A quantitative analysis including clinical data from two large university centres of dermatology over a time period of 4 years (2003-06) has been performed. Characteristics and trends of case-mix index, number of cases, average age, length of stay (LOS), surgical and medical treatments and in-patient case groups were studied in detail.

RESULTS

It was found that the case-mix index values increased after the introduction period, but subsequently declined on the initial value. At the same time, an increase of dermatological hospital admissions can be noticed parallel to a significant reduction of LOS (P < 0.001) and a moderate increase of average age (P < 0.001). Analysis of DRG assignment revealed an initial significant decline of surgical in-patient procedures and increasing medical treatments, however, without obvious long-term changes. Furthermore, a growing importance for dermatological oncology and inflammable skin diseases within the in-patient setting could be observed.

CONCLUSIONS

The introduction of the G-DRG system in Germany induced changes in in-patient care affecting hospital admission rates, LOS and cases treated in an in-patient setting. In-patient activities have not been reduced with the DRG introduction; however, long-term interdisciplinary research approaches are needed to explore the future impact on health care providing and quality of health care in depth.

Regulation of the lemon-fruit V-ATPase by variable stoichiometry and organic acids

The lemon-fruit V-ATPase can exist in two forms: nitrate-sensitive and nitrate-insensitive. Here we report the results of measurements of H+ /ATP stoichiometries using two kinetic methods: one based on steady-state DpH and one based on initial rates of H+-pumping. Our findings indicate that the nitrate-insensitive fruit V-ATPase has an H+ /ATP stoichiometry of ~1, while both the nitrate-sensitive fruit V-ATPase and the epicotyl V-ATPase have stoichiometries of 2, under zero-load conditions. As DpH increases, the stoichiometry of the nitrate-sensitive fruit V-ATPase decreases to 1. Under similar conditions, the stoichiometry of the epicotyl enzyme remains 2. Thus, the pH-dependent variable stoichiometry of the lemon-fruit V-ATPase may represent a key factor in juice sac vacuolar hyperacidification. On the other hand, the H+ /ATP stoichiometry of the epicotyl V-ATPase can decrease from 2 to 1 in the presence of a membrane potential. The low pH of the fruit vacuole is not due solely to the lower H+/ATP stoichiometry of its pump. We show that lumenal citrate and malate improve the coupling of both the epicotyl and fruit V-ATPases and enhance their ability to generate a pH gradient. Since citrate accumulation is restricted to fruit vacuoles, it may be another important determinant of vacuolar pH.

Optimizing coding quality: the role of the electronic medical record in the context of diagnosis related groups

In 2003, a new prospective payment system will be introduced in Germany, which is based on the Australian Refined Diagnosis related Groups (AR-DRGs). Physicians must code diagnoses and procedures themselves. Inaccurately or incompletely coded patient records can result in considerable underpayment, so enhancing physicians' coding compliance and competence seems crucial. Coding shall be well integrated in the electronic patient record, providing a simple interface with background information, which is invoked out of the clinical documentation. This paper describes an existing implementation and possible further development.

Towards integration of clinical decision support in commercial hospital information systems using distributed, reusable software and knowledge components

PROBLEM

Clinicians' acceptance of clinical decision support depends on its workflow-oriented, context-sensitive accessibility and availability at the point of care, integrated into the Electronic Patient Record (EPR). Commercially available Hospital Information Systems (HIS) often focus on administrative tasks and mostly do not provide additional knowledge based functionality. Their traditionally monolithic and closed software architecture encumbers integration of and interaction with external software modules. Our aim was to develop methods and interfaces to integrate knowledge sources into two different commercial hospital information systems to provide the best decision support possible within the context of available patient data.

METHODS

An existing, proven standalone scoring system for acute abdominal pain was supplemented by a communication interface. In both HIS we defined data entry forms and developed individual and reusable mechanisms for data exchange with external software modules. We designed an additional knowledge support frontend which controls data exchange between HIS and the knowledge modules. Finally, we added guidelines and algorithms to the knowledge library.

RESULTS

Despite some major drawbacks which resulted mainly from the HIS' closed software architectures we showed exemplary, how external knowledge support can be integrated almost seamlessly into different commercial HIS. This paper describes the prototypical design and current implementation and discusses our experiences.

Telepathology network: conceptual groundwork and evaluation

Telepathology uses telecommunication technology to transmit microscopic images for diagnostic or teaching purposes. Basic requirements for a telepathology system are described. Usage scenarios for a telepathology network are presented including applications in intraoperative frozen section diagnosis, scientific collaboration and computer based training. Results of an evaluation of 4 currently available telepathology systems are presented.

Integrating knowledge based functionality in commercial hospital information systems

Successful integration of knowledge-based functions in the electronic patient record depends on direct and context-sensitive accessibility and availability to clinicians and must suit their workflow. In this paper we describe an exemplary integration of an existing standalone scoring system for acute abdominal pain into two different commercial hospital information systems using Java/Corba technolgy.

[Electronic documentation in medicine; flexible concepts versus isolated solutions]

Computer-based medical documentation so far proved advantageous especially through standardization of data entry and increased access speed. Additional benefits can be achieved through the implementation of integrated, cross-project documentation tools and their integration into the clinical work-flow, which allow data to be used for a wide variety of applications (e.g. quality management, clinical research, clinic management). The presence of incompatible documentation software often complicates the realization of these goals. Implementation of new documentation tools therefore should consider flexibility and multiple-use of data as primary design goals. In the presented paper requirements for flexible documentation tools are introduced. The Entity-Attribute-Value-Model is described as a possible means of implementation. Practical experiences made with a prototype application are reported.

The vacuolar H+-ATPase of lemon fruits is regulated by variable H+/ATP coupling and slip

Lemon fruit tonoplasts, unlike those of seedling epicotyls, contain nitrate-insensitive H+-ATPase activity (Müller, M. L., Irkens-Kiesecker, U., Rubinstein, B., and Taiz, L. (1996) J. Biol. Chem. 271, 1916-1924). However, the degree of nitrate-insensitivity fluctuates during the course of the year with a seasonal frequency. Nitrate uncouples H+ pumping from ATP hydrolysis both in epicotyls and in nitrate-sensitive fruit V-ATPases. Neither bafilomycin nor oxidation cause uncoupling. The initial rate H+/ATP coupling ratios of epicotyl and the nitrate-sensitive fruit proton pumping activities are the same. However, the H+/ATP coupling ratio of the nitrate-insensitive fruit H+ pumping activity is lower than that of nitrate-sensitive and epicotyl V-ATPases. Several properties of the nitrate-insensitive H+-ATPase of the fruit indicate that it is a modified V-ATPase rather than a P-ATPase: 1) insensitivity to low concentrations of vanadate; 2) it is initially strongly uncoupled by nitrate, but regains coupling as catalysis proceeds; 3) both the nitrate-sensitive and nitrate-insensitive fruit H+-pumps have identical Km values for MgATP, and show similar pH-dependent slip and proton leakage rates. We conclude that the ability of the juice sac V-ATPase to build up steep pH gradients involves three factors: variable coupling, i.e. the ability to regain coupling under conditions that initially induce uncoupling; a low pH-dependent slip rate; the low proton permeability of the membrane.

Differential immunological cross-reactions with antisera against the V-ATPase of Kalanchoë daigremontiana reveal structural differences of V-ATPase subunits of different plant species

Two antisera (ATP88 and ATP95) raised against the V-ATPase holoenzyme of Kalanchoë daigremontiana were tested for their cross-reactivity with subunits of V-ATPases from other plant species. V-ATPases from Kalanchoë blossfeldiana, Mesembryanthemum crystallinum, Nicotiana tabacum, Lycopersicon esculentum, Citrus limon, Lemna gibba, Hordeum vulgare and Zea mays were immunoprecipitated with an antiserum against the catalytic V-ATPase subunit A of M. crystallinum. As shown by silver staining and Western blot analysis with ATP88, subunits A, B, C, D and c were present in all immunoprecipitated V-ATPases. In contrast, ATP95 recognized the whole set of subunits only in K. blossfeldiana, M. crystallinum, H. vulgare and Z. mays. This differential cross reactivity of ATP95 indicates the presence of structural differences of certain V-ATPase subunits. Based on the Bafilomycin A1-sensitive ATPase activity of tonoplast enriched vesicles, and on the amount of V-ATPase solubilized and immunoprecipitated, the specific ATP-hydrolysis activity of the V-ATPases under test was determined. The structural differences correlate with the ability of V-ATPases from different species to hydrolyze ATP at one given assay condition for ATP-hydrolysis measurements. Interestingly V-ATPases showing cross-reactivity of subunits A, B, C, D and c with ATP95 showed higher rates of specific ATP hydrolysis compared to V-ATPases containing subunits which were not labeled by ATP95. Thus, V-ATPases with high turnover rates in our assay conditions may show common structural characteristics which separate them from ATPases with low turnover rates.

Purification and reconstitution of the vacuolar H+-ATPases from lemon fruits and epicotyls

The vacuolar H+-ATPases (V-ATPases) of lemon fruits and epicotyls were detergent-solubilized, purified by column chromatography, and reconstituted into artificial proteoliposomes. During purification, a vanadate- and nitrate-sensitive ATPase activity, consisting of partially disassembled V-ATPase complexes, was resolved from the V-ATPase peak. ATPase and H+-transport activities of the purified, reconstituted V-ATPases of both fruit and epicotyl exhibited similar inhibitor profiles, except that the fruit V-ATPase retained partial vanadate sensitivity. Since the V-ATPase activity of native fruit tonoplast vesicles is insensitive to inhibitors (Müller, M. L., Irkens-Kiesecker, U., Rubinstein, B., and Taiz, L. (1996) J. Biol. Chem. 271, 1916-1924), membrane lipids or other factors may protect the fruit V-ATPase from inactivation in vivo. A kinetic analysis of H+-pumping and H+-leakage indicated that the reconstituted epicotyl V-ATPase exhibited twice as much intrinsic uncoupling or slip as the reconstituted fruit V-ATPase. Comparison of their subunit compositions by SDS-polyacrylamide gel electrophoresis indicated that the reconstituted fruit V-ATPase is enriched in two polypeptides of 33/34 and 16 kDa. Moreover, the stalks of negatively stained juice sac V-ATPases appeared thicker than those of epicotyl V-ATPases in electron micrographs.

The ultrastructure of campaniform sensilla on the eye of the cricket, Gryllus campestris

The structure of the campaniform sensilla of the cricket eye was investigated by light and electron microscopy. Each sensillum is innervated by a single bipolar neuron. Its axon extends through the retina into a side-branch of the nervus tegumentarius. The dendrite extends through a cuticular channel to the surface of the cornea. The distal part of the dendrite, the sensory process, contains a tubular body and is attached to a cuticular cap which is obliquely inserted into the exocuticle between the corneal lenslets. Some particular structural features as well as the function of the campaniform sensillum of the cricket eye are discussed.