Diffusion and interaction dynamics of the cytosolic peroxisomal import receptor PEX5

Cellular functions rely on proper actions of organelles such as peroxisomes. These organelles rely on the import of proteins from the cytosol. The peroxisomal import receptor PEX5 takes up target proteins in the cytosol and transports them to the peroxisomal matrix. However, its cytosolic molecular interactions have so far not directly been disclosed. Here, we combined advanced optical microscopy and spectroscopy techniques such as fluorescence correlation spectroscopy and stimulated emission depletion microscopy with biochemical tools to present a detailed characterization of the cytosolic diffusion and interaction dynamics of PEX5. Among other features, we highlight a slow diffusion of PEX5, independent of aggregation or target binding, but associated with cytosolic interaction partners via its N-terminal domain. This sheds new light on the functionality of the receptor in the cytosol as well as highlighting the potential of using complementary microscopy tools to decipher molecular interactions in the cytosol by studying their diffusion dynamics.

Breakthrough instruments and products steady-state and time-resolved photoluminescence using the FluoTime 300 spectrometer with a FluoMic add-on

This report highlights the combination of the FluoTime 300 photoluminescence spectrometer with a FluoMic add-on as a powerful tool for photophysical research and applications, yielding spectral, temporal, and spatial information on a wide range of samples. The steady-state and time-resolved measurement capabilities of this combination are demonstrated reflecting a broad range of applications.

Time domain diffuse Raman spectrometer based on a TCSPC camera for the depth analysis of diffusive media

We present a time domain diffuse Raman spectrometer for depth probing of highly scattering media. The system is based on, to the best of our knowledge, a novel time-correlated single-photon counting (TCSPC) camera that simultaneously acquires both spectral and temporal information of Raman photons. A dedicated non-contact probe was built, and time domain Raman measurements were performed on a tissue mimicking bilayer phantom. The fluorescence contamination of the Raman signal was eliminated by early time gating (0-212 ps) the Raman photons. Depth sensitivity is achieved by time gating Raman photons at different delays with a gate width of 106 ps. Importantly, the time domain can provide time-dependent depth sensitivity leading to a high contrast between two layers of Raman signal. As a result, an enhancement factor of 2170 was found for our bilayer phantom which is much higher than the values obtained by spatial offset Raman spectroscopy (SORS), frequency offset Raman spectroscopy (FORS), or hybrid FORS-SORS on a similar phantom.

Inhibitors of PEX14 disrupt protein import into glycosomes and kill Trypanosoma parasites

The parasitic protists of the Trypanosoma genus infect humans and domestic mammals, causing severe mortality and huge economic losses. The most threatening trypanosomiasis is Chagas disease, affecting up to 12 million people in the Americas. We report a way to selectively kill Trypanosoma by blocking glycosomal/peroxisomal import that depends on the PEX14-PEX5 protein-protein interaction. We developed small molecules that efficiently disrupt the PEX14-PEX5 interaction. This results in mislocalization of glycosomal enzymes, causing metabolic catastrophe, and it kills the parasite. High-resolution x-ray structures and nuclear magnetic resonance data enabled the efficient design of inhibitors with trypanocidal activities comparable to approved medications. These results identify PEX14 as an "Achilles' heel" of the Trypanosoma suitable for the development of new therapies against trypanosomiases and provide the structural basis for their development.

Time domain diffuse correlation spectroscopy with a high coherence pulsed source: in vivo and phantom results

Diffuse correlation spectroscopy (DCS), combined with time-resolved reflectance spectroscopy (TRS) or frequency domain spectroscopy, aims at path length (i.e. depth) resolved, non-invasive and simultaneous assessment of tissue composition and blood flow. However, while TRS provides a path length resolved data, the standard DCS does not. Recently, a time domain DCS experiment showed path length resolved measurements for improved quantification with respect to classical DCS, but was limited to phantoms and small animal studies. Here, we demonstrate time domain DCS for in vivo studies on the adult forehead and the arm. We achieve path length resolved DCS by means of an actively mode-locked Ti:Sapphire laser that allows high coherence pulses, thus enabling adequate signal-to-noise ratio in relatively fast (~1 s) temporal resolution. This work paves the way to the translation of this approach to practical in vivo use.

European consensus-based (S2k) Guideline on the Management of Herpes Zoster - guided by the European Dermatology Forum (EDF) in cooperation with the European Academy of Dermatology and Venereology (EADV), Part 1: Diagnosis

Herpes zoster (HZ, shingles) is a frequent medical condition which may severely impact the quality of life of affected patients. Different therapeutic approaches to treat acute HZ are available. The aim of this European project was the elaboration of a consensus-based guideline on the management of patients who present with HZ, considering different patient populations and different localizations. This interdisciplinary guideline aims at an improvement of the outcomes of the acute HZ management concerning disease duration, acute pain and quality of life of the affected patients and at a reduction of the incidence of postherpetic neuralgia and other complications. The guideline development followed a structured and predefined process, considering the quality criteria for guidelines development as suggested by the AGREE II instrument. The steering group was responsible for the planning and the organization of the guideline development process (Division of Evidence based Medicine, dEBM). The expert panel was nominated by virtue of clinical expertise and/or scientific experience and included experts from the fields of dermatology, virology/infectiology, ophthalmology, otolaryngology, neurology and anaesthesiology. Recommendations for clinical practice were formally consented during the consensus conference, explicitly considering different relevant aspects. The guideline was approved by the commissioning societies after an extensive internal and external review process. In this first part of the guideline, diagnostic means have been evaluated. The expert panel formally consented recommendations for the management of patients with (suspected) HZ, referring to the assessment of HZ patients, considering various specific clinical situations. Users of the guideline must carefully check whether the recommendations are appropriate for the context of intended application. In the setting of an international guideline, it is generally important to consider different national approaches and legal circumstances with regard to the regulatory approval, availability and reimbursement of diagnostic and therapeutic interventions.

European consensus-based (S2k) Guideline on the Management of Herpes Zoster - guided by the European Dermatology Forum (EDF) in cooperation with the European Academy of Dermatology and Venereology (EADV), Part 2: Treatment

Herpes zoster (HZ, shingles) is a frequent medical condition which may severely impact the quality of life of affected patients. Different therapeutic approaches to treat acute HZ are available. The aim of this European project was the elaboration of a consensus-based guideline on the management of patients who present with HZ, considering different patient populations and different localizations. This interdisciplinary guideline aims at an improvement of the outcomes of the acute HZ management concerning disease duration, acute pain and quality of life of the affected patients and at a reduction in the incidence of postherpetic neuralgia (PHN) and other complications. The guideline development followed a structured and pre-defined process, considering the quality criteria for guidelines development as suggested by the AGREE II instrument. The steering group was responsible for the planning and the organization of the guideline development process (Division of Evidence-Based Medicine, dEBM). The expert panel was nominated by virtue of clinical expertise and/or scientific experience and included experts from the fields of dermatology, virology/infectiology, ophthalmology, otolaryngology, neurology and anaesthesiology. Recommendations for clinical practice were formally consented during the consensus conference, explicitly considering different relevant aspects. The guideline was approved by the commissioning societies after an extensive internal and external review process. In this second part of the guideline, therapeutic interventions have been evaluated. The expert panel formally consented recommendations for the treatment of patients with HZ (antiviral medication, pain management, local therapy), considering various clinical situations. Users of the guideline must carefully check whether the recommendations are appropriate for the context of intended application. In the setting of an international guideline, it is generally important to consider different national approaches and legal circumstances with regard to the regulatory approval, availability and reimbursement of diagnostic and therapeutic interventions.

Evidence-based (S3) Guideline on (anogenital) Lichen sclerosus

Lichen sclerosus (LS) is an inflammatory skin disease that usually involves the anogenital area. All patients with symptoms or signs suspicious of lichen sclerosus should be seen at least once initially by a physician with a special interest in the disease in order to avoid delay in diagnosis, as early treatment may cure the disease in some and reduce or prevent scarring. The diagnosis is made clinically in most cases. Biopsies should only be performed under certain circumstances. The gold standard for treatment remains potent to very potent topical steroids; however, mild and moderate disease in boys and men may be cured by circumcision. Certain triggers should be avoided. http://www.euroderm.org/images/stories/guidelines/2014/S3-Guideline-on-Lichen-sclerosus.pdf http://www.awmf.org/fachgesellschaften/mitgliedsgesellschaften/visitenkarte/fg/deutsche-gesellschaft-fuer-gynaekologie-und-geburtshilfe-dggg.html.

Risk of complications due to anticoagulation during dermatosurgical procedures: a systematic review and meta-analysis

Background Management of anticoagulation and anti-platelet drugs during cutaneous surgery is still a challenge for many dermatologists and standards of care with respect to stopping, continuing or bridging vary widely. Methods We performed a systematic review (Medline, Cochrane Library, until August 27th, 2013) of studies assessing the risk of complications due to anticoagulation during cutaneous surgery. Primary outcomes were mild-moderate and severe postsurgical bleeding. The secondary outcomes were excessive and uncontrollable intraoperative bleeding and other postsurgical complications as wound dehiscence, erythema, wound infection. Results 1.287 publications were identified and 10 studies were included into the review. The frequencies of bleeding in the control groups in general were low (about 1%). In patients on aspirin, increased risks were seen neither with respect to mild-moderate postoperative bleeding (RR 1.1, CI 0.5-2.3), nor with respect to severe bleeding (RR 0.9, CI 0.2-4.6). The studies with patients on warfarin showed a risk for mild-moderate bleeding that was three times as high as in controls (RR 3.2, CI 1.4-7.1) and for severe bleeding that was 15 times higher (RR 14.8, CI 2.7-80.4). In general the study sizes were small and the methodological quality low. Conclusion The risk of bleeding due to a medication with aspirin seems to be negligible. With warfarin, the risk is increased; an exact estimate of the risk increase is difficult to give, because of the lack of sufficient high quality studies. A two-fold increase appears likely, the 15-fold increase is most likely due to statistical reasons arising from the rareness of the event in the small number of included patients. Stopping, bridging or continuing a medication should always be an individual decision. In accordance with guidelines from internal medicine for most patients it will be recommendable to continue with the medication.

The natural history of actinic keratosis: a systematic review

Knowledge about the development of untreated actinic keratosis (AK) and risk of progression into squamous cell carcinoma (SCC) is important. Therefore, we set out to synthesize primary data on the natural history of AK. We carried out a systematic literature search (Medline, Medline in Process, Embase, Cochrane) of studies on the natural course of AK, regarding (i) progression and regression rates per lesion-year, (ii) changes in total lesion counts over time, and (iii) spontaneous field regression and recurrence rates, taking into account studies on participants without immunosuppression and history of skin cancer, immunosuppressed patients and participants with a history of skin cancer and sunscreen use. Twenty-four eligible studies were identified providing data on at least one of the outcomes. Progression rates of AK to SCC ranged from 0% to 0·075% per lesion-year, with a risk of up to 0·53% per lesion in patients with prior history of nonmelanoma skin cancer. Rates of regression of single lesions ranged between 15% and 63% after 1 year. The data available on recurrence rates of single lesions 1 year after regression indicate a recurrence rate of 15-53%. Data on the relative change of total AK count over time are heterogeneous, and range from -53% to +99·1%. Spontaneous complete field regression rates range from 0% to 21%, with recurrences in 57%. In general, the available data are limited. Important methodological limitations apply. Currently, no reliable estimates concerning the frequency of AK developing into invasive carcinoma can be given, and further studies are needed.

Study of perceptions of the extent to which guideline recommendations are binding: a survey of commonly used terminology

BACKGROUND

Doctors are more likely to implement guidelines in their everyday practice if the recommendations contained in them are understandable. So far, there has been little standardization in the wording of guideline recommendations. It would be important to know how certain terms are understood by guideline users. In this study, doctors were asked in a survey about what they considered to be the level of obligation carried by various formulations that are commonly used in guidelines to recommend particular courses of action.

METHODS

An online survey of physicians (mostly dermatologists) was carried out in which they were asked to rate, on a visual analog scale, what they perceived to be the level of obligation of various common formulations for guideline recommendations.

RESULTS

The terms "muss" (must) and "darf nicht" (must not) were interpreted as being maximally binding. The two closely related German words "soll" (shall) and "sollte" (should) were considered highly binding, as were negative formulations such as "wird nicht empfohlen" (is not recommended). The perceived level of obligation of "soll" did not differ from that of "sollte" to any detectable extent, nor was there any detectable distinction between the various negative formulations studied. Formulations with the words "wird empfohlen" (is recommended), "kann empfohlen werden" (can be recommended), or other "kann" (can) expressions were considered to be only mildly or moderately binding. In general, there was marked variation in the perceived level of obligation of formulations located in the low and middle ranges.

CONCLUSION

These findings suggest that guideline users do not necessarily perceive recommendation strengths as the guideline authors intended. It might be better if positive recommendations came in only two different strengths, while a single recommendation strength might suffice for negative ones. Further studies should shed more light on this question.

Management of anticoagulation during dermatosurgical procedures in Germany - results from a cross-sectional study

BACKGROUND

Treatment with antiplatelet drugs (APD) and vitamin K antagonists (VKA) can be a challenge during the management of dermatosurgical interventions.

METHODS

We performed a cross-sectional study on the perioperative management of APD and VKA in dermatological private practices and clinics in Germany, using anonymized, standardized questionnaires.

RESULTS

233 responses were evaluated (response rate 37 %). Skin biopsies are performed in 82.7 % of offices and in 90.8 % of clinics despite treatment with VKA. Small excisions are done in 62.5 % of offices and 76.9 % of clinics during treatment with VKA, for large excision this applies to 11.9 % of offices and 33.8 % of clinics. Low-dose treatment with APD (#100 mg) does not hinder 80.4 % of private practices and 89.2 % of clinics to perform small excisions as well as 36.3 % and 53.8 %, respectively, to perform large excisions. Of private practitioners 67.3 % and 83.1 % of clinic-based dermato-surgeons do not consider high-dose APD a contraindication for small excisions, and 25.0 % and 41.5 %, respectively, for large excisions. Most frequently switching to heparin is performed 6-8 days prior to surgery and switching back 0-2 days after surgery.

CONCLUSIONS

Large differences in the perioperative management of anticoagulant therapy during dermatosurgical procedures have been identified. Further studies and guidelines should be developed.

S3 - Guidelines on the treatment of psoriasis vulgaris (English version). Update

Psoriasis vulgaris is a common and often chronic inflammatory skin disease. The incidence of psoriasis in Western industrialized countries ranges from 1.5% to 2%. Patients afflicted with severe psoriasis vulgaris may experience a significant reduction in quality of life. Despite the large variety of treatment options available, surveys have shown that patients still do not received optimal treatments. To optimize the treatment of psoriasis in Germany, the Deutsche Dermatologi sche Gesellschaft (DDG) and the Berufsverband Deutscher Dermatologen (BVDD) have initiated a project to develop evidence-based guidelines for the management of psoriasis. They were first published in 2006 and updated in 2011. The Guidelines focus on induction therapy in cases of mild, moderate and severe plaque-type psoriasis in adults including systemic therapy, UV therapy and topical therapies. The therapeutic recommendations were developed based on the results of a systematic literature search and were finalized during a consensus meeting using structured consensus methods (nominal group process).

Efficacy of systemic therapies for moderate-to-severe psoriasis: a systematic review and meta-analysis of long-term treatment

BACKGROUND

Despite the chronicity of psoriasis, most systematic reviews focus on short-term treatment.

METHODS

The systematic search strategy and results from the German Psoriasis Guidelines were adapted. To update the data a literature search in Medline, Embase and the Cochrane Library was conducted. The proportion of participants achieving ≥75% decrease in Psoriasis Area and Severity Index (PASI) as well as Dermatology Life Quality Index (DLQI) reduction at different time points were assessed. Trials were summarized with respect to time periods and study designs. Suitable trials were included in a meta-analysis. Particular attention was paid to statistical approaches of handling dropouts.

RESULTS

A total of 33 articles including 27 trials totaling 6575 patients with active treatment were included in the systematic review. Seven randomized controlled trials were eligible for the meta-analysis. Over a 24 week treatment period infliximab [risk difference (RD) 78%, 95% confidence interval (CI) 72-83%] and ustekinumab 90 mg every 12 weeks (RD 77%, 95% CI 71-83%) were the most efficacious treatments. Adalimumab (RD: 60%, 95% CI 45-74%) showed results within the range of different etanercept dosages (etanercept 50 mg once weekly: RD 62%, 95% CI, 52-72%), (etanercept 25 mg twice weekly: RD 45%, 95% CI 34-56%), (etanercept 50 mg twice weekly: RD 56%, 95% CI 49-62%) and (etanercept 50 mg twice weekly until week 12, then 25 mg twice weekly: RD 50%, 95% CI 42-57%). After 24 weeks a decrease in efficacy for inflximab, adalimumab and etanercept was observed.

CONCLUSIONS

More sufficient data is required to draw reliable conclusions in extended long-term treatment and head-to-head comparisons are necessary.

[S2k-guideline for therapy of acne]

To optimize the treatment of acne in Germany, the German Society of Dermatology (DDG) and the Association of German Dermatologists (BVDD) initiated a project to develop consensus-based guidelines for the management of acne. The Acne Guidelines focus on induction therapy, maintenance therapy and treatment of post-acne scarring. They include an evaluation of the most commonly used therapeutic options in Germany. In addition, they offer detailed information on how to administer the various treatments and on contraindications, adverse drug reactions, and drug interactions, taking into account gender and special conditions such as pregnancy and lactation. The Acne Guidelines were developed following the recommendations of the Association of Scientific Medical Societies in Germany (AWMF). The treatment recommendations were developed by an expert group and finalized by an interdisciplinary consensus conference. The first choice treatments for acute acne according to acne type are as follows: 1) comedonal acne: topical retinoids; 2) mild papular/pustular acne: fixed or sequential combinations of BPO and topical retinoids or of BPO and topical antibiotics; 3) moderate papular/pustular acne: oral antibiotic plus BPO or plus topical retinoid, or in a fixed combination 4) acne papulo-pustulosa nodosa and acne conglobata: oral antibiotic plus topical retinoid plus BPO or oral isotretinoin. For maintenance treatment: topical retinoid or its combination with BPO. Particular attention should be paid to compliance and quality of life. Additional treatment options are discussed in the main body of the text.

European S3-guidelines on the systemic treatment of psoriasis vulgaris

Of the 131 studies on monotherapy or combination therapy assessed, 56 studies on the different forms of phototherapy fulfilled the criteria for inclusion in the guidelines. Approximately three-quarters of all patients treated with phototherapy attained at least a PASI 75 response after 4 to 6 weeks, and clearance was frequently achieved (levels of evidence 2 and 3). Phototherapy represents a safe and very effective treatment option for moderate to severe forms of psoriasis vulgaris. The onset of clinical effects occurs within 2 weeks. Of the unwanted side effects, UV erythema from overexposure is by far the most common and is observed frequently. With repeated or long-term use, the consequences of high, cumulative UV doses (such as premature aging of the skin) must be taken into consideration. In addition, carcinogenic risk is associated with oral PUVA and is probable for local PUVA and UVB. The practicability of the therapy is limited by spatial, financial, human, and time constraints on the part of the physician, as well as by the amount of time required by the patient. From the perspective of the cost-bearing institution, phototherapy has a good cost-benefit ratio. However, the potentially significant costs for, and time required of, the patient must be considered.

Comparison and accuracy of methods to determine the confocal volume for quantitative fluorescence correlation spectroscopy

Single molecule detection based on fluorescent labels offers the possibility to gain not only qualitative but also quantitative insight into specific functions of complex biological systems. Fluorescence correlation spectroscopy is one of the favourite techniques to determine concentrations and diffusion constants as well as molecular brightness of molecules in the pico- to nano-molar concentration range, with broad applications in biology and chemistry. Although fluorescence correlation spectroscopy in principle has the potential to measure absolute concentrations and diffusion coefficients, the necessity to know the exact size and shape of the confocal volume very often hampers the possibility to obtain quantitative results and restricts fluorescence correlation spectroscopy to relative measurements mainly. The determination of the confocal volume in situ is difficult because it is sensitive to optical alignment and aberrations, optical saturation and variations of the index of refraction as observed in biological specimen. In the present contribution, we compare different techniques to characterize the confocal volume and to obtain the confocal parameters by fluorescence correlation spectroscopy curve fitting, a fluorescence correlation spectroscopy dilution series and confocal scanning of fluorescent beads. The results are compared in the view of quantitative fluorescence correlation spectroscopy measurement and analysis. We investigate how unavoidable artefacts caused by a non-ideal confocal volume can be experimentally determined and validated.

Comparison and accuracy of methods to determine the confocal volume for quantitative fluorescence correlation spectroscopy

Single molecule detection based on fluorescent labels offers the possibility to gain not only qualitative but also quantitative insight into specific functions of complex biological systems. Fluorescence correlation spectroscopy is one of the favourite techniques to determine concentrations and diffusion constants as well as molecular brightness of molecules in the pico- to nano-molar concentration range, with broad applications in biology and chemistry. Although fluorescence correlation spectroscopy in principle has the potential to measure absolute concentrations and diffusion coefficients, the necessity to know the exact size and shape of the confocal volume very often hampers the possibility to obtain quantitative results and restricts fluorescence correlation spectroscopy to relative measurements mainly. The determination of the confocal volume in situ is difficult because it is sensitive to optical alignment and aberrations, optical saturation and variations of the index of refraction as observed in biological specimen. In the present contribution, we compare different techniques to characterize the confocal volume and to obtain the confocal parameters by fluorescence correlation spectroscopy curve fitting, a fluorescence correlation spectroscopy dilution series and confocal scanning of fluorescent beads. The results are compared in the view of quantitative fluorescence correlation spectroscopy measurement and analysis. We investigate how unavoidable artefacts caused by a non-ideal confocal volume can be experimentally determined and validated.

Translating psoriasis treatment guidelines into clinical practice - the need for educational interventions and strategies for broad dissemination

RATIONALE

Evidence-based guidelines can make a substantial contribution to improving medical care. However, it is important to ensure that guidelines are: (1) developed in areas in which they are needed the most; and (2) translated effectively into everyday clinical practice.

OBJECTIVES

To evaluate the need for guidelines in the treatment of psoriasis vulgaris, the success of the dissemination activities undertaken to date, and the potential benefits of educational interventions in encouraging guideline compliance.

METHODS

All dermatologists working in the Berlin-Brandenburg region of Germany were invited to attend a workshop on the psoriasis treatment guidelines. Participants could take part in a survey examining the general need for psoriasis guidelines and the success of previous dissemination activities.

RESULTS

A total of 42% of survey participants had not received a copy of the guidelines prior to the workshop. Of those who had received a copy, only 15% had studied the guidelines in detail. In total, 76% of survey participants felt that physicians' low levels of confidence in administering systemic treatments had resulted in these treatment options being used less frequently than they should. Seventy-nine per cent of survey participants believed that the guidelines would be helpful in improving physicians' confidence and ultimately lead to an increased use of systemic treatments.

CONCLUSION

The results of the present study indicate that there is a great need for guidelines on the treatment of psoriasis vulgaris in Germany, especially in light of dermatologists' low levels of confidence administering systemic treatments. Strategies for broad dissemination are essential for proper guideline implementation.

Low prescription rate for systemic treatments in the management of severe psoriasis vulgaris and psoriatic arthritis in dermatological practices in Berlin and Brandenburg, Germany: results from a patient registry

BACKGROUND

Many treatment options are available for the management of psoriasis vulgaris. However, detailed data on prescription behaviour in Germany, especially with regard to the use of new treatment options (e.g. biologics) in private practices, are lacking.

OBJECTIVE

To assess the treatment choices being made in the management of psoriasis vulgaris and psoriatic arthritis in private dermatological practices.

METHODS

We established a patient registry that documented the treatment decisions taken during 4797 patient visits between January 2006 and September 2006 with regard to disease activity and concomitant psoriatic arthritis.

RESULTS

Corticosteroids were the most frequently prescribed topical treatment, and methotrexate and fumaric acid esters were the most frequently prescribed systemic treatments. Biologics were prescribed in only 2% of patient visits. Systemic treatments were prescribed in only 31% of visits made by patients suffering from moderate to severe psoriasis (which was diagnosed in 48% of all patient visits) and in only 58% of visits made by patients suffering from psoriatic arthritis (which was diagnosed in 12% of all patient visits).

CONCLUSIONS

Anti-psoriatic treatment was too often limited to topical agents. The rather small percentage of patients with moderate to severe psoriasis or psoriatic arthritis who received systemic therapy indicates that the use of systemic treatments in our sample was too restrictive. Novel therapeutic options such as biologics were rarely used in private practices. New strategies to improve the quality of care provided to patients suffering from severe psoriasis are needed.

Non-invasive detection of fluorescence from exogenous chromophores in the adult human brain

This is the first report on results proving that fluorescence of exogenous dyes inside the human brain can be excited and detected non-invasively at the surface of the adult head. Boli of indocyanine green (ICG) were intravenously applied to healthy volunteers, and the passage of the contrast agent in the brain was monitored by detecting the corresponding fluorescence signal following pulsed laser excitation at 780 nm. Our hypothesis that the observed fluorescence signal contains a considerable cortical fraction was corroborated by performing measurements with picosecond temporal resolution and analyzing distributions of times of arrival of photons, hence taking advantage of the well-known depth selectivity of that method. Our experimental findings are explained by Monte Carlo simulations modeling the head as a layered medium and taking into account realistic bolus kinetics within the extra- and intracerebral compartment. Although a particular non-specific dye (ICG) was used, the results clearly demonstrate that fluorescence-mediated imaging of the adult human brain is generally feasible. In particular, we will discuss how these results serve as proof of concept for non-invasive fluorescence brain imaging and may thus open the door towards optical molecular imaging of the human brain.

Time-Resolved Confocal Fluorescence Imaging and Spectrocopy System with Single Molecule Sensitivity and Sub-Micrometer Resolution

We present novel technical features and results from a two channel confocal fluorescence lifetime microscope, which allows to efficiently investigate fluorescence dynamics down to the single molecule level. The MicroTime 200 time-resolved fluorescence microscope offers a multicolor excitation where different picosecond diode lasers are used. For imaging and positioning purposes we utilize a compact Piezo scanner which allows, due to a novel scanning algorithm and synchronisation technique, a superior movement and positioning accuracy. The data acquisition is completely based on time-correlated single photon counting, where every photon is detected and stored individually with its specific timing information (Time-Tagged Time-Resolved mode). This multiparameter data acquisition scheme offers the opportunity to analyse the parameter dependencies in a multitude of different ways. Standard intensity analysis can be used to reconstruct 2D-images or the temporal evolution (time trace) of the fluorescence of a single spot. The information from the two distinct detector channels additionally allows to investigate the polarisation of the emitted light or its spectral composition, for example for analysis of Fluorescence Resonance Energy Transfer (FRET). The timing information down to a picosecond scale offers the possibility not only to reconstruct fluorescence decay constants of each pixel for the purpose of Fluorescence Lifetime Imaging (FLIM) but also to analyze the fluorescence fluctuation correlation function of any single spot of interest. The flexible multichannel detector scheme enables in this case also a cross-correlation between spectrally separated parts of the emission light, or even identical parts of the fluorescence to eliminate detector artifacts. The photon arrival coincidence analysis can also be expanded in the sub-ns range to study fluorescence antibunching in the fluorescence emission of single molecules. The ability of combining these different pieces of temporal information allows the construction of extremely powerful analysis methods and assays. We demonstrate a variety of these capabilities with results obtained from fluorescently labeled latex beads, biological samples, and single molecules excited in the blue or red wavelength region.

Peroxisome biogenesis

Peroxisome biogenesis conceptually consists of the (a) formation of the peroxisomal membrane, (b) import of proteins into the peroxisomal matrix and (c) proliferation of the organelles. Combined genetic and biochemical approaches led to the identification of 25 PEX genes-encoding proteins required for the biogenesis of peroxisomes, so-called peroxins. Peroxisomal matrix and membrane proteins are synthesized on free ribosomes in the cytosol and posttranslationally imported into the organelle in an unknown fashion. The protein import into the peroxisomal matrix and the targeting and insertion of peroxisomal membrane proteins is performed by distinct machineries. At least three peroxins have been shown to be involved in the topogenesis of peroxisomal membrane proteins. Elaborate peroxin complexes form the machinery which in a concerted action of the components transports folded, even oligomeric matrix proteins across the peroxisomal membrane. The past decade has significantly improved our knowledge of the involvement of certain peroxins in the distinct steps of the import process, like cargo recognition, docking of cargo-receptor complexes to the peroxisomal membrane, translocation, and receptor recycling. This review summarizes our knowledge of the functional role the known peroxins play in the biogenesis and maintenance of peroxisomes. Ideas on the involvement of preperoxisomal structures in the biogenesis of the peroxisomal membrane are highlighted and special attention is paid to the concept of cargo protein aggregation as a presupposition for peroxisomal matrix protein import.