Temporal change of DNA methylation subclasses between matched newly diagnosed and recurrent glioblastoma

The longitudinal transition of phenotypes is pivotal in glioblastoma treatment resistance and DNA methylation emerged as an important tool for classifying glioblastoma phenotypes. We aimed to characterize DNA methylation subclass heterogeneity during progression and assess its clinical impact. Matched tissues from 47 glioblastoma patients were subjected to DNA methylation profiling, including CpG-site alterations, tissue and serum deconvolution, mass spectrometry, and immunoassay. Effects of clinical characteristics on temporal changes and outcomes were studied. Among 47 patients, 8 (17.0%) had non-matching classifications at recurrence. In the remaining 39 cases, 28.2% showed dominant DNA methylation subclass transitions, with 72.7% being a mesenchymal subclass. In general, glioblastomas with a subclass transition showed upregulated metabolic processes. Newly diagnosed glioblastomas with mesenchymal transition displayed increased stem cell-like states and decreased immune components at diagnosis and exhibited elevated immune signatures and cytokine levels in serum. In contrast, tissue of recurrent glioblastomas with mesenchymal transition showed increased immune components but decreased stem cell-like states. Survival analyses revealed comparable outcomes for patients with and without subclass transitions. This study demonstrates a temporal heterogeneity of DNA methylation subclasses in 28.2% of glioblastomas, not impacting patient survival. Changes in cell state composition associated with subclass transition may be crucial for recurrent glioblastoma targeted therapies.

Fibroblast Growth Factor (FGF) 23 and FGF Receptor 4 promote cardiac metabolic remodeling in chronic kidney disease

Chronic kidney disease (CKD) is a global health epidemic that significantly increases mortality due to cardiovascular disease. Left ventricular hypertrophy (LVH) is an important mechanism of cardiac injury in CKD. High serum levels of fibroblast growth factor (FGF) 23 in patients with CKD may contribute mechanistically to the pathogenesis of LVH by activating FGF receptor (FGFR) 4 signaling in cardiac myocytes. Mitochondrial dysfunction and cardiac metabolic remodeling are early features of cardiac injury that predate development of hypertrophy, but these mechanisms of disease have been insufficiently studied in models of CKD. Wild-type mice with CKD induced by adenine diet developed LVH that was preceded by morphological changes in mitochondrial structure and evidence of cardiac mitochondrial and metabolic dysfunction. In bioengineered cardio-bundles and neonatal rat ventricular myocytes grown in vitro, FGF23-mediated activation of FGFR4 caused a mitochondrial pathology, characterized by increased bioenergetic stress and increased glycolysis, that preceded the development of cellular hypertrophy. The cardiac metabolic changes and associated mitochondrial alterations in mice with CKD were prevented by global or cardiac-specific deletion of FGFR4. These findings indicate that metabolic remodeling and eventually mitochondrial dysfunction are early cardiac complications of CKD that precede structural remodeling of the heart. Mechanistically, FGF23-mediated activation of FGFR4 causes mitochondrial dysfunction, suggesting that early pharmacologic inhibition of FGFR4 might serve as novel therapeutic intervention to prevent development of LVH and heart failure in patients with CKD.

Testosterone affects type I/type II interferon response of neutrophils during hepatic amebiasis

Differences in immune response between men and women may influence the outcome of infectious diseases. Intestinal infection with Entamoeba histolytica leads to hepatic amebiasis, which is more common in males. Previously, we reported that innate immune cells contribute to liver damage in males in the murine model for hepatic amebiasis. Here, we focused on the influences of sex and androgens on neutrophils in particular. Infection associated with neutrophil accumulation in the liver was higher in male than in female mice and further increased after testosterone treatment in both sexes. Compared with female neutrophils, male neutrophils exhibit a more immature and less activated status, as evidenced by a lower proinflammatory N1-like phenotype and deconvolution, decreased gene expression of type I and type II interferon stimulated genes (ISGs) as well as downregulation of signaling pathways related to neutrophil activation. Neutrophils from females showed higher protein expression of the type I ISG viperin/RSAD2 during infection, which decreased by testosterone substitution. Moreover, ex vivo stimulation of human neutrophils revealed lower production of RSAD2 in neutrophils from men compared with women. These findings indicate that sex-specific effects on neutrophil physiology associated with maturation and type I IFN responsiveness might be important in the outcome of hepatic amebiasis.

Epigenetic profiling reveals a strong association between lack of 5-ALA fluorescence and EGFR amplification in IDH-wildtype glioblastoma

Background

5-aminolevulinic acid (5-ALA) fluorescence-guided resection increases the percentage of complete CNS tumor resections and improves the progression-free survival of IDH-wildtype glioblastoma patients. A small subset of IDH-wildtype glioblastoma shows no 5-ALA fluorescence. An explanation for these cases is missing. In this study, we used DNA methylation profiling to further characterize non-fluorescent glioblastomas.

Methods

Patients with newly diagnosed and recurrent IDH-wildtype glioblastoma that underwent surgery were analyzed. The intensity of intraoperative 5-ALA fluorescence was categorized as non-visible or visible. DNA was extracted from tumors and genome-wide DNA methylation patterns were analyzed using Illumina EPIC (850k) arrays. Furthermore, 5-ALA intensity was measured by flow cytometry on human gliomasphere lines (BT112 and BT145).

Results

Of 74 included patients, 12 (16.2%) patients had a non-fluorescent glioblastoma, which were compared to 62 glioblastomas with 5-ALA fluorescence. Clinical characteristics were equally distributed between both groups. We did not find significant differences between DNA methylation subclasses and 5-ALA fluorescence (P = .24). The distribution of cells of the tumor microenvironment was not significantly different between the non-fluorescent and fluorescent tumors. Copy number variations in EGFR and simultaneous EGFRvIII expression were strongly associated with 5-ALA fluorescence since all non-fluorescent glioblastomas were EGFR-amplified (P < .01). This finding was also demonstrated in recurrent tumors. Similarly, EGFR-amplified glioblastoma cell lines showed no 5-ALA fluorescence after 24 h of incubation.

Conclusions

Our study demonstrates an association between non-fluorescent IDH-wildtype glioblastomas and EGFR gene amplification which should be taken into consideration for recurrent surgery and future studies investigating EGFR-amplified gliomas.

DISCERN: deep single-cell expression reconstruction for improved cell clustering and cell subtype and state detection

BACKGROUND

Single-cell sequencing provides detailed insights into biological processes including cell differentiation and identity. While providing deep cell-specific information, the method suffers from technical constraints, most notably a limited number of expressed genes per cell, which leads to suboptimal clustering and cell type identification.

RESULTS

Here, we present DISCERN, a novel deep generative network that precisely reconstructs missing single-cell gene expression using a reference dataset. DISCERN outperforms competing algorithms in expression inference resulting in greatly improved cell clustering, cell type and activity detection, and insights into the cellular regulation of disease. We show that DISCERN is robust against differences between batches and is able to keep biological differences between batches, which is a common problem for imputation and batch correction algorithms. We use DISCERN to detect two unseen COVID-19-associated T cell types, cytotoxic CD4+ and CD8+ Tc2 T helper cells, with a potential role in adverse disease outcome. We utilize T cell fraction information of patient blood to classify mild or severe COVID-19 with an AUROC of 80% that can serve as a biomarker of disease stage. DISCERN can be easily integrated into existing single-cell sequencing workflow.

CONCLUSIONS

Thus, DISCERN is a flexible tool for reconstructing missing single-cell gene expression using a reference dataset and can easily be applied to a variety of data sets yielding novel insights, e.g., into disease mechanisms.

Kidney outcome after mild to moderate COVID-19

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has a remarkable kidney tropism. While kidney effects are common in severe coronavirus disease 2019 (COVID-19), data on non-severe courses are limited. Here we provide a multilevel analysis of kidney outcomes after non-severe COVID-19 to test for eventual kidney sequela.

METHODS

This cross-sectional study investigates individuals after COVID-19 and matched controls recruited from the Hamburg City Health Study (HCHS) and its COVID-19 program. The HCHS is a prospective population-based cohort study within the city of Hamburg, Germany. During the COVID-19 pandemic the study additionally recruited subjects after polymerase chain reaction-confirmed SARS-CoV-2 infections. Matching was performed by age, sex and education. Main outcomes were estimated glomerular filtration rate (eGFR), albuminuria, Dickkopf3, haematuria and pyuria.

RESULTS

A total of 443 subjects in a median of 9 months after non-severe COVID-19 were compared with 1328 non-COVID-19 subjects. The mean eGFR was mildly lower in post-COVID-19 than non-COVID-19 subjects, even after adjusting for known risk factors {β = -1.84 [95% confidence interval (CI) -3.16 to -0.52]}. However, chronic kidney disease [odds ratio (OR) 0.90 (95% CI 0.48-1.66)] or severely increased albuminuria [OR 0.76 (95% CI 0.49-1.09)] equally occurred in post-COVID-19 and non-COVID-19 subjects. Haematuria, pyuria and proteinuria were also similar between the two cohorts, suggesting no ongoing kidney injury after non-severe COVID-19. Further, Dickkopf3 was not increased in the post-COVID-19 cohort, indicating no systematic risk for ongoing GFR decline [β = -72.19 (95% CI -130.0 to -14.4)].

CONCLUSION

While mean eGFR was slightly lower in subjects after non-severe COVID-19, there was no evidence for ongoing or progressive kidney sequela.

Epigenetic neural glioblastoma enhances synaptic integration and predicts therapeutic vulnerability

Neural-tumor interactions drive glioma growth as evidenced in preclinical models, but clinical validation is nascent. We present an epigenetically defined neural signature of glioblastoma that independently affects patients' survival. We use reference signatures of neural cells to deconvolve tumor DNA and classify samples into low- or high-neural tumors. High-neural glioblastomas exhibit hypomethylated CpG sites and upregulation of genes associated with synaptic integration. Single-cell transcriptomic analysis reveals high abundance of stem cell-like malignant cells classified as oligodendrocyte precursor and neural precursor cell-like in high-neural glioblastoma. High-neural glioblastoma cells engender neuron-to-glioma synapse formation in vitro and in vivo and show an unfavorable survival after xenografting. In patients, a high-neural signature associates with decreased survival as well as increased functional connectivity and can be detected via DNA analytes and brain-derived neurotrophic factor in plasma. Our study presents an epigenetically defined malignant neural signature in high-grade gliomas that is prognostically relevant.

A 12-month randomised pilot trial of the Alzheimer's and music therapy study: a feasibility assessment of music therapy and physical activity in patients with mild-to-moderate Alzheimer's disease

BACKGROUND

The Alzheimer's and Music Therapy (ALMUTH) study is the first randomised controlled trial (RCT) design with 12 months of active non-pharmacological therapy (NPT) implementing music therapy (MT) and physical activity (PA) for participants with Alzheimer's disease (AD). The aim of the present article is to retrospectively examine the inclusion of mild-to-moderate Alzheimer's Disease patients into the main ALMUTH study protocol and to determine if continued inclusion of AD patients is warranted.

METHODS

The randomised pilot trial was conducted as a parallel three-arm RCT, reflecting the experimental design of the ALMUTH study. The trial was conducted in Bergen, Norway, and randomisation (1:1:1) was performed by an external researcher. The study was open label and the experimental design features two active NPTs: MT and PA, and a passive control (no intervention, CON) in Norwegian speaking patients with AD who still live at home and could provide informed consent. Sessions were offered once per week (up to 90 min) up to 40 sessions over 12 months. Baseline and follow-up tests included a full neuropsychological test battery and three magnetic resonance imaging (MRI) measurements (structural, functional, and diffusion weighted imaging). Feasibility outcomes were assessed and were determined as feasible if they met the target criteria.

RESULTS

Eighteen participants with a diagnosis of mild-to-moderate AD were screened, randomised, and tested once at baseline and once after 12-months. Participants were divided into three groups: MT (n = 6), PA (n = 6), and CON (n = 6). Results of the study revealed that the ALMUTH protocol in patients with AD was not feasible. The adherence to the study protocol was poor (50% attended sessions), with attrition and retention rates at 50%. The recruitment was costly and there were difficulties acquiring participants who met the inclusion criteria. Issues with study fidelity and problems raised by staff were taken into consideration for the updated study protocol. No adverse events were reported by the patients or their caregivers.

CONCLUSIONS

The pilot trial was not deemed feasible in patients with mild-to-moderate AD. To mitigate this, the ALMUTH study has expanded the recruitment criteria to include participants with milder forms of memory impairment (pre-AD) in addition to expanding the neuropsychological test battery. The ALMUTH study is currently ongoing through 2023.

TRIAL REGISTRATION

Norsk Forskningsråd (NFR) funded. Regional Committees for Medical and Health Research Ethics (REC-WEST: reference number 2018/206).

CLINICALTRIALS

gov: NCT03444181 (registered retrospectively 23 February 2018, https://clinicaltrials.gov/ct2/show/NCT03444181 ).

BIOM-33. TEMPORAL HETEROGENEITY OF DNA METHYLATION SUBCLASSES BETWEEN MATCHED NEWLY DIAGNOSED AND RECURRENT IDH-WILDTYPE GLIOBLASTOMA

Spatiotemporal heterogeneity is a major factor contributing to the devastating prognosis of isocitrate-dehydrogenase (IDH)-wildtype glioblastoma. Genome-wide DNA methylation profiling allows the stratification into several DNA methylation subgroups of IDH-wildtype glioblastoma, which were shown to have a spatial heterogeneity in newly diagnosed tumors. However, the temporal heterogeneity and its clinical relevance of DNA methylation subgroups remains inconclusive. Tumor tissue obtained from first and recurrence surgery of 31 patients diagnosed with IDH-wildtype glioblastoma was subjected to DNA methylation profiling. DNA methylation profiles were analyzed for temporal heterogeneity and correlated with clinical data, survival outcome and copy number variations. In addition, deconvolution of immune cells and unsupervised hierarchical clustering using pairwise Pearson correlation coefficients of the 10.000 most variable CpG features was performed. Of all patients with matched tumor tissue, 4 (12.9%) patients had a non-matching brain tumor classifier output at recurrence. Within the remaining 27 patients, a transition of the dominant DNA methylation subclass was observed in 8 (29.6%) glioblastomas with a most frequent transition to the mesenchymal subclass (62.5%). A subclass transition was more likely after incomplete removal of contrast-enhanced tumor parts at first surgery (p = 0.04). Tumor location, adjuvant treatment, and time between primary and recurrence surgery did not influence the transition. Immune cell proportions from deconvolution data, tumor purity or specific CpG sites were not correlated with a subclass transition. Survival analyses revealed a comparable outcome for patients with or without subclass transition. Our findings demonstrate the temporal heterogeneity of DNA methylation subclasses in 29.6% of IDH-wildtype glioblastoma. We identified clinical factors and showed that a subclass transition did not impact the survival outcome. However, a possible DNA methylation subclass transition must be taken into consideration for future targeted therapies at recurrence.

DeepGRP: engineering a software tool for predicting genomic repetitive elements using Recurrent Neural Networks with attention

BACKGROUND

Repetitive elements contribute a large part of eukaryotic genomes. For example, about 40 to 50% of human, mouse and rat genomes are repetitive. So identifying and classifying repeats is an important step in genome annotation. This annotation step is traditionally performed using alignment based methods, either in a de novo approach or by aligning the genome sequence to a species specific set of repetitive sequences. Recently, Li (Bioinformatics 35:4408-4410, 2019) developed a novel software tool dna-brnn to annotate repetitive sequences using a recurrent neural network trained on sample annotations of repetitive elements.

RESULTS

We have developed the methods of dna-brnn further and engineered a new software tool DeepGRP. This combines the basic concepts of Li (Bioinformatics 35:4408-4410, 2019) with current techniques developed for neural machine translation, the attention mechanism, for the task of nucleotide-level annotation of repetitive elements. An evaluation on the human genome shows a 20% improvement of the Matthews correlation coefficient for the predictions delivered by DeepGRP, when compared to dna-brnn. DeepGRP predicts two additional classes of repeats (compared to dna-brnn) and is able to transfer repeat annotations, using RepeatMasker-based training data to a different species (mouse). Additionally, we could show that DeepGRP predicts repeats annotated in the Dfam database, but not annotated by RepeatMasker. DeepGRP is highly scalable due to its implementation in the TensorFlow framework. For example, the GPU-accelerated version of DeepGRP is approx. 1.8 times faster than dna-brnn, approx. 8.6 times faster than RepeatMasker and over 100 times faster than HMMER searching for models of the Dfam database.

CONCLUSIONS

By incorporating methods from neural machine translation, DeepGRP achieves a consistent improvement of the quality of the predictions compared to dna-brnn. Improved running times are obtained by employing TensorFlow as implementation framework and the use of GPUs. By incorporating two additional classes of repeats, DeepGRP provides more complete annotations, which were evaluated against three state-of-the-art tools for repeat annotation.

Clonal expansion and activation of tissue-resident memory-like Th17 cells expressing GM-CSF in the lungs of severe COVID-19 patients

Hyperinflammation contributes to lung injury and subsequent acute respiratory distress syndrome (ARDS) with high mortality in patients with severe coronavirus disease 2019 (COVID-19). To understand the underlying mechanisms involved in lung pathology, we investigated the role of the lung-specific immune response. We profiled immune cells in bronchoalveolar lavage fluid and blood collected from COVID-19 patients with severe disease and bacterial pneumonia patients not associated with viral infection. By tracking T cell clones across tissues, we identified clonally expanded tissue-resident memory-like Th17 cells (Trm17 cells) in the lungs even after viral clearance. These Trm17 cells were characterized by a a potentially pathogenic cytokine expression profile of IL17A and CSF2 (GM-CSF). Interactome analysis suggests that Trm17 cells can interact with lung macrophages and cytotoxic CD8+ T cells, which have been associated with disease severity and lung damage. High IL-17A and GM-CSF protein levels in the serum of COVID-19 patients were associated with a more severe clinical course. Collectively, our study suggests that pulmonary Trm17 cells are one potential orchestrator of the hyperinflammation in severe COVID-19.

New 5-Aminolevulinic Acid Esters—Efficient Protoporphyrin Precursors for Photodetection and Photodynamic Therapy¶

Photodetection (PD) and photodynamic therapy (PDT) with 5-aminolevulinic acid (ALA)-induced protoporphyrin IX (PPIX) accumulation are approaches to detect and treat dysplasia and early cancer in the gastrointestinal tract and in the urinary bladder. Because ALA-induced PPIX production is limited, we synthesized ALA ester hydrochlorides 3-22 and tested them in two different in vitro models (gastrointestinal tract: HT29-CCD18; urinary bladder: J82-UROTSA). PPIX accumulation after incubation with 0.12 mmol/L for 3 h and PPIX accumulation as a function of different incubation times were measured using flow cytometry. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays were performed to check cellular dark toxicity. Phototoxicity after irradiation was tested. ALA nonafluorohexylester hydrochloride 11, ALA thiohexylester hydrochloride 13 and ALA dibenzyldiester dihydrochloride 19 induced appreciably increased PPIX levels and showed improved phototoxicity compared with the references ALA hydrochloride 1, ALA hexylester hydrochloride 3 and ALA benzylester hydrochloride 4. Thus, the new compounds 11, 13 and 19 are promising compounds for PD and PDT.

Improving the use of 5-aminolevulinic acid (ALA)-induced protoporphyrin IX (PPIX) for the gastrointestinal tract by esterification--an in vitro study

Possible approaches to improve the diagnostic and therapeutic effects of 5-aminolevulinic acid (ALA)-induced protoporphyrin IX (PPIX) are the esterification of ALA for enhanced uptake and the choice of wavelength for irradiation. The human colonic cell lines HT29 [G2] and CCD18 (fibroblasts) were incubated with 0.6 mM ALA, ALA-hexylester or -benzylester respectively, and for further assays with hypotaurine, in addition. PPIX-accumulation was analyzed by flow cytometry and fluorescence spectroscopy. PPIX formation kinetics were continuously recorded. Incubated cells were irradiated with an incoherent light source lambda = 400-700 nm or lambda = 590-700 nm, respectively. After PDT treatment, clonogenicity assays were performed to determine cell viability. Esterification leads to increased PPIX-accumulation, decreased time for production of detectable amounts of PPIX as well as increased response to PDT. Tumor specificity is always maintained or exceeds values for ALA alone. ALA enters the cells via beta transporter whereas esters by passive diffusion. Altering irradiation wavelengths showed the independence of wavelength rather than light dose. Results emphasize the role of heme metabolism for generating tumor specificity rather than the process of ALA-uptake, an important detail for future clinical application.

The effects of 5-aminolevulinic acid esters on protoporphyrin IX production in human adenocarcinoma cell lines

Photodynamic diagnosis (PDD) and photodynamic therapy (PDT) using 5-aminolevulinic acid (ALA)-induced protoporphyrin IX (PPIX) is an interesting approach to detect and treat dysplasia and early cancers in the gastrointestinal tract. Because of low lipophilicity resulting in poor penetration across cell membranes, high doses of ALA should be administered in order to reach clinically relevant levels of PPIX. One way of increasing PPIX accumulation is derivatization of ALA into a more lipophilic molecule. In our in vitro study, different esterifications of ALA were investigated to analyze the effects on PPIX accumulation in human adenocarcinoma cell lines. For systematic analysis of cell type-specific PPIX accumulation, three human adenocarcinoma cell lines (SW480, HT29 and CaCo2) and a fibroblast cell line (CCD18) were tested. 3-(4,5-Dimethylthiazole-2-yl)-2,5-biphenyl tetrazolium bromide (MTT) assays were performed to ensure that the ALA esters showed no cellular dark toxicity. Different concentrations (ranging from 0.012 to 0.6 mmol/L, 3 h) and incubation times (5, 10, 30, 180 min; 0.12 mmol/L) were examined. PPIX accumulation was measured using flow cytometry. ALA esters, especially ALA-hexylester and ALA-benzylester, induced significant higher PPIX levels in adenocarcinoma cell lines when compared with ALA and may be promising candidates for PDT and PDD.

The effects of 5-aminolevulinic acid esters on protoporphyrin IX production in human adenocarcinoma cell lines

Photodynamic diagnosis (PDD) and photodynamic therapy (PDT) using 5-aminolevulinic acid (ALA)-induced protoporphyrin IX (PPIX) is an interesting approach to detect and treat dysplasia and early cancers in the gastrointestinal tract. Because of low lipophilicity resulting in poor penetration across cell membranes, high doses of ALA should be administered in order to reach clinically relevant levels of PPIX. One way of increasing PPIX accumulation is derivatization of ALA into a more lipophilic molecule. In our in vitro study, different esterifications of ALA were investigated to analyze the effects on PPIX accumulation in human adenocarcinoma cell lines. For systematic analysis of cell type-specific PPIX accumulation, three human adenocarcinoma cell lines (SW480, HT29 and CaCo2) and a fibroblast cell line (CCD18) were tested. 3-(4,5-Dimethylthiazole-2-yl)-2,5-biphenyl tetrazolium bromide (MTT) assays were performed to ensure that the ALA esters showed no cellular dark toxicity. Different concentrations (ranging from 0.012 to 0.6 mmol/L, 3 h) and incubation times (5, 10, 30, 180 min; 0.12 mmol/L) were examined. PPIX accumulation was measured using flow cytometry. ALA esters, especially ALA-hexylester and ALA-benzylester, induced significant higher PPIX levels in adenocarcinoma cell lines when compared with ALA and may be promising candidates for PDT and PDD.

Protoporphyrin IX distribution following local application of 5-aminolevulinic acid and its esterified derivatives in the tissue layers of the normal rat colon

Photodynamic diagnosis and especially therapy after sensitization with 5-aminolevulinic acid (ALA) is hampered by limitations of uptake and distribution of ALA due to its hydrophilic nature. Chemical modification of ALA into its more lipophilic esters seems to be promising to overcome these problems. The aim of the present study was to investigate the comparative kinetics of protoporphyrin IX (PPIX) fluorescence in rat colonic tissue after topical application of ALA and its esterified derivatives, ALA-hexylester (h-ALA), ALA-methylester (m-ALA) and ALA-benzylester (b-ALA). Fluorescence intensity induced by PPIX in normal colonic tissue was quantified using fluorescence microscopy at 1, 2, 4, 6 and 8 h after sensitization. Mucosa exhibited higher fluorescence levels compared to the underlying submucosa or smooth muscle. Peak fluorescence intensities were seen 4 h after local sensitization with 86.0 mol ml(-1) ALA (513 +/- 0.57 counts per pixel), 6.6 mol ml(-1) m-ALA (508 +/- 35.50) and 4.8 mol ml(-1) h-ALA (532 +/- 128.80), and 6 h after sensitization with 4.6 mol ml(-1) b-ALA (468 +/- 190.27). A 13-18 times lower concentration of ALA esters was required for fluorescence intensities reached with ALA alone. A similar degree of the fluorescence ratio between mucosa and muscularis (5-6:1) was detected for ALA and its derivatives. The time point of the maximum value of this ratio was consistent with peak fluorescence levels for ALA and each ALA-ester. The clinical feasibility and the advantages of topical ALA ester-based fluorescence for detection of malignant and premalignant lesions need further investigations.

[Arteriovenous fistula in the tabatière region--primary shunt in chronic hemodialysis]

The number of patients with end-stage renal disease treated by chronic hemodialysis is permanently increased. An assumption of a long-term and successful treatment is the durable functioning vascular access. The method of choice worldwide is the typical Cimino fistula on the distal forearm, but a more peripheral arterio-venous fistula is possible. A fistula in the Tabatière region has proved to be excellent in our experience with 51 patients operated between January 1985 and March 1987. The surgical technique, results, and advantages of this vascular access operation are described.