Vanderstichele, H.M.J.

Neurofilament ELISA validation (Article)

2010-01-31T00:00:00Z

Background: Neurofilament proteins (Nf) are highly specific biomarkers for neuronal death and axonal degeneration. As these markers become more widely used, an inter-laboratory validation study is required to identify assay criteria for high quality performance. Methods: The UmanDiagnostics NF-light ®enzyme-linked immunoabsorbent assays (ELISA) for the neurofilament light chain (NfL, 68 kDa) was used to test the intra-assay and inter-laboratory coefficient of variation (CV) between 35 laboratories worldwide on 15 cerebrospinal fluid (CSF) samples. Critical factors, such as sample transport and storage, analytical delays, reaction temperature and time, the laboratories' accuracy and preparation of standards were documented and used for the statistical analyses. Results: The intra-laboratory CV averaged 3.3% and the inter-laboratory CV 59%. The results from the test laboratories correlated with those from the reference laboratory (R = 0.60, p < 0.0001). Correcting for critical factors improved the strength of the correlation. Differences in the accuracy of standard preparation were identified as the most critical factor. Correcting for the error introduced by variation in the protein standards improved the correlation to R = 0.98, p < 0.0001 with an averaged inter-laboratory CV of 14%. The corrected overall inter-rater agreement was subtantial (0.6) according to Fleiss' multi-rater kappa and Gwet's AC1 statistics. Conclusion: This multi-center validation study identified the lack of preparation of accurate and consistent protein standards as the main reason for a poor inter-laboratory CV. This issue is also relevant to other protein biomarkers based on this type of assay and will need to be solved in order to achieve an acceptable level of analytical accuracy. The raw data of this study is available online.

Increased total-Tau levels in cerebrospinal fluid of pediatric hydrocephalus and brain tumor patients (Article)

2008-07-01T00:00:00Z

Total Tau (t-Tau), hyperphosphorylated Tau (p-Tau(181P)) and β-amyloid(1-42)in cerebrospinal fluid (CSF) have shown to be markers of neuronal and axonal degeneration in various neurological and neurodegenerative diseases. The aim of this study was to evaluate the influence of the presence of a brain tumor and hydrocephalus on t-Tau, p-Tau(181P)and β-amyloid(1-42)levels in CSF of pediatric patients. t-Tau, p-Tau(181P)and β-amyloid(1-42)levels were simultaneously quantified by xMAP®technology in 22 lumbar and 15 ventricular CSF samples from newly diagnosed pediatric brain tumor patients and 39 lumbar and 12 ventricular CSF samples from pediatric patients without a brain tumor. t-Tau, p-Tau(181P)and β-amyloid(1-42)levels in both lumbar and ventricular CSF were not significantly correlated with age. t-Tau levels in lumbar CSF were elevated in brain tumor patients, being especially high in medulloblastoma patients. Lumbar CSF p-Tau(181P)levels were lower in brain tumor patients compared to normal controls. Ventricular levels of t-Tau, p-Tau(181P)and β-amyloid(1-42)were not significantly different between the brain tumor patients and non-tumor patients, but t-Tau levels were significantly increased in patients with radiological signs of hydrocephalus. Two patients with an infected ventriculo-peritoneal drain also had high CSF t-Tau levels. In conclusion, high t-Tau levels in CSF are found in pediatric patients with a brain tumor, patients with hydrocephalus and patients with a serious CNS infection, reflecting neuronal and axonal damage. Ongoing studies should determine whether these neurodegenerative markers in CSF can be used to monitor neuronal and axonal degeneration in these patients during therapy and long-term follow up.

The Glu318Gly substitution in presenilin 1 is not causally related to Alzheimer disease (Article)

1999-01-01T00:00:00Z

Peritubular myoid cells from immature rat testes secrete activin-A and express activin receptor type II in vitro (Article)

1994-01-01T00:00:00Z

The expression of activin type II and IIB receptors and inhibin alpha-, beta A-, and beta B-subunit messenger RNAs (mRNAs), and the secretion of immunoreactive and bioactive activin during culture of testicular peritubular myoid cells and peritubular myoid cell lines were studied. Cultured peritubular myoid cells and cell lines expressed high levels of inhibin beta A-subunit mRNA and some inhibin alpha- and beta B-subunit mRNA. Activin receptor type II mRNA was also detected, whereas activin receptor type IIB mRNA expression was not found. Expression of the beta A-subunit mRNA was present immediately after isolation of the cells and increased during culture in Eagle's Minimum Essential Medium containing 10% fetal calf serum. beta A-Subunit mRNA expression was not regulated by the synthetic androgen R1881. Western blotting of peritubular myoid cell- and peritubular cell line-conditioned media with a polyclonal antiserum against recombinant activin-A revealed the presence of 25-kilodalton activin-A, whereas activin bioactivity was detected using the animal cap assay. Because of the secretion of activin-A by peritubular myoid cells, the effects of recombinant activin-A on Sertoli cell inhibin and transferrin secretion were examined. Activin-A stimulated both basal and FSH-stimulated inhibin and transferrin production by Sertoli cells after 72 h of culture. These effects resemble the effects of the testicular paracrine factor PmodS on Sertoli cell function. It is concluded that activin-A is secreted by peritubular cells in vitro and that activin-A shares a number of effects on Sertoli cell function with PmodS.

Activin is produced by rat Sertoli cells in vitro and can act as an autocrine regulator of Sertoli cell function (Article)

1993-01-01T00:00:00Z

Regulation of androgen receptor (AR) mRNA expression was studied in Sertoli cells and peritubular myoid cells isolated from immature rat testis, and in the lymph node carcinoma cell line derived from a human prostate (LNCaP). Addition of dibutyryl-cyclic AMP (dbcAMP) to Sertoli cell cultures resulted in a rapid transient decrease in AR mRNA expression (5 h), which was followed by a gradual increase in AR mRNA expression (24-72 h). This effect of dbcAMP mimicked follicle-stimulating hormone (FSH) action. In peritubular myoid cells, there was only a moderate but prolonged decrease during incubation in the presence of dbcAMP, and in LNCaP cells no effect of dbcAMP on AR mRNA expression was observed. When Sertoli cells or peritubular myoid cells were cultured in the presence of androgens, AR mRNA expression in these cell types did not change. This is in contrast to LNCaP cells, that showed a marked reduction of AR mRNA expression during androgen treatment. In the present experiments, transcriptional regulation of AR gene expression in Sertoli cells and LNCaP cells was also examined. Freshly isolated Sertoli cell clusters were transfected with a series of luciferase reporter gene constructs, driven by the AR promoter. It was found that addition of dbcAMP to the transfected Sertoli cells resulted in a small but consistent increase in reporter gene expression (which was interpreted as resulting from AR promoter activity); a construct that only contained the AR 5' untranslated region of the cDNA sequence did not show such a regulation. The same constructs, transfected into LNCaP cells, did not show any transcriptional down-regulation when the synthetic androgen R1881 was added to the cell cultures. A nuclear transcription elongation experiment (run-on), however, demonstrated that androgen-induced AR mRNA down-regulation in LNCaP cells resulted from an inhibition of AR gene transcription. The present results indicate that in Sertoli cells and LNCaP cells, hormonal effects on AR gene transcription play a role in regulation of AR expression. However, AR gene transcription in these cells is differentially regulated.