Stable long-term outcomes after cochlear implantation in subjects with TMPRSS3 associated hearing loss: a retrospective multicentre study.

BACKGROUND: The spiral ganglion hypothesis suggests that pathogenic variants in genes preferentially expressed in the spiral ganglion nerves (SGN), may lead to poor cochlear implant (CI) performance. It was long thought that TMPRSS3 was particularly expressed in the SGNs. However, this is not in line with recent reviews evaluating CI performance in subjects with TMPRSS3-associated sensorineural hearing loss (SNHL) reporting overall beneficial outcomes. These outcomes are, however, based on variable follow-up times of, in general, 1 year or less. Therefore, we aimed to 1. evaluate long-term outcomes after CI implantation of speech recognition in quiet in subjects with TMPRSS3-associated SNHL, and 2. test the spiral ganglion hypothesis using the TMPRSS3-group. METHODS: This retrospective, multicentre study evaluated long-term CI performance in a Dutch population with TMPRSS3-associated SNHL. The phoneme scores at 70 dB with CI in the TMPRSS3-group were compared to a control group of fully genotyped cochlear implant users with post-lingual SNHL without genes affecting the SGN, or severe anatomical inner ear malformations. CI-recipients with a phoneme score ≤ 70% at least 1-year post-implantation were considered poor performers and were evaluated in more detail. RESULTS: The TMPRSS3 group consisted of 29 subjects (N = 33 ears), and the control group of 62 subjects (N = 67 ears). For the TMPRSS3-group, we found an average phoneme score of 89% after 5 years, which remained stable up to 10 years post-implantation. At both 5 and 10-year follow-up, no difference was found in speech recognition in quiet between both groups (p = 0.830 and p = 0.987, respectively). Despite these overall adequate CI outcomes, six CI recipients had a phoneme score of ≤ 70% and were considered poor performers. The latter was observed in subjects with residual hearing post-implantation or older age at implantation. CONCLUSION: Subjects with TMPRSS3-associated SNHL have adequate and stable long-term outcomes after cochlear implantation, equal to the performance of genotyped patient with affected genes not expressed in the SGN. These findings are not in line with the spiral ganglion hypothesis. However, more recent studies showed that TMPRSS3 is mainly expressed in the hair cells with only limited SGN expression. Therefore, we cannot confirm nor refute the spiral ganglion hypothesis.

Extended Resections for Advanced Gallbladder Cancer: Results from a Nationwide Cohort Study.

BACKGROUND: Extended resections (i.e., major hepatectomy and/or pancreatoduodenectomy) are rarely performed for gallbladder cancer (GBC) because outcomes remain inconclusive. Data regarding extended resections from Western centers are sparse. This Dutch, multicenter cohort study analyzed the outcomes of patients who underwent extended resections for locally advanced GBC. METHODS: Patients with GBC who underwent extended resection with curative intent between January 2000 and September 2018 were identified from the Netherlands Cancer Registry. Extended resection was defined as a major hepatectomy (resection of ≥ 3 liver segments), a pancreatoduodenectomy, or both. Treatment and survival data were obtained. Postoperative morbidity, mortality, survival, and characteristics of short- and long-term survivors were assessed. RESULTS: The study included 33 patients. For 16 of the patients, R0 resection margins were achieved. Major postoperative complications (Clavien Dindo ≥ 3A) occurred for 19 patients, and 4 patients experienced postoperative mortality within 90 days. Recurrence occurred for 24 patients. The median overall survival (OS) was 12.8 months (95% confidence interval, 6.5-19.0 months). A 2-year survival period was achieved for 10 patients (30%) and a 5-year survival period for 5 patients (15%). Common bile duct, liver, perineural and perivascular invasion and jaundice were associated with reduced survival. All three recurrence-free patients had R0 resection margins and no liver invasion. CONCLUSION: The median OS after extended resections for advanced GBC was 12.8 months in this cohort. Although postoperative morbidity and mortality were significant, long-term survival (≥ 2 years) was achieved in a subset of patients. Therefore, GBC requiring major surgery does not preclude long-term survival, and a subgroup of patients benefit from surgery.

Nationwide study of patients with head and neck paragangliomas carrying SDHB germline mutations.

BACKGROUND: Germline mutations in the succinate dehydrogenase B (SDHB) gene predispose to hereditary paraganglioma (PGL) syndrome type 4. The aim of this study was to evaluate the clinical characteristics and outcome of treatment strategies for patients with head and neck paraganglioma (HNPGL) carrying SDHB germline mutations. METHODS: This was a retrospective evaluation of patients with HNPGL carrying SDHB germline mutations in the Netherlands. RESULTS: In a Dutch nationwide cohort study of SDHB germline mutation carriers, 54 patients with a total of 62 HNPGLs were identified. Forty-one of 54 patients (76 per cent) visited the outpatient clinic because of associated complaints. Eight patients (15 per cent) had multiple PGLs. One patient (2 per cent) developed a phaeochromocytoma and three (6 per cent) developed a malignant PGL. Twenty-seven patients (50 per cent) had an operation for their HNPGL and 15 (28 per cent) received radiotherapy. Three patients with HNPGL (6 per cent) were diagnosed with additional non-paraganglionic tumours. CONCLUSION: If an SDHB germline mutation is identified in a patient with HNPGL, the clinician should be aware of the variable manifestations of the SDHB-linked tumour syndrome, the risk of catecholamine excess, concurrent phaeochromocytoma, and association with non-paraganglionic tumours.

The penetrance of paraganglioma and pheochromocytoma in SDHB germline mutation carriers.

Germline mutations in succinate dehydrogenase B (SDHB) predispose to hereditary paraganglioma (PGL) syndrome type 4. The risk of developing PGL or pheochromocytoma (PHEO) in SDHB mutation carriers is subject of recent debate. In the present nationwide cohort study of SDHB mutation carriers identified by the clinical genetics centers of the Netherlands, we have calculated the penetrance of SDHB associated tumors using a novel maximum likelihood estimator. This estimator addresses ascertainment bias and missing data on pedigree size and structure. A total of 195 SDHB mutation carriers were included, carrying 27 different SDHB mutations. The 2 most prevalent SDHB mutations were Dutch founder mutations: a deletion in exon 3 (31% of mutation carriers) and the c.423+1G>A mutation (24% of mutation carriers). One hundred and twelve carriers (57%) displayed no physical, radiological or biochemical evidence of PGL or PHEO. Fifty-four patients had a head and neck PGL (28%), 4 patients had a PHEO (2%), 26 patients an extra-adrenal PGL (13%). The overall penetrance of SDHB mutations is estimated to be 21% at age 50 and 42% at age 70 when adequately corrected for ascertainment. These estimates are lower than previously reported penetrance estimates of SDHB-linked cohorts. Similar disease risks are found for different SDHB germline mutations as well as for male and female SDHB mutation carriers.

Homozygous TMEM127 mutations in 2 patients with bilateral pheochromocytomas.

Pheochromocytoma (PCC) and paraganglioma (PGL) are rare neuroendocrine tumors that are hereditary in up to 50% of patients. The gene encoding transmembrane-protein-127 (TMEM127) is one of the PCC/PGL-susceptibility genes with an autosomal dominant inheritance pattern. Here, we report 2 patients with bilateral PCC who both harbored a homozygous TMEM127-mutation. In a 31-year-old mentally retarded patient, the homozygous c.410-2A > G mutation was discovered during an update of DNA analysis. A 26-year-old mentally retarded patient was found to have a homozygous c.3G > A mutation. The parents of both patients were consanguineous. We reviewed previously reported clinical features of TMEM127 mutation carriers and compared our findings with case descriptions of homozygous mutations in other PGL/PCC-susceptibility genes. Homozygosity for an autosomal dominant inherited disorder is an extremely rare phenomenon and has, to our knowledge, not been reported before for the gene encoding TMEM127. In the present cases, the clinical picture does not seem to be very different from heterozygous TMEM127 mutation carriers, except for a relatively large tumor size and more pronounced plasma metanephrine concentration. It is unclear whether the mental retardation is causally related to homozygosity of the TMEM127 mutations. Updating genetic screening in patients in whom PCC/PGL has been diagnosed in the past should be considered as it might provide clinically relevant information.

Evaluation of the XRCC1 gene as a phenotypic modifier in BRCA1/2 mutation carriers. Results from the consortium of investigators of modifiers of BRCA1/BRCA2.

BACKGROUND: Single-nucleotide polymorphisms (SNPs) in genes involved in DNA repair are good candidates to be tested as phenotypic modifiers for carriers of mutations in the high-risk susceptibility genes BRCA1 and BRCA2. The base excision repair (BER) pathway could be particularly interesting given the relation of synthetic lethality that exists between one of the components of the pathway, PARP1, and both BRCA1 and BRCA2. In this study, we have evaluated the XRCC1 gene that participates in the BER pathway, as phenotypic modifier of BRCA1 and BRCA2. METHODS: Three common SNPs in the gene, c.-77C>T (rs3213245) p.Arg280His (rs25489) and p.Gln399Arg (rs25487) were analysed in a series of 701 BRCA1 and 576 BRCA2 mutation carriers. RESULTS: An association was observed between p.Arg280His-rs25489 and breast cancer risk for BRCA2 mutation carriers, with rare homozygotes at increased risk relative to common homozygotes (hazard ratio: 22.3, 95% confidence interval: 14.3-34, P<0.001). This association was further tested in a second series of 4480 BRCA1 and 3016 BRCA2 mutation carriers from the Consortium of Investigators of Modifiers of BRCA1 and BRCA2. CONCLUSIONS AND INTERPRETATION: No evidence of association was found when the larger series was analysed which lead us to conclude that none of the three SNPs are significant modifiers of breast cancer risk for mutation carriers.

Conceptual binding: integrated visual cues reduce processing costs in bimanual movements.

In discrete reaction time (RT) tasks, it has been shown that nonsymmetric bimanual movements are initiated slower than symmetric movements in response to symbolic cues. By contrast, no such RT differences are found in response to direct cues ("direct cue effect"). Here, we report three experiments showing that the direct cue effect generalizes to rhythmical bimanual movements and that RT cost depends on different cue features: 1) symbolic versus direct or 2) integrated (i.e., action of both hands is indicated as one entity) versus dissociated (i.e., action of each hand is indicated separately). Our main finding was that dissociated symbolic cues were most likely processed serially, resulting in the longest RTs, which were substantially reduced with integrated symbolic cues. However, extra RT costs for switching to nonsymmetrical bimanual movements were overcome only when the integrated cues were direct. We conclude that computational resources might have been exceeded when the response needs to be determined for each hand separately, but not when a common response for both hands is selected. This supports the idea that bimanual control benefits from conceptual binding.

Further clinical and molecular delineation of the 9q subtelomeric deletion syndrome supports a major contribution of EHMT1 haploinsufficiency to the core phenotype.

BACKGROUND: The 9q subtelomeric deletion syndrome (9qSTDS) is clinically characterised by moderate to severe mental retardation, childhood hypotonia and facial dysmorphisms. In addition, congenital heart defects, urogenital defects, epilepsy and behavioural problems are frequently observed. The syndrome can be either caused by a submicroscopic 9q34.3 deletion or by intragenic EHMT1 mutations leading to haploinsufficiency of the EHMT1 gene. So far it has not been established if and to what extent other genes in the 9q34.3 region contribute to the phenotype observed in deletion cases. This study reports the largest cohort of 9qSTDS cases so far. METHODS AND RESULTS: By a multiplex ligation dependent probe amplification (MLPA) approach, the authors identified and characterised 16 novel submicroscopic 9q deletions. Direct sequence analysis of the EHMT1 gene in 24 patients exhibiting the 9qSTD phenotype without such deletion identified six patients with an intragenic EHMT1 mutation. Five of these mutations predict a premature termination codon whereas one mutation gives rise to an amino acid substitution in a conserved domain of the protein. CONCLUSIONS: The data do not provide any evidence for phenotype-genotype correlations between size of the deletions or type of mutations and severity of clinical features. Therefore, the authors confirm the EHMT1 gene to be the major determinant of the 9qSTDS phenotype. Interestingly, five of six patients who had reached adulthood had developed severe psychiatric pathology, which may indicate that EHMT1 haploinsufficiency is associated with neurodegeneration in addition to neurodevelopmental defect.

A genome-wide linkage scan in a Dutch family identifies a premature ovarian failure susceptibility locus.

BACKGROUND: Premature ovarian failure (POF) is characterized by elevated gonadotrophins and amenorrhea before the age of 40 years and occurs approximately in 1% of women. POF etiology is highly heterogeneous with a wide spectrum of etiological pathogenic mechanisms including genetic causes. These mostly involve numerical, structural or monogenic defects on the X-chromosome. Mutations in a small number of autosomal genes (such as FOXL2 and NOBOX) have been identified as a cause of POF. However, in most cases, the disease underlying mechanisms are largely unknown. METHODS: We performed a genome-wide linkage analysis in a relatively large Dutch family with seven patients suffering from POF, showing a dominant pattern of inheritance. A genome-wide analysis, using 50K single nucleotide polymorphism arrays, was combined with conventional parametric linkage analysis. RESULTS: We identified three genomic regions on chromosomes 5, 14 and 18 yielding suggestive linkage (multipoint LOD score of 2.4 for each region). After inclusion of one elder unaffected family member, only the region on chromosome 5 remains as a putative POF locus. In addition, we investigated a second family (three living patients over three generations) for the regions on chromosome 5, 14 and 18. Haplotype analysis supported only the locus on chromosome 5q14.1-q15. CONCLUSION: We performed the first genome-wide linkage search in familial POF and identified a region on chromosome 5q14.1-q15, which may harbor a novel POF susceptibility gene.

Congenital diaphragmatic hernia associated with duplication of 11q23-qter.

Congenital diaphragmatic hernia (CDH) is a relatively common birth defect with a high mortality. Although little is known about its etiology, there is increasing evidence for a strong genetic contribution. Both numerical and structural chromosomal abnormalities have been described in patients with CDH. Partial trisomy 11q and partial trisomy 22 associated with the common t(11;22) has been reported in several cases of CDH. It has been assumed that the diaphragmatic defect seen in these individuals was primarily due to duplication of material from chromosome 22q11. However, in this report we describe a family with a t(11;12) in which one of two brothers with partial trisomy 11q has a left sided posterolateral CDH. This is the second case of CDH in partial trisomy 11q due to an unbalanced translocation other than t(11;22). Using array-based comparative genomic hybridization and fluorescent in situ hybridization, we mapped the breakpoints in both brothers and their mother who is a balanced translocation carrier. Our results suggest that duplication of one or more genes on a approximately 19 Mb region of 11q23.3-qter predisposes to the development of CDH. These effects may be the primary cause of CDH in individuals t(11;22) or may be additive to effects from the duplication of chromosome 22 material. We also conclude that the partial trisomy 11q syndrome has a variable phenotype and that CDH should be added to the spectrum of anomalies that can be present in this syndrome.

Congenital diaphragmatic hernia and chromosome 15q26: determination of a candidate region by use of fluorescent in situ hybridization and array-based comparative genomic hybridization.

Congenital diaphragmatic hernia (CDH) has an incidence of 1 in 3,000 births and a high mortality rate (33%-58%). Multifactorial inheritance, teratogenic agents, and genetic abnormalities have all been suggested as possible etiologic factors. To define candidate regions for CDH, we analyzed cytogenetic data collected on 200 CDH cases, of which 7% and 5% showed numerical and structural abnormalities, respectively. This study focused on the most frequent structural anomaly found: a deletion on chromosome 15q. We analyzed material from three of our patients and from four previously published patients with CDH and a 15q deletion. By using array-based comparative genomic hybridization and fluorescent in situ hybridization to determine the boundaries of the deletions and by including data from two individuals with terminal 15q deletions but without CDH, we were able to exclude a substantial portion of the telomeric region from the genetic etiology of this disorder. Moreover, one patient with CDH harbored a small interstitial deletion. Together, these findings allowed us to define a minimal deletion region of approximately 5 Mb at chromosome 15q26.1-26.2. The region contains four known genes, of which two--NR2F2 and CHD2--are particularly intriguing gene candidates for CDH.

Genetics and developmental biology of oesophageal atresia and tracheo-oesophageal fistula: lessons from mice relevant for paediatric surgeons.

Oesophageal atresia and tracheo-oesophageal fistula are relatively frequently occurring foregut malformations of which the aetiology and pathogenesis are poorly understood. Recent results of molecular genetic studies, in particular the use of single and compound mutant mice, have yielded a tremendous increase in the understanding of the molecular mechanisms involved in normal and abnormal foregut morphogenesis. In the introduction of this paper, we review the very early stages of normal and abnormal embryology of the foregut derivatives and the separation of the foregut into a ventral respiratory part and a dorsal digestive part. After that, we describe the genes that have been demonstrated to play an important role in these processes.

Early diagnosis of Wolf-Hirschhorn syndrome triggered by a life-threatening event: congenital diaphragmatic hernia.

Wolf-Hirschhorn syndrome (WHS, OMIM 194190) is a chromosomal disorder characterized by retarded mental and physical growth, microcephaly, Greek helmet appearance of the facies, seizures/epilepsy. Closure defects of lip or palate, and cardiac septum defects occur in 30-50% of cases. Its cause is a deletion in the short arm of chromosome 4. We present a male patient, born after 37 weeks gestation, as the fourth pregnancy of non-consanguineous healthy parents, with unilateral cleft lip and palate, hypertelorism, a right-sided ear tag, and mild epispadias. At age 10 weeks he developed acute respiratory distress and acute bowel obstruction requiring emergency laparotomy. This revealed a left-sided posterolateral diaphragmatic defect, type Bochdalek, with incarceration of the small intestines necessitating major bowel resection. Clinical genetic investigation suggested a chromosome anomaly, but regular karyotyping was normal. However, FISH analysis showed a microdeletion in the short arm of chromosome 4 (4p-), consistent with WHS. A combination of this syndrome with congenital diaphragmatic hernia (CDH) has been rarely described. CDH can present either as an isolated defect at birth, or with multiple congenital abnormalities, or as part of a defined syndrome or chromosomal disorder. Therefore CDH, although not common in WHS, can lead to its diagnosis relatively early in life. We strongly recommend a clinical genetic evaluation of each CDH patient with facial anomalies taking into consideration 4p- deletion syndrome.

Congenital diaphragmatic hernia: an evaluation of the prognostic value of the lung-to-head ratio and other prenatal parameters.

OBJECTIVES: A retrospective analysis of the prognostic significance of the lung-to-head ratio (LHR) and other prenatal parameters on the outcome of fetuses with left-sided congenital diaphragmatic hernia (CDH). METHODS: A total of 26 fetuses with isolated left CDH without chromosomal abnormalities were included. Twenty-one LHR measurements could retrospectively be calculated from the last available ultrasonographic recordings before birth. The relationship between LHR and fetal outcome and the gestational age dependency of this relation was tested. Cutoff levels as previously published were applied to determine their predictive value in this population. The association between other prenatal predictive variables and fetal outcome was also determined. Survival was defined as discharge from the hospital. RESULTS: The overall survival rate was 50%. There was a statistically significant difference between the mean LHR of the survivors compared to the mean LHR of the nonsurvivors (1.78 vs 1.02), whereas the mean gestational age of these two groups did not differ. LHR was not gestational age dependent in the prediction of fetal outcome. The cutoff levels LHR <1, 1-1.4, >1.4 showed a good applicability in the prediction of fetal outcome within the present study population with a 100% survival if LHR >1.4 and a 100% mortality if LHR <1. An intrathoracic position of the stomach, mediastinal shift, polyhydramnios as individual variables and early diagnosis (<25 weeks' gestation) revealed to be poor sonographic predictors for fetal outcome. CONCLUSION: LHR proved to be a good predictor for fetal outcome, independent of gestational age at the time of the measurement. To substantiate our observation, a prospective multicenter study is warranted.

Single rapid real-time monitored isothermal RNA amplification assay for quantification of human immunodeficiency virus type 1 isolates from groups M, N, and O.

Because human immunodeficiency virus type 1 (HIV-1) subtypes and circulating recombinant forms (CRFs) are spreading rapidly worldwide and are becoming less confined to a geographical area, RNA assays that can detect and quantify all HIV-1 isolates reliably are in demand. We have developed a fast, real-time monitored RNA assay based on an isothermal nucleic acid sequence-based amplification technology that amplifies a part of the long terminal repeat region of the HIV-1 genome. Real-time detection was possible due to the addition of molecular beacons to the amplification reaction that was monitored in a fluorimeter with a thermostat. The lower level of detection of the assay was 10 HIV-1 RNA molecules per reaction, and the lower level of quantification was 100 copies of HIV-1 RNA with a dynamic range of linear quantification between 10(2) and 10(7) RNA molecules. All HIV-1 groups, subtypes, and CRFs could be detected and quantified with equal efficiency, including the group N isolate YBF30 and the group O isolate ANT70. To test the clinical utility of the assay, a series of 62 serum samples containing viruses that encompassed subtypes A through G and CRFs AE and AG of HIV-1 group M were analyzed, and these results were compared to the results of a commercially available assay. This comparison showed that the quantification results correlated highly (R(2) = 0.735) for those subtypes that could be well quantified by both assays (subtypes B, C, D, and F), whereas improved quantification was obtained for subtypes A and G and CRFs AE and AG. A retrospective study with six individuals infected with either a subtype A, B, C, or D or an AG isolate of HIV-1 group M, who were treated with highly active antiretroviral therapy, revealed that the assay was well suited to the monitoring of therapy effects. In conclusion, the newly developed real-time monitored HIV-1 assay is a fast and sensitive assay with a large dynamic range of quantification and is suitable for quantification of most if not all subtypes and groups of HIV-1.

Establishment of new transmissible and drug-sensitive human immunodeficiency virus type 1 wild types due to transmission of nucleoside analogue-resistant virus.

Sequence analysis of human immunodeficiency virus type 1 (HIV-1) from 74 persons with acute infections identified eight strains with mutations in the reverse transcriptase (RT) gene at positions 41, 67, 68, 70, 215, and 219 associated with resistance to the nucleoside analogue zidovudine (AZT). Follow-up of the fate of these resistant HIV-1 strains in four newly infected individuals revealed that they were readily replaced by sensitive strains. The RT of the resistant viruses changed at amino acid 215 from tyrosine (Y) to aspartic acid (D) or serine (S), with asparagine (N) as a transient intermediate, indicating the establishment of new wild types. When we introduced these mutations and the original threonine (T)-containing wild type into infectious molecular clones and assessed their competitive advantage in vitro, the order of fitness was in accord with the in vivo observations: 215Y < 215D = 215S = 215T. As detected by real-time nucleic acid sequence-based amplification with two molecular beacons, the addition of AZT or stavudine (d4T) to the viral cultures favored the 215Y mutant in a dose-dependent manner. Our results illustrate that infection with nucleoside analogue-resistant HIV leads in newly infected individuals to mutants that are sensitive to nucleoside analogues, but only a single mutation removed from drug-resistant HIV. Such mutants were shown to be transmissible, stable, and prone to rapid selection for resistance to AZT or d4T as soon as antiretroviral therapy was administered. Monitoring of patients for the presence of new HIV-1 wild types with D, S, or N residues at position 215 may be warranted in order to estimate the threat to long-term efficacy of regimens including nucleoside analogues.

Establishment of an Embryotoxicity Assay with Green Fluorescence Protein-expressing Embryonic Cell-derived Cardiomyocytes.

Transgenic embryonic stem cells were used to determine the embryotoxic effects of chemicals on the development of embryonic tissues. This investigation supports an ongoing validation study, aimed at reducing the time-consuming procedure currently in use, and at providing more-objective and more-detailed information on the embryotoxic potentials of chemicals. Green fluorescence protein (GFP) was used as a reporter gene and was linked to a human α-cardiac-specific promoter. The expression of GFP was switched on after specific activation of the human α-actin promoter. This permitted the easy quantification of cardiac cells by using a fluorescence-activated cell sorter (FACS). The percentage of cardiac precursor cells was calculated from the FACS-distribution pattern of cells which fluoresced versus the total number of cells. The percentage of cardiac precursor cells increased from 25% in embryoid bodies on day 3, to 86% on day 7. However, in 11-day-old embryoid bodies, the percentage decreased to 35%. Five chemicals with known embryotoxic potentials were compared with respect to the IC50 (concentration causing 50% inhibition of measured effect) values obtained by various in vitro endpoints (for example, cytotoxicity, morphology). The results showed a higher sensitivity of endpoints used for the analysis of specific effects on the selected target tissue. The data also showed the need to develop in vitro methods with specific endpoints which account for the complexity of embryotoxicology.

Effects of Embryotoxic Chemicals on the In vitro Differentiation of Genetically Engineered Embryonic Stem Cells into Cardiac Cells.

A project has been started using transgenic embryonic stem cells as a toxicological endpoint in order to register chemical effects on the development of embryonic tissues which are known to be sensitive during their differentiation. The green fluorescent protein (GFP) is used as a reporter gene and is linked to a cardiac specific promotor. This construct is integrated into the native DNA of undifferentiated embryonic stem cells. The expression of GFP was switched on after specific activation of the promotor (human-alpha-actin) which allows a quantification of cardiac cells using the fluorescence activated cell sorter. Kinetic analysis shows a differentiation of 25% on cells with activated human-alpha-actin promotor on day 3, increasing to 86% on day 7, and decreasing again to 35% on day 11. The known animal teratogens retinoic acid and 5-fluorouracil were chosen and the measurements were compared to the IC(50) values given by other in vitro endpoints in order to investigate the potential of this toxicological endpoint. The results show a higher sensitivity of endpoints which analysed specific effects on a selected target tissue. The exposure of embryonic stem cells to chemicals lead to the following IC(50) values: 1.149+/-0.170 ng/ml (cytotoxicity) versus 0.216+/-0.126 ng/ml (GFP expression) after treatment with retinoic acid and 54.2+/-5.2 ng/ml (cytotoxicity) versus 26.7+/-2 ng/ml (GFP expression) after treatment with 5-fluorouracil. The data shows the necessity to develop specific in vitro methods which take the complexity of embryotoxicology into account.

Induction of prothrombin synthesis by K-vitamins compared in vitamin K-deficient and in brodifacoum-treated rats.

Vitamin K is a group name for a number of prenylated 2-methyl-1,4-naphtoquinones, which may differ in their ability to function as a cofactor for prothrombin biosynthesis. To quantify the bioactivity of different forms of vitamin K, two experimental animal systems are frequently used: vitamin K-deficient rats and anticoagulated rats. In this paper both models are compared, and it is shown that the results obtained depend on the model used. The main reason for this discrepancy is the difference in recycling of vitamin K-epoxide, which results in a 500 times higher vitamin K requirement in anticoagulated rats. Absorption and hepatic accumulation of long chain menaquinones seem to be restricted to a maximum, whereas also the lipophilic nature of long chain menaquinones may hamper the quinone-quinol reduction in anticoagulated animals. If these data may be extrapolated to patients, food items rich in K1 and MK-4 would be expected to influence the stability of oral anticoagulation to a much larger extent than food items primarily containing higher menaquinones.