Identification of an alternative triglyceride biosynthesis pathway

Triacylglycerols (TAGs) are the main source of stored energy in the body, providing an important substrate pool for mitochondrial beta-oxidation. Imbalances in the amount of TAGs are associated with obesity, cardiac disease and various other pathologies1,2. In humans, TAGs are synthesized from excess, coenzyme A-conjugated fatty acids by diacylglycerol O-acyltransferases (DGAT1 and DGAT2)3. In other organisms, this activity is complemented by additional enzymes4, but whether such alternative pathways exist in humans remains unknown. Here we disrupt the DGAT pathway in haploid human cells and use iterative genetics to reveal an unrelated TAG-synthesizing system composed of a protein we called DIESL (also known as TMEM68, an acyltransferase of previously unknown function) and its regulator TMX1. Mechanistically, TMX1 binds to and controls DIESL at the endoplasmic reticulum, and loss of TMX1 leads to the unconstrained formation of DIESL-dependent lipid droplets. DIESL is an autonomous TAG synthase, and expression of human DIESL in Escherichia coli endows this organism with the ability to synthesize TAG. Although both DIESL and the DGATs function as diacylglycerol acyltransferases, they contribute to the cellular TAG pool under specific conditions. Functionally, DIESL synthesizes TAG at the expense of membrane phospholipids and maintains mitochondrial function during periods of extracellular lipid starvation. In mice, DIESL deficiency impedes rapid postnatal growth and affects energy homeostasis during changes in nutrient availability. We have therefore identified an alternative TAG biosynthetic pathway driven by DIESL under potent control by TMX1.

Preliminary evaluation of a smartphone application (DelApp) for identification of delirium in sub-Saharan Africa

OBJECTIVE

In sub-Saharan Africa (SSA), there are no validated screening tools for delirium in older adults, despite the known vulnerability of older people to delirium and the associated adverse outcomes. This study aimed to assess the effectiveness of a brief smartphone-based assessment of arousal and attention (DelApp) in identification of delirium amongst older adults admitted to the medical department of a tertiary referral hospital in Northern Tanzania.

METHOD

Consecutive admissions were screened using the DelApp during a larger study of delirium prevalence and risk factors. All participants subsequently underwent detailed clinical assessment for delirium by a research doctor. Delirium and dementia were identified against DSM-5 criteria by consensus.

RESULTS

Complete data for 66 individuals were collected of whom 15 (22.7%) had delirium, 24.5% had dementia without delirium and 10.6% delirium superimposed on dementia. Sensitivity and specificity of the DelApp for delirium were 0.87 and 0.62 respectively (AUROC 0.77) and 0.88 and 0.73 (AUROC 0.85) for major cognitive impairment (dementia and delirium combined). Lower DelApp score was associated with age, significant visual impairment (<6/60 acuity), illness severity, reduced arousal and DSM-5 delirium on univariable analysis, but on multivariable logistic regression only arousal remained significant.

CONCLUSION

In this setting, the DelApp performed well in identifying delirium and major cognitive impairment but did not differentiate delirium and dementia. Performance is likely to have been affected by confounders including uncorrected visual impairment and reduced level of arousal without delirium. Negative predictive value was nevertheless high, indicating excellent "rule out" value in this setting.

Unexpected moves: a conformational change in MutSα enables high-affinity DNA mismatch binding

The DNA mismatch repair protein MutSα recognizes wrongly incorporated DNA bases and initiates their correction during DNA replication. Dysfunctions in mismatch repair lead to a predisposition to cancer. Here, we study the homozygous mutation V63E in MSH2 that was found in the germline of a patient with suspected constitutional mismatch repair deficiency syndrome who developed colorectal cancer before the age of 30. Characterization of the mutant in mouse models, as well as slippage and repair assays, shows a mildly pathogenic phenotype. Using cryogenic electron microscopy and surface plasmon resonance, we explored the mechanistic effect of this mutation on MutSα function. We discovered that V63E disrupts a previously unappreciated interface between the mismatch binding domains (MBDs) of MSH2 and MSH6 and leads to reduced DNA binding. Our research identifies this interface as a 'safety lock' that ensures high-affinity DNA binding to increase replication fidelity. Our mechanistic model explains the hypomorphic phenotype of the V63E patient mutation and other variants in the MBD interface.

Introduction to the Special Issue: Policies for Inclusive Development in Africa

While there is increasing academic analysis and policy concern regarding growing inequality and the need for more inclusive development trajectories, it is equally important to advance our understanding of the pathways to attain more inclusive development in practice. This paper serves as the introduction to a special issue examining the empirical outcomes and processes of inclusive development policies in selected countries in Africa. The paper presents a policy implementation and assessment framework as a lens that connects the different case studies. The framework links general inclusive development strategies in employment, social protection and governance, to the participation and representation of the various stakeholders as well as the monetary and non-monetary transaction costs in accessing and/or implementing these programmes on the ground in different national and sub-national contexts. Based on the findings of the 9 case studies, the paper also advances policy directions and operational frameworks to attain more inclusive development in practice.

Economic Consequences of Ill-Health in Rural Ethiopia

We use three years of household panel data to analyze the effects of ill-health on household economic outcomes in rural Ethiopia. We examine the immediate effects of various ill-health measures on health expenditure and labor supply, the subsequent coping responses, and finally the effect on income and consumption. We find evidence of substantial economic risk in terms of increased health expenditure and reduced agricultural productivity. Households are able to smooth consumption by resorting to intra-household labor substitution, borrowing and depleting assets. However, maintaining current consumption through borrowing and depletion of assets is unlikely to be sustainable and displays the need for health financing reforms and safety nets that reduce the financial consequences of ill-health.

The Coronary Sinus Reducer; 5-year Dutch experience

Background

Refractory angina is a growing and major health-care problem affecting millions of patients with coronary artery disease worldwide. The Coronary Sinus Reducer (CSR) is a device that may be considered for the relief of symptoms of refractory angina. It causes increased venous pressure leading to a dilatation of arterioles and reduced arterial vascular resistance in the sub-endocardium. This study describes the 5‑year Dutch experience regarding safety and efficacy of the CSR.

Methods

One hundred and thirty-two patients with refractory angina were treated with the CSR. The primary efficacy endpoint of the study was Canadian Cardiovascular Society (CCS) class improvement between baseline and 6‑month follow-up. The primary safety endpoint was successful CSR implantation in the absence of any device-related events.

Results

Eighty-five patients (67%) showed improvement of at least 1 CCS class and 43 patients (34%) of at least 2 classes. Mean CCS class improved from 3.17 ± 0.61 to 2.12 ± 1.07 after implantation (P < 0.001). The CSR was successfully implanted in 99% of the patients and only minor complications during implantation were reported.

Conclusion

The CSR is a simple, safe, and effective option for most patients with refractory angina. However, approximately thirty percent of the patients showed no benefit after implantation. Future studies should focus on the exact underlying mechanisms of action and reasons for non-response to better identify patients that could benefit most from this therapy.

Electronic supplementary material

The online version of this article (10.1007/s12471-020-01525-8) contains supplementary material, which is available to authorized users.

Extensive trimming of short single-stranded DNA oligonucleotides during replication-coupled gene editing in mammalian cells

Through transfection of short single-stranded oligodeoxyribonucleotides (ssODNs) small genomic alterations can be introduced into mammalian cells with high precision. ssODNs integrate into the genome during DNA replication, but the resulting heteroduplex is prone to detection by DNA mismatch repair (MMR), which prevents effective gene modification. We have previously demonstrated that the suppressive action of MMR can be avoided when the mismatching nucleotide in the ssODN is a locked nucleic acid (LNA). Here, we reveal that LNA-modified ssODNs (LMOs) are not integrated as intact entities in mammalian cells, but are severely truncated before and after target hybridization. We found that single additional (non-LNA-modified) mutations in the 5’-arm of LMOs influenced targeting efficiencies negatively and activated the MMR pathway. In contrast, additional mutations in the 3’-arm did not affect targeting efficiencies and were not subject to MMR. Even more strikingly, homology in the 3’-arm was largely dispensable for effective targeting, suggestive for extensive 3’-end trimming. We propose a refined model for LMO-directed gene modification in mammalian cells that includes LMO degradation.

The first step of many gene editing approaches in mammalian cells is to generate a targeted DNA lesion. By administering a repair template as second step, endogenous DNA repair mechanisms can be misled to introduce specific gene variants. However, subtle gene modification can also be achieved with high precision through a one-action protocol in the absence of DNA breaks. We have shown before that short single-stranded DNA molecules (LMOs) are very useful to introduce and study genetic variants that may predispose patients to cancer. While LMOs are known to integrate into the genome during DNA replication, the precise mechanism is poorly understood. We targeted mouse embryonic stem cells with differently designed LMOs to examine their effectiveness and editing outcomes. Based on these results we conclude that the two LMO termini are processed at different moments during the gene editing process. While the 3’-arm is degraded prior to LMO binding to the target site, the 5’-arm is degraded afterwards. Counterintuitively we also observe that partial degradation of the 3’-arm increases targeting efficiencies. Taken together our data provides novel mechanistic insight into our understanding of replication-coupled gene editing and may guide future LMO design strategies.

Three-step site-directed mutagenesis screen identifies pathogenic MLH1 variants associated with Lynch syndrome

BACKGROUND

Inactivating mutations in the MLH1 DNA mismatch repair (MMR) gene underlie 42% of Lynch syndrome (LS) cases. LS is a cancer predisposition causing early onset colorectal and endometrial cancer. Nonsense and frameshift alterations unambiguously cause LS. The phenotype of missense mutations that only alter a single amino acid is often unclear. These variants of uncertain significance (VUS) hinder LS diagnosis and family screening and therefore functional tests are urgently needed. We developed a functional test for MLH1 VUS termed 'oligonucleotide-directed mutation screening' (ODMS).

METHODS

The MLH1 variant was introduced by oligonucleotide-directed gene modification in mouse embryonic stem cells that were subsequently exposed to the guanine analogue 6-thioguanine to determine whether the variant abrogated MMR.

RESUTS

In a proof-of-principle analysis, we demonstrate that ODMS can distinguish pathogenic and non-pathogenic MLH1 variants with a sensitivity of >95% and a specificity of >91%. We subsequently applied the screen to 51 MLH1 VUS and identified 31 pathogenic variants.

CONCLUSION

ODMS is a reliable tool to identify pathogenic MLH1 variants. Implementation in clinical diagnostics will improve clinical care of patients with suspected LS and their relatives.

Leaving no one behind? Social inclusion of health insurance in low- and middle-income countries: a systematic review

BACKGROUND

One way to achieve universal health coverage (UHC) in low- and middle-income countries (LMIC) is the implementation of health insurance schemes. A robust and up to date overview of empirical evidence assessing and substantiating health equity impact of health insurance schemes among specific vulnerable populations in LMICs beyond the more common parameters, such as income level, is lacking. We fill this gap by conducting a systematic review of how social inclusion affects access to equitable health financing arrangements in LMIC.

METHODS

We searched 11 databases to identify peer-reviewed studies published in English between January 1995 and January 2018 that addressed the enrolment and impact of health insurance in LMIC for the following vulnerable groups: female-headed households, children with special needs, older adults, youth, ethnic minorities, migrants, and those with a disability or chronic illness. We assessed health insurance enrolment patterns of these population groups and its impact on health care utilization, financial protection, health outcomes and quality of care.

RESULTS

The comprehensive database search resulted in 44 studies, in which chronically ill were mostly reported (67%), followed by older adults (33%). Scarce and inconsistent evidence is available for individuals with disabilities, female-headed households, ethnic minorities and displaced populations, and no studies were yielded reporting on youth or children with special needs. Enrolment rates seemed higher among chronically ill and mixed or insufficient results are observed for the other groups. Most studies reporting on health care utilization found an increase in health care utilization for insured individuals with a disability or chronic illness and older adults. In general, health insurance schemes seemed to prevent catastrophic health expenditures to a certain extent. However, reimbursements rates were very low and vulnerable individuals had increased out of pocket payments.

CONCLUSION

Despite a sizeable literature published on health insurance, there is a dearth of good quality evidence, especially on equity and the inclusion of specific vulnerable groups in LMIC. Evidence should be strengthened within health care reform to achieve UHC, by redefining and assessing vulnerability as a multidimensional process and the investigation of mechanisms that are more context specific.

Loss of p53 suppresses replication-stress-induced DNA breakage in G1/S checkpoint deficient cells

In cancer cells, loss of G1/S control is often accompanied by p53 pathway inactivation, the latter usually rationalized as a necessity for suppressing cell cycle arrest and apoptosis. However, we found an unanticipated effect of p53 loss in mouse and human G1-checkpoint-deficient cells: reduction of DNA damage. We show that abrogation of the G1/S-checkpoint allowed cells to enter S-phase under growth-restricting conditions at the expense of severe replication stress manifesting as decelerated DNA replication, reduced origin firing and accumulation of DNA double-strand breaks. In this system, loss of p53 allowed mitogen-independent proliferation, not by suppressing apoptosis, but rather by restoring origin firing and reducing DNA breakage. Loss of G1/S control also caused DNA damage and activation of p53 in an in vivo retinoblastoma model. Moreover, in a teratoma model, loss of p53 reduced DNA breakage. Thus, loss of p53 may promote growth of incipient cancer cells by reducing replication-stress-induced DNA damage.

BMI-for-age in South Asian children of 0-20 years in the Netherlands: secular changes and misclassification by WHO growth references

BACKGROUND

South Asians are prone to cardiometabolic disease at lower BMI levels than most other ethnic groups, starting in childhood. The magnitude of BMI misclassifications is unknown.

AIM

To compare the BMI distribution of contemporary South Asian 0-20 year olds in the Netherlands with: (1) The South Asian norm reference (secular trends); and (2) The WHO child growth standard and reference.

SUBJECTS AND METHODS

The BMI-for-age distribution of 6677 routine measurements of 3322 South Asian children, aged 0-20 years, was described with the LMS method and BMI z-scores.

RESULTS

The BMI distribution in South Asian 0-4 year olds was almost similar to the norm reference (mean BMI z-score = 0.11, skewness = 0.31, SD = 1.0), whereas in 5-19 year olds the distribution had shifted upwards (mean = 0.53) and widened (skewness = -0.12, SD = 1.08). Overweight (incl. obesity) and obesity peaked at 8-10 years, at 45-48% and 35-37%, respectively. Relative to the WHO references, the BMI distribution was left-shifted at ages 0-4 years (mean BMI z-score = -0.46, skewness = 0.23, SD = 0.98) and widened at ages 5-20 years (mean = 0.05; skewness = -0.02, SD = 1.40). At most ages, thinness rates were significantly higher and obesity rates lower than based on South Asian norms.

CONCLUSIONS

A secular change of BMI-for-age in South Asian children mostly affected children >4 years. WHO references likely under-estimate overweight and obesity rates in South Asian children.

Suspected Lynch syndrome associated MSH6 variants: A functional assay to determine their pathogenicity

Lynch syndrome (LS) is a hereditary cancer predisposition caused by inactivating mutations in DNA mismatch repair (MMR) genes. Mutations in the MSH6 DNA MMR gene account for approximately 18% of LS cases. Many LS-associated sequence variants are nonsense and frameshift mutations that clearly abrogate MMR activity. However, missense mutations whose functional implications are unclear are also frequently seen in suspected-LS patients. To conclusively diagnose LS and enroll patients in appropriate surveillance programs to reduce morbidity as well as mortality, the functional consequences of these variants of uncertain clinical significance (VUS) must be defined. We present an oligonucleotide-directed mutagenesis screen for the identification of pathogenic MSH6 VUS. In the screen, the MSH6 variant of interest is introduced into mouse embryonic stem cells by site-directed mutagenesis. Subsequent selection for MMR-deficient cells using the DNA damaging agent 6-thioguanine (6TG) allows the identification of MMR abrogating VUS because solely MMR-deficient cells survive 6TG exposure. We demonstrate the efficacy of the genetic screen, investigate the phenotype of 26 MSH6 VUS and compare our screening results to clinical data from suspected-LS patients carrying these variant alleles.

The colorectal and endometrial cancer predisposition Lynch syndrome (LS) is caused by an inherited heterozygous defect in one of four DNA mismatch repair (MMR) genes. Deleterious mutations (e.g., protein-deleting or -truncating) in DNA MMR genes unambiguously allow for the clinical diagnosis LS and hence enable appropriate surveillance measures to be taken to reduce cancer risk and ensure early detection of tumors. However, currently about one-third of detected MMR gene variants are subtle with less clear functional consequences: missense mutations affecting a single amino acid may be innocuous, hence not causing LS, or partially or fully destroy protein function. As long as uncertainty exists about their pathogenicity, such mutations are labeled ‘variants of uncertain (clinical) significance’ (VUS). VUS hamper genetic counseling and therefore the need for functional testing of VUS is widely recognized. To functionally annotate MMR gene VUS, we have developed a high content cellular assay in which the VUS is introduced in a cell culture by oligonucleotide-directed gene modification. Should the VUS be deleterious for MMR, the modified cells survive exposure to the guanine analog 6-thioguanine (6TG) and 6TG-resistant colonies appear. Should the mutation not affect MMR, no colonies appear. Here we present the adaptation and application of this protocol to the functional annotation of variants of the MMR gene MSH6. Implementation of our assay in clinical genetics laboratories will provide clinicians with information for proper counseling of mutation carriers and treatment of their of tumors.

Sulforaphane formation and bioaccessibility are more affected by steaming time than meal composition during in vitro digestion of broccoli

Broccoli is a rich source of the glucosinolate glucoraphanin (GR). After hydrolysis of GR by the endogenous enzyme myrosinase, sulforaphane (SF) or sulforaphane nitrile (SFN) are produced, depending on environmental conditions. How the conversion of GR and bioaccessibility of released breakdown products are affected by steaming (raw, 1min, 2min and 3min steamed) and meal composition (protein or lipid addition) was studied with an in vitro digestion model (mouth, stomach, intestine, but not colonic digestion). The main formation of SF and SFN occurred during in vitro chewing. The contents of GR, SF and SFN did not change after further digestion, as the irreversible inactivated myrosinase under gastric conditions caused no further GR hydrolysis. SF concentrations were up to 10 times higher in raw and 1min steamed broccoli samples after digestion compared to longer-steamed broccoli. Protein or lipid addition had no influence on the formation and bioaccessibility of SF or SFN.

Temozolomide increases the number of mismatch repair-deficient intestinal crypts and accelerates tumorigenesis in a mouse model of Lynch syndrome

BACKGROUND & AIMS

Lynch syndrome, a nonpolyposis form of hereditary colorectal cancer, is caused by inherited defects in DNA mismatch repair (MMR) genes. Most patients carry a germline mutation in 1 allele of the MMR genes MSH2 or MLH1. With spontaneous loss of the wild-type allele, cells with defects in MMR exist among MMR-proficient cells, as observed in healthy intestinal tissues from patients with Lynch syndrome. We aimed to create a mouse model of this situation to aid in identification of environmental factors that affect MMR-defective cells and their propensity for oncogenic transformation.

METHODS

We created mice in which the MMR gene Msh2 can be inactivated in a defined fraction of crypt base columnar stem cells to generate MSH2-deficient intestinal crypts among an excess of wild-type crypts (Lgr5-CreERT2;Msh2(flox/-) mice). Intestinal tissues were collected; immunohistochemical analyses were performed for MSH2, along with allele-specific PCR assays. We traced the fate of MSH2-deficient crypts under the influence of different external factors.

RESULTS

Lgr5-CreERT2;Msh2(flox/-) mice developed more adenomas and adenocarcinomas than control mice; all tumors were MSH2 deficient. Exposure of Lgr5-CreERT2;Msh2(flox/-) mice to the methylating agent temozolomide caused MSH2-deficient intestinal stem cells to proliferate more rapidly than wild-type stem cells. The MSH2-deficient intestinal stem cells were able to colonize the intestinal epithelium and many underwent oncogenic transformation, forming intestinal neoplasias.

CONCLUSIONS

We developed a mouse model of Lynch syndrome (Lgr5-CreERT2;Msh2(flox/-) mice) and found that environmental factors can modify the number and mutability of the MMR-deficient stem cells. These findings provide evidence that environmental factors can promote development of neoplasias and tumors in patients with Lynch syndrome.

Consumer behaviour towards vegetables: a study on domestic processing of broccoli and carrots by Dutch households

BACKGROUND

Preferences for sensory properties (e.g. taste and texture) are assumed to control cooking behaviour with respect to vegetables. Conditions such as the cooking method, amount of water used and the time-temperature profile determine the nutritional quality (e.g. vitamins and phytochemicals) of cooked vegetables. Information on domestic processing and any underlying motives can be used to inform consumers about cooking vegetables that are equally liked and are nutrient-rich.

METHODS

Two online self-reporting questionnaires were used to identify domestic processing conditions of broccoli and carrots by Dutch households. Questions on various aspects of domestic processing and consumer motives were included. Descriptive data analysis and hierarchical cluster analysis were performed for both vegetables, separately, to group consumers with similar motives and behaviour towards vegetables.

RESULTS

Approximately 70% of consumers boiled vegetables, 8-9% steamed vegetables, 10-15% stir fried raw vegetables and 8-10% stir fried boiled vegetables. Mainly texture was used as a way to decide the 'doneness' of the vegetables. For both vegetables, three clusters of consumers were identified: texture-orientated, health-orientated, or taste-orientated. The texture-orientated consumers are identified as the most prevalent (56-59%) group in the present study. Statistically significant associations are found between domestic processing conditions and clusters, whereas no such association are found between demographic details and clusters.

CONCLUSIONS

A wide variation in domestic processing of broccoli and carrots is found in the present study. Mainly sensory properties (i.e. texture and taste) determined the domestic processing conditions. The findings of the present study can be used to optimise cooking to yield vegetables that meet consumer's specific sensory preference and are higher in nutrients, and as well as to communicate with target consumer groups.

High amounts of broccoli in pasta-like products: nutritional evaluation and sensory acceptability

Pasta and noodles were enriched with concentrations of broccoli powder (BP) up to 30% (v/v). To ensure the benefits from the broccoli nutrients, their leakage during cooking should be prevented. Such leakage is determined by the microstructure. In a previous study we have shown that the microstructure can change dramatically in such broccoli-enriched products. In this article we investigated the amount of nutrients retained within the product. As a representative of nutrients we have chosen glucosinolates (GLs). Therefore, we have investigated the concentration of these phytochemicals in dried and cooked pasta and noodles. We have found that glucosinolates present in the pasta and noodles increase linearly with the volume fraction of BP up to 20%. At 30% BP the retained amount of GLs was equal to that of 20% BP and did not increase further. Therefore incorporation of 30% BP does not lead to additional health benefits over incorporation of 20% BP. We conclude that the nutritional function of our pasta-like products can be improved by enrichment up to 20% broccoli. This value is much higher than that found in common commercial products (which is a few percent). In this article we also briefly address the sensory acceptability of such products. Up to 20% broccoli the products turned out to remain acceptable. Combining this with our results on texture analysis we conclude that the GLs release, sensory acceptability and textural properties are related via the microstructure.

Effect of water content and temperature on inactivation kinetics of myrosinase in broccoli (Brassica oleracea var. italica)

Broccoli belongs to the Brassicaceae plant family consisting of widely eaten vegetables containing high concentrations of glucosinolates. Enzymatic hydrolysis of glucosinolates by endogenous myrosinase (MYR) can form isothiocyanates with health-promoting activities. The effect of water content (WC) and temperature on MYR inactivation in broccoli was investigated. Broccoli was freeze dried obtaining batches with WC between 10% and 90% (aw from 0.10 to 0.96). These samples were incubated for various times at different temperatures (40-70°C) and MYR activity was measured. The initial MYR inactivation rates were estimated by the first-order reaction kinetic model. MYR inactivation rate constants were lower in the driest samples (10% WC) at all studied temperatures. Samples with 67% and 90% WC showed initial inactivation rate constants all in the same order of magnitude. Samples with 31% WC showed intermediate initial inactivation rate constants. These results are useful to optimise the conditions of drying processes to produce dried broccoli with optimal MYR retention for human health.

Pitfalls in the desulphation of glucosinolates in a high-throughput assay

Glucosinolates are phytochemicals with health promoting properties. Determination as desulpho-glucosinolates is widely used and a desulphation in microtiter plates has been applied to reach high throughput. The use of various sulphatase concentrations and volumes throughout literature necessitates the identification of an appropriate desulphation procedure in microtiter plates. High sulphatase concentrations (≥15 mg/ml) decreased the concentration of the internal standard glucotropaeolin, whereas the other glucosinolates were less affected. Due to the calculation based on the recovery of glucotropaeolin, this leads to an overestimation of GL concentrations after desulphation with high sulphatase concentrations. A glucosidase side-activity, present in the crude sulphatase powder, is likely causing this phenomenon. At lower sulphatase concentrations (1 mg/ml) glucoiberin and glucoraphanin were insufficiently desulphated. Combining these effects results in a small range of applicable sulphatase concentrations. A purified sulphatase preparation resulted in good recoveries for a diversity of samples and is hence recommended for high throughput desulphation in microtiter plates.

Strong relationships between disease activity, foot-related impairments, activity limitations and participation restrictions in children with juvenile idiopathic arthritis

OBJECTIVES

To assess possible relationships between disease activity, foot-related impairments, activity limitations and participation restrictions in children with juvenile idiopathic arthritis (JIA).

METHODS

Thirty-four children were studied. Disease activity was assessed with the Juvenile Arthritis Disease Activity Score in 71 joints (JADAS-71). Foot-related impairments, activity limitations and participation restrictions were measured with the Juvenile Arthritis Foot Disability Index (JAFI), the Childhood Health Assessment Questionnaire (CHAQ), self-reported or parent-reported and doctor-reported VAS scales. Relationships were quantified with Spearman's correlation coefficient.

RESULTS

The mean age was 12.4±3.7 years, the median disease duration 1.5 years (interquartile range (IQR) 1.0-4.0), 88% were girls, and 76% had polyarticular disease course. The median JADAS-71 score (range 0-101) was 6 (IQR 1-13). On the JAFI sub-scores (range 0-4) 88% of the children reported some foot-related impairments (median 1.1, IQR 0.4-2.0); 82% reported some foot-related activity limitations (median 0.9, IQR 0.3-2.0), and 65% reported some foot-related participation restrictions (median 0.6, IQR 0-2.1). The median CHAQ score was 0.9 (IQR 0.1-1.8). The JADAS-71 correlated with all impairment, activity limitation and participation restriction variables (r=0.48-0.81, p<0.01). Most of the impairment variables correlated with activity limitation (r=0.39, p<0.05 to r=0.92, p<0.01) and participation restriction variables (r=0.44, p<0.05 to r=0.81, p<0.01). All activity limitation variables correlated with participation restriction variables (r=0.62-0.84, p<0.01).

CONCLUSIONS

We observed strong relationships between disease activity, foot-related impairments, activity limitations and participation restrictions in children with JIA, and therefore suggest that standard screening for foot problems should be included in follow-up care for JIA patients.

Generation of double-knockout embryonic stem cells

Gene inactivation in mouse embryonic stem (ES) cells usually affects a single allele that is subsequently transmitted to the mouse germline. Upon breeding to homozygosity the consequences of complete gene ablation can be studied in the context of the complete organism. In many cases, it can be useful to study the consequences of gene ablation already in ES cells, for example, when a cellular phenotype is expected. This requires both alleles of a gene to be disrupted. Besides consecutive targeting by using different selectable marker genes, homozygosity for gene disruption can also be obtained by selecting cells for duplication of (part of) the chromosome carrying the targeted allele with concomitant loss of the wild-type allele.

Changes in striatal dopamine D2 receptor binding in pre-clinical Huntington's disease

BACKGROUND

Carriers of the Huntington disease (HD) mutation develop a progressive neurodegenerative disorder after a pre-clinical phase. We examined the value of (11)C-raclopride PET (RAC) as a biomarker for pre-clinical HD pathophysiology.

METHODS

In a prospective cohort study with clinical and neuropsychological assessment we collected complete RAC data in 18 pre-clinical mutation carriers (HD-PMC) and 11 controls. Follow-up was 2 years. We calculated striatal RAC binding potential (BP) to measure dopamine D2 receptor availability.

RESULTS

No HD-PMC had overt neuropsychological dysfunction. RAC-BP in putamen was abnormal in up to 44% of HD-PMC. The rate of RAC-BP decline (2.6% per year) was not significantly higher than in controls. Follow-up putaminal BP correlated weakly with predicted distance to onset of clinical HD (P = 0.034), but the rate of decline did not. Three HD-PMC developed motor abnormalities suspect for HD but did not show an increased rate of decline of putaminal BP.

CONCLUSIONS

Many HD-PMC have striatal abnormalities but we found no clearly increased rate of D2 receptor changes around the onset of clinical HD. A longer follow-up of the present study cohort is needed to establish the value of RAC-BP in assessing the risk of clinical conversion from striatal D2 binding data.

In vivo significance of the G2 restriction point

Loss of activity of the retinoblastoma pathway is a common event in human cancer. Mouse models have revealed that tumorigenesis by loss of Rb was accelerated by concomitant loss of the cell cycle inhibitor p27KIP1. This has been attributed to reduced apoptosis and weakening of the G1 checkpoint. However, the role of p27KIP1 in a recently identified G2 restriction point may offer an alternative explanation for this synergy. Here, we have investigated the significance of the G2 restriction point in Rb-deficient pituitaries. We show that Rb loss in the pituitary gland activated the G2 restriction point, as evidenced by the appearance of cyclin B1-p27KIP1 complexes. Somewhat unexpectedly, these complexes remained present in Rb-deficient tumors. These results indicate that the G2 restriction point does operate in vivo. However, in the pituitary gland, this mechanism seems to retard rather than to prevent tumor growth.

Feasibility study for the development of certified reference materials for specific migration testing. Part 2: Estimation of diffusion parameters and comparison of experimental and predicted data

This paper describes the second part of a project whose main objective was to develop the know-how to produce certified reference materials (CRMs) for specific migration testing. Certification parameters discussed are the diffusion coefficient, D(P), the respective polymer-specific coefficient, A(P), of the migrant polymer combinations and the partitioning coefficient, K(P,F), describing the partitioning of the migrant between the polymer and a food simulant. The parameters were determined for 16 preliminary candidate CRMs. Each parameter was determined by one laboratory. The six materials most suitable as reference materials were selected and the parameters then determined by four laboratories. The coefficients resulting from this small-scale interlaboratory comparison study can be regarded as the most reliable values available to date. These coefficients were applied for a comparison of experimental and predicted migration data. The experimental migration data arose from the same project and were determined by one laboratory for the first 16 materials and subsequently by four laboratories for the six materials selected in the second phase. Overall, experimental and predicted migration data fit together quite well. Roughly half of the predicted data were within +/-10%; almost all predicted data were within +/-40% compared with the experimental data.

Generation of a mouse mutant by oligonucleotide-mediated gene modification in ES cells

Oligonucleotide-mediated gene targeting is emerging as a powerful tool for the introduction of subtle gene modifications in mouse embryonic stem (ES) cells and the generation of mutant mice. However, its efficacy is strongly suppressed by DNA mismatch repair (MMR). Here we report a simple and rapid procedure for the generation of mouse mutants using transient down regulation of the central MMR protein MSH2 by RNA interference. We demonstrate that under this condition, unmodified single-stranded DNA oligonucleotides can be used to substitute single or several nucleotides. In particular, simultaneous substitution of four adjacent nucleotides was highly efficient, providing the opportunity to substitute virtually any given codon. We have used this method to create a codon substitution (N750F) in the Rb gene of mouse ES cells and show that the oligonucleotide-modified Rb allele can be transmitted through the germ line of mice.

Effective oligonucleotide-mediated gene disruption in ES cells lacking the mismatch repair protein MSH3

We have previously demonstrated that site-specific insertion, deletion or substitution of one or two nucleotides in mouse embryonic stem cells (ES cells) by single-stranded deoxyribo-oligonucleotides is several hundred-fold suppressed by DNA mismatch repair (MMR) activity. Here, we have investigated whether compound mismatches and larger insertions escape detection by the MMR machinery and can be effectively introduced in MMR-proficient cells. We identified several compound mismatches that escaped detection by the MMR machinery to some extent, but could not define general rules predicting the efficacy of complex base-pair substitutions. In contrast, we found that four-nucleotide insertions were largely subject to suppression by the MSH2/MSH3 branch of MMR and could be effectively introduced in Msh3-deficient cells. As these cells have no overt mutator phenotype and Msh3-deficient mice do not develop cancer, Msh3-deficient ES cells can be used for oligonucleotide-mediated gene disruption. As an example, we present disruption of the Fanconi anemia gene Fancf.

Tissue-specific tumor suppressor activity of retinoblastoma gene homologs p107 and p130

The retinoblastoma gene family consists of three genes: RB, p107, and p130. While loss of pRB causes retinoblastoma in humans and pituitary gland tumors in mice, tumorigenesis in other tissues may be suppressed by p107 and p130. To test this hypothesis, we have generated chimeric mice from embryonic stem cells carrying compound loss-of-function mutations in the Rb gene family. We found that Rb/p107- and Rb/p130-deficient mice were highly cancer prone. We conclude that in a variety of tissues tumor development by loss of pRB is suppressed by its homologs p107 and p130. The redundancy of the retinoblastoma proteins in vivo is reflected by the behavior of Rb-family-defective mouse embryonic fibroblasts in vitro.

Alternative fatty food simulants and diffusion kinetics of nylon 12 food packaging

The migration of laurolactam and cyclic di- and trimer of nylon 12 was assessed using three different films and five food simulants (olive oil, isooctane, 95% ethanol, 50% ethanol, water). Substitute test conditions for migration into olive oil according to European Union Directive EC/97/48 were applied using 95% ethanol and isooctane. Results showed that 95% ethanol overestimated while isooctane underestimated the respective migration into olive oil. Water was the best olive oil substitute, as migration of laurolactam into water and olive oil using the same temperature gave similar results. Additionally, diffusion kinetics of laurolactam were investigated by migration kinetic studies using isooctane and olive oil. Diffusion coefficients determined with isooctane were significantly higher than those found using olive oil. It was proved that isooctane had an interaction and olive oil was inert to the polymer. The diffusion conductance parameter, A(p), for nylon 12 determined using olive oil ranged from 0.3 to 0.6.

DNA mismatch repair deficiency stimulates N-ethyl-N-nitrosourea-induced mutagenesis and lymphomagenesis

The primary role of the mismatch repair (MMR) system is the avoidance of mutations caused by replication and recombination errors. Furthermore, the lethality of methylating agents has been attributed to the processing of O(6)-methylguanine lesions in DNA by MMR. Loss of the MSH2 protein completely abolishes repair function and results in reduced cell killing by methylating agents and accelerated accumulation of methylation-damage-induced mutations. This has raised the question as to whether MMR is also involved in the cellular response to other genotoxic insults. Here we describe that in mice deficient for Msh2, lymphomagenesis was strongly accelerated by an ethylating agent, N-ethyl-N-nitrosourea (ENU), given at a dose that did not induce lymphomas in wild-type mice. This suggests that MMR deficiency and ENU-induced mutagenesis synergistically collaborate in inducing tumorigenesis. To study the interaction between MMR and ENU-induced DNA damage, we compared the lethality and mutagenicity of ENU in MSH2-proficient and -deficient mouse embryonic stem cells. Although MSH2-deficiency only slightly reduced the lethality of ENU, it strongly enhanced the mutagenicity of ENU. Mutation analysis of ENU-induced Hprt mutants revealed that base substitutions occurred predominantly at A-T base-pairs. These results suggest that MMR modulates the processing of ethylation damage at AT base-pairs.

Targeted gene modification in mismatch-repair-deficient embryonic stem cells by single-stranded DNA oligonucleotides

Gene targeting through homologous recombination in murine embryonic stem (ES) cells is already strongly suppressed by DNA mismatch-repair (MMR)-dependent anti-recombination when targeting construct and target locus differ at <1% of the nucleotide positions. We demonstrate that MMR activity also raises a strong impediment to gene modification mediated by small synthetic DNA oligonucleotide sequences. In the absence of the DNA MMR gene MSH2, synthetic single-stranded deoxyribo-oligonucleotides can be used to site-specifically modify the ES cell genome. We show that PCR-based procedures can be used to identify and clone modified cells. By this method we have substituted a single codon in the retinoblastoma gene.

Modelling the effect of oil/fat content in food systems on flavour absorption by LLDPE

One of the phenomena in food-packaging interactions is flavour absorption. Absorption of flavour compounds from food products into food-packaging materials can result in loss of flavour compounds or an unbalance in the flavour profile changing a product's quality. The food matrix influences the amounts of absorbed flavour compounds; the presence of oil or fat especially determines the ability to absorb flavour compounds from the food to the package. On the other hand, the polarity of the flavour compound itself is a characteristic that also influences the level of absorption into synthetic polymers. A model based on the effect of the polarity (logP) of flavour compounds and on their partitioning coefficients between the food (matrix) and the packaging material is described. The model can be used for predicting absorption of flavour compounds from foods into LLDPE. However, an attempt to apply the proposed model on real foods shows serious limitations of the model for (very) low fat products. Predictive values deviate from the measured values, probably due to other interaction phenomena, e.g. with proteins. Predictive and measured values from a product with a substantial amount of fat match much better, suggesting that the model is valid for products having a substantial amount of (free) fat.