The molecular basis of medium-chain acyl-CoA dehydrogenase (MCAD) deficiency in compound heterozygous patients: is there correlation between genotype and phenotype?

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is the most commonly recognized defect of mitochondrial beta-oxidation. It is potentially fatal, but shows a wide clinical spectrum. The aim of the present study was to investigate whether any correlation exists between MCAD genotype and disease phenotype. We determined the prevalence of the 14 known and seven previously unknown non-G985 mutations in 52 families with MCAD deficiency not caused by homozygosity for the prevalent G985 mutation. This showed that none of the non-G985 mutations are prevalent, and led to the identification of both disease- causing mutations in 14 families in whom both mutations had not previously been reported. We then evaluated the severity of the mutations identified in these 14 families. Using expression of mutant MCAD in Escherichia coli with or without co-overexpression of the molecular chaperonins GroESL we showed that five of the missense mutations affect the folding and/or stability of the protein, and that the residual enzyme activity of some of them could be modulated to a different extent depending on the amounts of available chaperonins. Thus, some of the missense mutations may result in relatively high levels of residual enzyme activity, whereas the mutations leading to premature stop codons will result in no residual enzyme activity. By correlating the observed types of mutations identified to the clinical/biochemical data in the 14 patients in whom we identified both disease-causing mutations, we show that a genotype/phenotype correlation in MCAD deficiency is not straightforward. Different mutations may contribute with different susceptibilities for disease precipitation, when the patient is subjected to metabolic stress, but other genetic and environmental factors may play an equally important role.      

Paracellular calcium transport across Caco-2 and HT29 cell monolayers

 Intestinal calcium absorption has been shown to include two processes, a saturable transcellular movement and a non-saturable paracellular pathway. The potential utility of cell monolayers for studying transepithelial intestinal calcium transport has already been demonstrated; however, simultaneous evaluation of the contribution of the saturable transcellular and of the non-saturable paracellular processes to the total transepithelial transport has not yet been attempted. The aim of this study was to investigate the contribution both of transcellular and paracellular transport processes to the total transepithelial calcium transport in two cell culture monolayers. Caco-2 cells and a clone derived from HT-29 cells (HT29-Cl.19A), two cell lines derived from colon adenocarcinomas which are known to be able to exhibit typical enterocytic differentiation, were used. Cell monolayers were grown on a permeable support and used after 15 days of culture when these cells express enterocytic differentiation and high transepithelial resistance. Isotopic transport rate measurements were performed in the absence of a chemical gradient. The paracellular route was evaluated using [³H]mannitol. Calcium and [³H]mannitol transport rates across cell monolayers were not significantly different. Augmentation of calcium uptake by 200 mM sorbitol did not significantly increase calcium or mannitol transepithelial transport; however, calcium accumulation in the cells was increased by about 200%. Modulation of the monolayer permeability by addition of 10 nM vasoactive intestinal polypeptide (VIP) or 0.5 mM carbachol treatment, which respectively increased and decreased the transepithelial resistance, consequently modified calcium and mannitol transport in a parallel manner. Our results show that Caco-2 and HT29-Cl.19A cell monolayers are good models for studying the calcium paracellular transport pathway. Received: 25 September 1996 / Received after revision: 14 March 1997 / Accepted: 26 March 1997     

Evaluation of exclusion prenatal and exclusion preimplantation genetic diagnosis for Huntington's disease in the Netherlands

van Rij MC, de Die‐Smulders CEM, Bijlsma EK, de Wert GMWR, Geraedts JP, Roos RAC, Tibben A. Evaluation of exclusion prenatal and exclusion preimplantation genetic diagnosis for Huntington's disease in the Netherlands. Individuals at 50% risk of Huntington's disease (HD) who prefer not to know their carrier status, might opt for exclusion prenatal diagnosis (ePND) or exclusion preimplantation genetic diagnosis (ePGD). This study aims to provide a better understanding of couples' motives for choosing ePND or ePND, and surveys couples' experiences in order to make recommendations for the improvement of counselling for exclusion testing. This qualitative retrospective interview study focussed on couples who underwent ePND or ePGD for HD in the period 1996–2010. Seventeen couples were included of which 13 had experienced ePND and 6 ePGD. Mean time‐interval since exclusion‐testing was 3.9 years. Couples' moral reservations regarding termination of pregnancy (TOP) or discarding healthy embryos were counterbalanced by the wish to protect their future child against HD. Seven couples had terminated a total of 11 pregnancies with a 50% HD risk, none showed regret. ePGD was used by couples who wanted to avoid (another) TOP. ePND and ePGD are acceptable reproductive options for a specific group of counsellees. To guarantee sound standards of care, it is imperative that candidate couples be given in‐depth non‐directive counselling about all possible scenarios, and adequate professional and psychological support prior to, during and after ePND/ePGD.     

Chronic eczematous eruptions of the elderly are associated with chronic exposure to calcium channel blockers: results from a case-control study

It has been suggested that chronic eczematous eruptions of the elderly could be associated with chronic drug exposure. To determine the drugs associated with these eruptions, we conducted a case-control study on 102 cases and 204 controls. Cases were consecutive patients older than 60 years presenting with an eczematous eruption that had evolved continuously or recurrently for more than 3 months without a reliable cause. Two controls were matched to each case on age, sex, in/outpatient origin, and center. Information about drug exposure was obtained from patients and their pharmacists. Drug use for more than 3 months within the year preceding the eruption was compared between cases and controls. An association was found between calcium channel blockers (CCB) and eczema, with a matched OR (odds ratio) of 2.5 (95% CI (confidence interval): 1.3-4.6). To ascertain the course of patients after CCB withdrawal, two ancillary studies were performed on 74 patients with eczematous eruptions from our department before the case-control study period, and on 101 patients registered in the French "Pharmacovigilance" database. Healing of these eruptions after CCB withdrawal occurred in 83 and 68% of these cases, respectively. The long-term use of CCB is a risk factor for chronic eczematous eruptions of the elderly.     

薤白中两种新甾体皂甙成分

从中药薤白(Allium macrostemon Bunge)鳞茎中分得两种流的甾体皂甙,薤白甙甲(macrostemonoside A,1)和薤白甙丁(macrostemonoside D,2),通过光谱(IR,MS,¹HNMR,¹³CNMR,¹H-¹H COSY和NOESY等)分析和衍生化研究,分别确定为:tigogenin-3-O-β-D-glucopyranosyl(1→2)[β-D-glucopyranosyl(1→3)]-β-D-glucopyranosyl(1→4)-β-D-galactopyranoside(1)和tigotenin-3-O-β-D-glucopyranosyl(1→2)[β-D-glucopyranosyl(1→3)(6-O-acetyl-β-D-glucopyranosyl)](1→4)-β-D-galactopyranoside(2)。     

Comparative analysis of Shwachman‐Diamond syndrome to other inherited bone marrow failure syndromes and genotype–phenotype correlation

Hashmi SK, Allen C, Klaassen R, Fernandez CV, Yanofsky R, Shereck E, Champagne J, Silva M, Lipton JH, Brossard J, Samson Y, Abish S, Steele M, Ali K, Dower N, Athale U, Jardine L, Hand JP, Beyene J, Dror Y. Comparative analysis of Shwachman‐Diamond syndrome to other inherited bone marrow failure syndromes and genotype–phenotype correlation. Our knowledge of the phenotypes of inherited bone marrow failure syndromes (IBMFSs) derives from case reports or case series in which only one IBMFS was studied. However, the substantial phenotypic overlap necessitates comparative analysis between the IBMFSs. Shwachman–Diamond syndrome (SDS) is an IBMFS that the appreciation of what comprises its clinical phenotype is still evolving. In this analysis we used data on 125 patients from the Canadian Inherited Marrow Failure Study (CIMFS), which is a prospective multicenter population‐based study. Thirty‐four cases of SDS patients were analyzed and compared to other patients with the four most common IBMFSs on the CIMFS: Diamond Blackfan anemia, Fanconi anemia (FA), Kostmann/severe congenital neutropenia and dyskeratosis congenita (DC). The diagnosis of SDS, FA and DC was often delayed relative to symptoms onset; indicating a major need for improving tools to establish a rapid diagnosis. We identified multiple phenotypic differences between SDS and other IBMFSs, including several novel differences. SBDS biallelic mutations were less frequent than in previous reports (81%). Importantly, compared to patients with biallelic mutations, patients with wild type SBDS had more severe hematological disease but milder pancreatic disease. In conclusion, comprehensive study of the IBMFSs can provide useful comparative data between the disorders. SBDS‐negative SDS patients may have more severe hematological failure and milder pancreatic disease.     

Current methods of diagnosis and treatment of scaphoid fractures

Fractures of the scaphoid bone mainly occur in young adults and constitute 2-7% of all fractures. The specific blood supply in combination with the demanding functional requirements can easily lead to disturbed fracture healing. Displaced scaphoid fractures are seen on radiographs. The diagnostic strategy of suspected scaphoid fractures, however, is surrounded by controversy. Bone scintigraphy, magnetic resonance imaging and computed tomography have their shortcomings. Early treatment leads to a better outcome. Scaphoid fractures can be treated conservatively and operatively. Proximal scaphoid fractures and displaced scaphoid fractures have a worse outcome and might be better off with an open or closed reduction and internal fixation. The incidence of scaphoid non-unions has been reported to be between 5 and 15%. Non-unions are mostly treated operatively by restoring the anatomy to avoid degenerative wrist arthritis.