Respiratory viruses and cot death.

Respiratory viruses and histological appearances of the lung were studied prospectively in an unselected series of 104 children who died between 1 week and 2 years of age. Thirty-one of the cases were cot deaths. Seven of these showed evidence of active virus infection in the lower respiratory tract. Similar evidence was found in two children who died from known causes and did not have a severe respiratory illness terminally. Although in some cases of cot death respiratory viruses may be responsible for a severe and rapidly overwhelming illness, the present results are compatible with an alternative hypothesis-namely, that minor respiratory illness may trigger sudden apnoea.     

Molecular and functional characterisation of mild MCAD deficiency

We report a novel mild variant of medium-chain acyl-CoA dehydrogenase deficiency (MCADD) diagnosed in four infants who, in neonatal screening, showed abnormal acylcarnitine profiles indicative of MCADD. Three patients showed completely normal urinary organic acids and phenylpropionic acid loading tests were normal in all four patients. Enzyme studies showed residual MCAD activities between "classical" MCADD and heterozygotes. ACADM gene analysis revealed compound heterozygosity for the common mutation K329E and a novel mutation, Y67H, in two cases, and homozygosity for mutation G267R and the novel mutation S245L, respectively, in two children of consanguineous parents. As in other metabolic disorders, the distinction between "normal" and "disease" in MCAD deficiency is blurring into a spectrum of enzyme deficiency states caused by different mutations in the ACADM gene potentially influenced by factors affecting intracellular protein processing.     

Oxidative stress induction by cis-4-decenoic acid: Relevance for MCAD deficiency

Patients affected by medium-chain acyl-CoA dehydrogenase deficiency (MCADD) suffer from acute episodes of encephalopathy whose underlying mechanisms are poorly known. The present work investigated the in vitro effect of cis-4-decenoic acid (cDA), which accumulates in MCADD, on important parameters of oxidative stress in cerebral cortex of young rats. cDA markedly induced lipid peroxidation, as verified by the increased levels of spontaneous chemiluminescence and thiobarbituric acid-reactive substances. Furthermore, cDA significantly increased carbonyl formation and sulphydryl oxidation, which is indicative of protein oxidative damage, and promoted 2′,7′-dihydrodichlorofluorescein oxidation. It was also observed that the non-enzymatic tissue antioxidant defenses were decreased by cDA, whereas the antioxidant enzyme activities catalase, superoxide dismutase and glutathione peroxidase were not altered. Moreover, cDA-induced lipid peroxidation and GSH reduction was totally blocked by free radical scavengers, suggesting that reactive species were involved in these effects. The data indicate that oxidative stress is induced by cDA in rat brain in vitro and that oxidative damage might be involved in the pathophysiology of the encephalopathy in MCADD.     

Oxidative stress induction by cis-4-decenoic acid: relevance for MCAD deficiency

Patients affected by medium-chain acyl-CoA dehydrogenase deficiency (MCADD) suffer from acute episodes of encephalopathy whose underlying mechanisms are poorly known. The present work investigated the in vitro effect of cis-4-decenoic acid (cDA), which accumulates in MCADD, on important parameters of oxidative stress in cerebral cortex of young rats. cDA markedly induced lipid peroxidation, as verified by the increased levels of spontaneous chemiluminescence and thiobarbituric acid-reactive substances. Furthermore, cDA significantly increased carbonyl formation and sulphydryl oxidation, which is indicative of protein oxidative damage, and promoted 2',7'-dihydrodichlorofluorescein oxidation. It was also observed that the non-enzymatic tissue antioxidant defenses were decreased by cDA, whereas the antioxidant enzyme activities catalase, superoxide dismutase and glutathione peroxidase were not altered. Moreover, cDA-induced lipid peroxidation and GSH reduction was totally blocked by free radical scavengers, suggesting that reactive species were involved in these effects. The data indicate that oxidative stress is induced by cDA in rat brain in vitro and that oxidative damage might be involved in the pathophysiology of the encephalopathy in MCADD.     

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency: diagnosis by acylcarnitine analysis in blood.

Medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency is a disorder of fatty acid catabolism, with autosomal recessive inheritance. The disease is characterized by episodic illness associated with potentially fatal hypoglycemia and has a relatively high frequency. A rapid and reliable method for the diagnosis of MCAD deficiency is highly desirable. Analysis of specific acylcarnitines was performed by isotope-dilution tandem mass spectrometry on plasma or whole blood samples from 62 patients with MCAD deficiency. Acylcarnitines were also analyzed in 42 unaffected relatives of patients with MCAD deficiency and in other groups of patients having elevated plasma C8 acylcarnitine, consisting of 32 receiving valproic acid, 9 receiving medium-chain triglyceride supplement, 4 having multiple acyl-coenzyme A dehydrogenase deficiency, and 8 others with various etiologies. Criteria for the unequivocal diagnosis of MCAD deficiency by acylcarnitine analysis are an elevated C8-acylcarnitine concentration (> 0.3 microM), a ratio of C8/C10 acylcarnitines of > 5, and lack of elevated species of chain length > C10. These criteria were not influenced by clinical state, carnitine treatment, or underlying genetic mutation, and no false-positive or false-negative results were obtained. The same criteria were also successfully applied to profiles from neonatal blood spots retrieved from the original Guthrie cards of eight patients. Diagnosis of MCAD deficiency can therefore be made reliably through the analysis of acylcarnitines in blood, including presymptomatic neonatal recognition. Tandem mass spectrometry is a convenient method for fast and accurate determination of all relevant acylcarnitine species.     

Is there a link between cot death and child abuse?

Forty five babies delivered in Oxford obstetric units who subsequently died unexpectedly in infancy were compared with 134 controls matched for maternal age, social class, parity, and year of birth to see whether five factors identified in an earlier study as predictive of subsequent child abuse would also predict the sudden infant death syndrome. Epidemiological findings had suggested certain similarities between the two events. In contrast with babies who were abused, four of the five factors did not distinguish between babies who died suddenly and unexpectedly and their controls, but there was a slight increase in the proportion of mothers of babies who died suddenly and unexpectedly for whom nursing staff thought that support and advice on feeding the baby were needed. Factors predictive of child abuse did not predict sudden infant death in this study.     

Niemann-Pick Type C1 deficiency in microglia does not cause neuron death in vitro

Niemann-Pick Type C (NPC) disease is an autosomal recessive disorder that results in accumulation of cholesterol and other lipids in late endosomes/lysosomes and leads to progressive neurodegeneration and premature death. The mechanism by which lipid accumulation causes neurodegeneration remains unclear. Inappropriate activation of microglia, the resident immune cells of the central nervous system, has been implicated in several neurodegenerative disorders including NPC disease. Immunohistochemical analysis demonstrates that NPC1 deficiency in mouse brains alters microglial morphology and increases the number of microglia. In primary cultures of microglia from Npc1(-/-) mice cholesterol is sequestered intracellularly, as occurs in other NPC-deficient cells. Activated microglia secrete potentially neurotoxic molecules such as tumor necrosis factor-α (TNFα). However, NPC1 deficiency in isolated microglia did not increase TNFα mRNA or TNFα secretion in vitro. In addition, qPCR analysis shows that expression of pro-inflammatory and oxidative stress genes is the same in Npc1(+/+) and Npc1(-/-) microglia, whereas the mRNA encoding the anti-inflammatory cytokine, interleukin-10 in Npc1(-/-) microglia is ~60% lower than in Npc1(+/+) microglia. The survival of cultured neurons was not impaired by NPC1 deficiency, nor was death of Npc1(-/-) and Npc1(+/+) neurons in microglia-neuron co-cultures increased by NPC1 deficiency in microglia. However, a high concentration of Npc1(-/-) microglia appeared to promote neuron survival. Thus, although microglia exhibit an active morphology in NPC1-deficient brains, lack of NPC1 in microglia does not promote neuron death in vitro in microglia-neuron co-cultures, supporting the view that microglial NPC1 deficiency is not the primary cause of neuron death in NPC disease.     

Identification of a new mutation in medium-chain acyl-CoA dehydrogenase (MCAD) deficiency.

A mutation involving an A-to-G nucleotide replacement at position 985 of the medium-chain acyl-CoA dehydrogenase (MCAD) cDNA was found in homozygous form in 18 unrelated MCAD-deficient families and in heterozygous form in 4 families. By PCR amplification and sequencing of cDNA from a compound heterozygote, we have detected a new mutation in an MCAD-deficient patient in whom one MCAD allele produces mRNA that is missing 4 bp in the MCAD cDNA, while the other allele carries the A-to-G-985 mutation. The presence of this 4-bp deletion was confirmed in the patient's genomic DNA by dot-blot hybridization with allele-specific oligonucleotide probes and by restriction analysis of PCR products. A rapid screening test for this 4-bp deletion was developed, based on mismatched primer PCR amplification. The deletion created a new restrictive-enzyme site which yielded two DNA fragments. The 4-bp deletion was not found in the three remaining MCAD chromosomes not harboring the A-to-G-985 mutation, nor it was present in 20 chromosomes from 10 unrelated normal Caucasians. The PCR-based method for screening these two mutations can detect over 93% of all MCAD mutations.     

Aerial release of bacteria from cot mattress materials and the sudden infant death syndrome

AIM: To investigate aerial release of bacteria from used cot mattresses and to assess factors that may influence this process. METHODS AND RESULTS: Movement on used mattresses, simulating that of an infant's head, significantly enhanced aerial release of naturally acquired bacteria from the polyurethane foams (total count data, P = 0.008; Staphylococcus aureus, P = 0.004) or from polyvinyl chloride covers (total count data, P = 0.001). Aerial release of naturally acquired bacteria from used cot mattresses showed high variability and was poorly correlated (R2 < or = 0.294) with bacterial cell density within the materials. In experiments involving inoculation of S. aureus and Escherichia coli onto the polyurethane of unused cot mattresses, aerial release of the species correlated well (R2 > or = 0.950) with inoculation density when simulated infant head movement was applied. Aerial release of these bacterial species from the material decreased with increase in width or aqueous content of the material, and was lower from polyurethane foam of a used cot mattress. CONCLUSIONS: Simulated infant movement and mattress related factors influence aerial release of bacteria from cot mattress materials. With simulated infant movement on cot mattress polyurethane foam, levels of airborne bacteria above the material are proportional to bacterial population levels inoculated onto the material. SIGNIFICANCE AND IMPACT OF THE STUDY: Cot mattresses harbouring relatively high levels of naturally acquired toxigenic bacteria, such as S. aureus, could pose a relatively high risk of infection to the infant's respiratory tract through increased aerial contamination. This has impact in the context of recent findings on cot mattress related risk factors for sudden infant death syndrome.     

Niemann-Pick Type C1 deficiency in microglia does not cause neuron death in vitro

Niemann-Pick Type C (NPC) disease is an autosomal recessive disorder that results in accumulation of cholesterol and other lipids in late endosomes/lysosomes and leads to progressive neurodegeneration and premature death. The mechanism by which lipid accumulation causes neurodegeneration remains unclear. Inappropriate activation of microglia, the resident immune cells of the central nervous system, has been implicated in several neurodegenerative disorders including NPC disease. Immunohistochemical analysis demonstrates that NPC1 deficiency in mouse brains alters microglial morphology and increases the number of microglia. In primary cultures of microglia from Npc1^−/− mice cholesterol is sequestered intracellularly, as occurs in other NPC-deficient cells. Activated microglia secrete potentially neurotoxic molecules such as tumor necrosis factor-α (TNFα). However, NPC1 deficiency in isolated microglia did not increase TNFα mRNA or TNFα secretion in vitro. In addition, qPCR analysis shows that expression of pro-inflammatory and oxidative stress genes is the same in Npc1^+/+ and Npc1^−/− microglia, whereas the mRNA encoding the anti-inflammatory cytokine, interleukin-10 in Npc1^−/− microglia is ~ 60% lower than in Npc1^+/+ microglia. The survival of cultured neurons was not impaired by NPC1 deficiency, nor was death of Npc1^−/− and Npc1^+/+ neurons in microglia-neuron co-cultures increased by NPC1 deficiency in microglia. However, a high concentration of Npc1^−/− microglia appeared to promote neuron survival. Thus, although microglia exhibit an active morphology in NPC1-deficient brains, lack of NPC1 in microglia does not promote neuron death in vitro in microglia-neuron co-cultures, supporting the view that microglial NPC1 deficiency is not the primary cause of neuron death in NPC disease.