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Biomedical subjects

M J Bennett

Publications and source records attributed to M J Bennett.

At least 109 records · Page 6Linked to original sources
PubMed1997

In-utero and post-delivery supplementation of motor neuron degeneration mutant mice with polyunsaturated fatty acids does not alter the clinical or pathological course.

We have studied the effects of polyunsaturated fatty acid (PUFA) supplementation in utero and throughout life in mnd mutant mice, a proposed model for juvenile neuronal ceroid lipofuscinosis (CLN-3). Unlike our earlier in-vitro studies in humans with CLN-3, and in-vitro studies in CLN-3 lymphoblasts, we saw no beneficial effects in electroretinographic, electron microscopic or clinical studies in the mnd mice. Electron microscopy of brain revealed a pattern which was not consistent with the characteristic ceroid patterns in CLN-3. Our data suggest that the mnd mouse is not responsive to PUFA supplementation and may not be an appropriate animal model for CLN-3.

Animals↗
PubMed1997

Effects of family history of heart disease, apolipoprotein E phenotype, and lipoprotein(a) on the response of children's plasma lipids to change in dietary lipids.

We examined the effects of family history of coronary artery disease (CAD), apolipoprotein E (apo E) phenotype, and lipoprotein(a) [Lp(a)] on the response of plasma lipids to change in dietary lipid intake after 3 mo of nutrition education in 125 children aged 4-10 y. The subjects were healthy children with elevated low-density-lipoprotein (LDL)-cholesterol concentrations who participated in the Children's Health Project, a nutrition-education program designed to lower plasma cholesterol by means of dietary modifications in accordance with recommendations of the National Cholesterol Education Program. Dietary and plasma lipids were measured by three 24-h recalls and assessments of two fasting plasma samples collected before and 3 mo after the start of intervention. Family history of CAD was determined by questionnaires administered to parents at baseline. Apo E phenotyping was done with isoelectric focusing followed by immunostaining; Lp(a) was measured with two-site immunoradiometric assays of frozen aliquots of plasma samples collected at baseline and 3 mo. After adjustment for intervention group, age, sex, and body mass index, analysis of covariance showed that baseline plasma lipid concentrations were the strongest independent predictors of change in plasma lipids after 3 mo. Plasma total and LDL-cholesterol concentrations in children with less family history of CAD were significantly more responsive to change in dietary cholesterol than concentrations in children with a stronger family history of CAD. Neither apo E phenotype nor Lp(a) significantly influenced change in plasma lipids independently or interactively with change in dietary lipids.

Apolipoproteins E↗
PubMed1997

Stability of long-chain and short-chain 3-hydroxyacyl-CoA dehydrogenase activity in postmortem liver.

Inherited enzyme defects in mitochondrial fatty acid oxidation (FAO) are associated with acute metabolic crisis and sudden death. Necropsy findings may be subtle, yielding no diagnosis and precluding genetic counseling. Preliminary identification of an FAO disorder requires the use of sophisticated tools (e.g., GC/MS) and specific body fluids, and the diagnosis rests on molecular analysis or enzyme assay. At present, confirmation of long-chain or short-chain 3-hydroxyacyl-CoA dehydrogenase deficiency relies on measurement of enzyme activity. Here, we report our examination of the effect of storage temperature (25, 4, -20, and -70 degrees C) and the postmortem interval on enzyme activities in rat and human liver. Enzyme activity decreases 50% in 30 h in samples stored at 25 degrees C, whereas 55 h at 4 degrees C is required to reach this value; freezing minimizes this loss. Regardless of rate of degradation, however, the short-chain to long-chain activity ratio remains constant--which should make it possible to differentiate postmortem degradation from enzyme deficiency.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1997

Clinical, biochemical, and morphologic investigations of a case of long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency.

We report the premortem and postmortem morphologic and histologic features and biochemical findings of a patient with long-chain 3-hydroxyacyl-CoA dehydrogenase (L-CHAD) deficiency and compare these with those described in previously reported cases of L-CHAD deficiency. In addition to chronic nonketotic hypoglycemia, hypotonia, and liver failure, this patient had chronic hemolytic anemia and delayed central nervous system myelination. These features have not been previously documented in L-CHAD deficiency.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1996

Structure of 3 alpha-hydroxysteroid/dihydrodiol dehydrogenase complexed with NADP+.

Rat liver 3 alpha-hydroxysteroid/dihydrodiol dehydrogenase (3 alpha-HSD) inactivates circulating steroid hormones and is involved in polycyclic aromatic hydrocarbon (PAH) carcinogenesis. It is the only HSD of known structure in the aldo-keto reductase (AKR) superfamily and may provide a paradigm for other mammalian HSDs in this family. The structure of the 3 alpha-HSD.NADP+ binary complex has been determined at 2.7 A resolution and refined to a crystallographic R-factor of 23.4% with good geometry. The model is similar to other binary complexes in the AKR superfamily in that NADP+ binds at the C-terminal end of an alpha/beta barrel. However, it is unique in that NADP+ is bound in two alternate conformations, probably because of the lack of a salt-linked "safety belt" over the pyrophosphate bridge. The structure supports a previously proposed catalytic mechanism for carbonyl reduction in which Tyr 55 is the general acid, and its effective pKa is lowered by the adjacent Lys 84. We present evidence that the structurally distinct short-chain dehydrogenase/reductase (SDR) superfamily may have convergently evolved a similar catalytic mechanism. Insight into substrate binding is offered by a crystal packing contact in which a neighboring molecule inserts a tryptophan residue (Trp 227) into an apolar cleft in 3 alpha-HSD. This cleft is proximal to the bound NADP+ cofactor and contains a surface of apolar residues (Leu 54, Trp 86, Leu 122, Phe 128, Phe 129, Leu 137, Phe 139), making it a likely candidate for the substrate-binding site. Thus, in forming this crystal contact, Trp 227 may mimic a portion of a bound steroid. In addition, we propose that a water molecule in the active site indicates the position of the hydroxyl oxygen in a 3 alpha-hydroxysteroid substrate. Knowledge of the position of this water molecule, combined with the stereochemistry of hydride transfer, suggests that the alpha face of a bound steroid will be oriented toward the side of the apolar cleft containing Trp 86.

3-Hydroxysteroid Dehydrogenases↗
PubMed1996

Arabidopsis AUX1 gene: a permease-like regulator of root gravitropism.

The plant hormone auxin regulates various developmental processes including root formation, vascular development, and gravitropism. Mutations within the AUX1 gene confer an auxin-resistant root growth phenotype and abolish root gravitropic curvature. Polypeptide sequence similarity to amino acid permeases suggests that AUX1 mediates the transport of an amino acid-like signaling molecule. Indole-3-acetic acid, the major form of auxin in higher plants, is structurally similar to tryptophan and is a likely substrate for the AUX1 gene product. The cloned AUX1 gene can restore the auxin-responsiveness of transgenic aux1 roots. Spatially, AUX1 is expressed in root apical tissues that regulate root gravitropic curvature.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1996

The counterion influence on cationic lipid-mediated transfection of plasmid DNA.

A panel of DOTAP analogs was prepared by altering the anionic counterion that accompanies the trimethylammonium polar domain. The transfection of plasmid DNA into NIH3T3 cells and mouse lung was examined using the counterion analogs. The in vitro transfection activity decreased as follows: DOTAP.bisulfate > trifluoromethanesulfonate approximately equal to iodide approximately equal to bromide > dihydrogenphosphate approximately equal to chloride approximately equal to acetate > sulfate. A similar activity trend was observed in vivo.

3T3 Cells↗
PubMed1996

Endocardial fibroelastosis and primary carnitine deficiency due to a defect in the plasma membrane carnitine transporter.

Endocardial fibroelastosis (EFE) has previously been shown to be associated with tissue carnitine deficiency, although the basis for the carnitine deficiency has not been documented. A patient with the classical features of EFE and marked deficiency of carnitine in heart muscle, skeletal muscle, and liver is presented in this report. Cultured skin fibroblasts from both parents demonstrated levels of carnitine uptake at 50% of the normal rate. This is consistent with heterozygosity for the plasma membrane carnitine transporter defect, indicating likely homozygosity for this recently recognized inborn error in the index patient.

Cardiomyopathy, Dilated↗
PubMed1996

Toxicity of cationic lipid-ribozyme complexes in human prostate tumor cells can mimic ribozyme activity.

Prostate tumor cell lines have been shown to both produce interleukin-6 (IL-6) and express the IL-6 receptor, suggesting a potential autocrine growth regulatory role for IL-6. We explored the role of IL-6 in the proliferation of the human prostatic carcinoma cell line, DU145, using ribozymes to inhibit IL-6 expression. Hammerhead-type ribozymes targeted against IL-6 mRNA sequences were prepared, and in vitro analyses were used to demonstrate that these molecules catalyzed the cleavage of IL-6 mRNA poly- nucleotide fragments. To test in situ activity, these ribozymes were transfected into DU145 cells using cationic transfection lipids, cytofectins. Treatment of cultured cells with ribozyme/cationic lipid complexes resulted in a reduction of IL-6 protein levels in the supernatant and reduced numbers of DU145 cells 48 h after treatment. However, similar results were also seen following treatment with control RNA/lipid complexes. This reduction in IL-6 levels and cell numbers was a function of the RNA/lipid complexes and was not seen with either lipid or RNA alone. Therefore, the reductions in IL-6 levels and cell numbers observed were not due to ribozyme-mediated cleavage of IL-6 mRNA, but rather reflected a dose-dependent, nonspecific toxic effect of the treatment with ribozyme/cytofectin complexes. This effect can resemble functional ribozyme activity, complicating analysis of the activity of synthetic ribozymes after transfection into cultured cells.

Base Sequence↗
PubMed1996

Late-onset holocarboxylase synthetase deficiency.

We report a 21-month-old female patient whose urine organic acid profile suggested a biotin utilization abnormality consistent with multiple carboxylase deficiency. For most previously reported patients, holocarboxylase synthetase deficiency has correlated with the early-onset variant of multiple carboxylase deficiency; conversely, biotinidase deficiency has been characteristic of the late-onset form. In vitro enzyme studies revealed that our patient suffered from holocarboxylase synthetase deficiency. We suggest that holocarboxylase synthetase deficiency should be considered in the differential diagnosis of older patients in whom there is suspicion of a defect in biotin metabolism.

Biotin↗
PubMed1996

Mammalian 3 alpha-hydroxysteroid dehydrogenases.

Mammalian 3 alpha-hydroxysteroid dehydrogenases (3 alpha-HSDs) regulate steroid hormone levels. For example, hepatic 3 alpha-HSDs inactivate circulating androgens, progestins, and glucocorticoids. In target tissues they regulate access of steroid hormones to steroid hormone receptors. For example, in the prostate 3 alpha-HSD acts as a molecular switch and controls the amount of 5 alpha-dihydrotestosterone that can bind to the androgen receptor, while in the brain 3 alpha-HSD can regulate the amount of tetrahydrosteroids that can alter GABAa receptor function. Molecular cloning indicates that these mammalian 3 alpha-HSDs belong to the aldo-keto reductase superfamily and that they are highly homologous proteins. Using the three-dimensional structure of rat liver 3 alpha-HSD as a template for site-directed mutagenesis, details regarding structure function relationships, including catalysis and cofactor and steroid hormone recognition have been elucidated. These details may be relevant to all mammalian 3 alpha-HSDs.

3-Hydroxysteroid Dehydrogenases↗
PubMed1996

Fetal polycystic kidney disease associated with glutaric aciduria type II: an inborn error of energy metabolism.

The findings of hyperechoic and enlarged fetal kidneys on routine antenatal ultrasonography is a non-specific finding that alerts the physician to a differential diagnosis of various genetic and non-genetic disorders, including fetal polycystic disease and Beckwith-Wiedeman syndrome. Detection of fetal or neonatal polycystic kidneys should alert the physician to the possibility of an associated lethal autosomal recessive inborn error of fatty acid metabolism known as multiple acyl-CoA-dehydrogenase defect (MADD). We report a case of fetal nephromegaly associated with rare inborn error of MADD. This case highlights the need for appropriate laboratory investigation of hyperechoic, enlarged fetal kidneys, and neonatal polycystic disease. The association of MADD with postnatally diagnosed polycystic disease of the kidney has been reported. The antenatal detection of nephromegaly followed by the subsequent postnatal diagnosis of MADD has not been previously reported. MADD should be considered in the differential diagnosis of this antenatal finding. Appropriate diagnostic procedures should be conducted, either pre- or postnatally, in order that appropriate genetic counseling may be provided for this autosomal recessively inherited disorder.

Acyl-CoA Dehydrogenases↗
PubMed1996

Is psychotherapy ever medically necessary?

The concept of medical necessity has its roots in payers' fear that mental health care will be overused by those with access to it. The author argues that such a fear was reinforced by practice patterns that were dominant before the advent of managed care, when large amounts of treatment were given to few patients, and receipt of such care was poorly correlated with clinical need. He reviews differences between traditional models of care and those that have emerged since the advent of managed care and prospective payment. Care is medically necessary when a diagnosable disorder exists and the patient has impaired function or is clinically unstable as a result and when treatment is demonstrably efficacious in restoring normalcy or reducing disability. The author describes how psychotherapy meets these criteria under three circumstances: when used as an adjunct to treatment strategies with demonstrated efficacy, when its efficacy alone is established for a given disorder, and as a "holding operation" when no effective treatment exists or is agreed to exist. New approaches, including brief or intermittent focused treatment, that reduce reliance on the use of treatment as a holding operation are described.

Health Maintenance Organizations↗
PubMed1996

Mitochondrial short-chain L-3-hydroxyacyl-coenzyme A dehydrogenase deficiency: a new defect of fatty acid oxidation.

We describe two children with deficiency of short-chain L-3-hydroxyacyl-CoA dehydrogenase, a new disorder of the mitochondrial beta-oxidation of straight-chain fatty acids. The patients presented with fasting-induced vomiting, and ketosis and low blood glucose, features typical of ketotic hypoglycemia were documented in one. Enzyme assays were performed in cultured skin fibroblasts. In whole fibroblast preparations there was reduced enzyme activity but high residual activity due to the presence of a nonmitochondrial enzyme. In isolated fibroblast mitochondria the residual enzyme activities were 5 and 6% of the normal controls. Activity in an obligate heterozygote was intermediate, suggesting that this is an autosomal recessive disorder.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1996

Maternal acute fatty liver of pregnancy associated with fetal trifunctional protein deficiency: molecular characterization of a novel maternal mutant allele.

Acute fatty liver of pregnancy (AFLP) is a devastating late gestational complication with many similarities to the inherited disorders of mitochondrial fatty acid oxidation. We report the molecular defects in a woman with AFLP and her infant who subsequently was diagnosed with trifunctional protein (TFP) deficiency. We used single-stranded conformation variance and DNA sequence analyses of the human TFP alpha-subunit gene, which encodes the long chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) activity, to demonstrate a C to T mutation (C1678T) in exon 16 present on one allele in the mother and the affected infant. This creates a premature termination codon (R524Stop) in the LCHAD domain. Using reverse transcriptase-PCR amplification of the alpha-subunit mRNA from cultured fibroblasts, we demonstrated that transcripts containing this R524Stop mutation are present at very low levels, presumably because of rapid mRNA degradation. The affected infant also had the common E474Q mutation (nucleotide G1528C) on the second allele. Thus, he is a compound heterozygote. The father and two normal siblings are heterozygous for this E474Q mutation. This initial delineation of the R524Stop mutation provides evidence of the heterogeneity of genetic defects responsible for TFP deficiency and AFLP.

3-Hydroxyacyl CoA Dehydrogenases↗