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Biomedical subjects

C M McDonald

Publications and source records attributed to C M McDonald.

At least 19 recordsLinked to original sources
PubMed2002

Antioxidant status of young children: response to an antioxidant supplement.

OBJECTIVE: To study oxidative stress indicators in healthy young children and their response to a commercially available fruit- and vegetable-based antioxidant supplement. DESIGN: Healthy children were randomly assigned to a placebo and a supplement (commercial antioxidant supplement produced from dried fruit and vegetable extracts and fortified with antioxidants, resembling a gummy-type candy). The placebo and the supplement were taken in 2 doses per day for 21 days. SUBJECTS: Participants were 39 children (26 boys and 13 girls) aged 5 to 10 years. Research was conducted at Primary Children's Medical Center and the University of Utah, Salt Lake City. MAIN OUTCOME MEASURES: Breath and urine samples were collected on days 1 and 21 and assayed for breath pentane and urine 8-hydroxydeoxyguanosine, malondialdehyde, nitrites, and 8-isoprostane as noninvasive indicators of oxidative stress. Urine oxygen radical absorbance capacity was measured at days 1 and 21 as an indirect indicator of the antioxidant capacity of the body. Three-day food records were collected at the beginning and end of the study to measure intake of dietary fruit; vegetable; and antioxidant vitamins A, C, and E. STATISTICAL ANALYSIS: Descriptive statistics, repeated measures analysis of variance, paired t tests, and Pearson r correlations. RESULTS: Markers of oxidative stress were not significantly different between the placebo and supplement groups at day 1 or day 21. The oxidative stress indicators of the healthy children in this study appear to be similar to those of healthy adults and were not changed by antioxidant supplementation. The diet record analyses indicated that mean fruit and vegetable intakes (2.75 servings/day) were similar to the national average intake for children in the United States. APPLICATIONS/CONCLUSIONS: This research presents original information on the subject of oxidative stress in healthy children. The results of this study may be useful as reference baseline markers to use in conjunction with clinical dietary evaluations and for future research with healthy children and with children in disease states who are subject to elevated levels of oxidative stress.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2001

Presynaptic congenital myasthenic syndrome due to quantal release deficiency.

OBJECTIVE: To provide clinical, electrophysiologic, and ultrastructural findings in three patients with a presynaptic congenital myasthenic syndrome (CMS). BACKGROUND: Familial infantile myasthenia and paucity of synaptic vesicles are the only two fully characterized CMS. We are describing here three patients with another form of presynaptic CMS characterized by deficiency of the action potential-dependent release without reduction of the spontaneous release of neurotransmitter from the nerve terminal. METHODS: The authors performed electromyography and anconeus muscle biopsies that included intracellular recordings and electron microscopy of the neuromuscular junction in three patients with presynaptic CMS. They also sequenced part of the P/Q-calcium alpha(1)-subunit gene (CACNA1A) and the acetylcholine receptor subunit (AChR) genes in these patients. RESULTS: In these patients there were additional neurologic findings including nystagmus and ataxia. In all three patients the end-plate potential quantal content (m) was markedly reduced but neither the amplitudes nor the frequencies of miniature end-plate potentials were diminished. Ultrastructurally, postsynaptic end-plate folds, nerve terminal size, and synaptic vesicle number were normal but double-membrane-bound sacs containing synaptic vesicles were present in the nerve terminal of all three patients. The screening of reported pathogenic mutations in the CACNA1A and a mutational analysis of AChR subunit genes were negative. CONCLUSION: This form of CMS appears to result only from a deficiency of the quantal release of neurotransmitter that may be due to an abnormal calcium mechanism or impaired endocytosis and recycling of synaptic vesicles.

Adolescent↗
PubMed2001

Peripheral neuropathies of childhood.

This article has provided a brief overview of the most common inherited and acquired peripheral nerve diseases encountered in childhood. The diagnostic approach of peripheral neuropathies in children often relies on some combination of careful history taking, physical examination findings, a careful determination of family history, electrodiagnostic studies, molecular genetic studies, sural nerve biopsy, and occasionally metabolic laboratory studies. Although pediatric mononeuropathies may have different causes than those observed in adults, the clinical presentations, diagnostic evaluation, and management of mononeuropathies are frequently similar in adults and children. Encouraging progress is being made in the management of acute inflammatory demyelinating polyneuropathy (AIDP), which is the most common acquired neuropathy of childhood. Rapid advances in molecular genetics over the past decade have had a significant impact on our diagnostic approach to hereditary motor sensory neuropathy in particular. In the future it is likely that the sequencing of genes, characterization of protein structure and function, and further elucidation of pathophysiology will have significant impacts on the treatment of many inherited peripheral neuropathies of childhood.

Age Distribution↗
PubMed2000

Magnetic resonance imaging of denervated muscle: comparison to electromyography.

The purpose of the study is to further assess the usefulness of short TI (time to inversion) recovery (STIR) magnetic resonance imaging (MRI) in detecting denervation of skeletal muscle compared to needle electromyography (EMG). Ninety subjects with clinical evidence of peripheral nerve injury or radiculopathy underwent STIR MRI and EMG of the affected limb. In 74 (82%) of these subjects, a positive correlation was found between STIR MRI and EMG (P < 0.009). STIR MRI has a relative sensitivity of 84% and specificity of 100% for detecting denervation. A subset of 28 subjects underwent quantitative assessments of signal intensity ratio (SIR) from the STIR MRI. The rank order correlation coefficient between the SIR and abnormal spontaneous activity on EMG was 0.70 (P < 0.001). Increased signal intensity on STIR MRI corresponds closely with spontaneous activity on EMG in denervated muscle. Although less sensitive than EMG in detecting muscle denervation, STIR MRI may be a useful adjunctive diagnostic tool in this setting.

Adult↗
PubMed1998

Mutations in the early growth response 2 (EGR2) gene are associated with hereditary myelinopathies.

The early growth response 2 gene (EGR2) is part of a multigene family encoding Cys2His2 type zinc-finger proteins and may play a role in the regulation of cellular proliferation. Egr2, (also known as Krox20) is the mouse orthologue of human EGR2 and was first identified as an immediate-early response gene, encoding a protein that binds DNA in a sequence-specific manner and acts as a transcription factor. Stable expression of Egr2 is specifically associated with the onset of myelination in the peripheral nervous system (PNS). Egr2(-/-) mice display disrupted hindbrain segmentation and development, and a block of Schwann-cell differentiation at an early stage. We hypothesized that Egr2 may be a transcription factor affecting late myelin genes and that human myelinopathies of the PNS may result from mutations in EGR2. In support of this hypothesis, we have identified one recessive and two dominant missense mutations in EGR2 (within regions encoding conserved functional domains) in patients with congenital hypomyelinating neuropathy (CHN) and a family with Charcot-Marie-Tooth type 1 (CMT1).

Adolescent↗
PubMed1998

Clinical approach to the diagnostic evaluation of progressive neuromuscular diseases.

This article has reviewed the clinical approach to the diagnostic evaluation of progressive neuromuscular diseases with an emphasis on relevant neuromuscular history, family history, clinical examination findings, laboratory studies, and a brief discussion of the role of muscle biopsy. Molecular genetic and immunocytochemistry studies of muscle have been major advances in the diagnostic evaluation of the neuromuscular disease patient; however, all diagnostic information must be interpreted within the context of relevant clinical information. In some instances, a precise diagnosis is not medically possible; however, the accurate characterization of an individual patient within the most appropriate NMD clinical syndrome often allows the clinician to provide the patient and family with accurate prognostic information and anticipatory guidance for the future. After synthesizing all available clinical and diagnostic information, the physiatrist or neurologist may at times determine that an NMD patient has an inappropriate diagnosis warranting further diagnostic evaluation. This issue focuses on the rehabilitation of progressive neuromuscular diseases with an emphasis on optimization of health, prevention or minimization of complications, and enhancement of quality of life. Appropriate rehabilitation approaches require an accurate diagnosis. In addition, patient quality of life in NMD depends on access to current and accurate information. The first step in providing accurate information and appropriate treatment is constantly ensuring that NMD patients have appropriate diagnoses based on a through evaluation of clinical information and appropriate application of current medical science and available diagnostic technology.

Biopsy↗
PubMed1998

Limb contractures in progressive neuromuscular disease and the role of stretching, orthotics, and surgery.

Contractures are exceedingly common impairments in selected progressive NMD conditions, particularly those with excessive fibrosis and fatty infiltration into muscle (i.e., dystrophic myopathies) and more severe NMD conditions, resulting in significant weakness and wheel-chair reliance, such as SMA. Less than antigravity strength produces an inability to achieve full active range of motion. Static positioning of limbs (generally in flexion) and lack of weight bearing results in fixed contractures. This article has reviewed the prevalence and distribution of contractures in specific NMD conditions. Aggressive rehabilitation strategies, including stretching, positioning, splinting, upright weight bearing, and orthopaedic surgical management may help minimize the degree of disability in NMD patients with contractures.

Activities of Daily Living↗
PubMed1998

Spinal deformity in progressive neuromuscular disease. Natural history and management.

Severe spinal deformity in progressive neuromuscular disease (NMD) leads to multiple problems, including poor sitting balance, difficulty with upright seating and positioning, pain, difficulty in attendant care, and potential exacerbation of underlying restrictive respiratory compromise. Severe scoliosis and pelvic obliquity can in some instances completely preclude upright sitting in a wheelchair. This article reviews the prevalence, natural history, and management of scoliosis in neuromuscular diseases at greatest risk for progressive spinal deformity.

Activities of Daily Living↗
PubMed1997

Urodynamic findings in the tethered spinal cord syndrome: does surgical release improve bladder function?

PURPOSE: We retrospectively reviewed 39 patients with a tethered spinal cord to evaluate whether surgical release positively influenced urological symptoms or urodynamic findings. MATERIALS AND METHODS: The patients were divided into 2 groups: group 1-11 with occult spinal dysraphism and group 2-28 with secondary spinal cord tethering after previous closure of a myelomeningocele or resection of a lipomyelomeningocele. Diagnosis was confirmed in all cases by magnetic resonance imaging or spinal ultrasound. A comprehensive urodynamic evaluation was done immediately preoperatively and 2 to 21 months (mean 7) postoperatively. RESULTS: In group 1 the most common preoperative urodynamic finding was hyperreflexia, which improved or resolved after untethering in 62.5% of the patients. Four adults also reported improved bladder sensation or decreased urgency. In group 2 the most common urodynamic finding was impaired compliance, followed closely by detrusor hyperreflexia. Urodynamic patterns of detrusor hyperreflexia or compliance improved in only 30% of the patients, while 48% had worsened patterns. Only 14% of group 2 had improved symptoms of urinary control but 28% had improved lower extremity function. CONCLUSIONS: Urological symptoms and urodynamic patterns may be improved by early surgical intervention in patients with occult spinal dysraphism. However, untethering did not consistently benefit patients with secondary spinal cord tethering.

Adolescent↗
PubMed1996

Focal posterior interosseous neuropathy in the presence of hereditary motor and sensory neuropathy, type I.

A 30-year-old male with hereditary motor and sensory neuropathy, type I (HMSN I), presented with asymmetric weakness of finger extension and radial deviation with left wrist extension, previously felt to be a manifestation of the peripheral neuropathy. Nerve conduction studies confirmed HMSN I; however, needle EMG revealed marked, ongoing axonal loss in muscles innervated by the left posterior interosseous nerve (PIN) only. At surgery there was focal fusiform swelling in the PIN at exit from the supinator muscle, compatible with localized hypertrophic neuropathy, which has not been reported before in HMSN I. A concomitant focal mononeuropathy should be considered in cases of hereditary neuropathy with marked asymmetry of weakness.

Adult↗
PubMed1995

Isolated femoral mononeuropathy to the vastus lateralis: EMG and MRI findings.

A 16-year-old female track athlete experienced sudden onset of right anterolateral thigh pain, initially thought to be cramping. After 2 months of continued postexercise pain she sought medical evaluation. A 3-cm thigh circumference discrepancy was noted on physical exam. She was referred for electromyography (EMG) and magnetic resonance imaging (MRI) studies. Femoral and screening nerve conduction studies were normal. Needle EMG revealed acute neuropathic changes confined to the right vastus lateralis only. These findings were confirmed by MRI, including short T1 inversion recovery (STIR) sequences. All other medical work-up was normal, including lumbar and pelvic MRI, and complete serologic studies. This case represents a unique presentation of an idiopathic femoral mononeuropathy isolated to the vastus lateralis only, which has not been previously reported. The highly unusual anatomical presentation of this case illustrates the emerging complementary usefulness of EMG and MRI in delineating neuromuscular pathology.

Action Potentials↗
PubMed1995

Rehabilitation of children with spinal dysraphism.

Tremendous advances have occurred over the past several decades in the comprehensive management of spinal dysraphism. Multiple specialists from varied surgical, medical, and allied health professions contribute to the rehabilitation management of children with spinal dysraphism. Rehabilitation goals and treatment strategies have been presented in the contexts of multiple functional outcome domains of critical importance to quality of life. In addition, the child with spinal dysraphism often has unique health care maintenance issues that require careful monitoring within a coordinated, interdisciplinary clinic setting. Prevention of neurologic, musculoskeletal, urologic, and medical complications is necessary for the child with spinal dysraphism to realize his or her maximum functional potential. A comprehensive rehabilitation program provides sufficient training, education, and long-term monitoring to enable the child not only to achieve self-sufficiency, but also to maintain an optimal level of function throughout life.

Activities of Daily Living↗
PubMed1994

Comparison of indices of traumatic brain injury severity as predictors of neurobehavioral outcome in children.

This study examined the ability of early measures of traumatic brain injury (TBI) severity to predict neurobehavioral and functional skill outcomes shortly after injury and at 1 year postinjury. Ninety-eight children aged 6 to 15 years with TBI were consecutively identified on presentation to two regional medical centers. Ten measures of TBI severity were subsequently administered: initial Glasgow Coma Scale (motor, eye, verbal, and total GCS), duration of loss of consciousness, Abbreviated Injury Scale Head score, GCS motor score at 3 days postinjury, days to reach a total GCS score of 15, days to reach a GCS motor score of six, and duration of posttraumatic amnesia (days to reach a 75% performance on the Children's Orientation and Amnesia Test [COAT]). Cases were matched individually with controls on the basis of age, gender, school grade, the classroom teacher's assessment of pre-morbid level of academic performance in reading and arithmetic, and pre-morbid behavior. Both groups received intellectual, neuropsychologic, academic, and functional skill assessments three weeks after the case achieved full orientation and 1 year later. The indices of injury severity that were most predictive of both early and 1-year outcome across all neurobehavioral and functional measures were (1) days to an age-adjusted 75% performance on the COAT, (2) days to a GCS score of 15, and (3) initial total GCS score. For most outcome areas, a single measure of severity predicted outcome almost as well as multiple measures. However, early and 1-year academic performance and 1-year memory performance were best predicted by considering multiple indices of brain injury severity. The GCS verbal and motor scores were better predictors of outcome than the GCS eye score. However, consideration of individual GCS subscores did not improve upon prediction of outcome versus the GCS total score. These results provide strong validation for the use of duration of posttraumatic amnesia, measured by the COAT, as a measure of TBI severity and a significant indicator of neurobehavioral and functional outcome in children.

Activities of Daily Living↗
PubMed1992

Analysis of adhesion and cytotoxicity of Tritrichomonas foetus to mammalian cells by use of monoclonal antibodies.

The relationship of Tritrichomonas foetus adhesion to mammalian cells and cytotoxicity to these targets was investigated. High-adherence and low-adherence lines of T. foetus, derived by repeated adhesion to HeLa cells, showed high and low cytotoxicity, respectively, to HeLa cells. When parasites were separated from targets by membranes (0.4-microns pore size), no cytotoxicity was detectable. Monoclonal antibodies elicited against T. foetus that lowered adhesion also lowered parasite-mediated cytotoxicity. Flow cytometry experiments revealed that the levels of an adhesion- and cytotoxicity-blocking antibody bound to the surface of high-adherence clones of T. foetus were higher than those in low-adherence clones. Western blots of parasite extracts separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis were probed with an anti-T. foetus antibody. A molecule with a molecular weight of approximately 190,000 composed of subunits with molecular weights of approximately 140,000 to 150,000 and approximately 65,000 was identified. Immunoprecipitation experiments with metabolically labeled T. foetus and the same antibody confirmed that similar subunits were synthesized by the parasite. These results indicate that adhesion of T. foetus to mammalian cells is an important step in cytotoxic damage of these targets and that a surface adhesin on the parasite is involved in the adhesion mechanism.

Adhesiveness↗