Biomedical subjects

L S Meadows

Publications and source records attributed to L S Meadows.

4 recordsLinked to original sources

PubMed2005

Sodium channels as macromolecular complexes: implications for inherited arrhythmia syndromes.

Mutations in cardiac ion channels and their auxiliary subunits can lead to life-threatening cardiac arrhythmias. In recent years it has become apparent that ion channels are part of large, multi-protein complexes, comprising not only the ion channels and their auxiliary subunits, but also components of the cytoskeleton, regulatory kinases and phosphatases, trafficking proteins, extracellular matrix proteins, and possibly even other ion channels. Disruption of any member of a particular ion channel complex has the potential to disrupt the function of the associated channels, resulting in paroxysmal disease. Understanding the molecular composition of individual ion channel signaling complexes in heart may yield important insights into the molecular basis of cardiac arrhythmias and may suggest novel therapeutic approaches to treatment of these life-threatening conditions.

Animals↗

PubMed2002

Functional modulation of human brain Nav1.3 sodium channels, expressed in mammalian cells, by auxiliary beta 1, beta 2 and beta 3 subunits.

Voltage-gated sodium channels consist of a pore-forming alpha subunit and two auxiliary beta subunits. Excitable cells express multiple alpha subtypes, designated Na(v)1.1-Na(v)1.9, and three beta subunits, designated beta1, beta2 and beta3. Understanding how the different alpha subtypes, in combination with the various beta subunits, determine sodium channel behavior is important for elucidating the molecular basis of sodium channel functional diversity. In this study, we used whole-cell electrophysiological recording to examine the properties of the human Na(v)1.3 alpha subtype, stably expressed in Chinese hamster ovary cells, and to investigate modulation of Na(v)1.3 function by beta1, beta2 and beta3 subunits. In the absence of beta subunits, human Na(v)1.3 formed channels that inactivated rapidly (tau(inactivation) approximately equals 0.5 ms at 0 mV) and almost completely by the end of 190-ms-long depolarizations. Using an intracellular solution with aspartate as the main anion, the midpoint for channel activation was approximately -12 mV. The midpoint for inactivation, determined using 100-ms conditioning pulses, was approximately -47 mV. The time constant for repriming of inactivated channels at -80 mV was approximately 6 ms. Coexpression of beta1 or beta3 did not affect inactivation time course or the voltage dependence of activation, but shifted the inactivation curve approximately 10 mV negative, and slowed the repriming rate ca. three-fold. beta2 did not affect channel properties, either by itself or in combination with beta1 or beta3. Na(v)1.3 expression is increased in damaged nociceptive peripheral afferents. This change in channel expression levels is correlated with the emergence of a rapidly inactivating and rapidly repriming sodium current, which has been proposed to contribute to the pathophysiology of neuropathic pain. The results of this study support the hypothesis that Na(v)1.3 may mediate this fast sodium current.

Animals↗

PubMed1994

Pyruvate dehydrogenase deficiency. Clinical presentation and molecular genetic characterization of five new patients.

Fibroblast cultures from five patients with early onset severe encephalopathy and lactic acidosis were studied for evidence of pyruvate dehydrogenase (PDH) deficiency. Three males had significantly reduced activity (0.29-0.45 nmol/mg protein/min versus normal controls 0.7-1.1 nmol/mg protein/min); two females had PDH activity within the normal range. However, as the majority of cases of PDH deficiency result from defects in the X-linked E1 alpha subunit and both females had biased patterns of X-inactivation (making it impossible to rule out the possibility that they were heterozygous for an E1 alpha gene defect) molecular genetic studies were performed. cDNA from the male patients was sequenced and mis-sense mutations found: Y243N (T-->A) in exon 7, D315A (G-->A) in exon 10 and R378H (G-->A) in exon 11. Single-strand conformation polymorphism analysis of amplified genomic DNA fragments and sequencing revealed a mis-sense mutation M282L (A-->C) in one female and a frameshift mutation caused by insertion of T (R288ins) in the other. Adding to recent descriptions of new mutations, this report emphasizes the allelic heterogeneity of the condition. The identification of mutations in females with a suggestive clinical phenotype, even when peripheral fibroblasts do not show deficient PDH activity, illustrates the importance of molecular analysis of this disease.

Base Sequence↗

PubMed1977

Nursing education in crisis: a computer alternative.

The impact of computer-assisted instruction upon the educational process is having its effect. The computer is being used in nursing education today to manage the educational environment, to instruct, to evaluate, to identify problem areas, to gather data, to manipulate data for research purposes and for continued education. As we struggle in our efforts for quality individualized education, we are minutely scrutinizing every aspect of the teaching learning process. We are not only examining how we teach but what we teach and why we are teaching it! Our deeper understanding of the process of education has helped us to delineate nursing process as content. Higher levels of instructional goals -- cognitive, affective and conative -- are resulting in education of the whole individual. The systematization of the learning process with the greater ease of accountability is leading nursing education to blaze promising new trails into the twenty-first century.

Computer-Assisted Instruction↗