Biomedical subjects

M L Hines

Publications and source records attributed to M L Hines.

4 recordsLinked to original sources

PubMed2000

Expanding NEURON's repertoire of mechanisms with NMODL.

Neuronal function involves the interaction of electrical and chemical signals that are distributed in time and space. The mechanisms that generate these signals and regulate their interactions are marked by a rich diversity of properties that precludes a "one size fits all" approach to modeling. This article presents a summary of how the model description language NMODL enables the neuronal simulation environment NEURON to accommodate these differences.

Models, Neurological↗

PubMed1999

Computational analysis of action potential initiation in mitral cell soma and dendrites based on dual patch recordings.

In olfactory mitral cells, dual patch recordings show that the site of action potential initiation can shift between soma and distal primary dendrite and that the shift is dependent on the location and strength of electrode current injection. We have analyzed the mechanisms underlying this shift, using a model of the mitral cell that takes advantage of the constraints available from the two recording sites. Starting with homogeneous Hodgkin-Huxley-like Na(+)-K(+) channel distribution in the soma-dendritic region and much higher sodium channel density in the axonal region, the model's channel kinetics and density were adjusted by a fitting algorithm so that the model response was virtually identical to the experimental data. The combination of loading effects and much higher sodium channel density in the axon relative to the soma-dendritic region results in significantly lower "voltage threshold" for action potential initiation in the axon; the axon therefore fires first unless the voltage gradient in the primary dendrite is steep enough for it to reach its higher threshold. The results thus provide a quantitative explanation for the stimulus strength and position dependence of the site of action potential initiation in the mitral cell.

Action Potentials↗

PubMed1997

The NEURON simulation environment.

The moment-to-moment processing of information by the nervous system involves the propagation and interaction of electrical and chemical signals that are distributed in space and time. Biologically realistic modeling is needed to test hypotheses about the mechanisms that govern these signals and how nervous system function emerges from the operation of these mechanisms. The NEURON simulation program provides a powerful and flexible environment for implementing such models of individual neurons and small networks of neurons. It is particularly useful when membrane potential is nonuniform and membrane currents are complex. We present the basic ideas that would help informed users make the most efficient use of NEURON.

Animals↗

PubMed1981

Conformation studies of histone H1(0) in comparison with histones H1 and H5.

The class of lysine-rich histones, H1, found in most eukaryotic cells is largely replaced by another class of lysine-rich histones, H5, in avian and other erythrocytes. Erythrocytes are transcriptionally inert and this state has been attributed to the presence of H5. Although there are many sequence differences between H1 and H5 both molecules have very similar structures with three well-defined domains: a flexible basic N-terminal region, an apolar globular central region and a flexible basic C-terminal region. The lengths of the N-terminal regions are different for H1 and H5 whereas the lengths of the central and C-terminal regions are very similar. Considerable interest attaches to the findings that another type of mammalian lysine-rich histone H1(0) has an apolar region exhibiting considerable sequence homology (70%) with the central globular region of H5. The abundance of H1 in cells has been found to correlate inversely with their mitotic activities. Conformational studies using high-resolution nuclear magnetic resonance and optical spectroscopy have been made of H1 and its conformational behaviour has been compared with those of H1 and H5. H1 has been found to contain a central globular region of similar size to those found in H1 and H5. However, the conformation and stability of the globular domain of H1 are very similar to the globular region of H5 rather than H1. H1 appears to be a hybrid containing a major feature of the H5 histone. The globular regions of H1 and H5 are known to bind to a specific site on the nucleosome sealing off two turns of DNA. It is proposed that H1 binds to the same site.

Amino Acid Sequence↗