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Matthew D Whim

Publications and source records attributed to Matthew D Whim.

6 recordsLinked to original sources
PubMed2006

Cytomegalovirus induces interferon-stimulated gene expression and is attenuated by interferon in the developing brain.

Cytomegalovirus (CMV) is considered the most common infectious agent causing permanent neurological dysfunction in the developing brain. We have previously shown that CMV infects developing brain cells more easily than it infects mature brain cells and that this preference is independent of the host B- and T-cell responses. In the present study, we examined the innate antiviral defenses against mouse (m) and human (h) CMVs in developing and mature brain and brain cells. mCMV infection induced interferon (IFN)-stimulated gene expression by 10- to 100-fold in both glia- and neuron-enriched cultures. Treatment of primary brain cultures with IFN-alpha, -beta, and -gamma or a synthetic RNA, poly(I:C), reduced the number of mCMV-infected cells, both in older cells and in fresh cultures from embryonic mouse brains. When a viral dose that killed almost all unprotected cells was used, IFN-protected cells had a natural appearance, and when they were tested with whole-cell patch clamp recording, they appeared physiologically normal with typical resting membrane potentials and action potentials. mCMV infection increased expression of representative IFN-stimulated genes (IFIT3, OAS, LMP2, TGTP, and USP18) in both neonatal and adult brains to similarly large degrees. The robust upregulation of gene expression in the neonatal brain was associated with a much higher degree of viral replication at this stage of development. In contrast to the case for downstream gene induction, CMV upregulated IFN-alpha/beta expression to a greater degree in the adult brain than in the neonatal brain. Similar to the case with cultured brain cells, IFN treatment of the developing brain in vivo depressed mCMV replication. In parallel work with cultured primary human brain cells, IFN and poly(I:C) treatment reduced hCMV infection and prevented virus-mediated cell death. These results suggest that coupling IFN administration with current treatments may reduce CMV infections in the developing brain.

Animals↗
PubMed2006

Near simultaneous release of classical and peptide cotransmitters from chromaffin cells.

Adrenal chromaffin cells are an important part of the neuroendocrine system and under stressful conditions release catecholamines into the blood, thus regulating many physiological processes. In addition to the catecholamines, chromaffin cells also synthesize a range of peptides, including neuropeptide Y. Although the catecholamines and peptides are both contained within dense core granules, whether they are copackaged is less clear. Here, I investigate whether a single dense core granule can be loaded with both types of transmitter molecules. Using amperometry and FMRFamide tagging, I simultaneously measure the secretion of the catecholamines and a neuropeptide from mouse chromaffin cells in vitro. I find that fusion of a single dense core granule releases both types of transmitters into the extracellular space. Significant amounts of peptide escape from a fusing granule in 1-2 ms: almost as rapidly as the catecholamines. This suggests that the kinetics of peptide secretion might not be as sluggish as sometimes thought.

Animals↗
PubMed2005

Regulation of the timing of MNTB neurons by short-term and long-term modulation of potassium channels.

The firing patterns of neurons in central auditory pathways encode specific features of sound stimuli, such as frequency, intensity and localization in space. The generation of the appropriate pattern depends, to a major extent, on the properties of the voltage-dependent potassium channels in these neurons. The mammalian auditory pathways that compute the direction of a sound source are located in the brainstem and include the connection from bushy cells in the anteroventral cochlear nucleus (AVCN) to the principal neurons of the medial nucleus of the trapezoid body (MNTB). To preserve the fidelity of timing of action potentials that is required for sound localization, these neurons express several types of potassium channels, including the Kv3 and Kv1 families of voltage-dependent channels and the Slick and Slack sodium-dependent channels. These channels determine the pattern of action potentials and the amount of neurotransmitter released during repeated stimulation. The amplitude of currents carried by one of these channels, the Kv3.1b channel, is regulated in the short term by protein phosphorylation, and in the long term, by changes in gene expression, such that the intrinsic excitability of the neurons is constantly being regulated by the ambient auditory environment.

Action Potentials↗
PubMed2004

FMRFamide tagging--how an ionotropic receptor can be used to measure peptide secretion.

In this chapter, we describe a technique, FMRFamide tagging, that in principle can be used to measure the release of any sequenced neuropeptide. The method relies upon the addition of an "electrophysiologically active" tag to the prohormone that encodes the neuropeptide of interest. Secretion of the electrophysiological tag (and thus the peptide of interest) is detected by activation of the ionotropic "tag receptor." Both the tagged prohormone and the tag receptor are expressed in the cell type under investigation. Since the tag and the neuropeptide of interest are on the same prohormone they are co-secreted and thus secretion of the tag reflects the co-secretion of the neuropeptide of interest. This method can be used to detect neuropeptide secretion on a millisecond timescale.

Animals↗
PubMed2002

Measuring peptide secretion using the FMRFamide tagging technique.

Peptides are transmitters produced by a wide variety of neurons and neuroendocrine cells. They mediate a remarkable range of physiological processes. To better understand the roles played by peptides, a number of methods have been developed that can monitor their secretion. Although each has particular strengths, they cannot rapidly detect the secretion of chemically defined peptides. However, a recently developed approach termed "FMRFamide-tagging" may be useful in this regard. A genetically encoded electrophysiological tag is attached to the peptide prohormone of interest. The "tagged" prohormone together with an ionotropic receptor that binds the tag are expressed in the cell type under investigation. Secretion of the tag (and the co-secreted peptide of interest) are revealed by rapid inward membrane currents that are due to the activation of the tag receptor. In this manner, peptide secretion can be followed on a millisecond time scale. This protocol gives the details of the approach and its potential application to a range of cell types.

Animals↗