PubMed Health⌕ Search

Biomedical subjects

Guy A Perkins

Publications and source records attributed to Guy A Perkins.

9 recordsLinked to original sources
PubMed2006

Nitric oxide-induced mitochondrial fission is regulated by dynamin-related GTPases in neurons.

Mitochondria are present as tubular organelles in neuronal projections. Here, we report that mitochondria undergo profound fission in response to nitric oxide (NO) in cortical neurons of primary cultures. Mitochondrial fission by NO occurs long before neurite injury and neuronal cell death. Furthermore, fission is accompanied by ultrastructural damage of mitochondria, autophagy, ATP decline and generation of free radicals. Fission is occasionally asymmetric and can be reversible. Strikingly, mitochondrial fission is also an early event in ischemic stroke in vivo. Mitofusin 1 (Mfn1) or dominant-negative Dynamin related protein 1 (Drp1(K38A)) inhibits mitochondrial fission induced by NO, rotenone and Amyloid-beta peptide. Conversely, overexpression of Drp1 or Fis1 elicits fission and increases neuronal loss. Importantly, NO-induced neuronal cell death was mitigated by Mfn1 and Drp1(K38A). Thus, persistent mitochondrial fission may play a causal role in NO-mediated neurotoxicity.

Adenosine Triphosphate↗
PubMed2006

Collaborative development of the Arrowsmith two node search interface designed for laboratory investigators.

Arrowsmith is a unique computer-assisted strategy designed to assist investigators in detecting biologically-relevant connections between two disparate sets of articles in Medline. This paper describes how an inter-institutional consortium of neuroscientists used the UIC Arrowsmith web interface http://arrowsmith.psych.uic.edu in their daily work and guided the development, refinement and expansion of the system into a suite of tools intended for use by the wider scientific community.

Journal Article↗
PubMed2006

Electron tomography of membrane-bound cellular organelles.

Electron microscope tomography produces three-dimensional reconstructions and has been used to image organelles both isolated and in situ, providing new insight into their structure and function. It is analogous to the various tomographies used in medical imaging. Compared with light microscopy, electron tomography offers an improvement in resolution of 30- to 80-fold and currently ranges from 3 to 8 nm, thus filling the gap between high-resolution structure determinations of isolated macromolecules and larger-scale studies on cells and tissues by light microscopy. Here, we provide an introduction to electron tomography and applications of the method in characterizing organelle architecture that also show its power for suggesting functional significance. Further improvements in labeling modalities, imaging tools, specimen preparation, and reconstruction algorithms promise to increase the quality and breadth of reconstructions by electron tomography and eventually to allow the mapping of the cellular proteomes onto detailed three-dimensional models of cellular structure.

Animals↗
PubMed2004

The structure-function correlates of mammalian rod and cone photoreceptor mitochondria: observations and unanswered questions.

Our previous work suggests that cone photoreceptor inner segment (CIS) mitochondria demand and produce more ATP than rods. The CISs utilize two complimentary strategies to increase ATP production: increase the absolute number of mitochondria and their cristae surface membrane area. In this treatise, we ask: How are crista junctions formed and regulated? Once formed, are there physical mechanisms that constrain their diameter? How are the constrictions in cristae regulated and is this key for cytochrome c release during apoptosis? What are their differences in rod and cone susceptibility to apoptotic cell death during calcium overload and oxidative stress?

Journal Article↗
PubMed2004

Disruption of mitochondrial function during apoptosis is mediated by caspase cleavage of the p75 subunit of complex I of the electron transport chain.

Mitochondrial outer membrane permeabilization and cytochrome c release promote caspase activation and execution of apoptosis through cleavage of specific caspase substrates in the cell. Among the first targets of activated caspases are the permeabilized mitochondria themselves, leading to disruption of electron transport, loss of mitochondrial transmembrane potential (DeltaPsim), decline in ATP levels, production of reactive oxygen species (ROS), and loss of mitochondrial structural integrity. Here, we identify NDUFS1, the 75 kDa subunit of respiratory complex I, as a critical caspase substrate in the mitochondria. Cells expressing a noncleavable mutant of p75 sustain DeltaPsim and ATP levels during apoptosis, and ROS production in response to apoptotic stimuli is dampened. While cytochrome c release and DNA fragmentation are unaffected by the noncleavable p75 mutant, mitochondrial morphology of dying cells is maintained, and loss of plasma membrane integrity is delayed. Therefore, caspase cleavage of NDUFS1 is required for several mitochondrial changes associated with apoptosis.

Adenosine Triphosphate↗
PubMed2004

Crosstalk between nitric oxide and zinc pathways to neuronal cell death involving mitochondrial dysfunction and p38-activated K+ channels.

Nitric oxide (NO) and zinc (Zn2+) are implicated in the pathogenesis of cerebral ischemia and neurodegenerative diseases. However, their relationship and the molecular mechanism of their neurotoxic effects remain unclear. Here we show that addition of exogenous NO or NMDA (to increase endogenous NO) leads to peroxynitrite (ONOO-) formation and consequent Zn2+ release from intracellular stores in cerebrocortical neurons. Free Zn2+ in turn induces respiratory block, mitochondrial permeability transition (mPT), cytochrome c release, generation of reactive oxygen species (ROS), and p38 MAP kinase activation. This pathway leads to caspase-independent K+ efflux with cell volume loss and apoptotic-like death. Moreover, Zn2+ chelators, ROS scavengers, Bcl-xL, dominant-interfering p38, or K+ channel blockers all attenuate NO-induced K+ efflux, cell volume loss, and neuronal apoptosis. Thus, these data establish a new form of crosstalk between NO and Zn2+ apoptotic signal transduction pathways that may contribute to neurodegeneration.

Animals↗
PubMed2003

Three-dimensional analysis of mouse rod and cone mitochondrial cristae architecture: bioenergetic and functional implications.

PURPOSE: Comparative studies of structure related to function offer a promising means of understanding the significance of differences in cytoarchitecture. Mitochondrial crista structure is linked tightly to mitochondrial function. Non-foveal cone photoreceptors of primates contain considerably more inner segment mitochondria and have higher oxidative enzyme activity than do rods. In addition, it is suggested that light-adapted cones have a higher aerobic ATP demand than light-adapted rods. Therefore, we investigated the oxidative metabolism and three-dimensional membrane architecture of mouse rod and cone inner segment mitochondria. METHODS: We determined the number, size, cytochrome c oxidase (CO) reactivity, and membrane architecture of rod and middle wavelength-sensitive (M) cone inner segment mitochondria from 21 day old light-adapted C57BL/6 mice using conventional electron microscopy and the three-dimensional approach of single- and double-tilt electron microscope tomography. Fourteen different measurements of mitochondrial substructures were analyzed. Photoreceptor oxygen consumption was determined in dark- and light-adapted retinas. RESULTS: Rod and cone mitochondria displayed an orthodox conformation. Cone inner segments, compared to rods, contained 2-fold more mitochondria and were more CO reactive. Rod and cone mitochondria had similar outer-inner membrane width, contact site width, diameter and density, crista width, number of cristae/volume, number of cristae segments/volume, and fraction of cristae with multiple segments. In contrast, cone mitochondria had narrower crista junctions, greater cristae connectivity, and approximately 3-fold more cristae membrane surface area compared to rods. The increased cristae membrane surface area in cones was accomplished by connecting more cristae segments together, rather than by creating more cristae. CONCLUSIONS: These results demonstrate that middle wavelength (M) cones have a different bioenergetic signature than do rods and suggest that the aerobic ATP demand and production is greater in light-adapted cones than in light-adapted rods. Cones utilize two complimentary strategies to increase their aerobic ATP production: increase the number of mitochondria and increase the cristae surface membrane area. The greater ATP generation by cones may also provide increased protection against metabolic insults and apoptosis compared to rods.

Adenosine Triphosphate↗
PubMed2003

Bcl-xL overexpression blocks bax-mediated mitochondrial contact site formation and apoptosis in rod photoreceptors of lead-exposed mice.

Photoreceptor apoptosis and resultant visual deficits occur in humans and animals with inherited and disease-, injury-, and chemical-induced retinal degeneration. A clinically relevant mouse model of progressive rod photoreceptor-selective apoptosis was produced by low-level developmental lead exposure and studied in combination with transgenic mice overexpressing Bcl-x(L) only in the photoreceptors. A multiparametric analysis of rod apoptosis and mitochondrial structure-function was performed. Mitochondrial cristae topography and connectivity, matrix volume, and contact sites were examined by using 3D electron tomography. Lead-induced rod-selective apoptosis was accompanied by rod Ca(2+) overload, rhodopsin loss, translocation of Bax from the cytosol to the mitochondria, decreased rod mitochondrial respiration and membrane potential, mitochondrial cytochrome c release, caspase-3 activation, and an increase in the number of mitochondrial contact sites. These effects occurred without mitochondrial matrix swelling, outer membrane rupture, caspase-8 activation, or Bid cleavage. Bcl-x(L) overexpression completely blocked all apoptotic events, except Ca(2+) overload, and maintained normal rod mitochondrial function throughout adulthood. This study presents images of mitochondrial contact sites in an in vivo apoptosis model and shows that Bcl-x(L) overexpression blocks increased contact sites and apoptosis. These findings extend our in vitro retinal studies with Pb(2+) and Ca(2+) and suggest that developmental lead exposure produced rod-selective apoptosis without mitochondrial swelling by translocating cytosolic Bax to the mitochondria, which likely sensitized the Pb(2+) and Ca(2+) overloaded rod mitochondria to release cytochrome c. These results have relevance for therapies in a wide variety of progressive retinal and neuronal degenerations where Ca(2+) overload, lead exposure, andor mitochondrial dysfunction occur.

Animals↗