Histochemical Investigation of the Modal Specificity of Taste

The taste mechanism was investigated in a primate (Macaca mulatta). Based on the hypothesis that intracellular enzymes contribute to the transduction of tastes to electric impulses by taste cells, a histochemical survey of the activity of several enzymes was made on taste buds from regions of the mouth associated with sweet, salt, sour, and bitter tastes. Considerable differences were noted among the modalities, which confirmed the hypothesis. An exclusively bitter enzyme was identified.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66599/2/10.1177_00220345720510050601.pd

<i>mito</i>-QC illuminates mitophagy and mitochondrial architecture <i>in vivo</i>

Autophagic turnover of mitochondria, termed mitophagy, is proposed to be an essential quality-control (QC) mechanism of pathophysiological relevance in mammals. However, if and how mitophagy proceeds within specific cellular subtypes in vivo remains unclear, largely because of a lack of tractable tools and models. To address this, we have developed “mito-QC,” a transgenic mouse with a pH-sensitive fluorescent mitochondrial signal. This allows the assessment of mitophagy and mitochondrial architecture in vivo. Using confocal microscopy, we demonstrate that mito-QC is compatible with classical and contemporary techniques in histochemistry and allows unambiguous in vivo detection of mitophagy and mitochondrial morphology at single-cell resolution within multiple organ systems. Strikingly, our model uncovers highly enriched and differential zones of mitophagy in the developing heart and within specific cells of the adult kidney. mito-QC is an experimentally advantageous tool of broad relevance to cell biology researchers within both discovery-based and translational research communities

The Release of Cytochrome c from Mitochondria during Apoptosis of NGF-deprived Sympathetic Neurons Is a Reversible Event

During apoptosis induced by various stimuli, cytochrome c is released from mitochondria into the cytosol where it participates in caspase activation. This process has been proposed to be an irreversible consequence of mitochondrial permeability transition pore opening, which leads to mitochondrial swelling and rupture of the outer mitochondrial membrane. Here we present data demonstrating that NGF-deprived sympathetic neurons protected from apoptosis by caspase inhibitors possess mitochondria which, though depleted of cytochrome c and reduced in size, remained structurally intact as viewed by electron microscopy. After re-exposure of neurons to NGF, mitochondria recovered their normal size and their cytochrome c content, by a process requiring de novo protein synthesis. Altogether, these data suggest that depletion of cytochrome c from mitochondria is a controlled process compatible with function recovery. The ability of sympathetic neurons to recover fully from trophic factor deprivation provided irreversible caspase inhibitors have been present during the insult period, has therapeutical implications for a number of acute neuropathologies

Muscle Fiber Viability, a Novel Method for the Fast Detection of Ischemic Muscle Injury in Rats

Acute lower extremity ischemia is a limb- and life-threatening clinical problem. Rapid detection of the degree of injury is crucial, however at present there are no exact diagnostic tests available to achieve this purpose. Our goal was to examine a novel technique - which has the potential to accurately assess the degree of ischemic muscle injury within a short period of time - in a clinically relevant rodent model. Male Wistar rats were exposed to 4, 6, 8 and 9 hours of bilateral lower limb ischemia induced by the occlusion of the infrarenal aorta. Additional animals underwent 8 and 9 hours of ischemia followed by 2 hours of reperfusion to examine the effects of revascularization. Muscle samples were collected from the left anterior tibial muscle for viability assessment. The degree of muscle damage (muscle fiber viability) was assessed by morphometric evaluation of NADH-tetrazolium reductase reaction on frozen sections. Right hind limbs were perfusion-fixed with paraformaldehyde and glutaraldehyde for light and electron microscopic examinations. Muscle fiber viability decreased progressively over the time of ischemia, with significant differences found between the consecutive times. High correlation was detected between the length of ischemia and the values of muscle fiber viability. After reperfusion, viability showed significant reduction in the 8-hour-ischemia and 2-hour-reperfusion group compared to the 8-hour-ischemia-only group, and decreased further after 9 hours of ischemia and 2 hours of reperfusion. Light- and electron microscopic findings correlated strongly with the values of muscle fiber viability: lesser viability values represented higher degree of ultrastructural injury while similar viability results corresponded to similar morphological injury. Muscle fiber viability was capable of accurately determining the degree of muscle injury in our rat model. Our method might therefore be useful in clinical settings in the diagnostics of acute ischemic muscle injury

Microscopical methods for the localization of Na + , K + -ATPase

Na + , K + -ATPase plays a central role in the ionic and osmotic homeostasis of cells and in the movements of electrolytes and water across epithelial boundaries. Microscopic localization of the enzyme is, therefore, of crucial importance in establishing the subcellular routes of electrolyte flow across structurally complex and functionally polarized epithelia. Recently developed approaches to the localization of Na + , K + -ATPase are reviewed. These methods rely on different properties of the enzyme and encompass cytochemical localization of the K + -dependent nitrophenylphosphatase component of the enzyme, autoradiographic localization of tritiated ouabain binding sites, and immunocytochemical localization of the holoenzyme and of its catalytic subunit. The rationales for each of these techniques are outlined as are the critieria that have been established to validate each method. The observed localization of Na + , K + -ATPase in various tissues is discussed, particularly as it relates to putative and hypothetical mechanisms that are currently thought to mediate reabsorptive and secretory electrolyte transport.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42850/1/10735_2005_Article_BF01005056.pd