Continuous rise in oxygen consumption during prolonged military loaded march in the heat with and without fluid replacement: a pilot study.

INTRODUCTION: V̇O2 drift, the rise in oxygen consumption during continuous exercise, has not been adequately reported during prolonged military marches. The purpose of this study was to analyse V̇O2 and energy expenditure (EE) during a loaded march with and without rehydration efforts. Second, the study aimed to compare EE throughout the march with predicted values using a validated model. METHODS: Seven healthy men (23±2 years; V̇O2max: 50.8±5.3 mL/kg/min) completed four 60 min loaded marches (20.4 kg at 50% V̇O2max) in a warm environment (30°C and 50% relative humidity). Three were preceded by hypohydration via a 4-hour cold water immersion (18°C). The control (CON) visit was a non-immersed euhydrated march. After water immersion, subjects were rehydrated with 0% (NO), 50% (HALF) or 100% (FULL) of total body mass lost. During exercise, V̇O2 and EE were collected and core temperature change was calculated. To determine if EE could be accurately predicted, values were compared with a calculated estimate using the US Army Load Carry Decision Aid (LCDA). RESULTS: At the start of exercise, there was no difference between conditions in V̇O2 (ALL: 24.3±0.3 mL/kg/min; p=0.50) or EE (ALL: 8.6±1.0 W/kg; p=0.68). V̇O2 (p=0.02) and EE (p<0.01) increased during exercise and were 12.3±10.0% and 12.8±9.5% greater, respectively, at 60 min across all trials and were not mitigated by rehydration amount. There was an effect of core temperature change on V̇O2 for each condition (CON: r=0.62; NO: r=0.47; HALF: r=0.70; FULL: r=0.55). LCDA-predicted values were different from measured EE during exercise. CONCLUSION: V̇O2 drift occurred during loaded military marches and was associated with increases in EE and core temperature change. Pre-exercise hypohydration with water immersion followed by rehydration did not influence the degree of drift. LCDA prediction of EE may not agree with measured values during prolonged loaded marches where V̇O2 drift occurs.

Monoclonal antibodies show that kinase C phosphorylation of GAP-43 during axonogenesis is both spatially and temporally restricted in vivo.

To study the role of kinase C phosphorylation in the distribution and function of GAP-43 we have generated a panel of mAbs that distinguish between GAP-43 that has been phosphorylated by kinase C and forms that have not. One class of antibodies, typified by 2G12/C7, reacts with only the phosphorylated form of GAP-43; it recognizes the peptide IQAS(PO4)FR equivalent to residues 38-43 that includes the single kinase C phosphorylation site at serine. Another, exemplified by 10E8/E7, reacts with both phosphorylated and nonphosphorylated forms. We have used the antibodies to study the distribution of kinase C-phosphorylated GAP-43 during axonogenesis and in the adult nervous system. Two major findings emerge. First, there is a lag between the initiation of axon outgrowth and the phosphorylation of GAP-43 by kinase C. The extent of this lag period varies between the different structures studied. In some cases, e.g., the trigeminal nerve, our result suggest that kinase C phosphorylation may be correlated with proximity of the growing axon to its target. Second, kinase C-phosphorylated GAP-43 is always spatially restricted to the distal axon. It is never seen either proximally or in cell bodies, even those with high levels of GAP-43 protein. This result also implies that GAP-43 is axonally transported in the non-kinase C phosphorylated form. Thus, kinase C phosphorylation of GAP-43 is not required for axon outgrowth or growth cone function per se and may be more related to interactions of the growth cone with its environment.

Neuregulin1 and ErbB expression in the uninjured and regenerating olfactory mucosa.

Neuregulin1, a protein involved in signaling through the ErbB receptors, is required for the proper development of multiple organ systems. A complete understanding of the expression profile of Neuregulin1 is complicated by the presence of multiple isoform variants that result from extensive alternative splicing. Remarkably, these numerous protein products display a wide range of divergent functional roles, making the characterization of tissue-specific isoforms critical to understanding signaling. Recent evidence suggests an important role for Neuregulin1 signaling during olfactory epithelium development and regeneration. In order to understand the physiological consequences of this signaling, we sought to identify the isoform-specific and cell type-specific expression pattern of Neuregulin1 in the adult olfactory mucosa using a combination of RT-qPCR, FACS, and immunohistochemistry. To complement this information, we also analyzed the cell-type specific expression patterns of the ErbB receptors using immunohistochemistry. We found that multiple Neuregulin1 isoforms, containing predominantly the Type I and Type III N-termini, are expressed in the uninjured olfactory mucosa. Specifically, we found that Type III Neuregulin1 is highly expressed in mature olfactory sensory neurons and Type I Neuregulin1 is highly expressed in duct gland cells. Surprisingly, the divergent localization of these Neuregulin isoforms and their corresponding ErbB receptors does not support a role for active signaling during normal turnover and maintenance of the olfactory mucosa. Conversely, we found that injury to the olfactory epithelium specifically upregulates the Neuregulin1 Type I isoform bringing the expression pattern adjacent to cells expressing both ErbB2 and ErbB3 which is compatible with active signaling, supporting a functional role for Neuregulin1 specifically during regeneration.

[Evolution of the interventional reperfusion strategy and reperfusion times in acute ST-segment elevation myocardial infarction]. / Évolution de la prise en charge interventionnelle et des délais de reperfusion à la phase aiguë de l'infarctus du myocarde avec sus-décalage du segment ST.

BACKGROUND: In patients with acute ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (pPCI), the recommended times (first medical contact-to-balloon (M2B) <120 or <90min, and door-to-balloon (D2B) <45min) are reached in less than 50% of patients. PURPOSE: To compare the interventional reperfusion strategy and reperfusion times between two series of consecutive STEMI patients referred for pPCI within 12hours of symptom onset, in 2007 and 2012. METHODS: Retrospective study of 182 patients, 87 admitted from January 2007 to March 2008 (period 1), and 95 admitted from January to December 2012 (period 2). The procedural characteristics and the different times between onset of pain and mechanical reperfusion were gathered and compared by non-parametric tests. RESULTS: Radial access, thromboaspiration, and drug eluting stents were more frequent, and cardiogenic shock was less common during period 2, compared with the period 1. The median time from first medical contact to balloon (M2B) decreased by 26% (135min, [quartiles: 113-183] in 2007 versus 100 [76-137] in 2012, P<0.001), in relation to the reduction in both prehospital times and time in the catheterization laboratory (D2B: 51 [44-65] and 44min [37-55], respectively, P<0.01). CONCLUSIONS: The D2B and M2B times significantly decreased in our centre between 2007 and 2012, and reached the recommended values in >60% of the cases. This may be explained by better coordination between emergency medical units and interventional cardiologists, and by the presence of two paramedics in the catheterization laboratory for 24/24 7/7 pPCI since 2010 in France, in accordance with recent national regulation.

The development of axonal connections in the central olfactory system of rats.

The development of the cytoarchitecture and axonal connections of the central olfactory system were studied in fetal and neonatal rats from E16. In contrast to neocortical development, the olfactory cortex lacks a distinct cortical plate. In the piriform cortex and the olfactory tubercle the cellular laminae emerge simultaneously, while in the anterior olfactory nucleus, there are morphogenetic gradients from superficial to deep as well as from caudal to rostral which parallel the known cytogenetic gradients. Parallel morphogenetic and cytogenetic gradients are also present in the lateral to medial axis of the olfactory tubercle. The projection from the olfactory bulb and the associational projections from the piriform cortex begin to develop well before birth. At E17 fibers from the bulb are limited to the lateral olfactory tract (LOT) and the molecular layer just deep to it, and then spread out caudally, laterally, and medially away from the LOT. This sequence of innervation parallels and predicts the density of innervation in the adult: those areas which are innervated first (such as the piriform cortex deep to the LOT) ultimately receive the heaviest innervation; conversely, those areas which are innervated very late (such as the medial olfactory tubercle) receive the lightest projection. The intracortical projections from the anterior and posterior piriform cortex extend into layer I ipsilaterally by E20 and obtain their adult distribution by the middle of the first postnatal week. On the other hand, fibers from the anterior olfactory nucleus and the entorhinal area do not reach their full adult extent until the second postnatal week. Similarly, the crossed projection of the anterior piriform cortex to the contralateral posterior piriform cortex does not grow into layer I until this later time. The timing of fiber ingrowth showed no relation to the trajectory or eventual areal or laminar termination of fibers. As with the olfactory bulb projection, the timing may influence the density of termination. Centrifugal fibers to the bulb are demonstrable around the time of birth both by the retrograde transport of horseradish peroxidase (HRP) and by the anterograde transport of 3H-leucine. The arrival of additional fibers during the remainder of the first postnatal week parallels the known cytogenetic and morphogenetic gradients in the areas in which they arise. The projections of the olfactory cortex to the lateral hypothalamic area and the mediodorsal thalamic nucleus are evident before birth. This correlates with the early generation of the cells which give rise to these projections.

The development of lamination of afferent fibers to the olfactory cortex in rats, with additional observations in the adult.

The complementary distribution of the fibers from the olfactory bulb and the intracortical associational fibers to layers Ia and Ib, respectively, of the olfactory cortex has been examined in both adult and neonatal rats, using horseradish peroxidase (HRP) and 3H-leucine as double tracers in the same animal. The observations presented here confirm and extend the previous demonstration (Price, '73) that in the adult the two projections are essentially nonoverlapping throughout the olfactory cortex. Indeed, when the distribution of axons from the olfactory bulb (labeled by HRP inserted into a cut in the LOT) is compared on the same section with that of associational fibers (labeled by 3H-leucine injected into the cortex), the overlap between the two projections is limited to a zone only 5-10 micron in width in both the piriform cortex and olfactory tubercle. In contrast, at P1 the two projections overlap throughout layer I, although the bulbar and associational fibers are slightly concentrated superficially and deeply in layer I, respectively. This overlap is especially prominent in the part of the anterior piriform cortex deep to the LOT. During the remainder of the first postnatal week, this overlap resolves and by P7 the segregation of the two sets of afferent fibers is nearly equivalent to that seen in the adult. However, there are several instances in adults where the segregation of these afferents does not develop. First, a relatively small population of aberrant axons derived from the LOT may be traced from layer Ia into layer Ib and then back to layer Ia. Most of these axons are large in diameter and lack the boutonlike varicosities found on smaller axons in layer Ia. They are most prominent in areas where the cortex is highly curved. Second, in layer I of the nucleus of the lateral olfactory tract, bulbar and associational fibers are extensively intermingled. In this case also, the bulbar fibers are large in diameter with only a few boutonlike varicosities. The developmental emergence of afferent segregation and its breakdown in cases where the fibers from the olfactory bulb do not form boutons suggest that an interaction between the two distinct sets of fibers and the dendritic field is responsible for the normal development of this segregation and that this interaction depends on the process of synaptogenesis.

Immunohistochemical identification of discrete subsets of rat olfactory neurons and the glomeruli that they innervate.

Glomeruli at the posterior margin of the main olfactory bulb differ in several respects from those located in the remainder of the bulb; e.g., the olfactory sensory neurons (OSNs) that project here exhibit a distinct biochemical phenotype and signal transduction pathway, the microcircuitry of the glomeruli is substantially altered, and the glomeruli are activated by unconventional odorants. In the present work, we report that the monoclonal antibodies 2C6 and MAb213 label distinct subsets of OSNs in the olfactory epithelium (OE), including their axons to their terminations in the main olfactory bulb (MOB). Neurons immunopositive with 2C6 are concentrated in the cul-de-sacs of ectoturbinates 1 and 2 and of endoturbinate IV. Unlike the vast majority of OSNs, 2C6(+) neurons express olfactory marker protein (OMP) at a low level, but their failure to stain with anti-GAP-43 labeling indicates that the OMP "weak" neurons are nonetheless mature. Glomeruli positive for 2C6 are bilaterally symmetrical and occupy reproducible positions along the posterior margin of the MOB. Three of these are very large, and we refer to them as the lateral, posterior ventral, and anterior ventral 2C6(+) necklace glomeruli. MAb213(+) neurons are concentrated in the posteriormost tips of the cul-de-sacs and recesses at the reflection of the OE at the cribriform plate. Like 2C6(+) neurons, MAb213(+) OSNs are weakly labeled with anti-OMP but are fully mature. MAb213(+) glomeruli are also bilaterally symmetrical; they occupy reproducible positions along the posterior margin of the MOB. The three largest glomeruli occupy lateral, posterior ventral, and posterior positions; the first two are found close to the aforementioned 2C6(+) glomeruli. MAb213 also intensely labels one of the glomeruli of the modified glomerular complex, a string of small glomeruli ventrally, and another string dorsal to the accessory olfactory bulb. Acetylcholinesterase (AChE) histochemical staining of adjacent sections showed that many, but not all, MAb213(+) glomeruli colocalize with dense or moderate AChE staining. Thus, it is likely that the "necklace olfactory glomeruli" (Shinoda et al., 1990, 1993) and the phosphodiesterase (PDE2)(+) glomeruli (Juilfs et al., 1997) are a subset(s) of the MAb213(+) glomeruli. On the other hand, 2C6(+) glomeruli are not associated with AChE staining. These data indicate that the 2C6(+) glomeruli comprise a novel subset in the posterior MOB. In addition to the 2C6(+) and MAb213(+) necklace glomeruli, there is another distinct set of glomeruli at the posterior margin of the bulb that are OMP(-), 2C6(-), and MAb213(-). In summary, the current work indicates that glomeruli at the posterior margin of the bulb, which are necklace glomeruli in terms of location and appearance, are actually heterogeneous and may subserve specialized functions within the olfactory system.

Reconstitution of the rat olfactory epithelium after methyl bromide-induced lesion.

The olfactory epithelium and its neuronal population are known to have a substantial capacity to recover after either direct injury or damage to the olfactory nerve. However, the mechanisms underlying that capacity for recovery, and indeed the limits on the recovery process, are not well understood. The aim of this study is to describe in detail the way in which the olfactory epithelium reconstitutes after direct injury. Adult male rats were exposed to 330 ppm methyl bromide (MeBr) gas for a single 6-hour period. The exposure destroys all of the neurons and sustentacular cells in over 95% of the olfactory epithelium of food-restricted rats and in over 90% of the epithelium in ad-libitum-fed rats of the same weight, yet substantial recovery of the olfactory epithelium occurs. In response to the lesion, cellular proliferation increases markedly beginning between 24 and 48 hours, peaks at 1 week, and persists at levels higher than the control level for more than 4 weeks after MeBr exposure. Even though proliferation accelerates promptly, the beginning of neuronal reconstitution is delayed; only a few immature neurons are observed 3 days after the lesion, yet they reappear in large numbers by the end of the first week. The first mature neurons emerge between 7 and 14 days after lesion and increase to near normal numbers by 4-6 weeks. In association with the restoration of the neuronal population, basal cell proliferation returns to control levels between 4 and 6 weeks after damage. Likewise, sustentacular cells, identifiable by anticytokeratin 18 labeling, reappear rapidly and reform a distinct lamina in the superficial aspect of the epithelium. They closely resemble their counterparts in control epithelium with regard to disposition and shape by 3 weeks after lesion and with regard to expression of olfactory-specific cytochrome P450s by 8 weeks. Thus, most areas of the epithelium are restored to a near normal appearance and cellular composition by the end of 8 weeks, suggesting that the MeBr paradigm for lesioning the epithelium offers significant advantages over techniques such as Triton X-100 or ZnSO4 irrigation. However, not all measures of epithelial status are normal even at 8 weeks. Immature neurons remain slightly more numerous than normal at this time. Furthermore, some areas of the olfactory epithelium do not recover after MeBr lesion and are replaced by respiratory epithelium.(ABSTRACT TRUNCATED AT 400 WORDS)

On the formation of neuromata in the primary olfactory projection.

Olfactory axons have been shown to grow aberrantly and form dense collections of axons, termed neuromas, in the olfactory epithelium of rats in which the olfactory bulb was ablated. Likewise, in human olfactory mucosa, collections of neurites have been noted in a variety of disease states, including Alzheimer's disease. We report here an immunohistochemical and electron microscopic analysis of aberrant axonal growth in the rat olfactory mucosa induced by experimental lesion. In particular, we have used the monoclonal antibody 2G12, which binds to the phosphorylated form of GAP-43, as an extremely sensitive marker for neuromatous axons, because it does not label neuronal cell bodies. In unilaterally bulbectomized rats, neuromas form in posterior olfactory epithelium on the operated side. Several lines of evidence, including serial section reconstruction, indicate that olfactory axons are induced to grow back into the epithelium at a distance from their point of origin as a consequence of bulbectomy, and are accompanied by glial cells from the olfactory nerve. Avulsion of a part of the olfactory nerve has similar effects as destruction of the olfactory bulb. Intraepithelial neuromas also develop in the olfactory mucosa of rats simultaneously exposed to methyl bromide gas and injected with 3-methyl indole; this treatment severely damages the olfactory epithelium directly. Exposure to methyl bromide alone causes milder damage, and the neuromas that form are transient. The evidence indicates that neuromas form after the epithelium is directly damaged because axons are trapped in the epithelium. Both of the mechanisms identified here should be taken into account when considering the findings in the human olfactory mucosa.

An immunochemical, ultrastructural, and developmental characterization of the horizontal basal cells of rat olfactory epithelium.

The olfactory epithelium, which retains a capacity for neurogenesis throughout life, contains two categories of basal cells, dark/horizontal and light/globose, neither of which is fully characterized with respect to their function during the processes of neurogenesis and epithelial reconstitution after injury. The aim of this study was to define the potential biological role(s) of dark/horizontal basal cells (D/HBCs) in the epithelium by performing immunochemical, electron microscopic, and developmental analyses of this cell population. The D/HBCs express several specific immunochemical characteristics, which include the rat homologues of human cytokeratins 5 and 14, which were identified on the basis of staining with subunit-specific monoclonal antibodies and two-dimensional immunoblot analysis of the immunoreactive proteins. Indeed, the D/HBCs are the only cells in the olfactory mucosa that express these specific cytokeratins. The D/HBCs also express an alpha-galactose or alpha-N-acetyl galactosamine moiety to which the I beta 4 isolectin from Bandeiraea simplicifolia binds. Moreover, the D/HBCs are heavily labeled by two different antibodies against the EGF receptor and by a monoclonal antibody that binds to phosphotyrosine. These characteristics are also common to the basal cells of respiratory epithelium. The electron microscopic analysis of the basal region of the olfactory epithelium and the light microscopic immunofluorescence observations demonstrate that the D/HBCs provide a bridge between the basal processes of some sustentacular cells and the basal lamina. The most striking ultrastructural feature of the D/HBCs is their enfolding of virtually all bundles of olfactory axons within tunnels formed where D/HBCs arch over the basal lamina. The intimacy of the arrangement between D/HBCs and olfactory axons suggests that signals may pass from axons to D/HBCs or vice-versa. With respect to the development of D/HBCs, cells that express cytokeratins 5 and 14 and the EGF receptor first appear near the boundary with respiratory epithelium late in development, but do not extend throughout the olfactory epithelium until the middle of the first postnatal week. Taken together, the present findings and previously published data suggest that D/HBCs help to maintain the structural integrity of the olfactory epithelium, participate in its recovery from injury, and may also function to signal the status of the neuronal population of the epithelium.

The development of physiological responses of the piriform cortex in rats to stimulation of the lateral olfactory tract.

Extracellular recording techniques in rats were used to follow the postnatal development of the evoked response of the piriform cortex to electrical stimulation of the lateral olfactory tract (LOT) from birth to adulthood. As in other species, LOT shock in adult rats produces short-latency activation of units in piriform cortex and an extracellular field potential consisting of three components: a surface-negative component, the A1 wave (corresponding to the cortical monosynaptic EPSP evoked by the LOT fibers); a second surface-negative component, the B1 wave (corresponding to reactivation of layer I dendrites by intracortical fibers); and a late surface-positive component, the period 2 wave. A conditioning shock 20-150 msec before the test shock profoundly inhibits both evoked unit activity and the B1 wave, while it facilitates the A1. At birth, units can be orthodromically activated by LOT stimulation in association with the A1 wave. There is also a surface-positive spikelike wave, the S wave, which represents the summation of cortical unit activity. The B1 wave is apparent early in the first postnatal week. However, in contrast to the prominent inhibition in the adults, for the first few days after birth, single-unit responses, multiple-unit activity, and the S wave are all facilitated by a preceding conditioning shock with intervals of 200 msec or less, in association with the facilitation of the A1 wave. A shift to inhibition is apparent with longer intershock intervals of 300-700 msec, which exceed the period during which paired shocks facilitate the A1 wave. During the remainder of the first two postnatal weeks,, partial suppression of evoked activity with intervals of less than 200 msec appears and progressively increases in strength, but inhibition at very long intershock intervals remains greater in magnitude. During this time, the duration of the inhibitory period also decreases to near the adult value of 200-300 msec. In the third postnatal week the pattern was similar to that in the adult, but the inhibition was still clearly weaker than in adults. These results suggest a delayed maturation of the cortical inhibitory circuitry; this conclusion has also been suggested by previously published observations in the developing neocortex and hippocampus. In addition, the acceleration with age of the conduction velocity of axons in the LOT was analyzed. The adult value of 9.6 m/sec was not achieved until some time after postnatal day 15, which parallels the myelinization of the tract as observed with the light microscope.

Reinnervation of the rat olfactory bulb after methyl bromide-induced lesion: timing and extent of reinnervation.

We used the inhalation of methyl bromide gas to produce a near-complete destruction of the rat olfactory epithelium and analyzed the reinnervation of the bulb during reconstitution of the epithelium. The degeneration of olfactory axons elicits a transient up-regulation of glial cell proliferation and glial fibrillary acidic protein expression in the olfactory nerve and olfactory nerve layer of the bulb. Anterograde transport after intranasal infusion of wheat germ agglutinin conjugated horseradish peroxidase demonstrates that the first nascent axons reach the bulb within the first week after lesion. Subsequently, a massive wave of fibers arrives at the bulb between 1 and 2 weeks postlesion, and enters the glomeruli between 2 and 3 weeks postlesion. However, the olfactory projection does not stabilize until 8 weeks after lesion judging from the return in growth associated protein-43 expression to control levels. The extent of reinnervation after lesion is correlated with the completeness with which the epithelium reconstitutes itself. In rats that are lesioned while fed ad libitum, there is near-complete reconstitution of the neuronal population, and the projection onto the bulb fills the glomerular layer in its entirety. However, in rats that are lesioned while food restricted, a significant fraction of olfactory epithelium becomes respiratory during its reconstitution, and the population of reinnervating fibers is less. As a consequence, the posterior half of the bulb remains hypoinnervated overall and denervated at its caudal margin. The preferential reinnervation of the anterior bulb in the food-restricted, methyl bromide gas-lesioned animals indicates that the mechanisms that guide the growth of the olfactory axons and restore receptotopy do not operate with the same precision in this setting as they do during development or during the lower level of turnover associated with the "normal" laboratory existence. Accordingly, we hypothesize that the persistence of a significant population of pre-existing neurons is needed to preserve receptotopy during reinnervation. In addition, the results suggest that in the face of massive turnover and a reduced afferent population, there is a tendency for reinnervating axons to fill available synaptic space.

Adult olfactory epithelium contains multipotent progenitors that give rise to neurons and non-neural cells.

We have infused replication-incompetent retroviral vectors into the nasal cavity of adult rats 1 day after exposure to the olfactotoxic gas methyl bromide (MeBr) to assess the lineage relationships of cells in the regenerating olfactory epithelium. The vast majority of the retrovirus-labeled clones fall into three broad categories: clones that invariably contain globose basal cells (GBCs) and/or neurons, clones that always include cells in the ducts of Bowman's glands, and clones that are composed of sustentacular cells only. Many of the GBC-related clones contain sustentacular cells and horizontal basal cells as well. Most of the duct-related clones contain gland cells, and some also include sustentacular cells. Thus, the destruction of both neurons and non-neuronal cells that is caused by MeBr activates two distinct types of multipotent cells. The multipotent progenitor that gives rise to neurons and non-neuronal cells is a basal cell, whereas the progenitor that gives rise to duct, gland, and sustentacular cells resides within the ducts, based on the pattern of sparing after lesion and the analysis of early regeneration by using cell type-specific markers. We conclude that the balance between multipotency and selective neuropotency, which is characteristic of globose basal cells in the normal olfactory epithelium, is determined by which cell types have been depleted and need to be replenished rapidly.

Time course of troponin I, myoglobulin, and cardiac enzyme release after electrical cardioversion.

The results of this study, conducted in 25 patients without myocardial infarction, showed that all the biologic markers of myocardial infarction, except the highly cardiospecific cardiac troponin I, increased in some patients after electrical cardioversion. These results allow us to conclude that electrical cardioversion, even preceded by a mechanical resuscitation of short duration, does not result in myocardial damage, and that cardiac troponin I is more accurate than creatine kinase-MB activity and creatine kinase-MB mass determination for the diagnosis of myocardial damage in patients who have undergone electrical cardioversion.

Transplantation of multipotent progenitors from the adult olfactory epithelium.

Mammalian olfactory epithelium produces new neurons rapidly throughout adulthood. Here, we demonstrate that precursor cells harvested from the adult olfactory epithelium, when transplanted into the nasal mucosa of host rats exposed previously to an olfactotoxic gas, engraft and participate in neuroepithelial reconstitution. In contrast to their normal neuronal fate in situ, grafted precursors harvested from bulbectomized donors produced non-neuronal cells as well as neurons. These results demonstrate that epithelial precursors activated following olfactory bulbectomy are not irreversibly committed to making neurons. Thus, olfactory progenitors are subject to a form of feedback control in vivo that regulates the types of cells that they produce within a broader-than-neuronal repertoire.

The aging olfactory epithelium: neurogenesis, response to damage, and odorant-induced activity.

Olfactory epithelium retains the capacity to recover anatomically after damage well into adult life and perhaps throughout its duration. None the less, olfactory dysfunctions have been reported widely for elderly humans. The present study investigates the effects of aging on the neurophysiological and anatomical status of the olfactory epithelium in barrier-raised Fischer 344X Brown Norway F1 hybrid rats at 7, 10, 25 and 32/35 months old. The posterior part of the olfactory epithelium in 32/35-month-old rats is well preserved. Globose basal cells are dividing, and new neurons are being born even at this advanced age. None the less, the numbers of proliferating basal cells and immature, GAP-43 (+) neurons are significantly decreased. Neurophysiological status was evaluated using voltage-sensitive dye techniques to assess inherent patterns of odorant-induced activity in the epithelium lining the septum and the medial surface of the turbinates. In middle and posterior zones of the epithelium, there were neither age-related changes in overall responsivity of this part of the olfactory epithelium to any of five odorants, nor shifts in the location of the odorant-induced hotspots. The inherent activity patterns elicited by the different odorants do become more distinct as a function of age, which probably reflects the decline in immature neurons and a slight, but not statistically significant, increase in mature neurons as a function of age. In contrast with the excellent preservation of posterior epithelium, the epithelium lining the anterodorsal septum and the corresponding face of the turbinates is damaged in the 32/35-month-old animals: in this part, horizontal basal cells are reactive, more basal cells and sustentacular cells are proliferating than in younger animals or in posterior epithelium of the same animals, and the neuronal population is less mature on average. Our findings indicate that degeneration of the olfactory epithelium is not an inevitable or pre-programmed consequence of the aging process, since the posterior zone of the epithelium is very well preserved in these barrier-protected animals. However, the deterioration in the anterior epithelium suggests that environmental insults can accumulate or become more severe with age and overwhelm the regenerative capacity of the epithelium. Alternatively, the regenerative capacity of the epithelium may wane somewhat with age. Either of these mechanisms or some combination of them can account for the functional and anatomical deterioration of the sense of smell associated with senescence in humans.

Odorant threshold following methyl bromide-induced lesions of the olfactory epithelium.

The present study assessed the functional consequences of peripheral olfactory destruction on the minimum detectable levels of stimulation for the odorants 2-propanol, D-limonene, and ethyl acetoacetate. Using standard operant techniques, eight Long-Evans rats were trained to criterion on an air versus odor differential response task. Odorant threshold was then determined on 10 consecutive testing sessions, using a computer-automated olfactometer and psychophysical tracking procedure. Following the last testing session, the rats were lesioned by exposing them to 330 ppm methyl bromide gas for 6 h. For each lesioned animal the anatomical state of the olfactory epithelium was evaluated relative to behavioral performance on the odorant threshold task at 3 days postlesion. For the group of rats, a comparison of pre- and postlesion performance demonstrated that, on the average, odor sensitivity was not altered by lesions that destroy roughly 95-98% of the epithelium. However, analysis of individual cases illustrated that two of the eight rats showed an elevation in odor sensitivity, albeit minimally, that was considered different from the prelesion performance. For those animals affected, we could extract no apparent relationship between the behavioral findings and the extent of anatomical damage. The results of this study demonstrate the remarkable capacity of the olfactory system to maintain normal or near-normal detection sensitivity in the face of massive damage. This capacity presumably reflects both the normal exposure of the epithelium to continual injury and the importance of maintained olfactory function for the survival of the animal.

Anterior distribution of human olfactory epithelium.

OBJECTIVES/HYPOTHESIS: To functionally investigate the distribution of the olfactory epithelium in humans by means of the electro-olfactogram (EOG) and anatomically located biopsy specimens. STUDY DESIGN: Prospective, nonrandomized, investigational. METHODS: Supra-threshold EOG recordings were made on 12 healthy, trained volunteers (6 women, 6 men; age range, 21-48 y). Vanillin was used as the stimulus, since it exclusively excites olfactory receptor neurons. The EOG was recorded with tubular electrodes that were placed using thin-fiber endoscopic guidance. Biopsy specimens were obtained of anterosuperior nasal cavity mucosa in the same regions as the positive EOGs in 15 smell-tested patients (7 women, 8 men; age range, 22-60 y) during routine nasal and sinus surgery. This biopsied tissue was histologically processed and stained for olfactory and neural proteins. RESULTS: Viable responses to EOG testing were obtained in 7 of 12 subjects. In these seven subjects it was possible to identify nine sites above or below the anterior middle turbinate insertion where EOGs were obtained. The biopsy results showed mature olfactory receptor neurons in this same area. CONCLUSIONS: Human olfactory epithelium appears to be distributed more anteriorly than previously assumed.

Cephalic angiotensin receptors mediating drinking to systemic angiotensin II.

In rats implanted with cannulae to allow delivery of solutions to the cerebral ventricular system, pretreatment with 5 mug or 0.5 mug of saralasin acetate (Sar1 Ala8 Angiotensin II), an angiotensin II competitive analog, significantly attenuated drinking to subcutaneous (SC) injections of 500 mug of angiotensin II. However, pretreatment with either SC (5 mug or 20 mug) or with intravenous (5 mug) saralasin had no effect on drinking to SC angiotensin II (500 mug). Intracranial (IC) injections of 5 mug of saralasin had no effect on drinking in response to SC injections of 0.8 cc of a 10 percent NaCl solution and did not attenuate ingestion of a milk solution in a dessert test. On the basis of the specificity and the greater efficacy shown by IC saralasin in attenuating drinking to systemically applied angiotensin II, it was concluded that circulating angiotensin II reaches brain periventricular receptors which mediate drinking.

Successful treatment of phantosmia with preservation of olfaction.

A 26-year-old woman had an 8-year history of phantosmia in her left nostril. The phantosmia could be eliminated by nostril occlusion or cocainization of the olfactory epithelium on the involved side. Because her symptoms and testing suggested a peripheral problem, a full-thickness "plug" of olfactory epithelium from under the cribriform plate (including all the fila olfactoria) was excised. At 5 weeks postoperatively, the phantosmia was completely gone, and her olfactory ability had returned to preoperative levels. Either the removal of abnormal peripheral olfactory neurons from the nose or the interruption of incoming signals to the olfactory bulb eliminated the phantosmia. This form of therapy for phantosmia offers an alternative to more radical procedures such as olfactory bulbectomy and may offer a significant sparing of olfactory ability.