Distribution Of Metabolic Activity Research Articles

Abstract 10622: Association of Sustained Ventricular Arrhythmias and Increased Cardiac Metabolic Activity Mimicking Cardiac Sarcoidosis

Introduction: Cardiac sarcoidosis (CS) is increasingly diagnosed using 18F-fluorodeoxyglucose positron emission tomography/CT (FDG-PET/CT). Patients with sustained ventricular tachycardia/fibrillation (VT/VF) and a positive FDG-PET/CT suggestive of CS often receive immunosuppressive therapy even in the absence of histologic documentation of non-caseating granulomas. Hypothesis: FDG-PET/CT performed early after sustained VT/VF can lead to increased myocardial FDG uptake mimicking CS. Methods: Consecutive patients with non-ischemic cardiomyopathy presenting with sustained VT/VF that underwent FDG-PET/CT immediately following the arrhythmic event were prospectively recruited. Patients with increased metabolic activity consistent with myocardial inflammation were followed. All patients received guideline-directed medical therapy, but without immunosuppressive therapy. Repeat FDG-PET/CT was performed ≥30 days after the last sustained VT/VF episode. Results: Six patients were enrolled with a mean age of 57.1 years (± 5.6), and a left ventricular ejection fraction of 47.5% (±14.8). Coronary artery disease and acute perimyocarditis were excluded. Initial presentation was electrical storm in 2 (33%), appropriate ICD or external shock in 3 (50%) and ATP in 1 (17%) case, respectively. Baseline FDG-PET/CT was performed a median 5.5 days (range 3-17) after sustained VT/VF termination. Distribution of metabolic activity was focal-multifocal in 4 (66%), focal-diffuse in 1 (17%) and focal in 1 (17%) case, respectively. Median SUVmax was 6.8 (range 4.9-18). No extracardiac metabolic foci were observed and histologic diagnosis of non-caseating granuloma could not be established in any patient. Repeat FDG-PET/CT (median after 139, range 38-448 days) showed complete FDG uptake regression in all patients. Final diagnosis of arrhythmogenic cardiomyopathy was made in all patients, and genetic testing was performed. Conclusion: Prolonged VT/VF episodes may result in increased myocardial FDG uptake, potentially leading to an overdiagnosis of CS. FDG-PET/CT to screen for CS should be performed at a VT/VF-free interval prior to immunosuppressive therapy.

Characterization of spatiotemporal electroactive anodic biofilm activity distribution using 1D simulations

Activity distribution limitation in electroactive biofilm remains an unclear phenomenon. Some observations using confocal microscopy have shown notable difference between activity close to the anode and activity at the liquid interface. A numerical model is developed in this work to describe biofilm growth and local biomass segregation in electroactive biofilm. Under our model hypothesis, metabolic activity distribution in the biofilm results from the competition between two limiting factors: acetate diffusion and electronic conduction in the biofilm. Influence of inactive biomass fraction (i.e. non-growing biomass fraction) properties (such as conductivity and density) is simulated to show variation in local biomass distribution. Introducing a dependence of effective diffusion to local density leads to a drastic biomass fraction segregation. Increasing density of inactive fraction reduces significantly acetate diffusion in biofilm, enhances biomass activity on the outer layer (liquid/biofilm interface) and maintains inner core largely inactive. High inactive fraction conductivity enhances biomass activity in the outer layer and enhances current production. Hence, investment in extracellular polymer substance (EPS), anchoring redox components, is benefit for biofilm electroactivity. However, under our model hypothesis it means that conductivity should be two order lower than biofilm conductivity reported in order to observe inner core active biomass segregation.

Rebound adenotonsillar and thymic uptake of 18F-FDG in paediatric patients with lymphoma

PurposeTo evaluate the treatment-dependent changes in FDG uptake in the adenoid, palatine tonsils, and thymus in paediatric patients with lymphoma. MethodsEight hundred PET/CT scans of 212 paediatric patients between 2007 and 2019 (mean age, 11.9 years; median follow-up, 26.2 months) were retrospectively reviewed for discernible FDG uptake in the adenoid (A+), palatine tonsils (P+), and thymus (T+). The distribution of metabolic activity in the interested lymphoid organs was examined. Statistical analysis was performed using SPSS packages. ResultsThere were 513 (64 %) A + scans, 548 (69 %) P + scans, 270 (48 %) T + scans identified. The percentage of A + was 88 % at baseline, decreased to 48 % at the end of treatment, and then rebounded to 73 % during follow up; P + went from 79 % to 45 % then to 82 %; and for T + was 75 %, 21 %, 72 %. SUVmax was significantly higher (P < 0.001) in scans performed during follow-up than that of the baseline (A + 7.0 ± 3.5 vs. 5.8 ± 2.5; P + 9.4 ± 3.5 vs. 8.2 ± 2.8; T + 4.0 ± 1.4 vs. 3.4 ± 1.1). A + and P + peaked between 6–12 months of follow-up with a SUVmax of 7.6 ± 3.2, 10.6 ± 3.2, accordingly; T + peaked within 3–12 months with a SUVmax of 4.4 ± 1.4. Despite that A + and T + were more commonly seen in younger patients at any given study time, evident uptake rebound persisted in patients aged ≥16. ConclusionsIn paediatric patients with lymphoma, evident and benign rebound adenotonsillar and thymic 18F-FDG uptake commonly occur during post-treatment surveillance.

Viewing a forelimb induces widespread cortical activations

Given that prerequisite of activating the mirror neuron system is the preshaping of the hand and its interaction with the object during observation of a reaching-to-grasp-an-object action, the effects of viewing the object, the reaching forelimb and the static hand may obscure the effects of observing the grasping action per se. To disentangle these effects, we employed the 14C-deoxyglucose quantitative autoradiographic method to map the functional activity in the entire cortex of monkeys (Macaca mulatta) which observed the experimenter performing non-goal-directed (purposeless) forelimb movements towards an object that was previously presented but no longer visible. Thus, our monkeys were exposed to the view of an object, a moving arm and a static hand with extended wrist and fingers. The distribution of metabolic activity was analyzed in 20μm thick brain sections, and two dimensional maps were reconstructed in the occipital operculum, the temporal, the lateral and medial parietal, the lateral and medial frontal, the lateral prefrontal and orbitofrontal cortices, including the cortex within the lunate, superior temporal, lateral, parietoccipital, intraparietal, central, arcuate and principal sulci. Increased metabolic activity, as compared to fixation-control monkeys, was measured in the forelimb representation of the primary motor and somatosensory cortices, the premotor cortices F2 and F5, cingulate motor areas, the secondary somatosensory cortex SII, the posterior intraparietal area 5 and areas TPOc and FST, in the hemisphere contralateral to the moving arm. Moreover, bilateral activations were elicited in areas pre-SMA, 8m, SSA and the somatorecipient area VS, the retroinsula, the auditory belt area CM, motion areas MT, MST, LOP/CIP, area 31, visual areas TEO, V6, V6Av and the parafoveal and peripheral visual representations of areas V1 and V2, respectively. Few parietal, auditory and visual areas were bilaterally depressed. In brief, a surprisingly wide cortical network is recruited even by mere observation of an arm executing goalless movements, which partially overlaps with the cortical network supporting the execution and observation of goal-directed forelimb actions. Interestingly, this overlap concerns mainly lower order sensory-motor rather than higher order association prefrontal and parietal cortices. Our results demonstrate that in order to reveal the net effects specifically induced by observation of a purposeful reaching-to-grasp action, the use of an appropriate control taking into account the effects of viewing the object to be grasped, the reaching arm and the static hand is crucial.

Distribution of metabolic activity (cytochrome oxidase) and immunoreactivity to calcium-binding proteins in the turtle brainstem auditory nuclei

Using histochemical and immunohistochemical techniques, distribution of activity of oxidative mitochondrial enzyme cytochrome oxidase (CO) and of immunoreactivity to calcium-binding proteins has been studied in spiral ganglion and auditory nuclei of brainstem in two turtle species. It has been shown that immunoreactivity to calbindin, parvalbumin, and calretinin in neurons and neuropil of nuclei of cochlear and superior olivary complexes, in nucleus of lateral lemniscus, and in spiral ganglion neurons coincides topographically with the high CO activity. The similarity of the studied metabolic and neurochemical characteristics of these auditory centers in reptiles, birds, and mammals indicates the existence of some common principles of their organization in amniotes in spite of phylogenetic differences and peculiarities of specialization of the auditory system in different species.

Metabolic activity of the thalamic and telencephalic auditory centers of reptiles

329 The lemniscal (classical projection) and extralemniscal parts of mammalian sensory systems, including the auditory system have different levels of metabolic activity. The lemniscal parts have a higher activity of cytochrome oxidase (CO) and an increased ability to accumulate 2-deoxyglucose (2-DG), whereas the extralemniscal parts are characterized by a lower level of metabolic activity [1]. A similar distribution of metabolic activity was observed in the auditory system of birds (in the mesencephalic, thalamic, and telencephalic auditory centers) [2‐4]. Earlier, we showed that the mesencephalic auditory center, torus semicircularis (TS), of some reptiles, such as turtles and lizards, has a higher CO activity in the central nucleus of the lemniscal pathway than in the peripheral extralemniscal part [5]. However, it is not clear whether the metabolic activity in the rostral centers of reptilian auditory system, viz. the auditory relay thalamic nucleus (n. reuniens, Re) and its projection zone in the telencephalon (the ventromedial part of anterior dorsal ventricular ridge, Advr), have selective distribution. In this work, we studied the distribution of the activity of the mitochondrial oxidative enzyme CO in the rostral auditory centers of two turtle species, Testudo horsfieldi and Emys orbicularis. The experiments were performed with four T. horsfieldi and four E. orbicularis. The CO activity was measured by the standard histochemical method [6] with the use of bovine heart cytochrome Σ (Sigma). The CO activity was estimated by the density of histochemical staining of frozen frontal brain slices with a thickness of 50 µ m. Thalamus. The distribution of the CO activity in the Re in both turtle species was similar and heterogeneous. In the rostral level of the thalamus, we found a CO-active band-shaped structure that continuously spread from the ventricle in the lateral direction below the ventral border of the thalamic center of the tectofugal visual system (Rot) and coincided with the location of the n. anterior (nA). The medial part of this structure is a rostral pole of Re (Figs. 1a and 2a). The middle Re level had two areas with a high CO activity. The larger dorsocentral area occupied almost the entire nucleus except for a small ventrolateral part and extended to the somatic nucleus n. ventralis (nV) below the Rot. This area was continuously connected with the rostral bandshaped structure (Figs. 1b and 2b). Like the rostral part of the Re, this area was filled with stained punctuate terminals with sparse CO-positive cells located in the lat

An optimization model of the photosynthetic leaf: the model of optimal photosynthetic CO2 fixation within leaves of mesophytic C3 plants.

The main function of the photosynthetic leaf is to convert light energy into chemical energy and to assimilate CO 2 . Coordination of these functions as related to the heterogeneous leaf structure and the distribution of metabolism within the leaf has been investigated in many studies [1‐5, etc.]. Presumably, after hundreds of millions of years of selection, the typical mesophytic leaf structure and the distribution of metabolic activity within it are relatively optimal. The stimuli that result in the formation of specific structural or functional features of the leaf may emerge through generalization of the experimental data using the unified theory of ecological utility. To describe the functioning of biological systems on the basis of the rule of maximal ecological utility (MEU) [6], the function of partial ecological utility is entered for each defined parameter of the system. It is possible to use any limited monomial function [7]. At optimal functioning of a system, the general utility as a product of partial utilities (in the case of their independence from each other) should be maximized. Some authors suppose that photosynthesis follows the light absorption gradient [8]. However, light absorption decreases from the top, illuminated surface to the bottom of the leaf [5], while the maximal CO 2 fixation occurs in the middle of palisade mesophyll [9]. The results imply that a significant amount of absorbed light energy may not be utilized directly for CO 2 fixation at the top of the leaf. It is possible that low photosynthesis in the upper layer of the palisade is due to excess illumination, which induces the formation of oxygen radicals (O 2 uptake under saturated light might reach 50% of its maximal evolution [10]). If the presumption is correct, the optimization of CO 2 fixation within the leaf should take place when the total utility of the two functions, (1) light absorption for photosynthesis and (2) protection from light intensities that can cause photodestruction, is maximized. The goal of the present work was to use the MEU rule to describe an optimal model of photosynthesis in a bifacial, mesophytic leaf of a C 3 plant. Let us consider this on a simplified model, where the leaf is a flat plate, and its surface is illuminated by light ( I 0 ; ν in the PAR range). The light is absorbed by chlorophyll ( a / b = 3/1 [9]) in a layer of phototrophic cells in the depth of the plate; the plate itself has the same absorption spectrum. In such a leaf, the function r ( z ) (partial utility of protection from photodestruction) and the function s ( z ) (partial utility of light absorption for photosynthesis) depend on the depth of the photosynthetic layer within the relative thickness ( h ) of the leaf (the variable h is incorporated by variable z , where

Early organic diagenesis: The significance of progressive subsurface oxidation fronts in pelagic sediments

Porewater and solid phase geochemical data at two contrasting NE Atlantic stations are reported. Station 10552, on the Cape Verde abyssal plain, is a site of slow pelagic accumulation ( ca. 0.4 cm kyr −1). Molecular oxygen is present in the sediment column to at least 2 m, and probably much deeper, labile organic-carbon is almost totally consumed in the upper few centimetres of the sediment. By contrast, at station 10554 on the Madeira abyssal plain, the pelagic sequence has been interrupted by the occasional deposition of organic-rich turbidites. Porewater oxygen and nitrate profiles show that subsurface organic metabolism of the organic-carbon associated with the uppermost turbidite layer is a significant fraction of the overall metabolism in the sediment column. This metabolism occurs at a relatively thin reaction front which progresses deeper into the turbidite with time. This phenomenon exerts a controlling influence on the present nutrient profile and redox succession. In a less extreme form, substrate distributions of this latter type are not uncommon in Atlantic sediments. A model has been developed which is controlled by both oxygen and nitrate data. This model permits a vertical profile of metabolic activity to be derived, and also gives estimates of the reaction rate constants and solid phase mixing rates at these two contrasting stations. About 30% of the total activity at station 10554 is located within the turbidite at the deepening reaction front; this is a non-steady-state condition. In fact, it is found that the integrated metabolic activity at the two stations is not dissimilar ( ca. 1–2 × 10 −13 moles cm −2 sec −1 ). The striking differences in redox profile are therefore primarily attributable to differences in the distribution of metabolic activity within the column.

Patterns of metabolic activity in cytoarchitectural area SII and surrounding cortical fields of the monkey.

The pattern of [14C]2-deoxyglucose (2-DG) labeling evoked by tactile stimuli was determined in cerebral cortical cytoarchitectural area SII and the fields that surround it (including area 7b, the retroinsular field (Ri), and the granular insular region (Ig) for a series of nine monkeys (macaca fascicularis). In all animals and for all tactile stimuli, the cortical labeling most frequently occurred in the form of patchlike aggregates of metabolically active neurons. Individual patches typically included laminae II-V, were most densely labeled in the central layers, and possessed limited tangential width. Analysis of the relations between patches of label in adjacent sections revealed that the metabolically active neurons form three-dimensional aggregates (termed modules or strips), which can extend for several millimeters. It is hypothesized that these metabolic modules may correspond to information-processing units within the cerebral cortex. Two-dimensional reconstructions of the 2-DG label in the hemispheres ipsilateral and contralateral to the somatic stimuli reveal that the strips of high metabolic activity are interspersed with regions of substantially less activity. In all cortical regions examined in this study, the strips were oriented roughly from anterior to posterior. Systematic changes in the place of the somatic stimulus led to systematic changes in the cortical location of the strips of metabolic label. Conversely, animals subjected to nearly identical tactile stimuli produced very similar patterns of metabolic activity. Comparison of the distribution of metabolic activity in area SII of the hemispheres ipsilateral and contralateral to the stimulus demonstrated that although the amount of labeling in SII ipsilateral to the stimulus was typically less than that present in SII of the contralateral hemisphere, it was both substantial and topographically highly organized. The labeling in the cytoarchitectural zones surrounding SII (i.e., 7b, Ri, and Ig), although clearly stimulus related, occupied extensively overlapping regions in all experiments even though the body regions stimulated were in widely different locations. As a result, a relative lack of topographical organization within these cortical fields is indicated.

Metabolic Activity Distribution in the Embryo of Naturally Aged Seeds of Durum Wheat

Summary The control of metabolic activity in old seeds was carried out with the aim to evaluate whether embryos from seeds which had lost their viability contain tissues still able to perform certain synthetic processes. Using labelling experiments with [ 3 H]-thymidine, [ 3 H]-uridine and [ 3 H]-lysine, analysis was conducted on DNA, RNA and protein synthesis of different areas from non-germinating embryos in comparison with young viable ones. Light microscope studies of sectioned autoradiographed tissues give evidence for the persistence, in some areas of aged embryos (first node and scutellum), of a marked synthetic activity similar to that of young embryos whereas other areas (shoot apex) have lost or reduced this capability. The results obtained allow to conclude that the loss of germination capacity due to a general damage in aged seeds is not accompanied, in all embryonic tissues, by the failure of synthetic capacities. The internal areas of embryo appear to be more isolated and less sensitive to damaging effects of external ageing factors.

The use of isolated cells to assess the contribution of the mucosal epithelium to the metabolism of the intestinal wall.

We have used suspensions of isolated cells to study the metabolism of the mucosal epithelium and to compare its activity with that of other tissues in the intestinal wall of guinea pig. Only 4% of the total glycolytic activity of the intestinal wall could be attributed to the mucosal epithelium. In contrast, about 76% of the activity was located in the intestinal muscle and the remaining 20% in the intervening tissue.Clearly the view that the major proportion of the glycolytic activity of the small intestine resides in the mucosal epithelium does not apply to the guinea pig. In the light of our results, it would be prudent to re-examine any conclusions about the distribution of metabolic activity throughout the gut wall if the supporting evidence has been drawn from experiments with mucosal homogenates.

Distribution of metabolic activity, phospholipid and hyaluronidase between the heads and tails of bull spermatozoa.

Distribution of metabolic activity, phospholipid and hyaluronidase between the heads and tails of bull spermatozoa.