Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “compartmentalization”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
PubMed2003

Stationary diffusion gradients associated with photosynthetic carbon flux-a study of compartmental versus diffusion-reaction models.

Metabolic processes usually involve diffusion of compounds in addition to their metabolic reactions. Such processes are adequately described by reaction-diffusion models (in the form partial differential equations) which are usually difficult and tedious to solve. Compartmental models (ordinary differential equations) are much easier to analyse but may be inadequate since they do not allow for spatial gradients. However, a compartmental model can be considered as the limit of a reaction-diffusion model for very fast diffusion (all diffusion coefficients D(j)--> infinity ). A compartmental model m(c) is termed "associated" to the reaction-diffusion model m(rd) if m(c) is the limit of m(rd) for all D(j)--> infinity. From the analytical solutions of a reaction-diffusion model and its associated compartmental model the extent of a diffusion gradient of m(rd) can be estimated by means of parameters from both m(c) and m(rd). This approach is extended to more complicated models that cannot be solved analytically. Gradients can be neglected and, consequently, the compartmental description be used, if the characteristic length s of the diffusion path is small compared with the distance a particle travels in time T(e), where T(e) is the characteristic time for the compartmental model. This ratio of lengths can also be expressed as the ratio of two times, namely the residence time s(2)/D(X) and the turnover time X(C)/v, where X(C) and v are the steady-state concentration of X and its import rate, respectively, for the associated compartmental model. Characteristic times are given for several simple reaction-diffusion systems in rectangular and spherical geometries. Intracellular gradients of HCO(3)(-) and CO(2) are calculated for some flux situations relevant to photosynthetic carbon fixation in green microalgae.

Biological Transport↗
PubMed2001

Development of a two-part transcription probe to determine the completeness of temporal and spatial compartmentalization of gene expression during bacterial development.

We have developed a two-part test, using the Bacillus subtilis sacB/SacY transcription antitermination system, to evaluate the completeness of temporal and spatial compartmentalization of gene expression during bacterial cell development. Transcription of sacY(1-55) (encoding a constitutively active form of the antiterminator, SacY) is directed by one promoter, whereas transcription of sacB'-'lacZ (the target of SacY action) is directed by the same or another promoter. To obtain beta-galactosidase activity, SacY(1-55) needs to be present when sacB'-'lacZ is being transcribed. We tested the system by analyzing the spatial compartmentalization of the activities of RNA polymerase final sigma factors, which are tightly regulated during sporulation of B. subtilis: final sigma(F) and then final sigma(G) in the prespore, final sigma(E) and then final sigma(K) in the mother cell. We have confirmed that the activities of final sigma(F) and final sigma(E) are spatially compartmentalized. We have demonstrated that there is also sharp temporal compartmentalization, with little or no overlap in the activities of final sigma(F) and final sigma(G) or of final sigma(E) and final sigma(K). In contrast, we found no compartmentalization of the activity of the main vegetative factor, final sigma(A), which continued to be active alongside all of the sporulation-specific final sigma factors. We also found no temporal compartmentalization of expression of loci that are activated during the development of competent cells of B. subtilis, a developmental program distinct from spore formation. A possible mechanism to explain the temporal compartmentalization of final sigma(F) and final sigma(G) activities is that the anti-sigma factor SpoIIAB transfers from final sigma(G) to final sigma(F).

Bacillus subtilis↗
PubMed1996

Analysis of the role of prespore gene expression in the compartmentalization of mother cell-specific gene expression during sporulation of Bacillus subtilis.

A hallmark of sporulation of Bacillus subtilis is the formation of two distinct cells by an asymmetric division. The development programs in these two cells involve the compartmentalized activities of sigma E in the larger mother cell and of sigma F in the smaller prespore. Activation of sigma E requires expression of the sigma F-directed gene spoIIR. By immunofluorescence microscopy of a strain containing a spoIIR-lacZ fusion, we have shown that spoIIR is transcribed exclusively in the prespore. By placing spoIIR under the control of PspoIIE, it was possible to express spoIIR before the spore septum was formed. Strains containing the PspoIIE-spoIIR construct activated sigma E only in the mother cell in organisms that underwent the asymmetric sporulation division. Thus, compartmentalization of sigma E activity did not require the compartmentalization of spoIIR expression. Nor did the compartmentalization of sigma E require SpoIIAA, SpoIIAB, sigma F, or sigma F-dependent transcription, all of which are required for prespore-specific gene expression. It is inferred that although sigma F and sigma E direct compartmentalized gene expression, neither of these sigma factors, nor the genes under their control, directs the process of compartmentalization.

Bacillus subtilis↗
PubMed1994

Compartmentalization of Ca2+ signaling and Ca2+ pools in pancreatic acini. Implications for the quantal behavior of Ca2+ release.

Streptolysin O-permeabilized pancreatic acini were used to study compartmentalization of Ca2+ signaling and Ca2+ pools. In these cells, the inositol 1,4,5-trisphosphate (IP3)-dependent Ca2+ channels could be activated by a number of agonists (carbachol, cholecystokinin, or bombesin) or by activation of the entire cellular phospholipase C pool with GTP gamma S. Surprisingly, each of the antagonists interacting with acinar cells inactivated the channels after stimulation with GTP gamma S. In addition, when permeabilized cells were stimulated with more than one agonist, any antagonist to the specific agonists employed inactivated the channels. The aberrant behavior of the antagonists in permeable cells was not related to a loss of specificity since (a) when added before GTP gamma S, the antagonists had no effect on Ca2+ release and (b) when cells were stimulated with a single agonist, the antagonists prevented only the effect of their specific agonist. The differential behavior of the antagonists in intact and permeable cells suggests a compartmentalization of Ca2+ signaling into separate, agonist-specific units that is modified by cell permeabilization. Further evidence for compartmentalization of signaling was obtained by showing that the partial agonist (the CCK octapeptide analogue JMV-180) can access and release only 50% of the cholecystokinin- or IP3-mobilizable Ca2+ pool in intact and permeable cells. Kinetic measurements revealed a multiphasic time course of agonist-evoked Ca2+ release in permeable cells. At high agonist concentrations, all phases were fast and merged into an apparent single event of Ca2+ release. The phases were separated by three independent protocols: reduction in agonist concentrations, addition of heparin, or addition of guanosine-5'-O-(thio)diphosphate. Since all protocols that caused phase separation reduce IP3-mediated Ca2+ release, these findings demonstrate heterogeneity in the affinity for IP3 of channels present in compartmentalized Ca2+ pools of the same cells. Compartmentalization of signaling and the heterogeneity in the affinity for IP3 resulted in a quantal agonist-evoked Ca2+ release. The overall findings are discussed in the context of an integrated model of compartmentalization of signaling complexes, Ca2+ pools, and IP3-activated Ca2+ channels.

Animals↗
PubMed2003

HIV-1 in genital tract and plasma of women: compartmentalization of viral sequences, coreceptor usage, and glycosylation.

Worldwide, 90% of HIV-1 infections are transmitted heterosexually. Because the genital mucosa are the sites of initial contact with HIV-1 for most exposed individuals, study of the virus from the genital tract is critical for the development of vaccines and therapeutics. Previous analyses of HIV-1 in various tissues have documented compartmentalization of viral genomes. Whether compartmentalization was associated with viral phenotypic differences or immune status, however, was not well understood. We compared HIV-1 gp120 env sequences from the genital tract and plasma of 12 women. Eight women displayed compartmentalized HIV-1 RNA genomes, with viral sequences from each site that were clearly discrete, yet phylogenetically related. The remaining four exhibited env sequences that were intermingled between the two sites. Women with compartmentalized HIV-1 genomes had higher CD4+ cell counts than those displaying intermingled strains (P = 0.02). Intrapatient HIV-1 recombinants comprising sequences that were characteristic of both sites were identified. We next compared viral phenotypes in each compartment. HIV-1 coreceptor usage was often compartmentalized (P 0.01). The number of N-linked glycosylation sites, associated with neutralization resistance, also differed between compartments (P < 0.01). Furthermore, disparities between the density of gp120 glycosylations in each compartment correlated with higher CD4+ counts (P = 0.03). These data demonstrate that the genital tract and plasma can harbor populations of replicating HIV-1 with different phenotypes. The association of higher CD4+ cell counts with compartmentalization of viral genomes and density of gp120 glycosylations suggests that the immune response influences the development of viral genotypes in each compartment. These findings are relevant to the prevention and control of HIV-1 infection.

Adult↗
PubMed1985

Diagnostic value of computerized exercise testing in men without previous myocardial infarction. A multivariate, compartmental and probabilistic approach.

The value of exercise testing for the diagnosis of coronary artery disease is disputed but very few studies have taken advantage of all recent improvements, namely computer averaging of the ECG signals, multivariate analysis of the data, a compartmental diagnostic approach and probabilistic interpretation of the results. These methods were tested in a group of 387 men who had a computer-assisted multistage maximal exercise test; none had a history of myocardial infarction. In 284 symptomatic patients, the diagnosis was made by arteriography; 103 ostensibly healthy men were also included. The computer-averaged ECG signals (X, Y, Z) recorded at maximal exercise, maximal heart rate, blood pressure and workload, and the onset of angina pectoris during exercise were submitted to a multivariate stepwise discriminant analysis. The pretest likelihood for CAD was calculated from age and history; the post-test likelihood was calculated from Bayes' theorem and the average information content of several diagnostic methods was assessed in categorical and compartmental models. By multivariate analysis, 5 variables collected at maximal exercise were selected, namely the heart-rate, the ST60 segment level, the onset of angina during the test, the workload and the slope of the ST segment in lead X. The average information content of the analysis using 5 variables was 44% in a categorical model versus 55% in a compartmental model (P less than 0.001). For comparison, the information content of the analysis using the ST60 segment level alone was only 16% in the categorical model and 27% in the compartmental model. The clinical value of these diagnostic methods (categorical versus compartmental, univariate versus multivariate) was assessed by a probabilistic classification of the patients. The classification provided by the analysis of the ST60 segment changes was barely better than that one provided by the simple history. The probabilistic use of a multivariate and compartmental analysis of the data led to a significantly better and more accurate classification of the patients (83% of correct classification).

Adult↗
PubMed2002

Optical compartmentation of vegetating algae species as a basis for their growth-specific characterization.

BACKGROUND: The number of microalgal strains known to date is enormous and continuously growing, and their characterization accordingly requires quick and reliable methodologies. METHODS: Asynchronously growing logarithmic (3- and 6-day cultures) and stationary (9-day cultures) phase cell populations of two algae species that are difficult to distinguish microscopically (one Chlorella sp., C. vulgaris [c-27], and another that might belong to the same genus, SA-3 algae exsymbiotic from Paramecium bursaria) were characterized by means of flow cytometry (FCM). Forward light scatter (FSC) of algae was monitored in association with their 90 degrees side light scatter (SSC) and fluorescence of endogenous chlorophyll (FL3-height). RESULTS: Two-parameter FSC versus SSC and FSC versus FL3-height plots distinctly showed growth-specific compartmentation of algae into discrete cell subpopulations staying at a particular stage of the life cycle, and numbers of cells constituting these subpopulations could be quantitated. The growth pattern of C. vulgaris (c-27) differed substantially from that of SA-3 algae, particularly in the late-logarithmic (6-day) cultures. At this phase of growth, C. vulgaris (c-27) cells compartmentalized into three subpopulations, whereas SA-3 cells compartmentalized into two subpopulations. Different compartmentations of optical signals from late-logarithmic phase SA-3 algae and C. vulgaris (c-27) likely were caused by the differences in timing of the life cycle stages of these types of cells. CONCLUSIONS: Growth-specific compartmentation of vegetating microalgae by FCM provides a good basis for characterization of morphologically similar algae species. Because algae are also present in symbiotic relationships with other organisms, this tool might be of potential interest for the study of symbiosis mechanisms.

Cell Compartmentation↗
PubMed1979

Network thermodynamic approach compartmental analysis. Na+ transients in frog skin.

We introduce a general network thermodynamic method for compartmental analysis which uses a compartmental model of sodium flows through frog skin as an illustrative example (Huf and Howell, 1974a). We use network thermodynamics (Mikulecky et al., 1977b) to formulate the problem, and a circuit simulation program (ASTEC 2, SPICE2, or PCAP) for computation. In this way, the compartment concentrations and net fluxes between compartments are readily obtained for a set of experimental conditions involving a square-wave pulse of labeled sodium at the outer surface of the skin. Qualitative features of the influx at the outer surface correlate very well with those observed for the short circuit current under another similar set of conditions by Morel and LeBlanc (1975). In related work, the compartmental model is used as a basis for simulation of the short circuit current and sodium flows simultaneously using a two-port network (Mikulecky et al., 1977a, and Mikulecky et al., A network thermodynamic model for short circuit current transients in frog skin. Manuscript in preparation; Gary-Bobo et al., 1978). The network approach lends itself to computation of classic compartmental problems in a simple manner using circuit simulation programs (Chua and Lin, 1975), and it further extends the compartmental models to more complicated situations involving coupled flows and non-linearities such as concentration dependencies, chemical reaction kinetics, etc.

Animals↗
PubMed2004

Contrasting effects of sigmaE on compartmentalization of sigmaF activity during sporulation of Bacillus subtilis.

Spore formation by Bacillus subtilis is a primitive form of development. In response to nutrient starvation and high cell density, B. subtilis divides asymmetrically, resulting in two cells with different sizes and cell fates. Immediately after division, the transcription factor sigmaF becomes active in the smaller prespore, which is followed by the activation of sigmaE in the larger mother cell. In this report, we examine the role of the mother cell-specific transcription factor sigmaE in maintaining the compartmentalization of gene expression during development. We have studied a strain with a deletion of the spoIIIE gene, encoding a DNA translocase, that exhibits uncompartmentalized sigmaF activity. We have determined that the deletion of spoIIIE alone does not substantially impact compartmentalization, but in the spoIIIE mutant, the expression of putative peptidoglycan hydrolases under the control of sigmaE in the mother cell destroys the integrity of the septum. As a consequence, small proteins can cross the septum, thereby abolishing compartmentalization. In addition, we have found that in a mutant with partially impaired control of sigmaF, the activation of sigmaE in the mother cell is important to prevent the activation of sigmaF in this compartment. Therefore, the activity of sigmaE can either maintain or abolish the compartmentalization of sigmaF, depending upon the genetic makeup of the strain. We conclude that sigmaE activity must be carefully regulated in order to maintain compartmentalization of gene expression during development.

Bacillus subtilis↗
PubMed2001

Compartmentation of photosynthesis in cells and tissues of C(4) plants.

Critical to defining photosynthesis in C(4) plants is understanding the intercellular and intracellular compartmentation of enzymes between mesophyll and bundle sheath cells in the leaf. This includes enzymes of the C(4) cycle (including three subtypes), the C(3) pathway and photorespiration. The current state of knowledge of this compartmentation is a consequence of the development and application of different techniques over the past three decades. Initial studies led to some alternative hypotheses on the mechanism of C(4) photosynthesis, and some controversy over the compartmentation of enzymes. The development of methods for separating mesophyll and bundle sheath cells provided convincing evidence on intercellular compartmentation of the key components of the C(4) pathway. Studies on the intracellular compartmentation of enzymes between organelles and the cytosol were facilitated by the isolation of mesophyll and bundle sheath protoplasts, which can be fractionated gently while maintaining organelle integrity. Now, the ability to determine localization of photosynthetic enzymes conclusively, through in situ immunolocalization by confocal light microscopy and transmission electron microscopy, is providing further insight into the mechanism of C(4) photosynthesis and its evolution. Currently, immunological, ultrastructural and cytochemical studies are revealing relationships between anatomical arrangements and photosynthetic mechanisms which are probably related to environmental factors associated with evolution of these plants. This includes interesting variations in the C(4) syndrome in leaves and cotyledons of species in the tribe Salsoleae of the family Chenopodiaceae, in relation to evolution and ecology. Thus, analysis of structure-function relationships using modern techniques is a very powerful approach to understanding evolution and regulation of the photosynthetic carbon reduction mechanisms.

Carbon Dioxide↗
PubMed1996

Focal altered compartmentation of repetitive B2 (Alu-like) sequences in rat liver following hepatocarcinogen exposure.

Rats were treated with low doses of the hepatocarcinogens dimethylnitrosamine or thioacetamide, and livers were examined 48 h later. These treatments are known to produce altered RNA compartmentation, wherein a class of repetitive RNA sequences normally restricted to the nucleus appears in the cytoplasm. Reverse transcription-PCR amplifications demonstrated that the sequences showing altered compartmentation consisted largely of a subfamily of the rodent B2 sequence family, the counterpart of human Alu sequences involved in retrotransposition. Northern blot analyses showed that these B2 sequences were found in cytoplasmic RNA as 170- to 360-nucleotide "sense" transcripts, and competition hybridization experiments established that B2 sequences represented most (if not all) of the sequences showing altered compartmentation. The major increase in B2 transcriptions in cytoplasmic RNA was not associated with any change in B2 transcription by RNA polymerase III. In situ hybridizations showed that the altered compartmentation of B2 sequences occurred in well-delineated foci within the rat liver; these foci consisted of a central region containing a prominent infiltrate of macrophages admixed with small hepatocytes and a peripheral region of histologically normal hepatocytes that showed evidence of oxidative damage. Altered compartmentation of B2 sequences may represent an important focal initiatory change in a subset of hepatocytes, whereas subsequent retrotranspositional events (associated with Alu-like sequences) could predispose initiated cell foci to alterations in promotion/progression phases.

Animals↗
PubMed1988

Relationship of the axonal and dendritic geometry of spiny projection neurons to the compartmental organization of the neostriatum.

Intracellular injection of HRP combined with immunocytochemistry for [Leu]enkephalin was used to demonstrate striatal spiny neuron dendritic and local axonal arborizations in the same section as enkephalin-rich patches (striosomes). Cobalt intensification of the first DAB reaction prior to the immunoperoxidase steps resulted in good contrast between the black reaction product in the intracellularly labeled cells and the brown staining for [Leu]enkephalin. Serial reconstructions of the labeled cells and nearby boundaries between the enkephalin-rich striosomes and enkephalin-poor matrix allowed the relationship between the arborizations of the labeled cells and these boundaries to be established. It was also possible to examine the relationship to compartmental boundaries of a second neuronal class consisting of large, pallidallike neurons whose somatodendritic morphology was outlined by immunoperoxidase-labeled terminals. We found that spiny projection neurons in both compartments have dendritic arbors and local axonal collaterals that are confined by compartmental boundaries. The termination or recurvature of dendrites at such boundaries suggests that the cellular basis of striatal compartmental organization is provided by this class of striatal neuron. On the other hand, large pallidumlike striatal neurons were found to have dendrites that extend across compartmental boundaries. These results support previous reports that striatal spiny projection neurons preserve the compartmental segregation of parallel striatal input-output systems, whereas other classes of striatal neurons may serve to provide limited integration between compartments.

Animals↗
PubMedDate not supplied

Distinguishing animal subsets in toxicokinetic studies: comparison of non-linear mixed effects modelling with non-compartmental methods.

The purpose of this study was to compare the ability of non-compartmental analysis and compartmental mixed effects modelling (MEM) to determine the existence and magnitude of exposure differences (i.e. exposure ratio estimates) between subsets of animals during destructive toxicokinetic studies. Data from five toxicokinetic studies of an experimental compound were analysed using a linear trapezoidal calculation of the area under the curve (non-compartmental analysis) or modelled using MEM. With the non-compartmental method the Bailer-Satterthwaite approximation was used to construct confidence intervals around the exposure estimates of each subset of animals and these were used to determine if exposure differed between the subsets. The MEM analyses were performed on the full datasets and on datasets with arbitrary reductions in the number of animal replicates. With MEM, additional model parameters were used to differentiate between subsets of animals, and were incorporated only if they were justified statistically. Estimates of the existence and magnitude of exposure differences between animal subsets were similar with the two techniques. The MEM analyses were influenced only marginally by substantial reductions in the number of animals studied and were less compromised by extremely limited or unbalanced data. These analyses show that MEM and non-compartmental methods are similarly effective at detecting exposure differences between animal subsets in toxicokinetic studies. Estimates provided by both methods were influenced by the degree of variance in the data. These results support the proposition that it may be possible to reduce the number of animals employed in toxicokinetic studies if MEM is used.

Animals↗
PubMed1995

Compartmentation and metabolic parameters of mitochondrial hexokinase and creatine kinase depend on the rate of oxidative phosphorylation.

Oxidative phosphorylation in rat heart mitochondria was stimulated by the presence of hexokinase, by simultaneous operation of mitochondrial hexokinase and creatine kinase, or by mitochondrial hexokinase plus exogenously added phosphofructokinase. Under these conditions, 32Pi studies were conducted to estimate the extent of ATP compartmentation in the mitochondria in the vicinity of the active sites of hexokinase and creatine kinase. In all cases studied the extent of ATP compartmentation at 500 microM ATP concentration was no more than 12%. Within the same experimental design, the extent of ATP compartmentation increased with an increase in the rate of oxidative phosphorylation. The degree of ATP compartmentation depended on the relative location of the enzyme and inner mitochondrial membrane: it was maximal in the vicinity of the creatine kinase active sites and minimal for that of phosphofructokinase. The difference in the extent of ATP compartmentation in the neighborhood of the active sites of hexokinase and creatine kinase diminished with an increase in the rate of oxidative phosphorylation. We conclude that there is an ATP concentration gradient in the mitochondrial intermembrane space during oxidative phosphorylation, the minimum concentration being at the surface of the inner membrane. It was found that stimulation of oxidative phosphorylation led to a decrease in the apparent constants, Km (MgATP) and Vmax, for the two enzymes, however, to different degrees. Possible reasons for the change in kinetic parameters of the above enzymes are discussed.

Adenosine Triphosphate↗
PubMed1983

Kinetic compartmental analysis of carnitine metabolism in the dog.

This study was undertaken to quantitate the dynamic parameters of carnitine metabolism in the dog. Six mongrel dogs were given intravenous injections of L-[methyl-3H]carnitine and the specific radioactivity of carnitine was followed in plasma and urine for 19-28 days. The data were analyzed by kinetic compartmental analysis. A three-compartment, open-system model [(a) extracellular fluid, (b) cardiac and skeletal muscle, (c) other tissues, particularly liver and kidney] was adopted and kinetic parameters (carnitine flux, pool sizes, kinetic constants) were derived. In four of six dogs the size of the muscle carnitine pool obtained by kinetic compartmental analysis agreed (+/- 5%) with estimates based on measurement of carnitine concentrations in different muscles. In three of six dogs carnitine excretion rates derived from kinetic compartmental analysis agreed (+/- 9%) with experimentally measured values, but in three dogs the rates by kinetic compartmental analysis were significantly higher than the corresponding rates measured directly. Appropriate chromatographic analyses revealed no radioactive metabolites in muscle or urine of any of the dogs. Turnover times for carnitine were (mean +/- SEM): 0.44 +/- 0.05 h for extracellular fluid, 232 +/- 22 h for muscle, and 7.9 +/- 1.1 h for other tissues. The estimated flux of carnitine in muscle was 210 pmol/min/g of tissue. Whole-body turnover time for carnitine was 62.9 +/- 5.6 days (mean +/- SEM). Estimated carnitine biosynthesis ranged from 2.9 to 28 mumol/kg body wt/day. Results of this study indicate that kinetic compartmental analysis may be applicable to study of human carnitine metabolism.

Animals↗
PubMed1996

Bioequivalence: individual and population compartmental modeling compared to the noncompartmental approach.

PURPOSE: The purpose of this study were to evaluate the use of individual compartmental and population compartmental methods for bioequivalence determination, and to determine their utility as adjuncts to the current methods used for bioequivalence assessment. METHODS: Data from three bioequivalence studies of chlorthalidone were analyzed with PCNONLIN using individual compartmental modeling and NONMEM for population analyses. These results were compared with results obtained from the traditional noncompartmental or SHAM (slopes, heights, areas, and moments) approach for bioequivalence assessment and the 90% confidence interval procedure. RESULTS: Individual compartmental modeling and population compartmental modeling techniques performed well on this routine set of bioequivalence data which displayed simple pharmacokinetic properties. A direct assessment of the analysis methods was made by comparing the final estimates and 90% confidence intervals for the test to reference ratios (T/R) of AUC and CMAX. The final estimates and 90% confidence intervals for AUC T/R and CMAX T/R were similar and suggest consistency of results, independent of the method used. CONCLUSIONS: These results demonstrate the utility of modeling techniques as adjuncts to the traditional noncompartmental approach for bioequivalence determination.

Chlorthalidone↗
PubMed1992

Compartmentalization of positive and negative self-knowledge: keeping bad apples out of the bunch.

Three studies examined whether categorical organization of knowledge about the self explains variance in self-esteem and depression beyond that which is accounted for by sheer amount of positive or negative content. Compartmentalization is the tendency to organize positive and negative knowledge about the self into separate, uniformly valenced categories (self-aspects). As long as positive self-aspects are activated, access to negative information should be minimized. Compartmentalization was associated with high self-esteem and low depression scores for individuals whose positive self-aspects were important; when negative self-aspects were important, compartmentalization was correlated with low self-esteem and high depression scores. An analysis of self-aspect labels showed that individuals with compartmentalized organization define negative self-aspects in especially narrow terms. A possible relationship between compartmentalized organization and cognitive complexity is discussed.

Achievement↗
PubMed2006

Compartmental signal modulation: Endosomal phosphatidylinositol 3-phosphate controls endosome morphology and selective cargo sorting.

It is increasingly recognized that the compartmental organization of signaling processes has a profound influence on cellular behavior. However, our inability to influence these compartmental events in a spatially restricted and acute manner limits our understanding of causation. To determine whether local compartmental loss of a phosphoinositide disrupts the normal traffic of specific cargoes through endosomes, we developed the use of a regulated dimerization device, here designed to compartmentally modify the phosphoinositide content of Rab5-positive endosomes. This modification is effected through the specific regulated recruitment of the 3-phosphatase myotubularin to endosomal membranes in intact cells. The selective manipulation of endosomal phosphatidylinositols (PIs) demonstrates that it is the phosphatidylinositol 3-phosphate (PtdIns3P) or its metabolite PtdIns(3,5)P2 within this compartment that determines the normal maturation of the endosomal compartment and the flux of receptors through it. On local loss of PtdIns3P/PtdIns(3,5)P2, the endosomal compartment itself fails to continue its normal maturation process, leading to the microtubule-dependent tubularization of the endosomal network. Furthermore, it is shown that endosomal PtdIns3P/PtdIns(3,5)P2 is necessary for transferrin receptor traffic through this compartment while having an effect on EGF receptor (EGFR) entry into and sorting from this endosome compartment. The ability to acutely and selectively influence compartmental behavior as exemplified here for endomsomes clearly illustrates the power of the approach used to dissect the role of localized signals and events.

Animals↗