Top PDF Elimination of self-reactive T cells in the thymus: a timeline for negative selection.

Elimination of self-reactive T cells in the thymus: a timeline for negative selection.

Elimination of self-reactive T cells in the thymus: a timeline for negative selection.

The elimination of autoreactive T cells occurs via thymocyte apoptosis and removal by thymic phagocytes, but the sequence of events in vivo, and the relationship between thymocyte death and phagocytic clearance, are unknown. Here we address these questions by following a synchronized cohort of thymocytes undergoing negative selection within a three-dimensional thymic tissue environment, from the initial encounter with a negative selecting ligand to thymocyte death and clearance. Encounter with cognate peptide–MHC complexes results in rapid calcium flux and migratory arrest in auto-reactive thymocytes over a broad range of peptide concentrations, followed by a lag period in which gene expression changes occurred, but there was little sign of thymocyte death. Caspase 3 activation and thymocyte loss were first detectable at 2 and 3 hours, respectively, and entry of individual thymocytes into the death program occurred asynchronously over the next 10 hours. Two-photon time-lapse imaging revealed that thymocyte death and phagocytosis occurred simultaneously, often with thymocytes engulfed prior to changes in chromatin and membrane permeability. Our data provide a timeline for negative selection and reveal close coupling between cell death and clearance in the thymus.
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Continuous activation of the CD122/STAT-5 signaling pathway during selection of antigen-specific regulatory T cells in the murine thymus.

Continuous activation of the CD122/STAT-5 signaling pathway during selection of antigen-specific regulatory T cells in the murine thymus.

pSTAT-5 by flow cytometry). Because STAT-5 functions as a inducer of Bcl-2 and Bcl-xL [41], which are crucial anti-apoptotic molecules, STAT-5 may also be involved in the survival of some thymocytes recognizing self-antigens. This signal may allow for a sufficient amount of time for the cells to up-regulate foxp3 under the influences of additional signals, such as TCR-induced CARMA-1 leading to c-rel activation [42]. In that respect, it has been suggested that a Bcl-2 transgene can rescue foxp3 expression in STAT-5-KO mice (unpublished observations cited in [9]) but not in CARMA-1 [10,11] or c-rel-KO mice [42], demonstrating that STAT-5 and foxp3 expression are not absolutely intertwined. It can then be deduced that STAT-5 activation might be more important for promoting survival of autoreactive nTreg cells than to directly induce foxp3 expression in the murine thymus.
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Bringing you negative selection, live and in color.

Bringing you negative selection, live and in color.

Technical limitations have heretofore forced researchers to study negative selection mainly in single-cell suspensions of dissociated thymic tissue, but Dzhagalov et al. were interested in how T cells behave during negative selection in the intact thymus. They decided to see if the first stage of negative selection (T cell activation) could be detected in slices of intact thymic tissue. For their studies, the authors used transgenic mice whose T cells all express the same TCR, a specially engineered one called F5 TCR that’s known to cause negative selection when stimulated with its cognate antigen (which isn’t normally present in the thymus). Dzhagalov et al. found that they could synchronously stimulate activation in the F5 T cell population by pipetting the antigen onto slices of thymic tissue.
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Triggering the TCR developmental checkpoin activates a therapeutically targetable tumor suppressive pathway in T-cell leukemia

Triggering the TCR developmental checkpoin activates a therapeutically targetable tumor suppressive pathway in T-cell leukemia

T cells mature in the thymus following a highly orches- trated process controlled by both cell-intrinsic (e.g., transcrip- tion factors) and cell-extrinsic (e.g., stroma-derived cytokines/ chemokines) molecular cues ( 28, 29 ). Cell-surface TCR αβ expression in DP thymocytes allows recognition of specifi c self-MHC/peptide to transduce a positive selection signal and maturation into single-positive thymocytes. DP thymocytes not receiving this signal die through lack of stimulation, whereas those whose TCR binds too strongly to self-MHC/ peptide undergo activation-induced apoptosis and negative selection ( 5, 30 ). In both situations, TCR binding to self- pMHC is the triggering event, but how TCR engagement leads to such divergent outcomes (survival and prolifera- tion versus death) remains unclear ( 31 ). Remarkably, these two contrasting processes are driven by a TCR signaling machinery of qualitatively similar composition ( 30 ). Available evidence indicates that the difference lies in the molecular interpretation of signals of different strength, which may rely on compartmentalization of key signaling players ( 32 ), and in the induction of divergent, complex transcriptional responses ( 14, 33 ). Indeed, it has been shown that a small increase in ligand affi nity for the TCR leads to a marked change in the subcellular localization (plasma membrane for negative selecting ligands vs. Golgi complex for positively selecting ones) of essential adaptors of the RAS signaling pathway. This compartmentalization induces the conversion of a small change in analogue input (affi nity for ligand) into a digital output (positive vs. negative selection; refs. 32, 34 ). Our results show that the antileukemic activity of anti-CD3 mAb depends upon TCR signaling cues, as it was impaired upon LAT silencing in T-ALL cells. This also suggests that, in the present experimental setting, antibody dependent cell- mediated cytotoxicity (ADCC)–like responses of the host play a minor role in anti-CD3 antileukemic properties. It
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Development of regulatory T cells in the human thymus : one step beyond =desenvolvimento de células T reguladoras no timo humano

Development of regulatory T cells in the human thymus : one step beyond =desenvolvimento de células T reguladoras no timo humano

Differentiation of blood-derived T cell progenitors to mature CD4 or CD8 T cells in the thymus is accomplished by sequential development through a series of stages that can be defined by the expression of CD3, CD4 and CD8. In humans, CD4-CD8-CD3- triple negative (TN) cells first acquire CD4 (CD4 immature single positive stage, CD4ISP stage) and then CD8 to become CD4+CD8+ (double positive stage, DP stage) cells. Upon T cell receptor (TCR) gene rearrangements, DP cells “test” their TCR for recognition of the antigen-presenting molecules named major histocompatibility complex (MHC). While cells that are unable to recognize self-MHC undergo “death by neglect”, DP thymocytes bearing TCRαβ complexes that can engage self-MHC molecules are signaled to survive, a process designated as “positive selection”, and to differentiate into functionally mature CD4 single positive (CD4+CD8-CD3high, CD4SP) or CD8 single positive (CD4-CD8+CD3high, CD8SP) T cells. Data from mouse models suggest that the strength and duration of TCR signaling is determinant in CD4 vs. CD8 lineage decision during thymic differentiation. Strong TCR signaling induces “negative selection”, resulting in programmed cell death of potentially auto-reactive cells. TCR signaling has been shown to be essential for Treg differentiation in the thymus. It has been proposed that Treg selection may occur within a very narrow window of affinity of TCR-ligand interactions, between positive selection of conventional CD4 T cells and negative selection of high-affinity self-reactive T cells. In agreement, increased self- reactivity is considered a unique feature of Tregs.
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Positive selection of natural poly-reactive B cells in the periphery occurs independent of heavy chain allelic inclusion.

Positive selection of natural poly-reactive B cells in the periphery occurs independent of heavy chain allelic inclusion.

Most of the naturally-occuring autoantibodies are poly-reactive and exist in healthy individ- uals [18, 19]. Recent studies have suggested that 5~20% of long-lived B cells are autoreactive in humans [2]. However, the role of receptor editing in the development of natural autoreactive B cells is not yet clear. Secondary recombination at the light (L) chain genetic loci generates a new μ chain that can either substitute the autoreactive L chain [20], or can be co-expressed on the cell surface as a “passenger” together with the original L chain, and can also associate with the heavy (H) chain separately. This later phenomenon is referred to as allelic inclusion [21, 22] and is a result of receptor editing. The co-expression of an “innocent” L chain can rescue B cells from negative selection by diluting the surface expression of the self-reactive BCR [23]. In addition to L chains, secondary rearrangement of V genes also happens at the H chain loci [24, 25]. However, the extent and function of H chain allelic inclusion are unknown. Given the dominant role V H plays in antigen recognition, it will be important to clarify the relationship
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Self-glycolipids modulate dendritic cells changing the cytokine profiles of committed autoreactive T cells.

Self-glycolipids modulate dendritic cells changing the cytokine profiles of committed autoreactive T cells.

The impact of glycolipids of non-mammalian origin on autoimmune inflammation has become widely recognized. Here we report that the naturally occurring mammalian glycolipids, sulfatide and b-GalCer, affect the differentiation and the quality of antigen presentation by monocyte-derived dendritic cells (DCs). In response to sulfatide and b-GalCer, monocytes develop into immature DCs with higher expression of HLA-DR and CD86 but lower expression of CD80, CD40 and CD1a and lower production of IL-12 compared to non-modulated DCs. Self-glycolipid-modulated DCs responded to lipopolysaccha- ride (LPS) by changing phenotype but preserved low IL-12 production. Sulfatide, in particular, reduced the capacity of DCs to stimulate autoreactive Glutamic Acid Decarboxylase (GAD65) - specific T cell response and promoted IL-10 production by the GAD65-specific clone. Since sulfatide and b-GalCer induced toll-like receptor (TLR)-mediated signaling, we hypothesize that self-glycolipids deliver a (tolerogenic) polarizing signal to differentiating DCs, facilitating the maintenance of self- tolerance under proinflammatory conditions.
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Histone deacetylase inhibitors impair the elimination of HIV-infected cells by cytotoxic T-lymphocytes.

Histone deacetylase inhibitors impair the elimination of HIV-infected cells by cytotoxic T-lymphocytes.

We propose that the net effects of HDACi treatment on HIV- specific T-cells in the majority of our functional assays involved contributions from both of these modes of suppression, particularly in the case of romidepsin. For example, the impaired abilities of romidepsin-treated CTL to eliminate HIV-infected target cells over 16 hour co-cultures likely resulted both from rapid suppres- sion of CTL function (CTL are capable of killing target cells within 2–10 minutes [46–48]) as well as apoptosis at later time-points post-exposure. This is supported by the observed exacerbation of this impairment following a 14 hour romidepsin wash-out period (Fig. 7). This is also directly visualized in Fig. 8A, and Supporting Movie S3. Here, following romidepsin treatment, apoptotic CTL are visible, but a CTL also remains viable (excludes sytox dye) throughout the 5:34 (h:mm) imaging, while failing to kill a target cell that it engages from 1:03 to 2:26. These two modes of HDACi-induced CTL impairment – inhibition of function in viable T-cells and reduction in T-cell viability (with the former leading to the latter in some cases) – have the potential to have different impacts in a therapeutic setting. It may be possible to mitigate the impact of transient CTL impairment on flush-and- kill eradication strategies by designing dosing schedules that target a temporal therapeutic window, whereby either HIV antigen expression occurs before CTL are substantially impaired, or persists while CTL are given time to functionally recover. A better understanding of the kinetics and durability of HIV antigen presentation from reactivated latently-infected cells is required to evaluate the plausibility of this approach. On the other hand, losses in viability of activated CTL, as we observed in vitro with romidepsin and, to a lesser extent, panobinostat, could result in an irreversible impairment of virus-specific cellular immune respons- es, particularly if HIV-specific T-cell responses are primed first, for example by therapeutic vaccination. Thus, our data suggest that the potential for a given HDACi to impair CTL function both in the first few hours of treatment when viability is intact, and over longer time-lines by the gradual induction of cell death should be considered in designing flush-and-kill approaches.
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Determination Of Longevity Of Teeth In Buckets Of Loading Equipment In Coal Mines - A Case Study

Determination Of Longevity Of Teeth In Buckets Of Loading Equipment In Coal Mines - A Case Study

Abstract: The life of bucket teeth in shovel and dragline deployed in handling of overburden rock is an important contributor to the stores cost and is also responsible for the loss of valuable availability and utilisation time of these critical equipment. To ascertain the effect of rock type on longevity of bucket teeth, a study has been conducted in two large opencast mines of Singrauli Coalfields. The results of this study is presented in this paper. There was a significant variation as compared to the actual figures of the mine, it establish useful relationship between the type of mineral present in the overburden and the life of bucket teeth of shovel and dragline.
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A Method To Find The Area Of Sector Without The Usage Of Angle Made By The Chord

A Method To Find The Area Of Sector Without The Usage Of Angle Made By The Chord

As we know that to find the area of sector the angle made by the chord (that is chord which divides the circle) is required. But in the below method we find the ratio of the segments of the circle. Thus by relating the area of segment to the area of sector the area of sector could be found. The ratio of area of segments is related to tangents that are drawn through diameter on either side.

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The Influence Of CSR Awareness On Consumer Purchase Decision Of A Telecommunication Network In Ghana A Case Of La Nkwantanag Madina Municipality

The Influence Of CSR Awareness On Consumer Purchase Decision Of A Telecommunication Network In Ghana A Case Of La Nkwantanag Madina Municipality

on overall company evaluations‖. Murray and Vogel (1997) have investigated the effect of associated CSR practices on consumers and presented similar findings. The CSR activities mentioned in the research are, for instance, environmental protection practices (energy conservation), engagement in acts to promote human welfare, corporate social marketing (electric safety education for schoolchildren), contribution to the economic development of the region, and consumer protection program. Their research found that CSR programs lead to improved customer attitudes towards the firm, including beliefs about the company‘s honesty, consumer responses, and increased support for the firm in labor or government disputes. Mohr et al. (2001) conducted a consumer interview project for investigating the impact of firms‘ CSR on consumer behavior. How well are consumers aware of the CSR level of individual firms? Are the purchase decisions of consumers affected by a firm‘s CSR, and how much? How do consumers think about firms‘ motivation for being socially responsible? Mohr et al. (2001) found that consumers are positive to business in general. It is not wrong to pursue economic interests. Consumers expect firms to be socially responsible. The attitudes of consumers toward socially responsible firms are more positive than toward irresponsible firms. Consumers are aware that socially responsible firms are helping themselves by practicing CSR. But this perception of consumers does not harm the positive consumer evaluations toward socially responsible firms. The study of Mohr et al. (2001) is enlightening for researchers, managers and policy makers. For managers specifically, it is clear that consumers do care about a firm‘s CSR and act accordingly. Some consumers are highly ethical in
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Assessment Of Some Acceleration Schemes In The Solution Of Systems Of Linear Equations.

Assessment Of Some Acceleration Schemes In The Solution Of Systems Of Linear Equations.

Many practical problems can be reduced to systems of linear equations Ax = b, where A, b are known matrices and x is a vector of unknowns. Systems of linear equations play a prominent role in economics, engineering, physics, chemistry, computer science and other fields of Pure and Applied Sciences [2]. A solution to a system of linear equations is a set of numerical values ….. that satisfies all the equations in a system [1]. There are two classes of iterative methods [3]: linear stationary and linear nonstationary. The stationary iterative methods are the Jacobi, Gauss-Seidel and SOR and Nonstationary include Krylov subspace methods: Conjugate Gradient, Minimal Residual, Quasi-Minimal Residual, Generalizes Minimal Residual and Biconjugate gradient methods. The choice of a method for solving linear systems will often depend on the structure of the matrix A. According to [8] ideally, iterative methods should have the property that for any starting vector , it converges to a solution Ax = b. [5] is of the view that examination of the Jacobi iterative method shows that in general one must save all the components of the vector while computing the components of the vector for an iterative method. According to Hadjidimos [6], the first step in the construction of solution of stationary iterative methods usually begins with splitting of matrix A. Thus, A = M – N where det M and M is easily invertible so that A = b is equivalent to = T + C , where T = and C = giving the iterative scheme = T + C , (k = 0,1,2……). [2] noted that for systems of linear equation A the splitting matrix may be chosen in a different way; that is, one can split matrix A as A = D L U where D is the diagonal matrix, L and U are strictly lower and strictly upper triangular matrices respectively. In solving the systems of linear equations Ax = b, therefore, we consider any convergent method which produces a sequence of iterates { [7] .Quite often the convergence is too slow and it has to be accelerated. According to [9] to improve the convergence rate of the basic iterative methods, one may transform the original system A = b into the preconditioned form PA = Pb, where � is called the preconditioned or a preconditioning matrix. Convergent numerical sequences occur quite often in natural Science and Engineering. Some of such sequences converge very slowly and their limits are not available without suitable convergent acceleration method. Some known acceleration schemes are: Chebyshev Extrapolation scheme [4] and residual Smoothing.
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CONTINUOUS CREATION IN THE PROBABILISTIC WORLD OF THE THEOLOGY OF CHANCE

CONTINUOUS CREATION IN THE PROBABILISTIC WORLD OF THE THEOLOGY OF CHANCE

I think we can answer this question in the positive: Yes, He can, because He is the most perfect being and His omnipotence is absolutely unlimited. A very important premise underlying the answer to the last question is that the risk is not so great, or even that it is very small. It is so because the nature and mechanism of the created world ensure with a very high proba- bility that all purposes intended by God will be attained without his causal action in the processes occurring in the world. The emergence of life in the universe is almost inevitable, because the universe is large and old enough, and biochemical mechanisms are very effective. The emergence of sentient beings was also almost inevitable because of longstanding and countless mutations and adaptations of living organisms to their environment. All this was very probable and hence in a sense necessary (inevitable). The great advantage of the non-deterministic world is its own creativity, which is possible because of the chance events happening in a way restricted only by the laws of nature. Thus, if one evolutionary path fails another one is opened. Perhaps a mutation suitable for the growth and development of a given species happened by chance and enabled it to survive in hard con- ditions and further develop. Elasticity and redundancy are very typical for the world of chance, but because of these properties, this world has a large number of possibilities and abilities to develop and regenerate after various natural catastrophes (Łukasiewicz 2006).
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The Economics of Sub-optimal Policies for Traffic Congestion

The Economics of Sub-optimal Policies for Traffic Congestion

Economic theory prescribes a (pigouvian) congestion tax in order to alleviate the negative effects of traffic congestion. It is simply a matter of internalizing a negative externality. However, traffic congestion is a pervasive problem in cities across the world, and a congestion tax is seldom applied. This paper tries to understand why this is the case. In order to do so, we estimate the welfare and traffic effects of alternative policies to be applied to the city of Sao Paulo; a congestion charge and a rotation system (or license plate restriction). With a dataset containing information on origin, destination and mode choice, we estimate a individual demand model for transportation mode. These demands are in turn used to run counter-factuals to evaluate the welfare costs of both policies. The results show that the congestion tax performs better than the rotation system in terms of aggregate welfare, but the distribution of these losses are very distinct. The congestion tax negatively affects a larger number of people with lower intensity than the rotation. Plus, the rotation system concentrates the heavier losses in an even smaller group, and thas little or no effect on driving decisions of those who owns more than one car. These results support the argument that the rotation system is chosen since it affects less people and causes little or no welfare loss on the richer portion of the population.
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An Analysis Of The Difference In Gender Level Of Cassava Production And Access To Land In Abia State Nigeria

An Analysis Of The Difference In Gender Level Of Cassava Production And Access To Land In Abia State Nigeria

technique was employed in sample selection. In the first stage, the three agricultural zones in the state were purposively selected. Aba, Umuahia and Ohafia. In the second stage three local governments actively involved in agricultural production was purposively selected from each of the agricultural zone making it a total of nine blocks. While In the third stage two communities was randomly selected from each of the local government. Twelve respondents was randomly selected from two sampling group. six each for male and female giving twelve respondents from each cell. A total of 218 respondents was selected for the study. The research instrument used for this study was structured questionnaire and scheduled interview. The result of the objective of the study was analyzed using descriptive statistics such as frequency, percentage, and mean inferential which involves the use of Z-test analysis. The formula used to compute the mean used in this study is specified below. The mean was computed by multiplying the frequency (f) of the responses under each response category by assigned value and dividing the (∑) of the product by the (N) no of respondents to the particular indicator as shown:
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Application of time-series analysis for prediction of molding sand properties in production cycle

Application of time-series analysis for prediction of molding sand properties in production cycle

The basic model used for residual data was simple linear mul- tivariate regression. However, for the 10 cases with largest pre- diction errors, also a regression tree model, based on the C&RT algorithm [8], was utilized. The regression trees are non- parametric, non-linear models which are particularly suitable for small data sets with unknown characteristics. Because of the small number of records for the daily based data, the regression tree algorithm was set to keep only 2 records in a leave. The prediction results were compared with those obtained from the linear model.
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The Existence Of Leading Islands Securing And The Border Areas Unitary State Of Indonesia An Analysis In Law Perspective

The Existence Of Leading Islands Securing And The Border Areas Unitary State Of Indonesia An Analysis In Law Perspective

Abstract: The research was carried with the aim to discover the existence of securing the foremost islands and state border region of the Republic of Indonesia reviewed from a legal perspective, which is directly related to the existence of security and dispute resolution methods as well as the governance of the foremost islands and border region in Kalimantan which bordering Malaysia. This study was conducted in Nunukan district and the surrounding provinces of Kalimantan, in this research method that used is normative legal analysis data with juridical and qualitative descriptive approach. The results showed that the security of foremost islands and border region of law perspective in accordance with the Law No. 34 of 2004 regarding the Indonesian National Army has not been implemented to the fullest to realize the security of foremost islands and border region as the frontline of the Republic of Indonesia. The existence of leading islands securing and the border region of the Republic of Indonesia still contain many weaknesses in terms of both governance and security.
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Assessment Of NPK In Human Male And Female Urine For Its Fertilising Potential In Agriculture

Assessment Of NPK In Human Male And Female Urine For Its Fertilising Potential In Agriculture

discharge into water is reduced by about 60% irrespective of the type of treatment [10]. Pure urine is sterile but there is the likelihood of cross-contamination with the use of urine separating (Ecosan) toilets [28]. According to Jönsson et al. (2000) separated urine contains a greater part of the total nutrients in normal sewage; 80% of N, 55% of P, and 60% of K in just 1.5% of the volume of the sewage. According to Rheiberger (1936), there are comparable levels of creatine, urea and ammonia nitrogens in urine among primates such as man, mangabeys, baboons and chimpanzees. However, he identified sex differences in creatinine nitrogen coefficients of the male mangabeys, baboons and chimpanzees to be higher than those in the female counterparts. In small cases there was reversal of the magnitude seen in the macaques species precluding an assumption as to the validity of the observation. In analysing sex differences in urine with respect to lysine and α - amino nitrogen, the mean excretion of α - amino nitrogen whether ―total,‖ ―free,‖ or ―bound,‖ was higher for females than for males [22]. Thus, it is possible that the higher rate of amino acid excretion observed in females might be correlated with the sexual cycle, although no evidence of this was observed in the case of the four amino acids studied by Thompson and Kirby (1949) when samples from the same subjects were taken at various stages of the menstrual cycle. The influence of sex (gender) on the level of NPK in human urine has received no attention. Therefore, there is a need to study the effect from the Ecological Sanitation (ECOSAN) perspective, especially under local conditions. This is because gender ECOSAN urinals are going to spring up with the advent of industries and ECOSAN concepts, especially in the developing countries. The use of urine in agriculture has been studied in countries such as Sweden, Germany, Switzerland, South Africa, Burkina Faso and Nigeria. In all these studies, the fertilizing ability of human urine was established as being comparable to that of chemical fertilizers, such as 21% N ammonia. However, in Ghana little U
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Managament quality of tools in the planned housing casting

Managament quality of tools in the planned housing casting

Subbotko, Methods of distribution of tool at units based on TM software of Guhring, Production Engineering Wroc ł aw University of Technology,(2006) 273- 280 (in Polish).. Bocheński, C[r]

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The Impact of the Expansion of the Bolsa Familia Program on the Time Allocation of Youths And Their Parents Lia Chitolina Miguel Nathan Foguel Naercio Menezes-Filho

The Impact of the Expansion of the Bolsa Familia Program on the Time Allocation of Youths And Their Parents Lia Chitolina Miguel Nathan Foguel Naercio Menezes-Filho

As the multinomial model is non-linear, the marginal effect of the treatment in a DID model is not the marginal impact of the interaction between time and treatment, but the difference of the cross-differences, as described by Puhani (2012). The results of Table 7 (in terms of marginal effects) show that the BVJ has a significant effect on the probability studying and working at the same time, but not on the other outcome variables. The estimated marginal effects mean that the probability of a youngster studying and working increases by 4.2 percentage points with the BVJ, compared with a baseline of 30% in the control group in 2006. The estimated coefficients for the categories ‘studying only’ and ‘working only’ were negative but not statistically significant. It seems, therefore, that treated adolescents do not quit their jobs to study because of the program, but do both activities at the same time. This raises questions about the long run impacts of the program, since the quality of the night classes is notoriously low in Brazil.
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