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Asian sand dust (ASD), a significant desert sand dust, contains sub-2.5 µm fine particles and adversely affects human health, particularly exacerbating respiratory diseases. Despite this, the intricate physiological responses triggered by inhaled ASD particles remain incompletely understood. This study aimed to comprehensively examine the respiratory effects of ASD, focusing on the spatial distribution of inhaled ASD fine particles within the lungs and the immediate physiological responses they incite. Intratracheal administration of ASD fine particles in mice resulted in efficient phagocytosis by alveolar macrophages (AMs), leading to subsequent neutrophilic inflammation. A subset of ASD-phagocytosed AMs underwent necroptosis, releasing interleukin-1α (IL-1α), causing an increase in chemokines and neutrophils. These responses occurred rapidly within hours of exposure, with endotoxin in ASD particles contributing to the process. Despite variations in desert sand dust composition based on collection locale and timing, this study’s findings provide a foundational basis for understanding the biological effects of desert sand dust. Insights gained into the biological responses to desert sand dust hold promise for developing preventive measures such as air purifiers, and therapeutic agents such as IL-1α neutralizing antibodies, antibacterial agents and cell death inhibitors for human diseases associated with such environmental exposures.

Several empirical studies have linked subway and ambient particle exposure to toxicity, pro-inflammatory responses, and vascular dysfunction. However, the health effects of pollutants generated from varying sources, particularly when combined with lipopolysaccharide (LPS), are still unexplored. Therefore, the aim of this study was to investigate the characteristic health effects of iron oxide particles (the main components of subway particles) in comparison with urban aerosols (UA) and vehicle exhaust particles (VEP), alone and in combination with LPS. This study revealed that iron oxides caused a more significant reduction in human umbilical vein endothelial cell viability, increased lactate dehydrogenase release, and decreased the production of plasminogen activator inhibitor-1, a fibrinolytic modulator, and endothelin-1, a vasoconstrictor, compared to those by VEP and UA at marginally toxic and toxic concentrations. While VEP and UA induced an increase in interleukin (IL)-6 production, iron oxides, particularly Fe3O4, increased IL-8 production at slightly toxic and non-cytotoxic concentrations. In addition, co-exposure of all particles and LPS at non-cytotoxic concentrations promoted pro-inflammatory cytokine (IL-6 and IL-8) production relative to exposure to the particles alone. Interestingly, the tendency towards either coagulation or fibrinolytic conditions was dependent on the concentration of exposed particles at the same LPS concentration. Furthermore, increases in inflammation, neutrophil and lymphocyte recruitment around blood vessels, and edema were observed in murine lungs exposed to a combination of iron oxides and LPS compared to those in mice exposed to iron oxide alone. Thus, iron oxide-rich subway particulate poses more health risks than outdoor ambient particles since they can significantly impair endothelial function, particularly through gross cellular and vascular homeostatic protein damage, and induce exacerbated inflammatory responses during co-exposure. These findings provide novel empirical evidence for epidemiological studies seeking mechanisms responsible for the observed health impact of transport- and occupational-related exposures on vascular dysfunction.

Abstract Diesel exhaust particles (DEPs) are very small (typically

Abstract The air quality in Upper Northern Thailand (UNT) deteriorates during seasonal vegetation fire events, causing adverse effects especially on respiratory health outcomes. This study aimed to quantitatively estimate respiratory morbidity from vegetation fire smoke exposure, and to assess the impact of a burning ban enforced in 2016 on morbidity burden in UNT. We computed daily population exposure to fire-originated PM10 and estimated its health burden during a 5-year period from 2014 to 2018 using daily fire-originated PM10 concentration and the concentration–response function for short-term exposure to PM10 from vegetation fire smoke and respiratory morbidity. In subgroups classified as children and older adults, the health burden of respiratory morbidity was estimated using specific effect coefficients from previous studies conducted in UNT. Finally, we compared the health burden of respiratory morbidity before and after burning ban enforcement. Approximately 130,000 hospital visits for respiratory diseases were estimated to be attributable to fire-originated PM10 in UNT from 2014 to 2018. This estimation accounted for 1.3% of total hospital visits for respiratory diseases during the 5-year period, and 20% of those during burning events. Age-specific estimates revealed a larger impact of PM10 in the older adult group. The number of hospital visits for respiratory diseases attributable to fire-originated PM10 decreased from 1.8% to 0.5% after the burning ban policy was implemented in the area. Our findings suggest that PM10 released from vegetation fires is a health burden in UNT. The prohibition of the burning using regulatory measure had a positive impact on respiratory morbidity in this area.

Measures for protecting against PM2.5 (particulate matter with aerodynamic diameters ≤2.5 µm), which exacerbates respiratory diseases, have not been established. The present study investigated the effects of extracts of curry powder and its components on pro-inflammatory responses, extracellular and intracellular reactive oxygen species (ROS) production, induced by the PM2.5 component, DEP (diesel exhaust particles). Airway epithelial cells were exposed to DEP in the presence of curry powder, or its major and/or anti-inflammatory components, clove and turmeric. Curry powder, clove, and turmeric inhibited DEP-induced IL-6 release and extracellular ROS; in the absence of clove and turmeric, these effects of curry powder were mild but similar. Among the other curry spices, cinnamon decreased IL-6 and extracellular ROS, and coriander decreased IL-6 alone. This is the first report on the protective effects of extracts of curry powder and its components, against PM2.5-induced airway inflammation, which may be partly through inhibition of extracellular ROS.

Although polycyclic aromatic hydrocarbons (PAHs) are toxic, the effects of oxidized PAHs on health and biological responses remain unclear. In this study, we examined the in vitro effects of varying concentrations of pyrene, a type of PAH, and its quinone forms, namely 4,5-pyrenequinone (PyQ) and 1,8-PyQ + 1,6-PyQ, on human lung epithelial (BEAS-2B) cells. We evaluated cell viability, apoptosis, and the production of interleukin (IL)-6, IL-8, soluble intercellular adhesion molecule-1 (sICAM-1), and reactive oxygen species (ROS). Exposure to 1 μM 4,5-PyQ or 1,8-PyQ + 1,6-PyQ increased the cellular activity. At 3 µM, 4,5-PyQ increased the number of late apoptotic and/or necrotic cells compared with those in the control, whereas 1,8-PyQ + 1,6-PyQ increased the number of dead cells. Exposure to 4,5-PyQ at 10 µM decreased IL-6 production and exposure to both 4,5-PyQ and 1,8-PyQ + 1,6-PyQ at 3 or 10 µM decreased IL-8 production. sICAM-1 production was increased after 1,8-PyQ + 1,6-PyQ exposure at 10 µM. In the presence of cells, 4,5-PyQ and 1,8-PyQ + 1,6-PyQ increased ROS production significantly in a concentration-dependent manner; similar results were observed with 1,8-PyQ + 1,6-PyQ without cells. Overall, our results suggest that oxidized PAHs induce stronger respiratory toxicity/inflammatory responses than PAHs.

Genotyping evidence that supports the interruption of endemic measles virus (MV) transmission is one of the essential criteria to be verified in achieving measles elimination. In Japan since 2014, MV genotype analyses have been performed for most of the measles cases in prefectural public health institutes nationwide. With this strong molecular epidemiological data, Japan was verified to have eliminated measles in March, 2015. However, even in the postelimination era, sporadic cases and small outbreaks of measles have been detected repeatedly in Japan. This study investigated the nationwide molecular epidemiology of MV between 2008 and 2017. The 891 strains in the total period between 2008 and 2017 belonged to seven genotypes (D5, D4, D9, H1, G3, B3, and D8) and 124 different MV sequence variants, based on the 450-nucleotide sequence region of the N gene (N450). The 311 MV strains in the postelimination era between 2015 and 2017 were classified into 1, 7, 8, and 32 different N450 sequence variants in D9, H1, B3, and D8 genotypes, respectively. Analysis of the detection period of the individual N450 sequence variants showed that the majority of MV strains were detected only for a short period. However, MV strains, MVs/Osaka.JPN/29.15/ [D8] and MVi/Hulu Langat.MYS/26.11/ [D8], which are named strains designated by World Health Organization (WHO), have been detected in many cases over 2 or 3 years between 2015 and 2017. The WHO-named strains have circulated worldwide, causing outbreaks in many countries. Epidemiological investigation revealed repeated importation of these WHO-named strains into Japan. To demonstrate the elimination status (interruption of endemic transmission) in situations with repeated importation of the same strains is challenging. Nevertheless, the detailed sequence analysis of individual MV strains and chronological analysis of these strains provided sufficient evidence to show that Japan has still maintained its measles elimination status in 2017.

Background: The elderly population has been the primary target of intervention to prevent heat-related illnesses. According to the literature, the highest risks have been observed among the elderly in the temperature–mortality relationship. However, findings regarding the temperature–morbidity relationship are inconsistent. Objectives: This study aimed to examine the association of temperature with ambulance dispatches due to acute illnesses, stratified by age group. Specifically, we explored the optimum temperature, at which the relative health risks were found to be the lowest, and quantified the health risk associated with higher temperatures among different age groups. Methods: We used the data for ambulance dispatches in Fukuoka, Japan, during May and September from 2005 to 2012. The data were grouped according to age in 20-year increments. We explored the pattern of the association of ambulance dispatches with temperature using a smoothing spline curve to identify the optimum temperature for each age group. Then, we applied a distributed lag nonlinear model to estimate the risks of the 85th–95th percentile temperature relative to the overall optimum temperature, for each age group. Results: The relative risk of ambulance dispatches at the 85th and 95th percentile temperature for all ages was 1.08 [95% confidence interval (CI): 1.05, 1.12] and 1.12 (95% CI: 1.08, 1.16), respectively. In comparison, among age groups, the optimum temperature was observed as 25.0°C, 23.2°C, and 25.3°C for those aged 0–19, 60–79, and ≥80, respectively. The optimum temperature could not be determined for those aged 20–39 and 40–59. The relative risks of high temperature tended to be higher for those aged 20–39 and 40–59 than those for other age groups. Conclusions: We did not find any definite difference in the effect of high temperature on ambulance dispatches for different age groups. However, more measures should be taken for younger and middle-aged people to avoid heat-related illnesses.

Family caregivers of patients with terminal-stage cancer have numerous roles as caregivers, which can influence their anticipatory grief. The purpose of this study was to clarify how talking to family caregivers of patients with terminal illness using the narrative approach can influence such caregivers’ process of anticipatory grief. We conducted the narrative approach as an intervention with two family caregivers several times and qualitatively analyzed their narratives. The results indicated that these family caregivers had two primary roles—family member and caregiver—and that family caregivers felt trapped in their caregiver role. The narrative approach helped them transition into the role needed for coping with the loss.

Patients with marked calcification of the basal ganglia and cerebellum have traditionally been referred to as having Fahr’s disease, but the nomenclature has been criticized for including heterogeneous etiology. We describe 3 patients with idiopathic bilateral striatopallidodentate calcinosis (IBSPDC). The patients were a 24-year-old man with mental deterioration, a 57-year-old man with parkinsonism and dementia, and a 76-year-old woman with dementia and mild parkinsonism. The former 2 patients showed severe calcification of the basal ganglia and cerebellum, and the latter patient showed severe calcification of the cerebellum. We found significantly increased levels of copper (Cu), zinc (Zn), iron (Fe) and magnesium (Mg), using inductively coupled plasma mass spectrometry in the CSF of all these 3 patients. The increased levels of Cu, Zn, Fe and Mg reflect the involvement of metabolism of several metals and/or metal-binding proteins during the progression of IBSPDC. More numerous patients with IBSPDC should be examined in other races to clarify the common mechanism of the disease and to investigate the specific treatment.

Hydrographic network maps produced by government institutions have been used to delimit Permanent Preservation Areas (PPAs) in Brazil. However, problems arising from discrepancies between those maps and field survey are frequent. To characterize and quantify such discrepancies, whether methodological or due to the scale of the maps or temporal changes, we mapped the springs and watercourses in five rural properties (adding up to 10,860 ha, in the municipalities of Brotas and Ribeirão Bonito, SP). Those maps were then compared with the regional hydrographic network mapped by IBGE and IGC. We verified, for the study area, an oversizing of 157% in the number of springs and 83% in the length of watercourses by IBGE, and 209% in the number of springs and 84% in the length of watercourses by IGC. Consequently, there was an oversizing of PPAs. We therefore consider that such maps can be used as an approximate reference for the hydrographic network, although they cannot provide a basis for legal decisions or environmental planning if they are not duly corrected by field verification. [ABSTRACT FROM AUTHOR]

This study examined the effects of high-impact and low-repetition jump training on the tibia bone and calcium and phosphorus-related factors in rats fed a phosphorus enriched diet. Forty-two male Wistar rats were assigned to four groups: normal diet sedentary control group; normal diet jump exercise group; high-phosphorus diet sedentary control group, and high-phosphorus diet jump exercise group. Rats in the two exercise groups underwent jump exercise for 2 wks. Data are presented as means ± SD. Two-way (diet x exercise) ANOVA and three-way ANOVA (diet x exercise x time points) were used. There was a significant positive exercise main effect on bone mineral content and bone mineral density of the tibia without any significant dietary main effect and interaction. Serum osteocalcin showed a significant exercise main effect and significant interaction. Serum inorganic phosphorus and fibroblast growth factor 23 were markedly increased by the high-phosphorus diet and suppressed by exercise. Serum total calcium was decreased by exercise. The results indicate that high-impact exercise has the potential not only to create local bone, but also to change calcium and phosphorus metabolism even under a high phosphorus diet. [ABSTRACT FROM AUTHOR]

This study examined the relationship between neurobehavioral changes and alterations in gene expression profiles in the brains of mice exposed to different levels of Hg0 during postnatal development. Neonatal mice were repeatedly exposed to mercury vapor (Hg0) at a concentration of 0.057 mg/m³ (low level), which was close to the current threshold value (TLV), and 0.197 mg/m³ (high level) for 24 hr until the 20th day postpartum. Behavioral responses were evaluated based on changes in locomotor activity in the open field test (OPF), learning ability in the passive avoidance response test (PA), and spatial learning ability in the Morris water maze (MM) at 12 weeks of age. No significant differences were observed in the three behavioral measurements between mice exposed to the low level of Hg0 and control mice. On the other hand, total locomotive activity in mice exposed to the high level of Hg0 was significantly decreased and central locomotion was reduced in the OPF task. Mercury concentrations were approximately 0.4 μg/g and 1.9 μg/g in the brains of mice exposed to the low and high levels of Hg0, respectively. Genomic analysis revealed that the expression of 2 genes was up-regulated and 18 genes was down-regulated in the low-level exposure group, while the expression of 3 genes was up-regulated and 70 genes was down-regulated in the high-level exposure group. Similar alterations in the expression of seven genes, six down-regulated genes and one up-regulated gene, were observed in both groups. The results indicate that an increase in the number of altered genes in the brain may be involved in the emergence of neurobehavioral effects, which may be associated with the concentration of mercury in the brain. Moreover, some of the commonly altered genes following exposure to both concentrations of Hg0 with and without neurobehavioral effects may be candidates as sensitive biomarker genes for assessing behavioral effects in the early stages of development. [ABSTRACT FROM AUTHOR]

Abstract  The frequency per week or day of high-impact, low-repetition jump exercise for osteogenic response was assessed by two experiments. In the first experiment, 48 11-week-old rats were randomly divided into five groups: a sedentary control (W0: n = 8), one exercise session per week (W1: n = 10), three exercise sessions per week (W3: n = 10), five exercise sessions per week (W5: n = 10), and seven exercise sessions per week (W7: n = 10). In the second experiment, 30 11-week-old rats were randomly divided into three groups: a sedentary control (D0: n = 10), one exercise session per day (D1: n = 10), and two exercise sessions per day (D2: n = 10). One exercise session consisted of 10 continuous jumps. After 8 weeks of the exercise period, the jump exercise increased the fat-free dry weight of the tibia in the W1 (7.5%, n.s.), W3 (12.6%, P P P P P [ABSTRACT FROM AUTHOR]

Abstract  Jump exercise in rats creates high-impact loading on lower limbs and results in the promotion of osteogenesis. Although we clarifi ed that a few loadings per day could increase bone mass and strength within 8 weeks, we did not observe an osteogenic response at the onset of the training period. The purpose of this study was to clarify whether the bone formation rate measured by the double-label immunofluorescence method increases with a few loadings for a short period. Forty female Wistar rats, 10 weeks old, were divided into a control group and three exercise groups: the 10 jumps/day (10 J) group, 40 jumps/day (40 J) group, and 100 jumps/day (100 J) group. The exercise groups were trained on days 1, 3, and 5, the fluorescent labels were injected on days 5 and 12, and the experiment ended on day 16. The bone formation rates were greater in all exercise groups compared with the control group and were significantly greater in the 40 J and 100 J groups than in the 10 J group. These data show that only 10 repetitions/day loading promotes the osteogenic response within a short period from the onset of the training. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) is a toxic heavy metal that has been shown to induce vascular diseases, such as atherosclerosis. We used DNA microarray to monitor the transcriptional response of human coronary artery endothelial cells (HCAEC) to a non-lethal dose of Cd (10 µM). Out of 35,035 human genes, Cd enhanced the expression of 3 metallothionein (MT)-I subisoform genes, including MT1E, MT1H and MT1B, and reduced the expression of 12 genes, including ISG20 and TK1, 2-fold or greater. [ABSTRACT FROM AUTHOR]

To examine the contribution of metallothionein (MT) to mercury accumulation in mouse tissues, 129 strain female mice and MT null mice were exposed to metallic mercury vapor at a sub-toxic level, and Hg levels in the brain, kidney and liver were determined on 1, 3 and 7 days after the exposure. After exposure to mercury vapor, significant Hg accumulation was observed in the brains of wild-type and MT-I/II null and MT-III null mice, as well as in the liver and kidneys. No strain difference was observed in the tissue Hg accumulations 24 hr after the exposure except for the kidneys, where the highest accumulation was found in MT-III null mice. Although the brains of MT-III null mice showed slightly higher Hg accumulation than the other two strains, no significant difference was observed except in the cerebrum on Day 7. Gel chromatograms of cerebrum soluble fractions revealed that a significant amount of Hg existed as an MT-bound form in all the mouse strains. On the other hand, MT-bound Hg was found as a minor fraction in soluble fractions of the kidneys and livers in wild-type and MT-III null mice. Despite a significant strain difference in total MT levels in the cerebrum, there was no difference among the three strains in the amount of Hg accumulated in the cerebrum and its distribution rates in MT fractions. The present study demonstrated that brain uptake of Hg0 and its accumulation as Hg2+ did not depend on the amount of MT isoform in the tissue, at least in the early phase. [ABSTRACT FROM AUTHOR]

In order to elucidate the transcriptional response of kidney epithelial cells to cadmium, the gene expression pattern was examined in normal rat kidney epithelial cells (NRK-52E cells) exposed to 50 μM cadmium for 4 hr using DNA microarray. Cadmium was found to increase the expression of 73 genes and decrease the expression of 42 genes in NRK-52E cells before the development of cytotoxicity. [ABSTRACT FROM AUTHOR]

A restauração de florestas ciliares temsido recomendada como a melhor estratégiavisando à proteção dos recursos hídricos e àrecuperação da biodiversidade. No entanto, quasenada se conhece sobre o papel hidrológico dasflorestas plantadas e seus efeitos protetores.O presente estudo teve como objetivo analisarcomparativamente alguns modelos de plantio demata ciliar em região de cerrado, para verificar sediferem quanto ao seu papel na interceptação daágua das chuvas e em sua influência na umidadedo solo, com reflexos sobre a função protetora dafloresta. Foram coletados, durante cinco meses,dados pluviométicos no interior de quatro modelosde plantio aos dezessete anos (um plantio mistocom espécies de cerrado e três plantios puros,com Pinus elliottii, Tapirira guianensis eAnadenanthera falcata) e em área aberta paracomparação. Para análises de umidade, foramcoletadas amostras compostas da camada superficialdo solo (0 a 20 cm) em cada uma das parcelas.Houve variação na porcentagem da água daschuvas interceptada pelas copas entre os diferentesmodelos, com o maior valor no plantio puro deTapirira guianensis (30,8%), espécie latifoliadaperenifólia e com a maior densidade de árvores.No outro extremo, o plantio de Anadenantherafalcata, uma espécie caducifólia de folhas muitopequenas, reteve apenas 12,5% da água daschuvas. A umidade do solo, como era esperado,foi inversamente proporcional à interceptação.Não se observou correlação entre a biomassaflorestal e a interceptação ou umidade do solo.Riparian forest restoration has beenreported as the most efficient strategy to protectwater resources and to recover biodiversity.However, few is known about the hydrologicalfunctioning of the planted forests and theirprotective effect. Some different riparian forestrestoration models were analized 17 years afterplanting, to verify the hypothesis that differentforest structure and composition are correlated todifferent hydrological processes. Rain interceptionalong five months and soil humidity (0-20 cm)were analyzed under a mixed stand with nativespecies, three pure stands (Pinus elliottii, Tapiriraguianensis and Anadenanthera falcata) and alsoin an open area (control). The highest interceptionrate (30.8%) was observed in the pure stand ofTapirira guianensis, which is evergreen and hasthe highest density. On the opposite, the deciduousstand of Anadenanthera falcata intercepted only12.5% of the precipitation. Soil humidity, as expected,was inversely proportional to the interception.No correlation was observed between basal area(biomass) and interception or soil humidity.

We compared the cadmium (Cd) concentration in the liver and kidney of different strains of mice after exposure to 50 ppm Cd for 30 days via drinking water. Cd concentration in the liver and kidney of C57BL/6J mice were higher than those of 129/Sv and DBA/2 mice. Since orally ingested heavy metals are absorbed in the small intestine and then widely distributed to target tissues, microarray analyses were performed to compare the expression levels of transport-related genes in the duodenum between C57BL/6J mice and 129/Sv or DBA/2 mice. The expression levels of 9 and 11 genes were elevated more than 2.0-fold and 13 and 12 genes were reduced less than 0.5-fold in 129/Sv mice and DBA/2 mice, respectively. Among these low expressed genes, 10 genes (Slc2a2, Slc5a1, Slc16a2, Slc22a13, Slc22a18, Slc25a11, Slc36a1, Slco6c1, Abca3 and Abcd1) were common between the two types of strains. These results suggest that some of those genes might be involved in Cd absorption and its toxicity. [ABSTRACT FROM AUTHOR]

Este trabalho apresenta os resultados de dois anos do monitoramento mensal das concentrações de sedimentos em suspensão, turbidez, cor aparente, oxigênio dissolvido e da temperatura das águas dos rios Paraibuna e Paraitinga, no Estado de São Paulo. Os valores médios encontrados para os dois rios foram, respectivamente - conyentração de sedimentos em suspensão: 13,0 mg.L- e 35,9 mgL1 ; turbidez: 20 FTU e 39 FTU; cor aparente: 95 UPC e 153 UPC; temperatura da água: l 7,2ºC e l 9,6ºC e oxigênio dissolvido: 9,3 mgL1 e 8,6 mg.L-1. Os maiores valores de sedimentos em suspensão, turbidez e cor na água do rio Paraitinga são indicadores de processos erosivos mais intensos nesta bacia hidrográfica. A diferença no uso e ocupação do solo é condição importante para estes resultados. A bacia hidrográfica do rio Paraitinga encontra-se ocupada majontariamente por pastagens desradadas, enquanto a bacia do rio Paraibuna esta melhor protegida por remanescentes de floresta natural. O clima mais quente, o maior tempo de residência da água na rede de canais da bacia e a ausência de matas ciliares contribuem para que as temperaturas da água sejam mais elevadas no rio Paraitinga. As maiores concentrações de oxigênio no rio Paraibuna são conseqüências das menores temperaturas da água e da maior capacidade de aeração, resultado de quedas d'água e corredeiras em grande quantidade ao longo do curso d'água.

RESUMO Embora exista uma crença generalizada de que plantar florestas aumenta a água dos rios e a quantidade de chuva, a ciência tem demonstrado que, na escala de microbacia hidrográfica: 1) a proporção da chuva anual que se torna recurso hídrico renovável é inversamente proporcional à biomassa arbórea e 2) mais floresta não significa mais chuva na mesma bacia. Ecossistemas naturais abertos como campos e savanas são, portanto, mais eficientes que florestas como geradores de recurso hídrico renovável e plantar árvores não aumenta a produção de água, embora melhore sua qualidade e contribua para regulação da vazão ao longo do ano. Uma vez preservados os ecossistemas naturais, adotar práticas de cultivo e conservação do solo que aumentem a infiltração da chuva em toda a bacia, trará contribuição maior do que o plantio de florestas para assegurar a vazão dos rios mesmo nos meses de estiagem, proporcionando os serviços ecossistêmicos dependentes dessa água.

ABSTRACT Competition for soil water is one of the major processes that drive the assembly of plant communities, particularly in regions subjected to long dry seasons. The relationship between plant density and soil water competition has strong, but poorly understood, practical implications for population dynamics, restoration and conservation. We planted seedlings of the pioneer legume tree Senegalia polyphylla in containers and assessed the effects of plant density on their resistance to water stress. We completely eliminated the above-ground parts (stem and shoots) of randomly selected plants at 60-days post-planting in order to create three different densities of seedlings. We saturated the soil of the remaining seedlings and then deprived them of additional water until all seedlings died. We assessed the time elapsed from water suppression to wilting and death of individual plants. We found a strong negative relationship between plant density and time to wilting or death. Seedlings survived water stress 80% longer when density was reduced by two-thirds. Planting in lower densities or reducing density by thinning should be considered as strategies to enhance resistance to water stress in drought-prone regions.