The last fifteen years have seen the application of the cancer stem cell hypothesis to tumors of the central nervous system,in particular to high grade glioma(HGG),the most aggressive and common brain cancer in adults...The last fifteen years have seen the application of the cancer stem cell hypothesis to tumors of the central nervous system,in particular to high grade glioma(HGG),the most aggressive and common brain cancer in adults.Seminal studies have shown that cancer stem cells(alternatively named tumor-initiating cells)are capable of self-renew and multipotency,similar to their normal counterpart.More importantly they give rise to tumors that closely mimic the phenotype and genotype of human HGG.The identification of neurogenic niches in adult rodent and human brain has further reinforced the hypothesis that HGG might derive from the malignant transformation occurring in these areas,especially in the sub-ventricular zone(SVZ),the largest and most well characterised stem cell niche.Following from evidence of animal model studies supporting this hypothesis,recently we investigated the role of the SVZ in neuro-oncogenesis using tissue material derived from HGG patients.We also described response to conventional chemo-therapies of cancer stem cells isolated from the SVZ and the tumor mass(T)of the same patients and reconstructed tumor evolution.In this review,such findings will be discussed in the context of the current literature on the biology of the SVZ in the normal and disease brain.展开更多
目的观察丹龙醒脑方对脑缺血再灌注模型大鼠侧脑室室管膜下区(SVZ)神经干细胞(NSCs)增殖与Hes1、Hes5表达的影响,探讨其促进内源性NSCs增殖的作用机制。方法将80只雄性SD大鼠随机分为假手术组、模型组、依达拉奉组(依达组)、丹龙醒脑方...目的观察丹龙醒脑方对脑缺血再灌注模型大鼠侧脑室室管膜下区(SVZ)神经干细胞(NSCs)增殖与Hes1、Hes5表达的影响,探讨其促进内源性NSCs增殖的作用机制。方法将80只雄性SD大鼠随机分为假手术组、模型组、依达拉奉组(依达组)、丹龙醒脑方组(丹龙组)。采用线栓法制备局灶性脑缺血再灌注模型,再灌注7 d后取缺血侧SVZ脑组织。Brdu免疫荧光法检测SVZ NSCs增殖,RT-q PCR、Western blot分别检测Hes1、Hes5 m RNA和蛋白的表达。结果与假手术组比较,其余各组Brdu阳性细胞率增加,Hes1、Hes5 m RNA及蛋白表达明显升高(P<0.01);与模型组比较,依达组、丹龙组Brdu阳性细胞率明显增加,Hes1、Hes5 m RNA及蛋白表达水平明显增强(P<0.01);丹龙组Hes1 m RNA表达水平优于依达组(P<0.01),其余指标均无明显差异。结论丹龙醒脑方可促进脑缺血再灌注后大鼠SVZ NSCs增殖,并上调Hes1、Hes5表达水平,其机制可能与激活Notch信号通路有关。展开更多
In this study, we investigated non-captive four-striped mice （Rhabdomys pumilio） for evidence that adult neurogenesis occurs in the adult brain of animal models in natural environment. Ki-67 （a marker for cell prol...In this study, we investigated non-captive four-striped mice （Rhabdomys pumilio） for evidence that adult neurogenesis occurs in the adult brain of animal models in natural environment. Ki-67 （a marker for cell proliferation） and doublecortin （a marker for immature neurons） immunos-taining conifrmed that adult neurogenesis occurs in the active sites of subventricular zone of the lateral ventricle with the migratory stream to the olfactory bulb, and the subgranular zone of the dentate gyrus of the hippocampus. No Ki-67 proliferating cells were observed in the striatum substantia nigra, amygdala, cerebral cortex or dorsal vagal complex. Doublecortin-immunore-active cells were observed in the striatum, third ventricle, cerebral cortex, amygdala, olfactory bulb and along the rostral migratory stream but absent in the substantia nigra and dorsal vagal complex. The potential neurogenic sites in the four-striped mouse species could invariably lead to increased neural plasticity.展开更多
The mechanisms that regulate neural stem cell(NSC)lineage progression and maintain NSCs within diffe rent domains of the adult neural stem cell niche,the subventricular zone are not well defined.Quiescent NSCs are arr...The mechanisms that regulate neural stem cell(NSC)lineage progression and maintain NSCs within diffe rent domains of the adult neural stem cell niche,the subventricular zone are not well defined.Quiescent NSCs are arranged at the apical ventricular wall,while mitotically activated NSCs are found in the basal,vascular region of the subventricular zone.Here,we found that ADAM 10(a disintegrin and metalloproteinase 10)is essential in NSC association with the ventricular wall,and via this adhesion to the apical domain,ADAM10 regulates the switch from quiescent and undiffe rentiated NSC to an actively prolife rative and differentiating cell state.Processing of JAMC(junctional adhesion molecule C)by ADAM 10 increases Rap1 GAP activity.This molecular machinery promotes NSC transit from the apical to the basal compartment and subsequent lineage progression.Understanding the molecular mechanisms responsible for regulating the proper positioning of NSCs within the subventricular zone niche and lineage progression of NSCs could provide new targets for drug development to enhance the regenerative prope rties of neural tissue.展开更多
目的评估单中心行大动脉调转术及主动脉弓重建一期矫治大动脉转位(transposition of the great arteries,TGA)或右心室双出口肺动脉瓣下室间隔缺损(Taussig-Bing)合并主动脉弓梗阻病变的手术疗效及预后。方法回顾性分析2011年1月到2021...目的评估单中心行大动脉调转术及主动脉弓重建一期矫治大动脉转位(transposition of the great arteries,TGA)或右心室双出口肺动脉瓣下室间隔缺损(Taussig-Bing)合并主动脉弓梗阻病变的手术疗效及预后。方法回顾性分析2011年1月到2021年12月,在广东省妇幼保健院进行动脉调转术和主动脉弓重建一期矫治的18例TGA或右心室双出口肺动脉瓣下室间隔缺损合并主动脉梗阻病变患者的术后近中期随访结果。结果18例患者均完成治疗,其中男14例,女4例。12例为右心室双出口肺动脉瓣下室间隔缺损,6例为TGA。主动脉弓部病变:主动脉缩窄14例,主动脉弓离断4例。患儿手术时的年龄为13(2~88)d,体质量为(3.5±0.8)kg。手术早期死亡2例,占11.1%。随访49(14~125)个月,随访期间无死亡患者。所有患者均行大动脉调转术及主动脉弓梗阻一期矫治:体外循环时间为(254±52)min,主动脉阻断时间为(124±23)min,术后住院时间为26(2~36)d。3例患者行再次手术干预(18.7%,3/16):1例患者为主动脉及右肺动脉狭窄,行经皮球囊成形术,效果欠佳,行外科手术治疗;1例患者行经皮主肺动脉球囊成形术,效果满意;1例主动脉吻合口狭窄患者,行经皮主动脉球囊成形术,效果满意。实际1年和5年免于再手术比例分别为100%和77%(95%CI:71%~91%),无再手术死亡患者。结论大动脉调转术及主动脉弓重建一期矫治TGA或右心室双出口肺动脉瓣下室间隔缺损合并主动脉弓梗阻病变患者的手术效果满意,有一定的再干预率,远期疗效需持续密切随访。展开更多
There is a growing body of evidence showing a close correlation between left ventricular mass with cardiovascular morbidity and overall mortality. Therefore, identifying the determinants of left ventricular hypertroph...There is a growing body of evidence showing a close correlation between left ventricular mass with cardiovascular morbidity and overall mortality. Therefore, identifying the determinants of left ventricular hypertrophy can be of great importance for cardiovascular prevention, for prognosis and therapeutic intervention. Objective: To assess the prevalence and identify the independent determinants of echocardiographic left ventricular hypertrophy in The MA-Ghreb and Sub-Saharan Africa Left-Ventricul ArGEometry Study (MAG-SALVAGES) participants. Methods: The MAG-SALVAGES is a community based study in which 100 asymptomatic Black Sub-Saharan African (BSSA) and 189 white skin Maghreb within the age of 18 to 55 years underwent a resting echocardiography. Multivariate logistic regression analysis was utilized to identify the independent determinants of LVH left ventricular hypertrophy. Results: Men represented the majority of the enrolled participants: 173 (59.9%). Echocardiographic left ventricular hypertrophy was seen in 10 (3.5%) participants. Age ≥40 years, female gender, overall obesity, abdominal obesity, hypertension status and less fruit consumption were significantly associated with echocardiography left ventricular hypertrophy. After adjusting for confounding factors, age ≥40 years, female gender, abdominal obesity and less fruit consumption were independently and significantly associated with echocardiographic left ventricular hypertrophy, as illustrated in the following equation: Y = 0.36 + 0.162 age >40 years + 2.69 female gender + 2.52 abdominal obesity + 1.31 less fruit consumption. Conclusion: Lifestyle changes for the prevention of abdominal obesity and encouraging fruit consumption may be beneficial in preventing left ventricular hypertrophy.展开更多
<div style="text-align:justify;"> <strong>Introduction</strong><span "=""><span>: Ventricular non-compaction, a cardiomyopathy recently described as likely to be ...<div style="text-align:justify;"> <strong>Introduction</strong><span "=""><span>: Ventricular non-compaction, a cardiomyopathy recently described as likely to be rare, belongs to the group of unclassified cardiomyopathy according to European Society of Cardiology. Few studies have been published on the ventricular non-compaction in sub-Saharan Africa. We aim to find out the various aspects, being diagnosis, therapeutic, in Togolese patients carrying the ventricular non-compaction. </span><b><span>Methodology</span></b><span>: This is a three</span></span><span>-</span><span>year</span><span> </span><span "=""><span>prospective and descriptive study conducted from January 2017 to December 2019 in the two University Hospital of Lomé. Patients having echocardiographic criteria of ventricular non-compaction were included in our study. </span><b><span>Results</span></b><span>: 10 patients (6 men and 4 women) were diagnosed for ventricular non-compaction during the study period. The mean age of patients was 32.3 years. The most frequent clinical manifestation was heart failure (7 patients). The main electrocardiogram anomaly was left ventricle hypertrophy (9 patients). The preferential segments were: apical (9 cases), apicolateral (8 cases), and septoapical (7 cases). The average ratio of non-compaction/compaction was 3.31. The main complication was thromboembolic event (4 patients). Angiotensin converting enzyme inhibitors and beta-blockers were essentially the medicines used. After a three (3) year follow-up, two (2) of the patients died. </span><b><span>Conclusion</span></b><span>: Tough ventricular non-compaction has been recently described</span></span><span>.</span><span> It is present in Togo. It displays many clinical manifestations and the prognosis is often guarded.</span> </div>展开更多
Background: Evidence that blacks have greater left ventricular mass (LVM) than whites has been demonstrated by large population-based American studies. However, to our knowledge, there is no study to date comparing LV...Background: Evidence that blacks have greater left ventricular mass (LVM) than whites has been demonstrated by large population-based American studies. However, to our knowledge, there is no study to date comparing LVM in Black Sub-Saharan Africans (BSSA) and the Maghreb white population. We compared LVM measured echocardiographically in asymptomatic BSSA and Maghreb. Methods and Results: A total of 100 asymptomatic BSSA and 189 Maghreb, (18 to 55 years old), underwent resting two-dimensional transthoracic echocardiography. LVM and geometry were assessed according to the 2015 American Society of Echocardiography and the European Association of Cardiovascular Imaging updated guidelines for cardiac chamber quantification. Crude or indexed LVM to body surface area or height2.7 was similar in BSSA and in Maghreb (132.7 ± 37.0 vs. 134.2 ± 35.7 g;73.1 ± 17.8 vs. 72.9 ± 16.2 g/m2;32.1 ± 9.8 vs. 33.6 ± 9.5 g/m2.7). However, the left ventricular posterior wall was thicker in BSSA. Patterns of left ventricular geometry (normal, concentric remodeling, or concentric or eccentric hypertrophy) were equally distributed among the two ethnic groups. Conclusions: Left ventricular posterior wall thickness but not LVM is greater in BSSA than in Maghreb.展开更多
Background: The influence of race/ethnicity on the relationship between sedentary screen time and left ventricular mass has been recently suggested, but remains a subject of debate, and has never been explored in Afri...Background: The influence of race/ethnicity on the relationship between sedentary screen time and left ventricular mass has been recently suggested, but remains a subject of debate, and has never been explored in Africa. Purpose: To determine whether there is a racial/ethnic influence on the relationship between sedentary screen time and left ventricular mass in MAGhreb and Sub Saharan Africa Left-Ventricul ArGEometry Study (MAG-SALVAGES) participants. Methods: 100 blacks sub-Saharan African and 187 white Maghreb aged 18 - 55 years underwent an interview on their behavioral measures, physical activity and eating habits. Their left ventricular mass has also been measured by a resting transthoracic echography according to the American Society of Echography. Generalized linear models evaluated a test-for-trend across higher levels of sedentary screen time in progressive models with left ventricular measurements as dependent variables. The study population was stratified into quartiles of sedentary screen time (separately for whites and blacks) and examined the joint association of sedentary screen time and LVM within quartiles of physical activity. Results: Among White Maghreb, higher screen time was associated with smaller left ventricular mass (P Conclusions: Sedentary screen time is associated with smaller left ventricular mass in White Maghreb, not in black sub-Saharan African. The lack of association in blacks supports a potential qualitative difference in the cardiovascular consequences of sedentary screen based behavior.展开更多
文摘The last fifteen years have seen the application of the cancer stem cell hypothesis to tumors of the central nervous system,in particular to high grade glioma(HGG),the most aggressive and common brain cancer in adults.Seminal studies have shown that cancer stem cells(alternatively named tumor-initiating cells)are capable of self-renew and multipotency,similar to their normal counterpart.More importantly they give rise to tumors that closely mimic the phenotype and genotype of human HGG.The identification of neurogenic niches in adult rodent and human brain has further reinforced the hypothesis that HGG might derive from the malignant transformation occurring in these areas,especially in the sub-ventricular zone(SVZ),the largest and most well characterised stem cell niche.Following from evidence of animal model studies supporting this hypothesis,recently we investigated the role of the SVZ in neuro-oncogenesis using tissue material derived from HGG patients.We also described response to conventional chemo-therapies of cancer stem cells isolated from the SVZ and the tumor mass(T)of the same patients and reconstructed tumor evolution.In this review,such findings will be discussed in the context of the current literature on the biology of the SVZ in the normal and disease brain.
文摘目的观察丹龙醒脑方对脑缺血再灌注模型大鼠侧脑室室管膜下区(SVZ)神经干细胞(NSCs)增殖与Hes1、Hes5表达的影响,探讨其促进内源性NSCs增殖的作用机制。方法将80只雄性SD大鼠随机分为假手术组、模型组、依达拉奉组(依达组)、丹龙醒脑方组(丹龙组)。采用线栓法制备局灶性脑缺血再灌注模型,再灌注7 d后取缺血侧SVZ脑组织。Brdu免疫荧光法检测SVZ NSCs增殖,RT-q PCR、Western blot分别检测Hes1、Hes5 m RNA和蛋白的表达。结果与假手术组比较,其余各组Brdu阳性细胞率增加,Hes1、Hes5 m RNA及蛋白表达明显升高(P<0.01);与模型组比较,依达组、丹龙组Brdu阳性细胞率明显增加,Hes1、Hes5 m RNA及蛋白表达水平明显增强(P<0.01);丹龙组Hes1 m RNA表达水平优于依达组(P<0.01),其余指标均无明显差异。结论丹龙醒脑方可促进脑缺血再灌注后大鼠SVZ NSCs增殖,并上调Hes1、Hes5表达水平,其机制可能与激活Notch信号通路有关。
基金supported by Individual Faculty Research GrantSwiss-South Africa Joint Research Progamme(SSAJRP)
文摘In this study, we investigated non-captive four-striped mice （Rhabdomys pumilio） for evidence that adult neurogenesis occurs in the adult brain of animal models in natural environment. Ki-67 （a marker for cell proliferation） and doublecortin （a marker for immature neurons） immunos-taining conifrmed that adult neurogenesis occurs in the active sites of subventricular zone of the lateral ventricle with the migratory stream to the olfactory bulb, and the subgranular zone of the dentate gyrus of the hippocampus. No Ki-67 proliferating cells were observed in the striatum substantia nigra, amygdala, cerebral cortex or dorsal vagal complex. Doublecortin-immunore-active cells were observed in the striatum, third ventricle, cerebral cortex, amygdala, olfactory bulb and along the rostral migratory stream but absent in the substantia nigra and dorsal vagal complex. The potential neurogenic sites in the four-striped mouse species could invariably lead to increased neural plasticity.
基金National Institutes of Health(NIH)Grants R01 RMH099384(to AA)and T32GM008444(to NM)。
文摘The mechanisms that regulate neural stem cell(NSC)lineage progression and maintain NSCs within diffe rent domains of the adult neural stem cell niche,the subventricular zone are not well defined.Quiescent NSCs are arranged at the apical ventricular wall,while mitotically activated NSCs are found in the basal,vascular region of the subventricular zone.Here,we found that ADAM 10(a disintegrin and metalloproteinase 10)is essential in NSC association with the ventricular wall,and via this adhesion to the apical domain,ADAM10 regulates the switch from quiescent and undiffe rentiated NSC to an actively prolife rative and differentiating cell state.Processing of JAMC(junctional adhesion molecule C)by ADAM 10 increases Rap1 GAP activity.This molecular machinery promotes NSC transit from the apical to the basal compartment and subsequent lineage progression.Understanding the molecular mechanisms responsible for regulating the proper positioning of NSCs within the subventricular zone niche and lineage progression of NSCs could provide new targets for drug development to enhance the regenerative prope rties of neural tissue.
文摘目的评估单中心行大动脉调转术及主动脉弓重建一期矫治大动脉转位(transposition of the great arteries,TGA)或右心室双出口肺动脉瓣下室间隔缺损(Taussig-Bing)合并主动脉弓梗阻病变的手术疗效及预后。方法回顾性分析2011年1月到2021年12月,在广东省妇幼保健院进行动脉调转术和主动脉弓重建一期矫治的18例TGA或右心室双出口肺动脉瓣下室间隔缺损合并主动脉梗阻病变患者的术后近中期随访结果。结果18例患者均完成治疗,其中男14例,女4例。12例为右心室双出口肺动脉瓣下室间隔缺损,6例为TGA。主动脉弓部病变:主动脉缩窄14例,主动脉弓离断4例。患儿手术时的年龄为13(2~88)d,体质量为(3.5±0.8)kg。手术早期死亡2例,占11.1%。随访49(14~125)个月,随访期间无死亡患者。所有患者均行大动脉调转术及主动脉弓梗阻一期矫治:体外循环时间为(254±52)min,主动脉阻断时间为(124±23)min,术后住院时间为26(2~36)d。3例患者行再次手术干预(18.7%,3/16):1例患者为主动脉及右肺动脉狭窄,行经皮球囊成形术,效果欠佳,行外科手术治疗;1例患者行经皮主肺动脉球囊成形术,效果满意;1例主动脉吻合口狭窄患者,行经皮主动脉球囊成形术,效果满意。实际1年和5年免于再手术比例分别为100%和77%(95%CI:71%~91%),无再手术死亡患者。结论大动脉调转术及主动脉弓重建一期矫治TGA或右心室双出口肺动脉瓣下室间隔缺损合并主动脉弓梗阻病变患者的手术效果满意,有一定的再干预率,远期疗效需持续密切随访。
文摘There is a growing body of evidence showing a close correlation between left ventricular mass with cardiovascular morbidity and overall mortality. Therefore, identifying the determinants of left ventricular hypertrophy can be of great importance for cardiovascular prevention, for prognosis and therapeutic intervention. Objective: To assess the prevalence and identify the independent determinants of echocardiographic left ventricular hypertrophy in The MA-Ghreb and Sub-Saharan Africa Left-Ventricul ArGEometry Study (MAG-SALVAGES) participants. Methods: The MAG-SALVAGES is a community based study in which 100 asymptomatic Black Sub-Saharan African (BSSA) and 189 white skin Maghreb within the age of 18 to 55 years underwent a resting echocardiography. Multivariate logistic regression analysis was utilized to identify the independent determinants of LVH left ventricular hypertrophy. Results: Men represented the majority of the enrolled participants: 173 (59.9%). Echocardiographic left ventricular hypertrophy was seen in 10 (3.5%) participants. Age ≥40 years, female gender, overall obesity, abdominal obesity, hypertension status and less fruit consumption were significantly associated with echocardiography left ventricular hypertrophy. After adjusting for confounding factors, age ≥40 years, female gender, abdominal obesity and less fruit consumption were independently and significantly associated with echocardiographic left ventricular hypertrophy, as illustrated in the following equation: Y = 0.36 + 0.162 age >40 years + 2.69 female gender + 2.52 abdominal obesity + 1.31 less fruit consumption. Conclusion: Lifestyle changes for the prevention of abdominal obesity and encouraging fruit consumption may be beneficial in preventing left ventricular hypertrophy.
文摘<div style="text-align:justify;"> <strong>Introduction</strong><span "=""><span>: Ventricular non-compaction, a cardiomyopathy recently described as likely to be rare, belongs to the group of unclassified cardiomyopathy according to European Society of Cardiology. Few studies have been published on the ventricular non-compaction in sub-Saharan Africa. We aim to find out the various aspects, being diagnosis, therapeutic, in Togolese patients carrying the ventricular non-compaction. </span><b><span>Methodology</span></b><span>: This is a three</span></span><span>-</span><span>year</span><span> </span><span "=""><span>prospective and descriptive study conducted from January 2017 to December 2019 in the two University Hospital of Lomé. Patients having echocardiographic criteria of ventricular non-compaction were included in our study. </span><b><span>Results</span></b><span>: 10 patients (6 men and 4 women) were diagnosed for ventricular non-compaction during the study period. The mean age of patients was 32.3 years. The most frequent clinical manifestation was heart failure (7 patients). The main electrocardiogram anomaly was left ventricle hypertrophy (9 patients). The preferential segments were: apical (9 cases), apicolateral (8 cases), and septoapical (7 cases). The average ratio of non-compaction/compaction was 3.31. The main complication was thromboembolic event (4 patients). Angiotensin converting enzyme inhibitors and beta-blockers were essentially the medicines used. After a three (3) year follow-up, two (2) of the patients died. </span><b><span>Conclusion</span></b><span>: Tough ventricular non-compaction has been recently described</span></span><span>.</span><span> It is present in Togo. It displays many clinical manifestations and the prognosis is often guarded.</span> </div>
文摘Background: Evidence that blacks have greater left ventricular mass (LVM) than whites has been demonstrated by large population-based American studies. However, to our knowledge, there is no study to date comparing LVM in Black Sub-Saharan Africans (BSSA) and the Maghreb white population. We compared LVM measured echocardiographically in asymptomatic BSSA and Maghreb. Methods and Results: A total of 100 asymptomatic BSSA and 189 Maghreb, (18 to 55 years old), underwent resting two-dimensional transthoracic echocardiography. LVM and geometry were assessed according to the 2015 American Society of Echocardiography and the European Association of Cardiovascular Imaging updated guidelines for cardiac chamber quantification. Crude or indexed LVM to body surface area or height2.7 was similar in BSSA and in Maghreb (132.7 ± 37.0 vs. 134.2 ± 35.7 g;73.1 ± 17.8 vs. 72.9 ± 16.2 g/m2;32.1 ± 9.8 vs. 33.6 ± 9.5 g/m2.7). However, the left ventricular posterior wall was thicker in BSSA. Patterns of left ventricular geometry (normal, concentric remodeling, or concentric or eccentric hypertrophy) were equally distributed among the two ethnic groups. Conclusions: Left ventricular posterior wall thickness but not LVM is greater in BSSA than in Maghreb.
文摘Background: The influence of race/ethnicity on the relationship between sedentary screen time and left ventricular mass has been recently suggested, but remains a subject of debate, and has never been explored in Africa. Purpose: To determine whether there is a racial/ethnic influence on the relationship between sedentary screen time and left ventricular mass in MAGhreb and Sub Saharan Africa Left-Ventricul ArGEometry Study (MAG-SALVAGES) participants. Methods: 100 blacks sub-Saharan African and 187 white Maghreb aged 18 - 55 years underwent an interview on their behavioral measures, physical activity and eating habits. Their left ventricular mass has also been measured by a resting transthoracic echography according to the American Society of Echography. Generalized linear models evaluated a test-for-trend across higher levels of sedentary screen time in progressive models with left ventricular measurements as dependent variables. The study population was stratified into quartiles of sedentary screen time (separately for whites and blacks) and examined the joint association of sedentary screen time and LVM within quartiles of physical activity. Results: Among White Maghreb, higher screen time was associated with smaller left ventricular mass (P Conclusions: Sedentary screen time is associated with smaller left ventricular mass in White Maghreb, not in black sub-Saharan African. The lack of association in blacks supports a potential qualitative difference in the cardiovascular consequences of sedentary screen based behavior.
