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G J Smith

Publications and source records attributed to G J Smith.

At least 37 records · Page 2Linked to original sources

Suppression of tumorigenicity of rat liver epithelial tumor cell lines by a putative human 11p11.2-p12 liver tumor suppressor locus.

We have previously identified and mapped a locus within human chromosome 11p11.2-p12 that suppresses the tumorigenic potential of a rat liver tumor cell line (termed GN6TF) which contains well defined chromosomal aberrations involving rat chromosomes 1, 4, 7, and 10. In the present study, we investigated the potential of this human 11p11.2-p12 liver tumor suppressor locus to suppress the tumorigenic potential of two other rat liver tumor cell lines (GN3TG and GP10TA) following microcell-mediated introduction of human chromosome 11. These tumor cell lines are aneuploid and contain chromosomal abnormalities that are similar to the GN6TF tumor line. The tumorigenic potential and other phenotypic characteristics of GN3TG-11neo and GP10TA-11neo microcell hybrid (MCH) cell lines were variable, and dependent upon the status of the introduced human chromosome 11. MCH cell lines that retained the region of 11p11. 2-p12 delineated by microsatellite markers D11S1385 and D11S903 exhibited suppression of tumorigenicity in vivo (decrease in tumorigenicity and/or elongation of latency), whereas, the tumorigenic potential of one MCH line that lacked markers in this region of human 11p11.2-p12, but retained flanking markers, was not changed from that of the parental tumor cell line. The chromosomal interval between microsatellite markers D11S1385 and D11S903 encompasses the previously localized minimal liver tumor suppressor region, suggesting that a common locus is responsible for tumor suppression among the rat liver tumor cell lines examined. The results of the present study have verified the presence of a liver tumor suppressor locus within human 11p11.2-p12, and have identified a substantial number of microsatellite markers that are closely linked to this tumor suppressor region. These chromosomal markers will facilitate positional cloning of candidate genes from this region, and may prove useful for determining the involvement of this locus in the pathogenesis of human liver cancer.

Animals↗

Induction of rat WT1 gene expression correlates with human chromosome 11p11.2-p12-mediated suppression of tumorigenicity in rat liver epithelial tumor cell lines.

We have previously identified and mapped a locus within human chromosome 11p11.2-p12 that suppresses the tumorigenic potential of some rat liver tumor cell lines. In the present study, possible molecular mechanisms of human 11p11.2-p12-mediated liver tumor suppression were investigated by examining gene expression patterns in suppressed and non-suppressed microcell hybrid (MCH) cell lines. The parental rat liver tumor cell lines (GN6TF and GP7TB) express moderate levels of p53 mRNA and protein, overexpress mRNAs for c-H-ras, c-myc, and TGFá, and do not express detectable levels of WT1 mRNA or protein. Suppression of tumorigenicity by human chromosome 11p11.2-p12 was not accompanied by significant alterations in the levels of expression of p53, c-myc, or TGFá. Expression of c-H-ras was decreased significantly in both suppressed and non-suppressed MCH cell lines, suggesting that down-regulation of c-H-ras is not directly responsible for tumor suppression. In contrast, the level of expression of WT1 correlated precisely with tumor suppression in this model system. All suppressed MCH cell lines expressed WT1 mRNA and protein at levels comparable to that of untransformed rat liver epithelial cells (WB-F344), whereas only trace WT1 mRNA and protein were detected in a non-suppressed MCH cell line. PCR analysis demonstrated that two suppressed MCH cell lines do not carry the human WT1 gene, indicating that WT1 expression in these lines originates from the rat locus. Furthermore, RT-PCR analysis showed that each of the four known splice variants of the WT1 mRNA are expressed in these suppressed MCH cell lines, recapitulating the expression pattern observed in the untransformed rat liver epithelial cells. Re-expression of tumorigenicity by suppressed MCH cell lines was accompanied by the coordinate loss of human chromosome 11p11.2-p12 and of WT1 gene expression, suggesting that one or more human 11p11.2-p12 genes are required for sustained expression of WT1 in these cell lines. Together, these results suggest that the molecular mechanism governing human chromosome 11p11.2-p12-mediated liver tumor suppression may involve induction of rat WT1 gene expression under the direct or indirect transcriptional regulation of a genetic locus (or loci) on human 11p11.2-p12.

Animals↗

Plasticity of the neoplastic phenotype in vivo is regulated by epigenetic factors.

Age of host and transplantation-site microenvironment influence the tumorigenic potential of neoplastically transformed liver epithelial cells. Tumorigenic BAG2-GN6TF rat liver epithelial cells consistently form tumors at ectopic sites, but differentially express tumorigenicity or hepatocytic differentiation in the liver depending on host age and route of cell transplantation into the liver. Direct inoculation into host livers concentrates tumor cells locally, resulting in undifferentiated tumors near the transplantation site in both young (3-month-old) and old (18-month-old) rats. Transplantation-site tumors regress within 1 month in the livers of young rats, but grow progressively in old rats. However, inoculation of cells into the spleen distributes transplanted cells individually throughout the liver, resulting in hepatocytic differentiation by tumor cells with concomitant suppression of their tumorigenicity in young rats. When transplanted into livers of old rats by splenic inoculation, or when young hepatic-transplant recipients are allowed to age, hepatocytic progeny of BAG2-GN6TF cells proliferate to form foci, suggesting that the liver microenvironment of old rats incompletely regulates the proliferation and differentiation of tumor cell-derived hepatocytes. Upon removal from the liver, BAG2-GN6TF-derived hepatocytes revert to an undifferentiated, aggressively tumorigenic phenotype. We posit that the spectrum between normal differentiation and malignant potential of these cells reflects the dynamic interaction of the specific transformation-related genotype of the cells and the characteristics of the tissue microenvironment at the transplantation site. Changes in the tissue milieu, such as those that accompany normal aging, may determine the ability of a genetically aberrant cell to produce a tumor.

Aging↗

The hepatitis B virus post-transcriptional regulatory element contains two conserved RNA stem-loops which are required for function.

Human Hepatitis B Virus (HBV) RNAs contain a cis -acting sequence, the post-transcriptional regulatory element (HPRE), which facilitates the cytoplasmic localization of intronless transcripts. Our previous studies have shown that the HPRE is composed of at least two independent sub-elements, HPREalpha and HPREbeta, which co-activate a reporter for RNA export in a greater than additive manner. Utilizing deletion, mutation and co-variational analyses, we have identified three regions important for full HPRE activity. The three separate regions of the HPRE function can function independently in a dose-dependent manner when multimerized. Two of these regions contain stem loops, HSLalpha and HSLbeta1, which are necessary for full HPRE function. These structures are conserved throughout the mammalian Hepadnaviruses. Disruption of either stem-loop structure by mutagenesis decreases HPRE function while compensatory mutations restore activity. The location of the stem-loops in the genome reveal that they are present in all of the HBV transcripts. HSLalpha and HSLbeta1 are likely to contain the binding sites for the cellular factor(s) which mediates HPRE function.

Base Sequence↗

Genomic fluidity is a necessary event preceding the acquisition of tumorigenicity during spontaneous neoplastic transformation of WB-F344 rat liver epithelial cells.

The genomic evolution of a cohort of WB-F344 rat liver epithelial cell lineages undergoing spontaneous neoplastic transformation was followed to define the mechanistic relationship between genomic instability and progression to the neoplastic phenotype. Eighteen independent populations of WB-F344 cells (initiated from a single diploid-founding population) were subjected to 12 cycles of selective growth at confluent cell density, and cellular DNA contents were measured after each selection cycle. Flow cytometry demonstrated significant gains in the amount of G1 DNA after selection cycles 3, 6, and 7 in 44% (8 of 18), 89% (16 of 18), and 39% (7 of 18) of the cell populations, respectively. All populations subsequently lost DNA and returned to a diploid or pseudo-diploid DNA content within 1 to 2 selection cycles after the appearance of an increased DNA content. Additionally, appearance and subsequent disappearance of aneuploid or tetraploid subpopulations was observed in 11% (2 of 18) and 83% (15 of 18) of the experimental lineages, respectively. Although perturbations of G1 DNA content were apparent as early as selection cycle 3, at least 8 cycles of selective growth were required for the acquisition of tumorigenicity. While the independent lineages demonstrated significant fluctuations in G1 DNA content between selection cycles 3 and 8, the majority (11 of 13) of the populations contained a diploid or pseudo-diploid DNA content at the time tumorigenicity was expressed. Genomic instability preceded the acquisition of tumorigenic potential in rat liver epithelial cells subjected to selective growth conditions of maintenance at confluence, and may be required for its expression.

Aneuploidy↗

Establishment of a functional HGF/C-MET autocrine loop in spontaneous transformants of WB-F344 rat liver stem-like cells.

A model of spontaneous malignant transformation was used to evaluate the molecular changes that take place in WB-F344 rat liver epithelial cells during neoplastic transformation and tumorigenesis. A comparison of wild-type low-passage WB-F344 cells to spontaneously transformed tumor cell lines revealed that the majority of the tumor cell lines have an increased capacity for autonomous proliferation and motility when maintained in serum-free media. In the current study, we show that c-met is expressed at some level in wild-type WB-F344 cells and in all of the spontaneously transformed tumor cell lines, and that 9/16 of the tumor cell lines have acquired hepatocyte growth factor (HGF) expression. In vitro growth of HGF-expressing tumor cell lines is inhibited as much as 68% by the addition of neutralizing antibodies to HGF or antisense HGF oligonucleotides, indicating that the production of HGF by the tumor cells is partially responsible for driving autonomous proliferation in a subset of tumor cell lines. Furthermore, conditioned media collected from HGF-expressing tumor cell lines stimulates DNA synthesis in wild-type WB-F344 cells, and this effect can be abrogated by pre-incubation of the conditioned media with neutralizing antibodies to HGF. Because HGF is a motility-promoting growth factor, all cell lines were evaluated to determine if expression of HGF stimulated motogenesis. All tumor cell lines (regardless of HGF expression) were highly motile in comparison with wild-type WB-F344 cells, with a 3.5-fold to 20-fold greater number of motile cells. The high basal rate of motility characteristic of the tumor cell lines is not a result of the production of HGF, because it is also a property of the cell lines that do not express HGF messenger RNA. Furthermore, tumor cell motility is not inhibited by antisense oligonucleotides or neutralizing antibodies. Establishment of an autocrine HGF/c-met loop in a subset of spontaneously transformed WB-F344 cell lines may influence development and/or expression of the tumorigenic phenotype by driving cellular proliferation.

Animals↗

Spontaneous neoplastic transformation of WB-F344 rat liver epithelial cells.

Several studies have shown that cultured rat liver epithelial cells transform spontaneously after chronic maintenance in a confluent state in vitro. In the present study, multiple independent lineages of low-passage WB-F344 rat liver epithelial stem-like cells were initiated and subjected in parallel to selection for spontaneous transformation to determine whether spontaneous acquisition of tumorigenicity was the result of events (genetic or epigenetic) that occurred independently and stochastically, or reflected the expression of a pre-existing alteration within the parental WB-F344 cell line. Temporal analysis of the spontaneous acquisition of tumorigenicity by WB-F344 cells demonstrated lineage-specific differences in the time of first expression of the tumorigenic phenotype, frequencies and latencies of tumor formation, and tumor differentiations. Although spontaneously transformed WB-F344 cells produced diverse tumor types (including hepatocellular carcinomas, cholangiocarcinomas, hepatoblastomas, and osteogenic sarcomas), individual lineages yielded tumors with consistent and specific patterns of differentiation. These results provide substantial evidence that the stochastic accumulation of independent transforming events during the selection regimen in vitro were responsible for spontaneous neoplastic transformation of WB-F344 cells. Furthermore, cell lineage commitment to a specific differentiation program was stable with time in culture and with site of transplantation. This is the first report of a cohort of related, but independent, rat liver epithelial cell lines that collectively produce a spectrum of tumor types but individually reproduce a specific tumor type. These cell lines will provide valuable reagents for investigation of the molecular mechanisms involved in the differentiation of hepatic stem-like cells and for examination of potential causal relationships in spontaneously transformed rat liver epithelial cell lines between molecular/cellular alterations and the ability to produce tumors in syngeneic animals.

Animals↗

Downregulation of the beta4 integrin subunit in prostatic carcinoma and prostatic intraepithelial neoplasia.

Integrins are adhesion receptors thought to be important in the process of cancer cell invasion and metastasis. Unlike other integrins, which attach a cell to extracellular matrix molecules, the alpha6beta4 integrin participates in the formation of hemidesmosomes, attaching epithelial cells to the basement membrane. Investigations of the alpha6beta4 integrin in human prostatic carcinoma have yielded conflicting results and have been primarily qualitative rather than quantitative. Expression of the beta4 integrin subunit was determined using rat monoclonal antibody 439-9B and image analysis in regions of benign prostatic epithelium (BPE), high-grade prostatic intraepithelial neoplasia (PIN), and prostatic carcinoma (CaP) in 38 patients treated by radical prostatectomy for clinically localized CaP. The beta4 integrin subunit was significantly downregulated in CaP compared with BPE; PIN stained intermediate in intensity between BPE and CaP. Thirty-four of 35 patients showed downregulation of the beta4 integrin subunit, and all 15 patients with PIN had downregulation of beta4 in PIN as compared with BPE. Degree of downregulation of the beta4 integrin subunit did not add prognostic significance to the information present at initial biopsy (age, clinical stage, clinical grade, and serum prostate-specific antigen level). There was no correlation between intensity of staining of CaP, absolute change in staining, or percent loss of beta4 integrin subunit staining with age, pathological stage, or Gleason's score. Downregulation of the beta4 integrin in CaP and PIN compared with BPE may be correlated with neoplastic transformation of the prostate and loss of hemidesmosomes or basal epithelial cells.

Aged↗

Isolation and characterization of propagable cell lines (HUNC) from the androgen-sensitive Dunning R3327H rat prostatic adenocarcinoma.

The Dunning H rat prostate tumor (R3327H) is a widely used experimental model of human prostatic adenocarcinoma (CaP). The Dunning H tumor has been characterized as androgen-sensitive, androgen-receptor (AR) positive, prostate-specific antigen and prostatic acid phosphatase (PAP) positive. To date, the tumor has been maintained by serial passage in vivo because of the lack of an in vitro cell line that retains the characteristics of the in vivo tumor. The objective of the present study was to establish a propagable cell line from R3327H adenocarcinoma that maintained androgen sensitivity and expression of AR, PSA and PAP. Tissue harvested from an in vivo R3327H tumor was dissociated with collagenase and placed into Richter's improved media (with supplements). A cytokeratin-positive epithelial cell line (HUNC-E) and a vimentin-positive stromal cell line (HUNC-S) were generated from the primary culture, subcultured continuously for >300 days, and passaged >50 times. Survival of the HUNC-E cell line in vitro depended on several media supplements, including nicotinamide, insulin, transferrin, selenium and epidermal growth factor (EGF). HUNC-E cells expressed AR and produced PSA and PAP throughout the culture period, as confirmed by immunocytochemistry and Western blot analyses. Addition of 14 nM testosterone (T) or dihydrotestosterone (DHT) to HUNC-E cells, stimulated DNA synthesis as well as anchorage-independent growth and PSA production, which demonstrated the androgen-sensitive nature of the cells in vitro. When HUNC-E and HUNC-S cells were combined in a 3:1 ratio and introduced subcutaneously into syngeneic male hosts, tumors formed in 2/3 animals with an average latency of 7 months. RT-PCR and immunocytochemical characterization of the HUNC cell lines revealed that the cells expressed several growth factors and their cognate receptors, including HGF, TGF-alpha and the TGF-betas, indicating the establishment of potential autocrine loops in the neoplastic cells. The HUNC-E and HUNC-S CaP cell lines, which retain the characteristics of the epithelial and stromal components of the in vivo R3327H tumor, will allow a more thorough and informative molecular and biological analysis of prostatic adenocarcinoma.

Acid Phosphatase↗

Expression of telomerase in normal and malignant rat hepatic epithelia.

Telomerase is a ribonucleoprotein that synthesizes telomeric DNA repeats onto the ends of chromosomes. More than 85% of human cancers express telomerase activity and a large proportion of human hepatocellular carcinomas are positive. To study the role of telomerase expression in rat hepatocarcinogenesis, telomerase activity was assayed in various rat tissues and in two types of liver epithelial cells: hepatocytes and hepatic epithelial stem-like cells. In the present study, we demonstrate that telomerase activity in rats is tissue-specific and stable with animal aging. Liver and testis were found to be telomerase positive, spleen had low or no activity, and kidney was negative. Telomerase activity did not change significantly in 18 month-old rats compared to 2 month-old rats, but was moderately (twofold) increased during liver regeneration induced by a 2/3's partial hepatectomy. Telomerase activity was detected in isolated rat hepatocytes and low passage hepatic epithelial stem-like cells (WB-F344). Telomerase activity displayed significant variations in a propagable clone of WB-F344 cells. At low passage levels after establishment in vitro (passages 4-9) non-tumorigenic WB-F344 cells expressed telomerase activity. During further in vitro passaging these cells lost expression of telomerase. Expression of telomerase in the tumor-derived lines of WB-F344 cells but not in the selectively cycled, parental lineages of these cells suggests that there may be a role for telomerase in hepatocarcinogenesis.

Aging↗

Risk factors for methotrexate-induced lung injury in patients with rheumatoid arthritis. A multicenter, case-control study. Methotrexate-Lung Study Group.

BACKGROUND: Toxicity limits the use of methotrexate. OBJECTIVE: To identify risk factors for methotrexate-induced lung injury in patients with rheumatoid arthritis. DESIGN: Case-control study. SETTING: One private and five academic rheumatology practices. PARTICIPANTS: Methotrexate recipients with rheumatoid arthritis with and without lung injury. MEASUREMENTS: Potential risk factors examined were sociodemographic and lifestyle characteristics, medical history, clinical and ancillary features and treatment of rheumatoid arthritis before methotrexate therapy, and characteristics of methotrexate therapy. Cases of lung injury were defined according to the modified criteria of Searles and McKendry. RESULTS: Ninety-four percent of the study participants were white, and 67% were women. Case-patients (n = 29) were older than controls (n = 82) (61.5 compared with 54.5 years of age). The strongest predictors of lung injury, after adjustment for other variables, were older age (odds ratio [OR], 5.1 [95% CI, 1.2 to 21.1]), diabetes (OR, 35.6 [CI, 1.3 to infinity]), rheumatoid pleuropulmonary involvement (OR, 7.1 [CI, 1.1 to 45.4]), previous use of disease-modifying antirheumatic drugs (OR, 5.6 [CI, 1.2 to 27.0]), and hypoalbuminemia (OR, 19.5 [CI, 3.5 to 109.7]). Previous use of disease-modifying antirheumatic drugs and hypoalbuminemia had very large attributable risks. CONCLUSION: Knowledge of the risk factors that predispose patients with rheumatoid arthritis to the toxic effects of methotrexate on the lung may provide a rationale for monitoring high-risk patients and may facilitate their management.

Antirheumatic Agents↗

Age-dependent induction of hepatic tumor regression by the tissue microenvironment after transplantation of neoplastically transformed rat liver epithelial cells into the liver.

Age is the biggest risk factor associated with the development of cancer. Whereas the incidence of neoplastic disease increases dramatically in aging humans and experimental animals, the effects of aging on tumorigenesis are poorly understood. Using a rodent model, we have previously shown that the microenvironment of the hepatic parenchyma regulates hepatic tumor formation from transplanted neoplastic cells in an age-dependent manner. In the current study, we have investigated the mechanistic basis for the age-dependent suppression of tumor formation by transplanted BAG2-GN6TF rat liver epithelial tumor cells. Examination of liver tissue at 7 and 14 days after transplantation of liver tumor cells revealed the presence of injection-site tumors in both young and old animals. With time, these tumors spontaneously regressed from young adult livers, leaving no tumor remnant and without evidence of injury to the parenchyma. In contrast, tumors detected in old animals at early time points after transplantation persisted for the remainder of the life of the host. Reduced cell proliferation and increased apoptotic cell death were detected in hepatic tumors in young rats relative to hepatic tumors in old rats. These observations suggest that the regression of hepatic tumors from young rats was the direct result of an increased ratio of cell death to cell birth, whereas the persistence and expansion of hepatic tumors in old rats was related to increased cell proliferation relative to cell death. Because young adult rats developed persistent (nonregressing) tumors after transplantation of BAG2-GN6TF cells to extrahepatic sites, the consistent regression of BAG2-GN6TF tumors from livers of young rats seemed to be largely a result of interactions between tumor cells and factors specific to the liver microenvironment. These data indicate that the hepatic microenvironment of young rats can negatively regulate the growth of transformed liver epithelial cells, but with increasing age, the ability of the hepatic microenvironment to suppress the growth of neoplastic tissue deteriorates. Age-associated alterations in tissue microenvironments may thus permit the development of tumors late in life.

Age Factors↗

Localization of a putative liver tumor suppressor locus to a 950-kb region of human 11p11.2-p12 using rat liver tumor microcell hybrid cell lines.

We previously demonstrated that a locus (or loci) linked to the D11S436 marker, which is within the approximately 6-Mb cen-p12 region of human chromosome 11, suppresses the tumorigenic potential of some rat liver epithelial tumor microcell hybrid (MCH) cell lines. To more precisely map this putative liver tumor suppressor locus, we examined 25 loci from human chromosome 11 in suppressed MCH cell lines. Detailed analysis of these markers revealed a minimal area of overlap among the suppressed MCH cell lines corresponding to the chromosomal region bounded by (but not including) microsatellite markers D11S1319 and D11S1958E and containing microsatellite markers D11S436, D11S554, and D11S1344. Direct examination of the kang ai 1 (KA/1) prostatic adenocarcinoma metastasis suppressor gene (which is closely linked to D11S1344) produced evidence suggesting that this locus was not responsible for tumor suppression in this model system. In addition, our data strongly suggested that the putative liver tumor suppressor locus was distinct from other known 11p tumor suppressor loci, including the multiple exotoses 2 locus (at 11p11.2-p12), Wilms' tumor 1 locus (at 11p13), and Wilms' tumor 2 locus (at 11p15.5). The results of this study significantly narrowed the chromosomal location of the putative liver tumor suppressor locus to a region of human 11p11.2-p12 that is approximately 950 kb. This advance forms the basis for positional cloning of candidate genes from this region and, in addition, identified a number of chromosomal markers that will be useful for determining the involvement of this locus in the pathogenesis of human liver cancer.

Animals↗

Clinical, laboratory, radiographic, and histopathologic features of methotrexate-associated lung injury in patients with rheumatoid arthritis: a multicenter study with literature review.

OBJECTIVE: To describe the clinical, laboratory, radiologic, and histopathologic features of methotrexate (MTX)-induced lung injury in a combined cohort of selected patients with rheumatoid arthritis (RA) and all cases reported in the English-language literature. METHODS: Retrospective combined cohort review and abstraction from the medical literature. Case reports were obtained from 6 centers that had 4 or more cases of potential MTX lung injury per site. RA patients who were seen between 1981 and 1993 and who satisfied predetermined criteria for the presence of MTX lung injury were identified. RESULTS: Twenty-seven patients satisfied the criteria for definite MTX lung injury, and 2 for probable MTX lung injury. Predominant clinical features of MTX lung injury included shortness of breath in 27 patients (93.1%), which was present for 23.5 +/- 22.3 days (mean +/- SD), cough in 24 (82.8%), present for 26.9 +/- 28.5 days, and fever in 20 (69.0%), present for 10.4 +/- 12.8 days. Five patients (17.2%) died, compared with 12 of 68 (17.6%) reported in the medical literature. Four of the 6 patients who were re-treated with MTX after an initial pulmonary event developed recurrent lung toxicity, resulting in 2 deaths, compared with a recurrence rate of 3 of 6 in the literature. CONCLUSION: MTX lung injury is most often a subacute process, in which symptoms are commonly present for several weeks before diagnosis. Approximately 50% of the cases are diagnosed within 32 weeks from initiation of MTX treatment. A patient who recovers from MTX lung injury should not be re-treated. Earlier recognition and drug withdrawal may avoid the serious and sometimes fatal outcome that has been observed in this and other studies.

Aged↗

Alexithymia in patients with eating disorders: an investigation using a new projective technique.

The concept of alexithymia was scrutinized in a group of female patients with eating disorders: 15 anorectics and 13 bulimics (mean age of 27 yr.), plus a control group of 21 (mean age 38 yr.). Subjects were interviewed and tested. In the main test an ambiguous face was flashed briefly on a screen opposite the viewer who had to describe her impressions. To enhance the ego-involvement, subliminal words (I, I ILL, I WELL) were presented before each exposure. Contrary to expectations the present patients used more emotional words than controls. Instead, they employed alternative strategies to avoid empathizing. The results were interpreted as indicating a pronounced incapacity for emotional understanding.

Adult↗