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T Morimoto

Publications and source records attributed to T Morimoto.

At least 181 records · Page 10Linked to original sources

Constitutive secretion of exogenous neurotransmitter by nonneuronal cells: implications for neuronal secretion.

Fibroblasts in cell culture were loaded with exogenous neurotransmitter acetylcholine (ACh). ACh secretion from loaded cells was detected by whole-cell patch clamp recordings from Xenopus myocytes manipulated into contact with ACh-loaded cells. Two different approaches were used for ACh loading. In the first approach, fibroblasts were incubated in the culture medium containing ACh. Recordings from myocytes revealed fast inward currents that resemble miniature endplate currents found at neuromuscular synapses. The currents observed in recordings from myocytes were due to exocytosis of ACh-containing vesicles. Although exogenous ACh penetrated through the plasma membrane of fibroblasts during incubation and was present in the cytoplasm at detectable levels, cytoplasmic ACh did not contribute to the quantal ACh secretion. In the second approach, exogenous ACh was loaded into the cytoplasm of fibroblasts by microinjection. Under these experimental conditions, fibroblasts also exhibited spontaneous quantal ACh secretion. Analysis of the exocytotic events in fibroblasts following two different protocols of ACh loading revealed that the vesicular compartments responsible for uptake of exogenous ACh are associated with the endocytic recycling pathway. Extrapolation of our results to neuronal cells suggest that in cholinergic neurons, in addition to genuine synaptic vesicles, ACh can be secreted by the vesicles participating in endosomal membrane recycling.

Acetylcholine↗

Prolonged discordant xenograft survival and delayed xenograft rejection in a pig-to-baboon orthotopic cardiac xenograft model.

OBJECTIVE: Our objectives were to study delayed xenograft rejection and the effectiveness of pretransplantation total lymphoid irradiation combined with immunosuppression on rejection in a pig-to-baboon cardiac xenograft model. METHODS: Baboons were treated with pretransplantation total lymphoid irradiation, cyclosporine A (INN: ciclosporin), and methotrexate. Orthotopic pig-to-baboon cardiac transplantations were performed after depletion of circulating xenoreactive natural antibody by pretransplantation donor organ hemoperfusion. Tissue samples were collected for immunologic and immunopathologic evaluation. RESULTS: Pig cardiac xenografts survived more than 18 and 19 days without evidence of hyperacute rejection. Immunologic analysis of serum samples demonstrated that circulating xenoreactive natural antibody levels did not return to pretransplantation levels. The production of xenoreactive natural antibodies from the recipient's splenocytes was inhibited completely. Histologic examination of xenografts showed the feature of acute vascular rejection. Immunohistochemical studies demonstrated infiltration of cardiac xenografts by large numbers of macrophages, small numbers of natural killer cells, and a few T cells. The infiltrating macrophages also showed expression of interleukin-1 and tumor necrosis factor. Diffuse deposition of immunoglobulin G, C1Q, C3, and fibrin on xenograft vasculature was observed. Interleukin-2 expression was not found in rejected cardiac xenografts. Xenograft endothelial cells also showed evidence of activation (expression of cytokines interleukin-1 and tumor necrosis factor). CONCLUSIONS: This study demonstrates prolonged discordant cardiac xenograft survival and delayed xenograft rejection in a pig-to-baboon model. The delayed xenograft rejection is mediated by both humoral and cellular mechanisms. Pretransplantation total lymphoid irradiation combined with cyclosporine A and methotrexate can inhibit xenoreactive natural antibody production but not elicited antipig antibody production and the xenoreactivity of macrophages.

Animals↗

Secreted form of beta-amyloid precursor protein activates protein kinase C and phospholipase Cgamma1 in cultured embryonic rat neocortical cells.

The secreted form of beta-amyloid precursor protein (sAPP) has been reported to exert various biological activities in cultured neurons. The signal transduction mechanisms underlying these physiological functions of sAPP remain unclear. We now report that treatment of neural cells with the secreted form of APP695 (sAPP695) leads to dose- and time-dependent increase in phosphorylation of the endogenous substrates with a molecular mass of 80, 57 and 43 kDa. Pretreatment of cells with protein kinase C (PKC) inhibitor H-7 reduced phosphorylation of the 80- and 43-kDa proteins in a dose-dependent manner. The effect of sAPP695 on the phosphorylation is mimicked by phorbol 12-myristate-13-acetate (PMA). Downregulation of PKC by prolonged treatment of cells with PMA abolished sAPP695-enhanced phosphorylation of the 80- and 43-kDa proteins, indicating PKC is involved in the sAPP695-enhanced phosphorylation of these proteins in the cells. We also suggest that the 80- and 43-kDa proteins phosphorylated by sAPP695-stimulation are the major PKC substrates myristoylated alanine-rich C-kinase substrate and growth-associated protein-43. Furthermore, we demonstrate that tyrosine phosphorylation of phospholipase Cgamma1 and formation of inositol 1,4,5-trisphosphate were increased by sAPP695-stimulation. These observations suggest that sAPP695 induces the activation of the signaling pathways through a stimulation of phosphoinositide-PKC cascade.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

Overexpression of synaptotagmin modulates short-term synaptic plasticity at developing neuromuscular junctions.

The level of synaptotagmin I or II in developing spinal neurons was increased by injection of synaptotagmin messenger RNA into early blastomeres of Xenopus embryos. The effect of overexpression of synaptotagmin on synaptic function was assayed in Xenopus nerve-muscle cultures within two days after injection. At neuromuscular synapses made by synaptotagmin-overexpressing neurons, the frequency of miniature postsynaptic currents was markedly reduced, while their mean amplitude was unchanged, as compared to those of control neurons in the same culture. The amplitude of evoked postsynaptic currents elicited by low-frequency test stimuli was not affected by overexpression. However, synapses made by synaptotagmin-overexpressing neurons exhibited significantly higher paired-pulse facilitation and reduced tetanus-induced depression of the synaptic response, and there was also an increased number of synaptic vesicles at regions 100-300 nm from the plasmalemma at such synapses. These results show that synaptotagmins can exert an inhibitory action on the spontaneous exocytosis of synaptic vesicles. The effects on short-term plasticity suggest that synaptotagmin may facilitate vesicular supply for the evoked release during higher frequency transmission.

Animals↗

The number of metastatic lymph nodes: a promising prognostic determinant for gastric carcinoma in the latest edition of the TNM classification.

BACKGROUND: The number of metastatic regional lymph nodes determines the new pN categories in the 5th edition of the TNM classification. STUDY DESIGN: Our retrospective study was conducted to compare the new method of defining lymph node status with the conventional classification, consisting of the anatomic extent of lymph node metastases, a well-established prognostic factor. The study was based on clinical data for 493 patients with gastric carcinomas who underwent potentially curative operations and had histologically confirmed nodal metastases. These patients were stratified into 1) n categories according to the Japanese Classification of Gastric Carcinoma, 2) the new pN categories, and 3) the pN categories determined by the number of metastatic perigastric nodes resected by standard D1 gastrectomy. Survival data were analyzed for each group. RESULTS: The number of metastatic nodes after D2 lymphadenectomy reflected prognosis well and was shown by multivariate analysis to be a strong independent prognostic factor. When the classification was performed limited to the metastatic perigastric nodes, stage migration was evident, but the variable remained competent as a prognostic indicator. CONCLUSIONS: The number of metastatic nodes is a promising determinant in the new international stage classification.

Adult↗

Pharmacological detection of AMPA receptor heterogeneity by use of two allosteric potentiators in rat hippocampal cultures.

1. In order to examine whether a recently developed allosteric potentiator for AMPA receptors, 4-[2-(phenylsulphonylamino)ethylthio]-2,6-difluoro-phenoxyaceta mide (PEPA), can be utilized as an indicator of AMPA receptor heterogeneity, the action of PEPA upon the increase of intracellular free calcium ion concentration ([Ca2+]i) elicited by AMPA was investigated in rat hippocampal cultures, and the action was compared with that of cyclothiazide, a well characterized allosteric modulator of AMPA receptors. 2. PEPA dose-dependently potentiated AMPA-induced increase of [Ca2+]i. In 90% (72 out of 80) of the cells in which cyclothiazide acts, PEPA potentiated the increased [Ca2+]i induced by AMPA with pronounced cell-to-cell variation in rat hippocampal cultures. 3. The ratio of the potentiation by PEPA to the potentiation by cyclothiazide (P/C ratio) also varied with cells between 0 and 2.15. It was found that the cultured hippocampal cells consisted of multiple populations with different P/C ratios. Among them two populations exhibited characteristic P/C ratios; low (0 to 0.15; 27 out of 80 cells, 34%) and high (> or = 2.00; 1 out of 80 cells, 1%) P/C ratios. The P/C ratios of the other populations were between 0.25 and 1.20, and these cells constituted 65% (52 out of 80 cells) of the cells tested. 4. Reverse transcriptase-polymerase chain reaction analysis suggested that GluR2-flip, GluR1-flip, GluR2-flop, and GluR1-flop were abundantly expressed (in this rank order) in the cultures used. 5. In Xenopus oocytes expressing GluR1, GluR3, or these subunits plus GluR2, the potentiation of AMPA response by PEPA and by cyclothiazide varied with subunit and splice-variant combinations, and the P/C ratio was between 0.19 and 2.20. Oocytes with low P/C ratios (0.19 to 0.50) and low sensitivity to PEPA potentiation (1.9 fold to 6.41 fold) were those expressing flip variants predominantly, and oocytes with high P/C ratios (1.8 to 2.2) were those expressing flop variants predominantly. Oocytes with intermediate P/C ratios (0.51 to 1.20) were those expressing various combinations of flip and flop variants, and it was impossible to specify the relative abundance of flip and flop variants in these cells. Therefore, the P/C ratio can be used to infer subunit/splice variant expression only when the ratio is low or high. 6. These results suggest that the potentiation by PEPA alone reveals cell-to-cell heterogeneity of AMPA receptors, but a comparison of the actions of PEPA and cyclothiazide further facilitates the detection of the heterogeneity.

Allosteric Regulation↗

The effect of a secreted form of beta-amyloid-precursor protein on intracellular Ca2+ increase in rat cultured hippocampal neurones.

1. The effects of secreted forms of beta-amyloid-precursor proteins (APP(S)s) on the intracellular Ca2+ concentration ([Ca2+]i) were investigated in rat cultured hippocampal neurones. APP695S, a secretory form of APP695, attenuated the increase in [Ca2+]i evoked by glutamate. In addition, APP695S itself evoked an increase in [Ca2+]i in 1 or 2 day-cultured hippocampal cells, but not in 7 to 13 day-cultured cells. 2. Eighty-one percent of neurones which were immunocytochemically positive for microtubule-associated protein 2 responded to APP695S with an increase in [Ca2+]i. 3. APP695S induced a transient rise in [Ca2+]i even in the absence of extracellular Ca2+ and produced an elevation in inositol-1,4,5-trisphosphate (IP3) in a concentration-dependent manner from 100 to 500 ng ml(-1). In the presence of extracellular Ca2+, APP695S caused a transient rise in [Ca2+]i followed by a sustained phase at high [Ca2+]i, suggesting Ca2+ entry from the extracellular space. 4. The [Ca2+]i elevation was mimicked by amino terminal peptides of APPs, but not by carboxy terminal peptides. 5. These results taken together suggest that APP695S induces an increase in [Ca2+]i in hippocampal neurones through an IP3-dependent mechanism that changes according to the stage of development.

Amyloid beta-Protein Precursor↗

ATP stimulation of Ca2+ -dependent plasminogen release from cultured microglia.

1. ATP (10-100 microM), but not glutamate (100 microM), stimulated the release of plasminogen from microglia in a concentration-dependent manner during a 10 min stimulation. However, neither ATP (100 microM) nor glutamate (100 microM) stimulated the release of NO. A one hour pretreatment with BAPTA-AM (200 microM), which is metabolized in the cytosol to BAPTA (an intracellular Ca2+ chelator), completely inhibited the plasminogen release evoked by ATP (100 microM). The Ca2+ ionophore A23187 induced plasminogen release in a concentration-dependent manner (0.3 microM to 10 microM). 2. ATP induced a transient increase in the intracellular calcium concentration ([Ca2+]i) in a concentration-dependent manner which was very similar to the ATP-evoked plasminogen release, whereas glutamate (100 microM) had no effect on [Ca2+]i (70 out of 70 cells) in microglial cells. A second application of ATP (100 microM) stimulated an increase in [Ca2+]i similar to that of the first application (21 out of 21 cells). 3. The ATP-evoked increase in [Ca2+]i was totally dependent on extracellular Ca2+, 2-Methylthio ATP was active (7 out of 7 cells), but alpha,beta-methylene ATP was inactive (7 out of 7 cells) at inducing an increase in [Ca2+]i. Suramin (100 microM) was shown not to inhibit the ATP-evoked increase in [Ca2+]i (20 out of 20 cells). 2'- and 3'-O-(4-Benzoylbenzoyl)-adenosine 5'-triphosphate (BzATP), a selective agonist of P2X7 receptors, evoked a long-lasting increase in [Ca2+]i even at 1 microM, a concentration at which ATP did not evoke the increase. One hour pretreatment with adenosine 5'-triphosphate-2', 3'-dialdehyde (oxidized ATP, 100 microM), a selective antagonist of P2X7 receptors, blocked the increase in [Ca2+]i induced by ATP (10 and 100 microM). 4. These data suggest that ATP may transit information from neurones to microglia, resulting in an increase in [Ca2+]i via the ionotropic P2X7 receptor which stimulates the release of plasminogen from the microglia.

Adenosine Triphosphate↗

Comparison of the most comfortable mandibular position with the intercuspal position using cephalometric analysis.

For evaluation of the most comfortable position (MCP) in edentulous subjects, as decided by mandibular position sense, the MCP was recorded in ten edentulous subjects and compared with the intercuspal position (ICP) of normal dentate persons. It was found that the MCP was at a lower mandibular position than the ICP; the facial height was markedly reduced in the former by a front-upward rotation of the mandible centering around the condyles. Thus, it has been suggested that the occlusal vertical dimension (OVD) of the MCP in the restored dentition is less than that of the original ICP.

Age Factors↗

Trichomonas tenax empyema in an immunocompromised patient with advanced cancer.

A 53-year-old male acromegalic patient with advanced rectal adenocarcinoma developed pleuritis in the course of cobalt irradiation, steroid treatment and chemotherapy. Examination of drained pleural fluid demonstrated numerous motile organisms, which were identified as Trichomonas tenax by Giemsa staining. Peptostreptococcus micros was also detected in the cultures of pleural fluid and blood. Treatment with metronidazole successfully eliminated the protozoa and cured the pyothorax.

Acromegaly↗

Thrombospondin-1 expression in human myometrium before and during pregnancy, before and during labor, and in human myometrial cells in culture.

The activation of latent transforming growth factor beta (L-TGFbeta) is essential for the action of TGFbeta, which, in turn, is involved in the regulation of expression of some progesterone-responsive genes. One mechanism by which TGFbeta is activated involves thrombospondin (TSP), a protein that binds extracellular proteins. Immunoreactive TSP (irTSP) protein and TSP-1 mRNA in myometrial tissues of ovulatory and pregnant women were localized by immunohistochemistry and in situ hybridization. IrTSP and TSP-1 mRNA were randomly distributed in myometrial smooth muscle cells of some, but not all, tissues of pregnant women at term before labor; but in some areas of most of these tissues, irTSP was intense and commonly localized extracellularly. Intense irTSP and TSP-1 mRNA in myocytes were more common in myometrium during labor. In myometrium from ovulatory women (n = 26), irTSP was localized primarily in vascular smooth muscle cells and was detected occasionally in scattered myocytes. Little TSP-1 mRNA was demonstrable by in situ hybridization in vessels or myocytes of myometrial tissue from ovulatory women (n = 7). By Northern analysis of total RNA, TSP-1 mRNA was detected in myometrial tissue of pregnant women and in human myometrial smooth muscle cells in culture. The levels of TSP-1 mRNA in myometrial tissues of pregnant women during labor (n = 18) were greater than those in myometrium at > 37 wk gestation before labor began (n = 25, p < 0.001). The ratios of TSP-1 to glyceraldehyde 3-phosphate dehydrogenase mRNAs in 3 myometrial tissues during oxytocin-induced labor were not statistically different from those in myometrium during spontaneous labor but were greater than those in myometrium before labor (p < 0.05). The level of TSP-1 mRNA in confluent human myometrial cells in culture was relatively high, was increased by treatment with fetal bovine serum, and was decreased by treatment with platelet-derived growth factor or activators of adenylyl cyclase or protein kinase C. Myometrial cells in culture constitute a useful model for studying the regulation of TSP-1 gene expression in human myometrium.

Adult↗

The role of radical gastrectomy with systematic lymphadenectomy for the diagnosis and treatment of primary gastric lymphoma.

OBJECTIVE: We evaluated the therapeutic efficacy of radical gastrectomy for primary B-cell lymphoma of the stomach and attempted to identify patients who could be adequately treated with surgery alone. SUMMARY BACKGROUND DATA: Several recent gastric lymphoma reports have discussed the therapeutic benefits of various treatment strategies for stage IE and IIE lymphoma. However, few studies have been based on patients accurately staged by systematic lymphadenectomy with subsequent pathologic examination. METHODS: A retrospective study was performed to evaluate the survival and biologic behavior of lesions in 60 patients with gastric lymphoma who were treated by radical gastrectomy alone. Tumors were classified according to the histopathologic concept of mucosa-associated lymphoid tissue (MALT)-derived lymphoma. RESULTS: A low histopathologic grade was associated with a significantly lower incidence of nodal metastasis (p = 0.07) and less extensive infiltration of the gastric wall (p < 0.005) despite larger tumor size. A 5-year survival rate of >95% was attained with surgery alone for MALT lymphoma and for true stage IE lymphoma diagnosed by pathologic examination of up to N2 lymph nodes routinely performed after radical gastrectomy. CONCLUSIONS: Surgery alone is adequate treatment for stage IE or pure MALT lymphoma, provided that the staging is performed after radical gastrectomy.

Adult↗

Spinal cord blood flow and pathophysiological changes after transient spinal cord ischemia in cats.

OBJECTIVE: The goal was to study the hemodynamics and regional pathophysiological changes in the spinal cord after transient vascular occlusion in cats. METHODS: We measured spinal cord blood flow (SCBF) continuously in the lumbar region with a laser-doppler flowmeter, before, during, and after spinal cord ischemia induced by balloon occlusion of the thoracic aorta, in 24 cats (divided into three groups) and simultaneously recorded the evoked spinal cord potentials (ESPs). In each group (n = 8), 10-, 20-, and 30-minute ischemic loading was performed. All animals were evaluated neurologically 36 hours later, and then their spinal cords were examined histologically. RESULTS: The amplitude of ESPs decreased 10 minutes and disappeared 20 minutes after occlusion. SCBF increased to as much as 2 times the control values after reperfusion and decreased gradually in all groups. Then, in all animals in the 10-minute group and six animals in the 20-minute group, SCBF returned to the control values, which were subsequently maintained throughout the experiment, and ESPs returned to normal patterns within 1 hour. For all animals in the 30-minute group and two in the 20-minute group, hypoperfusion after recirculation, irreversible amplitude changes in ESPs, postischemic paraparesis, and pathological ischemic changes in the lower thoracic and lumbar spinal segments were recognized. CONCLUSION: Our results showed that > 20-minute occlusion of the thoracic aorta in cats resulted in irreversible spinal perfusion disorders and that the monitoring of SCBF and ESPs could be useful for predicting potential neurological deficits. Furthermore, postischemic hypoperfusion may have an important role in the development of secondary spinal cord ischemia, resulting in severe neurological dysfunction. This observation suggested the possibility of therapeutic modification of the secondary processes inducing hypoperfusion after spinal ischemia.

Angiography↗

The effect of sevoflurane on myogenic motor-evoked potentials induced by single and paired transcranial electrical stimulation of the motor cortex during nitrous oxide/ketamine/fentanyl anesthesia.

To overcome anesthetic-induced depression of myogenic motor-evoked potentials (MEPs), several techniques of stimulation using paired pulses or trains of pulses are used. This study investigated the effect of sevoflurane on myogenic MEPs induced by single and paired transcranial electrical stimulation of the motor cortex. Nine patients undergoing elective spinal surgery were anesthetized with fentanyl-N2O-ketamine. Partial neuromuscular blockade (single-twitch height 15% of baseline) was maintained with vecuronium. Single and paired (interstimulus interval 2 milliseconds) electrical stimuli were delivered to the scalp, and compound muscle action potentials were recorded from the left and right tibialis anterior muscles. In all patients, baseline MEPs were recorded from both the left and right anterior tibialis muscles (in a total of 18 legs). During the administration of 0.25 MAC and 0.5 MAC sevoflurane, MEPs induced by stimulation with a single pulse could be recorded in 12 of 18 and 4 of 18 legs, respectively, and MEP amplitude was significantly reduced to 48% and 4% of the control value, respectively. During the administration of 0.75 MAC sevoflurane, MEPs following single-pulse stimulation could not be recorded in any legs. The success rate of MEP recording during the administration of sevoflurane was greater after paired stimulation than after single stimulation, and percentage MEP amplitude (percentage of the control value after single stimulation but before sevoflurane) after paired stimulation was significantly higher than after single stimulation before and during the administration of 0.25 MAC and 0.5 MAC sevoflurane. The success rate of MEP recording and MEP amplitude after paired stimulation decreased in a dose-dependent manner during the administration of sevoflurane. These results suggest that although facilitation by the second stimulus was considerable, paired stimuli are still not sufficient to overcome the depressant effects of sevoflurane in clinically used concentrations.

Action Potentials↗

Role of plasma osmolality in the delayed onset of thermal cutaneous vasodilation during exercise in humans.

To elucidate the role of increased plasma osmolality (Posmol), which occurs during exercise in the regulation of cutaneous vasodilation (CVD) during exercise, we determined the relationship between the change in esophageal temperature (DeltaTes) required to elicit CVD (DeltaTes threshold for CVD) and Posmol during light and moderate exercise (30 and 55% of peak oxygen consumption, respectively) and passive body heating. Then we compared the relationship with the data obtained in our previous study [A. Takamata, K. Nagashima, H. Nose, and T. Morimoto. Am. J. Physiol. 273 (Regulatory Integrative Comp. Physiol. 42): R197-R204, 1997], in which we determined the relationships during passive body heating following isotonic (0.9% NaCl) or hypertonic (2 or 3% NaCl) saline infusions in the same subjects. Posmol values at 5 min after the onset of exercise were 287.5 +/- 0.9 mosmol/kgH2O during light exercise and 293.0 +/- 1.2 mosmol/kgH2O during moderate exercise. Posmol just before passive body heating was 289.9 +/- 1.4 mosmol/kgH2O. The DeltaTes threshold for CVD was 0.09 +/- 0.05 degrees C during light exercise, 0.31 +/- 0. 09 degrees C during moderate exercise, and 0.10 +/- 0.05 degrees C during passive body heating. The relationship between the DeltaTes threshold for CVD and Posmol was shown to be on the same regression line both during exercise and during passive body heating with or without infusions [A. Takamata, K. Nagashima, H. Nose, and T. Morimoto. Am. J. Physiol. 273 (Regulatory Integrative Comp. Physiol. 42): R197-R204, 1997]. Our data suggest that the elevated body core temperature threshold for CVD during exercise could be the result of increased Posmol induced by exercise and is not due to reduced plasma volume or the intensity of the exercise itself.

Adult↗

Effect of continuous negative-pressure breathing on skin blood flow during exercise in a hot environment.

To assess the impact of continuous negative-pressure breathing (CNPB) on the regulation of skin blood flow, we measured forearm blood flow (FBF) by venous-occlusion plethysmography and laser-Doppler flow (LDF) at the anterior chest during exercise in a hot environment (ambient temperature = 30 degreesC, relative humidity = approximately 30%). Seven male subjects exercised in the upright position at an intensity of 60% peak oxygen consumption rate for 40 min with and without CNPB after 20 min of exercise. The esophageal temperature (Tes) in both conditions increased to 38.1 degreesC by the end of exercise, without any significant differences between the two trials. Mean arterial pressure (MAP) increased by approximately 15 mmHg by 8 min of exercise, without any significant difference between the two trials before CNPB. However, CNPB reduced MAP by approximately 10 mmHg after 24 min of exercise (P < 0.05). The increase in FBF and LDF in the control condition leveled off after 18 min of exercise above a Tes of 37.7 degreesC, whereas in the CNPB trial the increase continued, with a rise in Tes despite the decrease in MAP. These results suggest that CNPB enhances vasodilation of skin above a Tes of approximately 38 degrees C by stretching intrathoracic baroreceptors such as cardiopulmonary baroreceptors.

Adult↗