Metástase hepática de tumor gastrointestinal estromal (gist) em cão: relato de caso / Hepatic metastasis of gastrointestinal stromal tumors (gist) in dog: case report

Os tumores mesenquimais originados a partir de células intersticiais de Cajal, denominados tumores gastrointestinais estromais (GIST) são raros em humanos e com incidência ainda desconhecida em cães. A diferenciação de GIST, leiomiossarcoma e leiomioma com base apenas em exames de imagem, morfológicos e colorações simples por meio da histologia é muitas vezes difícil, sendo indicada realização de imuno-histoquímica. Foi atendida uma cadela, sem padrão racial definido, oito anos, 17kg de peso corporal, com discreto aumento de volume abdominal, sendo evidenciada por ultrassom abdominal neoformação intra-abdominal em região mesogástrica, sem demais alterações clínicas. Durante celiotomia exploratória, identificou-se que a neoformação intestinal localizava-se em jejuno, optando pela realização de enterectomia, sendo posteriormente diagnosticada como leiomiossarcoma pela análise histopatológica. Preconizou-se a instituição de quimioterapia adjuvante com o uso de doxorrubicina (30 mg/m²), a cada 21 dias, totalizando seis sessões. Após dez meses do tratamento cirúrgico, a paciente foi submetida a novo estadiamento clínico, sendo visibilizado, mediante ultrassom abdominal neoformações sólidas em fígado. A partir de biópsia hepática guiada por ultrassom com agulha “tru-cut” e análise histológica e imuno-histoquímica, definiu-se que as neoformações hepáticas eram metástases de GIST, instituindo o tratamento com fosfato de toceranib (Palladia®). Desde o momento da enterectomia ao óbito da paciente, contabilizou-se 20,4 meses de sobrevida global.

Mesenchymal tumors originating from interstitial cells of Cajal, called stromal gastrointestinal tumors (GIST) are rare in humans and their incidence is still unknown in dogs. The differentiation of GIST, leiomyosarcoma and leiomyoma based only on imaging, morphological and simple staining through histology is often difficult, and immunohistochemistry is indicated. A female dog, mixed breed, eight years old, 17kg of body weight, with a slight increase in abdominal volume, and ultrasound evidence of an intra-abdominal neoformation in the mesogastric region, without other clinical changes was seen. During exploratory celiotomy, it was identified that the intestinal neoformation in jejunum, opting for enterectomy, being identified as leiomyosarcoma according to histopathological analysis. Adjuvant chemotherapy was instituted using doxorubicin (30mg / m²) every 21 days, totaling six sessions. The patient underwent a new clinical staging, 10 months after enterectomy, where were visualized, by abdominal ultrasound, neoformations in the liver. Based on ultrasound guided liver biopsy with “tru-cut” needle and histological and immunohistochemical analysis, the neoformation was defined as GIST liver metastasis, being instituted treatment with toceranib phosphate (Palladia®). From the time of enterectomy to the death of the patient, 20,4 months of overall survival were counted.

Metástase hepática de tumor gastrointestinal estromal (gist) em cão: relato de caso / Hepatic metastasis of gastrointestinal stromal tumors (gist) in dog: case report

Os tumores mesenquimais originados a partir de células intersticiais de Cajal, denominados tumores gastrointestinais estromais (GIST) são raros em humanos e com incidência ainda desconhecida em cães. A diferenciação de GIST, leiomiossarcoma e leiomioma com base apenas em exames de imagem, morfológicos e colorações simples por meio da histologia é muitas vezes difícil, sendo indicada realização de imuno-histoquímica. Foi atendida uma cadela, sem padrão racial definido, oito anos, 17kg de peso corporal, com discreto aumento de volume abdominal, sendo evidenciada por ultrassom abdominal neoformação intra-abdominal em região mesogástrica, sem demais alterações clínicas. Durante celiotomia exploratória, identificou-se que a neoformação intestinal localizava-se em jejuno, optando pela realização de enterectomia, sendo posteriormente diagnosticada como leiomiossarcoma pela análise histopatológica. Preconizou-se a instituição de quimioterapia adjuvante com o uso de doxorrubicina (30 mg/m²), a cada 21 dias, totalizando seis sessões. Após dez meses do tratamento cirúrgico, a paciente foi submetida a novo estadiamento clínico, sendo visibilizado, mediante ultrassom abdominal neoformações sólidas em fígado. A partir de biópsia hepática guiada por ultrassom com agulha “tru-cut” e análise histológica e imuno-histoquímica, definiu-se que as neoformações hepáticas eram metástases de GIST, instituindo o tratamento com fosfato de toceranib (Palladia®). Desde o momento da enterectomia ao óbito da paciente, contabilizou-se 20,4 meses de sobrevida global.(AU)

Mesenchymal tumors originating from interstitial cells of Cajal, called stromal gastrointestinal tumors (GIST) are rare in humans and their incidence is still unknown in dogs. The differentiation of GIST, leiomyosarcoma and leiomyoma based only on imaging, morphological and simple staining through histology is often difficult, and immunohistochemistry is indicated. A female dog, mixed breed, eight years old, 17kg of body weight, with a slight increase in abdominal volume, and ultrasound evidence of an intra-abdominal neoformation in the mesogastric region, without other clinical changes was seen. During exploratory celiotomy, it was identified that the intestinal neoformation in jejunum, opting for enterectomy, being identified as leiomyosarcoma according to histopathological analysis. Adjuvant chemotherapy was instituted using doxorubicin (30mg / m²) every 21 days, totaling six sessions. The patient underwent a new clinical staging, 10 months after enterectomy, where were visualized, by abdominal ultrasound, neoformations in the liver. Based on ultrasound guided liver biopsy with “tru-cut” needle and histological and immunohistochemical analysis, the neoformation was defined as GIST liver metastasis, being instituted treatment with toceranib phosphate (Palladia®). From the time of enterectomy to the death of the patient, 20,4 months of overall survival were counted.(AU)

Concentration-dependence of dithiothreitol effects on rat distal colon electrophysiology

Dithiothreitol (DTT), at 1 mmol/L or higher, is widely used as a mucolytic in gastrointestinal research. Previous observations suggest that it may be toxic to the mucosa. DTT effects on the mucosal electrical behavior were assessed. Cumulative concentration-response relationships of DTT effects on rat distal colon mucosa were studied. Isolated mucosa preparations were mounted in an Ussing chamber under short-circuit conditions. The effects of concentrations ranging from 1 mumol/L to 1 mmol/L, applied to either the mucosal or serosal side, were studied. As compared with control, untreated preparations, DTT depressed short-circuit current at 10 mumol/L and higher when applied to the serosal side, and at 50 mumol/L and higher when applied to the mucosal side of the epithelium. On the other hand, transepithelial resistivity showed a progressive increase with DTT applied to either side at a concentration of up to 500 mumol/L, while at the highest concentration (1 mmol/L) a marked decrease in resistivity occurred. Neither the short-circuit current decrease, nor the resistivity collapse showed recovery after repeated rinsing with DTT-free solution. It is concluded that DTT affects epithelial electrical properties at low concentrations, and therefore its use as a mucolytic for electrophysiological studies should be discouraged.

Concentration-dependence of dithiothreitol effects on rat distal colon electrophysiology

Dithiothreitol (DTT), at 1 mmol/L or higher, is widely used as a mucolytic in gastrointestinal research. Previous observations suggest that it may be toxic to the mucosa. DTT effects on the mucosal electrical behavior were assessed. Cumulative concentration-response relationships of DTT effects on rat distal colon mucosa were studied. Isolated mucosa preparations were mounted in an Ussing chamber under short-circuit conditions. The effects of concentrations ranging from 1 mumol/L to 1 mmol/L, applied to either the mucosal or serosal side, were studied. As compared with control, untreated preparations, DTT depressed short-circuit current at 10 mumol/L and higher when applied to the serosal side, and at 50 mumol/L and higher when applied to the mucosal side of the epithelium. On the other hand, transepithelial resistivity showed a progressive increase with DTT applied to either side at a concentration of up to 500 mumol/L, while at the highest concentration (1 mmol/L) a marked decrease in resistivity occurred. Neither the short-circuit current decrease, nor the resistivity collapse showed recovery after repeated rinsing with DTT-free solution. It is concluded that DTT affects epithelial electrical properties at low concentrations, and therefore its use as a mucolytic for electrophysiological studies should be discouraged.(AU)

Sodium-deprived rat distal colon epithelial response to acute hypoxia and reoxygenation.

In normal rat distal colon isolated mucosa, basal short-circuit current (Isc) is mostly due to chloride secretion. Isc is depressed by a brief (5 min) acute hypoxia and overshoots above baseline during reoxygenation. Sodium deprivation raises serum aldosterone levels and leads to expression of functional epithelial sodium channels which are amiloride-sensitive. Thus, in sodium-deprived rats (SDRs) Isc is dependent on electrogenic sodium absorption. Since the ion primarily responsible for the Isc is different in each functional condition, it is not known whether hypoxia and reoxygenation affect SDRs epithelial response in the same way as in normal rats. Therefore the electrical behavior of isolated mucosa preparations from normal and SDRs was studied in an Ussing chamber, and the effect of the epithelial sodium channel blocker, amiloride sensitive, basal Isc than controls. Their response to hypoxia (expressed as a fraction of basal Isc) was similar to controls but upon reoxygenation their recovery was incomplete. SDRs response to hypoxia was not affected by amiloride at any concentration tested. However, post-hypoxic recovery was modified by amiloride in a concentration-dependent way: it was incomplete at 10(-8) M, complete at 10(-6) M, and at 10(-4) M it overshooted above baseline values. Therefore, in sodium-deprived rats, sodium channel blockade reverts the pattern of blunted recovery to the overshooting pattern seen normal rats. These results may be explained by two non-mutually exclusive hypotheses: Epithelial sodium channel blockade in sodium-deprived rats might (1) unmask a basal chloride conductance, and (2) interfere with a negative interaction between sodium chloride conductances.

Concentration-dependence of dithiothreitol effects on rat distal colon electrophysiology.

Dithiothreitol (DTT), at 1 mmol/L or higher, is widely used as a mucolytic in gastrointestinal research. Previous observations suggest that it may be toxic to the mucosa. DTT effects on the mucosal electrical behavior were assessed. Cumulative concentration-response relationships of DTT effects on rat distal colon mucosa were studied. Isolated mucosa preparations were mounted in an Ussing chamber under short-circuit conditions. The effects of concentrations ranging from 1 mumol/L to 1 mmol/L, applied to either the mucosal or serosal side, were studied. As compared with control, untreated preparations, DTT depressed short-circuit current at 10 mumol/L and higher when applied to the serosal side, and at 50 mumol/L and higher when applied to the mucosal side of the epithelium. On the other hand, transepithelial resistivity showed a progressive increase with DTT applied to either side at a concentration of up to 500 mumol/L, while at the highest concentration (1 mmol/L) a marked decrease in resistivity occurred. Neither the short-circuit current decrease, nor the resistivity collapse showed recovery after repeated rinsing with DTT-free solution. It is concluded that DTT affects epithelial electrical properties at low concentrations, and therefore its use as a mucolytic for electrophysiological studies should be discouraged.

Sodium-deprived rat distal colon epithelial response to acute hypoxia and reoxygenation.

In normal rat distal colon isolated mucosa, basal short-circuit current (Isc) is mostly due to chloride secretion. Isc is depressed by a brief (5 min) acute hypoxia and overshoots above baseline during reoxygenation. Sodium deprivation raises serum aldosterone levels and leads to expression of functional epithelial sodium channels which are amiloride-sensitive. Thus, in sodium-deprived rats (SDRs) Isc is dependent on electrogenic sodium absorption. Since the ion primarily responsible for the Isc is different in each functional condition, it is not known whether hypoxia and reoxygenation affect SDRs epithelial response in the same way as in normal rats. Therefore the electrical behavior of isolated mucosa preparations from normal and SDRs was studied in an Ussing chamber, and the effect of the epithelial sodium channel blocker, amiloride sensitive, basal Isc than controls. Their response to hypoxia (expressed as a fraction of basal Isc) was similar to controls but upon reoxygenation their recovery was incomplete. SDRs response to hypoxia was not affected by amiloride at any concentration tested. However, post-hypoxic recovery was modified by amiloride in a concentration-dependent way: it was incomplete at 10(-8) M, complete at 10(-6) M, and at 10(-4) M it overshooted above baseline values. Therefore, in sodium-deprived rats, sodium channel blockade reverts the pattern of blunted recovery to the overshooting pattern seen normal rats. These results may be explained by two non-mutually exclusive hypotheses: Epithelial sodium channel blockade in sodium-deprived rats might (1) unmask a basal chloride conductance, and (2) interfere with a negative interaction between sodium chloride conductances.

Concentration-dependence of dithiothreitol effects on rat distal colon electrophysiology.

Dithiothreitol (DTT), at 1 mmol/L or higher, is widely used as a mucolytic in gastrointestinal research. Previous observations suggest that it may be toxic to the mucosa. DTT effects on the mucosal electrical behavior were assessed. Cumulative concentration-response relationships of DTT effects on rat distal colon mucosa were studied. Isolated mucosa preparations were mounted in an Ussing chamber under short-circuit conditions. The effects of concentrations ranging from 1 mumol/L to 1 mmol/L, applied to either the mucosal or serosal side, were studied. As compared with control, untreated preparations, DTT depressed short-circuit current at 10 mumol/L and higher when applied to the serosal side, and at 50 mumol/L and higher when applied to the mucosal side of the epithelium. On the other hand, transepithelial resistivity showed a progressive increase with DTT applied to either side at a concentration of up to 500 mumol/L, while at the highest concentration (1 mmol/L) a marked decrease in resistivity occurred. Neither the short-circuit current decrease, nor the resistivity collapse showed recovery after repeated rinsing with DTT-free solution. It is concluded that DTT affects epithelial electrical properties at low concentrations, and therefore its use as a mucolytic for electrophysiological studies should be discouraged.

Oxygen diffusive barriers of rat distal colon: role of subepithelial tissue, mucosa, and mucus gel layer.

The contributions of subepithelial tissue, mucosa, and mucus gel layer as restraints for oxygen diffusion in rat distal colon in vitro were assessed by comparing oxygen transfer through preparations of isolated submucosa, isolated mucosa with and without the superficial mucus gel layer, and mucosa-submucosa mounted as flat sheets in a diffusion chamber. One side of the chamber was gassed with 95% O2-5% CO2 while the time course of oxygen concentration rise was measured in the continuously stirred opposite side, initially equilibrated with near-zero oxygen solution. The procedure does not affect epithelial viability. Diffusion in isolated mucosa was the same before and after KCN (5 mM) treatment, suggesting that epithelial oxygen consumption does not influence transfer rates. Subepithelial tissue, mucosa, and mucus gel layer are roughly responsible, respectively, for 12%, 56%, and 32% of oxygen diffusive hindrance. Diffusion coefficients range from 13% (mucosa-submucosa) to 54% (isolated submucosa) of that of water. Subepithelial tissue accounts for about 12% of total diffusive restraint.

Asymmetrical oxygen availability from serosal and luminal sides of rat distal colon epithelium.

Short-circuit current (Isc) and transepithelial potential difference (PD) of the rat distal colon mucosa are sensitive to acute hypoxia in vitro. The relative contribution of luminal and serosal oxygenation in sustaining Isc and PD was assessed. Rat distal colon Isc and PD responses to hypoxia and reoxygenation of preparations of mucosa-submucosa, and of isolated mucosa (with and without the mucus gel layer), mounted in an Ussing chamber, and of sacs of everted and non-everted isolated mucosa, were measured. In Ussing chambers, a 5-min total (bilateral) hypoxia reduces Isc and PD by 50 to 70%, while an overshoot was observed on reoxygenation. Serosal hypoxia caused about the same effect as total hypoxia, with complete recovery on reoxygenation. Luminal hypoxia had no effect in either Isc or PD. After total hypoxia, selective serosal reoxygenation allowed complete recovery of Isc and PD; addition of luminal reoxygenation did not further increase Isc and PD. Luminal reoxygenation after total hypoxia did not modify the decrease in Isc and PD, but addition of serosal reoxygenation led to complete recovery. A similar behaviour was seen in isolated mucosa preparations without the mucus gel layer. Baseline Isc and PD of everted sacs were about 45% of those of non-everted sacs, but their response to a hypoxic challenge was slightly attenuated. On reoxygenation, both everted and non-everted sacs showed complete recovery. Summing up: serosal oxygenation is both necessary and sufficient to sustain rat distal colon Isc and PD, while luminal oxygenation is not; there seems to exist a barrier, different from the mucus gel layer, for oxygen access from the luminal side of the epithelium; and distal colon isolated mucosa everted sac preparations are suboptimally oxygenated.