Acute extracellular fluid volume changes increase ileocolonic resistance to saline flow in anesthetized dogs

We determined the effect of acute extracellular fluid volume changes on saline flow through 4 gut segments (ileocolonic, ileal, ileocolonic sphincter and proximal colon), perfused at constant pressure in anesthetized dogs. Two different experimental protocols were used: hypervolemia (iv saline infusion, 0.9% NaCl, 20 ml/min, volume up to 5% body weight) and controlled hemorrhage (up to a 50% drop in mean arterial pressure). Mean ileocolonic flow (N = 6) was gradually and significantly decreased during the expansion (17.1%, P<0.05) and expanded (44.9%, P<0.05) periods while mean ileal flow (N = 7) was significantly decreased only during the expanded period (38%, P<0.05). Mean colonic flow (N = 7) was decreased during expansion (12%, P<0.05) but returned to control levels during the expanded period. Mean ileocolonic sphincter flow (N = 6) was not significantly modified. Mean ileocolonic flow (N = 10) was also decreased after hemorrhage (retracted period) by 17% (P<0.05), but saline flow was not modified in the other separate circuits (N = 6, 5 and 4 for ileal, ileocolonic sphincter and colonic groups, respectively). The expansion effect was blocked by atropine (0.5 mg/kg, iv) both on the ileocolonic (N = 6) and ileal (N = 5) circuits. Acute extracellular fluid volume retraction and expansion increased the lower gastrointestinal resistances to saline flow. These effects, which could physiologically decrease the liquid volume being supplied to the colon, are possible mechanisms activated to acutely balance liquid volume deficit and excess.

Gastroduodenal resistance and neural mechanisms involved in saline flow decrease elicited by acute blood volume expansion in anesthetized rats

We have previously demonstrated that blood volume (BV) expansion decreases saline flow through the gastroduodenal (GD) segment in anesthetized rats (Xavier-Neto J, dos Santos AA & Rola FH (1990) Gut, 31: 1006-1010). The present study attempts to identify the site(s) of resistance and neural mechanisms involved in this phenomenon. Male Wistar rats (N = 97, 200-300 g) were surgically manipulated to create four gut circuits: GD, gastric, pyloric and duodenal. These circuits were perfused under barostatically controlled pressure (4 cmH2O). Steady-state changes in flow were taken to reflect modifications in circuit resistances during three periods of time: normovolemic control (20 min), expansion (10-15 min), and expanded (30 min). Perfusion flow rates did not change in normovolemic control animals over a period of 60 min. BV expansion (Ringer bicarbonate, 1 ml/min up to 5% body weight) significantly (P<0.05) reduced perfusion flow in the GD (10.3 ± 0.5 to 7.6 ± 0.6 ml/min), pyloric (9.0 ± 0.6 to 5.6 ± 1.2 ml/min) and duodenal (10.8 ± 0.4 to 9.0 ± 0.6 ml/min) circuits, but not in the gastric circuit (11.9 ± 0.4 to 10.4 ± 0.6 ml/min). Prazosin (1 mg/kg) and yohimbine (3 mg/kg) prevented the expansion effect on the duodenal but not on the pyloric circuit. Bilateral cervical vagotomy prevented the expansion effect on the pylorus during the expansion but not during the expanded period and had no effect on the duodenum. Atropine (0.5 mg/kg), hexamethonium (10 mg/kg) and propranolol (2 mg/kg) were ineffective on both circuits. These results indicate that 1) BV expansion increases the GD resistance to liquid flow, 2) pylorus and duodenum are important sites of resistance, and 3) yohimbine and prazosin prevented the increase in duodenal resistance and vagotomy prevented it partially in the pylorus

Variations in gastric emptying of liquid elicited by acute blood volume changes in awake rats

We have observed that acute blood volume expansion increases the gastroduodenal resistance to the flow of liquid in anesthetized dogs, while retraction decreases it (Santos et al. (1991) Acta Physiologica Scandinavica, 143: 261-269). This study evaluates the effect of blood volume expansion and retraction on the gastric emptying of liquid in awake rats using a modification of the technique of Scarpignato (1980) (Archives Internationales de Pharmacodynamie et de Therapie, 246: 286-294). Male Wistar rats (180-200 g) were fasted for 16 h with water ad libitum and 1.5 ml of the test meal (0.5 mg/ml phenol red solution in 5% glucose) was delivered to the stomach immediately after random submission to one of the following protocols: 1) normovolemic control (N = 22), 2) expansion (N = 72) by intravenous infusion (1 ml/min) of Ringer-bicarbonate solution, volumes of 1, 2, 3 or 5% body weight, or 3) retraction (N = 22) by controlled bleeding (1.5 ml/100 g). Gastric emptying of liquid was inhibited by 19-51.2% (P<0.05) after blood volume expansion (volumes of 1, 2, 3 or 5% body weight). Blood volume expansion produced a sustained increase in central venous pressure while mean arterial pressure was transiently increased during expansion (P<0.05). Blood volume retraction increased gastric emptying by 28.5-49.9% (P<0.05) and decreased central venous pressure and mean arterial pressure (P<0.05). Infusion of the shed blood 10 min after bleeding reversed the effect of retraction on gastric emptying. These findings suggest that gastric emptying of liquid is subject to modulation by the blood volume.

Reference values for lung function tests: I. Static volumes

Static lung volume (LV) measurements have a number of clinical and research applications; however, no previous studies have provided reference values for such tests using a healthy sample of the adult Brazilian population. With this as our main purpose, we prospectively evaluated 100 non-smoking subjects (50 males and 50 females), 20 to 80 years old, randomly selected from more than 8,000 individuals. Gender-specific linear prediction equations were developed by multiple regression analysis with total lung capacity (TLC), functional residual capacity (FRC), residual volume (RV), RV/TLC ratio and inspiratory capacity (IC) as dependent variables, and with age, height, weight, lean body mass and indexes of physical fitness as independent ones. Simpler demographic and anthropometric variables were as useful as more complex measurements in predicting LV values, independent of gender and age (R2 values ranging from 0.49 to 0.78, P<0.001). Interestingly, prediction equations from North American and European studies overestimated the LV at low volumes and underestimated them at high volumes (P<0.05). Our results, therefore, provide a more appropriate frame of reference to evaluate the normalcy of static lung volume values in Brazilian males and females aged 20 to 80 years.

Ventilation with high tidal volume induces inflammatory lung injury

Mechanical ventilation with high tidal volumes (V T) has been shown to induce lung injury. We examined the hypothesis that this procedure induces lung injury with inflammatory features. Anesthetized male Wistar rats were randomized into three groups: group 1 (N = 12): V T = 7 ml/kg, respiratory rate (RR) = 50 breaths/min; group 2 (N = 10): V T = 21 ml/kg, RR = 16 breaths/min; group 3 (N = 11): V T = 42 ml/kg, RR = 8 breaths/min. The animals were ventilated with fraction of inspired oxygen of 1 and positive end-expiratory pressure of 2 cmH2O. After 4 h of ventilation, group 3, compared to groups 1 and 2, had lower PaO2 [280 (range 73-458) vs 517 (range 307-596), and 547 mmHg (range 330-662), respectively, P<0.05], higher wet lung weight [3.62 ± 0.91 vs 1.69 ± 0.48 and 1.44 ± 0.20 g, respectively, P<0.05], and higher wet lung weight/dry lung weight ratio [18.14 (range 11.55-26.31) vs 7.80 (range 4.79-12.18), and 6.34 (range 5.92-7.04), respectively, P<0.05]. Total cell and neutrophil counts were higher in group 3 compared to groups 1 and 2 (P<0.05), as were baseline TNF-alpha concentrations [134 (range <10-386) vs 16 (range <10-24), and 17 pg/ml (range <10-23), respectively, P<0.05]. Serum TNF-alpha concentrations reached a higher level in group 3, but without statistical significance. These results suggest that mechanical ventilation with high V T induces lung injury with inflammatory characteristics. This ventilatory strategy can affect the release of TNF-alpha in the lungs and can reach the systemic circulation, a finding that may have relevance for the development of a systemic inflammatory response.

Pentoxifylline decreases tumor necrosis factor and interleukin-1 during high tidal volume

Tumor necrosis factor-alpha (TNF-alpha) is one of the most important proinflammatory cytokines which plays a central role in host defense and in the acute inflammatory response related to tissue injury. The major source of TNF-alpha are immune cells such as neutrophils and macrophages. We tested the hypothesis that pentoxifylline, a methylxanthine derivative, down-regulates proinflammatory cytokine expression during acute lung injury in rats. Male Wistar rats weighing 250 to 450 g were anesthetized ip with 50 mg/kg sodium thiopental and randomly divided into three groups: group 1 (N = 7): tidal volume (V T) = 7 ml/kg, respiratory rate (RR) = 50 breaths/min and normal saline infusion; group 2 (N = 7): V T = 42 ml/kg, RR = 9 breaths/min and normal saline infusion; group 3 (N = 7): V T = 42 ml/kg, RR = 9 breaths/min and pentoxifylline infusion. The animals were ventilated with an inspired oxygen fraction of 1.0, a positive end-expiratory pressure of 3 cmH2O, and normal saline or pentoxifylline injected into the left femoral vein. The mRNA of TNF-alpha rapidly increased in the lung tissue within 180 min of ventilation with a higher V T with normal saline infusion. The concentrations of inflammatory mediators were decreased in plasma and bronchoalveolar lavage (BAL) in the presence of higher V T with pentoxifylline infusion (TNF-alpha: plasma, 102.2 ± 90.9 and BAL, 118.2 ± 82.1; IL-1ß: plasma, 45.2 ± 42.7 and BAL, 50.2 ± 34.9, P < 0.05). We conclude that TNF-alpha produced by neutrophil influx may function as an alert signal in host defense to induce production of other inflammatory mediators.

Cyst infection in hospital-admitted autosomal dominant polycystic kidney disease patients is predominantly multifocal and associated with kidney and liver volume

Positron-emission tomography/computed tomography (PET/CT) has improved cyst infection (CI) management in autosomal dominant polycystic kidney disease (ADPKD). The determinants of kidney and/or liver involvement, however, remain uncertain. In this study, we evaluated clinical and imaging factors associated with CI in kidney (KCI) and liver (LCI) in ADPKD. A retrospective cohort study was performed in hospital-admitted ADPKD patients with suspected CI. Clinical, imaging and surgical data were analyzed. Features of infected cysts were evaluated by PET/CT. Total kidney (TKV) and liver (TLV) volumes were measured by CT-derived multiplanar reconstruction. CI was detected in 18 patients who experienced 24 episodes during an interval of 30 months (LCI in 12, KCI in 10 and concomitant infection in 2). Sensitivities of CT, magnetic resonance imaging and PET/CT were 25.0, 71.4, and 95.0%. Dysuria (P<0.05), positive urine culture (P<0.01), and previous hematuria (P<0.05) were associated with KCI. Weight loss (P<0.01) and increased C-reactive protein levels (P<0.05) were associated with LCI. PET/CT revealed that three or more infected cysts were present in 70% of the episodes. TKV was higher in kidney-affected than in LCI patients (AUC=0.91, P<0.05), with a cut-off of 2502 mL (72.7% sensitivity, 100.0% specificity). TLV was higher in liver-affected than in KCI patients (AUC=0.89, P<0.01) with a cut-off of 2815 mL (80.0% sensitivity, 87.5% specificity). A greater need for invasive procedures was observed in LCI (P<0.01), and the overall mortality was 20.8%. This study supports PET/CT as the most sensitive imaging method for diagnosis of cyst infection, confirms the multifocal nature of most hospital-admitted episodes, and reveals an association of kidney and liver volumes with this complication.

Efeito do número de sementes e do volume de água na condutividade elétrica de sementes de Dalbergia nigra (Vell.) Fr.All. ex Benth.

O presente trabalho teve como objetivos verificar o efeito do número de sementes e do volume de água utilizada no teste de condutividade elétrica (CE) para avaliar o vigor de três lotes de sementes de Dalbergia nigra (jacarandá-da-bahia) e correlacionar esses resultados com os dados de germinação em laboratório e em viveiro. Os testes de germinação em laboratório e viveiro foram conduzidos com quatro repetições de 25 sementes. O teste de CE foi realizado com 25, 50 e 75 sementes embebidas a 75, 100 e 125ml de água, por diferentes períodos. A porcentagem de germinação e de plântulas normais em laboratório, indicaram o lote III como de qualidade inferior aos lotes I e II. A primeira contagem da germinação e o índice de velocidade de germinação em laboratório e a emergência, índice de velocidade de emergência e porcentagem de plântulas normais em viveiro identificaram o lote II como superior ao lote I e o III como inferior. A CE diminui com o aumento do volume de água e aumentou com o período de embebição. A diferenciação dos lotes foi mais eficiente, quando se utilizou 75ml de água deionizada e amostras de 50 sementes com pelo menos 36 horas de embebição, com valores de CE menores nos lotes I e II do que no lote II. Os coeficientes de correlação simples entre a CE e as demais características avaliadas, em laboratório e viveiro, foram elevados e significativos, evidenciando alta associação entre os mesmos. Assim, pode-se recomendar que o teste de CE seja conduzido a 25ºC, com amostras de 50 sementes embebidas em 75ml de água deionizada, por períodos iguais ou superiores a 36 horas de embebição, para determinar a qualidade fisiológica de lotes de sementes de jacarandá-da-bahia.