133Xe clearance estimates the effect of vasopressin on peritoneal blood flow in rats

BACKGROUND/AIMS: When assessing the peritoneal microcirculation with invasive methods, interference with the mechanisms of vaso-regulation may occur. The 133Xe clearance technique renders the possibility, by minimal invasiveness, to estimate the influence of a vasoactive agent on the peritoneal microcirculation. METHODOLOGY: Ten to 15MBq of 133Xe were injected in the abdominal cavity in thirty-eight Wistar-FU (W-FU) rats and 35 Lister-Hooded (LH) rats. A NaI (Tl)-scintillation detector registered activity before and during vasopressin infusion. Gamma camera imaging confirmed the washout from the abdominal cavity. The laser Doppler flowmetry technique was used as a comparison. RESULTS: Vasopressin at 0.07 IU/kg/min IV significantly reduced 133Xe-clearance by 37% (p = 0.029) and 52% (p=0.036) and laser Doppler flowmetry by 69% (p=0.0019) and 44% (p=0.0039) in W-FU and LH rats, respectively. A linear correlation between dose of vasopressin and relative decrease in 133Xe clearance was demonstrated in the W-FU rat model (r2=0.98, p=0.023). The 133Xe clearance from the abdominal cavity in rat using a single-compartment model or the slow compartment in a double-compartment model gave reproducible information. CONCLUSIONS: The usefulness of this mini-invasive technique for sequential measurements before and during intervention will render the 133Xe clearance suitable for assessment of blood flow changes in the abdominal cavity.     

Effects of auranofin on leukotriene production and leukotriene stimulated neutrophil function

Arachidonic acid is metabolized in neutrophils by lipoxygenase to leukotrienes, which are suggested to play a central role in inflammation. The antirheumatic drug auranofin (4 g/ml) was found not to inhibit neutrophil production of the lipoxygenase products 5-HETE, 15-HETE and LTB₄,in vitro when stimulated with the calcium ionophore A23187. Auranofin, however, modulated neutrophil aggregation, enzyme release and chemotaxis induced by LTB₄. The results suggest that auranofin may exert some of its antirheumatic effects through affecting neutrophil responses to leukotrienes.Supported by grants from: Swedish National association against Rheumatism, King Gustav V 80 years Fund, Tore Nilssons Fund, P and A Hedlunds Fund, Swedish Society for Medical Research, Förenade Liv Mutual Group Life Insurance Company, Stockholm, Sweden.     

Direct Effects of TNF-α on Local Fuel Metabolism and Cytokine Levels in the Placebo-Controlled,Bilaterally Infused Human Leg: Increased Insulin Sensitivity,Increased Net Protein Breakdown,and Increased IL-6 Release

Tumor necrosis factor-α (TNF-α) has widespread metabolic actions. Systemic TNF-α administration, however, generates a complex hormonal and metabolic response. Our study was designed to test whether regional, placebo-controlled TNF-α infusion directly affects insulin resistance and protein breakdown. We studied eight healthy volunteers once with bilateral femoral vein and artery catheters during a 3-h basal period and a 3-h hyperinsulinemic-euglycemic clamp. One artery was perfused with saline and one with TNF-α. During the clamp, TNF-α perfusion increased glucose arteriovenous differences (0.91 ± 0.17 vs. 0.74 ± 0.15 mmol/L, P = 0.012) and leg glucose uptake rates. Net phenylalanine release was increased by TNF-α perfusion with concomitant increases in appearance and disappearance rates. Free fatty acid kinetics was not affected by TNF-α, whereas interleukin-6 (IL-6) release increased. Insulin and protein signaling in muscle biopsies was not affected by TNF-α. TNF-α directly increased net muscle protein loss, which may contribute to cachexia and general protein loss during severe illness. The finding of increased insulin sensitivity, which could relate to IL-6, is of major clinical interest and may concurrently act to provide adequate tissue fuel supply and contribute to the occurrence of systemic hypoglycemia. This distinct metabolic feature places TNF-α among the rare insulin mimetics of human origin.Originally, tumor necrosis factor-α (TNF-α) was identified as an endogenous pyrogen or “cachectin” (1) because of its biological properties of inducing fever, cachexia, and muscle protein loss in various states of disease (2–4). TNF-α is a key component of an inflammatory response and one of the most potent proinflammatory cytokines released by innate immune cells that induces release of other cytokines, including interleukin-6 (IL-6) (5,6). TNF-α plays an important role in the pathophysiology of sepsis, and there seems to be a relation between the TNF-α level and the severity of disease (7–9). Finally, TNF-α has been associated with states of constant low-grade inflammation, eventually leading to insulin resistance and overt diabetes (10,11). In line with this, it has been shown that plasma levels of TNF-α are correlated with BMI; weight loss leads to a decrease in plasma levels of TNF-α (12,13).Systemic infusion of TNF-α induces insulin resistance and increased lipolysis in humans (6,14,15), whereas the effects on protein metabolism are less clear (16). A number of studies have shown that anti–TNF-α treatment increases insulin sensitivity in patients with inflammatory chronic diseases (17–19), whereas other reports have failed to confirm this relationship (20–23). Furthermore, studies investigating TNF-α neutralization in type 2 diabetic patients and in patients with metabolic syndrome show no effect of anti–TNF-α treatment on insulin sensitivity (24,25). TNF-α activates the hypothalamopituitary axis and stimulates the release of stress hormones, such as epinephrine, glucagon, cortisol, and growth hormone into the blood (26,27); all of these counter-regulatory stress hormones generate insulin resistance (27–29), and glucocorticoids generate muscle loss (30). Thus, TNF-α invariably generates release of both other cytokines and stress hormones, and it is uncertain to which extent the metabolic actions of TNF-α are intrinsic or caused by other cytokines or stress hormones in humans.The current study was therefore designed to define the direct metabolic effects of TNF-α in human muscle. Since all previous human studies assessing the metabolic actions of TNF-α have used systemic administration, making discrimination between direct and indirect effects impossible, we infused TNF-α directly into the femoral artery and compared the effects to the saline-infused contralateral leg.     

Macrophage function and surgery. A clinical review with special reference to phagocytosis.

Present knowledge of macrophage phagocytosis in the context of surgical trauma is reviewed. The historical and morphologic background of the reticuloendothelial system and the mononuclear phagocyte system is surveyed. The physiology of the phagocytic process and methods of measurement are summarized and the influence on phagocytosis of shock, sepsis, cancer, parenteral nutrition and surgical procedures such as liver resection and splenectomy is discussed. Conclusions are that multiple factors may depress macrophage phagocytosis during surgery and that, in order to maintain immune defence balance, traumatic manipulation of tissue and abdominal organs must be minimized.     

Initial caries diagnosis in rat molars, using laser fluorescence

Scoring of enamel caries in rat molars in ordinary light and in laser fluorescence was compared. Fifty rats were infected with Streptococcus mutans; 5 served as control rats, and the other 45 were fed a cariogenic diet for 15-20 days. With Keyes's system, the total enamel caries score for 35 of the test rats was 29.1 lesions per rat (l/r) in ordinary light and 39.6 l/r in laser fluorescence. The corresponding scores for fissure caries were 15.9 l/r and 21.6 l/r, respectively. Fissure caries scores of thin, longitudinal, central sections from the molars of the 10 remaining test rats were 18.0 l/r in ordinary light, 21.4 l/r in laser fluorescence, and 17.1 l/r in microradiographic analysis. In conclusion, the use of laser fluorescence improves scoring of early enamel carious lesions in rat molars, offering potential reductions in test time and/or sucrose load in animal caries research.     

Influence on plasma beta-N-acetyl-D-glucosaminidase of reticuloendothelial stimulation and depression: an experimental study in rats

Plasma levels of the lysosomal enzyme, beta-N-acetyl-D-glucosaminidase (EC 3.2.1.30; 2-acetamido-2-deoxy-beta-D-glucoside acetamidodeoxyglucohydrolase ) were estimated 120 minutes after intravenous injection of zymosan in rats. Different groups of animals were investigated according to pretreatment with agents influencing reticuloendothelial activity. Pretreatment for two days with the reticuloendothelial stimulating agent, zymosan, or the reticuloendothelial suppressing agent, methyl palmitate, did not influence the basal plasma levels of beta-N-acetyl-D-glucosaminidase. In all groups after zymosan injection, plasma beta-N-acetyl-D-glucosaminidase activity was increased in comparison with basal levels. The increase of enzyme activity was most pronounced after pretreatment with zymosan and differed significantly from enzyme activity after pretreatment with methyl palmitate. Alcohol administration in combination with zymosan did not cause a further rise of beta-N-acetyl-D-glucosaminidase activity in normal rats nor in rats pretreated with zymosan. The observations suggest that plasma levels of beta-N-acetyl-D-glucosaminidase in rats after a standardized zymosan injection are related to the functional status of the reticuloendothelial system (RES).     

Urinary polyamine excretion as related to cell death and cell proliferation induced by carbon tetrachloride intoxication

This study addresses the question whether urinary polyamine excretion is related to cell death or cell proliferation. CCl₄ intoxication of the rat was used as the experimental model. Treatment with CCl₄, a hepatotoxic haloalkane, produces an initial phase of liver cell death succeeded by a regenerative phase of growth, during which the liver is restored. The highest rate of putrescine (and spermidine) excretion occurred during the first 24 hr of CCl₄ intoxication and coincided with the period of maximum liver damage. During subsequent liver regeneration the rate of excretion of both polyamines decreased.