Ethanol impairs post-prandial hepatic protein metabolism.

The effects of acute ethanol ingestion on whole body and hepatic protein metabolism in humans are not known. To simulate social drinking, we compared the effects of the association of a mixed meal (632 kcal, 17% amino acids, 50% glucose, 33% lipids) with a bottle of either table wine (ethanol content 71 g) or water on the estimates ([1-14C]-leucine infusion) of whole body protein breakdown, oxidation, and synthesis, and on the intravascular fractional secretory rates (FSR) of hepatically (albumin, fibrinogen) and extrahepatically (IgG) synthesized plasma proteins in two randomized groups (ethanol n = 7, water n = 7) of healthy nonalcoholic volunteers. Each study was carried out for 8 h. Protein kinetics were measured in the overnight post-absorptive state, over the first 4 h, and during a meal infusion (via a nasogastric feeding tube at constant rate) combined with the oral ingestion of wine or water, over the last 4 h. When compared with water, wine ingestion during the meal reduced (P < 0.03) by 24% the rate of leucine oxidation, did not modify the estimates of whole body protein breakdown and synthesis, reduced (P < 0.01) by approximately 30% the FSR of albumin and fibrinogen, but did not affect IgG FSR. In conclusion, 70 g of ethanol, an amount usual among social drinkers, impairs hepatic protein metabolism. The habitual consumption of such amounts by reducing the synthesis and/or secretion of hepatic proteins might lead to the progressive development of liver injury and to hypoalbuminemia also in the absence of protein malnutrition.     

Prolonged exposure of human pancreatic islets to high glucose concentrations in vitro impairs the beta-cell function.

The aim of the present study was to clarify whether prolonged in vitro exposure of human pancreatic islets to high glucose concentrations impairs the function of these cells. For this purpose, islets isolated from adult cadaveric organ donors were cultured for seven days in RPMI 1640 medium supplemented with 10% fetal calf serum and containing either 5.6, 11, or 28 mM glucose. There was no glucose-induced decrease in islet DNA content or signs of morphological damage. However, islets cultured at 11 or 28 mM glucose showed a 45 or 60% decrease in insulin content, as compared to islets cultured at 5.6 mM glucose. Moreover, when such islets were submitted to a 60-min stimulation with a low (1.7 mM) followed by a high (16.7 mM) concentration of glucose, the islets cultured at 5.6 mM glucose showed a higher insulin response to glucose than those of the two other groups. Islets cultured at the two higher glucose concentrations showed increased rates of insulin release in the presence of low glucose, and a failure to enhance further the release in response to an elevated glucose level. Islets cultured at 28 mM glucose showed an absolute decrease in insulin release after stimulation with 16.7 mM glucose, as compared to islets cultured at 5.6 mM glucose. The rates of glucose oxidation, proinsulin biosynthesis, and total protein biosynthesis were similar in islets cultured at 5.6 or 11 mM glucose, but they were decreased in islets cultured at 28 mM glucose. These combined results suggest that lasting exposure to high glucose concentrations impairs the function of human pancreatic islets.     

Nitric oxide directly impairs intestinal barrier function

Excess production of nitric oxide (NO) has been implicated in endotoxin-induced loss of gut barrier function in vivo. Thus, we tested the direct effect of NO on the barrier function of intestinal mucosal membranes suspended ex vivo in Ussing chambers and on IEC-6 enterocyte monolayers. In these experiments, ex vivo-mounted ileal membranes or IEC-6 cell enterocyte monolayers were exposed to the NO donor, S-nitroso-N-acetyl-penicillamine (SNAP) over a dose range (10 microm to 2 mM) or medium. SNAP at concentrations of 1 or 2 mM, but not 10 or 100 microM, increased the rates of bacterial translocation (BT) across both the ileal membranes and the IEC-6 monolayers by >1 log (P < 0.05), as well as the permeability of the IEC-6 monolayers to phenol red (P < 0.05). The ileal membranes exposed to 1 or 2 mM SNAP for 3 h manifested histologic evidence of mucosal injury and decreases in electrical resistance and potential difference values (P < 0.05), while the IEC-6 cells exposed to SNAP for 18 h had increased levels of cell death (P < 0.05). Since NO produced locally by stimulated enterocytes could contribute to barrier dysfunction, NO production, iNOS mRNA levels, and monolayer permeability were measured in enterocytes (IEC-6 and Caco-2) exposed to medium, endotoxin (lipopolysaccharide [25 microg/mL]) or a cytokine mixture (IL-1beta 10 ng/mL, TNF-alpha 10 ng/mL, and INF-gamma 250 U/mL) for 6 or 24 h. Endotoxin increased NO production, iNOS mRNA expression, and monolayer permeability in the IEC-6, but not the Caco-2 cells, while exposure to the cytokine mixture increased both NO production, iNOS mRNA expression, and monolayer permeability in both the IEC-6 and Caco-2 cell lines. Based on the results of these studies it appears that NO can directly increase ileal mucosal membrane and enterocyte monolayer permeability and BT and that increased NO production and iNOS mRNA expression is associated with endotoxin- and/or cytokine-induced loss of enterocyte monolayer barrier function.     

Uraemia suppresses central dopaminergic metabolism and impairs motor activity in rats

OBJECTIVE: Uraemia often provokes various neurological disorders, such as mental changes, malperception, confusion, seizures and coma. Since changes in neurotransmissions induce neurological symptoms, we investigated changes in the monoamine metabolism and motor activity in uraemic rats. DESIGN: Prospective, randomised, controlled animal study. SUBJECTS: Male Wistar rats. INTERVENTIONS: Acute renal failure was induced by occlusion of bilateral renal arteries for 60 min, and the motor activity and brain monoamine turnover were examined 48 h later. The brain monoamine turnover was evaluated by the depletion of norepinephrine (NE) and dopamine (DA) induced by alpha-methyl-p-tyrosine (alpha-MT), or the accumulation of 5-hydroxyindoleacetic acid (5-HIAA) induced by probenecid. MEASUREMENTS AND RESULTS: Marked damage in renal function was found in animals subjected to renal ischaemia 48 h after the operation. The motor activity of the uraemic rats was impaired. The turnover of DA in the striatum, mesencephalon and hypothalamus was decreased in these rats. The turnover of NE and 5-hydroxytryptamine (5-HT) was unchanged in all regions examined. CONCLUSIONS: Suppression of the central DA turnover appears to be involved in the impairment of motor activity in uraemic rats.     

Effect of single dose surfactant on pulmonary function

Sequential changes in pulmonary mechanics in response to single dose exogenous surfactant instillation were studied in 15 preterm neonates who had hyaline membrane disease (HMD). The infants were part of a larger double-blind national study. Birth weight ranged from 0.88 to 1.55 kg, and gestational age was between 27 to 32 wk. There were six infants in the surfactant group and nine in the placebo group. Pulmonary mechanics were studied before and at 2, 24, 60, and 96 h after surfactant or sham instillation using a pneumotachometer and an esophageal balloon catheter. The variables studied were dynamic compliance (Cdyn), pulmonary resistance, work of breathing, tidal volume, and minute ventilation. Infants in the surfactant group showed an immediate and significant (p less than .05) improvement in gas exchange ratio, decreased mean airway pressure (9.7 +/- 0.9 to 7.9 +/- 0.4 cm H2O) and airway resistance (133 +/- 6.3 to 92 +/- 14.9 cm H2O/L.sec) (p less than .05). Changes in Cdyn were noted only at 24 h after surfactant instillation. In the control group, gradual improvement occurred after the initial deterioration. The findings suggest that the immediate improvement in oxygenation after surfactant instillation is the result of factors other than changes in lung compliance, such as improved ventilation/perfusion and better capillary stability with decreased leakage of fluid into alveoli.     

早产鼠高氧肺损伤中肺表面活性物质的代谢变化

目的：探讨早产鼠高氧肺损伤对其肺表面活性物质蛋白（SP）基因表达及肺表面活性物质（PS）代谢的影响。方法：孕21日SD早产鼠仔96只被随机分为高氧暴露组（48只,常压高氧舱中,氧体积分数＞0．95）和空气对照组（48只,正常空气中）,高氧暴露7日后,采用逆转录－聚合酶链反应（RT－PCR）和双相薄层层析法（2D－TLC）观察了8只鼠肺SP mRNA水平和PS含量;对20只鼠肺支气管肺泡灌洗液（BALF）肺组织干重／湿重和10只鼠肺组织学变化也进行了分析。结果：与空气对照组比较,高氧暴露组发展为肺损伤,肺组织有明显水肿、出血;BALF中蛋白含量、细胞数和肺组织干重／湿重明显增加（P均＜0．05）,而PS含量未见明显变化（P均＞0．05）。SP－A mRNA和SP－BmRNA增加（P均＜0．05）,SP－C mRNA变化未达统计学意义（P＞0．05）。结论：早产鼠早期高氧肺损伤并不明显影响PS含量的变化,但可导致SP－A mRNA和SP－B mRNA增加,这种基因表达的向上调节可能是机体的一种保护性应激反应。     

HES 130/0.4 impairs haemostasis and stimulates pro-inflammatory blood platelet function

Introduction  

Hydroxyethyl starch (HES) solutions are widely used for volume replacement therapy but are also known to compromise coagulation, impair renal function and increase long-term mortality. To test the hypotheses that HES 130/0.4 has fewer adverse effects than HES 200/0.5 and exerts anti-inflammatory properties, we compared the effects of HES 130/0.4, HES 200/0.5 and saline on in vitro haemostasis and pro-inflammatory platelet function.     

Neutrophil depletion impairs natural killer cell maturation, function, and homeostasis

Natural killer (NK) cells are bone marrow (BM)-derived granular lymphocytes involved in immune defense against microbial infections and tumors. In an N-ethyl N-nitrosourea (ENU) mutagenesis strategy, we identified a mouse mutant with impaired NK cell reactivity both in vitro and in vivo. Dissection of this phenotype showed that mature neutrophils were required both in the BM and in the periphery for proper NK cell development. In mice lacking neutrophils, NK cells displayed hyperproliferation and poor survival and were blocked at an immature stage associated with hyporesponsiveness. The role of neutrophils as key regulators of NK cell functions was confirmed in patients with severe congenital neutropenia and autoimmune neutropenia. In addition to their direct antimicrobial activity, mature neutrophils are thus endowed with immunoregulatory functions that are conserved across species. These findings reveal novel types of cooperation between cells of the innate immune system and prompt examination of NK cell functional deficiency in patients suffering from neutropenia-associated diseases.     

Permanent atrial fibrillation impairs the function of circulating endothelial progenitor cells

Objective: to determine whether functions of endothelial progenitor cells (EPCs) were impaired in patients with permanent atrial fibrillation (AF).

Methods: 35 patients with permanent AF (AF group) and 35 age and sex matched controls (control group) were collected. The numbers of circulating CD34⁺/KDR⁺ cells were determined with flow cytometry in the two groups. Cell proliferation, tube formation, nitric oxygen (NO) and vascular endothelial growth factor (VEGF) were assayed.

Results: the numbers of CD34⁺/KDR⁺ cells were lower in the AF group than the control group (20.01 ± 12.66 /10⁵ vs 77.93 ± 58.93 /10⁵,p = 0.022). Colony formation unit (CFU) of EPCs were decreased in AF group compared to the control group（1.76 ± 0.59 CFU vs 3.45 ± 0.82 CFU, p = 0.0000). The AF group had lower cell proliferation ability than control group（0.401 ± 0.113 A vs 0.558 ± 0.130 A, p = 0.004). Tube formation ability was decreased in AF patients compared to controls（434.30 ± 96.22μm/mm² vs 568.09 ± 196.17μm/mm²,p = 0.041). AF patients had lower VEGF secretion than controls (27.35 ± 9.93 ng/L vs 41.86 ± 7.31 ng/L,p = 0.001）,they also had lower NO secretion than controls（16.55 ± 6.92μmol/l vs 23.65 ± 5.48,p = 0.012).

Conclusions: proliferation, tube formation and paracrine of EPCs were reduced in patients with permanent AF.     

Thyrocyte-specific Gq/G11 deficiency impairs thyroid function and prevents goiter development

The function of the adult thyroid is regulated by thyroid-stimulating hormone (TSH), which acts through a G protein-coupled receptor. Overactivation of the TSH receptor results in hyperthyroidism and goiter. The Gs-mediated stimulation of adenylyl cyclase-dependent cAMP formation has been regarded as the principal intracellular signaling mechanism mediating the action of TSH. Here we show that the Gq/G11-mediated signaling pathway plays an unexpected and essential role in the regulation of thyroid function. Mice lacking the alpha subunits of Gq and G11 specifically in thyroid epithelial cells showed severely reduced iodine organification and thyroid hormone secretion in response to TSH, and many developed hypothyroidism within months after birth. In addition, thyrocyte-specific Galphaq/Galpha11-deficient mice lacked the normal proliferative thyroid response to TSH or goitrogenic diet, indicating an essential role of this pathway in the adaptive growth of the thyroid gland. Our data suggest that Gq/G11 and their downstream effectors are promising targets to interfere with increased thyroid function and growth.     

Hyperventilation impairs brain function in acute cerebral air embolism in pigs

OBJECTIVE: To evaluate, in a model of cerebral air embolism (CAE), the effects of ventilation-induced hypocapnia and hyperoxemia on intracranial pressure (ICP), cerebral perfusion pressure (CPP), brain oxygen (PbrO(2)), brain carbon dioxide (PbrCO(2)), brain pH (brpH) and levels of brain glucose and lactate. DESIGN AND SETTING: Prospective animal study in a university medical center. SUBJECTS: Fifteen Landrace/Yorkshire pigs. INTERVENTIONS: In 15 anesthetized pigs ICP, PbrO(2), PbrCO(2) and brpH were measured with multi-parameter sensors, and brain glucose and lactate by microdialysis. All these parameters were recorded for 2 h after injection of air into the internal carotid artery. Nine animals were hyperventilated (PaCO(2 )+/-25 mmHg) and hyperoxygenated (FiO(2) 1.0) and six animals were normoventilated (PaCO(2)()+/-40 mmHg with an FiO(2) 0.4) and served as controls. RESULTS. In the treatment group the ICP rose from 8+/-1 to 52+/-6 mmHg, which was similar to that in the control group (12+/-1 to 57+/-8 mmHg). At the end of the 2-h study period, there were no significant differences in PbrO(2), PbrCO(2) and brpH between the two groups. The decreased brain glucose and increased brain lactate reached severe pathological values in both groups by the end of the 2-h study period. CONCLUSIONS: Hypocapnia and hyperoxemia in acute CAE did not improve pathological functional brain parameters compared with normoventilated controls. Similarly, the pathological changes in brain glucose/lactate could also not be improved by hypocapnia and hyperoxemia.     

A Glanzmann's mutation in beta 3 integrin specifically impairs osteoclast function

Osteoclastic bone resorption requires cell-matrix contact, an event mediated by the alpha v beta 3 integrin. The structural components of the integrin that mediate osteoclast function are, however, not in hand. To address this issue, we generated mice lacking the beta 3 integrin gene, which have dysfunctional osteoclasts. Here, we show the full rescue of beta 3(-/-) osteoclast function following expression of a full-length beta 3 integrin. In contrast, truncated beta 3, lacking a cytoplasmic domain (h beta 3c), is completely ineffective in restoring function to beta 3(-/-) osteoclasts. To identify the components of the beta 3 cytoplasmic domain regulating osteoclast function, we generated six point mutants known, in other circumstances, to mediate beta integrin signaling. Of the six, only the S(752)P substitution, which also characterizes a form of the human bleeding disorder Glanzmann's thrombasthenia, fails to rescue beta 3(-/-) osteoclasts or restore ligand-activated signaling in the form of c-src activation. Interestingly, the double mutation Y(747)F/Y(759)F, which disrupts platelet function, does not affect the osteoclast. Thus similarities and distinctions exist in the mechanisms by which the beta 3 integrin regulates platelets and osteoclasts.     

Fenofibrate impairs rat mitochondrial function by inhibition of respiratory complex I

Fibrates are used for the treatment of dyslipidemia and known to affect mitochondrial function in vitro. To better understand the mechanisms underlying their mitochondrial effects, fibrate actions on complex I of the respiratory chain and cell respiration were studied in vitro. In homogenates of rat skeletal muscle, fenofibrate, and to a lesser extent clofibrate, reduced the activity of complex I (10, 30, and 100 microM fenofibrate: -41 +/- 7%, -70 +/- 2%, and -78 +/- 4%; 100 microM clofibrate: -27 +/- 7%; p < 0.005 each). Inhibition of complex I by fenofibrate (100 microM) was confirmed by reduced state 3 respiration of isolated mitochondria consuming glutamate + malate as substrates for complex I (-33 +/- 4%; p < 0.0005), but not of such consuming succinate as substrate for complex II (-8 +/- 4%; NS). In isolated rat muscle, 24-h fenofibrate exposure (25, 50, and 100 microM) decreased CO(2) production from palmitate (-15 +/- 7%, -23 +/- 8%, and -22 +/- 7%; p < 0.05 each) and increased lactate release (+15 +/- 5%, +14 +/- 5%, and + 17 +/- 6%; p < 0.02 each) indicating impaired cell respiration. Ciprofibrate and gemfibrocil (but not bezafibrate) impaired cell respiration without any inhibition of complex I. Our findings support the notion that individual fibrates induce mitochondrial dysfunction via different molecular mechanisms and show that fenofibrate predominantly acts by inhibition of complex I of the respiratory chain.