超声发射方式对实验兔血脑屏障通透性的影响

目的探讨微泡介导下超声发射方式对实验兔血脑屏障通透性的影响。方法依据超声不同发射方式将20只清洁级新西兰大白兔随机分为两组,即连续发射组和间断触发组,各10只。观察在匀速注射微泡、相同超声能量参数下不同发射方式辐照兔脑组织情况,同时采用伊文思蓝示踪法评价血脑屏障通透性的变化情况。结果超声连续发射组、间断发射组靶区单位脑组织中伊文思蓝含量分别为(11.04±1.53)μg/g、(32.55±2.56)μg/g,两组比较差异有统计学意义(P<0.05)。结论在匀速注射微泡,相同超声能量参数辐照靶区脑组织时,间断触发方式较连续发射方式更能促进血脑屏障通透性增加。     

Early changes in blood-brain barrier permeability after porto-caval shunt and liver ischaemia

Summary. The brain oedema, distribution space (DS) and brain uptake index (BUI), of l -glucose, inulin, B₁₂ vitamin and of three polypeptidic hormones of increasing molecular weight (angiotensin-I, gastrin and insulin) were measured in the rat after sham operation, porto-caval shunt (PCS) or liver ischaemia. At an early stage following PCS or liver ischaemia brain oedema was not constant, and was only demonstrable after liver ischaemia in a large number of animals. Substances without an active transport and with a low diffusion coefficient such as l -glucose and inulin had a very low BUI, unchanged even if the ³H₂O brain content or the DS were modified. B₁₂ vitamin, DS and BUI were very high and did not change after liver ischaemia or PCS. Insulin DS and BUI were low in the three groups of animals, whereas it decreased after PCS for gastrin. A significant increase of BUI and DS (without any cerebral oedema) was demonstrated for angiotensin-I, a polypeptidic hormone of molecular weight 1300. This polypeptidic marker is in the same range of MW as the preliminary recently recognized medium-sized molecules which may be involved in the pathogenesis of encephalopathy during experimental acute liver failure. However, not only the MW, but the nature of such polypeptides may be of importance in the genesis of this limited impairment of BBB permeability.     

肺复张手法对急性肺损伤大鼠肺泡上皮细胞屏障功能的影响

目的 观察肺复张手法对急性肺损伤（ALI）大鼠肺泡上皮细胞屏障功能的影响。方法雄性清洁级SD大鼠48只，静脉注射脂多糖（LPS）复制ALI模型，随机分为对照组、ALI模型组（ALI组）、小潮气量（VT）通气组（LV组）和肺复张联合小VT通气组（SI组）。采用控制性肺膨胀（SI）实施肺复张手法。机械通气4h后，观察肺组织病理学改变；采用末端脱氧核苷酸转移酶介导的dUTP缺口末端标记法（TUNEL）检测肺泡上皮细胞凋亡情况；用重力法测定血管外肺水（EVLW）含量；用单核素示踪技术测定肺泡上皮细胞通透性改变；用逆转录-聚合酶链反应（RT—PCR）检测肺组织肺泡表面活性蛋白-C（SP—C）mRNA表达；用酶联免疫吸附法（ELISA）检测支气管肺泡灌洗液（BALF）中白细胞介素-6（IL-6）和IL-10浓度。结果 光镜下，SI组肺组织损伤程度轻于ALI组和LV组。LV组凋亡肺泡上皮细胞散在分布，SI组凋亡上皮细胞明显减少。与对照组相比，ALI组、LV组及SI组肺损伤评分和EVLW均显著升高；与ALI组比较，LV组和SI组肺损伤评分显著降低，SI组肺损伤评分及EVLW显著低于LV组（P均〈0．05）。与对照组相比，ALI组、LV组及SI组肺组织SP—C mRNA表达均显著降低，而SI组肺组织SP—C mRNA表达显著高于LV组（P〈0．05），但与ALI组比较差异无显著性。ALI组、LV组和SI组BALF中IL-6和IL-10浓度均显著高于对照组（P均〈0．05），SI组IL-6浓度显著低于LV组（P〈0．05）。各组肺泡上皮细胞通透性间比较差异均无显著性。结论 肺复张手法可以减轻ALI肺组织病理损伤，增加肺泡上皮细胞SP—C mRNA的合成，下调肺部炎症反应，改善肺泡上皮细胞屏障功能。     

谷氨酰胺对急性肺损伤大鼠肺泡上皮屏障功能的影响

目的:观察谷氨酰胺对急性肺损伤大鼠肺泡上皮屏障功能及紧密连接(TJ)特征性蛋白occludin和黏附连接蛋白E-cadherin的影响。方法:40只SD大鼠随机分为对照组、谷氨酰胺处理组(Gln组)、内毒素处理组(LPS组)、谷氨酰胺并内毒素处理组(Gln+LPS组)。测定支气管肺泡渗透性、运用免疫印迹测定和RT-PCR测定肺泡Ⅱ型上皮细胞中occludin和E-cadherin的蛋白及mRNA表达。结果:内毒素导致支气管肺泡上皮渗透性明显增高2倍左右(P<0.01);补充谷氨酰胺可以明显改善由内毒素处理引起的支气管肺泡上皮渗透性增高(P<0.05),但Gln+LPS组支气管肺泡渗透性仍较对照组及Gln组增高(P<0.05)。免疫印迹和RT-PCR显示在LPS组的occludin和E-cadherin蛋白和mRNA表达水平均较对照组及Gln组的低(P<0.01);在Gln+LPS组中occludin和E-cadherin的蛋白和mRNA表达水平较LPS组的高(P<0.05),而较对照组及Gln组的表达水平低(P<0.05)。结论:实验提示内毒素通过降低TJ分子occludin和E-cadherin的mRNA、蛋白表达水平导致肺泡上皮屏障功能受损,补充谷氨酰胺通过上调其mRNA、蛋白表达水平而对肺泡上皮屏障功能有保护作用。     

Effects of leukotriene B4 in the human lung. Recruitment of neutrophils into the alveolar spaces without a change in protein permeability.

Leukotriene B4 (LTB4) is a major product of human alveolar macrophages and has potent chemotactic activity for neutrophils (PMN) in vitro. To evaluate the effects of LTB4 in the normal human lung, we instilled LTB4 (5 X 10(-7)M, 10 ml) into a subsegment of the right middle lobe and 0.9% NaCl (10 ml) into a subsegment of the lingula using a fiberoptic bronchoscope in 12 healthy human volunteers. 4 h later, we performed bronchoalveolar lavage of the same subsegments. Compared with the NaCl instillation, LTB4 caused a large increase in lavage total cells (NaCl = 6.8 +/- 1.0 X 10(6) vs. LTB4 = 26.4 +/- 5.0 X 10(6), P less than 0.01), most of which were PMN (NaCl = 12.2 +/- 4.6% vs. LTB4 = 55.7 +/- 6.0%, P less than 0.001). In contrast, there was only a small increase in lavage total protein, and the lavage total protein correlated weakly with lavage total cells and PMN. The production of superoxide anion by the lavage PMN in response to phorbol myristate acetate was similar to that of peripheral blood PMN. The migration of lavage PMN was normal toward the chemotactic peptide FMLP, but reduced toward LTB4 and zymosan-activated human serum. Morphometric analysis using transmission electron microscopy indicated a selective loss of small granules in the lung neutrophils as compared with peripheral blood neutrophils. The data indicate that in the normal human lung, LTB4 can recruit active PMN into the airspaces without causing a significant change in the protein permeability of the epithelial barrier.     

Insulin increases glucose transfer across the blood-brain barrier in man.

The influence of insulin on unidirectional flux of glucose across the blood-brain barrier and on net uptake of glucose by the brain was investigated in seven fasting patients. The unidirectional extraction, E, of [14C]D-glucose was determined using 36Cl- as an intravascular reference, by the indicator dilution method. 0.4 U insulin/kg body wt was infused intravenously over 30 min while blood glucose was maintained constant by glucose infusion. Six determinations were made in each patient, two before, two during insulin infusion, and two after. In connection with each blood-brain barrier study, arterial and cerebral venous samples were taken for measurement of glucose, oxygen, insulin, K+, and phosphate. Cerebral blood flow (CBF) was measured in each patient. The main finding was an increased extraction of glucose from 14 to 21% and a highly significant increase in unidirectional flux (CBF X unidirectional extraction X arterial glucose concentration) from 0.46 to 0.66 mumol/g X min during insulin infusion (plasma insulin approximately 1,500 microU/ml). The net brain uptake of glucose (CBF X arterio-venous difference for glucose) as unaltered during the investigation period of 45 min, which is too short a time for insulin to penetrate the barrier. It follows that the backflux of glucose from the brain was increased during insulin application. The effect of insulin might be a speeding up of the glucose carrier in analogy to heart muscle.     

Glomerular permeability barrier in the rat. Functional assessment by in vitro methods.

The formation of glomerular ultrafiltrate is dependent on the prevailing hemodynamic forces within the glomerular microcirculation and the intrinsic properties of the filtration barrier. However, direct assessment of the permeability barrier is difficult with most available techniques. We used confocal microscopy to image 1-micron thick optical cross-sections of isolated intact glomeruli and glomeruli denuded of cells and quantitated dextran (70,000 mol wt) diffusion from the capillary lumen. Dextran permeance was 11 times greater for the acellular filtration barrier than the intact peripheral capillary. Consideration of the basement membrane and cells as series resistors demonstrated that cells of the filtration barrier contribute 90% of the total resistance to macromolecular permeance. Using a different approach, dextran sieving coefficients for acellular glomeruli consolidated as a multilayer sheet in a filtration cell were similar to those for intact glomeruli in vivo at radii 30-36 A and approximately 50 times greater at a dextran radius of 60 A. The presence of cells significantly reduced hydraulic permeability determined on consolidated intact or acellular glomeruli in an ultrafiltration cell with 50 mmHg applied pressure. The glomerular basement membrane does restrict macromolecular permeability but cells are important determinants of the overall macromolecular and hydraulic permeability of the glomerulus.     

不同液体治疗对急性肺损伤大鼠肺泡上皮细胞屏障功能的影响

目的 观察不同液体治疗对急性肺损伤(ALI)大鼠肺泡上皮细胞屏障功能的影响.方法 ①与对照组比较,LPS组、NS组肺损伤评分明显升高(P均<0.05);与NS组比较,5%人血白蛋白(ALB)组、6%羟乙基淀粉130/0.4(HES)组评分均明显降低(P均<0.05),4%琥珀酰明胶(GEL)组无明显差异(P>0.05),且后3组间比较差异也无统计学意义.②与对照组比较,LPS组、NS组肺W/D比值明显升高(P均<0.05);ALB组、HES组、GEL组均较NS组明显下降(P均<0.05),3组间比较无差异.③LPS组、NS组肺泡上皮通透性均较对照组明显升高(P均<0.05);ALB组、HES组、GEL组肺泡上皮通透性均较NS组明显降低,且后两组明显低于ALB组(P均<0.05),但仍高于对照组.④LPS组、NS组、ALB组、GEL组肺组织SP-C mRNA表达较对照组、HES组明显下降(P均<0.05);而HES组和对照组间无明显差异(P>0.05).⑤各组肺泡上皮细胞凋亡指数(AI)明显高于对照组(P均<0.05);ALB组、HES组AI较NS组明显下降(P均<0.05),但与GEL组无明显差异(P均>0.05).结论 胶体液较NS更能改善ALI大鼠肺泡上皮通透性,保护上皮细胞屏障功能.     

Increased cardiac output increases lung water in canine permeability pulmonary edema

We investigated the effects of increased cardiac output (CO) on oleic acid pulmonary edema in 14 open-chest, anesthetized, mechanically ventilated dogs. Pulmonary artery wedge pressure (Pawp) was adjusted to approximately 9 mm Hg via a left atrial balloon and CO to 1.7 L · m⁻¹ via systemic arteriovenous fistulas (AVF); five minutes after oleic acid (0.08 mL · kg⁻¹), dogs were randomly divided into two groups, high CO and low CO. In the high CO group, CO was increased by opening the AVFs. Pawp was maintained at 9 mm Hg for four hours in all dogs. The average CO time in the high CO group was 3.9 L · min⁻¹ and 1.3 L · min⁻¹ in the low CO group (P < .01). Lung water accumulation was significantly increased in the high CO group with a wet weight/ body weight ratio of 29 g ò kg⁻¹v 21 g · kg ⁻¹ in the low CO group (P < .004). With time, mean pulmonary artery pressure increased significantly (P < .05) in both groups, but was not different between groups at any time. While pulmonary vascular resistance remained constant in the high CO group, it increased markedly (P < .05) in the low CO group, possibly due to a decrease in pulmonary vascular surface area. The increase in lung water accumulation in the high CO group is probably due to prevention of pulmonary vascular derecruitment and therefore a greater perfused pulmonary vascular surface area.     

白细胞介素-12在荷瘤肺的变化

目的 为了观察肺癌患者肺泡巨噬细胞的抗肿瘤免疫功能。方法 以Elisa法检测肺癌患者荷瘤侧及非荷瘤侧肺泡巨噬细胞产生的IL－12，同时外周血单核细胞产生的IL－12，设良性肺病组为对照组。结果 肺癌组非荷瘤侧肺泡巨噬细胞产生IL－12较对照组低，而荷瘤侧肺泡巨噬细胞产生IL－12较对照组高；肺癌组外周血单核细胞产生IL－12较对照组低。结论 肺癌患者机体存在抗肿瘤免疫缺陷，但肺癌组织临近肺泡巨噬细胞抗肿瘤免疫活性增强，这可能是机体自身的一种抗肿瘤免疫调节。     

Additive effect of intravascular complement activation and brief episodes of hypoxia in producing increased permeability in the rabbit lung.

Systemic complement activation with intravascularly administered cobra venom factor (CVF) or infusion of either zymosan-activated rabbit plasma or a fifth component of complement fragment with anaphylatoxin activity in the rabbit have not caused significant increases in bronchoalveolar lavage albumin in rabbits (Webster, R. O., G. L. Larsen, B. C. Mitchell, A. J. Goins, and P. M. Henson. 1982. Am. Rev. Respir. Dis. 125:335-340). To assess if another stimulus (hypoxia) acting in concert with complement activation can produce significant lung injury, rabbits were challenged with CVF alone, 10 min of 12% oxygen alone, or CVF followed by a 10-min exposure to 12% oxygen. Either stimulus alone caused no significant changes in arterial oxygen, pulmonary resistance, or dynamic compliance during the 240 min of observation after either stimulus, and neither stimulus alone caused increased albumin accumulation in bronchoalveolar lavage over a 30-min period at the end of the experiment. However, the combination of insults significantly altered arterial oxygen, pulmonary resistance, and dynamic compliance while also increasing albumin and neutrophils recovered by lavage. The increase in lavage albumin did not appear to be due to hemodynamic events in that the pulmonary artery pressure increased acutely after CVF infusion and again during the hypoxic exposure, but was normal when albumin accumulation in the lung was measured. Neutrophil depletion with nitrogen mustard abolished all of these changes induced by CVF plus hypoxia. In addition, meclofenamate pretreatment and infusion during the 4-h study abolished the increases in lavage albumin and neutrophils as well as the increase in pulmonary artery pressure after CVF. Meclofenamate pretreatment did not, however, block accumulation of albumin in the lung (interstitium). We conclude that complement activation, as an isolated event, will not cause a significant increase in lavage albumin in this model. However, combining complement activation with an episode of hypoxia will lead to an increase in lavage albumin that is dependent on the presence of neutrophils for its expression. Meclofenamate treatment will prevent increases in lavage albumin and neutrophils while not preventing albumin accumulation in the lung (interstitium), suggesting a product of the cyclooxygenase pathway of arachidonic acid metabolism is needed to produce movement of albumin and/or neutrophils across the alveolar epithelium in this model.     

Developmental changes in the rabbit sinus node action potential and its response to adrenergic agonists

We used standard microelectrode techniques to study developmental changes in the transmembrane potentials of sinus nodes from 1- to 10-day-old and adult rabbits superfused with Tyrode's solution at 37 degrees C. Maximum diastolic potential did not change with age, but action potential amplitude in day 1 to 3 hearts was lower than that in adults. Sinus cycle length (SCL) also was shorter in the young sinus nodes. In experiments on beta adrenergic stimulation the reduction of SCL in the young occurred at lower isoproterenol concentrations than in the adult, but the maximum reduction in SCL was the same at both ages (-40%). The alpha agonist, phenylephrine, had no age-dependent effect on SCL or action potential characteristics in either age group. In addition, the inhibitory effect of alpha stimulation demonstrated previously in automatic fibers of the ventricular specialized conducting system and atrium did not occur in sinus node. Studies of Purkinje fibers demonstrated this inhibitory effect to be voltage-dependent; it did not occur at membrane potentials in the range of those in the sinus node. Our results suggest that whereas developmental changes in the response to beta adrenergic stimulation are demonstrable in the sinus node, there are no such changes in the response to alpha adrenergic stimulation.     

Developmental changes in the rat atriopeptin hormonal system.

We undertook a study of fetal synthesis, storage, and release of atriopeptin (AP). Plasma levels of both atriopeptin immunoreactivity (APir) and the NH2-terminal fragment of the prohormone immunoreactivity (NTFir) were very high in the fetus (4 and 20 times the maternal plasma, respectively). However, the atrial content of the AP was low, but surprisingly, ventricular content of AP was quite high (relative to the adult) in the fetus and fell postnatally. Atrial AP messenger RNA (mRNA) increased with postnatal age, whereas ventricular mRNA was extremely high in the fetus and fell rapidly after birth. High fetal plasma peptide levels may derive from the mother since infusion of exogenous atriopeptin 24 into the mother resulted in parallel increases in fetal and maternal peptide levels. Fetal plasma APir and NTFir levels partially reflect the markedly reduced total renal metabolic capacity compared with that of the adult. Plasma levels fell progressively after birth; whereas neonatal atrial content rose substantially. Plasma AP and NTF were simultaneously elevated in both the maternal and fetal circulation after vasopressin injection of the mother. The fetus can also respond to exogenous stimuli (vasopressin or indomethacin--presumably via ductal closure) and promptly release substantial amounts of peptide into its circulation. Thus, it appears that the AP hormonal system is functional during fetal life and responds avidly to increases in intracardiac pressure as does the mature animal.     

Transport across the blood-brain barrier: stereoselectivity and PET-tracers.

This article reviews positron emission tomography (PET) studies of labeled enantiomers of different PET-tracers from the early 1980s. Comparative studies on stereoselective behavior of the transport of tracers across the blood-brain barrier (BBB) are discussed. Tracers are transported through the BBB into the brain, via diffusion or via several transport systems. These transport systems are able to transport endogenous and exogenous compounds from the blood into the brain, and visa versa. A clear difference exists in BBB transport of the enantiomers of several tracers. In addition, in most cases, binding of these labeled enantiomers to receptors/transporters is stereoselective. Finally, use of the biological inactive labeled enantiomer for the measurement of nonspecific binding is discussed. Given the differences in transport and binding, it is concluded that quantitative PET studies can only be performed using pure enantiomers.     

Glucocorticoids accelerate fetal maturation of the epidermal permeability barrier in the rat.

The cutaneous permeability barrier to systemic water loss is mediated by hydrophobic lipids forming membrane bilayers within the intercellular domains of the stratum corneum (SC). The barrier emerges during day 20 of gestation in the fetal rat and is correlated with increasing SC thickness and increasing SC lipid content, the appearance of well-formed lamellar bodies in the epidermis, and the presence of lamellar unit structures throughout the SC. Because glucocorticoids accelerate lung lamellar body and surfactant maturation in man and experimental animals, these studies were undertaken to determine whether maternal glucocorticoid treatment accelerates maturation of the epidermal lamellar body secretory system. Maternal rats were injected with betamethasone or saline (control) on days 16-18, and pups were delivered prematurely on day 19. Whereas control pups exhibited immature barriers to transepidermal water loss (8.16 +/- 0.52 mg/cm2 per h), glucocorticoid-treated pups exhibited competent barriers (0.74 +/- 0.14 mg/cm2 per h; P < 0.001). Glucocorticoid treatment also: (a) accelerated maturation of lamellar body and SC membrane ultrastructure; (b) increased SC total lipid content twofold; and (c) increased cholesterol and polar ceramide content three- to sixfold. Thus, glucocorticoids accelerate the functional, morphological, and lipid biochemical maturation of the permeability barrier in the fetal rat.     

PEEP-induced changes in lung volume in acute respiratory distress syndrome. Two methods to estimate alveolar recruitment

Purpose

Lung volumes, especially functional residual capacity (FRC), are decreased in acute respiratory distress syndrome (ARDS). Positive end-expiratory pressure (PEEP) contributes to increased end-expiratory lung volume (EELV) and to improved oxygenation, but differentiating recruitment of previously nonaerated lung units from distension of previously open lung units remains difficult. This study evaluated simple methods derived from bedside EELV measurements to assess PEEP-induced lung recruitment while monitoring strain.

Methods

Prospective multicenter study in 30 mechanically ventilated patients with ARDS in five university hospital ICUs. Two PEEP levels were studied, each for 45?min, and EELV (nitrogen washout/washin technique) was measured at both levels, with the difference (??) reflecting PEEP-induced lung volume changes. Alveolar recruitment was measured using pressure-volume (PV) curves. High and low recruiters were separated based on median recruitment at high PEEP. Minimum predicted increase in lung volume computed as the product of ??PEEP by static compliance was subtracted from ??EELV as an independent estimate of recruitment. Estimated and measured recruitments were compared. Strain induced by PEEP was also calculated from the same measurements.

Results

FRC was 31?±?11% of predicted. Median [25th?C75th percentiles] PEEP-induced recruitment was 272 [187?C355] mL. Estimated recruitment correlated with recruited volume measured on PV curves (???=?0.68), with a slope close to identity. The ??EELV/FRC ratio differentiated high from low recruiters (110 [76?C135] vs. 55 [23?C70]%, p?=?0.001). Strain increase due to PEEP was larger in high recruiters (p?=?0.002).

Conclusion

PEEP-induced recruitment and strain can be assessed at the bedside using EELV measurement. We describe two bedside methods for predicting low or high alveolar recruitment during ARDS.     

Enhanced water permeability across a physiological droplet interface bilayer doped with fullerenes

We measure the water permeability across a physiological lipid bilayer produced by the droplet interface bilayer (DiB) technique. This lipid bilayer can be considered as physiologically relevant because it presents a lipidic composition close to human cell membranes. The measured water permeability coefficients across this lipid bilayer are reported as a function of the cholesterol concentration. It is found that the water permeability coefficients decreased with increasing cholesterol concentration, in agreement with the existing literature. And, consistently, the extracted corresponding activation energies increase with increasing cholesterol concentration in the lipid bilayer. Hence having demonstrated the robustness of the experimental system, we extend this study by exploring the influence of fullerenes on the water permeability of a physiological lipid bilayer. Interestingly, we observe a significant increase of the measured water permeability coefficients across this lipid bilayer for large fullerenes concentration. This enhanced permeability might be related to the conductive properties of fullerenes.

We measure the water permeability across a physiological lipid bilayer produced by the droplet interface bilayer technique.     

Charting the course across the blood-brain barrier

The blood-brain barrier (BBB) presents a significant obstacle to delivery of targeted therapies to brain tumors. In this issue of the JCI, Staquicini and colleagues apply an in vivo phage-displayed library of random peptides to identify differentially expressed peptides that can be used to transport targeted agents across the intact BBB. The authors uncover a non-canonical, peptide-mediated iron-mimicry mechanism to induce transport of the transferrin/transferrin receptor complex across the BBB. They then demonstrate the ability of phage-targeting approaches to deliver therapeutic cargo and molecular imaging reporters across the BBB in an intracranial glioblastoma mouse model.