Homeostatic regulation of the immune system by receptor tyrosine kinases of the Tyro 3 family

Receptor tyrosine kinases and their ligands mediate cell-cell communication and interaction in many organ systems, but have not been known to act in this capacity in the mature immune system. We now provide genetic evidence that three closely related receptor tyrosine kinases, Tyro 3, Axl, and Mer, play an essential immunoregulatory role. Mutant mice that lack these receptors develop a severe lymphoproliferative disorder accompanied by broad-spectrum autoimmunity. These phenotypes are cell nonautonomous with respect to lymphocytes and result from the hyperactivation of antigen-presenting cells in which the three receptors are normally expressed.

IKK1-deficient mice exhibit abnormal development of skin and skeleton

IkappaB kinases (IKKs) IKK1 and IKK2 are two putative IkappaBalpha kinases involved in NF-kappaB activation. To examine the in vivo functions of IKK1, we generated IKK1-deficient mice. The mutant mice are perinatally lethal and exhibit a wide range of developmental defects. Newborn mutant mice have shiny, taut, and sticky skin without whiskers. Histological analysis shows thicker epidermis, which is unable to differentiate. Limbs and tail are wrapped inside the skin and do not extend properly out of the body trunk. Skeleton staining reveals a cleft secondary palate, split sternebra 6, and deformed incisors. NF-kappaB activation mediated by TNFalpha and IL-1 is diminished in IKK1-deficient mouse embryonic fibroblast (MEF) cells. The IKK complex in the absence of IKK1 is capable of phosphorylating IkappaBalpha and IkappaBbeta in vitro. Our results support a role for IKK1 in NF-kappaB activation and uncover its involvement in skin and skeleton development. We conclude further that the two related kinases IKK1 and IKK2 have distinct functions and can not be substituted for each other's functions.

Patterns of Growth and Decline in Lung Function in Persistent Childhood Asthma

BACKGROUND

Tracking longitudinal measurements of growth and decline in lung function in patients with persistent childhood asthma may reveal links between asthma and subsequent chronic airflow obstruction.

METHODS

We classified children with asthma according to four characteristic patterns of lung-function growth and decline on the basis of graphs showing forced expiratory volume in 1 second (FEV1), representing spirometric measurements performed from childhood into adulthood. Risk factors associated with abnormal patterns were also examined. To define normal values, we used FEV1 values from participants in the National Health and Nutrition Examination Survey who did not have asthma.

RESULTS

Of the 684 study participants, 170 (25%) had a normal pattern of lung-function growth without early decline, and 514 (75%) had abnormal patterns: 176 (26%) had reduced growth and an early decline, 160 (23%) had reduced growth only, and 178 (26%) had normal growth and an early decline. Lower baseline values for FEV1, smaller bronchodilator response, airway hyperresponsiveness at baseline, and male sex were associated with reduced growth (P<0.001 for all comparisons). At the last spirometric measurement (mean [±SD] age, 26.0±1.8 years), 73 participants (11%) met Global Initiative for Chronic Obstructive Lung Disease spirometric criteria for lung-function impairment that was consistent with chronic obstructive pulmonary disease (COPD); these participants were more likely to have a reduced pattern of growth than a normal pattern (18% vs. 3%, P<0.001).

CONCLUSIONS

Childhood impairment of lung function and male sex were the most significant predictors of abnormal longitudinal patterns of lung-function growth and decline. Children with persistent asthma and reduced growth of lung function are at increased risk for fixed airflow obstruction and possibly COPD in early adulthood. (Funded by the Parker B. Francis Foundation and others; ClinicalTrials.gov number, NCT00000575.).

Tyro-3 family receptors are essential regulators of mammalian spermatogenesis

We have generated and analysed null mutations in the mouse genes encoding three structurally related receptors with tyrosine kinase activity: Tyro 3, Axl, and Mer. Mice lacking any single receptor, or any combination of two receptors, are viable and fertile, but male animals that lack all three receptors produce no mature sperm, owing to the progressive death of differentiating germ cells. This degenerative phenotype appears to result from a failure of the tropic support that is normally provided by Sertoli cells of the seminiferous tubules, whose function depends on testosterone and additional factors produced by Leydig cells. Tyro 3, Axl and Mer are all normally expressed by Sertoli cells during postnatal development, whereas their ligands, Gas6 and protein S, are produced by Leydig cells before sexual maturity, and by both Leydig and Sertoli cells thereafter. Here we show that the concerted activation of Tyro 3, Axl and Mer in Sertoli cells is critical to the role that these cells play as nurturers of developing germ cells. Additional observations indicate that these receptors may also be essential for the tropic maintenance of diverse cell types in the mature nervous, immune and reproductive systems.

Gut-derived mesenteric lymph but not portal blood increases endothelial cell permeability and promotes lung injury after hemorrhagic shock

OBJECTIVE

To determine whether gut-derived factors leading to organ injury and increased endothelial cell permeability would be present in the mesenteric lymph at higher levels than in the portal blood of rats subjected to hemorrhagic shock. This hypothesis was tested by examining the effect of portal blood plasma and mesenteric lymph on endothelial cell monolayers and the interruption of mesenteric lymph flow on shock-induced lung injury.

SUMMARY BACKGROUND DATA

The absence of detectable bacteremia or endotoxemia in the portal blood of trauma victims casts doubt on the role of the gut in the generation of multiple organ failure. Nevertheless, previous experimental work has clearly documented the connection between shock and gut injury as well as the concept of gut-induced sepsis and distant organ failure. One explanation for this apparent paradox would be that gut-derived inflammatory factors are reaching the lung and systemic circulation via the gut lymphatics rather than the portal circulation.

METHODS

Human umbilical vein endothelial cell monolayers, grown in two-compartment systems, were exposed to media, sham-shock, or postshock portal blood plasma or lymph, and permeability to rhodamine (10K) was measured. Sprague-Dawley rats were subjected to 90 minutes of sham or actual shock and shock plus lymphatic division (before and after shock). Lung permeability, pulmonary myeloperoxidase levels, alveolar apoptosis, and bronchoalveolar fluid protein content were used to quantitate lung injury.

RESULTS

Postshock lymph increased endothelial cell monolayer permeability but not postshock plasma, sham-shock lymph/plasma, or medium. Lymphatic division before hemorrhagic shock prevented shock-induced increases in lung permeability to Evans blue dye and alveolar apoptosis and reduced pulmonary MPO levels. In contrast, division of the mesenteric lymphatics at the end of the shock period but before reperfusion ameliorated but failed to prevent increased lung permeability, alveolar apoptosis, and MPO accumulation.

CONCLUSIONS

Gut barrier failure after hemorrhagic shock may be involved in the pathogenesis of shock-induced distant organ injury via gut-derived factors carried in the mesenteric lymph rather than the portal circulation.

Mammalian Chk2 is a downstream effector of the ATM-dependent DNA damage checkpoint pathway

In response to DNA damage and replication blocks, cells activate pathways that arrest the cell cycle and induce the transcription of genes that facilitate repair. In mammals, ATM (ataxia telangiectasia mutated) kinase together with other checkpoint kinases are important components in this response. We have cloned the rat and human homologs of Saccharomyces cerevisiae Rad 53 and Schizosaccharomyces pombe Cds1, called checkpoint kinase 2 (chk2). Complementation studies suggest that Chk2 can partially replace the function of the defective checkpoint kinase in the Cds1 deficient yeast strain. Chk2 was phosphorylated and activated in response to DNA damage in an ATM dependent manner. Its activation in response to replication blocks by hydroxyurea (HU) treatment, however, was independent of ATM. Using mass spectrometry, we found that, similar to Chk1, Chk2 can phosphorylate serine 216 in Cdc25C, a site known to be involved in negative regulation of Cdc25C. These results suggest that Chk2 is a downstream effector of the ATM-dependent DNA damage checkpoint pathway. Activation of Chk2 might not only delay mitotic entry, but also increase the capacity of cultured cells to survive after treatment with gamma-radiation or with the topoisomerase-I inhibitor topotecan.

Regulation of cell migration by the calcium-dependent protease calpain

Integrin receptors play an important role during cell migration by mediating linkages and transmitting forces between the extracellular matrix and the actin cytoskeleton. The mechanisms by which these linkages are regulated and released during migration are not well understood. We show here that cell-permeable inhibitors of the calcium-dependent protease calpain inhibit both beta1 and beta3 integrin-mediated cell migration. Calpain inhibition specifically stabilizes peripheral focal adhesions, increases adhesiveness, and decreases the rate of cell detachment. Furthermore, these inhibitors alter the fate of integrin receptors at the rear of the cell during migration. A Chinese hamster ovary cell line expressing low levels of calpain I also shows reduced migration rates with similar morphological changes, further implicating calpain in this process. Taken together, the data suggest that calpain inhibition modulates cell migration by stabilizing cytoskeletal linkages and decreasing the rate of retraction of the cell's rear. Inhibiting calpain-mediated proteolysis may therefore be a potential therapeutic approach to control pathological cell migration such as tumor metastasis.

Ephrin-B reverse signaling is mediated by a novel PDZ-RGS protein and selectively inhibits G protein-coupled chemoattraction

Transmembrane B ephrins and their Eph receptors signal bidirectionally. However, neither the cell biological effects nor signal transduction mechanisms of the reverse signal are well understood. We describe a cytoplasmic protein, PDZ-RGS3, which binds B ephrins through a PDZ domain, and has a regulator of heterotrimeric G protein signaling (RGS) domain. PDZ-RGS3 can mediate signaling from the ephrin-B cytoplasmic tail. SDF-1, a chemokine with a G protein-coupled receptor, or BDNF, act as chemoattractants for cerebellar granule cells, with SDF-1 action being selectively inhibited by soluble EphB receptor. This study reveals a pathway that links reverse signaling to cellular guidance, uncovers a novel mode of control for G proteins, and demonstrates a mechanism for selective regulation of responsiveness to neuronal guidance cues.

Topographic guidance labels in a sensory projection to the forebrain

Visual connections to the mammalian forebrain are known to be patterned by neural activity, but it remains unknown whether the map topography of such higher sensory projections depends on axon guidance labels. Here, we show complementary expression and binding for the receptor EphA5 in mouse retina and its ligands ephrin-A2 and ephrin-A5 in multiple retinal targets, including the major forebrain target, the dorsal lateral geniculate nucleus (dLGN). These ligands can act in vitro as topographically specific repellents for mammalian retinal axons and are necessary for normal dLGN mapping in vivo. The results suggest a general and economic modular mechanism for brain mapping whereby a projecting field is mapped onto multiple targets by repeated use of the same labels. They also indicate the nature of a coordinate system for the mapping of sensory connections to the forebrain.

Gene microarray identification of redox and mitochondrial elements that control resistance or sensitivity to apoptosis

Multigenic programs controlling susceptibility to apoptosis in response to ionizing radiation have not yet been defined. Here, using DNA microarrays, we show gene expression patterns in an apoptosis-sensitive and apoptosis-resistant murine B cell lymphoma model system both before and after irradiation. From the 11,000 genes interrogated by the arrays, two major patterns emerged. First, before radiation exposure the radioresistant LYar cells expressed significantly greater levels of message for several genes involved in regulating intracellular redox potential. Compared with LYas cells, LYar cells express 20- to 50-fold more mRNA for the tetraspanin CD53 and for fructose-1,6-bisphosphatase. Expression of both of these genes can lead to the increase of total cellular glutathione, which is the principle intracellular antioxidant and has been shown to inhibit many forms of apoptosis. A second pattern emerged after radiation, when the apoptosis-sensitive LYas cells induced rapid expression of a unique cluster of genes characterized by their involvement in mitochondrial electron transport. Some of these genes have been previously recognized as proapoptotic; however others, such as uncoupling protein 2, were not previously known to be apoptotic regulatory proteins. From these observations we propose that a multigenic program for sensitivity to apoptosis involves induction of transcripts for genes participating in mitochondrial uncoupling and loss of membrane potential. This program triggers mitochondrial release of apoptogenic factors and induces the "caspase cascade." Conversely, cells resistant to apoptosis down-regulate these biochemical pathways, while activating pathways for establishment and maintenance of high intracellular redox potential by means of elevated glutathione.

Restoration of tight junction structure and barrier function by down-regulation of the mitogen-activated protein kinase pathway in ras-transformed Madin-Darby canine kidney cells

In the Madin-Darby canine kidney epithelial cell line, the proteins occludin and ZO-1 are structural components of the tight junctions that seal the paracellular spaces between the cells and contribute to the epithelial barrier function. In Ras-transformed Madin-Darby canine kidney cells, occludin, claudin-1, and ZO-1 were absent from cell-cell contacts but were present in the cytoplasm, and the adherens junction protein E-cadherin was weakly expressed. After treatment of the Ras-transformed cells with the mitogen-activated protein kinase kinase (MEK1) inhibitor PD98059, which blocks the activation of mitogen-activated protein kinase (MAPK), occludin, claudin-1, and ZO-1 were recruited to the cell membrane, tight junctions were assembled, and E-cadherin protein expression was induced. Although it is generally believed that E-cadherin-mediated cell-cell adhesion is required for tight junction assembly, the recruitment of occludin to the cell-cell contact area and the restoration of epithelial cell morphology preceded the appearance of E-cadherin at cell-cell contacts. Both electron microscopy and a fourfold increase in the transepithelial electrical resistance indicated the formation of functional tight junctions after MEK1 inhibition. Moreover, inhibition of MAPK activity stabilized occludin and ZO-1 by differentially increasing their half-lives. We also found that during the process of tight junction assembly after MEK1 inhibition, tyrosine phosphorylation of occludin and ZO-1, but not claudin-1, increased significantly. Our study demonstrates that down-regulation of the MAPK signaling pathway causes the restoration of epithelial cell morphology and the assembly of tight junctions in Ras-transformed epithelial cells and that tyrosine phosphorylation of occludin and ZO-1 may play a role in some aspects of tight junction formation.

Computed Tomography Assessment of Positive End-expiratory Pressure-induced Alveolar Recruitment in Patients with Acute Respiratory Distress Syndrome

Computed tomography (CT) assessment of positive end-expiratory pressure (PEEP)-induced alveolar recruitment is classically achieved by quantifying the decrease in nonaerated lung parenchyma on a single juxtadiaphragmatic section (Gattinoni's method). This approach ignores the alveolar recruitment occurring in poorly aerated lung areas and may not reflect the alveolar recruitment of the entire lung. This study describes a new CT method in which PEEP-induced alveolar recruitment is computed as the volume of gas penetrating in poorly and nonaerated lung regions following PEEP. In 16 patients with acute respiratory distress syndrome a thoracic spiral CT scan was performed in ZEEP and PEEP 15 cm H(2)O. According to the new method, PEEP induced a 119% increase in functional residual capacity (FRC). PEEP-induced alveolar recruitment was 499 +/- 279 ml whereas distension and overdistension of previously aerated lung areas were 395 +/- 382 ml and 28 +/- 6 ml, respectively. The alveolar recruitment according to Gattinoni's method was 26 +/- 24 g and no correlation was found between both methods. A significant correlation was found between PEEP-induced alveolar recruitment and increase in Pa(O(2)) only when recruitment was assessed by the new method (Rho = 0.76, p = 0.003), suggesting that it may be more accurate than Gattinoni's method.

Effect of chronic heat exposure on fat deposition and meat quality in two genetic types of chicken

The effects of chronic heat stress on growth, proportion of carcass and fat deposition, and meat quality were investigated in 2 genetic types of chickens. One hundred and eight 5-wk-old male chickens from a commercially fast-growing strain (Arbor Acres, AA) and a locally slow-growing species (Beijing You chicken, BJY) were kept in the following conditions: constant optimal ambient temperature at 21 degrees C and ad libitum feeding (21AL), constant high ambient temperature at 34 degrees C and ad libitum feeding (34AL), and constant optimal ambient temperature 21 degrees C and pair-fed to the 34AL chickens (21PF). The results showed that feed intakes were decreased by heat exposure in both type of chickens at 8 wk of age (P<0.001). At 34 degrees C, AA broilers exhibited greatly decreased weight gain (22.38 vs. 61.45 g/d for 21AL) and lower breast proportion compared with 21AL, while the relevant indices of BJY chickens were not affected in hot condition. Abdominal fat deposition of BJY chickens was enhanced by heat exposure (P<0.05). Fat deposition of AA broilers was decreased in heat-exposed and pair-fed chickens. Abdominal and intermuscular fat deposition in 34AL birds, however, were enhanced compared with 21PF birds (P<0.01). The L* values, drip loss, initial pH, and shear force of breast meat in BJY chickens were not affected by treatments. In AA birds, chronic heat stress increased L* values and drip loss compared with 21AL, but pH and shear force were not affected by treatments. The results from this study indicated that the impact of heat stress was breed dependent and that BJY chickens showed higher resistance to high ambient temperature, which could be related to their increased feed efficiency and deposition of abdominal fat under heat exposure.

A mapping label required for normal scale of body representation in the cortex

The neocortical primary somatosensory area (S1) consists of a map of the body surface. The cortical area devoted to different regions, such as parts of the face or hands, reflects their functional importance. Here we investigated the role of genetically determined positional labels in neocortical mapping. Ephrin-A5 was expressed in a medial > lateral gradient across S1, whereas its receptor EphA4 was in a matching gradient across the thalamic ventrobasal (VB) complex, which provides S1 input. Ephrin-A5 had topographically specific effects on VB axon guidance in vitro. Ephrin-A5 gene disruption caused graded, topographically specific distortion in the S1 body map, with medial regions contracted and lateral regions expanded, changing relative areas up to 50% in developing and adult mice. These results provide evidence for within-area thalamocortical mapping labels and show that a genetic difference can cause a lasting change in relative scale of different regions within a topographic map.

Sperm from beta 1,4-galactosyltransferase-null mice are refractory to ZP3-induced acrosome reactions and penetrate the zona pellucida poorly

A variety of sperm surface components have been suggested to mediate gamete recognition by binding to glycoside ligands on the egg coat glycoprotein ZP3. The function of each of these candidate receptors is based upon varying degrees of circumstantial and direct evidence; however, the effects on fertilization of targeted mutations in any of these candidate receptors have not yet been reported. In this paper, we describe the effects of targeted mutations in beta1,4-galactosyltransferase, the best studied of the candidate receptors for ZP3. Surprisingly, galactosyltransferase-null (gt[−/−]) males are fertile; however, sperm from gt(−/−) males bind less radiolabeled ZP3 than wild-type sperm, and are unable to undergo the acrosome reaction in response to either ZP3 or anti-galactosyltransferase antibodies, as do wild-type sperm. In contrast, gt(−/−) sperm undergo the acrosome reaction normally in response to calcium ionophore, which bypasses the requirement for ZP3 binding. The inability of gt(−/−) sperm to undergo a ZP3-induced acrosome reaction renders them physiologically inferior to wild-type sperm, as assayed by their relative inability to penetrate the egg coat and fertilize the oocyte in vitro. Thus, although ZP3 binding and subsequent induction of the acrosome reaction are dispensable for fertilization, they impart a physiological advantage to the fertilizing sperm. A second strain of mice was created that is characterized by a loss of of the long galactosyltransferase isoform responsible for ZP3-dependent signal transduction, but which maintains normal levels of Golgi galactosylation. Sperm from these mice show that the defective sperm-egg interactions in gt(−/−) mice are due directly to a loss of the long galactosyltransferase isoform from the sperm surface and are independent of the state of intracellular galactosylation during spermatogenesis.

delta-catenin, an adhesive junction-associated protein which promotes cell scattering

The classical adherens junction that holds epithelial cells together consists of a protein complex in which members of the cadherin family linked to various catenins are the principal components. delta-catenin is a mammalian brain protein in the Armadillo repeat superfamily with sequence similarity to the adherens junction protein p120(ctn). We found that delta-catenin can be immunoprecipitated as a complex with other components of the adherens junction, including cadherin and beta-catenin, from transfected cells and brain. The interaction with cadherin involves direct contact within the highly conserved juxtamembrane region of the COOH terminus, where p120(ctn) also binds. In developing mouse brain, staining with delta-catenin antibodies is prominent towards the apical boundary of the neuroepithelial cells in the ventricular zone. When transfected into Madin-Darby canine kidney (MDCK) epithelial cells delta-catenin colocalized with cadherin, p120(ctn), and beta-catenin. The Arm domain alone was sufficient for achieving localization and coimmunoprecipitation with cadherin. The ectopic expression of delta-catenin in MDCK cells altered their morphology, induced the elaboration of lamellipodia, interfered with monolayer formation, and increased scattering in response to hepatocyte growth factor treatment. We propose that delta-catenin can regulate adhesion molecules to implement the organization of large cellular arrays necessary for tissue morphogenesis.

A search for proteins that interact genetically with histone H3 and H4 amino termini uncovers novel regulators of the Swe1 kinase in Saccharomyces cerevisiae

In a genetic screen for second-site mutations that are lethal in combination with a deletion of the amino terminus of histone H3, we have uncovered three new gene products that regulate the Saccharomyces cerevisiae Swe1 kinase. The Swe1 protein kinase phosphorylates tyrosine residue 19 of Cdc28 and inhibits its activity. One histone synthetic-lethal gene, HSL1, encodes a putative protein kinase that has high sequence and functional homology to fission yeast cdr1/nim1, an inhibitory kinase of wee1. Another gene, HSL7, is a novel negative regulator of Swe1 function. Sequences similar to Hsl7 exist in Caenorhabditis elegans and humans. In addition, we have isolated a dosage-dependent suppressor, OSS1, of hsl1 and hsl7. OSS1 is important for the transcriptional repression of SWE1 and CLN2 in G2. Mutations in HSL1 and HSL7 therefore cause hyperactivity of the Swe1 kinase, which in turn decreases mitotic Cdc28 kinase activity. Moreover, HSL5 is identical to CDC28, further suggesting that it is the decreased Cdc28 kinase activity in these hsl mutants that causes lethality in the histone mutant background. Because neither HSL1 nor HSL7 is essential in yeast, and histone transcription is unaffected by the hsl5/cdc28 mutation, it is unlikely that synthetic lethality results from reduced transcription of HSL1 and HSL7 caused by histone mutations, or from reduced histone transcription when Cdc28 kinase activity is compromised. We suggest that these cell cycle regulators function in a pathway upstream of both histones H3 and H4, thereby modulating histone function in the cell cycle.

Selective phosphorylation of adult tau isoforms in mature hippocampal neurons exposed to fibrillar A beta

How senile plaques and neurofibrillary tangles are linked represents a major gap in our understanding of the pathophysiology of Alzheimer's disease. We characterized a hippocampal neuronal culture system in which tau undergoes maturation in vivo; rat neurons maintained in culture for more than 3 weeks replicated the splicing and phosphorylation changes that tau undergoes upon maturation in situ. Using this model system, we induced an Alzheimer-like neuritic dystrophy following the application of fibrillar beta-amyloid. The dystrophy consisted of focal distortions and swellings within the neurites and an altered phosphorylation of the adult tau isoforms. Fibrillar beta-amyloid induced the concomitant activation of MAP kinase and GSK3 beta. The aberrant activation of several signaling pathways may lead to the abnormal phosphorylation of tau and neuritic degeneration.

Snake venoms and hemostasis

Snake venoms are complex mixtures of biologically active proteins and peptides. Many of them affect hemostasis by activating or inhibiting coagulant factors or platelets, or by disrupting endothelium. Based on sequence, these snake venom components have been classified into various families, such as serine proteases, metalloproteinases, C-type lectins, disintegrins and phospholipases. The various members of a particular family act selectively on different blood coagulation factors, blood cells or tissues. For almost every factor involved in coagulation or fibrinolysis there is a venom protein that can activate or inactivate it. Venom proteins affect platelet function by binding or degrading vWF or platelet receptors, activating protease-activated receptors or modulating ADP release and thromboxane A2 formation. Some venom enzymes cleave key basement membrane components and directly affect capillary blood vessels to cause hemorrhaging. L-Amino acid oxidases activate platelets via H2O2 production.

Regional distribution of gas and tissue in acute respiratory distress syndrome. II. Physiological correlations and definition of an ARDS Severity Score. CT Scan ARDS Study Group

OBJECTIVES

(a) To assess whether differences in lung morphology observed in patients with adult respiratory distress syndrome (ARDS) are associated with differences in cardiorespiratory parameters, lung mechanics, and outcome. (b) To propose a new ARDS Severity Score to identify patients with a high mortality risk.

DESIGN

Prospective study over a 53-month period.

SETTING

Fourteen-bed surgical intensive care unit of a university hospital.

PATIENTS AND PARTICIPANTS

Seventy-one consecutive patients with early ARDS.

MEASUREMENTS AND RESULTS

Cardiorespiratory parameters were measured using a Swan-Ganz catheter, the pressure-volume (PV) curve was measured using the gross syringe method, and fast spiral computed tomography (CT) was performed. Patients with diffuse attenuations (n = 16) differed from patients with lobar attenuations (n = 26) regarding: (a) mortality rate (75% vs. 42%, p = 0.05), (b) incidence of primary ARDS (82% vs. 50%, p = 0.03), (c) respiratory compliance (47 +/- 12 vs. 64 +/- 16 ml per cmH2O(-1) p = 0.04), and (d) lower inflexion point (8.4 +/- 2.0 vs. 4.6 +/- 2.0 cmH2O, p = 0.001). A third group of patients with patchy attenuations (n = 29) had a mortality rate of 41 %, a respiratory compliance of 56 +/- 18 ml per cmH2O(-1) and a lower inflexion point of 6.3 +/- 2.7 cmH2O. The bedside chest radiograph accurately assessed lung morphology in only 42% of the patients. In contrast to the scores based on the bedside chest radiograph, a new ARDS Severity Score based on CT lung morphology and cardiorespiratory parameters identified a subgroup of patients with a high mortality rate (> or = 60%).

CONCLUSIONS

In patients with ARDS, differences in lung morphology are associated with differences in outcome and lung mechanics. A new ARDS Severity Score based on CT lung morphology and cardiorespiratory parameters accurately identified patients with the most severe forms of ARDS and a mortality rate above 60%.

A lung computed tomographic assessment of positive end-expiratory pressure-induced lung overdistension

The aim of this study was to assess positive end-expiratory pressure (PEEP)-induced lung overdistension and alveolar recruitment in six patients with acute lung injury (ALI) using a computed tomographic (CT) scan method. Lung overdistension was first determined in six healthy volunteers in whom CT sections were obtained at FRC and at TLC with a positive airway pressure of 30 cm H2O. In patients, lung volumes were quantified by the analysis of the frequency distribution of CT numbers on the entire lung at zero end-expiratory pressure (ZEEP) and PEEP. In healthy volunteers at FRC, the distribution of the density histograms was monophasic with a peak at -791 +/- 12 Hounsfield units (HU). The lowest CT number observed was -912 HU. At TLC, lung volume increased by 79 +/- 35% and the peak CT number decreased to -886 +/- 26 HU. More than 70% of the increase in lung volume was located below -900 HU, suggesting that this value can be considered as the threshold separating normal aeration from overdistension. In patients with ALI, at ZEEP the distribution of density histograms was either monophasic (n = 3) or biphasic (n = 3). The mean CT number was -319 +/- 34 HU. At PEEP 13 +/- 3 cm H2O, lung volume increased by 47 +/- 19% whereas mean CT number decreased to -538 +/- 171 HU. PEEP induced a mean alveolar recruitment of 320 +/- 160 ml and a mean lung overdistension of 238 +/- 320 ml. In conclusion, overdistended lung parenchyma of healthy volunteers is characterized by a CT number below -900 HU. This threshold can be used in patients with ALI for differentiating PEEP-induced alveolar recruitment from lung overdistension.

The NFAT-related protein NFATL1 (TonEBP/NFAT5) is induced upon T cell activation in a calcineurin-dependent manner

NFAT DNA binding complexes regulate programs of cellular activation and differentiation by translating receptor-dependent signaling events into specific transcriptional responses. NFAT proteins, originally defined as calcium/calcineurin-dependent regulators of cytokine gene transcription in T lymphocytes, are expressed in many different cell types and represent critical signaling intermediates that mediate an increasingly wide spectrum of biologic responses. Recent studies have identified a novel protein containing a region of similarity to the NFAT DNA binding domain. Here we demonstrate that this protein, designated NFATL1 (also known as tonicity enhancer binding protein and NFAT5) is expressed at high levels in the thymus but is undetectable in mature lymphocytes. However, NFATL1 can be induced in both primary quiescent T lymphocytes and differentiated Th1 and Th2 cell populations upon mitogen- or Ag receptor-dependent activation. The induction of NFATL1 protein, as well as NFATL1-dependent transcription, is inhibited by cyclosporin A and FK506, and expression of constitutively active calcineurin induces NFATL1-dependent transcription. Overexpression of NFATc1 and inhibition of NFATc activity through the use of a dominant negative NFATc1 protein have no affect on NFATL1-dependent transcription, indicating that NFATc proteins do not play a role in the calcineurin-dependent induction of NFATL1. Interestingly, induction of NFATL1 by a hyperosmotic stimulus is not blocked by the inhibition of calcineurin. Moreover, osmotic stress response genes such as aldose reductase are not induced upon T cell activation. Thus inducible expression of NFATL1 represents a mechanism by which receptor-dependent signals as well as osmotic stress signals are translated into transcriptional responses that regulate cell function.

A time course study of the protective effect of mesenteric lymph duct ligation on hemorrhagic shock-induced pulmonary injury and the toxic effects of lymph from shocked rats on endothelial cell monolayer permeability

BACKGROUND

We have previously documented that lymphatic duct division protects against shock-induced lung injury when tested 3 hours post-shock and that lymph collected at 3 hours post-shock increases endothelial cell monolayer permeability. However, whether lymph collected at other time points post-shock also increases endothelial cell permeability is not known. We tested the protective effects of lymphatic division on lung permeability at 6, 12, and 24 hours post-shock and the ability of lymph collected before, during, and hourly (up to 6 hours) after shock to increase endothelial cell monolayer permeability.

METHODS

At 3, 6, 12, or 24 hours after sham or actual shock (30 mm Hg for 90 min), lung permeability was measured by using Evans blue dye in rats subjected to sham or actual mesenteric duct ligation. In separate experiments, the ability of lymph collected from rats subjected to shock or sham shock to increase human umbilical vein endothelial cell (HUVEC) monolayer permeability to a 40 kd dextran rhodamine permeability probe. Lymph was tested at 10% and 1% concentrations.

RESULTS

Hemorrhagic shock induced a 3- to 4-fold increase in lung permeability compared with sham-shock rats when tested at 3, 6, 12, or 24 hours post-shock. Lymphatic division prevented this increase in lung permeability at each of these time points. Sham shock lymph did not increase HUVEC permeability, while lymph from the shocked rats did, whether tested at 1% or 10%. Lymph samples collected during the shock period and hourly for 6 hours post-shock all increased HUVEC permeability; however, the greatest relative increase in HUVEC permeability was observed in the 3- and 6- hour post-shock samples.

CONCLUSIONS

Lung injury after hemorrhagic shock appears to be caused by toxic factors carried in the mesenteric lymph, and factors capable of increasing HUVEC permeability initially appear in the lymph during the shock period and increase over time.

Targeted mutation in beta1,4-galactosyltransferase leads to pituitary insufficiency and neonatal lethality

Despite much attention, the function of oligosaccharide chains on glycoproteins and glycolipids remains largely unknown. Our understanding of oligosaccharide function in vivo has been limited to the use of reagents and targeted mutations that eliminate entire classes of oligosaccharide chains. However, most biological functions for oligosaccharides have been attributed to specific terminal sequences on these glycoside chains; yet, there have been few studies that examine the consequences of modifying terminal oligosaccharide structures in vivo. To address this issue, mice were created bearing a targeted mutation in beta1,4-galactosyltransferase (GalTase), an enzyme responsible for elaboration of many of the proposed biologically active carbohydrate epitopes. Most GalTase-null mice died within the first few weeks after birth and were characterized by stunted growth, thin skin, sparse hair, and dehydration. In addition, spermatogenesis was delayed, the lungs were poorly developed, and the adrenal cortices were poorly stratified. The few surviving adults had puffy skin (myxedema) and difficulty delivering pups at birth (dystocia) and failed to lactate (agalactosis). All of these defects are consistent with endocrine insufficiency, which was confirmed by markedly decreased levels of serum thyroxine. The polyglandular nature of the endocrine insufficiency is indicative of a failure of the anterior pituitary gland to stimulate the target endocrine organs. Previous in vitro studies have suggested that incomplete glycosylation of anterior pituitary hormones leads to the creation of hormone antagonists, which down-regulate subsequent endocrine function, producing polyglandular endocrine insufficiency. In GalTase-null mice, the anterior pituitary acquired a normal secretory phenotype during neonatal development indicative of normal glycoprotein hormone synthesis and secretion. However, as expected, the gland was devoid of GalTase activity. These results support a requirement for terminal oligosaccharide sequences for anterior pituitary hormone function. The fact that approximately 10% of the GalTase-null mice survive the neonatal period indicates the presence of a previously unrecognized compensatory pathway for glycoprotein hormone glycosylation and/or action.