Cloning and characterization of the thyroid iodide transporter

Iodide (I-) is an essential constituent of the thyroid hormones T3 and T4, and is accumulated by the thyroid. The transport of iodide, the first step in thyroid hormogenesis, is catalysed by the Na+/I- symporter, an intrinsic membrane protein that is crucial for the evaluation, diagnosis and treatment of thyroid disorders. Although several other important thyroid proteins involved in hormogenesis have been characterized, the Na+/I- symporter has not. Here we report the isolation of a complementary DNA clone that encodes this symporter, as a result of functional screening of a cDNA library from a rat thyroid-derived cell line (FRTL-5) in Xenopus laevis oocytes. Oocyte microinjection of an RNA transcript made in vitro from this cDNA clone elicited a more than 700-fold increase in perchlorate-sensitive Na+/I- symport activity over background. To our knowledge, this is the first iodide-transporting molecule to have its cDNA cloned, providing a missing link in the thyroid hormone biosynthetic pathway.

Diffusion spectrum magnetic resonance imaging (DSI) tractography of crossing fibers

MRI tractography is the mapping of neural fiber pathways based on diffusion MRI of tissue diffusion anisotropy. Tractography based on diffusion tensor imaging (DTI) cannot directly image multiple fiber orientations within a single voxel. To address this limitation, diffusion spectrum MRI (DSI) and related methods were developed to image complex distributions of intravoxel fiber orientation. Here we demonstrate that tractography based on DSI has the capacity to image crossing fibers in neural tissue. DSI was performed in formalin-fixed brains of adult macaque and in the brains of healthy human subjects. Fiber tract solutions were constructed by a streamline procedure, following directions of maximum diffusion at every point, and analyzed in an interactive visualization environment (TrackVis). We report that DSI tractography accurately shows the known anatomic fiber crossings in optic chiasm, centrum semiovale, and brainstem; fiber intersections in gray matter, including cerebellar folia and the caudate nucleus; and radial fiber architecture in cerebral cortex. In contrast, none of these examples of fiber crossing and complex structure was identified by DTI analysis of the same data sets. These findings indicate that DSI tractography is able to image crossing fibers in neural tissue, an essential step toward non-invasive imaging of connectional neuroanatomy.

Thyroid Na+/I- symporter. Mechanism, stoichiometry, and specificity

The rat thyroid Na+/I- symporter (NIS) was expressed in Xenopus laevis oocytes and characterized using electrophysiological, tracer uptake, and electron microscopic methods. NIS activity was found to be electrogenic and Na+-dependent (Na+ >> Li+ >> H+). The apparent affinity constants for Na+ and I- were 28 +/- 3 mM and 33 +/- 9 microM, respectively. Stoichiometry of Na+/anion cotransport was 2:1. NIS was capable of transporting a wide variety of anions (I-, ClO3-, SCN-, SeCN-, NO3-, Br-, BF4-, IO4-, BrO3-, but perchlorate (ClO4-) was not transported. In the absence of anion substrate, NIS exhibited a Na+-dependent leak current (approximately 35% of maximum substrate-induced current) with an apparent Na+ affinity of 74 +/- 14 mM and a Hill coefficient (n) of 1. In response to step voltage changes, NIS exhibited current transients that relaxed with a time constant of 8-14 ms. Presteady-state charge movements (integral of the current transients) versus voltage relations obey a Boltzmann relation. The voltage for half-maximal charge translocation (V0.5) was -15 +/- 3 mV, and the apparent valence of the movable charge was 1. Total charge was insensitive to [Na+]o, but V0.5 shifted to more negative potentials as [Na+]o was reduced. NIS charge movements are attributed to the conformational changes of the empty transporter within the membrane electric field. The turnover rate of NIS was >/=22 s-1 in the Na+ uniport mode and >/=36 s-1 in the Na+/I- cotransport mode. Transporter density in the plasma membrane was determined using freeze-fracture electron microscopy. Expression of NIS in oocytes led to a approximately 2. 5-fold increase in the density of plasma membrane protoplasmic face intramembrane particles. On the basis of the kinetic results, we propose an ordered simultaneous transport mechanism in which the binding of Na+ to NIS occurs first.

Characterization of the thyroid Na+/I- symporter with an anti-COOH terminus antibody

The Na+/I- symporter (NIS) is the plasma membrane protein that catalyzes active I- transport in the thyroid, the first step in thyroid hormone biogenesis. The cDNA encoding NIS was recently cloned in our laboratory and a secondary structure model proposed, suggesting that NIS is an intrinsic membrane protein (618 amino acids; approximately 65.2 kDa predicted molecular mass) with 12 putative transmembrane domains. Here we report the generation of a site-directed polyclonal anti-COOH terminus NIS antibody (Ab) that immunoreacts with a approximately 87 kDa-polypeptide present in membrane fractions from a rat thyroid cell line (FRTL-5). The model-predicted cytosolic-side location of the COOH terminus was confirmed by indirect immunofluorescence experiments using anti-COOH terminus NIS Ab in permeabilized FRTL-5 cells. Immunoreactivity was competitively blocked by the presence of excess synthetic peptide. Treatment of membrane fractions from FRTL-5 cells, Xenopus laevis oocytes, and COS cells expressing NIS with peptidyl N-glycanase F converted the approximately 87 kDa-polypeptide into a approximately 50 kDa-species, the same relative molecular weight exhibited by NIS expressed in E. coli. Anti-NIS Ab immunoprecipitated both the NIS precursor molecule (approximately 56 kDa) and the mature approximately 87 kDa form. Furthermore, a direct correlation between circulating levels of thyroid-stimulating hormone and NIS expression in vivo was demonstrated.

N-linked glycosylation of the thyroid Na+/I- symporter (NIS). Implications for its secondary structure model

The Na+/I- symporter (NIS), a 618-amino acid membrane glycoprotein that catalyzes the active accumulation of I- into thyroid cells, was identified and characterized at the molecular level in our laboratory (Dai, G., Levy, O., and Carrasco, N. (1996) Nature 379, 458-460). Because mature NIS is highly glycosylated, it migrates in SDS-polyacrylamide gel electrophoresis as a broad polypeptide of higher molecular mass (approximately 90-110 kDa) than nonglycosylated NIS (approximately 50 kDa). Using site-directed mutagenesis, we substituted both separately and simultaneously the asparagine residues in all three putative N-linked glycosylation consensus sequences of NIS with glutamine and assessed the effects of the mutations on function and stability of NIS in COS cells. All mutants were active and displayed 50-90% of wild-type NIS activity, including the completely nonglycosylated triple mutant. This demonstrates that to a considerable extent, function and stability of NIS are preserved in the partial or even total absence of N-linked glycosylation. We also found that Asn225 is glycosylated, thus proving that the hydrophilic loop that contains this amino acid residue faces the extracellular milieu rather than the cytosol as previously suggested. We demonstrated that the NH2 terminus faces extracellularly as well. A new secondary structure model consistent with these findings is proposed.

Etomoxir-induced PPARalpha-modulated enzymes protect during acute renal failure

Regulation of fatty acid beta-oxidation (FAO) represents an important mechanism for a sustained balance of energy production/utilization in kidney tissue. To examine the role of stimulated FAO during ischemia, Etomoxir (Eto), clofibrate, and WY-14,643 compounds were given 5 days prior to the induction of ischemia/reperfusion (I/R) injury. Compared with rats administered vehicle, Eto-, clofibrate-, and WY-treated rats had lower blood urea nitrogen and serum creatinines following I/R injury. Histological analysis confirmed a significant amelioration of acute tubular necrosis. I/R injury led to a threefold reduction of mRNA and protein levels of acyl CoA oxidase (AOX) and cytochrome P4A1, as well as twofold inhibition of their enzymatic activities. Eto treatment prevented the reduction of mRNA and protein levels and the inhibition of the enzymatic activities of these two peroxisome proliferator-activated receptor-alpha (PPARalpha) target genes during I/R injury. PPARalpha null mice subjected to I/R injury demonstrated significantly enhanced cortical necrosis and worse kidney function compared with wild-type controls. These results suggest that upregulation of PPARalpha-modulated FAO genes has an important role in the observed cytoprotection during I/R injury.

Synthesis of 3,4-disubstituted isoquinolines via palladium-catalyzed cross-coupling of o-(1-alkynyl)benzaldimines and organic halides

[reaction: see text] 3,4-Disubstituted isoquinolines have been prepared in good yields by the palladium-catalyzed cross-coupling of N-tert-butyl-o-(1-alkynyl)benzaldimines with aryl, allylic, and alkynyl halides.

Quantitative MR imaging of carpal tunnel syndrome

OBJECTIVE

Previous MR imaging studies have produced evidence of changes to structures within the wrist believed to be associated with carpal tunnel syndrome. In an attempt to resolve the conflicting and inconclusive results of these studies, we report here the results of an MR imaging study at a field strength of 3.0 T, which is higher than that previously reported.

SUBJECTS AND METHODS

Patients with carpal tunnel syndrome and control groups of asymptomatic subjects were studied using MR imaging. We evaluated electrophysiologically the median nerve function of the affected wrists of all patients. A gradient-recalled echo pulse sequence was used to study 13 3-mm-thick slices within the wrist of each patient or asymptomatic subject. Spatial resolution was approximately 0.3 x 0.3 mm2. The median nerve and other structures associated with the carpal tunnel, which were clearly shown on the MR images, were analyzed to yield structural data.

RESULTS

Analysis revealed that the cross-sectional area of the nerve within and proximal to the carpal tunnel was approximately 50% larger in patients with carpal tunnel syndrome than in asymptomatic subjects. We found no significant difference in the area of the nerve within the carpal tunnel compartment compared with the area of the nerve proximal to the carpal tunnel either in patients or in asymptomatic subjects. Also, flattening of the nerve on entering the carpal tunnel was not significantly different in patients than in asymptomatic subjects. In patients an increase in the palmar bowing of the flexor retinaculum was found only at the level of the hamate compared with that found in asymptomatic subjects. The cross-sectional area of the carpal tunnel was of a similar size in patients and in asymptomatic subjects. Comparison of electrodiagnostic results indicated no correlations between the MR parameters and electrophysiologic dysfunction of the median nerve for patients.

CONCLUSION

The only statistically significant differences found between patients with carpal tunnel syndrome and asymptomatic subjects were that the median nerve was approximately 50% larger within and proximal to the carpal tunnel in patients with carpal tunnel syndrome and palmar bowing of the flexor retinaculum occurred in patients only at the level of the hamate.

Altered cytokine production and impaired antimycobacterial immunity in protein-malnourished guinea pigs

Protein malnutrition leads to multiple detrimental alterations of host immune responses to mycobacterial infection. In this study, we demonstrated that splenocytes from low-protein (LP) guinea pigs vaccinated 6 weeks previously with attenuated Mycobacterium tuberculosis H37Ra failed to control the accumulation of virulent M. tuberculosis H37Rv in cocultured autologous peritoneal macrophages, despite the fact that they were able to control the accumulation of virulent tubercle bacilli in cocultured syngeneic peritoneal macrophages from normally nourished guinea pigs as successfully as did those from high-protein (HP) counterparts. Vaccine-induced growth control of virulent M. tuberculosis H37Rv in these cocultures appeared to be mediated by CD4 lymphocytes but not CD8 cells. Tuberculin (purified protein derivative [PPD])-induced lymphoproliferation was markedly impaired in vaccinated LP guinea pigs, and the depletion of CD4 lymphocytes significantly decreased lymphocyte proliferation whereas CD8 cell depletion did not. Protein malnutrition also impaired the abilities of cells from vaccinated LP guinea pigs to produce cytokines, including interferon, tumor necrosis factor alpha (TNF-alpha) and transforming growth factor beta (TGF-beta), in response to PPD, despite the demonstration of higher serum levels of TNF-alpha and TGF-beta after an intravenous injection of PPD into LP guinea pigs. In contrast, peritoneal macrophages from protein-malnourished guinea pigs produced a higher level of TGF-beta 4 days after infection in vitro with M. tuberculosis H37Rv than did those from protein adequate controls. These results suggest that dietary protein malnutrition impairs vaccine-induced resistance to M. tuberculosis, in part, by altering the cytokine profile to favor macrophage deactivation.

Na(+)-I- symport activity is present in membrane vesicles from thyrotropin-deprived non-I(-)-transporting cultured thyroid cells

The active accumulation of I- in the thyroid gland is mediated by the Na(+)-I- symporter and driven by the Na+ gradient generated by the Na+/K(+)-ATPase. Thyrotropin (TSH) stimulates thyroidal I- accumulation. Rat thyroid-derived FRTL-5 cells require TSH to accumulate I-. TSH withdrawal for over 7 days results in complete loss of Na(+)-I-symport activity in these cells [Weiss, S. J., Philp, N. J. and Grollman, E. F. (1984) Endocrinology 114, 1090-1098]. Surprisingly, membrane vesicles prepared from FRTL-5 cells maintained in TSH-free medium [TSH(-)cells]accumulate I-, suggesting that the absence of Na(+)-I- symport activity in TSH(-) cells cannot be due solely to a decrease in the biosynthesis of either the symporter or a putative activating factor. This finding indicates that the Na(+)-I- symporter is present, probably in an inactive state, in TSH(-) cells despite their lack of Na(+)-I- symport activity. Na(+)-I- symport activity in thyroid membrane vesicles is enhanced when conditions for vesicle preparation favor proteolysis. Subcellular fractionation studies in both TSH(+) and TSH(-) cells show that Na(+)-I- symport activity is mostly associated with fractions enriched in plasma membrane rather than in intracellular membranes, suggesting that the Na(+)-I- symporter may constitutively reside in the plasma membrane and may be activated by TSH.

Purification of a novel calcium-independent phospholipase A2 from rabbit kidney

We have recently identified a cytosolic calcium-independent phospholipase A2 (PLA2) that represents the major measurable PLA2 activity in rabbit proximal tubules (Portilla, D., Shah, S. V., Lehman, P. A., and Creer, M. H.(1994) J. Clin. Invest. 93, 1609-1615). We now report the 3200-fold purification of this PLA2 to homogeneity from rabbit kidney cortex through sequential column chromatography including anion exchange, hydrophobic interaction, Mono Q, hydroxylapatite, phenyl-Sepharose, and chromatofocusing fast protein liquid chromatography from rabbit kidney cortex. The purified enzyme had a molecular mass of 28 kDa, possessed a specific activity of 1.2 micronol/mg min and a neutral pH optimum, and exhibited a preferential hydrolysis toward sn-2 fatty acid from diradylglycerophospholipids. The purified polypeptide hydrolyzed plasmenylcholine > phosphatidylcholine glycerophospholipids and selectively cleaved phospholipids containing arachidonic acid at the sn-2 position in comparison to oleic acid. Antibodies against the purified protein precipitated all of the soluble calcium-independent PLA2 activity from rabbit kidney cortex. These data altogether suggest that the 28-kDa protein in the kidney represents a novel class of calcium-independent PLA2.

The effects of external compression on venous blood flow and tissue deformation in the lower leg

External pneumatic compression of the lower legs is effective as prophylaxis against deep vein thrombosis. In a typical application, inflatable cuffs are wrapped around the patient's legs and periodically inflated to prevent stasis, accelerate venous blood flow, and enhance fibrinolysis. The purpose of this study was to examine the stress distribution within the tissues, and the corresponding venous blood flow and intravascular shear stress with different external compression modalities. A two-dimensional finite element analysis (FEA) was used to determine venous collapse as a function of internal (venous) pressure and the magnitude and spatial distribution of external (surface) pressure. Using the one-dimensional equations governing flow in a collapsible tube and the relations for venous collapse from the FEA, blood flow resulting from external compression was simulated. Tests were conducted to compare circumferentially symmetric (C) and asymmetric (A) compression and to examine distributions of pressure along the limb. Results show that A compression produces greater vessel collapse and generates larger blood flow velocities and shear stresses than C compression. The differences between axially uniform and graded-sequential compression are less marked than previously found, with uniform compression providing slightly greater peak flow velocities and shear stresses. The major advantage of graded-sequential compression is found at midcalf. Strains at the lumenal border are approximately 20 percent at an external pressure of 50 mmHg (6650 Pa) with all compression modalities.

Uterine natural killer cells are targets for a trophoblast cell-specific cytokine, prolactin-like protein A

PRL-like protein A (PLP-A) is a member of the PRL family expressed in trophoblast cells coincident with establishment of the chorioallantoic placenta. The purpose of this investigation was to identify targets for PLP-A. Using an alkaline phosphatase-tagging strategy, we show that PLP-A specifically interacts with a population of natural killer (NK) lymphocytes within the mesometrial compartment of decidua from pregnant and pseudopregnant rats. These observations are supported by the codistribution of PLP-A targets with cells expressing the rat NK cell surface marker, gp42, the absence of PLP-A binding in conceptuses from NK cell-deficient tg epsilon26 mice, and the specific interaction of PLP-A with a rat NK cell line, RNK-16. We have further demonstrated that PLP-A effectively suppresses RNK-16 cell cytolytic activities. Our results provide evidence for a new paradigm of embryonic-maternal communication involving a PLP-A signaling pathway between trophoblast cells and uterine NK lymphocytes.

Allocation of helper T-cell epitope immunodominance according to three-dimensional structure in the human immunodeficiency virus type I envelope glycoprotein gp120

The specificity and intensity of CD4(+) helper T-cell responses determine the effectiveness of immune effector functions. Promiscuously immunodominant helper T-cell epitopes in the human immunodeficiency virus (HIV) envelope glycoprotein gp120 could be important in the development of broadly protective immunity, but the underlying mechanisms of immunodominance and promiscuity remain poorly defined. In this study, gp120 helper T-cell epitopes were systematically mapped in CBA/J and BALB/c mice by restimulation assays using a set of overlapping peptides spanning the entire sequence of the gp120 encoded by HIV strain 89.6. The results were analyzed in the context of the HIV gp120 structure determined by x-ray crystallography. One major finding was that all of the promiscuously immunodominant gp120 sequences are located in the outer domain. Further analyses indicated that epitope immunogenicity in the outer domain correlates with structural disorder in adjacent N-terminal segments, as indicated by crystallographic B-factors or sequence divergence. In contrast, the correlation was poor when the analysis encompassed the entire gp120 sequence or was restricted to only the inner domain. These findings suggest that local disorder promotes the processing and presentation of adjacent epitopes in the outer domain of gp120 and therefore reveal how three-dimensional structure shapes the profile of helper T-cell epitope immunogenicity.

The effect of combined arterial hemodynamics on saphenous venous endothelial nitric oxide production

INTRODUCTION

Evidence exists that an ideal bypass conduit should have a functional endothelial cell surface combined with mechanical properties similar to those of native arteries. We hypothesized that the effect of combined arterial levels of pulsatile shear stress, flow, and cyclic strain would enhance saphenous venous endothelial cell nitric oxide (NO) production, and that variations in these "ideal" conditions could impair this function. We studied NO production as a measure of endothelial function in response to different hemodynamic conditions.

METHODS

Human adult saphenous venous endothelial cells were cultured in 10-cm silicone tubes, similar in diameter (5 mm) and compliance (6%) to a medium-caliber peripheral artery (eg, popliteal). Tube cultures were exposed to arterial conditions: a combined pressure (120/80 mm/Hg; mean, 100 mm/Hg), flow (mean, 115 mL/min) and cyclic strain (2%), with a resultant pulsatile shear stress of 4.8 to 9.4 dyne/cm2 (mean, 7.1). Identical tube cultures were used to study variations in these conditions. Modifications of the system included a noncompliant system, a model with nonpulsatile flow, and a final group exposed to pulsatile pressure with no flow. NO levels were measured with a fluorometric nitrite assay of conditioned media collected at 0, 0.25, 0.5, 1, 2, and 4 hours. Experimental groups were compared with cells exposed to nonpulsatile, nonpressurized low flow (shear stress 0.1 dyne/cm2) and static cultures.

RESULTS

All experimental groups had greater rates of NO production than cells under static conditions (P <.05). Cells exposed to ideal conditions produced the greatest levels of NO. Independent decreases in compliance, flow, and pulsatility resulted in significantly lower rates of NO production than those in the group with these conditions intact (vs noncompliant P <.05, vs nonflow P <.05, and vs nonpulsatile P <.05).

CONCLUSIONS

Our results show that in the absence of physiologically normal pulsatility, cyclic strain, and volume flow, endothelial NO production does not reach the levels seen under ideal conditions. Pulsatile flow and compliance (producing flow with cyclic stretch) play a key role in NO production by vascular endothelium in a three-dimensional hemodynamically active model. This correlates biologically with clinical experience linking graft inflow and runoff and the mechanical properties of the conduit to long-term patency.

Nutritional modulation of host responses to mycobacteria

Nutritional status determines the generation and functioning of cellular and molecular components of the immune system which are responsible for host resistance to various infectious diseases, including tuberculosis. Studies carried out by us and others have demonstrated that malnutrition exerts detrimental effects on many aspects of host immune responses against mycobacterial infection. First, dietary deficiencies of single nutrients, such as protein and zinc, cause thymic atrophy and impair the generation and maturation of T lymphocytes in animal models of tuberculosis, resulting in reduced number of immunocompetent T cells in lymphoid compartments including the blood. Second, deficiencies of protein, zinc and vitamin D impair T-cell functions, including decreased production of the Th1 cytokines IL-2 and IFN-gamma, and depressed dermal tuberculin reactions and PPD-induced lymphoproliferation in guinea pigs and mice infected with virulent Mycobacterium tuberculosis. Third, protein malnutrition causes trapping or sequestration of reactive T lymphocytes and loss of tuberculosis resistance following BCG vaccination. Finally, protein malnutrition potentiates M. tuberculosis H37Rv-infected monocyte-macrophages to produce higher levels of TGF-beta1 a cytokine which has been implicated as a likely mediator of immunosuppression and immunopathogenesis in tuberculosis.

Aspergillus antigen-induced eosinophil differentiation in a murine model

Eosinophilia is a prominent feature of the cellular response in allergic and parasitic diseases. Allergic bronchopulmonary aspergillosis due to colonization of the lungs of some asthmatics with Aspergillus fumigatus is characterized by high levels of serum immunoglobulin E and peripheral blood (PB) and lung eosinophilia. This study investigates the role of eosinophils in the pathogenesis of allergic bronchopulmonary aspergillosis by using a mouse model. BALB/c mice were immunized intranasally and intraperitoneally with A. fumigatus antigens (Ag), and the eosinophils in PB and bone marrow (BM) were enumerated. Eosinophilopoiesis in BM cultures was studied in the presence of murine recombinant interleukin-5 (mrIL-5) and supernatants from pokeweed mitogen-stimulated spleen cells as the source of eosinophil differentiation factors. Eosinophils were quantitated by direct counting and by estimating eosinophil peroxidase activity. The results indicate that the percentage of eosinophils in the PB (5.77 +/- 1.17) and the BM (11.19 +/- 4.31) of mice exposed to A. fumigatus Ag was higher than in controls (PB, 2.42 +/- 0.76; BM, 5.12 +/- 2.79; P less than 0.01 for both). Similarly, a significant increase in eosinophils was observed in the BM population from mice exposed to A. fumigatus Ag compared with that in controls when cultured with murine recombinant interleukin-5 (23.13 +/- 7.14 versus 13.77 +/- 5.79, P less than 0.01), indicating that the mice exposed to A. fumigatus Ag had significantly greater numbers of eosinophil precursors in their BM. This study demonstrates that A. fumigatus Ag may be involved in the in vivo commitment of stem cells in the eosinophil differentiation pathway.

An in vitro cell culture system to study the influence of external pneumatic compression on endothelial function

PURPOSE

External pneumatic compression (EPC) is an effective means of prophylaxis against deep venous thrombosis. However, its mechanism remains poorly understood. Understanding of the biological consequences of EPC is an important goal for optimizing performance of the EPC-generating device and providing guidance for clinical use. We present a new in vitro cell culture system (Venous Flow Simulator) that simulates blood flow and vessel collapse conditions during EPC, and we examine the influence of these factors on endothelial cell (EC) fibrinolytic activity and vasomotor function.

METHODS

An in vitro cell culture system was designed to replicate the hemodynamic shear stress and vessel wall strain associated with induced blood flow during different modes of EPC. Human umbilical vein endothelial cells were cultured in the system and subjected to intermittent flow, vessel collapse, or a combination of the two. The biologic response was assessed through changes in EC morphology and the expression of fibrinolytic factors tissue plasminogen activator, plasminogen activator inhibitor type 1, profibrinolytic receptor (annexin II), and vasomotor factors endothelial nitric oxide synthase and endothelin-1.

RESULTS

The cells remained attached and viable after being subjected to intermittent pulsatile flow (F) and tube compression (C). In F and F + C, cells aligned in the direction of flow after 6 hours. Northern blot analysis of messenger RNA shows that there is an upregulation of tissue plasminogen activator expression (1.95 +/- 0.19 in F and 2.45 +/- 0.46 in FC) and endothelial nitric oxide synthase expression (2.08 +/- 0.25 in F and 2.11 +/- 0.21 in FC). Plasminogen activator inhibitor type 1, annexin II, and endothelin 1 show no significant change under any experimental conditions. The results also show that pulsatile flow, more than vessel compression, influences EC morphology and function.

CONCLUSION

Effects on ECs of intermittent flow and vessel collapse, either individually or simultaneously, were simulated with an in vitro system of new design. Initial results show that intermittent flow associated with EPC upregulates EC fibrinolytic potential and influences factors altering vasomotor tone. The system will facilitate future studies of EC function during EPC.

Enhancement of murine IgE antibody detection by IgG removal

RATIONALE

Although animal models for the study of allergic reactions are desirable, the use of mice has been hindered by the lack of sufficiently sensitive in vitro immunoglobulin epsilon (IgE) antibody assays. The aim of this study was to enhance IgE antibody measurements by immunoglobulin gamma (IgG) depletion.

METHODS

Seven- to eight-week-old female mice of four strains (C3H/HeJ, CBA/J, C57Bl/6J, and Balb/c) were immunized (20 mice/group) with shrimp or peanut extracts using Al(OH)(3) as adjuvant. Following immunization, animals were sacrificed by exsanguination and the sera of each group pooled. Initial measurements of IgE antibody levels by enzyme-linked immunosorbent assay (ELISA) were relatively low; IgG and IgE reactivity patterns by immunoblot were similar. Thus, sera from shrimp or peanut immunized mice were depleted of IgG (absorbed 3-6 times with immobilized protein G) and then tested for IgE antibody to shrimp or peanut allergen.

RESULTS

A 3- to 5-fold increase in IgE antibody reactivity as measured by ELISA was demonstrated when >80-90% of the IgG was removed. This increase in detection of allergen-specific IgE occurred in sera from all mouse strains and to all allergens tested. In addition, reactivity of IgE antibodies to peanut or shrimp allergens by immunoblot increased visually approximately 4- to 10-fold.

CONCLUSIONS

These studies indicate that allergen-specific IgG antibodies, which may be in more than 100-fold excess to IgE antibodies, interferes with detection of allergen-specific IgE, probably by competitive binding to allergenic epitopes. Substantial depletion of IgG antibodies (>80%) result in a significant increase in the sensitivity of the antibody measurements.

cDNA cloning and expression of a novel family of enzymes with calcium-independent phospholipase A2 and lysophospholipase activities

Previous studies have suggested that activation of calcium-independent PLA2 (CaIPLA2) is an early event in cell death after hypoxic injury in proximal tubule cells. An approximately 28-kD CaIPLA2 with preferential activity toward plasmalogen phospholipids has been recently purified from rabbit kidney cortex (D. Portilla and G. Dai, J Biol Chem 271, 15,451-15,457, 1996). Their report describes the cloning of a full-length rat cDNA encoding CaIPLA2, using sequences derived from the purified rabbit kidney cortex enzyme. In addition, cDNA from rabbit kidney that encode the rabbit homologue of the enzyme and a closely related isoform were isolated. The rat cDNA is predicted to encode an approximately 24-kD protein, and each cDNA contains the sequence G-F-S-Q-G, which fits the active site consensus sequence G-X-S-X-G of carboxylesterases. Several lines of evidence (DNA sequence comparison, Southern blot analysis, and examination of the expressed sequence tag database) show that CaIPLA2 enzymes are encoded by a multigene family in rats, mice, rabbits, and humans. Northern analysis of various tissues from the rat indicated that the CaIPLA2 gene is ubiquitously expressed, with highest mRNA abundance observed in the kidney and small intestine. The rat CaIPLA2 cDNA, when expressed in a baculovirus expression system, and the purified rabbit kidney cortex protein exhibit both CaIPLA2 and lysophospholipase activities. The cloned CaIPLA2 cDNA are expected to aid in understanding the role of CaIPLA2 in cell death after hypoxic/ischemic cell injury.

Molecular characterization of a new abortive infection system (AbiU) from Lactococcus lactis LL51-1

This study reports on the identification and characterization of a novel abortive infection system, AbiU, from Lactococcus lactis. AbiU confers resistance to phages from the three main industrially relevant lactococcal phage species: c2, 936, and P335. The presence of AbiU reduced the efficiency of plaquing against specific phage from each species as follows: 3.7 x 10(-1), 1.0 x 10(-2), and 1.0 x 10(-1), respectively. abiU involves two open reading frames, abiU1 (1,772 bp) and abiU2 (1,019 bp). Evidence indicates that AbiU1 is responsible for phage resistance and that AbiU2 may downregulate phage resistance against 936 and P335 type phages but not c2 type phage. AbiU appeared to delay transcription of both phage 712 and c2, with the effect being more marked on phage c2.

Effects of modulating TGF-beta 1 on immune responses to mycobacterial infection in guinea pigs

SETTING

TGF-beta 1 has been implicated as an important mediator of immuno-suppression in clinical tuberculosis.

OBJECTIVE

The objective was to determine the role of TGF-beta 1 in experimental pulmonary tuberculosis in the guinea pig.

DESIGN

Groups of guinea pigs, maintained on either a low protein (LP) diet or an isocaloric high protein (HP) diet, were challenged via the respiratory route with virulent Mycobacterium tuberculosis H37Rv. Ten days post-infection, guinea pigs were given daily intraperitoneal injections of recombinant human TGF-beta 1 (rhTGF-beta 1 tau for 10 consecutive days). Following the treatment, guinea pigs were euthanized, and PPD-induced proliferation of peripheral blood mononuclear cells (PBMCs) was assessed and disease resistance measured by recovery of mycobacteria from the lungs and spleens. In a second set of experiments, groups of HP and LP guinea pigs were vaccinated with attenuated M. tuberculosis H37Ra. Six weeks later, the effects of rhTGF-beta 1 on lymphoproliferation and cytokine production were determined.

RESULTS

Protein deficiency significantly impaired host anti-tuberculosis resistance, as expected. Treatment with rhTGF-beta 1 significantly increased mycobacterial loads in the tissues of guinea pigs and decreased the PPD-induced proliferation of PBMCs from both LP and HP guinea pigs. PPD-driven lymphoproliferation, TNF-alpha and IFN production were significantly suppressed in vaccinated, protein-deficient guinea pigs, and rhTGF-beta 1 further inhibited lymphoproliferation and cytokine production.

CONCLUSION

Both in vivo and in vitro results indicate that TGF-beta 1 exerts immunosuppressive activity and exacerbates the progression of experimental pulmonary tuberculosis in both normally nourished and protein-deficient guinea pigs.