Altered immune responses in mice lacking inducible nitric oxide synthase

Nitric oxide (NO) is important in many biological functions. It is generated from L-arginine by the enzyme NO synthase (NOS). The cytokine-inducible NOS (iNOS) is activated by several immunological stimuli, leading to the production of large quantities of NO which can be cytotoxic. To define the biological role of iNOS further, we generated iNOS mutant mice. These are viable, fertile and without evident histopathological abnormalities. However, in contrast to wild-type and heterozygous mice, which are highly resistant to the protozoa parasite Leishmania major infection, mutant mice are uniformly susceptible. The infected mutant mice developed a significantly stronger Th1 type of immune response than the wild-type or heterozygous mice. The mutant mice showed reduced nonspecific inflammatory response to carrageenin, and were resistant to lipopolysaccharide-induced mortality.

Sperm morphology, motility, and concentration in fertile and infertile men

BACKGROUND

Although semen analysis is routinely used to evaluate the male partner in infertile couples, sperm measurements that discriminate between fertile and infertile men are not well defined.

METHODS

We evaluated two semen specimens from each of the male partners in 765 infertile couples and 696 fertile couples at nine sites. The female partners in the infertile couples had normal results on fertility evaluation. The sperm concentration and motility were determined at the sites; semen smears were stained at the sites and shipped to a central laboratory for an assessment of morphologic features of sperm with the use of strict criteria. We used classification-and-regression-tree analysis to estimate threshold values for subfertility and fertility with respect to the sperm concentration, motility, and morphology. We also used an analysis of receiver-operating-characteristic curves to assess the relative value of these sperm measurements in discriminating between fertile and infertile men.

RESULTS

The subfertile ranges were a sperm concentration of less than 13.5 x 10(6) per milliliter, less than 32 percent of sperm with motility, and less than 9 percent with normal morphologic features. The fertile ranges were a concentration of more than 48.0 x 10(6) per milliliter, greater than 63 percent motility, and greater than 12 percent normal morphologic features. Values between these ranges indicated indeterminate fertility. There was extensive overlap between the fertile and the infertile men within both the subfertile and the fertile ranges for all three measurements. Although each of the sperm measurements helped to distinguish between fertile and infertile men, none was a powerful discriminator. The percentage of sperm with normal morphologic features had the greatest discriminatory power.

CONCLUSIONS

Threshold values for sperm concentration, motility, and morphology can be used to classify men as subfertile, of indeterminate fertility, or fertile. None of the measures, however, are diagnostic of infertility.

ECE-1: a membrane-bound metalloprotease that catalyzes the proteolytic activation of big endothelin-1

Endothelin-1 (ET-1), a 21-residue vasoactive peptide, is produced in vascular endothelial cells from the 38-residue inactive intermediate big endothelin-1 via a specific cleavage at Trp-21-Val-22. The protease that catalyzes the conversion, endothelin-converting enzyme (ECE), constitutes a potential regulatory site for the production of the active peptide. We report the identification of ECE-1, a novel membrane-bound neutral metalloprotease that is expressed abundantly in endothelial cells in vivo and is structurally related to neutral endopeptidase 24.11 and Kell blood group protein. When transfected into cultured cells that normally secrete only big ET-1, the ECE-1 cDNA conferred the ability to secrete mature ET-1. In transfected cells, ECE-1 processes endogenously synthesized big ET-1 as well as exogenously supplied big ET-1, which interacts with ECE-1 on the cell surface. ECE-1 may provide a target for pharmacological intervention to alter ET-1 production.

Involvement of caspases in proteolytic cleavage of Alzheimer's amyloid-beta precursor protein and amyloidogenic A beta peptide formation

The amyloid-beta precursor protein (APP) is directly and efficiently cleaved by caspases during apoptosis, resulting in elevated amyloid-beta (A beta) peptide formation. The predominant site of caspase-mediated proteolysis is within the cytoplasmic tail of APP, and cleavage at this site occurs in hippocampal neurons in vivo following acute excitotoxic or ischemic brain injury. Caspase-3 is the predominant caspase involved in APP cleavage, consistent with its marked elevation in dying neurons of Alzheimer's disease brains and colocalization of its APP cleavage product with A beta in senile plaques. Caspases thus appear to play a dual role in proteolytic processing of APP and the resulting propensity for A beta peptide formation, as well as in the ultimate apoptotic death of neurons in Alzheimer's disease.

A proinflammatory role for IL-18 in rheumatoid arthritis

IL-18 is a novel cytokine with pleiotropic activities critical to the development of T-helper 1 (Th1) responses. We detected IL-18 mRNA and protein within rheumatoid arthritis (RA) synovial tissues in significantly higher levels than in osteoarthritis controls. Similarly, IL-18 receptor expression was detected on synovial lymphocytes and macrophages. Together with IL-12 or IL-15, IL-18 induced significant IFN-gamma production by synovial tissues in vitro. IL-18 independently promoted GM-CSF and nitric oxide production, and it induced significant TNF-alpha synthesis by CD14(+) macrophages in synovial cultures; the latter effect was potentiated by IL-12 or IL-15. TNF-alpha and IFN-gamma synthesis was suppressed by IL-10 and TGF-beta. IL-18 production in primary synovial cultures and purified synovial fibroblasts was, in turn, upregulated by TNF-alpha and IL-1beta, suggesting that monokine expression can feed back to promote Th1 cell development in synovial membrane. Finally, IL-18 administration to collagen/incomplete Freund's adjuvant-immunized DBA/1 mice facilitated the development of an erosive, inflammatory arthritis, suggesting that IL-18 can be proinflammatory in vivo. Together, these data indicate that synergistic combinations of IL-18, IL-12, and IL-15 may be of importance in sustaining both Th1 responses and monokine production in RA.

Quantitative evaluation of carotid plaque composition by in vivo MRI

OBJECTIVE

This study evaluates the ability of MRI to quantify all major carotid atherosclerotic plaque components in vivo.

METHODS AND RESULTS

Thirty-one subjects scheduled for carotid endarterectomy were imaged with a 1.5T scanner using time-of-flight-, T1-, proton density-, and T2-weighted images. A total of 214 MR imaging locations were matched to corresponding histology sections. For MRI and histology, area measurements of the major plaque components such as lipid-rich/necrotic core (LR/NC), calcification, loose matrix, and dense (fibrous) tissue were recorded as percentages of the total wall area. Intraclass correlation coefficients (ICCs) were computed to determine intrareader and inter-reader reproducibility. MRI measurements of plaque composition were statistically equivalent to those of histology for the LR/NC (23.7 versus 20.3%; P=0.1), loose matrix (5.1 versus 6.3%; P=0.1), and dense (fibrous) tissue (66.3% versus 64%; P=0.4). Calcification differed significantly when measured as a percentage of wall area (9.4 versus 5%; P<0.001). Intrareader and inter-reader reproducibility was good to excellent for all tissue components, with ICCs ranging from 0.73 to 0.95.

CONCLUSIONS

MRI-based tissue quantification is accurate and reproducible. This application can be used in therapeutic clinical trials and in prospective longitudinal studies to examine carotid atherosclerotic plaque progression and regression.

Metal nanoparticle-based electrochemical stripping potentiometric detection of DNA hybridization

A new nanoparticle-based electrical detection of DNA hybridization, based on electrochemical stripping detection of the colloidal gold tag, is described. In this protocol, the hybridization of a target oligonucleotide to magnetic bead-linked oligonucleotide probes is followed by binding of the streptavidin-coated metal nanoparticles to the captured DNA, dissolution of the nanometer-sized gold tag, and potentiometric stripping measurements of the dissolved metal tag at single-use thick-film carbon electrodes. An advanced magnetic processing technique is used to isolate the DNA duplex and to provide low-volume mixing. The influence of relevant experimental variables, including the amounts of the gold nanoparticles and the magnetic beads, the duration of the hybridization and gold dissolution steps, and the parameters of the potentiometric stripping operation upon the hybridization signal, is examined and optimized. Transmission electron microscopy micrographs indicate that the hybridization event leads to the bridging of the gold nanoparticles to the magnetic beads. Further signal amplification, and lowering of the detection limits to the nanomolar and picomolar domains, are achieved by precipitating gold or silver, respectively, onto the colloidal gold label. The new electrochemical stripping metallogenomagnetic protocol couples the inherent signal amplification of stripping metal analysis with discrimination against nonhybridized DNA, the use of microliter sample volumes, and disposable transducers and, hence, offers great promise for decentralized genetic testing.

Selective expression of a stable cell surface molecule on type 2 but not type 1 helper T cells

T helper cell type 1 (Th1) and 2 (Th2) are central to immune regulation. However, no stable cell surface marker capable of distinguishing and separating these two subsets of CD4(+) cells has yet been found. Using differential display PCR, we have identified a gene encoding a cell membrane bound molecule, originally designated ST2L, T1, DER4, or Fit, expressed constitutively and stably on the surface of murine Th2s, but not Th1s even after stimulation with a range of immunological stimuli. Antibody against a peptide derived from ST2L strongly and stably labeled the surface of cloned Th2s but not Th1s, and Th2s but not Th1s derived from naive T cells of ovalbumin T cell receptor-alpha/beta transgenic mice. Three-color single cell flow cytometric analysis shows that cell surface ST2L coexpressed with intracellular interleukin (IL)-4, but not with interferon (IFN)-gamma. The antibody selectively lysed Th2s in vitro in a complement-dependent manner. In vivo, it enhanced Th1 responses by increasing IFN-gamma production and decreasing IL-4 and IL-5 synthesis. It induced resistance to Leishmania major infection in BALB/c mice and exacerbated collagen-induced arthritis in DBA/1 mice. Thus, ST2L is a stable marker distinguishing Th2s from Th1s and is also associated with Th2 functions. Hence, it may be a target for therapeutic intervention.

Synaptic clustering of AMPA receptors by the extracellular immediate-early gene product Narp

Narp (neuronal activity-regulated pentraxin) is a secreted immediate-early gene (IEG) regulated by synaptic activity in brain. In this study, we demonstrate that Narp possesses several properties that make it likely to play a key role in excitatory synaptogenesis. Narp is shown to be selectively enriched at excitatory synapses on neurons from both the hippocampus and spinal cord. Overexpression of recombinant Narp increases the number of excitatory but not inhibitory synapses in cultured spinal neurons. In transfected HEK 293T cells, Narp interacts with itself, forming large surface clusters that coaggregate AMPA receptor subunits. Moreover, Narp-expressing HEK 293T cells can induce the aggregation of neuronal AMPA receptors. These studies support a model in which Narp functions as an extracellular aggregating factor for AMPA receptors.

Stable transduction of quiescent CD34(+)CD38(-) human hematopoietic cells by HIV-1-based lentiviral vectors

We compared the efficiency of transduction by an HIV-1-based lentiviral vector to that by a Moloney murine leukemia virus (MLV) retroviral vector, using stringent in vitro assays of primitive, quiescent human hematopoietic progenitor cells. Each construct contained the enhanced green fluorescent protein (GFP) as a reporter gene. The lentiviral vector, but not the MLV vector, expressed GFP in nondivided CD34(+) cells (45.5% GFP+) and in CD34(+)CD38(-) cells in G0 (12.4% GFP+), 48 hr after transduction. However, GFP could also be detected short-term in CD34(+) cells transduced with a lentiviral vector that contained a mutated integrase gene. The level of stable transduction from integrated vector was determined after extended long-term bone marrow culture. Both MLV vectors and lentiviral vectors efficiently transduced cytokine-stimulated CD34(+) cells. The MLV vector did not transduce more primitive, quiescent CD34(+)CD38(-) cells (n = 8). In contrast, stable transduction of CD34(+)CD38(-) cells by the lentiviral vector was seen for over 15 weeks of extended long-term culture (9.2 +/- 5.2%, n = 7). GFP expression in clones from single CD34(+)CD38(-) cells confirmed efficient, stable lentiviral transduction in 29% of early and late-proliferating cells. In the absence of growth factors during transduction, only the lentiviral vector was able to transduce CD34(+) and CD34(+)CD38(-) cells (13.5 +/- 2.5%, n = 11 and 12.2 +/- 9.7%, n = 4, respectively). The lentiviral vector is clearly superior to the MLV vector for transduction of quiescent, primitive human hematopoietic progenitor cells and may provide therapeutically useful levels of gene transfer into human hematopoietic stem cells.

The presenilin 1 protein is a component of a high molecular weight intracellular complex that contains beta-catenin

The presenilin (PS) genes associated with Alzheimer disease encode polytopic transmembrane proteins which undergo physiologic endoproteolytic cleavage to generate stable NH2- and COOH-terminal fragments (NTF or CTF) which co-localize in intracellular membranes, but are tightly regulated in their stoichiometry and abundance. We have used linear glycerol velocity and discontinuous sucrose gradient analysis to investigate the distribution and native conformation of PS1 and PS2 during this regulated processing in cultured cells and in brain. The PS1 NTF and CTF co-localize in the endoplasmic reticulum (ER) and in the Golgi apparatus, where they are components of a approximately 250-kDa complex. This complex also contains beta-catenin but not beta-amyloid precursor protein (APP). In contrast, the PS1 holoprotein precursor is predominantly localized to the rough ER and smooth ER, where it is a component of a approximately 180-kDa native complex. PS2 forms similar but independent complexes. Restricted incorporation of the presenilin NTF and CTF along with a potentially functional ligand (beta-catenin) into a multimeric complex in the ER and Golgi apparatus may provide an explanation for the regulated accumulation of the NTF and CTF.

Hydrogen bonds and salt bridges across protein-protein interfaces

To understand further, and to utilize, the interactions across protein-protein interfaces, we carried out an analysis of the hydrogen bonds and of the salt bridges in a collection of 319 non-redundant protein-protein interfaces derived from high-quality X-ray structures. We found that the geometry of the hydrogen bonds across protein interfaces is generally less optimal and has a wider distribution than typically observed within the chains. This difference originates from the more hydrophilic side chains buried in the binding interface than in the folded monomer interior. Protein folding differs from protein binding. Whereas in folding practically all degrees of freedom are available to the chain to attain its optimal configuration, this is not the case for rigid binding, where the protein molecules are already folded, with only six degrees of translational and rotational freedom available to the chains to achieve their most favorable bound configuration. These constraints enforce many polar/charged residues buried in the interface to form weak hydrogen bonds with protein atoms, rather than strongly hydrogen bonding to the solvent. Since interfacial hydrogen bonds are weaker than the intra-chain ones to compete with the binding of water, more water molecules are involved in bridging hydrogen bond networks across the protein interface than in the protein interior. Interfacial water molecules both mediate non-complementary donor-donor or acceptor-acceptor pairs, and connect non-optimally oriented donor-acceptor pairs. These differences between the interfacial hydrogen bonding patterns and the intra-chain ones further substantiate the notion that protein complexes formed by rigid binding may be far away from the global minimum conformations. Moreover, we summarize the pattern of charge complementarity and of the conservation of hydrogen bond network across binding interfaces. We further illustrate the utility of this study in understanding the specificity of protein-protein associations, and hence in docking prediction and molecular (inhibitor) design.

Voxel-based morphometry using the RAVENS maps: methods and validation using simulated longitudinal atrophy

Statistical analysis of anatomical maps in a stereotaxic space has been shown to be a useful tool in population-based studies for quantifying local anatomical differences or changes, without a priori assumptions about the location and extent of the regions of interest. This paper presents an extension and validation of a previously published methodology, referred to as RAVENS, for characterizing regional atrophy in the brain. A new method for elastic, volume-preserving spatial normalization, which allows for accurate quantification of very localized atrophy, is used. The RAVENS methodology was tested on images with simulated atrophy within two gyri: precentral and superior temporal. It was found to accurately determine the regions of atrophy, despite their localized nature and the interindividual variability of cortical structures. Moreover, it was found to perform substantially better than the voxel-based morphology method of SPM'99. Improved sensitivity was achieved at the expense of human effort involved in defining a number of sulcal curves that serve as constraints on the 3D elastic warping.

Regulation of the immune response by nitric oxide differentially produced by T helper type 1 and T helper type 2 cells

The balance between T helper type 1 (Th 1) and T helper type 2 (Th2) cells determines the outcome of many important diseases. Using cloned murine T cell lines, evidence is provided that Th1, but not Th2, cells can be activated by specific antigens or a T cell mitogen, concanavalin A, to produce large amounts of nitric oxide (NO). Furthermore, NO can inhibit the secretion of interleukin (IL)-2 and interferon-gamma by Th1 cells but has no effect on IL-4 production by Th2 cells. Th1 and Th2 cells can, thus, be distinguished by their differential production of and susceptibility to NO. NO exerts a self-regulatory effect on Th1 cells which are implicated in immunopathology.

A giant outburst two years before the core-collapse of a massive star

The death of massive stars produces a variety of supernovae, which are linked to the structure of the exploding stars. The detection of several precursor stars of type II supernovae has been reported (see, for example, ref. 3), but we do not yet have direct information on the progenitors of the hydrogen-deficient type Ib and Ic supernovae. Here we report that the peculiar type Ib supernova SN 2006jc is spatially coincident with a bright optical transient that occurred in 2004. Spectroscopic and photometric monitoring of the supernova leads us to suggest that the progenitor was a carbon-oxygen Wolf-Rayet star embedded within a helium-rich circumstellar medium. There are different possible explanations for this pre-explosion transient. It appears similar to the giant outbursts of luminous blue variable stars (LBVs) of 60-100 solar masses, but the progenitor of SN 2006jc was helium- and hydrogen-deficient (unlike LBVs). An LBV-like outburst of a Wolf-Rayet star could be invoked, but this would be the first observational evidence of such a phenomenon. Alternatively, a massive binary system composed of an LBV that erupted in 2004, and a Wolf-Rayet star exploding as SN 2006jc, could explain the observations.

Selective expression and functions of interleukin 18 receptor on T helper (Th) type 1 but not Th2 cells

Interleukin (IL)-18 induces interferon (IFN)-gamma synthesis and synergizes with IL-12 in T helper type 1 (Th1) but not Th2 cell development. We report here that IL-18 receptor (IL-18R) is selectively expressed on murine Th1 but not Th2 cells. IL-18R mRNA was expressed constitutively and consistently in long-term cultured clones, as well as on newly polarized Th1 but not Th2 cells. IL-18 sustained the expression of IL-12Rbeta2 mRNA, indicating that IL-18R transmits signals that maintain Th1 development through the IL-12R complex. In turn, IL-12 upregulated IL-18R mRNA. Antibody against an IL-18R-derived peptide bound Th1 but not Th2 clones. It also labeled polarized Th1 but not Th2 cells derived from naive ovalbumin-T cell antigen receptor-alphabeta transgenic mice (D011.10). Anti-IL-18R antibody inhibited IL-18- induced IFN-gamma production by Th1 clones in vitro. In vivo, anti-IL-18R antibody reduced local inflammation and lipopolysaccharide-induced mortality in mice. This was accompanied by shifting the balance from Th1 to Th2 responses, manifest as decreased IFN-gamma and proinflammatory cytokine production and increased IL-4 and IL-5 synthesis. Therefore, these data provide a direct mechanism for the selective effect of IL-18 on Th1 but not Th2 cells. They also show that the synergistic effect of IL-12 and IL-18 on Th1 development may be due to the reciprocal upregulation of their receptors. Furthermore, IL-18R is a cell surface marker distinguishing Th1 from Th2 cells and may be a therapeutic target.

Switch from Myc/Max to Mad1/Max binding and decrease in histone acetylation at the telomerase reverse transcriptase promoter during differentiation of HL60 cells

Recent evidence suggests that the Myc and Mad1 proteins are implicated in the regulation of the gene encoding the human telomerase reverse transcriptase (hTERT), the catalytic subunit of telomerase. We have analyzed the in vivo interaction between endogenous c-Myc and Mad1 proteins and the hTERT promoter in HL60 cells with the use of the chromatin immunoprecipitation assay. The E-boxes at the hTERT proximal promoter were occupied in vivo by c-Myc in exponentially proliferating HL60 cells but not in cells induced to differentiate by DMSO. In contrast, Mad1 protein was induced and bound to the hTERT promoter in differentiated HL60 cells. Concomitantly, the acetylation of the histones at the promoter was significantly reduced. These data suggest that the reciprocal E-box occupancy by c-Myc and Mad1 is responsible for activation and repression of the hTERT gene in proliferating and differentiated HL60 cells, respectively. Furthermore, the histone deacetylase inhibitor trichostatin A inhibited deacetylation of histones at the hTERT promoter and attenuated the repression of hTERT transcription during HL60 cell differentiation. In addition, trichostatin A treatment activated hTERT transcription in resting human lymphocytes and fibroblasts. Taken together, these results indicate that acetylation/deacetylation of histones is operative in the regulation of hTERT expression.

Evidence favoring the role of the gut as a cytokine-generating organ in rats subjected to hemorrhagic shock

There is increasing evidence of an association between intestinal injury and the development of a septic state and distant organ failure. Since this phenomenon can occur in the absence of detectable systemic bacterial translocation (BT), we tested the hypothesis that shock-induced intestinal injury will result in the gut becoming a cytokine-generating organ by measuring interleukin 6 (IL-6) and tumor necrosis factor (TNF) levels in the portal blood, cardiac blood, and intestinal lymph of rats subjected to sham, 30, 60, or 90 min of hemorrhagic shock (30 mm Hg). These blood and lymph samples, as well as the mesenteric lymph nodes (MLN), spleens, and livers, were cultured for translocating bacteria. Although all the portal and cardiac blood samples were sterile, the portal blood levels of TNF and IL-6 were increased to a greater extent than simultaneously obtained cardiac blood samples in rats subjected to 60 or 90 min of shock (p < .05). The lymph IL-6 levels increased but were similar between the groups. BT was limited to the MLN and occurred in a dose-dependent fashion with 38, 63, and 100% of the animals having culture-positive MLNs after 30, 60, or 90 min of shock, respectively. In conclusion, after hemorrhagic shock, the gut appears to become a cytokine liberating organ even in the absence of detectable bacteria in the portal circulation.

Cleavage of plasma membrane calcium pumps by caspases: a link between apoptosis and necrosis

Neuronal death, which follows ischemic injury or is triggered by excitotoxins, can occur by both apoptosis and necrosis. Caspases, which are not directly required for necrotic cell death, are central mediators of the apoptotic program. Here we demonstrate that caspases cleave and inactivate the plasma membrane Ca(2+) pump (PMCA) in neurons and non-neuronal cells undergoing apoptosis. PMCA cleavage impairs intracellular Ca(2+) handling, which results in Ca(2+) overload. Expression of non-cleavable PMCA mutants prevents the disturbance in Ca(2+) handling, slows down the kinetics of apoptosis, and markedly delays secondary cell lysis (necrosis). These findings suggest that caspase-mediated cleavage and inactivation of PMCAs can lead to necrosis, an event that is reduced by caspase inhibitors in brain ischemia.

A Novel Pathway Regulating Lipopolysaccharide-Induced Shock by ST2/T1 Via Inhibition of Toll-Like Receptor 4 Expression

ST2/ST2L, a member of the IL-1R gene family, is expressed by fibroblasts, mast cells, and Th2, but not Th1, cells. It exists in both membrane-bound (ST2L) and soluble forms (ST2). Although ST2L has immunoregulatory properties, its ligand, cellular targets, and mode of action remain unclear. Using a soluble ST2-human IgG fusion protein, we demonstrated that ST2 bound to primary bone marrow-derived macrophages (BMM) and that this binding was enhanced by treatment with LPS. The sST2 treatment of BMMs inhibited production of the LPS-induced proinflammatory cytokines IL-6, IL-12, and TNF-alpha but did not alter IL-10 or NO production. Treatment of BMMs with sST2 down-regulated expression of Toll-like receptors-4 and -1 but induced nuclear translocation of NF-kappaB. Administration of sST2 in vivo after LPS challenge significantly reduced LPS-mediated mortality and serum levels of IL-6, IL-12, and TNF-alpha. Conversely, blockade of endogenous ST2 through administration of anti-ST2 Ab exacerbated the toxic effects of LPS. Thus, ST2 has anti-inflammatory properties that act directly on macrophages. We demonstrate here a novel regulatory pathway for LPS-induced shock via the ST2-Toll-like receptor 4 route. This may be of considerable therapeutic potential for reducing the severity and pathology of inflammatory diseases.

Automated vocal analysis of naturalistic recordings from children with autism, language delay, and typical development

For generations the study of vocal development and its role in language has been conducted laboriously, with human transcribers and analysts coding and taking measurements from small recorded samples. Our research illustrates a method to obtain measures of early speech development through automated analysis of massive quantities of day-long audio recordings collected naturalistically in children's homes. A primary goal is to provide insights into the development of infant control over infrastructural characteristics of speech through large-scale statistical analysis of strategically selected acoustic parameters. In pursuit of this goal we have discovered that the first automated approach we implemented is not only able to track children's development on acoustic parameters known to play key roles in speech, but also is able to differentiate vocalizations from typically developing children and children with autism or language delay. The method is totally automated, with no human intervention, allowing efficient sampling and analysis at unprecedented scales. The work shows the potential to fundamentally enhance research in vocal development and to add a fully objective measure to the battery used to detect speech-related disorders in early childhood. Thus, automated analysis should soon be able to contribute to screening and diagnosis procedures for early disorders, and more generally, the findings suggest fundamental methods for the study of language in natural environments.

Downregulation of telomerase reverse transcriptase mRNA expression by wild type p53 in human tumor cells

The p53 tumor suppressor protein inhibits the formation of tumors through induction of cell cycle arrest and/or apoptosis. In the present study we demonstrated that p53 is also a powerful inhibitor of human telomerase reverse transcriptase (hTERT), a key component for telomerase. Activation of either exogenous temperature-sensitive (ts) p53 in BL41 Burkitt lymphoma cells or endogenous wild type (wt) p53 at a physiological level in MCF-7 breast carcinoma cells triggered a rapid downregulation of hTERT mRNA expression, independently of the induction of the p53 target gene p21. Co-transfection of an hTERT promoter construct with wt p53 but not mutant p53 in HeLa cells inhibited the hTERT promoter activity. Furthermore, the activation of the hTERT promoter in Drosophila Schneider SL2 cells was completely dependent on the ectopic expression of Sp1 and was abrogated by wt p53. Finally, wt p53 inhibited Sp1 binding to the hTERT proximal promoter by forming a p53-Sp1 complex. Since activation of telomerase, widely observed in human tumor cell lines and primary tumors, is a critical step in tumorigenesis, wt p53-triggered inhibition of hTERT/telomerase expression may reflect yet another mechanism of p53-mediated tumor suppression. Our findings provide new insights into both the biological function of p53 and the regulation of hTERT/telomerase expression.

Protein binding versus protein folding: the role of hydrophilic bridges in protein associations

The role of hydrophilic bridges between charged, or polar, atoms in protein associations has been examined from two perspectives. First, statistical analysis has been carried out on 21 data sets to determine the relationship between the binding free energy and the structure of the protein complexes. We find that the number of hydrophilic bridges across the binding interface shows a strong positive correlation with the free energy; second, the electrostatic contribution of salt bridges to binding has been assessed by a continuum electrostatics calculation. In contrast to protein folding, we find that salt bridges across the binding interface can significantly stabilize complexes in some cases. The different contributions of hydrophilic bridges to folding and to binding arise from the different environments to which the involved hydrophilic groups are exposed before and after the bridges are formed. These groups are more solvated in a denatured protein before folding than on the surface of the combining proteins before binding. After binding, they are buried in an environment whose residual composition can be much more hydrophilic than the one after folding. As a result, the desolvation cost of a hydrophilic pair is lower, and the favorable interactions between the hydrophilic pair and its surrounding residues are generally stronger in binding than in folding. These results complement our recent finding that while hydrophobic effect in protein-protein interfaces is significant, it is not as strong as that observed in the interior of monomers. Taken together, these studies suggest that while the types of forces in protein-protein interaction and in protein folding are similar, their relative contributions differ. Hence, association of protein monomers which do not undergo significant conformational change upon binding differs from protein folding, implying that conclusions (e.g. statistics, energetics) drawn from investigating folding may not apply directly to binding, and vice versa.

In vitro characterization of five humanized OKT3 effector function variant antibodies

Orthoclone OKT 3 (mOKT3) is a highly effective agent for the reversal of steroid-resistant renal allograft rejection. However, its wider use has been limited by the development of a human anti-mouse antibody response (HAMA) and by the "cytokine release syndrome" (CRS). CRS has been associated with T cell/monocyte activation and, secondarily, with activation of the complement cascade. These processes are mediated through Abs' Fc regions by their abilities to cross-link T cells and mononuclear cells and to activate complements. To alleviate these problems, a group of five huIgG1- and huIgG4-based OKT3 wild-type antibodies and their corresponding Fc mutants with altered residues at amino acids 234, 235, and 318, reported to be required for FcgammaRI and FcgammaRII binding and complement fixation, were constructed. Characterization of these humanized OKT3 Abs, denoted huOKT3gamma1, huOKT3gamma4, huOKT3gamma1(A(234), A(235)), huOKT3gamma4(A(234), A(235)), and huOKT3gamma1(A(318)), has demonstrated that huOKT3gamma1(A(234), A(235)) and huOKT3gamma4(A(234), A(235)), and have at least a 100-fold reduced binding to FcgammaRI and FcgammaRII. As expected, they are much less potent in the induction of T cell activation and cytokine release, yet retain in vitro immunosuppressive effects as potent as those of mOKT3. Unexpectedly, while huOKT3gamma1(A(318)) did not show any reduction in its ability to bind C1q and to fix a complement, huOKT3gamma1(A(234), A(235)) was completely inactive. The in vitro characteristics of huOKT3gamma1(A(234), A(235)) are consistent with recent in vivo studies, in which this Ab showed greatly reduced HAMA and CRS with the retention of its ability to reverse ongoing graft rejection in man.