Associative linking for collaborative thinking: Self-organization of content in online Q&A communities via user-generated links

Virtual collaborative Q&A communities generate shared knowledge through the interaction of people and content. This knowledge is often fragmented, and its value as a collective, collaboratively formed product, is largely overlooked. Inspired by work on individual mental semantic networks, the current study explores the networks formed by user-added associative links as reflecting an aspect of self-organization within the communities' collaborative knowledge sharing. Using eight Q&A topic-centered discussions from the Stack Exchange platform, it investigated how associative links form internal structures within the networks. Network analysis tools were used to derive topological indicator metrics of complex structures from associatively-linked networks. Similar metrics extracted from 1000 simulated randomly linked networks of comparable sizes and growth patterns were used to generate estimated sampling distributions through bootstrap resampling, and 99% confidence intervals were constructed for each metric. The discussion-network indicators were compared against these. Results showed that participant-added associative links largely led to networks that were more clustered, integrated, and included posts with more connections than those that would be expected in random networks of similar size and growth pattern. The differences were observed to increase over time. Also, the largest connected subgraphs within the discussion networks were found to be modular. Limited qualitative observations have also pointed to the impacts of external content-related events on the network structures. The findings strengthen the notion that the networks emerging from associative link sharing resemble other information networks that are characterized by internal structures suggesting self-organization, laying the ground for further exploration of collaborative linking as a form of collective knowledge organization. It underscores the importance of recognizing and leveraging this latent mechanism in both theory and practice.

Mitochondrial augmentation of hematopoietic stem cells in children with single large-scale mitochondrial DNA deletion syndromes

Patients with single large-scale mitochondrial DNA (mtDNA) deletion syndromes (SLSMDs) usually present with multisystemic disease, either as Pearson syndrome in early childhood or as Kearns-Sayre syndrome later in life. No disease-modifying therapies exist for SLSMDs. We have developed a method to enrich hematopoietic cells with exogenous mitochondria, and we treated six patients with SLSMDs through a compassionate use program. Autologous CD34⁺ hematopoietic cells were augmented with maternally derived healthy mitochondria, a technology termed mitochondrial augmentation therapy (MAT). All patients had substantial multisystemic disease involvement at baseline, including neurologic, endocrine, or renal impairment. We first assessed safety, finding that the procedure was well tolerated and that all study-related severe adverse events were either leukapheresis-related or related to the baseline disorder. After MAT, heteroplasmy decreased in the peripheral blood in four of the six patients. An increase in mtDNA content of peripheral blood cells was measured in all six patients 6 to 12 months after MAT as compared baseline. We noted some clinical improvement in aerobic function, measured in patients 2 and 3 by sit-to-stand or 6-min walk testing, and an increase in the body weight of five of the six patients suffering from very low body weight before treatment. Quality-of-life measurements as per caregiver assessment and physical examination showed improvement in some parameters. Together, this work lays the ground for clinical trials of MAT for the treatment of patients with mtDNA disorders.

Transcriptomic Analysis of Monocyte-Derived Non-Phagocytic Macrophages Favors a Role in Limiting Tissue Repair and Fibrosis

Monocyte-derived macrophages are readily differentiating cells that adapt their gene expression profile to environmental cues and functional needs. During the resolution of inflammation, monocytes initially differentiate to reparative phagocytic macrophages and later to pro-resolving non-phagocytic macrophages that produce high levels of IFNβ to boost resolutive events. Here, we performed in-depth analysis of phagocytic and non-phagocytic myeloid cells to reveal their distinct features. Unexpectedly, our analysis revealed that the non-phagocytic compartment of resolution phase myeloid cells is composed of Ly6C^medF4/80⁻ and Ly6C^hiF4/80^lo monocytic cells in addition to the previously described Ly6C⁻F4/80⁺ satiated macrophages. In addition, we found that both Ly6C⁺ monocytic cells differentiate to Ly6C⁻F4/80⁺macrophages, and their migration to the peritoneum is CCR2 dependent. Notably, satiated macrophages expressed high levels of IFNβ, whereas non-phagocytic monocytes of either phenotype did not. A transcriptomic comparison of phagocytic and non-phagocytic resolution phase F4/80⁺ macrophages showed that both subtypes express similar gene signatures that make them distinct from other myeloid cells. Moreover, we confirmed that these macrophages express closer transcriptomes to monocytes than to resident peritoneal macrophages (RPM) and resemble resolutive Ly6C^lo macrophages and monocyte-derived macrophages more than their precursors, inflammatory Ly6C^hi monocytes, recovered following liver injury and healing, and thioglycolate-induced peritonitis, respectively. A direct comparison of these subsets indicated that the non-phagocytic transcriptome is dominated by satiated macrophages and downregulate gene clusters associated with excessive tissue repair and fibrosis, ROS and NO synthesis, glycolysis, and blood vessel morphogenesis. On the other hand, non-phagocytic macrophages enhance the expression of genes associated with migration, oxidative phosphorylation, and mitochondrial fission as well as anti-viral responses when compared to phagocytic macrophages. Notably, conversion from phagocytic to satiated macrophages is associated with a reduction in the expression of extracellular matrix constituents that were demonstrated to be associated with idiopathic pulmonary fibrosis (IPF). Thus, macrophage satiation during the resolution of inflammation seems to bring about a transcriptomic transition that resists tissue fibrosis and oxidative damage while promoting the restoration of tissue homeostasis to complete the resolution of inflammation.

IFN-β is a macrophage-derived effector cytokine facilitating the resolution of bacterial inflammation

The uptake of apoptotic polymorphonuclear cells (PMN) by macrophages is critical for timely resolution of inflammation. High-burden uptake of apoptotic cells is associated with loss of phagocytosis in resolution phase macrophages. Here, using a transcriptomic analysis of macrophage subsets, we show that non-phagocytic resolution phase macrophages express a distinct IFN-β-related gene signature in mice. We also report elevated levels of IFN-β in peritoneal and broncho-alveolar exudates in mice during the resolution of peritonitis and pneumonia, respectively. Elimination of endogenous IFN-β impairs, whereas treatment with exogenous IFN-β enhances, bacterial clearance, PMN apoptosis, efferocytosis and macrophage reprogramming. STAT3 signalling in response to IFN-β promotes apoptosis of human PMNs. Finally, uptake of apoptotic cells promotes loss of phagocytic capacity in macrophages alongside decreased surface expression of efferocytic receptors in vivo. Collectively, these results identify IFN-β produced by resolution phase macrophages as an effector cytokine in resolving bacterial inflammation.

Placenta-Derived Adherent Stromal Cell Therapy for Hematopoietic Disorders: A Case Study of PLX-R18

The ephemeral placenta provides a noncontroversial source of young, healthy cells of both maternal and fetal origin from which cell therapy products can be manufactured. The 2 advantages of using live cells as therapeutic entities are: (a) in their environmental-responsive, multifactorial secretion profile and (b) in their activity as a “slow-release drug delivery system,” releasing secretions over a long time frame. A major difficulty in translating cell therapy to the clinic involves challenges of large-scale, robust manufacturing while maintaining product characteristics, identity, and efficacy. To address these concerns early on, Pluristem developed the PLacental eXpanded (PLX) platform, the first good manufacturing practice–approved, 3-dimensional bioreactor-based cell growth platform, to enable culture of mesenchymal-like adherent stromal cells harvested from the postpartum placenta. One of the products produced by Pluristem on this platform is PLX-R18, a product mainly comprising placental fetal cells, which is proven in vivo to alleviate radiation-induced lethality and to enhance hematopoietic cell counts after bone marrow (BM) failure. The identified mechanism of action of PLX-R18 cells is one of the cell-derived systemic pro-hematopoietic secretions, which upregulate endogenous secretions and subsequently rescue BM and peripheral blood cellularity, thereby boosting survival. PLX-R18 is therefore currently under study to treat both the hematopoietic syndrome of acute radiation (under the US Food and Drug Administration [FDA]’s Animal Rule) and the incomplete engraftment after BM transplantation (in a phase I study). In the future, they could potentially address additional hematological indications, such as aplastic anemia, myelodysplastic syndrome, primary graft failure, and acute or chronic graft versus host disease.

A-to-I RNA editing in the rat brain is age-dependent, region-specific and sensitive to environmental stress across generations

BACKGROUND

Adenosine-to-inosine (A-to-I) RNA editing is an epigenetic modification catalyzed by adenosine deaminases acting on RNA (ADARs), and is especially prevalent in the brain. We used the highly accurate microfluidics-based multiplex PCR sequencing (mmPCR-seq) technique to assess the effects of development and environmental stress on A-to-I editing at 146 pre-selected, conserved sites in the rat prefrontal cortex and amygdala. Furthermore, we asked whether changes in editing can be observed in offspring of stress-exposed rats. In parallel, we assessed changes in ADARs expression levels.

RESULTS

In agreement with previous studies, we found editing to be generally higher in adult compared to neonatal rat brain. At birth, editing was generally lower in prefrontal cortex than in amygdala. Stress affected editing at the serotonin receptor 2c (Htr2c), and editing at this site was significantly altered in offspring of rats exposed to prereproductive stress across two generations. Stress-induced changes in Htr2c editing measured with mmPCR-seq were comparable to changes measured with Sanger and Illumina sequencing. Developmental and stress-induced changes in Adar and Adarb1 mRNA expression were observed but did not correlate with editing changes.

CONCLUSIONS

Our findings indicate that mmPCR-seq can accurately detect A-to-I RNA editing in rat brain samples, and confirm previous accounts of a developmental increase in RNA editing rates. Our findings also point to stress in adolescence as an environmental factor that alters RNA editing patterns several generations forward, joining a growing body of literature describing the transgenerational effects of stress.

Placenta-derived PLX-PAD mesenchymal-like stromal cells are efficacious in rescuing blood flow in hind limb ischemia mouse model by a dose- and site-dependent mechanism of action

BACKGROUND

In peripheral artery disease (PAD), blockage of the blood supply to the limbs, most frequently the legs, leads to impaired blood flow and tissue ischemia. Pluristem's PLX-PAD cells are placenta-derived mesenchymal stromal-like cells currently in clinical trials for the treatment of peripheral artery diseases.

METHODS

In this work, the hind limb ischemia (HLI) mouse model was utilized to study the efficacy and mechanism of action of PLX-PAD cells. ELISA assays were performed to characterize and quantitate PLX-PAD secretions in vitro.

RESULTS

PLX-PAD cells administered intramuscularly rescued blood flow to the lower limb after HLI induction in a dose-dependent manner. While rescue of blood flow was site-dependent, numerous administration regimes enabled rescue of blood flow, indicating a systemic effect mediated by PLX-PAD secretions. Live PLX-PAD cells were more efficacious than cell lysate in rescuing blood flow, indicating the importance of prolonged cytokine secretion for maximal blood flow recovery. In vitro studies showed a multifactorial secretion profile including numerous pro-angiogenic proteins; these are likely involved in the PLX-PAD mechanism of action.

DISCUSSION

Live PLX-PAD cells were efficacious in rescuing blood flow after the induction of HLI in the mouse model in a dose- and site-dependent manner. The fact that various administration routes of PLX-PAD rescued blood flow indicates that the mechanism of action likely involves one of systemic secretions which promote angiogenesis. Taken together, the data support the further clinical testing of PLX-PAD cells for PAD indications.

Parallel embryonic transcriptional programs evolve under distinct constraints and may enable morphological conservation amidst adaptation

Embryonic development evolves by balancing stringent morphological constraints with genetic and environmental variation. The design principle that allows developmental transcriptional programs to conserve embryonic morphology while adapting to environmental changes is still not fully understood. To address this fundamental challenge, we compare developmental transcriptomes of two sea urchin species, Paracentrotus lividus and Strongylocentrotus purpuratus, that shared a common ancestor about 40 million years ago and are geographically distant yet show similar morphology. We find that both developmental and housekeeping genes show highly dynamic and strongly conserved temporal expression patterns. The expression of other gene sets, including homeostasis and response genes, show divergent expression which could result from either evolutionary drift or adaptation to local environmental conditions. The interspecies correlations of developmental gene expressions are highest between morphologically similar developmental time points whereas the interspecies correlations of housekeeping gene expression are high between all the late zygotic time points. Relatedly, the position of the phylotypic stage varies between these two groups of genes: developmental gene expression shows highest conservation at mid-developmental stage, in agreement with the hourglass model while the conservation of housekeeping genes keeps increasing with developmental time. When all genes are combined, the relationship between conservation of gene expression and morphological similarity is partially masked by housekeeping genes and genes with diverged expression. Our study illustrates various transcriptional programs that coexist in the developing embryo and evolve under different constraints. Apparently, morphological constraints underlie the conservation of developmental gene expression while embryonic fitness requires the conservation of housekeeping gene expression and the species-specific adjustments of homeostasis gene expression. The distinct evolutionary forces acting on these transcriptional programs enable the conservation of similar body plans while allowing adaption.

Do Bacterial Symbionts Govern Aphid's Dropping Behavior?

Defensive symbiosis is amongst nature's most important interactions shaping the ecology and evolution of all partners involved. The pea aphid, Acyrthosiphon pisum Harris (Hemiptera: Aphididae), harbors one obligatory bacterial symbiont and up to seven different facultative symbionts, some of which are known to protect the aphid from pathogens, natural enemies, and other mortality factors. Pea aphids typically drop off the plant when a mammalian herbivore approaches it to avoid incidental predation. Here, we examined whether bacterial symbionts govern the pea aphid dropping behavior by comparing the bacterial fauna in dropping and nondropping aphids of two A. pisum populations, using two molecular techniques: high-throughput profiling of community structure using 16 S reads sequenced on the Illumina platform, and diagnostic polymerase chain reaction (PCR). We found that in addition to the obligatory symbiont, Buchnera aphidicola, the tested colonies of A. pisum harbored the facultative symbionts Serratia symbiotica, Regiella insecticola and Rickettsia, with no significant differences in infection proportions between dropping and nondropping aphids. While S. symbiotica was detected by both techniques, R. insecticola and Rickettsia could be detected only by diagnostic PCR. We therefore conclude that A. pisum's dropping behavior is not affected by its bacterial symbionts and is possibly affected by other factors.

Transcriptome profiling of the dynamic life cycle of the scypohozoan jellyfish Aurelia aurita

Background

The moon jellyfish Aurelia aurita is a widespread scyphozoan species that forms large seasonal blooms. Here we provide the first comprehensive view of the entire complex life of the Aurelia Red Sea strain by employing transcriptomic profiling of each stage from planula to mature medusa.

Results

A de novo transcriptome was assembled from Illumina RNA-Seq data generated from six stages throughout the Aurelia life cycle. Transcript expression profiling yielded clusters of annotated transcripts with functions related to each specific life-cycle stage. Free-swimming planulae were found highly enriched for functions related to cilia and microtubules, and the drastic morphogenetic process undergone by the planula while establishing the future body of the polyp may be mediated by specifically expressed Wnt ligands. Specific transcripts related to sensory functions were found in the strobila and the ephyra, whereas extracellular matrix functions were enriched in the medusa due to high expression of transcripts such as collagen, fibrillin and laminin, presumably involved in mesoglea development. The CL390-like gene, suggested to act as a strobilation hormone, was also highly expressed in the advanced strobila of the Red Sea species, and in the medusa stage we identified betaine-homocysteine methyltransferase, an enzyme that may play an important part in maintaining equilibrium of the medusa’s bell. Finally, we identified the transcription factors participating in the Aurelia life-cycle and found that 70% of these 487 identified transcription factors were expressed in a developmental-stage-specific manner.

Conclusions

This study provides the first scyphozoan transcriptome covering the entire developmental trajectory of the life cycle of Aurelia. It highlights the importance of numerous stage-specific transcription factors in driving morphological and functional changes throughout this complex metamorphosis, and is expected to be a valuable resource to the community.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1320-z) contains supplementary material, which is available to authorized users.

Early and late response of Nematostella vectensis transcriptome to heavy metals

Environmental contamination from heavy metals poses a global concern for the marine environment, as heavy metals are passed up the food chain and persist in the environment long after the pollution source is contained. Cnidarians play an important role in shaping marine ecosystems, but environmental pollution profoundly affects their vitality. Among the cnidarians, the sea anemone Nematostella vectensis is an advantageous model for addressing questions in molecular ecology and toxicology as it tolerates extreme environments and its genome has been published. Here, we employed a transcriptome-wide RNA-Seq approach to analyse N. vectensis molecular defence mechanisms against four heavy metals: Hg, Cu, Cd and Zn. Altogether, more than 4800 transcripts showed significant changes in gene expression. Hg had the greatest impact on up-regulating transcripts, followed by Cu, Zn and Cd. We identified, for the first time in Cnidaria, co-up-regulation of immediate-early transcription factors such as Egr1, AP1 and NF-κB. Time-course analysis of these genes revealed their early expression as rapidly as one hour after exposure to heavy metals, suggesting that they may complement or substitute for the roles of the metal-mediating Mtf1 transcription factor. We further characterized the regulation of a large array of stress-response gene families, including Hsp, ABC, CYP members and phytochelatin synthase, that may regulate synthesis of the metal-binding phytochelatins instead of the metallothioneins that are absent from Cnidaria genome. This study provides mechanistic insight into heavy metal toxicity in N. vectensis and sheds light on ancestral stress adaptations.

Fundamental differences in endoreplication in mammals and Drosophila revealed by analysis of endocycling and endomitotic cells

Throughout the plant and animal kingdoms specific cell types become polyploid, increasing their DNA content to attain a large cell size. In mammals, megakaryocytes (MKs) become polyploid before fragmenting into platelets. The mammalian trophoblast giant cells (TGCs) exploit their size to form a barrier between the maternal and embryonic tissues. The mechanism of polyploidization has been investigated extensively in Drosophila, in which a modified cell cycle--the endocycle, consisting solely of alternating S and gap phases--produces polyploid tissues. During S phase in the Drosophila endocycle, heterochromatin and specific euchromatic regions are underreplicated and reduced in copy number. Here we investigate the properties of polyploidization in murine MKs and TGCs. We induced differentiation of primary MKs and directly microdissected TGCs from embryonic day 9.5 implantation sites. The copy number across the genome was analyzed by array-based comparative genome hybridization. In striking contrast to Drosophila, the genome was uniformly and integrally duplicated in both MKs and TGCs. This was true even for heterochromatic regions analyzed by quantitative PCR. Underreplication of specific regions in polyploid cells is proposed to be due to a slower S phase, resulting from low expression of S-phase genes, causing failure to duplicate late replicating genomic intervals. We defined the transcriptome of TGCs and found robust expression of S-phase genes. Similarly, S-phase gene expression is not repressed in MKs, providing an explanation for the distinct endoreplication parameters compared with Drosophila. Consistent with TGCs endocycling rather than undergoing endomitosis, they have low expression of M-phase genes.

CEL-Seq: single-cell RNA-Seq by multiplexed linear amplification

High-throughput sequencing has allowed for unprecedented detail in gene expression analyses, yet its efficient application to single cells is challenged by the small starting amounts of RNA. We have developed CEL-Seq, a method for overcoming this limitation by barcoding and pooling samples before linearly amplifying mRNA with the use of one round of in vitro transcription. We show that CEL-Seq gives more reproducible, linear, and sensitive results than a PCR-based amplification method. We demonstrate the power of this method by studying early C. elegans embryonic development at single-cell resolution. Differential distribution of transcripts between sister cells is seen as early as the two-cell stage embryo, and zygotic expression in the somatic cell lineages is enriched for transcription factors. The robust transcriptome quantifications enabled by CEL-Seq will be useful for transcriptomic analyses of complex tissues containing populations of diverse cell types.

Developmental control of gene copy number by repression of replication initiation and fork progression

Precise DNA replication is crucial for genome maintenance, yet this process has been inherently difficult to study on a genome-wide level in untransformed differentiated metazoan cells. To determine how metazoan DNA replication can be repressed, we examined regions selectively under-replicated in Drosophila polytene salivary glands, and found they are transcriptionally silent and enriched for the repressive H3K27me3 mark. In the first genome-wide analysis of binding of the origin recognition complex (ORC) in a differentiated metazoan tissue, we find that ORC binding is dramatically reduced within these large domains, suggesting reduced initiation as one mechanism leading to under-replication. Inhibition of replication fork progression by the chromatin protein SUUR is an additional repression mechanism to reduce copy number. Although repressive histone marks are removed when SUUR is mutated and copy number restored, neither transcription nor ORC binding is reinstated. Tethering of the SUUR protein to a specific site is insufficient to block replication, however. These results establish that developmental control of DNA replication, at both the initiation and elongation stages, is a mechanism to change gene copy number during differentiation.

Identification of functional elements and regulatory circuits by Drosophila modENCODE

To gain insight into how genomic information is translated into cellular and developmental programs, the Drosophila model organism Encyclopedia of DNA Elements (modENCODE) project is comprehensively mapping transcripts, histone modifications, chromosomal proteins, transcription factors, replication proteins and intermediates, and nucleosome properties across a developmental time course and in multiple cell lines. We have generated more than 700 data sets and discovered protein-coding, noncoding, RNA regulatory, replication, and chromatin elements, more than tripling the annotated portion of the Drosophila genome. Correlated activity patterns of these elements reveal a functional regulatory network, which predicts putative new functions for genes, reveals stage- and tissue-specific regulators, and enables gene-expression prediction. Our results provide a foundation for directed experimental and computational studies in Drosophila and related species and also a model for systematic data integration toward comprehensive genomic and functional annotation.

Transcription of steroidogenic acute regulatory protein in the rodent ovary and placenta: alternative modes of cyclic adenosine 3', 5'-monophosphate dependent and independent regulation

Steroid hormone synthesis is a vital function of the adrenal cortex, serves a critical role in gonadal function, and maintains pregnancy if normally executed in the placenta. The substrate for the synthesis of all steroid hormones is cholesterol, and its conversion to the first steroid, pregnenolone, by the cholesterol side-chain cleavage cytochrome P450 (CYP11A1) enzyme complex takes place in the inner mitochondrial membranes. Steroidogenic acute regulatory protein (STAR) facilitates the rate-limiting transfer of cholesterol from the outer mitochondrial membrane to CYP11A1 located in the inner organelle membranes. The current study explored the mechanisms controlling transcription of the Star gene in primary cell cultures of mouse placental trophoblast giant cells and rat ovarian granulosa cells examined throughout the course of their functional differentiation. Our findings show that the cis-elements required for Star transcription in the rodent placenta and the ovary are centered in a relatively small proximal region of the promoter. In placental trophoblast giant cells, cAMP is required for activation of the Star promoter, and the cis-elements mediating a maximal response were defined as cAMP response element 2 and GATA. EMSA studies show that placental cAMP-responsive element binding protein (CREB)-1 and activating transcription factor-2 (ATF2) bind to a -81/-78 sequence, whereas GATA-2 binds to a -66/-61 sequence. In comparison, patterns of Star regulation in the ovary suggested tissue-specific and developmental controlled modes of Star transcription. During the follicular phase, FSH/cAMP induced CREB-1 dependent activity, whereas upon luteinization STAR expression becomes cAMP and CREB independent, a functional shift conferred by FOS-related antigen-2 displacement of CREB-1 binding, and the appearance of a new requirement for CCAAT enhancer-binding protein beta and steroidogenic factor 1 that bind to upstream elements (-117/-95). These findings suggest that during evolution, the promoters of the Star gene acquired nonconsensus sequence elements enabling expression of a single gene in different organs, or allowing dynamic temporal changes corresponding to progressing phases of differentiation in a given cell type.

Transcriptional regulation of the cholesterol side chain cleavage cytochrome P450 gene (CYP11A1) revisited: binding of GATA, cyclic adenosine 3',5'-monophosphate response element-binding protein and activating protein (AP)-1 proteins to a distal novel cluster of cis-regulatory elements potentiates AP-2 and steroidogenic factor-1-dependent gene expression in the rodent placenta and ovary

The first and key enzyme controlling the synthesis of steroid hormones is cholesterol side chain cleavage cytochrome P450 (P450scc, CYP11A1). This study sought to elucidate overlooked modes of regulation of P450scc transcription in the rodent placenta and ovary. Transcription of P450scc requires two clusters of cis-regulatory elements: a proximal element (-40) known to bind either activating protein 2 (AP-2) in the placenta, or steroidogenic factor 1 in the ovary, and a distal region of the promoter (-475/-447) necessary for potentiation of the AP-2/steroidogenic factor 1-dependent activity up to 7-fold. In primary cultures of mouse trophoblast giant cells and rat ovarian granulosa cells, binding of trans-factors to the distal regulatory sequences generated transcriptional activity in a tissue-specific pattern: in the placenta, cAMP response element (CRE)-binding protein 1 (CREB-1) and GATA-2 binding generates promoter activity in a cAMP-independent manner, whereas in ovarian cells, CREB-1 and GATA-4 are required for FSH responsiveness. However, as ovarian follicles advance toward ovulation, elevated Fra-2 expression replaces CREB-1 function by binding the same CRE(1/2) motif. Our findings suggest that upon onset of follicular recruitment, CREB-1 mediates FSH/cAMP signaling, which switches to cAMP-independent expression of P450scc in luteinizing granulosa cells expressing Fra-2. In the placenta, the indispensable role of CREB-1 was demonstrated by use of dominant-negative CREB-1 mutant, but neither cAMP nor Ser133 phosphorylation of CREB-1 is required for P450scc transcription. These observations suggest that placental regulation of P450scc expression is subjected to alternative signaling pathway(s) yet to be found.

Transcriptional activation of the steroidogenic acute regulatory protein (StAR) gene: GATA-4 and CCAAT/enhancer-binding protein beta confer synergistic responsiveness in hormone-treated rat granulosa and HEK293 cell models

Steroidogenic acute regulatory protein (StAR) mediates translocation of cholesterol to the inner membranes of steroidogenic mitochondria, where it serves as a substrate for steroid synthesis. Transcription of StAR in the gonads and adrenal cells is upregulated by trophic hormones, involves downstream signaling pathways and a cohort of trans-factors acting as activators or suppressors of StAR transcription. This study suggests that a 21 basepair long sequence positioned at -81/-61 of the murine StAR promoter is sufficient to confer a robust hormonal activation of transcription in ovarian granulosa cells treated with FSH. We show that recombinant GATA-4 and CCAAT/enhancer-binding protein beta (C/EBPbeta) bind to the promoter at -66/-61 and -81/-70 and activate transcription of a reporter gene when co-expressed in heterologous human embryonic kidney 293 (HEK293) cells. In this cell model, C/EBPbeta and GATA-4 synergize in a sequence dependent manner and p300/CBP further maximizes their joint activities. Inhibitors of the transcriptional activators, such as liver-enriched inhibiting protein (C/EBPbeta-LIP), Friend of GATA-4 (FOG-2) protein and the viral E1A protein abolished the respective factor-dependent activities in HEK293 cells. Binding assays suggest that a dual binding of C/EBPbeta and GATA-4 to the promoter depends on the molar ratio of the factors present while demonstrating GATA-4 predominant association with the promoter DNA. This pattern may reflect on StAR expression at the time of corpus luteum formation when C/EBPbeta levels peak, as does StAR expression.

Analysis of trophoblast giant cell steroidogenesis in primary cultures

Placental progesterone synthesis in humans prevents abortion of the fetus by maintaining uterine quiescence and low myometrial excitability. In rodents, a transient steroidogenic output is observed in the trophoblast giant cells during mid-pregnancy. Although the exact role of this locally produced progesterone is not clear, rodent trophoblast giant cells are an important cell model for studying the regulation of placental steroidogenesis. This chapter describes the methods we developed to analyze the regulation of genes involved in progesterone biosynthesis in miniature cultures of primary trophoblast cells from rodents. These genes include cholesterol side chain cleavage cytochrome P450 (P450scc) and its accessory proteins, steroidogenic acute regulatory protein (StAR) and 3beta-hydroxysteroid dehydrogenase/isomerase (3betaHSD). To obtain giant cells, uterine implantation sites are sliced in half, and the trophoblast giant cell layers are separated from the surrounding decidua by scraping. Cells can subsequently be separated by gentle enzymatic digestion with trypsin, or collagenase, and plated for further study in vitro. This chapter provides instructions, insights, and comments instrumental for performing in situ visualization of giant cell mRNA and proteins, analyzing enzyme activities, and conducting promoter analyses with a limited number of cells.

Using the eye fixation speculum as an adjunct to pterygium surgery

A technique is described that overcomes the two biggest problems facing the surgeon when dissecting a pterygium from the cornea-bleeding and eye movement. Our technique however, requires only minimal anesthesia (topical and subconjunctival) and the use of a disposable speculum and suction ring. An added advantage is this particular speculum gives good exposure of the superior bulbar conjunctiva; this facilitates harvesting a conjunctival autograft.

Mutations of the 22- and 27-kD zein promoters affect transactivation by the Opaque-2 protein

By utilizing a homologous transient expression system, we have demonstrated that the Opaque-2 (O2) gene product O2 confers positive trans-regulation on a 22-kD zein promoter. This trans-acting function of the O2 protein is mediated by its sequence-specific binding to a cis element (the O2 target site) present in the 22-kD zein promoter. A multimer of a 32-bp promoter fragment containing this O2 target site confers transactivation by O2. A single nucleotide substitution in the O2 target sequence not only abolishes O2 binding in vitro, but also its response to transactivation by O2 in vivo. We have also demonstrated that an amino acid domain including the contiguous basic region and the heptameric leucine repeat is essential for the trans-acting function of the O2 protein. Similar but not identical O2 target sequence motifs can be found in the promoters of zein genes of different molecular weight classes. Conversion of such a motif in the 27-kD zein promoter to an exact O2 target sequence by site-directed mutagenesis was sufficient to increase the binding affinity of the O2 protein in vitro and to confer transactivation by O2 in vivo.

Pheochromocytoma: an unusual presentation and sequela

A 40-year-old male presenting with exercise-induced headaches was found to have a pheochromocytoma which was subsequently removed. His blood pressure was never recorded as elevated. He went on to develop recurrence of asthma, which had been absent for at least 20 years, 48 h postoperatively. This is the first case of pheochromocytoma manifesting as exercise-induced headache in the absence of detectable hypertension.

Induction of an ATP-polymerizing enzyme in TMV-infected tobacco and its homology to the human 2'-5' A synthetase

Several reports have indicated that tobacco carries an enzyme (APE) that, in the presence of poly (rI):(rC), polymerizes ATP to oligoadenylates. This paper demonstrates that the tobacco APE system comprises several proteins (estimated sizes: 32, 42, 67, and 84 +/- 10% kD). Only one of these proteins (the "67-kD" form) binds to poly (rI):(rC). This APE form has been purified by affinity chromatography on a synthetic ds-RNA column. Four tobacco proteins, including the purified one, crossreact with antibodies against the human enzyme, 2'-5' A synthetase. The ATP-binding capacity of some of these proteins has also been demonstrated. The amount of plant oligoadenylates obtained by polymerizing ATP with the purified APE form allows, for the first time, their direct analysis by TLC. The TLC analysis indicated that the oligomer produced by APE is not identical to the 2'-5' oligoadenylate. The appearance of the 2'-5' A-related proteins correlates with the build up of TMV infection, and the pattern of their stimulation and turnover was established. Nucleic acid hybridization indicates homology of tobacco DNA and RNA sequences with cloned cDNA of the human 2'-5' A synthetase gene. The stimulation in tobacco, upon TMV infection, of mRNA species homologous to the above human cDNA has been demonstrated. The analogy between the plant and the human system is discussed.

Two antiviral proteins from tobacco: purification and characterization by monoclonal antibodies to human beta-interferon

Polyclonal antibodies to human beta-interferon reacted specifically with two plant proteins (gp22 and gp35) by Western blot analysis of crude protein extracts from tobacco leaves infected with tobacco mosaic virus. Immunoaffinity chromatography of these extracts on a column of immobilized monoclonal antibodies to human beta-interferon and then reversed-phase HPLC yielded gp22 and gp35 in a pure state. Both proteins reacted with the Schiff reagent and concanavalin A (indicating their glycoprotein nature) and exhibited antiviral activity (inhibiting tobacco mosaic virus replication in tobacco-leaf discs at concentrations of ng/ml). Each protein was cleaved by cyanogen bromide and the resultant peptides, separated by HPLC, were sequenced as far as the Edman degradation allowed, giving a total of 61 amino acid residues for gp22 and 105 residues for gp35, which represent 30-50% of their expected length. Computer analyses of the sequenced segments revealed no significant homology to human beta-interferon, each other, or any other recorded sequence.

Treatment of recurrent upper respiratory infection in children

The care of a child with recurrent upper respiratory infections can be a frustrating experience for the physician, parent and patient.In this presentation, the history, age incidence, etiology and therapy of recurrent respiratory infection are discussed. As in other conditions the importance of the history cannot be over-emphasized. This alone may indicate the appropriate form of therapy. The age incidence in 32 pediatric patients is presented. Regular daily administration of sulfonamide can be an effective prophylaxis. The indications for tonsillectomy and adenoidectomy are discussed, and a respiratory vaccine has also been found effective.When these measures were unsuccessful, a trial of sodium cromoglycate was undertaken in 32 children, approximately 60 percent of whom improved within ten days. Repeated respiratory infection in children may sensitize the mucosa of the respiratory tract with consequent liberation of histamine.

Prophylactic chemotherapy with low-dosage trimethoprim-sulfamethoxazole following acute urinary tract infections in children

The cases of 10 children with acute and recurrent infection of the urinary tract are presented. Their ages were between 7 weeks and 9 years. Five of the children had been previously treated with a combination of sulfisoxazole, ampicillin, mandelamine and nitrofurantion and four of these children had "breakthrough" infections. When trimethoprim-sulfamethoxazole was administered twice weekly no further infections were noted in four of these five patients. The second group of five children were started on trimethoprim-sulfamethoxazole from the start of their infection and treatment was continued twice weekly for 5 to 7 months. No recurrence of infection of the urine has been detected up to the present time. It is concluded that treatment with trimethoprim-sulfamethoxazole initiated at the outset of urinary tract infection and twice weekly is a valuable drug in children, provided the organism responsible for the infection is sensitive to this agent.

Scalp Vein Infusion

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