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At least 145 records · Page 8Linked to original sources
PubMed1993

Immunohistochemical detection of tumor necrosis factor-alpha, other cytokines and adhesion molecules in human livers with alcoholic hepatitis.

This immunohistochemical study was designed to investigate the possible contribution to and topographical distribution of some important cytokines, such as tumour necrosis factor alpha (TNF alpha) and interleukins, in acute alcoholic hepatitis. The well-known inductive capacity of these cytokines with respect to the expression and/or up-regulation of adhesion molecules, such as intercellular adhesion molecule-1 (ICAM-1) and endothelial leukocyte adhesion molecule-1 (ELAM-1), was a further point to be studied. Moreover, the proposed induction of adhesion molecules might also be associated with the activation and attraction of a special population of inflammatory cells characteristic for alcoholic hepatitis. Frozen liver samples from patients who died with signs of acute alcoholic hepatitis were evaluated using the alkaline phosphatase anti-alkaline phosphatase immunostaining technique and also single and double indirect immunofluorescence. In acute alcoholic hepatitis TNF alpha could be detected predominantly in ballooned hepatocytes, which often contained alcoholic hyalin (Mallory bodies). Moreover, TNF alpha showed a co-distribution with ICAM-1 expressed in the membranes of hepatocytes and with the occurrence of CD11b positive polymorphonuclear leukocytes (neutrophils) suggesting a possible major role of the beta 2-integrin Mac-1 as a ligand for ICAM-1. No induction of ELAM-1 could be found. In alcoholic hepatitis cytokines may be responsible for the induction of the adhesion molecule ICAM-1 on hepatocytic membranes and activate a defined population of inflammatory cells, thus contributing to the characteristic histological picture of acute alcoholic hepatitis with its concentration of neutrophils especially in areas with ballooned Mallory body-containing hepatocytes. Our results are in line with clinical findings showing high levels of TNF alpha and interleukin-1 in sera of patients with alcoholic hepatitis and with the already reported expression of ICAM-1 on hepatocytes.

Antigens, CD↗
PubMed1993

Regulation of substance P is similar to that of vasoactive intestinal peptide after axotomy or explantation of the rat superior cervical ganglion.

The regulation of the expression of substance P (SP) in the rat superior cervical ganglion was compared to that of vasoactive intestinal peptide (VIP) in vivo after axotomy and in vitro after explantation. Previous studies have demonstrated that both neuropeptides increase after explantation, depolarization, and decentralization; however, whereas VIP expression increases after postganglionic axotomy, SP expression reportedly does not. To compare the effect of axotomy on these two peptides directly, the content of both was determined in individual ganglia at various times after surgery. The level of VIP-like immunoreactivity (IR) is increased at 2 days, reaches a peak at 6 days, and then declines by 14 days to approximately half its peak value. The level of SP-IR also increases 2 days after axotomy, but returns to control values by day 6. The increase in SP-IR is accompanied by an increase in beta-preprotachykinin mRNA, suggesting that the elevation in SP content is due, at least in part, to enhanced peptide synthesis. Immunocytochemical localization of SP-IR revealed the presence of immunoreactive principal neurons in axotomized, but not in sham-operated ganglia. Similarities in the regulation of these two neuropeptides were also investigated in organ culture by examining the effects of dexamethasone and interleukin-1 beta on VIP content, since the former has been shown to prevent the increase in SP in culture, while the latter has been found to enhance this increase (Kessler, Adler, Bell, et al., 1983, Neuroscience 9:309-321; Freidin and Kessler, 1991, Proc. Natl. Acad. Sci. USA 88:3200-3203; Hart, Shadiack, and Jonakait, 1991, J. Neurosci. Res. 29:282-291). As with SP expression, dexamethasone reduces the increase in VIP expression, while interleukin-1 beta increases it. Thus, both in vivo and in vitro, similar changes in VIP and SP expression are observed following a number of experimental manipulations, suggesting that expression of the two peptides is regulated by qualitatively similar mechanisms in sympathetic neurons.

Animals↗
PubMed1991

Molecular events involved in transcriptional activation of heat shock genes become progressively refractory to heat stimulation during aging of human diploid fibroblasts.

We examined the induction, by heat shock, of heat shock transcription factor (HSTF) DNA-binding and hsp 70 gene promoter activities during aging of the IMR-90 human diploid fibroblasts. Cells with population doubling level (PDL) ranging from 15-48 were heat shocked at temperatures of 39, 42, and 45 degrees C for various time periods; the binding of HSTF to its consensus DNA was determined by gel retardation assay and the promoter activity of the human hsp 70 gene was analyzed by transient expression of reporter gene activity. We observed that the induction of HSE-binding activity was inversely related to the PDL of the cells used. Importantly, as cells progress through their life span, a higher temperature and a longer period of heat shock were needed to evoke an optimal increase in HSE-binding activity. A substantial and rapid (within 30 min) increase in HSE-binding activity was observed when PDL 20 cells were heat shocked at 39, 42, or 45 degrees C. However, PDL 35 cells did not respond to 39 degrees C, and PDL 48 cells responded slowly to heat shock at 45 degrees C, but not 39 or 42 degrees C. Experiments on the heat induced increase in hsp 70 promoter driven reporter gene expression provided similar information on the age-dependent decrease in transcriptional activation of hsps. These results were further corroborated by quantitation of the abundance of mRNA of hsp 70. Analysis of the cAMP induced expression of the rat somatostatin promoter driven CAT gene provided evidence that the decrease in transcriptional activation of hsps in aging diploid cells was not a reflection of a generalized dysfunction of signal transduction. We conclude that functional changes in the heat shock response occur before cells lose their capacity to replicate, and we suggest that these changes are likely to have a central role in the expression of the aging phenotype.

Base Sequence↗
PubMed1995

GapIII, a new brain-enriched member of the GTPase-activating protein family.

Ras GTPase-activating proteins (GAPs) are negative regulators of ras, which controls proliferation and differentiation in many cells. Ras GAPs have been found in a variety of species from yeast to mammals. We describe here a newly identified mammalian GAP, GapIII, which was obtained by differential screening of a rat oligodendrocyte cDNA library. GapIII putatively encodes a 834 amino acid protein with a predicted molecular weight of 96 kDa, which contains a consensus GAP-related domain (GRD). The protein encoded by this cDNA has high homology with Gap1m, which was recently identified as a putative mammalian homolog of Drosophila Gap1. These proteins contain three structural domains, an N-terminal calcium-dependent phospholipid binding domain, GRD, and a C-terminal PH/Btk domain. Because of the sequence homology and the structural similarities of this protein with Gap1m, we hypothesize that GapIII and Gap1m may be members of a mammalian GAP gene family, separate from p120GAP, neurofibromin (NF1), and IQGAP. To confirm the GapIII protein activity, constructs containing different GapIII-GRD domains were transformed into iral mutant yeast to determine their relative ability to replace IRA1 functionally. Constructs that contained essentially the full-length protein (all three domains), the GRD alone, or the GRD plus PH/Btk domain suppressed heat shock sensitivity of ira1, whereas constructs that contained the GRD with part of the PH/Btk domain had only a weak ability to suppress heat shock sensitivity. These results suggest that the GapIII GRD itself is sufficient to down-regulate ras proteins in yeast. Expression of GapIII mRNA (4.2 kb) was examined by Northern analysis and in situ hybridization. This mRNA was expressed at highest levels in the brain, where its expression increased with development. Lower levels of the mRNA were expressed in the spleen and lung. Among neural cells, GapIII mRNA was expressed in neurons and oligodendrocytes, but not in astrocytes. Interestingly, the expression pattern in brain is reminiscent of type 1 NF1 expression reported by Gutmann et al. (Cell Growth Differ in press, 1995). We propose that in addition to p120GAP and neurofibromin, the GapIII/Gap1m family may be important for modulating ras activity in neurons and oligodendrocytes during normal brain development and in particular in the adult brain.

Animals↗
PubMed1992

Specific distribution of an epididymal 50 kDa protein revealed by an anti-Mos protein monoclonal antibody.

An anti-Mos protein monoclonal antibody, 4A6, was used to investigate the distribution of the antigen in the epididymis, in which the c-mos gene is reportedly expressed. The 4A6-reactive antigen was found on the basement membrane and luminal surface of the epithelial cells in the caput epididymis of BALB/c male mice as well as in the proximal corpus epididymis, the cauda epididymis, and the vas deferens. The 4A6 antigen was also found on the luminal surface of the epithelial cells in the epididymis of male germ cell-deficient C57BL/6J-Wv/Wv mice. This confirmed that the 4A6 antigen does not derive entirely from the testicular c-Mos protein but is synthesized in the epididymis. Western blot analysis revealed that the molecular weight of the epididymal 4A6 antigen was 50 kDa, which is unusually high for the c-Mos protein. With its specific distribution in the epididymis, the protein should play a specific role in functions of the epididymis.

Animals↗
PubMed1995

The small cysteine-rich protein P14 of beet necrotic yellow vein virus regulates accumulation of RNA 2 in cis and coat protein in trans.

The effect of null mutations of the small cysteine-rich protein P14 encoded by RNA 2 of beet necrotic yellow vein virus has been investigated using in vitro transcripts of viral RNA to infect Chenopodium quinoa protoplasts. The P14 mutations down-regulated RNA 2 accumulation by approximately 10- to 50-fold. Accumulation of minus-strand RNA 2 was also diminished but RNA 1 accumulation was much less affected. The inhibition of RNA 2 accumulation could not be complemented in trans by providing P14 from another source (either a second molecule of RNA 2 or an RNA 3-based replicon) containing and expressing the P14 gene. The P14 null mutations dramatically inhibited accumulation of viral coat protein, which is encoded by the 5'-proximal gene on RNA 2, but this effect could be complemented in trans, indicating that it occurs by a mechanism distinct from that affecting RNA 2 accumulation. Transient expression experiments were also carried out in which a plasmid expressing P14 and plasmids expressing a reporter gene placed downstream of potential translational control sequences (the 5'-noncoding sequences of RNAs 2, 3, or 4) were introduced into C. quinoa or Nicotiana tabacum leaves by microprojectile bombardment. Coexpression of P14 produced a 3- to 4-fold stimulation of reporter gene expression levels for all the constructs. The lack of sequence specificity suggests that this phenomenon is not directly related to the RNA 2-specific stimulation of coat protein accumulation observed in a viral infection.

Base Sequence↗
PubMed1994

In vivo characterisation of a translational enhancer upstream from the coat protein open reading frame of potato virus S.

The 101 nucleotide region upstream from the ATG of the potato virus S (PVS) coat protein gene was isolated and the effect of this region on the translation of a downstream open reading frame analysed in vivo. Translation was monitored using the reporter genes B-glucuronidase (GUS) and luciferase (LUC). Translational enhancement was assayed transiently using DNA microprojectile bombardment into both leaf and pollen tissue and also by polyethylene glycol mediated transfection of tobacco protoplasts. In both cases the presence of this region resulted in a 2-3 fold increase in translation when compared to reporter expression with synthetic leader and authentic plant leader constructs. Tobacco plants stability transformed with this PVS 101 nucleotide region and downstream GUS gene gave 4 times the level of translation over synthetic leader GUS control plants.

Base Sequence↗
PubMed2026

Site-specific gene integration by recombinase-mediated cassette exchange in anhydrobiotic Pv11 cells.

Pv11 cells, derived from Polypedilum vanderplanki, uniquely tolerate complete desiccation (anhydrobiosis). Although a CRISPR/Cas9-based precise integration method (CRIS-PITCh) has been developed for Pv11 cells, a CRISPR-free strategy that fixes both the genomic locus and transgene copy number has not yet been established. Here, we implement recombinase-mediated cassette exchange (RMCE) in Pv11 cells and generate master cell lines that retain anhydrobiosis following genetic engineering. We first evaluated the activity of multiple site-specific recombinases in Pv11 cells using a transient two-plasmid reporter assay. Flp, Cre, and Bxb1 recombinases all excised a test cassette and activated a green fluorescent protein (GFP) reporter, whereas phiC31 integrase mediated recombination at the DNA sequence level but did not induce reporter expression under our construct configuration. To enable genomic RMCE, we inserted an FRT/FRT3-landing pad (LP) into a previously identified genomic safe-harbor locus using CRIS-PITCh and isolated clonal master cell lines by single-cell sorting. Using the established master line, Flp-based RMCE achieved site-specific cassette exchange at the LP, producing HaloTag fluorescence and drug resistance upon successful exchange. In addition, the expected post-exchange sequence was confirmed by sequencing. We further established an all-in-one RMCE vector combining the Flp recombinase and donor cassette on a single plasmid. Together, these results demonstrate locus-defined, single-copy transgene integration in anhydrobiotic Pv11 cells via RMCE and provide a standardized, CRISPR-free workflow for routine genetic manipulation in this unique cell line. This workflow facilitates both fundamental research and applied biotechnological applications using desiccation-tolerant cells.

Anhydrobiosis↗
PubMed1989

A comparison between different models of the relation between recorded intradental nerve impulse activity and reported pain in man.

In this study three different models of the relation between intradental nerve impulse activity (INA) and pain report, expressed by finger-span (FS), in man were investigated. The techniques were (i) a previously described mathematical model, (ii) the relation between the Areas of INA and FS and (iii) the relation between the Peaks of INA and FS. Their usefulness in 533 clinical experiments on 15 subjects were evaluated by means of a statistical analysis of the variability and accuracy of the models. It was shown that the mathematical model was the most accurate and stable method of the three different methods investigated. This was indicated by, among other things, a significantly smaller variability for the mathematical model within experimental sessions than between sessions. The two other methods were found to be of less scientific value since they had an undesired high variability within sessions, and also showed contradicting results during control conditions.

Adult↗
PubMed1994

Identification of a mannose-acetate-specific 87-kDa receptor responsible for human NK and LAK activity.

Target cell recognition and cytotoxicity of human CD56+ NK and LAK cells is readily inhibited by acetylated mannose. Two respective NK cell receptor candidates were isolated from human leukocyte lysates by mannose acetate affinity chromatography. The 87-kDa receptor showed sequence homologies with lactoferrin and the 59-kDa receptor represented a complex of two Ca-binding proteins MRP-8 and MRP-14 reportedly expressed only by cells of myeloid origin. The 87-kDa receptor exhibited heterogeneity in isoelectric focusing and behaved entirely differently from lactoferrin. Preincubation of tumor target cells with the 87-kDa receptor inhibited competitively target cell recognition and cytotoxicity of human CD56+ NK and LAK cells.

Acetylation↗
PubMed1991

Priming action of inositol hexakisphosphate (InsP6) on the stimulated respiratory burst in human neutrophils.

After priming by a number of different host, bacterial and chemical agents, human neutrophils may be stimulated to produce a greater respiratory burst than would be elicited by the stimulus alone. Other neutrophil functions may be similarly enhanced by pre-exposure to a priming agent. We describe here a new extracellular role for inositol hexakisphosphate (InsP6) as a priming agent for a variety of human neutrophil functional responses. Preincubation of the cells with InsP6 alone (up to 250 microM) has no stimulatory effect upon the basal production of reactive oxygen intermediates but the response to a subsequent stimulus (FMLP, PMA or phagocytic particles) is substantially enhanced. Levels 100-200% higher than 'stimulus only' controls have been recorded. Peak enhancement of the FMLP-induced oxidative response occurs after 1-2 min preincubation with InsP6 and the effect is dose-dependent (maximum at approx. 100 microM InsP6). As others have shown FMLP stimulation of superoxide anion production has no external Ca2+ dependence but the presence of low levels of Ca2+ and Mg2+ (0.1 mM) during priming appears to be an essential requirement for full expression. Reports of intracellular concentrations of InsP6 in mammalian cells in the 30-100 microM range suggest that the local release of this inositol polyphosphate from damaged or effect cells could have a physiologically important modulatory role on neutrophil functions.

Calcium↗
PubMed2026

DAZL-targeted inducible kill switches enable efficient ablation of chicken primordial germ cells.

Competition from endogenous primordial germ cells (PGCs) in recipient embryos limits the generation of fully donor-derived offspring in avian surrogate-host systems. An inducible and germline-restricted ablation strategy is therefore needed to create sterile recipients without compromising somatic development. Using CRISPR/Cas9-mediated homology-directed repair, we inserted three inducible suicide-gene cassettes (iCaspase9, RapaCasp9, and CD) into the endogenous DAZL locus of chicken PGCs. All knock-in lines showed stable reporter expression and retained typical PGC morphology. Comparative functional analyses identified iCaspase9 activated by AP20187 as the most sensitive and specific ablation system, achieving near-complete killing at nanomolar concentrations without detectable toxicity in control cells. RapaCasp9 induced with rapamycin also ablated engineered PGCs efficiently, but rapamycin caused marked non-specific growth inhibition in control cells. Replacing rapamycin with the synthetic A/C heterodimerizer AP21967 largely eliminated this off-target toxicity while preserving rapid and robust killing. By contrast, yeast-derived CD variants did not substantially improve 5-fluorocytosine sensitivity in chicken PGCs. DAZL-restricted iCaspase9/AP20187 and the optimized RapaCasp9/AP21967 system provide efficient inducible kill switches for chicken PGCs in vitro. These platforms establish a practical genetic toolkit for generating sterile surrogate hosts to support avian genome editing, germline replacement, and Sire Dam Surrogate breeding.

CRISPR/Cas9↗
PubMed1995

Comparison of coronary lesions obtained by directional coronary atherectomy in unstable angina, stable angina, and restenosis after either atherectomy or angioplasty.

The present study investigated the incidence of the histopathologic lesions and of growth factor expression in a consecutive series of directional coronary atherectomy (DCA) samples from 40 unstable angina pectoris patients without prior acute myocardial infarction and compared the findings with those obtained in DCA samples from 18 patients with stable angina without previous infarction and 18 patients with restenosis. We investigated coronary thrombosis, neointimal hyperplasia, and inflammation. For unstable angina, we correlated the angiographic Ambrose plaque subtypes with the histopathologic findings. The immunophenotype of plaque cells and the growth factor expression were assessed with specific antibodies for cell characterization and for the expression of basic fibroblast and platelet-derived AA and AB growth factors and receptors. The incidence of coronary thrombosis was 35% in patients with unstable angina, 17% in those with stable angina, and 11% in patients with restenosis. Neointimal hyperplasia was found in 38% of unstable angina cases, in 17% of stable angina cases, and in 83% of restenosis cases. Inflammation without thrombus or accelerated progression occurred in 20% of unstable angina and 6% of stable angina samples. In 52% of unstable angina cases, inflammation coexisted with thrombosis and/or neointimal hyperplasia. In the unstable angina group, 71% of the plaques with thrombus had a corresponding angiographic pattern of complicated lesions. The growth factor expression, reported as percentage of cells immunostaining with different growth factor antibodies, was highest in restenosis, followed by unstable angina and stable angina lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Isolation of a cDNA clone encoding a biologically active thyroid hormone receptor.

We have isolated a c-erbA cDNA clone from a GH3 cell library. The clone, denoted erb62, is 4.5 kilobases long and encodes a 461-amino acid beta-type c-erbA protein. This c-erbA protein binds 3,5,3'-triiodothyronine (T3) and T3 analogs with affinities similar to those of the authentic T3 receptor. By RNA gel blot analysis, erb62 hybridizes to a 6-kilobase RNA found in organs that express T3 receptors--e.g., heart, kidney, and brain. A COS-cell transient cotransfection system was used to show that erb62 encodes a biologically active T3 receptor. An oligonucleotide, corresponding to a portion of the rat growth hormone gene 5'-flanking region that contains a T3 response element, was inserted on the 5' side of the herpes simplex virus thymidine kinase promoter in a chloramphenicol acetyltransferase-expressing plasmid. Reporter gene expression directed by this hybrid promoter was T3 inducible only if this plasmid was cotransfected with an erb62-expressing plasmid.

Amino Acid Sequence↗
PubMed1989

Monoclonal antibodies to human lymphocyte homing receptors define a novel class of adhesion molecules on diverse cell types.

A 90-kD lymphocyte surface glycoprotein, defined by monoclonal antibodies of the Hermes series, is involved in lymphocyte recognition of high endothelial venules (HEV). Lymphocyte gp90Hermes binds in a saturable, reversible fashion to the mucosal vascular addressin (MAd), a tissue-specific endothelial cell adhesion molecule for lymphocytes. We and others have recently shown that the Hermes antigen is identical to or includes CD44 (In[Lu]-related p80), human Pgp-1, and extracellular matrix receptor III-molecules reportedly expressed on diverse cell types. Here, we examine the relationship between lymphoid and nonlymphoid Hermes antigens using serologic, biochemical, and, most importantly, functional assays. Consistent with studies using mAbs to CD44 or Pgp-1, mAbs against five different epitopes on lymphocyte gp90Hermes reacted with a wide variety of nonhematolymphoid cells in diverse normal human tissues, including many types of epithelium, mesenchymal elements such as fibroblasts and smooth muscle, and a subset of glia in the central nervous system. To ask whether these non-lymphoid molecules might also be functionally homologous to lymphocyte homing receptors, we assessed their ability to interact with purified MAd using fluorescence energy transfer techniques. The Hermes antigen isolated from both glial cells and fibroblasts--which express a predominant 90-kD form similar in relative molecular mass, isoelectric point, and protease sensitivity to lymphocyte gp90Hermes--was able to bind purified MAd. In contrast, a 140-160-kD form of the Hermes antigen isolated from squamous epithelial cells lacked this capability. Like lymphocyte binding to mucosal HEV, the interaction between glial gp90Hermes and MAd is inhibited by mAb Hermes-3, but not Hermes-1, suggesting that similar molecular domains are involved in the two binding events. The observation that the Hermes/CD44 molecules derived from several nonlymphoid cell types display binding domains homologous to those of lymphocyte homing receptors suggests that these glycoproteins represent a novel type of cell adhesion/recognition molecule (H-CAM) potentially mediating cell-cell or cell-matrix interactions in multiple tissues.

Antibodies, Monoclonal↗
PubMed1995

Decreased expression of glutathione S-transferases and increased fatty change in peroxisomal enzyme-negative foci induced by clofibrate in rat livers.

Alteration in glutathione S-transferase (GST) isoenzymes was compared with that of a peroxisomal enzyme, enoyl-CoA hydratase (ECH), during hepatocarcinogenesis caused by clofibrate (CF) administration in male Sprague-Dawley rats. The amount of alpha class GST forms, determined by single radial immunodiffusion using anti-GST 1-2 antibody, was inversely correlated with that of ECH and was decreased at week 2 of CF administration to approximately 50% of the value prior to treatment and then slightly increased to 70% of the control value by week 15, without change thereafter up to 93 weeks. Resolution of GST subunits by high performance liquid chromatography revealed an approximately 60% decrease in the amounts of subunits 1 and 3 at week 93 and a 25% decrease in the amounts of subunits 2 and 4. Immunohistochemical staining of rat livers revealed hepatic foci and minifoci negative for ECH at week 60 and thereafter. Almost all ECH-negative foci (95.1-97.9%) were clear cell in character, along with a somewhat lower proportion (68.0-73.8%) of ECH-negative minifoci. Numerous fat-positive granules were detected in 78.3% of those lesions exhibiting a clear cell change. Although the amounts of GST and ECH exhibited contrasting patterns of alteration in whole livers following CF administration, the expression of both alpha and mu class GST forms was decreased in the majority of ECH-negative foci at week 93, but were not altered in minifoci. The repression of GST forms appeared to be a later event than the loss of ECH or the clear cell change in CF-associated hepatic lesions and was in clear contrast to the enhanced expression reported for preneoplastic lesions induced by mutagenic carcinogens.

Animals↗
PubMed1995

Dissecting a locus control region: facilitation of enhancer function by extended enhancer-flanking sequences.

Using transgenic mice, we have defined novel gene regulatory elements, termed "facilitators." These elements bilaterally flank, by up to 1 kb, a 200-bp T-cell-specific enhancer domain in the human adenosine deaminase (ADA) gene. Facilitators were essential for gene copy-proportional and integration site-independent reporter expression in transgenic thymocytes, but they had no effect on the enhancer in transfected T cells. Both segments were required. Individual segments had no activity. A lack of facilitator function caused positional susceptibility and prevented DNase I-hypersensitive site formation at the enhancer. The segments were required to be at opposed ends of the enhancer, and they could not be grouped together. Reversing the orientation of a facilitator segment caused a partial loss of function, suggesting involvement of a stereospecific chromatin structure. trans-acting factor access to enhancer elements was modeled by exposing nuclei to a restriction endonuclease. The enhancer domain was accessible to the 4-cutter DpnII in a tissue- and cell-type-specific fashion. However, unlike DNase I hypersensitivity and gene expression, accessibility to the endonuclease could occur without the facilitator segments, suggesting that an accessible chromatin domain is an intermediate state in the activational pathway. These results suggest that facilitators (i) are distinct from yet positionally constrained to the enhancer, (ii) participate in a chromatin structure transition that is necessary for the DNase I hypersensitivity and the transcriptional activating function of the enhancer, and (iii) act after cell-type-specific accessibility to the enhancer sequences is established by factors that do not require the facilitators to be present.

Adenosine Deaminase↗
PubMed1995

Vasoactive intestinal peptide: an important trophic factor and developmental regulator?

It has been proposed that vasoactive intestinal peptide (VIP) or a very closely related peptide has important actions very early in embryonic development. Recent data supporting this hypothesis are that subnanomolar concentrations of VIP significantly increased the growth rate of cultured embryonic day-9.5 (E9.5) mouse embryos, and that embryos at this and later stages exhibit a high degree of VIP binding in the brain stem and spinal cord. It is not known whether VIP is derived from the fetus, placenta, or mother at these early stages, or whether VIP acts in this culture system in place of a related peptide. The earliest reported expression of VIP in rat embryos is at E13.5, when the peptide and mRNA are expressed transiently in a high percentage of cells in the rat stellate ganglia. The time course of events mapped in other sympathetic ganglia at this stage suggest that transient expression of VIP in the ganglia might function to regulate neuroblast and/or glial cell proliferation, maturation or survival. Tissue culture studies indicate that VIP can support many of these trophic functions at concentrations that are the same or lower than that necessary to increase cAMP levels by way of classical VIP receptors. For example, VIP at 10(-10) M stimulates the release of neurotrophic factors from glial cells and maximally stimulates the proliferation of astrocytes. Two VIP receptors encoded on different genes have now been cloned. Both are members of the seven transmembrane G-protein-coupled receptor family and, when expressed in mammalian cells, mediate an increase in cAMP.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗