A ligand binding domain mutation in the mouse glucocorticoid receptor functionally links chromatin remodeling and transcription initiation

We utilized the mouse mammary tumor virus (MMTV) long terminal repeat (LTR) in vivo to understand how the interaction of the glucocorticoid receptor (GR) with a nucleosome-assembled promoter allows access of factors required for the transition from a repressed promoter to a derepressed, transcriptionally competent promoter. A mutation (C644G) in the ligand binding domain (LBD) of the mouse GR has provided information regarding the steps required in the derepression/activation process and in the functional significance of the two major transcriptional activation domains, AF1 and AF2. The mutant GR activates transcription from a transiently transfected promoter that has a disordered nucleosomal structure, though significantly less well than the wild-type GR. With an integrated, replicated promoter, which is assembled in an ordered nucleosomal array, the mutant GR does not activate transcription, and it fails to induce chromatin remodeling of the MMTV LTR promoter, as indicated by nuclease accessibility assays. Together, these findings support a two-step model for the transition of a nucleosome-assembled, repressed promoter to its transcriptionally active, derepressed form. In addition, we find that the C-terminal GR mutation is dominant over the transcription activation function of the N-terminal GR activation domain. These findings suggest that the primary activation function of the C-terminal activation domain is different from the function of the N-terminal activation domain and that it is required for derepression of the chromatin-repressed MMTV promoter.

Inhibition of histone deacetylation augments dihydrotestosterone induction of androgen receptor levels: an explanation for trichostatin A effects on androgen-induced chromatin remodeling and transcription of the mouse mammary tumor virus promoter

The integrated mouse mammary tumor virus (MMTV) promoter has provided an excellent model system with which to study the impact of steroid hormones on transcriptional activation in the context of a defined chromatin structure. The hormone response element (HRE) of this promoter is positioned on a phased nucleosome which becomes remodeled in response to steroids. One possible mechanism of chromatin remodeling by steroid receptors could involve recruitment of coactivators which alter the histone acetylation status of the HRE nucleosome. To examine how the androgen receptor (AR) influences transcription and chromatin remodeling and to assess whether changes in histone acetylation are involved in these effects, we determined whether the specific histone deacetylase inhibitor trichostatin A (TSA) influenced basal- and androgen-mediated transcriptional activation of the integrated MMTV promoter in the mouse L-cell fibroblast cell line 29+. These cells harbor the MMTV promoter integrated in the genome and express only one steroid hormone receptor subtype, i.e., the AR. Surprisingly, we found that treatment of the cells with TSA alone had virtually no effect on transcription and chromatin remodeling of the MMTV promoter nor on AR levels. However, pretreatment with TSA augmented the DHT effects on all three parameters. These results suggest that histone acetylation changes at the MMTV B nucleosome per se are not alone sufficient to induce chromatin remodeling and subsequent induction of MMTV transcription. Rather, the histone deacetylase inhibitor TSA exerts a portion of its effect on MMTV chromatin remodeling and transcriptional activation indirectly through increases in AR levels.

Human Genome Project and cystic fibrosis--a symbiotic relationship

When Watson and Crick determined the structure of DNA in 1953, a biological revolution began. One result of this revolution is the Human Genome Project. The primary goal of this international project is to obtain the complete nucleotide sequence of the human genome by the year 2005. Although molecular biologists and geneticists are most enthusiastic about the Human Genome Project, all areas of clinical medicine and fields of biology will be affected. Cystic fibrosis is the most common, inherited, lethal disease of white persons. In 1989, researchers located the cystic fibrosis gene on the long arm of chromosome 7 by a technique known as positional cloning. The most common mutation (a 3-base pair deletion) of the cystic fibrosis gene occurs in 70% of patients with cystic fibrosis. The knowledge gained from genetic research on cystic fibrosis will help researchers develop new therapies (e.g., gene) and improve standard therapies (e.g., pharmacologic) so that a patient's life span is increased and quality of life is improved. The purpose of this review is twofold. First, the article provides an overview of the Human Genome Project and its clinical significance in advancing interdisciplinary care for patients with cystic fibrosis. Second, the article includes a discussion of the genetic basis, pathophysiology, and management of cystic fibrosis.

Astrocytic demise precedes delayed neuronal death in focal ischemic rat brain

Active neuronal-glial interaction is important in the maintenance of brain homeostasis and is vital for neuronal survival following brain injury. The time course of post-ischemic astroglial dysfunction and neuronal death was studied in the spontaneously hypertensive rat (SHR) brain following permanent middle cerebral artery occlusion (MCAO). In situ hybridization with 35S-labeled riboprobes for GFAP and GLUT3 was used to monitor mRNA expression in glia and neurons. Astrocytic proteins GFAP, vimentin, S100, Glutathione-S-Transferase Yb (GST Yb) and neuronal protein TG2 were detected by immunofluorescence. Cells were co-stained with in situ end labeling (ISEL) to detect DNA fragmentation, a hallmark of cell death. GFAP mRNA expression declined rapidly in the ischemic region of the cortex and was almost absent by 12 h. Immunohistochemical studies revealed a parallel decline in the corresponding protein: a reduction in GFAP staining was apparent in the infarct after 3 h and by 24 h, there was essentially no remaining GFAP. Three other glial proteins (vimentin, S100 and GST Yb) disappeared from infarct over a similar time course. A few ISEL positive cells were observed in the infarct at 6 h, but maximal detection was not seen until 24-48 h. Most of the ISEL-positive cells were neurons, identified by co-staining with the neuronal marker TG2. Few cells expressing GFAP or other glial markers were positive at any time point. Neuronal GLUT3 mRNA declined more slowly than GFAP mRNA in the ischemic core and disappeared during the period of neuronal death. Concurrent with the loss of GFAP mRNA and protein expression in the infarct, there was a rapid rise in GFAP mRNA in the peri-infarct region of ipsilateral hemisphere and proximal region of the contralateral hemisphere. This was followed by the enhanced GFAP protein expression characteristic of reactive astrocytes, but over a significantly slower time course. These studies show that MCAO leads to a rapid decline of GFAP mRNA and glial proteins, which appears to precede the decline in neuronal mRNA and neuronal death within the infarct. Early astroglial dysfunction may play a critical role in determining the outcome of acute hypoxic-ischemic injury by compromising neuronal-glial interactions.

Conformation of the Bax C-terminus regulates subcellular location and cell death

Bax, a pro-apoptotic member of the Bcl-2 family, translocates from the cytosol to the mitochondria during programmed cell death. We report here that both gain-of-function and loss-of-function mutations can be achieved by altering a single amino acid in the Bax hydrophobic C-terminus. The properly mutated C-terminus of Bax can target a non-relevant protein to the mitochondria, showing that specific conformations of this domain alone allow mitochondrial docking. These data along with N-terminus epitope exposure experiments suggest that the C- and the N-termini interact and that upon triggering of apoptosis, Bax changes conformation, exposing these two domains to insert into the mitochondria and regulate the cell death machinery.

Biopharmaceutical approaches for developing and assessing oral peptide delivery strategies and systems: in vitro permeability and in vivo oral absorption of salmon calcitonin (sCT)

PURPOSE

To evaluate a biopharmaceutical approach for selecting formulation additives and establishing the performance specifications of an oral peptide delivery system using sCT as a model peptide.

METHODS

The effect of formulation additives on sCT effective permeability and transepithelial electrical resistance (TEER) was evaluated in side-by-side diffusion chambers using rat intestinal segments. Baseline regional oral absorption of sCT was evaluated in an Intestinal and Vascular Access Port (IVAP) dog model by administration directly into the duodenum, ileum, and colon by means of surgically implanted, chronic catheters. The effect of varying the input rate and volume of the administered solution on the extent of sCT absorption was also evaluated. Citric acid (CA) was utilized in all studies to cause a transient reduction in local pH. In vitro samples and plasma samples were analyzed by radioimmunoassay (RIA). Two oral delivery systems were prepared based on the results of the in vitro and IVAP studies, and evaluated in normal dogs.

RESULTS

Maximal permeability enhancement of sCT was observed using taurodeoxycholate (TDC) or lauroyl carnitine (LC) in vitro. Ileal absorption of sCT was higher than in other regions of the intestine. Low volume and bolus input of solution formulations was selected as the optimal condition for the IVAP studies since larger volumes or slower input rates resulted in significantly lower sCT bioavailability (BA). Much lower BA of sCT was observed when CA was not used in the formulation. The absolute oral bioavailability (mean+/-SD) in dogs for the control (sCT + CA) and two proprietary sCT delivery systems was 0.30%+/-0.05%, 1.10+/-0.18%, and 1.31+/-0.56%, respectively.

CONCLUSIONS

These studies demonstrate the utility of in vitro evaluation and controlled in vivo studies for developing oral peptide delivery strategies. Formulation additives were selected, the optimal intestinal region for delivery identified, and the optimal release kinetics of additives and actives from the delivery system were characterized. These methods were successfully used for devising delivery strategies and fabricating and evaluating oral sCT delivery systems in animals. Based on these studies, sCT delivery systems have been fabricated and tested in humans with favorable results.

PCR based targeted genomic and cDNA differential display

We previously described a targeted genomic differential display method (TGDD: Broude NE, Chandra A, Smith CL. Differential display of genomic subsets containing specific interspersed repeats. Proc. Natl. Acad. Sci. USA 1997;94:4548-53). In that method, presently characterized as method I, targeting was accomplished by capturing DNA fragments containing specific a sequence by hybridization with complementary single-stranded DNA. The captured fragments were amplified by PCR. Here, we describe method II where targeting is accomplished by PCR using primers specific to the target sequence. Method II takes advantage of PCR suppression to eliminate fragments not containing the target sequence (Siebert PDA, Chenchik A, Kellogg DE, Lukyanov KA and Lukyanov SA. An improved PCR method for walking in uncloned genomic DNA. Nucleic Acids Res 1995;23:1087-1088). Targeting focuses analysis on and around interesting areas and additionally serves to reduce the complexity of the amplified subset. These approaches are useful to amplify genome subsets containing a variety of targets including various conserved sequences coding for cis-acting elements or protein motifs.

The role of nucleotide binding and hydrolysis in the function of the fission yeast cdc18(+) gene product

The fission yeast cdc18(+) gene is required for both initiation of DNA replication and the mitotic checkpoint that normally inhibits mitosis in the absence of DNA replication. The cdc18(+) gene product contains conserved Walker A and B box motifs. Studies of other ATPases have shown that these motifs are required for nucleotide binding and hydrolysis, respectively. We have observed that mutant strains in which either of these motifs is disrupted are inviable. The effects of these mutations were examined by determining the phenotypes of mutant strains following depletion of complementing wild-type Cdc18. In both synchronous and asynchronous cultures, the nucleotide-hydrolysis motif mutant (DE286AA) arrests with a 1C-2C DNA content, and thus exhibits no obvious defects in entry into S phase or in the mitotic checkpoint. In contrast, in cultures synchronized by hydroxyurea arrest and release, the nucleotide-binding motif mutant (K205A) exhibits the null phenotype, with 1C and <1C DNA content, indicating a block in entry into S phase and loss of checkpoint control. In asynchronous cultures this mutant exhibits a mixed phenotype: a percentage of the population displays the null phenotype, while the remaining fraction arrests with a 2C DNA content. Thus, the phenotype exhibited by the K205A mutant is dependent on the cell-cycle position at which wild-type Cdc18 is depleted. These data indicate that both nucleotide binding and hydrolysis are required for Cdc18 function. In addition, the difference in the phenotypes exhibited by the nucleotide-binding and hydrolysis motif mutants is consistent with a two-step model for Cdc18 function in which nucleotide binding and hydrolysis are required for distinct aspects of Cdc18 function that may be executed at different points in the cell cycle.

Clinical usefulness of 3% hydrogen peroxide in acute upper GI bleeding: a pilot study

BACKGROUND

A major problem in the endoscopic management of acute upper gastrointestinal (GI) bleeding is the presence of blood and clots overlying the bleeding source, preventing visualization of the lesion. A simple alternative is to alter the characteristics of blood such that it not only becomes easier to remove but also becomes translucent. We report the results of a pilot study on the use of hydrogen peroxide in patients with acute upper GI bleeding.

METHODS

Patients with acute upper GI bleeding were studied if the presence of blood or clots obscured the site of bleeding. The potential site of bleeding was initially sprayed with 200 mL water and then with 200 mL 3% hydrogen peroxide mixed with simethicone.

RESULTS

In 6 patients with acute upper GI bleeding, hydrogen peroxide spray resulted in good to excellent visualization of the bleeding source. Hemostasis occurred in 2 patients who were actively bleeding. There were no adverse effects or complications.

CONCLUSIONS

Hydrogen peroxide significantly enhanced clot dissolution and endoscopic visualization in patients with acute upper GI bleeding.

Rolling circle amplification of DNA immobilized on solid surfaces and its application to multiplex mutation detection

A new method of amplifying short DNA molecules immobilized on a solid support has been developed. This method uses a solid-phase rolling circle replication reaction, termed rolling circle amplification (RCA). The probe consists of a single-stranded DNA primer anchored at the 5' terminus to a solid support and a single stranded DNA template hybridized to the immobilized primer. Here, DNA ligase was used to circularize the template, and DNA polymerase I was used to extend the immobilized primer in a rolling circle replication reaction. This method was used to identify a known polymorphism in BRCA1 exon 5. These results demonstrate that RCA offers considerable promise to facilitate effective mutation screening of DNA using a solid-phase format.

Proteasome-dependent degradation of the human estrogen receptor

In eukaryotic cells, the ubiquitin-proteasome pathway is the major mechanism for the targeted degradation of proteins with short half-lives. The covalent attachment of ubiquitin to lysine residues of targeted proteins is a signal for the recognition and rapid degradation by the proteasome, a large multi-subunit protease. In this report, we demonstrate that the human estrogen receptor (ER) protein is rapidly degraded in mammalian cells in an estradiol-dependent manner. The treatment of mammalian cells with the proteasome inhibitor MG132 inhibits activity of the proteasome and blocks ER degradation, suggesting that ER protein is turned over through the ubiquitin-proteasome pathway. In addition, we show that in vitro ER degradation depends on ubiquitin-activating E1 enzyme (UBA) and ubiquitin-conjugating E2 enzymes (UBCs), and the proteasome inhibitors MG132 and lactacystin block ER protein degradation in vitro. Furthermore, the UBA/UBCs and proteasome inhibitors promote the accumulation of higher molecular weight forms of ER. The UBA and UBCs, which promote ER degradation in vitro, have no significant effect on human progesterone receptor and human thyroid hormone receptor beta proteins.

Differential localization and activity of the A- and B-forms of the human progesterone receptor using green fluorescent protein chimeras

Subcellular localization and transcriptional activity of green fluorescent protein-progesterone receptor A and B chimeras (GFP-PRA and GFP-PRB) were examined in living mammalian cells. Both GFP-PRA and B chimeras were found to be similar in transcriptional activity compared with their non-GFP counterparts. GFP-PRA and PRA were both weakly active, while GFP-PRB and PRB gave a 20- to 40-fold induction using a reporter gene containing the full-length mouse mammary tumor virus long-terminal repeat linked to the luciferase gene (pLTRluc). Using fluorescence microscopy, nuclear/cytoplasmic distributions for the unliganded and hormone activated forms of GFP-PRA and GFP-PRB were characterized. The two forms of the receptor were found to have distinct intracellular distributions; GFP-PRA was found to be more nuclear than GFP-PRB in four cell lines examined. The causes for and implications of this differential localization of the A and B forms of the human PR are discussed.

Differential sequencing with mass spectrometry

Differential or genetic sequencing requires searching sample DNA for variations with respect to a reference sequence. Conventional detection techniques are too labor and cost expensive for use in diagnostic applications, therefore new technologies will be required. Measurement techniques based on mass spectrometry (MS) possess the potential for high-throughput, high fidelity measurement of sequence variation. Unambiguous detection of polymorphic sequences has been demonstrated, even in heterozygous samples. Automated reproducible measurements of microscopic arrays of samples will enable the high-throughput detection required for large-scale applications. Computational simulation and analysis of experimental parameters prior to experimentation will provide the optimization necessary for development of robust, reproducible measurements.

The Angelman syndrome-associated protein, E6-AP, is a coactivator for the nuclear hormone receptor superfamily

In this study, we found that the E6-associated protein (E6-AP/UBE3A) directly interacts with and coactivates the transcriptional activity of the human progesterone receptor (PR) in a hormone-dependent manner. E6-AP also coactivates the hormone-dependent transcriptional activities of the other members of the nuclear hormone receptor superfamily. Previously, it was shown that E6-AP serves the role of a ubiquitin-protein ligase (E3) in the presence of the E6 protein from human papillomavirus types 16 and 18. Our data show that the ubiquitin-protein ligase function of E6-AP is dispensable for its ability to coactivate nuclear hormone receptors, showing that E6-AP possesses two separable independent functions, as both a coactivator and a ubiquitin-protein ligase. Disruption of the maternal copy of E6-AP is correlated with Angelman syndrome (AS), a genetic neurological disorder characterized by severe mental retardation, seizures, speech impairment, and other symptoms. However, the exact mechanism by which the defective E6-AP gene causes AS remains unknown. To correlate the E6-AP coactivator function and ubiquitin-protein ligase functions with the AS phenotype, we expressed mutant forms of E6-AP isolated from AS patients and assessed the ability of each of these mutant proteins to coactivate PR or provide ubiquitin-protein ligase activity. This analysis revealed that in the majority of the AS patients examined, the ubiquitin-protein ligase function of E6-AP was defective whereas the coactivator function was intact. This finding suggests that the AS phenotype results from a defect in the ubiquitin-proteosome protein degradation pathway.

Discrimination of DNA duplexes with matched and mismatched tandem repeats by T4 endonuclease VII

A simple in situ method for scoring short tandem DNA repeat length has been developed using T4 endonuclease VII. This method measures tandem repeated simple sequences embedded in unique sequences. Single-stranded loops are formed on duplexes containing mismatched (different) numbers of tandem repeats. No single stranded loops are formed on structures containing matched (identical) numbers of tandem repeats. The matched and mismatched loop structures were distinguished and differentially labeled by enzymatic treatment with T4 endonuclease VII.

High polymorphism level of genomic sequences flanking insertion sites of human endogenous retroviral long terminal repeats

The polymorphism at the multitude of loci adjacent to human endogenous retrovirus long terminal repeats (LTRs) was analyzed by a technique for whole genome differential display based on the PCR suppression effect that provides selective amplification and display of genomic sequences flanking interspersed repeated elements. This strategy is simple, target-specific, requires a small amount of DNA and provides reproducible and highly informative data. The average frequency of polymorphism observed in the vicinity of the LTR insertion sites was found to be about 12%. The high incidence of polymorphism within the LTR flanks together with the frequent location of LTRs near genes makes the LTR loci a useful source of polymorphic markers for gene mapping.

A review of digital image networking technologies for radiation oncology treatment planning

Dosimetrists, physicists, and physicians rely heavily upon digital imaging modalities in their daily work. In the current healthcare marketplace, many radiotherapy facilities operate satellite centers or may be undergoing mergers with other service providers in their community. As a consequence, the development of network-based radiotherapy image communication may yield a significant impact on the clinical operation of such centers. Digital image networking will become an everyday tool in radiotherapy treatment planning in the near future. As responsible users of this technology, an accurate perception of what the network does is essential and enhances our ability to utilize it. This article presents a review of the network architecture and transmission standards necessary for understanding and developing a radiotherapy image network.

Postcastration eventration in 18 horses: the prognostic indicators for long-term survival (1985-1995)

Castration of horses is considered a common and routine surgical procedure, but the potential for complications is high. By far the most serious of these is eventration. The objectives of this study were to determine the long-term survival of horses undergoing surgical treatment of indirect (1) inguinal eventration of the small intestine following castration, and to identify prognostic indicators for survival. The case records of 18 horses undergoing surgical treatment of postcastration eventration (PCE) between 1985 and 1995 were reviewed. Follow-up information was obtained by telephone interviews 2 to 13 y postoperatively. A Cox proportional hazard regression model was fitted to determine which clinical features were of significant influence to survival. Clinical features with a significant negative influence on survival were an inguinal surgical approach for correction, an increased length of prolapsed bowel, and performance of bowel resection and anastomosis. Significant postoperative complications developed in 89% of cases; 44% of cases in the "inguinal" surgical approach group developed peritonitis, compared with 10% in the "midline" approach group. Of all horses in this study, 72% were discharged from the hospital; however, only 40% of horses in the inguinal approach group were discharged. The long term survival rate (> 1 y) for all horses in this study was 44%, with a median survival time of 3-1/2 mo.

Renal stone analysis: is there any clinical value?

It has usually been assumed that the analysis of recovered renal stones should be routinely done. This concept has recently been challenged. Very little work has been done to correlate analytical results with clinical findings and the impact of this information on clinical management. This paper reviews current concepts of stone formation, how this information can be used to interpret stone analysis results and how stone analyses results can be used in clinical-decision-making.

In vitro glucocorticoid receptor binding and transcriptional activation by topically active glucocorticoids

Mometasone furoate (MF, CAS 83919-23-7, Sch 32088), budesonide (BUD, CAS 51372-29-3), fluticasone propionate (FP, CAS 80474-14-2), and triamcinolone acetonide (TA, CAS-76-25-5) are corticosteroids that are either currently available or under development for allergic rhinitis and asthma. The relative affinity of these drugs for the glucocorticoid receptor and their ability to stimulate glucocorticoid receptor-mediated transactivation of gene expression were analyzed. All of the test compounds had a higher affinity for the recombinant glucocorticoid receptor than the reference glucocorticoid receptor ligand, dexamethasone (DEX, CAS 50-02-2). In addition, all compounds showed greater potency than dexamethasone in stimulating transcription of a synthetic target gene regulated by a glucocorticoid response element. Of the compounds tested, mometasone furoate had the highest relative binding affinity for the glucocorticoid receptor, followed by fluticasone propionate, budesonide, and triamcinolone acetonide. Similarly, mometasone furoate was the most potent stimulator of glucocorticoid receptor-mediated transactivation of gene expression, followed by fluticasone propionate, tri-amcinolone acetonide, and budesonide. These in vitro studies provide a sensitive means to compare the potency of glucocorticoids and may reliably predict the in vivo topical potency of these drugs.

PROFILE: Sailing the Shoals of Adaptive Management: The Case of Salmon in the Pacific Northwest

/ Emerging ecosystem science builds on adaptive management as an approach to dealing with salmon problems in the Pacific Northwest. Adaptive management brings scientific and democratic processes together. However, managers, the public, resource users, and scientists differ in their views on the causes of salmon decline. Managers emphasize habitat loss and over-harvest as the primary causes; commercial fishers point to habitat loss, management practices, and predators; and the public gives greatest weight to water pollution and ocean drift nets. Scientific studies of salmon often produce results that seem contradictory or unclear to the public. For adaptive management to be effective, scientists' and the public need to better understand one another's perspectives.KEY WORDS: Perception; Fishery management; Salmon; Pacific Northwest; Science

Functional subnuclear partitioning of transcription factors

After many years of reductionistic approaches to characterize molecular mechanisms involved in transcription, the number of factors recognized to take part in this process has increased remarkably and continues to grow. When considering posttranslational modifications in conjunction with the large number of factors involved in modulating the activity of transcription complex components, the overall intricacy becomes staggering. After two decades of intensive molecular investigations, there has been a concerted effort to integrate these findings with cellular approaches to understand transcription on a more global level. This sort of reasoning actually revisits studies of approximately 20 years ago that considered the functional consequences of steroid receptor association with nuclear structure. With an abundance of new molecular probes and increasingly powerful instruments to detect them in fixed and, more recently, live cells, the issue of functional subnuclear organization is receiving increased attention. In this report, we focus on advances in characterizing the functional significance of transcription factor association with the nucleoskeleton. In particular, we consider recent biochemical and "molecular morphology" data that point to the importance of dynamic spatial and solubility partitioning of gene regulators with nuclear architecture.

Current perspectives on pain upon injection of drugs

A limitation in the administration of parenteral products is the pain caused upon injection. Injection site pain has been predominately associated with intravenous, intramuscular, and subcutaneous administration. It becomes important for the formulation scientist to have a basic understanding of the physiology underlying the pain process, as well as the pharmaceutical factors associated with injection site pain. Initially, this review will provide the reader with a primer on the mediation of pain in the periphery and a compilation of those drugs that have been associated with pain on injection. In addition, this review will present important considerations and general formulation approaches or methods that have been used to overcome pain on injection. Finally, a brief overview of the various experimental systems used to investigate injection site pain is discussed.