PubMed Health⌕ Search

Biomedical subjects

D Metzger

Publications and source records attributed to D Metzger.

At least 37 records · Page 2Linked to original sources
PubMed2000

Characterization of the fasting-induced adipose factor FIAF, a novel peroxisome proliferator-activated receptor target gene.

Fasting is associated with significant changes in nutrient metabolism, many of which are governed by transcription factors that regulate the expression of rate-limiting enzymes. One factor that plays an important role in the metabolic response to fasting is the peroxisome proliferator-activated receptor alpha (PPARalpha). To gain more insight into the role of PPARalpha during fasting, and into the regulation of metabolism during fasting in general, a search for unknown PPARalpha target genes was performed. Using subtractive hybridization (SABRE) comparing liver mRNA from wild-type and PPARalpha null mice, we isolated a novel PPARalpha target gene, encoding the secreted protein FIAF (for fasting induced adipose factor), that belongs to the family of fibrinogen/angiopoietin-like proteins. FIAF is predominantly expressed in adipose tissue and is strongly up-regulated by fasting in white adipose tissue and liver. Moreover, FIAF mRNA is decreased in white adipose tissue of PPARgamma +/- mice. FIAF protein can be detected in various tissues and in blood plasma, suggesting that FIAF has an endocrine function. Its plasma abundance is increased by fasting and decreased by chronic high fat feeding. The data suggest that FIAF represents a novel endocrine signal involved in the regulation of metabolism, especially under fasting conditions.

Adipose Tissue↗
PubMed2000

p300 mediates functional synergism between AF-1 and AF-2 of estrogen receptor alpha and beta by interacting directly with the N-terminal A/B domains.

Estrogen receptor (ER) alpha and beta mediate estrogen actions in target cells through transcriptional control of target gene expression. For 17beta-estradiol-induced transactivation, the N-terminal A/B domain (AF-1) and the C-terminal E/F domain (AF-2) of ERs are required. Ligand binding is considered to induce functional synergism between AF-1 and AF-2, but the molecular mechanism remains unknown. To clarify this synergism, we studied the role of reported AF-2 coactivators, p300/CREB binding protein, steroid receptor coactivator-1/transcriptional intermediary factor-2 (SRC-1/TIF2) family proteins and thyroid hormone receptor-associated protein-220/(vitamin D3 receptor-interacting protein- 205-(TRAP220/DRIP205) on the AF-1 activity in terms of synergism with the AF-2 function. We found that neither any of the SRC-1/TIF2 family coactivators nor TRAP220/DRIP205 is potent, whereas p300 potentiates the AF-1 function of both human ERalpha and human ERbeta. Direct interactions of p300 with the A/B domains of ERalpha and ERbeta were observed in an in vitro glutathione S-transferase pull-down assay in accordance with the interactions in yeast and mammalian two-hybrid assays. Furthermore, mutations in the p300 binding sites (56-72 amino acids in ERalpha and 62-72 amino acids in ERbeta) in the A/B domains caused a reduction in ligand-induced transactivation functions of both ERalpha and ERbeta. Thus, these findings indicate that ligand-induced functional synergism between AF-1 and AF-2 is mediated through p300 by its direct binding to the A/B regions of ERalpha and ERbeta.

Animals↗
PubMed2000

Temporally controlled somatic mutagenesis in smooth muscle.

Ligand-dependent site-specific recombinases are powerful tools to engineer the mouse genome in specific somatic cell types at selected times during pre- and postnatal development. Current efforts are primarily directed towards increasing the efficiency of this recombination system in mice. We have generated transgenic mouse lines expressing a tamoxifen-activated Cre recombinase, CreER(T2), under the control of the smooth muscle-specific SM22 promoter. Both a randomly integrated transgene [SM-CreER(T2)(tg)] and a transgene that has been "knocked in" into the endogenous SM22 locus [SM-CreER(T2)(ki)] were expressed in smooth muscle-containing tissues. The level of CreER(T2) expression and tamoxifen-induced recombination was lower in SM-CreER(T2)(tg) mice compared with SM-CreER(T2)(ki) mice. Whereas no recombinase activity could be detected in vehicle-treated SM-CreER(T2)(ki) mice, administration of tamoxifen induced the excision of a loxP-flanked reporter transgene in up to 100% of smooth muscle cells. The recombined genome persisted for at least four months after tamoxifen treatment. SM-CreER(T2)(ki) transgenic mice should be useful to study the effects of various somatic mutations in smooth muscle.

Animals↗
PubMed2000

A Brg1 null mutation in the mouse reveals functional differences among mammalian SWI/SNF complexes.

Mammalian SWI/SNF complexes utilize either brahma (Brm) or brahma-related gene 1 (Brg1) catalytic subunits to remodel nucleosomes in an ATP-dependent manner. Brm was previously shown to be dispensable, suggesting that Brm and Brg1 are functionally redundant. To test this hypothesis, we have generated a Brg1 null mutation by gene targeting, and, surprisingly, homozygotes die during the periimplantation stage. Furthermore, blastocyst outgrowth studies indicate that neither the inner cell mass nor trophectoderm survives. However, experiments with other cell types demonstrate that Brg1 is not a general cell survival factor. In addition, Brg1 heterozygotes are predisposed to exencephaly and tumors. These results provide evidence that biochemically similar chromatin-remodeling complexes have dramatically different functions during mammalian development.

Animals↗
PubMed2000

[Whole-body cryotherapy in rehabilitation of patients with rheumatoid diseases--pilot study].

UNLABELLED: Cryotherapy as a whole-body cold therapy (with cold air cooled by addition of nitrogen blown on the patients in an open cabin) for treatment of inflammatory rheumatic diseases already started in Bad Säckingen in 1986. In 1996, a new cold chamber (this time a closed chamber without any addition of nitrogen) based on compressor technology was introduced. The aim of our study was to test whether significant pain relief could be achieved by means of this cold therapy. Furthermore, we were interested in the practicability and acceptance of this new technique. Wellbeing during the treatment application and pain level were assessed using verbal and numerical rating scales. The sample consisted of 120 consecutive patients (75% women, age: 30-67 yrs, M = 52.6 yrs). These patients were suffering from primary fibromyalgia (40.7%), rheumatoid arthritis (17.3%), chronic low back pain (16.4%), ankylosing spondylitis (10.9%), osteoarthritis (9.1%), secondary fibromyalgia (3.6%) and other autoimmune diseases (1.8%) (mean duration of symptoms: 4 yrs). The patients were treated 2.5 minutes on average in the main chamber (mean temperature: -105 degrees C). The patients' statements concerning their pain level were analyzed by means of analyses of variance with repeated measures and paired-sample t-tests. RESULTS: The pain level after application of the cold therapy decreases significantly. The pain reduction lasts about 90 minutes. The initial pain level decreases during the whole time of treatment, no significant improvement, though, can be shown from the middle to the end of the four-weeks treatment. According to the results of our study, there is evidence that the whole-body cold therapy generates important short-term effects and somewhat weaker effects over the treatment period as a whole. Short-term pain reduction facilitates intensive application of physiotherapy and Occupational Therapy. The treatment procedure is practicable, and all in all well tolerated. From the patients' point of view, whole-body cold therapy is an essential part of the rehabilitation programme.

Adult↗
PubMed2000

Targeted somatic mutagenesis in mouse epidermis.

Gene targeting in the mouse is a powerful tool to study mammalian gene function. The possibility to efficiently introduce somatic mutations in a given gene, at a chosen time and/or in a given cell type will further improve such studies, and will facilitate the generation of animal models for human diseases. To create targeted somatic mutations in the epidermis, we established transgenic mice expressing the bacteriophage P1 Cre recombinase or the tamoxifen-dependent Cre-ER(T2) recombinase under the control of the human keratin 14 (K14) promoter. We show that LoxP flanked (floxed) DNA segments were efficiently excised in epidermal keratinocytes of K14-Cre transgenic mice. Furthermore, Tamoxifen administration to adult K14-Cre-ER(T2) mice efficiently induced recombination in the basal keratinocytes, whereas no background recombination was detected in the absence of ligand treatment. These two transgenic lines should be very useful to analyse the functional role of a number of genes expressed in keratinocytes.

Animals↗
PubMed1999

Temporally-controlled site-specific mutagenesis in the basal layer of the epidermis: comparison of the recombinase activity of the tamoxifen-inducible Cre-ER(T) and Cre-ER(T2) recombinases.

Conditional DNA excision between two LoxP sites can be achieved in the mouse using Cre-ER(T), a fusion protein between a mutated ligand binding domain of the human estrogen receptor (ER) and the Cre recombinase, the activity of which can be induced by 4-hydroxy-tamoxifen (OHT), but not natural ER ligands. We have recently characterized a new ligand-dependent recombinase, Cre-ER(T2), which was approximately 4-fold more efficiently induced by OHT than Cre-ER(T) in cultured cells. In order to compare the in vivo efficiency of these two ligand-inducible recombinases to generate temporally-controlled somatic mutations, we have engineered transgenic mice expressing a LoxP-flanked (floxed) transgene reporter and either Cre-ER(T) or Cre-ER(T2) under the control of the bovine keratin 5 promoter that is specifically active in the epidermis basal cell layer. No background recombinase activity could be detected, while recombination was induced in basal keratinocytes upon OHT administration. Interestingly, a dose-response study showed that Cre-ER(T2) was approximately 10-fold more sensitive to OHT induction than Cre-ER(T).

Animals↗
PubMed1999

Mammalian TAF(II)30 is required for cell cycle progression and specific cellular differentiation programmes.

The two alleles of the 30 kDa TATA-binding protein associated factor (TAF(II)30) gene, have been targeted by homologous recombination in murine F9 embryonal carcinoma cells and subsequently disrupted using a Cre recombinase-loxP strategy. The TAF(II)30-null cells are not viable, but are rescued by the expression of human TAF(II)30. Cells lacking TAF(II)30 are blocked in G(1)/G(0) phase of the cell cycle and undergo apoptosis. In agreement with the G(1) arrest phenotype, the expression of cyclin E is impaired and the retinoblastoma protein is hypophosphorylated in the TAF(II)30-null cells. Interestingly, retinoic acid (RA) treatment prevented TAF(II)30-null cell death and induced primitive endodermal differentiation. In contrast, the RA- and cAMP-induced parietal endodermal differentiation was impaired in the TAF(II)30-null cells. Thus, TAF(II)30 is not indispensable for class II gene transcription in general, but seems to be required for the expression of a subset of genes.

Animals↗
PubMed1999

Non-injection substance use correlates with risky sex among men having sex with men: data from HIVNET.

Associations between substance use and sexual behavior were examined among 3220 seronegative men who have sex with men (MSM) in a HIV vaccine preparedness study. Relationships between current and past substance use and current sexual risk were evaluated using crude odds ratios and logistic regression to adjust for confounding variables. Heroin and injection drug use were uncommon (< 2%). Substances most often used were alcohol (89%), marijuana (49%), nitrite inhalants (29%), amphetamines or similarly acting stimulants (21%), cocaine 14% and hallucinogens (14%). Increased adjusted odds for unprotected sex were significantly associated with current heavy alcohol use (OR 1.66; CI 1.18, 2.33), past alcohol problems (OR 1.25; CI 1.05, 1.48), and current drug use (OR 1.26; CI 1.08, 1.48). When associations with specific drugs and nitrite inhalants were examined separately, current use of cocaine and other stimulants (OR 1.25; CI 1.01, 1.55), hallucinogens (OR 1.40; CI 1.10, 1.77), and nitrite inhalants (some (OR 1.61; CI 1.35, 1.92); heavy (OR 2.18; CI 1.48, 3.20)), were independently associated with unprotected sex. Those with past drug use or past heavy alcohol use but not currently using demonstrated no increase in sexual risk, suggesting an important role for substance-focused interventions in risk reduction efforts among MSM.

AIDS Vaccines↗
PubMed1999

Engineering the mouse genome by site-specific recombination.

Site-specific recombination systems are powerful tools for introducing predetermined modifications into eukaryotic genomes. Recent advances allow the manipulation of chromosomal DNA in a spatially and temporally controlled manner in mice, offering unprecedented possibilities for studying mammalian genome function and for generating animal models for human diseases.

Animals↗
PubMed1999

Periampullary carcinomas: a special entity of duodenal tumors.

DEFINITION: Periampullary carcinomas are rare and constitute a special entity, as diagnosed earlier and having a better prognosis than other duodenal tumors. METHODS: In the present study, we retrospectively reviewed the medical records of 16 patients with periampullary carcinomas over 10 years. RESULTS: 16 patients, 10 men and 6 women (median age 66.7 years, range 42-80) had a malignant periampullary tumor. Initial symptoms were jaundice (88%), weight loss (69%), nausea and vomiting (50%) and abdominal pain (38%). Gastro-duodenoscopy, ERCP, ultrasound and CT scan were the most useful diagnostic tools. Histologically all the tumors were adenocarcinomas and solitary tumors. 91% were stage pT1 or pT2 tumors, localized in the duodenal wall without any infiltration of the pancreas. 36% of the tumors had metastasized either in lymph nodes or distant organs at diagnosis (18% pN1, 18% pM1). Resectability rate was 81%, curative resection was achieved in 62%. The operations performed were pancreatico-duodenectomy (n = 8), local tumor resection (n = 5) and palliative bypass (n = 3). Morbidity and reoperation rate were 37.5% and 18.8%, respectively; 30-day mortality was 0%. The 1- and 5-year survival rates were 58.3% and 33.3%, respectively. CONCLUSIONS: Compared to carcinomas of the small bowel or the exocrine pancreas periampullary carcinomas have a far better 5-year survival rate of more than 30%. Aggressive diagnostic workup in case of the leading symptom jaundice and radical operative therapy are key factors to achieve this goal.

Adult↗
PubMed1999

Purification and identification of p68 RNA helicase acting as a transcriptional coactivator specific for the activation function 1 of human estrogen receptor alpha.

The estrogen receptor (ER) regulates the expression of target genes in a ligand-dependent manner. The ligand-dependent activation function AF-2 of the ER is located in the ligand binding domain (LBD), while the N-terminal A/B domain (AF-1) functions in a ligand-independent manner when isolated from the LBD. AF-1 and AF-2 exhibit cell type and promoter context specificity. Furthermore, the AF-1 activity of the human ERalpha (hERalpha) is enhanced through phosphorylation of the Ser(118) residue by mitogen-activated protein kinase (MAPK). From MCF-7 cells, we purified and cloned a 68-kDa protein (p68) which interacted with the A/B domain but not with the LBD of hERalpha. Phosphorylation of hERalpha Ser(118) potentiated the interaction with p68. We demonstrate that p68 enhanced the activity of AF-1 but not AF-2 and the estrogen-induced as well as the anti-estrogen-induced transcriptional activity of the full-length ERalpha in a cell-type-specific manner. However, it did not potentiate AF-1 or AF-2 of ERbeta, androgen receptor, retinoic acid receptor alpha, or mineralocorticoid receptor. We also show that the RNA helicase activity previously ascribed to p68 is dispensable for the ERalpha AF-1 coactivator activity and that p68 binds to CBP in vitro. Furthermore, the interaction region for p68 in the ERalpha A/B domain was essential for the full activity of hERalpha AF-1. Taken together, these findings show that p68 acts as a coactivator specific for the ERalpha AF-1 and strongly suggest that the interaction between p68 and the hERalpha A/B domain is regulated by MAPK-induced phosphorylation of Ser(118).

Adenocarcinoma↗
PubMed1998

A chimeric Cre recombinase inducible by synthetic,but not by natural ligands of the glucocorticoid receptor.

We have developed a new ligand-dependent chimeric recombinase (Cre-GRdex) by fusing the site-specific Cre recombinase to the ligand binding domain (LBD) of a mutant human glucocorticoid receptor (GRdex). The synthetic glucocorticoid receptor (GR) ligands dexamethasone, triamcinolone acetonide and RU38486efficiently induce recombinase activity in F9 murine embryonal carcinoma cells expressing constitutively Cre-GRdex. In contrast, no recombinase activity was detected in the absence of ligand or in the presence of the natural GR ligands corticosterone, cortisol or aldosterone. Moreover, physiological concentrations of these natural GR ligands do not affect Cre-GRdexrecombinase activity induced by dexamethasone. Thus, as previously shown using Cre-oestrogen receptor (ER) fusion proteins, Cre-GRdexmight be useful for achieving loxP site-directed mutagenesis in cultured cells and spatio-temporally controlled somatic cell mutagenesis in transgenic mice.

Aldosterone↗
PubMed1998

Readiness of high-risk populations in the HIV Network for Prevention Trials to participate in HIV vaccine efficacy trials in the United States.

OBJECTIVE: To determine the willingness of populations at high risk of HIV-1 infection to participate in HIV vaccine efficacy trials, determine factors influencing decision-making, and evaluate knowledge levels of vaccine trial concepts. DESIGN: Cross-sectional study. METHODS: HIV-1-negative homosexual men, male and female injecting drug users and non-injecting women at heterosexual risk were recruited in eight cities in the United States (n=4892). RESULTS: A substantial proportion of the study population (77%) would definitely (27%) or probably (50%) be willing to participate in a randomized vaccine efficacy trial. Increased willingness was associated with high-risk behaviors, lower education level, being uninsured or covered by public insurance, and not having been in a previous vaccine preparedness study. Altruism and a desire for protection from the vaccine were major motivators for participation. Major concerns included positive HIV-1 antibody test due to vaccine, safety of the vaccine, and possible problems with insurance or foreign travel. Baseline knowledge of vaccine trial concepts was low. CONCLUSIONS: It is likely that high-risk volunteers will be willing to enroll in HIV vaccine efficacy trials. A variety of participant and community educational strategies are needed to address participant concerns, and to ensure understanding of key concepts prior to giving consent for participation.

AIDS Vaccines↗
PubMed1998

Mouse P450RAI (CYP26) expression and retinoic acid-inducible retinoic acid metabolism in F9 cells are regulated by retinoic acid receptor gamma and retinoid X receptor alpha.

We have cloned a mouse cDNA homolog of P450RAI, a cytochrome P450 belonging to a new family (CYP26), which has previously been isolated from zebrafish and human cDNAs and found to encode a retinoic acid-inducible retinoic acid hydroxylase activity. The cross-species conservation of the amino acid sequence is high, particularly between the mouse and the human enzymes, in which it is over 90%. Like its human and zibrafish counterparts, the mouse P450RAI cDNA catalyzes metabolism of retinoic acid into 4-OH-retinoic acid, 4-oxo-retinoic acid, 18-OH-retinoic acid, and unidentified water-soluble metabolites when transfected into COS-1 cells. Retinoic acid-inducible retinoic acid metabolism has previously been observed in F9 murine embryonal carcinoma cells and some derivatives lacking retinoid receptors. We were interested in determining whether P450RAI could be responsible for retinoic acid metabolism in F9 cells and in studying the effect of retinoid receptor ablation on P450RAI expression. In wild-type F9 cells and derivatives lacking RAR gamma, RAR alpha, and/or RXR alpha, we observed a direct relationship between the level of retinoic acid metabolic activity and retinoic acid-induced P450RAI mRNA. These experiments, as well as others using synthetic receptor subtype-specific retinoids, suggest that the RAR gamma and RXR alpha receptors mediate the effects of retinoic acid on the expression of the P450RAI gene.

Amino Acid Sequence↗
PubMed1998

Immunostimulatory activity of LT-IIa, a type II heat-labile enterotoxin of Escherichia coli.

Certain bacterial molecules potentiate immune responses to parenterally administered antigens. One such molecule that has been intensely investigated is cholera toxin, a type I heat-labile enterotoxin produced by the Gram-negative bacterium Vibrio cholerae. Immunization with a mixture of a foreign antigen and cholera toxin enhances the immune response to the antigen. Similar adjuvant activity is associated with LT-I, a closely related type I heat-labile enterotoxin produced by Escherichia coli. The adjuvant activities of LT-IIa, a member of the type II heat-labile enterotoxins produced by E. coli, have not been described. LT-IIa and CT differ significantly in amino acid sequence of the B polypeptides and in receptor binding affinity. In this study, rats were subcutaneously immunized with fimbrillin, a protein isolated from the bacterium Porphyromonas gingivalis, and with fimbrillin in combination with LT-IIa, the prototypical type II enterotoxin. Previous studies documented that fimbrillin administered alone is a poor immunogen. Animals immunized with the mixture of fimbrillin and LT-IIa produced high titers of specific IgG antibody directed against fimbrillin. Anti-fimbrillin antibody titers in sera from animals receiving the combination of LT-IIa + fimbrillin were comparable to those obtained from sera of animals immunized with cholera toxin + fimbrillin. The results of these experiments demonstrate that LT-IIa exhibits an adjuvant activity that is equal to that of cholera toxin. Recombinant methods have been established for producing large amounts of LT-IIa, an advantage that will likely provide an economic impetus to consider incorporating the enterotoxin as an immunostimulatory agent in future vaccines.

Adjuvants, Immunologic↗