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W Schaffner

Publications and source records attributed to W Schaffner.

At least 55 records · Page 3Linked to original sources
PubMed2000

Characterization of the mouse gene for the heavy metal-responsive transcription factor MTF-1.

MTF-1 is a zinc finger transcription factor that mediates the cellular response to heavy metal stress; its targeted disruption in the mouse leads to liver decay and embryonic lethality at day E14. Recently, we have sequenced the entire MTF-1 gene in the compact genome of the pufferfish Fugu rubripes. Here we have defined the promoter sequences of human and mouse MTF-1 and the genomic structure of the mouse MTF-1 locus. The transcription unit of MTF-1 spans 42 kb (compared to 8.5 kb in Fugu) and is located downstream of the gene for a phosphatase (INPP5P) in mouse, human, and fish. In all of these species, the MTF promoter region has the features of a CpG island. In both mouse and human, the 5' untranslated region harbors conserved short reading frames of unknown function. RNA mapping experiments revealed that in these two species, MTF-1 mRNA is transcribed from a cluster of multiple initiation sites from a TATA-less promoter without metal-responsive elements. Transcription from endogenous and transfected MTF-1 promoters was not affected by heavy metal load or other stressors, in support of the notion that MTF-1 activity is regulated at the posttranscriptional level. Tissue Northern blots normalized for poly A+ RNA indicate that MTF-1 is expressed at similar levels in all tissues, except in the testes, that contain more than 10-fold higher mRNA levels.

5' Untranslated Regions↗
PubMed1999

Transmission of tuberculosis in a jail.

BACKGROUND: Outbreaks of tuberculosis are uncommonly recognized in jails. In 1996, an increase in active tuberculosis cases was noted among inmates of a large urban jail. OBJECTIVES: To determine the source and extent of a tuberculosis outbreak in an urban jail and to recommend control measures. DESIGN: Retrospective cohort study. SETTING: Urban jail. PATIENTS: Inmates and guards with tuberculosis. INTERVENTION: Outbreak evaluation and control. MEASUREMENTS: Medical records of inmates and guards with tuberculosis were reviewed, and inmates were interviewed. DNA fingerprinting was performed on Mycobacterium tuberculosis isolates. RESULTS: From 1 January 1995 through 31 December 1997, active tuberculosis was diagnosed in 38 inmates and 5 guards from the jail. Nineteen (79%) of the 24 culture-positive inmates had isolates with DNA fingerprints matching those of other inmates. Isolates from both culture-positive guards matched the predominant inmate strain; only 6 (14%) of 43 isolates from infected persons in the community had this pattern. The median length of incarceration of all inmates in the jail was 1 day; the median length of continuous incarceration before diagnosis of tuberculosis in inmates was 138 days. Inmates with tuberculosis had been incarcerated a median of 15 times. Forty-three percent of persons in this city with tuberculosis diagnosed from January 1995 through July 1997 had been incarcerated in the jail at some time before diagnosis. CONCLUSIONS: Traditional and molecular epidemiologic investigations suggest that tuberculosis was transmitted among inmates and guards in an urban jail. Aggressive measures to screen for active tuberculosis upon incarceration are important for preventing spread of disease in jails and to the surrounding community.

Cohort Studies↗
PubMed1999

Phytoestrogen kaempferol (3,4',5,7-tetrahydroxyflavone) protects PC12 and T47D cells from beta-amyloid-induced toxicity.

In clinical studies, it has been shown that estrogen replacement therapy in menopause is strongly correlated with a reduced risk of the development of Alzheimer's disease (AD). In in vitro experiments, it was demonstrated that estradiol protects cells against the toxic effects of beta-amyloid, the major component of plaques in brains of AD patients. Therefore, estrogens have become interesting candidates for a possible treatment of neurodegeneration. In plants, a class of compounds has been identified that bind to human estrogen receptor, so-called phytoestrogens, which are part of our daily diet. Here, we compared the effects of alpha- and beta-estradiol with plant-derived kaempferol on beta-amyloid peptide-induced toxicity in PC12 neuroblastoma and T47D human breast cancer cells. The present results demonstrate a protective effect of kaempferol comparable to that observed with estradiol. The effects of the weak estrogen receptor agonists alpha-estradiol and kaempferol were found to be similar to the effects of the strong estrogen receptor agonist beta-estradiol, suggesting a mode of action independent from the nuclear estrogen receptor.

Alzheimer Disease↗
PubMed1999

Carriage of multidrug-resistant Streptococcus pneumoniae and impact of chemoprophylaxis during an outbreak of meningitis at a day care center.

Three cases of meningitis due to multidrug-resistant serotype 14 Streptococcus pneumoniae occurred at a day care center (DCC) over 5 days. Cultures of nasopharyngeal samples were done at the index DCC, 2 comparison DCCs, and a pediatrics practice. Isolates were serotyped and subtyped by pulsed-field gel electrophoresis (PFGE) with SmaI. Pneumococcal carriage rates ranged from 44%-65% at the 3 DCCs and 29% in the pediatrics practice. Carriage of multidrug-resistant serotype 14 S. pneumoniae was noted in 13%-19% of children at the 3 DCCs. An outbreak strain was identified by PFGE at the index DCC and 1 other DCC; a closely related strain was found in the third DCC. Carriage of the outbreak strain was associated with being age 0-24 months, antibiotic use, upper respiratory tract infections, and otitis media. DCC contacts of the ill children were offered chemoprophylaxis with rifampin and clindamycin, which produced a profound but transient decrease in carriage. No additional cases occurred.

Bacterial Vaccines↗
PubMed1999

Newly recognized focus of La Crosse encephalitis in Tennessee.

La Crosse virus is a mosquito-borne arbovirus that causes encephalitis in children. Only nine cases were reported in Tennessee during the 33-year period from 1964-1996. We investigated a cluster of La Crosse encephalitis cases in eastern Tennessee in 1997. Medical records of all suspected cases of La Crosse virus infection at a pediatric referral hospital were reviewed, and surveillance was enhanced in the region. Previous unreported cases were identified by surveying 20 hospitals in the surrounding 16 counties. Mosquito eggs were collected from five sites. Ten cases of La Crosse encephalitis were serologically confirmed. None of the patients had been discharged from hospitals in the region with diagnosed La Crosse encephalitis in the preceding 5 years. Aedes triseriatus and Aedes albopictus were collected at the case sites; none of the mosquitos had detectable La Crosse virus. This cluster may represent an extension of a recently identified endemic focus of La Crosse virus infection in West Virginia.

Adolescent↗
PubMed1999

Family cluster of Rocky Mountain spotted fever.

Soon after a patient from Tennessee died of Rocky Mountain spotted fever (RMSF), several family members developed symptoms suggestive of the disease and were treated presumptively for RMSF. Fifty-four persons visiting the index patient's home were interviewed; serum samples were collected from 35. Three additional cases of RMSF were confirmed, all of which occurred in first-degree relatives. Time spent at the family home and going into the surrounding woods were significantly associated with developing antibodies to Rickettsia rickettsii. Ticks were collected and examined for rickettsiae by polymerase chain reaction analysis. Because hyperendemic foci and family clusters of RMSF can occur, when a case is suspected clinicians should be vigilant for signs and symptoms consistent with R. rickettsii infection in other persons who may have been similarly exposed.

Antibodies, Bacterial↗
PubMed1999

Characterization of the transcription factor MTF-1 from the Japanese pufferfish (Fugu rubripes) reveals evolutionary conservation of heavy metal stress response.

The pufferfish Fugu rubripes was recently introduced as a new model organism for genomic studies, since it contains a full set of vertebrate genes but only 13% as much DNA as a mammal. Fugu genes tend to be smaller and densely spaced due to shortening of introns and intergenic spacers. We isolated the Fugu gene for the metal-responsive transcription factor MTF-1 (MTF1), a mediator of heavy metal regulation and oxidative stress response previously characterized in mammals. In addition, most of the cDNA sequence was also determined. The 780 amino acid MTF-1 protein of Fugu is very similar to that of mouse and human, with 90% amino acid identity in the DNA binding zinc finger domain and 57% overall identity. Expression of the pufferfish cDNA in mammalian cells shows that Fugu MTF-1 has the same DNA binding specificity as its mammalian counterpart and also induces transcription in response to zinc and cadmium. The protein-coding part of the Fugu MTF-1 gene spans 6.4 kb and consists of 11 exons. Upstream region and first exon constitute a CpG island. The distance between stop codon and polyadenylation motifs is >2 kb, suggesting a very long 3' untranslated mRNA region, followed by another CpG island which may represent the promoter of the next gene downstream. Part of the MTF-1 genomic structure was also determined in the mouse, and some striking similarities were found: for example, the upstream adjacent gene in both species is INPP5P, encoding a phosphatase. The mouse MTF-1 promoter is also embedded in a CpG island, which however shares no sequence similarity to the one of Fugu. The Fugu CpG island is shorter than the one of the mouse and has no elevated [G+C] content; these and other data indicate that CpG islands of fish may represent a primordial stage of CpG island evolution.

Amino Acid Sequence↗
PubMed1999

The heavy metal-responsive transcription factor-1 (MTF-1) is not required for neural differentiation.

The zinc finger transcription factor MTF-1 is essential for proper response to heavy metal load and other stress conditions in vertebrates, and also contributes to the maintenance of the cellular redox state. Target genes include metallothioneins (MT-I and MT-II) and gamma-glutamylcysteine synthetase (gamma-GCS), an enzyme involved in glutathione biosynthesis. Although MTF-1 is expressed ubiquitously, the primary defect in null mutant mice is hepatocyte necrosis, which results in embryonic lethality around day E14 and prevents the analysis of delayed effects on other organs. To assess the impact of MTF-1 deficiency on the function of the mature central nervous system, we employed the neural grafting strategy. Neuroectodermal brain tissue obtained from transgenic mouse embryos at gestational day 12.5 was transplanted into the caudoputamen of adult wild-type mice. 33 days later, grafts derived from MTF-1 deficient mice consisted of fully differentiated neuroectodermal tissue and showed no differences to heterozygous control grafts. This indicates that MTF-1 is dispensable for the development and differentiation of the nervous system. Such transplants devoid of MTF-1 may provide a useful tool for the further investigation of the effect of cell stress, including oxidative stress.

Animals↗
PubMed1998

Embryonic lethality and liver degeneration in mice lacking the metal-responsive transcriptional activator MTF-1.

We have shown previously that the heavy metal-responsive transcriptional activator MTF-1 regulates the basal and heavy metal-induced expression of metallothioneins. To investigate the physiological function of MTF-1, we generated null mutant mice by targeted gene disruption. Embryos lacking MTF-1 die in utero at approximately day 14 of gestation. They show impaired development of hepatocytes and, at later stages, liver decay and generalized edema. MTF-1(-/-) embryos fail to transcribe metallothionein I and II genes, and also show diminished transcripts of the gene which encodes the heavy-chain subunit of the gamma-glutamylcysteine synthetase, a key enzyme for glutathione biosynthesis. Metallothionein and glutathione are involved in heavy metal homeostasis and detoxification processes, such as scavenging reactive oxygen intermediates. Accordingly, primary mouse embryo fibroblasts lacking MTF-1 show increased susceptibility to the cytotoxic effects of cadmium or hydrogen peroxide. Thus, MTF-1 may help to control metal homeostasis and probably cellular redox state, especially during liver development. We also note that the MTF-1 null mutant phenotype bears some similarity to those of two other regulators of cellular stress response, namely c-Jun and NF-kappaB (p65/RelA).

Animals↗
PubMed1998

Hypericum perforatum inhibits the binding of mu- and kappa-opioid receptor expressed with the Semliki Forest virus system.

The effects of Hypericum perforatum extracts on in vitro [3H]naloxone binding to the human mu- and rat kappa-opioid receptors were studied in chinese hamster ovary (CHO) cells using the Semliki Forest virus (SFV) expression system. Binding of [3H]naloxone to the mu- and kappa-opioid receptor was inhibited in the presence of Hypericum extracts showing IC50 values of approximately 25 and 90 micrograms/ml, respectively. In contrast, extracts of Valeriana officinalis did not inhibit binding to the mu-opioid receptor. Also, single constituents of H. perforatum like the flavonoids quercetin and kaempferol and the glycosilated flavonoid quercitrin did not inhibit [3H]naloxone binding to the mu-opioid receptor up to a concentration of 10 microM. The present in vitro data may suggest a new possible mechanism for the anti-depressant effect of H. perforatum.

Animals↗
PubMed1998

Use of hepatitis A vaccine in a community-wide outbreak of hepatitis A.

Hepatitis A outbreaks in communities are often difficult to control. From July 1994 through June 1995, 676 cases of hepatitis A were reported in Shelby County, Tennessee. With the licensure of a hepatitis A vaccine in February 1995, a new tool for outbreak control became available. During August-October 1995, a mass vaccination campaign was conducted. A total of 34,054 children received the first dose of hepatitis A vaccine. From December 1995 through December 1996, the number of hepatitis A cases reported inside the intervention area declined by 64%; outside the intervention area, the number of cases declined by 40%. The precise contribution of the vaccine campaign to the decline in the number of outbreak cases is difficult to quantify because community outbreaks often wane over time. The vaccine campaign may have hastened the decline of the number of outbreak cases. Future interventions should consider an earlier campaign with greater vaccine coverage.

Adolescent↗
PubMed1998

Nosocomial transmission of a drug-sensitive W-variant Mycobacterium tuberculosis strain among patients with acquired immunodeficiency syndrome in Tennessee.

OBJECTIVE: To use DNA fingerprinting to characterize nosocomial spread of Mycobacterium tuberculosis following hospitalization of a patient with acquired immunodeficiency syndrome and active pulmonary tuberculosis, for whom respiratory isolation was not initiated promptly. DESIGN: Epidemiological investigation. SETTING: A tertiary-care medical center in Tennessee. PARTICIPANTS: Patients and healthcare workers potentially exposed to the infectious patient in 1992. RESULTS: Of 172 healthcare workers exposed, 35 (20%) were judged to have acquired tuberculous infection. Risk of acquisition was greatest for nurses and medical receptionists. Active tuberculosis later developed in one healthcare worker and one hospitalized patient. Nosocomial transmission was supported by epidemiological evidence and DNA fingerprinting. The outbreak strain of Mycobacterium tuberculosis differed from other isolates at this hospital, but its DNA hybridization pattern was highly similar to that of the multidrug-resistant outbreak strain W that has been prevalent in New York City, suggesting a common strain ancestry. However, the Tennessee isolates were susceptible to all first-line antituberculous agents. CONCLUSIONS: This report suggests the possibility that a molecular characteristic(s) shared by these successful outbreak strains is associated with increased transmissibility or pathogenicity and emphasizes the need for continued vigilance for tuberculosis in the nosocomial setting.

AIDS-Related Opportunistic Infections↗
PubMed1998

Homologous recombination and DNA-end joining reactions in zygotes and early embryos of zebrafish (Danio rerio) and Drosophila melanogaster.

A linear DNA with partial sequence redundancy can be recircularized in cells by either nonhomologous end joining (NEJ) or by homologous recombination (HR). We have studied the relative contributions of these processes in zygotes or early embryos of species that serve as model organisms for developmental genetics. Thus, we have microinjected a linearized plasmid substrate into zygotes of zebrafish (Danio rerio) or into the posterior end of Drosophila melanogaster early embryos before pole cell formation. Similar to the situation observed previously in Xenopus zygotes/early embryos, we detected a large preponderance of DNA-end joining over homologous recombination. A comparison of end-joined junctions revealed that from the three species tested, zebrafish introduced the least number of sequence distortions upon DNA-end joining, while Drosophila produced the largest deletions (average 14 bp) with occasional nucleotide patch insertions, reminiscent of the N nucleotides at V(D)J junctions in mammalian immune receptor genes. Double-strand gap repair by homologous sequences ('homologous recombination') involving a bimolecular reaction was readily detectable in both zebrafish and Drosophila. This involved specifically designed recombination substrates consisting of a mutagenized linear plasmid and DNA fragments carrying the wild-type sequence. Our results show that the basic machinery for homologous recombination is present at early developmental stages of these two genetic model organisms. However, it seems that for any experimental exploitation, such as targeted gene disruption, one would have to inhibit or bypass the overwhelming DNA-end joining activity.

Animals↗