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Biomedical subjects

W Schaffner

Publications and source records attributed to W Schaffner.

At least 199 records · Page 11Linked to original sources
PubMed1989

DNA phylogeny of the extinct marsupial wolf.

The phylogenetic affiliation of the extinct marsupial wolf (Thylacinus cynocephalus), which once was widespread in Australia, has been uncertain. On the basis of morphology, some systematists argue that the thylacine was most closely related to an extinct group of South American carnivorous marsupials, the borhyaenids, whereas others consider it to be closer to Australian carnivorous marsupials. Here we use direct sequencing by means of the polymerase chain reaction (PCR) to compare 219 bases of mitochondrial (mt) DNA from museum specimens of the marsupial wolf and representatives of six genera of extant marsupials. In agreement with the results of an antigenic study of albumin, our genetic data suggest that the marsupial wolf was more closely related to other Australian marsupial carnivores than to those of South America. Thus, the marsupial wolf represents an example of convergent morphological evolution to South American carnivorous marsupials as well as to true wolves.

Amino Acid Sequence↗
PubMed1989

Fatal carbon monoxide poisoning at a motel.

One man died and four other persons required hospitalization following accidental exposure to carbon monoxide at a motel. In spite of prompt diagnosis of the index cases, a search for the source of exposure and for other possible victims was delayed more than ten hours. Subsequent investigation revealed that air conditioning units drew carbon monoxide from the gas heaters for the motel's indoor swimming pools into three adjacent guest rooms through structural defects in the walls. Emergency care providers must remember that in environmental exposures, other persons may continue to be at risk, and efforts must be made to identify them.

Adult↗
PubMed1989

Octamer transcription factors bind to two different sequence motifs of the immunoglobulin heavy chain promoter.

All promoters of immunoglobulin heavy chain genes contain three conserved sequence motifs: a heptamer motif CTCATGA, an octamer motif ATGCAAAT, and a TATA box. We show that, despite their different sequences, both the heptamer and the octamer motif are bound by the same octamer transcription factors (Oct factors, also referred to as OTFs), namely the lymphoid-specific proteins Oct-2A and Oct-2B, as well as the ubiquitous protein Oct-1. Even though binding to the octamer motif is stronger, a single heptamer motif can bind Oct proteins and mediate transcriptional activity in lymphoid cells. Furthermore, factor binding to the octamer motif facilitates binding to the nearby heptamer motif. We propose that the heptamer element plays a role early in B-cell differentiation to ensure that the heavy chain promoters are transcriptionally activated before the light chain promoters, which do not contain the heptamer motif.

Base Sequence↗
PubMed1989

Long-range activation of transcription by SV40 enhancer is affected by "inhibitory" or "permissive" DNA sequences between enhancer and promoter.

The transcriptional enhancer effect is used in many, if not all, organisms for remote control of gene transcription. An enhancer DNA can dramatically stimulate transcription of a linked gene from positions either 5' or 3' to the gene. Both the proximal promoter and the distal enhancer sequences are binding sites for transcription factors. Interaction between promoter and enhancer is mediated by these factors, presumably via looping out of the intervening DNA. Here we report that the extent of remote activation by an enhancer depends on characteristics of that intervening DNA. Using Beta-globin and SV40 T-antigen test genes, we show that the effect of an SV40 enhancer is transmitted to the responsive promoter, with little or no loss of efficiency, through certain segments of mammalian DNA derived from rabbit beta-globin or mouse alpha-globin gene regions. By contrast, a strong reduction of enhancer activity is observed with certain spacer segments of prokaryotic DNA (from plasmid pBR322 or phage lambda) or sequences of high (G + C) content from eukaryotic genes. We have analyzed more closely sequences that are more or less permissive for transmission of the transcriptional enhancer effect. It appears that these permissive sequences generally have a high (A + T) content and notably a very low abundance of CpG dinucleotides. By contrast, (G + C)-rich DNA segments with high local densities of CpG were the most deleterious for long-range enhancer action. We note that the latter sequence composition is typical for "CpG islands" of many mammalian genes, including housekeeping genes and the human alpha-globin gene. This may be related to the finding that promoters of most cell type-specific genes, whose activity depends on a strong enhancer, do not contain CpG islands. Most likely, the spacer DNAs of typical cell type-specific genes have evolved to allow maximal transmission of the enhancer effect.

Animals↗
PubMed1989

Mycobacterium chelonae: a cause of nodular skin lesions with a proclivity for renal transplant recipients.

PURPOSE: Infections due to Mycobacterium chelonae are uncommon. Several renal transplant recipients at our medical center have developed M. chelonae infections during the past several years, so we decided to review our recent experience with M. chelonae infections. PATIENTS AND METHODS: The clinical microbiology laboratory records of four Vanderbilt University Affiliated Hospitals were reviewed. Ten patients with M. chelonae tissue or blood infections were identified between 1982 and July 1988. RESULTS: All infections involved the skin and subcutaneous tissue. Three infections developed at the sites of medical injections. The remaining seven infections occurred in renal transplant recipients and produced a clinically distinctive syndrome. All were indolent tender nodular lesions on the extremities, usually the lower legs. Systemic symptoms were absent, and white blood cell counts were within normal limits. Diagnosis required tissue biopsy and cultures that were incubated for a month. Therapy consisted of surgical excision combined with long-term antibiotics. Even so, some patients had a chronic, relapsing course. CONCLUSION: Although other diagnoses must be considered, the presumptive diagnosis of M. chelonae infection is suggested by the appearance of nodular erythematous lesions on the legs of a renal transplant recipient.

Adult↗
PubMed1989

CpG methylation of the cAMP-responsive enhancer/promoter sequence TGACGTCA abolishes specific factor binding as well as transcriptional activation.

In mammals and other vertebrates, cytosine methylation in CpG sites is often negatively correlated with gene activity. Because methylation of the promoter region is most crucial for this effect, the simplest hypothesis is that CpG methylation interferes with the binding of specific transcription factors. We have examined this hypothesis with two different transcription factor-binding sites that contain a CpG dinucleotide, namely the cAMP-responsive element (CRE; 5'-TGACGTCA) and the Sp1-binding site (5'-GTGAGGCGGTGAGACT). We have reported previously that CpG methylation of the Sp1-binding site affected neither factor binding nor transcription in HeLa cells, which may be related to the fact that Sp1 is typically associated with promoters of housekeeping genes. In contrast, CREs are often associated with promoters of cell type-specific genes. A synthetic oligonucleotide containing two tandem CREs derived from the gene encoding the human glycoprotein hormone alpha-subunit was cloned upstream of a reporter gene. Transcription of this gene was dependent on the CRE sequences in both PC12 and HeLa cells. Bandshift and methylation interference assays show that similar, if not the same, factor(s) bind to the CRE in both cell lines, even though induction by cAMP was only observed in PC12 cells. CpG methylation of the CRE consensus sequences (TGACGTCA) resulted in loss of specific factor binding, as well as loss of transcriptional activity in vitro and in vivo, in both cell types. This suggests that the inactivity of methylated promoters can, at least in some cases, be explained by their inability to bind specific transcription factors.

Base Sequence↗
PubMed1989

Changing trends in infection control and hospital epidemiology.

From the staphylococcal era through the gram-negative era into the AIDS era, hospital infection control has evolved into a dynamic discipline whose horizons are broadening to include many of the challenges facing hospitals today.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Identification of a novel lymphoid specific octamer binding protein (OTF-2B) by proteolytic clipping bandshift assay (PCBA).

The octamer sequence ATGCAAAT is found in the promoters of immunoglobulin (Ig) heavy and light chain genes and in the heavy chain enhancer and is a major determinant of the cell type specific expression of Ig genes in B cells. An apparent paradox is that the same sequence serves as an upstream promoter or enhancer element in a variety of housekeeping genes such as the histone H2B and U snRNA genes. The differential usage of this regulatory sequence motif is thought to be mediated by different species of octamer binding proteins. One species of 100 kd, designated OTF-1, is present in all cell types and may exert its activating function only when it can interact with additional adjacent transcription factors. The lymphoid cell specific octamer binding protein of 60 kd (OTF-2A) specifically stimulates Ig promoters which consist essentially of a TATA-box and an octamer sequence upstream of it. Here we present evidence for yet another B cell specific octamer binding protein of 75 kd (OTF-2B). From several findings, including the absence of OTF-2B (but not OTF-2A) from a lymphocyte line that cannot respond to the IgH enhancer, we propose a role of the novel octamer factor in the long range activation by the IgH enhancer. We have used the proteolytic clipping bandshift assay (PCBA) technique to distinguish the three different forms found in B cells. This analysis indicates that the 75 kd-species OTF-2B is closely related to the 60 kd species OTF-2A.

Animals↗
PubMed1988

A zinc-responsive factor interacts with a metal-regulated enhancer element (MRE) of the mouse metallothionein-I gene.

Heavy metal ions are effective inducers of metallothionein gene transcription. The metal response is dependent on short DNA motifs, so-called MREs (metal responsive elements) that occur in multiple copies in the promoter region of these genes. We have analysed an MRE of the mouse metallothionein-I gene (MREd) and we demonstrate that this can function over long distances as a bona fide metal ion-inducible enhancer. The transcription factor Sp1 and a zinc-inducible factor, designated MTF-1, bind to the MREd enhancer in vitro. The combined use of MREd mutants in a transient assay in HeLa cells and a competition band shift assay show that the zinc-inducible formation of the MTF-1/DNA complex in vitro correlates with zinc-inducible transcription in vivo. A chemical methylation interference assay revealed remarkably similar but non-identical guanine interference patterns for the MTF-1 and Sp1 complexes, which may mean that MTF-1 is related to the Sp1 factor.

Animals↗
PubMed1988

Risk of sudden infant death syndrome after immunization with the diphtheria-tetanus-pertussis vaccine.

To evaluate recent immunization against diphtheria, tetanus, and pertussis (DTP) as a possible risk factor for sudden infant death syndrome (SIDS), we studied the rates of SIDS after the administration of DTP vaccine in a cohort of 129,834 children who were born in four urban Tennessee counties during the period from 1974 through 1984. All the children received at least one DTP immunization in the first year of life at county health-department clinics or from Medicaid providers. Computerized immunization records from these sources were linked with Tennessee birth and death certificates to establish the cohort, ascertain the timing of immunization, and identify cases of SIDS. These children represented 42 percent of the births in the four counties. Among these children, 204 deaths occurred at the ages of 29 to 365 days; 109 deaths were classified as due to SIDS. We estimated the risk of SIDS according to the length of time, up to 30 days, since DTP immunization and compared it with the risk 31 days or more after immunization to calculate the relative risk. With control for age, the relative risk from 0 to 3 days after DTP immunization was 0.18 (95 percent confidence interval, 0.04 to 0.8); from 4 to 7 days, 0.17 (95 percent confidence interval, 0.04 to 0.7); from 8 to 14 days, 0.75 (95 percent confidence interval, 0.4 to 1.5); and from 15 to 30 days, 1.0 (95 percent confidence interval, 0.6 to 1.6). A multivariate analysis in which we controlled for age, sex, race, year, birth weight, and Medicaid enrollment, produced similar results. We conclude that in this large population of children there was no increase in the risk of SIDS after immunization with the DTP vaccine.

Analysis of Variance↗
PubMed1988

Nonsteroidal anti-inflammatory drug use and death from peptic ulcer in elderly persons.

STUDY OBJECTIVE: To determine the association between current non-aspirin nonsteroidal anti-inflammatory drug (NSAID) use and fatal peptic ulcers or upper gastrointestinal hemorrhage. DESIGN: Nested case control study using a linked Medicaid-death certificate database. SETTING: Tennessee Medicaid enrollees aged 60 and greater from 1976 to 1984. PATIENTS: One hundred twenty-two patients, "the cases," had a terminal hospitalization and a peptic ulcer or upper gastrointestinal hemorrhage confirmed by hospital chart review. Population controls (n = 3897) were matched to potential cases by age, sex, race, calendar year, and nursing home status. MEASUREMENTS AND MAIN RESULTS: "Cases" more frequently filled a prescription for an NSAID within 30 days before onset of illness than controls (34% compared with 11%; adjusted odds ratio, 4.7; 95% CI, 3.1 to 7.2). This association between fatal ulcer disease and current NSAID use was consistent in three age groups, women and men, whites and nonwhites, and community and nursing home dwellers. There was no significant association between case status and previous NSAID use (adjusted odds ratio, 1.9; 95% CI, 0.7 to 4.7). CONCLUSIONS: The findings of this study add to the growing evidence that NSAIDs can increase the risk for clinically serious peptic ulcer disease in the elderly.

Aged↗
PubMed1988

Heavy metal ions in transcription factors from HeLa cells: Sp1, but not octamer transcription factor requires zinc for DNA binding and for activator function.

Zinc is an important cofactor for many enzymes involved in nucleic acid metabolism such as DNA and RNA polymerases, reverse transcriptase and tRNA synthetases. We have developed an inducible in vitro transcription system using metal-depleted nuclear extracts to reveal the presence and functional relevance of heavy metal ions in transcription factors. Using protein-DNA binding assays (band shift and DNAase I footprint) we show that Sp1, a promoter-specific vertebrate transcription factor that binds to the "GC box" (Sequence in text), is reversibly inactivated by metal-depletion. Zinc is required for specific DNA binding in vitro and is also essential for Sp1 factor-directed transcription. In contrast, another factor from HeLa cells, the so-called octamer transcription factor (OTF) that binds to the sequence 5'-ATGCAAATNA, is not affected by metal-depletion and thus seems not to be a zinc metalloprotein.

Base Sequence↗
PubMed1988

Redundancy of information in enhancers as a principle of mammalian transcription control.

In contrast to prokaryotes, in which strong transcriptional signals can be located within very short DNA segments, typical mammalian enhancers are about 200 base-pairs long. We reasoned that a minimal length of enhancer-active DNA is required for a high transcription rate in higher eukaryotes, and that segments from a single enhancer or from different enhancers might be multimerized or combined to satisfy such a requirement. To test this, enhancer fragments from different viruses were joined in a recombinant simian virus 40 (SV40) and screened for efficiency of viral growth. The 48 combinations tested show that the hypothesis is basically correct. For example, two subfunctional heterologous enhancer fragments can together form a functional enhancer. No enhancer shorter than 84 base-pairs could promote SV40 growth, i.e. in no case did we find a short "superstrong" enhancer segment. To test whether multimerization of a short fragment would result in a strong enhancer, we have synthesized a 50 base-pair enhancer segment derived from Herpesvirus saimiri. One to six copies of this oligonucleotide gave an incremental increase in enhancer activity. We propose, therefore, that mammalian gene regulation is based on a redundancy of information that can be provided either by a combination of different DNA sequence elements, or by multiple copies of the same element. Also, the finding of strong and weak enhancers suggests that in most cases an enhancer is permanently required for transcription of a gene, rather than acting in an all-or-none fashion to establish a transcription complex, after which it becomes dispensable.

Animals↗