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E Henderson

Publications and source records attributed to E Henderson.

At least 55 records · Page 3Linked to original sources
PubMed1997

Analysis of the role of E2A-encoded proteins in insulin gene transcription.

Pancreatic beta-cell type-specific transcription of the insulin gene is mediated, in part, by factors in the basic helix-loop-helix (bHLH) family that act on a site within the insulin enhancer, termed the E1-box. Expression from this element is regulated by a heteromeric protein complex containing ubiquitous (i.e. the E2A- and HEB-encoded proteins) and islet-enriched members of the bHLH family. Recent studies indicate that the E2A- and HEB-encoded proteins contain a transactivation domain, termed AD2, that functions more efficiently in transfected beta-cell lines. In the present report, we extend this observation by demonstrating that expression of full-length E2A proteins (E47, E12, and E2/5) activates insulin E element-directed transcription in a beta-cell line-selective manner. Stimulation required functional interactions with other key insulin gene transcription factors, including its islet bHLH partner as well as those that act on the RIPE3b1 and RIPE3a2 elements of the insulin gene enhancer. The conserved AD2 domain in the E2A proteins was essential in this process. The effect of the E2A- and HEB-encoded proteins on insulin gene expression was also analyzed in mice lacking a functional E2A or HEB gene. There was no apparent difference in insulin production between wild type, heterozygote, and homozygous mutant E2A or HEB mice. These results suggest that neither the E2A- or HEB-encoded proteins are essential for insulin transcription and that one factor can substitute for the other to impart normal insulin E1 activator function in mutant animals.

Animals↗
PubMed1997

Application of atomic force microscopy to visualization of DNA, chromatin, and chromosomes.

The scanning force microscope (SFM, also called the atomic force microscope, AFM) provides a new and powerful method for visualization and manipulation of biological samples. Its high precision and sensitivity allow the investigator to interrogate samples at very high spatial resolution and simultaneously accumulate a variety of data types, including topography, viscoelasticity, chemical properties, and local friction. We provide here a brief review of the literature describing the current state of the art in the application of SFM to the study of DNA, chromatin and chromosomes, and some examples from this laboratory. Suggestions for future directions of this technology are also presented.

Animals↗
PubMed1996

Scanning force microscopy reveals ellipsoid shape of chicken erythrocyte nucleosomes.

Scanning force microscopy was used to investigate the conformation of hypotonic spread chicken erythrocyte nucleosomes. Nucleosomal chains were prepared in low-salt conditions and fixed before centrifugation onto glass coverslips and air drying. The images of single nucleosomes were isolated by image processing, and the height and geometry of the resulting three-dimensional structures were investigated. An average nucleosome height of 4.2 +/- 1.1 nm was determined. A virtual cross section at half-maximum height of the nucleosome structure was used for a characterization of the nucleosome geometry. The shape of this cross section was best described by an ellipse with an aspect ratio (major/minor axis) of approximately 1.30.

Animals↗
PubMed1996

Should infection control practitioners do follow-up of staff exposures to patient blood and body fluids?

BACKGROUND: The purpose of this study was to determine the efficiency of a joint infection control/occupational health program for the follow-up of accidental blood or bloody body fluid exposures in health care workers. METHODS: A comprehensive staff follow-up program for all blood exposures with known patient sources was initiated in 1989, consisting of patient follow-up by the Infection Control Department (risk assessment for hepatitis B virus [HBV] and [HIV] infection and obtaining of consent for HIV testing) and staff follow-up by the Occupational Health Department. In 1992 a mailed survey was conducted to examine exposure follow-up policies and responsibilities in large teaching hospitals across Canada. RESULTS: A total of 924 blood exposures with known patient sources were reported between January 1989 and December 1993. HIV and HBV screening was obtained for 67.9% and 87.6% of patients assessed as at low risk and 82.3% and 92.2% of those assessed as at high risk for infection, respectively. Two previously unknown HIV-seropositive patients were identified, one of whom had been classified as at low risk (one of 530 [0.19%] patients at low risk who underwent screening). Primary reasons for screening being missed were patient discharge (46.3%) or communication problems (18.0%). The requirement for informed written consent before HIV screening accounted for the difference in completed HIV and HBV screens. Results of the hospital survey indicated that 40.8% of Canadian hospitals follow up all patients who are involved in blood exposures; however, most hospitals still rely on the physician to obtain consent (87.6%). CONCLUSIONS: Use of ICPs to screen patients involved in staff blood exposures during regular hours may be the most efficient method of follow-up, particularly if supplemented by a backup team of health professionals on nights and weekends. Although screening all patients for HBV/HIV may detect patients with undisclosed high-risk behaviors, institutions must decide whether the practice is cost-effective in areas of low prevalence.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Significant savings achieved by implementing event related outdating.

The event related outdating(ERO) theory is based on the assumption that items that are properly cleaned, wrapped, sterilized, stored and handled will remain sterile indefinitely unless the integrity of the package becomes compromised. The authors describe how one Surgical Suite (performing approximately 600 cases/month) implemented an ERO program with estimated annual savings of almost $10,000/year.

Alberta↗
PubMed1996

Volume determination of human metaphase chromosomes by scanning force microscopy.

The scanning force microscopy (SFM) yields the topography of the investigated surface. A procedure was developed which starts from this three-dimensional information to estimate the volume of a biological specimen. The volume of spread human metaphase chromosomes was determined in air and rehydrated in aqueous buffer. A difference of the determined volume of a air-dried metaphase chromosome set was found compared to values from electron microscopic investigations, and could be correlated with differences in the hydration state of the chromosomes. SFM-based relative volumes of air-dried chromosomes resembles literature data regarding volume range and distribution. Possible application of SFM-based relative volume measurements for chromosome classification purposes is discussed.

Algorithms↗
PubMed1995

Visualization of nucleosomal substructure in native chromatin by atomic force microscopy.

Intact rDNA minichromosomes from Tetrahymena thermophila were isolated as native chromatin and imaged by atomic force microscopy (AFM). AFM measurements of condensed rDNA chromatin were consistent with a 30 nm fiber that frequently (87% of molecules observed) contained stretches of nucleosome cores arranged in a zig-zag conformation. Examination of rDNA chromatin in a dispersed conformation by tapping mode AFM in low humidity resulted in high resolution images of partially dissociated nucleosome cores and associated linker DNA. A majority of these nucleosome cores contained six to eight smaller particles with dimensions consistent with those of individual histones. Many of the nucleosome cores showed a striking resemblance to the wedge (35%), axial (15%), and front (6%) views of the nucleosome histone octamer modeled by Arents et al. [Arents, G., Burlingame, R. W., Wang, B.-C., Love, W.E., & Moudrianakis, E. N. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 10148-10152]. This direct visualization of histone subunits and nucleosomal substructure in native chromatin illustrates the potential use of AFM to localize individual proteins in condensed cellular chromatin.

Animals↗
PubMed1995

A new DNA nanostructure, the G-wire, imaged by scanning probe microscopy.

G-DNA is a polymorphic family of quadruple helical nucleic acid structures containing guanine tetrad motifs [G-quartets; Williamson, J.R., Raghuraman, M.K. and Cech, T.R. (1989) Cell 59, 871-880; Williamson, J.R. (1993) Proc. Natl. Acad. Sci. USA 90, 3124-3124]. Guanine rich oligonucleotides that are self-complimentary, as found in many telomeric G-strand repeat sequences, form G-DNA in the presence of monovalent and/or divalent metal cations. In this report we use the atomic force microscope (AFM) to explore the structural characteristics of long, linear polymers formed by the telomeric oligonucleotide d(GGGGTTGGGG) in the presence of specific metal cations. In the AFM these polymers, termed G-wires, appear as filaments whose height and length are determined by the metal ions present during the self-assembly process. The highly ordered, controllable self-assembly of G-wires could provide a basis for developing advanced biomaterials.

Base Sequence↗
PubMed1995

Dynamic imaging of purified individual synaptic vesicles.

The atomic force microscope (AFM) was used to directly image purified synaptic vesicles. Individual secretory vesicles (approximately 50 nm diameter) were resolved with the AFM when imaged either dry or in solution. Vesicles were observed repeatedly for periods of greater than 2 h. To ask whether the AFM can detect structural change of vesicles the osmolarity of the bathing medium was reduced from 330 to 110 mOsm. Hypo-osmotic treatment caused an expansion and flattening of the vesicles. Thus, using the AFM it is possible to resolve individual vesicles and follow changes in vesicular structure. This opens the possibility that the secretory event can be reconstituted and visualized in vitro in order to elucidate the roles of synaptic proteins in synaptic transmission.

Animals↗
PubMed1995

Imaging and manipulating chromosomes with the atomic force microscope.

Polytene chromosomes from the salivary gland cells of Drosophila melanogaster were examined by atomic force microscopy. The atomic force microscope (AFM) was capable of resolving chromosomal features down to the limits of the tip sharpness, about 500 A for pyramidal-shaped tips. Resolution was increased to 300 A by using electron beam deposited (EBD) tips with high aspect ratios. This significantly exceeds the resolution obtainable with conventional optical microscopes, but at the cost of compromising the structural integrity of the sample. A reasonable compromise was achieved by using oxide-sharpened tips. In this case high resolution was obtained without sample degradation, but when desired these tips were also capable of sample disintegration with increased scanning force and rate. Thus, oxide-sharpened tips were used to precisely dissect defined chromosomal regions to illustrate their potential use in genetic mapping efforts. This study illustrates the utility of the AFM in the characterization and manipulation of chromosomes and chromosomal DNA.

Animals↗
PubMed1995

Incidence of hospital-acquired infections associated with caesarean section.

A retrospective cohort study was conducted to determine the incidence of post-caesarean infections in a Canadian community teaching hospital using computer algorithms designed for the diagnosis of nosocomial infections. Inferential chart review was done on 1335 women delivered by lower-segment caesarean section (793 primary and 542 secondary) at the Calgary General Hospital between January 1985 and April 1988. The overall infection rates were 42.1 and 46.1% for women delivered by primary and secondary caesarean section, respectively. Incisional surgical wound infection accounted for the largest proportion of post-caesarean infections found. Women delivered by primary caesarean section had significantly higher rates of endometritis, deep surgical wound infection and bacteraemia than those delivered by secondary section. All types of post-caesarean infection, except asymptomatic bacteriuria, caused the duration of the post-partum hospital stay to be significantly increased.

Alberta↗
PubMed1995

Impact of free verotoxin testing on epidemiology of diarrhea caused by verotoxin-producing Escherichia coli.

During a 10-week period in the summer of 1990, an epidemiologic investigation of the prevalence of verotoxin (VT)-producing Escherichia coli infection was conducted in Calgary, Alberta, Canada. Consecutive stool specimens (n = 3,577) were cultured for E. coli O157:H7, and fecal filtrates were tested for free VTs (FVTs). E. coli O157:H7 was recovered from 22 specimens (0.6%), but VT was detected in 74 specimens (2.1%). Sixty-nine stool specimens positive for FVTs or E. coli O157:H7 were probed for VT genes by colony blot hybridization; 22 of 38 VT gene probe-positive isolates were non-O157:H7 E. coli organisms. Fourteen of 22 strains could not be induced to produce VT in vitro, despite the presence of FVTs in the stool sample, positivity on colony blot hybridization, positive PCR probes with the primers described by Pollard et al. (D. R. Pollard, W. M. Johnson, H. Lior, S. D. Tyler, and K. R. Rozee, J. Clin. Microbiol. 28:540-545, 1990) or Gannon et al. (V. P. Gannon, R. K. King, J. Y. Kim, and E. J. Golsteyn-Thomas, Appl. Environ. Microbiol. 58:3809-3815, 1992) (but not those described by Karch and Meyer [H. Karch and T. Meyer, J. Clin. Microbiol. 27:2751-2757, 1989]), and positive Southern blot analysis of isolates in 10 of 14 strains. The patient survey questionnaire showed that E. coli O157:H7 infection was associated with bloody diarrhea of short duration, whereas infection with other serotypes or persistence of FVT only was associated with longer-duration nonbloody diarrheal illness. We conclude that (i) detection of FVT in stools enhances the diagnosis of VT infection threefold over cultures for E. coli O157:H7, (ii) cultures for E.coli O157:H7 detect the majority of organisms of that serotype, (iii) the spectrum of disease produced by organisms of non-O157:H7 serotypes may include less severe but more protracted illness, and (iv) differences in the in vivo and in vitro expression of toxin and results of genetic probe studies highlight the need to examine control mechanisms of toxin production.

Adolescent↗
PubMed1995

Identification and characterization of a putative telomere end-binding protein from Tetrahymena thermophila.

Telomeric DNA of Tetrahymena thermophila consists of a long stretch of (TTGGGG)n double-stranded repeats with a single-stranded (TTGGGG)2 3' overhang at the end of the chromosome. We have identified and characterized a protein that specifically binds to a synthetic telomeric substrate consisting of duplex DNA and the 3' telomeric repeat overhang. This protein is called TEP (telomere end-binding protein). A change from G to A in the third position of the TTGGGG overhang repeat converts the substrate to a human telomere analog and reduces the binding affinity approximately threefold. Changing two G's to C's in the TTGGGG repeats totally abolishes binding. However, permutation of the Tetrahymena repeat sequence has only a minor effect on binding. A duplex structure adjacent to the 3' overhang is required for binding, although the duplex need not contain telomeric repeats. TEP does not bind to G-quartet DNA, which is formed by many G-rich sequences. TEP has a greatly reduced affinity for RNA substrates. The copy number of TEP is at least 2 x 10(4) per cell, and it is present under different conditions of cell growth and development, although its level varies. UV cross-linking experiments show that TEP has an apparent molecular mass of approximately 65 kDa. Unlike other telomere end-binding proteins, TEP is sensitive to high salt concentrations.

Animals↗
PubMed1995

c-jun inhibits insulin control element-mediated transcription by affecting the transactivation potential of the E2A gene products.

Pancreatic beta-cell-type-specific transcription of the insulin gene is principally controlled by trans-acting factors which influence insulin control element (ICE)-mediated expression. The ICE activator is composed, in part, of the basic helix-loop-helix proteins E12, E47, and E2-5 encoded by the E2A gene. Previous experiments showed that ICE activation in beta cells was repressed in vivo by the c-jun proto-oncogene (E. Henderson and R. Stein, Mol. Cell. Biol. 14:655-662, 1994). Here we focus on the mechanism by which c-Jun inhibits ICE-mediated activation. c-Jun was shown to specifically repress the transactivation potential of the E2A proteins. Thus, we found that the activity of GAL4:E2A fusion constructs was inhibited by c-Jun. The transrepression capabilities of c-Jun were detected only in pancreatic islet cell lines that contained a functional ICE activator. Repression of GAL4:E2A was mediated by the basic leucine zipper regions of c-Jun, which are also the essential regions of this protein necessary for controlling ICE activator-stimulated expression in vivo. The specific target of c-Jun repression was the transactivation domain (located between amino acids 345 and 408 in E12 and E47) conserved in E12, E47, and E2-5. In contrast, the activation domain unique to the E12 and E47 proteins (located between amino acids 1 and 99) was unresponsive to c-Jun. Our results indicate that c-Jun inhibits insulin gene transcription in beta cells by reducing the transactivation potential of the E2A proteins present in the ICE activator complex.

Adenoviridae↗
PubMed1995

The role of the insulin control element and RIPE3b1 activators in glucose-stimulated transcription of the insulin gene.

The most important regulator of insulin expression in islet beta-cells is glucose, which stimulates insulin gene transcription, protein synthesis, and secretion. Glucose-induced insulin gene transcription is regulated by cis-acting elements found within the 5'-flanking region of the insulin gene. We previously demonstrated that the insulin control element (ICE, -100 to -91) and RIPE3b1 (-115 to -107) elements mediated this response in the HIT T-15 beta-cell line. In this study, we examined more closely how these insulin gene control elements regulate glucose-induced transcription. RIPE3b1 element binding was shown to be induced by glucose in both mouse beta TC-6 and beta TC-3 cell lines, although higher glucose concentrations were necessary in the beta-cells (beta TC-6) that responded to physiological glucose concentrations. RIPE3b1 binding was also regulated in glucose-stimulated beta- cells by various effectors of this response. The RIPE3b1 or ICE elements were shown to independently direct glucose-stimulated expression from minimal heterologous promoter constructs. We conclude that the RIPE3b1 and ICE elements are the principal mediators of glucose-stimulated transcription of the insulin gene.

Animals↗
PubMed1995

Scanning force microscopy of chromatin.

Scanning force microscopy (SFM) is a new method to obtain the topography of surfaces with nanometer-resolution. The ability to image under liquids makes the technique attractive for biological applications, especially for the determination of the ultrastructure of biomolecules under native conditions. One growing field of interest is the investigation of chromatin and chromatin-related structures. Different levels of chromatin condensation were the subject of several previous SFM investigations, from the nucleosomal chain, to the 30-nm fiber, ending with the metaphase chromosome. The SFM yielded new information on such fundamental problems as the core spacing of the nucleosomal chain, the internal structure of the 30-nm fiber and the banding mechanism of metaphase chromosomes. Other investigations dealt with the SFM characterization of polytene chromosomes. This paper reviews the state-of-the-art in SFM chromatin research and discusses future developments in this field.

Animals↗
PubMed1995

A study comparing LETZ and CO2 laser treatment for cervical intra epithelial neoplasia with and without associated human papilloma virus.

OBJECTIVE: To evaluate the recurrence of cervical intraepithelial neoplasia (CIN) following treatment with CO2 laser ablation and loop excision of the transformation zone (LETZ) and its correlation with the presence of HPV. METHODS: Six hundred and forty two women diagnosed as having CIN were treated either by CO2 laser (318) or LETZ (324) and were followed up for a minimum of 12 months. Recurrence rates in each group were evaluated and correlated with the presence or absence of HPV prior to treatment. RESULTS: There was a considerably higher rate of recurrent disease observed after treatment with laser ablation than LETZ (9% after LETZ and 37% after laser ablation) p < 0.001. Two hundred and sixty four women (41%) had HPV infection prior to treatment and 29% of these required further treatment for recurrent CIN whereas there were only 11% of women out of the 374 who had no evidence of HPV infection p < 0.001. CONCLUSION: Treatment of CIN in the presence of HPV infection results in higher failure rates and this is significantly increased when the treatment is by laser ablation rather than by LETZ.

Adolescent↗