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Biomedical subjects

L Harrington

Publications and source records attributed to L Harrington.

At least 19 recordsLinked to original sources
PubMed1998

Reconstitution of human telomerase activity in vitro.

Telomerase is a ribonucleoprotein enzyme complex that adds single-stranded telomere DNA to chromosome ends [1]. The RNA component of telomerase contains the template for telomeric DNA addition and is essential for activity [1,2]. Telomerase proteins have been identified in ciliates, yeast and mammals [3-12]. In Saccharomyces cerevisiae, the Est2 protein is homologous to the 123 kDa reverse transcriptase subunit of Euplotes telomerase, and is essential for telomerase activity [8]. In humans, telomerase activity is associated with the telomerase RNA hTR [13], the telomerase RNA-binding protein TP1/TLP1 [5,12] and the TP2 protein encoded by the human EST2 homolog [12] (also known as TRT1, hEST2 or TCS1 [9-11]). The minimal complex sufficient for activity is, however, unknown. We have reconstituted human telomerase activity in reticulocyte lysates and find that only exogenous hTR and TP2 are required for telomerase activity in vitro. Recognition of telomerase RNA by TP2 was species specific, and nucleotides 10-159 of hTR were sufficient for telomerase activity. Telomerase activity immunoprecipitated from the reticulocyte lysate contained hTR and recombinant TP2. Substitution of conserved amino acid residues in the reverse transcriptase domain of TP2 completely abolished telomerase activity. We suggest that TP2 and hTR might represent the minimal catalytic core of human telomerase.

Carrier Proteins↗
PubMed1998

Ultrasonographic and clinical predictors of intussusception.

OBJECTIVE: The objective of this study was to determine the positive and negative clinical predictors of intussusception and the correlation of ultrasonography and air enema in establishing this diagnosis. STUDY DESIGN: This was a prospective descriptive cohort study. SETTING: This study was performed in a tertiary care pediatric emergency department. PARTICIPANTS: Eighty-eight of 245 candidates were assessed for clinical predictors of intussusception. All 245 cases were examined for correlation between ultrasonography and air enema. INTERVENTIONS: A questionnaire, ultrasonography, and air enema were used. RESULTS: Thirty-five of the 88 patients assessed for clinical predictors were positive for intussusception. Significant positive predictors were right upper quadrant abdominal mass (positive predictive value [PPV] 94%), gross blood in stool (PPV 80%), blood on rectal examination (PPV 78%), the triad of intermittent abdominal pain, vomiting, and right upper quadrant abdominal mass (PPV 93%, p = 0.0001), and the triad with occult or gross blood per rectum (PPV 100%, p = not significant). Significant negative predictors were a combination of > or = 3 of 10 clinically significant negative features (negative predictive value 77%, p = 0.035). Of the total 245 cases, intussusception (as confirmed by doughnut, target, or pseudokidney sign) was ruled out by ultrasonography in 97.4%. Alternate ultrasound findings comprised 27% of negative cases. CONCLUSIONS: Excellent positive predictors of intussusception were identified prospectively. Although no reliable negative predictors were found, patients at low risk may be screened by ultrasonography.

Air↗
PubMed1998

Refined genetic mapping of the darier locus to a <1-cM region of chromosome 12q24.1, and construction of a complete, high-resolution P1 artificial chromosome/bacterial artificial chromosome contig of the critical region.

Darier disease (DD) (MIM 124200) is an autosomal dominant skin disorder characterized by loss of adhesion between epidermal cells and by abnormal keratinization. We present linkage analysis showing, in four families, key recombination events that refine the location of the DD locus on chromosome 12q23-24.1 to a region of <1 cM. We have constructed a YAC/P1 artificial chromosome (PAC)/bacterial artificial chromosome (BAC)-based physical map that encompasses this refined DD region. The map consists of 35 YAC, 69 PAC, 16 BAC, and 2 cosmid clones that were ordered by mapping 54 anonymous sequence-tagged sites. The critical region is estimated to be 2.4 Mb in size, with an average marker resolution of 37.5 kb. The refinement of the critical interval excludes the ALDH2, RPL6, PTPN11, and OAS genes, as well as seven expressed sequence tags (ESTs) previously mapped in the DD region. The three known genes (ATP2A2, PPP1CC, and SCA2) and the 10 ESTs mapped within the critical region are not obvious candidates for the DD gene. Therefore, this detailed integrated physical, genetic, and partial transcript map provides an important resource for the isolation of the DD gene and, possibly, other disease genes.

Chromosome Mapping↗
PubMed1997

Human telomerase contains evolutionarily conserved catalytic and structural subunits.

We have cloned and characterized a human gene encoding TP2 (telomerase-associated protein 2), a protein with similarity to reverse transcriptases and the catalytic telomerase subunits from Saccharomyces cerevisiae and Euplotes aediculatus. Indirect immunofluorescence revealed that TP2 was localized to the nucleus. Using antibodies to endogenous and epitope-tagged TP2, we found that TP2 was associated specifically with human telomerase activity and the recently identified telomerase-associated protein TP1. Mutation of conserved residues within the reverse transcriptase domain of TP2 severely reduced associated telomerase activity. These results suggest that telomerase is an evolutionarily conserved multisubunit complex composed of both structural and catalytic subunits.

Amino Acid Sequence↗
PubMed1997

A mammalian telomerase-associated protein.

The telomerase ribonucleoprotein catalyzes the addition of new telomeres onto chromosome ends. A gene encoding a mammalian telomerase homolog called TP1 (telomerase-associated protein 1) was identified and cloned. TP1 exhibited extensive amino acid similarity to the Tetrahymena telomerase protein p80 and was shown to interact specifically with mammalian telomerase RNA. Antiserum to TP1 immunoprecipitated telomerase activity from cell extracts, suggesting that TP1 is associated with telomerase in vivo. The identification of TP1 suggests that telomerase-associated proteins are conserved from ciliates to humans.

Amino Acid Sequence↗
PubMed1997

Complications of Fleet enema administration and suggested guidelines for use in the pediatric emergency department.

INTRODUCTION: Hypertonic sodium phosphate enema solutions are commonly used for the treatment of acute constipation in the pediatric emergency department. The potential for severe metabolic derangement and death in children with gastrointestinal and/or renal abnormalities and these reported as normal has been documented in the literature. OBJECTIVE: To develop guidelines for the safe and effective use of hypertonic sodium phosphate enema solutions such as Fleet enema, in the pediatric emergency department setting. RESOURCES: A comprehensive review of the literature was conducted using the MEDLINE database for the time period 1966 to September 1995. Resources used within our institution, the Hospital for Sick Children, Toronto, Ontario, included Staff of the Emergency and General Surgery Departments. SUMMARY: The guidelines provided will promote safe use of hypertonic sodium phosphate enema solutions for the treatment of acute constipation in children presenting to the emergency department.

Acute Disease↗
PubMed1997

Reciprocal inhibitory paracrine pathways link histamine and somatostatin secretion in the fundus of the stomach.

The present study was designed to examine the functional linkage between histamine and somatostatin secretion in the fundus of the stomach. In segments of rat fundic mucosa, superfusion with thioperamide (H3 antagonist) increased somatostatin and decreased histamine secretion; superfusion with (R)(-)-alpha-methylhistamine (H3 agonist) had the opposite effect, decreasing somatostatin and increasing histamine secretion. The pattern implied that endogenous histamine, acting via H3 receptors, exerts an inhibitory paracrine influence on somatostatin secretion. Superfusion with somatostatin antibody (1:250) increased histamine secretion, implying that endogenous somatostatin, in turn, exerts an inhibitory paracrine influence on histamine secretion. Somatostatin antibody also abolished the decrease in histamine secretion induced by thioperamide and the increase in histamine secretion induced by (R)(-)-alpha-methylhistamine, implying that changes in histamine secretion induced by activation of H3 receptors reflect changes in somatostatin secretion. Superfusion with the muscarinic agonist methacholine alone and in the presence of either H3 agonist or H3 antagonist confirmed the existence of reciprocal inhibitory pathways linking somatostatin and histamine. We conclude that fundic histamine and somatostatin secretion are linked via reciprocal inhibitory paracrine pathways that serve to amplify the regulatory influence of somatostatin.

Animals↗
PubMed1996

Somatostatin receptor subtype 2 mediates inhibition of gastrin and histamine secretion from human, dog, and rat antrum.

BACKGROUND & AIMS: In gastric antrum, somatostatin exerts a tonic inhibitory influence on gastrin and histamine secretion. Five different subtypes of somatostatin receptors, designated sst1-5, have been identified. sst2, sst3, and sst5 subtypes have been localized to the stomach by molecular biological techniques. The aim of this study was to identify the sst subtype regulating gastrin and histamine secretion in human, dog, and rat stomach. METHODS: Mucosal segments from human, dog, and rat antrum were superfused with various concentrations of somatostatin 14 and somatostatin analogues selective for sst2, sst3, and sst5. Gastrin and histamine were measured by radioimmunoassay. RESULTS: Somatostatin 14 and the sst2 agonist EC 5-20 inhibited gastrin and histamine secretion from all three species in a concentration-dependent manner, whereas the sst3 and sst5 agonists had no significant effect. Neutralization of endogenous somatostatin with the somatostatin antibody increased gastrin and histamine secretion. The increases were not affected by the gastrin antagonist but were abolished by the sst2 agonist, implying that the inhibitory influence of ambient somatostatin is exerted directly on the histamine cell rather than indirectly via changes in gastrin secretion. CONCLUSIONS: Somatostatin inhibits gastrin and histamine secretion in human, dog, and rat antrum by activating sst2 receptors on gastrin and histamine cells.

Animals↗
PubMed1995

Gel shift and UV cross-linking analysis of Tetrahymena telomerase.

Telomerase is an unusual ribonucleoprotein that synthesizes new telomeres onto chromosome ends. The enzyme has been most extensively characterized in ciliates, where the RNA component has been cloned from several species, and its elongation properties have been characterized in detail. To understand the substrate specificity and protein composition of telomerase, we have used gel shift and UV cross-linking to characterize the enzyme from the ciliate Tetrahymena thermophila. In a mobility shift assay, a complex was identified that contained telomerase RNA, co-purified with telomerase activity, and was sensitive to nuclease treatment. The mobility shift complexes specifically formed using several different single-stranded, telomeric sequences but not non-telomeric primers. These results suggest that the specificity of telomerase for G-rich primer sequences occurs at least in part at the level of primer binding. UV cross-linking analysis identified a 100-kDa cross-linked protein that may be a telomerase component.

Animals↗
PubMed1995

Dual inhibitory pathways link antral somatostatin and histamine secretion in human, dog, and rat stomach.

BACKGROUND & AIMS: The secretion and function of antral histamine are not known. The aims of this study were to characterize the mechanisms of histamine release from the gastric antrum of humans, dogs, and rats and to determine whether histamine can influence the secretion of somatostatin and gastrin. METHODS: Somatostatin, gastrin, and histamine secretion from superfused antral segments was measured using radioimmunoassay. RESULTS: Superfusion with thioperamide (H3 antagonist) increased somatostatin and decreased gastrin and histamine secretion in all three species; superfusion with (r)-alpha-methylhistamine (H3 agonist) had the opposite effect. The pattern implied that endogenous histamine, acting via H3 receptors, exerts an inhibitory paracrine influence on somatostatin secretion, which in turn regulates gastrin secretion. Superfusion with somatostatin antibody increased histamine secretion; the increase was not affected by the gastrin antagonist L-365,260, implying that it was not mediated by the concurrent increase in gastrin but by suppression of an inhibitory pathway linking somatostatin and histamine. Superfusion with methacholine alone and in the presence of either the H3 agonist or antagonist confirmed the existence of reciprocal inhibitory pathways linking somatostatin and histamine. CONCLUSIONS: Antral histamine in humans, dogs, and rats is linked to antral somatostatin via reciprocal inhibitory paracrine pathways that serve to amplify the regulatory influence of somatostatin.

Animals↗
PubMed1995

Complete nucleotide sequence of the herpesvirus simiae glycoprotein G gene and its expression as an immunogenic fusion protein in bacteria.

The nucleotide sequence of a 2384 bp portion within the unique short (Us) region of the herpesvirus simiae (simian herpes B virus; SHBV) genome is presented. A partial and a complete open reading frame (ORF) were found within this nucleotide sequence. The partial ORF encodes the C terminus (147 amino acids) of a protein kinase which is highly conserved in the herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) and simian agent 8 (SA8) Us regions. The complete ORF is located 3' to the partial ORF within the 2384 bp sequence and encodes a 593 amino acid glycoprotein which appears to be closely related to the SA8 glycoprotein G (gG), but shares little amino acid similarity with gG of HSV-1 and -2. However, the complete ORF shares certain features conserved among most alphaherpesvirus gGs, notably three highly conserved cysteine residues and an adjacent N-glycosylation site. Therefore, it was concluded that this complete ORF encodes the SHBV gG. The 358 amino acid C-terminal portion of SHBV gG was expressed in Escherichia coli as a fusion protein and this was detected by immunoblotting with sera from cynomolgus monkeys which were either experimentally or naturally infected with SHBV. The purified fusion protein was inoculated into rabbits to raise an antiserum which recognized a number of apparently SHBV gG-specific protein bands in extracts from SHBV-infected simian cells.

Amino Acid Sequence↗
PubMed1995

Determination of radiation energy emitted by light activation units.

Since the introduction in the 1970s of single paste composite materials, there has been a rapid increase in the range of both materials and activation light units. This investigation is being undertaken as part of a larger study where the characteristics of both composite materials, light activation units and composite material/light activation unit combinations, are being evaluated. This section of the study was undertaken to determine the characteristics of four light activation units. The equipment was developed to measure radiation energy over a wide range of illumination. This range can be from the relatively low intensity of radiation transmitted through restorative materials to the intensities of direct radiation from light activation units. The four light units tested had various radiation outputs between 225,000 lx and 75,000 lx. All the units, apart from one, showed a decrease in light output with successive applications. The units emitted radiation outside the optimum range of 440-500 nm, which may produce damaging radiation and glare. Although the extreme intensities varied threefold the effect on depth of cure of one-material varied by only 16%.

Composite Resins↗
PubMed1995

Differences in the hypothalamic-pituitary-adrenal axis of black and white men.

We previously found that, following intravenous administration of ovine corticotropin-releasing hormone (CRH), the plasma ACTH concentrations of Black women were approximately twice as high as those of White women; however, there were no corresponding differences in cortisol response. To determine whether this difference in ACTH secretion is also present in men, we studied the hypothalamic-pituitary-adrenal axis of 10 Black and 10 White weight-, age-, and education-matched men. Waist-to-hip ratio, 24-hour urine free cortisol excretion, and ACTH and cortisol responses to 1 microgram/kg ovine CRH were determined. There were no racial differences in waist-to-hip ratio, 24-hour urine free cortisol excretion, baseline free or total plasma cortisol and ACTH concentrations, or plasma cortisol response to CRH. However, CRH-stimulated plasma ACTH concentrations, measured in an extraction polyclonal radioimmunoassay, were significantly greater in Blacks than in Whites at all time points between 30 and 180 min after administration of CRH (area under curve (AUC) 1,796 +/- 245 pmol/l.min in Blacks vs. 1,278 +/- 121 pmol/l.min in Whites, p < 0.001). Neither cortisol nor ACTH AUCs were significantly correlated with Body Mass Index in Black or White men. We conclude that there are differences in the HPA axis of Black and White men similar to those found previously in women. The physiology underlying these differences remains to be understood.

Adrenocorticotropic Hormone↗
PubMed1993

Temporal covariation of soluble interleukin-2 receptor levels, daily stress, and disease activity in rheumatoid arthritis.

OBJECTIVE: To examine synchronous changes in soluble interleukin-2 receptor (sIL-2R) levels, daily indicators of emotional stress, joint inflammation, and reported pain in patients with rheumatoid arthritis (RA). METHODS: Fourteen patients were studied on each of 6 occasions, 2 weeks apart. Measures included daily ratings of mood disturbance, undesirable events, and joint pain; clinical examination of joint swelling; and serum assays of sIL-2R. Pooled within-person correlations among these variables were calculated. RESULTS: Consistent with the results of previous research, joint inflammation covaried directly with sIL-2R levels. Changes in mood disturbance were unrelated to changes in joint inflammation, but increases in mood disturbance were linked with decreases in sIL-2R levels and increases in reported joint pain. CONCLUSION: These findings provide preliminary evidence that psychoimmune processes may be implicated in short-term changes in RA disease activity.

Adult↗
PubMed1993

Polymerase chain reaction for detection of herpesvirus simiae (B virus) in clinical specimens.

A polymerase chain reaction (PCR) was designed which is specific to Macaca fascicularis (cynomolgus monkey) isolates of B virus. The PCR primers produced the expected 188 basepair product from the Cyno 2 strain and seven other cynomolgus monkey isolates of B virus. Oligomer hybridization with a 31-mer oligonucleotide was used to confirm the origin of this product. The PCR failed to amplify DNA of Epstein-Barr virus, cytomegalovirus, varicella-zoster virus, and other alphaherpesviruses (herpes simplex virus types 1 and 2, four SA 8 isolates and three rhesus isolates of B virus). PCR testing of swabs obtained from four orally-infected cynomolgus monkeys confirmed the presence of B virus DNA in samples previously shown to be positive by culture. In addition, PCR detected B virus in several swabs from infected monkeys that were culture negative. Total DNA extracts from the trigeminal and sacral ganglia of these animals were tested by nested PCR and B virus DNA was detected in the trigeminal ganglia of 3 of the 4 orally-infected cynomolgus monkeys. Nested PCR did not detect B virus DNA in total DNA extracts obtained from the brains of the four monkeys.

Animals↗
PubMed1993

Procainamide-induced psychosis.

The occurrence of procainamide-induced psychosis has not been mentioned previously in the nursing literature and is rarely reported in the medical literature. With the increasing use of procainamide in patients with both atrial and ventricular dysrhythmias, it is quite possible that nurses may encounter the phenomenon more frequently. It is also possible that it has been mistaken previously for ICU or psychologically-induced psychosis. Nurses routinely monitoring patients for physiologic effects of procainamide should also be alert for psychological effects as well. The onset of acute psychological sequelae such as procainamide-induced psychosis further complicates care of physiologically compromised patients. Rapid identification and intervention is important. It is especially important to listen to patient and family cues.

Aged↗