Search PubMed⌕ Search

Biomedical subjects

J Abbott

Publications and source records attributed to J Abbott.

At least 73 records · Page 4Linked to original sources
PubMed1993

Cooperative binding of the Escherichia coli repressor of biotin biosynthesis to the biotin operator sequence.

Regulation of biotin biosynthesis and retention in Escherichia coli depends on a complex set of coupled protein-protein, protein-nucleic acid, and protein-small molecule interactions. The complexity of the biotin system is analogous to that found in gene regulatory systems from other prokaryotes and from eukaryotes. Quantitative understanding of these systems requires thermodynamic studies of the individual contributing interactions. We have initiated such studies of the biotin regulatory interactions. The assembly states of the biotin operon repressor (BirA) and its complex with the allosteric effector, bio-5'-AMP, have been determined by analytical gel filtration chromatography. Both the apo- and holo-repressors are monomeric at protein concentrations several orders of magnitude higher than those required for DNA binding. Results of stoichiometric DNA binding measurements indicate that the BirA-biotin operator (bioO) complex consists of two holo-repressor monomers per operator site. Equilibrium binding of BirA to bioO has been measured using the quantitative DNase footprint technique. Analysis of the data indicates that the binding process is best described by a cooperative model. An upper limit for the cooperative free energy is estimated to be between -2.0 and -3.0 kcal/mol.

Adenine Nucleotides↗
PubMed1993

Ruptured ectopic pregnancy after medical management: current conservative management strategies.

A case of hypotension caused by hemorrhage in a patient receiving systemic methotrexate to treat a known ectopic pregnancy is presented. A primary goal of gynecologic practice in the 1990s is to conserve tubal patency and fertility. Consequently, ectopic pregnancy is more frequently being managed by conservative strategies. The emergency physician must be familiar with conservative methods for the management of ectopic pregnancy and the complications that may cause emergency presentations in these patients.

Adult↗
PubMed1993

Loss and grief reactions after spontaneous miscarriage in the emergency department.

STUDY OBJECTIVE: To describe the psychological and functional consequences of miscarriage in women after emergency department treatment and to identify variables that are associated with feelings of loss and grief. DESIGN: A prospective telephone follow-up study. SETTING: The ED of an urban teaching hospital. TYPE OF PARTICIPANTS: A consecutive sample of 44 women who were treated for miscarriage. MAIN RESULTS: Women were contacted a median of 17.5 days after their miscarriage. Although the pregnancy had been planned by only 12 women (28%), 30 (70%) stated they wanted the pregnancy once they knew they were pregnant. Women commonly felt a sense of loss (82%) and most experienced some limitations with daily functioning (77%). Although wanting the pregnancy was associated with a sense of loss, 40% of the women who did not want the pregnancy experienced loss. CONCLUSION: Grief reactions are pervasive after spontaneous miscarriage. There is no subgroup of women who could be expected not to experience loss and grief. The ED management of the woman who miscarries should address the anticipated loss and grief.

Abortion, Spontaneous↗
PubMed1993

Early experience with dobutamine stress testing and cardiac cine-tomographic imaging in the elderly: antianginal effects of nifedipine-GITS.

OBJECTIVE: To determine the effects of nifedipine-GITS (GITS = gastrointestinal transport system) on angina and cardiovascular responses to stress-dobutamine infusion, we used ultrafast cine-computed tomography (CT) to assess regional wall motion, myocardial perfusion, and indices of ventricular filling and emptying. DESIGN: Randomized, double-blind placebo-controlled efficacy study after an open-label dose titration phase. SETTING: University of California, San Francisco. PATIENTS: Elderly patients (> 60 years; n = 9:8 male, 1 female) with coronary artery disease by history and diagnostic treadmill or coronary angiography. INTERVENTION: After a 3-week open-label dose-titration phase, eight subjects were randomized to receive either placebo or nifedipine-GITS at the highest tolerated dose for 2 weeks, followed by a crossover to the alternate therapy for 2 weeks. One declined because of singulus in the open-label period. MAIN OUTCOME MEASURES: Symptomatic angina relief (frequency and nitroglycerin consumption), dobutamine stress responses (time to ischemia during dobutamine infusions, cardiac output, cardiac ejection fraction, ventricular segmental wall motion, and perfusion as measured by ultrafast cine-CT), and reported adverse effects. RESULTS: When compared with placebo, nifedipine-GITS administration was associated with less frequent angina and nitroglycerin consumption (NS) and significantly decreased systolic blood pressure. Nifedipine-GITS administration also increased resting supine heart rates. Dobutamine infusions increased heart rate, cardiac output, cardiac ejection fraction, and stroke volume and induced angina symptoms. Neither double product at angina nor systolic indices of cardiac function in response to dobutamine differed between nifedipine-GITS and placebo, although heart rate responses were greater during nifedipine. A trend toward increased peak filling rates was seen during dobutamine stress in the nifedipine-administration period. In most subjects (6/8), perfusion and regional wall motion abnormalities were not visualized on regional wall motion abnormalities were not visualized on either rest or stress cine-CT studies. Edema without congestive heart failure occurred frequently during nifedipine-GITS administration. CONCLUSIONS: These data suggest that (1) dobutamine stress can be used to induce cardiac ischemia in elderly patients with coronary artery disease, (2) nifedipine-GITS provides symptomatic angina relief in elderly patients, (3) peripheral edema is frequent in elderly patients on nifedipine-GITS, and (4) ultrafast computed cine-tomography testing can be used to assess ventricular performance, but current methodology may not detect perfusion or wall motion abnormalities during angina.

Age Factors↗
PubMed1993

Making the commitment to managed care.

To develop and to implement managed care requires support from key participants including administrators, physicians, nurse managers and all healthcare providers. This multidisciplinary approach assures success and increases support when making the move toward managed care.

Goals↗
PubMed1992

A cost description of an adult cystic fibrosis unit and cost analyses of different categories of patients.

BACKGROUND: There is little information on the costs of running an adult cystic fibrosis centre. The aim of this study was to provide detailed costs to assist funding and planning for these patients. METHODS: The cost of a regional adult cystic fibrosis centre serving 119 cystic fibrosis patients, categorised according to four treatment regimens, was determined. District health authority, family health service authority, and voluntary resources used from April 1989 to March 1990 were determined, with appropriate bases for allocation of costs and patient based costs from local information. RESULTS: The total annual cost of treating the 119 patients was 980,646 pounds, with an average cost 8241 pounds per patient. An outpatient reviewed at three monthly intervals cost 2792 pounds a year; an outpatient receiving intravenous antibiotics cost 8606 pounds; an inpatient receiving intravenous antibiotics cost 13,501 pounds; and a patient needing a high level of care cost 19,955 pounds. Medication accounted for 57% (561,395 pounds) of the total cost. CONCLUSIONS: This analysis has helped us to secure funding for patients with cystic fibrosis and it facilitates the prediction of future requirements. The study also indicates the limitations of using average patient costs and difficulties as a result of the poorly structured British National Health Service accounting and information systems.

Adolescent↗
PubMed1992

Treatment of ununited tibial fractures: a comparison of surgery and pulsed electromagnetic fields (PEMF).

The use of pulsed electromagnetic fields (PEMF) is gaining acceptance for the treatment of ununited fractures. The results of 44 articles published in the English language literature have been compiled to assess the effectiveness of PEMF vs surgical therapy. For ununited tibial fractures, 81% of reported cases healed with PEMF vs 82% with surgery. After multiple failed surgeries, the success rate of PEMF is reported to be greater than with surgery; this discrepancy increases with additional numbers of prior surgeries. In infected nonunions, the results of surgical treatment decreased by 21% and were less than the results utilizing PEMF (69% vs 81%). In open fractures, surgical healing exceeded PEMF (89% vs 78%), whereas in closed injuries PEMF cases healed more frequently (85% vs 79%). In general, PEMF treatment of ununited fractures has proved to be more successful than noninvasive traditional management and at least as effective as surgical therapies. Given the costs and potential dangers of surgery, PEMF should be considered an effective alternative. Experience supports its role as a successful method of treatment for ununited fractures of the tibia.

Electromagnetic Fields↗
PubMed1992

CAPD disconnect systems: UK peritonitis experience.

We reviewed peritonitis (P) experience of four UK units using single use Y (Freeline T.M., Baxter UK)(F) and Twinbag (Solo T.M., Baxter UK) (S) disconnect systems, which incorporate the 'Flush Before Fill' principle. We aim to show clinical achievements, in varying circumstances, in the light of previously published in vitro study results. Each unit recorded P data, i.e., rates, causative organisms, and recurrences (R) over a 12 month period (Sept 89-Aug 90). This data was then analysed by system, by unit and in total. Each unit had similar definitions for P and R, but had varying system selection criteria. Unit 1 had a fairly open criteria for F use, then became more selective at the same time as introducing S. In unit 2, F, and then S, were first choice systems for all (inc. blind diabetics). Unit 3 trains every pt. on non-disconnect System 2, then pt. choice determines if they are retained onto a disconnect system. Unit 4 had a more highly selected population. Results, expressed as episodes/patient month, were as follows: [table: see text] We conclude that it is possible to achieve a low incidence of P, especially that caused by S. epidermidis, particularly with S. It would seem the extent is related to pt. to system selection criteria. The effects of R and ES/TI need to be addressed.

Humans↗
PubMed1991

alpha-Conotoxins, small peptide probes of nicotinic acetylcholine receptors.

alpha-Conotoxins, a family of small peptides from the venoms of the Conus marine moluscs, are selective, snake alpha-neurotoxin-competitive antagonists of the nicotinic acetylcholine receptor. A new alpha-conotoxin, SIA, has been purified, sequenced, and synthesized. Cross-linking with bivalent reagents and photoaffinity labeling of the acetylcholine receptor with alpha-conotoxin yield covalent adducts. Surprisingly, cross-linking to other subunits is considerably more efficient than to the alpha subunit. The relative efficiency of photoactivatable cross-linking to different subunits of the receptor is a function of placement of the photoactivatable group on the toxin. Since the structures of alpha-conotoxins can be solved by 2D NMR [see Pardi et al. (1989) Biochemistry 28, 5494-5508; Kobayashi et al. (1989) Biochemistry 28, 4853-4860], this family of toxins should provide a set of new ligands for probing the acetylcholine receptor with considerable precision.

Affinity Labels↗
PubMed1991

Return to work during the year following first myocardial infarction.

This study considers the importance of demographic and psychosocial variables in return to work following a first myocardial infarction. Those patients who returned to work within two months of their infarct, compared with those who had not returned, tended to be younger and of higher socio-economic status. They were also more likely to have an internal locus of control and to have attributed their MI to occupational stressors. Conversely, patients who had not resumed employment one year following their infarction, in comparison with those who had, were likely to be of lower socio-economic status and to have been more depressed immediately following their heart attack.

Follow-Up Studies↗
PubMed1990

Ectopic pregnancy: ten common pitfalls in diagnosis.

Ectopic pregnancy (EP) is a common, life-threatening complication of pregnancy. Modern technology (ultrasonography and improved pregnancy tests) should facilitate the diagnosis of EP. However, in a retrospective review of 65 cases of confirmed EP managed over 18 months at an urban teaching hospital, only 37 of 65 patients (57%, Cl95 = 44%, 69%) received prompt diagnosis and treatment; delays occurred in 28 patients (43%). In 10 of the 27 delayed cases, the diagnosis of EP was not even considered at the time of the first visit. In patients with a delayed diagnosis, morbidity (transfusions, cardiovascular instability, progression of illness) did occur. Diagnostic pitfalls that resulted in delayed care were reviewed, delays most commonly occurred in patients with a benign examination or "atypical" pain. Risk factors for EP were missed (7 patients, 25%), subtle clues to blood loss were often ignored (10 patients, 36%), and passage of tissue was thought to exclude EP (2 patients). Ultrasound was only helpful for half of the diagnoses and was misinterpreted in 27%. A dry or serous culdocentesis occurred frequently. In five patients, a falling or low quantitative human chorionic gonadotropin level was believed to indicate a completed abortion. The authors conclude that almost half of EPs are still missed on the first physician visit; errors and pitfalls in diagnosis are still common in the 1980s.

Adolescent↗
PubMed1990

Serous culdocentesis in ectopic pregnancy: a report of two cases caused by coexistent corpus luteum cysts.

Two cases of women with large-volume serous culdocentesis results are presented. Both patients ultimately had ectopic pregnancies diagnosed surgically, and aspiration into coexistent corpus luteum cysts caused the "false-negative" culdocentesis results. The accuracy of culdocentesis and its continued role in the workup of the patient with possible ectopic pregnancy is reviewed. Because the corpus luteum is a cystic structure present in all pregnancies during the first seven weeks, cyst aspiration is always a possibility and should be suspected when large amounts of serous fluid are obtained by culdocentesis. Such results should be considered nondiagnostic and do not exclude a coexistent ectopic pregnancy.

Adult↗
PubMed1989

The scintigraphic characteristics of ventricular pre-excitation through Mahaim fibers with the use of phase analysis.

The phase image pattern of blood pool scintigrams was blindly assessed in 11 patients exhibiting conduction through Mahaim pathways, including 6 nodoventricular and 5 fasciculoventricular. These patterns were compared with the phase image findings in normal subjects, patients with left and right bundle branch block in the absence of pre-excitation and patients with pre-excitation through atrioventricular (AV) connections. In all patients with a Mahaim pathway, the site of earliest phase angle was septal or paraseptal. Phase progression was asymmetric and the pre-excited ventricle demonstrated the earliest mean ventricular phase angle in 10 of 11 patients. This pattern, and the associated ventricular phase difference, appeared to vary from that in normal subjects and in those with a septal AV connection, in whom phase progression is generally symmetric. Scintigraphic phase analysis provided localizing information and presented patterns consistent with Mahaim pathways. Although not able to differentiate among Mahaim pathway subtypes, these phase patterns differed from those in normal subjects, those with right and left lateral free wall pathways and most patients with a septal AV pathway. However, the phase pattern of patients with a Mahaim pathway may not differ from that of patients with a septal AV connection displaying an asymmetric pattern of phase progression, or those with left and right bundle branch block in the absence of pre-excitation. Objective, yet imperfect phase measurements supported these differences. Such image findings may complement the often complex electrophysiologic evaluation of patients presenting with pre-excitation.

Adult↗
PubMed1987

Transcriptional patterns in the X chromosome of Sciara coprophila following exposure to magnetic fields.

We previously demonstrated that exposure of salivary gland cells of the dipteran, Sciara coprophila, to either asymmetrical or symmetrical changing magnetic fields results in an increase in the incorporation of radioactive uridine into RNA. The present report is an analysis of the grain count distribution over the X chromosome of Sciara in transcription autoradiograms following exposure of the salivary gland cells to two pulsed magnetic signals and a 72-Hz sine wave signal. The results show augmented uptake of 3H-uridine into nascent RNA chains following short exposures of the cells to magnetic fields. Transcription is augmented in previously active loci, as well as at chromosome regions that are not detectable as active in control cells. The quantitative pattern of RNA synthesis in transcription autoradiograms is hypothesized to be signal specific on the basis of differences in grain counts over significantly labelled chromosome sites.

Animals↗