Search PubMed⌕ Search

Biomedical subjects

J Cooper

Publications and source records attributed to J Cooper.

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

Measurement of J/psi and psi(2S) polarization in pp collisions at sqrt[s] = 1.8 TeV.

We have measured the polarization of J/psi and psi(2S) mesons produced in pp collisions at sqrt[s] = 1.8 TeV, using data collected at the Collider Detector at Fermilab during 1992-1995. The polarization of promptly produced J/psi [psi(2S)] mesons is isolated from those produced in B-hadron decay, and measured over the kinematic range 4 [5.5]<P(T)<20 GeV/c and |y|<0.6. For P(T) greater than or approximately equal 12 GeV/c we do not observe significant polarization in the prompt component.

Journal Article↗
PubMed2000

Strategies for the avoidance of faeces by grazing sheep.

Experiments were conducted to investigate which environmental cues were used by sheep when discriminating against patches of pasture contaminated with faeces. The influence of the spatial distribution of contaminated patches and the parasite infection status of sheep on avoidance of contaminated patches and ingestion of parasite larvae was also investigated. In experiment 1, sheep infected with the parasite Ostertagia circumcincta were given the opportunity to graze in uncontaminated or aggregated contaminated patches. Patch contamination comprised of either faeces from sheep infected with O. circumcincta larvae, faeces from uninfected sheep, or O. circumcincta larvae only. Infected sheep discriminated against faeces from parasite-infected animals and faeces from uninfected animals equally. Sheep did not discriminate against patches contaminated with parasite larvae only. In experiment 2, sheep infected with O. circumcincta and uninfected sheep grazed experimental plots with differing spatial patterns of faecal-contaminated patches, allowing animals the opportunity to forage in contaminated or uncontaminated patches of herbage. Plots were also grazed by infected and uninfected animals that were fistulated at the oesophagus to enable the collection of ingested herbage. Sheep spent a greater proportion of their time foraging in uncontaminated patches than in contaminated patches. Where patches were highly aggregated, infected animals spent a greater proportion of total grazing time in uncontaminated patches than did uninfected animals, and grazed uncontaminated patches for longer on each sampling occasion. On grazing plots where all patches were contaminated, the difference between the numbers of larvae isolated from pasture herbage and ingested herbage was greatest for infected animals. In this situation, infected animals avoided parasites most. On grazing plots consisting of both contaminated and uncontaminated patches, the difference between the numbers of larvae isolated from pasture herbage and ingested herbage was greatest for uninfected animals. In this situation, uninfected animals were most effective at parasite avoidance as they consumed fewer parasite larvae relative to what was available on pasture.

Journal Article↗
PubMed2000

Search for scalar top and scalar bottom quarks in pp collisions at square root s=1.8 TeV.

We have searched for direct pair production of scalar top and scalar bottom quarks in 88 pb-1 of pp collisions at sqrt[s]=1.8 TeV with the CDF detector. We looked for events with a pair of heavy flavor jets and missing energy, consistent with scalar top (bottom) quark decays to a charm (bottom) quark and a neutralino. The numbers of events that pass our selections show no significant deviation from standard model expectations. We compare our results to the next-to-leading order scalar quark production cross sections to exclude regions in scalar quark-neutralino mass parameter space.

Journal Article↗
PubMed2000

Search for a W' boson via the decay mode W'-->munumu in 1.8 TeV pp collisions.

We report the results of a search for a W' boson produced in pp collisions at a center-of-mass energy of 1.8 TeV using a 107 pb-1 data sample recorded by the Collider Detector at Fermilab. We consider the decay channel W'-->&munumu and search for anomalous production of high transverse mass munumu lepton pairs. We observe no excess of events above background and set limits on the rate of W' boson production and decay relative to standard model W boson production and decay using a fit of the transverse mass distribution observed. If we assume standard model strength couplings of the W' boson to quark and lepton pairs, we exclude a W' boson with invariant mass less than 660 GeV/c2 at 95% confidence level.

Journal Article↗
PubMed2000

Ventral subiculum administration of the somatostatin receptor agonist MK-678 increases dopamine levels in the nucleus accumbens.

Somatostatin (or somatotropin-release inhibitory factor, SRIF) binding and in situ hybridisation studies have indicated a high expression of receptor subtypes throughout the rat brain and, in particular, in subregions of the hippocampus and subiculum. In vitro, somatostatin and related peptides, including seglitide (MK-678), hyperpolarize subicular neurones of the burst firing type-a response, which may have functional consequences for their output. One major projection from the subiculum is to the nucleus accumbens. The functional consequence of somatostatin receptor stimulation in the ventral subiculum has been assessed by measuring extracellular levels of dopamine in the ipsilateral nucleus accumbens. In anaesthetised rats, administration of seglitide (MK-678), a somatostatin analogue with selectivity for the SRIF-1 receptor (comprising somatostatin sst2, sst3 and sst5 subtypes) significantly increased extracellular levels of dopamine in the ipsilateral nucleus accumbens shell. The result suggests that hyperpolarization of subicular neurones by MK-678 may lead to activation of the subiculo-accumbens projection system, and an associated increase in dopaminergic function.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2000

Stimulating effect of biologically modified low density lipoproteins on ADP-induced aggregation of washed platelets persists in absence of specific binding.

Oxidized low density lipoproteins are closely associated with atherosclerosis and also might be directly involved in thrombosis because they have been shown to mediate a stimulating effect on human platelets. In this work, we used biologically modified low density lipoproteins (i.e., low density lipoproteins sufficiently oxidized to show specificity for the macrophage scavenger receptor system) to examine if specific binding of the oxidized apolipoprotein moiety to the platelet surface is a prerequisite for the platelet-stimulating effects reported by other authors. We find that biologically modified low density lipoproteins show specific binding to human platelets (K(d)=5.83+/-0.4 microg/mL, 3850+/-620 sites/platelet) and strongly augment both ADP- and thrombin-induced aggregation of washed platelets. Maleylated albumin, an antagonist of oxidized low density lipoproteins binding to all currently classified scavenger receptors, is able to reduce platelet oxidized low density lipoproteins binding to background levels. Nevertheless, maleylated albumin is not able to exert any kind of normalizing effect on the augmented ADP-induced aggregation response observed in the presence of biologically modified low density lipoproteins. From these data, we conclude that specific binding of oxidatively modified apolipoprotein B to the platelet surface is not essential to the process of platelet stimulation. Therefore, we conclude that these stimulating effects may be mediated by unidentified compounds formed in the lipid phase of the lipoproteins.

Adenosine Diphosphate↗
PubMed2000

In situ prosthetic graft repair of a mycotic aneurysm of the aorta after orthotopic liver transplantation.

BACKGROUND: Vascular complications after liver transplant are associated with a high incidence of graft failure and mortality. Mycotic aneurysms, although uncommon, carry the additional risk of infection and rupture. METHODS: We report a case of a 51-year-old woman who developed a mycotic aneurysm of the aorta secondary to construction of an infrarenal donor iliac artery graft during a retransplant. We evaluated risk factors for the aneurysm, appropriate diagnosis, and potential treatments. RESULTS: The aneurysm was repaired with an in situ prosthetic graft. The patient is alive with good liver function 31 months posttreatment. CONCLUSIONS: The use of in situ prosthetic grafts for repair of mycotic aneurysms is appropriate in certain situations and may be life-saving.

Aneurysm, Infected↗
PubMed2000

Reaction of mock jurors to testimony of a court appointed expert.

A study was conducted to assess the impact of court appointed experts on the judgments of mock jurors. A civil proceeding was adopted for the experiment. Mock jurors heard testimony about a plaintiff's injury in an automobile accident. In some conditions, medical testimony for the plaintiff and defendant was provided by experts hired by each side. In other conditions, a medical expert appointed by the court testified in addition to the two adversarial experts. In one of these conditions, the court expert sided with the plaintiff; in another, the expert sided with the defendant. The plaintiff in the case was always an individual. The defendant was sometimes a corporation and sometimes an individual. The results showed that mock jurors sided with the court appointed expert in every condition except when the expert favored a corporate defendant. The results were discussed in terms of heuristic processing of persuasive information.

Criminal Law↗
PubMed2000

Human alpha6 AChR subtypes: subunit composition, assembly, and pharmacological responses.

Many nicotinic acetylcholine receptor (AChR) subunits are known to be co-expressed with the alpha6 subunit in neurons. Because alpha6beta4 AChRs assemble inefficiently and alpha6beta2 AChRs not at all, more complex mixtures of human subunit cDNAs were tested for their abilities to form functional AChRs when expressed in Xenopus oocytes. alpha6beta4beta3 AChRs produced the largest and most consistent responses. alpha6alpha3beta2 AChRs exhibited reduced potency for ACh and increased potency and efficacy for nicotine compared to alpha3beta2 AChRs, but similar resistance to functional inactivation after prolonged exposure to nicotine. alpha6alpha4beta2 AChRs differed little in potency or efficacy for ACh or nicotine compared to alpha4beta2 AChRs, and had similarly high sensitivity to inactivation by prolonged exposure to nicotine. Co-expression of alpha6 and beta2 cRNAs resulted in large numbers of (3)H-epibatidine binding sites in the form of large aggregates but not in functional pentameric AChRs. Co-expression of alpha6, beta2, and alpha5 resulted in assembly of some functional pentameric AChRs. Chimeras with the large extracellular domain of alpha6 and the rest from either alpha3 or alpha4 efficiently formed functional AChRs. Thus, the extracellular domain of alpha6 efficiently assembles with beta2 to form ACh binding sites, but more C-terminal domains cause difficulties in forming pentameric AChRs. Chimeric alpha6/alpha3 and alpha6/alpha4 AChRs containing either beta2 or beta4 subunits were blocked by alpha-conotoxin MII which had previously been reported to be specific for alpha3beta2 AChRs.

Animals↗
PubMed2000

The "hired gun" effect: assessing the effect of pay, frequency of testifying, and credentials on the perception of expert testimony.

Three experiments addressed the proposition that jurors use short cuts in processing information when confronted with expert scientific testimony. The results of the first two studies demonstrated that experts who are highly paid for their testimony and who testify frequently are perceived as "hired guns." They are neither liked nor believed. The results of the third experiment replicated the hired gun effect and showed that it is most likely to occur when the testimony is complex and cannot be easily processed. The results were discussed in terms of the theoretical differences between central and peripheral processing of persuasive messages in a legal context.

Adolescent↗
PubMed2000

The Bayesian approach improves the electrocardiographic diagnosis of broad complex tachycardia.

Despite numerous attempts at devising algorithms for diagnosing broad complex tachycardia (BCT) on the basis of the electrocardiogram (ECG), misdiagnosis is still common. The reason for this may lie with difficulty in implementing existent algorithms in practice, due to imperfect ascertainment of ECG features within them. An attempt was made to approach the problem afresh with the Bayesian inference by the construction of a diagnostic algorithm centered around the likelihood ratio (LR). Previously studied ECG features most effective in discriminating ventricular tachycardia (VT) from supraventricular tachycardia with aberrant conduction (SVTAC), according to their LR values, were selected for inclusion into a Bayesian diagnostic algorithm. A test set of 244 BCT ECGs was assembled and shown to three independent observers who were blinded to the diagnoses made at electrophysiological study. Their diagnostic accuracy by the Bayesian algorithm was compared against that by clinical judgement with the diagnoses from EPS as the criterial standard. Clinical judgement correctly diagnosed 35% of SVTAC, 85% of VT, and 47% of fascicular tachycardia. In comparison, by the Bayesian algorithm devised, 52% of SVTAC, 95% of VT, and 97% of fascicular tachycardia were correctly diagnosed. The Bayesian algorithm devised has proved to be superior to the clinical judgement of the observers who participated in this study, and theoretically will obviate the problem of imperfect ascertainment of ECG features. Hence, it holds the promise for being an effective tool for routine use in clinical practice.

Algorithms↗
PubMed2000

Accommodative and vergence findings in ocular myasthenia: a case analysis.

Myasthenia gravis (MG) is a neuromuscular disorder that affects skeletal muscles, in particular, the extraocular muscles. Response variability is a hallmark sign. Detailed findings are described in a patient with MG in which the presenting sign was accommodative insufficiency. Objective accommodative findings were recorded 3 years before the onset of myasthenia, soon after the initial diagnosis was made, and then after the treatment commenced with pyridostigmine. In addition, clinical measurements were obtained periodically at different times of the day for various binocular motor functions, including near point of convergence, phoria, fusional and accommodative amplitudes, and relative accommodation. The disease adversely affected all accommodative and vergence findings, with fatigue being the primary disturbance. The therapeutic administration of pyridostigmine improved static measurements of accommodation and vergence and reduced asthenopia. The objective dynamic measurements of accommodation, vergence, and versions were less affected. These findings provide a clear demonstration that both intrinsic and extrinsic ocular muscles may be affected in the prepresbyopic myasthenic patient.

Accommodation, Ocular↗
PubMed2000

Out-of-area travel from rural and urban counties: a study of ambulatory care sensitive hospitalizations for New York State residents.

Rural patients who are admitted to hospitals outside their residence county or who travel great distances for hospitalization deprive local rural hospitals of revenue. To provide more information about such rural residents, we studied their characteristics compared to those admitted in the same county. Characteristics studied included illness severity, demographics and county resources. To validate the findings and to provide a different analytic approach, characteristics of residents who travel long distances for admission were also studied. We studied admissions for ambulatory care sensitive conditions, as they might be most responsive to policy changes such as increasing recruitment of local primary-care physicians. Hospital discharges during 1994 for 248,656 New York State residents were studied. We constructed multivariate models using logistic regression and ordinary least squares methods. The models were applied to residents in three types of geographic location along an urban-rural continuum. Outside admissions were associated with younger age, higher illness severity and fewer county hospital resources. Same county admissions were associated with nonwhite race, and lack of insurance. Surprisingly, in rural counties, outside admissions were directly associated with increased primary-care providers. Results from the distance model generally supported findings from the outside admission model.

Ambulatory Care↗
PubMed2000

The effect of age and duration of disease on airway structure in fatal asthma.

We hypothesized that if airway remodeling is related to duration of asthma, that when matched for severity, the airways of older adults should show greater alterations than the airways of younger adults. Using standard morphometric techniques, we compared airways with basement membrane perimeters (Pbm) between 2 and 10 mm from young individuals who died of asthma (n = 14, range 17-23 yr), and older individuals with fatal asthma (n = 13, range 40-49 yr). Comparisons were also made with normal airways from age-matched adults. Wall area was increased in old individuals with fatal asthma compared with young individuals with fatal asthma, primarily due to greater adventitial area, whereas wall area in young individuals with fatal asthma was not different from control subjects. Within muscle bundles the connective tissue matrix was increased around individual cells in individuals with asthma, unrelated to age. After adjustment for this change, smooth muscle area in both asthma groups was still greater than in age-matched control subjects, in old individuals with fatal asthma 4-fold greater (p = 0.04), and in young individuals with fatal asthma 2-fold greater (p = 0.03). Airway narrowing was increased in old versus young individuals with fatal asthma, with both groups more narrowed than control subjects. Intralumenal obstruction and subepithelial collagen in the two asthma groups were significantly greater than in control subjects, but there was no age effect. These data provide support for the hypothesis that there is an increase in airway wall area, including smooth muscle, and airway narrowing with increasing duration of severe asthma or with older age. The observation that total wall thickness was not greater in young individuals with young fatal asthma than in control subjects suggests that factors other than airway wall geometry contribute to the pathogenesis of fatal attacks in this age group.

Adolescent↗
PubMed2000

Curative radiotherapy for anterior commissure laryngeal carcinoma.

There is continuing controversy surrounding the most effective treatment of glottic carcinoma involving the anterior commissure (AC). Surgery has been the preferred method of treatment, since studies previously indicated early tumor invasion of the thyroid cartilage at the AC, thereby assuming less curability by radiotherapy (RT). Subsequent laryngeal anatomic studies and refinement of RT techniques have brought into question the ineffectiveness of curative irradiation. A retrospective review of 174 patients with early-stage glottic carcinoma treated with standard fractionation curative RT revealed 34 patients with T1 and T2 lesions involving the AC. Allowing for a follow-up of at least 3 years, we observed only a 12% (4 of 34 patients) local recurrence rate after RT alone, with excellent voice quality and no major complications related to the irradiation. The 4 local recurrences were controlled by total laryngectomy, although 2 patients developed distant metastatic disease. Radiotherapy represents an effective method of treating T1 squamous cell carcinoma of the glottis with AC involvement. The small number of T2 glottic carcinomas in this study prevents a meaningful conclusion concerning treatment of these lesions.

Aged↗