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Biomedical subjects

K Fox

Publications and source records attributed to K Fox.

At least 145 records · Page 8Linked to original sources
PubMed1994

Perceived locus of causality, goal orientations, and perceived competence in school physical education classes.

Ryan & Connell (1989) have demonstrated that different types of behavioural regulation can be located on a continuum of perceived autonomy or perceived locus of causality. The present study applied their formulation in the context of school physical education (PE) and examined the relationships of perceived autonomy, perceived competence and goal orientations with intrinsic interest across two PE activities. School students aged 12-14 years (N = 85) completed an adapted version of the Self-Regulation Questionnaire (Ryan & Connell, 1989) and measures of perceived competence and intrinsic interest separately for two PE activities. They also completed the British version of the Task and Ego Orientation in Sport Questionnaire (Duda, Fox, Biddle & Armstrong, 1992). Students appeared to be differentially motivated for the two activities due to different perceptions of autonomy. Structural equation modelling analysis showed that perceived autonomy and task orientation had direct effects on intrinsic interest for both the activities. Perceived competence, however, was positively associated with intrinsic interest only for one of the activities. The implications of the results for the practice of physical education are discussed.

Achievement↗
PubMed1994

The cortical component of experience-dependent synaptic plasticity in the rat barrel cortex.

Rats were raised with altered tactile experience from P0 by removing all but one vibrissa (D1) from one side of the face (D1-spared animals). This procedure (univibrissa rearing) has previously been shown to cause neurons in cortical barrels surrounding D1 to develop greater than normal responses to D1 vibrissa stimulation and smaller than normal responses to principal vibrissa stimulation (Fox, 1992). In this study, it was found that the potentiated D1 responses could be attenuated by acute microlesions placed in the D1 barrel, while principal vibrissa responses were unchanged or even slightly elevated for the same cases. The ratio of the average D1 to principal vibrissa response was approximately proportional to the volume of tissue damaged in the D1 barrel. This result implies that the synaptic plasticity seen in cortex of D1-spared animals is due to synaptic changes that take place within the barrel cortex rather than to relay of changes occurring at a subcortical level. In addition, lesions aimed at the septum between D1 and an adjacent barrel almost completely abolished responses to D1 stimulation in that barrel, including short-latency responses (5-10 msec). Only neurons severed horizontally from D1 were affected. Neurons that maintained a connection with the D1 barrel via a bridge of septal tissue preserved their usual elevated levels of response to D1 stimulation and their aberrant short-latency responses. This result implies that pathways radiating out from the D1 barrel/column, and connecting neurons in the D1 barrel to cells in surrounding barrels, undergo synaptic plasticity induced by univibrissa rearing.

Animals↗
PubMed1994

Quality of care in public and private primary health care facilities: structural comparisons in Jamaica.

This article examines the quality of care provided by Jamaican primary health care clinics by comparing various structural quality indexes derived from a nationwide 1990 survey of 366 public clinics and 189 private clinics. This comparison points up important differences in the quality of care being provided by public versus private and urban versus rural facilities that might not have been anticipated. Among other things, the study found that the public clinics provided better prenatal diagnosis and counseling and more family planning services than the private clinics. However, the private clinics tended to be better condition, better equipped and supplied, and better able to provide certain laboratory test results in a timely manner. Comparison of urban and rural public clinics indicated that the urban clinics were somewhat better provisioned with equipment, supplies, and pharmaceuticals. However, the rural clinics appeared to be in better repair. Comparison of basic and higher-level public clinics showed the basic clinics to be in better condition and more fully staffed than the higher-level clinics while having similar perinatal diagnostic capabilities. However, the higher-level public clinics tended to have an overall profile more resembling that of the private clinics, being better equipped and supplied than the basic clinics. While structural measures of quality such as those employed here tend to poorly estimate health outcomes, they do serve as good indicators of access to services where resources are severely constrained. For policy-makers, the results presented here could prove useful in guiding concrete interventions, summarizing the structural elements of health care quality at different types of facilities, and providing a method for less costly evaluation of programs designed to improve services at primary health care clinics.

Ambulatory Care Facilities↗
PubMed1993

Postsynaptic control of plasticity in developing somatosensory cortex.

The rearrangement of synaptic connections during normal and deprived development is though to be controlled by correlations in afferent impulse activity. A favoured model is based on post-synaptic detection of synchronously active afferents; synapses are stabilized when pre- and postsynaptic activity is correlated and weakened or eliminated when their activity is uncorrelated. Most evidence for this model comes from demonstrations that correlated afferent input is necessary for the segregation of eye-dominant inputs in the developing vertebrate visual system and that critical period plasticity of ocular dominance columns in cat visual cortex is disrupted by blockade of postsynaptic transmission. We tested whether the developmental plasticity of somatosensory columns, known as 'barrels', in rodent primary somatosensory cortex (S1) is similar to that of ocular dominance columns. We report here that the selective disruption of postsynaptic activation in rat S1 by application of a glutamate receptor antagonist inhibits rearrangements in the somatotopic patterning of thalamocortical afferents induced by manipulations of the sensory periphery during the critical period. These findings show that postsynaptic activation has a prominent role in critical period plasticity in S1 cortex.

2-Amino-5-phosphonovalerate↗
PubMed1993

The investigation and rectification of field placement errors in the delivery of complex head and neck fields.

PURPOSE: To evaluate a novel technique for resolving field placement errors into their components and to quantify the improvement in accuracy potentially achievable by translation and rotation of the radiation beam. METHODS AND MATERIALS: One hundred and eighty-five films (both simulator and portal) from seventeen patients receiving radiotherapy to the head and neck region were analyzed in pairs. The computer based comparisons of complex fields with curved edges employed the intersections of perpendiculars from two reference points with the field periphery to define field match points. Field placement errors were resolved into those due to patient motion within the immobilization shell and those due to incorrect beam position, orientation, or shape. RESULTS: The median and the 95 percentile of the distribution of differences between prescribed (simulator) fields and treated (portal) fields referenced to the patients anatomy were 4.4 mm and 8.9 mm, respectively. The analysis suggests that with appropriate translation and rotation of the beam with respect to the immobilization shell these figures could be reduced to 3.1 mm and 8.2 mm, respectively, confirming the large contribution of patient motion within the shell to field placement accuracy. Comparisons between treated fields indicated smaller variability during treatment than between simulation and treatment. CONCLUSION: The perpendicular intersection method described here was found appropriate for the identification of field match points. The distributions of field placement errors were similar to those in a published study of straight edged fields. Translation and rotation of the applied field with respect to the immobilization shell would generally result in only a small improvement in field placement accuracy.

Head and Neck Neoplasms↗
PubMed1993

Recurrent anterior uveitis induced by multiple systemic injections of muramyl dipeptide.

The development of new therapeutic modalities in the treatment of uveitis has been greatly aided by the availability of suitable animal models. The endotoxin model excellently mimics many features of acute anterior uveitis. A new model that exhibits many features of recurrent anterior uveitis is described here. Muramyl dipeptide, MDP, is a synthetic monomer of Gram positive and Gram negative bacterial cell walls. The molecule is highly inflammatory, but unlike endotoxin does not elicit an antibody response. After a single injection (4 hr post-injection), acute anterior segment changes include massive engorgement of peri-limbal blood vessels, anterior chamber flare, fibrin deposits and heterophil (neutrophil) infiltration which subside within 24-48 hr. There is also break-down of the blood-aqueous barrier. With multiple injections the exacerbations and remissions continue to be observed after each injection but the disease progresses to a recurrent form including the development of synechiae and a mononuclear infiltrate into the anterior segment. The ocular changes are paralleled by changes in the bloodstream with recurrent heterophilia. Thus MDP does not elicit ocular or systemic tolerance. This new model of anterior uveitis should allow study of many of the events that occur in recurrent uveitis in man.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1993

Do NMDA receptors have a critical function in visual cortical plasticity?

The theoretical framework, by which we understand the function of NMDA receptors, is derived, in large part, from work conducted on the hippocampal slice preparation, where NMDA receptors are crucial for a form of synaptic plasticity known as long-term potentiation (LTP). Establishing their role in plasticity mechanisms in the neocortex is proving to be far more difficult than originally envisaged, in part due to the fact that the operation of NMDA receptors is different in the intact animal than in vitro. For example, NMDA receptors are activated at low levels of sensory input in intact animals but only by high levels of input in slice preparations. Recent results suggest that a re-evaluation of the role of NMDA receptors in neocortical plasticity is required. Here we discuss some of the issues and introduce four criteria by which any factor supposedly involved in plasticity can be judged. NMDA receptors fulfill more of these criteria than any of the other factors so far investigated in the visual cortex, but maybe this is because they have been studied more intensively.

Animals↗
PubMed1993

Neuroendocrine carcinoma of the colon. Correct diagnosis is important.

Neuroendocrine carcinomas of the colon and rectum are unusual and have in the past been misrepresented as either carcinoid tumors or undifferentiated cancers. Colorectal neuroendocrine tumors comprise a clinicopathologic spectrum that ranges from indolent to highly aggressive. The case discussed illustrates the importance of the right diagnosis because it will affect treatment and may better predict the clinical course.

Adult↗
PubMed1993

Role of beta-hemolytic group C streptococci in pharyngitis: incidence and biochemical characteristics of Streptococcus equisimilis and Streptococcus anginosus in patients and healthy controls.

The biochemical characteristics and the isolation rates of the two Lancefield group C streptococcal species (S. equisimilis and S. anginosus) from patients with pharyngitis and asymptomatic controls were compared. Some 239 strains of beta-hemolytic group C streptococci were isolated from 1,480 patients (209 strains) with pharyngitis and 227 controls (30 strains). A total of 44 strains displayed broad hemolysis, were Voges-Proskauer test negative, and produced glucuronidase. Some 72.7% of these strains also fermented ribose. A second group of 159 strains was Voges-Proskauer test positive and glucuronidase negative; 98.8% also displayed minute hemolysis and only 3.7% fermented ribose. These two groups represent typical large-colony S. equisimilis and small-colony S. anginosus, respectively. A small number of strains (36 in total) exhibited intermediate characteristics; morphologically, all 36 strains resembled S. anginosus, but 6 strains biochemically resembled S. equisimilis. No strains of S. equisimilis fermented sorbitol (unlike S. zooepidemicus) and all fermented trehalose (unlike S. equi). The structural carbohydrate profiles of S. equisimilis and S. anginosus both included galactosamine (consistent with their being group C organisms), but the profiles were not distinguishable. In total, 78.5% of strains from controls and 83.3% of strains from patients were determined to be the species S. anginosus. S. equisimilis was isolated from 3.0% of patients and 2.2% of controls, and S. anginosus was isolated from 11.1% of patients and 11.0% of controls. Thus, S. equisimilis and S. anginosus are both members of the normal flora of asymptomatic individuals. The incidence and biochemical characteristics of these two species are similar in patients who are healthy and those who have disease. However, a companion article provides clinical evidence associating S. equisimilis (but not s. anginosus) with pharyngitis.

Adult↗
PubMed1993

Role of group C beta-hemolytic streptococci in pharyngitis: epidemiologic study of clinical features associated with isolation of group C streptococci.

All Lancefield group C beta-hemolytic streptococci isolated over 12 months from college students with clinical pharyngitis and age-matched healthy controls were identified. Clinical features of upper respiratory tract infection and pyogenic pharyngitis as well as colony counts were tabulated for each patient according to throat culture results. Of 1,480 patients, Lancefield group C Streptococcus equisimilis was isolated from 45 (3%) patients and Streptococcus anginosus ("Streptococcus milleri") was isolated from 164 (11.1%) patients. Patients from whom S. equisimilis was isolated had clinical features more suggestive of pyogenic infection than did patients from whom S. anginosus was isolated. Colony counts on primary throat culture plates from patients from whom S. equisimilis and Streptococcus pyogenes were isolated were higher than those from patients from whom S. anginosus was isolated. This study presents epidemiologic evidence supporting a role for S. equisimilis in causing pharyngeal infection and for S. anginosus as representing part of the normal oropharyngeal flora.

Adult↗
PubMed1993

Determination of carbohydrate profiles of Bacillus anthracis and Bacillus cereus including identification of O-methyl methylpentoses by using gas chromatography-mass spectrometry.

Bacillus anthracis and Bacillus cereus are closely related pathogenic organisms that are difficult to differentiate phenotypically or genotypically. It is well known that vegetative and spore forms of bacilli are quite distinct both morphologically and chemically, but spore-specific chemical markers allowing these species to be distinguished have not been previously described. By using gas chromatography-mass spectrometry, vegetative cells and spores of the two species were shown to exhibit distinct carbohydrate profiles. Profiles of vegetative B. anthracis typically contained high levels of galactose but did not contain galactosamine, whereas B. cereus contained galactosamine and generally low levels of galactose. Spore cultures exhibited unique carbohydrate profiles compared with those of vegetative cultures. B. anthracis spore profiles contained rhamnose alone, whereas B. cereus spore profiles contained rhamnose and fucose. Additionally, two spore-specific O-methylated methylpentoses were discovered. Both B. anthracis and B. cereus spores contained 3-O-methyl rhamnose, whereas B. cereus spores also contained 2-O-methyl rhamnose. Carbohydrate profiling is demonstrated to be a powerful tool for differentiating the two closely related species. Differentiation does not depend on whether organisms are in the vegetative or spore stage of growth.

Bacillus anthracis↗
PubMed1993

Endothelium dependent and independent responses in coronary artery disease measured at angioplasty.

OBJECTIVE--To investigate the effects of substance P and papaverine, two drugs that increase coronary blood flow by different mechanisms, on vasomotion in stenotic coronary arteries at percutaneous transluminal coronary angioplasty (PTCA). DESIGN--Coronary blood flow responses to substance P and papaverine were measured in stenotic coronary arteries at the time of PTCA with quantitative angiography and a Doppler flow probe. SETTING--A cardiothoracic referral centre. PATIENTS--15 patients undergoing elective PTCA of a discrete epicardial coronary artery stenosis. INTERVENTIONS--Pharmacological coronary flow reserve was determined with papaverine 5-10 minutes before and after successful PTCA. Endothelium dependent responses to 2 minute infusions of substance P (10-15 pmol.min-1) were assessed immediately before PTCA. MAIN OUTCOME MEASURES--Coronary blood flow responses and changes in epicardial coronary artery area at stenotic, proximal, and distal sites with papaverine and substance P. RESULTS--Stenotic sites dilated with papaverine before PTCA (17.7%(6.9%) (mean (SEM)) area increase, p < 0.05 v baseline). Substance P dilated stenotic sites (16.8%(5.7%) area increase, p < 0.05) and proximal (14.3%(5.4%), p < 0.05) and distal sites (41.7%(9.3%), p < 0.005). Coronary flow reserve increased but did not reach normal values after PTCA (2.3(0.4) before PTCA v 3.0(0.4) after PTCA, p < 0.05) and was associated with an increase in peak flow with papaverine. Angioplasty did not alter baseline flow. After PTCA papaverine caused significant vasoconstriction at the stenotic site (-13.6%(4.3%) area decrease, p < 0.05). There was a negative correlation (r = -0.68, p < 0.05) between the dilator response with papaverine before PTCA and the constrictor response after PTCA. CONCLUSIONS--Substance P causes endothelium dependent dilatation in atheromatous coronary arteries, even at sites of overt atheroma. The cause of the paradoxical constrictor response to papaverine after PTCA is uncertain, but unopposed flow mediated vasoconstriction (the myogenic response) after balloon induced endothelial denudation may be one of several contributory factors.

Angioplasty, Balloon, Coronary↗
PubMed1993

Prognostic significance of transient ST segment changes after coronary artery bypass surgery: a long-term (4-10 year) follow up study.

OBJECTIVE: To assess the long-term (four to 10 years) prognostic significance of transient ST segment changes on ambulatory ST segment monitoring after coronary artery bypass grafting (CABG). PATIENTS AND METHODS: 76 patients (67 men, nine women) underwent CABG between 1982 and 1984 (n = 31) and between 1987 and 1988 (n = 45) and at a mean age of 57. All underwent 48 hours of ambulatory ST segment monitoring at a mean of 19 weeks after surgery. The results were available for assessment. All general practitioners were contacted and patients' notes reviewed. Patients were contacted by telephone. Details were recorded of intervening events (acute myocardial infarction, unstable angina, need for further revascularisation, and deaths). Event free survival curves were produced for those with and without transient ST segment changes during routine postoperative ambulatory ST segment monitoring. RESULTS: During 3213 hours of monitoring after CABG, 21 (27.6%) of 76 patients had transient ST segment changes, of which 70% were silent. Over a mean 70 month follow up period, patients with such ischaemic changes were no more likely to have either an objective (myocardial infarction or cardiac death) or subjective (unstable angina or another revascularisation) event than those patients without ischaemic changes. This finding was the same in patients operated on between 1987 and 1988 and between 1982 and 1984. CONCLUSIONS: Although ambulatory ST segment monitoring is becoming increasingly popular in some countries as a routine investigation for ischaemia in various coronary subgroups, the findings of such an investigation, when performed after CABG, do not help to identify a subgroup more likely to have an adverse outcome during up to 10 years of follow up. There seems to be no reason to perform this investigation after surgery, and particularly to refer patients for reinvestigation because of the detection of predominantly silent ST segment changes of uncertain relevance.

Adult↗
PubMed1993

Coronary flow reserve in patients with chest pain and normal coronary arteries.

BACKGROUND: Many studies have shown that coronary flow reserve is reduced in patients with chest pain and angiographically normal coronary arteries. The methods used to assess coronary blood flow have varied, but in nearly all reports dipyridamole has been used to bring about vasodilatation. This study was designed to assess whether the apparent impairment of coronary flow reserve seen with dipyridamole could be reproduced with either papaverine or adenosine, which induce maximum coronary blood flow by different mechanisms. METHODS: 25 patients with chest pain and angiographically normal coronary arteries were studied with an intracoronary Doppler flow probe and quantitative angiography to determine epicardial coronary artery area, coronary blood flow velocity, coronary flow reserve, and coronary vascular resistance index (CVRI, the ratio of resistance after intervention to basal resistance). All patients received papaverine 8 mg. Eight patients with positive exercise tests received intracoronary papaverine (8 and 10 mg), intracoronary adenosine (6, 20, 60 micrograms), and high-dose intravenous dipyridamole (0.84 mg/kg). RESULTS: The velocity ratio (peak after intervention: baseline) (mean (SEM)) after 8 mg papaverine was 3.3 (0.2) (n = 25) and the coronary flow reserve was 4.1 (0.3) (n = 25). There were no differences between patients with a positive (n = 16) or negative (n = 9) exercise test. In eight patients coronary flow reserve was measured after increasing doses of papaverine, adenosine, and dipyridamole. Coronary flow reserve was 4.5 (0.3) with papaverine, 4.8 (0.3) with adenosine, and 3.5 (0.4) with dipyridamole (p = 0.08 v papaverine and adenosine). CVRI was 0.22 (0.01) with papaverine, 0.21 (0.02) with adenosine, and 0.29 (0.03) with dipyridamole (p < 0.05 v papaverine, p = 0.09 v adenosine). CONCLUSIONS: These results indicate that measurement of coronary flow reserve and CVRI in patients with chest pain and normal coronary arteries depends on the pharmacological stimulus. Normal values were obtained with papaverine in all patients, irrespective of the exercise test response. In patients with a positive exercise test significantly lower values were obtained with dipyridamole than with papaverine, or adenosine. The reported impairment of coronary flow reserve in patients with angina and normal coronary arteries may reflect the variability in response to different pharmacological agents. The mechanism underlying this variability is unknown, but may involve an abnormality of adenosine metabolism in the myocardium.

Adenosine↗