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Biomedical subjects

K Fox

Publications and source records attributed to K Fox.

At least 91 records · Page 5Linked to original sources
PubMed1997

Diagnosis and treatment of the cracked tooth.

This review paper discusses the recognised factors which predispose to cracked-tooth syndrome. In addition, common presenting symptoms and the various methods to aid clinical diagnosis of this problem are examined. The incidence of the condition is reported and the prognosis of the various forms of fracture, as suggested by clinical presentation, are outlined with reference to the available literature. Benefits and relative demerits of traditional and more modern treatment options are presented and recommendations made for future research.

Cracked Tooth Syndrome↗
PubMed1996

Tenuous link between ischaemic threshold and both ambulatory ischaemia and symptom status over time in stable angina: a 5-year follow-up study.

This study evaluates changes in ischaemic threshold over a 5-year period in patients with stable angina pectoris, who did not suffer any intervening cardiac event. Changes in ischaemic threshold are related to alterations in symptomatic status and ambulatory ischaemia. Over long-term follow-up, there is a significant fall in ischaemic threshold in such patients (mean heart rate at onset of ischaemia fell from 104 +/- 17.8 to 97 +/- 17.4 bpm: P < 0.001), but this is not matched by a worsening of either symptoms or ischaemia during daily life. In the 68% of patients that had a reduction in ischaemic threshold of > or = 5 bpm, 68% had either definite reduction or no change in symptoms and 84% had either reduction, abolition or no change in transient ischaemic activity. The dissociation between ischaemic threshold, ambulatory ischaemia and symptoms has implications for long-term monitoring and management of the patient with stable angina.

Adult↗
PubMed1996

Glutamate receptor blockade at cortical synapses disrupts development of thalamocortical and columnar organization in somatosensory cortex.

The segregation of thalamocortical inputs into eye-specific stripes in the developing cat or monkey visual cortex is prevented by manipulations that perturb or abolish neural activity in the visual pathway. Such findings show that proper development of the functional organization of visual cortex is dependent on normal patterns of neural activity. The generalisation of this conclusion to other sensory cortices has been questioned by findings that the segregation of thalamocortical afferents into a somatotopic barrel pattern in developing rodent primary somatosensory cortex (S1) is not prevented by activity blockade. We show that a temporary block of N-methyl-D-aspartate (NMDA) and non-NMDA glutamate receptors in rat S1 during the critical period for barrel development disrupts the topographic refinement of thalamocortical connectivity and columnar organization. These effects are evident well after the blockade is ineffective and thus may be permanent. Our findings show that neural activity and specifically the activation of postsynaptic cortical neurons has a prominent role in establishing the primary sensory map in S1, as well as the topographic organization of higher order synaptic connections.

2-Amino-5-phosphonovalerate↗
PubMed1996

Requirement for alpha-CaMKII in experience-dependent plasticity of the barrel cortex.

The mammalian sensory neocortex exhibits experience-dependent plasticity such that neurons modify their response properties according to changes in sensory experience. The synaptic plasticity mechanism of long-term potentiation requiring calcium-calmodulin-dependent kinase type II (CaMKII) could underlie experience-dependent plasticity. Plasticity in adult mice can be induced by changes in the patterns of tactile input to the barrel cortex. This response is strongly depressed in adult mice that lack the gene encoding alpha-CaMKII, although adolescent animals are unaffected. Thus, alpha-CaMKII is necessary either for the induction or for the expression of plasticity in adult mice.

Animals↗
PubMed1996

Hypertension and heart disease.

Peripheral blood pressure and heart disease are closely linked. Hypertension is not only associated with, but also a cause of, heart disease and evidence is mounting that treating hypertension reduces cardiac events. The knowledge and management of blood pressure is a key element of cardiac care.

Heart Diseases↗
PubMed1996

Mechanisms underlying experience-dependent potentiation and depression of vibrissae responses in barrel cortex.

Plasticity was studied in the barrel cortex of rats and mice. Vibrissae deprivation in adult and adolescent animals caused changes in the response properties of cortical neurons to stimulation of spared and deprived vibrissae. Plasticity involved both potentiation of spared vibrissae responses and depression of deprived vibrissae responses in layer II/III of the cortex. Vibrissae response potentiation was found to require alpha CaMKII in adult cortex. Vibrissae response depression was not found to occur in adult cortex but was found in adolescent animals for the principal vibrissa. Preliminary results suggested that vibrissae response depression exhibits both hetero- and homosynaptic components.

Animals↗
PubMed1996

Effects of intermittent androgen suppression on the stem cell composition and the expression of the TRPM-2 (clusterin) gene in the Shionogi carcinoma.

The proportion of tumorigenic stem cells and the expression of the apoptosis-related gene, TRPM-2 (clusterin), were studied in populations of Shionogi carcinoma cells subjected to multiple cycles of androgen withdrawal and replacement (intermittent androgen suppression). The parent androgen-dependent cell line was initially transplanted into a male mouse which was castrated when the estimated weight of the resultant tumour became approximately 3 g. After the tumour had regressed to 40% or less of the original weight, it was transplanted into the next non-castrated male. This was repeated for four cycles of transplantation and castration-induced apoptosis before the tumour progressed to an androgen-independent state. The proportion of total stem cells in the tumour, as determined by in vivo limiting dilution assays in male mice, was constant during the first three cycles but increased 15-fold between the third and fourth cycles. In the parent androgen-dependent tumour before androgen ablation, the androgen-independent stem cell population formed 0.8% of the total stem cell compartment. After the fourth cycle this population increased to 47%; a population of similar size (33%, P = 0.8) was found in the androgen-independent recurrent form of the tumour induced by one-time castration. Whether androgen withdrawal therapy was intermittent or continuous, conversion to androgen independence thus occurred when one-third to one-half of the total stem cell compartment was populated by androgen-independent stem cells. The androgen-repressed TRPM-2 (clusterin) gene was actively expressed in regressing tumours after androgen ablation, and also became constitutively expressed in non-regressing tumours after the first and subsequent cycles of androgen withdrawal. Staining of cytoplasm and nuclei with anti-clusterin antibody was observed in androgen-dependent tumour cells after each cycle of intermittent androgen suppression; the nuclear staining was more intense in recurrent androgen-independent cells. The anomalous nuclear localization of clusterin, an anti-cytolytic TRPM-2 encoded protein, may serve to inhibit early events in the apoptotic process and thereby foster the generation and outgrowth of androgen-independent stem cells in an androgen-depleted environment.

Androgens↗
PubMed1996

Registration of births, stillbirths and infant deaths in Jamaica.

BACKGROUND: Vital statistics underestimate the prevalence of perinatal and infant deaths. This is particularly significant when these parameters affect eligibility for international assistance for newly emerging nations. OBJECTIVE: To determine the level of registration of livebirths, stillbirths and infant deaths in Jamaica. METHODOLOGY: Births, stillbirths and neonatal deaths identified during a cross-sectional study (1986); and infant deaths identified in six parishes (1993) were matched to vital registration documents filed with the Registrar General. RESULTS: While 94% of livebirths were registered by one year of age (1986), only 13% of stillbirths (1986) and 25% of infant deaths (1993) were registered. Post neonatal deaths were more likely to be registered than early neonatal deaths. Frequently the birth was not registered when the infant died. Birth registration rates were highest in parishes with high rates of hospital deliveries (rs = 0.97, P < 0.001) where institutions notify the registrar of each birth. Hospital deaths, however, were less likely to be registered than community deaths as registrars are not automatically notified of these deaths. CONCLUSIONS: To improve vital registration, institutions should become registration centres for all vital events occurring there (births, stillbirths, deaths). Recommendations aimed at modernizing the vital registration system in Jamaica and other developing countries are also made.

Birth Certificates↗
PubMed1996

Absolute identification of muramic acid, at trace levels, in human septic synovial fluids in vivo and absence in aseptic fluids.

This is the first report of a study employing the state-of-the-art technique of gas chromatography-tandem mass spectrometry for absolute identification of muramic acid (a marker for peptidoglycan) at trace levels in a human or animal body fluid or tissue. Daughter mass spectra of synovial fluid muramic acid peaks (> or = 30 ng/ml) were identical to those of pure muramic acid. Absolute chemical identification at this level represents a 1,000-fold increase in sensitivity over previous gas chromatography-mass spectrometry identifications. Muramic acid was positively identified in synovial fluids during infection and was eliminated over time but was absent from aseptic fluids.

Arthritis, Infectious↗
PubMed1996

Early continuous ST segment monitoring in unstable angina: prognostic value additional to the clinical characteristics and the admission electrocardiogram.

BACKGROUND AND OBJECTIVE: In unstable angina, clinical characteristics, resting electrocardiography, and early continuous ST segment monitoring have been individually reported to identify subgroups at increased risk of adverse outcome. It is not known, however, whether continuous ST monitoring provides additional prognostic information in such a setting. DESIGN: Observational study of 212 patients with unstable angina without evidence of acute myocardial infarction admitted to district general hospitals, who had participated in a randomised study comparing heparin and aspirin treatment versus aspirin alone. METHODS: Clinical variables and a 12 lead electrocardiogram (ECG) were recorded at admission, and treatment was standardised to include aspirin, atenolol, diltiazem, and intravenous glyceryl trinitrate, in addition to intravenous heparin (randomised treatment). Continuous ST segment monitoring was performed for 48 h and all inhospital adverse events were recorded. RESULTS: The admission ECG was normal in 61 patients (29%), showed ST depression in 59 (28%) (17 > or = 0.1 mV), and T wave changes in a further 69 (33%). The remaining 23 had Q waves (18), right bundle branch block (four), or ST elevation (one). During 8963 h of continuous ST segment monitoring (mean 42.3 h/patient), 132 episodes of transient myocardial ischaemia (104 silent) were recorded in 32 patients (15%). Forty patients (19%) had an adverse event (cardiac deaths (n = 3), non-fatal myocardial infarction (n = 6) and, emergency revascularisation (n = 31)). Both admission ECG ST depression (P = 0.02), and transient ischaemia (P < 0.001) predicted an increased risk of non-fatal myocardial infarction or death, while no patients with a normal ECG died or had a myocardial infarction. Adverse outcome was predicted by admission ECG ST depression (regardless of severity) (odds ratio (OR) 3.41) (P < 0.001), and maintenance beta blocker treatment (OR 2.95) (P < 0.01). A normal ECG predicted a favourable outcome (OR 0.38) (P = 0.04), while T wave or other ECG changes were not predictive of outcome. Transient ischaemia was the strongest predictor of adverse prognosis (OR 4.61) (P < 0.001), retaining independent predictive value in multivariate analysis (OR 2.94) (P = 0.03), as did maintenance beta blocker treatment (OR 2.85) (P = 0.01) and admission ECG ST depression, which showed a trend towards independent predictive value (OR 2.11) (P = 0.076). CONCLUSIONS: Patients with unstable angina and a normal admission ECG have a good prognosis, while ST segment depression predicts an adverse outcome. Transient myocardial ischaemia detected by continuous ST segment monitoring in such patients receiving optimal medical treatment provides prognostic information additional to that gleaned from the clinical characteristics or the admission ECG.

Adrenergic beta-Antagonists↗
PubMed1996

Women with chest pain: is exercise testing worthwhile?

OBJECTIVE: To determine the diagnostic value of the exercise tolerance test (ETT) in women presenting with chest pain. DESIGN: Prospective study of all women presenting to a centre with chest pain between 1987 and 1993 who were assessed by an ETT and coronary angiography. SETTING: The outpatient clinic of one consultant cardiologist in a tertiary referral centre. PATIENTS: All women referred to this outpatient clinic with chest pain were screened. For inclusion, patients had to perform ETT and undergo coronary angiography. Of the 347 referred during this period, 142 were excluded because they were unable to perform ETT or because of Q waves or other abnormalities on their resting electrocardiogram. RESULTS: Overall the sensitivity of the ETT was 68% and the specificity was 61%, with a positive predictive value of 0.61 and a negative predictive value of 0.68. There were 42 false positive and 31 false negative ETT results (36% of the study group). The predictive value of a negative test was higher in younger women (< 52 years) than in the older group (> or = 52 years) (P = 0.004), but the positive predictive value in the two groups was not significantly different. The predictive value of a negative test was also higher in those with two or fewer risk factors than in those with three or more risk factors (P = 0.001). The negative predictive value for those women above 52 years with three or more risk factors (24% of the study group) was only 0.25. Lack of chest pain during ETT was associated with a higher negative predictive value in the younger group than in the older women (P = 0.006). CONCLUSIONS: In women with chest pain use of the ETT was a misleading predictor of the presence or absence of coronary disease in 36% of these patients. In particular, a negative test in older women with three or more risk factors had a very low predictive value. The inclusion of risk factors and division by age can, however, be used to identify a population at intermediate risk for coronary artery disease in whom the ETT result has the highest diagnostic utility.

Adult↗
PubMed1996

Time course of experience-dependent synaptic potentiation and depression in barrel cortex of adolescent rats.

1. Plasticity could be induced in (S1) barrel cortex of adolescent rats by reducing the complement of vibrissae on one side of the muzzle to a single whisker for a period of 7, 20, or 60 days. The effect of deprivation was assessed by quantitatively by measuring cortical responses to stimulation of the spared and regrown deprived vibrissae. Vibrissa responses were evoked using a standard stimulus generated by an electromechanical stimulator and measured using poststimulus time histogram analysis. 2. Cells located in layers II/III were found to be plastic beyond postnatal day 28 (P28), whereas cells located in layer IV were not. The vibrissa dominance distribution was shifted significantly toward the spared vibrissa after 7, 20, and 60 days of deprivation for cells located in layers II/III of barrel columns surrounding the D1 column (P < 0.0001, 2-factor analysis of variance). The vibrissa dominance distribution did not shift significantly for cells located in layer IV of surrounding barrels for any of the durations of deprivation tested (P > 0.1). After 7 days of deprivation, 37% of the cells located in layers II/III of the columns deprived vibrissae showed greater responses to the spared vibrissae than to their deprived principal vibrissa, compared with 11% in normally reared adolescent animals and 3% in adults. The percentage of cells dominated by the spared vibrissa was 65% after 20 days of deprivation and 43% after 60 days. 3. For cells located in layers II/III, short-term deprivation (7 days) caused a decrease in the absolute magnitude of response to stimulation of the deprived vibrissa (reduction to approximately 28% of control levels). However, no change could be detected in the spared (D1) vibrissa input to the same deprived columns. Therefore the increase in D1 dominance registered in the deprived columns was mainly due to a decrease in principal vibrissa response and no change in the spared D1 vibrissa response. 4. The first increase in spared vibrissa response was seen after 20 days of deprivation. The response magnitude cells located in layers II/III increased to 70% above control levels. Responses to deprived vibrissa stimulation were depressed at 20 days of deprivation (reduction to 35% of control), implying that the vibrissa dominance shift at 20 days was due to both an increase in spared vibrissa response and a decrease in deprived vibrissa response. 5. The spared vibrissa response was increased after 60 days of deprivation (110% above control) in both near and far halves of the barrel columns surrounding D1. On average, the deprived vibrissa response was depressed at 60 days (84% of control), although less than at 20 or 7 days, because of recovery of responsiveness in the far half of the deprived barrel column. Layer II/III cells located in the half of the barrel column farthest from the spared D1 barrel column showed normal levels of deprived vibrissa input, whereas cells located in the half of the barrel column closest to the spared D1 barrel column still exhibited depressed levels of deprived vibrissa input (54% of control). 6. Control experiments suggested that depression of the deprived vibrissa response could not be explained by nonspecific effects. Depression was not a function of animal's age, because normally reared P28 and adult animals showed similar principal vibrissa response levels. It was not a result of nonspecific depression of cortical responses. because the decreased response only occurred in cells of deprived barrel columns and not spared barrel columns (recorded in the same animals). Depression was not due to altered vibrissa mechanics, because the spared vibrissa response was similarly depressed in animals in which the vibrissae had been trimmed rather than removed. Finally, depression was input specific at 7 and 20 days, because only the deprived vibrissa responses were depressed, whereas spared vibrissa responses were either at control levels or at elevated levels for the same cells. 7.

Analysis of Variance↗
PubMed1996

Vertical Banded Gastroplasty and Distal Gastric Bypass as Primary Procedures: A Comparison.

BACKGROUND: Comparing primary vertical banded gastroplasty (VBG) and distal gastric bypass (DGBP) patients might assist decision-making based on patient profiles and desired outcomes. METHODS: A prospective study of 81 vertical banded gastroplasty and 60 distal gastric bypass patients. Technical aspects, complications, weight loss, post-op compliance and satisfaction are reported. Length of follow-up is 48 months (VBG) and 36 (DGBP). Lost-to-follow-up 41% (VBG) and 22% (DGBP). Ten per cent of VBGs were revised, with 1% takedown. Three percent DGBPs were converted to proximal GBPs. Demographics are comparable. RESULTS: Operative time was 40 min VBG and 88 DGBP; blood loss 187 cc vs 335 cc; and hospital stay 3 versus 4 days. Exclusive VBG complications include: 1% staple-line leak, 4% intra-abdominal abscess, 1% respiratory failure, 5% pneumonia, 1% intra-abdominal bleed, 1% small bowel obstruction, 2% infected incision, 2% fistula, 2% stenotic or obstructed obstructed stoma, and 1% bezoar. Exclusive DGBP complications include: 2% GI bleed, 12% marginal ulcer, 5% reflux esophagitis, 13% hypocalcemia, 23% hypovitaminosis A and D (12% requiring B12 therapy). Shared complications include hypoproteinemia 6% VBG versus 40% DGBP; excess vomiting (>6 months post-op), 7% versus 10%, excess diarrhea 2% versus 20%, dehydration 1% versus 8%, re-hospitalization 4% versus 15% (hyperalimentation), post-op cholecystectomy 1% versus 5%, weight regain 48% versus 1%. VBG experienced an average of 64% excess weight loss at 36 months versus DGBP 89% excess weight loss. VBG follow-up compliance is generally poor but good for DGBP. Compliance with diet and supplements is equivalent (50%). Satisfaction is 85% and 93% respectively. CONCLUSION: The DGBP provides better long-term weight loss, but nutritional deficiencies occur more often and require close follow-up. The surgery is more complex, but as a primary procedure there are few major complications.

Journal Article↗
PubMed1996

Relationship between donor/recipient lung size mismatch and functional outcome in single lung transplantation for COPD.

Single lung transplantation is an effective treatment for patients with severe chronic obstructive pulmonary disease. Pulmonary hyperinflation, which is seen in most patients with severe chronic obstructive pulmonary disease, makes the task of appropriately matching the donor and recipient difficult. It seems that the optimal matching strategy remains undefined. No correlation between donor/recipient size match (actual and predicted) and the degree of functional improvement after single lung transplantation was found. There were no significant differences noted when comparing the functional outcomes of right and left lung transplant recipients. It was concluded that the chronic hyperinflation associated with severe chronic obstructive pulmonary disease allows for the use of significantly larger donors. The use of expanded donor/recipient size match criteria in patients with severe chronic obstructive pulmonary disease may shorten the waiting period prior to single lung transplantation and provide better utilization of donor organs.

Aged↗
PubMed1996

Assessing a murmur, saving a life: current trends in the management of hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy, formerly called idiopathic hypertrophic subaortic stenosis (IHSS), is the leading cause of sudden cardiac death in young people. Hypertrophic cardiomyopathy is a non-dilated cardiomyopathy primarily affecting the left ventricle, left atria, intraventricular septum, and mitral valve. It is an autosomal dominant genetic disorder that impairs diastolic and systolic function. Diagnosis is complex due to the heterogeneity of the disease. Symptoms and morphology are not always related and clinical signs may be absent or limited to a soft systolic murmur. The first symptom of hypertrophic cardiomyopathy is frequently sudden cardiac death. Echocardiogram is an accurate diagnostic tool. Asymptomatic patients are generally not treated. Treatment for symptomatic patients begins with beta or calcium channel blockers. Antiarrhythmics may be added to protect against sudden cardiac death. Surgical intervention is done if other treatments fall and involves removal of a portion of the obstructive septum. Operative mortality is 5% with a 60% reduction in symptoms. A promising alternative to surgery is dual-chamber pacemakers. Patient and family teaching is the emphasis of long-term management.

Adolescent↗
PubMed1995

From antianginal drugs to myocardial cytoprotective agents.

The existing major classes of antianginal drugs improve quality of life in patients with coronary artery disease, but mortality in these patients remains unacceptably high. In order to limit the complications of the disease, it is vital to limit myocyte loss. Potentially, this can be achieved not only by prophylaxis, but also by protection, against ischemia. Any therapy that increases myocardial resistance to ischemia will protect against cell death and prolong the life of the myocyte, and possibly the patient. The mechanisms of cell damage during ischemia, and possible therapeutic interventions, are discussed.

Heart↗