Biomedical subjects
Publications and source records attributed to R W Evans.
The pathogenic Neisseria have a siderophore-independent iron-uptake system reliant on a direct interaction between the bacterial cell and transferrin. In the meningococcus this uptake system is dependent on two surface-exposed transferrin-binding proteins. This short account will review our current knowledge of the transferrin-mediated iron-acquisition system of pathogenic Neisseria.
BACKGROUND: The most common adjunct to the visual and tactile clinical examination for dental caries is the bitewing radiograph. The aim of this study was to report on treatment planning decisions made by Victorian dentists when given a range of predetermined radiographic scenarios. METHODS: A postal survey was conducted to obtain data from 550 dentists selected systematically (every fourth dentist) from the register of the Dental Board of Victoria (1996). RESULTS: The survey response rate was 64 per cent. Fifty per cent of responding dentists selected an operative intervention for radiographic lesions confined to enamel. CONCLUSIONS: A review of current dental literature does not support this approach because a large proportion of proximal tooth surfaces that have associated radiolucencies confined to enamel are not cavitated. This study supports the need for continuing education programmes on the management of dental caries; such programmes should follow an evidence-based model.
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A careful and complete headache history supplemented by a neurologic and general physical examination, as appropriate, enables the astute physician to diagnose most headaches correctly without diagnostic testing. When indications are present (see Box 1), some headache patients with a normal physical examination require testing even though the yield may be low. Failure to test may result in misdiagnosis of potentially serious and life-threatening causes of headaches, such as brain tumors, chronic meningitis, SAH, and temporal arteritis.
The authors' Survey of headache specialists highlights a number of controversial issues in migraine management including the following: acute treatment, focusing on use of triptans, and preventative medications; treatment of migraine with prolonged aura and basilar migraine; and the use of oral contraceptives in migraine. Interestingly, the prevalence of migraine among the headache specialists themselves is much higher than in the general population. Although triptans have revolutionized the acute treatment of migraine, treatment is still problematic for the sizable percentages of patients with an incomplete or no response and recurrence of headache. Triptans are generally very safe when the physician, aware of the potential for coronary artery vasoconstriction, appropriately screens patients before and during their use. Serotonin syndrome as a complication of triptan use is quite rare. Although there is no definite evidence of teratogenesis, triptans should not be taken during pregnancy unless the potential benefit justifies the potential risk to the fetus. Caution is also advised when using a triptan during breastfeeding. The United States Headache Consortium parameters, which consider indications for preventative treatment and propose general principles of management, are reviewed. Unfortunately, the experience of many migraineurs with preventative medications is less than satisfactory because of side effects or lack of efficacy. Treatment of both migraine with prolonged aura and basilar migraine is anecdotally based. Many headache specialists do not use beta blockers for prevention for those with prolonged aura and basilar migraines because of concerns over the potential limitation of compensatory vasodilatory capacitance. There are seven case reports in the literature of an association between stroke and the use of beta blockers in migraineurs. Prevention using divalproex sodium and verapamil is favored by many headache specialists. Triptans are contraindicated in the treatment of patients with hemiplegic or basilar migraine because of concern over the potential for cerebral vasoconstriction. The frequency of migraine is usually unchanged with the use of oral contraceptives although, occasionally, migraine may occur for the first time or increase in frequency. Studies have produced conflicting results as to whether low-dose estrogen oral contraception increases the risk of stroke. Migraine alone increases the risk of stroke, at least in women under the age of 45 years. Most women with migraine without aura and migraine with visual aura lasting less than 1 hour can safely use low-dose estrogen oral contraceptives when there are no other contraindications. Those with aura symptoms such as hemiparesis or dysphasia or prolonged focal neurologic symptoms and signs lasting more than 1 hour should avoid starting low-dose estrogen oral contraceptives and stop the medication if they are already taking it.
In this nested case-control study, lipoprotein (a) [Lp(a)] concentrations and apo(a) isoform size were measured in serum samples obtained from men participating in the prospective Multiple Risk Factor Intervention Trial (MRFIT). Serum from men aged 35 to 57 years and stored for up to 20 years were analyzed for Lp(a) levels (n=736) and isoform size (n=487), respectively. Cases involved nonfatal myocardial infarctions (MI; n=98), documented during the active phase of the study that ended on February 28, 1982 and coronary heart disease (CHD) deaths (n=148) monitored through 1990. Median Lp(a) levels did not differ between cases and controls and mean apo(a) size did not vary between cases and controls in the entire study population. When adjusted for age and Lp(a) concentration, logistic regression analysis indicated that small apo(a) isoforms were associated with CHD deaths among smokers (OR 3.31; 95% CI 1.07-10.28).
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A headache associated with focal neurological signs and symptoms is always a clinical dilemma.
The differential diagnosis of "the worst headache of my life" is illustrated by the following history.
In older patients with migraine, the distinction between a migrainous aura and a transient ischemic episode can be difficult, as this case illustrates.
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OBJECTIVE: The objective of this study was to confirm that endothelial dysfunction is present in preeclampsia and absent in transient hypertension of pregnancy, and to determine whether the cardiovascular risk factor homocysteine is associated with the degree of endothelial dysfunction. METHODS: We measured cellular fibronectin (as a marker of endothelial injury) and total plasma homocysteine in samples collected at the time of admittance to labor and delivery in 17 women with preeclampsia (increased blood pressure, proteinuria, and hyperuricemia), 16 women with transient hypertension of pregnancy (only increased blood pressure), and 34 normal pregnant women. Each subject with preeclampsia was matched by prepregnancy body mass index, race, and gestational age at delivery to one subject with transient hypertension of pregnancy and two controls. RESULTS: Cellular fibronectin was found to be significantly increased in women with preeclampsia compared to subjects with transient hypertension of pregnancy or normal pregnant women (22.9 +/- 14.1 microg/mL versus 10.9 +/- 5.4 and 10.1 +/- 6.2 microg/mL, respectively, p<0.0001). Similarly, total plasma homocysteine was also significantly increased in the women with preeclampsia compared to subjects with transient hypertension of pregnancy or normal pregnant women (8.3 +/- 2.5 microM versus <5.5 +/- 2.2 and 5.4 +/- 3.4 microM respectively, p<0.01). However, contrary to our hypothesis, there was no apparent association between cellular fibronectin and homocysteine. CONCLUSIONS: The increased concentrations of homocysteine observed in preeclampsia are not a general feature of all hypertensive complications of pregnancy. Furthermore, endothelial dysfunction is present in preeclampsia and is not evident in transient hypertension of pregnancy. However, the apparent endothelial dysfunction in preeclampsia is not explained by the increase in homocysteine concentrations observed.