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Biomedical subjects

E O'Brien

Publications and source records attributed to E O'Brien.

At least 91 records · Page 5Linked to original sources
PubMed1996

The importance of thrombus organization and stellate cell phenotype in collagen I gene expression in human, coronary atherosclerotic and restenotic lesions.

OBJECTIVES: Collagen synthesis is one of the major mechanisms of primary atherosclerotic plaque growth and is likely to be similarly important in restenosis. The patterns of collagen gene expression in human restenosis and associations with thrombosis/hemorrhage have not been described. METHODS: Using human coronary artery samples obtained via the atherectomy catheter, we compared primary plaques (40 specimens) and restenotic lesions (41 specimens) for type I collagen gene expression using immunocytochemistry (SPI.D8 antibody to type I procollagen, an intracellular precursor of mature collagen) with subsequent computer image analysis. RESULTS: Scattered positive cells were identified in specific, non-random patterns. According to logistic regression analyses, type I procollagen gene expression seems to be more closely associated with certain morphological features (organized thrombus, microvessels, regions enriched with stellate cells) than with belonging to a primary vs. a restenotic sample. However, there may be a tendency for restenotic tissue to have slightly higher numbers of type I procollagen-positive cells than primary lesion tissue. CONCLUSIONS: Symptomatic primary and restenotic lesions exhibit similar patterns of type I collagen gene expression. Plaque microvessels and thrombi/hemorrhages (common features of both kinds of advanced lesions) might stimulate collagen synthesis equally well irrelevant to the nature of the lesion.

Adult↗
PubMed1996

Theodore Caldwell Janeway (1872-1917): the quest for precision.

The memory of Theodore Caldwell Janeway wafts through the mists of time but faintly. Yet for those few who have read his remarkable book The Clinical Study of Blood-Pressure published in New York in 1904, (see reference 1) he emerges as one of the major clinical scientists in the field of hypertension in the 20th-century. In this monograph he outlines with prescient clarity the limitations of sphygmomanometry and demonstrates the diurnal variability of blood pressure (BP) and the effects of varying stresses on BP. Such was his appreciation of haemodynamics, that had a serendipitous muse been at his side we might speak today of the Janeway rather than of the Korotkoff sounds.

Education, Medical↗
PubMed1996

The dilemma of choice: which bladder for accurate blood pressure measurement?

This paper reviews the literature on a century-old controversy relating to the error that may be introduced to blood pressure measurement by using a cuff with a bladder of inappropriate dimensions for the arm for which it is intended. The use of cuffs containing inappropriate bladders is a serious source of error which must inevitably lead to incorrect diagnosis in practice and erroneous conclusions in hypertension research. There is unequivocal evidence that either too narrow or too short a bladder (undercuffing) will cause overestimation of blood pressure and there is growing evidence that too wide or too long a bladder (overcuffing) may cause underestimation of blood pressure. Undercuffing has the effect in clinical practice of overdiagnosing hypertension and overcuffing leads to hypertensive subjects being diagnosed as normotensive. Either eventuality has serious implications for the epidemiology of hypertension and clinical practice. A detailed review of the literature permits a definitive statement on bladder dimensions for a given arm circumference and clearly indicates that substantial error is caused by the use of inappropriate cuffs. On the basis of this review and aware of the advances in cuff design, the features for an "Adult Cuff", which would be applicable to all adult arms, are proposed in this paper, and it is hoped that manufacturers may take up the challenge of producing such a cuff.

Adult↗
PubMed1996

Review: a century of confusion; which bladder for accurate blood pressure measurement?

This paper reviews the literature on a century-old controversy relating to the error that may be introduced to blood pressure (BP) measurement by using a cuff with a bladder of inappropriate dimensions for the arm for which it is intended. The use of cuffs containing inappropriate bladders is a serious source of error which must inevitably lead to incorrect diagnosis in practice, and erroneous conclusions in hypertension research. There is unequivocal evidence that either too narrow or too short a bladder (undercuffing) will cause overestimation of BP and there is growing evidence that too wide or too long a bladder (overcuffing) may cause underestimation of BP. Undercuffing has the effect in clinical practice of overdiagnosing hypertension and overcuffing leads to hypertensive subjects being diagnosed as normotensive. Either eventuality has serious implications for the epidemiology of hypertension and clinical practice. A detailed review of the literature permits a definitive statement on bladder dimensions for a given arm circumference and clearly indicates that substantial error is caused by the use of inappropriate cuffs. On the basis of this review and aware of the advances in cuff design, the features for an 'Adult Cuff', which would be applicable to all adult arms, are proposed in this paper, and it is hoped that manufacturers may take up the challenge of producing such a cuff.

Adult↗
PubMed1995

The ambulatory blood pressure in normotensive and hypertensive subjects: results from an international database.

OBJECTIVE: To delineate more precisely an operational threshold for making clinical decisions based on ambulatory blood pressure (ABP) measurement by studying the ABP in subjects who were diagnosed as either normotensive or hypertensive by conventional blood pressure (CBP) measurement. SUBJECTS: Twenty-four research groups recruited 7069 subjects. Of these, 4577 were normotensive (systolic CBP < or = 140 mmHg and diastolic CBP < or = 90 mmHg) and 1773 were hypertensive (systolic CBP > or = 160 mmHg and/or diastolic CBP > or = 90 mmHg). Of the latter, 1324 had systolic and 1310 had diastolic hypertension. RESULTS: Ninety-five percent of the normotensive subjects had a 24-h ABP below (systolic and diastolic, respectively) 133 and 82 mmHg. Of the patients with systolic hypertension, 24% had a 24-h systolic ABP of < 133 mmHg. Similarly, 30% of those with diastolic hypertension had a 24-h diastolic ABP of < 82 mmHg. The probability that hypertensive patients had a 24-h ABP below these thresholds was higher in women than in men, increased with age and was 2- to 4-fold greater if the CBP of the patient had been measured at only one visit and if fewer than 3 CBP measurements had been averaged to establish the diagnosis of hypertension. By contrast, for each 10-mmHg increment in systolic CBP, this probability decreased by 54% for the 24-h systolic ABP and by 25% for the 24-h diastolic ABP, and for each 5 mmHg increment in diastolic CBP it increased by 6 and 9%, respectively. CONCLUSION: The ABP distributions of the normotensive subjects included in the present international database were not materially different from those in previous reports in the literature. One-fifth to more than one-third of the hypertensive patients had an ABP which was below the 95th centile of the ABP in normotensive subjects, but this proportion decreased if the hypertensive patients had shown a higher CBP upon repeated measurement. The prognostic implications of elevated CBP in the presence of normal ABP remain to be determined.

Adolescent↗
PubMed1995

Ambulatory blood pressure measurement and the occurrence of hypertensive organ involvement.

Target organ involvement in hypertensive patients carries a poor prognosis, especially echocardiographically demonstrated left ventricular hypertrophy. Conventional blood pressure measurement correlates with target organ damage and mortality. 24-Hour ambulatory blood pressure measurement (ABPM) is a better predictor of target organ involvement than conventional blood pressure measurement, but there is as yet only scant evidence that 24-hour ABPM predicts mortality. The techniques for assessing target organ involvement and the superiority of ABPM over conventional measurement in predicting target organ damage are reviewed. It is argued that if 24-hour ABPM predicts target organ damage better than conventional measurement, then the likelihood is that it will also be a better predictor of mortality than conventional measurement. The studies underway to determine this important issue are reviewed.

Arteries↗
PubMed1995

Mechanism research of cryoanalgesia.

The sciatic nerves of rabbits were frozen at different temperatures (-20 degrees C, -60 degrees C, -100 degrees C, -140 degrees C, and -180 degrees C). The morphology and function of the frozen nerves were examined with light microscopy (hematoxylin and eosinophilin stain and a histochemical thiocholine method) and electron microscopy. The function of the nerve after freezing was assessed using short latency somatosensory evoked potentials, sensory conduction velocity, and electromyogram at various intervals after freezing. There were no changes in morphology or function of nerves cryolesioned at -20 degrees C. The nerve fibers cryolesioned at -60 degrees C showed signs of freezing degeneration and lost their conductive function although, these nerves all recovered. Approximately half of nerve fibers cryolesioned at -100 degrees C showed Wallerian degeneration, and although the time to remyelination was delayed, nerve regeneration was still complete. At -140 degrees C and -180 degrees C the nerve fibers showed immediate necrosis, with destruction of basal membranes and proliferation of collagen fibers. The results explained the mechanism of cryoanalgesia. Our study demonstrates that cryo-temperatures lower than -140 degrees C will cause permanent alterations in nerve morphology and function, whereas warmer temperatures do not result in permanent nerve damage and are therefore not likely to provide long-term analgesia to patients.

Analgesia↗
PubMed1995

Disease heterogeneity: does it impact our ability to detect dietary associations with breast cancer?

It is generally believed that breast cancer is a multistage process and that multiple and varying genetic events occur on the pathway to disease. We hypothesize that disease heterogeneity has an impact on our ability to identify risk factors. If a genetic alteration occurred in 50% of cases and a risk factor was associated only with that specific alteration, a risk estimate of 1.6 would be detected rather than the true risk estimate of 2.5 if analyses had been limited to those cases with the genetic alteration. Based on the literature we know that many genetic alterations occur in less than 50% of breast tumors. Thus, if environmental factors are related to some, but not all genetic alterations, we are decreasing our ability to identify potentially important risk factors. We therefore hypothesize that identification of dietary factors associated with breast cancer has been hampered by our inability to identify and capture the unique disease pathways which exist and contribute to the heterogeneity of common cancers such as breast cancer.

Breast Neoplasms↗