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Biomedical subjects

J Evans

Publications and source records attributed to J Evans.

At least 415 records · Page 23Linked to original sources
PubMed1987

Migration and health.

Explore the source record for details and available documents.

Acquired Immunodeficiency Syndrome↗
PubMed1987

[Echocardiographic aspects of false intraventricular tendons].

A series of 4260 consecutive echocardiographic examinations, performed in 5 Cardiological Centers was examined, identifying 125 intraventricular false tendons (FTs) in 100 cases (55 normals and 45 with heart disease) of whom 31 were female and 69 male, aged 3 to 82 years. An anatomo-morphological study was possible in 9 cases, dead for stroke or heart failure, on autopsy, and in 7, on heart surgery. A phonocardiogram was performed in all normals and in 20 patients. On echocardiography, FTs appeared as an echo-producing string-like structure, straight between the septum and the ventricular free wall, mobile during the cardiac cycle, without systolic thickening and any relation with the atrioventricular valvular apparatus. The prevalence of FTs was 2.3%; it was 3.2% to 5.3% in younger people. FTs were located in the right ventricle (4 cases), left ventricle (95 cases) or in both (1 case). Their site was left apical (45 FTs), right apical (2 FTs), right (3 FTs) and left (20 FTs), upper septum-to-free wall (55 cases). In 1 case hypertrophy of trabeculae of the left ventricle was detected. FTs were single (79 cases), double (19 cases), multiple (2 cases), short (42 cases), long (58 cases), thick (45 cases) and thin (55 cases). They showed a membrane-like motion (thick FTs-45 cases) and a valve-like motion (thin FTs-55 cases). Innocent murmur was detected in 50 of 55 normals and related to thin FTs. Of 16 cases examined anatomically and histologically, FTs were fibrous in their distal portion and fibro-muscular in the proximal one in 12 cases, whereas they were entirely fibrous-muscular in 4 cases. The site and location of FTs detected by echo were confirmed by anatomy in all cases. In 4 cases other 9 FTs, not detected on echocardiography, were found. These data suggest that echocardiography is a useful tool to detect intraventricular FTs and differentiate them from other echo-producing structures. Although a relationship between FTs and heart disease has not been found, their presence could be responsible of innocent murmur in many normal subjects.

Adolescent↗
PubMed1987

Ultrastructural analysis of enamel formation during in vitro development using chemically-defined medium.

To test the hypothesis that enamel biomineralization is regulated by sequential expression of an intrinsic genetic program, we designed experiments to determine if a serumless, chemically-defined medium is permissive for position-dependent ameloblast differentiation and subsequent enamel tissue-specific biomineralization in vitro. In the absence of serum or other exogenous growth factors, Swiss Webster strain mouse embryonic (15- and 16-days gestation) mandibular first molar tooth organs (cap stage) developed within 21 days in vitro into well-defined molar tooth organs expressing dentine and enamel biomineralization. Analysis of data obtained from von Kossa histochemistry for calcium salt formation, as well as ultrastructural information obtained from x-ray microanalysis, electron diffraction, transmission electron microscopy and scanning electron microscopy documented tissue-specific patterns of calcium hydroxyapatite formation in the absence of serum within organotypic cultures in vitro. An as yet unknown intrinsic genetic program regulates enamel formation in vitro.

Animals↗
PubMed1986

[Detection by contrast ultrasonography of patent foramen ovale before neurosurgery].

Air embolism may occur during neurosurgery if performed in the seated position. Paradoxical systemic air embolism represents a potentially severe complication in case of patent foramen ovale. Contrast echocardiography detected such a malformation in 10/100 patients, which contra-indicated the sitting position in these 10 patients. No episode of paradoxical air embolism was observed in the 90 remaining patients, although 16 cases of pulmonary air embolism were detected during surgery.

Adult↗
PubMed1986

The effect of food on the oral administration of 6-mercaptopurine.

The effect of food on the bioavailability of 6-mercaptopurine (6-MP) has been investigated. Seven patients were studied on two separate occasions. On the first occasion 6-MP was administered p.o. after an overnight fast and on the second, 15 min after a standard breakfast. 6-MP concentrations were determined by high-performance liquid chromatography. Variable plasma drug levels were observed between individual subjects in the fasting state. The peak levels of 6-MP were lower and took longer to be achieved following administration after a standard breakfast than after an overnight fast. In two subjects levels were undetectable (less than 20 ng/ml). In view of these observations it is suggested that 6-MP should be administered before food if maximum blood levels are to be achieved.

Administration, Oral↗
PubMed1986

Neutrophil LTA4 hydrolases and leukotriene B4 receptors: effects of leukotriene epoxides and their enzymatic products.

A selection of inhibitors of rat and human neutrophil LTA4 hydrolases have been studied in vitro using partially purified enzymes. 5(S)trans 5,6 oxido-7,9-trans-11-cis-eicosatrienoic acid (LTA3) and 5(S)trans 5,6 oxido, 7,9-trans, 11,14,17-cis-eicosapentaenoic acid (LTA5) have been shown to inhibit neutrophil LTA4 hydrolases in a time-dependent manner. The products of hydrolysis of LTA3, LTA4 and LTA5 by human and rat neutrophil LTA4 hydrolase have been shown to displace [3H] LTB4 binding to human and rat neutrophil membranes. The order of displacement of [3H] LTB4 is LTB4 = LTB3 greater than LTB5 and this correlated well with their biological potencies for enhancement of neutrophil aggregation and chemokinesis.

Animals↗
PubMed1986

Value and limitations of computer analysis of digital subtraction angiography in the assessment of coronary flow reserve.

Conventional coronary angiography has significant limitations in quantifying the severity and functional significance of coronary stenoses. However, coronary reactive hyperemia is an excellent physiologic indicator of coronary reserve. Digital subtraction angiography offers the potential to analyze coronary blood flow dynamics quantitatively. Therefore we assessed the accuracy of digital angiographic methods to detect and quantify reductions in coronary flow reserve secondary to stenoses of varying magnitude in an experimental canine preparation. Studies were performed in nine anesthetized open-chest dogs with an electromagnetic flow (EMF) probe and two pneumatic occluders positioned on the left circumflex coronary artery. One occluder served to induce reactive hyperemia by temporary total occlusion, while the other served to produce variable gradations of stenosis. Digital angiography was performed after the subselective injection of contrast under basal conditions and during reactive hyperemia. Time-intensity curves were obtained from digital angiograms for both a coronary and a myocardial region of interest. Measurements included area under the curve, time to peak contrast, and contrast disappearance rate. An index of coronary reserve was computed as the ratio of hyperemic to basal measurements for each of these methods. Coronary blood flow ranged from 6.5 to 142 ml/min, with hyperemic to basal EMF flow ratios of 0.80 to 4.2:1. The index derived from contrast decay rate showed a poor correlation with EMF (r = .34). The correlation between measurements of time to peak myocardial contrast and coronary blood flow was r = .68 (y = 0.16 x + 0.97). The area under the time-intensity curve from a coronary region of interest showed a close correlation with coronary blood flow (y = 0.91 x + 0.1, r = .86). Thus estimates of coronary reserve by computer analysis of digital subtraction angiograms can yield information regarding the physiologic consequences of coronary stenoses.

Angiography↗
PubMed1985

Malignant fibrous histiocytoma of the liver.

A 59-yr-old man was admitted to the hospital for evaluation of right upper quadrant pain, anorexia, weight loss, and low-grade fever of 2-mo duration. During his evaluation, an abnormal liver ultrasound and computed tomography scan demonstrated what proved to be an avascular hepatic lesion. At surgery, the diagnosis of malignant fibrous histiocytoma was established. We present herein our findings of what we believe to be the first reported study of malignant fibrous histiocytoma of the liver.

Histiocytoma, Benign Fibrous↗
PubMed1985

Characterization of biological properties of synthetic and biological leukotriene B3.

Leukotriene B3 was chemically synthesized and its ability to aggregate rat polymorphonuclear leukocytes (PMN) and to enhance chemokinesis of human leukocytes demonstrated. In both these assays the potency of synthetic leukotriene B3 was marginally less than that of leukotriene B4. Rat PMN incubated with leukotriene A3 were very inefficient in the enzymatic conversion of this epoxide to leukotriene B3. However, the leukotriene B3 produced was able to aggregate rat PMN. These results suggest that unlike leukotriene B5, the proinflammatory properties of leukotriene B3 are similar to those of leukotriene B4. However, since the enzymatic conversion of leukotriene A3 to leukotriene B3 is extremely poor it seems unlikely that leukotriene B3 itself has any major role in vivo.

Animals↗
PubMed1985

Supramolecular assemblies of mRNA direct the coordinated synthesis of type I procollagen chains.

Registration of the three procollagen alpha chains and assembly of the triple-helical procollagen molecules takes place in the rough endoplasmic reticulum, but the exact location and timing of assembly is not known. As part of a study of the mechanism of molecular assembly, intact collagen-producing polyribosomes from embryonic chicken tendon fibroblasts have been examined by the techniques of rotary shadowing and electron microscopy. Intact mRNA strands corresponding in length to approximately 4500 bases and complete procollagen alpha (I) chains have been observed. The mRNA strands are comprised of two mRNA chains. The ribosomes are present in pairs separated along the duplex strand by about 100 nm. The intact polysome is asymmetric; two duplex strands join, and large ribosome aggregates appear. These aggregates are dispersed by collagenase digestion, leaving separate duplex strands with ribosome pairs intact. Ribonuclease digestion yields mixtures of monosomes and ribosome aggregates. Sequential ribonuclease and collagenase digestions yield only monosomes. We propose that each ribosome reads one mRNA chain, so that each pair is thus translating two chains in synchrony. Thus, the complex morphology of the collagen-producing polyribosomes suggests that the organization of a single molecule begins by the organization of the mRNA chains themselves.

Animals↗
PubMed1985

Thermoelastic properties of uniaxially deformed lung strips.

We examined the temperature dependence of small degassed hamster lung strip mechanics to develop insights into the molecular basis of lung elasticity. Quasi-static length-tension curves of adapted lung strips were generated at 10, 23, 37, 50, and 80 degrees C; quasi-static tension-temperature plots (QSTT) at strains of 0.5, 0.75, and 1.0 were then formulated. Static tension-temperature (STT) plots at strain 1 were independently generated from other strips. Stress relaxation was evaluated as a function of temperature at different strains; hysteresis ratio was calculated as a parameter of mechanical efficiency. Between 23 and 37 degrees C, the slopes of the QSTT plots at the different strains were close to zero. The slope of the STT plot was slightly positive, indicating that the tension developed by a stretched strip was primarily due to entropic changes with length, suggesting that strips behave like rubber polymers near physiological temperature. Between 10 and 23 degrees C, the slope of the QSTT curve was zero at the two lowest strains but was negative at strain 1; and slope of the STT curve was zero at strain 1. These data indicated that collagen fiber and possibly glycosaminoglycan function was abnormally affected at 10 degrees C. Between 50 and 80 degrees C at strain 1, the slopes of both the QSTT and STT plots at all strains were positive. These data suggested that elastic fiber function was altered between 50 and 80 degrees C such that both internal energetic and entropic contributions to the tension were changed. Stress relaxation and hysteresis data were consistent with these findings.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗