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Biomedical subjects

J Meyer

Publications and source records attributed to J Meyer.

At least 685 records · Page 38Linked to original sources
PubMed1990

Measurement of intracardiac dimensions and structures in normal young adult subjects by transesophageal echocardiography.

Transesophageal echocardiography (TEE) has proven to be an excellent diagnostic means of diagnosing different cardiac diseases. To distinguish between normal and pathologic findings, standardized measurements of well-defined cross-sectional planes are necessary. Therefore, the 2-dimensional echocardiographic data of 25 healthy volunteers were obtained. In 13 men and 12 women, aged 19 to 30 years, recordings of the left ventricular short-axis view, the 2- or 4-chamber view with the left and right atria, the long axes of the left and right ventricles, the mitral and tricuspid valve ring and the atrial septum were analyzed. Furthermore, the aortic valve plane and the ascending and descending aorta were also measured. All data are given as mean values +/- 2 times the standard deviation. End-diastolic and end-systolic left ventricular anterior-to-posterior diameter of the left ventricular short axis was 2.5 +/- 0.3 cm/m2 and 1.7 +/- 0.3 cm/m2, with the fractional shortening ranging from 27 to 42%. The end-systolic lateral diameter was 2.4 +/- 0.5 cm/m2 for the left atrium and 2.4 +/- 0.4 cm/m2 for the right atrium, and the end-systolic anterior-to-posterior diameter was 1.5 +/- 0.6 cm/m2 for the left atrium and 2.1 +/- 0.6 cm/m2 for the right atrium. End-diastolic diameters of 3.4 +/- 0.6 cm/m2 and 2.8 +/- 0.4 cm/m2 were obtained for the long axis of the left ventricle and for the right ventricle. Measurements ranged from 1.5 to 2.2 cm/m2 for the end-diastolic diameter of the mitral ring and from 1.3 to 2.0 cm/m2 for the tricuspid ring.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Blood-brain barrier characteristic enzymatic properties in cultured brain capillary endothelial cells.

Isolated brain capillary endothelial cells contain high activity levels of the blood-brain barrier (BBB) marker enzymes gamma-glutamyltranspeptidase (gamma-GT) and alkaline phosphatase (ALP). In primary culture the activities of these specific enzymes decrease with increasing cell proliferation to a constant low value characteristic for a confluent monolayer. However, activities are retained in non-proliferating cells. After passage of cells from a confluent cell monolayer a further reduction of enzyme activity was observed which corresponds to the newly triggered cell proliferation. Culture of cerebral endothelial cells on structural components of the native vascular basement membrane-like type IV collagen, fibronectin, laminin or a commercially available basement membrane cannot prevent the activity decrease of both gamma-GT and ALP. Antiserum raised against a native renal dog gamma-GT binds to the cerebral endothelial gamma-GT and suppresses its activity. The relative activity decrease induced by a given amount of anti-gamma-GT-antiserum is constant at all times in culture. This result clearly shows that the observed decrease in gamma-GT activity in proliferating cells in culture correlates to a decreased number of enzyme molecules per cell and not to an inhibition of expressed enzymes. Possibly the de novo synthesis of this enzyme is prevented in vitro. In contrast to the loss of the activity of the BBB marker enzymes gamma-GT and ALP, the activity of angiotensin-converting enzyme (ACE), a marker for all vascular endothelial cells, is highly preserved in cultured cerebral endothelial cells.

Alkaline Phosphatase↗
PubMed1990

Expression of CD44 confers a new adhesive phenotype on transfected cells.

The function of the CD44 glycoprotein as an adhesion molecule was directly tested by transformation of a CD44 cDNA into mouse fibroblasts. This cDNA was expressed as a heavily modified cell surface protein reactive with monoclonal antibodies that recognize glycoproteins now identified in primates as CD44. Independent transfectants exhibited a new self-adhesive phenotype, forming large aggregates when placed in suspension. In variants derived from a clone of cells, aggregation competence segregated with expression of the transfected gene. This CD44-mediated adhesion was blocked specifically by monoclonal antibodies binding one immunologically defined region of CD44. Nontransfected L cells did not self-aggregate but were capable of adhering to the transfectants, indicating that at least one ligand for this adhesion molecule is expressed by mouse fibroblasts.

Animals↗
PubMed1990

Analysis of risk factors for restenosis after PTCA.

To identify risk factors for restenosis, we evaluated data in 473 patients with single-vessel percutaneous transluminal coronary angioplasty (PTCA) and control angiography after 6 months. Restenosis, defined as (1) loss greater than 50% of the initial gain, and (2) stenosis greater than 50% was found in 138 patients (29.2%). Univariate analysis revealed eight factors related to restenosis: (1) duration of symptoms less than 1 month (P = 0.005), (2) unstable angina (P = 0.004), (3) high-grade stenosis before PTCA (P = 0.014), (4) large residual stenosis after PTCA (P = 0.001), (5) insufficient improvement of stenosis (P = 0.042), (6) prolonged single inflation time (P = 0.017), (7) prolonged total inflation time (P = 0.055), and (8) low inflation pressure (P = 0.028). Multivariate analysis revealed four factors significantly related to restenosis: (1) large residual stenosis after PTCA (P = 0.0001), (2) prolonged single inflation time (P = 0.0047), (3) unstable angina (P = 0.0127), and (4) high-grade stenosis before PTCA (P = 0.0179). Modification of procedural factors might be helpful to reduce the risk of restenosis after successful PTCA.

Aged↗
PubMed1990

Coronary stent implantation in acute vessel closure 48 hours after an unsatisfactory coronary angioplasty.

We report the implantation of a balloon-expandable stent in a patient with acute vessel closure in the state of evolving myocardial infarction following 48 hr after unsatisfactory coronary angioplasty. The stent was implanted after successful recanalization of an occluded left anterior descending artery, with repeated unsatisfactory results of balloon angioplasty. Adjunct thrombolytic therapy was contraindicated. No residual stenosis was documented in immediate control angiograms, or after 24 hr, 3 weeks, and 4 months.

Angina, Unstable↗
PubMed1990

Parametric assessment of myocardial perfusion during interventional cardiac catheterization by means of X-ray densitometry-short-and long-term results.

X-ray densitometric evaluation of digital subtraction angiocardiograms allows an assessment of myocardial perfusion by means of the parameter 'MEAN RISE TIME' (MRT), defined as the time from the onset of local myocardial contrast medium opacification to the point of maximum opacification. Best results are obtained when the response of that parameter is compared before and after stimulation of coronary flow by papaverine. A prolongation of this parameter, especially after papaverine, was indicative of an impairment of myocardial perfusion, when compared to the results of TL-201 scintigraphy. In 50 patients with single vessel coronary artery disease the results of MRT pre and post papaverine before and after coronary angioplasty, as well as after 6 months were evaluated for 204 post-stenotic regions-of-interest. Before angioplasty papaverine induced a significant prolongation of post-stenotic MRT was measured 2.3 s +/- 0.9 s vs 3.1s +/- 0.8s; p less than 0.01), while after successful angioplasty post-stenotic MRT was measured significantly shorter after stimulation of coronary flow (2.6s +/- 1.0s vs. 1.9s +/- 0.9s; p less than 0.01). This indicated an improvement in myocardial perfusion. Nevertheless, 16/50 patients still presented pathological results of post-stenotic MRT after papaverine, although angioplasty was regarded successful. These patients presented a markedly higher rate of restenosis (14/16 patients after 6 months), a higher rate of dissections at the dilation site and a higher rate of dilated vessels, supplying myocardial areas after a Q-wave myocardial infarction. Thus, these results demonstrate the additional information about the short-and long-term outcome of an angioplasty procedure by densitometric myocardial perfusion analysis.

Absorptiometry, Photon↗
PubMed1990

The influence of the interdigestive migrating myoelectric complex on the gastric emptying of liquids.

It is unknown how the interdigestive migrating motor complex influences the gastric emptying of liquids. Therefore, the gastric emptying rate of 50- and 200-mL volumes of phenol red solution were measured while monitoring contractile activity. Motor activity was recorded using a hydraulic manometric system and expressed as either the proximity of dosing time to time of appearance of phase III or as a motility index, defined as (contractile area)/(sampling interval time). After an initial lag period, emptying was log linear. With a 50-mL oral dose, the mean gastric emptying rate of the log-linear phase was successively faster during phase I (0.018 +/- 0.003 min-1), phase II (0.083 +/- 0.031 min-1), and late phase II/III (0.171 +/- 0.066 min-1) (P less than 0.05). Similarly, the mean lag time decreased successively with phases I, II, and late II/III (19.1 +/- 12.4, 7.6 +/- 5.6, and 3.8 +/- 2.8 minutes, respectively). At a 200-mL oral dose, there was no difference in the emptying rate between phase I and phase II (0.104 +/- 0.0014 vs. 0.110 +/- 0.041 min-1), but the emptying rate during late phase II/III was significantly greater (0.236 +/- 0.069 min-1); lag time was not dependent on phase. There was a statistical difference in the overall mean emptying rate between the 50- and 200-mL volumes. Also, during phase I, the emptying rate was faster for the 200-mL volume. This study shows a strong dependence of liquid gastric emptying rate and lag time on interdigestive antral motility, the emptying of small volumes being more dependent on motility phase than that of large volumes. Phase-related fluctuations in contractile activity can account for much of the reported variability in gastric emptying data. Furthermore, this study suggests that dose volume and interdigestive motor activity at the time of drug administration can affect absorption and onset of therapeutic response for some drugs.

Analysis of Variance↗
PubMed1990

Sublingual administration of captopril versus nitroglycerin in patients with severe congestive heart failure.

Angiotensin-converting enzyme inhibition has proven to be a successful approach for the long-term treatment of patients with congestive heart failure. This investigation compared the acute hemodynamic changes after sublingual administration of the angiotensin-converting enzyme inhibitor captopril with those after nitroglycerin. A total of 24 patients with severe left heart failure (New York Heart Association classes III and IV) were given 25 mg captopril and 0.8 mg nitroglycerin sublingually in this randomized, cross-over study. Hemodynamic monitoring revealed a clear improvement in pre- and afterload parameters for both drugs (P less than 0.01 and P less than 0.001), while captopril induced a higher increase in cardiac index (+49.2% vs. +25%), stroke volume index (+53.5% vs. +25.7%), and stroke work index (+55% vs. +28%) than nitroglycerin (P less than 0.001). Although not statistically significant, the onset of change for most hemodynamic parameters was measured earlier after nitroglycerin (after 12-19 vs. 16-22 minutes). Captopril revealed later peak effects (after 47-84 vs. 25-55 minutes, P less than 0.001) and a longer sustained improvement in hemodynamic values (return to baseline values after 117-162 vs. 68-120 minutes, P less than 0.001). No side effects occurred after either captopril or nitroglycerin in this study. Thus, these results indicate there is an early improvement in hemodynamic parameters after the sublingual administration of both drugs in patients with severe congestive heart failure, and that captopril induces a more pronounced and prolonged improvement than nitroglycerin.

Administration, Sublingual↗
PubMed1990

Plasmid analysis and restriction fragment length polymorphisms of chromosomal DNA allow a distinction between Borrelia burgdorferi strains.

We examined the relationships of the genomes of five strains of Borrelia burgdorferi isolated from ticks, two from North America, including the type strain B31, and three from Switzerland. We determined restriction fragment length polymorphisms by using eight cloned DNA fragments as hybridization probes to genomic Southern blots. Two divergent patterns were observed, represented by B31 and one Swiss strain on the one hand and the two other Swiss strains on the other. The second American strain resembled B31. One of the DNA probes allowed distinction between the closely related strains within a group. The close resemblance of one Swiss strain to the North American strains suggests the possibility of their European origin. All five strains carried a circular plasmid of about 29 kb, and three contained an additional species of about 9 kb, both of which exhibited homology between the strains. The profiles of linear plasmids revealing species of 5.1 kb to 58 kb reflected the polymorphisms of chromosomal DNAs. Linear plasmids of similar size shared DNA sequence homology. Some of the smaller plasmids tended to become lost during cultivation.

Animals↗
PubMed1990

[Color-coded Doppler sonography of primary and secondary liver tumors].

50 Patients with 78 focal liver lesions were examined via colour-coded Doppler system to study the vascularity of metastatic lesions and primary benign and malignant liver tumours. According to the amount of detectable colour Doppler signals, tumour vascularity was graded into 4 types. Metastases (n = 40) and cavernous haemangiomas (n = 12) seemed to be avascular with no evidence of increased vascularity (Type I/II). Conversely primary liver cancer (PLCA) (n = 7) and focal nodular hyperplasia (FNH) (n = 16) mainly produced arterial Doppler signals within the tumour (Type III/IV). AV shunts and partial portal vein thrombosis could be demonstrated in PLCA. Doppler colour flow imaging for detection of tumour vascularity may thus add to the specificity of ultrasonic tumour diagnosis.

Adenoma↗
PubMed1990

Site-specific DNA recombination system Min of plasmid p15B: a cluster of overlapping invertible DNA segments.

Plasmid p15B of Escherichia coli 15T- carries a 3.5-kilobase segment that undergoes frequent DNA inversion mediated by the DNA inversion enzyme Min, a member of the Din family of site-specific recombinases. While the previously described Din inversion systems invert a DNA segment between two crossover sites in inverted orientation, the Min system produces more complex DNA rearrangements. These have been physically characterized by electron microscopy and by restriction cleavage analysis. The results can best be explained by a model that involves six crossover sites (called mix) and predicts 240 isomeric forms of the invertible region. The model was confirmed by sequencing the six mix sites in plasmids that contain the invertible DNA segments in a frozen configuration. All mix sites fit the dix consensus sequence, and they are all good substrates for DNA inversion when carried in inverted orientation. Recombination between two mix sites in direct orientation was rare, in line with the notion that Din inversion systems are topologically biased to the inversion reaction. Another recently described multiple inversion system, the shufflon of the E. coli plasmid R64, is neither functionally nor structurally related to the Min system of p15B.

Chromosome Deletion↗
PubMed1990

New bundle branch block after coronary artery bypass grafting--evaluation by CK-MB isoenzyme analysis and transoesophageal echocardiography.

Twelve patients with a new complete bundle branch block after coronary artery bypass grafting underwent transoesophageal echocardiography (TEE). The results of TEE were compared with the pre-operative ventriculography, CK-MB isoenzyme time-release curves and clinical course. In eight patients with transient right bundle branch block or bifascicular block, low CK-MB activities and an uncomplicated postoperative course, transoesophageal echocardiography showed no new segmental wall motion abnormalities apart from a paradoxical septal movement in five. A persistent right or left bundle branch block was associated with either elevated isoenzyme activities, transoesophageal echocardiographic evidence of new segmental wall motion disturbance or both in four patients. One patient died because of fatal arrhythmia and one suffered from a prolonged low cardiac output syndrome. A transient bundle branch block is usually a benign electrocardiographic finding. In case of a persistent bundle branch block associated with elevated CK MB isoenzymes, new left ventricular wall motion disturbances indicating a peri-operative myocardial injury are easily detected by transoesophageal echocardiography.

Aged↗
PubMed1990

Short- and long-term outcome after PTCA in patients with stable and unstable angina.

Acute results and follow-up data over a period of 36 months after attempted PTCA in 406 patients with stable angina and 202 patients with unstable angina are reported. The rate of acute complications (death, myocardial infarction and bypass grafting (CABG) amounted to 1.5% in stable and 6.4% in unstable patients (P less than 0.005). Within the first week after PTCA a significantly lower percentage (1.7% vs 10.4%) of cardiac events (death, myocardial infarction, CABG and repeat PTCA) was observed in the stable group (P less than 0.001). During a 12-month follow-up period, another 16.3% of the patients in the stable group and 30.7% of unstable patients suffered a new cardiac event (P less than 0.001). The long-term follow-up of 36 months revealed no significant difference in the event rate between stable and unstable patients (5.4% in both groups). The cumulative rate of myocardial infarction within 3 years after PTCA was significantly lower (3.7% vs 9.4%) in the stable group (P less than 0.005). The cumulative mortality amounted to 3.0% in stable and 6.4% in unstable patients (P less than 0.05) and the incidence of repeated PTCA was 8.1% and 19.3% respectively (P less than 0.001). The crossover rate to CABG was 10.1% in stable and 17.8% in unstable patients (P less than 0.01). The total rate of any cardiac event thus amounted to 24.9% in stable and 53.0% in unstable patients (P less than 0.001) within a 3-year follow-up period. At the end of follow-up, 74% of the stable patients were asymptomatic, compared with 60% of unstable patients (P less than 0.01). 45% of the stable group patients and 28% of the unstable patients were not on antianginal treatment (P less than 0.01). We conclude that PTCA in unstable angina carries a markedly enhanced risk of acute complications and cardiac events in the early phase after PTCA. In the long run, patients with stable angina have a better quality of life with regard to medical treatment and angina symptoms.

Adult↗
PubMed1990

Constant-flow ventilation during experimental left ventricular failure.

The efficacy of constant-flow ventilation (CFV) was investigated in dogs with normal heart function (control phase, n = 8) and after development of left ventricular failure (LVF phase, n = 8). Heated, humidified and oxygen-enriched air (inspired oxygen fraction (Fio2) = 0.4) was continuously delivered via two catheters positioned within each mainstem bronchus at two flow rates (1.2 and 1.6 l/kg/min). Conventional mechanical ventilation (CMV) with positive end-expiratory pressure (PEEP) of 0.5 kPa was used as reference ventilation. During control, neither CMV with PEEP nor CFV revealed severe impairment of cardiopulmonary performance. Alveolo-arterial PO2 difference (P(A-a)O2) increased significantly during CFV1.2 and CFV1.6, indicating a higher degree of ventilation-perfusion (VA/Q) inhomogeneity. Acute left ventricular failure (LVF) was induced by proximal occlusion of the left anterior descending (LAD) coronary artery. Cardiac output (CO), maximum velocity of pressure development (dP/dtmax) and mixed venous PO2 decreased (P less than or equal to 0.05), whereas left ventricular end-diastolic pressure (LVEDP) and pulmonary capillary wedge pressure (PCWP) increased (P less than or equal to 0.05). Extravascular lung water (EVLW), as determined by thermal-dye technique, increased from 10.1 ml/kg to 20.9 ml/kg (P less than or equal to 0.01). Oxygenation, but not CO2 elimination, deteriorated in the LVF phase. There were no haemodynamic differences between CMV with PEEP and CFV1.2, but cardiopulmonary performance deteriorated with CFV1.6. Gas exchange was significantly more impaired during CFV1.2 and CFV1.6 due to increased VA/Q mismatching. However, there were no significant differences for P(A-a)O2 values between CFVControl and CFVLVF.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗