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Biomedical subjects

J Meyer

Publications and source records attributed to J Meyer.

At least 667 records · Page 37Linked to original sources

[Experimental evaluation of the accuracy and safety of intraluminal ultrasound].

In this in vitro investigation, we studied the feasibility and accuracy as well as the safety of intravascular ultrasound imaging. Plastic cylinders were used in order to validate measurements of luminal area, perimeter, diameter, and wall thickness. Fifty-nine segments of human arteries were also examined by intravascular ultrasound; then the results regarding the luminal area, perimeter, and wall thickness were compared with the corresponding histopathologic section. Close correlations were found in plastic cylinder studies (r = 0.999, 0.999, 0.998, and 0.994 for area, perimeter, diameter, and wall thickness, respectively). There was also an excellent correlation between intravascular ultrasound imaging and pathologic measurements (r = 0.993, 0.994, and 0.915 for luminal area, perimeter, and wall thickness). Five different cylinders, with a volume of 2, 5, 10, 20, and 50 mls, were employed to evaluate the effect of ultrasound on temperature. Ten blood samples anticoagulated with EDTA were used to detect the effects of ultrasound on blood elements. In the course of time, the ultrasound caused a slight increase of solution temperature (from 23.9 degrees C to 24.6 degrees C after 1-h examination in a 2-ml cylinder) and the temperature change became less obvious as the solution volume increased (the temperature raised 0.3 degrees C in the 2-ml cylinder, 0.1 degrees C in the 20-ml cylinder, but no change was detectable in the 50-ml cylinder after 10 min). No significant differences about WBC, RBC, and platelet counts were found between test and control group (p greater than 0.1) before and 5, 10, 15, 30, and 60 min after ultrasound examination.(ABSTRACT TRUNCATED AT 250 WORDS)

Arteriosclerosis↗

[Left ventricular inflow behavior in dual chamber stimulation with differential atrioventricular conduction: an echocardiography study].

The influence of the AV interval on early passive (E) and late active diastolic filling (A) during transmitral flow was analyzed in patients with AV sequential pacing. In 16 patients with dual-chamber pacemakers at the age of 25 to 76 years CW- and color Doppler echocardiography was used to determine inflow time (t), flow velocity (Vmax), the E/A ratio, the time-velocity integral (TVI), and the inflow jet at constant AV sequential pacing (80 bpm) with various AV interval settings (50-100-150-200-250 ms). The inflow pattern was compared to findings in 16 normals (age 26 +/- 7 years). The prolongation of the AV interval from 50 to 250 ms resulted in the following changes: 1) Decrease of tE: 220 +/- 30 ms to 170 +/- 40 ms (p less than 0.05), of VmaxE: 78 +/- 12 to 68 +/- 14 cm/s) (ns) and of TVI-E: 8.5 +/- 2.1 to 5.6 +/- 1.7 cm (p less than 0.001); 2) Increase of tA: 140 +/- 30 to 270 +/- 60 ms (p less than 0.001), of VmaxA: 48 +/- 18 to 73 +/- 24 cm/s (p less than 0.001) and of TVI-A: 2.4 +/- 1.1 to 6.1 +/- 2.9 cm (p less than 0.001); 3) Decrease of the E/A ratio from 1.6 +/- 05 to 0.85 +/- 02. Longer AV intervals shortened the total diastolic filling period and produced more diastolic aliasing without change of the relative diastolic inflow jet. The AV interval of 150 ms was associated with an abnormal high atrial component of transmitral inflow, as found with abnormal diastolic LV function.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

[Collaterals do not prevent infarcts in subacute vascular stenosis following initially successful vascular stent implantation].

UNLABELLED: Sufficient collateralization may prevent acute myocardial infarction despite complete obstruction of a coronary artery. Nevertheless, it is unclear if collaterals which regressed after restoration of antegrade flow may be recruited fast enough to prevent myocardial infarction in case of subacute coronary artery thrombosis. In 50 patients (pts) (48 males, two females, age 60 +/- 7.6 years) with high-grade coronary artery stenosis and collaterals from the contralateral non-diseased coronary artery, stenting devices (Palmaz-Schatz) were implanted. In seven patients subacute thrombosis of the stent occurred. Six patients developed myocardial infarcts with a CKmax greater than 100 U/l (mean 943 +/- 635 U/l). One patient was treated by intravenous thrombolysis, three pts with acute PTCA, one patient with both, and one patient had CABG after unsuccessful PTCA; no patient died. There was no statistical correlation to the degree of collateralization and time after, or location of stent implantation, most likely because of the small number of cases. CONCLUSION: This retrospective study shows that collaterals in humans with a high-grade coronary artery stenosis which has regressed after restoration of sufficient antegrade blood-flow cannot be recruited fast enough to prevent myocardial necrosis in case of subacute coronary artery occlusion. This is in contrast to earlier results obtained in animal studies.

Aged↗

[Effect of molsidomine on fibrinolytic activity: a double-blind, randomized study].

The influence of molsidomine on endogenous fibrinolytic activity was studied in a double-blind, randomized, placebo-controlled trial involving 12 male healthy volunteers. When measured 3 h after oral intake of molsidomine (16 mg, slow-release formulation) the activity of tissue plasminogen activator (t-PA) in plasma was significantly increased from 1.1 +/- 0.1 to 1.6 +/- 0.1 IU/ml. In contrast, the activity of plasminogen activator inhibitor (PAI-I) decreased from 17 +/- 2 to 12 +/- 1 AU/ml. The ratio of t-PA/PAI-I (x 100), calculated as index for the endogenous fibrinolytic activity increased significantly from 8.1 +/- 1.1 to 14.5 +/- 1.6. The ratio was unaltered after intake of placebo. Additionally, collagen-induced platelet aggregation was significantly inhibited following intake of molsidomine. The results demonstrate a significant increase in endogenous fibrinolytic activity after oral intake of molsidomine. These effects may be of therapeutic value in patients with coronary heart disease and unstable angina.

Administration, Oral↗

[Modification of thrombocyte function in diagnostic and therapeutic interventions in cardiology].

In patients with coronary heart disease platelet activity may be pathologically increased. Administration of platelet inhibitor drugs is an established treatment principle. The interactions between platelet activation, platelet inhibitor drugs like acetylsalicylic acid (ASA) or molsidomine and the endogenous fibrinolysis were studied in three trials. Platelet aggregation and thromboxane synthesis are dose- dependently inhibited after oral intake of ASA (0, 10, 30, 100 or 500 mg/d) Additional intake of the antianginal agent and nitric oxide donator Molsidomine (8 mg) results in a synergistic platelet inhibitor effect characterized by a significantly delayed aggregation response. In a group of patients with coronary artery stenoses platelet activity was markedly enhanced, when compared to healthy individuals. During physical exercise platelet activity was even further enhanced and plasma t-PA-activity was increased by a factor of 2.2. The stimulation of the endogenous fibrinolytic system was markedly reduced when compared to healthy subjects. Following successful coronary angioplasty 393 patients were randomized to receive either molsidomine (2 x 8 mg/d) or ASA (1 x 500 mg/d) plus nifedipine (3 x 20 mg/d). Coronary angiography performed after the 6 month treatment period revealed a restenosis rate of 29% in the molsidomine group and of 33% in patients treated with ASA + nifedipine. This difference was not statistically significant.

Angioplasty, Balloon, Coronary↗

[Bacterial contamination, familial occurrence and periodontal disease].

The pathogenesis of the various periodontal diseases cannot only be explained on the basis of the relationship of specific bacteria to the clinical features of the disease. The microbiologic examination of various members of the same family, either by culturing or by the use of the DNA probe often showed similarities among several individuals in the same family. This could be accounted for on the basis of bacterial transmission or by contamination. These observations suggest the incidence of familial and genetic factors in the etiology of some forms of periodontitis.

Adult↗

[TMJ-function following orthognathic surgery].

86 patients with dentofacial anomalies were examined to evaluate signs and symptoms of the stomatognathic system after orthognathic surgery. Clinical signs and symptoms were graded according to the anamnestic and clinical dysfunction index of Helkimo. Restriction of mouth opening in 37 patients influenced the anamnestic dysfunction index mainly to higher postoperative levels although the occurrence of symptoms as pain and tmj sounds decreased. No relationship between tmj pain-dysfunction and type of dysgnathia, surgical approach, molar support before and after surgery, age and sex was noted. It is concluded that surgical correction of dentofacial anomalies has a possible benefitialeffect on certain symptoms as tmj pain, but relief or impairment of clinical signs cannot be predicted preoperatively.

Adolescent↗

[Enoximone and ventricular arrhythmia in chronic heart failure].

Potentially malignant ventricular arrhythmias are common in chronic heart failure. The aggravation of such arrhythmias has many causes in these patients and cannot be predicted. Therefore, proarrhythmia due to PDE-inhibitors which increase cytosolic calcium levels by specific inhibition of the degradation of cyclo-AMP may be difficult to recognize. A retrospective analysis of 24-h Holter ECG was performed in 31 patients (NYHA classes III and IV) under long-term enoximone therapy. At baseline, 68% of the patients had ventricular couplets and nonsustained ventricular tachycardia. After a mean treatment period of 7 months, 10% of the patients showed a significant increase, 16% a significant decrease (greater than 90%) of ventricular couplets and salvos, and an additional 32% of the patients showed a significant decrease (greater than 70%) of single PVCs. The change of the arrhythmia profile was not related to the clinical course in these patients. Furthermore, 24-h Holter recordings were analyzed in a randomized long-term trial with captopril and enoximone that included 20 patients of NYHA class II. Despite comparable baseline findings, a reduction of cardiopulmonary exercise capacity was observed in patients treated with enoximone, but not with captopril. However, the arrhythmia profile was similar in both treatment groups. These findings suggest that, in most patients with advanced chronic heart failure, long-term enoximone therapy is not associated with an important increase of ventricular arrhythmias. According to the 24-h Holter findings of the European Enoximone Data Bank, proarrhythmia can be expected in 12% of all patients. Control of the arrhythmia profile, however, is mandatory, because the incidence of proarrhythmia cannot be predicted in the individual patient.

Angiotensin-Converting Enzyme Inhibitors↗

[The effect of PTCA on clinical outcome in patients with coronary single vessel disease].

We evaluated a 3-year clinical follow-up in 53 patients with unsuccessful PTCA, due to failure to reach the lesion (control-group) in comparison to a "matched pairs" group of 53 patients, in whom PTCA had been performed (PTCA-group). There were no deaths in the PTCA-group compared to 3 deaths (5.7%) in the control-group (ns). Two patients (3.8%) and three patients (5.7%), respectively, suffered an acute transmural myocardial infarction during the follow-up period (ns). Coronary artery bypass grafting (CABG) had been performed in five patients (9.4%) following PTCA, and in 17 patients (32.1%) of the control-group (p less than 0.002). The overall rate of serious cardiac events (death, myocardial infarction or CABG) amounted to 13.2% (seven patients) in the PTCA-group and to 43.4% (23 patients) in the control-group (p less than 0.002). Only in the PTCA-group was a repeat PTCA performed in 15 patients (28.3%) with restenosis (p less than 0.00003). 35 of 53 patients in the PTCA-group (66%) and 27 of 50 survivors in the control-group were free of symptoms at the end of follow-up (ns). These results demonstrate that PTCA in patients with single-vessel disease is followed by a marked reduction of serious cardiac events, predominantly of bypass-operations, but the necessity of a second PTCA-procedure in case of restenosis has to be considered.

Angioplasty, Balloon, Coronary↗

[Long-term results of elective percutaneous transluminal coronary angioplasty. A clinico-angiography study of 289 consecutive patients].

289 consecutive patients (255 male, 34 female, 50 +/- 6 years) had an elective single-vessel-PTCA between October 1978 and March 1983. A clinical long-term follow-up was obtained after 4.7 (3-10) years. The PTCA success-rate was 73% with a non steerable balloon catheter being used in 95% of the cases. For 271/289 patients with follow-up (94%), the 56-month-survival rate was 96%, the incidence of non-fatal myocardial infarctions 11%, and the need for a second intervention (PTCA and/or bypass surgery) was 39%. The most favorable long-term outcome was observed in patients without need of a second intervention (97% survival, 7% non-fatal myocardial infarction, 83% without cardiac complaints during everyday life), and in patients with elective bypass surgery after an unsuccessful PTCA (100% survival, 5% myocardial infarction). 32/138 (23%) of patients without a second intervention during follow-up underwent an angiographic control after an average of 4.7 years. In comparison with the first follow-up angiogram 6 months after PTCA, the mean residual stenosis at the PTCA-site showed a slight decrease. It is concluded that PTCA offers good clinical and angio-graphic long-term results in single-vessel disease, with an excellent prognosis of patients without need for a second intervention.

Angioplasty, Balloon, Coronary↗

Circulating catecholamine concentrations in cocaine-exposed neonates: a pilot study.

Twenty newborns, 12 with prenatal exposure to cocaine and an unexposed control group of 8, were studied to determine concentrations of circulating catecholamines and their relationship to newborn behavior. Birth weight of the cocaine-exposed neonates was significantly lower than that of the control group. Gestational age, length, and head circumference of the cocaine-exposed neonates were also lower, although the differences did not reach statistical significance. Between 24 and 48 hours of age, circulating concentrations of norepinephrine, dopamine, and the catecholamine precursor dihydroxyphenylalanine were measured and behavior was assessed using the Neonatal Behavioral Assessment Scale. Mean dihydroxyphenylalanine concentrations were increased in the cocaine-exposed newborns (10.3 ng/mL vs 5.9 ng/mL, P = .055), while there was no difference between the groups in mean norepinephrine or dopamine concentrations. There was a significant negative correlation between norepinephrine concentration and orientation cluster score for the cocaine-exposed newborns (r2 = .6979, P = .005). norepinephrine concentration did not correlate with the score for any other behavioral cluster, nor did dopamine or dihydroxyphenylalanine concentration correlate with the score for any cluster. These preliminary data from a pilot study suggest that catecholamine activity is increased in cocaine-exposed newborns and may play a role in neurobehavioral disturbances associated with prenatal exposure to this drug.

Birth Weight↗

[Reference values of global and regional myocardial function for stress echocardiography].

Two-dimensional echocardiography has become a sensitive method to differentiate between normal and pathological myocardial function during exercise. Examining 50 healthy volunteers we determined normal values for global and regional left-ventricular function during bicycle exercise. Ejection fraction increased from 59 +/- 10% at rest to 85 +/- 7% at 210 watts workload, endsystolic volume decreased from 22.1 ml/m2 at rest to 7.1 ml/m2 at 210 watts. Enddiastolic volume showed a tendency to decrease from 55 +/- 21 ml/m2 at rest to 45 +/- 23 ml/m2 at 210 watts. Quantitative analysis showed an extended distribution both for Centerline- and Radiant-Method, during exercise Centerline-Method was superior. Two-dimensional echocardiography is useful for assessment of global and regional myocardial function during exercise. Decrease of ejection fraction or increase of endsystolic volume seems to be a pathological marker. Enddiastolic volume is a less useful parameter for evaluating left-ventricular function during stress. Quantitative analysis of left ventricular wall motion can be applied with restrictions.

Adult↗

[The effect of PEEP-ventilation on gas exchange and airway closure in experimental pulmonary emphysema].

The benefits of mechanical ventilation with positive end-expiratory pressure (PEEP) are well documented, especially for patients with acute respiratory failure. PEEP increases functional residual capacity (FRC) and reduces closing volume (CV) and ventilation-perfusion mismatching. Little is known about the effects of PEEP in patients with chronic obstructive pulmonary disease, where closing volume and ventilation-perfusion mismatching are increased. We investigated the effects of PEEP in a canine model of panlobular emphysema (PLE). METHODS. After completion of control-period measurements, PLE was induced in eight dogs by intratracheal application of 20 ml aerosolized 16% papain solution. Three weeks later the effects of continuous positive-pressure ventilation (CPPV, PEEP 10 cmH2O) on gas exchange, FRC, and CV were investigated. Conventional intermittent positive-pressure ventilation (IPPV) served as reference. Measurements of CV were done using both the foreign gas bolus method and the single-breath oxygen test. FRC was determined by the nitrogen dilution technique. RESULTS. The papain-induced emphysema produced a deteriation in oxygenation, enlargement of FRC and CV, and an increase in quasi-static lung compliance. CPPV led to a further increase of FRC, but gas exchange was not improved nor was CV reduced. In the PLE period, mean pulmonary arterial pressures (MPAP) were higher during both modes of ventilation. CPPV tended to increase MPAP and pulmonary capillary wedge pressure when compared with IPPV. Systemic hemodynamic conditions were stable throughout the experiment. CONCLUSIONS. The application of PEEP to emphysematous lungs seemed to enlarge FRC, predominantly in the nondependent rather than in the dependent lung regions, which are prone to airway closure. In patients with emphysema, ventilation with PEEP may further deteriorate the impaired distribution of ventilation and thus counteract any improvement of gas exchange.

Animals↗

[Angiographic and histologic findings in high frequency rotational ablation in coronary arteries in vitro].

High-frequency rotational angioplasty is a recently developed method for coronary angioplasty in the catheter laboratory. An elliptical burr tip (phi 1.25-2.0 mm) with embedded diamant chips (phi 40-50 microns) is rotated by a helical drive shaft at 150,000-180,000 rpm. The burr is advanced over a 0.009-inch coaxial guide wire. To show the effects of this approach in diseased and healthy vessels, which may be present before and behind a stenosis, 17 atherosclerotic coronary arteries of nine human hearts, and 18 normal coronary arteries of nine pig hearts were treated by this method in vitro. Standardized coronary angiography was performed before and after Rotablator treatment, followed by histological examination. From these data the burr-to-vessel-diameter ratio was calculated for each vessel segment and compared with the angiographical and histological outcome. Partial or complete removal of the circumference of the innermost vessel wall layers was observed regularly. The average removal of tissue in human coronary arteries was limited to the intimal layer and in the pig coronary arteries to the internal elastic membrane. In the pig coronary arteries no intimal tears or dissections occurred, in human coronary arteries tears could be seen frequently (13 of 17 vessels (76%)). Media tears were observed in 3 of 17 vessels; one (2%) media dissection could be demonstrated; no perforation occurred. Thus, the in vitro studies suggest that coronary rotational angioplasty has only a slight effect on the vessel segment next to a stenosis, regardless of the burr-to-vessel-diameter ratio.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗

Rubredoxin from Clostridium thermosaccharolyticum. Amino acid sequence, mass-spectrometric and preliminary crystallographic data.

Rubredoxin isolated from the thermophilic bacterium Clostridium thermosaccharolyticum has been sequenced and crystallized. The 52-residue sequence is similar to those of rubredoxins occurring in other anaerobic bacteria, but displays some unique features, including a tryptophan residue in position 4, two consecutive proline residues in positions 25 and 26, and an aspartic acid residue in position 41. The molecular mass (5988 Da) of the native rubredoxin has been measured by electrospray-ionization m.s., thus establishing the applicability of the technique to this type of iron-sulphur protein. C. thermosaccharolyticum rubredoxin crystallizes as dark-red elongated prisms with a flat diamond cross-section. The X-ray diffraction shows symmetry consistent with space group P2(1)2(1)2(1). Cell parameters are: a = 2.73 nm, b = 2.98 nm, c = 6.49 nm.

Amino Acid Sequence↗