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Biomedical subjects

K D Müller

Publications and source records attributed to K D Müller.

At least 55 records · Page 3Linked to original sources

Early diagnosis and medical treatment of the persistent ductus arteriosus in infants.

Diagnosis of an isolated patent ductus arteriosus (PDA) is usually straightforward. If at later age it is associated with pulmonary hypertension, however, the symptoms may be variable and more difficult to assess. In the age group primarily discussed here, pulmonary hypertension is frequently present, so diagnosis cannot be based on physical findings alone. Echocardiography and Doppler echocardiography are essential diagnostic procedures; however, cardiac catheterization and angiography may still be needed especially in cases with associated heart defects. At present, surgical closure of the PDA is the therapy of choice in infants. In preterm newborns, an attempt by medical treatment is indicated and often promising. Unfortunately, there are no interventional techniques available at present for duct closure in this age group, whereas in some centers catheter closure of a PDA is successfully employed in older children.

Ductus Arteriosus, Patent↗

[Double nuclide myocardial scintigraphy with thallium 201 and iodine 123-heptadecanoic acid--the possibilities in cardiological diagnosis].

UNLABELLED: We studied in 11 patients the individual variable pattern of coronary blood supply after the end of diagnostic coronary catheterisation by intracoronary injection of T1201 into the left and J 123-heptadeconic acid into the right coronary artery. In 4 static views computer aided quantitative analysis of circumferential profiles was performed. Based on Schlesinger's criteria three types of coronary arterial patterns were defined (right, left preponderant, balanced) after the presentation in the angiographic projections. CONCLUSIONS: Sharp boders between different perfusion areas could be detected by the gamma camera. If patients with right preponderant circulation are compared with balanced circulation, the perfusion areas of the left coronary artery are greater in all cases with balanced circulation than expected. More important for the indication of coronary artery surgery is that a considerable area of the left ventricular myocardium is perfused by the right coronary artery independent of the anatomical perfusion pattern with the exception of the left preponderant type.

Coronary Disease↗

[Comparison of T1201 stress scintigraphy and rest and stress ventriculography with respect to the degree of stenosis and collateral findings].

The influence of coronary obstructions and collaterals on the results of T1 201 myocardial scans and regional wall motion on ventriculography at rest and after pacing was examined with digital observer-independent methods, whereby criteria for positive and negative findings were defined in advance. The results indicate the high accuracy of 201-thallium scans in the detection of coronary artery disease in symptomatic single vessel disease, when the lesions obstruct greater than 60% of the vascular diameter. Cineventriculography at rest is inefficient as a test for this purpose. Ventriculography after pacing produced regional dysfunction in most of the patients and was comparable in its accuracy to T1 201 scans. A correlation of severity of stenoses and regional wall motion was not possible in the presented population. Collateral function is able to provide O2 supplies for normal myocardial function at rest and becomes insufficient during exercise and pacing. These results of T1201 stress scintigraphy correspond with results of stress ventriculography.

Adult↗

[Diagnostic possibilities of 1- and 2-dimensional Doppler and contrast echocardiography in congenital heart defects].

Indications and accuracy of real-time one- and two-dimensional echocardiography in combination with Doppler- and contrast methods in the noninvasive diagnosis of congenital cardiac malformations are presented. In contrast to the conventional 1-dimensional (M-Mode) echocardiography the 2-dimensional approach provides precise anatomic cardiac details in almost all cardiac lesions. Even complex congenital cardiac heart disorders and situs abdominalis can readily be differentiated. In some lesions like hypoplastic left heart syndrome, pericardial effusion, different forms of cardiomyopathy, uncomplicated bicuspid aortic valves, acute bacterial endocarditis, patent ductus arteriosus in prematures and in cardiovascular tumors cardiac catheterization is not indicated. In the remaining malformations 2-dimensional echocardiography is an excellent screening test and provides accurate and detailed informations with regard to spatial anatomy and valve morphology so that invasive studies can be performed with less contrast agent and hence with greater safety. With the use of contrast echocardiography right-to-left shunting, in some cases even left-to-right shunts, due to negative contrast effects can be demonstrated. Pulsed and continuous Doppler echocardiography allows noninvasive detection of valvular stenoses and -incompetence, aorto-pulmonic connections and small atrial- or ventricular septal defects. Pressure gradients, cardiac output and left to right shunting can be determined accurately.

Cardiac Output↗

[Quantification of atrial septal defects of the secundum type by subcostal 2-dimensional echocardiography].

Visualization of the interatrial septum (IAS) was most consistently achieved by subcostal 2-dimensional echocardiography (s2-DE) as compared with the apical and parasternal view. This approach also enabled a quantitative assessment of isolated atrial septal defects of secundum type (ASD II). The study group consisted of 33 children aged 5-14, mean 8 years, with ASD II (2 patent foramina ovale) and normal pulmonary vascular resistance. A good correlation was demonstrated between the end-diastolic diameter of the defect measured by s2-DE and left-to-right shunt determined by the Fick principle (r = 0.89). With respect to the endsystolic diameter of the defect, the correlation was less favourable (r = 0.76). This may be explained by the greater variability of the maximal defect in size in end-systole determined frame-by-frame. In conclusion, the size of an ASD II can be evaluated with accuracy by s2-DE. School children with isolated ASD II and diameters larger than 15 mm, corresponding to a 40% left-to-right shunt, will need surgical closure. However, surgery is not indicated in defects less than 11 mm and shunts smaller than 30%. In questionable cases we would be in favour of surgical closure.

Adolescent↗

A new polyene with antimycotic activity produced by a streptomycete from the rhizosphere of an indoor plant.

From the rhizosphere of a potted Sanseviera trifasciata, a Streptomyces griseus strain with a broad antifungal activity was isolated; in the soil of this plant, a sole hyphomycete, Aspergillus niger, was found in pure culture at 37 degrees C. This streptomycete produced a polyene, belonging to the pentaene group. It was found to inhibit, in vitro, the growth of all the 123 strains tested; the strains belonging to the genera Aspergillus, Cryptococcus, Candida, Trichophyton, Epidermophyton, Microsporum, Penicillium and Mucor. An antimycotic activity of this substance was also found to be present after i.v. administration to white mice infected with Cr. neoformans. Toxicological tests will have to show if this polyene could be considered as a candidate antimycotic drug. The soil of potted indoor plants is discussed as a possible habitat for streptomycetes with defined antifungal activities.

Animals↗

Effect of intraaortic balloon counterpulsation (IABP) on myocardial infarct size and collateral flow in an experimental dog model.

To determine the influence of IABP on infarct size and collateral blood flow in each of 12 openchest anaesthetised mongrel dogs two small branches of the left coronary artery were occluded consecutively. The perfusion areas of both branches were comparable in size. IABP was started immediately before ligation of the first branch for a 90-min period followed by a reperfusion period of 90 min. Subsequently the second vessel was also occluded for 90 min as a control without IABP while myocardial oxygen consumption remained constant and was then reperfused. Infarct size was expressed as a percentage of the perfusion area. A difference in infarct size with and without IABP (18 +/- 17, 18 +/- 10% respectively) could not be observed. However a significant increase of collateral blood flow due to IABP in the subendocardial layer from 8.9 +/- 4.8 to 14.9 +/- 4.6 ml/100 g/min (p less than 0.05) was prevalent. In the subepicardial layer the augmentation from 23.7 +/- 19.9 to 26.9 +/- 15.2 was not significant. Thus, in spite of a small increase of collateral blood flow in the subendocardial layer of the ischemic myocardium the infarct size was not reduced by IABP in our dog model.

Animals↗

Characterization of an intracellular serine protease from sporulating cells of Bacillus brevis.

Sporulating cells of Bacillus brevis ATCC 9999 produced a high level of an intracellular serine protease when grown in nutrient medium. The protease activity in the crude extracts of this strain appeared at hour 5 (t5) after the end of exponential growth and increased gradually during sporulation, reaching a maximum at t12 to t13. The enzyme isolated in a partially purified state showed a pH optimum between 7.3 and 9.0 and had an apparent molecular weight of about 60,000. The activity was completely inhibited by phenylmethylsulfonyl fluoride, diisopropyl fluorophosphate, EDTA, and ethylene glycol-bis(beta-aminoethyl ether)-N,N-tetraacetic acid. The protease possessed a high activity for azocoll and low activities for azocasein and 14C-labeled hemoglobin. It cleaved the cyclic decapeptide gramicidin S specifically at the peptide linkage between valine and ornithine and hydrolyzed the oxidized insulin B-chain mainly at peptide bonds 4-5 (Glu-His), 6-7 (Leu-CysSO3H), and 15-16 (Leu-Tyr). No catalysis of bond cleavage by the enzyme on a variety of small peptides or esters was detected. Unlike other Bacillus species, B. brevis ATCC 9999 grown in nutrient medium excreted no extracellular proteases.

Bacillus↗

Changes in myocardial oxygen consumption 45 minutes after experimental coronary occlusion do not alter infarct size.

The influence of myocardial oxygen consumption (MVO2) at the moment of coronary occlusion on the size of the ensuing infarct was investigated in two groups of anaesthetised dogs. In one group (n = 9) coronary occlusion was produced at a high MVO2, estimated to be 14.6 +/- 2.1 cm3 O2 X min-1 X 100g-1 which was changed midway during the occlusion period of 90 min to a low MVO2 estimated to be 6.7 +/- 1.6. In the second group (n = 9) the MVO2, was elevated after 45 min an estimate of 5.1 +/- 0.9 to one of 13.2 +/- 3.7 cm3 X min-1 X 100g-1. In this way the MVO2 averaged over the entire 90 min occlusion period was equal in both groups. Infarct size expressed as a percentage of perfusion area was 68 +/- 28% in group 1 and 32 +/- 30% in group 2 (P less than 0.025). The mass of the perfusion areas did not differ significantly between the groups. Haemodynamics changes were similar in both groups except for a higher rate in group 1 in the period with low MVO2 (109 vs 66 per min, P less than 0.001). Collateral flow was not different between the two groups 45 min after occlusion. It is concluded that the MOV2 at the moment of occlusion significantly influences infarct size. Drastic changes of MVO2 induced at 45 min (ie at half time of the occlusion period of 90 min) had no measurable effect on infarct size.

Animals↗

The effect of changes in cardiac frequency on left and right ventricular dP/dt max at different contractile states of the myocardium.

In 17 canine heart-lung preparations the dependence of frequency potentiation of the right and left ventricular myocardium on the basic inotropic state of the heart was investigated. The effect of unipolar stimulation of the right atrium on dP/dt max in both ventricles was measured. The aortic pressure was maintained constant. Shortly after isolation of the heart, a stepwise increase of rate from 140 to 200 beats/min only had a very weak influence on left ventricular dP/dt max. With deterioration of the myocardium the frequency potentiation of dP/dt max increased considerably. End-diastolic pressure regularly decreased with rising cardiac frequency. Since the real positive inotropic effect is masked by the concomitant fall in diastolic loading, the end-diastolic pressure was maintained constant in a second group of 8 hearts during rate variation. The most pronounced inotropic effect was now found shortly after isolation of the heart. A rate increase of 30 beats/min resulted in a 20% rise of dP/dt max. The frequency potentiation decreased with deterioration of the heart resulting in a 12% dP/dt max increase at an estimated inotropic state of 50% of control. When the contractile state of the heart was improved above the control state by calcium application the frequency potentiation of the myocardium decreased. In the right ventricle similar results were obtained except for the fact that no significant correlation between the steepness of the frequency characteristics and the contractile state of the heart could be found when the end-diastolic pressure was kept constant.

Animals↗

[Detection of right-to-left shunts by one- and twodimensional contrast echocardiography (author's transl)].

33 children with different congenital cardiac malformations--aged one day to twelve and a half years--were investigated by peripheral and central, 1- and 2 dimensional contrast echocardiography. 11 patients were studied during routinely performed cardiac catheterization and 23 in the early postoperative period (one patient pre- and postoperatively.) Contrast echocardiography peripherally performed represents a very sensitive diagnostic method to detect right-to-left shunting at atrial and/or ventricular levels. Quantification of shunts seems to be possible, if standardization can be achieved. Contrast echocardiography centrally performed can detect right-to-left shunts in residual postoperative defects, delineate and identify intra- and extracardiac structures, assess "low-output" states and should be applied in complex cardia malformations.

Age Factors↗

The M. omohyoideus of the mouse as a convenient mammalian muscle preparation. A study of junctional and extrajunctional acetylcholine receptors by noise analysis and cooperativity.

Muscles from cats, rats, guinea pigs and mice have been investigated as preparations for visualizing mammalian neuromuscular junctions with the aid of Nomarski interference optics. The M. omohyoideus of the mouse was found to be most convenient. Electrophysiological investigations showed that an endplate is normally surrounded by a population of perijunctional receptors. For junctional receptors in the endplate, a Hill coefficient of nH = 2.6 for acetylcholine was determined at 38 degrees C, decreasing to a value of 2.3 at room temperature. For both perijunctional and extrajunctional receptors (the latter occurring after denervation), the coefficient nH was 1.9. Noise analysis revealed a channel conductance gamma which changed abruptly from 22.4 +/- 1.0 pS (10--23 degrees C) to 45.6 +/- 3.9 pS (34--39 degrees C) in a very small temperature range around 25.5 degrees C. The mean channel lifetime tau was 0.3 ms at 39 degrees C and 1.0 ms at 23 degrees C.

Animals↗