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Biomedical subjects

N Hahn

Publications and source records attributed to N Hahn.

At least 37 records · Page 2Linked to original sources
PubMed1985

[Computed tomography of the heart. Technic for quantitative evaluation of the perfusion of the ischemic myocardial region. Experimental basis].

A CT standard procedure has been developed in six series of experiments, using 62 anaesthetised dogs in order to quantitative relative blood flow through ischaemic heart muscle. Measurements of cardiac dynamics by means of contrast media were less strictly controlled. The use of the standardised procedures with contrast injections is necessary because of the variable perfusion and washout intervals of the contrast in normal and ischaemic myocardium.

Animals↗
PubMed1985

Cerebrospinal fluid uptake and peripheral distribution of centrally acting drugs: relation to lipid solubility.

In an anaesthetized dog model, serum kinetics and CSF entry were determined after i.v. administration of the following 8 drugs: salicylic acid (as acetylsalicylic acid), antipyrine, acetaminophen (paracetamol), lidocaine (lignocaine), trimipramine, amitriptyline, haloperidol, and imipramine. Kinetic variables were evaluated in relation to in-vitro lipophilicity, measured by the reverse-phase high-pressure liquid chromatographic (HPLC) retention index. After correction for individual values of serum binding (determined as the CSF: serum ratio at equilibrium), in-vivo volume of distribution was highly correlated with HPLC retention (r = 0.92). Conversely, the time of peak CSF concentration and the CSF entry half-life were negatively correlated with HPLC retention (r = -0.83 and -0.63, respectively). Thus lipophilicity is a physiochemical property which has an influence on the peripheral distribution of drugs as well as their rate of entry into CSF.

Animals↗
PubMed1984

Relation of myocardial blood flow and initial cardiac uptake of 15-(p-123I-phenyl)-pentadecanoic acid in the canine heart.

In 8 pentobarbital-anesthetized mongrel dogs the correlation between regional myocardial blood flow (RMBF) and regional cardiac uptake of 15-(p-123I-phenyl)-pentadecanoic acid (IPPA) was determined. Three animals were studied under control conditions, in three dogs an acute ischemia was produced by LAD ligation, and two dogs were paced at 195 beats/min. RMBF values were 20-50 ml/min X 100 g in acutely ischemic myocardium. 90-120 ml/min X 100 g under normal conditions and 200-250 ml/min X 100 g during pacing-induced stimulation. Total cardiac uptake of IPPA was 4.5-6% of the injected dose. In normal and acutely ischemic myocardium a good correlation between RMBF and IPPA uptake was obtained. Under stimulated conditions only a moderate increase of IPPA accumulation was found. At RMBF values above 150-170 ml/min X 100 g an upper limit of IPPA uptake was observed and can be explained by limited diffusion or an increased utilization of alternative substrates.

Animals↗
PubMed1983

[Electrical and motor activity of the rectum following low anastomosis].

Electrical and motor activity of smooth muscle of the canine rectum was registered by transanal recording following low rectum anastomosis. The relaxation reflex of the anal canal had disappeared distal of the anastomosis in the first postoperative week, and electrical slow waves and pressure waves were desynchronized proximal and distal of the anastomosis. The resting pressure of the rectal wall had increased above preoperative values. After wound healing had accomplished the relaxation reflex and the synchronization of electrical and mechanical activity proximal and distal of the anastomosis did occur again. It is concluded that the rectal wall provides the pathways for the relaxation reflex of the anal canal. After wound healing has finished these pathways are restored across the anastomosis.

Action Potentials↗
PubMed1983

[Relations between ventricle function, myocardial oxygen consumption and coronary circulation following sublingual administration of nitroglycerin].

The relationships between ventricular function, coronary blood flow, and myocardial oxygen consumption after sublingual administration of 1.6 mg nitroglycerin (TNG) were investigated in 12 patients. Left ventricular volumes, determined from cineventriculograms (enddiastolic volume index and endsystolic volume index), decreased (p less than 0.005) after TNG, as did left ventricular peak pressure (p less than 0.01), left ventricular enddiastolic pressure (p less than 0.005), mean aortic pressure (p less than 0.005), and mean pulmonary artery pressure (p less than 0.001). Due to the decrease in enddiastolic volume and the insignificant change in stroke volume, ejection fraction increased (p less than 0.05). Heart rate did not change significantly. In spite of an increase in the vessel diameter (13%, p less than 0.005), systolic and diastolic coronary blood flow, measured by means of a photodensitometric technique, decreased insignificantly by an average of approx. 15%. Similarly the change in myocardial oxygen consumption, calculated according to Bretschneider, decreased insignificantly by an average of approx. 10%. The correlation of changes in coronary blood flow and myocardial oxygen consumption was evaluated statistically by the use of the 2 X 2 contingency table in conjunction with the chi 2 McNamar test: patients with a decrease in myocardial oxygen consumption also showed a decrease in coronary blood flow (p less than 0.05). This implies that coronary blood flow is determined by myocardial oxygen consumption, which is altered by the systemic effects of TNG.

Adult↗
PubMed1982

[Experimental myocardial infarct in computerized tomography].

The findings on computer tomography after ligation of the coronary artery of a dogs heart are described. The ischaemic area can be differentiated from normal myocardium by its hypo-dense appearance. The localisation and size of the ischaemic area correlates with the scintigraphic findings. The known morphological and functional changes after intravenous oxyfedrin (positively inotropic, increased myocardial blood-flow) can also be seen on the computer tomogram (after oxyfedrin: myocardial thickening, reduction in cross-sectional area of the left ventricle, improved contraction, increased density of the ischaemic area). This confirms the possible diagnostic role of CT in the elucidation of changes in the left ventricle in the course of coronary disease.

Animals↗
PubMed1982

Assessment of regional myocardial uptake and metabolism of omega-(p-123I-phenyl) pentadecanoic acid with serial single-photon emission tomography.

The utility of myocardial imaging and assessment of regional myocardial metabolism of omega-(123I-paraphenyl-)pentadecanoic acid (I-PPA) by means of serial single-photon tomography is demonstrated in animal experiments. High quality cross sectional images of dog hearts with clear delineation of left ventricular walls are obtained. Myocardial infarcts are visualized as areas of deficient radioactivity uptake. I-PPA elimination from non-infarcted myocardial regions is significantly (p less than 0.001) prolonged when compared with unaffected controls. Hence, not only localized absence of uptake of free fatty acid by infarcted myocardium can be demonstrated with serial single-photon tomography but also general impairment of cardiac FFA-metabolism.

Animals↗
PubMed1981

[The action of oxyfedrine on haemodynamics, inotropism and blood perfusion of the partially ischaemic myocardium after digoxin premedication. Studies on anaesthetized dogs (author's transl)].

The effect exerted on the partially ischaemic heart when administering 0.9 mg/kg L-3-(beta-hydroxy-alpha-methylphenethylamino)-3'-methoxypropiophenone (oxyfedrine, ildamen) approx. 10 min after i.v. application of 0.05 mg/kg digoxin was tested on 20 dogs previously anaesthetized with propiomazine-pentobarbital. The following parameters were studied and subsequently compound with the results of former trials of ours' without digoxin premedication: aortic pressure (ASP, ADP), left-ventricular pressure (LVSP, LVEDP), heart rate (HR), cardiac output (HMV), stroke volume (SV), dp/dtmax, dp/dtmax/IP, t-dp/dtmax, blood flow in the normal and partially ischaemic myocardium, the latter being measured with heat conductance probes and labelled microspheres. ASP and ADP show the same reduction--as compared with the control value--both after the administration of oxyfedrine with and without digoxin premedication. After digoxin premedication oxyfedrine led to a somewhat less marked reduction of LVSP; on premedication with digoxin LVEDP was slightly increased whereas it was reduced after additional administration of oxyfedrine as was also the case without digoxin pretreatment. The increase in HR after oxyfedrine is almost the same as without digoxin pretreatment. Also the increase in HMV and the SV lowering are not influenced by digoxin. By administration of oxyfedrine dp/dtmax is always increased by the same amount, starting from the already increased value after digoxin premedication, which is probably an additive effect. The same applies to the quotient dp/dtmax/IP. After oxyfedrine the time t-dp/dtmax is lowered by the same amount, irrespective of a digoxin premedication. Oxyfedrine does not produce a further increase in the heat conductance values after previous application of digoxin; when measuring the blood flow with labelled microspheres the same result was found, which means that by previous administration of digoxin the circulatory effect of oxyfedrine is obviously inhibited. Summing up one can say that by combining the active principles digoxin and oxyfedrine the function parameters of the heart can be influenced only positively.

Anesthesia↗
PubMed1981

Contrast media-induced side effects on excitation and conduction of electrical activity in the heart on intracardiac application. Investigations in anaesthetized dogs.

In several series of experiments with intracardiac application in anaesthetized dogs, the following contrast media were tested for their adverse effects on excitation and conduction of electrical activity in the heart. Diatrizoate, lysine-diatrizoate, lysine-sodium-diatrizoate, ioxaglate, iopamidol, iodamide, ioxitalamate, ioglicinate and metrizamide. Blood pressure and, using the His' bundle-ECG technique, the parameters P0-P1 (heart rate), A1-H1 period (conduction time in the AV-node), and H1-V1 period (conduction time in the TAWARA branches) were measured. A statistical correlation exists between osmolarity and blood pressure (higher osmolarity causes a greater decrease in blood pressure), as well as between osmolality and decrease in heart rate (higher osmolarity causes a greater decrease in heart rate). The delay in conduction time in the AV-node correlates only with viscosity and sodium content (increased viscosity with increased sodium content delays the time of conduction). A tendency towards delay in conduction in the TAWARA branches could not be correlated to any one of the physico-chemical parameters studied.

Anesthesia, General↗
PubMed1980

[Experimental investigations on the effect of etilefrinhydrochloride (Effortil) on heart and circulation of animals with partial ischaemic damage of the myocardium (author's transl)].

The effect of Etilefrin on the blood flow of normal and partial ischaemic myocardium with heat conductance probes as well as on the ventricular dynamics was investigated on 11 dogs under propiomazine-pentobarbital narcosis. Etilefrin was applied in doses of 0.04 mg/kg bw. and 0.2 mg/kg bw. At low doses, the blood flow was only elevated in normal myocardium, likewise the systolic aortic pressure, the diastolic aortic pressure decreased, the heart frequency was elevated, whereas the systolic pressure in the left ventricle was only slightly increased for a short time, the enddiastolic pressure unchanged, dp/dtmax rose significantly, but the heart minute volume only slightly. At higher doses, elevation of blood flow also appeared in partial ischaemic myocardium, the aortic pressure, systolic and diastolic, decreased considerably at first and then 20 min. p.i. rose to above the control value. The heart frequency was more elevated than at lower doses, the pressures in the left ventricle showed no obvious changes, dp/dtmax and heart minute volume were likewise considerably elevated. Radiological measurements of the ejection fraction and the mean circumferential fiber shortening velocity at higher Etilefrin doses showed also a positive inotropic effect. In consideration of this fact, therapy with Etilefrin appears useful in disturbances of cardiac function and at least shows no contraindication by means of myocardial blood flow.

Animals↗
PubMed1978

Tissue response to overdenture therapy.

Patients who had received overdenture treatment provided with uniform standards were recalled and studied. Two examiners simultaneously and independently evaluated the tissue response using a variety of indices. Data comparisons were made between overlaid teeth and control teeth and between overlaid teeth as a function of time to assess any effects of the treatment. Patients who did not apply fluoride to retained tooth roots had a high incidence of caries. No other significant differences were noted between the health of overlaid teeth compared to control teeth. Patients demonstrated large variations in their ability to maintain low plaque levels and healthy tissues. Despite this, on a longitudinal basis over 2 years, patients were able to maintain plaque levels and gingival response at clinically acceptable standards.

Consumer Behavior↗
PubMed1977

[Local ventricular wall motion, local myocardial flow, and blood flow distribution in a poststenotic myocardial region in patients with coronary heart disease (author's transl)].

In 10 patients with coronary heart disease, local ventricular wall motion, local poststenotic flow, and distribution of myocardial perfusion were determined in the underperfused myocardium before and after 8 mg of Oxyfedrin intravenously. In 8 of the 10 patients there was a uniform reaction consisting of an improvement of wall motion, increase in flow, and homogeneity of flow distribution. These parallel changes of local wall movement and local blood flow in a poststenotic underperfused part of the myocardium can most probably be explained by the positively inotropic action of Oxyfedrin with a consecutive increase in blood flow. The results show that a therapeutic affect in patients with a coronary stenosis less than 60% in the left descending artery can be obtained with a positively inotropic substance.

Adult↗
PubMed1977

Tumor cure and cell survival after localized radiofrequency heating.

Radiofrequency electromagnetic fields at 13.56 MHz were used to heat locally EMT-6 sarcomas and KHJJ carcinomas in BALB/cKa mice. Temperature profiles obtained in tumors during treatment showed uniform temperature distribution throughout the tumor volume with no systemic hyperthermia. Temperature could be maintained at a stable level throughout treatment by adjustment of power. Tumors were treated at 43 degrees, 43-5 degrees, and 44 degrees, for 5, 10, 20, 30, and 40 min. The EMT-6 tumor was highly sensitive to cure by radiofrequency heating: a 5-min exposure at 44 degrees resulted in cure of almost 50% of the tumors. Cure rate was a function of temperature and of duration of exposure. The KHJJ carcinoma was somewhat more resistant to cure by radiofrequency heating, although most of the animals treated at 43.5 degrees or above were cured of their tumors. In an effort to explain the remarkable effectiveness of radiofrequency heating, tumor cell survival studies were done on EMT-6 tumors treated in situ. Cell inactivation by radiofrequency heating was similar to that for hot water bath heating. However, direct cell killing cannot account for the observed cures, and an additional mechanism must be responsible for tumor eradication.

Animals↗