Biomedical subjects

A Hartmann

Publications and source records attributed to A Hartmann.

At least 325 records · Page 18Linked to original sources

PubMed1994

Dosimetry of large, irregularly shaped fields by the circle method. A feasibility study.

The Circle Method is an algorithm for dose calculation in an irregularly shaped field. The algorithm is based on measurements of circle fields at the therapy machine in use. A separation into primary and scattered radiation components is not necessary. Clarkson's sector-integration method and an off-axis correction are embodied. Experimental and calculated dose values agree within +/- 2.8% in the treatment field and under block shieldings.

Algorithms↗

PubMed1994

Immersion and perfusion staining with 2,3,5-triphenyltetrazolium chloride (TTC) compared to mitochondrial enzymes 6 hours after MCA-occlusion in primates.

2,3,5-triphenyltetrazolium chloride (TTC) is commonly applied in rodents and cats as a marker of infarcted tissue as early as 20 min after the onset of focal ischaemia. At this stage it is suggested that it reflects hypoperfusion rather than failure of respiratory chain. Immersion of brain slices in TTC solution is preferable in comparison to perfusion with TTC in order to ensure, that enough TTC enters the post-occlusion tissue. We compared immersion technique versus perfusion technique 6 h after permanent occlusion of the left middle cerebral artery in 18 baboons. In addition, we assessed the function of the respiratory chain enzymes of stained and unstained tissue in three baboons. The immersion technique revealed an absence of TTC staining limited to subcortical structures in two animals. In seven experiments TTC indicated involvement of almost the entire MCA territory. The extent of the ischaemic lesion indicated by the perfusion technique was very similar. Tissue samples from the presumed infarcted areas revealed normal mitochondrial function. We conclude that perfusion and immersion technique do not cause significant different ischaemic delineation 6 h after middle cerebral artery occlusion. TTC staining appears to be a reliable method of evaluating volume of infarction in primates. Furthermore, absence of TTC staining 6 h after stroke onset is caused by energy or oxygen depletion rather than by mitochondrial injury.

Animals↗

PubMed1994

Correlation between long-chain acylcarnitine in serum and myocardium after heart transplantation in humans.

The concentrations of free, short-chain, and long-chain acylcarnitine were determined in 19 right ventricular endomyocardial biopsies and in serum from 14 patients after orthotopic heart transplantation and 3 nontransplanted control patients with normal cardiac function. Coronary angiography was normal in all patients. Left ventricular ejection fraction as measured by radionuclide ventriculography was not different between heart-transplanted and control patients (60.3 +/- 6.7% and 61.7 +/- 10.7%, respectively). Myocardial and serum carnitine concentrations in heart-transplanted patients were not different from control patients (myocardium: free carnitine 11.8 +/- 4.8 vs 7.1 +/- 7.1, short-chain acylcarnitine 4.5 +/- 2.1 vs 5.8 +/- 2.0, long-chain acylcarnitine 4.9 +/- 3.8 vs 3.9 +/- 3.2 mumol/g noncollagen protein; serum: free carnitine 32.6 +/- 11.2 vs 32.0 +/- 9.9, short-chain acylcarnitine 7.3 +/- 5.2 vs 5.1 +/- 1.3, long-chain acylcarnitine 4.1 +/- 2.7 vs 4.8 +/- 4.0 mumol/L). There was a highly significant correlation between myocardial and serum long-chain acylcarnitine (r = 0.76, P < 0.001). The data suggest that carnitine metabolism is not altered after heart transplantation.

Adult↗

PubMed1994

Does physical activity induce DNA damage?

The single cell gel electrophoresis (SCG) assay (comet assay) is a sensitive technique for detecting the presence of DNA strand-breaks and alkali-labile damage in individual cells. This technique was used to study peripheral blood cells from three volunteers after physical activity. The test subjects had to run on a treadmill and were checked for blood pressure and ECG, lactate concentration and creatine kinase activity. Blood was taken before and several times during and after the run. In a first multiple step test, the volunteers ran as long as possible with increasing speed. In a second test they had to run for 45 min with a fixed individual speed which was defined to ensure an aerobic metabolism. In the first test, the white blood cells of all subjects showed increased DNA migration in the SCG assay. The effect was seen 6 h after the end of the exercise and reached its maximum 24 h later. After 72 h, DNA migration decreased to about control level. The distribution of DNA migration among cells clearly demonstrated that the majority of white blood cells exhibited increased DNA migration and that the effect was not only due to a small fraction of damaged cells. From the same blood samples, blood cultures were set up to study a possible effect on the frequency of sister chromatid exchanges (SCE), another indicator for genotoxic effects. However, there was no significant increase in SCE in any of the cultures. In the second exercise, during aerobic metabolism, the effect on DNA migration was not seen.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Reduction of cerebral blood flow with induced tachycardia in rats and in patients with coronary artery disease and premature ventricular contractions.

A reduction of cerebral blood flow (CBF) was observed in experimental studies in rats immediately after the onset of parasystolic rhythm or with stable, but haemodynamically compromising, tachycardias. Based on these data and with a view to studying the effects of premature ventricular contractions (PVCs) on the cerebral circulation in humans, CBF was measured using the 133-Xenon inhalation method in 24 age matched human controls (group A1: age 58.5 +/- 6.2 years; group A2: 52.2 +/- 7.8 years) in nine coronary artery disease (CAD) patients without PVCs (B), in 11 CAD patients with frequent PVCs (> 300.h-1) (C) and in nine patients, after exclusion of CAD by angiography, also with frequent PVCs (> 300.h-1) (D). Holter monitoring was performed during the CBF measurement. CBF determined in the human control groups A1 and A2 was 79.9 +/- 9.9 ml.100 g.-1 min-1 and 81.5-13.0 ml. 100 g-1 min-1, respectively. CBF was 74.1 +/- 13.6 ml . 100 g.-1 min-1 (P = 0.267 vs A1) in group B, 65.8 +/- 11.8 ml.100 g-1 min-1 (P = 0.004 vs A1) in group C and 74.2 +/- 15.6 ml.100 g.-1 min-1 (P = 0.218 vs A2) in group D. The significant reduction of CBF in CAD patients with frequent PVCs suggests that arrhythmias have a significant impact on CBF. Non-CAD patients with frequent PVCs did not show significant CBF decreases in comparison with controls. One can hypothetize that an impairment of electrical postextrasystolic potentiation, due to premature ventricular depolarization, and hence myocardial dysfunction leads to CBF reduction in CAD patients. The CBF reduction with CAD could also reflect concomitant coronary and cerebral arteriosclerosis.

Aged↗

PubMed1994

Endothelium-dependent and endothelium-independent vasomotion in large coronary arteries and in the microcirculation after cardiac transplantation.

Endothelium-dependent and endothelium-independent vasodilation of the epicardial conduit vessels and the microcirculatory coronary vessels was investigated with cumulative doses of acetylcholine (ACh 50 micrograms and 100 micrograms i.c.), nitroglycerin (0.3 mg i.c.) and dipyridamole (0.56 mg.kg-1 i.v.) in 17 patients (3 female/14 male; age: 47 +/- 3.6 years) with angiographically normal coronary arteries 40 +/- 5.1 months after cardiac transplantation. The effect of ACh on large conduit arteries was evaluated angiographically. Coronary blood flow velocity changes were measured utilizing an 8F Judkins style 20 MHz Doppler catheter positioned in the left main coronary artery. A coronary flow index was calculated from the mean Doppler flow velocity and the computed cross-sectional vascular area. After 50 micrograms of ACh the diameter of proximal, middle and distal segments of the left anterior descending coronary artery decreased significantly by 7.6 +/- 2.06% (P < 0.05), 10.6 +/- 3.5% (P < 0.01) and 12.6 +/- 3.29% (P < 0.01) and after 100 micrograms ACh by 10.5 +/- 2.4% (P < 0.05), 13.0 +/- 3.7% (P < 0.01) and 15.3 +/- 3.9% (P < 0.01). The endothelium-independent vasodilator nitroglycerin (0.3 mg i.c.) induced an increase in vascular diameter of 14.4 +/- 3.1% (P < 0.01), 18.6 +/- 4.1% (P < 0.01) and 20.8 +/- 2.9% (P < 0.01) in proximal, mid and distal segments of the left anterior descending coronary artery.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗

PubMed1994

The pharmacokinetics of fluconazole after a single intravenous dose in AIDS patients.

The pharmacokinetics of fluconazole after a single 100 mg i.v. dose were studied in 10 healthy subjects (5 M; 5 F) and 10 HIV-positive patients (8 M; 2 F). The mean value of plasma clearance was 25% lower in the patient groups (17 +/- 6 (s.d.) vs 23 +/- 4 ml min-1; 95% CI of difference -11 to -0.7; P < 0.05). This difference may have been related to slightly reduced kidney function in the patient group (mean creatinine clearance -18%) but is unlikely to be clinically significant. Therefore, no adjustment of the dose of intravenously administered fluconazole appears to be necessary in AIDS patients without clinical signs of enteropathy.

Acquired Immunodeficiency Syndrome↗

PubMed1994

In situ analysis of microbial consortia in activated sludge using fluorescently labelled, rRNA-targeted oligonucleotide probes and confocal scanning laser microscopy.

Activated sludge flocs are complex consortia of various micro-organisms. The community structures of samples taken from municipal sewage treatment plants were characterized using fluorescently labelled, 16S and 23S rRNA-targeted oligonucleotide probes in combination with confocal scanning laser microscopy (CSLM). In comparison with conventional epifluorescence microscopy, CSLM considerably improved the capability to visualize directly the spatial distribution of defined bacterial populations inside the sludge flocs. Analyses could be performed at high resolution undisturbed by problems such as autofluorescence or limited spatial resolution in thick samples. In addition, CSLM was used to analyse some structural properties of paraformaldehyde-fixed activated sludge flocs, such as floc size and homogeneity. Typical floc sizes were found to be in the range between 5 and 50 microns. Whereas most of the flocs were completely colonized by bacteria, there were also examples of flocs containing gas bubbles or particles in the interior.

Bacteria↗

PubMed1994

Cutting and skin-ablative properties of pulsed mid-infrared laser surgery.

BACKGROUND: Pulsed mid-infrared lasers allow a precise removal of soft tissues with only minimal thermal damage. OBJECTIVE: To study the potential dermatosurgical usefulness of currently available systems at different wavelengths (2010-nm Thulium:YAG laser, 2100-nm Holmium:YAG laser, 2790-nm Erbium:YSGG laser, and 2940-nm Erbium:YAG laser) in vivo on pig skin. METHODS: Immediate effects and wound healing of superficial laser-abrasions and incisions were compared with those of identical control lesions produced by dermabrasion, scalpel incisions, or laser surgery performed by a 1060-nm Nd:YAG and a 1060-nm CO2 laser (continuous and superpulsed mode). RESULTS: Best efficiency and least thermal injury was found for the pulsed Erbium:YAG laser, leading to ablative and incisional lesions comparable to those obtained by dermabrasion or superficial scalpel incisions, respectively. CONCLUSION: In contrast to other mid-infrared lasers tested, the 2940-nm Erbium:YAG laser thus provides a potential instrument for future applications in skin surgery, especially when aiming at a careful ablative removal of delicate superficial lesions with maximum sparing of adjacent tissue structures. However, in the purely incisional application mode pulsed mid-infrared lasers, though of potential usefulness in microsurgical indications (eg, surgery of the cornea), do not offer a suggestive alternative to simple scalpel surgery of the skin.

Aluminum Silicates↗

PubMed1994

Accidental metabolic acidosis during hemodialysis.

Three incidents of metabolic acidosis during hemodialysis in 3 different patients are presented. Two patients became severely ill but recovered completely after treatment. In the third patient, the event was recognized before the acidosis became symptomatic. In all cases the acidosis was caused by an unbalanced supply of acidic dialysis concentrate. Two events were caused by mistaking acidic dialysis concentrate for acetate. In the third patient, the supply line from the bicarbonate concentrate jug was broken. The conductivity cell alarm was not activated during any of the incidents and in only 1 case during reconstruction of the accidents. The efficacy and safety of the conductivity cell alarm system regarding prevention of acid/base disturbances during hemodialysis are discussed.

Acidosis↗

PubMed1994

Noninvasive methods in the early detection of restenosis after percutaneous transluminal angioplasty in peripheral arteries.

In a prospective study, several noninvasive methods were evaluated in the early detection of restenosis after percutaneous transluminal angioplasty in peripheral arteries. Sensitivity and specificity of various noninvasive resting and exercise methods for the detection of restenosis were determined. It is concluded that noninvasive follow-up after percutaneous transluminal angioplasty in peripheral arteries requires exercise testing with determination of ankle-arm index or segmental arterial pulse oscillography for the early detection of restenosis.

Aged↗

PubMed1994

Myocardial and cerebral hemodynamics during tachyarrhythmia-induced hypotension in the rat.

BACKGROUND: The different vulnerabilities of heart and brain to hypotension and hypoxia have been discussed. Hemorrhagic or cardiogenic hypotension appears to cause greater cerebral lesions than drug-induced hypotension. The present model was established to evaluate myocardial blood flow (MBF) and function of the heart and cerebral blood flow (CBF) during tachyarrhythmias and to characterize the capacity of blood flow regulation in the heart and brain during tachycardia-induced borderline hypotension. METHODS AND RESULTS: MBF and CBF were determined with radiolabeled microspheres. Coronary and central venous oxygen tensions were measured to estimate myocardial and cerebral oxygen consumption (MVO2 and CVO2). Measurements were performed in 62 Sprague-Dawley rats during sinus rhythm and high-rate left ventricular pacing and after hemorrhage. In control rats, MBF and CBF were 5.08 +/- 1.07 and 1.09 +/- 0.29 mL.g-1.min-1. MBF increased (7.21 +/- 1.98 mL.g-1.min-1, P < .05), whereas CBF decreased (0.99 +/- 0.29 mL.g-1.min-1, P = NS) during normotensive high-rate pacing. MBF and CBF dropped to 4.27 +/- 2.24 mL.g-1.min-1 (P = NS) and 0.68 +/- 0.29 mL.g-1.min-1 (P < .05) during pacing-induced borderline hypotension and decreased further during severe hypotension (1.77 +/- 0.81 mL.g-1.min-1, P < .01; 0.45 +/- 0.18 mL.g-1.min-1, P < .01). During borderline hypotension due to hemorrhage, MBF and CBF were 4.05 +/- 0.95 mL.g-1.min-1 (P = NS) and 0.71 +/- 0.23 mL.g-1.min-1 (P < .05). MVO2 and CVO2 were 72.7 +/- 15.4 and 12.7 +/- 3.3 mL.100 g-1.min-1 in control rats. MVO2 increased during normotensive pacing (100.3 +/- 27.4 mL.100 g-1.min-1, P = NS). Mean MVO2 was reduced during pacing-induced borderline hypotension (64.1 +/- 35.6 mL.100 g-1.min-1, P = NS) and severe hypotension (29.8 +/- 15.4 mL.100 g-1.min-1, P < .05). CVO2 decreased in correlation to CBF. Coronary and cerebrovascular resistance and autoregulation indexes indicated a maintenance of MBF regulation and a failure of CBF regulation during borderline hypotensive tachycardias. These results show a dissociation of MBF and CBF after onset of hypotensive tachycardias. Thus, brain tissue appears to be jeopardized at an earlier stage than myocardial muscle during tachyarrhythmias. CONCLUSIONS: The proposed hypotension model is suitable to analyze tachyarrhythmia-induced hemodynamic changes and end-organ perfusion in the presence of myocardial dysfunction. It has the potential to test therapeutic strategies in the treatment of tachycardias.

Animals↗

PubMed1994

Contrasting short-term effects of nifedipine on glomerular and tubular functions in glomerulonephritic patients.

The short-term effects of nifedipine on glomerular hemodynamics, sieving function, and renal tubular function were assessed in 10 patients suffering from biopsy-verified chronic glomerulonephritis. Three weeks of nifedipine treatment after 2 wk of placebo significantly reduced the blood pressure from 153 +/- 6/90 +/- 3 to 139 +/- 6/84 +/- 4 mm Hg (mean +/- SE; P < 0.05). Renal vascular resistance was reduced from 0.54 +/- 0.10 to 0.46 +/- 0.08 mm Hg/mL per minute. However, GFR (44.3 +/- 7 mL/min), effective RPF (265 +/- 37 mL/min), and filtration fraction (0.17 +/- 0.01) remained unchanged. The excretion of albumin of 1,318 +/- 395 micrograms/min was not affected by nifedipine. The glomerular sieving estimated by use of the fractional dextran clearance technique revealed no significant change by nifedipine compared with placebo in the range of 30 to 60 A of hydrodynamic dextran radius. Fractional proximal reabsorption (lithium clearance method) was reduced by nifedipine from 53 +/- 5 to 46 +/- 4% (P < 0.05). Also, the excretion of beta 2-microglobulin and N-acetyl-beta-glucosaminidase increased from 10.98 +/- 4.62 to 11.86 +/- 4.74 mg/24 h (P < 0.05) and from 19.7 +/- 4.2 to 25.3 +/- 7.0 nmol/h per micromoles of creatinine (P = 0.05), respectively. It was concluded that nifedipine treatment acutely represses proximal tubular function but is without significant effect on glomerular sieving and albuminuria in these patients.

Adult↗

PubMed1994

[Cerebral circulation in patients with dilated cardiomyopathy and aortic valve diseases].

The present study was performed in order to investigate the effect of dilated cardiomyopathy and severe aortic valve disease on cerebral blood flow. Cerebral perfusion was determined in 39 healthy volunteers representing two control groups of different age (77.7 +/- 8.7; 79.7 +/- 8.1 ml/100 g/min), in 7 patients with dilated cardiomyopathy (64.0 +/- 4.7 ml/100 g/min), in 11 patients with severe aortic stenosis (71.1 +/- 14.8 ml/100 g/min), and in 6 patients with severe aortic regurgitation (54.6 +/- 5.8 ml/100 g/min). Regional cerebral blood flow was measured with the 133Xenon inhalation method. Cerebral blood flow in severe aortic regurgitation patients (p = 0.006) was markedly and significantly reduced versus controls, whereas in dilated cardiomyopathy patients (p = 0.197) and in patients with severe aortic stenosis (p = 0.111) cerebral blood flow was not significantly reduced. A chronic adaptation of cerebral blood flow to the profound reduction of cardiac output is assumed in dilated cardiomyopathy patients. The collapsing pulse and the maximal reduction of mean arterial blood pressure in severe aortic regurgitation patients cause the reduction of autoregulatory capacity of cerebral blood flow with subsequent decrease of brain perfusion. Measurement of cerebral blood flow appears to be suitable for evaluation of perfusion deficits due to cardiac abnormalities. It provides an additional parameter for estimating the indication of valve replacement in patients with aortic valve disease.

Adult↗

PubMed1994

[Intermittent focal cerebral ischemia in hypotension due to pacemaker syndrome].

A pacemaker syndrome manifested as transient sensoric aphasia in a 68-year-old woman with a VVI-pace-maker implanted after SA-block. The attack occurred during long-term blood pressure recording and Holter monitoring. Borderline hypotension was documented during ventricular pacing which induced a retrograde excitation of the atrium. Clinical investigations excluded any intracranial abnormality, any source of embolism or stenosis of extra- and intracranial cerebral arteries. Cerebral blood flow measurements revealed a significant increase during pacing at elevated heart rate. Therefore, a device for AV-sequential pacing was implanted and basic pacing rate was elevated. The present case report indicates that focal and not only global cerebral ischemia can be produced by an impairment of systemic hemodynamics due to hypotension and a pacemaker syndrome. Improvement of cerebral blood flow during pacing is an unexpected finding contrasting with the concept of autoregulation. In addition, pacemaker implantation should be discussed in patients with transient cerebral perfusion deficits if an improvement of cerebral blood flow is documented along with rising heart rate.

Aged↗

PubMed1994

Reopening of chronic coronary occlusions by low-speed rotational angioplasty.

Total occlusions are found in 10% to 20% of patients undergoing coronary angioplasty. The low-speed rotational angioplasty system (ROTACS) was developed as an addition to conventional guidewire techniques in chronic occlusions. It can be employed if the passage of the obstructed vascular segment with a conventional guidewire fails. The results in 200 patients presented here indicate that angioplasty expands the option of nonsurgical coronary revascularization.

Angioplasty↗

PubMed1994

[Lacunar brain infarct in carotid occlusion].

The etiology of lacunar CCT lesions is controversial. We report a patient with recurrent ischemia in the territory of the right internal carotid artery. CCT initially showed a fresh non-lacunar lesion in the area of the basal ganglia and internal capsule. Subsequently, repeat CCT revealed a singular lacunar defect in the internal capsule. The Doppler sonographic investigations showed an internal carotid artery occlusion. This case supports the hypothesis that an embolic or hemodynamic etiology of the lacunae is possible.

Aged↗

PubMed1994

[The significance of clinical prodromes for dosage estimation after whole-body radiation exposure].

BACKGROUND: The triage of victims after radiation injury is complicated by missing dose values and the fact that most tissues react after a latency period. PATIENTS AND METHODS: We evaluated 63 patients undergoing total body irradiation as conditioning regime before bone marrow transplantation in order to find a relation between prodromal symptoms and dose. RESULTS: Emesis after radiation exposure hints to doses greater than 1.5 Gy. A rise of body temperature above 37 degrees C up to five hours after exposure is related to doses exceeding 2.5 Gy, while an acute onset of diarrhoea is an indicator of a severe accident with more than 9 Gy. CONCLUSION: Besides blood counts and chromosome analyses a careful evaluation of prodromal symptoms can help to classify the severity of radiation accidents.

Acute Disease↗