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Biomedical subjects

A Hartmann

Publications and source records attributed to A Hartmann.

At least 361 records · Page 20Linked to original sources
PubMed1993

PET study of changes in local brain hemodynamics and oxygen metabolism after unilateral middle cerebral artery occlusion in baboons.

Local cerebral hemodynamics and oxygen metabolism were measured by positron emission tomography (PET) with the oxygen-15 (15O) steady-state method in baboons, immediately before (T0), 1 (T1), and 3-4 (T2) h after permanent middle cerebral artery occlusion (MCAO). At T1, there was a marked fall in both cerebral blood flow (CBF) and the CBF/cerebral blood volume (CBV) ratio in the occluded territory; these changes were sustained at T2, indicating stable reduction in cerebral perfusion pressure and lack of spontaneous reperfusion within this time range. Compared with preocclusion conditions, the oxygen extraction fraction (OEF) in the occluded territory was elevated at both T1 and T2, indicative of a persistent oligemia/ischemia for up to 3 h after MCAO. At T2, however, this OEF increase had lessened, concomitantly with a decline in cerebral metabolic rate of oxygen (CMRO2). This impairment of oxidative metabolism occurred earlier in the deep, compared with the cortical, MCA territories; in the latter, the CMRO2 was essentially preserved at T1 and only moderately reduced at T2, possibly suggesting prolonged viability. Finally, no significant changes in CBF or CMRO2 were observed in the contralateral MCA territory in this time range after MCAO. Despite methodological limitations (mainly partial volume effects related to PET imaging, which may have resulted in an underestimation of true changes and an overlooking of heterogeneous changes) our study demonstrates the feasibility of the combined PET-MCAO paradigm in baboons; this experimental approach should be valuable in investigating the pathophysiology and therapy of acute stroke.

Animals↗
PubMed1993

Procedural results and patient selection in recanalization of chronic coronary occlusions by low speed rotational angioplasty.

From 1988 to 1991, 200 consecutive patients (18 female, 182 male, mean age 55.4 +/- 9 years) with chronic coronary occlusions resistant to recanalization by conventional techniques were treated by low speed rotational angioplasty. Indication was based on preserved left ventricular contraction and on exercise-induced symptoms or exercise induced signs of myocardial ischaemia. Duration of occlusion ranged from 1 to 192 months (median 6 months, interquartile range 4-9 months, mean 12 +/- 26 months). Success rate was 91% in occlusions 4 weeks-3 months old, 72% in occlusions 4-6 months old, 55% in occlusions 6-12 months old and 8% in occlusions older than 12 months. In 99 of 116 successfully treated patients (85%) follow-up angiography was performed 4 months after recanalization. In 80/99 (81%) patients the vessel remained open. Fifty of these 80 patients needed no further intervention, while 30/80 of the patients had restenosis treated by a second PTCA in 28 patients. Nineteen of the 99 (19%) patients had reocclusions. Including cases submitted to a second dilation, and angiographically determined long-term patency 4 months after successful recanalization was thus achieved in 78/99 (78%) of patients. Minor complications included asymptomatic dissection in the recanalized vascular region. Serious complications occurred in two proximal occlusions of the left anterior descending coronary artery dissecting into the adjacent circumflex branch, and embolism into distal parts of recanalized vessels. It is concluded that in selected patients low speed rotational angioplasty (Rotacs) is a safe technique applicable to chronic total coronary occlusions even if the duration of occlusion exceeds 6 months and after conventional techniques have failed.(ABSTRACT TRUNCATED AT 250 WORDS)

Atherectomy, Coronary↗
PubMed1993

Effects of nitrendipine and lisinopril on blood pressure and sodium excretion in ciclosporin-associated hypertension after heart transplantation.

Hypertension associated with ciclosporin A may be mediated by sodium and volume retention. Therefore, the effects of an antihypertensive therapy (6 weeks) with nitrendipine (10-20 mg twice daily) or lisinopril (10-20 mg once daily) on office blood pressure, 24-hour ambulatory blood pressure, and left ventricular function were evaluated in a randomised, double-blind cross-over trial in patients after heart transplantation. Nitrendipine and lisinopril were equally effective in lowering office and ambulatory systolic and diastolic blood pressures. After an acute sodium load (210 mval/2 h i.v.), sodium excretion was significantly increased during therapy with lisinopril but only slightly during nitrendipine, indicating that angiotensin-converting enzyme inhibition may improve the sodium-retaining state of heart transplant recipients associated with ciclosporin A.

Adult↗
PubMed1993

Combined radiochemotherapy with carboplatin in the treatment of advanced head and neck carcinomas.

From 1987 to 1991, 100 evaluable patients with advanced head and neck carcinomas (T2-4, N0-3) were treated with radiotherapy and simultaneous carboplatin. Tumors were located in the oral cavity in 33 patients, oropharynx in 8 patients, and hypopharynx in 7 patients. Four patients had a tumor of the epipharynx, 3 of the larynx, and 45 had involvement of two or more compartments. Radiotherapy was performed in a fractionation of 5 x 2 Gy/week up to a dose of 50 Gy. Carboplatin was administered in a dose of 60 or 70 mg/m2 from days 1-5 and 29-33. After a 2-week interval, tumor involution was evaluated and a decision was made on the patients' operability. In cases of inoperability, radiotherapy was continued up to a dose of 70-74 Gy. Thirty patients underwent surgery after 50 Gy. Eight patients showed a histologically complete remission (CR), 7 showed microscopic residual tumor, and 15 showed macroscopic tumor. Seventy patients were treated with radiotherapy and concomitant carboplatin only. Thirty-nine of them achieved a CR and 30 a partial remission (PR). The residual tumor was operable in 8 of the latter patients. Only a minor response was achieved in the remaining patient. At the end of the treatment 77 patients achieved a CR with this combined modality. From 1990 to 1992, 20 patients with locally advanced head and neck carcinomas underwent hyperfractionated accelerated radiotherapy (2 x 1.6 Gy/day, 5 days per week: total dose, 64-67.2 Gy) and simultaneous intravenous carboplatin (60 mg/m2, days 1-5 and 29-33) in a pilot study. Fifteen patients had T4 and 5 had T3 tumors. Six weeks after the end of treatment, 16 patients (80%) had CR, and PR was seen in the other 4 patients (20%). Overall and disease-free survival at 1 year was 82 and 81%, respectively. Although acute side effects were more pronounced compared with conventional irradiation, this treatment regimen is feasible and the initial CR rate of 80% is encouraging. Because of the results achieved with hyperfractionated accelerated radiotherapy, we initiated a multicenter randomized study in November 1991. Patients with advanced head and neck carcinomas are either randomized for conventional radiotherapy with carboplatin or hyerfractionated accelerated irradiation with carboplatin. Results will be forthcoming.

Actuarial Analysis↗
PubMed1993

Data analysis in behavioral cerebral blood flow activation studies using xenon-133 clearance.

BACKGROUND AND PURPOSE: Three mainstream strategies exist to detect the responses of regional cerebral blood flow to functional activation. We tested the significance of changes in raw regional cerebral blood flow data, regional cerebral blood flow data normalized by division by global cerebral blood flow (dependent model of the regional-to-global cerebral blood flow relation), and regional cerebral blood flow data treating global cerebral blood flow as a covariate (independent model). Both latter models attempt to enhance regional sensitivity by removing global effects. We examined the sensitivity and pitfalls of these three strategies in behavioral activation studies. METHODS: These three strategies of data analysis were applied to changes in regional cerebral blood flow induced by a visuospatial problem-solving task in 38 healthy subjects as measured by the intravenous xenon-133 method with 32 stationary detectors. RESULTS: Mental activation increased blood flow in all regions of interest. Raw data were most sensitive and reliable to detect responses to mental stimulation. Both the independent and dependent models to remove global effects were less sensitive and falsely indicated deactivation in regions that were clearly stimulated. CONCLUSIONS: In behavioral activation paradigms, safe data analysis should be restricted to using raw regional cerebral blood flow increases without normalization or separation of global from regional effects. Studies using complex stimulation tasks should be scrutinized for global cerebral blood flow effects confounding regional responses.

Behavior↗
PubMed1993

[Effect of frequent ventricular extrasystole on brain circulation in patients with coronary heart disease].

Animal experiments using the microsphere method indicate a 8% reduction of mean cerebral blood flow during parasystolic rhythm induced by ventricular pacing in comparison to a control group with sinus rhythm. The parasystolic rhythm causes changes of systemic arterial blood pressure, which are comparable to the hemodynamic effects of frequent premature ventricular contractions. Because a reduction of cerebral blood flow induced by frequent premature ventricular beats can be assumed by the results of the laboratory investigations, cerebral blood flow was determined in a clinical study in 19 coronary artery disease patients and in 11 healthy, age-adjusted volunteers using the 133Xenon-inhalation method, in order to investigate the effect of ventricular ectopics on cerebral perfusion. Simultaneously Holter monitoring was performed during cerebral blood flow measurements. Cerebral blood flow was estimated by the initial slope index, which is calculated from the early decay of the clearance curve, and by the mean cerebral blood flow index, which is calculated by the stochastic method. Grey matter blood flow is estimated by the two-compartment analysis. Cerebral blood flow in coronary artery disease patients is reduced versus controls. The initial slope indices were 45.2 +/- 5.1 s-1 and 57.4 +/- 7.2(-1), respectively (p < 0.01). In patients with frequent ventricular ectopic activity (739/h) an additional reduction of cerebral blood flow was observed. The initial slope index was 42.6 +/- 6.3 s-1 (p < 0.01). The reduction of cerebral blood flow in coronary artery disease patients is partially due to the coincidence of coronary and cerebral artery disease. Frequent ventricular premature contractions might cause an additional reduction.

Adult↗
PubMed1993

Identification of Azospirillum species by RFLP and pulsed-field gel electrophoresis.

Pulsed-field gel electrophoresis (PFGE) was applied to analyse the restriction fragment length polymorphism of Azospirillum brasilense and Azospirillum lipoferum strains. Genomic DNA was digested by rarely cutting restriction enzymes and subjected to PFGE using the Rotaphor system. The restrictions with SpeI produced 10-20 fragments with sizes from about 10 kb to 900 kb. The separation resulted in a strain-specific banding pattern in almost every case. After Southern blotting and hybridization with 23S rRNA gene probes, the species could be determined. With the combination of both methods, identification of re-isolates from soil at the species and strain level is possible.

Azospirillum↗
PubMed1993

[Improved left ventricular ejection fraction directly after transluminal coronary angioplasty].

The purpose of this study was to evaluate if left ventricular ejection fraction (EF) at rest can improve already during the first 4 h after successful transluminal coronary angioplasty (PTCA). Measurements were carried out with the CardioScint LV Function Monitor Version 1.3. Comparison of ejection fraction values evaluated by the CardioScint Monitor revealed a good correlation with usual equilibrium radionuclide ventriculography (n = 28; r = 0.89). Also, intra- and interobserver variability was low (n = 26; r = 0.94 and n = 21; r = 0.92 respectively). Two hundred follow-up-measurements in eight patients over a time period of 4 h revealed a significant decrease of EF from 45 +/- 12% to 39 +/- 18% (p = 0.037) (reference group). This decrease was due to a continuous increase of background activity. The study population consisted of 14 patients with successful PTCA (dilatation from 85 +/- 7 to 34 +/- 9% linear vessel diameter). To evaluate the hemodynamic significance of the coronary lesion, left ventricular ejection fraction was registered during the balloon occlusion of the vessel. After dilatation, 25 EF measurements were carried out in each patient over the following 4 h (350 values). During PTCA, EF decreased from 52 +/- 16 to 37 +/- 9% (p = 0.0027). During the 4-h follow-up EF slightly decreased from 50 +/- 8 to 46 +/- 9% (p = 0.07).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

[Heart volume determination as an indication of rejection after orthotopic heart transplantation].

Endomyocardial biopsy in cardiac transplantation is still the most exact test (gold standard) to confirm or exclude a suspected rejection. Up to now, all available noninvasive tests suffer from a low sensitivity and specificity. For a further reduction of biopsies early available noninvasive methods are desirable. In the data presented a comparison between histological findings and heart volume measurements is shown in 40 patients (112 histological findings) after orthotopic cardiac transplantation. In 46 cases with no evidence of histological rejection the echocardiographically or radiologically determined heart volume was 869 +/- 142 ml/1.73 m2 body surface area, compared to 1026 +/- 178 ml/1.73 m2 in 29 cases with mild cardiac rejection. In 37 cases with a moderate or severe rejection heart volume as 1094 +/- 181 ml/1.73 m2. The diagnosis of a moderate or severe rejection by biopsy is combined with a heart volume above 950 ml/1.73 m2 with a sensitivity of 78% and a specificity of 73%. Intramyocardial edema as well as an increase in right and left ventricular volumes due to heart failure may be the causes for heart volume increase in rejection. Thus, heart volume measurement which can be performed easily during routine echocardiography gives additional information about whether a rejection has to be assumed or can be excluded. Today, sensitivity and specificity of the test does not allow a reduction of biopsy frequency. Further investigations are necessary to analyze the course of heart volume changes during an episode of rejection.

Biopsy↗
PubMed1993

Recanalization of chronic arterial occlusions: low-speed rotational angioplasty. 5 years experience in peripheral and coronary vessels.

Chronic complete occlusions still represent the major technical limitation of percutaneous transluminal angioplasty, both in peripheral and coronary vessels. The clinical use of low-speed rotational angioplasty started in 1986 for the peripheral and in 1987 for the coronary arteries, and has already become part of the clinical routine in several centres. Up to now more than 350 patients with peripheral and 250 patients with coronary occlusions have been treated in Frankfurt; a multicentre questionnaire already contains information about 1,252 patients with peripheral vessel obstructions. In peripheral occlusions the acute success rate was more than 80% if low speed rotational angioplasty was used as the first attempt; after failure of conventional techniques still more than 60% of the vessels could be recanalized successfully. In addition to occlusions of the arteries of the lower limb, indications now may include the iliac artery and the subclavian artery. In each of the patients with chronic coronary occlusions an attempt with conventional techniques had failed before. Following a learning curve, which was also influenced by a better understanding of morphological preconditions, the acute success has now reached 70%. Both in patients with peripheral and those with coronary occlusions the technique turned out to be a safe procedure. Early angiographically documented long-term results in both indications are comparable with conventional balloon techniques. It is concluded that the use of low-speed rotational angioplasty (ROTACS) can improve the results of non-operative invasive treatment, both in peripheral and in coronary arteries.

Angioplasty↗
PubMed1993

[Left ventricular function during symptomatic and asymptomatic myocardial ischemia].

Transluminal coronary angioplasty (PTCA) causes transient occlusion of the coronary artery and temporary ischemia of the left ventricle. Left ventricular dysfunction during silent and symptomatic episodes of myocardial ischemia during PTCA was evaluated continuously with a newly developed miniature, non-imaging scintillation probe. Parameters of left ventricular function were compared before and during balloon inflations of 60 s duration: ejection fraction (EF), indices of end-systolic and end-diastolic volumes (ESV, EDV), peak ejection and peak filling rates (PER, PFR). 13 patients (age 54 +/- 7.4 years) were symptomatic, 10 patients (age 61 +/- 8 years) were asymptomatic. Impairment of left ventricular function during ischemia did not show any significant differences between the symptomatic and asymptomatic patients. It is therefore concluded that symptomatic and asymptomatic episodes of myocardial ischemia during PTCA cause similar impairment of systolic and diastolic left ventricular function. The degree of left ventricular dysfunction during PTCA cannot be estimated on the basis of clinical symptoms.

Aged↗
PubMed1993

[Main branch stenosis after bypass operation. Indications for elective PTCA].

The unprotected left main stenosis still represents one of the contraindications of PTCA; recently developed concepts using percutaneous bypass techniques have not changed this fact so far. However, following bypass grafting the procedure can be done with low risk and may improve prognosis in case of later bypass occlusion. This study should clarify whether a higher rate of bypass occlusion is caused by postsurgical left main PTCA. From October 1981 to January 1991 a left main stenosis was dilated in 41 patients, 2 weeks to 12 years (mean 3.5 years) after bypass grafting. To date, 17/65 venous bypass grafts were already occluded, and 72.4% of the patients suffered from typical angina. In 34/41 patients (82.9%) PTCA was successful, severe complications (death, emergency surgery or myocardial infarction) did not occur and clinical improvement was achieved in 80% of symptomatic patients. Four months later, 26/34 patients (76.5%) had angiographic follow-up. Fifteen restenoses were found and a second PTCA was performed in 9/15. None of the venous bypass grafts, open at the time of the first PTCA, was occluded at follow-up. In one case PTCA of the left main stenosis turned out to be life-saving 7 years later because an occlusion of RCA- and LCX-bypasses occurred and the LAD graft showed a subtotal thrombosis. It is concluded that PTCA of left main stenosis after bypass grafting is a safe procedure and does not lead to a higher rate of venous bypass occlusions. A prognostic indication seems to be justified.

Adult↗
PubMed1992

[Reopening chronic arterial occlusions].

Chronic complete occlusions still represent the major technical limitation of percutaneous transluminal balloon angioplasty, both in peripheral and coronary vessels. The clinical use of low speed rotational angioplasty (ROTACS) started in 1986 for the peripheral and in 1987 for the coronary vessels, and has already become part of the clinical routine in several centers. Up to now, more than 300 patients with peripheral and more than 200 patients with coronary occlusions were treated in Frankfurt. In peripheral occlusions the acute success rate was more than 80% if used as the first attempt; after failure of conventional techniques still more than 60% of the vessels could be recanalized successfully. In addition to occlusions of the arteries of the lower limbs, the indication now includes the iliac artery and several other indications are under investigation. In each of the patients with chronic coronary occlusions an attempt with conventional techniques had failed before. Following a learning curve, which was also influenced by a better understanding of morphological preconditions, the acute success rate has now reached 70%. Both in patients with peripheral and those with coronary occlusions no deaths occurred. First angiographically documented long-term results in both indications are comparable to conventional balloon angioplasty. It is concluded that the use of low speed rotational angioplasty (ROTACS) can improve the results of nonoperative invasive treatment, both in peripheral and in coronary arteries.

Angiography↗
PubMed1992

[Drug therapy of hypertrophic cardiomyopathy].

INTRODUCTION: Hypertrophy of the myocardium occurring in hypertrophic cardiomyopathy (HCM) may affect different locations of the left ventricle. If the hypertrophy is sited in the region of the basal septum, obstruction of the left ventricular outflow tract (hypertrophic obstructive cardiomyopathy [HOCM]) occurs. characteristic of left ventricular function in HCM is hypercontractility and disordered diastolic relaxation. THERAPEUTIC APPROACHES: In the medical treatment of HCM, the calcium antagonists play a leading role. They improve relaxation and, through their negative inotropic effect, decrease the intraventricular gradient. Although beta-blockers reduce the gradient in outflow tract obstruction, they do not improve relaxation. In individual cases the use of diuretics and anti-arrhythmic agents may be necessary; in the case of atrial fibrillation the use of marcumar is recommended. CAUTIONARY REMARK: In the event of dental treatment or invasive diagnostic procedures being necessary, prophylactic measures against endocarditis should be initiated.

Adrenergic beta-Antagonists↗
PubMed1992

Differentiation and retrodifferentiation of human myeloid leukemia cells is associated with reversible induction of cell cycle-regulatory genes.

Treatment of human myeloid leukemia cells (HL-60, U-937, THP-1) with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) is associated with differentiation along the monocytic lineage. This induction by TPA is characterized in part by growth arrest and the appearance of differentiated monocytic phenotype. The present studies demonstrate that myeloid leukemia cells exit the cell cycle to G0-G1 between 24 and 36 h following TPA treatment. This G0-G1 arrest was accompanied by down-regulation of the cell cycle-regulatory genes cdc2, cyclin A, cyclin B, and cdc25. Similar findings were obtained for histones H1 and H4. Cell cycle progression of synchronized U-937 cells revealed low to undetectable mRNA levels for these genes in G1 and maximal transcription in G2-M phase. Results obtained from mRNA half-life studies demonstrate that the stability of cdc2, cyclin A, cyclin B, and cdc25 transcripts is similar in control and TPA-treated U-937 cells. Nuclear run-on assays demonstrated down-regulation of histone gene transcription, while there was no signal detectable for the cell cycle-regulatory genes. The present findings also demonstrate that long term culture of TPA-differentiated U-937 cells is associated with a decrease in G0-G1-arrested cells and an increase of cells in S and G2-M after 25 days. This reentry into the cell cycle was accompanied by loss of adherence, down-regulation of markers for the monocytic phenotype, and induction of the cell cycle-regulatory genes. This process of retrodifferentiation was completed after 36 days when patterns of cell cycle-regulatory and histone gene expression were identical to that in untreated U-937 cells.

Cell Cycle↗
PubMed1992

Fifteen years' experience with renal transplantation in systemic amyloidosis.

At our center 62 renal transplantations (31 living donor and 31 cadaveric donor grafts) have been performed in 58 patients with amyloid renal disease since 1974. The amyloidosis was secondary to rheumatic disease in 74% of the patients. Predialytic transplantation was performed in 28% of the patients. Mean follow-up time was 5.1 years (0.3-14.5 years). One-year actuarial patient survival was 79%, decreasing to 65% after 5 years. First graft survival was 74% at 1 year and 62% at 5 years. Patient death with a functioning graft caused 16 out of 25 graft losses. Infections caused 11 out of 18 deaths (61%), more than half of them within 3 months. Renal transplant amyloid was diagnosed in about 10% of the cases (6/62); however, only about 3% of the grafts (2/62) were lost. These long-term results encourage transplantation in amyloid renal end-stage disease.

Adolescent↗