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Biomedical subjects

F Ebner

Publications and source records attributed to F Ebner.

At least 55 records · Page 3Linked to original sources
PubMed1992

Interstitial 1.06 Nd:YAG laser thermotherapy for brain tumors under real-time monitoring of MRI: experimental study and phase I clinical trial.

This paper presents the experimental and clinical results of interstitial 1.06 Nd:YAG laser thermotherapy (ILTT) for brain tumors under real-time monitoring by magnetic resonance imaging. The authors chose a laser heat source for interstitial thermotherapy of brain tumors for several important reasons: (1) Laser heat delivery is less complicated and more controlled; (2) laser effects on tissue can be tested, monitored, and controlled by MRI. A 1.064 nm Nd:YAG laser and a specially designed laser optic fiber (ILTT) were used in C.W. mode this study. The laser was used at 4 W at a C.W. mode pulse and total exposure duration was 10 minutes (total energy was 2400 joules). Temperature distribution was determined with a microprocessor-based thermometer and by the levels of the signal intensity under MRI. The relationship between the temperature and MRI signal intensity allowed exploration of the possibility of using MRI as a noninvasive temperature monitoring method. Two patients with glioblastoma and one patient with a brain metastasis were treated with this modality. The results and indications are presented and discussed.

Brain Neoplasms↗
PubMed1992

Cervical cancer: serial MR imaging before and after primary radiation therapy--a 2-year follow-up study.

Serial magnetic resonance imaging studies were performed in 28 patients undergoing primary radiation therapy for invasive cervical cancer. T2-weighted spin-echo pulse sequences with long repetition times (2,500 msec) and echo times (30-100 msec) were used at a field strength of 1.5 T. Eighteen tumors responded promptly to radiation therapy with a volume reduction and significant decrease of signal intensity in the early posttreatment phase (1-3 months) and with total tumor regression at 1-6 months (immediate responders). At 6 months seven tumors were visible as residual tumors with declining signal intensity; all seven of these tumors had resolved at 9 months (delayed responders). Thus, a delayed response with residual tumor at 6 months was still compatible with subsequent clinical cure. The tumors showed progression and no marked change in signal intensity (nonresponders). Primary tumors with a volume of more than 50 cm3 were more likely to have no or delayed response. An early (2-3 months) and significant decrease in the signal intensity and volume of a tumor indicates a favorable response. Large primary tumors may show a delayed response.

Adenocarcinoma↗
PubMed1992

Diagnostic problems in nodular regenerative hyperplasia (nodular transformation) of the liver. Review of the literature and report of two cases.

Nodular regenerative hyperplasia (NRH) is a rare lesion of the liver associated with portal hypertension in more than half of patients. We present two cases demonstrating complications and diagnostic problems of NRH and review the pathogenesis, clinical, radiologic, and pathologic features of 240 cases in the literature. Patient 1 died from variceal bleeding as a complication of NRH. Patient 2 presented with ascites. Sonographic, computed-tomographic and magnetic resonance findings did not differ from liver cirrhosis. Three needle biopsies showed nonspecific reactive hepatitis. Wedge liver biopsy provided the correct diagnosis of NRH and a shunt operation was performed. Non-Hodgkin's lymphoma (centroblastic type) was diagnosed three years after NRH. At present there is no clinical or radiologic evidence of progression of NRH in this patient. The diagnosis of NRH cannot be made without histologic examination. Correct diagnosis is difficult in percutaneous needle biopsy. Therefore, laparoscopically guided liver biopsy or wedge biopsy is often necessary for diagnosis. NRH should be included in the differential diagnosis of portal hypertension. Portal diversion can be considered.

Biopsy↗
PubMed1991

The association with receptors regulates the Na+,K(+)-ATPase inhibitory potency of some cardioactive steroids.

The onset of inhibition of Na+,K(+)-ATPase from guinea-pig myocardium was quantified with pseudo-first-order rate constants in a series of 14 cardioactive steroids. From these data the association and dissociation rate constants of the steroid-receptor complex were calculated. It was then found that the association of the steroids with receptors but not the dissociation of the steroid-receptor complex determined the largely different inhibitory potencies. Consistent with this finding, at equieffective steroid concentrations the rates of inhibition varied only slightly. The correlation of the association rate with the hydrophobicity of the compounds suggests that hydrophobic interactions facilitate the access of the steroid to the receptor. A conformational transition of the vicinity of the receptor subsequent to the formation of the steroid-receptor complex seems to alter the hydrophobic properties of the receptor environment to make the dissociation rate independent from hydrophobicity.

Animals↗
PubMed1991

Mitochondrial encephalomyopathy--two years follow-up by MRI.

A case of mitochondrial encephalomyopathy (MEM) followed-up by MRI for 2 1/2 y is presented. MRI showed gross, diffusely distributed white matter lesions in both hemispheres predominantly in frontal, parietal, temporal and occipital locations a marked ventriculomegaly indicative of cerebral atrophy. Except a slight increase of the cerebral atrophy there were no changes in the follow-up examinations. There are no specific MRI findings in MEM, the diagnosis is established by the synopsis of MRI, laboratory data and muscle biopsy.

Atrophy↗
PubMed1991

The control of the contraction of myocytes from guinea-pig heart by the resting membrane potential.

1. The influence of different holding potentials (-120 to -70 mV) on the contraction of enzymatically dispersed myocytes from guinea-pig hearts was evaluated. Contractions were elicited by repetitive depolarizations to 0 mV at 0.5 Hz. 2. While ineffective at 140 and 5 mmol l-1 [Na+]o and pipette Na+, respectively, depolarization of the resting membrane with the holding potential increased myocyte shortening at reduced Na+ gradients ([Na+]o 70 or [Na+]i 10-15 mmol l-1). Elevated intracellular Na+ after Na(+)-pump inhibition with ouabain 1-10 mumol l-1 was similarly effective with regard to the inotropic response to different holding potentials. 3. At -70 mV holding potential, reduction of [Na+]o from 140 to 70 mmol l-1 increased myocyte shortening and induced an inwardly directed component of the holding current which peaked at -44 +/- 10 pA and declined thereafter in parallel with the inotropic effect. The relation of this inward current to [Ca2+]i was confirmed by experiments at high Ca2+ buffer capacity where [Na+]o reduction induced a Ni(2+)-insensitive, outwardly directed component (36 +/- 15 pA) of the holding current. The observed inward current is suggested to reflect the extrusion of [Ca2+]i in exchange for [Na+]o as a counter-regulatory mechanism which limits the increase of [Ca2+]i. 4. The interventions which increased the strength of the contraction also enhanced the transient tail current after repolarization, suggesting its close relation to [Ca2+]i. This finding confirmed the pattern found with cell shortening. 5. It is concluded that under certain conditions, voltage-dependent and Na(+)-dependent Na(+)-Ca2+ exchange during the interval between the contractions is relevant to the diastolic concentration of [Ca2+]i which in turn determines the accumulation of Ca2+ in the sarcoplasmic reticulum and the magnitude of the subsequent contraction.

Animals↗
PubMed1991

Myocardial infarction. Secondary prevention with nifedipine.

The rationale for the use of nifedipine in patients with acute myocardial infarction (MI) is based on the various cardiovascular actions of the compound: reduction of myocardial oxygen consumption by attenuation of cardiac and vascular smooth muscle tension; augmentation of oxygen and substrate supply after increased coronary blood flow with dilatation of epicardial coronary arteries (particularly in coronary obstructions) and dilatation of coronary resistance and collateral vessels; myocardial 'protection', i.e. reduction of myocardial damage via a complex intracellular mechanism, the primary outcome of which is the maintenance of an energy level sufficient to preserve the ionic homeostasis of the myocyte. The effect of nifedipine on reinfarction and mortality rates was evaluated in 6 well designed studies involving 8670 patients with evolving or established acute MI. Compared with placebo, short term therapy (for up to 6 months) with nifedipine 30 to 120 mg/day initiated, in some patients, as early as 3 hours after the onset of symptoms did not reduce either reinfarction rate or mortality. In one study (SPRINT I) [Israeli Sprint Study Group 1988], where a regimen of nifedipine 30 mg/day was only started 7 to 21 days after infarction, the exceptionally low mortality rate (5.7%) over 10 months in the placebo group precluded the demonstration of a beneficial effect of nifedipine. These results collectively suggest that nifedipine does not prevent the 'secondary' coronary events of plaque rupture and thrombus formation associated with MI and sudden cardiac death. However, the suppression of early lesions by nifedipine (as demonstrated in the INTACT study [Lichtlen et al. 1990]) might reduce 'primary' progression and improve the long term survival after MI.

Female↗
PubMed1991

[Value of magnetic resonance tomography after primary irradiation of carcinoma of the cervix uteri: evaluation of therapeutic success and follow-up].

This study investigates the reliability of magnet resonance imaging in the evaluation of response to therapy and in follow-up after primary irradiation (RTX) of uterine cervical carcinomas in 25 patients (follow-up eleven to 39 months). Most of the tumors showed six months after RTX a significant reduction of volume and signal intensity in T2 weighted images. 20/25 (80%) showed a total tumor regression, 5/25 (20%) had a residual tumor (all of them had a primary tumor volume higher than 50 ccm). Four patients got a recurrent tumor in follow-up. Residual and recurrent tumors showed like the primary in heavily T2 weighted images significant higher signal intensity than fibrosis. Therefore posttreatment fibrosis is distinguishable from residual or recurrent neoplasm. Early radiation fibrosis (less than 6 months after RTX) showed higher signal intensity than fibrosis in later stages. This fact may be the cause of false positive results in searching for residual tumor within the first six months after RTX. Our results indicate that magnet resonance imaging is a reliable method to evaluate tumor response after radiation treatment and to detect recurrent neoplasm. The results of a greater patient population over a longer period of follow-up will be presented in future.

Adenocarcinoma↗
PubMed1990

[Craniocervical amyloid tumor with destructive spondyloarthropathy and myelocompression as a rare complication of long-term dialysis].

Dialysis-associated amyloidosis has become a frequent and sometimes disabling complication in long-term dialysis patients. The main protein implicated in amyloidosis is beta 2 microglobulin, which accumulates in patients with renal insufficiency. We report on a 47-year-old patient, who was on haemodialysis treatment for 17 years. After a period of 15 years on dialysis treatment he underwent surgery for a carpal tunnel syndrome. Two years later he developed destructive spondyloarthropathy of the cervical region and destruction of the occipital bone. He lost stability of his neck necessitating his remaining mainly in the lying position. Since the type of dialysis membrane may play an important role in the pathogenesis of dialysis-associated amyloidosis, a dialysator with a polysulfone membrane, which is assume to have a beneficial effect on the progression of amyloidosis, was established.

Amyloidosis↗
PubMed1990

Intraoperative plus external beam irradiation in nonresectable lung cancer: assessment of local response and therapy-related side effects.

Since 1987, 24 patients with inoperable non-small-cell lung cancer (NSCLC), stage T1-3 N0-2 M0, have undergone lymph node dissection and intraoperative radiation therapy (IORT) to the primary with 10-20 Gy. Patient selection criteria were nonresectability based on severe cardiorespiratory impairment, no radiological evidence of distant metastases and a Karnofsky performance status of greater than 80. In 18 patients the IORT procedure was followed by an external beam radiation series (EBR) including the tumor with 46 Gy and the regional lymph nodes with 46/56 Gy. The tumor response was assessed by CAT-scan volumetry before the institution of IORT, 4 weeks later, before the onset of EBR, 8 weeks after the combined treatment course and on a 3 months basis thereafter. Prospectively, MRI of the thorax with/without Gadolinium-DTPA was performed to examine contrast enhancement and signal behavior of the tumor, in an attempt to differentiate residual disease compared to therapy-related collateral damage. So far, 18 patients have completed the combined treatment course with a median follow-up of 11 months (range 4.5 to 25 months). The overall local response rate (CR and PR) was 88.2%. In detail, 11 complete responses, 6 partial responses and one minimal response were observed. The overall and recurrence-free survival at 25 months was 49.6% and 83.3%, respectively.

Aged↗
PubMed1990

Intraoperative radiation therapy combined with external irradiation in nonresectable non-small-cell lung cancer: preliminary report.

Twenty-one patients with nonresectable non-small-cell lung cancer (15 squamous-cell, 4 adeno, 2 large-cell; T1-T3, N0-N2, all M0) underwent lymph node dissection and intraoperative irradiation of the tumor (IORT) with doses between 10 and 20 Gy (energies: 7 to 20 MeV electron beam). Postoperatively, 46-56 Gy external beam irradiation (8 or 23 MeV photon beam) were delivered to the mediastinum and 46 Gy to the tumor bearing area. Fifteen patients were available for follow-up investigations. The CT-scan tumor volumetry 4 weeks postoperatively showed a significant overall decrease (Wilcoxon test: p less than 0.05) with eight minor responses (MR) (tumor regressions between 4 and 45%) and six partial responses (PR) (between 50 and 84%). One case was not evaluable. A second volumetry after external irradiation was done in 14 patients, 18 weeks after IORT, showing 3 complete responses, 10 partial responses (62 to 84%), and 1 minor response (28%). The recent volumetries (10 patients) between 4.5 and 16.5 months after IORT showed 7 complete responses and 3 partial responses (63 to 94%). One patient died from intrabronchial hemorrhage at 7 weeks. Three others died from unrelated causes, 6, 12 and 14 months, respectively, after IORT and in one further case the cause of death at 15 months was local tumor regrowth. Within the median time elapsed since IORT (12 months) only this one case of local regrowth and one further case of distant spread were observed.

Aged↗
PubMed1990

Intraoperative radiation with external irradiation: an alternative for nonresectable non-small-cell lung cancer?

In 15 patients with nonresectable non-small-cell lung carcinoma (NSCLC) (10 squamous, 1 large cell, 4 adenocarcinomas; T1-T3, N0-N2, all M0), lymph node dissection and intraoperative irradiation of the tumour (IORT) with doses between 10 and 20 Gy (11-20 MeV electron beam) was performed. Four weeks postoperatively 46-56 Gy external irradiation (8 or 23 MeV photons) was delivered to the mediastinum and 46 Gy to the tumour-bearing area. Four weeks postoperatively, 8 minor responses (MR, tumour regression between 4% and 45%) and 6 partial responses (PR, 50%-84%) were found. In 1 case, CT was inconclusive. Eighteen weeks after IORT, volumetry showed 3 CR, 9 PR (62% to 94%) and 1 28% MR. One patient died from intrabronchial hemorrhage 7 weeks after IORT (50% PR). Two others (both CR) died from unrelated causes, 6 and 12 months, respectively, after IORT. One patient (62% PR) died after 14 months from an unknown cause. Another patient died at 15 months from local relapse after CR. The latest CT volume assessment between 7.5 and 21.5 months, respectively, yielded 8 CR, and 1 63% PR. One further case of local CR has developed contralateral pulmonary metastasis after 10 months. All these patients are alive and well. The median time elapsed since IORT is 12.5 months, 10 patients have survived more than 12 months.

Aged↗
PubMed1990

[Staging of cervix cancer using MRT].

In a prospective study the results of FIGO staging and MR staging in uterine cervical carcinoma were compared with the findings of stepwise serial examination of en-bloc-resected specimens in 28 patients. Overall accuracy of MR staging was 59% compared to 41% in FIGO staging. Sensitivity in assessing parametrial tumour extension was 85% in MRI and 64% in clinical examination. Specificity was 74% in MRI and 69% in physical examination. Accuracy in parametrial tumour extension was 67 per cent in FIGO-Classification and 80 per cent in MRI.

Adult↗
PubMed1990

Multiple sclerosis in childhood: contribution of serial MRI to earlier diagnosis.

The authors report six children (five girls, one boy) aged 11 to 13 years, of whom four had clinically definite multiple sclerosis (MS) and two had laboratory-supported definite MS. All had brain white matter abnormalities indicative of MS. In three cases, positive findings on the first MRI contributed significantly to their early diagnosis. Follow-up MRI studies over an average period of five months detected morphological changes in three of the children, although there was no concomitant clinical evidence. This raises the question of whether changes in clinically 'silent' lesions on follow-up MRI are antecedents of the essential MS criterion of dissemination over time, which could lead to earlier diagnosis of childhood MS. With cranial computerized tomography (CT) during the first clinical attack, a large focus with a lamellar structure mimicked a brain tumour in two patients. As CT also misses additional small lesions, it should no longer be used as the primary diagnostic method.

Adolescent↗
PubMed1990

Factors influencing the onset of ouabain inhibition of Na,K-ATPase from guinea-pig myocardium.

1. The onset of ouabain inhibition was quantified by analysis with an integrated rate equation from experiments in which the activity of Na,K-ATPase from guinea-pig myocardium had been altered with adenosine 5'-triphosphate (ATP, 0.3-9 mmoll-1) in the absence and presence of a detergent. 2. Under control conditions with increasing ouabain (0.1-100 mumoll-1) and ATP (0.3-1 mmoll-1) concentrations, inhibition developed faster. The acceleration by ouabain became less effective at saturating concentrations leading to a non-linear relationship between pseudo-first-order rate constants of inhibition and ouabain concentration. With a rise of ATP to 3 and 9 mmoll-1, i.e., near total Mg concentration (5 mmoll-1), inhibition was retarded presumably because the free concentrations of Mg and uncomplexed ATP changed. Varying the ATP concentration had little effect on ouabain potency at steady state; Hill coefficients were less than 1. 3. The detergent alamethicin (23 micrograms ml-1) neither interfered with Na,K-ATPase activity nor with inhibition at steady state but accelerated its onset. This supports a role for a lipid barrier in the development of inhibition. 4. While the reaction of low concentrations of ouabain with the receptors seemed to govern inhibition rate, with an increase in steroid concentration in the presence of alamethicin, ATP-dependent enzyme activity interfered with the onset of inhibition. The transition of the enzyme between ouabain-sensitive and ATP-hydrolytic conformations consequently causes the non-linear concentration-dependence of pseudo-first-order rate constants. As the Hill coefficient was less than 1, a reaction of ouabain with two receptors also could have contributed to the special concentration-dependence of inhibition rates.

Adenosine Triphosphate↗