Search PubMed⌕ Search

Biomedical subjects

G Becker

Publications and source records attributed to G Becker.

At least 127 records · Page 7Linked to original sources
PubMed1997

Rescue therapy with tacrolimus in simultaneous pancreas/kidney transplantation.

Tacrolimus has been effective both in primary and rescue therapy following steroid and OKT3-resistant acute rejection in liver and kidney transplantation. Due to the effects of tacrolimus on glucose metabolism, there has been concern about its use in simultaneous pancreas/kidney transplantation. We report on the results of six patients (three female, three male, age 35.2 +/- 7.3 years) converted from cyclosporin A to tacrolimus following simultaneous pancreas/kidney transplantation in steroid-resistant acute rejection. Tacrolimus was induced 2.8 +/- 1.7 months (range 1-4.8 months) after transplantation; follow-up was 3-18 months. Following conversion, creatinine levels declined in all patients [3.5 +/- 1.2 mg/dl before conversion, 3.0 +/- 1.9 mg/dl (n = 6) at three months, 1.4 +/- 0.1 mg/ dl at 1 year (n = 3)]. Before conversion, fasting blood glucose levels averaged 154 +/- 33 mg/dl, with three patients receiving insulin. Three months later no patient required insulin, the mean glucose level being 107 +/- 23 mg/dl (n = 6); at 1 year it was 92 +/- 9 mg/dl (n = 3). One patient lost his pancreatic graft after 4 months due to a mycotic aneurysm. We conclude that conversion to tacrolimus is a safe and effective treatment in cases of steroid-resistant rejections following pancreas/ kidney transplantation.

Administration, Oral↗
PubMed1997

Direct reaction of oximes with sarin, soman, or tabun in vitro.

The direct reaction of seven pyridinium oximes with the nerve agents sarin, soman, and tabun was followed by a spectrophotometric method. The half-lives (t1/2) of the oximes, the first- and second-order rate constants (k1, k2), and the maximal reaction velocity (vmax) were calculated according to changes in the absorbance of the zwitterion (betaine) peak. In all cases the reaction velocity of the nerve agents with any of the oximes was highest with tabun, followed by sarin and then soman. Comparing the reaction rates of three therapeutically used oximes with the same nerve agent, the highest rate was obtained for soman with obidoxime, for sarin with 2-PAM, and for tabun with HI 6. The maximal reaction velocities reveal that the detoxification of the nerve agents by direct reaction with oximes and the subsequent decomposition of the phosphonyl oxime in vivo do not substantially contribute to the therapeutic effect of these antidotes.

Antidotes↗
PubMed1997

Stigma, disclosure, and family functioning among parents of children conceived through donor insemination.

OBJECTIVE: To examine the influence of gender, male infertility factor, and other demographic variables on stigma and whether parents tell their children that they were conceived by donor insemination (DI) and to ascertain if stigma and the disclosure decision affect parental bonding with the child or the quality of the interparental relationship. DESIGN: One hundred eighty-four San Francisco Bay Area couples who had become parents by DI were asked to complete a self-administered questionnaire. SETTING: A private infertility practice. PATIENT(S): Eighty-two men and 94 women who completed the questionnaire. MAIN OUTCOME MEASURE: A questionnaire assessing disclosure, stigma, parental bonding, and the quality of the interparental relationship. RESULT(S): Factors that increased the couple's likelihood of disclosure included younger age, azoospermia, lower stigma scores, and having more than one DI child. Fathers who scored higher on stigma reported less parental warmth and parental fostering of independence. CONCLUSION(S): Because the decision regarding disclosure of DI treatment was not linked to parental bonding with the child or to the quality of the interparental relationship, we cannot conclude that nondisclosure is harmful to family relationships or is a symptom of family problems. The husband's perceptions of stigma however, may affect the father--child relationship adversely.

Adult↗
PubMed1997

Myofibroblasts and arteriolar sclerosis in human diabetic nephropathy.

We examined the biopsy specimens of 62 patients with diabetic nephropathy to establish whether the myofibroblast (MF) has a role in progressive interstitial fibrosis and to ascertain whether a relationship existed between MF activity and severity of arteriolosclerosis. MF were identified by morphology and alpha smooth muscle actin (alpha SMA) immunostaining. Analysis of vascular injury was performed by counting the number of interstitial arterioles after staining endothelial cells with von Willebrand factor (VWF) antibody. Arteriosclerosis was quantified by using a computer-aided image analyzer to measure the arteriolar wall surface and total arteriolar surface area, and the ratio of wall to total surface area was expressed as the index of arteriosclerosis (IA). Fractional area of interstitium (IFA), alpha SMA, and collagen III (Coll III) were quantitated by point counting. Results were related to structural and functional parameters using rank correlation coefficients. There was a strong correlation between IFA and Coll III staining (r = 0.83; P < 0.001). The alpha SMA staining correlated with IFA (r = 0.56; P < 0.001) and Coll III (r = 0.47; P < 0.001), and there were significant correlations between alpha SMA and total urinary protein (r = 0.47; P < 0.001), renal function (plasma creatinine) at time of biopsy (r = 0.51; P < 0.001), and the percent change in plasma creatinine after 4 years (delta Cr) (r = 0.37; P = 0.01). The IA correlated significantly with Coll III (r = 0.29; P = 0.02), glomerular filtration rate (GFR) (r = 0.39; P = 0.008), and creatinine (r = 0.33; P = 0.01), but no correlation was observed between alpha SMA and IA (r = 0.16; P = 0.23) or IA and delta Cr (r = -0.04; P = 0.6). Strong correlations could be shown between arteriolar density, IFA (r = 0.75; P < 0.001), alpha SMA (r = -0.36; P = 0.034), and Coll III (r = -0.66; P < 0.0001). The MF appears to have a significant role in the progression of diabetic nephropathy. Ischemia secondary to arteriosclerosis may contribute to interstitial fibrosis through fibroblast modulation into MF.

Adult↗
PubMed1997

[Transcranial color-coded duplex ultrasound in interventional therapy of cerebral aneurysms. A pilot study].

PURPOSE: To assess the diagnostic potential of transcranial colour-coded duplex sonography in the recognition of residual perfusion of coiled cerebral aneurysms. METHOD: 10 patients (7 female, 3 male) with angiographically verified cerebral aneurysms (basilar artery n = 2, mean size 8.5 mm; supraclinoid internal cerebral artery n = 2, mean size 15.5 mm; posterior communicating artery n = 2, mean size 7 mm; anterior communicating artery n = 2, mean size 4.5 mm) were examined by TCCD using a 2.25 MHz probe immediately following embolisation and 12-24 hours prior to angiographic evaluation. RESULTS: 9 patients had a sufficient temporal bone window. Transtemporal localization of the embolised aneurysms was feasible in 7 of the 9 cases. One partially thrombosed aneurysm of the basilar artery (1 mm) and one completely thrombosed aneurysm of the anterior communicating artery could not be visualised. In 7 cases no discrepancies between TCCD and angiography were evident, since rest, perfusion (n = 6) and complete thrombosis were unanimously diagnosed as such. Mean size of the rest perfused lumina was 4.4 mm (minimum 1.5 mm; maximum 8 mm). Platinum coils appeared as hyperechogenic lesions with an echogenicity comparable to the skull. CONCLUSION: With TCCD residual perfusion of coiled aneurysms was feasible in most cases. The method seems to be specific but not sensitive in the detection of incompletely coiled aneurysms. Limitations are insufficient transtemporal bone windows and inaccessible aneurysm location, especially the anterior communicating artery.

Adult↗
PubMed1997

Five years of stereotactic radiosurgery at the University of Tübingen--a critical review of the method.

At the University of Tübingen a Linac based stereotactic system for radiosurgery has been used since 1991. The floorstand system (SRS 200, Phillips) developed at Gainsville is used in combination with a Cosman Roberts Weels system by Radionics. The floorstand enables the gantry to be rotated vertically and the table to be rotated in the horizontal plane. Additionally, patient's movements are reduced by the fixation of the stereotactic ring to the stereotactic floorstand. We report our experience with the first 50 patients treated between December 1991 and June 1995. The patients were treated with an interdisciplinary approach. This cooperation eases the transition from radiosurgery to other methods such as embolization, operation, and other radiooncologic treatment options.

Adult↗
PubMed1997

Transport of propionate across the distal colonic epithelium of guinea pig in the presence and absence of bicarbonate and of chloride.

Short-chain fatty acids (SCFA) are rapidly absorbed in the large intestine. However, the mechanisms involved have not been fully delineated. Findings indicate that absorption of SCFA occurs in the undissociated form as well as by an anion exchange, whereby marked species and segmental differences are present. The guinea pig distal colon has certain peculiarities. Unidirectional fluxes of propionate across guinea pig distal colon were studied under short-circuit current conditions in Ussing chambers. Removal of bicarbonate caused reduction of mucosal-to-serosal fluxes by 30%, serosal-to-mucosal fluxes were little affected. In chloride-free solution unidirectional fluxes were also reduced. However, in the presence of transepithelial chloride-gradients with the Cl(-)-free solution only at the luminal side, no such effects were seen. Findings support the presence of SCFA(-)-HCO3- exchange in guinea pig distal colon. Chloride seems not of major importance for SCFA transport.

Animals↗
PubMed1997

Parkinson's disease and depression: evidence for an alteration of the basal limbic system detected by transcranial sonography.

OBJECTIVES: Depression is a frequent symptom in Parkinson's disease. Compelling evidence suggests a role of the brainstem in the control of mood and cognition. In patients with unipolar depression transcranial sonography (TS) studies have shown structural alteration of the mesencephalic brainstem raphe which could suggest an involvement of the basal limbic system in the pathogenesis of primary mood disorders. The objective of the present study was to evaluate whether a similar alteration could be found in depressed patients with Parkinson's disease using TS. METHODS: Thirty patients with Parkinson's disease and 30 age and sex adjusted controls were examined by TS. Raphe echogenicity was rated semiquantitatively. The severity of motor symptoms and depression was rated using standard research instruments. RESULTS: Raphe echogenicity was significantly reduced in depressed patients with Parkinson's disease compared with nondepressed patients with Parkinson's disease and control subjects. Raphe echogenicity correlated negatively with degree of motor impairment, and differences in raphe echo between depressed and non-depressed patients with Parkinson's disease were upheld when motor impairment was controlled for. CONCLUSION: These preliminary findings suggest that, as in unipolar depression, a morphological alteration of the brainstem raphe might be involved in the pathogenesis of depression in Parkinson's disease. This raphe alteration may reflect involvement in the basal limbic system in the pathogenesis of secondary depression. This concept is in line with current knowledge on the pathogenesis of both depression in Parkinson's disease and primary depressive disorders.

Aged↗
PubMed1997

Clinical, morphological, biochemical, and neuroradiological features of mitochondrial encephalomyopathies. Presentation of 19 patients.

Nineteen patients (9 females, 10 males) with mitochondrial encephalomyopathies (ME) were studied. The diagnosis was established according to clinical and histopathological criteria. Leading clinical features were chronic progressive external ophthalmoplegia (CPEO) and muscle weakness in 95% of the patients. Pigmentary retinopathy was seen in 63%, and was always associated with CPEO. Hypacusis was present in 47% and cerebellar ataxia in 63% of patients. Clinical or electrophysiological signs of involvement of the central nervous system (CNS) were found in 21% of the patients. In muscle biopsy ragged red fibers were the predominant histopathological findings (100% of the patients), while COX-negative fibers were seen in 74%, deletions of the mitochondrial DNA in 42%, and defects of the respiratory chain in 32% of the patients. Increased blood lactate levels were found in 79% of the patients. Needle electromyography revealed myopathic features in 74%, features of denervation in 16%, and was normal in the remainder. Imaging studies showed cerebral atrophy in 58%, cerebellar atrophy in 16%, and hyperintense lesions of the white matter, pyramidal tract or extrapyramidal system in 16% of the cases. It is concluded that the clinical manifestations of ME can be very variable. Diagnosis of ME should be always considered in young patients presenting with CPEO and muscle weakness. In most cases, diagnosis can be made by a few selected investigations, while detection of genetic abnormalities may lead to the diagnosis in the remaining cases.

Adult↗
PubMed1997

[Event related potentials and emotional pictures:effect of stimulus presentation time].

The perception of the emotional content of a stimulus is a preattentive automatic process which causes an emotional reaction. As the ongoing stream of behavior might be disturbed by the emotional reaction, a controlled process is initialited at the same time, which normally leads to an inhibition of the emotional response. By means of event related potentials it should be possible to observe these controlled processes. In a first study using photographs from the International Affective Picture System, Diedrich et al. (1997) reported enhanded P300 amplitudes for emotional stimuli, even when the task distracted from the emotional content of the stimuli. This was interpreted as an index of the additional, controlled information processing elicited by the emotional content of the stimuli. Additionally, Diedrich et al. observed a frontel slow positivity, which might indicate the inhibition of the emotional response. However, this frontal slow wave might also be explained by the stimulus presentation time, which lasted 500 ms. This study is a conceptual replication of the experiment of Diedrich et al. Stimulus presentation time of neutral and emotional slides was varied in three steps (250 ms, 500 ms and 2000 ms). Subjects either performed a structural or an emotion-focused task on the stimuli. The results for the P300 component were exactly replicated. However, the variation of slow frontal positivity differed from that in the first study. Differences in the intensity of the emotional stimuli are discussed as a reason für this result.

Adult↗
PubMed1997

Transcranial duplex ultrasound: experience with contrast enhancing agents.

Transcranial duplex real time sonography (TCCS) is a non-invasive imaging modality that allows repetitive examinations of central nervous system vascular and parenchymal anatomy; a broad spectrum of cerebral pathology may be disclosed: vascular changes include ischemic and hemorrhagic stroke, arteriosclerotic vascular degeneration, arteno-venous malformations and aneurysms, as well as neoplastic and degenerative parenchymal disorders. Imaging was performed with a duplex ultrasound system, employing a 2.25 resp. 2.0 MHz phased-array transducer. Imaging was achieved through the acoustic bone window of the temporal bone and through the foramen magnum. For three-dimensional image reconstruction a mechanical position sensor and online video grabbing was applied. To evaluate the potential of a transpulmonary stable ultrasound contrast enhancing agent we used galactose-based SH U 508 A (Levovist, Schering, Berlin) with 1 to 6 i.v. injections per patient in a phase 2/3 clinical protocol. The signal to noise ratio is significantly improved; the Doppler signal intensity is increased by approx. 25 dB. Levovist was well tolerated and no adverse events occurred, approx. 30% of patients had a sensation of heat and slight pain at the injection site during and shortly after the injection. With the increase in signal intensity, the complete circle of Willis, the peripheral arterial branches, the vertebro-basilar system and the basal venous system may be depicted. In addition, tumour parenchyma vascularisation may be detected, as well as improved delineation of arteriovenous malformations and aneurysms. Three dimensional image reconstruction may represent a novel option in contrast enhanced transcranial duplex imaging including additional information about 3D structure and continuity.

Adolescent↗
PubMed1996

Primary T-cell lymphoma of the cerebellum. A case report.

Most primary CNS non-Hodgkin lymphomas are of B-cell lineage. Only a very few immunocytochemically well documented cases of T-cell lymphomas have been reported. We report a case of a high malignant T-cell lymphoma localized primarily to the vermis of the cerebellum and compare the characteristics of the clinicopathological presentation with those of B-cell lymphomas as well as with the other T-cell lymphomas reported.

Aged↗
PubMed1996

Correlation of intra-operative ultrasound with histopathologic findings after tumour resection in supratentorial gliomas. A method to improve gross total tumour resection.

The aim of this study was to evaluate whether intra-operative ultrasound (= IOUS) is a suitable tool to detect residual tumour tissue after gross total resection in supratentorial gliomas. During a period of 18 months 45 patients with supratentorial gliomas (38 high-grade and 9 low-grade, according to the WHO-grading system [42]) were operated on. A series of 78 biopsies was taken from the resection cavity under continuous sonographic control at the end of surgery. Gross total tumour resection was intended in 34 patients (= 76%). The biopsy specimens were matched with the sonographic features at each biopsy site. The sonographic appearance of the resection margins were classified into 2 groups: (1) Irregular hyperechoic areas extending from the cavity into the iso-echogenic brain tissue and (2) a dense small (< or = 3 mm in diameter) rather regular hyperechoic rim surrounding the resection cavity. 47 out of 53 biopsies taken from hyperechoic areas (group I) (36 high-grade/11 low-grade) revealed solid tumour tissue (= 89%). 34 (= 72%) of these 47 areas were microscopically assessed as inconspicuous by the surgeon. 6 samples (4 high-grade/2 low-grade) contained tumour infiltration zone. 25 biopsies (23 high-grade/2 low-grade) taken from the hyperechoic rim [group 2] were diagnosed as follows: Normal brain tissue in 11, tumour infiltration zone in 8 and solid tumour tissue in 6 cases. Of 34 cases with "gross total removal" according to the surgeon's assessment 25 showed sonographic signs of residual tumour tissue, which was confirmed histologically as solid tumour tissue in 22 of these cases. It is concluded, that IOUS following resection of supratentorial gliomas can detect residual tumour tissue with high specificity and thus improve gross total resection. However, a thin hyperechoic rim surrounding the resection cavity (less than 3 mm in diameter) is a non-specific finding, which can mask thin residual tumour layers and therefore needs further evaluation of its nature.

Biopsy↗
PubMed1996

[Gamma knife versus stereotactic linear accelerator. Utilization, clinical results and cost-benefit relations].

INTRODUCTION: The principles of radiosurgery were developed in 1951 by Leksell. Their technical realization led to the development of the gamma knife and stereotactically modified linear accelerator. METHODS: In addition to the gamma knife, we present the different principles of convergent beam irradiation (radiosurgery with linear accelerator), the further development to fractionated stereotactic conformal radiotherapy, and the necessary quality-assurance steps. RESULTS: The greatest uncertainties in the precision of radiosurgery result from medical imaging (CT 0.7 x 0.7 x 1 mm; DSA 1-5 mm; MR angiography < 2 mm). The focusing accuracy of the gamma knife (+/- 0.3 mm) can also be achieved today by linear accelerators using a stereotactic floorstand. For the same indication and the same dosage for the target volume, there are no clinical differences between the gamma knife and the linear accelerator (AVM: 80% complete obliteration; metastases: 85% local tumor control; AN: 90% tumor control). However, there are greater differences in costs. There is no constellation where the gamma knife is just as expensive or more cost-effective than the linear accelerator treatment. The most cost-effective solution is modification of an available linear accelerator, resulting in treatment costs per patient of 9,201.25 DM (50 patients/year). CONCLUSION: There seem to be no methodological, physical, clinical or cost reasons for using a gamma knife, especially because the trend is going towards fractionated conformation radiotherapy instead of the application of high single doses.

Brain Neoplasms↗
PubMed1996

Treatment planning for bicentric stereotactic irradiation.

We have investigated a bicentric stereotactic convergent beam irradiation technique for the treatment of irregularly shaped, especially elongated, target volumes. Depending on the size and shape of the target volume optimum values for the isocenter distance, collimator apertures and dose inhomogeneity have been determined which serve as starting parameters for the interactive optimization of dose distribution. The treatment planning system of the stereotactic unit SRS-200 (Philips) has been used to calculate the parameter tables. However, the presented results are also applicable to other stereotactic systems.

Film Dosimetry↗