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Biomedical subjects

D Schmidt

Publications and source records attributed to D Schmidt.

At least 415 records · Page 23Linked to original sources
PubMed1989

[Experimental determination of weighting functions in magnetic resonance tomography].

Weighting functions are defined and calculated for the pulse sequences spin-echo and inversion recovery. These weighting functions make possible a qualitative discussion of the term "weighting" in MR imaging. Furthermore, a new method has been developed to determine weighting functions experimentally. A comparison between the results obtained and the theoretical predictions shows a sufficiently good agreement. This method can also be applied with other pulse sequences.

Humans↗
PubMed1989

[New aspects of nephroblastoma (Wilms tumor) and other metanephrogenic neoplasms].

We differentiate (continuing the scheme of the National Wilms' Tumor Study) three groups of Wilms' tumors (WT), which for practical reasons also encompass WT variants: 1. a group of low-grade malignant tumors comprising 9.3% of cases (congenital mesoblasticnephroma; cystic, partially differentiated nephroblastoma); 2. the main group of tumors with histologically standard malignancy and constituting 77.7% of cases, against which a combined therapy is used depending upon age and stage of spread; and 3. a small group of tumors of high-grade malignancy (anaplastic WT, clear cell sarcoma of the kidney; malignant rhabdoid tumor of the kidney). This latter group constitutes only 13% of cases but is responsible for a high percentage of total deaths due to WT. To the tumor group with standard malignancy belong the classic triphasic WT (without anaplasia) as well as WT "with quantitative deviations", in which either the blastemic, the epithelial, or the stroma component dominates. In the differential diagnosis the relatively frequent blastemic WT must be differentiated from other so-called small, round, and blue cell tumors of childhood, especially the undifferentiated neuroblastomas. Pseudo-rosettes and cytokeratin expression are signs of an "early" epithelial differentiation. Anaplastic WT (comprising 6.1% of our cases) are diagnosed according to the criteria of BECKWITH and PALMER (1978). They are aneuploid tumors and occur predominantly in children over two years of age. By contrast, the histogenetic still undefined clear cell sarcomas and malignant rhabdoid tumors of the kidney occur chiefly in children under two. Both tumors are diploid, notwithstanding their high-grade malignancy. Clear cell sarcoma, which contains a high content of vessels and comprises 3.7% of our cases, consists of cells with weakly stained and partially vacuolized cytoplasm. In contrast to normal WT, clear cell sarcoma often progresses to bone metastases. Malignant rhabdoid tumor (2.7% of our cases) possesses cells with large, roundish nuclei, pale chromatin, very prominent nucleoli and characteristic spherical intermediate filament condensations. Cross striation and myoglobin are never present. Malignant rhabdoid tumor is not a genuine kidney tumor; it may also occur extrarenally. Low-grade congenital mesoblastic nephroma is a spindel cell tumor often exhibiting high cellularity and characterized by fingerlike projections extending into the adjacent kidney tissue. Nephroblastomatosis, with preferential perilobular localization, is a potential WT precursor found in 25% to 40% of all nephrectomy specimens containing WT and in all cases of bilateral and multifocal WT. Nevertheless, only a small proportion of the usually very small "nephrogenic remnants" lead by way of an adenomatous proliferation to manifestation of WT.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenocarcinoma↗
PubMed1989

[Nephroblastomas (Wilms' tumors) and special variations of nephroblastomas].

The results of the National Wilms' Tumor Study (NWTS) enabled the subdivision of nephroblastomas into subtypes with "favorable and unfavorable histology". Nephroblastomas with "unfavorable histology" could be discriminated by identifying those tumors not responding to therapeutic regimes proven successful for most cases with "favorable histology". A major disadvantage of the NWTS classification has been the exclusion of cytodifferentiated nephroblastoma variants, which, in contrast to typical nephroblastomas, can be cured by complete nephrectomy with wide excision of perinephric soft tissue. In the current study all types of nephroblastoma and nephroblastoma variants were included to encompass the whole morphological spectrum which these tumors may assume. This unselected material is necessary to define the relation between morphology and prognosis and to compare the treatment results of various clinical trials. Three hundred and four cases of nephroblastoma and related neoplasms on file at the Pediatric Tumor Registry, Kiel, were investigated by conventional light microscopy, electron microscopy, immunohistochemistry and DNA-flow cytometry. Of the "typical" nephroblastomas 50% occurred in the left kidney, 45% in the right kidney, and 5% were bilateral. Five cases were located in extrarenal sites. There were 121 males and 114 females. The peak incidence was noted in the third year of life. Of 135 patients 111 are alive and well, nine are living with disease, and 10 patients have died of disease. The blastemal predominant and stromal predominant types in our study were more frequent than in the NWTS. By contrast, the mixed and epithelial predominant types were more frequent in the NWTS. Patients with nephroblastomas of mixed or blastemal predominant type were older than those with epithelial predominant or stromal predominant type. Electron microscopy showed that nephroblastoma is derived from metanephric blastema. Blastemal cells are capable of differentiating into tubular epithelial cells and stromal cells. Undifferentiated blastemal cells contain exclusively vimentin intermediate filaments, better differentiated blastemal cells vimentin and cytokeratin, and stromal cells exclusively vimentin. Preoperative radio- and/or chemotherapy led to a marked reduction of undifferentiated blastema and poorly differentiated tubules, whereas better differentiated tubules, striated muscle, hyaline cartilage, cells with anaplastic and sarcomatous elements were not affected. Thus, identification of highly malignant nephroblastomas with anaplasia and sarcomatous renal tumors was even possible after preoperative treatment. Congenital mesoblastic nephroma (CMN; n = 17) is a low-grade malignant, cytodifferentiated nephroblastoma which very rarely occurs beyond the fourth month of life and has an excellent prognosis, provided it has been completely resected.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1989

Immunodetection of cathepsin D in neuritic plaques found in brains of patients with dementia of Alzheimer type.

The aspartic endopeptidase cathepsin D was immunolocalized in 21 human cadaver brains from patients with dementia and controls. Immunoreactive cathepsin D was found to be present in multiple neurons, neuritic plaques, some macroglial cells, and microvessels. It is suggested that the enzyme might be involved in certain posttranslational changes of cystoskeletal compounds that lead to the formation and/or further growth of neuritic plaques and neurofibrillary tangles.

Aged↗
PubMed1989

[Clinical relevance of calcium antagonists in the treatment of epilepsy].

The antiepileptic effects of dihydropyridine derivates and flunarizine are currently evaluated in controlled clinical trials following earlier reports of their antiepileptic action in experimental animal models of epilepsy and promising pilot studies in human epilepsy. Other calcium antagonists such as verapamil or diltiazem have proved less effective in experimental models. They penetrate poorly into the CNS (Verapamil) and are difficult to evaluate clinically due to relevant pharmacokinetic interactions with antiepileptic drugs.

Calcium Channel Blockers↗
PubMed1989

Prolonged ventricular support using a centrifugal pump.

The Biomedicus centrifugal pump was required to provide prolonged ventricular support to 13 patients with hemodynamic instability: 11 after cardiovascular surgical procedures, 1 after myocardial infarction and 1 after failure of a heart transplant. The duration of support ranged from 3.5 hours to 9 days (mean 72 hours). Complications included bleeding in six patients, renal insufficiency in three and central nervous system deficit in three. Six patients (46%) were successfully weaned from the pump. The patient with graft failure had hyperacute rejection of a second heart. Five patients were discharged from the hospital. There was one death 8 months postoperatively. Prolonged ventricular support with the centrifugal pump may allow recovery of potentially reversible ventricular dysfunction in selected patients after cardiac surgical procedures.

Adolescent↗
PubMed1989

[Malignant peripheral neuroectodermal tumors. Histological and immunohistological conditions in 41 cases].

In view of the personal observation that malignant peripheral neuroectodermal tumours (MPNT) can present different histological growth patterns, 41 cases of MPNT were histologically and immunohistochemically studied. The median age of the 41 patients was 15 years (range: 9 months - 23 years). There were 27 males and 14 females. Most tumours (23/41) were located in the thoracopulmonary region. In 31/41 cases there was bone as well as soft tissue involvement. The following histopathological patterns were found: Ewing's sarcoma-like (n = 7), atypical Ewing's sarcoma-like (n = 4), neuroblastoma-like (n = 8), rhabdomyosarcoma-like (n = 8), and hemangiopericytoma-like (n = 1). In 2 cases combined patterns were noted, one tumour being characterized by neuroblastoma-like and Burkitt's lymphoma-like features. Most cases of MPNT differed from the cytological features of typical Ewing's sarcoma in that they contained hyperchromatic nuclei with distinct nucleoli. Some reticulin fibrils were found in between the cells of some cases. Immunohistochemically, 19/23 cases reacted positively to vimentin, 29/32 to neuron specific enolase (NSE), 16/28 to protein S-100, and 1/9 to glial fibrillary acidic protein. 12/24 cases reacted positively to NSE and protein S-100. Neurofilaments and desmin were not found in the formalin fixed material of the present study. The results show that most cases of MPNT can be distinguished from typical Ewing's sarcoma by cytological and histological findings. Differential diagnosis from atypical Ewing's sarcoma, neuroblastoma, and rhabdomyosarcoma is possible by immunohistochemistry.

Adolescent↗
PubMed1989

[Technical quality assurance in conventional x-ray diagnosis using medico-technical radiologists].

Without the x-ray assistant, regularly involved in everyday practice, technical quality assurance can hardly be accomplished. Therefore a model for the organization of quality assurance was developed and tested in practice. It implies accountable technical checks by the technician, that are controlled by a quality supervisor, and are subsequently evaluated by the radiation physics department. This positively influences quality consciousness of the radiographers and therefore the quality itself.

Germany, East↗
PubMed1988

The association of hepatocellular carcinoma in childhood with hepatitis B virus infection.

Eleven cases of hepatocellular carcinoma (HCC) in childhood were investigated by immunohistochemistry for association with hepatitis B virus (HBV) infection. Seven of 11 cases (64%) demonstrated positivity for hepatitis B surface antigen (HBsAG), whereas all 11 were negative for hepatitis B core antigen (HBcAG). Cirrhosis was absent in all cases, and other causes for HCC in childhood were not found. All children with HBV-associated HCC died within 6 months of diagnosis. The median survival time of these children was 2 months. Only one child with HCC of trabecular subtype without HBV association is still living after 18 months. However, this child has metastases and a local recurrence. Three other children with HCC of fibrolamellar subtype are free of disease after 2, 5, and 6 years, respectively. The high number of cases of HBV-associated HCC shows the important role of HBV infection as an etiologic factor for the development of childhood HCC in middle Europe.

Carcinoma, Hepatocellular↗
PubMed1988

Malignant peripheral neuroectodermal tumors. A retrospective analysis of 42 patients.

The clinical presentation of the disease and the results of treatment in 42 patients with malignant peripheral neuroectodermal tumors (MPNT) entered into the Cooperative Ewing's, soft tissue, and neuroblastoma trials of the German Society of Pediatric Oncology were retrospectively analyzed. Within the Ewing's sarcoma trial, patients with chest wall lesions were particularly analysed for MPNT features. The period of observation ranged from 15 to 86 months; the median relapse-free time was 24 months. There were 28 male and 14 female patients, the median age of patients was 15 years (range, 9 months-23 years). Thirty-two patients had localized disease (M0), and ten patients presented with primary metastases (M1). The predominant location of the tumors was the thoracopulmonary region, followed by the extremities, the abdominal/pelvic, and head and neck region. Thirty-one of 42 tumors involved the adjacent bone. The disease-free survival according to Kaplan-Meier life-table analysis was 56% +/- 11% for Stage M0 patients at 3 years. Nine of ten patients with M1 disease showed progression of their disease. Most patients had combined modality treatment with surgery, chemotherapy and radiation therapy. Best results were obtained with extensive surgery. Radiation doses ranged from 20 to 60 Gy and could not be correlated with the outcome of the disease. Most recurrences occurred at the site of the primary tumor. In patients with primary chemotherapy after biopsy-proven diagnosis, the responsiveness of this disease to chemotherapy could be demonstrated. Combination chemotherapy containing anthracyclines and high doses of alkylating agents appeared superior.

Actuarial Analysis↗
PubMed1988

Cerebral manifestation of hydatid disease in a child.

The case of a 9-year-old-boy with a left frontal hydatid cyst is reported. The infection was transmitted by a dog, the final host and a companion of the child. Recovery without complications was accomplished after puncturing, systemic antihelminthic therapy using mebendazole and, finally, total removal of the cyst.

Brain Diseases↗
PubMed1988

Comparison of 10 enzyme immunoassays for detection of antibody to human immunodeficiency virus type 2 in West African sera.

The efficacies of nine enzyme-linked immunosorbent assays (EIA) for antibody to human immunodeficiency virus type 1 (HIV-1) and one EIA for antibody to HIV-2 in detecting antibody to HIV-2 were studied. The competitive EIAs for antibody to HIV-1 were less sensitive than the indirect EIAs. The overall prevalence of positive results was between 28 and 51% with the competitive EIAs and between 70 and 93% with the indirect EIAs. Most of the EIAs were less sensitive in detecting antibody to HIV-2 in sera from people with acquired immunodeficiency syndrome-like diseases than in sera from symptomless individuals. The results indicate that there is a high degree of cross-reactivity between HIV-1 and HIV-2 by EIA, indicating that serotype specificity must be determined by Western blot (immunoblot) with both sets of viral antigens. The results are relevant for discussing public health strategies, especially the screening of blood donors; competitive EIAs for antibody to HIV-1 are not sensitive enough to be used in areas where HIV-2 is prevalent (West Africa).

Antibodies, Viral↗
PubMed1988

Oxytocin induces a transient increase in cytosolic free [Ca2+] in renal tubular epithelial cells: evidence for oxytocin receptors on LLC-PK1 cells.

We examined the effects of oxytocin on renal tubular epithelial LLC-PK1 cells. In cells loaded with Fura 2, we found that 1 microM oxytocin induced a rapid increase in cytosolic free [Ca2+]i from 120 nM to 250 nM within 12 sec. [Ca2+]i then decreased and leveled at 148 nM. Calcium was mobilized from intra- and extra-cellular sources. Oxytocin-induced calcium mobilization was dose dependent (EC50 between 5 and 30 nM). Oxytocin also stimulated calcium efflux which was blocked by the selective oxytocin antagonist KB-5-21. Calcium mobilization was a likely consequence of enhanced phosphatidylinositol turnover, because oxytocin rapidly increased the formation of inositol phosphates including Ins1,4,5P3. Calcium transients were induced by oxytocin and the oxytocin selective analog AM-2-40 and blocked by the oxytocin-selective antagonist KB-5-21. Lysine vasopressin, the selective V2 agonist dDAVP, and the V1-selective agonist SK&F 105349 were at least 10- to 100-fold less potent than oxytocin and exhibited only partial agonist activity. Using peptide analogs, a poor correlation was found between antagonism of oxytocin-induced calcium transients of LLC-PK1 cells and pig kidney V2 and rat liver V1 receptor affinity. These data indicate that oxytocin-induced calcium transients in LLC-PK1 cells were not mediated by V1 or V2 vasopressin receptors, but by oxytocin receptors. However, the poor correlation between antagonism at the LLC-PK1 receptors and the rat uterus oxytocin receptors suggests marked differences in antagonist recognition. We have also identified specific, saturable, high affinity oxytocin-binding sites of low density on intact LLC-PK1 cells (KD = 1.9 nM; Bmax = 3.2 fmol/10(6) cells). The relative analog affinities for these binding sites correlated well with their effects on oxytocin-induced calcium transients. We conclude that in LLC-PK1 cells, oxytocin stimulates a transient rise in cytosolic free [Ca2+]i and the formation of inositol phosphates, including Ins1,4,5P3. The effects on [Ca2+]i probably are not mediated by V1 and V2 vasopressin receptors, but by putative oxytocin receptors.

Animals↗
PubMed1988

[Adult T-cell leukemia associated with HTLV1 and positive HIV2 serology in an African woman].

We report a case of acute adult T-cell leukemia associated with HTLV1 infection in a young African woman. The leukemic proliferation consisted of CD4-, CD25-positive lymphoid cells with typically convoluted nuclei and monoclonal integration of the HTLV1-proviral DNA. The clinical course was characterized by a rapid progression of the leukemia with development of hypercalcemia, resistance to chemotherapy, and the presence of multiple opportunistic infections. The additional finding of a seropositivity for HIV2 raises the problem of the respective contribution of the two retroviruses in this patient's disease.

Acquired Immunodeficiency Syndrome↗