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R Schmidt

Publications and source records attributed to R Schmidt.

At least 451 records · Page 25Linked to original sources
PubMed1992

Hepatic contrast-enhancing properties of manganese-mesoporphyrin and manganese-TPPS4. A comparative magnetic resonance imaging study in rats.

OBJECTIVES: Manganese (III) mesoporphyrin (Mn-mesoporphyrin), a synthetic and stable complex, was investigated for its hepatic magnetic resonance imaging (MRI) properties and compared with manganese tetrakis-(4 sulfonatophenyl) porphyrin (Mn-TPPS4). METHODS: Liver abscesses (n = 10) and tumors (n = 14) were induced in rats. These rats then underwent MRI at 2.0 T. Animals received one of the two contrast agents, and measurement of lesion enhancement was performed. RESULTS: At an intravenous dose of 0.035 mmol/kg, Mn-mesoporphyrin caused significant enhancement of normal liver parenchyma and increased the lesion-to-liver contrast in both the models of heptic liver abscess and metastatic liver disease. Mn-TTPS4 at an intravenous dose of 0.04 mmol/kg typically enhanced both lesion and normal liver parenchyma and therefore did not improve the lesion-to-liver contrast. CONCLUSIONS: The hepatotrophic properties of Mn-mesoporphyrin indicate its potential as an intravenous contrast agent for liver imaging.

Animals↗
PubMed1992

Tetrazolium [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] reduction by mycoplasmas.

We investigated 22 mycoplasma and acholeplasma species for their ability to reduce tetrazolium salts by using the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. The test results were evaluated visually, as well as spectrophotometrically, by using an enzyme-linked immunosorbent assay reader. Our results were very similar to the results obtained when the tetrazolium salt reduction assay described by Aluotto et al. was used. However, the MTT reduction assay appeared to be better because it is faster, more objective and sensitive, easier to evaluate, and less expensive; in addition, it allows quantitative determinations. By using regression analysis a linear correlation between formazan production and the number of colony-forming units was demonstrated for all of the species investigated, indicating that the MTT assay can also be used for growth, toxicity, or chemosensitivity tests for the mycoplasma species that are capable of reducing tetrazolium salts.

Acholeplasma↗
PubMed1992

Differential expression of calgranulin A and B in various epithelial cell lines and reconstructed epidermis.

The monoclonal antibody F12, raised against epidermal cells from a psoriatic lesion, decorated antigens highly expressed in psoriatic epidermis and in cultured normal human keratinocytes. In normal human skin, F12 reacted only with follicular keratinocytes. Characterization of the immunoprecipitated antigens by two-dimensional gel electrophoresis revealed their identity with calgranulin A and B. A semiquantitative study with various established epithelial cell lines demonstrated that the expression of calgranulin A and B in hyperproliferative keratinocytes correlates with their potential to undergo terminal differentiation. In epidermis reconstructed in vitro, the antigen expression was stimulated by retinoids and suppressed under vitamin A starvation.

Antibodies, Monoclonal↗
PubMed1992

The prevalence of cerebral damage varies with migraine type: a MRI study.

Studies on the prevalence of MRI signal abnormalities in the brains of migraineurs have yielded controversial results. In order to provide further data on this issue we reviewed the MRI scans of 38 migraine patients without current neurologic symptoms (mean age 35.8 +/- 11.9 years). In addition, we compared the findings in those 24 migraineurs under 50 years without major cerebrovascular risk factors (mean age 30.1 +/- 9.0 years) to that in 14 headache and risk factor free volunteers (mean age 37.8 +/- 5.3 years). Overall, focal areas of hyperintense signal were seen in 15 (39%) patients. They were present on both proton density and T2-weighted spin-echo sequences. Lesion prevalence varied according to the type of headache (18% in migraine without aura, 53% in migraine with typical aura, 38% in basilar migraine). The subset of migraine patients under 50 years exhibited MRI signal abnormalities more than twice as often as controls (33% vs. 14%). Punctate white matter hyperintensities were the predominant finding and were seen in 10 of 15 individuals with MRI lesions. More striking signal abnormalities consisted of symmetrical areas of hyperintensity lateral to the posterior horns in two 24 year old patients and of extensive white matter damage with lacunar infarcts in a 59 year old woman. Our findings confirm a higher prevalence of MRI lesions in a mixed group of migraineurs than in headache free individuals. Signal abnormalities are most often non-specific, however their occurrence relates to the type of migraine.

Adolescent↗
PubMed1992

Comparison of magnetic resonance imaging in Alzheimer's disease, vascular dementia and normal aging.

MRI scans of 27 patients with probable Alzheimer's disease (mean age 68.2 years), 31 patients with vascular dementia (mean age 69.9 years) and 18 normal controls (mean age 66.3 years) were compared to evaluate possible distinguishing parenchymal abnormalities among these groups. Atrophy was quantitated by subjective rating, linear and volumetric measurements. A number of findings were significantly more common in vascular dementia than in the other subsets. These included (1) basal ganglionic/thalamic hyperintense foci, (2) thromboembolic infarctions, (3) confluent white matter and (4) irregular periventricular hyperintensities. Signal abnormalities on intermediate T2-weighted scans in the uncal-hippocampal or insular cortex were frequently and almost exclusively noted in Alzheimer's disease. Moderate and severe cortical and ventricular atrophy and a third ventricular to intracranial width ratio larger than 7% were good discriminators between demented groups and normally aging controls. Selective atrophy measurements, however, failed to separate dementia syndromes. These results suggest that MRI has the potential to increase the accuracy of the clinical diagnosis of Alzheimer's disease and vascular dementia.

Aged↗
PubMed1992

[Ergotism and ischemia of the limbs].

Clinical ergotism as seen today results almost exclusively from the intake of ergotamine tartrate in the treatment of migraine headache. Vasospasm of peripheral arteries is the leading clinical picture. Besides the formation of collaterals and a secondary thrombosis, the vasospasm is one of the specific findings in arteriography. Early diagnosis and withdrawal of the medication makes complete restitution possible. In all other cases intraarterial or intravenous infusion of sodium nitroprusside has turned out to be the most effective therapy. Balloon dilatation or operative intervention are an alternative therapy in those cases, where amputation of the limbs seems to be necessary.

Adult↗
PubMed1992

Renal malignancy in peritoneal dialysis patients with acquired cystic kidney disease.

A known complication of long-term hemodialysis, acquired cystic kidney disease (ACKD) has been reported infrequently in association with chronic ambulatory peritoneal dialysis (CAPD). The duration of end stage renal failure (ESRF) is thought to correlate with the development of ACKD. Renal cell carcinoma has been reported in 4-10% of patients with ACKD. Two patients on CAPD for more than 6 years without prior hemodialysis treatment developed renal malignancy in the setting of ACKD. Flank and abdominal pain was the presenting symptom in both patients neither of whom had hematuria. Renal ultrasound detected cystic lesions consistent with ACKD; malignant masses were ultimately identified by CT scan. Both patients underwent flank radical nephrectomy, resumed CAPD early in the postoperative period and continue on CAPD 9 and 4 months after surgery. One patient has since developed hepatic metastasis. ACKD is an important risk factor for the development of renal cell carcinoma not only in maintenance hemodialysis patients but also in the CAPD population. A high index of suspicion and serial ultrasound screening for ACKD is warranted in patients with long-term dialysis-dependence.

Carcinoma, Renal Cell↗
PubMed1992

Improved nutritional follow-up of peritoneal dialysis patients with bioelectrical impedance.

A threat to survival in renal failure, malnutrition in continuous ambulatory peritoneal dialysis patients (CAPD) is often occult as CAPD patients often gain weight masking actual protein malnutrition. Bioelectrical impedance (BEI) accurately assesses body composition in CAPD patients and uncovers subtle changes in lean body mass (LBM) that escape indirect anthropometric detection. Segregating parameters of body composition is crucial to nutritional management of CAPD patients in whom fat may account for overall weight gain. While both skin-fold methods and BEI correctly distinguished thin and overweight patients in terms of fat mass, only BEI accurately segregated these patients by LBM (P = 0.007). Serial weights of 39 CAPD patients followed longitudinally for three or more months did not correlate with BEI-measured changes in LBM. LBM was lost in 49% of patients as determined by BEI, while serial weights detected a loss of LBM in 36% of these patients. Strikingly, by serial weights, 64% of patients demonstrated weight gain; however, in 24% of these an actual loss of LBM was demonstrated by BEI. BEI provides specific quantitation of LBM in CAPD patients with changing body habitus and unrecognized nutritional derangement.

Adult↗
PubMed1992

Enhanced peritoneal dialysis delivery with PD-PLUS.

We prospectively studied the effects of enhanced continuous ambulatory peritoneal dialysis (CAPD) on the normalized protein catabolic rate (NPCR) and Kprt/V of two patients with zero residual renal function and marginal or below minimal HCFA values on urea kinetic modeling (Kprt/V = 0.21). Predictable increases in NPCR (from 0.61 to 0.76 and from 0.73 to 0.81 gm/kg/day, respectively) were seen after two weeks of enhanced CAPD achieved by the addition of a fifth nighttime exchange by a portable, easily operable, automated device (PD-PLUS).

Creatinine↗
PubMed1992

Effect of diet composition on renal morphology in diabetic rats.

Streptozotocin-induced diabetic rats were fed rodent diets with standard (4.5%) or high (10%) polyunsaturated fatty acid content for up to 12 months. Diabetic rats fed a standard diet developed thickening of glomerular basement membrane (GBM) when compared to similarly fed controls (285 +/- 21 vs. 243 +/- 18 nm, respectively; p = 0.0003). No differences in GBM thickening were observed between control and diabetic rats fed high-fat diets (188 +/- 23 vs. 195 +/- 21 nm, respectively; p = n.s.). Regardless of diabetes, all rats fed high polyunsaturated fat diets had decreased GBM thickness compared to standard-fed rats (p = 0.0001). Glomerular and mesangial volumes were similar in control and diabetic rats fed standard or high fat diets. Diets high in polyunsaturated fatty acids prevent GBM thickening in diabetes and reduce GBM thickness in control rats.

Animals↗
PubMed1992

Use of bioelectrical impedance for the nutritional assessment of chronic hemodialysis patients.

Although malnutrition poses a significant risk to the well-being of chronic hemodialysis patients, their nutritional assessment is usually empirical. We studied body composition by bioelectrical impedance (BEI) prospectively in 39 patients followed for 5-12 months. BEI correctly discriminated between underweight and overweight patients in terms of fat mass (21 +/- 5 vs. 34 +/- 10%; p = 0.002), lean body mass (78 +/- 4 vs. 67 +/- 10%; p = 0.004) and total body water (57 +/- 3 vs. 49 +/- 7%; p = 0.002), respectively. Serial body weights did not correlate with changes in lean body mass (LBM) as measured by BEI. While 28% of patients lost weight, 41% lost LBM. Most striking is the contrast between the patients who showed no change in LBM by BEI and those whose body weight remained neutral (3 vs. 28%). BEI is a most sensitive clinical tool for assessing changes in LBM in hemodialysis patients.

Body Composition↗
PubMed1992

Advantage of three-dimensional treatment planning for localized radiotherapy of early stage prostatic cancer.

Conventional two-dimensional (2-d) treatment planning was compared to three-dimensional (3-d) treatment planning for patients with prostatic carcinoma. Both types of treatment planning were performed for all ten patients with five fixed fields. In 3-d planning we used irregular shaped fields. For further evaluation we performed conventional planning in rotation technique in two patients. The target volume included prostate, seminal vesicles and a surrounding security margin of 2 cm. Using the MPR-version of the MEVAPLAN planning system, the three-dimensional dose calculations were performed. For the volumes of interest (VOI's) we discussed quality of the dose distribution concerning homogeneity in the target volume and isodose distribution in the organs at risk, which are the rectum and the urinary bladder. We defined the tumor encompassing reference isodose (ca. 95%) for the calculation of the involved rectum- and bladder volume. Using the five-field technique our results show a reduction of the radiation related rectum- and bladder volume concerning the tumor encompassing reference isodose (ca. 95%) for the rectum in between 9.5 and 36.6% (median: 19%, n = 10) and for the urinary bladder in between 15.7 and 47.8% (median: 28%, n = 10). Calculated for 80% of the reference isodose the difference for the rectum was 15.7 to 31.3% (median: 23%) and for the urinary bladder 24.5 to 56.7% (median: 42%). A significant reduction of radiation related side-effects concerning rectum and urinary bladder can be expected by a reduction of volume involvement and a consecutive dosage limitation.

Humans↗
PubMed1992

Visualization of 3-D treatment plans with fast neutrons.

The treatment planning for radiotherapy with fast neutrons requires modifications of the planning systems used for photons. The neutron- and photon-component of the treatment fields must be determined and can then be used for separate calculations. The corrections for inhomogeneities are performed by use of attenuation coefficients and the corresponding corrections for changes in the kerma. The treatment planning system MEVAPLAN (Siemens) was modified to follow these requirements. Thus treatment planning for 14 MeV DT-neutrons could be performed. The multiplanar option is used to calculate 3D-dose distributions based on up to 40 serial CT slices. The generated three-dimensional dose matrix and the CT data are transferred via magnetic tape to the visualization system VOXEL-MAN developed at the University Hospital of Hamburg. This system uses a ray casting algorithm based on the generalized Voxel-model to display detailed 3D-images of human anatomy together with the calculated dose distribution. Different treatment plans for neutrons and photons are calculated and visualized. Various manipulations of the data-sets are displayed to improve the critical examination of the simulated dose distribution and to discern the quality of treatment techniques.

Fast Neutrons↗
PubMed1992

[Site-dependent psychopathologic symptoms in brain tumors exemplified by olfactory meningioma].

Despite the propagation of imaging techniques in recent years, brain neoplasms are still identified too late in many cases, not least because of a disregard or misinterpretation of early psychiatric symptoms. By means of a detailed report of a case of olfactorius meningioma, together with a summary of 13 other cases from the same hospital over the past 15 years, it is demonstrated that a specious psychodynamic "understanding" may delay the correct diagnosis. Possible reasons for the initial false diagnosis are considered in detail.

Cranial Nerve Neoplasms↗
PubMed1991

Uptake, cytotoxicity and metabolism of m-azidopyrimethamine and related lipophilic antifolates in SV-K14 human keratinocytes in vivo.

The growth-inhibitory properties of a series of lipophilic diaminopyrimidine antifolates were evaluated in comparison with methotrexate (MTX) against SV-K14 human keratinocytes in vitro under folate-dependent and folate-independent conditions. Under folate-dependent conditions metoprine (DDMP) proved more cytotoxic than MTX, despite the greater inhibitory activity of the latter compound against mammalian dihydrofolate reductase (DHFR), possibly reflecting differences in cellular accumulation. The significantly lower activity of both compounds under folate-independent conditions indicated DHFR as the primary target. Pyrimethamine (PYM), m-azidopyrimethamine (MZP) and m-aminopyrimethamine (MAP), a metabolite of MZP, were approximately equiactive but less cytotoxic than MTX or DDMP. The unexpected activity of MAP, an inferior DHFR inhibitor, suggests differences in the mechanism of action or cellular transport of the drug, although the reduction of cytotoxicity observed under folate-independent conditions indicate folate metabolism as the cytotoxic locus. In contrast, the cytotoxicity of PYM or MZP was not reduced under folate-independent conditions implying an alternative mechanism of action. The uptake of 2-[14C]pyrimethamine by SV-K14 keratinocytes was rapid with steady-state intracellular concentrations being observed after approximately 100 min, partition of drug into the plasma membrane preceding redistribution and extensive accumulation within the particulate cell components. The previously reported NADPH-dependent metabolism of MZP to MAP by murine liver microsome preparations was not observed with SV-K14 keratinocytes nor with murine skin homogenates in the present study.

Animals↗