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Biomedical subjects

R Felix

Publications and source records attributed to R Felix.

At least 667 records · Page 37Linked to original sources
PubMed1988

Bisphosphonates inhibit 1,25-dihydroxyvitamin D3-induced increase of osteocalcin in plasma of rats in vivo and in culture medium of rat calvaria in vitro.

In order to test whether bisphosphonates, which are potent inhibitors of osteoclastic bone resorption, may also act upon osteoblasts, we studied the effect of dichloromethylenebisphosphonate (Cl2MBP) and 4-amino-1-hydroxybutylidene-1,1-bisphosphonate (AHBuBP) on in vivo levels and in vitro release of osteocalcin, a bone-specific protein produced by osteoblasts. In rats, 161 mumol/kg of Cl2MBP or 1.61 mumol/kg AHBuBP strongly inhibited the increase of plasma osteocalcin induced by 1,25(OH)2D3. The inhibition was measurable within 24 hours after the administration of bisphosphonate and was independent of any change in bone resorption. The effect upon osteocalcin release was also present in calvaria cultures. 250 microM Cl2MBP strongly inhibited the osteocalcin release induced by 10(-8) M 1,25(OH)2D3. In the presence of 1,25(OH)2D3, protein synthesis and DNA synthesis were also decreased, whereas in the absence of 1,25(OH)2D3, protein synthesis was increased. Thus, bisphosphonates affect the production of a bone-specific protein by osteoblasts in addition to their inhibitory action on osteoclasts.

Alendronate↗
PubMed1988

[A multislice gradient-echo sequence for contrast medium-enhanced MR diagnosis of intracranial tumors].

A multislice gradient echo sequence (FLASH) was compared with a conventional spin-echo (SE) technique with regard to its value for contrast enhanced MR diagnosis. In 28 patients with cerebral tumours, SE images (SE 400/30; four images/3.4 minutes) and FLASH images (FLASH 315/14; 15 images/1.4 minutes) were obtained before and after gadolinium DTPA. After gadolinium-DTPA results were comparable for both techniques with respect to contrast enhancement, tumor contrast and delineation. Because of the higher efficiency of the FLASH 315/14 technique, this sequence is the method of choice for contrast enhanced cerebral MR imaging.

Adult↗
PubMed1988

[Oral contrast media for magnetic resonance tomography of the abdomen. III. Initial patient research with gadolinium-DTPA].

32 patients with abdominal tumours or inflammatory abdominal diseases were examined by MRI (0.5 T) prior to and after oral administration of gadolinium-DTPA (Gd-DTPA). T1- and T2-weighted sequences were employed. 10 ml/kg body weight of a Gd-DTPA formulation were administered (1.0 mmol/l, 15 g mannitol/l). Gd-DTPA provided markedly hyperintensive opacification of the gastrointestinal tract. In 19 of 32 studies Gd-DTPA-enhanced scans showed improved delineation of abdominal pathologies. In most cases Gd-DTPA-enhanced T1-weighted multislice gradient echo images provided the most useful diagnostic result. Meteorism and diarrhea were recorded in 13 patients.

Abdomen↗
PubMed1988

[Early detection of multiple sclerosis: MR findings in the initial manifestations of multiple sclerosis].

The MR results in 21 patients showing the initial manifestations of multiple sclerosis (MS) were compared with those in 45 patients with a long history of MS. As in the old cases, MR proved a very sensitive technique during the early manifestations, with abnormal findings in 20 out of the 21 patients. The relatively characteristic MR findings in long-standing MS (predominant peri-ventricular involvement with a relatively typical pattern) was seen in the early stages is only rare cases. The value of MR during the initial manifestations of MS is in cases where the clinical findings are not conclusive and laboratory diagnosis (evoked potentials, CSF findings) are indefinite. In these patients the findings of multiple lesions in the brain can confirm the suspected diagnosis of MS.

Adult↗
PubMed1988

[Magnetic resonance tomography of paranasal sinus tumors using gadolinium-DTPA and multi-echo sequences].

We report on the use of magnetic resonance tomography for tumours of the paranasal sinuses. The value of gadolinium-DTPA was investigated in a prospective study. For tissue characterisation and determination of the extent of the disease, combined use of T2-weighted multi-echo sequences and plain and contrast examinations with T1-weighted spin-echo sequences are superior to CT. CT must be used, however, to demonstrate bone changes. Endocranial tumour extension can be demonstrated more precisely with magnetic resonance than with CT.

Adult↗
PubMed1988

[Ischemic brain infarct: combined determination of regional cerebral blood flow and volume by SPECT].

A combined measurement of regional cerebral blood flow (r CBF) and volume (r CBV) by SPECT was performed in 15 patients with ischaemic cerebral infarction. For measurement of r CBF 99mTc-HMPAO was used, and for r CBV 99mTc-labelled red blood cells. Patients with acute or subacute cerebral infarction (n = 10) showed elevation of r CBV whereas r CBF was either reduced or elevated. Patients with chronic cerebral infarction (n = 5) showed reduction of both r CBF and r CBV. The combined measurement of both r CBF and r CBV by SPECT allows imaging and semiquantitative evaluation of haemodynamic changes in ischaemic cerebral infarction at various stages. The resulting data may be helpful in describing the pathophysiologic compensatory mechanisms.

Aged↗
PubMed1988

[MR imaging of the meninges: normal and pathological findings].

The MR appearance of normal and pathological meninges was studied in 23 patients. Amongst twelve normals, T1-weighted images demonstrated the meninges as slightly hyperintense density structures (compared with CSF) which increased in signal intensity somewhat after the administration of gadolinium-DTPA. On T2-weighted images, the subarachnoid space and meninges were isointense. In eleven patients with inflammatory disease or tumourous infiltration of the meninges, abnormal findings were evident in the unenhanced images as well as after administration of gadolinium-DTPA. Compared with CT, MR proved greatly superior in the diagnosis of meningeal abnormalities.

Adult↗
PubMed1988

MR imaging of the gastrointestinal tract: value of Gd-DTPA.

To determine the value of gadolinium-DTPA (Gd-DTPA) as an MR contrast material for the gastrointestinal tract, we obtained T1-, T2-, and proton-density-weighted MR scans of the abdomen in 20 volunteers before and after oral administration of the compound (10 ml/kg of a 0.5- or 1.0-mM solution). Gd-DTPA was given either alone or with mannitol (15 or 30 g/l). Opacification of the small bowel after the administration of 1.0 mM Gd-DTPA was superior to that achieved after administration of the 0.5-mM solution. In the absence of Gd-DTPA, the pancreas could be delineated partly in 11 cases. After administration of Gd-DTPA, the pancreas could be well differentiated from stomach and duodenum in 16 of 20 cases. In the absence of mannitol, two of the five subjects had homogeneous opacification of the entire small bowel. When Gd-DTPA was given with either 15 or 30 g mannitol/l, homogeneous opacification of the entire small bowel was obtained in nine of 10 volunteers. Diarrhea not discomforting to the volunteers was noted in four of 20 cases. No abnormal blood tests were recorded after administration of Gd-DTPA. The results suggest that oral administration of Gd-DTPA (1.0 mM) given with mannitol (15 g/l) is effective as an MR contrast agent for the gastrointestinal tract. The formulation was found to be safe in a small series of 20 volunteers.

Adult↗
PubMed1988

Production of calcification inhibitors by rat calvaria and bone cells in culture.

Inhibition of calcium phosphate crystal formation was assessed in conditioned medium from cultured rat calvaria and rat calvaria cells. The amount of inhibitor activity was measured by determining the amount of hydroxyapatite needed to induce calcium phosphate precipitation in a solution with a constant calcium phosphate supersaturation. Rat calvaria in culture released inhibitor activity. This activity was separated by chromatography on a Bio-Gel P4 column into a high molecular weight (HMW) fraction and a low molecular weight (LMW) fraction. The latter contained, among others, citrate and pyrophosphate (PPi), but the concentration of these was too low to account for the total activity observed. The identity of the HMW and the remaining LMW inhibitors are at present unknown. Various populations of calvaria cells also produced these two types of inhibitors, 20% of the LMW being due to PPi. Fibroblasts produced only the HMW type of inhibitors. These results suggest that cells might control the process of biologic calcification by regulating the amount of inhibitors they produce.

Animals↗
PubMed1988

[Ultrasound findings in patients with AIDS].

The ultrasonographic findings of 43 patients with AIDS and ARC were analyzed. In 63% an enlarged liver, in 66% an enlarged spleen, partially with focal lesions, and in 21% enlarged abdominal lymph nodes were diagnosed. The typical parenchymal lesions of the kidney (focal segmental glomerulosclerosis) were not observed. Abdominal ultrasound is the first diagnostic procedure to perform in patients with AIDS and ARC with the suspicion of abdominal pathology. With additional thin needle puncture of the lesions a histological verification of the pathologic findings is possible.

AIDS-Related Complex↗
PubMed1988

[Digital radiographic image enhancement in bone diagnosis--initial clinical results].

34 patients with skeletal alterations mostly in the periphery were investigated by digital image intensifier radiography (DIIR). A high resolution image-intensifier system (1024 x 1024 matrix, 40 cm, 28 cm, 14 cm image intensifier, maximal spatial resolution: 3.6 lp/mm) was available. The image quality was diagnostic sufficient in 76% using DIIR. A good or very good image quality of fine-structures was obtained only in 41%. The quality deficits in comparison to conventional radiograms were particularly obvious in investigation of the phalangeals. Logarithmic amplification and software upgrading lead after these first clinical investigations to a better image quality.

Adult↗
PubMed1988

[Comparative clinical studies of myocardial blood flow in coronary heart disease with two nifedipine preparations].

Clinical, ergometric and scintigraphic examinations were performed before and after oral administration of a commercially available nifedipine preparation used as a standard (reference preparation; dosage: 3 x 10 mg/d) in 21 patients with angiographically verified coronary artery disease. In an open comparison study the same parameters were investigated after a 4 week course of a different nifedipine preparation as a test preparation (Corotrend; dosage: 3 x 10 mg/d). The study was performed in order to determine whether there were quantitative differences in myocardial microperfusion when different galenical preparations of nifedipine were used. There were no statistically significant differences between the two nifedipine preparations in the test parameters recorded. Both substances were associated with highly significant increases in microperfusion as compared to findings in the washout phase. Clinical effects on incidence of chest pain and on reductions in blood pressure were comparable. Patients demonstrated slightly better exercise tolerance with the reference agent, and computerised impulse-rate analysis of the tomoscintigrams demonstrated somewhat better microperfusion with this drug, though the differences between the two agents did not attain statistical significance. As the result of this analysis the two drugs would appear to be equivalent in clinical potency.

Aged↗
PubMed1988

[Magnetic resonance tomography (MRT) in bronchial cancer].

Comparative studies were made of 47 patients suffering from histologically and cytologically confirmed bronchial carcinoma, using CT and MRT respectively. CT examinations were performed before and after intravenous administration of contrast medium, whereas the MR examinations were conducted via EEG-triggered T1 and T2 marked SE sequences in the axial and coronary planes. Both methods were assessed in respect of tumour visualisation and documentation of tumour spread. Staging of tumour and lymph nodes yielded largely concurring results for CT and MRT. Exceptions were seen in 7 of 10 patients with malignant involvement of the pericardium and in 3 of 27 patients with lymph node metastases located mediastinally and subcarinally where only MRT showed a positive involvement of the pericardium or lymph nodes (with possible consequences for the staging of the tumour or lymph nodes). Decisive advantages of MRT compared with CT were seen in the identification of infiltration of the aortic-wall, in the differentiation of the poststenotic syndrome, in the visualisation of the thoracic wall infiltration and functional information on blood flow rate in upper venolus obstruction caused by a carcinoma.

Carcinoma, Bronchogenic↗