Biomedical subjects

D Wolf

Publications and source records attributed to D Wolf.

231 records · Page 13Linked to original sources

PubMedDate not supplied

[Comparative dosimetry study of two methods of intensity modulation performed on the same accelerator].

Intensity modulated radiation therapy (IMRT) is an advanced method of conformal radiotherapy. It permits optimal dose distribution to the target volume while preserving surrounding normal tissues. IMRT, with a multileaf collimator, can be realised in two different ways: either the segmented mode, which consists of combining small elementary static field, or the dynamic mode, which consists of moving the leaves while irradiating. The purpose of this work was to study these two methods of modulation on a Varian linear accelerator equipped with a collimator consisting of 40 pairs of one-centimetre-wide leaves. The measurements, obtained by using a diode array, showed that the quality of the irradiation in the dynamic mode does not depend on either the dose rate or the duration of the irradiation. In the segmented mode, weak magnitude segments are preferable, but increase the errors in the delivered dose. Comparisons of various profiles showed that the measured profiles are consistent with those programmed. Both modes seem to be equivalent for step-shaped profiles. In the case of profiles with constant slope, the segmentation generated by the segmented method deteriorates the profile. Even though the choice of technique is strongly dependent on the material available, the dynamic mode presents greater flexibility of use and has been chosen in our institution for IMRT.

Calibration↗

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Cooperation between gene encoding p53 tumour antigen and ras in cellular transformation.

The protein p53 is highly expressed in a large variety of transformed cell types originating from diverse species. These include cells transformed by Simian virus 40 (SV40), adenovirus and Abelson virus, as well as a variety of chemically transformed cells. Substantial amounts of p53 are also present in certain non-transformed cells, for example, some embryonic tissues. The protein may be localized in different cellular compartments in normal and transformed cells. The strong correlation between tumorigenicity and high levels of p53 suggests an important role of p53 in tumorigenesis. We report here experiments in which we have co-transfected the murine cellular gene encoding for p53 with a ras gene into primary rat embryo fibroblasts. Our results indicate that the p53-encoding gene can play a causal role in the conversion of normal fibroblasts into tumorigenic cells.

Animals↗

PubMedDate not supplied

Human p53 gene localized to short arm of chromosome 17.

The p53 gene codes for a nuclear protein that has an important role in normal cellular replication. The concentration of p53 protein is frequently elevated in transformed cells. Transfection studies show that the p53 gene, in collaboration with the activated ras oncogene, can transform cells. Chromosomal localization may provide a better understanding of the relationship of p53 to other human cellular genes and of its possible role in malignancies associated with specific chromosomal rearrangements. A recent study mapped the human p53 gene to the long arm of chromosome 17 (17q21-q22) using in situ chromosomal hybridization. Here, by Southern filter hybridization of DNAs from human-rodent hybrids, we have localized the p53 gene to the short arm of human chromosome 17.

Chromosome Mapping↗

PubMedDate not supplied

Focal nodular hyperplasia of the liver after intraconazole treatment.

A 38-year-old woman developed focal nodular hyperplasia of the liver after she had received a 4-month treatment with intraconazole 200 mg/d for a fungal infection of her fingernails. Because the patient underwent yearly liver ultrasound examinations because of the removal of a breast carcinoma, when the tumor was discovered incidentally, it was clear that it had developed within the past year after she had begun receiving intraconazole. Although various chemical agents and drugs have been considered as possible etiologic factors in the development of focal nodular hyperplasia of the liver, cases occurring after intraconazole therapy have not been reported before. Apart from the theoretical considerations with regard to the pathogenesis of nodular hyperplasia of the liver, this case could gain practical importance, as it shows a new adverse effect of a drug that has been used in more than 34 million patients over the past 10 years. Furthermore, this case should draw attention to the possibility of drug-induced benign hepatic tumors, as they may mimic malignant and metastatic disorders, which might be especially alarming in patients undergoing routine examinations after removal of malignant tumors, such as our patient.

Adult↗

PubMedDate not supplied

Massive intracranial bleeding requiring emergency splenectomy in a patient with CMV-associated thrombocytopenia.

We describe a previously healthy male patient, with severe immune thrombocytopenic purpura (ITP) following CMV infection which was refractory to steroids and intravenous immunoglobulin, who developed massive intracranial bleeding. Despite an extremely low platelet count (2x10(9)/liter) which was refractory to platelet transfusions, successful emergency splenectomy was performed, with rapid resolution of the thrombocytopenia. Bleeding complications are extremely rare in viral-associated ITP. Emergency splenectomy should be considered in the presence of life-threatening bleeding when other modalities fail to produce a rise in the platelet count. Infection with CMV should be ruled out in cases of severe, treatment-resistant ITP.

Cerebral Hemorrhage↗

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The influence of formamide on thermal denaturation profiles of DNA and metaphase chromosomes in suspension.

Systematic photometric studies are presented to analyze the thermal denaturation behaviour with and without formamide of metaphase chromosome suspensions in comparison to DNA solutions. Temperature dependent hyperchromicity measurements at 256 nm and 313 nm were performed using an appropriately designed computer-controlled photometer device. Due to an upright optical axis, this allowed absorbance measurements with negligible sedimentation effects not only for solutions of pure DNA, but also for particle suspensions of isolated metaphase chromosomes. This device has a temperature resolution of +/- 0.5 degrees C and an optical sensitivity of 10(-3) to 10(-4) optical density. For calf thymus DNA the reduction of the melting point with the increase of formamide in the solution was measured at pH 7.0 and pH 3.2. The good correlation of the theoretical approximation to experimental data indicated the suitability of the apparatus to quantitatively describe DNA conformation changes induced by thermal denaturation. For metaphase chromosome preparations of Chinese hamster culture cells, absorbance changes were measured between 20 degrees C and 95 degrees C with a temperature gradient of 1 degrees C/min. These measurements were performed at pH 7.0 and at pH 3.2. The denaturation profiles (= first derivative of the absorbance curve) resulted in a highly variable peak pattern at 256 nm and 313 nm indicating complex conformation changes. A statistical evaluation of the temperature values of the peak maxima resulted in temperature ranges typical for chromosomal conformation changes during thermal treatment. Especially the range of highest temperature values was independent from pH modifications. For pH 3.2 the influence of formamide on the denaturation behaviour of metaphase chromosome preparations was analyzed. In contrast to pure DNA solutions, a reduction of the "melting point" (i.e. the maximum temperature at which a conformation change takes place) was not found. However, the denaturation behaviour depended on the duration of formamide treatment before the measurement.

Animals↗

PubMedDate not supplied

Clinical characteristics of the West Nile fever outbreak, Israel, 2000.

West Nile (WN) virus is endemic in Israel. The last reported outbreak had occurred in 1981. From August to October 2000, a large-scale epidemic of WN fever occurred in Israel; 417 cases were confirmed, with 326 hospitalizations. The main clinical presentations were encephalitis (57.9%), febrile disease (24.4%), and meningitis (15.9%). Within the study group, 33 (14.1%) hospitalized patients died. Mortality was higher among patients >70 years (29.3%). On multivariate regressional analysis, independent predictors of death were age >70 years (odds ratio [OR] 7.7), change in level of consciousness (OR 9.0), and anemia (OR 2.7). In contrast to prior reports, WN fever appears to be a severe illness with high rate of central nervous system involvement and a particularly grim outcome in the elderly.

Adolescent↗

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