Biomedical subjects

C Vandecasteele

Publications and source records attributed to C Vandecasteele.

42 records · Page 3Linked to original sources

PubMed1982

Uptake of 13N-ammonia by human tumours as studied by positron emission tomography.

Tumour uptake of 13N-labelled ammonia was studied by means of positron emission computerised axial tomography in 46 patients with various extensive neoplastic conditions. Eleven of the patients have been followed sequentially before, during and after radio- and/or chemotherapeutic treatment. Substantial accumulation of 13NH3 (up to five times the amount found in comparable normal tissues) was noted in some cases of breast cancer and their metastases, as well as in soft tissue sarcomas, in malignant neck nodes secondary to head and neck tumours, in lung tumours and their metastases, in melanomas, in malignant lymphomas, in metastasis prostatic carcinoma and in the case of ovarian carcinoma examined. Little or no extra uptake of 13NH3 was found ion necrotic or non-malignant tumours or in primary brain tumours, or in some primary breast cancer which otherwise appeared well vascularized and actively growing. In those patients who were followed sequentially, 13NH3 uptake could be seen to decrease with tumour regression. However, during the course of a radiotherapeutic treatment a transitory increase of 13NH3 uptake could be observed. If the therapy had not been successful, 13NH3 uptake was found to persist after treatment. Uptake of 13NH3 in tumours is to be regarded as the result of a complex interaction of both circulatory and metabolic influences. Studies using more specific tracers of flow and tissue metabolism will probably help to unravel the contributory physiological components.

Aged↗

PubMedDate not supplied

Charged-particle activation analysis of biological material.

Charged-particle activation analysis offers a number of interesting possibilities for the determination of trace elements in biological material. It allows the determination of those elements that are difficult or impossible to determine by neutron activation, such as Li, B, Al, Si, V, Cr, Ni, Cd, Sn, Tl, and Pb. Up to now, protons have been successfully applied to samples of both vegetal and human origin. A number of difficulties have to be overcome, one of which is excessive heating of the samples owing to the limited range of the charged particles, thus giving rise to a high energy deposition in a small volume. Moreover, the sample composition has to be known to allow the calculation of the range of the particles. An interesting alternative has been proposed using an internal standard together with a standard additions procedure. Proton activation analysis was tested on a wide variety of reference materials, giving evidence that accurate results can be obtained for many trace elements, even when applying a purely instrumental method. Thus, the method can also be applied in the certification of reference materials, since nuclear methods are independent of chemical properties of the sample.

Activation Analysis↗

PubMedDate not supplied

Determination of trace elements in human serum by inductively coupled plasma-mass spectrometry. Comparison with nuclear analytical techniques.

The determination of trace and ultratrace elements in human serum by ICP-MS is described. The accuracy of the method is tested using a "second generation" human serum reference material. Elements determined include Fe, Co, Cu, Zn, Br, Rb, Sr, Mo, and Cs. The method is compared to nuclear analytical methods (NAA, PIXE). Perspectives for the future are also discussed.

Evaluation Studies as Topic↗

PubMedDate not supplied

Determination of mercury in human serum and packed blood cells by neutron activation analysis.

A method is described for the determination of mercury in human blood serum and packed blood cells employing neutron activation analysis. Great attention was devoted to the collection and manipulation of the samples. The accuracy and precision of the method were tested by analyzing biological reference materials and by comparing the concentrations measured in a number of serum samples to those obtained by another, independent technique (cold vapor atomic absorption spectrometry) in the same samples. The article reports the levels measured in blood serum and packed blood cells samples from 15 adult volunteers, as well as the figures determined in a "second-generation" biological reference material (freeze-dried human serum), prepared and conditioned at the University of Ghent.

Adult↗

PubMedDate not supplied

PET studies of changes in cerebral blood flow and oxygen metabolism after unilateral microembolization of the brain in anesthetized dogs.

Cerebral blood flow and oxygen metabolism have been measured with the steady-state oxygen-15 technique and positron emission tomography in anesthetized dogs. Regional microembolization was induced by infusing Sephadex particles (diameter, 40 micron) into one of the common carotid arteries. In the first series of experiments, 2.5 mg Sephadex was infused, and the dogs were examined within 3-4 hours after embolization. In a second series 0.55 mg Sephadex was infused, and the dogs were examined either in the first 3-4 hours or 24-48 hours after embolization. Cerebral blood flow, oxygen extraction ratio, and cerebral oxygen utilization were measured at 3 PCO2 levels. In the acute experiments, cerebral oxygen utilization in the embolized hemisphere was 6 (0.55 mg Sephadex) and 25% (2.5 mg Sephadex) lower than on the contralateral side. While cerebral blood flow was symmetrically distributed in normocapnia and hypocapnia, it was 9 (0.55 mg Sephadex) and 35% (2.5 mg Sephadex) lower in the embolized hemisphere during hypercapnia. In normocapnia and hypocapnia the lower oxygen utilization in the embolized hemisphere was characterized by a lower oxygen extraction ratio, and in hypercapnia by an unchanged (0.55 mg Sephadex) or by a higher (2.5 mg Sephadex) extraction ratio. The different effect on oxygen extraction ratio in the control and embolized hemispheres resulted in images of uncoupling between perfusion and oxygen demand that varied according to the PCO2. The experiments also showed a fall in cerebral blood flow in the embolized hemisphere after 3-4 hours, indicating delayed hypoperfusion. After 24-48 hours, blood flow was about 10% higher in the embolized hemisphere, and this was observed at the 3 PCO2 levels, while the oxygen extraction ratio was systematically lower. Oxygen utilization in the embolized hemisphere was depressed to practically the same extent as in acute experiments. It can be concluded that between 4 and 24 hours after microembolization the cerebral microcirculation shows important changes, with installation of luxury perfusion in the face of an unchanging decreased oxygen metabolism.

Anesthesia↗

PubMedDate not supplied

Histone H1 kinase activity in one-cell mouse embryos blocked in the G2 phase by X-irradiation.

The activation of the p34cdc2/cyclin B complex is responsible for driving the cell cycle from the G2- to the M-phase. To investigate the effects of irradiation on the activity of the p34cdc2/cyclin B complex in preimplantation embryos, we irradiated one-cell mouse embryos with 2.5 Gy of X-rays at the early pronuclear stage, and measured the fluctuations of histone H1 kinase activity (a biochemical indicator of the kinase activity of the p34cdc2) at different times during the radiation-induced G2-arrest. BALB/c embryos were chosen for these experiments, since earlier results obtained in our laboratory had shown that such a treatment induces a G2-arrest of about 20 hours in more than 90% of the embryos. Our data showed that histone H1 kinase activity of irradiated embryos remained at a very low level during the period of G2-arrest. The level of activity found during late division of the G2-arrested embryos was also significantly lower in comparison with that of control embryos or irradiated embryos dividing without delay. All together, our results suggest that a) low levels of histone H1 kinase activity are sufficient for the division of one-cell embryos, b) there could be a link between the levels of histone H1 kinase activity in mitosis and the health status of the embryo.

Animals↗