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Biomedical subjects

J G Kok

Publications and source records attributed to J G Kok.

7 recordsLinked to original sources
PubMed2000

No acute antimigraine efficacy of CP-122,288, a highly potent inhibitor of neurogenic inflammation: results of two randomized, double-blind, placebo-controlled clinical trials.

CP-122,288 is a highly potent inhibitor of neurogenic plasma extravasation in animal models at doses without vasoconstrictor effect. We evaluated the acute antimigraine efficacy of intravenous and oral CP-122,288 in two double-blind studies. In a crossover design, patients randomly received 31.25 microg of CP-122,288 intravenously, placebo, or both. In the oral study, patients received placebo or one of four doses of CP-122,288 between 3.125 and 312.5 microg, using a novel "up and down" design for randomization. Both studies were stopped prematurely when target efficacy could not be achieved. Responder rates were 29% for CP-122,288 versus 30% for placebo (difference, -1%; 95% CI, -24-22%; intravenous study) and an overall rate of 25% for CP-122,288 versus 0% for placebo (difference, 25%; 95% CI; 10-40%; oral study). CP-122,288 was not clinically effective at doses and plasma concentrations in excess of those required to inhibit neurogenic plasma extravasation in animals. Neurogenic plasma extravasation is unlikely to play a crucial role in the pathophysiology of migraine headache.

Administration, Oral↗
PubMed1999

Finding mechanisms responsible for the spectral distribution of electron beams produced by a linear accelerator.

The measured electron spectra of linear accelerators from several manufacturers differ in comparison to the spectral form and width. As part of our investigations of linac performance and stability, we analyzed the electron spectra of our linacs. After building a spectrometer the electron spectra were measured. The measured spectral widths were comparable with the results published in the literature. It appeared that the phase of the recycled radio pulse in combination with the limited bandwidth of the bending magnet are responsible for unusual (multipeak) electron spectra. The scatter filters only have a relatively small widening effect on the spectrum. There was no indication that multipeak or wide spectra are related to linac instabilities.

Electrons↗
PubMed1985

Cerebrospinal fluid rhinorrhea during treatment with bromocriptine for prolactinoma.

A 47-year-old man exhibited loss of libido and impotence in association with plasma hyperprolactinemia and a pituitary mass with downward extension of the tumor to the sphenoid sinus and to the suprasellar cisterns. Bromocriptine, 15 mg daily, reduced the hyperprolactinemia as well as tumor size. After 8 months on this therapy, the patient developed overt CSF liquorrhea. Five days after discontinuation of bromocriptine, the CSF rhinorrhea stopped, and when bromocriptine was given again 2 weeks later, CSF rhinorrhea returned within 3 days. We believe this phenomenon to be due to retraction of tumor by bromocriptine exposing a defect in the sella floor. Transient occurrence of CSF rhinorrhea can be considered as a consequence of tumor regression in patients on bromocriptine. The possibility of this complication, especially in patients with downward extension of tumor, should be noted.

Bromocriptine↗
PubMed1984

Multiple pterygium syndrome. A report of two unrelated cases.

Clinical description as well as differential diagnosis are presented of two unrelated patients with the so-called Multiple Pterygium Syndrome. In literature pathological alterations of muscle structures in some patients have been described. In our two patients no evidence was found for a neuromuscular disease, nor for a disease state of the central nervous system.

Child↗
PubMedDate not supplied

Fixed bending current for Elekta SL25 linear accelerators.

In a medical linear accelerator a bending magnet is used to bend the electron beam produced by the accelerator tube, in the treatment direction. For each electron energy the strength of the magnetic field has to be set to a specific level. Changing the magnetic field strength is done by changing the electric current through the bending magnet. When electron energy and magnetic field strength are not matched, performance of the linac can be affected. As electron energy, magneticfield strength and electrical current through the bending magnet are related to each other, it is reasonable to assume that for each electron energy the correct bending current can be predetermined. This calculated bending current reduces the number of variable parameters used to set up a treatment beam. Predetermining a variable simplifies the tuning procedures. It also prevents a deviation of the electron beam energy being compensated by variation of the bending current. Preventing false machine settings can contribute to increase linac performance and reduce down time and cost of ownership.

Calibration↗