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Biomedical subjects

K Kristensen

Publications and source records attributed to K Kristensen.

At least 73 records · Page 4Linked to original sources
PubMed1988

Assessment of the arterial input curve for [99mTc]-d,l-HM-PAO by rapid octanol extraction.

The in vitro conversion of the lipophilic molecule [99mTc]-d,l-hexamethylpropyleneamine oxime [( 99mTc]-d,l-HM-PAO) to a hydrophilic form was studied in saline, plasma, and blood at 37 degrees C by paper chromatography and by octanol extraction. The octanol:saline ratio was 79.9. From this value and the corresponding octanol: plasma and octanol:blood partitioning values, an estimate of the transport of the lipophilic compound by various components of blood was made: 20% is carried in hemoglobin, 53% by the plasma proteins and 27% by the water phases of the red blood cell and plasma. Octanol extraction provided a rapid method for measuring the radiochemical purity (RCP) of lipophilic [99mTc]-d,l-HM-PAO. In saline, the RCP declined with a half-life of more than 1 h. In human plasma and whole blood, the conversion of [99mTc]-d,l-HM-PAO was biexponential due to the differences in the conversion rates of the d and l isomeric forms. The initial half-life representing the conversion rate of the l form was 1.7 min in blood and 1.4 min in plasma, while the conversion half-life of the d form was 7.4 and 24.4 min, respectively. In vivo, the RCP of arterial blood sampled after an i.v. bolus injection showed an initial peak value of 75% (68-79%) during the initial, first passage of the bolus. It declined to approximately 35% (29-40%) after 1.5 min and reached very low levels (about 1%) at 6 to 10 min. Quantitative measurements of cerebral blood flow using [99mTc]-d,l-HM-PAO necessitates a rapid method for RCP determination in arterial blood such as the one described here.

Arteries↗
PubMed1987

Serial studies of cerebral blood flow using 99Tcm-HMPAO: a comparison with 133Xe.

We have compared the regional distribution of 99Tcm-HMPAO with regional cerebral blood flow (rCBF). CBF was measured by single photon emission computerized tomography (SPECT) using a TOMOMATIC 64 after 133Xe inhalation in 41 patients. With the same SPECT device the distribution of 99Tcm-HMPAO was measured after i.v. injection. High resolution (HR) and low resolution (LR) studies were performed yielding a resolution of 6 to 10 mm (HR) and 15 to 20 (LR). 99Tcm-HMPAO images showed close resemblance to xenon-133 CBF tomograms. Only about 20% of the (decay corrected) brain counts were lost during the first 24 h post injection. A slight decrease in contrast was measured comparing side-to-side asymmetry ratios from the serial studies. This loss of contrast is mainly due to back-diffusion and clearance of a part of the 99Tcm-HMPAO complex from the brain. It could be corrected for by a linearization algorithm. The slight loss of contrast will not be of any importance for the clinical use of this tracer complex.

Brain↗
PubMed1986

Biodistribution in rats of 99Tcm-labelled human serum albumin.

Three different 99Tcm-human serum albumin (HSA) preparations were simultaneously studied by high pressure liquid chromatography (HPLC) and gamma camera techniques in rats. The products contained variable amounts of 99Tcm-human albumin, 99Tcm-tin colloid and a 99Tcm-low molecular weight complex. The biological half life varied from 55 to 132 min and the bladder excretion for the first 60 min from 2 to 31%. Separated HPLC fractions of 99Tcm-albumin and 99Tcm-tin colloid both showed considerably longer biological half life when injected separately than when injected in the unfractionated preparation. A final evaluation of the quality of such products seem to require evaluation in humans.

Animals↗
PubMed1986

Evaluation of a 99Tcm bound brain scanning agent for single photon emission computed tomography.

D,L HM-PAO-99Tcm (PAO) is a lipophilic tracer complex which is avidly taken up by the brain. We have compared the regional distribution of PAO with regional cerebral blood flow (CBF). CBF was measured by single photon emission computed tomography (SPECT) by Tomomatic 64 after 133Xe inhalation in 41 patients. With the same SPECT the distribution of PAO was measured after intravenous injection. High resolution (HR) and low resolution (LR) studies were performed yielding a resolution of 6-10 mm (HR) and 15-20 mm (LR). PAO images showed close resemblance to 133Xe CBF tomograms. Only 20 per cent of the (decay corrected) brain counts were lost during 24 hours.

Brain↗
PubMed1983

Anaphylactic reaction to orthoiodohippurate.

A case of an anaphylactic reaction following administration of 125I- and 131I-o-iodohippurate in a 32-year-old woman is reported. The patient had a renography performed because of hematuria. She was known to react to an intravenous pyelography previously performed with an anaphylactic shock. The importance of reporting all adverse reactions to radiopharmaceuticals for central registration is stressed.

Adult↗
PubMed1983

Central nervous system dysfunction as early sign of neuronal ceroid lipofuscinosis (Batten's disease).

During a survey of neuronal ceroid lipofuscinosis (Batten's disease), two younger siblings of patients were found to have the characteristic vacuolation in 11 to 17 per cent of their lymphocytes. The children were four to five years of age and did not have any overt signs or symptoms of the disease. However, they both had markedly reduced auditory memory-span before decreased vision and funduscopic changes developed. The subsequent course of the disease confirmed the diagnosis. It is concluded that neuronal ceroid lipofuscinosis may affect mental functions much earlier than previously believed.

Age Factors↗
PubMed1981

Evaluation of methods for sizing of colloidal radiopharmaceuticals.

Many different quality control methods have been proposed for characterization of colloidal radiopharmaceuticals, as particle size seems to be of importance for the resulting biological distribution. Membrane filtration techniques using polycarbonate sheet filters (Nuclepore) is a simple technique. For a number of products good correlation was obtained to particle sizes measured by photon correlation spectroscopy (Nanosizer). For several preparations an increase in particle size with time was observed.

Colloids↗
PubMed1981

Reduced systolic blood pressure in fingers of patients with generalized scleroderma (acrosclerosis).

Segmental systolic blood pressure was measured on upper arm, wrist, proximal and middle pahlanx in 10 patients suffering from generalized scleroderma of the acrosclerosis type and in 5 normal. Systolic pressure was measured by the strain-gauge technique before and after abolition of sympathetic vasoconstrictor activity by local heating and by nerve block. Arm and wrist pressures were equal in the two groups, but a significant reduction in finger pressure was found in the patients. Finger pressure was unaltered after sympathetic blockade, both in the patients and in the normals. The pressure drop from wrist to finger in the patients suggests an increased flow resistance in the palmer arch and digital arteries which was probably not caused by an augmented sympathetic vasoconstrictor activity, as sympathetic blockade did not influence finger systolic pressure. Sympathectomy cannot be expected to relieve Raynaud's attacks in these patients.

Adult↗
PubMed1980

Fission MO-99/Tc-99m Generators -- a study of their performance and quality.

Five 99mTc-generators, based on fission Mo-99, from five different manufacturers were studied in April and May of 1977 -- with regard to their performance and to the quality of the eluates. The study covers types of generators not already dealt with in a previous publication [5]. One generator was overloaded with Mo-99; one generator had Tc-99m yields below 70%. One generator yielded eluates containing appreciable gamma-emitting impurities other than Mo-99. Two generators yielded eluates containing trace amounts of Al+++. The content of alpha- and pure beta-emitting nuclidic impurities (other than Tc-99) were in all cases below the limits set in the DLS 79 [2] monograph on Tc-99m pertechnetate obtained from fission Mo-99.

Drug Contamination↗
PubMed1978

Amino acid transport in human ciliary epithelium.

A statistical study of the co-variation of the concentrations of 19 amino acids and related compounds from 21 persons was performed as a factor analysis of Caq/Cpl and of Caq. Six factors explained about 83% of the observed variation. Factor 1 showed a correlation to alpha-amino-N-butyric acid, valine, methionine, isoleucine, leucine, tyrosine and phenylalanine, factor 2 to lysine, histidine, arginine and glutamine (containing serine), factor 3 to taurine and proline, factor 4 to glycine and cystine, factor 5 to urea and factor 6 to glutamic acid. Only alanine and threonine showed a correlation to different factors in the Caq/Cpl- and the Caq-matrix. This correlation of groups of substances to different and independent factors is considered to be an argument in favour of the existence of six transport systems in the ciliary epithelium for the investigated substances.

Amino Acids↗
PubMed1977

Microbial contamination of radionuclide generators.

Technetium-99m generators were grossly contaminted using 5 different strains of microorganisms. Elution of the generators showed that the number of microorganisms was reduced by a factor of 10(4)-10(6). There were no indications that the generators would support bacterial growth. It is concluded that it would be acceptable from a microbiologic point of view to omit autoclaving and membrane filtration of the final product provided that proper aseptic techniques are applied.

Bacteria↗
PubMed1976

Comparative evaluation of 99mTc-generators.

A total of 34 99mTc-generators from eight different manufactures were studied in 1974 and 1975 with regard to their performance and to the quality of the eluates. With some exceptions the generators performed well and proved their ability to act as a reliable source of 99mTc-pertechnetate. Two cases of mechanical malfunction and two cases with a low elution yield of 99mTc were observed. Four generators were overloaded with 99Mo. The 99mTc-pertechnetate did in most cases fulfil the requirements of the Nordic Pharmacopeia.

Chemical Industry↗