PubMed Health⌕ Search

Biomedical subjects

J Karlsen

Publications and source records attributed to J Karlsen.

At least 19 recordsLinked to original sources
PubMed2006

Measurement of diffusion through calcium alginate gel matrices.

The diffusion of high molecular weight dextran samples and low molecular weight quinine sulphate in homogenous calcium alginate gel matrices was studied. An experimental design suitable for studying the diffusion of substances from or through a gel sample was established. The experimental results indicate that the different types of molecules diffuse in the gel by different mechanisms. The diffusion rate of the molecules in the gel is dependent on gel composition.

Alginates↗
PubMed2006

Preparation of a radionuclide/gel formulation for localised radiotherapy to a wide range of organs and tissues.

Localised radiotherapy by instillation of radiolabeled particles is being used to treat rheumatoid arthritis and certain tumors. Such therapy is limited to organs and tissues capable of retaining the radioactive compound until the radioactivity is sufficiently low, and the leakage to other parts of the body is no longer unacceptable. In this study, radiolabeled particles, i.e. 90Y-silica colloid particles, were encapsulated in calcium alginate gels, and the leakage of radioactivity from the gels was monitored. The purpose of the study was to develop a formulation suitable for the localised delivery of radiation therapy to a wide range of organs and tissues. An injectable gel formulation was developed, liberating only small amounts of radioactivity into the surrounding medium. The formulation is a viscous liquid at room temperature and forms a gel on heating to normal body temperature. Thus, it should be suitable for the localised delivery of radiolabeled particles to a wide range of organs and tissues. The study also includes a formulation exhibiting time-dependent gelation. However, this formulation was not found to be suitable for the purpose.

Alginates↗
PubMed2005

Nasal administration of carbamazepine using chitosan microspheres: in vitro/in vivo studies.

The nasal route is used both for local therapies and, more recently, for the systemic administration of drugs, as well as for the delivery of peptides and vaccines. In this study the nasal administration of Carbamazepine (CBZ) has been studied using microspheres constituted by chitosan hydrochloride (CH) or chitosan glutamate (CG). Blank microspheres were also prepared as a comparison. The microspheres were produced using a spray-drying technique and characterized in terms of morphology (scanning electron microscopy, SEM), drug content, particle size (laser diffraction method) and thermal behaviour (differential scanning calorimetry, DSC). In vitro drug release studies were performed in phosphate buffer (pH 7.0). In vivo tests were carried out in sheep using the microparticles containing chitosan glutamate, chosen on the basis of the results of in vitro studies. The results were compared to those obtained after the nasal administration of CBZ (raw material) alone. For the evaluation of in vivo data statistical analysis was carried out using the unpaired t-test. Spray-drying was a good technique of preparation of CBZ-loaded microspheres. The loading of the drug into the polymeric network always led to an increase in the dissolution rate compared to CBZ raw material. The microspheres obtained using chitosan glutamate had the best behaviour both in vitro and in vivo. They increased the drug concentration in the serum when compared to the nasal administration of the pure drug (Cmax 800 and 25 ng/ml for microspheres and pure drug, respectively). The results obtained indicate that the loading of CBZ in chitosan glutamate microspheres increases the amount of the drug absorbed through the nose.

Administration, Intranasal↗
PubMed1999

Toxicity of gamma irradiated liposomes. 1. In vitro interactions with blood components.

Gamma irradiation is a potential technique for sterilisation of liposome suspensions. Unfortunately, gamma irradiation may result in chemical degradation of the phospholipids and the toxicological aspects have to be considered. The effects of liposome composition and gamma irradiation on the interactions of the liposomes with the hemostatic mechanisms (hemolysis, aggregation and coagulation) were studied. Non-irradiated liposome suspensions showed no hemolysis of erythrocytes. After irradiation, up to 3.1% hemolysis was measured. Least hemolysis was observed with irradiated liposomes composed of unsaturated or charged phospholipids. The negatively charged DSPG-liposomes (both non-irradiated and irradiated) induced aggregation of platelets as observed by the spectrophotometric method. However, no aggregates were seen in the microscope or measured by the aggregometer. Negatively charged liposomes also affected the coagulation cascade where prolonged coagulation times were measured. Irradiation of the liposome suspensions resulted in even longer coagulation times. The prolonged coagulation times correlated to some extent with the measured binding and depletion of calcium from plasma by the negatively charged liposomes.

Blood Coagulation↗
PubMed1999

Toxicity of gamma irradiated liposomes. 2. In vitro effects on cells in culture.

In this study, the effects of liposome composition and gamma irradiation on their interactions with cell cultures were studied. The cytotoxicity test and the growth inhibition test clearly revealed toxic effects of liposomes composed of unsaturated phospholipids and gamma irradiation of these preparations enhanced their toxic effects. The murine fibroblast cell-line L 929 was less affected compared to the macrophage cell-line RAW 264 with a higher endocytic capacity. On the other hand, both gamma irradiated and non-irradiated liposomes composed of saturated phospholipids were non-toxic for the cells and irradiation did not affect their drug delivery properties. Hence, it seems that gamma irradiation is appropriate for sterilisation of these liposomes.

Animals↗
PubMed1997

Zeta potentials of human enamel and hydroxyapatite as measured by the Coulter DELSA 440.

The zeta potential of human enamel is of physiological importance for interactions between enamel surfaces and the surrounding aqueous medium of saliva. The zeta potentials of both enamel and hydroxyapatite (HA) have been examined previously by various techniques. In this study, we examined the zeta potential of human enamel and HA using the Coulter DELSA 440, which, by a laser, makes independent Doppler shift measurements of moving particles in an electric field at 4 different angles, providing advantages over previous techniques. The enamel and HA particles were suspended directly in different phosphate buffers, or first incubated for 2 hrs in parotid (PS) or whole saliva (HWS) and then suspended in the same buffers. The enamel and HA particles exhibited an overall net surface potential of -15 to -30 mV, depending on the buffer content. Incubation in PS and HWS gave less negative potentials of -8 to -14 mV. In our previous studies, the salivary micelle-like structures (SMSs), seen in TEM of parotid saliva, were observed to have a zeta potential of -9 mV (Rykke et al., 1996). The zeta potential determinations in this study support the concept of an adsorption of mostly SMSs to the enamel surfaces, with a change of the zeta potential of the enamel and HA toward that of the SMSs.

Adsorption↗
PubMed1995

Electrical methods for skin moisture assessment.

Skin sites on 8 test subjects were treated with moisturizers, and different electrical measuring methods were compared regarding their quality in the assessment of the induced changes in the stratum corneum hydration level. Low frequency susceptance measurements were found preferable to high frequency admittance measurements, and the advantages of monopolar measurements with the three-electrode system are described.

Adult↗
PubMed1993

Kinetics of thiamin and thiamin phosphate esters in human blood, plasma and urine after 50 mg intravenously or orally.

The concentrations of thiamin and thiamin monophosphate and diphosphate in plasma and whole blood samples were assessed in six healthy subjects for 12 h and in urine for 24 h following an IV and PO bolus dose of 50 mg thiamin HCl. Unphosphorylated thiamin increased rapidly in plasma after IV administration and then decreased to its initial value within 12 h in all but one subject; the half-life was 96 min. Thiamin mono and -diphosphate increased moderately (56%), and decreased slowly; the half-life of diphosphate was 664 min. Within 24 h, 53% of the administered dose was recovered in the urine, indicating a restricted distribution. After oral administration, the peak thiamin concentration in plasma was reached after 53 min and the concentration then had increased to 179% of its initial value. The elimination half-life was 154 min, and only 2.5% of the given dose was recovered in the urine. The relative bioavailability of thiamin was 5.3%. A moderate amount of the administered thiamin was stored in blood. Other body tissues must play an important part, therefore, in the distribution of thiamin.

Administration, Oral↗
PubMed1991

Concomitant determination of thiamin and its phosphate esters in human blood and serum by high-performance liquid chromatography.

A high-performance liquid chromatographic method for the simultaneous determination of thiamin and thiamin phosphate esters in human blood or serum has been developed. The eluent consists of acetonitrile and phosphate buffer, in the ratios 90:10 (v/v) for the elution of thiamine and 60:40 (v/v) for the phosphate esters. The four compounds are eluted within 15 min. The detection limit is 13-16 fmol. Between-assay variation is 5-11%. Samples of whole blood and serum from 30 healthy adults were analysed. The following reference values were obtained for 15 females 15 males (nM, mean +/- S.D.). In serum: thiamin, 10.9 +/- 2.9/16.9 +/- 3.3; thiamin monophosphate, 8.3 +/- 1.5/3.7 +/- 1.5. In whole blood: thiamin, 29.6 +/- 10.0/33.4 +/- 10.4; thiamin monophosphate, 9.7 +/- 2.3/10.9 +/- 5.1; thiamin diphosphate, 121 +/- 29.6/165 +/- 40.4.

Chromatography, High Pressure Liquid↗
PubMed1991

Failure to induce toxicity in lambs by administering saponins from Narthecium ossifragum.

It has been suggested that saponins produced by Narthecium ossifragum (Bog asphodel) may be the direct cause of the toxicity leading to the hepatogenous photosensitivity disease alveld seen in Norwegian lambs. Lambs fed large quantities of freeze-dried N. ossifragum did not develop alveld. Chemical investigations on the freeze-dried material and fresh N. ossifragum showed no difference in their saponin content. These results indicate that alveld is not caused solely by the saponins produced by N. ossifragum.

Animals↗
PubMed1989

Characterization of the morphological properties of welding fume particles by transmission electron microscopy and digital image analysis.

The morphological characteristics of welding fume particles have been determined using transmission electron microscopy (TEM) and automatic image analysis (AIA). Two personal samples and one background sample were collected using a new, easy to handle sampling method, during tungsten inert gas (TIG) and manual metal arc (MMA) welding on Inconel in the same shop. The collection method gave samples which were suitable for TEM and AIA. Electron micrographs were taken in a transmission electron microscope and further analyzed using an image analysis unit. Aggregates composed of many individual particles were analyzed both for the parameters of the aggregate and for the parameters of the individual particles by using an algorithm based on a grain boundary reconstruction technique. The morphological parameters allowed the welding fume's particulate matter to be divided into three types - here called small, medium, and large - with a somewhat unclear distinction between medium and large. Medium and large particles occur either as individual particles or as clusters of approximately spherical particles with average diameters of 0.07 and 0.15 microm, respectively. Small particles occur almost exclusively as long chains or lace-like structures of aggregates of particles, often in the range of 5-10 microm. The aggregates have an average projected area of 2.6 x 10-3 microm2 and are composed of several hundred individual particles.

Air Pollutants↗
PubMed1988

Obstetric behavior and ultrasonic uterine characteristics of oligomenorrheic women.

Two groups of age-, parity-, and pregnancy-matched women, viz. 78 with oligomenorrhea (A) and 78 with normal menstrual intervals (B), plus all women with regular menstruation but in whom severe Müllerian malformations had been diagnosed during the same period (C) were followed in a prospective study to detect complications, sonographic changes, and the serum oxytocinase concentration during pregnancy and labor. Among the matched groups A and B, ultrasonic scanning revealed uterine changes in 45% and 9%, respectively (p less than 0.0005) during the 2nd trimester. Among the oligomenorrheic women who had HSG, fairly mild Müllerian malformations were found in 40%. The sonographic method in these mild and moderate anomalies had its limitations, and the findings were interpreted in several cases as fibroma or contractions. Complications occurred in 51% of the group A women who carried their pregnancies to term versus 20% in group B (p less than 0.0005). Among the primiparae the complication rates were 47% and 22%, respectively (p less than 0.025). Bleeding in early pregnancy (25%), an unstable fetal lie (28%), malpresentations (14%), and premature contractions or delivery (11%) were more common in group A (p less than 0.05-0.01). On stratification of the oligomenorrheic group without or with Müllerian anomalies (A1 and A2) the overall complication rates were 55% and 73%, respectively, and 86% in group C. Mutually, these differences are not statistically different, but all differ significantly from the control group (B) (p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Studies on curcumin and curcuminoids. IX: Investigation of the photobiological activity of curcumin using bacterial indicator systems.

The dye curcumin is a natural, nontoxic food constituent. On irradiation with visible light, curcumin proves to be phototoxic for Salmonella typhimurium and Escherichia coli, even at very low concentrations. The observed phototoxicity makes curcumin a potential photosensitizing drug which might find application in the phototherapy of, for example, psoriasis, cancer, and bacterial and viral diseases.

Catechols↗
PubMed1986

Studies on curcumin and curcuminoids. VIII. Photochemical stability of curcumin.

The photodecomposition of curcumin when exposed to UV/visible radiation is studied. The main degradation products are identified. The reaction mechanisms are investigated and the order of the over-all degradation reactions and the half-lives of curcumin in different solvents and in the solid state are determined.

Catechols↗
PubMed1986

Methotrexate in infusion solutions--a stability test for the hospital pharmacy.

The stability of methotrexate solutions, subject to a freeze-thaw procedure, has been investigated. According to our results these solutions can be produced in batches in the hospital pharmacy and thawed to room temperature immediately before use without any degradation of methotrexate within the time limits given.

Chemical Phenomena↗
PubMed1981

Rapid isothermal gas--liquid chromatographic determination of tricyclic antidepressants in serum with use of a nitrogen-selective detector.

A rapid and simple gas--liquid chromatographic method suitable for routine use is described for quantitation of tricyclic antidepressants. The method can be used for quantitation of amitriptyline, nortriptyline, imipramine, desmethylimipramine, doxepin, desmethyldoxepin, clomipramine, desmethylclomipramine, trimipramine, desmethyltrimipramine and dibenzepine. The method involves one extraction with hexane--isopropyl alcohol, no derivative formation of the metabolites and chromatography using an OV-25 liquid phase which permits isothermal quantitation of the different drugs within 5--10 min. Standard curves for the different tricyclic antidepressants were linear over the concentration range tested (10--1500 micrograms/l) and the maximum coefficient of variation was 7.7%.

Antidepressive Agents, Tricyclic↗