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Biomedical subjects

K Christiansen

Publications and source records attributed to K Christiansen.

At least 91 records · Page 5Linked to original sources
PubMed1988

Cost-efficiency of a long-acting cephalosporin agent.

In a prospective longitudinal study of patients in a general surgical ward, the relative cost-efficiencies of a long-acting third generation cephalosporin (ceftriaxone--mean plasma elimination t 1/2 390 min) and a short-acting second generation cephalosporin (cephamandole: mean plasma elimination t 1/2 32 min) were determined. The total cost of therapy for 24 h was +32.88 for cephamandole and +22.78 for ceftriaxone, that is, a reduction of 31%. Considerable cost containment can be achieved by using third generation cephalosporin agents that only require the administration of one intravenous injection per day.

Abdomen↗
PubMed1987

Mapping of sequence-specific chromatin proteins by a novel method: topoisomerase I on Tetrahymena ribosomal chromatin.

DNA derived from the 5' spacers of the rRNA genes from Tetrahymena has unusual electrophoretic properties. These properties made it possible to devise a simple electrophoretic procedure for isolating specific rDNA spacer fragments from preparations of total nuclear DNA, enabling us to study DNA modifications at the level of unfractionated nuclei. We have employed the method to study the distribution of topoisomerase I binding sites on the r-chromatin (ribosomal chromatin) of Tetrahymena at the DNA sequence level. The presence of topoisomerase I in situ was detected by its ability to introduce single-strand cleavages into DNA. The positions of the cleavages were determined on DNA sequencing gels after isolation of the fragments. Topoisomerase I binding in r-chromatin is sequence specific and cleavage is confined to a 16 base-pair conserved sequence element previously determined to be a high-affinity binding site for topoisomerase I in vitro. The high degree of sequence specificity may be of important functional significance, as we find a similar sequence specificity with enzymes isolated from five evolutionarily distant species, indicating that preference for the 16 base-pair element is an intrinsic property of eukaryotic type I topoisomerases.

Animals↗
PubMed1987

Androgen levels and components of aggressive behavior in men.

Serum concentrations of testosterone (Tser), 5 alpha-dihydrotestosterone (DHT), and free testosterone (Tsal) in saliva were determined in 117 healthy young men between the ages of 20 and 30. A battery of standardized tests and projective techniques were administered simultaneously in order to measure various components of aggression, including sexual aggressiveness. All three androgens show reliable positive correlations with self-ratings of spontaneous aggression. Dominance exhibits a positive, statistically significant correlation to Tser and to DHT. In addition, DHT is negatively related to the scale restraint of aggression. These results support previous findings about Tser and point to the importance of other androgens--especially DHT--for this aspect of endocrine-affect relationships. Interest in sexual aggression yielded no significant results for Tser and DHT (Tsal shows a low positive correlation). The ratio DHT/Tser, however, correlates significantly with this component of aggression.

Adult↗
PubMed1987

Sex hormones and cognitive functioning in men.

Blood and saliva samples were obtained from 117 healthy young men, following which radioimmunoassays were used to determine the serum concentrations of testosterone (Tser), 5 alpha-dihydrotestosterone (DHT), and the level of free testosterone (Tsal) in the saliva. The cognitive functioning was determined by five spatial and six verbal ipsative test scores, reflecting intra-individual variance in the performance of these tasks, independent of the person's general level of achievement. Within the normal physiological range of androgen levels--especially Tser and to a lesser extent DHT and Tsal--showed a significantly positive correlation with measures of spatial ability and field dependence-independence and a significantly negative correlation with measures of verbal production.

Adult↗
PubMed1986

Incorporation of cytochrome b5 into endoplasmic reticulum vesicles as protein-lysophospholipid micelles.

Cytochrome b5 is incorporated into vesicles of the endoplasmic reticulum as protein-lysophosphatidylcholine micelles. Cytochrome b5 becomes firmly bound to the membrane and at the same time lysophosphatidylcholine is acylated by acyltransferases of the endoplasmic reticulum and converted into the membrane component phosphatidylcholine. The possibility of an insertion of cytochrome b5 into the endoplasmic reticulum in vivo by this mechanism is discussed.

Carboxypeptidases↗
PubMed1986

Relations between sex hormone levels and sexual behavior in men.

Using a sample of 33 healthy young men, 6 blood samples were obtained in the course of 2 weeks, and testosterone, dihydrotestosterone, and estradiol levels determined. The amount of free testosterone in the saliva was also ascertained for 23 of the subjects. All participants kept a daily record of their sexual activity during the investigational period. An interindividual comparison revealed a significant positive correlation between serum testosterone levels and the frequency of orgasms as well as a significant negative correlation between estradiol concentrations and the frequency of sexual activity without orgasm. The comparison of hormone levels to sexual behavior, prior to and after the individual sampling, reveals significant positive correlations between the serum testosterone and the extent of the free testosterone on the one hand and both the preceding and subsequent frequency of orgasms on the other. The estradiol levels showed a significant negative correlation with both the preceding and the subsequent frequencies of sexual activity without orgasm.

Adult↗
PubMed1985

Use of carboxypeptidase Y in studies of the mode of insertion of cytochrome b5 into lipid vesicles.

Carboxypeptidase Y preparations from baker's yeast have been found to exhibit endopeptidase activity when cytochrome b5 was used as substrate. As the susceptibility of cytochrome b5 to attack by carboxypeptidase Y has been used to distinguish between two modes of insertion of cytochrome b5 into lipid bilayer, one which has the C terminal buried in the lipid bilayer and one which has a free C terminal, caution should be taken when employing carboxypeptidase Y preparations for this type of studies.

Animals↗
PubMed1985

Reconstitution of cytochrome b5 into lipid vesicles in a form which is nonsusceptible to attack by carboxypeptidase Y.

Pig liver cytochrome b5 is reconstituted into lipid vesicles by a method whereby cytochrome b5-lysophospholipid micelles are fused with liposomes. The reconstitution method inserts cytochrome b5 into the lipid bilayer in a mode which renders the C-terminal part of cytochrome b5 nonsusceptible to attack by carboxypeptidase Y. The effect of the lipid composition of the vesicles on the mode of insertion has been examined, when cytochrome b5 is reconstituted using the presently described method and methods previously used to reconstitute this protein, namely the direct incorporation method and the cholate dialysis method.

Animals↗
PubMed1985

A procedure for removal of interfering phospholipids in the separation and analysis of proteins.

A procedure for removal of phospholipids from aqueous samples is described. It is simple and rapid and can be used generally in cases where phospholipids interfere with spectrophotometric, chromatographic, electrophoretic, or other methods. The procedure is based on the hydrolysis of phospholipids by phospholipase C and removal of the formed diacylglycerol by centrifugation or extraction into an inert, apolar solvent, like petroleum ether, which does not solve or have a denaturating effect on most proteins.

Animals↗
PubMed1985

Sex hormones and stress in the human male.

Six blood samples were obtained from each of a group of 33 healthy males between the ages of 19 and 31, following which radioimmunoassays were used to determine the serum concentrations of testosterone (Tser), 5 alpha-dihydrotestosterone (DHT), and estradiol (E2). In addition, the free testosterone (Tsal) was also measured using saliva samples provided by 23 of the subjects. A questionnaire of our own design was administered together with the Sixteen Personality Factor Questionnaire (16 PF-Test) at the time of the first blood sample in order to check the long-term stress loads of our subjects as well as their abilities to deal with stress. During the investigational period, subjects kept daily records of their sleeping and working hours and noted the appearance of stressful situations. Weather data for Hamburg was also included as a variable in this study. A number of significant relationships between sex hormones and stress could be ascertained; however, it should be kept in mind that the correlation coefficients are low and explain only a small percentage of the variance between the variables. The stress variables "weather condition" and the "Q4" factor of the 16 PF-Test are significantly related to E2 (intersubject correlations). For all samples of all subjects, psychic stress correlates positively with the ratio of Tsal/Tser. There is a significant positive intersubject relationship between Tsal and long-term plus concurrent somatic stress, while somatic stressors on the day preceding a blood and saliva sample (acute somatic stress) correlate positively with Tsal and Tser.

Adult↗
PubMed1983

Reconstitution of a protein into lipid vesicles using natural detergents.

A method is described for reconstitution of a protein into lipid vesicles using one of the natural detergents lysophosphatidylcholine or lysophosphatidic acid. The intestinal microvillus enzyme, aminopeptidase N (EC 3.4.11.2) is incorporated into lipid vesicles prepared from a total lipid extract of the microvillus membrane. The method is based on fusion of aminopeptidase-lysophospholipid micelles with liposomes prepared by sonication. The incorporation of the protein into the lipid bilayer is analyzed by gel permeation chromatography and sucrose density gradient centrifugation. The coincidence of the protein and lipid profiles is used to evaluate protein incorporation. The incorporation is visualized by electron microscopy with negative staining. The method has the advantage of using natural detergents, lysophospholipids, which are minor but natural constituents of biological membranes. The method could be of value as a tool in studies of mechanisms of insertion of newly synthesized proteins into biological membranes.

Aminopeptidases↗
PubMed1982

Purification of microvillus membrane vesicles from pig small intestine by immunoadsorbent chromatography.

Microvillus membrane vesicles from pig small intestine, isolated by hypotonic lysis, Mg2+ aggregation of contaminants and differential centrifugation, have been further purified by immunoadsorbent chromatography. The vesicles adhere to an immunoadsorbent prepared by coupling antibodies raised against three of the principal proteins of the brush border membrane (aminopeptidase, sucrase-isomaltase and lactase) to Sepharose 4B. After the contaminants are removed by washing, the adherent vesicles are released from the immunoabsorbent by applying shear forces. The purity of the immunoadsorbed vesicles has been established by electron microscopy and by measuring the activity of marker enzymes. The enrichment factor is 1.17 +/- 0.02 for aminopeptidase and 0.70 +/- 0.05 for 5'-nucleotidase. The contamination of the preparation before immunoadsorption constitutes 10% of the membrane protein and consists mainly of basolateral membrane fragments as judged from marker enzyme determinations and the lipid composition.

Animals↗