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Biomedical subjects

R Karlsson

Publications and source records attributed to R Karlsson.

At least 109 records · Page 6Linked to original sources
PubMed1981

On the ultrastructural organization of the microfilament system and the possible role of profilactin.

This paper summarizes results of studies on human glia cells concerning the ultrastructural relationships in the microfilament system and the possible role of the profilactin complex. It presents electron micrographs of the leading lamella of cells grown on solid substratum, visualizing the organization of the microfilament system in this highly motile part of the cell at high resolution and at what appears to be a high level of preservation. These results are linked to observations made in our laboratory of the biochemical basis for the dramatic rearrangements occurring in platelets in response to thrombin stimulation. Taken together these results lead to a relatively detailed model for the mechanism of cell motility.

Actins↗
PubMed1980

Visualization of the peripheral weave of microfilaments in glia cells.

A peripheral weave of microfilaments is visualized in human glia cells. In this weave small numbers of microfilaments converge to structures in the cell edge. Similar assemblies of microfilaments seem to be attached to structures on the surface of microspikes. Together with filaments splaying from the paracrystalline arrangement in microspikes, these units make up the peripheral weave. The filaments of the weave come in close contact with each other and with filaments of internal actin fibres.

Actins↗
PubMed1980

Three-dimensional observations of red blood cell deformation in capillaries.

The shape changes of red blood cells (RBCs) flowing in narrow glass capillaries have been studied by the use of two microscopes viewing the cells simultaneously at right angles along a horizontal and a vertical optical axis. The observations show that the primary mode of deformation of RBCs in a narrow capillary is a folding or bending about the longitudinal axis of the capillary rather than a compression and extension of the cells in the plane of the original disk, which has been suggested previously [10].

Capillaries↗
PubMed1979

Use of an enzyme thermistor in continuous measurements and enzyme reactor control.

The enzyme thermistor measures the heat produced by the action of an immobilized enzyme on a substrate present in the sample. Its application in analysis of discrete samples, e.g., in clinical chemistry, is well documented, but it has not been used so far for continuous measurements. We decribe here the application of the enzyme thermistor for continuous monitoring and control of enzyme reactors. An enzyme thermistor filled with coimmobilized glucose oxidase and catalase was used to measure the amount of glucose in the outflow from a column reactor containing immobilized lactase acting on a lactose solution pumped through the reactor. The lactose conversion was kept on a constant level, irrespective of the actual enzymatic activity in the reactor, by regulating the flow through the reactor. The experiments were carried out with aqueous solutions of lactose as well as with whey from cow's milk.

Calorimetry↗
PubMed1978

Effect of a field program based on systematic plaque control on caries and gingivitis in schoolchildren after 3 years.

The effect of a field program, based on systematic plaque control, on caries and gingivitis was tested during a 3-year period on 1,100 schoolchildren. Once every 3rd week the children were given oral hygiene instructions, professional toothcleaning and fluorides topically delivered by specially trained dental nurses. The children of a control group of approximately the same number of pupils, participated in a preventive program consisting of mouthrinsings once every 2nd week with a 0.2% sodium fluoride solution. The children of the third and fourth grades were, at the start of the experiment, selected as reference groups and then continuously examined once every year. At the end of the trial the mean reduction of surfaces haboring plaque and units with gingival inflammation was 59% and 73%, respectively. The reduction in caries increment was 51%.

Adolescent↗
PubMed1976

Chemical studies of marine invertebrates. XVI. Structure and absolute configuration of lobosterol, a novel polyoxygenated sterol from the alcyonacean Lobophytum pauciflorum (clelenterata, octocorallia).

Lobosterol [(24S)-24-methylcholestane-3beta,4beta,5beta,25-tetrol-6-one 25 monoacetate] has been isolated from the Alcyonacean Lobophytum pauciflorum. The structural elucidation of this novel polyoxygenated sterol was achieved by chemical and spectroscopic evidence, and by X-ray diffraction analysis.

Acetylation↗
PubMed1975

The smoking habits of men with intermittent claudication.

Smoking habits among 54 male patients with intermittent claudication (IC) and 200 healthy 50-year-old men from the same county have been studied. The prevalence of smokers at the age of 50 was 98% among the IC patients against 46% among the healthy controls. The percentage of heavy smokers and the total tobacco consumptiion were not significantly different in the two groups. However, the percentage of smokers who began to smoke before the age of 15 was significantly higher in IC patients than in the healthy group, 28% to 7%.

Adult↗
PubMedDate not supplied

Affinity analysis of non-steady-state data obtained under mass transport limited conditions using BIAcore technology.

Binding data obtained with Biacore instrumentation is often evaluated using a kinetic transport model where reaction rate constants and a mass transport coefficient are used to describe the interaction. Here the use of a simplified model, an affinity transport model, for determination of the affinity (K(D)) but not the kinetics (k(a), k(d)) has been investigated. When binding rates were highly governed by mass transport effects the two models returned the same affinity and gave similar residuals, but k(a) and k(d) values found with the kinetic transport model were unreliable. On the other hand the affinity transport model failed to describe the data when binding curves were less influenced by mass transport effects. Under such circumstances the kinetic transport model returned correct k(a) and k(d) values. Depending on the outcome of the analysis the affinity transport model can therefore be used to reduce uncertainties of the kinetic parameters or as an easy way to determine K(D) values from non-steady-state data. The use of the affinity transport model is illustrated with simulated data and with binding data obtained for the interaction between a 439 Da thrombin inhibitor and immobilized thrombin. Since it is more difficult to resolve high k(a) values for low molecular weight analytes, the affinity transport model may be particularly useful for affinity analysis involving fast reactions between such analytes and immobilized protein targets.

Antithrombins↗
PubMedDate not supplied

Detection of antigen-antibody interactions by surface plasmon resonance. Application to epitope mapping.

Surface plasmon resonance (SPR) detection requires no labeling of antigen or antibodies and allows quantification of two or more interacting molecular species. The automated SPR instrument used here consists of an optical detection unit, an integrated liquid handling unit, and an autosampler. A first molecule is immobilized to the dextran modified surface of the sensor chip. By sequential introduction, the stepwise formation of multimolecular complexes can then be monitored. A two-site binding assay which allows characterization of MoAb epitope specificities is described. A polyclonal rabbit anti-mouse IgG1 (RAMG1) immobilized to the dextran surface is used to capture the first MoAb from unprocessed hybridoma culture supernatants. After introducing the antigen, the ability of a second MoAb to bind to the antigen is tested. The analysis cycle which is fully automated can be performed more than 100 times using the same RAMG1 surface. Since the detection principle allows monitoring of each reactant in the consecutive formation of a multimolecular complex, multi-site binding experiments can be performed. Five MoAbs recognizing different epitopes on an antigen were shown to bind sequentially, forming a hexamolecular complex. MoAbs were further characterized by inhibition analysis using synthetic peptides derived from the primary structure of their antigen. As a model system MoAbs against recombinant HIV-1 core protein p24 were used in all experiments.

Amino Acid Sequence↗
PubMedDate not supplied

Kinetic analysis of the interaction between protein A domain variants and human Fc using plasmon resonance detection.

A real-time biospecific interaction analysis (BIA) was performed to study the specific interaction between the Fc portion of human immunoglobulin G1 (Fc1) and a one domain analogue (designated Z) of staphylococcal protein A, in monovalent (Z) and divalent (ZZ) forms, and five different single amino acid substituted Z variants (L17D, N28A, F30A, I31A, K35A). Experimental BIA data were used to calculate association rate constants (kon), dissociation rate constants (koff) and affinity constants (Kaff). The divalent form (ZZ) showed a higher affinity for Fc1 mainly because of a slower off rate. Out of the five mutant Z proteins, four (L17D, N28A, I31A, K35A) showed a decreased affinity to Fc1 compared to the parent Z molecule. Surprisingly, two (L17D, I31A) of these four had the major effect of a decreased binding energy as a lowered kon while the other two (N28A, K35A) mutant proteins showed an increased koff as the major kinetic difference from Z in their binding to Fc1. For five of the six different Z variants, as well as for the ZZ molecule, calculated Kaff and calculated differences in binding free energies relative to the parent Z molecule (delta delta G), are in good agreement with the corresponding values obtained in a competitive displacement assay using radioactively labeled Z as a tracer (Cedergren et al., (1993) Prot. Eng. 6, 441-448). However, the I31A variant, with a measured kon that was more than three orders of magnitude lower than that of Z in the BIA assay, showed a significantly weaker affinity to Fc1 when calculated from the BIA data compared to the competitive displacement assay. The discrepancy between these two methods for Z(I31A) is discussed as well as possible explanations for the unexpected large effect of lowered kon for two of the mutant Z proteins.

Amino Acid Sequence↗
PubMedDate not supplied

Conformational diversity of catalytic cores of protein kinases.

X-ray crystallography of the protein kinase family has provided an impressive array of crystal structures, setting the stage for rational design of specific inhibitors of these vitally important regulators of the signaling pathways of the cell. Initial work on the first crystal structure of a protein kinase, cyclic AMP-dependent protein kinase, has provided evidence of conformational changes suggested to be critical for the common catalytic event of transferring the gamma phosphate from ATP onto the targeted protein. This review updates the current status of the extent of conformational diversity of the protein kinase family and suggests that both the nature and the extent of those changes can provide a rationale for the increased occurrence of specific protein kinase inhibitors targeted at the ATP-binding site. It focuses on the fact that in addition to the sequence diversities in ATP binding clefts reported recently, there is conformational diversity in the beta sheets of the upper domains of the catalytic cores. This difference is directly related to the regulation of kinases by multiple mechanisms.

Animals↗
PubMedDate not supplied

Lifetime number of partners as the only independent risk factor for human papillomavirus infection: a population-based study.

BACKGROUND AND OBJECTIVES: Previous studies of relationships between genital human papillomavirus infection and tentative risk factors have yielded conflicting results, possibly because of inaccuracy of the viral detection methods used and differences in selection criteria. GOAL OF THIS STUDY: To determine human papillomavirus prevalence and identify risk factors in a group of young Swedish women. STUDY DESIGN: This was a population-based study involving completion of a structured questionnaire, analysis of cervical scrapings for human papillomavirus and Chlamydia trachomatis, and serologic tests for C. trachomatis and herpes simplex virus antibodies. RESULTS: The prevalence of human papillomavirus infection was 22% among the sexually active women and 4% among the virgins. A number of factors were associated with human papillomavirus prevalence in univariate analysis, but logistic regression analysis showed that lifetime number of male sexual partners was the only independent risk factor for human papillomavirus infection (adjusted odds ratio, 7.45; 95% CI, 2.79-19.92 for six or more partners vs. one partner). CONCLUSION: Human papillomavirus infection is a prevalent sexually transmitted disease among young Swedish women, and the lifetime number of male sexual partners is a major risk factor.

Adult↗