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Biomedical subjects

M Mulder

Publications and source records attributed to M Mulder.

8 recordsLinked to original sources
PubMed1992

Heparan sulphate proteoglycans are involved in the lipoprotein lipase-mediated enhancement of the cellular binding of very low density and low density lipoproteins.

We found that LPL enhances the binding to HepG2 cells and fibroblasts of both VLDL and apoE free LDL. In the presence of 1.7 micrograms/ml of purified bovine LPL, the binding of LDL and VLDL was up to 60 fold increased as compared to the control binding. In addition, LPL enhances the binding in LDL-receptor negative fibroblasts to the same extent as it does in normal fibroblasts. The presence of 10 mM of EGTA could not prevent the LPL-mediated enhancement of the binding of both LDL and VLDL to fibroblasts, indicating that the binding is calcium independent. Furthermore, up- and down regulation of the LDL receptor did not influence the binding of these lipoproteins in the presence of LPL. Strikingly, we found that the enhancing effect of LPL on the binding of LDL and VLDL to HepG2 cells could be abolished by preincubation of the cells with heparinase, suggesting that heparan sulphate proteoglycans are involved in the LPL-mediated stimulation. We hypothesize that the enhancement of the cellular binding of LDL and VLDL in the presence of LPL is caused by an LPL-bridging between proteoglycans present on the plasma membrane and the lipoproteins, and that the LDL receptor and LRP are not involved.

Cell Membrane↗
PubMed1992

A model for clinical evaluation.

After grappling for years with the problems associated with clinical evaluation in nursing, and becoming increasingly aware of the importance of this aspect of the clinical teaching process, the researcher resolved to make an in-depth study of the state of clinical evaluation in nursing. The study was undertaken in the second semester of 1990. The most important findings of this research were discussed in a previous article (Mulder, M. and Viljoen, JJ. 1992. Die stand van kliniese evaluering aan Suider-Afrikaanse Universiteite. CURATIONIS, Vol. 15, No. 1, 29-41). The second aim of the study, i.e. the development of a proto-theoretical model for clinical evaluation, is discussed in this article. Since there was no existing model for Southern Africa which reflected the researcher's philosophy and view of clinical evaluation, she constructed one as an implicit part of the main recommendations of the research. This model is presented as the ideal for clinical evaluation. The model can be used by evaluators and researchers to assess, plan, implement, remedy and to solve problems of clinical evaluation. It can also be used to direct future research.

Clinical Competence↗
PubMed1992

[The status of clinical evaluation at South African universities].

The fact that clinical evaluation is a difficult and complex task of nursing education has been emphasized in the nursing literature since the early seventies. It is, nevertheless, a most important component of the teaching-learning process of nursing students and it has definite advantages. It: contributes to the improvement of the standard of nursing care; helps to identify problem areas for research; and contributes to high level professional preparation. In the light of these factors the aims of the study were to: determine and describe the position of clinical evaluation as a component of the teaching of undergraduate students in departments of nursing at universities in Southern Africa; draw up a proto-theoretical model for clinical evaluation. The second aim will be fully discussed in a follow-up article. The empirical data showed that nursing educationists in Southern Africa are not entirely up to standard regarding the skills required for clinical evaluation.

Clinical Competence↗
PubMed1991

The binding of human lipoprotein lipase treated VLDL by the human hepatoma cell line HepG2.

It has been suggested that besides the LDL-receptor, hepatocytes possess an apo E or remnant receptor. To evaluate which hepatic lipoprotein receptor is involved in VLDL remnant catabolism, we studied the binding of VLDL remnants to HepG2 cells. Native VLDL was obtained from type IIb hyperlipidemic patients and treated with bovine milk lipoprotein lipase (LPL). This LPL-treated VLDL (LPL-VLDL) was used as representative for VLDL remnants. Our results show that LPL-VLDL binds with high affinity to HepG2 cells. Competition experiments showed that the binding of 125I-labelled LPL-VLDL is inhibited to about 30% of the control value by the simultaneous addition of an excess of either unlabelled LDL or LPL-VLDL. Preincubation of HepG2 cells with LDL resulted in a reduction of the binding of LDL and LPL-VLDL to 34 and 55% of the control value, whereas preincubation of the cells with heavy HDL (density between 1.16 and 1.21 g/ml) stimulated the binding of LDL and LPL-VLDL to about 230% of the control value. Preincubation of the cells with insulin (250 nM/l) also stimulated the binding of both LDL and LPL-VLDL (175 and 143% of the control value, respectively). We conclude that LPL-VLDL binds to the LDL-receptor of HepG2 cells and that no evidence has been obtained for the presence on HepG2 cells of an additional receptor that is involved in the binding of VLDL remnants.

Binding, Competitive↗
PubMed1991

Positive regulation of jun/AP-1 by E1A.

Proteins encoded by the adenovirus E1A oncogene are capable of positive and negative transcriptional regulation of both viral and cellular genes. E1A regulatory function is commonly thought to involve modifications of specific cellular factors that interact with responsive promoters. In this report we present evidence that E1A induces the activity of the jun/AP-1 transcription factor in three different cell types: P19, JEG-3, and HeLa. AP-1 binds to 12-O-tetradecanoylphorbol-13-acetate (TPA)-responsive elements (TREs); therefore, E1A might modulate a specific signal transduction pathway normally induced by activation of the protein kinase C. Binding of jun/AP-1 to a TRE is induced in all cell types studied when E1A is expressed. We observe that the expression of endogenous c-jun and jun B genes is induced by E1A, which directly transactivates the promoters of c-fos, c-jun, and jun B. Similar inducibility is obtained by treatment with retinoic acid and differentiation of P19-embryonal carcinoma cells. The E1A 13S product transactivates TRE sequences and cooperates with c-jun in the transcriptional stimulation. The 12S E1A product does not activate a TRE sequence, but cotransfection with c-jun circumvents this lack of stimulation. Coexpression of c-fos and E1A 12S, however, blocks the transactivation by c-jun, suggesting an important role for fos in determining the dominance of the 12S or 13S protein.

Adenovirus Early Proteins↗
PubMed1990

Components of Stroop-like interference in word reading.

Previous research has shown that the naming of the picture of, for example, a guitar is substantially delayed when it is accompanied by the name of an object from the same semantic category (e.g., piano) as compared to a nonword control (e.g., xxxxx). La Heij (1988a) has shown that a large part of this Stroop-like interference effect can be attributed to two semantic characteristics of the distractor word: its semantic similarity to the target picture and its semantic relevance in the task at hand. Furthermore, it was argued that the locus of these two interference effects is the process of target-name retrieval. If this is true, semantic interference effects should diminish or disappear when, instead of a picture-naming task, a word-reading task is used. In the present study this prediction is tested. The effects of four distractor characteristics are examined: semantic relatedness, semantic relevance, response set membership and wordness. In contrast to the original picture-naming task only the effect of wordness reached significance. The results of experiments 2 and 3 show that the absence of significant semantic context effects in experiment 1 is not simply due to the fact that a distractor word has less time to affect a word-reading response. The results are taken to support a name-retrieval account of semantic interference in color and picture naming.

Adult↗
PubMed1978

Non-electrolyte permeability as a tool for studying membrane fluidity.

1. The reflection coefficient for the permeation of thiourea through bilayers of phosphatidylcholine is a function of the fatty-acid composition of the lipid molecules. By means of these reflection coefficients an index for membrane fluidity has been given to each of those lipids, relative to that of egg phosphatidylcholine. 2. The maximum number of water molecules that can copermeate with each molecule of solute by means of solute-solvent interaction is a function of the packing of the lipid molecules in the bilayer. This parameter has been used in this paper for characterizing the fluidity of cholesterol-containing membranes and for membranes with their lipids in the gel state.

Chemical Phenomena↗