Biomedical subjects

N Lourens

Publications and source records attributed to N Lourens.

3 recordsLinked to original sources

PubMed1998

Two roles for caveolae in the cardiac myocyte?

The presence of caveolae in many cell types including heart myocytes is well established. It is hypothesized that caveolae may play a role in the storing of excess Ca2+ and may be instrumental in Ca2+ transients during contraction and relaxation in pathological conditions. Furthermore, the presence of substances in caveolae and in their membranes may imply a role in the importing and exporting of key molecules under physiological and pathological conditions. Secretory activity is also suggested by an electron micrograph of rat heart muscle.

Animals↗

PubMed1995

Characterization of mucus glycoproteins in the intestinal mucosa of the African elephant (Loxodonta africana) following lectin histochemistry.

The glycoproteins of the small intestines, caecum and colon of three adult elephants and one recently weaned elephant calf were examined by means of lectin histochemistry. Tissue sections were histochemically stained with peroxidase-labelled concanavalin A (Con A), asparagus-pea (TPA), peanut (PNA) and wheat-germ (WGA) lectins. Con A and TPA showed no binding activity in the intestinal tract of the adult elephants or the duodenum and ileum of the elephant calf, but did show a small amount of binding activity in the caecum and colon of the calf. WGA bound very intensely throughout the intestinal tracts of the adults and of the calf--especially with the goblet cells located in the crypts of Lieberkuhn and the glands of Brunner--decreasing in intensity towards the luminal surface of the intestinal tract. PNA stained the glands of Brunner of the duodenum faintly and the goblet cells of the ileum moderately, with no staining of the caecum and faint staining of the colon. These results show the distribution of Con A-, WGA-, PNA- and TPA-binding sites, and the changes that take place in the type of glycoprotein secreted after a change in the diet of the animal.

Animals↗

PubMed1994

Electron microscopic study of human sperm membrane isolation.

OBJECT: Our purpose was to isolated pure, homogeneous human sperm membranes, free of cellular contaminants. METHODS: Donor semen samples collected after masturbation were stored at -70 degrees C and eventually pooled. Each attempt at sperm membrane isolation required 800 x 10(6) spermatozoa which were sonicated by ultrasound (40% output; Vibra Cell). The effect of sonication time (3 x 5, 3 x 15, and 180 sec) on membrane isolation was investigated. Sonicated samples were centrifuged (500 g, 5 min) and the supernatant was pipetted off. The supernatant of the centrifuged sample was layered on either a sucrose cushion (supernatant on 1.6 M sucrose) or a discontinuous sucrose gradient and centrifuged (100,000 g, 1 hr). Contents of supernatants of sonicated samples and fractions (sucrose interfaces) were then fixed in 1.0% tannic acid and 2.5% buffered glutaraldehyde and examined electron microscopically using standard procedures. RESULTS: (1) The optimal sonification time was found to be 3 x 15 sec. (2) Membrane isolation using a sucrose cushion was found to be inadequate, showing significant cellular contamination. (3) Sperm membrane isolation from the sucrose interface between 0.75 and 1.05 M sucrose was found to be most effective. CONCLUSION: The advantage of this method is its simplicity. The drawback of this method is the large number of spermatozoa required for membrane purification.

Cell Fractionation↗