Biomedical subjects

S Voelkel

Publications and source records attributed to S Voelkel.

4 recordsLinked to original sources

PubMed1998

Estradiol as an antioxidant: incompatible with its physiological concentrations and function.

Estradiol has been documented to inhibit the oxidation of low density lipoprotein (LDL). We show that physiological concentrations of estradiol do not inhibit the oxidation of LDL by copper. LDL samples isolated from a) premenopausal and postmenopausal women and from b) women at different time periods during their menstrual cycle, who differ vastly in plasma estradiol levels, were also oxidized at the same rates by copper. In contrast, LDL samples isolated from c) women who were hyperstimulated during in vitro fertilization (IVF), with estradiol concentrations above 2000 pg/ml, were resistant to oxidation by copper. However, these LDL samples were also oxidized at a higher rate by peroxidases. More importantly, subjects with high estradiol levels also showed an increase in myeloperoxidase (MPO) protein in the plasma. Based on these results, we conclude that at physiologic concentrations, it is unlikely that estradiol could act as an antioxidant. In fact, the ability of estradiol to induce MPO and become a prooxidant might instead suggest that MPO-mediated oxidative clearance of LDL from plasma by liver might favorably influence the outcome of atherosclerosis.

Adult↗

PubMed1997

The micro-robotic laboratory: optical trapping and scissing for the biologist.

With the addition of tightly focused laser beams, microscopes have been turned into elaborate preparative tools that permit not only allow detailed observation of a specimen but also the capture, displacement, and microdissection of biological samples in vitro with astonishing ease and accuracy. Laser-Tweezers are used to capture and manipulate cells and organelles. LaserScissors are used to perform microdissections at the submicrometer level. After a short technical description of the instrumentation and its principles of operation, several examples of applications are given relevant to the field of clinical research that could only be achieved using such modern technology. For instance, LaserTweezers and LaserScissors offer a unprecedented means to study the immune response to cancer, to control the growth of nerve cells, or expand the significance of assisted reproductive technologies. It is suggested that newly developing procedures and assays using laser-assisted technologies will prove beneficial for future clinical laboratory testing.

Animals↗

PubMed1995

Management aspects of induced twinning in beef suckler cows using in vitro fertilised embryos.

Twin and single pregnancies were induced in two groups of oestrus-synchronised beef cows by using a combination of artificial insemination and the transfer of in vitro fertilised (IVF) embryos. Single IVF embryos transferred non-surgically to the uterine horn contralateral to the corpus luteum of 43 previously inseminated cows resulted in a calving rate of 72 per cent with a twinning rate of 38.7 per cent. In 45 cows, two IVF embryos were transferred non-surgically to one uterine horn resulting in a calving rate of 51.1 per cent with a twinning rate of 39.1 per cent. The median gestation length for cows bearing twins was 10 days shorter than that of cows bearing single calves (P < 0.001). The proportions of cows that received assistance at calving were similar for twin and single births (57 per cent vs 45 per cent, P > 0.05), but the incidence of retained fetal membranes was much higher after the birth of twins (62 per cent vs 3 per cent, P < 0.001). Nineteen per cent of twin calves were stillborn compared with 6 per cent of single calves (P > 0.05). The median birthweight of the twin calves was 32 kg (68 per cent of the median weight of single calves). The nutrition of twin-bearing cows in late pregnancy was adequate when assessed in terms of their plasma glucose, non-esterified fatty acid and beta-hydroxybutyrate concentrations. Serum immunoglobulin concentrations were similar in single and twin calves suggesting that the passive transfer of antibody was not compromised in the twin calves.

Animal Nutritional Physiological Phenomena↗

PubMed1994

Optical manipulations of human gametes.

Optical manipulations of human gametes are described indicating their potential for use in in vitro fertilization and preimplantation-assisted zona pellucida hatching. Successful manipulations are demonstrated using focused laser beams in association with microscopy. The micromanipulation and selection of male gametes were achieved using an optical-trapping infrared laser diode. The opening of the zona pellucida surrounding the egg (assisted hatching) was performed using a pulsed, nitrogen-pumped dye laser. Clinical applications for laser-assisted reproduction techniques are discussed.

Female↗