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Biomedical subjects

M Lieberman

Publications and source records attributed to M Lieberman.

250 records · Page 14Linked to original sources
PubMedDate not supplied

Na+/K+ pump inhibition induces cell shrinkage in cultured chick cardiac myocytes.

Myocardial cell swelling occurs in ischemia and in reperfusion injury before the onset of irreversible injury. Swelling has been attributed to failure of the Na+/K+ pump and the accumulation of intracellular Na+. To evaluate the role of the pump-leak model of cell volume maintenance, short term changes in cell volume in response to Na+/K+ pump inhibition were studied in aggregates of cultured embryonic chick cardiac myocytes using optical and biochemical methods. Exposure to 100 microM ouabain over 20 min induced cell shrinkage of approximately 10%. Cell water was also decreased by Na+/K+ pump inhibition; incubation for 1 hr either in the presence of 100 microM ouabain or in K(+)-free solution reduced cell water by 18.4% and 28.4% respectively. When exposed to ouabain in the absence of extracellular Ca2+, the aggregates swelled by approximately 15%, indicating that extracellular Ca2+ was required for the ouabain-induced shrinkage to occur. Ouabain still caused shrinkage, however, in the presence of the Ca2+ channel blockers verapamil (10 microM) and nifedipine (10 microM), suggesting that Na+/Ca2+ exchange, rather than Ca2+ channels, is the route for Ca2+ influx during Na+/K+ pump inhibition. Efflux of amino acids (taurine, aspartate, glutamate, glycine and alanine) from confluent monolayers of chick heart cells exposed to ouabain for 20 min was nearly double that observed in control solution. These results suggest that, during Na+/K+ pump inhibition, chick heart cells can limit accumulation of intracellular sodium by means of Na+/Ca2+ exchange, and that a rise in intracellular [Ca2+], also mediated by Na+/Ca2+ exchange, promotes the loss of amino acids and ions to cause cell shrinkage. Therefore, swelling during ischemic injury may not result from Na+/K+ pump failure alone, but may reflect the exhaustion of alternative volume regulatory transport mechanisms.

Amino Acids↗
PubMedDate not supplied

Scanning tunneling microscopy and spectroscopy investigations of QCA molecules.

Quantum-dot cellular automata (QCA), a computation paradigm based on the Coulomb interactions between neighboring cells. The key idea is to represent binary information, not by the state of a current switch (transistor), but rather by the configuration of charge in a bistable cell. In its molecular realization, the QCA cell can be a single molecule. QCA is ideally suited for molecular implementation since it exploits the molecule's ability to contain charge, and does not rely on any current flow between the molecules. We have examined using an UHV-STM some of the QCA molecules like silicon phthalocyanines and Fe-Ru complexes on Au (111) and Si (111) surfaces, which are suitable candidates for the molecular QCA approach.

Journal Article↗
PubMedDate not supplied

Developmental patterns in security of attachment to mother and father in late childhood and early adolescence: associations with peer relations.

This study examined developmental differences in two dimensions of attachment security (parental availability and child dependency on parents) in late childhood (N = 274) and early adolescence (N = 267) and their association with peer relations. Children's perceptions of mother's availability and boys' perceptions of father's availability did not differ as a function of age. Dependency on parents, however, decreased with age. Findings highlight the importance of distinguishing between parental availability and reliance on parental help when measuring attachment developmentally. Children's reports of positive friendship qualities and lack of conflict in their best friendships were related to attachment to both mother and father, whereas the presence of a reciprocated friendship and popularity were not. Father availability was a particularly important predictor of lower conflict with best friends. Findings indicate that the quality of parent-child attachment generalizes primarily to the quality of children's close peer relations.

Adolescent↗
PubMedDate not supplied

Electrophysiological properties of rat heart cells in vitro and in tissue culture.

Some electrical properties of right ventricles of neonatal rats and of aggregates from collagenase-dissociated cells from the same tissue are compared. The duration of the action potential does not change upon changing the stimulation frequency both in ventricles and aggregates; a decrease in temperature increases duration in both preparations to the same extent. The take-off potential and the maximal rate of rise of the action potential decrease in the same way in both preparations, while the time course of these changes is also comparable. It is concluded that the dissociation and aggregation procedure does not interfere with the membrane properties upon which the measured parameters are based; thus, aggregates are well suited for a realistic voltage-clamp analysis.

Action Potentials↗
PubMedDate not supplied

Timing of orthodontic tooth movement in a case with traumatized and avulsed anterior teeth.

A traumatic injury to a patient undergoing orthodontic treatment resulted in avulsion, dislodgement, and fracture of upper anterior teeth. Deciding when to institute endodontic treatment and when to resume orthodontic treatment was based upon minimizing the changes for ankyloses and root resorption. Endodontic treatment was carried out two weeks after trauma, and orthodontic treatment continued three weeks after trauma. Radiographs taken six months, one year, and two years after orthodontic completion showed progressive root resorption to the avulsed tooth and minimum root resorption to the remaining anterior teeth.

Adolescent↗