It is known that guidance cues play important roles in neuronal outgrowth and axonal path-finding. These guidance cues, when bound to the receptors on nerve growth cones, trigger a series of signal transduction pathways that result in dynamic rearrangement of cytoskeleton in neuronal cells. Although enormous studies have been suggested that intracellular calcium concentration is crucial in regulation of neurite outgrowth and cytoskeleton rearrangement, the precise molecular mechanism underlying growth cone guidance is not well understood. The aim of our studies is to set up an evaluation system, growth cone turning assay, which is suitable and reproducible for exploration of the molecular mechanism of guidance cue-induced growth cone turning. The 1-day-old cultured spinal neurons of Xenopus laevis and the approved attractive guidance cue, cAMP, were used in our growth cone turning assay. We evaluate the effects of neuronal developmental stage, size of pressure, frequency and duration in cAMP-induced growth cone turning. We found application of cAMP with a pressure of 2 Hz in frequency and 20 ms in duration can elicit a reliable growth cone attractive response in cultured spinal motoneurons with 14~18 hours in age. Depletion of intracellular calcium store with thapsigargin in calcium-free Ringer could significantly abolish cAMP-induced growth cone turning. The cAMP-induced growth cone turning was not blunted when calcium was omitted from extracellular fluid or bath application of calcium channel inhibitor suggesting calcium influx is not responsible for the growth cone attractive effect of cAMP. Application of membrane-permeable inhibitors of ryanodine receptors but not inositol 1,4,5-trisphosphate (IP3) effectively occluded the attractive effect elicited by cAMP. The cAMP-induced growth cone turning was unapparent under the presence of Li+, a blocker of IP3 formation. It has been suggest besides block IP3 formation, Li+ is also involved in modulation of several signaling pathways including GSK3-£] dependent signaling. However, bath application of GSK3-£] inhibitor has no significant effect on cAMP-induced growth cone turning. Taken together, our results suggest ryanodine-mobilized intracellular Ca2+ store play a major role in cAMP-induced growth cone turning. Moreover, our result on surveying various embryonic stage, drug application protocol also establish a good condition for neuronal growth cone turning assay, which can be used in exploring the molecular mechanism of growth cone path-finding.

Recent research has shown an association between low dietary calcium intake and obesity in adults as well as overweight in young children; however, this relationship has not been investigated in adolescents. The purpose of this study was to examine the relationship between inadequate calcium intake and overweight in adolescents. The hypothesis of this study was that there is a negative correlation between dietary calcium intake and overweight in adolescents. The study population consisted of middle school and high school students (n = 102) in a local school district. The gender and ethnic distributions of the sample were as follows: 74% female, 26% male, 63% Caucasian, 16% African-American, 12% Hispanic, and 8% other. Dietary calcium and energy intakes were assessed using a previously validated calcium-focused food frequency questionnaire (FFQ) for youths. Calcium intake was also assessed using a single question on daily milk consumption. The FFQ was administered by trained interviewers to groups of three to five students. Body fat was assessed using body mass index for age (BMI-for-age) and sum of triceps and subscapular skinfolds (STS). The mean reported calcium intake was 1,972 ± 912 mg/day, and mean reported energy intake was 3,421 ± 1,710 kcals/day. Reported calcium intake from the FFQ was inflated since approximately 75% reported drinking less than three glasses of milk a day. According to BMI-for-age, 29% were classified as at risk of overweight or overweight. Using STS, 39% were classified as overweight. Chi-square analysis using either method of dietary calcium intake and either method of overweight assessment did not show dependence between categories of calcium intake and level of weight or body fat. This study failed to show a relationship between dietary calcium intake and risk of overweight or overweight in adolescents.

Activation of a5??1 integrin potentiates L-type calcium current in vascular smooth muscle, which is partly mediated by tyrosine phoshorylation of the a1c channel subunit. Expressed rabbit VSM and neuronal isoforms are also potentiated by a5??1 integrin activation and require dual phosphorylation of a1c by PKA and c-Src. To explore common mechanisms of regulation by a5??1 integrin, whole cell patch clamp experiments were used to investigate the effects of a5??1 integrin antibody on expressed cardiac calcium channels. In HEK cells transfected with a1c, ??2a and a2-d1 subunits alone, currents increased 1.8 ?? 2.0 fold on application of a5??1 antibody. The potentiation was almost completely abolished on the application of PKI, a highly specific Protein Kinase A (PKA) inhibitor. The expressed currents increased 2.0 ?? 2.2 fold on application of PKA activator 8-Br-cAMP, and abolished by PKI. Our results suggest that regulation of L-type calcium channels by a5??1 integrin is a general mechanism shared by VSM, neuronal and cardiac channels. However, in the cardiac isoform, only PKA phosphorylation is involved.

Academic dissertation--Department of physical chemistry--Åbo akademi University, 2004. / Bibliogr. p. 61-64.

Thèse doctorat : Génie des Matériaux : INSA LYON : 2003. Thèse doctorat : Génie des Matériaux : Ecole Mohammadia d'ingénieurs, Rabat : 2003. / Thèse soutenue en co-tutelle. Titre provenant de l'écran-titre. Bibliogr. p. 105-119.

Thesis (M. Med. Sc.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 68-72).

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 214-219). Available also in a digital version from Dissertation Abstracts.

Thesis (M.S.) in Food Science and Human Nutrition--University of Maine, 2002. / Includes vita. Includes bibliographical references (leaves 32-34).

Thesis (M. Sc.)--University of Hong Kong, 1973. / Typewritten.

Thesis (M. Sc.)--University of Hong Kong, 1969. / Typewritten.