Biomedical subjects

Viet Do

Publications and source records attributed to Viet Do.

3 recordsLinked to original sources

PubMed2003

In vivo recordings of long-term potentiation and long-term depression in the dentate gyrus of the neonatal rat.

Previous in vitro studies demonstrated that long-term potentiation (LTP) could be elicited at medial perforant path (MPP) synapses onto hippocampal granule cells in slices from 7-day-old rats. In contrast, in vivo studies suggested that LTP at perforant path synapses could not be induced until at least days 9 or 10 and then in only a small percentage of animals. Because several characteristics of the oldest granule cells are adult-like on day 7, we re-examined the possibility of eliciting LTP in 7-day-old rats in vivo. We also recorded from 8- and 9-day-old rats to further elucidate the occurrence and magnitude of LTP in neonates. With halothane anesthesia, all animals in each age group exhibited synaptic plasticity of the excitatory postsynaptic potential following high-frequency stimulation of the MPP. In 7-day-old rats, LTP was elicited in 40% of the animals and had an average magnitude of 143%. Long-term depression (LTD) alone (magnitude of 84%) was induced in 40% of the animals, while short-term potentiation (STP) alone (magnitude of 123%) was induced in 10%. STP followed by LTD was elicited in the remaining 10%. Data were similar for all ages combined. In addition, the N-methyl-d-aspartate (NMDA) antagonist (R,S)-3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) blocked the occurrence of LTP at each age and doubled the percentage of animals expressing LTD alone for all ages combined. These results demonstrate that tetanic stimulation can elicit LTP or LTD at MPP synapses in 7-day-old rats, supporting our premise that at least a portion of the dentate gyrus is functional at this early age.

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PubMed2002

Urodynamic changes at 18 months post-therapy in patients treated with external beam radiotherapy for prostate carcinoma.

PURPOSE: To quantify the effect of radiotherapy (RT) on urodynamics at 18 months post-therapy, using urodynamic study, in prostate cancer patients undergoing definitive external beam RT. METHODS AND MATERIALS: A total of 17 patients with clinically localized prostate cancer were accrued into a single-arm prospective study. Fifteen of 17 patients completed scheduled multichannel video-urodynamic study at baseline as well as 3 and 18 months after RT. Baseline quantitative urodynamic parameters were compared with those at 18 months post-RT to assess the nature and extent of urodynamic change brought about by RT. These quantitative changes were further correlated to the change in self-assessed qualitative urinary function measured by International Prostate Symptom Score (IPSS), Quality of Life assessment index (QoL), and urinary functional inquiry. RESULTS: The statistically significant quantitative changes detected by the urodynamic study at 18 months post-RT were decrease in bladder capacity and bladder volume at first sensation in both the supine and upright position, and reduction in bladder volume at desire to void in the supine position. In our cohort, the mean reduction in bladder capacity was 100 mL in the supine position and 54 mL in the upright position. No statistically significant change was observed with regard to pressure, maximum flow rate, voided volume, or postvoid residual volume. Furthermore, there was no statistically significant change in bladder compliance, bladder instability, or bladder outlet obstruction. No statistically significant change in self-assessed qualitative urological function was observed between baseline and 18 months post-RT, measured by the 3 parameters (IPSS, QoL, and urinary frequency over 24 h). CONCLUSIONS: This is the first quantitative study that prospectively evaluated the effect of RT on urodynamics in prostate cancer patients receiving definitive RT. The statistically significant changes at 18 months post-RT were reduction in bladder capacity, reduction in bladder volume at first sensation, and decrease in bladder volume at desire to void. Despite the decrease in these parameters, there was no statistically significant adverse effect of RT on bladder compliance, bladder stability, or bladder outlet flow. This observation corresponded well with no significant change in IPSS, QoL, or urinary frequency over 24 h. Furthermore, these results confirm the notion that most prostate cancer patients generally tolerate RT very well.

Aged↗

PubMed2002

NMDA receptor antagonists sustain LTP and spatial memory: active processes mediate LTP decay.

Although long-term potentiation (LTP) is long-lasting, it is not permanent and decays within weeks after its induction. Little is known about the processes underlying this decay. Here we assessed the contribution of synaptic activity to LTP decay by determining the effect of the competitive NMDA receptor antagonist CPP on the decay of perforant path-dentate LTP. CPP blocked decay over a one-week period when administered daily following the induction of LTP, and blocked decay of the late, protein-synthesis-dependent phase of LTP when administered two days after LTP induction. CPP administered for a five-day period following spatial memory training enhanced subsequent memory retention. These data suggest that LTP is normally a persistent process that is actively reversed by NMDA receptor activation, and that both the early and late phases of LTP are dynamic processes regulated by NMDA receptors. These data also support the view that LTP is involved in maintaining spatial memory.

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