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Biomedical subjects

D Jeon

Publications and source records attributed to D Jeon.

12 recordsLinked to original sources
PubMed2006

Impaired long-term memory and long-term potentiation in N-type Ca2+ channel-deficient mice.

Voltage-dependent N-type Ca(2+) channels, along with the P/Q-type, have a crucial role in controlling the release of neurotransmitters or neuromodulators at presynaptic terminals. However, their role in hippocampus-dependent learning and memory has never been examined. Here, we investigated hippocampus-dependent learning and memory and synaptic plasticity at hippocampal CA3-CA1 synapses in mice deficient for the alpha(1B) subunit of N-type Ca(2+) channels. The mutant mice exhibited impaired learning and memory in the Morris water maze and the social transmission of food preference tasks. In particular, long-term memory was impaired in the mutant mice. Interestingly, among activity-dependent long-lasting synaptic changes, theta burst- or 200-Hz-stimulation-induced long-term potentiation (LTP) was decreased in the mutant, compared with the wild-type mice. This type of LTP is known to require brain-derived neurotrophic factor (BDNF). It was found that both BDNF-induced potentiation of field excitatory postsynaptic potentials and facilitation of the frequency of miniature excitatory postsynaptic currents (mEPSCs) were reduced in the mutant. Taken together, these results demonstrate that N-type Ca(2+) channels are required for hippocampus-dependent learning and memory, and certain forms of LTP.

Analysis of Variance↗
PubMed2002

Anisotropic free-energy limit of halos in high-intensity accelerators.

We study halo emittance growth in anisotropic beams and show that the rms emittance growth resulting from mismatch is highly anisotropic, depending on the tune ratio. We find that the free-energy limit calculated by Reiser [J. Appl. Phys. 70, 1919 (1991)] for an axisymmetric 1D halo can be extended to 2D if understood as an upper bound to the rms emittance growth averaged per degree of freedom. The thus-obtained "free-energy limit" of an ideal transport system is compared with the halo rms emittance growth in simulations of the Spallation Neutron Source linac.

Journal Article↗
PubMed2000

Observation of a hybrid spin resonance

A new type of spin depolarization resonance has been observed at the Brookhaven Alternating Gradient Synchrotron (AGS). This spin resonance is identified as a strong closed-orbit sideband around the dominant intrinsic spin resonance. The strength of the resonance was proportional to the 9th harmonic component of the horizontal closed orbit and proportional to the vertical betatron oscillation amplitude. This "hybrid" spin resonance cannot be overcome by the partial snake at the AGS, but it can be corrected by the harmonic orbit correctors.

Journal Article↗
PubMed2000

Induction of osteopontin gene expression during mammary gland involution and effects of glucocorticoid on its expression in mammary epithelial cells.

To understand the molecular mechanisms of mammary gland involution, an involution-induced clone was identified from a cDNA library of mouse mammary gland by differential screening. Characterization of a clone by sequencing and northern analysis showed that expression of the osteopontin gene was induced during involution of mouse mammary gland. But induction of the osteopontin gene was not observed in apoptotic HC11 mammary epithelial cells under serum starvation. In HC11 cells, dexamethasone treatment from the seeding stage showed five-fold induction of osteopontin gene expression, but the expression was not changed when dexamethasone was added to confluent cells.

Animals↗
PubMed1999

Effects of overlapping parametric resonances on the particle diffusion process.

The evolution of the beam distribution in a double-rf system with a phase modulation on either the primary or secondary rf cavity was measured. We find that the particle diffusion process obeys the Einstein relation if the phase space becomes globally chaotic. When dominant parametric resonances still exist in the phase space, particles stream along the separatrices of the dominant resonance, and the beam width exhibits characteristic oscillatory structure. The particle-tracking simulations for the double-rf system are employed to reveal the essential diffusion mechanism. Coherent octupolar motion has been observed in the bunch beam excitation. The evolution of the longitudinal phase space in the octupole mode is displayed.

Journal Article↗
PubMed1999

Effects of resonances on halo formation in high-intensity storage rings.

Numerical calculations for the Spallation Neutron Source accumulator ring indicate that lattice resonances excited by the space-charge potential can increase a mismatch significantly by deforming the beam distribution in phase space. Hence increased mismatch leads to enhanced envelope oscillations that are driving the 2:1 parametric resonance leading to halo formation, even for initially matched beams. We have observed this behavior for the 2 nu(x) - 2 nu(y) = 0 resonance and for the 4 nu(y) = 23 resonance. This mechanism for halo formation peculiar to rings through resonance driven mismatch is very sensitive to the tunes, which emphasizes the importance of a careful choice of operating point in tune space.

Journal Article↗
PubMed1999

Sequence of a cDNA encoding mouse F1F0-ATP synthase g subunit.

A pregnant-induced clone was identified by differential screening from a cDNA library of mouse mammary gland. The clone was identified as a full-length cDNA encoding the F1F0-ATP synthase g subunit. Comparison of the deduced amino acid sequences of mouse ATP synthase g subunit with those of bovine species showed 86% identity. The high levels of ATP synthase g subunit mRNA were detected in heart and uterine tissues.

Amino Acid Sequence↗
PubMed1996

Iron metabolism-related genes and mitochondrial genes are induced during involution of mouse mammary gland.

To understand molecular mechanisms of mammary gland involution, several clones were isolated after the primary differential screening of a total 40,000 pfu of involution-specific cDNA library, and further characterized. The partial sequences and Northern analysis revealed that iron metabolism-related genes and mitochondrial genes were induced during mammary gland involution. The expression of the lactoferrin gene was induced at involution days 1, 2, and 3. The expression of ferritin heavy chain gene was induced at involution days 1, 2, 3 and 4. Cytochrome oxidase subunit 1 and cytochrome oxidase subunit 2 genes were induced at involution days 4 and 7. The expression of cytochrome b gene was induced at involution day 7. These results imply that iron metabolism and mitochondrial function may be altered during mammary gland involution.

Animals↗