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Biomedical subjects

T Yoon

Publications and source records attributed to T Yoon.

11 recordsLinked to original sources
PubMed2006

Activin receptor-like kinase 7 induces apoptosis of pancreatic beta cells and beta cell lines.

AIMS/HYPOTHESIS: Activin receptor-like kinase 7 (ALK7), a member of the type I receptor serine/threonine kinases of the TGF-beta superfamily, was recently reported to regulate cell proliferation and apoptosis. We hypothesised that ALK7 may play a role in modulating pancreatic beta cell proliferation and/or apoptosis. METHODS: We detected ALK7 expression in beta cells using RT-PCR, immunostaining and western blotting. Constitutively active, dominant negative or wild-type ALK7 was introduced into beta cells using adenoviral delivery. Proliferation was assessed using (3)H-thymidine incorporation and apoptosis was quantified using terminal deoxynucleotidyl transferase biotin-dUTP nick end labelling detection, DNA degradation analysis and caspase-3 assays. RESULTS: Induction of constitutively active ALK7 in beta cells resulted in growth inhibition and enhanced apoptosis; no effect was seen with INS-1 cells expressing wild-type or dominant negative ALK7. Elevated glucose concentrations and fatty acid (palmitate) markedly increased expression levels of ALK7 transcripts and proteins in INS-1 and rat islets and increased beta cell apoptosis. Activation of ALK7 increased Smad2 phosphorylation, reduced protein kinase B (Akt) kinase activity and was associated with increased levels of the bioactive forms of caspase-3, whereas co-expression of constitutively active ALK7 with dominant negative Smad2 or constitutively active Akt significantly diminished ALK7-induced growth inhibition and apoptosis in INS-1 cells. Although overexpression of constitutively active Akt significantly reduced ALK7-induced growth inhibition and ALK7-enhanced beta cell apoptosis, ALK7-stimulated Smad2 phosphorylation was not affected. CONCLUSIONS/INTERPRETATION: These results suggest that the pancreatic beta cell apoptosis induced by ALK7 activation occurs via the activation of two distinct downstream pathways: the suppression of Akt activation and the activation of the Smad2-caspase-3 cascade.

Activin Receptors, Type I↗
PubMed2006

Our algorithm for nasal reconstruction.

Nasal reconstruction is always challenging for plastic surgeons. Its midfacial localisation and the relationship between convexities and concavities of nasal subunits make impossible to hide any sort of deformity without a proper reconstruction. Nasal tissue defects can be caused by tumor removal, trauma or by any other insult to the nasal pyramid, like cocaine abuse, developing an irreversible sequela. Due to the special characteristics of the nasal pyramid surface, the removal of the lesion or the debridement must be performed according to nasal subunits as introduced by Burget. Afterwards, the reconstructive technique or a combination of them must be selected according to the size and the localisation of the defect created, and tissue availability to fulfil the procedure. An anatomical reconstruction must be completed as far as possible, trying to restore the nasal lining, the osteocartilaginous framework and the skin cover. In our department, 35 patients were operated on between 2000 and 2002: three bilobed flaps, five nasolabial flaps, two V-Y advancement flaps from the sidewall, three dorsonasal flaps modified by Ohsumi, 19 paramedian forehead flaps, three cheek advancement flaps, three costocondral grafts, two full-thickness skin grafts and two auricular helix free flaps for alar reconstruction. All flaps but one free flap survived with no postoperative complications. After 12-24 months of follow-up, all reconstructions remained stable from cosmetic and functional point of view. Our aim is to present our choice for nasal reconstruction according to the size and localization of the defect, and donor tissue availability.

Adult↗
PubMed2004

Reconstruction of soft-tissue defects of the heel with local fasciocutaneous flaps.

Soft tissue heel defects reconstruction represents a challenge for plastic surgeons because of the poor availability of regional tissue to perform the reconstruction. We divide the heel on the anterior or weight-bearing heel and the posterior or non-weight-bearing heel. Our preferences are the fasciocutaneous instep flap for anterior heel defects and the reverse sural flap for posterior heel defects. We have performed 11 reconstructions of the heel. The complications were total necrosis of 1 instep flap in a previously irradiated patient and 1 case of partial tip necrosis in a reverse sural flap. Functional recovery has been very satisfactory for both procedures. Regional island flaps are for us the first therapeutic option because the skin is similar to the lost one and less time consuming than a free-flap reconstruction.

Heel↗
PubMed2003

Patterns of changes in temperament and character inventory scales in subjects with obsessive-compulsive disorder following a 4-month treatment.

OBJECTIVE: The purpose of this study was to assess changes in the temperament and character patterns in subjects with obsessive-compulsive disorder (OCD) following the treatment for obsessive/compulsive and accompanying depressive symptoms. METHOD: Study subjects were 35 patients who met the DSM-IV criteria for OCD. All subjects were assessed with the Temperament and Character Inventory (TCI), the Yale-Brown Obsessive-Compulsive Scale, the Beck Depression Inventory, and the Beck Anxiety Inventory before and after a 4-month treatment. RESULTS: Harm Avoidance (HA) scores in OCD subjects before treatment significantly decreased after treatment. However, the Self-Directedness scores, which were significantly lower than healthy comparison subjects before treatment, did not change. In addition, Reward Dependence scores in OCD subjects, which were not significantly different from healthy comparison subjects before treatment, significantly increased after treatment. CONCLUSION: The TCI pattern of untreated OCD subjects (high HA and low Self-Directedness, relative to healthy comparison subjects) and the decrease of HA scores and no change in Self-Directedness scores following a successful treatment suggest that temperaments are more amenable to treatment than characters.

Adolescent↗
PubMed2001

The p48 subunit of the damaged-DNA binding protein DDB associates with the CBP/p300 family of histone acetyltransferase.

DDB has been implicated in DNA repair as well as transcription. Mutations in DDB have been correlated with the repair-deficiency disease, xeroderma pigmentosum group E (XP-E). The XP-E cells exhibit deficiencies in global genomic repair, suggesting a role for DDB in that process. DDB also possesses a transcription stimulatory activity. We showed that DDB could function as a transcriptional partner of E2F1. But the mechanism by which DDB stimulates E2F-regulated transcription or carry out its DNA repair function is not understood. To investigate the mechanisms, we looked for nuclear proteins that interact with DDB. Here we show that DDB associates with the CBP/p300 family of proteins, in vivo and in vitro. We suggest that DDB participates in global genomic repair by recruiting CBP/p300 to the damaged-chromatin. It is possible that the histone acetyltransferase activities of the CBP/p300 proteins induce chromatin remodeling at the damaged-sites to allow recruitment of the repair complexes. The observation offers insights into both transcription and repair functions of DDB.

Acetyltransferases↗
PubMed2001

Efficient prediction methods for the micro-pressure wave from a high-speed train entering a tunnel using the Kirchhoff formulation.

The compression wave generated by a high-speed train emerging from the exit portal of a tunnel gives rise to an impulsive noise called a micro-pressure wave. In this study, new methods for the prediction of sonic-boom noise are proposed. The first method combines acoustic monopole analysis and the method of characteristics with the Kirchhoff method. The compression wave from a train entering a tunnel is calculated by an approximate compact Green's function, and the resultant noise at the tunnel exit is predicted by a linear Kirchhoff formulation. The second method couples the Kirchhoff formulation with the Euler equation, which is solved numerically for the generation and propagation of the compression wave. Numerical prediction of the compression wave, the propagation in the tunnel, and the micro-pressure wave obtained by the present methods are compared with measured data. The numerical results exhibit a reasonable agreement with the experimental data. The proposed methods in this study are shown to be very useful design tools for the nose shape of trains and the geometry of tunnels, and they can be utilized to minimize the pressure fluctuation in the tunnel and the corresponding booming noise.

Journal Article↗
PubMed2000

Identification of the self-interaction of rat TCTP/IgE-dependent histamine-releasing factor using yeast two-hybrid system.

To further understand the biological function of translationally controlled tumor protein (TCTP), also known as IgE-dependent histamine-releasing factor (HRF), the yeast two-hybrid system was used to screen interacting molecules. We isolated cDNA clones coding for TCTP/HRF, suggesting that it may have a self-interacting property. Domain mapping of the interaction revealed that the C-terminal region of residue 126-172 is involved in self-interaction. The self-interacting property of TCTP/HRF was further supported by FPLC gel-filtration chromatography and coimmunoprecipitation analysis from transfected COS-7 cells. Our data suggests that TCTP/HRF may have a potential to self-interact through the C-terminal region, and the self-interaction property may be related to its biological function.

Animals↗
PubMed2000

Comparison of eccentric and concentric isokinetic exercise testing after anterior cruciate ligament reconstruction.

Evaluation of muscle function can be helpful in rehabilitation programs with knee injuries. The purposes of this study were to evaluate muscle performance and functional level through eccentric and concentric isokinetic testing after anterior cruciate ligament reconstruction, and to determine whether eccentric and concentric isokinetic values were correlated with functional level using the Modified Cincinnati Scale (MCS). In order to compare the characteristics of eccentric and concentric parameters, we tested 24 male patients (mean age; 31.1 years) after primary reconstruction of ruptured anterior cruciate ligaments of the knee (mean duration; 20.2 months), at angular velocities of 60 degree/sec using Cybex 6000 isokinetic dynamometer. We also evaluated the functional level using the MCS. The values of peak torque of the involved knee extensors and flexors were significantly lower than the uninvolved limb in all eccentric and concentric tests (p<0.01). The deficiency ratios of peak torque in knee extensors were significantly larger than knee flexors in both eccentric and concentric tests (p<0.01). The MCS was inversely correlated with the deficiency ratio in peak torque of eccentric knee extensors (p<0.05). These results suggest that eccentric knee extensor training is essential to restore the functional capacity of the injured knee and that isokinetic evaluation is necessary to plan rehabilitation programs to correct possible imbalances which may be predispose subjects to future injury.

Adult↗
PubMed1998

Isoform-specific interaction of the cytoplasmic domains of Na,K-ATPase.

The Na,K-ATPase is a heterodimer consisting of an alpha and a beta subunit, which exchanges intracellular Na+ for extracellular K+ using the energy of ATP hydrolysis. Several studies have demonstrated that the enzyme exists as an (alphabeta)2 heterotetramer, an oligomer of alphabeta dimers within the cell membrane, at least during some portion of the transport cycle although its functional significance is unknown. In our study, we employed the yeast two-hybrid system to identify the cytoplasmic domains of the Na,K-ATPase which might be involved in intersubunit and/or intrasubunit interactions to form higher order oligmers. Our data demonstrate that the N-terminus and the cytoplasmic loop 1 of the alpha2 subunit interact with each other, while those of the alpha1 subunit do not, suggesting that the interaction is isoform-specific. Therefore, the N-terminal and the cytoplasmic loop 1 might be the regions where the alpha2 subunit, which are involved in alpha alpha interactions, stabilize Na,K-ATPase as alphabeta protomer, diprotomer, or higher order oligomer because the interaction can be intrasubunit as well as intersubunit interactions. Our study suggests that there may be an isoform-specific difference in the alpha-alpha interaction and that the isoform-specific interaction may contribute significantly to the differences of the physiological function and regulation among the alpha isoforms.

Animals↗