Life-threatening bleeding of bilateral maxillary arteries in maxillofacial trauma: report of two cases.
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Adult↗
Biomedical subjects
Chien-Chung Chen
Publications and source records attributed to Chien-Chung Chen.
Spatial summation of face information.
Do all parts of the face contribute equally to face detection or are some parts more detectable than others? To evaluate this issue, we studied detection of the presence of normalized frontal-face images within aperture windows of varying extent. We performed a face summation study using two-alternative forced-choice psychophysics. The face stimuli were scaled to equal eye-to-chin distance, centered on the bridge of the nose, and windowed by fourth-power Gaussian envelopes of various sizes. The faces were intermixed with control stimuli consisting inverted faces to test for configuration effects, split-half inverted faces to perturb the symmetry, and phase-scrambled versions of the faces with equal Fourier energy. Face detectability improved rapidly at first, then at a progressively shallower rate for larger window sizes, in a similar fashion for the three face-based stimulus types. The spectrally equated noise stimuli were less detectable than the face stimuli for all except the smallest apertures. The results were fit with a model incorporating global face-specific and local nonspecific spatial integration mechanisms. Detection of the noise images was consistent with local detection mechanisms accessed through a wide-field attention mechanism. The data for face detection implied detection mechanisms that integrated linearly up to some small size, integrated more slowly up to an intermediate size, and failed to gain any improvement for information beyond some larger size. This performance supports the concept of a specialized face configuration mechanism operating at detection threshold, similar in extent among the observers.
Artifacts↗
Dissociated roles of the middle frontal gyri in the processing of Chinese characters.
The present study examined a hypothesis that the right middle frontal gyrus participates in processing orthography of Chinese characters, while the left middle frontal gyrus mediates access to phonology and semantics. Brain activation during three character tasks, which required processing orthography, phonology, or semantics of Chinese characters, respectively, was measured by functional magnetic resonance imaging. Comparable neural activity in the right middle frontal gyrus was observed in all three character tasks that always demand orthographical processing. In contrast, the left middle frontal gyrus showed greater activation in the phonological and semantic tasks than in the orthographic task. These results suggest that the right and left middle frontal gyrus have dissociable functions in achieving Chinese character recognition.
Adult↗
Face configuration processing in the human brain: the role of symmetry.
Symmetry is an important cue in face perception. We manipulated symmetry and other configurational variables to study their role in face processing in the human brain. We employed 2 types of symmetry: image symmetry (where one part of the image is defined as the mirrored transform of the other part about an axis) and object symmetry (where the spatial relationships among the image components are interpreted as parts of a symmetric 3-dimensional object). We compared blood oxygenation level dependent responses in healthy human observers for upright front-view faces with responses to different symmetry-controlled images. The cortical areas activated by the face images, relative to Fourier-matched scrambled images, were the fusiform (FFA) and occipital (OFA) face areas, the middle occipital gyri (MOG), and areas around the superior temporal and intraoccipital sulci (IOS). Contrasting faces and their image-symmetric scrambled versions showed a similar activation pattern except in the right OFA, suggesting an involvement in facial symmetry processing. The upright versus inverted faces (with the same image symmetry but unfamiliar object identity) showed robust differential activation in the FFA, OFA, MOG, IOS, and precuneus. The response to frontal-view versus 3/4-view faces (having the same object symmetry but disrupted image symmetry) showed little differential activation in the FFA or the OFA but strong responses in the MOG and IOS, suggesting that face processing in the FFA and the OFA is holistic and viewpoint invariant.
Brain Mapping↗
Evidence for elongated receptive field structure for mechanisms subserving stereopsis.
To study the spatial extent and shape of the binocular disparity mechanisms subserving depth perception, we employ the spatial summation paradigm of contrast threshold for front/back depth discrimination at a fixed binocular disparity. The stimuli were Gabor patches with disparity set at either 4 or 8 arcmin and spatial frequency set at an optimal value of 4 cy/deg. Contrast threshold was measured as a function of length and width of the Gabor patches to determine the aspect ratio of greatest efficiency. The space constant of the Gaussian envelope varied between 0.0375 degrees and 0.9 degrees in either vertical or horizontal directions, or both simultaneously. For vertical elongation of the Gabor patches, discrimination sensitivity improved by 4-6 dB for a doubling of the length of the Gabor patches, then reduced more slowly as the length further increased. However, extending the Gabor patches horizontally across cycles produced little or no sensitivity improvement. Instead, discrimination performance collapsed in a fashion that is incompatible with many models of disparity processing. The results imply that the main mechanisms subserving stereoscopic depth discrimination are vertically elongated for vertical-bar Gabors and encounter special difficulties integrating horizontal disparity information. Disparity discrimination sensitivity for very small targets was also much greater than predicted by the single-mechanism fit, implying the presence of a second, independent mechanism with a very small summation field, which may underlie the fine stereoscopic processing system.
Contrast Sensitivity↗
LeuO protein delimits the transcriptionally active and repressive domains on the bacterial chromosome.
LeuO protein relieves bacterial gene silencer AT8-mediated transcriptional repression as part of a promoter relay mechanism found in the ilvIH-leuO-leuABCD gene cluster. The gene silencing activity has recently been characterized as a nucleoprotein filament initiated at the gene silencer. In this gene locus, the nucleoprotein filament cis-spreads toward the target leuO promoter and results in the repression of the leuO gene. Although the cis-spreading nature of the transcriptionally repressive nucleoprotein filament has been revealed, the mechanism underlying LeuO-mediated gene silencing relief remains unknown. We have demonstrated here that LeuO functions analogously to the eukaryotic boundary element that delimits the transcriptionally active and repressive domains on the chromosome by blocking the cis-spreading pathway of the transcriptionally repressive heterochromatin. Given that one LeuO-binding site is positioned between the gene silencer and the target promoter, the simultaneous presence of a second LeuO-binding site synergistically enhances the blockade, resulting in a cooperative increase in LeuO-mediated gene silencing relief. A known DNA loop-forming protein, the lac repressor (LacI), was used to confirm that cooperative protein binding via DNA looping is responsible for the blocking synergy. Indeed, a distal LeuO site located downstream cooperates with the LeuO sites located upstream of the leuO gene, resulting in synergistic relief for the repressed leuO gene via looping out the intervening DNA between LeuO sites in the ilvIH-leuO-leuABCD gene cluster.
Binding Sites↗
Lateral modulation of BOLD activation in unstimulated regions of the human visual cortex.
After staring at a blank region surrounded by a dynamic background for a few seconds, observers report a twinkle aftereffect in the unstimulated blank region. The significance of this twinkle aftereffect is that it occurs at a location that received no stimulation, and therefore reflects a rebound from lateral inhibition within the dynamic processing system. To study this inhibitory rebound effect, the blood oxygenation level dependent (BOLD) activation in the visual cortex was measured while the observers were viewing a flickering pin-wheel pattern alternating with a blank test. Retinotopic regions corresponding to the inter-wedge regions in the pin-wheel pattern showed activation negatively correlated with the test sequence. While the BOLD activation in the visual cortex is generally considered to be retinotopically driven by the visual stimuli, we were able to show a sustained negative activation in the unstimulated regions, with properties that correspond to those of the inhibitory rebound of the perceived aftereffect.
Adult↗
Penetrating ocular injury caused by venomous snakebite.
PURPOSE: To report the case of a patient who experienced a penetrating ocular injury with direct intraocular injection of venom from a snakebite. DESIGN: Case report. METHODS: A 34-year-old man was bitten by a snake on his right eye. The snake was identified as Deinagkistrodon acutus. Antivenom was provided, but facial swelling, periorbital ecchymoses, massive subconjunctival hemorrhage, severe corneal edema, and exophthalmos of the right eye were noted. Dyspnea due to airway edema then developed. RESULTS: He received emergent intubation. Evisceration was performed, and a continuously active bleeding scleral wound was found. No local infection developed under systemic and topical antibiotics. Pathologic examination of the excised cornea showed necrosis on the endothelial side. CONCLUSIONS: Early evisceration was the treatment of choice for treatment of a penetrating ocular injury caused by venomous snakebite. Maintaining stable life signs and prevention of infection remained the major concerns.
Adult↗
A cis-spreading nucleoprotein filament is responsible for the gene silencing activity found in the promoter relay mechanism.
Transcription-generated DNA supercoiling plays a decisive role in a promoter relay mechanism for the coordinated expression of genes in the Salmonella typhimurium ilvIH-leuO-leuABCD gene cluster. A similar mechanism also operates to control expression of the genes in the Escherichia coli ilvIH-leuO-leuABCD gene cluster. However, the mechanism underlying the DNA supercoiling effect remained elusive. A bacterial gene silencer AT8 was found to be important for the repression state of the leuO gene as part of the promoter relay mechanism. In this communication, we demonstrated that the gene silencer AT8 is a nucleation site for recruiting histone-like nucleoid structuring protein to form a cis-spreading nucleoprotein filament that is responsible for silencing of the leuO gene. With a DNA geometric similarity rather than a DNA sequence specificity, the E. coli gene silencer EAT6 was capable of replacing the histone-like nucleoid structuring protein nucleation function of the S. typhimurium gene silencer AT8 for the leuO gene silencing. The interchangeability between DNA geometrical elements for supporting the silencing activity in the region is consistent with a previous finding that a neighboring transcription activity determines the outcome of the gene silencing activity. The geometric requirement, which was revealed for this silencing activity, explains the decisive role of transcription-generated DNA supercoiling found in the promoter relay mechanism.
Acetolactate Synthase↗
Changes of the cardiac architectures and functions for chronic hemodialysis patients with dry weight determined by echocardiography.
BACKGROUND/AIMS: Left ventricular hypertrophy (LVH) has long been known as an independent risk factor for cardiovascular deaths, in both dialysis and general populations. Numerous factors influence the pathophysiology of LVH. However, extracellular fluid may have a particularly important influence on this impact. Inferior vena cava diameter (IVCD) estimation is a non-invasive and relatively convenient method for obtaining a good correlation with the intravascular fluid status, and may obtain an optimal dry weight (DW) for chronic hemodialysis patients. This study estimates the DW of end-stage renal disease (ESRD) patients by echocardiographic measurement of the IVCD to observe changes in cardiac morphology and function. METHODS: A total of 88 patients, ranging from 26 to 90 (59.4 +/- 13.3) years of age, were involved in this study. The patients were divided into study (n = 48) and control (n = 40) groups. All patients received IVCD assessment via echocardiography bi-monthly for 1 year. In the study group patients, DW was adjusted according to the IVCD by echocardiography. Meanwhile, in the control group patients, DW was adjusted based on traditional clinical parameters. All patients underwent cardiac examinations and measurements, including left ventricular mass (LVM), wall thickness, chamber size and left ventricular systolic function by echocardiography, at the beginning and end of the study. RESULTS: Both groups displayed comparable clinical and biochemical parameters. The IVCD index correlated well with the cardiac parameters estimated by echocardiography. The LVM and left ventricular mass index (LVMI) was reduced significantly in the study group patients (from 200 +/- 64.2 to 187 +/- 63.2 g, p = 0.021; from 132 +/- 37.6 to 123 +/- 37.3 g/m(2), p = 0.014, respectively). Furthermore, the study group patients with fluid overload, named study subgroup A, displayed significant differences not only in LVM and LVMI, but also in septal wall thickness, left ventricular end-diastolic dimension and left atrial dimension. In contrast, the control group displayed no changes in these cardiac architectures during the study period. CONCLUSION: Adjusting DW via the IVCD measured by echocardiography for hemodialysis patients may prevent the progression of chamber dilatation and LVH, especially for patients with fluid overload.
Adult↗
Pattern detection: interactions between oriented and concentric patterns.
Target threshold vs. pedestal contrast (TvC) functions for a vertical and a concentric target were measured on a vertical, a horizontal, a plaid or a concentric Gabor pedestal. All patterns had Guassian envelopes. All except one of the TvC functions had a dipper shape, that is, the target threshold first decreased and then increased with the pedestal contrast. The TvC function for a vertical target on a horizontal pedestal was monotonically increasing. A divisive inhibition model with two orientation selective mechanisms, sensitive to vertical and horizontal, fits the data reasonably well. A significant improvement in fit is obtained by adding one or two more mechanisms. These additional mechanisms are different for different observers. Some are consistent with oblique receptive fields, some with concentric receptive fields, and some are indeterminate.
Humans↗
Recurrent herpetic keratouveitis following YAG laser peripheral iridotomy.
OBJECTIVE: To report recurrent herpetic keratouveitis following YAG laser peripheral iridotomy. METHODS: Case report. RESULTS: A 64-year-old woman with a history of dendritic keratitis underwent Nd:YAG laser peripheral iridotomy and developed geographic epithelial keratitis with stromal keratouveitis. Culture of a corneal swab grew herpes simplex virus type I. Keratouveitis subsided with acyclovir and corticosteroid therapy. CONCLUSIONS: Recurrent herpetic keratouveitis may be induced by YAG laser iridotomy.
Acyclovir↗
Enhancement of quality of life with adjustment of dry weight by echocardiographic measurement of inferior vena cava diameter in patients undergoing chronic hemodialysis.
BACKGROUND/AIMS: Ideal dry weight (DW) can serve as a marker of good quality of life (QOL) in patients receiving chronic hemodialysis. The size of the inferior vena cava (IVC) reflects the intravascular fluid status, and the diameter of IVC correlates indirectly with DW in these patients. Adjusting DW using echocardiographic measurement of the diameter of the IVC thus may be useful in maintenance of a better QOL in patients receiving chronic hemodialysis. METHODS: This study included 119 patients with ages ranging between 27 and 90 years (mean +/- standard deviation of 58.3 +/- 12.8). All of the patients received the IVC diameter (IVCD) measurement by echocardiography every 2 months for 1 year. The study group included 68 patients in whom the DW were adjusted by echocardiographic measurement of the IVCD, while the control group included 51 patients in whom the DW was adjusted by the conventional method. QOL was evaluated using the short form 36 questionnaire (SF-36) at the beginning and at the end of the study. Besides, the Kt/V(urea) value, a parameter of total urea clearance, was measured at the beginning and at the end of the study in patients of both groups. RESULTS: The scores of physical functioning, physical role functioning, general health and physical component summary showed a prominent improvement in the study group but not in the control group. The impact of periodic echocardiographic evaluation also demonstrated a significant change in the scores of physical functioning, physical role functioning and physical component summary in the study group. Furthermore, the Kt/V(urea) value, a parameter of total urea clearance, also increased significantly in the study group. CONCLUSION: Ideal DW is better adjusted by periodic echocardiographic measurement of the IVCD in patients undergoing chronic hemodialysis. Maintenance of a better DW leads to improve hemodialysis quality and QOL in these patients.
Activities of Daily Living↗
LeuO-mediated transcriptional derepression.
To understand the coordination of gene expression in the Salmonella typhimurium ilvIH-leuO-leuABCD gene cluster, we had previously identified a 72-bp AT-rich (78% A+T) DNA sequence element, AT4, which was capable of silencing transcription in a promoter nonspecific manner. LeuO protein provided in trans relieved (derepressed) AT4-mediated gene silencing (transcriptional repression), but underlying mechanisms remained unclear. In the present communication, the 72-bp DNA sequence element is further dissected into two functional elements, AT7 and AT8. LeuO binds to the 25-bp AT7, which lies closest to the leuO promoter in the AT4 DNA. After deletion of the AT7 DNA sequence responsible for LeuO binding from AT4, the remaining 47-bp AT-rich (85% A+T) DNA sequence, termed AT8, retains the full bi-directional gene-silencing activity, which is no longer relieved by LeuO. LeuO-mediated transcriptional derepression is restored when the LeuO binding site, AT7, is placed within close proximity to the gene silencer AT8. As a pair of functionally coupled transcription elements, the presence of an equal copy number of AT7 and AT8 within proximity is important for the transcription control. The characterization provides clues for future elucidation of the molecular details whereby LeuO negates the gene-silencing activity.
Base Sequence↗
Transcription-driven DNA supercoiling and gene expression control.
DNA supercoiling plays important roles in gene expression regulation, although, the underlying mechanisms whereby DNA supercoiling modulates gene expression remain elusive. The fact that the transcription process itself generates DNA supercoiling has further complicated the issue. Transcription-driven DNA supercoiling is local and transient. Such a DNA supercoiling effect is likely to play important roles in controlling complex gene expression regulation. Using the suppression of the leu-500 mutation in Salmonella typhimurium topA mutants as a model system, we put forward our view of the effects of transcription-driven DNA supercoiling on gene expression control.
Animals↗
Statistical properties of BOLD magnetic resonance activity in the human brain.
We investigated the random variability of BOLD (blood oxygen level dependent) activation during rest, or null-hypothesis, conditions in which the observers were neither receiving controlled sensory stimuli nor performing cognitive tasks. The data indicate that the distributions for the BOLD variation across space are skewed, with non-Gaussian tails, while the distributions for the temporal variation within individual voxels are predominantly Gaussian. The proportion of voxels that show non-Gaussian properties is highly correlated with the magnitude of head movement of the observers. In all observers, the white matter showed less variability than the gray matter. The distributions for the spatial and the temporal variations are robust across observers despite differences in the data acquisition methods (EPI vs. spiral) and magnetic field strength (1.5 vs. 3 T). In most cases, the non-Gaussian tails of the spatial distribution can be eliminated by normalizing the amplitude in each voxel to its standard deviation before cumulating across voxels. We therefore recommend such a normalization procedure before any data manipulations are performed on fMRI data.
Adult↗
Separating the effects of response nonlinearity and internal noise psychophysically.
A psychophysical method is proposed to separate the contrast dependence of internal response and its noise. The resulting contrast relationships represent a signature of the visual processing stage that limits the human observer's performance. The method was applied to contrast discrimination for sustained and transient Gabor patches with a 3 cycle/deg spatial carrier. For both stimulus types the predominant noise was found to be multiplicative with a power exponent of 0.76-0.85 and the source of this noise preceded by an accelerating signal transducer with a power of 2-2.7. These exponents combine to account for the classic compressive power of about 0.4 for the signal-to-noise ratio in contrast discrimination. The estimated transducer acceleration suggests that there is a direct computation of contrast energy in the visual cortex.
Adolescent↗
The unique criterion constraint: a false alarm?
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Humans↗