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Biomedical subjects

J C Hsu

Publications and source records attributed to J C Hsu.

At least 55 records · Page 3Linked to original sources
PubMed1997

Neuroimaging in intractable complex partial seizures.

We retrospectively analyzed 19 patients with intractable complex partial seizures who underwent temporal lobectomy and compared the usefulness of various imaging techniques in diagnosis and localization. Pathologic findings consistent with mesial temporal sclerosis were found in 12 patients arteriovenous malformations in four, tumors in three, and coexistence of a tumor and mesial temporal sclerosis in one. Electroencephalography and single photon emission computed tomography detected lateralized functional abnormality in two patients when computed tomography (CT) and magnetic resonance imaging (MRI) showed equivocal results. Both CT and MRI showed all arteriovenous malformations and tumors. CT detected only four cases of mesial temporal sclerosis, while MRI showed nine cases. Detection, delineation and diagnosis of lesions responsible for complex partial seizures are essential for good surgical results. Thus, the importance of image studies, especially MRI, should be emphasized in patients with complex partial seizures.

Adolescent↗
PubMed1997

Magnetic resonance imaging in patients with hemodialysis-related arthropathy.

From April 1993 to December 1993, we prospectively studied the knees of 15 patients (mean age, 48 +/- 11 yr) receiving long-term hemodialysis (mean duration, 9 +/- 4 yr) using magnetic resonance imaging (MRI) techniques including, T1 weighted spin-echo, multiplanar gradient recalled, and postcontrast T1 with chemical shift-selective, fat-saturation pulse sequences. Analysis of these images revealed that the three findings most indicative of hemodialysis-related arthropathy were intramedullary, cortical and soft tissue lesions. Knee pain was significantly correlated with the presence of soft tissue lesions. Cortical lesions were usually associated with soft tissue lesions. Inflammatory changes adjacent to soft tissue lesions were demonstrated in postcontrast studies in all patients with soft tissue lesions. Increases in water content in those lesions appeared to increase the signal intensity. Our results indicate that MRI is useful in demonstrating the extent of hemodialysis-related arthropathy involvement, especially in hemodialysis patients suffering from knee pain.

Adult↗
PubMed1997

Proton magnetic resonance spectroscopy in patients with complex partial seizures.

We prospectively studied eight patients with complex partial seizures, using single-voxel proton magnetic resonance spectroscopy (MRS). Control data from 12 healthy volunteers were obtained with the same MRS protocol. The ratios between the peak areas of N-acetylaspartate, creatine and phosphocreatine (Cr), and choline-containing compounds (Cho) were analyzed. The results showed statistically significant lower N-acetylaspartate:Cr, N-acetylaspartate:Cho, and N-acetylaspartate: Cho + Cr ratios, and a higher Cho:Cr ratio in the mesial temporal lobes of the patient group than in healthy controls. Because N-acetylaspartate is located in the neurons and Cho and Cr in the glial cells, these observations represent the underlying neuronal loss and reactive astrocytosis in the epileptogenic foci. MRS can detect abnormal metabolic changes in most complex partial seizure patients with normal electroencephalography and magnetic resonance images. MRS can also identify bitemporal abnormalities which are a common feature in patients with complex partial seizures. Proton MRS could not confirm the specific location of seizure foci. Further investigation with quantitative spectral analysis and correlation with surgical outcome is needed to improve the contribution of MRS to the diagnosis and localization of seizure foci.

Adult↗
PubMed1997

Evoked facial nerve EMG and brainstem auditory evoked potential monitoring in cerebellopontine angle tumor resection.

BACKGROUND: The preservation of normal nerve function or identification of nerve route is critical in some surgeries of cerebellopontine angle tumors. Over the last 5 years, intraoperative facial nerve electromyogram (EMG) and brainstem auditory evoked potential (BAEP) were applied for evaluation of facial nerve integrity and brainstem function in patients while undergoing resection of cerebellopontine angle (CPA) tumor. This report represents the retrospective analysis of our results. METHODS: The inhalational anesthesia with 1-1.5% isoflurane in pure O2 was used. Muscle relaxation was maintained with continuous infusion of atracurium. The degree of muscle relaxation was aimed at a T4/T1 ratio of train-of-four response more than 20% of the adductus pollicis upon ulnar nerve stimulation at the wrist. In 236 patients suffering from CPA tumor without facial palsy, the EMG of the mentalis muscle ipisilateral to the tumor was obtained through stimulation of the facial nerve. The stimulation was applied with a nerve finder, which delivered an electrical stimulation of a single 2 mamp direct current. The EMG finding was compared with the clinical result. In 198 patients, BAEP was used to monitor the brainstem function during tumor resection. In case of intact hearing the BAEP was taken ipsilateral to the operation side and in case with total hearing loss contralateral BAEP to operation side was used. For BAEP stimulation, 90 db click sound stimulation with frequency of 11.26 Hz was applied to both ears. BAEP signals were obtained and recorded at the mastoid region of either side in reference to the vertex. The EMG and BAEP signals were recorded and saved to an evoked potential monitor. RESULTS: In facial nerve EMG monitoring, there were two false positive and no false negative tests. Except for the two false positive tests, the postoperative clinical results in the other cases were compatible with the intraoperative facial nerve EMG findings. In BAEP monitoring, there were twenty-eight positive tests. CONCLUSIONS: The low incidence of false negative test suggests that facial nerve EMG is valuable in detection of facial nerve function in CPA tumor resection. Intraoperative BAEP abnormality is possibly useful in identifying postoperative brainstem dysfunction.

Adult↗
PubMed1996

Cerebral ischemia alters the regional hippocampal expression of the rat m1 muscarinic acetylcholine receptor gene.

We investigated the dynamics of the gene expression of the m1 subtype of muscarinic cholinergic receptor in the rat hippocampus following transient global ischemia. This receptor represents the dominant phosphoinositide linked muscarinic receptor in the hippocampus, and is recognized to modulate various aspects of neuronal activity in the hippocampus. Our results demonstrate that following severe transient global ischemia, m1 receptor expression is altered in the hippocampus in a time dependent manner. Expression levels declined in the dentate gyrus within 3 h of insult, reached minimal levels by 6 h, and then slowly recover to control levels. Expression levels in the CA1 and CA3 decreased as well, but did not reach minimal levels until 24 h post-insult. By day 3, expression levels in all regions except CA1, where vulnerable neurons began to drop out, had returned to control levels. These results demonstrate that transient alterations in the gene expression levels for the m1 muscarinic receptor occur in all subfields of the hippocampus following transient forebrain ischemia.

Animals↗
PubMed1996

Molecular biology in nutrition research: modeling of folate metabolism.

Model CHO cells obtained by transfecting CHO mutants with the E. coli and human folylpolyglutamate synthetase genes have proven useful for assessing the role of folylpolyglutamates in one carbon metabolism and for delineating how folate intracellular stores are regulated. Cells expressing enzymes in specific subcellular compartments, expressing enzymes with different substrate specificity's, and expressing enzyme activity at different levels, all in a common background, in this case the CHO cell, has allowed the development of kinetic models for assessing the role of folypolyglutamate synthetase in folate retention and in the cytotoxicity of antifolates.

Animals↗
PubMed1996

Acute health hazards of firefighters after fighting a department store fire.

The purpose of this study was to evaluate the health hazards of firefighters after fighting a department store fire which lasted for 40 hours. Respiratory symptoms of 168 firefighters were collected and the pulmonary functions of 149 firefighters were measured by spirometer two days after fighting the fire and compared to 32 controls. The principal symptoms manifested by firefighters were burning eyes and mucous membrane irritation. Cross-sectional study of the pulmonary functions showed that FEV1.0, FEV1.0/FVC and the flow rates (MMF, FEF25%, and FEF75%) in smoking exposed firefighters were significantly lower than those in smoking controls. However, only FEV1.0 (%) was significantly lower in nonsmoking exposed firefighters than in nonsmoking controls. Both FVC and FEV1.0 showed a declining trend with the duration of fire fighting. This study provides further evidence that firefighters are exposed to irritants during fighting a fire. Exposure to the combustion products could lead to pulmonary function defects, especially in smoking firefighters.

Case-Control Studies↗
PubMed1995

Dissection of the Torso signal transduction pathway in Drosophila.

Cell fate choice at the anterior and posterior embryonic termini of the Drosophila embryo requires the activation of a signal transduction pathway regulated by the receptor tyrosine kinase Torso. When Torso, which is uniformly distributed in the egg cell membrane, becomes activated locally at the termini, it triggers a phosphorylation cascade that culminates with localized expression of the transcription factors, tailless and huckebein. Expression of tailless and huckebein in turn determines terminal cell fates. Several genes have been characterized which encode proteins that are involved in Torso signaling: the adaptor protein Drk, the GTP-binding protein Ras1, the guanine nucleotide exchange factor Son of sevenless, and the kinases D-Raf and D-Mek. Genetic and molecular evidence supports a model in which these proteins lie in the same biochemical pathway. When activated by its ligand the membrane-bound receptor tyrosine kinase Torso initiates a signal transduction pathway mediated by Drk, Sos, and Ras1, which in turn activates a phosphorylation cascade mediated by the kinases D-Raf and D-Mek, which ultimately control the localized expression of the transcription factors tailless and huckebein. Recently, we found that D-Raf can be partially activated by Torso in the absence of Ras1, a finding supported by the phenotype of embryos lacking either Drk or Sos activity, as well as by the phenotype of a D-raf mutation that abolishes binding of Ras1 to D-Raf. These findings indicate that full D-Raf activation requires input not only from Ras1 but also from an as yet uncharacterized Ras1-independent pathway. In addition to these molecules we have characterized the putative protein tyrosine phosphatase Corkscrew as a positive transducer downstream of Torso.

Animals↗
PubMed1994

A temperature-sensitive MEK mutation demonstrates the conservation of the signaling pathways activated by receptor tyrosine kinases.

MEK, a dual specificity threonine/tyrosine kinase, has been postulated to be a convergent point for signaling from receptor protein tyrosine kinases (RTKs) and G-protein-coupled receptors. In contrast to yeast and mammalian cells where several MEKs have been isolated, only one Drosophila MEK (D-Mek) has been characterized to date. Previous studies have shown that D-Mek acts in the Torso RTK signaling pathway. To demonstrate that D-Mek also operates downstream of other RTKs, we generated a temperature-sensitive allele of D-mek (D-mekts) by site-directed mutagenesis based on the amino acid change of a yeast cdc2ts mutation. Using D-mekts, we show that in addition to its role in Torso signaling, D-Mek operates in the Sevenless and in the Drosophila epidermal growth factor RTK pathways. Because loss-of-function mutations in D-mek and the upstream receptors give rise to similar phenotypes, it suggests that D-mek is the only MEK activated by Drosophila RTKs. In addition, we demonstrate that different RTK pathways respond differently to alteration in D-Mek activity.

Alleles↗
PubMed1994

Genetic and molecular analyses of mutations involved in Drosophila raf signal transduction.

We have identified dominant mutations that suppress the lethality associated with an R217-->L mutation in the GTP.Ras binding region (CR1) of the Drosophila raf (D-raf) serine/threonine kinase. Four intragenic and seven extragenic suppressors were recovered. Each of the four intragenic mutations contains one compensatory amino acid change located in either the CR1 or the kinase domain of D-raf. The seven extragenic suppressors represent at least four genetic loci whose effects strongly suggest that they participate in both the sevenless and Drosophila EGF receptor (DER) signaling pathways. One of these mutations, Su(D-raf)34B, is an allele of D-mek which encodes the known signaling molecule MAPK kinase (MEK). A D83V mutation in D-MEK is identified and shown to be sufficient to confer the dominant activity of Su(D-raf)34B.

Amino Acid Sequence↗
PubMed1994

Electrocochleographic monitoring in endolymphatic sac surgery for Menière's disease.

OBJECTIVE: To determine the efficacy of intraoperative electrocochleographic monitoring during endolymphatic sac-ballooning surgery for Menière's disease. DESIGN: At each of five surgical steps, the eighth nerve action potential (AP) amplitude and latency, summating potential (SP) amplitude, and SP/AP amplitude ratio were recorded. Data were analyzed using repeated measure analysis of variance. PATIENTS: Electrocochleographs were successfully recorded in 97 patients during endolymphatic sac-ballooning surgery. Forty patients had an abnormal baseline ratio (group 1), and 57 patients had a normal baseline ratio. RESULTS: Data showed that the SP/AP amplitude ratio reductions were significant only in group 1 patients. The SP/AP amplitude ratio was reduced in two thirds of the group 1 patients and unchanged in roughly the same proportion of group 2 patients. A significant reduction of SP/AP amplitude ratios was found to be always associated with prominent SP/AP ratios at the baseline, irrespective of glycerol test results, and only in cases of classic Menière's disease, indicating that this dominant ratio is a very reliable indicator of Menière's disease and endolymphatic hydrops. Importantly, reductions of SP/AP amplitude ratios were observed at every step to be consistently due to AP increase rather than SP decrease. CONCLUSIONS: It is theorized that the dominant SP/AP amplitude ratio found in patients with Menière's disease and endolymphatic hydrops is caused by the inhibition of AP activity rather than by the enhancement of the SP resulting from the displacement of the basilar membrane toward the scala tympani owing to hydropic endolymph, as is generally believed. We conclude that electrocochleograpic monitoring is useful during endolymphatic sacballooning surgery to provide a definitive delineation of the endolymphatic sac and its lumen; this delineation is the key to the success of such surgery.

Action Potentials↗
PubMed1994

Magnetic resonance imaging of chronic myocardial infarcts in formalin-fixed human autopsy hearts.

BACKGROUND: In post-myocardial infarction patients, three-dimensional structure of the infarct as well as infarct size are likely to be important factors affecting mortality, cardiac function, and arrhythmias. Current morphological methods for determining three-dimensional infarct structure in autopsied hearts are inexact and time consuming. The cardiac magnetic resonance imaging techniques used in living patients have shown potential in determining infarct size and structure but have limited resolution for morphometric postmortem studies. The recent development of magnetic resonance microscopy raises the possibility that three-dimensional infarct structure can be quantified at microscopic levels in autopsied hearts. The purpose of this study was to determine the ability of magnetic resonance imaging at different spatial resolutions to differentiate infarcted from noninfarcted myocardium. METHODS AND RESULTS: Magnetic resonance imaging was performed at 2.0 T on cross sections taken from 10 autopsied hearts containing old myocardial infarcts. T1 was derived from six images with repetition times (TRs) for each image ranging from 100 to 3200 milliseconds. T2 was derived from multi-echo images with echo times (TEs) ranging from 10 to 60 milliseconds. Resolution was approximately 400 x 400 microns in 2-mm-thick slices. Sites of infarcted and noninfarcted tissue were identified from histological sections taken from each slice, and the T1 and T2 values of these sites were obtained. Microscopic images were acquired with voxels of 100 x 100 x 625 microns, representing tissue volumes more than 1000-fold smaller than conventional clinical images. In all cases, T1 of infarcted tissue (459 +/- 266 milliseconds, mean +/- SD) was greater than that of noninfarcted tissue (272 +/- 163 milliseconds). Also, in all cases, T2 of infarcted tissue (49 +/- 14 milliseconds) was greater than that of noninfarcted tissue (35 +/- 8 milliseconds). CONCLUSIONS: T1 and T2 values for infarcted tissue are significantly different from those of noninfarcted tissue (P < .001). Based on these findings, it should be possible to develop techniques to perform three-dimensional imaging and quantitation of infarcts with a resolution of 400 microns or less. When volumetric three-dimensional imaging was performed using a T1-weighted sequence, the resulting 256(3) arrays supported isotropic resolution at 400 microns (voxel volume, 0.064 mm3). Subsequent volume rendering using a compositing algorithm clearly shows the infarcted areas in three dimensions. The techniques demonstrate the potential for quantitative three-dimensional cardiac morphometry using magnetic resonance imaging.

Algorithms↗
PubMed1994

Findings of anomalous pulmonary venous return using MRI.

This study represents a preliminary retrospective assessment of the value of spin-echo magnetic resonance imaging (MRI) in detecting and describing total or partial anomalous pulmonary venous return (APVR). MRI was performed in 21 cases of APVR; orthogonal planes were used in all. Of the 21 cases, 19 were classified as total APVR (TAPVR) and two were partial APVR (PAPVR). Of the 19 cases of TAPVR, seven supracardiac, nine cardiac, one infracardiac and two mixed type were noted. The detection rate of each pulmonary vein combined in all three planes was 57% in the right superior pulmonary vein (RSPV), 62% in the left superior pulmonary vein (LSPV), 76% in the right inferior pulmonary vein (RIPV), and 86% in the left inferior pulmonary vein (LIPV). The axial plane was most effective (RSPV: 38%; LSPV: 52%; RIPV: 71%; LIPV: 81%). The coronal plane offered a better detection rate than the axial plane in RSPV (43%) and additional information of bronchial and visceral situs. Imaging of the combined axial and coronal planes was sufficient to evaluate each individual pulmonary vein. The sagittal plane gave no additional information in this respect. Accurate identification of pulmonary venous confluence and anomalous pulmonary venous channel was 95% (20/21). Limitation of echocardiography and and angiocardiography makes cardiac MRI important in assessing pulmonary vein and pulmonary venous confluence. It obviates the need for invasive angiocardiography and is an important supplement to an inadequate echo.

Adolescent↗
PubMed1994

Spontaneous rupture of the liver associated with pregnancy: a report of two cases.

Spontaneous rupture of the liver associated with pregnancy is a rare and grave complication, usually occurring in preeclampsia or eclampsia. Two cases of ruptured subcapsular hematoma of the right liver during pregnancy are reported. The first case was a 19-year-old woman who had suffered from epigastralgia and absent fetal heart beat in the 32nd week of gestation. The second case was a 31-year-old female who complained of nausea and right upper quadrant pain in the 35th week of pregnancy. Both had preeclampsia, and developed shock with disseminated intravascular coagulation soon after admission. Both received surgery and were found to have ruptured hematoma over the right liver. Finally, the first patient died of renal failure, but the second survived because preoperative diagnosis had been exact. Greater suspicion, then awareness of diagnosis can lead to better timing of surgery and an improved prognosis for mother and child.

Adult↗
PubMed1993

Regulation of folate and one-carbon metabolism in mammalian cells. II. Effect of folylpoly-gamma-glutamate synthetase substrate specificity and level on folate metabolism and folylpoly-gamma-glutamate specificity of metabolic cycles of one-carbon metabolism.

The effect of folylpoly-gamma-glutamate synthetase (FPGS) levels on folate accumulation was investigated in Chinese hamster ovary cells expressing various levels of human and Escherichia coli FPGS activity. At low medium folate concentrations, folate accumulation was limited by influx and was independent of FPGS activity except in cells expressing extremely low levels of FPGS. Essentially all transported folate was metabolized to retained polyglutamate derivatives, the chain length of which varied with the level of FPGS activity. As medium folate concentration increased through the physiological to the pharmacological range, cellular folate accumulation became proportional to FPGS activity and the chain length of intracellular folates decreased. At high folate concentrations, competition between substrates for FPGS limited the extent of polyglutamylation and less than 5% of transported folate was retained by the cell. Pteroyltriglutamates functioned as effectively as the longer chain length polyglutamates normally found in mammalian cells in the metabolic cycles of de novo purine and thymidylate biosynthesis but were unable to support glycine and methionine synthesis. Transfectants expressing human FPGS and containing folates of glutamate chain length ranging from four to eight were equally effective at supporting glycine synthesis, and transfectants expressing higher levels of FPGS were able to grow in the absence of methionine. Growth in the absence of methionine required high (nonphysiological) intracellular folate levels and longer chain length polyglutamates.

Animals↗
PubMed1993

Promoter-specific trans-activation and inhibition mediated by JunB.

Nuclear levels of c-Jun, JunB, c-Fos, and LRF-1 (liver regeneration factor) are high for a large fraction of the G1 phase in regenerating liver and mitogen-stimulated hepatic cells. Previously, JunB was regarded as a less potent transcriptional activator than c-Jun that could also function as a repressor. However, we found that, like c-Jun, JunB alone or LRF-1/JunB strongly transactivates a cAMP-responsive promoter. Unlike c-Jun, JunB represses several AP-1 or activator of transcription factor site-containing promoters, and this inhibition is greatly enhanced in the presence of LRF-1. Here, we identify separate regions of JunB required for trans-activation and repression of these promoters. Deletion analysis shows that the region involved in trans-activation function is highly conserved among all Jun family members and corresponds to activator domain (A1) of c-Jun. In contrast, repression is maximal in the presence of both the DNA-binding domain and a region proximal to the basic region that is highly divergent among Jun proteins. Functional distinctions between Jun proteins during induction of the growth response and tumorigenesis may be accounted for by promoter-specific activation and repression mediated by regional differences in Jun family proteins.

3T3 Cells↗
PubMed1993

[Computed tomography of gastric carcinoma using water as a contrast agent].

To overcome the problem of poor mixing of gastrointestinal tract contents with a diluted iodinated contrast agent in abdominal computed tomography, pure water was adopted as an oral contrast agent. In 25 cases of clinically suspected gastric carcinoma, a subsequent pathological examination revealed six cases of early gastric cancer and 19 cases of advanced gastric cancer. We performed CT of the stomach using the following revised procedure: patients were given 600-1000 mL of water by mouth after an intramuscular dose of Buscopan to distend and immobilize the stomach. Gastric mucosal enhancement and the poorer enhanced submucosal layer were demonstrated by a bolus intravenous injection of iodine-containing contrast medium using an automatic injector synchronized with the CT machine. Based on abnormal gastric wall thickening and the abnormal mural enhancement patterns, an accuracy of 96% was attained in differentiating early gastric cancer from advanced gastric cancer, but the detection rates for extragastric invasion, gastric ulcers and lymphadenopathy were 67%, 43% and 63%, respectively. CT staging of gastric cancer was 72%, and was especially accurate for stages I and IV. Water as oral contrast agent for CT of the GI tract was readily accepted by patients and caused no side effects. Using water as an oral contrast for gastric CT is of great help in staging gastric cancer.

Adult↗