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Biomedical subjects

C M Chen

Publications and source records attributed to C M Chen.

At least 127 records · Page 7Linked to original sources
PubMed1998

Cross-reference weighted least square estimates for positron emission tomography.

An efficient new method, termed as the cross-reference weighted least square estimate (WLSE) [CRWLSE], is proposed to integrate the incomplete local smoothness information to improve the reconstruction of positron emission tomography (PET) images in the presence of accidental coincidence events and attenuation. The algebraic reconstruction technique (ART) is applied to this new estimate and the convergence is proved. This numerical technique is based on row operations. The computational complexity is only linear in the sizes of pixels and detector tubes. Hence, it is efficient in storage and computation for a large and sparse system. Moreover, the easy incorporation of range limits and spatially variant penalty will not deprive the efficiency. All this makes the new method practically applicable. An automatically data-driven selection method for this new estimate based on the generalized cross validation is also studied. The Monte Carlo studies demonstrate the advantages of this new method.

Mathematics↗
PubMed1998

Effect of butylidenephthalide on calcium mobilization in isolated rat aorta.

Butylidenephthalide (Bdph), an antispasmodic compound originally isolated from the rhizome of Ligusticum chuaxiong, has a selective anti-anginal effect without changing blood pressure. Experiments have been performed to determine the mechanism of this action. Synthetic Z-butylidenephthalide concentration-dependently relaxed phenylephrine (1 microM)- or KCl (60 mM)-induced precontractions of intact and denuded rat aorta rings. The relaxation induced by Bdph was endothelium-independent. Bdph (30-300 microM) concentration-dependently reduced cumulative phenylephrine- and KCl-induced contractions of intact rat aortic rings and non-competitively inhibited their log concentration-response curves. The pD2' values of Bdph for phenylephrine- and KCl-induced contraction were 3.66+/-0.13 (n = 8) and 3.71+/-0.07 (n = 8), respectively, which were not significantly different from each other. Bdph also concentration-dependently reduced cumulative Ca2+-induced contractions of intact rat aortic rings in high-KCl (60 mM) Ca2+-free physiological salt solution and non-competitively inhibited its log concentration-response curve. The pD2' value of Bdph for the Ca2+-induced contractions was 3.21+/-0.01 (n = 7) which was significantly different from the pD2' value obtained from the cumulative KCl-induced contractions. These results suggest that Bdph inhibits calcium release from calcium stores more selectively than calcium influx from extracellular space via voltage-dependent calcium channels. The inhibition by Bdph of calcium release from KCl-sensitive calcium stores might be similar to its inhibition of calcium release from phenylephrine-sensitive calcium stores. However, because phenylephrine generates inositol-1,4,5-trisphosphate (IP3) whereas KCl does not, the inhibitory effect of Bdph might not be related to IP3 production.

Animals↗
PubMed1998

ABT-378, a highly potent inhibitor of the human immunodeficiency virus protease.

The valine at position 82 (Val 82) in the active site of the human immunodeficiency virus (HIV) protease mutates in response to therapy with the protease inhibitor ritonavir. By using the X-ray crystal structure of the complex of HIV protease and ritonavir, the potent protease inhibitor ABT-378, which has a diminished interaction with Val 82, was designed. ABT-378 potently inhibited wild-type and mutant HIV protease (Ki = 1.3 to 3.6 pM), blocked the replication of laboratory and clinical strains of HIV type 1 (50% effective concentration [EC50], 0.006 to 0.017 microM), and maintained high potency against mutant HIV selected by ritonavir in vivo (EC50, </=0. 06 microM). The metabolism of ABT-378 was strongly inhibited by ritonavir in vitro. Consequently, following concomitant oral administration of ABT-378 and ritonavir, the concentrations of ABT-378 in rat, dog, and monkey plasma exceeded the in vitro antiviral EC50 in the presence of human serum by >50-fold after 8 h. In healthy human volunteers, coadministration of a single 400-mg dose of ABT-378 with 50 mg of ritonavir enhanced the area under the concentration curve of ABT-378 in plasma by 77-fold over that observed after dosing with ABT-378 alone, and mean concentrations of ABT-378 exceeded the EC50 for >24 h. These results demonstrate the potential utility of ABT-378 as a therapeutic intervention against AIDS.

Animals↗
PubMed1998

Hirayama disease: MR diagnosis.

We report the MR findings in two cases of Hirayama disease, a kind of cervical myelopathy related to flexion movements of the neck. In flexion MR studies, we can see the striking and pathognomonic picture of anterior shifting of posterior dura at the lower cervical spinal canal. In nonflexion studies, we find that asymmetric cord atrophy, especially at the lower cervical cord, though subtle, is highly suggestive of Hirayama disease. When it is seen, a flexion MR study is warranted to prove this diagnosis.

Adolescent↗
PubMed1998

Acute closed humeral shaft fractures treated with dynamic compression plate.

BACKGROUND: To define the efficacy of dynamic compression plates (DCPs) for the treatment of closed humeral shaft fractures. METHODS: A total of 165 patients with closed humeral shaft fractures were studied retrospectively. There were 120 patients who underwent open reduction and internal fixation with DCPs and no bone grafting (BG). Forty-five patients received the same procedures with BG. The mean follow-up period was 93 months. RESULTS: In the DCP without BG group, the average blood loss was 350 ml, operation time was 105 minutes, hospital stay was 8.5 days and fracture union time was 13.5 weeks. In the DCP with BG group, the average blood loss was 525 ml, operation time was 115 minutes, hospital stay was 7.9 days and fracture union time was 9.2 weeks. CONCLUSIONS: In our experience, DCPs are effective for surgical fixation of humeral shaft fractures. Prophylactic BG is recommended for cases with more comminution.

Adolescent↗
PubMed1997

Myasthenia gravis and Charcot-Marie-Tooth disease type 1A: an unusual combination of diseases.

Concurrence of myasthenia gravis (MG) and Charcot-Marie-Tooth type 1 (CMT1A) neuropathy is rare. We describe a 60-year-old woman with MG and genetically proved CMT1A. The fluctuating ocular symptoms and proximal limb weakness were markedly improved by pyridostigmine treatment. Recognition of the possible association of MG and CMT1A in the same patient is important because the therapeutic result is rewarding.

Charcot-Marie-Tooth Disease↗
PubMed1997

Spontaneous spinal epidural haematomas with repeated remission and relapse.

We present a case of spontaneous spinal epidural haematoma (SSEH) with a rare clinical course of repeated spontaneous recovery and relapse. The patient suffered three episodes of upper-back pain of sudden onset followed by sensory and motor dysfunction after weight lifting. In the first two episodes, the neurological deficits recovered spontaneously and completely. In the last episode, paraplegia persisted even after emergency surgery. Serial studies with computed tomographic (CT) myelography and magnetic resonance imaging (MRI) demonstrated the remitting and relapsing course of the SSEHs. The possible causes of the SSEHs and the mechanisms of spontaneous recovery are discussed.

Diagnosis, Differential↗
PubMed1997

Breast mass due to alveolar soft part sarcoma of the pectoris major muscle.

We present a case of alveolar soft part sarcoma (ASPS) of the pectoris major muscle in a 20-year-old female. She felt a mass in her right side breast for 7 years. The lesion was almost the same size with occasional throbbing pain and tenderness. Fine needle aspiration of the tumor was performed in the OPD and suspicious abnormal cells were reported. Ultrasound (US) examination of the breast revealed a large heterogeneously hypoechoic lesion contiguous to the pectoris major muscle. Profound color flow signals were evident in both central and peripheral regions of the mass. Spectral Doppler US showed high flow velocity in the tumor vessels with resistivity index of 0.73. Surgical intervention was performed and the histological examination yielded a diagnosis of ASPS.

Adolescent↗
PubMed1997

Klebsiella meningitis in Taiwan: an overview.

Klebsiella infection has been considered to be an uncommon cause of meningitis. To determine its incidence and clinical features, we reviewed the microbiologic records of cerebrospinal fluid (CSF) and blood cultures and the medical records of patients with bacterial meningitis admitted between 1981 and 1995. Klebsiella meningitis was diagnosed in 79 patients with 83 episodes. All patients had klebsiella isolated from CSF and/or blood and typical symptoms and signs of acute bacterial meningitis. Of these, 74 were over 16 years of age and 2 of the 5 children were infants. There was an increased prevalence rate of klebsiella meningitis after 1986. Of the 83 episodes, only 9 occurred between 1981 and 1986, accounting for 7.8% of 115 cases with CSF and/or blood culture-proven acute bacterial meningitis, whereas in 1987-95, there were 74 episodes accounting for 17.7% of 419 bacteriologically proven cases. K. pneumoniae accounted for 69 episodes, K. oxytoca, 11 episodes and K. ozaenae, 3 episodes. Male gender, diabetes mellitus and liver cirrhosis were commonly associated with K. pneumoniae meningitis. Neurosurgical procedures were frequently associated with K. oxytoca meningitis. All three patients with K. ozaenae meningitis had a primary disease of the nasopharyngeal pathway. The mortality rate due to K. pneumoniae was 48.5%, K. oxytoca, 10% and K. ozaenae, 0%. In patients with K. pneumoniae meningitis, poor prognostic factors included age over 60 years, diabetes mellitus, bacteremia and severe neurological deficits on the first day of treatment.

Adolescent↗
PubMed1997

Two tandemly repeated telomere-associated sequences in Nicotiana plumbaginifolia.

Two tandemly repeated telomere-associated sequences, NP3R and NP4R, have been isolated from Nicotiana plumbaginifolia. The length of a repeating unit for NP3R and NP4R is 165 and 180 nucleotides respectively. The abundance of NP3R, NP4R and telomeric repeats is, respectively, 8.4 x 10(4), 6 x 10(3) and 1.5 x 10(6) copies per haploid genome of N. plumbaginifolia. Fluorescence in situ hybridization revealed that NP3R is located at the ends and/or in interstitial regions of all 10 chromosomes and NP4R on the terminal regions of three chromosomes in the haploid genome of N. plumbaginifolia. Sequence homology search revealed that not only are NP3R and NP4R homologous to HRS60 and GRS, respectively, two tandem repeats isolated from N. tabacum, but that NP3R and NP4R are also related to each other, suggesting that they originated from a common ancestral sequence. The role of these repeated sequences in chromosome healing is discussed based on the observation that two to three copies of a telomere-similar sequence were present in each repeating unit of NP3R and NP4R.

Base Sequence↗
PubMed1997

Endothelium-dependent higenamine-induced aortic relaxation in isolated rat aorta.

The pharmacological action of higenamine in isolated rat aorta was investigated. Although the beta-adrenoceptor antagonist propranolol (1 x 10(-5) M) completely blocked the beta-adrenoceptor agonist higenamine in inducing a positive chronotropic activity in isolated mouse atria, the higenamine-induced aortic relaxation was not completely antagonized by this concentration of propranolol. The present data also demonstrate that the higenamine-induced aortic relaxation was attenuated in the absence of endothelium. These findings suggest that the beta-adrenoceptor specificity to higenamine in aorta is different from that of beta-1 in atria; moreover, the beta-adrenoceptors sensitive to higenamine are mainly located in the endothelial layer.

Adrenergic beta-Agonists↗
PubMed1997

Closed humeral shaft fractures: a prospective evaluation of surgical treatment.

OBJECTIVE: We tried to define the roles of the rigid dynamic compression plate (DCP) and the semi-rigid Ender nail (EN) in the treatment of closed humeral shaft fractures. DESIGN: A prospective, randomized clinical study was performed with detailed comparison parameters. MATERIALS AND METHODS: Ninety-one closed humeral shaft fractures were treated. Randomly, 30 humeri were treated with open reduction and internal fixation with DCP and no bone grafting (BG), 29 were treated with the same procedure but with BG, and 32 were treated with closed reduction and internal fixation with Ender nails. The average follow-up period was 32 months (range, 13-54 months). MEASUREMENTS AND MAIN RESULTS: In the group with DCP without BG, the average blood loss was 270 mL, operation time was 92 minutes, hospital length of stay was 6.5 days, and union time was 12.5 weeks. In the group with DCP with BG, the average blood loss was 325 mL, operation time was 108 minutes, hospital length of stay was 6.9 days, and union time was 9.4 weeks. In the EN group, the average blood loss was 114 mL, operation time was 54 minutes, hospital length of stay was 5.6 days, and union time was 9.9 weeks. Analysis of variance and Fisher's exact test were used to evaluate the statistical significance. CONCLUSION: In our experience, for humeral shaft fractures fixed surgically, EN is better than DCP without BG. When DCP is chosen for the means of fixation, prophylactic BG is recommended, especially in cases with more comminution.

Analysis of Variance↗
PubMed1997

Severe rhabdomyolysis with good recovery in a patient with head injury: case report.

OBJECTIVE AND IMPORTANCE: We report a case of head injury, in which a hyperosmolar state evolved during the course of treatment, complicated by severe rhabdomyolysis and acute renal failure, which subsequently resulted in a good recovery after intensive supportive treatment. To our knowledge, such high levels of creatine kinase in a patient with head injury and rhabdomyolysis have not been reported. CLINICAL PRESENTATION AND INTERVENTION: A 19-year-old male patient with head injury sustained a compound fracture of the frontal region. He received a hyperosmolar agent to treat brain edema and developed a hyperosmolar state and diabetes insipidus 1 day after the accident. There were no obvious associated injuries at physical examination. After admission to the intensive care unit, the patient developed myoglobinuria and rhabdomyolysis; serum creatine kinase was elevated to a peak of 650,000 IU/L. Four days later, acute renal failure was noted. The patient's myoglobinuria and rhabdomyolysis gradually declined, and he eventually recovered from acute renal failure after supportive treatment and dialysis. CONCLUSION: We postulate that the hyperosmolar state of the patient was the major cause of his severe rhabdomyolysis. Associated hypokalemia and hypophosphatemia are also predisposed to rhabdomyolysis. The most serious complication in rhabdomyolysis is acute renal failure, but most patients who receive supportive treatment and can survive despite the complications can expect to have normal renal function restored.

Acute Kidney Injury↗
PubMed1997

Colonic transit time assessed by 67 Ga-citrate in a case-series of patients with recto-sigmoid adenomas.

One plausible mechanism by which dietary factors may influence colorectal carcinogenesis is through their effect on intestinal transit time. This study examined colonic transit by means of oral 67Ga-citrate in a case-series of patients who had developed recto-sigmoid adenoma. Adenoma patients had a significantly shorter transit time than constipated patients (P = 0.01) and our results also suggest (but do not show conclusively) that colonic transit in adenoma patients is similar to that of normal controls. Although these findings require confirmation from a larger study, they raise the hypothesis that colonic transit times are not delayed in patients who harbour recto-sigmoid adenomas.

Adenoma↗
PubMed1997

Stereoselectivity of butylidenephthalide on voltage-dependent calcium channels in guinea-pig isolated ileum.

Two geometric isomers, the Z- and the E- forms, can be separated from synthetic mixtures of butylidenephthalide (Bdph). Z-Bdph (50-100 microM) non-competitively inhibited Ca(2+)-induced contractions in depolarized (K+, 60 mM) guinea-pig ileum longitudinal smooth muscle, with a pD2' value of 3.88 +/- 0.20 (n = 5). However, E-Bdph (20-100 microM) competitively inhibited these contractions with a pA2 value of 4.56 +/- 0.18 (n = 5) which was significantly (P < 0.05) greater than the pD2' value of Z-Bdph. In contrast, the two isomers had no stereoselective inhibitory action on Ca2+ influx through pre- or post-junctional membranes of cholinergic nerve endings from which the transmitter acetylcholine is released or on Ca2+ release from intracellular stores. Therefore, the trans-Z and cis-E forms of Bdph might have geometric stereoselectivity for voltage-dependent calcium channels (VDC) in guinea-pig longitudinal smooth muscle. Both isomers might inhibit more selectively the contractile twitch responses evoked by electrical stimulation than by cumulative acetylcholine- or carbachol-induced transient contractions in guinea-pig ileum longitudinal smooth muscle.

Animals↗
PubMed1997

Direct interaction of hepatitis C virus core protein with the cellular lymphotoxin-beta receptor modulates the signal pathway of the lymphotoxin-beta receptor.

Previous studies suggest that the core protein of hepatitis C virus (HCV) has a pleiotropic function in the replication cycle of the virus. To understand the role of this protein in HCV pathogenesis, we used a yeast two-hybrid protein interaction cloning system to search for cellular proteins physically interacting with the HCV core protein. One such cellular gene was isolated and characterized as the gene encoding the lymphotoxin-beta receptor (LT-betaR). In vitro binding analysis demonstrated that the HCV core protein binds to the C-terminal 98 amino acids within the intracellular domain of the LT-betaR that is involved in signal transduction, although the binding affinity of the full-length HCV core protein was weaker than that of its C-terminally truncated form. Our results also indicated that the N-terminal 40-amino-acid segment of the HCV core protein was sufficient for interaction with LT-betaR and that the core protein could form complexes with the oligomeric form of the intracellular domain of LT-betaR, which is a prerequisite for downstream signaling of this receptor. Similar to other members of the tumor necrosis factor (TNF) receptor superfamily, LT-betaR is involved in the cytotoxic effect of the signaling pathway, and thus we have elucidated the biological consequence of interaction between the HCV core protein and LT-betaR. Our results indicated that in the presence of the synergizing agent gamma interferon, the HCV core protein enhances the cytotoxic effects of recombinant forms of LT-betaR ligand in HeLa cells but not in hepatoma cells. Furthermore, this enhancement of the cytolytic activity was cytokine specific, since in the presence of cycloheximide, the expression of the HCV core protein did not elicit an increase in the cytolytic activity of TNF in both HeLa and hepatoma cells. In summary, the HCV core protein can associate with LT-betaR, and this protein-protein interaction has a modulatory effect on the signaling pathway of LT-betaR in certain cell types. Given the known roles of LT-betaR/LT-alpha1,beta2 receptor-ligand interactions in the normal development of peripheral lymphoid organs and in triggering cytolytic activity and NF-kappaB activation in certain cell types, our finding implies that the HCV core protein may aggravate these biological functions of LT-betaR, resulting in pathogenesis in HCV-infected cells.

Binding Sites↗