Biomedical subjects

C C Shen

Publications and source records attributed to C C Shen.

At least 19 recordsLinked to original sources

PubMed2001

A high-resolution absolute-dated late Pleistocene Monsoon record from Hulu Cave, China.

Oxygen isotope records of five stalagmites from Hulu Cave near Nanjing bear a remarkable resemblance to oxygen isotope records from Greenland ice cores, suggesting that East Asian Monsoon intensity changed in concert with Greenland temperature between 11,000 and 75,000 years before the present (yr. B.P.). Between 11,000 and 30,000 yr. B.P., the timing of changes in the monsoon, as established with 230Th dates, generally agrees with the timing of temperature changes from the Greenland Ice Sheet Project Two (GISP2) core, which supports GISP2's chronology in this interval. Our record links North Atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer East Asian Monsoon originates.

Journal Article↗

PubMed2001

Harmonic leakage and image quality degradation in tissue harmonic imaging.

Image quality degradation caused by harmonic leakage was studied for finite amplitude distortion-based harmonic imaging. Various sources of harmonic leakage, including transmit waveform, signal bandwidth, and system nonlinearity, were investigated using both simulations and hydrophone measurements. Effects of harmonic leakage in the presence of sound velocity inhomogeneities were also considered. Results indicated that sidelobe levels of the harmonic beam pattern were directly affected by harmonic leakage when the harmonic signal was obtained by filtering out the fundamental signal. Because sidelobe levels also increase with the bandwidth of the transmitted signal, a trade-off exists between axial resolution and contrast resolution. It is concluded that accurate control of the frequency content of the waveform prior to propagation is necessary to optimize imaging performance of tissue harmonic imaging. The filtering technique was also compared with the pulse inversion technique. It was shown that the pulse inversion technique effectively suppresses harmonic leakage at the cost of imaging frame rate and potential motion artifacts.

Computer Simulation↗

PubMed2001

Tissue harmonic image analysis based on spatial covariance.

The van Cittert-Zernike theorem has been widely used to describe spatial covariance of the pressure field backscattered from a speckle object. Spatial covariance contains important information in the context of correlation-based correction of sound velocity inhomogeneities. Previous work was primarily based on spatial covariance analysis for linear imaging. In this paper, we extend the analysis to tissue harmonic imaging. Specifically, we investigate effects of the signal-to-noise ratio (SNR) and sound velocity inhomogeneities on spatial covariance. Results from tissue harmonic imaging are also compared with those from linear imaging. Both simulations and experiments are performed. At high SNRs, although both linear imaging and tissue harmonic imaging have spatial covariance functions close to theory, the spatial covariance of tissue harmonic imaging is consistently lower than that of linear imaging regardless of the presence of sound velocity inhomogeneities. At low SNRs, on the other hand, spatial covariance of tissue harmonic imaging is significantly affected. Because the tissue harmonic signal is much weaker than the linear counterpart, the low SNR reduces the accuracy of correlation-based estimation. It is concluded that the linear signal is more suitable for correlation-based correction of sound velocity inhomogeneities, despite the fact that tissue harmonic imaging generally has improved image quality over linear imaging.

Ultrasonography↗

PubMed2001

Delayed multidose treatment with nicotinamide extends the degree and duration of neuroprotection by reducing infarction and improving behavioral scores up to two weeks following transient focal cerebral ischemia in Wistar rats.

A single, delayed dose of nicotinamide (NAm) was shown to be protective against focal cerebral ischemia in rats, but the protection was limited to three to seven days following stroke. The investigation reported here was conducted to examine if the use of multiple doses of NAm, administered after the onset of focal cerebral ischemia, would extend the duration of neuroprotection compared with a single dose treatment regimen. Male Wistar rats were subjected to transient focal cerebral ischemia by occluding the right middle cerebral artery (MCAo) for two hours. Following MCAo, motor and sensory behavioral tests were performed daily and the cerebral infarct volumes were measured at two weeks after sacrifice. Each animal was placed into one of four groups that received either normal saline alone (Group S), one (Group A), two (Group B), or three (Group C) doses of NAm (500 mg/kg). Each animal, therefore, received three treatments over two weeks, with the first dose administered intravenously two hours after the onset of MCAo. Single and multiple doses of NAm reduced the infarction (p < 0.01) and improved (p < 0.05) the neurologic sensory and motor behavior when compared with the saline-treated animals up to two weeks after stroke. Moreover, animals that received multiple doses of NAm recuperated full motor function not different from normal, preoperative motor behavior. Delayed treatment with NAm given as multiple doses, therefore, further enhances the extent and duration of neuroprotection by significantly reducing cerebral infarct volumes, improving neurologic behavioral scores, and confers a complete motor recovery up to two weeks from the onset of focal cerebral ischemia in Wistar rats.

Animals↗

PubMed2001

Endoscope-assisted microsurgery for treatment of a suprasellar craniopharyngioma presenting precocious puberty.

Being the most common childhood tumor to involve the hypothalamus and pituitary gland, craniopharyngioma, a histologically benign tumor, is usually related to growth retardation and hypogonadism. The presentation of precocious puberty is very rare for a hypothalamic craniopharyngioma. Here, we report such a case. The female patient had presented with symptoms of menarche and breast development since she was 6 years old. Hormonal therapy with a gonadotropin-releasing hormone analogue was instituted to cease precocious puberty but was unsuccessful. Magnetic resonance imaging of the sella showed a 1-cm tumor in the hypothalamic area. Through a pterional approach, the tumor was removed en bloc with endoscope-assisted microsurgery. After the operation, our patient's symptoms improved, so the hormone therapy was discontinued. This extremely unique association of craniopharyngioma and precocious puberty, the causes and mechanisms involved along with the advantages of endoscope-assisted microsurgery are discussed.

Child↗

PubMed2001

Cerebral intraventricular hemorrhage caused by a large cerebral arteriovenous malformation at 31 years after diagnosis.

Cerebral arteriovenous malformation (AVM) has an overall 2% to 4% annual risk of hemorrhage. The annual risk of hemorrhage does not decrease with age. However, the natural history of non-operative AVM is difficult to follow up consistently for more than 30 years. In this report, we present a case with a large cerebral AVM which developed a major bleeding causing intraventricular hemorrhage (IVH) 31 years after the diagnosis. A male patient was proved to have a cerebral AVM in the right corpus callosum by cerebral angiography at ages 20 and 28. He was found losing consciousness due to rupture of AVM with IVH at age 51. A small cerebral aneurysm and a dilated vein (aneurysm) of Galen were noted also. A craniotomy with removal of the hematoma and microsurgical resection of the AVM was performed immediately, and the patient regained normal respiration and consciousness about 2 months and 7 months after craniotomy, respectively. We recommend that neurosurgeons should play active roles in encouraging young patients with large AVMs to receive microsurgical resection.

Age Factors↗

PubMed2000

Differential alteration of catecholamine release during chemical hypoxia is correlated with cell toxicity and is blocked by protein kinase C inhibitors in PC12 cells.

Release of neurotransmitters, including dopamine and glutamate, has been implicated in hypoxia/ischemia-induced alterations in neuronal function and in subsequent tissue damage. Although extensive studies have been done on the mechanism underlying the changes in glutamate release, few have examined the mechanism that is responsible for the changes in catecholamines. Rat pheochromocytoma-12 (PC12) cells synthesize, store, and release catecholamines including DA and NE. Therefore, we used HPLC and ED to evaluate extracellular DA and NE concentrations in a medium during chemical hypoxia in PC12 cells. Chemical hypoxia produced by KCN induced differential release of DA and NE. Under normal glucose conditions, KCN induced release of NE, but not DA. Under glucose-free conditions, KCN-induced release of DA was elevated transiently, whereas the release of NE increased progressively. Under parallel conditions, KCN biphasically elevated the level of cytosolic free calcium ([CA(2+)](i)) in glucose-free DMEM, peaking at 95 +/- 18 nM at 1,107 +/- 151 s, followed by a new plateau level at 249 +/- 24 nM sustained from 4,243 +/- 466 to 5,263 +/- 440 s. Cell toxicity, as measured by LDH release, was increased significantly by KCN in glucose-free DMEM but was diminished in the presence of glucose, and was correlated with DA release by chemical hypoxia. The protein kinase C (PKC) inhibitor GO6976 or staurosporine inhibited KCN-induced LDH release as well as the release of NE and DA. Taken together, selective activation of DA but not NE was correlated with the LDH release by chemical hypoxia, and was diminished with GO6976 or staurosporine. These results suggest that selective activation of PKC isoforms is involved in the chemical hypoxia-induced DA release, which may lead to neuronal cell toxicity.

Animals↗

PubMed2000

A novel agarofuran sesquiterpene, celahin D from Celastrus hindsii Benth.

A novel agarofuran sesquiterpene polyol ester, 1beta,2beta,6alpha,15beta-tetracetoxy-8 beta,9alpha-dibenzoyloxy-beta- dihydroagarofuran (celahin D) (1), two known analogues of 1,1beta-acetoxy-8beta,9alpha-dibenzoyloxy-4al pha6alpha-dihydroxy-2beta(alphamethylbutanoyloxy)-beta-++ +dihydroagarofuran (2) and beta-acetoxy-8beta,9alpha-dibenzoyloxy-6alpha-hy droxy-2beta(alpha -methylbutanoyloxy)-beta-dihydroagarofuran (3), and a known cytotoxic sesquiterpene pyridine alkaloid, emarginatine E (4) were isolated from the stems of Celastrus hindsii Benth. Three known triterpenes, loranthol (5), lupenone (6) and friedelinol (7) were also obtained from the titled plant. Structural elucidation of compound 1 was established by 2D NMR spectra.

Magnetic Resonance Spectroscopy↗

PubMed2000

Endoscopic endonasal transsphenoidal surgery for pituitary tumors.

BACKGROUND: The traditional transsphenoidal approach for pituitary surgery can be performed via transnasal, transseptal, or sublabial routes through unilateral or bilateral nostrils. It requires wide mucosal and septal dissection and postoperative nasal packing. Endoscopic surgery has been widely used because it allows excellent visualization with minimal invasion. Recently, it has also been applied to pituitary surgery. METHODS: From January, 1997 to February, 1999, 40 patients with pituitary adenomas underwent the transsphenoidal approach using a rigid endoscope via one nostril. Among the 40 cases, 18 were prolactinomas, seven were growth hormone-secreting adenomas and 15 were nonfunctional adenomas. RESULTS: After surgery, complete resolution or improvement of symptoms and restoration of normal hormone levels were achieved in 16 patients with prolactinomas, five with growth hormone-secreting adenomas and 12 with nonfunctional macroadenomas. One patient with a recurrent microprolactinoma needed a second operation to remove the cavernous portion of the tumor. Another male patient with a macroprolactinoma who experienced galactorrhea and gynecomastia showed improvement of clinical symptoms after the operation. Two patients with residual growth hormone-secreting macroadenomas in the cavernous sinus needed Sandostatin treatment. Three patients with nonfunctional macroadenomas underwent nearly total resection leaving residual tumor in the cavernous sinus, which then required adjuvant radiotherapy. No complications related to this approach were encountered in the patients during the follow-up period. CONCLUSIONS: Endonasal transsphenoidal endoscopic surgery can be employed for treating pituitary tumors without septal or sublabial complications. Postoperative suffering was reduced and hospitalization was shortened by this mini-invasive procedure. This surgical procedure can be used for both microadenomas and macroadenomas.

Adenoma↗

PubMed1999

Antioxidant principles from Ephemerantha lonchophylla.

One dihydrostilbene and three phenanthrene antioxidants were isolated from an ethanolic extract of the Chinese herbal Ephemerantha lonchophylla. One of these compounds, ephemeranthone (4) is a new natural product. Denbinobin (1) and 3-methylgigantol (3) have been previously isolated from this plant, and 3-ethoxy-5-hydroxy-7-methoxy-1,4-phenanthraquinone (2) is an artifact. The structures of these compounds were determined by spectroscopic analysis. The antioxidative activities for inhibiting human low density lipoprotein oxidation in vitro of compounds 1-4 were determined, and only 4 was active (5.3 times that of probucol).

Antioxidants↗

PubMed1999

Effects of transmit focusing on finite amplitude distortion based second harmonic generation.

Generation of the second harmonic signal was studied for finite amplitude distortion based harmonic imaging. Acoustic field amplitudes along the range axis of a fixed focus transducer were measured using a PVDF needle hydrophone. Results indicated that on-axis amplitudes strongly depended on the f-number at both the fundamental and the second harmonic frequencies. Differences of the on-axis amplitudes between the two frequencies were also investigated. To explore the possibility of increasing harmonic generation by extending the depth of focus, a two-focus transducer was employed. Hydrophone measurements, pulse-echo imaging and simulations were performed. Although the increase in harmonic generation depended on specific imaging parameters, the effectiveness of improving the harmonic signal-to-noise ratio (SNR) by increasing the depth of field was clearly demonstrated. Degradation in contrast resolution associated with the two-focus transducer was also evaluated. It was found that the contrast resolution was still significantly better than that of the fundamental image at the same frequency. Results of the study using the two-focus transducers can be generalized to imaging systems with full dynamic transmit focusing capabilities. In other words, it is expected that dynamic transmit focusing can improve the SNR of finite amplitude distortion based second harmonic imaging while improving the contrast resolution over fundamental imaging.

Ultrasonics↗

PubMed1998

Cytotoxicity of curcuminoids and some novel compounds from Curcuma zedoaria.

Bioassay-directed fractionation of an EtOH extract of Curcuma zedoaria led to isolation of an active curcuminoid, which was identified as demethoxycurcumin (2) by comparison of its 1H and 13C NMR spectra with literature data and by direct comparison with synthetic material. Curcumin (1) and bisdemethoxycurcumin (3) were also obtained. Curcuminoids (1-3) were synthesized and demonstrated to be cytotoxic against human ovarian cancer OVCAR-3 cells. The observed CD50 values of 1, 2, and 3 were 4.4, 3.8, and 3.1 microg/mL, respectively. Three additional novel compounds, 3, 7-dimethylindan-5-carboxylic acid (4), curcolonol (5), and guaidiol (6), were also isolated from the EtOH extract. The structures and relative stereochemistry of 4-6 were determined by spectroscopic methods and X-ray crystallographic analysis.

Antineoplastic Agents, Phytogenic↗

PubMed1998

Tuberculum sellae meningiomas: clinical manifestation, radiologic diagnosis, surgery and visual outcome.

BACKGROUND: Most patients with tuberculum sellae meningioma (TSM) present with visual symptoms mimicking a pituitary macroadenoma. Accurate preoperative differentiation is important because TSM requires a craniotomy, whereas the transsphenoidal route is preferred for removal of most pituitary macroadenomas. METHODS: From 1989 to 1994, five patients with TSM were treated at Taichung Veterans General Hospital. All were female, ranging in age from 20 to 60 years. This paper is a retrospective review of clinical features, diagnostic methods, treatment and postoperative visual recovery. RESULTS: The most common symptom, with a duration of one month to two years, was asymmetrical visual loss. Abnormal endocrine levels were found in one patient (prolactin: 47.91 ng/ml). Another patient was misdiagnosed as having a pituitary adenoma by coronal view computed tomography (CT) and underwent a transsphenoidal operation. Later, an accurate diagnosis was made using magnetic resonance imaging (MRI). She then underwent another operation--unilateral subfrontal craniotomy with total removal of the tumor. The other patients were preoperatively diagnosed as having meningioma by MRI. They also underwent unilateral subfrontal craniotomy with total removal of tumor. All patients showed good visual improvement after their operation. The extent of visual improvement was closely related to the duration of preoperative visual loss. There was no tumor recurrence after a follow-up period of six months to five years (mean, two years and six months). CONCLUSIONS: It should be emphasized that the diagnosis of TSM must first be based on clinical symptoms and signs, or "chiasma-syndrome". It can be accurately diagnosed preoperatively by sagittal view MRI. Early diagnosis will increase the chances of a good postoperative visual outcome.

Adult↗

PubMed1998

Surgical management of intracranial arteriovenous malformation associated with aneurysms.

BACKGROUND: The association of intracranial arteriovenous malformation (AVM) with aneurysm(s) is hazardous, and various forms of treatment have been suggested. Most authors agree that surgery for these combined lesions should be directed toward the symptomatic lesion first. This may be difficult, however, especially when the source of the hemorrhage is unclear. METHODS: Between 1985 and 1996, 12 patients with combined AVM and aneurysm(s) were treated at this institution. Clinical presentations included headache and hemorrhage in all patients, limb weakness in three patients, and seizure in one patient. Hemorrhage types included subarachnoid hemorrhage (SAH), intracerebral hemorrhage (ICH) and intraventricular hemorrhage (IVH). To avoid the intraoperative rupture of aneurysms during resection of the AVM, these were routinely clipped first, followed by total extirpation of the AVM. RESULTS: SAH, ICH and/or IVH simultaneously presented in seven patients (58.3%). According to the surgical findings, bleeding resulted from the aneurysm in 10 patients and AVM in two patients. There was a high incidence of combined lesions in the posterior circulation (67%) in our series. Among the patients with combined lesions in the posterior circulation, half had multiple aneurysms. A total of 21 aneurysms were found in the 12 patients, with five patients harboring multiple aneurysms. Among the 12 patients, 10 had good results. Eight patients received one-stage operations and two received two-stage operations. Two patients died, one of massive rebleeding from multiple giant aneurysms with SAH, IVH and ICH after ventricular drainage, and the other died of massive bleeding during resection of a large AVM. CONCLUSIONS: It is difficult to predict bleeding sources preoperatively by radiologic images. Our experience has led to the belief that the safest approach is to treat the aneurysm before microsurgical resection of the AVM. Most of our patients were surgically treated in one approach and showed good results.

Adult↗

PubMed1998

Microsurgical management of intracranial epidermoid cysts.

BACKGROUND: Intracranial epidermoid cysts are slow-growing congenital neoplasms that usually spread and adhere to critical neurovascular structures along the basal cistern, particularly the cerebellopontine angle (CPA) and parasellar region. Clinical symptoms include trigeminal neuralgia, headache and dizziness, progressive hemiparesis, unstable gait and hemifacial spasm. With the aid of modern imaging techniques, such as computed tomography (CT) and magnetic resonance imaging (MRI), an effective microsurgical approach can be planned preoperatively to completely remove tumors and avoid complications. METHODS: Twenty-six patients with intracranial epidermoid cysts were microsurgically treated between July 1984 and June 1997. Diagnostic procedures included enhanced CT and/or CT cisternography and MRI. All patients underwent microsurgical treatment for tumor removal. RESULTS: Total tumor removal was achieved in 12 patients (46.2%), near-total removal in seven (26.9%), partial removal in six (23.1%) and stereotactic biopsy in one patient (3.8%). Postoperative deterioration of the neurologic condition was found in three patients who required further surgery, aseptic meningitis in four patients and communicating hydrocephalus requiring shunting in three patients. The functional prognoses were excellent in 23 patients (88.5%), good in two patients (7.7%) and fair in one patient (3.8%). Among the 26 patients, three died of pneumonia three, six and nine months after surgery, respectively. CONCLUSIONS: MRI is particularly useful for defining the anatomic limits of tumor tissue and surgical planning. The surgical results were excellent in patients with near-total tumor removal, as well as in patients with total removal. Aggressive surgical tumor removal may result in transient, but significant, cranial nerve palsy and should be avoided. Perioperative administration of steroids and wound protection may be beneficial for preventing the development of postoperative aseptic meningitis and hydrocephalus.

Adult↗

PubMed1998

Glial cell-specific differences in response to alkylation damage.

Oligodendrocytes are preferentially sensitive to the toxic, carcinogenic, and teratogenic effects of methylnitrosourea (MNU). The mechanisms responsible for this enhanced sensitivity have not been fully elucidated. One of the most vulnerable cellular targets for this chemical is mitochondrial DNA (mtDNA). To determine if differences in mtDNA damage and repair capacity exist among the different CNS glial cell types, the effects of MNU exposure on oligodendroglia, astroglia, and microglia cultured separately from neonatal rat brain were compared. Quantitative determinations of mtDNA initial break frequencies and repair efficiencies showed that whereas no cell type-specific differences in initial mtDNA damage were detected, mtDNA repair in oligodendrocytes, oligodendrocyte progenitors, and microglia was significantly reduced compared to that of astrocytes. In astrocytes, and all other cell types previously evaluated in our laboratory, >60% of N-methylpurines were removed from the mtDNA by 24 hr. In contrast, only 35% of lesions were removed from mtDNA of oligodendrocytes, oligodendrocyte progenitors, and microglia during the same time period. Mitochondrial perturbations by a variety of xenobiotics have been linked to apoptosis. In the present study, apoptosis, as determined by DNA laddering and ultrastructural analysis, was clearly induced by MNU treatment of cultured oligodendrocyte progenitors and microglia, but not in astroglia. These data demonstrate a correlation between diminished mtDNA repair capacity and the induction of apoptosis. However, further experimentation is necessary to determine if a causal relationship exists and contributes to the vulnerability of oligodendroglia following exposure to N-nitroso compounds in the environment or in chemotherapeutic regimen.

Alkylating Agents↗

PubMed1998

Os odontoideum: a case report and review.

There are five types of odontoid anomalies: os odontoideum, ossiculum terminale, hypoplasia of the odontoid, aplasia of the odontoid base and aplasia of the odontoid. All five anomalies may lead to atlantoaxial instability. Their clinical signs, symptoms and treatments are identical. Only radiographic findings are distinctive. The incidence of odontoid anomalies is uncertain. A 15-year-old boy was hospitalized with progressive numbness of his limbs on the right side for one month. Os odontoideum was confirmed by cervical radiography and magnetic resonance imaging. The lesion was stabilized with autogenous iliac bone fusion and Halifax interlaminar clamp fixation. Treatment with posterior fusion of the C1-C2 vertebrae proved successful. The clinical variations, etiology, diagnosis and surgical management of odontoid anomalies are discussed.

Adolescent↗

PubMed1997

Molecular origin of the mosaic sequence arrangements of higher primate alpha-globin duplication units.

The human adult alpha-globin locus consists of three pairs of homology blocks (X, Y, and Z) interspersed with three nonhomology blocks (I, II, and III), and three Alu family repeats, Alu1, Alu2, and Alu3. It has been suggested that an ancient primate alpha-globin-containing unit was ancestral to the X, Y, and Z and the Alu1/Alu2 repeats. However, the evolutionary origin of the three nonhomologous blocks has remained obscure. We have now analyzed the sequence organization of the entire adult alpha-globin locus of gibbon (Hylobates lar). DNA segments homologous to human block I occur in both duplication units of the gibbon alpha-globin locus. Detailed interspecies sequence comparisons suggest that nonhomologous blocks I and II, as well as another sequence, IV, were all part of the ancestral alpha-globin-containing unit prior to its tandem duplication. However, sometime thereafter, block I was deleted from the human alpha1-globin-containing unit, and block II was also deleted from the alpha2-globin-containing unit in both human and gibbon. These were probably independent events both mediated by independent illegitimate recombination processes. Interestingly, the end points of these deletions coincide with potential insertion sites of Alu family repeats. These results suggest that the shaping of DNA segments in eukaryotic genomes involved the retroposition of repetitive DNA elements in conjunction with simple DNA recombination processes.

Adult↗