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Y Chen

Publications and source records attributed to Y Chen.

At least 1,117 records · Page 62Linked to original sources
PubMed1999

Human immunodeficiency virus-associated pericardial effusion: report of 40 cases and review of the literature.

BACKGROUND: Human immunodeficiency virus (HIV)-associated pericardial effusion is common. We present its clinical features, cause, and prognosis on the basis of a review of 40 cases at a single public hospital. METHODS: A retrospective study was conducted of 122 patients with pericardial effusion (of which 40 were HIV associated) admitted to Queens Hospital Center from January 1988 to April 1997. A review of the literature is also presented. RESULTS: Forty patients with HIV-associated pericardial effusion represent 33% of the 122 patients with pericardial effusion admitted during that period. The most common symptom of the 40 patients was dyspnea (75%). Echocardiogram detected small effusions in 18 (45%), moderate effusions in 10 (25%), and large effusions in 12 (30%). Sixteen (40%) patients had cardiac tamponade, in 15 of whom pericardiocentesis or pericardiostomy was performed. Causes of cardiac tamponade were Mycobacterium species in 3 (19%), Streptococcus pneumoniae in 1 (6%), Staphylococcus aureus in 1 (6%), Kaposi's sarcoma in 1 (6%), and unknown in 10 (63%). In comparison, causes of cardiac tamponade in 74 cases of acquired immunodeficiency syndrome in the literature were 45% idiopathic, 20% mycobacteria, 19% bacteria, 7% lymphoma, 5% Kaposi's sarcoma, 3% viruses, and 1% fungus. Thirteen of the 40 patients were lost to follow-up. Among the other 27, 11 (41%) were alive at 3 months and 5 (19%) at 1 year. Ten of the 27 patients had cardiac tamponade, of whom 5 (50%) were alive at 3 months and 3 (30%) at 1 year. CONCLUSIONS: HIV-associated pericardial effusion is the most common type of pericardial effusion in our inner city hospital. Causes are diverse. The development of pericardial effusion predicts a poor prognosis in HIV infection.

Adult↗
PubMed1999

Assessment of central and peripheral fusion and near and distance stereoacuity in intermittent exotropic patients before and after strabismus surgery.

PURPOSE: To determine whether central fusion and distance stereoacuity are useful as objective measures in assessing the need for and success of surgery for intermittent exotropia (X[T]). METHODS: A prospective, institutional, clinical trial was conducted of 26 consecutive patients with X(T) who were undergoing strabismus surgery in whom fusion (central and peripheral) and stereoacuity (at near and distance) were assessed preoperatively and postoperatively, as well as in 112 normal subjects. To obtain accurate measurements with sensory tests, the lower age was limited to 5 years for inclusion. A successful surgical alignment was defined as an exotropia of 10 prism diopters or less at 6 m. Sensory and motor outcome measures were determined 1 year after surgery. RESULTS: The successful surgical alignment rate was 69%. All patients with X(T) demonstrated peripheral fusion, whereas 35% demonstrated central suppression preoperatively and postoperatively. Central fusion was not predictive of surgical outcome (P = .078); however, there was a trend toward less surgical success in patients with central suppression. Patients with X(T) exhibited good near stereoacuity before and after surgery. Distance stereoacuity in patients with X(T) preoperatively was significantly diminished compared with normal subjects (P < .001) and was improved in 58% postoperatively. Patients who achieved successful surgical alignment had a greater likelihood of demonstrating distance stereoacuity improvement postoperatively than patients who failed to achieve successful surgical alignment (P = .003). Patients with central suppression were unlikely to improve their distance stereoacuity postoperatively (P = .014). CONCLUSIONS: Successful surgery may improve distance stereoacuity. Better distance stereoacuity and central fusion are frequently associated with better surgical success in X(T).

Adolescent↗
PubMed1999

The photon counting histogram in fluorescence fluctuation spectroscopy.

Fluorescence correlation spectroscopy (FCS) is generally used to obtain information about the number of fluorescent particles in a small volume and the diffusion coefficient from the autocorrelation function of the fluorescence signal. Here we demonstrate that photon counting histogram (PCH) analysis constitutes a novel tool for extracting quantities from fluorescence fluctuation data, i.e., the measured photon counts per molecule and the average number of molecules within the observation volume. The photon counting histogram of fluorescence fluctuation experiments, in which few molecules are present in the excitation volume, exhibits a super-Poissonian behavior. The additional broadening of the PCH compared to a Poisson distribution is due to fluorescence intensity fluctuations. For diffusing particles these intensity fluctuations are caused by an inhomogeneous excitation profile and the fluctuations in the number of particles in the observation volume. The quantitative relationship between the detected photon counts and the fluorescence intensity reaching the detector is given by Mandel's formula. Based on this equation and considering the fluorescence intensity distribution in the two-photon excitation volume, a theoretical expression for the PCH as a function of the number of molecules in the excitation volume is derived. For a single molecular species two parameters are sufficient to characterize the histogram completely, namely the average number of molecules within the observation volume and the detected photon counts per molecule per sampling time epsilon. The PCH for multiple molecular species, on the other hand, is generated by successively convoluting the photon counting distribution of each species with the others. The influence of the excitation profile upon the photon counting statistics for two relevant point spread functions (PSFs), the three-dimensional Gaussian PSF conventionally employed in confocal detection and the square of the Gaussian-Lorentzian PSF for two photon excitation, is explicitly treated. Measured photon counting distributions obtained with a two-photon excitation source agree, within experimental error with the theoretical PCHs calculated for the square of a Gaussian-Lorentzian beam profile. We demonstrate and discuss the influence of the average number of particles within the observation volume and the detected photon counts per molecule per sampling interval upon the super-Poissonian character of the photon counting distribution.

Diffusion↗
PubMed1999

Effect of vitamin E and N-acetylcysteine on phosphatidylserine externalization and induction of coagulation by high-glucose-treated human erythrocytes.

This study examines the effect of high glucose levels on the markers of oxidative stress, phosphatidylserine (PS) externalization, and induction of coagulation by high-glucose-treated red blood cells (RBCs). Washed normal RBCs were suspended to 15% hematocrit in phosphate-buffered saline and incubated with different concentrations of glucose for 24 hours in a shaking water bath at 37 degrees C. This treatment caused depletion of vitamin E and accumulation of vitamin E-quinone and malondialdehyde ([MDA] an end product of lipid peroxidation), externalization of PS in the membrane bilayer, and induction of coagulation by RBCs. Pretreatment of RBCs with N-acetylcysteine (NAC) and vitamin E reduced membrane lipid peroxidation, PS externalization, and the tendency of high-glucose-treated RBCs to clot plasma. This study provides further evidence for the increased oxidative stress in RBCs exposed to high glucose levels. In addition, it suggests a role for membrane lipid peroxidation in the PS externalization in the membrane bilayer and in the induction of clotting by RBCs exposed to hyperglycemia. It also suggests that certain antioxidants can decrease cellular damage and restore certain cellular functions in diabetes.

Acetylcysteine↗
PubMed1999

Management of nonfunctioning pituitary adenomas with suprasellar extensions by transsphenoidal microsurgery.

BACKGROUND: We evaluated the feasibility and therapeutic effectiveness of transsphenoidal microsurgical removal of nonfunctioning pituitary adenomas with suprasellar extensions. The diagnostic modes, surgical technique, and outcome were reviewed in 208 patients with pituitary adenomas extending beyond the sella turcica who were treated by transsphenoidal microsurgery. All patients except three presented with significantly diminished visual acuity and visual field defects. METHODS: Diagnosis was confirmed by skull X-ray plain films, CT, or MRI scanning. Operations were performed via a transsphenoidal approach under microscope. A subarachnoid catheter was preoperatively inserted in the lumbar cistern, through which saline was slowly injected during operation to increase the intracranial pressure so as to move the suprasellar tumor into the operative field to aid the removal. RESULTS: In this series, gross total removal of an adenoma in 146 cases (70.2%) and subtotal removal in 50 cases (24.0%) was achieved; partial removal was carried out in the remaining 12 cases (5.8%) of fibrous or dumbbell-shaped adenomas. There were no deaths in this group. Follow-up review (median 3.8 years) in 187 patients revealed that 97.8% of those with preoperative diminished visual acuity had postoperative improvement; 2.2% had no change, and none deteriorated significantly. Among 181 patients with preoperative visual field defects, postoperative improvement was good in 169 (93.4%), and poor in 12 (6.6%). The major complications were diabetes insipidus and cerebrospinal fluid rhinorrhea, which occurred in 13.5% and 4.8% of patients, respectively. The tumors recurred in 12 patients (6.4%) who were considered to have a macroscopically complete removal at surgery. Continuing growth of residual tumors was found in 31 (16.6%) based on visual acuity decrease, visual field defects, and CT or MRI examination. Of the recurrent and residual tumors, 4, 9, 17, and 13 cases belonged to Grades A, B, C, and D, respectively. CONCLUSIONS: Comparison with transfrontal surgery suggests that these results are as good as those of transfrontal procedures and that the incidence of serious side effects is considerably lower. We consider that the microsurgical removal of pituitary tumors by the transsphenoidal approach is safe and effective even in very large or giant adenomas, since it allows rapid and adequate decompression of the optic nerves and chiasm.

Adenoma↗
PubMed1999

Thermal conformational changes of bovine fibrinogen by differential scanning calorimetry and circular dichroism.

The thermal denaturation of bovine fibrinogen has been investigated using differential scanning calorimetry (DSC) and circular dichroism (CD) spectroscopy. Differential scanning calorimetry measurements were carried out while changing the scan-rate. The transition at 57 degrees C was found to be irreversible and highly scan-rate dependent, suggesting that the denaturation is, at least in part, under kinetic control. The secondary structural changes at various temperatures were monitored by far-ultraviolet CD spectroscopy. These results show that the DSC transition for the thermal denaturation of bovine fibrinogen can be interpreted in terms of a kinetic process, N --> F, where k is a first-order kinetic constant that changes with temperature according to the Arrhenius equation. An important transition peak was observed at 78.8 degrees C which is attributed to the C-terminal parts of the Aalpha chains of fibrinogen.

Animals↗
PubMed1999

Ethylenediamine-palladium(II) complexes with pyridine and its derivatives: synthesis, molecular structure and initial antitumor studies.

The synthesis of four mononuclear palladium complexes of general formula [Pd(en)Cl(L)]NO3 (en = ethylenediamine; L = pyridine (I), 4-methylpyridine (II), 4-hydroxypyridine (III) or 4-aminopyridine (IV) has been achieved. The structure of these compounds was studied by elemental analysis, IR, far-IR and 1H NMR; complex I was analyzed by X-ray diffraction. The crystal of [Pd(en)(pyridine)Cl]NO3 is monoclinic, space group P21/c (a = 7.990(2), b = 16.058(3), c = 9.846(2) A, beta = 103.81(3) degrees, Z = 4, R = 0.067, Rw = 0.066). The Pd(II) atom exhibits an approximately square planar coordination with bond lengths in the range 2.017-2.042 A for Pd-N and 2.320 A for Pd-Cl. In order to determine the donor strength of the aromatic pyridine ligands, the stability constants of binary complex ML2+ (M = [Pd(en) (H2O)2]2+; L = pyridine, 4-Me-pyridine, 4-OH-pyridine and 4-NH2-pyridine) were determined by potentiometric pH titration in aqueous solution (T = 25 degrees C, I = 0.1 mol l-1 NaNO3). The results show that the stability constants of the binary complexes systematically increase with increasing pKa of the pyridines. The above four palladium complexes, [Pt(en)(pyridine)Cl]NO3 and cis-diamminedichloroplatinum (II) (cis-DDP) were assayed for cytotoxicity in vitro against the human leukemia cell line HL-60, and compounds I, II, III and cis-DDP show significant cytotoxic activity against HL-60.

Antineoplastic Agents↗
PubMed1999

Differences in soft tissue profile changes following mandibular setback in Chinese men and women.

PURPOSE: This study investigated the soft tissue profile changes after surgical correction of mandibular prognathism in Chinese patients and evaluated the sex differences in the ratios of soft tissue to hard tissue change. PATIENTS AND METHODS: Forty-three adult Chinese patients (18 men and 25 women) with mandibular prognathism were treated by intraoral oblique or vertical ramus osteotomy. Lateral cephalometric radiographs were taken presurgically and between 6 to 12 months postsurgically, and specific soft and hard tissue points were digitized and analyzed with a computer-aided system. RESULTS: As a result of surgical setback of the mandible, the soft tissue to hard tissue change ratios were: Li:Ii = 0.71:1, Si:B = 0.90:1, Pg':Pg = 0.94:1 for the males; and Li:Ii = 0.82:1, Si:B = 0.92:1, Pg':Pg = 1.06:1 for the females. CONCLUSION: The changes in soft tissue were closely correlated with the hard tissue movement after surgical setback of mandible. The average ratios of soft tissue to hard tissue change in horizontal direction appear to show a gender difference, which suggests the need for different ratios when predicting the results of orthognathic surgery.

Adult↗
PubMed1999

The experience in the treatment of patients with extensive full-thickness burns.

The aim of the present study is to analyze the changes of cure rate and the main causes of death in the last 40 years, and to summarize our experience in the treatment of extensive full-thickness burn patients. The clinical characteristics, cure rate and main causes of death of 73 cases with total burned area more than 90% TBSA and full-thickness burn area more than 70% TBSA were analyzed retrospectively. Among them, 21 cases (28.8%) were cured and 52 cases (71.2%) died. The cure rate increased significantly in the recent years, and the main causes of death changed from shock and sepsis in the time period 1959-1978 to sepsis and MODS in the past two decades. Due to the improvement of early comprehensive management of burn shock, aggressive surgical approach to full-thickness burn wound and potent systemic supporting measures, the survival rate increased significantly.

Adult↗
PubMed1999

Reduced Mg2+ blockade of synaptically activated N-methyl-D-aspartate receptor-channels in CA1 pyramidal neurons in kainic acid-lesioned rat hippocampus.

Unilateral kainic acid lesion in the hippocampus caused a long-term change in the balance between excitatory and inhibitory drive onto CA1 pyramidal cells, making these cells hyperexcitable several weeks post-lesion. In this study, we have shown an enhanced N-methyl-D-aspartate receptor-mediated component in the excitatory synaptic transmission together with a reduced GABA(A) receptor-mediated inhibition in CA1 pyramidal cells one-week post kainic acid lesion. In these cells, pharmacologically isolated N-methyl-D-aspartate receptor-mediated whole-cell excitatory postsynaptic currents were significantly larger at negative holding potentials, and the voltage-dependence of N-methyl-D-aspartate receptor channels was shifted in the hyperpolarizing direction. The plot of relative conductance (g/gMax) shifted significantly (P<0.01) to more negative holding potentials by 19 mV (-28+/-4 mV in control slices and -47+/-4 mV in kainic acid slices) at the half maximal conductance point (g/gMax =0.5). This shift gives a larger N-methyl-D-aspartate receptor-mediated component in the excitatory synaptic transmission at resting membrane potentials (around -60 mV). The shifted voltage dependence is highly sensitive to extracellular Mg2+ ions. Moderate increases in [Mg2+]o from 1 mM to 2.6 mM more than compensated for the negative shift and effectively suppressed the population epileptiform bursting activity. Fitting the voltage dependence to an ionic block model revealed a higher dissociation constant of N-methyl-D-aspartate receptor channels for Mg2+ in kainic acid-lesioned slices (52 mM at 0 mV; 330 microM at -60 mV) than in control slices (7.7 mM at 0 mV; 93 microM at -60 mV). While a simple single site model adequately fitted the control data for [Mg2+]o at 1 mM and 2.6 mM, no consistent model of this form was found for the kainic acid-lesioned slices. These results revealed changed properties of N-methyl-D-aspartate receptor channels in the kainic acid-lesioned model of epilepsy. The reduced Mg2+ blockade of N-methyl-D-aspartate receptor channels contributed significantly to the epileptiform bursting activity.

2-Amino-5-phosphonovalerate↗
PubMed1999

Characterization of the Ets-type protein ER81 in Xenopus embryos.

A function for FGF-type peptide growth factors has been implied for early mesodermal patterning events in Xenopus laevis. FGF signalling operates via the MAP kinase cascade that can directly activate the transcription of organizer-expressed genes, such as Xbra and Xegr-1. We have recently provided evidence for a critical role of Ets-type transcription factors in FGF mediated Xegr-1 transcription activation. Here, we report on the identification of the Xenopus Ets-type protein ER81 that is expressed in a pattern overlapping with the ones of Xegr-1 and Xbra during gastrulation. Microinjection in XER81 encoding mRNA into ventral blastomeres of Xenopus embryos results in the induction of ectopic, tail-like protrusions, whereas dorsal overexpression results in disturbed eye development. In the animal cap assay, ectopic expression of XER81 is found to interfere with activin mediated induction of Xegr-1 and gsc, but not with the Xbra response to activin.

Activins↗
PubMed1999

Expression of Fgfr2 in the early mouse embryo indicates its involvement in preimplantation development.

We report that the IIIc transcriptional alternative of Fgfr2 is transcribed in the unfertilized egg and that during early zygotic transcription, messages encoded by both Fgfr2 alternatives (IIIc and IIIb) are present. The Fgfr2 protein was first detected in peripheral blastomeres of compacted morulae. Trophectoderm specificity of Fgfr2 became obvious in the early blastocyst and with maturation its localization underwent further specification, Fgfr2 concentration increased at the abembryonic pole and decreased at the embryonic pole. Moreover Fgfr2 expression became markedly asymmetrical along the animal-vegetal axis of the mature blastocyst. Our observations indicate a role for Fgfr2 in trophectoderm growth and specification and in the orientation and polarity of the preimplantation conceptus.

Animals↗
PubMed1999

JNK2 and IKKbeta are required for activating the innate response to viral infection.

Viral infection or double-stranded (ds) RNA induce interferons (IFN) and other cytokines. Transcription factors mediating IFN induction are known, but the signaling pathways that regulate them are less clear. We now describe two such pathways. The first pathway leading to NF-kappaB depends on the dsRNA-responsive protein kinase (PKR), which in turn activates IKB kinase (IKK) through the IKKbeta subunit. The second viral-and dsRNA-responsive pathway is PKR independent and involves Jun kinase (JNK) activation leading to stimulation of AP-1. Both IKKbeta and JNK2 are essential for efficient induction of type I IFN and other cytokines in response to viral infection or dsRNA. This study establishes a general role for these kinases in activation of innate immune responses.

3T3 Cells↗
PubMed1999

Highly sensitive radioactive in situ hybridization using full length hydrolyzed riboprobes to detect alpha 2 adrenoceptor subtype mRNAs in adult and developing rat brain.

The mRNA expression of highly homologous alpha 2 adrenoceptor subtypes was determined using a highly sensitive in situ hybridization protocol that allowed the detection of low abundance mRNA. Full-length 35S-labeled riboprobes specific for alpha 2A, alpha 2B and alpha 2C adrenoceptors were used for maximal sensitivity. The probes were hydrolyzed to an average length of 600 bp which, in combination with proteinase K digestion, resulted in optimal probe penetration in developmental and adult tissue. The expression intensity could be quantified and the ontogeny of receptor mRNA expression determined. At the same time receptor binding sites or functional proteins could be detected simultaneously in adjacent sections, because fresh frozen and post-fixed tissue was used.

Animals↗
PubMed1999

2,2-Diphenyl-1-picrylhydrazyl radical-scavenging active components from Polygonum multiflorum thunb.

An activity-directed fractionation and purification process was used to identify the antioxidative components of Polygonum multiflorum Thunb. (PM). Dried root of PM was extracted with 95% ethanol and then separated into water, ethyl acetate, and hexane fractions. Among these only the ethyl acetate phase showed strong antioxidant activity by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) test when compared with water and hexane phases. The ethyl acetate fraction was then subjected to separation and purification using silica gel column chromatography and Sephadex LH-20 chromatography. Three compounds showing strong antioxidant activity were identified by spectral methods ((1)H NMR, (13)C NMR, and MS) and by comparison with authentic samples to be gallic acid, catechin, and 2,3,5, 4'-tetrahydroxystilbene 2-O-beta-D-glucopyranoside.

Antioxidants↗
PubMed1999

Isolation of norditerpenoid alkaloids from flowers of aconitum lycoctonum

The structures of two new lycoctonine-type alkaloids having an acetoxy group at C-6, 6-O-acetyldemethylenedelcorine (1) and 6-O-acetyl-14-O-methyldelphinifoline (2), isolated from the flowers of Aconitum lycoctonum, were determined by spectroscopic analysis. In addition, 14-O-methyldelphinifoline (4), gigactonine (5), and lycoctonine (6) were obtained.

Journal Article↗