Biomedical subjects

Yue Yuan

Publications and source records attributed to Yue Yuan.

25 records · Page 2Linked to original sources

PubMed2003

Potential of magnetic resonance lymphography with intrapulmonary injection of gadopentetate dimeglumine for visualization of the pulmonary lymphatic basin in dogs: preliminary results.

PURPOSE: To evaluate a new approach of magnetic resonance (MR) lymphography with intraalveolar injection of a conventional extracellular contrast agent (gadopentetate dimeglumine) for imaging lymphatic basin draining from specific portions of the lung. METHODS: Three-dimensional T1-weighted spoiled gradient-recalled echo MR sequence images were acquired serially before and for 40 minutes after intraalveolar injection of gadopentetate dimeglumine in a total of 14 anesthetized beagle dogs. Six of these dogs received 1 mL undiluted and low-concentration (75%) contrast agent into the same portion of the right caudal lobe during a 7-day interval. In all dogs, including these 6 dogs, MR lymphography was repeated with injection of the low-concentration contrast agent into different lung regions at 7-day intervals to evaluate the differences of the visualized draining lymphatic station. Lymphatic enhancement was quantified by percent increases of signal intensity against precontrast. Postmortem examination of the lymphatic anatomy was performed in 7 of these animals. RESULTS: In all dogs, the lymphatic station draining from the injection sites was visualized within 5 minutes after contrast injection. The maximum percent increase of signal intensity of the same middle tracheobronchial lymph nodes was significantly greater with a low-concentration (75%) contrast agent than with an undiluted one in the same 6 dogs (n = 6, 247.6 +/- 30.5% vs. 204.2 +/- 33.8%; P < 0.01). Different lymphatic stations draining from the different injection sites were visualized in all dogs. In a total of 12 MR studies that showed extended nodal enhancement after injection of the low-concentration contrast agent, the enhancement peak of the most proximal nodes (n = 12) from the injection sites appeared earlier than that of their distant nodes (n = 12), with a maximum percent increase of signal intensity of 249.8 +/- 42.4%. The visualized lymph nodes were found in the appropriate locations postmortem, with significant correlation for nodal sizes (r = 0.965; P < 0.0001). CONCLUSION: MR lymphography with low-concentration gadopentetate dimeglumine can quickly and sufficiently visualize the drainage lymphatic station from specific lung portions, and may have the potential of sentinel node mapping in lung cancer.

Animals↗

PubMed2003

Determining appropriate substrate conversion for enzymatic assays in high-throughput screening.

It is generally accepted that the conversion of substrate should be kept at less than 10% of the total substrate used when studying enzyme kinetics. However, 10% or less substrate conversion often will not produce sufficient signal changes required for robust high-throughput screening (HTS). To increase the signal-to-background ratio, HTS is often performed at higher than 10% substrate conversion. Because the consequences of high substrate conversion are poorly understood, the screening results are sometimes questioned by enzymologists. The quality of an assay is judged by the ability to detect an inhibitor under HTS conditions, which depends on the robustness of the primary detection signal (Z factor) and the sensitivity to an inhibitor. The assay sensitivity to an inhibitor is reflected in the observed IC(50) value or percent inhibition at a fixed compound concentration when single-point data are collected. The major concern for an enzymatic assay under high substrate conversion is that the sensitivity of the screen may be compromised. Here we derive the relationship between the IC(50) value for a given inhibitor and the percentage of substrate conversion using a first-order kinetic model under conditions that obey Henri-Michaelis-Menten kinetics. The derived theory was further verified experimentally with a cAMP-dependent protein kinase. This model provides guidance for assay developers to choose an appropriate substrate conversion in designing an enzymatic assay, balancing the needs for robust signal and sensitivity to inhibitors.

Catalysis↗

PubMed2003

[Causes of ineffectiveness of microvascular decompression for hemifacial spasm].

OBJECTIVE: To study causes of ineffectiveness of microvascular decompression (MVD) in treatment of hemifacial spasm (HFS). METHODS: Reoperative MVD was performed in 23 HFS patients with previous ineffective MVD. In the patients, the main causes of ineffectiveness included misjudgment of compressing vessels (7 patients), improper insertion of decompressing grafts (9), improper selection of grafts (5) and small grafts (2). RESULTS: Symptoms of HFS disappeared immediately after the second MVD in 21 patients and delayed in 2 patients (after 2 weeks, 6 weeks). No recurrence of HFS was noted during the follow-up period of 1.0 - 6.0 years (mean 3.4 years). CONCLUSIONS: MVD is an effective microsurgical method for treating HFS. Accurate judgement of compressing vessels and proper decompression are the key to surgical effectiveness.

Adult↗

PubMed2003

Visualization of normal and interrupted lymphatic drainage in dog legs with interstitial MR lymphography using an extracellular MR contrast agent, gadopentetate dimeglumine.

PURPOSE: The capability of the interstitial magnetic resonance lymphography (MR-LG) using a widely available extracellular contrast agent, gadopentetate dimeglumine, for the visualization of normal and interrupted lymphatic drainage was tested in dog legs. MATERIALS AND METHODS: With a 7-day interval, 1 mL and 2 mL undiluted gadopentetate dimeglumine were injected intradermally into the dorsal foot of both hind legs of 12 dogs. T1-weighted 3-dimensional (3D) spoiled gradient-echo (repetition time/echo time = 6.7/1.6 ms) and maximum intensity projection (MIP) images covering the legs and pelvic region were acquired at 1.5 T for 10 minutes after 30 seconds gentle massage at the injection sites. These dogs also underwent the MR-LG with 2 mL of this contrast agent 7 days after surgical ligation of the popliteal lymphatic vessels. RESULTS: In the normal dogs, the interstitial MR-LG quickly and consistently visualized the direct connection of the lymphatic vessels and lymph nodes draining from the injection sites up to the inguinal region, without any late adverse effects. The enhancement effect was significantly greater with a 2-mL dose than with a 1-mL dose. After lymphatic obstruction, the MR-LG clearly revealed the anatomic compromises of the lymphatics, such as poor enhancement of the affected lymphatic vessels and lymph nodes, collateral lymphatic vessels, abnormal soft-tissue enhancement, and delayed lymphatic migration of the contrast agent. The topographic 3D images provided a comprehensive anatomy of these normal and compromised lymphatic drainage. CONCLUSION: Although gadopentetate dimeglumine is not lymphotropic, the interstitial MR-LG using this T1-contrast agent appears to have potential for quick and sufficient mapping of the lymphatic drainage from the injection sites and for the characterization of interrupted lymph flow.

Animals↗

PubMed2002

NMR investigation of the dynamics of tryptophan side-chains in hemoglobins.

NMR relaxation measurements of 15N spin-lattice relaxation rate (R(1)), spin-spin relaxation rate (R(2)), and heteronuclear nuclear Overhauser effect (NOE) have been carried out at 11.7T and 14.1T as a function of temperature for the side-chains of the tryptophan residues of 15N-labeled and/or (2H,15N)-labeled recombinant human normal adult hemoglobin (Hb A) and three recombinant mutant hemoglobins, rHb Kempsey (betaD99N), rHb (alphaY42D/betaD99N), and rHb (alphaV96W), in the carbonmonoxy and the deoxy forms as well as in the presence and in the absence of an allosteric effector, inositol hexaphosphate (IHP). There are three Trp residues (alpha14, beta15, and beta37) in Hb A for each alphabeta dimer. These Trp residues are located in important regions of the Hb molecule, i.e. alpha14Trp and beta15Trp are located in the alpha(1)beta(1) subunit interface and beta37Trp is located in the alpha(1)beta(2) subunit interface. The relaxation experiments show that amino acid substitutions in the alpha(1)beta(2) subunit interface can alter the dynamics of beta37Trp. The transverse relaxation rate (R(2)) for beta37Trp can serve as a marker for the dynamics of the alpha(1)beta(2) subunit interface. The relaxation parameters of deoxy-rHb Kemspey (betaD99N), which is a naturally occurring abnormal human hemoglobin with high oxygen affinity and very low cooperativity, are quite different from those of deoxy-Hb A, even in the presence of IHP. The relaxation parameters for rHb (alphaY42D/betaD99N), which is a compensatory mutant of rHb Kempsey, are more similar to those of Hb A. In addition, TROSY-CPMG experiments have been used to investigate conformational exchange in the Trp residues of Hb A and the three mutant rHbs. Experimental results indicate that the side-chain of beta37Trp is involved in a relatively slow conformational exchange on the micro- to millisecond time-scale under certain experimental conditions. The present results provide new dynamic insights into the structure-function relationship in hemoglobin.

Amino Acid Substitution↗

PubMed2002

Imaging findings of an intercostal hemangioma.

SUMMARY: The authors present the imaging findings in a 44-year-old woman with a rare intercostal hemangioma that originated from the connective tissue between the intercostal muscle and parietal pleura and protruded into the thoracic cavity. The contrast-enhanced computed tomography (CT) showed a markedly enhancing mass, whereas dynamic magnetic resonance (MR) images showed heterogeneous and strong enhancement with incomplete early eccentric enhancement peripherally followed by complete filling-in on delayed scans. The imaging features of CT and MR imaging of a hemangioma may be useful for proper preoperative diagnosis.

Adult↗

PubMedDate not supplied

Role of high-resolution CT in the diagnosis of small pulmonary nodules coexisting with potentially operable lung cancer.

PURPOSE: The purpose of this study was to evaluate whether high-resolution CT (HRCT) could facilitate the preoperative diagnosis of one or two small nodules of 1 cm or less coexisting with a lung cancer, i.e., coexisting small nodule. MATERIALS AND METHODS: This study included 27 coexisting small nodules in 24 potentially operable lung cancer patients. An observer study was performed by five radiologists. The observer performances in differentiating malignant from benign coexisting small nodules were evaluated on conventional CT and HRCT using receiver operating characteristic (ROC) analysis. RESULTS: The area under the ROC curve of five observers was 0.731 on HRCT and 0.578 on conventional CT in the differential diagnosis of coexisting small nodules. A significant diagnostic improvement was found on HRCT (p=0.031). This was especially evident for nodules of ground-glass attenuation (p=0.005). CONCLUSION: HRCT plays an important role in determining the treatment of potentially operable lung cancer patients with coexisting small nodules.

Adenocarcinoma↗