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Biomedical subjects

L X Chen

Publications and source records attributed to L X Chen.

29 records · Page 2Linked to original sources
PubMed1990

[Enhancement of absorption of tetramethylpyrazine by synthetic borneol].

Sprague-Dawley rats were given ig tetramethylpyrazine phosphate (TMP) 5 mg/kg with or without previous borneol 5 mg/kg. The plasma TMP concentrations were analysed by GC method, and the data were treated by NONLIN program. The Cmax were 931 and 562 ng/ml, respectively, (P less than 0.01); while the AUC were 68,849 and 37,174, respectively, (P less than 0.05). It is suggested that the borneol enhances the absorption of the TMP but not in elimination.

Absorption↗
PubMed1989

Phagaquosonogram (PASG) diagnosis for cancer of gastric cardia. A preliminary study of 223 patients.

Phagaquosonographies (PASG) of 100 normal subjects and 223 patients with cardiac cancer (CC) were analyzed. The apparatus was self-designed and self-manufactured. The wave patterns and the pre-ejection period and other 8 quantitative indices in PASG were compared and patients with CC were found to have abnormal levels (P less than 0.01). The phagaquosonograms in 82 patients with esophageal, gastric or cardias (non-cancer) diseases served as controls. The PASG showed positive results in 97.3%, suspicious in 2.3% and negative in 0.4% of CC cases and 100% negative in the normal subjects. It was 1.2% positive, 8.5% suspicious and 90.3% negative in the esophageal, cardiac or gastric non-cancer diseases. PASG has high sensitivity (97.3%), and typical characteristics (98.8%). It is shown that this method can be used in screening, diagnosis, differential diagnosis and prediction of prognosis of cardiac cancer.

Aged↗
PubMed1987

Picosecond time-resolved fluorescence of ribonuclease T1. A pH and substrate analogue binding study.

The tryptophyl fluorescence of ribonuclease T1 decays monoexponentially at pH 5.5, tau = 4.04 ns but on increasing pH, a second short-lived component of 1.5 ns appears with a midpoint between pH 6.5 and 7.0. Both components have the same fluorescence spectrum. Acrylamide quenches both fluorescence components, and the short-lived component is quenched fivefold faster than the predominant long component. Binding of the substrate analogue 2'-guanylic acid at pH 5.5 quenches the fluorescence by 20% and introduces a second decay component, tau = 1.16 ns. Acrylamide quenches both tryptophyl decay components, with similar quenching rates. The fluorescence anisotropy decay of ribonuclease T1 was consistent with a molecule the size of ribonuclease T1 surrounded by a single layer of water at pH 7.4, even though the anisotropy decay at pH 5.5 deviated from Stokes-Einstein behavior. The fluorescence data were interpreted with a model where the tryptophyl residue exists in two conformations, remaining in a hydrophobic pocket. The acrylamide quenching is interpreted with electron transfer theory and suggests that one conformer has the nearest atom approximately 3 A from the protein surface, and the other, approximately 2 A.

Acrylamide↗
PubMed1986

[Phagosonogram (PSG) in cancer of the gastric cardia--a preliminary study of 100 patients and 100 normal subjects].

Phagosonography of 100 normal subjects and 100 patients with cardiac cancer (CC) is described. The apparatus was self-designed and self-manufactured. The pre-ejection period and other 8 quantitative indexes in PSG were compared and abnormal level existed in patients with CC (P less than 0.01). The phagosonograms drawn in 54 patients with esophageal, cardiac or gastric benign diseases served as control. The diagnostic accuracy of PSG was 97% positive, 3% suspicious in CC and 100% negative in the normal subjects. It was 3.7% suspicious in the esophageal, cardiac or gastric diseases. PSG is very important in the early diagnosis of CC and is also of value in the prediction of a successful operation. The authors believe that PSG can reflect the changes in cardiac and esophageal motor function. In CC, the PSG changes are mainly due to the malfunction in the dilation and contraction of the lower esophageal sphincter. This malfunction shows itself earlier than the pathomorphology and provides a basis for the early diagnosis of CC. Phagosonography is a new method in the research on the motor function of the sound producing viscera, the diagnosis of their diseases and the observation of the treatment result. Being able to be performed with the patients in physiological and non-invasive state, it is suitable for screening.

Aged↗
PubMed1985

Electrostatic interactions in sperm whale myoglobin. Site specificity, roles in structural elements, and external electrostatic potential distributions.

The electrostatic free energy contribution to the stability of sperm whale ferrimyoglobin was evaluated according to the static accessibility modified Tanford-Kirkwood model. The electrostatic free energy contribution of each distinct structural element was divided into one term arising from interactions between it and other elements (interelemental) and another from interactions within the particular element itself (intraelemental). At pH 7 the majority of the terms were found to be stabilizing. The interelemental terms are the dominant ones for most structural elements. The small interelemental terms of the C and D helices are compensated by large intraelemental interactions which stabilize these short helices. Perturbations in pH can be accommodated by the structural elements through a redistribution of stabilizing and destabilizing interactions. The electrostatic potentials calculated at the surface of the protein indicate that the internal compensation of local potentials achieved during folding results in a generally neutral protein-solvent interface save for two distinct areas of nonzero potential. The accessibility of each charged atom to solvent was analyzed in terms of the surface area lost to charged, polar and nonpolar atoms separately. The net solvent accessibility lost parallels closely that lost to nonpolar atoms alone, indicating a specific role for nonpolar atoms in defining dielectric shielding of charged atoms, aside from their participation in the well-known hydrophobic interactions.

Amino Acids↗
PubMedDate not supplied

Diagnosing early rheumatoid arthritis (RA). What are the problems and opportunities?

Early diagnosis is being appropriately emphasized in RA, as early DMARD treatment can be very effective. ACR criteria are useful but may not perform as well in early disease. These criteria depend on clinical examination, which is subject to over- and under-interpretation. Ultrasound and MRI may offer advantages. Laboratory tests and synovial fluid analyses may contribute, but are often not definitive. All of these data, synovial biopsies and a variety of other features can guide prognosis as well as diagnosis. Consideration of the whole patient, including education levels and coping strategies, can help. Aggressive management is proposed for most patients once the diagnosis is firm. Strategies are needed to arrange that patients are seen at a very early stage by rheumatologists knowledgeable in the treatment of early arthritis. Early diagnosis is receiving increasing emphasis in RA, with the recognition that erosive irreversible disease can occur in the first months and that a variety of treatments can clearly prevent or slow disease progression (1, 2). Most studies addressing early RA use the American Rheumatism Association (ARA), now the American College of Rheumatology (ACR), criteria (3) for purposes of uniformity although these criteria have been shown to be less valid in early disease (4). Early DMARD treatment can make a difference, but there are a number of unanswered or partially answered questions about diagnosis that remain to be addressed. We review this area, focusing on work from our own research and how this has guided our thinking.

Arthritis, Rheumatoid↗