Search PubMed⌕ Search

Biomedical subjects

L Chen

Publications and source records attributed to L Chen.

At least 1,369 records · Page 76Linked to original sources
PubMed1991

Hemodynamic response to BMI model PIAB catheter.

Using the BMI model PIAB catheter designed and produced by our laboratory, we carried out serial animal experiments to evaluate its hemodynamic effects in goats. The animal experiments and comparison tests indicated that BAPDP = 24, PSP = 22; BAEDP = 8, EDP = 14; BAPSP = 20, PSP = 22. The various hemodynamic parameters of our PIAB catheter are equivalent to or better than those of imported products. But the price of our PIAB catheter is much lower than that of foreign products. It has been used in some hospitals, showing satisfactory results.

Animals↗
PubMed1991

[The study on ultrastructure of gap junction of rat atrial myocytes in primary culture].

We have studied the ultrastructure of gap junction of rat atrial myocytes of primary culture in situ embedded by ultramicrotomy. We observed a kind of gap junction-associated vesicles (GJAV), a kind of cluster of particles which are surrounded by plasma membrane, and a concatenate GJAV complexes (CGJAVC) in some big clusters. We found that both of GJAV and CGJAVC are very near the plasma membrane at the intercellular space, and at the same time they are usually adjacent the assembled GJ. So we infered that they are the pre-body or midproduct of the assembled GJ probably. This article analysed these observes and probed into the process about how to assemble the gap junction.

Animals↗
PubMed1991

Mandible metastasis as the initial manifestation of breast carcinoma--report of a case.

A case is presented in which the only positive subjective and clinical findings were numbness of the lower lip and chin, generalized tooth mobility with dull pain, and swelling of the right lower jaw. After an appropriate and careful workup, in conjunction with other medical colleagues, a definitive diagnosis of adenocarcinoma of breast metastasis to the mandible was made, which was confirmed by a histopathologic examination. Radiographs disclosed radiolucent change with an irregular and a moth-eaten appearance in the mandibular trabeculation and loss of the lamina dura of several teeth. As this case demonstrates, the diagnosis of metastatic disease of the jaws requires a high degree of diagnostic astuteness, because of the many possible clinical signs and symptoms which can be nonspecific and can resemble diseases of an inflammatory origin. Accordingly, a histologic evaluation is essential in establishing a definitive diagnosis. The case report emphasizes the need for consideration of metastatic disease in the differential diagnosis of unknown oral lesions, especially in the mandible.

Adenocarcinoma↗
PubMed1991

[Roles of oxytocin, serotonin and norepinephrine in regulation of prolactin release during stress].

The stimulating effects of oxytocin (OT), norepinephrine (NE) and serotonin on prolactin (PRL) release in vitro and in vivo have been well documented. In this paper, experiments were made to further demonstrate their roles in regulation of restraint stress-induced PRL release. Male Sprague-Dawley rats were used and carefully handled according to all requirements for stress experiments. Cerebral injection of anti-OT antiserum and 6-OHDA significantly attenuated the increase of PRL during stress, whereas 5,6-dihydroxytryptamine appeared to have no effect on stress-induced increase of PRL. Plasma PRL in animals injected with methysergide showed that the stress increased even more markedly as compared with control animals. However, there was no difference between methysergide-injected animals with and without stress. The results indicate that OT as well as NE may play an important role in stress-induced PRL release, while the serotoninergic (5-HT) system may not.

Animals↗
PubMed1991

[The dumb-bell orbital dermoid].

Bony resorption was a characteristic radiogram finding in a series of 25 cases of dumb-bell orbital dermoid, and a definitive diagnosis of the nature and locality of the tumor could be done by ultrasonography, CT, or MRI. In all the 25 cases, the mass was lodged between the orbit and the temporal fossa, the frontal sinus, or the cranial fossa like a dumb-bell. The authors emphasized the use of X-ray, ultrasonography, CT or MRI before operation, and thorough clearance of the cystic and fistula wall with cauterization by carbolic acid was imperative for the prevention of recurrences.

Adolescent↗
PubMed1991

[Gas chromatograms of fatty acids from Rickettsia and their similarities].

Fatty acid compositions of 7 strains of Rickettsia were analyzed by a on-line GC/MS system. These strains were R. prowazekii E, R. conorii Simko, R. rickettsii R, R. sibirica Barbash and 246, R. sinkiangensis Jinghe, and R. heilungkiangensis 54. The samples were purified by means of the concentrated salt-ether method. There were about 50 peaks in the fatty acid profiles, and 16 of these peaks were determined, i.e. C22:0, C19:0, C18:0, C18:1, C18:2, C17:0, C16:0, C16:1, 3-OH-C14:0, C15:0, C14:0, C13:0, 2-OH-C12:0, C12:0, 2-OH-C10:0, and C11:0. The major fatty acids were the saturated straight chain acids (e.g. C16:0, C18:0, C14:0) and the unsaturated straight chain acids (e.g. C18:1, C18:2, C16:1). Similarities of fatty acid profiles of tested strains were discriminated by the improved Kulik-Vincent method. The result showed that the KV's coefficient of strains Jinghe and 246 was 97.0%, and the KV's coefficient of strains 54 and the others was 81.6-94.6%.

Fatty Acids↗
PubMed1991

[Polyphenols from leaves of Euphorbia hirta L].

Six compounds have been isolated from the leaves of Euphorbia hirta and identified as gallic acid, quercitrin, myricitriu, 3,4-di-O-galloylquinic acid, 2,4,6-tri-O-galloyl-D-glucose and 1,2,3,4, 6-penta-O-galloyl-beta-D-glucose on the basis of physicochemical and spectroscopic methods.

Drugs, Chinese Herbal↗
PubMed1990

Free ADP levels in transgenic mouse liver expressing creatine kinase. Effects of enzyme activity, phosphagen type, and substrate concentration.

ADP is an important regulator of hepatic metabolism. Despite its importance the level of free ADP in the liver remains controversial. Recently, we engineered transgenic mice which express high levels of creatine kinase in liver. The reaction catalyzed by creatine kinase was assumed to be at equilibrium and used to calculate a free ADP level of 0.059 mumol/g wet weight. In this report we test the equilibrium assumption by studying the free ADP level as a function of enzyme activity or substrate content. Over a 5-fold range of creatine kinase activity, from 150-800 mumol/min/g wet weight, there was no change in the free ADP level. The average value of ADP for these mice was 0.061 +/- 0.016 mumol/g wet weight. Similarly, altering hepatic creatine content from 1.6 to 30 mumol/g wet weight had no effect on the calculated total free ADP level. The average value of ADP for the creatine levels was 0.048 +/- 0.015 mumol/g wet weight. Finally, the free ADP level was calculated using the equilibrium with cyclocreatine rather than creatine as substrate. The equilibrium of the reaction with cyclocreatine lies 30 times more toward phosphorylation than does the equilibrium with creatine. A free ADP level of 0.063 +/- 0.031 mumol/g wet weight was calculated using cyclocreatine. This value is not different from that found with creatine. These results show that the equilibrium assumption used to calculate free ADP levels in transgenic mouse liver is valid, and the presence of creatine kinase does not affect ADP levels.

Adenosine Diphosphate↗
PubMed1990

Underexpression of beta cell high Km glucose transporters in noninsulin-dependent diabetes.

The role of defective glucose transport in the pathogenesis of noninsulin-dependent diabetes (NIDDM) was examined in Zucker diabetic fatty rats, a model of NIDDM. As in human NIDDM, insulin secretion was unresponsive to 20 mM glucose. Uptake of 3-O-methylglucose by islet cells was less than 19% of controls. The beta cell glucose transporter (GLUT-2) immunoreactivity and amount of GLUT-2 messenger RNA were profoundly reduced. Whenever fewer than 60% of beta cells were GLUT-2-positive, the response to glucose was absent and hyperglycemia exceeded 11 mM plasma glucose. We conclude that in NIDDM underexpression of GLUT-2 messenger RNA lowers high Km glucose transport in beta cells, and thereby impairs glucose-stimulated insulin secretion and prevents correction of hyperglycemia.

3-O-Methylglucose↗
PubMed1990

Effects of peptide hydrophobicity and charge state on molecular ion yields in plasma desorption mass spectrometry.

Plasma desorption mass spectra were obtained for a series of peptides, grouped in four mass ranges having approximately 9, 20, 30, and 40 amino acid residues. Within each group, the individual peptides differed in hydrophobicity, charge state, and retention time, as measured on a reversed-phase HPLC column. Comparison of the molecular ion intensities in the positive ion mass spectra of peptides from each group showed a strong dependence upon hydrophobicity and no correlation with charge state. Plasma desorption mass spectra of mixtures of all the peptides within each mass range generally resulted in the desorption of a single residue and suppression of the ion signal from other components. In most cases, this could be correlated with hydrophobicity, as calculated from the Bull and Breese index; however, a better correlation existed when the results were compared with reversed-phase retention times. In general the spectra of mixtures were not influenced by charge state (except in the absence of hydrophobic peptides), as the same component in each peptide mixture produced the most abundant ions in both positive and negative ion spectra.

Amino Acid Sequence↗
PubMed1990

Metabolism-based covalent bonding of the heme prosthetic group to its apoprotein during the reductive debromination of BrCCl3 by myoglobin.

The reductive metabolism of BrCCl3 by ferrous myoglobin leads to the alteration of the prosthetic heme to form products that can be dissociated from the protein and to those that are irreversibly bound to the protein. The major dissociable or soluble heme metabolites have recently been characterized. In this study, the irreversibly bound heme product was characterized by Edman degradation, amino acid analysis, and electronic absorption and mass spectrometry of peptides derived from the altered protein. It was found that the prosthetic heme was modified by a CCl2 moiety derived from BrCCl3 and was covalently bound to histidine residue 93, the normal proximal ligand to the heme-iron. The data are consistent with a mechanism by which the trichloromethyl radical reacts with the heme to form an intermediate that either can alkylate the proximal histidine residue or form soluble metabolites. The covalent bonding of the heme prosthetic moiety to the apoprotein likely leads to a change in the tertiary structure of the protein that may be responsible for its altered catalytic activity as well as its enhanced susceptibility to proteolysis. Similar processes may account, at least in part, for the covalent alteration of the heme prosthetic group of other hemoproteins caused by xenobiotics and endogenous substrates.

Amino Acid Sequence↗
PubMed1990

Ionic currents in retrogradely labeled trigeminothalamic neurons in slices of rat medulla.

We have recorded the ionic currents of identified trigeminothalamic neurons in medulla slices in vitro. Trigeminothalamic cells were first retrogradely labeled by injecting fluorescent latex microspheres in the thalamus of a 7- to 10-day-old rat. Two days later, thin slices (80-100 microns) were prepared from the lower medulla of the injected rat. Whole cell recordings were performed on the labeled cells located in the spinal trigeminal nucleus caudalis using the patch clamp technique. The voltage dependent inward sodium, inward calcium and outward potassium currents are qualitatively similar to those obtained from the enzymatically dissociated trigeminothalamic neurons. Successful application of this thin slice method opens the opportunity of studying synaptic circuitry in the trigeminothalamic system.

Animals↗
PubMed1990

Hyaluronic acid synthesis and gap junction endocytosis are necessary for normal expansion of the cumulus mass.

The application of a quantitative videographic technique has provided an opportunity to compare the quantitative volumetric expansion of cultured oocyte complexes (COCs) to quantitative changes in gap junction down-regulation and hyaluronic acid synthesis and to investigate the effects of physiological agents that influence these processes. Results of these experiments support the idea that the down-regulation of cumulus gap junctions is required for the initial phase of cumulus cell disaggregation and confirm earlier reports that hyaluronic acid synthesis plays a major role in additional expansion of the cumulus. These studies also provide evidence that the degree of expansion observed in culture lacking substrates of hyaluronic synthesis is significantly attentuated when compared with expansion occurring in vivo and that the failure of cultured complexes to expand maximally can be overcome by the addition of substrates of hyaluronic acid synthesis to the culture medium.

Animals↗