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Biomedical subjects

F Liu

Publications and source records attributed to F Liu.

At least 559 records · Page 31Linked to original sources
PubMed1995

Angiographically 'silent' plaque in the left main coronary artery detected by intravascular ultrasound.

BACKGROUND: Left main coronary artery (LMCA) atherosclerosis is a high-risk disease but its occurrence is often underestimated by coronary angiography. Intravascular ultrasound (IVUS) has been shown to be more accurate and sensitive than coronary angiography in identifying coronary atherosclerotic lesions. METHODS: Ninety-two patients (55 men and 37 women, aged 55.4 +/- 10.4 years) found to have angiographically normal coronary arteries or ambiguous lesions of the LMCA were examined by IVUS after diagnostic cardiac catheterization. The cross-sectional areas of the vessel, lumen, and atherosclerotic plaque (if any) of the LMCA were determined and the percentage area and diameter of stenosis were calculated. RESULTS: Atherosclerotic plaques in the LMCA were detected in 31 of the 92 patients (34%); 83% of the plaques were eccentric, and 17% contained calcium deposits. In patients with plaques detected by IVUS, the vessel area was 23.3 +/- 6.1 mm2. The plaque area was 6.3 +/- 3.3 mm2 (1.8-16.7 mm2). The area of stenosis was 31.6 +/- 12.1% (12-57.2%). The diameter of stenosis was 19.3 +/- 7.2% (8.7-34.6%). The area of stenosis was over 50% in four patients. The vessel area (23.3 +/- 6.1 mm2) in patients with plaques was larger than that in those without plaques (19.0 +/- 6.5 mm2, P < 0.01). CONCLUSION: Coronary angiography considerably underestimates the occurrence of atherosclerotic stenoses in the LMCA because of coronary remodelling and methodological limitations. The greater sensitivity and accuracy of IVUS in detecting LMCA lesions, at both early and advanced stages, is of great clinical importance in patient management.

Adult↗
PubMed1995

Has transesophageal echocardiography changed the approach to patients with suspected or known infective endocarditis?

Infective endocarditis is still a great clinical challenge. Its diagnosis is difficult to establish, and mortality has remained around 30%. Early diagnosis and optimal treatment are crucial fo prognosis improvement. Echocardiography plays an indispensable role in the management of this disease, especially with the recently introduced approach, transesophageal echocardiography (TEE). TEE can overcome the limitations of transthoracic echocardiography (TTE) and is superior to TTE in almost every way in providing earlier and more information for the diagnosis and treatment of infective endocarditis. TEE detects valve vegetations with much higher sensitivity and specificity than TTE. It can demonstrate smaller vegetations in the early stage of the disease and vegetations on atypical locations (e.g., mitral valve annulus), and provides detailed characterization of vegetations (e.g., location, size, mobility, and changes during treatment). Such information is of great prognostic value and may help in selecting proper treatment. TEE is more sensitive for detecting complications, such as mitral valve perforation, abscess, and subaortic complications, which respond poorly to medicine and for which timely surgery may be the best treatment. For those with prosthetic valve endocarditis, TEE is especially useful because TTE is greatly limited by the acoustic shadow of prostheses. Both positive and negative results of TEE examination are valuable for confirming or excluding infective endocarditis. TEE also plays a unique role in intraoperative monitoring and can assess surgical results before the chest is closed. TEE has become an invaluable tool for the diagnosis and management of patients with suspected or known infective endocarditis.

Diagnosis, Differential↗
PubMed1995

Human type II receptor for bone morphogenic proteins (BMPs): extension of the two-kinase receptor model to the BMPs.

Bone morphogenic proteins (BMPs) are universal regulators of animal development. We report the identification and cloning of the BMP type II receptor (BMPR-II), a missing component of this receptor system in vertebrates. BMPR-II is a transmembrane serine/threonine kinase that binds BMP-2 and BMP-7 in association with multiple type I receptors, including BMPR-IA/Brk1, BMPR-IB, and ActR-I, which is also an activin type I receptor. Cloning of BMPR-II resulted from a strong interaction of its cytoplasmic domain with diverse transforming growth factor beta family type I receptor cytoplasmic domains in a yeast two-hybrid system. In mammalian cells, however, the interaction of BMPR-II is restricted to BMP type I receptors and is ligand dependent. BMPR-II binds BMP-2 and -7 on its own, but binding is enhanced by coexpression of type I BMP receptors. BMP-2 and BMP-7 can induce a transcriptional response when added to cells coexpressing ActR-I and BMPR-II but not to cells expressing either receptor alone. The kinase activity of both receptors is essential for signaling. Thus, despite their ability to bind to type I and II receptors receptors separately, BMPs appear to require the cooperation of these two receptors for optimal binding and for signal transduction. The combinatorial nature of these receptors and their capacity to crosstalk with the activin receptor system may underlie the multifunctional nature of their ligands.

Activin Receptors↗
PubMed1995

Restriction fragment length polymorphisms in polymerase chain reaction amplified ribosomal DNAs of three Trichogramma (Hymenoptera: Trichogrammatidae) species.

Restriction fragment length polymorphisms from PCR amplified ribosomal DNAs of three Trichogramma species, T. minutum, T. brassicae, and T. near sibiricum, were studied. Length variation in the internal transcribed spacer (ITS) region was observed. The ITS region of T. brassicae is about 1350 base pairs (bp) in length and those of T. minutum and T. near sibiricum are 1300 bp. These three species also differ in the size of their ITS1 and ITS2 regions. Restriction enzyme digestions of these regions showed unique banding patterns for each species. The amplified 18S region of ribosomal DNA is about 1800 bp in length and showed no length variation between the three species of Trichogramma. Restriction enzyme digestion of this region by BamHI differentiated T. brassicae from the other two species. Restriction site maps of the ITS and 18S regions were constructed for each species. The amplified 28S region is about 1700 bp for these three species. Restriction of this region by RsaI and SacII differentiates these three species. The reported results indicate that these species of Trichogramma can be clearly differentiated from one another by nuclear ribosomal DNA markers.

Animals↗
PubMed1995

Restoration of tumor oxygenation after cytotoxic therapy by a perflubron emulsion/carbogen breathing.

Female, Fisher 344 rats bearing 13762 mammary carcinoma implanted subcutaneously in a hind limb were treated with standard therapeutic single doses of antitumor treatments of several types including: 1) antitumor alkylating agents (cisplatin, cyclophosphamide); 2) natural products (adriamycin, taxol and etoposide); 3) antimetabolites (5-flourouracil); 4) hypoxic cell selective agents (mitomycin C, SR-4233) as well as 5) fractionated radiation therapy (3 Gray daily for 5 days). The oxygen levels in the tumors were measured in the absence of treatment and 24 hrs. after treatment using an Eppendorf p02 histograph. Fifty- to sixty-points were measured per tumor and 8-10 tumors comprised each group. The tumors were more hypoxic post treatment with every anticancer drug or radiation. The percent of p02 readings < or = 5 mmHg in the untreated tumors ranged from 85% (x-rays) to 59% (etoposide). Administration of the perflubron emulsion (8 ml/kg) and carbogen breathing (95% O2/5% CO2) increased the oxygenation of the tumors such that the percent of pO2 readings < or = 5 mmHg was 32% in the untreated controls and ranged from 27% (x-rays) to 56% (adria) in the treated tumors. These results indicate that administration of a perflubron emulsion/carbogen can increase the oxygen content of tumors when hypoxia is the result of cytotoxic therapy.

Animals↗
PubMed1995

Increased tumor oxygenation and radiation sensitivity in two rat tumors by a hemoglobin-based, oxygen-carrying preparation.

The rat 13762 mammary carcinoma and the rat 9L gliosarcoma were grown subcutaneously in a hind limb of female, Fisher 344 rats. The oxygen content of the tumors was determined using an Eppendorf pO2 histograph. Fifty-to-sixty oxygen measurements were made per tumor and there were 8-to-10 animals per group. The percent of pO2 readings < or = 5 mmHg in the mammary carcinoma was 49%, this was decreased to 34% by administration of the hemoglobin preparation (8 ml/kg) and further decreased to 29% when carbogen (95% O2/5% CO2) breathing was added to administration of the hemoglobin preparation. The percent of pO2 readings < or = 5 mmHg in the gliosarcoma was 49%, this was decreased to 24% by administration of the hemoglobin preparation and further decreased to 0% when carbogen breathing was added to administration of the hemoglobin preparation. Therapeutic response was assessed over a single-dose range of radiation therapy (10, 20 and 30 Gray). The dose modifying factor produced by the hemoglobin preparation/air was 1.6 and by the hemoglobin preparation/carbogen was 2.7 in the rat 13762 mammary carcinoma. The dose modifying factor produced by the hemoglobin preparation/air was 1.9 and by the hemoglobin preparation/carbogen was 2.9 in the rat 9L gliosarcoma. Administration of a hemoglobin-based oxygen carrier reduced tumor hypoxia and increased tumor response to radiation therapy.

Adenocarcinoma↗
PubMed1995

Quantification of steady state expression of mRNA for alpha-1 adrenergic receptor subtypes using reverse transcription and a competitive polymerase chain reaction.

Three distinct alpha-1 adrenergic receptor subtypes (alpha-1a, alpha-1b and alpha-1d) have been identified through molecular cloning. Expression of alpha-1 adrenergic receptor mRNA has been detected in several tissues, but previous studies with Northern blot analysis or RNase protection assays have provided only semiquantitative information. Furthermore, the mRNA distribution of these subtypes in many rat tissues is unknown. In the present study, we quantified alpha-1a, alpha-1b and alpha-1d adrenergic receptor mRNA in 19 adult rat tissues through the use of reverse transcription (RT) and a competitive polymerase chain reaction (PCR). This procedure used internal cRNA standards as competitive templates that contained sequences complementary to the primers for alpha-1a, alpha-1b and alpha-1d adrenergic receptors and that differed in molecular size from the native sequences. Total RNA was harvested from 19 freshly dissected organs of the rat. The PCR products were labeled by inclusion of alpha-32P-dCTP in the PCR. After electrophoresis, ratios of competing to native radio-labeled products were used to interpolate the amount of native RNA originally present in each sample. The results revealed that the relative abundance of alpha-1a adrenergic receptor mRNA among various tissues was as follows: vas deferens > colon > or = stomach > or = cerebral cortex > heart > or = small intestine > or = testis > prostate. The relative rank order of alpha-1b adrenergic receptor mRNA expression was heart > or = cerebral cortex > liver, whereas that of alpha-1d adrenergic receptor mRNA was vas deferens > cerebral cortex > or = aorta > adrenal gland.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

[Role of energy metabolism in nutrition management of critically ill patients].

Indirect calorimetric measurements were made with a MedGraphics Critical Care Monitor (CCM) desktop analysis system in the observation of critically ill and malnourished patient's energy expenditure. In 15 critically ill patients, predicted energy requirements based on 1.75 times BEE calculated by Harris-Benedict formula or corrected Harris-Benedict formula averaged 32.7% and 27.8% greater than metabolic expenditure measured by indirect calorimetry respectively. In the 20 unstressed malnourished patients, predicted energy requirements based on the Harris-Benedict (BEE) formula averaged 15% to 20% higher than metabolic expenditure measured by indirect calorimetry. When the critically ill patients' total energy intakes were 1.2 times resting energy expenditure, their nutritional state could be maintained in normal conditions. While the malnourished patients were provided with 1.5 x REE in energy intake, the malnourished state could be reversed. We believed that the critically ill and malnourished patients' energy expenditures are better measured than predicted and their nutritional regimens should be guided under the computerized indirect calorimetry.

Adult↗
PubMed1995

Percutaneous endovascular embolization of intracerebral arteriovenous malformations. Experience in 72 cases.

Endovascular therapeutic embolization of arteriovenous malformations (AVMs) of the brain was performed in 72 patients between October 1986 and March 1993. From October 1986 to May 1991, 38 patients in this series were treated with isobuty1-2-cyanoacrylate (IBCA) glue. After June 1991, in the remaining 34 patients the embolic materials used included surgical silk (5-0), polyvinyl alcohol (PVA), ethanol, and estrogen. After treatment, 29 patients (40.3%) had complete angiographic obliteration of AVM, 15 (21%) transient neurologic postembolization deficit, and 3 (4%) permanent deficit without death. Embolic agents and procedures are discussed as to their curative effects, safety, normal perfusion pressure breakthrough (NPPB) problem, with silk mixture fluid being considered preferable.

Adolescent↗
PubMed1995

[Clinical analysis of 20 cases of idiopathic interstitial pulmonary fibrosis].

This paper describes 20 cases of idiopathic diffuse interstitial pulmonary fibrosis. The clinical manifestations are dry cough, chronic progressive dyspnea, clubbed fingers and velcros rales. CT (HRCT) scanning were performed in 8 patients and the results were compared with the common X-ray chest films, the images of HRCT were more clearer than common chest films, the fine grain shadows, which can not be shown on the common X-ray chest films, were shown on HRCT. The final diagnosis is based on the transbronchial lung biopsy or open lung biopsy.

Adult↗
PubMed1995

Neuroligand-evoked calcium-dependent release of excitatory amino acids from Schwann cells.

Bradykinin caused a receptor-mediated increase in release of the excitatory amino acids (EAAs) glutamate and aspartate from Schwann cell cultures obtained from dorsal root ganglia (DRG) together with an increase in the cytoplasmic level of free calcium. Perturbations which inhibited brady-kinin-induced calcium mobilization prevented the release of EAAs from glia. The addition of ionomycin caused a calcium-dependent release of EAAs. Therefore, bradykinin causes calcium dependent-release of EAAs from DRG Schwann cells. Bradykinin did not cause cell swelling and p-chloromercuriphenylsulfonic acid, an inhibitor of the electrogenic glutamate transporter, did not reduce bradykinin-induced EAA release. Therefore, bradykinin stimulates EAA release from Schwann cells through a mechanism that is neither the previously described volume regulated release mechanism nor due to the reversal of the glutamate transporter.

Animals↗
PubMed1995

[Experimental studies on the quality of sophora powder].

In this paper, the contents of total flavonoids, essential oil, tannin, trace elements along with bacteriostatic action in Sophora Powder have been measured. These studies present a scientific evaluation on the quality of Sophora Powder.

Drug Combinations↗
PubMed1995

[Effects of over feeding on the energy expenditure and substrates oxidative rate in surgical patients].

In this study, computerized indirect calorimetric measurements were made using a medical graphics critical care monitor (CCM) desktop analysis system in the observation of metabolic state of 20 patients complicated with external gastrointestinal fistula. While these malnourished patients were provided with 1.5 x REE in total energy intake, the malnutrition state could be reversed. But with 1.75 or 2.0 x REE or up total energy intake, the general nutritional state could not be improved faster, the O2 consumption and CO2 production and energy expenditure increased, while the net glucose oxidation increased and net lipid oxidation decreased or net lipogenesis occurred simultaneously. We believed that superfluous energy intake is harmful to critically ill patients and may lead to cell injury and dysfunction.

Adolescent↗
PubMed1995

Development of a polymer-enzyme immunoassay method and its application.

Both poly(N-isopropylacrylamide) and poly(N-isopropylacrylamide)-antibody (PINP-Ab)-labelled enzyme adhered quickly and tightly to cellulose acetate/nitrate membrane either below (less efficiently) or above (more efficiently) the lower critical solution temperature, and the retention of PINP-Ab on the membrane increased over 30-fold when compared with the unconjugated Ab. These characteristics were used to develop a novel polymer-enzyme-linked immunoassay method: homogeneous antigen-antibody immune-complexation reaction and a heterogeneous separation process. By using a simple horseradish-peroxidase-labelled antibody as a probe, we applied this method to the detection of human serum hepatitis B surface antigen (HBsAg). This immunoassay system can detect as little as 1 ng/ml of HBsAg. The advantages of this method are: (a) fast homogeneous immune complexation; (b) a rapid heterogeneous separation process; (c) high sensitivity; and (d) low non-specific background.

Acrylic Resins↗
PubMed1995

A new and cheap medical examination system with artificial intelligence.

This is a medical examination system with artificial intelligence. It is used to find persons who want to obtain higher professional posts in the medical field, including doctors, dentists, nurses, pharmaceutists, etc. It has a question bank of 536,000 multiple choice questions (MCQs), of which 59,500 have pictures. Ten percent of the MCQs is updated every year; the old MCQs in the question bank are used as exercises for the persons who want to obtain higher professional posts. The system, with three distinctive degrees of difficulty, is applicable to three different professional posts: the assistant physician, the resident, and the attending physician. It ensures the general level of assessment for the same professional post, regardless of when one wants to take the system. In addition, the system also guarantees the consistency of the following three factors: the constituent of sub-professions, the classification of MCQs, and the degree of difficulty of each MCQ. Another feature of the system is that the passing score need not be the traditional standard passing score of 60. The passing score is determined by the system according to the requirements of the different professional posts and the degree of difficulty of the MCQs in the system. Therefore, the new method for passing the system is more rational than the traditional one. Moreover, the final score given by the system will be standardized to eliminate sampling errors. The reliability of the system will also be tested after each examination. If the coefficient of reliability is lower than 0.85, the scores will be canceled and examination will be repeated. The system can accept 96 persons simultaneously taking the examination with on-line computers. The people who work in remote places can take examination in their hospital with a personal computer linked via telephone. The system has already been approved by the relevant authoritative departments in China. It has been running successfully for more than six years. During this period of time, 125,645 candidates have taken the exam; 64,078 have passed the examination and have been promoted to higher professional posts. The system runs on local area network and uses a program written in PROLOG and FoxPro. It is estimated that the total cost of developing the system is less than $46,000 (US).

Artificial Intelligence↗