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Biomedical subjects

M Liang

Publications and source records attributed to M Liang.

At least 91 records · Page 5Linked to original sources
PubMed1994

A brief introduction to the critical reading of the clinical literature.

Clinicians are bombarded by reports of new diagnostic tests or treatments for patients with spine problems. To provide the best possible patient care, clinicians need to be able to critically appraise the results of such studies for validity and relevance to patient care. Important questions to be asked of any description of diagnostic or treatment studies are the following questions: 1) Are the patients described in detail so that you can decide whether they are comparable to those that you see in your practice? 2) Are the treatments or assessments described well enough so that you could provide the same for your patients? 3) Was a clinically relevant endpoint measured? 4) Is there an appropriate comparison group? 5) Are potential sources of bias appropriately attended to? 6) Are the results clinically significant?

Humans↗
PubMed1994

Antigenic and molecular characterization of hantavirus isolates from China.

Hemorrhagic fever with renal syndrome (HFRS) is caused by certain viruses in the genus Hantavirus, family Bunyaviridae, and is a major public health problem in China. By using molecular and serological tests, we characterized 15 hantaviruses isolated either from patients with HFRS or from rodents captured in endemic areas of China. By cross plaque-reduction neutralization tests performed with rabbit immune sera, we identified two serologically distinct groups of viruses, comprised of those related to Hantaan virus, and those related to Seoul virus. To study the genetic relationships among these viruses, we amplified a 330 base pair region of the medium (M) genome segment of each isolate by reverse transcription and polymerase chain reaction (PCR) and compared the nucleotide sequences to those of other, well-characterized hantaviruses. In addition, we PCR-amplified and analyzed the entire coding region of the small (S) genome segment of each isolate by restriction enzyme digestion with a battery of enzymes. The results of our genetic analyses of both the M and S segments of these isolates confirmed our serological data, indicating that Hantaan and Seoul viruses co-circulate in endemic disease regions of China. We constructed a phylogenetic tree based on multiple alignment of the partial M segment sequences. The resulting dendrogram distinguished three genetic subtypes of Hantaan viruses and one type of Seoul virus.

Animals↗
PubMed1994

[Biological study on prognosis of laryngeal carcinoma with regional metastatic lymph nodes].

The purpose of this study is to find out the biological feature of laryngeal cancer and metastatic lymph nodes with DNA Image Analysis, Argyrophilic Nucleolar Organizer Region (AgNOR), Carcinoembryonic Antigen (EA) and Estrogen Receptor (ER) 30 patients were included in this study. It was found that carcinomatous tissues showed a statistically significantly higher DNA content, AgNOR content, and positive reaction of CEA and ER than those of normal tissue (P < 0.01). Paired comparisons were performed in primary tumor and metastases and didn't show statistical difference (P > 0.05). The group with survival time over 5 years had a significantly lower DNA content, AgNOR content, CEA positive reaction of metastases and higher ER positive reaction of metastases than those with less than 5 years survival (P < 0.01). But there no was consistant relationship between primary tumor CEA or ER positive reaction and survival time (P > 0.05). The patients who accepted radiotheraphy had better prognosis than those who didn't (P < 0.05). The above results indicate that the combined analysis of metastases and primary tumor will provide a good feature for biological activity. In addition, radiotherapy before and after operation will be beneficial.

Carcinoembryonic Antigen↗
PubMed1993

Molecular and antigenic characterization of HV114, a hantavirus isolated from a patient with haemorrhagic fever with renal syndrome in China.

The relationship of a Hantaan-like virus (HV114), isolated from a patient with haemorrhagic fever with renal syndrome in Hubei Province, People's Republic of China, to other pathogenic hantaviruses was evaluated by cross-neutralization studies and nucleotide sequence analysis of the M genome segment. Plaque reduction neutralization assays indicated that HV114 is closely related to prototype Hantaan (HTN) virus, strain 76-118, which was originally isolated from an Apodemus field mouse in Korea. Comparison of the M genome segments of HTN 76-118 and HV114 revealed sequence identity of 84.7% and 95.4% for nucleotides and deduced amino acids, respectively. These data demonstrate that HV114 and 76-118 are two closely related but different isolates of HTN virus, establishing the scientific basis for testing and future use in China of a recombinant vaccine expressing the genome of HTN virus strain 76-118.

Amino Acid Sequence↗
PubMed1993

Comparison of three techniques to inflate the bronchial cuff of left polyvinylchloride double-lumen tubes.

Correct inflation of the cuff of any breathing tube is important; overinflation can damage the mucosa of the tracheobronchial tree and underinflation will cause a leak. Three different techniques to determine cuff seal/leak during inflation of the bronchial cuff of left double-lumen endobronchial tubes (DLT) were each evaluated in 10 patients. DLT size was chosen from a formula based on the patient's height and sex. In the first technique, designated the positive pressure technique of bronchial cuff inflation (PPT), the bronchial side of the DLT is pressurized during connection of the tracheal side to a beaker of water. Air bubbles will appear in the beaker in the absence of bronchial seal. The second technique, designated the CO2 analysis technique of bronchial cuff inflation (CAT), is based on analysis of CO2 content of gas sampled from the tracheal side of the DLT during ventilation of its bronchial side. When the bronchus is sealed, the normal CO2 waveform changes to a flat line. In the third technique, designated the negative pressure technique of bronchial cuff inflation (NPT), suction is applied to the tracheal side of the DLT. The absence of bronchial seal will result in collapse of the reservoir bag within a breathing system connected to the bronchial side of the tube. The bronchial sealing volumes were 1.1 +/- 0.9 mL, 0.9 +/- 0.7 mL, and 0.3 +/- 0.4 mL (mean +/- SD) when measured with the PPT, CAT, and NPT, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Epidermal growth factor activates phospholipase C in rat hepatocytes via a different mechanism from that in A431 or rat1hER cells.

Epidermal growth factor (EGF) can stimulate inositol lipid hydrolysis in rat hepatocytes and can accelerate GTP/GDP exchange in hepatic membranes. Both of these responses can be abolished by pretreatment with pertussis toxin, suggesting that EGF may regulate phospholipase C (PLC) activity via a guanine nucleotide-binding regulatory protein (G protein) in liver cells. In contrast, in A431 human epidermoid carcinoma cells EGF can induce a rapid phosphorylation of PLC-gamma on tyrosine residues that increases the activity of immunoprecipitated PLC-gamma, suggesting that tyrosine phosphorylation of PLC-gamma may be the mechanism for EGF-stimulated inositol trisphosphate production in these cells. To determine the importance of the phosphorylation of PLC-gamma on tyrosine residues in a system where the EGF receptor apparently couples to a G protein, the effect of EGF on tyrosine phosphorylation of PLC-gamma was examined in rat hepatocytes. PLC-gamma was immunoprecipitated from cell lysates with a PLC-gamma antiserum and its tyrosine phosphorylation state was determined using both Western blot analysis with phosphotyrosine antibodies and direct measurement of phosphorylated amino acids. The results were compared with analogous experiments performed with A431 cells and another cultured cell line expressing high levels of human EGF receptors, Rat1hER fibroblasts. Although the amount of PLC-gamma in rat hepatocytes is similar to that in A431 cells and slightly higher than that in Rat1hER cells, EGF causes a barely detectable increase in the phosphorylation of PLC-gamma on tyrosine in hepatocytes, whereas it stimulates a significant degree of phosphorylation of PLC-gamma on tyrosine in Rat1hER or A431 cells. Pretreatment of hepatocytes with pertussis toxin abolishes the ability of EGF to activate PLC, as determined by an increase in intracellular Ca2+, but has no effect on the small amount of phosphate incorporated into tyrosine residues on the PLC-gamma protein, demonstrating that this low level of PLC-gamma phosphorylation does not correlate with changes in PLC activity. The data suggest that phosphorylation of PLC-gamma on tyrosine is not important for EGF-enhanced PLC activity in hepatocytes. This conclusion implies that EGF may use a mechanism to regulate PLC activity in hepatocytes that is different from that used in cultured cells expressing high levels of EGF receptors.

Animals↗
PubMed1987

Agonists and phorbol esters desensitize beta-adrenergic receptors by different mechanisms.

Exposure of 1321N1 human astrocytoma cells to the protein kinase C (PKC) activator phorbol 12-myristate, 13-acetate (PMA) led to a rapid and concentration-dependent decrease in isoproterenol (ISO)-stimulated adenylate cyclase (AC) activity in cell lysates. This desensitization of beta-adrenergic receptor (BAR) function was mimicked by mezerein, which also activates PKC, but not by 4-O-methyl-PMA, which is a very weak activator of PKC. Pretreatment with PMA led to desensitization of AC activity stimulated by ISO and by prostaglandin E1, in contrast to the beta-receptor-specific desensitization induced by ISO. Stimulation of AC activity by forskolin and by fluoride remained unaltered. The extent of desensitization observed with PMA plus ISO was greater than with either agent alone. Desensitization with PMA did not result in internalization of BAR, as assessed by sucrose density gradient centrifugation assays and by assays of competition by the hydrophilic ligand ISO for radioligand binding to intact cell receptors. PMA pretreatment did not alter the apparent affinity of the agonist ISO for intact cell BAR, nor was the potency of ISO for stimulation of AC activity altered. The protein kinase inhibitor H7 [1-(5-isoquinolinesulfonyl)-2-methylpiperazine] inhibited the desensitization induced by PMA but not that induced by ISO. These results indicate that activation of PKC can lead to desensitization of receptor-stimulated AC activity but that agonist-induced desensitization of BAR-stimulated AC activity occurs by a different mechanism.

Adenylyl Cyclases↗
PubMed1987

[3H]propylbenzilylcholine mustard-labeling of muscarinic cholinergic receptors that selectively couple to phospholipase C or adenylate cyclase in two cultured cell lines.

Although both second messenger response systems are fully functional in both cell lines, activation of muscarinic cholinergic receptors only results in inhibition of adenylate cyclase in NG108-15 neuroblastoma X glioma cells and stimulation of phosphoinositide hydrolysis in 1321N1 human astrocytoma cells. Muscarinic receptors on both cell types were covalently labeled with [3H]propylbenzilylcholine mustard ([3H]PBCM), and the mobilities of the [3H]PBCM-labeled species of both cells were compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. 1321N1 and NG108-15 cells each primarily expressed a single [3H]PBCM-labeled species with an apparent size of approximately 92,000 and 66,000 Da, respectively. [3H]PBCM labeling was completely inhibited by 1 microM atropine or by down-regulation of muscarinic receptors by an overnight incubation with carbachol. The apparent size of the [3H]PBCM-labeled species of both cell lines was not altered by treatment with a series of protease inhibitors or by treatment with dithiothreitol and iodoacetamide. Since muscarinic receptors are glycoproteins, the contribution of carbohydrate groups to the difference in apparent size of the [3H]PBCM-labeled proteins was determined by treatment of [3H]PBCM-labeled membranes with endoglycosidase F, an enzyme that removes both complex and high mannose type N-linked carbohydrate chains. Endoglycosidase F treatment reduced the apparent size of the [3H]PBCM-labeled species in 1321N1 cells from 92,000 to approximately 77,000 Da and in NG108-15 cells from 66,000 to 45,000 Da. Neuraminidase produced no further reduction of the apparent size of the [3H]PBCM-labeled species from either cell after endoglycosidase F treatment, suggesting the absence of sialic acid containing O-linked carbohydrate chains on the muscarinic receptors of the two cell lines. The results suggest that different muscarinic receptor proteins may be responsible for the two different biochemical responses to muscarinic receptor activation.

Adenylyl Cyclases↗
PubMed1987

Patient education program to teach energy conservation behaviors to patients with rheumatoid arthritis: a pilot study.

We report a prospective, randomized pilot study comparing a new workbook-based program, designed to teach patients with rheumatoid arthritis (RA) energy conservation behaviors, with standard occupational therapy (OT). Sixteen patients took part in the new program and nine received the standard therapy. Data on the number of tender or swollen joints, grip strength, walk time, activities of daily living, psychologic adjustment to illness, and daily activity log, were measured before and three months after intervention. Eleven percent of those who received standard therapy and 50% of those who received the workbook increased their amount of physically active time (p = .10). Twenty-two percent of the control group and 50% of those in the workbook group achieved a better balance of rest and physical activity (p = .07). We conclude that the adoption of energy conservation behaviors is different in the two groups. This initial study suggests that interrupting physical activity with rest periods may result in increased physical activity in patients with RA.

Arthritis, Rheumatoid↗
PubMed1984

Feasibility of willingness-to-pay measurement in chronic arthritis.

Quantification of nonmonetary aspects of disease is a major challenge for economic analysts. Using the amounts of money recipients are willing to pay for nonmonetary benefits has theoretical appeal, but it has proven difficult to implement. Difficulties encountered include noncomprehension by subjects, misrepresentation of preferences, extraneous determinants of answers, and ethical concerns. In a preliminary exploration of feasibility, 184 patients with osteoarthritis and rheumatoid arthritis were asked their willingness to pay (WTP) for hypothetical complete cure. With minimal pressure put on the patients to respond, 27 percent gave plausible answers. People with more schooling, with paid employment, or who were having more treatments for their arthritis were more likely to respond. Patients were willing on average to pay 17 percent of family income for arthritis cure. Methods for measuring WTP are being strengthened and may soon play an important role in health services research.

Arthritis↗
PubMed1982

Roentgenograms in primary care patients with acute low back pain: a cost-effectiveness analysis.

For patients visiting a primary care office practice for acute low back pain, we compared the benefits, risks, and costs of obtaining a roentgenogram of the lumbar spine routinely at the initial visit with performing a roentgenogram only if the patient's pain does not improve during and eight-week follow-up period. The cost-effectiveness analysis indicated that, to avert one day of physical suffering in a population of patients, the population would have to be subjected to the additional risk of 3,188 mrad of radiation and an additional cost of $2,072. While, in the individual case, circumstances might lead to a different conclusion, in general, the risks and costs of obtaining lumbar roentgenograms at the initial visit in patients with acute low back pain do not seem to justify the relatively small associated benefit.

Acute Disease↗