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Biomedical subjects

G Liu

Publications and source records attributed to G Liu.

At least 559 records · Page 31Linked to original sources
PubMed1994

Potential use of soluble CD44 in serum as indicator of tumor burden and metastasis in patients with gastric or colon cancer.

Soluble CD44 is present in the serum of normal individuals (2.7 +/- 1.1 nM). The concentration of soluble CD44 in the serum is elevated in patients with advanced gastric (24.2 +/- 9.8 nM) or colon cancer (30.8 +/- 11 nM). Serum CD44 concentration correlated with tumor metastasis and tumor burden. Surgical resection of tumors resulted in decreases in serum CD44 levels. By Western blot analysis, monoclonal anti-CD44 antibody reacted with a major protein with molecular weight between 130,000 and 190,000. In addition, two proteins with molecular weights of 72,000 and 80,000 can also be identified. Therefore, different CD44 isoforms may be present in the serum of cancer patients. Serum CD44 concentrations may be an indicator of tumor burden and metastasis in patients with malignant diseases.

Adenocarcinoma↗
PubMed1994

3-dimensional functional imaging of human brain using echo-shifted FLASH MRI.

A 3-dimensional MRI method has been developed for functional mapping of the human brain, based on blood oxygenation level dependent (BOLD) contrast mechanisms. The method uses recently introduced principles of echo-shifted FLASH to acquire a single 3D data set in 20 s. The technique was tested on a conventional 1.5 Tesla clinical scanner with a standard head coil using visual stimulation with a 8 Hz flashing white light, or a varying checkerboard pattern. Areas of increased signal intensity were identified in the visual cortex, consistent with the known functional organization.

Brain↗
PubMed1994

Fast volume scanning with frequency-shifted BURST MRI.

We introduce a modified BURST imaging technique with reduced saturation effects and improved signal-to-noise ratio. The method applies a frequency shift to the RF excitation pulse on successive repetitions. It allows collection of 3D datasets of human brain within a few seconds, on a standard clinical scanner at 1.5 Tesla.

Brain↗
PubMed1994

Effect of 24-h blood pressure levels and circadian blood pressure rhythm on left ventricular structure and function in isolated systolic hypertension.

Forty-one participants (mean age 69 +/- 5.6 years) were examined by fully automatic blood pressure monitor and Doppler echocardiography to gain information on the ambulatory blood pressure and the left ventricular structure and function in isolated systolic hypertension. Cumulative sum (cusum)-derived statistics was used to quantify circadian blood pressure rhythm and 24-h blood pressure levels were defined as mean blood pressure values during 24 h, waking (06:00-22:00 h) and sleeping (22:00-06:00 h) periods, respectively. Most of the derivatives of ambulatory blood pressure, including cusum-derived statistics and 24-h blood pressure levels, were significantly related with the left ventricular structural (left ventricular posterior wall and interventricular septum thickness) and functional (acceleration time in the left ventricular outflow tract and early diastolic deceleration time) indexes. Among the left ventricular structural and functional indexes, interventricular septum thickness at end diastole had the strongest correlation with sleeping diastolic mean blood pressure (r = 0.41, P < 0.01), left ventricular posterior wall at end diastole, the best with 24-h systolic mean blood pressure (r = 0.41, P < 0.01), acceleration time the strongest with systolic cusum-derived circadian alteration magnitude (r = 0.49, P < 0.01) and early diastolic deceleration time the greatest with diastolic cusum-derived trough blood pressure (r = 0.45, P < 0.01). We conclude that left ventricular structural changes rely on 24-h systolic and diastolic blood pressure levels, whereas left ventricular functional variations may be more dependent upon circadian blood pressure rhythm in elderly patients with isolated systolic hypertension.

Aged↗
PubMed1994

Privatization of the medical market in socialist China: a historical approach.

A Socialist-Market Economy was defined as a target model for China's economic reform by China's 14th National Congress in 1992. Such an innovative change in China's more than a decade long economic reform has brought both new challenges and opportunities for its health care system reform as it moves toward a market determination mechanism and involvement of the private sector. A better understanding of the nature and history of the Chinese private medical market and its dynamic socio-economic environment would certainly shed a great deal of light onto the accomplishments of the health care reform. Research in this area, however, is almost non-existent at either national or international levels. The present study attempts to fill this gap by providing a comprehensive assessment of both historical and prospective development of the Chinese private medical market. Three stages are defined to present the tortuous development of this market over the last four decades, coupled with our critiques of the underlying merits and problems. Predictions are also made on the future perspective of the private market, and its possible impact and role in shaping the reform of the entire Chinese health care system. The government's role as well as its future strategy to cope with the issues surrounding Chinese health care reform are also summarized. The study concludes with five health policy recommendations aimed at facilitating China's health care reform via more market-oriented determination of resources allocation, production, and distribution, coupled with promotion of the private sector's involvement while minimizing its potential adverse side effects.

Ambulatory Care Facilities↗
PubMed1994

Functional brain MR imaging based on bolus tracking with a fast T2*-sensitized gradient-echo method.

Dynamic physiological scanning, based on temporary changes in local field homogeneity during the passage of a contrast agent bolus, has been performed hitherto with echo-planar imaging (EPI) or conventional gradient-recalled techniques (FLASH). Here, it is shown that the T2* sensitivity of conventional FLASH techniques can be improved drastically on a conventional whole body instrument by delaying the gradient-echo until the subsequent TR-period without increasing total imaging time. Examples are given for a full k-space matrix (128 x 256) obtained within 2 s with a TE of 25 ms, resulting in images free of artifacts. The method is applied to bolus tracking through the brain of healthy volunteers during visual stimulation and in the dark. An average increase of regional cerebral blood volume (rCBV) in the visual cortex of 10.9% (n = 9, p = .001) was found.

Blood Volume↗
PubMed1994

High-efficiency gene transfer to autologous rabbit jugular vein grafts using adenovirus-transferrin/polylysine-DNA complexes.

Within the first year, 15-20% of coronary artery saphenous bypass vein grafts (SVGs) occlude because of thrombosis or progressive intimal hyperplasia. One potential new strategy to reduce this complication would be to introduce antithrombotic or antiproliferative genes in vein grafts before implantation. The success of this approach requires an efficient DNA delivery system. In the present study we tested the feasibility of using adenovirus-transferrin/polylysine-DNA complexes (TfAdpl/DNA) to achieve high-efficiency gene transfer into vascular interposition vein grafts. All studies used the Escherichia coli LacZ (beta-galactosidase [beta-Gal]) reporter gene under the control of the cytomegalovirus (CMV) earlier promoter and enhancer (pCMV/LacZ). Autologous rabbit jugular vein segments were incubated ex vivo for 60 min in a solution of TfAdpl/DNA complexes (1.2 x 10(10) biotinylated adenovirus particles, 2,430 ng of streptavindylated polylysine. 10 micrograms of plasmid DNA, and 9 micrograms of transferrin-polylysine per ml), and then reimplanted across the ligated right carotid artery. Control veins were incubated in TfAdpl solution in which DNA was omitted. A total of six grafts were treated with TfAdpl/DNA, and two grafts were treated with TfAdpl. Veins were harvested 3 (n = 3) and 7 (n = 3) days later and beta-Gal activity was determined by X-Gal chromogen staining. All six TfAdpl/DNA-treated grafts stained intensely blue, whereas control grafts were negative. Microscopic examination of serial sections revealed intracellular blue granules consistent with beta-Gal activity to be present in all of the endothelial cells and in numerous medial and advential cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoviridae↗
PubMed1994

Aryl hydrocarbon (Ah) receptor-independent induction of Cyp1a2 gene expression by acenaphthylene and related compounds in B6C3F1 mice.

Treatment of B6C3F1 mice with acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene and dibenzofuran resulted in induction of hepatic microsomal methoxyresorufin O-deethylase (MROD) activity. Acenaphthylene was the most potent inducer of MROD, a Cyp1a2-dependent activity, and was utilized as a prototypical inducer for this group of tricyclic hydrocarbons. Acenaphthylene (300 mg/kg) caused a > 80-fold induction of hepatic microsomal MROD activity; no induction was observed in kidney or lung. Analysis of induced hepatic microsomes with antibodies to Cyp1a1 and Cyp1a2 showed that acenaphthylene induced immunoreactive Cyp1a2 but not Cyp1a1 proteins and subsequent mRNA analysis confirmed with a cDNA probe for Cyp1a1 and Cyp1a2 that acenaphthylene induced Cyp1a2 but not Cyp1a1 mRNA. Results from nuclear run-on experiments using hepatic nuclei showed that acenaphthylene caused an approximately 4-fold increase in the rate of Cyp1a2 gene transcription in B6C3F1 mice. Results of competitive binding studies indicated that the tricyclic hydrocarbons did not competitively displace [3H]2,3,7,8-tetrachlorodibenzo-p-dioxin or [3H]benzo[a]pyrene from the mouse hepatic cytosolic aryl hydrocarbon (Ah) receptor or 4S carcinogen binding protein respectively. The data indicate that acenaphthylene and related tricyclic hydrocarbons induce Cyp1a2 gene expression in B6C3F1 mice via an Ah receptor-independent pathway. Thus, tricyclic hydrocarbons induce Cyp1a2 without the co-induction of Cyp1a1 and therefore these relatively non-toxic compounds can be used to further probe the role of Cyp1a2 in the metabolism and metabolic activation of diverse chemical carcinogens.

Acenaphthenes↗
PubMed1994

Immunochemical characterization of the ATP-stimulated glucocorticoid-receptor-translocation promoter from various organs of rat.

We previously found a novel endogenous factor in rat liver cytosol, named ATP-stimulated glucocorticoid-receptor-translocation promoter (ASTP), that increased the binding of activated glucocorticoid-receptor to nuclei in the presence of ATP. In this work, we immunized rabbits with the purified ASTP protein and characterized the antibodies with regard to titer, cross-reactivity and specificity. An IgG fraction from sera of the immunized rabbits contained specific antibodies to ASTP. The anti-ASTP IgG could precipitate the ASTP protein without the activity. Immunoblot analysis revealed a major band of 48 kDa in rat liver cytosol that migrated to the same position as the purified ASTP protein by SDS-PAGE, and an additional minor band of about 50 kDa. Monospecific antibodies purified from the IgG fraction using the antigen (the purified 48-kDa ASTP protein) immobilized on a polyvinylidene difluoride membrane also reacted with both the 48-kDa ASTP protein and the 50-kDa protein in rat liver cytosol, suggesting that this 50-kDa protein is immunologically related to the 48-kDa ASTP protein. Densitometric quantification of immunoblots demonstrated that the rat kidney cytosol contained ASTP protein at a concentration of about 20% of that of liver cytosol. Other tissues such as brain, skeletal muscle, heart, and lung, contained neither the ASTP protein nor the activity.

Adenosine Triphosphate↗
PubMed1994

Haemodynamic, renal and hormonal responses to enalkiren in four patients with post-surgical oliguria.

1. The haemodynamic and hormonal responses of four patients with acute post-surgical oliguria (urine output < 0.5 mL/kg per h) were measured in response to the renin inhibitor enalkiren. Enalkiren was infused at 0.01 up to 0.1 mg/kg per h for up to 4 h. 2. Enalkiren infusion was associated with a progressive fall in blood pressure, clinically significant in three of the four patients. Systemic vascular resistance fell in proportion to blood pressure fall. Cardiac output and pulse rate remained unchanged. Effective renal plasma flow rose in all four cases (236 +/- 19 to 327 +/- 38). There was no change in urine flow rate, or urinary sodium excretion. 3. Plasma renin activity (ng angiotensin I/mL per h) fell from 1.9 +/- 0.5 to 0.02 +/- 0.01 (P < 0.04), plasma angiotensin II (pg/mL) fell from 104 +/- 93 to 7.7 +/- 1.5, and plasma aldosterone (ng/dL) fell from 32 +/- 8 to 21 +/- 9 (P = 0.03) at the highest infusion dose. 4. Enalkiren inhibited plasma renin activity with reduced plasma angiotensin II and aldosterone concentrations. This was associated with vasodilation, reduced blood pressure and maintained cardiac output. There was no beneficial effect on renal function in these patients with post-surgical oliguria.

Aldosterone↗
PubMed1994

Early changes in airway smooth muscle hyperresponsiveness.

To study asthmatic airway smooth muscle we developed a canine model of ragweed pollen sensitized, airway hyperresponsiveness because of the difficulties in obtaining human tissue. Tracheal and bronchial smooth muscles from sensitized dogs were shown to possess greater ability to shorten and higher maximum shortening velocity (Vo), both of which contribute to the excessive narrowing of airways typical of human asthma. However, maximum force production remained normal, demonstrating the dissociation between the behaviour of shortening and force. Because we found no evidence of inflammation, hypertrophy, or hyperplasia in the sensitized airway smooth muscles, we felt this is a model of early disease and should provide insight into early and perhaps primary pathogenetic mechanisms. Vo is known to be determined by actomyosin ATPase, which in smooth muscle is activated via phosphorylation of the 20-kDa myosin light chain (MLC20) by myosin light chain kinase (MLCK). Therefore, ATPase activity, MLC20 phosphorylation, and MLCK were investigated. Sensitized tracheal and bronchial smooth muscles showed significantly higher ATPase activity, and a higher level of MLC20 phosphorylation, resulting from increased MLCK activity, a consequence of the measured increase in total quantity of MLCK rather than in specific activity. Since MLCK is activated by binding with Ca(2+)-calmodulin complex, intracellular Ca2+ concentration and calmodulin activity were also assessed, but no difference was found between sensitized and control animals. Our study suggests that increased MLCK quantity may be the cause of airway hyperresponsiveness found in sensitized animals, and future investigation should be focused on depicting the reason for the elevated MLCK.

Animals↗
PubMed1994

Identification and characterization of CCK-B/gastrin receptors in human pancreatic cancer cell lines.

The gastrointestinal peptide cholecystokinin (CCK) is known to stimulate growth of human pancreatic cancer in a receptor-mediated fashion. The purpose of this study was to characterize the receptor responsible for the trophic effects of CCK in cancer cells. With the use of homogenates of PANC-1 human pancreatic cancer cells grown in vitro, the binding characteristics and optimal conditions of radiolabeled selective CCK-receptor antagonists ([3H]L-365,260 and [3H]L-364,718) were examined. Specific and saturable binding was detected with [3H]L-365,260, and Scatchard analysis revealed that the data were consistent for a single site of binding with a binding affinity of 4.3 +/- 0.6 nM and a binding capacity (Bmax) of 283 +/- 68 fmol/mg protein in log phase cells. Binding was dependent on protein concentration, time, temperature, and pH and was sensitive to Na+, K+, Mg2+, and ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. In contrast to log phase cells, Bmax decreased by 80 and 92% in confluent and postconfluent cultures, respectively. Subcellular fractionation studies revealed that binding was in the membrane fraction. Competition experiments indicated that L-365,260 and gastrin were more effective at displacing the radiolabeled L-365,260 than CCK. No binding was detected with the CCK-A antagonist [3H]L-364,718. Assays performed with [3H]L-365,260 on five additional human pancreatic cancer cell lines in vitro and tumor tissue from xenografts in nude mice also revealed specific and saturable binding. These results provide the first identification of a CCK-B/gastrin receptor in human pancreatic cancer cells and tumors and explain the effects of CCK on the growth of this malignancy.

Humans↗
PubMed1994

Myosin light chain phosphatase activity in ragweed pollen-sensitized canine tracheal smooth muscle.

We have reported that myosin light chain phosphorylation is increased in contracting airway smooth muscle from hyperresponsive, ragweed pollen-sensitized dogs. This alteration is manifest physiologically in smooth muscle tissue from sensitized animals as it demonstrates faster shortening velocity and increased shortening capacity. One of the mechanisms underlying the defect is increased myosin light chain kinase activity; it is not known whether modulation of myosin phosphatase activity contributes to enhanced myosin light chain phosphorylation in sensitized canine smooth muscle. We describe a myosin phosphatase assay that we have used to compare the enzyme's activity in crude tracheal smooth muscle tissue homogenates from control and sensitized airway smooth muscle. Twenty kilodalton myosin light chain phosphorylation was initiated with Mg(2+)-ATP, and maximum levels were reached within 40 s; peak phosphorylation levels were stable for at least 3 min. The relative stoichiometry of 20 kD myosin light chain phosphorylation was estimated by chemiluminescent immunoblot assay. Smooth muscle phosphatase activity was estimated by the rate of decline in peak light chain phosphorylation, while myosin light chain kinase was inhibited indirectly with trifluoperazine, with EGTA, or directly by a synthetic peptide inhibitor. Okadaic acid, an inhibitor of phosphatase activity, curbed the decline in light chain phosphorylation seen after myosin light chain kinase inhibition, indicating that the light chain dephosphorylation observed was the result of smooth muscle phosphatase activity. Addition of okadaic acid to the samples led to a 30 to 40% increase in the peak myosin light chain phosphorylation attained for all samples. This indicates that similar populations of phosphatases were present in the homogenates of both control and sensitized tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Allergens↗
PubMed1994

Patterns of coagulopathy during liver transplantation: experience with the first 75 cases using thrombelastography.

Using both conventional laboratory clotting profile and thrombelastography, coagulation status was monitored intraoperatively during liver transplantation in the first 75 cases performed at the Austin Hospital between June 1988 and October 1992. Superimposed on a baseline coagulopathy due to liver disease is a specific pattern of coagulation disturbance which occurs during a liver transplant. Fibrinolysis occurs in the anhepatic stage, worsens with early reperfusion and then spontaneously resolves. In addition reperfusion is associated with a transient clotting defect. If blood loss is excessive, coagulopathy due to massive transfusion may compound the situation. Thrombelastography is a measurement technique allowing rapid on-site assessment of functional clotting status. It is particularly useful in liver transplant surgery. In combination with clinical bleeding assessment it facilitates selective use of component therapy (fresh frozen plasma, platelets and cryoprecipitate) and specific drug treatment only when it is appropriate. It also acts as a liver function test, being especially useful in assessing the graft after reperfusion.

Blood Coagulation↗
PubMed1994

Blood loss and transfusion requirements in liver transplantation: experience with the first 75 cases.

The blood loss data and transfusion requirements including blood bank, salvaged washed red cells, fresh frozen plasma and cryoprecipitate were analysed for the first 75 cases of liver transplantation performed at the Austin Hospital between June 1988 and October 1992. The mean blood loss was 8.8 litres (standard deviation 14.1) with a median value of 4.0 litres. Blood product use expressed as mean number of units (SD) was bank red blood cells 7.1 (12.7), washed red blood cells 3.9 (5.9), fresh frozen plasma 7.1 (9.1), platelets 5.1 (7.4), and cryoprecipitate 1.7 (5.1). These results demonstrate that liver transplantation can be performed without imposing excessive demands on blood transfusion services. Management should include surgical techniques to minimize bleeding and use of autologous transfusion. Use of component therapy (FFP, platelets and cryoprecipitate) should not be empirical. It should be selective on the basis of clinical bleeding assessment and guided by results of the laboratory coagulation profile and changes in thrombelastographic (TEG) parameters.

Adolescent↗