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Biomedical subjects

B J Wu

Publications and source records attributed to B J Wu.

At least 19 recordsLinked to original sources
PubMed2004

Membrane lipids and sodium pumps of cattle and crocodiles: an experimental test of the membrane pacemaker theory of metabolism.

The influence of membrane lipid composition on the molecular activity of a major membrane protein (the sodium pump) was examined as a test of the membrane pacemaker theory of metabolism. Microsomal membranes from the kidneys of cattle (Bos taurus) and crocodiles (Crocodylus porosus) were found to possess similar sodium pump concentrations, but cattle membranes showed a four- to fivefold higher enzyme (Na(+)-K(+)-ATPase) activity when measured at 37 degrees C. The molecular activity of the sodium pumps (ATP/min) from both species was fully recoverable when delipidated pumps were reconstituted with membrane from the original source (same species). The results of experiments involving species membrane crossovers showed cattle sodium pump molecular activity to progressively decrease from 3,245 to 1,953 (P < 0.005) to 1,031 (P < 0.003) ATP/min when subjected to two cycles of delipidation and reconstitution with crocodile membrane as a lipid source. In contrast, the molecular activity of crocodile sodium pumps progressively increased from 729 to 908 (P < 0.01) to 1,476 (P = 0.01) ATP/min when subjected to two cycles of delipidation and reconstitution with cattle membrane as a lipid source. The lipid composition of the two membrane preparations showed similar levels of saturated ( approximately 31-34%) and monounsaturated ( approximately 23-25%) fatty acids. Cattle membrane had fourfold more n-3 polyunsaturated fatty acids (11.2 vs. 2.9%) but had a reduced n-6 polyunsaturate content (29 vs. 43%). The results support the membrane pacemaker theory of metabolism and suggest membrane lipids and their polyunsaturates play a significant role in determining the molecular activity of the sodium pump.

Alligators and Crocodiles↗
PubMed2001

Eccentric contractions affect muscle membrane phospholipid fatty acid composition in rats.

This study investigated if prior eccentric contractions, and thus mechanical strain and muscle damage, exert an effect on the muscle membrane phospholipid fatty acid composition in rats, and whether a possible effect could be attenuated by dietary supplements. Twenty-three rats were randomised to three groups who received chow with added fish oil (n = 8), vitamin C (n = 8) or no supplement (n = 7). After 3 weeks of feeding, calf muscles on one side were stimulated electrically during anaesthesia causing eccentric contractions. Two days later the white gastrocnemius, a part of the stimulated calf muscle, was excised from both legs. In the muscles stimulated to contract eccentrically, compared to the control muscles, the proportion of arachidonic acid, C20:4,n-6 (17.7 +/- 0.6; 16.4 +/- 0.4% of total fatty acids, respectively) and docosapentanoeic acid, C22:5,n-3 (2.9 +/- 0.1 and 2.7 +/- 0.1% of total fatty acids, respectively) was uniformly higher across groups (P < 0.02) with no differences between diet groups. The proportion of long chain polyunsaturates was also significantly higher in the eccentrically contracted (39.9 +/- 0.6% of total fatty acids) compared to the control leg (38.2 +/- 0.6% of total fatty acids; P < 0.01). In contrast no differences were observed in the fatty acid composition of the triacylglycerols stored within the muscle. Thus one severe bout of eccentric contractions modulates the fatty acid composition of the muscle membrane phospholipids when compared to a control leg, and supplemental intake of fish oil or vitamin C did not attenuate this effect.

Animals↗
PubMed2001

Training affects muscle phospholipid fatty acid composition in humans.

Training improves insulin sensitivity, which in turn may affect performance by modulation of fuel availability. Insulin action, in turn, has been linked to specific patterns of muscle structural lipids in skeletal muscle. This study investigated whether regular exercise training exerts an effect on the muscle membrane phospholipid fatty acid composition in humans. Seven male subjects performed endurance training of the knee extensors of one leg for 4 wk. The other leg served as a control. Before, after 4 days, and after 4 wk, muscle biopsies were obtained from the vastus lateralis. After 4 wk, the phospholipid fatty acid contents of oleic acid 18:1(n-9) and docosahexaenoic acid 22:6(n-3) were significantly higher in the trained (10.9 +/- 0.5% and 3.2 +/- 0.4% of total fatty acids, respectively) than the untrained leg (8.8 +/- 0.5% and 2.6 +/- 0.4%, P < 0.05). The ratio between n-6 and n-3 fatty acids was significantly lower in the trained (11.1 +/- 0.9) than the untrained leg (13.1 +/- 1.2, P < 0.05). In contrast, training did not affect muscle triacylglycerol fatty acid composition. Citrate synthase activity was increased by 17% in the trained compared with the untrained leg (P < 0.05). In this model, diet plays a minimal role, as the influence of dietary intake is similar on both legs. Regular exercise training per se influences the phospholipid fatty acid composition of muscle membranes but has no effect on the composition of fatty acids stored in triacylglycerols within the muscle.

Adult↗
PubMed2001

Molecular activity of Na(+)/K(+)-ATPase from different sources is related to the packing of membrane lipids.

The activity of the ubiquitous Na(+)/K(+)-ATPase represents a substantial portion of the resting metabolic activity of cells, and the molecular activity of this enzyme from tissues of different vertebrates can vary several-fold. Microsomes were prepared from the kidney and brain of the rat (Rattus norvegicus) and the cane toad (Bufo marinus), and Na(+)/K(+)-ATPase molecular activity was determined. The membrane lipids surrounding this enzyme were isolated and phospholipids prepared. 'Surface pressure/area' isotherms were measured in monolayers for both membrane lipids and phospholipids using classic Langmuir trough techniques. Microsomal lipid composition was also measured. Whilst significant correlations were observed between membrane composition and Na(+)/K(+)-ATPase molecular activity, the strongest correlations were found between the molecular activity and parameters describing the packing of the surrounding membrane lipids and phospholipids. The influence of membrane lipid composition, especially membrane acyl composition, on the activity of a membrane protein mediated by physical properties of the lipids may represent a fundamental principle applicable to other membrane proteins.

Animals↗
PubMed2000

Relationships between the fatty acid composition of muscle and erythrocyte membrane phospholipid in young children and the effect of type of infant feeding.

Muscle membrane fatty acid (FA) composition is linked to insulin action. The aims of this study were to compare the FA composition of muscle and erythrocyte membrane phospholipid in young children; to investigate the effect of diet on these lipid compositions; and to investigate differential incorporation of FA into muscle, erythrocyte and adipose tissue membrane phospholipid, and adipose tissue triglyceride. Skeletal muscle biopsies and fasting blood samples were taken from 61 normally nourished children (45 males and 16 females), less than 2 yr old (means +/- SE, 0.80 +/- 0.06 yr), undergoing elective surgery. Adipose tissue samples were taken from 15 children. There were significant positive correlations between muscle and erythrocyte docosahexaenoic acid (DHA) (r = 0.44, P < 0.0001), total n-3 polyunsaturated fatty acids (PUFA) (r = 0.39, P = 0.002), and the n-6/n-3 PUFA ratio (r = 0.39, P = 0.002). Adipose tissue triglyceride had lower levels of long-chain PUFA, especially DHA, than muscle and erythrocytes (0.46 +/- 0.18% vs. 2.44 +/- 0.26% and 3.17 +/- 0.27%). Breast-fed infants had higher levels of DHA than an age-matched group of formula-fed infants in both muscle (3.91 +/- 0.21% vs. 1.94 +/- 0.18%) and erythrocytes (3.81 +/- 0.40% vs. 2.65 +/- 0.23%). The results of this study show that (i) erythrocyte FA composition is a reasonable index of muscle DHA, total n-3 PUFA, and the n-6/n-3 PUFA ratio; (ii) breast feeding has a potent effect on the FA composition of all these tissues; and (iii) there is a wide range in long-chain PUFA levels in muscle, erythrocytes, and adipose tissue.

Adipose Tissue↗
PubMed2000

An uncommon presentation of a common disease: the importance of the history in medicine.

A 32-year-old recent Russian immigrant, mother of a 20-month-old son, presented with right hip pain. She had a history of peptic ulcer disease and a positive Helicobacter pylori serology. Her pain was not relieved by analgesics. Spine and pelvic films were unremarkable. A bone scan was consistent with metastatic disease. She underwent several diagnostic tests including computed tomography of the chest and abdomen, magnetic resonance imaging of the spine, mammogram, and breast ultrasound. A bone marrow biopsy revealed adenocarcinoma, primary site unknown. An upper endoscopy performed eight weeks after her initial presentation showed an ulcerating gastric carcinoma. She was treated with chemotherapy but died two months after diagnosis. Our patient had an uncommon presentation of a common disease. Recognizing her country of origin, and other risk factors, may have facilitated an earlier diagnosis.

Adenocarcinoma↗
PubMed1999

Short- and long-term outcomes after percutaneous transluminal coronary angioplasty in chronic hemodialysis patients.

The aim of this study was to obtain data on the outcomes of chronic hemodialysis patients who underwent percutaneous transluminal coronary angioplasty (PTCA). A retrospective chart analysis identified 31 such patients between August 1992 and October 1996. The mean follow-up period was 12.4 +/- 11.7 months. Angiographic success was achieved in 39 of 41 (95.1%) stenoses attempted. There were three in-hospital deaths. Clinical success was achieved in 28 of 31 patients (90%). Two of the 28 survivors were lost to follow-up. Recurrent angina developed within 6 months in 14 of 26 patients (53.8%). Eleven and 17 of the 26 patients (42.3% and 65.4%) died within 6 and 14 months, respectively, after the PTCA procedure. Ten of the 17 deaths (58.8%) were due to cardiovascular events. Our study suggests that PTCA is technically feasible with high angiographic success rate in chronic hemodialysis patients. In-hospital mortality rate and rate of recurrent angina are high. Long-term prognosis is poor.

Aged↗
PubMed1999

What role for membranes in determining the higher sodium pump molecular activity of mammals compared to ectotherms?

The major body organs of mammals have sodium pumps that turn over energy (ATP) three to four times faster than those of ectotherms, at the same temperature. To examine if membranes play a role in these differences in molecular activity, membrane cross-over experiments were performed using two representative species, Rattus norvegicus and Bufo marinus. Microsomal membrane of kidney and brain displayed characteristic molecular activity differences (three- to four-fold) between the species. These molecular activity differences could be removed by delipidation. Pre-existing molecular activities and differences could be restored when reconstituted with original membrane. Using the same reconstitution method, species membrane cross-over experiments resulted in toad sodium pumps in rat membrane significantly increasing (approximately 30-40%) and rat sodium pumps in toad membrane significantly decreasing (approximately 40%) activities in both kidney and brain. Analysis of membrane composition showed reduced cholesterol content and differences in the fatty acids of phospholipids with higher overall unsaturation in the mammal. The scope for membranes to determine protein performance and its broader implications for metabolism are discussed.

Animals↗
PubMed1996

Perinatal maturation of the auditory brain stem response: changes in path length and conduction velocity.

OBJECTIVE: The goal of this study was to correlate developmental data on brain stem auditory path length with data on auditory brain stem response (ABR) conduction time. This was done to estimate changing axonal conduction velocity during the perinatal period. DESIGN: Pathway length was determined by three-dimensional reconstruction of postmortem fetal and infant brain stems in an AutoCAD system. Brain stem conduction time was obtained from previous ABR studies of premature, term, and post-term infants. The process of correlation of path length and conduction time was based on a model of ABR generation (Ponton, Moore, & Eggermont, this issue) that assumes that the III-IV interpeak interval represents activity in an asynaptic pathway and, thus, consists of only axonal conduction time. RESULTS: Brain stem conduction time is adult-like by the time of term birth. However, the brain stem auditory pathway continues to lengthen postnatally, with portions of the pathway not reaching adult dimensions until 3 yr of age. We determined lengths at various perinatal ages for three different segments of the auditory pathway. Each segment began at the cochlear nucleus (site of wave III generation) and ended at a more rostral location that is a possible site of wave IV generation. Conduction velocity was estimated by dividing path length by axonal conduction time (III-IV interpeak interval). All three assumed sites of generation of wave IV gave estimates of a threefold increase in conduction velocity between 29 wk CA and adulthood. However, three highly discrepant measures of absolute conduction velocity were obtained for the different path segments. The most reasonable conduction velocity estimates, from 5 m/sec at 29 wk conceptional age to 20 m/sec in adults, were produced by assuming a site of generation for wave IV near the contralateral medial superior olivary nucleus. CONCLUSIONS: Prenatally, increasing conduction velocity more than compensates for increasing path length, causing ABR conduction time to decrease. Postnatally, increasing conduction velocity exactly compensates for increasing path length while ABR conduction time remains stable. Different aspects of myelin development may underlie these two phenomena.

Evoked Potentials, Auditory, Brain Stem↗
PubMed1996

[Development of calcium fluorescent probes and their application in life sciences].

It is well known that calcium is the key second intracellular messenger. Techniques using calcium fluorescent probes have been rapidly developed during the last decade, and have become one of the most important methods to measure intracellular free Ca2+ concentrations. This trend was even more accelerated after the development of a new generation of calcium fluorescent probes and the laser scanning confocal microscopy. In this article we will review the development of calcium fluorescent probes, the mechanisms and methods of measuring intracellular free Ca2+ concentrations, the properties of new calcium fluorescent probes, and their applications in life sciences.

Aminoquinolines↗
PubMed1993

[A comparative study on cholagogic effect of Artemisia].

The result suggests that the cholagogic effect of A. anethoides, A. haichowenesis and A. capillaris are not different significantly (P > 0.05), but the duration of action caused by anethoides and haichowenesis is longer than that caused capillaris. The cholagogic effect of A. capillaris collected in seedling, flower budding (beginning of autumn) and preflower periods were also investigated separately, and the preflower collection was found more cholagogic.

Animals↗
PubMed1992

[Effects of arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid on tension of rabbit aortic strips].

The purpose of the investigation was to determine the effects of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and arachidonic acid (AA) on the isolated rabbit aortic strips. The results showed that (1) the rabbit aortic strips with intact endothelium contracted in a dose-dependent manner to exogenous AA between the concentrations of 2.5 x 10(-6) mol/L and 4 x 10(-5) mol/L. EPA did not affect the tension of the relaxing strips, but inhibited the contractile response to AA (2 x 10(-5) mol/L), IC50 = 9.94 x 10(-6) mol/L. DHA showed no significant effect on the contractile response to AA. (2) In the endothelium-damaged rabbit aorta, the contraction of strips to AA was drastically diminished. The inhibitory effect of EPA on the contraction to AA was almost vanished. (3) The contraction of rabbit aortic strips to AA was shown to be abolished by indomethacin (1.5 x 10(-5) mol/L), a cyclooxygenase inhibitor. (4) Radioimmunoassay showed that exogenous AA increased the tissue levels of 6-keto-PGF1 alpha, TXB2 and their ratio. Lower dose of EPA (1.5 x 10(-6) or 1.5 x 10(-5) mol/L) did not affect the tissue levels of 6-keto-PGF1 alpha and TXB2. However, EPA at higher concentrations decreased the metabolites of AA significantly. These findings suggest that exogenous AA induces the contraction of rabbit aortic strips in vitro, which is related to the endothelial cells and mediated by the metabolites(s) of cyclooxygenase, likely endothelium-derived contracting factor (EDCF).(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗
PubMed1990

A cloned human CCAAT-box-binding factor stimulates transcription from the human hsp70 promoter.

The basal promoter of the human hsp70 gene is predominantly controlled by a CCAAT element at position -70 relative to the transcriptional initiation site. We report the isolation of a novel cDNA clone encoding a 114-kDa polypeptide that binds to the CCAAT element of the hsp70 promoter. Expression of this CCAAT-binding factor (CBF) cDNA activated transcription from cotransfected hsp70 promoter-reporter gene constructs in a CCAAT-dependent manner. CCAAT-binding factor shows no homology to the previously identified human CCAAT transcription factor or rat CCAAT/enhancer-binding protein.

Amino Acid Sequence↗
PubMed1989

[Determination of aspirin and nicotinic acid in plasma when used in combination].

An ultraviolet spectrophotometric method has been developed for indirect determination of aspirin (ASA) using the difference between total salicylic acid and free salicylic acid in rabbit plasma. Recoveries of salicylic acid were found to be above 98.4% and the method was linear from 8-160 micrograms with a correlation coefficient of 0.9999. The coefficient of variation was less than 3.85%. Using this method for ASA and Carlson's method for nicotinic acid (NA), the plasma concentrations of these two drugs were determined when they were used iv alone or in combination in rabbits. The results analysed by a micro-computer were fitted to a two compartment open model with first-order elimination. Among the pharmacokinetic parameters of NA, T1/2 (beta) and AUC0-infinity for the group (n = 6) treated with NA 50 mg/kg in combination with ASA 50 mg/kg were 2.3374 h and 361.63 micrograms.h/ml, respectively, both significantly different from those for the group (n = 6) treated with NA 50 mg/kg alone which were 0.9846 h and 157.71 micrograms.h/ml, respectively (p less than 0.01). For ASA, no significant differences were demonstrated. The mechanism and significance of the prolonged T1/2 (beta) of NA were discussed.

Animals↗