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Biomedical subjects

S M Wu

Publications and source records attributed to S M Wu.

At least 109 records · Page 6Linked to original sources
PubMed1994

["Pinch-off sign" and spontaneous fracture of an implanted central venous catheter: report of a case].

Percutaneous subclavian implantation of an indwelling central venous catheter is an easy technique and provides convenient venous access for long-term intravenous therapy. Although rarely reported, spontaneous fracture of the catheter is an ominous complication which requires a prompt diagnosis and urgent treatment. We present a case of "pinch-off sign" resulting in a spontaneous fracture of an indwelling central venous catheter. A 49-year-old female breast cancer patient was admitted and Port-A-Cath was implanted for chemotherapy. Immediately after the implantation, fluid infusion and blood withdrawal was smooth until clinical "pinch-off sign" developed 3 weeks later. Chest X ray revealed no abnormal findings. Extravasation of antineoplastic drugs was noted 113 days after operation. Fracture of the indwelling catheter was found at the clavicle-rib junction. The fractured fragment was removed with a transvenous snare under fluoroscope. There was no hemodynamic derangement during the peri-operative period. Microscopy studies suggested that intermittent pressure on the catheter between the clavicle and the first rib may be responsible. The catheter wore on the medial side ue to a tearing and scissoring effect associated with free shoulder joint movement exerted additional forces on this wearing point which led to catheter fracture. The relationship between the spontaneous catheter fracture and "pinch-off sign" is reviewed. Our suggestions are: (1) By avoiding the traditional cannulation of the median subclavian vein, the lateral subclavian vein, infraclavicular axillary vein or internal jugular vein should be better routes for implantation. (2) Chest X ray (anterior-posterior and lateral view) should be examined routinely 3 weeks after the operation.(ABSTRACT TRUNCATED AT 250 WORDS)

Catheterization, Central Venous↗
PubMed1993

Synaptic transmission from rods to rod-dominated bipolar cells in the tiger salamander retina.

Synaptic transmission between photoreceptors and bipolar cells was studied in dark-adapted tiger salamander retinas. Based on the relative light sensitivity, bipolar cells, either depolarizing (DBC) or hyperpolarizing (HBC), fell into two groups: one receives inputs primarily from rods (rod-dominated bipolar cells, DBCR and HBCR) and the other receives inputs primarily from cones (cone-dominated bipolar cells, DBCC and HBCC). The input-output relations of the rod-DBCR and rod-HBCR synapses were determined by plotting the voltage responses of the rod and DBCR (or HBCR) to dim 500-nm light steps, which polarizes only the rods but not the cones. The slope gains of both synapses were the highest near the dark rod voltage (-2.5 for the rod-DBCR synapse and 4.0 for the rod-HBCR synapse), and they (the absolute values) became progressively smaller at more hyperpolarized rod voltages.

Acclimatization↗
PubMed1993

Expression of pregnancy-specific beta 1-glycoprotein genes in hematopoietic cells.

The presence of PSG in blood cells has been demonstrated by immunohistochemical staining. However, the origin of those proteins is not known. This report examines the expression of the PSG genes in different types of freshly isolated blood cells. RNA isolated from bone marrow and peripheral blood cells of healthy individuals was analyzed for PSG transcripts by reverse transcriptase-polymerase chain reaction using synthetic oligonucleotide primers specific for the PSG genes. The level of expression of the PSG genes in different types of cells exhibited significant individual variation. Trace amounts of PSG transcripts could be detected in polymorphonuclear cells (PMN), monocytes and B lymphocytes while T lymphocytes always contained the highest level of transcript. The expression of PSG genes in the blood cells apparently was not affected by the method of isolation nor by overnight culturing of these cells except in the case when lymphocytes were separated by rosetting with sheep red blood cells. All reported PSG transcripts were detected in blood cells. Both type I and type II transcripts of the PSG genes were detected in blood cells with the exception of type II transcript of PSG5 and PSG11 which were only found in the placenta. Tissue specificity in the expression or alternative splicing of some of the PSG family members was implicated.

Alternative Splicing↗
PubMed1993

Role of cortisol in hypoosmoregulation in larvae of the tilapia (Oreochromis mossambicus).

The total cortisol content in tilapia was 55 pg immediately following fertilization, then decreased abruptly and maintained a lower level of 10-20 pg until hatching; after hatching the cortisol content increased to 50 pg by the 7th day. Fertilized eggs were incubated in either 32% saltwater or fresh water and sampled at various developmental stages. Both groups showed dramatic changes in cortisol content following development. However, no significant difference in the cortisol level was found between the two groups. Tilapia larvae, hatched in fresh water, were reared with feed containing 0 (control) or 150 mg/kg wt/day cortisol, corticosterone, 17 alpha-hydroxyprogesterone (17 alpha-OHP) or 11 alpha-deoxycortisol (11 alpha-DC) for 8 days and then transferred directly to 27.5% saltwater. Those reared with corticosterone, 17 alpha-OHP, or 11 alpha-DC, similar to the control, all died within 4-8 hr after the transfer. However, the larvae treated with cortisol showed a much higher survival rate of 40-60%. The tissue osmolality in the control larvae, 394.3 +/- 3.7 (mmol/kg), increased abruptly after transfer to 26% saltwater and reach a peak, 681.5 +/- 47.5, before the larvae all died (12th hr after the transfer). In contrast, tissue osmolality in cortisol-treated (150 mg/kg wt/day for 12 days) larvae was 570.7 +/- 62.6 at the 12th hr and then began to decrease to 448.5 +/- 9.4 at the 24th hr and 386.0 at the 48th hr. These findings suggest that cortisol could play a critical role in the hypoosmoregulation in tilapia larvae.

Animals↗
PubMed1993

Effects of GABA on horizontal cells in the tiger salamander retina.

Application of gamma-aminobutyric acid (GABA) slows down the horizontal cell response time course (HCRRT) and induces membrane depolarization in horizontal cells (HCs) after synaptic inputs are blocked by Co2+. We present evidence that suggests both effects are probably mediated by GABAA receptors which open chloride channels in the HC membrane. In any given concentration of GABA, ranged from 0 to 100 microM, the HC membrane potential (VHC) in saturating light and in the presence of 100 microM Co2+ are identical. This result suggests that GABA in both light and 100 microM Co2+ opens the same amount of chloride channels (same gCl) so that VHC determined by chloride and leak conductances has the same value. Higher concentrations of Co2+ (> 300 microM) not only blocks synaptic transmission from photoreceptors to HCs, but also acts as an antagonist that suppresses the GABA-mediated depolarization in HCs.

Ambystoma↗
PubMed1993

Localization and modulatory actions of zinc in vertebrate retina.

Zinc ions are colocalized with glutamatergic synaptic vesicles in vertebrate photoreceptors and may act as a diffusible molecular switch regulating neurotransmitter signaling at two distinct sites in the outer retina. In the dark, extracellular zinc acts presynaptically at rods and cones to minimize the depletion of tonically released glutamate, and selectively reduces GABA-mediated depolarization in horizontal cells, accelerating the response kinetics of the second-order cells. The discovery of zinc ions in photoreceptors provides a mechanism for gain control, kinetics modulation, and the balance of rod vs cone output at the first synapse in the visual system.

Animals↗
PubMed1993

Vitamin-mineral supplement use and nutritional status of athletes.

Dietary, anthropometric, and chronic disease risk factors (CDRF) including blood lipids and blood pressure (BP), were measured in 91 vitamin-mineral supplement users (SU) and nonusers (NU) representing a wide range of athletic interests. Supplements were used by 46 (51%) subjects; 100% of female athletes and 51% of male athletes used supplements while none of a group of 15 control female subjects currently used supplements. Both dietary intake and energy expenditure were measured using 7-day records. Adiposity was determined from body weight, body mass index, and skinfolds. Total cholesterol, high-density lipoprotein cholesterol, serum ferritin, hemoglobin, hematocrit, zinc, copper, and vitamin C were based on 12-hour fasting blood samples. Dietary intake (excluding supplements) for SU tended to be greater than NU for vitamin C, thiamin, riboflavin, niacin, B6, B12, folate, calcium, iron and magnesium. Plasma vitamin C levels were significantly higher among SU than NU of both gender groups (p < 0.05). Although SU may exhibit additional healthy lifestyle practices, lipid profiles for many of these athletes were unfavorable with regard to CDRF.

Adipose Tissue↗
PubMed1993

Relative contribution of rod and cone inputs to bipolar cells and ganglion cells in the tiger salamander retina.

1. The relative contribution of rod and cone inputs to bipolar and ganglion cells were studied by comparing the response-irradiance relations, spectral sensitivities, and response waveforms of these neurons recorded from the isolated, flat-mounted tiger salamander retina under dark-adapted conditions. 2. Bipolar cells could be differentiated both on the basis of the polarity of the light response and on their relative rod/cone input. Thus some depolarizing bipolar cells appeared more strongly influenced by rod input (DBCR), whereas others were more influenced by cone input (DBCC). Similarly, hyperpolarizing bipolar cells could be divided into those that received rod-dominant input (HBCR) or cone-dominant input (HBCC). 3. The light onset response of sustained-ON ganglion cells reflected both rod-dominant input from DBCRs and cone-dominant input from DBCCs. 4. OFF ganglion cells displayed both a rod-dominant sustained light offset response and a cone-dominant transient light offset response, suggesting input from both HBCRs and HBCCs. 5. In ON-OFF ganglion cells, the light onset response was strongly rod dominated and was presumably mediated by DBCRs, whereas the light offset response displayed both rod and cone influence, suggesting input from HBCRs and HBCCs. The contribution of cones to the light onset response of ON-OFF ganglion cells was only observed in the presence of a rod-adapting background light. 6. A suppression of the light offset responses of OFF and ON-OFF ganglion cells was observed, which was dependent both on the wavelength and irradiance of the light stimulus. 7. These results indicate that the photoreceptor inputs to bipolar cells in the tiger salamander retina are segregated such that they form separate rod-dominant and cone-dominant pathways. Thus the response properties of the different types of ganglion cells are influenced not only by the excitatory and inhibitory inputs they receive from the bipolar and amacrine cells but also whether these inputs are provided through rod-dominant or cone-dominant pathways. The functional implications of these findings are discussed.

Ambystoma↗
PubMed1993

Identification of glutamate receptor subtypes mediating inputs to bipolar cells and ganglion cells in the tiger salamander retina.

1. The effects of glutamate receptor agonists and antagonists on bipolar cells and ganglion cells were studied with the use of intracellular and extracellular recording in the superfused, isolated, flat-mounted tiger salamander retina. The goal of the experiments was to correlate glutamate receptor subtypes with their localization at specific synaptic sites in the tiger salamander retina. The drugs tested were the kainate/alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), the N-methyl-D-aspartate (NMDA) receptor antagonist 3-(C+/-)-2-carboxy-piperazin-4-yl)-propyl-1-phosphonic acid (CPP) and L-2-amino-4-phosphonobutyrate (L-AP4). 2. The light responses of hyperpolarizing bipolar cells were suppressed by 20 microM CNQX, whereas L-AP4 had no effect on their light responses. In contrast, 20 microM CNQX had no effect on depolarizing bipolar cells, whereas L-AP4 abolished the light responses of these cells. 3. The light offset responses of OFF and ON-OFF ganglion cells were completely blocked by concentrations of CNQX as low as 5 microM. The light onset responses of ON-OFF ganglion cells were blocked when the concentration of CNQX was raised to 20 microM. In addition, 30 microM CPP partially blocked the light onset responses of ON-OFF ganglion cells but had a lesser effect on the light offset responses. 4. Twenty micromolars of CNQX blocked a transient component, and 20 microM CPP blocked a sustained component of the light response of sustained-ON ganglion cells.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1992

Modulation of synaptic gain by light.

Although synaptic transmission in the retina has been assumed to be static, it appears that the voltage gains of the synapses between photoreceptors and second-order cells can be enhanced by light. Voltage gains of the synapses between rods and bipolar (or horizontal) cells are about 10 times higher in the presence of dim background light than in darkness. This increase in synaptic gain may compensate for the loss of rod light responsiveness caused by weak background light so that the animal can maintain good rod sensitivity under moonlight or starlight, the natural lighting condition for mating and food catching.

Ambystoma↗
PubMed1992

Stereochemical analysis of betamethasone and dexamethasone by derivatization and high-performance liquid chromatography.

A simple and economical high-performance liquid chromatographic method has been developed for the simultaneous determination of betamethasone and dexamethasone. The method is based on the derivatization of the structural epimers of betamethasone and dexamethasone with a homochiral reagent, N-carbobenzoxy-L-phenylalanine. The derivatives obtained were easily recognized by a non-chiral silica column with n-hexane-dichloromethane-isopropanol (100:100:4, v/v/v) as a mobile phase and a good separation was obtained for quantitation. The method was satisfactorily applied to the determination of betamethasone and dexamethasone in tablets.

Betamethasone↗
PubMed1992

Cortisol content of eggs and larvae of teleosts.

The whole-animal content of the cortisol was measured in embryos and larvae of tilapia (Oreochromis mossambicus), rainbow trout (Oncorhynchus mykiss), ayu (Plecoglossus altivelis), milkfish (Chanos chanos), and yellowfin bream (Acanthropagrus latus) by radioimmunoassay following the validation of an extraction method. The total cortisol content in tilapia was 50.3 +/- 19.1 pg immediately following fertilization, then decreased abruptly and maintained a lower level of 10-17 pg until larval hatching; after hatching the cortisol content increased to 47.2 +/- 11.9 pg by the seventh day. Newly hatched rainbow trout had 60.3 +/- 6.4 pg cortisol and then increased their cortisol level slowly to 83.0 +/- 7.2 pg by the fifth day after hatching. Ayu larvae contained 5.2 pg cortisol immediately following hatching. On the other hand, pelagic milkfish revealed a much lower cortisol level, being undetectable from hatching until the second day and ranging from 0.4 to 3.7 pg from the third to seventh day after hatching. Yellowfin bream, demonstrating a similarity to milkfish, were not found to have any detectable cortisol from hatching until the third day, but presented 1.6-7.7 pg from the fifth to seventh day after hatching. The presence and clearance of cortisol during early development of fertilized eggs of tilapia suggest a maternal origin of the hormone. The amount of cortisol deposited in the larval body of tilapia increased after hatching from 25% to nearly 100% of the total cortisol in whole larvae, while that in the larval yolk sac decreased to an undetectable level, implying that the increased cortisol may be produced or secreted by the larva. The possible role of cortisol in larval development is discussed.

Animals↗
PubMed1992

Feedback connections and operation of the outer plexiform layer of the retina.

The primary feedback control apparatus in the outer retina is the sign-inverting feedback synapse between horizontal cells and cones. In many lower vertebrates horizontal cells release GABA in darkness, which opens Cl- channels in cones. Input-output relations of the feedback synapse reveal that the synaptic gain is light-dependent with the highest negative gain near the dark horizontal cell potential. The horizontal cell-cone feedback synapse improves the reliability of the photoreceptor output synapses. It also modulates the dynamic range and mediates color opponency and surround responses in second-order retinal neurons.

Animals↗
PubMed1992

Associations of cardiovascular disease risk factors with measures of energy expenditure and caloric intake in a farm population.

The purpose of this study was to examine the relationships of several cardiovascular disease risk factors [blood pressure (BP), total cholesterol (TC), high-density-lipoprotein cholesterol (HDL-C), and the HDL-C:TC ratio], as well as the body mass index (BMI) and percent body fat with daily energy intake (EI) and daily energy expenditure (EE) of North Carolina farmers and their wives. Data were collected from 195 subjects. Daily EI and EE were estimated from 4-day food and 4-day activity records, respectively, collected on the same days. Pearson correlation coefficients for chronic disease risk factors with both EI and EE were generally low. When compared to EI, EE was more highly correlated with both lean body mass (r = 0.88) and BMI (r = 0.73), and was less time consuming and easier for the subjects to use. EE obtained from a reliable activity record may be a more practical tool for assessing the possible relationship(s) of energy metabolism to chronic disease risk factors.

Adult↗
PubMed1992

Plasma amino acid responses of trained athletes to two successive exhaustion trials with and without interim carbohydrate feeding.

The purpose of this research was to measure changes in selected plasma amino acids (AA) during two successive exercise trials to exhaustion. Eleven trained male athletes completed these trials at weeks 4, 6, 8 and 12. Blood samples for each test were collected after a 12-hour fast at times (in minutes) 0 (Resting), 45, 90, 135, 180, at exhaustion (EI), after a 20-minute recovery period, and at the second exhaustion (EII). At the end of EI, subjects consumed an artificially sweetened water replacement (placebo) treatment or a carbohydrate (CHO) replacement (1.1 g CHO/kg BW) in order to determine any effect of CHO replacement on changes in energy substrates or AA, adjusted for plasma volume changes. From baseline to EI, alpha-aminobutyric acid, alanine, glycine, isoleucine, serine, valine threonine, and tyrosine decreased significantly (p less than or equal to 0.05), while taurine increased significantly. During the recovery period following EI, isoleucine, leucine, ornithine, phenylalanine, tyrosine, urea and valine increased significantly. From the end of recovery until EII, alanine, aspartic acid, glycine, isoleucine, leucine, ornithine, phenylalanine, serine, threonine, tyrosine and valine decreased significantly. CHO replacement had no effect on the mean change scores for any AA from EI to the end of the recovery period and affected only serine, citrulline, glycine and threonine from the end of the recovery period to EII.

Adolescent↗
PubMed1991

Cloning and expression of the cDNA for human gamma-glutamyl carboxylase.

The cDNA for human gamma-glutamyl carboxylase, which accomplishes the post-translational modification required for the activity of all of the vitamin K-dependent proteins, was cloned. The enzyme is a 758-residue integral membrane protein and appears to have three transmembrane domains near its amino terminus. The hydrophilic COOH-terminal half of the carboxylase has 19.3 percent identity with soybean seed lipoxygenase. Expression of the cloned cDNA resulted in an increase in carboxylase activity in microsomes of transfected cells compared to mock-transfected cells.

Amino Acid Sequence↗
PubMed1991

Feedforward lateral inhibition in retinal bipolar cells: input-output relation of the horizontal cell-depolarizing bipolar cell synapse.

Lateral inhibition is the ubiquitous strategy used by visual neurons for spatial resolution throughout the animal kingdom. It has been a puzzle whether lateral inputs in retinal bipolar cells are mediated by the horizontal cell (HC)-cone feedback synapse, by the HC-bipolar cell feedforward synapse, or by both. By blocking the central inputs of the depolarizing bipolar cells (DBCs) with L-2-amino-4-phosphonobutyrate, we were able to eliminate the contribution of the feedback synapse and to demonstrate the postsynaptic light response in DBCs mediated by the HC-DBC feedforward synapse. The HC-DBC feedforward synapse contributes roughly one-third of the surround response whereas the HC-cone-DBC feedback synapse probably contributes the rest.

Ambystoma↗