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Biomedical subjects

J Yu

Publications and source records attributed to J Yu.

At least 145 records · Page 8Linked to original sources
PubMed1999

The predictive value of white cell or CD34+ cell count in the peripheral blood for timing apheresis and maximizing yield.

BACKGROUND: The collection of peripheral blood stem and progenitor cells (PBPCs) for transplantation can be time-consuming and expensive. Thus, the utility of counting CD34+ cells and white cells (WBCs) in the peripheral blood was evaluated as a predictor of CD34+ cell yield in the apheresis component. STUDY DESIGN AND METHODS: The WBC and CD34+ cell counts in the peripheral blood and the apheresis components from 216 collections were assessed. Sixty-three patients underwent mobilization with chemotherapy plus filgrastim, and 17 patients and 14 allogeneic PBPC donors did so with filgrastim alone. The relationship between the number of WBC and CD34+ cells in the peripheral blood and in the apheresis component was analyzed by using rank correlation and linear regression analysis. RESULTS: The correlation coefficient for CD34+ cells per liter of peripheral blood with CD34+ cell yield (x 10(6)/kg) was 0.87 (n = 216 collections). This correlation existed for many patient and collection variables. However, patients with acute myeloid leukemia had fewer CD34+ cells in the apheresis component at any level of peripheral blood CD34+ cell count. Components collected from patients with CD34+ cell counts below 10 x 10(6) per L in the peripheral blood contained a median of 0.75 x 10(6) CD34+ cells per kg. When the WBC count in the blood was below 5.0 x 10(9) per L, the median number of CD34+ cells in the peripheral blood was 5.6 x 10(6) per L (range, 1.0-15.5 x 10(6)/L). A very poor correlation was found between the WBC count in the blood and the CD34+ cell yield (p = 0.12, n = 158 collections). CONCLUSION: The number of CD34+ cells, but not WBCs, in the peripheral blood can be used as a predictor for timing of apheresis and estimating PBPC yield. This is a robust relationship not affected by a variety of patient and collection factors except the diagnosis of acute myeloid leukemia. Patients who undergo mobilization with chemotherapy and filgrastim also should undergo monitoring of peripheral blood CD34+ cell counts, beginning when the WBC count in the blood exceeds 1.0 to 5.0 x 10(9) per L.

Adolescent↗
PubMed1999

Effects of genistein and daidzein on membrane characteristics of HCT cells.

Genistein and daidzein are two major isoflavonoids in soybeans. They have received increasing attention because of their possible role in cancer prevention. In the present investigation, the human colon tumor (HCT) cell line was used to investigate the effect of isoflavonoids on cell growth with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide colorimetric assay. We found that genistein and/or daidzein could inhibit growth in HCT cells. The 50% inhibitory concentrations of genistein and daidzein were 15 and 40 microM, respectively. Fluorescent polarization, quasielastic light scattering, and circular dichroism were used to study the influence of isoflavonoids on membrane characteristics of HCT cells, including membrane fluidity, density of cell surface charge, and membrane protein conformation. Membrane fluidity of HCT cells was obviously reduced by genistein, but not by daidzein. The effect of genistein was time and dose dependent. In addition, genistein and daidzein could reduce the density of cell surface charge and increase the order of membrane protein conformation. All these changes may represent one of the mechanisms of the effect of isoflavonoids on growth inhibition, differentiation promotion, and transfer interference in a tumor cell line.

Anticarcinogenic Agents↗
PubMed1999

Poloxamine 1107 sealing of radiopermeabilized erythrocyte membranes.

PURPOSE: Lipid peroxidation-mediated permeabilization of cell membranes following intense ionizing irradiation is well documented. This form of membrane radiopermeabilization leads to rapid exhaustion of cellular high-energy compounds, resulting in the acute onset of cellular necrosis. Strategies to reverse the process of necrosis and preserve cell viability require membrane sealing. This report documents the relative efficacy of Poloxamine 1107, a non-ionic surfactant, compared with other polymers, in sealing radiopermeabilized cell membranes. MATERIALS AND METHODS: Isolated erythrocytes were exposed to 600 Gy 60Co irradiation at a dose rate of 1.3 Gy/s. Different polymer compounds were added 10 min later to the irradiated cell suspensions. At 2 h later the haemoglobin content in the supernatants was determined spectrophotometrically. RESULTS: Compared with the non-treated irradiated control, Poloxamine 1107 significantly reduced the leakage of haemoglobin from irradiated erythrocytes. Poloxamer 188 and dextran at equal concentrations had no significant reverse effect on the irradiation-mediated increased membrane permeability. The amount of haemoglobin released from irradiated erythrocytes was inversely related to the Poloxamine 1107 concentration. CONCLUSIONS: This study demonstrates the capability of Poloxamine 1107 to seal radiopermeabilized cell membranes. Thus, surfactants such as Poloxamine 1107 might be useful as a therapeutic agent in the treatment of high-dose radiation injuries since cellular necrosis due to metabolic exhaustion following radiopermeabilization of their membranes might be prevented.

Cell Membrane Permeability↗
PubMed1999

Effects of chlorophyll availability on phycobilisomes in Synechocystis sp. PCC 6803.

Inactivation of the chlL gene in Synechocystis sp. PCC 6803 resulted in negligible chlorophyll content when the mutant was grown in darkness. Upon phycocyanin excitation at 580 nm, the 77K fluorescence spectrum of dark-grown cells showed three peaks at 648 nm, 665 nm, and 685 nm, this last being the largest. This reflects the functional presence of major components of phycobilisomes, including phycocyanin, allophycocyanin, and the terminal emitter, and efficient energy transfer between these components. As expected, no fluorescence emission peaks corresponding to chlorophyll in the photosystems were observed. Intact phycobilisomes could be isolated from the dark-grown chlL-deletion mutant. However, the phycobilisomes had a lower efficiency of energy transfer than did those isolated from the light-grown mutant, probably because of a decreased phycobilisome stability in the absence of chlorophyll. Exposing the dark-grown chlL-deletion mutant to light triggered the biosynthesis of chlorophyll. For the first 6 h in the light, upon phycocyanin excitation at 580 nm, the 77K fluorescence emission spectrum of greening cells was identical to that of dark-grown cells that lacked significant amounts of chlorophyll. With increased chlorophyll synthesis, gradual energy transfer from phycobilisomes to the two photosystems can be demonstrated.

Bacterial Proteins↗
PubMed1999

Enhancement of spectral analysis of myoelectric signals during static contractions using wavelet methods.

In this paper, we introduce wavelet packets as an alternative method for spectral analysis of surface myoelectric (ME) signals. Both computer synthesized and real ME signals are used to investigate the performance. Our simulation results show that wavelet packet estimate has slightly less mean square error (MSE) than Fourier method, and both methods perform similarly on the real data. Moreover, wavelet packets give us some advantages over the traditional methods such as multiresolution of frequency, as well as its potential use for effecting time-frequency decomposition of the nonstationary signals such as the ME signals during dynamic contractions. We also introduce wavelet shrinkage method for improving spectral estimates by significantly reducing the MSE's for both Fourier and wavelet packet methods.

Action Potentials↗
PubMed1999

The carboxy-terminal portion of the aflatoxin pathway regulatory protein AFLR of Aspergillus parasiticus activates GAL1::lacZ gene expression in Saccharomyces cerevisiae.

AFLR, a DNA-binding protein of 444 amino acids, transactivates the expression of aflatoxin biosynthesis genes in Aspergillus parasiticus and Aspergillus flavus, as well as the sterigmatocystin synthesis genes in Aspergillus nidulans. We show here by fusion of various aflR coding regions to the GAL4 DNA-binding coding region that the AFLR carboxyl terminus contained a region that activated GAL1::lacZ gene expression in Saccharomyces cerevisiae and that the AFLR internal region was required for the activation activity. Compared to the AFLR carboxy-terminal fusion protein (AFLRC), a mutant AFLRC retained approximately 75% of the activation activity after deletion of three acidic amino acids, Asp365, Glu366, and Glu367, in a previously identified acidic stretch. Removal of the carboxy-terminal amino acid, Glu444, did not affect the activation activity. Substitutions of acidic Glu423, Asp439, or Asp436/Asp439 with basic amino acids, Lys and His, resulted in 10- to 15-fold-lower activation activities. Strikingly, the Asp436His mutation abolished the activation activity. Substitutions of basic His428 and His442 with acidic Asp resulted in 20 and 40% decreases in the activation activities, respectively. Simultaneous substitutions of Arg427, Arg429, and Arg431 with Leu also significantly decreased the activation activity; the decrease was approximately 50-fold. Results suggest that the AFLR carboxy-terminal region is involved in transcription activation and that total acidity in this region is not a major determinant of AFLR's activation ability in S. cerevisiae.

Amino Acid Sequence↗
PubMed1999

The cloned locus of enterocyte effacement from enterohemorrhagic Escherichia coli O157:H7 is unable to confer the attaching and effacing phenotype upon E. coli K-12.

The locus of enterocyte effacement (LEE) pathogenicity island of enterohemorrhagic Escherichia coli (EHEC) O157:H7 possesses the same genes in identical order and orientation as the LEE of enteropathogenic E. coli (EPEC) O127:H6 but is unable to form attaching and effacing (A/E) lesions or to secrete Esp proteins when it is cloned in an E. coli K-12 background. The A/E phenotype could not be restored by trans complementation with a variety of cloned EPEC LEE fragments, suggesting functional and/or regulatory differences between the LEE pathogenicity islands of EPEC O127:H6 and EHEC O157:H7.

Chromosome Mapping↗
PubMed1999

Signals from the Ras, Rac, and Rho GTPases converge on the Pak protein kinase in Rat-1 fibroblasts.

Ras plays a key role in regulating cellular proliferation, differentiation, and transformation. Raf is the major effector of Ras in the Ras > Raf > Mek > extracellular signal-activated kinase (ERK) cascade. A second effector is phosphoinositide 3-OH kinase (PI 3-kinase), which, in turn, activates the small G protein Rac. Rac also has multiple effectors, one of which is the serine threonine kinase Pak (p65(Pak)). Here we show that Ras, but not Raf, activates Pak1 in cotransfection assays of Rat-1 cells but not NIH 3T3 cells. We tested agents that activate or block specific components downstream of Ras and demonstrate a Ras > PI 3-kinase > Rac/Cdc42 > Pak signal. Although these studies suggest that the signal from Ras through PI 3-kinase is sufficient to activate Pak, additional studies suggested that other effectors contribute to Pak activation. RasV12S35 and RasV12G37, two effector mutant proteins which fail to activate PI 3-kinase, did not activate Pak when tested alone but activated Pak when they were cotransfected. Similarly, RacV12H40, an effector mutant that does not bind Pak, and Rho both cooperated with Raf to activate Pak. A dominant negative Rho mutant also inhibited Ras activation of Pak. All combinations of Rac/Raf and Ras/Raf and Rho/Raf effector mutants that transform cells cooperatively stimulated ERK. Cooperation was Pak dependent, since all combinations were inhibited by kinase-deficient Pak mutants in both transformation assays and ERK activation assays. These data suggest that other Ras effectors can collaborate with PI 3-kinase and with each other to activate Pak. Furthermore, the strong correlation between Pak activation and cooperative transformation suggests that Pak activation is necessary, although not sufficient, for cooperative transformation of Rat-1 fibroblasts by Ras, Rac, and Rho.

3T3 Cells↗
PubMed1999

Miscarriage prevention tea affects plasma beta-endorphin concentrations in women with early threatened abortions.

Twenty threatened abortive patients in the 7-8th week of gestation were treated with a classical miscarriage prevention tea (Shou-Tai-Tang) combined with psychological consultation. All of the patients had a history of unexplained recurrent abortions. This treatment succeeded in sixteen out of 20 patients. The plasma concentrations of beta-endorphin (beta-EP), gonadotrophin releasing hormone (GnRH), human chorionic gonadotrophin (hCG), and progesterone (P4) were measured by radioimmunoassay before and after treatment. Compared to control subjects, beta-EP levels were significantly higher, while GnRH, hCG, and P4 were lower than before treatment. Concentrations of these peptides/hormones returned to normal ranges after successful treatment.

Abortion, Spontaneous↗
PubMed1999

Pulmonary rapidly adapting receptor stimulation does not increase airway resistance in anesthetized rabbits.

In open-chest artificially ventilated rabbits, removal followed by replacement of positive end-expiratory pressure (PEEP maneuver) favors stimulation of airway rapidly adapting receptors (RARs). The purpose of the present study was to determine whether activation of RARs can cause bronchoconstriction. We measured airway pressure, airflow, and tidal volume, and calculated dynamic lung compliance and total lung resistance. PEEP maneuver increased airway pressure swings (16.4 +/- 4% above control; p = 0.0016) and decreased compliance (to 84.8 +/- 2.8% of control; p = 0.0002) without changing resistance (108.0 +/- 4.4% of control; p = 0.85). On the other hand, the resistance increased greatly (93 +/- 13%, p < 0.01) after intravenous injection of acetylcholine or electrical stimulation of vagal efferents, indicating that our system could detect increases in the resistance. In a separate group, we stimulated RARs by stroking the trachea with a cotton tip (tickling), tickling produced cough, manifested by increased pressure and flow without resistance changing. These changes were abolished after paralysis with succinylcholine. Because we did not detect an increase in airflow resistance during activation of RARs by the PEEP maneuver and tickling, we conclude that increase in resistance may not be an important reflex component of airway RARs.

Acetylcholine↗
PubMed1999

Pulmonary edema develops after recurrent obstructive apneas.

There are anecdotal reports of pulmonary edema after a night of recurrent obstructive apneas (OAs) in humans, but no data on lung water, gas exchange, filling pressure, or cardiac output (Q) exist in these patients. By clamping the endotracheal tube of eight intubated, anesthesized dogs, we created repetitive OAs of 45-s duration at 30-s intervals, for 8 h. Five additional dogs without apneas, but identically instrumented, were studied simultaneously, serving as nonapneic controls. Sa (O(2)) was measured by intraarterial catheter, pulmonary capillary wedge pressure (Pcw), continuous cardiac output (Q), and mixed venous oxygen saturation (Sv(O(2))) were measured by flotation catheter. Basal and hourly hemodynamics and blood gases (arterial and venous) under steady state respiration were measured. Venous admixture (Q S/Q T) was calculated by standard equations. Pa(O(2)) from the beginning to the end of the experiment fell from 89.6 to 82.8 mm Hg in apneic animals and from 92.2 to 85.5 mm Hg in controls. The Q S/Q T increased in both groups but more so in the apnea group (3.3 to 19.4%) than in nonapneic controls (3.1 to 7.9%). Neither Q nor Pcw changed significantly in either group. Lung wet/dry weight was 5.40 +/- 0.93 in apneic animals and 5.00 +/- 0.67 in controls. Light microscopy showed gross alveolar fluid in three apneic dogs, and electron microscopy showed interstitial fluid in two additional apneic dogs. One of the lung edema dogs expired of acute heart failure in the seventh hour of the experiment. Worsening of gas exchange and histology suggest that lung edema can result from recurrent OAs.

Animals↗
PubMed1999

Targeting of functional antibody-CD59 fusion proteins to a cell surface.

Complement is involved in the pathogenesis of many diseases, and there is great interest in developing inhibitors of complement for therapeutic application. CD59 is a natural membrane-bound inhibitor of the cytolytic complement membrane attack complex (MAC). In this study, the preparation and characterization of antibody-CD59 (IgG-CD59) chimeric fusion proteins are described. Constructs were composed of soluble CD59 fused to an antibody-combining site at the end of CH1, after the hinge (H), and after CH3 Ig regions. The antigen specificity of each construct was for the hapten 5-dimethylamino-naphthalene-1-sulfonyl (dansyl). Correct folding of each IgG-CD59 fusion partner was indicated by recognition with anti-CD59 antibodies specific for conformational determinants and by IgG-CD59 binding to dansyl. The IgG-CD59 fusion proteins all bound specifically to dansyl-labeled Chinese hamster ovary cells and provided targeted cells, but not untargeted cells, with effective protection from complement-mediated lysis. Data indicate that CD59 must be positioned in close proximity to the site of MAC formation for effective function, and that modes of membrane attachment other than glycophosphatidylinositol linkage can affect CD59 functional activity.

Animals↗
PubMed1999

Hydrogen peroxide in the lung parenchyma stimulates vagally mediated phrenic activity.

STUDY OBJECTIVE: To elucidate the mechanism of hyperpnea and tachypnea, which are the common findings in cardiopulmonary patients. RATIONALE: Recently, it was found that activating pulmonary afferents by directly injecting hypertonic saline solution into the lung periphery causes a vagally mediated neural hyperpnea and tachypnea, ie, the excitatory lung reflex. Since reactive oxygen species are released during a variety of pulmonary diseases, we examined whether hydrogen peroxide (H(2)O(2)), a common mediator in cardiopulmonary diseases, can initiate the same excitatory lung reflex. MEASUREMENTS AND RESULTS: We recorded phrenic efferent activity in anesthetized, open chest, artificially ventilated rabbits as an index of respiratory drive and examined the respiratory responses to injections of H(2)O(2) (10 micromol in 0.1 mL). The responses were compared with those to hypertonic saline solution (8.1%, 0.1 mL). H(2)O(2) and hypertonic saline solution increased both the rate (mean [+/- SEM], 43 +/- 8% and 61 +/- 10%, respectively; n = 30; p = 0.001) and the amplitude of phrenic bursts (12 +/- 2% and 20 +/- 4%, respectively; n = 30; p = 0.033). These responses were abolished by bilateral vagotomy. CONCLUSION: H(2)O(2) can initiate the excitatory lung reflex. Therefore, mediator(s) released in pulmonary diseases could be one of the mechanisms causing hyperpnea and tachypnea.

Animals↗
PubMed1999

Drinking-driving and riding with drunk drivers among young adults: an analysis of reciprocal effects.

OBJECTIVE: This research attempts to test the hypothesis that a reciprocal relationship exists between drinking-driving (DD) and riding with drunk drivers (RWDD) among youth. METHOD: Analyses were performed on data from the 1996 New York State Youth Alcohol Survey. The sample is composed of 16- to 24-year-olds who used alcohol and drove automobiles (N = 993). LISREL software was employed to examine the hypothesized simultaneous system between drinking-driving and riding with drunk drivers. Alcohol use, driving patterns and perception of negative consequences of drinking-driving behavior were included as independent variables. RESULTS: The reciprocity between drinking-driving and riding with drunk drivers is composed of a relatively strong positive effect of DD on RWDD and a minimal effect of RWDD on DD. Alcohol use has a consistent effect on both drinking-driving and riding with drunk drivers. Frequency of weekend driving tends to increase the likelihood of drinking-driving, but not riding with drunk drivers. Youths' perceived likelihood of being arrested if caught drinking-driving appears to have a moderate negative association with drinking-driving and riding with drunk drivers for underage youths. CONCLUSIONS: The simultaneous system between drinking-driving and riding with drunk drivers tends to be dominated by the effect of the former on the latter. Involvement in drinking-driving among youths is likely to increase the chance of riding with drunk drivers, whereas involvement in RWDD may not necessarily increase the chance of DD. Possible explanations for this finding are discussed. Future research may focus on measurement errors of drinking-driving and riding with drunk drivers to further examine the relationship between these behaviors.

Adolescent↗
PubMed1999

Metabolism of antitumor hydroxymethylacylfulvene by rat liver cytosol.

Acylfulvenes are a potent class of antitumor agents derived from illudin S, a fungal sesquiterpene. Illudin S possesses antitumor activity but has a poor therapeutic index. Acylfulvene is 100-fold less toxic against human lung adenocarcinoma cells than illudin S, but inhibits tumor growth in human xenografts, opposite to illudin S. An analog of acylfulvene, MGI 114 (hydroxymethylacylfulvene), shows much greater efficacy, producing complete tumor regression in xenograft models. MGI 114 is currently in phase II clinical trials. Cytotoxicity of MGI 114, like that of illudin S, is believed to involve both chemical reaction and enzymatic reduction. Enzymatic reduction by a cytosolic NADPH-dependent enzyme (from rat liver) produced an aromatic metabolite similar to that formed from illudin S. However, the reaction occurred more slowly. In addition, four new metabolites were isolated, two hydroxylated derivatives and two in which the primary allylic hydroxyl was replaced by hydride. All retained the reactive centers of the parent MGI 114.

Animals↗
PubMed1999

Magnetic resonance imaging. Application to family practice.

OBJECTIVE: To review indications, contraindications, and risks of using magnetic resonance imaging (MRI) in order to help primary care physicians refer patients appropriately for MRI, screen for contraindications to using MRI, and educate patients about MRI. QUALITY OF EVIDENCE: Recommendations are based on classic textbooks, the policies of our MRI group, and a literature search using MEDLINE with the MeSH headings magnetic resonance imaging, brain, musculoskeletal, and spine. The search was limited to human, English-language, and review articles. Evidence in favour of using MRI for imaging the head, spine, and joints is well established. For cardiac, abdominal, and pelvic conditions, MRI has been shown useful for certain indications, usually to complement other modalities. MAIN MESSAGE: For demonstrating soft tissue conditions, MRI is better than computed tomography (CT), but CT shows bone and acute bleeding better. Therefore, patients with trauma or suspected intracranial bleeding should have CT. Tumours, congenital abnormalities, vascular structures, and the cervical or thoracic spine show better on MRI. Either modality can be used for lower back pain. Cardiac, abdominal, and pelvic abnormalities should be imaged with ultrasound or CT before MRI. Contraindications for MRI are mainly metallic implants or shrapnel, severe claustrophobia, or obesity. CONCLUSIONS: With the increasing availability of MRI scanners in Canada, better understanding of the indications, contraindications, and risks will be helpful for family physicians and their patients.

Adult↗
PubMed1999

Evidence for an inactive transposable mariner-like element in Anopheles albimanus.

Transposable elements may eventually be used as transformation vectors of anti-Plasmodium genes in natural populations of Anopheles mosquitoes. The mariner transposable element is widespread in most animal phyla and we wished to test for its presence in the important Latin American malaria vector, Anopheles albimanus. Degenerate primers were designed from the consensus of insect mariner elements and used in a polymerase chain reaction to amplify a fragment of the predicted size from An. albimanus. The fragment was cloned, sequenced, and determined to be a mariner-like element through multiple alignment with known insect mariner elements. Dot blot and Southern blot analyses showed only one or a few elements per haploid genome. The cloned fragment was used as a probe to isolate similar sequences from an An. albimanus genomic DNA library. A 659-base-pair clone was 57% similar at the DNA level with mariner elements from Anopheles gambiae, Chrysoperla ptorapunda, and Haematobia irritans. This low sequence similarity is comparable to that found among mariner-like elements in all insects. However, conserved amino acid motifs were not discovered nor was a single open reading frame found. These aspects suggest that the An. albimanus mariner-like element may represent an ancient transposition event but that the element is no longer active, the typical open reading frame having been disrupted through nucleotide insertions and deletions.

Animals↗