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Biomedical subjects

J Yu

Publications and source records attributed to J Yu.

At least 973 records · Page 54Linked to original sources
PubMedDate not supplied

Role of hydroxyl containing residues in the intracellular region of rat bradykinin B(2) receptor in signal transduction, receptor internalization, and resensitization.

In past reports we illustrated the importance of Y131, Y322, and T137 within the intracellular (IC) face of the rat bradykinin B2 receptor (rBKB2R) for signal transduction and receptor maintenance (Prado et al. [1997] J. Biol. Chem. 272:14638-14642; Prado et al. [1998] J. Biol. Chem. 273:33548-33555). In this report, we mutate the remaining hydroxyl possessing residues located within the rBKB2R IC region. Exchange of S139A (IC2) or T239V (IC3) did not affect BK activated phosphatidylinositol (PI) turnover or receptor internalization. Chimeric exchange of the last 34 amino acids of BKB2R C-terminus with the corresponding 34 amino acids of the rat angiotensin II AT1a receptor (rAT1aR), both containing an S/T cluster, resulted in a mutant with normal endocytosis and BK activated PI turnover. A more selective chimera of these S/T clusters, with an exchange of BKB2R (333-351) with a rAT1aR fragment (326-342), resulted in a receptor with a retarded internalization but a normal BK activated PI turnover. Subsequent mutation of rBKB2R T344V showed little change in receptor uptake but a pronounced loss of BK activated PI turnover. The mutation of S335A, S341A, S348A, and S350A resulted in very poor receptor internalization and loss of activated PI turnover. Closer examination of this serine cluster illustrated that the replacement of S348A led to poor internalization; whereas the retention of S348 and mutation of S341A resulted in a receptor with a much greater internalization than WT. These and other results suggest that the presence of S348 promotes internalization while the presence of S341 dampens it. Conversely, S341 and S350 proved important for receptor signaling. In sum, our results illustrate that the distal C-terminus including its S/T cluster is important for both rBKB2R internalization and signal transduction. Individual S/T residues within this cluster appear involved in either signal transmission or receptor uptake capacity. However, replacement of the entire distal tail region with the corresponding rAT1aR sequence, also containing an S/T cluster, enables the BKB2R/AT1aR chimera to act in a very similar manner to wild type rBKB2R.

Amino Acid Sequence↗
PubMedDate not supplied

Distribution of normal and abnormal fluid collections in the glenohumeral joint: implications for MR arthrography.

Although magnetic resonance (MR) images of the glenohumeral joint frequently demonstrate intraarticular fluid, no specific criteria have, to the authors' knowledge, been published that allow accurate assessment of the amount of fluid present. Also, despite the increasing use of MR arthrography of the shoulder, the optimal amount of intraarticular fluid that should be used with this technique has not been determined. The authors progressively distended the glenohumeral joint in six cadaveric shoulder specimens with a dilute gadopentetate dimeglumine solution and obtained MR images after injection of 2, 5, 10, 15, and 20 mL of the solution. The pattern of fluid distribution was evaluated, and these results were then used to estimate the amount of fluid that was present in the glenohumeral joint on MR images of 20 shoulders obtained in 12 asymptomatic volunteers. In 14 of these shoulders, intraarticular fluid was present; however, in none was more than 2 mL evident. Results of the cadaveric study also indicated that 15 mL of intraarticular fluid appears to be the optimal amount for MR arthrography.

Adult↗
PubMedDate not supplied

Prolonged positive contrast enhancement with Gd-EOB-DTPA in experimental liver tumors: potential value in tissue characterization.

To evaluate the potential of the hepatobiliary magnetic resonance (MR) imaging contrast agent gadolinium EOB-DTPA (ethoxybenzyl diethylenetriaminepentaacetic acid) for the characterization of hepatic tumors, 79 primary and six implanted hepatomas in 38 rats were studied. MR imaging findings after administration of Gd-DTPA (0.3 mmol/kg) and Gd-EOB-DTPA (30 mumol/kg) were correlated with microangiographic and histologic findings. Gd-EOB-DTPA produced a strong liver enhancement, which caused prompt negative contrast enhancement (CE) in all implanted hepatomas and in 77 of 79 primary hepatomas. A positive CE that lasted up to 2 hours was found in two of 79 primary hepatomas, both of which were highly differentiated (grade I) hepatocellular carcinomas (HCCs). The rest were moderately differentiated to undifferentiated HCCs (grades II-IV). Rim enhancement, which corresponded histologically to peritumoral malignant infiltration sequestering normal hepatocytes, was seen around all implanted and some primary hepatomas. Positive tumor CE after administration of Gd-EOB-DTPA in this study is much less frequent but much more specific in comparison with the results of previous studies with manganese-DPDP (N,N'-dipyridoxylethylenediamine-N,N'-diacetate 5,5'-bis[phosphate]). These findings may help further discriminate hepatic tumors.

Animals↗
PubMedDate not supplied

The culture of chicken embryo fibroblast cells on microcarriers to produce infectious bursal disease virus.

The cultures of chicken embryo fibroblast (CEF) cells in flasks, spinner bottles, and bioreactors were studied. The growth and metabolism characteristics of CEF cells and the feasibility of the CEF cell culture in bioreactor were investigated. The plating process of the CEF cells on GT-2 microcarriers in spinner bottles was studied, and a plating kinetic model was presented. The culture of CEF cells in 1.5 L CelliGen bioreactor to produce infectious bursal disease virus (IBDV) had met success. Whereas the additive microcarriers were fed during the culture, the cell density was increased 10 times as against seed cells adhering to microcarriers and the virus titer was as high as 7.5. All the aforementioned experimental results have laid the foundation for high density culture of CEF cells and process scale-up.

Animals↗
PubMedDate not supplied

Repeated immunolesions display diminished stress response signal.

Cholinergic basal forebrain neurons (CBFNs) retrogradely transport neurotrophins released in the hippocampus and cortex as part of a general response to injury in a process that is impaired in the aged rodent and can be spared by the exogenous addition of pharmacological doses of nerve growth factor (NGF). This observation suggests that components of stress response signal transduction pathways in the aged CNS can be exogenously activated. The extent and mechanism of the endogenous stimulation of NGF in response to injury can be mimicked via treatment with 192 IgG-saporin of rat CNS, an immunolesion model. Here we report on the use of a conditioning lesion paradigm to determine if repeated partial immunolesions have a conditioning effect on the immunolesion-induced increases in NGF protein or decreases in choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activity. We report that chronic repeated immunolesions, as used here, were not as effective as a one time equivalent immunolesion in terms of induced NGF protein increases or decreasing ChAT and AChE activity in the hippocampus and cortex. Thus, chronic lesions resulting in cholinergic impairment typical of the aged CNS may differ from acute toxic models as a result of desensitization due to a conditioning effect of chronic subthreshold lesioning events in the CNS.

Acetylcholinesterase↗
PubMedDate not supplied

L-asparaginase release from Escherichia coli cells with K2HPO4 and Triton X100.

A method to release L-asparaginase (EC 3.5.1.1) from ATCC Escherichia coli 11303 cells by chemical permeabilization was studied. It was found that a combination of K2HPO4 and Triton X100 was effective. The influences of K2HPO4 concentration, Triton concentration, E. coli cell concentration and pH on the release of enzyme and proteins were investigated in detail. Experimental results showed that 12.5% (w/v) K2HPO4, 2% (w/v) Triton X100 and 3 x 10(8) cells/mL made the amount of enzyme released over 70%. L-Asparaginase in K2HPO4 and Triton solution could remain stable at least for 24 h. The release effect of K2HPO4 and Triton X100 used simultaneously was better than that of K2HPO4 and Triton X100 used separately in succession. Electron microscopy indicated that the chemical treatment altered the surface structure of E. coli cells but did not break them. As the method does not produce a large amount of cell fragments and the amount of enzyme released is relatively high, it can be thought to be an valuable and economic method to release intracellular enzyme.

Asparaginase↗
PubMedDate not supplied

Accumulation of a heat shock-like protein during differentiation of human erythroid cell line K562.

The human erythroid cell line K562 provides a model system for studying erythroid differentiation and eukaryotic gene regulation. These cells express glycophorin A, spectrin and i antigen. They accumulate embryonic and fetal haemoglobins on induction of erythroid differentiation with haemin, sodium butyrate or hydroxyurea. In the present study, the protein composition of K562 cells during haemin-mediated induction of erythroid maturation was analysed by two-dimensional gel electrophoresis. Under conditions in which haemin did not effect cell viability and proliferation, a protein of approximately 70,000 molecular weight (MW) accumulated in the differentiated K562 cells. The accumulation appears to be due to an increase in the rate of RNA synthesis for this protein. The protein is related in sequence to a 70,000-MW heat shock protein. An antigenically related protein was also demonstrated in human bone marrow and accumulates at particular stages of human erythroid maturation.

Cell Differentiation↗
PubMedDate not supplied

Importance of FSH-releasing protein and inhibin in erythrodifferentiation.

Inhibin is a hypophysiotropic hormone which selectively suppresses the secretion of pituitary follicle-stimulating hormone. It has been isolated from gonadal fluids and characterized as a protein heterodimer consisting of an alpha subunit and one of two beta subunits (beta A or beta B). FSH-releasing protein (FRP), also named activin, is a dimer consisting of two inhibin beta-chains. A factor from conditioned medium of a leukaemia cell line has been isolated which can induce mouse Friend cells to become benzidine-positive, and which shares a similar N-terminal sequence with porcine FRP. In this report, we find that FRP and inhibin modulate both the induction of haemoglobin accumulation in a human erythroleukaemic cell line, K562, and the proliferation of erythroid progenitor cells in human bone marrow culture. These two proteins could constitute a novel humoral regulatory control of erythropoiesis which would involve two types of related protein dimers with functionally opposite effects.

Activins↗
PubMedDate not supplied

Tests of six cotton (Gossypium hirsutum L.) mutants for association with aneuploids.

Genetic mutants are useful tools for basic and applied research to elucidate the developmental and regulatory processes of the cotton plant (Gossypium hirsutum L.). Their value is enhanced with knowledge of their location in the genome. The results of aneuploid tests used to locate mutant loci on specific chromosomes in G. hirsutum L. are reported. Thirty-four monosomes and telosomes, representing 18 of the 26 chromosomes, were used in combination with six mutants that were associated with nine loci. The mutant loci were glandless stem and boll (gl1gl6), immature fiber (im), Ligon lintless-2 (Li2), methylation (me), nonpinking (np1np2), and Raimondal (Ra1Ra2). We found that im was associated with chromosome 3 that contains linkage group VI (accessory involucre and frego bract); Li2 was associated with chromosome 18 that contains linkage group XVI (open bud and yellow pollen-2); and me was associated with chromosome 9. The remaining three mutants were not associated with the aneuploids in the tests. Knowledge of these chromosome assignments provides a valuable reference for specific studies of mutants and for further genome mapping efforts.

Aneuploidy↗
PubMedDate not supplied

Role of contrast agent perfusion and of diffusion in the NMR signal enhancement of liver lesions.

Both perfusion and diffusion contribute to NMR signal enhancement after intravenous injection of a nonspecific contrast agent. In the present study the roles of perfusion and diffusion in the contrast enhancement of induced liver lesions in the rat and the rabbit were evaluated. This was done by comparing Gd-DOTA absolute enhancement signal-to-noise versus time plots of various lesions with the findings from microangiography and histology. Four types of enhancement could be recognized. Diffusion was the major factor in the delayed enhancement seen in lesions that had large extravascular diffusion space.

Animals↗
PubMedDate not supplied

Mn-DPDP enhanced MRI in experimental bile duct obstruction.

To assess both the effect of Mn-DPDP as a hepatobiliary-specific contrast agent in bile duct obstruction and the relative role of liver and kidney in the elimination of this agent from the body, an animal experiment was set up. Twelve rats were used and divided into three groups. In group 1 the common bile duct was ligated, in group 2 bile duct ligation was limited to one lobe, and group 3 served as control. Magnetic resonance T1-weighted SE images were obtained before and after the injection of 25 mumol/kg of Mn-DPDP during the first 2 h and at day 1, 2, 3, 4, and, in some animals, up to 21 days. In normal rats the absolute enhancement signal-to-noise ratio (S/N) versus time plots obtained from the liver after Mn-DPDP injection returned to precontrast values within 24 h. In the group with common bile duct ligation, important liver enhancement persisted up to 21 days. In the group with selective obstruction, liver intensity normalized after 3 days. The S/N plots from spleen, renal cortex, and obstructed liver lobe showed similarities in time course. The present data indicate that Mn elimination is strongly impaired in the presence of bile duct obstruction. Renal glomerular filtration is ineffective in eliminating Mn from the body. The persisting splenic and renal cortical enhancement suggests that free Mn or some Mn-DPDP metabolite either is strongly bound to plasma proteins and acts as a blood pooling agent and/or is uptaken by the splenic or renal parenchyma.

Animals↗
PubMedDate not supplied

Pictorial essay. MRI of the glenoid labrum with gross anatomic correlation.

The objective of this pictorial essay is to illustrate the magnetic resonance image (MRI) appearance of the glenoid labrum and the perilabral structures with and without instillation of intraarticular contrast material. Ten cadaveric shoulder specimens underwent axial MRI using various MR pulse sequences. The shoulders then were transversely sectioned, and the gross morphology of the labrum and perilabral structures was evaluated and correlated with the MR images. The contrast-enhanced sequences allowed for improved anatomic visualization of the structures evaluated.

Aged↗
PubMedDate not supplied

A study of the pathogenesis and prevention of central pontine myelinolysis in a rat model.

The development of central pontine myelinolysis was studied in rats. Severe hyponatraemia was induced using vasopressin tannate and 2.5% dextrose in water and then rapidly corrected with hypertonic saline alone, hypertonic saline and dexamethasone simultaneously, or hypertonic saline plus dexamethasone 24 h later. The permeability of the blood-brain barrier was evaluated using the extravasation of Evans blue dye and the expression of inducible nitric oxide synthase (iNOS) in the brain was examined using Western blot analysis. Histological sections were examined for demyelinating lesions. In rats receiving hypertonic saline alone, Evans blue dye content and expression of iNOS began to increase 6 and 3 h, respectively, after rapid correction of hyponatraemia and demyelinating lesions were seen. When dexamethasone was given simultaneously with hypertonic saline, these increases were inhibited and demyelinating lesions were absent. These effects were lost if dexamethasone injection was delayed. Disruption of the blood-brain barrier and increased iNOS expression may be involved in the pathogenesis of central pontine myelinolysis, and early treatment with dexamethasone may help prevent the development of central pontine myelinolysis.

Animals↗
PubMedDate not supplied

An occupational risk survey of a refractory brick company in Ha Noi, Viet Nam.

Viet Nam has an increasing need for building materials, including refractory bricks. Little is known regarding the occupational hazards incurred in brick manufacturing. To determine the occupational health hazards posed by a refractory brick operation in Ha Noi, Viet Nam, a cross-sectional occupational risk survey was conducted, focusing on respirable dust hazards. It included an industrial hygiene walk-through and gravimetric dust analysis. Noise, heat, lack of head protection, and dust exposure were hazards identified at the brick-manufacturing site. Respiratory protection involved a three-layer cloth mask that had not been tested for efficacy. Silica dust exposure levels exceeded the Vietnamese permissible exposure level by almost fivefold based on gravimetric assessment and estimated silica content. This brick manufacturing site contains significant injury and respiratory illness hazards. Further investigations are necessary to begin to develop occupational safety measures at the site.

Accidents, Occupational↗
PubMedDate not supplied

Dielectric properties of human glioma and surrounding tissue.

Dielectric properties of human glioma and surrounding tissue from five patients were measured. Experiments were performed at frequencies of 5-500 MHz at 24 +/- 0.5 degrees C using a Network Analyser and a coaxial line capacitive sensor. The permittivity and conductivity of tumours were 30% higher than that of the surrounding tissues due to their higher water content. The characteristic of less differentiation in tumours clearly was reflected in the dielectric properties, namely a smaller parameter for the relaxation time distribution of the tumour's dielectric relaxation. With the dielectric data, the power absorption ratios of tumour to surrounding tissue were calculated for four representative electromagnetic (EM) irradiation cases. The calculation shows that power absorption ratios are strongly dependent on the incident direction of the EM wave and optimum frequency. To improve therapeutic efficiency, it is appropriate to have the electric field vector (E) parallel to the interface of tumour/surrounding tissue at optimum frequencies around 100 MHz, and the case of E perpendicular to the interface must be avoided in applications of EM hyperthermia for brain tumours.

Adult↗