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Biomedical subjects

H Ji

Publications and source records attributed to H Ji.

At least 145 records · Page 8Linked to original sources
PubMed1994

Influence of carbon dioxide gas perfusion to thermal distribution of sapphire probe. A comparative study with saline.

RATIONALE AND OBJECTIVES: A previous study confirmed that the direct laser-thermal conduction of the sapphire probe with carbon dioxide gas perfusion increased the width of the laser-recanalized channel. This caused us to further investigate the thermal distribution characteristics of the sapphire probe when lasing with CO2 gas perfusion. METHODS: The surface temperature of a sapphire probe in a circulation model using 37 degrees C flowing whole blood was measured. Two hundred and sixteen measurements were obtained by directly contacting a flexible thermocouple wire onto the sapphire probe at different sites: 1) metal connector; 2) lateral side of the sapphire crystal; 3) top of the sapphire crystal; and 4) 3 mm in front of the sapphire probe. During lasing with a neodymium-yttrium-aluminum garnet (Nd-YAG) laser, the CO2 gas or saline was infused through the sapphire probe at different flow rates. RESULTS: The lateral side of the sapphire crystal was heated up to 75 degrees C when lasing without any perfusion, but up to 220 degrees C when lasing with CO2 gas perfusion. At all four sites, the mean temperature increases were statistically higher (P < .01) with CO2 gas than with saline perfusion. The mean peak temperatures increased with increasing flows of CO2 gas perfusion and decreased with increasing flows of saline perfusion. CONCLUSIONS: The thermal conduction from the sapphire probe can be significantly enhanced by increasing flows of CO2 gas perfusion. This may play an important role in creating a greater diameter of the recanalized channel and in better delaying the formation of restenosis or re-occlusion after laser recanalization of atheromatous arteries.

Aluminum Oxide↗
PubMed1994

Regulation of angiotensin II receptors in rat brain during dietary sodium changes.

Activation of the renin-angiotensin system by sodium deficiency is associated with reciprocal changes in the expression of angiotensin II receptors in adrenal glomerulosa and vascular smooth muscle cells. The effects of dietary sodium changes on the expression of brain angiotensin receptor subtype 1 (AT1) mRNAs were examined in rats maintained on normal, low, and high sodium intake for 3 weeks. Plasma aldosterone and renin activity were elevated in rats maintained on a low salt diet compared with normal rats and were reduced in rats maintained on a high salt diet. These results are consistent with previous findings on the effects of altered dietary sodium on the renin-angiotensin system. The expression of AT1A and AT1B receptor subtype mRNAs was determined by quantitative reverse transcriptase-polymerase chain reaction during changes in sodium intake. The results revealed that sodium deprivation enhanced the expression of AT1B receptors in decorticated brains by 164% compared with high sodium intake. Conversely, high sodium diet increased the expression of AT1A receptors by 155% in the brain compared with low sodium intake. These data suggest that AT1A and AT1B receptors play reciprocal roles in central mechanisms for the control of fluid homeostasis. Further analysis of the molecular biology of angiotensin II receptor regulation in the brain may provide new insights into the interplay between the renin-angiotensin system and blood pressure regulation and also into the role of angiotensin II in the pathogenesis of essential hypertension.

Aldosterone↗
PubMed1994

[The application of PCR technique in genetic diagnosis of non-Hodgkin's lymphoma].

In this study, specimens from 59 cases of non-Hodgkin's lymphoma (NHL) were immunophenotyped with L26 and UCHL-I McAb, then investigated for gene rearrangement by PCR technique. The results showed that the rates of positive amplification of clonal IgH and TCR beta gene rearrangement were 71.4% (10/14) and 83.3% (10/12) respectively in the fresh tissues, and the IgH (semi-nested PCR technique) and TCR beta were 80% (12/15) and 73.3% (11/15) respectively in paraffin embedded tissues. Definitive diagnosis was made for the 6 cases which could not be diagnosed by routine and immunohistochemical methods, and all 6 exhibited IgH or TCR beta single band. No cases with pseudopositive amplification were discovered. This study suggested that the PCR technique was the most specific, sensitive and rapid detection method for clonal gene rearrangement in NHL.

DNA, Neoplasm↗
PubMed1994

Antiviral effects on mouse leukemia virus replication by oligodeoxynucleotides in vitro and in vivo.

Oligodeoxynucleotides (Oligomers) including modified and unmodified, homo- and heterooligomers were tested for their ability to inhibit mouse SRS leukemia virus (SRSV)-induced proliferation of cells, colony formation, syncytium formation and reverse transcriptase (RT) activity in vitro. Phosphorothioate analogs complementary to Mo-MuLV sequences, as well as noncomplementary homooligomers, were found to be active. Unmodified homooligomer (dC14) also showed inhibition of growth of ascitic lymphoma carrying SRS virus. Our study suggests that different classes of oligonucleotides may inhibit SRSV replication with different mechanisms.

Animals↗
PubMed1993

p53 protein expression in breast cancer as related to histopathological characteristics and prognosis.

Formalin-fixed, paraffin-embedded biopsies of 193 women with primary breast cancer followed-up for over 10 years were analysed immunohistochemically for the expression of p53 protein. Altogether, 58% (113/193) of the tumors were positive for p53 protein. Over-expression of p53 was associated with the ductal type, high-grade tumors, dense stromal inflammatory cell infiltrate, high S-phase fraction, high mitotic frequency and high values of the nuclear factors. In univariate analysis, intense p53 over-expression predicted a poor outcome, whereas a short recurrence-free survival (RFS) was related to p53 negativity. In axillary lymph-node-negative (ANN) tumors, p53 negativity was related to short RFS, and in axillary lymph-node-positive (ANP) tumors this inverse relationship was statistically significant. In Cox's analysis, p53 protein over-expression had no independent prognostic value comparable with the well-established prognostic factors. However, p53 protein accumulation was an independent indicator of long RFS in the entire cohort, in ANP tumors and in rapidly proliferating tumors. The results indicate a dual role for p53 protein over-expression in breast cancer prognosis. The low survival probability associated with intensively p53-positive tumors is probably related to rapid cancer-cell proliferation, whereas the long RFS of p53-positive tumors might be explained by the development of circulating antibodies to p53 protein. The role of p53 protein in breast cancer is incompletely understood, and the p53 gene should be subjected to detailed analysis of specific mutations.

Adult↗
PubMed1993

Molecular cloning, sequencing and functional expression of an amphibian angiotensin II receptor.

Xenopus laevis and mammalian angiotensin AT1 receptors couple to the phospholipase C signal transduction pathway. However, amphibian AII receptors (xAT), unlike mammalian AT1 receptors, do not recognize the non-peptide antagonist Dup 753. To investigate the basis of this distinction, we have isolated a 3.0 kb Xenopus myocardial xAT cDNA that encodes a 41,039 MW protein containing 362 amino acids. The xAT receptor has 60% amino acid identity and 65% nucleotide homology with the coding regions of known mammalian AT1 receptors. xAT receptors expressed in Xenopus oocytes mediate AII-induced Ca2+ mobilization and are pharmacologically distinct from mammalian AT1 receptors. xAT transcripts are present in Xenopus lung, liver, kidney, spleen, and heart, but not in adrenal, intestine, and smooth muscle. Comparative analysis of xAT and AT1 receptors should facilitate elucidation of the structural basis of their binding and activation properties.

Amino Acid Sequence↗
PubMed1993

Epidermal growth factor induces serine phosphorylation of stathmin in a human colon carcinoma cell line (LIM 1215).

Changes in protein phosphorylation in the human colon carcinoma cell line LIM 1215 after stimulation with epidermal growth factor (EGF) have been analyzed by two-dimensional gel electrophoresis and phosphoamino acid analysis. In addition to a number of tyrosine-phosphorylated proteins, a family of small proteins (M(r) 19,000-20,000) is maximally phosphorylated on serine within 5 min of EGF stimulation. One member of the family has been purified by a combination of two-dimensional electrophoresis and reversed-phase high performance liquid chromatography and identified by amino acid sequence analysis as stathmin. Although phosphorylation of stathmin has been reported previously in leukemia cells and following stimulation of hemopoietic or lymphoid cells with several mitogenic agents, this is the first report of stathmin phosphorylation in response to EGF.

Amino Acid Sequence↗
PubMed1993

Hotspots for unselected Ty1 transposition events on yeast chromosome III are near tRNA genes and LTR sequences.

A collection of yeast strains bearing single marked Ty1 insertions on chromosome III was generated. Over 100 such insertions were physically mapped by pulsed-field gel electrophoresis. These insertions are very nonrandomly distributed. Thirty-two such insertions were cloned by the inverted PCR technique, and the flanking DNA sequences were determined. The sequenced insertions all fell within a few very limited regions of chromosome III. Most of these regions contained tRNA coding regions and/or LTRs of preexisting transposable elements. Open reading frames were disrupted at a far lower frequency than expected for random transposition. The results suggest that the Ty1 integration machinery can detect regions of the genome that may represent "safe havens" for insertion. These regions of the genome do not contain any special DNA sequences, nor do they behave as particularly good targets for Ty1 integration in vitro, suggesting that the targeted regions have special properties allowing specific recognition in vivo.

Base Sequence↗
PubMed1993

Rapid purification of double-stranded DNA by triple-helix-mediated affinity capture.

A simple and rapid method for the preparation of highly pure plasmid DNA has been developed. The DNA is directly captured from bacterial cell lysates by formation of a triple-helical structure between the plasmid dsDNA and a 20-base biotinylated oligonucleotide attached to streptavidin-coated magnetic beads and then eluted from the beads in pH 9 buffer solution. No phenol extraction, ethanol precipitation, RNase digestion, or CsCl gradient centrifugation is required. A general purpose cloning vector, pHJ19, was constructed for this application from pUC19 DNA by insertion of a 40-base sequence suitable for triple-helix formation. The approach was also found suitable for the purification of lambda bacteriophage DNA.

Bacterial Proteins↗
PubMed1993

Structure of synthetic peptide analogues of an eggshell protein of Schistosoma mansoni.

The peptide (Gly-L-Tyr-L-Asp-L-Lys-L-Tyr)6, referred to as F4-6, was synthesized as a model for a schistosome eggshell protein in which the Gly-Tyr-Asp-Lys-Tyr consensus sequence is repeated over 40 times. Analysis by CD, Fourier transform infrared spectroscopy, potentiometric and spectrophotomertric titrations, NMR, and molecular modeling suggests that F4-6 forms some type of left-handed structure. A likely possibility appears to be a left-handed alpha-helix stabilized by Lysi-Aspi +4 salt bridges and possibly Aspi-Tyri +4 hydrogen bonding and Tyr-Tyr interactions. Spectroscopic studies of a number of F4-6 analogues support this conclusion. For example, substitution of D-Ala for Gly produces a peptide with enhanced left-handed helical spectral characteristics, whereas an L-Ala substitution results in a peptide with minimal structure. These studies suggest that the F4 protein from Schistosoma mansoni may be the first example of a naturally occurring protein devoid of proline and carbohydrate that forms a left-handed helix composed of L-amino acids, although alternative forms of other left-handed structures have yet to be rigorously excluded.

Amino Acid Sequence↗
PubMed1993

Megakaryocytopoiesis and platelet production: does stem cell factor play a role?

Megakaryocytopoiesis, resulting in the production and release of platelets, is a multistage procession of cellular differentiation and maturation which is regulated by a constellation of cytokines. Since thrombocytopenia is a frequent dose-limiting toxicity of chemotherapy, newly-identified cytokines have been actively investigated for their potential megakaryocyte/platelet-promoting properties. Stem cell factor (SCF, also known as mast cell growth factor, Steel factor or Kit ligand) has been found to synergize with GM-CSF, IL-6, IL-3, IL-11 or Epo to increase the numbers of megakaryocyte-containing colonies (i.e., CFU-Meg, BFU-Meg, CFU-GMM, CFU-GEMM). On the other hand, SCF increased the number of megakaryocytes per colony in the presence of IL-3, GM-CSF or IL-6. SCF also stimulated the proliferation of specific megakaryocytic cell lines (i.e., CMK, M-07e). SCF did not, however, alter megakaryocyte markers or increase cell ploidy. Thus, SCF appears to expand the committed myeloid progenitor compartments, rather than increase the rate of megakaryocyte maturation or the number of platelets released. We describe studies in which SCF stimulated murine CFU-Meg alone and in the presence of IL-3. However, a decrease in cultured cell plating density resulted in ablation of this SCF-stimulation of CFU-Meg colonies. CFU-Meg colony stimulation by SCF was dose dependent, even under serum-free conditions. The effects of SCF in other in vitro and in vivo animal model systems are reviewed.

Animals↗
PubMed1993

Effect of heat treatment on the microstructure of plasma-sprayed hydroxyapatite coating.

One of the claimed benefits of plasma-sprayed hydroxyapatite coatings on metal prostheses is the generation of enhanced bone bonding. However, plasma-sprayed hydroxyapatite undergoes a range of transformations during spraying, and the final microstructures produced are complex, with a variety of phases present. The microstructures of plasma-sprayed hydroxyapatite coatings on titanium alloy substrate which have been subjected to post-heat treatment at 950 degrees C have been characterized using transmission electron microscopy. It was demonstrated that heat treatment can modify the coating microstructure and improve adhesion between coating and substrate. The results of chemical analysis revealed an increase in the Ca:P ratios, accompanied by the transformation of calcium phosphate phases from amorphous to crystalline. These transformations are related to phosphorus diffusion into the titanium alloy substrate, which results in the formation of a Ti3P phase.

Alloys↗
PubMed1993

Differential activation of inositol 1,4,5-trisphosphate-sensitive calcium pools by muscarinic receptors in Xenopus laevis oocytes.

Muscarinic acetylcholine (ACh) receptors activate the phospholipase C signal transduction pathway to promote the formation of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] and the consequent elevation of cytoplasmic calcium (Ca2+). The inositol phosphate and Ca(2+)-mobilization responses to ACh were analyzed in Xenopus oocytes possessing endogenous receptors, and in oocytes expressing exogenous receptors from injected muscarinic RNA transcripts, to evaluate the patterns of signal transduction mediated by native and expressed receptors. Activation of native ACh receptors elicited dose- and time-dependent increases in Ins(1,4,5)P3 and inositol bisphosphate (InsP2) production. ACh-induced Ins(1,4,5)P3 production increased rapidly within the first 2 min and continued to rise over the next 20 min. ACh was a much more effective stimulus of inositol phosphate production at native (up to 35-fold) than at expressed receptors (less than 2-fold). In contrast, measurements of Ca(2+)-mobilization in oocytes injected with the Ca(2+)-specific photoprotein, aequorin, revealed that ACh stimulation of expressed receptors evoked up to 200-fold increase in light emission, whereas ACh stimulation of native receptors elicited less than a 2-fold response. These observations indicate that the oocyte possesses functionally distinct agonist-sensitive Ca2+ pools which differ markedly in their sensitivity to Ins(1,4,5)P3 production and suggest that these pools are mobilized by different effector mechanisms. The finding that the magnitude of the intra-oocyte Ca2+ response is not necessarily determined by the degree of Ins(1,4,5)P3 production, but rather by another aspect of the signal transduction pathway (e.g. the nature and/or location of the Ins(1,4,5)P3 releasable Ca2+ pool), reveals an additional level of complexity in the transduction mechanisms responsible for intracellular Ca2+ signaling.

Acetylcholine↗
PubMed1993

Atrial natriuretic factor activates cyclic adenosine 3',5'-monophosphate phosphodiesterase in Xenopus laevis oocytes and potentiates progesterone-induced maturation via cyclic guanosine 5'-monophosphate accumulation.

Xenopus oocytes were found to express atrial natriuretic factor (ANF) receptors that activate guanylate cyclase and stimulate cyclic guanosine 5'-monophosphate (cGMP) production in a dose- and time-dependent manner. A truncated fragment of ANF, known to bind to mammalian ANF receptors without stimulating cGMP accumulation, did not elicit a cGMP response in oocytes. In addition, preincubation with ANF increased the number of oocytes that underwent progesterone-induced maturation. The maximally effective dose of ANF (1 microM) elevated intracellular and extracellular cGMP accumulation from 50 to 200 and 5 to 800 fmol/oocyte, respectively, and increased the number of maturing oocytes by up to 3-fold. ANF's effects on progesterone-induced maturation were mimicked by nonhydrolyzable analogues of cGMP. ANF and 8-Br-cGMP had no effect on maturation in the absence of progesterone, indicating that elevation of cGMP alone is not sufficient to induce maturation. Dibutyryl-cGMP was as effective as 8-Br-cGMP, whereas 8-Br-guanosine monophosphate, 8-Br-guanosine, and 8-Br-cyclic inosine monophosphate did not potentiate ovum maturation. In Xenopus oocytes, an initial step in progesterone-induced maturation is the reduction of intracellular cAMP levels; both ANF and 8-Br-cGMP lowered cAMP levels and enhanced progesterone's ability to do so. This decrease in cAMP levels was attributable to increased cAMP-phosphodiesterase activity, which was enhanced by both ANF and 8-Br-cGMP. These findings, and the presence of functional ANF receptors on Xenopus oocytes, demonstrate that ANF can participate in ovum development by stimulation of cGMP accumulation and activation of cAMP phosphodiesterase, thereby potentiating progesterone's ability to decrease cAMP levels and promote ovum maturation.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1993

Megakaryocyte colony-stimulating factor (Meg-CSF) is a unique cytokine specific for the megakaryocyte lineage.

The regulation of megakaryocytopoiesis and platelet production has not yet been clearly elucidated. Several cytokines have been shown to be capable of producing megakaryocyte colonies from bone marrow [i.e. Interleukin (IL)-3, granulocyte-macrophage (GM)-colony-stimulating factor (CSF), erythropoietin (Epo)]. In addition, other activities have been reported to stimulate megakaryocyte precursors, yet a megakaryocyte-CSF (Meg-CSF) has not been purified to homogeneity and IL-3, GM-CSF and/or Epo often contaminate purification attempts which could account for the activities. A Meg-CSF has been isolated from the urine of patients with aplastic anaemia and purified by sequential ultrafiltration, cation exchange, G-50 chromatography, preparative PAGE, chromatofocusing and cation exchange HPLC. The activity of this material is 2-4 x 10(4) CFU-Meg/mg as measured in a murine marrow, serum-containing assay. This activity also stimulates CFU-Meg in the absence of adherent accessory cells and in serum-free cultures, indicative of the direct stimulation on CFU-Meg. Immunoassays, colony forming assays, and proliferation assays demonstrate that purified Meg-CSF has no GM-CSF, IL-3, M-CSF, G-CSF or IL-1 alpha, -3, -6, -9 and -11. In confirmation of these results, neutralizing antibody to IL-6 also did not abrogate Meg-CSF activity. Therefore the previously-reported megakaryocyte colony-stimulating activity in purified aplastic anaemia patient urine is due to a unique cytokine: Meg-CSF.

Anemia, Aplastic↗