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Biomedical subjects

Y Luo

Publications and source records attributed to Y Luo.

At least 469 records · Page 26Linked to original sources
PubMed1993

Demonstration of presynaptic protein kinase C activation following long-term potentiation in rat hippocampal slices.

Pharmacological and biochemical evidence implicate the Ca2+ and phospholipid-dependent protein kinase C in long-term potentiation. The in vitro hippocampal slice preparation was used to demonstrate redistribution of protein kinase C from cytosol to membrane and protein kinase C-dependent phosphorylation of the presynaptic growth-associated protein-43 substrate following long-term potentiation induction in area CA1. Protein kinase C translocation was assessed using both quantitative immunoblotting with a monoclonal antibody recognizing a common epitope in the alpha and beta isoforms of protein kinase C and Ca2+ and phospholipid-dependent phosphorylation of exogenous histone substrate. Slices examined 5 min after tetanus-induced spike potentiation showed no change in protein kinase C redistribution, whereas slices examined at 15-, 30- and 60-min intervals all showed a similar degree of protein kinase C translocation to membrane, although only at 15 min was the effect statistically significant. Additionally, an increase in protein kinase C-dependent growth-associated protein 43 phosphorylation was observed 10 min after high-frequency stimulation. The translocation of protein kinase C and phosphorylation of growth-associated protein 43 were dependent upon high-frequency (repetitive 400 Hz) afferent stimulation, as no effects were observed in slices receiving low-frequency (1 Hz) or no stimulation. The N-methyl-D-aspartate receptor antagonist, DL-2-amino-5-phosphonovaleric acid (50 microM), inhibited induction of long-term potentiation, redistribution of protein kinase C and phosphorylation of growth-associated protein 43. A significant redistribution of the predominantly presynaptic protein kinase C isoform, protein kinase C-alpha, was also detected 15 min after induction of long-term potentiation using an alpha-isoform-specific monoclonal antibody. These observations support a presynaptic role for protein kinase C and growth-associated protein 43 in the early maintenance phase of LTP, and further suggest that a retrograde messenger produced postsynaptically following N-methyl-D-aspartate receptor activation mediates these effects.

2-Amino-5-phosphonovalerate↗
PubMed1993

A structure-activity relationship study of batracylin analogues.

A number of isoindolo[1,2-b]quinazolines and some benzo[4,5]isoquinolino[1,2-b]quinazolines as structural modification analogues of the antitumor compound batracylin were synthesized and evaluated against HL-60 cell growth and in topoisomerase II-mediated DNA cleavage assays. Of the compounds studied, 10,12-dihydro-7,8-methylenedioxyisoindolo[1,2-b]quinazolin-1 2(10H)-one (1d), 2-amino-10,12-dihydroisoindolo[1,2-b]quinazolin-12(10H)-one (1p), and 2-amino-7,8-methylenedioxy-10,12-dihydroisoindolo[1,2-b] quinazolin-12(10H)-one (1ab) exhibited good inhibitory activities against HL-60 cell lines as well as induction of topo II-mediated DNA cleavage activities.

Antineoplastic Agents↗
PubMed1993

A gene for Hirschsprung disease maps to the proximal long arm of chromosome 10.

Hirschsprung disease (HSCR) is a frequent congenital disorder (1 in 5,000 newborns) of unknown origin characterized by the absence of parasympathetic intrinsic ganglion cells of the hindgut. Taking advantage of a proximal deletion of chromosome 10q (del 10q11.2-q21.2) in a patient with total colonic aganglionosis, and of a high-density genetic map of microsatellite DNA markers, we performed genetic linkage analysis in 15 non-syndromic long-segment and short-segment HSCR families. Multipoint linkage analysis indicated that the most likely location for a HSCR locus is between loci D10S208 and D10S196, suggesting that a dominant gene for HSCR maps to 10q11.2, a region to which other neural crest defects have been mapped.

Base Sequence↗
PubMed1993

Close linkage with the RET protooncogene and boundaries of deletion mutations in autosomal dominant Hirschsprung disease.

Tight linkage with the RET proto-oncogene (Zmax = 3.41 at theta = 0.00), analysis of recombinants and detection of a familial microdeletion in a large pedigree restrict the mapping of the Hirschsprung (HSCR) gene previously localized on proximal 10q. The molecular characterization of the familial microdeletion and of 3 additional cytogenetically visible de novo deletions, isolated in somatic cell hybrids, identify a smallest region of overlap of 250 Kb. This contains the RET proto-oncogene where missense mutations causing multiple endocrine neoplasia type 2A (MEN 2A) phenotype were recently found. The pentagastrin test (which detects preclinical forms of MEN 2A or B) is negative in adult HSCR patients with deletions of the RET gene. This represents a good candidate for the search of mutations causing HSCR.

Cell Line↗
PubMed1993

Defining topological equivalences in protein structures by means of a dynamic programming algorithm.

An automatic algorithm for defining topological equivalences in protein structures is presented. The algorithm is based on a dynamic programming technique and self-consistent scoring method. We have used it to align pairs of similar protein structures of several protein families and to identify recurrent structural domains in aspartic proteinase 2APR. Its ability to find suboptimal paths permits a thorough comparison of proteins at each level in the hierarchy of the protein structure: secondary structure, super-secondary structure, domain and entire globular structure. The algorithm has been extended to the structure alignment of ribonucleic acid and can be extended to the structure alignment of any linear polymer.

Algorithms↗
PubMed1993

Juxtaposition between activation and basic domains of human immunodeficiency virus type 1 Tat is required for optimal interactions between Tat and TAR.

trans activation of the human immunodeficiency virus type 1 long terminal repeat requires that the viral trans activator Tat interact with the trans-acting responsive region (TAR) RNA. Although the N-terminal 47 amino acids represent an independent activation domain that functions via heterologous nucleic acid-binding proteins, sequences of Tat that are required for interactions between Tat and TAR in cells have not been defined. Although in vitro binding studies suggested that the nine basic amino acids from positions 48 to 57 in Tat bind efficiently to the 5' bulge in the TAR RNA stem-loop, by creating several mutants of Tat and new hybrid proteins between Tat and the coat protein of bacteriophage R17, we determined that this arginine-rich domain is not sufficient for interactions between Tat and TAR in vivo. Rather, the activation domain is also required and must be juxtaposed to the basic domain. Thus, in vitro TAR RNA binding does not translate to function in vivo, which suggests that other proteins are important for specific and productive interactions between Tat and TAR.

Amino Acid Sequence↗
PubMed1993

Functional analysis of interactions between Tat and the trans-activation response element of human immunodeficiency virus type 1 in cells.

Transcriptional trans-activation of the human immunodeficiency virus type 1 long terminal repeat requires that the virally encoded Tat effector interacts with its target trans-activation response element (TAR) RNA stem-loop. Although the arginine-rich region of Tat from amino acids 49 to 59 is sufficient to bind to TAR RNA in vitro, the RNA-binding domain of Tat has not been defined in vivo. Human immunodeficiency virus type 1 also encodes the Rev protein, which acts through an RNA stem-loop called the Rev-response element to transport unspliced and singly spliced viral RNA species from the nucleus to the cytoplasm. To map the RNA-binding domain of Tat, we performed assays that relied on Rev function using the heterologous RNA-tethering mechanism of Tat and the TAR. By examining the effects of selected targeted mutations of Tat on the abilities of hybrid Tat/Rev proteins to rescue the expression of unspliced mRNA via the TAR, we demonstrated that residues throughout the N-terminal 59 amino acids of Tat are required for binding of Tat and TAR RNA in vivo.

Animals↗
PubMed1993

A model of stress relaxation in cross-bridge systems: effect of a series elastic element.

Many experimental protocols employed in the study of muscle mechanics use tension transients as a probe of the magnitudes of the kinetic rates in the underlying cross-bridge dynamics. These transients could potentially be modified by the elastic elements that exist both within the fiber and at the points of attachment to the experimental apparatus. To better understand the magnitude of such modifications, we have used computer simulation to investigate the transients that would be expected for cross bridges acting on an actin filament attached to an elastic element. The original model of cross-bridge mechanics by A.F. Huxley was used (Prog. Biophys. 7: 255-318, 1957). After an isometric equilibrium is achieved, a tension transient is produced by changing the dissociation rate constant, g1, while holding the attachment rate constant, f1, fixed. This decreases the number of attached, force-producing cross bridges. We find that the tension transients are markedly slowed by the presence of even a few (> or = 2) nanometers of series elastic strain per half-sarcomere. Thus some rate constants inferred from mechanical transients (e.g., those induced by caged ligands) may underestimate the actual kinetic rates of the cross-bridge processes.

Animals↗
PubMed1993

[Improvement of prostacyclin-thromboxane A2 balance in patients with acute myocardial infarction by intermittent aspirin].

Forty two patients with acute myocardial infarction (AMI) were randomly distributed to the following groups: (1) the non-aspirin-treated group; (2) the daily-aspirin-treated group (aspirin, 300mg, once everyday); (3) the intermittent-aspirin-treated group (aspirin, 300mg, once every three days). In addition to the three groups, a group of normal subjects was selected. Blood was taken by venipuncture of the antecubital vein in patients on the first, second, seventh, fourteenth and twenty-first hospitalized days. The plasma levels of 6-keto-prostaglandin F1 alpha(6-keto-PGF1 alpha) and thromboxane B2(TXB2) were measured respectively by the scintillation counting of radioimmunoassay. The ratio of 6-keto-PGF1 alpha to TXB2 (K/T ratio) was also calculated. Conclusions were as follows: (1) Intermittent treatment with low-dose aspirin is superior to daily treatment in improving the PGI2/TXA2 balance in patients with AMI. (2) Daily low-dose aspirin has cumulative inhibitory effects on PGI2 and TXA2 synthesis in AMI patients. While intermittent treatment has the same cumulative inhibitory effect on TXA2 synthesis as daily treatment, but no cumulative inhibitory effect on PGI2 synthesis.

6-Ketoprostaglandin F1 alpha↗
PubMed1993

[Study on degradation of phenols in water].

The degradation of phenols in water and the effects of microbiolism, pH and dissolved oxygen (DO) on the degradation were investigated. The results showed that the degradation of phenols in water was mainly that of biochemistry, which depends on the existence of microbiolism. The most suitable pH for the degradation was 6 to 9, and no effects of DO on it were found. The accustomization of microbiolism with phenols would accelerate the degradation.

Hydrogen-Ion Concentration↗
PubMed1993

[Effects of "he xiang zhuang gongfu" on respiratory function in healthy adults].

Eleven healthy adults who practised He Xiang Zhuang Gongfu (HGF) were followed for 6 months; 15 pulmonary function tests were determined before HGF practice, 2 months and 6 months after HGF practice. All 11 subjects took the HGF exercise every day for 30 minutes. Samplings were taken before subjects had ever practised HGF as control value, immediately and 30 minutes after HGF exercise. In the 2nd month and 6th month of HGF practice. The results indicated that VO2 decreased after 2 and 6 months HGF practice, and the effect even persisted to 30 minutes after HGF exercise, indicating that HGF may reduce metabolic rate and decrease the oxygen consumption of body. The possible mechanism was discussed. MVV had an up tendency after HGF practice, which suggested the possibility of strengthening respiratory muscle by HGF. HGF may be a good physical exercise and can induce a wakeful hypometabolic physiologic state.

Adult↗
PubMed1993

[A comparative study on the nasolance and graph pattern of cleft palate patients before and after operation].

The aim of the present study is to compare the nasolance score and graphic pattern of the nasometric registration before and after cleft palate repair. Sixty cleft palate patients were studied with nasometer. One month after operation the nasolance is significantly lower as compared with the preoperation sequence and the number of "up and down" pattern has increased significantly. These results indicate that the velopharygeal function starts to recover one month after operation and the speech training can be given at the mean time. The speech results should be assessed at least three months after operation.

Adolescent↗
PubMed1993

Pathologic changes of mammillary body in clinical and experimental brain hemorrhage.

The histomorphologic changes of the mammillary bodies (MB) in 31 patients and 8 spontaneously hypertensive rats with brain hemorrhage were studied by light and electron microscopy. The results showed that the frequency of the ischemic change neurons in medial nucleus in MB is much higher than that in hippocampal CA1 section and multiplicated double-deck or multistratum basal lamina formed a network or branch pattern, which indicate that MB may be of important function.

Adult↗
PubMed1993

[Preconcentration of trace Fe, Mn, Cu and Cd in water with charcoal and determination by flame atomic absorption spectroscopy].

The absorption of Fe, Mn, Cu and Cd by charcoal and the influence of pH, particle size and temperature on absorption were studied. A method for the preconcentration of these irons in water was established, and with flame atomic absorption spectroscopy a content as low as microgram/L could be determined. The recovery and the coefficient of variance (n = 6) were in the range of 90-113% and 2.6-9.9%, respectively. The proposed method is simple, rapid, accurate reproducible and suitable for the preconcentration and determination of titled metal irons in different kinds of water.

Cadmium↗
PubMed1992

A novel B cell-derived coactivator potentiates the activation of immunoglobulin promoters by octamer-binding transcription factors.

A novel B cell-restricted activity, required for high levels of octamer/Oct-dependent transcription from an immunoglobulin heavy chain (IgH) promoter, was detected in an in vitro system consisting of HeLa cell-derived extracts complemented with fractionated B cell nuclear proteins. The factor responsible for this activity was designated Oct coactivator from B cells (OCA-B). OCA-B stimulates the transcription from an IgH promoter in conjunction with either Oct-1 or Oct-2 but shows no significant effect on the octamer/Oct-dependent transcription of the ubiquitously expressed histone H2B promoter and the transcription of USF- and Sp1-regulated promoters. Taken together, our results suggest that OCA-B is a tissue-, promoter-, and factor-specific coactivator and that OCA-B may be a major determinant for B cell-specific activation of immunoglobulin promoters. In light of the evidence showing physical and functional interactions between Oct factors and OCA-B, we propose a mechanism of action for OCA-B and discuss the implications of OCA-B for the transcriptional regulation of other tissue-specific promoters.

B-Lymphocytes↗
PubMed1992

Preliminary crystallographic analyses of the N-terminal lobe of recombinant human serum transferrin.

The N-terminal lobe of recombinant human serum transferrin (residues 1 to 337) has been crystallized in a form suitable for high-resolution three-dimensional X-ray crystallographic analyses. Crystals are of the orthorhombic space group P2(1)2(1)2(1), with unit cell dimensions of a = 44.9 A, b = 57.0 A and c = 135.9 A, and diffract to beyond 2 A resolution. Further studies show that isomorphous crystals of specifically designed mutants of this protein can also be grown. Structural studies of both recombinant and mutant protein forms will provide a basis for understanding the mechanism by which human serum transferrin functions.

Crystallization↗
PubMed1992

Effects of atropine on hippocampal theta cells and complex-spike cells.

The medial septal nuclei are essential for the naturally occurring hippocampal theta rhythm. Evidence that the rhythmic activity of the septum is carried via cholinergic afferents to the hippocampus has been: (a) the existence of a cholinergic septo-hippocampal projection, and (b) the sensitivity of one type of theta rhythm to antimuscarinic agents or cholinergic depletion. The muscarinic action of acetylcholine on pyramidal cells, however, is too slow to carry even a 4 Hz signal. Recent in vitro studies have confirmed a fast excitatory response by some hippocampal interneurons to muscarinic agonists. In urethane anesthetized rats, iontophoretic application of atropine to 17 hippocampal theta cells (presumed interneurons) during the theta rhythm, reduced their firing rates to an average of 24% of control rates. The effect of iontophoretic atropine application to 4 CA1 complex-spike cells (presumed pyramidal cells) was a selective elimination of their bursting activity with no significant effect on overall firing rate. The data suggest that: (1) interneuronal firing, during the hippocampal theta rhythm, is dominated by an excitatory cholinergic input and not by excitatory collaterals of pyramidal cells; and (2) somatic burst firing by CA1 pyramidal cells requires the presence of acetylcholine.

Acetylcholine↗