Biomedical subjects

L Luo

Publications and source records attributed to L Luo.

At least 163 records · Page 9Linked to original sources

PubMed1998

[Hepatitis B virus antigen-induced specific TCR V beta gene subfamily amplifications and their diversity].

The human immune system confronts various antigens, then the recognitive structures of T lymphocytes must be diverse. In this study, we analyzed the TCR V beta 1-20 gene repertoire by reverse transcription-polymerase chain reaction (RT-PCR) in peripheral blood lymphocytes (PBLs) from individuals vaccinated with recombinant hepatitis B vaccine and PBLs from healthy donors stimulated by supernatants of the HepG2 2215 cell line transfected by HBV-DNA. The specific amplifications of V beta 6, 14, V beta 6, 15 were observed in PBLs after vaccination and stimulation by HepG2 2215 cell line respectively. The results suggest that the V beta segments may be the specific recognitive units for these antigens and involved in restriction and cytotoxicity.

Cells, Cultured↗

PubMed1998

[Application of constrained simulated annealing to 3D stereotactic radiotherapy treatment planning].

In this paper, linear programming and constrained simulated annealing are combined to optimize X-knife stereotactic radiotherapy treatment planning. In the first phase, linear programming reduces the resolution space, which is favourable to the adoption of little granularity in the second phase. Our experiment demonstrates that after the two-phase optimization, we attain the expected result.

Algorithms↗

PubMed1997

Genghis Khan (Gek) as a putative effector for Drosophila Cdc42 and regulator of actin polymerization.

The small GTPases Cdc42 and Rac regulate a variety of biological processes, including actin polymerization, cell proliferation, and JNK/mitogen-activated protein kinase activation, conceivably via distinct effectors. Whereas the effector for mitogen-activated protein kinase activation appears to be p65PAK, the identity of effector(s) for actin polymerization remains unclear. We have found a putative effector for Drosophila Cdc42, Genghis Khan (Gek), which binds to Dcdc42 in a GTP-dependent and effector domain-dependent manner. Gek contains a predicted serine/threonine kinase catalytic domain that is 63% identical to human myotonic dystrophy protein kinase and has protein kinase activities. It also possesses a large coiled-coil domain, a putative phorbol ester binding domain, a pleckstrin homology domain, and a Cdc42 binding consensus sequence that is required for its binding to Dcdc42. To study the in vivo function of gek, we generated mutations in the Drosophila gek locus. Egg chambers homozygous for gek mutations exhibit abnormal accumulation of F-actin and are defective in producing fertilized eggs. These phenotypes can be rescued by a wild-type gek transgene. Our results suggest that this multidomain protein kinase is an effector for the regulation of actin polymerization by Cdc42.

Actins↗

PubMed1997

The preferential mode analysis of DNA sequence.

After reviewing approaches to the nucleotide correlation of DNA sequences the preferential mode analysis method is emphasized and discussed in detail. The preferred modes and poor modes in coding regions, as well as in introns, 5'-caps and 3'-tails are found through the statistical analysis of sequence data of all kinds of species in GenBank. The relation between the preferential mode analysis and informational parameter method is deduced. It is discovered that in higher species the coding sequences preferentially use the strong-weak bond (strong bond=C,G; weak bond=A, T) language and many noncoding regions (introns, 5'-caps, 3'-tails) use purine-pyrimidine language. The application of different languages in coding and noncoding sequences is a result of evolution, and it may be related to the functional differences in these two regions. Furthermore, we find that many preferential triplets in coding sequences can be expressed in a form of (* W S) (W=A,T; S=C,G), which may be explained by its relation to t-RNA abundance. The systematic change of some mode contents with evolution has also been found.

Animals↗

PubMed1997

Clinical treatment planning optimization by Powell's method for gamma unit treatment system.

PURPOSE: This article presents a new optimization method for stereotactic radiosurgery treatment planning for gamma unit treatment system. METHODS AND MATERIALS: The gamma unit has been utilized in stereotactic radiosurgery for about 30 years, but the usual procedure for a physician-physicist team to design a treatment plan is a trial-and-error approach. Isodose curves are viewed on two-dimensional computed tomography (CT) or magnetic resonance (MR) image planes, which is not only time consuming but also seldom achieves the optimal treatment plan, especially when the isocenter weights are regarded. We developed a treatment-planning system on a computer workstation in which Powell's optimization method is realized. The optimization process starts with the initial parameters (the number of isocenters as well as corresponding 3D isocenters' coordinates, collimator sizes, and weight factors) roughly determined by the physician-physicist team. The objective function can be changed to consider protection of sensitive tissues. RESULTS: We use the plan parameters given by a well-trained physician-physicist team, or ones that the author give roughly as the initial parameters for the optimization procedure. Dosimetric results of optimization show a better high dose-volume conformation to the target volume compared to the doctor's plan. CONCLUSION: This method converges quickly and is not sensitive to the initial parameters. It achieves an excellent conformation of the estimated isodose curves with the contours of the target volume. If the initial parameters are varied, there will be a little difference in parameters' configuration, but the dosimetric results proved almost to be the same.

Algorithms↗

PubMed1997

Interleukin 1-induced calcium signalling in chondrocytes requires focal adhesions.

The cytokine interleukin 1 (IL-1) is an important mediator of connective-tissue destruction in arthritic joints but the mechanisms by which IL-1 mediates signal transduction in chondrocytes is poorly understood. Previous results have indicated that IL-1 receptors co-localize with focal adhesions [Qwarnstrom, Page, Gillis and Dower (1988) J. Biol. Chem. 263, 8261-8269], discrete adhesive domains of cells that function in cell attachment and possibly in signal transduction. We have determined whether focal adhesions restrict IL-1-induced Ca2+ signalling in primary cultures of bovine chondrocytes. In cells grown for 24 h on fibronectin, the basal intracellular Ca2+ ion concentration ([Ca2+]i) was 100+/-3 nM. Optimal increases of [Ca2+]i above baseline were induced by 10 nM IL-1 (183+/-30 nM above baseline). There was no significant difference between cells plated on fibronectin or type II collagen (P>0.2; 233+/-90 nM above baseline). Ca2+ transients were significantly decreased by the inclusion of 0.5 mM EGTA in the bathing buffer (74+/-11 nM above baseline), and 1 microM thapsigargin completely blocked Ca2+ transients. Cells plated on poly-(l-lysine) or suspended cells showed no Ca2+ increases, whereas cells grown on fibronectin exhibited IL-1-induced Ca2+ responses that corresponded temporally to the time-dependent cell spreading after plating on fibronectin. Cells plated on poly-(l-lysine) and incubated with fibronectin-coated beads exhibited vinculin staining in association with the beads. In identical cell preparations, IL-1 induced a 136+/-39 nM increase of [Ca2+]i above baseline in response to 10 nM IL-1beta. There were no IL-1-induced Ca2+ increases when cells on poly-(l-lysine) were incubated with fibronectin-coated beads for only 15 min at 37 degrees C, in cells maintained for 3 h at 4 degrees C, in cells incubated with BSA beads for 3 h at 37 degrees C, or in cells pretreated with cytochalasin D. Labelling of IL-1 receptors with 125I-IL-1beta showed 3-fold more specific labelling of focal adhesion complexes in cells incubated with fibronectin-coated beads compared with cells incubated with BSA-coated beads, indicating that IL-1 receptor binding or the number of IL-1 receptors was increased in focal adhesions. These results indicate that, in chondrocytes, IL-1-induced Ca2+ signalling is dependent on focal adhesion formation and that focal adhesions recruit IL-1 receptors by redistribution in the cell membrane.

Animals↗

PubMed1997

Mutation pattern in the Bruton's tyrosine kinase gene in 26 unrelated patients with X-linked agammaglobulinemia.

Mutation pattern was characterized in the Bruton's tyrosine kinase gene (BTK) in 26 patients with X-linked agammaglobulinemia, the first described immunoglobulin deficiency, and was related to BTK expression. A total of 24 different mutations were identified. Most BTK mutations were found to result in premature termination of the translation product. Mutations were detected in most BTK exons with a predominance of frameshift and nonsense mutations in the 5' end of the gene and missense mutations in its 3' part, corresponding to the catalytic domain of the enzyme. Nonsense and frameshift mutations were associated with diminished levels of BTK mRNA expression, except for a frameshift mutation in exon 17 and two nonsense mutations in exon 2, indicating that these cases are not confined to penultimate exons. One amino acid substitution (R28H) was found in the pleckstrin homology domain's residue, which is mutated in mice bearing the X-linked immunodeficiency phenotype; another substitution (R307G) was identified in the src homology domain 2. All remaining amino acid substitutions were found in the catalytic domain of Btk.

Agammaglobulinaemia Tyrosine Kinase↗

PubMed1997

The protective role of selenium on the toxicity of cisplatin-contained chemotherapy regimen in cancer patients.

The effect of selenium (Se) in reducing the toxicity of cisplatin in cancer patients was studied. Forty-one patients were randomized into group A (20 patients with Se administration in first cycle of chemotherapy as study cases and without Se in second cycle of chemotherapy as control) and group B (21 patients without Se in first cycle of chemotherapy and with Se in second cycle of chemotherapy). The 4000 micrograms per day of Se as Seleno-Kappacarrageenan were administered from 4 before to 4 d after chemotherapy for study cases. The serum Se increased from 70.4 +/- 22.86 to 157.04 +/- 60.23 ng/mL (P < 0.001) in patients received Se. The cisplatin dosage was iv administration in 60-80 mg/m2 on the first day. The results showed that the peripheral WBC counts on day 14 after initiation of chemotherapy in study cases was significantly higher than the controls (3.35 +/- 2.01 vs 2.31 +/- 1.38 [x10(9)L])/L, p < 0.05). On the other hand, the consumption of GCSF for the cases was significantly less than the controls (110.1 +/- 82.2 vs 723.6 +/- 192.6 IU, p < 0.05). The volumes of blood transfusion for the study group were also significantly less than the controls (0 vs 62 +/- 38 mL, p < 0.05). The nephrotoxicity of cisplatin was measured by urine enzymes (NAG, GGT, AAP, LAP, and ALP) were determined prior to and at 2, 24, 48, and 72 h after initiation of chemotherapy. The urine enzymes NAG, GGT, AAP, and ALP after chemotherapy for cases were significantly lower than the controls. No toxicity of Seleno-Kappacarrageenan was noted. The above results suggest that the Se can be used as an agent for reducing the nephrotoxicity and bone marrow suppression induced by cisplatin.

Administration, Oral↗

PubMed1997

Rho family GTP-binding proteins in growth cone signalling.

Rho family GTP-binding proteins regulate various aspects of the actin cytoskeleton in a wide variety of organisms. Recent evidence suggests that they may also be important components of the signalling pathways that link the reception of extracellular cues to the regulation of the cytoskeleton in neuronal growth cones.

Actins↗

PubMed1997

Clustering of missense mutations in the ataxia-telangiectasia gene in a sporadic T-cell leukaemia.

Ataxia-telangiectasia (A-T) is a recessive multi-system disorder caused by mutations in the ATM gene at 11q22-q23 (ref. 3). The risk of cancer, especially lymphoid neoplasias, is substantially elevated in A-T patients and has long been associated with chromosomal instability. By analysing tumour DNA from patients with sporadic T-cell prolymphocytic leukaemia (T-PLL), a rare clonal malignancy with similarities to a mature T-cell leukaemia seen in A-T, we demonstrate a high frequency of ATM mutations in T-PLL. In marked contrast to the ATM mutation pattern in A-T, the most frequent nucleotide changes in this leukaemia were missense mutations. These clustered in the region corresponding to the kinase domain, which is highly conserved in ATM-related proteins in mouse, yeast and Drosophila. The resulting amino-acid substitutions are predicted to interfere with ATP binding or substrate recognition. Two of seventeen mutated T-PLL samples had a previously reported A-T allele. In contrast, no mutations were detected in the p53 gene, suggesting that this tumour suppressor is not frequently altered in this leukaemia. Occasional missense mutations in ATM were also found in tumour DNA from patients with B-cell non-Hodgkin's lymphomas (B-NHL) and a B-NHL cell line. The evidence of a significant proportion of loss-of-function mutations and a complete absence of the normal copy of ATM in the majority of mutated tumours establishes somatic inactivation of this gene in the pathogenesis of sporadic T-PLL and suggests that ATM acts as a tumour suppressor. As constitutional DNA was not available, a putative hereditary predisposition to T-PLL will require further investigation.

Amino Acid Sequence↗

PubMed1997

Spinal strychnine alters response properties of nociceptive-specific neurons in rat medial thalamus.

Experiments in both conscious and anesthetized animals indicate that intrathecal (i.t.) strychnine (STR; glycine receptor antagonist) produces acute, reversible allodynia, as evidenced by inappropriate behavioral and autonomic responses to cutaneous tactile stimuli. Although STR is known to produce disinhibition of afferent input to the spinal cord, changes in spinal reflexes cannot fully explain the complex behaviors observed following i.t. STR. Which supraspinal sites are involved in STR-dependent allodynia and how this abnormal somatosensory message is relayed to these sites remain to be determined. The medial thalamus contains many nociceptive-specific (NS) neurons and is believed to be involved in mediating the affective-motivational aspects of pain. It is thus important to determine whether spinally administered STR elicits changes in the responses of medial thalamic NS neurons. Extracellular single-unit recordings were conducted in urethan-anesthetized rats (290-490 g). A detailed characterization of 20 thalamic NS units (1 per rat; 2 in 1 case) was conducted before and immediately after i.t. STR (40 microg). Initially, all of the units in this study were classified as NS, because they were excited by noxious pinch but not by innocuous tactile stimuli. After i.t. STR, all (formerly NS) units exhibited significant responses to innocuous tactile stimuli (brush and/or air jet) applied to lumbar or sacral dermatomes. This effect of STR on thalamic NS neurons was acute and reversible. The majority of units (11 of 20) also exhibited an increase in spontaneous firing rate. Although the complete pinch receptive field (RF) could not be determined for all units, the available data indicate that the RFs for brush stimulation after i.t. STR were substantially different from the pre-STR pinch RFs for all but three units. The same i.t. STR injection that caused the observed changes in medial thalamus also produced allodynia, in the form of brush-evoked cardiovascular or motor responses, in 18 of the 19 rats. The ability of NS cells in medial thalamus to respond to tactile input after i.t. STR suggests that the STR lowers the threshold of nociceptive neurons that project directly and/or indirectly to medial thalamus. These observations suggest that ascending nociceptive pathways and medial thalamic structures contribute to the expression of STR-dependent allodynia.

Animals↗

PubMed1997

Altered receptive fields and sensory modalities of rat VPL thalamic neurons during spinal strychnine-induced allodynia.

Altered receptive fields and sensory modalities of rat VPL thalamic neurons during spinal strychnine-induced allodynia. J. Neurophysiol. 78: 2296-2308, 1997. Allodynia is an unpleasant sequela of neural injury or neuropathy that is characterized by the inappropriate perception of light tactile stimuli as pain. This condition may be modeled experimentally in animals by the intrathecal (i.t.) administration of strychnine, a glycine receptor antagonist. Thus after i.t. strychnine, otherwise innocuous tactile stimuli evoke behavioral and autonomic responses that normally are elicited only by noxious stimuli. The current study was undertaken to determine how i.t. strychnine alters the spinal processing of somatosensory input by examining the responses of neurons in the ventroposterolateral thalamic nucleus. Extracellular, single-unit recordings were conducted in the lateral thalamus of 19 urethan-anaesthetized, male, Wistar rats (342 +/- 44 g; mean +/- SD). Receptive fields and responses to noxious and innocuous cutaneous stimuli were determined for 19 units (1 per animal) before and immediately after i.t. strychnine (40 microgram). Eighteen of the animals developed allodynia as evidenced by the ability of otherwise innocuous brush or air jet stimuli to evoke cardiovascular and/or motor reflexes. All (3) of the nociceptive-specific units became responsive to brush stimulation after i.t. strychnine, and one became sensitive to brushing over an expanded receptive field. Expansion of the receptive field, as determined by brush stimulation, also was exhibited by all of the low-threshold mechanoreceptive units (14) and wide dynamic range units (2) after i.t. strychnine. The use of air jet stimuli at fixed cutaneous sites also provided evidence of receptive field expansion, because significant unit responses to air jet developed at 13 cutaneous sites (on 7 animals) where an identical stimulus was ineffective in evoking a unit response before i.t. strychnine. However, the magnitude of the unit response to cutaneous air jet stimulation was not changed at sites that already had been sensitive to this stimulus before i.t. strychnine. The onset of allodynia corresponded with the onset of the altered unit responses (i.e., lowered threshold/receptive field expansion) for the majority of animals (9), but the altered unit response either terminated concurrently with symptoms of allodynia (6) or, more frequently, outlasted the symptoms of allodynia (10) as the effects of strychnine declined. The present results demonstrate that the direct, receptor-mediated actions of strychnine on the spinal processing of sensory information are reflected by changes in the receptive fields and response properties of nociceptive and nonnociceptive thalamic neurons. These changes are consistent with the involvement of thalamocortical mechanisms in the expression of strychnine-induced allodynia and, moreover, suggest that i.t. strychnine also produces changes in innocuous tactile sensation.

Animals↗

PubMed1997

Clinical observation of Chinese drugs in prevention of neonatal hyperbilirubinemia.

Observation of the preventive and curative effects of Herba Artemisiae Scopariae [symbol: see text], Fructus Gardeniae [symbol: see text], Radix Scutellariae [symbol: see text] and Radix et Rhizoma Rhei Preparata [symbol: see text] in 30 cases of neonatal hyperbilirubinemia showed that both the peak value of serum total bilirubin and the incidence of hyperbilirubinemia were obviously lower than that in the control group.

ABO Blood-Group System↗

PubMed1997

[Clinical experience in the treatment of chronic radiation ulcer in 32 cases].

A retrospective study was carried out, aiming at a proper treatment to the chronic radiation ulcer that is often difficult to deal with. Thirty-two cases of chronic radiation ulcer have been treated in the department since 1983. The cause, site, features and method of treatment were summarized. Thirty-one cases were cured, 26 cases healed by the first intention, 5 cases healed by the second intention. One died. It is emphasized that more knowledge should be gained for understanding and treatment of the chronic radiation ulcer. Different methods of debridement and repair should be performed according to the site, depth and pathologic features of the ulcer. To improve local circulation, an island flap is the first choice of treatment.

Breast Neoplasms↗

PubMed1997

[Effect of acute moderate isovolumic hemodilution on the pharmacokinetics of vecuronium].

OBJECTIVE: To determine the effect of acute moderate isovolemic hemodilution on pharmacokinetics of vecuronium. METHODS: Twenty-six adult patients, ASA grade I, undergoing elective plastic surgery, were randomly divided equally into the control and hemodilution group. The blood samples were taken for 5 hours following intravenous bolus of 100 micrograms/kg of vecuronium in two groups. The plasma concentrations of vecuronium were determined with an improved fluorometry and the pharmacokinetic parameters were obtained by fitting the data with a 3P87 program. RESULTS: The disposition of vecuronium can be best described by a three compartment open model. As comparison with the control group, the values of Vc and Vdss in hemodilution group were greater than that in the control, while T1/2 beta was markedly prolonged in this group. There were no significant differences in T1/2 phi, T1/2 alpha, K12, K21, K13, K31, K10, MRT, AUC, and Cl between the two groups. CONCLUSION: Acute moderate isovolemic hemodilution could change the pharmacokinetics of vecurinium, particularly in distribution and elimination phases.

Adolescent↗

PubMed1997

[MA891--an established spontaneous mouse mammary adenocarcinoma cell line and its immunologic characteristics].

OBJECTIVE: To characterize the immunologic properties of an established mouse mammary tumor cell line MA891. METHODS: From a spontaneous mouse mammary adenocarcionma (TA2 MA891) of TA2 mouse origin, an in vitro passaged cell line MA891 was maintained in RPMI1640 with 10% new born calf serum. The immunogenecity of MA891 was studied by classical tumor transplantation rejection assay, generation of cytotoxic T lymphocytes (CTL) by syngeneic secondary mixed lymphocyte-tumor cell culture (MLTC) and cytotoxic assay of tumor infiltrating lymphocytes (TIL). RESULTS: MA891 maintained the high metastatic potential of the parental TA2 MA891 tumor passaged in vivo. Transplantation rejection studies indicated that amputation of a hind limb with growing tumor in the footpad did not protect the mice from a second subcutaneous challenge of the same tumor. The cytotoxic activities of both CTL and TIL were shown to be very weak. CONCLUSION: MA891 is a mouse tumor of very low immunogenecity. It can be used as a mouse tumor model for studying cancer metastasis in humans.

Adenocarcinoma↗

PubMed1997

[Modulation of invasiveness and invasion/metastasis-associated gene expression of a mouse mammary adenocarcinoma by interferons].

OBJECTIVE: To investigate the effects of IFNs on the in vitro invasiveness and the expression of several genes related to invasion and metastatic behavior of MA-891 cells. METHODS: The invasiveness was assessed by penetration through a matrigel-coated filter. Cell surface antigen and mRNA levels were analyzed by flow cytometry and Northern blot respectively. RESULTS: IFN-gamma pretreatment increased the invasiveness of MA-891 (P < 0.01). Pretreatment with IFN-alpha decreased the invasiveness of cells, but it was not statistically significant. Cell surface ICAM-1 was not found on MA-891 cells even after treatment with IFN-alpha, but was strongly induced after IFN-gamma treatment. Another adhesion molecule CD44v mRNA, absent on MA-891 cells, could not be induced to express by either IFN. Both 72,000 and 92,000 type IV collagenase mRNAs were detectable in MA-891 cells. The 72 kD-type IV collagenase expression was up-regulated by IFN-gamma and IFN-alpha, but the levels of expression were significantly higher in cells treated with IFN-gamma than those treated with IFN-alpha. IFN-gamma and IFN-alpha treatment had little or no effect on expression of the 92,000 type IV collagenase. Treatment with IFN-gamma had no effects on antimetastasis nm23 gene expression whereas treatment with IFN-alpha resulted in marked up-regulation of its expression. CONCLUSION: IFN-gamma and IFN-alpha differ in their effects on the expression of genes related to invasion and metastasis of MA-891 cells, thereby differentially modulating metastatic potential.

3T3 Cells↗

PubMed1997

[Prediction and binding of a mutant p53 peptide to MHC class I molecule].

OBJECTIVE: To predict tumor antigenic peptides from the intact amino acid sequence of tumor antigens, thereby providing a guide to the design and development of tumor peptide-based vaccines. METHODS: Antigenic peptides were predicted by using a computer program PEPMOTIF based on MHC class I allele-specific consensus motifs; and a scoring system was established to assess the likelihood of the peptides to bind to MHC class I molecules. MHC class I-peptide binding assay and MHC class I-peptide stabilization assay were used to determine the binding ability and affinity of the predicted peptides. RESULTS: Three peptides derived from mouse mutant p53 were predicted. mp53P132F(LNKLFFQL) was shown to bind to H-2Kb, but not H-2Db. mp53P246S (MGGMNRSPIL) and mp53P270C (GRDSFEVCV) bound to neither H-2Kb nor H-2Db. A relationship was found between peptide scores and binding of the peptides to the relevant MHC class I molecules. CONCLUSION: The computer program PEPMOTIF combining with a scoring system is a simple and efficient tool for predicting MHC class I binding peptides derived from antigenic proteins.

Animals↗