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Biomedical subjects

C Li

Publications and source records attributed to C Li.

At least 1,117 records · Page 62Linked to original sources
PubMed1992

Characterization and chromosomal mapping of the gene encoding the cellular DNA binding protein HTLF.

A region of the human T-cell leukemia virus long terminal repeat (HTLV-I LTR) located between -155 and -117 is important in the regulation of gene expression by the ets family of transcription factors. In an attempt to identify additional cellular transcription factors that bind to this portion of the HTLV-I LTR, we used lambda gt11 expression cloning with oligonucleotides corresponding to this element. A 1239-bp cDNA was isolated from a Jurkat cDNA library, which encoded a protein capable of binding to this purine-rich region. This protein, which we designated human T-cell leukemia virus enhancer factor (HTLF), contains a domain with homology to the recently described fork head DNA binding domain. Chromosome mapping of the HTLF gene demonstrated that it was localized to human chromosome 2p16-p22. HTLF is a unique cellular gene that may function in the transcriptional regulation of HTLV-I LTR.

Amino Acid Sequence↗
PubMed1992

Characterization and chromosomal mapping of the gene encoding the cellular DNA binding protein ILF.

Recently we isolated a cellular DNA binding protein, designated interleukin enhancer binding factor (ILF), that binds to purine-rich regulatory motifs in both the HIV-1 LTR and the IL2 promoter. Further analysis of the ILF gene reveals the existence of two mRNA species, both of which encode proteins containing the recently described fork head DNA binding domain. Gel retardation analysis demonstrates that the portion of the ILF protein with homology to the fork head domain is sufficient to mediate DNA binding to a number of related purine-rich sequences. ILF mRNA is expressed constitutively in both lymphoid and nonlymphoid tissues. Chromosomal mapping localizes the ILF gene to human chromosome 17q25, which is a site of chromosomal translocations in some cases of human acute myelogous leukemias. These studies further characterize the structure of the cellular DNA binding protein ILF and may prove valuable in the molecular analysis of possible translocations affecting this gene.

Amino Acid Sequence↗
PubMed1992

Experimental studies on penetrating heterokeratoplasty with human corneal grafts in monkey eyes.

In nine rhesus monkeys, human corneal grafts were used for penetrating keratoplasty in one eye of each. The data were divided into three groups according to the size of grafts. Group 1 (n = 3) received 5.5-mm human corneal grafts in 5.0-mm recipient beds; group 2 (n = 3) received 6.2-mm human corneal grafts in 6.0-mm beds; and group 3 (n = 3) received 7.5-mm grafts in 7.0-mm beds. Five of nine eyes in groups 1 and 2 (55%) maintained graft clarity for more than 1 year, but only two of the three in group 1 maintained clear human corneal grafts for 32 and 36 months, respectively. However, the three grafts in the third group maintained transparency for only 4-7 months. Our findings suggest that xenogeneic corneal grafts may have a greater success rate in humans than previously believed.

Adolescent↗
PubMed1992

Terrestrial gamma radiation dose in Hong Kong.

The first reactor of the Daya Bay nuclear power plant, 30 km from Hong Kong, is expected to begin operation in 1992. As a result, residents in Hong Kong are concerned with potential exposure to man-made and natural radiation. Therefore, the Radioisotope Unit of the University of Hong Kong performed studies to estimate Hong Kong's natural background radiation and the potential exposure to local residents, the results of which are presented here.

Background Radiation↗
PubMed1992

Characterization of gene organization and promoter region of the rat dopamine D1 receptor gene.

Genomic and cDNA clones encoding the rat D1 receptor were isolated and sequenced. Comparison of the D1 receptor cDNA and genomic sequences revealed that the rat D1 receptor gene is organized into two exons separated by a small intron in the 5' untranslated region of its mRNA. The transcription start site is located 864 bp upstream from the translational initiation site. The 5'-flanking sequences of the D1 receptor gene do not contain TATA and CAAT canonical sequences, but have a high G+C content, potential cyclic AMP and glucocorticoid response element sequences, and binding sites for transcription factors such as Sp1, Ap1, and Ap2. Transfection studies using the D1 5'-flanking sequence and CAT gene fusion constructs have demonstrated that (1) the D1 promoter is active in D1-expressing neuroblastoma NS20Y cells, but inactive in D1-deficient glioma C6 and kidney 293 cells, (2) the information contained within 735 bp of 5'-flanking sequence of the D1 gene appears to be sufficient to confer its cell-specific expression, and (3) the D1 gene promoter responds to cyclic AMP induction, suggesting the existence of an auto-regulation mechanism by which the stimulation of D1 receptor exerts a positive feedback on its own gene expression.

Amino Acid Sequence↗
PubMed1992

Pericardiovascular approach to cardiac assist: acute feasibility study.

We tested the hypothesis that external synchronized compression of the cardiovascular system can achieve effective hemodynamic assistance while circumventing problems associated with the blood-polymer interface in traditional cardiac assist devices. Ten dogs were studied to develop and test prototype devices and evaluate their hemodynamic effectiveness. Copulsation assistance was studied in animals with fibrillating hearts using Anstadt pericardiac cups. Mean systolic arterial pressure of 81.2 mm Hg and cardiac output of 2.9 L/min were achieved. Counterpulsation assistance was studied by inflating during diastole a balloon placed between the thoracic aorta and periaortic sheath and deflating the balloon during systole. In 4 dogs, 25 +/- 8.6% (SEM) of diastolic augmentation and 8.3 +/- 1.2% of systolic unloading were achieved. These preliminary results indicate the feasibility of a pericardiovascular approach to cardiac assistance. Further device development and the integration of copulsation and counterpulsation may improve cardiac output, reduce cardiac afterload, augment coronary perfusion, and ultimately benefit patients with severe heart failure.

Animals↗
PubMed1992

Distribution of an L-isoaspartyl protein methyltransferase in eubacteria.

A protein carboxyl methyltransferase (EC 2.1.1.77) that recognizes age-damaged proteins for potential repair or degradation reactions has been found in all vertebrate tissues and cells examined to date. This enzyme catalyzes the transfer of methyl groups from S-adenosylmethionine to the carboxyl groups of D-aspartyl or L-isoaspartyl residues that are formed spontaneously from normal L-aspartyl and L-asparaginyl residues. A similar methyltransferase has been found in two bacterial species, Escherichia coli and Salmonella typhimurium, suggesting that this enzyme performs an essential function in all cells. In this study, we show that this enzyme is present in cytosolic extracts of six additional members of the alpha and gamma subdivisions of the purple bacteria: Pseudomonas aeruginosa (gamma), Rhodobacter sphaeroides (alpha), and the gamma enteric species Klebsiella pneumoniae, Enterobacter aerogenes, Proteus vulgaris, and Serratia marcescens. DNA probes from the E. coli methyltransferase gene hybridized only to the chromosomal DNA of the enteric species. Interestingly, no activity was found in the plant pathogen Erwinia chrysanthemi, a member of the enteric family, nor in Rhizobium meliloti or Rhodopseudomonas palustris, two members of the alpha subdivision. Additionally, we could not detect activity in the four gram-positive species Bacillus subtilis, B. stearothermophilus, Lactobacillus casei, and Streptomyces griseus. The absence of enzyme activity was not due to the presence of inhibitors in the extracts. These results suggest that many cells may not have the enzymatic machinery to recognize abnormal aspartyl residues by methylation reactions. Since the nonenzymatic degradation reactions that generate these residues occur in all cells, other pathways may be present in nature to ensure that these types of altered proteins do not accumulate and interfere with normal cellular physiology.

Amino Acid Sequence↗
PubMed1992

Acute pulmonary edema induced by overdosage of phenothiazines.

Three schizophrenic adults with previous histories of using phenothiazine derivatives developed acute pulmonary edema after taking large amounts of these drugs. The clinical manifestations included coma (three), hypothermia (two), tachycardia (two), miosis (two) and hypotension (one). All three patients underwent gastric lavage and were treated supportively. The fulminant pulmonary edema in the three cases resolved within 18 to 40 h. The etiology of pulmonary edema following overdosage of phenothiazines remains unknown. The authors hypothesize that the most likely pathogenesis is a drug-induced neurogenic pulmonary edema resulting from a disturbance of hypothalamic function.

Acute Disease↗
PubMed1992

Tissue compatibility of tyrosine-derived polycarbonates and polyiminocarbonates: an initial evaluation.

Compression-molded disks of two tyrosine-derived polymers [poly(desaminotyrosyl-tyrosine-hexyl ester carbonate) and poly(desaminotyrosyl-tyrosine hexyl ester iminocarbonate)], two polymers derived from Bisphenol A [poly(Bisphenol A iminocarbonate) and poly(Bisphenol A N-phenyliminocarbonate)], and two clinically used standard materials [poly(D,L-lactic acid) and high-density polyethylene] were implanted subcutaneously in the back of Sprague-Dawley rats. The tissue response elicited by these materials was evaluated histologically at 7, 30, and 120 days postimplantation, based on the total cell density (including fibroblasts, monocytes, giant cells, and macrophages) at the implantation site. The tissue response observed for the two tyrosine-derived polymers was mild, comparable to the two standard materials, medical-grade poly(L-lactic acid) and high density polyethylene. The two Bisphenol A-containing polymers elicited significantly more severe tissue responses. These results indicate that the use of derivatives of the natural amino acid L-tyrosine in the synthesis of degradable implant materials improved the tissue compatibility of these materials relative to chemically related polymers that contain Bisphenol A, an industrial diphenol. The tyrosine-derived polyiminocarbonate and polycarbonate are therefore promising candidates for a detailed evaluation of their biocompatibility, including long-term implantation studies in higher mammals.

Animals↗
PubMed1992

[The risk factors of proliferative vitreoretinopathy after operation of retinal detachment].

160 failure cases (160 eyes) following retinal reattachment surgery were reviewed. 62 cases with proliferative vitreoretinopathy were divided into proliferative vitreoretinopathy (PVR) group, the other cases (98 cases) without PVR changes were divided into NO PVR group. The clinical characteristics of two groups were compared in order to determine the risk factors in the development of server PVR after surgical repair of retinal detachment. The study shows that retinal detachment with uveitis and low tension, preoperative and post-operative vitreous hemorrhage, multiple operations were the highly significant risk factors. Once these factors existed simultaneously, the incidence of PVR increased. The way how to prevent and decrease the occurrence of PVR were suggested in the series.

Eye Diseases↗
PubMed1992

The value of hysteroscopy in the diagnosis of infertility and habitual abortion.

Ninety cases of infertility and habitual abortion were analyzed by hysteroscopy between April 1983 and July 1990 in PUMC hospital. Abnormal changes of the uterine cavity were seen in 74.4%. The result of hysterosalpingography corresponded with that of hysteroscopy in 62.5%, and the result of B-ultrasound corresponded to that of hysteroscopy in 52.5%. The diagnosis of adhesion and polyps of the uterine cavity was made accurately by hysteroscopy, and both could be operated under hysteroscopy. After operative removal of the adhesion, an IUD should be put into the uterine cavity for 3 months. In 60 cases operations were performed during or after hysteroscopy. Of the 45 patients followed, 19 achieved pregnancy. Five patients achieved pregnancy after operative removal of the adhesion. It is concluded that hysteroscopy is more important than B-ultrasound and hysterosalpingography in the examination and treatment of infertility.

Abortion, Habitual↗
PubMed1992

[Effect of prefrontal cortex on the neuronal activity of the nucleus raphe magnus in rats].

The unit discharge of neurons in nucleus raphe magnus (NRM) were recorded with glass microelectrodes in 33 waking and tubocurarine-immobilized rats. It is observed that effects of the noxious stimulation and prefrontal cortex (PFC) stimulation on spontaneous discharges of NRM neurons and effects of PFC stimulation on noxious-evoked discharges of NRM neurons by stimulating sural nerve. The results indicated that noxious stimulation and PFC stimulation could increase spontaneous discharge of most (68.18% and 60.82% respectively) NRM neurons. It was also noted that most (49/80) NRM neurons altered their spontaneous discharge in response to noxious stimulation and PFC stimulation in a similar manner. The remainder (31/80) opposite manners. PFC stimulation could alter the response of NRM neurons to noxious stimulation. PFC stimulation could enhance or reduce noxious-evoked discharge in NRM neurons which alter their spontaneous discharge in response to noxious stimulation and PFC stimulation in a similar manner. PFC stimulation could reduce noxious-evoked discharge in NRM neurons which alter their spontaneous discharge in opposite manners. The above results suggest that PFC and NRM have a functional relation. PFC could modulate nociceptive response and it might be partly responsible for influence on activity of neurons in NRM.

Animals↗
PubMed1992

[Study on the capillary permeability of myocardium in diabetic rats].

The alteration of myocardial capillary permeability (MCP) in experimental diabetic rat was investigated by using cationic ferritin as a tracer. Diabetes was induced by injection of streptozocin (70mg/kg b.w.ip.). Vehicle injected, age and body weight-matched rats were served as the controls. The myocardial tissue was examined by the end of 2,7, and 9 months or even longer after diabetes induction. Results showed that (1) MCP was significantly increased in diabetic rats in comparing with that of the controls; (2) The increase of permeability became more pronounced with prolongation of the course of diabetes; and (3) the increase of MCP preceded the capillary basal laminar thickening demonstrated by electron microscopy. These findings suggest that increased MCP may play a role in the pathogenesis of basal laminar thickening and myocardial complications in diabetic state.

Animals↗
PubMed1992

Dynamic cardiomyoplasty for hemodynamic support during acute pulmonary hypertension. An experimental study.

The efficacy of dynamic cardiomyoplasty for hemodynamic support during acute pulmonary hypertension was studied. Five dogs underwent a right latissimus dorsi cardiomyoplasty. Each dog was later studied in a short-term experiment. A graded acute pulmonary hypertension was induced by infusion of glass microspheres into the pulmonary artery. This resulted in decrease in pulmonary artery flow, systemic pressure, and systemic flow. The cardiomyoplasty was then stimulated with a new R wave synchronous rate-responsive pulse-train stimulator (Prometheus system). This pacemaker delivers a pulse train with the duration of stimulation determined as a proportion of the RR interval. At an optimal level of hemodynamic impairment, the dynamic cardiomyoplasty was able to immediately improve pulmonary artery flow 26.4% +/- 5.84% (standard error of the mean) (p less than 0.005, paired t test), mean systemic arterial pressure 11.6% +/- 3.7% (p less than 0.05), and thoracic aortic flow 15.7% +/- 6.3% (p less than 0.05). The degree of improvement in hemodynamic variables could be correlated with the magnitude of hemodynamic impairment present (e.g., r = 0.78; p less than 0.005 for pulmonary blood flow). We conclude that a significant beneficial effect of dynamic cardiomyoplasty on hemodynamics in short-term canine pulmonary hypertension is demonstrated in this study. Thus cardiomyoplasty may be useful in patients with right heart failure associated with increased pulmonary vascular resistance.

Acute Disease↗
PubMed1992

Effects and mechanism of low [K]o on the critical potential of effective refractory period in guinea pig ventricular muscle cells.

1.5 mM KCl Tyrode's solution enabled the critical potential (-55-60 mV) of effective refractory period to shift in a positive direction in guinea pig ventricular muscle cells. In 1.5 mM KCl Tyrode's solution, the probability of testing AP's initial potential positive to -54 mV in the repolarizing phase was as high as 80% (n = 10), but the percentage in 4.5 mM [K]o group was only 11% (n = 35). The mean value of the positive shift was 30.2 +/- SD 17 mV. Testing APs had higher values of overshoots (mean = 23 +/- 13.8 mV); their mean Vmax was 98 V/s. Early after depolarization and positive inotropic effects appeared. 13.5 mM KCl, in contrast to 1.5 mM KCl, produced contrary effects. Phenomena indicated that early after depolarization in low [K]o was associated with the positive shift of critical potential of effective refractory period. Above-mentioned effects of 1.5 mM KCl could not be completely eliminated by verapamil, but could be abolished by an inactivation promoting agent of sodium channel, lidocaine 7.4 x 10(-5) M (n = 10). The results suggest that accelerating recovery time and shifting recovery potential in the positive direction of inactivated sodium channel might be the principal reasons for the effects of low [K]o. The role of the Na+ pump inhibitor, ouabain, was not similar to that of 1.5 mM KCl Tyrode's solution except for positive inotropic effect.

Animals↗
PubMed1992

Alternatively spliced transcripts of the flp-1 gene encode distinct FMRFamide-like peptides in Caenorhabditis elegans.

We have isolated and characterized several cDNAs and the corresponding genomic region of a gene encoding multiple FMRFamide-like neuropeptides from the nematode Caenorhabditis elegans. The gene, named flp-1, consists of six exons of which four encode FMRFamide-like peptides. The cDNA and genomic sequences revealed that two distinct transcripts are generated by the use of an alternative 3' splice acceptor site between exons 3 and 4. This alternative splice results in the substitution of AGSDPNFLRFG for one of the copies of SADPNFLRFG found in the other translation product. Based on PCR analysis of RNA from mixed-stage animals, both transcripts are expressed. This gene is the first example of a distinct FMRFamide-like peptide being derived from alternative splicing, suggesting a unique role for the substituted peptide in the animal.

Amino Acid Sequence↗