Biomedical subjects

H Li

Publications and source records attributed to H Li.

At least 1,423 records · Page 79Linked to original sources

PubMed1996

Factors accounting for different responses of pulmonary and cerebral vessels to hypoxia.

The roles of sympathicus, sensory neuropeptides (SNP), cyclooxygenase metabolites (COX-M), lipoxygenase metabolites (LOX-M), endothelium derived relaxing factor (EDRF), reactive oxygen (ROS) and potassium channels (PC) in the hypoxic pulmonary vasoconstriction (HPV) and hypoxic cerebral vasodilation (HCVD) were investigated in intact rats, rabbits and dogs. The results showed that during hypoxia, the excitation of sympathicus caused a constriction of both pulmonary and cerebral vessels, while SNP, EDRF and the opening of voltage sensitive PC caused the dilation of both of them; LOX-M mediated HPV and HCVD, COX-M might serve as their modulators; the blockade of ATP sensitive PC induced by hypoxia mediated HPV, but had no effect on HCVD; the reduction of O2-. in the lung might potentiate HPV, however, O2-. remained unchanged in brain during hypoxia. It is suggested that the alterations of LOX-M, ROS and the ATP sensitive PC are the factors accounting for the difference in the response of pulmonary and cerebral vessels to hypoxia.

Animals↗

PubMed1996

Treatment of tuberculous pleurisy with effusion by artificial pneumothorax.

57 patients were divided into two groups at random. The patients of two groups were all given standard treatments with anti-tuberculous drugs. Treatment group received artificial pneumothorax to help the cure. Results showed that the frequency and quantity of drawing liquid in the treatment group were obviously less than those in the control group and the duration of the complete liquid absorption was shortened markedly in the treatment group and that total effective rate in treatment group (92.5%) was obviously higher than that of the control group (83.33%). We found that the artificial pneumothorax could raise the intra-pleural pressure by 0.20-0.39 kPa, reduce leakage in parietal pleurae and increase the absorption in visceral layer evidently. As it can isolate the two layers of pleurae from one another by the air in thorax, the incidence of pleurae adhesion can be decreased.

Adolescent↗

PubMed1996

C-Ha-ras oncogene in oral leukoplakia tissues.

The amplification and the G-T mutation at codon 12 of the C-Ha-ras oncogene in oral leukoplakia tissues were analyzed by using polymerase chain reaction (PCR) and molecular biologic technique. The results showed that these tissues had no amplification of Ha-ras oncogene. Only one case harbored G-T mutation in 11 oral leukoplakias, but this mutation was absent in 10 normal oral mucosal tissues. The possible role and significance of C-Ha-ras oncogene in oral precancerous lesions were also discussed.

Base Sequence↗

PubMed1996

S103L reactive chondroitin sulfate proteoglycan (aggrecan) mRNA expressed in developing chick brain and cartilage is encoded by a single gene.

A large chondroitin sulfate proteoglycan (CSPG) identified in embryonic chick brain, and synthesized exclusively by neurons in a developmentally expressed pattern that coincides with migration and establishment of neuronal nuclei, reacts with a monoclonal antibody (S103L) developed against the cartilage-specific CSPG, aggrecan. The relationship of the brain and cartilage S103L CSPGs was established by chemical, biosynthetic and molecular analyses. Significant posttranslational differences (absence of keratan sulfate (KS), less CS, and different sulfation patterns) distinguish the brain S103L species from the cartilage S103L species. However, quantitative and qualitative Northern analysis, cassette RT-PCR and direct cloning and sequencing of the entire brain-specific S103L CSPG coding sequence, all indicate that the brain and cartilage core proteins are identical. Thus, although the S103L CSPG synthesized by chick brain and cartilage are the product of a single gene, they are clearly biochemically distinct and differentially expressed proteoglycan products, suggesting tissue specific roles for these proteoglycan homologs.

Aggrecans↗

PubMed1996

Characterization of the structure and function of the gene for transcription factor BF-1, an essential regulator of forebrain development.

Brain factor-1 (BF-1) is a winged-helix transcription factor which has been shown to be essential for the development of the cerebral hemispheres. We report here the cloning and characterization of the mouse BF-1 gene. We have identified two classes of alternatively spliced mouse BF-1 cDNA which are transcribed from distinct promoters. Both classes of cDNA encode identical BF-1 proteins. The class 1 mouse cDNA is the homolog of the previously reported rat and human BF-1 cDNAs, and accounts for about 90-95% of BF-1 expression in brain. Primer extension analyses show that the major promoter, P1, is TATA-less and has multiple transcription start sites. We identified neural cell lines which express BF-1 primarily from the P1 promoter, including the OBL21a and OBL21 cell lines derived from the olfactory bulb. Expression of BF-1 is highest in proliferating OBL21 cells, declining as the cells differentiate in vitro. This correlates well with the reduction of BF-1 expression as the cells of the telencephalic neuroepithelium differentiate. Using these cells, we demonstrate that the genomic region between -3.7kb and -79 bp upstream of the P1 promoter contains cell-specific enhancer activity in transient transfection assays.

Animals↗

PubMed1996

Cultured epidermal sheet grafting with Hemaseel HMN fibrin sealant on nude mice.

Grafting of cultured epidermal sheets is a promising technique for skin restoration in extensive burns, but the technique has some limitations, resulting in variable graft takes. These experiments were designed to evaluate the innocuity of Hemaseel HMN fibrin sealant in the grafting process and in vivo evolution of cultured epidermis. A total of 30 mice were grafted, 15 were controls, 15 received tissue sealant application before the deposition of the cultured human epidermal sheets. Seven days after transplantation, compared to controls, the percentage of graft take over the total surface area grafted was greater in animals that had received the tissue sealant application. No difference was found 14 and 21 days postgrafting. In contrast, the percentage of graft take over the bony area (spinal) was significantly increased in animals grafted with previous application of sealant compared to controls at 7, 14 and 21 days postgrafting. Immunohistological and ultrastructural analysis showed that the evolution of the cultured human epidermis after transplantation was similar in both groups. The basement membrane was well structured 21 days after transplantation. The sealant was present at 4 days but not at 21 days postgrafting. Therefore, we conclude that the application of fibrin sealant before cultured epidermal sheet deposition on nude mouse graft bed is innocuous and enhances their mechanical stability. Since in this nude mouse system Hemaseel HMN fibrin sealant increased the percentage of graft take over areas difficult to engraft, we think that it may be advantageous in cultured epidermal sheet grafting on burn patients.

Animals↗

PubMed1996

Distribution of atrial electrogram types during atrial fibrillation: effect of rapid atrial pacing and intercaval junction ablation.

OBJECTIVES: This study examined the anatomic distribution types and possible determinant of atrial electrogram types during atrial fibrillation. BACKGROUND: Different types of atrial electrograms during atrial fibrillation have been observed and classified, but their anatomic distribution patterns, determinants and potential usefulness in guiding future catheter ablation are unknown. METHODS: Two animal models of atrial fibrillation were used: the sterile pericarditis model (n = 10) and the rapid atrial pacing model (400 beats/min for 6 weeks, n = 6). The atrial electrogram of atrial fibrillation and the atrial effective refractory period were obtained from multiple sites of the right and left atrium. In addition, decremental rapid atrial stimulation was applied to the site of shortest and longest atrial effective refractory periods until atrial fibrillation induction in a subgroup of nine dogs. Ablation of the intercaval junction was performed using the radiofrequency catheter technique in dogs with atrial fibrillation duration > 1 min. RESULTS: In both models, organized atrial electrograms (type I) were predominantly observed at the left atrial sites and the right atrial appendage, whereas disorganized atrial electrograms (type III) were mainly observed at the right posterolateral atrium. The distribution of the atrial electrogram types closely followed that of the atrial effective refractory period, with the shortest atrial effective refractory period corresponding to organized atrial electrograms (type I) and the longest atrial effective refractory period corresponding to disorganized atrial electrograms (type III). The correlation of atrial electrogram type with the atrial effective refractory period was further demonstrated by the effect of rapid atrial stimulation. When rapid atrial stimulation was applied to the site with the shortest atrial effective refractory period, disorganized atrial electrograms were observed at sites with the longest atrial effective refractory period, whereas 1:1 atrial capture was still present at the stimulation site. Ablation of the intercaval junction made atrial fibrillation noninducible or tended to shorten the atrial fibrillation duration (from 26.4 +/- 24.2 to 8.8 +/- 22.6 min in the pericarditis group, p = 0.02, and from 33.7 +/- 29.2 to 12.1 +/- 23.8 min in the rapid pacing group, p = 0.09) but did not change the atrial electrogram types during atrial fibrillation. CONCLUSIONS: Various types of atrial electrograms are present at different locations during atrial fibrillation. The atrial electrogram characteristics of atrial fibrillation at a specific location are related to the atrial effective refractory period, with short effective refractory periods associated with organized atrial electrograms and long effective refractory periods associated with disorganized electrograms.

Animals↗

PubMed1996

The nanomelic mutation in the aggrecan gene is expressed in chick chondrocytes and neurons.

We have established the presence of at least two large chondroitin sulfate proteoglycans in the developing chick brain, one that reacts exclusively with HNK-1, a carbohydrate epitope found on several neural specific molecules, and one that reacts with S103L, a defined peptide epitope in the CS-2 domain of the cartilage-specific chondroitin sulfate proteoglycan (CSPG), aggrecan. In order to determine the relationships between the two distinct S103L-reactive CSPGs from cartilage (chondrocytes) and brain (neurons), as well as among the three large CSPGs expressed in brain, S103L, HNK-1 and versican, we studied the expression of these multiple proteoglycan species in the brain of nanomelic chicks. We have previously shown that homozygous embryos expressing the nanomelic phenotype exhibit a single point mutation in the aggrecan gene. In the present study, the S103L CSPG is not accumulated or synthesized by embryonic chick CNS tissue or E8CH neuronal cultures derived from nanomelic chick embryo cerebral hemispheres. In contrast, expression of both versican and the HNK-1 CSPG was normal in the mutant embryo CNS. Pulse chase experiments demonstrated the presence of the 380 kDa precursor in normal neurons and the 300 kDa truncated precursor in nanomelic neurons. Northern blot analysis revealed normal-sized mRNA but reduced levels of expression of the S103L CSPG message in nanomelic neurons, while expression of the versican message was comparable in normal and nanomelic neurons. Most conclusively, the point mutation previously identified in nanomelic cartilage mRNA was also identified in nanomelic brain mRNA. Together these results provide evidence that a single aggrecan gene is expressed in both cartilage and CNS tissue leading to the production of identical core proteins which then undergo differential and tissue-specific post-translation processing, resulting in the characteristic tissue-specific proteoglycans. Furthermore, versican and the HNK-1 CSPG, although structurally and chemically similar to the S103L CSPG, are the products of separate genes.

Animals↗

PubMed1996

Elimination rate of fat emulsion particles from plasma in Japanese subjects as determined by a triglyceride clamp technique.

The elimination rate of emulsion triglyceride (TG) from plasma was investigated in Japanese subjects by a plasma TG clamp technique. Two different studies were performed. In Study 1, a lipid emulsion (20% long-chain triglyceride emulsion: LCT) was infused into a healthy research associate to achieve a certain concentration of TG in the plasma. Thereafter, the infusion rate was adjusted to maintain the chosen concentrations of TG in plasma (namely, 4-5 mmol/L, 3-4 mmol/L, and approximately 2 mmol/L) over a period of 160 min by measuring plasma TG concentrations at 10-min intervals. Concentrations of TG in plasma were clamped within 2.13 +/- 0.13 mmol/L by an infusion rate of 0.10 g.kg-1.h-1, within 3.34 +/- 0.20 mmol/L by an infusion rate of 0.14 g.kg-1.h-1, and within 4.46 +/- 0.22 mmol/L by an infusion rate of 0.11 g.kg-1.h-1. The mean rate of infusion of emulsified TG that had maintained the steady concentrations of TG in plasma was limited to the very narrow range of 0.12 +/- 0.02 g of TG.kg-1.h-1 regardless of the chosen concentration of TG in plasma. Concentrations of nonesterified fatty acids (NEFA) also remained at a fixed level of 1.378 +/- 0.103 mEq/L regardless of the chosen concentration of TG in the plasma. Study 2 was undertaken to determine whether plasma TG concentration reached a plateau during a period when emulsion TG was infused into three different subjects at a rate of 0.12 g.kg-1.h-1. The plasma TG concentrations were steady at a level of 2.04 +/- 0.32 mmol/L, and the plasma NEFA concentrations remained at a fixed level of 1.33 +/- 0.13 mEq/L, over a period of 160 min after 50-min priming infusion. These results indicate that the plasma TG elimination rate was limited to the narrow range of 0.12 +/- 0.02 g.kg-1.h-1 when the fat emulsion was infused into Japanese subjects in a steady state. However, the plasma TG elimination rate in Japanese subjects appeared to be lower than that of Europeans. This may be due to a difference in lipoprotein lipase activity caused by different dietary habits, namely, a lower fat intake.

Adult↗

PubMed1996

Evaluation of several Dupont portal film systems.

The sensitometric curves (also known as the characteristic curves, or more commonly as the H-D curves after Hurler and Driffield who first used such curves in 1890 to describe the response of photographic film to light) of three DuPont portal films (CRONEX 10T, 10TL and Ultra-Vision C) in combination with two DuPont cassettes (CRONEX Radiation Therapy and Radiation Therapy Verification) were produced utilizing a 60Co beam and a 18 MV beam. The results are compared with that of a Kodak portal film system (T-Mat G/RA film and X-Onratic V cassette). The sensitometric curves of the DuPont films in the Kodak cassette were also measured. The results show that the Kodak system is superior to the DuPont systems with respect to the imaging quality and the feasibility of film techniques, and that if the DuPont films are used, significant improvements can be made by combining the DuPont films with the Kodak cassette.

Cobalt Radioisotopes↗

PubMed1996

Sudden death in patients with implantable cardioverter-defibrillators.

UNLABELLED: Of the 733 patients with implantable cardioverter-defibrillators (ICDs) from 1982 to 1995 in our center, 20 died suddenly while the ICD was activated. This number included 16 men and four women with a mean age of 60 +/- 8 years and ejection fractions of 24.2% +/- 8.6%. ICDs were implanted for drug refractory ventricular tachycardia (VT) in 13 patients and for resucitated cardiac arrest in seven patients. The clinical VT was associated with syncope in 7 of 13 patients. VT was induced in 18 patients and was hemodynamically unstable in 12 patients. Shock therapies associated with syncope were delivered in 7 of 15 patients during the follow-up. This subgroup of patients survived a median of only 18 months after ICD implant. Ventricular fibrillation-defibrillation was found to surround death in nine patients. CONCLUSIONS: (1) Sudden death victims of the ICD population are characterized by poor left ventricular function and hemodynamically unstable ventricular tachyarrhythmias. (2) Ventricular tachyarrhythmias are the major cause of sudden death in ICD patients.

Aged↗

PubMed1996

Identification by subtractive hybridization of a spectrum of novel and unexpected genes associated with in vitro differentiation of human cytotrophoblast cells.

We have previously demonstrated that epidermal growth factor (EGF), colony stimulating factor-1 (CSF-I), and granulocyte-monocyte colony stimulating factor (GMCSF) stimulate, while transforming growth factor beta 1 (TGF beta 1) inhibits, cytotrophoblast differentiation. To identify genes mediating EGF induced differentiation, we constructed a subtracted cDNA library between undifferentiated cytotrophoblast and differentiating cytotrophoblast. We identified six novel genes and four known syncytial products alpha-human chorionic gonadotrophin (alpha hCG) pregnancy-specific beta 1-glycoprotein, 3 beta-hydroxysteroid dehydrogenase, and plasminogen activator inhibitor type 1 whose mRNAs increased during differentiation. Ten other genes were identified whose mRNAs increased during differentiation. Five of these (keratin 19, calcreticulin, heat shock protein 27, serum and glucocorticoid-regulated kinase and adrenomedullin) were not previously reported to be expressed in placenta. Five other genes known to be expressed in placenta were identified. keratin 8, fibronectin, mitochondrial ATP synthase, 1119, and cytosolic copper-zinc superoxide dismutase (SOD-1). Several of these genes may have regulatory functions in trophoblast differentiation.

3-Hydroxysteroid Dehydrogenases↗

PubMed1996

Conformational dynamics in cytochrome P450-substrate interactions.

There now are four known cytochrome P450 crystal structures. Two of these, P450cam and P450eryF, are substrate-bound while P450terp and the heme domain of P450BM-3 are substrate-free. Here we describe a preliminary analysis of the P450BM-3 heme domain complexed with the 16-carbon fatty acid substrate, palmitoleic acid. A comparison of the substrate-free and -bound structures shows that a large conformational change in the substrate access channel accompanies substrate binding. This new information, together with the substrate-bound structures of P450cam and P450eryF, reveals which regions of P450 are the most important in controlling the dynamics of substrate binding and recognition.

Bacterial Proteins↗

PubMed1996

Halicylindramides D and E, antifungal peptides from the marine sponge Halichondria cylindrata.

Halicylindramides D (1) and E (2) have been isolated from the marine sponge Halichondria cylindrata. Halicylindramide D is a tridecapeptide with the N-terminus blocked by a formyl group and the C-terminus lactonized with a threonine residue, while halicylindramide E is a truncated linear peptide with a C-terminal amide. Their structures, including absolute stereochemistry, were determined by a combination of spectral and chemical methods. Halicylindramide D was antifungal against Mortierella ramanniana and cytotoxic against P-388 murine leukemia cells.

Amino Acid Sequence↗

PubMed1996

Niruriside, a new HIV REV/RRE binding inhibitor from Phyllanthus niruri.

During the screening of natural products for their ability to inhibit the binding of HIV-REV protein to [33P]-labeled RRE RNA, one novel compound, niruriside (1), was isolated from the MeOH extract of the dried leaf of Phyllanthus niruri L. by bioassay-guided fractionation. The structure of niruriside was determined by spectroscopic methods. Niruriside showed specific inhibitory activity against the binding of REV protein to RRE RNA with an IC50 value of 3.3 microM; however, niruriside did not protect CEM-SS cells from acute HIV infection at concentrations up to 260 microM using an XTT dye reduction assay.

Antiviral Agents↗

PubMed1996

Effects on cultured neonatal mouse calvaria of the flavonoids isolated from Boerhaavia repens.

A MeOH extract from the whole plant of Boerhaavia repens was found to inhibit bone resorption induced by parathyroid hormone (PTH) in tissue culture. Systematic separation of the MeOH extract afforded one new and two known flavonoid glycosides, namely, eupalitin 3-O-beta-D-galactopyranosyl-(1-->2)-beta-D-glucopyranoside (1), eupalitin 3-O-beta-D-galactopyranoside (2), and 6-methoxykaempferol 3-O-beta-D-(1-->6)-robinoside (3). The structure of the new compound 1 was determined using spectroscopic techniques. The inhibitory activity of these substances toward bone resorption induced by PTH was evaluated, and compounds 1 and 2 were found to exhibit significant activity.

Animals↗

PubMed1996

Quantitative changes of amino acid distributions in the rat vestibular nuclear complex after unilateral vestibular ganglionectomy.

Changes of amino acid concentrations in the vestibular nuclear complex (VNC) during lesion-induced vestibular compensation were studied in rats after unilateral vestibular ganglionectomy. Distributions of 12 amino acids within the VNC were measured at 2,4,7, and 30 days after surgery, using microdissection of freeze-dried brain sections and HPLC. Glutamate decreased on the lesioned side in nearly all VNC regions. Changes were fully developed 2 days after lesion and persisted through 30 days. In some regions, glutamate decreased also on the unlesioned side, especially at longer survival times, so that bilateral asymmetries became reduced. Aspartate changes were similar to those of glutamate on either side. Lesion-induced glutamine asymmetry was usually opposite to that of glutamate. Although GABA concentration decreased at early survival times, it recovered at later times and sometimes increased in dorsal parts of lateral and medial nuclei. Taurine changes were similar to those of GABA in most regions. Glycine change was primarily limited to a bilateral decrease in the dorsal part of the lateral vestibular nucleus. Concentrations of other amino acids were much lower, but some showed postlesion changes.

Amino Acids↗

PubMed1996

Ras-regulated hypophosphorylation of the retinoblastoma protein mediates neuronal differentiation in PC12 cells.

To investigate the role of the retinoblastoma protein pRB in neuronal differentiation, we have measured the accumulation of hypophosphorylated pRB in PC12 cells stimulated by nerve growth factor (NGF). NGF induced the accumulation of hypophosphorylated pRB within 30 min and the level peaked after 12 h. Viral Kiras, cyclic AMP (cAMP), and 12-O-tetradecanoylphorbol 13-acetate (TPA) also induced the hypophosphorylation of pRB, but epidermal growth factor and interleukin-6 did not. The extent of hypophosphorylation of pRB correlated well with the capacity of these factors to stimulate neurite outgrowth. The constitutively activated Ras induced persistent shift of the phosphorylation state of pRB toward hypophosphorylation. A dominant negative form of cHa-Ras suppressed significantly induction of the hypophosphorylation of pRB by NGF, but not by cAMP. Taken together, these results suggest that the hypophosphorylation of pRB triggered by NGF is mediated by a Ras-dependent pathway. Furthermore, microinjection of a monoclonal antibody specific for the hypophosphorylated form of pRB blocked the neurite outgrowth initiated by NGF. These results suggest a crucial role of pRB in withdrawal of cells from the cell cycle and in neuronal differentiation of PC12 cells.

Animals↗