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Biomedical subjects

Y Y Li

Publications and source records attributed to Y Y Li.

At least 19 recordsLinked to original sources
PubMed1992

Cells transfected with human interleukin 6 cDNA acquire binding sites for the hepatitis B virus envelope protein.

Earlier studies revealed that human interleukin 6 (IL-6) contains recognition sites for the hepatitis B virus (HBV) envelope (env) protein, and that IL-6 and anti-IL-6 antibodies, respectively, inhibited the interaction of cells expressing a receptor for HBV with the preS(21-47) segment of the HBV env protein, encompassing the complementary attachment site for IL-6. This suggested that IL-6 mediates HBV-cell interactions. We report that: (a) Chinese hamster ovary cells transfected with human IL-6 cDNA and Spodoptera frugiperda ovarian insect cells infected with recombinant baculovirus carrying human IL-6 cDNA expressed receptors for the preS(21-47) region of the HBV env protein, indicating that expression of IL-6 on the surface of cells is sufficient to endow them with receptors for HBV. (b) Among peptides covering the entire sequence of human IL-6 and the corresponding antipeptide antibodies, the peptide IL-6[35-66] and anti-IL-6[35-66] most effectively inhibited the interaction between human hepatoma HepG2 cells and the preS(21-47) ligand, suggesting that this region of the human IL-6 sequence encompasses a binding site for the HBV env protein. (c) Studies with replacement set peptides from the preS(21-47) sequence indicated that residues 21-25, 28, 31, 33-35, 39, and 43-45 can be replaced by alanine (serine) residues, while all the other residues are essential for maintaining the cell receptor/IL-6 binding activity. Further delineation of complementary sites on IL-6 and on the HBV env protein may contribute to the design of compounds inhibiting HBV replication.

Amino Acid Sequence↗
PubMed1992

Basement membrane and its components on lymphocyte adhesion, migration, and proliferation.

During inflammation and recirculation, lymphocytes migrate into tissues by traversing the capillary endothelium, a process known as extravasation. After crossing the endothelial cells, lymphocytes come into contact with the basement membrane, which is a specialized layer of extracellular matrix containing predominantly laminin, collagen type IV, entactin, and heparan sulfate proteoglycans. In tissue invasion by inflammatory cells and metastatic tumor cells, the basement membrane serves as a substratum for cell adhesion and migration. However, the role of basement membrane in lymphocyte extravasation remains unclear. In this study, we investigated the effect of basement membrane on lymphocyte adhesion, migration, and proliferation, using matrigel as a model for basement membrane. We observed that matrigel promotes both lymphocyte adhesion and migration, with entactin primarily responsible for promoting adhesion and laminin for promoting migration. In addition, activation of lymphocytes by anti-CD3 enhances their adhesion and migration on matrigel-coated substratum. We also observed that matrigel inhibits the proliferation of lymphocytes stimulated by Con A. Furthermore, we demonstrated that laminin is the matrigel component responsible for inhibiting lymphocyte proliferation. However, matrigel has no effect on the proliferation of lymphocytes stimulated by LPS. These results suggest that matrigel has different effects on lymphocyte subpopulations. In agreement with the results on proliferation, matrigel also inhibits the production of IL-2 by Con A-stimulated lymphocytes.

Animals↗
PubMed1992

LEU2 gene homolog in Kluyveromyces lactis.

A DNA fragment that can complement the leu2 mutation of Saccharomyces cerevisiae was cloned from the genomic library of Kluyveromyces lactis. The nucleotide sequence revealed an open reading frame of 362 codons, 75% homologous to S. cerevisiae LEU2 gene. The upstream region contained a CCGGAACCGG sequence identical to the site of leucine-specific control of LEU2. Further upstream, there is a partial open reading frame homologous to rat ribosomal protein L7.

Amino Acid Sequence↗
PubMed1992

Altered cytokine production in black patients with keloids.

The treatment of keloids in black patients remains a medical dilemma. Previous studies have focused on primary alterations in the metabolism of fibroblasts as the key in the etiology of this condition. Yet alterations in the production of various cytokines which may alter fibroblast responses secondarily have received little attention. Twelve black patients with clinical and histological diagnosis of keloids and eight black control volunteers were studied. Peripheral blood mononuclear-cell (PBMC) fractions from both groups were assayed for production of interleukin-1 (IL-1), interleukin-2 (IL-2), interleukin-6 (IL-6), alpha-interferon (IFN-alpha), beta-interferon (IFN-beta), gamma-interferon (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), and tumor necrosis factor-beta (TNF-beta). The production of IFN-alpha, IFN-gamma, and TNF-beta were markedly depressed in keloid patients compared to normal controls. However, IL-1 and IL-2 production was not significantly different between the two groups. In contradistinction, keloid patients produce greater amounts of IL-6, TNF-alpha, and IFN-beta. Altered levels of immunoregulatory cytokines may play a significant role in the net increase in collagen which characterizes keloid formation.

Black People↗
PubMed1992

Differential inhibition of human basal keratinocyte growth to silver sulfadiazine and mafenide acetate.

The impact of topical antimicrobial agents on improving the survival of patients with major thermal injuries is significant. However, the effects of these agents on cells responsible for wound healing has only recently received attention. Fresh human basal keratinocytes were grown in serum-free modified MCDB 153 medium under standard tissue culture conditions. Cells were subsequently exposed to concentrations of silver sulfadiazine and mafenide acetate as low as 1/100 of that used clinically over a period of 5-7 days. Cellular responses documented with hemocytometer cells counts, cellular protein assays, phase-contrast microscopy, and transmission electron microscopy show only severe toxicity to mafenide acetate. Such data imply that inhibition of wound epithelialization is greater with the use of mafenide acetate than with the use of silver sulfadiazine.

Cell Count↗
PubMed1992

Changes in serum osmolality and osmolar discrepancy in burned patients.

Forty-three patients with burns of various depth and burn surface area were studied to determine the relationship between burn severity and changes of serum osmolality. The results showed that the osmolality in four patients who died were significantly higher than the osmolalities of survivors with very serious burns, whose osmolalities decreased gradually to normal level. Hyperosmolality and obvious osmolar discrepancy often co-exist. It is suggested that the changes of osmolality and osmolar discrepancy can reflect the burn severity and prognosis of the patients.

Adolescent↗
PubMed1992

Epidemiology of Helicobacter pylori in southern China: identification of early childhood as the critical period for acquisition.

A large cross-sectional study to investigate the prevalence and possible modes of transmission of Helicobacter pylori was done in southern China. Serum samples (1727) were collected from Guangzhou city and three rural areas of Guangdong Province, and the prevalence of H. pylori infection was determined using an ELISA. Each subject completed a questionnaire. The overall prevalence of H. pylori infection was 44.2%; a significantly higher prevalence was found in Guangzhou (52.4%) than in the rural areas (38.6%). This difference was generally reflected in the group 0-5 years old, but the rate of increase in seroprevalence for H. pylori over 5 years of age was similar (1%/year). This study provides important new data on the acquisition of H. pylori, particularly in the early years of life, and shows that density of living conditions is a prime determinant in the acquisition of H. pylori.

Adolescent↗
PubMed1992

Characterization of a circular plasmid from the yeast Kluyveromyces waltii.

A new plasmid was found in the yeast Kluyveromyces waltii. This high-copy-number plasmid, named pKW1, is a double-stranded circular DNA plasmid of 5619 bp. It has several features characteristic of the 2 mu-type plasmids: presence of two inverted repeats and four open reading frames, as well as the interconversion of two isomeric forms. However, the nucleotide sequence shows little homology with known yeast plasmids. An ARS function was localized within a segment of 545 bp near one of the inverted repeats. Chimeric plasmids carrying this segment efficiently transformed K. waltii. A strain of K. waltii cured of the plasmid (cir degree) was also obtained. In the pKW1 sequence, a functionally neutral region was found at which foreign DNA can be inserted with little effect on plasmid stability. Such constructions carrying the full sequence of pKW1 replicated autonomously in a cir degree host and were particularly stable. pKW1-derived full-sequence plasmids also transformed K. thermotolerans, but not K. lactis.

Base Sequence↗
PubMed1992

Energy metabolism of rabbit retina as related to function: high cost of Na+ transport.

Experiments designed to examine the energy requirements of neurophysiological function were performed on isolated rabbit retina. Function was altered by photic stimulation or by function-specific drugs, and the response of energy metabolism was assessed by simultaneous measurements of O2 consumption and lactate production. In other experiments, the supply of O2 or glucose was reduced and the effect on energy metabolism and electrophysiological function was observed. Energy requirements under control conditions in darkness were high, with O2 consumption (per gm dry wt) at 11.3 mumol min-1, with lactate production at 14.8 mumol min-1, and with the derived value for glucose consumption at 9.3 mumol min-1 and for high-energy phosphate (approximately P) generation at 82.6 mumol min-1. Energy reserves were small. Removing glucose abolished the b-wave of the electroretinogram (ERG) with a t1/2 of 1 min, but did not immediately affect O2 consumption or the PIII of the ERG. Removing O2 caused increases of up to 2.7-fold in glycolysis (Pasteur effect) and caused both PIII and b-wave to fail, with a t1/2 of about 5 min. Neurotransmission through the inner retina was supported almost entirely by glycolysis, as evidenced by large increases in lactate production in response to flashing light and decreases in response to transmitter blockers (2.3-fold overall change), with no change in O2 consumption. Phototransduction, on the other hand, was normally supported by oxidative metabolism. The dark current accounted for 41% of the retina's O2 consumption. With O2 reduced, the dark current was partially supported by glycolysis, which accounts (at least in part) for the large Pasteur effect. Na+ transport by NaK ATPase accounted for about half of all energy used, as evidenced by the response to strophanthidin, that is, for 49% of the oxidative energy and 58% of the glycolytic energy. The t1/2 for the turnover of intracellular Na+ was calculated from these data to be less than 1 min. Changes in temperature caused changes in the amplitude of light-evoked electrical responses of 6.5% per degree and caused changes in both O2 consumption and glycolysis of 6.8% per degree (Q10 = 1.9). A surprisingly large fraction of oxidative energy, corresponding to about 40% of the total energy generated, could not be assigned to phototransduction, to neurotransmission, to Na+ transport for other purposes, or to vegetative metabolism. We cannot account for its usage, but it may be related to the (previously reported) rapid turnover of the gamma-phosphate of retinal GTP, the function of which also remains unknown.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

[Circulating autoantibodies against beta-adrenergic receptors in patients with heart diseases].

Patients with different heart diseases, dilated cardiomyopathy, valvular heart disease, hypertension, ischemic heart disease or myocarditis showed manifestations of autoimmunity and down-regulation of beta-adrenergic receptors. Autoantibodies against beta-adrenergic receptors in these patients were detected with radioligand binding inhibition assay. The results suggested that the down-regulation of cardiac beta-adrenergic receptors in these patients may be mediated by autoimmunity. Autoantibodies against beta-adrenergic receptor were not related to any specific heart diseases, but to the severity of heart failure irrespective of its etiology. The significance of these autoantibodies in heart failure was discussed.

Adult↗
PubMed1992

Energy requirements of glutamatergic pathways in rabbit retina.

In vitro rabbit retina was used as an example of CNS tissue in experiments designed to measure the energy requirements associated with the activation of different types of glutamate receptors. Retinas were exposed to glutamate and to four analogs: kainate, 2-amino-4-phosphonobutyric acid (APB), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), and 2-amino-5-phosphonovaleric acid (APV). The changes in O2 consumption and lactate production were determined using a recently developed experimental system that permitted simultaneous measurements of the rates at which O2 was removed from the medium and acid was added. The glutamatergic agents had relatively little effect on oxidative metabolism, but they caused large changes in glycolysis. Kainate increased retinal lactate production by 50%, whereas APB, CNQX, and APV reduced it by 23%, 19%, and 35%, respectively. Glutamate increased lactate production by 16% when administered after APB, but decreased it by 12% when administered after CNQX. The changes in energy metabolism coincided with changes in electrophysiological function. Since the energy metabolism of many retinal cells was presumably not much affected by the glutamatergic agents, the changes measured as a percent of total retinal glycolysis must have reflected considerably larger fractional changes in the cells most affected. From the response to inhibitors, it seems probable that even under resting conditions in darkness, activity in glutamatergic pathways is responsible for more than 50% of the glycolytically derived energy used by the cells involved. It also seems probable (particularly from the response to kainate) that under some circumstances the cells' energy metabolism and/or transport capability cannot meet the requirements imposed by glutamate-induced increases in function.(ABSTRACT TRUNCATED AT 250 WORDS)

2-Amino-5-phosphonovalerate↗
PubMed1992

[Experimental research on the effective mechanism of jianweiling].

The purpose of this study is to find out the effective mechanism of Jianweiling (JWL) in treating some gastrointestinal (GI) diseases. The functions of GI movement, bile and pancreatic secretion and intestinal absorption were measured after giving JWL to the experimental rats. The results showed that JWL could adjust GI movement once it was in abnormal conditions. When the gastrointestine was in paralysis under the influence of abdominal operation, JWL could make GI myoelectric activity return to normal; and JWL could relax it when the gastrointestine was in a cramp state resulted from Neostigmini Methylsulfurici injection. In addition, the pancreatic secretion, the amylase activity in pancreatic juice and the intestinal absorption for D-xylose in JWL group were obviously better than those of the control groups. These results suggested that the effective mechanism of JWL on some GI diseases can be realized by adjusting and promoting GI functions in various ways.

Amylases↗
PubMed1992

A new human interferon-gamma mutant harboring EGF receptor-interfering sequence possesses high antiproliferative activity.

An interferon gamma (IFN-gamma) mutant gene harboring an additional epidermal growth factor (EGF) sequence at its 3' terminal was constructed and highly expressed in E. coli by using pBV220 as a vector. The new fusion protein-IFN-gamma-EGF possesses not only high antiviral activity, but also high antiproliferative effect as demonstrated by 3H-TdR incorporation method using CN II cells which are rich in EGF receptors.

Amino Acid Sequence↗
PubMed1992

Oxyntic and antral gastritis in the People's Republic of China: diagnosis and relationship to Helicobacter pylori.

This study investigates the relationship between gastritis and Helicobacter pylori infection in the Chinese population. Particular focus was placed upon the grading of gastritis, using the recently developed "Sydney system." Five diagnostic procedures were used to establish H. pylori status, all of which were found to be highly sensitive and specific. Histological chronic gastritis was reported in 93/108 (86.1%) of the patients examined, H. pylori infection being present in 73/93 (78.5%), and in no patient with histologically normal mucosae. There was a relatively high incidence of idiopathic antral gastritis within the gastritic population, 20/93 (21.5%). In the H. pylori-positive group, 10/73 (13.7%) had pangastritis, 57/73 (78.1%) had pangastritis-antrum-predominant, and 6/73 (8.2%) had antral-only gastritis. The level of activity was significantly higher in the antrum; however, the distribution of bacteria between the antrum and body was not significantly different. There is a need for additional studies examining the specific topographical relationship between H. pylori, the histology, and gastroduodenal disease.

Adolescent↗
PubMed1992

Effects of copper and selenium on electric parameters of cultured myocardial cells damaged by xanthine-xanthine oxidase.

Addition of xanthine 0.42 mmol.L-1 and xanthine oxidase 5.3 nmol.L-1 (X-XO) to the culture medium increased the amplitude of ESR spectra of myocardial cells, demonstrating an increase in free radical contents; diminished the action potential parameters significantly and reduced the input impedances from 0.34 +/- 0.11 to 0.24 +/- 0.1 M omega, expressing a typical electrical appearance of membrane damage. Supplying Cu 62.5 ng.ml-1 and/or Se 173 ng.ml-1 to the medium brought all of the electric parameters and the free radical content of myocardial cells back to normal. The results indicate that both the two trace elements are able to scavenge free radicals, thus antagonizing X-XO, which induces damage to myocardial cells.

Action Potentials↗
PubMed1991

Dimensions of face in Asia in the perspective of geography and prehistory.

Data from 24 craniofacial dimensions were compiled for samples representing all the human populations of the world. These were converted into C scores and used to construct Euclidean Distance dendrograms. The populations of the world are best depicted as 8 major regional clusters representing: Africa, Amerind, Asia-Mainland, Australo-Melanesia, Eskimo-Siberia, Europe, India, and Jomon-Pacific. The mainland Asian cluster divided into northern and southern components. The Neolithic in both areas is less clearly associated with the northern or southern components and may represent the form of their undifferentiated precursors. This needs to be tested by the addition of further specimens and an adequate sample from South China. Mongols are peripheral members of the Asia-Mainland cluster and should not be thought of as typifying the region as a whole. The use of the term "Mongoloid" is inappropriate in both theory and practice.

Asia↗
PubMed1991

Evaluation of HemoQuant test and enteroclysis in estimating the sites of obscure gastrointestinal bleeding.

The HemoQuant test includes the measurement of total fecal hemoglobin (Hb) or porphyrin derived from heme, and of intestinal converted fraction (ICF) which is the performed porphyrin probably by bacteria during enterocolic transit. The mean +/- SD of HemoQuant in 31 healthy subjects was 0.57 +/- 0.49 mg Hb/g stool, values above 2 mg Hb/g stool are considered to be positive. In patients with upper GI bleeding (n = 44), small bowel bleeding (n = 11) and large bowel bleeding (n = 16), the ICF ranged 0.03-23%, 0.09-20.20% and 0.35-11.0%, respectively. There was major overlap in individual ICF due to some influencing factors such as the quantity of fecal blood and the enterocolic transit. We conclude that HemoQuant is a sensitive assay for detection of fecal occult blood, but ICF is not helpful in estimating the anatomic site of bleeding. Seventy-one patients with GI bleeding of obscure origin underwent enteroclysis. The results showed 77.5% had definite lesions in the small bowel, but 22.5% still were undefined. It is suggested that enteroclysis should be performed without delay if upper and lower GI endoscopic studies are negative.

Adult↗