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Biomedical subjects

X Jiang

Publications and source records attributed to X Jiang.

At least 361 records · Page 20Linked to original sources
PubMed1996

Adriamycin stimulates proliferation of human lymphoblastic leukaemic cells via a mechanism of hydrogen peroxide (H2O2) production.

It is becoming clear that adriamycin cytotoxicity may be mediated by semiquinone-free radicals derived from the drug itself and reactive oxygen species (ROS). Recent evidence supports the concept that low concentrations of ROS are able to stimulate cell proliferation, and, based on the observation that subtoxic concentrations of adriamycin can also induce cell proliferation, we hypothesize that low concentrations of adriamycin stimulate cell proliferation by a ROS generation mechanism. We have employed spin-trapping and electron spin resonance (ESR) spectroscopy to investigate the nature of the adriamycin-generated ROS. The spin trap 3,5-dibromo-4-nitrosobenzenesulphonate (DBNBS), which is oxidized in the presence of H2O2 and peroxidase enzymes, was used to produce a characteristic three-line spectrum, and it was found that an identical spectrum was produced by human lymphoblastic leukaemic cells (CCRF-CEM cells) after exposure to adriamycin. We tested our hypothesis further by exposing CCRF-CEM cells to subtoxic concentrations of adriamycin (10(-8), 10(-9) and 10(-10) M) and low concentrations of H2O2 (10(-8), 10(-9) and 10(-10) M) and subsequently monitored cell proliferation. We found that low concentrations of both adriamycin and H2O2 significantly stimulate CCRF-CEM cell proliferation. We therefore conclude that subtoxic concentrations of adriamycin are likely to induce cell proliferation via an H2O2 mediated mechanism.

Cell Division↗
PubMed1996

Translation initiation region plays an important role in the expression of human thrombopoietin in Escherichia coli.

A mutant human thrombopoietin (TPO) gene with a modified translation initiation region (TIR) sequence was created by site-specific mutagenesis based on the PCR technique. This mutant TPO gene encoded the same amino acid sequence as wild-type TPO gene. The wild-type TPO gene was expressed in E. coli with very low efficiency. The mutant TPO gene could reach an expression level of up to 10% of total cellular proteins in E. coli, which was much higher than the wild-type gene. The recombinant protein was mainly in the form of inclusion body which could acquire in vitro activities of human thrombopoietin after refolding.

Escherichia coli↗
PubMed1996

Lymphokine-activated killer cells lyse Listeria-infected hepatocytes and produce elevated quantities of interferon-gamma.

The bulk of Listeria monocytogenes injected intravenously into mice is taken up in the liver, where hepatocytes serve as the principal site of intracellular replication. NK cells have been implicated in host defenses to a variety of intracellular pathogens. To explore the role of NK cells in resistance to listerial infections of the liver, lymphokine-activated natural killer (LAK) cells were cocultured with Listeria-infected hepatocytes. The aspartate aminotransferase activity in the medium (evidence of cytotoxicity and hepatocyte damage) was elevated significantly in these cultures. Conversely, the viability of intracellular Listeria organisms was reduced. Increased quantities of interferon-gamma (IFN-gamma) were also detected. IFN-gamma production by LAK cells was modulated by interleukin (IL)-2 and IL-12. These findings suggest that the response of LAK cells to infected hepatocytes may play a critical role in host defenses to Listeria organisms taken up in the liver.

Animals↗
PubMed1996

Survival of Vibrio parahaemolyticus at low temperatures under starvation conditions and subsequent resuscitation of viable, nonculturable cells.

Morphological changes of Vibrio parahaemolyticus from rods to spheres took place after a culture was subjected to starvation at a wide range of temperatures. Scanning electron micrographs revealed that starved spherical cells gradually developed a rippled cell surface with blebs and an extracellular filamentous substance adhesive to the cell surface. Cells starved at a low temperature for certain intervals were counted by various bacterial enumeration methods, including plate count, direct viable count, and total cell count for both Kanagawa-positive and -negative strains. The results indicated that this species could reach the nonculturable stage in 50 to approximately 80 days during starvation at 3.5 degrees C. Kanagawa-negative strain 38C6 lost culturability more slowly than Kanagawa-positive strain 38C1 at low temperature. As detected by thiosulfate-citrate-bile salts-sucrose plate count, a high percentage of the surviving cells at 3.5 degrees C in starvation medium were possibly injured by the low temperature rather than by starvation. Both addition of nalidixic acid to the starved cultures and the most-probable-number method demonstrated that the cells recovered after a temperature upshift probably represented the regrowth of a few surviving cells. These surviving cells were capable of growth and multiplication with limited nutrients at an extraordinary rate when the temperature was upshifted.

Cell Division↗
PubMed1996

[Combustion under microgravity and technique of fire prevention and suppression in space cabin].

This is a brief review on microgravity combustion, along with the discussion of the fundamental characteristics of combustion and fire processes under microgravity. Recent research activities in microgravity combustion and space fire prevention were emphasized. In addition, the potential use of flame-inhibiting atmospheres in the space cabin was introduced. The technique of fire detection and extinguishment in spacecraft environments was also discussed.

Fire Extinguishing Systems↗
PubMed1996

Racial (black-white) differences in insulin secretion and clearance in adolescents: the Bogalusa heart study.

OBJECTIVE: Earlier we found black-white contrast in insulin levels in adolescents. The purpose of this study is to assess whether this difference is attributable to alterations in insulin secretion and/or clearance. METHODS: Fasting circulating insulin and C-peptide concentrations were examined in 1157 adolescents aged 11 to 18 years from a biracial community. Fasting plasma C-peptide, C-peptide to insulin ratio, and glucose to insulin ratio were used as indices of insulin secretion, hepatic insulin clearance, and insulin sensitivity, respectively. RESULTS: After adjusting several covariates (age, sexual maturation, and obesity), black adolescents had higher insulin levels (14.99 vs 12.66 microU/mL in girls). However, they had lower C-peptide levels than their white counterparts, indicating lower insulin secretion by pancreatic beta cells in black adolescents. Moreover, black adolescents had lower levels of C-peptide to insulin ratio than white adolescents (0.14 vs 0.17), suggesting reduced hepatic insulin clearance in black adolescents. In addition, significantly lower levels of glucose to insulin ratio in black girls suggest a reduced insulin sensitivity in this group. Further, differences in insulin levels between white and black girls disappeared after adjusting for differences in C-peptide to insulin ratio. CONCLUSION: These data suggest that elevated insulin levels observed in black adolescents, especially in black girls, may be attributed to their decreased hepatic insulin clearance, not hypersecretion of insulin.

Adolescent↗
PubMed1996

A mutation causing Alport syndrome with tardive hearing loss is common in the western United States.

Mutations in the COL4A5 gene, located at Xq22, cause Alport syndrome (AS), a nephritis characterized by progressive deterioration of the glomerular basement membrane and usually associated with progressive hearing loss. We have identified a novel mutation, L1649R, present in 9 of 121 independently ascertained families. Affected males shared the same haplotype of eight polymorphic markers tightly linked to COL4A5, indicating common ancestry. Genealogical studies place the birth of this ancestor >200 years ago. The L1649R mutation is a relatively common cause of Alport syndrome in the western United States, in part because of the rapid growth and migratory expansion of mid-nineteenth-century pioneer populations carrying the gene. L1649R affects a highly conserved residue in the NC1 domain, which is involved in key inter- and intramolecular interactions, but results in a relatively mild disease phenotype. Renal failure in an L1649R male typically occurs in the 4th or 5th decade and precedes the onset of significant hearing loss by approximately 10 years.

Adolescent↗
PubMed1996

[Molecular mechanism of suppressing lambda N gene's expression in E. coli ribosomal protein S12 streptomycin-dependent mutant].

Using the polymerase chain reaction (PCR) method, the rpsLd gene was amplified and cloned, which encodes the streptomycin-dependent (Smd) mutant of ribosomal protein S12 in E.coli T83. The result of DNA sequencing showed an AAA to CAA mutation at codon 42, leading to the substitution of glutamine (Gln, Q) for lysine (Lys, K). According to the principle of Garnier, we predicted that there might be alterations in the secondary structural propensity of protein S12 due to the mutation. The outcome indicated that the beta-turn propensity at position 42 and its nearby region was increased evidently and the relative position of relevant subdomains were changed. As a result, the special conformation of the whole protein S12 was influenced. In view of that ribosomal proteins and ribosomal RNAs (rRNA) mutually adapted in structures and functions, the probable molecular mechanism. That how protein S12 Smd mutant in E.coli T83 suppressed lambda N gene's expression is discussed.

Amino Acid Sequence↗
PubMed1996

Ultracytochemical localization of alkaline phosphatase (ALPase) activity in neutrophils of the rat lung following injection of lipopolysaccharide.

Alkaline phosphatase (ALPase) activity in neutrophils was examined by enzyme ultracytochemistry at sites of experimentally induced acute inflammation in the rat lung and compared with those in non-inflammatory regions. Neutrophil accumulations in the lung were stimulated by intraperitoneal (IP) injection and intratracheal (IT) instillation of lipopolysaccharide (LPS), an endotoxin from Escherichia coli. Microsliced sections of fixed lung were incubated in a cerium-based reaction medium for the detection of ALPase activity. As cytochemical controls, sections were incubated in a substrate-free medium or in a medium containing 2 mM levamisole for inhibition of ALPase activity. Both IP and IT injections resulted in a significant accumulation of neutrophils in the lung, however, their histological distributions differed, the former stimulating high accumulations within the capillaries and interalveolar spaces, and the latter within the confines of the alveolar spaces. In neutrophils from controls and non-inflamed regions of the lung, ALPase activity was detected as an electron-dense reaction product localized predominantly to small spherical and tubular membrane-bounded cytoplasmic compartments. In the IP-injected rats, prominent ALPase activity was observed at their plasma membrane surfaces, most notably at sites of endothelial cell contact. Following IT instillation of LPS, neutrophils suspended in the alveolar spaces showed a reduced plasma membrane reactivity, however, at type I pneumocyte contact regions, enzyme activity was significantly increased. In all cases, ALPase activity was not detected at the endothelial plasma membranes. Some reaction, however, was seen on the microvilli of the type II surfactant-producing cells. These results indicate that ALPase activity of rat neutrophils in the lung can be increased by LPS injection and that its activity may also be related to the sites of cell-cell interaction and cell surroundings.

Acute Disease↗
PubMed1996

Relation of obesity to insulin secretion and clearance in adolescents: the Bogalusa Heart Study.

OBJECTIVE: Earlier we found elevated insulin levels in obese children and adolescents. The present study examines whether alterations in insulin secretion and/or clearance contribute to hyperinsulinemia in obese adolescents. METHODS: Fasting circulating insulin and C-peptide concentrations were examined in 1157 adolescents, aged 11-18 y, from a biracial (black/white) community. In this epidemiologic study, plasma C-peptide was used as a noninvasive measure of insulin secretion by beta cells, C-peptide to insulin ratio as an indicator of hepatic insulin extraction, and insulin to glucose ratio as a measure of insulin sensitivity. Body mass index (BMI) was used as an index of obesity, since it is strongly associated with insulin levels and the C-peptide to insulin ratio more so than with measures of skinfolds and percent body fatness. RESULTS: Obese individuals (BMI > 90th P) had higher levels of plasma insulin (23.7 mu/ml vs 11.7 mu/ml), C-peptide (2.7 ng/ml vs 1.7 ng/ml), and insulin to glucose ratio (0.29 vs 0.15), and lower C-peptide to insulin ratio (0.13 vs 0.16) than non-obese adolescents (all P < 0.001). Elevated C-peptide and decreased C-peptide to insulin ratio were noted in subjects with both obesity and hyperinsulinemia (insulin > 90th P) versus those without these conditions (P < 0.001). Individuals with obesity and low insulin clearance (C-peptide/insulin < 10th P) had 18-fold higher prevalence of hyperinsulinemia versus those without these conditions. Although black adolescents, despite their lower percent body fat, had higher insulin and lower C-peptide and C-peptide to insulin ratio than their white counterparts, BMI related positively to insulin and C-peptide, and inversely with C-peptide to insulin ratio in both races. CONCLUSIONS: These data suggest that both increased insulin secretion and decreased insulin clearance contribute to hyperinsulinema in obese adolescents.

Adolescent↗
PubMed1996

Detection of bovine fetal Y-specific Sry sequence from maternal blood.

Two pairs of primers were designed based on the sequence of bovine Sry and applied to the assay of Sry sequence from maternal blood using the polymerase chain reaction. Of the total twenty DNA samples from peripheral blood of late pregnant cow, nine appeared positive with male-specific Sry sequence. The fetal sex predicted by the PCR analysis of maternal blood DNA accorded with the sex of babies on delivery in 16 cows (the remaining four were false negative). Our methods showed that bovine Sry sequence can be directly detected from the maternal blood for identifying fetal sex.

Animals↗
PubMed1996

[A human bone marrow cell line (B3HM) inducing leukemia in mouse].

Human bone marrow mononuclear cells were cultured on a layer of stromal cells derived from bone marrow of a patient with esophageal cancer. After five-week cultivation, the mononuclear cells could grow independently of stromal cells in liquid culture and had been passaged over 50 generations with a doubling time of 48 hours. The cell line thus established is called B3HM. The growth of B3HM appeared anchorage independent in semi-solid culture and produced 423 +/- 87.7 colonies per 5 X 10(4) cells. Immunofluorescence analysis showed that the cells were CD19+, CD20+, CD13+, CD15+, with both B cell and granulocyte surface markers. The cells or cell homogenate could induce leukemia when inoculated in nude mice and "615" inbred mice. The induced mouse leukemia was transplantable and L3T4 positive in more than 80% of the leukemic cells. The pathogenesis of the induced mouse leukemia is worthy of further investigation.

Aged↗
PubMed1996

[Gastric devascularization for acute gastric mucosal lesion and bleeding].

Thirteen patients with acute gastric mucosal lesion and bleeding were treated with gastric devascularization. Of all, 11 apparently stopped bleeding, two failed to respond to the procedure, one rebled, and three died. Clinical analysis of the patients suggested that low blood pressure, damage of liver function, serious infection, acidosis and uremia were precipitating factors of the disease and for AGML in portal hypertension, the effect of this procedure was poor. Meanwhile, the etiology and pathological mechanism of AGML, the selection of operation types for the disease, and the anatomical and physiological bases of gastric devascularization were also discussed.

Adult↗
PubMed1996

[Clinical study and application of 3DCT in oral and maxillofacial regions].

3DCT reconstruction as a new roentgenographic technique has not been used so much in oral and maxillofacial regions in our country. From May 1993 to May 1995, 72 cases of 3DCT reconstruction have been performed by a Siemens Plus-s CT scanner for the maxillofacial injuries and jaw bone diseases. The 3DCT reconstruction of soft tissuses has been used too. It is showed that 3DCT reconstruction is a useful technique for the diagnosis and surgical planning of diseases in oral and maxillofacial regions.

Adolescent↗
PubMed1996

[Characterization of renal pelvic carcinoma with US and color Doppler flow imaging].

Ultrasonography (US) was utilized to assess 22 patients with renal pelvic carcinomas, The neoplasms were demonstrated as hypoechoic mass in 81.82%, and as visualized hyperechoic mass in 18.18%; Their echogenicity was highly correlated with gross pathology. Among all the cases, 5 patients were investigated with color Doppler Flow Imaging (CDFI), and none of them demonstrated the high-frequency Doppler shifted signals seen in renal cell carcinomas. Therefore CDFI may help to differentiate renal pelvic carcinomas from renal cell carcinomas.

Adult↗
PubMed1996

[Effects of preoperative transcatheter hepatic arterial chemoembolization (TAE) on the prognosis of patients with hepatic carcinoma undergoing tumor resection].

This study consists of 77 hepatocellular carcinoma patients. Twenty-six (Group A) received preoperative TAE and 51 did not (Group B). Group A and B were further divided into two subgroups according to their tumor size i.e. Group A1 and B1 (tumor size 3-8 cm); Group A2 and B2 (tumor size > 8 cm). The 1-, 2-, 3-year disease free survival rates were 50.0%, 33.3%, 16.6% for Group A1 and 72.7%, 54.2%, 39.7% for Group B1; 75.0%, 56.2%, 45.0% for Group A2 and 38.9%, 32.4%, 10.8% for Group B2 respectively. The 1-, 3-, 5-years survival rates were 85.7%, 31.2%, 0 for Group A1 and 84.8%, 58.7%, 27.9% for Group B1; 91.6%, 82.5%, 53.0% for Group A2 and 77.8%, 30.1%, 0 for Group B2 respectively. There were significant differences between Group A2 and B2 both in disease free survival rate and 5-year survival rate (P < 0.05). The results also demonstrated that the preoperative TAE did worsen the prognosis of patients with tumor size between 3-8 cm (Group A1) with disease free survival rate and 5-year survival rate shorter than that of Group A2.

Antineoplastic Agents↗
PubMed1995

Structural predictions for the ligand-binding region of glycoprotein hormone receptors and the nature of hormone-receptor interactions.

BACKGROUND: Glycoprotein hormones influence the development and function of the ovary, testis and thyroid by binding to specific high-affinity receptors. The extracellular domains of these receptors are members of the leucine-rich repeat (LRR) protein superfamily and are responsible for the high-affinity binding. The crystal structure of a glycoprotein hormone, namely human choriogonadotropin (hCG), is known, but neither the receptor structure, mode of hormone binding, nor mechanism for activation, have been established. RESULTS: Despite very low sequence similarity between exon-demarcated LRRs in the receptors and the LRRs of porcine ribonuclease inhibitor (RI), the secondary structures for the two repeat sets are found to be alike Constraints on curvature and beta-barrel geometry from the sequence pattern for repeated beta alpha units suggest that the receptors contain three-dimensional structures similar to that of RI. With the RI crystal structure as a template, models were constructed for exons 2-8 of the receptors. The model for this portion of the choriogonadotropin receptor is complementary in shape and electrostatic characteristics to the surface of hCG at an identified focus of hormone-receptor interaction. CONCLUSIONS: The predicted models for the structures and mode of hormone binding of the glycoprotein hormone receptors are to a large extent consistent with currently available biochemical and mutational data. Repeated sequences in beta-barrel proteins are shown to have general implications for constraints on structure. Averaging techniques used here to recognize the structural motif in these receptors should also apply to other proteins with repeated sequences.

Amino Acid Sequence↗